CN116970353A

CN116970353A - Double-sided adhesive sheet

Info

Publication number: CN116970353A
Application number: CN202310452494.6A
Authority: CN
Inventors: 横川亮祐; 奥村友香; 渡边博之
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2022-04-28
Filing date: 2023-04-25
Publication date: 2023-10-31
Also published as: JP2023163333A

Abstract

The present invention relates to a double-sided adhesive sheet. The invention provides a double-sided adhesive sheet which has excellent reworkability and high design freedom of an adhesive layer. The double-sided adhesive sheet (1) has a base layer (2) and adhesive layers (3, 4) provided on both sides of the base layer (2). The base material layer (2) has a core layer (21) and resin layers (22, 23), the core layer (21) contains a styrene-based elastomer as a main component, and the resin layers (22, 23) provide both surfaces of the base material layer (2) and are harder than the core layer (21). The elongation of the base material layer (2) is 700% or more, and the 100% modulus of the base material layer (2) is 4.0MPa or less.

Description

Double-sided adhesive sheet

Technical Field

The present invention relates to a double-sided adhesive sheet.

Background

In recent years, electronic devices such as home appliances, office automation equipment, mobile phones (smart phones and the like), digital cameras, PDAs (personal digital assistants) and the like have been widely used. For example, a mobile phone, which is a representative device of a portable device, has a tendency to make its main components thinner and larger in screen size. In general, a display portion of a portable device mainly includes an LCD module and a backlight unit, and various sheet-like members are laminated in order to exhibit functions of light emission, reflection, light shielding, light guide, and the like. In addition, recent mobile phones often employ an organic electroluminescent display that is more expensive than an LCD module. A double-sided adhesive sheet (double-sided adhesive tape) for assembly (joining) of these components is used.

The double-sided pressure-sensitive adhesive sheet is required to have a pressure-sensitive adhesive strength equal to or higher than a predetermined level so that adhesion failure such as peeling and dislocation does not occur during use. On the other hand, when repairing, replacing, inspecting, recycling, and the like a member having an adherend to which a double-sided adhesive sheet is attached, it is sometimes necessary to peel off the double-sided adhesive sheet. In such a case, it is required to be able to easily peel the double-sided adhesive sheet from the adherend, that is, to have reworkability.

As a method of peeling a double-sided adhesive sheet while suppressing damage of an adherend, the following method (stretch peeling method) has been proposed: the double-sided adhesive sheet attached to the adherend is held and stretched, and the double-sided adhesive sheet is elongated and deformed to reduce the adhesive area, thereby being removed from the adherend in the horizontal direction (shearing direction).

As a double-sided adhesive sheet that can be peeled by such a stretch peeling method, for example, an adhesive tape using a substrate having high flexibility (for example, patent document 1) and an adhesive tape having a filler added to an adhesive layer (for example, patent document 2) are known.

Prior art literature

Patent literature

Patent document 1: international publication No. 2019/003933

Patent document 2: international publication No. 2019/167922

Disclosure of Invention

Problems to be solved by the invention

However, in the case of using an adhesive layer having high adhesion, the conventional adhesive sheet using a base material having high flexibility has a problem that the base material is easily torn off during stretch releasing and is difficult to stretch releasing.

When the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive layer to which the filler is added is intended to be peeled off by stretching, the adhesive force is lowered due to the presence of the filler at the interface between the pressure-sensitive adhesive layer and the adherend, and stretching and peeling are easy. However, the following problems exist due to the addition of the filler: the filler may be aggregated in the adhesive layer and the like, so that the desired appearance may not be exhibited, and the thickness of the adhesive layer may need to be set to be equal to or smaller than the particle size of the filler so that the filler is present at the interface.

As described above, the conventional pressure-sensitive adhesive sheet having reworkability has the following problems: the adhesive layer having high adhesion cannot be used, and the adhesive layer has a low degree of freedom in design because of restrictions such as restrictions on the appearance and thickness of the adhesive layer.

The present invention has been made in view of such circumstances, and an object thereof is to provide a double-sided pressure-sensitive adhesive sheet having excellent reworkability and a high degree of freedom in design of a pressure-sensitive adhesive layer.

Means for solving the problems

The present inventors have made intensive studies to achieve the above object, and as a result, have found that if a double-sided pressure-sensitive adhesive sheet having a specific base material layer is used, reworkability is excellent and the degree of freedom in designing the pressure-sensitive adhesive layer is high. The present invention has been completed based on these findings.

That is, the present invention provides a double-sided adhesive sheet having a base layer and adhesive layers provided on both sides of the base layer, wherein,

the base material layer has a core layer containing a styrene-based elastomer as a main component and a resin layer which is provided on both surfaces of the base material layer and is harder than the core layer,

the elongation of the base material layer is 700% or more, and the 100% modulus of the base material layer is 4.0MPa or less.

The proportion of the total thickness of the core layer containing the styrene-based elastomer as a main component in the base material layer is preferably 60% or more relative to the total thickness of the base material layer.

The ratio of the thickness of each of the resin layers in the base material layer is preferably 2.5% or more with respect to the total thickness of the base material layer.

Preferably, a ratio of a total thickness of the resin layer to a total thickness of the core layer in the base material layer [ the former: the latter is 3: 97-45: 55.

The resin layer is preferably a layer containing a polyolefin resin as a main component.

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

The double-sided adhesive sheet is preferably used for fixing members of an electric and electronic apparatus to each other.

In addition, the present invention provides an electric and electronic apparatus having the above-described double-sided adhesive sheet, and the above-described double-sided adhesive sheet fixes members to each other with two adhesive faces.

Effects of the invention

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, the reworkability is excellent, and the adhesive force of the adhesive layer can be improved, and the desired appearance and thickness can be obtained.

Drawings

Fig. 1 is a schematic cross-sectional view of a double-sided adhesive sheet according to an embodiment of the present invention.

Description of the reference numerals

1. Double-sided adhesive sheet

2. Substrate layer

21. Core layer

22. Resin layer (first resin layer)

23. Resin layer (second resin layer)

3. 4 adhesive layer

Detailed Description

[ double-sided adhesive sheet ]

The double-sided adhesive sheet of the present invention comprises at least a base layer and adhesive layers provided on both sides of the base layer.

The base material layer has at least a core layer containing a styrene-based elastomer as a main component and a resin layer which is provided on both surfaces of the base material layer and is harder than the core layer. In the present specification, a resin layer that is harder than the core layer may be referred to as a "hard resin layer". That is, the base material layer includes, in order, 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. The core layer is a layer located between the first resin layer and the second resin layer. The base material layer may have a layer other than the core layer, the first resin layer, and the second resin layer.

The base material layer has a layer containing a styrene-based elastomer as a main component and has moderate flexibility, and is not easily broken during stretching. In addition, by having the hard resin layer providing both surfaces of the base material layer, the components in the adhesive layer are not easily transferred to the core layer, and the fracture resistance of the core layer is not easily lowered.

The elongation of the base material layer is 700% or more, preferably 800% or more, more preferably 850% or more, and even more preferably 900% or more. The elongation of 700% or more makes it difficult to break the double-sided adhesive sheet when stretched. The elongation of the base material layer may be, for example, 5000% or less, 3000% or less, or 2000% or less. The elongation is elongation at break and is measured at 23℃under 50% RH under conditions of a sample size of 10 mm. Times.50 mm, a chuck pitch of 10mm, a stretching speed of 300 mm/min, and a stretching direction of 180 ℃.

The 100% modulus of the base material layer is 4.0MPa or less, preferably 3.8MPa or less. By the above 100% modulus of 4.0MPa or less, the force applied to the hands when stretching the double-sided adhesive sheet is small, and the double-sided adhesive sheet is less likely to break. The 100% modulus is, for example, 0.1MPa or more, and may be 0.5MPa or more or 1.0MPa or more. The 100% modulus was calculated as the stress at 100% elongation measured at 23℃under 50% RH conditions under conditions of a sample size of 10mm by 50mm, a chuck pitch of 10mm, a elongation speed of 300 mm/min and a elongation direction of 180 ℃.

