Adhesive tape

Abstract

To provide an adhesive tape that is suitably used for fixing an abrasive pad to a surface plate of a polishing machine and can continue polishing for a long time.SOLUTION: An adhesive tape contains a substrate and an adhesive layer. The adhesion to an abrasive pad is 50 N / 25 mm or more. In a creep resistance test, the amount of displacement 3 minutes after loading of 50 gf at 60°C in a shear direction is 5 μm or more and 50 μm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive tape.

Background Art

[0002] In a process of polishing a semiconductor wafer, a glass substrate for liquid crystal, etc. to a predetermined thickness (for example, a Chemical-Mechanical-Polishing (CMP) process), polishing is performed using a polishing pad (polishing cloth) fixed to a surface plate of a polishing machine. In order to fix the polishing pad to the surface plate of the polishing machine, usually, a double-sided adhesive tape is used. This double-sided adhesive tape for fixing the polishing pad is required to have sufficient adhesive strength so that the polishing pad does not peel off during polishing, and to be able to be peeled off again from the surface plate without leaving any adhesive residue when replacing the used polishing pad.

[0003] As a double-sided adhesive tape for fixing a polishing pad, for example, in Patent Documents 1 and 2, a specific thermally active adhesive is provided on one side of a plastic film support, and a re-peelable adhesive layer is provided on the other surface of the plastic film support, and a double-sided adhesive tape for fixing a polishing material in which the thermally active adhesive layer serves as a bonding surface with the polishing material is described.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The performance requirements for double-sided adhesive tapes used to fix polishing pads are becoming more sophisticated year by year. For example, there is a demand to maximize the time that polishing can be continued with a single polishing pad, or to increase the number of workpieces that can be polished with a single polishing pad (improvement of the "polishing rate"). In particular, in recent years, in order to increase the polishing speed, the amount of strongly acidic or strongly alkaline slurry liquid used during polishing has been increased, and softer polishing pads than before have been used. Polyurethane foam, for example, is being considered as such a polishing pad.

[0006] The present invention aims to provide an adhesive tape that is suitably used for fixing a polishing pad to the base plate of a polishing machine and that allows polishing to be continued for a long period of time. [Means for solving the problem]

[0007] Disclosure 1 is an adhesive tape having a base material and an adhesive layer, wherein the adhesive force to an abrasive pad is 50 N / 25 mm or more, and in a creep resistance test, the displacement after 3 minutes when a load of 50 gf is applied in the shear direction at 60°C is 5 μm or more and 50 μm or less. Disclosure 2 is the adhesive tape of Disclosure 1, having an adhesive strength of 30 N / 25 mm or more to SUS. Disclosure 3 is an adhesive tape according to Disclosure 1 or 2, wherein the adhesive layer contains a (meth)acrylic copolymer and a crosslinking agent, and when GPC measurement is performed on the sol component of the adhesive layer by differential refractometer RI detection, the proportion of molecules with a molecular weight of 500,000 or more is 1% to 20% in the region of molecular weight of 5,000 or more. Disclosure 4 is an adhesive tape according to Disclosure 1, 2, or 3, wherein when GPC measurement is performed on the sol component of the adhesive layer using differential refractometer RI detection, the peak (Mp) of the molecular weight distribution in the region of molecular weight of 5000 or more is 100,000 or more and 400,000 or less. Disclosure 5 states that the adhesive layer has a storage modulus G'(100°C) of 3.5 × 10⁻⁶ at 100°C. 4 This is an adhesive tape according to disclosure 1, 2, 3, or 4, having a Pa of 1 or higher. Disclosure 6 is an adhesive tape according to Disclosure 1, 2, 3, 4, or 5, wherein the adhesive layer further comprises a tackifying resin, the softening temperature of the tackifying resin is 100°C or higher and 180°C or lower, and the content of the tackifying resin is 10 parts by weight or higher and 50 parts by weight or lower per 100 parts by weight of the (meth)acrylic copolymer. Disclosure 7 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, or 6, wherein the (meth)acrylic copolymer contains 8% by weight or more of constituent units derived from carboxyl group-containing monomers. Disclosure 8 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the (meth)acrylic copolymer has a content of 25% by weight or more and 70% by weight or less of structural units derived from alkyl (meth)acrylate having an alkyl group having 4 or fewer carbon atoms, and a content of 22% by weight or more and 67% by weight or less of structural units derived from alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms. Disclosure 9 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the substrate is a polyester resin film or a polypropylene resin film and has a thickness of 10 μm or more and 200 μm or less. Disclosure 10 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the adhesive layer has a thickness of 10 μm or more and 150 μm or less. Disclosure 11 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, having the adhesive layer on both sides of the substrate. Disclosure 12 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11 used to fix a polishing pad to a surface plate of a polishing machine. The present invention will be described in detail below.

[0008] With polishing pads that are softer than conventional ones, the surface has many voids and is rough, which can result in poor adhesion of the adhesive tape and insufficient adhesive strength. In addition, increasing the polishing speed can cause the temperature to rise due to frictional heat and strong shear forces to be applied, making the adhesive layer more prone to shifting or peeling. For this reason, in order to continue polishing for a long time, the adhesive tape needs to have excellent adhesion to the polishing pad and also excellent resistance to shifting or peeling when strong shear forces are applied at high temperatures (creep resistance). The inventors investigated adjusting the adhesive strength to a polishing pad and the amount of displacement when a specific load is applied in the shear direction during a creep resistance test to a specific range in an adhesive tape having a base material and an adhesive layer. The inventors found that such an adhesive tape can be suitably used to fix a polishing pad to the base plate of a polishing machine, allowing polishing to continue for a long time, and thus completed the present invention.

[0009] The adhesive tape of the present invention is an adhesive tape having a base material and an adhesive layer, wherein the adhesive force to the polishing pad is 50 N / 25 mm or more. By having an adhesive strength of 50 N / 25 mm or more to the polishing pad, the adhesive tape can have high adhesion to the polishing pad and is less likely to peel off the polishing pad. The preferred lower limit of the adhesive strength to the polishing pad is 55 N / 25 mm, and the more preferred lower limit is 60 N / 25 mm. There is no particular upper limit to the adhesive strength to the polishing pad mentioned above, but a preferred upper limit is 100 N / 25 mm.

[0010] The polishing pads mentioned above are not particularly limited and include, for example, foams such as polyurethane foam and polyolefin foam, and polishing pads made by impregnating a nonwoven fabric made of polyester fibers with polyurethane. Among these, polyurethane foam is preferred. The polishing pad described above has many voids on its surface and is rough. Its surface roughness Sa is not particularly limited, but a preferred lower limit is 1 μm, a preferred upper limit is 100 μm, a more preferred lower limit is 1.5 μm, and a more preferred upper limit is 50 μm. The contact area ratio of the polishing pad is also not particularly limited, but a preferred lower limit is 50%, a preferred upper limit is 100%, and a more preferred lower limit is 60%. Surface roughness Sa refers to a parameter obtained by extending the arithmetic mean height of a line to a surface. The contact area ratio refers to the area occupied by the resin on the outermost surface. If the polishing pad is made of foam and sliced ​​to an arbitrary thickness, the polishing pad lacks a skin layer, and voids due to foaming are present on its surface, reducing the contact area of ​​the polishing pad. Specifically, as the polishing pad mentioned above, for example, a polyurethane foam sliced ​​to a thickness of 3 mm (with PPG as the main raw material, TDI as the main isocyanate, and MOCA as the curing agent) (surface roughness Sa is 3.99 μm, contact area ratio is 77%) can be used.

[0011] When measuring the adhesive strength to the polishing pad mentioned above, the following method can be used, for example. Specifically, the adhesive tape is cut into strips 25 mm wide to form a test piece. After washing with ethanol and wiping the polishing pad dry, the test piece is placed on the polishing pad so that the adhesive layers face each other. A 2 kg rubber roller is passed back and forth once at a speed of 300 mm / min over the test piece to bond it to the polishing pad. This laminate is passed through a laminator (ACCO Brands Japan, Multi Laminator GDRH355 A3) once under the conditions of a roll temperature of 85°C, a roll gap of 2 mm, and a speed of 7.5 rpm, and pressed with a pressure of 1.2 MPa. After that, the sample is left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50% to obtain a test sample. Using a tensile testing machine, a 180° peel test of the test sample will be performed in accordance with JIS Z0237, with a peeling speed of 300 mm / min and a peeling angle of 180°.

[0012] The adhesive strength of the adhesive tape of the present invention to SUS is not particularly limited, but is preferably 30 N / 25 mm or more. By having an adhesive strength to SUS of 30 N / 25 mm or more, the adhesive tape of the present invention can have a higher adhesive strength even to an adherend having a rough surface such as a polishing pad. A more preferable lower limit of the adhesive strength to SUS is 33 N / 25 mm, and an even more preferable lower limit is 35 N / 25 mm. The upper limit of the adhesive strength to SUS is not particularly limited, but a preferable upper limit is 70 N / 25 mm.

