Adhesive sheet and polishing pad with adhesive sheet

Abstract

A purpose of the present invention is to provide an adhesive sheet which exhibits excellent shear strength and excellent slurry resistance at high temperatures, while having excellent releasability that enables peeling without adhesive residue. Another purpose of the present invention is to provide a polishing pad with an adhesive sheet, said polishing pad having the above-described adhesive sheet. The present invention is an adhesive sheet which has at least one adhesive layer, wherein: the adhesive layer contains a base polymer, a tackifying resin (T1) that has a hydroxyl value of less than 20 mgKOH / g, and a tackifying resin (T2) that has a hydroxyl value of from 20 mgKOH / g to 120 mgKOH / g; the base polymer is a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound; and with respect to the adhesive layer, the content of the tackifying resin (T1) relative to 100 parts by weight of the base polymer is from 10 parts by weight to 60 parts by weight, and the content of the tackifying resin (T2) relative to 100 parts by weight of the base polymer is from 1 part by weight to 40 parts by weight.

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet, and also to an adhesive sheet-attached polishing pad having the adhesive sheet. [Background technology]

[0002] In processes for polishing semiconductor wafers, liquid crystal glass substrates, and the like to a predetermined thickness (e.g., chemical-mechanical-polishing (CMP) processes), polishing is performed using a polishing cloth fixed to the platen of a polishing machine. A double-sided adhesive sheet is usually used to fix the polishing cloth to the platen of the polishing machine. This double-sided adhesive sheet for fixing the polishing cloth is required to have sufficient adhesive strength to prevent the polishing cloth from peeling off during polishing, and also to be able to be removed from the platen without leaving any adhesive residue when replacing the used polishing cloth.

[0003] As an example of a double-sided adhesive sheet for fixing an abrasive cloth, Patent Documents 1 and 2 describe a double-sided adhesive tape for fixing an abrasive material, which has a specific heat-activated adhesive on one side of a plastic film support and a re-peelable adhesive layer on the other side of the plastic film support, with the heat-activated adhesive layer being the bonding surface with the abrasive material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-145611 [Patent Document 2] Japanese Patent Application Publication No. 6-172721 Summary of the Invention [Problem to be solved by the invention]

[0005] The performance required of double-sided pressure-sensitive adhesive sheets for fixing a polishing cloth is becoming more and more advanced every year. For example, during polishing, the pressure-sensitive adhesive layer is more likely to slip or peel off due to temperature rise caused by frictional heat or strong shear force. In particular, in recent years, the use of strongly acidic or strongly alkaline slurry liquids during polishing has made the pressure-sensitive adhesive layer more susceptible to deterioration due to the effects of acid or alkali, making the pressure-sensitive adhesive layer more likely to slip or peel off. However, if high adhesive strength is imparted to the adhesive layer by, for example, adding a tackifying resin in order to prevent slippage or peeling, the adhesive layer is likely to become more adhesive, making it difficult to remove it from the surface plate without leaving any adhesive residue. Therefore, there is a demand for a double-sided pressure-sensitive adhesive sheet for fixing abrasive cloths that has both high levels of resistance to slippage or peeling when exposed to strong shear forces at high temperatures or to strongly acidic or strongly alkaline slurry solutions, and high removability that allows the sheet to be removed from the surface plate without leaving any adhesive residue.

[0006] An object of the present invention is to provide a pressure-sensitive adhesive sheet that has excellent shear strength and slurry resistance at high temperatures and that can be removed without leaving any adhesive residue, and a polishing pad with the pressure-sensitive adhesive sheet that includes the pressure-sensitive adhesive sheet. [Means for solving the problem]

[0007] The present invention is a pressure-sensitive adhesive sheet having at least one pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer comprises a base polymer, a tackifier resin (T1) having a hydroxyl value of less than 20 mgKOH / g, and a tackifier resin (T2) having a hydroxyl value of 20 mgKOH / g or more and 120 mgKOH / g or less, wherein the base polymer is a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, and the pressure-sensitive adhesive layer contains 10 parts by weight or more and 60 parts by weight or less of the tackifier resin (T1) per 100 parts by weight of the base polymer, and 1 part by weight or more and 40 parts by weight or less of the tackifier resin (T2) per 100 parts by weight of the base polymer. The present invention will be described in detail below.

[0008] The present inventors have investigated a pressure-sensitive adhesive layer containing a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymer, which can be used as a bonding surface for a polishing machine platen. The present inventors have further investigated tackifier resins to be added to such pressure-sensitive adhesive layers. As a result, the present inventors have found that by using, among tackifier resins, a tackifier resin (T1) having a relatively low hydroxyl value within a specific range and a tackifier resin (T2) having a relatively high hydroxyl value within a specific range, each in specific amounts, it is possible to improve both shear strength and slurry resistance at high temperatures, as well as removability without adhesive residue. This has led to the completion of the present invention.

