JP4583722B2 - Method for detecting pinhole and method for producing membrane electrode assembly - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pinhole detection method for inspecting whether or not a pinhole is generated in a film or film such as a polymer film of a fuel cell, and a method for producing a membrane electrode assembly (hereinafter referred to as MEA).
[0002]
[Prior art]
Solid polymer fuel cells are characterized by low operating temperature and high output density, and are therefore being developed as power sources for next-generation automobiles and batteries for household cogeneration systems. A fuel cell has a structure in which a laminate (hereinafter referred to as a stack) is housed in a container. The stack is a basic structural unit (hereinafter referred to as a module) composed of an MEA having a structure in which an electrolytic membrane is sandwiched between a fuel electrode and an air electrode, and a separator that is a conductive gas separation / supply plate sandwiched between adjacent MEAs. 10 are stacked (the number is determined according to the required output voltage). The MEA has a structure in which an anode catalyst layer that is a fuel electrode, a polymer membrane that is an electrolytic membrane, and a cathode catalyst layer that is an air electrode are sandwiched between conductive gas diffusion layers (hereinafter referred to as GDL (Gas Diffusion Layer)). The heart of the fuel cell. For example, the thickness of each layer is 15 μm for the anode catalyst layer, 30 μm for the polymer membrane, and 15 μm for the cathode catalyst layer.
[0003]
The most common cause of MEA failure in the manufacturing stage is the occurrence of minute pinholes of several μm in the polymer film. When a normal MEA without a pinhole is used as a fuel cell, hydrogen (fuel gas) is separated from electrons at the fuel electrode and ionized, hydrogen ions move in the electrolyte, and hydrogen ions recombine with electrons at the air electrode. It returns to hydrogen and then combines with oxygen in the air to become water. In this case, the Gibbs free energy of the reaction in which water is generated from hydrogen and oxygen is directly converted into electric energy (driving force for moving hydrogen ions in the electrolyte) with extremely high efficiency. If there is a pinhole, the hydrogen of the fuel electrode is not ionized and moves to the air electrode as a gas, and is combined with oxygen by the catalyst at the air electrode to become water. In this case, Gibbs free energy is released in situ as thermal energy rather than electrical energy. The MEA is locally heated in the pinhole and deteriorates. As this progresses, the battery becomes defective.
[0004]
In the manufacture of polymer electrolyte fuel cells, there is a process to check whether or not pinholes are generated in the polymer membrane, which is an electrolytic membrane, and to eliminate the polymer membranes that have pinholes as defective products It is done. In the pinhole detection method of the conventional example, the characteristics of the completed stack are inspected to determine whether or not the defective module is included in the stack. As a result of inspection, when it is found that a module having a characteristic failure is included in the stack, the defective module in the stack is replaced. However, the work of disassembling the completed stack, replacing the defective module, and reassembling the stack requires a great deal of labor. Before being assembled into the stack, preferably before being assembled into the MEA, it is inspected whether the polymer film has pinholes, and the polymer film having pinholes is removed from the production process. If it can be eliminated, the yield of the assembled stack or MEA can be greatly improved, and the effective number of manufacturing steps can be greatly reduced.
[0005]
Examples of the MEA manufacturing method include a coating method.
The coating method is an MEA manufacturing method in which an anode catalyst layer, a polymer film, and a cathode catalyst layer are sequentially applied onto a base material such as PET (Polyethylene Terephthalate). The cause of pinhole generation is that pinholes are generated due to bubbles or the like that have entered the polymer material when the polymer film is applied, and there are fine gaps in the anode catalyst layer. The material is sucked in and pinholes are generated. In both cases, it is necessary to inspect the presence or absence of pinholes after applying the polymer film. In that case, it is necessary to inspect whether there is a pinhole in the transparent or translucent polymer film in a state where the non-transparent catalyst layer exists under the polymer film.
[0006]
Conventionally, a number of pinhole detection methods have been proposed. For example, a set of a halogen light source and an optical sensor arranged with a transparent or translucent film as a test object sandwiched between them in the film running direction. Install two places along. A halogen light source irradiates light onto a transparent or translucent film. An optical sensor receives light transmitted through the film. When there is a pinhole, the amount of light received by the photosensor is greatly increased as compared with a place where there is no pinhole. There is a method of detecting pinholes on the film by utilizing this (see Patent Document 1). This method cannot be applied to pinhole detection of a film or film in which a non-transparent film or film is adhered and adhered to a transparent or translucent film or film that is an inspection object.