[0013] When measuring the adhesive strength to SUS, for example, the following method can be adopted. That is, the adhesive tape is cut into a strip with a width of 25 mm to obtain a test piece. After cleaning with ethanol and wiping dry, the test piece is placed on the SUS that has been wiped dry so that the adhesive layer faces. A 2 kg rubber roller is reciprocated once at a speed of 300 mm / min on the test piece to bond the test piece and the SUS. Then, it is left standing for 24 hours at a temperature of 23°C and a relative humidity of 50% to obtain a test sample. Using a tensile tester, in accordance with JIS Z0237, a 180° peel test of the test sample is performed at a peel rate of 300 mm / min and a peel angle of 180°.

[0014] In the creep resistance test, the displacement amount of the adhesive tape of the present invention after 3 minutes from applying a load of 50 gf at 60°C is 5 μm or more and 50 μm or less. By the displacement amount being 5 μm or more, the adhesive tape of the present invention can suppress heat accumulation by releasing stress in the shear direction. As a result, it is possible to suppress the rapid increase in temperature, the evaporation of the slurry liquid, and the crashing of the electric circuit of the workpiece to be polished. By the displacement amount being 50 μm or less, the adhesive tape has improved shear strength at high temperatures, and displacement from the polishing pad is suppressed. A preferable lower limit of the displacement amount is 7 μm, a preferable upper limit is 40 μm, a more preferable lower limit is 9 μm, and a more preferable upper limit is 35 μm.

[0015] When measuring the displacement amount in the creep resistance test, for example, the following method can be adopted. Fig. 1 shows a schematic diagram illustrating the method for the creep resistance test (measurement of shear strength) of an adhesive tape. The adhesive tape is cut into pieces with a width of 10 mm and a length of 120 mm, and is lined with a PET film with a thickness of 25 μm to produce Test Specimen 1. As shown in Fig. 1, Test Specimen 1 is attached to the stainless steel measuring terminal portion 2 of the testing machine with an adhesive area of 10×10 mm. The temperature of the stainless steel measuring terminal portion 2 is set to 60°C. A mirror-finished quartz block 3 (chromium-evaporated on quartz glass) is placed on the attachment surface of Test Specimen 1, and a 50 gf weight 5 is attached to Test Specimen 1. After applying the load by the weight 5, the displacement amount (shift amount) (μm) in the direction of the arrow in the figure 3 minutes later is measured from the movement amount of the mirror-finished quartz block 3 on Test Specimen 1 by a laser interferometer 4 (manufactured by Keyence Corporation, SI-F10 or its equivalent), and this is taken as the displacement amount.

[0016] From the viewpoint of adjusting the adhesive strength to the polishing pad and the displacement amount within the above ranges, the adhesive layer contains a (meth)acrylic copolymer and a crosslinking agent, and when GPC measurement by differential refractometer RI detection is performed on the sol component of the adhesive layer, in the region where the molecular weight is 5000 or more, the ratio of the molecular weight of 500,000 or more is preferably 1% or more and 20% or less. In this specification, (meth)acrylic means acrylic or methacrylic.

[0017] Here, the "sol component" means the component obtained by removing the "gel component" from the adhesive layer. That is, the relationship "sol fraction (wt%) = 100 (wt%) - gel fraction (wt%)" holds. The "gel component" is a component with low fluidity in which the above (meth)acrylic copolymer and, if necessary, an adhesion-imparting resin are crosslinked through the above crosslinking agent to form a crosslinked structure, and the "sol component" is a component with high fluidity that is not involved in such a crosslinked structure. In GPC measurement by differential refractometer RI detection, mainly the molecular weight distribution of the (meth)acrylic copolymer contained in the sol component of the adhesive layer can be known.

[0018] The sol component of the adhesive layer described above can be obtained, for example, by immersing the adhesive layer in tetrahydrofuran (THF) at 23°C for 24 hours and removing the insoluble components by filtering through a 200-mesh wire mesh. When performing GPC measurements of the sol component of the above-mentioned adhesive layer using differential refractometer radioisotope detection, for example, the following method can be employed. That is, using a SHOKO LF-804 column, the sol component of the above-mentioned adhesive layer is analyzed by gel permeation chromatography (GPC) (Waters 2690 Separations Model) and the molecular weight distribution in terms of polystyrene is measured. Eluent: Tetrahydrofuran (THF) Flow rate: 0.4mL / min Detector: Differential refractometer RI Column temperature (measurement temperature): 40℃ Injection volume: 20μL

[0019] If the proportion of molecules with a molecular weight of 500,000 or more (proportion of high molecular weight components) is 1% or more, the cohesive force of the bulk of the adhesive layer increases, and the shear strength at high temperatures improves. If the proportion of molecules with a molecular weight of 500,000 or more is 20% or less, the fluidity of the bulk of the adhesive layer does not decrease more than necessary, so the adhesive layer can have high adhesion to the polishing pad. The preferred lower limit for the proportion of molecules with a molecular weight of 500,000 or more is 2.5%, the preferred upper limit is 15%, the more preferred lower limit is 4%, and the more preferred upper limit is 10%.

[0020] When the sol component of the adhesive layer is subjected to GPC measurement by differential refractometer RI detection, it is preferable that the peak (Mp) of the molecular weight distribution in the region of molecular weight of 5000 or more is between 100,000 and 400,000. If the peak (Mp) of the molecular weight distribution described above is 100,000 or higher, the proportion of high molecular weight components increases and the proportion of low molecular weight components decreases, thereby increasing the bulk cohesive force of the adhesive layer and improving the shear strength at high temperatures. If the peak (Mp) of the molecular weight distribution described above is 400,000 or lower, the proportion of high molecular weight components decreases and the proportion of low molecular weight components increases, thereby increasing the bulk fluidity of the adhesive layer and enabling it to have higher adhesion to the polishing pad. A more preferable lower limit for the peak (Mp) of the molecular weight distribution described above is 120,000, a more preferable upper limit is 350,000, an even more preferable lower limit is 150,000, and an even more preferable upper limit is 300,000. Note that the molecular weight distribution peak (Mp) refers to the molecular weight at the highest peak in the molecular weight distribution curve. Even if there are shoulders or more than one peak in the molecular weight distribution curve, the molecular weight distribution peak (Mp) still refers to the molecular weight at the highest peak in the molecular weight distribution curve.

[0021] The method for adjusting the proportion of molecules with a molecular weight of 500,000 or more and the peak (Mp) of the molecular weight distribution to the above range for the sol component of the adhesive layer is not particularly limited. Examples of methods for adjusting these to the above range include adjusting the composition of the (meth)acrylic copolymer, making the composition of the (meth)acrylic copolymer more uniform, reducing the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the (meth)acrylic copolymer, adjusting the polymerization reaction time and polymerization reaction temperature of the (meth)acrylic copolymer, adjusting the monomer concentration used in the polymerization of the (meth)acrylic copolymer, adjusting the type and amount of polymerization initiator and catalyst added to the (meth)acrylic copolymer, adjusting the type and amount of polymerization solvent used to polymerize the (meth)acrylic copolymer, and adding a chain transfer agent during the polymerization of the (meth)acrylic copolymer.

[0022] More specifically, a method using a (meth)acrylic copolymer obtained by living radical polymerization is preferred. Living radical polymerization is a polymerization method in which molecular chains grow without being hindered by side reactions such as termination reactions or chain transfer reactions. In living radical polymerization, the reaction proceeds without the deactivation of terminal radicals and without the generation of new radical species during the reaction. During the reaction, all molecular chains polymerize while reacting uniformly with the monomer, and the composition of all molecular chains approaches uniformity. Therefore, living radical polymerization yields copolymers with more uniform molecular weight and composition compared to free radical polymerization, and the generation of low molecular weight components can be suppressed. As a result, the composition of the (meth)acrylic copolymer tends to be more uniform, and the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) tends to be smaller. When the (meth)acrylic copolymer has constituent units derived from crosslinkable functional group-containing monomers such as carboxyl group-containing monomers, the crosslinking points in the (meth)acrylic copolymer tend to be more uniformly distributed.

[0023] Furthermore, by adjusting the amount of polymerization initiator added for the living radical polymerization, adjusting the polymerization reaction temperature, or adjusting the polymerization reaction time, the weight-average molecular weight (Mw) of the (meth)acrylic copolymer can be adjusted, and the peak (Mp) of the molecular weight distribution for the sol component of the adhesive layer can be adjusted to the above range. The amount of polymerization initiator added for the above-mentioned living radical polymerization is not particularly limited, but a preferred lower limit is 0.01 parts by weight and a preferred upper limit is 0.5 parts by weight per 100 parts by weight of the monomer mixture constituting the (meth)acrylic copolymer. A more preferred lower limit for the above amount is 0.02 parts by weight and a more preferred upper limit is 0.3 parts by weight.

