Adhesive sheet, joint, and method for separating the joint

Abstract

The present invention pertains to an adhesive sheet having a band shape and provided with an adhesive layer, said adhesive sheet comprising a slanted part formed in a tapering shape such that the width thereof tapers toward one end of the adhesive sheet in the longitudinal direction.

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet, a bonding body, and a method for separating the bonding body. [Background technology]

[0002] In electronic component manufacturing processes, there is a growing demand for rework to improve yield and for recycling, which involves disassembling and recovering components after use. To meet these demands, double-sided adhesive sheets that possess both a certain level of adhesive strength and a certain level of peelability are sometimes used to join components together in electronic component manufacturing processes. Patent documents 1 and 2 disclose prior art related to this type of re-peelable adhesive sheet.

[0003] Patent documents 1 and 2 describe a tabbed adhesive product comprising an extendable adhesive sheet and tabs provided at the ends of the adhesive sheet.

[0004] Furthermore, as a double-sided adhesive sheet that achieves both adhesive strength and peelability, an adhesive sheet (electropeelable adhesive sheet) is known that has an electropeelable adhesive layer made of an electropeelable adhesive composition that peels off when a voltage is applied to the adhesive layer (Patent Document 3). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-75231 [Patent Document 2] Japanese Patent Application Publication No. 2017-75228 [Patent Document 3] International Publication No. 2017 / 064925 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the sticky products with tabs described in Patent Documents 1 and 2 prevent deformation and damage of the adherend by providing tabs at the ends of the stretchable adhesive sheet, and no consideration has been given to non-stretchable adhesive sheets. There is a demand for an adhesive sheet having better peelability.

[0007] The present invention has been conceived under such circumstances, and an object thereof is to provide an adhesive sheet having excellent adhesive strength and better peelability. Another object is to provide a bonded body having excellent adhesive strength and good peelability, and a method for separating such a bonded body.

Means for Solving the Problems

[0008] As a result of intensive research, the present inventors have found that the above problems can be achieved by an adhesive sheet having a specific structure.

[0009] The present invention has the following configuration. 〔1〕 A strip-shaped adhesive sheet provided with an adhesive layer, An adhesive sheet provided with an inclined portion formed in a tapered shape whose width tapers toward one end in the longitudinal direction of the adhesive sheet. 〔2〕 The adhesive sheet according to 〔1〕, provided with a tab provided at the end. 〔3〕 The adhesive sheet according to 〔1〕 or 〔2〕, wherein the ratio of the length of the inclined portion to the length of the adhesive sheet in the longitudinal direction is 5% or more. 〔4〕 The adhesive sheet according to any one of 〔1〕 to 〔3〕, wherein the ratio of the width of the end portion to the width of the adhesive sheet is 50% or less. 〔5〕 The adhesive sheet according to any one of 〔1〕 to 〔4〕, wherein the adhesive layer is an electrically peelable adhesive layer whose adhesive strength decreases when a voltage is applied. 〔6〕 The adhesive sheet according to 〔5〕, wherein the electrically peelable adhesive layer contains a polymer and an ionic liquid. [7] The adhesive sheet according to [6], wherein the anion of the ionic liquid is at least one selected from the group consisting of bis(fluorosulfonyl)imide anions and bis(trifluoromethanesulfonyl)imide anions. [8] The adhesive sheet according to [6] or [7], wherein the cation of the ionic liquid is at least one selected from the group consisting of nitrogen-containing onium cations, sulfur-containing onium cations, and phosphorus-containing onium cations. [9] A bonding body comprising an adhesive sheet as described in any one of items (1) to (8), a first adherend, and a second adherend.

[10] A method for separating the joint described in [9], A method for separating a bonded body, comprising initiating the separation of the first bonded body and the second bonded body from the outer edge of the portion of the first bonded body or the second bonded body joined by the inclined portion of the adhesive sheet. [Effects of the Invention]

[0010] The present invention provides an adhesive sheet and a bond having excellent adhesive strength and good release properties. It also provides a method for separating a bond with good release properties. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic top view of an adhesive sheet according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic perspective view showing another configuration example (embodiment) of the adhesive sheet according to the present invention. [Figure 3] Figures 3(a), (b), and (c) are schematic cross-sectional views of an adhesive sheet according to one embodiment of the present invention. [Figure 4] Figure 4 is a cross-sectional view showing an example of the laminated structure of the adhesive sheet of the present invention. [Figure 5] Figure 5 is a cross-sectional view showing another example of the laminated structure of the adhesive sheet of the present invention. [Figure 6] Figure 6 is a schematic cross-sectional view showing an example of the edge of the adhesive sheet shown in Figure 1. [Figure 7] Figure 7 is a schematic cross-sectional view of a joint in which a first adherend and a second adherend are bonded together using an adhesive sheet according to a modified example of one embodiment of the present invention. [Figure 8] Figure 8 is a schematic top view showing one example (embodiment) of the configuration of the adhesive sheet when it is attached to the first adherend and the second adherend. [Figure 9] Figure 9 is a diagram illustrating the method for preparing test samples in the examples. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below.

[0013] In this specification, "strip shape" means a shape that extends linearly and has a width (length in a direction perpendicular to the direction of linear extension). The above-mentioned strip shape is a shape that has a predetermined length in the direction of linear extension and a width shorter than that length, and is a concept that includes rectangular shapes and strip shapes. Therefore, the term "strip shape" can be rephrased as "long shape". A strip shape according to one embodiment may have a shape that extends linearly, but may also have a shape that extends curvedly, and may include shapes that have both a linearly extending portion and a curvedly extending portion. The width of the above-mentioned strip shape does not have to be constant.

[0014] Furthermore, in this specification, "tab" is used to mean a "knob" that serves as the starting point (starting point of pulling) when pulling the adhesive sheet, and there are no particular restrictions on other elements (shape, material, etc.). Typically, a tab is large enough to be grasped with fingers and has a shape that allows for grasping with fingers (for example, a flat rectangular shape), but since it is also possible to pull the tab using a machine or tool, it does not need to be large enough to be grasped with fingers, and there are no restrictions on its shape. For example, a tab with a perforation can be very small in size, as it is possible to pull it by inserting a hook through the perforation. A typical tab is a flat shape that is continuous with the adhesive sheet, and it is preferable that it does not stretch when pulled, or if it does stretch, it has less elongation than the adhesive sheet.

[0015] [Adhesive sheet] An adhesive sheet according to an embodiment of the present invention is a strip-shaped adhesive sheet having an adhesive layer, and includes an inclined portion that is tapered in shape, with the width narrowing towards one end in the longitudinal direction of the adhesive sheet. By incorporating an inclined section, when peeling off an adhesive sheet attached to a substrate, stress is applied to the substrate around the inclined section, allowing for peeling with less force than peeling from other areas, resulting in superior peelability. Therefore, there is no need to apply large stress to a part of the interface between the adhesive layer and the substrate during peeling, which has advantages such as not deforming the substrate. Figure 1 is a schematic top view showing one example (embodiment) of the configuration of an adhesive sheet according to an embodiment of the present invention. The adhesive sheet 100 shown in Figure 1 has an inclined portion 40 at one end in the longitudinal direction of the adhesive sheet 100, which is formed in a tapered shape so that the width tapers towards the other end 41. In Figure 1, the inclined portion 40 is indicated by a point with an inclination length L2. In Figure 1, the width tapers linearly toward the other end 41 (hereinafter sometimes simply referred to as "end 41"), but it may also taper in a curved shape. An adhesive sheet according to an embodiment of the present invention may be provided with tabs at its edges. For example, a tab 50 with length L3 (tab length L3) may be provided at the end 41. In Figure 1, the width of the tab is the same as the width W2 of the end, but the width of the tab and the width W2 of the end may be different.

[0016] Figure 2 is a schematic perspective view showing another configuration example (embodiment) of an adhesive sheet according to an embodiment of the present invention. The adhesive sheet 100 shown in Figure 2 further comprises a base material 20, and comprises the base material 20 and an adhesive layer 10 disposed on both sides of the base material 20.

[0017] The other end of the adhesive sheet 100 in the longitudinal direction (the end opposite to the end 41) may or may not have an inclined portion 40.

[0018] An adhesive sheet 100 having such a shape can exhibit good adhesive strength to rectangular objects (for example, the casings and components of electronic devices such as personal computers, mobile phones, smartphones, digital cameras, tablet PCs, portable music players, portable game consoles, and chargers (e.g., batteries)). The adhesive sheet 100 also has a strip shape.

[0019] In Figure 1, the sum of the inclined portion length L2 and the length of the non-inclined portion L1 is the total length L of the adhesive sheet 100. In embodiments of the present invention, it is preferable that the ratio of the length of the inclined portion 40 (inclined length L2) to the longitudinal length L (total length L) of the adhesive sheet 100 is 5% or more. By setting the ratio of the inclined length L2 to 5% or more, peeling can be performed with less force, and the peeling force (force required for peeling) can be suppressed. It is more preferable that the ratio of the inclined length L2 to the longitudinal length L (total length L) of the adhesive sheet is 10% or more, and even more preferable that it is 20% or more. Furthermore, from the viewpoint of maintaining adhesive strength, it is preferable that the ratio of the inclined length L2 to the longitudinal length L (total length L) of the adhesive sheet is 100% or less, and more preferable that it is 70% or less.

