Double-sided adhesive sheet

Abstract

To provide a double-sided adhesive sheet that offers superior reworkability and has a high degree of freedom in the design of an adhesive layer.SOLUTION: A double-sided adhesive sheet 1 has a substrate layer 2, and adhesive layers 3, 4 provided on both sides of the substrate layer 2. The substrate layer 2 has a core layer 21 primarily composed of a styrenic elastomer and resin layers 22, 23 that provide both surfaces of the substrate layer 2 and are harder than the core layer 21. The substrate layer 2 has an elongation of 700% or more and a 100% modulus of 4.0 MPa or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, electronic devices such as home appliances, office automation equipment, mobile phones (smartphones, etc.), digital cameras, and PDAs (Personal Digital Assistants) have become widely used. For example, mobile phones, a representative portable device, tend to have thinner and larger screens for their main components. Typically, the display part of a portable device consists mainly of an LCD module and a backlight unit, with various sheet-like components layered to perform functions such as light emission, reflection, light shielding, and light guidance. Furthermore, recent mobile phones often employ organic electroluminescent displays, which are even more expensive than LCD modules. Double-sided adhesive sheets (double-sided adhesive tape) are used for assembling (joining) these components.

[0003] Double-sided adhesive sheets are required to exhibit a certain level of adhesive strength to prevent adhesion defects such as peeling or shifting during their service life. On the other hand, when repairing, replacing, inspecting, or recycling components to which double-sided adhesive sheets are attached, it may be necessary to remove the double-sided adhesive sheets. In such cases, the double-sided adhesive sheets must be easily removable from the adherend, i.e., they must have reworkability.

[0004] As a method for removing double-sided adhesive sheets while suppressing damage to the adherend, a method has been proposed in which a portion of the double-sided adhesive sheet attached to the adherend is grasped and pulled, causing the sheet to stretch and deform, reducing the adhesive area, and removing it from the adherend in a horizontal direction (shear direction) (stretch peeling method).

[0005] Examples of double-sided adhesive sheets that can be peeled off by such a stretch peeling method include adhesive tapes using a highly flexible base material (e.g., Patent Document 1) and adhesive tapes in which a filler is added to the adhesive layer (e.g., Patent Document 2). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2019 / 003933 [Patent Document 2] International Publication No. 2019 / 167922 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, conventional adhesive sheets using highly flexible substrates had a problem in that, when using a highly adhesive layer, the substrate tended to tear during stretching and peeling, making stretching and peeling difficult.

[0008] Adhesive sheets using an adhesive layer with added fillers tend to have reduced adhesive strength and are easily peeled off by stretching when the sheet is attempted to be peeled off by stretching, because the fillers are interposed at the interface between the adhesive layer and the adherend. However, adding fillers presents problems such as the possibility that the fillers may aggregate in the adhesive layer, preventing the desired appearance from being achieved, and the need to make the thickness of the adhesive layer less than or equal to the particle size of the fillers in order to keep the fillers at the aforementioned interface.

[0009] Thus, conventional adhesive sheets with reworkability have limitations such as the inability to use an adhesive layer with high adhesive strength, and restrictions on the appearance and thickness of the adhesive layer, resulting in a lack of design freedom for the adhesive layer.

[0010] This invention was conceived under these circumstances, and its purpose is to provide a double-sided adhesive sheet that offers excellent reworkability and a high degree of design freedom for the adhesive layer. [Means for solving the problem]

[0011] As a result of diligent research to achieve the above objectives, the inventors of this invention have found that a double-sided adhesive sheet having a specific substrate layer offers excellent reworkability and a high degree of design freedom for the adhesive layer. This invention was completed based on these findings.

[0012] In other words, the present invention is a double-sided adhesive sheet comprising a base layer and adhesive layers provided on both sides of the base layer. The above-mentioned base material layer comprises a core layer mainly composed of a styrene-based elastomer and a resin layer harder than the core layer that provides both surfaces of the base material layer. The present invention provides a double-sided adhesive sheet having an elongation of 700% or more of the base material layer and a 100% modulus of 4.0 MPa or less of the base material layer.

[0013] Preferably, the ratio of the total thickness of the core layer, which is mainly composed of the styrene-based elastomer, to the total thickness of the base layer is 60% or more.

[0014] The ratio of the thickness of each resin layer in the above-mentioned base material layer is preferably 2.5% or more of the total thickness of the base material layer.

[0015] The ratio [former:latter] of the total thickness of the resin layer in the base material layer to the total thickness of the core layer is preferably 3:97 to 45:55.

[0016] The above resin layer is preferably a layer mainly composed of polyolefin resin.

[0017] The proportion of filler in the adhesive layer is preferably 20% by mass or less relative to the total amount of the adhesive layer.

[0018] The above-mentioned double-sided adhesive sheet is preferably used for fixing components together in electrical and electronic equipment.

[0019] The present invention also provides an electric and electronic device including the above double-sided adhesive sheet, wherein the double-sided adhesive sheet fixes members to each other on both adhesive surfaces.

Advantages of the Invention

[0020] The double-sided adhesive sheet of the present invention is excellent in reworkability and has a high degree of freedom in the design of the adhesive layer. Therefore, while having excellent reworkability, for example, the adhesive strength of the adhesive layer can be made high, and the appearance and thickness can be made as desired.

Brief Description of the Drawings

[0021] [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

[0022] [Double-sided Adhesive Sheet] The double-sided adhesive sheet of the present invention includes at least a base material layer and adhesive layers provided on both surfaces of the base material layer.