[0024] Among the living radical polymerization methods described above, living radical polymerization using an organotellurium polymerization initiator differs from other living radical polymerization methods in that it does not protect monomers containing crosslinkable functional groups, such as carboxyl group-containing monomers, and can polymerize them with the same initiator to obtain copolymers with uniform molecular weight and composition. Therefore, monomers containing crosslinkable functional groups, such as carboxyl group-containing monomers, can be easily copolymerized.

[0025] The above-mentioned organotellurium polymerization initiator is not particularly limited as long as it is commonly used in living radical polymerization, and examples include organotellurium compounds and organotellide compounds. Examples of the above organic tellurium compounds include (methylteranyl-methyl)benzene, (1-methylteranyl-ethyl)benzene, (2-methylteranyl-propyl)benzene, 1-chloro-4-(methylteranyl-methyl)benzene, 1-hydroxy-4-(methylteranyl-methyl)benzene, 1-methoxy-4-(methylteranyl-methyl)benzene, 1-amino-4-(methylteranyl-methyl)benzene, 1-nitro-4-(methylteranyl-methyl)benzene, 1-cyano-4-(methylteranyl-methyl)benzene, and 1-methylcal Bonyl-4-(methylteranyl-methyl)benzene, 1-phenylcarbonyl-4-(methylteranyl-methyl)benzene, 1-methoxycarbonyl-4-(methylteranyl-methyl)benzene, 1-phenoxycarbonyl-4-(methylteranyl-methyl)benzene, 1-sulfonyl-4-(methylteranyl-methyl)benzene, 1-trifluoromethyl-4-(methylteranyl-methyl)benzene, 1-chloro-4-(1-methylteranyl-ethyl)benzene, 1-hydroxy-4-(1-methylteranyl-ethyl)benzene, 1-meth Xy-4-(1-methylteranyl-ethyl)benzene, 1-amino-4-(1-methylteranyl-ethyl)benzene, 1-nitro-4-(1-methylteranyl-ethyl)benzene, 1-cyano-4-(1-methylteranyl-ethyl)benzene, 1-methylcarbonyl-4-(1-methylteranyl-ethyl)benzene, 1-phenylcarbonyl-4-(1-methylteranyl-ethyl)benzene, 1-methoxycarbonyl-4-(1-methylteranyl-ethyl)benzene, 1-phenoxycarbonyl-4-(1-methylteranyl-ethyl)benzene 1-Sulfonyl-4-(1-methylteranyl-ethyl)benzene, 1-Trifluoromethyl-4-(1-methylteranyl-ethyl)benzene, 1-Chloro-4-(2-methylteranyl-propyl)benzene, 1-Hydroxy-4-(2-methylteranyl-propyl)benzene, 1-Methoxy-4-(2-methylteranyl-propyl)benzene, 1-Amino-4-(2-methylteranyl-propyl)benzene, 1-Nitro-4-(2-methylteranyl-propyl)benzene, 1-Cyano-4-(2-methylteranyl-propyl)benzene,1-Methylcarbonyl-4-(2-methylteranyl-propyl)benzene, 1-Phenylcarbonyl-4-(2-methylteranyl-propyl)benzene, 1-Methoxycarbonyl-4-(2-methylteranyl-propyl)benzene, 1-Phenoxycarbonyl-4-(2-methylteranyl-propyl)benzene, 1-Sulfonyl-4-(2-methylteranyl-propyl)benzene, 1-Trifluoromethyl-4-(2-methylteranyl-propyl)benzene, 2-(methylteranyl-methyl)pyridine, 2-(1- Examples include methylteranyl-ethyl)pyridine, 2-(2-methylteranyl-propyl)pyridine, methyl 2-methylteranyl-ethanoate, methyl 2-methylteranyl-propionate, methyl 2-methylteranyl-2-methylpropionate, ethyl 2-methylteranyl-ethanoate, ethyl 2-methylteranyl-propionate, ethyl 2-methylteranyl-2-methylpropionate, methylteranylacetonitrile, methylteranylpropionitrile, and methyl-2-methylteranylpropionitrile. The methylteranyl group in these organic tellurium compounds may be ethylteranyl group, n-propylteranyl group, isopropylteranyl group, n-butylteranyl group, isobutylteranyl group, t-butylteranyl group, phenylteranyl group, etc. Furthermore, these organic tellurium compounds may be used individually or in combination of two or more.

[0026] Examples of the above-mentioned organic telluride compounds include dimethyl diterlide, diethyl diterlide, di-n-propyl diterlide, diisopropyl diterlide, dicyclopropyl diterlide, di-n-butyl diterlide, di-sec-butyl diterlide, di-tert-butyl diterlide, dicyclobutyl diterlide, diphenyl diterlide, bis-(p-methoxyphenyl) diterlide, bis-(p-aminophenyl) diterlide, bis-(p-nitrophenyl) diterlide, bis-(p-cyanophenyl) diterlide, bis-(p-sulfonylphenyl) diterlide, dinaphthyl diterlide, and dipyridyl diterlide. These organic telluride compounds may be used alone or in combination of two or more. Among these, dimethyl diterlide, diethyl diterlide, di-n-propyl diterlide, di-n-butyl diterlide, and diphenyl diterlide are preferred.

[0027] Furthermore, within the limits that do not impair the effects of the present invention, an azo compound may be used as a polymerization initiator in addition to the above-mentioned organic tellurium polymerization initiator for the purpose of accelerating the polymerization rate. The above azo compounds are not particularly limited as long as they are commonly used in radical polymerization, for example, 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis(cyclohexane-1-carbonitride), 1-[(1-cyano-1- [methylethyl)azo]formamide, 4,4'-azobis(4-cyanovaleric acid), dimethyl-2,2'-azobis(2-methylpropionate), dimethyl-1,1'-azobis(1-cyclohexanecarboxylate), 2,2'-azobis{2-methyl-N-[1,1'-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl] )propionamide], 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 2,2'-azobis[2-(2-imidazoline-2-yl)propane] dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazoline-2- Examples include yl]propane dihydrochloride, 2,2'-azobis[2-(2-imidazoline-2-yl)propane], 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate, 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, and 2,2'-azobis(2,4,4-trimethylpentane). These azo compounds may be used alone or in combination of two or more.

[0028] In the above-described living radical polymerization, a dispersion stabilizer may be used. Examples of such dispersion stabilizers include polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, ethylcellulose, poly(meth)acrylic acid, poly(meth)acrylic acid ester, polyethylene glycol, and the like. Conventional methods known as living radical polymerization can be used, such as solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization. In the above-described living radical polymerization, when a polymerization solvent is used, the polymerization solvent is not particularly limited. For example, nonpolar solvents such as hexane, cyclohexane, octane, toluene, and xylene, or highly polar solvents such as water, methanol, ethanol, propanol, butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, and N,N-dimethylformamide can be used. These polymerization solvents may be used alone or in combination of two or more. Furthermore, the polymerization temperature is preferably 0 to 110°C from the viewpoint of polymerization rate.

[0029] On the other hand, in free radical polymerization, radical species are continuously generated during the reaction and added to the monomer, causing polymerization to proceed. Therefore, in free radical polymerization, molecular chains may be formed in which the growing terminal radicals are deactivated during the reaction, or molecular chains that are grown by newly generated radical species during the reaction. Therefore, compared to living radical polymerization, free radical polymerization results in a more heterogeneous copolymer composition, including copolymers with relatively low molecular weights. However, free radical polymerization may be used from the perspective of shortening reaction time and reducing costs.

[0030] While employing the above-mentioned free radical polymerization, the following methods are preferred for making the composition of the (meth)acrylic copolymer more uniform or for reducing the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the (meth)acrylic copolymer. Specifically, a method using a (meth)acrylic copolymer obtained by relatively mild polymerization conditions within the above-mentioned free radical polymerization, in which the polymerization temperature and the concentration of the monomer mixture are kept constant. Examples of polymerization methods that result in such relatively mild polymerization conditions include free radical isothermal polymerization, and free radical boiling point polymerization, in which half of the monomer mixture and a polymerization initiator are added to the reaction vessel to start polymerization, and then the remaining half of the monomer mixture is added dropwise or all at once.

[0031] The polymerization time for the above free radical polymerization is not particularly limited, but it is preferably relatively short, with a preferred lower limit of 2 hours and a preferred upper limit of 10 hours. If the polymerization time for the above free radical polymerization is within the above range, the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the (meth)acrylic copolymer will be a relatively small value. A more preferred lower limit for the polymerization time for the above free radical polymerization is 3 hours, and a more preferred upper limit is 8 hours.

[0032] Examples of polymerization initiators used in the above-mentioned free radical polymerization include organic peroxides and azo compounds as described above. Examples of the above-mentioned organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate.