[0007]
As another method, a polarizing film which is an inspection object in which a red release film and a transparent film are laminated is placed on a support base. The polarizing film is irradiated with green illumination light that is complementary to the red color of the release film, and the inspector observes the reflected light. The green light incident on the release film is absorbed by the red release film and cannot be seen. Only green light reflected by the surface of the transparent film reaches the inspector's eyes. There is a method in which an inspector can detect only surface irregularities including pinholes on the front side of the transparent film of the polarizing film (the side in contact with the release film is the back side), dust attached to the surface, and the like (Patent Document 2). reference). This method is a method for detecting unevenness, dirt, etc. on the surface of the polarizing film, and cannot detect only pinholes penetrating the transparent film. Also, it cannot be used when the transparency of the transparent film is high. For example, this method cannot be used for detection of pinholes in MEA polymer films or films of fuel cells in which surface irregularities do not matter and only pinholes penetrating the transparent film cause defects.
[0008]
As another method, a light source, a polarizing plate, a transparent sheet as an inspection object, another polarizing plate, and a light receiving unit are arranged in this order. There is a method in which light is emitted from a light source to a transparent film, and a light receiving unit detects light transmitted through a polarizing plate, a transparent sheet, and another polarizing plate (see Patent Document 3). This method is also not applicable to pinhole detection of a film or film in which a non-transparent film or film is adhered and adhered to a transparent or translucent film or film that is an inspection object.
[0009]
[Patent Document 1]
JP 2000-146861 A
[Patent Document 2]
JP 2001-108630 A
[Patent Document 3]
Japanese Patent Laid-Open No. 06-18445
[0010]
[Problems to be solved by the invention]
As described above, in order to detect pinholes existing in a film or film of a transparent or semi-transparent inspection object existing on a non-transparent film or film, the detection method has the following four conditions. It is necessary. (1) It has a detection sensitivity for detecting pinholes of several μm in size, (2) It is a non-destructive inspection and a non-contact inspection, and (3) It can be inspected in a non-vacuum state. (4) It is possible to detect pinholes in a transparent or translucent film or film existing on a non-transparent surface (for example, a film). Conventionally, there has been no pinhole detection method having these four conditions.
[0011]
The present invention satisfies these conditions, and pinhole detection that can accurately detect pinholes of several μm existing in a film or film of a transparent or translucent inspection object existing on a nontransparent film or film It is an object of the present invention to provide a method and a method for producing a membrane electrode assembly.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is a method for detecting the presence or absence of pinholes in a transparent or translucent polymer film (inspection object) formed on a non-transparent anode catalyst layer, The anode catalyst layer emits fluorescence on the molecular film. Hateful Irradiate with short wavelength light To generate light from the polymer film , The passing wavelength is longer than the wavelength of the irradiation light In the band near the wavelength at which the amount of light generated from the polymer film peaks A light receiving wavelength filter is used to receive the light generated from the polymer film through the light receiving wavelength filter and detect the presence or absence of pinholes in the polymer film based on the amount of the received light; This is a pinhole detection method characterized.
[0013]
The present invention detects the reaction light according to the amount of the constituent material of the test object, for example, in the case of a reflection type configuration, regardless of the state of the surface opposite to the input surface of the irradiation light, Existence can be inspected with high accuracy, non-destructive and non-contact, and pinholes of several μm existing in transparent or translucent inspection objects existing on non-transparent films and films can be accurately detected. .
Further, the irradiation light is ultraviolet light, and the inspection object receives only light having a wavelength near a wavelength at which the amount of fluorescence generated in response to the ultraviolet light reaches a peak.
[0014]
Certain organic substances (for example, polymer films such as perfluorosulfonic acid films) generate strong reaction light that is fluorescent when excited with ultraviolet light. On the other hand, the catalyst layer formed in the lower layer of the polymer film by MEA or the like of the fuel cell hardly emits fluorescence even when irradiated with light having a short wavelength. The present invention can detect pinholes generated in a polymer film formed on a catalyst layer with high sensitivity, for example, in a MEA manufacturing process of a fuel cell.
Further, the irradiation light is visible light, and only the light having a wavelength in the vicinity of the wavelength at which the amount of light generated when the inspection target causes Raman scattering by the visible light reaches a peak is received.
