Adhesive sheets and adhesive sheet combinations

Abstract

To provide an adhesive layer or the like which can be stored at room temperature, can complete adhesion without undergoing a curing treatment step after heat and pressure bonding, and can suppress adhesion defects even when placed in a high-temperature and high-humidity environment after bonding. The adhesive includes a first thermosetting adhesive layer 14 having a first glass transition temperature and a second thermosetting adhesive layer 16 having a second glass transition temperature higher than the first glass transition temperature, laminated together. The first and second adhesive layers each contain a polyurethane resin having a reactive functional group and a crosslinking agent. The first adhesive layer has a storage modulus (G') at 100°C. 100 ) is 5.0 × 10 4 Pa or more 6.6×10 5 Pa or less, and G' 100 Storage modulus (G') at 120°C 120 ) is 0.3 or less, and the second adhesive layer is 100 is 6.6 x 10 5 Pa > 1.0 x 10 7 Pa or less, and G' 100 G' for 120 The adhesive laminate 100 has a rate of decrease of 0.5 or less.

Description

[Technical Field]

[0001] The present invention relates to an adhesive laminate, an adhesive sheet, and a combination of adhesive sheets, and more particularly to an adhesive laminate including a thermosetting adhesive layer, and a thermosetting adhesive sheet including a thermosetting adhesive layer, which can be used for sealing fuel cells, etc., and a combination of such adhesive sheets. [Background technology]

[0002] In recent years, fuel cells have been attracting much attention as a means of curbing global warming and environmental destruction, as well as a next-generation power generation system, and research and development into them is currently underway. Fuel cells generate energy through the electrochemical reaction between hydrogen and oxygen, and examples of such fuel cells include phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, and polymer electrolyte fuel cells. Among these, polymer electrolyte fuel cells are attracting attention as a power source for automobiles (two-wheeled and four-wheeled vehicles), portable power sources, and the like, because they can be started at room temperature, are small in size, and have high output.

[0003] In a polymer electrolyte fuel cell, a fuel gas (e.g., a gas containing mainly hydrogen) supplied to an anode is ionized on an electrode catalyst, and the hydrogen ions are transported to a cathode through a solid polymer electrolyte membrane. The electrons generated at the anode are extracted to an external circuit and used as direct current electrical energy. An oxidant gas (e.g., a gas containing mainly oxygen or air) is supplied to the cathode, and the hydrogen ions react with the oxygen molecules that have received the electrons to produce water.

[0004] A fuel cell has a stack structure in which many cells are stacked. The cell stack includes an electrode assembly (MEA) having an electrolyte membrane and electrodes, separators that sandwich the MEA, and sealants (gaskets, subgaskets) that seal around the electrode members and between adjacent separators. Hot melt adhesives are known as such sealants, for example, as disclosed in Patent Document 1. As a sealant other than hot melt adhesives, for example, Patent Document 2 discloses an adhesive sheet that uses an adhesive resin composition containing a crystalline polyester resin and an amorphous polyester resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 216402 [Patent Document 2] Patent Publication No. 2015-017237 Summary of the Invention [Problem to be solved by the invention]

[0006] During fuel cell use, adhesive sheets used for sealing are exposed to high-temperature, high-humidity environments. It is desirable for adhesive sheets to maintain high sealing properties even in such environments. Furthermore, when forming a cell stack while sealing specific locations of an MEA with an adhesive sheet, it is desirable for the adhesive sheet to be easy to handle and adhere. However, the sealing material in Patent Document 1 is a hot-melt adhesive, which has issues with heat resistance and moisture resistance. Furthermore, the adhesive sheet in Patent Document 2 is capable of low-temperature adhesion, but it usually requires storage or transportation at low temperatures to maintain an uncured or semi-cured state after sheet formation until the adhesion process. Furthermore, the adhesion process with the MEA requires long periods of pressing at high temperatures, which requires a long adhesion operation and may cause thermal damage to the MEA. Furthermore, a curing process such as heat treatment or aging is required after the adhesion process.

[0007] An object of the present invention is to provide an adhesive laminate including a thermosetting adhesive layer that can be stored at room temperature, that completes adhesion after heat and pressure bonding without going through a curing treatment step, and that can suppress adhesion defects such as lifting, peeling, and voids even when placed in a high-temperature, high-humidity environment after adhesion, an adhesive sheet including such an adhesive laminate, and a combination of such adhesive sheets. [Means for solving the problem]

[0008] In order to solve the above problems, the adhesive laminate, adhesive sheet, and adhesive sheet combination according to the present invention have the following configurations.

[0009] [1] The adhesive laminate according to the present invention comprises a first thermosetting adhesive layer formed from a cured product of a thermosetting adhesive composition and having a first glass transition temperature, and a second thermosetting adhesive layer formed from a cured product of the thermosetting adhesive composition and having a second glass transition temperature higher than the first glass transition temperature, laminated together, wherein the first thermosetting adhesive layer and the second thermosetting adhesive layer each contain a polyurethane resin having a reactive functional group and a crosslinking agent, and the first thermosetting adhesive layer has a storage modulus (G') at 100°C. 100 ) is 5.0 × 10 4 Pa or more 6.6×10 5 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120 Furthermore, the second thermosetting adhesive layer has a storage modulus (G') at 100°C of 0.3 or less. 100 ) is 6.6 × 10 5 Pa > 1.0 x 10 7 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120 ) is less than 0.5.

[0010] [2] In the above aspect [1], the first glass transition temperature may be 15°C or higher and lower than 50°C, and the second glass transition temperature may be 50°C or higher and 100°C or lower.

[0011] [3] In the above aspect [1] or [2], the reactive functional group of the polyurethane resin may include a carboxy group, and the crosslinking agent may include a polyfunctional epoxy crosslinking agent.

[0012] [4] In the above aspect [3], the ratio (b / a) of the molar amount (a) of the carboxyl groups in the polyurethane resin to the molar amount (b) of the epoxy groups in the polyfunctional epoxy crosslinking agent may be 1.0 or more and 10.0 or less.

[0013] [5] In any of the above aspects [1] to [4], the second thermosetting adhesive layer may have a thickness greater than that of the first thermosetting adhesive layer. Furthermore, the first thermosetting adhesive layer may have a thickness of 1 μm or more and 6 μm or less, and the second thermosetting adhesive layer may have a thickness of 8 μm or more and 30 μm or less.

[0014] [6] The adhesive laminate may be formed on a surface of a base film to constitute an adhesive sheet. That is, the adhesive sheet according to the present invention is an adhesive sheet having a base film and any one of the adhesive laminates [1] to [5] above, with the adhesive laminate formed on the surface of the base film. The first thermosetting adhesive layer is formed on one surface of the base film, and the second thermosetting adhesive layer is formed on the surface of the first thermosetting adhesive layer opposite to the surface that contacts the base film.

[0015] [7] In the above aspect [6], the substrate film may be a film made of at least one resin material selected from the group consisting of polyarylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyphenylene sulfide, polysulfone, polyethersulfone, and polyetheretherketone.

[0016] [8] The adhesive sheet may further have a second substrate film, and may have a third thermosetting adhesive layer formed from a cured product of a thermosetting adhesive composition as part of the thermosetting adhesive layer. Here, the third thermosetting adhesive layer may be formed on one side of the second substrate film, and the second substrate film may sandwich the second thermosetting adhesive layer and the first thermosetting adhesive layer between the second substrate film and the third thermosetting adhesive layer. The third thermosetting adhesive layer contains a polyurethane resin having reactive functional groups and a crosslinking agent, and has a storage modulus (G') at 100°C. 100 ) is 5.0 × 10 4 Pa or more 6.6×10 5 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120 ) is not more than 0.3, and the third glass transition temperature is lower than the second glass transition temperature.

[0017] [9] In the above aspect [8], the second substrate film may be a film made of at least one resin material selected from the group consisting of polyarylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyphenylene sulfide, polysulfone, polyethersulfone, and polyetheretherketone.

[0018]

[10] In the above aspect [8] or [9], the third glass transition temperature may be 15°C or higher and lower than 50°C.

[0019]

[11] The adhesive sheet may be used in combination with another adhesive sheet. That is, the adhesive sheet combination according to the present invention comprises a first adhesive sheet and a second adhesive sheet, the first adhesive sheet comprising any one of the adhesive laminates [1] to [5] above, and the second adhesive sheet comprising at least one of the first thermosetting adhesive layer and the second thermosetting adhesive layer.

[0020]

[12] Alternatively, the adhesive sheet combination according to the present invention comprises a first adhesive sheet and a second adhesive sheet, the first adhesive sheet comprising the adhesive laminate of any one of [1] to [5] above, and the second adhesive sheet comprising a third thermosetting adhesive layer formed from a cured product of a curable adhesive composition. The third thermosetting adhesive layer comprises a polyurethane resin having reactive functional groups and a crosslinking agent, and has a storage modulus (G') at 100°C. 100 ) is 5.0 × 10 4 Pa or more 6.6×10 5 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120 ) is 0.3 or less, and has a third glass transition temperature lower than the second glass transition temperature. [Effects of the Invention]

[0021] The adhesive laminate of the present invention having the configuration [1] above, or an adhesive sheet having a substrate film disposed on one side of the adhesive laminate and the other side exposed, can complete adhesion after thermocompression bonding without a curing process because the first and second thermosetting adhesive layers, which have different glass transition temperatures, have the above-mentioned specified material composition and physical properties. When the adhesive laminate or adhesive sheet of the present invention is used to seal the periphery of a solid polymer electrolyte membrane in a fuel cell, by thermocompression bonding the adhesive laminate or adhesive sheet, in which the first and second thermosetting adhesive layers have the above-mentioned specified material composition and physical properties, to the solid polymer electrolyte membrane, adhesion can be completed without a curing process after thermocompression bonding, and the periphery of the solid polymer electrolyte membrane in the fuel cell can be sealed. Furthermore, even in a high-temperature, high-humidity environment, adhesion defects such as lifting, peeling, and voids can be suppressed, and good adhesion can be effectively maintained. This adhesive laminate also has excellent storage stability.

[0022] Furthermore, the adhesive laminate or adhesive sheet is particularly suitable for use in a manner that takes advantage of the fact that two layers having different physical properties are laminated as the thermosetting adhesive layer. For example, the adhesive laminate or adhesive sheet may be arranged so that the first and second thermosetting adhesive layers come into contact with the objects to be bonded or the environments to which they are exposed are suitable for the desired bonding form, depending on the first and second glass transition temperatures.

[0023] For example, if there is a difference in temperature or humidity between the environment to which one side of the adhesive laminate or adhesive sheet is exposed and the environment to which the other side is exposed, the adhesive laminate or adhesive sheet may be positioned so that the second thermosetting adhesive layer having a second glass transition temperature higher than the first glass transition temperature is positioned on the side exposed to the high temperature or high humidity environment.

[0024] Furthermore, for example, depending on the material or physical properties of the object to which the first and second thermosetting adhesive layers are to be adhered, the adhesive laminate or adhesive sheet may be arranged so that the thermosetting adhesive layer having physical properties more suitable for adhering to the object, out of the first and second thermosetting adhesive layers having different physical properties such as glass transition temperature, is in contact with the object.

[0025] As described above, by arranging the first and second thermosetting adhesive layers in directions appropriate for the environment and object, the adhesive laminate or adhesive sheet can further suppress adhesion defects such as lifting, peeling, and voids even when placed in a high-temperature, high-humidity environment, and can effectively maintain good adhesion. Therefore, the adhesive laminate of the present invention, or an adhesive sheet containing the adhesive laminate, can be suitably used as a material that imparts adhesion to locations that are subject to high temperatures and high humidity, such as sealing materials for fuel cells.

[0026] Furthermore, for example, if the adhesive surface of the adhesive laminate or adhesive sheet is exposed until it is bonded to the object, the adhesive laminate or adhesive sheet may be positioned so that a second thermosetting adhesive layer having a second glass transition temperature higher than the first glass transition temperature is exposed as the adhesive surface. By positioning the adhesive laminate or adhesive sheet in this manner, the stickiness of the exposed adhesive surface at room temperature is further reduced, preventing foreign matter from adhering to the adhesive surface, and even if foreign matter does adhere to the adhesive surface, the foreign matter can be more easily removed, improving workability in handling the adhesive laminate or adhesive sheet.

[0027] As in the above embodiment [2], when the first glass transition temperature of the first thermosetting adhesive layer is 15°C or higher and lower than 50°C, the adhesion of the first thermosetting adhesive layer to the substrate film is improved. Furthermore, when the second glass transition temperature is 50°C or higher and 100°C or lower, adhesion of the second thermosetting adhesive layer to the adhesion target, such as the electrolyte membrane of a fuel cell, can be maintained while more effectively suppressing adhesion defects such as lifting, peeling, and voids in high-temperature, high-humidity environments. Furthermore, stickiness of the second thermosetting adhesive layer at room temperature is effectively suppressed. Therefore, even if the adhesive surface of the second thermosetting adhesive layer is exposed, adhesion of foreign matter to the second thermosetting adhesive layer can be suppressed, and even if foreign matter does adhere, it can be easily removed. Therefore, in an environment where foreign matter is likely to adhere, the adhesive laminate or adhesive sheet can be positioned so that the second thermosetting adhesive layer faces the adhesion target, improving adhesion workability.

[0028] Furthermore, even when the first glass transition temperature is 15°C or higher but lower than 50°C and the second glass transition temperature is 50°C or higher but lower than 100°C, as described above, by arranging the adhesive laminate or adhesive sheet in accordance with the respective glass transition temperatures so that the combination of the object to which each thermosetting adhesive layer is adhered or the environment to which it is exposed and the glass transition temperature of each thermosetting adhesive layer provides good adhesion and resistance to high temperatures and high humidity, it is possible to more effectively suppress adhesion defects such as lifting, peeling, and voids in high temperature and high humidity environments.

