Adhesive agent laminate, adhesive sheet, and combination of adhesive sheets

Abstract

Provided is an adhesive layer which can be stored at room temperature, for with which bonding is completed after thermocompression bonding without undergoing a curing step, and which can suppress bonding defects even if placed in a high-temperature, high-humidity environment following bonding.　An adhesive agent laminate 100 according to the present invention includes, in an alternately layered manner, a first thermosetting adhesive agent layer 14 having a first glass transition temperature and a second thermosetting adhesive agent layer 16 having a second glass transition temperature that is higher than that of the first thermosetting adhesive agent layer 14. The first and second adhesive agent layers each contain a crosslinking agent and a polyurethane-based resin having a reactive functional group. The first adhesive agent layer has a storage elastic modulus at 100°C (G'100) of 5.0×104 Pa-6.6×105 Pa, and a decrease rate of the storage elastic modulus at 120°C (G'120) relative to G'100 of 0.3 or less. The second adhesive agent layer has a G'100 of more than 6.6×105 Pa and not more than 1.0×107 Pa, and a decrease rate of G'120 relative to G'100 of 0.5 or less.

Description

Adhesive laminates, adhesive sheets, and combinations of adhesive sheets

[0001] The present invention relates to adhesive laminates, adhesive sheets, and combinations of adhesive sheets, and more particularly to adhesive laminates including a thermosetting adhesive layer, thermosetting adhesive sheets including a thermosetting adhesive layer, and combinations of such adhesive sheets, which can be used for sealing fuel cells and the like.

[0002] In recent years, fuel cells have attracted considerable attention as a means of mitigating global warming and environmental destruction, as well as as a next-generation power generation system, and are being actively researched and developed. Fuel cells generate energy through the electrochemical reaction of hydrogen and oxygen, and examples include phosphoric acid fuel cells, molten carbonate fuel cells, solid electrolyte 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) and portable power supplies because they can be started at room temperature, are small, and have high output.

[0003] In a polymer electrolyte fuel cell, the fuel gas supplied to the anode electrode, for example, a gas mainly containing hydrogen, is ionized on the electrode catalyst and moves to the cathode electrode via the polymer electrolyte membrane. The electrons generated at the anode electrode are extracted into an external circuit and used as DC electrical energy. On the cathode side, an oxidizing gas, for example, a gas mainly containing oxygen or air, is supplied, and hydrogen ions react with oxygen molecules that have received electrons to produce water.

[0004] Furthermore, fuel cells have a stack structure in which numerous cells are stacked. The cell stack comprises an electrode structure (MEA) having an electrolyte membrane and electrodes, a separator that sandwiches it, and a sealing material (gasket, sub-gasket) for sealing around the electrode members and between adjacent separators. As such a sealing material, hot melt adhesives are known, such as those disclosed in Patent Document 1. As a sealing material other than hot melt adhesives, for example, Patent Document 2 discloses an adhesive sheet using an adhesive resin composition containing a crystalline polyester resin and an amorphous polyester resin.

[0005] International Publication No. 2019 / 216402, Patent Publication No. 2015-017237

[0006] When fuel cells are in use, the adhesive sheets used for sealing are exposed to high temperature and high humidity environments. It is desirable that the adhesive sheets maintain high sealing performance even in such environments. Furthermore, when forming a cell stack while sealing predetermined areas of the MEA with the adhesive sheets, it is preferable that the handling and bonding operations of the adhesive sheets be simple. However, the sealing material in Patent Document 1 is a hot melt adhesive, which has problems with heat resistance and humidity resistance. In addition, although the adhesive sheet in Patent Document 2 is capable of low-temperature bonding, it is usually necessary to store or transport it at low temperatures in order to maintain an uncured or semi-cured state until the bonding process after the sheet is formed. Moreover, since it is necessary to press at high temperatures for a long time during the bonding process with the MEA, the bonding operation takes a long time and there is a risk of thermal damage to the MEA during the bonding operation. Furthermore, after the bonding process, curing processes such as heat treatment and aging are required.

[0007] The object of the present invention is to provide an adhesive laminate containing a thermosetting adhesive layer that can be stored at room temperature, completes bonding without a curing process after heat pressing, and suppresses adhesion defects such as lifting, peeling, and voids even when exposed to high temperature and high humidity environments after bonding, as well as an adhesive sheet containing such an adhesive laminate, and a combination of such adhesive sheets.

[0008] To solve the above problems, the adhesive laminate, adhesive sheet, and combination of adhesive sheets according to the present invention have the following configuration.

[0009] [1] The adhesive laminate according to the present invention is formed from a cured product of a thermosetting adhesive composition, and includes a first thermosetting adhesive layer having a first glass transition temperature and a second thermosetting adhesive layer formed from a cured product of a thermosetting adhesive composition and having a second glass transition temperature higher than the first glass transition temperature, the first thermosetting adhesive layer and the second thermosetting adhesive layer being laminated with each other. The thermosetting adhesive compositions constituting the first thermosetting adhesive layer and the second thermosetting adhesive layer each contain a polyurethane resin having reactive functional groups and a crosslinking agent. The first thermosetting adhesive layer has a storage elastic modulus (G' １００ ) at 100 °C of 5.0×10 ４ Pa or more and 6.6×10 ５ Pa or less, and a decrease rate of the storage elastic modulus (G' １００ ) at 120 °C with respect to the storage elastic modulus (G' １２０ ) at 100 °C of 0.3 or less. Further, the second thermosetting adhesive layer has a storage elastic modulus (G' １００ ) at 100 °C exceeding 6.6×10 ５ Pa and 1.0×10 ７ Pa or less, and a decrease rate of the storage elastic modulus (G' １００ ) at 120 °C with respect to the storage elastic modulus (G' １２０ ) at 100 °C of 0.5 or less.

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

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

[0012] [4] In the aspect of [3] above, 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 carboxy group of the polyurethane resin to the molar amount (b) of the epoxy group of the polyfunctional epoxy-based crosslinking agent may be 1.0 or more and 10.0 or less.

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

[0014] [6] The adhesive laminate may be formed on the surface of the base film to constitute an adhesive sheet. In other words, the adhesive sheet according to the present invention comprises a base film and any of the adhesive laminates described in [1] to [5] above, wherein the adhesive laminate is 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 opposite to the surface of the base film that is in contact with the first thermosetting adhesive layer.

[0015] [7] In the embodiment of [6] above, the base 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 base film, and may also 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 surface of the second base film, and the second base film may sandwich the second thermosetting adhesive layer and the first thermosetting adhesive layer between itself and the base film via the third thermosetting adhesive layer. The thermosetting adhesive composition constituting the third thermosetting adhesive layer contains a polyurethane resin having a reactive functional group and a crosslinking agent, and the third thermosetting adhesive layer has a storage modulus of elasticity (G') at 100°C. １００ ) is 5.0 x 10 ４ Pa or more 6.6×10 ５It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０ The rate of decrease of ) is 0.3 or less, and it may have a third glass transition temperature lower than the second glass transition temperature.

[0017] [9] In the embodiment described in [8] above, the second base 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 embodiment of [8] or [9] above, the third glass transition temperature may be 15°C or more and less than 50°C.

[0019]

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

[0020]

[12] Alternatively, a combination of adhesive sheets according to the present invention includes a first adhesive sheet and a second adhesive sheet, wherein the first adhesive sheet includes any of the adhesive laminates described in [1] to [5] above, and the second adhesive sheet includes a third thermosetting adhesive layer formed from a cured product of a curable adhesive composition. The thermosetting adhesive composition constituting the third thermosetting adhesive layer contains a polyurethane resin having a reactive functional group and a 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 It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０The rate of decrease of ) is 0.3 or less, and it has a third glass transition temperature that is lower than the second glass transition temperature.

[0021] An adhesive laminate according to the present invention having the configuration described in [1] above, or an adhesive sheet in which a base film is placed on one side of the adhesive laminate and the other side is exposed, can complete adhesion after heating and pressing without undergoing a curing process, because the first and second thermosetting adhesive layers, which have different glass transition temperatures, have the predetermined material composition and physical properties described above. When the adhesive laminate or adhesive sheet according to the present invention is used to seal the periphery of a solid polymer electrolyte membrane in a fuel cell, the adhesive laminate or adhesive sheet, in which the first and second thermosetting adhesive layers have the predetermined material composition and physical properties described above, can be heated and pressed together with the solid polymer electrolyte membrane to complete adhesion after heating and pressing without undergoing a curing process, thereby sealing the periphery of the solid polymer electrolyte membrane in the fuel cell. Furthermore, even when placed in a high-temperature and 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 above-mentioned adhesive laminate or adhesive sheet is particularly suitable for applications that take advantage of the fact that it consists of two layers with different physical properties, acting as a thermosetting adhesive layer. For example, depending on the first and second glass transition temperatures, the adhesive laminate or adhesive sheet may be arranged such that the object to be bonded or the environment to which the first and second thermosetting adhesive layers are exposed is suitable for the desired bonding form.

[0023] For example, if there is a difference in temperature and 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 such that a second thermosetting adhesive layer having a second glass transition temperature higher than the first glass transition temperature is located in the direction 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 bonded, the adhesive laminate or adhesive sheet may be arranged such that the thermosetting adhesive layer having the physical properties most suitable for bonding to the object, among the first and second thermosetting adhesive layers which have mutually different physical properties such as glass transition temperatures, comes into contact with the object.

[0025] As described above, by arranging the first and second thermosetting adhesive layers of the adhesive laminate or adhesive sheet in directions suitable for the environment and object, adhesion defects such as lifting, peeling, and voids can be further suppressed even in high-temperature and high-humidity environments, and better adhesion can be effectively maintained. Therefore, the adhesive laminate according to the present invention, or the adhesive sheet containing the adhesive laminate, can be suitably used as a material to provide adhesion in locations that are subject to high temperature 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 adheres to the object, the adhesive laminate or adhesive sheet may be arranged 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 arranging the adhesive laminate or adhesive sheet in this way, the stickiness of the exposed adhesive surface at room temperature is further reduced, preventing foreign matter from adhering to the adhesive surface. In addition, even if foreign matter adheres to the adhesive surface, its removal becomes easier, improving the workability of handling the adhesive laminate or adhesive sheet.