[0009] The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having at least one pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer contains a base polymer, which is a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound (hereinafter also simply referred to as a "block copolymer"). The pressure-sensitive adhesive layer contains the block copolymer, which provides the pressure-sensitive adhesive layer with sufficiently high shear strength at high temperatures. Furthermore, since the block copolymer has a relatively low polarity, the pressure-sensitive adhesive layer contains the block copolymer, which makes it more difficult for a slurry liquid to penetrate into the pressure-sensitive adhesive layer than, for example, when an acrylic polymer is contained, thereby improving the pressure-sensitive adhesive layer's resistance to slurry at high temperatures. Furthermore, the pressure-sensitive adhesive layer contains the block copolymer, which reduces the adhesion of the pressure-sensitive adhesive layer compared to, for example, when a natural rubber is contained, thereby improving removability.

[0010] The monovinyl-substituted aromatic compound 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 monovinyl-substituted aromatic compounds may be used alone or in combination of two or more.

[0011] The conjugated diene compound 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 compounds may be used alone or in combination of two or more.

[0012] The block copolymer is not particularly limited as long as it has rubber elasticity at room temperature and has a hard segment portion made of the monovinyl-substituted aromatic compound and a soft segment portion made of the conjugated diene compound. The block copolymer also includes a hydrogenated product of a block copolymer of the monovinyl-substituted aromatic compound and the conjugated diene compound. Specific examples of the block copolymer include styrene-isoprene-styrene (SIS) block copolymer, styrene-butadiene-styrene (SBS) block copolymer, styrene-butadiene-butylene-styrene (SBBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-ethylene-propylene-styrene (SEPS) block copolymer, hydrogenated styrene-butylene rubber (HSBR), and styrene-isobutylene-styrene (SIBS) block copolymer. Among these, SIS block copolymers and SEBS block copolymers are preferred, as they further suppress the adhesion of the pressure-sensitive adhesive layer and improve removability, and SIS block copolymers are more preferred. Furthermore, the block copolymer is preferably a hydrogenated product, as they improve the shear strength of the pressure-sensitive adhesive layer at high temperatures. These block copolymers may be used alone, or two or more types may be used in combination.

[0013] The block copolymer may contain a diblock copolymer of the hard segment portion and the soft segment portion, in addition to a triblock copolymer of the hard segment portion and the soft segment portion. The content of the diblock copolymer in the block copolymer is not particularly limited, but a preferred lower limit is 10% by weight and a preferred upper limit is 40% by weight. If the content of the diblock copolymer is 10% by weight or more, the adhesive strength of the pressure-sensitive adhesive layer is further suppressed and removability is further improved. If the content of the diblock copolymer is 40% by weight or less, the pressure-sensitive adhesive layer can be prevented from becoming too hard, the adhesive strength of the pressure-sensitive adhesive layer can be sufficient, and the shear strength and slurry resistance of the pressure-sensitive adhesive layer at high temperatures can be further sufficiently improved. A more preferred lower limit of the content of the diblock copolymer is 20% by weight and a more preferred upper limit is 35% by weight.

[0014] The content of the hard segment moiety in the block copolymer (also referred to as the "styrene content" when the monovinyl-substituted aromatic compound is styrene) is not particularly limited, but a preferred lower limit is 5 wt% and a preferred upper limit is 25 wt%. If the hard segment moiety content is 5 wt% or more, the adhesive strength of the pressure-sensitive adhesive layer is further suppressed and removability is further improved. If the hard segment moiety content is 25 wt% or less, the pressure-sensitive adhesive layer can be prevented from becoming too hard, the adhesive strength of the pressure-sensitive adhesive layer can be sufficient, and the shear strength and slurry resistance of the pressure-sensitive adhesive layer at high temperatures can be further improved. A more preferred lower limit of the hard segment moiety content is 10 wt% and a more preferred upper limit is 20 wt%.

[0015] 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 layer is increased, and the shear strength at high temperatures is further improved. 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.).

[0016] The pressure-sensitive adhesive layer contains a tackifier resin (T1) having a hydroxyl value of less than 20 mgKOH / g and a tackifier resin (T2) having a hydroxyl value of 20 mgKOH / g or more and 120 mgKOH / g or less. The pressure-sensitive adhesive layer contains a tackifier resin, which provides the pressure-sensitive adhesive layer with sufficiently high shear strength at high temperatures. Furthermore, the pressure-sensitive adhesive layer contains, among other tackifier resins, a tackifier resin (T1) having a relatively low hydroxyl value within the above range and a tackifier resin (T2) having a relatively high hydroxyl value within the above range, which improves the pressure-sensitive adhesive layer's resistance to slurry at high temperatures, suppresses adhesion buildup, and improves removability. This is presumably due to the following reasons.

