Double-sided adhesive sheet

Abstract

This invention provides a double-sided adhesive sheet with excellent impact resistance and reprocessability. The double-sided adhesive sheet 1 of this invention comprises an adhesive layer 2. The thickness of the double-sided adhesive sheet 1 is 500 μm or less. The adhesive layer 2 contains a base polymer and fillers. The average particle size of the fillers is 80 μm or less. The breaking stress of the double-sided adhesive sheet 1 is 0.5 MPa or more, and the breaking strain is 600% or more. The volume ratio of the fillers relative to the total mass of the adhesive layer 2 is preferably 0.01 × 10⁻⁶. -2~20×10 -2cm 3g.

Description

Technical Field

[0001] This invention relates to a double-sided adhesive sheet. Prior Technology

[0002] In recent years, miniaturization of portable devices such as mobile phones, digital cameras, and PDAs (Personal Digital Assistants) has been progressing. Consequently, the various electronic components they carry are also striving for miniaturization and thinning. For example, mobile phones, as a representative portable device, show a trend towards thinning of their main components. Typically, the display portion of a portable device mainly comprises an LCD (liquid crystal display) module and a backlight unit, which, to perform functions such as light emission, reflection, light blocking, and light guiding, consists of layers of various sheet-like components. Therefore, double-sided adhesive sheets (double-sided tape) are used to assemble (join) these components.

[0003] For example, portable electronic devices are frequently at risk of being dropped due to their usage. Therefore, double-sided adhesive sheets used in portable electronic devices are required to be impact-resistant, meaning they should not easily break or detach from components due to the impact of dropping the device.

[0004] As a double-sided adhesive sheet material with excellent impact resistance for use in portable electronic devices, such as those disclosed in known patent documents 1 to 3. Previous technical documents Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-128453 Patent Document 2: Japanese Patent Application Publication No. 2020-128454 Patent Document 3: Japanese Patent Application Publication No. 2021-24907 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] On the other hand, when repairing, replacing, inspecting, or reusing components with adhered bodies to which double-sided adhesive sheets are attached, there are situations where it is necessary to peel off the double-sided adhesive sheets. In such cases, reworkability is required, that is, the double-sided adhesive sheets should be easily peeled off from the adhered body. Patent documents 1-3 do not mention the superiority of both impact resistance and reworkability.

[0008] The present invention was conceived based on this situation, and its purpose is to provide a double-sided adhesive sheet with excellent impact resistance and reprocessability. [Technical means to solve the problem]

[0009] The inventors, through dedicated research to achieve the aforementioned objectives, discovered that by using a double-sided adhesive sheet that lacks a substrate, contains specific fillers in its adhesive layer, and possesses specific properties, excellent impact resistance and reprocessability can be achieved. This invention is based on these insights.

[0010] That is, the present invention provides a double-sided adhesive sheet, which includes an adhesive layer, and The thickness of the aforementioned double-sided adhesive sheet is less than 500 μm. The aforementioned adhesive layer contains a base polymer and fillers. The average particle size of the above-mentioned fillers is below 80 μm. The breaking stress is above 0.5 MPa, and the breaking strain is above 600%.

[0011] The volume ratio of the filler relative to the total mass of the adhesive layer is preferably 0.01×10⁻² to 20×10⁻² cm³ / g.

[0012] The content of the filler in the adhesive layer is preferably more than 0 parts by mass and less than 30 parts by mass relative to the total amount of the base polymer (100 parts by mass).

[0013] The filler is preferably one or more of the following: fillers whose surface contains organic matter other than acrylic resin, fillers whose surface contains inorganic matter, and fillers with a hollow structure.

[0014] The adhesive layer is preferably an acrylic adhesive layer containing an acrylic polymer as the base polymer.

[0015] The aforementioned acrylic polymers preferably have structural parts derived from acrylic oligomers.

[0016] The adhesive layer described above is preferably composed of an adhesive-improving resin.

[0017] The storage modulus G' of the adhesive layer at 23°C is preferably 0.09 MPa or higher.

[0018] The optimal peel strength at 180°C for stainless steel sheets is above 20 N / 25 mm.

[0019] The aforementioned double-sided adhesive sheet is preferably used for fixing components to each other in electrical and electronic machinery.

[0020] Furthermore, the present invention provides an electrical and electronic machine comprising the aforementioned double-sided adhesive sheet, and The aforementioned double-sided adhesive sheet uses two adhesive surfaces to fix the components to each other. [Effects of the Invention]

[0021] The double-sided adhesive sheet of this invention has excellent impact resistance and reprocessability. Therefore, for example, when used in portable electronic devices, it is not easily peeled off when subjected to a drop impact, and when intentionally peeling off the double-sided adhesive sheet, it is easy to peel off without breaking the adhesive sheet. Simple Explanation of the Diagram

[0022] Figure 1 is a cross-sectional view of a double-sided adhesive sheet according to one embodiment of the present invention. Implementation

[0023] [Double-sided adhesive sheet] The double-sided adhesive sheet of the present invention is a double-sided adhesive sheet containing an adhesive layer, and is a so-called "substrate-free" double-sided adhesive sheet that does not have a substrate.

[0024] The adhesive layer described above contains a base polymer and fillers as essential components. The fillers have an average particle size of 80 μm or less. In this specification, the adhesive layer is sometimes referred to as "the adhesive layer of the present invention".

[0025] Furthermore, in this specification, the term "base polymer" refers to the main component of the polymer composition of the adhesive constituting the adhesive layer, for example, containing more than 50% by mass of polymer composition. The content ratio of the base polymer in the aforementioned adhesive layer relative to 100% by mass of the total amount of the adhesive layer is preferably 60% by mass or more, and more preferably 70% by mass or more.

[0026] The adhesive layer constituting the double-sided adhesive sheet of the present invention can be a single layer or a multilayer. When the double-sided adhesive sheet of the present invention comprises a plurality of adhesive layers, all of the plurality of adhesive layers are adhesive layers of the present invention. The plurality of adhesive layers can be the same adhesive layer or adhesive layers with different compositions, thicknesses, physical properties, etc.

[0027] Figure 1 is a cross-sectional schematic diagram showing one embodiment of the double-sided adhesive sheet of the present invention. As shown in Figure 1, the double-sided adhesive sheet 1 includes a single layer of adhesive layer 2 of the present invention. Release pads 3 and 4 are respectively attached to the adhesive surface of the adhesive layer 2.

[0028] (Adhesive layer of the present invention) The adhesive constituting the adhesive layer of the present invention is not particularly limited, and examples include: acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, and mixtures thereof), polysiloxane adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, and fluorinated adhesives. Among these, acrylic adhesives are preferred as the adhesive constituting the adhesive layer in terms of adhesion, weather resistance, cost, and ease of adhesive design. The adhesive layer is preferably an acrylic adhesive layer containing an acrylic adhesive. Only one type of adhesive may be used, or two or more types may be used.

[0029] The aforementioned acrylic adhesive layer contains an acrylic polymer as its base polymer. This acrylic polymer is a polymer containing acrylic monomers (monomers having a (meth)acrylic group in the molecule) as monomeric components. That is, the aforementioned acrylic polymer contains structural units derived from acrylic monomers. Furthermore, only one type of acrylic polymer may be used, or two or more types may be used. Also, the aforementioned acrylic polymer may contain only one type of acrylic monomer as a monomeric component, or it may contain two or more types of acrylic monomers as monomeric components. Furthermore, in this specification, "(meth)acrylic" refers to "acrylic" and / or "methacrylic" (either "acrylic" or "methacrylic"), and the same applies otherwise.

[0030] The aforementioned acrylic polymer is preferably a polymer composed (formed) using an acrylic monomer (A) having two or more non-aromatic rings as an essential monomer component. That is, the aforementioned acrylic polymer preferably contains an acrylic monomer (A) as a structural unit. The aforementioned acrylic polymer may contain only one acrylic monomer (A) as a monomer component, or it may contain two or more acrylic monomers (A) as monomer components.

[0031] Examples of non-aromatic rings with two or more rings include: non-aromatic hydrocarbon rings with two or more rings and non-aromatic heterocycles with two or more rings. These non-aromatic rings can be either saturated or unsaturated. Examples of non-aromatic hydrocarbon rings with two or more rings include: bicyclic aliphatic hydrocarbon rings or bridging hydrocarbon rings with three or more rings. Examples of bicyclic hydrocarbon rings include: pinane rings, pinene rings, alkyl rings, noralkyl rings, and noralkylene rings. Examples of aliphatic hydrocarbon rings with three or more rings (bridging hydrocarbon rings with three or more rings) include: bicyclic pentane rings, bicyclic pentene rings, adamantane rings, tricyclic pentane rings, and tricyclic pentene rings.

[0032] The number of atoms in the non-aromatic ring is preferably 6 to 12, more preferably 7 to 10. Furthermore, in the acrylic monomer (A), the non-aromatic ring is preferably directly bonded to the (meth)acrylic acid group, or bonded to the (meth)acrylic acid group via an oxygen atom or an alkyl group.

[0033] As for the aforementioned non-aromatic ring with two or more rings, it is preferably a non-aromatic hydrocarbon ring with two or more rings, more preferably a non-aromatic hydrocarbon ring with two or three rings, and even more preferably a alkyl ring, a noralkyl ring, a noralkylene ring, a dicyclopentane ring, or a dicyclopentene ring. As for the group having the aforementioned non-aromatic ring with two or more rings in the acrylic monomer (A), it is preferably a dicyclopentyl, a dicyclopentenyl, or an isoalkyl group.

[0034] The Tg of the homopolymer of acrylic monomer (A) is preferably above 0°C, more preferably above 10°C, and even more preferably above 60°C. If the above Tg is above 0°C, the impact resistance is even better. The above Tg is, for example, below 200°C.

[0035] Furthermore, the "glass transition temperature (Tg) during homopolymer formation" (sometimes simply referred to as "the Tg of the homopolymer") in this specification refers to the "glass transition temperature (Tg) of the homopolymer of that monomer," specifically, values ​​are listed in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1987). Furthermore, the Tg of homopolymers of monomers not described in the aforementioned literature is obtained, for example, by the following measurement method (refer to Japanese Patent Application Publication No. 2007-51271). Specifically, 100 parts by mass of monomer, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 200 parts by mass of ethyl acetate as the polymerization solvent are added to a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser. Nitrogen gas is introduced while stirring for 1 hour. After removing oxygen from the polymerization system, the temperature is raised to 63°C, and the reaction is carried out for 10 hours. Subsequently, the solution was cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by mass. This homopolymer solution was then cast onto a release liner and dried to produce a test sample (sheet-like homopolymer) approximately 2 mm thick. The test sample was then punched into a disc shape with a diameter of 7.9 mm and placed between parallel plates. While applying a shear stress at a frequency of 1 Hz using a viscoelasticity testing machine (trade name "ARES", manufactured by Rheometrics), the viscoelasticity was measured in shear mode at a temperature range of -70 to 150°C and a heating rate of 5°C / min. The peak temperature of tanδ was taken as the Tg of the homopolymer.