[0023] The base material layer includes at least a core layer mainly composed of a styrene-based elastomer and a resin layer harder than the core layer that provides both surfaces of the base material layer. In this specification, the resin layer harder than the core layer may be referred to as a "hard resin layer". That is, the base material layer includes a first hard resin layer (first resin layer) that provides one surface of the base material layer, a core layer, and a second hard resin layer (second resin layer) that provides the other surface of the base material layer in this order. The core layer is a layer located between the first resin layer and the second resin layer. The base material layer may include layers other than the core layer, the first resin layer, and the second resin layer.

[0024] By providing a layer mainly composed of a styrene elastomer as the core layer, the base material layer has appropriate flexibility and is difficult to break when pulled. Further, by providing the hard resin layers that provide both surfaces of the base material layer, the components in the adhesive layer are less likely to migrate to the core layer, and the fracture resistance of the core layer is less likely to decrease.

[0025] The elongation of the above-mentioned base material layer is 700% or more, preferably 800% or more, more preferably 850% or more, and even more preferably 900% or more. An elongation of 700% or more makes the double-sided adhesive sheet less likely to break when pulled. The elongation of the above-mentioned base material layer may also be, for example, 5000% or less, 3000%, or 2000% or less. The above elongation is the elongation at break, measured under conditions of a sample size of 10mm x 50mm, a chuck distance of 10mm, a tensile speed of 300mm / min, and a tensile direction of 180°, in an environment of 23°C and 50%RH.

[0026] The 100% modulus of the above-mentioned base material layer is 4.0 MPa or less, preferably 3.8 MPa or less. A 100% modulus of 4.0 MPa or less ensures that the force applied to the hand when pulling the double-sided adhesive sheet is relatively small, making the sheet less likely to break. The 100% modulus may be, for example, 0.1 MPa or more, 0.5 MPa or more, or 1.0 MPa or more. The 100% modulus is calculated as the stress at 100% elongation when measured under the conditions of a sample size of 10 mm x 50 mm, a chuck distance of 10 mm, a tensile speed of 300 mm / min, and a tensile direction of 180°, in an environment of 23°C and 50% RH.

[0027] 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 layer 2 and adhesive layers 3 and 4 provided on both sides of the base layer 2, respectively. The base layer 2 comprises a core layer 21 mainly composed of a styrene-based elastomer and a resin layer (first resin layer) 22 and a resin layer (second resin layer) 23 that are harder than the core layer 21 and provide both surfaces of the base layer 2. The elongation of the base layer 2 is 700% or more, and the 100% modulus of the base layer 2 is 4.0 MPa or less.

[0028] (base material layer) The above-mentioned base material layer comprises at least a core layer mainly composed of a styrene-based elastomer and the above-mentioned rigid resin layers (first resin layer and second resin layer). The two above-mentioned rigid resin layers are layers that provide the surface of the base material layer, i.e., surface layers. The above-mentioned core layer is a layer located between the two above-mentioned rigid resin layers, and may be a single layer or a multi-layer layer. If the above-mentioned core layer is a multi-layer layer, the multiple core layers may be layers with the same thickness, composition, etc., or may be different layers. In addition, the above-mentioned first resin layer and the above-mentioned second resin layer may be layers with the same thickness, composition, etc., or may be different layers.

[0029] Examples of the styrene-based elastomers include styrene-butadiene copolymer (SB), styrene-isoprene copolymer (SI), styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-styrene block copolymer (SBS), styrene-isobutylene-styrene copolymer (SIBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene block copolymer (SEP), styrene-ethylene-propylene-styrene block copolymer (SEPS), and modified versions thereof, as well as other styrene-diene copolymers. The copolymers are preferably block copolymers. The styrene-based elastomers may be used individually or in combination of two or more types.

[0030] The styrene-based elastomer is the resin with the highest mass percentage among the resins constituting the core layer. The content of the styrene-based elastomer in the core layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on 100% by mass of the total amount of the core layer.

[0031] The hard resin layer described above is a resin layer that is harder than the core layer described above. Examples of hardness that can be compared between the hard resin layer and the core layer include residual stress, elastic modulus, Young's modulus, and hardness measured by nanoindentation.

[0032] The hard resin layer mentioned above includes layers mainly composed of resins harder than styrene-based elastomers. Examples of resins harder than styrene-based elastomers include polyethylene resins (low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, etc.), polypropylene resins (random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, etc.), polybutene, polymethylpentene, ionomers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester (random, alternating) copolymers, ethylene-vinyl acetate copolymer (EVA), ethylene-propylene copolymer, cyclic olefin polymers, and ethylene-butene copolymers. Examples include polyolefin resins such as ethylene-hexene copolymers; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonates; polyimide resins; polyether ether ketones; polyetherimides; polyamides such as aramids and fully aromatic polyamides; polyphenyl sulfides; fluororesins; polyvinyl chloride; polyvinylidene chloride; cellulose resins such as triacetylcellulose (TAC); silicone resins; acrylic resins such as polymethyl methacrylate (PMMA); polysulfones; polyarylates; and polyvinyl acetate. One type of the above resin may be used, or two or more types may be used.

[0033] Among the above resins, polyolefin resins are preferred from the viewpoint of excellent processability, such as ease of winding, and ease of stretching and resistant to breakage when pulled. Polyethylene resins are even more preferred from the viewpoint of excellent anchoring properties of the adhesive layer and less likelihood of breakage or adhesive residue on the adherend when the double-sided adhesive sheet is pulled, with low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene being particularly preferred.

[0034] The resin that is harder than the styrene-based elastomer is preferably the resin that has the highest mass percentage among the resins constituting the hard resin layer. The content of the resin that is harder than the styrene-based elastomer (especially polyolefin resin) in the hard resin layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on 100% by mass of the total amount of the hard resin layer.