[0015]
When a substance (for example, a polymer film such as a perfluorosulfonic acid film) is excited with visible light or near infrared light, Raman scattering occurs depending on the molecular shape of the substance. The generated Raman scattered light has a narrow peak with a wavelength that is different from the wavelength of the irradiation light and that varies depending on the molecular shape of the substance. The wavelength of the Raman scattered light varies depending on the molecular shape of the substance. Therefore, for example, the polymer film such as MEA of the fuel cell and the catalyst layer formed thereunder have different wavelengths of Raman scattered light. Since the half-value width of the spectrum of Raman scattered light is narrow, it is easy to discriminate between the Raman scattered light of the polymer film and the Raman scattered light of the catalyst layer.
The present invention can detect pinholes generated in a transparent or translucent film formed on a non-transparent film with high sensitivity based on the amount of light around the peak wavelength of Raman scattered light.
According to the present invention, for example, even when a catalyst layer formed in a lower layer of a polymer membrane such as MEA of a fuel cell emits fluorescence when irradiated with ultraviolet light, the pinhole of the polymer membrane that is an inspection object is formed. It can be detected.
[0016]
Further, the irradiation light is X-rays, and only X-rays having a wavelength in the vicinity of a wavelength at which the intensity of fluorescent X-rays generated when the inspection object reacts to the X-rays reaches a peak are received.
Certain organic substances (for example, polymer films such as perfluorosulfonic acid films) generate intense reaction light that is fluorescent X-rays when excited by X-rays. On the other hand, the catalyst layer formed in the lower layer of the polymer film by MEA or the like of the fuel cell does not emit fluorescent X-rays even when irradiated with X-rays. The present invention can detect pinholes generated in a polymer film formed on a catalyst layer with high sensitivity, for example, in a MEA manufacturing process of a fuel cell.
[0017]
Furthermore, a predetermined material is applied on the base to form an anode catalyst layer, and another predetermined material is applied thereon to form a polymer film, and the presence or absence of pinholes in the polymer film is inspected. The membrane electrode assembly production method is characterized in that a cathode catalyst layer is formed by applying another predetermined material thereon only when it is determined to be a non-defective product in the inspection.
[0018]
According to the present invention, since the yield of the completed MEA is extremely good, the rate at which the stack is repaired due to poor characteristics after the stack is completed is greatly reduced. The present invention realizes a MEA production method that has a good yield and can reduce the number of repair steps in a later process by a coating method. An inexpensive fuel cell can be realized by the production method of the present invention.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments that specifically show the best mode for carrying out the present invention will be described below with reference to the drawings.
[0020]
Embodiment 1
Hereinafter, a pinhole detection device, a pinhole detection method, and a MEA production method according to Embodiment 1 of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a configuration of a pinhole detection device according to Embodiment 1 of the present invention. In FIG. 1, 2 is a polymer film, 1 is a pinhole generated in the polymer film 2, 3 is a catalyst layer, 4 is a base film, 5 is an illumination light source, 6 is an illumination wavelength filter, 7 is a light projection lens, 8 Is the illumination light output from the illumination light source 5, 9 is the light whose wavelength is shifted, 10 is the light receiving lens, 11 is the light receiving wavelength filter, 12 is the optical sensor, 13 is the pinhole detector, 14 is the monitor TV, 15 is the controller , 16 is an X-axis drive unit, 17 is a Y-axis drive unit, 18 is a work chuck, 19 is an X-axis, and 20 is a Y-axis.
[0021]
The inspection objects (the polymer film 2, the catalyst layer 3, and the base film 4) are in a state of an intermediate process of manufacturing the MEA of the fuel cell. An MEA production method in the present embodiment will be described. First, a predetermined material is applied on the base to produce the anode catalyst layer 3 having a thickness of 15 μm. The catalyst layer 3 is a black non-transparent substance in which a catalyst such as platinum is mixed in a conductor such as carbon. Next, another predetermined material is applied on the catalyst layer 3 to form a transparent or translucent polymer film 2 having a thickness of 30 μm. The polymer film 2 is a transparent material such as a perfluorosulfonic acid film. In the state made up to this point, whether or not there is a pinhole in the polymer film 2 is inspected by a pinhole detection method described below. The polymer membrane 2, the catalyst layer 3, and the base film 4 shown in FIG. 1 are those at the time when the production of the polymer membrane is completed. Only when it is determined in the inspection that the polymer film 2 does not have a pinhole of a predetermined threshold value or more, another predetermined material is applied thereon to form a cathode catalyst layer. In this way, MEA is produced with a high yield by the coating method.
