WO2023282007A1

WO2023282007A1 - Double-sided adhesive sheet

Info

Publication number: WO2023282007A1
Application number: PCT/JP2022/024101
Authority: WO
Inventors: 啓迪住田; 卓也藤田; 直宏加藤
Original assignee: 日東電工株式会社
Priority date: 2021-07-06
Filing date: 2022-06-16
Publication date: 2023-01-12
Also published as: JP2023008631A; CN117545816A; KR20240032058A

Abstract

Provided is a double-sided adhesive sheet having excellent impact resistance and reworkability.　A double-sided adhesive sheet 1 comprises an adhesive layer 2 and has a thickness of at most 500 μm. The adhesive layer 2 is an acrylic adhesive layer including an acrylic polymer as a base polymer. The acrylic polymer contains a structural unit derived from an acrylic monomer (A) having at least two non-aromatic rings. The adhesive layer 2 has a peak top of tan δ, of −20 to 0 °C, and the value of the peak top is at least 0.8.

Description

double-sided adhesive sheet

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

In recent years, mobile devices such as mobile phones, digital cameras, and PDAs (Personal Digital Assistants) are becoming smaller. Therefore, various electronic components mounted thereon are being made smaller and thinner. For example, a mobile phone, which is a typical mobile device, tends to have thinned main components. Usually, the display part of a portable device is mainly composed of an LCD module and a backlight unit, and various sheet-like parts are laminated in order to exhibit functions such as light emission, reflection, light blocking, and light guiding. Therefore, a double-sided adhesive sheet (double-sided adhesive tape) is used for assembling (bonding) these parts.

For example, portable electronic devices are often exposed to the risk of falling due to their usage patterns. For this reason, double-sided pressure-sensitive adhesive sheets used in portable electronic devices are required to have impact resistance so that they are less likely to be damaged or peeled off from parts due to the impact of dropping the portable electronic device.

For example, Patent Documents 1 to 3 disclose, for example, known double-sided pressure-sensitive adhesive sheets that are used in mobile electronic devices and have excellent impact resistance.

JP 2020-128453 A JP 2020-128454 A Japanese Patent Application Laid-Open No. 2021-24907

On the other hand, when repairing, replacing, inspecting, recycling, etc., a member having an adherend to which a double-sided adhesive sheet is attached, it may be necessary to peel off the double-sided adhesive sheet. In such a case, it is required that the double-sided pressure-sensitive adhesive sheet can be easily peeled from the adherend, that is, that it has reworkability. Patent Documents 1 to 3 do not mention that both impact resistance and reworkability are excellent.

The present invention was conceived under such circumstances, and its object is to provide a double-sided pressure-sensitive adhesive sheet that has excellent impact resistance and excellent reworkability.

As a result of intensive studies to achieve the above object, the present inventors have found that a double-sided pressure-sensitive adhesive sheet having no substrate, wherein the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive sheet is a base polymer containing a specific monomer component as a constituent component It has been found that excellent impact resistance and excellent reworkability are achieved by including and having specific properties. The present invention has been completed based on these findings.

That is, the present invention is a double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer,
The double-sided pressure-sensitive adhesive sheet has a thickness of 500 μm or less,
The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer,
The acrylic polymer contains structural units derived from an acrylic monomer (A) having two or more non-aromatic rings,
The pressure-sensitive adhesive layer has a tan δ peak top between −20° C. and 0° C., and the peak top value is 0.8 or more to provide a double-sided pressure-sensitive adhesive sheet.

The proportion of structural units derived from the acrylic monomer (A) in the acrylic polymer is preferably 1 to 15% by mass.

The acrylic polymer preferably contains structural units derived from a (meth)acrylic acid alkyl ester (B) having a linear or branched alkyl group with 2 to 7 carbon atoms.

The (meth)acrylic acid alkyl ester (B) is preferably butyl (meth)acrylate.

The proportion of structural units derived from the (meth)acrylic acid alkyl ester (B) in the acrylic polymer is preferably 50% by mass or more.

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

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

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

The 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.

The adhesive layer preferably further contains a tackifying resin.

The breaking stress is preferably 0.9 MPa or more.

The breaking strain is preferably 60% or more.

The storage elastic modulus G' of the pressure-sensitive adhesive layer at 23°C is preferably 0.09 MPa or more.

The double-sided pressure-sensitive adhesive sheet is preferably for fixing members to each other in electrical and electronic equipment.

The present invention also provides an electrical and electronic device comprising the double-sided pressure-sensitive adhesive sheet, wherein both pressure-sensitive adhesive surfaces of the double-sided pressure-sensitive adhesive sheet fix members to each other.

The double-sided pressure-sensitive adhesive sheet of the present invention has excellent impact resistance and excellent reworkability. Therefore, when used in portable electronic devices, for example, it is difficult to peel off when subjected to a drop impact, and when the double-sided pressure-sensitive adhesive sheet is intentionally peeled off, the pressure-sensitive adhesive sheet is easily peeled off without being broken.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of the double-sided adhesive sheet which concerns on one Embodiment of this invention.

[Double-sided adhesive sheet]
The double-sided pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer, and is a so-called "substrate-less" double-sided pressure-sensitive adhesive sheet that does not have a substrate.

The above pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. The acrylic polymer contains structural units derived from an acrylic monomer having two or more non-aromatic rings (sometimes referred to as "acrylic monomer (A)"). In this specification, the pressure-sensitive adhesive layer may be referred to as "the pressure-sensitive adhesive layer of the present invention".

The pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive sheet of the present invention may be a single layer or multiple layers. When the double-sided pressure-sensitive adhesive sheet of the present invention is composed of a plurality of pressure-sensitive adhesive layers, each of the plurality of pressure-sensitive adhesive layers is the pressure-sensitive adhesive layer of the present invention. The plurality of pressure-sensitive adhesive layers may be the same pressure-sensitive adhesive layer, or may be pressure-sensitive adhesive layers having different compositions, thicknesses, physical properties, and the like.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the double-sided pressure-sensitive adhesive sheet of the present invention. As shown in FIG. 1, a double-sided pressure-sensitive adhesive sheet 1 is composed of a single pressure-sensitive adhesive layer 2 of the present invention. Release liners 3 and 4 are attached to the adhesive surfaces of the adhesive layer 2, respectively.

(Adhesive layer of the present invention)
The pressure-sensitive adhesive layer of the present invention is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer exhibiting adhesiveness. In this specification, the base polymer refers to a main component among the polymer components in the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, for example, a polymer component contained in an amount exceeding 50% by mass.

The content of the base polymer in the pressure-sensitive adhesive layer is preferably 60% by mass or more, more preferably 70% by mass or more, relative to 100% by mass of the total amount of the pressure-sensitive adhesive layer.

The above acrylic polymer is a polymer containing an acrylic monomer (a monomer having a (meth)acryloyl group in the molecule) as a monomer component that constitutes the polymer. That is, the acrylic polymer contains structural units derived from acrylic monomers. In addition, acrylic polymer may use only 1 type, and may use 2 or more types. Moreover, the said acrylic polymer may contain only 1 type of acrylic monomers as a monomer component, and may contain 2 or more types. In the present specification, "(meth)acrylic" means "acrylic" and/or "methacrylic" (one or both of "acrylic" and "methacrylic"), and the same applies to others. .

The above acrylic polymer is a polymer composed (formed) of an acrylic monomer (A) having two or more non-aromatic rings as an essential monomer component. That is, the acrylic polymer contains an acrylic monomer (A) as a structural unit. The acrylic polymer may contain only one type of acrylic monomer (A) as a monomer component, or may contain two or more types thereof.

The bicyclic or more non-aromatic ring includes a bicyclic or more non-aromatic hydrocarbon ring and a bicyclic or more non-aromatic heterocyclic ring. The non-aromatic ring may be either saturated or unsaturated. Examples of the non-aromatic hydrocarbon ring having two or more rings include bridged hydrocarbon rings such as bicyclic aliphatic hydrocarbon rings and tricyclic or more aliphatic hydrocarbon rings. Bicyclic hydrocarbon rings include pinane ring, pinene ring, bornane ring, norbornane ring, norbornene ring and the like. Tricyclic or higher aliphatic hydrocarbon rings (tricyclic or higher bridged hydrocarbon rings) include, for example, dicyclopentane ring, dicyclopentene ring, adamantane ring, tricyclopentane ring, tricyclopentene ring and the like. .

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

The bicyclic or higher non-aromatic ring is preferably a bicyclic or higher non-aromatic hydrocarbon ring, more preferably a bicyclic or tricyclic non-aromatic hydrocarbon ring, and more preferably bornane. ring, norbornane ring, norbornene ring, dicyclopentane ring, and dicyclopentene ring. A dicyclopentanyl group, a dicyclopentenyl group, and an isobornyl group are preferable as the group having two or more non-aromatic rings, which the acrylic monomer (A) has.

