JP4815901B2 - Hydrogen purification filter and method for producing the same - Google Patents

Description

  The present invention relates to a hydrogen purification filter and a method for producing the same, and more particularly to a hydrogen purification filter used in a reformer or the like for steam reforming various hydrocarbon fuels to produce a hydrogen rich gas, The present invention relates to a manufacturing method that can be manufactured.

In recent years, global environmental and energy / resource problems have become apparent, and fuel cells have been attracting attention as one of energy supply systems that harmonize these with industry. A fuel cell directly produces hydrogen gas or hydrogen-rich gas obtained by reforming a hydrocarbon-based fuel such as natural gas, gasoline, butane gas, or methanol by electrochemical reaction with oxygen in the air. It is the electric power generating apparatus which takes out. The fuel cell using the hydrogen-rich gas includes a reformer that generates hydrogen-rich gas by steam reforming a hydrocarbon-based fuel, a fuel cell body that generates electricity, a converter that converts the generated DC electricity into AC, and the like It consists of
Such a fuel cell may be a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a solid electrolyte fuel cell (SOFC), an alkaline type, depending on the electrolyte used in the fuel cell body, the reaction mode, and the like. There are five types of fuel cells (AFC) and polymer electrolyte fuel cells (PEFC). Among these, the polymer electrolyte fuel cell (PEFC) is advantageous in that the electrolyte is solid compared to other fuel cells such as a phosphoric acid fuel cell (PAFC) and an alkaline fuel cell (AFC). Have the requirements.

However, the polymer electrolyte fuel cell (PEFC) uses platinum as the catalyst and has a low operating temperature, so that the electrode catalyst is poisoned by a small amount of CO, and the performance deterioration is particularly remarkable in a high current density region. There is. For this reason, it is necessary to reduce the CO concentration contained in the reformed gas (hydrogen-rich gas) generated by the reformer to about 10 ppm.
As one of means for purifying hydrogen by removing CO from the reformed gas, a hydrogen purification filter having a hydrogen separation membrane that allows only hydrogen such as sulfonated polyimide has been developed (Patent Document 1).
JP 2003-265937 A

However, the hydrogen separation membrane is formed by laminating a pair of glass substrates on which the applied hydrogen separation membrane is undried, and then drying to form a hydrogen separation membrane, which is then immersed in warm water. Then, the hydrogen separation membrane is peeled off and collected, and placed on a support and dried to produce. There is a problem that the process is complicated and workability is poor.
Further, the hydrogen permeation rate in the hydrogen separation membrane is inversely proportional to the film thickness. For this reason, it is required to reduce the thickness of the hydrogen separation membrane. However, when the thin hydrogen separation membrane is peeled off and collected in warm water, there is a problem that the hydrogen separation membrane is easily damaged due to tension with the water surface.

In addition, when fixing a hydrogen separation membrane on a porous support such as carbon paper, it is difficult to ensure the adhesion between the support and the hydrogen separation membrane. There was a problem that the hydrogen separation membrane was likely to be deteriorated due to friction between the support and the support.
Furthermore, to constitute a hydrogen purification filter, a pair of cells having a labyrinth groove for sandwiching a hydrogen separation membrane supported by a support, and a seal frame for sealing the periphery of the support and the hydrogen separation membrane There is a problem that many components other than the hydrogen separation membrane are necessary.
The present invention has been made in view of the above circumstances, and provides a hydrogen purification filter exhibiting excellent hydrogen permeation efficiency in hydrogen purification and a production method for easily producing such a filter. Objective.

In order to achieve such an object, the hydrogen purification filter of the present invention comprises a pair of porous supports having a plurality of pores, and a hydrogen-permeable resin membrane sandwiched between the porous supports , transmitting resin film, the surface of the portion not in contact with the porous support, and a smooth der so that structure than the surface of the portion in contact with the porous support.
As another aspect of the present invention, the porous support has a configuration in which the thickness is in the range of 10 to 100 μm.
As another aspect of the present invention, the porous support is configured such that the total area of the openings of the holes on the hydrogen permeable resin membrane side occupies 20 to 70% of the hole forming region of the porous support.
As another aspect of the present invention, the hydrogen permeable resin film has a thickness in the range of 1 to 20 μm.
As another aspect of the present invention, the porous support is configured such that the surface roughness Ra on the hydrogen permeable resin membrane side is in the range of 0.02 to 2 μm.
As another aspect of the present invention, the porous support is configured to have a holding edge outside the hole forming region.