[0017] Typically, when a slurry liquid penetrates into the pressure-sensitive adhesive layer at high temperatures (around 60°C), the ionic substances contained in the slurry liquid undergo molecular migration to the interface between the pressure-sensitive adhesive layer and the adherend, and the ionic substances are adsorbed onto the surface of the adherend, causing the pressure-sensitive adhesive layer to shift or peel off. In the pressure-sensitive adhesive sheet of the present invention, since the pressure-sensitive adhesive layer contains the tackifier resin (T2) with a relatively high polarity, it is believed that the tackifier resin (T2) undergoes molecular migration to the interface between the pressure-sensitive adhesive layer and the adherend at high temperatures (around 60°C), forming a layer containing a large amount of tackifier resin at the interface. This layer is believed to prevent ionic substances contained in the slurry liquid from adsorbing to the surface of the adherend, improving the slurry resistance of the pressure-sensitive adhesive layer at high temperatures. Furthermore, when the tackifier resin is the only resin, the pressure-sensitive adhesive layer has improved slurry resistance at high temperatures, but the layer containing a large amount of the tackifier resin has too high a polarity, which tends to increase adhesion and reduce removability. In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer contains the tackifier resin (T1) in addition to the tackifier resin (T2), so that the polarity of the layer containing a large amount of the tackifier resin can be adjusted to an appropriate range, thereby improving the slurry resistance of the pressure-sensitive adhesive layer at high temperatures, suppressing increased adhesion, and improving removability.

[0018] The hydroxyl value of the tackifier resin (T1) is not particularly limited as long as it is less than 20 mgKOH / g, but is preferably less than 5 mgKOH / g. The lower limit of the hydroxyl value of the tackifier resin (T1) is not particularly limited, and may be 0 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.

[0019] The softening point of the tackifier resin (T1) is not particularly limited, but a preferred lower limit is 110°C. If the softening point of the tackifier resin (T1) is 110°C or higher, the heat resistance of the pressure-sensitive adhesive layer is increased, and the shear strength at high temperatures is further improved. A more preferred lower limit of the softening point of the tackifier resin (T1) is 115°C. The upper limit of the softening point of the tackifier resin (T1) is not particularly limited, but a substantial upper limit is about 160°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.

[0020] Specific examples of the tackifier resin (T1) include petroleum resins, terpene resins, styrene resins, and hydrogenated versions thereof. These tackifier resins (T1) may be used alone or in combination of two or more. Among these, terpene resins are preferred. More specific examples of the petroleum resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, C5 / C9 copolymer petroleum resins, and alicyclic petroleum resins. More specific examples of the terpene resins include α-pinene polymers, β-pinene polymers, dipentene polymers, and modified terpene resins, which are modified versions of these polymers. Examples of modifications of the modified terpene resins include phenol-modification, styrene-modification, hydrogenation-modification, and hydrocarbon-modification. More specific examples of the modified terpene resins include styrene-modified terpene resins and hydrogenated terpene resins. More specific examples of the styrene resins include styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene-styrene copolymers, styrene-aliphatic polymers, α-methylstyrene-styrene-aliphatic copolymers, and phenol-modified styrene resins.

[0021] The tackifier resin (T1) may be two or more types of tackifier resins, and in this case, the tackifier resin (T1) preferably contains the styrene resin. When the tackifier resin (T1) contains the styrene resin, the shear strength of the pressure-sensitive adhesive layer at high temperatures is further improved. The content of the styrene resin in the pressure-sensitive adhesive layer relative to 100 parts by weight of the base polymer is not particularly limited, but a preferred lower limit is 3 parts by weight, a preferred upper limit is 40 parts by weight, a more preferred lower limit is 5 parts by weight, a more preferred upper limit is 30 parts by weight, an even more preferred lower limit is 10 parts by weight, and an even more preferred upper limit is 20 parts by weight.

[0022] In the PSA layer, the content of the tackifier resin (T1) relative to 100 parts by weight of the base polymer is at least 10 parts by weight, and at most 60 parts by weight. When the content of the tackifier resin (T1) is at least 10 parts by weight, the PSA layer is prevented from increasing in adhesion when used in combination with the tackifier resin (T2), improving removability while also achieving a sufficiently high shear strength at high temperatures. When the content of the tackifier resin (T1) is at most 60 parts by weight, the PSA layer is prevented from increasing in adhesion and improving removability. The preferred lower limit of the tackifier resin (T1) content is 20 parts by weight, and the preferred upper limit is 50 parts by weight, with a more preferred lower limit being 30 parts by weight and a more preferred upper limit being 40 parts by weight.