Fig. 1 is a schematic cross-sectional view showing one embodiment of the double-sided adhesive sheet of the present invention. As shown in fig. 1, the double-sided adhesive sheet 1 has a base layer 2, and an adhesive layer 3 and an adhesive layer 4 provided on both sides of the base layer 2, respectively. The base material layer 2 has 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 which provide both surfaces of the base material layer 2 and are harder than the core layer 21. The elongation of the base material layer 2 is 700% or more, and the 100% modulus of the base material layer 2 is 4.0MPa or less.

(substrate layer)

The base material layer includes at least a core layer containing a styrene-based elastomer as a main component and the hard resin layer (first resin layer and second resin layer). The two hard resin layers are layers that provide the surface of the base material layer, i.e., surface layers. The core layer may be a layer located between two hard resin layers, and the core layer may be a single layer or a plurality of layers. In the case where the core layer is a plurality of layers, the plurality of core layers may be layers having the same thickness, composition, or the like, or may be layers having different thicknesses, compositions, or the like. The first resin layer and the second resin layer may be the same layer in thickness, composition, or the like, or may be layers different in thickness, composition, or the like.

Examples of the styrene-based elastomer include: styrene-diene copolymers such as 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 products thereof. The above copolymer is preferably a block copolymer. The styrene-based elastomer may be used alone or in combination of two or more.

The styrene-based elastomer is the resin having the highest mass ratio among the resins constituting the core layer. The content of the styrene-based elastomer in the core layer is preferably 50 mass% or more, more preferably 60 mass% or more, still more preferably 70 mass% or more, and particularly preferably 80 mass% or more, based on 100 mass% of the total amount of the core layer.

The hard resin layer is harder than the core layer. The hardness of the hard resin layer and the core layer may be, for example: residual stress, modulus of elasticity, young's modulus, hardness measured by nanoindentation, and the like.

The hard resin layer may be a layer mainly composed of a resin harder than the styrene-based elastomer. Examples of the resin harder than the styrene-based elastomer include: polyolefin resins such as 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, homo polypropylene, etc.), polybutene, polymethylpentene, ionomers, ethylene- (meth) acrylic acid copolymers, ethylene- (meth) acrylic acid ester (random, alternating) copolymers, ethylene-vinyl acetate copolymers (EVA), ethylene-propylene copolymers, cyclic olefin polymers, ethylene-butene copolymers, ethylene-hexene copolymers, etc.; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene terephthalate (PBT), and the like; a polycarbonate; polyimide-based resins; polyether ether ketone; a polyetherimide; polyamides such as aromatic polyamides and wholly aromatic polyamides; polyphenylene sulfide; fluorine-containing resin; polyvinyl chloride; polyvinylidene chloride; cellulose resins such as triacetyl cellulose (TAC); a polysiloxane resin; acrylic resins such as polymethyl methacrylate (PMMA); polysulfone; polyarylate; polyvinyl acetate, and the like. The resin may be used alone or in combination of two or more.

Among these resins, polyolefin resins are preferred from the viewpoint of excellent workability such as easy winding and the like, and easy elongation at the time of stretching and less breakage, and polyethylene resins are more preferred from the viewpoint of excellent anchoring property of the adhesive layer, less breakage at the time of stretching the double-sided adhesive sheet, and adhesive residue on an adherend, and low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene are particularly preferred.

The resin harder than the styrene-based elastomer is preferably a resin having the highest mass ratio among the resins constituting the hard resin layer. The content of the resin (particularly, polyolefin resin) harder than the styrene-based elastomer in the hard resin layer is preferably 50 mass% or more, more preferably 60 mass% or more, still more preferably 70 mass% or more, and particularly preferably 80 mass% or more, based on 100 mass% of the total amount of the hard resin layer.

The proportion of the thickness (total thickness) of the core layer containing the styrene-based elastomer as a main component in the base material layer is preferably 60% or more, more preferably 70% or more, still more preferably 75% or more, and particularly preferably 80% or more, relative to 100% of the total thickness of the base material layer. When the ratio is 60% or more, the 100% modulus of the base material layer tends to become lower. The above ratio is preferably 98% or less, more preferably 95% or less. When the above ratio is 98% or less, breakage is less likely to occur when the double-sided adhesive sheet is stretched.

The ratio of the thickness of the hard resin layer (thickness of each layer) in the base material layer is preferably 2.5% or more, more preferably 3% or more, relative to 100% of the total thickness of the base material layer. When the ratio is 2.5% or more, the components in the adhesive layer are not easily transferred to the core layer, and the adhesive layer is excellent in anchoring property, and is not easily broken when the double-sided adhesive sheet is stretched, and the adhesive paste on the adherend remains. The above ratio is preferably 15% or less, more preferably 12.5% or less.

The ratio of the total thickness of the hard resin layer in the base layer to the total thickness of the core layer [ the former: the latter is preferably 3: 97-45: 55, more preferably 5: 95-35: 65, more preferably 8: 92-25: 75. when the above ratio is 3: if 97 or more, the components in the adhesive layer are not easily transferred to the core layer, and the adhesive layer is excellent in anchoring property, and is not easily broken when the double-sided adhesive sheet is stretched, and the adhesive paste on the adherend remains. When the above ratio is 45: when 55 or less, the 100% modulus of the base material layer tends to be lower.

The thickness of the base layer is preferably 30 μm or more, more preferably 50 μm or more, from the viewpoint of excellent function as a support and the difficulty of breakage when stretching the double-sided adhesive sheet. The thickness of the base layer is preferably 1mm or less, more preferably 500 μm or less, and even more preferably 300 μm or less, from the viewpoint of further excellent stretch releasability.

The base material layer can be produced by forming a film by a known or conventional method. Examples of the film forming method include: a roll film forming method, a casting method in an organic solvent, a blow extrusion method in a closed system, a T-die extrusion method, a coextrusion method, a dry lamination method, and the like.

For the purpose of improving the adhesion, the retention, and the like, the surface of the base material layer may be subjected to physical treatments such as corona discharge treatment, plasma treatment, sanding treatment, ozone exposure treatment, flame exposure treatment, high-voltage electric shock exposure treatment, and ionizing radiation treatment; chemical treatments such as chromic acid treatment; surface treatment such as easy adhesion treatment with a coating agent (primer). The entire surface of the base material layer is preferably subjected to a surface treatment for improving adhesion.

(adhesive layer)

The pressure-sensitive adhesive layers provided on both sides of the base layer in the double-sided pressure-sensitive adhesive sheet may be the same pressure-sensitive adhesive layer or may be pressure-sensitive adhesive layers having different compositions, thicknesses, physical properties, and the like. The pressure-sensitive adhesive layers provided on both sides of the base layer may be a single layer or may be a plurality of layers each having the same composition or different layers having different thicknesses, physical properties, and the like.

As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, known or conventional pressure-sensitive adhesives can be used, and examples thereof include, but are not particularly limited to: acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixed systems thereof, and the like), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, fluorine-containing adhesives, styrene adhesives, and the like. Among them, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive, a silicone pressure-sensitive adhesive or a rubber pressure-sensitive adhesive from the viewpoints of adhesion, weather resistance, cost and ease of design of the pressure-sensitive adhesive. The binder may be used alone or in combination of two or more.

The acrylic pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer. The acrylic polymer is a polymer containing an acrylic monomer (a monomer having a (meth) acryloyl group in a molecule) as a monomer component constituting the polymer. That is, the above acrylic polymer contains a structural unit derived from an acrylic monomer. The acrylic polymer may be used alone or in combination of two or more. The acrylic polymer may contain only one kind of acrylic monomer as a monomer component, or may contain two or more kinds of acrylic monomers as a monomer component. In the present specification, "(meth) acrylic acid" means "acrylic acid" and/or "methacrylic acid" ("acrylic acid" and "methacrylic acid" either or both), and the other is the same.