[0035] The ratio of the thickness (total thickness) of the core layer, which mainly consists of the styrene-based elastomer, to the total thickness of the base layer is preferably 60% or more, more preferably 70% or more, even more preferably 75% or more, and particularly preferably 80% or more, relative to 100% of the total thickness of the base layer. When the ratio is 60% or more, the 100% modulus of the base layer tends to be lower. The ratio is preferably 98% or less, and more preferably 95% or less. When the ratio is 98% or less, the double-sided adhesive sheet is less likely to break when pulled.

[0036] The ratio of the thickness of the hard resin layer in the base material layer (thickness per layer) is preferably 2.5% or more, and more preferably 3% or more, relative to the total thickness of the base material layer (100%). When the ratio is 2.5% or more, the components in the adhesive layer are less likely to migrate to the core layer, and the adhesive layer has excellent anchoring properties, making it less likely for the double-sided adhesive sheet to break or leave adhesive residue on the adherend when pulled. The ratio is preferably 15% or less, and more preferably 12.5% ​​or less.

[0037] The ratio [former:latter] of the total thickness of the hard resin layer in the base layer to the total thickness of the core layer is preferably 3:97 to 45:55, more preferably 5:95 to 35:65, and even more preferably 8:92 to 25:75. When the ratio is 3:97 or higher, the components in the adhesive layer are less likely to migrate to the core layer, and the anchoring to the adhesive layer is excellent, making it less likely for the double-sided adhesive sheet to break or leave adhesive residue on the adherend when pulled. When the ratio is 45:55 or lower, the 100% modulus of the base layer tends to be lower.

[0038] The thickness of the above-mentioned substrate layer is preferably 30 μm or more, and more preferably 50 μm or more, from the viewpoint of excellent functionality as a support and less likely to break when the double-sided adhesive sheet is pulled. The thickness of the above-mentioned substrate layer is preferably 1 mm or less, more preferably 500 μm or less, and even more preferably 300 μm or less, from the viewpoint of superior stretchable peelability.

[0039] The above-mentioned substrate layer can be fabricated by known or conventional methods. Examples of film formation methods include calendering, casting in organic solvents, inflation extrusion in a closed system, T-die extrusion, co-extrusion, and dry lamination.

[0040] The surface of the above-mentioned substrate layer 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, retention, etc. It is preferable that the surface treatment to improve adhesion is applied to the entire surface of the substrate layer.

[0041] (Adhesive layer) In the above-described double-sided adhesive sheet, the adhesive layers provided on both sides of the base layer may be the same adhesive layer, or they may be adhesive layers with different compositions, thicknesses, physical properties, etc. The adhesive layers provided on both sides of the base layer may each be a single layer, or they may be multiple layers composed of the same or different compositions, thicknesses, physical properties, etc.

[0042] The adhesive constituting the above adhesive layer can be any known or conventional adhesive, and is not particularly limited, but 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, silicone adhesives, and rubber 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.

[0043] The above acrylic adhesive layer 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] Examples of (meth)acrylic acid esters having the above-mentioned aromatic hydrocarbon group include phenyl (meth)acrylate and benzyl (meth)acrylate.

[0050] In order to appropriately exhibit the basic properties such as tackiness of 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, 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, 98% by mass or less, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Examples of the above-mentioned alkoxysilyl group-containing monomers include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0057] Examples of the above-mentioned glycidyl group-containing monomers include glycidyl (meth)acrylate and methylglycidyl (meth)acrylate.

[0058] 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.

[0059] Examples of the above-mentioned phosphate group-containing monomers include 2-hydroxyethyl acryloyl phosphate.

[0060] 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, more preferably 1% by mass or more, even more preferably 5% by mass or more, and may also be 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more. Furthermore, from the viewpoint of obtaining an adhesive layer with appropriate flexibility, the total proportion is preferably 50% by mass or less, and more preferably 40% by mass or less.

[0061] The monomer components constituting the above 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.

[0062] 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.

[0063] 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.

[0064] The above-mentioned acrylic polymer may have structural components derived from acrylic oligomers. Examples of such acrylic polymers include polymers comprising another acrylic polymer that is a precursor of the above-mentioned acrylic polymer (sometimes referred to as "acrylic polymer (A)") which can constitute the above-mentioned acrylic polymer by polymerization, and a polymer reaction product of a composition containing the above-mentioned acrylic oligomer. Having structural components derived from acrylic oligomers results in higher fracture strain and superior reworkability. The composition containing the above-mentioned acrylic oligomer may further contain monomer components (sometimes referred to as "monomer component (B)"). The acrylic polymer (A), the above-mentioned acrylic oligomer, and monomer component (B) may each be used individually or in combination of two or more types.

[0065] Furthermore, the above-mentioned acrylic polymer may be a polymerization product obtained by polymerizing a composition containing one or more selected from the group consisting of acrylic partial polymers, acrylic oligomers, and monomer component (B). In the case of a polymerization product obtained by polymerizing a composition consisting only of monomer component (B), monomer component (B) contains at least an acrylic monomer. Among these, a polymerization product of a composition containing an acrylic partial polymer is preferred. The above-mentioned "partial polymer" may also be referred to as "prepolymer," "syrup," etc. Only one type of acrylic partial polymer, acrylic oligomer, and monomer component (B) may be used, or two or more types may be used.

[0066] Acrylic polymer (A), the above-mentioned acrylic partial polymer, and the above-mentioned acrylic oligomer are all compounds composed of acrylic monomers as essential monomer components. Examples of acrylic monomers and monomer component (B) that constitute acrylic polymer (A), the above-mentioned acrylic partial polymer, and the above-mentioned acrylic oligomer include those exemplified and described above as monomer components constituting the acrylic polymer.