The Tg of the homopolymer of the acrylic monomer (A) is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 60°C or higher. When the Tg is 0°C or higher, the impact resistance is more excellent. The above Tg is, for example, 200° C. or less.

In this specification, the "glass transition temperature (Tg) when forming a homopolymer" (sometimes simply referred to as "Tg of the homopolymer") means "the glass transition temperature of the homopolymer of the monomer ( Tg)", specifically, numerical values are listed in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1987). The Tg of a homopolymer of a monomer not described in the above literature refers to, for example, a value obtained by the following measuring method (see JP-A-2007-51271). That is, a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser was charged with 100 parts by mass of a monomer, 0.2 parts by mass of 2,2'-azobisisobutyronitrile and ethyl acetate as a polymerization solvent. 200 parts by mass are added and stirred for 1 hour while nitrogen gas is introduced. After oxygen is removed from the polymerization system in this manner, the temperature is raised to 63° C. and the reaction is allowed to proceed for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by mass. The homopolymer solution is then cast onto a release liner and dried to form a test sample (sheet homopolymer) having a thickness of about 2 mm. Then, this test sample was punched out into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (trade name “ARES”, manufactured by Rheometrics Co., Ltd.). The viscoelasticity is measured in the shear mode at a heating rate of 5°C/min in the region of -70 to 150°C, and the peak top temperature of tan δ is defined as the Tg of the homopolymer.

Specific examples of the acrylic monomer (A) include (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring such as isobornyl (meth)acrylate; 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, 2-ethyl-2-adamantyl (meth)acrylate, and the like (meth)acrylic acid esters having a tricyclic or higher aliphatic hydrocarbon ring.

The proportion of the acrylic monomer (A) in the total amount of 100% by mass of all monomer components constituting the acrylic polymer is preferably 1 to 30% by mass, more preferably 2 to 13% by mass. When the above ratio is 1% by mass or more, reworkability is improved. When the above proportion is 30% by mass or less, the tan δ peak top value of the pressure-sensitive adhesive layer is high, and the impact resistance and reworkability are excellent.

The acrylic polymer is composed (formed) of an acrylic monomer (A) and a (meth)acrylic acid alkyl ester (sometimes referred to as "(meth)acrylic acid alkyl ester (B)") as a monomer component. Polymers are preferred.

The (meth)acrylic acid alkyl ester (B) is preferably a (meth)acrylic acid alkyl ester having a linear or branched alkyl group. In addition, only 1 type may be used for (meth)acrylic-acid alkylester (B), and 2 or more types may be used for it.

The (meth)acrylic acid alkyl ester having a linear or branched alkyl group is not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, ( meth)isopropyl acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, (meth)acrylate isopentyl acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, (meth)acrylate ) isononyl acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, (meth)acrylate Tetradecyl acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate (stearyl (meth)acrylate), isostearyl (meth)acrylate, (meth)acrylic (Meth)acrylic acid alkyl esters having a straight or branched chain alkyl group having 1 to 20 carbon atoms such as nonadecyl acid and eicosyl (meth)acrylate. Among them, the (meth)acrylic acid alkyl ester having a linear or branched alkyl group has a linear or branched alkyl group having 2 to 7 carbon atoms from the viewpoint of further improving impact resistance. A (meth)acrylic acid alkyl ester having such a compound is preferable, and butyl (meth)acrylate is more preferable. It may also contain methyl (meth)acrylate.

The ratio of the (meth)acrylic acid alkyl ester (B) in the total amount of 100% by mass of all the monomer components constituting the acrylic polymer is not particularly limited, but is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 80% by mass or more. When the above ratio is 50% by mass or more, it is possible to form a pressure-sensitive adhesive layer that has a good quantitative balance with the acrylic monomer (A) and has good adhesion even if it is thin. The ratio is preferably 99% by mass or less, more preferably 95% by mass or less. Moreover, it is preferable that the ratio of butyl (meth)acrylate is within the above range.

The above acrylic polymer may contain a copolymerizable monomer together with the acrylic monomer (A) and the (meth)acrylic acid alkyl ester (B) as monomer components constituting the polymer. That is, the acrylic polymer may contain a copolymerizable monomer as a structural unit. The above copolymerizable monomers may be used alone or in combination of two or more.

As the copolymerizable monomer, a carboxy group-containing monomer and/or an acid anhydride monomer are preferable from the viewpoint of being able to form a pressure-sensitive adhesive layer having good adhesiveness even if it is thin. Examples of the carboxy group-containing monomer 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 monomer include maleic anhydride and itaconic anhydride.

The ratio of the carboxy group-containing monomer and/or the acid anhydride monomer in the total amount of 100% by mass of all the monomer components constituting the acrylic polymer is not particularly limited, but is preferably 0.2% by mass or more, More preferably, it is 1% by mass or more. The above ratio is preferably 15% by mass or less, more preferably 10% by mass or less. When the above ratio is within the above range, the acrylic monomer (A) and the (meth)acrylic acid alkyl ester (B) have a good quantitative balance and form a pressure-sensitive adhesive layer having good adhesion even if it is thin. It becomes possible.

The copolymerizable monomer may further contain a functional group-containing monomer for the purpose of introducing a cross-linking point into the acrylic polymer or increasing the cohesion of the acrylic polymer. Examples of functional group-containing monomers include hydroxyl group-containing monomers, nitrogen atom-containing monomers (excluding acrylic monomers (A)), keto group-containing monomers, alkoxysilyl group-containing monomers, and sulfonic acid group-containing monomers. , phosphate group-containing monomers, and the like. Only one kind of the functional group-containing monomer may be used, or two or more kinds thereof may be used.

Examples of the hydroxy group-containing monomer include 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, (4-hydroxymethylcyclohexyl) methyl (meth) ) hydroxyalkyl (meth)acrylates such as acrylates; unsaturated alcohols such as vinyl alcohol and allyl alcohol; polypropylene glycol mono(meth)acrylates;

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

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

Examples of the alkoxysilyl group-containing monomer include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-( meth)acryloxypropylmethyldiethoxysilane and the like.

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth) ) acryloyloxynaphthalenesulfonic acid and the like.

Examples of the phosphoric acid group-containing monomer include 2-hydroxyethyl acryloyl phosphate.

The ratio of the functional group-containing monomer in the total amount of 100% by mass of all the monomer components constituting the acrylic polymer is, 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 ratio may be, for example, 40% by mass or less, 20% by mass or less, or may be substantially absent. In the present specification, the term "substantially not included" refers to unintentional inclusion, such as unavoidable mixing, rather than active blending. It is 0.01% by mass or less.

The copolymerizable monomer may further contain other monomers. Examples of the 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 vinyl toluene; 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; methoxyethyl (meth)acrylate, ethoxyethyl (meth ) alkoxy group-containing monomers such as acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; (meth) acrylic acid aryl esters such as phenyl (meth) acrylate, and (meth) acrylic acid such as phenoxyethyl (meth) acrylate Aryloxyalkyl esters, (meth)acrylic acid esters having an aromatic ring such as arylalkyl (meth)acrylates such as benzyl (meth)acrylate; cyclo(meth)acrylates such as cyclohexyl (meth)acrylate Alkyl esters and the like can be mentioned.

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

The acrylic polymer may contain, as a monomer component constituting the polymer, a polyfunctional monomer copolymerizable with the monomer component forming the acrylic polymer, in order to form a crosslinked structure in the polymer skeleton. . Examples of the polyfunctional monomer include hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, penta Polyfunctional (meth)acrylates such as erythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate; epoxy (meth)acrylates (e.g., poly glycidyl (meth)acrylate), polyester (meth)acrylate, urethane (meth)acrylate, and other monomers having a (meth)acryloyl group and other reactive functional groups in the molecule. Only one kind of the polyfunctional monomer may be used, or two or more kinds thereof may be used. In addition, the above polyfunctional monomer exhibits the same function as a cross-linking agent described later, and can also correspond to a cross-linking agent.

The acrylic polymer may have a structure derived from an acrylic oligomer. Examples of such an acrylic polymer include a polymer containing an acrylic polymer (sometimes referred to as "acrylic polymer (C)") and a polymerization reaction product of a composition containing the acrylic oligomer. Having a structural part derived from an acrylic oligomer results in higher breaking strain and better reworkability. The composition containing the acrylic oligomer may further contain a monomer component (sometimes referred to as "monomer component (D)"). Each of the acrylic polymer (C), the acrylic oligomer, and the monomer component (D) may be used alone or in combination of two or more.

