Double-sided adhesive tape

Abstract

To provide a double-sided adhesive tape that has excellent shock absorbency across a wide temperature range, in particular in a low temperature range.SOLUTION: This double-sided adhesive tape has an adhesive layer on both surface sides of a base material layer, where the storage modulus E' of the entire double-sided adhesive tape, when measured at a frequency of 1 Hz at -25°C to 120°C, is within the range of 1.0×105 Pa-1.0×108 Pa.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a double-sided adhesive tape.

Background Art

[0002] When an impact is applied to a device with a display, such as by dropping, there is a problem that the display screen may crack.

[0003] Therefore, for the purpose of absorbing such an impact, the adoption of a double-sided adhesive tape having excellent shock absorbency has been proposed (for example, Patent Document 1).

[0004] However, in all of a wide temperature range, particularly in a low temperature region, there is a problem that the shock absorbency of a conventional shock-absorbing adhesive tape decreases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a double-sided adhesive tape having excellent shock absorbency in all of a wide temperature range, particularly in a low temperature region.

Means for Solving the Problems

[0007] The double-sided adhesive tape of the present invention is a double-sided adhesive tape having adhesive layers on both sides of a base material layer, wherein a storage elastic modulus E' measured at a frequency of 1 Hz at -25°C to 120°C for the entire double-sided adhesive tape is in the range of 1.0×10 5 Pa to 1.0×10 8 Pa.

[0008] In one embodiment, the storage elastic modulus E' of the base material layer measured at a frequency of 1 Hz at -25°C to 120°C is 1.0×10 5 Pa to 1.0×10 8 Pa.

[0009] In one embodiment, the maximum value of the storage elastic modulus G' of the pressure-sensitive adhesive layer measured at a frequency of 1 Hz at -25°C to 120°C is 1.0×10 10 Pa or less.

[0010] In one embodiment, the adhesive force of the pressure-sensitive adhesive layer to the SUS plate at 23°C, 50% RH, at a tensile speed of 300 mm / min and a 180-degree peel is 5 N / 20 mm or more.

[0011] In one embodiment, the base material layer contains at least one polar functional group-containing polymer selected from condensation polymers and polyaddition polymers.

[0012] In one embodiment, the polar functional group-containing polymer is at least one selected from polyamide, polyurethane, and polyurea.

[0013] In one embodiment, the polar functional group-containing polymer has at least one selected from an ether bond and an ester bond.

[0014] In one embodiment, the pressure-sensitive adhesive layer contains at least one selected from acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, and urethane pressure-sensitive adhesives.

[0015] In one embodiment, the adhesive tape of the present invention is an impact-absorbing tape for displays.

Advantages of the Invention

[0016] According to the present invention, it is possible to provide a double-sided adhesive tape that is excellent in shock absorption in all wide temperature ranges, particularly in a low temperature range.

Brief Description of the Drawings

[0017]

Figure 1

Embodiments for Carrying Out the Invention

[0018] ≪≪Double-sided Adhesive Tape≫≫ The double-sided adhesive tape according to an embodiment of the present invention is an adhesive tape having adhesive layers on both sides of a base material layer. That is, the double-sided adhesive tape 1000 according to an embodiment of the present invention is a double-sided adhesive tape having adhesive layers 200a and 200b on both sides of the base material layer 100 as shown in FIG. 1.

[0019] The adhesive layer 200a and the adhesive layer 200b may be adhesive layers having the same composition as each other, or may be adhesive layers having different compositions.

[0020] The adhesive layer 200a and the adhesive layer 200b may have the same thickness as each other, or may have different thicknesses.

[0021] The base material layer may be one layer, or may be two or more layers. The base material layer is preferably one layer in terms of being able to more effectively exhibit the effects of the present invention.

[0022] The adhesive layer may be one layer, or may be two or more layers. The adhesive layer is preferably one layer in terms of being able to more effectively exhibit the effects of the present invention.

[0023] The double-sided adhesive tape according to an embodiment of the present invention may have any other appropriate layer other than the base material layer and the adhesive layer as long as the effects of the present invention are not impaired.

[0024] The double-sided adhesive tape according to an embodiment of the present invention may be provided with any appropriate release liner on the surface of the base material layer of the adhesive layer on the opposite side for protection until use.

[0025] Examples of the release liner include a release liner in which the surface of a base material (liner base material) such as paper or a plastic film is silicone-treated, and a release liner in which the surface of a base material (liner base material) such as paper or a plastic film is laminated with a polyolefin resin. Examples of the plastic film as the liner base material include a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

[0026] The thickness of the release liner is preferably 1 μm to 500 μm, more preferably 3 μm to 450 μm, still more preferably 5 μm to 400 μm, and particularly preferably 10 μm to 300 μm.

[0027] The release liner is preferably subjected to a release treatment on at least one surface. As the release treatment, any appropriate release treatment can be adopted as long as the effects of the present invention are not impaired.

[0028] The total thickness d of the double-sided adhesive tape according to an embodiment of the present invention is preferably 1 μm to 500 μm, more preferably 5 μm to 450 μm, still more preferably 10 μm to 400 μm, particularly preferably 15 μm to 350 μm, and most preferably 30 μm to 300 μm. If the total thickness d of the double-sided adhesive tape according to an embodiment of the present invention is within the above range, the effects of the present invention can be more exhibited.

[0029] The double-sided adhesive tape according to an embodiment of the present invention has a storage elastic modulus E' measured at a frequency of 1 Hz over the range of -25°C to 120°C for the entire double-sided adhesive tape, which is in the range of 1.0×10 5 Pa to 1.0×10 8 Pa. The above storage elastic modulus E' is preferably in the range of 3.0×10 5 Pa to 1.0×10 8 Pa, more preferably in the range of 5×10 5 Pa to 1.0×10 8 Pa, even more preferably in the range of 8.0×10 5 Pa to 9.9×10 7 Pa, and particularly preferably in the range of 1.0×10 6 Pa to 9.85×10 7 Pa. If the storage elastic modulus E' of the entire double-sided adhesive tape is within the above range, it is possible to provide a double-sided adhesive tape that is excellent in shock absorption in all temperature ranges, particularly in the low-temperature region.

[0030] The double-sided adhesive tape according to an embodiment of the present invention has a storage elastic modulus E' measured at a frequency of 1 Hz at -25°C for the entire double-sided adhesive tape, which is preferably 1.0×10 8 Pa or less, more preferably 9.9×10 7 Pa or less, even more preferably 9.75×10 7 Pa or less, and particularly preferably 9.6×10 7 Pa or less. The lower limit value of the storage elastic modulus E' measured at a frequency of 1 Hz at -25°C is preferably 5.0×10 6 Pa or more. If the storage elastic modulus E' of the entire double-sided adhesive tape measured at a frequency of 1 Hz at -25°C is within the above range, it is possible to provide a double-sided adhesive tape that is even more excellent in shock absorption in all temperature ranges, particularly in the low-temperature region.

[0031] The double-sided adhesive tape according to an embodiment of the present invention has a storage elastic modulus E' measured at a frequency of 1 Hz at 23°C for the entire double-sided adhesive tape, which is preferably 1.0×10 8 Pa or less, more preferably 3.0×106 is less than Pa, more preferably 2.5×10 6 is less than Pa, particularly preferably 2.3×10 6 is less than Pa. The lower limit value of the storage elastic modulus E' measured at a frequency of 1 Hz at 23°C is preferably 5.0×10 5 Pa or more. If the storage elastic modulus E' of the entire double-sided adhesive tape measured at a frequency of 1 Hz at 23°C is within the above range, a double-sided adhesive tape with excellent shock absorbency can be provided over the entire wide temperature range, particularly in the low temperature region.

[0032] For the double-sided adhesive tape according to an embodiment of the present invention, the storage elastic modulus E' of the entire double-sided adhesive tape measured at a frequency of 1 Hz at 80°C is preferably 1.0×10 8 is less than Pa, more preferably 3.0×10 6 is less than Pa, still more preferably 2.9×10 6 is less than Pa. The lower limit value of the storage elastic modulus E' measured at a frequency of 1 Hz at 80°C is preferably 5.0×10 5 Pa or more. If the storage elastic modulus E' of the entire double-sided adhesive tape measured at a frequency of 1 Hz at 80°C is within the above range, a double-sided adhesive tape with excellent shock absorbency can be provided over the entire wide temperature range, particularly in the low temperature region.