[0067] The acrylic polymer (A) may be a polymer that forms the base polymer on its own, or it may be a polymer that forms the base polymer together with the polymerization reaction product of the composition containing the acrylic oligomer.

[0068] The acrylic polymer (A) contains an acrylic monomer as a constituent unit. Preferably, the acrylic polymer (A) contains the hydrocarbon group-containing (meth)acrylic acid ester mentioned above as a constituent unit. Among the hydrocarbon group-containing (meth)acrylic acid esters, alkyl (meth)acrylates having linear or branched aliphatic hydrocarbon groups are preferred, and alkyl (meth)acrylates having linear or branched aliphatic hydrocarbon groups with 1 to 20 carbon atoms (preferably 2 to 12, more preferably 4 to 10) are more 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 adhesiveness more appropriate. The acrylic monomer included as a constituent unit may be one type or two or more types.

[0069] The proportion of hydrocarbon group-containing (meth)acrylic acid ester in 100% by mass of the total amount of all monomer components constituting the acrylic polymer (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more. The above proportion is preferably 99% by mass or less, and more preferably 95% by mass or less.

[0070] The acrylic polymer (A) may contain the above copolymerizable monomer as a constituent unit. Among the above copolymerizable monomers, hydroxyl group-containing monomers and / or nitrogen atom-containing monomers are preferred.

[0071] The proportion of hydroxyl group-containing monomers and / or nitrogen atom-containing monomers in 100% by mass of the total amount of all monomer components constituting the acrylic polymer (A) is not particularly limited, but is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, and may be 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more. Furthermore, the sum of the above proportions is preferably 50% by mass or less, and more preferably 40% by mass or less, from the viewpoint of obtaining an adhesive layer with appropriate flexibility.

[0072] Unlike the complete polymer, the above-mentioned acrylic partial polymer is obtained by polymerizing the monomer component, for example, with a polymerization conversion rate of 95% by mass or less. The polymerization conversion rate is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. The polymerization conversion rate is preferably 1% by mass or more, more preferably 5% by mass or more.

[0073] The weight-average molecular weight of the above acrylic oligomer is preferably 2500 to 10000, and more preferably 3000 to 8000. The weight-average molecular weight can be determined by converting it to polystyrene equivalent using the GPC method. For example, it can be measured using the high-speed GPC instrument "HPLC-8120GPC" manufactured by Tosoh Corporation under the following conditions. Column: TSKgel SuperHZM-H / HZ4000 / HZ3000 / HZ2000 Solvent: tetrahydrofuran Flow rate: 0.6ml / min

[0074] The above acrylic oligomer contains an acrylic monomer as a constituent unit. Preferably, the above acrylic oligomer contains a (meth)acrylic acid ester having an alicyclic hydrocarbon group as a constituent unit. The above acrylic monomer contained as a constituent unit may be one or two or more.

[0075] The proportion of (meth)acrylic acid ester having an alicyclic hydrocarbon group in the total amount of all monomer components constituting the above acrylic oligomer is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more. The above proportion is preferably 90% by mass or less, and more preferably 80% by mass or less.

[0076] The above acrylic oligomer preferably contains an alkyl (meth)acrylate as a constituent unit. Methyl methacrylate (MMA) is preferred as the alkyl (meth)acrylate. The proportion of the alkyl (meth)acrylate in the total monomer components constituting the above acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more. The above proportion is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. The above acrylic oligomer may also contain the above copolymerizable monomer as a constituent unit.

[0077] The content of the above acrylic oligomer is preferably 0.5 to 35 parts by mass, more preferably 2 to 30 parts by mass, and even more preferably 4 to 20 parts by mass, based on 100 parts by mass of the total amount of the acrylic polymer (A) and / or the above acrylic partial polymer. When the content is within the above range, the fracture stress tends to be higher, resulting in superior reworkability.

[0078] The above-mentioned acrylic polymer and acrylic polymer (A) are obtained by polymerizing a composition containing one or more selected from the group consisting of the above-mentioned acrylic partial polymer, the above-mentioned acrylic oligomer, and monomer component (B). While these polymerization methods are not particularly limited, examples 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.

[0079] 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.

[0080] 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 acrylic 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.

[0081] 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.

[0082] 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.

[0083] 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(η. 5 Examples include -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.

[0084] 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.

[0085] 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.

[0086] The adhesive layer may contain a tackifying resin. When a tackifying resin is included, the adhesive layer tends to have better adhesion even when it is thin. When the adhesive layer contains an acrylic adhesive and / or a rubber adhesive and a tackifying resin, it has excellent adhesion to the adherend and is less likely to peel off.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The adhesive layer described above may or may not contain a filler. The double-sided adhesive tape of the present invention has excellent stretch-peelability even with high adhesive strength, so there is no need to reduce the adhesive strength by adding a filler.

[0094] The filler content in the adhesive layer is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less, based on 100 parts by mass of the total amount of the base polymer, and may be substantially absent. When the content is 35 parts by mass or less, aggregation of the filler in the adhesive layer is less likely to occur, resulting in a good appearance.

[0095] The proportion of the filler in the adhesive layer is preferably 20% by mass or less, more preferably 17% by mass or less, even more preferably 12% by mass or less, and particularly preferably 10% by mass or less, based on 100% by mass of the total amount of the adhesive layer, and may be substantially absent. When the content is 20% by mass or less, aggregation of the filler in the adhesive layer is less likely to occur, resulting in a good appearance.

[0096] Examples of fillers include particulate organic and inorganic materials. Materials constituting the inorganic materials include, for example, metals such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, and stainless steel; metal oxides such as aluminum oxide, silicon dioxide, 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 hydrotalcite. Examples include metal hydroxides and hydrated metal compounds such as 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.