[0027] As described in [2] above, when the first glass transition temperature of the first thermosetting adhesive layer is 15°C or higher and less 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 defects such as lifting, peeling, and voids in high-temperature and high-humidity environments can be more effectively suppressed while maintaining the adhesion of the second thermosetting adhesive layer to the object to be bonded, such as the electrolyte membrane of a fuel cell. In addition, the stickiness of the second thermosetting adhesive layer at room temperature is effectively suppressed. As a result, even if the adhesive surface of the second thermosetting adhesive layer is exposed, the adhesion of foreign matter to it can be suppressed, and even if foreign matter adheres, it can be easily removed. Therefore, by arranging the adhesive laminate or adhesive sheet so that the second thermosetting adhesive layer is facing an environment where foreign matter is likely to adhere, the workability of bonding can be improved.

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

[0029] As in the embodiment described in [3] above, when the reactive functional group of the polyurethane resin includes a carboxyl group and the crosslinking agent includes a polyfunctional epoxy crosslinking agent, the reactivity between the polyurethane resin and the crosslinking agent is increased in both the first thermosetting adhesive layer and the second thermosetting adhesive layer.

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

[0031] As described in [5] above, when the thickness of the second thermosetting adhesive layer, which has a higher glass transition temperature than the first thermosetting adhesive layer, is made thicker than the thickness of the first thermosetting adhesive layer, the high heat and humidity resistance, which is a physical property of the thicker second thermosetting adhesive layer, is strongly exhibited. Therefore, when a laminated sheet formed by laminating the first and second thermosetting adhesive layers is placed in a high-temperature, high-humidity environment, the resistance of the adhesive laminate to the high-temperature, high-humidity environment can be increased. In particular, by setting the thickness of the first thermosetting adhesive layer to 1 μm or more and 6 μm or less, the adhesion of the first thermosetting adhesive layer can be ensured to a high degree, and the resistance to the high-temperature, high-humidity environment can be increased. Furthermore, by setting the thickness of the second thermosetting adhesive layer to 8 μm or more and 30 μm or less, the adhesion of the second thermosetting adhesive layer can be ensured to a high degree, and the adhesive laminate or adhesive sheet can be formed to be thin.

[0032] The adhesive laminate of the present invention, having the configuration of any of the above [1] to [5], and comprising the first and second thermosetting adhesive layers, may be formed on one surface of a base film and used as an adhesive sheet. An adhesive sheet having the configuration of above [6] is also one such form.

[0033] In adhesive sheets equipped with a base film, including films made from the predetermined resin materials listed in the embodiment of [7] above, compared to laminate sheets containing a thermosetting adhesive layer without a base film, the surface of the thermosetting adhesive layer covered by the base film is not exposed to the surface of the laminate, and it does not become sticky. This improves the handling of the laminate sheet and makes it easier to perform processes such as placing it on the object to be bonded. Examples of objects to be bonded include fuel cell electrode membranes (MEAs) composed of electrolyte membranes and catalyst layers.

[0034] When constructing an adhesive sheet using an adhesive laminate, as described above, the direction in which the first thermosetting adhesive layer and the second thermosetting adhesive layer are arranged can be appropriately selected depending on the environment and the object to be bonded, and the adhesive laminate can be formed on the surface of the base film. In particular, the adhesive sheet having the configuration of [6] above has the first thermosetting adhesive layer on the surface of the base film, and the second thermosetting adhesive layer is exposed on the surface opposite to the surface of the base film that is in contact with the first thermosetting adhesive layer. In this case, by utilizing the fact that the first and second thermosetting adhesive layers, which are composed of cured products of the thermosetting adhesive composition, have the predetermined materials and physical properties, and in particular that the glass transition temperature of the second thermosetting adhesive layer is higher than that of the first thermosetting adhesive layer, excellent adhesive properties can be obtained in both the bonding of the adhesive laminate to the base film and the bonding of the adhesive laminate to the object to be bonded. In other words, by forming the first thermosetting adhesive layer on the surface of the base film, good adhesion is achieved between this first thermosetting adhesive layer and the base film. On the other hand, by using the second thermosetting adhesive layer, which has high humidity and heat resistance, in contact with the object to be bonded and using it for bonding the object, adhesion defects such as lifting, peeling, and voids of the adhesive sheet can be effectively suppressed even in high temperature and high humidity environments.

[0035] As in the configuration described in [8] above, the adhesive sheet may further include a second base film. Alternatively, the adhesive sheet may further include a third thermosetting adhesive layer formed from a cured product of a thermosetting adhesive composition as part of the thermosetting adhesive layer, and this third thermosetting adhesive layer may have the predetermined material composition and physical properties described above. In this case, the third thermosetting adhesive layer is formed on one surface of the second base film, and the second base film may sandwich the second thermosetting adhesive layer and the first thermosetting adhesive layer between itself and the base film via the third thermosetting adhesive layer. In other words, the second base film may be laminated on the surface of the second thermosetting adhesive layer opposite to the surface adjacent to the first thermosetting adhesive layer, via the third thermosetting adhesive layer. In such a configuration, the surface of the second thermosetting adhesive layer covered by the second base film is not exposed, preventing the adhesion of foreign matter, and allowing foreign matter to be easily removed even if it adheres. Furthermore, the handling of the adhesive sheet is improved, making it easier to perform processes such as placing it on the object to be bonded. As the second base film, a film made of the predetermined resin material listed in the embodiments of [9] above can be used, similar to the base film described above.

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

[10] above, the adhesion between the third thermosetting adhesive layer and the second substrate film is improved by forming the third thermosetting adhesive layer in contact with the surface of the second substrate film.

[0037] The combination of adhesive sheets having the configurations described in

[11] and

[12] above comprises a first adhesive sheet containing an adhesive laminate according to 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 having different glass transition temperatures, and these thermosetting adhesive layers have the predetermined material configuration and physical properties described above. 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 heating and pressing them together, bonding can be completed without going through a curing process after heating and pressing. This combination of adhesive sheets 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 thermosetting adhesives constituting the first and second adhesive sheets can be selected so that the object to be bonded or the environment to which each of these thermosetting adhesive layers is exposed is suitable for the desired bonding form. As a result, the combination of adhesive sheets sandwiching the object to be bonded can suppress adhesion defects such as lifting, peeling, and voids even when exposed to high temperature and high humidity environments, and can effectively maintain good adhesion. Therefore, the combination of adhesive sheets according to the present invention can be suitably used as a sealing material for fuel cells.

[0038] This is a perspective view of an adhesive sheet according to one embodiment of the present invention. (a) is a perspective view of an MEA with a sub-gasket made of the adhesive sheet of Figure 1 installed. (b) is a cross-sectional view of the perspective view of (a) cut by a plane perpendicular to the y-axis direction. (a) is a perspective view of an MEA with a sub-gasket made of the adhesive sheet according to one embodiment of the present invention installed. (b) is a cross-sectional view of the perspective view of (a) cut by a plane perpendicular to the y-axis direction. This is a perspective view showing a second adhesive sheet that constitutes the adhesive sheet of Figure 3. (a) is a perspective view showing an MEA with a sub-gasket made of the adhesive sheet according to a modified form. (b) is a cross-sectional view of the perspective view of (a) cut by a plane perpendicular to the y-axis direction.

[0039] The following describes adhesive laminates, adhesive sheets, and combinations of adhesive sheets according to embodiments of the present invention. An adhesive sheet according to an embodiment of the present invention is constructed by including an adhesive laminate according to an embodiment of the present invention. Furthermore, a combination of adhesive sheets according to an embodiment of the present invention is constructed by including an adhesive sheet according to an embodiment of the present invention. In the following, unless otherwise specified, various physical properties are measured at room temperature (approximately 23°C) in the atmosphere.

[0040] [1] Adhesive Sheet and Adhesive Laminate <Structure of Adhesive Sheet> Figure 1 is a perspective view of an adhesive sheet 100 according to one embodiment of the present invention. As shown in Figure 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 the first adhesive layer 14. The first adhesive layer 14 and the second adhesive layer 16 constitute 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] The use and shape of the adhesive sheet 100 are not particularly limited, but Figure 1 shows a case where the adhesive sheet 100 constitutes a sub-gasket of a fuel cell. In other words, an opening W1 is provided in the central part of the adhesive sheet 100 as a through-hole-like region that penetrates the adhesive sheet 100. As shown in Figures 2(a) and 2(b), the adhesive sheet 100 is used together with an electrolyte membrane / electrode structure (hereinafter referred to as MEA) 3, in which electrodes 3e are arranged on both sides of an electrolyte membrane 3m, and functions as a sealing material that seals the periphery of the MEA 3. Generally, a solid polymer electrolyte membrane is used as the electrolyte membrane in the MEA, and these can also be used here. The polymer electrolyte contained in the solid polymer electrolyte membrane can be an electrolyte having proton conductivity. For example, fluorine-based polymer electrolytes and hydrocarbon-based polymer electrolytes can be used as polymer electrolytes. For fluorine-based polymer electrolytes, polymer electrolytes having a tetrafluoroethylene skeleton can be used. Examples of polymer electrolytes having a tetrafluoroethylene skeleton include Nafion from DuPont, Flemion from Asahi Glass, Aciplex from Asahi Kasei, and Gore-Select from Gore Japan (all are registered trademarks). Examples of hydrocarbon polymer electrolytes include sulfonated polyether ketones, sulfonated polyethersulfones, sulfonated polyetherethersulfones, sulfonated polysulfides, and sulfonated polyphenylenes.

[0042] <Base Film> The specific composition of the base film 12 is not particularly limited. Examples of base film 12 include polymer films and glass films. The thickness of the base film 12 is not particularly limited, but from the viewpoint of handling, it is preferably in the range of 12 μm to 500 μm. More preferably, the thickness of the base film 12 is 38 μm or more, even more preferably 50 μm or more, while on the other hand, it is preferably 200 μm or less, and even more preferably 100 μm or less. In general, "film" refers to something with a thickness of less than 0.25 mm, but even if the thickness is 0.25 mm or more, if it is flexible, it is included in "film".

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

[0044] The base film 12 may consist of a single layer comprising one or more of the above-mentioned polymer materials, or it may consist of two or more layers, such as a layer comprising one or more of the above-mentioned polymer materials and a layer comprising one or more of different polymer materials.

