Patent Publication Number: US-11652215-B2

Title: Method of manufacturing and device for manufacturing membrane-catalyst assembly

Description:
TECHNICAL FIELD 
     The present invention relates to a method of manufacturing a member including a polymer electrolyte membrane and a catalyst layer bonded to the polymer electrolyte membrane, that is, a membrane-catalyst assembly, which is used in electrochemical devices such as polymer electrolyte fuel cells, as well as to a device for manufacturing a membrane-catalyst assembly. 
     BACKGROUND ART 
     Fuel cells are a kind of power generator from which electric energy is extracted by electrochemical oxidation of a fuel such as hydrogen or methanol, and have recently attracted attention as a clean energy source. Above all, polymer electrolyte fuel cells have a low standard operating temperature of around 100° C. and a high energy density. Therefore, polymer electrolyte fuel cells are expected to be widely applied to relatively small distributed power generation facilities as well as to power generators for mobile objects such as automobiles and ships. Polymer electrolyte membranes (hereinafter sometimes simply referred to as “electrolyte membranes”) are key materials of polymer electrolyte fuel cells. In recent years, use of polymer electrolyte membranes in hydrogen infrastructure-related equipment such as solid polymer electrolyte membrane water electrolyzers and electrochemical hydrogen pumps is also under consideration. 
     In the application of the polymer electrolyte membrane to such electrochemical devices, a member including an electrolyte membrane and a catalyst layer bonded to the electrolyte membrane is used. A typical example of such a member is a catalyst layer-attached electrolyte membrane including an electrolyte membrane and a catalyst layer formed on a surface of the electrolyte membrane. 
     For example, the following method is known as a method of manufacturing a catalyst layer-attached electrolyte membrane. First, a catalyst solution is applied to a surface of a sheet made of polytetrafluoroethylene (PTFE) or the like and having excellent releasability, which is used as a temporary base material. Then, the solvent in the applied catalyst solution is evaporated to form a dried catalyst layer. Further, the dried catalyst layer and an electrolyte membrane are thermocompression-bonded together using a flat press or a roll press to transfer the catalyst layer to the polymer electrolyte membrane. Finally, the temporary base material is separated from the catalyst layer transferred to the polymer electrolyte membrane. The method of transferring the once dried catalyst layer to the electrolyte membrane is employed because if the solvent in the catalyst solution adheres to the electrolyte membrane, the solvent may swell the electrolyte membrane to cause wrinkles, and the electrolyte membrane may be deformed. 
     When the dried catalyst layer is thermocompression-bonded to the electrolyte membrane, however, the adhesion between the catalyst layer and the electrolyte membrane may be insufficient unless the catalyst layer and the electrolyte membrane are pressed at high temperature and high pressure for a long time. Meanwhile, if the catalyst layer and the electrolyte membrane are subjected to harsh thermocompression bonding conditions in order to improve the adhesion therebetween, the catalyst layer may be compressed and deformed, resulting in reduced gas diffusivity and poor power generation performance, or the electrolyte membrane may be subjected to thermal stress and damaged, resulting in poor durability. However, if the temperature and pressure of the pressing are simply reduced in order to reduce the damage to the catalyst layer and the electrolyte membrane, the pressing time needs to be increased to compensate for the reduction, so that the productivity is greatly reduced. 
     Therefore, various techniques have been proposed in order to achieve satisfactory adhesion between the electrolyte membrane and the catalyst layer while relaxing the thermocompression bonding conditions. For example, the following methods have been proposed: a method of semi-drying a catalyst solution, and bonding a catalyst layer to an electrolyte membrane with a slight amount of a solvent component remaining in the catalyst layer as in Patent Document 1; and a method of applying a solution containing a binder resin having proton conductivity to a surface of a dried catalyst layer, and bonding the catalyst layer to an electrolyte membrane before the solution is completely dried as in Patent Document 2. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Patent No. 4240272 
     Patent Document 2: Japanese Patent Laid-open Publication No. 2013-69535 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     According to the method described in Patent Document 1, it is possible to ensure satisfactory adhesion between the electrolyte membrane and the catalyst layer under relaxed thermocompression bonding conditions without causing wrinkles in the electrolyte membrane by leaving the solvent component in the catalyst layer to such an extent that only the joint surface of the electrolyte membrane to the catalyst layer may be softened. However, it is difficult to control the drying so that the amount of the remaining solvent will be uniform on the entire surface of the catalyst layer while partially removing the solvent in the catalyst solution by heating. Therefore, due to the difference in the degree of drying in the surface of the catalyst layer, products having a high interfacial resistance between the electrolyte membrane and the catalyst layer, and products having wrinkles due to deformation of the electrolyte membrane or cracks in the surface of the catalyst layer are mixed, and the products have unstable quality. In addition, the amount of the remaining solvent has a narrow margin, and the reduction of productivity may lead to an increase in cost. Further, since the solvent composition of the catalyst solution is limited, it is difficult to flexibly change the type of catalyst layer. 
     According to the method described in Patent Document 2, the solution containing a binder resin having proton conductivity is applied to the joint surface of the catalyst layer to the electrolyte membrane, and the catalyst layer is bonded to the electrolyte membrane before the solution is completely dried. Thus, the solution serves as an adhesive, and the method can ensure satisfactory adhesion between the electrolyte membrane and the catalyst layer even at low temperature and low pressure. However, use of the solution containing a binder resin having proton conductivity for bonding the electrolyte membrane to the catalyst layer increases the manufacturing cost. Further, the method also has the following problems: the binder resin is a component similar to that of the electrolyte membrane, so that the binder resin substantially increases the thickness of the electrolyte membrane and increases the electric resistance; and the organic solvent in the solution remaining at the interface between the electrolyte membrane and the catalyst layer may deteriorate the power generation performance. 
     An object of the present invention is to provide, in the manufacture of a member including a polymer electrolyte membrane and a catalyst layer bonded to the polymer electrolyte membrane (the member is hereinafter referred to as a “membrane-catalyst assembly”), a manufacturing method that achieves both the relaxation of thermocompression bonding conditions (pressing pressure, pressing temperature, and pressing time) and the improvement of adhesion between the catalyst layer and the electrolyte membrane with high productivity. 
     Solutions to the Problems 
     The present invention for solving the above-mentioned problems provides a method of manufacturing a membrane-catalyst assembly including an electrolyte membrane and a catalyst layer bonded to the electrolyte membrane, the method including a liquid application step of applying a liquid to a surface of the catalyst layer before bonding, and a thermocompression bonding step of bonding, to the electrolyte membrane, the catalyst layer to which the liquid is applied by thermocompression bonding. 
     The present invention also provides a device for manufacturing a membrane-catalyst assembly including an electrolyte membrane and a catalyst layer bonded to the electrolyte membrane, the device including a liquid applicator that applies a liquid to a surface of the catalyst layer before bonding, and a thermocompression bonding unit that bonds, to the electrolyte membrane, the catalyst layer to which the liquid is applied by thermocompression bonding. 
     Effects of the Invention 
     According to the present invention, it is possible to manufacture a membrane-catalyst layer assembly while achieving both the relaxation of thermocompression bonding conditions (pressing pressure, pressing temperature, and pressing time) and the improvement of adhesion between the catalyst layer and the electrolyte membrane with high productivity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view showing a schematic configuration of a device for manufacturing a membrane-catalyst assembly according to a first embodiment of the present invention. 
         FIG.  2    is a side view showing a schematic configuration of the device for manufacturing a membrane-catalyst assembly according to a second embodiment of the present invention. 
         FIG.  3    is a side view showing a schematic configuration for forming a first catalyst layer in the device for manufacturing a membrane-catalyst assembly according to a third embodiment of the present invention. 
