JP2017174572A - Manufacturing method of membrane/electrode assembly for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a membrane/electrode assembly capable of suppressing reduction of flatness caused by influences of a dimensional change in a solid polymer electrolyte membrane.SOLUTION: A manufacturing method includes: a sticking step of sticking laminate films 5 and 5 on a front face and a rear face of a solid polymer electrolyte membrane 10 in such a manner that a cross section of at least one side is exposed; a catalyst layer formation part removal step of removing a catalyst layer formation part 2 of the laminate film 5, thereby exposing the front face and the rear face of the solid polymer electrolyte membrane 10; an application step of applying a catalyst ink 3 to the exposed front and rear faces of the solid polymer catalyst membrane 10 while heating the catalyst ink on a heating part; and a drying step of drying the catalyst ink 3, thereby forming a catalyst layer 50. A drying time in the drying step is equal to or shorter than 30 seconds.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a membrane-electrode assembly (MEA) of a fuel cell.

As a conventional method for producing a membrane electrode assembly, a transfer substrate provided with a catalyst layer having a desired shape and a solid polymer electrolyte membrane are subjected to thermocompression bonding with a hot press, a heat laminating roll, etc., and then the substrate is peeled off. A method has been proposed.
For example, Patent Document 1 discloses a technique using a hot press and a technique using a heat laminating roll. The above-described method using a heat laminating roll involves contacting a long solid polymer electrolyte membrane with a transfer substrate provided with a catalyst layer having a desired shape disposed on both sides thereof, and heating with a pair of heat laminating rolls. The solid polymer electrolyte membrane and the catalyst layer are integrally joined by pressure bonding, and then only the base material is peeled off from the catalyst layer using a pair of peeling rolls, and the catalyst layer is separated from the solid polymer electrolyte. Transferred to the film surface.

On the other hand, Patent Document 2 is provided with a gasket member in order to prevent gas leakage at the exposed portion of the surface of the solid polymer electrolyte membrane and intensive deterioration of a region where the catalyst layer in the electrolyte is not formed after the thermal transfer. Thus, a technique for obtaining a membrane electrode assembly is disclosed.
Here, in the method for applying the gasket member of Patent Document 2, in order to completely cover the outer periphery of the catalyst layer that has already been formed, in order to completely eliminate the exposed portion between the catalyst layer and the solid polymer electrolyte membrane, There is no choice but to ride a gasket member on the catalyst layer. Since the riding section does not participate in the power generation of the fuel cell, there is a concern that the utilization efficiency of the catalyst layer is lowered.

  In addition to the thermal transfer method described above, there is a method for forming a catalyst layer by directly applying and drying a catalyst ink on a solid polymer electrolyte membrane as disclosed in Patent Document 3. Since this method does not require a transfer substrate / transfer process, cost reduction and process simplification are possible. However, even in this method, as in Patent Document 2, the gasket member is applied after the formation of the catalyst layer, so that the utilization efficiency of the catalyst layer is lowered.

  Further, as in Patent Document 4, after a mask material having an opening that has been hollowed into an electrode shape in advance is bonded to the solid polymer electrolyte membrane, the catalyst ink is formed in the same manner as Patent Document 3 to form a catalyst layer. There is also a technique. However, in this method, since the openings are opened on the front and back surfaces of the solid polymer electrolyte membrane before coating, the solid polymer electrolyte membrane portion moves flexibly. A dimensional change occurs in the solid polymer electrolyte membrane due to permeation of the contained solvent. Since the dimensional change of the solid polymer electrolyte membrane portion whose dimension has changed and the electrolyte membrane portion in the non-opening portion are greatly different, the planarity of the obtained MEA is deteriorated. An MEA with poor planarity has a problem that it is difficult to incorporate it into a power generation cell.

Japanese Patent Laid-Open No. 10-64574 Japanese Patent No. 5720810 JP 2015-162308 A Japanese Patent No. 4737924

  The present invention has been made in view of the above points, and there is no decrease in the utilization efficiency of the catalyst layer due to the rise of the gasket material, and the decrease in planarity of the membrane electrode assembly is suppressed while using a simple process. An object of the present invention is to provide a method for producing a membrane electrode assembly that can be used.

