Double-sided adhesive sheet

Abstract

To provide an adhesive sheet excellent in impact resistance and reworkability.SOLUTION: There is provided a double-sided adhesive sheet 1 which has a base material 2 and adhesive layers 3 and 4 provided on both surfaces of the base material 2. The base material 2 has a maximum loss tanδ at a frequency of 10 kHz to 3.5 MHz at 23°C of 0.83 or less and a thickness of 40 μm or more. The adhesive layers 3, 4 have a Z-axis adhesive strength at 23°C of 0.6 MPa or more and a strain of 100% or more. The adhesive sheet 1 has a tensile rupture strength of 5 MPa or more and a strain at rupture of 100% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a double-sided adhesive sheet. [Background technology]

[0002] Adhesive sheets used in portable electronic devices such as mobile phones, digital cameras, and PDAs (Personal Digital Assistants) require various properties, including high adhesive strength. For example, in addition to having high adhesive strength, they must not peel off even when subjected to impact, and must not be subjected to strong impacts to components.

[0003] Patent Document 1 describes an impact-absorbing adhesive sheet using a substrate having an impact-absorbing layer in which the maximum value of the loss tangent tanδ at a specific frequency at 23°C is adjusted to be above a specific value. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2016 / 093133 [Overview of the project] [Problems that the invention aims to solve]

[0005] In recent years, in order to achieve the Sustainable Development Goals (SDGs) adopted at the 2015 UN Summit, industrial bonding materials, including adhesive sheets, have been required to be easily disassembled (reworkable) at any time and in any way, in order to increase the recycling and reuse rate of the materials being bonded (adhered objects). For this reason, adhesive sheets are sometimes expected to have excellent functions in both impact resistance, meaning they will not peel off even when subjected to impact, and reworkability.

[0006] In this respect, while shock-absorbing adhesive sheets like the one described in Patent Document 1 excel at absorbing energy when subjected to impacts such as drops, they also dissipate the deformation energy necessary for dismantling, making dismantling time-consuming. Increasing rigidity and reducing dissipated energy would compromise shock absorption, thus reducing impact resistance. For this reason, it is difficult to achieve both impact resistance and reworkability with conventional adhesive sheets that use the shock-absorbing layer described in Patent Document 1 as a base material.

[0007] This invention was conceived under these circumstances, and its purpose is to provide a double-sided adhesive sheet that is highly impact-resistant and highly reworkable. [Means for solving the problem]

[0008] As a result of diligent research to achieve the above objective, the inventors of this invention have found that, with a specific adhesive sheet, it is possible to provide a double-sided adhesive sheet that is excellent in impact resistance and reworkability. This invention was completed based on these findings.

[0009] In other words, the present invention comprises a base material and an adhesive layer provided on both sides of the base material. The above substrate has a maximum loss tangent tanδ of 0.83 or less at 23°C and frequencies from 10kHz to 3.5MHz, and a thickness of 40μm or more. The Z-axis adhesive strength of the above adhesive layer at 23°C is 0.6 MPa or higher, and the strain is 100% or higher. The present invention provides a double-sided adhesive sheet having a tensile breaking strength of 5 MPa or more and a strain of 100% or more at the time of fracture.

[0010] When the above-mentioned double-sided adhesive sheet is attached to a stainless steel plate in a 2cm x 2cm size and peeled off under conditions of a temperature of 23°C and a peeling angle of 30°, it is preferable that the time required for complete peeling is 120 seconds or less.

[0011] The above double-sided adhesive sheet preferably has a thickness of 60 to 400 μm.

[0012] The adhesive constituting the adhesive layer preferably contains at least an acrylic adhesive, a polyester adhesive, a rubber adhesive, or a urethane adhesive.

[0013] The adhesive layer preferably contains a filler whose surface is composed of an olefin resin.

[0014] The base material preferably contains at least a polyurethane resin, a rubber resin, or a polyolefin resin.

[0015] The above double-sided adhesive sheet is preferably used for fixing members to each other in electric and electronic devices.

[0016] Also, the present invention provides an electric and electronic device including the above double-sided adhesive sheet, where the double-sided adhesive sheet fixes members to each other on both adhesive surfaces.

Advantages of the Invention

[0017] According to the double-sided adhesive sheet of the present invention, it is possible to provide an adhesive sheet having excellent impact resistance and excellent reworkability. Therefore, for example, when used in a portable electronic device, even when it receives a dropping impact or the adherend is deformed, breakage or peeling is unlikely to occur, and yet it can be easily peeled off when intentionally trying to peel off the double-sided adhesive sheet.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic cross-sectional view of a double-sided adhesive sheet according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0019] [Double-sided Adhesive Sheet] A double-sided adhesive sheet according to one embodiment of the present invention comprises a base material and adhesive layers provided on both sides of the base material.

[0020] Figure 1 is a schematic cross-sectional view showing one embodiment of the double-sided adhesive sheet of the present invention. As shown in Figure 1, the double-sided adhesive sheet 1 comprises a base material 2, an adhesive layer 3 provided on one side of the base material 2, and an adhesive layer 4 provided on the other side of the base material 2. Release liners may be provided on the surfaces of the adhesive layer 3 and the adhesive layer 4, respectively.

[0021] (base material) The above-mentioned substrate is an element that functions as a support in a double-sided adhesive sheet. The above-mentioned substrate may be a single layer or a laminate of the same or different types of substrates.

[0022] The above substrate has a maximum loss tangent tanδ of 0.83 or less at 23°C and frequencies from 10kHz to 3.5MHz. This frequency range corresponds to the frequency range for impact from drops, and the fact that the maximum value of tanδ in this frequency range is 0.83 or less provides excellent impact resistance as well as excellent reworkability.

[0023] The maximum value of tanδ is 0.83 or less, and from the viewpoint of superior reworkability, it is preferably 0.80 or less, more preferably 0.75 or less, even more preferably 0.70 or less, even more preferably 0.65 or less, even more preferably 0.60 or less, and particularly preferably 0.50 or less. The maximum value of tanδ is, for example, 0.10 or more, preferably 0.20 or more, more preferably 0.25 or more, even more preferably 0.30 or more, and particularly preferably 0.35 or more. When the above substrate is composed of multiple layers (laminated bodies), the maximum value of tanδ is 0.83 or less for all substrates.

[0024] Examples of the above-mentioned substrates include plastic substrates (e.g., plastic films), porous materials such as paper, cloth, and nonwoven fabrics, nets, and foamed sheets. Plastic substrates (particularly plastic films) are preferred as the above-mentioned substrate. Furthermore, it is preferable that the above-mentioned substrate be a non-foamed sheet.

[0025] Examples of resins constituting the above-mentioned plastic substrate include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, and ethylene-hexene copolymer; polyurethane resins; rubber resins (natural rubber, synthetic rubber, mixtures thereof, etc.): polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyether ether ketone; polyetherimide; polyamides such as aramid and fully aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; and silicone resin. One type of the above resin may be used, or two or more types may be used.

[0026] The above resin may be a thermoplastic resin or a thermosetting resin, but a thermoplastic resin is preferred. The above thermoplastic resin may be a thermoplastic elastomer such as a thermoplastic polyurethane elastomer. The above thermoplastic polyurethane elastomer (TPU) consists of a hard phase (hard segment) and a soft phase (soft segment).

[0027] Among the above-mentioned base materials, it is preferable that they contain at least a polyurethane resin, a polyester resin, a rubber resin, or a polyolefin resin, from the viewpoint of easily keeping the maximum value of tanδ within the above range.

[0028] The above polyurethane resins are typically obtained by reacting a polyisoanate with a long-chain polyol, a chain extender, and, if necessary, other isocyanate-reactive compounds.

[0029] The above polyisocyanates are compounds having two or more isocyanate groups in their molecules. Examples of the above polyisocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and aromatic aliphatic polyisocyanates. Other examples of the above polyisocyanates include dimers, trimers, reaction products, or polymers of the above aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and / or aromatic aliphatic polyisocyanates (e.g., dimers and trimers of diphenylmethane diisocyanate, reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, etc.). Only one type of polyisocyanate may be used, or two or more types may be used.

[0030] Examples of the long-chain polyols mentioned above include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, and polyacrylic polyols. The number-average molecular weight of the long-chain polyol is usually 500 or more, preferably 500 to 10000, more preferably 600 to 6000, and even more preferably 800 to 4000. One type of long-chain polyol may be used, or two or more types may be used.

[0031] As the above-mentioned chain extender, chain extenders commonly used in the production of polyurethane elastomers can be used, such as low molecular weight polyols and polyamines. The molecular weight of the chain extender is usually less than 500, preferably 300 or less. One type of chain extender may be used, or two or more types may be used.