In the method for producing a hydrogen purification filter of the present invention, a thin film forming step of forming a thin film having an undried surface by applying a resin composition for a hydrogen permeable resin film to one surface of each of a pair of supports. And a pair of supports so that the thin films are in contact with each other, and then, the thin film is dried to form a hydrogen permeable resin film, and each of the hydrogen permeable resin films is sandwiched. A plurality of holes are formed in the support by etching to form a porous support, and the hole forming step is performed to expose the hydrogen permeable resin film in the holes.
As another aspect of the present invention, the surface of the pair of supports used in the thin film forming step that forms the thin film has a smooth surface corresponding to the hole formed in the hole forming step. The structure was such that the portion of [2] was roughened.
As another aspect of the present invention, the surface roughness Ra of the smooth surface is 0.1 μm or less, and the surface roughness Ra of the roughened portion is in the range of 0.02 to 2 μm. .

Such a hydrogen purification filter of the present invention has high mechanical strength because the hydrogen permeable resin membrane is sandwiched between the porous supports from both sides, and the hydrogen permeable resin membrane can be thinned to improve the hydrogen permeation performance. In addition, the handleability is extremely good, and other members such as cells and seal frames are unnecessary, and the structure is simple. For example, the holding edge of the porous support (the part outside the hole forming region) ) Can be used simply by sandwiching them, and the convenience of use is high.
In addition, the method for producing a hydrogen purification filter of the present invention forms a porous portion by directly forming a hole in a support on which a hydrogen permeable resin film is formed, and therefore, the number of steps is smaller than that of a conventional production method. Since the hydrogen permeable resin film is not peeled off, the hydrogen permeable resin film can be prevented from being damaged, and the production efficiency is high. Further, since the hydrogen permeable resin film is directly formed on the porous support, It is possible to produce a hydrogen purification filter having high adhesion and high performance and high durability.

Embodiments of the present invention will be described below with reference to the drawings.
[Hydrogen purification filter]
FIG. 1 is a partial plan view showing an embodiment of the hydrogen purification filter of the present invention, and FIG. 2 is a cross-sectional view of the hydrogen production filter shown in FIG. 1 and 2, the hydrogen purification filter 1 of the present invention includes a hydrogen permeable resin film 2 and a pair of porous supports 4 and 4 that sandwich the hydrogen permeable resin film 2 from both sides. Each porous support 4, 4 has a plurality of holes 5 so as to face each other with the hydrogen permeable resin film 2 interposed therebetween.

The hydrogen permeable resin film 2 constituting the hydrogen purification filter 1 may be made of a resin such as sulfonated polyimide, aromatic polyimide, polyparaxylene, polyester, polybenzimidazole, cellulose acetate, and polyglutamic acid. it can. The thickness of the hydrogen permeable resin film 2 can be, for example, in the range of 1 to 20 μm, preferably 1 to 10 μm. If the thickness of the hydrogen permeable resin film 2 is less than 1 μm, the film strength is insufficient, and if it exceeds 20 μm, the hydrogen permeation performance is undesirably lowered.
Such a hydrogen permeable resin film 2 is such that the surface of the part not in contact with the porous supports 4 and 4 (the part exposed in the hole 5) is from the surface of the part in contact with the porous supports 4 and 4. Is also preferably smooth.

The material of the pair of porous supports 4 and 4 constituting the hydrogen purification filter 1 may be, for example, austenitic, ferritic stainless steel, aluminum, copper or the like such as SUS304, SUS316, or SUS430. Moreover, the thickness of each porous support body 4 and 4 can be suitably set, for example in the range of 10-100 micrometers, Preferably it is 20-50 micrometers. When the thickness of each of the porous supports 4 and 4 is less than 10 μm, the strength of the hydrogen purification filter 1 is insufficient, and when the thickness exceeds 100 μm, it is difficult to form the fine pores 5 and 5 with high accuracy. Absent. The surface 4a of the porous supports 4 and 4 joined to the hydrogen permeable resin film 2 has a surface roughness Ra of 0.02 to 2 μm, preferably 0.02 to 1 μm. . When the surface roughness Ra of the surface 4a of the porous supports 4 and 4 is less than 0.02 μm, the adhesion strength between the hydrogen permeable resin film 2 and the porous support 4 becomes insufficient, and the surface roughness Ra exceeds 2 μm. When the hydrogen permeable resin film 2 is thin, there is a risk of film breakage or the like, which is not preferable.
In addition, surface roughness Ra in this invention measures the measurement site | part of length 250 micrometers in 20 seconds by 20 mg of loads using the stylus type surface shape measuring device DEKTAK made from SLOAN.