[0097] Examples of materials constituting the above-mentioned organic matter include polymers such as polystyrene, acrylic resin (e.g., polymethyl methacrylate), phenolic resin, benzoguanamine resin, urea resin, silicone resin, polyester, polyurethane, polyethylene, polypropylene, polyamide (e.g., nylon), polyimide, and polyvinylidene chloride.

[0098] The average particle size of the filler as a whole 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). Having an average particle size greater than or equal to the above value is preferable in that it maintains good 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 is small, the deterioration of adhesive performance tends to be suppressed. A small average particle size is also desirable in terms of the appearance of the adhesive layer. In this specification, the average particle size of the filler refers to the particle size (50% median diameter) at which the cumulative particle size by weight in the particle size distribution obtained by measurement based on the sieving method becomes 50%.

[0099] 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.

[0100] The thickness of the adhesive layer (total thickness of the adhesive layer on one side) is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. A thickness of 10 μm or more provides superior adhesion to the adherend. The thickness of the adhesive layer is, for example, 500 μm or less, preferably 300 μm or less. A thickness of 500 μm or less allows for a thinner double-sided adhesive sheet. The thicknesses of the adhesive layers on both sides may be the same or different.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] (Double-sided adhesive sheet) The thickness of the double-sided adhesive sheet is preferably 100 to 1500 μm, more preferably 120 to 1200 μm, and even more preferably 150 to 1000 μm. If the thickness is 100 μm or more, the double-sided adhesive sheet is less likely to break when pulled. If the thickness is 1500 μm or less, the thickness of the double-sided adhesive sheet can be made thinner. Note that the thickness of the double-sided adhesive sheet refers to the thickness from one adhesive surface to the other adhesive surface, i.e., the thickness of the adhesive body, and does not include the release liner.

[0105] Preferably, the above double-sided adhesive sheet can be stretched and peeled off without damaging the base layer when pulled at a tensile speed of 300 mm / min in the direction of the SUS304BA plate after being sandwiched and bonded between two SUS304BA plates.

[0106] The adhesive strength when peeling off a 180° angle (tensile speed 300 mm / min) after one adhesive surface of the above double-sided adhesive sheet is attached to a SUS304BA plate and left for 30 minutes in an environment of 23°C and 50%RH is preferably 2N / 20mm or more, more preferably 5N / 20mm or more, and even more preferably 8N / 20mm or more. When the above peeling adhesive strength is 2N / 20mm or more, the adhesion to the adherend is excellent. From the viewpoint of excellent reworkability, the above peeling adhesive strength is preferably 50N / 20mm or less, more preferably 40N / 20mm or less, and even more preferably 35N / 20mm or less. It is preferable to back the adhesive surface opposite the adhesive surface on which the adhesive strength is measured with a plastic film such as a PET film before measuring. Furthermore, it is preferable that the above peeling adhesive strength of both adhesive surfaces of the above double-sided adhesive sheet is within the above range.

[0107] The above-mentioned double-sided adhesive sheet may have a release liner attached to the surface (adhesive side) of the adhesive layer until use. The adhesive surfaces on both sides of the above-mentioned double-sided adhesive sheet may each be protected by two release liners, or they may be protected by a single release liner with both sides being release surfaces, in a roll-like winding form (winding body). The release liner is used as a protective material for the adhesive layer and is peeled off when the sheet is applied to the substrate. The release liner is not necessarily required.

[0108] 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.

[0109] 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. In particular, the above-mentioned double-sided adhesive sheet is preferably used for applications in which components provided in electrical and electronic equipment are bonded to each of the adhesive surfaces of the double-sided adhesive sheet, that is, for fixing components together in electrical and electronic equipment. The above-mentioned double-sided adhesive sheet may be used for either 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 bonded. Thus, when a double-sided adhesive sheet is used, for example, for fixing or temporarily fixing components (parts) provided in electrical and electronic equipment, the frequency of removing the double-sided adhesive sheet is particularly high.

[0110] 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.

[0111] 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, binocular, goggles, and head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, and earwear-type devices attached to the ears like earphones), 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 systems, 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.

[0112] Furthermore, the above-mentioned double-sided adhesive sheet can be used in parts that are repeatedly folded or wound up. For this reason, the above-mentioned double-sided adhesive sheet is preferably used for bonding components in electrical and electronic equipment that is folded, such as flexible displays (particularly foldable displays), and for bonding components (particularly between components) in electrical and electronic equipment that is wound up, such as rollable displays. [Examples]

[0113] Examples are given below to explain the present invention in more detail, but the present invention is not limited to these examples in any way.

[0114] Example 1 (Preparation of Adhesive Composition) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 100 parts by mass of butyl acrylate (BA), 5 parts by mass of vinyl acetate (VAc), 3 parts by mass of acrylic acid (AA), 0.1 part by mass of 2-hydroxyethyl acrylate (HEA), 0.2 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and toluene as a polymerization solvent were charged, and solution polymerization was carried out at 60°C for 6 hours to obtain a toluene solution of an acrylic polymer. The Mw of this acrylic polymer was 55×10 4 It was. Based on 100 parts by mass of the acrylic polymer contained in the above toluene solution, 40 parts by mass of a polymerized rosin ester resin (product name "Pencil D-125", softening point 125°C, manufactured by Arakawa Chemical Industries, Ltd.) as a tackifier resin and 2 parts by mass of an isocyanate crosslinking agent (trade name "Coronate L", manufactured by Tosoh Corporation) were added and mixed to prepare an adhesive composition (adhesive composition A).