[0032] From the viewpoint of easily keeping the maximum value of tanδ within the above range, the above polyurethane resin preferably includes a polyether polyol as the long-chain polyol (polyether polyol-based polyurethane resin). Furthermore, it may also include a polyester polyol as the long-chain polyol (polyester polyol-based polyurethane resin).

[0033] The polyurethane resin described above preferably includes a rigid polyurethane resin, from the viewpoint of easily keeping the maximum value of tanδ within the above range. If the rigid polyurethane resin contains two or more types of polyurethane resins, it is the polyurethane resin with the highest hardness. The Shore hardness D of the rigid polyurethane resin is preferably 30 or higher, and more preferably 40 or higher. The Shore hardness D of the rigid polyurethane resin is, for example, 50 or lower.

[0034] The polyurethane resin described above may contain, together with the rigid polyurethane, a polyurethane resin with a lower hardness than the rigid polyurethane (a flexible polyurethane resin). The Shore hardness A of the flexible polyurethane resin is preferably 70 or less, and more preferably 66 or less. The Shore hardness A of the flexible polyurethane resin is preferably 40 or more, and more preferably 50 or more.

[0035] The proportion of the rigid polyurethane resin in the polyurethane resin is preferably more than 50% by mass, more preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the polyurethane resin (100% by mass), from the viewpoint of easily keeping the maximum value of tanδ within the above range. The above proportion is not particularly limited and may be 99% by mass or less, or 95% by mass or less.

[0036] The above-mentioned substrate may contain other resins, such as rubber resins, along with the polyurethane resin. In particular, from the viewpoint of easily keeping the maximum value of tanδ within the above range, it is preferable to include a rubber resin together with the rigid polyurethane resin.

[0037] The ratio of polyurethane resin to the total of polyurethane resin and rubber resin in the above-mentioned substrate is preferably more than 50% by mass, more preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of easily keeping the maximum value of tanδ within the above range. The above ratio is not particularly limited and may be 99% by mass or less, or 90% by mass or less.

[0038] The proportion of thermoplastic resin (particularly one or more resins selected from the group consisting of polyurethane resins, rubber resins, and polyolefin resins) in the above-mentioned substrate is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the total amount of the above-mentioned substrate (100% by mass).

[0039] The above-mentioned substrate can be manufactured by known or conventional methods, such as extrusion molding, inflation molding, T-die casting, and calender roll molding.

[0040] The above-mentioned base material may contain various additives such as fillers (inorganic fillers, organic fillers, etc.), colorants (pigments and dyes), dispersants (surfactants, etc.), anti-aging agents, antioxidants, UV absorbers, antistatic agents, lubricants, and plasticizers. The proportion of each additive is less than 30% by mass (for example, less than 20% by mass, typically less than 10% by mass) of the total mass of the above-mentioned base material.

[0041] The above-mentioned substrate may include auxiliary layers. Examples of the above-mentioned auxiliary layers include a colored layer, a reflective layer, a primer layer, and an antistatic layer provided on the surface of the substrate.

[0042] The surface of the substrate may be subjected to surface treatments such as physical treatments like corona discharge treatment, plasma treatment, sandblasting, ozone exposure treatment, flame exposure treatment, high-voltage electric shock exposure treatment, and ionization radiation treatment; chemical treatments like chromic acid treatment; or surface treatments such as easy adhesion treatment with a coating agent (primer) in order to improve adhesion and retention with the adhesive layer. It is preferable that the surface treatment to improve adhesion is applied to the entire surface of the substrate.

[0043] The thickness of the above-mentioned substrate is not particularly limited, but is 40 μm or more, preferably 50 μm or more. When the above-mentioned thickness is 40 μm or more, the reworkability is superior. The above-mentioned thickness is not particularly limited, but for example it may be 380 μm or less, 250 μm or less, or 100 μm or less.

[0044] (Adhesive layer) The adhesive layers provided on both sides of the substrate in the above-mentioned double-sided adhesive sheet may be the same adhesive layer, or they may be adhesive layers with different compositions, thicknesses, physical properties, etc. Furthermore, the adhesive layer provided on one side of the substrate may be a single layer, or it may be a multi-layered layer composed of the same or different layers with different compositions, thicknesses, physical properties, etc.

[0045] The adhesive constituting the above adhesive layer can be any known or conventional adhesive, and is not particularly limited. Examples include acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixtures thereof, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, fluorine adhesives, and styrene adhesives. Among these, acrylic adhesives, polyester adhesives, rubber adhesives, and urethane adhesives are preferred as adhesives constituting the adhesive layer in terms of adhesion, weather resistance, cost, and ease of designing the adhesive. One type of adhesive may be used, or two or more types may be used.

[0046] The above acrylic adhesive contains an acrylic polymer as a base polymer. The above acrylic polymer is a polymer that contains an acrylic monomer (a monomer having a (meth)acryloyl group in its molecule) as a monomer component constituting the polymer. That is, the above acrylic polymer contains constituent units derived from an acrylic monomer. Note that only one type of acrylic polymer may be used, or two or more types may be used. Furthermore, the above acrylic polymer may contain only one type of acrylic monomer as a monomer component, or two or more types may be contained. In this specification, "(meth)acrylic" means "acrylic" and / or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and the same applies to other terms.

[0047] In this specification, the base polymer refers to the main polymer component in the adhesive constituting the adhesive layer, for example, the polymer component present in more than 50% by mass. The content of the base polymer in the adhesive layer is preferably 60% by mass or more, and more preferably 70% by mass or more, based on 100% by mass of the total amount of the adhesive layer.

[0048] The above acrylic polymer is preferably a polymer that contains the largest mass percentage of constituent units derived from (meth)acrylic acid ester. Examples of the above (meth)acrylic acid ester include hydrocarbon group-containing (meth)acrylic acid esters. Examples of the above hydrocarbon group-containing (meth)acrylic acid ester include alkyl (meth)acrylic acid esters having linear or branched aliphatic hydrocarbon groups, cycloalkyl (meth)acrylic acid esters having alicyclic hydrocarbon groups, and aryl (meth)acrylic acid esters having aromatic hydrocarbon groups. Only one type of hydrocarbon group-containing (meth)acrylic acid ester may be used, or two or more types may be used.

[0049] Examples of the above alkyl (meth)acrylate esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and methyl (meth)acrylate. Examples include isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0050] Among the alkyl (meth)acrylate esters mentioned above, alkyl (meth)acrylate esters having linear or branched aliphatic hydrocarbon groups with 1 to 20 carbon atoms (preferably 2 to 12, more preferably 4 to 10) are preferred. When the number of carbon atoms is within the above range, it is easier to adjust the glass transition temperature of the acrylic polymer and to make the tackiness more appropriate.

[0051] Examples of (meth)acrylic acid esters having the above-mentioned alicyclic hydrocarbon group include (meth)acrylic acid esters having a monocyclic aliphatic hydrocarbon ring such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate; (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring such as isobornyl (meth)acrylate; and (meth)acrylic acid esters having three or more aliphatic hydrocarbon rings such as dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0052] Examples of (meth)acrylic acid esters having the above-mentioned aromatic hydrocarbon group include phenyl (meth)acrylate and benzyl (meth)acrylate.

[0053] In order to appropriately exhibit the basic properties such as tackiness due to the hydrocarbon group-containing (meth)acrylic acid ester in the adhesive layer, the proportion of the hydrocarbon group-containing (meth)acrylic acid ester in the total monomer components constituting the acrylic polymer is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, and may be 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount (100% by mass) of the total monomer components. Furthermore, from the viewpoint of enabling copolymerization with other monomer components and obtaining the effects of those other monomer components, the above proportion may be 99.9% by mass or less, and may be 98% by mass or less, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

[0054] The above acrylic polymer may contain constituent units derived from other monomer components copolymerizable with the above hydrocarbon group-containing (meth)acrylic acid ester for the purpose of modifying it to improve cohesiveness or introduce crosslinking points. Examples of the above other monomer components include polar group-containing monomers such as hydroxyl group-containing monomers, nitrogen atom-containing monomers, carboxyl group-containing monomers, acid anhydride monomers, keto group-containing monomers, alkoxysilyl group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, and phosphate group-containing monomers. Each of the above other monomer components may be used individually or in combination of two or more.

[0055] Examples of the above-mentioned hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

[0056] Examples of nitrogen atom-containing monomers include amide group-containing monomers, amino group-containing monomers, cyano group-containing monomers, and monomers having a nitrogen atom-containing ring. Examples of amide group-containing monomers include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide. Examples of amino group-containing monomers include aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and t-butylaminoethyl(meth)acrylate. Examples of cyano group-containing monomers include acrylonitrile and methacrylonitrile. Examples of monomers having the nitrogen atom-containing ring mentioned above include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, and N-(meth)acryloylmorpholine.