[0023] The hydroxyl value of the tackifier resin (T2) is not particularly limited as long as it is 20 mgKOH / g or more and 120 mgKOH / g or less, but is more preferably 30 mgKOH / g or more and 80 mgKOH / g or less. When a tackifier resin (T3) having a hydroxyl value exceeding 120 mgKOH / g is used instead of the tackifier resin (T2), the slurry resistance of the pressure-sensitive adhesive layer at high temperatures is improved, but adhesion tends to increase and removability is reduced.

[0024] The softening point of the tackifier resin (T2) is not particularly limited, but a preferred lower limit is 120°C. If the softening point of the tackifier resin (T2) is 120°C or higher, the heat resistance of the pressure-sensitive adhesive layer is increased, and the shear strength at high temperatures is further improved. A more preferred lower limit of the softening point of the tackifier resin (T2) is 140°C. The upper limit of the softening point of the tackifier resin (T2) is not particularly limited, but a practical upper limit is about 180°C.

[0025] Specific examples of the tackifier resin (T2) include coumarone resins, terpene phenol resins, rosin resins, rosin derivative resins, etc. These tackifier resins (T2) may be used alone or in combination of two or more. The coumarone resin may be, for example, a resin containing coumarone and indene as monomer components constituting the resin skeleton (main chain). Examples of monomer components that can constitute the resin skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0026] The terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue. The terpene phenol resin is a concept that encompasses both a copolymer of a terpene and a phenol compound (a terpene-phenol copolymer resin) and a phenol-modified terpene resin obtained by modifying a terpene homopolymer or copolymer (a terpene resin, typically an unmodified terpene resin) with phenol. The terpene constituting the terpene phenol resin is not particularly limited, but is preferably a monoterpene such as α-pinene, β-pinene, limonene, etc. Limonene includes d-, l- and d / l-forms (dipentene).

[0027] 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.

[0028] 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.

[0029] The tackifier resin (T2) preferably contains two or more types of tackifier resins. In particular, the tackifier resin (T2) more preferably contains a coumarone resin. The coumarone resin interacts with the hard segment moieties in the base polymer, stabilizing the physical crosslinks between the hard segment moieties. Therefore, when the tackifier resin (T2) contains the coumarone resin, the heat resistance and bulk strength of the PSA layer are enhanced, and the shear strength at high temperatures is further improved. The content of the coumarone resin in the adhesive layer relative to 100 parts by weight of the base polymer is not particularly limited, but a preferred lower limit is 5 parts by weight, a preferred upper limit is 30 parts by weight, a more preferred lower limit is 10 parts by weight, a more preferred upper limit is 20 parts by weight, an even more preferred lower limit is 12.5 parts by weight, and an even more preferred upper limit is 17.5 parts by weight.

[0030] It is also more preferable that the tackifier resin (T2) contains at least one tackifier resin selected from the group consisting of terpene phenol resins, rosin resins, and rosin derivative resins (hereinafter also referred to as "terpene phenol resins, etc."). When the tackifier resin (T2) contains the terpene phenol resins, etc., the slurry resistance of the pressure-sensitive adhesive layer at high temperatures is further improved. Of the terpene phenol resins, etc., terpene phenol resins are more preferable because they further improve the slurry resistance of the pressure-sensitive adhesive layer at high temperatures. The content of the terpene phenol resin etc. per 100 parts by weight of the base polymer in the adhesive layer is not particularly limited, but a preferred lower limit is 1 part by weight, a preferred upper limit is 15 parts by weight, a more preferred lower limit is 5 parts by weight, and a more preferred upper limit is 10 parts by weight.

[0031] It is particularly preferable that the tackifier resin (T2) contains both the coumarone resin and the terpene phenol resin, etc., because this can improve both the shear strength at high temperatures and the slurry resistance at high temperatures while maintaining a balance between them.

[0032] In the PSA layer, the lower limit of the content of the tackifier resin (T2) relative to 100 parts by weight of the base polymer is 1 part by weight, and the upper limit is 40 parts by weight. If the content of the tackifier resin (T2) is 1 part by weight or more, the PSA layer will have sufficiently high shear strength at high temperatures and improved slurry resistance at high temperatures. If the content of the tackifier resin (T2) is 40 parts by weight or less, the PSA layer will be prevented from increasing in adhesion and will have improved removability. The lower limit of the content of the tackifier resin (T2) is preferably 3 parts by weight, and the upper limit is preferably 35 parts by weight, more preferably 5 parts by weight, and more preferably 30 parts by weight.

[0033] The pressure-sensitive adhesive layer is not particularly limited by the total content of the tackifier resin (T1) and the tackifier resin (T2) relative to 100 parts by weight of the base polymer, but a preferred lower limit is 20 parts by weight and a preferred upper limit is 80 parts by weight. If the total content of the tackifier resin (T1) and the tackifier resin (T2) is 80 parts by weight or less, the adhesive strength of the pressure-sensitive adhesive layer is suppressed and removability is further improved. A more preferred lower limit of the total content of the tackifier resin (T1) and the tackifier resin (T2) is 40 parts by weight and a more preferred upper limit is 60 parts by weight.