[0020] The ratio of the edge width W2 to the width W of the adhesive sheet is preferably 90% or less, more preferably 75% or less, and even more preferably 50% or less. By making the ratio of the edge width W2 50% or less, peeling can be done with less force, and the peeling force (the force required for peeling) can be reduced. In embodiments of the present invention, it is preferable that the ratio of the width W2 of the edge to the width W of the adhesive sheet 100 is 50% or less. Furthermore, from the viewpoint of maintaining adhesive strength, the ratio of the width W2 of the edge to the width W of the adhesive sheet is more preferably 10% or more, and even more preferably 20% or more. The width W of the adhesive sheet is the width of the portion of the strip-shaped adhesive sheet excluding the inclined portion. Furthermore, if the inclined length L2 is equal to the longitudinal length L (total length L) of the adhesive sheet, the width W of the adhesive sheet is defined as the width of the end opposite to the width W2 of one end.

[0021] The width of the adhesive sheet 100 tapers towards the end 41, and at the end 41 shown in Figure 1, the width W2 of the end is narrower than the width W by the length of the inclined widths W1 and W3. The lengths of the inclined widths W1 and W3 may be the same or different, but from the viewpoint of adhesion, it is preferable that the inclined widths W1 and W3 are the same length.

[0022] Depending on the shape and size of the substrate and the application location, adhesive sheets with a ratio (L / W) of approximately 2 or higher tend to have excellent peelability and handling properties. There is no particular upper limit to the ratio (L / W), but from the viewpoint of strength and handling, the ratio (L / W) may be approximately 50 or less.

[0023] The adhesive sheet according to the embodiment of the present invention has a strip shape, and may, for example, have a strip-shaped portion in part. The adhesive sheet typically has a linear shape as in the above embodiment, but is not limited to this. It may also have a curved shape or a shape that combines straight lines and curves (for example, a V-shape, a U-shape, an arc shape, a wave shape, a zigzag shape, etc.). The adhesive sheet of this embodiment may be, for example, in the form of a roll, a sheet, or a single leaf. Alternatively, it may be an adhesive sheet processed into various shapes. Note that "adhesive sheet" also includes the meaning of "adhesive tape." That is, the adhesive sheet of this embodiment may be an adhesive tape having a tape-like form.

[0024] (Composition of the adhesive sheet) An adhesive sheet according to an embodiment of the present invention comprises an adhesive layer. Figure 3(a) is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. The adhesive sheet 110 shown in Figure 3(a) may be a substrate-less double-sided adhesive sheet consisting only of an adhesive layer 10.

[0025] An adhesive sheet according to an embodiment of the present invention may further comprise a base material and an adhesive layer disposed on at least one side of the base material. Figure 3(b) is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. This adhesive sheet 120 further comprises a base material 20, and the base material 20 and an adhesive layer 10 disposed on both sides of the base material 20. Figure 3(c) is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. This adhesive sheet 130 comprises a base material 20 and an adhesive layer 10 disposed on one side of the base material 20. In the adhesive sheets shown in Figures 3(b) and 3(c), the substrate 20 may have an extended portion that extends beyond the adhesive layer 10 and is exposed in the direction of surface expansion, and this extended portion may be the tab 50 in Figure 1.

[0026] The adhesive layer constituting the above adhesive sheet preferably exhibits adhesiveness upon pressure. The above adhesive sheet (essentially the adhesive layer) may be an adhesive sheet that exhibits adhesiveness at room temperature (25°C), or an adhesive sheet that exhibits adhesiveness upon heating. An adhesive sheet that exhibits adhesiveness upon heating may exhibit adhesiveness after being cooled to room temperature after heating.

[0027] Furthermore, the adhesive layer 10 may be an electrorelease adhesive layer. In the case of an adhesive sheet 120 in which the adhesive layer 10 is arranged on both sides of the substrate 20 as shown in Figure 3(b), one of the adhesive layers 10 may be an electrorelease adhesive layer, or both adhesive layers 10 may be electrorelease adhesive layers. Adhesive sheets containing an electropenetrating adhesive layer (electropenetrating adhesive sheets) are preferably designed to firmly bond components when no voltage is applied, and to be easily peeled off with minimal force when voltage is applied. By including the inclined portion 40, the electropenetrating adhesive sheet can be peeled from the outer edge of the portion joined by the inclined portion, thereby reducing the stress required to initiate peeling. When voltage is applied, cleavage peeling can be achieved by applying a small stress to a part of the interface between the adhesive layer and the adherend, preferably the outer edge of the portion joined by the inclined portion. Therefore, there is no need to apply a large stress to a part of the interface between the adhesive layer and the adherend to peel it off, which has advantages such as not deforming the adherend.

[0028] Here, cleavage peeling refers to peeling along the interface between the adhesive layer and the adherend. Cleavage peeling allows the entire interface between the adhesive layer and the adherend to be easily peeled off, eliminating the need to apply large stresses to a portion of the interface, as is done with peel peeling, and thus avoiding deformation of the adherend. In embodiments of the present invention, the cleavage delamination may be spontaneous delamination or not, but spontaneous delamination is preferred. Furthermore, spontaneous delamination refers to the peeling (cleavage) along the interface between the adherend and the adhesive layer, and the spontaneous separation of the adhesive layer from the adherend without applying stress to any part of the interface between the adhesive layer and the adherend. Spontaneous delamination also includes cases where delamination occurs while the material is stationary, where delamination occurs spontaneously during movement to the next process, and where the adherend and adhesive layer separate due to the weight of the adherend or the adhesive layer itself. Examples of cleavage delamination other than natural delamination include cases where a slight stress is applied to a portion of the interface between the adhesive layer and the adherend, causing the adhesive layer to peel off from one end of the adherend without deformation or damage to the adhesive layer or adherend.

[0029] In this embodiment, if the adhesive layer 10 is an electrorelease type adhesive layer, the adhesive sheet may also have a base material, a conductive layer, an electrical conductive base material, an intermediate layer, and a primer layer in addition to the adhesive layer. In this embodiment, if the adhesive layer 10 is an electrorelease type adhesive layer, the adhesive sheet may further include other adhesive layers that do not have electrorelease properties.

[0030] The electro-peelable adhesive sheet of this embodiment may have a separator (release liner) for the purpose of protecting the electro-peelable adhesive layer and the surface of other adhesive layers, but such release liner is not included in the electro-peelable adhesive sheet of this embodiment.

[0031] The structure of the adhesive sheet in this embodiment, when the adhesive layer 10 is an electro-peelable adhesive layer, is not particularly limited, but adhesive sheet X2 showing a laminated structure in Figure 4 and adhesive sheet X3 showing a laminated structure in Figure 5 are preferred. The adhesive sheet X2 is a double-sided adhesive sheet with a substrate having a layer structure consisting of an adhesive layer 2, an electrically conductive substrate 5 (substrate 3 and conductive layer 4), and an electropenetrating adhesive layer 1. The adhesive sheet X3 is a double-sided adhesive sheet with a substrate having a layer structure consisting of an adhesive layer 2, an electrically conductive substrate 5 (substrate 3 and conductive layer 4), an electro-peelable adhesive layer 1, an electrically conductive substrate 5 (substrate 3 and conductive layer 4), and an adhesive layer 2. In the electrically conductive substrate 5 of the adhesive sheets X2 and X3 shown in Figures 4 and 5, the substrate 3 is not essential, and only the conductive layer 4 may be present. Also, the adhesive sheet X2 in Figure 4 may be a single-sided adhesive sheet without the adhesive layer 2.

[0032] In an embodiment of the present invention, the adhesive sheet X2 may, for example, as shown in Figure 6, have an extended portion that extends beyond the electropenetrating adhesive layer 1 and the adhesive layer 2 in the direction of surface expansion of the conductive substrate 5, and this extended portion may be a tab 50.

[0033] Furthermore, in such a configuration, the electrical connection between one terminal of the voltage application device or DC power supply device and the current-carrying substrate can be easily achieved via the extension portion of the current-carrying substrate.

[0034] The electropenetrating adhesive sheet may also be a double-sided electropenetrating adhesive sheet, as shown in the modified example in Figure 7. The electropenetrating adhesive sheet shown in Figure 7 has a laminated structure in which an electrically conductive substrate 5 and an adhesive layer 2 are laminated on both sides of the electropenetrating adhesive layer 1. In the modified example shown in Figure 7, the double-sided electro-peelable adhesive sheet may be attached to the first adherend 15 with one side of the adhesive layer 2 and to the second adherend 16 with the other side of the adhesive layer 2. Furthermore, the double-sided electro-peelable adhesive sheet may have an extended portion that extends beyond one of the conductive substrates 5 and the first adherend 15 in its surface expansion direction, as shown in Figure 7, and this extended portion may be a tab 50. In such a configuration, it becomes easier to achieve an electrical connection between one terminal of a voltage-applying device and the conductive substrate 5 via the extended portion. As shown in Figure 7, it is preferable that the conductive layer 4 in the extended portion is not exposed from the viewpoint of corrosion prevention, and may be covered with an electropenetrating adhesive layer 1. Alternatively, the extended portion may be a tab 50.

