Adhesive tape

Abstract

To provide an adhesive tape that has high adhesion to a rough surface and excellent shear strength at high temperatures.SOLUTION: An adhesive tape contains a substrate and an adhesive layer. The adhesive layer contains a methacryl copolymer and a crosslinker. When sol components of the adhesive layer is subjected to GPC measurement by differential refractive index detector RI detection, in a region with a molecular weight of 5000 or more, the proportion of component with a molecular weight of 150,000 or less is 5% or more and 20% or less and the proportion of component with a molecular weight of 500,000 or more is 1% or more and 20% 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 re-peeled from the surface plate without leaving any adhesive residue when replacing the used polishing pad.

[0003] As the double-sided adhesive tape for fixing the 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 the abrasive material in which the thermally active adhesive layer serves as a bonding surface with the abrasive 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, to increase the polishing speed in order to improve polishing efficiency, it is necessary to increase the amount of strongly acidic or strongly alkaline slurry liquid used during polishing, as well as to use a soft polishing pad. Polyurethane foam, for example, is being considered as such a soft polishing pad. However, soft polishing pads have many voids on their surface and a rough surface, which results in poor adhesion of the double-sided adhesive tape used to fix the polishing pad, and insufficient adhesive strength, which is a problem. Furthermore, increasing the polishing speed to improve polishing efficiency can lead to increased temperature due to frictional heat and the application of strong shear forces, which can easily cause the adhesive layer to shift or peel off. Double-sided adhesive tapes for fixing polishing pads are therefore required to have excellent resistance to shifting or peeling (creep resistance) when strong shear forces are applied at high temperatures.

[0006] The present invention aims to provide an adhesive tape that has high adhesion to rough surfaces and excellent shear strength at high temperatures. In particular, the present invention aims to provide an adhesive tape that has high adhesion to polishing pads having rough surfaces and excellent shear strength at high temperatures. [Means for solving the problem]

[0007] Disclosure 1 is an adhesive tape having a substrate and an adhesive layer, 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, in the region of molecular weight of 5000 or more, the proportion of molecular weights of 150,000 or less is 5% to 20%, and the proportion of molecular weights of 500,000 or more is 1% to 20%. Disclosure 2 is an adhesive tape of Disclosure 1 in which, when GPC measurement is performed on the sol component of the adhesive layer by differential refractometer RI detection, the peak (Mp) of the molecular weight distribution in the region of molecular weight of 5000 or more is between 150,000 and 400,000. Disclosure 3 is an adhesive tape according to Disclosure 1 or 2, wherein, when GPC measurement is performed on the sol component of the adhesive layer using differential refractometer RI detection, the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) in the region of molecular weight of 5000 or more is 2.5 or less. Disclosure 4 states that the adhesive layer has a storage modulus G'(100°C) of 4 × 10⁻⁶ at 100°C. 4 This is an adhesive tape according to disclosure 1, 2, or 3, having a Pa of 1 or higher. Disclosure 5 is an adhesive tape according to Disclosure 1, 2, 3, or 4, 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 60 parts by weight or lower per 100 parts by weight of the (meth)acrylic copolymer. Disclosure 6 is an adhesive tape according to Disclosure 1, 2, 3, 4, or 5, wherein the (meth)acrylic copolymer contains 8% by weight or more of constituent units derived from carboxyl group-containing monomers. Disclosure 7 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, or 6, 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 8 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the adhesive layer has a thickness of 10 μm or more and 150 μm or less. Disclosure 9 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, having the adhesive layer on both sides of the substrate. Disclosure 10 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8 or 9 used to fix a polishing pad to a surface plate of a polishing machine. The present invention will be described in detail below.

[0008] The inventors of the present invention investigated the optimization of the molecular weight distribution of the sol component of an adhesive layer containing a (meth)acrylic copolymer and a crosslinking agent, which can be used as an adhesive layer for fixing a polishing pad to the base plate of a polishing machine, particularly for the bonding surface with the polishing pad. Specifically, when GPC measurements were performed on the sol component of the adhesive layer using differential refractometer RI detection, the inventors investigated adjusting the proportion of low molecular weight components with a molecular weight of 150,000 or less and high molecular weight components with a molecular weight of 500,000 or more to a specific range in the region of molecular weight of 5,000 or more. The inventors of the present invention found that an adhesive tape having such an adhesive layer has high adhesive strength to rough surfaces and excellent shear strength at high temperatures, thus completing 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 layer contains a (meth)acrylic copolymer and a crosslinking agent. When the sol component of the adhesive layer is subjected to GPC measurement using differential refractometer RI detection, the proportion of molecules with a molecular weight of 150,000 or less is 5% to 20% in the region of molecular weight of 5,000 or more, and the proportion of molecules with a molecular weight of 500,000 or more is 1% to 20%. In this specification, (meth)acrylic means acrylic or methacrylic.