Here, the “predetermined threshold value” is an arbitrary value. For example, the threshold value is a threshold value for the size of one pinhole. The threshold value may be a fixed threshold value or a floating threshold value. For example, a pass / fail judgment may be made by applying a predetermined threshold to the result of differential processing of the image.
[0022]
Returning to the description of FIG. The work chuck 18, the X axis 19 and the Y axis 20 are included in the inspection stage. The control unit 15 controls the X-axis drive unit 16 and the Y-axis drive unit 17 to drive the work chuck 18 of the inspection stage in the X-axis direction and the Y-axis direction. The work chuck 18 of the inspection stage mounts the base film 4 on which the catalyst layer 3 and the polymer film 2 as the inspection object are formed.
[0023]
The pinhole detection device and the pinhole detection method of the present embodiment are intended to detect a pinhole 1 of about 1 μm existing in a polymer film 2 that is an inspection object.
Of the light emitted from the illumination light source 5 which is a mercury lamp, the illumination wavelength filter 6 passes only ultraviolet light having a wavelength of 300 nm or less. The light that has passed through the illumination wavelength filter 6 is collected by the light projecting lens 7 and irradiated onto the inspection object as illumination light 8. The illumination light 8 is area illumination that irradiates a wider range than the inspection visual field described later.
The illumination light 8 applied to the inspection object excites the inspection object and changes to fluorescence 9 whose wavelength is shifted to the long wavelength side. The fluorescence 9 is collected by the light receiving lens 10.
The light receiving wavelength filter 11 passes only light having a wavelength of 320 nm to 430 nm out of the fluorescence 9 collected by the light receiving lens 10. The optical sensor 12 receives light that has passed through the light receiving lens 10.
The optical sensor 12 converts the fluorescence that has passed through the light receiving wavelength filter 11 into an electrical detection signal and outputs the electrical detection signal to the pinhole detector 13. The optical sensor 12 of the embodiment is an area CCD.
[0024]
In the first embodiment, the size of the inspection object is 100 mm × 100 mm. The pinhole detection device needs to inspect the entire surface of the inspection object.
In order to detect the pinhole 1 of 1 μm, the pixel resolution is set to 1 μm. The optical sensor 12 uses 2000 pixels × 2000 pixels, and the inspection visual field size is set to 2 mm × 2 mm.
As shown in FIG. 3, the control unit 15 moves the inspection object at a pitch of the inspection visual field size. The optical sensor 12 inputs an image, and the pinhole detection unit 13 performs image processing for 2500 visual fields.
[0025]
The electronic shutter function of the optical sensor 12 is used to speed up pinhole inspection. The optical sensor 12 does not input an image after the control unit 15 stops the X-axis driving unit 16 for each field of view, but the X-axis driving unit 16 moves the inspection object at a constant speed in the X-axis direction. The optical sensor 12 continuously inputs images with the electronic shutter function operated, and the pinhole detector 13 processes the input images. When the inspection object is moved by one field of view in the Y-axis direction, the optical sensor 12 inputs an image after the control unit 15 stops the Y-axis driving unit 17. That is, the inspection object is scanned relative to the inspection visual field in the X-axis direction and the Y-axis direction. In the embodiment, when the pinhole detection unit 13 completes the image processing within 0.05 seconds, the pinhole detection device can perform inspection in 0.05 seconds per 2 mm × 2 mm visual field. As shown in FIG. 3, the optical sensor 12 moves the inspection object at a speed of 40 mm / second in the X-axis direction of the main scanning direction while the X-axis drive unit 16 moves 0.0001 seconds every 0.05 seconds. Input an image with the electronic shutter. The pinhole detection apparatus can complete the inspection of the entire surface of the inspection object in 125 seconds.
[0026]
The pinhole detection unit 13 includes an A / D converter 131, an image processing unit 132, an image determination unit 133, and an image generation unit 134. The pinhole detector 13 detects whether or not there is a pinhole in the polymer film by the method described below, and outputs the detection result.
In the first embodiment, the pinhole detection unit 13 is a personal computer.
The A / D converter 131 converts the output signal of the optical sensor 12 into a digital signal.
The image processing unit 132 and the image determination unit 133 are functions that the CPU executes by software. The image processing unit 132 creates a bright and dark image corresponding to the intensity (light quantity) of fluorescence received by the optical sensor 12 for each field of view, and outputs the bright and dark image to the image determination unit 133.