Further, the acrylic polymer may be a polymerization reaction product obtained by polymerizing a composition containing one or more selected from the group consisting of an acrylic partial polymer, an acrylic oligomer, and a monomer component (D). good. In addition, in the case of a polymerization reaction product obtained by polymerizing a composition consisting only of the monomer component (D), the monomer component (D) contains at least an acrylic monomer. Among them, a polymerization reaction product of a composition containing an acrylic partial polymer is preferred. The above-mentioned "partially polymerized product" may also be referred to as "prepolymer", "syrup", and the like. Each of the acrylic partial polymer, acrylic oligomer, and monomer component (D) may be used alone or in combination of two or more.

The acrylic polymer (C), the acrylic partial polymer, and the acrylic oligomer are all compounds composed of an acrylic monomer as an essential monomer component. The acrylic monomer and the monomer component (D), which are monomer components constituting the acrylic polymer (C), the acrylic partial polymer, and the acrylic oligomer, are exemplified as the monomer components constituting the acrylic polymer. and those described.

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

The acrylic polymer (C) contains an acrylic monomer as a structural unit. The acrylic polymer (C) preferably contains a (meth)acrylic acid alkyl ester (B) as a structural unit. The (meth)acrylic acid alkyl ester (B) is preferably a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 2 to 7 carbon atoms, more preferably butyl (meth)acrylate. is. The acrylic monomer contained as the structural unit may be of one type or two or more types.

The proportion of the (meth)acrylic acid alkyl ester (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. above, more preferably at least 65% by mass. The ratio is preferably 99% by mass or less, more preferably 95% by mass or less.

The acrylic polymer (C) may contain the above copolymerizable monomer as a structural unit. Among the above-mentioned copolymerizable monomers, a carboxy group-containing monomer and/or acid Anhydride monomers are preferred. Moreover, the acrylic polymer (C) may contain the acrylic monomer (A) as a structural unit.

The ratio of the carboxy group-containing monomer and/or the acid anhydride monomer in the total amount of 100% by mass of all monomer components constituting the acrylic polymer (C) is not particularly limited, but is preferably 0.2% by mass or more. It is preferably 1% by mass or more, more preferably 1% by mass or more. The 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 ratio is within the above range, a pressure-sensitive adhesive layer is formed that has a good quantitative balance with the (meth)acrylic acid alkyl ester (B), has excellent impact resistance, and has good adhesion even if it is thin. It becomes possible.

Unlike the complete polymer, the acrylic partial polymer is obtained by polymerizing the monomer components at a polymerization conversion rate of 95% by mass or less, for example. The polymerization conversion rate is preferably 70% by mass or less, more preferably 60% by mass or less, still 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.

The above acrylic partial polymer contains an acrylic monomer as a structural unit. The above acrylic partial polymer preferably contains a (meth)acrylic acid alkyl ester (B) as a structural unit. The (meth)acrylic acid alkyl ester (B) is preferably a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 2 to 7 carbon atoms, more preferably butyl (meth)acrylate. is. The acrylic monomer contained as the structural unit may be of one type or two or more types.

The proportion of the (meth)acrylic acid alkyl ester (B) in 100% by mass of the total amount of all monomer components constituting the acrylic partial polymer is preferably 50% by mass or more, more preferably 60% by mass. above, more preferably at least 65% by mass. The ratio is preferably 99% by mass or less, more preferably 95% by mass or less.

The acrylic partial polymer may contain the copolymerizable monomer as a structural unit. Among the above-mentioned copolymerizable monomers, a carboxy group-containing monomer and/or acid Anhydride monomers are preferred.

The ratio of the carboxy group-containing monomer and/or the acid anhydride monomer in the total amount of 100% by mass of all the monomer components constituting the acrylic partial polymer is not particularly limited, but is preferably 0.2% by mass or more. It is preferably 1% by mass or more, more preferably 1% by mass or more. The 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 ratio is within the above range, the quantitative balance between the acrylic monomer (A) and the (meth)acrylic acid alkyl ester (B) is good, the impact resistance is excellent, and the adhesion is good even if the film is thin. It becomes possible to form a pressure-sensitive adhesive layer having

In addition, the acrylic partial polymer may contain an acrylic monomer (A) as a structural unit. In this case, the proportion of the acrylic monomer (A) in the total amount of 100% by mass of all the monomer components constituting the partially polymerized product is not particularly limited, but is preferably 3% by mass or more, more preferably 10% by mass. % by mass or more. The ratio is preferably 40% by mass or less, more preferably 30% by mass or less.

The acrylic oligomer preferably has a weight average molecular weight of 2,500 to 10,000, more preferably 3,000 to 8,000. In addition, the said weight average molecular weight can be calculated|required by polystyrene conversion by GPC method. For example, it can be measured under the following conditions using a high-speed GPC apparatus "HPLC-8120GPC" manufactured by Tosoh Corporation.
Column: TSKgel SuperHZM-H/HZ4000/HZ3000/HZ2000
Solvent: Tetrahydrofuran Flow rate: 0.6 ml/min

The above acrylic oligomer contains an acrylic monomer as a structural unit. The acrylic oligomer preferably contains an acrylic monomer (A) as a structural unit. The acrylic monomer contained as the structural unit may be of one type or two or more types.

The acrylic monomer (A) accounts for preferably 40% by mass or more, more preferably 50% by mass or more, and still more preferably 55% by mass in the total amount of 100% by mass of all monomer components constituting the acrylic oligomer. % by mass or more. The ratio is preferably 90% by mass or less, more preferably 80% by mass or less.

The acrylic oligomer preferably contains a (meth)acrylic acid alkyl ester (B) as a structural unit. As the (meth)acrylic acid alkyl ester (B), methyl methacrylate (MMA) is preferable. The proportion of the (meth)acrylic acid alkyl ester (B) in all monomer components constituting the acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more. The proportion is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. Further, the acrylic oligomer may contain the copolymerizable monomer as a structural unit.

The content of the acrylic oligomer is preferably 0.5 to 35 parts by mass, more preferably 2 parts by mass, with respect to the total amount of 100 parts by mass of the acrylic polymer (C) and/or the acrylic partial polymer. to 20 parts by mass, more preferably 4 to 10 parts by mass. When the content is within the above range, the storage elastic modulus G' tends to be high and the breaking stress tends to be high, resulting in better reworkability.

The acrylic polymer and the acrylic polymer (C) are obtained by polymerizing a composition containing one or more selected from the group consisting of the acrylic partial polymer, the acrylic oligomer, and the monomer component (D). be done. These polymerization methods are not particularly limited, but include, for example, a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a thermal polymerization method, and a polymerization method by active energy ray irradiation (active energy ray polymerization method). Among them, the bulk polymerization method, the thermal polymerization method, and the active energy ray polymerization method are preferable from the viewpoints of the transparency of the pressure-sensitive adhesive layer and the cost.

In addition, various general solvents may be used in the polymerization of the above-mentioned monomer components. Examples of the solvent include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; cyclohexane, methylcyclohexane and the like. alicyclic hydrocarbons; and organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. In addition, a solvent may use only 1 type, and may use 2 or more types.

Upon polymerization of the above-mentioned monomer components, etc., a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator) may be used depending on the type of polymerization reaction. In addition, a polymerization initiator may use only 1 type, and may use 2 or more types.

The thermal polymerization initiator is not particularly limited. , benzoyl peroxide, hydrogen peroxide, etc.), substituted ethane-based initiators such as phenyl-substituted ethane, aromatic carbonyl compounds, redox-based polymerization initiators, and the like. Among them, the azo polymerization initiator disclosed in JP-A-2002-69411 is preferable. Examples of the azo polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis(2-methylpropionate)dimethyl, 4,4'-azobis-4-cyanovaleric acid and the like. The amount of the thermal polymerization initiator to be used may be a normal amount, for example, 0.005 to 1 part by mass, preferably 0.01 to 1 part by mass based on 100 parts by mass of the monomer component. can do.

The photopolymerization initiator is not particularly limited. Examples include active 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 photopolymerization initiators and titanocene photopolymerization initiators. Examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, anisole methyl ether and the like. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, 4-(t-butyl ) and dichloroacetophenone. Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like. be done. Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of the benzoin-based photopolymerization initiator include benzoin. Examples of the benzyl-based photopolymerization initiator include benzyl. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, and the like. Examples of the ketal photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of the acylphosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. . Examples of the titanocene photopolymerization initiator include bis(η ⁵ -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl ) and titanium. The amount of the photopolymerization initiator used may be a normal amount, for example, 0.01 to 3 parts by mass, preferably 0.1 to 1.5 parts by mass with respect to 100 parts by mass of the monomer component. You can choose from

The above acrylic polymer may be crosslinked with a crosslinking agent. By using a cross-linking agent, it is possible to form a cross-linked structure in the acrylic polymer in the acrylic pressure-sensitive adhesive layer and control the gel fraction. The cross-linking agent is appropriately selected according to the functional groups in the side chains of the acrylic partial polymer, for example. As the above-mentioned cross-linking agent, only one kind of the above-mentioned cross-linking agent may be used, or two or more kinds thereof may be used.