[0036] As acrylic monomers (A), examples include: isomethacrylates such as (meth)acrylate having a bicyclic aliphatic hydrocarbon ring; and (meth)acrylates having a tricyclic or more aliphatic hydrocarbon ring, such as (meth)acrylate, ...

[0037] The proportion of acrylic monomer (A) in 100% by mass of all monomer components constituting the above-mentioned acrylic polymer is preferably 1-30% by mass, more preferably 2-13% by mass. If the above proportion is 1% by mass or more, the reprocessability is better. If the above proportion is 30% by mass or less, the peak value of tanδ of the adhesive layer becomes higher, and the impact resistance and reprocessability are better.

[0038] The aforementioned acrylic polymer is preferably a polymer formed by using alkyl methacrylate (sometimes referred to as "alkyl methacrylate (B)") and acrylic monomer (A) together as monomer components.

[0039] Alkyl methacrylate (B) is preferably exemplified by alkyl methacrylates having straight-chain or branched alkyl groups. Furthermore, only one type of alkyl methacrylate (B) may be used, or two or more types may be used.

[0040] Alkyl methacrylates having straight-chain or branched alkyl groups are not particularly limited, and examples include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, dibutyl methacrylate, terbutyl methacrylate, pentyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, nonyl methacrylate, and isononyl methacrylate. Alkyl methacrylates, including decyl methacrylate, isodecanyl methacrylate, undecyl methacrylate, dodecyl methacrylate (laurate methacrylate), tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate (stearyl methacrylate), isostearyl methacrylate, nonadecanyl methacrylate, and eicosyl methacrylate, are straight-chain or branched alkyl esters having 1 to 20 carbon atoms. From the viewpoint of further improving impact resistance, the aforementioned alkyl methacrylates having straight-chain or branched alkyl esters are preferably alkyl methacrylates having 2 to 7 carbon atoms, and more preferably butyl methacrylate. Methyl methacrylate may also be included.

[0041] The proportion of alkyl (meth)acrylate (B) in 100% by mass of all monomer components constituting the above-mentioned acrylic polymer is not particularly limited, but is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more. If the above proportion is 50% by mass or more, the stoichiometric balance with the acrylic monomer (A) is good, and an adhesive layer with good adhesion even when thin is formed. The above proportion is preferably 99% by mass or less, more preferably 95% by mass or less. Furthermore, the proportion of butyl (meth)acrylate is preferably within the above range.

[0042] The aforementioned acrylic polymer may contain comonomers as monomeric components, together with acrylic monomers (A) and (meth)acrylate alkyl esters (B). That is, the aforementioned acrylic polymer may contain comonomers as structural units. Only one type of comonomer may be used, or two or more types may be used.

[0043] From the viewpoint that the aforementioned copolymerizable monomers can form an adhesive layer with good adhesion even when relatively thin, monomers containing carboxyl groups and / or acid anhydride monomers are preferred. Examples of the aforementioned carboxyl-containing monomers include: acrylic acid, methacrylic acid, carboxyethyl methacrylate, carboxypentyl methacrylate, itconic acid, maleic acid, fumaric acid, and butenoic acid. Examples of the aforementioned acid anhydride monomers include: maleic anhydride and itconic anhydride.

[0044] The proportion of carboxyl-containing monomers and / or anhydride monomers in 100% by mass of all monomer components constituting the above-mentioned acrylic polymer is not particularly limited, but is preferably 0.2% by mass or more, more preferably 1% by mass or more. The above proportion is preferably 15% by mass or less, more preferably 10% by mass or less. If the above proportion is within the above range, the stoichiometric balance with the acrylic monomer (A) and (meth)acrylate alkyl ester (B) is good, and an adhesive layer with good adhesion even when relatively thin can be formed.

[0045] As the aforementioned copolymerizable monomers, monomers containing functional groups may be used to introduce crosslinking points into acrylic polymers or to improve the cohesive strength of acrylic polymers. Examples of such functionalized monomers include: monomers containing hydroxyl groups, monomers containing nitrogen atoms (excluding those belonging to acrylic monomers (A)), monomers containing ketone groups, monomers containing alkoxysilyl groups, monomers containing sulfonic acid groups, and monomers containing phosphate groups. Only one of the aforementioned functionalized monomers may be used, or two or more may be used.

[0046] Examples of hydroxyl-containing monomers include: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylaurate methacrylate, methyl methacrylate (4-hydroxymethylcyclohexyl) methacrylate, and other hydroxyalkyl methacrylates; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and polypropylene glycol mono(meth)acrylate.

[0047] Examples of monomers containing nitrogen atoms include: monomers containing amide groups, monomers containing amine groups, and monomers containing cyano groups. Examples of monomers containing amide groups include: (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethylpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide. Examples of monomers containing amine groups include: aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and tributylaminoethyl (meth)acrylate. Examples of monomers containing cyano groups include: acrylonitrile and methacrylonitrile.

[0048] Examples of ketone-containing monomers include: diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetate, vinyl acetate, etc.

[0049] Examples of monomers containing alkoxysilyl groups include 3-(meth)propenyloxypropyltrimethoxysilane, 3-(meth)propenyloxypropyltriethoxysilane, 3-(meth)propenyloxypropylmethyldimethoxysilane, and 3-(meth)propenyloxypropylmethyldiethoxysilane.

[0050] Examples of monomers containing sulfonic acid groups include: styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamide propanesulfonic acid, (meth)acrylate sulfonyl propane, (meth)acryloxynaphthalene sulfonic acid, etc.

[0051] Examples of the aforementioned phosphate-containing monomers include 2-hydroxyethylpropenyl phosphate.

[0052] The percentage of functionalized monomers in 100% by mass of the total monomer components constituting the aforementioned acrylic polymer can be, for example, 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 5% by mass or more, or 10% by mass or more. Such percentages can be, for example, 40% by mass or less, 20% by mass or less, or substantially absent. Furthermore, in this specification, "substantially absent" means unintentionally present, not intentionally, due to unavoidable mixing rather than active blending, such as 0.05% by mass or less, or 0.01% by mass or less.

[0053] As the aforementioned copolymerizable monomers, other monomers may be further included. Examples of such other monomers include: vinyl acetate, vinyl propionate, vinyl laurate, and other vinyl ester monomers; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyltoluene; olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate-containing monomers such as 2-(meth)propenyloxyethyl isocyanate; alkoxy-containing monomers such as methoxyethyl acrylate and ethoxyethyl acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; aryl esters of (meth)acrylate such as phenyl acrylate, aryloxyalkyl esters of (meth)acrylate such as phenoxyethyl acrylate, and arylalkyl esters of (meth)acrylate such as benzyl acrylate; and cyclohexyl esters of (meth)acrylate such as cycloalkyl esters.

[0054] The percentage of the aforementioned other monomers in 100% by mass of all monomer components constituting the above-mentioned acrylic polymer may be, for example, 0.05% by mass or more, or 0.5% by mass or more. Such percentages may be, for example, 20% by mass or less, 10% by mass or less, or 5% by mass or less, or may be substantially absent.

[0055] In order to form a cross-linked structure in the polymer backbone of the aforementioned acrylic polymer, a multifunctional monomer that can copolymerize with the monomer components that form the acrylic polymer may be included as a monomer component constituting the polymer. Examples of such multifunctional monomers include: hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and other multifunctional (meth)acrylates; epoxy (meth)acrylates (e.g., poly(meth)acrylate glycidyl acrylate), polyester (meth)acrylates, and urethane (meth)acrylates, etc., which are monomers having (meth)acrylic acid groups and other reactive functional groups within their molecules. Only one of the aforementioned multifunctional monomers may be used, or two or more may be used. Furthermore, the aforementioned multifunctional monomers perform the same functions as the crosslinking agents described below, and can also be considered equivalent to crosslinking agents.

[0056] The aforementioned acrylic polymer may have a structural portion derived from an acrylic oligomer. Examples of such an acrylic polymer include polymers comprising an acrylic polymer (sometimes referred to as "acrylic polymer (C)") and a composition containing the aforementioned acrylic oligomer. Having a structural portion derived from the acrylic oligomer results in higher breaking strain and better reprocessability. The composition containing the aforementioned acrylic oligomer may further contain a monomer component (sometimes referred to as "monomer component (D)"). The acrylic polymer (C), the aforementioned acrylic oligomer, and the monomer component (D) may each be used individually or in combination with more than one.

[0057] Furthermore, the aforementioned acrylic polymer can be a polymer obtained by polymerizing a composition comprising one or more elements selected from the group consisting of acrylic partial polymers, acrylic oligomers, and monomer components (D). Moreover, in the case where the polymer is obtained by polymerizing a composition containing only monomer component (D), the monomer component (D) contains at least an acrylic monomer. The aforementioned "partial polymer" is sometimes also referred to as a "prepolymer," "syrup," etc. Only one of the acrylic partial polymer, acrylic oligomer, and monomer component (D) may be used, or two or more may be used.

[0058] Acrylic polymer (C), the aforementioned acrylic partial polymer, and the aforementioned acrylic oligomer are all compounds composed of acrylic monomers as essential monomer components. As for the acrylic monomers and monomer components (D) that constitute acrylic polymer (C), the aforementioned acrylic partial polymer, and the aforementioned acrylic oligomer, examples of monomer components constituting the aforementioned acrylic polymer can be cited and explained.

[0059] The acrylic polymer (C) may be a polymer that forms the base polymer alone, or it may be a polymer that forms the base polymer together with a polymeric reactant containing the acrylic oligomer.

[0060] The acrylic polymer (C) contains acrylic monomers as structural units. Preferably, the acrylic polymer (C) contains alkyl (meth)acrylate (B) as a structural unit. As the alkyl (meth)acrylate (B), it is preferably an alkyl (meth)acrylate with a straight-chain or branched alkyl group having 2 to 7 carbon atoms, and more preferably butyl (meth)acrylate. The acrylic monomers contained as the above structural units may be only one type, or may be two or more types.

[0061] The proportion of alkyl (meth)acrylate (B) in 100% by mass of all monomer components constituting the acrylic polymer (C) 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.

[0062] The acrylic polymer (C) may contain the aforementioned comonomers as structural units. From the viewpoint that it can form an adhesive layer with good adhesion even when thin, and that it has improved cohesiveness and impact resistance, carboxyl-containing monomers and / or acid anhydride monomers are preferred as comonomers. Furthermore, the acrylic polymer (C) may contain acrylic monomers (A) as structural units.

[0063] The proportion of carboxyl-containing monomers and / or anhydride monomers in 100% by mass of all monomer components constituting the acrylic polymer (C) is not particularly limited, but is preferably 0.2% by mass or more, more preferably 1% by mass or more. The above proportion is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. If the above proportion is within the above range, the stoichiometric balance with (meth)acrylate (B) is good, the impact resistance is excellent, and an adhesive layer with good adhesion even when thin is formed.