[0035] The base material 3 is not particularly limited, but examples include paper-based base materials such as paper, fiber-based base materials such as cloth and nonwoven fabric, plastic-based base materials such as films and sheets made of various plastics (polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, acrylic resins such as polymethyl methacrylate, etc.), and laminates thereof. The base material may have a single layer or a multi-layer form. The base material may be subjected to various treatments as needed, such as back treatment, antistatic treatment, and primer treatment.

[0036] The conductive layer 4 is not particularly limited as long as it is a conductive layer, but may be a metal-based substrate such as a metal foil (e.g., aluminum, magnesium, copper, iron, tin, gold, etc.), a metal plate (e.g., aluminum, magnesium, copper, iron, tin, silver, etc.), a conductive polymer, or a metal vapor-deposited film provided on the substrate 3.

[0037] The conductive substrate 5 is not particularly limited as long as it is a substrate having a conductive layer (conducts electricity), but examples include substrates on which a metal layer has been formed on the surface. For example, a metal layer may be formed on the surface of the substrate exemplified above by methods such as plating, chemical vapor deposition, or sputtering. Examples of the metal layer include the metals, metal plates, and conductive polymers exemplified above.

[0038] In the case where the adhesive sheet shown in Figure 3(a) is an electro-peelable adhesive sheet, it is preferable that the adherends on both sides are adherends having a metal adhesion surface. In the case of adhesive sheet X2, it is preferable that the adherend on the electro-peelable adhesive layer 1 side is an adherend having a metal adhesion surface.

[0039] Examples of metal-bonded surfaces include conductive surfaces made of metals such as aluminum, copper, iron, magnesium, tin, gold, silver, and lead, with surfaces made of metals containing aluminum being particularly preferred. Examples of adherends having a metal-bonded surface include sheets, parts, and plates made of metals such as aluminum, copper, iron, magnesium, tin, gold, silver, and lead. Examples of adherends other than those having a metal-bonded surface include, but are not particularly limited, fibrous sheets such as paper, cloth, and nonwoven fabrics, and films and sheets of various plastics.

[0040] From the viewpoint of initial adhesive strength, the thickness of the electro-peelable adhesive layer 1 is preferably 1 μm or more and 1000 μm or less. The upper limit of the thickness of the electro-peelable adhesive layer 1 is more preferably 500 μm, even more preferably 100 μm, and particularly preferably 30 μm, while the lower limit is more preferably 3 μm, even more preferably 5 μm, and particularly preferably 8 μm. Note that if the adhesive sheet is a substrate-less double-sided adhesive sheet (adhesive sheet 110 shown in Figure 3(a)) consisting of only one adhesive layer (electro-peelable adhesive layer), the thickness of the adhesive layer (electro-peelable adhesive layer) is the thickness of the adhesive sheet.

[0041] From the viewpoint of adhesive strength, the thickness of the adhesive layer 2 is preferably 1 μm or more and 2000 μm or less. The upper limit of the thickness of the adhesive layer 2 is more preferably 1000 μm, even more preferably 500 μm, and particularly preferably 100 μm, while the lower limit is more preferably 3 μm, even more preferably 5 μm, and particularly preferably 8 μm.

[0042] The thickness of the base material 3 is preferably 10 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, even more preferably 300 μm, and particularly preferably 100 μm, while the lower limit is more preferably 12 μm, and even more preferably 25 μm.

[0043] The thickness of the conductive layer 4 is preferably 0.001 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, even more preferably 300 μm, even more preferably 50 μm, and even more preferably 10 μm, while the lower limit is more preferably 0.01 μm, even more preferably 0.03 μm, and even more preferably 0.05 μm.

[0044] The thickness of the conductive substrate 5 is preferably 10 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, even more preferably 300 μm, particularly preferably 100 μm, and the lower limit is more preferably 12 μm, even more preferably 25 μm.

[0045] The surface of the adhesive layer (electro-peelable adhesive layer and other adhesive layers) of the adhesive sheet in this embodiment may be protected by a separator (release liner). The release liner is not particularly limited, but examples include a release liner in which the surface of a substrate (liner substrate) such as paper or plastic film is treated with silicone, and a release liner in which the surface of a substrate (liner substrate) such as paper or plastic film is laminated with a polyolefin resin. The thickness of the release liner is not particularly limited, but is preferably 10 μm or more and 100 μm or less.

[0046] The thickness of the adhesive sheet in this embodiment is preferably 20 μm or more and 3000 μm or less. The upper limit of the thickness is more preferably 1000 μm, even more preferably 300 μm, particularly preferably 200 μm, and the lower limit is more preferably 30 μm, even more preferably 50 μm.

[0047] In particular, in the case of the adhesive sheet X2 shown in Figure 4, the thickness of the adhesive sheet is preferably 50 μm or more and 2000 μm or less. The upper limit of the thickness is more preferably 1000 μm, even more preferably 200 μm, and the lower limit is more preferably 80 μm, even more preferably 100 μm.

[0048] In particular, in the case of the adhesive sheet X3 shown in Figure 5, the thickness of the adhesive sheet is preferably 100 μm or more and 3000 μm or less. The upper limit of the thickness is more preferably 1000 μm, even more preferably 300 μm, the lower limit is more preferably 150 μm, and even more preferably 200 μm.

[0049] [Adhesive layer] The adhesive layer can be formed by an adhesive composition, and the adhesive composition preferably contains a polymer. The adhesive layer may be an electro-peelable adhesive layer that has the property of decreasing adhesive strength when a voltage is applied. The adhesive layer formed by the adhesive composition according to the embodiment of the present invention preferably has excellent heat resistance. An adhesive layer with excellent heat resistance can be used in manufacturing processes for electronic devices and the like that are subjected to high temperatures. The adhesive layer is preferably an electro-releasable adhesive layer whose adhesive strength decreases when a voltage is applied, and the electro-releasable adhesive layer preferably contains a polymer and an electrolyte, and more preferably contains a polymer and an ionic liquid. Furthermore, if the adhesive layer is an electropenetrating adhesive layer, the adhesive strength is sufficiently reduced by applying voltage, making cleavage and peeling possible.

[0050] The following describes the adhesive compositions according to embodiments of the present invention. In this specification, the adhesive strength when no voltage is applied may be referred to as "initial adhesive strength." Furthermore, the property of adhesive strength decreasing when voltage is applied is called "electrodeposition," and a large decrease in adhesive strength due to voltage application is sometimes described as "excellent electrodeposition."

[0051] <Components of the adhesive composition> (polymer) The adhesive composition of this embodiment preferably contains a polymer. In this embodiment, the polymer is not particularly limited as long as it is a general organic polymer compound, for example, a monomer polymer or partial polymer. The monomer may be a single monomer or a mixture of two or more monomers. A partial polymer means a polymer in which at least a portion of the monomer or monomer mixture is partially polymerized.

[0052] The polymer in this embodiment is not particularly limited as long as it is commonly used as an adhesive and has adhesive properties, but examples include acrylic polymers, rubber polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, fluoropolymers, and epoxy polymers. The polymers can be used alone or in combination of two or more types.

[0053] When the adhesive layer is an electropenetrating adhesive layer, it is preferable that the relative permittivity of the polymer be high in order to increase the relative permittivity of components other than the ionic liquid and improve electropenetration. From this viewpoint, it is particularly preferable that the polymer in this embodiment contains at least one selected from the group consisting of polyester polymers and acrylic polymers having carboxyl groups and / or hydroxyl groups. Since polyester polymers have hydroxyl groups that are easily polarized at their ends, and since acrylic polymers having carboxyl groups and / or hydroxyl groups have carboxyl groups and / or hydroxyl groups that are easily polarized, a polymer with a relatively high relative permittivity can be obtained by using these polymers. The total content of polyester polymers and acrylic polymers having carboxyl groups and / or hydroxyl groups in the polymer of this embodiment is preferably 60% by mass or more, and more preferably 80% by mass or more. Furthermore, in order to increase cost, productivity, and initial adhesive strength, the polymer in this embodiment is preferably an acrylic polymer. In other words, the adhesive composition of this embodiment is preferably an acrylic adhesive composition containing an acrylic polymer as the polymer.

[0054] The acrylic polymer preferably contains monomer units derived from alkyl (meth)acrylate esters having an alkyl group with 1 to 14 carbon atoms (formula (1) below). Such monomer units are suitable for obtaining high initial adhesion. Furthermore, when the adhesive layer is an electropenetrating adhesive layer, the alkyl group R in formula (1) below is used to increase the dielectric constant of components other than the ionic liquid and improve electropenetration. b The number of carbon atoms is preferably small, particularly preferably 8 or less, and more preferably 4 or less. CH2=C(R a )COOR b (1) [R in equation (1) a R is a hydrogen atom or a methyl group, b [This is an alkyl group having 1 to 14 carbon atoms, which may have substituents.]