The cross-linking agent is not particularly limited. cross-linking agent, metal salt cross-linking agent, carbodiimide cross-linking agent, oxazoline cross-linking agent, aziridine cross-linking agent, amine cross-linking agent, hydrazine cross-linking agent, silicone cross-linking agent, silane cross-linking agent (silane coupling agent), etc. mentioned.

The content of the cross-linking agent is not particularly limited, but is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass with respect to 100 parts by mass of the total amount of the monomer components constituting the acrylic polymer. parts, particularly preferably 0.5 to 10 parts by mass.

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

Examples of the 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 hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate and the like.

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

Examples of the aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, and 2,2′-diphenylmethane diisocyanate. , 4,4′-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4′-diisocyanate, 2,2′-diphenylpropane-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate , 4,4′-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3′-dimethoxydiphenyl-4,4′-diisocyanate , xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, and the like.

Examples of the isocyanate-based cross-linking agent include trimethylolpropane/tolylene diisocyanate adduct (trade name “Coronate L”, manufactured by Tosoh Corporation), trimethylolpropane/hexamethylene diisocyanate adduct (trade name “Coronate HL ”, manufactured by Tosoh Corporation), trimethylolpropane/xylylene diisocyanate adduct (trade name “Takenate D-110N”, manufactured by Mitsui Chemicals, Inc.).

In addition, in the aqueous dispersion of the modified acrylic polymer prepared by emulsion polymerization, it is not necessary to use an isocyanate-based cross-linking agent. agents can also be used.

The content of the isocyanate-based cross-linking agent when using the isocyanate-based cross-linking agent as the cross-linking agent is not particularly limited, but is 0.5 parts by mass with respect to 100 parts by mass of the total amount of the monomer components constituting the acrylic polymer. The above is preferable, more preferably 1 part by mass or more, and still more preferably 1.5 parts by mass or more. The 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.

Examples of the epoxy-based cross-linking agent (polyfunctional epoxy compound) include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidyl aminomethyl)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, sorbitol polyglycidyl ether , glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipate diglycidyl ester, o-phthalate diglycidyl ester, triglycidyl-tris(2 -hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Moreover, as said epoxy-type crosslinking agent, the commercial item, such as a brand name "Tetrad C" (made by Mitsubishi Gas Chemical Company, Inc.), is mentioned, for example.

Although the content of the epoxy-based cross-linking agent when using the epoxy-based cross-linking agent as the cross-linking agent is not particularly limited, it exceeds 0 parts by mass with respect to the total amount of 100 parts by mass of the monomer components constituting the acrylic polymer. is preferably 1 part by mass or less, more preferably 0.001 to 0.5 parts by mass, still more preferably 0.002 to 0.2 parts by mass, still more preferably 0.005 to 0.1 parts by mass, particularly preferably It is 0.008 to 0.05 parts by mass.

As the above-mentioned peroxide-based cross-linking agent, any one that generates radical active species by heat and promotes cross-linking of the base polymer can be used as appropriate. It is preferred to use a peroxide with a temperature of 80-160°C, more preferably a peroxide with a temperature of 90-140°C.

Examples of the peroxide-based crosslinking agent include di(2-ethylhexyl) peroxydicarbonate (1-minute half-life temperature: 90.6° C.), di(4-t-butylcyclohexyl) peroxydicarbonate (1 minute half-life temperature: 92.1 ° C.), di-sec-butyl peroxydicarbonate (1 minute half-life temperature: 92.4 ° C.), t-butyl peroxyneodecanoate (1 minute half-life temperature: 103 .5 ° C.), t-hexyl peroxypivalate (1 minute half-life temperature: 109.1 ° C.), t-butyl peroxypivalate (1 minute half-life temperature: 110.3 ° C.), dilauroyl peroxide ( 1 minute half-life temperature: 116.4° C.), di-n-octanoyl peroxide (1 minute half-life temperature: 117.4° C.), 1,1,3,3-tetramethylbutylperoxy-2-ethyl Hexanoate (1 minute half-life temperature: 124.3 ° C.), di (4-methylbenzoyl) peroxide (1 minute half-life temperature: 128.2 ° C.), dibenzoyl peroxide (1 minute half-life temperature: 130. 0° C.), t-butyl peroxyisobutyrate (1 minute half-life temperature: 136.1° C.), 1,1-di(t-hexylperoxy)cyclohexane (1 minute half-life temperature: 149.2° C.) etc.

The half-life of the peroxide-based cross-linking agent is an index that represents the decomposition rate of the peroxide, and refers to the time it takes for the residual amount of the peroxide to halve. The decomposition temperature for obtaining a half-life at an arbitrary time and the half-life time at an arbitrary temperature are described in the manufacturer's catalog etc. For example, NOF Corporation's "Organic Peroxide Catalog 9th Edition (May 2003)”. In addition, as a method for measuring the residual peroxide decomposition amount after the reaction treatment, for example, HPLC (high performance liquid chromatography) can be used. More specifically, for example, about 0.2 g of the adhesive after reaction treatment is taken out, immersed in 10 ml of ethyl acetate, extracted with a shaker at 25° C. and 120 rpm for 3 hours, and then extracted at room temperature for 3 hours. Allow to stand for days. Next, 10 ml of acetonitrile is added, shaken at 120 rpm at 25° C. for 30 minutes, and about 10 μl of the extract obtained by filtering through a membrane filter (0.45 μm) is injected into HPLC for analysis. It can be a peroxide amount.

The content of the cross-linking agent when a peroxide-based cross-linking agent is used as the cross-linking agent is not particularly limited. preferably 0.02 to 2 parts by mass, more preferably 0.05 to 1 part by mass.

Also, as the cross-linking agent, an organic cross-linking agent or a polyfunctional metal chelate may be used in combination. Polyfunctional metal chelates are those in which polyvalent metals are covalently or coordinately bonded to organic compounds. 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. mentioned. Atoms in the organic compounds that are covalently or coordinately bonded include oxygen atoms, and the organic compounds include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds, and the like.

Among them, it is preferable that the above-mentioned cross-linking agent includes an isocyanate-based cross-linking agent. Further, it is more preferable to contain another cross-linking agent together with the isocyanate-based cross-linking agent. As the other cross-linking agent, an epoxy-based cross-linking agent is preferable. When such a cross-linking agent is used, a combination with the above-mentioned acrylic polymer (in particular, a combination with the preferred acrylic polymer described above) can provide a pressure-sensitive adhesive layer that is thin but has excellent adhesion.

The adhesive layer of the present invention preferably further contains a tackifying resin. With a tackifying resin, the adhesive layer tends to have better adhesion even though it is thinner. When the pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer and a tackifying resin, it has excellent adhesion to the adherend and is more difficult to peel off.

Examples of the tackifying resin include phenol-based tackifying resins, terpene-based tackifying resins, rosin-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, and elastomer-based tackifying resins. resins, ketone-based tackifying resins, and the like. Other examples of the tackifier resin include low polymers of (meth)acrylic acid alkyl esters such as low polymers of dicyclopentanyl methacrylate (DCPMA) and methyl methacrylate (MMA). Only one type of the tackifying resin may be used, or two or more types may be used.

Examples of the phenol-based tackifier resin include terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, and rosin phenol resins. The terpene phenol resin is a polymer containing a terpene residue and a phenol residue, and is a copolymer of a terpene and a phenol compound (terpene-phenol copolymer resin), a homopolymer or a copolymer of a terpene. Phenol-modified ones (phenol-modified terpene resins) can be mentioned. Examples of terpenes constituting the terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (d-form, l-form, d/l-form (dipentene), etc.). The above hydrogenated terpene phenol resin is a resin having a structure obtained by hydrogenating the above terpene phenol resin. The above alkylphenol resin is a resin (oily phenolic resin) obtained from alkylphenol and formaldehyde. Examples of the alkylphenol resin include novolac type and resol type. The rosin phenol resin is a phenol-modified rosin or various rosin derivatives described later. The rosin phenol resin can be obtained, for example, by adding phenol to rosins or various rosin derivatives described later with an acid catalyst and thermally polymerizing them.

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

The rosin-based tackifying resins include rosins and rosin derivative resins. Examples of the rosins include unmodified rosins (fresh rosins) such as gum rosin, wood rosin and tall oil rosin; disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.). Examples of the rosin derivative resin include derivatives of the above rosins. Examples of the rosin derivative resin include rosin esters such as an unmodified rosin ester that is an ester of an unmodified rosin and an alcohol, and a modified rosin ester that is an ester of a modified rosin and an alcohol; Unsaturated fatty acid-modified rosins modified with fatty acids; Unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; Rosins or rosin alcohols obtained by reducing the carboxy groups of the above rosin derivatives; Rosins Alternatively, metal salts of the various rosin derivatives described above may be used. Specific examples of the rosin esters include unmodified rosin or modified rosin methyl ester, triethylene glycol ester, glycerin ester, pentaerythritol ester, and the like.