         FIG.  4    is a side view showing a schematic configuration for forming a second catalyst layer in the device for manufacturing a membrane-catalyst assembly according to the third embodiment of the present invention. 
         FIG.  5    is a side view showing a schematic configuration for forming a first catalyst layer in the device for manufacturing a membrane-catalyst assembly according to a fourth embodiment of the present invention. 
         FIG.  6    is a side view showing a schematic configuration for forming a second catalyst layer in the device for manufacturing a membrane-catalyst assembly according to the fourth embodiment of the present invention. 
         FIG.  7    is a side view showing a schematic configuration for illustrating a different method for separating temporary base materials in the device for manufacturing a membrane-catalyst assembly according to the first embodiment of the present invention. 
         FIG.  8    is a side view showing a schematic configuration for illustrating heat shield plates in the device for manufacturing a membrane-catalyst assembly according to the first embodiment of the present invention. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     The operations of the present invention may include the following, although the present invention is not limited to the following in any way. In the thermocompression bonding step, the electrolyte membrane and the catalyst layer are compressed with a liquid applied to the joint surface of the catalyst layer to the electrolyte membrane, so that the air present at the interface is removed, and substantially the liquid alone is present between the electrolyte membrane and the catalyst layer. When heat is further applied in this state, the liquid evaporates and the interface is evacuated, so that the adhesion between the catalyst layer and the electrolyte is improved. Further, since the electrolyte membrane comes into contact with the liquid and softens, the adhesion between the catalyst layer and the electrolyte membrane is further improved. Since the electrolyte membrane is held by the compression in the thermocompression bonding while being in contact with the liquid, the occurrence of swelling is prevented. Further, the liquid evaporated at the interface passes through the pores of the catalyst layer having a porous structure, and is discharged to the outside of the membrane-catalyst assembly. 
     As used herein, the term “membrane-catalyst assembly” is a term that means not only a so-called catalyst layer-attached electrolyte membrane including an electrolyte membrane and a catalyst layer formed on a surface of the electrolyte membrane, but also any laminate having a joint surface between an electrolyte membrane and a catalyst layer. For example, a membrane-electrode assembly, which includes a so-called gas diffusion electrode including a base material made of gas-permeable carbon paper or the like and a catalyst layer formed on one surface of the base material, and an electrolyte membrane bonded to the gas diffusion electrode, is also one aspect of the “membrane-catalyst assembly”. In addition, an operation of bonding, to one surface of an electrolyte membrane already having a catalyst layer on the other surface, a catalyst layer (only a catalyst layer, or a gas diffusion electrode or the like) is also included in the “manufacture of a membrane-catalyst assembly”. 
     [Electrolyte Membrane] 
     The electrolyte membrane used in the method of manufacturing a membrane-catalyst assembly and the device for manufacturing a membrane-catalyst assembly of the present invention has proton conductivity. The electrolyte membrane is not particularly limited as long as it operates as an electrolyte membrane used in polymer electrolyte fuel cells, solid polymer electrolyte membrane water electrolyzers, electrochemical hydrogen pumps and the like, and may be a known or commercially available product. The electrolyte membrane used may be a fluorine-based electrolyte membrane made of perfluorosulfonic acid or a hydrocarbon-based electrolyte membrane made of a hydrocarbon-based polymer obtained by imparting proton conductivity to a hydrocarbon-based skeleton. 
     In particular, a hydrocarbon-based electrolyte membrane has a higher glass transition temperature and larger shrinkage deformation during heating than those of a fluorine-based electrolyte membrane, and it is often difficult to find transfer conditions with excellent productivity in common thermocompression bonding methods. Therefore, the manufacturing method and the manufacturing device of the present invention can be preferably applied to a hydrocarbon-based electrolyte membrane. 
     [Catalyst Layer] 
     The catalyst layer used in the method of manufacturing a membrane-catalyst assembly and the device for manufacturing a membrane-catalyst assembly of the present invention is not particularly limited as long as it operates as a catalyst layer used in polymer electrolyte fuel cells, solid polymer electrolyte membrane water electrolyzers, electrochemical hydrogen pumps and the like. In general, it is possible to use a catalyst layer having a porous structure and including conductive particles such as carbon particles, catalyst particles supported on the conductive particles, such as platinum particles or platinum alloy particles, and an electrolyte component having proton conductivity, such as an ionomer. 
     Examples of preferable conductive particles include particles of carbon materials such as oil furnace black, gas furnace black, acetylene black, thermal black, graphite, carbon nanotubes, and graphene, and metal oxides such as tin oxide. Examples of preferable catalyst particles include particles of single noble metals such as platinum, iridium, ruthenium, rhodium, and palladium, alloys of manganese, iron, cobalt, nickel, copper, zinc or the like with platinum, and ternary alloys of these metals with platinum and ruthenium. Examples of a preferable electrolyte component include perfluorocarbon sulfonic acid-based polymers such as Nafion (registered trademark, manufactured by The Chemours Company), Aquivion (registered trademark, manufactured by Solvay Specialty Polymers), FLEMION (registered trademark, manufactured by Asahi Glass Co., Ltd.), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), and Fumion F (registered trademark, manufactured by FuMA-Tech GmbH), and hydrocarbon-based polymers such as polysulfone sulfonic acid, polyaryletherketone sulfonic acid, polybenzimidazole alkylsulfonic acid, polybenzimidazole alkylphosphonic acid, polystyrene sulfonic acid, polyetheretherketone sulfonic acid, and polyphenyl sulfonic acid. 
     The catalyst solution is not particularly limited as long as it is a solution containing these catalyst layer materials dispersed in a solvent that evaporates by drying, and is capable of forming the catalyst layer on the electrolyte membrane. In general, the solvent used is preferably water, an alcohol such as methanol, ethanol, 1-propanol, 2-propanol, tert-butanol, or ethylene glycol, or N,N-dimethylformamide or N-methyl-2-pyrrolidone. 
     [Liquid Application Step] 
     The liquid application step is a step of applying a liquid to a surface of the catalyst layer before bonding, that is, a joint surface of the catalyst layer to the electrolyte membrane. The term “application of a liquid” means to produce a state in which the liquid is attached to the surface of the catalyst layer in an exposed state. It is desirable to prevent the liquid from substantially permeating into the catalyst layer. If the liquid permeates into the catalyst layer, the electrolyte component in the catalyst layer dissolves to reduce the strength of the catalyst layer, so that cracks are likely to occur in the thermocompression bonding step. Further, in the case of a catalyst layer preliminarily supported on a base material, if the liquid permeates into the catalyst layer and reaches the interface between the catalyst layer and the base material, the releasability of the catalyst layer from the base material may deteriorate. 
     In the liquid application step, the liquid is not particularly limited as long as it is a material that evaporates by heating in the subsequent thermocompression bonding step and has no toxicity to the electrolyte membrane and the catalyst layer. For example, water, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and tert-butanol, and mixtures thereof can be used, but it is desirable to use a liquid containing at least water. If the liquid undergoes a sudden temperature change during thermocompression bonding, wrinkles may occur in the electrolyte membrane. However, a water-containing liquid can prevent such damages because water has a higher boiling point and a higher specific heat than those of the above-mentioned alcohols, and undergoes a gradual temperature rise during thermocompression bonding. Further, since water has a lower capability of permeating into the catalyst layer than alcohols do, it is possible to prevent the occurrence of cracks due to the permeation of the liquid into the catalyst layer. Moreover, use of the water-containing liquid enables to carry out the present invention at low cost, and can also reduce the environmental load of the manufacture. Even if the liquid remains in the membrane-catalyst assembly manufactured by the manufacturing method or the manufacturing device of the present invention, the liquid does not have any effect on the performance the equipment in which the liquid is used as long as the liquid is water. In the water-containing liquid, the content rate of water is more preferably 50 mass % to 100 mass %, still more preferably 90 mass % to 100 mass %, and even more preferably 100 mass %. In other words, it is most preferable to use pure water as the liquid. Herein, “pure water” is high-purity water that does not contain impurities, and refers to water at a level of grade A4 of JIS K0557(1998) that is collected through a reverse osmosis membrane and an ion exchange resin and obtained using a commercially available pure water production machine, or water of the equivalent quality. 
