Double-sided adhesive tape

Abstract

A double-sided adhesive tape according to the present disclosure comprises: a base material layer (10); a first adhesive layer (20) that is laminated on a first surface (111) of the base material layer (10); and a second adhesive layer (30) that is laminated on a second surface (112) of the base material layer (10) which is on the reverse side of the first surface (111). The base material layer (10) comprises: at least one base material (11) that is selected from the group consisting of non-woven fabrics and paper base materials; and thermally expandable particles (12). The present disclosure provides a double-sided adhesive tape having high adhesive force and good removability.

Description

Double-sided adhesive tape

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

[0002] Double-sided adhesive tapes are excellent in workability and are used for fixing members of various structures such as home appliance members, automobile parts, and housing building materials. On the other hand, when reusing or recycling members of a structure fixed by a double-sided adhesive tape, it is necessary to peel off the double-sided adhesive tape from the member. As a re-peelable double-sided adhesive tape, for example, the adhesive sheets described in Patent Documents 1 to 5 are known as the prior art. The adhesive layer of the adhesive sheets described in Patent Documents 1 to 5 contains thermally expandable microspheres. When the adhesive sheet attached to the adherend is heated, the thermally expandable microspheres in the adhesive layer expand, and the adhesive sheet can be peeled off from the adherend.

[0003] Japanese Patent No. 4588021, Japanese Patent No. 4671815, Japanese Patent No. 4947921, Japanese Patent No. 5036270, Japanese Patent No. 5349803

[0004] However, when the adhesive layer contains thermally expandable microspheres, the adhesive strength of the adhesive sheet may decrease. On the other hand, if the content of the thermally expandable microspheres in the adhesive layer is reduced to increase the adhesive strength of the adhesive sheet, the thermal peelability of the adhesive sheet may deteriorate. Therefore, an object of the present invention is to provide a double-sided adhesive tape having high adhesive strength and good re-peelability.

[0005] The present inventor has intensively studied to solve the above problems. As a result, it has been found that the above problems can be solved by providing the base material layer with thermally expandable particles in addition to the base material, and the present invention has been completed. The gist of the present invention is as follows [1] to

[14] .

[0006] [1] A double-sided adhesive tape comprising a base material layer, a first adhesive layer laminated on the first surface of the base material layer, and a second adhesive layer laminated on the second surface opposite to the first surface of the base material layer, wherein the base material layer comprises at least one base material selected from the group consisting of non-woven fabric and paper base material and thermally expandable particles. [2] The basis weight of the base material is 3 to 30 g / m ２The double-sided adhesive tape according to [1] above. [3] The density of the base material is 0.1 to 0.8 g / cm ３ The double-sided adhesive tape according to [1] or [2] above. [4] The double-sided adhesive tape according to any one of [1] to [3] above, wherein the thickness of the base material is 5 to 100 μm. [5] The double-sided adhesive tape according to any one of [1] to [4] above, wherein the average particle diameter of the thermally expandable particles is 30 μm or less. [6] The double-sided adhesive tape according to any one of [1] to [5] above, wherein the first adhesive layer and the second adhesive layer are formed of an acrylic adhesive. [7] The double-sided adhesive tape according to any one of [1] to [6] above, wherein the thickness of the first adhesive layer is 80 μm or less. [8] The storage elastic modulus of the first adhesive layer at 23°C is 0.8×10 ５ to 5.0×10 ５ Pa. The double-sided adhesive tape according to any one of [1] to [7] above. [9] The double-sided adhesive tape according to any one of [1] to [8] above, wherein the glass transition temperature of the first adhesive layer is -20 to 20°C.

[10] The content of the thermally expandable particles in the base material layer is 1 to 15 g / m ２ The double-sided adhesive tape according to any one of [1] to [9] above.

[11] The content of the thermally expandable particles in the base material layer is 2 g / m ２ or more. The double-sided adhesive tape according to any one of [1] to

[10] above.

[12] The double-sided adhesive tape according to any one of [1] to

[11] above, wherein the thermally expandable particles are contained at least on the first surface of the base material layer.

[13] The double-sided adhesive tape according to

[12] above, wherein the content of the thermally expandable particles on the first surface of the base material layer is greater than the content of the thermally expandable particles on the second surface of the base material layer.

[14] The double-sided adhesive tape according to any one of [1] to

[13] above, wherein the ratio (average particle diameter / thickness) of the average particle diameter of the thermally expandable particles after thermal expansion to the thickness of the first adhesive layer is 0.5 or more.

[0007] According to the present invention, it is possible to provide a double-sided adhesive tape having high adhesive strength and good re-peelability.

[0008] Figure 1 is a schematic cross-sectional view showing a double-sided adhesive tape according to one embodiment of the present disclosure. Figures 2(a) and 2(b) are cross-sectional views illustrating the re-peelability of the double-sided adhesive tape according to one embodiment of the present disclosure. Figure 3 is a schematic cross-sectional view showing a double-sided adhesive tape according to one embodiment of the present disclosure. Figures 4(a) and 4(b) are cross-sectional views illustrating the re-peelability of the double-sided adhesive tape according to one embodiment of the present disclosure.

[0009] [Double-Sided Adhesive Tape] The double-sided adhesive tape of this disclosure comprises a base layer, a first adhesive layer laminated on a first surface of the base layer, and a second adhesive layer laminated on a second surface opposite to the first surface of the base layer, wherein the base layer comprises at least one substrate selected from the group consisting of nonwoven fabrics and paper substrates, and thermally expandable particles. As a result, the double-sided adhesive tape of this disclosure has high adhesive strength and good re-peelability.

[0010] (Base layer) The base layer of the double-sided adhesive tape of this disclosure comprises at least one base material selected from the group consisting of nonwoven fabrics and paper base materials, and thermally expandable particles.

[0011] <Substrate> The substrate of the substrate layer in the double-sided adhesive tape of this disclosure is at least one substrate selected from the group consisting of nonwoven fabrics and paper substrates. This allows the adhesive from the first adhesive layer and the second adhesive layer to be impregnated into the substrate, thereby suppressing the generation of adhesive residue on the adherend when the double-sided adhesive tape is peeled off from the adherend. Using a nonwoven fabric or paper substrate makes it easier to incorporate thermally expandable particles into the substrate. The substrate may be a single layer or multiple layers, but from the viewpoint of suppressing the generation of adhesive residue when re-peeling, it is preferable that the substrate be a single layer.

[0012] The fibers used for the non-woven fabric are not particularly limited. Examples of the fibers used for the non-woven fabric include cotton, rayon fiber, polyester fiber, polypropylene fiber, nylon fiber, acrylic fiber, vinylon fiber, glass fiber, etc. When the fibers used for the non-woven fabric are cotton and rayon fiber, the non-woven fabric is manufactured by methods such as needle punching, chemical bonding, spunlace, etc. When the fibers used for the non-woven fabric are polyester fiber and polypropylene fiber, the non-woven fabric is manufactured by methods such as spunbond, needle punching, etc. When the fibers used for the non-woven fabric are nylon fiber, the non-woven fabric is manufactured by methods such as spunbond, chemical bonding, etc. When the fibers used for the non-woven fabric are acrylic fiber, the non-woven fabric is mainly manufactured by needle punching. When the fibers used for the non-woven fabric are vinylon fiber and glass fiber, the non-woven fabric is mainly manufactured by the wet method.

[0013] The paper base material is not particularly limited. Examples of the paper base material include kraft paper, glassine paper, fine paper, tissue paper, etc. From the viewpoints of the impregnation property of the adhesive and the ease of supporting the thermally expandable particles, tissue paper is preferable among these paper base materials.

[0014] The basis weight of the base material is preferably 3 to 30 g / m ２ ². When the basis weight of the base material is 3 g / m ２ ² or more, the strength of the base material can be further increased. When the basis weight of the base material is 30 g / m ２ ² or less, the impregnation of the adhesive from the first adhesive layer and the second adhesive layer into the base material becomes easier, and when peeling the double-sided adhesive tape from the adherend, the occurrence of adhesive residue on the adherend can be further suppressed. From such viewpoints, the basis weight of the base material is more preferably 4 g / m ２ ² or more, still more preferably 5 g / m ２ ² or more, even more preferably 7 g / m ２ ² or more, particularly preferably 10 g / m ２ ² or more, and also more preferably 27 g / m ２ ² or less, still more preferably 25 g / m ２ ² or less, even more preferably 24 g / m ２The following is more more preferable: 4 to 27 g / m² ２ More preferably 5 to 25 g / m ２ More preferably 7 to 25 g / m ２ Particularly preferably 10 to 24 g / m² ２ The basis weight of the substrate can be measured by the method described in the examples below. The basis weight of the substrate can be calculated by dividing the mass of the substrate by the area of ​​the substrate.

