Double-sided adhesive sheet

Abstract

To provide a double-sided adhesive sheet easily peelable from any side, with smaller rate dependence, and unlikely to break an adherend already bonded, when removing a release liner.SOLUTION: A double-sided adhesive sheet 1 includes a substrate layer 2, a first adhesive layer 3, a second adhesive layer 4, a first release liner 5 and a second release liner 6. With regard to both of the first and second release liners 5, 6, a peel force (pulling rate 10000 mm / min) to the adhesive layer is 0.49 N / 50 mm or less, a peel force (pulling rate 300 mm / min) to the adhesive layer is 0.23 N / 50 mm or less, a difference of the peel force (pulling rate 10000 mm / min) and the peel force (pulling rate 300 mm / min) is 0.25 N / 50 mm or less. A difference of peel forces (pulling rate 10000 mm / min) of the first and second release liners 5, 6 is 0.40 N / 50 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a double-sided pressure-sensitive adhesive sheet. [Background technology]

[0002] In recent years, mobile devices such as mobile phones, digital cameras, and PDAs (Personal Digital Assistants) have become smaller. As a result, the various electronic components mounted on them are also being made smaller and thinner. For example, the main components of mobile phones, which are representative of mobile devices, tend to be made thinner. The display part of a mobile device usually consists mainly of an LCD module and a backlight unit, and various sheet-like components are layered to achieve functions such as light emission, reflection, light blocking, and light guiding. Therefore, a double-sided adhesive sheet (double-sided adhesive tape) has been devised for use in assembling (joining) these components.

[0003] The double-sided pressure-sensitive adhesive sheet may have a structure including a base layer, pressure-sensitive adhesive layers laminated on both sides of the base layer, and release liners laminated on the adhesive surfaces of the two pressure-sensitive adhesive layers (see, for example, Patent Document 1).

[0004] In the above 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 is usually different from the peel strength between the release liner laminated on the other pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer. This is because the peeling workability of the release liner is excellent. When using such a double-sided pressure-sensitive adhesive sheet, first, the release liner on the side with a small peel strength (light release side) of the double-sided pressure-sensitive adhesive sheet is peeled off and attached to one of the members of the adherend, and then the release liner on the side with a large peel strength (heavy release side) is peeled off and attached to the other member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2016-535151 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in a double-sided PSA sheet having release liners on both sides, if the difference in release strength between the light release side and the heavy release side is too large, "floating" (gaps) may occur at the interface between the release liner on the side opposite to the release liner to be peeled and the surface of the PSA layer, or peeling may occur at the interface between the release liner on the opposite side and the surface of the PSA layer (the so-called "split-off phenomenon"). In addition, if normal peeling is not possible unless peeled from one of the release liners (e.g., the light release side), the workability is poor when using the double-sided PSA sheet in a product processing line. For this reason, it is required that the release liner can be easily peeled from either side.

[0007] In addition, the release force of a release liner can vary depending on the pulling speed (peel speed) when peeling it from the adhesive layer. Since the processing speed on a product processing line differs depending on the production type, it is required that the speed dependency (pulling speed dependency) when peeling the release liner is small, so that the adhesive layer can be peeled while suppressing damage over a wide speed range.

[0008] Furthermore, when using a double-sided pressure-sensitive adhesive sheet, usually, first, one release liner is peeled off and the exposed adhesive surface is attached to one adherend, and then the other release liner is peeled off and the exposed adhesive surface is attached to the other adherend. Here, if the one adherend to which the double-sided pressure-sensitive adhesive sheet is attached first is brittle and easily crumbles, the one adherend may be destroyed by the peeling stress when the other release liner is peeled off. For this reason, it is required that the adherend already attached is not easily destroyed when the release liner is peeled off.

[0009] The present invention was devised under these circumstances, and its object is to provide a double-sided pressure-sensitive adhesive sheet that can be easily peeled off from either side when peeling off the release liner, has little speed dependency, and is less likely to destroy an adherend that has already been bonded to it. [Means for solving the problem]

[0010] As a result of intensive research into achieving the above object, the present inventors have found that a double-sided PSA sheet having a base layer, in which various physical properties relating to the peel force of the release liner from an adhesive are within specific ranges, allows the release liner to be easily peeled from either side when peeled, has little speed dependency, and is less likely to destroy an adherend that has already been bonded. The present invention was completed based on these findings.

[0011] That is, the present invention provides a tape comprising a base layer, first and second pressure-sensitive adhesive layers laminated on both sides of the base layer, a first release liner laminated on an adhesive surface of the first pressure-sensitive adhesive layer, and a second release liner laminated on an adhesive surface of the second pressure-sensitive adhesive layer, the first release liner has a peel force A1 to the adhesive surface when peeled from the first pressure-sensitive adhesive layer at a tensile speed of 10,000 mm / min and a peel angle of 180° at 23°C and 50% RH, and the second release liner has a peel force B1 to the adhesive surface when peeled from the second pressure-sensitive adhesive layer at a tensile speed of 10,000 mm / min and a peel angle of 180° at 23°C and 50% RH, both of which are 0.49 N / 50 mm or less; the peel force A2 of the first release liner to the adhesive surface when peeled from the first pressure-sensitive adhesive layer at a tensile speed of 300 mm / min and a peel angle of 180° at 23°C and 50% RH, and the peel force B2 of the second release liner to the adhesive surface when peeled from the second pressure-sensitive adhesive layer at a tensile speed of 300 mm / min and a peel angle of 180° at 23°C and 50% RH are both 0.23 N / 50 mm or less, The difference between the peel force A1 and the peel force A2 is 0.25 N / 50 mm or less, The difference between the peel force B1 and the peel force B2 is 0.25 N / 50 mm or less, The double-sided pressure-sensitive adhesive sheet has a difference between the peel strength A1 and the peel strength B1 of 0.40 N / 50 mm or less.

[0012] The thickness from the adhesive surface of the first pressure-sensitive adhesive layer to the adhesive surface of the second pressure-sensitive adhesive layer is preferably 100 μm or less.

[0013] The thickness of each of the first and second release liners is preferably 10 to 100 μm.

[0014] It is preferable that the peel strength of the adhesive surface of the first adhesive layer or the second adhesive layer against a stainless steel plate, measured under conditions of 23°C, 50% RH, a tensile speed of 300 mm / min and a peel angle of 180°, is 3 N / 25 mm or more.

[0015] The thickness from the adhesive surface of the first pressure-sensitive adhesive layer to the adhesive surface of the second pressure-sensitive adhesive layer is preferably 8 to 50 μm.

[0016] It is preferable that both of the peeling force A1 and the peeling force B1 are 0.27 N / 50 mm or less.

[0017] It is preferable that both of the peeling force A2 and the peeling force B2 are 0.11 N / 50 mm or less.

[0018] It is preferable that the difference between the peeling force A1 and the peeling force A2 is 0.18 N / 50 mm or less, and the difference between the peeling force B1 and the peeling force B2 is 0.18 N / 50 mm or less.

[0019] The difference between the peeling force A1 and the peeling force B1 is preferably 0.17 N / 50 mm or less.

[0020] The difference between the peeling force A2 and the peeling force B2 is preferably 0.17 N / 50 mm or less.

[0021] The first and second release liners preferably comprise a substrate and a release treatment layer provided on at least one surface of the substrate.

[0022] The release treatment layer is preferably a silicone-based release treatment layer.

[0023] The double-sided pressure-sensitive adhesive sheet is preferably used for bonding the first and / or second pressure-sensitive adhesive layer to graphite.

