JP7160965B2 - double-sided adhesive sheet - Google Patents

Description

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

In recent years, miniaturization of mobile devices such as mobile phones, digital cameras, and PDAs (Personal Digital Assistants) has progressed. 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 pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive tape) has been devised for use in assembling (bonding) these parts.

As the double-sided pressure-sensitive adhesive sheet, a structure including a pressure-sensitive adhesive layer and release liners laminated on both sides of the pressure-sensitive adhesive layer is sometimes used (see, for example, Patent Document 1).

Like the pressure-sensitive adhesive sheet disclosed in Patent Document 1, in the double-sided pressure-sensitive adhesive sheet, the peel strength between the release liner laminated on one pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer laminated on the other pressure-sensitive adhesive layer The release force between the release liner and the adhesive layer is usually different. This is because the release liner is excellent in release workability. When using such a double-sided pressure-sensitive adhesive sheet, first, the release liner on the side of the double-sided pressure-sensitive adhesive sheet with a smaller release force (light release side) is peeled off and adhered to any member of the adherend, It is used by peeling off the release liner on the side having a large release force (heavy release side) and attaching it to the other member.

JP 2018-127582 A

The release liner may have different release forces depending on the tensile speed (peeling speed) when it is released from the pressure-sensitive adhesive layer. In the product processing line, the processing speed varies depending on the product type, but the speed dependence (tensile speed dependence) when peeling the release liner is possible, such as the fact that it is possible to peel while suppressing the breakage of the adhesive layer in a wide range of speeds. Small is required.

In the case of using a double-sided PSA sheet, the adhesive surface exposed by peeling one release liner is usually attached to one adherend, and then the other release liner is peeled off to bond the exposed adhesive surface. is attached to the other adherend for use. Here, if the one adherend to which the double-sided pressure-sensitive adhesive sheet is attached first is fragile and easily displaced, the one adherend is destroyed by the peeling stress when the other release liner is peeled off. Sometimes. Therefore, when the release liner is peeled off, it is required that the adherend that has already been bonded is less likely to break.

The present invention was conceived under such circumstances, and an object of the present invention is to reduce speed dependency when peeling a release liner and to prevent the destruction of an adherend that has already been bonded. To provide a double-faced pressure-sensitive adhesive sheet which is difficult to

The inventors of the present invention have made intensive studies to achieve the above object, and have found that a double-sided pressure-sensitive adhesive sheet having no base layer and having various physical properties related to the release force of the release liner to the pressure-sensitive adhesive layer within a specific range. It has been found that the pressure-sensitive adhesive sheet has little dependence on the speed when the release liner is peeled off, and the adherend that has already been bonded is less likely to break. The present invention has been completed based on these findings.

That is, the present invention comprises an adhesive layer, a first release liner laminated on one adhesive surface of the adhesive layer, and a second release liner laminated on the other adhesive surface of the adhesive layer. ,
When the first release liner is peeled from the pressure-sensitive adhesive layer at 23° C. and 50% RH at a tensile speed of 10000 mm/min and a peel angle of 180°, the peel force A1 against the adhesive surface is 0.50 N/50 mm or less. and
When the first release liner is peeled from the pressure-sensitive adhesive layer at 23° C. and 50% RH at a tensile speed of 300 mm/min and a peel angle of 180°, the peel force A2 against the adhesive surface is 0.27 N/50 mm or less. and
The difference between the peeling force A1 and the peeling force A2 is 0.22 N/50 mm or less,
The release force A1, and the release force B1 of the second release liner against the adhesive surface when peeled from the adhesive layer at 23° C. and 50% RH at a tensile speed of 10000 mm/min and a peel angle of 180°. difference is higher than 0 N/50 mm and 0.30 N/50 mm or less.

The thickness of the adhesive layer is preferably 100 μm or less.

The thickness of each of the first and second release liners is preferably 10-100 μm.

The peel force B1 is preferably smaller than the peel force A1.

At least one adhesive surface of the pressure-sensitive adhesive layer has a peel strength of 3 N/25 mm or more against a stainless steel plate measured at 23° C. and 50% RH under conditions of a tensile speed of 300 mm/min and a peel angle of 180°. preferable.

The thickness of the adhesive layer is preferably 5 to 50 μm.

The peel force A1 is preferably 0.26 N/50 mm or less.

The peel force A2 is preferably 0.13 N/50 mm or less.

The difference between the peeling force A1 and the peeling force A2 is preferably 0.18 N/50 mm or less.

The difference between the peel force A1 and the peel force B1 is preferably greater than 0 N/50 mm and 0.17 N/50 mm or less.

The difference between the peeling force A2 and the peeling force B2 is preferably 0.13 N/50 mm or less.

The first and second release liners preferably comprise a substrate and a release treated layer provided on at least one surface of the substrate.

The release treated layer is preferably a silicone-based release treated layer.

The double-sided pressure-sensitive adhesive sheet is preferably used for bonding at least one pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer to graphite.

The double-sided pressure-sensitive adhesive sheet is preferably used for bonding at least one pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer to a metal plate.

The double-sided pressure-sensitive adhesive sheet of the present invention has little dependence on speed when releasing the release liner. In addition, when peeling off the release liner remaining on the double-sided PSA sheet with one adhesive surface of the double-sided PSA sheet of the present invention attached to an adherend, the already attached adherend is less likely to break.