[0033] The double-sided adhesive tape according to an embodiment of the present invention has a ratio of the storage elastic modulus E' measured at -25°C and a frequency of 1 Hz to the storage elastic modulus E' measured at 80°C and a frequency of 1 Hz (storage elastic modulus E'(-25°C) / storage elastic modulus E'(80°C)) of preferably 40.0 or less, more preferably 35.0 or less, still more preferably 30.0 or less, and particularly preferably 18.0 or less for the entire double-sided adhesive tape. The lower limit of the above ratio (storage elastic modulus E'(-25°C) / storage elastic modulus E'(80°C)) is preferably 1.0 or more. If the ratio of the storage elastic modulus E' measured at -25°C and a frequency of 1 Hz to the storage elastic modulus E' measured at 80°C and a frequency of 1 Hz (storage elastic modulus E'(-25°C) / storage elastic modulus E'(80°C)) for the entire double-sided adhesive tape is within the above range, it is possible to provide a double-sided adhesive tape that is particularly excellent in shock absorption in all temperature ranges, particularly in the low temperature range.

[0034] The double-sided adhesive tape according to an embodiment of the present invention has a storage elastic modulus E' measured at -25°C to 120°C and a frequency of 1 Hz for the base material layer, preferably in the range of 1.0×10 5 Pa to 1.0×10 8 Pa, more preferably in the range of 3.0×10 5 Pa to 8.0×10 7 Pa, still more preferably in the range of 5.0×10 5 Pa to 5.0×10 7 Pa, and particularly preferably in the range of 1.0×10 6 Pa to 2.0×10 7 Pa. If the storage elastic modulus E' of the base material layer is within the above range, it is possible to provide a double-sided adhesive tape that is particularly excellent in shock absorption in all temperature ranges, particularly in the low temperature range.

[0035] The double-sided adhesive tape according to an embodiment of the present invention has a maximum value of the storage elastic modulus G' measured at -25°C to 120°C and a frequency of 1 Hz for the adhesive layer, preferably 1.0×10 10 Pa or less, more preferably 1.0×10 2 Pa to 5.0×10 9within the range of Pa, more preferably 5.0×10 2 Pa to 1.0×10 9 Pa, and particularly preferably 1.0×10 3 Pa to 7.0×10 8 Pa. If the maximum value of the storage elastic modulus G' of the adhesive layer is within the above range, a double-sided adhesive tape with excellent shock absorption can be provided in all temperature ranges, particularly in the low-temperature range.

[0036] The double-sided adhesive tape according to an embodiment of the present invention has an adhesive force of the adhesive layer to the SUS plate at 23°C, 50% RH, a tensile speed of 300 mm / min, and a 180-degree peel, preferably 5 N / 20 mm or more, more preferably 5 N / 20 mm to 100 N / 20 mm, still more preferably 5 N / 20 mm to 50 N / 20 mm, particularly preferably 5 N / 20 mm to 30 N / 20 mm, and most preferably 5 N / 20 mm to 20 N / 20 mm. If the adhesive force of the adhesive layer to the SUS plate at 23°C, 50% RH, a tensile speed of 300 mm / min, and a 180-degree peel is within the above range, a double-sided adhesive tape with excellent shock absorption can be provided in all temperature ranges, particularly in the low-temperature range.

[0037] ≪Base material layer≫ The thickness of the base material layer is preferably 1 μm to 500 μm, more preferably 2 μm to 400 μm, still more preferably 3 μm to 300 μm, and particularly preferably 5 μm to 200 μm. If the thickness of the base material layer is within the above range, a double-sided adhesive tape with excellent shock absorption can be provided in all temperature ranges, particularly in the low-temperature range.

[0038] As the material of the base material layer, any appropriate material can be adopted as long as the effects of the present invention are not impaired. Such materials preferably include at least one polar functional group-containing polymer selected from condensation polymers and polyaddition polymers. That is, the base material layer preferably includes at least one polar functional group-containing polymer selected from condensation polymers and polyaddition polymers.

[0039] The content ratio of at least one polar functional group-containing polymer selected from condensation polymers and polyaddition polymers in the base material layer is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, still more preferably 90% by weight to 100% by weight, particularly preferably 95% by weight to 100% by weight, and most preferably 98% by weight to 100% by weight in terms of more effectively expressing the effects of the present invention.

[0040] At least one polar functional group-containing polymer selected from condensation polymers and polyaddition polymers has a polar functional group such as a carbonyl group in the polymer main chain, and intermolecular forces stronger than those of radical polymerization-based polymers act, and it can have a network structure that does not depend on covalent bonds. Polymers having many network structures depending on covalent bonds may have too high elasticity and may reduce the unevenness followability. In condensation polymers and polyaddition polymers having a network structure that does not depend on covalent bonds, the intermolecular force due to polar functional groups is weaker than the intermolecular force generated by covalent bonds, and stress can be easily relaxed by deformation or the like even with a smaller energy (energy such as work done by stress, etc.). After relaxation, intermolecular forces act again between polar functional groups (for example, the combination of polar functional groups that generate intermolecular forces changes), and in all of a wide temperature range, particularly in the low temperature region, a double-sided adhesive tape with excellent shock absorbability can be provided.

[0041] The polar functional group-containing polymer is preferably at least one selected from polyamides, polyurethanes, and polyureas. Polymers containing hydrogen-bonding polar functional groups such as polyamides, polyurethanes, and polyureas (more precisely, hydrogen-bonding polar functional groups having hydrogen donor properties) have intermolecular forces that can be broken with energy about 1 / 10 of that of covalent bonds (the combination of hydrogen-bonding functional groups that generate intermolecular forces changes), and can be effectively broken by the thermal energy given at about room temperature or the energy generated by the work done by stress generated by bending or the like. Therefore, a double-sided adhesive tape with excellent shock absorbency can be provided over the entire wide temperature range, particularly in the low temperature region.

[0042] The base material layer more preferably contains a polar functional group-containing polymer that is a polyaddition polymer. In polyaddition polymers, monomers having various functional groups can be adopted, and the operation of converting from monomers to polymers is easy, and by taking advantage of these characteristics, various properties can be imparted to the polyaddition polymer.

[0043] The polar functional group-containing polymer that is a polyaddition polymer may have at least one selected from ether bonds and ester bonds. An ether bond can be introduced by adopting a monomer having an ether bond when obtaining a polyaddition polymer. An ester bond can be introduced by adopting a monomer having an ester bond when obtaining a polyaddition polymer. For example, when polyurethane is adopted as the polar functional group-containing polymer, examples of the polyurethane having an ether bond include ether-based polyurethanes. Examples of the polyurethane having an ester bond include ester-based polyurethanes.

[0044] Examples of ether-based polyurethanes include urethane acrylate resins. For example, a urethane acrylate resin can be prepared by polymerizing a precursor containing a polyether segment, a (meth)acrylic segment, and a urethane segment to form an oligomer under conditions where the molecular weight can be controlled. Then, various additives are added to this to prepare a coating composition for forming a resin film. This is applied onto a support substrate and crosslinked to obtain a urethane acrylate resin film on the support substrate. More specifically, a urethane acrylate oligomer can be prepared by pre-polymerizing a polyether polyol, a compound containing an isocyanate group, and a hydroxyalkyl (meth)acrylate, or an acrylic-modified polyether polyol and a compound containing an isocyanate group. Appropriate additives are then added thereto to form a coating composition for forming a resin film. This is applied onto a support substrate and crosslinked to obtain a urethane acrylate resin film on the support substrate.

[0045] Examples of polyether polyols include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and various derivatives thereof.

[0046] Examples of hydroxyalkyl (meth)acrylates include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0047] Examples of the compound containing an isocyanate group include a resin containing an isocyanate group, an oligomer containing an isocyanate group, and a monomer containing an isocyanate group. Examples of the compound containing an isocyanate group include (poly) isocyanates such as methylene bis-4-cyclohexyl isocyanate, trimethylolpropane adduct of tolylene diisocyanate, trimethylolpropane adduct of hexamethylene diisocyanate, trimethylolpropane adduct of isophorone diisocyanate, isocyanurate of tolylene diisocyanate, isocyanurate of hexamethylene diisocyanate, biuret of hexamethylene isocyanate, and blocked products of these isocyanates.