[0015] The density of the base material is preferably 0.1 to 0.8 g / cm³. ３ The density of the base material is 0.1 g / cm³. ３ The above conditions result in good support of the thermally expandable particles to the substrate, improving peelability from the adherend. ３ The following conditions make it easier for the adhesive from the first and second adhesive layers to penetrate the substrate, and further suppress the generation of adhesive residue on the adherend when peeling the double-sided adhesive tape from the adherend. From this viewpoint, the density of the substrate is more preferably 0.2 g / cm³. ３ The above is preferable, and more preferably 0.25 g / cm³. ３ The above is a more preferable 0.3 g / cm³. ３ The above applies, and more preferably 0.7 g / cm³. ３ The following, and more preferably 0.65 g / cm³ ３ The following, and more preferably 0.6 g / cm³ ３ The following, and more preferably 0.2 to 0.7 g / cm³ ３ And more preferably 0.25 to 0.65 g / cm³. ３ More preferably, 0.3 to 0.6 g / cm³ ３ The density of the substrate can be measured by the method described in the examples below. The density of the substrate can be calculated by dividing the mass of the substrate by the area and thickness of the substrate.

[0016] The thickness of the base material is preferably 5 to 100 μm. If the thickness of the base material is 5 μm or more, the strength of the base material can be further increased. If the thickness of the base material is 100 μm or less, the double-sided adhesive tape can be made even thinner. From this viewpoint, the thickness of the base material is more preferably 5 μm or more, even more preferably 7 μm or more, even more preferably 10 μm or more, also more preferably 95 μm or less, even more preferably 90 μm or less, even more preferably 85 μm or less, particularly preferably 80 μm or less, especially preferably 75 μm or less, particularly preferably 70 μm or less, more preferably 5 to 95 μm, even more preferably 5 to 90 μm, even more preferably 5 to 85 μm, particularly preferably 5 to 80 μm, particularly preferably 7 to 75 μm, and particularly preferably 10 to 70 μm.

[0017] <Thermally Expandable Particles> The thermally expandable particles are preferably composed of a shell and a volatile expanding agent encapsulated as a core. The shell constituting the thermally expandable particles preferably contains a polymer compound. The polymer compound is preferably a polymer containing units derived from a nitrile monomer, and more preferably a polymer containing units derived from a nitrile monomer and units derived from a monomer having a carboxyl group and / or a (meth)acrylic acid ester monomer. Furthermore, the polymer compound is preferably a polymer of a monomer composition containing a nitrile monomer, and more preferably a polymer of a monomer composition containing a nitrile monomer and a monomer having a carboxyl group and / or a (meth)acrylic acid ester monomer.

[0018] The above-mentioned nitrile monomers are not particularly limited and include, for example, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumanitrile, or mixtures thereof. Among these, acrylonitrile and methacrylonitrile are particularly preferred. These may be used individually or in combination of two or more.

[0019] The preferred lower limit for the nitrile monomer content in the above monomer composition is 20% by mass, and the preferred upper limit is 99% by mass. A content of 20% by mass or more enhances the gas barrier properties of the shell and improves the foaming ratio. A content of 99% by mass or less improves heat resistance and prevents yellowing. A more preferred lower limit is 30% by mass, and a more preferred upper limit is 98% by mass.

[0020] As monomers having a carboxyl group, for example, radically polymerizable unsaturated carboxylic acid monomers having a carboxyl group and having 3 to 8 carbon atoms can be used. Specifically, examples include unsaturated dicarboxylic acids and their anhydrides, or monoesters and derivatives of unsaturated dicarboxylic acids, which may be used alone or in combination of two or more. Examples of unsaturated dicarboxylic acids include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, as well as maleic acid, itaconic acid, fumaric acid, citraconic acid, and chloromaleic acid. Examples of monoesters of unsaturated dicarboxylic acids include monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconic acid, monoethyl itaconic acid, and monobutyl itaconic acid. Among these, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid are particularly preferred.

[0021] The preferred lower limit and preferred upper limit of the content of the monomer having the carboxyl group in the above monomer composition is 5% by mass. A content of 5% by mass or more allows for an increase in the maximum foaming temperature, while a content of 50% by mass or less allows for an improvement in the foaming ratio. A more preferred lower limit is 10% by mass, and a more preferred upper limit is 30% by mass.

[0022] As the above (meth)acrylic acid ester monomer, (meth)acrylic acid esters are preferred, and in particular, alkyl methacrylate esters such as methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate, or alicyclic, aromatic, and heterocyclic methacrylate esters such as cyclohexyl methacrylate, benzyl methacrylate, and isobornyl methacrylate are preferred.

[0023] The preferred lower limit for the content of the (meth)acrylic acid ester monomer in the above monomer composition is 0.1% by mass, and the preferred upper limit is 25% by mass. By setting the content of the other monomers to 0.1% by mass or more, the dispersibility of the composition using thermally expandable particles can be improved, and by setting it to 25% by mass or less, the gas barrier properties of the cell walls can be improved, thereby improving thermal expandability. The more preferred lower limit for the content of the (meth)acrylic acid ester monomer is 0.3% by mass, and the more preferred upper limit is 22% by mass.

[0024] The above monomer composition preferably contains a crosslinkable monomer having two or more double bonds in its molecule. The above crosslinkable monomer acts as a crosslinking agent. By including the above crosslinkable monomer, the strength of the shell can be enhanced, and the cell wall becomes less likely to rupture during thermal expansion.

[0025] Examples of the above crosslinkable monomers include monomers having two or more radically polymerizable double bonds. Specific examples include, for example, divinylbenzene, di(meth)acrylate, and trifunctional or more (meth)acrylates. Examples of the above di(meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Other examples include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane di(meth)acrylate, and dimethylol-tricyclodecane di(meth)acrylate. Furthermore, polyethylene glycol di(meth)acrylate with a weight-average molecular weight of 200 to 600 may also be used. Examples of the three-functional (meth)acrylates mentioned above include trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and triallylformal tri(meth)acrylate. Examples of four- or more-functional (meth)acrylates include pentaerythritol tetra(meth)acrylate and dipentaerythritol hexa(meth)acrylate. Among these, three-functional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and two-functional (meth)acrylates such as polyethylene glycol can crosslink relatively uniformly on acrylonitrile-based shells.

[0026] The preferred lower limit for the content of the crosslinkable monomer in the above monomer composition is 0.1% by mass, and the preferred upper limit is 1.0% by mass. By setting the content of the crosslinkable monomer to 0.1% by mass or more, the effect as a crosslinking agent can be fully exhibited, and by setting the content of the crosslinkable monomer to 1.0% by mass or less, it is possible to improve the foaming ratio of the thermally expandable particles. A more preferred lower limit for the content of the crosslinkable monomer is 0.15% by mass, and a more preferred upper limit is 0.9% by mass.

[0027] The above monomer composition preferably contains the above nitrile monomer and other monomers other than monomers having a carboxyl group, (meth)acrylic acid ester monomers, and crosslinkable monomers. By including the above other monomers, the miscibility between the heat-expandable particles and the matrix resin such as a thermoplastic resin is improved, and the foamed molded article using the heat-expandable particles can have an excellent appearance. Examples of the above other monomers include vinyl monomers such as vinyl chloride, vinylidene chloride, vinyl acetate, and styrene. These may be used individually or in combination of two or more.

[0028] The above monomer composition may contain a thermosetting resin in addition to the above nitrile monomer, monomer having a carboxyl group, (meth)acrylic acid ester monomer, crosslinkable monomer, and other monomers. Examples of the above thermosetting resin include epoxy resin, phenolic resin, melamine resin, urea resin, polyimide resin, and bismaleimide resin. Among these, epoxy resin and phenolic resin are preferred.

[0029] The epoxy resins mentioned above are not particularly limited and include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, dicyclopentadiene type epoxy resin, glycidylamine type epoxy resin, etc. The phenol resins mentioned above include, for example, novolac type phenol resin, resol type phenol resin, benzyl ether type phenol resin, etc. Among these, novolac type phenol resin is preferred.

[0030] The thermosetting resin described above preferably has two or more functional groups that react with carboxyl groups in one molecule. Having two or more functional groups that react with carboxyl groups makes the curability of the thermosetting resin stronger. In particular, if the monomer composition contains a monomer having a carboxyl group, the heat generated during heating and foaming causes the carboxyl group and the thermosetting resin to bond more strongly, which significantly improves heat resistance and durability. It is preferable that the thermosetting resin does not have radically polymerizable double bonds.