In the present specification, the base polymer means a main component of polymer components in the adhesive constituting the adhesive layer, for example, a polymer component in an amount of more than 50 mass%. The content of the base polymer in the pressure-sensitive adhesive layer is preferably 60 mass% or more, more preferably 70 mass% or more, based on 100 mass% of the total pressure-sensitive adhesive layer.

The acrylic polymer is preferably a polymer having the largest content of structural units derived from (meth) acrylic esters in terms of mass ratio. Examples of the (meth) acrylate include hydrocarbon group-containing (meth) acrylates. Examples of the hydrocarbon group-containing (meth) acrylate include: alkyl (meth) acrylate having a linear or branched aliphatic hydrocarbon group, cycloalkyl (meth) acrylate and other (meth) acrylate having an alicyclic hydrocarbon group, aryl (meth) acrylate and other (meth) acrylate having an aromatic hydrocarbon group, and the like. The hydrocarbon group-containing (meth) acrylate may be used alone or in combination of two or more.

Examples of the alkyl (meth) acrylate include: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and the like.

Among these alkyl (meth) acrylates, preferred are alkyl (meth) acrylates having a linear or branched aliphatic hydrocarbon group having 1 to 20 carbon atoms (preferably 2 to 12 carbon atoms, more preferably 4 to 10 carbon atoms). When the number of carbon atoms is within the above range, the glass transition temperature of the acrylic polymer can be easily adjusted, and the adhesiveness can be easily improved.

Examples of the (meth) acrylate having an alicyclic hydrocarbon group include: (meth) acrylic esters having a monocyclic aliphatic hydrocarbon ring such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, and cyclooctyl (meth) acrylate; (meth) acrylic esters having a bicyclic aliphatic hydrocarbon ring such as isobornyl (meth) acrylate; and (meth) acrylic esters having an aliphatic hydrocarbon ring having three or more rings, such as tetrahydrodicyclopentadiene (meth) acrylate, tetrahydrodicyclopentadiene oxyethyl (meth) acrylate, tetrahydrotricyclopentadienyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, and 2-ethyl-2-adamantyl (meth) acrylate.

Examples of the (meth) acrylate having an aromatic hydrocarbon group include: phenyl (meth) acrylate, benzyl (meth) acrylate, and the like.

In order to properly exhibit basic properties such as adhesiveness due to the hydrocarbon group-containing (meth) acrylate in the pressure-sensitive adhesive layer, the proportion of the hydrocarbon group-containing (meth) acrylate in the total monomer components is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, relative to the total amount (100% by mass) of the total monomer components constituting the acrylic polymer. The proportion may be 99.9% by mass or less, or 98% by mass or less, 95% by mass or less, 90% by mass or less, or 80% by mass or less, from the viewpoint of the effect of copolymerizing other monomer components to obtain the other monomer components.

The acrylic polymer may contain a structural unit derived from another monomer component copolymerizable with the hydrocarbon group-containing (meth) acrylate for the purpose of modification such as improvement of cohesive force and introduction of crosslinking points. Examples of the other monomer component include: and polar group-containing monomers such as hydroxyl group-containing monomers, nitrogen atom-containing monomers, carboxyl group-containing monomers, acid anhydride monomers, ketone group-containing monomers, alkoxysilyl group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers. The other monomer components may be used singly or in combination of two or more.

Examples of the hydroxyl group-containing monomer 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, 4-hydroxymethylcyclohexyl (meth) acrylate, and the like.

Examples of the nitrogen atom-containing monomer include: an amide group-containing monomer, an amino group-containing monomer, a cyano group-containing monomer, a monomer having a ring containing a nitrogen atom, and the like. Examples of the amide group-containing monomer include: (meth) acrylamide, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol propane (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, and the like. Examples of the amino group-containing monomer include: aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, and the like. Examples of the cyano group-containing monomer include: acrylonitrile, methacrylonitrile. Examples of the monomer having a nitrogen atom-containing ring include: n-vinyl-2-pyrrolidone, N-methyl vinyl pyrrolidone, N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrazine, N-vinyl pyrrole, N-vinyl imidazole, N-vinyl Oxazole, N-vinylmorpholine, N-vinylcaprolactam, N- (meth) acryloylmorpholine and the like.

Examples of the carboxyl group-containing monomer include: acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and the like. Examples of the acid anhydride monomer include: maleic anhydride, itaconic anhydride, and the like.

Examples of the ketone group-containing monomer include: diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate, and the like.

Examples of the alkoxysilyl group-containing monomer include: 3- (meth) acryloxypropyl trimethoxysilane, 3- (meth) acryloxypropyl triethoxysilane, 3- (meth) acryloxypropyl methyldimethoxysilane, 3- (meth) acryloxypropyl methyldiethoxysilane, and the like.

Examples of the glycidyl group-containing monomer include: glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and the like.

Examples of the sulfonic acid group-containing monomer include: styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfonic acid, (meth) acrylamidopropane sulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloxynaphthalene sulfonic acid.

Examples of the phosphate group-containing monomer include: 2-hydroxyethyl acrylate phosphate, and the like.

The total of the proportions of the polar group-containing monomers in the total monomer components (100 mass%) constituting the acrylic polymer is not particularly limited, but is preferably 0.1 mass% or more, more preferably 1 mass% or more, still more preferably 5 mass% or more, and may be 10 mass% or more, 15 mass% or more, 20 mass% or more, or 25 mass% or more, from the viewpoint of better exertion of the effects caused by the use of the polar group-containing monomers. In addition, from the viewpoint of obtaining an adhesive layer having moderate flexibility, the total of the above proportions is preferably 50 mass% or less, more preferably 40 mass% or less.

As the monomer component constituting the acrylic polymer, other monomers may be further contained. Examples of the other monomer 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 vinyl toluene; 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; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether, and the like.

The proportion of the other monomer may be, for example, 0.05 mass% or more and 0.5 mass% or more, based on 100 mass% of the total amount of all the monomer components constituting the acrylic polymer. The proportion may be, for example, 20 mass% or less, 10 mass% or less, or 5 mass% or less, or the other monomer may be substantially not contained.

The weight average molecular weight (Mw) of the acrylic polymer is preferably 5X 10 ⁴ The above is more preferably 10×10 ⁴ The above is more preferably 20×10 ⁴ The above is particularly preferably 30×10 ⁴ The above. When the Mw is 5X 10 ⁴ In this way, an adhesive exhibiting good cohesiveness can be easily obtained. In addition, the Mw is preferably 500X 10 ⁴ The following is given. When the Mw is 500X 10 ⁴ In the following, since an adhesive exhibiting moderate fluidity (mobility of the polymer chain) is easily formed, reworkability is excellent.

The acrylic polymer may have a structural part derived from an acrylic oligomer. Examples of such an acrylic polymer include: a polymer comprising a polymerization reaction product of another acrylic polymer (sometimes referred to as "acrylic polymer (a)") which is a precursor of the acrylic polymer capable of constituting the acrylic polymer by polymerization, and a composition comprising the acrylic oligomer. When the structural unit derived from the acrylic oligomer is provided, the fracture stress is high, and the reworkability is further excellent. The composition containing the above acrylic oligomer may further contain a monomer component (sometimes referred to as "monomer component (B)"). The acrylic polymer (a), the acrylic oligomer and the monomer component (B) may be used singly or in combination.

The acrylic polymer may be a polymerization reaction product obtained by polymerizing a composition containing at least one selected from the group consisting of an acrylic partial polymer, an acrylic oligomer, and a monomer component (B). In the case where the acrylic polymer is a polymerization reaction product obtained by polymerizing a composition composed only of the monomer component (B), the monomer component (B) contains at least an acrylic monomer. Among these, polymerization reaction products of compositions comprising acrylic part polymers are preferred. The "partial polymer" is sometimes referred to as "prepolymer", "slurry", etc. The acrylic partial polymer, acrylic oligomer and monomer component (B) may each be used alone or in combination of two or more.