[0048] Examples of the ester-based polyurethane include adipate-based (ester-based) polyurethane, polycaprolactone-based (ester-based) polyurethane, and the like.

[0049] When a monomer having an ether bond is employed to obtain the polyaddition polymer, the elasticity of the polyaddition polymer can be weakened and molecular flexibility can be imparted. When a monomer having an ester bond is employed to obtain the polyaddition polymer, rigidity can be imparted to the polyaddition polymer. Therefore, for example, by appropriately combining a monomer having an ether bond and a monomer having an ester bond, or by employing them alone when obtaining the polyaddition polymer, the elasticity and rigidity of the polyaddition polymer can be adjusted, and a double-sided adhesive tape having excellent shock absorbency in all temperature ranges, particularly in the low temperature range, can be provided.

[0050] When using polyurethane (preferably ether-based polyurethane or ester-based polyurethane) as the polar functional group-containing polymer, a hydroxyl group-containing monomer may be employed when obtaining the polyurethane. When a hydroxyl group-containing monomer is used in obtaining the polyurethane, the isocyanate monomer and the hydroxyl group-containing monomer used in the polyaddition reaction for obtaining the polyurethane can react to introduce a covalent network structure. Further, the hydroxyl group-containing monomer can be imparted all at once as a raw material of the polyurethane, and the labor such as imparting after preparing the raw materials of the polyurethane can be simplified.

[0051] As the polar functional group-containing polymer, polyurethane (preferably ether-based polyurethane or ester-based polyurethane) is preferable in terms of being able to more effectively exhibit the effects of the present invention. Polyurethane is a polymer compound synthesized by subjecting a polyol (for example, diol) and a polyisocyanate (for example, diisocyanate) to a polyaddition reaction at a predetermined ratio.

[0052] Examples of the polyurethane (preferably ether-based polyurethane or ester-based polyurethane) include thermoplastic polyurethane (TPU) and thermosetting polyurethane. However, in all of a wide temperature range, particularly in the low temperature region, thermosetting polyurethane is preferable in terms of being able to provide a double-sided adhesive tape having excellent shock absorbency. In terms of being able to more effectively exhibit the effects of the present invention, the thermosetting polyurethane is preferably at least one selected from the group consisting of thermosetting ether-based polyurethane and thermosetting ester-based polyurethane, and more preferably at least one selected from the group consisting of thermosetting urethane acrylate resin and thermosetting polycaprolactone-based (ester-based) polyurethane resin.

[0053] Examples of polyols that can be used in the synthesis of polyurethanes include diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, polyoxytetramethylene glycol, diethylene glycol, polyethylene glycol, and polypropylene glycol; polyester polyols that are polycondensates of the above diols and dicarboxylic acids (e.g., adipic acid, azelaic acid, sebacic acid); carbonate diols such as polyalkylene carbonate diol; and the like. These may be used alone or in combination of two or more.

[0054] Examples of polyisocyanates that can be used in the synthesis of polyurethanes include aromatic, aliphatic, and alicyclic diisocyanates, and oligomers (e.g., dimers, trimers) of these diisocyanates. Examples of the above diisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, butane-1,4-diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and the like. These may be used alone or in combination of two or more.

[0055] In addition to polyols and polyisocyanates, other copolymerization components may be introduced into the polyurethane. Examples of other copolymerization components include monocarboxylic acids, dicarboxylic acids, polycarboxylic acids having three or more functional groups, hydroxycarboxylic acids, alkoxycarboxylic acids, and derivatives thereof. The other copolymerization component may be only one kind, or two or more kinds. The content ratio of the other copolymerization component is preferably less than 30% by weight, more preferably less than 10% by weight, and still more preferably less than 5% by weight in the polyurethane.

[0056] ≪Adhesive layer≫ The thickness of the adhesive layer is preferably 1 μm to 500 μm, more preferably 3 μm to 300 μm, still more preferably 5 μm to 200 μm, and particularly preferably 10 μm to 120 μm. When the thickness of the adhesive layer is within the above range, a double-sided adhesive tape excellent in shock absorbency can be provided in all temperature ranges, particularly in the low temperature region.

[0057] The adhesive layer contains a base polymer. The base polymer may be only one kind, or two or more kinds. The content ratio of the base polymer in the adhesive layer is preferably 30% by weight to 95% by weight, more preferably 40% by weight to 90% by weight, and still more preferably 50% by weight to 80% by weight in terms of more effectively expressing the effects of the present invention.

[0058] As the base polymer, at least one selected from acrylic polymers, rubber polymers, silicone polymers, and urethane polymers is preferably used in terms of more effectively expressing the effects of the present invention. That is, the adhesive layer preferably contains at least one selected from acrylic adhesives containing acrylic polymers, rubber adhesives containing rubber polymers, silicone adhesives containing silicone polymers, and urethane adhesives containing urethane polymers. Hereinafter, acrylic adhesives will be described in detail as representative examples.

[0059] <Acrylic adhesive> The acrylic pressure-sensitive adhesive contains an acrylic polymer as a base polymer. The acrylic pressure-sensitive adhesive may contain a tackifier resin. The acrylic pressure-sensitive adhesive may contain a crosslinking agent.

[0060] When the acrylic pressure-sensitive adhesive contains an acrylic polymer, a tackifier resin, and a crosslinking agent, the content ratio of the total amount of the acrylic polymer, the tackifier resin, and the crosslinking agent to the total amount of the acrylic pressure-sensitive adhesive is preferably 95% by weight or more, more preferably 97% by weight or more, and still more preferably 99% by weight or more in terms of more effectively expressing the effects of the present invention.

[0061] (Acrylic polymer) As the acrylic polymer, a polymer of a monomer component preferably contains an alkyl (meth) acrylate as a main monomer and may further contain a comonomer copolymerizable with the main monomer. Here, the main monomer refers to a component that occupies more than 50% by weight of the entire monomer component.

[0062] As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used. CH2=C(R 1 )COOR 2 (1)

[0063] Here, R 1 in the above formula (1) is a hydrogen atom or a methyl group, and R 2 is a linear alkyl group having 1 to 20 carbon atoms (hereinafter, such a carbon atom number range may be represented as "C1-20"). From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive layer, etc., R 2 is preferably a linear alkyl group of C1-14, more preferably a linear alkyl group of C2-10, and still more preferably a linear alkyl group of C4-8. Here, "linear" means including linear and branched.

[0064] R 2Examples of the alkyl (meth)acrylate in which the alkyl group is a C1-20 chain alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate and the like. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0065] As the alkyl (meth)acrylate, n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) are preferably exemplified in terms of more effectively exhibiting the effects of the present invention.

[0066] The content ratio of alkyl (meth)acrylate in all monomer components used for the synthesis of the acrylic polymer is preferably 55% by weight or more, more preferably 60% by weight or more, still more preferably 65% by weight or more, still more preferably 70% by weight or more, particularly preferably 85% by weight or more, and most preferably 90% by weight or more, in terms of more effectively expressing the effects of the present invention. The upper limit of the content ratio of alkyl (meth)acrylate is preferably 99.5% by weight or less, and more preferably 99% by weight or less. However, the acrylic polymer may be substantially obtained by polymerizing only alkyl (meth)acrylate.

[0067] R 2 When using an alkyl (meth)acrylate in which R is a C4-8 linear alkyl group, the ratio of the alkyl (meth)acrylate in which R 2 is a C4-8 linear alkyl group among the alkyl (meth)acrylates contained in the monomer component is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more, particularly preferably 95% by weight or more, and most preferably 99% to 100% by weight, in terms of more effectively expressing the effects of the present invention.

[0068] As one embodiment (I) of the acrylic polymer, an acrylic polymer in which 80% by weight or more of all monomer components is n-butyl acrylate (BA) can be mentioned. In this case, the content ratio of n-butyl acrylate (BA) in all monomer components is preferably 82% to 99% by weight, preferably 85% to 98% by weight, still more preferably 87% to 97% by weight, particularly preferably 89% to 96% by weight, and most preferably 91% to 95% by weight, in terms of more effectively expressing the effects of the present invention.