[0024] The double-sided pressure-sensitive adhesive sheet is preferably used for bonding the first and / or second pressure-sensitive adhesive layer to a metal plate. Effect of the Invention

[0025] The double-sided pressure-sensitive adhesive sheet of the present invention can be easily peeled off from either side when the release liner is peeled off with little speed dependency, and when one adhesive side of the double-sided pressure-sensitive adhesive sheet of the present invention is attached to an adherend and the release liner remaining on the double-sided pressure-sensitive adhesive sheet is peeled off, the adherend that has already been attached is unlikely to be destroyed. [Brief description of the drawings]

[0026] [Figure 1] 1 is a schematic cross-sectional view of a double-sided pressure-sensitive adhesive sheet according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] [Double-sided adhesive sheet] The double-sided pressure-sensitive adhesive sheet of the present invention comprises at least a base layer and a pressure-sensitive adhesive layer laminated on both sides of the base layer. The double-sided pressure-sensitive adhesive sheet also comprises a release liner laminated on each of the pressure-sensitive adhesive layers laminated on both sides of the base layer. That is, the double-sided pressure-sensitive adhesive sheet at least comprises a base layer, a first pressure-sensitive adhesive layer laminated on one side of the base layer, a second pressure-sensitive adhesive layer laminated on the other side of the base layer, a first release liner laminated on the adhesive surface of the first pressure-sensitive adhesive layer, and a second release liner laminated on the adhesive surface of the second pressure-sensitive adhesive layer. In this specification, the structure of 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". The adhesive surface of the first pressure-sensitive adhesive layer facing the first release liner may be referred to as the "first adhesive surface", and the adhesive surface of the second pressure-sensitive adhesive layer facing the second release liner may be referred to as the "second adhesive surface".

[0028] Fig. 1 is a cross-sectional schematic diagram 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 base layer 2, a first pressure-sensitive adhesive layer 3, a second pressure-sensitive adhesive layer 4, a first release liner 5, and a second release liner 6. The first release liner 5 is laminated such that its release-treated surface faces the adhesive surface (first adhesive surface) 3a of the first pressure-sensitive adhesive layer 3. The second release liner 6 is laminated such that its release-treated surface faces the adhesive surface (second adhesive surface) 4a of the second pressure-sensitive adhesive layer 4. The double-sided pressure-sensitive adhesive sheet may be in a form wound into a roll (rolled body) while being protected by two release liners.

[0029] The thickness of the adhesive body in the double-sided adhesive sheet, i.e., the thickness from the adhesive surface (first adhesive surface) of the first adhesive layer to the adhesive surface (second adhesive surface) of the second adhesive layer, is preferably 100 μm or less, more preferably 8 to 50 μm. If the thickness is 100 μm or less, various electronic components on which the adhesive sheet is mounted can be made smaller or thinner. If the thickness is 8 μm or more, the thickness of the base layer and the adhesive layer can be made thicker, resulting in better punching processability and adhesion to adherends.

[0030] The thickness of each of the first release liner and the second release liner is preferably 10 to 100 μm, more preferably 25 to 75 μm, and even more preferably 30 to 50 μm. When the thickness is 10 μm or more, the release liner can be more easily peeled off from the pressure-sensitive adhesive body. When the thickness is 100 μm or less, various electronic components on which the pressure-sensitive adhesive sheet is mounted can be made smaller or thinner. The thickness of the first release liner and the thickness of the second release liner may be the same or different.

[0031] The peeling force (sometimes referred to as "peeling force A1") of the first release liner against the adhesive surface (first adhesive surface) when peeled from the first adhesive layer under conditions of 23°C, 50% RH, a tensile speed of 10000 mm / min, and a peeling angle of 180° is 0.49 N / 50 mm or less, preferably 0.27 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. By having a peeling force A1 of 0.49 N / 50 mm or less, the peeling force is small even at a tensile speed as high as 10000 mm / min, and the first release liner can be easily peeled from the adhesive body. In addition, when the second adhesive layer is first bonded to the adherend and then the first release liner is peeled off, the adherend is unlikely to be destroyed. From the viewpoint that the first release liner is unlikely to fall off the adhesive body when the adhesive sheet is unused, the peeling force A1 is preferably 0.05 N / 50 mm or more.

[0032] The peel force (sometimes referred to as "peeling force A2") of the first release liner against the adhesive surface (first adhesive surface) when peeled from the first adhesive layer under conditions of 23°C, 50% RH, a pulling speed of 300 mm / min, and a peeling angle of 180° is 0.23 N / 50 mm or less, preferably 0.18 N / 50 mm or less, and more preferably 0.11 N / 50 mm or less. By having a peel force A2 of 0.23 N / 50 mm or less, the peel force is small even at a relatively slow pulling speed, and the first release liner can be easily peeled from the adhesive body. In addition, when the second adhesive layer is first attached to the adherend and then the first release liner is peeled off, the adherend is unlikely to be destroyed. From the viewpoint that the first release liner is unlikely to fall off the adhesive body when the adhesive sheet is unused, the peel force A2 is preferably 0.03 N / 50 mm or more.

[0033] The difference between the peel force A1 and the peel force A2 is 0.25 N / 50 mm or less, preferably 0.18 N / 50 mm or less, more preferably 0.12 N / 50 mm or less, and even more preferably 0.08 N / 50 mm or less. When the difference is 0.25 N / 50 mm or less, the tensile speed dependency is small, making it applicable to a wide range of processing speeds, and enabling the first release liner to be easily peeled off while preventing damage to the first pressure-sensitive adhesive layer.

[0034] The peeling force (sometimes referred to as "peeling force B1") of the second release liner against the adhesive surface (second adhesive surface) when peeled from the second adhesive layer under conditions of 23°C, 50% RH, a tensile speed of 10000 mm / min, and a peeling angle of 180° is 0.49 N / 50 mm or less, preferably 0.27 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. By having a peeling force B1 of 0.49 N / 50 mm or less, the peeling force is small even at a tensile speed as high as 10000 mm / min, and the second release liner can be easily peeled from the adhesive body. In addition, when the first adhesive layer is first bonded to the adherend and then the second release liner is peeled off, the adherend is unlikely to be destroyed. From the viewpoint that the second release liner is unlikely to fall off from the adhesive body when the adhesive sheet is unused, the peeling force B1 is preferably 0.05 N / 50 mm or more.

[0035] The peeling force (sometimes referred to as "peeling force B2") of the second release liner against the adhesive surface (second adhesive surface) when peeled from the second adhesive layer under conditions of 23°C, 50% RH, a pulling speed of 300 mm / min, and a peeling angle of 180° is 0.23 N / 50 mm or less, preferably 0.18 N / 50 mm or less, and more preferably 0.11 N / 50 mm or less. By having a peeling force B2 of 0.23 N / 50 mm or less, the peeling force is small even at a relatively slow pulling speed, and the second release liner can be easily peeled from the adhesive body. In addition, when the first adhesive layer is first attached to the adherend and then the second release liner is peeled off, the adherend is unlikely to be destroyed. From the viewpoint that the second release liner is unlikely to fall off the adhesive body when the adhesive sheet is unused, the peeling force B2 is preferably 0.03 N / 50 mm or more.

[0036] The difference between the peel force B1 and the peel force B2 is 0.25 N / 50 mm or less, preferably 0.18 N / 50 mm or less, more preferably 0.12 N / 50 mm or less, and even more preferably 0.08 N / 50 mm or less. When the difference is 0.25 N / 50 mm or less, the tensile speed dependency is small, making it applicable to a wide range of processing speeds, and enabling the second release liner to be easily peeled off while preventing damage to the second pressure-sensitive adhesive layer.