[0045] <Adhesive Layers> 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 base 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 compositions (hereinafter sometimes simply referred to as adhesive compositions) that constitute each adhesive layer 14 and 16 are thermosetting, and the adhesive sheet 100 comprising the first adhesive layer 14 and the second adhesive layer 16 functions as a thermosetting adhesive sheet. Before use, the first adhesive layer 14 and the second adhesive layer 16 of the adhesive sheet 100 are cured while leaving some uncured material (in a semi-cured state). When bonding to an object to be bonded (adhesion object), such as MEA3, the second adhesive layer 16 is placed on top of the MEA3 as shown in Figure 2(b), and the adhesive laminate 30 consisting of the first adhesive layer 14 and the second adhesive layer 16 is heated and pressed together to bond the adhesive sheet 100 to the MEA3. 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 the need for low-temperature storage. In this specification, the concept of adhesion includes tackiness, that is, pressure-sensitive adhesion, where adhesion occurs between the object to be bonded and the object to be bonded by applying pressure, even without heating.

[0047] (Characteristics of the adhesive layer) (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 viewpoint, 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, sufficient initial peeling force can be obtained between the first adhesive layer 14 and the base film 12 at relatively low temperatures such as room temperature. From this viewpoint, 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 object to be bonded, such as MEA3, can be made 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, even if the adhesive sheet 100 is placed in a high-temperature, high-humidity environment, adhesion defects such as lifting, peeling, and voids between the second adhesive layer 16 and the object to be bonded, such as MEA3, can be effectively suppressed. 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 suppresses the adhesion of foreign matter to the surface of the second adhesive layer 16, and also makes it easier to remove any foreign matter that does adhere. For example, when the second adhesive layer 16 is kept exposed for bonding to an object such as MEA3, by designing the second adhesive layer 16 to have a second glass transition temperature of 50°C or higher through the selection of specific constituent materials, the adhesion of foreign matter to the exposed surface can be suppressed, and any foreign matter that does adhere can be easily removed. In this way, the handling of the adhesive sheet 100 is improved by setting the second glass transition temperature to 50°C or higher.

[0050] As described above, it is preferable to set the glass transition temperature of the first adhesive layer 14 to 15°C or more and less than 50°C, and the glass transition temperature of the second adhesive layer 16 to 50°C or more and 100°C or less, to form the first adhesive layer 14 on the surface of the base film 12, and then directly form the second adhesive layer 16 on that surface. In the case of a sub-gasket formed using an adhesive sheet 100 configured in this way, by overlapping the electrolyte membrane 3m of MEA3 on the exposed surface of the second adhesive layer 16 and heat-pressing it, the adhesion between the base film 12 and MEA3 can be improved, and adhesion defects such as lifting, peeling, and voids can be more effectively suppressed even when the MEA3 with the sub-gasket is placed in a high-temperature, high-humidity environment.

[0051] (2) Shear storage modulus of the first adhesive layer 14 at 100°C (G' １００ ) is 5.0 x 10 ４ It is Pa or higher. 5.0 × 10 ４ If the pressure is Pa or higher, the first adhesive layer 14 is moderately cured even before heat pressing, so bonding can be completed with short pressing time. Furthermore, from the viewpoint of further enhancing this effect, the G' of the first adhesive layer 14 １００ Preferably 7.0 × 10 ４ Pa or higher, more preferably 1.0 × 10 ５ It is Pa or higher. Also, the G' of the first adhesive layer 14 １００ 6.6 × 10 ５ It is less than or equal to Pa. 6.6 × 10５ If the pressure is below Pa, the first adhesive layer 14 can maintain its elasticity even at high temperatures, thus providing good adhesion. G' of the first adhesive layer 14 １００ Preferably 3.0 × 10 ５ It is less than or equal to Pa.

[0052] The shear storage modulus (G') of the second adhesive layer 16 at 100°C １００ ) is 6.6 × 10 ５ It is greater than Pa. 6.6 × 10 ５ If Pa is greater than the target material, the bonding process with MEA3 and other materials can be completed without going through a curing process after heating and pressing. Furthermore, from the viewpoint of further enhancing this effect, the G' of the second adhesive layer 16 １００ Preferably 7.0 × 10 ５ It is Pa or higher. Also, the G' of the second adhesive layer 16 １００ is 1.0 × 10 ７ It is less than or equal to Pa. 1.0 × 10 ７ If the pressure is below Pa, the second adhesive layer 16 can maintain its elasticity even at high temperatures, thus achieving good adhesion. １００ Preferably 5.0 × 10 ６ Pa or less, more preferably 3.0 × 10 ６ It is less than or equal to Pa.

[0053] The shear storage modulus (G') of the first adhesive layer 14 at 100°C １００ The shear storage modulus (G') at 120°C relative to ) １２０ The rate of decrease of (G') is 0.3 or less. If this rate of decrease 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 and high humidity environment. Furthermore, from the viewpoint of further enhancing this effect, the rate of decrease is preferably 0.25 or less, more preferably 0.2 or less. There is no particular limit to the lower limit of the rate of decrease, but it is usually -0.1 or more, preferably 0 or more. Note that the rate of decrease of (G') is 0.3 or less. １００ - G' １２０ ) / G' １００ It can be calculated using the following formula.

[0054] The shear storage modulus (G') of the second adhesive layer 16 at 100°C １００ The shear storage modulus (G') at 120°C relative to ) １２０ The rate of decrease of the second adhesive layer 16 is 0.5 or less. If this rate of decrease 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 and high humidity environment. Furthermore, from the viewpoint of further enhancing this effect, the rate of decrease is preferably 0.45 or less, more preferably 0.4 or less. There is no particular limit to the lower limit of the rate of decrease, but it is usually -0.1 or more, 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 ) is not particularly limited, but both are 5.0 x 10 ４ It is preferable that the pressure be Pa or higher. 5.0 × 10 ４ If the pressure is Pa or higher, it becomes easier to maintain adhesive strength even in high-temperature environments, thus further improving heat and humidity resistance. Furthermore, from the viewpoint of further enhancing this effect, the G' of adhesive layers 14 and 16 １２０ More preferably, 7.0 × 10 ４ Pa or higher, more preferably 1.0 × 10 ５ It is Pa or higher. Also, the G' of adhesive layers 14 and 16 １２０ is 1.0 × 10 ７ It is preferable that it be Pa or less. 1.0 × 10 ７ If the pressure is below Pa, the adhesive layers 14 and 16 can maintain their elasticity even at high temperatures, thus providing good adhesion. G' of adhesive layers 14 and 16 １２０ More preferably 5.0 × 10 ６ Pa or less, more preferably 3.0 × 10 ６ It is less than or equal to Pa.

[0056] As described above, the first adhesive layer 14 and the second adhesive layer 16 constituting the adhesive laminate 30 have the predetermined glass transition temperature and storage modulus, so that the first adhesive layer 14 exhibits high adhesion at relatively low temperatures, such as near room temperature, while the second adhesive layer 16 exhibits high adhesion in high-temperature and high-humidity environments. Therefore, as the main adhesion mechanism of the adhesive laminate 30, the first adhesive layer 14 acts to provide sufficient adhesion when bonding to objects where sufficient adhesion cannot be obtained with the second adhesive layer 16 at room temperature, for example, when bonding to polymer materials used as the base film 12, while the second adhesive layer 16 is thought to act to maintain high adhesion in high-humidity and high-temperature environments.

[0057] As described above, the second adhesive layer 16 has a higher glass transition temperature than the first adhesive layer 14, and its shear storage modulus (G') at 100°C is higher. １００ ) is also higher. Such differences in the physical properties of the first adhesive layer 14 and the second adhesive layer 16 can be achieved by selecting the component composition of the adhesive composition constituting the first adhesive layer 14 and the second adhesive layer 16. For example, in the adhesive composition constituting the second adhesive layer 16, a polyurethane resin with a higher glass transition temperature can be used than that of the first adhesive layer 14. Means of increasing the glass transition temperature of polyurethane resin include using compounds with a high glass transition temperature as polyisocyanates or polyols that constitute the polyurethane resin, increasing the molecular weight, introducing a ring structure into the main chain, and increasing the amount of ring structure introduced. These means 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 temperature required to increase the free volume by heating, thus increasing the glass transition temperature of the polyurethane resin. In addition, adding fillers to the adhesive composition is also effective in increasing the glass transition temperature.

[0058] (3) Thickness of the layers 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 the physical properties of the adhesive laminate 30 as a whole. The first adhesive layer 14 has a low glass transition temperature and may have difficulty withstanding high humidity and high temperature environments while maintaining its strength, whereas the second adhesive layer 16 has a high glass transition temperature and excellent resistance to humidity and heat. Reflecting this, the adhesive laminate 30 as a whole, with the second adhesive layer 16 formed to be thicker, can be made to have excellent resistance to humidity and heat.

[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 bonded, such as MEA3. 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 fuel cells.

[0061] (4) Other Characteristics The gel fraction of the first adhesive layer 14 and the second adhesive layer 16 is not particularly limited, but it is preferable that both adhesive layers have a gel fraction of 70% by mass or more. A gel fraction of 70% by mass or more means that the crosslinking reaction of the first and second adhesive layers 14 and 16 is progressing. Therefore, in the bonding process with the object to be bonded, such as MEA3, bonding can be completed without going through a curing process after heating and pressing. And the bond with the object to be bonded becomes strong in a short time. In addition, the storage stability of the adhesive layers 14 and 16 is excellent, and adhesion defects such as lifting, peeling, and voids can be suppressed even when placed in a high temperature and high humidity environment. Furthermore, since the adhesive layers 14 and 16 can easily remain in an uncured or semi-cured state until the bonding process, it is particularly suitable for storing the adhesive sheet 100 stably at room temperature without low temperature storage. The gel fraction is preferably 80% by mass or more, more preferably 85% by mass or more, and the upper limit is 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 the first adhesive layer 14, the adhesive strength between the base film 12 and the object to be bonded, such as MEA3, 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) The adhesive compositions constituting the first adhesive layer 14 and the second adhesive layer 16 contain a polyurethane resin having reactive functional groups, as described above. By using a polyurethane resin, each adhesive layer 14 and 16 will have appropriate flexibility and heat and humidity resistance. A polyurethane resin is a general term for compounds that contain 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 raw materials. For example, the type of main chain and side chains that make up the molecule changes physical properties such as flexibility and heat and humidity resistance. For example, increasing the molecular weight raises the glass transition temperature. Also, by making the main chain and side chains highly resistant to hydrolysis, the hydrolysis resistance of the polyurethane resin as a whole can be improved. Therefore, by selecting the raw materials of the polyurethane contained in the first adhesive layer 14 and the second adhesive layer 16, taking into account the glass transition temperature and hydrolysis resistance, etc., according to the environment to which each adhesive layer 14 and 16 are exposed and the object to be bonded, the first adhesive layer 14 and the second adhesive layer 16 can be made to have suitable flexibility, adhesion, heat and humidity resistance, etc.