[0115] (Production of Double-Sided Adhesive Sheet) The adhesive composition A was applied onto a polyethylene terephthalate (PET) release liner (product name "MRF38", manufactured by Mitsubishi Chemical Corporation) so that the final thickness (thickness of the adhesive layer) was 50 μm, and dried at 100°C for 2 minutes to form an adhesive layer (adhesive layer A). Then, the prepared adhesive layer A was respectively bonded to both sides of a base material layer A (an elastomer film having the physical properties shown in Table 1, a three-layer structure of PE / SEPS / PE, manufactured by Nippon MatTai Corporation) to obtain a laminate. The obtained laminate was passed through a laminator once at a temperature of 50°C, a pressure of 0.5 MPa, and a conveying speed of 0.5 m / min, and then aged in an oven at 50°C for 1 day to produce the double-sided sheet of Example 1.

[0116] Example 2 (Preparation of Adhesive Composition) A styrene-isoprene block copolymer (product name "Quintac 3520", manufactured by Nippon Zeon Co., Ltd., styrene content 15% by mass, diblock ratio 78% by mass) as a base polymer, 20 parts by mass of aromatic petroleum resin (product name "Nisseki Neopolymer 150", manufactured by JX Nippon Oil & Energy Corporation, softening point 155°C, hydroxyl value less than 1 mg KOH / g), 40 parts by mass of terpene phenol resin, 30 parts by mass of terpene resin, 0.75 parts by mass of isocyanate crosslinking agent (product name "Coronate L", manufactured by Tosoh Corporation) based on solid content, 1 part by mass of antioxidant, and toluene as a solvent were stirred and mixed to prepare an adhesive composition (adhesive composition B) with a solid content concentration of 50% by mass. Here, two types of terpene phenol resins were used: "YS Polystar S145" (manufactured by Yasuhara Chemical Co., Ltd., softening point 145°C, hydroxyl value 100 mg KOH / g) and "YS Polystar T145" (manufactured by Yasuhara Chemical Co., Ltd., softening point 145°C, hydroxyl value 60 mg KOH / g), in a 1:1 mass ratio, with a total of 40 parts by mass. As a terpene resin, "YS Resin PX1150N" (manufactured by Yasuhara Chemical Co., Ltd., softening point 115°C, hydroxyl value less than 1 mg KOH / g) was used. As an antioxidant, "IRGANOX CB612" (manufactured by BASF, a blend of "IRGAFOS 168" (manufactured by BASF) and "IRGANOX 565" (manufactured by BASF) in a 2:1 mass ratio) was used.

[0117] (Preparation of double-sided adhesive sheets) An adhesive layer (adhesive layer B) was formed using adhesive composition B instead of adhesive composition A, and a double-sided adhesive sheet of Example 2 was prepared in the same manner as in Example 1, except that adhesive layer B was used instead of adhesive layer A.

[0118] Example 3 (Preparation of adhesive composition) A silicone resin (product name "SD4592PSA", manufactured by Dow Toray Industries, Inc.) as a base polymer, 100 parts by mass, a curing agent (product name "BY24-741", manufactured by Dow Toray Industries, Inc.), 0.2 parts by mass, a catalyst (product name "SRX212", manufactured by Dow Toray Industries, Inc.), and toluene as a solvent were stirred and mixed to prepare an adhesive composition (adhesive composition C) with a solid content of 40% by mass.

[0119] (Preparation of double-sided adhesive sheets) Adhesive composition C was applied to a fluorosilicone (K1) treated release liner (manufactured by Fujiko Co., Ltd.) on a PET substrate (38 μm) to a final thickness (thickness of the adhesive layer) of 50 μm, and dried at 150°C for 3 minutes to form an adhesive layer (adhesive layer C). The prepared adhesive layer C was then bonded to both sides of substrate layer A to obtain a laminate. The obtained laminate was passed through a laminator once at a temperature of 50°C, a pressure of 0.5 MPa, and a transport speed of 0.5 m / min, and then aged in a 50°C oven for 1 day to produce the double-sided adhesive sheet of Example 3.

[0120] Example 4 (Preparation of adhesive composition) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 93 parts by mass of butyl acrylate (BA), 7 parts by mass of acrylic acid (AA), 0.05 parts by mass of 4-hydroxybutyl acrylate (4HBA), and ethyl acetate as a polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.1 parts by mass of AIBN was added as a polymerization initiator, and solution polymerization was carried out at 60°C for 6 hours to obtain a solution of acrylic polymer. The Mw of this acrylic polymer was 132 × 10⁻⁶ 4 The Mw / Mn ratio was 5.85. To 100 parts by mass of the acrylic polymer contained in the above toluene solution, 1.5 parts by mass of isocyanate crosslinking agent (product name "Coronate L", manufactured by Tosoh Corporation), 0.01 parts by mass of epoxy crosslinking agent (product name "Tetrad C", manufactured by Mitsubishi Gas Chemical Company, Inc.), 15 parts by mass of terpene phenol resin (product name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd., softening point 145°C, hydroxyl value 70-110 mgKOH / g), and 15 parts by mass of (meth)acrylic oligomer were added and stirred to prepare an adhesive composition (adhesive composition D).

[0121] The (meth)acrylic oligomer used was prepared by the following method. Specifically, 95 parts by mass of cyclohexyl methacrylate (CHMA), 5 parts by mass of acrylic acid (AA), 10 parts by mass of AIBN as a polymerization initiator, and toluene as a polymerization solvent were charged into a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel. The mixture was stirred in a nitrogen stream for 1 hour to remove oxygen from the polymerization system, and then the temperature was raised to 85°C and the mixture was reacted for 5 hours to obtain a (meth)acrylic oligomer with a solid content of 50% by mass. The Mw of the obtained (meth)acrylic oligomer was 3600.