[0029] As in the above embodiment [3], when the reactive functional group of the polyurethane resin contains a carboxy group and the crosslinking agent contains a polyfunctional epoxy crosslinking agent, the reactivity of the polyurethane resin with the crosslinking agent is increased in each of the first thermosetting adhesive layer and the second thermosetting adhesive layer.

[0030] Furthermore, as in the above embodiment [4], when the ratio (b / a) of the molar amount (a) of the carboxyl groups of the polyurethane resin to the molar amount (b) of the epoxy groups of the polyfunctional epoxy crosslinking agent is 1.0 or more and 10.0 or less, a high crosslink density is obtained in each of the first thermosetting adhesive layer and the second thermosetting adhesive layer, and a suitable storage modulus is easily achieved. In addition, the adhesion of each of the first thermosetting adhesive layer and the second thermosetting adhesive layer to the object to be bonded is improved.

[0031] As in the above embodiment [5], when the second thermosetting adhesive layer, which has a higher glass transition temperature than the first thermosetting adhesive layer, is formed thicker than the first thermosetting adhesive layer, the high humidity and heat resistance, a physical property of the thick second thermosetting adhesive layer, is strongly exhibited. Therefore, when a laminate sheet in which the first and second thermosetting adhesive layers are stacked is placed in a high-temperature, high-humidity environment, the adhesive laminate's resistance to the high-temperature, high-humidity environment can be improved. In particular, by setting the thickness of the first thermosetting adhesive layer to 1 μm or more and 6 μm or less, the adhesive strength of the first thermosetting adhesive layer can be ensured and its resistance to the high-temperature, high-humidity environment can be improved. Furthermore, by setting the thickness of the second thermosetting adhesive layer to 8 μm or more and 30 μm or less, the adhesive strength of the second thermosetting adhesive layer can be ensured and the adhesive laminate or adhesive sheet can be formed thin.

[0032] The adhesive laminate of the present invention, which has the first and second thermosetting adhesive layers, such as those having any of the structures [1] to [5] above, may be configured to be formed on one side of a substrate film and used as an adhesive sheet. An adhesive sheet having the structure [6] above is one such form.

[0033] In an adhesive sheet having a substrate film, including a film made of a predetermined resin material as enumerated in the embodiment [7] above, compared to a laminate sheet including a thermosetting adhesive layer without a substrate film, the surface of the thermosetting adhesive layer covered by the substrate film is not exposed on the surface of the laminate and is not sticky, making the laminate sheet easier to handle and facilitating processes such as placement on an object to be bonded. An example of an object to be bonded is a fuel cell electrode membrane (MEA) composed of an electrolyte membrane and a catalyst layer.

[0034] When an adhesive sheet is constructed using an adhesive laminate, the orientation of the first and second thermosetting adhesive layers can be appropriately selected depending on the environment and the object to be adhered, and the adhesive laminate can be formed on the surface of the substrate film, as described above. In particular, an adhesive sheet having the configuration [6] above has a first thermosetting adhesive layer on the surface of the substrate film, and the second thermosetting adhesive layer is exposed on the surface of the first thermosetting adhesive layer opposite the surface that contacts the substrate film. In this case, it is important that the first and second thermosetting adhesive layers, which are made of a cured product of the thermosetting adhesive composition, have the physical properties of the above-mentioned specified material, and in particular, that the second thermosetting adhesive layer have a glass transition temperature lower than that of the first thermosetting adhesive layer. of The high glass transition temperature of the thermosetting adhesive layer allows for excellent adhesive properties to be obtained both in the adhesion between the adhesive laminate and the substrate film and in the adhesion between the adhesive laminate and the object to be adhered. In other words, by forming a first thermosetting adhesive layer on the surface of the substrate film, the adhesion between this first thermosetting adhesive layer and the substrate film is excellent. Meanwhile, by bringing a second thermosetting adhesive layer, which has high humidity and heat resistance, into contact with the object to be adhered and using it to adhere the object to be adhered, adhesion defects such as lifting, peeling, and voids in the adhesive sheet can be effectively suppressed even in high-temperature, high-humidity environments.

[0035] As in the configuration [8] above, the adhesive sheet may further include a second substrate film. Alternatively, the adhesive sheet may further include a third thermosetting adhesive layer formed from a cured product of the thermosetting adhesive composition as part of the thermosetting adhesive layer, and this third thermosetting adhesive layer may have the above-mentioned predetermined material composition and physical properties. In this case, the third thermosetting adhesive layer may be formed on one side of the second substrate film, and the second substrate film may sandwich the second thermosetting adhesive layer and the first thermosetting adhesive layer between them via the third thermosetting adhesive layer. In other words, the second substrate film may be laminated on the side of the second thermosetting adhesive layer opposite the side adjacent to the first thermosetting adhesive layer via the third thermosetting adhesive layer. In this configuration, the surface of the second thermosetting adhesive layer covered by the second substrate film is not exposed, preventing foreign matter from adhering to it and, even if foreign matter does adhere, making it easy to remove. In addition, the adhesive sheet becomes easier to handle, facilitating processes such as placement on the object to be adhered. As with the above-mentioned base film, the second base film can be a film made of a predetermined resin material listed in the embodiment [9] above.

[0036] Furthermore, if the glass transition temperature of the third thermosetting adhesive layer is lower than the glass transition temperature of the second thermosetting adhesive layer, and further if the glass transition temperature of the third thermosetting adhesive layer is 15°C or higher and lower than 50°C as in the above embodiment

[10] , the adhesion between the third thermosetting adhesive layer and the second base film can be improved by forming the third thermosetting adhesive layer so that it is in contact with the surface of the second base film.

[0037] The combination of adhesive sheets having the configurations

[11] and

[12] above includes a first adhesive sheet containing the adhesive laminate of the present invention in combination with a second adhesive sheet. The first adhesive sheet has a first thermosetting adhesive layer and a second thermosetting adhesive layer with different glass transition temperatures, and these thermosetting adhesive layers have the above-mentioned predetermined material composition and physical properties. By sandwiching the object to be bonded between the first or second thermosetting adhesive layer of the first adhesive sheet and the thermosetting adhesive layer of the second adhesive sheet and then thermocompressing the bond, bonding can be completed without a curing process after thermocompression bonding. This adhesive sheet combination also has excellent storage stability. Furthermore, depending on the glass transition temperatures of the first and second thermosetting adhesive layers constituting the first adhesive sheet and the thermosetting adhesive layer constituting the second adhesive sheet, the combination and arrangement of the thermosetting adhesives constituting the first and second adhesive sheets can be selected to suit the bonded object or the environment to which each of these thermosetting adhesive layers will be exposed, etc., for the desired bonding form. This allows the combination of adhesive sheets sandwiching an object to be bonded to be prevented from developing adhesion defects such as lifting, peeling, and voids, even when placed in a high-temperature, high-humidity environment, and allows good adhesion to be effectively maintained. Therefore, the combination of adhesive sheets according to the present invention can be suitably used as a sealing material for fuel cells. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is a perspective view of an adhesive sheet according to one embodiment of the present invention. [Figure 2] (a) is a perspective view of an MEA provided with a subgasket made of the adhesive sheet of Fig. 1. (b) is a cross-sectional view taken along a plane perpendicular to the y-axis direction in the perspective view of (a). [Figure 3] 1(a) is a perspective view of an MEA equipped with a subgasket made of an assembled adhesive sheet according to one embodiment of the present invention, and FIG. 1(b) is a cross-sectional view taken along a plane perpendicular to the y-axis direction in the perspective view of FIG. [Figure 4]4 is a perspective view showing a second adhesive sheet constituting the adhesive sheet assembly of FIG. 3. FIG. [Figure 5] 1(a) is a perspective view showing an MEA provided with a subgasket made of an assembled adhesive sheet according to a modified embodiment, and FIG. 1(b) is a cross-sectional view taken along a plane perpendicular to the y-axis direction in the perspective view of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0039] The adhesive laminate, adhesive sheet, and combination of adhesive sheets according to an embodiment of the present invention will be described below. An adhesive sheet according to an embodiment of the present invention is constituted by including an adhesive laminate according to an embodiment of the present invention. Furthermore, an adhesive sheet combination according to an embodiment of the present invention is constituted by including an adhesive sheet according to an embodiment of the present invention. Hereinafter, unless otherwise specified, various physical property values ​​are values ​​measured at room temperature (about 23°C) in the atmosphere.

[0040] [1] Adhesive sheets and adhesive laminates <Adhesive sheet configuration> Fig. 1 is a perspective view of an adhesive sheet 100 according to one embodiment of the present invention. As shown in Fig. 1, the adhesive sheet 100 according to one embodiment of the present invention has a base film 12, a first adhesive layer 14 formed on the surface of the base film 12, and a second adhesive layer 16 formed on the surface of this first adhesive layer 14. The first adhesive layer 14 and the second adhesive layer 16 form an adhesive laminate 30 consisting of two adhesive layers. The second adhesive layer 16 is exposed on the outermost surface of the adhesive sheet 100 as a whole.

[0041] While the application and shape of the adhesive sheet 100 are not particularly limited, FIG. 1 shows a case in which the adhesive sheet 100 constitutes a subgasket for a fuel cell. That is, an opening W1 is provided in the center of the adhesive sheet 100 as a through-hole-like region penetrating the adhesive sheet 100. As shown in FIGS. 2(a) and 2(b), the adhesive sheet 100 is used with a membrane electrode assembly (hereinafter referred to as MEA) 3, which has electrodes 3e disposed on both sides of an electrolyte membrane 3m, and functions as a sealant that seals the periphery of the MEA 3. A solid polymer electrolyte membrane is generally used as the electrolyte membrane in an MEA, and such a membrane may also be used here. A proton-conductive electrolyte can be used as the polymer electrolyte contained in the solid polymer electrolyte membrane. Examples of polymer electrolytes that can be used include fluorine-based polymer electrolytes and hydrocarbon-based polymer electrolytes. A polymer electrolyte having a tetrafluoroethylene skeleton can be used as the fluorine-based polymer electrolyte. Examples of polymer electrolytes having a tetrafluoroethylene skeleton include Nafion manufactured by DuPont, Flemion manufactured by Asahi Glass, Aciplex manufactured by Asahi Kasei, and Gore-Select manufactured by Gore Japan (all of which are registered trademarks).Examples of hydrocarbon-based polymer electrolytes include sulfonated polyether ketone, sulfonated polyether sulfone, sulfonated polyether ether sulfone, sulfonated polysulfide, and sulfonated polyphenylene.

[0042] <Base film> The specific configuration of the substrate film 12 is not particularly limited. Examples of the substrate film 12 include a polymer film and a glass film. The thickness of the substrate film 12 is not particularly limited, but from the viewpoint of handleability, it is preferably in the range of 12 μm or more and 500 μm or less. More preferably, the thickness of the substrate film 12 is 38 μm or more, and even more preferably 50 μm or more, while it is 200 μm or less, and even more preferably 100 μm or less. Note that the term "film" generally refers to a film having a thickness of less than 0.25 mm, but even if the thickness is 0.25 mm or more, it is considered to be a "film" as long as it is flexible.

[0043] When the base film 12 is a polymer film, examples of the polymer material constituting the base film 12 include polyester resins such as polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, and liquid crystal polyester, polycarbonate resin, poly(meth)acrylate resin, polystyrene resin, polyamide resin, polyphthalamide resin, polyimide resin, polyacrylonitrile resin, polypropylene resin, polyethylene resin, polyolefin resins such as polycycloolefin resin and cycloolefin copolymer resin, polyphenylene sulfide resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, polyvinylidene fluoride resin, silicone resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, and polyarylate resin. The polymer material of the base film 12 may be composed of only one of these materials, or may be composed of a combination of two or more materials by lamination or the like. Among these, from the viewpoints of heat resistance and mechanical properties, polyarylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyphenylene sulfide, polysulfone, polyethersulfone, and polyetheretherketone resins are preferred, and the base film 12 should preferably be made of at least one resin material selected from the group consisting of these resins.

[0044] The base film 12 may be composed of a single layer containing one or more of the above polymeric materials, or may be composed of two or more layers, such as a layer containing one or more of the above polymeric materials and a layer containing one or more of a different polymeric material.

[0045] <Adhesive layer> Each of the first thermosetting adhesive layer 14 and the second thermosetting adhesive layer 16 constituting the adhesive laminate 30 is formed from a cured product of a thermosetting adhesive composition containing a polyurethane resin having reactive functional groups and a crosslinking agent. The first thermosetting adhesive layer 14 (hereinafter sometimes simply referred to as the first adhesive layer 14) has a first glass transition temperature, and the second thermosetting adhesive layer 16 (hereinafter sometimes simply referred to as the second adhesive layer 16) has a second glass transition temperature higher than the first glass transition temperature. In the adhesive sheet 100, the first adhesive layer 14 is formed directly on one surface of the substrate film 12, and the second adhesive layer 16 is further formed directly on the surface of the first adhesive layer 14.