[0055] Examples of alkyl (meth)acrylate esters having an alkyl group with 1 to 14 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, 1,3-dimethylbutyl acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, and 2-ethylbutyl (meth)acrylate. Examples include heptyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate, n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, and 2-methoxyethyl acrylate. Among these, n-butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, and 2-methoxyethyl acrylate are preferred. Alkyl (meth)acrylate esters having an alkyl group with 1 to 14 carbon atoms can be used alone or in combination of two or more.

[0056] The proportion of alkyl (meth)acrylate ester having an alkyl group with 1 to 14 carbon atoms relative to the total monomer components (100% by mass) constituting the acrylic polymer is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more. When the proportion of alkyl (meth)acrylate ester having an alkyl group with 1 to 14 carbon atoms is 70% by mass or more, it is easier to obtain a large initial adhesive strength.

[0057] As an acrylic polymer, it is preferable to include monomer units derived from alkyl (meth)acrylate esters having alkyl groups with 1 to 14 carbon atoms, as well as monomer units derived from polar group-containing monomers copolymerizable with the alkyl groups, for the purpose of modifying cohesive strength, heat resistance, crosslinkability, etc. The monomer units can provide crosslinking sites and are suitable for obtaining high initial adhesion. Furthermore, if the adhesive layer is an electropenetrating adhesive layer, it is preferable to include monomer units derived from polar group-containing monomers from the viewpoint of increasing the dielectric constant of components other than ionic liquids and improving electropenetration.

[0058] Examples of polar group-containing monomers include carboxyl group-containing monomers, hydroxyl group-containing monomers, cyano group-containing monomers, vinyl group-containing monomers, aromatic vinyl monomers, amide group-containing monomers, imide group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, vinyl ether monomers, N-acryloylmorpholine, sulfo group-containing monomers, phosphate group-containing monomers, and acid anhydride group-containing monomers. Among these, carboxyl group-containing monomers, hydroxyl group-containing monomers, and amide group-containing monomers are preferred due to their excellent cohesiveness, and carboxyl group-containing monomers are particularly preferred. Carboxyl group-containing monomers are especially suitable for obtaining high initial adhesion. Polar group-containing monomers can be used alone or in combination of two or more types.

[0059] Examples of carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Acrylic acid is particularly preferred. Carboxyl group-containing monomers can be used alone or in combination of two or more.

[0060] Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-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)acrylate, N-methylol (meth)acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are particularly preferred. Hydroxyl group-containing monomers can be used individually or in combination of two or more.

[0061] Examples of amide group-containing monomers include acrylamide, methacrylamide, N-vinylpyrrolidone, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, and diacetoneacrylamide. Amide group-containing monomers can be used alone or in combination of two or more.

[0062] Examples of cyano group-containing monomers include acrylonitrile and methacrylonitrile.

[0063] Examples of vinyl group-containing monomers include vinyl acetate, vinyl propionate, and vinyl esters such as vinyl laurate, with vinyl acetate being particularly preferred.

[0064] Examples of aromatic vinyl monomers include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes.

[0065] Examples of imide group-containing monomers include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0066] Examples of amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0067] Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allyl glycidyl ether.

[0068] Examples of vinyl ether monomers include methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

[0069] The proportion of polar group-containing monomers to the total monomer components (100% by mass) constituting the acrylic polymer is preferably 0.1% by mass or more and 35% by mass or less. The upper limit of the proportion of polar group-containing monomers is more preferably 25% by mass, even more preferably 20% by mass, the lower limit is more preferably 0.5% by mass, even more preferably 1% by mass, and particularly preferably 2% by mass. When the proportion of polar group-containing monomers is 0.1% by mass or more, cohesive force is easily obtained, so adhesive residue is less likely to occur on the surface of the adherend after peeling off the electrorelease adhesive layer, and electrorelease properties are improved. 35When the mass percentage is less than %, it becomes easier to prevent the electro-release adhesive layer from adhering excessively to the substrate and causing excessive peeling. In particular, when the mass percentage is between 2% and 20%, it becomes easier to achieve both peelability from the substrate and adhesion between the electro-release adhesive layer and other layers.

[0070] Furthermore, the monomer components constituting the acrylic polymer may include polyfunctional monomers in order to introduce a cross-linked structure into the acrylic polymer and facilitate obtaining the necessary cohesive force.

[0071] Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, divinylbenzene, and N,N'-methylenebisacrylamide. Polyfunctional monomers can be used individually or in combination of two or more.

[0072] The content of polyfunctional monomers relative to the total monomer components (100% by mass) constituting the acrylic polymer is preferably 0.1% by mass or more and 15% by mass or less. The upper limit of the polyfunctional monomer content is more preferably 10% by mass, and the lower limit is more preferably 3% by mass. A polyfunctional monomer content of 0.1% by mass or more is preferable because it easily improves the flexibility and adhesion of the electrorelease adhesive layer. A polyfunctional monomer content of 15% by mass or less makes it easier to obtain appropriate adhesion without the cohesive force becoming too high.

[0073] Polyester polymers are typically polymers having a structure in which polycarboxylic acids such as dicarboxylic acids or their derivatives (hereinafter also referred to as "polycarboxylic acid monomers") and polyhydric alcohols such as diols or their derivatives (hereinafter referred to as "polyhydric alcohol monomers") are condensed together.

[0074] The polycarboxylic acid monomer is not particularly limited, but examples include adipic acid, azelaic acid, dimer acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dodecenyl succinic anhydride, fumaric acid, succinic acid, dodecanediic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, maleic acid, maleic anhydride, itaconic acid, citraconic acid, and derivatives thereof. Polycarboxylic acid monomers can be used individually or in combination of two or more types.

[0075] The polyhydric alcohol monomer is not particularly limited, but examples include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, 1,9-nonanediol, 2-methyloctanediol, 1,10-decanediol, and derivatives thereof. Polyhydric alcohol monomers can be used alone or in combination of two or more types.

[0076] Furthermore, the polymer in this embodiment may also contain an ionic polymer. An ionic polymer is a polymer having ionic functional groups. The inclusion of an ionic polymer in the polymer increases the dielectric constant of the polymer and improves its electrolytic properties. When the polymer contains an ionic polymer, the content of the ionic polymer is preferably 0.05 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the polymer.

[0077] In this embodiment, the polymer can be obtained by (co)polymerizing monomer components. The polymerization method is not particularly limited, but examples include solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization (active energy ray polymerization). Solution polymerization is particularly preferred from the viewpoint of cost and productivity. When copolymerized, the polymer may be a random copolymer, block copolymer, alternating copolymer, graft copolymer, etc.

[0078] Solution polymerization methods are not particularly limited, but include methods in which monomer components, polymerization initiators, etc., are dissolved in a solvent, heated to polymerize, and a polymer solution containing the polymer is obtained.

[0079] Various common solvents can be used as solvents in solution polymerization. Examples of such solvents (polymerization solvents) include aromatic hydrocarbons such as toluene, benzene, and xylene; esters such as ethyl acetate and n-butyl acetate; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. Solvents can be used individually or in combination of two or more.

[0080] The amount of solvent used is not particularly limited, but it is preferably 10 parts by mass or more and 1000 parts by mass or less relative to the total monomer components constituting the polymer (100 parts by mass). The upper limit of the amount of solvent used is more preferably 500 parts by mass, and the lower limit is more preferably 50 parts by mass.

[0081] Polymerization initiators used in solution polymerization are not particularly limited, but include peroxide-based polymerization initiators and azo-based polymerization initiators. Peroxide-based polymerization initiators are not particularly limited, but include peroxycarbonates, ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxyesters. More specifically, examples include benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(t-butylperoxy)cyclododecane. The azo polymerization initiator is not particularly limited, but includes 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(2-methylpropionic acid)dimethyl, 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobis(cyclohexane-1-carbonitride), 2,2′-azobis(2,4,4-trimethylpentane), and 4,4′-azobis Examples include -4-cyanovaleric acid, 2,2′-azobis(2-amidinopropane)dihydrochloride, 2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis(2-methylpropionamidine)disulfate, 2,2′-azobis(N,N′-dimethylene isobutylamidine)hydrochloride, and 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate. Polymerization initiators can be used alone or in combination of two or more.

[0082] The amount of polymerization initiator used is not particularly limited, but it is preferably 0.01 parts by mass or more and 5 parts by mass or less relative to the total monomer components constituting the polymer (100 parts by mass). The upper limit of the amount of polymerization initiator used is more preferably 3 parts by mass, and the lower limit is more preferably 0.05 parts by mass.

[0083] In solution polymerization, the heating temperature during polymerization is not particularly limited, but is, for example, between 50°C and 80°C. The heating time is not particularly limited, but is, for example, between 1 hour and 24 hours.