[0057] Examples of the above carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the above acid anhydride monomers include maleic anhydride and itaconic anhydride.

[0058] Examples of the above-mentioned keto group-containing monomers include diacetone(meth)acrylamide, diacetone(meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetacetate, and vinyl acetacetate.

[0059] Examples of the above-mentioned alkoxysilyl group-containing monomers include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0060] Examples of the above-mentioned glycidyl group-containing monomers include glycidyl (meth)acrylate and methylglycidyl (meth)acrylate.

[0061] Examples of the above-mentioned sulfonic acid group-containing monomers include styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

[0062] Examples of the above-mentioned phosphate group-containing monomers include 2-hydroxyethyl acryloyl phosphate.

[0063] The total proportion of the polar group-containing monomers in the total monomer components (100% by mass) constituting the above acrylic polymer is not particularly limited, but from the viewpoint of better exhibiting the effects of using polar group-containing monomers, it is preferably 0.1% by mass or more, and more preferably 1% by mass or more. Furthermore, from the viewpoint of obtaining an adhesive layer with appropriate flexibility, the total proportion is preferably 10% by mass or less, and more preferably 8% by mass or less.

[0064] The monomer components constituting the above-mentioned acrylic polymer may further include other monomers. Examples of these other monomers include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyltoluene; olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; and vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether.

[0065] The proportion of the other monomers in the total amount of all monomer components constituting the above acrylic polymer (100% by mass) may be, for example, 0.05% by mass or more, or 0.5% by mass or more. The above proportion may also be, for example, 20% by mass or less, 10% by mass or less, or 5% by mass or less, and may be substantially absent.

[0066] The weight-average molecular weight (Mw) of the above acrylic polymer is 5 × 10 4 It is preferable that the number be greater than or equal to 10 × 10 4 More preferably 20 × 10 4 In particular, 30 × 10 4 That's all. The above Mw is 5 × 10 4 When the above is true, an adhesive exhibiting good cohesiveness is easily obtained. Also, the above Mw is 500 × 10 4 The following is preferable: The above Mw is 500 × 10 4 The following conditions make it easier to form an adhesive that exhibits moderate fluidity (mobility of polymer chains), resulting in excellent reworkability.

[0067] The above-mentioned acrylic polymer is obtained by polymerizing a composition containing at least an acrylic monomer. While not particularly limited, these polymerization methods include solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, and polymerization by active energy ray irradiation (active energy ray polymerization). Among these, bulk polymerization, thermal polymerization, and active energy ray polymerization are preferred in terms of transparency of the adhesive layer and cost. Furthermore, the resulting acrylic polymer may be a random copolymer, block copolymer, graft copolymer, or any other type.

[0068] The above polyester adhesive contains a polyester resin as a base polymer. The above polyester resin is a polymer containing a polyol and a polycarboxylic acid as monomer components constituting the polymer. That is, the above polyester resin contains constituent units derived from a polyol and constituent units derived from a polycarboxylic acid. The above polyester resin may be used alone or two or more types.

[0069] Examples of polycarboxylic acids include dicarboxylic acids and trivalent or higher carboxylic acids. Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, dimethylglutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, dodecanedioic acid, sebacic acid, thiodipropionic acid, and diglycolic acid; dimer acids of unsaturated fatty acids; 1,2-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and 4-methyl-1,2-cyclohexanedicarboxylic acid. Examples include alicyclic dicarboxylic acids such as carboxylic acids, norbornanedicarboxylic acid, and adamantanedicarboxylic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, and dodecenyl succinic anhydride; aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, orthophthalic acid, benzylmalonic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-dicarboxydiphenyl ether, and naphthalenedicarboxylic acid; and derivatives thereof. Examples of the above derivatives include carboxylate salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters. Examples of trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, trimesic acid, and trimer acid. The above polycarboxylic acids may be used individually or in combination of two or more types.

[0070] Examples of the above polyols include diols and polyols with a valentity of 3 or higher. Examples of diols include (poly)alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, and polytetramethylene glycol; 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-hexanediol, 2,2 Examples include aliphatic diols such as 4-trimethyl-1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; dimer diols; alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecanediethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; and aromatic diols such as 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-,m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and their ethylene oxide and propylene oxide adducts. Examples of polyols with a valent or higher valent nucleotide include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, and adamantanetriol. One or more of these polyols may be used.

[0071] The total content of constituent units derived from dicarboxylic acids and constituent units derived from diols in the above polyester resin is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and particularly preferably 99% by mass or more (for example, 99 to 100% by mass) based on 100% by mass of the total amount of constituent units derived from monomers constituting the above polyester resin.

[0072] The content of constituent units derived from polycarboxylic acids in the above polyester resin is, for example, 0.5 equivalents or more per polyol equivalent, preferably 0.58 equivalents or more, more preferably 0.66 equivalents or more, even more preferably 0.83 equivalents or more, even more preferably 0.88 equivalents or more, and particularly preferably 0.95 equivalents or more. Furthermore, the above content is, for example, 2.0 equivalents or less per polyol equivalent, preferably 1.7 equivalents or less, more preferably 1.5 equivalents or less, even more preferably 1.2 equivalents or less, even more preferably 1.1 equivalents or less, and particularly preferably 1.05 equivalents or less.

[0073] The equivalent ratio of constituent units derived from polycarboxylic acids and constituent units derived from polyols in the above-mentioned polyester resin is not particularly limited, and an appropriate equivalent ratio can be set considering the desired polymer properties and synthesizability. A high equivalent ratio of polycarboxylic acids allows for easy expression of properties based on polycarboxylic acids. Similarly, a high equivalent ratio of polyols allows for easy expression of properties based on polyols.

[0074] Various common solvents may be used in the polymerization of monomer components. Examples of such solvents include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. One or more of these solvents may be used.

[0075] The polymerization initiators, chain transfer agents, emulsifiers, etc., used in the radical polymerization of monomer components are not particularly limited and can be selected and used as appropriate. The weight-average molecular weight of the polymer can be controlled by the amount of polymerization initiator and chain transfer agent used and the reaction conditions, and the appropriate amounts used are adjusted according to the type of agent.

[0076] Depending on the type of polymerization reaction, various polymerization initiators can be used for the polymerization of monomer components, including thermal polymerization initiators and photopolymerization initiators (photoinitiators). One type of polymerization initiator may be used, or two or more types may be used.

[0077] The above-mentioned thermal polymerization initiators are not particularly limited, but examples include azo polymerization initiators, peroxide polymerization initiators (e.g., persulfates such as dibenzoyl peroxide, tert-butyl permaleate, potassium persulfate, benzoyl peroxide, hydrogen peroxide, etc.), substituted ethane initiators such as phenyl-substituted ethane, aromatic carbonyl compounds, redox polymerization initiators, etc. Among these, the azo polymerization initiator disclosed in Japanese Patent Application Publication No. 2002-69411 is preferred. Examples of the above-mentioned azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid)dimethyl, and 4,4'-azobis-4-cyanovaleric acid. The amount of thermal polymerization initiator used can be the usual amount, for example, it can be selected from a range of 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, per 100 parts by mass of monomer component.

[0078] The above-mentioned photopolymerization initiators are not particularly limited, but examples include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. Other examples include acylphosphine oxide-based photopolymerization initiators and titanocene-based photopolymerization initiators. Examples of the above-mentioned benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl ether. Examples of the above acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of the above α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of the above aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of the above photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of the above benzoin-based photopolymerization initiators include benzoin. Examples of the above benzyl-based photopolymerization initiators include benzyl. Examples of the benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. Examples of the ketal-based photopolymerization initiators include benzyldimethyl ketal.Examples of the thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of the acylphosphine oxide-based photopolymerization initiators include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Examples of the titanocene-based photopolymerization initiators include bis(η5-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium. The amount of photopolymerization initiator used can be the usual amount, for example, it can be selected from a range of 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, per 100 parts by mass of monomer component.

[0079] The acrylic polymer and polyester resin described above may contain structural components derived from the crosslinking agent. That is, the acrylic polymer and polyester resin may be crosslinked with the crosslinking agent. By using the crosslinking agent, a crosslinked structure can be formed in the acrylic polymer in the acrylic adhesive layer, and the gel fraction can be controlled. Furthermore, the crosslinking agent has the effect of crosslinking polyesters together and can also function as a chain extender for polyester resins. When the crosslinking agent is used, a crosslinked structure is formed in the base polymer in the adhesive layer, improving the cohesive force. Only one type of crosslinking agent may be used, or two or more types may be used.

[0080] The above-mentioned crosslinking agents are not particularly limited, but examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, amine-based crosslinking agents, hydrazine-based crosslinking agents, silicone-based crosslinking agents, and silane-based crosslinking agents (silane coupling agents).