[0031] Examples of functional groups that react with the carboxyl group include glycidyl groups, phenol groups, methylol groups, and amino groups. Among these, glycidyl groups are preferred. The functional groups that react with the carboxyl group may be the same type or two or more types.

[0032] The preferred lower limit for the content of the thermosetting resin in the above monomer composition is 0.01% by mass, and the preferred upper limit is 30% by mass. By setting the content of the thermosetting resin to 0.01% by mass or more, the compressive resistance during heat foaming can be improved. By setting the content of the thermosetting resin to 30% by mass or less, the gas barrier properties of the shell are improved and the foaming properties are improved. A more preferred lower limit is 0.1% by mass, and a more preferred upper limit is 15% by mass.

[0033] A polymerization initiator is added to the above monomer composition in order to polymerize the monomer. Suitable polymerization initiators include, for example, dialkyl peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, and azo compounds. Specific examples include dialkyl peroxides such as methyl ethyl peroxide, di-t-butyl peroxide, and dicumyl peroxide; diacyl peroxides such as isobutyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and 3,5,5-trimethylhexanoyl peroxide. Other examples include t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, and 1,1,3,3-tetramethylbutyl peroxyneodecanoate. Other examples include peroxyesters such as cumyl peroxyneodecanoate and (α,α-bis-neodecanoylperoxy)diisopropylbenzene; bis(4-t-butylcyclohexyl)peroxydicarbonate, di-n-propyl-oxydicarbonate, and diisopropyl peroxydicarbonate. Furthermore, examples include peroxydicarbonates such as di(2-ethylethylperoxy)dicarbonate, dimethoxybutyl peroxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate. In addition, examples include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 1,1'-azobis(1-cyclohexanecarbonile).

[0034] The preferred lower limit for the weight-average molecular weight of the polymer compound constituting the shell is 100,000, and the preferred upper limit is 2,000,000. If it is less than 100,000, the strength of the shell may decrease, and if it exceeds 2,000,000, the strength of the shell may become too high, and the foaming ratio may decrease.

[0035] The above shell may further contain, as necessary, stabilizers, ultraviolet absorbers, antioxidants, antistatic agents, flame retardants, silane coupling agents, colorants, etc.

[0036] The thermally expandable particles can contain a volatile expander as a core agent within the shell. The volatile expander is a substance that becomes gaseous at a temperature below the softening point of the polymer constituting the shell, and a low-boiling point organic solvent is preferred.

[0037] Examples of the above-mentioned volatile swelling agent (core agent) include hydrocarbons with fewer than 8 carbon atoms, hydrocarbons with 8 or more carbon atoms, petroleum ethers, chlorofluorocarbons, and tetraalkylsilanes. Examples of hydrocarbons with fewer than 8 carbon atoms include ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, and heptane. Examples of hydrocarbons with 8 or more carbon atoms include isooctane, octane, decane, isododecane, dodecane, and hexanedecane. Examples of the above-mentioned chlorofluorocarbons include CCl3F, CCl2F2, CClF3, CClF2-CCLF2, and others. Examples of the above-mentioned tetraalkylsilanes include tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane. Among these, isobutane, n-butane, n-pentane, isopentane, n-hexane, and mixtures thereof are preferred. These volatile expanding agents may be used in combination of two or more types. Furthermore, in this disclosure, hydrocarbons with fewer than 8 carbon atoms and hydrocarbons with 8 or more carbon atoms may be used in combination. For example, it is preferable to use pentane and isooctane in combination. Additionally, as a volatile expanding agent, a pyrolysis-type compound that decomposes into a gaseous state upon heating may be used.

[0038] Furthermore, in the above-mentioned thermally expandable particles, the content of the core agent is preferably 15 to 30% by mass. By keeping it within this range, excellent resistance to shear during molding can be achieved, and the foaming ratio can be improved. A more preferable lower limit for the content of the core agent is 18% by mass, and a more preferable upper limit is 24% by mass.

[0039] For thermally expandable particles, the preferred lower limit of the foaming initiation temperature (Ts) is 70°C, and the preferred upper limit is 250°C. By keeping it within this range, in the case of injection molding, especially in core-back foaming molding where the mold is opened to the desired foaming point after the mold is fully filled with resin material, it is possible to prevent the resin temperature from cooling down during the core-back foaming process, which would prevent the foaming ratio from increasing. A more preferred lower limit of the foaming initiation temperature (Ts) is 75°C, a more preferred upper limit is 180°C, a more preferred lower limit is 80°C, a more preferred upper limit is 150°C, an even more preferred lower limit is 110°C, an even more preferred upper limit is 150°C, an even more preferred lower limit is 120°C, and an even more preferred upper limit is 130°C.

[0040] The thermally expandable particles have a preferred lower limit of 110°C for their maximum foaming temperature (Tmax) and a preferred upper limit of 270°C. By keeping the temperature within this range, heat resistance can be increased, preventing the thermally expandable particles from bursting or shrinking in high-temperature regions or during molding processes. Furthermore, foaming due to shearing during masterbatch pellet production can be prevented, allowing for the stable production of unfoamed masterbatch pellets. A more preferred lower limit is 115°C, an even more preferred lower limit is 120°C, an even more preferred lower limit is 130°C, a particularly preferred lower limit is 150°C, a particularly preferred lower limit is 160°C, a more preferred upper limit is 230°C, an even more preferred upper limit is 225°C, an even more preferred upper limit is 210°C, a particularly preferred upper limit is 200°C, and a particularly preferred upper limit is 180°C. In this specification, the maximum foaming temperature refers to the temperature at which the diameter of the thermally expandable particles reaches its maximum (maximum displacement) when the particles are heated from room temperature and their diameter is measured. Furthermore, the thermally expandable particles of this disclosure have a preferred lower limit of 300 μm and a preferred upper limit of 2000 μm for the maximum displacement (Dmax). Within this range, an appropriate foaming ratio is obtained, and the desired foaming performance can be acquired.

[0041] The average particle diameter of the thermally expandable particles is preferably 30 μm or less. When the average particle diameter of the thermally expandable particles is 30 μm or less, the impregnation of the adhesive from the first adhesive layer and the second adhesive layer into the substrate becomes even easier, and the occurrence of adhesive residue on the adherend when peeling the double-sided adhesive tape from the adherend can be further suppressed. From this viewpoint, the average particle diameter of the thermally expandable particles is more preferably 20 μm or less, and even more preferably 17 μm or less. The average particle diameter of the thermally expandable particles is preferably 3 μm or more. When the average particle diameter of the thermally expandable particles is 3 μm or more, the re-peelability of the double-sided adhesive tape can be further improved. From this viewpoint, the average particle diameter of the thermally expandable particles is more preferably 4 μm or more, even more preferably 5 μm or more, even more preferably 8 μm or more, and particularly preferably 10 μm or more. The average particle diameter of the thermally expandable particles can be measured by the method described in the examples below. The average particle size of the thermally expandable particles can be measured using a particle size distribution measurement method in laser scattering, either for the thermally expandable particles used or for thermally expandable particles extracted from double-sided tape before heating. More specifically, the average particle size can be measured using a particle size distribution analyzer (for example, Shimadzu Corporation's product name "SALD-2000J") after dispersing the thermally expandable particles in a predetermined solvent (e.g., water). Here, the average particle size refers to the volume average particle size. Thermally expandable particles can be extracted from double-sided tape, for example, by dissolving the adhesive in a solvent.

[0042] Examples of commercially available thermally expandable particles include EXPANCEL from AkzoNobel, ADVANCEL from Sekisui Chemical Co., Ltd., Matsumoto Microspheres from Matsumoto Oil & Fat Pharmaceutical Co., Ltd., and Microspheres from Kureha Corporation.

[0043] The content of thermally expandable particles in the substrate layer is preferably 1 to 15 g / m². ２ The content of thermally expandable particles is 1 g / m ２ The above results in even better re-peelability of the double-sided adhesive tape. The content of thermally expandable particles is 15 g / m². ２The following conditions further facilitate the impregnation of the adhesive from the first and second adhesive layers into the substrate. From this viewpoint, the content of thermally expandable particles in the substrate layer is more preferably 2 g / m². ２ The above is preferable to 3 g / m ２ The above is preferable to 10 g / m². ２ The following is more preferably 8 g / m ２ More preferably, 7 g / m ２ The following is particularly preferable: 6 g / m ２ The following is more preferable: 2 to 10 g / m ２ More preferably 3 to 8 g / m ２ More preferably 3 to 7 g / m ２ Particularly preferably 3 to 6 g / m ２ The amount of thermally expandable particles in the substrate layer can be calculated by subtracting the basis weight of the substrate from the basis weight of the substrate layer.