The acrylic polymer (a), the acrylic partial polymer, and the acrylic oligomer are each a compound containing an acrylic monomer as an essential monomer component. The acrylic monomer as the monomer component (B) and as the monomer components constituting the acrylic polymer (a), the acrylic partial polymer and the acrylic oligomer may be exemplified by those exemplified and described above as the monomer components constituting the acrylic polymer.

The acrylic polymer (a) may be a polymer alone forming the base polymer, or may be a polymer forming the base polymer together with a polymerization reaction product of the composition containing the acrylic oligomer.

The acrylic polymer (a) contains an acrylic monomer as a structural unit. The acrylic polymer (a) preferably contains the above-mentioned (meth) acrylate containing a hydrocarbon group as a structural unit. Among these, alkyl (meth) acrylates having a linear or branched aliphatic hydrocarbon group are preferable, and alkyl (meth) acrylates having a linear or branched aliphatic hydrocarbon group having 1 to 20 carbon atoms (preferably 2 to 12 carbon atoms, more preferably 4 to 10 carbon atoms) are more preferable. When the number of carbon atoms is within the above range, the glass transition temperature of the acrylic polymer can be easily adjusted, and the adhesiveness can be easily improved. The acrylic monomer contained as the structural unit may be one kind or two or more kinds.

The proportion of the hydrocarbon group-containing (meth) acrylate is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 65% by mass or more, based on 100% by mass of the total amount of all the monomer components constituting the acrylic polymer (a). The above ratio is preferably 99 mass% or less, more preferably 95 mass% or less.

The acrylic polymer (A) may contain the above-mentioned copolymerizable monomer as a structural unit. Among these copolymerizable monomers, hydroxyl group-containing monomers and/or nitrogen atom-containing monomers are preferable.

The proportion of the hydroxyl group-containing monomer and/or the nitrogen atom-containing monomer in 100 mass% of the total amount of all the monomer components constituting the acrylic polymer (a) is not particularly limited, but is preferably 0.1 mass% or more, more preferably 1 mass% or more, still more preferably 5 mass% or more, and may be 10 mass% or more, 15 mass% or more, 20 mass% or more, or 25 mass% or more. In addition, from the viewpoint of obtaining an adhesive layer having moderate flexibility, the total of the above proportions is preferably 50 mass% or less, more preferably 40 mass% or less.

The acrylic partial polymer is obtained by polymerizing a monomer component at a polymerization conversion rate of, for example, 95 mass% or less, unlike the full polymer. The polymerization conversion is preferably 70 mass% or less, more preferably 60 mass% or less, further preferably 50 mass% or less, further preferably 40 mass% or less, particularly preferably 35 mass% or less. The polymerization conversion is preferably 1 mass% or more, more preferably 5 mass% or more.

The weight average molecular weight of the acrylic oligomer is preferably 2500 to 10000, more preferably 3000 to 8000. The weight average molecular weight can be obtained by GPC and converted to polystyrene. For example, the measurement can be performed under the following conditions using a high-speed GPC apparatus "HPLC-8120GPC" manufactured by Tosoh Corp.

Column: TSKgel SuperHZM-H/HZ4000/HZ3000/HZ2000

Solvent: tetrahydrofuran (THF)

Flow rate: 0.6 ml/min

The above acrylic oligomer contains an acrylic monomer as a structural unit. The above-mentioned acrylic oligomer preferably contains a (meth) acrylate having an alicyclic hydrocarbon group as a structural unit. The acrylic monomer contained as the structural unit may be one kind or two or more kinds.

The proportion of the (meth) acrylate having an alicyclic hydrocarbon group is preferably 40% by mass or more, more preferably 50% by mass or more, and still more preferably 55% by mass or more, based on 100% by mass of the total amount of all the monomer components constituting the acrylic oligomer. The proportion is preferably 90% by mass or less, more preferably 80% by mass or less.

The above acrylic oligomer preferably contains an alkyl (meth) acrylate as a structural unit. As the alkyl (meth) acrylate, methyl Methacrylate (MMA) is preferable. The proportion of the alkyl (meth) acrylate in the entire monomer components constituting the acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more. The proportion is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 45% by mass or less. The acrylic oligomer may contain the copolymerizable monomer as a structural unit.

The content of the 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 acrylic partial polymer. When the content is within the above range, fracture stress tends to be high, and reworkability is further excellent.

The acrylic polymer and the acrylic polymer (a) are obtained by polymerizing a composition containing at least one selected from the group consisting of the acrylic partial polymer, the acrylic oligomer, and the monomer component (B). The polymerization method is not particularly limited, and examples thereof include: a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a thermal polymerization method, a polymerization method using irradiation of active energy rays (active energy ray polymerization method), and the like. Among them, the bulk polymerization method, the thermal polymerization method, and the active energy ray polymerization method are preferable in terms of transparency of the adhesive layer, cost, and the like. The acrylic polymer obtained may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

In the polymerization of the monomer component, various general solvents can be used. Examples of the solvent 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; organic solvents such as ketones including methyl ethyl ketone and methyl isobutyl ketone. The solvent may be used alone or in combination of two or more.

The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization of the monomer component are not particularly limited, and may be appropriately selected and used. The weight average molecular weight of the acrylic polymer can be controlled by the amount of the polymerization initiator, the amount of the chain transfer agent, and the reaction conditions, and the amount of the chain transfer agent to be used is appropriately adjusted according to the kind of the polymerization initiator, the chain transfer agent, and the reaction conditions.

As the polymerization initiator used in the polymerization of the monomer component, a thermal polymerization initiator, a photopolymerization initiator (photoinitiator), or the like can be used depending on the kind of polymerization reaction. The polymerization initiator may be used alone or in combination of two or more.

The thermal polymerization initiator is not particularly limited, and examples thereof include: azo-based polymerization initiators, peroxide-based polymerization initiators (e.g., persulfates such as dibenzoyl peroxide, t-butyl peroxymaleate, and potassium persulfate), phenyl-substituted ethane-based initiators such as benzoyl peroxide, and hydrogen peroxide, aromatic carbonyl compounds, and redox-type polymerization initiators. Among them, the azo-based polymerization initiator disclosed in Japanese patent application laid-open No. 2002-69411 is preferable. The azo-based polymerization initiator may be: 2,2 '-azobisisobutyronitrile, 2' -azobis (2-methylbutyronitrile), dimethyl 2,2 '-azobis (2-methylpropionate), 4' -azobis (4-cyanovaleric acid), and the like. The amount of the thermal polymerization initiator to be used may be a usual amount, and for example, the amount of the thermal polymerization initiator to be used may be selected from the range of, for example, 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, relative to 100 parts by mass of the monomer component.

The photopolymerization initiator is not particularly limited, and examples thereof include: benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, alpha-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzil photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, thioxanthone photopolymerization initiator, and the like. Furthermore, there may be mentioned: acyl phosphine oxide photopolymerization initiator and titanocene photopolymerization initiator. Examples of the benzoin ether photopolymerization initiator include: benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-dimethoxy-1, 2-diphenylethane-1-one, anisole methyl ether, and the like. Examples of the acetophenone photopolymerization initiator include: 2, 2-diethoxyacetophenone, 2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, 4-t-butyldichloroacetophenone, and the like. Examples of the α -ketol photopolymerization initiator include: 2-methyl-2-hydroxy-propiophenone and 1- [4- (2-hydroxyethyl) phenyl group ]-2-methylpropan-1-one and the like. Examples of the aromatic sulfonyl chloride photopolymerization initiator include: 2-naphthalenesulfonyl chloride, and the like. Examples of the photoactive oxime-type photopolymerization initiator include: 1-phenyl-1, 1-propanedione-2- (O-ethoxycarbonyl) oxime and the like. Examples of the benzoin photopolymerization initiator include: benzoin, and the like. Examples of the benzil photopolymerization initiator include: benzil, etc. Examples of the benzophenone photopolymerization initiator include: benzophenone, benzoylbenzoic acid, 3' -dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α -hydroxycyclohexylphenyl ketone, and the like. Examples of the ketal photopolymerization initiator include: benzil dimethyl shrinkKetones, and the like. Examples of the thioxanthone photopolymerization initiator include: thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-diisopropylthioxanthone, dodecylthioxanthone, and the like. Examples of the acylphosphine oxide photopolymerization initiator include: 2,4, 6-trimethylbenzoyl diphenyl phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) phenylphosphine oxide, and the like. Examples of the titanocene-based photopolymerization initiator include: bis (eta) ⁵ -2, 4-cyclopentadien-1-yl) -bis (2, 6-difluoro-3- (1H-pyrrol-1-yl) phenyl) titanium and the like. The amount of the photopolymerization initiator to be used may be a usual amount, and for example, may be selected from the range of 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, relative to 100 parts by mass of the monomer component.

