Double-sided adhesive sheet

Abstract

To provide a double-sided adhesive sheet excellent in impact resistance and also excellent in reworkability.SOLUTION: A double-sided adhesive sheet 1 includes an adhesive layer 2. The double-sided adhesive sheet is 500 μm thick or less. The adhesive layer 2 is an acrylic adhesive layer including an acrylic polymer as a base polymer. The acrylic polymer includes a constitutional unit derived from an acrylic monomer (A) having two or more non-aromatic rings. The adhesive layer has a peak top of tanδ between -20 to 0°C. A value of the peak top is 0.8 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a double-sided adhesive sheet.

Background Art

[0002] In recent years, miniaturization of portable devices such as mobile phones, digital cameras, and PDAs (Personal Digital Assistants) has been progressing. Therefore, various electronic components to be mounted are also being miniaturized and thinned. For example, in a mobile phone, which is a typical portable device, the main components are each tending to be thinner. Usually, the display portion of a portable device mainly consists of an LCD module and a backlight unit, and various sheet-like components are laminated to exhibit functions such as light emission, reflection, light shielding, and light guiding. Therefore, a double-sided adhesive sheet (double-sided adhesive tape) is used for assembling (bonding) these components. <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0006] On the other hand, when repairing, replacing, inspecting, or recycling a component that has a double-sided adhesive sheet attached to it, it may be necessary to remove the double-sided adhesive sheet. In such cases, it is required that the double-sided adhesive sheet can be easily removed from the component, i.e., that it has reworkability. Patent documents 1 to 3 do not mention excellence in both impact resistance and reworkability.

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

[0008] As a result of diligent research to achieve the above objectives, the inventors have found that a double-sided adhesive sheet without a substrate, in which the adhesive layer constituting the double-sided adhesive sheet contains a base polymer composed of specific monomer components and has specific properties, exhibits excellent impact resistance and excellent reworkability. The present invention was completed based on these findings.

[0009] In other words, the present invention is a double-sided adhesive sheet comprising an adhesive layer, The thickness of the above double-sided adhesive sheet is 500 μm or less. The above adhesive layer is an acrylic adhesive layer containing an acrylic polymer as the base polymer. The above acrylic polymer contains constituent units derived from an acrylic monomer (A) having two or more non-aromatic rings. The present invention provides a double-sided adhesive sheet in which the adhesive layer has a tanδ peak top between -20 and 0°C, and the value of the peak top is 0.8 or greater.

[0010] The proportion of constituent units derived from the acrylic monomer (A) in the above acrylic polymer is preferably 1 to 15% by mass.

[0011] The above acrylic polymer preferably contains a structural unit derived from an alkyl (meth)acrylate (B) having a linear or branched alkyl group with 2 to 7 carbon atoms.

[0012] The above alkyl (meth)acrylate (B) is preferably butyl (meth)acrylate.

[0013] The proportion of the structural unit derived from the above alkyl (meth)acrylate (B) in the above acrylic polymer is preferably 50% by mass or more.

[0014] The above acrylic polymer preferably has a structural part derived from an acrylic oligomer.

[0015] The above acrylic oligomer preferably contains a structural unit derived from the above acrylic monomer (A).

[0016] The content of the above acrylic oligomer is preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the total amount of the above acrylic partial polymer.

[0017] The above acrylic monomer (A) preferably contains one or more groups selected from the group consisting of a dicyclopentanyl group, a dicyclopentenyl group, and an isobornyl group.

[0018] The above adhesive layer preferably further contains an adhesion - imparting resin.

[0019] The breaking stress is preferably 0.9 MPa or more.

[0020] The breaking strain is preferably 60% or more.

[0021] The storage elastic modulus G' of the above adhesive layer at 23°C is preferably 0.09 MPa or more.

[0022] The above double-sided adhesive sheet is preferably used for fixing members in electric and electronic devices.

[0023] The present invention also provides an electric and electronic device including the above double-sided adhesive sheet, wherein the double-sided adhesive sheet fixes members on both adhesive surfaces.

Effect of the Invention

[0024] The double-sided adhesive sheet of the present invention is excellent in impact resistance and reworkability. Therefore, for example, when used in a portable electronic device, it is difficult to peel off when receiving a dropping impact, and when attempting to peel off the double-sided adhesive sheet intentionally, the adhesive sheet can be peeled off easily without breaking.

Brief Description of the Drawings

[0025] [Figure 1] It is a schematic cross-sectional view of a double-sided adhesive sheet according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0026] [Double-sided Adhesive Sheet] The double-sided adhesive sheet of the present invention is a double-sided adhesive sheet composed of an adhesive layer and is a so-called "substrate-free" double-sided adhesive sheet without a substrate.

[0027] The above adhesive layer is an acrylic adhesive layer containing an acrylic polymer as a base polymer. The above acrylic polymer contains a structural unit derived from an acrylic monomer having a bicyclic or higher non-aromatic ring (sometimes referred to as "acrylic monomer (A)"). In this specification, the above adhesive layer may be referred to as "the adhesive layer of the present invention".

[0028] The adhesive layer constituting the double-sided adhesive sheet of the present invention may be a single layer or multiple layers. When the double-sided adhesive sheet of the present invention is composed of multiple adhesive layers, each of these multiple adhesive layers is an adhesive layer of the present invention. These multiple adhesive layers may be the same adhesive layer, or they may be adhesive layers with different compositions, thicknesses, physical properties, etc.

[0029] Figure 1 is a schematic cross-sectional view showing one embodiment of the double-sided adhesive sheet of the present invention. As shown in Figure 1, the double-sided adhesive sheet 1 is composed of a single layer of adhesive layer 2 of the present invention. Release liners 3 and 4 are bonded to the adhesive surface of the adhesive layer 2, respectively.

[0030] (The adhesive layer of the present invention) The adhesive layer of the present invention is an acrylic adhesive layer containing an acrylic polymer as a base polymer that exhibits adhesiveness. In this specification, the base polymer refers to the main component of the polymer component in the adhesive constituting the adhesive layer, for example, the polymer component present in more than 50% by mass.

[0031] The content of the base polymer in the adhesive layer is preferably 60% by mass or more, and more preferably 70% by mass or more, based on 100% by mass of the total amount of the adhesive layer.

[0032] The above-mentioned acrylic polymer is a polymer that contains an acrylic monomer (a monomer having a (meth)acryloyl group in its molecule) as a monomer component constituting the polymer. That is, the above-mentioned acrylic polymer contains constituent units derived from an acrylic monomer. Note that only one type of acrylic polymer may be used, or two or more types may be used. Furthermore, the above-mentioned acrylic polymer may contain only one type of acrylic monomer as a monomer component, or two or more types may be contained. In this specification, "(meth)acrylic" refers to "acrylic" and / or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and the same applies to other terms.

[0033] The above acrylic polymer is a polymer composed (formed) using acrylic monomers (A) having two or more non-aromatic rings as essential monomer components. That is, the above acrylic polymer contains acrylic monomers (A) as constituent units. The above acrylic polymer may contain only one type of acrylic monomer (A) as a monomer component, or it may contain two or more types.

[0034] Examples of the above two or more non-aromatic rings include two or more non-aromatic hydrocarbon rings and two or more non-aromatic heterocycles. The above non-aromatic rings may be saturated or unsaturated. Examples of the above two or more non-aromatic hydrocarbon group rings include bicyclic aliphatic hydrocarbon rings and bridged hydrocarbon rings such as three or more aliphatic hydrocarbon rings. Examples of bicyclic hydrocarbon rings include pinane rings, pinene rings, bornane rings, norbornane rings, norbornene rings, etc. Examples of three or more aliphatic hydrocarbon rings (three or more bridged hydrocarbon rings) include dicyclopentane rings, dicyclopentene rings, adamantane rings, tricyclopentane rings, tricyclopentene rings, etc.

[0035] The number of atoms constituting the ring in the above non-aromatic ring is preferably 6 to 12, and more preferably 7 to 10. Furthermore, in the acrylic monomer (A), the above non-aromatic ring is preferably directly bonded to the (meth)acryloyl group, or bonded to the (meth)acryloyl group via an oxygen atom or an oxyalkylene group.

[0036] Among the two or more non-aromatic rings mentioned above, two or more non-aromatic hydrocarbon rings are preferred, more preferably two or three non-aromatic hydrocarbon rings, and more preferably bornane rings, norbornane rings, norbornene rings, dicyclopentane rings, and dicyclopentene rings. The groups having two or more non-aromatic rings in the acrylic monomer (A) are preferably dicyclopentanyl group, dicyclopentenyl group, and isobornyl group.

[0037] The Tg of the acrylic monomer (A) homopolymer is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 60°C or higher. A Tg of 0°C or higher results in superior impact resistance. The Tg is, for example, 200°C or lower.

