Adhesive sheet

Abstract

To provide an adhesive sheet that can improve handling properties and adhesive strength.SOLUTION: An adhesive sheet for a fuel cell includes an adhesive layer having irregularities on at least one surface, the relationship between the pressure applied to the adhesive sheet required for adhesion to an adherend and the irregularities satisfies a specified formula (1).SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Regarding fuel cells as disclosed in Patent Document 1, various technologies have been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 discloses a fuel cell cell in which a bonding layer made of an adhesive or a pressure-sensitive adhesive is disposed around a MEGA, thereby bonding separators to each other. In the case of an adhesive with high adhesive strength, it is sticky and difficult to handle. In the case of an adhesive with reduced stickiness for easy handling, the adhesive strength is low.

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide an adhesive sheet capable of improving handleability and adhesive force.

Means for Solving the Problems

[0006] That is, the present disclosure includes the following aspects. <1> An adhesive sheet for a fuel cell, wherein the adhesive sheet includes an adhesive layer, The adhesive layer has unevenness on at least one surface, An adhesive sheet in which the relationship between the pressing force applied to the adhesive sheet required for adhesion to the adherend and the unevenness satisfies the following formula (1). Formula (1): F0 > σ0×S1 F0 is the pressing force, σ0 is the plastic stress of the adhesive layer, and S1 is the cross-sectional area of the unevenness at half the height of the unevenness of the adhesive layer.

[0007] <2> The adhesive sheet according to <1>, wherein the adhesive layer is at least one selected from the group consisting of a thermosetting elastomer, a thermoplastic elastomer, and a resin.

[0008] <3> The adhesive sheet according to <1> or <2>, comprising a core layer and the adhesive layer on at least one surface of the core layer.

[0009] <4> A method for pressing an adhesive sheet for a fuel cell, When adhering the adhesive sheet according to any one of <1> to <3> to an adherend, the adhesive sheet and the adherend are pressed with a pressing force that satisfies the formula (1).

Advantages of the Invention

[0010] The adhesive sheet of the present disclosure can improve handleability and adhesion.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments according to the present disclosure will be described. In addition, matters other than those specifically mentioned in this specification and necessary for the implementation of the present disclosure (for example, general configurations and manufacturing processes of adhesive sheets that do not characterize the present disclosure) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the content disclosed in this specification and common general technical knowledge in the relevant field. Also, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships. 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 mainly a gas containing hydrogen, and may be hydrogen. The oxidant gas is a gas containing oxygen, and may be oxygen, air, etc. In the present disclosure, the fuel gas and the oxidant gas are collectively referred to as reaction gas or gas. In the present disclosure, adhesion means that the object adherend adheres by intermolecular force without heating.

[0013] In the present disclosure, there is provided an adhesive sheet for a fuel cell, the adhesive sheet includes an adhesive layer, the adhesive layer has irregularities on at least one surface, and there is provided an adhesive sheet in which the relationship between the pressing force applied to the adhesive sheet required for adhesion to the adherend and the irregularities satisfies the following formula (1). Formula (1): F0 > σ0×S1 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.

[0014] Soft adhesives have strong adhesive force but are prone to stickiness, making handling difficult. On the other hand, hard adhesives are less sticky but have weak adhesive force because they do not undergo elastic deformation. Especially when the adhesive is a sealing member of a fuel cell, a pressure resistance exceeding 100 kPa is required against gas and cooling water, and a strong adhesive force is necessary. Soft adhesives tend to soften as the temperature rises. In the case of a fuel cell with a maximum operating temperature of one hundred and dozens of degrees, instead of interfacial peeling of the adhesive, cohesive failure of the bulk occurs and leaks are likely to occur.

[0015] In the present disclosure, there is provided an adhesive sheet that is difficult to adhere during handling such as installation and can exhibit a strong adhesive force when pressurized. In the present disclosure, by providing irregularities on the surface of the adhesive layer of the adhesive sheet, it is difficult to adhere during handling of the adhesive sheet. Also, when the adhesive sheet is pressurized, the stress is high and it is easily plastically deformed. Furthermore, when a high adhesive force is desired, a force that becomes the stress of plastic deformation is applied to plastically deform the adhesive sheet, so that even after the load is removed, intermolecular forces act and a strong adhesive force is maintained. The adhesive sheet of the present disclosure is suitable for use in sealing members of a fuel cell that need to seal gas and water at high temperatures by adhering them together.