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 includes at least a pressure-sensitive adhesive layer and release liners laminated on both sides of the pressure-sensitive adhesive layer. That is, the double-sided pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer, a first release liner laminated on one pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer, and a second release liner laminated on the other pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer. at least. In this specification, the double-sided pressure-sensitive adhesive sheet of the present invention excluding the first and second release liners may be referred to as an "adhesive body". Further, the adhesive surface of the adhesive layer facing the first release liner may be referred to as "first adhesive surface", and the adhesive surface of the adhesive layer facing the second release liner may be referred to as "second adhesive surface". .

The double-sided pressure-sensitive adhesive sheet is a so-called "substrate-less" double-sided pressure-sensitive adhesive sheet that does not have a substrate. When the double-sided pressure-sensitive adhesive sheet is substrate-less, the double-sided pressure-sensitive adhesive sheet tends to be excellent in impact absorption, and the product using the double-sided pressure-sensitive adhesive layer tends to be excellent in impact resistance.

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, the double-sided pressure-sensitive adhesive sheet 1 includes a pressure-sensitive adhesive layer 2, a first release liner 3, and a second release liner 4. As shown in FIG. The first release liner 3 is laminated such that the release-treated surface faces the adhesive surface (first adhesive surface) 2 a of the adhesive layer 2 . The second release liner 4 is laminated so that the release-treated surface faces the adhesive surface (second adhesive surface) 2 b of the adhesive layer 2 . The double-sided pressure-sensitive adhesive sheet may be in the form of being wound into a roll while being protected by two release liners (wound body).

The thickness of the adhesive body in the double-sided pressure-sensitive adhesive sheet, that is, the thickness of the pressure-sensitive adhesive layer is preferably 100 μm or less, more preferably 5 to 50 μm, still more preferably 10 to 30 μm. When the thickness is 100 µm or less, various electronic components on which the pressure-sensitive adhesive sheet is mounted can be miniaturized or thinned. Moreover, when the thickness is 5 μm or more, the impact absorption is excellent, and the impact resistance of the product using the double-sided pressure-sensitive adhesive layer is excellent.

Each of the first release liner and the second release liner preferably has a thickness of 10 to 100 μm, more preferably 25 to 75 μm. When the thickness is 10 µm or more, the release liner can be more easily peeled off from the adhesive. When the thickness is 100 µm or less, various electronic components on which the pressure-sensitive adhesive sheet is mounted can be miniaturized or thinned. The thickness of the first release liner and the thickness of the second release liner may be the same or different.

The release force (" peel force A1") is 0.50 N/50 mm or less, preferably 0.26 N/50 mm or less, more preferably 0.20 N/50 mm or less, and even more preferably 0.15 N/50 mm or less. is. When the peel force A1 is 0.50 N/50 mm or less, the peel force is small even at a high tensile speed of 10000 mm/min, and the first release liner can be easily peeled from the pressure-sensitive adhesive layer. In addition, when the first release liner is peeled off after the second pressure-sensitive adhesive surface is attached to the adherend first, the adherend is less likely to break. The release force A1 is preferably 0.05 N/50 mm or more from the viewpoint of preventing the first release liner from falling off from the adhesive body when the adhesive sheet is not used.

The release force (" The peel force A2") is 0.27 N/50 mm or less, preferably 0.18 N/50 mm or less, and more preferably 0.13 N/50 mm or less. When the peel force A2 is 0.27 N/50 mm or less, the peel force is small even at a relatively moderate pulling speed, and the first release liner can be easily peeled from the pressure-sensitive adhesive layer. In addition, when the first release liner is peeled off after the second pressure-sensitive adhesive surface is attached to the adherend first, the adherend is less likely to break. The release force A2 is preferably 0.03 N/50 mm or more from the viewpoint of preventing the first release liner from falling off from the adhesive body when the adhesive sheet is not used.

The difference between the peel force A1 and the peel force A2 is 0.22 N/50 mm or less, preferably 0.18 N/50 mm or less, more preferably 0.12 N/50 mm or less, and still more preferably 0.08 N/50 mm. It is below. When the above difference is 0.22 N/50 mm or less, the tension speed dependency is small, and it is applicable to a wide range of processing speeds, and the first release liner can be easily peeled off while suppressing breakage of the pressure-sensitive adhesive layer. can.

The release force (" It may be referred to as “peeling force B1”) is preferably smaller than the above peeling force A1, more preferably 0.20 N/50 mm or less, still more preferably 0.15 N/50 mm or less, and particularly preferably 0.13 N/ 50 mm or less. The release force B1 is preferably 0.05 N/50 mm or more from the viewpoint of preventing the second release liner from falling off from the adhesive body when the adhesive sheet is not used.

The release force (" B2”) is preferably smaller than the above-mentioned peel force A2, more preferably 0.20 N/50 mm or less, still more preferably 0.15 N/50 mm or less, and particularly preferably 0.12 N/ 50 mm or less. The release force B2 is preferably 0.03 N/50 mm or more from the viewpoint that the second release liner is less likely to come off from the adhesive body when the adhesive sheet is not used.

The difference between the peel force B1 and the peel force B2 is preferably 0.15 N/50 mm or less, more preferably 0.10 N/50 mm or less, and even more preferably 0.05 N/50 mm or less. When the difference is 0.15 N/50 mm or less, the tension speed dependency is small, and it is applicable to a wide range of working speeds.