Examples of the hydrocarbon-based tackifying resin include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, and aliphatic/aromatic petroleum resins (styrene-olefin copolymers, etc.). , aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone-indene-based resins.

The content of the tackifying resin in the pressure-sensitive adhesive layer of the present invention is not particularly limited, but for example, 1 part by mass or more (for example, 1 to 100 parts by mass), preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more. When the content is 1 part by mass or more, even if the pressure-sensitive adhesive layer is thin, it has even better adhesion. The content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, from the viewpoint of excellent heat-resistant cohesive strength.

The adhesive layer of the present invention may contain fillers. Addition of a filler tends to further improve impact resistance. Only one type of the filler may be used, or two or more types may be used.

The shape of the filler is not particularly limited, and a particulate or fibrous filler can be used. Among them, a particulate form is preferable. The filler may be either an organic substance or an inorganic substance.

Examples of materials constituting the above inorganic substances include metals such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, and stainless steel; aluminum oxide, silicon oxide (silicon dioxide), titanium oxide, zirconium oxide, and zinc oxide. , tin oxide, copper oxide, nickel oxide and other metal oxides; aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide, zirconium oxide water hydrates, tin oxide hydrates, basic magnesium carbonate, hydrotalcite, dawsonite, borax, zinc borate and other metal hydroxides and hydrated metal compounds; silicon carbide, boron carbide, nitrogen carbide, calcium carbide, etc. Carbide; nitrides such as aluminum nitride, silicon nitride, boron nitride, gallium nitride; carbonates such as calcium carbonate; titanates such as barium titanate and potassium titanate; carbon black, carbon tube (carbon nanotube), carbon fiber , carbonaceous materials such as diamond; inorganic materials such as glass; natural raw material particles such as volcanic shirasu, clay, sand, and the like.

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

The filler may have a hollow body structure. The hollow portion (internal space of the hollow particles) of the filler having the hollow body structure 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.

As the filler, among others, a filler whose surface is composed of an organic or inorganic substance other than an acrylic resin and a filler having a hollow body structure are preferable. These fillers have little interaction with the acrylic component in the acrylic pressure-sensitive adhesive layer or have a hollow body structure, so that the pressure-sensitive adhesive layer is less likely to break when stretched, and is more excellent in reworkability.

The average particle diameter 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 still more preferably 10 μm or more. When the average particle diameter is within the above range, the pressure-sensitive adhesive layer can have an appropriate hardness. As a result, the apparent cohesive strength of the pressure-sensitive adhesive layer is increased, the breaking stress and breaking strain are within appropriate ranges, and the impact resistance and reworkability can be further improved. In addition, the said average particle diameter is a median diameter (D50) measured by a dynamic light-scattering method.

The content of the filler in the pressure-sensitive 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, with respect to 100 parts by mass as the total amount of the base polymer. More preferably, it is 0.4 to 6 parts by mass. When the content is 30 parts by mass or less, the breaking stress and breaking strain are within appropriate ranges, and both impact resistance and reworkability are excellent.

The proportion of the filler in the adhesive layer of the present invention is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, relative to 100% by mass of the total amount of the adhesive layer. When the above ratio is within the above range, the hardness of the pressure-sensitive adhesive layer can be made appropriate. Moreover, it is excellent in reworkability.

The adhesive layer of the present invention may contain a coloring agent. The pressure-sensitive adhesive layer is colored by containing a coloring agent, and the double-sided pressure-sensitive adhesive sheet of the present invention is excellent in 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. A black colorant is preferable from the viewpoint of better visibility and light-shielding properties. The coloring agent may contain only one kind, or may contain two or more kinds. The proportion of the coloring agent in the pressure-sensitive adhesive layer of the present invention is preferably 0.5 to 10% by weight, more preferably 1 to 6% by weight, based on 100% by weight of the total amount of the pressure-sensitive adhesive layer.

Examples of black colorants include carbon black, carbon nanotubes, graphite (graphite), copper oxide, manganese dioxide, azo pigments such as azomethine azo black, aniline black, perylene black, titanium black, cyanine black, activated carbon, and ferrite. , magnetite, chromium oxide, iron oxide, molybdenum disulfide, complex oxide-based black dyes, 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. As a black colorant, C.I. I. Solvent Black 3, 7, 22, 27, 29, 34, 43, 70; C.I. I. Direct Black 17, 19, 22, 32, 38, 51, 71; C.I. I. Acid Black 1, 2, 24, 26, 31, 48, 52, 107, 109, 110, 119, 154; C.I. I. Disperse Black 1, 3, 10, 24; C.I. I. Pigment Black 1 and Pigment Black 7 are also included.

As a cyan colorant, for example, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95; C.I. I. Acid Blue 6, 45; C.I. I. 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; C.I. I. Bat Blue 4; 60, C.I. I. Pigment Green 7 and the like.

As a magenta colorant, for example, C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 52, 58, 63, 81, 82, 83, 84, 100, 109, 111, 121, 122; C.I. I. disperse thread 9;C. I. Solvent Violet 8, 13, 14, 21, 27; C.I. I. Disperse Violet 1; C.I. I. Basic red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; C.I. I. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28 and the like. Examples of magenta colorants include C.I. I. 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, 48:2, 48:3, 48:4, 49, 49:1, 50, 51, 52, 52:2, 53:1, 54, 55, 56, 57:1, 58, 60, 60:1, 63, 63:1, 63:2, 64, 64:1, 67, 68, 81, 83, 87, 88, 89, 90, 92, 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, 193, 202, 206, 207, 209, 219, 222, 224, 238, 245; I. Pigment Violet 3, 9, 19, 23, 31, 32, 33, 36, 38, 43, 50; C.I. I. Batred 1, 2, 10, 13, 15, 23, 29, 35 and the like.

Examples of yellow colorants include C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162; I. Pigment Orange 31, 43; C.I. I.

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, 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; I. Bat Yellow 1, 3, 20 and the like.

The pressure-sensitive adhesive layer of the present invention may optionally further contain a cross-linking accelerator, an anti-aging agent, an antioxidant, a plasticizer, a softening agent, a surfactant, an antistatic agent, a surface lubricant, a leveling agent, and a light stabilizer. Additives such as agents, ultraviolet absorbers, polymerization inhibitors, foil-like materials, and rust preventives may be contained within a range that does not impair the effects of the present invention. Only one kind of the above additives may be used, or two or more kinds thereof may be used.

The pressure-sensitive adhesive layer of the present invention has a tan δ peak top between -20 and 0°C, as described above. The peak top value is 0.8 or more, preferably 1.2 or more, and more preferably 1.5 or more. Having a peak top of tan δ between −20 and 0° C. provides excellent impact resistance when, for example, a member to which a double-sided pressure-sensitive adhesive sheet is applied is dropped at high speed. When the peak top value is 0.8 or more, the impact resistance and reworkability are further improved.

The adhesive layer of the present invention preferably has a storage modulus G' at 23°C of 0.09 MPa or more, more preferably 0.10 MPa or more, and still more preferably 0.15 MPa or more. When the storage elastic modulus G' is 0.09 MPa or more, it has an appropriate hardness at room temperature and is more excellent in reworkability. The storage elastic modulus G' is preferably 0.25 MPa or less. The storage modulus G' can be calculated using a dynamic viscoelasticity measurement (DMA) device.

The pressure-sensitive adhesive layer of the present invention may be in any form, such as an emulsion type, a solvent type (solution type), an active energy ray-curable type, or a heat-melting type (hot-melt type). Among them, solvent-type and active-energy-ray-curable adhesive compositions are preferred because they facilitate the formation of an adhesive layer with excellent productivity.

Examples of the active energy rays include ionizing radiation such as α-rays, β-rays, γ-rays, neutron beams and electron beams, and ultraviolet rays, with ultraviolet rays being particularly preferred. That is, the active energy ray-curable pressure-sensitive adhesive layer is preferably an ultraviolet-curable pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer of the present invention can be formed, for example, by applying (coating) a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer onto a release liner and drying and curing the resulting pressure-sensitive adhesive composition layer, or It can be produced by applying (coating) the pressure-sensitive adhesive composition onto a release liner and irradiating the resulting pressure-sensitive adhesive composition layer with active energy rays to cure it. Moreover, you may heat-dry further as needed.