[0065] For example, when a sub-gasket for a fuel cell is constructed using the adhesive sheet 100 according to this embodiment, the second adhesive layer 16 is heat-pressed onto the electrolyte membrane 3m of the MEA3 and exposed to a hotter and more humid environment than the first adhesive layer 14. Therefore, in terms of heat resistance and hydrolysis resistance, the second adhesive layer 16 is more important than the first adhesive layer 14. For this reason, in the physical properties of the second adhesive layer 16, heat resistance should be prioritized, and a polyurethane resin should be constructed by selecting main chains and side chains of a type that have high hydrolysis resistance and glass transition temperature. Examples of polyurethane resins include ester-based polyurethane resins using polyols having ester bonds (-COO-) in their molecular structure, ether-based polyurethane resins using polyols having ether bonds (-O-) in their molecular structure, and polycarbonate-based polyurethane resins using polyols having carbonate ester bonds (-OCOO-) in their molecular structure. Among these, it is preferable to use a polycarbonate-based polyurethane resin or an ether-based polyurethane resin with a relatively low ester bond content to have high hydrolysis resistance (heat resistance). Furthermore, the glass transition temperature can be adjusted by the type of polyisocyanate and low molecular weight diol that form the hard segment of the polyurethane resin, and the type 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 resin may have two or more isocyanate groups in one molecule. From the viewpoint of the glass transition temperature, flexibility, and heat and humidity resistance 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 isocyanates constituting the polyurethane resin include aromatic, aliphatic, aromaticaliphatic, and alicyclic isocyanates. Examples of aromatic isocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyli isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylenedi isocyanate, 1,4-phenylenedi isocyanate, tolylene diisocyanate, xylylene diisocyanate, and m-tetramethylxylylene diisocyanate. Examples of aliphatic isocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropyl 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 their molecules, and examples 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(isocyanate-methyl)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 include a large amount of aromatic diisocyanates such as benzene-1,3-diisocyanate in the adhesive layer, and when flexibility is required, aliphatic diisocyanates such as hexamethylene diisocyanate may be used. 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. In addition, an isocyanate group-terminated prepolymer obtained by reacting a polyol with an excess of polyisocyanate may be used as an intermediate for polyurethane resins.

[0069] The polyol constituting the polyurethane resin may have two or more hydroxyl groups in one molecule. From the viewpoint of the glass transition temperature, flexibility, and heat and humidity resistance of the first adhesive layer 14 and the second adhesive layer 16, diols or triols are preferred, and diols are more preferred.

[0070] In this embodiment, the 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-hexaneglycol, 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 tricyclodecane. Examples include alicyclic glycols such as diols, tricyclodecanedimethylol, spiroglycols, hydrogenated bisphenol A, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A; aromatic glycols such as paraxylene glycol, metaxylene glycol, orthoxylene glycol, 1,4-phenylene glycol, ethylene oxide adducts of 1,4-phenylene glycol, bisphenol A, bisphenol A-ethylene oxide adduct polyols, bisphenol A-propylene oxide adduct polyols, and bisphenol A-ethylenepropylene copolymer polyols; and polyether diols, polyester diols, polyether ester diols, polycarbonate diols, and polyolefin diols.

[0071] Among those listed above, polyether diols 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-hexaneglycol, 2,2,4-trimethyl-1,3 Examples of polyether ester diols include those obtained by polycondensation with (such as 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 to low molecular weight diols, such as polycaprolactone, polymethylvalerolactone, etc. Examples of polyether ester diols include those obtained by ring-opening polymerization of a cyclic ether to a polyester diol, and those obtained by polycondensation of a polyether diol and 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 de-dioling or de-alcoholizing a low molecular weight diol with an alkylene carbonate or dialkyl carbonate. Examples of polyolefin diols include polybutadiene polyol, hydrogenated polybutadiene polyol, and polyisoprene polyol.

[0072] As polyols constituting the polyurethane resin, those listed here can be appropriately selected and used for each adhesive layer, taking into consideration the moisture and heat resistance and glass transition temperature of the first adhesive layer 14 and the second adhesive layer 16, respectively. For example, polyols that contain many double bonds and have a ring structure rather than an aliphatic structure tend to have higher glass transition temperatures. The glass transition temperature of a polyol can be obtained, for example, by measuring its viscoelastic behavior using a dynamic viscoelasticity measuring device and determining the temperature at which the loss tangent (tanδ) is maximum. Polyols can be used individually or in combination of two or more types.

[0073] The polyurethane resin may also be a polyurethane urea resin having urea bonds, from the viewpoint of improving heat resistance, water resistance, and impact resistance. The polyurethane urea resin has a structure in which an amine is bonded to a urethane resin having isocyanate groups at the ends. The amine may be any amine having two or more amino groups in one molecule, and from the viewpoint of the glass transition temperature, flexibility, and heat and moisture resistance of the first adhesive layer 14 and the second adhesive layer 16, diamine or triamine is preferred, and diamine is more preferred.

[0074] Known amines can be used as amines, for example, 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 amines obtained by converting the carboxyl group of a dimer acid to an amino group. For example, amines that contain many double bonds and have a ring structure rather than an aliphatic structure tend to have higher glass transition temperatures. 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 moisture and heat resistance 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 better.

[0076] The reactive functional groups in a polyurethane resin are not particularly limited as long as they are functional groups that can react with a crosslinking agent to form bonds. 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 viewpoint of availability and reactivity with crosslinking agents. In a polyurethane resin, the reactive functional groups may be directly bonded to the polyurethane chain, such as in the polyol moiety, or introduced into side chains bonded to the polyurethane chain.

[0077] When the polyurethane resin has a carboxyl group, the acid value of the polyurethane resin is preferably 4.0 mg KOH / g or higher and 40 mg KOH / g or lower. 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. It is even more preferable if the acid value is 6.0 mg KOH / g or higher and 8.0 mg KOH / g or higher. On the other hand, it is even more preferable if the acid value is 30 mg KOH / g or lower and 20 mg KOH / g or lower.

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

[0079] Epoxy crosslinking agents are compounds that have two or more epoxy groups as reactive groups in a single molecule. 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-xylenediamine, 1,1,2,2-tetrakis(3-glycidyloxyphenyl)ethane, diglycidylaniline, diamineglycidylamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether Examples 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, diglycidyl adipate ester, diglycidyl o-phthalate 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 in one molecule are preferred from the viewpoint of high adhesion and heat resistance.

[0081] The crosslinking agent in the adhesive composition is preferably a liquid with a viscosity of 10 mPa·s or more at 25°C, or a solid with 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. On the other hand, 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 epoxy crosslinking agents) is preferably 50 g / eq or more, more preferably 100 g / eq or more, and even more preferably 150 g / eq or more. On the other hand, 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. If the molecular weight of the crosslinking agent and the content of the reactive group in each of the first adhesive layer 14 and the second adhesive layer 16 are within the above range, good adhesion and moisture and heat resistance can be obtained between the object to be bonded, such as MEA3, and the base film 12.

[0082] The crosslinking agent content in the adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, particularly preferably 5 parts by mass or more, 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, per 100 parts by mass of polyurethane resin. If the crosslinking agent content in each of the first adhesive layer 14 and the second adhesive layer 16 is within the above range, good adhesion and moisture and heat resistance can be obtained between the object to be bonded, such as MEA3, and the base film 12.

[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 of reactive functional groups of the polyurethane resin, such as carboxyl groups (a), to the molar amount of reactive groups of the crosslinking agent, such as epoxy groups of the epoxy crosslinking agent (b), is preferably 1.0 or higher, more preferably 1.1 or higher, and even more preferably 1.3 or higher. On the other hand, the molar ratio is preferably 10.0 or lower, more preferably 8.0 or lower, and even more preferably 7.0 or lower. If the molar ratio is 1.0 or higher, a sufficient crosslinking density can be obtained, and the storage modulus can be made suitable. If the molar ratio is 10.0 or lower, the adhesion to the object to be bonded is increased in both the first adhesive layer 14 and the second adhesive layer 16, peeling and the like are effectively suppressed, and durability is improved.

[0084] (Other Additives) In addition to polyurethane resin and crosslinking agent, other additives may be added to the adhesive composition constituting the first adhesive layer 14 and the second adhesive layer 16. Examples of other additives include crosslinking accelerators, crosslinking retarders, fillers, plasticizers, softeners, release aids, silane coupling agents, dyes, pigments, colorants, fluorescent whitening agents, antistatic agents, wetting agents, surfactants, thickeners, antifungal agents, preservatives, oxygen absorbers, ultraviolet absorbers, antioxidants, near-infrared absorbers, water-soluble quenchers, fragrances, metal deactivators, nucleating agents, alkylating agents, flame retardants, lubricants, processing aids, etc. These are appropriately selected and added depending on the application and purpose of the adhesive sheet 100, that is, the specific type and composition of the object to which the adhesive sheet 100 is to be bonded, such as MEA3, and the usage environment.

[0085] Of the additives mentioned above, the fillers are blended for purposes such as improving moisture and heat resistance, adjusting the elastic modulus, and making the adhesive sheet 100 tack-free to improve the removal of adhering foreign matter. The fillers may be either inorganic or organic fillers. Examples of inorganic fillers include inorganic particles such as silica, alumina, calcium carbonate, talc, and clay. Examples of organic fillers include resin particles made from 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 for Manufacturing Thermosetting Adhesive Compositions> The adhesive compositions constituting the first adhesive layer 14 and the second adhesive layer 16 can each be manufactured by mixing a polyurethane resin, a crosslinking agent, and other additives as needed. The adhesive composition may also be a solution diluted with a suitable solvent to achieve 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 individually or in mixtures of two or more. The amount of solvent used is not particularly limited and should be adjusted as appropriate so that the adhesive composition has a viscosity suitable for coating. However, from the viewpoint of coating properties, for example, 1% to 90% by mass of the total diluted solution is preferred, more preferably 10% to 80% by mass, and even more preferably 20% to 70% by mass.