The difference between the peel force A1 and the peel force B1 is greater than 0 N/50 mm and 0.30 N/50 mm or less, more preferably greater than 0 N/50 mm and 0.20 N/50 mm or less, still more preferably 0 N/50 mm or less. It is 0.15 N/50 mm or less, more preferably 0 N/50 mm or more and 0.10 N/50 mm or less, and particularly preferably 0 N/50 mm or more and 0.05 N/50 mm or less. When the difference is greater than 0 N/50 mm, that is, the release force of the first release liner and the release force of the second release liner are different at a tensile speed of 10000 mm/min, the release liner can be easily peeled off from the release liner with the smaller release force. be able to. When the difference is 0.30 N/50 mm or less, when peeling off the release liner remaining on the double-sided pressure-sensitive adhesive sheet with one pressure-sensitive adhesive surface of the double-sided pressure-sensitive adhesive sheet attached to the adherend, the adhesion of the pressure-sensitive adhesive Since the difference between the release force to the body and the release force of the release liner to the adhesive body is small, the peel stress applied to the adherend is small, and the adherend that has already been laminated is less likely to break. The difference between the peeling force A1 and the peeling force B1 indicates an absolute value.

The difference between the peel force A2 and the peel force B2 is preferably 0.13 N/50 mm or less, more preferably 0.07 N/50 mm or less, still more preferably 0.04 N/50 mm or less. When the difference is 0.13 N/50 mm or less, when peeling off the release liner remaining on the double-sided pressure-sensitive adhesive sheet with one adhesive surface of the double-sided pressure-sensitive adhesive sheet attached to the adherend, the adherend of the pressure-sensitive adhesive Since the difference between the release force of the release liner and the release force of the release liner against the adhesive body is small, the peel stress applied to the adherend is small, and even at a relatively slow processing speed, the already laminated adherend is difficult to destroy. The difference between the peeling force A2 and the peeling force B2 indicates an absolute value. The peeling force A2 and the peeling force B2 may be the same or different. When the peeling force A2 and the peeling force B2 are different, either one may have a larger value.

Each peel force can be measured based on JIS Z0237:2000. Each release force tends to depend on the type of release liner used (particularly, in the case of a release liner having a substrate and a release layer, the type and composition of the release layer in contact with the pressure-sensitive adhesive layer).

(Adhesive layer)
The pressure-sensitive adhesive layer in the double-sided pressure-sensitive adhesive sheet may be a single layer or multiple layers composed of the same or different layers.

The adhesive constituting the adhesive layer is not particularly limited, but for example, acrylic adhesive, rubber adhesive (natural rubber, synthetic rubber, mixture thereof, etc.), silicone adhesive, polyester adhesives, urethane-based adhesives, polyether-based adhesives, polyamide-based adhesives, fluorine-based adhesives, and the like. Among them, acrylic pressure-sensitive adhesives are preferable as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer from the viewpoints of adhesion, weather resistance, cost, and ease of designing the pressure-sensitive adhesive. The pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive layer composed of an acrylic pressure-sensitive adhesive. Only one kind of the pressure-sensitive adhesive may be used, or two or more kinds thereof may be used.

The acrylic pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer. The acrylic polymer is a polymer containing an acrylic monomer (a monomer having a (meth)acryloyl group in the molecule) as a monomer component constituting 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.

In this specification, the base polymer refers to a main component among the polymer components used in the pressure-sensitive adhesive layer, for example, a polymer component contained in an amount of more than 50% by mass. The content of the acrylic polymer in the acrylic 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 acrylic pressure-sensitive adhesive layer.

The acrylic polymer is preferably a polymer composed (formed) of a (meth)acrylic acid alkyl ester as an essential monomer component. That is, the acrylic polymer preferably contains a (meth)acrylic acid alkyl ester as a structural unit. In the present specification, "(meth)acrylic" means "acrylic" and/or "methacrylic" (one or both of "acrylic" and "methacrylic"), and the same applies to others. .

Preferred examples of the (meth)acrylic acid alkyl ester as an essential monomer component include (meth)acrylic acid alkyl esters having a linear or branched alkyl group. In addition, only 1 type may be used for (meth)acrylic-acid alkylester, and 2 or more types may be used for them.

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 1 to 18 (preferably 2 to 4) carbon atoms (meth) ) acrylic acid alkyl esters are preferred.

The ratio of the (meth)acrylic acid alkyl ester in the total amount of 100% by mass of all the monomer components constituting the acrylic polymer is not particularly limited, but is 50% by mass or more (for example, 50 to 100% by mass). more preferably 70% by mass or more, still more preferably 85% by mass or more, and particularly preferably 90% by mass or more. The proportion is preferably less than 100% by mass, more preferably 99.5% by mass or less, still more preferably 98% by mass or less, and particularly preferably 97% by mass or less. When the above ratio is within the above range, it is possible to form a pressure-sensitive adhesive layer that has a good quantitative balance with the copolymerizable monomer and has good adhesion even if it is thin.

The acrylic polymer may contain a copolymerizable monomer together with the (meth)acrylic acid alkyl ester as a monomer component 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 monomer components constituting the acrylic polymer is not particularly limited, but is preferably 0.2% by mass or more. , more preferably 0.5% by mass or more, still more preferably 1% by mass or more, and particularly preferably 2% by mass or more. The proportion is preferably 15% by mass or less, more preferably 12% by mass or less, even more preferably 10% by mass or less, and particularly preferably 7% by mass or less. When the above ratio is within the above range, it is possible to form a pressure-sensitive adhesive layer that has a good quantitative balance with the (meth)acrylic acid alkyl ester and has good adhesion even if it is thin.