[0044] In the substrate layer, the thermally expandable particles are preferably located on at least the first surface side of the substrate layer. This allows the adhesive strength of at least the first adhesive layer of the double-sided adhesive tape to be reduced when heated. However, the thermally expandable particles may be located not only on the first surface side of the substrate layer but also on the second surface side. The thermally expandable particles are preferably adhered to the surface of the substrate with a binder resin, for example, by adhering them to the first surface with a binder resin so that they are located on the first surface side. Alternatively, they may be present on both the first and second surface sides by adhering them to the surface of the substrate with a binder resin on both the first and second surfaces. Furthermore, in order to more securely fix the thermally expandable particles to the substrate, the thermally expandable particles may be embedded in the surface of the substrate.

[0045] Furthermore, it is preferable that the content of thermally expandable particles on the first surface of the base layer is greater than the content of thermally expandable particles on the second surface of the base layer. As a result, when the double-sided adhesive tape is heated with both sides attached to an adherend, the first adhesive layer expands while being supported by the second adhesive layer and the base layer, making it easier to expand appropriately. This allows the adhesive strength of one adhesive layer (the first adhesive layer) of the double-sided adhesive tape to be appropriately lowered, resulting in good peelability. In addition, as a result, the influence of the expansion of thermally expandable particles on the first surface of the base layer on the first side of the base layer in the double-sided adhesive tape is greater than the influence of the expansion of thermally expandable particles on the second surface of the base layer in the double-sided adhesive tape. When the thermally expandable particles expand, the surface on the first side of the base layer in the double-sided adhesive tape is easier to peel off than the surface on the second side of the base layer in the double-sided adhesive tape. In this case, the base layer may have thermally expandable particles only on the surface on the first side of the base layer, or it may have them on both the first and second surface sides. Furthermore, if the substrate layer has thermally expandable particles on both the first and second surfaces of the substrate layer, a certain amount of thermally expandable particles may be provided on both the first and second surfaces, for example, approximately the same amount of thermally expandable particles may be provided on both the first and second surfaces. By providing a certain amount of thermally expandable particles on both the first and second surfaces, the adhesive strength of the first and second adhesive layers can be reduced, and the double-sided adhesive tape can be peeled off on both surfaces of the double-sided adhesive tape.

[0046] A substrate layer comprising a substrate and thermally expandable particles can be manufactured, for example, by preparing a coating by mixing thermally expandable particles and a binder resin in a certain ratio, applying the coating to the substrate using a coating machine such as an impregnation coating machine or a gravure printing roll machine, and then drying it. The coating method is not particularly limited, but examples include roll coating and spray coating.

[0047] By applying the paint to only one side of the substrate, the content of thermally expandable particles on the first surface of the substrate layer can be made greater than the content of thermally expandable particles on the second surface. Depending on the type of substrate, specifically if the density or basis weight is high, thermally expandable particles can be present only on the first surface. Also, depending on the type of substrate, specifically if the density or basis weight is low, the thermally expandable particles will pass through the substrate during coating and move from the first surface to the second surface, resulting in the presence of thermally expandable particles not only on the first surface but also on the second surface. Furthermore, by applying the paint to both sides of the substrate, thermally expandable particles can be present on both the first and second surfaces of the substrate layer. In this case, the amount of thermally expandable particles present on the first and second surfaces of the substrate layer can be adjusted by adjusting the amount of paint applied. In a preferred embodiment of this disclosure, the substrate layer includes the substrate and a layer containing (or consisting of) thermally expandable particles and a binder resin on the first surface of the substrate.

[0048] The ratio of thermally expandable particles to binder resin is preferably about 6:1 to 2:1 by mass, and more preferably about 5:1 to 3:1. The coating amount of the above paint may be about 4 to 50% by mass relative to the substrate layer, more preferably 12 to 25% by mass, preferably 4% or more by mass, more preferably 12% or more by mass, and preferably 50% or less by mass, and more preferably 25% or less by mass. The binder resin is preferably an acrylic acid ester type binder. After preparing the substrate layer by supporting the thermally expandable particles on the substrate, the substrate layer may be subjected to pressure treatment with a supercalender roll as needed. By performing this supercalender roll processing, a substrate layer having a high density and smooth surface can be obtained.

[0049] (Adhesive Layer) The double-sided adhesive tape of this disclosure may comprise a first adhesive layer laminated on a first surface of a substrate layer and a second adhesive layer laminated on a second surface opposite to the first surface of the substrate layer. The first and second adhesive layers of the double-sided adhesive tape of this disclosure are made of an adhesive. The adhesive is formed from an adhesive composition described later and consists of solid components obtained by removing the solvent from each component constituting the adhesive composition. The type of adhesive is not particularly limited, and for example, acrylic adhesives, rubber adhesives, urethane adhesives, etc., can be used. Among these, from the viewpoint of the impregnation of the adhesive into the substrate, the interlayer strength between the substrate and the adhesive layer, and the adhesive strength of the adhesive layer, it is preferable that the first and second adhesive layers are formed from an acrylic adhesive. The acrylic adhesive will be described in detail below.

[0050] <Acrylic Adhesive> The adhesive layer made of an acrylic adhesive is formed by an adhesive composition containing an acrylic polymer (A), as described below.

[0051] ≪Acrylic Polymer (A)≫ Acrylic polymer (A) is obtained by polymerizing monomers that include at least an acrylic monomer. Furthermore, it is preferable that the acrylic polymer is a polymer containing a reactive functional group. A reactive functional group is a functional group that is reactive with the crosslinking agent described later. Examples of acrylic polymers include copolymers of a functional group-containing monomer (a1) having a reactive functional group and an acrylic monomer (a2) other than the functional group-containing monomer (a1), or copolymers of the above monomers (a1) and (a2) and other monomers (a3) ​​other than (a1) and (a2). The reactive functional group is not particularly limited as long as it has active hydrogen and is reactive with the crosslinking agent described later, and examples include hydroxyl groups, amino groups, carboxyl groups, etc. Among these functional groups, the carboxyl group is preferred.

[0052] The monomer having a hydroxyl group is not particularly limited, but examples include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate, as well as allyl alcohol. Among these, hydroxyl group-containing (meth)acrylates are preferably used. Note that (meth)acrylate is used as a term to mean either acrylate or methacrylate, or both. Furthermore, examples of monomers having a carboxyl group include methacrylic acid and acrylic acid. Among these, as the functional group-containing monomer (a1) having a reactive functional group, monomers having a carboxyl group are preferred, and acrylic acid is more preferred.

[0053] Examples of acrylic monomers (a2) include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isomiristyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, and aromatic group-containing (meth)acrylates such as benzyl (meth)acrylate. Alkyl (meth)acrylates are preferred as acrylic monomers (a2), alkyl (meth)acrylates with 1 to 12 carbon atoms in the alkyl group are more preferred, and alkyl (meth)acrylates with 1 to 12 carbon atoms in the alkyl group are even more preferred. As the acrylic monomer (a2), n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isononyl (meth)acrylate are preferred, and among these, n-butyl acrylate, 2-ethylhexyl acrylate, and isononyl acrylate are more preferred. In the acrylic polymer (A), the amount of alkyl (meth)acrylate used in the acrylic monomer (a2) is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and also preferably 100% by mass or less, for example, 70% by mass or more and 100% by mass or less, preferably 80% by mass or more and 100% by mass or less, and more preferably 90% by mass or more and 100% by mass or less.

[0054] Other monomers (a3) ​​are not particularly limited as long as they can copolymerize with acrylic monomers, and examples include styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, and divinylbenzene; compounds having vinyl ester groups such as vinyl acetate and vinyl propionate; N-vinylpyrrolidone, N-vinylmorpholin, (meth)acrylonitrile, N-cyclohexylmaleimide, N-phenylmaleimide, N-laurylmaleimide, N-benzylmaleimide, n-propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, and tert-butyl vinyl ether. Among these, vinyl acetate is preferred as the other monomer (a3).

[0055] The amount of monomer used in the acrylic polymer (A) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 14 parts by mass or less, preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass or less, even more preferably 3 to 14 parts by mass, per 100 parts by mass of the acrylic monomer (a2). The amount of other monomers (a3) ​​other than the reactive functional group-containing monomer (a1) and the acrylic monomer (a2) is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, per 100 parts by mass of the acrylic monomer (a2). Furthermore, the total amount of the functional group-containing monomer (a1) having a reactive functional group and the acrylic monomer (a2) in the total monomer components used in the acrylic polymer (A) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The upper limit is 100% by mass.

[0056] Acrylic polymers (A) are obtained by polymerizing the above-mentioned monomers using conventional polymerization methods, such as turbidity polymerization, emulsion polymerization, and solution polymerization. Of these polymerization methods, solution polymerization is preferred because it easily yields high molecular weight polymers and does not contain surfactants or dispersants that can easily affect tackiness. Peroxide-based polymerization initiators and azo-based polymerization initiators are used as polymerization initiators.