[0084] The weight-average molecular weight of the polymer is not particularly limited, but is preferably between 100,000 and 5,000,000. The upper limit of the weight-average molecular weight is more preferably 4,000,000, even more preferably 3,000,000, and the lower limit is more preferably 200,000, even more preferably 300,000. When the weight-average molecular weight is 100,000 or more, the cohesive force is reduced, which effectively suppresses the problem of adhesive residue remaining on the surface of the adherend after the electrorelease adhesive layer is removed. Furthermore, when the weight-average molecular weight is 5,000,000 or less, it effectively suppresses the problem of insufficient wettability on the surface of the adherend after the electrorelease adhesive layer is removed.

[0085] The weight-average molecular weight was obtained by measuring using gel permeation chromatography (GPC). More specifically, for example, it can be measured using the "HLC-8220GPC" (manufactured by Tosoh Corporation) GPC measuring device under the following conditions and calculated using the standard polystyrene equivalent value. (Weight average molecular weight measurement conditions) • Sample concentration: 0.2% by mass (Tetrahydrofuran solution) • Sample injection volume: 10 μL • Sample columns: TSKguardcolumn SuperHZ-H (1 tube) + TSKgel SuperHZM-H (2 tubes) • Reference column: TSKgel SuperH-RC (1 tube) • Eluent: Tetrahydrofuran (THF) ·Flow rate: 0.6mL / min • Detector: Differential refractometer (RI) Column temperature (measurement temperature): 40°C

[0086] The glass transition temperature (Tg) of the polymer is not particularly limited, but it is preferably 0°C or lower because it suppresses the decrease in initial adhesive strength, more preferably -10°C or lower, and even more preferably -20°C or lower. Furthermore, it is particularly preferable to have a temperature of -40°C or lower because the rate of decrease in adhesive strength due to voltage application is particularly large, and most preferably -50°C or lower.

[0087] The glass transition temperature (Tg) can be calculated, for example, based on the following equation (Y) (Fox equation). 1 / Tg=W1 / Tg1+W2 / Tg2++Wn / Tgn (Y) [In equation (Y), Tg is the glass transition temperature of the polymer (unit: K), Tgi(i=1, 2, ...n) is the glass transition temperature when monomer i forms a homopolymer (unit: K), and Wi(i=1, 2, ...n) represents the mass fraction of monomer i in the total monomer components.] The above formula (Y) is the calculation formula when the polymer is composed of n types of monomer components: monomer 1, monomer 2, ..., monomer n.

[0088] The glass transition temperature when forming a homopolymer refers to the glass transition temperature of the homopolymer of the monomer in question, and specifically refers to the glass transition temperature (Tg) of a polymer formed using only one monomer (sometimes referred to as "monomer X") as the monomer component. The specific values ​​are given in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). For homopolymers not listed in the aforementioned literature, the glass transition temperature (Tg) refers to a value obtained, for example, by the following measurement method: In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 100 parts by mass of monomer X, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 200 parts by mass of ethyl acetate as the polymerization solvent are added, and the mixture is stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system in this manner, the temperature is raised to 63°C and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution with a solid content of 33% by mass. Next, this homopolymer solution is cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. Then, approximately 1-2 mg of this test sample is weighed into an aluminum open cell, and the reversing heat flow (specific heat component) behavior of the homopolymer is obtained using a temperature-modulated DSC (product name "Q-2000", manufactured by T.A. Instruments Co., Ltd.) at a heating rate of 5°C / min under a nitrogen atmosphere of 50 ml / min. Referring to JIS-K-7121, the glass transition temperature (Tg) of the homopolymer is defined as the temperature at the point where a line equidistant in the vertical axis direction from the line extending from the low-temperature baseline and high-temperature baseline of the obtained reversing heat flow intersects with the curve of the step-like change portion of the glass transition.

[0089] The polymer content in the adhesive composition of this embodiment is preferably 50% by mass or more and 99.9% by mass or less, based on the total amount of the adhesive composition (100% by mass), with the upper limit being more preferably 99.5% by mass, even more preferably 99% by mass, and the lower limit being more preferably 60% by mass, even more preferably 70% by mass. However, when the adhesive composition contains a solvent, it is preferable that the content of the polymer relative to the total amount of the adhesive composition excluding the solvent falls within the above range.

[0090] When the adhesive layer is an electrically peelable adhesive layer, the electrolyte contained in the electrically peelable adhesive layer is a substance that can be ionized into anions and cations. Examples of such electrolytes include ionic liquids, alkali metal salts, alkaline earth metal salts, and the like. From the viewpoint of achieving good electrical peelability in the electrically peelable adhesive layer, an ionic liquid is preferable as the electrolyte contained in the electrically peelable adhesive layer. An ionic liquid is a salt that is liquid at room temperature (about 25°C) and contains anions and cations.

[0091] (Ionic liquid) The ionic liquid in the present embodiment is not particularly limited as long as it is a molten salt (room temperature molten salt) composed of a pair of anions and cations and is liquid at 25°C. Examples of anions and cations are given below. Among the ionic substances obtained by combining these, those that are liquid at 25°C are ionic liquids, and those that are solid at 25°C are not ionic liquids but are ionic solids described later.

[0092] Examples of the anion of the ionic liquid include, for example, (FSO2)2N - , (CF3SO2)2N - , (CF3CF2SO2)2N - , (CF3SO2)3C - , Br - , AlCl4 - , Al2Cl7 - , NO3 - , BF4 - , PF6 - , CH3COO - , CF3COO - , CF3CF2CF2COO - , CF3SO3 - , CF3(CF2)3SO3 - , AsF6 - , SbF6 - , and F(HF) n -These are some examples. Among them, as an anion, (FSO2)2N - [Bis(fluorosulfonyl)imido anion] and (CF3SO2)2N - Anions of sulfonylime compounds such as [bis(trifluoromethanesulfonyl)imide anion] are preferred because they are chemically stable and suitable for improving electrolysis properties.

[0093] In ionic liquids, nitrogen-containing onium, sulfur-containing onium, and phosphorus-containing onium cations are preferred because they are chemically stable and suitable for improving electrolysis, with imidazolium-based, ammonium-based, pyrrolidinium-based, and pyridinium-based cations being more preferred.

[0094] Examples of imidazolium-based cations include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-heptyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-nonyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, and 1-dodecyl-3-methylimidazolium cation. Examples include mucations, 1-tridecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1-pentadecyl-3-methylimidazolium cation, 1-hexadecyl-3-methylimidazolium cation, 1-heptadecyl-3-methylimidazolium cation, 1-octadecyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, 1-benzyl-3-methylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, and 1,3-bis(dodecyl)imidazolium cation.

[0095] Examples of pyridinium-based cations include 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, and 1-octyl-4-methylpyridinium cation.

[0096] Examples of pyrrolidinium-based cations include 1-ethyl-1-methylpyrrolidinium cation and 1-butyl-1-methylpyrrolidinium cation.

[0097] Examples of ammonium-based cations include tetraethylammonium cation, tetrabutylammonium cation, methyltrioctylammonium cation, tetradecyltrihexylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0098] As an ionic liquid, from the viewpoint of significantly reducing the rate of decrease in adhesive strength when voltage is applied, it is preferable to select cations with a molecular weight of 160 or less as the constituent cations, as shown above (FSO2)2N - [Bis(fluorosulfonyl)imido anion] or (CF3SO2)2N -An ionic liquid containing [bis(trifluoromethanesulfonyl)imide anion] and a cation with a molecular weight of 160 or less is particularly preferred. Examples of cations with a molecular weight of 160 or less include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-ethyl-1-methylpyrrolidinium cation, 1-butyl-1-methylpyrrolidinium cation, tetraethylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0099] Furthermore, cations represented by the following formulas (2-A) to (2-D) are also preferred as cations of the ionic liquid.

[0100] [ka]

[0101] R in equation (2-A) 1 R represents a hydrocarbon group having 4 to 10 carbon atoms (preferably a hydrocarbon group having 4 to 8 carbon atoms, more preferably a hydrocarbon group having 4 to 6 carbon atoms), and may contain heteroatoms. 2 and R 3 R represents the same or different hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms (preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms, and even more preferably a hydrocarbon group having 2 to 4 carbon atoms), and may also contain heteroatoms. However, if the nitrogen atom forms a double bond with an adjacent carbon atom, 3 It does not exist.

[0102] R in equation (2-B) 4R represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), and may contain heteroatoms. 5 , R 6 , and R 7 These represent, either identically or differently, a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms (preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms, and even more preferably a hydrocarbon group having 2 to 4 carbon atoms), and may also contain heteroatoms.

[0103] R in equation (2-C) 8 R represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), and may contain heteroatoms. 9 , R 10 , and R 11 These represent, either identically or differently, a hydrogen atom or a hydrocarbon group having 1 to 16 carbon atoms (preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 8 carbon atoms), and may also contain heteroatoms.