[0037] The difference between the peeling force A1 and the peeling force B1 is 0.40 N / 50 mm or less, preferably 0.17 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 0.40 N / 50 mm or less, the release liner can be easily peeled off from either side of the double-sided pressure-sensitive adhesive sheet. In addition, 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 stuck to the adherend, the difference between the peeling force of the adhesive body to the adherend and the peeling force of the release liner to the adhesive body is small, so that the peeling stress applied to the adherend is small, and the adherend already stuck is unlikely to break. The difference between the peeling force A1 and the peeling force B1 indicates an absolute value. The peeling force A1 and the peeling force B1 may be the same or different. When the peeling force A1 and the peeling force B1 are different, either one may be the larger value.

[0038] The difference between the peeling force A2 and the peeling force B2 is preferably 0.17 N / 50 mm or less, more preferably 0.12 N / 50 mm or less, even more preferably 0.08 N / 50 mm or less, and particularly preferably 0.06 N / 50 mm or less. When the difference is 0.17 N / 50 mm or less, the release liner can be easily peeled off from either side of the double-sided pressure-sensitive adhesive sheet even at a relatively slow processing speed. In addition, when peeling off the release liner remaining on the double-sided pressure-sensitive adhesive sheet in a state where one adhesive surface of the double-sided pressure-sensitive adhesive sheet is attached to an adherend, the difference between the peeling force of the adhesive body to the adherend and the peeling force of the release liner to the adhesive body is small, so that the peeling stress applied to the adherend is small, and the adherend already attached is unlikely to break even at a relatively slow processing speed. 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 be the larger value.

[0039] The above-mentioned release forces can be measured in accordance with JIS Z0237: 2000. The above-mentioned release forces tend to depend heavily on the type of release liner used (particularly, for release liners having a substrate and a release treatment layer, the type and composition of the release treatment layer in contact with the pressure-sensitive adhesive layer).

[0040] (base material layer) The substrate layer is an element that functions as a support in the double-sided pressure-sensitive adhesive sheet. By providing the substrate layer, the double-sided pressure-sensitive adhesive sheet has excellent punching processability, and when the release liner remaining on the double-sided pressure-sensitive adhesive sheet is peeled off in a state where one adhesive surface of the double-sided pressure-sensitive adhesive sheet is attached to an adherend, the adherend that has already been attached is unlikely to be destroyed. For example, the substrate layer is preferably a plastic substrate (particularly a plastic film). The substrate layer may be a single layer or a laminate of the same or different substrates.

[0041] Examples of the resin constituting the plastic substrate include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, very low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, and ethylene-hexene copolymer; polyurethane; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyether ether ketone; polyetherimide; polyamides such as aramid and fully aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; and silicone resin. Only one of the above resins may be used, or two or more of them may be used.

[0042] As the base layer, from the viewpoint of excellent transparency, a plastic film is preferable, a polyester film or a polyolefin film is more preferable, and a polyethylene terephthalate film is particularly preferable.

[0043] The substrate layer may contain various additives such as fillers (inorganic fillers, organic fillers, etc.), colorants (pigments or dyes), dispersants (surfactants, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, etc. The blending ratio of the various additives is about less than 30% by weight (e.g., less than 20% by weight, typically less than 10% by weight) relative to 100% by weight of the total mass of the substrate layer.

[0044] The substrate layer may include an auxiliary layer, such as a colored layer, a reflective layer, an undercoat layer, or an antistatic layer, which is provided on the surface of the substrate layer.

[0045] The surface of the substrate layer may be subjected to a surface treatment such as a physical treatment such as corona discharge treatment, plasma treatment, sand mat processing treatment, ozone exposure treatment, flame exposure treatment, high-voltage shock exposure treatment, ionizing radiation treatment, etc., a chemical treatment such as chromate treatment, an easy-adhesion treatment using a coating agent (primer), etc., for the purpose of improving adhesion and retention with the pressure-sensitive adhesive layer. The surface treatment for improving adhesion is preferably applied to the entire surface of the substrate layer.

[0046] The thickness of the base layer is preferably 40 μm or less, more preferably 25 μm or less, even more preferably 15 μm or less, even more preferably 13 μm or less, and particularly preferably 12 μm or less, from the viewpoint of excellent conformity to the fine unevenness of the adherend surface when the pressure-sensitive adhesive body is attached. Also, the thickness of the base layer is preferably 2 μm or more, more preferably 4 μm or more, from the viewpoint of excellent function as a support and excellent punching properties.

[0047] (Adhesive layer) The first and second adhesive layers in the double-sided adhesive sheet may be the same adhesive layer, or may be adhesive layers with different compositions, thicknesses, physical properties, etc. In this specification, when the first adhesive layer and the second adhesive layer are used collectively without distinction, they may be simply referred to as "adhesive layers". Each of the first and second adhesive layers may be a single layer, or may be a multilayer composed of the same or different layers.

[0048] The adhesive constituting the adhesive layer is not particularly limited, and examples thereof include acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, a mixture thereof, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, and fluorine adhesives. Among them, acrylic adhesives are preferred as the adhesive constituting the adhesive layer in terms of adhesion, weather resistance, cost, and ease of adhesive design. The adhesive layer is preferably an acrylic adhesive layer composed of an acrylic adhesive. Only one type of adhesive may be used, or two or more types may be used.

[0049] 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 a constituent unit derived from the acrylic monomer. Only one type of acrylic polymer may be used, or two or more types may be used.

[0050] 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 mass%. The content of the acrylic polymer in the acrylic pressure-sensitive adhesive layer is preferably 60 mass% or more, more preferably 70 mass% or more, relative to 100 mass% of the total amount of the acrylic pressure-sensitive adhesive layer.

[0051] The acrylic polymer is preferably a polymer constituted (formed) with an alkyl (meth)acrylate ester as an essential monomer component. That is, the acrylic polymer preferably contains an alkyl (meth)acrylate ester as a constituent unit. In this specification, "(meth)acrylic" refers to "acrylic" and / or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and the same applies to others.

[0052] The (meth)acrylic acid alkyl ester as the essential monomer component is preferably a (meth)acrylic acid alkyl ester having a linear or branched alkyl group. The (meth)acrylic acid alkyl ester may be used alone or in combination of two or more.

[0053] The (meth)acrylic acid alkyl ester having a linear or branched alkyl group is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and the like. Examples of the (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms include isononyl acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate (stearyl (meth)acrylate), isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Among these, the (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 18 carbon atoms (preferably 2 to 4) is preferred.

[0054] The proportion of the (meth)acrylic acid alkyl ester in the total amount (100% by mass) of all monomer components constituting the acrylic polymer is not particularly limited, but is preferably 50% by mass or more (for example, 50 to 100% by mass), more preferably 70% by mass or more, even 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, even more preferably 98% by mass or less, and particularly preferably 97% by mass or less. When the proportion is within the above range, a pressure-sensitive adhesive layer having a good quantitative balance with the copolymerizable monomer and good adhesion even when thin can be formed.

[0055] 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 constituent unit. The copolymerizable monomer may be used alone or in combination of two or more kinds.

[0056] The copolymerizable monomer is preferably a carboxyl group-containing monomer and / or an acid anhydride monomer, from the viewpoint of forming a thin adhesive layer having good adhesion. Examples of the carboxyl 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.