[0033] Among the polymerization initiators used in the above-mentioned free radical polymerization, polymerization initiators having functional groups are preferred. By using a polymerization initiator having the above-mentioned functional group, it becomes easier to adjust the proportion of the sol component of the adhesive layer with a molecular weight of 500,000 or more, and the peak (Mp) of the molecular weight distribution, to the above-mentioned range. In other words, by using a polymerization initiator having the above-mentioned functional group, a functional group can be introduced to the ends of the (meth)acrylic copolymer. In particular, a functional group can be introduced to the ends of molecular chains (also called "non-crosslinkable low molecular weight chains") of the (meth)acrylic copolymer that do not have constituent units derived from a crosslinkable functional group-containing monomer and have a relatively small molecular weight. Since such low molecular weight chains are incorporated into the crosslinked structure via the crosslinking agent by having a functional group at their ends, the cohesive force of the bulk of the adhesive layer is further increased, and the shear strength at high temperatures is further improved. Furthermore, even if they do not participate in the crosslinked structure, the low molecular weight chains can form conjugates (e.g., dimers) with each other via the crosslinking agent or via a combination of the crosslinking agent and a tackifying resin, etc., which may be blended as needed, by having a functional group at their ends. In such cases, the (meth)acrylic copolymer contained in the sol component of the adhesive layer can be said to have a higher molecular weight overall. Therefore, the cohesive force of the bulk of the adhesive layer is further increased, and the shear strength at high temperatures is further improved. The above functional groups are not particularly limited and include, for example, hydroxyl groups, carboxyl groups, silyl groups, glycisyl groups, amino groups, amide groups, nitrile groups, alkoxy groups, acetoacetyl groups, etc. Among these, hydroxyl groups and carboxyl groups are preferred. Examples of polymerization initiators having the above functional groups include, among the polymerization initiators mentioned above, 2,2'-azobis{2-methyl-N-[1,1'-bis(hydroxymethyl)-2-hydroxyethyl]propionamide} and 4,4'-azobis(4-cyanovaleric acid (valeric acid)). These polymerization initiators having functional groups may be used alone or in combination of two or more.

[0034] The amount of polymerization initiator added is not particularly limited, but by keeping the amount of polymerization initiator added within the above range, with a preferred lower limit of 0.01 parts by weight and a preferred upper limit of 0.5 parts by weight per 100 parts by weight of the monomer mixture, it becomes easier to adjust the proportion of molecules with a molecular weight of 500,000 or more in the sol component of the adhesive layer, and the peak (Mp) of the molecular weight distribution, to the above range. A more preferred lower limit for the amount of polymerization initiator added is 0.02 parts by weight, and a more preferred upper limit is 0.3 parts by weight.

[0035] In the above free radical polymerization, a chain transfer agent may be used. The above-mentioned chain transfer agents are not particularly limited and include, for example, lauryl mercaptan, mercaptopropionic acid, mercaptosuccinic acid, 3-mercapto-1,2-propanediol, 1-butanethiol, cyclohexyl 3-mercaptopropionate, 2-ethylhexyl mercaptoacetate, 1-hexadecanethiol, 2-mercaptoethanol, mercaptoacetic acid, ethyl mercaptoethyl acetate, 1-octanthiol, tridecyl 3-mercaptopropionate, thiophenol, and other thiol compounds. Also, 2,4-diphenyl-4-methyl-1-pentene is another example. These chain transfer agents may be used alone or in combination of two or more.

[0036] Among these, chain transfer agents having functional groups are preferred. By using a chain transfer agent having the above-mentioned functional group, it becomes easier to adjust the proportion of the sol component of the adhesive layer with a molecular weight of 500,000 or more, and the peak (Mp) of the molecular weight distribution, to the above-mentioned range. In other words, by using a chain transfer agent having the above-mentioned functional group, a functional group can be introduced to the end of the low molecular weight chain, similar to the case where a polymerization initiator having the above-mentioned functional group is used. As a result, the cohesive force of the bulk of the adhesive layer is further increased, and the shear strength at high temperatures is further improved. The above functional groups are not particularly limited, and examples include hydroxyl groups, carboxyl groups, silyl groups, glycisyl groups, amino groups, amide groups, nitrile groups, alkoxy groups, and acetoacetyl groups. Among these, hydroxyl groups and carboxyl groups are preferred, and hydroxyl groups are more preferred. The number of functional groups in the chain transfer agent having the above functional groups is not particularly limited, but it is preferable that there be multiple functional groups, as this makes it easier to create a high-dimensional crosslinking structure and network, and thus increases the cohesive force of the bulk of the adhesive layer. Examples of the above-mentioned chain transfer agents having the above functional groups include mercaptopropionic acid, mercaptosuccinic acid, and thiol compounds such as 3-mercapto-1,2-propanediol. These chain transfer agents having functional groups may be used alone or in combination of two or more.

[0037] The amount of the chain transfer agent added is not particularly limited, but a preferred lower limit is 0.01 parts by weight and a preferred upper limit is 0.5 parts by weight per 100 parts by weight of the monomer mixture. By keeping the amount of the chain transfer agent within the above range, it becomes easier to adjust the proportion of molecules with a molecular weight of 500,000 or more in the sol component of the adhesive layer, and the peak (Mp) of the molecular weight distribution, to the above range. A more preferred lower limit for the amount of the chain transfer agent added is 0.02 parts by weight and a more preferred upper limit is 0.3 parts by weight.

[0038] In the free radical polymerization described above, as in the living radical polymerization described above, the dispersion stabilizer, polymerization solvent, polymerization temperature, etc. described above may be used.

[0039] The above (meth)acrylic copolymer is not particularly limited, but it is preferable that it contains constituent units derived from alkyl (meth)acrylate having an alkyl group having 4 or fewer carbon atoms. The alkyl (meth)acrylate having an alkyl group with 4 or fewer carbon atoms is not particularly limited, and examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and butyl (meth)acrylate. These alkyl (meth)acrylates having an alkyl group with 4 or fewer carbon atoms may be used alone or in combination of two or more. Among these, butyl (meth)acrylate is preferred.

[0040] The content of the constituent units derived from alkyl (meth)acrylate having an alkyl group with 4 or fewer carbon atoms is not particularly limited, but a preferred lower limit is 25% by weight and a preferred upper limit is 70% by weight. If the content is 25% by weight or more, the glass transition temperature (Tg) of the (meth)acrylic copolymer becomes sufficiently high, so the cohesive force of the bulk of the adhesive layer increases and the shear strength at high temperatures improves. If the content is 70% by weight or less, the glass transition temperature (Tg) of the (meth)acrylic copolymer does not become too high, the fluidity of the bulk of the adhesive layer increases and it can have a higher adhesive force to the polishing pad. A more preferred lower limit of the content is 30% by weight, a more preferred upper limit is 65% by weight, an even more preferred lower limit is 35% by weight, and an even more preferred upper limit is 60% by weight.

[0041] The above (meth)acrylic copolymer preferably contains constituent units derived from alkyl (meth)acrylate having an alkyl group with 6 or more carbon atoms. The alkyl (meth)acrylate having an alkyl group with 6 or more carbon atoms is not particularly limited, but it is preferable that the alkyl group has 6 to 16 carbon atoms, and more preferably that it has 6 to 12 carbon atoms. Furthermore, the alkyl (meth)acrylate having an alkyl group with 6 or more carbon atoms may or may not have branched alkyl groups, but it is preferable that it does not have branched alkyl groups. Because the alkyl group of the alkyl (meth)acrylate having an alkyl group with 6 or more carbon atoms has a linear structure, the adhesive layer has a low storage modulus at low temperatures to room temperature, but a high storage modulus at high temperatures, thus improving the shear strength at high temperatures and providing higher adhesion to the polishing pad. Examples of alkyl (meth)acrylates having an alkyl group with 6 or more carbon atoms include n-heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, 2-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, lauryl(meth)acrylate, myristyl(meth)acrylate, cetyl(meth)acrylate, isostearyl(meth)acrylate, and arachidyl(meth)acrylate. These alkyl (meth)acrylates having an alkyl group with 6 or more carbon atoms may be used alone or in combination of two or more. Among these, n-heptyl(meth)acrylate and 2-ethylhexyl(meth)acrylate are preferred. In this specification, (meth)acrylate means acrylate or methacrylate.

[0042] The content of the constituent units derived from alkyl (meth)acrylate having an alkyl group with 6 or more carbon atoms is not particularly limited, but a preferred lower limit is 22% by weight and a preferred upper limit is 67% by weight. If the content is 22% by weight or more, the glass transition temperature (Tg) of the (meth)acrylic copolymer becomes sufficiently low, which increases the fluidity of the bulk adhesive layer and allows for higher adhesion to the polishing pad. If the content is 67% by weight or less, the glass transition temperature (Tg) of the (meth)acrylic copolymer does not become too low, which further increases the cohesive force of the bulk adhesive layer and further improves the shear strength at high temperatures. A more preferred lower limit for the content is 27% by weight, a more preferred upper limit is 62% by weight, an even more preferred lower limit is 32% by weight, and an even more preferred upper limit is 57% by weight.