[0088] <Method for Manufacturing Adhesive Sheets> 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 surface of a base film 12, and then a drying and curing process is carried out by 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, and then a drying and curing process is carried out by heat treatment. After that, the adhesive sheet 100 can be formed by methods such as curing (aging) as necessary. This method of sequentially forming the first adhesive layer 14 and the second adhesive layer 16 through drying and curing, and further curing as necessary, is preferable from the viewpoint of adhesion between the base film 12 and the first adhesive layer 14, and adhesion between the first adhesive layer 14 and the second adhesive layer 16.

[0089] 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 can be used for coating the adhesive composition, as well as various printing methods such as inkjet printing, offset printing, screen printing, and flexographic printing. Furthermore, before coating the adhesive composition constituting the first adhesive layer 14, the surface of the base film 12 may be subjected to surface treatments such as corona treatment, plasma treatment, hot air treatment, ozone treatment, and ultraviolet treatment. In particular, corona treatment is preferable from the viewpoint of adhesion between the base film 12 and the first adhesive layer 14.

[0090] The drying and curing process is not particularly limited as long as it removes the solvents used in each adhesive composition and allows it to cure, but it is preferable to carry it 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. It is preferable to leave some uncured material (semi-cured) in each adhesive composition.

[0091] Curing can be performed for approximately 3 to 20 days at 40°C to 80°C, preferably for approximately 4 to 7 days at 60°C. The crosslinking reaction proceeds by performing the above drying and curing steps, and the curing step as needed. At this time, it is preferable to set the curing conditions so that the gel fraction of the first adhesive layer 14 and the second adhesive layer 16 is 70% by mass or more. This curing step makes it possible to strengthen the adhesion of the adhesive sheet 100 to the object to be bonded, such as MEA3, in the bonding step by short-time heat pressing. As described above, the stickiness of the exposed portion of the second adhesive layer 16 at room temperature is mitigated as the glass transition temperature increases. Therefore, by adjusting the glass transition temperature by selecting the resin and other components that make up the adhesive composition of the second adhesive layer 16, it is possible to suppress the adhesion of foreign matter to the second adhesive layer 16 and to easily remove any foreign matter that does adhere.

[0092] The adhesive sheet 100 may have a release sheet on the surface of the second adhesive layer 16 until it is used. 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 the object to be bonded. Examples of release sheets include paper such as glassine paper, coated paper, laminated paper, and various plastic sheets coated with a release agent such as silicone resin. If the second adhesive layer 16 is not tacky, a release sheet with tackiness on at least one side may be used. As for the plastic sheet used for the release sheet, those listed as the base film 12 can be used as appropriate. There are no particular restrictions on the thickness of the release sheet, but it is usually 10 μm to 150 μm.

[0093] <Method of using the adhesive sheet> The use of the adhesive sheet 100 is not particularly limited, but as described above, it can be suitably used, for example, as a sealing material for fuel cells, and especially as a sub-gasket for the MEA3. For example, as shown in Figures 2(a) and 2(b), the adhesive sheet 100 and the MEA3 are laminated by bringing the surface of the adhesive sheet 100 in which the second adhesive layer 16 is exposed into contact with the MEA3, particularly the area where the solid electrolyte membrane 3m is exposed. At this time, the adhesive sheet 100 is positioned so that the solid electrolyte membrane 3m of the MEA3 faces the opening W1 of the adhesive sheet 100 via the electrode 3e as appropriate. Then, the adhesive sheet 100 is heated while pressure is applied in the direction of pressing it against the MEA3, and the second adhesive layer 16 is bonded to the MEA3. Examples of pressure include 0.5 to 10 MPa, heating temperature includes 130 to 230°C, and pressurizing and heating time includes 3 to 60 seconds. Furthermore, after the heat-pressing process, it can be used in subsequent processes such as lamination of power generation cells without undergoing hardening 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, which includes 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 opposite to the surface of the base film 12 that the first adhesive layer 14 is in contact with. By using the base film 12 in this way, the handling of the adhesive sheet 100 is improved, and operations such as lamination with MEA3 are made easier. However, the adhesive laminate 30 according to the embodiment of the present invention is not limited to being a component of the adhesive sheet 100 together with the base film 12, as long as it is configured to include 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 that case, the self-supporting adhesive laminate 30 is used in contact with the object to be bonded, with the surface of the first adhesive layer 14 and / or the surface of the second adhesive layer 16. Furthermore, when the adhesive laminate 30 together with the base film 12 constitutes an adhesive sheet 100, in that adhesive sheet 100, the adhesive laminate 30 does not need to be in contact with the base film 12 with the surface of the first adhesive layer 14 and the second adhesive layer 16 exposed; it may be in contact with the base film 12 with the surface of the second adhesive layer 16 and the first adhesive layer 14 exposed.

[0095] Whether the adhesive laminate 30 is used alone or together with the base film 12 to form an adhesive sheet 100, the direction in which the adhesive laminate 30 is positioned (front and back direction) can be appropriately determined according to the intended use of the adhesive laminate 30 and adhesive sheet 100. Specifically, the adhesive laminate 30 or adhesive sheet 100 should be positioned such that the object to which the first adhesive layer 14 and the second adhesive layer 16 come into contact or the environment to which they are exposed is suitable for the desired bonding form, according to the physical properties of the first adhesive layer 14 and the second adhesive layer 16, such as the first and second glass transition temperatures. For example, the adhesive laminate 30 can be positioned such that the second adhesive layer 16 faces the direction exposed to a higher temperature and humidity environment, while the first adhesive layer 14 faces the direction that is not exposed to high temperatures and humidity, but where high adhesion at room temperature is required.

[0096] In the adhesive sheet 100 according to the embodiment described in detail above, an adhesive laminate 30 consisting of a first adhesive layer 14 and a second adhesive layer 16 is provided on only one side of the base film 12. However, the adhesive laminate 30 may be provided on both sides of the base film 12. Furthermore, in the adhesive sheet 100 according to the embodiment described in detail above, an adhesive laminate 30 consisting of only two layers, the first adhesive layer 14 and the second adhesive layer 16, was provided on the surface of the base film 12. However, the adhesive laminate 30 may have other layers on the outside (below) of the first adhesive layer 14 and / or on the outside (above) of the second adhesive layer 16. For example, a third adhesive layer can be provided on the surface of the second adhesive layer 16. In this case, the third adhesive layer may suitably have the same configuration and composition as the preferred embodiment described next for the third adhesive layer 24 that constitutes the adhesive sheet. Furthermore, a second base film may be provided on the surface of a structure in which an adhesive laminate 30 is provided on the surface of a 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 the base film 12 and / or the second base film in a certain area, the adhesive laminate 30 can be used for bonding to an external object. It should be noted that an adhesive sheet in this form, in which an adhesive laminate 30 is sandwiched between two base films, can also be considered as a first adhesive sheet and a second adhesive sheet that are combined in the adhesive sheet described next, with their adhesive layers facing each other and in contact. The preferred form of the components of the adhesive sheet described next can also be applied as a suitable form of adhesive sheet in which an adhesive laminate 30 is sandwiched between two base films.

[0097] [2] Combinations of Adhesive Sheets Next, combinations of adhesive sheets according to embodiments of the present invention will be described. Combinations of adhesive sheets include a first adhesive sheet and a second adhesive sheet, and may hereafter be referred to as a combined adhesive sheet. In a combined adhesive sheet according to embodiments of the present invention, at least the first adhesive sheet among the first adhesive sheet and the second adhesive sheet includes the adhesive laminate according to embodiments of the present invention described above.

[0098] <Configuration of the Adhesive Sheet> The adhesive sheet 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, as shown in Figures 3(a) and 3(b). The configuration of the first adhesive sheet 100 is the same as that of the adhesive sheet 100 shown in Figure 1 and described in detail above, and the same reference numerals are used for each component, and their description is omitted.

[0099] As shown in Figure 4, the second adhesive sheet 200, which constitutes the 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 is provided in the center of the second adhesive sheet 200, penetrating it. This opening W2 is the same in size, shape, and position as the opening W1 provided in the first adhesive sheet 100.

[0100] The constituent materials of the second base film 22 are not particularly limited, but it is preferable to select from the various materials listed as preferred examples of constituent materials for the base film 12 used in the adhesive sheet 100 in its standalone state. In addition to the constituent materials, the same suitable configurations as those listed for the base film 12 above can be adopted for the film, such as thickness.

[0101] The third adhesive layer 24 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 x 10 ４ Pa or more 6.6×10 ５ It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa.１００ Storage modulus (G') at 120°C for ) １２０ The rate of decrease of the third adhesive layer is 0.3 or less, and the third glass transition temperature is 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 that were listed as preferred forms for the first adhesive layer 14 formed on one surface of the base film 12 in the above embodiment can also be adopted as preferred 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 constitute the bonded adhesive sheet 300 may be different from each other or the same, as long as they satisfy the above-mentioned requirements.

[0102] To manufacture the second adhesive sheet 200, for example, the same manufacturing method as for the adhesive sheet 100 in its standalone state may be applied, with a third adhesive layer 24 formed in place of the first adhesive layer 14, and the second adhesive layer 16 not formed. In other words, the thermosetting adhesive composition constituting the third adhesive layer 24 may be directly applied to one surface of the (second) base film 22, and then a drying and curing process by heat treatment may be carried out.