[0038] In this specification, "glass transition temperature (Tg) when a homopolymer is formed" (sometimes simply referred to as "Tg of the homopolymer") means "the glass transition temperature (Tg) of the monomer homopolymer," and specifically, the numerical value is given in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1987). For Tg of a monomer homopolymer not listed in the above-mentioned literature, the value refers to a value obtained by, for example, the following measurement method (see Japanese Patent 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 a polymerization solvent are added to a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, and the mixture is stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, the temperature is raised to 63°C and the reaction is carried out for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution with a solid content of 33% by mass. Next, this homopolymer solution is cast onto a release liner and dried to produce a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. This test sample is then punched out into a disc shape with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity is measured using a viscoelasticity tester (product name "ARES", manufactured by Rheometrics) in shear mode while applying a shear strain at a frequency of 1 Hz, in a temperature range of -70 to 150°C, and at a heating rate of 5°C / min. The peak top temperature of tanδ is defined as the Tg of the homopolymer.

[0039] Examples of acrylic monomers (A) include, for example, (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring such as isobornyl (meth)acrylate; and (meth)acrylic acid esters having three or more aliphatic hydrocarbon rings such as dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0040] The proportion of acrylic monomer (A) in 100% by mass of the total amount of all monomer components constituting the above acrylic polymer is preferably 1 to 30% by mass, and more preferably 2 to 13% by mass. When the above proportion is 1% by mass or more, the reworkability is improved. When the above proportion is 30% by mass or less, the peak top value of tanδ in the adhesive layer becomes higher, resulting in improved impact resistance and reworkability.

[0041] The above acrylic polymer is preferably a polymer composed (formed) of an acrylic monomer (A) and an alkyl (meth)acrylate (sometimes referred to as "alkyl (meth)acrylate (B)") as monomer components.

[0042] Preferably, alkyl esters (meth)acrylates (B) are alkyl esters (meth)acrylates having linear or branched alkyl groups. Note that only one type of alkyl ester (meth)acrylate (B) may be used, or two or more types may be used.

[0043] The alkyl (meth)acrylate ester having a linear or branched alkyl group is not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and (meth) Examples of alkyl (meth)acrylates having a linear or branched alkyl group having 1 to 20 carbon atoms include isononyl acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate (stearyl (meth)acrylate), isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Among these, alkyl (meth)acrylates having a linear or branched alkyl group having 2 to 7 carbon atoms are preferred from the viewpoint of further improving impact resistance, and butyl (meth)acrylate is preferred. It may also contain methyl (meth)acrylate.

[0044] The proportion of alkyl (meth)acrylate (B) in 100% by mass of the total amount of all monomer components constituting the above 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. When the above proportion is 50% by mass or more, the quantitative balance with the acrylic monomer (A) is good, and it becomes possible to form an adhesive layer with good adhesion even when thin. The above proportion is preferably 99% by mass or less, and more preferably 95% by mass or less. Furthermore, it is preferable that the proportion of butyl (meth)acrylate is within the above range.

[0045] The above acrylic polymer may contain copolymerizable monomers as monomer components, along with acrylic monomer (A) and alkyl (meth)acrylate ester (B). That is, the above acrylic polymer may contain copolymerizable monomers as constituent units. Only one type of copolymerizable monomer may be used, or two or more types may be used.

[0046] From the viewpoint of being able to form an adhesive layer with good adhesion even when thin, carboxyl group-containing monomers and / or acid anhydride monomers are preferred as the copolymerizable monomers. Examples of the carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the acid anhydride monomers include maleic anhydride and itaconic anhydride.

[0047] The proportion of carboxyl group-containing monomers and / or acid anhydride monomers in the total amount of all monomer components constituting the above acrylic polymer (100% by mass) is not particularly limited, but is preferably 0.2% by mass or more, and more preferably 1% by mass or more. The above proportion is preferably 15% by mass or less, and more preferably 10% by mass or less. When the above proportion is within the above range, the quantitative balance between the acrylic monomer (A) and the alkyl (meth)acrylate (B) is good, and it becomes possible to form an adhesive layer with good adhesion even when thin.

[0048] The copolymerizable monomers described above may further include functional group-containing monomers for the purpose of introducing crosslinking points into the acrylic polymer or enhancing the cohesive strength of the acrylic polymer. Examples of functional group-containing monomers include hydroxyl group-containing monomers, nitrogen atom-containing monomers (excluding those corresponding to acrylic monomer (A)), keto group-containing monomers, alkoxysilyl group-containing monomers, sulfonic acid group-containing monomers, and phosphate group-containing monomers. Only one type of functional group-containing monomer may be used, or two or more types may be used.

[0049] Examples of the above-mentioned hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and polypropylene glycol mono(meth)acrylate.

[0050] Examples of nitrogen atom-containing monomers include amide group-containing monomers, amino group-containing monomers, and cyano group-containing monomers. Examples of amide group-containing monomers include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide. Examples of amino group-containing monomers include aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and t-butylaminoethyl(meth)acrylate. Examples of cyano group-containing monomers include acrylonitrile and methacrylonitrile.

[0051] Examples of the above-mentioned keto group-containing monomers include diacetone(meth)acrylamide, diacetone(meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetacetate, and vinyl acetacetate.

[0052] Examples of the above-mentioned alkoxysilyl group-containing monomers include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0053] Examples of the above-mentioned sulfonic acid group-containing monomers include styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

[0054] Examples of the above-mentioned phosphate group-containing monomers include 2-hydroxyethyl acryloyl phosphate.

[0055] The proportion of the functional group-containing monomer in 100% by mass of the total amount of all monomer components constituting the above acrylic polymer may 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. The above proportion may be, for example, 40% by mass or less, 20% by mass or less, or substantially absent. In this specification, substantially absent means that it is included unintentionally, such as when it is inevitably mixed in, rather than being actively blended, for example, 0.05% by mass or less, or 0.01% by mass or less.

[0056] The copolymerizable monomers described above may further include other monomers. Examples of these other monomers include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyltoluene; olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; aromatic ring-containing (meth)acrylic acid esters such as aryl (meth)acrylates such as phenyl (meth)acrylate, aryloxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate, and arylalkyl (meth)acrylates such as benzyl (meth)acrylate; and cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate.

[0057] The proportion of the other monomers in the total amount of all monomer components constituting the above acrylic polymer (100% by mass) may be, for example, 0.05% by mass or more, or 0.5% by mass or more. The above proportion may also be, for example, 20% by mass or less, 10% by mass or less, or 5% by mass or less, and may be substantially absent.

[0058] The above-mentioned acrylic polymer may contain polyfunctional monomers copolymerizable with the monomer components forming the acrylic polymer as monomer components constituting the polymer, in order to form a crosslinked structure within its polymer backbone. Examples of the above-mentioned polyfunctional monomers include polyfunctional (meth)acrylates such as hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; monomers having a (meth)acryloyl group and other reactive functional groups in the molecule, such as epoxy (meth)acrylate (e.g., polyglycidyl (meth)acrylate), polyester (meth)acrylate, and urethane (meth)acrylate. Only one of the above-mentioned polyfunctional monomers may be used, or two or more may be used. Furthermore, the above-mentioned polyfunctional monomers exhibit similar functions to the crosslinking agents described later and may also qualify as crosslinking agents.

[0059] The above-mentioned acrylic polymer may have structural components derived from acrylic oligomers. Examples of such acrylic polymers include polymers comprising an acrylic polymer (sometimes referred to as "acrylic polymer (C)") and a polymerization reaction product of a composition containing the above-mentioned acrylic oligomer. Having structural components derived from acrylic oligomers results in higher fracture strain and superior reworkability. The composition containing the above-mentioned acrylic oligomer may further contain monomer components (sometimes referred to as "monomer component (D)"). The acrylic polymer (C), the above-mentioned acrylic oligomer, and monomer component (D) may each be used individually or in combination of two or more types.

[0060] Furthermore, the above-mentioned acrylic polymer may be a polymerization product obtained by polymerizing a composition containing one or more selected from the group consisting of acrylic partial polymers, acrylic oligomers, and monomer component (D). In the case of a polymerization product obtained by polymerizing a composition consisting only of monomer component (D), monomer component (D) contains at least an acrylic monomer. Among these, a polymerization product of a composition containing an acrylic partial polymer is preferred. The above-mentioned "partial polymer" may also be referred to as "prepolymer," "syrup," etc. Only one type of acrylic partial polymer, acrylic oligomer, and monomer component (D) may be used, or two or more types may be used.

