JP2004330636A - Method of manufacturing nozzle plate of inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely control a shape of a hole structural body having a drilled projected through hole by communicating a shape for guiding ink to an ejection side with a straight shape. <P>SOLUTION: This manufacturing method comprises a conductive film forming process for forming a conductive film on one face of a non-conductive transparent substrate, a first electroform layer forming process for forming a first electroform layer on the conductive film, a second electroform layer forming process for forming a second electroform layer on the first electroform layer, and a nozzle plate forming process for forming a nozzle plate for an inkjet head from a laminated material formed in the second electroform layer forming process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a nozzle plate for an inkjet head.
[0002]
[Prior art]
2. Description of the Related Art A conventional nozzle plate is known in the form of a film formed by irradiating a plastic film with a laser beam or piercing a nozzle port by chemical corrosion by an etching method or the like.
[0003]
The nozzle plate obtained by this method has a so-called straight shape having a substantially cylindrical nozzle opening. During ink jet recording, it is necessary to constantly supply ink to the discharge side of the nozzle port.However, with a straight nozzle port, although the ink discharge direction is stable, the ink is not actively attracted to the discharge side, and as a result the recording is performed. Occasionally ink breakage or shortage occurs easily. Also, when a multi-nozzle nozzle plate is used, mask processing is performed, for example, when irradiating a laser beam. However, even if the same mask is used, it is difficult to make the irradiation conditions and the like uniform for all nozzle openings. Variations occur in the shape of the nozzle port. In addition, since a plastic film is used, there is a problem in strength and durability.If the film is thickened to compensate for insufficient strength, the laser beam applied to the film will attenuate in the film. There is a possibility that a difference occurs in the hole diameters between the terminal ends, so that it is impossible to reliably pierce the nozzle port. In addition, the aspect ratio, which is the ratio between the diameter and the depth of the nozzle port, is limited to about 1, and it is difficult to perform processing with more uniform specifications.
[0004]
On the other hand, as a conventional nozzle plate, a metal film formed by electroforming is known. In particular, this method is widely known as a processing method suitable for manufacturing a component having a fine shape.
[0005]
In this method, for example, as shown in FIG. 7A, a non-conductive (insulating) film 310 is formed on a conductive substrate 200 by a photolithography method using a photosensitive material, that is, a resist. It is formed so that Next, as shown in FIG. 7B, electroforming is performed using the conductive substrate 200 as an electrode to form an electroformed structure 110. Finally, the conductive substrate 200 and the non-conductive film 310 are formed. Separated from the electroformed structure 110, a nozzle plate having a hole having a curved cross section as shown in FIG. 7C is obtained. A hole having such a wall surface formed with a constant curvature and having a shape in which the size of the hole gradually varies as the hole becomes deeper is called a bellmouth-shaped hole.
[0006]
In the nozzle plate obtained by this method, the bell-mouthed side having a larger hole diameter is used as an ink introduction side, and the side having a smaller hole diameter is used as an ink ejection side. In this case, very good performance can be obtained in inducing the ink to the ejection side, but the ink ejection direction is not stable because there is almost no straight portion. This electroforming is a porous electroforming method for forming a donut-shaped hole, and the diameter of the nozzle opening is determined by the diameter of the hole portion where the electroformed layer is not formed. However, since it is difficult to control the electroforming conditions, the diameter tends to vary. In addition, in order to compensate for the disadvantage of not having a straight portion, it is conceivable to increase the thickness of the electroformed layer and eventually form a straight-shaped portion. Since it is difficult to control the electroforming conditions of the bellows, the bell mouth shape tends to vary.
[0007]
Therefore, Patent Literature 1 discloses a technique of forming a straight portion and a bell mouth shape by forming two electroformed layers.