[0034] The pressure-sensitive adhesive layer may contain a tackifier resin (T3) having a hydroxyl value of more than 120 mgKOH / g. The content of the tackifier resin (T3) relative to 100 parts by weight of the base polymer is not particularly limited, but a preferred upper limit is 5 parts by weight. If the content of the tackifier resin (T3) is 5 parts by weight or less, the adhesive strength of the pressure-sensitive adhesive layer is suppressed and removability is improved. A more preferred upper limit of the content of the tackifier resin (T3) is 2.5 parts by weight, and an even more preferred upper limit is 0.1 parts by weight. However, it is particularly preferable that the pressure-sensitive adhesive layer does not contain the tackifier resin (T3), that is, the content of the tackifier resin (T3) is 0 part by weight.

[0035] The pressure-sensitive adhesive layer may further contain additives such as a filler, an antioxidant, an antioxidant, and a colorant.

[0036] The thickness of the pressure-sensitive adhesive layer is not particularly limited, with a preferred lower limit of 20 μm and a preferred upper limit of 100 μm. If the thickness of the pressure-sensitive adhesive layer is within the above range, the adhesive strength of the pressure-sensitive adhesive layer will be sufficient, and the shear strength and slurry resistance of the pressure-sensitive adhesive layer at high temperatures will be sufficiently improved. The more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 40 μm, and the more preferred upper limit is 85 μm.

[0037] The pressure-sensitive adhesive sheet of the present invention further comprises a substrate, and preferably comprises the above-mentioned pressure-sensitive adhesive layer on one side of the substrate, and more preferably comprises another pressure-sensitive adhesive layer on the other side of the substrate. In such a case, it is preferable that the above-mentioned pressure-sensitive adhesive layer serves as a surface to be bonded to the platen of a polishing machine, and that the other pressure-sensitive adhesive layer serves as a surface to be bonded to a polishing cloth, abrasive, polishing pad, etc. The substrate is not particularly limited, but a resin film is preferred. The resin film is not particularly limited, and examples thereof include polyester resin film, polypropylene resin film, etc. Among these, polyester resin film is preferred because it is flat, has little thickness variation, and has high strength, and among polyester resin films, polyethylene terephthalate film is more preferred. The substrate may contain additives such as fillers, ultraviolet absorbers, light stabilizers, and antistatic agents within limits that do not impair the physical properties of the substrate.

[0038] The thickness of the substrate is not particularly limited, but a preferred lower limit is 12 μm and a preferred upper limit is 300 μm. If the thickness of the substrate is 12 μm or more, the substrate can be prevented from breaking when the pressure-sensitive adhesive sheet is re-peeled, thereby further improving the re-peeling property of the pressure-sensitive adhesive sheet. If the thickness of the substrate is 300 μm or less, it is easy to adjust the pressure when pressing the pressure-sensitive adhesive sheet onto the adherend, and sufficient adhesive strength can be obtained. A more preferred lower limit of the thickness of the substrate is 20 μm and a more preferred upper limit is 250 μm.

[0039] The another adhesive layer may have the same composition, thickness, etc. as the adhesive layer described above, i.e., the adhesive layer that becomes the surface to be bonded to the platen of the polishing machine, or may have a different composition, thickness, etc. When the adhesive layer has a composition different from that of the adhesive layer described above, it is preferable that the other adhesive layer contains an adhesive used in ordinary adhesive sheets, such as an acrylic resin-based adhesive, a rubber-based adhesive, a silicone-based adhesive, or a urethane-based adhesive.

[0040] The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited. For example, when the pressure-sensitive adhesive sheet has the above-mentioned substrate and pressure-sensitive adhesive layers of the same composition and thickness on both sides of the substrate, the following method can be mentioned. First, a pressure-sensitive adhesive solution containing the block copolymer, the tackifier resin (T1), and the tackifier resin (T2) 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. A total of two laminate sheets are produced in the same manner. Next, the pressure-sensitive adhesive layers of the two laminate sheets are transferred to a substrate and laminated together to obtain a pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the substrate.

[0041] FIG. 1 shows a cross-sectional view schematically illustrating one embodiment of the pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive sheet 1 shown in FIG. 1 has a pressure-sensitive adhesive layer 3a on one surface of a substrate 2. FIG. 2 shows a cross-sectional view schematically illustrating another embodiment of the pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive sheet 1 shown in FIG. 2 has a pressure-sensitive adhesive layer 3a on one surface of a substrate 2, and another pressure-sensitive adhesive layer 3b on the other surface. The pressure-sensitive adhesive layers 3a and 3b may have the same composition, thickness, etc., or may have different compositions, thicknesses, etc. Although the pressure-sensitive adhesive sheets shown in FIGS. 1 and 2 each have a substrate, the pressure-sensitive adhesive sheet of the present invention is not limited to this form and may not have a substrate.