[0064] The aforementioned acrylic-based partial polymer differs from the complete polymer in that it is obtained by polymerizing monomer components, for example, at 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, further preferably 50% by mass or less, 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, and more preferably 5% by mass or more.

[0065] The aforementioned acrylic polymer contains acrylic monomers as structural units. Preferably, the aforementioned acrylic polymer contains alkyl (meth)acrylate (B) as a structural unit. As alkyl (meth)acrylate (B), it is preferably an alkyl (meth)acrylate with a straight-chain or branched alkyl group having 2 to 7 carbon atoms, and more preferably butyl (meth)acrylate. The acrylic monomers contained as the aforementioned structural units may be only one type, or may be two or more types.

[0066] The proportion of alkyl (meth)acrylate (B) in 100% by mass of all monomer components constituting the aforementioned acrylic polymer 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, more preferably 95% by mass or less.

[0067] The aforementioned acrylic polymers may contain the aforementioned comonomers as structural units. From the viewpoint that these comonomers can form an adhesive layer with good adhesion even when thin, and that they also exhibit improved cohesiveness and impact resistance, carboxyl-containing monomers and / or acid anhydride monomers are preferred.

[0068] The proportion of carboxyl-containing monomers and / or anhydride monomers in 100% by mass of all monomer components constituting the aforementioned acrylic polymer is not particularly limited, but is preferably 0.2% by mass or more, more preferably 1% by mass or more. The above proportion is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. If the above proportion is within the above range, the stoichiometric balance with acrylic monomer (A) and (meth)acrylate alkyl ester (B) is good, the impact resistance is excellent, and an adhesive layer with good adhesion even when thin is formed.

[0069] Furthermore, the aforementioned acrylic-based partial polymer may contain acrylic monomers (A) as structural units. In this case, the percentage of acrylic monomers (A) in 100% by mass of all monomer components constituting the aforementioned partial polymer is not particularly limited, but is preferably 3% by mass or more, more preferably 10% by mass or more. The aforementioned percentage is preferably 40% by mass or less, more preferably 30% by mass or less.

[0070] The weight-average molecular weight of the aforementioned acrylic oligomers is preferably 2500-10000, more preferably 3000-8000. Furthermore, the aforementioned weight-average molecular weight can be obtained by GPC and conversion to polystyrene. For example, a high-speed GPC apparatus, HPLC-8120GPC, manufactured by Tosoh Corporation, can be used for determination under the following conditions. Column: TSKgel SuperHZM-H / HZ4000 / HZ3000 / HZ2000 Solvent: Tetrahydrofuran Flow rate: 0.6 ml / min

[0071] The aforementioned acrylic oligomers contain acrylic monomers as structural units. Preferably, the aforementioned acrylic oligomers contain acrylic monomer (A) as a structural unit. The acrylic monomer contained as the aforementioned structural unit may be only one type, or may be two or more types.

[0072] The proportion of acrylic monomer (A) in 100% by mass of all monomer components constituting the above-mentioned acrylic oligomers 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.

[0073] The aforementioned acrylic oligomer preferably contains alkyl (meth)acrylate (B) as a structural unit. Alkyl (meth)acrylate (B) is preferably methyl methacrylate (MMA). The proportion of alkyl (meth)acrylate (B) in all monomer components constituting the aforementioned acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more. The aforementioned proportion is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. Furthermore, the aforementioned acrylic oligomer may contain the aforementioned comonomer as a structural unit.

[0074] The content of the aforementioned acrylic oligomers relative to 100 parts by mass of the acrylic polymer (C) and / or the aforementioned acrylic fractional polymers is preferably 0.5 to 35 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 4 to 10 parts by mass. If the content is within the above range, there is a tendency for a higher storage modulus G' and higher breaking stress, resulting in better reprocessability.

[0075] The aforementioned acrylic polymers and acrylic polymer (C) are obtained by polymerizing a composition containing one or more components selected from the group consisting of the aforementioned acrylic polymers, the aforementioned acrylic oligomers, and monomer components (D). There are no particular limitations on the polymerization method; examples include solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, and polymerization by irradiation with active energy lines (active energy line polymerization). Among these, bulk polymerization, thermal polymerization, and active energy line polymerization are preferred in terms of adhesive layer transparency and cost.

[0076] Furthermore, various common solvents can be used during the polymerization of the aforementioned 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 ketones such as methyl ethyl ketone and methyl isobutyl ketone. Moreover, only one solvent may be used, or two or more solvents may be used.

[0077] When polymerizing the aforementioned monomer components, polymerization initiators such as thermal polymerization initiators or photopolymerization initiators (photoinitiators) can be used, depending on the type of polymerization reaction. Furthermore, only one polymerization initiator may be used, or two or more may be used.

[0078] There are no particular limitations on the aforementioned thermal polymerization initiators. Examples include: azo polymerization initiators, peroxide polymerization initiators (such as benzoyl peroxide, tributyl maleate peroxide, potassium persulfate and other persulfates, 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 aforementioned azo polymerization initiators include: 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid) dimethyl ester, 4,4'-azobis-4-cyanopentanoic acid, etc. The amount of thermal polymerization initiator used is only the usual amount, for example, it can be selected from 0.005 to 1 part by mass relative to 100 parts by mass of monomer component, preferably in the range of 0.01 to 1 part by mass.

[0079] The aforementioned photopolymerization initiators are not particularly limited, and examples include: benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-keto alcohol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and 9-oxosulfuron-methyl-2-ethylhexylene ... Examples of photopolymerization initiators include: phosphine oxide-based photopolymerization initiators and titanium ceramsite-based photopolymerization initiators. Examples of 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 acetophenone-based photopolymerization initiators include: 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tert-butyl)dichloroacetophenone. Examples of α-ketool-based photopolymerization initiators include: 2-methyl-2-hydroxyphenylacetone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropane-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, etc. Examples of ketal-based photopolymerization initiators include benzoin dimethyl ketal. Photopolymerization initiators, such as 9-oxosulfuron-methyl. 2-Chloro-9-oxosulfur 2-Methyl-9-oxosulfur 2,4-Dimethyl-9-oxosulfur Isopropyl-9-oxosulfuron 2,4-Diisopropyl-9-oxosulfuron Dodecyl-9-oxosulfur Examples of phosphine oxide-based photopolymerization initiators include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Examples of titanium cyclopentadiene-based photopolymerization initiators include bis(n-5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrolo-1-yl)-phenyl)titanium. The amount of photopolymerization initiator used is only the usual amount, for example, it can be selected from, for example, 0.01 to 3 parts by weight, preferably 0.1 to 1.5 parts by weight, relative to 100 parts by weight of the monomer component.

[0080] The aforementioned acrylic polymers can be crosslinked using a crosslinking agent. By using a crosslinking agent, crosslinked structures can be formed in the acrylic polymers within the acrylic adhesive layer, thereby controlling the gel fraction. The crosslinking agent is appropriately selected based on the functional groups present in the side chains of, for example, the acrylic polymer. Only one crosslinking agent may be used, or two or more may be used.

[0081] The crosslinking agents mentioned above are not particularly limited. Examples include: isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, aziridine-based crosslinking agents, amine-based crosslinking agents, hydrazine-based crosslinking agents, polysiloxane-based crosslinking agents, and silane-based crosslinking agents (silane coupling agents), etc.

[0082] The content of the crosslinking agent is not particularly limited, but is preferably 0.001 to 20 parts by mass relative to 100 parts by mass of the monomer components constituting the acrylic polymer, more preferably 0.01 to 15 parts by mass, and even more preferably 0.5 to 10 parts by mass.

[0083] The aforementioned isocyanate-based crosslinking agents are compounds (polyfunctional isocyanate compounds) having an average of two or more isocyanate groups per molecule. Examples of such isocyanate-based crosslinking agents include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

[0084] Examples of the aforementioned aliphatic polyisocyanates include: 1,2-epoxyethyl diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0085] Examples of the aforementioned alicyclic polyisocyanates include: isoflavone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated phenyl dimethyl diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0086] Examples of the aforementioned aromatic polyisocyanates include: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'- Diisocyanates, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, terephthalene diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, phenylene dimethyl-1,4-diisocyanate, phenylene dimethyl-1,3-diisocyanate, etc.

[0087] Furthermore, examples of the aforementioned isocyanate-based crosslinking agents include: trimethylolpropane / toluene diisocyanate adduct (trade name "Coronate L", manufactured by Tosoh Corporation), trimethylolpropane / hexamethylene diisocyanate adduct (trade name "Coronate HL", manufactured by Tosoh Corporation), and trimethylolpropane / phenylenedimethyl diisocyanate adduct (trade name "Takenate D-110N", manufactured by Mitsui Chemicals Co., Ltd.), among other commercially available products.

[0088] Furthermore, in the aqueous dispersion of modified acrylic polymers prepared by emulsification polymerization, isocyanate-based crosslinking agents may not be used. However, when necessary, end-capped isocyanate-based crosslinking agents may be used to facilitate reaction with water.

[0089] When an isocyanate-based crosslinking agent is used as the crosslinking agent, the content of the isocyanate-based crosslinking agent is not particularly limited. However, relative to 100 parts by mass of the total monomer components constituting the acrylic polymer, it is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more. The aforementioned content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.

[0090] Examples of epoxy crosslinking agents (multifunctional epoxy compounds) include: N,N,N',N'-tetraglycidyl-m-phenylenediamine, diglycidyl aniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and sorbitol. Examples of epoxy crosslinking agents include polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tri(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, and bisphenol-S-diglycidyl ether. Additionally, epoxy resins having two or more epoxy groups within the molecule can also be cited. Furthermore, commercially available products such as "Tetrad C" (manufactured by Mitsubishi Gas Chemical Co., Ltd.) can also be cited as examples of the aforementioned epoxy crosslinking agents.

[0091] When using an epoxy-based crosslinking agent as the aforementioned crosslinking agent, the content of the epoxy-based crosslinking agent is not particularly limited. Relative to the total amount of monomer components constituting the aforementioned acrylic polymer (100 parts by mass), it is preferably more than 0 parts by mass and less than 1 part by mass, more preferably 0.001 to 0.5 parts by mass, further preferably 0.002 to 0.2 parts by mass, further preferably 0.005 to 0.1 parts by mass, and even more preferably 0.008 to 0.05 parts by mass.

[0092] As the aforementioned peroxide-based crosslinking agent, any agent that generates free radical active species through heat to crosslink the base polymer is suitable for use. Considering workability or stability, it is preferable to use a peroxide with a 1-minute half-life temperature of 80~160°C, and even more preferably a peroxide with a temperature of 90~140°C.