The image determination unit 133 determines the location and size of the pinhole 1 based on the bright and dark image for each field of view corresponding to the fluorescence intensity created by the image processing unit 132.
[0027]
The image generation unit 134 generates an image indicating the location and size of the pinhole 1 for each inspection visual field. The monitor television 14 displays this image. FIG. 2 shows an example of an image generated by the image generation unit 134.
The portion where the pinhole 1 exists is dark because no fluorescence is generated. The image determination unit 133 detects this dark part by image processing. For example, the location and size of the pinhole 1 can be calculated by extracting a region where the amount of light received by the optical sensor 12 is less than a predetermined threshold and calculating the area and the center of gravity position by labeling. The operator can check each image on the monitor television 14, or can display other screens on the monitor television 14 at the time of maintenance for convenience. The image determination unit 133 may automatically determine the quality of the inspection object based on the size of the pinhole 1.
[0028]
The light receiving wavelength filter 11 will be described. The light receiving wavelength filter 11 is a filter that passes only light having a wavelength of 320 nm to 430 nm. The reason for this will be described with reference to FIG.
The graph of FIG. 4 is data obtained by irradiating the polymer film 2 and the catalyst layer 3 with ultraviolet light having a wavelength of 280 nm as excitation light and measuring the respective spectral characteristics with a spectrophotometer. The polymer film 2 or the catalyst layer 3 reacts with the excitation light and emits light shifted to the longer wavelength side than the excitation light. FIG. 4 shows the spectral intensity of light emitted from the polymer film 2 and the catalyst layer 3. The polymer film 2 has a light intensity peak at 367.6 nm. On the other hand, the catalyst layer 3 has a small amount of light in the entire wavelength region. Therefore, when the wavelength is around 367.6 nm, the difference in the amount of light between the portion where the polymer film 2 exists and the portion where the pinhole 1 occurs is clear.
[0029]
As shown in FIG. 4, if only light having a fluorescence peak wavelength of around 367.6 nm is extracted by the light receiving wavelength filter 11, the pinhole 1 and the portion where the polymer film 2 exists with a high S / N ratio. It is possible to discriminate from a place where a certain polymer film 2 does not exist. Based on this, the light receiving wavelength filter 11 is a filter that passes only light having a wavelength of 320 nm to 430 nm, as shown by the shaded area in FIG. Since the pass band of the light receiving wavelength filter 11 does not include the wavelength of the excitation light (280 nm), the portion where the polymer film 2 exists at a higher S / N ratio and the portion where the polymer film 2 that is the pinhole 1 does not exist Can be discriminated.
If the light receiving wavelength filter 11 is not used, the S / N ratio is lowered and the detection performance is lowered. Further, when the inspection object is simply irradiated with white light without using fluorescence, and the pinhole is inspected by the intensity of the reflected light, it depends on the brightness and darkness of the surface of the polymer film 2 and the presence or absence of the pinhole 1. It is impossible to distinguish between light and dark, and pinhole 1 cannot be detected.
[0030]
Next, the reason why ultraviolet light (wavelength = 280 nm) is selected as the excitation light and the illumination wavelength filter 6 will be described. As a result of measuring the fluorescence intensity from the polymer film 2 with the above spectrophotometer while changing the wavelength of the excitation light, it was found that the shorter the wavelength, the stronger the fluorescence intensity. There is a mercury lamp as a short wavelength light source which can be obtained at a relatively low cost. The shortest wavelength peak of the mercury lamp is 280.4 nm. Therefore, the illumination wavelength filter 6 is a filter that passes only light having a wavelength of 300 nm or less, and illuminates the inspection object with ultraviolet light having a peak at 280.4 nm.
[0031]
In the present embodiment, the object to be inspected is in a state where the polymer film 2 is formed on the catalyst layer 3, but it is also possible to inspect the polymer film alone.
From the detection principle, there is a correlation between the amount of the polymer film 2 and the amount of fluorescent light. By using the density data of the light and dark image output by the image determination unit 133, not only the pinhole 1, but also the bubbles inside the polymer film 2 in which the amount of the polymer film 2 fluctuates, the thickness of the polymer film 2 and so on. Samurai etc. can also be detected.
In this embodiment, the incident light source is an area illumination, and the optical sensor 12 is an area CCD. However, an inspection object is obtained by using a combination of line illumination and line CCD, or a combination of point light receiving elements such as point illumination and photomal. May be scanned.