     The liquid may contain a solid material in a dissolved or dispersed state as long as the liquid has fluidity as a whole and provides the effects of the present invention. 
     In the liquid application step, the liquid application method is not particularly limited, and examples of the method include a method of forming a uniform coating film on the surface of the catalyst layer using a gravure coater, a die coater, a comma coater, or the like, a method of immersing a catalyst transfer sheet in a liquid tank containing the liquid, and a method of applying the liquid to the surface of the catalyst layer in a droplet form. The method of applying the liquid to the surface of the catalyst layer in a droplet form is particularly preferable. Herein, the term “droplet form” refers to a state in which innumerable droplets are attached to the surface of the catalyst layer. The term “droplets” refers to, among masses of the liquid aggregated by surface tension, masses having a size of 1 cm 2  or less on the catalyst layer. In the case where the liquid is applied in the droplet form, it is possible to uniformly apply the minimum necessary amount of the liquid for softening the electrolyte membrane to the joint surface. Note that the applied droplets are “uniform” means that the total amount of the liquid applied per 1 cm 2  of the joint surface is the same at any position in the joint surface. Further, even a liquid that tends to repel the catalyst layer and hardly forms a uniform coating film, such as water, can be easily applied in a droplet form. Further, in the case where the liquid is in a droplet form, the area of contact between the liquid and the catalyst layer is small, so that it is possible to minimize the permeation of the liquid into the catalyst layer before the thermocompression bonding. Since the droplets are spread on the interface and unite with the neighboring droplets due to the compression in the thermocompression bonding step, it is possible to soften the electrolyte membrane at the whole interface. 
     In the liquid application step, it is preferable to apply the liquid so that the amount of liquid at the start of compression bonding in the thermocompression bonding step may be 0.1 μL or more and 5 μL or less per 1 cm 2  of the surface of the catalyst layer. If the amount of liquid in the thermocompression bonding step is less than 0.1 μL per 1 cm 2 , the electrolyte membrane may not be sufficiently softened and adhesion may be insufficient, or part of droplets may not unite with each other by the compression in the thermocompression bonding step, and some parts of the electrolyte membrane will not be softened. If the amount of liquid exceeds 5 μL per 1 cm 2 , the liquid may drip during transportation, or not substantially the total amount of the liquid evaporates by the heating during thermocompression bonding, so that the electrolyte membrane may swell due to the liquid remaining at the interface at the moment the compression is released. The amount of liquid is more preferably 0.1 μL or more and 0.8 μL or less per 1 cm 2  of the surface of the catalyst layer. The amount of liquid can be measured by attaching, to the surface of the catalyst layer of the catalyst transfer sheet, a sample piece such as a PET film piece whose weight has been measured so as to stack the sample piece on the catalyst layer, applying the liquid to the catalyst layer in the liquid application step, removing the sample base material with the liquid immediately before the sample piece comes into contact with the electrolyte membrane in the thermocompression bonding step and measuring the weight of the sample base material with the liquid, and calculating the volume of the liquid per 1 cm 2  from the weight difference. The sample piece in the measurement may be a square piece with a side of 1 cm to 10 cm. 
     Further, the smaller the average diameter of the applied droplets is, the more preferable it is. More specifically, the average diameter of the droplets is preferably 300 μm or less in a state where the droplets are attached to the base material. The smaller the average diameter of the droplets is, the shorter the distance between the droplets is, so that the droplets can unite with each other with a smaller amount of liquid during compression in the thermocompression bonding step. 
     In the liquid application step, the means for applying the liquid in a droplet form is not particularly limited, and examples of the usable means include a method of spraying the droplets by a sprayer or inkjet, a method of condensing the droplets on the joint surface in a humidified atmosphere, and a method of spraying the liquid in a mist form using an ultrasonic transducer or the like. The method of spraying the droplets by a sprayer is preferable from the viewpoint that the liquid can be efficiently applied with the amount of liquid being controlled. The sprayer for spraying the droplets is not particularly limited, and a two-fluid spray nozzle or the like that is used to atomize and spray the liquid by compressed air can be used. 
     [Thermocompression Bonding Step] 
     The catalyst layer that has been subjected to the liquid application step is then subjected to a thermocompression bonding step in which the catalyst layer is thermocompression-bonded to the electrolyte membrane. The thermocompression bonding step is a step of bonding the catalyst layer to the electrolyte membrane by heating and compressing the catalyst layer and the electrolyte membrane in a stacked state in which the surface of the catalyst layer to which the liquid is applied is in contact with the electrolyte membrane. 
     In the thermocompression bonding step, the time from when the catalyst layer comes into contact with the electrolyte membrane until the compression force acts on the catalyst layer and the electrolyte membrane is desirably 0.1 seconds or less. If the time is longer than 0.1 seconds, the electrolyte membrane is likely to swell due to adhesion of the liquid, whereas when the time is 0.1 seconds or less, swelling is prevented because the adhesion of the liquid and the fixation of the electrolyte membrane by thermocompression bonding proceed substantially at the same time. 
     The heating temperature in the thermocompression bonding step is not particularly limited, but is preferably equal to or higher than the boiling point of the liquid applied to the catalyst layer (hereinafter referred to as the “boiling point of the liquid”) and 220° C. or less. The heating temperature is the maximum temperature at the joint surface between the electrolyte membrane and the catalyst layer during the thermocompression bonding step, and can be measured using a thermocouple. If the heating temperature is equal to or lower than the boiling point of the liquid, it takes time to evaporate the liquid and the productivity is reduced. Alternatively, if the heating temperature exceeds 220° C., the electrolyte membrane may be damaged by heat. The heating temperature in the thermocompression bonding step is more preferably equal to or higher than the boiling point of the liquid and 160° C. or less. The term “boiling point of the liquid” refers to the boiling point at an external pressure of 1 atm. When the liquid to be evaporated has a single composition, the term means the boiling point of the liquid. When the liquid to be evaporated is a mixture, the term means the highest boiling point among those of the single components in the mixture. 
     The pressure applied to the electrolyte membrane and the catalyst layer in the thermocompression bonding step may be appropriately set, but is preferably 1 MPa or more and 20 MPa or less. If the pressure is less than 1 MPa, the electrolyte membrane and the catalyst layer may not be sufficiently adhered to each other. If the pressure exceeds 20 MPa, excessive pressure may be applied to the catalyst layer and the electrolyte membrane, so that the structure of the catalyst layer may be destroyed, and mechanical damage to the electrolyte membrane may increase, resulting in deterioration of durability and power generation performance. The pressure in the thermocompression bonding step is more preferably 1 MPa to 10 MPa. 
     The form of compression in the thermocompression bonding step is not particularly limited, and may be a mode of a line contact in which the electrolyte membrane and the catalyst layer come into contact with each other in a single line form as with a hot press roll, or a mode of a surface contact in which the electrolyte membrane and the catalyst layer come into contact with each other in a plane form over a certain width in the transport direction as with a double-belt pressing mechanism. 
     The manufacturing method of the present invention has been described above, and as can be easily understood from the above description and the following description of embodiments, the present specification also discloses a manufacturing device as described below for carrying out the manufacturing method. 
     (1) A device for manufacturing a membrane-catalyst assembly including an electrolyte membrane and a catalyst layer bonded to the electrolyte membrane, the device including: 
     a liquid applicator that applies a liquid to a surface of the catalyst layer before bonding; and 
     a thermocompression bonding unit that bonds, to the electrolyte membrane, the catalyst layer to which the liquid is applied by thermocompression bonding. 