Further, the plurality of pores 5 and 5 of the porous supports 4 and 4 may be provided in the entire area of the porous supports 4 and 4, and as shown in FIG. 4 hole forming regions 6 (regions hatched in FIG. 3), and holding edge portions 7 may be disposed outside the hole forming regions 6. Such hole portions 5 and 5 have a total area of openings on the hydrogen permeable resin film 2 side (the hatched portion in FIG. 1) so that the hole formation region 6 (the hole portions in the entire area of the porous supports 4 and 4 is a hole portion). , The entire surface of the porous supports 4 and 4 is a hole forming region), and it is desirable that it is in the range of 30 to 60%. When the total area of the openings of the holes 5 and 5 is less than 20% of the hole forming region 6, the hydrogen permeation performance of the hydrogen purification filter 1 becomes insufficient, and when it exceeds 70%, the porous supports 4 and 4 This is not preferable because the mechanical strength is reduced.
Such a hydrogen purification filter 1 of the present invention has a structure in which the hydrogen permeable resin film 2 is sandwiched between the porous supports 4 and 4 from both sides, and has high mechanical strength. For this reason, even if the hydrogen permeable resin film 2 is thinned to improve the hydrogen permeation performance, the handleability is very good.

In the above example, the holes 5 and 5 are tapered circular openings in which the opening on the hydrogen permeable resin film 2 side is narrow, but there is no limitation on the opening shape and arrangement of the holes 5 and 5, For example, the opening shape may be an elliptical shape, an oval shape, a stripe shape, or the like. Further, the major axis direction of the elliptical shape, the elliptical shape, and the line direction of the stripe shape may be the same direction or different directions in the front and back porous supports 4 and 4. For example, as shown in FIG. 4, the stripe-shaped line direction (arrow a direction) may be set so that the front and back porous supports 4 and 4 form 90 °. In this example, the crossing portion of the stripe-shaped holes perpendicular to each other through the hydrogen permeable resin film is the hydrogen permeable portion. Note that the stripe-shaped holes in FIG. 4 are indicated by straight lines for convenience, and the number and pitch are also indicated for convenience.
In the above example, the outer shape of the hydrogen purification filter 1 is a square, but is not limited to this, and the outer shape is arbitrarily set, such as a circle, an ellipse, a triangle, or a pentagon or more polygon. be able to.

FIG. 5 is a diagram for illustrating an example of a usage state of the hydrogen purification filter 1 of the present invention. In FIG. 5, the end surface 12 a of the connection portion 12 of the reformed gas supply pipe 11 and the end surface 22 a of the connection portion 22 of the hydrogen discharge pipe 21 are fixedly connected by a fixing member 31. Then, the hydrogen purification filter 1 is mounted with the holding edge 7 sandwiched between the recess 13 formed in the end surface 12a of the connection portion 12 and the recess 23 formed in the end surface 22a of the connection portion 22. ing. Grooves 14 and 24 are formed in the recesses 13 and 23 so as to correspond to the holding edge 7, and the grooves 14 and 24 are harder than the porous supports 4 and 4 (holding edge 7). Gaskets (or rubber O-rings) 15 and 25 made of low metal are disposed. As described above, the hydrogen purification filter 1 of the present invention does not require other members such as a cell and a seal frame and is simple in structure, but is simply mounted so as to sandwich the holding edge 7 as shown in the figure. Can be used in
In addition, the hole 5 of the hydrogen purification filter 1 in FIG. 5 is shown by a straight line for convenience, and the number and pitch are also shown for convenience.
The embodiment of the hydrogen purification filter described above is an example, and the present invention is not limited to this.