[0046] The thermosetting adhesive composition (hereinafter sometimes simply referred to as the adhesive composition) constituting each adhesive layer 14, 16 is thermosetting, and the adhesive sheet 100 comprising the first adhesive layer 14 and the second adhesive layer 16 functions as a thermosetting adhesive sheet. In the adhesive sheet 100 before use, the first adhesive layer 14 and the second adhesive layer 16 are cured (semi-cured) with some uncured material remaining. When bonding the adhesive sheet 100 to an object to be bonded (adherend), such as an MEA 3, the second adhesive layer 16 is superimposed on the MEA 3 as shown in FIG. 2(b), and an adhesive laminate 30 consisting of the first adhesive layer 14 and the second adhesive layer 16 is heated and pressed to bond the adhesive sheet 100 to the MEA 3. By leaving the first adhesive layer 14 and the second adhesive layer 16 in a semi-cured state, the adhesive sheet 100 can be stored stably at room temperature without requiring low-temperature storage. In this specification, the concept of adhesiveness includes pressure-sensitive adhesiveness, that is, adhesiveness between the material and the object to be bonded is achieved by applying pressure without heating when bonding the material to the object to be bonded.

[0047] (adhesive layer characteristics) (1) Glass transition temperature The first glass transition temperature of the first adhesive layer 14 is preferably 15°C or higher. If the first glass transition temperature is 15°C or higher, adhesion defects such as lifting, peeling, and voids between the base film 12 and the second adhesive layer 16 can be effectively suppressed even when the adhesive sheet 100 is placed in a high-temperature, high-humidity environment. From this perspective, the first glass transition temperature is more preferably 17°C or higher, and even more preferably 20°C or higher. On the other hand, the first glass transition temperature is preferably less than 50°C. If the first glass transition temperature is less than 50°C, a sufficient initial peel strength can be obtained between the first adhesive layer 14 and the base film 12 at a relatively low temperature, such as room temperature. From this perspective, the first glass transition temperature is more preferably less than 48°C, and even more preferably less than 45°C.

[0048] The second glass transition temperature of the second adhesive layer 16 is preferably 100°C or lower. When the second glass transition temperature is 100°C or lower, the adhesion to the adhesion object, for example, the MEA 3, can be particularly good. From this viewpoint, the second glass transition temperature is more preferably 98°C or lower, and even more preferably 95°C or lower. On the other hand, the second glass transition temperature is preferably 50°C or higher. When the second glass transition temperature is 50°C or higher, adhesion defects such as lifting, peeling, and voids between the second adhesive layer 16 and the adhesion object, such as the MEA 3, can be effectively suppressed even when the adhesive sheet 100 is placed in a high-temperature, high-humidity environment. From this viewpoint, the second glass transition temperature is more preferably 55°C or higher, and even more preferably 60°C or higher.

[0049] Furthermore, if the second glass transition temperature is 50°C or higher, the stickiness of the surface of the second adhesive layer 16 at room temperature is reduced. This reduces the adhesion of foreign matter to the surface of the second adhesive layer 16, and even if foreign matter does adhere, it becomes easier to remove. For example, when the second adhesive layer 16 is kept exposed in order to adhere to an object to be adhered, such as an MEA 3, designing the second adhesive layer 16 so that the second glass transition temperature is 50°C or higher, for example, by selecting specific constituent materials, it is possible to reduce the adhesion of foreign matter to the exposed surface, and even if foreign matter does adhere, it becomes easier to remove. In this way, by making the second glass transition temperature 50°C or higher, the handleability of the adhesive sheet 100 is improved.

[0050] As described above, it is preferable to set the glass transition temperature of first adhesive layer 14 to be equal to or higher than 15°C but lower than 50°C, and the glass transition temperature of second adhesive layer 16 to be equal to or higher than 50°C but lower than 100°C, to form first adhesive layer 14 on the surface of base film 12, and then form second adhesive layer 16 directly on that surface. In the case of a subgasket formed using adhesive sheet 100 configured in this manner, by overlapping electrolyte membrane 3m of MEA 3 on the exposed surface of second adhesive layer 16 and thermocompression bonding, it is possible to improve the adhesion between base film 12 and MEA 3, and more effectively suppress adhesion defects such as lifting, peeling, and voids even when MEA 3 provided with the subgasket is placed in a high-temperature, high-humidity environment.

[0051] (2) Storage modulus The shear storage modulus (G') of the first adhesive layer 14 at 100°C 100 ) is 5.0 × 10 4 Pa or more. 5.0×10 4 If the G' of the first adhesive layer 14 is not less than 100 Pa, the first adhesive layer 14 is appropriately cured even before the thermocompression bonding, and therefore the bonding can be completed in a short time. 100 is preferably 7.0 x 10 4 Pa or more, more preferably 1.0×10 5 Pa or more. Also, G' of the first adhesive layer 14 100 is 6.6 x 10 5 Pa or less. 6.6×10 5 If the G' of the first adhesive layer 14 is equal to or less than Pa, the first adhesive layer 14 can maintain its elasticity even at high temperatures, and therefore the adhesiveness can be improved. 100 is preferably 3.0 x 10 5 Pa or less.

[0052] The shear storage modulus (G') of the second adhesive layer 16 at 100°C 100 ) is 6.6 × 10 5 Pa. 6.6×10 5If the G' of the second adhesive layer 16 is greater than Pa, the adhesion can be completed without a curing process after heat and pressure bonding in the adhesion process with an object to be adhered, such as the MEA 3. 100 is preferably 7.0 x 10 5 Pa or more. Also, G' of the second adhesive layer 16 100 is 1.0 x 10 7 Pa or less. 1.0×10 7 If the pressure is equal to or less than Pa, the second adhesive layer 16 can maintain its elasticity even at high temperatures, and therefore the adhesiveness can be improved. 100 is preferably 5.0 x 10 6 Pa or less, more preferably 3.0×10 6 Pa or less.

[0053] The shear storage modulus (G') of the first adhesive layer 14 at 100°C 100 ) versus shear storage modulus (G') at 120 ° C 120 ) is 0.3 or less. If this reduction rate is 0.3 or less, the crosslinking reaction in the first adhesive layer 14 has progressed sufficiently, and adhesion defects such as lifting, peeling, and voids can be suppressed even when the adhesive sheet 100 is placed in a high-temperature, high-humidity environment. From the viewpoint of further enhancing this effect, the reduction rate is preferably 0.25 or less, and more preferably 0.2 or less. There is no particular lower limit for the reduction rate, but it is usually -0.1 or more, and preferably 0 or more. The reduction rate is determined by the relationship (G' 100 -G' 120 ) / G' 100 It can be calculated using the formula:

[0054] The shear storage modulus (G') of the second adhesive layer 16 at 100°C 100 ) versus shear storage modulus (G') at 120 ° C 120) is 0.5 or less. If this reduction rate is 0.5 or less, the crosslinking reaction in the second adhesive layer 16 has progressed sufficiently, and adhesion defects such as lifting, peeling, and voids can be suppressed even when the adhesive sheet 100 is placed in a high-temperature, high-humidity environment. To further enhance this effect, the reduction rate is preferably 0.45 or less, and more preferably 0.4 or less. There is no particular lower limit to the reduction rate, but it is usually -0.1 or more, and preferably 0 or more.

[0055] The shear storage modulus (G') of the first adhesive layer 14 and the second adhesive layer 16 at 120°C 120 ) are not particularly limited, but are both 5.0 × 10 4 It is preferable that the viscosity is 5.0×10 Pa or more. 4 If the adhesive strength is equal to or greater than 100 Pa, the adhesive strength can be easily maintained even in a high temperature environment, and the humidity and heat resistance can be further improved. 120 is more preferably 7.0 × 10 4 Pa or more, more preferably 1.0 × 10 5 In addition, the G' of the adhesive layers 14 and 16 is 120 is 1.0 x 10 7 It is preferable that the pressure is 1.0×10 Pa or less. 7 If the G' of the adhesive layers 14 and 16 is equal to or less than Pa, the adhesive layers 14 and 16 can maintain their elasticity even at high temperatures, thereby achieving good adhesiveness. 120 is preferably 5.0×10 6 Pa or less, more preferably 3.0 × 10 6 Pa or less.

[0056] As described above, the first adhesive layer 14 and the second adhesive layer 16 constituting the adhesive laminate 30 have the above-mentioned predetermined glass transition temperature and storage modulus, so that the first adhesive layer 14 exhibits high adhesion at relatively low temperatures, such as around room temperature, while the second adhesive layer 16 exhibits high adhesion in high-temperature, high-humidity environments. Therefore, it is thought that the main adhesion mechanism of the adhesive laminate 30 is that the first adhesive layer 14 acts to provide sufficient adhesive strength when adhering to an object for which the second adhesive layer 16 does not have sufficient adhesive strength at room temperature, such as when adhering to a polymer material used as the base film 12, and that the second adhesive layer 16 acts to maintain high adhesive strength in high-humidity, high-temperature environments.

[0057] As described above, the second adhesive layer 16 has a higher glass transition temperature and a lower shear storage modulus (G') at 100°C than the first adhesive layer 14. 100 ) is also higher. Such a difference in physical properties between the first adhesive layer 14 and the second adhesive layer 16 can be achieved by selecting the component compositions of the adhesive compositions constituting the first adhesive layer 14 and the second adhesive layer 16. For example, a polyurethane resin with a higher glass transition temperature can be used in the adhesive composition constituting the second adhesive layer 16 than in the adhesive composition constituting the first adhesive layer 14. Methods for increasing the glass transition temperature of a polyurethane resin include using a compound with a high glass transition temperature as the polyisocyanate or polyol constituting the polyurethane resin, increasing the molecular weight, introducing a ring structure into the main chain, or increasing the amount of ring structure introduced. These methods contribute to reducing the free volume of the polymer chain of the polyurethane resin. The smaller the free volume of the polymer chain, the higher the glass transition temperature of the polyurethane resin, since higher temperatures are required to increase the free volume by heating. Adding a filler to the adhesive composition is also effective in increasing the glass transition temperature.

[0058] (3) Layer thickness In the adhesive sheet 100, it is preferable that the thickness of the second adhesive layer 16 is greater than the thickness of the first adhesive layer 14. This allows the physical properties of the second adhesive layer 16 to be strongly expressed as physical properties of the entire adhesive laminate 30. The first adhesive layer 14 has a low glass transition temperature, and in high-humidity and high-temperature environments, it may be difficult for it to withstand high humidity and heat while maintaining its strength, whereas the second adhesive layer 16 has a high glass transition temperature and excellent humidity and heat resistance. Reflecting this, the adhesive laminate 30 as a whole, in which the second adhesive layer 16 is formed thicker, achieves excellent humidity and heat resistance.

[0059] The thickness of the first adhesive layer 14 is preferably 1 μm or more, more preferably 1.2 μm or more, and even more preferably 1.5 μm or more, from the viewpoint of ensuring high adhesion to the base film 12. On the other hand, the thickness of the first adhesive layer 14 is preferably 6 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less, from the viewpoint of improving resistance in high-temperature and high-humidity environments.

[0060] The thickness of the second adhesive layer 16 is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more, from the viewpoint of ensuring high adhesion to the object to be adhered, such as the MEA 3. On the other hand, the thickness of the second adhesive layer 16 is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less, from the viewpoint of keeping the thickness of the adhesive sheet 100 small and reducing the size of components constructed using the adhesive sheet 100, such as a fuel cell.

[0061] (4) Other characteristics The gel fractions of the first adhesive layer 14 and the second adhesive layer 16 are not particularly limited, but are preferably 70% by mass or greater for both adhesive layers. A gel fraction of 70% by mass or greater indicates that the crosslinking reaction of the first and second adhesive layers 14, 16 has progressed. Therefore, in the bonding process with an object to be bonded, such as an MEA 3, bonding can be easily completed after thermocompression bonding without a curing treatment. Furthermore, strong adhesion to the object to be bonded can be achieved in a short time. Furthermore, the adhesive layers 14, 16 have excellent storage stability, and adhesion defects such as lifting, peeling, and voids can be suppressed even in high-temperature, high-humidity environments. Furthermore, because the adhesive layers 14, 16 tend to remain uncured or semi-cured until the bonding process, they are particularly suitable for storing the adhesive sheet 100 stably at room temperature without the need for low-temperature storage. The gel fraction is preferably 80% by mass or greater, more preferably 85% by mass or greater, with an upper limit of 100% by mass.

[0062] For an adhesive laminate 30 consisting of two layers, a first adhesive layer 14 formed on the surface of a base film 12 and a second adhesive layer 16 formed on the surface of this first adhesive layer 14, the adhesive strength to an object to be adhered, such as the base film 12 and MEA 3, at 23°C is preferably 1 N / 10 mm or more, more preferably 1.2 N / 10 mm or more, and even more preferably 2 N / 10 mm or more.

[0063] (Polyurethane resin) As described above, the adhesive composition constituting the first adhesive layer 14 and the second adhesive layer 16 contains a polyurethane resin having a reactive functional group. The use of a polyurethane resin provides each of the adhesive layers 14, 16 with appropriate flexibility and moisture and heat resistance. Polyurethane resin is a general term for compounds containing two or more urethane bonds in one molecule. Polyurethane resins have a structure obtained by polymerizing polyisocyanate and polyol.

[0064] Polyurethane resins can be freely designed by selecting the raw materials. For example, physical properties such as flexibility and moist heat resistance change depending on the types of main chains and side chains that make up the molecule. For example, increasing the molecular weight increases the glass transition temperature. Furthermore, by configuring the main chain and side chains to be highly hydrolysis-resistant, the hydrolysis resistance of the polyurethane resin as a whole can be improved. Therefore, by selecting the polyurethane raw materials contained in the first adhesive layer 14 and the second adhesive layer 16 taking into account the glass transition temperature, hydrolysis resistance, etc., depending on the environment to which each adhesive layer 14, 16 will be exposed and the objects to be bonded, the first adhesive layer 14 and the second adhesive layer 16 can each have suitable flexibility, adhesion, moist heat resistance, etc.