[0093] Examples of peroxide-based crosslinking agents include: di(2-ethylhexyl) peroxide dicarbonate (1-minute half-life temperature: 90.6°C), di(4-tert-butylcyclohexyl) peroxide dicarbonate (1-minute half-life temperature: 92.1°C), dibutyl peroxide dicarbonate (1-minute half-life temperature: 92.4°C), tert-butyl peroxide neodecanoate (1-minute half-life temperature: 103.5°C), tert-hexyl peroxide pentaminate (1-minute half-life temperature: 109.1°C), tert-butyl peroxide pentaminate (1-minute half-life temperature: 110.3°C), and dibutyl peroxide dicarbonate. The following substances are listed: cinnamic acid (1-minute half-life temperature: 116.4℃), dioctyl peroxide (1-minute half-life temperature: 117.4℃), 1,1,3,3-tetramethylbutyl peroxide (1-minute half-life temperature: 124.3℃), di(4-methylbenzoyl peroxide) (1-minute half-life temperature: 128.2℃), dibenzoyl peroxide (1-minute half-life temperature: 130.0℃), tributyl peroxide (1-minute half-life temperature: 136.1℃), and 1,1-di(tert-hexylperoxy)cyclohexane (1-minute half-life temperature: 149.2℃).

[0094] The half-life of the aforementioned peroxide-based crosslinking agent is an indicator of the decomposition rate of the peroxide, referring to the time until half of the residual peroxide remains. The decomposition temperature used to obtain the half-life at any given time, or the half-life time at any given temperature, is listed in manufacturer catalogs, such as the "Organic Peroxide Catalog, 9th Edition (May 2003)" of Nippon Oil Co., Ltd. Furthermore, methods for determining the amount of peroxide remaining after reaction treatment can be, for example, by HPLC (High Performance Liquid Chromatography). More specifically, for example, approximately 0.2 g of the reacted adhesive is taken each time, immersed in 10 ml of ethyl acetate, extracted by shaking at 120 rpm for 3 hours at 25°C, and then allowed to stand at room temperature for 3 days. Then, 10 ml of acetonitrile was added, and the mixture was shaken at 120 rpm for 30 minutes at 25°C. Approximately 10 μl of the extract obtained by filtration through a membrane filter (0.45 μm) was injected into an HPLC system for analysis, which was used as the amount of peroxide after the reaction treatment.

[0095] When using a peroxide-based crosslinking agent as the crosslinking agent, the content of the crosslinking agent is not particularly limited. It is preferable to contain less than 2 parts by mass relative to 100 parts by mass of the monomer components constituting the acrylic polymer, more preferably 0.02 to 2 parts by mass, and even more preferably 0.05 to 1 part by mass.

[0096] Furthermore, organic crosslinking agents or multifunctional metal chelates can be used in conjunction with the aforementioned crosslinking agents. Multifunctional metal chelates are those in which a multivalent metal is covalently or coordinately bonded to an organic compound. Examples of multivalent metal atoms include: Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, etc. Examples of atoms in the covalently or coordinately bonded organic compounds include oxygen atoms, and examples of organic compounds include: alkyl esters, alcohols, carboxyloxy compounds, ethers, ketones, etc.

[0097] As the aforementioned crosslinking agent, it is preferable to contain an isocyanate-based crosslinking agent. More preferably, it contains other crosslinking agents along with the isocyanate-based crosslinking agent. As the aforementioned other crosslinking agent, an epoxy-based crosslinking agent is preferred. If such a crosslinking agent is used, by combining it with the aforementioned acrylic polymer (especially with the aforementioned preferred acrylic polymer), an adhesive layer with excellent adhesion, even if relatively thin, can be produced.

[0098] The adhesive layer of this invention, by containing fillers with a specific average particle size, achieves a suitable hardness. This results in an adhesive layer with increased apparent cohesive strength, suitable breaking stress and breaking strain, and excellent impact resistance and reprocessability. Only one type of filler may be used, or two or more may be used.

[0099] The filler described above is in particle shape. The average particle size of the filler is 80 μm or less, preferably 60 μm or less, and more preferably 40 μm or less. The average particle size is preferably 0.5 μm or more, more preferably 1.5 μm or more, and even more preferably 10 μm or more. Furthermore, the average particle size is determined by dynamic light scattering method using the median diameter (D50). When the adhesive layer of the present invention contains two or more fillers, the average particle size of the filler is the average particle size of all fillers.

[0100] The filler material mentioned above can be either organic or inorganic. Examples of materials constituting the aforementioned inorganic substances include: metals such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, and stainless steel; metal oxides such as alumina, silicon dioxide, titanium dioxide, 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, magnesium aluminum carbonate, sodium aluminum carbonate, 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 substances such as carbon black, carbon nanotubes, carbon fibers, and diamond; inorganic materials such as glass; and natural raw material particles such as volcanic white sand, clay, and sand.

[0101] Examples of materials constituting the aforementioned organic compounds include: polystyrene, acrylic resins (e.g., polymethyl methacrylate), phenolic resins, benzoguanamine resins, urea resins, polysiloxane resins, polyesters, polyurethane, polyethylene, polypropylene, polyamides (e.g., nylon), polyimide, polyvinylidene chloride, and other polymers.

[0102] The aforementioned packing material may have a hollow structure. The hollow portion (the internal space of the hollow particles) of such a packing material may be in a vacuum state or filled with a medium. Examples of such media include inert gases such as nitrogen and argon, or air and volatile solvents.

[0103] As the filler mentioned above, fillers with organic or inorganic substances other than acrylic resin on their surface are preferred, as are fillers with a hollow structure. These fillers have less interaction with the acrylic components in the acrylic adhesive layer, or because they have a hollow structure, the adhesive layer is less likely to break when extended, resulting in better reprocessability.

[0104] Relative to the total mass of the adhesive layer of the present invention, the volume ratio of the filler is preferably 0.01×10⁻² to 20×10⁻² cm³ / g, more preferably 0.5×10⁻² to 10×10⁻² cm³ / g, and even more preferably 1×10⁻² to 7×10⁻² cm³ / g. If the volume ratio is within the above range, the breaking stress and breaking strain are within a suitable range, and both impact resistance and reprocessability are superior. Furthermore, if the volume ratio is 20×10⁻² cm³ / g or less, the initial adhesion to the adhered object is superior. The volume ratio of the filler is calculated as [volume of filler in the adhesive layer (cm³) / total mass of the adhesive layer (g)].

[0105] The filler content in the adhesive layer of the present invention is preferably more than 0 parts by mass and less than 30 parts by mass relative to the total amount of the base polymer (100 parts by mass), more preferably 0.008 to 10 parts by mass, and even more preferably 0.4 to 6 parts by mass. If the content is less than 30 parts by mass, the breaking stress and breaking strain are within a suitable range, and both impact resistance and reprocessability are superior.

[0106] The filler ratio in the adhesive layer of the present invention is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, relative to 100% of the total amount of the adhesive layer. If the ratio is within the above range, the hardness of the adhesive layer can be made moderate. Furthermore, it exhibits excellent reprocessability.

[0107] The adhesive layer of the present invention preferably further contains an adhesive-imparting resin. If it contains an adhesive-imparting resin, the adhesive layer tends to have better adhesion even if it is thinner. When the adhesive layer contains an acrylic polymer as a base polymer and an adhesive-imparting resin, the adhesion to the adherend is excellent, and it is less prone to peeling.

[0108] Examples of adhesive-imparting resins include: phenolic adhesive-imparting resins, terpene adhesive-imparting resins, rosin adhesive-imparting resins, hydrocarbon adhesive-imparting resins, epoxy adhesive-imparting resins, polyamide adhesive-imparting resins, elastic adhesive-imparting resins, and ketone adhesive-imparting resins. Other examples of adhesive-imparting resins include oligomers of dicyclopentyl methacrylate (DCPMA) and methyl methacrylate (MMA), and oligomers of alkyl methacrylates. Only one of the above adhesive-imparting resins may be used, or two or more may be used.

[0109] Examples of phenolic adhesive resins include: terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, and rosin phenolic resins. The terpene phenol resins are polymers containing terpene and phenol residues, and examples include: copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins), and phenol-modified homopolymers or copolymers of terpenes (phenol-modified terpene resins). Examples of terpenes constituting the terpene phenol resins include: monoterpenes such as α-pinene, β-pinene, and limonene (d-formyl, l-formyl, d / l-formyl (dipentene)). The hydrogenated terpene phenol resins are resins having a structure obtained by hydrogenating the terpene phenol resins described above. The alkylphenol resins are resins obtained from alkylphenols and formaldehyde (oil-based phenolic resins). Examples of alkylphenol resins include, for example, phenolic varnish-type and soluble phenolic-type resins. The rosin phenolic resins are phenol-modified products of rosin or various rosin derivatives described below. The aforementioned rosin phenolic resin can be obtained, for example, by a method of adding phenol to rosin or various rosin derivatives with an acid catalyst and then performing thermal polymerization.

[0110] Examples of terpene-based adhesive-imparting resins include polymers of terpenes such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene (typically monoterpenes). These terpene polymers can be homopolymers of a single terpene or copolymers of two or more terpenes. Examples of terpene homopolymers include α-pinene polymers, β-pinene polymers, and dipentene polymers. The modified terpene-based adhesive-imparting resins are those that modify the aforementioned terpene resins (modified terpene resins). Examples of modified terpene resins include styrene-modified terpene resins and hydrogenated terpene resins.

[0111] Examples of rosin-based adhesive resins include rosin-based resins and rosin derivative resins. Examples of rosin-based resins include unmodified rosin (raw rosin) such as rosin gum, wood rosin, and tall oil rosin; and modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosin) obtained by hydrogenation, disproportionation, polymerization, etc. Examples of rosin derivative resins include derivatives of the aforementioned rosin-based resins. Examples of rosin derivative resins include: unmodified rosin esters (as esters of unmodified rosin and alcohols) and modified rosin esters (as esters of modified rosin and alcohols); unsaturated fatty acid-modified rosin (rosin modified with unsaturated fatty acids); unsaturated fatty acid-modified rosin esters (rosin esters modified with unsaturated fatty acids); rosin alcohols (rosin alcohols obtained by reducing the carboxyl groups of rosin or the aforementioned rosin derivatives); and metal salts of rosin or the aforementioned rosin derivatives. Specific examples of the aforementioned rosin esters include: methyl esters, triethylene glycol esters, glyceryl esters, and pentaerythritol esters of unmodified or modified rosin.

[0112] Examples of hydrocarbon-based adhesive resins 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, benzofuran (coumarone) resins, and benzofuran-indene resins.

[0113] The content of the adhesive resin in the adhesive layer is not particularly limited, but relative to 100 parts by mass of the total monomer components constituting the acrylic polymer, it is preferably 1 part by mass or more (e.g., 1 to 100 parts by mass), more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more. If the above content is 1 part by mass or more, the adhesive layer, even if thinner, will have even better adhesion. From the viewpoint of excellent heat resistance and cohesiveness, the above content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less.