[0042] The uses of the pressure-sensitive adhesive sheet of the present invention are not particularly limited, but because it has excellent shear strength and slurry resistance at high temperatures and excellent removability that allows it to be removably removed without leaving any adhesive residue, it is preferably used to fix a polishing cloth, abrasive, polishing pad, etc. to the platen of a polishing machine in the process of polishing semiconductor wafers, liquid crystal glass substrates, etc. to a predetermined thickness. Examples of such polishing processes include chemical-mechanical-polishing (CMP) processes. A polishing pad with adhesive sheet, in which the adhesive sheet of the present invention and a polishing pad are laminated together, also constitutes one aspect of the present invention.

[0043] The polishing pad is not particularly limited, and may be any polishing pad made of an absorbent material, nonwoven fabric, polyurethane, or the like, which is fixed to the platen of a polishing machine, and also includes polishing cloth, abrasive material, and the like. The pressure-sensitive adhesive sheet of the present invention may have only one layer of the polishing pad, or may have multiple layers of the polishing pad. The polishing pad with adhesive sheet of the present invention is not particularly limited as long as it is made up of the adhesive sheet of the present invention and the above-mentioned polishing pad laminated together, and may further have another adhesive sheet, etc. in addition to the adhesive sheet of the present invention and the above-mentioned polishing pad.

[0044] Figure 3 is a cross-sectional view showing a schematic diagram of one embodiment of the polishing pad with adhesive sheet of the present invention attached to a platen. The polishing pad with adhesive sheet 5 shown in Figure 3 is formed by laminating an adhesive sheet 1 and a polishing pad 4, with the adhesive sheet 1 side fixed to the platen 6 of a polishing machine. The adhesive sheet 1 has an adhesive layer 3a on one side of the substrate 2 and another adhesive layer 3b on the other side. The adhesive layers 3a and 3b may have the same composition, thickness, etc., or may have different compositions, thicknesses, etc., as long as at least the adhesive layer 3b, which is the surface attached to the platen 6, is an adhesive layer as described above. [Effects of the Invention]

[0045] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that has excellent shear strength and slurry resistance at high temperatures and excellent removability, which allows it to be removably removed without leaving any adhesive residue. Furthermore, according to the present invention, it is possible to provide a polishing pad with a pressure-sensitive adhesive sheet that has the pressure-sensitive adhesive sheet. [Brief explanation of the drawings]

[0046] [Figure 1] 1 is a cross-sectional view schematically illustrating one embodiment of a pressure-sensitive adhesive sheet of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing another embodiment of the pressure-sensitive adhesive sheet of the present invention. [Figure 3] 1 is a cross-sectional view schematically showing an embodiment of the polishing pad with adhesive sheet of the present invention attached to a surface plate. DETAILED DESCRIPTION OF THE INVENTION

[0047] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0048] The block copolymers used were SIS (styrene-isoprene-styrene block copolymers) 1 to 3 manufactured by Zeon Corporation, SEBS (styrene-ethylenebutylene-styrene copolymer) 1 manufactured by JSR Corporation, and natural rubber, as shown in Table 1. Crepe Rubber No. 1 manufactured by Toyota Tsusho Corporation was used as the natural rubber.

[0049] [Table 1]

[0050] The tackifying resins used were tackifying resin (T1), tackifying resin (T2), and tackifying resin (T3) shown in Table 2 below. The C5 petroleum resin M-100 was manufactured by Arakawa Chemical Industries, Ltd., the terpene resins PX1000 and PX1150 were manufactured by Yasuhara Chemical Co., Ltd., and the styrene resin FTR2120 was manufactured by Mitsui Chemicals, Inc. The coumarone resin V-120 was manufactured by Nitto Chemical Co., Ltd., the terpene phenol resins T-130, T-160, S-145, and G-150 were manufactured by Yasuhara Chemical Co., Ltd., and the rosin ester resin A-125 was manufactured by Arakawa Chemical Industries, Ltd.

[0051] [Table 2]

[0052] ( Reference example 1) As shown in Table 3 below, a pressure-sensitive adhesive solution was prepared by adding 10 parts by weight of tackifier resin (T1) and 15 parts by weight of tackifier resin (T2) to 100 parts by weight of the block copolymer and stirring. 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 50 μm, and then dried at 110°C for 5 minutes to prepare a laminate sheet having a pressure-sensitive adhesive layer on the release-treated surface of the polyethylene terephthalate film. A total of two laminate sheets were prepared in the same manner.