[0043] The above (meth)acrylic copolymer preferably has constituent units derived from a monomer containing a crosslinkable functional group. Because the (meth)acrylic copolymer has structural units derived from the above-mentioned crosslinkable functional group-containing monomer, the (meth)acrylic copolymer, and optionally the tackifying resin, etc., construct a crosslinked structure via the crosslinking agent, thereby increasing the bulk cohesive force of the adhesive layer and improving the shear strength at high temperatures. Examples of the above-mentioned crosslinkable functional group include hydroxyl groups, carboxyl groups, silyl groups, glycisyl groups, amino groups, amide groups, nitrile groups, alkoxy groups, and acetoacetyl groups. Among these, hydroxyl groups and carboxyl groups are preferred because they allow for easy adjustment of the bulk cohesive force of the adhesive layer.

[0044] Examples of the hydroxyl group-containing monomers mentioned above include (meth)acrylic acid esters having hydroxyl groups, such as 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate. Examples of the above-mentioned carboxyl group-containing monomers include (meth)acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, and fumaric acid. Among these, acrylic acid is preferred. Examples of the above-mentioned glycidyl group-containing monomers include glycidyl (meth)acrylate. Examples of the above-mentioned amide group-containing monomers include hydroxyethylacrylamide, isopropylacrylamide, and dimethylaminopropylacrylamide. Examples of the above-mentioned nitrile group-containing monomers include acrylonitrile.

[0045] The content of the constituent units derived from the above-mentioned crosslinkable functional group-containing monomer is not particularly limited, but a preferred lower limit is 0.05% by weight and a preferred upper limit is 20% by weight. If the content is 0.05% by weight or more, the cohesive force of the bulk of the adhesive layer is further increased, and the shear strength at high temperatures is further improved. If the content is 20% by weight or less, the fluidity of the bulk of the adhesive layer is further increased, and it can have a higher adhesive force to the polishing pad. A more preferred lower limit for the content is 0.1% by weight and a more preferred upper limit is 15% by weight. In particular, when the (meth)acrylic copolymer contains structural units derived from the carboxyl group-containing monomer, the preferred lower limit of the content of these structural units is 8% by weight. If the content is 8% by weight or more, the glass transition temperature (Tg) of the (meth)acrylic copolymer becomes sufficiently high, thereby increasing the bulk cohesive force of the adhesive layer and improving the shear strength at high temperatures. Furthermore, if the content is 8% by weight or more, the polarity of the (meth)acrylic copolymer also increases, allowing the adhesive layer to have higher adhesive strength to highly polar adherends. A more preferred lower limit of the content is 9% by weight, and a more preferred lower limit is 10% by weight.

[0046] Furthermore, if the (meth)acrylic copolymer contains structural units derived from the hydroxyl group-containing monomer, the preferred upper limit of the content of such structural units is 0.5% by weight. If the content is 0.5% by weight or less, the reaction between the (meth)acrylic copolymer and the crosslinking agent proceeds mildly, making it easier to adjust the proportion of molecules with a molecular weight of 500,000 or more in the sol component of the adhesive layer, and the peak (Mp) of the molecular weight distribution, within this range. A more preferred upper limit of the content of structural units derived from the hydroxyl group-containing monomer is 0.1% by weight. The lower limit of the content of structural units derived from the hydroxyl group-containing monomer is not particularly limited; it is preferable to be as close to 0% by weight as possible, and may even be 0% by weight.

[0047] The above (meth)acrylic copolymer may optionally contain alkyl (meth)acrylate having an alkyl group having 4 or fewer carbon atoms, alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms, and structural units derived from other copolymerizable polymerizable monomers other than those derived from the above crosslinkable functional group-containing monomer.

[0048] The weight-average molecular weight (Mw) of the (meth)acrylic copolymer is not particularly limited, but from the viewpoint of adjusting the peak (Mp) of the molecular weight distribution for the sol component of the adhesive layer to the above range, a preferred lower limit is 150,000, a preferred upper limit is 450,000, a more preferred lower limit is 170,000, and a more preferred upper limit is 400,000. Furthermore, the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the (meth)acrylic copolymer is not particularly limited, but from the viewpoint of adjusting the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the sol component of the adhesive layer to the above range, a preferred upper limit is 10, a more preferred upper limit is 5, an even more preferred upper limit is 2.5, and an even more preferred upper limit is 2. Furthermore, the weight-average molecular weight (Mw) of the (meth)acrylic copolymer, and the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) can be measured in the same manner as when performing GPC measurement by differential refractometer RI detection on the sol component of the adhesive layer.

[0049] The above crosslinking agent is not particularly limited, and depending on the type of crosslinkable functional group of the (meth)acrylic copolymer, for example, isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-type crosslinking agents, etc., may be selected and used. Among these, isocyanate-based crosslinking agents are preferred because they can selectively crosslink hydroxyl groups and carboxyl groups and the crosslinking structure is easy to control. Examples of the above isocyanate-based crosslinking agents include Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.), Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Mytec NY260A (manufactured by Mitsubishi Chemical Corporation). By appropriately adjusting the type or amount of the crosslinking agent, it becomes easier to adjust the cohesive force of the bulk adhesive layer. The number of functional groups in the above-mentioned crosslinking agent is not particularly limited, but it is preferable that it be multivalent, as this makes it easier to create a higher-dimensional crosslinking structure and network, and thus increases the bulk cohesive force of the adhesive layer.

[0050] The amount of the crosslinking agent is not particularly limited, but is preferably 0.01 to 10 parts by weight, and more preferably 0.1 to 7 parts by weight, per 100 parts by weight of the (meth)acrylic copolymer.

[0051] Preferably, the adhesive layer further contains a tackifying resin. By including a tackifying resin in the adhesive layer, the adhesive layer can have a higher adhesive strength to the adherend.

[0052] The softening temperature of the tackifying resin is not particularly limited, but a preferred lower limit is 100°C and a preferred upper limit is 180°C. If the softening temperature is 100°C or higher, the heat resistance of the adhesive layer increases, and the shear strength at high temperatures is further improved. If the softening temperature is 180°C or lower, the adhesive layer becomes more flexible and can have higher adhesion to the polishing pad. A more preferred lower limit for the softening temperature is 110°C, a more preferred upper limit is 170°C, an even more preferred lower limit is 120°C, and an even more preferred upper limit is 165°C. The softening temperature is the softening temperature measured according to the JIS K2207 ring-and-ball method.

[0053] The hydroxyl value of the tackifying resin is not particularly limited, but a preferred lower limit is 25 mg KOH / g, a preferred upper limit is 150 mg KOH / g, a more preferred lower limit is 30 mg KOH / g, and a more preferred upper limit is 100 mg KOH / g. The hydroxyl value can be measured according to JIS K1557 (phthalic anhydride method).

[0054] The tackifying resin mentioned above is not particularly limited and includes rosin-based resins such as rosin ester resins, terpene-based resins such as terpene phenol resins, petroleum-based resins, etc. Among these, rosin ester resins, terpene phenol resins, and combinations thereof are preferred, with terpene phenol resins being more preferred. The terpene phenol resin exhibits good compatibility with the (meth)acrylic copolymer, facilitates grafting with the (meth)acrylic copolymer, and is easily incorporated into the adhesive layer. As a result, the surface of the adhesive layer becomes polymer-rich and flexible, enabling it to have higher adhesion to the polishing pad. On the other hand, the grafting of the terpene phenol resin with the (meth)acrylic copolymer increases the bulk cohesive force of the adhesive layer, thus improving the shear strength of the adhesive layer at high temperatures.

[0055] The rosin ester resins mentioned above are resins obtained by esterifying rosin resins mainly composed of abietic acid, disproportionated rosin resins, hydrogenated rosin resins, or dimers of resin acids such as abietic acid (polymerized rosin resins) with alcohol. The hydroxyl value is adjusted to the above range by incorporating some of the hydroxyl groups of the alcohol used in esterification into the resin without being used for esterification. Examples of alcohols include polyhydric alcohols such as ethylene glycol, glycerin, and pentaerythritol. Furthermore, rosin ester resin is obtained by esterifying rosin resin, disproportionate rosin ester resin is obtained by esterifying disproportionate rosin resin, hydrogenated rosin ester resin is obtained by esterifying hydrogenated rosin resin, and polymerized rosin ester resin is obtained by esterifying polymerized rosin resin. The terpene phenol resin mentioned above is a resin obtained by polymerizing terpenes in the presence of phenol.