[0114] The adhesive layer of this invention may contain a colorant. By containing a colorant, the adhesive layer is colored, resulting in excellent visibility and designability of the double-sided adhesive sheet of this invention. The colorant can be a pigment or a dye. Examples of colorants include black colorants, cyanide colorants, magenta colorants, and yellow colorants. From the viewpoint of superior visibility and light-blocking properties, black colorants are preferred. The colorant may contain only one type or more types. The ratio of the colorant in the adhesive layer of this invention to 100% by mass of the total amount of the adhesive layer is preferably 0.5 to 10% by mass, more preferably 1 to 6% by mass.

[0115] Examples of black pigments include: carbon black, carbon nanotubes, graphite (black lead), copper oxide, manganese dioxide, azo pigments such as iminoazo black, aniline black, perylene black, titanium black, anthocyanin black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, complex oxide-based black pigments, anthraquinone-based organic black dyes, and azo-based organic black dyes. Examples of carbon blacks include: furnace black, chimney black, acetylene black, thermal carbon black, and lamp black. Examples of black colorants include: CI Solvent Black 3, Solvent Black 7, Solvent Black 22, Solvent Black 27, Solvent Black 29, Solvent Black 34, Solvent Black 43, Solvent Black 70; CI Direct Black 17, Direct Black 19, Direct Black 22, Direct Black 32, Direct Black 38, Direct Black 51, Direct Black 71; CI Acid Black 1, Acid Black 2, Acid Black 24, Acid Black 26, Acid Black 31, Acid Black 48, Acid Black 52, Acid Black 107, Acid Black 109, Acid Black 110, Acid Black 119, Acid Black 154; CI Dispersion Black 1, Dispersion Black 3, Dispersion Black 10, Dispersion Black 24; CI Pigment Black 1, Pigment Black 7, etc.

[0116] Examples of cyanide-based colorants include: CI Solvent Blue 25, Solvent Blue 36, Solvent Blue 60, Solvent Blue 70, Solvent Blue 93, Solvent Blue 95; CI Acid Blue 6, Acid Blue 45; CI Pigment Blue 1, Pigment Blue 2, Pigment Blue 3, Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Blue 15:5, Pigment Blue 15:6, Pigment Blue 16, Pigment Blue 17, Pigment Blue 17:1, Pigment Blue 18, Pigment Blue 22, Pigment Blue 25, Pigment Blue 56, Pigment Blue 60, Pigment Blue 63, Pigment Blue 65, Pigment Blue 66; CI Vat Blue 4, Vat Blue 60; CI Pigment Green 7, etc.

[0117] Examples of carmine-based colorants include: CI Solvent Red 1, Solvent Red 3, Solvent Red 8, Solvent Red 23, Solvent Red 24, Solvent Red 25, Solvent Red 27, Solvent Red 30, Solvent Red 49, Solvent Red 52, Solvent Red 58, Solvent Red 63, Solvent Red 81, Solvent Red 82, Solvent Red 83, Solvent Red 84, Solvent Red 100, Solvent Red 109, Solvent Red 111, Solvent Red 121, Solvent Red 122; CI Disperse Red 9; CI Solvent Violet 8, Solvent Violet 13, Solvent Violet 14, Solvent Violet 21, Solvent Violet 27; CI Disperse Violet 1; CI Alkali Basic Red 1, Basic Red 2, Basic Red 9, Basic Red 12, Basic Red 13, Basic Red 14, Basic Red 15, Basic Red 17, Basic Red 18, Basic Red 22, Basic Red 23, Basic Red 24, Basic Red 27, Basic Red 29, Basic Red 32, Basic Red 34, Basic Red 35, Basic Red 36, Basic Red 37, Basic Red 38, Basic Red 39, Basic Red 40; Basic Violet 1, Basic Violet 3, Basic Violet 7, Basic Violet 10, Basic Violet 14, Basic Violet 15, Basic Violet 21, Basic Violet 25, Basic Violet 26, Basic Violet 27, Basic Violet 28, etc.Furthermore, examples of carmine-based colorants include: CI Pigment Red 1, Pigment Red 2, Pigment Red 3, Pigment Red 4, Pigment Red 5, Pigment Red 6, Pigment Red 7, Pigment Red 8, Pigment Red 9, Pigment Red 10, Pigment Red 11, Pigment Red 12, Pigment Red 13, Pigment Red 14, Pigment Red 15, Pigment Red 16, Pigment Red 17, Pigment Red 18, Pigment Red 19, Pigment Red 21, Pigment Red 22, Pigment Red 23, Pigment Red 30, Pigment Red 31, Pigment Red 32, Pigment Red 37, Pigment Red 38, Pigment Red 39, Pigment Red 40, Pigment Red 41, Pigment Red 42, and Pigment Red 48:1. Pigment Red 48:2, Pigment Red 48:3, Pigment Red 48:4, Pigment Red 49, Pigment Red 49:1, Pigment Red 50, Pigment Red 51, Pigment Red 52, Pigment Red 52:2, Pigment Red 53:1, Pigment Red 54, Pigment Red 55, Pigment Red 56, Pigment Red 57:1, Pigment Red 58, Pigment Red 60, Pigment Red 60:1, Pigment Red 63, Pigment Red 63:1, Pigment Red 63:2, Pigment Red 64, Pigment Red 64:1, Pigment Red 67, Pigment Red 68, Pigment Red 81, Pigment Red 83, Pigment Red 87, Pigment Red 88, Pigment Red 89, Pigment Red 90, Pigment Red Pigment Red 92, Pigment Red 101, Pigment Red 104, Pigment Red 105, Pigment Red 106, Pigment Red 108, Pigment Red 112, Pigment Red 114, Pigment Red 122, Pigment Red 123, Pigment Red 139, Pigment Red 144, Pigment Red 146, Pigment Red 147, Pigment Red 149, Pigment Red 150, Pigment Red 151, Pigment Red 163, Pigment Red 166, Pigment Red 168, Pigment Red 170, Pigment Red 171, Pigment Red 172, Pigment Red 175, Pigment Red 176, Pigment Red 177, Pigment Red 178, Pigment Red 179, Pigment Red 184, Pigment Pigment Red 185, Pigment Red 187, Pigment Red 190, Pigment Red 193, Pigment Red 202, Pigment Red 206, Pigment Red 207, Pigment Red 209, Pigment Red 219, Pigment Red 222, Pigment Red 224, Pigment Red 238, Pigment Red 245; CI Pigment Violet 3, Pigment Violet 9, Pigment Violet 19, Pigment Violet 23, Pigment Violet 31, Pigment Violet 32, Pigment Violet 33, Pigment Violet 36, Pigment Violet 38, Pigment Violet 43, Pigment Violet 50; CI Vapor Red 1, Vapor Red 2, Vapor Red 10, Vapor Red 13, Vapor Red 15, Vapor Red 23, Vapor Red 29, Vapor Red 35, etc.

[0118] Examples of yellow colorants include: CI Solvent Yellow 19, Solvent Yellow 44, Solvent Yellow 77, Solvent Yellow 79, Solvent Yellow 81, Solvent Yellow 82, Solvent Yellow 93, Solvent Yellow 98, Solvent Yellow 103, Solvent Yellow 104, Solvent Yellow 112, Solvent Yellow 162; CI Pigment Orange 31, Pigment Orange 43; CI Pigment Yellow 1, Pigment Yellow 2, Pigment Yellow 3, Pigment Yellow 4, Pigment Yellow 5, Pigment Yellow 6, Pigment Yellow 7, Pigment Yellow 10, Pigment Yellow 11, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 15, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow 23, Pigment Yellow 24, Pigment Yellow 34, Pigment Yellow 35, Pigment Yellow 37, Pigment Yellow 42, Pigment Yellow 53, Pigment Yellow 55, Pigment Yellow 65, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75. Pigment Yellow 81, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 94, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 100, Pigment Yellow 101, Pigment Yellow 104, Pigment Yellow 108, Pigment Yellow 109, Pigment Yellow 110, Pigment Yellow 113, Pigment Yellow 114, Pigment Yellow 116, Pigment Yellow 117, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 129, Pigment Yellow 133, Pigment Yellow 138, Pigment Yellow 139, Pigment Yellow 147, Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 153, Pigment Yellow 154, Pigment Yellow 155, Pigment Yellow 156, Pigment Yellow 167, Pigment Yellow 172, Pigment Yellow 173, Pigment Yellow 180, Pigment Yellow 185, Pigment Yellow 195; CI Vapor Yellow 1, Vapor Yellow 3, Vapor Yellow 20, etc.

[0119] The adhesive layer of this invention may, as needed and without impairing the effects of this invention, contain additives such as crosslinking accelerators, anti-aging agents, antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, foils, and rust inhibitors. Only one of the above additives may be used, or two or more may be used.

[0120] The adhesive layer of the present invention preferably has a tanδ peak between -20°C and 0°C. Furthermore, the value of the aforementioned peak is preferably 0.8 or higher, more preferably 1.2 or higher, and even more preferably 1.5 or higher. When a tanδ peak is present between -20°C and 0°C, the impact resistance is excellent, for example, when components using double-sided adhesive sheets are dropped at high speeds. Moreover, if the peak value is 0.8 or higher, the impact resistance is even better, and the reprocessability is also excellent.

[0121] The adhesive layer of the present invention preferably has a storage modulus G' of 0.09 MPa or more at 23°C, more preferably 0.10 MPa or more, and even more preferably 0.15 MPa or more. If the storage modulus G' is 0.09 MPa or more, it exhibits moderate hardness at room temperature and superior reprocessability. The storage modulus G' is preferably 0.25 MPa or less. The storage modulus G' can be calculated using a dynamic viscoelasticity (DMA) measuring device.

[0122] The adhesive layer of this invention can be in any form, such as emulsion type, solvent type (solution type), active energy line curing type, hot melt type, etc. Among these, solvent type and active energy line curing type adhesive compositions are preferred in terms of ease of obtaining an adhesive layer with excellent productivity.

[0123] Examples of the aforementioned active energy lines include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet radiation, with ultraviolet radiation being particularly preferred. That is, the aforementioned active energy line-cured adhesive layer is preferably an ultraviolet-cured adhesive layer.

[0124] The adhesive layer of the present invention can be manufactured, for example, by applying an adhesive composition for forming the adhesive layer onto a release liner and allowing the resulting adhesive composition layer to dry and harden; or by applying the aforementioned adhesive composition onto a release liner and irradiating the resulting adhesive composition layer with active energy lines to harden it. Furthermore, heating and drying may be performed as needed.

[0125] Examples of adhesive compositions forming the adhesive layer of the present invention include: acrylic adhesive compositions with an acrylic polymer as an essential component, or acrylic adhesive compositions with a monomer mixture containing the aforementioned acrylic polymer, the aforementioned acrylic oligomer, or the aforementioned acrylic monomer as essential components. For the former, examples include solvent-based acrylic adhesive compositions. For the latter, examples include active energy line curing type acrylic adhesive compositions.