[0016] The adhesive sheet of the present disclosure includes an adhesive layer. The adhesive layer has irregularities on at least one surface. The adhesive layer only needs to have irregularities on at least one side of the surface, and may have irregularities on both sides.

[0017] The relationship between the pressing force applied to the adhesive sheet required for adhesion to the adherend and the irregularities satisfies the following formula (1). Formula (1): F0 > σ0×S1 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.

[0018] Figure 1 is a schematic diagram showing an example of the adhesive sheet of the present disclosure. As shown in FIG. 1, the adhesive sheet of the present disclosure may be a single sheet of an adhesive layer 10 having irregularities 11 on both sides. By satisfying the relationship between the cross-sectional area S1 of the irregularities at half the height of the height of the irregularities of the adhesive layer and the pressing force F0 with the formula (1), the gaps between the irregularities are filled by the plastic deformation of the adhesive sheet.

[0019] FIG. 2 is a graph showing an example of the relationship between the stroke and the stress. As shown in FIG. 2, the adhesive sheet can be plastically deformed by applying a pressure that becomes the stress of plastic deformation. The plastic stress σ0 of the present disclosure is a region where plastic deformation occurs, and means a region above the plastic deformation line in FIG. 2.

[0020] FIG. 3 is a schematic diagram showing an example of a method for pressing the adhesive sheet of the present disclosure. As shown in FIG. 3, by providing irregularities 11 on the surface of the adhesive layer 10, (A) there are few grounding surfaces during normal times, there is little stickiness, and handling is good, (B) it becomes easy to plastically deform under a load during pressing, and (C) after removing the load, intermolecular forces act and strong adhesiveness is maintained. In the present disclosure, when adhering the adhesive sheet and the adherend, the adhesive sheet and the adherend are pressed with a pressing force that satisfies the formula (1). That is, while pressing the adhesive sheet with a load of F0 so that the relationship between the concavo-convex shape of the adhesive layer and the pressing force satisfies the formula (1) and plastically deforming the adhesive layer, the adhesive sheet and the adherend are adhered. Thereby, the handleability of the adhesive sheet can be improved, and the adhesiveness can be improved. From the viewpoints of miniaturization and cost reduction of the fuel cell manufacturing equipment, the pressing force F0 may be several kN or less.

[0021] The adhesive layer may be at least one selected from the group consisting of a thermosetting elastomer, a thermoplastic elastomer, and a resin. With these materials, desired strength can be exhibited under the environment of high-temperature operation of the fuel cell, starting at sub-zero temperature of the fuel cell, water, acid, and the like. The thickness of the adhesive layer may be 5 μm or more, may be 30 μm or more from the viewpoint of ensuring adhesiveness, and may be 100 μm or less, may be 40 μm or less from the viewpoint of reducing the cell thickness.

[0022] FIG. 4 is a schematic diagram showing another example of the adhesive sheet of the present disclosure. As shown in FIG. 4, in the adhesive sheet of the present disclosure, the adhesive layer 10 may be disposed on one side of one adherend 20, and one adherend 20 and the other adherend 20 may be adhered by the adhesive layer 10.

[0023] The adhesive sheet may include a core layer and the adhesive layer on at least one surface of the core layer. The adhesive sheet may include the adhesive layer on both surfaces of the core layer. FIG. 5 is a schematic diagram showing another example of the adhesive sheet of the present disclosure. As shown in FIG. 5, the adhesive sheet 100 of the present disclosure may be a three-layer sheet including a core layer 30 and the adhesive layer 10 on both surfaces of the core layer 30.

[0024] The core layer may be a structural member having gas barrier properties and insulating properties, and may be formed of a material whose structure does not change even under the temperature conditions during thermocompression bonding in the manufacturing process of the fuel cell. Specifically, the material of the core layer may be, for example, resins such as 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 (polyether sulfone), PPSU (polyphenyl sulfone), LCP (liquid crystal polymer), epoxy resin, etc. The material of the core layer may be a rubber material such as EPDM (ethylene propylene diene rubber), fluorine-based rubber, silicon-based rubber, etc. The thickness of the core layer may be 5 μm or more, may be 30 μm or more, from the viewpoint of ensuring insulation, and may be 100 μm or less, may be 90 μm or less from the viewpoint of reducing the cell thickness.

[0025] If the adhesive sheet is too hard, a large pressure and large equipment are required to cause plastic deformation. Therefore, in the range of the operating temperature of the fuel cell (for example, -40°C to 150°C), the elastic modulus is 10 -5 Pa to 10 -7 Pa may be sufficient.