The method of detecting the pinhole 1 by image processing may be a floating threshold value instead of a fixed threshold value. Further, differential processing may be used.
[0032]
Using the method described in this embodiment, pinhole inspection of a polymer membrane for a fuel cell is performed, and an MEA is manufactured using a polymer membrane 2 that is confirmed to have no pinhole 1 having a diameter of 1 μm or more. To do. Thereby, the non-defective product rate of MEA can be improved significantly. Compared to the case where a defect in the polymer film is discovered in a later process, the production man-hour loss can be greatly reduced.
[0033]
<< Embodiment 2 >>
Hereinafter, a pinhole detection device, a pinhole detection method, and a MEA production method according to Embodiment 2 of the present invention will be described with reference to FIGS. 1, 5, and 6. The overall configuration of the pinhole detection apparatus according to the present embodiment is the same as the overall configuration of the pinhole detection apparatus according to Embodiment 1 shown in FIG. Only different parts will be described below.
The pinhole detection device of the second embodiment is different from that of the first embodiment only in the illumination light source 5, the illumination wavelength filter 6, and the light receiving wavelength filter 11. The illumination light source 5 of Embodiment 2 is a halogen lamp, and the illumination wavelength filter 6 is a filter that allows only light having a wavelength of 745 nm to 755 nm to pass therethrough. The inspection object is irradiated with visible light having a wavelength band of 745 to 755 nm as illumination light 8.
The light receiving wavelength filter 11 is a filter that passes only light having a wavelength of 780 nm to 840 nm.
[0034]
The reason for such a configuration and advantages over the first embodiment will be described with reference to FIGS. 4, 5, and 6.
In the first embodiment, the catalyst layer 3 is a black non-transparent substance in which a catalyst such as platinum is mixed in a conductor such as carbon, and light emission when excited by ultraviolet light is in the entire wavelength range as shown in FIG. It was small enough. However, the catalyst layer 3 is an important factor affecting the performance of the fuel cell, and has been improved. The main point of the improvement is the change of the raw materials for the catalyst and conductor. When the raw material of the catalyst layer 3 is changed, the raw material may generate strong fluorescence.
As shown in the catalyst 2 in FIG. 5, the catalyst layer 3 may generate fluorescence having a light amount close to the light amount emitted from the polymer film 2. In the characteristics of FIG. 5, it is difficult to discriminate between the polymer film 2 and the portion where the polymer film 2 that is the pinhole 1 does not exist. In this case, it is difficult to detect the pinhole by the method of the first embodiment.
[0035]
As a phenomenon in which a substance reacts with excitation light and the wavelength of light shifts to the longer wavelength side, there is a phenomenon called Raman scattering, apart from fluorescence. The characteristic of Raman scattering is that a light emission peak appears not in a wide wavelength range like fluorescence but in a narrow wavelength range specific to a substance. In general, Raman scattering tends to occur when the wavelength of excitation light is longer than visible light.
[0036]
The graph of FIG. 6 is data obtained by irradiating the polymer film 2 and the catalyst layer 3 with visible light having a wavelength of 750 nm as excitation light and measuring the respective spectral characteristics with a spectrophotometer.
In the graph of FIG. 6, the data of the polymer film 2 is an actual measurement value, and the data of the catalyst layer 3 is a predicted value. In the case of Raman scattering, it is impossible in principle that another substance has a peak at the same place, so that it has peaks at different wavelengths as shown in the figure.
Therefore, as shown in FIG. 6, by using the light receiving wavelength filter 11 that passes only light having a wavelength of 780 nm to 840 nm, the polymer film 2 and the polymer film 2 that is the pinhole 1 are not present. Can be discriminated with a high S / N ratio.
According to the method of Embodiment 2, the raw material of the catalyst layer 3 is changed for improvement, and the pinhole 1 existing in the polymer film 2 is surely detected even when the catalyst layer 3 generates slightly stronger fluorescence by ultraviolet light. It becomes possible to do.
[0037]
In this embodiment, the illumination light source 5 uses a halogen lamp for the purpose of cost reduction, but a laser may be used. When a laser is used, the illumination wavelength filter 6 may be unnecessary because the wavelength range of the light source itself is narrow.