[0057] The ratio of the carboxyl group-containing monomer and / or acid anhydride monomer in the total amount of all monomer components constituting the acrylic polymer (100% by mass) is not particularly limited, but is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and particularly preferably 2% by mass or more. The ratio 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 ratio is within the above range, the adhesive layer has a good quantitative balance with the (meth)acrylic acid alkyl ester, and can be formed with good adhesion even if it is thin.

[0058] The copolymerizable monomer may further include a functional group-containing monomer for the purpose of introducing a crosslinking point into the acrylic polymer or increasing the cohesive force of the acrylic polymer. The functional group-containing monomer may include a hydroxy group-containing monomer, an epoxy group-containing monomer, a nitrogen atom-containing monomer, a keto group-containing monomer, an alkoxysilyl group-containing monomer, a sulfonic acid group-containing monomer, and a phosphoric acid group-containing monomer. Among them, a hydroxy group-containing monomer and a nitrogen atom-containing monomer are preferred. The functional group-containing monomer may be used alone or in combination of two or more.

[0059] Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and polypropylene glycol mono(meth)acrylate.

[0060] Examples of the epoxy group-containing monomer include glycidyl group-containing monomers such as glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0061] Examples of the nitrogen atom-containing monomer include amide group-containing monomer, amino group-containing monomer, cyano group-containing monomer, and monomer 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, and N-butoxymethyl(meth)acrylamide. Examples of the amino group-containing monomer include aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and t-butylaminoethyl(meth)acrylate. 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, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, and N-(meth)acryloylmorpholine.

[0062] 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.

[0063] Examples of the alkoxysilyl group-containing monomer include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0064] Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

[0065] The above-mentioned phosphoric acid group-containing monomer includes, for example, 2-hydroxyethyl acryloyl phosphate.

[0066] The ratio of the functional group-containing monomer in the total amount of all monomer components constituting the acrylic polymer (100% by mass) may be, for example, 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 5% by mass or more, or 10% by mass or more. The ratio may be, for example, 40% by mass or less, 20% by mass or less, or may not be substantially contained. In this specification, "substantially not contained" refers to unintentional inclusion, such as unavoidable inclusion, rather than active incorporation, and is, for example, 0.05% by mass or less, 0.01% by mass or less.

[0067] The copolymerizable monomer may further include 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; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate; aryl (meth)acrylates (e.g., phenyl (meth)acrylate), and aryloxyalkyl (meth)acrylates (e.g., phenoxyethyl (meth)acrylate). acrylate), aromatic ring-containing (meth)acrylates such as arylalkyl (meth)acrylate (for example, benzyl (meth)acrylate); olefin-based monomers such as ethylene, propylene, isoprene, butadiene, isobutylene, etc.; chlorine-containing monomers such as vinyl chloride, vinylidene chloride, etc.; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate, etc.; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, etc.; vinyl ether-based monomers such as methyl vinyl ether, ethyl vinyl ether, etc.

[0068] The proportion of the other monomers in the total amount (100% by mass) of all monomer components constituting the acrylic polymer may be, for example, 0.05% by mass or more, 0.5% by mass or more, and may be, for example, 20% by mass or less, 10% by mass or less, 5% by mass or less, or may be substantially absent.

[0069] The acrylic polymer may contain a polyfunctional monomer copolymerizable with the monomer component forming the acrylic polymer as a monomer component constituting the polymer in order to form a crosslinked structure in the polymer skeleton. Examples of the polyfunctional monomer include monomers having a (meth)acryloyl group and other reactive functional groups in the molecule, such as hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy(meth)acrylate (e.g., polyglycidyl(meth)acrylate), polyester(meth)acrylate, and urethane(meth)acrylate. The polyfunctional monomer may be used alone or in combination of two or more. The polyfunctional monomer exhibits the same function as the crosslinking agent described below, and may also serve as a crosslinking agent.

[0070] 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 for example, solution polymerization method, emulsion polymerization method, bulk polymerization method, polymerization method by active energy ray irradiation (active energy ray polymerization method) and the like can be mentioned.Among them, from the viewpoint of transparency of the pressure-sensitive adhesive layer, cost, etc., solution polymerization method and active energy ray polymerization method are preferred, and solution polymerization method is more preferred.

[0071] In addition, various common solvents may be used when polymerizing the monomer components. Examples of the solvent include organic solvents such as esters such as ethyl acetate and n-butyl acetate, aromatic hydrocarbons such as toluene and benzene, aliphatic hydrocarbons such as n-hexane and n-heptane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, and ketones such as methyl ethyl ketone and methyl isobutyl ketone. Note that only one type of solvent may be used, or two or more types may be used.

[0072] In the polymerization of the above-mentioned monomer components, a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator) may be used depending on the type of polymerization reaction. Note that only one type of polymerization initiator may be used, or two or more types may be used.

[0073] The thermal polymerization initiator is not particularly limited, but examples thereof include azo polymerization initiators, peroxide polymerization initiators (e.g., persulfates such as dibenzoyl peroxide, tert-butyl permaleate, potassium persulfate, benzoyl peroxide, hydrogen peroxide, etc.), substituted ethane initiators such as phenyl-substituted ethane, aromatic carbonyl compounds, redox polymerization initiators, etc. Among them, the azo polymerization initiators disclosed in JP-A-2002-69411 are preferred. Examples of the azo polymerization initiators include 2,2'-azobisisobutyronitrile (hereinafter sometimes referred to as "AIBN"), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionate) dimethyl, and 4,4'-azobis-4-cyanovaleric acid. The amount of the thermal polymerization initiator used may be a normal amount, and can be selected, for example, from the range of 0.005 to 1 part by mass, preferably 0.01 to 1 part by mass, per 100 parts by mass of the monomer component.

[0074] The photopolymerization initiator is not particularly limited, but examples thereof include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. Other examples include acylphosphine oxide-based photopolymerization initiators and titanocene-based photopolymerization initiators. Examples of the benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl ether. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of the aromatic sulfonyl chloride-based 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, etc. Examples of the ketal-based photopolymerization initiator include benzyl dimethyl ketal, etc.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-diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Examples of the titanocene-based photopolymerization initiator include bis(η. 5 -2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium. The amount of the photopolymerization initiator used may be a normal amount, and may be selected, for example, from the range of 0.01 to 3 parts by mass, preferably 0.1 to 1.5 parts by mass, relative to 100 parts by mass of the monomer component.

[0075] The pressure-sensitive adhesive layer may contain a tackifier resin. When the pressure-sensitive adhesive layer contains a tackifier resin, the pressure-sensitive adhesive layer tends to have better adhesion even if it is thin. When the pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer and a tackifier resin, the pressure-sensitive adhesive layer has excellent adhesion to the adherend and is less likely to peel off.

[0076] Examples of the tackifier resin include phenol-based tackifier resins, terpene-based tackifier resins, rosin-based tackifier resins, hydrocarbon-based tackifier resins, epoxy-based tackifier resins, polyamide-based tackifier resins, elastomer-based tackifier resins, and ketone-based tackifier resins. 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 tackifier resin may be used, or two or more types may be used.