One aspect of the method for producing a membrane / electrode assembly for solving the above problems is a bonding step in which a laminated film is bonded to the front and back surfaces of the solid polymer electrolyte membrane so that at least one side of the cross section is exposed. When,
Removing the catalyst layer forming part of the laminated film to expose the surface and the back surface of the solid polymer electrolyte membrane; and
An application step of applying the catalyst ink to the exposed front and back surfaces of the solid polymer electrolyte membrane while heating on the heating unit;
A drying step of drying the catalyst ink to form a catalyst layer,
The drying time in the drying step is 30 seconds or less.

Here, in the membrane electrode assembly manufacturing method, the volatile component of the catalyst ink in the coating step is water and a solvent having higher volatility than water, and the mass ratio of water to the solvent is 6: 4-4. : 6 is preferable.
Moreover, in the said membrane electrode assembly manufacturing method, it is preferable that the heating temperature by the said heating part in the said application | coating process is 70 degreeC or more and less than 120 degreeC.
Moreover, in the said membrane electrode assembly manufacturing method, it is preferable to perform the said application | coating process and the said drying process sequentially on the surface and back surface of a solid polymer electrolyte membrane.
Moreover, in the said membrane electrode assembly manufacturing method, it is preferable to perform the said application | coating process and the said drying process simultaneously on the surface and back surface of a solid polymer electrolyte membrane.

  According to one embodiment of the present invention, it is possible to suppress a decrease in flatness due to an influence of a dimensional change of a solid polymer electrolyte membrane.

It is the schematic which shows one Embodiment of the manufacturing method of a membrane electrode assembly.

Hereinafter, an embodiment of a method for producing a membrane electrode assembly will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and modifications such as design changes can be added based on the knowledge of those skilled in the art. Embodiments to which such modifications are added Are also included in the scope of the embodiments of the present invention.
The manufacturing method of the membrane electrode assembly of this embodiment includes a bonding step, a catalyst layer forming part removing step, a coating step, and a drying step.

A pasting process is a process of pasting a lamination film on the surface and the back of a solid polymer electrolyte membrane, respectively, so that a section of at least one side may be exposed.
The catalyst layer forming portion removing step is a step of removing the catalyst layer forming portion of the laminated film to expose the front and back surfaces of the solid polymer electrolyte membrane.
The application step is a step of applying the catalyst ink to the exposed front and back surfaces of the solid polymer electrolyte membrane while heating on the heating unit. The volatile component of the catalyst ink is water and a solvent having higher volatility than water, and the mass ratio of water to the solvent is preferably 6: 4 to 4: 6. Moreover, it is preferable that the heating temperature by the said heating part is 70 degreeC or more and less than 120 degreeC.
The drying step is a step of drying the catalyst ink to form a catalyst layer, and the drying time in this drying step is 30 seconds or less.

<Bonding process>
First, as shown to Fig.1 (a), as a bonding process, the electrolyte membrane base material 12 formed by bonding a pair of laminated films 5 and 5 to the surface and back surface of the solid polymer electrolyte membrane 10 is produced.
Here, the laminated film 5 is formed by laminating a gas barrier film 1 having an adhesive layer and a plastic film 4 having an adhesive layer. The laminated film 5 is bonded to the front and back surfaces of the solid polymer electrolyte membrane 10 through the adhesive layer of the gas barrier film 1.
The electrolyte membrane substrate 12 has a configuration in which at least one side of the cross section of the solid polymer electrolyte membrane 10 is exposed without being completely covered with the laminated films 5 and 5. The laminated film 5 has a catalyst layer forming portion 2 having a shape that matches the shape of the catalyst layer described later.
Next, as shown in FIG. 1B, the electrolyte membrane substrate 12 is loaded on the heating unit 20 in a state where the electrolyte membrane substrate 12 is held smoothly.

<Catalyst layer formation part removal process>
Next, as the catalyst layer forming portion removing step, as shown in FIG. 1 (c), the catalyst layer forming portion 2 of the laminated film 5 on the upper surface from the electrolyte membrane substrate 12 is removed, and one of the solid polymer electrolyte membranes 10 is removed. Expose the part.
<Application process>
Next, as a coating process, as shown in FIG. 1 (d), the liquid catalyst ink 3 is coated on the electrolyte membrane substrate 12 with a coating device.