[0069] As another embodiment (II) of the acrylic polymer, an acrylic polymer in which 50% by weight or more and less than 80% by weight of all monomer components is n-butyl acrylate (BA) can be mentioned. In this case, the content ratio of n-butyl acrylate (BA) in all monomer components is preferably 52% by weight to 80% by weight or less, more preferably 55% by weight to 80% by weight, still more preferably 60% by weight to 80% by weight, particularly preferably 63% by weight to 80% by weight, and most preferably 65% by weight to 80% by weight, in terms of being able to more effectively exhibit the effects of the present invention. In this embodiment, all monomer components may further contain 2-ethylhexyl acrylate (2EHA) in a proportion less than that of n-butyl acrylate (BA).

[0070] As another embodiment (III) of the acrylic polymer, an acrylic polymer in which less than 50% by weight of all monomer components is 2-ethylhexyl acrylate (2EHA) can be mentioned. In this case, the content ratio of 2-ethylhexyl acrylate (2EHA) in all monomer components is preferably more than 0% by weight and 48% by weight or less, more preferably 5% by weight to 45% by weight, still more preferably 10% by weight to 43% by weight, particularly preferably 15% by weight to 40% by weight, and most preferably 20% by weight to 35% by weight, in terms of being able to more effectively exhibit the effects of the present invention. All monomer components may further contain n-butyl acrylate (BA) in a proportion higher than that of 2-ethylhexyl acrylate (2EHA).

[0071] As another embodiment (IV) of the acrylic polymer, an acrylic polymer in which 50% by weight or more of all monomer components is n-butyl acrylate (BA) and less than 50% by weight of all monomer components is 2-ethylhexyl acrylate (2EHA) can be mentioned. In this case, the content ratio of n-butyl acrylate (BA) in all monomer components is preferably 52% by weight to 80% by weight or less, more preferably 55% by weight to 80% by weight, still more preferably 60% by weight to 80% by weight, particularly preferably 63% by weight to 80% by weight, and most preferably 65% by weight to 80% by weight in terms of more effectively expressing the effects of the present invention. Also, in this case, the content ratio of 2-ethylhexyl acrylate (2EHA) in all monomer components is preferably more than 0% by weight and 48% by weight or less, more preferably 5% by weight to 45% by weight, still more preferably 10% by weight to 43% by weight, particularly preferably 15% by weight to 40% by weight, and most preferably 20% by weight to 35% by weight in terms of more effectively expressing the effects of the present invention.

[0072] In the acrylic polymer, other monomers (A) may be copolymerized as long as the effects of the present invention are not impaired. The other monomers (A) may be only one type or two or more types. The other monomers (A) can be used, for example, for the purpose of adjusting the glass transition temperature (Tg) of the acrylic polymer, adjusting the adhesive performance, etc. Examples of the other monomers (A) that can improve the cohesive force and heat resistance of the adhesive include, for example, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl esters, aromatic vinyl compounds, etc., and vinyl esters are preferred. Specific examples of vinyl esters include, for example, vinyl acetate (VAc), vinyl propionate, vinyl laurate, etc., and vinyl acetate (VAc) is preferred.

[0073] The content ratio of other monomer (A) in all monomer components is preferably 0.001 wt% to 40 wt%, more preferably 0.01 wt% to 40 wt%, still more preferably 0.1 wt% to 20 wt%, particularly preferably 0.5 wt% to 10 wt%, and most preferably 1 wt% to 5 wt%.

[0074] In the acrylic polymer, other monomer (B) may be copolymerized as long as the effects of the present invention are not impaired. Other monomer (B) may be only one kind or two or more kinds. Other monomer (B) is a monomer that can introduce a functional group that can be a crosslinking base point into the acrylic polymer or can contribute to the improvement of adhesion. For example, it includes a hydroxyl group (OH group) - containing monomer, a carboxy group - containing monomer, an acid anhydride group - containing monomer, an amide group - containing monomer, an amino group - containing monomer, an imide group - containing monomer, an epoxy group - containing monomer, (meth)acryloylmorpholine, vinyl ethers, and the like.

[0075] As one embodiment of the acrylic polymer, an acrylic polymer copolymerized with a carboxy group - containing monomer as other monomer (B) can be mentioned. Examples of the carboxy group - containing monomer include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like. Among these, in terms of being able to more express the effects of the present invention, as the carboxy group - containing monomer, preferably, acrylic acid (AA) and methacrylic acid (MAA) are mentioned, and more preferably, acrylic acid (AA) is used.

[0076] When a carboxyl group-containing monomer is adopted as the other monomer (B), the content ratio of the other monomer (B) in all the monomer components is preferably 0.1% by weight to 10% by weight, more preferably 0.2% by weight to 8% by weight, still more preferably 0.5% by weight to 5% by weight, particularly preferably 0.7% by weight to 4% by weight, and most preferably 1% by weight to 3% by weight in terms of more effectively expressing the effects of the present invention.

[0077] In the acrylic polymer, other monomers (C) may be copolymerized within a range that does not impair the effects of the present invention. The other monomers (C) may be only one kind or two or more kinds. Examples of the other monomers (C) include hydroxyl group-containing monomers. Examples of the hydroxyl group-containing monomers include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; polypropylene glycol mono (meth) acrylate; N-hydroxyethyl (meth) acrylamide; and the like. Among these, as the hydroxyl group-containing monomer, in terms of more effectively expressing the effects of the present invention, hydroxyalkyl (meth) acrylates in which the alkyl group is a straight chain having 2 to 4 carbon atoms are preferably included, and specifically, for example, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are included.

[0078] When a hydroxyl group-containing monomer is adopted as the other monomer (C), the content ratio of the other monomer (C) in all the monomer components is preferably 0.001% by weight to 10% by weight, more preferably 0.01% by weight to 5% by weight, still more preferably 0.02% by weight to 2% by weight, particularly preferably 0.03% by weight to 1% by weight, and most preferably 0.04% by weight to 0.5% by weight in terms of more effectively expressing the effects of the present invention.

[0079] The Tg of the base polymer can be, for example, -80°C or higher in terms of more effectively expressing the effects of the present invention. The base polymer (preferably an acrylic polymer) is designed such that its Tg is preferably -15°C or lower from the viewpoint of enhancing the deformability of the pressure-sensitive adhesive layer in the shear direction. In some embodiments, the Tg of the base polymer is, for example, preferably -25°C or lower, more preferably -40°C or lower, and even more preferably -50°C or lower. The Tg of the base polymer is designed such that, for example, the Tg is preferably -70°C or higher (more preferably -65°C or higher, even more preferably -60°C or higher) from the viewpoint of enhancing cohesion and shape recovery.

[0080] The Tg of the base polymer refers to a value obtained from Fox's equation based on the Tg of the homopolymer of each monomer constituting the base polymer and the weight fraction (copolymerization ratio based on weight) of the monomer. Fox's equation is a relational equation between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. 1 / Tg = Σ(Wi / Tgi)

[0081] In the above Fox's equation, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K). As the Tg of the homopolymer, the values described in known materials shall be adopted.

[0082] As the Tg of the homopolymer, for example, specifically, the following values can be used. 2-ethylhexyl acrylate -70°C n-butyl acrylate -55°C Acrylic acid 106°C 2-hydroxyethyl acrylate -15°C 4-hydroxybutyl acrylate -40°C

[0083] For the Tg of homopolymers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) can be used. When multiple numerical values are described in the above "Polymer Handbook", the conventional value is adopted. For monomers not described in the above "Polymer Handbook", the catalog values of the monomer manufacturing companies are adopted. As the Tg of the homopolymer of a monomer that is not described in the above "Polymer Handbook" and for which the catalog values of the monomer manufacturing companies are not provided either, the value obtained by the measurement method described in JP-A-2007-51271 shall be used.