[Method for producing hydrogen purification filter]
Next, the manufacturing method of the hydrogen purification filter of this invention is demonstrated.
FIG. 6 is a process diagram showing an embodiment of the method for producing a hydrogen purification filter of the present invention, taking the above-described hydrogen purification filter 1 of the present invention as an example.
In the production method of the present invention, first, in the thin film formation step, the resin composition for the hydrogen permeable resin film is applied to one surface of the pair of supports 3 and 3, and the surface 2 ′ a is in an undried state. 'Is formed (FIG. 6A).
As the supports 3 and 3, for example, austenite-based, ferrite-based stainless steel substrate, aluminum substrate, copper substrate or the like such as SUS304, SUS316, or SUS430 can be used. The thickness of this support body 3 and 3 can be suitably set, for example within the range of 10-100 micrometers, Preferably it is 20-50 micrometers.

  As the resin composition for the hydrogen permeable resin film, for example, a resin composition containing a resin such as sulfonated polyimide, aromatic polyimide, polyparaxylene, polyester, polybenzimidazole, cellulose acetate, or polyglutamic acid can be used. The thin film 2 ′ can be formed by, for example, a casting method, a rubbing method, a gas-liquid interface development film forming method, a vapor deposition polymerization method, etc. Can be formed into a thin film 2 'whose surface 2'a is undried. The thickness of such a thin film 2 'can be set so that the thickness of the hydrogen permeable resin film 2 formed in the contact drying process described later is in the range of 1 to 20 µm, preferably 1 to 10 µm.

Next, in the close-contact drying step, the pair of supports 3 and 3 are overlapped so that the thin films 2 'and 2' are in contact with each other (FIG. 6B), and then the integrated thin film 2 'is formed. By drying, a hydrogen permeable resin film 2 is formed (FIG. 6C). The thin film 2 ′ can be dried under pressure (for example, 100 to 300 kg / cm ² ) from both sides of the supports 3 and 3, and the hydrogen permeable resin film 2 can be dried by drying under vacuum. It is possible to suppress the occurrence of pinholes.
Next, in the hole forming step, first, resist patterns 8 and 9 having a plurality of openings 8a and 9a are formed on the surfaces of the supports 3 and 3 holding the hydrogen permeable resin film 2 (FIG. 6 ( D)). Next, using the resist patterns 8 and 9 as a mask, the supports 3 and 3 are etched from both sides to form porous supports 4 and 4 having a plurality of fine holes 5 and 5 (FIG. 6 ( E)). The hydrogen permeable resin film 2 is exposed in the formed hole 5, and the hydrogen purification filter 1 of the present invention is obtained by removing the resist patterns 8 and 9.

The resist patterns 8 and 9 can be formed, for example, by applying a material selected from conventionally known positive and negative photosensitive resist materials, and exposing and developing through a predetermined mask. Each opening 8a of the resist pattern 8 faces each opening 9a of the resist pattern 9 with the supports 3 and 3 interposed therebetween. The opening areas of the openings 8a and 9a determine the holes 5 and 5 of the porous supports 4 and 4, and are appropriately set in consideration of the etching conditions, the materials and thicknesses of the supports 3 and 3, and the like. be able to.
Since the hydrogen purification filter 1 manufactured as described above is formed into the porous supports 4 and 4 by directly forming the holes 5 and 5 in the supports 3 and 3 on which the hydrogen permeable resin film 2 is formed, Compared to the method, the number of steps is small. Moreover, the process which peels the hydrogen permeable resin film 2 is unnecessary, and damage to the hydrogen permeable resin film 2 can be prevented. Furthermore, since the hydrogen permeable resin film 2 is directly formed on the porous supports 4 and 4 (supports 3 and 3), the adhesion between the two becomes high.

  In the method for producing a hydrogen purification filter of the present invention, the surface of the pair of supports 3 and 3 used in the thin film forming step is subjected to a roughening treatment in advance on the surfaces on which the thin films 2 'and 2' are formed. 3 and 3 and the hydrogen-permeable resin film 2 can be further improved in adhesion. That is, as shown in FIG. 7, the surface 3a of the surfaces of the supports 3 and 3 excluding the portion 3b corresponding to the holes 5 and 5 formed in the hole forming step (hatched in FIG. 7). The surface can be roughened. This roughening treatment can be performed by forming a resist pattern in the portion 3b and using the resist pattern as a mask by soft etching, sandblasting, roughening plating, or the like. The surface roughness Ra can be in the range of 0.02 to 2 μm. If the surface roughness Ra of the roughened portion 3a is less than 0.02 μm, the adhesion between the support 3, 3 and the hydrogen permeable resin film 2 cannot be improved, and if it exceeds 2 μm, the hydrogen permeable resin The thickness of the film 2 is not uniform, which is not preferable.