[0057] The acrylic polymer (A) preferably has a weight-average molecular weight of 300,000 to 2,000,000, and more preferably 400,000 to 1,500,000. Keeping the weight-average molecular weight within this range makes it easier to maintain good retention, tackiness, and adhesive properties of the adhesive layer. The weight-average molecular weight is the weight-average molecular weight on a standard polystyrene basis, measured by gel permeation chromatography (GPC). In the adhesive composition, the acrylic polymer may be the main component, and is usually 50% by mass or more, preferably 70% by mass or more, more preferably 75% by mass or more, preferably 98% by mass or less, more preferably 97% by mass or less, preferably 70 to 98% by mass, and more preferably 75 to 97% by mass, based on the total amount of the adhesive composition (based on solid content).

[0058] <<Tackifying Resin>> The adhesive composition preferably contains a tackifying resin in addition to the acrylic polymer (A). The tackifying resin is preferably at least one selected from polymerized rosin, disproportionated rosin, and terpene phenol.

[0059] Examples of polymerized rosins include polymerized rosins obtained by polymerizing rosin, ester compounds of polymerized rosins, such as ester compounds of diabietic acid. Commercially available polymerized rosins include Bencel KK (manufactured by Arakawa Chemical Industries, Ltd.), Bencel D160 (manufactured by Arakawa Chemical Industries, Ltd.), Bencel D135 (manufactured by Arakawa Chemical Industries, Ltd.), and Bencel D125 (manufactured by Arakawa Chemical Industries, Ltd.).

[0060] Examples of disproportionated rosins include disproportionated rosins obtained by disproportionating rosin, ester compounds of disproportionated rosins, such as ester compounds of dehydroabietic acid. Commercially available disproportionated rosins include Super Ester A125 (manufactured by Arakawa Chemical Industries, Ltd.), Super Ester A115 (manufactured by Arakawa Chemical Industries, Ltd.), W125 (manufactured by Arakawa Chemical Industries, Ltd.), and W100 (manufactured by Arakawa Chemical Industries, Ltd.).

[0061] Terpene phenols are resins that possess both terpene and phenolic structures. Commercially available terpene phenols include YS Polystar G150 and YS Polystar T130 (manufactured by Yasuhara Chemical Co., Ltd.).

[0062] The tackifying resin may be used alone or in combination of two or more types. The content of the tackifying resin is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, even more preferably 35 parts by mass or less, preferably 1 to 60 parts by mass, even more preferably 2 to 50 parts by mass, even more preferably 3 to 40 parts by mass, and even more preferably 5 to 35 parts by mass, per 100 parts by mass of the acrylic polymer.

[0063] <Crosslinking Agent> The adhesive composition preferably contains a crosslinking agent. That is, the adhesive layer is preferably formed by crosslinking the adhesive contained in the adhesive composition with a crosslinking agent. As the crosslinking agent, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents are preferably used.

[0064] The isocyanate crosslinking agent is not particularly limited as long as it is a compound having two or more isocyanate groups in one molecule. Examples include isocyanate compounds such as toluene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, tetramethylxylylene diisocyanate, and trimethylolpropane tolylene diisocyanate adducts. Furthermore, commercially available products include burette polyisocyanate compounds such as Sumijoule N (manufactured by Sumitomo Bayer Urethane Co., Ltd.), polyisocyanate compounds having an isocyanurate ring such as Desmodule IL, HL (manufactured by Bayer AG Co., Ltd.), Coronate EH (manufactured by Nippon Polyurethane Co., Ltd.), and adduct polyisocyanate compounds such as Sumijoule L (manufactured by Sumitomo Bayer Urethane Co., Ltd.) and Coronate HL (manufactured by Nippon Polyurethane Co., Ltd.). In addition, blocked isocyanate compounds in which the above isocyanate groups are blocked may also be used. The epoxy crosslinking agent is not particularly limited as long as it is a compound having two or more epoxy groups in one molecule. Examples include diglycidylaniline, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, 1,3-bis(N,N-diglycidylaminoethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-m-xylenediamine. Examples of commercially available epoxy crosslinking agents include E-AX and E-5C (manufactured by Soken Chemical Co., Ltd.). Examples of metal chelating crosslinking agents include chelating compounds in which the metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc., but aluminum chelates in which the central metal is aluminum are preferred. Examples of commercially available products include aluminum chelate A and aluminum chelate M manufactured by Kawaken Fine Chemical Co., Ltd.

[0065] The crosslinking agent content in the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, preferably 2.0 parts by mass or less, more preferably 1.2 parts by mass or less, preferably 0.01 to 2.0 parts by mass, and more preferably 0.02 to 1.2 parts by mass per 100 parts by mass of the acrylic polymer. The gel fraction indicating the degree of crosslinking of the adhesive layer is preferably 30% by mass or more, more preferably 35% by mass or more, preferably 80% by mass or less, more preferably 55% by mass or less, preferably 30 to 80% by mass, and more preferably 35 to 55% by mass. By keeping the gel fraction within the above range, it becomes easier to maintain good holding power and tackiness of the adhesive layer.

[0066] <<Organic Solvents>> The adhesive composition may contain an organic solvent. The organic solvent may be the solvent used when synthesizing the acrylic polymer, or it may be added after the synthesis of the acrylic polymer. Examples of organic solvents include alcohols such as ethyl acetate, toluene, methanol, ethanol, and isopropyl alcohol, with ethyl acetate being preferred. One organic solvent may be used alone, or two or more may be used in combination.

[0067] <<Other Components>> The adhesive composition of this disclosure may also contain fillers, antioxidants, UV inhibitors, plasticizers, viscosity modifiers, etc., to the extent that they do not impede the effects of the present invention. The adhesive composition of this disclosure may or may not contain the above-mentioned thermally expandable particles. In this disclosure, "containing the above-mentioned thermally expandable particles" means that the thermally expandable particles are uniformly distributed throughout the composition.

[0068] <Thickness> The thickness of the first adhesive layer is preferably 80 μm or less. When the thickness of the first adhesive layer is 80 μm or less, the adhesive strength is more easily reduced by the thermally expandable particles, making it easier to make the double-sided adhesive tape thinner. From this viewpoint, the thickness of the first adhesive layer is more preferably 60 μm or less, and even more preferably 55 μm or less. Also, the thickness of the first adhesive layer is preferably 10 μm or more. When the thickness of the first adhesive layer is 10 μm or more, it is easier to ensure the adhesive strength of the first adhesive layer before the thermally expandable particles expand. From this viewpoint, the thickness of the first adhesive layer is more preferably 15 μm or more, even more preferably 20 μm or more, and even more preferably 25 μm or more. Also, the thickness of the second adhesive layer is preferably 30 μm or more. When the thickness of the second adhesive layer is 30 μm or more, the adhesive strength of the second adhesive layer can be increased, and the impregnation of the adhesive into the substrate becomes easier. The thickness of the second adhesive layer is more preferably 40 μm or more, even more preferably 50 μm or more, preferably 100 μm or less, more preferably 90 μm or less, for example 80 μm or less.

[0069] The thicknesses of the first adhesive layer and the second adhesive layer may be the same or different, but if the thicknesses of the first and second adhesive layers are different, it is preferable that the thickness of the first adhesive layer is smaller than the thickness of the second adhesive layer. As described above, in this disclosure, it is preferable to have thermally expandable particles on the first surface side on which the first adhesive layer is provided, and the adhesive force of the first adhesive layer can be easily reduced by heating. On the other hand, if the thickness of the second adhesive layer is greater than the thickness of the first adhesive layer, the second adhesive layer supports the expansion of the thermally expandable particles on the first adhesive layer side, making it easier to properly expand the thermally expandable particles on the first adhesive layer side. For the reasons stated above, when the thicknesses of the first adhesive layer and the second adhesive layer are different, the ratio of the thickness of the second adhesive layer to the thickness of the first adhesive layer (thickness of the second adhesive layer / thickness of the first adhesive layer) is preferably 1 or more, more preferably 1.2 or more, even more preferably 1.3 or more, even more preferably 1.4 or more, for example 1.5 or more, and preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, even more preferably 4 or less, for example 3 or less.