[0084] As a method for obtaining an acrylic polymer, for example, various polymerization methods known as synthesis methods for acrylic polymers, such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, etc., can be appropriately adopted. Among these polymerization methods, the solution polymerization method can be preferably used. As the monomer supply method during solution polymerization, a batch charging method in which the total amount of the monomer components is supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc. can be appropriately adopted. The polymerization temperature can be appropriately selected according to the types of monomers and solvents used, the type of polymerization initiator, etc., and is preferably 20°C or higher, more preferably 30°C or higher, still more preferably 40°C or higher, preferably 170°C or lower, more preferably 160°C or lower, still more preferably 140°C or lower. As a method for obtaining an acrylic polymer, active energy ray irradiation polymerization such as photopolymerization performed by irradiating light such as UV (typically performed in the presence of a photopolymerization initiator) or radiation polymerization performed by irradiating radiation such as β-rays and γ-rays may be adopted.

[0085] The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from any suitable organic solvents. For example, aromatic compounds such as toluene (typically, aromatic hydrocarbons), acetate esters such as ethyl acetate, aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane, etc. can be mentioned.

[0086] The initiator (polymerization initiator) used for polymerization can be appropriately selected from any suitable polymerization initiator according to the type of polymerization method. The polymerization initiator may be only one kind or two or more kinds. Examples of such polymerization initiators include azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN); persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; and the like. Another example of the polymerization initiator includes a redox initiator formed by a combination of a peroxide and a reducing agent.

[0087] The amount of the polymerization initiator used is preferably 0.005 parts by weight to 1 part by weight, more preferably 0.01 parts by weight to 1 part by weight, based on 100 parts by weight of the total monomer components.

[0088] The Mw of the acrylic polymer is preferably 10×10 4 ~500×10 4 and more preferably 10×10 4 ~150×10 4 and even more preferably 20×10 4 ~75×10 4 and particularly preferably 35×10 4 ~65×10 4 Here, Mw refers to the value in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, the model name "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) can be used.

[0089] (tackifier resin) The acrylic-based pressure-sensitive adhesive may contain a tackifier resin in terms of more effectively exhibiting the effects of the present invention. Examples of the tackifier resin include rosin-based tackifier resins, terpene-based tackifier resins, hydrocarbon-based tackifier resins, epoxy-based tackifier resins, polyamide-based tackifier resins, elastomer-based tackifier resins, phenol-based tackifier resins, ketone-based tackifier resins, and the like. The tackifier resin may be only one type or two or more types.

[0090] In terms of more effectively exhibiting the effects of the present invention, the amount of the tackifier resin used is preferably 5 parts by weight to 70 parts by weight, more preferably 10 parts by weight to 60 parts by weight, still more preferably 15 parts by weight to 50 parts by weight, still more preferably 20 parts by weight to 45 parts by weight, particularly preferably 25 parts by weight to 40 parts by weight, based on 100 parts by weight of the base polymer.

[0091] In terms of more effectively exhibiting the effects of the present invention, the tackifier resin preferably contains a tackifier resin TL having a softening point of less than 105°C. The tackifier resin TL can effectively contribute to improving the deformability of the pressure-sensitive adhesive layer in the surface direction (shearing direction). From the viewpoint of obtaining a higher effect of improving deformability, the softening point of the tackifier resin used as the tackifier resin TL is preferably 50°C to 103°C, more preferably 60°C to 100°C, still more preferably 65°C to 95°C, particularly preferably 70°C to 90°C, and most preferably 75°C to 85°C.

[0092] The softening point of the tackifying resin is defined as the value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at a low temperature and carefully filled into a ring placed on a flat metal plate, taking care not to form bubbles. After it has cooled, the raised part including the upper end of the ring is cut off with a slightly heated small knife. Next, a support (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured until the depth is 90 mm or more. Then, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin so as not to touch each other, and the temperature of the glycerin is maintained at 20 °C plus or minus 5 °C for 15 minutes. Next, the steel ball is placed on the center of the surface of the sample in the ring and placed at a fixed position on the support. Next, the distance from the upper end of the ring to the glycerin surface is maintained at 50 mm, a thermometer is placed, the center position of the mercury bulb of the thermometer is set at the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating should hit the middle between the center and the edge of the bottom of the container to ensure even heating. Note that the rate of increase in the bath temperature after reaching 40 °C since the start of heating must be 5.0 plus or minus 0.5 °C per minute. The temperature is read when the sample gradually softens and flows out of the ring and finally touches the bottom plate, and this is taken as the softening point. The softening point is measured for two or more samples simultaneously, and the average value is adopted.

[0093] As the amount of the tackifying resin TL used, in terms of more effectively expressing the effects of the present invention, it is preferably 5 to 50 parts by weight, more preferably 10 to 45 parts by weight, still more preferably 15 to 40 parts by weight, particularly preferably 20 to 35 parts by weight, and most preferably 25 to 32 parts by weight with respect to 100 parts by weight of the base polymer.

[0094] As the tackifying resin TL, one or more selected appropriately from among the tackifying resins exemplified above with a softening point of less than 105 °C can be adopted. The tackifying resin TL preferably contains a rosin-based resin.

[0095] Examples of rosin-based resins that can preferably be adopted as the tackifier resin TL include rosin esters such as unmodified rosin esters and modified rosin esters. Examples of the modified rosin ester include hydrogenated rosin ester.

[0096] The tackifier resin TL preferably contains a hydrogenated rosin ester in that the effects of the present invention can be more effectively exhibited. The softening point of the hydrogenated rosin ester is preferably less than 105°C, more preferably 50°C to 100°C, still more preferably 60°C to 90°C, particularly preferably 70°C to 85°C, and most preferably 75°C to 85°C in that the effects of the present invention can be more effectively exhibited.

[0097] The tackifier resin TL may contain a non-hydrogenated rosin ester. Here, the non-hydrogenated rosin ester is a concept comprehensively referring to those other than the hydrogenated rosin ester among the above-mentioned rosin esters. Examples of the non-hydrogenated rosin ester include unmodified rosin ester, disproportionated rosin ester, polymerized rosin ester, and the like.

[0098] The softening point of the non-hydrogenated rosin ester is preferably less than 105°C, more preferably 50°C to 100°C, still more preferably 60°C to 90°C, particularly preferably 70°C to 85°C, and most preferably 75°C to 85°C in that the effects of the present invention can be more effectively exhibited.

[0099] In addition to the rosin-based resin, the tackifier resin TL may contain other tackifier resins. As the other tackifier resins, one or more kinds appropriately selected from those having a softening point of less than 105°C among the tackifier resins exemplified above can be adopted. For example, the tackifier resin TL may contain a rosin-based resin and a terpene resin.

[0100] The content ratio of the rosin-based resin in the tackifying resin TL to the whole is preferably more than 50% by weight, more preferably 55% to 100% by weight, still more preferably 60% to 99% by weight, particularly preferably 65% to 97% by weight, and most preferably 75% to 97% by weight, in terms of being able to more effectively exhibit the effects of the present invention.

[0101] In terms of being able to more effectively exhibit the effects of the present invention, the tackifying resin may contain a combination of the tackifying resin TL and a tackifying resin TH having a softening point of 105°C or higher (preferably 105°C to 170°C).

[0102] As the tackifying resin TH, one or more types appropriately selected from those of the tackifying resins exemplified above having a softening point of 105°C or higher can be employed. The tackifying resin TH may contain at least one selected from rosin-based tackifying resins (for example, rosin esters) and terpene-based tackifying resins (for example, terpene phenol resins).

[0103] (Crosslinking agent) The acrylic adhesive can contain a crosslinking agent. The crosslinking agent may be only one type or two or more types. By using the crosslinking agent, appropriate cohesive force can be imparted to the acrylic adhesive. The crosslinking agent can also help to adjust the displacement distance and return distance in the holding force test. The acrylic adhesive containing the crosslinking agent can be obtained, for example, by forming an adhesive layer using an adhesive composition containing the crosslinking agent. The crosslinking agent can be contained in the acrylic adhesive in the form after the crosslinking reaction, the form before the crosslinking reaction, a partially crosslinked form, an intermediate or composite form thereof, etc. Typically, the crosslinking agent is contained in the acrylic adhesive mainly in the form after the crosslinking reaction.