<Drying process>
Next, as a drying process, the volatile components of the catalyst ink 3 are removed by the heat of the heating unit 20. Then, as shown in FIG.1 (e), the catalyst layer 50 which has a desired shape is obtained by peeling the plastic film 4 with an adhesion layer.
Thereafter, the electrolyte membrane substrate 12 is turned upside down and loaded on the heating unit 20 while being kept smooth.
Next, as shown in FIG. 1 (f), after removing the catalyst layer forming portion 2 of the laminated film 5 on the upper surface from the electrolyte membrane substrate 12 again, as shown in FIG. Then, the liquid catalyst ink 3 is applied onto the electrolyte membrane substrate 12, and the volatile components are removed by the heat of the heating unit 20.
Next, as shown in FIG. 1H, the catalyst layer 50 having a desired shape is obtained by peeling off the plastic film 4 in the same manner as the already processed opposite surface.

Through the above steps, as shown in FIG. 1I, a membrane electrode assembly 18 having catalyst layers 50, 50 on both sides is obtained.
The above steps are examples in which the coating step and the drying step are sequentially performed on the front and back surfaces of the solid polymer electrolyte membrane, but the coating step and the drying step are performed on the front and back surfaces of the solid polymer electrolyte membrane. You may do it at the same time.
Here, the solid polymer electrolyte membrane 10 is a polymer material that exhibits good proton conductivity in a wet state. The catalyst ink 3 is formed of powdered carbon carrying a catalyst made of platinum or an alloy of platinum and another metal and a resin, and forms a catalyst layer 50 by drying and solidification.

Hereinafter, although the specific example of the material which comprises the solid polymer electrolyte membrane 10, the catalyst layer 50, the gas barrier film 1 which has an adhesion layer, and the plastic film 4 which has an adhesion layer is given, this invention is not limited to these.
As the polymer material constituting the solid polymer electrolyte membrane 10, specifically, a hydrocarbon polymer electrolyte or a fluorine polymer electrolyte can be used. As the hydrocarbon polymer electrolyte membrane, electrolyte membranes such as sulfonated polyether ketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfide, and sulfonated polyphenylene can be used. As the fluorine-based polymer electrolyte, for example, Nafion (registered trademark) manufactured by DuPont, Flemion (registered trademark) manufactured by Asahi Glass, Aciplex (registered trademark) manufactured by Asahi Kasei, Gore Select (registered trademark) manufactured by Gore, etc. can be used. Since the hydrocarbon electrolyte membrane is less permeable and swelled by the solvent than the fluorine polymer electrolyte, it is more preferable to apply the catalyst ink to the solid electrolyte membrane. The thickness of the solid polymer electrolyte membrane 10 is about 5 μm to 100 μm.

As resin which comprises the catalyst layer 50, the thing similar to the said polymeric material can be used.
The catalyst constituting the catalyst layer 50 includes platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, A metal such as aluminum or platinum and an alloy thereof, or an oxide or double oxide thereof can be used. Among these, platinum and platinum alloys are more preferable. Moreover, since the activity of a catalyst will fall when the particle size of a catalyst is too large, and stability of a catalyst will fall when it is too small, 0.5 nm or more and 20 nm or less are preferable.

The powder carbon constituting the catalyst layer 50 is not particularly limited as long as it is in the form of fine particles and has conductivity and does not attack the catalyst. Specifically, carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, fullerene, or the like can be used. The particle size of the powder carbon is preferably about 10 nm to 100 nm smaller than the catalyst.
The catalyst layer 50 can be obtained by applying and drying the catalyst ink 3 prepared by dispersing the above materials in a solvent and water on the solid polymer electrolyte membrane 10. In order to disperse the above-mentioned material suitably, the solvent having a lower boiling point than water can be dried before penetrating into the solid polymer electrolyte membrane 10 and swells, so that it is lower than water. It is more preferable to use lower alcohols such as ethanol having a boiling point, 1-propanol, and 2-propanol.

Furthermore, the surface of the catalyst ink 3 is preferably dried on the heating unit 20 at a speed of 30 seconds or less. Ink that needs to be dried for more than 30 seconds is not preferable because the contained alcohol penetrates into the solid polymer electrolyte membrane 10 and the electrolyte membrane swells.
The base material layer of the gas barrier film 1 and the plastic film 4 is not particularly limited as long as it has a glass transition temperature equal to or higher than the heating temperature in the heating unit 20. For example, polyethylene naphthalate, polyethylene terephthalate, polyimide, polyparban Polymer films such as acid aramid, polyamide (nylon), polysulfone, polyethersulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyetherimide, and polyacrylate can be used. Moreover, heat resistant fluororesins such as ethylene tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroperfluoroalkyl vinyl ether copolymer, and polytetrafluoroethylene can also be used.