[0081] The content of the crosslinking agent is not particularly limited, but is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and especially preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the total amount of monomer components constituting the acrylic polymer and / or polyester resin.

[0082] The above-mentioned isocyanate-based crosslinking agent is a compound having an average of two or more isocyanate groups per molecule (polyfunctional isocyanate compound). Examples of the above-mentioned isocyanate-based crosslinking agent include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and the like.

[0083] Examples of the above-mentioned aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; and 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0084] Examples of the above-mentioned alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0085] Examples of the above aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diisocyanate. Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropanediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0086] In addition, commercially available isocyanate-based crosslinking agents include, for example, trimethylolpropane / tolylene diisocyanate adduct (product name "Coronate L", manufactured by Tosoh Corporation), trimethylolpropane / hexamethylene diisocyanate adduct (product name "Coronate HL", manufactured by Tosoh Corporation), and trimethylolpropane / xylylene diisocyanate adduct (product name "Takenate D-110N", manufactured by Mitsui Chemicals, Inc.).

[0087] In addition, while isocyanate-based crosslinking agents are not required for aqueous dispersions of modified acrylic polymers prepared by emulsion polymerization, if necessary, blocked isocyanate-based crosslinking agents can be used because they react readily with water.

[0088] When an isocyanate-based crosslinking agent is used as the above crosslinking agent, the content of the isocyanate-based crosslinking agent is not particularly limited, but is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, based on 100 parts by mass of the total amount of monomer components constituting the acrylic polymer and / or polyester resin. The above content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.

[0089] Examples of the epoxy crosslinking agents (polyfunctional epoxy compounds) mentioned above include N,N,N',N'-tetraglycidyl-m-xylenediline, 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, and sorbitol polyglycidyl ether. Examples of epoxy crosslinking agents include diglycidyl ethers, glycerol polyglycidyl ethers, pentaerythritol polyglycidyl ethers, polyglycerol polyglycidyl ethers, sorbitan polyglycidyl ethers, trimethylolpropane polyglycidyl ethers, diglycidyl adipate esters, diglycidyl o-phthalate esters, triglycidyl-tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ethers, bisphenol-S-diglycidyl ethers, and epoxy resins having two or more epoxy groups in their molecules. In addition, commercially available epoxy crosslinking agents such as the trade name "Tetrad C" (manufactured by Mitsubishi Gas Chemical Company, Inc.) can also be used.

[0090] When an epoxy crosslinking agent is used as the above crosslinking agent, the content of the epoxy crosslinking agent is not particularly limited, but is preferably more than 0 parts by mass and 1 part by mass or less, more preferably 0.001 to 0.5 parts by mass, even more preferably 0.002 to 0.2 parts by mass, even more preferably 0.005 to 0.1 parts by mass, even more preferably 0.008 to 0.1 parts by mass, and particularly preferably 0.009 to 0.05 parts by mass.

[0091] As the above-mentioned peroxide-based crosslinking agent, any agent that generates radical active species upon heat to promote crosslinking of the base polymer can be used as appropriate. However, considering workability and stability, it is preferable to use a peroxide with a 1-minute half-life temperature of 80 to 160°C, and more preferably a peroxide with a half-life temperature of 90 to 140°C.

[0092] Examples of the above peroxide-based crosslinking agents include di(2-ethylhexyl)peroxydicarbonate (half-life temperature at 1 minute: 90.6°C), di(4-t-butylcyclohexyl)peroxydicarbonate (half-life temperature at 1 minute: 92.1°C), di-sec-butylperoxydicarbonate (half-life temperature at 1 minute: 92.4°C), t-butylperoxyneodecanoate (half-life temperature at 1 minute: 103.5°C), t-hexylperoxypivalate (half-life temperature at 1 minute: 109.1°C), t-butylperoxypivalate (half-life temperature at 1 minute: 110.3°C), and dilauroyl peroxy Examples include peroxide (half-life temperature at 1 minute: 116.4°C), di-n-octanoyl peroxide (half-life temperature at 1 minute: 117.4°C), 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate (half-life temperature at 1 minute: 124.3°C), di(4-methylbenzoyl) peroxide (half-life temperature at 1 minute: 128.2°C), dibenzoyl peroxide (half-life temperature at 1 minute: 130.0°C), t-butyl peroxyisobutyrate (half-life temperature at 1 minute: 136.1°C), and 1,1-di(t-hexylperoxy)cyclohexane (half-life temperature at 1 minute: 149.2°C).

[0093] The half-life of the peroxide-based crosslinking agent mentioned above is an indicator of the decomposition rate of the peroxide, and refers to the time it takes for the amount of remaining peroxide to be halved. The decomposition temperature required to obtain a half-life at any given time, and the half-life time at any given temperature, are described in manufacturer catalogs, for example, in NOF Corporation's "Organic Peroxide Catalog, 9th Edition (May 2003)". The amount of remaining decomposed peroxide after reaction treatment can be measured, for example, by HPLC (High-Performance Liquid Chromatography). More specifically, for example, approximately 0.2 g of the adhesive after reaction treatment is taken, immersed in 10 ml of ethyl acetate, and extracted by shaking at 120 rpm at 25°C for 3 hours, then left to stand at room temperature for 3 days. Next, 10 ml of acetonitrile is added, shaken at 120 rpm at 25°C for 30 minutes, filtered through a membrane filter (0.45 μm), and approximately 10 μl of the resulting extract is injected into HPLC for analysis to determine the amount of peroxide after reaction treatment.

[0094] When a peroxide-based crosslinking agent is used as the crosslinking agent, the content of the crosslinking agent is not particularly limited, but it is preferably 2 parts by mass or less, more preferably 0.02 to 2 parts by mass, and even more preferably 0.05 to 1 part by mass, based on 100 parts by mass of the total amount of monomer components constituting the acrylic polymer and / or polyester resin.

[0095] Furthermore, organic crosslinking agents or polyfunctional metal chelates may be used in combination as the crosslinking agent. Polyfunctional metal chelates are those in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. Examples of atoms in the organic compound that form covalent or coordinate bonds include oxygen atoms, and examples of organic compounds include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.

[0096] Among the above crosslinking agents, it is preferable to include an isocyanate-based crosslinking agent. It is even more preferable to include another crosslinking agent together with the isocyanate-based crosslinking agent. Among the above other crosslinking agents, an epoxy-based crosslinking agent is preferred. When such a crosslinking agent is used, a combination with the above acrylic polymer and / or the above polyester resin (particularly the preferred combination with the above acrylic polymer and / or the above polyester resin) can be made to create an adhesive layer that is thin but has superior adhesion.

[0097] Examples of the above-mentioned rubber-based adhesives include natural rubber-based adhesives; isoprene rubber, polyisobutylene rubber, butyl rubber, ethylene-propylene rubber, styrene-butadiene rubber, styrene-isoprene rubber, styrene-ethylene-propylene-styrene rubber, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer, styrene-ethylene-propylene block copolymer, recycled rubber, and modified versions thereof. Furthermore, if the above-mentioned rubber-based adhesive is a copolymer, it may be either a block copolymer or a random copolymer.

[0098] Examples of the above-mentioned silicone-based adhesives include silicone rubber and silicone resin mainly composed of organopolysiloxane, or those obtained by adding crosslinking agents such as siloxane-based crosslinking agents and peroxide-based crosslinking agents to these and then crosslinking and polymerizing them.

[0099] The adhesive layer may contain a tackifying resin. When a tackifying resin is included, the adhesive layer tends to have better adhesion even when thin. When the adhesive layer contains an acrylic adhesive and / or a polyester adhesive and a tackifying resin, it has excellent adhesion to the adherend and is less likely to peel off.

[0100] Examples of the tackifying resins mentioned above include phenolic tackifying resins, terpene tackifying resins, rosin tackifying resins, hydrocarbon tackifying resins, epoxy tackifying resins, polyamide tackifying resins, elastomer tackifying resins, and ketone tackifying resins. One type of tackifying resin may be used, or two or more types may be used.

[0101] Examples of the above-mentioned phenolic tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, and rosin phenol resins. The above-mentioned terpene phenol resins are polymers containing terpene residues and phenol residues, and include copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins), and phenol-modified homopolymers or copolymers of terpenes (phenol-modified terpene resins). Examples of terpenes constituting the above-mentioned terpene phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (d-isomer, l-isomer, d / l-isomer (dipentene) etc.). The above-mentioned hydrogenated terpene phenol resins are resins having a structure obtained by hydrogenating the above-mentioned terpene phenol resins. The above-mentioned alkylphenol resins are resins obtained from alkylphenols and formaldehyde (oily phenol resins). Examples of the above-mentioned alkylphenol resins include novolac type and resol type. The above-mentioned rosin phenol resins are phenol-modified products of rosins or various rosin derivatives described later. The above-mentioned rosin-phenol resin can be obtained, for example, by adding phenol to rosins or various rosin derivatives described later using an acid catalyst and then thermally polymerizing them.