[0026] Examples of the adherend include a separator, a resin frame, an electrolyte membrane, a gas diffusion layer, and a catalyst layer.

[0027] The adhesive sheet of the present disclosure is for a fuel cell. The fuel cell may have only one fuel cell single cell (cell, fuel cell cell), or may be a fuel cell stack (stack) in which a plurality of single cells are stacked. In the present disclosure, both the single cell and the fuel cell stack may be referred to as a fuel cell in some cases. The number of single cells stacked in the fuel cell stack is not particularly limited, and may be, for example, 2 to several hundreds.

[0028] The single cell may have a power generation body. The shape of the power generation body may be rectangular in plan view. The power generation body may be a membrane electrode assembly (MEA) including an electrolyte membrane and two electrodes. The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of the solid polymer electrolyte membrane include fluorine-based electrolyte membranes such as thin films of perfluorosulfonic acid containing moisture, and hydrocarbon-based electrolyte membranes. Examples of the electrolyte membrane may include Nafion membranes (manufactured by DuPont). One of the two electrodes is an anode (fuel electrode), and the other is a cathode (oxidant electrode). The electrode includes a catalyst layer and may optionally include a gas diffusion layer. The power generation body may be a membrane electrode gas diffusion layer assembly (MEGA). The catalyst layer includes a catalyst, and the catalyst may include a catalyst metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, a carrier having electron conductivity, and the like. As the catalyst metal, for example, platinum (Pt), an alloy composed of Pt and other metals (for example, a Pt alloy mixed with cobalt, nickel, etc.) can be used. The catalyst metal used as the cathode catalyst and the catalyst metal used as the anode catalyst may be the same or different. The electrolyte may be a fluororesin or the like. As the fluororesin, for example, a Nafion solution or the like may be used. The above catalyst metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalyst metal (catalyst-supported carrier) and the electrolyte may be mixed. Examples of the carrier for supporting the catalyst metal include carbon materials such as commercially available carbon.

[0029] The gas diffusion layer (GDL) may be composed of a base material and a mesoporous layer (MPL). The GDL may have a base material on the side in contact with the separator and an MPL on the side in contact with the catalyst layer. The base material may be a conductive member having gas permeability or the like. Examples of the base material include carbon porous bodies such as carbon cloth and carbon paper, and metal porous bodies such as metal mesh and foamed metal. The MPL may include a mixture of a water-repellent resin such as PTFE and a conductive material such as carbon black. The MPL may contain an antioxidant such as Ce. The antioxidant can prevent the generation of radicals.

[0030] The single cell may include a separator. The separator collects the current generated by power generation and functions as a partition. In a single cell, the separator is usually arranged on both sides in the stacking direction of the power generation part so that a pair of separators sandwich the power generation part. One of the pair of separators is an anode separator, and the other is a cathode separator. The anode separator may have grooves serving as fuel gas flow paths on the surface on the power generation part side. The cathode separator may have grooves serving as oxidant gas flow paths on the surface on the power generation part side. The separator may have holes that constitute a manifold such as supply holes and discharge holes for allowing a fluid to flow in the stacking direction of the single cell. Examples of the separator may include dense carbon obtained by compressing carbon to make it gas-impermeable, and press-molded metals (such as iron, titanium, and stainless steel, etc.). The single cell may be provided with an insulating resin frame disposed on the outer side (outer periphery) in the plane direction of the membrane electrode assembly 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 the space between the anode separator and the cathode separator while holding the membrane electrode assembly in its 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.

[0031] The fuel cell stack may have gaskets, resin sheets, etc. for sealing each gas between single cells and the like. The resin sheet may be the adhesive sheet of the present disclosure.

Explanation of Signs

[0032] 10. Adhesive layer 11. Concavo-convex 20. Adherend 30. Core layer 100. Adhesive sheet

Claims

1. An adhesive sheet for a fuel cell, wherein the adhesive sheet includes an adhesive layer, the adhesive layer has irregularities on at least one surface, and a relationship between a pressing force applied to the adhesive sheet required for adhesion to an adherend and the irregularities satisfies the following formula (1). An adhesive sheet. Formula (1): F0 > σ0 × S1 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 a height that is half of the height of the irregularities of the adhesive layer.

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 on at least one surface of the core layer.

4. A method for pressing an adhesive sheet for a fuel cell, wherein when the adhesive sheet according to claim 1 and an adherend are adhered, the adhesive sheet and the adherend are pressed with a pressing force that satisfies the formula (1). A method for pressing an adhesive sheet.

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