[0053] A polyethylene terephthalate film was prepared as a substrate. One laminate sheet was laminated on one side of the substrate with its pressure-sensitive adhesive layer facing the substrate, and the pressure-sensitive adhesive layer was transferred to and integrated with the substrate, and the other laminate sheet was laminated on the other side of the substrate with its pressure-sensitive adhesive layer facing the substrate, and the pressure-sensitive adhesive layer was transferred to and integrated with the substrate, thereby obtaining a double-sided pressure-sensitive adhesive sheet having 50 μm-thick pressure-sensitive adhesive layers on both sides of the substrate.

[0054] ( Reference example 2 ~15, Example 16 ~21, Comparative Examples 1~5) Except for the types and amounts of the block copolymer, tackifier resin (T1), tackifier resin (T2) and tackifier resin (T3) being changed as shown in Table 3 or 4, Reference example In the same manner as in 1, a double-sided PSA sheet was obtained.

[0055] <Evaluation> Reference example, The double-sided PSA sheets obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Tables 3 and 4.

[0056] (1) Evaluation of removability A test specimen was prepared by cutting a double-sided PSA sheet into a 25 mm x 75 mm piece, peeling off the release film on one side, and attaching it to a 23 μm thick polyethylene terephthalate (PET) film as a backing. In a 23°C environment, the release film covering the other adhesive side of the test specimen was peeled off, and the test specimen was pressed onto the surface of a stainless steel (SUS304) plate using a 2 kg roller, moving back and forth once. This was left in the same environment for 20 minutes to obtain a test sample before heat treatment. The test sample before heat treatment was left in a 60°C atmosphere for 7 days to obtain a test sample after heat treatment. The resulting test samples before and after heat treatment were evaluated for adhesive residue and measured for adhesion growth rate using the following methods.

[0057] (Evaluation of adhesive residue) After the heat treatment, the double-sided pressure-sensitive adhesive sheet was peeled off from the test sample, and the stainless steel plate was inspected for adhesive residue.

[0058] (Measurement of adhesion growth rate) The double-sided PSA sheet test sample was measured for 180° peel strength before and after heat treatment in an atmosphere of 23°C by peeling it in a 180° direction at a rate of 300 mm / min using a tensile tester in accordance with JIS Z 0237. The adhesion enhancement of the double-sided PSA sheet was calculated from the 180° peel strength before and after heat treatment using the following formula. Adhesion enhancement rate (%) = {(180° peel strength after heat treatment) / (180° peel strength before heat treatment) - 1} x 100

[0059] The adhesion enhancement rate was calculated only for cases where no adhesive residue was found in the evaluation of adhesive residue. In the evaluation of adhesive residue, cases where there was no adhesive residue and the adhesion increase rate was less than 5% were marked with a ◎; cases where there was no adhesive residue and the adhesion increase rate was 5% or more were marked with a ○; and cases where there was adhesive residue in the evaluation of adhesive residue were marked with an ×.

[0060] (2) Evaluation of slurry resistance A test piece was prepared by cutting a double-sided PSA sheet into a 25 mm × 75 mm piece, peeling off the release film from one side, and attaching it to a 23 μm-thick polyethylene terephthalate (PET) film as a backing. In an environment of 23°C, the release film covering the other adhesive side of the test piece was peeled off, and the test piece was pressed onto the surface of a stainless steel (SUS304) plate by rolling a 2 kg roller back and forth once to obtain a test sample before immersion in the chemical solution. An alkaline chemical solution was prepared by diluting Semi-Sperse 25 (manufactured by Cabot Microelectronics) 1:1 with ion-exchanged water. The test sample before immersion in the chemical solution was immersed in the alkaline chemical solution for 7 days in an atmosphere at 60°C. The test sample was then removed from the alkaline chemical solution, washed with ion-exchanged water, and dried at 23°C for 1 hour to obtain the test sample after immersion in the chemical solution. The obtained test samples before and after immersion in the chemical solution were evaluated for peeling after immersion in the chemical solution and the rate of change in 180° peel strength was measured by the following methods.

[0061] (Evaluation of peeling after immersion in chemical solution) After immersion in the chemical solution, the test samples were observed for peeling of the double-sided PSA sheet from the stainless steel plate. If there was no peeling of the double-sided PSA sheet, it was marked "none," if there was only slight peeling at the edge of the double-sided PSA sheet, it was marked "edge," and if there was peeling over the entire surface, it was marked "total peeling."

[0062] (Measurement of 180° peel strength change rate) In an atmosphere of 23°C, the double-sided PSA sheet of the test sample was peeled in a 180° direction at a rate of 300 mm / min using a tensile tester to measure the 180° peel strength before and after immersion in the chemical solution, in accordance with JIS Z 0237. The rate of change (%) in the 180° peel strength of the PSA layer before and after immersion in the chemical solution was calculated using the following formula. Change rate (%) = {(180° peel strength after immersion in alkaline chemical solution) / (180° peel strength before immersion in alkaline chemical solution) - 1} x 100

[0063] The 180° peel strength change rate was calculated only for cases where there was no peeling of the double-sided PSA sheet or only slight peeling at the edges in the peel evaluation after immersion in the chemical solution (when judged as "none" or "edge"). A case in which peeling after immersion in the chemical solution was evaluated as "none" and the rate of change in 180° peel strength was reduced by less than 20% was evaluated as ◎; a case in which peeling after immersion in the chemical solution was evaluated as "none" but the 180° peel strength was reduced by 20% or more, or peeling after immersion in the chemical solution was evaluated as "edges", was evaluated as ○; and a case in which peeling after immersion in the chemical solution was evaluated as "complete peeling" was evaluated as ×.