The pressure-sensitive adhesive composition (acrylic pressure-sensitive adhesive composition) forming the pressure-sensitive adhesive layer of the present invention includes, for example, an acrylic pressure-sensitive adhesive composition containing an acrylic polymer as an essential component, or the acrylic partial polymer, An acrylic pressure-sensitive adhesive composition containing, as an essential component, the above-mentioned acrylic oligomer or a monomer mixture containing the above-mentioned acrylic monomer can be used. The former includes, for example, a so-called solvent-type acrylic pressure-sensitive adhesive composition. Also. Examples of the latter include so-called active energy ray-curable acrylic pressure-sensitive adhesive compositions.

The pressure-sensitive adhesive composition preferably contains an acrylic polymer (C) and/or an acrylic partial polymer, and may further contain the acrylic oligomer. Preferably, the pressure-sensitive adhesive composition further contains a cross-linking agent. In addition, it may contain a tackifying resin, a filler, a coloring agent, and the like.

(Double-sided adhesive sheet)
The double-sided pressure-sensitive adhesive sheet of the invention is composed of the pressure-sensitive adhesive layer of the invention. The thickness of the double-sided pressure-sensitive adhesive sheet is 500 μm or less, preferably 300 μm or less, more preferably 200 μm or less. When the thickness is 500 µm or less, the thickness of the double-sided pressure-sensitive adhesive sheet can be reduced. The thickness of the double-sided pressure-sensitive adhesive sheet is preferably over 10 μm, more preferably 30 μm or more, and even more preferably 50 μm or more. When the thickness is more than 10 µm, the impact resistance and reworkability are more excellent. The thickness of the double-sided pressure-sensitive adhesive sheet refers to the thickness from one pressure-sensitive adhesive surface to the other pressure-sensitive adhesive surface, that is, the thickness of the pressure-sensitive adhesive body, and does not include the release liner.

The breaking stress of the double-sided pressure-sensitive adhesive sheet of the present invention is preferably 0.9 MPa or more, more preferably 1.0 MPa or more. When the breaking stress is 0.9 MPa or more, the pressure-sensitive adhesive layer is less likely to break when stretched, and is more excellent in reworkability. The breaking stress is preferably 3.0 MPa or less, more preferably 2.0 MPa or less. The above breaking stress is a value measured under the conditions of a sample size of 40 mm×40 mm, a thickness of about 0.2 mm, a distance between chucks of 10 mm, and a tensile speed of 50 mm/min under an environment of 23° C. and 50% RH.

The breaking strain of the double-sided pressure-sensitive 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 pressure-sensitive adhesive layer is less likely to break when stretched, and is more excellent in reworkability. The breaking strain is a value measured under the conditions of a sample size of 40 mm×40 mm, a thickness of about 0.2 mm, a distance between chucks of 10 mm, and a tensile speed of 50 mm/min, under an environment of 23° C. and 50% RH.

The double-sided pressure-sensitive adhesive sheet of the present invention preferably has an energy (load x height) before one of the stainless steel plates is peeled off, as measured by the following DuPont impact test, and is preferably 0.1 or more. It is preferably 0.2 or more, more preferably 0.3 or more.
<Shock resistance test>
A frame-shaped double-sided adhesive sheet with an outer diameter of 24.5 mm square and a width of 2 mm was placed on a stainless steel plate with a hole in the center of a square with an outer diameter of 2 mm and an outer diameter of 50 mm, and a stainless steel plate with a square with an outer diameter of 3 mm and an outer diameter of 25 mm. It is sandwiched between plates and pressed, left to stand in an environment at a temperature of 50° C. for 2 hours, and then returned to room temperature to obtain an evaluation sample. Using a DuPont impact tester, the weight and height of the drop weight on the above evaluation sample were changed by 50 mm from 50 to 500 mm at 100 g, changed by 50 mm from 350 to 500 mm at 150 g, and 400 to 500 mm at 200 g. At 300 g, the energy is changed by 50 mm from 350 to 500 mm, and the energy is increased until peeling occurs. At this time, the energy that has already been evaluated is not tested, and the load and height are set so that the amount of energy does not overlap. After that, the energy until at least one of the stainless steel plates peels off is calculated by multiplying the load by the height.

The double-sided pressure-sensitive adhesive sheet may have a release liner attached to the surface (adhesive surface) of the pressure-sensitive adhesive layer until use. The adhesive surfaces on both sides of the double-sided pressure-sensitive adhesive sheet may be protected by two release liners, respectively, or one release liner having release surfaces on both sides is wound into a roll. It may be protected in a form (wound body). A release liner is used as a protective material for the pressure-sensitive adhesive layer, and is peeled off when applied to an adherend. Note that the release liner may not necessarily be provided.

As the release liner, a conventional release paper or the like can be used, and is not particularly limited. etc. Examples of the base material having the release treatment layer include plastic films and paper surface-treated with release agents such as silicone, long-chain alkyl, fluorine, and molybdenum sulfide. Examples of the fluorine-based polymer in the low-adhesive substrate made of the fluorine polymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chloro fluoroethylene-vinylidene fluoride copolymer and the like. Examples of the non-polar polymer include olefin resins (eg, polyethylene, polypropylene, etc.). The release liner can be formed by a known or commonly used method. Also, the thickness of the release liner is not particularly limited.

The double-sided pressure-sensitive adhesive sheet is preferably for attaching to electrical and electronic members, which is used by being attached to members provided in electrical and electronic equipment. The above-mentioned double-sided pressure-sensitive adhesive sheet is particularly preferably used for bonding parts provided in electrical and electronic equipment to both adhesive surfaces of the double-sided pressure-sensitive adhesive sheet, i.e., for fixing members to each other in electrical and electronic equipment. . The double-sided pressure-sensitive adhesive sheet may be used for fixing the members together or temporarily fixing them. For example, when a double-sided adhesive sheet is used for fixing or temporarily fixing parts provided in electrical and electronic equipment, there are cases in which it is necessary to peel off the double-sided adhesive sheet and rework due to a problem in attaching the double-sided adhesive sheet. Also, there are cases where the double-sided pressure-sensitive adhesive sheet must be peeled off in order to repair, replace, inspect, recycle, or the like a member having an adherend to which the double-sided pressure-sensitive adhesive sheet is attached. Thus, when the double-sided pressure-sensitive adhesive sheet is used, for example, for fixing or temporarily fixing parts (members) provided in electrical and electronic equipment, the frequency of removing the double-sided pressure-sensitive adhesive sheet is particularly high.

The above-mentioned double-sided pressure-sensitive adhesive sheet is preferably used by pasting the outer frames of optical members (especially electrical and electronic devices) together. Therefore, the double-sided pressure-sensitive adhesive sheet can be preferably used even if it has a width of 5 mm or less, preferably 3 mm or less.

"Electrical and electronic equipment" refers to equipment that corresponds to at least either electrical equipment or electronic equipment. Examples of the electric/electronic devices include image display devices such as liquid crystal displays, electroluminescence displays, and plasma displays, and mobile electronic devices.

Examples of the portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, and various wearable devices (for example, wrist wear types that are worn on the wrist like wristwatches, clips, straps, etc. that are attached to a part of the body) Modular type to be worn, eyewear type including eyeglass type (monocular type and binocular type, including head-mounted type), clothing type that can be attached to shirts, socks, hats, etc. in the form of accessories, ears such as earphones earwear type, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information equipment, Examples include portable radios, portable televisions, portable printers, portable scanners, and portable modems. In this specification, the term “portable” means not only being able to be carried but also having a level of portability that allows individuals (standard adults) to relatively easily carry it. shall mean. The double-sided pressure-sensitive adhesive sheet is used, for example, so that the pressure-sensitive adhesive layer adheres to the member of the portable electronic device.

Although the present invention will be described in more detail below with reference to examples, the present invention is not limited by these examples.

Production Example 1: Synthesis of Acrylic Oligomer (1) In a flask, dicyclopentanyl methacrylate (DCPMA, Tg: 175°C): 60 parts by mass, methyl methacrylate (MMA): 40 parts by mass, α-thioglycerol: 3 Parts by mass, 2,2'-azobisisobutyronitrile: 0.2 parts by mass, and ethyl acetate: 65 parts by mass were added. After the flask was fully filled with nitrogen and polymerized at 70° C. for 5 hours, 0.1 part by mass of 2,2′-azobisisobutyronitrile was added and polymerized at 80° C. for 8 hours. Thereafter, ethyl acetate was distilled off from the reaction solution, and the residue was dried with a vacuum dryer to obtain an acrylic oligomer (weight average molecular weight: 5080).

Production Example 2: Synthesis of Acrylic Oligomer (2) In a flask, dicyclopentenyl acrylate (Tg: 97°C): 60 parts by mass, methyl methacrylate (MMA): 40 parts by mass, α-thioglycerol: 3 parts by mass, 2,2′-Azobisisobutyronitrile: 0.2 parts by mass and ethyl acetate: 65 parts by mass were charged. After the flask was fully filled with nitrogen and polymerized at 70° C. for 5 hours, 0.1 part by mass of 2,2′-azobisisobutyronitrile was added and polymerized at 80° C. for 8 hours. Thereafter, ethyl acetate was distilled off from the reaction solution, and the residue was dried with a vacuum dryer to obtain an acrylic oligomer (weight average molecular weight: 7600).