[0070] <Storage Modulus> The storage modulus of the first adhesive layer at 23°C is preferably 0.8 × 10⁻⁶ ５ ~5.0 x 10 ５ The pressure is Pa. The storage modulus of the first adhesive layer at 23°C is 0.8 × 10⁻⁶. ５ ~5.0 x 10 ５ If the storage modulus is Pa, the thermally expandable particles can be appropriately expanded within the adhesive layer, and the adhesive strength can also be set to an appropriate value. From this viewpoint, the storage modulus of the first adhesive layer at 23°C is more preferably 0.9 × 10⁻⁶. ５ Pa or higher, and more preferably 1.0 × 10 ５ Pa or higher, more preferably 4.5 × 10 ５ Pa or less, and more preferably 4.0 × 10 ５ Pa or less, more preferably 0.9 × 10 ５ ~4.5 x 10 ５ Pa, and more preferably 1.0 × 10 ５ ~4.0 x 10 ５ It is Pa. Also, from a similar viewpoint, the storage modulus of the second adhesive layer at 23°C is preferably 0.8 × 10⁻⁶. ５ Pa or higher, more preferably 0.9 × 10 ５ Pa or higher, and more preferably 1.0 × 10 ５ The pressure is Pa or higher, preferably 5.0 × 10⁻⁶. ５ Pa or less, more preferably 4.5 × 10 ５ Pa or less, and more preferably 4.0 × 10 ５ It is Pa or less, preferably 0.8 × 10 ５ ~5.0 x 10 ５ Pa, and more preferably 0.9 × 10 ５ ~4.5 x 10 ５ Pa, and more preferably 1.0 × 10 ５ ~4.0 x 10 ５The storage modulus is Pa. The storage modulus of the first adhesive layer and the second adhesive layer may be the same or different. The storage modulus can be calculated, for example, by measuring the dynamic viscoelastic spectrum using a DVA-200 (manufactured by IT Measurement Control Co., Ltd.) under the following conditions: shear mode: 10 Hz, strain: 0.1%, temperature range: -40°C to 150°C, and heating rate: 3°C / min.

[0071] <Glass Transition Temperature> The glass transition temperature (Tg) of the first adhesive layer is preferably -20°C or higher. When the glass transition temperature of the first adhesive layer is -20°C or higher, the cohesive force is not too low, and when the thermally expandable particles expand due to heating, it is possible to suppress the residue of the adhesive of the first adhesive layer on the surface of the expanded thermally expandable particles. From this viewpoint, the glass transition temperature (Tg) of the first adhesive layer is more preferably -18°C or higher, even more preferably -15°C or higher, and even more preferably -13°C or higher. Furthermore, the glass transition temperature (Tg) of the first adhesive layer is preferably 20°C or lower. When the glass transition temperature of the first adhesive layer is 20°C or lower, it is possible to suppress the cohesive force from being too high, and the adhesive strength of the first adhesive layer can be exhibited at a high level. From this viewpoint, the glass transition temperature (Tg) of the first adhesive layer is more preferably 18°C ​​or lower, even more preferably 15°C or lower, and even more preferably 10°C or lower. Furthermore, from the above viewpoint, the glass transition temperature (Tg) of the first adhesive layer is preferably -20 to 20°C, more preferably -18 to 18°C, even more preferably -15 to 15°C, and even more preferably -13 to 10°C. The glass transition temperature (Tg) of the first adhesive layer can be adjusted by the type and amount of monomers constituting the polymer of the adhesive of the first adhesive layer. The glass transition temperature (Tg) of the second adhesive layer is preferably -20°C or higher. When the glass transition temperature of the second adhesive layer is -20°C or higher, the cohesive force is not too low, and when the thermally expandable particles expand due to heating, it is possible to suppress the residue of the adhesive of the second adhesive layer on the surface of the expanded thermally expandable particles. From this viewpoint, the glass transition temperature (Tg) of the second adhesive layer is more preferably -18°C or higher, even more preferably -15°C or higher, and even more preferably -13°C or higher. Furthermore, the glass transition temperature (Tg) of the second adhesive layer is preferably 20°C or lower. If the glass transition temperature of the second adhesive layer is 20°C or lower, excessive cohesive force can be suppressed, and the adhesive strength of the second adhesive layer can be increased. From this viewpoint, the glass transition temperature (Tg) of the first adhesive layer is more preferably 18°C ​​or lower, even more preferably 15°C or lower, and even more preferably 10°C or lower.Furthermore, from the above viewpoint, the glass transition temperature (Tg) of the second adhesive layer is preferably -20 to 20°C, more preferably -18 to 18°C, even more preferably -15 to 15°C, and even more preferably -13 to 10°C. The glass transition temperature (Tg) of the second adhesive layer can be adjusted by the type and amount of monomers constituting the polymer of the adhesive of the first adhesive layer. The glass transition temperature (Tg) of the first adhesive layer and the glass transition temperature (Tg) of the second adhesive layer may be the same or different. The glass transition temperature (Tg) can be calculated, for example, by measuring the dynamic viscoelastic spectrum using a DVA-200 (manufactured by IT Measurement Control Co., Ltd.) under the conditions of shear mode: 10 Hz, strain amount: 0.1%, temperature range: -40°C to 150°C, and heating rate: 3°C / min.

[0072] <Ratio of average particle diameter of thermally expandable particles to thickness of adhesive layer> When the adhesive layer is provided with thermally expandable particles on the first adhesive layer side of the substrate (i.e., the first surface), the ratio of the average particle diameter of the thermally expandable particles after thermal expansion to the thickness of the first adhesive layer (average particle diameter / thickness) is preferably 0.5 or more. Here, the thickness of the first adhesive layer refers to the thickness before thermal expansion. When the above ratio (average particle diameter / thickness) is 0.5 or more, the re-peelability of the double-sided adhesive tape when the thermally expandable particles expand can be further improved. From this viewpoint, the ratio of the average particle diameter of the thermally expandable particles after thermal expansion to the thickness of the first adhesive layer (average particle diameter / thickness) is more preferably 0.7 or more, and even more preferably 0.9 or more. Furthermore, there is no particular upper limit to the range of the ratio of the average particle diameter of the thermally expandable particles after thermal expansion to the thickness of the first adhesive layer (average particle diameter / thickness), but it is preferably 5.0 or less. If the ratio of the average particle diameter of the thermally expandable particles after thermal expansion to the thickness of the first adhesive layer (average particle diameter / thickness) is 5.0 or less, it is possible to suppress the peeling of the expanded particles from the first adhesive layer after thermal expansion. From this viewpoint, the ratio of the average particle diameter of the thermally expandable particles after thermal expansion to the thickness of the first adhesive layer (average particle diameter / thickness) is more preferably 4.0 or less, and even more preferably 3.0 or less.

[0073] <Layer Structure of Removable Adhesive Tape> The double-sided adhesive tape according to the embodiment of the present disclosure will be described below with reference to the drawings. Note that the double-sided adhesive tape of the present disclosure is not limited to what is shown in the drawings. As shown in Figure 1, the double-sided adhesive tape 1A according to one embodiment of the present disclosure may comprise a base layer 10A, a first adhesive layer 20 laminated on a first surface 111 of the base layer 10A, and a second adhesive layer 30 laminated on a second surface 112 opposite to the first surface 111 of the base layer 10A. The base layer 10A may comprise a base material 11 and thermally expandable particles 12 provided on the surface of the base material 11 on the side of the base layer 10A facing the first surface. In this case, although not shown, thermally expandable particles may also be provided on the surface of the base material 11 on the side of the base layer 10A facing the second surface, but the content of thermally expandable particles 12 on the first surface 111 of the base layer 10A will be greater than the content of thermally expandable particles on the second surface 112 of the base layer 10A.

[0074] As shown in Figure 2(a), the double-sided adhesive tape 1A can be used to bond two adherends 40 and 50 together. In this case, when the double-sided adhesive tape 1A interposed between the adherends 40 and 50 is heated and the thermally expandable particles 12 expand, as shown in Figure 2(b), the thermally expandable particles 12 swell outward from the surface of the first adhesive layer 20, and the swollen thermally expandable particles 12 reduce the adhesive force of the double-sided adhesive tape 1A to the adherend 40, allowing the double-sided adhesive tape 1A to be easily peeled off the adherend 40.

[0075] Furthermore, in another embodiment of the present disclosure, the double-sided adhesive tape may be configured such that the adhesive strength of both adhesive layers is reduced by thermally expandable particles. Specifically, as shown in Figure 3, the double-sided adhesive tape 1B in another embodiment of the present disclosure may comprise a base layer 10B, a first adhesive layer 20 laminated on a first surface 111 of the base layer 10B, and a second adhesive layer 30 laminated on a second surface 112 opposite to the first surface 111 of the base layer 10B. The base layer 10B may comprise a base material 11, thermally expandable particles 12 provided on the surface of the base material 11 on the side of the first surface of the base layer 10B, and thermally expandable particles 13 provided on the surface of the base material 11 on the side of the second surface of the base layer 10B.