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 cohesive strength of the acrylic polymer. Examples of functional group-containing monomers include hydroxyl group-containing monomers, epoxy group-containing monomers, nitrogen atom-containing monomers, keto group-containing monomers, alkoxysilyl group-containing monomers, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers. Among them, hydroxyl group-containing monomers and nitrogen atom-containing monomers are preferred. 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 epoxy group-containing monomer include glycidyl group-containing monomers such as glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allyl glycidyl ether.

Examples of the nitrogen atom-containing monomer include amide group-containing monomers, amino group-containing monomers, cyano group-containing monomers, and monomers having a nitrogen atom-containing ring. 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 monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, and N-vinylpyrazine. , N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine and the like.

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 vinyltoluene; ) acrylate, cyclopentyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate and other cycloalkyl (meth)acrylates; aryl (meth)acrylates (e.g. phenyl (meth)acrylate), aryloxyalkyl ( Aromatic ring-containing (meth)acrylates such as meth)acrylates (e.g. phenoxyethyl (meth)acrylate), arylalkyl (meth)acrylates (e.g. benzyl (meth)acrylate); ethylene, propylene, isoprene, butadiene, isobutylene, etc. Olefin-based monomers; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate and vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether.

The proportion of the other monomers in 100% by mass of the total amount 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 Erythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy (meth)acrylate (e.g. polyglycidyl (meth)acrylate), polyester Examples thereof include monomers having (meth)acryloyl groups and other reactive functional groups in the molecule such as (meth)acrylates and urethane (meth)acrylates. 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 base polymer such as the acrylic polymer contained in the pressure-sensitive adhesive layer is obtained by polymerizing monomer components. The polymerization method is not particularly limited, but includes, for example, a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a polymerization method by active energy ray irradiation (active energy ray polymerization method), and the like. Among them, the solution polymerization method and the active energy ray polymerization method are preferable, and the solution polymerization method is more preferable, from the viewpoints of the transparency of the pressure-sensitive adhesive layer and the cost.

Moreover, 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.

Polymerization initiators such as thermal polymerization initiators and photopolymerization initiators (photoinitiators) may be used in the polymerization of the above monomer components 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 (hereinafter sometimes referred to as “AIBN”), 2,2′-azobis-2-methylbutyronitrile, 2,2 dimethyl'-azobis(2-methylpropionate), 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-based 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-based 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. can be selected from

The pressure-sensitive adhesive layer may contain 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 tackifying 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.

Examples of the rosin-based tackifying resin 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 is not particularly limited, but is preferably 1 part by mass or more (for example, 1 to 100 parts by mass) with respect to 100 parts by mass of the total amount of the base polymer. is 5 parts by mass or more, more preferably 10 parts by mass or more, and still 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 pressure-sensitive adhesive layer preferably contains a cross-linking agent. By including a cross-linking agent, for example, the acrylic polymer in the acrylic pressure-sensitive adhesive layer can be cross-linked to control the gel fraction. Only one kind of the crosslinking 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 in the pressure-sensitive adhesive layer 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 base polymer. parts, particularly preferably 0.5 to 10 parts by mass.

The 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 the isocyanate-based cross-linking agent is used as the cross-linking agent is not particularly limited, but is preferably 0.5 parts by mass or more, more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the total amount of the base polymer. is 1 part by mass or more, 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.

The content of the epoxy-based cross-linking agent when the epoxy-based cross-linking agent is used as the cross-linking agent is not particularly limited, but the content of the epoxy-based cross-linking agent exceeds 0 mass parts and is 1 mass part or less with respect to the total amount of 100 mass parts of the base polymer. Preferably, 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 0.008 to 0.008 parts by mass. 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 representing the rate of decomposition of the peroxide, and refers to the time until the residual amount of the peroxide is halved. 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 in the case of using a peroxide-based cross-linking agent as the cross-linking agent is not particularly limited, but it is preferably 2 parts by mass or less, more preferably 2 parts by mass or less with respect to 100 parts by mass of the acrylic polymer. is 0.02 to 2 parts by mass, more preferably 0.05 to 1 part by mass.

In addition, 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.

As the cross-linking agent, it is preferable to include 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 acrylic polymer (especially a combination with the preferred acrylic polymer described above) can provide a pressure-sensitive adhesive layer that is thin but has even better adhesion.

If necessary, the pressure-sensitive adhesive layer further contains a crosslinking accelerator, an antioxidant, a filler (organic filler, inorganic filler, etc.), a colorant (pigment, dye, etc.), an antioxidant, a plasticizer, Additives such as softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, granular materials, foil materials, and rust inhibitors are used to achieve the effects of the present invention. may be contained within a range that does not impair the Only one kind of the above additives may be used, or two or more kinds thereof may be used.

(Release liner)
The release liner is an element that covers and protects the surface of the adhesive (adhesive surface), and is peeled off from the adhesive when the double-sided adhesive sheet is attached to an adherend for use. The first and second release liners in the double-sided pressure-sensitive adhesive sheet are release liners that differ in at least one of structure, composition, thickness, physical properties, and the like. In this specification, when the first release liner and the second release liner are collectively used without distinguishing between them, they may simply be referred to as "release liner". For example, the double-sided PSA sheet is prepared by first peeling off one release liner, bonding the exposed PSA layer surface (adhesive surface) to one adherend, and then peeling off the other release liner to expose the adhesive. It is used by bonding the agent layer surface (adhesive surface) to the other adherend.