[0102] Examples of the above-mentioned terpene-based tackifying resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. The above-mentioned polymer of terpenes may be a single polymer of one terpene or a copolymer of two or more terpenes. Examples of single-polymer terpenes include α-pinene polymers, β-pinene polymers, and dipentene polymers. The above-mentioned modified terpene-based tackifying resin is a modified version of the above-mentioned terpene resin (modified terpene resin). Examples of the above-mentioned modified terpene resin include styrene-modified terpene resins and hydrogenated terpene resins.

[0103] Examples of the above-mentioned rosin-based tackifying resins include rosins and rosin derivative resins. Examples of the above-mentioned rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins) obtained by hydrogenating, disproportionating, polymerization, etc., of these unmodified rosins. Examples of the above-mentioned rosin derivative resins include derivatives of the above-mentioned rosins. Examples of the above-mentioned rosin derivative resins include rosin esters such as unmodified rosin esters, which are esters of unmodified rosin and alcohols, and modified rosin esters, which are esters of modified rosin and alcohols; unsaturated fatty acid modified rosins obtained by modifying rosins with unsaturated fatty acids; unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups of rosins or the above-mentioned various rosin derivatives; and metal salts of rosins or the above-mentioned various rosin derivatives. Specific examples of the above-mentioned rosin esters include methyl esters of unmodified or modified rosin, triethylene glycol esters, glycerol esters, and pentaerythritol esters.

[0104] Examples of the hydrocarbon-based tackifying resins mentioned above include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic-aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins.

[0105] The content of the tackifying resin in the adhesive layer is not particularly limited, but is, for example, 1 part by mass or more (for example, 1 to 100 parts by mass) per 100 parts by mass of the total amount of the base polymer, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more. When the content is 1 part by mass or more, the adhesive layer has even better adhesion even when it is thin. From the viewpoint of excellent heat resistance and cohesiveness, the content is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less.

[0106] The above adhesive layer may or may not contain a filler. Including the filler reduces the tackiness of the adhesive layer when attempting to intentionally peel off the double-sided adhesive sheet, resulting in improved reworkability. The filler may be used alone or two or more types.

[0107] Examples of fillers include particulate organic and inorganic materials. Examples of materials constituting the inorganic materials include metals such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, and stainless steel; metal oxides such as aluminum oxide, silicon oxide (silicon dioxide, silica), titanium oxide, zirconium oxide, zinc oxide, tin oxide, copper oxide, and nickel oxide; aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, basic magnesium carbonate, and hydrotalus. Examples include metal hydroxides and hydrated metal compounds such as oxalite, dosonite, borax, and zinc borate; carbides such as silicon carbide, boron carbide, nitrogen carbide, and calcium carbide; nitrides such as aluminum nitride, silicon nitride, boron nitride, and gallium nitride; carbonates such as calcium carbonate; titanates such as barium titanate and potassium titanate; carbon-based materials such as carbon black, carbon tubes (carbon nanotubes), carbon fibers, and diamonds; inorganic materials such as glass; and natural raw material particles such as volcanic ash, clay, and sand.

[0108] Examples of materials constituting the above-mentioned organic matter include polystyrene, acrylic resin (e.g., polymethyl methacrylate), phenolic resin, benzoguanamine resin, urea resin, silicone resin, polyester, polyurethane, polyolefin (polymers with one or more α-olefins as monomer components; for example, polyethylene such as LLDPE, LDPE, HDPE, polypropylene, etc.), polyamide (e.g., nylon, etc.), polyimide, polyvinylidene chloride, and other polymers.

[0109] The filler described above may have a hollow structure. The hollow portion of the filler having the hollow structure (the space inside the hollow particle) may be in a vacuum state or may be filled with a medium. Examples of the medium include inert gases such as nitrogen and argon, air, and volatile solvents.

[0110] Among the above fillers, fillers whose surface is composed of an organic or inorganic material other than the base polymer type, and fillers having a hollow structure are preferred. The organic material other than the base polymer type is, for example, an organic material other than an acrylic polymer when the base polymer is an acrylic polymer, and an organic material other than a polyester resin when the base polymer is a polyester resin.

[0111] The above-mentioned filler may be a filler with different internal and external compositions (core-shell type filler), or it may be a filler with the same internal and external composition (filler without a boundary between internal and external).

[0112] Examples of fillers whose surfaces are composed of organic materials other than the base polymer include fillers whose surfaces are composed of olefin resins and fillers whose surfaces are composed of silicone resins. Examples of fillers whose surfaces are composed of olefin resins include olefin-based fillers which are composed entirely of olefin resins and fillers whose surfaces are composed of olefin resins and whose interiors are composed of different materials. Examples of fillers whose surfaces are composed of silicone resins include silicone-based fillers which are composed entirely of silicone resins and fillers whose surfaces are composed of silicone resins and whose interiors are composed of different materials. Such fillers have little interaction with the acrylic components in the acrylic adhesive layer and the monomer components in the polyester adhesive layer, are less likely to break when the adhesive layer is stretched, and have superior reworkability.

[0113] Examples of filler shapes include spherical, flake-like (scaly), dendritic, fibrous, and amorphous (polyhedral). Among these, spherical is preferred from the viewpoint of excellent uniform dispersion.

[0114] The average particle size of the entire filler is, for example, 0.5 μm or more, preferably 0.8 μm or more (for example, 3 μm or more, typically 5 μm or more). When the average particle size is not less than the above numerical value, it is preferable in terms of favorably maintaining the viscosity and dispersibility of the adhesive composition. The upper limit of the average particle size is, for example, 50 μm or less, preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 15 μm or less. When the average particle size becomes smaller, the decrease in adhesive performance tends to be suppressed. It is also desirable that the average particle size is small from the viewpoint of the appearance of the adhesive layer. In the present specification, the average particle size of the filler refers to the particle size (50% median diameter) at which the cumulative particle size on a weight basis is 50% in the particle size distribution obtained by measurement based on the sieving method.

[0115] The volume ratio of the filler to the total mass of the adhesive layer is 0.01×10 -2 ~30×10 -2 cm 3 / g, more preferably 0.1×10 -2 ~25×10 -2 cm 3 / g, even more preferably 0.5×10 -2 ~20×10 -2 cm 3 / g, even more preferably 0.7×10 -2 ~10×10 -2 cm 3 / g, particularly preferably 1×10 -2 ~7×10 -2 cm 3 / g. When the volume ratio is within the above range, both impact resistance and reworkability are excellent. The volume ratio of the filler is calculated as [volume of the filler in the adhesive layer (cm 3 ) / total mass of the adhesive layer (g)].

[0116] The content of the filler in the adhesive layer is preferably more than 0 parts by mass and 40 parts by mass or less, more preferably 0.008 to 30 parts by mass, even more preferably 0.1 to 20 parts by mass, even more preferably 0.2 to 10 parts by mass, and particularly preferably 0.4 to 6 parts by mass, based on 100 parts by mass of the total amount of the base polymer. When the content is 40 parts by mass or less, both impact resistance and reworkability are improved.

[0117] The proportion of the filler in the adhesive layer is preferably 0.05 to 30% by mass, more preferably 0.1 to 20% by mass, even more preferably 0.5 to 10% by mass, and particularly preferably 1 to 5% by mass, based on 100% by mass of the total amount of the adhesive layer. When the proportion is within the above range, the hardness of the adhesive layer can be made appropriate. Furthermore, it exhibits excellent reworkability.

[0118] The adhesive layer may, if necessary, further contain additives such as crosslinking agents, crosslinking accelerators, anti-aging agents, antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, foil-like materials, rust inhibitors, and colorants (dyes, pigments, etc.), to the extent that they do not impair the effects of the present invention. Each of the above additives may be used individually or in combination of two or more.

[0119] The above-mentioned rust inhibitors are compounds that prevent rust and corrosion of metals. When the substrate is metal, rust and corrosion can be suppressed when the above-mentioned double-sided adhesive sheets are bonded together. Examples of the above-mentioned rust inhibitors include amine compounds, benzotriazole compounds, and nitrites. Other examples include ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, dicyclohexylamine benzoate, urea, urotropin, thiourea, phenyl carbamate, and cyclohexylammonium-N-cyclohexylcarbamate (CHC). One type of the above-mentioned rust inhibitor may be used, or two or more types may be used.

[0120] The content of the above-mentioned rust inhibitor is not particularly limited, but is preferably 0.02 to 15 parts by mass per 100 parts by mass of the base polymer. If the content is 0.02 parts by mass or more, good corrosion prevention performance is more easily obtained. If the content is 15 parts by mass or less, transparency is more easily ensured.