     (2) The device according to the item (1), wherein the liquid applicator applies the liquid to the surface of the catalyst layer in a droplet form. 
     (3) The device according to the item (2), wherein the liquid applicator is a sprayer. 
     Hereinafter, specific embodiments of the present invention will be described with reference to schematic diagrams of the manufacturing device for achieving the manufacturing method of the present invention. It is to be noted that the following description is provided for facilitating the understanding of the present invention, and does not limit the present invention in any way. However, as can be easily understood by those skilled in the art, references to preferable aspects and variations in individual embodiments are to be interpreted as descriptions of the manufacturing method or the manufacturing device of the present invention as a superordinate concept. In the present specification, the upper part of each drawing is referred to as “upper” and the lower part thereof is referred to as “lower” for convenience, but the vertical direction of each drawing does not necessarily mean the vertical direction from the ground. 
     First Embodiment: Manufacture of Catalyst Layer-Attached Electrolyte Membrane—1 
       FIG.  1    is a side view showing a schematic configuration of a device for manufacturing a catalyst layer-attached electrolyte membrane, which is one embodiment of a device for manufacturing a membrane-catalyst assembly of the present invention. 
     In a device  100  for manufacturing a membrane-catalyst assembly according to this embodiment, a catalyst layer-attached electrolyte membrane is manufactured as follows. 
     An electrolyte membrane  10  is unwound from an electrolyte membrane supply roll  11 , and supplied to a thermocompression bonding section P through a guide roll  12 . Catalyst transfer sheet supply rolls  21 A and  21 B are provided above and below the unwound electrolyte membrane  10 , respectively. A catalyst layer to be bonded to the upper surface of the electrolyte membrane  10  is formed using a catalyst transfer sheet  20 A. The catalyst transfer sheet  20 A is produced by preliminarily applying a catalyst solution to a sheet serving as a base material, for example. The catalyst transfer sheet  20 A is unwound from the catalyst transfer sheet supply roll  21 A in a state where the base material supports the catalyst layer, and is transported through a backup roll  31 A and a guide roll  22 A in this order with the base material side reverse to the catalyst layer-formed surface of the catalyst transfer sheet  20 A being supported on the rolls. (Since the base material is separated after the catalyst layer and the electrolyte membrane are bonded together, it is also called a temporary base material.) A catalyst transfer sheet  20 B for forming a catalyst layer on the lower surface of the electrolyte membrane  10  is unwound from the catalyst transfer sheet supply roll  21 B, and is transported through a backup roll  31 B and a guide roll  22 B in this order with the base material side of the catalyst transfer sheet  20 B being supported on the rolls. In this way, the catalyst transfer sheets  20 A and  20 B are supplied to the thermocompression bonding section P so that the surfaces of the catalyst transfer sheets  20 A and  20 B on which the catalyst layers are formed may face the electrolyte membrane  10 . 
     The material of the base material of the catalyst transfer sheets  20 A and  20 B is not particularly limited, and may be a hydrocarbon-based plastic film typified by those of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), polyimide, and polyphenylene sulfide, or a fluorine-based film typified by those of perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), and an ethylene-tetrafluoroethylene copolymer (ETFE). 
     It is more preferable that the base material have air permeability. Having air permeability means to have a property of being capable of permeating gases, and examples of a case where the base material has air permeability include a case where the base material has pores communicating in the thickness direction thereof. Use of a base material having air permeability enables to effectively discharge the liquid vapor generated during thermocompression bonding even when the base material is still bonded to the catalyst layer. The base material having air permeability may be, for example, a porous material formed from the above-mentioned material. 
     For the guide rolls  12 ,  22 A, and  22 B, it is preferable to use an expander roll in order to eliminate wrinkles and slacks of the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  21 B supplied to the thermocompression bonding section P. 
     The device  100  for manufacturing a membrane-catalyst assembly according to this embodiment is configured to transfer the catalyst layer to each of both surfaces of the electrolyte membrane  10 , but may be configured to transfer the catalyst layer to only one surface of the electrolyte membrane  10 . 
     In this embodiment, a spray nozzle  30 A is provided so as to face the catalyst transfer sheet  20 A supported on the backup roll  31 A. The spray nozzle  30 A has a discharge port directed toward the central axis of the backup roll  31 A, and is provided at a position separated from the backup roll  31 A by a predetermined distance. At least one spray nozzle  30 A is provided in the width direction of the catalyst transfer sheet  20 A in accordance with the width of the base material of the catalyst transfer sheet  20 A. 
     The spray nozzle  30 A discharges water supplied from a water supply tank (not shown) from the discharge port to apply droplets to the joint surface of the catalyst layer to the electrolyte membrane. 
     Further, the spray nozzle  30 A and a space S in which the droplets from the discharge port of the spray nozzle  30 A fly to the catalyst layer are surrounded by a nozzle chamber  32 A. To the nozzle chamber  32 A, a pressure reducing tank  34 A for reducing the pressure in the space S is connected by piping via a valve  33 A for switching to pressure reduction. Since the pressure reducing tank  34 A makes the space S have a negative pressure relative to the environmental pressure of the manufacturing device, the outside air is slightly sucked into the space S from the gap provided between the nozzle chamber  32 A and the catalyst transfer sheet  20 A, and excess droplets from the spray nozzle  30 A are prevented from scattering around. The water collected in the nozzle chamber  32 A is discharged from a drain (not shown) provided in the nozzle chamber  32 A, and returned to the water supply tank and reused. 
     The above-mentioned description is a description of the liquid applicator for the catalyst transfer sheet  20 A, and the description of the liquid applicator (a spray nozzle  30 B, a nozzle chamber  32 B, a valve  33 B, and a pressure reducing tank  34 B) provided for the catalyst transfer sheet  20 B is omitted because the latter liquid applicator has a similar configuration to that of the former liquid applicator. 
     In this way, the electrolyte membrane  10 , and the catalyst transfer sheets  20 A and  20 B with the liquid applied to the joint surfaces to the electrolyte membrane  10  are supplied to the thermocompression bonding section P, and pass between hot press rolls  40 A and  40 B. As shown in  FIG.  8   , it is preferable to provide heat shield plates  41 A and  41 B between the catalyst transfer sheet  20 A and the hot press roll  40 A and between the catalyst transfer sheet  20 B and the hot press roll  40 B, respectively. Providing the heat shield plates  41 A and  41 B prevents the liquid applied to the catalyst transfer sheets  20 A and  20 B from evaporating before the heat pressing due to the radiant heat radiated from the hot press rolls  40 A and  40 B. 
     The hot press rolls  40 A and  40 B are connected to a driving unit (not shown), and can rotate at a controlled speed. The hot press rolls  40 A and  40 B rotate at a constant speed while applying heat and pressure to the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  20 B. Accordingly, the hot press rolls  40 A and  40 B, while transporting the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  20 B at a synchronized transport speed, thermocompression-bond the catalyst layer to each of both surfaces of the electrolyte membrane  10  to form a membrane-catalyst layer assembly  13   a . For the hot roll presses  40 A and  40 B, the heating device, pressurizing device, and the like are not shown. 
     The materials of the hot press rolls  40 A and  40 B are not particularly limited, but it is desirable that one of the rolls be made of a metal such as stainless steel, and the other roll have a structure in which the roll is covered with a surface layer made of an elastic body such as a resin or an elastomer material typified by a rubber. In the case of a combination of metal rolls, the contact width for compression is too small and the compression time required for bonding may not be secured, or the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  20 B may not be uniformly compressed in the width direction. Alternatively, in the case of a combination of rolls covered with a surface layer made of a rubber, the heat is poorly transferred and it may be difficult to sufficiently heat the electrolyte membrane and the catalyst layers. It is possible to sufficiently heat the electrolyte membrane and the catalyst layers with one of the hot press rolls  40 A and  40 B made of a metal, and to maintain a satisfactory line contact between the electrolyte membrane and the catalyst layers and uniformize the line pressure in the width direction of the base material with the other press roll having a surface layer made of an elastic body, because the press roll flexibly changes the shape following the catalyst transfer sheets  20 A and  20 B. 