[0008]
[Patent Document 1]
JP 2003-1829 A
[Problems to be solved by the invention]
By the way, even in the technique described in Patent Document 1, as in the above case, the diameter of the straight portion is the same as that of the void portion where the electroformed layer was not formed by the first porous electroforming process. Since the diameter and the bellmouth shape are determined by the thickness of the electroformed layer, the diameter and the bellmouth shape on the ink ejection side are likely to vary. This is a serious problem when aiming for a multi-nozzle.
[0010]
The present invention has been made in view of the above circumstances, and has a shape in which ink is guided to the ejection side and a straight shape are communicated with each other, and the shape of a hole structure having a perforated projecting through hole is precisely formed. It is an object of the present invention to provide a method for manufacturing a nozzle plate for an inkjet head that enables control.
It is another object of the present invention to provide a method of manufacturing a nozzle plate for an ink jet head, which has a good liquid separation at the time of ink ejection and enables highly accurate ink landing.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the invention according to claim 1 includes a conductive film forming step of forming a conductive film on one surface of a non-conductive transparent substrate;
The resist material on the conductive film is applied to form a resist layer, the resist layer is subjected to proximity exposure and development processing, the exposed conductive film is subjected to electroforming as an electrode, and then the resist remaining after development is developed. A first electroformed layer forming step of separating a layer and a conductive film formed on a surface thereof to form a first electroformed layer on the conductive film;
A negative resist material is applied from the surface of the non-conductive transparent substrate on which the first electroformed layer is formed to form a resist layer, and the non-conductive transparent substrate is formed from the other surface of the non-conductive transparent substrate. Exposing and developing the resist layer through the transparent conductive substrate, performing electroforming using the exposed first electroformed layer as an electrode, and forming a second electroformed layer on the first electroformed layer A second electroformed layer forming step;
Separating the first electroformed layer, the resist layer remaining after the exposure and development treatment, and the non-conductive transparent substrate from the laminate obtained in the second electroformed layer forming step, And a nozzle plate forming step of forming a nozzle plate.
[0012]
According to the first aspect of the present invention, a conductive film is formed on one surface of the non-conductive transparent substrate in a conductive film forming step, and the conductive film is formed in a first electroformed layer forming step. A resist layer is further formed on the substrate.
[0013]
Further, in the first electroformed layer forming step, proximity exposure is performed while maintaining a predetermined interval through a mask having a circular hole in the resist layer, and development processing is performed, so that only the portion of the resist layer that is masked and not exposed is exposed. Is removed, and the conductive film is exposed in this portion. On the other hand, the exposed portion remains protruding even after the development processing, and this resist layer has a tapered shape.
[0014]
Further, electroforming is performed using the exposed conductive film as an electrode to form a first electroformed layer. After the formation of the first electroformed layer, the tapered resist layer is peeled off, and the conductive film facing the tapered resist layer is dissolved and removed using a solvent or the like.
[0015]
Next, in a second electroformed layer forming step, a resist layer is formed on the surface of the first electroformed layer including the tapered holes. A so-called back exposure process is performed in which exposure is performed from the other surface of the non-conductive transparent substrate, that is, the surface on which the first electroformed layer is not formed.
[0016]
In the back exposure process, the portion where the first electroformed layer is formed is masked, and only the portion of the resist layer exposed to the tapered holes is exposed.
[0017]
Subsequently, by performing a developing process, a portion of the resist layer that has been masked and has not been exposed to light is removed. On the other hand, the exposed portion of the resist layer remains. The remaining resist layer has the same shape as the tapered holes, and has a cylindrical shape having the same diameter as the bottom surface. Further, an electroforming process is performed using the first electroformed layer as an electrode to form a second electroformed layer on the first electroformed layer.
[0018]
In the nozzle plate forming step, the non-electroconductive transparent substrate, the first electroformed layer, and the second electroformed layer are left from the electroformed structure obtained in the second electroformed layer forming step except for the second electroformed layer. The resist layer remaining after the development processing performed in the casting layer forming step is separated to obtain a nozzle plate for an inkjet head. Each of the obtained nozzle openings has a hole structure in which the tapered shape is a shape on the side to attract ink, and a straight shape having the same shape and diameter as the cylindrical resist is communicated with the tapered shape.