[0121] Among these, benzotriazole compounds are preferred because they offer a good balance of compatibility with the base polymer, adhesive reliability, transparency, and corrosion prevention properties, as well as excellent appearance.

[0122] The content of the benzotriazole compound is not particularly limited, but is preferably 0.02 to 3 parts by mass, more preferably 0.02 to 2.5 parts by mass, and even more preferably 0.02 to 2 parts by mass, per 100 parts by mass of the base polymer.

[0123] The thickness of the adhesive layer (total thickness of the adhesive layer on one side) is not particularly limited, but is preferably 12.5 μm or more, more preferably 20 μm or more, even more preferably 40 μm or more, even more preferably 50 μm or more, and particularly preferably 60 μm or more. When the thickness is 12.5 μm or more, the impact resistance of the double-sided adhesive sheet is superior. The thickness of the adhesive layer is, for example, 200 μm or less, preferably 100 μm or less. When the thickness is 200 μm or less, the thickness of the double-sided adhesive sheet can be made thinner. The thickness of the adhesive layers on both sides may be the same or different.

[0124] The Z-axis adhesive strength of the adhesive layer described above at 23°C is 0.6 MPa or higher, preferably 0.7 MPa or higher. When the Z-axis adhesive strength is 0.6 MPa or higher, the double-sided adhesive sheet is less likely to peel off from the adherend when subjected to impact. When the double-sided adhesive sheet has multiple adhesive layers on one side of the substrate, it is preferable that the Z-axis adhesive strength of at least one adhesive layer at 23°C is within the above range, and it is more preferable that the Z-axis adhesive strength of all adhesive layers at 23°C is within the above range.

[0125] The strain (Z-axis adhesive strain) of the adhesive layer at 23°C is 100% or more, preferably 150% or more, and more preferably 200% or more. When the strain is 100% or more, the double-sided adhesive sheet is less likely to deform when subjected to impact and less likely to peel off from the adherend. The strain is, for example, 1000% or less. When the double-sided adhesive sheet has multiple adhesive layers on one side of the substrate, it is preferable that the strain at 23°C of at least one adhesive layer is within the above range, and it is more preferable that the strain at 23°C of all adhesive layers is within the above range. Furthermore, for the same adhesive layer, the Z-axis adhesive strength at 23°C is within the above range, and the strain is within the above range.

[0126] The adhesive layer may be in any form, such as emulsion type, solvent type (solution type), active energy ray curing type, or hot melt type. Among these, solvent type and active energy ray curing type adhesive compositions are preferred because they make it easier to obtain an adhesive layer with excellent productivity.

[0127] Examples of the active energy rays mentioned above include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet rays, with ultraviolet rays being particularly preferred. In other words, the active energy ray-curable adhesive layer is preferably an ultraviolet-curable adhesive layer.

[0128] The above-mentioned adhesive layer can be manufactured, for example, by applying an adhesive composition for forming the adhesive layer onto a release liner and drying and curing the resulting adhesive composition layer, or by applying the above-mentioned adhesive composition onto a release liner and curing the resulting adhesive composition layer by irradiating it with active energy rays. Furthermore, if necessary, it may be further heated and dried.

[0129] (Double-sided adhesive sheet) The thickness of the double-sided adhesive sheet is preferably 60 to 400 μm, and more preferably 100 to 300 μm. A thickness of 60 μm or more provides superior impact resistance. A thickness of 400 μm or less allows for a thinner double-sided adhesive sheet. Note that the thickness of the double-sided adhesive sheet refers to the thickness from one adhesive surface to the other, i.e., the thickness of the adhesive material, and does not include the release liner.

[0130] The ratio of the thickness of the base material to the total thickness (thickness of the adhesive) of the double-sided adhesive sheet is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more. When the ratio is 10% or more, reworkability is improved. The ratio is preferably 65% ​​or less, more preferably 60% or less, and even more preferably 50% or less. When the ratio is 65% or less, the thickness of the adhesive layer becomes relatively thicker, resulting in improved impact resistance.

[0131] The ratio of the total thickness of the adhesive layer to the total thickness of the double-sided adhesive sheet (thickness of the adhesive body) is preferably 35% or more, more preferably 40% or more, and even more preferably 50% or more. When the ratio is 35% or more, impact resistance is superior. When the ratio is 90% or less, more preferably 80% or less, and even more preferably 70% or less. When the ratio is 90% or less, the thickness of the base material becomes relatively thicker, and reworkability is superior.

[0132] The ratio of the total thickness of the adhesive layer on one side to the total thickness (thickness of the adhesive body) of the double-sided adhesive sheet is preferably 17% or more, more preferably 20% or more, and even more preferably 25% or more. When the ratio is 17% or more, impact resistance is superior. When the ratio is 45% or less, more preferably 40% or less, and even more preferably 35% or less. When the ratio is 45% or less, the thickness of the base material becomes relatively thicker, and reworkability is superior.

[0133] The tensile breaking strength of the above double-sided adhesive sheet is 5 MPa or more, preferably 10 MPa or more, and more preferably 20 MPa or more. When the tensile breaking strength is 5 MPa or more, the double-sided adhesive sheet is less likely to deform when subjected to impact and is less likely to peel off from the adherend. The tensile breaking strength is, for example, 50 MPa or less.

[0134] The strain at the time of fracture of the above double-sided adhesive sheet (tensile fracture strain) is 100% or more, preferably 200% or more, more preferably 300% or more, and even more preferably 500% or more. When the above strain is 100% or more, the double-sided adhesive sheet is less likely to deform when subjected to impact and is less likely to peel off from the adherend. The above strain at the time of fracture is, for example, 1000% or less.

[0135] The above double-sided adhesive sheet, when attached to a stainless steel plate in a 2cm x 2cm size, is peeled off under conditions of a temperature of 23°C and a peeling angle of 30°, preferably has a rework time of 120 seconds or less, more preferably 100 seconds or less, even more preferably 70 seconds or less, and particularly preferably 40 seconds or less. If the total of the above times is 120 seconds or less, the reworkability is excellent. If adhesive remains on the adherend after peeling off the double-sided adhesive sheet, the adherend surface is wiped with a solvent, and the above rework time includes the time until the adhesive is removed by wiping. Furthermore, the above rework time when at least one adhesive side of the above double-sided adhesive sheet is attached should be within the above range.

[0136] The above double-sided adhesive sheet preferably has an impact absorption capacity of 0.44 J or more, more preferably 0.50 J or more, and even more preferably 0.70 J or more. An impact absorption capacity of 0.44 J or more provides superior impact resistance.

[0137] The above-mentioned double-sided adhesive sheet may have a release liner attached to the surface (adhesive side) of the adhesive layer until use. Each adhesive side of the above-mentioned double-sided adhesive sheet may be protected by two release liners, or it may be protected in a roll-like form (winding body) by a single release liner with both sides being release surfaces. The release liner is used as a protective material for the adhesive layer and is peeled off when it is attached to the object. Note that the release liner is not necessarily required.

[0138] The above-mentioned release liner can be conventional release paper or the like, and is not particularly limited, but examples include a substrate having a release treatment layer, a low-adhesion substrate made of a fluoropolymer, or a low-adhesion substrate made of a nonpolar polymer. Examples of the substrate having the release treatment layer include plastic films and paper surface-treated with release agents such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide. Examples of fluorine-based polymers in the low-adhesion substrate made of a fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. Examples of the above-mentioned nonpolar polymer include olefin resins (e.g., polyethylene, polypropylene, etc.). The release liner can be formed by known or conventional methods. The thickness of the release liner is also not particularly limited.

[0139] The above-mentioned double-sided adhesive sheet is preferably used for attaching electrical and electronic components, by being bonded to components provided in electrical and electronic equipment. The above-mentioned double-sided adhesive sheet is preferably used for bonding components provided in electrical and electronic equipment to each of its two adhesive surfaces, that is, for fixing components together in electrical and electronic equipment. The above-mentioned double-sided adhesive sheet may be used for fixing components together or for temporary fixing. For example, when a double-sided adhesive sheet is used for fixing or temporarily fixing components provided in electrical and electronic equipment, there may be cases where the double-sided adhesive sheet must be peeled off and reworked due to a problem in the application process, or where the double-sided adhesive sheet must be peeled off in order to repair, replace, inspect, or recycle a component to which the double-sided adhesive sheet has been attached. Thus, when a double-sided adhesive sheet is used, for example, for fixing or temporarily fixing components provided in electrical and electronic equipment, the frequency of removing the double-sided adhesive sheet is particularly high.

