Adhesive sheet

Abstract

The invention provides an adhesive sheet, which can improve the processability and the adhesive force. The adhesive sheet for a fuel cell is provided with an adhesive layer, the adhesive layer has irregularities on at least one surface, and the relationship between the pressure applied to the adhesive sheet necessary for adhesion to an adherend and the irregularities satisfies a predetermined formula (1).

Description

Technical Field

[0001] The present disclosure relates to an adhesive sheet. Background Art

[0002] Various techniques have been proposed for fuel cells as disclosed in Patent Document 1.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015-035312

[0004] Patent Document 2: Japanese Unexamined Patent Application Publication No. H09-157612

[0005] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2009-155504

[0006] In Patent Document 1, a fuel cell core is disclosed in which a bonding layer made of an adhesive or an adhesive agent is disposed around a MEGA, and the separators are bonded to each other through the bonding layer. Since it sticks in the case of an adhesive having a high adhesive strength, it is difficult to handle, and in the case of an adhesive that suppresses sticking to facilitate handling, the adhesive strength is low. Summary of the Invention

[0007] The present disclosure has been made in view of the above actual situation, and its main object is to provide an adhesive sheet that can improve processability and can improve adhesive force.

[0008] That is, the present disclosure includes the following aspects.

[0009] <1> An adhesive sheet for a fuel cell, wherein

[0010] the adhesive sheet has an adhesive layer,

[0011] the adhesive layer has irregularities on at least one surface,

[0012] the relationship between the pressing force applied to the adhesive sheet required for adhesion to an adherend and the irregularities satisfies the following formula (1),

[0013] Formula (1): F0 > σ0 × S1.

[0014] F0 is the pressing force, σ0 is the plastic stress of the adhesive layer, and S1 is the cross-sectional area of the irregularities at half the height of the height of the irregularities of the adhesive layer.

[0015] <2> The adhesive sheet according to <1>, wherein

[0016] the adhesive layer is at least one selected from the group consisting of a thermosetting elastomer, a thermoplastic elastomer, and a resin.

[0017] <3>The adhesive sheet according to <1> or <2>, wherein,

[0018] The adhesive sheet includes a core layer and the adhesive layer located on at least one surface of the core layer.

[0019] <4>A method for pressing an adhesive sheet, which is a method for pressing an adhesive sheet for a fuel cell,

[0020] When bonding the adhesive sheet described in any one of <1> to <3> above to an adherend, the adhesive sheet and the adherend are pressed with a pressing force that satisfies the above formula (1).

[0021] The adhesive sheet of the present disclosure can improve processability and adhesion. Description of the Drawings

[0022] Figure 1 It is a schematic diagram showing an example of the adhesive sheet of the present disclosure.

[0023] Figure 2 It is a chart showing an example of the relationship between stroke and stress.

[0024] Figure 3 It is a schematic diagram showing an example of the method for pressing the adhesive sheet of the present disclosure.

[0025] Figure 4 It is a schematic diagram showing another example of the adhesive sheet of the present disclosure.

[0026] Figure 5 It is a schematic diagram showing another example of the adhesive sheet of the present disclosure. Detailed Description of the Invention

[0027] Hereinafter, embodiments of the present disclosure will be described. Among them, events required for the implementation of the present disclosure other than those specifically mentioned in this specification (for example, general configurations and manufacturing processes of adhesive sheets that do not constitute features of the present disclosure) can be grasped as design matters of those skilled in the art in this field based on the prior art. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in this field.

[0028] In addition, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect actual dimensional relationships.

[0029] In the present disclosure, the gas supplied to the anode of the fuel cell is a fuel gas (anode gas), and the gas supplied to the cathode of the fuel cell is an oxidant gas (cathode gas). The fuel gas is a gas mainly containing hydrogen, and may also be hydrogen. The oxidant gas is a gas containing oxygen, and may also be oxygen, air, etc. In the present disclosure, the fuel gas and the oxidant gas are collectively referred to as reaction gas or gas.

[0030] In the present disclosure, adhesion means that the adherend of the object can be adhered by intermolecular forces even without heating.

[0031] In the present disclosure, there is provided an adhesive sheet for a fuel cell,

[0032] The above adhesive sheet includes an adhesive layer,

[0033] The above adhesive layer has irregularities on at least one surface,

[0034] The relationship between the pressing force applied to the above adhesive sheet required for adhesion to the adherend and the above irregularities satisfies the following formula (1).