[0104] In formula (2-D), X represents a nitrogen, sulfur, or phosphorus atom, and R 12 , R 13 , R 14 , and R 15 R represents a hydrocarbon group having 1 to 16 carbon atoms, either identical or different, (preferably a hydrocarbon group having 1 to 14 carbon atoms, more preferably a hydrocarbon group having 1 to 10 carbon atoms, even more preferably a hydrocarbon group having 1 to 8 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 6 carbon atoms), and may contain heteroatoms. However, if X is a sulfur atom, R 12 It does not exist.

[0105] The molecular weight of cations in ionic liquids is, for example, 500 or less, preferably 400 or less, more preferably 300 or less, even more preferably 250 or less, particularly preferably 200 or less, and most preferably 160 or less. It is also usually 50 or more. It is believed that cations in ionic liquids have the property of moving towards the cathode side when a voltage is applied in the electropenetrating adhesive layer, and becoming concentrated near the interface between the electropenetrating adhesive layer and the adherend. In the present invention, this results in a decrease in adhesive strength during voltage application compared to the initial adhesive strength, leading to electropenetration. Cationics with a small molecular weight, such as 500 or less, are preferable because they facilitate the movement of cations towards the cathode side in the electropenetrating adhesive layer, thus increasing the rate of decrease in adhesive strength during voltage application.

[0106] Examples of commercially available ionic liquids include "Elexel AS-110," "Elexel MP-442," "Elexel IL-210," "Elexel MP-471," "Elexel MP-456," and "Elexel AS-804" from Daiichi Kogyo Seiyaku Co., Ltd., "HMI-FSI" from Mitsubishi Materials Corporation, and "CIL-312" and "CIL-313" from Nippon Carlit Co., Ltd.

[0107] The ionic conductivity of the ionic liquid is preferably 0.1 mS / cm or higher. More preferably 1 mS / cm or higher, even more preferably 3 mS / cm or higher, even more preferably 5 mS / cm or higher, even more preferably 10 mS / cm or higher, especially preferably 15 mS / cm or higher, and most preferably 20 mS / cm or higher. There is no particular upper limit, but having the above ionic conductivity ensures that the adhesive strength is sufficiently reduced even at low voltages. The ionic conductivity can be measured, for example, by the AC impedance method using a Solartron 1260 frequency response analyzer.

[0108] The ionic liquid content (amount blended) in the adhesive composition of this embodiment is preferably 0.5 parts by mass or more per 100 parts by mass of polymer from the viewpoint of reducing adhesive strength during voltage application, and preferably 30 parts by mass or less from the viewpoint of increasing initial adhesive strength. From the same viewpoint, it is more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, particularly preferably 10 parts by mass or less, and most preferably 5 parts by mass or less. Furthermore, it is more preferably 0.6 parts by mass or more, even more preferably 0.8 parts by mass or more, particularly preferably 1.0 part by mass or more, and most preferably 1.5 parts by mass or more.

[0109] (Other ingredients) The adhesive composition of this embodiment may contain one or more components other than polymers and ionic liquids (hereinafter sometimes referred to as "other components"), as necessary, to the extent that they do not impair the effects of the present invention. The other components that may be contained in the adhesive composition of this embodiment will be described below.

[0110] The adhesive composition of this embodiment may contain an ionic additive. For example, an ionic solid can be used as the ionic additive.

[0111] An ionic solid is an ionic substance that is solid at 25°C. The ionic solid is not particularly limited, but for example, any solid ionic substance obtained by combining anions and cations as exemplified in the section describing ionic liquids above can be used. When the adhesive composition contains an ionic solid, the content of the ionic solid is preferably 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of polymer.

[0112] The adhesive composition of this embodiment may optionally contain a crosslinking agent for the purpose of improving creep and shear properties by crosslinking the polymer. Examples of crosslinking agents include isocyanate-based crosslinking agents, carbodiimide-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, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents. Examples of isocyanate-based crosslinking agents include toluene diisocyanate and methylene bisphenyl isocyanate. Examples of epoxy-based crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediline, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and 1,6-hexanediol diglycidyl ether. If a crosslinking agent is included, the preferred content is 0.1 parts by mass or more and 50 parts by mass or less per 100 parts by mass of polymer. The crosslinking agent can be used alone or in combination of two or more types.

[0113] The adhesive composition of this embodiment may optionally contain polyethylene glycol to assist in the movement of the ionic liquid when a voltage is applied. Polyethylene glycol with a number average molecular weight of 200 to 6000 can be used. When polyethylene glycol is included, the content is preferably 0.1 parts by mass to 30 parts by mass per 100 parts by mass of polymer.

[0114] The adhesive composition of this embodiment may optionally contain a conductive filler for the purpose of imparting conductivity to the adhesive composition. The conductive filler is not particularly limited, and general known or conventional conductive fillers can be used, such as graphite, carbon black, carbon fiber, or metal powders such as silver or copper. When a conductive filler is included, the content is preferably 0.1 parts by mass or more and 200 parts by mass or less per 100 parts by mass of polymer.

[0115] The adhesive composition of this embodiment also contains fillers, plasticizers, anti-aging agents, antioxidants, pigments (dyes), flame retardants, solvents, surfactants (leveling agents), rust inhibitors, Adhesive The polymer may contain various additives such as resins, corrosion inhibitors, and antistatic agents. The total content of these components is not particularly limited as long as the effects of the present invention are achieved, but it is preferably 0.01 parts by mass to 20 parts by mass, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of polymer.

[0116] Examples of fillers include silica, iron oxide, zinc oxide, aluminum oxide, titanium oxide, barium oxide, magnesium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, pyrophyllite clay, kaolin clay, and calcined clay. The plasticizer can be a commonly used plasticizer in general resin compositions, such as paraffin oil, process oil, liquid rubber such as liquid polyisoprene, liquid polybutadiene, and liquid ethylene-propylene rubber, tetrahydrophthalic acid, azelaic acid, benzoic acid, phthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, citric acid, and their derivatives, dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), and isodecyl succinate. Examples of anti-aging agents include hindered phenol compounds, aliphatic and aromatic hindered amine compounds, and others. Examples of antioxidants include butylhydroxytoluene (BHT) and butylhydroxyanisole (BHA). Examples of pigments include inorganic pigments such as titanium dioxide, zinc oxide, ultramarine, red iron oxide, lithopon, lead, cadmium, iron, cobalt, aluminum, hydrochloride salts, and sulfates, as well as azo pigments and organic pigments such as copper phthalocyanine pigments. Examples of rust inhibitors include zinc phosphate, tannic acid derivatives, phosphate esters, basic sulfonates, and various rust-inhibiting pigments. Examples of adhesion promoters include titanium coupling agents and zirconium coupling agents. Common examples of antistatic agents include quaternary ammonium salts, or hydrophilic compounds such as polyglycolic acid and ethylene oxide derivatives. Examples of tackifying resins include rosin-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, hydrocarbon-based tackifying resins, ketone-based tackifying resins, as well as polyamide-based tackifying resins, epoxy-based tackifying resins, and elastomer-based tackifying resins. These tackifying resins can be used individually or in combination of two or more types. Examples of corrosion inhibitors include carbodiimide compounds, adsorption-type inhibitors, and chelate-forming metal deactivators. For example, those described in Japanese Patent Publication No. 2019-059908 can be used.

[0117] The conductive substrate 5 is not particularly limited as long as it includes a substrate 3 and a conductive layer 4. For example, it may be a substrate 3 with a conductive layer formed on its surface, or the conductive layer may be formed on the surface of the substrate as exemplified above by a method such as plating, chemical vapor deposition, or sputtering.

[0118] Electropeelable adhesive sheets can be attached to conductive materials to form a bonded structure. Examples of conductive materials include adherends such as metal adherends, and examples of metal adherends include surfaces made of metals mainly composed of aluminum, copper, iron, magnesium, tin, gold, silver, and lead, with surfaces made of metals containing aluminum being particularly preferred. Examples of adherends having a metal adherend include sheets, parts, and plates made of metals mainly composed of aluminum, copper, iron, magnesium, tin, gold, silver, and lead. Examples of adherends other than those having a metal adherend include, but are not particularly limited, fibrous sheets such as paper, cloth, and nonwoven fabrics, and films and sheets of various plastics.

[0119] (Method of manufacturing adhesive sheets) The method for manufacturing the adhesive sheet of this embodiment can be a known or conventional manufacturing method. For the electropenetrating adhesive layer in the adhesive sheet of this embodiment, one method is to apply a solution of the adhesive composition of this embodiment dissolved in a solvent as needed onto a release liner, and then dry and / or cure it. For other adhesive layers, one method is to apply a solution of the adhesive composition, which does not contain ionic liquids or additives, dissolved in a solvent as needed onto a release liner, and then dry and / or cure it. The solvent and release liner can be those listed above.

[0120] Conventional coaters (e.g., gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray roll coaters, etc.) can be used for application.

[0121] By the above method, an electropenetrating adhesive layer and other adhesive layers can be manufactured.

[0122] (Method for electrolyzing adhesive sheets) In this embodiment, when peeling the adhesive sheet from the adherend, it is preferable to start peeling from the inclined portion, and if the adhesive sheet has tabs at the ends of the inclined portion, it is preferable to peel it by pulling the tabs perpendicular to the adherend surface.