[0103] <Method of using the adhesive sheet> Next, a method of using the adhesive sheet 300 described above by bonding it to an object to be bonded will be explained. Here, the object to be bonded will be referred to as MEA. First, the surface of the first adhesive sheet 100 on which the second adhesive layer 16 is formed is brought into contact with the MEA3, in particular the area where the solid electrolyte membrane 3m is exposed, and the first adhesive sheet 100 and MEA3 are laminated together. At this time, as shown in Figures 3(a) and 3(b), the opening W1 of the first adhesive sheet 100 is positioned so that it faces one side of the solid electrolyte membrane 3m of the MEA3 via an electrode 3e as appropriate. Also, 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 MEA3, in particular the area where the solid electrolyte membrane 3m is exposed, and the second adhesive sheet 200 and MEA3 are laminated together. At this time, the opening W2 of the second adhesive sheet 200 is positioned so that it faces the other side of the solid electrolyte membrane 3m of the MEA3 via an appropriate electrode 3e. In this way, the MEA3 is sandwiched between the first adhesive sheet 100 and the second adhesive sheet 200 that constitute the bonded adhesive sheet 300, and this laminate is heated and pressed to bond the second adhesive layer 16, the MEA3, and the third adhesive layer 24 to each other. Examples of the pressure used during heating and pressing include 0.5 to 10 MPa, the heating temperature is 130 to 230°C, and the pressurizing and heating time is 3 to 60 seconds.

[0104] In detail, the peripheral portion 3A of the MEA3 (the area of ​​the solid electrolyte membrane 3m 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. Furthermore, 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 MEA3 and the portion of the third adhesive layer 24 that does not overlap with the peripheral portion 3A of the MEA3 are bonded in a state where the second adhesive layer 16 and the third adhesive layer 24 are in direct contact with each other. As a result, the peripheral portion 3A of the MEA3 is sealed by the second adhesive layer 16 and the third adhesive layer 24. In this configuration, the base film 12 and the second base film 22 are bonded to each other via an adhesive laminate 40 consisting of three layers of thermosetting adhesive: a first adhesive layer 14, a second adhesive layer 16, and a third adhesive layer 24. As shown in Figures 3(a) and 3(b), the bonded sheet 300 with this configuration can function as a sub-gasket for the MEA3.

[0105] In the embodiment described herein, a third adhesive layer 24 is formed on one surface of the second base film 22 to form a second adhesive sheet 200. Then, the second adhesive sheet 200 is laminated onto the surface of the first adhesive sheet 100, on which the MEA 3 is superimposed on the surface of the second adhesive layer 16, and the two sheets are heat-pressed to form a bonded adhesive sheet 300 that serves as a sub-gasket for the MEA 3. The procedure for forming the sub-gasket for the MEA 3 is not limited to this. For example, after superimposing the MEA 3 onto 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 heat-pressed thereafter. Examples of pressures include 0.5 to 10 MPa, heating temperatures include 130 to 230°C, and pressurizing and heating times include 3 to 60 seconds.

[0106] <Adhesive Sheet in Modified Form> Here, as a modified form of the adhesive sheet 300 according to the embodiment described above, an adhesive sheet 400 is shown together with MAE3 in Figures 5(a) and 5(b). This adhesive sheet 400 is constructed as a combination of a first adhesive sheet 100 and a second adhesive sheet 200, similar to the adhesive sheet 300 described above. The layer configuration of the first adhesive sheet 100 and the second adhesive sheet 200, as well as the composition of each layer, are the same as those of the adhesive sheet 300 described above.

[0107] However, the adhesive sheet 400 differs from the adhesive sheet 300 in the size of the opening W3 provided in the second adhesive sheet 200. In the adhesive sheet 300, the second adhesive sheet 200 also had an opening W2 of the same size as the opening W1 of the first adhesive sheet 100, but in the adhesive sheet 400 shown in Figure 5, the opening W3 provided in the second adhesive sheet 200 is larger than the opening W1 provided in the first adhesive sheet 100. As the second adhesive sheet 200 has a larger opening W3, when the adhesive sheet 400 is attached to the MEA3 as a sub-gasket, as shown in the figure, a portion of the solid electrolyte membrane 3m of the MEA3 that is not sandwiched between the electrodes 3e is exposed in the opening W3.

[0108] As for the method of using this adhesive sheet 400 by bonding it to the MEA 3, a method can be taken similar to that for the adhesive sheet 300 described above, in which the first adhesive sheet 100 and the MEA 3 are laminated together, and then the second adhesive sheet 200 is laminated on top of that. However, as an alternative method, it is preferable to first bond the first adhesive sheet 100 and the second adhesive sheet 200 together, and then incorporate the MEA into the adhesive sheet 400 which is the bonded body. Specifically, first, the first adhesive sheet 100 and the second adhesive sheet 200 are laminated together such that the second adhesive layer 16 and the third adhesive layer 24 are in contact. At this time, the first adhesive sheet 100 and the second adhesive sheet 200 are positioned so that the opening W1 of the first adhesive sheet 100 and the peripheral area 16A outside the opening W1 of the second adhesive sheet 200 are located in the area inside the opening W3 provided in the second adhesive sheet 200. As a result, when the first adhesive sheet 100 and the second adhesive sheet 200 are superimposed, the peripheral region 16A of the surface of the second adhesive layer 16 surrounding 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 and 200 are bonded together by heating and pressing, for example, by applying a pressure of 2 MPa for 5 seconds at 80°C. The conditions for heating and pressing are not limited to these, but preferred conditions include, for example, a temperature of room temperature to 150°C, a pressure of 0.5 to 10 MPa, and a pressurizing and heating time of 3 to 60 seconds.

[0109] Alternatively, another method may be used to form a third adhesive layer 24 on the surface of the second adhesive layer 16 of the first adhesive sheet 100, which is formed by overlapping the MEA3, in an area excluding the peripheral region 16A surrounding the opening W1, and then laminate the second base film 22 and heat-press it. Examples of pressures include 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 bonded adhesive sheet 400 by joining the two adhesive sheets 100 and 200 using any of the methods described above, a curing process may be performed on the bonded adhesive sheet 400 in the same manner as described for the adhesive sheet 100 in Figure 1, if necessary.

[0110] When using the bonded adhesive sheet 400 configured in this way as a sub-gasket, as shown in Figures 5(a) and 5(b), the MEA3 is laminated on the second adhesive layer 16 exposed in the peripheral region 16A within the opening W3 of the second adhesive sheet 200, such that the electrolyte membrane 3m of the MEA3 faces the opening W1 of the first adhesive sheet 100 via the electrode 3e as appropriate. It is preferable to design the size of the openings W1 and W3 so that the MEA3 can pass through the opening W3, the electrolyte membrane 3m of the MEA3 covers the opening W1, and the peripheral portion 3A of the MEA3 overlaps the portion of the second adhesive layer 16 that is exposed in the peripheral region 16A. By bonding the bonded adhesive sheet 400 and the MEA3 in this overlapped state by heat and pressure bonding, the bonded adhesive sheet 400 can function as a sub-gasket for the MEA3. As described above, examples of pressures include 0.5 to 10 MPa, heating temperatures of 130 to 230°C, and pressurizing and heating times of 3 to 60 seconds.

[0111] In this modified form of the adhesive sheet 400, when the two adhesive sheets 100 and 200 are joined together, the second adhesive layer 16 of the first adhesive sheet 100 has its surface exposed within the peripheral region 16A located inside the periphery of the opening W3, while outside the peripheral region 16A, its surface 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 MEA3 is covered by the second base film 22 and is not exposed on the outermost surface of the adhesive sheet 400. This improves the handling of the adhesive sheet 400. Furthermore, it suppresses the adhesion of foreign matter to the adhesive sheet 400, and even if foreign matter adheres, it can be easily removed. Furthermore, when positioning the bonded adhesive sheet 400, which is formed by joining two adhesive sheets 100 and 200, with the MEA3, aligning the MEA3 with the opening W3 of the second adhesive sheet 200 automatically positions the opening W1 of the first adhesive sheet 100 facing the MEA3, thus improving the workability of the bonding process between the MEA3 and the bonded adhesive sheet 400.

[0112] <Other forms of bonded adhesive sheets> In the above, in the second adhesive sheet 200 constituting the bonded adhesive sheets 300 and 400, the third adhesive layer 24 provided on the surface of the second base film 22 is defined as having a storage modulus of elasticity (G') at 100°C. １００ ) is 5.0 x 10 ４ Pa or more 6.6×10 ５ It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０A third adhesive layer was used that had a decrease rate of 0.3 or less and 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 applied. For example, at least one of the first adhesive layer 14 and the second adhesive layer 16 may be applied as an adhesive layer formed on the surface of the second base film 22. In particular, when the second adhesive sheet 200 is made of the same material as the base film 12 and has the first adhesive layer 14 formed on its surface, the bonded adhesive sheets 300 and 400 formed by joining the two adhesive sheets 100 and 200 will have a laminated structure that is symmetrical in the thickness direction. When forming a second adhesive sheet 200 by forming both the first adhesive layer 14 and the second adhesive layer 16 on the surface of the second base film 22, the first adhesive layer 14 can be formed on the surface of the second base film 22, and the second adhesive layer 16 can be formed on the surface of the first adhesive layer 14, similar to the first adhesive sheet 100.

[0113] Furthermore, although the above description assumed that the adhesive sheet 300 (or 400; hereafter the same in this paragraph) is composed of a combination of two adhesive sheets 100 and 200, as mentioned above, it is also possible to consider a single adhesive sheet 300 as having a structure comprising 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 that 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 base film 12 via the third adhesive layer 24. Thus, when considered as a single adhesive sheet 300, in the embodiment 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 a second base film 22, provided on only one side of the base film 12. However, the adhesive laminate 40 and the second base film 22 may be provided on both sides of the base film 12.

[0114] Furthermore, as described above in 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 a first adhesive layer 14 and a second adhesive layer 16, without using a base film 12. Similarly, the second adhesive sheet 200 may be configured as a self-supporting adhesive layer consisting of a third adhesive layer 24, without using a second base film 22. A combined adhesive sheet 300 (400) may be formed by combining these self-supporting adhesive laminates 30 and a self-supporting third adhesive layer 24. In such combined embodiments, the two adhesive sheets 100 and 200 can be laminated with the MEA 3 sandwiched between the second adhesive layer 16 and the third adhesive layer 24, and then heat-pressed to be used as a sub-gasket for use with the MEA. In this case, the adhesive laminate 40 is composed of 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 embodiments described above, the adhesive sheet 100 and the combined adhesive sheets 300 and 400 are configured to have an opening and bonded to the MEA3 to form a sub-gasket. However, the adhesive sheets and combinations of adhesive sheets according to the present invention are not necessarily used as sub-gaskets and can be configured in a shape appropriate to the application and used in locations in fuel cells where sealing is required. Furthermore, they are not limited to fuel cells and can be suitably used for sealing in locations that become hot and humid.