[0035] Formula (1): F0>σ0×S1

[0036] F0 is the above pressing force, σ0 is the plastic stress of the above adhesive layer, and S1 is the cross-sectional area of the above irregularities at half of the height of the above irregularities of the above adhesive layer.

[0037] Since the soft adhesive has a strong adhesive force but is easily stuck, it is difficult to handle. On the other hand, since the hard adhesive is difficult to stick but does not elastically deform, the adhesive force is weak.

[0038] Especially when the adhesive is a sealing component of a fuel cell, a pressure resistance exceeding 100 kPa is required for gas and cooling water, and a firm adhesive force is required.

[0039] For a soft adhesive, if the temperature becomes higher, softening easily progresses. In the case of a fuel cell with a maximum operating temperature of one hundred and dozens of degrees, instead of interface peeling of the adhesive, it becomes bulk condensation failure, and leakage is likely to occur.

[0040] In the present disclosure, there is provided an adhesive sheet that is difficult to stick during operations such as setting and can exhibit strong adhesive force when pressed. In the present disclosure, by providing irregularities on the surface of the adhesive layer of the adhesive sheet, it is difficult to stick during the operation of the adhesive sheet. In addition, when the adhesive sheet is pressed, the stress is high and it is prone to plastic deformation. And when a high adhesive force is desired, the adhesive sheet is plastically deformed by applying a force that becomes the stress for plastic deformation. Thus, even after removing the load, intermolecular forces act, ensuring strong adhesive force. The adhesive sheet of the present disclosure is suitable for use in sticking components of a fuel cell that need to seal gases and water at high temperatures to each other for sealing.

[0041] The adhesive sheet of the present disclosure includes an adhesive layer.

[0042] The adhesive layer has irregularities on at least one surface. The adhesive layer only needs to have irregularities on at least one of the surfaces, and it may also have irregularities on both surfaces.

[0043] The relationship between the pressing force applied to the above-mentioned adhesive sheet required for adhesion to the adherend and the above-mentioned irregularities satisfies the following formula (1).

[0044] Formula (1): F0>σ0×S1

[0045] F0 is the above-mentioned pressing force, σ0 is the plastic stress of the above-mentioned adhesive layer, and S1 is the cross-sectional area of the above-mentioned irregularities at the half-height of the height of the above-mentioned irregularities of the above-mentioned adhesive layer.

[0046] Figure 1 It is a schematic diagram showing an example of the adhesive sheet of the present disclosure.

[0047] As Figure 1 shown, the adhesive sheet of the present disclosure can be a single sheet of an adhesive layer 10 having irregularities 11 on both surfaces.

[0048] By the relationship between the cross-sectional area S1 of the above-mentioned irregularities at the half-height of the height of the above-mentioned irregularities of the adhesive layer and the pressing force F0 satisfying the above formula (1), the gaps of the irregularities are filled by the plastic deformation of the adhesive sheet.

[0049] Figure 2 It is a chart showing an example of the relationship between stroke and stress.

[0050] As Figure 2 shown, by applying a pressure that becomes the stress for plastic deformation, the adhesive sheet can be plastically deformed. The plastic stress σ0 of the present disclosure is the region where plastic stress is generated, and it refers to the region above the plastic deformation line of Figure 2 .

[0051] Figure 3 It is a schematic diagram showing an example of the pressing method of the adhesive sheet of the present disclosure.

[0052] As Figure 3 shown, by having unevenness 11 on the surface of the adhesive layer 10, (A) there are fewer grounding surfaces, less sticking, and good handling during normal times, (B) it is easily plastically deformed by the load during pressurization, and (C) after removing the load, intermolecular forces act, ensuring a strong adhesive force.

[0053] In the present disclosure, when bonding the adhesive sheet to the adherend, the adhesive sheet and the adherend are pressed with a pressing force that satisfies the above formula (1). That is, while plastically deforming the adhesive layer by pressing the adhesive sheet with a load of F0 in such a manner that the relationship between the uneven shape of the adhesive layer and the pressing force satisfies the above formula (1), the adhesive sheet and the adherend are bonded. Thereby, the handleability of the adhesive sheet can be improved, and the adhesive force can be increased.