[0061] Acrylic polymer (C), the above-mentioned acrylic partial polymer, and the above-mentioned acrylic oligomer are all compounds composed of acrylic monomers as essential monomer components. Examples of acrylic monomers and monomer components (D) that constitute acrylic polymer (C), the above-mentioned acrylic partial polymer, and the above-mentioned acrylic oligomer include those exemplified and described above as monomer components constituting the acrylic polymer.

[0062] The acrylic polymer (C) may be a polymer that forms the base polymer on its own, or it may be a polymer that forms the base polymer together with the polymerization reaction product of the composition containing the acrylic oligomer.

[0063] The acrylic polymer (C) contains an acrylic monomer as a constituent unit. Preferably, the acrylic polymer (C) contains an alkyl (meth)acrylate (B) as a constituent unit. Preferably, the alkyl (meth)acrylate (B) is an alkyl (meth)acrylate having a linear or branched alkyl group with 2 to 7 carbon atoms, and more preferably butyl (meth)acrylate. The acrylic monomer included as a constituent unit may be one or two or more.

[0064] The proportion of alkyl (meth)acrylate (B) in 100% by mass of the total amount 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.

[0065] The acrylic polymer (C) may contain the above copolymerizable monomer as a constituent unit. Among the above copolymerizable monomers, carboxyl group-containing monomers and / or acid anhydride monomers are preferred from the viewpoint of being able to form an adhesive layer with good adhesion even when thin, and having improved cohesive force and superior impact resistance. The acrylic polymer (C) may also contain the acrylic monomer (A) as a constituent unit.

[0066] The proportion of carboxyl group-containing monomers and / or acid anhydride monomers in 100% by mass of the total amount 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. When the above proportion is within the above range, a good quantitative balance with the alkyl (meth)acrylate ester (B) is achieved, making it possible to form an adhesive layer that has excellent impact resistance and good adhesion even when thin.

[0067] Unlike the complete polymer, the above-mentioned acrylic partial polymer is obtained by polymerizing the monomer component, for example, with a polymerization conversion rate of 95% by mass or less. The polymerization conversion rate is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. The polymerization conversion rate is preferably 1% by mass or more, more preferably 5% by mass or more.

[0068] The above acrylic partial polymer contains an acrylic monomer as a constituent unit. Preferably, the above acrylic partial polymer contains an alkyl (meth)acrylate (B) as a constituent unit. Preferably, the alkyl (meth)acrylate (B) is an alkyl (meth)acrylate having a linear or branched alkyl group having 2 to 7 carbon atoms, and more preferably butyl (meth)acrylate. The above constituent unit may consist of only one acrylic monomer or two or more.

[0069] The proportion of alkyl (meth)acrylate (B) in 100% by mass of the total amount of all monomer components constituting the above acrylic partial 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, and more preferably 95% by mass or less.

[0070] The above acrylic partial polymer may contain the above copolymerizable monomer as a constituent unit. Among the above copolymerizable monomers, carboxyl group-containing monomers and / or acid anhydride monomers are preferred from the viewpoint of being able to form an adhesive layer with good adhesion even when thin, and having improved cohesive strength and superior impact resistance.

[0071] The proportion of carboxyl group-containing monomers and / or acid anhydride monomers in 100% by mass of the total amount of all monomer components constituting the above acrylic partial 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. When the above proportion is within the above range, a good quantitative balance is achieved between the acrylic monomer (A) and the alkyl (meth)acrylate ester (B), making it possible to form an adhesive layer that has excellent impact resistance and good adhesion even when thin.

[0072] Furthermore, the above-mentioned acrylic partial polymer may contain acrylic monomer (A) as a constituent unit. In this case, the proportion of acrylic monomer (A) in 100% by mass of the total amount of all monomer components constituting the above partial polymer is not particularly limited, but is preferably 3% by mass or more, and more preferably 10% by mass or more. The above proportion is preferably 40% by mass or less, and more preferably 30% by mass or less.

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

[0074] The above acrylic oligomer contains an acrylic monomer as a constituent unit. Preferably, the above acrylic oligomer contains an acrylic monomer (A) as a constituent unit. The acrylic monomer included as a constituent unit may be one type or two or more types.

[0075] The proportion of acrylic monomer (A) in 100% by mass of the total amount of all monomer components constituting the above acrylic oligomer is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more. The above proportion is preferably 90% by mass or less, and more preferably 80% by mass or less.

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

[0077] The content of the above acrylic oligomer is preferably 0.5 to 35 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 4 to 10 parts by mass, based on 100 parts by mass of the total amount of the acrylic polymer (C) and / or the above acrylic partial polymer. When the content is within the above range, the storage modulus G' tends to be high and the fracture stress tends to be high, resulting in superior reworkability.

[0078] The above-mentioned acrylic polymer and acrylic polymer (C) are obtained by polymerizing a composition containing one or more selected from the group consisting of the above-mentioned acrylic partial polymer, the above-mentioned acrylic oligomer, and monomer component (D). While these polymerization methods are not particularly limited, examples include solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, and polymerization by active energy ray irradiation (active energy ray polymerization). Among these, bulk polymerization, thermal polymerization, and active energy ray polymerization are preferred in terms of transparency of the adhesive layer and cost.

[0079] Furthermore, various general solvents may be used in the polymerization of the above-mentioned monomer components. Examples of such solvents include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. Note that one solvent may be used alone, or two or more solvents may be used.

[0080] When polymerizing the above monomer components, polymerization initiators such as thermal polymerization initiators and photopolymerization initiators (photoinitiators) may be used depending on the type of polymerization reaction. Note that only one polymerization initiator may be used, or two or more may be used.

[0081] The above-mentioned thermal polymerization initiators are not particularly limited, but examples include azo polymerization initiators, peroxide polymerization initiators (e.g., persulfates such as dibenzoyl peroxide, tert-butyl permaleate, potassium persulfate, benzoyl peroxide, hydrogen peroxide, etc.), substituted ethane initiators such as phenyl-substituted ethane, aromatic carbonyl compounds, redox polymerization initiators, etc. Among these, the azo polymerization initiator disclosed in Japanese Patent Application Publication No. 2002-69411 is preferred. Examples of the above-mentioned azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid)dimethyl, and 4,4'-azobis-4-cyanovaleric acid. The amount of thermal polymerization initiator used can be the usual amount, for example, it can be selected from a range of 0.005 to 1 part by mass, preferably 0.01 to 1 part by mass, per 100 parts by mass of monomer component.

[0082] The above-mentioned photopolymerization initiators are not particularly limited, but examples include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. Other examples include acylphosphine oxide-based photopolymerization initiators and titanocene-based photopolymerization initiators. Examples of the above-mentioned benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl ether. Examples of the above acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of the above α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of the above aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of the above photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of the above benzoin-based photopolymerization initiators include benzoin. Examples of the above benzyl-based photopolymerization initiators include benzyl. Examples of the benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. Examples of the ketal-based photopolymerization initiators include benzyldimethyl ketal.Examples of the thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of the acylphosphine oxide-based photopolymerization initiators include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Examples of the titanocene-based photopolymerization initiators include bis(η. 5 Examples include -2,4-cyclopentadiene-1-yl)bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium. The amount of photopolymerization initiator used can be the usual amount, for example, it can be selected from a range of 0.01 to 3 parts by mass, preferably 0.1 to 1.5 parts by mass, per 100 parts by mass of monomer component.

[0083] The above acrylic polymer may be crosslinked with a crosslinking agent. By using a crosslinking agent, a crosslinked structure can be formed in the acrylic polymer in the acrylic adhesive layer, and the gel fraction can be controlled. The crosslinking agent can be appropriately selected depending on the functional groups in the side chains of, for example, an acrylic partial polymer. As for the crosslinking agent, only one type may be used, or two or more types may be used.

[0084] The above-mentioned crosslinking agents are not particularly limited, but examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, amine-based crosslinking agents, hydrazine-based crosslinking agents, silicone-based crosslinking agents, and silane-based crosslinking agents (silane coupling agents).

[0085] The content of the above crosslinking agent is not particularly limited, but is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and especially preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the total amount of monomer components constituting the acrylic polymer.

[0086] The above-mentioned isocyanate-based crosslinking agent is a compound having an average of two or more isocyanate groups per molecule (polyfunctional isocyanate compound). Examples of the above-mentioned isocyanate-based crosslinking agent include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and the like.

[0087] Examples of the above-mentioned aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; and 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0088] Examples of the above-mentioned alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0089] Examples of the above aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diisocyanate. Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropanediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0090] In addition, commercially available isocyanate-based crosslinking agents include, for example, trimethylolpropane / tolylene diisocyanate adduct (product name "Coronate L", manufactured by Tosoh Corporation), trimethylolpropane / hexamethylene diisocyanate adduct (product name "Coronate HL", manufactured by Tosoh Corporation), and trimethylolpropane / xylylene diisocyanate adduct (product name "Takenate D-110N", manufactured by Mitsui Chemicals, Inc.).