[0077] Examples of the phenol-based tackifier resin include terpene phenol resin, hydrogenated terpene phenol resin, alkyl phenol resin, and rosin phenol resin. The terpene phenol resin is a polymer containing a terpene residue and a phenol residue, and examples thereof include a copolymer of a terpene and a phenol compound (terpene-phenol copolymer resin), and a homopolymer or copolymer of a terpene modified with phenol (phenol modified terpene resin). Examples of the terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (d-form, l-form, d / l-form (dipentene), etc.). The hydrogenated terpene phenol resin is a resin having a structure obtained by hydrogenating the terpene phenol resin. The alkyl phenol resin is a resin (oil-based phenol resin) obtained from an alkyl phenol and formaldehyde. Examples of the alkyl phenol resin include novolac type and resol type. The rosin phenol resin is a phenol modified product of rosins or various rosin derivatives described below. The rosin phenol resin can be obtained, for example, by adding phenol to rosins or various rosin derivatives described below in the presence of an acid catalyst and then thermally polymerizing the resulting mixture.

[0078] The terpene-based tackifying resin includes polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. The terpene polymer may be a homopolymer of one type of terpene, or a copolymer of two or more types of terpenes. Examples of homopolymers of one type of terpene 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 resin include styrene-modified terpene resin and hydrogenated terpene resin.

[0079] Examples of the rosin-based tackifier resin include rosins and rosin derivative resins. Examples of the rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins) obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, and the like. Examples of the rosin derivative resin include derivatives of the rosins. Examples of the rosin derivative resin include rosin esters such as unmodified rosin esters, which are esters of unmodified rosin and alcohols, and modified rosin esters, which are esters of modified rosin and alcohols; unsaturated fatty acid modified rosins obtained by modifying rosin with unsaturated fatty acids; unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups of rosins or the various rosin derivatives described above; and metal salts of rosins or the various rosin derivatives described above. Specific examples of the rosin esters include methyl esters, triethylene glycol esters, glycerin esters, and pentaerythritol esters of unmodified or modified rosin.

[0080] Examples of the hydrocarbon tackifier resin include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins.

[0081] The content of the tackifier resin in the pressure-sensitive adhesive layer is not particularly limited, but is, for example, 1 part by mass or more (e.g., 1 to 100 parts by mass) relative to 100 parts by mass of the total amount of the base polymer, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more. When the content is 1 part by mass or more, the pressure-sensitive adhesive layer has better adhesion even if it is thin. From the viewpoint of excellent heat-resistant cohesive strength, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less.

[0082] The pressure-sensitive adhesive layer preferably contains a crosslinking agent. By containing the crosslinking agent, for example, the acrylic polymer in the acrylic pressure-sensitive adhesive layer can be crosslinked, and the gel fraction can be controlled. The crosslinking agent may be used alone or in combination of two or more.

[0083] The crosslinking agent is not particularly limited, but examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, amine-based crosslinking agents, hydrazine-based crosslinking agents, silicone-based crosslinking agents, and silane-based crosslinking agents (silane coupling agents).

[0084] The content of the crosslinking 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, and particularly preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the total amount of the base polymer.

[0085] The isocyanate crosslinking agent is a compound having an average of two or more isocyanate groups per molecule (a polyfunctional isocyanate compound). Examples of the isocyanate crosslinking agent include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

[0086] 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 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0087] 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; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0088] Examples of the aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, Examples of the diisocyanate include 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, and xylylene-1,3-diisocyanate.

[0089] Examples of the isocyanate crosslinking agent include commercially available products such as trimethylolpropane / tolylene diisocyanate adduct (product name "Coronate L", manufactured by Tosoh Corporation), trimethylolpropane / hexamethylene diisocyanate adduct (product name "Coronate HL", manufactured by Tosoh Corporation), and trimethylolpropane / xylylene diisocyanate adduct (product name "Takenate D-110N", manufactured by Mitsui Chemicals, Inc.).

[0090] In addition, in the aqueous dispersion of the modified acrylic polymer prepared by emulsion polymerization, it is not necessary to use an isocyanate-based crosslinking agent. However, if necessary, a blocked isocyanate-based crosslinking agent can be used since it easily reacts with water.

[0091] When an isocyanate-based crosslinking agent is used as the crosslinking agent, the content of the isocyanate-based crosslinking agent is not particularly limited, but is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the total amount of the base polymer. 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.

[0092] Examples of the epoxy crosslinking agent (polyfunctional epoxy compound) include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, and ethylene glycol diglycidyl ether. Examples of the epoxy crosslinking agent include glycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid 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. Examples of the epoxy crosslinking agent include commercially available products such as "Tetrad C" (manufactured by Mitsubishi Gas Chemical Co., Ltd.).

[0093] When an epoxy-based crosslinking agent is used as the crosslinking agent, the content of the epoxy-based crosslinking agent is not particularly limited, but is preferably more than 0 part by mass and not more than 1 part by mass, more preferably 0.001 to 0.5 parts by mass, even more preferably 0.002 to 0.2 parts by mass, still more preferably 0.005 to 0.1 parts by mass, and particularly preferably 0.008 to 0.05 parts by mass, relative to 100 parts by mass of the total amount of the base polymer.

[0094] As the peroxide-based crosslinking agent, any peroxide-based crosslinking agent that generates radical active species by heat and promotes crosslinking of the base polymer can be used as appropriate. Taking into consideration workability and stability, it is preferable to use a peroxide with a 1-minute half-life temperature of 80 to 160°C, and it is more preferable to use a peroxide with a 1-minute half-life temperature of 90 to 140°C.

[0095] 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-butylperoxydicarbonate (1-minute half-life temperature: 92.4° C.), t-butylperoxyneodecanoate (1-minute half-life temperature: 103.5° C.), t-hexylperoxypivalate (1-minute half-life temperature: 109.1° C.), t-butylperoxypivalate (1-minute half-life temperature: 110.3° C.), dilauroylperoxy 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-ethylhexanoate (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-butylperoxyisobutyrate (1-minute half-life temperature: 136.1°C), 1,1-di(t-hexylperoxy)cyclohexane (1-minute half-life temperature: 149.2°C), and the like.

[0096] The half-life of the peroxide-based crosslinking agent is an index showing the decomposition rate of the peroxide, and refers to the time until the remaining amount of the peroxide is reduced to half. The decomposition temperature for obtaining the half-life at any time and the half-life time at any temperature are described in the manufacturer's catalog, for example, NOF Corp.'s "Organic Peroxide Catalog 9th Edition (May 2003)". The amount of decomposed peroxide remaining after the reaction can be measured, for example, by HPLC (high performance liquid chromatography). More specifically, for example, about 0.2 g of the adhesive after the reaction is taken out, immersed in 10 ml of ethyl acetate, and shaken and extracted for 3 hours at 25°C and 120 rpm in a shaker, and then allowed to stand at room temperature for 3 days. Next, 10 ml of acetonitrile is added, shaken for 30 minutes at 25°C and 120 rpm, and filtered through a membrane filter (0.45 μm). About 10 μl of the extract obtained is injected into HPLC for analysis, and can be used as the amount of peroxide after the reaction.

[0097] When a peroxide-based crosslinking agent is used as the crosslinking agent, the content of the crosslinking agent is not particularly limited, but is preferably 2 parts by mass or less, more preferably 0.02 to 2 parts by mass, and even more preferably 0.05 to 1 part by mass, relative to 100 parts by mass of the acrylic polymer.

[0098] In addition, the crosslinking agent may be used in combination with an organic crosslinking agent or a polyfunctional metal chelate. The polyfunctional metal chelate is a compound in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. Examples of atoms in the organic compound that are covalently or coordinately bonded include oxygen atoms, and examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.