     As for the material of the elastic body, when a rubber is used, examples of usable materials include a fluororubber, a silicon rubber, an EPDM (ethylene-propylene-diene rubber), neoprene, a CSM (chlorosulfonated polyethylene rubber), a urethane rubber, a NBR (nitrile rubber), and ebonite. It is preferable that the elastic body have a rubber hardness in the range of 70 to 97° according to the Shore A standard. If the hardness is less than 70°, the amount of deformation of the elastic body is large, and the contact width for compression with the catalyst transfer sheets  20 A and  20 B is too large, so that the pressure required for bonding the electrolyte membrane  10  to the catalyst layers may not be secured. Conversely, if the hardness exceeds 97°, the amount of deformation of the elastic body is small, and the contact width for compression is too small, so that the compression time required for bonding may not be secured. 
     The means for heating the hot press rolls  40 A and  40 B is not particularly limited, and various heaters, and heat media such as steam and oil can be used. Further, the heating temperature may be the same or different for the upper and lower rolls. 
     The method of controlling the compression force of the hot press rolls  40 A and  40 B is not particularly limited, and the compression force may be controlled using a pressurizing unit such as a hydraulic cylinder, or may be controlled in accordance with the size of a gap provided between the hot press rolls  40 A and  40 B, which is adjusted to a certain size through position control using a servomotor or the like. 
     In this embodiment, the hot press rolls  40 A and  40 B as a line contact mechanism are used in the thermocompression bonding section P, but the present invention is not limited thereto. The mechanism may be a mechanism for compressing the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  20 B by a plurality of line contacts using a plurality of rolls, or a double-belt pressing mechanism for compressing the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  20 B by a surface contact. When a plurality of pairs of rolls are used, the number of rolls provided is not particularly limited, but is preferably 2 to 10 pairs. 
     In this way, the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  20 B pass through the thermocompression bonding section P, and the catalyst layer is transferred to each of both surfaces of the electrolyte membrane  10 , whereby the membrane-catalyst assembly (catalyst layer-attached electrolyte membrane)  13   a  is formed. 
     Then, temporary base materials  24 A and  24 B are separated from the membrane-catalyst assembly  13   a  as a catalyst layer-attached electrolyte membrane. 
     When the temporary base materials  24 A and  24 B have air permeability, the separation method is not particularly limited. For example, the temporary base materials  24 A and  24 B can be separated while the membrane-catalyst assembly  13   a  is passed between guide rolls  23 A and  23 B. While the temporary base materials are present on the catalyst layers, the temporary base materials support the electrolyte membrane with the catalyst layers interposed between the temporary base materials and the electrolyte membrane, so that an effect of preventing the electrolyte membrane from swelling is obtained. Therefore, when it is difficult to evaporate almost the total amount of the liquid only by the thermocompression bonding step, an additional drying step may be provided to dry the liquid between the time when the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  20 B pass through the thermocompression bonding section P and the time when the temporary base materials are separated. When the temporary base materials  24 A and  24 B do not have air permeability, it is preferable to separate the temporary base materials  24 A and  24 B from the membrane-catalyst assembly  13   a  in such a manner that the temporary base material  24 A is held by the hot press roll  40 A and the temporary base material  24 B is held by the hot press roll  40 B as shown in  FIG.  7   . When the temporary base materials are separated immediately after thermocompression bonding and the catalyst layers are exposed, it is possible to effectively discharge the liquid vapor generated in the thermocompression bonding step. 
     The temporary base materials separated from the membrane-catalyst layer assembly  13   a  pass over the guide rolls  23 A and  23 B, respectively, and wound up on temporary base material take-up rolls  25 A and  25 B, respectively. The membrane-catalyst assembly  13   a  from which the temporary base materials  24 A and  24 B have been separated is fed by a feeding roll  14  and wound into a roll by a take-up roll  15 . 
     The feeding roll  14  can be connected to a driving unit (not shown), and it is possible to transport the electrolyte membrane  10  at a controlled speed when the press rolls  40 A and  40 B do not compress the electrolyte membrane  10  and the catalyst transfer sheets  20 A and  20 B. 
     Second Embodiment: Manufacture of Membrane-Electrode Assembly—1 
       FIG.  2    is a side view showing a schematic configuration of a device for manufacturing a membrane-electrode assembly, which is one embodiment of a device for manufacturing a membrane-catalyst assembly of the present invention. 
     In a device  101  for manufacturing a membrane-catalyst assembly according to the embodiment shown in  FIG.  2   , a membrane-electrode assembly is manufactured as follows. The description of the parts similar to those in the first embodiment will be omitted. 
     In the second embodiment, instead of the catalyst transfer sheets used in the first embodiment, gas diffusion electrodes  80 A and  80 B are supplied from gas diffusion electrode supply rolls  81 A and  81 B, respectively. The gas diffusion electrode supply rolls  81 A and  81 B are provided above and below an unwound electrolyte membrane  10 , respectively. The gas diffusion electrode  80 A to be bonded to the upper surface of the electrolyte membrane  10  is unwound from the gas diffusion electrode supply roll  81 A, and is transported through a backup roll  31 A and a guide roll  22 A in this order with the gas diffusion electrode base material side reverse to the catalyst layer-formed surface of the gas diffusion electrode  80 A being supported on the rolls. The gas diffusion electrode  80 B to be bonded to the lower surface of the electrolyte membrane  10  is unwound from the gas diffusion electrode supply roll  81 B, and is transported through a backup roll  31 B and a guide roll  22 B in this order with the gas diffusion electrode base material side reverse to the catalyst layer-formed surface of the gas diffusion electrode  80 B being supported on the rolls. In this way, the gas diffusion electrodes  80 A and  80 B are supplied to a thermocompression bonding section P so that the surfaces of the gas diffusion electrodes  80 A and  80 B on which the catalyst layers are formed may face the electrolyte membrane  10 . 
     The electrolyte membrane  10 , and the gas diffusion electrodes  80 A and  80 B with a liquid applied to the joint surfaces to the electrolyte membrane  10  are supplied to the thermocompression bonding section P, and pass between hot press rolls  40 A and  40 B and bonded together to form a membrane-catalyst assembly (membrane-electrode assembly)  13   b . The membrane-catalyst assembly  13   b  as a membrane-electrode assembly is fed by a feeding roll  14  and wound into a roll by a membrane-catalyst assembly take-up roll  15 . 
     Third Embodiment: Manufacture of Catalyst Layer-Attached Electrolyte Membrane—2 
     In the third embodiment, first, a first catalyst layer is formed on one surface of an electrolyte membrane using a catalyst layer forming apparatus  102  shown in  FIG.  3   . The first catalyst layer is formed as follows. 
     In this embodiment, an electrolyte membrane  10 ′ in a state of being supported on a support is supplied to the catalyst layer forming apparatus  102 . The material of the support for the electrolyte membrane is not particularly limited, but a PET film can be used, for example. 
     The electrolyte membrane  10 ′ with the support is unwound from an electrolyte membrane supply roll  11 , and supplied to a catalyst solution coater  72  through a guide roll  12 . The catalyst solution coater  72  is provided so as to face the electrolyte membrane  10 ′ supported on a backup roll  73 . To the catalyst solution coater  72 , a catalyst solution is supplied from a catalyst solution tank  70  using a catalyst solution feeding pump  71 , and the catalyst solution coater  72  forms a coating film by applying the supplied catalyst solution to the electrolyte membrane. The method for applying the catalyst solution in the catalyst solution coater  72  is not particularly limited. Methods such as a gravure coater, a die coater, a comma coater, a roll coater, a spray coater, and a screen printing method can be employed. 
     Then, the coating film of the catalyst solution formed on the electrolyte membrane is dried by a dryer  74 , and the solvent in the catalyst solution is evaporated to form a dried first catalyst layer. The method for drying the catalyst solution in the dryer  74  is not particularly limited. A method of blowing a heat medium such as hot air, or a heat oven method using a heater can be employed. 