[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 in the preparation and evaluation of samples is carried out in air at room temperature.

[0117] <Preparation of Samples> (Example 1) - Preparation of Adhesive Composition As the adhesive composition for the first adhesive layer, 11.6 parts by mass (solid content) of the following crosslinking agent <1> (Toyo Chem's "HD-901"), which is an epoxy crosslinking agent, was added to 100 parts by mass of the solid content of the following resin <1> (Toyo Chem's "VA-9320L2"), which is a polyurethane resin, and then toluene was added to make the solid content concentration 19% by mass to prepare the adhesive composition.

[0118] As the adhesive composition for the second adhesive layer, 11.7 parts by mass (solid content) of the following crosslinking agent <1> (Toyo Chem's "HD-901"), which is an epoxy crosslinking agent, was added to 100 parts by mass of the solid content of the following polyurethane resin <2> (Toyo Chem's "VA-9315"), and the adhesive composition for the second adhesive layer was prepared in the same manner as the adhesive composition for the first adhesive layer.

[0119] - Preparation of the adhesive sheet A first adhesive layer was formed by applying the adhesive composition of the first adhesive layer to one side of a polyethylene naphthalate (PEN) film (Toyobo's "Teonex Q51") using a Baker-type film applicator so that the thickness after drying was 2 μm, and then heating at 150°C for 3 minutes. Subsequently, a second adhesive layer was formed by applying the adhesive composition of the second adhesive layer to the surface of the dried first adhesive layer using a Baker-type film applicator so that the thickness after drying was 10 μm, and then heating at 150°C for 3 minutes. Then, the release surface of a release film (Higashiyama Film's "HY-S10", silicone-based PET release film, thickness 25 μm) was bonded to the surface where the second adhesive layer was exposed. After that, the sheet was aged at 60°C for 6 days to produce an adhesive sheet having two adhesive layers, the first and second.

[0120] (Examples 2-7) The adhesive composition and aging conditions were as shown in Table 1, and adhesive sheets were prepared in the same manner as in Example 1.

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

[0122] - Preparation of the adhesive sheet: The adhesive composition for the first adhesive layer was applied to one side of a polyethylene naphthalate (PEN) film (Toyobo's "Teonex Q51") 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 the first adhesive layer. Subsequently, 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 to a thickness of 10 μm after drying, and the film was heated at 150°C for 3 minutes to form the second adhesive layer, thereby preparing the first adhesive sheet.

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

[0124] Subsequently, the side of the first adhesive sheet where the second adhesive layer is exposed and the side of the second adhesive sheet where the third adhesive layer is exposed were placed on top of each other, and the sheets were heated and pressed together for 5 seconds using an AS ONE small-scale hot press machine "H400-15" at 80°C with a pressure of 2 MPa. After that, the sheets were aged at 60°C for 6 days to produce bonded sheets of each embodiment, each having three adhesive layers: the first, second, and third.

[0125] (Comparative Examples 1-5) The adhesive compositions and aging conditions of each comparative example were as shown in Table 1, and the adhesive compositions of each comparative example were prepared in the same manner as in Example 1, and adhesive sheets were made accordingly.

[0126] (Comparative Examples 6 and 7) The adhesive composition was prepared using the formulation shown in Table 1, and the adhesive composition for the second adhesive layer was prepared in the same manner as in Example 1. The composition was prepared so that the solid content concentration was 20% by mass.

[0127] - Preparation of adhesive sheets A second adhesive layer was applied to one side of a polyethylene naphthalate (PEN) film (Toyobo's "Teonex Q51") using a Baker-type film applicator to a thickness of 10 μm after drying, and the second adhesive layer was formed by heating at 150°C for 3 minutes. Then, the release side of a release film (Higashiyama Film's "HY-S10", a silicone-based PET release film, 25 μm thick) was bonded to the side where the second adhesive layer was exposed. After that, the sheet was aged at 60°C for 6 days to produce an adhesive sheet. In these comparative examples, adhesive sheets with a single adhesive layer were prepared by applying only the adhesive composition of the second adhesive layer to the polyethylene naphthalate (PEN) film without applying the adhesive composition of the first adhesive layer.

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

[0129] - Preparation of adhesive sheet A first adhesive layer was formed by applying the adhesive composition of the first adhesive layer to one side of a polyethylene naphthalate (PEN) film (Toyobo's "Teonex Q51") using a Baker-type film applicator so that the thickness after drying was 2 μm, and then heating at 150°C for 3 minutes. Subsequently, the release side of a release film (Higashiyama Film's "HY-S10", silicone-based PET release film, thickness 25 μm) was bonded to the side where the first adhesive layer was exposed. After that, the sheet was aged at 60°C for 6 days to prepare an adhesive sheet. In this comparative example, an adhesive sheet with only one adhesive layer was prepared by applying only the adhesive composition of the first adhesive layer to the polyethylene naphthalate (PEN) film, without applying the adhesive composition of the second adhesive layer.

[0130] (Comparative Example 9) Preparation of Adhesive Composition The composition 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.

[0131] - Preparation of the adhesive sheet: The adhesive composition for the second adhesive layer was applied to one side of a polyethylene naphthalate (PEN) film (Toyobo's "Teonex Q51") using a Baker-type film applicator so that the thickness after drying was 10 μm. The second adhesive layer was formed by heating at 150°C for 3 minutes, and the first adhesive sheet was prepared.

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

[0133] Subsequently, the side of the first adhesive sheet where the second adhesive layer was exposed and the side of the second adhesive sheet where the third adhesive layer was exposed were placed on top of each other, and the sheets were heated and pressed together for 5 seconds at 80°C with a pressure of 2 MPa using an AS ONE small-scale hot press machine "H400-15". After that, the sheets were aged at 60°C for 6 days to produce a bonded sheet containing the second and third adhesive layers.

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

[0135] - Preparation of the adhesive sheet: In the same manner as the adhesive sheets in Comparative Examples 6 and 7 above, the adhesive composition for the second adhesive layer was applied so that the thickness after drying was 10 μm, and the second adhesive layer was formed by heating at 150°C for 3 minutes. Then, the side with the exposed second adhesive layer was placed on top of one side of a polyethylene naphthalate (PEN) film (Toyobo's "Teonex Q51") which did not have an adhesive layer or other layer formed on its surface, and the two were heated and pressed together for 5 seconds by applying a pressure of 2 MPa at 80°C using AS ONE's small heat press machine "H400-15". After that, the sheet was aged at 60°C for 6 days to produce an adhesive sheet having the second adhesive layer.

[0136] The materials used to prepare the samples for Examples 1 to 11 and Comparative Examples 1 to 11 are as follows: • Resin <1>: VA-9320L2 (manufactured by Toyo Chem, polyurethane resin, solvent: toluene / isopropanol, solids content 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 Toyo Chem, polyurethane resin, solvent: toluene / isopropanol, solids content 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 Toyo Chem, 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 Toyo Chem, 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 Toyo Chem, 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 Toyo Chem, 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>: Aron Mighty AS-350 (manufactured by Toagosei, modified epoxy resin, solvent: toluene, methanol, ethylene glycol monomethyl ether, dimethylformamide, xylene, diethylene glycol dimethyl ether, solids content concentration: 30% by mass) • Resin <8>: VA-9315H1 (manufactured by Toyo Chem, polyurethane resin, solvent: toluene, isopropanol, solids content 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 Toyo Chem, 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 Toyo Chem, 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 Toyo Chem, trifunctional epoxy resin, solvent: toluene / methyl ethyl ketone, solids content concentration: 60.0% by 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) Each adhesive composition prepared above to form the adhesive layer for each sample was 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, and this process was repeated until a thickness of 0.5 mm was achieved. After that, test samples were prepared by aging under predetermined conditions corresponding to each sample. The shear storage modulus (G') from -40°C to 150°C was measured for these samples using a viscoelasticity measuring device (TA Instrument's "Discovery HR-2"). The measurement conditions were as follows: shear mode, geometry: 8 mm diameter parallel plate, axial force: 1.0 N, normal load: 1.0 N, frequency: 1 Hz, 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'), was maximized 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, 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 in, and after shaking gently, it was left 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. After drying, the 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) The total thickness of the adhesive sheet at the stage when each layer was formed was measured using a thickness measuring instrument (TH-104 manufactured by Tester Industries). 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 peeling force) In Examples 1 to 7 and Comparative Examples 1 to 8, which were constructed as single adhesive sheets, the release sheet was peeled from the adhesive layer, a solid polymer electrolyte membrane (DuPont "Nafion PFSA NR-212", thickness: 50.8 μm) was placed on the surface of the exposed adhesive layer, and a test sample was prepared by heating and pressing it for 5 seconds at a temperature of 150°C and a pressure of 2 MPa using an AS ONE small heat press machine "H400-15". In Examples 8 to 11 and Comparative Examples 9 to 11, the bonded sheets 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 them, and each bonded sheet was used as a test sample.

[0141] After storing the prepared test samples at room temperature (23°C) for 30 minutes, they were cut to a size of 10 mm in width and 150 mm in length. The peel force was measured according to the method of JIS Z 0237 (2009) using a Shimadzu Corporation precision universal testing machine "AUTOGRAPH® AGS-1kNX, 50N load cell" under conditions of a peel speed of 10 mm / min and a peel angle of 180°, and the initial peel force was evaluated. In Examples 1 to 7 and Comparative Examples 1 to 8, the peel force between the PEN film and the solid polymer electrolyte membrane was measured, and in Examples 8 to 11 and Comparative Examples 9 to 11, the peel force between two PEN films was measured. In all cases, if the peel force is generally greater than 1 N / 10 mm, it can be said that the peel force is sufficiently large and sufficient adhesion has been achieved.