[0099] As the crosslinking agent, it is preferable to include an isocyanate-based crosslinking agent. It is more preferable to include another crosslinking agent together with the isocyanate-based crosslinking agent. As the other crosslinking agent, an epoxy-based crosslinking agent is preferable. When such a crosslinking agent is used, it is possible to obtain a pressure-sensitive adhesive layer that is thin but has excellent adhesion by combining it with the acrylic polymer (particularly, by combining it with the above-mentioned preferred acrylic polymer).

[0100] If necessary, the pressure-sensitive adhesive layer may further contain additives such as crosslinking accelerators, antiaging agents, fillers (organic fillers, inorganic fillers, etc.), colorants (pigments, dyes, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, granular materials, foil-like materials, and rust inhibitors, within the range that does not impair the effects of the present invention. The above-mentioned additives may be used alone or in combination of two or more.

[0101] The thickness of the pressure-sensitive adhesive layer (each of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer) is not particularly limited, but is preferably 1 to 90 μm, and more preferably 3 to 50 μm. When the thickness is 1 μm or more, the adhesion of the double-sided pressure-sensitive adhesive sheet is higher. When the thickness is 90 μm or less, the thickness of the double-sided pressure-sensitive adhesive sheet can be made thinner. The thicknesses of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be the same or different.

[0102] (Release liner) The release liner is an element for covering and protecting the surface (adhesive surface) of the adhesive, 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 adhesive sheet may be of the same configuration, or may be release liners with different structures, compositions, thicknesses, physical properties, etc. In this specification, when the first release liner and the second release liner are used collectively without distinction, they may be simply referred to as "release liners". The double-sided adhesive sheet is used, for example, by first peeling off one release liner and attaching the exposed adhesive layer surface (adhesive surface) to one adherend, and then peeling off the other release liner and attaching the exposed adhesive layer surface (adhesive surface) to the other adherend.

[0103] The release liner is not particularly limited, and can be appropriately selected from known or conventional release liners. The release liner includes a substrate (substrate for release liner) having a release treatment layer on at least one side thereof, a low adhesion substrate made of fluoropolymer, and a low adhesion substrate made of non-polar polymer. The substrate may be a single layer, or a laminate of the same or different substrates.

[0104] The substrate of the release liner may be a plastic substrate, paper, foam, metal foil, or other thin material, and is preferably a plastic substrate. The plastic substrate may be any of the plastic substrates exemplified and described above as the substrate layer. Among these, a plastic film is preferred, more preferably a polyester film or a polyolefin film, and particularly preferably a polyethylene terephthalate film.

[0105] 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, even more preferably 8 to 60 μm, and particularly preferably 12 to 40 μm. When the thickness is 5 μm or more, the workability when peeling off the release liner is excellent. When the thickness is 100 μm or less, the rigidity is prevented from increasing, the conformity to the surface of the pressure-sensitive adhesive layer is excellent, and lifting of the release liner in the double-sided pressure-sensitive adhesive sheet is unlikely to occur. In addition, the roll diameter when wound into a rolled body is not too large. The thicknesses of the substrates in the first release liner and the second release liner may be the same or different.

[0106] The release agent constituting the release treatment layer is not particularly limited, and examples thereof include silicone-based release treatment agents, fluorine-based release treatment agents, long-chain alkyl-based release treatment agents, and molybdenum sulfide-based release treatment agents. Among these, silicone-based release treatment agents are preferred. The release treatment agents may be used alone or in combination of two or more.

[0107] The mass per area of ​​the release treatment layer is, for example, 0.01 to 5 g / m 2 and preferably 0.05 to 3 g / m 2 , and 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, and more preferably 0.3 to 2 μm.

[0108] Examples of release liners having a release treatment layer on one side of the above-mentioned substrate include commercially available products such as "Diafoil MHA", "Diafoil MHC", "Diafoil MHE", and "Diafoil MRF F4" (all manufactured by Mitsubishi Chemical Corporation), "SC05", "SCA0" (manufactured by Fujiko Co., Ltd.), "MFAS", "MDAS" (manufactured by Toray Industries, Inc.), and "SL1110-036" (manufactured by Sunliky).

[0109] Examples of the fluoropolymer in the low-adhesive substrate made of the fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc. Examples of the non-polar polymer include olefin resins (e.g., polyethylene, polypropylene, etc.).

[0110] (Double-sided adhesive sheet) The peel strength (adhesive strength to SUS) of the first adhesive surface or the second adhesive surface measured at 23°C, 50% RH, a tensile speed of 300 mm / min, and a peel angle of 180° against a stainless steel plate (SUS plate) is preferably 3 N / 25 mm or more, more preferably 10 N / 25 mm or more. The peel strength is, for example, 30 N / 25 mm or less, preferably 25 N / 25 mm. The adhesive strength to SUS is preferably satisfied for at least one of the first adhesive surface and the second adhesive surface, and more preferably satisfied for both in terms of excellent workability. The adhesive strength to SUS can be measured based on JIS Z0237:2000.

[0111] When the release liner has a release treatment layer composed of a silicone-based release treatment agent, when the release liner is peeled from the double-sided PSA sheet at a tensile speed of 300 mm / min and a peel angle of 180°, the amount of silicone that migrates from the release treatment layer to the PSA layer (transferred amount) is 0.003 to 0.012 g / m per unit area, calculated as polydimethylsiloxane. 2 and more preferably 0.006 to 0.010 g / m 2 The migration amount is 0.003 g / m 2 When the amount of transfer is 0.012 g / m or more, the transfer of the adhesive from the adhesive layer to the release liner is suppressed, and the adhesive body tends to have better adhesiveness. 2When the amount is less than 100%, the transfer of the release treatment agent from the release liner to the pressure-sensitive adhesive layer is suppressed, and the adhesive body tends to have better adhesion. The amount of silicone transfer is preferably satisfied for at least one of the first release liner and the second release liner, and more preferably satisfied for both.

[0112] Here, the above "per unit area" refers to "per unit area of ​​the adhesive layer in the portion where the adhesive layer and the release liner are attached to each other." The amount of silicone migration is determined by a method using fluorescent X-ray analysis.

[0113] When the release liner has a release treatment layer made of a silicone-based release treatment agent, when the release liner is peeled from the double-sided pressure-sensitive adhesive sheet at a tensile speed of 300 mm / min and a peel angle of 180°, the ratio (proportion) of the amount of silicone that migrates from the release treatment layer to the pressure-sensitive adhesive layer is preferably less than 30 mass% in terms of polydimethylsiloxane. The ratio (transfer rate) of silicone is preferably satisfied for at least one of the first release liner and the second release liner, and more preferably satisfied for both. The ratio of silicone that migrates from the release treatment layer of the release liner to the pressure-sensitive adhesive layer is determined using the results of silicone migration by fluorescent X-ray analysis.

[0114] The double-sided pressure-sensitive adhesive sheet is preferably used, for example, in optical members of electric and electronic devices, when attaching (mounting) various members or parts to a predetermined site (for example, a housing, etc.). The term "electrical and electronic devices" refers to devices that fall into at least one of electrical and electronic devices. Examples of the electric and electronic devices include image display devices such as liquid crystal displays, electroluminescent displays, and plasma displays, and mobile electronic devices. The double-sided pressure-sensitive adhesive sheet is preferably used by adhering to internal members of optical members (particularly, electric and electronic devices), and is particularly preferably used to fix internal members of optical members (particularly, electric and electronic devices).

[0115] Examples of the portable electronic device include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including glasses (monocular and binocular devices, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc. in the form of accessories, and earwear devices attached to the ears like earphones), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, and portable modems. In this specification, the term "portable" does not mean that the device is merely portable, but rather that the device has a level of portability that allows an individual (average adult) to carry the device relatively easily. The double-sided pressure-sensitive adhesive sheet is used, for example, so that the pressure-sensitive adhesive layer adheres to the components of the portable electronic device.