[0123] In this embodiment, if the adhesive layer in the adhesive sheet is an electro-peelable adhesive layer, it is preferable to apply a voltage to the electro-peelable adhesive layer to generate a potential difference in the thickness direction of the electro-peelable adhesive layer, thereby reducing the adhesive strength, and then begin peeling the adhesive sheet from the inclined portion away from the adherend. For example, in the case of an adhesive sheet, if the adherend has metal-adhering surfaces on both sides, the adhesive strength can be reduced and the sheet can be peeled off by applying an electric current to the metal-adhering surfaces on both sides and applying a voltage to the electro-peelable adhesive layer. In the case of the adhesive sheet X2, if the side with the electrorelease adhesive layer is an adherend having a metal adherend, the adhesive strength can be reduced and the sheet can be peeled off by applying a voltage to the electrorelease adhesive layer by passing an electric current between the conductive adherend and the conductive layer 4. In the case of adhesive sheet X3, it can be peeled off by applying a voltage to the electrorelease adhesive layer by energizing the conductive layers 4 on both sides. It is preferable to connect terminals to one end and the other end of the adhesive sheet so that the voltage is applied to the entire electrorelease adhesive layer. Note that if the adherend has a metal adherend, the above-mentioned one end and the other end may be part of the adherend having a metal adherend. Note that when peeling, water may be added to the interface between the metal adherend and the electrorelease adhesive layer before applying the voltage.

[0124] The applied voltage and voltage application time during electrolysis are not particularly limited, as long as the adhesive layer or adhesive sheet can be removed from the adherend. Preferred ranges are shown below. The applied voltage is preferably 1V or higher, more preferably 3V or higher, and even more preferably 6V or higher. It is also preferably 100V or lower, more preferably 50V or lower, even more preferably 30V or lower, and particularly preferably 15V or lower. The voltage application time is preferably 60 seconds or less, more preferably 40 seconds or less, even more preferably 20 seconds or less, and particularly preferably 10 seconds or less. In such cases, workability is excellent. Also, the shorter the application time, the better, but it is usually 1 second or more.

[0125] (Uses of adhesive sheets) Conventional re-peelable technologies include adhesive layers that harden and peel off with ultraviolet (UV) irradiation or adhesive layers that peel off with heat. However, adhesive sheets using such adhesive layers cannot be used when ultraviolet (UV) irradiation is difficult or when heat damages the adherend. The adhesive sheet according to the embodiment of the present invention does not use ultraviolet (UV) or heat and has excellent peeling power, so it can be easily cleaved and peeled off by applying voltage without damaging the adherend. Due to the above characteristics, the adhesive sheet according to the embodiment of the present invention is suitable for fixing secondary batteries (e.g., lithium-ion battery packs) used in mobile terminals such as smartphones, mobile phones, laptops, video cameras, and digital cameras to their casings. Furthermore, the adhesive sheet according to the embodiment of the present invention is suitable for fixing applications in semiconductor manufacturing processes and inspection (e.g., ceramic capacitors and lithium-ion batteries). In addition, the adhesive sheet according to the embodiment of the present invention is suitable for protective applications in metal processing processes (e.g., stainless steel sheets for railways).

[0126] Furthermore, examples of rigid members to be joined by the adhesive sheet according to the embodiment of the present invention include silicon substrates for semiconductor wafer applications, sapphire substrates, SiC substrates and metal base substrates for LEDs, TFT substrates and color filter substrates for displays, and base substrates for organic EL panels. Examples of fragile members to be joined by the double-sided adhesive sheet include semiconductor substrates such as compound semiconductor substrates, silicon substrates for MEMS devices, passive matrix substrates, surface cover glass for smartphones, OGS (One Glass Solution) substrates in which a touch panel sensor is attached to the cover glass, organic substrates mainly composed of silsesquioxane and organic-inorganic hybrid substrates, flexible glass substrates for flexible displays, and graphene sheets.

[0127] [Joint structure, method for separating joint structures] Next, the joint and the method for separating the joint will be described. The bonding body of this embodiment comprises the adhesive sheet, a first adherend, and a second adherend. In other words, the joint of this embodiment is a joint in which a first adherend and a second adherend are joined together by the aforementioned adhesive sheet.

[0128] Figure 8 is a schematic top view showing one example (embodiment) of a joint in which a first adherend 15 and a second adherend 16 are joined by an adhesive sheet 100. In the joint shown in Figure 8, the adhesive sheet 100 has double-sided adhesive properties in order to join the first adherend 15 and the second adherend 16. The adhesive sheet 100 also has a strip shape that extends in a straight line. In Figure 8, the adhesive sheet 100 is sandwiched between the first adherend 15 and the second adherend 16 and is adhered to the first adherend 15 and the second adherend 16. Specifically, the adhesive surface of the adhesive sheet 100 is adhered to the first adherend 15 and the second adherend 16, respectively.

[0129] The method for separating the bonded body in this embodiment is a method for separating the bonded body by initiating the separation of the first adherend and the second adherend from the outer edge of the portion of the first adherend and the second adherend joined by the inclined portion of the adhesive sheet. In Figure 8, it is preferable to initiate the separation of the first adherend and the second adherend from the outer edge 17 of the first adherend 15. Furthermore, if the adhesive sheet 100 has tabs, as shown in Figure 1 and Figure 9 later described in the embodiment, the tabs may be separated by pulling them perpendicular to the surface to be adhered. Because the adhesive sheet has an inclined section, when separation begins from the outer edge of the portion joined by the inclined section, the stress required to initiate peeling of the adhesive sheet can be reduced. This eliminates the need to apply large stress to a part of the interface between the adhesive layer and the adherend during peeling, resulting in advantages such as not deforming the adherend.

[0130] In this embodiment, if the adhesive layer 10 in the adhesive sheet 100 is an electro-peelable adhesive layer, the first adherend 15 and the second adherend 16 may be adherends having a metallic adherend surface. Examples of adherends having a metallic adherend surface include those made of metals mainly composed of aluminum, copper, iron, magnesium, tin, gold, silver, and lead, with metals containing aluminum being particularly preferred. In the case where the adhesive layer in the adhesive sheet of this embodiment is an electrorelease adhesive layer, it is preferable to apply a voltage to the electrorelease adhesive layer to generate a potential difference in the thickness direction of the electrorelease adhesive layer, thereby reducing the adhesive strength, and then initiate the separation of the first adherend and the second adherend from the outer edge.

[0131] Examples of the bonded bodies of this embodiment include a bonded body comprising an adhesive sheet, which is an electro-peelable adhesive layer 1, and adherends (a first adherend and a second adherend) having metal adherend surfaces on both sides; a bonded body bonded by an adhesive sheet X2, which comprises a first adherend with a metal adherend surface on the electro-peelable adhesive layer 1 side and a second adherend on the adhesive layer 2 side; and a bonded body bonded by an adhesive sheet X3, which comprises adherends (a first adherend and a second adherend) on both sides of the adhesive layer 2. [Examples]

[0132] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to these examples.

[0133] (Preparation of acrylic polymer solutions) As monomer components, 87 parts by mass of n-butyl acrylate (BA), 10 parts by mass of 2-methoxyethyl acrylate (MEA), 3 parts by mass of acrylic acid (AA), and 150 parts by mass of ethyl acetate as a polymerization solvent were placed in a separable flask and stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the mixture was heated to 63°C and reacted for 6 hours. Subsequently, ethyl acetate was added to obtain an acrylic polymer solution with a solid content of 40% by mass.

[0134] [Example 1] (Preparation of an electropenetrating adhesive layer) 100 parts by mass of the acrylic polymer (solution) obtained above, and 0.4 parts by mass of the crosslinking agent V-05. Mass part Four parts by mass of ionic liquid AS-110, additives (three parts by mass of adsorption inhibitor AMINE O, 0.3 parts by mass of Irgacor DSSG, and 0.8 parts by mass of chelate-forming metal deactivator Irgamet 30), and ethyl acetate were added and stirred and mixed to obtain an electrolytic adhesive composition (solution) with a solid content concentration of 25% by mass. The obtained electro-peelable adhesive composition (solution) was applied to the peel-treated surface of a polyethylene terephthalate peel-off liner (product name "MRF38", manufactured by Mitsubishi Plastics, Inc.) using an applicator to achieve a uniform thickness. Next, it was heated and dried at 150°C for 3 minutes, and the peel-treated surface of the polyethylene terephthalate peel-off liner (product name "MRE38", manufactured by Mitsubishi Plastics, Inc.) was laminated onto the adhesive using a hand roller to obtain an electro-peelable adhesive layer with a thickness of 50 μm.