[0065] For example, when constructing a subgasket for a fuel cell using the adhesive sheet 100 according to this embodiment, the second adhesive layer 16 is heat-pressed to the electrolyte membrane 3m of the MEA 3 and is exposed to a higher temperature and humidity environment than the first adhesive layer 14. Therefore, moisture resistance and hydrolysis resistance are more important for the second adhesive layer 16 than for the first adhesive layer 14. Therefore, moisture resistance is prioritized in the physical properties of the second adhesive layer 16, and a polyurethane-based resin can be constructed by selecting a main chain and side chain that provide high hydrolysis resistance and a high glass transition temperature. Examples of polyurethane resins include ester-based polyurethane resins using polyols with ester bonds (-COO-) in their molecular structure, ether-based polyurethane resins using polyols with ether bonds (-O-) in their molecular structure, and polycarbonate-based polyurethane resins using polyols with carbonate ester bonds (-OCOO-) in their molecular structure. Among these, polycarbonate-based polyurethane resins or ether-based polyurethane resins with a relatively low content of ester bonds are preferred because of their high hydrolysis resistance (moisture and heat resistance). The glass transition temperature can be adjusted by the types of polyisocyanate and low-molecular-weight diol that form the hard segment of the polyurethane resin, and the types of polyether and polyester that form the soft segment. The components that are preferably used to adjust the glass transition temperature are as follows:

[0066] The polyisocyanate constituting the polyurethane-based resin may be any polyisocyanate having two or more isocyanate groups in one molecule, and from the viewpoint of the physical properties such as the glass transition temperature, flexibility, and moist heat resistance of each of the first adhesive layer 14 and the second adhesive layer 16, diisocyanate or triisocyanate is preferred, and diisocyanate is more preferred.

[0067] In this embodiment, examples of the isocyanates constituting the polyurethane resin include aromatic, aliphatic, araliphatic, and alicyclic isocyanates. Examples of aromatic isocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, m - Tetramethylxylylene diisocyanate is an example. Examples of aliphatic isocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. Aromatic aliphatic isocyanates refer to aliphatic isocyanates having one or more aromatic rings in the molecule, and examples thereof include m- or p-xylylene diisocyanate (XDI), α,α,α',α'-tetramethylxylylene diisocyanate (TMXDI), and the like. Examples of alicyclic isocyanates include cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, methylcyclohexane diisocyanate, and norbornane diisocyanate.

[0068] Among these, when a high glass transition temperature is required for each adhesive layer, it is preferable to incorporate a large amount of an aromatic diisocyanate such as benzene-1,3-diisocyanate in the adhesive layer. When flexibility is required, it is preferable to use an aliphatic diisocyanate such as hexamethylene diisocyanate. The isocyanates listed above can be appropriately selected and used for each adhesive layer. Polyisocyanates can be used alone or in combination of two or more. Furthermore, isocyanate-terminated prepolymers obtained by reacting polyol with excess polyisocyanate can be used as intermediates for polyurethane resins.

[0069] The polyol constituting the polyurethane-based resin may be any polyol having two or more hydroxyl groups in one molecule, and from the viewpoint of the physical properties such as the glass transition temperature, flexibility, and moist heat resistance of each of the first adhesive layer 14 and the second adhesive layer 16, a diol or triol is preferred, and a diol is more preferred.

[0070] In the present embodiment, examples of polyols constituting the polyurethane resin include aliphatic glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, polytetramethylene glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-ethyl-1,3-hexane glycol, 2,2,4-trimethyl-1,3-pentanediol, 3,3-dimethylolheptane, 1,9-nonanediol, and 2-methyl-1,8-octanediol; 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and tricyclodecanediol. alicyclic glycols such as paraxylene glycol, metaxylene glycol, orthoxylene glycol, 1,4-phenylene glycol, an ethylene oxide adduct of 1,4-phenylene glycol, bisphenol A, bisphenol A-ethylene oxide adduct, bisphenol A-propylene oxide adduct, and bisphenol A-ethylene propylene copolymer polyol; aromatic glycols such as polyether diol, polyester diol, polyether ester diol, polycarbonate diol, and polyolefin diol.

[0071] Among the above-listed polyether diols, examples include those obtained by ring-opening polymerization of cyclic ethers, such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Polyester diols include dicarboxylic acids (succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, etc.) or their anhydrides and low molecular weight diols (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, polytetramethylene glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-ethyl-1,3-hexane glycol, 2,2,4-trimethyl-1,3 1,4-Phenylene glycol, 2-pentanediol, 3,3-dimethylolheptane, 1,9-nonanediol, 2-methyl-1,8-octanediol, cyclohexanedimethanol, bishydroxyethoxybenzene, paraxylene glycol, metaxylene glycol, orthoxylene glycol, 1,4-phenylene glycol, etc.), such as polyethylene adipate, polypropylene adipate, polybutylene adipate, polyhexamethylene adipate, polybutylene sebacate, etc.; and those obtained by ring-opening polymerization of lactones with low-molecular-weight diols, such as polycaprolactone, polymethylvalerolactone, etc. Examples of polyetherester diols include those obtained by ring-opening polymerization of a polyester diol with a cyclic ether, and those obtained by polycondensation of a polyether diol with a dicarboxylic acid, such as poly(polytetramethylene ether) adipate. Examples of polycarbonate diols include polybutylene carbonate, polyhexamethylene carbonate, and poly(3-methyl-1,5-pentylene) carbonate, which are obtained by removing the diol or alcohol from a low-molecular-weight diol and an alkylene carbonate or a dialkyl carbonate. Examples of polyolefin diols include polybutadiene polyols, hydrogenated polybutadiene polyols, and polyisoprene polyols.

[0072] From among the polyols listed here as constituents of polyurethane-based resins, an appropriate polyol can be selected and used for each adhesive layer, taking into consideration the moist heat resistance and glass transition temperature of each of the first adhesive layer 14 and the second adhesive layer 16. For example, polyols containing more double bonds or having a structure containing a cyclic structure rather than an aliphatic structure tend to have a higher glass transition temperature. The glass transition temperature of a polyol can be obtained, for example, by measuring the viscoelastic behavior using a dynamic viscoelasticity measuring device and determining the temperature at which the loss tangent (tan δ) is maximized. Polyols can be used alone or in combination of two or more.

[0073] The polyurethane resin may be a polyurethane urea resin further having a urea bond to enhance heat resistance, water resistance, and impact resistance. The polyurethane urea resin has a structure in which, for example, an amine is bonded to a urethane resin having an isocyanate group at its terminal. The amine may be any amine having two or more amino groups per molecule. From the viewpoint of the physical properties such as the glass transition temperature, flexibility, and moist heat resistance of the first adhesive layer 14 and the second adhesive layer 16, diamines or triamines are preferred, and diamines are more preferred.

[0074] Known amines can be used as the amine, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and dimer diamine, in which the carboxyl groups of dimer acid are converted to amino groups. For example, amines containing more double bonds or having a structure containing a ring structure rather than an aliphatic structure tend to have a higher glass transition temperature. The amines can be used alone or in combination of two or more.

[0075] The weight-average molecular weight (Mw) of the polyurethane resin is preferably 5,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. On the other hand, Mw is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 150,000 or less. If Mw is 5,000 or more, the moist heat resistance of each of the first adhesive layer 14 and the second adhesive layer 16 can be improved, and if it is 1,000,000 or less, the coating workability of the adhesive composition will be improved.

[0076] The reactive functional group possessed by the polyurethane resin is not particularly limited as long as it is a functional group capable of reacting with a crosslinking agent to form a bond. Examples include hydroxyl groups, phenolic hydroxyl groups, methoxymethyl groups, carboxyl groups, amino groups, epoxy groups, oxetanyl groups, oxazoline groups, oxazine groups, aziridine groups, thiol groups, isocyanate groups, blocked isocyanate groups, blocked carboxyl groups, and silanol groups. The polyurethane resin may contain one or more of these reactive functional groups. Among these, hydroxyl groups, carboxyl groups, amino groups, and epoxy groups are particularly preferred, with carboxyl groups being more preferred from the standpoints of availability and reactivity with crosslinking agents. In the polyurethane resin, the reactive functional group may be directly bonded to the polyurethane chain, such as a polyol moiety, or may be introduced into a side chain bonded to the polyurethane chain.

[0077] When the polyurethane resin has a carboxy group, the acid value of the polyurethane resin is preferably 4.0 mgKOH / g or more and 40 mgKOH / g or less. By setting the acid value of the polyurethane resin within the above range, the crosslinking density with the crosslinking agent can be optimized, making it easier to keep the storage modulus of the first adhesive layer 14 and the second adhesive layer 16 at 100°C and 120°C within a suitable range. The acid value is more preferably 6.0 mgKOH / g or more and 8.0 mgKOH / g or more. On the other hand, the acid value is more preferably 30 mgKOH / g or less and 20 mgKOH / g or less.

[0078] (Crosslinking agent) As described above, the adhesive composition constituting the first adhesive layer 14 and the second adhesive layer 16 contains a crosslinking agent in addition to a polyurethane resin. The crosslinking agent is a compound having two or more reactive groups per molecule that can react with reactive functional groups possessed by the polyurethane resin, and forms crosslinks between molecular chains of the polyurethane resin when the adhesive composition is heated. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, melamine resin-based crosslinking agents, and urea resin-based crosslinking agents. Among these, epoxy-based crosslinking agents are more preferred from the viewpoints of adhesion, heat resistance, etc.

[0079] An epoxy crosslinking agent is a compound having two or more epoxy groups as reactive groups in one molecule. The epoxy crosslinking agents may be used alone or in combination of two or more types.

[0080] Examples of epoxy crosslinking agents include bisphenol A type epoxy resins, epichlorohydrin type epoxy resins, ethylene glycidyl ether, N,N,N',N'-tetrakis(2,3-epoxypropyl)-1,4-phenylenediamine, N,N,N',N'-tetrakis(oxiran-2-ylmethyl)-4,4'-methylenebisaniline, N,N-diglycidyl-4-(glycidyloxy)aniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,1,2,2-tetrakis(3-glycidyloxyphenyl)ethane, diglycidylaniline, diamine glycidylamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether. Examples of epoxy crosslinking agents include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, and bisphenol-S-diglycidyl ether. Among these epoxy crosslinking agents, polyfunctional epoxy crosslinking agents having 3 to 5 epoxy groups per molecule are preferred in terms of high adhesion and heat resistance.

[0081] The crosslinking agent in the adhesive composition is preferably a liquid having a viscosity of 10 mPa·s or more at 25°C, or a solid having a softening point of 100°C or less. The molecular weight of the crosslinking agent in the adhesive composition is preferably 200 or more, more preferably 400 or more, and even more preferably 600 or more. Meanwhile, the molecular weight is preferably 1300 or less, more preferably 1100 or less, and even more preferably 900 or less. The functional group equivalent of the reactive group of the crosslinking agent in the adhesive composition (epoxy equivalent in the case of an epoxy-based crosslinking agent) is preferably 50 g / eq or more, more preferably 100 g / eq or more, and even more preferably 150 g / eq or more. Meanwhile, the functional group equivalent is preferably 1000 g / eq or less, more preferably 600 g / eq or less, even more preferably 400 g / eq or less, and particularly preferably 250 g / eq or less. In each of the first adhesive layer 14 and the second adhesive layer 16, if the molecular weight of the crosslinking agent and the content of reactive groups are within the above ranges, good adhesion and moist heat resistance can be obtained between the object to be adhered, such as MEA 3, and the base film 12.

[0082] The content of the crosslinking agent in the adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and particularly preferably 5 parts by mass or more, per 100 parts by mass of the polyurethane resin, and is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less. If the content of the crosslinking agent in each of the first adhesive layer 14 and the second adhesive layer 16 is within the above range, good adhesion and moist heat resistance can be obtained between the substrate film 12 and the object to be adhered, such as the MEA 3.

[0083] In the adhesive compositions of the first adhesive layer 14 and the second adhesive layer 16, the ratio (b / a) of the molar amount (a) of the reactive functional group of the polyurethane resin, such as a carboxyl group, to the molar amount (b) of the reactive group of the crosslinking agent, such as an epoxy group, of the epoxy crosslinking agent, is preferably 1.0 or more, more preferably 1.1 or more, and even more preferably 1.3 or more. Meanwhile, the molar ratio is preferably 10.0 or less, more preferably 8.0 or less, and even more preferably 7.0 or less. A molar ratio of 1.0 or more ensures sufficient crosslink density and a favorable storage modulus. A molar ratio of 10.0 or less enhances the adhesion of the first adhesive layer 14 and the second adhesive layer 16 to the bonded object, effectively suppressing peeling and improving durability.

[0084] (Other additives) In addition to the polyurethane resin and crosslinking agent, other additives may be blended into the adhesive composition constituting the first adhesive layer 14 and the second adhesive layer 16. Examples of such additives include crosslinking accelerators, crosslinking retarders, fillers, plasticizers, softeners, release aids, silane coupling agents, dyes, pigments, dyes, fluorescent brighteners, antistatic agents, wetting agents, surfactants, thickeners, antifungal agents, preservatives, oxygen absorbers, UV absorbers, antioxidants, near-infrared absorbers, water-soluble quenchers, fragrances, metal deactivators, nucleating agents, alkylating agents, flame retardants, lubricants, and processing aids. These additives are appropriately selected and blended depending on the application and purpose of the adhesive sheet 100, i.e., the specific type and configuration of the bonded object to which the adhesive sheet 100 is to be applied, such as the MEA 3, and the usage environment.

[0085] Of the above additives, fillers are blended for purposes such as improving moist heat resistance, adjusting the modulus of elasticity, and making the adhesive sheet 100 tack-free to improve the removability of adhered foreign matter. The filler may be either an inorganic filler or an organic filler. Examples of inorganic fillers include inorganic particles such as silica, alumina, calcium carbonate, talc, and clay. Examples of organic fillers include resin particles made of resins such as (meth)acrylic resin, styrene resin, styrene-(meth)acrylic resin, urethane resin, polyamide resin, silicone resin, epoxy resin, phenolic resin, polyethylene resin, and cellulose.