[0019]
As described above, the shape of the hole structure having the protruding through holes serving as the nozzle ports, that is, the shape for guiding the ink to the ejection side and the straight shape are determined by the shape of the resist layer obtained by developing after the proximity exposure. That is, since it is sufficient to manage the conditions of proximity exposure, which is relatively easy to manage, without being affected by the electroforming conditions for which accurate management is difficult as in the past, the shape of the nozzle opening can be precisely adjusted. It becomes possible to control easily.
[0020]
The invention according to claim 2 is characterized in that in the second electroformed layer forming step, after exposing and developing the resist layer, a release layer is formed on the exposed surface of the first electroformed layer. I have.
According to the invention described in claim 2, by forming a release layer between the first electroformed layer and the second electroformed layer, the first electroformed layer and the second electroformed layer in the nozzle plate forming step are formed. Can easily be separated. Therefore, when the first electroformed layer and the second electroformed layer are both formed of the same material, the electroformed layers can be easily separated.
[0021]
The invention according to claim 3 is characterized in that the release layer is an oxide film obtained by performing an oxide film treatment on a surface of the first electroformed layer.
According to the invention as set forth in claim 3, by forming an oxide film as a release layer on the surface of the first electroformed layer, the first electroformed layer and the second electroformed layer in the nozzle plate forming step are formed. Separation becomes easy.
[0022]
According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, in the second electroformed layer forming step, a water-repellent layer is formed on an exposed surface before the electroforming process. It is characterized by being formed.
According to the fourth aspect of the present invention, by providing the water-repellent layer on the surface of the perforated portion on the ink discharge side, the liquid separation at the time of ink discharge in this portion is good, and it is possible to land ink with high precision. And a nozzle plate for an ink jet head to be provided.
[0023]
The invention according to claim 5 is characterized in that the water repellent layer is obtained by eutectoid plating a material having water repellency and a material forming the first electroformed layer.
According to the invention as set forth in claim 5, a material having water repellency is formed by eutectoid plating a material having water repellency which does not normally show electrical conductivity with the same material as the material forming the first electroformed layer. Can be reliably arranged on the surface of the first electroformed layer. Thereby, the above-described effects can be obtained more efficiently.
[0024]
In the invention according to claim 6, in the invention according to any one of claims 1 to 3, in the second electroformed layer forming step, the electroforming treatment is performed by eutectoid plating with a material having water repellency. It is characterized by performing in.
According to the sixth aspect of the present invention, the second electroformed layer itself is provided with water repellency, so that the liquid separation at the time of ink ejection at the perforated portion on the ink ejection side is good and the ink landing with high precision is achieved. Can be provided.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 illustrates an embodiment of a conductive film forming step which constitutes the present invention. In this step, a sputtering is performed on one surface of a non-conductive transparent substrate 1 as shown in FIG. As shown in FIG. 1B, a conductive film 2 which is a uniform thin film is formed by a method, an electroless plating method, or the like.
[0026]
Here, the non-conductive transparent substrate 1 is, for example, a borosilicate glass having a thickness of 0.5 mm, and the conductive film 2 is, for example, a 0.1 μm-thick Nip (nickel phosphorus) film formed by a sputtering method. It was used.
[0027]
FIG. 2 illustrates an embodiment of a first electroformed layer forming step constituting the present invention. First, as shown in FIG. 2A, a resist material is applied to the surface of the conductive film 2 to form a resist. The layer 3 is formed. Here, as a resist material, a negative resist, for example, AZ5200E manufactured by Client Japan Co., Ltd. is used, and the thickness of the resist layer 3 is, for example, 50 μm.