[0104] The amount of the crosslinking agent used is preferably 0.005 parts by weight to 10 parts by weight, more preferably 0.01 parts by weight to 7 parts by weight, still more preferably 0.05 parts by weight to 5 parts by weight, particularly preferably 0.1 parts by weight to 4 parts by weight, and most preferably 1 part by weight to 3 parts by weight, per 100 parts by weight of the base polymer, in terms of more effectively expressing the effects of the present invention.

[0105] Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, metal chelate-based crosslinking agents, peroxides and other crosslinking agents. In terms of more effectively expressing the effects of the present invention, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred, and isocyanate-based crosslinking agents are more preferred.

[0106] As the isocyanate-based crosslinking agent, a compound having two or more isocyanate groups (including isocyanate regenerable functional groups in which the isocyanate group is temporarily protected by a blocking agent or oligomerization, etc.) in one molecule can be used. Examples of the isocyanate-based crosslinking agent include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate; and the like.

[0107] As the isocyanate crosslinking agent, more specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl isocyanate; trimethylolpropane / tolylene diisocyanate trimer adducts (for example, manufactured by Tosoh Corporation, trade name: Coronate L), trimethylolpropane / hexamethylene diisocyanate trimer adducts (for example, manufactured by Tosoh Corporation, trade name: Coronate HL), isocyanurate bodies of hexamethylene diisocyanate (for example, manufactured by Tosoh Corporation, trade name: Coronate HX), etc. isocyanate adducts; trimethylolpropane adducts of xylylene diisocyanate (for example, manufactured by Mitsui Chemicals, Inc., trade name: Takenate D110N), trimethylolpropane adducts of xylylene diisocyanate (for example, manufactured by Mitsui Chemicals, Inc., trade name: Takenate D120N), trimethylolpropane adducts of isophorone diisocyanate (for example, manufactured by Mitsui Chemicals, Inc., trade name: Takenate D140N), trimethylolpropane adducts of hexamethylene diisocyanate (for example, manufactured by Mitsui Chemicals, Inc., trade name: Takenate D160N); polyether polyisocyanates, polyester polyisocyanates, and adducts thereof with various polyols; polyisocyanates polyfunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc.; and the like. Among these, aromatic isocyanates and alicyclic isocyanates are preferred in terms of being able to achieve a good balance between deformability and cohesive force.

[0108] The amount of the isocyanate crosslinking agent used is preferably 0.005 parts by weight to 10 parts by weight, more preferably 0.01 parts by weight to 7 parts by weight, still more preferably 0.05 parts by weight to 5 parts by weight, particularly preferably 0.1 parts by weight to 4 parts by weight, and most preferably 1 part by weight to 3 parts by weight, based on 100 parts by weight of the base polymer, in terms of more effectively expressing the effects of the present invention.

[0109] When the monomer component constituting the acrylic polymer contains a hydroxyl group-containing monomer, in terms of being able to more effectively exhibit the effects of the present invention, the weight ratio of the isocyanate-based crosslinking agent to the hydroxyl group-containing monomer is preferably more than 20 and less than 50, more preferably 22 to 45, still more preferably 25 to 40, particularly preferably 27 to 40, and most preferably 30 to 35.

[0110] When the acrylic pressure-sensitive adhesive contains the tackifier resin TL having a softening point of 105°C or lower, in terms of being able to more effectively exhibit the effects of the present invention, the weight ratio of the tackifier resin TL to the isocyanate-based crosslinking agent is preferably more than 2 and less than 15, more preferably 5 to 13, still more preferably 7 to 12, and particularly preferably 7 to 11.

[0111] As the epoxy crosslinking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule can be used. Examples of the epoxy crosslinking agent include N,N,N’,N’-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcin diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Commercially available products of the epoxy crosslinking agent include, for example, products named "Tetrad C", "Tetrad X", etc. manufactured by Mitsubishi Gas Chemical Company, Inc.

[0112] The amount of the epoxy crosslinking agent used is preferably 0.005 parts by weight to 10 parts by weight, more preferably 0.01 parts by weight to 5 parts by weight, still more preferably 0.015 parts by weight to 1 part by weight, still more preferably 0.015 parts by weight to 0.5 part by weight, particularly preferably 0.015 parts by weight to 0.3 part by weight, and most preferably 0.15 parts by weight to 0.3 part by weight, in terms of more effectively expressing the effects of the present invention, based on 100 parts by weight of the base polymer.

[0113] (Other components) The acrylic adhesive may contain various common additives in the field of adhesives, such as colorants (pigments, dyes, etc.), leveling agents, crosslinking aids, plasticizers, softeners, fillers, antistatic agents, antioxidants, ultraviolet absorbers, antioxidants, light stabilizers, etc., as necessary. For such various additives, conventionally known ones can be used by conventional methods.

[0114] When a colorant (pigment, dye, etc.) is employed as other components, the amount used is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, still more preferably 0.05 to 1 part by weight, and particularly preferably 0.1 to 1 part by weight, based on 100 parts by weight of the base polymer.

[0115] ≪≪Applications≫≫ The double-sided adhesive tape according to the embodiment of the present invention is excellent in shock absorption in all wide temperature ranges, particularly in the low-temperature region. Taking advantage of this feature, the double-sided adhesive tape according to the embodiment of the present invention can be used, for example, as a shock-absorbing tape for displays.

Examples

[0116] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited thereto in any way. In the following description, "parts" and "%" are based on weight unless otherwise specified.

[0117] <Measurement of the storage elastic modulus E' of the entire double-sided adhesive tape> Using RSA-G2 (TA Instruments Japan Co., Ltd.) as a dynamic viscoelasticity measuring device, a sample with a sheet width of 10 mm was placed on the measuring device tensile jig at a measurement interval of 20 mm, and the measuring environment oven was changed to the measurement start temperature. After confirming that the temperature of the measurement environment was stable, the temperature was raised at a rate of 5 °C / min from the lower limit temperature of the temperature in the predetermined temperature range of the measurement. The frequency during measurement was 1 Hz, tensile deformation was applied, and the generated stress was calculated as the storage elastic modulus E' while controlling the amount of deformation strain in the region where the sheet did not undergo permanent deformation.

[0118] <Measurement of the storage elastic modulus E' of the base material layer> Using an RSA-G2 (TA Instruments Japan Co., Ltd.) as a dynamic viscoelasticity measuring device, a sample with a sheet width of 10 mm was placed on the tensile jig of the measuring device at a measurement interval of 20 mm, and the measurement environment oven was changed to the measurement start temperature. After confirming that the temperature of the measurement environment was stable, the temperature was increased at a rate of 5 °C / min from the lower limit temperature of the temperature in the predetermined temperature range of the measurement. The frequency during measurement was 1 Hz to apply tensile deformation, and while controlling the amount of deformation strain in the region where the sheet did not undergo permanent deformation, the generated stress was calculated as the storage elastic modulus E'.

[0119] <Measurement of the storage elastic modulus G' of the adhesive layer> Using an ARES-G2 (TA Instruments Japan Co., Ltd.) as a dynamic viscoelasticity measuring device, a sample with a sheet thickness of 1 mm to 2 mm was placed on a predetermined measuring device jig, and the measurement environment oven was changed to the measurement start temperature. After confirming that the temperature of the measurement environment was stable, the temperature was increased at a rate of 5 °C / min from the lower limit temperature of the temperature in the predetermined temperature range of the measurement. The frequency during measurement was 1 Hz to apply shear deformation, and while controlling the amount of deformation strain in the region where the sheet did not undergo permanent deformation, the generated stress was calculated as the storage elastic modulus G'.

[0120] <Adhesive force> The adhesive force refers to the 180-degree peel strength (180-degree peel adhesion) to a stainless steel plate. The 180-degree peel strength is measured as follows: After attaching a single-sided adhesive tape (product name "No. 31B", manufactured by Nitto Denko Corporation, total thickness 50 μm) to the surface of one of the two adhesive layers of the adhesive sheet, the adhesive sheet is cut into a measurement sample with a width of 20 mm and a length of 100 mm. In an environment of 23°C and 50% RH, the adhesive surface of the above measurement sample is pressure-bonded to the surface of a stainless steel plate (SUS304BA plate) with a 2 kg roll for one round trip. After leaving this in the same environment for 30 minutes, using a universal tensile-compression testing machine, in accordance with JIS Z 0237:2000, under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees, the peel strength (N / 20 mm) is measured. As the universal tensile-compression testing machine, the product named "Autograph AG-10G type tensile testing machine" manufactured by Shimadzu Corporation was used.