[0126] The adhesive composition described above preferably contains an acrylic polymer (C) and / or a portion thereof, as well as fillers, and may further contain the aforementioned acrylic oligomers. The adhesive composition may further contain a crosslinking agent. Additionally, it may contain an adhesive-improving resin or a colorant.

[0127] (Double-sided adhesive sheet) The double-sided adhesive sheet of the present invention comprises the adhesive layer of the present invention. The thickness of the double-sided adhesive sheet is 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less. By making the thickness 500 μm or less, the thickness of the double-sided adhesive sheet can be reduced. The thickness of the double-sided adhesive sheet is preferably more than 10 μm, more preferably more than 30 μm, and even more preferably more than 50 μm. If the thickness exceeds 10 μm, the impact resistance and reprocessability are superior. Furthermore, the thickness of the double-sided adhesive sheet refers to the thickness from one adhesive surface to the other, i.e., the thickness of the adhesive body, excluding the release liner.

[0128] The breaking stress of the double-sided adhesive sheet of the present invention is 0.5 MPa or more, preferably 0.7 MPa or more, more preferably 0.9 MPa or more, and even more preferably 1.0 MPa or more. By setting the breaking stress to 0.5 MPa or more, the adhesive layer is less likely to break during extension, resulting in excellent reprocessability. The breaking stress is preferably 3.0 MPa or less, more preferably 2.0 MPa or less. If the breaking stress is 3.0 MPa or less, the impact resistance and reprocessability are even better. The breaking stress was measured at 23°C and 50%RH under the following conditions: sample size 40 mm × 40 mm, thickness approximately 0.2 mm, clamp spacing 10 mm, and tensile speed 50 mm / min.

[0129] The breaking strain of the double-sided adhesive sheet of the present invention is 600% or more, preferably 1000% or more, more preferably 1300% or more, and even more preferably 1500% or more. By achieving a breaking stress of 600% or more, the adhesive layer is less prone to breakage during extension, resulting in excellent reprocessability. The breaking strain was measured at 23°C and 50%RH under the following conditions: sample size 40 mm × 40 mm, thickness approximately 0.2 mm, clamp spacing 40 mm, and tensile speed 50 mm / min.

[0130] The energy (load × height) of the double-sided adhesive sheet of the present invention before peeling off any stainless steel sheet, as determined by the following DuPont impact test, is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. Impact Resistance Test A double-sided adhesive sheet with an outer diameter of 24.5 mm and a width of 2 mm was placed between a 2 mm thick, 50 mm square stainless steel plate with a central hole and a 3 mm thick, 25 mm square stainless steel plate, and pressed together. The sample was then left to stand at 50°C for 2 hours and then allowed to return to room temperature to serve as the evaluation sample. Using a DuPont impact testing machine, the drop weight and drop height of the above evaluation sample were set as follows: 100 g, with increments of 50 mm from 50 mm to 500 mm; 150 g, with increments of 50 mm from 350 mm to 500 mm; 200 g, with increments of 50 mm from 400 mm to 500 mm; and 300 g, with increments of 50 mm from 350 mm to 500 mm, continuously increasing the energy until peeling occurred. At this point, no further testing was conducted on the energy at which the evaluation was completed; the load and height were set in a way that the energy was not repeated. Subsequently, the energy up to the point of peeling off at least one stainless steel plate is calculated as load × height.

[0131] The 180° peel strength (adhesion to SUS) of the double-sided adhesive sheet of the present invention, measured according to JIS Z0237 (2000), to stainless steel sheet (SUS sheet) is preferably 20 N / 25 mm or more, more preferably 25 N / 25 mm or more, and even more preferably 30 N / 25 mm or more. If the adhesion to SUS is 20 N / 25 mm or more, it exhibits good initial adhesion to the adherend. To ensure excellent reprocessability, the adhesion to SUS is preferably 50 N / 25 mm or less, more preferably 45 N / 25 mm or less.

[0132] The aforementioned double-sided adhesive sheet can have a release liner attached to the surface of the adhesive layer (adhesive side) before use. Furthermore, each adhesive side of the aforementioned double-sided adhesive sheet can be protected separately by two release liners, or it can be protected by a single release liner with both sides serving as the release surface, wound into a roller shape (wound body). The release liner serves as a protective material for the adhesive layer and is peeled off when attached to the substrate. Moreover, the release liner is not always necessary.

[0133] As the aforementioned release liner, conventional release paper or the like can be used, without particular limitation. Examples include: substrates with a release treatment layer, low-adhesion substrates containing fluoropolymers, or low-adhesion substrates containing non-polar polymers. Examples of substrates with a release treatment layer include: plastic films or papers with surface treatments performed using release agents such as polysiloxane, long-chain alkyl, fluorine, or molybdenum sulfide. Examples of fluoropolymers in the aforementioned low-adhesion substrates containing fluoropolymers include: polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. Examples of non-polar polymers include: olefin resins (e.g., polyethylene, polypropylene). Furthermore, the release liner can be formed using known or conventional methods. The thickness of the release liner is also not particularly limited.

[0134] The aforementioned double-sided adhesive sheet is preferably used for attaching electrical and electronic components to components in electrical and electronic machinery. More preferably, it is used for attaching parts in electrical and electronic machinery to both adhesive surfaces of the double-sided adhesive sheet, i.e., for fixing components in electrical and electronic machinery to each other. The aforementioned double-sided adhesive sheet can be used for either fixing or temporarily fixing the aforementioned components to each other. For example, when the double-sided adhesive sheet is used for fixing or temporarily fixing parts in electrical and electronic machinery, sometimes an abnormality occurs during the attachment process, requiring the double-sided adhesive sheet to be peeled off for secondary processing; or sometimes, it is necessary to peel off the double-sided adhesive sheet for repair, replacement, inspection, or reuse of components with adhered bodies attached to it. Thus, when double-sided adhesive sheets are used for fixing or temporarily fixing parts (components) in electrical and electronic machinery, the frequency of removing the double-sided adhesive sheets is particularly high.

[0135] The aforementioned double-sided adhesive sheet is preferably used for bonding the outer frames of optical components (especially electrical and electronic equipment) to each other. Therefore, the aforementioned double-sided adhesive sheet can be used even if it is 5 mm or less, preferably 3 mm or less in width.

[0136] Furthermore, the term "electrical and electronic machinery" refers to any machine that is either an electrical machine or an electronic machine. Examples of such electrical and electronic machinery include: image display devices such as liquid crystal displays, electroluminescent displays, and plasma displays, as well as portable electronic machines.

[0137] Examples of portable electronic devices mentioned above include: mobile phones, smartphones, tablets, laptops, various wearable devices (such as wristwatches worn on the wrist, modular devices worn on a part of the body by clips or ropes, including eyeglasses (monocular or binocular; also including headbands), clothing devices such as accessories attached to shirts, socks, hats, etc., and earphones attached to the ears), digital cameras, digital video recorders, audio devices (walkmans, IC (integrated circuit) recorders, etc.), computers (calculators, etc.), portable game consoles, electronic dictionaries, electronic notebooks, e-books, vehicle information machines, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. Furthermore, in this specification, the term "portable" is not sufficient to simply mean "carryable," but rather refers to a level of portability that allows a person (a standard adult) to move it relatively easily. The aforementioned double-sided adhesive sheet is used, for example, by means of an adhesive layer tightly bonded to the components of the aforementioned portable electronic device. [Example]

[0138] The following examples illustrate the invention in more detail, but the invention is not limited to these examples.

[0139] Manufacturing Example 1: Synthesis of Acrylic Oligomers In a flask, 60 parts by weight of dicyclopentyl methacrylate (DCPMA, Tg: 175℃), 40 parts by weight of methyl methacrylate (MMA), 3 parts by weight of α-thioglycerol, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and 65 parts by weight of ethyl acetate were added. The flask was fully filled with nitrogen, and polymerization was carried out at 70℃ for 5 hours. Then, 0.1 parts by weight of 2,2'-azobisisobutyronitrile were added, and polymerization was carried out at 80℃ for 8 hours. Subsequently, ethyl acetate was removed from the reaction solution by distillation, and the product was dried using a vacuum dryer to obtain an acrylic oligomer (weight average molecular weight: 5080).

[0140] Example 1 In a reactor equipped with a thermometer, stirrer, nitrogen inlet pipe, and reflux condenser, add 68 parts by mass of toluene, 95 parts by mass of butyl acrylate (BA), and 5 parts by mass of acrylic acid (AA), and perform nitrogen purging for more than 1 hour. Add azobisisobutyronitrile (AIBN) as an initiator, then raise the internal bath temperature to 62°C and maintain the same temperature until the reaction is almost complete. Afterward, cool to stop the polymerization reaction. Relative to the obtained polymer: 100 parts by weight, add 5 parts by weight of the acrylic oligomer obtained in Manufacturing Example 1, 5 parts by weight of the isocyanate compound (trade name "Coronate L", manufactured by Tosoh Co., Ltd.), and 0.02 parts by weight of the epoxy compound (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Co., Ltd.), and then add 20 parts by weight of the terpene phenolic adhesive resin (trade name "YS POLYSTER T115", manufactured by Yasuhara Chemical Co., Ltd.), 0.1 parts by weight of polyethylene powder as filler (trade name "FLOTHENE UF-80", manufactured by Sumitomo Seika Co., Ltd.), and 6 parts by weight of a black pigment containing carbon black (trade name "Multilac A903", manufactured by TOYO COLOR Co., Ltd.) to prepare an adhesive composition.

[0141] The above adhesive composition was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Co., Ltd.) that had undergone a release treatment on one side with polysiloxane, and then dried to form an adhesive layer with a thickness of 200 μm, thus producing the double-sided adhesive sheet of Example 1.

[0142] Examples 2-4 Except for changing the filler dosage as shown in Table 1, the double-sided adhesive sheets of each embodiment were made in the same manner as in Example 1.

[0143] Example 5 Except that 1 part by weight of polysiloxane rubber particles (trade name "TREFIL E-606", manufactured by Toray Co., Ltd.) was used instead of 0.1 parts by weight of polyethylene powder (trade name "FLOTHENE UF-80", manufactured by Sumitomo Seika Co., Ltd.) as filler, the double-sided adhesive sheet of Example 5 was prepared in the same manner as in Example 1.

[0144] Examples 6-8 Except for changing the filler dosage as shown in Table 1, the double-sided adhesive sheets of each embodiment were prepared in the same manner as in Example 5.

[0145] Example 9 Except for using 0.01 parts by weight of hollow microspheres (trade name "MFL-81GCA", manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., shell composition: acrylonitrile copolymer, surface treated with calcium carbon) instead of 0.1 parts by weight of polyethylene powder (trade name "FLOTHENE UF-80", manufactured by Sumitomo Seika Co., Ltd.) as filler, the double-sided adhesive sheet of Example 9 was prepared in the same manner as in Example 1.