[0076] As shown in Figure 4(a), the double-sided adhesive tape 1B can be used to bond two adherends 40 and 50 together. In this case, when the double-sided adhesive tape 1B interposed between the adherends 40 and 50 is heated and the thermally expandable particles 12 expand, as shown in Figure 4(b), the thermally expandable particles 12 and 13 swell outward from the surfaces of the first adhesive layer 20 and the second adhesive layer 30, respectively. The swollen thermally expandable particles 12 and 13 reduce the adhesive force of the double-sided adhesive tape 1A to the adherends 40 and 50, allowing the double-sided adhesive tape 1A to be easily peeled off the adherends 40 and 50.

[0077] <Applications> The applications of the double-sided adhesive tape disclosed herein are not particularly limited, but it is preferably used in applications where it is intended to be applied and removed. For example, it is preferably used for fixing components of various structures, including home appliance components, automobile parts, and building materials. For example, the double-sided adhesive tape disclosed herein is preferably used for fixing highly flexible components such as waterproofing materials and cushioning materials, specifically for fixing waterproofing materials and cushioning materials, or for temporary or permanent fixing of films such as resin and rubber.

[0078] [Method for Manufacturing Double-Sided Adhesive Tape] The method for manufacturing the double-sided adhesive tape of this disclosure is not particularly limited, but it can be obtained by coating an adhesive composition containing an organic solvent such as toluene, esters, ketones, or alcohols onto the surface of a release film, drying it, and then laminating the resulting adhesive layer to a substrate.

[0079] Examples of the present invention are described below. However, the present invention is not limited to the following examples.

[0080] The measurement and evaluation methods are as follows: <Storage modulus and glass transition temperature (Tg) of the adhesive layer> The storage modulus and glass transition temperature (Tg) of the adhesive layer were calculated by measuring the dynamic viscoelastic spectrum using a DVA-200 (manufactured by IT Measurement Control Co., Ltd.) under the following conditions: shear mode: 10 Hz, strain: 0.1%, temperature range: -40°C to 150°C, heating rate: 3°C / min.

[0081] <Content of thermally expandable particles> The content of thermally expandable particles was calculated by subtracting the basis weight of the base material from the basis weight of the base material layer.

[0082] <Average Particle Size of Thermally Expandable Particles> The average particle size of thermally expandable particles was measured using a laser scattering particle size distribution method on the thermally expandable particles used, or thermally expandable particles extracted from double-sided tape before heating. After dispersing the thermally expandable particles in a predetermined solvent (e.g., water), the average particle size was measured using a particle size distribution analyzer (e.g., Shimadzu Corporation's product name "SALD-2000J"). In addition to physically removing the thermally expandable particles from the double-sided tape using a spatula, the adhesive was dissolved in ethyl acetate, and only the thermally expandable particles were extracted. The average particle size of the thermally expandable particles after thermal expansion was also measured by extracting the thermally expanded fine particles from the heated double-sided tape using the same method as described above. Note that the average particle size refers to the volume average particle size.

[0083] <Initial Adhesion> A 23 μm thick PET film was attached to the second adhesive layer surface of the double-sided adhesive tape, ensuring no air bubbles were trapped. Next, the adhesive layer side of the double-sided adhesive tape that was attached to the PET film, but not to the PET film, was applied to the surface of an aluminum plate (manufactured by Standard Test Piece Co., Ltd., product name "A1050") at a speed of 30 mm / min using a 2 kg pressure rubber roller in an environment of room temperature (23°C) and relative humidity of 50%. After leaving it in this environment for 30 minutes, the 180-degree peel strength at a width of 25 mm was measured at a speed of 3 mm / min in accordance with the method of JIS Z0237, and this was defined as the initial adhesion (N / 25 mm).

[0084] <Adhesion after heating> (Examples 1-8 and Comparative Example 1) A 23 μm thick PET film was attached to one side of a double-sided adhesive tape, ensuring no air was trapped inside. Next, the adhesive layer side of the double-sided adhesive tape attached to the PET film, which was not attached to the PET film, was applied to the surface of an aluminum plate (manufactured by Standard Test Piece Co., Ltd., product name "A1050") at a speed of 30 mm / min using a 2 kg pressure rubber roller in an environment of room temperature (23°C) and relative humidity of 50%. After that, the aluminum side was heated on a 110°C hot plate and left for 3 minutes, then left at room temperature for 30 minutes. Following this, the 180-degree peel strength at a width of 25 mm was measured at a speed of 3 mm / min in accordance with the method of JIS Z0237, and this was defined as the adhesion after heating (N / 25 mm). Note that the adhesion after heating is the adhesion of the double-sided adhesive tape after the thermally expandable particles have been thermally expanded.

[0085] (Examples 9 and 10) The adhesive strength after heating was evaluated in the same manner as in Examples 1 to 8 and Comparative Example 1, except that the temperature of the hot plate was changed from 110°C to 140°C. The foaming start temperature and maximum foaming temperature of the foamed particles used as thermally expandable particles in Examples 9 and 10 were higher than those of the foamed particles used as thermally expandable particles in Examples 1 to 8, so the temperature of the hot plate was changed as described above.

[0086] <Change in Adhesion Strength> The change in adhesion strength was calculated by dividing the adhesion strength after heating by the initial adhesion strength.

[0087] <Evaluation of Removability> The removability of double-sided adhesive tapes was evaluated according to the following criteria: A: The rate of change in adhesive strength is 20% or less. B: The rate of change in adhesive strength is greater than 20% but 50% or less. C: The rate of change in adhesive strength is greater than 50%.

[0088] (Example 1) <Production of acrylic polymer> In a reactor equipped with a thermometer, stirrer, condenser, dropping funnel and nitrogen gas inlet, a monomer mixture consisting of 82 g of n-butyl acrylate, 5 g of 2-ethylhexyl acrylate, 10 g of ethyl acrylate, 3 g of acrylic acid, and 0.2 g of 2-hydroxyethyl methacrylate was dissolved in 83 g of ethyl acetate. At the reflux point, 0.1 parts by mass of azobisisobutyronitrile was added as a polymerization initiator. The mixture was refluxed for 5 hours to obtain a solution of acrylic copolymer, and then the solution was cooled. To the obtained solution, per 100 parts by mass of acrylic polymer solids, based on the amount of active ingredients, 15 parts by mass of rosin resin (product name "Pensel D-135", manufactured by Arakawa Chemical Industries, Ltd.) as a tackifying resin (C), 10 parts by mass of terpene phenol resin (product name "YS Polystar T-160", manufactured by Yasuhara Chemical Co., Ltd.), 10 parts by mass of rosin resin (product name "Super Ester A-75", manufactured by Arakawa Chemical Industries, Ltd.), and 1.9 parts by mass of desmodulo (product name, manufactured by Copestro, active ingredient amount 55% by mass) as a crosslinking agent (B) were added and stirred until homogeneous to obtain an acrylic polymer solution.

[0089] <Manufacturing of the base layer> Nonwoven fabric as the base material (manufactured by Nippon Paper Papilia Co., Ltd., product name "SPC", thickness 40 μm, basis weight 14 g / m²) ２ A thermally expandable particle was prepared. Foaming particle 1 (manufactured by Noryon, product name "EXPANCEL 032-DU-40", average particle size 13 μm, foaming start temperature: 80-95°C, maximum foaming temperature: 120-135°C) was prepared as the thermally expandable particle. A water-diluted mixture of 75 parts by mass of the thermally expandable particle and 25 parts by mass of an acrylic ester-based binder (manufactured by Toagosei Co., Ltd., product name "Aron NM-7090") as the binder resin was prepared, and after coating one side of the above substrate using an impregnation coating machine, it was dried to produce a substrate layer. The coating amount of thermally expandable particles was 5 g / m². ２ That's what I decided.

[0090] <Manufacturing of Adhesive Composition and Adhesive Tape> To the obtained acrylic polymer solution, 0.08 parts by mass of epoxy crosslinking agent (manufactured by Soken Chemical Co., Ltd., trade name "E-5C") was added as a crosslinking agent to the acrylic polymer, which is the non-volatile component of the acrylic polymer solution. Then, the mixture was uniformly mixed to obtain adhesive composition A. Next, the solution containing the obtained adhesive composition was applied to the release-treated surface of a 50 μm thick release polyethylene terephthalate (PET) film, which had a release treatment applied to one side, using a doctor knife, and the coating solution was dried by heating at 110°C for 10 minutes to obtain adhesive layers with thicknesses of 25 μm and 75 μm, respectively. A double-sided adhesive tape was obtained by attaching the first adhesive layer (25 μm) and the second adhesive layer (75 μm) to both sides of a base layer. The first adhesive layer was the adhesive layer on the side of the base layer on which the thermally expandable particles were supported, and the second adhesive layer was the adhesive layer on the side of the base layer on which the thermally expandable particles were not supported.