[0091] Furthermore, while isocyanate-based crosslinking agents are not required for aqueous dispersions of modified acrylic polymers prepared by emulsion polymerization, blocked isocyanate-based crosslinking agents can be used if necessary, as they react readily with water.

[0092] When an isocyanate-based crosslinking agent is used as the above crosslinking agent, the content of the isocyanate-based crosslinking agent is not particularly limited, but is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, based on 100 parts by mass of the total amount of monomer components constituting the acrylic polymer. The above content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.

[0093] Examples of the epoxy crosslinking agents (polyfunctional epoxy compounds) mentioned above include N,N,N',N'-tetraglycidyl-m-xylenediline, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and sorbitol polyglycidyl ether. Examples of epoxy crosslinking agents include diglycidyl ethers, glycerol polyglycidyl ethers, pentaerythritol polyglycidyl ethers, polyglycerol polyglycidyl ethers, sorbitan polyglycidyl ethers, trimethylolpropane polyglycidyl ethers, diglycidyl adipate esters, diglycidyl o-phthalate esters, triglycidyl-tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ethers, bisphenol-S-diglycidyl ethers, and epoxy resins having two or more epoxy groups in their molecules. In addition, commercially available epoxy crosslinking agents such as the trade name "Tetrad C" (manufactured by Mitsubishi Gas Chemical Company, Inc.) can also be used.

[0094] When an epoxy crosslinking agent is used as the crosslinking agent, the content of the epoxy crosslinking agent is not particularly limited, but is preferably more than 0 parts by mass and 1 part by mass or less, more preferably 0.001 to 0.5 parts by mass, even more preferably 0.002 to 0.2 parts by mass, even more preferably 0.005 to 0.1 parts by mass, and particularly preferably 0.008 to 0.05 parts by mass, based on 100 parts by mass of the total amount of monomer components constituting the acrylic polymer.

[0095] As the above-mentioned peroxide-based crosslinking agent, any agent that generates radical active species upon heat to promote crosslinking of the base polymer can be used as appropriate. However, considering workability and stability, it is preferable to use a peroxide with a 1-minute half-life temperature of 80 to 160°C, and more preferably a peroxide with a half-life temperature of 90 to 140°C.

[0096] Examples of the above peroxide-based crosslinking agents include di(2-ethylhexyl)peroxydicarbonate (half-life temperature at 1 minute: 90.6°C), di(4-t-butylcyclohexyl)peroxydicarbonate (half-life temperature at 1 minute: 92.1°C), di-sec-butylperoxydicarbonate (half-life temperature at 1 minute: 92.4°C), t-butylperoxyneodecanoate (half-life temperature at 1 minute: 103.5°C), t-hexylperoxypivalate (half-life temperature at 1 minute: 109.1°C), t-butylperoxypivalate (half-life temperature at 1 minute: 110.3°C), and dilauroyl peroxy Examples include peroxide (half-life temperature at 1 minute: 116.4°C), di-n-octanoyl peroxide (half-life temperature at 1 minute: 117.4°C), 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate (half-life temperature at 1 minute: 124.3°C), di(4-methylbenzoyl) peroxide (half-life temperature at 1 minute: 128.2°C), dibenzoyl peroxide (half-life temperature at 1 minute: 130.0°C), t-butyl peroxyisobutyrate (half-life temperature at 1 minute: 136.1°C), and 1,1-di(t-hexylperoxy)cyclohexane (half-life temperature at 1 minute: 149.2°C).

[0097] The half-life of the peroxide-based crosslinking agent mentioned above is an indicator of the decomposition rate of the peroxide, and refers to the time it takes for the amount of remaining peroxide to be halved. The decomposition temperature required to obtain a half-life at any given time, and the half-life time at any given temperature, are described in manufacturer catalogs, for example, in NOF Corporation's "Organic Peroxide Catalog, 9th Edition (May 2003)". The amount of remaining decomposed peroxide after reaction treatment can be measured, for example, by HPLC (High-Performance Liquid Chromatography). More specifically, for example, approximately 0.2 g of the adhesive after reaction treatment is taken, immersed in 10 ml of ethyl acetate, and extracted by shaking at 120 rpm at 25°C for 3 hours, then left to stand at room temperature for 3 days. Next, 10 ml of acetonitrile is added, shaken at 120 rpm at 25°C for 30 minutes, filtered through a membrane filter (0.45 μm), and approximately 10 μl of the resulting extract is injected into HPLC for analysis to determine the amount of peroxide after reaction treatment.

[0098] When a peroxide-based crosslinking agent is used as the above crosslinking agent, the content of the crosslinking agent is not particularly limited, but it is preferably 2 parts by mass or less per 100 parts by mass of the total amount of 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.

[0099] Furthermore, organic crosslinking agents or polyfunctional metal chelates may be used in combination as the crosslinking agent. Polyfunctional metal chelates are those in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. Examples of atoms in the organic compound that form covalent or coordinate bonds include oxygen atoms, and examples of organic compounds include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.

[0100] Among the crosslinking agents mentioned above, it is preferable to include an isocyanate-based crosslinking agent. It is even more preferable to include another crosslinking agent together with the isocyanate-based crosslinking agent. Among the other crosslinking agents mentioned above, an epoxy-based crosslinking agent is preferred. When such a crosslinking agent is used, a thin adhesive layer with superior adhesion can be made by combining it with the acrylic polymer (especially the preferred acrylic polymer mentioned above).

[0101] The adhesive layer of the present invention preferably further contains a tackifying resin. When a tackifying resin is included, the adhesive layer tends to have better adhesion even when it is thin. When the adhesive layer contains an acrylic polymer as a base polymer and a tackifying resin, it has excellent adhesion to the adherend and is less likely to peel off.

[0102] Examples of the tackifying resins mentioned above include phenolic tackifying resins, terpene tackifying resins, rosin tackifying resins, hydrocarbon tackifying resins, epoxy tackifying resins, polyamide tackifying resins, elastomer tackifying resins, and ketone tackifying resins. Other examples of the tackifying resins mentioned above include low polymers of alkyl (meth)acrylates, such as low polymers of dicyclopentanyl methacrylate (DCPMA) and methyl methacrylate (MMA). One type of tackifying resin may be used, or two or more types may be used.

[0103] Examples of the above-mentioned phenolic tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, and rosin phenol resins. The above-mentioned terpene phenol resins are polymers containing terpene residues and phenol residues, and include copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins), and phenol-modified homopolymers or copolymers of terpenes (phenol-modified terpene resins). Examples of terpenes constituting the above-mentioned terpene phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (d-isomer, l-isomer, d / l-isomer (dipentene) etc.). The above-mentioned hydrogenated terpene phenol resins are resins having a structure obtained by hydrogenating the above-mentioned terpene phenol resins. The above-mentioned alkylphenol resins are resins obtained from alkylphenols and formaldehyde (oily phenol resins). Examples of the above-mentioned alkylphenol resins include novolac type and resol type. The above-mentioned rosin phenol resins are phenol-modified products of rosins or various rosin derivatives described later. The above-mentioned rosin-phenol resin can be obtained, for example, by adding phenol to rosins or various rosin derivatives described later using an acid catalyst and then thermally polymerizing them.

[0104] Examples of the above-mentioned terpene-based tackifying resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. The above-mentioned polymer of terpenes may be a single polymer of one terpene or a copolymer of two or more terpenes. Examples of single-polymer terpenes include α-pinene polymers, β-pinene polymers, and dipentene polymers. The above-mentioned modified terpene-based tackifying resin is a modified version of the above-mentioned terpene resin (modified terpene resin). Examples of the above-mentioned modified terpene resin include styrene-modified terpene resins and hydrogenated terpene resins.

[0105] Examples of the above-mentioned rosin-based tackifying resins include rosins and rosin derivative resins. Examples of the above-mentioned rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins) obtained by hydrogenating, disproportionating, polymerization, etc., of these unmodified rosins. Examples of the above-mentioned rosin derivative resins include derivatives of the above-mentioned rosins. Examples of the above-mentioned rosin derivative resins include rosin esters such as unmodified rosin esters, which are esters of unmodified rosin and alcohols, and modified rosin esters, which are esters of modified rosin and alcohols; unsaturated fatty acid modified rosins obtained by modifying rosins with unsaturated fatty acids; unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups of rosins or the above-mentioned various rosin derivatives; and metal salts of rosins or the above-mentioned various rosin derivatives. Specific examples of the above-mentioned rosin esters include methyl esters of unmodified or modified rosin, triethylene glycol esters, glycerol esters, and pentaerythritol esters.