[0146] Examples 10-11 Except for changing the filler dosage as shown in Table 1, the double-sided adhesive sheets of each embodiment were made in the same manner as in Example 9.

[0147] Example 12 Compared to the polymer prepared in Example 1: 100 parts by weight, the following were added: 5 parts by weight of the acrylic oligomer obtained in Manufacturing Example 1, 5 parts by weight of the isocyanate crosslinking agent (trade name "Coronate L", manufactured by Tosoh Co., Ltd.), and 0.03 parts by weight of the epoxy crosslinking agent (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Co., Ltd.). Then, 20 parts by weight of the terpene phenolic adhesive resin (trade name "YS POLYSTER T115", manufactured by Yasuhara Chemical Co., Ltd.), 0.01 parts by weight of the hollow microspheres (trade name "MFL-010CA", manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., shell composition: acrylonitrile copolymer, surface treated with calcium carbonate), and 6 parts by weight of the black pigment containing carbon black (trade name "Multilac A903", manufactured by TOYO COLOR Co., Ltd.), to obtain an adhesive composition.

[0148] Except for using the adhesive composition obtained above, the double-sided adhesive sheet of Example 12 was prepared in the same manner as in Example 1.

[0149] Examples 13-14 Except for changing the amount of epoxy crosslinking agent and filler as shown in Tables 1 and 2, the double-sided adhesive sheets of each embodiment were made in the same manner as in Example 12.

[0150] Example 15 Except for using 0.01 parts by weight of hollow microspheres (trade name "MFLUPR60", manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., shell composition: acrylonitrile copolymer, surface treated with calcium carbonate) instead of 0.01 parts by weight of hollow microspheres (trade name "MFL-010CA", manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) as filler, the double-sided adhesive sheet of Example 15 was prepared in the same manner as in Example 12.

[0151] Examples 16-17 Except for changing the amount of epoxy crosslinking agent and filler as shown in Table 2, the double-sided adhesive sheets of each embodiment were made in the same manner as in Example 15.

[0152] Example 18 Compared to the polymer prepared in Example 1: 100 parts by weight, 5 parts by weight of isocyanate-based crosslinking agent (trade name "Coronate L", manufactured by Tosoh Co., Ltd.), and 0.02 parts by weight of epoxy-based crosslinking agent (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Co., Ltd.) were added, followed by 20 parts by weight of terpene-phenolic adhesive resin (trade name "YS POLYSTER T115", manufactured by Yasuhara Chemical Co., Ltd.), 5 parts by weight of spherical polysiloxane rubber powder (trade name "DOWSIL EP-2600", manufactured by Dow Toray Co., Ltd.), and 6 parts by weight of a black pigment containing carbon black (trade name "Multilac A903", manufactured by TOYO COLOR Co., Ltd.), to obtain an adhesive composition.

[0153] Except for using the adhesive composition obtained above, the double-sided adhesive sheet of Example 18 was prepared in the same manner as in Example 1.

[0154] Examples 19-20 Except for changing the filler dosage as shown in Table 2, the double-sided adhesive sheets of each embodiment were made in the same manner as in Example 18.

[0155] Example 21 In addition to using 5 parts by weight of spherical polysiloxane rubber powder (trade name "DOWSIL EP-2600", manufactured by Dow Toray Co., Ltd.) and 5 parts by weight of polyethylene particles (trade name "Flow beads HE-3040", manufactured by Sumitomo Seika Co., Ltd.) as filler, the double-sided adhesive sheet of the example was made in the same manner as in Example 18.

[0156] Example 22 Except for using 10 parts by weight of polyethylene particles (trade name "Flow beads HE-3040", manufactured by Sumitomo Seika Co., Ltd.) instead of 5 parts by weight of spherical polysiloxane rubber powder (trade name "DOWSIL EP-2600", manufactured by Dow Toray Co., Ltd.) as filler, the double-sided adhesive sheet of Example 22 was prepared in the same manner as in Example 18.

[0157] Comparative Example 1 Except for not adding fillers, the double-sided adhesive sheet of Comparative Example 1 was prepared in the same manner as in Example 1.

[0158] Comparative Example 2 Except that the filler dosage was set to 40 parts by weight, the double-sided adhesive sheet of Comparative Example 2 was prepared in the same manner as in Example 1.

[0159] Comparative Example 3 Compared to the polymer prepared in Example 1: 100 parts by weight, the following were added: 5 parts by weight of the acrylic oligomer obtained in Manufacturing Example 1, 5 parts by weight of the isocyanate compound (trade name "Coronate L", manufactured by Tosoh Co., Ltd.), and 0.02 parts by weight of the epoxy compound (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Co., Ltd.). Then, 20 parts by weight of the terpene phenolic adhesive resin (trade name "YS POLYSTER T115", manufactured by Yasuhara Chemical Co., Ltd.), 5 parts by weight of polyethylene powder as filler (trade name "FLOTHENE UF-80", manufactured by Sumitomo Seika Co., Ltd.), and 6 parts by weight of black pigment containing carbon black (trade name "Multilac A903", manufactured by TOYO COLOR Co., Ltd.), to prepare an adhesive composition.

[0160] The adhesive composition obtained above was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Co., Ltd.) that had undergone a release treatment on one side with polysiloxane, and then dried to form an adhesive layer with a thickness of 178 μm. Furthermore, the release liner (trade name "MRE#25", manufactured by Mitsubishi Chemical Co., Ltd.) on the surface of the adhesive layer is peeled off, exposing the adhesive layer. One side of the PET film (12 μm thick), which will become the substrate layer, is then pressed onto the exposed surface of the adhesive layer. Thus, a single-sided adhesive sheet (190 μm thick) of Comparative Example 3, in which an adhesive layer is formed on the substrate layer, is produced.

[0161] Comparative Example 4 Except that 2 parts by weight of polyethylene particles (trade name "Flow beads CL-2507", manufactured by Sumitomo Seika Co., Ltd.) were used instead of 0.1 parts by weight of polyethylene powder (trade name "FLOTHENE UF-80", manufactured by Sumitomo Seika Co., Ltd.) as filler, the double-sided adhesive sheet of Comparative Example 4 was prepared in the same manner as in Example 1.

[0162] <Evaluation> The adhesive layers and adhesive sheets obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in the table. Furthermore, the dosage of each component in the table represents parts by mass.

[0163] (1) Dynamic viscoelasticity measurement An adhesive layer with a thickness of approximately 2 mm was prepared by overlapping multiple adhesive layers produced in the examples and comparative examples. This adhesive layer was punched into a disc shape with a diameter of 7.9 mm to obtain a sample. The sample was placed between parallel plates and fixed, and dynamic viscoelasticity was measured using a viscoelasticity testing machine (trade name "ARES Rheometer", manufactured by TA Instruments) at 23°C and 50% RH under the following conditions. The storage modulus G' (23°C) and the peak value of tanδ were calculated. Furthermore, it was confirmed that a peak value of tanδ existed in all adhesive layers within the range of -20 to 0°C. Measurement mode: Shear mode Temperature range: -70℃ to 150℃ Heating rate: 5℃ / minute Measurement frequency: 1 Hz

[0164] (2) Breaking stress and breaking strain The adhesive sheets obtained in the examples and comparative examples were cut to dimensions of 40 mm in width and 40 mm in length to obtain test pieces. At 23°C and 50%RH, all release liner pads were peeled off to expose the adhesive sheet. Tensile tests were performed on the test pieces using a universal tensile and compression testing machine (product name "TCM-1kNB", manufactured by Minebea) with a clamping distance of 10 mm and a tensile speed of 50 mm / min. The SS curve was calculated, and the stress (breaking stress) and strain (breaking strain) at the point of breakage were measured. Furthermore, it is preferable to apply powder to the adhesive surface of the clamping area during the test to pre-treat the effects of adhesive stickiness.

[0165] (3) Impact resistance The double-sided adhesive sheet (in Comparative Example 3, the single-sided adhesive sheet with a release liner) sandwiched between release liners, prepared in the examples and comparative examples, was punched into a frame shape with an outer diameter of 24.5 mm and a width of 2 mm. The release liner was then peeled off from the adhesive sheet and placed between a 2 mm thick, 50 mm square stainless steel plate with a central hole and a 3 mm thick, 25 mm square stainless steel plate, and pressed together. The sample was then left to stand at 50°C for 2 hours and then returned to room temperature as an evaluation sample. A cylindrical measuring stage with a length of 50 mm, an outer diameter of 49 mm, and an inner diameter of 43 mm was set on the base of a DuPont impact testing machine (manufactured by Toyo Seiki Co., Ltd.). A square stainless steel plate (without holes) was placed on the stage with the test piece facing downwards. A stainless steel impactor with a front radius of 3.1 mm was placed on the test piece. The weight and drop height of the dropped weights were set as follows: 100 g with increments of 50 mm from 50 mm to 500 mm; 150 g with increments of 50 mm from 350 mm to 500 mm; 200 g with increments of 50 mm from 400 mm to 500 mm; and 300 g with increments of 50 mm from 350 mm to 500 mm, continuously increasing the energy until peeling occurred. At this point, no test was conducted to evaluate the energy achieved; the load and height were set in a way that the energy was not repeated. Subsequently, the energy before peeling off at least one stainless steel plate (in Comparative Example 3, the stainless steel plate adhered to the adhesive layer) was calculated as load × height, and the result was obtained.

[0166] (4) Adhesion to SUS The adhesive sheets prepared in the examples and comparative examples were cut to dimensions of 20 mm in width and 100 mm in length to prepare sample pieces. In the case of double-sided adhesive sheets, a 50 μm thick PET film was attached to one adhesive side of the adhesive sheet as a substrate. The adhesive side of the sample piece was pressed onto a stainless steel plate (SUS304BA plate) at 23°C and 50%RH to prepare the test sample. The pressing was performed by reciprocating a 2 kg roller once. After the test sample was placed at 23°C and 50%RH for 30 minutes, the peel strength [N / 25 mm] was measured using a tensile testing machine according to JIS Z0237 (2000) at a tensile speed of 300 mm / min and a peel angle of 180°. Furthermore, the tensile testing machine used was the Autograph AG-IS50N Precision Universal Testing Machine (manufactured by Shimadzu Corporation).