[0086] <Method of manufacturing the thermosetting adhesive composition> The adhesive compositions constituting the first adhesive layer 14 and the second adhesive layer 16 can each be produced by mixing a polyurethane resin, a crosslinking agent, and other additives used as needed. The adhesive composition may be a solution diluted with an appropriate solvent to have a viscosity suitable for forming the first adhesive layer 14 and the second adhesive layer 16.

[0087] Examples of solvents include aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate, propyl acetate, isopropyl acetate, and butyl acetate; cellosolve-based solvents such as ethyl cellosolve; and alcohol-based solvents such as ethanol, isopropyl alcohol, n-butyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether. These solvents may be used alone or in combination. The amount of solvent used is not particularly limited, and may be adjusted as needed to provide an adhesive composition with a viscosity suitable for coating. From the viewpoint of coatability, the amount is preferably 1% to 90% by mass, more preferably 10% to 80% by mass, and even more preferably 20% to 70% by mass of the total diluted solution.

[0088] <Method of manufacturing adhesive sheet> To manufacture the adhesive sheet 100 of this embodiment, for example, a thermosetting adhesive composition constituting the first adhesive layer 14 is directly applied to one side of the base film 12, followed by a drying and curing process using heat treatment. Subsequently, a thermosetting adhesive composition constituting the second adhesive layer 16 is directly applied to the surface of the dried and cured thermosetting adhesive composition, followed by a drying and curing process using heat treatment. The adhesive sheet 100 can then be formed by a method such as aging, if necessary. This method of forming the first adhesive layer 14 and the second adhesive layer 16 sequentially through drying and curing, followed by aging, if necessary, is preferred from the viewpoint of adhesion between the base film 12 and the first adhesive layer 14, and between the first adhesive layer 14 and the second adhesive layer 16.

[0089] The adhesive composition can be applied by various coating methods, such as reverse gravure coating, direct gravure coating, die coating, bar coating, wire bar coating, roll coating, spin coating, dip coating, spray coating, knife coating, and kiss coating, or various printing methods, such as inkjet printing, offset printing, screen printing, and flexographic printing. Furthermore, before applying the adhesive composition that constitutes the first adhesive layer 14, the surface of the base film 12 may be subjected to a surface treatment such as corona treatment, plasma treatment, hot air treatment, ozone treatment, or ultraviolet treatment. In particular, corona treatment is recommended from the viewpoint of adhesion between the base film 12 and the first adhesive layer 14.

[0090] The drying and curing steps are not particularly limited as long as they can remove the solvents and harden the adhesive compositions, but are preferably carried out at a temperature of 60°C to 200°C for about 20 to 300 seconds. In particular, the drying temperature is preferably 120°C to 150°C. The cured state of each adhesive composition is preferably such that some uncured material remains (semi-cured state).

[0091] The curing may be performed, for example, at 40°C to 80°C for about 3 to 20 days, preferably at 60°C for about 4 to 7 days. The crosslinking reaction proceeds by performing the drying and curing steps, and optionally a curing step. The curing conditions are preferably set so that the gel fractions of the first adhesive layer 14 and the second adhesive layer 16 are 70% by mass or greater. This curing step strengthens the adhesiveness of the adhesive sheet 100 to the bonding object, such as the MEA 3, in a short-term bonding step using heat and pressure. As described above, the stickiness of the exposed portion of the second adhesive layer 16 at room temperature is reduced as the glass transition temperature increases. Therefore, adjusting the glass transition temperature by selecting the resins and other components constituting the adhesive composition of the second adhesive layer 16 can prevent foreign matter from adhering to the second adhesive layer 16 and facilitate its removal, even if foreign matter does adhere.

[0092] The adhesive sheet 100 may have a release sheet on the surface of the second adhesive layer 16 until use. The release sheet is used as a protective material for the second adhesive layer 16 and is peeled off when the adhesive sheet 100 of the present invention is attached to an object to be adhered. Examples of release sheets include paper such as glassine paper, coated paper, and laminated paper, and various plastic sheets coated with a release agent such as a silicone resin. Furthermore, when the second adhesive layer 16 does not have adhesive properties, a release sheet having adhesive properties on at least one side may be used. As the plastic sheet used for the release sheet, any of the plastic sheets exemplified as the base film 12 can be used as appropriate. There are no particular limitations on the thickness of the release sheet, but it is usually 10 μm to 150 μm.

[0093] <How to use the adhesive sheet> The adhesive sheet 100 is not particularly limited in its intended use, but as described above, it can be suitably used, for example, as a sealing material for fuel cells, particularly as a subgasket for the MEA 3. For example, as shown in FIGS. 2(a) and 2(b), the adhesive sheet 100 and the MEA 3 are laminated together by contacting the exposed surface of the second adhesive layer 16 of the adhesive sheet 100 with the MEA 3. At this time, the adhesive sheet 100 is positioned so that the solid electrolyte membrane 3m of the MEA 3 faces the opening W1 of the adhesive sheet 100, with the electrode 3e interposed therebetween. The adhesive sheet 100 is then heated while applying pressure in a direction pressing it against the MEA 3, thereby bonding the second adhesive layer 16 to the MEA 3. Examples of pressures include a pressure of 0.5 to 10 MPa, a heating temperature of 130 to 230°C, and a pressure and heating time of 3 to 60 seconds. After the thermocompression bonding process, the adhesive sheet 100 can be used in subsequent processes, such as laminating power-generating cells, without undergoing curing processes such as heat treatment or aging.

[0094] <Other Forms of Adhesive Sheets and Adhesive Laminates> In the adhesive sheet 100 according to the embodiment described in detail above, an adhesive laminate 30 including a first adhesive layer 14 having predetermined physical properties and a second adhesive layer 16 having predetermined physical properties laminated together was formed on the surface of the base film 12. That is, the first adhesive layer 14 was formed on one surface of the base film 12, and the second adhesive layer 16 was formed on the surface of the first adhesive layer 14 opposite the surface that contacts the base film 12. In this way, the use of the base film 12 improves the handleability of the adhesive sheet 100 and facilitates operations such as lamination with the MEA 3. However, the adhesive laminate 30 according to the embodiment of the present invention is not limited to being configured as an adhesive sheet 100 together with the base film 12, as long as it is configured as including a first adhesive layer 14 having predetermined physical properties and a second adhesive layer 16 having predetermined physical properties laminated together. For example, the adhesive laminate 30 may be used alone without the base film 12. In this case, the self-standing adhesive laminate 30 is used by bringing the surface of the first adhesive layer 14 and / or the surface of the second adhesive layer 16 into contact with the object to be adhered. Furthermore, when the adhesive laminate 30 and the base film 12 form an adhesive sheet 100, the adhesive laminate 30 does not necessarily have to come into contact with the base film 12 on the surface facing the first adhesive layer 14, with the second adhesive layer 16 exposed, but may come into contact with the base film 12 on the surface facing the second adhesive layer 16, with the first adhesive layer 14 exposed.

[0095] Whether the adhesive laminate 30 is used alone or when it is used together with the substrate film 12 to form the adhesive sheet 100, the direction in which the adhesive laminate 30 is arranged (front-to-back direction) may be determined as appropriate depending on the intended use of the adhesive laminate 30 and the adhesive sheet 100. Specifically, the adhesive laminate 30 or the adhesive sheet 100 may be arranged so that the objects to which the first adhesive layer 14 and the second adhesive layer 16 come into contact or the environment to which they are exposed are suitable for the desired adhesive form, depending on the physical properties of the first adhesive layer 14 and the second adhesive layer 16, such as the first glass transition temperature and the second glass transition temperature. For example, the adhesive laminate 30 may be arranged so that the second adhesive layer 16 faces the side of the front or back surface of the adhesive laminate 30 that will be exposed to a higher temperature and humidity environment, and the first adhesive layer 14 faces the side that is not subject to relatively high temperatures and humidity but requires high adhesion at room temperature.

[0096] In the adhesive sheet 100 according to the embodiment described in detail above, the adhesive laminate 30 consisting of the first adhesive layer 14 and the second adhesive layer 16 is provided on only one side of the base film 12, but the adhesive laminate 30 may be provided on both sides of the base film 12. In the adhesive sheet 100 according to the embodiment described in detail above, the adhesive laminate 30 consisting of only two layers, the first adhesive layer 14 and the second adhesive layer 16, is provided on one side of the base film 12. However, the adhesive laminate 30 may have other layers on the outer side (below) of the first adhesive layer 14 and / or the outer side (above) of the second adhesive layer 16. For example, a third adhesive layer may be provided on the surface of the second adhesive layer 16. Furthermore, a second base film may be provided on the surface of the structure in which the adhesive laminate 30 is provided on the surface of the base film 12. In other words, the adhesive laminate 30 may be sandwiched between the base film 12 and the second base film. In this case, by removing a portion of the base film 12 and / or the second base film, the adhesive laminate 30 can be used to adhere to an external object to be adhered. Note that an adhesive sheet in this manner in which the adhesive laminate 30 is sandwiched between two base films can also be considered to be a pair of adhesive sheets, described below, in which the combined first and second adhesive sheets are in contact with each other with their adhesive layers facing each other, and the preferred forms described below for the components of a pair of adhesive sheets can also be suitably applied to an adhesive sheet in which the adhesive laminate 30 is sandwiched between two base films.

[0097] [2] Combining adhesive sheets Next, a combination of adhesive sheets according to an embodiment of the present invention will be described. The combination of adhesive sheets includes a first adhesive sheet and a second adhesive sheet, and may be referred to as a set of adhesive sheets hereinafter. In the set of adhesive sheets according to an embodiment of the present invention, at least the first adhesive sheet of the first and second adhesive sheets includes the adhesive laminate according to an embodiment of the present invention described above.

[0098] <Configuration of the adhesive sheet assembly> As shown in Figures 3(a) and 3(b), an adhesive sheet set 300 according to one embodiment of the present invention is composed of a combination of a first adhesive sheet 100 and a second adhesive sheet 200. The structure of the first adhesive sheet 100 is similar to that of the adhesive sheet 100 in its standalone state shown in Figure 1 and described in detail above, and the same reference numerals are used for the respective components, and description thereof will be omitted.

[0099] As shown in Figure 4, the second adhesive sheet 200 constituting the composite adhesive sheet 300 has a second base film 22 and a third thermosetting adhesive layer 24. The third adhesive layer 24 is formed on one surface of the second base film 22. An opening W2 penetrating the second adhesive sheet 200 is provided in the center of the second adhesive sheet 200. This opening W2 has the same size, shape, and formation position as the opening W1 provided in the first adhesive sheet 100.

[0100] The constituent material of the second base film 22 is not particularly limited, but is preferably selected from the various materials listed as suitable examples of the constituent material of the base film 12 used in the aforementioned standalone adhesive sheet 100. In addition to the constituent material, the same suitable configurations as those listed for the base film 12 above, such as thickness, can also be used as the constituent material.

[0101] The third adhesive layer 24 contains a polyurethane resin having a reactive functional group and a crosslinking agent, and has a storage modulus (G' 100 ) is 5.0 × 10 4 Pa or more 6.6×10 5 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120) is 0.3 or less, and has a third glass transition temperature lower than the second glass transition temperature. The requirements for this third adhesive layer 24 are the same as those for the first adhesive layer 14 described above, and the same configurations as those given as suitable forms for the first adhesive layer 14 formed on one side of the base film 12 in the above embodiment can also be used as suitable forms for this third adhesive layer 24. However, the first adhesive layer 14 included in the first adhesive sheet 100 and the third adhesive layer 24 included in the second adhesive sheet 200 that make up the combined adhesive sheet 300 may be either different from each other or the same as long as they meet the above-mentioned specified requirements.

[0102] To manufacture the second adhesive sheet 200, for example, the same manufacturing method as for the above-described adhesive sheet 100 in a standalone state may be applied, with the third adhesive layer 24 being formed in place of the first adhesive layer 14, and the second adhesive layer 16 being omitted. In other words, the thermosetting adhesive composition that constitutes the third adhesive layer 24 may be directly applied to one surface of the base film 22, and then a drying and curing process may be carried out by heat treatment.

[0103] <How to use the adhesive sheet> Next, a method for using the above-described assembled adhesive sheet 300 by adhering it to an object to be adhered will be described. Here, the object to be adhered is an MEA. First, the surface of the first adhesive sheet 100 on which the second adhesive layer 16 has been formed is brought into contact with the MEA 3, and the first adhesive sheet 100 and the MEA 3 are laminated together. At this time, as shown in FIGS. 3(a) and 3(b), the opening W1 of the first adhesive sheet 100 is aligned so that it faces one side of the solid electrolyte membrane 3m of the MEA 3, with the electrode 3e appropriately interposed therebetween. Furthermore, the surface of the second adhesive sheet 200 on which the third adhesive layer 24 is exposed is brought into contact with the other side of the MEA 3, and the second adhesive sheet 200 and the MEA 3 are laminated together. At this time, the opening W2 of the second adhesive sheet 200 is aligned so that it faces the other side of the solid electrolyte membrane 3m of the MEA 3, with the electrode 3e appropriately interposed therebetween. In this manner, with the MEA 3 sandwiched between the first adhesive sheet 100 and the second adhesive sheet 200 that make up the combined adhesive sheet 300, this laminate is heated and pressed to bond together the second adhesive layer 16, the MEA 3, and the third adhesive layer 24. The pressure during the heating and pressing may be, for example, 0.5 to 10 MPa, the heating temperature 130 to 230°C, and the pressure and heating time 3 to 60 seconds.