[0054] From the viewpoints of miniaturization and cost reduction of the fuel cell manufacturing equipment, the pressing force F0 can be several kN or less.

[0055] The adhesive layer can be at least one selected from the group consisting of a thermosetting elastomer, a thermoplastic elastomer, and a resin. As long as it is these materials, it can exhibit the desired strength during high-temperature operation of the fuel cell, during startup at the freezing point of the fuel cell, and in environments such as water and acid.

[0056] Regarding the thickness of the adhesive layer, from the viewpoint of ensuring adhesiveness, it can be 5 μm or more, or can be 30 μm or more. From the viewpoint of reducing the cell thickness, it can be 100 μm or less, or can be 40 μm or less.

[0057] Figure 4 is a schematic diagram showing another example of the adhesive sheet of the present disclosure.

[0058] As Figure 4 shown, the adhesive sheet of the present disclosure can also have an adhesive layer 10 disposed on one surface of one adherend 20, and bond one adherend 20 and another adherend 20 through the adhesive layer 10.

[0059] The adhesive sheet can include a core layer and the adhesive layer located on at least one surface of the core layer. The adhesive sheet can also have the adhesive layer on both surfaces of the core layer.

[0060] Figure 5 is a schematic diagram showing another example of the adhesive sheet of the present disclosure.

[0061] As Figure 5 shown, the adhesive sheet 100 of the present disclosure can be a three-layer sheet including a core layer 30 and adhesive layers 10 located on both surfaces of the core layer 30.

[0062] The core layer only needs to be a structural component with airtightness and insulation, and can be formed of a material whose structure does not change under the temperature conditions during thermocompression bonding in the manufacturing process of the fuel cell. Specifically, the material of the core layer can be, for example, polyethylene, polypropylene (PP), PC (polycarbonate), PPS (polyphenylene sulfide), PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PA (polyamide), PI (polyimide), PS (polystyrene), PPE (polyphenylene ether), PEEK (polyether ether ketone), cycloolefin, PES (polyethersulfone), PPSU (polyphenylsulfone), LCP (liquid crystal polymer), epoxy resin and other resins. The material of the core layer can also be rubber materials such as EPDM (ethylene propylene diene rubber), fluorine-based rubber, and silicone-based rubber.

[0063] Regarding the thickness of the core layer, from the perspective of ensuring insulation, it can be 5 μm or more, and can also be 30 μm or more. From the perspective of reducing the thickness of the battery cell, it can be 100 μm or less, and can also be 90 μm or less.

[0064] Since if the adhesive sheet is too hard, a large pressure and large equipment are required to make it plastically deformed, within the operating temperature range of the fuel cell (for example, -40°C to 150°C), the elastic modulus can be 10 -5 Pa to 10 -7 Pa.

[0065] Examples of the adherend include a separator, a resin frame, an electrolyte membrane, a gas diffusion layer, a catalyst layer, etc.

[0066] The adhesive sheet of the present disclosure is used in a fuel cell.

[0067] The fuel cell can be a fuel cell with a single fuel cell (cell, fuel cell cell), or a fuel cell stack (stack) in which a plurality of single cells are stacked.

[0068] In the present disclosure, sometimes both the single cell and the fuel cell stack are referred to as fuel cells.

[0069] The number of single cells stacked in the fuel cell stack is not particularly limited, and can be, for example, 2 to several hundred.

[0070] The single cell can have a power generation body.

[0071] The shape of the power generation body can be rectangular in plan view.

[0072] The power generation body can be a membrane electrode assembly (MEA) including an electrolyte membrane and two electrodes.

[0073] The electrolyte membrane can be a solid polymer electrolyte membrane. As the solid polymer electrolyte membrane, for example, fluorine-based electrolyte membranes such as thin films of perfluorosulfonic acid containing water, and hydrocarbon-based electrolyte membranes can be cited. As the electrolyte membrane, for example, it can be a Nafion membrane (manufactured by DuPont) etc.

[0074] One of the two electrodes is the anode (fuel electrode), and the other is the cathode (oxidant electrode).

[0075] The electrode includes a catalyst layer, and can include a gas diffusion layer as needed. The power generation body can be a membrane electrode gas diffusion layer assembly (MEGA).