[0121] <Impact absorbency> The impact absorbency is indicated by the pressure when an iron ball is dropped. A double-sided adhesive tape cut to 70 mm × 70 mm is placed centered on a stainless steel plate (SUS plate: 10 mm × 150 mm × 150 mm), and on top of that, a pressure measurement film (manufactured by Fuji Film Co., Ltd., Prescale (type MS)) of 70 mm × 70 mm is placed centered. Then, a stainless steel plate (SUS plate: 5 mm × 70 mm × 70 mm) is placed centered on top of that, and an iron ball (96 g) is dropped centered from a height of 40 cm. Next, the pressure measurement film is taken out, the image is captured with a pressure image analysis device scanner GT-F740 (manufactured by Fuji Film Co., Ltd.), and the pressure is analyzed with a Prescale pressure image analysis system FPD-8010J (manufactured by Fuji Film Co., Ltd.).

[0122] 〔Example 1〕 Into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a cooler, 68 parts of n-butyl acrylate (BA) as a monomer component, 29 parts of 2-ethylhexyl acrylate (2EHA), 3 parts of acrylic acid (AA), and 0.04 parts of 4-hydroxybutyl acrylate (4HBA) were charged, along with 0.07 parts of 2,2’-azobisisobutyronitrile (AIBN) as a polymerization initiator and 151 parts of toluene as a polymerization solvent. Solution polymerization was carried out at 65°C for 5 hours and then at 80°C for 2 hours to obtain a toluene solution of an acrylic polymer (A). The weight average molecular weight of this acrylic polymer (A) was 440,000. To 100 parts of the acrylic polymer (A) contained in the above toluene solution, 30 parts of a tackifier resin (hydrogenated rosin glycerin ester, trade name "Haritack SE10" manufactured by Harima Kasei Co., Ltd.) and 3 parts of an isocyanate-based crosslinking agent (trade name "Coronate L" manufactured by Tosoh Corporation) were added to prepare an adhesive composition (A). Two commercially available release liners (biaxially stretched polyester film-based release liner with a single-sided release treatment layer, thickness 50 μm, trade name "Diafoil MRF#50" manufactured by Mitsubishi Chemical Corporation) were prepared. The above adhesive composition (A) was applied to one surface (release surface) of each release liner so that the thickness after drying would be 50 μm, and dried at 120°C for 5 minutes. In this way, adhesive layers (first adhesive layer and second adhesive layer) with a thickness of 50 μm composed of an acrylic adhesive (A) corresponding to the adhesive composition (A) were formed on the release surfaces of the above two release liners, respectively. As a base material layer, a thermosetting polyurethane resin film with a thickness of 100 μm (a polycaprolactone-based (ester-based) polyurethane resin film with a thickness of 100 μm, 100% modulus = 1.8 MPa, manufactured by Toray Industries, Inc.) was prepared. The first adhesive layer and the second adhesive layer formed on the above two release liners were bonded to the first surface and the second surface of this base material layer. The above release liners were left as they were on the adhesive layers and used to protect the surfaces (adhesive surfaces) of the adhesive layers. The obtained structure was passed once through a laminator at 80°C (0.3 MPa, speed 0.5 m / min), and then aged in an oven at 50°C for 3 days. In this way, an adhesive tape (1) was obtained. The results are shown in Table 1.

[0123] [Example 2] Into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a cooler, 100 parts of n-butyl acrylate (BA) as a monomer component, 5 parts of vinyl acetate (VAc), 3 parts of acrylic acid (AA), and 0.1 part of 2-hydroxyethyl acrylate (HEA), 0.25 part of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 200 parts of toluene as a polymerization solvent were charged, and solution polymerization was carried out at 60 °C for 6 hours and then at 75 °C for 3 hours to obtain a toluene solution of an acrylic polymer (B). The weight average molecular weight of this acrylic polymer (B) was 550,000. To 100 parts of the acrylic polymer (B) contained in the above toluene solution, 10 parts of a tackifier resin (manufactured by Harima Kasei Co., Ltd., polymerized rosin ester, trade name "Haritack PCJ"), 10 parts of a tackifier resin (manufactured by Harima Kasei Co., Ltd., hydrogenated rosin glycerin ester, trade name "Haritack SE10"), 5 parts of a tackifier resin (manufactured by Rika Hercules Co., Ltd., trade name "Hercolyn D"), 15 parts of a phenol-modified rosin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "Sumilite PR12603N"), and 2 parts of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate L") were added to prepare an adhesive composition (B). Two commercially available release liners (manufactured by Mitsubishi Chemical Corporation, trade name "Diafoil MRF#50" (biaxially stretched polyester film-based release liner with a single-sided release treatment layer, thickness 50 μm)) were prepared. The adhesive composition (B) was applied to one surface (release surface) of each release liner so that the thickness after drying was 50 μm, and dried at 120 °C for 5 minutes. In this way, an adhesive layer (first adhesive layer and second adhesive layer) with a thickness of 50 μm composed of an acrylic adhesive (B) corresponding to the adhesive composition (B) was formed on the release surfaces of the above two release liners, respectively. As the base material layer, a thermosetting polyurethane resin film (manufactured by Toray Industries, Inc., a polycaprolactone-based (ester-based) polyurethane resin film with a thickness of 100 μm (100% modulus = 1.8 MPa)) was prepared. The first adhesive layer and the second adhesive layer formed on the two release liners were bonded to the first surface and the second surface of this base material layer. The release liner was left as it was on the adhesive layer and used to protect the surface (adhesive surface) of the adhesive layer. The obtained structure was passed once through a laminator at 80°C (0.3 MPa, speed 0.5 m / min), and then aged in an oven at 50°C for 3 days. In this way, an adhesive tape (2) was obtained. The results are shown in Table 1.

[0124] [Example 3] Into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a cooler, 100 parts of n-butyl acrylate (BA) as a monomer component, 3 parts of vinyl acetate (VAc), 2 parts of acrylic acid (AA), and 0.2 part of 2-hydroxyethyl acrylate (HEA) were charged, along with 0.25 part of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator and 200 parts of toluene as a polymerization solvent. Solution polymerization was carried out at 60°C for 6 hours and then at 75°C for 3 hours to obtain a toluene solution of an acrylic polymer (C). The weight average molecular weight of this acrylic polymer (C) was 600,000. To 100 parts of the acrylic polymer (C) contained in the toluene solution, 10 parts of an adhesion-imparting resin (manufactured by Harima Kasei Co., Ltd., polymerized rosin ester, trade name "Haritack PCJ"), 10 parts of an adhesion-imparting resin (manufactured by Harima Kasei Co., Ltd., hydrogenated rosin glycerin ester, trade name "Haritack SE10"), 5 parts of an adhesion-imparting resin (manufactured by Rika Hercules Co., Ltd., trade name "Hercorin D"), 15 parts of a phenol-modified rosin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "Sumilite PR12603N"), 2 parts of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate L"), and 0.2 part of a black pigment (manufactured by Dainichi Seika Kogyo Co., Ltd., "NAF-5091 Black") were added to prepare an adhesive composition (C). Two commercially available release liners (manufactured by Mitsubishi Chemical Corporation, product name "Diafoil MRF#50" (biaxially stretched polyester film-based release liner with a single-sided release treatment layer, thickness 50 μm)) were prepared. The above adhesive composition (C) was applied to one surface (release surface) of each release liner so that the thickness after drying would be 50 μm, and it was dried at 120°C for 5 minutes. In this way, adhesive layers (first adhesive layer and second adhesive layer) with a thickness of 50 μm composed of the acrylic-based adhesive (C) corresponding to the adhesive composition (C) were formed on the release surfaces of the above two release liners, respectively. Toluene: 50 parts, polytetramethylene glycol (manufactured by Mitsubishi Chemical Corporation, PTMG2000): 330 parts, hexamethylene diisocyanate: 50 parts, hexamethylene diisocyanate isocyanurate-modified type (manufactured by Mitsui Chemicals, Inc., Takenate (registered trademark) D-170N): 2 parts, dibutyltin laurate: 0.02 parts, hydroquinone monomethyl ether: 0.02 parts, 2-hydroxyethyl acrylate: 11 parts were mixed and held at 70°C for 5 hours, and then diluted with toluene to obtain a toluene solution of oligomer A with a solid content concentration of 60% by weight. 100 parts of the obtained toluene solution of oligomer (P) with a solid content concentration of 60% by weight, hindered phenol-based antioxidant (manufactured by BASF Japan Ltd., IRGANOX1010): 5 parts, photoinitiator (manufactured by BASF Japan Ltd., IRGACURE184): 1.5 parts were mixed and diluted with methyl ethyl ketone to obtain a resin film-forming coating composition (Q) with a solid content concentration of 40% by weight. As a support substrate, a 50-μm-thick polyester film (manufactured by Toray Industries, Inc., product name "Lumirror (registered trademark) R75X") provided with a release layer was used. Using a continuous coating apparatus by a slot die coater, the resin film-forming coating composition (Q) was applied onto the release layer of the support substrate while adjusting the discharge flow rate so that the thickness of the cured resin film would be 100 μm, and then dried and cured. The resin film was peeled off from the support substrate to obtain a thermosetting urethane acrylate resin film (R) with a thickness of 100 μm (100% modulus = 2.0 MPa). The drying temperature was 80°C, and the curing conditions for ultraviolet rays (UV rays) were an irradiation output of 400 mW / cm 2 , an integrated light amount of 1200 mJ / cm2 was used. The obtained thermosetting urethane acrylate resin film (R) was used as the base material layer, and the first adhesive layer and the second adhesive layer formed on the two release liners were laminated on the first surface and the second surface of this base material layer. The release liner was left as it was on the adhesive layer and used to protect the surface (adhesive surface) of the adhesive layer. The obtained structure was passed once through a laminator at 80 °C (0.3 MPa, speed 0.5 m / min), and then aged in an oven at 50 °C for 3 days. In this way, an adhesive tape (3) was obtained. The results are shown in Table 1.