[0091] (Example 2) Thin paper as the base material (manufactured by Nippon Paper Industries Co., Ltd., product name "Thin Paper B", thickness 30 μm, basis weight 14 g / m²) ２ ) was prepared. Otherwise, the procedure was the same as in Example 1 to obtain the double-sided adhesive tape of Example 2.

[0092] (Example 3) Thin paper as the base material (manufactured by Nippon Paper Industries Co., Ltd., product name "Thin Paper K", thickness 45 μm, basis weight 23 g / m²) ２ We prepared the following. The amount of thermally expandable particles to be applied was 6 g / m². ２ The process was carried out in the same manner as in Example 1 to obtain the double-sided adhesive tape of Example 3.

[0093] (Example 4) The thickness of the first adhesive layer was set to 50 μm. Otherwise, the procedure was the same as in Example 1 to obtain the double-sided adhesive tape of Example 4.

[0094] (Example 5) <Production of Acrylic Polymer> In a reactor equipped with a thermometer, stirrer, condenser, dropping funnel and nitrogen gas inlet, a monomer mixture consisting of 66.4 g of n-butyl acrylate, 25.6 g of 2-ethylhexyl acrylate, 2.8 g of acrylic acid, and 0.5 g of 2-hydroxyethyl methacrylate was dissolved in 83 g of ethyl acetate. At the reflux point, 4 mmol of lauroyl peroxide was added as a polymerization initiator from the start of polymerization to 4 hours to polymerize the acrylic monomer. After 4 hours, 2 mmol of further polymerization initiator was added as needed from 4 to 6 hours to reduce residual monomer. Then, to further reduce residual monomer and residual initiator, the reaction was continued for 10 hours. After that, 4.7 g of vinyl acetate monomer was added and the solution was cooled. To the obtained solution, 10 parts by mass of rosin resin (trade name "Pensel D-160", manufactured by Arakawa Chemical Industries, Ltd.) as a tackifying resin (C) and 1.4 parts by mass of desmodulo (trade name, manufactured by Copestro, active ingredient amount 55% by mass) as a crosslinking agent (B) were added to 100 parts by mass of acrylic polymer solids, based on the amount of active ingredients, and the mixture was stirred until homogeneous to obtain an acrylic polymer solution.

[0095] <Manufacturing of Adhesive Composition and Adhesive Tape> To the obtained acrylic polymer solution, 1.2 parts by mass of an isocyanate crosslinking agent (manufactured by COVESTRO, trade name "Desmodulo") was added as a crosslinking agent to 100 parts by mass of the acrylic polymer, which is the non-volatile component of the acrylic polymer solution. Then, the mixture was uniformly mixed to obtain adhesive composition B. Next, the solution containing the obtained adhesive composition was applied to the release-treated surface of a 50 μm thick release polyethylene terephthalate (PET) film, which had a release treatment applied to one side, using a doctor's knife, and the coating solution was dried by heating at 110°C for 10 minutes to obtain adhesive layers with thicknesses of 25 μm and 75 μm, respectively. A double-sided adhesive tape was obtained by attaching the first adhesive layer (25 μm) and the second adhesive layer (75 μm) to both sides of a base layer. The first adhesive layer was the adhesive layer on the side of the base layer on which the thermally expandable particles were supported, and the second adhesive layer was the adhesive layer on the side of the base layer on which the thermally expandable particles were not supported.

[0096] (Example 6) The amount of thermally expandable particles to be applied is 3 g / m² ２The process was carried out in the same manner as in Example 1 to obtain the double-sided adhesive tape of Example 6.

[0097] (Example 7) The amount of thermally expandable particles to be applied is 2 g / m² ２ The procedure was otherwise the same as in Example 1 to obtain the double-sided adhesive tape of Example 7.

[0098] (Example 8) Nonwoven fabric as the base material (manufactured by Nippon Paper Papilia Co., Ltd., product name "TF Nonwoven Fabric", thickness 61 μm, basis weight 16 g / m²) ２ We prepared the following. The amount of thermally expandable particles to be applied was 3 g / m². ２ The procedure was otherwise the same as in Example 1 to obtain the double-sided adhesive tape of Example 8.

[0099] (Example 9) Nonwoven fabric as the base material (manufactured by Nippon Paper Papilia Co., Ltd., product name "TF Nonwoven Fabric", thickness 61 μm, basis weight 16 g / m²) ２ We prepared the following: As thermally expandable particles, we prepared foamed particles 2 (manufactured by Noryon, product name "EXPANCEL 092-DU-40", average particle size 12 μm, foaming start temperature: 123-133°C, maximum foaming temperature: 170-180°C). The coating amount of thermally expandable particles was 3 g / m². ２ The procedure was otherwise the same as in Example 1 to obtain the double-sided adhesive tape of Example 9.

[0100] (Example 10) Nonwoven fabric as the base material (manufactured by Nippon Paper Papilia Co., Ltd., product name "TF Nonwoven Fabric", thickness 61 μm, basis weight 16 g / m²) ２ We prepared the following: As thermally expandable particles, we prepared foaming particle 3 (manufactured by Sekisui Chemical Co., Ltd., product name "ADVANCEL EML101", average particle size 15 μm, foaming start temperature: 115-130°C, maximum foaming temperature: 155-175°C). The coating amount of thermally expandable particles was 3 g / m². ２ The procedure was otherwise the same as in Example 1 to obtain the double-sided adhesive tape of Example 10.

[0101] (Comparative Example 1) Nonwoven fabric as the base layer (manufactured by Nippon Paper Papilia Co., Ltd., product name "SPC", thickness 40 μm, basis weight 14 g / m²) ２ ) was used. Otherwise, the procedure was the same as in Example 1 to obtain the double-sided adhesive tape of Comparative Example 1.

[0102] The evaluation results are shown in Table 1.

[0103] The double-sided adhesive tapes of Examples 1 to 10 had good re-peelability because the base layer contained thermally expandable particles. On the other hand, the double-sided adhesive tape of Comparative Example 1 had poor re-peelability because the base layer did not contain thermally expandable particles.

[0104] 1A, 1B Double-sided adhesive tape 10A, 10B Base layer 11 Base material 12, 13 Thermally expandable particles 20 First adhesive layer 30 Second adhesive layer 40, 50 Adhesion

Claims

1. A double-sided adhesive tape comprising a base layer, a first adhesive layer laminated on a first surface of the base layer, and a second adhesive layer laminated on a second surface of the base layer opposite to the first surface, wherein the base layer comprises at least one base material selected from the group consisting of nonwoven fabrics and paper base materials, and thermally expandable particles.

2. The basis weight of the aforementioned substrate is 3 to 30 g / m². ２ The double-sided adhesive tape according to claim 1.

3. The density of the substrate is 0.1 to 0.8 g / cm³. ３ 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 thickness of the substrate is 5 to 100 μm.

5. The double-sided adhesive tape according to any one of claims 1 to 4, wherein the average particle diameter of the thermally expandable particles is 30 μm or less.

6. The double-sided adhesive tape according to any one of claims 1 to 5, wherein the first adhesive layer and the second adhesive layer are formed from an acrylic adhesive.

7. The double-sided adhesive tape according to any one of claims 1 to 6, wherein the thickness of the first adhesive layer is 80 μm or less.

8. The storage modulus of the first adhesive layer at 23°C is 0.8 × 10⁻⁶. ５ ~5.0 x 10 ５ A double-sided adhesive tape according to any one of claims 1 to 7, wherein the material is Pa.

9. The double-sided adhesive tape according to any one of claims 1 to 8, wherein the glass transition temperature of the first adhesive layer is -20 to 20°C.

10. The content of the thermally expandable particles in the substrate layer is 1 to 15 g / m². ２ The double-sided adhesive tape according to any one of claims 1 to 9.

11. The content of the thermally expandable particles in the substrate layer is 2 g / m² ２ The above describes the double-sided adhesive tape according to any one of claims 1 to 10.

12. The double-sided adhesive tape according to any one of claims 1 to 11, wherein at least the first surface of the base material layer contains the thermally expandable particles.

13. The double-sided adhesive tape according to claim 12, wherein the content of the thermally expandable particles on the first surface of the base material layer is greater than the content of the thermally expandable particles on the second surface of the base material layer.

14. The double-sided adhesive tape according to any one of claims 1 to 13, wherein the ratio of the average particle diameter of the thermally expandable particles after thermal expansion to the thickness of the first adhesive layer (average particle diameter / thickness) is 0.5 or more.

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