Examples of the rubber-based adhesive include: a natural rubber-based adhesive; 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 block copolymer, reclaimed rubber, modified products thereof, and the like. In addition, when the rubber-based adhesive is a copolymer, the adhesive may be either a block copolymer or a random copolymer.

Examples of the silicone-based adhesive include: silicone rubber or silicone resin containing organopolysiloxane as a main component; or a substance obtained by adding a crosslinking agent such as a silicone-based crosslinking agent or a peroxide-based crosslinking agent to these, and crosslinking and polymerizing them.

The adhesive layer may contain a tackifying resin. When the tackifying resin is contained, the adhesive layer tends to have better adhesion even if it is thin. When the pressure-sensitive adhesive layer contains an acrylic pressure-sensitive adhesive and/or a rubber pressure-sensitive adhesive and a tackifying resin, the pressure-sensitive adhesive layer has excellent adhesion to an adherend and is less likely to peel off.

Examples of the tackifying resin include: phenolic tackifying resins, terpene tackifying resins, rosin tackifying resins, hydrocarbon tackifying resins, epoxy tackifying resins, polyamide tackifying resins, elastomeric tackifying resins, ketone tackifying resins, and the like. The tackifying resin may be used alone or in combination of two or more.

The phenolic tackifying resins include: terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, rosin phenol resins. The terpene-phenol resin is a polymer containing terpene residues and phenol residues, and examples thereof 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 terpene phenol resin include: mono terpenes such as alpha-pinene, beta-pinene, limonene (d-form, l-form, d/l-form (terpineol), etc.). The hydrogenated terpene phenol resin is a resin having a structure obtained by hydrogenating the terpene phenol resin. The alkylphenol resin is a resin (oleoresin) obtained from alkylphenol and formaldehyde. Examples of the alkylphenol resin include: alkylphenol resins of the novolac type and resol type. The rosin phenol resin is a phenol modified product of rosins or various rosin derivatives described later. The rosin phenol resin can be obtained, for example, by a method in which a phenol is added to a rosin or various rosin derivatives described later by an acid catalyst and subjected to thermal polymerization.

The terpene-based tackifying resins include: polymers of terpenes (typically monoterpenes) such as alpha-pinene, beta-pinene, d-limonene, l-limonene, terpineol and the like. The terpene polymer may be a terpene homopolymer or a terpene copolymer of two or more kinds. As a homopolymer of terpenes, there can be mentioned: alpha-pinene polymers, beta-pinene polymers, terpineol polymers, and the like. The modified terpene-based tackifying resin is a substance obtained by modifying the terpene resin (modified terpene resin). The modified terpene resin may be: styrene-modified terpene resins, hydrogenated terpene resins, and the like.

The rosin-based tackifying resin includes rosin-based and rosin derivative resins. Examples of the rosin include: unmodified rosins (raw rosins) such as gum rosin, wood rosin, tall oil rosin, and the like; modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, other chemically modified rosins, etc.) obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc.), and the like. The rosin derivative resin may be a rosin derivative. Examples of the rosin derivative resin 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 carboxyl groups of rosin or various rosin derivatives; rosin or metal salts of the above rosin derivatives. Specific examples of the rosin esters include: methyl esters, triethylene glycol esters, glycerol esters, pentaerythritol esters, and the like of unmodified or modified rosin.

The hydrocarbon tackifying resins include: aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene-olefin copolymers and the like), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone indene resins and the like.

The content of the tackifying resin in the adhesive layer is not particularly limited, and the content of the tackifying resin in the adhesive layer is, for example, 1 part by mass or more (for example, 1 part by mass to 100 parts by mass), 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, relative to 100 parts by mass of the total amount of the base polymer. When the content is 1 part by mass or more, the adhesive layer has more excellent adhesion even if it is thin. 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, from the viewpoint of excellent heat-resistant cohesive force.

The adhesive layer may or may not contain a filler. The double-sided pressure-sensitive adhesive tape of the present invention has excellent stretch releasability even if it has high adhesive strength, and therefore, it is not necessary to reduce the adhesive strength by adding a filler.

The content of the filler in the pressure-sensitive adhesive layer is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, 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 free of the filler. When the content is 35 parts by mass or less, aggregation of the filler is less likely to occur in the adhesive layer, resulting in a good appearance.

The proportion of the filler in the pressure-sensitive adhesive layer is preferably 20 mass% or less, more preferably 17 mass% or less, still more preferably 12 mass% or less, particularly preferably 10 mass% or less, relative to 100 mass% of the total amount of the pressure-sensitive adhesive layer, and may be substantially free of the filler. When the content is 20 mass% or less, aggregation of the filler is less likely to occur in the adhesive layer, resulting in a good appearance.

The filler may be a particulate organic material or an inorganic material. Examples of the material constituting the inorganic substance include: metals such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, stainless steel, and the like; metal oxides such as aluminum oxide, silicon oxide (silica), titanium oxide, zirconium oxide, zinc oxide, tin oxide, copper oxide, and nickel oxide; metal hydroxides and hydrated metal compounds such as 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, hydrotalcite, dawsonite, 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 substances such as carbon black, carbon tubes (carbon nanotubes), carbon fibers, and diamond; inorganic materials such as glass; natural raw material particles such as volcanic sand, clay, sand, etc.

Examples of the material constituting the organic substance include: polystyrene, acrylic resins (e.g., polymethyl methacrylate), phenol resins, phenylguanamine resins, urea-formaldehyde resins, silicone resins, polyesters, polyurethanes, polyethylene, polypropylene, polyamides (e.g., nylon, etc.), polyimide, polyvinylidene chloride, etc., polymers, and the like.

The average particle diameter 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, and typically 5 μm or more). When the average particle diameter is not less than the above value, it is preferable from the viewpoint of maintaining the viscosity and dispersibility of the adhesive composition satisfactorily. The upper limit of the average particle diameter is, for example, 50 μm or less, preferably 30 μm or less, more preferably 25 μm or less, and still more preferably 15 μm or less. When the average particle diameter becomes smaller, the adhesive property tends to be suppressed from decreasing. From the viewpoint of the appearance of the adhesive layer, the average particle diameter is preferably small. In the present specification, the average particle diameter of the filler means a particle diameter (50% median particle diameter) when the cumulative particle size on a weight basis in the particle size distribution obtained by measurement by the sieving method is 50%.

The pressure-sensitive adhesive layer may further contain, as necessary, in a range not to impair the effect of the present invention: crosslinking agents, crosslinking accelerators, antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, foils, rust inhibitors, colorants (dyes, pigments, etc.), and the like. The above additives may be used singly or in combination of two or more.

The thickness of the pressure-sensitive adhesive layer (the total thickness of the pressure-sensitive adhesive layer on one side) is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more, and still more preferably 20 μm or more. When the thickness is 10 μm or more, the adhesion to an adherend is more excellent. The thickness of the pressure-sensitive adhesive layer is, for example, 500 μm or less, preferably 300 μm or less. When the thickness is 500 μm or less, the thickness of the double-sided adhesive sheet can be made thinner. The thickness of the adhesive layers on the two surfaces may be the same or different.

The pressure-sensitive adhesive layer may be in any form, and may be, for example, emulsion type, solvent type (solution type), active energy ray-curable type, hot melt type (hot melt type), or the like. Among them, a solvent-based or active energy ray-curable adhesive layer is preferable from the viewpoint of easy availability of an adhesive layer excellent in productivity.