[0064] (3) Shear strength measurement The double-sided PSA sheet was cut into a 15 mm x 15 mm piece, the release film on one side was peeled off, and the sheet was pressed against the surface of a stainless steel (SUS304) plate using a 2 kg roller, with one stroke back and forth, to prepare a test piece. In a 23°C environment, the release film covering the other adhesive side of the test piece was peeled off, and the test piece was thermocompressed to the surface of a stainless steel (SUS304) plate at 80°C and a pressure of 3 kg / cm2 for 10 seconds to obtain a test sample. In a 60°C atmosphere, the double-sided PSA sheet of the test sample was peeled off in the direction of the shear stress at a rate of 10 mm / min, and the shear strength was measured. If the shear strength was 160 [N / 15 x 15 mm] or more, it was marked with a ◎; if it was less than 160 [N / 15 x 15 mm] and 120 [N / 15 x 15 mm] or more, it was marked with a ○; if it was less than 120 [N / 15 x 15 mm] and 80 [N / 15 x 15 mm] or more, it was marked with a △; if it was less than 80 [N / 15 x 15 mm], it was marked with an ×.

[0065] [Table 3]

[0066] In addition, Reference example 6 and Reference example In the evaluation of removability, No. 14 was judged to be good (no adhesive residue was left behind and the adhesion increase rate was 5% or more), but the adhesion increase rate was over 20%.

[0067] [Table 4] [Industrial Applicability]

[0068] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that has excellent shear strength and slurry resistance at high temperatures and excellent removability, which allows it to be removably removed without leaving any adhesive residue. Furthermore, according to the present invention, it is possible to provide a polishing pad with a pressure-sensitive adhesive sheet that has the pressure-sensitive adhesive sheet. [Explanation of symbols]

[0069] 1 adhesive sheet 2 Base material 3a,3b Adhesive layer 4 polishing pads 5 Polishing pads with adhesive sheets 6 Surface plate (polishing machine)

Claims

1. A pressure-sensitive adhesive sheet having at least one pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer contains a base polymer, a tackifier resin (T1) having a hydroxyl value of less than 5 mgKOH / g, and a tackifier resin (T2) having a hydroxyl value of 20 mgKOH / g or more and 120 mgKOH / g or less, the base polymer is a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, The tackifier resin (T2) contains a coumarone resin and a terpene phenol resin, In the pressure-sensitive adhesive layer, the content of the tackifier resin (T1) relative to 100 parts by weight of the base polymer is 10 parts by weight or more and 60 parts by weight or less, the content of the tackifier resin (T2) relative to 100 parts by weight of the base polymer is 6 parts by weight or more and 40 parts by weight or less, and the content of the coumarone resin relative to 100 parts by weight of the base polymer is 5 parts by weight or more and 30 parts by weight or less. A pressure-sensitive adhesive sheet characterized by:

2. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the tackifier resin (T1) has a softening point of 110° C. or higher.

3. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the tackifier resin (T2) has a softening point of 120° C. or higher.

4. 4. The pressure-sensitive adhesive sheet according to claim 1, wherein the tackifier resin (T2) is two or more types of tackifier resins.

5. 5. The pressure-sensitive adhesive sheet according to claim 1, wherein the tackifier resin (T1) contains a terpene resin.

6. 6. The pressure-sensitive adhesive sheet according to claim 1, wherein the tackifier resin (T1) contains a styrene resin.

7. 7. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer contains 5 parts by weight or less of a tackifier resin (T3) having a hydroxyl value exceeding 120 mgKOH / g per 100 parts by weight of the base polymer.

8. 8. The pressure-sensitive adhesive sheet according to claim 1, wherein the block copolymer has a diblock copolymer content of 10% by weight or more and 40% by weight or less.

9. 9. The pressure-sensitive adhesive sheet according to claim 1, wherein the block copolymer is a hydrogenated product.

10. 10. The pressure-sensitive adhesive sheet according to claim 1, further comprising a substrate, the pressure-sensitive adhesive layer being provided on one surface of the substrate, and another pressure-sensitive adhesive layer being provided on the other surface of the substrate.

11. 11. A polishing pad with adhesive sheet, comprising the adhesive sheet according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 laminated on a polishing pad.

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