The release liner is not particularly limited, and can be appropriately selected and used from known or commonly used release liners. The release liner includes a substrate (substrate for release liner) having a release treatment layer on at least one surface, a low-adhesive substrate made of a fluoropolymer, and a low-adhesive substrate made of a non-polar polymer. mentioned. The base material may be a single layer or a laminate of the same or different base materials.

Examples of the substrate of the release liner include plastic substrates, paper, foams, various thin sheets such as metal foil, and the like, and plastic substrates are preferred.

Examples of the resin constituting the plastic substrate include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymerized polypropylene, block copolymerized polypropylene, and homopolypropylene. , polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene- Polyolefin resins such as butene copolymers and ethylene-hexene copolymers; polyurethanes; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonates; polyimides; polyamide such as aramid and wholly aromatic polyamide; polyphenyl sulfide; fluorine resin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; Only one kind of the above resin may be used, or two or more kinds thereof may be used.

Among them, the plastic substrate is preferably a plastic film, more preferably a polyester film or a polyolefin film, and particularly preferably a polyethylene terephthalate film.

The thickness of the substrate in the release liner (the thickness of the substrate in each of the first release liner and the second release liner) is not particularly limited, but is preferably 5 to 100 μm, more preferably 5 to 75 μm, and even more preferably. 8 to 60 μm, particularly preferably 12 to 40 μm. When the thickness is 5 μm or more, the workability in peeling off the release liner is excellent. When the thickness is 100 µm or less, it is possible to prevent the rigidity from increasing, to provide excellent conformability to the surface of the pressure-sensitive adhesive layer, and to prevent the release liner from floating on the double-sided pressure-sensitive adhesive sheet. In addition, the diameter of the roll when used as a roll does not become too large. The thickness of the substrates of the first release liner and the second release liner may be the same or different.

The release treatment agent constituting the release treatment layer is not particularly limited, and examples thereof include silicone release agents, fluorine release agents, long-chain alkyl release agents, molybdenum sulfide release agents, and the like. . Among them, a silicone-based release agent is preferable. Only one type of the release agent may be used, or two or more types may be used.

The mass per area of the release treatment layer is, for example, 0.01 to 5 g/m ² , preferably 0.05 to 3 g/m ² , more preferably 0.2 to 1 g/m ² . The thickness of the release treatment layer is, for example, 0.03 to 10 μm, preferably 0.1 to 5 μm, more preferably 0.3 to 2 μm.

Examples of the release liner having a release-treated layer on one side of the substrate include trade names "Diafoil MHA", "Diafoil MHC", "Diafoil MHE", and "Diafoil MRF F4" (Mitsubishi Chemical Co., Ltd.), trade name “SC05”, trade name “SCA0” (manufactured by Fujiko Co., Ltd.), trade name “MFAS”, trade name “MDAS” (manufactured by Toray Industries, Inc.), trade name “SL1110-036” ( Sunliky) and other commercial products can be used.

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.).

(Double-sided adhesive sheet)
Peel strength against stainless steel plate (SUS plate) measured at 23 ° C., 50% RH, tensile speed 300 mm / min, peel angle 180 ° of the first adhesive surface or the second adhesive surface (vs. SUS adhesive force) is preferably 3 N/25 mm or more, more preferably 8 N/25 mm or more. Moreover, the peel strength is, for example, 30 N/25 mm or less, preferably 25 N/25 mm. At least one of the first adhesive surface and the second adhesive surface preferably satisfies the adhesive strength to SUS, and more preferably satisfies at least the first adhesive surface from the viewpoint of excellent workability. The adhesive strength to SUS can be measured based on JIS Z0237:2000.

When the release liner has a release layer composed of a silicone-based release agent, when the release liner is peeled off from the double-sided PSA sheet at a peeling speed of 300 mm/min and a peel angle of 180°, the adhesive layer is separated from the release layer. The amount of silicone that migrates (migration amount) to polydimethylsiloxane is preferably 0.003 to 0.012 g/m ² per unit area, more preferably 0.006 to 0.010 g/m ² be. When the migration amount is 0.003 g/m ² or more, migration of the PSA from the PSA layer to the release liner is suppressed, and the tackiness of the PSA tends to be more excellent. When the migration amount is 0.012 g/m ² or less, migration of the release treatment agent from the release liner to the adhesive layer is suppressed, and the adhesive property of the adhesive body tends to be more excellent. It is preferable that at least one of the first release liner and the second release liner be satisfied with the migration amount of silicone, and it is more preferable that both be satisfied.

Here, the above-mentioned "per unit area" means "per unit area of the pressure-sensitive adhesive layer in the portion where the pressure-sensitive adhesive layer and the release liner are bonded to each other". The amount of silicone migration is determined by a method using fluorescent X-ray analysis.

When the release liner has a release layer composed of a silicone-based release agent, when the release liner is peeled off from the double-sided PSA sheet at a peeling speed of 300 mm/min and a peel angle of 180°, the adhesive layer is separated from the release layer. It is preferable that the ratio (ratio) of the amount of silicone migrated to be less than 30% by mass in terms of polydimethylsiloxane. At least one of the first release liner and the second release liner preferably satisfies the ratio (migration rate) of the silicone, and more preferably both of the first release liner and the second release liner. The proportion of silicone that migrates from the release-treated layer of the release liner to the pressure-sensitive adhesive layer can be determined using the result of the amount of silicone migrated by fluorescent X-ray analysis.