In this embodiment, 750 nm is used as the wavelength of light emitted from the illumination light source 5 through the illumination wavelength filter 6. Since Raman scattering occurs from visible light to near infrared light, the illumination wavelength may be visible light (about 400 nm to about 750 nm) or near infrared light (wavelength is about 750 nm to about 2500 nm). When the illumination wavelength is changed, the passband of the light receiving wavelength filter 11 needs to be changed accordingly.
[0038]
Using the method described in this embodiment, pinhole inspection of a polymer membrane for a fuel cell is performed, and an MEA is manufactured using a polymer membrane 2 that has been confirmed to have no pinhole 1 having a diameter of 1 μm or more. To do. Thereby, the non-defective product rate of MEA can be improved significantly. Compared to the case where a defect in the polymer film is discovered in a later process, the production man-hour loss can be greatly reduced.
[0039]
<< Embodiment 3 >>
A pinhole detection device, a pinhole detection method, and a MEA production method according to Embodiment 3 of the present invention will be described with reference to FIGS.
FIG. 7 is a diagram illustrating the configuration of the pinhole detection device according to the third embodiment. In FIG. 7, the same blocks as those in the pinhole detection device of the first embodiment are denoted by the same reference numerals. Description of the same blocks as those in the first embodiment is omitted, and only different blocks are described. The difference from the first embodiment is that an X-ray source 71 is provided instead of the illumination light source 5, the illumination wavelength filter 6, and the light projecting lens 7 of the first embodiment, and the light reception wavelength filter 11 and the optical sensor 12 are replaced by X. This is that a line filter 72, an X-ray scintillator 73, and a CCD camera 74 are provided.
[0040]
When a substance is irradiated with X-rays, a part of the X-rays absorbed by the substance is emitted as fluorescent X-rays having specific energy (wavelength) depending on the type of each element. This fluorescent X-ray is visualized by an X-ray scintillator 73 and detected by a CCD camera 74. The wavelength of this fluorescent X-ray is a value unique to the substance. In the pinhole detection apparatus according to the third embodiment, the presence or absence of a pinhole is detected by installing an X-ray filter 72 that passes only the wavelength range specific to the substance in front of the X-ray scintillator 73, and the detection result is obtained. Output as an image.
[0041]
The merit of inspecting pinholes using X-rays will be described with reference to FIG. FIG. 8 is a diagram showing spectral characteristics when the polymer film 2 and the catalyst layer 3 are irradiated with continuous X-rays. Due to the polymer film 2, fluorescent X-rays having a sharp peak are generated around a wavelength of about 0.3 mm. An X-ray filter 72 that transmits fluorescent X-rays of this portion of wavelength is manufactured and installed with a metal such as nickel. The pinhole detector 13 receives the image data detected by the CCD camera 74 and detects a pinhole. With this configuration, it is possible to discriminate the polymer film 2 from a portion where the polymer film 2 that is the pinhole 1 does not exist with a high S / N ratio.
[0042]
Using the method described in this embodiment, pinhole inspection of a polymer membrane for a fuel cell is performed, and an MEA is manufactured using a polymer membrane 2 that has been confirmed to have no pinhole 1 having a diameter of 1 μm or more. To do. Thereby, the non-defective product rate of MEA can be improved significantly. Compared to the case where a defect in the polymer film is discovered in a later process, the production man-hour loss can be greatly reduced.
[0043]
In the above embodiment, the pinhole detection of the polymer film of MEA of the fuel cell manufactured by the coating method was performed. The application target of the present invention is not limited to this. For example, a transparent or translucent polymer film can be inspected in a single state, and pinholes existing there can be detected. In this case, the light source and the light receiving unit may be arranged on the same side with respect to the transparent or semi-transparent polymer film as the inspection object, or the light source and the light receiving unit may be transparent or semi-transparent as the inspection object. The structure arrange | positioned on both sides of a transparent polymer film may be sufficient. The object to be inspected may be non-transparent as long as the loss of the substance can be detected by any of the above methods.
The present invention can also be applied to detecting pinholes in a thin film formed on the surface of a thick object.
In the embodiment of the present invention, the object to be inspected is a polymer film, but is not limited thereto, and may be a single thin film or a film laminated in multiple layers.
[0044]
【The invention's effect】
As described above, according to the pinhole detection method of the present invention, the film reacts with the light that is irradiated with the light that reacts with the constituent material of the film to be inspected, and the film is generated in response to the light. Of the light, only light in a specific wavelength range is detected, and the pinhole is inspected based on the detected light amount.