Examples of the active energy ray include: particularly, ultraviolet rays are preferable, such as ionizing radiation, ultraviolet rays, etc., such as α rays, β rays, γ rays, neutron rays, and electron rays. That is, the active energy ray-curable adhesive layer is preferably an ultraviolet ray-curable adhesive layer.

The adhesive layer can be produced, for example, as follows: coating (applying) an adhesive composition for forming an adhesive layer on a release liner, and drying and curing the resulting adhesive composition layer; the adhesive composition is coated (applied) on a release liner, and the resulting adhesive composition layer is irradiated with active energy rays to be cured. Further, if necessary, the heat drying may be further performed.

(double-sided adhesive sheet)

The thickness of the double-sided pressure-sensitive adhesive sheet is preferably 100 μm to 1500 μm, more preferably 120 μm to 1200 μm, and even more preferably 150 μm to 1000 μm. When the thickness is 100 μm or more, the double-sided adhesive sheet is less likely to break when stretched. When the thickness is 1500 μm or less, the thickness of the double-sided adhesive sheet can be made thinner. The thickness of the double-sided adhesive sheet refers to the thickness from one adhesive surface to the other, that is, the thickness of the adherend, excluding the release liner.

The double-sided adhesive sheet is preferably capable of being stretch-peeled without breaking the base layer when stretched in the face direction of the SUS304BA plate from a state of being sandwiched between 2 SUS304BA plates and bonded at a stretching speed of 300 mm/min.

The 180 ° peel adhesion (stretching speed 300 mm/min) after one adhesive surface of the double-sided adhesive sheet is bonded to a SUS304BA plate and left to stand at 23 ℃ for 30 minutes under 50% rh is preferably 2N/20mm or more, more preferably 5N/20mm or more, and still more preferably 8N/20mm or more. When the peel adhesion is 2N/20mm or more, the adhesion to an adherend is excellent. The peel adhesion is preferably 50N/20mm or less, more preferably 40N/20mm or less, and even more preferably 35N/20mm or less, from the viewpoint of excellent reworkability. It is preferable that the adhesive surface on the opposite side of the adhesive surface where the adhesive force is measured by lining the adhesive surface with a plastic film such as a PET film. In addition, it is preferable that the peel adhesion force of both the adhesive surfaces of the double-sided adhesive sheet is within the above range.

The double-sided adhesive sheet may be bonded with a release liner on the surface (adhesive surface) of the adhesive layer until the time of use. The two-sided pressure-sensitive adhesive sheets may be each protected on both sides by 2 release liners, or may be each protected in a roll-like form (roll) by 1 release liner having both sides as release surfaces. The release liner is used as a protective material for the adhesive layer and is peeled off when attached to an adherend. It should be noted that a release liner may not be necessary.

The release liner may be a conventional release paper, and examples thereof include, but are not particularly limited to: a substrate having a release treatment layer, a low-tackiness substrate comprising a fluoropolymer, a low-tackiness substrate comprising a nonpolar polymer, and the like. Examples of the substrate having the release treatment layer include: plastic films, papers, etc., surface-treated with a release treating agent such as silicones, long-chain alkyls, fluorine-containing compounds, molybdenum sulfide, etc. Examples of the fluoropolymer in the low-tackiness base material containing a fluoropolymer include: polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylfluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, and the like. Examples of the nonpolar polymer include: olefin resins (e.g., polyethylene, polypropylene, etc.), and the like. The release liner can be formed by a known or conventional method. In addition, the thickness of the release liner is not particularly limited.

The double-sided adhesive sheet is preferably used for attaching an electric and electronic component to be used by bonding the double-sided adhesive sheet to a component of an electric and electronic device. The double-sided adhesive sheet is particularly preferably used for the purpose of attaching components of electric and electronic devices to both adhesive surfaces of the double-sided adhesive sheet, that is, for fixing members of the electric and electronic devices to each other. The double-sided adhesive sheet may be used for any of the purposes of fixing the members to each other and the purposes of temporarily fixing the members to each other. For example, when the double-sided adhesive sheet is used for fixing or temporarily fixing components of an electrical and electronic apparatus, the double-sided adhesive sheet may be peeled off and reworked due to a failure occurring in the adhesion work of the double-sided adhesive sheet, and the double-sided adhesive sheet may be peeled off for repair, replacement, inspection, and recycling of a member having an adherend to which the double-sided adhesive sheet is adhered. In this way, when the double-sided adhesive sheet is used for fixing or temporarily fixing a component (member) of an electrical and electronic apparatus, for example, the frequency of removing the double-sided adhesive sheet is particularly high.

The term "electric and electronic equipment" refers to equipment corresponding to at least one of electric equipment and electronic equipment. Examples of the electric and electronic devices include: image display devices such as liquid crystal displays, electroluminescent displays, and plasma displays; portable electronic devices, and the like.

Examples of the portable electronic device include: a mobile phone, a smart phone, a tablet computer, a notebook computer, various wearable devices (for example, a wrist-worn type worn on the wrist like a wristwatch, a module type worn on a part of the body with a clip, a band, or the like, an eye-worn type including a glasses type (a single-eye type, a double-eye type, a goggle type, and a head-worn type), a clothing type mounted on a shirt, a sock, a hat, or the like, for example, in the form of accessories, an ear-worn type worn on the ear like, or the like, as headphones), a digital camera, a digital video camera, an acoustic device (a portable music player, an IC recorder, or the like), a calculator (an electronic calculator, or the like), a portable game machine, an electronic dictionary, an electronic notepad, an electronic book, an in-vehicle information device, a portable radio, a portable television, a portable printer, a portable scanner, a portable modem, or the like. In the present specification, "portable" means not only portable but also portable at a level that can be carried by an individual (standard adult) relatively easily. The double-sided adhesive sheet is used, for example, such that an adhesive layer adheres to a member of the portable electronic device.

The double-sided adhesive sheet can be used for a portion to be used in a repeatedly folded manner or a portion to be used in a wound manner. Therefore, the double-sided adhesive sheet is preferably used as a member in an electric and electronic apparatus to be used in a bending manner, for example, an electric and electronic apparatus having a bendable image display device (flexible display) (particularly, a foldable image display device (foldable display)); in an electrical and electronic apparatus used in a winding manner, for example, in an electrical and electronic apparatus having a windable image display device (windable display), members (particularly, members are bonded to each other).

Examples (example)

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1

(preparation of adhesive composition)

Into a reaction vessel having a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser and a 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 performed at 60 ℃ for 6 hours, to thereby obtain a toluene solution of an acrylic polymer. The Mw of the acrylic polymer was 55X 10 ⁴ 。

To 100 parts by mass of the acrylic polymer contained in the toluene solution, 40 parts by mass of a polymerized rosin ester resin (product name "Pensel D-125", softening point 125 ℃, manufactured by kawa chemical co., ltd.) and 2 parts by mass of an isocyanate-based crosslinking agent (product name "Coronate L", manufactured by eastern co., ltd.) were added and mixed, thereby preparing an adhesive composition (adhesive composition a).

(production of double-sided adhesive sheet)

The adhesive composition a was coated on a polyethylene terephthalate (PET) -based release liner (trade name "MRF38", manufactured by mitsubishi chemical corporation) in such a manner that the final thickness (thickness of the adhesive layer) was 50 μm, and dried at 100 ℃ for 2 minutes, thereby forming an adhesive layer (adhesive layer a). Then, the adhesive layers a thus produced were bonded to both surface sides of a base layer a (an elastomer film having physical properties shown in table 1, a three-layer structure of PE/SEPS/PE, manufactured by japan macadam corporation), respectively, to obtain a laminate. The obtained laminate was passed through a laminator at a temperature of 50℃and a pressure of 0.5MPa and a conveying speed of 0.5 m/min for 1 time, and then aged in an oven at 50℃for 1 day, whereby a double-sided adhesive sheet of example 1 was produced.