On the other hand, the portion 3 b not subjected to the roughening treatment corresponds to the positions of the holes 5 and 5, and the surface shape of the portion 3 b is transferred to the exposed surface of the hydrogen permeable resin film 2. For this reason, it is preferable that the surface roughness Ra ′ of the portion 3b not subjected to the roughening treatment is a smooth surface of 0.1 μm or less. Of course, the surface roughness Ra ′ is smaller than the surface roughness Ra. If the surface roughness Ra ′ of the portion 3b exceeds 0.1 μm, the hydrogen permeable resin film 2 exposed to the holes 5 and 5 when the holes 5 and 5 are formed in the subsequent hole forming process. This is not preferable because the surface becomes rough and there is a portion having a large film thickness, which deteriorates the hydrogen permeation performance.
The measurement of the surface roughness Ra and Ra ′ is performed in the same manner as the measurement of the surface roughness Ra.
The embodiment of the method for producing the hydrogen purification filter described above is an exemplification, and the present invention is not limited to this.

Next, the present invention will be described in more detail by showing more specific examples.
[Example 1]
Two SUS304 substrates (50 mm × 50 mm square shape) with a thickness of 30 μm were prepared as a support, and a resin composition for a hydrogen permeable resin film having the following composition was applied four times to one surface of the SUS304 substrate by a casting method. (Total coating amount: solid content 50 g / m ² ) to form a thin film having an undried surface. (Thin film formation process)
Next, the above SUS304 substrates were stacked so that the thin films were in contact with each other, and dried (100 ° C., 6 hours) in a state of being pressurized (300 kg / cm ² ) from both sides of the SUS304 substrate. Thus, a hydrogen permeable resin film having a thickness of 5.0 μm sandwiched between the SUS304 substrates was formed. (End of contact drying process)

  Next, a photosensitive resist material (OFPR manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied to each SUS304 substrate sandwiching the hydrogen permeable resin film by a dipping method (application amount: 7 μm (when dried)). Next, a photomask M1 having a plurality of circular openings having an opening size (opening diameter) of 90 μm in a square area of 40 mm × 40 mm arranged in an apex of an equilateral triangle having a side of 120 μm is provided on both sides. It distribute | arranged on a resist coating film, the resist coating film was exposed through these photomasks M1, and developed using sodium hydrogencarbonate. In addition, alignment was performed so that the centers of the openings of the opposing photomask M1 coincided with each other through the SUS304 substrate (hydrogen permeable resin film). As a result, a resist pattern having a circular opening having an opening size (opening diameter) of 95 μm was formed on each SUS304 substrate. As described above, the center of each circular opening formed in the SUS304 substrate coincided with the center of the opening facing the SUS304 substrate (hydrogen permeable resin film).

Next, using the resist pattern as a mask, each SUS304 substrate was etched by a spray method under the following conditions.
(Etching conditions)
・ Temperature: 50 ℃
・ Ferric chloride concentration: 45 Baume ・ Pressure: 0.30 MPa
After the above etching treatment was completed, the resist pattern was removed using sodium hydroxide and washed with water. Thereby, a plurality of holes were formed in each SUS304 substrate to form a porous support. (End of hole formation process)

  As described above, the hydrogen purification filter of the present invention was obtained. The pores of the porous support constituting the hydrogen purification filter had a tapered shape with an opening diameter on the surface side of 95 μm and an opening diameter on the inner side (hydrogen permeable resin film side) of 80 μm. Further, the total area of the openings on the inner side occupies 40% of the square hole forming region of 40 mm × 40 mm.