[0116] The double-sided pressure-sensitive adhesive sheet is preferably used to attach at least one of its adhesive surfaces to a brittle material such as graphite, since the adherend to which the adhesive body is already attached is unlikely to break. It may also be used to attach at least one of its adhesive surfaces to a material harder than the brittle material (e.g., a metal plate such as a SUS plate). In particular, it is preferably used to attach one of its adhesive surfaces (especially the adhesive surface that is attached first) to a brittle material such as graphite. In addition, it is preferable that the adherend attached to the other adhesive surface (especially the adhesive surface that is attached later) is a material harder than the brittle material (e.g., a metal plate such as a SUS plate). EXAMPLES

[0117] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples in any way. It should be noted that Example 24 is provided as a reference example.

[0118] 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 replacement was performed for 1 hour or more. Azobisisobutyronitrile was added as an initiator, and then the temperature of the inner bath was raised to 62°C and maintained at the same temperature until the reaction was almost completed, and then the polymerization reaction was terminated by cooling. To 100 parts by mass of the obtained polymer, 3 parts by mass of an isocyanate compound (trade name "Coronate L", manufactured by Tosoh Corporation) and 0.01 parts by mass of an epoxy compound (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Co., Ltd.) were added, and 20 parts by mass of a terpene phenol-based tackifier resin (trade name "YS Polystar T115", manufactured by Yasuhara Chemical Co., Ltd.) were further added to prepare a pressure-sensitive adhesive composition.

[0119] The above-mentioned adhesive composition was applied onto the release-treated layer of a release liner (trade name "Diafoil MHA", manufactured by Mitsubishi Chemical Corporation, a polyethylene terephthalate film with one side subjected to release treatment with a silicone-based release agent) as a first release liner, and dried to form a first adhesive layer. Then, one side of a PET film to be a base layer was laminated onto the surface of the above-mentioned first adhesive layer. On the other hand, the above-mentioned adhesive composition was applied onto the release-treated layer of a release liner (trade name "SC05", manufactured by Fujiko Co., Ltd., a polyethylene terephthalate film with one side subjected to release treatment with a silicone-based release agent) as a second release liner, and dried to form a second adhesive layer. Next, the above-mentioned second adhesive layer was attached to the other side of the above-mentioned base layer. In this way, a double-sided adhesive sheet was prepared in which an adhesive layer was laminated on each of both sides of the base layer, and further a release liner was laminated on each of both adhesive layers. The thickness of the base layer, the thickness of the adhesive layer, and the thickness of the release liner are as shown in Table 1. The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer have the same thickness.

[0120] Examples 2 to 24, Comparative Example 3 Double-sided PSA sheets were prepared in the same manner as in Example 1, except that the thickness of the base layer, the thickness of the adhesive layer, the type of release liner, the thickness of the release liner, etc. were changed as shown in Tables 1 and 2.

[0121] Comparative Example 1 The adhesive composition prepared in Example 1 was applied onto the release-treated layer of a release liner (trade name "Diafoil MHA", manufactured by Mitsubishi Chemical Corporation, a polyethylene terephthalate film with a release treatment applied to one side with a silicone-based release agent) as a first release liner, and dried to form an adhesive layer. Then, the release-treated layer of a release liner (trade name "SC05", manufactured by Fujiko Co., Ltd.) as a second release liner was attached to the exposed adhesive surface of the adhesive layer. In this way, a double-sided adhesive sheet in which release liners were laminated on both sides of the adhesive layer was prepared. The thickness of the adhesive layer and the thickness of the release liner are as shown in Table 2.

[0122] Comparative Examples 2 and 4 Double-sided PSA sheets were prepared in the same manner as in Comparative Example 1, except that the type and thickness of the release liner were changed as shown in Table 2.

[0123] The release liners shown in the table are all polyethylene terephthalate films each having one side 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. SCA0: Product name "SCA0", manufactured by Fujiko Co., Ltd. MRF F4: Product name "Diafoil MRF F4", manufactured by Mitsubishi Chemical Corporation MRV: Product name "Diafoil MRV", manufactured by Mitsubishi Chemical Corporation

[0124] <Evaluation> The double-sided PSA sheets obtained in the Examples and Comparative Examples were evaluated as follows, and the results are shown in the Table.

[0125] (1) Release strength of release liner A sheet piece with a width of 50 mm and a length of 150 mm was cut out from the double-sided adhesive sheet. For the peeling force A1, the sheet piece was used as it is as a measurement sample. For the peeling force B1, the first release liner of the sheet piece was peeled off, and a PET film with a thickness of 50 μm was attached to the exposed adhesive surface to back it, and this was used as a measurement sample. The opposite side of each measurement sample to the side where the peeling force was measured was attached to a Bakelite plate with double-sided tape and fixed to a base, and a 180° peeling test was performed using a tensile tester in accordance with JIS Z0237 to measure the 180° peeling adhesive force [N / 50 mm] from the surface of the adhesive layer of the release liner. This was defined as the "peeling force of the release liner". The measurement was performed under the conditions of 23°C ± 2°C, 50% ± 5% RH, peel angle of 180°, tensile speed of 10000 mm / min, and tensile speed of 300 mm / min. The number of tests (n number) was 3, and the average value was calculated.

[0126] (2) Amount of silicone transferred From the double-sided pressure-sensitive adhesive sheet, the release liner laminated on the pressure-sensitive adhesive layer opposite to the pressure-sensitive adhesive layer for which the silicone transfer amount is to be measured is peeled off, and a PET film having a thickness of 50 μm is attached to back it up. The backed pressure-sensitive adhesive sheet is cut into a rectangular shape of 50 mm x 50 mm to obtain a measurement sample. The measurement sample is placed in a 70 ° C. dryer with a load of 5 kg for 24 hours, then the load is removed, the sample is taken out of the dryer, and the sample is kept at 23 ° C. for another 2 hours. The release liner on the side for which the silicone transfer amount is to be measured is peeled off from the measurement sample at a pulling speed of 300 mm / min and a peel angle of 180 °, and the amount of Si present per area equivalent to a circle with a diameter of 30 mm is determined as X-ray intensity (cps: counts per second) for the exposed adhesive surface by a fluorescent X-ray analyzer. Then, the silicone amount (silicone transfer amount) of the pressure-sensitive adhesive layer (g / m ) is calculated from the X-ray intensity (cps) of the adhesive surface of the obtained pressure-sensitive adhesive layer. 2 The conversion formula is 100 kcps = 0.60 g / m 2 In measuring the amount of silicone migration, a fluorescent X-ray analyzer with the product name "ZSX100E" (manufactured by RIGAKU Corporation) was used, and Rh was used as the X-ray source. RX-4 was used as the analyzing crystal, and the X-ray intensity was measured by setting the output to 50 kV and 70 mA.