[0106] Examples of the hydrocarbon-based tackifying resins mentioned above include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic-aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins.

[0107] The content of the tackifying resin in the adhesive layer of the present invention is not particularly limited, but is, for example, 1 part by mass or more (for example, 1 to 100 parts by mass) per 100 parts by mass of the total amount of monomer components constituting the acrylic polymer, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more. When the content is 1 part by mass or more, the adhesive layer has even better adhesion even when it is thin. From the viewpoint of excellent heat resistance and cohesiveness, the content is preferably 60 parts by mass or less, and more preferably 50 parts by mass or less.

[0108] The adhesive layer of the present invention may contain a filler. The inclusion of a filler tends to further improve impact resistance. One type of filler may be used, or two or more types may be used.

[0109] The shape of the filler is not particularly limited, and particulate or fibrous fillers can be used. Particulate fillers are preferred. The filler may be either organic or inorganic.

[0110] Examples of materials constituting the above inorganic substances include metals such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, and stainless steel; metal oxides such as aluminum oxide, silicon dioxide, titanium oxide, zirconium oxide, zinc oxide, tin oxide, copper oxide, and nickel oxide; aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, basic magnesium carbonate, and hydrotalcite. Examples include metal hydroxides and hydrated metal compounds such as dosonite, borax, and zinc borate; carbides such as silicon carbide, boron carbide, nitrogen carbide, and calcium carbide; nitrides such as aluminum nitride, silicon nitride, boron nitride, and gallium nitride; carbonates such as calcium carbonate; titanates such as barium titanate and potassium titanate; carbon-based materials such as carbon black, carbon tubes (carbon nanotubes), carbon fibers, and diamonds; inorganic materials such as glass; and natural raw material particles such as volcanic ash, clay, and sand.

[0111] Examples of materials constituting the above-mentioned organic matter include polymers such as polystyrene, acrylic resin (e.g., polymethyl methacrylate), phenolic resin, benzoguanamine resin, urea resin, silicone resin, polyester, polyurethane, polyethylene, polypropylene, polyamide (e.g., nylon), polyimide, and polyvinylidene chloride.

[0112] The filler described above may have a hollow structure. The hollow portion of the filler having the hollow structure (the space inside the hollow particle) may be in a vacuum state or may be filled with a medium. Examples of the medium include inert gases such as nitrogen and argon, air, and volatile solvents.

[0113] Among the above fillers, fillers whose surface is composed of organic or inorganic materials other than acrylic resins, and fillers having a hollow structure are preferred. These fillers have little interaction with the acrylic components in the acrylic adhesive layer, or have a hollow structure, making them less likely to break when the adhesive layer is stretched, and thus offering superior reworkability.

[0114] The average particle size of the particulate filler is preferably 80 μm or less, more preferably 60 μm or less, and even 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. When the average particle size is within the above range, the hardness of the adhesive layer can be made appropriate. This increases the apparent cohesive force of the adhesive layer, bringing the fracture stress and fracture strain within an appropriate range, and improving impact resistance and reworkability. The average particle size is the median diameter (D50) measured by dynamic light scattering.

[0115] The content of the filler in the adhesive layer of the present invention is preferably more than 0 parts by mass and 30 parts by mass or less, more preferably 0.008 to 10 parts by mass, and even more preferably 0.4 to 6 parts by mass, based on 100 parts by mass of the total amount of the base polymer. When the content is 30 parts by mass or less, the fracture stress and fracture strain are within an appropriate range, resulting in superior impact resistance and reworkability.

[0116] The proportion of the filler in the adhesive layer of the present invention is preferably 0.5 to 10% by mass, and more preferably 1 to 5% by mass, based on 100% by mass of the total amount of the adhesive layer. When the proportion is within the above range, the hardness of the adhesive layer can be made appropriate. Furthermore, it exhibits excellent reworkability.

[0117] The adhesive layer of the present invention may contain a coloring agent. By including a coloring agent, the adhesive layer is colored, and the double-sided adhesive sheet of the present invention has excellent visibility and design. The coloring agent may be a pigment or a dye. Examples of coloring agents include black coloring agents, cyan coloring agents, magenta coloring agents, and yellow coloring agents. From the viewpoint of superior visibility and light-shielding properties, black coloring agents are preferred. The adhesive layer of the present invention may contain only one type of coloring agent or two or more types. The proportion of the coloring agent in the adhesive layer of the present invention is preferably 0.5 to 10% by mass, and more preferably 1 to 6% by mass, based on 100% by mass of the total amount of the adhesive layer.

[0118] Examples of black colorants include carbon black, carbon nanotubes, graphite, copper oxide, manganese dioxide, azo pigments such as azomethine azoblack, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, complex oxide black pigments, anthraquinone-based organic black dyes, and azo-based organic black dyes. Examples of carbon black include furnace black, channel black, acetylene black, thermal black, and lamp black. Examples of black colorants include CI Solvent Black 3, 7, 22, 27, 29, 34, 43, and 70; CI Direct Black 17, 19, 22, 32, 38, 51, and 71; CI Acid Black 1, 2, 24, 26, 31, 48, 52, 107, 109, 110, 119, and 154; CI Disperse Black 1, 3, 10, and 24; and CI Pigment Black 1 and 7.

[0119] Examples of cyan-based colorants include CI Solvent Blue 25, 36, 60, 70, 93, 95; CI Acid Blue 6, 45; CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:5, 15:6, 16, 17, 17:1, 18, 22, 25, 56, 60, 63, 65, 66; CI Bat Blue 4, 60, and CI Pigment Green 7.

[0120] Examples of magenta-based colorants include CI Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 52, 58, 63, 81, 82, 83, 84, 100, 109, 111, 121, 122; CI Disperse Red 9; CI Solvent Violet 8, 13, 14, 21, 27; CI Disperse Examples include Violet 1; CI Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; CI Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28, etc. Furthermore, as magenta-based colorants, for example, CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 42, 48:1, Same 48:2, same 48:3, same 48:4, same 49, same 49:1, same 50, same 51, same 52, same 52:2, same 53:1, same 54, same 55, same 56, same 57:1, same 58, same 60, same 60:1, same 63, same 63:1, same 63:2, same 64, same 64:1, same 67, same 68, same 81, same 83, same 87, same 88, same 89, same 90, same 92, same 101 , 104, 105, 106, 108, 112, 114, 122, 123, 139, 144, 146, 147, 149, 150, 151, 163, 166, 168, 170, 171, 172, 175, 176, 177, 178, 179, 184, 185, 187, 190 Examples include 193, 202, 206, 207, 209, 219, 222, 224, 238, and 245; CI Pigment Violet 3, 9, 19, 23, 31, 32, 33, 36, 38, 43, and 50; CI Bat Red 1, 2, 10, 13, 15, 23, 29, and 35.

[0121] Examples of yellow colorants include CI Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162; CI Pigment Orange 31, 43; CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 24, 34, 35, 37, 42, 53, 55, 65, 73, 74. Examples include 75, 81, 83, 93, 94, 95, 97, 98, 100, 101, 104, 108, 109, 110, 113, 114, 116, 117, 120, 128, 129, 133, 138, 139, 147, 150, 151, 153, 154, 155, 156, 167, 172, 173, 180, 185, 195; CI Bat Yellow 1, 3, 20, etc.

[0122] The adhesive layer of the present invention may optionally further 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, foil-like materials, and rust inhibitors, to the extent that they do not impair the effects of the present invention. Each of the above additives may be used individually or in combination of two or more.

[0123] As described above, the adhesive layer of the present invention has a tanδ peak between -20 and 0°C. The value of this peak peak is 0.8 or higher, preferably 1.2 or higher, and more preferably 1.5 or higher. Having a tanδ peak peak between -20 and 0°C provides excellent impact resistance, for example, when a component to which the double-sided adhesive sheet is applied is dropped at high speed. Furthermore, a peak peak value of 0.8 or higher provides even better impact resistance and excellent reworkability.

[0124] The adhesive layer of the present invention preferably has a storage modulus G' of 0.09 MPa or higher at 23°C, more preferably 0.10 MPa or higher, and even more preferably 0.15 MPa or higher. When the storage modulus G' is 0.09 MPa or higher, it has a moderate hardness at room temperature and is more reworkable. Preferably, the storage modulus G' is 0.25 MPa or lower. The storage modulus G' is measured using a dynamic viscoelasticity measurement (DMA) device.

[0125] The adhesive layer of the present invention may be in any form, for example, an emulsion type, a solvent type (solution type), an active energy ray curing type, or a hot melt type. Among these, solvent-type and active energy ray curing adhesive compositions are preferred because they make it easier to obtain an adhesive layer with excellent productivity.