[Example 2]
In the thin film formation step, the hydrogen purification filter of the present invention was produced in the same manner as in Example 1 except that the following roughening treatment was performed on the SUS304 substrate before forming a thin film having an undried surface. .
In the roughening treatment, first, a photosensitive resist material (OFPR manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied to one surface of each SUS304 substrate by a dipping method (application amount: 7 μm (when dried)). Next, a photomask M2, which is the same as the photomask M1 used in Example 1 except that the opening size (opening diameter) of the opening is 95 μm, is arranged on one resist coating film, and this photomask M2 is arranged. Then, the resist coating film was exposed and developed using sodium bicarbonate. As a result, a circular resist pattern having a diameter of 95 μm was formed on the SUS304 substrate.

Next, using the resist pattern as a mask, each SUS304 substrate was soft etched under the following conditions.
(Etching conditions)
・ Temperature: 40 ℃
・ Ferric chloride concentration: 45 Baume ・ Pressure: 0.1 MPa

After the above etching treatment was completed, the resist pattern was removed using sodium hydroxide and washed with water. As a result, a roughening process was performed on each SUS304 substrate so as to leave a circular smooth surface having a diameter of 95 μm. As a result of measuring the surface roughness Ra of the surface subjected to the roughening treatment under the following measurement conditions, it was 0.08 μm. Further, the surface roughness Ra ′ of the smooth surface was 0.03 μm.
(Measurement conditions for surface roughness Ra, Ra ')
Using a stylus type surface profile measuring device DEKTAK made by SLOAN, length 250μm
The measurement site was measured for 20 seconds with a load of 20 mg.

  It can be used in various fields that require high-purity hydrogen-rich gas.

It is a fragmentary top view which shows one Embodiment of the hydrogen purification filter of this invention. It is sectional drawing in the AA of the hydrogen purification filter shown by FIG. It is a top view of the hydrogen purification filter of the present invention. It is a top view of the porous substrate which comprises the hydrogen purification filter of this invention. It is a figure for showing an example of the use condition of the hydrogen purification filter of the present invention. It is process drawing which shows one Embodiment of the manufacturing method of the hydrogen purification filter of this invention. It is a figure for demonstrating the roughening process in the manufacturing method of the hydrogen purification filter of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hydrogen purification filter 2 ... Hydrogen permeable resin film 3 ... Support body 4 ... Porous support body 5 ... Hole 6 ... Hole formation area 7 ... Holding edge 2 '... Thin film

Claims (9)

A pair of porous supports having a plurality of pores, and a hydrogen-permeable resin film sandwiched between the porous supports, the surface of the hydrogen-permeable resin film not contacting the porous support, hydrogen purification filter, wherein smoothing der Rukoto than the surface of the portion in contact with the porous support.   The hydrogen purification filter according to claim 1, wherein the porous support has a thickness in a range of 10 to 100 μm.   The said porous support body occupies 20 to 70% of the hole formation area of a porous support body in the total area of the opening of the said hole part by the side of a hydrogen permeable resin film, The Claim 1 or Claim 2 characterized by the above-mentioned. Hydrogen purification filter.   The hydrogen purification filter according to any one of claims 1 to 3, wherein the hydrogen permeable resin membrane has a thickness in a range of 1 to 20 µm.   The hydrogen purification filter according to any one of claims 1 to 4, wherein the porous support has a surface roughness Ra on the hydrogen permeable resin membrane side in a range of 0.02 to 2 µm. The hydrogen purification filter according to any one of claims 1 to 5 , wherein the porous support has a holding edge outside the hole forming region. In the method for producing a hydrogen purification filter,
A thin film forming step of applying a resin composition for a hydrogen permeable resin film to one surface of each of a pair of supports to form a thin film having an undried surface;
A close-contact drying process in which the pair of supports are overlapped so that the thin films are in contact with each other, and then the thin films are dried to form a hydrogen-permeable resin film,
A step of forming a porous support by forming a plurality of holes in each support sandwiching the hydrogen permeable resin film to form a porous support, and exposing the hydrogen permeable resin film to the holes. A method for producing a hydrogen purification filter. The surface of the pair of supports used in the thin film forming step on which the thin film is formed has a smooth surface corresponding to the hole formed in the hole forming step, and the other portions are roughened. The method for producing a hydrogen purification filter according to claim 7 .   9. The hydrogen purification according to claim 8, wherein the smooth surface has a surface roughness Ra of 0.1 μm or less, and the surface roughness Ra of the roughened portion is in the range of 0.02 to 2 μm. A method for manufacturing a filter.

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