Production Example 3: Synthesis of acrylic oligomer (3) Dicyclopentanyl acrylate (DCPA, Tg: about 100°C): 60 parts by mass, methyl methacrylate (MMA): 40 parts by mass, α-thioglycerol: 3 parts by mass, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 65 parts by mass of ethyl acetate were added. After the flask was fully filled with nitrogen and polymerized at 70° C. for 5 hours, 0.1 part by mass of 2,2′-azobisisobutyronitrile was added and polymerized at 80° C. for 8 hours. Thereafter, ethyl acetate was distilled off from the reaction solution, and the residue was dried with a vacuum dryer to obtain an acrylic oligomer (weight average molecular weight: 5900).

Production Example 4: Synthesis of acrylic oligomer (4) Dicyclopentenyloxyethyl acrylate (Tg: about 100°C): 60 parts by mass, methyl methacrylate (MMA): 40 parts by mass, α-thioglycero- 3 parts by mass of mol, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 65 parts by mass of ethyl acetate were added. After the flask was fully filled with nitrogen and polymerized at 70° C. for 5 hours, 0.1 part by mass of 2,2′-azobisisobutyronitrile was added and polymerized at 80° C. for 8 hours. Thereafter, ethyl acetate was distilled off from the reaction solution, and the residue was dried with a vacuum dryer to obtain an acrylic oligomer (weight average molecular weight: 3000).

Production Example 5: Synthesis of Acrylic Oligomer (5) In a flask, cyclohexyl methacrylate (Tg: 66°C): 60 parts by mass, methyl methacrylate (MMA): 40 parts by mass, α-thioglycerol: 3 parts by mass , 2,2′-azobisisobutyronitrile: 0.2 parts by mass, and ethyl acetate: 65 parts by mass were charged. After the flask was fully filled with nitrogen and polymerized at 70° C. for 5 hours, 0.1 part by mass of 2,2′-azobisisobutyronitrile was added and polymerized at 80° C. for 8 hours. Thereafter, ethyl acetate was distilled off from the reaction solution, and the residue was dried with a vacuum dryer to obtain an acrylic oligomer (weight average molecular weight: 3600).

Example 1
A reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser was charged with 68 parts by weight of toluene, 95 parts by weight of butyl acrylate (BA), and 5 parts by weight of acrylic acid (AA). Nitrogen substitution was performed for more than one hour. Add azobisisobutyronitrile as an initiator, then raise the temperature of the inner bath to 62°C, maintain the same temperature, and continue until the reaction is almost complete, then cool to complete the polymerization reaction. let me Polymer obtained: 100 parts by mass, acrylic oligomer (1) obtained in Production Example 1: 5 parts by mass, isocyanate compound (trade name "Coronate L", manufactured by Tosoh Corporation): 5 parts by mass and Epoxy compound (trade name “Tetrad C”, manufactured by Mitsubishi Gas Chemical Co., Ltd.): 0.02 parts by mass is added, and a terpene phenol-based tackifying resin (trade name “YS Polystar T115”, manufactured by Yasuhara Chemical Co., Ltd.): 20 Parts by mass, and a black pigment containing carbon black (trade name “Multilac A903”, manufactured by Toyocolor Co., Ltd.): 6 parts by mass were added to prepare an adhesive composition.

The pressure-sensitive adhesive composition is coated on a release-treated layer of a 38 μm-thick polyethylene terephthalate film (product name “MRF #38”, manufactured by Mitsubishi Chemical Corporation) whose one side has been release-treated with silicone, and dried. A double-sided pressure-sensitive adhesive sheet of Example 1 was produced by forming a pressure-sensitive adhesive layer of 200 μm.

Example 2
The polymer prepared in Example 1: 100 parts by mass, the acrylic oligomer (1) obtained in Production Example 1: 2.5 parts by mass, an isocyanate cross-linking agent (trade name "Coronate L", Tosoh Corporation ): 5 parts by mass, and an epoxy cross-linking agent (trade name “Tetrad C”, manufactured by Mitsubishi Gas Chemical Co., Ltd.): 0.02 parts by mass, and a terpene phenol-based tackifying resin (trade name “YS Polyster T115", manufactured by Yasuhara Chemical Co., Ltd.): 20 parts by mass, polyethylene powder as a filler (trade name "Flosen UF-80", manufactured by Sumitomo Seika Co., Ltd.): 2 parts by mass, and a black pigment containing carbon black (trade name "Multilac A903", manufactured by Toyocolor Co., Ltd.): 6 parts by mass were added to obtain an adhesive composition.

A double-sided PSA sheet of Example 2 was produced in the same manner as in Example 1, except that the PSA composition obtained above was used.

Examples 3-7
A double-sided pressure-sensitive adhesive sheet of each example was prepared in the same manner as in Example 2 except that the amount of the acrylic oligomer (1) obtained in Production Example 1 or the thickness of the pressure-sensitive adhesive layer was changed as shown in Table 1. made.

Example 8
As monomer components, butyl acrylate (BA): 70 parts by mass, acrylic acid (AA): 5 parts by mass, and isobornyl acrylate (IBXA, Tg: 97 ° C.): 25 parts by mass were mixed into a liquid monomer mixture ( monomer composition), 2,2-dimethoxy-1,2-diphenylethan-1-one (trade name “OMNIRAD651”, manufactured by IGM Resins B.V.) as a photopolymerization initiator: 0.05 parts by mass After blending, the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature: 30 ° C.) was pulsed with ultraviolet light until it reached about 15 Pa s, and a partial polymer (polymerization yield: about 8%) was obtained (partially polymerized product).

Syrup obtained above: 100 parts by mass, isocyanate cross-linking agent (trade name "Coronate L", manufactured by Tosoh Corporation): 5 parts by mass, and epoxy cross-linking agent (trade name "Tetrad C", Mitsubishi Gas Chemical Co., Ltd.): 0.02 parts by mass, and further terpene phenolic tackifier resin (trade name “YS Polyster T115”, manufactured by Yasuhara Chemical Co., Ltd.): 20 parts by mass, polyethylene powder as a filler (trade name “Flosen UF-80", manufactured by Sumitomo Seika Co., Ltd.): 2 parts by mass, and a black pigment containing carbon black (trade name "Multilac A903", manufactured by Toyocolor Co., Ltd.): After adding 6 parts by mass, disper It was mixed uniformly using the above, and then defoamed to obtain an acrylic pressure-sensitive adhesive composition.

The resulting acrylic pressure-sensitive adhesive composition was coated on a 38-μm-thick polyethylene terephthalate film (product name “MRF#38”, manufactured by Mitsubishi Chemical Corporation) whose one side was treated with silicone for release, and the pressure-sensitive adhesive layer thickness was 200 μm. was applied using an applicator to form a coating layer.

Next, a 25 μm-thick polyethylene terephthalate film (product name “MRE #25”, manufactured by Mitsubishi Chemical Corporation) whose one side was release-treated with silicone was coated with the coating layer so that the release-treated surface was on the side of the coating layer. , oxygen was cut off. After that, from the upper surface of this film, a black light lamp was used to irradiate ultraviolet rays with an illuminance of 4 mW/cm ² (UV checker "UVR-T1", manufactured by Topcon Corporation, maximum sensitivity at measurement: about 350 nm) for 180 seconds. A pressure-sensitive adhesive layer having a thickness of 200 μm was formed to prepare a double-sided pressure-sensitive adhesive sheet.

Example 9
The acrylic oligomer (1) obtained in Production Example 1: The same as in Example 2 except that 5 parts by mass of the acrylic oligomer (2) obtained in Production Example 2 was used in place of 2.5 parts by mass. A double-sided pressure-sensitive adhesive sheet of Example 9 was prepared.

Example 10
The acrylic oligomer (1) obtained in Production Example 1: The same as in Example 2 except that 5 parts by mass of the acrylic oligomer (3) obtained in Production Example 3 was used in place of 2.5 parts by mass. A double-sided pressure-sensitive adhesive sheet of Example 10 was produced.

Example 11
Same as Example 2, except that 5 parts by mass of the acrylic oligomer (4) obtained in Production Example 4 was used in place of 2.5 parts by mass of the acrylic oligomer (1) obtained in Production Example 1. A double-sided pressure-sensitive adhesive sheet of Example 11 was prepared.

Comparative example 1
A double-sided pressure-sensitive adhesive sheet of Comparative Example 1 was produced in the same manner as in Example 2, except that the acrylic oligomer (1) obtained in Production Example 1 was not blended.