[0167] (5) Reprocessability The adhesive sheets obtained from the examples and comparative examples were cut into 10 mm × 50 mm sizes as evaluation samples. The release liner (for double-sided adhesive sheets, the release liner on the light-peel side) was peeled off from the evaluation samples, and the adhesive surface of the adhesive sheet was laminated (using a 2 kg roller for one reciprocating motion) onto a stainless steel substrate and stored at 50°C for 24 hours. Subsequently, for double-sided adhesive sheets, the release liner on the heavy-peel side was peeled off, and the short-side end was peeled off from the stainless steel sheet. In this state, the adhesive sheet was stretched relative to the substrate at a peel angle of 30° to attempt peeling it off and confirm its reprocessability. Furthermore, the reprocessability was evaluated according to the following criteria. Moreover, the reprocessability required for practical use is 2 or more of the following criteria, preferably 3 or more. Grade 1: Tape is broken and cannot be peeled off. Grade 2: The tape can be peeled off without breaking when stretched at a speed of less than 0.2 m / min. Grade 3: The tape can be peeled off without breaking when stretched at a speed of 0.2 m / min or higher.

[0168] [Table 1] (Table 1) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 polymer BA 95 95 95 95 95 95 95 95 95 95 95 95 95 AA 5 5 5 5 5 5 5 5 5 5 5 5 5 Adhesion-improving agent YS POLYSTER T115 20 20 20 20 20 20 20 20 20 20 20 20 20 Crosslinking agent Tetrad C 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.03 0.05 Coronate L 5 5 5 5 5 5 5 5 5 5 5 5 5 pigment Multilac A903 6 6 6 6 6 6 6 6 6 6 6 6 6 oligomers DCPMA / MMA=60 / 40 5 5 5 5 5 5 5 5 5 5 5 5 5 filler FLOTHENE UF-80 0.1 1 5 10 0 0 0 0 0 0 0 0 0 WOOD FILE E-606 0 0 0 0 1 2 5 10 0 0 0 0 0 MFL-81GCA 0 0 0 0 0 0 0 0 0.01 0.1 2 0 0 MFL-010CA 0 0 0 0 0 0 0 0 0 0 0 0.01 0.1 MFLUPR60 0 0 0 0 0 0 0 0 0 0 0 0 0 Flow beads CL-2507 0 0 0 0 0 0 0 0 0 0 0 0 0 DOWSIL EP-2600 0 0 0 0 0 0 0 0 0 0 0 0 0 Flow beads HE-3040 0 0 0 0 0 0 0 0 0 0 0 0 0 Average particle size of the filler [μm] 25 25 25 25 2 2 2 2 20 20 20 10 10 Specific gravity of the filler [g / cm³] 0.9 0.9 0.9 0.9 0.98 0.98 0.98 0.98 0.2 0.2 0.2 0.5 0.5 Filler content relative to 100 parts by weight of the base polymer [parts by weight] 0.1 1.0 4.8 9.5 1.0 1.9 4.8 9.5 0.01 0.1 1.9 0.01 0.1 The volume ratio of filler in the total mass of the adhesive layer [×10⁻² cm³ / g] 0.08 0.81 3.94 7.61 0.74 1.48 3.62 6.99 0.04 0.37 7.25 0.01 0.15 The percentage of acrylic monomers (A) in all monomer components [mass %] 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 The percentage of alkyl (meth)acrylate (B) in all monomer components [mass %] 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 92.4 Substrate none none none none none none none none none none none none none Substrate thickness [μm] 0 0 0 0 0 0 0 0 0 0 0 0 0 Adhesive layer thickness [μm] 200 200 200 200 200 200 200 200 200 200 200 200 200 Adhesive sheet thickness [μm] 200 200 200 200 200 200 200 200 200 200 200 200 200 Adhesion to SUS [N / 25 mm] 37 34 32 31 34 32 32 31 37 35 31 37 37 Impact resistance 0.3 0.3 0.3 0.4 0.4 0.4 0.5 0,5 0.3 0.4 0.5 0.3 0.4 Storage modulus G'(23℃)[MPa] 0.16 0.16 0.17 0.17 0.16 0.17 0.17 0.17 0.16 0.17 0.17 0.16 0.16 Breaking stress[Mpa] 0.7 0.9 1.2 1.3 0.7 1.0 1.1 1.2 0.7 0.7 1.2 0.7 0.7 Fracture strain [%] 1367 1444 1723 1812 1421 1632 1732 1768 1376 1400 1765 1352 1401 Reprocessing 3 3 3 3 3 3 3 3 3 3 3 3 3

[0169] [Table 2] (Table 2) Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 Example 20 Example 21 Example 22 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 polymer BA 95 95 95 95 95 95 95 95 95 95 95 95 95 AA 5 5 5 5 5 5 5 5 5 5 5 5 5 Adhesion-improving agent YS POLYSTER T115 20 20 20 20 20 20 20 20 20 20 20 20 20 Crosslinking agent Tetrad C 0.05 0.03 0.05 0.05 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Coronate L 5 5 5 5 5 5 5 5 5 5 5 5 5 pigment Multilac A903 6 6 6 6 6 6 6 6 6 6 6 6 6 oligomers DCPMA / MMA=60 / 40 5 5 5 5 0 0 0 0 0 5 5 5 5 filler FLOTHENE UF-80 0 0 0 0 0 0 0 0 0 0 40 5 0 TREFIL E-606 0 0 0 0 0 0 0 0 0 0 0 0 0 MFL-81GCA 0 0 0 0 0 0 0 0 0 0 0 0 0 MFL-010CA 2 0 0 0 0 0 0 0 0 0 0 0 0 MFLUPR60 0 0.01 0.1 2 0 0 0 0 0 0 0 0 0 Flow beads CL-2507 0 0 0 0 0 0 0 0 0 0 0 0 2 DOWSIL EP-2600 0 0 0 0 5 10 20 5 0 0 0 0 0 Flow beads HE-3040 0 0 0 0 0 0 0 5 10 0 0 0 0 Average particle size of the filler [μm] 10 60 60 60 2 2 2 ※1 11 - 25 25 180 Specific gravity of the filler [g / cm³] 0.5 0.12 0.12 0.12 0.98 0.98 0.98 ※2 0.96 - 0.9 0.9 0.9 Filler content relative to 100 parts by weight of the base polymer [parts by weight] 1.9 0.01 0.1 1.9 5.0 10.0 20.0 10.0 10.0 0 38.1 4.8 1.9 The volume ratio of filler in the total mass of the adhesive layer [×10⁻² cm³ / g] 2.90 0.06 0.61 12.07 3.75 7.24 13.51 7.31 7.39 0 25.2 3.94 1.61 The percentage of acrylic monomers (A) in all monomer components [mass %] 2.9 2.9 2.9 2.9 0 0 0 0 0 2.9 2.9 2.9 2.9 The percentage of alkyl (meth)acrylate (B) in all monomer components [mass %] 92.4 92.4 92.4 92.4 95.0 95.0 95.0 95.0 95.0 92.4 92.4 92.4 92.4 Substrate none none none none none none none none none none none PET none Substrate thickness [μm] 0 0 0 0 0 0 0 0 0 0 0 12 0 Adhesive layer thickness [μm] 200 200 200 200 200 200 200 200 200 200 200 178 200 Adhesive sheet thickness [μm] 200 200 200 200 200 200 200 200 200 200 200 190 200 Adhesion to SUS [N / 25 mm] 32 37 34 28 29 29 31 30 30 37 20 32 twenty two Impact resistance 0.5 0.3 0.4 0.5 0.5 0.5 0.5 0.5 0.5 0.2 0.1 0.1 0.1 Storage modulus G'(23℃)[MPa] 0.17 0.16 0.17 0.17 0.14 0.13 0.18 0.13 0.15 0.15 0.22 0.17 0.19 Breaking stress[Mpa] 1.1 0.7 0.7 1.5 0.8 0.7 1.0 0.8 1.0 0.6 1.9 5.0 1.7 Fracture strain [%] 1699 1352 1423 1912 1962 3497 3294 3491 2956 890 567 60 670 Reprocessing 3 3 3 3 3 3 3 3 3 2 2 1 2 ※1 The average particle size of the filler is between 2 and 11 μm. ※2 The specific gravity of "DOWSIL EP-2600" is 0.98 g / cm³, and the specific gravity of "Flow beads HE-3040" is 0.96 g / cm³.

[0170] As shown in Tables 1 and 2, the double-sided adhesive sheet of the present invention is confirmed to have excellent impact resistance and reprocessability. On the other hand, as shown in Table 2, in any of the following cases, there is no case where the breaking stress and breaking strain are small without filler (Comparative Example 1), the breaking strain is small even with filler (Comparative Example 2), the case where there is a substrate layer and the breaking strain is small (Comparative Example 3), and the case where the average particle size of the filler is large (Comparative Example 4), there is no case where both impact resistance and reprocessability are excellent.

[0171] 1: Double-sided adhesive sheet 2: Adhesive layer 3: Peeling the liner 4: Peeling the liner

Claims

1. A double-sided adhesive sheet comprising an adhesive layer, wherein the thickness of the double-sided adhesive sheet is 500 μm or less, the adhesive layer comprises a base polymer and a filler, the filler having an average particle size of 80 μm or less, the double-sided adhesive sheet having a breaking stress of 0.5 MPa or more, a breaking strain of 600% or more, and satisfying the following (i) and / or (ii): (i) the filler is an organic material whose surface is composed of at least one selected from the group consisting of phenolic resin, benzoguanamine resin, urea resin, polysiloxane resin, polyester, polyurethane, polyethylene, polypropylene, polyamide, and polyimide; (ii) the adhesive layer is an acrylic adhesive layer comprising an acrylic polymer and an acrylic oligomer as the base polymer.

2. The double-sided adhesive sheet as claimed in claim 1, wherein the volume ratio of the filler relative to the total mass of the adhesive layer is 0.01×10-2 to 20×10-2 cm3 / g.

3. The double-sided adhesive sheet as claimed in claim 1 or 2, wherein the content of the filler in the adhesive layer is more than 0 parts by mass and less than 30 parts by mass relative to the total amount of the base polymer of 100 parts by mass.

4. The double-sided adhesive sheet as claimed in claim 1 or 2, wherein the filler is selected from one or more fillers comprising an organic material other than an acrylic resin on its surface, an inorganic material on its surface, and a hollow structure.

5. The double-sided adhesive sheet as claimed in claim 1 or 2, wherein the adhesive layer is an acrylic adhesive layer containing an acrylic polymer as the base polymer.

6. The double-sided adhesive sheet as claimed in claim 5, wherein the acrylic polymer has a structural portion derived from an acrylic oligomer.

7. The double-sided adhesive sheet as claimed in claim 1 or 2, wherein the adhesive layer contains an adhesive-imparting resin.

8. The double-sided adhesive sheet as requested in item 1 or 2, wherein the storage modulus G' of the adhesive layer at 23°C is 0.09 MPa or higher.

9. The double-sided adhesive sheet of request item 1 or 2 shall have a 180° peel strength of 20 N / 25 mm or more against stainless steel sheet.

10. The double-sided adhesive sheet as claimed in item 1 or 2 is used for securing components to each other in electrical and electronic machinery.

11. An electrical and electronic machine comprising a double-sided adhesive sheet as claimed in claim 10, wherein the double-sided adhesive sheet has two adhesive surfaces that fasten members to each other.

Images