[0122] (Preparation of double-sided adhesive sheets) An adhesive layer (adhesive layer D) was formed using adhesive composition D instead of adhesive composition A, and a double-sided adhesive sheet of Example 4 was prepared in the same manner as in Example 1, except that adhesive layer D was used instead of adhesive layer A.

[0123] Example 5 The double-sided adhesive sheet of Example 5 was prepared in the same manner as in Example 1, except that base layer B (an elastomer film with the physical properties shown in Table 1, a 3-layer structure of PE / SEPS / PE, manufactured by Nippon Matai Co., Ltd.) was used instead of base layer A.

[0124] Example 6 A double-sided adhesive sheet for Example 6 was prepared in the same manner as in Example 1, except that base layer C (an elastomer film with the physical properties shown in Table 1, a 3-layer structure of PE / SEPS / PE, manufactured by Nippon Matai Co., Ltd.) was used instead of base layer A.

[0125] Example 7 The double-sided adhesive sheet of Example 7 was prepared in the same manner as in Example 1, except that base layer D (an elastomer film with the physical properties shown in Table 1, a 3-layer structure of PE / SEPS / PE, manufactured by Nippon Matai Co., Ltd.) was used instead of base layer A.

[0126] Example 8 The double-sided adhesive sheet of Example 8 was prepared in the same manner as in Example 1, except that base layer E (an elastomer film with the physical properties shown in Table 1, a 3-layer structure of PE / SEPS / PE, manufactured by Nippon Matai Co., Ltd.) was used instead of base layer A.

[0127] Example 9 (Preparation of adhesive composition) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 100 parts by mass of butyl acrylate (BA), 5 parts by mass of vinyl acetate (VAc), 3 parts by mass of acrylic acid (AA), 0.1 parts by mass of 2-hydroxyethyl acrylate (HEA), 0.2 parts by mass of AIBN as a polymerization initiator, and toluene as a polymerization solvent were charged. Solution polymerization was carried out at 60°C for 6 hours to obtain a toluene solution of an acrylic polymer. The Mw of this acrylic polymer was 55 × 10⁻⁶. 4 That was the case. To 100 parts by mass of the acrylic polymer contained in the above toluene solution, 40 parts by mass of polymerized rosin ester resin (product name "Pensel D-125", softening point 125°C, manufactured by Arakawa Chemical Industries, Ltd.) as a tackifying resin, 2 parts by mass of isocyanate crosslinking agent (product name "Coronate L", manufactured by Tosoh Corporation), and 30 parts by mass of aluminum hydroxide particles (product name "Hydgley Light H-21", manufactured by Showa Denko K.K.) as a filler were added and mixed to prepare an adhesive composition (adhesive composition E). The filler used in this example has an average particle size of 27 μm, with 40% or more of particles having a diameter of less than 25 μm and 0% of particles having a diameter of less than 1 μm.

[0128] (Preparation of double-sided adhesive sheets) An adhesive layer (adhesive layer E) was formed using adhesive composition E instead of adhesive composition A, and a double-sided adhesive sheet of Example 9 was prepared in the same manner as in Example 1, except that adhesive layer E was used instead of adhesive layer A.

[0129] Comparative Example 1 A double-sided adhesive sheet of Comparative Example 1 was prepared in the same manner as in Example 1, except that base layer F (a polyurethane film having the physical properties shown in Table 2, manufactured by Nippon Matai Co., Ltd.) was used instead of base layer A.

[0130] Comparative Example 2 A double-sided adhesive sheet for Comparative Example 2 was prepared in the same manner as in Example 9, except that base layer F (a polyurethane film having the physical properties shown in Table 2, manufactured by Nippon Matai Co., Ltd.) was used instead of base layer A.

[0131] Comparative Example 3 A double-sided adhesive sheet for Comparative Example 3 was prepared in the same manner as in Example 1, except that base layer G (a thermoplastic elastomer film having the physical properties shown in Table 2, manufactured by Nippon Matai Co., Ltd.) was used instead of base layer A.

[0132] Comparative Example 4 A double-sided adhesive sheet for Comparative Example 4 was prepared in the same manner as in Example 1, except that base layer H (product name "Silklon NES85", urethane elastomer film, manufactured by Okura Industries Co., Ltd.) was used instead of base layer A.

[0133] Comparative Example 5 A double-sided adhesive sheet for Comparative Example 5 was prepared in the same manner as in Example 1, except that base layer I (product name "Trefan #40", polypropylene film, manufactured by Toray Industries, Inc.) was used instead of base layer A.

[0134] <Rating> The substrate layers used in the examples and comparative examples, as well as the resulting double-sided adhesive sheets, were evaluated as follows. The results are shown in the table.

[0135] (1) Elongation at break, 100% modulus The base material layer was punched out to 10 mm x 50 mm, set in a tensile testing machine (product name "AG-20kNG", manufactured by Shimadzu Corporation) with a 10 mm gap between chucks in the longitudinal direction, and stretched in the 180° direction at a tensile speed of 300 mm / min until fracture. The elongation at fracture was calculated from the measurement results, and the stress at 100% elongation was calculated as the 100% modulus.

[0136] (2) Ratio of core layer to surface layer ([Surface layer / Core layer / Surface layer]) The cross-section of the substrate layer was observed using a scanning electron microscope (product name "S-3400N," manufactured by Hitachi, Ltd.), and the ratio of the thicknesses of each layer constituting the substrate layer was calculated. Note that substrate layers F to I used in the comparative example were single layers and therefore were not measured.