[0104] Specifically, the peripheral portion 3A of the MEA 3 (the region of the solid electrolyte membrane 3m that is not sandwiched between the electrodes 3e) is sandwiched between the second adhesive layer 16 and the third adhesive layer 24, and is fixed between the base film 12 and the second base film 22. Outside the openings W1 and W2, the portion of the second adhesive layer 16 that does not overlap with the peripheral portion 3A of the MEA 3 and the portion of the third adhesive layer 24 that does not overlap with the peripheral portion 3A of the MEA 3 are bonded together in a state where the second adhesive layer 16 and the third adhesive layer 24 are in direct contact with each other. This seals the peripheral portion 3A of the MEA 3 by the second adhesive layer 16 and the third adhesive layer 24. In this case, the base film 12 and the second base film 22 are bonded to each other via a three-layer thermosetting adhesive laminate 40 consisting of a first adhesive layer 14, a second adhesive layer 16, and a third adhesive layer 24. An adhesive sheet 300 having such a configuration can function as a subgasket for the MEA 3, as shown in Figures 3(a) and 3(b).

[0105] In the embodiment described herein, a third adhesive layer 24 is formed on one surface of a second base film 22 to form a second adhesive sheet 200. Then, the second adhesive sheet 200 is laminated on the surface of a first adhesive sheet 100, which has an MEA 3 laminated on the surface of the second adhesive layer 16, and the laminated adhesive sheet 300 is configured as a subgasket for the MEA 3 by thermocompression bonding. The procedure for constructing a subgasket for the MEA 3 is not limited to this. For example, after the MEA 3 is laminated on the surface of the second adhesive layer 16, a third adhesive layer 24 may be formed to cover the exposed portion of the second adhesive layer 16 and the peripheral portion 3A of the MEA 3, and then the second base film 22 may be laminated and thermocompression bonded. The pressure may be 0.5 to 10 MPa, the heating temperature may be 130 to 230°C, and the pressure and heating time may be 3 to 60 seconds.

[0106] <Modified Adhesive Sheet> Here, as a variation of the assembled adhesive sheet 300 according to the embodiment described above, assembled adhesive sheet 400 is shown in Figures 5(a) and 5(b) together with MAE 3. Like the assembled adhesive sheet 300 described above, this assembled adhesive sheet 400 is configured as a combination of a first adhesive sheet 100 and a second adhesive sheet 200, and the layer configurations of the first adhesive sheet 100 and the second adhesive sheet 200 and the composition of each layer are also similar to those of the assembled adhesive sheet 300 described above.

[0107] However, the assembly adhesive sheet 400 differs from the assembly adhesive sheet 300 in the size of the opening W3 provided in the second adhesive sheet 200. In the assembly adhesive sheet 300, the second adhesive sheet 200 also had an opening W2 of the same size as the opening W1 in the first adhesive sheet 100, but in the assembly adhesive sheet 400 of Fig. 5, the opening W3 provided in the second adhesive sheet 200 is larger in size than the opening W1 provided in the first adhesive sheet 100. By providing the large opening W3 in the second adhesive sheet 200, as shown in the figure, when the assembly adhesive sheet 400 is attached to the MEA 3 as a subgasket, a portion of the solid electrolyte membrane 3m of the MEA 3 that is not sandwiched between the electrodes 3e is exposed in the opening W3.

[0108] A method for adhering this assembled adhesive sheet 400 to an MEA 3 can be used by laminating a first adhesive sheet 100 and an MEA 3, and then laminating a second adhesive sheet 200 on top of them, as with the assembled adhesive sheet 300. However, another suitable method is to first bond the first adhesive sheet 100 and the second adhesive sheet 200 together, and then incorporate the MEA into the assembled adhesive sheet 400. Specifically, the first adhesive sheet 100 and the second adhesive sheet 200 are first laminated so that the second adhesive layer 16 and the third adhesive layer 24 are in contact with each other. At this time, the first adhesive sheet 100 and the second adhesive sheet 200 are aligned so that the opening W1 of the first adhesive sheet 100 and the peripheral region 16A outside the opening W1 are positioned within the region inside the opening W3 provided in the second adhesive sheet 200. As a result, with the first adhesive sheet 100 and the second adhesive sheet 200 superimposed on each other, a peripheral region 16A of the surface of the second adhesive layer 16 that surrounds the opening W1 is exposed within the opening W3 without being covered by the second adhesive sheet 200. With the first adhesive sheet 100 and the second adhesive sheet 200 superimposed in this manner, the two adhesive sheets 100, 200 are bonded together by thermocompression, for example, at 80°C and a pressure of 2 MPa for 5 seconds. The thermocompression bonding conditions are not limited to these, and preferred conditions include a temperature of room temperature to 150°C, a pressure of 0.5 to 10 MPa, and a pressure and heating time of 3 to 60 seconds.

[0109] Alternatively, as yet another method, after forming a third adhesive layer 24 on the surface of the second adhesive layer 16 of the first adhesive sheet 100 on which the MEA 3 is superimposed, in an area excluding the peripheral area 16A surrounding the opening W1, Second The substrate film 22 may be laminated and then heat-pressurized, for example, at a pressure of 0.5 to 10 MPa, a heating temperature of 130 to 230° C., and a pressurizing and heating time of 3 to 60 seconds. After forming the assembled adhesive sheet 400 by joining two adhesive sheets 100, 200 using any of the methods described above, if necessary, a curing process can be carried out on the assembled adhesive sheet 400 in the same manner as described for the adhesive sheet 100 in Figure 1.

[0110] When the assembled adhesive sheet 400 configured in this manner is used as a subgasket, as shown in Figures 5(a) and 5(b), the MEA 3 is laminated on the second adhesive layer 16 exposed in the peripheral region 16A within the opening W3 of the second adhesive sheet 200 so that the electrolyte membrane 3m of the MEA 3 faces the opening W1 of the first adhesive sheet 100 via the appropriate electrode 3e. The sizes of the opening W1 and the opening W3 are preferably designed so that the MEA 3 can pass through the opening W3, the electrolyte membrane 3m of the MEA 3 covers the opening W1, and the peripheral portion 3A of the MEA 3 overlaps the portion of the second adhesive layer 16 exposed in the peripheral region 16A. By bonding the assembled adhesive sheet 400 and the MEA 3 in this overlapping state using heat and pressure bonding, the assembled adhesive sheet 400 can function as a subgasket for the MEA 3. As mentioned above, the pressure may be, for example, 0.5 to 10 MPa, the heating temperature may be 130 to 230° C., and the pressure / heating time may be, for example, 3 to 60 seconds.

[0111] In the assembled adhesive sheet 400 according to this modified embodiment, when the two adhesive sheets 100, 200 are joined together, the surface of the second adhesive layer 16 of the first adhesive sheet 100 is exposed in a peripheral region 16A located inside the periphery of the opening W3, while the surface outside the peripheral region 16A is covered by the second adhesive sheet 200. In other words, the portion of the second adhesive layer 16 other than the peripheral region 16A that is bonded to the MEA 3 is covered by the second base film 22 and is not exposed on the outermost surface of the assembled adhesive sheet 400. This improves the handleability of the assembled adhesive sheet 400. Furthermore, adhesion of foreign matter to the assembled adhesive sheet 400 can be suppressed, and even if foreign matter does adhere, it can be easily removed. Furthermore, when positioning the bond between the assembled adhesive sheet 400, which is made by joining two adhesive sheets 100, 200, and the MEA 3, by aligning the MEA 3 with the opening W3 of the second adhesive sheet 200, the opening W1 of the first adhesive sheet 100 will automatically be positioned facing the MEA 3, thereby improving the workability of the bonding process between the MEA 3 and the assembled adhesive sheet 400.

[0112] <Other forms of assembled adhesive sheets> In the above, in the second adhesive sheet 200 constituting the adhesive sheet set 300, 400, the third adhesive layer 24 provided on the surface of the second base film 22 is a layer having a storage modulus at 100°C (G' 100 ) is 5.0 × 10 4 Pa or more 6.6×10 5 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120) is 0.3 or less and has a third glass transition temperature lower than the second glass transition temperature. However, the third adhesive layer 24 is not limited to those having such physical properties, and any thermosetting adhesive layer can be used. For example, at least one of the first adhesive layer 14 and the second adhesive layer 16 may be used as an adhesive layer formed on the surface of the second base film 22. In particular, when the second adhesive sheet 200 is formed by forming the first adhesive layer 14 on the surface of the second base film 22 made of the same material as the base film 12, the combined adhesive sheets 300, 400 formed by joining the two adhesive sheets 100, 200 will have a structure symmetrical in the thickness direction. When forming a second adhesive sheet 200 by forming both a first adhesive layer 14 and a second adhesive layer 16 on the surface of a second base film 22, similar to the first adhesive sheet 100, the first adhesive layer 14 is formed on the surface of the second base film 22, and the second adhesive layer 16 is formed on the surface of the first adhesive layer 14.

[0113] In the above description, the adhesive sheet set 300 (or 400; the same applies hereinafter in this paragraph) has been considered to be configured as a combination of two adhesive sheets 100 and 200. However, as mentioned above, one adhesive sheet 300 may be , baseIt can also be considered as a structure having a base film 12, an adhesive laminate 40 consisting of a first adhesive layer 14, a second adhesive layer 16, and a third adhesive layer 24, and a second base film 22. In this case, the third thermosetting adhesive layer 24 is formed on one surface of the second base film 22, and the second base film 22 has a structure in which the second adhesive layer 16 and the first adhesive layer 14 are sandwiched between the second base film 22 and the base film 12 via the third adhesive layer 24. In this way, when considered as a single adhesive sheet 300, in the form described above, the adhesive sheet 300 has an adhesive laminate 40 consisting of a first adhesive layer 14, a second adhesive layer 16, and a third adhesive layer 24, and further a second substrate film 22, provided on only one side of the base film 12, but the adhesive laminate 40 and second substrate film 22 may also be provided on both sides of the base film 12.

[0114] Furthermore, as explained above with regard to the embodiment of the single adhesive sheet 100, the first adhesive sheet 100 may be configured as a self-supporting adhesive laminate 30 consisting of the first adhesive layer 14 and the second adhesive layer 16 without using the base film 12. Similarly, the second adhesive sheet 200 may be configured as a self-supporting adhesive layer consisting of the third adhesive layer 24 without using the second base film 22. The self-supporting adhesive laminate 30 and the self-supporting third adhesive layer 24 may then be combined to form a combined adhesive sheet 300 (400). Even in such a combined embodiment, the two adhesive sheets 100, 200 can be laminated together with the MEA 3 sandwiched between the second adhesive layer 16 and the third adhesive layer 24, and then heat-pressed to form a subgasket for use with the MEA. In this case, the adhesive laminate 40 is configured from three adhesive layers consisting of the first adhesive layer 14, the second adhesive layer 16, and the third adhesive layer 24, and is self-supporting.

[0115] In the above embodiments, the adhesive sheet 100 and the combined adhesive sheets 300, 400 are formed into a shape with an opening and adhered to the MEA 3 to form a subgasket, but the adhesive sheet of the present invention and the combination of adhesive sheets of the present invention do not necessarily have to be used as a subgasket and can be formed into a shape according to the application and used in any location in a fuel cell that requires sealing. Furthermore, they are not limited to fuel cells and can be suitably used for sealing locations that are subject to high temperatures and humidity. [Example]

[0116] The present invention will be described in detail below using examples and comparative examples. However, the present invention is not limited to these examples. Unless otherwise specified, each step of preparing and evaluating a sample was carried out in air at room temperature.

[0117] <Sample preparation> Example 1 Preparation of adhesive composition The adhesive composition of the first adhesive layer is a polyurethane resin, and the following resin is used: <1> (Toyochem "VA-9320L2") for 100 mass parts of solid content, the following epoxy crosslinking agent <1> To the mixture was added 11.6 parts by mass (solid content) of an adhesive agent ("HD-901" manufactured by Toyochem), and toluene was further added so that the solid content concentration became 19% by mass, thereby preparing an adhesive composition.

[0118] The adhesive composition for the second adhesive layer is a polyurethane resin, and <2> ("VA-9315" manufactured by Toyochem) for 100 mass parts of solid content, the following epoxy crosslinking agent <1> An adhesive composition for the second adhesive layer was prepared in the same manner as in the preparation of the adhesive composition for the first adhesive layer, by adding 11.7 parts by mass (solid content) of TOYOCHEM's "HD-901".

[0119] - Preparation of adhesive sheets The adhesive composition for the first adhesive layer was applied to one side of a polyethylene naphthalate (PEN) film ("Teonex Q51" manufactured by Toyobo) using a Baker-type film applicator to a thickness of 2 μm after drying, and the film was heated at 150°C for 3 minutes to form a first adhesive layer. The adhesive composition for the second adhesive layer was then applied to the dried surface of the first adhesive layer using a Baker-type film applicator to a thickness of 10 μm after drying, and the film was heated at 150°C for 3 minutes to form a second adhesive layer. The release surface of a release film ("HY-S10" manufactured by Higashiyama Film, a silicone-based PET release film, 25 μm thick) was then bonded to the exposed surface of the second adhesive layer. The film was then aged at 60°C for 6 days to produce an adhesive sheet having two adhesive layers, the first and second.

[0120] Examples 2 to 7 The formulations of the adhesive compositions and the aging conditions were as shown in Table 1, and adhesive sheets were prepared in the same manner as in Example 1 above.

[0121] (Examples 8 to 11) Preparation of adhesive composition The formulation of the adhesive composition was as shown in Table 2, and the adhesive composition for the first adhesive layer, the adhesive composition for the second adhesive layer, and the adhesive composition for the third adhesive layer were prepared for each example in the same manner as the preparation of the adhesive composition in Example 1 above.