[0076] The catalyst layer includes a catalyst. The catalyst can include a catalyst metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, and a carrier having electron conductivity, etc.

[0077] As the catalyst metal, for example, platinum (Pt) and alloys composed of Pt and other metals (for example, Pt alloys mixed with cobalt and nickel etc.) can be used. The catalyst metal used as the cathode catalyst and the catalyst metal used as the anode catalyst can be the same or different.

[0078] As the electrolyte, it can be a fluorine-based resin etc. As the fluorine-based resin, for example, Nafion solution etc. can be used.

[0079] The above-mentioned catalyst metal is supported on a carrier. In each catalyst layer, the carrier supporting the catalyst metal (catalyst-supported carrier) can be mixed with the electrolyte.

[0080] Carriers for supporting the catalyst metal, for example, carbon materials such as commercially available carbon etc. can be cited.

[0081] The gas diffusion layer (GDL) can be composed of a base material and a mesoporous layer (MPL).

[0082] The GDL can have a base material on the side in contact with the separator and an MPL on the side in contact with the catalyst layer.

[0083] The base material can be a conductive component having air permeability etc.

[0084] As the base material, for example, carbon porous bodies such as carbon cloth and carbon paper, metal meshes, and metal porous bodies such as foamed metal etc. can be cited.

[0085] The MPL can include a mixture of a hydrophobic resin such as PTFE and a conductive material such as carbon black.

[0086] The MPL can include an antioxidant such as Ce. Through the antioxidant, the generation of free radicals can be prevented.

[0087] A single cell may include a separator.

[0088] The separator collects the current generated by power generation and functions as a partition wall. The separator is usually disposed on both sides in the stacking direction of the power generation unit in such a manner that a pair of separators sandwich the power generation unit. One of the pair of separators is an anode separator, and the other is a cathode separator.

[0089] The anode separator may have grooves on the surface on the power generation unit side that form a fuel gas flow path.

[0090] The cathode separator may have grooves on the surface on the power generation unit side that form an oxidant gas flow path.

[0091] The separator may have holes such as supply holes and discharge holes for allowing a fluid to flow in the stacking direction of the single cell, which constitute a manifold.

[0092] As the separator, for example, it may be compressed carbon formed into an airtight dense carbon, and a stamped metal (such as iron, titanium, and stainless steel, etc.).

[0093] The single cell may include a resin frame for insulation disposed on the outer side (outer periphery) in the plane direction of the membrane electrode assembly disposed between the anode separator and the cathode separator. The resin frame is formed into a plate-like and frame-like shape using a thermoplastic resin, and seals between the anode separator and the cathode separator while holding the membrane electrode assembly in the central region. As the resin frame, for example, resins such as PE, PP, PET, and PEN can be used. The resin frame may be the adhesive sheet of the present disclosure.

[0094] The fuel cell stack may have gaskets, resin sheets, etc. for sealing each gas between the single cells, etc. The resin sheet may be the adhesive sheet of the present disclosure.

[0095] Explanation of Reference Numerals

[0096] 10... Adhesive layer; 11... Concavities and convexities; 20... Adherend; 30... Core layer; 100... Adhesive sheet.

Claims

1. An adhesive sheet for a fuel cell, wherein: The adhesive sheet comprises an adhesive layer, The adhesive layer has concavities and convexities on at least one surface, The relationship between the pressure applied to the adhesive sheet and the concavities and convexities required for bonding to an adherend satisfies the following formula (1): Formula (1): F0>σ0×S1, F0 is the applied force, σ0 is the plastic stress of the adhesive layer, and S1 is the cross-sectional area of ​​the concavities and convexities of the adhesive layer at a height half the height of the concavities and convexities.

2. The adhesive sheet according to claim 1, wherein The adhesive layer is at least one selected from the group consisting of a thermosetting elastomer, a thermoplastic elastomer, and a resin.

3. The adhesive sheet according to claim 1, wherein The adhesive sheet includes a core layer and the adhesive layer located on at least one surface of the core layer.

4. A method for pressurizing an adhesive sheet, which is a method for pressurizing an adhesive sheet for a fuel cell, wherein: When the pressure-sensitive adhesive sheet according to claim 1 is bonded to an adherend, the pressure-sensitive adhesive sheet and the adherend are pressurized with a pressure satisfying the above formula (1).

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