The double-sided pressure-sensitive adhesive sheet preferably has an energy (load x height) of 0.04 J or more before one of the first and second release liners is peeled off, as measured by a DuPont impact test. More preferably, it is 0.06J or more. When the energy is 0.04 J or more, the impact absorption is excellent. The DuPont impact test can be performed by the method described in Examples.

The peak top strength at -10 ° C. of the loss tangent (tan δ), which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in dynamic viscoelasticity measurement, is excellent in shock absorption. From the viewpoint, it is preferably 0.5 or more, more preferably 1.0 or more. The upper limit of the peak top intensity is, for example, about 3. The peak top intensity can be measured by the method described in Examples.

The double-sided pressure-sensitive adhesive sheet is preferably used, for example, in optical members such as electrical and electronic devices, when various members or parts are attached (attached) to predetermined portions (eg, housings, etc.). The term "electrical/electronic equipment" refers to equipment corresponding to at least one of electrical equipment and 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. Above all, the double-sided pressure-sensitive adhesive sheet is preferably used by being attached to an internal member of an optical member (especially an electrical/electronic device), and is used for fixing an internal member of an optical member (especially an electrical/electronic device). is particularly preferred.

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.

The double-sided pressure-sensitive adhesive sheet is preferably used for bonding at least one adhesive surface to a brittle substance such as graphite, since the adherend to which the pressure-sensitive adhesive has already been bonded is less likely to break. Also, it may be used to bond at least one of the adhesive surfaces to a material harder than the brittle material (for example, a metal plate such as a SUS plate). In particular, it is preferably used for bonding one adhesive surface (particularly, the adhesive surface to be bonded first) to a brittle substance such as graphite. Also, the adherend to be bonded to the other adhesive surface (particularly, the adhesive surface to be bonded later) is preferably a material harder than the brittle material (for example, a metal plate such as a SUS plate).

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

Example 1
A reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser was charged with 68 parts of toluene, 95 parts by mass of butyl acrylate (BA), and 5 parts by mass of acrylic acid (AA), and nitrogen was added for 1 hour or more. replaced. 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 3 parts by mass of an isocyanate compound (trade name "Coronate L", manufactured by Tosoh Corporation) and 0.01 mass of an epoxy compound (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Company, Inc.) with respect to 100 parts by mass of the obtained polymer and 20 parts by mass of a terpene phenol-based tackifying resin (trade name “YS Polystar T115” manufactured by Yasuhara Chemical Co., Ltd.) was added to prepare a pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition was applied to a release liner as a first release liner (trade name “Diafoil MHA” manufactured by Mitsubishi Chemical Corporation, one side of a polyethylene terephthalate film subjected to release treatment with a silicone-based release agent). and dried to form an adhesive layer. Then, the release treated layer of a release liner (trade name “SC05”, Fujiko Co., Ltd., manufactured by Fujiko Co., Ltd., one side of a polyethylene terephthalate film subjected to a release treatment with a silicone-based release agent) as the second release liner was coated with the above adhesive. Laminated to the exposed adhesive side of the layer. Thus, a double-sided pressure-sensitive adhesive sheet was produced in which release liners were laminated on both sides of the pressure-sensitive adhesive layer. Table 1 shows the thickness of the adhesive layer and the thickness of the release liner.

Examples 2-14, Comparative Examples 2-3
A double-sided pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the thickness of the pressure-sensitive adhesive layer, the type of release liner, the thickness of the release liner, etc. were changed as shown in Tables 1 and 2.

Comparative example 1
The pressure-sensitive adhesive composition prepared in Example 1 was applied to a release liner as a first release liner (trade name: "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation, and one side of a polyethylene terephthalate film was subjected to a release treatment with a silicone-based release agent. It was coated on the release treatment layer of the first adhesive layer and dried to form a first pressure-sensitive adhesive layer. Then, one surface of a PET film serving as a substrate layer was laminated on the surface of the first pressure-sensitive adhesive layer. On the other hand, the pressure-sensitive adhesive composition was applied onto the release treatment layer of a release liner (trade name “SC05”, manufactured by Fujiko Co., Ltd.) as a second release liner and dried to form a second pressure-sensitive adhesive layer. Next, the second pressure-sensitive adhesive layer was attached to the other surface of the base material layer. In this way, a double-sided PSA sheet was produced in which PSA layers were laminated on both sides of the base material layer, and release liners were laminated on both PSA layers. Table 2 shows the thickness of the substrate layer, the thickness of the pressure-sensitive adhesive layer, and the thickness of the release liner. The thickness of the first adhesive layer and the thickness of the second adhesive layer are the same.

Each of the release liners shown in the table is a polyethylene terephthalate film whose one side has been subjected to a release treatment with a silicone-based release agent, as described below.
MHA: Product name "Diafoil MHA" manufactured by Mitsubishi Chemical Corporation MHC: Product name "Diafoil MHC" manufactured by Mitsubishi Chemical Corporation MHE: Product name "Diafoil MHE" manufactured by Mitsubishi Chemical Corporation MFAS: Product name " MFAS” manufactured by Toray Industries, Inc. MDAS: product name “MDAS” manufactured by Toray Industries, Inc. SL1110-036: product name “SL1110-036” manufactured by Sunliky SC05: product name “SC05” manufactured by Fujiko Co., Ltd. MRF F4: product Name "Diafoil MRF F4" manufactured by Mitsubishi Chemical Corporation SCA0: trade name "SCA0" MRF manufactured by Fujiko Co., Ltd.: trade name "Diafoil MRF" MRV manufactured by Mitsubishi Chemical Corporation: trade name "Diafoil MRV" Manufactured by Mitsubishi Chemical Corporation

<Evaluation>
The double-sided pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in the table.