Since the base material of the gas barrier film 1 becomes a membrane electrode assembly as a gasket, polyethylene naphthalate is particularly preferable in consideration of both gas barrier properties and heat resistance. In consideration of the fact that the base material of the plastic film 4 is not affected by the catalyst ink and is peeled off, it is particularly preferable to use polyethylene terephthalate.
The pressure-sensitive adhesive layers of the gas barrier film 1 and the plastic film 4 may be acrylic, urethane-based, silicone-based, rubber-based, or the like, such as adhesion to the base material layer and the solid polymer electrolyte membrane 10, and heating. In view of the heat resistance in the part 20, it is more preferable that it is acrylic.

  In order to suppress the overlap and the generation of gaps between the laminated film 5 and the catalyst layer forming part 2 to be removed before coating, a cut is made in the laminated film 5 and the catalyst layer forming part 2 is applied to the laminated film 5, and then the It is preferable to obtain the electrolyte membrane base material 12 by pasting with the molecular electrolyte membrane 10. As a result, the solid polymer electrolyte membrane 10 does not directly contact air until immediately before the application of the catalyst ink 3, so that not only can the dimensional change due to moisture absorption be suppressed, but also when the thin solid polymer electrolyte membrane 10 is used. Can also ensure rigidity.

  Furthermore, since the laminated films 5 and 5 exist on the front and back surfaces of the solid polymer electrolyte membrane 10 even when the catalyst ink 3 is applied, the dimensional change of the portion of the solid polymer electrolyte membrane that touches the catalyst ink 3 is suppressed. Can do. Further, since there is no overlap or gap in the catalyst layer forming part 2 applied by the above method, even if the electrolyte membrane substrate 12 is wound in a roll shape, no trace is generated in the solid polymer electrolyte membrane 10. Therefore, it is possible to manufacture in a large amount with a roll-to-roll suitable for manufacturing with the same quality.

In the cross section of the electrolyte membrane substrate 12 obtained by bonding the laminated film 5 and the solid polymer electrolyte membrane 10, the cross section of one side of the solid polymer electrolyte membrane 10 is exposed. By this exposed portion, moisture can enter and exit during heating drying and cooling in the heating portion 20, and the flatness of the obtained membrane electrode assembly 18 can be suppressed.
Since the heating temperature in the heating unit 20 is about the boiling point of the solvent contained in the catalyst ink 3, it is preferably 70 ° C. or higher, and since it contains water, it is dried in 30 seconds or less. It is more preferable that Furthermore, if it is 120 ° C. or higher, it is not preferable because there is a risk of ignition due to the reaction between the solvent and the catalyst. Moreover, the heating part 20 may be flat or roll-shaped, and it is preferable to smooth the electrolyte membrane substrate 12 by adsorption or tension.

The coating apparatus that forms the catalyst layer 50 on the electrolyte membrane substrate 12 may be any coating device as long as the catalyst layer can be coated with a uniform thickness, and a method such as a die coater method or a roll coater method can be used. In order to obtain the membrane electrode assembly 18, it is necessary to form the catalyst layers 50, 50 on the front and back surfaces of the solid polymer electrolyte membrane 10, but the solid polymer electrolyte membrane 10 may be sequentially formed on each side. It is possible to perform both sides at the same time.
In the method for manufacturing a membrane electrode assembly, it is preferable that all processes are continuous in consideration of manufacturing efficiency, but all processes may be discontinuous in consideration of the yield of the coating process of the catalyst layer 50.

According to the membrane electrode assembly manufacturing method described above, since the dimensional change of the solid polymer electrolyte membrane 10 can be suppressed, the high quality membrane electrode assembly 18 having excellent flatness can be manufactured. In addition, by sticking a sheet having a discontinuous plane on the front and back surfaces of the solid polymer electrolyte membrane 10, even if the solid polymer electrolyte membrane is used in a roll-to-roll method without wrinkles, unnecessary winding marks The manufacturing method of the membrane electrode assembly which can suppress generation | occurrence | production can be provided.
The membrane electrode assembly with good flatness obtained in the present embodiment is a laminate of separators for supplying reaction gas to each electrode in the fuel cell and discharging moisture generated by electrochemical reaction and excess gas. Sometimes there are no gaps. That is, according to this embodiment, it is possible to obtain a membrane electrode assembly in which the power generation performance does not deteriorate.