[0140] The above-mentioned double-sided adhesive sheet is preferably used to bond the outer frames of optical components (especially electrical and electronic equipment) together. For this reason, the above-mentioned double-sided adhesive sheet can preferably be used even if it has a width of 5 mm or less, and more preferably 3 mm or less.

[0141] Furthermore, "electrical and electronic equipment" refers to equipment that falls under either electrical equipment or electronic equipment. Examples of such electrical and electronic equipment include image display devices such as liquid crystal displays, electroluminescent displays, and plasma displays, as well as portable electronic devices.

[0142] Examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear-type devices worn on the wrist like watches, modular-type devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular types, including head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, earwear-type devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information equipment, portable radios, portable televisions, portable printers, portable scanners, and portable modems. In this specification, "portable" means not merely being able to carry something, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily. The above-mentioned double-sided adhesive sheet is used, for example, so that the adhesive layer adheres closely to the components of the above-mentioned portable electronic device.

[0143] The double-sided adhesive sheet of the present invention provides a double-sided adhesive sheet with excellent impact resistance and reworkability. For example, when used in portable electronic devices, it is less likely to break or peel off even if it is subjected to a drop or the adherend is deformed, yet it can be easily peeled off when someone intentionally tries to remove the double-sided adhesive sheet. [Examples]

[0144] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples. The amounts of each component and physical properties of the substrate, adhesive layer, and adhesive sheet prepared in each example and comparative example are shown in the table. The amounts of each component in the table are expressed in parts by mass.

[0145] Example 1 (Preparation of the adhesive layer) In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 68 parts by mass of toluene, 95 parts by mass of butyl acrylate (BA), and 5 parts by mass of acrylic acid (AA) were charged, and the reactor was purged with nitrogen for more than 1 hour. 0.2 parts by mass of azobisisobutyronitrile (AIBN) was added as an initiator, and the internal bath temperature was then raised to 62°C, maintained at the same temperature, and continued until the reaction was almost complete. After that, the reactor was cooled to terminate the polymerization reaction. To 100 parts by mass of the obtained polymer, 5 parts by mass of an isocyanate compound (trade name "Coronate L," manufactured by Tosoh Corporation) and 0.02 parts by mass of an epoxy compound (trade name "Tetrad C," manufactured by Mitsubishi Gas Chemical Company, Inc.) were added, and then 20 parts by mass of a terpene phenol-based tackifying resin (trade name "YS Polystar T115," manufactured by Yasuhara Chemical Co., Ltd.) and 0.8 parts by mass of benzotriazole were added to prepare an adhesive composition.

[0146] The above adhesive composition was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) whose one side had been released with silicone, and dried at 100°C for 3 minutes to form an adhesive layer (70 μm thick).

[0147] (Making adhesive sheets) The adhesive layers obtained above were bonded to both sides of the substrate to produce the double-sided adhesive sheet of Example 1. A urethane film (product name "Esmar URS ET-B", Shore hardness D:90, manufactured by Nippon Matai Co., Ltd.) was used as the substrate.

[0148] Example 2 A double-sided adhesive sheet for Example 2 was prepared in the same manner as in Example 1, except that a urethane elastomer film (product name "DUS213", Shore hardness D:93, manufactured by Seedam Co., Ltd.) was used as the base material, and the thickness of the adhesive layer was changed as shown in the table.

[0149] Example 3 (Preparation of the adhesive layer) In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 68 parts by mass of toluene, 95 parts by mass of butyl acrylate (BA), and 5 parts by mass of acrylic acid (AA) were charged, and the reactor was purged with nitrogen for more than 1 hour. 0.2 parts by mass of azobisisobutyronitrile (AIBN) was added as an initiator, and the internal bath temperature was then raised to 62°C, maintained at the same temperature, and continued until the reaction was almost complete. After that, the reactor was cooled to terminate the polymerization reaction. To 100 parts by mass of the obtained polymer, 5 parts by mass of an isocyanate compound (trade name "Coronate L", manufactured by Tosoh Corporation) and 0.02 parts by mass of an epoxy compound (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Company, Inc.) were added. Furthermore, 20 parts by mass of a terpene phenol-based tackifying resin (trade name "YS Polystar T115", manufactured by Yasuhara Chemical Co., Ltd.), 2 parts by mass of polyethylene powder as a filler (trade name "Flowsen UF-80", manufactured by Sumitomo Seika Co., Ltd.), and 0.8 parts by mass of benzotriazole were added to prepare an adhesive composition.

[0150] The above adhesive composition was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) with one side release-treated with silicone, and dried at 100°C for 3 minutes to form an adhesive layer (50 μm thick). The weight-average molecular weight of the acrylic polymer in the adhesive layer was 600,000.

[0151] (Making adhesive sheets) A double-sided adhesive sheet of Example 3 was prepared in the same manner as in Example 2, except that the adhesive layer obtained above was used.

[0152] Example 4 A double-sided adhesive sheet for Example 4 was prepared in the same manner as in Example 3, except that a urethane-based film (product name "Esmar URS ET-B", Shore hardness D:90, manufactured by Nippon Matai Co., Ltd.) was used as the base material, and the thickness of the adhesive layer was changed as shown in the table.

[0153] Example 5 (Preparation of the adhesive layer) In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 3 parts by mass of an isocyanate compound (product name "Coronate HX," manufactured by Tosoh Corporation) were added to 100 parts by mass of the resin content of a polyester polymer solution (product name "Nichigo Polyester NP-110S50EO," solid content concentration: 50% by mass, manufactured by Mitsubishi Chemical Corporation). Furthermore, 20 parts by mass of a terpene phenol-based tackifying resin (product name "YS Polyester T115," manufactured by Yasuhara Chemical Co., Ltd.), 2 parts by mass of polyethylene powder as a filler (product name "Flowsen UF-80," manufactured by Sumitomo Seika Co., Ltd.), and 0.8 parts by mass of benzotriazole were added to prepare an adhesive composition.

[0154] The above adhesive composition was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) whose one side had been released with silicone, and dried at 100°C for 3 minutes to form an adhesive layer (80 μm thick).

[0155] (Making adhesive sheets) The adhesive layers obtained above were bonded to both sides of a urethane film (product name "Esmar URS ET-B", Shore hardness D:90, manufactured by Nippon Matai Co., Ltd.) to produce the double-sided adhesive sheet of Example 5.

[0156] Comparative Example 1 (Preparation of the adhesive layer) In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 68 parts by mass of toluene, 95 parts by mass of butyl acrylate (BA), and 5 parts by mass of acrylic acid (AA) were charged, and the reactor was purged with nitrogen for more than 1 hour. 0.2 parts by mass of azobisisobutyronitrile (AIBN) was added as an initiator, and the internal bath temperature was then raised to 62°C, maintained at the same temperature, and continued until the reaction was almost complete. After that, the reactor was cooled to terminate the polymerization reaction. To 100 parts by mass of the obtained polymer, 5 parts by mass of an isocyanate compound (trade name "Coronate L", manufactured by Tosoh Corporation) and 0.02 parts by mass of an epoxy compound (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Company, Inc.) were added. Furthermore, 20 parts by mass of a terpene phenol-based tackifying resin (trade name "YS Polystar T115", manufactured by Yasuhara Chemical Co., Ltd.), 2 parts by mass of polyethylene powder as a filler (trade name "Flowsen UF-80", manufactured by Sumitomo Seika Co., Ltd.), and 0.8 parts by mass of benzotriazole were added to prepare an adhesive composition.

[0157] The above adhesive composition was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) whose one side had been released with silicone, and dried at 100°C for 3 minutes to form an adhesive layer (70 μm thick).

[0158] (Preparation of base material) In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 68 parts by mass of toluene, 95 parts by mass of butyl acrylate (BA), and 5 parts by mass of acrylic acid (AA) were charged, and the reactor was purged with nitrogen for more than 1 hour. 0.2 parts by mass of azobisisobutyronitrile was added as an initiator, and the internal bath temperature was then raised to 62°C, maintained at the same temperature, and continued until the reaction was almost complete. After that, the reactor was cooled to terminate the polymerization reaction. To 100 parts by mass of the obtained polymer, 5 parts by mass of an isocyanate compound (trade name "Coronate L," manufactured by Tosoh Corporation) and 0.1 parts by mass of an epoxy compound (trade name "Tetrad C," manufactured by Mitsubishi Gas Chemical Company, Inc.) were added to prepare a resin composition. The above resin composition was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) whose one side had been release-treated with silicone, and dried at 100°C for 3 minutes to form a base sheet (100 μm).

[0159] (Making adhesive sheets) The adhesive layers obtained above were bonded to both sides of the above-mentioned base sheet to prepare the double-sided adhesive sheet of Comparative Example 1.

[0160] <Rating> The substrates and double-sided adhesive sheets obtained in the examples and comparative examples were evaluated as follows. The results are shown in the table.