[0122] - Preparation of adhesive sheets The adhesive composition for the first adhesive layer was applied to one side of a polyethylene naphthalate (PEN) film ("Teonex Q51" manufactured by Toyobo) using a Baker-type film applicator so that the thickness after drying would be 2 μm, and the first adhesive layer was formed by heating at 150°C for 3 minutes. Thereafter, the adhesive composition for the second adhesive layer was applied to the surface of the dried first adhesive layer using a Baker-type film applicator so that the thickness after drying would be 10 μm, and the film was heated at 150°C for 3 minutes to form a second adhesive layer, and a first adhesive sheet was produced.

[0123] Furthermore, the adhesive composition for the third adhesive layer was applied to one side of another polyethylene naphthalate (PEN) film using a Baker film applicator in the same manner as above so that the thickness after drying would be 2 μm, and the film was heated at 150°C for 3 minutes to form a third adhesive layer, thereby producing a second adhesive sheet.

[0124] The exposed surface of the first adhesive sheet with the second adhesive layer was then placed on the exposed surface of the second adhesive sheet with the third adhesive layer, and they were heat-pressed for 5 seconds at 80°C and a pressure of 2 MPa using an AS ONE small heat press "H400-15." This was then aged at 60°C for 6 days to produce a composite adhesive sheet for each example having three adhesive layers (first, second, and third).

[0125] (Comparative Examples 1 to 5) The adhesive composition formulations and aging conditions were as shown in Table 1, and the adhesive compositions of each comparative example were prepared in the same manner as in Example 1 above, and the respective adhesive sheets were produced.

[0126] (Comparative Examples 6 and 7) Preparation of adhesive composition An adhesive composition for the second adhesive layer was prepared in the same manner as in Example 1, using the blending composition shown in Table 1. The composition was adjusted to have a solids concentration of 20 mass %.

[0127] - Preparation of adhesive sheets A second adhesive layer was applied to one side of a polyethylene naphthalate (PEN) film ("Teonex Q51" manufactured by Toyobo Co., Ltd.) using a Baker-type film applicator to a thickness of 10 μm after drying, and the film was heated at 150°C for 3 minutes to form a second adhesive layer. The release surface of a release film ("HY-S10" manufactured by Higashiyama Film Co., Ltd., a silicone-based PET release film, 25 μm thick) was then attached to the exposed side of the second adhesive layer. This was then aged at 60°C for 6 days to produce an adhesive sheet. In these comparative examples, adhesive sheets with a single adhesive layer were each produced by applying only the adhesive composition for the second adhesive layer to a polyethylene naphthalate (PEN) film without applying the adhesive composition for the first adhesive layer.

[0128] (Comparative Example 8) Preparation of adhesive composition The adhesive composition for the first adhesive layer was prepared in the same manner as in Example 1 above, using the blending composition shown in Table 1.

[0129] - Preparation of adhesive sheets The adhesive composition for the first adhesive layer was applied to one side of a polyethylene naphthalate (PEN) film ("Teonex Q51" manufactured by Toyobo) using a Baker-type film applicator so that the thickness after drying was 2 μm, and the first adhesive layer was formed by heating at 150 °C for 3 minutes. The release surface of a release film ("HY-S10" manufactured by Higashiyama Film, a silicone-based PET release film, 25 μm thick) was then attached to the exposed side of the first adhesive layer. This was then aged at 60 °C for 6 days to produce an adhesive sheet. In this comparative example, only the adhesive composition for the first adhesive layer was applied to the polyethylene naphthalate (PEN) film, and an adhesive sheet with a single adhesive layer was produced without applying the adhesive composition for the second adhesive layer.

[0130] (Comparative Example 9) Preparation of adhesive composition The formulation of the adhesive composition was as shown in Table 2, and the adhesive composition for the second adhesive layer and the adhesive composition for the third adhesive layer were prepared in the same manner as the preparation of the adhesive composition in Example 1 above.

[0131] - Preparation of adhesive sheets The adhesive composition for the second adhesive layer was applied to one side of a polyethylene naphthalate (PEN) film ("Teonex Q51" manufactured by Toyobo) using a Baker-type film applicator so that the thickness after drying would be 10 μm, and the film was heated at 150°C for 3 minutes to form a second adhesive layer, thereby producing a first adhesive sheet.

[0132] Furthermore, the adhesive composition for the third adhesive layer was applied to one side of another polyethylene naphthalate (PEN) film using a Baker film applicator in the same manner as above so that the thickness after drying would be 1 μm, and the film was heated at 150°C for 3 minutes to form a third adhesive layer, thereby producing a second adhesive sheet.

[0133] The exposed surface of the first adhesive sheet with the second adhesive layer was then placed on the exposed surface of the second adhesive sheet with the third adhesive layer, and they were heat-pressed for 5 seconds at 80°C and a pressure of 2 MPa using an AS ONE small heat press "H400-15." This was then aged at 60°C for 6 days to produce a combined adhesive sheet including the second and third adhesive layers.

[0134] (Comparative Examples 10 and 11) Preparation of adhesive composition The adhesive composition for each comparative example was prepared by setting the formulation as shown in Table 2 and preparing the adhesive composition for the second adhesive layer in the same manner as the adhesive compositions in Comparative Examples 6 and 7 above.

[0135] - Preparation of adhesive sheets As with the adhesive sheets in Comparative Examples 6 and 7, the adhesive composition for the second adhesive layer was applied to a dried thickness of 10 μm and heated at 150°C for 3 minutes to form a second adhesive layer. The exposed surface of the second adhesive layer was then placed on one side of a polyethylene naphthalate (PEN) film (Teonex Q51 manufactured by Toyobo) without any other adhesive layer formed on its surface, and the film was heated and pressed for 5 seconds at 80°C and a pressure of 2 MPa using a compact heat press (H400-15) manufactured by AS ONE. The film was then aged at 60°C for 6 days to produce an adhesive sheet with a second adhesive layer.

[0136] The materials used to prepare the samples of Examples 1 to 11 and Comparative Examples 1 to 11 are as follows. ·resin <1> VA-9320L2 (manufactured by Toyochem, polyurethane resin, solvent: toluene / isopropanol, solids concentration: 23.3% by mass, reactive functional group: carboxyl group, acid value: 10 mg KOH / g, viscosity at 25°C: 7,400 mPa·s, molecular weight: 113,000) ·resin <2> VA-9315 (manufactured by Toyochem, polyurethane resin, solvent: toluene / isopropanol, solids concentration: 22.0% by mass, reactive functional group: carboxyl group, acid value: 10 mg KOH / g, viscosity at 25°C: 3,500 mPa·s, molecular weight: 108,000) ·resin <3> VA-9315H2 (manufactured by Toyochem, polyurethane resin, solvent: toluene / isopropanol, solids concentration: 21.3% by mass, reactive functional group: carboxyl group, acid value: 10 mg KOH / g, viscosity at 25°C: 7.00 mPa·s, molecular weight: 129,000) ·resin <4> VA-9320L1 (manufactured by Toyochem, polyurethane resin, solvent: toluene / isopropanol, solids concentration: 23.3% by mass, reactive functional group: carboxyl group, acid value: 10 mg KOH / g, viscosity at 25°C: 117,000 mPa·s, molecular weight: 129,000) ·resin <5> VA-9302 (manufactured by Toyochem, polyurethane resin, solvent: toluene / isopropanol, solids concentration: 25.7% by mass, reactive functional group: carboxyl group, acid value: 10 mg KOH / g, viscosity at 25°C: 3,400 mPa·s, molecular weight: 129,000) ·resin <6> VA-9320 (manufactured by Toyochem, polyurethane resin, solvent: toluene / isopropanol, solids concentration: 23.3% by mass, reactive functional group: carboxyl group, acid value: 10 mg KOH / g, viscosity at 25°C: 6,300 mPa·s, molecular weight: 106,000) ·resin <7> Aronmighty AS-350 (manufactured by Toagosei, modified epoxy resin, solvent: toluene, methanol, ethylene glycol monomethyl ether, dimethylformamide, xylene, diethylene glycol dimethyl ether, solids concentration: 30% by mass) ·resin <8> VA-9315H1 (manufactured by Toyochem, polyurethane resin, solvent: toluene / isopropanol, solids concentration: 22.2% by mass, reactive functional group: carboxyl group, acid value: 10 mg KOH / g, viscosity at 25°C: 5,900 mPa·s, molecular weight: 118,000) ·resin <9> VA-9320L3 (manufactured by Toyochem, polyurethane resin, solvent: toluene / isopropanol, solids concentration: 23.2% by mass, reactive functional group: carboxyl group, acid value: 10 mg KOH / g, viscosity at 25°C: 4,600 mPa·s, molecular weight: 106,000) Crosslinking agent <1> HD-901 (manufactured by Toyochem, tetrafunctional epoxy resin, solvent: toluene-methyl ethyl ketone, solids concentration: 50.0% by mass, epoxy equivalent: 200 g / eq, softening point: 92°C, viscosity at 25°C: 15 mPa·s, molecular weight: approximately 800) Crosslinking agent <2> : HD-902 (manufactured by Toyochem, trifunctional epoxy resin, solvent: toluene-methyl ethyl ketone, solids concentration: 60.0 mass%, epoxy equivalent: 208 g / eq, viscosity at 25°C: 20 mPa·s, molecular weight: approximately 620)

[0137] <Evaluation method> (storage modulus, glass transition temperature) The adhesive compositions prepared above to form the adhesive layers of each sample were applied to the release surface of a release film (Higashiyama Film's "HY-S10," a silicone-based PET release film, 25 μm thick) and dried at 150°C for 3 minutes to form an adhesive layer. The same adhesive composition was then applied to the formed adhesive layer and dried at 150°C for 3 minutes, repeating this process until the laminate reached a thickness of 0.5 mm. Each sample was then aged under the specified conditions to prepare test samples. The shear storage modulus (G') of these samples was measured from -40°C to 150°C using a viscoelasticity measuring device (TA Instrument's "Discovery HR-2"). The measurement conditions were shear mode, geometry: 8 mm diameter parallel plates, axial force: 1.0 N, normal load: 1.0 N, frequency: 1 Hz, and heating rate: 5°C / min. In addition, the loss modulus (G") was also measured using the same measuring device, and the temperature at which the loss tangent (tanδ) calculated by dividing the loss modulus (G") by the storage modulus (G') (G" / G') reached its maximum value was defined as the glass transition temperature (Tg).

[0138] (gel fraction) The mass w1 of a wire mesh (400 mesh) cut to a width of 50 mm and a length of 120 mm was measured. From the adhesive sheet prepared above as a sample for measuring the storage modulus, 0.1 g of each adhesive layer was taken and wrapped in wire mesh to prepare a sample, and the mass w2 of this sample was measured. The sample was placed in a glass bottle, 40 g of toluene was poured into it, and the sample was shaken lightly, then allowed to stand at room temperature (25°C) for 76 hours. After standing, the sample was removed from the glass bottle and left at room temperature for 12 hours, and then dried in a vacuum oven at 100°C for 4 hours. The dried sample was cooled to room temperature, and the mass w3 was measured, and the gel fraction was calculated using the following formula. Gel fraction (mass%) = ((w3-w1) / (w2-w1)) × 100

[0139] (Thickness) Using a thickness measuring device ("TH-104" manufactured by Tester Sangyo), the total thickness of the entire adhesive sheet at the stage when each layer was formed was measured, and the thickness of the adhesive layer was determined by subtracting the thickness of the base film (and release film) from this total thickness.

[0140] (Initial peel strength) In Examples 1 to 7 and Comparative Examples 1 to 8, which were configured as a single adhesive sheet, the release sheet was peeled off from the adhesive layer, and a solid polymer electrolyte membrane ("Nafion PFSA NR-212" manufactured by DuPont, thickness: 50.8 μm) was superimposed on the exposed surface of the adhesive layer, and the test samples were prepared by heating and pressing the membrane for 5 seconds at a temperature of 150°C and a pressure of 2 MPa using a small heat press machine "H400-15" manufactured by AS ONE. In Examples 8 to 11 and Comparative Examples 9 to 11, the adhesive sheet assembly prepared as described above had a structure in which two polyethylene naphthalate (PEN) films were bonded together by one or more adhesive layers sandwiched between the two films, and each was used as a test sample as is.

[0141] The prepared test samples were stored at room temperature (23°C) for 30 minutes and then cut into pieces 10 mm wide and 150 mm long. The peel force was measured at a peel rate of 10 mm / min and a peel angle of 180° using a Shimadzu Corporation precision universal testing machine, "AUTOGRAPH (registered trademark) AGS-1kNX, 50N load cell," in accordance with the method of JIS Z 0237 (2009), to evaluate the initial peel force. In Examples 1 to 7 and Comparative Examples 1 to 8, the peel force between a PEN film and a solid polymer electrolyte membrane was measured, while in Examples 8 to 11 and Comparative Examples 9 to 11, the peel force between two PEN films was measured. In all cases, a peel force greater than approximately 1 N / 10 mm was considered to be sufficiently strong and sufficient adhesion was achieved.

[0142] (Removal force after boiling) Test samples prepared in the same manner as the samples used to evaluate the initial peel strength were cut into a size of 10 mm wide and 150 mm long, and immersed in boiling water at 98°C or higher for 270 hours.The peel strength was then measured under the same conditions as in the evaluation of the initial peel strength using a precision universal testing machine, "AUTOGRAPH (registered trademark) AGS-1kNX, 50N load cell," and evaluated as the peel strength after boiling.If the peel strength after boiling is generally greater than 1N / 10mm, it can be said that the peel strength is sufficiently large and sufficient adhesion has been achieved.