Example 2

(preparation of adhesive composition)

100 parts by mass of a styrene-isoprene block copolymer (trade name "Quintac 3520", manufactured by japanese patent No. Weng Zhushi, the styrene content is 15% by mass, the diblock ratio is 78% by mass), 20 parts by mass of an aromatic petroleum resin (trade name "rishi neooligomer 150", manufactured by JX rishi energy co., ltd., the softening point is 155 ℃ and the hydroxyl value is less than 1 mgKOH/g), 40 parts by mass of a terpene phenol resin, 30 parts by mass of a terpene resin, 0.75 part by mass of an isocyanate-based crosslinking agent (trade name "Coronate L", manufactured by eastern co., ltd., the same) based on the solid content, 1 part by mass of an antioxidant, and toluene as a solvent were mixed by stirring, thereby preparing an adhesive composition (adhesive composition B) having a solid content of 50% by mass.

Here, as the terpene phenol resin, 1:1 and two materials, namely, a trade name "YS Polyster S145" (manufactured by Anyuan chemical Co., ltd., softening point: 145 ℃ C., hydroxyl value: 100 mgKOH/g) and a trade name "YS Polyster T145" (manufactured by Anyuan chemical Co., ltd., softening point: 145 ℃ C., hydroxyl value: 60 mgKOH/g), were used in such a manner that the total amount thereof was 40 parts by mass. As terpene Resin, the product name "YS Resin PX1150N" (manufactured by Ann Yuan Chemicals Co., ltd., softening point 115 ℃ C., hydroxyl value less than 1 mgKOH/g) was used. As the antioxidant, a blend compound having a mass ratio of 2:1 of "IRGANOX CB612" (manufactured by BASF corporation, trade name "IRGAFOS 168" (manufactured by BASF corporation) to "IRGANOX 565" (manufactured by BASF corporation) was used.

(production of double-sided adhesive sheet)

A double-sided adhesive sheet of example 2 was produced in the same manner as in example 1, except that the adhesive composition B was used instead of the adhesive composition a to form an adhesive layer (adhesive layer B), and the adhesive layer B was used instead of the adhesive layer a.

Example 3

(preparation of adhesive composition)

100 parts BY mass of a silicone resin (trade name "SD4592PSA", manufactured BY Tao Shidong Co., ltd.), 0.2 part BY mass of a curing agent (trade name "BY24-741", manufactured BY Tao Shidong Co., ltd.), 0.9 part BY mass of a catalyst (trade name "SRX212", manufactured BY Tao Shidong Co., ltd.) and toluene as a solvent were mixed with stirring, thereby preparing an adhesive composition (adhesive composition C) having a solid content of 40% BY mass.

(production of double-sided adhesive sheet)

The adhesive composition C was coated on a release liner (manufactured by Fujiko corporation) obtained by subjecting a PET base material (38 μm) to a fluorosilicone (K1) treatment so that the final thickness (thickness of the adhesive layer) was 50 μm, and dried at 150 ℃ for 3 minutes, thereby forming an adhesive layer (adhesive layer C). Then, the produced adhesive layers C were bonded to both surface sides of the base material layer a, respectively, to obtain a laminate. The obtained laminate was passed through a laminator at a temperature of 50℃and a pressure of 0.5MPa and a conveying speed of 0.5 m/min for 1 time, and then aged in an oven at 50℃for 1 day, whereby a double-sided adhesive sheet of example 3 was produced.

Example 4

(preparation of adhesive composition)

93 parts by mass of Butyl Acrylate (BA), 7 parts by mass of Acrylic Acid (AA), 0.05 part by mass of 4-hydroxybutyl acrylate (4 HBA) and ethyl acetate as a polymerization solvent were charged into a reaction vessel having a stirrer, a thermometer, a nitrogen inlet pipe, a reflux condenser and a dropping funnel, and stirred for 2 hours while introducing nitrogen. After removing oxygen in the polymerization system in this manner, 0.1 part by mass of AIBN as a polymerization initiator was added, and solution polymerization was performed at 60℃for 6 hours, thereby obtaining a solution of an acrylic polymer. The Mw of the acrylic polymer was 132X 10 ⁴ Mw/Mn was 5.85.

An adhesive composition (adhesive composition D) was prepared by adding 1.5 parts by mass of an isocyanate-based crosslinking agent (trade name "cornonate L", manufactured by eastern co., ltd.), 0.01 part by mass of an epoxy-based crosslinking agent (trade name "tetra C", manufactured by mitsubishi gas chemical co., ltd.), 15 parts by mass of a terpene-phenol resin (trade name "YS polyester S145", manufactured by angyuan chemical co., ltd.) to 100 parts by mass of the acrylic polymer contained in the above solution, and 15 parts by mass of a (meth) acrylic oligomer, and stirring and mixing the mixture.

As the above (meth) acrylic oligomer, a (meth) acrylic oligomer prepared by the following method is used. Specifically, to a reaction vessel having a stirrer, a thermometer, a nitrogen inlet pipe, a reflux condenser and a dropping funnel, 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, and stirred in a nitrogen gas stream for 1 hour to remove oxygen in the polymerization system, then heated to 85 ℃ and reacted for 5 hours, thereby obtaining a (meth) acrylic oligomer having a solid content concentration of 50% by mass. The Mw of the resulting (meth) acrylic oligomer was 3600.

(production of double-sided adhesive sheet)

A double-sided adhesive sheet of example 4 was produced in the same manner as in example 1, except that the adhesive composition D was used instead of the adhesive composition a to form an adhesive layer (adhesive layer D), and the adhesive layer D was used instead of the adhesive layer a.

Example 5

A double-sided adhesive sheet of example 5 was produced in the same manner as in example 1, except that the base layer B (an elastomer film having the physical properties shown in table 1, a three-layer structure of PE/SEPS/PE, manufactured by japan macadam corporation) was used instead of the base layer a.

Example 6

A double-sided adhesive sheet of example 6 was produced in the same manner as in example 1, except that the base layer C (an elastomer film having the physical properties shown in table 1, a three-layer structure of PE/SEPS/PE, manufactured by japan macadam co.) was used instead of the base layer a.

Example 7

A double-sided adhesive sheet of example 7 was produced in the same manner as in example 1, except that the base layer D (an elastomer film having the physical properties shown in table 1, a three-layer structure of PE/SEPS/PE, manufactured by japan macadam co.) was used instead of the base layer a.

Example 8

A double-sided adhesive sheet of example 8 was produced in the same manner as in example 1, except that the base layer E (an elastomer film having the physical properties shown in table 1, a three-layer structure of PE/SEPS/PE, manufactured by japan macadam co.) was used instead of the base layer a.

Example 9

(preparation of adhesive composition)

Into a reaction vessel having a stirrer, a thermometer, a nitrogen inlet pipe, a reflux condenser and a 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) and 0.2 part by mass of the mixture were charged as polymerization primersAIBN as a hair agent and toluene as a polymerization solvent, and solution polymerization was carried out at 60℃for 6 hours, thereby obtaining a toluene solution of an acrylic polymer. The Mw of the acrylic polymer was 55X 10 ⁴ 。

To 100 parts by mass of the acrylic polymer contained in the toluene solution, 40 parts by mass of a polymerized rosin ester resin (product name "Pensel D-125", softening point 125 ℃, manufactured by the product of the schin chemical industry, inc.), 2 parts by mass of an isocyanate-based crosslinking agent (product name "Coronate L", manufactured by the product of the eastern co., ltd.) and 30 parts by mass of aluminum hydroxide particles (product name "Heidi Light H-21", manufactured by the product of the zhao electric company) as a filler were added and mixed, thereby preparing an adhesive composition (adhesive composition E). The filler used in this example had an average particle diameter of 27. Mu.m, a proportion of particles having a particle diameter of less than 25. Mu.m, 40% or more, and a proportion of particles having a particle diameter of less than 1. Mu.m, 0%.

(production of double-sided adhesive sheet)

A double-sided adhesive sheet of example 9 was produced in the same manner as in example 1, except that the adhesive composition E was used instead of the adhesive composition a to form an adhesive layer (adhesive layer E), and the adhesive layer E was used instead of the adhesive layer a.