[0127] (3) Removability of release liner The double-sided adhesive sheet was cut into pieces of 50 mm×300 mm in size, and each release liner was peeled off at a tensile speed of 300 mm / min to 10,000 mm / min, during which the presence or absence of the so-called “floating” phenomenon was confirmed. Specifically, when one release liner (the release liner to be evaluated) was peeled off, it was visually confirmed whether peeling occurred reliably at the interface between the release liner on the peeling side and the surface of the adhesive layer (adhesive surface) and whether the release liner on the peeling side could be easily peeled off from the double-sided adhesive sheet, whether the other release liner (the release liner on the side not peeled off) was not floating off the adhesive surface of the adhesive body, and whether peeling occurred at the interface between the release liner on the peeling side and the adhesive surface and whether peeling did not occur at the interface between the other release liner and the adhesive surface. The evaluation criteria for the releasability of the release liners were as follows: ◯: When one of the release liners was peeled off, it was easy to peel off, and there was no lifting or peeling (crying and separating) at the interface between the other release liner and the surface of the pressure-sensitive adhesive layer. ×: When one release liner was peeled off, lifting or peeling (weaving and separation) was observed at the interface between the other release liner and the surface of the pressure-sensitive adhesive layer.

[0128] (4) Punching workability The double-sided adhesive sheet was processed (cut) to a depth where the second release liner on the opposite side was half-cut by inserting a processing blade from the second release liner side. After 60 seconds, the first release liner was removed from the laminate of the second release liner and the adhesive body. The degree of glue overflow at the processed end surface of the adhesive body on the first adhesive layer side was observed under a microscope. Those with glue overflow of 0.01 mm or more were evaluated as "x", and those with glue overflow of less than 0.01 mm were evaluated as "○".

[0129] (5) Adhesion to SUS The double-sided adhesive sheet was cut to a size of 25 mm wide and 100 mm long. Then, the release liner opposite to the release liner to be measured was peeled off from the double-sided adhesive sheet, and a PET film having a thickness of 50 μm was attached to the exposed adhesive surface to form a test piece. In an environment of 23° C. and 50% RH, the release liner to be measured of the above test piece was peeled off, and the exposed adhesive surface was pressed against a stainless steel plate (SUS304BA plate) to form a measurement sample. The above pressing was performed by moving a 2 kg roller back and forth once. After leaving the above measurement sample in an environment of 23° C. and 50% RH for 30 minutes, the peel strength [N / 25 mm] was measured using a tensile tester "Precision Universal Testing Machine Autograph AG-IS 50N" (manufactured by Shimadzu Corporation) in accordance with JIS Z0237:2000 under conditions of a tensile speed of 300 mm / min and a peel angle of 180°, and this value was taken as the adhesive strength to SUS.

[0130] (6) Destruction of the adherend The double-sided adhesive sheet was cut to a size of 50 mm wide and 300 mm long. Then, one release liner was peeled off from the double-sided adhesive sheet, and the exposed adhesive surface was attached to a graphite sheet. The other release liner was then peeled off from the double-sided adhesive sheet under conditions of 23°C ± 2°C, 50% ± 5% RH, peel angle of 180°, and tensile speed of 10000 mm / min. At that time, the graphite sheet was evaluated as "x" if damage was confirmed, and as "○" if no damage was confirmed. The evaluation was performed from both the first release liner side and the second release liner side.

[0131] [Table 1]

[0132] [Table 2]

[0133] As shown in Tables 1 and 2, the double-sided pressure-sensitive adhesive sheet of the present invention can be easily peeled off from either side when the release liner is peeled off, and the difference in peel force between a tensile speed of 300 mm / min and a tensile speed of 10,000 mm / min is small, and it was evaluated that the speed dependency is small. Furthermore, when one adhesive surface of the double-sided pressure-sensitive adhesive sheet of the present invention is attached to an adherend and the release liner remaining on the double-sided pressure-sensitive adhesive sheet is peeled off, no damage was confirmed in the graphite sheet already attached, and it was evaluated that the adherend is unlikely to be broken. It was also evaluated that the punching processability is excellent. On the other hand, when there is no base layer (Comparative Examples 1, 2, and 4), even when the release liner used in the examples was used, it was not easy to peel off from at least one side, and further, damage to the graphite sheet was confirmed. In addition, the punching processability was also poor. Even when there is a base layer, when the difference between the peel force A1 and the peel force A2 or the difference between the peel force A1 and the peel force B1 was large (Comparative Example 3), the results were similar to those of other comparative examples. [Explanation of symbols]

[0134] 1 double-sided adhesive sheet 2 Base material layer 3 First adhesive layer 3a 1st adhesive side 4 Second adhesive layer 4a 2nd adhesive side 5 First release liner 6 Second release liner

Claims

1. a base layer, first and second pressure-sensitive adhesive layers laminated on both sides of the base layer, a first release liner laminated on the adhesive surface of the first pressure-sensitive adhesive layer, and a second release liner laminated on the adhesive surface of the second pressure-sensitive adhesive layer; the first release liner has a peel strength A1 of 0.27 N / 50 mm or less on the adhesive surface when peeled from the first pressure-sensitive adhesive layer at a tensile speed of 10,000 mm / min and a peel angle of 180° at 23° C. and 50% RH; and the second release liner has a peel strength B1 of 0.20 N / 50 mm or less on the adhesive surface when peeled from the second pressure-sensitive adhesive layer at a tensile speed of 10,000 mm / min and a peel angle of 180° at 23° C. and 50% RH. the first release liner has a peel force A2 on the adhesive surface when peeled from the first pressure-sensitive adhesive layer at a pulling speed of 300 mm / min and a peel angle of 180° at 23° C. and 50% RH, and the second release liner has a peel force B2 on the adhesive surface when peeled from the second pressure-sensitive adhesive layer at a pulling speed of 300 mm / min and a peel angle of 180° at 23° C. and 50% RH, both of which are 0.18 N / 50 mm or less; The difference between the peel force A1 and the peel force A2 is 0.25 N / 50 mm or less, The difference between the peel force B1 and the peel force B2 is 0.25 N / 50 mm or less, The difference between the peel force A1 and the peel force B1 is 0.40 N / 50 mm or less, The double-sided pressure-sensitive adhesive sheet, wherein the first release liner and the second release liner differ in one or more selected from the group consisting of composition, thickness, and physical properties.

2. The double-sided pressure-sensitive adhesive sheet according to claim 1 , wherein the thickness from the adhesive surface of the first pressure-sensitive adhesive layer to the adhesive surface of the second pressure-sensitive adhesive layer is 100 μm or less.

3. 3. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein each of the first and second release liners has a thickness of 10 to 100 μm.

4. 4. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the adhesive surface of the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer has a peel strength from a stainless steel plate of 3 N / 25 mm or more, measured under conditions of 23° C., 50% RH, a tensile speed of 300 mm / min, and a peel angle of 180°.

5. 5. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the thickness from the adhesive surface of the first pressure-sensitive adhesive layer to the adhesive surface of the second pressure-sensitive adhesive layer is 8 to 50 μm.

6. 6. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the peel strength A1 and the peel strength B1 are both 0.11 N / 50 mm or less.

7. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the difference between the peel force A1 and the peel force A2 is 0.18 N / 50 mm or less, and the difference between the peel force B1 and the peel force B2 is 0.18 N / 50 mm or less.

8. 8. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the difference between the peel strength A1 and the peel strength B1 is 0.17 N / 50 mm or less.

9. 9. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the difference between the peel strength A2 and the peel strength B2 is 0.17 N / 50 mm or less.

10. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the first and second release liners comprise a substrate and a release treatment layer provided on at least one surface of the substrate.

11. The double-sided pressure-sensitive adhesive sheet according to claim 10 , wherein the release treatment layer is a silicone-based release treatment layer.

12. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 11, wherein the first and / or second pressure-sensitive adhesive layer is attached to graphite.

13. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 12, wherein the first and / or second pressure-sensitive adhesive layer is attached to a metal plate.

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