     A membrane-first catalyst layer assembly  16  including the electrolyte membrane and the first catalyst layer formed on the electrolyte membrane is fed by a feeding roll  14  and wound into a roll by a take-up roll  17  with the support attached to the membrane-first catalyst layer assembly  16 . 
     Then, a second catalyst layer is formed on a surface of the electrolyte membrane reverse to the surface on which the first catalyst layer is formed using a device  103  for manufacturing a membrane-catalyst assembly according to an embodiment shown in  FIG.  4   . The second catalyst layer is formed as follows. 
     The membrane-first catalyst layer assembly  16  is unwound from a supply roll  18  and passes on a guide roll  12 , and a support  51  is separated from the interface with the electrolyte membrane via guide rolls  26 A and  26 B. The support  51  separated in this process is wound on a support take-up roll  50 . 
     On a first catalyst layer surface of the membrane-first catalyst layer assembly  16  from which the support  51  has been separated, a cover film  61  unwound from a cover film supply roll  60  is laminated via guide rolls  27 A and  27 B, and then the membrane-first catalyst layer assembly  16  with the cover film  61  is supplied to a thermocompression bonding section P. The cover film  61  may be laminated before the support  51  is separated. 
     The cover film  61  is used to protect the first catalyst layer during the step of forming the second catalyst layer, and the material of the cover film  61  is not particularly limited as long as it does not interfere with the function of the catalyst layer by the attachment and detachment. In general, it is possible to use natural fiber sheets typified by paper, hydrocarbon-based plastic films typified by those of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), polyimide, and polyphenylene sulfide, fluorine-based films typified by those of perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), and an ethylene-tetrafluoroethylene copolymer (ETFE), and materials obtained by applying an acrylic pressure-sensitive adhesive, a urethane acrylate pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a silicone pressure-sensitive adhesive or the like to the above-mentioned materials to improve adhesion to an adherend. A material having improved adhesion also provides an effect of preventing the electrolyte membrane from swelling because the material can support the electrolyte membrane while the electrolyte membrane is in contact with the liquid. 
     To the membrane-first catalyst layer assembly  16  supplied to the thermocompression bonding section P, the second catalyst layer is thermocompression-bonded in a state where the first catalyst layer is covered with the cover film by the liquid application step and the thermocompression bonding step similar to those in the first embodiment to form a membrane-catalyst assembly (catalyst layer-attached electrolyte membrane)  13   c.    
     The membrane-catalyst assembly  13   c  as a catalyst layer-attached electrolyte membrane that has passed through the thermocompression bonding section P passes between guide rolls  23 A and  23 B. During the passage, a temporary base material  24 A is separated from the membrane-catalyst layer assembly  13   c , and wound up on a temporary base material take-up roll  25 A. The membrane-catalyst assembly  13   c  from which the temporary base material  24 A has been separated is fed by a feeding roll  14  and wound into a roll by a catalyst layer-attached electrolyte membrane take-up roll  15 . The membrane-catalyst assembly  13   c  may be wound up with the cover film  61  bonded thereto, or the cover film  61  may be separated from the membrane-catalyst assembly  13   c  with a hot press roll  40 B immediately after pressing. When the membrane-catalyst assembly  13   c  is wound up with the cover film  61  bonded thereto, it is possible to prevent wrinkles and elongation of the catalyst layer-attached electrolyte membrane, and to protect the catalyst layer from physical damages due to external factors. Further, when the cover film  61  is separated immediately after thermocompression bonding and the catalyst layer is exposed, it is possible to effectively discharge the liquid vapor generated in the thermocompression bonding step. In this case, the catalyst layer can be protected with a new cover film before the membrane-catalyst assembly  13   c  is wound up. 
     Fourth Embodiment: Manufacture of Catalyst Layer-Attached Electrolyte Membrane—3 
     In the fourth embodiment, first, a first catalyst layer is formed on one surface of an electrolyte membrane using a device  104  for manufacturing a membrane-catalyst assembly according to an embodiment shown in  FIG.  5   . The first catalyst layer is formed as follows. 
     In this embodiment, an electrolyte membrane  10 ′ in a state of being supported on a support is supplied to the catalyst layer forming apparatus  104 . The electrolyte membrane  10 ′ with the support is unwound from an electrolyte membrane supply roll  11 , and supplied to a thermocompression bonding section P. To the electrolyte membrane  10 ′ supplied to the thermocompression bonding section P, the first catalyst layer is thermocompression-bonded by the liquid application step and the thermocompression bonding step similar to those in the first embodiment to form a membrane-first catalyst layer assembly  16 ′. 
     The membrane-first catalyst layer assembly  16 ′ including the support and a temporary base material of a catalyst transfer sheet  20 A is fed by a feeding roll  14  and wound into a roll by a take-up roll  17 . 
     Then, a second catalyst layer is formed on a surface of the electrolyte membrane reverse to the surface on which the first catalyst layer is formed using a catalyst layer forming apparatus  105  according to an embodiment shown in  FIG.  6   . The second catalyst layer is formed as follows. 
     The membrane-first catalyst layer assembly  16 ′ is unwound from a supply roll  18 , and a support  51  is separated from the interface with the electrolyte membrane via guide rolls  26 A and  26 B. The support  51  separated in this process is wound on a support take-up roll  50 . 
     On the membrane-first catalyst layer assembly  16 ′ from which the support  51  has been separated, the second catalyst layer is formed by a catalyst solution coater  72  and a dryer  74  similar to those in the third embodiment to form a membrane-catalyst assembly (catalyst layer-attached electrolyte membrane)  13   d.    
     The membrane-catalyst assembly  13   d  as a catalyst layer-attached electrolyte membrane is fed by a feeding roll  14 , and the membrane-catalyst assembly  13   d  including the temporary base material is wound into a roll by a catalyst layer-attached electrolyte membrane take-up roll  15 . 
     EXAMPLES 
     Hereinafter, the present invention will be more specifically described with reference to examples, but the present invention is not limited to these examples. 
     In Examples 1 to 6, a catalyst transfer sheet roll (width of base material: 100 mm, thickness: 8 μm) was used as a catalyst transfer sheet. The catalyst transfer sheet roll was obtained by applying, to a continuous band-shaped PTFE sheet as a base material, a catalyst coating liquid containing a Pt-supported carbon catalyst TEC10E50E manufactured by Tanaka Kikinzoku Kogyo K.K. and a Nafion (registered trademark) solution, then drying the catalyst coating liquid to give a catalyst transfer sheet, and forming the catalyst transfer sheet into a roll (amount of supported platinum: 0.3 mg/cm 2 ). 
     The electrolyte membranes of Examples 2 to 6 were manufactured with reference to the manufacturing method described in Japanese Patent Laid-open Publication No. 2018-60789. 
     Example 1 
     Using a device having the schematic configuration shown in  FIG.  1   , the catalyst layer was transferred from the above-mentioned catalyst transfer sheet to one surface of a commercially available “Nafion (registered trademark)” membrane, trade name NR211 (thickness: 25 μm) used as an electrolyte membrane according to the method described in the above-mentioned first embodiment. 
     In the liquid application step, 100% pure water was applied to the catalyst layer in a droplet form in an amount of 0.4 μL per 1 cm 2  using a flat spray nozzle CBIMV 80005S manufactured by H. IKEUCHI &amp; CO., LTD. 
     In the thermocompression bonding step, a pair of hot press rolls each having a diameter of 250 mm was used. One of the rolls was a stainless steel roll, and the other roll was a fluororubber roll having a hardness of 90° (Shore A). The hot press rolls applied a pressure of 3.0 MPa. The pressure is a value measured using a Prescale film manufactured by FUJIFILM Corporation. The rolls had a surface temperature of 160° C., and the heating temperature measured with a thermocouple provided at the joint interface was found to be 115° C. The electrolyte membrane and the catalyst transfer sheet were transported at a transport speed of 4.0 m/min. 
     As a result of visual evaluation of the obtained membrane-catalyst assembly, there was no transfer failure of the catalyst layer nor swelling or wrinkles of the electrolyte membrane, and the membrane-catalyst assembly was of high quality. 
     Example 2 
     Using a device having the schematic configuration shown in  FIG.  1   , the catalyst layer was transferred from the catalyst transfer sheet same as the one used in Example 1 to one surface of a polyetherketone-based polymer electrolyte membrane made of a polymer represented by the following formula (G1) according to the method described in the above-mentioned first embodiment. 
     