According to the present invention, it is possible to obtain an advantageous effect that a pinhole detection device and a pinhole detection method capable of accurately detecting a pinhole of several μm generated in a polymer film can be realized.
According to the present invention, it is possible to obtain an advantageous effect that pinholes of several μm existing in a film of a transparent or translucent inspection object existing on a non-transparent film can be accurately detected.
[0045]
According to the present invention, it is possible to obtain an advantageous effect that a MEA production method by a coating method that can significantly reduce the number of repair steps in a subsequent process can be realized. According to the present invention, an inexpensive fuel cell can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a pinhole detection device according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of an image including a pinhole output by the pinhole detection apparatus according to the first embodiment of the present invention.
FIG. 3 is a diagram showing an operation in which the pinhole detection apparatus according to the first embodiment of the present invention inspects the entire surface of the inspection object.
FIG. 4 is a graph showing the wavelength distribution of fluorescence emitted when ultraviolet light is irradiated to a polymer film and a catalyst.
FIG. 5 is a graph showing the wavelength distribution of fluorescence emitted when ultraviolet light is irradiated to a polymer film and two types of catalysts.
FIG. 6 is a graph showing the wavelength distribution of Raman scattering generated when a polymer film and a catalyst are irradiated with visible light.
FIG. 7 is a diagram showing a configuration of a pinhole detection device according to a third embodiment of the present invention.
FIG. 8 is a graph showing a fluorescent X-ray wavelength distribution emitted when X-rays are irradiated to a polymer film and a catalyst.
[Explanation of symbols]
1 pinhole
2 Polymer membrane
3 catalyst layer
4 Film base
5 Illumination light source
6 Illumination wavelength filter
7 Projection lens
8 Illumination light
9 Light generated by the substance
10 Light receiving lens
11 Receiving wavelength filter
12 Optical sensor
13 Pinhole detector
14 Monitor TV
15 Control unit
16 X-axis drive unit
17 Y-axis drive unit
18 Work chuck
19 X axis
20 Y axis
71 X-ray source
72 X-ray filter
73 X-ray scintillator
74 CCD camera
132 Image processing unit
133 Image determination unit

Claims (8)

A method for detecting the presence or absence of pinholes in a transparent or translucent polymer film formed on a non-transparent anode catalyst layer,
Irradiating the polymer membrane with light having a short wavelength that causes the anode catalyst layer to hardly emit fluorescence, and generating light from the polymer membrane ;
Using a light receiving wavelength filter in a band in the vicinity of the wavelength at which the amount of light generated from the polymer film reaches a peak at a wavelength longer than the wavelength of the irradiation light, the light generated from the polymer film is Receives light through a wavelength filter,
A pinhole detection method, comprising: detecting the presence or absence of a pinhole in the polymer film based on the amount of the received light. Irradiating the polymer film with ultraviolet light having a short wavelength of 300 nm or less as the irradiation light,
The polymer film receives the fluorescence generated in response to the ultraviolet light through a light receiving wavelength filter having a pass wavelength of 320 to 430 nm,
The pinhole detection method according to claim 1, wherein presence or absence of a pinhole in the polymer film is detected based on the amount of the received light. Irradiating the polymer film with visible light having the short wavelength of 745 to 755 nm as the irradiation light,
The polymer film receives light generated by Raman scattering by the visible light through a light receiving wavelength filter having a passing wavelength of 780 to 840 nm,
The pinhole detection method according to claim 1, wherein presence or absence of a pinhole in the polymer film is detected based on the amount of the received light. The pinhole detection method according to claim 1, wherein the irradiation light is light that has passed through an irradiation wavelength filter that allows the light having the short wavelength to pass therethrough. The pinhole detection method according to any one of claims 1 to 4, wherein the polymer film is a polymer film for a fuel cell. The pinhole detection method according to claim 2, wherein the polymer film is a perfluorosulfonic acid film. The pinhole detection method according to claim 1, wherein the irradiation light, the ultraviolet light, or the visible light is scanned relative to the polymer film. A predetermined material is applied on the base to produce the anode catalyst layer,
Applying other predetermined material on it to produce the polymer film,
The presence or absence of pinholes in the polymer film is inspected by the pinhole detection method according to any one of claims 1 to 7,
A method for producing a membrane electrode assembly, wherein a cathode catalyst layer is formed by applying another predetermined material thereon only when it is determined to be a non-defective product in the inspection.

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