(1) Release force of release liner A sheet piece having a width of 50 mm and a length of 150 mm was cut out from the double-sided pressure-sensitive adhesive sheet. For the peel force A1, the above sheet piece was used as a measurement sample as it was. For the peel force B1, the first release liner of the sheet piece was peeled off, and the exposed adhesive surface was backed with a PET film having a thickness of 50 μm, which was used as a sample for measurement. The side opposite to the side on which the peel force is measured is attached to a bakelite plate with double-sided tape and fixed to a pedestal, and a tensile tester is used to perform a 180° peel test in accordance with JIS Z0237. 180° peeling adhesive force [N/50 mm] from the surface of the adhesive layer of the release liner was measured. This was referred to as "the release force of the release liner". The measurement was performed in an atmosphere of 23° C.±2° C. and 50%±5% RH, under the conditions of a peeling angle of 180°, a tensile speed of 10000 mm/min and a tensile speed of 300 mm/min. The number of tests (n number) was 3, and the average value was calculated.

(2) Amount of Silicone Migration From the double-sided PSA sheet, the release liner laminated on the PSA layer on the opposite side of the PSA layer where the amount of silicone migration was to be measured was peeled off, and a PET film with a thickness of 50 μm was adhered and backed. This backed pressure-sensitive adhesive sheet was cut into a rectangular shape of 50 mm×50 mm to obtain a measurement sample. This measurement sample was placed in a dryer at 70° C. with a load of 5 kg applied for 24 hours, then the load was removed, removed from the dryer, and held at 23° C. for 2 hours. From the measurement sample, the release liner on the side where the amount of silicone migration is to be measured is peeled off at a peeling speed of 300 mm/min and a peeling angle of 180°. was determined as X-ray intensity (cps: counts per second) by a fluorescent X-ray analyzer. Then, from the X-ray intensity (cps) of the adhesive surface of the obtained adhesive layer, the amount of silicone in the adhesive layer (amount of silicone transferred) [g/m ² ] was calculated in terms of polydimethylsiloxane. The conversion formula is 100 kcps=0.60 g/m ² . In addition, in the measurement of the amount of silicone migration, a product name "ZSX100E" (manufactured by RIGAKU Co., Ltd.) was used as a fluorescent X-ray analyzer, and Rh was used as an X-ray source. RX-4 was used as an analyzing crystal, and the X-ray intensity was measured by setting the output to 50 kV and 70 mA.

(3) Releasability of release liner A double-sided pressure-sensitive adhesive sheet is cut into a size of 50 mm x 300 mm, and the second release liner is peeled off at a tensile speed of 300 mm/min to 10000 mm/min. I checked the presence or absence of Specifically, when the second release liner is peeled off, peeling occurs reliably at the interface between the second release liner and the surface of the pressure-sensitive adhesive layer (adhesive surface), and the second release liner is separated from the double-sided pressure-sensitive adhesive sheet. Whether the second release liner can be easily peeled, whether the first release liner is floating from the adhesive surface of the adhesive body, and whether peeling does not occur at the interface between the first release liner and the adhesive surface. It was visually confirmed whether peeling occurred at the interface between the adhesive surface and the adhesive surface. The evaluation criteria for the releasability of the release liner are as follows.
◯: When the second release liner was peeled off, the peeling was easy, and neither lifting nor peeling (tear separation) occurred at the interface between the first release liner and the pressure-sensitive adhesive layer surface.
x: When the second release liner was peeled off, lifting or peeling (tear separation) was observed at the interface between the first release liner and the pressure-sensitive adhesive layer surface.

(4) Impact resistance The double-sided pressure-sensitive adhesive sheet was punched out into a frame shape with a width of 2 mm and an outer shape of 24.5 mm square to obtain an evaluation sample. An evaluation sample is placed between a stainless steel plate with a hole in the center of a square with a thickness of 2 mm and an outer diameter of 50 mm × 50 mm and a square stainless steel plate (outer diameter of 25 mm square, thickness of 3 mm), and the pressure is applied. It was pressure-bonded so as to apply uniformly (62 N×10 seconds), then allowed to stand at 50° C. for 2 hours, taken out, and returned to 23° C. to obtain a test piece. 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. was placed on the bottom side. A stainless steel striker 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 in increments of 50 mm from 50 mm to 500 mm at 100 g, in increments of 50 mm from 350 mm to 500 mm at 150 g, to 200 g. The energy was changed by 50 mm from 400 mm to 500 mm at 300 g, and was changed by 50 mm from 350 mm to 500 mm at 300 g, and 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 either one of the first and second release liners was peeled off was calculated as load×height.

(5) Peak top strength of tan δ at −10° C. Adhesive layers were laminated to prepare a test sample having a thickness of about 2 mm. This test sample was punched 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). The viscoelasticity was measured in shear mode at 70 to 150°C at a heating rate of 5°C/min to obtain the peak top strength of tan δ (loss tangent) at -10°C.