[0135] The abbreviations for ionic liquids, crosslinking agents, adsorption inhibitors, and chelating metal deactivators are as follows:

[0136] (Ionic liquid) AS-110: Cation: 1-ethyl-3-methylimidazolium cation, Anion: bis(fluorosulfonyl)imide anion, Trade name "Elexel AS-110", Manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (Crosslinking agent) V-05: Polycarbodiimide resin, product name "Carbodilite V-05", manufactured by Nisshinbo Chemical Co., Ltd. (Adsorption-type inhibitor) AMINE O: 2-(8-heptadecene-1-yl)-4,5-dihydro-1H-imidazole-1-ethanol, trade name "AMINE O", manufactured by BASF Japan Ltd. Irgacor DSSG: Sodium sebacate, trade name "Irgacor DSSG", manufactured by BASF Japan Ltd. (Chelating metal deactivator) Irgamet 30: N,N-bis(2-ethylhexyl)-[(1,2,4-triazole-1-yl)methyl]amine, trade name "Irgamet 30", manufactured by BASF Japan Ltd.

[0137] (Preparation of electropenetrating adhesive sheets) The polyethylene terephthalate release liner (MRE38) of the obtained electro-peelable adhesive layer was peeled off, and the conductive layer side of a metal-layered film (product name "MetalMe TS", manufactured by Toray Film Processing Co., Ltd., thickness 50 μm), which is a laminate in which a conductive layer (metal layer (aluminum vapor-deposited layer)) and a substrate (polyethylene terephthalate (PET)) are laminated in that order, was bonded to the surface of the exposed electro-peelable adhesive layer to form laminate 1. Furthermore, double-sided tape (product name "No. 56405", manufactured by Nitto Denko Corporation) was applied to the substrate side of laminate 1, resulting in laminate 2, where one side is an electro-peelable adhesive layer and the other side is another adhesive layer. The double-sided tape was applied so that laminate 1 extended 30 mm beyond the other adhesive layer. The laminate 2 was cut to a size of 20 (W) mm in width, 90 mm in total length, and 30 mm in tab length (L3). It was then cut to form a strip shape with an inclined section having an inclined width W1 of 5 mm, an end width W2 of 10 mm, an inclined width W3 of 5 mm, an inclined length L2 of 30 mm, a total length L of 90 mm, a tab width of 10 mm, and a tab length L3 of 30 mm, thus forming the adhesive sheet (electropeelable adhesive sheet) of Example 1.

[0138] (Fabrication of the joint) The polyethylene terephthalate release liner (MRF38) of the electropenetrating adhesive sheet obtained above was peeled off, and a stainless steel plate (SUS304BA, size: 60mm x 130mm) was attached to the peeled surface as a conductive adherend, as shown in Figure 9, so that the tab 50 of the electropenetrating adhesive sheet (adhesive sheet X2) protruded from the adherend (second adherend 16), and it was pressed once back and forth with a 2kg roller. Furthermore, the release liner on the other adhesive layer side was peeled off, and an acrylic plate (40 mm x 100 mm, 3 mm thick) was attached to the peeled surface as the first adherend 15, pressed down with 5 kg for 10 seconds, and left for 30 minutes in an environment of 23°C to obtain a bonded body consisting of a SUS304BA plate / electro-peelable adhesive layer (adhesive sheet) / acrylic plate as shown in Figure 9.

[0139] (Adhesion strength test) Adhesion strength tests were conducted on the joints prepared using the method described above as test samples. Using a peel tester (product name "Small Tabletop Tester EZ-SX", manufactured by Shimadzu Corporation), the adhesive strength (tab side) was measured by pulling the tab portion of the adhesive sheet vertically while holding down the SUS304BA plate in the joint (tensile speed: 150 mm / min, peel temperature: 23°C). Furthermore, for the fabricated joint, the adhesive strength (opposite side) was measured by pulling the end of the adhesive sheet opposite the tab side in a vertical direction while holding down the SUS304BA plate in the joint (tensile speed: 150 mm / min, peel temperature: 23°C). The ratio of the adhesive strength (tab side) to the adhesive strength (opposite side) was also calculated.

[0140] (Electropeeling force test) The bonded body prepared using the above method was used as a test sample for an electropenetration test. The electro-peel force (tab side and opposite side) was measured in the same manner as the above adhesive strength test, except that a negative electrode was attached to the SUS304BA plate of the bonded body and a positive electrode was attached to the aluminum vapor-deposited surface of the metal layered film before peeling, and the adhesive strength was measured while the voltage was still applied after applying a 50V voltage for 10 seconds. The ratio of the peel force (tab side) to the peel force (opposite side) was calculated.

[0141] (Shear adhesion test) The joints prepared using the method described above were used as test samples for shear adhesion strength testing. The tensile shear bonding strength between SUS304BA plate and acrylic plate in a jointed structure was measured using a tensile testing machine (Minebea, model number: TG-100kN). The measurement was performed at 25°C with a tensile speed of 5 mm / min. The obtained values ​​were converted to shear bonding strength per unit area.

[0142] [Examples 2-12] The adhesive sheets and joints were manufactured in the same manner as in Example 1, except that the shape of the adhesive sheet was changed as shown in Tables 1 and 2. In Examples 11 and 12, the size of the stainless steel plate was changed to 60 mm x 200 mm, and the size of the acrylic plate was changed to 40 mm x 180 mm.

[0143] [Comparative Example 1] The adhesive sheet and bonded body were manufactured in the same manner as in Example 1, except that the shape of the adhesive sheet was changed to a strip shape with a width of 20 mm, a length of 90 mm, and a tab width of 20 mm, without the provision of an inclined section.

[0144] [Comparative Example 2] The adhesive sheet and bonded body were manufactured in the same manner as in Example 1, except that the shape of the adhesive sheet was changed to a strip shape with a width of 40 mm, a length of 90 mm, and a tab width of 40 mm, without the provision of an inclined section.

[0145] [Comparative Example 3] The adhesive sheet and bonded body were manufactured in the same manner as in Example 1, except that the shape of the adhesive sheet was changed to a strip shape with a width of 40 mm, a length of 180 mm, and a tab width of 40 mm, without the provision of an inclined section, and the size of the stainless steel plate was changed to 60 mm x 200 mm and the size of the acrylic plate to 40 mm x 180 mm.

[0146] The results obtained for Examples 1-12 and Comparative Examples 1-3 are shown in Tables 1 and 2.

[0147] [Table 1]

[0148] [Table 2]

[0149] The results in Tables 1 and 2 show that, because the adhesive sheets of Examples 1 to 12 have a tapered inclined portion, the peeling force from the tab side is reduced compared to Comparative Examples 1 to 3, which do not have an inclined portion, and they can be peeled off with less stress. Furthermore, making the width of the end portion (end portion 41) smaller than the width of the adhesive sheet tended to reduce the peeling force. In Examples 11 and 12, where the total length of the adhesive sheet was increased, a decrease in peeling force was observed, similar to Example 1. It was shown that the greater the ratio of the inclined length to the total length of the adhesive sheet, the lower the peeling force, and the smaller the width of the edges (the thinner the tab), the lower the peeling force.

[0150] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of the present invention. [Industrial applicability]

[0151] The present invention provides an adhesive sheet and a bond having excellent adhesive strength and good release properties. It also provides a method for separating a bond with good release properties.

[0152] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2021-057809 filed on March 30, 2021, the contents of which are incorporated herein by reference. [Explanation of Symbols]

[0153] 100, 110, 120, 130, X2, X3 Adhesive Sheets 2.10 Adhesive layer 1. Electropeelable adhesive layer 3, 20 base material 4. Conductive layer 5 Base material for current carrying 15. First Adhesion 16. Second Adhesion 17 Outer edge 40 Slope 41 End 50 tabs W width W1 Slope width W2 End width W3 slope width L total length L1 Length excluding the inclined section L2 slope length L3 tab length

Claims

1. A strip-shaped adhesive sheet having an adhesive layer, The adhesive layer is an electro-peelable adhesive layer whose adhesive strength decreases when a voltage is applied. An adhesive sheet having an inclined portion that is tapered in shape, with the width narrowing towards one end in the longitudinal direction of the adhesive sheet.

2. The adhesive sheet according to claim 1, further comprising a tab provided at the end.

3. The adhesive sheet according to claim 1 or 2, wherein the ratio of the length of the inclined portion to the length of the adhesive sheet in the longitudinal direction is 5% or more.

4. The adhesive sheet according to any one of claims 1 to 3, wherein the ratio of the width of the edge to the width of the adhesive sheet is 50% or less.

5. The adhesive sheet according to claim 4, wherein the electropenetrating adhesive layer contains a polymer and an ionic liquid.

6. The adhesive sheet according to claim 5, wherein the anion of the ionic liquid is at least one selected from the group consisting of bis(fluorosulfonyl)imide anions and bis(trifluoromethanesulfonyl)imide anions.

7. The adhesive sheet according to claim 5 or 6, wherein the cation of the ionic liquid is at least one selected from the group consisting of nitrogen-containing onium cations, sulfur-containing onium cations, and phosphorus-containing onium cations.

8. A bonding body comprising an adhesive sheet according to any one of claims 1 to 7, a first adherend, and a second adherend.

9. A method for separating a joint according to claim 8, A method for separating a bonded body, comprising initiating the separation of the first bonded body and the second bonded body from the outer edge of the portion of the first bonded body or the second bonded body joined by the inclined portion of the adhesive sheet.

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