[0126] Examples of the active energy rays mentioned above include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet rays, with ultraviolet rays being particularly preferred. In other words, the active energy ray-curable adhesive layer is preferably an ultraviolet-curable adhesive layer.

[0127] The adhesive layer of the present invention can be manufactured, for example, by applying an adhesive composition for forming an adhesive layer onto a release liner and drying and curing the resulting adhesive composition layer, or by applying the adhesive composition onto a release liner and curing the resulting adhesive composition layer by irradiating it with active energy rays. Furthermore, if necessary, it may be further heated and dried.

[0128] Examples of adhesive compositions for forming the adhesive layer of the present invention (acrylic adhesive compositions) include acrylic adhesive compositions comprising an acrylic polymer as an essential component, or acrylic adhesive compositions comprising a monomer mixture containing the above-mentioned acrylic partial polymer, the above-mentioned acrylic oligomer, or the above-mentioned acrylic monomer as essential components. Examples of the former include so-called solvent-type acrylic adhesive compositions. Examples of the latter include so-called active energy ray-curable acrylic adhesive compositions.

[0129] The above adhesive composition preferably contains an acrylic polymer (C) and / or an acrylic partial polymer, and may further contain the above acrylic oligomer. The above adhesive composition preferably further contains a crosslinking agent. In addition, it may contain tackifying resins, fillers, colorants, etc.

[0130] (Double-sided adhesive sheet) The double-sided adhesive sheet of the present invention is composed of 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 having a thickness of 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 greater than 10 μm, more preferably 30 μm or more, and even more preferably 50 μm or more. When the thickness is greater than 10 μm, the impact resistance and reworkability are improved. Note that the thickness of the double-sided adhesive sheet refers to the thickness from one adhesive surface to the other adhesive surface, i.e., the thickness of the adhesive body, and does not include the release liner.

[0131] The breaking stress of the double-sided adhesive sheet of the present invention is preferably 0.9 MPa or higher, and more preferably 1.0 MPa or higher. When the breaking stress is 0.9 MPa or higher, the adhesive layer is less likely to break when stretched, resulting in superior reworkability. The breaking stress is preferably 3.0 MPa or lower, and more preferably 2.0 MPa or lower. The breaking stress was measured under the following conditions: sample size 40 mm x 40 mm, thickness approximately 0.2 mm, chuck distance 10 mm, tensile speed 50 mm / min, in an environment of 23°C and 50% RH.

[0132] The breaking strain of the double-sided adhesive sheet of the present invention is preferably 60% or more, more preferably 700% or more, and even more preferably 1000% or more. When the breaking stress is 60% or more, the adhesive layer is less likely to break when stretched, resulting in superior reworkability. The above breaking strain was measured under the conditions of a sample size of 40 mm x 40 mm, a thickness of approximately 0.2 mm, a chuck distance of 10 mm, and a tensile speed of 50 mm / min, in an environment of 23°C and 50% RH.

[0133] The energy (load × height) of the double-sided adhesive sheet of the present invention, measured by the DuPont impact test described below, before either stainless steel plate peels off, is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. <Impact Resistance Test> A frame-shaped double-sided adhesive sheet with an outer diameter of 24.5 mm and a width of 2 mm is sandwiched and pressed between a stainless steel plate with a thickness of 2 mm and an outer diameter of 50 mm with a hole in the center, and a stainless steel plate with a thickness of 3 mm and an outer diameter of 25 mm. The sheet is left to stand in an environment of 50°C for 2 hours, and then returned to room temperature to be used as an evaluation sample. Using a DuPont impact tester, the evaluation sample is subjected to the following changes: the weight of the drop and the drop height are changed in 50 mm increments from 50 to 500 mm with a 100 g weight, in 50 mm increments from 350 to 500 mm with a 150 g weight, in 50 mm increments from 400 to 500 mm with a 200 g weight, and in 50 mm increments from 350 to 500 mm with a 300 g weight, so that the energy increases until peeling occurs. At this time, energy levels that have already been evaluated are not tested, and the load and height are set so that the amount of energy does not overlap. Subsequently, the energy expended before at least one of the stainless steel plates detached is calculated as load × height.

[0134] The above-mentioned double-sided adhesive sheet may have a release liner attached to the surface (adhesive side) of the adhesive layer until use. The adhesive sides of the above-mentioned double-sided adhesive sheet may each be protected by two release liners, or they may be protected by a single release liner with both sides being release surfaces, in a roll-like winding form (winding body). The release liner is used as a protective material for the adhesive layer and is peeled off when the sheet is applied to the substrate. The release liner is not necessarily required.

[0135] The above-mentioned release liner can be conventional release paper or the like, and is not particularly limited, but examples include a substrate having a release treatment layer, a low-adhesion substrate made of a fluoropolymer, or a low-adhesion substrate made of a nonpolar polymer. Examples of substrates having a release treatment layer include plastic films and paper surface-treated with release agents such as silicone-based, long-chain alkyl-based, fluorine-based, and molybdenum sulfide. Examples of fluorine-based polymers in the low-adhesion substrate made of a fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. Examples of the above-mentioned nonpolar polymer include olefin resins (e.g., polyethylene, polypropylene, etc.). The release liner can be formed by known or conventional methods. The thickness of the release liner is also not particularly limited.

[0136] The above-mentioned double-sided adhesive sheet is preferably used for attaching electrical and electronic components, by being bonded to components provided in electrical and electronic equipment. In particular, the above-mentioned double-sided adhesive sheet is preferably used for applications in which components provided in electrical and electronic equipment are bonded to each of the adhesive surfaces of the double-sided adhesive sheet, that is, for fixing components together in electrical and electronic equipment. The above-mentioned double-sided adhesive sheet may be used for either fixing components together or for temporary fixing. For example, when a double-sided adhesive sheet is used for fixing or temporarily fixing components provided in electrical and electronic equipment, there may be cases where the double-sided adhesive sheet must be peeled off and reworked due to a problem in the application process, or where the double-sided adhesive sheet must be peeled off in order to repair, replace, inspect, or recycle a component to which the double-sided adhesive sheet has been bonded. Thus, when a double-sided adhesive sheet is used, for example, for fixing or temporarily fixing components (parts) provided in electrical and electronic equipment, the frequency of removing the double-sided adhesive sheet is particularly high.

[0137] The above-mentioned double-sided adhesive sheet is preferably used to bond the outer frames of optical components (especially electrical and electronic equipment) together. For this reason, the above-mentioned double-sided adhesive sheet can preferably be used even if it has a width of 5 mm or less, and more preferably 3 mm or less.

[0138] Furthermore, "electrical and electronic equipment" refers to equipment that falls under either electrical equipment or electronic equipment. Examples of such electrical and electronic equipment include image display devices such as liquid crystal displays, electroluminescent displays, and plasma displays, as well as portable electronic devices.

[0139] Examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear-type devices worn on the wrist like watches, modular-type devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular types, including head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, earwear-type devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information equipment, portable radios, portable televisions, portable printers, portable scanners, and portable modems. In this specification, "portable" means not merely being able to carry something, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily. The above-mentioned double-sided adhesive sheet is used, for example, so that the adhesive layer adheres closely to the components of the above-mentioned portable electronic device. [Examples]

[0140] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0141] Manufacturing Example 1: Synthesis of Acrylic Oligomer (1) In a flask, 60 parts by mass of dicyclopentanyl methacrylate (DCPMA, Tg: 175°C), 40 parts by mass of methyl methacrylate (MMA), 3 parts by mass of α-thioglycerol, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 65 parts by mass of ethyl acetate were added. The flask was thoroughly filled with nitrogen and polymerized at 70°C for 5 hours. Then, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and polymerization was carried out at 80°C for 8 hours. After that, ethyl acetate was removed from the reaction mixture by distillation, and the mixture was further dried in a vacuum dryer to obtain an acrylic oligomer (weight-average molecular weight: 5080).

[0142] Manufacturing Example 2: Synthesis of Acrylic Oligomer (2) In a flask, 60 parts by mass of dicyclopentenyl acrylate (Tg: 97°C), 40 parts by mass of methyl methacrylate (MMA), 3 parts by mass of α-thioglycerol, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 65 parts by mass of ethyl acetate were added. The flask was thoroughly filled with nitrogen and polymerized at 70°C for 5 hours. Then, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and polymerization was carried out at 80°C for 8 hours. After that, ethyl acetate was removed from the reaction mixture by distillation, and the mixture was dried in a vacuum dryer to obtain an acrylic oligomer (weight-average molecular weight: 7600).