[0010] Here, "sol component" refers to the component remaining after removing the "gel component" from the adhesive layer. That is, the relationship "sol fraction (weight %) = 100 (weight %) - gel fraction (weight %)" holds true. The "gel component" is a low-fluidity component in which the (meth)acrylic copolymer, tackifying resin (if necessary), etc., construct a crosslinked structure via the crosslinking agent, while the "sol component" is a highly fluid component that does not participate in such a crosslinked structure. GPC measurement using differential refractometer RI detection allows us to primarily determine the molecular weight distribution of the (meth)acrylic copolymer contained in the sol component of the adhesive layer.

[0011] 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

[0012] If the proportion of components with a molecular weight of 150,000 or less (the proportion of low molecular weight components) is 5% or more, the fluidity of the bulk of the adhesive layer increases, and it can have high adhesive strength to rough surfaces. If the proportion of components with a molecular weight of 150,000 or less is 20% or less, the cohesive force of the bulk of the adhesive layer does not decrease more than necessary, and the shear strength of the adhesive layer at high temperatures improves. The preferred lower limit for the proportion of components with a molecular weight of 150,000 or less is 7%, the preferred upper limit is 18%, the more preferred lower limit is 8%, and the more preferred upper limit is 15%.

[0013] 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 bulk cohesive force 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 bulk fluidity of the adhesive layer does not decrease excessively, so the adhesive layer can have high adhesion to rough surfaces. 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%.

[0014] When GPC measurement with differential refractometer RI detection is performed on the sol component of the adhesive layer, it is preferable that the peak (Mp) of the molecular weight distribution is 150,000 or more and 400,000 or less in the region where the molecular weight is 5,000 or more. If the peak (Mp) of the molecular weight distribution is 150,000 or more, the proportion of high molecular weight components increases and the proportion of low molecular weight components decreases. Therefore, the cohesive force of the bulk of the adhesive layer further increases and the shear strength at high temperature is further improved. If the peak (Mp) of the molecular weight distribution is 400,000 or less, the proportion of high molecular weight components decreases and the proportion of low molecular weight components increases. Therefore, the fluidity of the bulk of the adhesive layer further increases and it can have a higher adhesive force to a rough surface. The more preferable lower limit of the peak (Mp) of the molecular weight distribution is 175,000, the more preferable upper limit is 350,000, the further preferable lower limit is 200,000, and the further preferable upper limit is 300,000. Note that the peak (Mp) of the molecular weight distribution means the molecular weight at the highest peak in the molecular weight distribution curve. Even when there is a shoulder or two or more peaks in the molecular weight distribution curve, the peak (Mp) of the molecular weight distribution means the highest peak in the molecular weight distribution curve.

[0015] When GPC measurement with differential refractometer RI detection is performed on the sol component of the adhesive layer, it is preferable that the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.5 or less in the region where the molecular weight is 5,000 or more. If the ratio (Mw / Mn) is 2.5 or less, the proportions of both low molecular weight components and high molecular weight components decrease. Therefore, the adhesive layer has further improved shear strength at high temperature and can have a higher adhesive force to a rough surface. The more preferable upper limit of the ratio (Mw / Mn) is 2, and the further preferable upper limit is 1.5.

[0016] Regarding the sol component of the adhesive layer, the method for adjusting the ratio of the molecular weight of 150,000 or less, the ratio of the molecular weight of 500,000 or more, the peak (Mp) of the molecular weight distribution, and the ratio (Mw / Mn) within the above ranges is not particularly limited. Examples of the method for adjusting these within the above ranges include, for example, a method for adjusting the composition of the (meth)acrylic copolymer, a method for making the composition of the (meth)acrylic copolymer more uniform, a method for reducing the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the (meth)acrylic copolymer, a method for adjusting the polymerization reaction time and polymerization reaction temperature of the (meth)acrylic copolymer, a method for adjusting the polymerization charge monomer concentration of the (meth)acrylic copolymer, a method for adjusting the type and addition amount of the polymerization initiator and catalyst of the (meth)acrylic copolymer, a method for adjusting the type and amount of the polymerization solvent of the (meth)acrylic copolymer, a method for adding a chain transfer agent during the polymerization of the (meth)acrylic copolymer, and the like.