Examples of the present invention will be specifically described below. However, the present invention is not limited only to these examples.
Example 1
<Manufacture of membrane electrode assembly>
Polyethylene of gas barrier film obtained by forming an acrylic adhesive layer (thickness 10 μm) on polyethylene naphthalate 90 mm wide (Teonex Q51 made by Teijin DuPont Film, thickness 12 μm) by roll-to-roll method, and laminating with a separator Similar to the naphthalate surface, a plastic film (Kimoto Prosave 25CBFS2) provided with an acrylic adhesive layer on polyethylene terephthalate having a width of 90 mm is bonded via a polyethylene terephthalate adhesive layer. Furthermore, a surface protective film (Sanect PAC-3-60T manufactured by Sanei Kaken Co., Ltd.) is bonded to the polyethylene terephthalate surface, and a 5cm x 5cm square punching process is used to cut from the polyethylene terephthalate separator side to the polyethylene naphthalate. After that, a laminated film having a catalyst layer forming part was obtained. Furthermore, in a roll-to-roll method, the separator on the polyethylene terephthalate of this laminated film is peeled off, and bonded to both sides of a hydrocarbon film (thickness 11 μm) on a solid polymer electrolyte membrane with a width of 95 mm, The roll of the electrolyte membrane base material in which the cross section of the solid polymer electrolyte membrane was exposed was obtained by peeling off the surface protective films on both sides. The obtained roll-shaped electrolyte membrane base material was cut out in the width direction and heated on the adsorption stage at 100 ° C. as a heating part, then the catalyst layer forming part was removed, and the catalyst ink was applied with a die coater for 30 seconds. Dried and provided a catalyst layer on one side. At this time, the composition of the catalyst ink consists of a fluorine-based polymer electrolyte membrane dispersion solution (SS700C / 25 manufactured by Asahi Kasei E-Materials), a platinum catalyst (TEC10F50E-HT manufactured by Tanaka Kikinzoku), water, and 1-propanol. The ratio (mass ratio) of the ink was 6: 4, and the solid content concentration in the ink was 8%. This electrolyte membrane substrate was reversed on the adsorption stage at 100 ° C., and after removing the catalyst layer forming portion 2 of the laminated film 5 having a discontinuous plane, the catalyst ink was applied and dried in the same manner. A membrane electrode assembly to which a catalyst layer was applied was obtained. Table 1 shows the evaluation results of the flatness of the obtained membrane / electrode assembly.

(Example 2)
A membrane / electrode assembly of Example 2 was produced in the same manner as in Example 1 except that the ratio of water and solvent in the catalyst ink and the drying completion time were changed as shown in Table 1. Table 1 shows the evaluation results of the flatness of the obtained membrane / electrode assembly.
In addition, the drying completion time in Table 1 indicates that the surface of the catalyst ink on the solid polymer electrolyte membrane has been sufficiently dried by visual observation, and the time taken at that time is shown as the drying completion time. .

(Example 3)
A membrane / electrode assembly of Example 3 was produced in the same manner as in Example 1 except that the drying temperature and drying completion time were changed as shown in Table 1. Table 1 shows the evaluation results of the flatness of the obtained membrane / electrode assembly.
Example 4
A membrane / electrode assembly of Example 4 was produced in the same manner as in Example 1 except that only the alcohol species in the catalyst ink was changed. Table 1 shows the evaluation results of the flatness of the obtained membrane / electrode assembly.
(Comparative Example 1)
The membrane / electrode assembly of Comparative Example 1 was prepared in the same manner as in Example 1 except that the solid polymer electrolyte membrane had a width of 80 mm and a roll of an electrolyte membrane substrate in which the cross section of the solid polymer electrolyte membrane was not exposed was produced. Was made. The results of the same evaluation as in Example 1 are shown in Table 1.