[0143] Manufacturing Example 3: Synthesis of Acrylic Oligomer (3) In a flask, 60 parts by mass of dicyclopentanyl acrylate (DCPA, Tg: approximately 100°C), 40 parts by mass of methyl methacrylate (MMA), 3 parts by mass of α-thioglycerol, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 65 parts by mass of ethyl acetate were added. The flask was thoroughly filled with nitrogen and polymerized at 70°C for 5 hours. Then, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and polymerization was carried out at 80°C for 8 hours. After that, ethyl acetate was removed from the reaction mixture by distillation, and the mixture was further dried in a vacuum dryer to obtain an acrylic oligomer (weight-average molecular weight: 5900).

[0144] Manufacturing Example 4: Synthesis of Acrylic Oligomer (4) In a flask, 60 parts by mass of dicyclopentenyloxyethyl acrylate (Tg: approximately 100°C), 40 parts by mass of methyl methacrylate (MMA), 3 parts by mass of α-thioglycerol, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 65 parts by mass of ethyl acetate were added. The flask was thoroughly filled with nitrogen and polymerized at 70°C for 5 hours. Then, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and polymerization was carried out at 80°C for 8 hours. After that, ethyl acetate was removed from the reaction mixture by distillation, and the mixture was further dried in a vacuum dryer to obtain an acrylic oligomer (weight-average molecular weight: 3000).

[0145] Manufacturing Example 5: Synthesis of Acrylic Oligomer (5) In a flask, 60 parts by mass of cyclohexyl methacrylate (Tg: 66°C), 40 parts by mass of methyl methacrylate (MMA), 3 parts by mass of α-thioglycerol, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 65 parts by mass of ethyl acetate were added. The flask was thoroughly filled with nitrogen and polymerized at 70°C for 5 hours. Then, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and polymerization was carried out at 80°C for 8 hours. After that, ethyl acetate was removed from the reaction mixture by distillation, and the mixture was dried in a vacuum dryer to obtain an acrylic oligomer (weight-average molecular weight: 3600).

[0146] Example 1 In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 68 parts by mass of toluene, 95 parts by mass of butyl acrylate (BA) acrylate, and 5 parts by mass of acrylic acid (AA) were charged, and the reactor was purged with nitrogen for more than 1 hour. Azobisisobutyronitrile was added as an initiator, and the internal bath temperature was then raised to 62°C, maintained at the same temperature, and continued until the reaction was almost complete. After that, the reactor was cooled to terminate the polymerization reaction. To 100 parts by mass of the obtained polymer, 5 parts by mass of the acrylic oligomer (1) obtained in Production Example 1, 5 parts by mass of an isocyanate compound (trade name "Coronate L", manufactured by Tosoh Corporation), and 0.02 parts by mass of an epoxy compound (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Company, Inc.) were added. Furthermore, 20 parts by mass of a terpene phenol-based tackifying resin (trade name "YS Polystar T115", manufactured by Yasuhara Chemical Co., Ltd.) and 6 parts by mass of a black pigment containing carbon black (trade name "Multirack A903", manufactured by Toyo Color Co., Ltd.) were added to prepare an adhesive composition.

[0147] The above adhesive composition was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) with one side release-treated with silicone, and dried to form a 200 μm thick adhesive layer, thereby producing the double-sided adhesive sheet of Example 1.

[0148] Example 2 To 100 parts by mass of the polymer prepared in Example 1, 2.5 parts by mass of the acrylic oligomer (1) obtained in Production Example 1, 5 parts by mass of an isocyanate crosslinking agent (product name "Coronate L", manufactured by Tosoh Corporation), and 0.02 parts by mass of an epoxy crosslinking agent (product name "Tetrad C", manufactured by Mitsubishi Gas Chemical Company, Inc.) were added. Further, 20 parts by mass of a terpene phenol tackifying resin (product name "YS Polystar T115", manufactured by Yasuhara Chemical Co., Ltd.), 2 parts by mass of polyethylene powder as a filler (product name "Flowsen UF-80", manufactured by Sumitomo Seika Co., Ltd.), and 6 parts by mass of a black pigment containing carbon black (product name "Multirack A903", manufactured by Toyo Color Co., Ltd.) were added to obtain an adhesive composition.

[0149] A double-sided adhesive sheet of Example 2 was prepared in the same manner as in Example 1, except that the adhesive composition obtained above was used.

[0150] Examples 3-7 Each example of the double-sided adhesive sheet was prepared in the same manner as in Example 2, except that the amount of acrylic oligomer (1) obtained in Production Example 1 or the thickness of the adhesive layer was changed as shown in Table 1.

[0151] Example 8 A liquid monomer mixture (monomer composition) was prepared by mixing 70 parts by mass of butyl acrylate (BA), 5 parts by mass of acrylic acid (AA), and 25 parts by mass of isobornyl acrylate (IBXA, Tg: 97℃) as monomer components. 0.05 parts by mass of 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name "OMNIRAD651", manufactured by IGM Resins BV) was added as a photopolymerization initiator. The mixture was then pulsed with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature: 30℃) reached approximately 15 Pa·s, yielding a syrup (partial polymer) containing a partial polymer (polymerization rate: approximately 8%) in which a portion of the monomer components had polymerized.

[0152] To 100 parts by mass of the syrup obtained above, 5 parts by mass of an isocyanate-based crosslinking agent (product name "Coronate L", manufactured by Tosoh Corporation) and 0.02 parts by mass of an epoxy-based crosslinking agent (product name "Tetrad C", manufactured by Mitsubishi Gas Chemical Company, Inc.) were added. Further, 20 parts by mass of a terpene phenol-based tackifying resin (product name "YS Polystar T115", manufactured by Yasuhara Chemical Co., Ltd.), 2 parts by mass of polyethylene powder as a filler (product name "Flowsen UF-80", manufactured by Sumitomo Seika Co., Ltd.), and 6 parts by mass of a black pigment containing carbon black (product name "Multirack A903", manufactured by Toyo Color Co., Ltd.) were added. The mixture was then uniformly mixed using a disperser, and subsequently degassed to obtain an acrylic adhesive composition.

[0153] The obtained acrylic adhesive composition was applied using an applicator to a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) that had been peel-treated on one side with silicone, so that the adhesive layer thickness was 200 μm, thereby forming a coated layer.

[0154] Next, a 25 μm thick polyethylene terephthalate film (product name "MRE#25", manufactured by Mitsubishi Chemical Corporation), with one side of which had been peel-treated with silicone, was covered with the coating layer so that the peel-treated side faced the coating layer, thereby blocking oxygen. After that, a black light lamp was used to illuminate the top surface of the film at an illuminance of 4 mW / cm². 2 A 200 μm thick adhesive layer was formed by irradiating the sheet with ultraviolet light (UV checker "UVR-T1", manufactured by Topcon Corporation, with a maximum sensitivity of approximately 350 nm during measurement) for 180 seconds, thereby creating a double-sided adhesive sheet.

[0155] Example 9 The double-sided adhesive sheet of Example 9 was prepared in the same manner as in Example 2, except that 5 parts by mass of acrylic oligomer (2) obtained in Production Example 2 were used instead of 2.5 parts by mass of acrylic oligomer (1) obtained in Production Example 1.

[0156] Example 10 The double-sided adhesive sheet of Example 10 was prepared in the same manner as in Example 2, except that 5 parts by mass of acrylic oligomer (3) obtained in Production Example 3 were used instead of 2.5 parts by mass of acrylic oligomer (1) obtained in Production Example 1.

[0157] Example 11 The double-sided adhesive sheet of Example 11 was prepared in the same manner as in Example 2, except that 5 parts by mass of acrylic oligomer (4) obtained in Production Example 4 were used instead of 2.5 parts by mass of acrylic oligomer (1) obtained in Production Example 1.

[0158] Comparative Example 1 A double-sided adhesive sheet of Comparative Example 1 was prepared in the same manner as in Example 2, except that the acrylic oligomer (1) obtained in Production Example 1 was not incorporated.

[0159] Comparative Example 2 A double-sided adhesive sheet for Comparative Example 2 was prepared in the same manner as in Example 2, except that the amount of acrylic oligomer (1) obtained in Production Example 1 was 40 parts by mass.

[0160] Comparative Example 3 An acrylic adhesive composition was prepared in the same manner as in Example 2, except that the amount of acrylic oligomer (1) obtained in Production Example 1 was changed to 5 parts by mass. The above adhesive composition was applied to the release layer of a 38 μm thick polyethylene terephthalate film (product name "MRF#38", manufactured by Mitsubishi Chemical Corporation) whose one side had been released with silicone, and dried to form an adhesive layer with a thickness of 178 μm. Then, the release liner (product name "MRE#25", manufactured by Mitsubishi Chemical Corporation) provided on the surface of the prepared adhesive layer was peeled off to expose the adhesive layer, and one side of the PET film (thickness 12 μm) that would serve as the base layer was laminated to the surface of the exposed adhesive layer. In this way, a single-sided adhesive sheet (thickness 190 μm) of Comparative Example 3 was prepared, in which an adhesive layer was formed on the base layer.