[0056] Examples of the above-mentioned disproportionated rosin ester resins include Arakawa Chemical Industries' Super Ester A75 (hydroxyl value 23 mg KOH / g, softening temperature 75°C), Super Ester A100 (hydroxyl value 16 mg KOH / g, softening temperature 100°C), Super Ester A115 (hydroxyl value 19 mg KOH / g, softening temperature 115°C), and Super Ester A125 (hydroxyl value 15 mg KOH / g, softening temperature 125°C). Examples of the above-mentioned hydrogenated rosin ester resins include Arakawa Chemical Industries' Pine Crystal KE-359 (hydroxyl value 42 mg KOH / g, softening temperature 100°C) and Ester Gum H (hydroxyl value 29 mg KOH / g, softening temperature 70°C). Examples of the polymerized rosin ester resins mentioned above include Pencel D135 (hydroxyl value 45 mg KOH / g, softening temperature 135°C) manufactured by Arakawa Chemical Industries, Ltd., Pencel D125 (hydroxyl value 34 mg KOH / g, softening temperature 125°C) manufactured by the same company, and Pencel D160 (hydroxyl value 42 mg KOH / g, softening temperature 160°C) manufactured by the same company. Examples of the above-mentioned terpene resins include YS Polystar G150 (hydroxyl value 140 mg KOH / g, softening temperature 150°C), YS Polystar T100 (hydroxyl value 60 mg KOH / g, softening temperature 100°C), YS Polystar G125 (hydroxyl value 140 mg KOH / g, softening temperature 125°C), YS Polystar T115 (hydroxyl value 60 mg KOH / g, softening temperature 115°C), YS Polystar T130 (hydroxyl value 60 mg KOH / g, softening temperature 130°C), and YS Polystar T160 (hydroxyl value 60 mg KOH / g, softening temperature 160°C), all manufactured by Yasuhara Chemical Co., Ltd. These tackifying resins may be used individually or in combination of two or more types.

[0057] The content of the tackifying resin is not particularly limited, but a preferred lower limit is 10 parts by weight and a preferred upper limit is 60 parts by weight relative to 100 parts by weight of the (meth)acrylic copolymer. If the content is 10 parts by weight or more, the glass transition temperature (Tg) of the adhesive layer will rise, which will increase the bulk cohesive force and further improve the shear strength at high temperatures. If the content is 60 parts by weight or less, the increase in the glass transition temperature (Tg) will prevent the adhesive layer from becoming too hard, and the adhesive layer will be able to have sufficient adhesive strength. A more preferred lower limit for the content is 15 parts by weight, a more preferred upper limit is 50 parts by weight, an even more preferred lower limit is 20 parts by weight, and an even more preferred upper limit is 45 parts by weight.

[0058] The adhesive layer may, if necessary, contain other resins, such as additives like plasticizers, emulsifiers, softeners, fillers, pigments, dyes, silane coupling agents, and antioxidants.

[0059] The storage modulus of the adhesive layer described above is not particularly limited, but the storage modulus G'(100°C) at 100°C is 3.5 × 10⁻⁶. 4 It is preferable that the storage modulus G'(100°C) at 100°C is 3.5 × 10⁻⁶. 4 If the Pa is above, the bulk cohesive force of the adhesive layer at high temperatures increases, and the shear strength at high temperatures improves. A more preferable lower limit for the storage modulus G'(100°C) at 100°C is 4 × 10⁻⁶. 4 Pa, a more preferable lower limit is 4.5 × 10⁻⁶. 4 It is Pa. The upper limit of the storage modulus G'(100°C) at 100°C is not particularly limited, but if it is too high, the storage modulus at room temperature will also increase, and the adhesive strength to the polishing pad will decrease, so a preferred upper limit is 2.0 × 10⁻⁶. 5 It is Pa.

[0060] For measuring the storage modulus G'(100°C) of the above-mentioned adhesive layer at 100°C, for example, the following method can be employed. That is, first, samples of the above-mentioned adhesive layer are stacked to create a laminate with a thickness of about 1 mm, and then cut into 6 mm × 10 mm pieces to obtain test specimens. Using a dynamic viscoelasticity measuring device (IT Measurement Control Co., Ltd., DVA-200), measurements are performed on the test specimens in shear mode under a nitrogen atmosphere, with a measurement temperature of -40 to 140°C, a heating rate of 5°C / min, a frequency of 10 Hz, and a strain of 0.08%.

[0061] The thickness of the adhesive layer described above is not particularly limited, but a preferred lower limit is 10 μm and a preferred upper limit is 150 μm. If the thickness is 10 μm or more, the adhesion of the adhesive layer to the adherend increases, and the peel resistance increases, so that it can have high adhesive strength to the polishing pad. If the thickness is 150 μm or less, the amount of displacement when a shear force is applied to the adhesive layer is reduced, so the shear strength of the adhesive layer at high temperatures is further improved. A more preferred lower limit for the thickness of the adhesive layer is 20 μm, a more preferred upper limit is 120 μm, an even more preferred lower limit is 40 μm, and an even more preferred upper limit is 100 μm.

[0062] The above-mentioned substrate is not particularly limited, but a resin film is preferred. The above-mentioned resin film is not particularly limited, and examples include polyester resin film, polypropylene resin film, etc. Among these, polyester resin film is preferred because it is flat, has little variation in thickness, and has high strength, and among polyester resin films, polyethylene terephthalate film is more preferred. The above-mentioned substrate may contain additives such as fillers, ultraviolet absorbers, light stabilizers, and antistatic agents, to the extent that it does not impair its physical properties. The thickness of the above-mentioned substrate is not particularly limited, but a preferred lower limit is 10 μm, a preferred upper limit is 200 μm, a more preferred lower limit is 15 μm, a more preferred upper limit is 150 μm, an even more preferred lower limit is 20 μm, and an even more preferred upper limit is 100 μm. When the thickness of the above-mentioned substrate is within the above range, the adhesive tape has appropriate rigidity, making it less likely to peel off the polishing pad and further suppressing slippage from the polishing pad.

[0063] The adhesive tape of the present invention is not particularly limited as long as it has the above-mentioned base material and the above-mentioned adhesive layer. The adhesive layer may be present on only one side of the base material, or on both sides of the base material. Alternatively, the adhesive layer may be present on only one side of the base material, and the other side may have an adhesive layer with a different composition and physical properties. In particular, it is preferable that the adhesive layer is present on only one side of the substrate, and that the other side has an adhesive layer with a different composition and properties. In this case, it is preferable that the adhesive layer is used on the surface that adheres to the polishing pad (polishing pad side adhesive layer), and the adhesive layer with a different composition and properties is used on the surface that adheres to the polishing machine's surface plate (surface plate side adhesive layer).

[0064] The adhesive layer on the surface plate side is not particularly limited, and for example, a (meth)acrylic adhesive, a rubber adhesive, etc., can be used for the adhesive layer on the surface plate side. Among these, a (meth)acrylic adhesive is preferred from the viewpoint of further increasing adhesive strength. The adhesive layer on the surface plate side may be the adhesive layer described above, but it is preferable that it is an adhesive layer having a different composition and physical properties from the adhesive layer on the polishing pad side. Conventional known adhesive layers can be used as such an adhesive layer.

[0065] The overall thickness of the adhesive tape of the present invention is not particularly limited, but a preferred lower limit is 30 μm and a preferred upper limit is 400 μm. When the overall thickness of the adhesive tape of the present invention is within the above range, the adhesive tape has appropriate rigidity, making it less likely to peel off the polishing pad and further suppressing slippage from the polishing pad. A more preferred lower limit for the overall thickness of the adhesive tape of the present invention is 55 μm, a more preferred upper limit is 300 μm, an even more preferred lower limit is 100 μm, and an even more preferred upper limit is 250 μm.

[0066] The method for manufacturing the adhesive tape of the present invention is not particularly limited. For example, when the substrate has adhesive layers on both sides, the following method can be used. First, an adhesive solution is prepared containing a (meth)acrylic copolymer, a crosslinking agent, and, if necessary, other components such as a tackifying resin. Next, the adhesive solution obtained above is applied to the release-treated surface of a release film, which has one side treated for release, and dried to produce a laminated sheet having an adhesive layer (polishing pad side adhesive layer) on the release-treated surface of the release film. In the same manner, a laminated sheet having an adhesive layer (surface plate side adhesive layer) on the release-treated surface of the release film is produced. Next, the adhesive layers of the two laminated sheets are transferred to a substrate and laminated together to obtain an adhesive sheet having adhesive layers on both sides of the substrate.

[0067] The applications of the adhesive tape of the present invention are not particularly limited, but because it has high adhesive strength to polishing pads and excellent shear strength at high temperatures, it is preferably used to fix polishing pads to the base plate of a polishing machine in a 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. The adhesive tape of the present invention is more preferably used on the surface that adheres to the polishing pad. The polishing pad described above is not particularly limited and may be any polishing pad made of an absorbent material, nonwoven fabric, polyurethane foam, etc., that is fixed to the base plate of a polishing machine. The adhesive tape of the present invention can have high adhesive strength even to polishing pads made of polyurethane foam, etc., that is, polishing pads that have many cavities on their surface and have a rough surface. [Effects of the Invention]

[0068] According to the present invention, it is possible to provide an adhesive tape that is suitable for fixing a polishing pad to the base plate of a polishing machine and that allows polishing to be continued for a long period of time. [Brief explanation of the drawing]

[0069] [Figure 1] This is a schematic diagram illustrating the method for creep resistance testing (measurement of shear strength) of adhesive tape. [Modes for carrying out the invention]

[0070] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0071] (Preparation of (meth)acrylic copolymer A (living radical polymerization)) 6.38 g (50 mmol) of tellurium (40 mesh, metallic tellurium, Aldrich) was suspended in 50 mL of tetrahydrofuran (THF), and 34.4 mL (55 mmol) of 1.6 mol / L n-butyllithium / hexane solution (Aldrich) was slowly added dropwise at room temperature. The reaction solution was stirred until the metallic tellurium was completely gone. 10.7 g (55 mmol) of ethyl-2-bromoisobutyrate was added to the reaction solution at room temperature, and the mixture was stirred for 2 hours. After the reaction was complete, the solvent was concentrated under reduced pressure, followed by vacuum distillation to obtain ethyl 2-methyl-2-n-butylteranyl-propionate (BTEE), a yellow oily substance.