(6) Adhesive strength to SUS A double-sided adhesive sheet was cut into a size of 25 mm in width and 100 mm in length. Then, the release liner to be measured and the release liner on the opposite side were peeled off from the double-sided pressure-sensitive adhesive sheet, and the exposed pressure-sensitive adhesive surface was backed with a PET film having a thickness of 50 μm to prepare a test piece. In an environment of 23° C. and 50% RH, the release liner of the sample piece to be measured was peeled off, and the exposed adhesive surface was pressed against a stainless steel plate (SUS304BA plate) to prepare a measurement sample. The pressure bonding was performed by reciprocating a 2 kg roller once. After leaving the measurement sample for 30 minutes in an environment of 23 ° C. and 50% RH, using a tensile tester "precision universal testing machine Autograph AG-IS 50N" (manufactured by Shimadzu Corporation), JIS Z0237 : 2000, the peel strength [N/25 mm] was measured under the conditions of a tensile speed of 300 mm/min and a peel angle of 180°, and this value was taken as the adhesion to SUS.

(7) Destruction of Adherend A double-sided pressure-sensitive adhesive sheet was cut into a size of 50 mm in width and 300 mm in length. Then, the second release liner was peeled off from the double-sided pressure-sensitive adhesive sheet, and the exposed pressure-sensitive adhesive surface was attached to the graphite sheet. After that, the first release liner was peeled off from the double-sided pressure-sensitive adhesive sheet under conditions of 23° C.±2° C., 50%±5% RH, a peeling angle of 180°, and a tensile speed of 10000 mm/min. At that time, a case where damage was confirmed in the graphite sheet was evaluated as "x", and a case where damage was not confirmed in the graphite sheet was evaluated as "good".

As shown in Tables 1 and 2, the double-sided pressure-sensitive adhesive sheet of the present invention has a small difference in release force between a tensile speed of 300 mm/min and a tensile speed of 10,000 mm/min when releasing the release liner, and has little speed dependency. was evaluated. Then, when peeling off the release liner remaining on the double-sided pressure-sensitive adhesive sheet in a state in which one adhesive surface of the double-sided pressure-sensitive adhesive sheet of the present invention is adhered to an adherend, no breakage is observed in the already-laminated graphite sheet. It was evaluated that the adherent was hard to break. In addition, the result of the DuPont impact test was good, and it was evaluated as being excellent in impact absorption. On the other hand, when the difference between the peeling force A1 and the peeling force A2 and the difference between the peeling force A1 and the peeling force B1 are large (Comparative Examples 1 and 2), the speed dependence is large, and the graphite sheet is also damaged. rice field. Moreover, when it had a base material layer (comparative example 1), it was inferior in impact absorption. When the difference between the peeling force A1 and the peeling force B1 was 0 N/50 mm, that is, when the peeling force A1 and the peeling force B1 were the same (Comparative Example 3), breakage of the graphite sheet was confirmed.

1 double-sided adhesive sheet 2 adhesive layer 2a first adhesive surface 2b second adhesive surface 3 first release liner 4 second release liner

Claims (15)

An adhesive layer, a first release liner laminated on one adhesive surface of the adhesive layer, and a second release liner laminated on the other adhesive surface of the adhesive layer,
When the first release liner is peeled from the pressure-sensitive adhesive layer at 23° C. and 50% RH at a tensile speed of 10000 mm/min and a peel angle of 180°, the peel force A1 against the adhesive surface is 0.50 N/50 mm or less. and
When the first release liner is peeled from the pressure-sensitive adhesive layer at 23° C. and 50% RH at a tensile speed of 300 mm/min and a peel angle of 180°, the peel force A2 against the adhesive surface is 0.27 N/50 mm or less. and
The difference between the peeling force A1 and the peeling force A2 is 0.22 N/50 mm or less,
The peeling force A1, and the peeling force B1 of the second release liner against the adhesive surface when peeled from the adhesive layer at 23° C. and 50% RH at a tensile speed of 10000 mm/min and a peeling angle of 180°. difference is higher than 0 N/50 mm and not more than 0.30 N/50 mm. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 100 µm or less. 3. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein each of said first and second release liners has a thickness of 10 to 100 μm. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein said peeling force B1 is smaller than said peeling force A1. The peel strength of at least one adhesive surface of the adhesive layer against a stainless steel plate measured at 23° C. and 50% RH at a tensile speed of 300 mm/min and a peel angle of 180° is 3 N/25 mm or more. The double-sided pressure-sensitive adhesive sheet according to any one of items 1 to 4. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer has a thickness of 5 to 50 µm. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the peel force A1 is 0.26 N/50 mm or less. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the peel force A2 is 0.13 N/50 mm or less. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the difference between the peeling force A1 and the peeling force A2 is 0.18 N/50 mm or less. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the difference between said peeling force A1 and said peeling force B1 is greater than 0 N/50 mm and 0.17 N/50 mm or less. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 10, wherein the difference between said peeling force A2 and said peeling force B2 is 0.13 N/50 mm or less. The double-sided pressure-sensitive adhesive sheet according to any one of Claims 1 to 11, wherein the first and second release liners comprise a substrate and a release treated layer provided on at least one surface of the substrate. 13. The double-sided pressure-sensitive adhesive sheet according to claim 12, wherein the release treated layer is a silicone-based release treated layer. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 13, which is used for laminating at least one pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer to graphite. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 14, which is used for bonding at least one pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer to a metal plate.

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