[0028]
Next, proximity exposure is performed on the resist layer 3 as shown in FIG. This proximity exposure is performed with the mask 4 having the circular holes 17 separated from the resist layer 3 by the interval t. The interval t at this time is about several tens μm to 100 μm, for example, 80 μm, and the diameter of the hole 17 is, for example, 25 μm. As the light source, a light source that emits ultraviolet light having a wavelength of 310 nm to 405 nm is preferably used. However, the light source is not limited to this, and may emit light of any wavelength as long as proximity exposure is possible.
[0029]
By exposing the mask 4 with a certain distance from the resist layer 3 in this manner, the mask 4 is irradiated in a wider range than the hole 17 to a certain extent, and the outside of the hole 17 is irradiated with a gradually weaker light amount. The irradiation area has a tapered shape. This irradiation area can always have the same shape as long as the resist layer 3 has no unevenness and the interval t between the mask 4 and the resist layer 3 during irradiation is kept constant.
[0030]
Subsequently, the laminate after the proximity exposure is subjected to a development treatment and, if necessary, a post-bake treatment to form an irradiation area of the resist layer 3 during the proximity exposure as shown in FIG. The remaining portion becomes a cured product 5 protruding above the conductive film 2 and remains. On the other hand, the region that has not been irradiated is removed by the developing process, and the conductive film 2 is exposed only in that region.
[0031]
Next, an electroforming process is performed using the exposed conductive film 2 as an electrode. As shown in FIG. 2D, the first electroformed layer 6 is formed on the conductive film 2 while controlling the plating growth. Here, the first electroformed layer 6 can be made of nickel by, for example, a nickel electroforming method. The metal material used in the electroforming process, in addition to nickel, metal materials that can be electroplated and grown, such as gold, copper, tin, zinc, cobalt, platinum, silver, lead and alloys containing these, etc. . The thickness of the first electroformed layer 6 is preferably the same as the thickness of the cured product 5. That is, when the thickness of the resist layer 3 is 50 μm as described above, the thickness of the cured product 5 is also 50 μm, so that the thickness of the first electroformed layer 6 is also preferably 50 μm.
[0032]
Subsequently, as shown in FIG. 2E, the cured product 5 and the conductive film formed on the surface of the cured product 5 are separated to obtain a tapered recessed pattern 7.
[0033]
FIG. 3 illustrates an embodiment of the second electroformed layer forming step constituting the present invention. First, as shown in FIG. A resist material is applied to form a resist layer 8. Here, as the resist material, a negative resist, for example, BMRC-1000PM manufactured by Tokyo Ohka Kogyo Co., Ltd. is used. When the thickness of the resist layer 8 is defined as, for example, the thickness from the non-conductive transparent substrate 1, It is 110 μm.
[0034]
Next, as shown in FIG. 3B, light irradiation is performed from a surface of the non-conductive transparent substrate 1 on which the first electroformed layer is not formed, that is, a back exposure method. As the light beam 9 at this time, for example, an ultraviolet ray is suitably used, and the irradiation intensity is, for example, 500 mJ / cm ² . The light is not limited to ultraviolet light, and any light can be used as long as it can expose the resist layer.
[0035]
By performing light irradiation by the back exposure method in this manner, the resist layer 8 is exposed while being masked by the first electroformed layer 6. Therefore, the irradiation area has a cylindrical shape with the same shape as the pattern 7 as the bottom surface. That is, it has a cylindrical shape whose cross section is the same as that of the mask used in the proximity exposure performed in FIG. 2B.
[0036]
Subsequently, the laminate after the light irradiation by the back exposure method is subjected to a development treatment and, if necessary, a post-bake treatment, so that the irradiation area of the resist layer 8 at the time of exposure as shown in FIG. The portion which has become a cylindrical cured product 10 protruding above the non-conductive transparent substrate 1 remains. As described above, when a mask having a diameter of 25 μm is used during the proximity exposure and the thickness of the resist layer 8 is 110 μm, the cured product 10 has a cylindrical shape having a diameter of 25 μm and a height of 110 μm. On the other hand, the region that has not been irradiated is removed by the developing process, and the first electroformed layer 6 is exposed only in that region.