       
         
         
             
             
         
       
     
     In the liquid application step, 100% pure water was applied to the catalyst layer in an amount of 0.4 μL per 1 cm 2  using a flat spray nozzle CBIMV 80005S manufactured by H. IKEUCHI &amp; CO., LTD. 
     In the thermocompression bonding step, a pair of hot press rolls each having a diameter of 250 mm was used. One of the rolls was a stainless steel roll, and the other roll was a fluororubber roll having a hardness of 90° (Shore A). The hot press rolls applied a pressure of 4.2 MPa. The pressure is a value measured using a Prescale film manufactured by FUJIFILM Corporation. The rolls had a surface temperature of 160° C., and the heating temperature measured with a thermocouple provided at the joint interface was found to be 115° C. The electrolyte membrane and the catalyst transfer sheet were transported at a transport speed of 4.0 m/min. 
     As a result of visual evaluation of the obtained membrane-catalyst assembly, there was no transfer failure of the catalyst layer nor swelling or wrinkles of the electrolyte membrane, and the membrane-catalyst assembly was of high quality. 
     Example 3 
     Using a device having the schematic configuration shown in  FIG.  1   , the catalyst layer was transferred from the above-mentioned catalyst transfer sheet to one surface of a polyarylene-based polymer electrolyte membrane made of a polymer represented by the following formula (G2) according to the method described in the above-mentioned first embodiment. 
     