[0161] (1) Tanδ of the base material The substrates prepared in the examples and comparative examples were cut to a width of 5 mm x 30 mm. The 30 mm long side was chucked with a 15 mm chuck spacing in a dynamic viscoelasticity measuring device (product name "Rheogel-E4000", manufactured by UBM Co., Ltd.), and the tensile viscoelastic modulus was measured in the range of -60°C to 100°C with a heating rate of 5°C / min. The maximum value of the loss tangent tanδ at 23°C for frequencies from 10 kHz to 3.5 MHz was calculated by synthesizing a master curve at a reference temperature of 23°C.

[0162] (2) Z-axis bonding force and Z-axis bonding strain The double-sided adhesive sheets, sandwiched between release liners as prepared in the examples and comparative examples, were punched out into a frame shape with an outer diameter of 24.5 mm and a width of 2 mm. The release liners were then peeled off the double-sided adhesive sheets, and the resulting pieces were sandwiched between a 2 mm thick, 50 mm square stainless steel plate with a hole in the center and a 3 mm thick, 25 mm square stainless steel plate. The pieces were then pressed together and left to stand at 50°C for 2 hours, before being returned to room temperature to be used as evaluation samples. A tensile testing machine, "Precision Universal Testing Machine Autograph AG-IS" (manufactured by Shimadzu Corporation), was used. A 10 mm diameter cylinder was attached to the upper jig of the tensile testing machine, and a base was placed on the lower side. The test piece was then placed on top of the base with the square stainless steel plate (the non-perforated stainless steel plate) facing downwards. The square stainless steel plate (the non-perforated stainless steel plate) was then pressed with the 10 mm diameter cylinder at a speed of 50 mm / min, and the stress and strain at the time of peeling were converted into energy. Z-axis bonding strength (MPa) = Stress required to detach (N) / Bonding area (mm²) 2 ) Z-axis bonding strain (%) = Amount of strain until delamination (mm) / Thickness (mm) × 100

[0163] (3) Tensile fracture strength and tensile fracture strain The double-sided adhesive sheets prepared in the examples and comparative examples were cut to a width of 10 mm and a length of 40 mm to obtain test specimens. A tensile testing machine, "Precision Universal Testing Machine Autograph AG-IS" (manufactured by Shimadzu Corporation), was used to chuck the test specimens with a chuck distance of 20 mm and perform a tensile test at a speed of 50 mm / min. The fracture stress and strain at the time of fracture were converted into energy. Tensile breaking strength (MPa) = (Breaking stress at the time of fracture (N) / Original cross-sectional area of ​​the test specimen (mm²) 2 ) Tensile fracture strain (%) = (Strain until fracture (mm) - Original length of specimen (mm)) / Original length of specimen (mm) × 100

[0164] (4) Impact resistance The double-sided adhesive sheets, sandwiched between release liners as prepared in the examples and comparative examples, were punched out into a frame shape with an outer diameter of 24.5 mm and a width of 2 mm. Then, the release liners were peeled off the double-sided adhesive sheets, and the sheets were sandwiched between a 2 mm thick, 50 mm square stainless steel plate with a hole in the center and a 3 mm thick, 25 mm square stainless steel plate, and pressed together. The samples were left to stand for 2 hours at a temperature of 50°C, and then returned to room temperature to be used as evaluation samples. A cylindrical measuring stand with a length of 50 mm, an outer diameter of 49 mm, and an inner diameter of 43 mm was placed on the base of a DuPont impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the test pieces were placed on it with the square stainless steel plate (the stainless steel plate without the hole) facing downwards. A stainless steel impact pin with a tip radius of 3.1 mm was placed on the test piece, and the drop weight and drop height were varied in 50 mm increments from 50 to 500 mm with a 100 g weight, from 350 to 500 mm with a 150 g weight, from 400 to 500 mm with a 200 g weight, and from 350 to 500 mm with a 300 g weight, so that the energy increased until delamination occurred. At this time, tests were not conducted for energy levels that had already been evaluated, and the load and height were set so that the amount of energy did not overlap. Subsequently, the energy before at least one of the stainless steel plates delaminated was calculated as load × height, and the obtained value is shown in the table as the impact absorption amount.

[0165] (5) Rework Test For the double-sided adhesive sheet after the "Z-axis adhesive strength" measurement described above, the short-side edge was peeled off the stainless steel plate, and the sheet was then pulled at a 30° angle to the adherend to remove it. The time it took for the double-sided adhesive sheet to completely peel off was measured as the rework time. If any adhesive remained on the adherend after the adhesive sheet was removed, the adherend surface was wiped with ethyl acetate, and the rework time included the time it took for the adhesive to be removed by wiping.

[0166] [Table 1]

[0167] As shown in Table 1, the double-sided adhesive sheet of the present invention was evaluated as having a large shock absorption capacity, excellent impact resistance, and excellent reworkability with a short rework time (Example). On the other hand, when the maximum value of the substrate's tanδ at frequencies of 10 kHz to 3.5 MHz exceeded 0.83 (Comparative Example 1), it was evaluated as having a long rework time and poor reworkability.

[0168] The following describes variations of the invention relating to this disclosure. [Note 1] The system comprises a base material and an adhesive layer provided on both sides of the base material. The substrate has a maximum loss tangent tanδ of 0.83 or less at 23°C and frequencies from 10 kHz to 3.5 MHz, and a thickness of 40 μm or more. The adhesive layer has a Z-axis adhesive strength of 0.6 MPa or more at 23°C, and a strain of 100% or more. A double-sided adhesive sheet having a tensile breaking strength of 5 MPa or more and a strain of 100% or more at the time of break. [Note 2] The double-sided adhesive sheet described in Note 1, which, when attached to a stainless steel plate in a 2cm x 2cm size, is peeled off at a temperature of 23°C and a peeling angle of 30°, and the time required for complete peeling is 120 seconds or less. [Note 3] A double-sided adhesive sheet as described in Note 1 or 2, with a thickness of 60 to 400 μm. [Note 4] The adhesive comprising the adhesive layer comprises at least an acrylic adhesive, a polyester adhesive, a rubber adhesive, or a urethane adhesive, as described in any one of Notes 1 to 3, for the double-sided adhesive sheet. [Note 5] The double-sided adhesive sheet according to any one of Notes 1 to 4, wherein the adhesive layer includes a filler whose surface is composed of an olefin resin. [Note 6] The base material is a double-sided adhesive sheet according to any one of Notes 1 to 5, comprising at least a polyurethane resin, a rubber resin, or a polyolefin resin. [Note 7] A double-sided adhesive sheet as described in any one of Notes 1 to 6, for fixing components together in electrical and electronic equipment. [Note 8] Equipped with the double-sided adhesive sheet described in Note 7, The aforementioned double-sided adhesive sheet is used to fix components together on both adhesive surfaces in an electrical and electronic device. [Explanation of symbols]

[0169] 1. Double-sided adhesive sheet 2 Base material 3,4 Adhesive layer

Claims

1. The device comprises a base material and an adhesive layer provided on both sides of the base material. The substrate comprises at least a polyurethane resin, a rubber resin, or a polyolefin resin. The adhesive constituting the adhesive layer comprises at least an acrylic adhesive, a polyester adhesive, a rubber adhesive, or a urethane adhesive. The substrate has a maximum loss tangent tanδ of 0.83 or less at 23°C and frequencies from 10 kHz to 3.5 MHz, and a thickness of 40 μm or more. The Z-axis adhesive strength of the adhesive layer at 23°C is 0.6 MPa or more, and the strain is 100% or more. A double-sided adhesive sheet having a tensile breaking strength of 5 MPa or more and a strain of 100% or more at the time of breaking.

2. The double-sided adhesive sheet according to claim 1, wherein when peeled off from a state where it is attached to a stainless steel plate in a size of 2 cm x 2 cm, under conditions of a temperature of 23°C and a peeling angle of 30°, the time required for complete peeling is 120 seconds or less.

3. A double-sided adhesive sheet according to claim 1 or 2, wherein the thickness is 60 to 400 μm.

4. The double-sided adhesive sheet according to claim 1 or 2, wherein the adhesive constituting the adhesive layer comprises at least an acrylic adhesive or a polyester adhesive.

5. The double-sided adhesive sheet according to claim 1 or 2, wherein the adhesive layer includes a filler whose surface is composed of an olefin resin.

6. The double-sided adhesive sheet according to claim 1 or 2, wherein the substrate comprises at least a polyurethane resin.

7. A double-sided adhesive sheet according to claim 1 or 2, for fixing components together in electrical and electronic equipment.

8. The double-sided adhesive sheet described in claim 7 is provided, The aforementioned double-sided adhesive sheet is used to fix components together on both adhesive surfaces in an electrical and electronic device.

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