[0143] <Test Results> The composition of each sample and the evaluation results are shown in Tables 1 and 2. For the blending composition of the adhesive composition, the content of each component is shown in parts by mass.

[0144] [Table 1]

[0145] [Table 2]

[0146] In Examples 1 to 7, the first and second adhesive layers were each formed from a cured product of a thermosetting adhesive composition containing a polyurethane resin having a reactive functional group and a crosslinking agent. The storage modulus (G') at 100°C of the first adhesive layer in contact with the PEN film was 100 ) is 5.0 × 10 4 Pa or more 6.6×10 5 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120 On the other hand, in the second adhesive layer in contact with the solid polymer electrolyte membrane, the decrease rate of the storage modulus (G' 100 ) is 6.6 × 10 5 Pa > 1.0 x 10 7 The storage modulus (G') at 100°C is 100) versus storage modulus at 120°C (G' 120 ) is 0.5 or less. The glass transition temperature Tg is higher in the second adhesive layer than in the first adhesive layer. Correspondingly, the adhesive sheet to which the solid polymer electrolyte membrane is pressed exhibits a large initial peel strength, as shown in the evaluation results, and bonding can be completed with short periods of heat and pressure. Furthermore, as can be seen from the fact that the peel strength after boiling is maintained at a high level, adhesion defects such as lifting, peeling, and voids can be suppressed even in high-temperature, high-humidity environments. Therefore, strong adhesion is obtained between the PEN film and the first adhesive layer, between the first adhesive layer and the second adhesive layer, and between the second adhesive layer and the solid polymer electrolyte membrane, which exhibits a large initial peel strength and is highly resistant to high-temperature, high-humidity environments.

[0147] In Comparative Example 1, the storage modulus (G') of the second adhesive layer at 100°C 100 ) is 6.6 × 10 5 Pa or less. Correspondingly, the peel strength between the solid polymer electrolyte membrane and the PEN film after boiling is insufficient. In Comparative Example 2, the second adhesive layer G' 100 is 1.0×10 7 Corresponding to the fact that the peel strength exceeded 100 Pa, the adhesiveness of the second adhesive layer was low, and when a sample for measuring the peel strength was prepared, it was not possible to adhere it to the solid polymer electrolyte membrane.

[0148] In Comparative Example 3, the storage modulus (G') of the first adhesive layer at 100°C 100 ) versus storage modulus at 120°C (G' 120 ) is greater than 0.3. Correspondingly, the peel strength after boiling between the solid polymer electrolyte membrane and the PEN film is insufficient, and the resistance to high temperatures and high humidity is poor. In Comparative Example 4, the storage modulus (G') of the first adhesive layer at 100°C 100 ) is 6.6 × 10 5 The storage modulus (G') at 100°C exceeds 100 ) versus storage modulus at 120°C (G' 120) is greater than 0.3. Correspondingly, the initial peel strength between the solid polymer electrolyte membrane and the PEN film is insufficient. This is thought to be because the adhesive strength between the first adhesive layer and the PEN film is insufficient. In Comparative Example 5, the storage modulus (G') of the first adhesive layer at 100°C 100 ) is 5.0 × 10 4 The storage modulus (G') at 100°C is less than 100 Pa. 100 ) versus storage modulus at 120°C (G' 120 ) decline rate exceeded 0.3. Correspondingly, the adhesiveness was clearly poor, and measurement of the initial peel strength was omitted. Furthermore, due to the poor adhesiveness and low resistance to high temperatures and humidity, the adhesive layer peeled off in the boiling test.

[0149] In Comparative Examples 6 and 7, only one layer of the second adhesive layer exists between the PEN film and the solid polymer electrolyte membrane, and the PEN film and the solid polymer electrolyte membrane are directly bonded by only this second adhesive layer. In Comparative Example 6, the storage modulus (G') of the second adhesive layer at 100°C was 100 ) is 6.6 × 10 5 Since the adhesive strength is below 100°C, the adhesive exhibits a relatively high adhesiveness to the PEN film, and a sufficient initial peel strength is obtained between the PEN film and the solid polymer electrolyte membrane. However, the first adhesive layer is not provided, and the second adhesive layer alone is unable to maintain its adhesiveness in a high-temperature, high-humidity environment, and the peel strength after boiling is insufficient. Furthermore, in Comparative Example 7, the storage modulus (G') of the second adhesive layer at 100°C 100 ) is 6.6 × 10 5 The adhesive strength exceeds Pa, and the adhesive strength to the PEN film is already insufficient from the initial state. In Comparative Example 8, only a single layer, the first adhesive layer, exists between the PEN film and the solid polymer electrolyte membrane, and the PEN film and the solid polymer electrolyte membrane are directly bonded by only this first adhesive layer. In Comparative Example 8, sufficient peel strength is obtained in the initial state, but the peel strength after boiling is insufficient. This shows that sufficient adhesive strength cannot be maintained in a high-temperature, high-humidity environment unless a second adhesive layer with predetermined physical properties is used. Comparative Examples 6 to 8 show that in order to obtain sufficiently high adhesive strength both in the initial state and after exposure to a high-temperature, high-humidity environment, both the first adhesive layer and the second adhesive layer having the specified physical properties are required.

[0150] In Examples 8 to 11, two PEN films are bonded with first to third adhesive layers therebetween. The first to third adhesive layers are each formed from a cured product of a thermosetting adhesive composition containing a polyurethane resin having reactive functional groups and a crosslinking agent. The first adhesive layer is in contact with one PEN film and the second adhesive layer on each side. The second adhesive layer is in contact with the first adhesive layer and the third adhesive layer on each side. The third adhesive layer is in contact with the second adhesive layer and the other PEN film on each side. In other words, the second adhesive layer is sandwiched between the first adhesive layer and the third adhesive layer, and the two PEN films are bonded with these three adhesive layers (first, second, and third) sandwiched between them. In Examples 8 to 11, the storage modulus (G') at 100°C of the first and third adhesive layers was measured. 100 ) is 5.0 × 10 4 Pa or more 6.6×10 5 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120 The decrease in the storage modulus (G') of the second adhesive layer at 100°C is 0.3 or less. 100 ) is 6.6 × 10 5 Pa > 1.0 x 10 7 The storage modulus (G') at 100°C is 100 ) versus storage modulus at 120°C (G' 120) was 0.5 or less. Correspondingly, as shown in the evaluation results of the initial peel strength, the first to third adhesive layers bonding two PEN films were able to complete bonding with short periods of heat and pressure, and sufficient adhesive strength was obtained. Furthermore, the high peel strength maintained after boiling indicates that poor adhesion such as lifting, peeling, and voids can be suppressed even in high-temperature, high-humidity environments. In other words, it was confirmed that in Examples 8 to 11, the first to third adhesive layers sandwiched between two PEN films provided strong adhesion with sufficient initial peel strength and high resistance to high-temperature, high-humidity environments.

[0151] In Comparative Example 9, only the second and third adhesive layers are present between the two PEN films. Both the second and third adhesive layers have a storage modulus (G') at 100°C. 100 ) is 6.6 × 10 5 Because the adhesive strength was lower than that of the adhesive strength of the adhesive tape, it exhibited a relatively high adhesive strength to the PEN film, and a sufficient initial peel strength was obtained between the two PEN films. However, because the first adhesive layer was not provided and the second adhesive layer alone was unable to maintain its adhesive strength in a high-temperature, high-humidity environment, the peel strength could not be maintained after boiling.

[0152] In Comparative Examples 10 and 11, only one layer, the second adhesive layer, is present between the two PEN films. Moreover, the storage modulus (G') of this second adhesive layer at 100°C was 100 ) is 6.6 × 10 5 Pa, and it cannot be expected that the sheet will exhibit high adhesive strength to PEN film. Correspondingly, the adhesion to PEN film was actually poor, and it was clear that a peel strength of more than 1 N / 10 mm could not be obtained, so measurement of the peel strength was omitted. Comparative Examples 9 to 11, like Comparative Examples 6 to 8, show that in order to obtain a sufficiently high adhesive strength both in the initial state and after exposure to a high-temperature, high-humidity environment, the first adhesive sheet needs both a first adhesive layer and a second adhesive layer with predetermined physical properties.

[0153] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the present invention. [Explanation of symbols]

[0154] 12 Base film 14 First adhesive layer 16 Second adhesive layer 22 Second base film 24 Third adhesive layer 100 adhesive sheet (first adhesive sheet) 200 Second adhesive sheet 300 pairs of adhesive sheets (combination of adhesive sheets) 400 pairs of adhesive sheets (combination of adhesive sheets) W1 opening W2 opening W3 opening

Claims

1. An adhesive sheet having a base film and an adhesive laminate, the adhesive laminate being formed on a surface of the base film, The adhesive laminate is a first thermosetting adhesive layer formed from a cured product of a thermosetting adhesive composition and having a first glass transition temperature; a second thermosetting adhesive layer formed from a cured product of the thermosetting adhesive composition and having a second glass transition temperature higher than the first glass transition temperature, and the thermosetting adhesive compositions constituting the first thermosetting adhesive layer and the second thermosetting adhesive layer each contain a polyurethane resin having a reactive functional group including a carboxy group and an acid value of 4.0 mgKOH / g or more and 40 mgKOH / g or less, and a crosslinking agent including a polyfunctional epoxy crosslinking agent; The first thermosetting adhesive layer has a storage modulus (G' １００ ) is 5.0 x 10 ４ Pa or more 6.6×10 ５ Pa or less, and the storage modulus at 100°C (G' １００ ) versus storage modulus at 120°C (G' １２０ ) is 0.3 or less, the first glass transition temperature is 15°C or more and less than 50°C, The second thermosetting adhesive layer has a storage modulus (G' １００ ) is 6.6 x 10 ５ Pa exceeding 1.0 x 10 ７ Pa or less, and the storage modulus at 100°C (G' １００ ) versus storage modulus at 120°C (G' １２０ ) is 0.5 or less, the second glass transition temperature is 50°C or more and 100°C or less, In the adhesive sheet, the first thermosetting adhesive layer is formed on one surface of the base film, and the second thermosetting adhesive layer is formed on the surface of the first thermosetting adhesive layer opposite to the surface that contacts the base film.

2. An adhesive sheet as described in claim 1, wherein in each of the thermosetting adhesive compositions constituting the first thermosetting adhesive layer and the second thermosetting adhesive layer, the ratio (b / a) of the molar amount (a) of the carboxyl groups of the polyurethane-based resin to the molar amount (b) of the epoxy groups of the multifunctional epoxy-based crosslinking agent is 1.0 or more and 10.0 or less.

3. 2. The adhesive sheet according to claim 1, wherein the first thermosetting adhesive layer has a thickness of 1 μm or more and 6 μm or less, and the second thermosetting adhesive layer has a thickness of 8 μm or more and 30 μm or less.

4. 2. The adhesive sheet according to claim 1, wherein the base film is a film composed of at least one resin material selected from the group consisting of polyarylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyphenylene sulfide, polysulfone, polyethersulfone, and polyetheretherketone.

5. the adhesive sheet further includes a second substrate film and a third thermosetting adhesive layer formed from a cured product of the thermosetting adhesive composition; the third thermosetting adhesive layer is formed on one surface of the second base film, and the second base film has a structure in which the second thermosetting adhesive layer and the first thermosetting adhesive layer are sandwiched between the second base film and the third thermosetting adhesive layer, The thermosetting adhesive composition constituting the third thermosetting adhesive layer contains a polyurethane resin having a reactive functional group including a carboxy group and an acid value of 4.0 mgKOH / g or more and 40 mgKOH / g or less, and a crosslinking agent including a polyfunctional epoxy crosslinking agent, and the third thermosetting adhesive layer has a storage modulus (G') at 100°C １００ ) is 5.0 x 10 ４ Pa or more 6.6×10 ５ Pa or less, and the storage modulus at 100°C (G' １００ ) versus storage modulus at 120°C (G' １２０ 2. The adhesive sheet according to claim 1, wherein the decrease rate of the viscosity coefficient of the adhesive sheet is 0.3 or less, and the adhesive sheet has a third glass transition temperature that is 15°C or more and less than 50°C, which is lower than the second glass transition temperature.

6. 6. The adhesive sheet according to claim 5, wherein the second base film is a film composed of at least one resin material selected from the group consisting of polyarylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyphenylene sulfide, polysulfone, polyethersulfone, and polyetheretherketone.

7. a first adhesive sheet; a second adhesive sheet; The first adhesive sheet is formed from the adhesive sheet according to any one of claims 1 to 4, A combination of adhesive sheets, wherein the second adhesive sheet includes at least one of the first thermosetting adhesive layer and the second thermosetting adhesive layer.

8. a first adhesive sheet; a second adhesive sheet; The first adhesive sheet is formed from the adhesive sheet according to any one of claims 1 to 4, the second adhesive sheet includes a third thermosetting adhesive layer formed from a cured product of a thermosetting adhesive composition; The thermosetting adhesive composition constituting the third thermosetting adhesive layer contains a polyurethane resin having a reactive functional group including a carboxy group and an acid value of 4.0 mgKOH / g or more and 40 mgKOH / g or less, and a crosslinking agent including a polyfunctional epoxy crosslinking agent, and the third thermosetting adhesive layer has a storage modulus (G') at 100°C １００ ) is 5.0 x 10 ４ Pa or more 6.6×10 ５ Pa or less, and the storage modulus at 100°C (G' １００ ) versus storage modulus at 120°C (G' １２０ ) is 0.3 or less, and the adhesive sheet has a third glass transition temperature that is 15°C or more and less than 50°C lower than the second glass transition temperature.

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