[0161] Comparative Example 4 A double-sided adhesive sheet for Comparative Example 4 was prepared in the same manner as in Example 2, except that 5 parts by mass of acrylic oligomer (5) obtained in Production Example 5 were used instead of 2.5 parts by mass of acrylic oligomer (1) obtained in Production Example 1.

[0162] <Rating> The adhesive layers and adhesive sheets obtained in the examples and comparative examples were evaluated as follows. The results are shown in the table. Note that the amount of each component in the table is in parts by mass.

[0163] (1) Dynamic viscoelasticity measurement A 2 mm thick adhesive layer was prepared by stacking multiple adhesive layers prepared in the examples and comparative examples. A sample of this adhesive layer, punched into a 7.9 mm diameter disc, was sandwiched and fixed between parallel plates. Dynamic viscoelasticity measurements were performed under the following conditions using a viscoelasticity tester (product name "ARES Rheometer", manufactured by T.A. Instruments Co., Ltd.) at 23°C and 50% RH, and the storage modulus G'(23°C) and the peak top value of tanδ were calculated. It was confirmed that a peak top of tanδ existed in the range of -20 to 0°C for all adhesive layers. Measurement mode: Shear mode Temperature range: -70℃ to 150℃ Heating rate: 5°C / min Measurement frequency: 1Hz

[0164] (2) Fracture stress, fracture strain Test specimens were obtained by cutting the adhesive sheets obtained in the examples and comparative examples to a size of 40 mm in width and 40 mm in length. Under conditions of 23°C and 50% RH, all release liners were peeled off to expose the adhesive sheets, and tensile tests were performed on the test specimens using a universal tensile and compression testing machine (product name "TCM-1kNB", manufactured by Minebea Co., Ltd.) with a chuck distance of 10 mm and a tensile speed of 50 mm / min to determine the SS curve, and the stress (breaking stress) and strain (breaking strain) at the time of fracture of the test specimen were measured. It is preferable to apply powder to the adhesive surface of the chuck area to eliminate the effect of stickiness of the adhesive during the test.

[0165] (3) Impact resistance The double-sided adhesive sheets (or single-sided adhesive sheets with a release liner in Comparative Example 3) prepared in the Examples and Comparative Examples were punched out into a frame shape with an outer diameter of 24.5 mm and a width of 2 mm. The release liner was then peeled off the adhesive sheet, and the resulting sample was pressed between a 2 mm thick, 50 mm square stainless steel plate with a hole in the center and a 3 mm thick, 25 mm square stainless steel plate. The sample was left to stand for 2 hours at 50°C, and then returned to room temperature to be used as an evaluation sample. A cylindrical measuring stand with a length of 50 mm, an outer diameter of 49 mm, and an inner diameter of 43 mm was placed on the base of a DuPont impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the test piece was placed on top of it with the square stainless steel plate (the stainless steel plate without the hole) facing downwards. A stainless steel impact pin with a tip radius of 3.1 mm was placed on the test piece, and the weight of the drop weight and the drop height were varied in 50 mm increments from 50 to 500 mm with a 100 g weight, in 50 mm increments from 350 to 500 mm with a 150 g weight, in 50 mm increments from 400 to 500 mm with a 200 g weight, and in 50 mm increments from 350 to 500 mm with a 300 g weight, so that the energy increased until delamination occurred. At this time, tests were not conducted for energy levels that had already been evaluated, and the load and height were set so that the amount of energy did not overlap. Subsequently, the energy before at least one of the stainless steel plates (in the case of Comparative Example 3, the stainless steel plate bonded to the adhesive layer) delaminate was calculated as load × height and the result was obtained.

[0166] (4) Reworkability A 10mm x 50mm sample was cut from the adhesive sheets obtained in the examples and comparative examples to serve as an evaluation sample. The release liner (the release liner on the lightly peelable side for double-sided adhesive sheets) was peeled off the evaluation sample, and the adhesive side of the adhesive sheet was laminated to a stainless steel substrate (using a 2kg roller for one pass). The samples were then heated and stored at 50°C for 24 hours. After that, for double-sided adhesive sheets, the release liner on the heavily peelable side was peeled off, the short-side edge was peeled from the stainless steel plate, and the adhesive sheet was attempted to be peeled off by pulling it at a peeling angle of 30° relative to the substrate to check its reworkability. The reworkability was then evaluated according to the following criteria. Note that the reworkability required for practical use is 2 or higher, preferably 3 or higher, according to the following criteria. Rank 1: The tape has torn and cannot be removed. Rank 2: The tape can be peeled off without tearing by pulling at a speed of less than 0.2 m / min. Rank 3: The tape can be peeled off without tearing by pulling at a speed of 0.2 m / min or faster.

[0167] [Table 1]

[0168] [Table 2]

[0169] As shown in Table 1, the double-sided adhesive sheet of the present invention was confirmed to have excellent impact resistance and reworkability. On the other hand, as shown in Table 2, when the acrylic polymer contained in the double-sided adhesive sheet did not contain acrylic monomers (A) having two or more non-aromatic rings as constituent units (Comparative Examples 1 and 4), the reworkability was poor. Furthermore, when the peak top value of tanδ in the adhesive layer was low (Comparative Example 2), and when a base layer was present (Comparative Example 3), both impact resistance and reworkability were poor. [Explanation of symbols]

[0170] 1. Double-sided adhesive sheet 2. Adhesive layer 3,4 Release Liner

Claims

1. It is a double-sided adhesive sheet consisting of an adhesive layer, The thickness of the double-sided adhesive sheet is 500 μm or less. The aforementioned adhesive layer is an acrylic adhesive layer containing an acrylic polymer as the base polymer. The acrylic polymer includes constituent units derived from an acrylic monomer (A) having two or more non-aromatic rings. The acrylic polymer is crosslinked with a crosslinking agent, and the content of the crosslinking agent is 0.001 to 20 parts by mass per 100 parts by mass of the total amount of monomer components constituting the acrylic polymer. The adhesive layer has a tanδ peak top between -20 and 0°C, and the value of the peak top is 0.8 or higher. The adhesive layer is a double-sided adhesive sheet satisfying (i) and / or (ii) below. (i) Contains a filler, the proportion of which is 0.5 to 10% by mass relative to 100% by mass of the total amount of the adhesive layer. (ii) Contains a pigment, the proportion of which is 0.5 to 10% by mass relative to 100% by mass of the total amount of the adhesive layer.

2. The double-sided adhesive sheet according to claim 1, wherein the proportion of constituent units derived from the acrylic monomer (A) in the acrylic polymer is 1 to 15% by mass.

3. The double-sided adhesive sheet according to claim 1 or 2, wherein the acrylic polymer comprises structural units derived from an alkyl (meth)acrylate (B) having a linear or branched alkyl group having 2 to 7 carbon atoms.

4. The double-sided adhesive sheet according to claim 3, wherein the alkyl (meth)acrylate (B) is butyl (meth)acrylate.

5. The double-sided adhesive sheet according to claim 3 or 4, wherein the proportion of constituent units derived from the alkyl (meth)acrylate (B) in the acrylic polymer is 50% by mass or more.

6. The double-sided adhesive sheet according to any one of claims 1 to 5, having a structural component derived from an acrylic oligomer as the acrylic polymer.

7. The double-sided adhesive sheet according to claim 6, wherein the acrylic oligomer includes a constituent unit derived from the acrylic monomer (A).

8. The double-sided adhesive sheet according to claim 7, wherein the content of the acrylic oligomer is 0.5 to 35 parts by mass per 100 parts by mass of the total amount of the acrylic polymer.

9. The double-sided adhesive sheet according to any one of claims 1 to 8, wherein the acrylic monomer (A) comprises one or more groups selected from the group consisting of a dicyclopentanyl group, a dicyclopentenyl group, and an isobornyl group.

10. The double-sided adhesive sheet according to any one of claims 1 to 9, wherein the adhesive layer further comprises a tackifying resin.

11. A double-sided adhesive sheet according to any one of claims 1 to 10, wherein the breaking stress is 0.9 MPa or more.

12. A double-sided adhesive sheet according to any one of claims 1 to 11, wherein the breaking strain is 60% or more.

13. The double-sided adhesive sheet according to any one of claims 1 to 12, wherein the storage modulus G' of the adhesive layer at 23°C is 0.09 MPa or more.

14. A double-sided adhesive sheet according to any one of claims 1 to 13, for fixing components together in electrical and electronic equipment.

15. The double-sided adhesive sheet described in claim 14, The aforementioned double-sided adhesive sheet is used to fix components together on both adhesive surfaces in an electrical and electronic device.

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