[0072] In an argon-purged glove box, 66 μL of prepared ethyl 2-methyl-2-n-butylteranyl-propionate (BTEE), 14 mg of 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN, manufactured by Wako Pure Chemical Industries, Ltd.), and 1 mL of ethyl acetate were added to the reaction vessel. The reaction vessel was then sealed and removed from the glove box. Subsequently, while introducing argon gas into the reaction vessel, a monomer mixture totaling 100 g (44 g of butyl acrylate (BA), 44 g of 2-ethylhexyl acrylate (2EHA), and 12 g of acrylic acid (AAc)) and 43 g of ethyl acetate as the polymerization solvent were added to the reaction vessel. The polymerization reaction was carried out at 50°C for 28 hours to obtain a solution containing (meth)acrylic copolymer A.

[0073] (Preparation of (meth)acrylic copolymer B (living radical polymerization)) (meth)acrylic copolymer B was prepared in the same manner as (meth)acrylic copolymer A, except that the amount of initiator was changed as shown in Table 1.

[0074] [Table 1]

[0075] (Preparation of (meth)acrylic copolymer C (free radical isothermal polymerization)) A reactor equipped with a thermometer, stirrer, and condenser was prepared. A total of 100 g of monomer mixture, 30 g of ethyl acetate, and 90 g of toluene were added to this reactor. The monomer mixture consisted of 44 g of butyl acrylate (BA), 44 g of 2-ethylhexyl acrylate (2EHA), and 12 g of acrylic acid (AAc). Argon gas was introduced into the reactor to remove dissolved oxygen, and the solution temperature was raised to 60°C by heating. Subsequently, 0.03 g of the chain transfer agent 3-mercapto-1,2-propanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the reactor, and 0.05 g of V-60 (2,2'-azobisisobutyronitrile, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a polymerization initiator. Polymerization was started under reflux. The polymerization reaction was carried out for 6 hours from the start of polymerization to obtain a solution containing (meth)acrylic copolymer C.

[0076] (Preparation of (meth)acrylic copolymers D-E (free radical isothermal polymerization)) (meth)acrylic copolymers D to E were prepared in the same manner as (meth)acrylic copolymer C, except that the amount of initiator, the type or amount of chain transfer agent, and the reaction time were changed as shown in Table 2.

[0077] [Table 2]

[0078] (Preparation of (meth)acrylic copolymer F (free radical boiling point polymerization)) A reactor equipped with a thermometer, stirrer, and condenser was prepared, and a total of 50 g of the monomer mixture and 90 g of ethyl acetate were added to the reactor. The monomer mixture consisted of 22 g of butyl acrylate (BA), 22 g of 2-ethylhexyl acrylate (2EHA), and 6 g of acrylic acid (AAc). After purging with nitrogen, the reactor was heated and reflux was started. Thirty minutes after the ethyl acetate boiled, 0.03 g of the chain transfer agent 3-mercapto-1,2-propanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added, and 0.04 g of V-60 (2,2'-azobisisobutyronitrile, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as polymerization initiator 1, and polymerization was started under reflux. After 30 minutes, the total of 50 g of the monomer mixture was added dropwise to the reactor over 1 hour using a dropping funnel. The monomer mixture added dropwise consisted of 22 g of butyl acrylate (BA), 22 g of 2-ethylhexyl acrylate (2EHA), and 6 g of acrylic acid (AAc). Subsequently, 0.15 g of V-60 (2,2'-azobisisobutyronitrile, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as polymerization initiator 2, and the polymerization reaction was carried out for a total of 6 hours from the start of polymerization to obtain a solution containing (meth)acrylic copolymer F.

[0079] (Preparation of (meth)acrylic copolymers G-K and a (free radical boiling point polymerization)) (meth)acrylic copolymers G to K and a were prepared in the same manner as (meth)acrylic copolymer F, except that the monomer composition, amount of solvent, amount of initiator, and type or amount of chain transfer agent were changed as shown in Table 3.

[0080] [Table 3]

[0081] (Example 1) (1) Manufacturing of adhesive tape Ethyl acetate was added to 100 parts by weight of the non-volatile content of the obtained (meth)acrylic copolymer-containing solution and stirred. Furthermore, 40 parts by weight of terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name "T160", hydroxyl value 60 mg KOH / g, softening temperature 160°C), which is a tackifying resin, and 4.5 parts by weight of isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate L45") were added and stirred to obtain an adhesive solution.

[0082] A polyethylene terephthalate film with one side treated for mold release was prepared. The adhesive solution obtained above was applied to the mold-release surface of this polyethylene terephthalate film to a thickness of 80 μm after drying, and dried at 110°C for 5 minutes to promote crosslinking of the (meth)acrylic copolymer in the (meth)acrylic copolymer-containing solution. This produced a laminated sheet having an adhesive layer (polishing pad side adhesive layer) on the mold-release surface of the polyethylene terephthalate film. A laminated sheet having an adhesive layer (surface plate side adhesive layer) on the mold-release surface of the mold-release film was produced in a similar manner. Next, a polyethylene terephthalate film (50 μm thick) was prepared as the base material. One laminated sheet was laminated onto one side of this base material, with the adhesive layer facing outwards, transferring and integrating the adhesive layer with the base material. The other laminated sheet was laminated onto the other side of the base material, with the adhesive layer facing outwards, transferring and integrating the adhesive layer with the base material. As a result, a double-sided adhesive tape was obtained in which an adhesive layer for the polishing pad side and an adhesive layer for the surface plate side were provided on both sides of the base material, respectively.

[0083] (2) GPC measurement of sol components (RI) The adhesive layer of double-sided adhesive tape was immersed in tetrahydrofuran (THF) at 23°C for 24 hours, and the insoluble components were removed by filtering through a 200-mesh wire mesh to obtain the sol component of the adhesive layer. The sol component of the obtained adhesive layer was subjected to GPC measurement by differential refractometer RI detection using the following method. Specifically, using a SHOKO LF-804 column, the sol component of the obtained adhesive layer was analyzed by gel permeation chromatography (GPC) (Waters, 2690 Separations Model), and the molecular weight distribution in polystyrene equivalent was measured. Eluent: Tetrahydrofuran (THF) Flow rate: 0.4mL / min Detector: Differential refractometer RI Column temperature (measurement temperature): 40℃ Injection volume: 20μL

[0084] Table 4 shows the proportion of molecules with a molecular weight of 500,000 or more in the obtained molecular weight distribution, as well as the peak (Mp) of the molecular weight distribution.

[0085] (3) Measurement of the storage modulus The storage modulus G'(100°C) of the adhesive layer of double-sided adhesive tape was measured at 100°C using the following method. First, samples of the adhesive layer were stacked to create a laminate with a thickness of approximately 1 mm, which was then cut into 6 mm × 10 mm specimens to obtain test pieces. A dynamic viscoelasticity analyzer (IT Measurement Control Co., Ltd., DVA-200) was used to measure the test pieces in shear mode under a nitrogen atmosphere, with a measurement temperature of -40 to 140°C, a heating rate of 5°C / min, a frequency of 10 Hz, and a strain of 0.08%.

[0086] (4-1) Adhesion to the polishing pad A polyurethane foam sliced ​​to a thickness of 3 mm was used as the polishing pad (primarily composed of PPG as a polyether polyol, TDI as an isocyanate, and MOCA as a curing agent). When this polyurethane foam was observed with a laser microscope, the surface roughness Sa was 3.99 μm and the contact area ratio was 77%.

[0087] A 25mm wide strip of double-sided adhesive tape was cut to form a test specimen. The release PET film on one side of the test specimen was peeled off, exposing the adhesive layer (the adhesive layer on the polishing pad side). After cleaning with ethanol and wiping dry, the test specimen was placed on the polishing pad so that the adhesive layers faced each other. A 2kg rubber roller was passed over the test specimen once at a speed of 300mm / min to bond the test specimen and the polishing pad. This laminate was passed through a laminator (ACCO Brands Japan, Multi Laminator GDRH355 A3) once under the conditions of a roll temperature of 85°C, a roll gap of 2mm, and a speed of 7.5rpm, and pressed with a pressure of 1.2MPa. After that, the specimen was left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50% to obtain the test sample. Using a tensile testing machine, a 180° peel test was performed on the test sample in accordance with JIS Z0237, with a peeling speed of 300 mm / min and a peeling angle of 180°.