[0137] (3) Reworkability A double-sided adhesive sheet was punched out into a rectangle measuring 10 mm wide x 50 mm long to obtain a test specimen. A 50 mm length of the above test specimen was sandwiched between two SUS304BA plates and bonded together to create a test sample. The exposed test specimen from the test sample was pulled in the direction of the SUS304BA plate (the adherend) at a tensile speed of 300 mm / min. The stretchability was then evaluated according to the following evaluation criteria. ○ (Good): The test specimen could be stretched and peeled off without damaging the substrate layer. △ (Unacceptable): The test piece could be stretched and peeled off without damaging the substrate layer, but the adhesive force to the adherend was insufficient. × (Defective): The double-sided adhesive sheet tore before it could be fully stretched and peeled off over a length of 50 mm.

[0138] (4) Exterior The surface of the coating film, after applying the adhesive composition to the release liner, was visually inspected and evaluated according to the following evaluation criteria. ○ (Good): No streaks or aggregates were observed. × (Poor): Streaks or aggregates were observed.

[0139] (5) Adhesive strength Double-sided adhesive tape was cut to a size of 20 mm wide and 100 mm long. Under conditions of 23°C and 50% RH, the release liner was peeled off to expose the adhesive surface, and a 25 μm thick polyethylene terephthalate (PET) film was bonded to one side. Then, the other adhesive side was bonded to the surface of a SUS304BA plate, and a 2 kg roller was pressed down once back and forth. After leaving this in a 23°C, 50% RH environment for 30 minutes, the peel strength (N / 20 mm) was measured using a tensile testing machine under conditions of a tensile speed of 300 mm / min and a peel angle of 180°. A universal tensile and compression testing machine (product name "TG-1kN", manufactured by Minebea Co., Ltd.) was used as the tensile testing machine.

[0140] [Table 1]

[0141] [Table 2]

[0142] As shown in Table 1, the double-sided adhesive sheets of the examples exhibited good stretchability regardless of the presence or absence of fillers, demonstrated excellent reworkability, and showed a high degree of design freedom for the adhesive layer. Furthermore, the double-sided adhesive sheets of Examples 1 to 8, which did not contain fillers in the adhesive layer, had a good appearance. On the other hand, when a substrate layer with an elongation at break of less than 700% or a 100% modulus exceeding 4.0 MPa was used, it was determined that the reworkability was poor and the design freedom for the adhesive layer was low.

[0143] The following describes variations of the invention relating to this disclosure. [Note 1] This is a double-sided adhesive sheet comprising a base layer and adhesive layers provided on both sides of the base layer. The substrate layer comprises a core layer mainly composed of a styrene-based elastomer and a resin layer harder than the core layer that provides both surfaces of the substrate layer. A double-sided adhesive sheet having an elongation of 700% or more of the base layer and a 100% modulus of 4.0 MPa or less of the base layer. [Note 2] The double-sided adhesive sheet according to Note 1, wherein the ratio of the total thickness of the core layer, which mainly consists of the styrene-based elastomer, to the total thickness of the base layer is 60% or more. [Note 3] The double-sided adhesive sheet according to Note 1 or 2, wherein the ratio of the thickness of each resin layer in the base material layer is 2.5% or more of the total thickness of the base material layer. [Note 4] The ratio [former:latter] of the total thickness of the resin layer in the base layer to the total thickness of the core layer is 3:97 to 45:55, a double-sided adhesive sheet as described in any one of Notes 1 to 3. [Note 5] The resin layer is a layer mainly composed of polyolefin resin, a double-sided adhesive sheet as described in any one of Notes 1 to 4. [Note 6] The double-sided adhesive sheet according to any one of Notes 1 to 5, wherein the proportion of filler in the adhesive layer is 20% by mass or less relative to the total amount of the adhesive layer. [Note 7] A double-sided adhesive sheet described in any one of Notes 1 to 6, for fixing components together in electrical and electronic equipment. [Note 8] An electrical and electronic device comprising the double-sided adhesive sheet described in Note 7, wherein the double-sided adhesive sheet fixes components together on both adhesive surfaces. [Explanation of symbols]

[0144] 1. Double-sided adhesive sheet 2 Base material layer 21 Core layer 22 Resin layer (first resin layer) 23 Resin layer (second resin layer) 3,4 Adhesive layer

Claims

1. A double-sided adhesive sheet comprising a base layer and adhesive layers provided on both sides of the base layer, The substrate layer comprises a core layer (excluding foam sheets) mainly composed of a styrene-based elastomer, and a resin layer harder than the core layer that provides both surfaces of the substrate layer. The elongation of the substrate layer is 700% or more, and the 100% modulus of the substrate layer is 4.0 MPa or less. The ratio of the total thickness of the resin layer in the base layer to the total thickness of the core layer [former:latter] is 3:97 to 45:

55. The aforementioned resin layer contains a polyethylene resin, The content ratio of the polyethylene resin is 50% by mass or more, relative to 100% by mass of the total amount of the resin layer. After one adhesive side is attached to a SUS304BA plate and left for 30 minutes in an environment of 23°C and 50% RH, the adhesive strength when peeled off at 180° (tensile speed 300 mm / min) is between 2 N / 20 mm and 50 N / 20 mm. Double-sided adhesive sheet.

2. The double-sided adhesive sheet according to claim 1, wherein the ratio of the total thickness of the core layer, which mainly consists of the styrene elastomer, to the total thickness of the base layer is 60% or more.

3. The double-sided adhesive sheet according to claim 1 or 2, wherein the ratio of the thickness of each resin layer in the base material layer is 2.5% or more of the total thickness of the base material layer.

4. The double-sided adhesive sheet according to claim 1 or 2, wherein the proportion of filler in the adhesive layer is 20% by mass or less relative to the total amount of the adhesive layer.

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

6. An electrical and electronic device comprising the double-sided adhesive sheet described in Claim 5, wherein the double-sided adhesive sheet fixes components together on both adhesive surfaces.

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