[0125] [Example 4] An adhesive tape (4) was obtained in the same manner as in Example 3, except that the blending amount of the black pigment (manufactured by Dainichi Seika Kogyo Co., Ltd., "NAF-5091 Black") was changed to 0.6 part. The results are shown in Table 1.

[0126] [Example 5] An adhesive tape (5) was obtained in the same manner as in Example 3, except that the base material layer was replaced with a thermosetting polyurethane resin film (manufactured by Toray Industries, Inc., a polycaprolactone-based (ester-based) polyurethane resin film with a thickness of 100 μm (100% modulus = 1.8 MPa)). The results are shown in Table 1.

[0127] [Example 6] An adhesive tape (6) was obtained in the same manner as in Example 5, except that the blending amount of the black pigment (manufactured by Dainichi Seika Kogyo Co., Ltd., "NAF-5091 Black") was changed to 0.6 part. The results are shown in Table 1.

[0128] [Comparative Example 1] An adhesive tape (C1) was obtained in the same manner as in Example 1, except that a thermoplastic polyurethane resin film with a thickness of 100 μm (manufactured by Okura Kogyo Co., Ltd., urethane elastomer film, trade name "Silkron") was used as the base material layer. The results are shown in Table 1.

[0129] [Comparative Example 2] As the base material layer, an adhesive tape (C2) was obtained in the same manner as in Example 2, except that a thermoplastic polyurethane resin film with a thickness of 100 μm (manufactured by Okura Kogyo Co., Ltd., urethane elastomer film, trade name "Silkron") was used. The results are shown in Table 1.

[0130] [Comparative Example 3] Into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a cooler, 95 parts of n-butyl acrylate (BA) as a monomer component, 5 parts by weight of acrylic acid (AA), 0.25 part of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 234 parts of ethyl acetate as a polymerization solvent were charged, and solution polymerization was carried out at 65°C for 9 hours to obtain an ethyl acetate solution of an acrylic polymer (D). The weight average molecular weight of this acrylic polymer (D) was 600,000. To 100 parts of the acrylic polymer (D) contained in the above toluene solution, 30 parts of a tackifier resin (terpene phenol resin, trade name "YS Polyster S145" manufactured by Yasuhara Chemical Co., Ltd.), 2 parts of an isocyanate-based crosslinking agent (trade name "Coronate L" manufactured by Tosoh Corporation), and 0.01 part of an epoxy-based crosslinking agent (trade name "Tetrad C" manufactured by Mitsubishi Gas Chemical Company, Inc.) were added to prepare an adhesive composition (D). Two commercially available release liners (manufactured by Mitsubishi Chemical Corporation, trade name "Diafoil MRF#50" (biaxially stretched polyester film-based release liner with a single-sided release treatment layer, thickness 50 μm)) were prepared. The adhesive composition (D) was applied to one surface (release surface) of each release liner so that the thickness after drying would be 50 μm, and dried at 120°C for 5 minutes. In this way, an adhesive layer (first adhesive layer and second adhesive layer) with a thickness of 50 μm composed of an acrylic adhesive (D) corresponding to the adhesive composition (D) was formed on the release surfaces of the above two release liners, respectively. As the base material layer, a thermosetting polyurethane resin film with a thickness of 100 μm (manufactured by Toray Industries, Inc., a caprolactam-based (ester-based) polyurethane resin film with a thickness of 100 μm (100% modulus = 1.8 MPa)) was prepared. The first adhesive layer and the second adhesive layer formed on the two release liners were bonded to the first surface and the second surface of this base material layer. The release liners were left on the adhesive layers as they were and used to protect the surfaces (adhesive surfaces) of the adhesive layers. The obtained structure was passed through a laminator at 80°C (0.3 MPa, speed 0.5 m / min) once, and then aged in an oven at 50°C for 3 days. In this way, an adhesive tape (C3) was obtained. The results are shown in Table 1.

[0131]

Table 1

Industrial Applicability

[0132] The double-sided adhesive tape according to the embodiment of the present invention is excellent in shock absorption in all wide temperature ranges, particularly in the low temperature region. Taking advantage of this feature, the double-sided adhesive tape according to the embodiment of the present invention can be used, for example, as a shock absorption tape for displays.

Explanation of Symbols

[0133] 1000 Double-sided adhesive tape 100 Base material layer 200a Adhesive layer 200b Adhesive layer

Claims

1. A double-sided adhesive tape having adhesive layers on both sides of a base material layer, wherein the base material layer contains at least one polar functional group-containing polymer selected from a condensation polymer and an addition polymer, the polar functional group-containing polymer has a carbonyl group in the polymer main chain as a polar functional group, The storage elastic modulus E' measured at a frequency of 1 Hz from -25°C to 120°C for the entire double-sided adhesive tape is in the range of 1.0×10 ５ Pa to 1.0×10 ８ Pa, a double-sided adhesive tape.

2. The storage elastic modulus E' of the base material layer measured at a frequency of 1 Hz at -25°C to 120°C is in the range of 1.0×10 ５ Pa to 1.0×10 ８ Pa, and the double-sided adhesive tape according to claim 1.

3. The maximum value of the storage elastic modulus G' measured at a frequency of 1 Hz at -25°C to 120°C of the adhesive layer is 1.0×10 １０ Pa or less. The double-sided adhesive tape according to claim 1 or 2.

4. The double-sided adhesive tape according to any one of Claims 1 to 3, wherein the adhesive layer has an adhesive force to a SUS plate of 5 N / 20 mm or more at 23°C, 50% RH, a peeling speed of 300 mm / min, and a 180-degree peel.

5. The double-sided adhesive tape according to any one of Claims 1 to 4, wherein the polar functional group-containing polymer is at least one selected from polyamide, polyurethane, and polyurea.

6. The double-sided adhesive tape according to any one of Claims 1 to 5, wherein the polar functional group-containing polymer has at least one selected from an ether bond and an ester bond.

7. The double-sided adhesive tape according to any one of Claims 1 to 6, wherein the adhesive layer contains at least one selected from an acrylic adhesive, a rubber adhesive, a silicone adhesive, and a urethane adhesive.

8. The double-sided adhesive tape according to any one of Claims 1 to 7, which is an impact-absorbing tape for a display.

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