Comparative example 1

A double-sided pressure-sensitive adhesive sheet of comparative example 1 was produced in the same manner as in example 1, except that the base layer F (polyurethane film having the physical properties shown in table 2, manufactured by japan macadam corporation) was used instead of the base layer a.

Comparative example 2

A double-sided adhesive sheet of comparative example 2 was produced in the same manner as in example 9, except that the base material layer F (polyurethane film having the physical properties shown in table 2, manufactured by japan macadam corporation) was used instead of the base material layer a.

Comparative example 3

A double-sided adhesive sheet of comparative example 3 was produced in the same manner as in example 1, except that the base material layer G (thermoplastic elastomer film having the physical properties shown in table 2, manufactured by japan macadam co.) was used instead of the base material layer a.

Comparative example 4

A double-sided adhesive sheet of comparative example 4 was produced in the same manner as in example 1, except that a base material layer H (trade name "silk NES85", manufactured by kaku-ku-koku) was used instead of the base material layer a.

Comparative example 5

A double-sided adhesive sheet of comparative example 5 was produced in the same manner as in example 1, except that the base material layer I (trade name "Torayfan #40", manufactured by dori corporation) was used instead of the base material layer a.

< evaluation >

The substrate layers used in examples and comparative examples and the obtained double-sided adhesive sheets were evaluated as follows. The results are shown in the table.

(1) Elongation at break, 100% modulus

The base material layer was punched out to 10mm×50mm, and set in a tensile tester (trade name "AG-20kNG", manufactured by shimeji corporation) at a chuck pitch of 10mm in the longitudinal direction, and elongated to break at a tensile speed of 300 mm/min in the 180 ° direction. The elongation at break was calculated from the measurement results, and the stress at 100% elongation was calculated as 100% modulus.

(2) Core to surface layer ratio ([ surface layer/core layer/surface layer ")

The cross section of the base material layer was observed by a scanning electron microscope (trade name "S-3400N", manufactured by Hitachi Co., ltd.) and the thickness ratio of each layer constituting the base material layer was calculated. The substrate layers F to I used in the comparative examples were single-layered, and thus were not measured.

(3) Reworkability of

The double-sided adhesive sheet was punched out into a rectangular shape having a width of 10mm×a length of 50mm, thereby obtaining a test piece. The test piece was laminated by sandwiching a 50mm long portion between 2 SUS304BA plates, thereby producing a test sample. The test piece exposed from the test sample was stretched at a stretching speed of 300 mm/min in the plane direction of the SUS304BA plate as an adherend. Then, stretchability was evaluated according to the following evaluation criteria.

O (good): the test piece can be pulled and peeled without damaging the base material layer.

Delta (fail): the test piece can be pulled and peeled without damaging the base material layer, but the adhesion to the adherend is insufficient.

X (bad): tearing occurred before stretching the double-sided adhesive sheet to peel it off for an entire length of 50 mm.

(4) Appearance of

The surface of the coating film when the adhesive composition was applied to the release liner was visually confirmed and evaluated according to the following evaluation criteria.

O (good): no streaks and no aggregates were observed.

X (bad): the generation of streaks or aggregates was observed.

(5) Adhesive force

The double-sided pressure-sensitive adhesive tape was cut into a size of 20mm in width and 100mm in length, the release liner was peeled off at 23℃under 50% RH to expose the adhesive surface, and a polyethylene terephthalate (PET) film having a thickness of 25 μm was laminated on one surface. Then, the other adhesive surface was bonded to the surface of the SUS304BA plate, and the press-bonding was performed by reciprocating a 2kg roller once. The resulting product was left to stand at 23℃under 50% RH for 30 minutes, and then the peel strength (N/20 mm) was measured using a tensile tester under conditions of a tensile speed of 300 mm/min and a peel angle of 180 ℃. As a tensile tester, a universal tensile compression tester (product name "TG-1kN", manufactured by Miibia Co., ltd.) was used.

TABLE 2

	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4	Comparative example 5
						Substrate layer	Substrate layer F	Substrate layer F	Base material layer G	Substrate layer H	Substrate layer I
Thickness of substrate layer [ mu ] m]	60	60	100	25	40
						Elongation at break [% ]	1249	1249	1726	1008	232
100% modulus [ MPa ]]	8.3	8.3	8.9	7.3	50
						Adhesive layer	Adhesive layer A	Adhesive layer E	Adhesive layer A	Adhesive layer A	Adhesive layer A
Reworkability of	×	Δ	×	×	×
						Appearance of	○	×	○	○	○
Adhesive force [ N/20mm]	8.1	2.5	9.0	7.2	7.5
						[ surface layer/core layer/surface layer ]]	(Single layer)	(Single layer)	(Single layer)	(Single layer)	(Single layer)

As shown in table 1, the double-sided adhesive sheet of examples showed good stretchability with or without filler, and was excellent in reworkability, indicating that the degree of freedom in design of the adhesive layer was high. The double-sided adhesive sheets of examples 1 to 8, which did not contain a filler in the adhesive layer, were excellent in appearance. On the other hand, when a base material layer having an elongation at break of less than 700% or a 100% modulus of more than 4.0MPa is used, reworkability is poor, and it is determined that the degree of freedom in designing the adhesive layer is low.

The following describes modifications of the disclosed invention.

[ appendix 1] A double-sided adhesive sheet having a base layer and adhesive layers provided on both sides of the base layer, wherein,

the base material layer has a core layer containing a styrene-based elastomer as a main component and a resin layer which provides both surfaces of the base material layer and is harder than the core layer,

The double-sided adhesive sheet according to appendix 2, wherein the proportion of the total thickness of the core layer containing the styrene-based elastomer as a main component in the base layer is 60% or more relative to the total thickness of the base layer.

The double-sided adhesive sheet according to any one of supplementary notes 3, wherein the ratio of the thickness of each of the resin layers in the base material layer to the total thickness of the base material layer is 2.5% or more.

[ additional note 4] the double-sided adhesive sheet according to any one of additional notes 1 to 3, wherein the ratio of the total thickness of the resin layer in the base material layer to the total thickness of the core layer [ the former: the latter is 3: 97-45: 55.

the double-sided adhesive sheet according to any one of supplementary notes 5 to 1 to 4, wherein the resin layer is a layer containing a polyolefin resin as a main component.

The double-sided adhesive sheet according to any one of supplementary notes 6, wherein the proportion of the filler in the adhesive layer is 20 mass% or less with respect to the total amount of the adhesive layer.

The double-sided adhesive sheet according to any one of supplementary notes 7 to 1 to 6, wherein the double-sided adhesive sheet is used for fixation of members to each other in an electric and electronic apparatus.

[ appendix 8] an electric/electronic apparatus, wherein the electric/electronic apparatus has the double-sided adhesive sheet of appendix 7, and the double-sided adhesive sheet fixes members to each other with two adhesive surfaces.

Claims

1. A double-sided adhesive sheet having a base material layer and adhesive layers provided on both sides of the base material layer, wherein,

2. The double-sided adhesive sheet according to claim 1, wherein a ratio of a total thickness of the core layer containing the styrene-based elastomer as a main component in the base material layer is 60% or more with respect to the total thickness of the base material layer.

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

4. The double-sided adhesive sheet according to claim 1 or 2, wherein a ratio of a total thickness of the resin layer in the base material layer to a total thickness of the core layer [ the former: the latter is 3: 97-45: 55.

5. The double-sided adhesive sheet according to claim 1 or 2, wherein the resin layer is a layer containing a polyolefin resin as a main component.

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

7. The double-sided adhesive sheet according to claim 1 or 2, wherein the double-sided adhesive sheet is used for fixation of members in an electric and electronic apparatus to each other.

8. An electric and electronic apparatus, wherein the electric and electronic apparatus has the double-sided adhesive sheet according to claim 7, and the double-sided adhesive sheet fixes members to each other with two adhesive faces.