(Comparative Example 2)
A membrane / electrode assembly of Comparative Example 2 was produced in the same manner as in Example 1 except that the ratio of the catalyst ink water and solvent and the drying completion time were changed as shown in Table 1. Table 1 shows the evaluation results of the flatness of the obtained membrane / electrode assembly.
(Comparative Example 3)
A membrane / electrode assembly of Comparative Example 3 was produced in the same manner as in Example 1 except that the drying temperature and drying completion time were changed as shown in Table 1. Table 1 shows the evaluation results of the flatness of the obtained membrane / electrode assembly.
(Comparative Example 4)
A membrane / electrode assembly of Comparative Example 4 was produced in the same manner as in Example 1 except that only the alcohol type in the catalyst ink was changed. Table 1 shows the evaluation results of the flatness of the obtained membrane / electrode assembly.

<Evaluation>
As shown in Table 1, it was confirmed that the planarity was not lowered by exposing the cross section of the solid polymer electrolyte membrane when the solid polymer electrolyte membrane and the laminated film were bonded (Example 1). Thereby, only in Example 1, it became easy to incorporate the membrane electrode assembly into the power generation cell of the fuel cell.
Further, in the ratio of water and solvent in Examples 1 and 2, since the drying was completed in about 30 seconds after the application and heating of the catalyst ink, the permeation into the solid polymer electrolyte membrane was suppressed, and the flatness due to swelling was reduced. The decline is also suppressed. However, in Comparative Example 2, it took 40 seconds to complete the drying, and it was confirmed that the planarity of the membrane electrode assembly was lowered. This decrease in planarity is caused by penetration into the solid polymer electrolyte membrane due to an increase in the amount of solvent.

Further, at the drying temperatures of Examples 1 and 3, since the drying was completed in about 30 seconds after the application and heating of the catalyst ink, the penetration into the solid polymer electrolyte membrane was suppressed, and the decrease in flatness due to swelling was also suppressed. It has been. However, in Comparative Example 3, it took 50 seconds to complete the drying, and it was confirmed that the planarity of the obtained membrane electrode assembly was lowered. This decrease in flatness is caused by the penetration into the solid polymer electrolyte membrane due to the long time required for completion of drying.
In addition, since the alcohols of Examples 1 and 4 volatilize preferentially over water, penetration into the solid polymer electrolyte membrane during application and drying is suppressed, and deterioration in flatness due to swelling is also suppressed. . However, since 1-butanol used in Comparative Example 4 is less volatile than water, it penetrates into the solid polymer electrolyte membrane during coating and drying, and the planarity of the membrane electrode assembly obtained is reduced. Was confirmed.

DESCRIPTION OF SYMBOLS 1 Gas barrier film 2 Catalyst layer formation part 3 Catalyst ink 4 Plastic film 5 Laminated | multilayer film 10 Solid polymer electrolyte membrane 12 Electrolyte membrane base material 18 Membrane electrode assembly 20 Heating part 50 Catalyst layer

Claims (5)

A laminating step of laminating a laminated film on each of the front and back surfaces of the solid polymer electrolyte membrane so that a cross section of at least one side is exposed;
A catalyst layer forming part removing step of removing the catalyst layer forming part of the laminated film and exposing the front and back surfaces of the solid polymer electrolyte membrane;
An application step of applying the catalyst ink to the exposed front and back surfaces of the solid polymer electrolyte membrane while heating on the heating unit;
Drying the catalyst ink to form a catalyst layer,
A method for producing a membrane electrode assembly for a fuel cell, wherein the drying time in the drying step is 30 seconds or less.   2. The fuel cell according to claim 1, wherein a volatile component of the catalyst ink in the coating step is water and a solvent having higher volatility than water, and a mass ratio of water to the solvent is 6: 4 to 4: 6. Manufacturing method of membrane electrode assembly.   3. The method of manufacturing a membrane electrode assembly for a fuel cell according to claim 1, wherein a heating temperature by the heating unit in the coating step is 70 ° C. or higher and lower than 120 ° C. 4.   The manufacturing method of the membrane electrode assembly of the fuel cell as described in any one of Claims 1-3 which performs the said application | coating process and the said drying process sequentially on the surface and back surface of a solid polymer electrolyte membrane.   The manufacturing method of the membrane electrode assembly of the fuel cell as described in any one of Claims 1-3 which performs the said application | coating process and the said drying process simultaneously on the surface and back surface of a solid polymer electrolyte membrane.

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