[0037]
Further, as shown in FIG. 4, it is preferable to form a release layer 12 on the surface of the first electroformed layer 6 as necessary. The release layer 12 functions as a release layer for separating the first electroformed layer 6 when separating a second electroformed layer described later. The release layer 12 can be formed, for example, by an oxide film layer obtained by oxidizing the surface of the first electroformed layer 6 using, for example, a dichromic acid solution. Other methods include immersing the whole in an alkaline solution to perform anodic oxidation, coating titanium nitride by sputtering to preferably form a layer having a thickness of 0.1 μm or less, and coating the whole with a hydrophilic colloid solution. To form a thin colloidal release film by adsorption. Although the figure shows a state in which the entirety of the release layer 12 is formed with a substantially uniform thickness, the permeation of a drug for forming the release layer 12 in the inclined portion near the cured product 10 is shown. There may be some distribution in the film thickness in this part due to ease of operation, but this distribution has no relation to the operation and effect of the present invention.
[0038]
Further, as shown in FIG. 5, it is preferable to form a water-repellent layer 13 on the release layer 12. Since the water-repellent layer 13 forms a perforated portion on the ink discharge side of the surface of the nozzle port, the water repellent layer 13 acts to improve the liquid separation at the nozzle port during ink discharge. The water-repellent layer 13 is formed by eutectoid plating of, for example, a polymer material having water repellency, for example, a polymer material made of a fluorine-containing compound, and the material of the first electroformed layer 6, for example, nickel. Can be. When the release layer 12 is not formed, it may be formed directly on the surface of the first electroformed layer 6.
[0039]
Returning to FIG. 3, next, an electroforming process is performed using the first electroformed layer 6 as an electrode. As shown in FIG. 3D, the second electroformed layer 11 is formed on the first electroformed layer 6 or the release layer 12 and the water-repellent layer 13 are formed while controlling plating growth. Then, it is formed on the layer exposed on the surface.
[0040]
Here, similarly to the case of forming the first electroformed layer 6, the second electroformed layer 11 can be made of nickel by, for example, a nickel electroforming method. The metal material used in the electroforming process, in addition to nickel, metal materials that can be electroplated and grown, such as gold, copper, tin, zinc, cobalt, platinum, silver, lead and alloys containing these, etc. .
[0041]
Further, the second electroformed layer 11 is formed by eutectoid plating of a polymer material having water repellency, for example, a polymer material made of a fluorine-containing compound and the material of the first electroformed layer 6, for example, nickel. It may be formed on one electroformed layer 6 or release layer 12. Thereby, the second electroformed layer 11 itself can have water repellency.
[0042]
The thickness of the second electroformed layer 11 is preferably the same as the thickness of the cured product 10. That is, when the thickness of the resist layer 8 is 110 μm as described above, the thickness of the cured product 10 is also 110 μm, so that the thickness of the second electroformed layer 11 is also preferably 110 μm.
[0043]
FIG. 6 illustrates an embodiment of a nozzle plate forming step constituting the present invention. From the laminate obtained in FIG. 3D, the first electroformed layer 6 and the conductive film 2, The cured product 10, the non-conductive transparent substrate 1 and, if necessary, the release layer 12 are separated to obtain a pore structure 14.
The hole structure 14 forms a nozzle plate for an inkjet head having a tapered ink inlet 15 and a straight ink outlet 16.
[0044]
According to the present embodiment, the shape of the hole structure having a protruding through hole that is a nozzle port, that is, the shape in which the ink is guided to the ejection side and the straight shape are the resist layers obtained by developing after the proximity exposure. Determined by the shape. That is, since it is sufficient to manage the conditions of proximity exposure, which is relatively easy to manage, without being affected by the electroforming conditions for which accurate management is difficult as in the past, the shape of the nozzle opening can be precisely adjusted. It becomes possible to control easily.