[0088] (4-2) Adhesion to SUS 1.5mm thick stainless steel was used.

[0089] A 25mm wide strip of double-sided adhesive tape was cut to form a test specimen. The release PET film on one side of the test specimen was peeled off, exposing the adhesive layer (the adhesive layer on the polishing pad side). After cleaning with ethanol and wiping dry, the test specimen was placed on the SUS (stainless steel) so that the adhesive layers faced each other. A 2kg rubber roller was passed back and forth once at a speed of 300mm / min over the test specimen to bond it to the SUS. The specimen was then left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50% to obtain the test sample. Using a tensile testing machine, a 180° peel test was performed on the test sample in accordance with JIS Z0237, with a peeling speed of 300 mm / min and a peeling angle of 180°.

[0090] (5) Creep resistance test (measurement of shear strength) Figure 1 shows a schematic diagram illustrating the method for creep resistance testing (measurement of shear strength) of adhesive tape. A piece of double-sided adhesive tape was cut to a width of 10 mm and a length of 120 mm, and backed with a PET film with a thickness of 25 μm to prepare test piece 1. As shown in Figure 1, test piece 1 was attached to the stainless steel measuring terminal section 2 of the testing machine with an adhesive area of ​​10 × 10 mm. The temperature of the stainless steel measuring terminal section 2 was set to 60°C. A mirror-finished quartz block 3 (quartz glass with chromium deposition) was placed on the attachment surface of test piece 1, and a 50 gf weight 5 was attached to test piece 1. Three minutes after applying the load with weight 5, the displacement (slip amount) (μm) in the direction of the arrow in the figure was measured from the movement of the mirror-finished quartz block 3 on test piece 1 using a laser interferometer 4 (Keyence Corporation, SI-F10), and was defined as the displacement amount.

[0091] (Examples 2-9, Comparative Examples 1-3) A double-sided adhesive tape was obtained in the same manner as in Example 1, except that the type or amount of (meth)acrylic copolymer, tackifying resin, and crosslinking agent was changed as shown in Table 4. Note that "T130" in Table 4 refers to a terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name "T130", hydroxyl value 60 mg KOH / g, softening temperature 130°C), which is a tackifying resin.

[0092] (Comparative Example 4) Instead of double-sided adhesive tape, I used a urethane hot melt sheet (Elfan UH-203, manufactured by Nippon Matai Co., Ltd.).

[0093] <Rating> The double-sided adhesive tapes obtained in the examples and comparative examples were evaluated as follows. The results are shown in Table 4.

[0094] (Polishing test) The polishing pad (polyurethane foam, surface roughness Sa 3.99 μm, contact area ratio 77%) was fixed to the polishing platen of the polishing machine (Lap Master LM-15E, manufactured by Lap Master SFT) using the obtained double-sided adhesive tape. The fixing was performed as follows. First, double-sided adhesive tape was placed on the polishing pad so that the adhesive layers on the polishing pad side faced each other. A 2kg rubber roller was passed back and forth once on the double-sided adhesive tape at a speed of 300mm / min to bond the double-sided adhesive tape and the polishing pad together. This laminate was passed through a laminator (ACCO Brands Japan, Multi Laminator GDRH355 A3) once under the conditions of a roll temperature of 85°C, a roll gap of 2mm, and a speed of 7.5rpm, and pressed with a pressure of 1.2MPa. After that, the polishing pad was fixed by letting it stand for 24 hours at a temperature of 23°C and a relative humidity of 50%. In the same way, the polishing pad was fixed onto the polishing platen via the adhesive layer on the platen side. A silicon etched wafer substrate (500 μm thick, 6-inch diameter) with an adhesive sheet attached to its surface was used as the workpiece. The adhesive sheet side of the workpiece was vacuum-suctioned to the suction head of the polishing machine. The suction head was rotated and lowered at 100 rpm, and the silicon etched wafer substrate was rubbed against the polishing platen rotating at 120 rpm, until a polishing yield of 120 g / cm² was achieved. 2 Polishing was performed while applying pressure. During this time, polishing slurry (GLANZOX1302, manufactured by Fujimi Incorporated) was supplied to the polishing platen at a slurry concentration of 1% and a flow rate of 35 mL / min. In addition, the wafer was replaced every two hours, and the polishing pad was cleaned with high-pressure water for 30 seconds (pressure 7 MPa, flow rate 7 L / min) at the time of replacement.

[0095] The above polishing process was repeated, and after 100 hours, the presence or absence of peeling or displacement of the adhesive layer (polishing pad side adhesive layer) of the double-sided adhesive tape securing the polishing pad was checked. In addition, the time until polishing could no longer be continued due to peeling or displacement of the adhesive layer (polishing pad side adhesive layer) of the double-sided adhesive tape securing the polishing pad, a rapid rise in temperature causing the slurry liquid to evaporate, or a crash in the electrical circuit of the silicon etched wafer substrate was measured.

[0096] [Table 4] [Industrial applicability]

[0097] According to the present invention, it is possible to provide an adhesive tape that is suitable for fixing a polishing pad to the base plate of a polishing machine and that allows polishing to be continued for a long period of time. [Explanation of Symbols]

[0098] 1 Test specimen 2. Stainless steel measuring terminal section 3. Mirror-polished quartz blocks 4. Laser interferometer 5 weights (50 gf)

Claims

1. An adhesive tape having a base material and an adhesive layer, The adhesive layer contains a (meth)acrylic copolymer and a crosslinking agent. The amount of the crosslinking agent is 7 parts by weight or less per 100 parts by weight of the (meth)acrylic copolymer. The adhesive strength to the polishing pad made of polyurethane foam, as measured by the following method, is 50 N / 25 mm or more. In the creep resistance test, the displacement after 3 minutes of applying a load of 50 gf in the shear direction at 60°C is between 5 μm and 50 μm. An adhesive tape characterized by the following features. [Method for measuring adhesive strength] Adhesive tape is cut into strips 25 mm wide to prepare test pieces. After washing with ethanol and wiping dry, the test pieces are placed on a polishing pad (surface roughness Sa of 3.99 μm, contact area ratio of 77%, thickness of 3 mm) so that the adhesive layers face each other. A 2 kg rubber roller is passed back and forth over the test piece at a speed of 300 mm / min to bond the test piece and the polishing pad. The resulting laminate is passed through a laminator once at a roll temperature of 85°C, a roll gap of 2 mm, and a speed of 7.5 rpm, and pressed with a pressure of 1.2 MPa. After that, the laminate is left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50% to obtain a test sample. Using a tensile testing machine, a 180° peel test is performed on the test sample in accordance with JIS Z0237, with a peeling speed of 300 mm / min and a peeling angle of 180°.

2. The adhesive tape according to claim 1, characterized in that its adhesive strength to SUS is 30 N / 25 mm or more.

3. The adhesive tape according to claim 1 or 2, characterized in that when GPC measurement is performed on the sol component of the adhesive layer by differential refractometer RI detection, the proportion of molecules with a molecular weight of 500,000 or more in the region of molecular weight of 5,000 or more is 1% or more and 20% or less.

4. The adhesive tape according to claim 1 or 2, characterized in that when GPC measurement is performed on the sol component of the adhesive layer using differential refractometer RI detection, the peak (Mp) of the molecular weight distribution in the region of molecular weight of 5000 or more is 100,000 or more and 400,000 or less.

5. The adhesive layer has a storage modulus G' (at 100°C) of 3.5 × 10⁻⁶. ４ The adhesive tape according to claim 1 or 2, characterized in that it has a pressure of Pa or higher.

6. The adhesive tape according to claim 1 or 2, wherein the adhesive layer further comprises a tackifying resin, the softening temperature of the tackifying resin is 100°C or higher and 180°C or lower, and the content of the tackifying resin is 10 parts by weight or higher and 50 parts by weight or lower per 100 parts by weight of the (meth)acrylic copolymer.

7. The adhesive tape according to claim 1 or 2, characterized in that the (meth)acrylic copolymer contains 8% by weight or more of structural units derived from carboxyl group-containing monomers.

8. The adhesive tape according to claim 1 or 2, characterized in that the (meth)acrylic copolymer has a content of 25% by weight or more and 70% by weight or less of constituent units derived from alkyl (meth)acrylate having an alkyl group having 4 or fewer carbon atoms, and a content of 22% by weight or more and 67% by weight or less of constituent units derived from alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms.

9. The adhesive tape according to claim 1 or 2, characterized in that the base material is a polyester resin film or a polypropylene resin film with a thickness of 10 μm or more and 200 μm or less.

10. The adhesive tape according to claim 1 or 2, characterized in that the adhesive layer has a thickness of 10 μm or more and 150 μm or less.

11. The adhesive tape according to claim 1 or 2, characterized in that the adhesive layer is provided on both sides of the substrate.

12. The adhesive tape according to claim 1 or 2, characterized in that it is used to fix a polishing pad to the surface plate of a polishing machine.

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