Comparative example 2
A double-sided pressure-sensitive adhesive sheet of Comparative Example 2 was produced in the same manner as in Example 2, except that the amount of the acrylic oligomer (1) obtained in Production Example 1 was changed to 40 parts by mass.

Comparative example 3
An acrylic pressure-sensitive adhesive composition was prepared in the same manner as in Example 2, except that the amount of the acrylic oligomer (1) obtained in Production Example 1 was changed to 5 parts by mass.
The pressure-sensitive adhesive composition is coated on a release-treated layer of a 38 μm-thick polyethylene terephthalate film (product name “MRF #38”, manufactured by Mitsubishi Chemical Corporation) whose one side has been release-treated with silicone, and dried. A 178 μm adhesive layer was formed.
Then, the release liner (trade name “MRE #25”, manufactured by Mitsubishi Chemical Corporation) provided on the surface of the prepared adhesive layer is peeled off to expose the adhesive layer, and the PET film (thickness 12 μm) was laminated on the exposed surface of the pressure-sensitive adhesive layer. Thus, a single-sided pressure-sensitive adhesive sheet (thickness: 190 μm) of Comparative Example 3, in which the pressure-sensitive adhesive layer was formed on the substrate layer, was produced.

Comparative example 4
The acrylic oligomer (1) obtained in Production Example 1: The same as in Example 2 except that 5 parts by mass of the acrylic oligomer (5) obtained in Production Example 5 was used in place of 2.5 parts by mass. Then, a double-sided pressure-sensitive adhesive sheet of Comparative Example 4 was produced.

<Evaluation>
The pressure-sensitive adhesive layers and pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in the table. In addition, the compounding quantity of each component in a table|surface shows a mass part.

(1) Measurement of dynamic viscoelasticity A pressure-sensitive adhesive layer having a thickness of about 2 mm was prepared by stacking a plurality of pressure-sensitive adhesive layers prepared in Examples and Comparative Examples. A disk-shaped sample with a diameter of 7.9 mm was punched out of this adhesive layer and fixed by sandwiching it between parallel plates. (manufactured by A Instruments Co., Ltd.), dynamic viscoelasticity was measured under the following conditions, and the peak top value of storage elastic modulus G′ (23° C.) and tan δ was calculated. It was confirmed that all pressure-sensitive adhesive layers had a tan δ peak top within the range of -20 to 0°C.
Measurement mode: Shear mode Temperature range: -70°C to 150°C
Heating rate: 5°C/min
Measurement frequency: 1Hz

(2) Breaking stress and breaking strain The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into a size of 40 mm in width and 40 mm in length to obtain test pieces. In an environment of 23° C. and 50% RH, all the release liners were peeled off to expose the adhesive sheet, and a universal tensile and compression tester (product name “TCM-1kNB” manufactured by Minebea Co., Ltd.) was used to test the distance between chucks of 10 mm. A tensile test was performed on the above test piece at a tensile speed of 50 mm/min to obtain an SS curve, and the stress (breaking stress) and strain (breaking strain) at the breakage of the test piece were measured. During the test, it is preferable to apply powder to the adhesive surface of the portion to be chucked to remove the stickiness of the adhesive.

(3) Impact resistance The double-sided pressure-sensitive adhesive sheets sandwiched between release liners prepared in Examples and Comparative Examples (single-sided pressure-sensitive adhesive sheet provided with a release liner for Comparative Example 3) were placed at an outer diameter of 24 mm. A frame of 5 mm square and 2 mm wide was punched out. After that, the release liner was peeled off from the adhesive sheet and sandwiched between a square stainless steel plate with a thickness of 2 mm and an outer diameter of 50 mm square with a hole in the center and a square stainless steel plate with an outer diameter of 3 mm and an outer diameter of 25 mm square. It was pressure-bonded, allowed to stand in an environment at a temperature of 50° C. for 2 hours, and then returned to room temperature to obtain an evaluation sample. A cylindrical measurement table with a length of 50 mm, an outer diameter of 49 mm, and an inner diameter of 43 mm is installed on the pedestal of a DuPont impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and a test piece is placed on it, a square stainless steel plate. (stainless steel plate without holes) was placed on the bottom side. A stainless steel striking core with a tip radius of 3.1 mm is placed on the test piece, and the weight and height of the falling weight are changed by 50 mm from 50 to 500 mm at 100 g, by 50 mm from 350 to 500 mm at 150 g, and then to 200 g. At 300 g, the energy was changed by 50 mm from 400 to 500 mm, and at 300 g by 50 mm from 350 to 500 mm, the energy was increased until peeling occurred. At this time, no test was performed on the energy that had already been evaluated, and the load and height were set so that the amount of energy would not overlap. After that, the energy until at least one of the stainless steel plates (for Comparative Example 3, the stainless steel plate attached to the adhesive layer) peeled off was calculated by multiplying the load by the height, and the result was obtained.

(4) Reworkability A piece of 10 mm x 50 mm was cut out from each of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples to prepare a sample for evaluation. Then, the release liner (releasing liner on the light release side for the double-sided adhesive sheet) was peeled off from the sample for evaluation, and the adhesive surface of the adhesive sheet was laminated on the stainless steel adherend (2 kg roller x 1 reciprocation). It was stored under heating for a period of time. After that, for the double-sided adhesive sheet, the release liner on the heavy release side was peeled off, the end of the short side was peeled off from the stainless steel plate, and the adhesive sheet was pulled at a peeling angle of 30° to the adherend to try to peel the adhesive sheet. Reworkability was confirmed. Then, reworkability was evaluated according to the following criteria. The reworkability required for practical use is 2 or more, preferably 3 or more in the following criteria.
Rank 1: The tape is torn and cannot be peeled. Rank 2: The tape is not torn and can be peeled off by pulling at a speed of less than 0.2 m/min. Rank 3: The tape is torn by pulling at a speed of 0.2 m/min or more. peelable without

As shown in Table 1, it was confirmed that the double-sided pressure-sensitive adhesive sheet of the present invention is excellent in both impact resistance and reworkability. On the other hand, as shown in Table 2, when the acrylic polymer contained in the double-sided pressure-sensitive adhesive sheet does not contain the acrylic monomer (A) having two or more non-aromatic rings as a structural unit (Comparative Examples 1 and 4). , was inferior in reworkability. Moreover, when the pressure-sensitive adhesive layer had a low tan δ peak top value (Comparative Example 2) and when it had a base layer (Comparative Example 3), the impact resistance was poor and the reworkability was also poor.

1 double-sided adhesive sheet 2 adhesive layers 3, 4 release liner

Claims

A double-sided adhesive sheet comprising an adhesive layer,
The double-sided pressure-sensitive adhesive sheet has a thickness of 500 μm or less,
The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer,
The acrylic polymer contains structural units derived from an acrylic monomer (A) having two or more non-aromatic rings,
The double-sided pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a tan δ peak top between -20 and 0°C, and the peak top value is 0.8 or more.
The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the proportion of structural units derived from the acrylic monomer (A) in the acrylic polymer is 1 to 15% by mass.
Both sides according to claim 1 or 2, wherein the acrylic polymer contains a structural unit derived from a (meth)acrylic acid alkyl ester (B) having a linear or branched alkyl group having 2 to 7 carbon atoms. adhesive sheet.
The double-sided pressure-sensitive adhesive sheet according to claim 3, wherein the (meth)acrylic acid alkyl ester (B) is butyl (meth)acrylate.
The double-sided pressure-sensitive adhesive sheet according to claim 3 or 4, wherein the proportion of structural units derived from the (meth)acrylic acid alkyl ester (B) in the acrylic polymer is 50% by mass or more.
The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the acrylic polymer has a structure derived from an acrylic oligomer.
The double-sided pressure-sensitive adhesive sheet according to claim 6, wherein the acrylic oligomer contains structural units derived from the acrylic monomer (A).
The double-sided pressure-sensitive adhesive sheet according to claim 7, wherein the content of the acrylic oligomer is 0.5 to 30 parts by mass with respect to 100 parts by mass of the total acrylic partial polymer.
The acrylic monomer (A) according to any one of claims 1 to 8, comprising one or more groups selected from the group consisting of a dicyclopentanyl group, a dicyclopentenyl group, and an isobornyl group. Double-sided adhesive sheet.
The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the pressure-sensitive adhesive layer further contains a tackifying resin.
The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 10, which has a breaking stress of 0.9 MPa or more.
The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 11, which has a breaking strain of 60% or more.
The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 12, wherein the storage elastic modulus G' of the pressure-sensitive adhesive layer at 23°C is 0.09 MPa or more.
The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 13, which is for fixing members together in electrical and electronic equipment.
Equipped with the double-sided pressure-sensitive adhesive sheet according to claim 14,
The electric/electronic device, wherein the double-sided pressure-sensitive adhesive sheet fixes the members to each other with both pressure-sensitive adhesive surfaces.