[0017] More specifically, a method using a (meth)acrylic copolymer obtained by living radical polymerization is preferred. Living radical polymerization is a polymerization in which the molecular chain grows without being hindered by side reactions such as termination reactions or chain transfer reactions. In living radical polymerization, the growing terminal radicals are not deactivated, and no new radical species are generated during the reaction, and the reaction proceeds. During the reaction, all molecular chains polymerize while uniformly reacting with the monomer, and the composition of all molecular chains approaches uniformity. Therefore, according to living radical polymerization, a copolymer having a more uniform molecular weight and composition can be obtained compared to free radical polymerization, and the generation of low molecular weight components and the like can be suppressed. Therefore, the composition of the (meth)acrylic copolymer tends to be more uniform, and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) tends to be small. When the (meth)acrylic copolymer has a structural unit derived from a crosslinkable functional group-containing monomer such as a carboxy group-containing monomer, the crosslinking points in the (meth)acrylic copolymer also tend to be more uniformly present.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] While employing the above-mentioned free radical polymerization, the following method is 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. That is, a method using a (meth)acrylic copolymer obtained by relatively mild polymerization conditions in which the polymerization temperature and the concentration of the monomer mixture are kept constant, even within the free radical polymerization described above. Examples of polymerization methods that provide such relatively mild polymerization conditions include free radical isothermal polymerization.

[0026] 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. These polymerization initiators may be used individually or in combination of two or more.

[0027] 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.

[0028] 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.

[0029] 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 strength to rough surfaces. 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.

[0030] 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 rough surfaces. 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.

[0031] 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, so the fluidity of the bulk adhesive layer increases and it can have higher adhesion to rough surfaces. If the content is 67% by weight or less, the glass transition temperature (Tg) of the (meth)acrylic copolymer does not become too low, the cohesive force of the bulk adhesive layer increases further and the shear strength at high temperatures improves further. 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.

[0032] 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.

[0033] 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.

[0034] 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 strength to rough surfaces. 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.

[0035] 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.

[0036] 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) for the sol component of the adhesive layer to the above range, a preferred upper limit is 2.5, and a 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.

[0037] 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.

[0038] The content of the above 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 above (meth)acrylic copolymer.

[0039] 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.

[0040] 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 rough surfaces. 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.

[0041] 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).

[0042] 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 adhesive strength to rough surfaces. 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The adhesive layer may, if necessary, contain other resins, such as additives including plasticizers, emulsifiers, softeners, fillers, pigments, dyes, silane coupling agents, and antioxidants.

[0047] The storage modulus of the adhesive layer described above is not particularly limited, but the storage modulus G'(100°C) at 100°C is 4 × 10⁻⁶. 4 It is preferable that the storage modulus G'(100°C) at 100°C is 4 × 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 4.5 × 10⁻⁶. 4 Pa, a more preferable lower limit is 5 × 10 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 rough surfaces will decrease. Therefore, a preferred upper limit is 2.0 × 10⁻⁶. 5 It is Pa.

[0048] 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%.

[0049] 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 rough surfaces. 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.

[0050] 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 12 μm, a preferred upper limit is 300 μm, a more preferred lower limit is 20 μm, and a more preferred upper limit is 250 μm.

[0051] 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, and the adhesive layer may be present on only one side of the base material, or on both sides of the base material. In particular, it is preferable that the adhesive layer be present on both sides of the base material.

[0052] The method for manufacturing the adhesive tape of the present invention is not particularly limited. For example, when the substrate has adhesive layers of the same composition and thickness 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 on the release-treated surface of the release film. A total of two laminated sheets are produced in the same manner. 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.

[0053] The applications of the adhesive tape of the present invention are not particularly limited, but because it has high adhesive strength to rough surfaces, especially polishing pads having rough surfaces, and excellent shear strength at high temperatures, it is preferably used to fix a polishing pad 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 the Chemical-Mechanical-Polishing (CMP) process. 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 soft polishing pads made of polyurethane foam, etc., that is, polishing pads that have many voids on their surface and have a rough surface. [Effects of the Invention]

[0054] According to the present invention, it is possible to provide an adhesive tape that has high adhesive strength to rough surfaces and excellent shear strength at high temperatures. [Brief explanation of the drawing]

[0055] [Figure 1] This is a schematic diagram illustrating the method for measuring the shear strength (creep resistance test) of double-sided adhesive tapes obtained in the examples and comparative examples. [Modes for carrying out the invention]

[0056] 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.