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

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

[0144]

[0145]

[0146] In Examples 1 to 7, the first and second adhesive layers are formed from cured products of thermosetting adhesive compositions containing a polyurethane resin having reactive functional groups and a crosslinking agent, respectively. In the first adhesive layer in contact with the PEN film, the storage modulus (G') at 100°C is set. １００ ) is 5.0 x 10 ４ Pa or more 6.6×10 ５ It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０ The rate of decrease of ) is 0.3 or less. On the other hand, in the second adhesive layer in contact with the solid polymer electrolyte membrane, the storage modulus (G') at 100°C is 0.3 or less. １００ ) is 6.6 x 10 ５ Exceeding Pa, 1.0 x 10 ７ It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０ The rate of decrease of ) is 0.5 or less. The glass transition temperature Tg is higher in the second adhesive layer than in the first adhesive layer. Corresponding to these factors, the adhesive sheet to which the solid polymer electrolyte membrane is pressed exhibits a large initial peel force, as shown in the evaluation results, and bonding can be completed with short-time heating and pressing. Furthermore, as can be seen from the fact that the peel force after boiling is maintained at a high temperature and humidity, adhesion defects such as lifting, peeling, and voids can be suppressed even when placed in a high temperature and humidity environment. Therefore, a 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, exhibiting a large initial peel force and high resistance to high humidity and high temperature 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. Corresponding to this, the peel strength after boiling between the solid polymer electrolyte membrane and the PEN film is insufficient. In Comparative Example 2, corresponding to the fact that G' １００ of the second adhesive layer exceeds 1.0×10 ７ Pa, the adhesiveness of the second adhesive layer is low, and when preparing a sample for measuring the peel strength, it could not adhere to the solid polymer electrolyte membrane.

[0148] In Comparative Example 3, the decrease rate of the storage modulus (G') of the first adhesive layer at 120 °C １００ with respect to the storage modulus (G') at 100 °C １２０ exceeds 0.3. Corresponding to this, the peel strength after boiling between the solid polymer electrolyte membrane and the PEN film is insufficient, and it is inferior in high-temperature and high-humidity resistance. In Comparative Example 4, the storage modulus (G') of the first adhesive layer at 100 °C １００ exceeds 6.6×10 ５ Pa, and the decrease rate of the storage modulus (G') of the first adhesive layer at 120 °C １００ with respect to the storage modulus (G') at 100 °C １２０ exceeds 0.3. Corresponding to this, the initial peel strength between the solid polymer electrolyte membrane and the PEN film is insufficient, which is presumably because the adhesive force between the first adhesive layer and the PEN film is not sufficiently obtained. In Comparative Example 5, the storage modulus (G') of the first adhesive layer at 100 °C １００ is lower than 5.0×10 ４ Pa, and the decrease rate of the storage modulus (G') of the first adhesive layer at 120 °C １００ with respect to the storage modulus (G') at 100 °C １２０ exceeds 0.3. Corresponding to this, the adhesiveness is clearly poor, and the measurement of the initial peel strength was omitted. Also, due to the poor adhesiveness and low high-temperature and high-humidity resistance, peeling of the adhesive layer occurred 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 adhered only by this second adhesive layer. In Comparative Example 6, since the storage elastic modulus (G’ １００ ) at 100 °C of the second adhesive layer is 6.6×10 ５ Pa or less, it shows a certain degree of high adhesiveness to the PEN film, so that a sufficient initial peeling force is obtained between the PEN film and the solid polymer electrolyte membrane. However, since the first adhesive layer is not provided, the adhesiveness cannot be maintained up to a high-temperature and high-humidity environment only by the second adhesive layer, and the peeling force after boiling is insufficient. Further, in Comparative Example 7, the storage elastic modulus (G’ １００ ) at 100 °C of the second adhesive layer is more than 6.6×10 ５ Pa, and the adhesiveness to the PEN film is already insufficient from the initial state. In Comparative Example 8, only one layer of 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 adhered only by this first adhesive layer. In this Comparative Example 8, although a sufficient peeling force in the initial state is obtained, the peeling force after boiling is insufficient. From this, it can be seen that without using a second adhesive layer having predetermined physical properties, sufficient adhesive force cannot be maintained in a high-temperature and high-humidity environment. Comparative Examples 6 to 8 show that in order to obtain a sufficiently high adhesive force both in the initial state and after passing through a high-temperature and high-humidity environment, both a first adhesive layer and a second adhesive layer having predetermined physical properties are required.

[0150] In Examples 8 to 11, two PEN films are bonded together by a first to third adhesive layer. Each of the first to third adhesive layers 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 adhesive layer is in contact with one PEN film and the second adhesive layer on each surface. The second adhesive layer is in contact with the first adhesive layer and the third adhesive layer on each surface. The third adhesive layer is in contact with the second adhesive layer and the other PEN film on each surface. In other words, the second adhesive layer is sandwiched between the first and third adhesive layers, and the two PEN films are bonded together with these three adhesive layers sandwiched between them. In Examples 8 to 11, the storage modulus (G') of the first and third adhesive layers at 100°C is... １００ ) is 5.0 x 10 ４ Pa or more 6.6×10 ５ It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０ The rate of decrease of ) is 0.3 or less. In addition, the storage modulus (G') of the second adhesive layer at 100°C is 0.3 or less. １００ ) is 6.6 x 10 ５ Exceeding Pa, 1.0 x 10 ７ It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０ The rate of decrease of ) is 0.5 or less. Corresponding to these findings, the first to third adhesive layers bonding the two PEN films can complete bonding with short-time heating and pressing, as shown in the evaluation results of the initial peel strength, and sufficient adhesive strength is obtained. Furthermore, since the peel strength is maintained at a high level after boiling, it can be seen that adhesion defects such as lifting, peeling, and voids can be suppressed even when placed in a high-temperature, high-humidity environment. In other words, in these Examples 8 to 11, it is confirmed that the first to third adhesive layers sandwiched between the two PEN films provide strong adhesion with sufficient initial peel strength and high resistance to high-humidity, high-temperature environments.

[0151] In Comparative Example 9, only two adhesive layers, a second and a third, exist between the two PEN films. Both the second and third adhesive layers have a storage modulus (G') at 100°C. １００ ) is 6.6 x 10 ５ Because the pressure is lower than Pa, it exhibits a relatively high degree of adhesion to the PEN film, resulting in sufficient initial peeling force between the two PEN films. However, since the first adhesive layer is not provided, and the second adhesive layer alone cannot maintain its adhesion even in high-temperature and high-humidity environments, the peeling force after boiling could not be maintained.

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

[0153] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention.

[0154] 12 Base film 14 First adhesive layer 16 Second adhesive layer 22 Second base film 24 Third adhesive layer 30 Adhesive laminate 40 Adhesive laminate 100 Adhesive sheet (first adhesive sheet) 200 Second adhesive sheet 300 Adhesive sheet set (combination of adhesive sheets) 400 Adhesive sheet set (combination of adhesive sheets) W1 Opening W2 Opening W3 Opening

Claims

1. 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 a thermosetting adhesive composition and having a second glass transition temperature higher than the first glass transition temperature, which are laminated with each other, and the thermosetting adhesive composition constituting the first thermosetting adhesive layer and the second thermosetting adhesive layer each contains a polyurethane resin having a reactive functional group and a crosslinking agent. The first thermosetting adhesive layer has a storage modulus (G' １００ ) of 5.0×10 ４ Pa or more and 6.6×10 ５ Pa or less at 100°C, and the reduction rate of the storage modulus (G' １００ ) at 120°C with respect to the storage modulus (G' １２０ ) at 100°C is 0.3 or less. The second thermosetting adhesive layer has a storage modulus (G' １００ ) of more than 6.6×10[[ID=1 3]] ５ Pa and 1.0×10 ７ Pa or less at 100°C, and the reduction rate of the storage modulus (G' １００ ) at 120°C with respect to the storage modulus (G' １２０ ) at 100°C is 0.5 or less. An adhesive laminate.

2. The adhesive laminate according to claim 1, wherein the first glass transition temperature is 15°C or more and less than 50°C, and the second glass transition temperature is 50°C or more and 100°C or less.

3. The adhesive laminate according to claim 1, wherein the reactive functional group of the polyurethane resin contains a carboxyl group, and the crosslinking agent contains a polyfunctional epoxy crosslinking agent.

4. The adhesive laminate according to claim 3, 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 of the carboxyl groups of the polyurethane resin (a) to the molar amount of the epoxy groups of the polyfunctional epoxy crosslinking agent (b) is 1.0 or more and 10.0 or less.

5. The adhesive laminate according to claim 1, wherein the thickness of the first thermosetting adhesive layer is 1 μm or more and 6 μm or less, and the thickness of the second thermosetting adhesive layer is 8 μm or more and 30 μm or less.

6. An adhesive sheet comprising a base film and an adhesive laminate according to any one of claims 1 to 5, wherein the adhesive laminate is formed on the surface of the base film, the first thermosetting adhesive layer being formed on one surface of the base film, and the second thermosetting adhesive layer being formed on the surface opposite to the surface of the base film that is in contact with the first thermosetting adhesive layer.

7. The adhesive sheet according to claim 6, 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.

8. The adhesive sheet further comprises a second base film and a third thermosetting adhesive layer formed from a cured product of a thermosetting adhesive composition, wherein 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 base film via the third thermosetting adhesive layer, the thermosetting adhesive composition constituting the third thermosetting adhesive layer contains a polyurethane resin having reactive functional groups and a 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 It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０ The adhesive sheet according to claim 7, wherein the rate of decrease of ) is 0.3 or less, and the third glass transition temperature is lower than the second glass transition temperature.

9. The adhesive sheet according to claim 8, 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.

10. The adhesive sheet according to claim 8, wherein the third glass transition temperature is 15°C or higher and less than 50°C.

11. A combination of adhesive sheets comprising a first adhesive sheet and a second adhesive sheet, wherein the first adhesive sheet comprises an adhesive laminate according to any one of claims 1 to 5, and the second adhesive sheet comprises at least one of the first thermosetting adhesive layer and the second thermosetting adhesive layer.

12. A first adhesive sheet and a second adhesive sheet, wherein the first adhesive sheet comprises an adhesive laminate according to any one of claims 1 to 5, the second adhesive sheet comprises a third thermosetting adhesive layer formed from a cured product of a curable adhesive composition, the thermosetting adhesive composition constituting the third thermosetting adhesive layer comprises a polyurethane resin having a reactive functional group and a 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 It is less than or equal to Pa, and the storage modulus (G') at 100°C is less than or equal to Pa. １００ Storage modulus (G') at 120°C for ) １２０ A combination of adhesive sheets having a decrease rate of ) of 0.3 or less and a third glass transition temperature lower than the second glass transition temperature.

Images