       
         
         
             
             
         
       
     
     (In the formula (G2), k, m, and n are integers, and k is 25, m is 380, and n is 8.) 
     The liquid application step and the thermocompression bonding step were performed in the same manner as in Example 2. 
     As a result of visual evaluation of the obtained membrane-catalyst assembly, there was no transfer failure of the catalyst layer nor swelling or wrinkles of the electrolyte membrane, and the membrane-catalyst assembly was of high quality. 
     Example 4 
     Using a device having the schematic configuration shown in  FIG.  1   , the catalyst layer was transferred from the above-mentioned catalyst transfer sheet to one surface of a polyethersulfone-based polymer electrolyte membrane including a segment represented by the following formula (G3) and a segment represented by the following formula (G4) according to the method described in the above-mentioned first embodiment. 
     
       
         
         
             
             
         
       
     
     (In the formulae (G3) and (G4), p, q, and r are integers, and p is 170, q is 380, and r is 4.) 
     The liquid application step and the thermocompression bonding step were performed in the same manner as in Example 2. 
     As a result of visual evaluation of the obtained membrane-catalyst assembly, there was no transfer failure of the catalyst layer nor swelling or wrinkles of the electrolyte membrane, and the membrane-catalyst assembly was of high quality. 
     Example 5 
     A catalyst layer-attached electrolyte membrane was manufactured according to the method described in the above-mentioned third embodiment. 
     Using an apparatus having the schematic configuration shown in  FIG.  3   , a catalyst solution was applied to one surface of the polyetherketone-based polymer electrolyte membrane made of the polymer represented by the formula (G1), and the catalyst solution was dried to form a first catalyst layer. The catalyst solution used was a catalyst coating liquid containing a Pt-supported carbon catalyst TEC10E50E manufactured by Tanaka Kikinzoku Kogyo K.K. and a Nafion (registered trademark) solution. The catalyst solution was dried at 120° C. for 5 minutes to give a catalyst layer having a thickness of 5 μm. 
     Then, using a device having the schematic configuration shown in  FIG.  4   , a second catalyst layer was transferred from the above-mentioned catalyst transfer sheet to the other surface of the polyetherketone-based polymer electrolyte membrane having the first catalyst layer to form the second catalyst layer. A cover film to be laminated on the first catalyst layer surface was Lumirror (registered trademark), a PET film manufactured by TORAY INDUSTRIES, INC. and having a thickness of 75 μm. The liquid application step and the thermocompression bonding step were performed by a method similar to that in Example 2. 
     When the cover film was separated from the obtained catalyst layer-attached electrolyte membrane, no deposits or the like were observed on the cover film. Further, as a result of visual evaluation of the obtained catalyst layer-attached electrolyte membrane, there was no transfer failure of the catalyst layer nor swelling or wrinkles of the electrolyte membrane, and the catalyst layer-attached electrolyte membrane was of high quality. 
     Example 6 
     A catalyst layer-attached electrolyte membrane was manufactured according to the method described in the above-mentioned fourth embodiment. 
     Using a device having the schematic configuration shown in  FIG.  5   , the first catalyst layer was transferred from the above-mentioned catalyst transfer sheet to one surface of the polyetherketone-based polymer electrolyte membrane made of the polymer represented by the formula (G1). The liquid application step and the thermocompression bonding step were performed by a method similar to that in Example 2. 
     Then, using an apparatus having the schematic configuration shown in  FIG.  6   , a catalyst solution similar to that of Example 5 was applied to the other surface of the electrolyte membrane having the first catalyst layer, and the catalyst solution was dried to form a second catalyst layer. 
     When the temporary base material was separated from the obtained catalyst layer-attached electrolyte membrane, no deposits or the like were observed on the temporary base material. Further, as a result of visual evaluation of the obtained catalyst layer-attached electrolyte membrane, there was no transfer failure of the catalyst layer nor swelling or wrinkles of the electrolyte membrane, and the catalyst layer-attached electrolyte membrane was of high quality. 
     Comparative Example 1 
     The catalyst layer was transferred from the same catalyst transfer sheet as that used in Example 1 to one surface of an electrolyte membrane in the same manner as in Example 2 except that the liquid application step was not performed. As a result of visual evaluation of the obtained membrane-catalyst assembly, transfer failure of the catalyst layer was observed. 
     DESCRIPTION OF REFERENCE SIGNS 
     
         
         
           
               100 ,  101 ,  103 ,  104 : Device for manufacturing membrane-catalyst assembly 
               102 ,  105 : Catalyst layer forming apparatus 
               10 ,  10 ′: Electrolyte membrane 
               11 ,  18 : Electrolyte membrane supply roll 
               13   a ,  13   b ,  13   c ,  13   d : Membrane-catalyst assembly 
               14 : Feeding roll 
               15 ,  17 : Membrane-catalyst assembly take-up roll 
               16 ,  16 ′: Membrane-first catalyst layer assembly 
               12 ,  22 A,  22 B,  23 A,  23 B,  26 A,  26 B,  27 A,  27 B: Guide roll 
               20 A,  20 B: Catalyst transfer sheet 
               21 A,  21 B: Catalyst transfer sheet supply roll 
               24 A,  24 B: Temporary base material 
               25 A,  25 B: Temporary base material take-up roll 
               30 A,  30 B: Spray nozzle 
               31 A,  31 B,  73 : Backup roll 
               32 A,  32 B: Nozzle chamber 
               33 A,  33 B: Valve 
               34 A,  34 B: Pressure reducing tank 
               40 A,  40 B: Hot press roll 
               41 A,  41 B: Heat shield plate 
               50 : Support take-up roll 
               51 : Support 
               60 : Cover film supply roll 
               70 : Catalyst solution tank 
               71 : Catalyst solution feeding pump 
               72 : Coater 
               74 : Dryer 
               80 A,  80 B: Gas diffusion electrode 
               81 A,  81 B: Gas diffusion electrode supply roll 
             P: Thermocompression bonding section 
             S: Space