[0057] (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.

[0058] 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.

[0059] (Preparation of (meth)acrylic copolymers B-J (living radical polymerization)) (meth)acrylic copolymers B to J were prepared in the same manner as (meth)acrylic copolymer A, except that the monomer composition, the amount of initiator, and the reaction time were changed as shown in Table 1.

[0060] [Table 1]

[0061] (Preparation of (meth)acrylic copolymer K (free radical constant-temperature polymerization)) A reactor equipped with a thermometer, stirrer, and condenser was prepared. A total of 100 g of the 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 was heated to a temperature of 60°C. Subsequently, 0.05 g of the chain transfer agent lauryl mercaptan (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 K.

[0062] (Preparation of (meth)acrylic copolymer L (free radical isothermal polymerization)) (meth)acrylic copolymer L was prepared in the same manner as (meth)acrylic copolymer K, except that the amount of initiator was changed as shown in Table 2.

[0063] [Table 2]

[0064] (Preparation of (meth)acrylic copolymer M (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 100 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, 0.04 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, a 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 M.

[0065] (Preparation of (meth)acrylic copolymer N (free radical boiling point polymerization)) (meth)acrylic copolymer N was prepared in the same manner as (meth)acrylic copolymer M, except that the monomer composition and the amount of solvent were changed as shown in Table 3.

[0066] [Table 3]

[0067] (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.

[0068] A polyethylene terephthalate film with one side treated for release was prepared. The adhesive solution obtained above was applied to the release-treated side 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, thereby producing a laminated sheet with an adhesive layer on the release-treated side of the polyethylene terephthalate film. Another laminated sheet was prepared in the same manner, resulting in a total of two of the above laminated sheets. 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, thereby transferring and integrating the adhesive layer with the base material. The other laminated sheet was then laminated onto the other side of the base material, with the adhesive layer facing outwards, thereby transferring and integrating the adhesive layer with the base material. As a result, a double-sided adhesive tape was obtained in which adhesive layers with a thickness of 80 μm were provided on both sides of the base material.

[0069] (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

[0070] Table 4 shows the proportion of molecules with a molecular weight of 150,000 or less, the proportion of molecules with a molecular weight of 500,000 or more, the peak of the molecular weight distribution (Mp), and the ratio (Mw / Mn) in the obtained molecular weight distribution.

[0071] (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%.

[0072] (Examples 2-10, Comparative Examples 1-5) 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.

[0073] <Rating> The double-sided adhesive tapes obtained in the examples and comparative examples were evaluated as follows. The results are shown in Table 4.

[0074] (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%.

[0075] Double-sided adhesive tape was cut into 25mm wide strips to prepare test specimens. The release PET film on one side of the test specimen was peeled off to expose the adhesive layer. 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 at a speed of 300mm / min for one pass, bonding the test specimen 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 sample 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°.

[0076] (2) Measurement of shear strength (creep resistance test) Figure 1 shows a schematic diagram illustrating the method for measuring the shear strength (creep resistance test) of the double-sided adhesive tapes obtained in the examples and comparative examples. 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.

[0077] (3) Overall evaluation If the adhesive force to the polishing pad measured in (1) above was 50 N / 25 mm or more, and the cohesive force displacement value measured in (2) above was 50 μm or less, it was marked as ○. If neither condition was met, it was marked as ×.

[0078] [Table 4] [Industrial applicability]

[0079] According to the present invention, it is possible to provide an adhesive tape that has high adhesive strength to rough surfaces and excellent shear strength at high temperatures. [Explanation of Symbols]

[0080] 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 (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. When GPC measurement was performed on the sol component of the adhesive layer using differential refractometer RI detection, it was found that in the region of molecular weight 5000 or more, the proportion of molecules with a molecular weight of 150,000 or less was 5% to 20%, and the proportion of molecules with a molecular weight of 500,000 or more was 1% to 20%. An adhesive tape characterized by the following features.

2. The adhesive tape according to claim 1, 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 150,000 or more and 400,000 or less.

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 using differential refractometer RI detection, the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) is 2.5 or less in the region of molecular weight of 5000 or more.

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

5. 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 60 parts by weight or lower per 100 parts by weight of the (meth)acrylic copolymer.

6. 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.

7. 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.

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

9. 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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