[0045]
Further, by forming a release layer 12 between the first electroformed layer 6 and the second electroformed layer 11, the first electroformed layer 6 and the second electroformed layer 11 in the nozzle plate forming step are formed. Can be easily separated. Therefore, when the first electroformed layer 6 and the second electroformed layer 11 are both formed of the same material, the electroformed layers can be easily separated.
[0046]
Further, by forming an oxide film on the surface of the first electroformed layer 6 as the release layer 12, the separation of the first electroformed layer 6 and the second electroformed layer 11 in the nozzle plate forming step becomes easy. .
[0047]
Further, by providing the water-repellent layer 13 on the surface of the perforated portion on the ink discharge side, a nozzle plate for an ink jet head is obtained which has good liquid separation at the time of ink discharge and enables highly accurate ink landing. be able to.
[0048]
In addition, a material having water repellency, which does not normally exhibit electrical conductivity, is eutectoid-plated with the same material as the material forming the first electroformed layer 6, so that the material having water repellency is formed on the first electroformed layer 6. On the surface of the device. Thereby, the above-described effects can be obtained more efficiently.
[0049]
Alternatively, the second electroformed layer 11 itself is made to have water repellency, so that the liquid separation at the time of ink ejection at the perforated portion on the ink ejection side is good, and the ink jet head nozzle that enables highly accurate ink landing. Board can be provided.
[0050]
【The invention's effect】
According to the first aspect of the present invention, the shape of the hole structure having the protruding through hole serving as the nozzle opening, that is, the shape for guiding the ink to the ejection side and the straight shape are obtained by developing after proximity exposure. Is determined by the shape of the resist layer. That is, since it is sufficient to manage the conditions of proximity exposure, which is relatively easy to manage, without being affected by the electroforming conditions for which accurate management is difficult as in the past, the shape of the nozzle opening can be precisely adjusted. It becomes possible to control easily.
[0051]
According to the invention described in claim 2, by forming a release layer between the first electroformed layer and the second electroformed layer, the first electroformed layer and the second electroformed layer in the nozzle plate forming step are formed. Can easily be separated. Therefore, when the first electroformed layer and the second electroformed layer are both formed of the same material, the electroformed layers can be easily separated.
[0052]
According to the invention as set forth in claim 3, by forming an oxide film as a release layer on the surface of the first electroformed layer, the first electroformed layer and the second electroformed layer in the nozzle plate forming step are formed. Separation becomes easy.
[0053]
According to the fourth aspect of the present invention, by providing the water-repellent layer on the surface of the perforated portion on the ink discharge side, the liquid separation at the time of ink discharge in this portion is good, and it is possible to land ink with high precision. And a nozzle plate for an ink jet head to be provided.
[0054]
According to the invention as set forth in claim 5, a material having water repellency is formed by eutectoid plating a material having water repellency which does not normally show electrical conductivity with the same material as the material forming the first electroformed layer. Can be reliably arranged on the surface of the first electroformed layer. Thereby, the above-described effects can be obtained more efficiently.
[0055]
According to the sixth aspect of the present invention, the second electroformed layer itself is provided with water repellency, so that the liquid separation at the time of ink ejection at the perforated portion on the ink ejection side is good and the ink landing with high precision is achieved. Can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an embodiment of a conductive film forming step constituting the present invention.
FIG. 2 is a view illustrating an embodiment of a first electroformed layer forming step constituting the present invention.
FIG. 3 is a diagram illustrating an embodiment of a second electroformed layer forming step constituting the present invention.
FIG. 4 is a diagram illustrating a preferred embodiment of the second electroformed layer forming step.
FIG. 5 is a view illustrating a preferred embodiment of the second electroformed layer forming step.
FIG. 6 is a diagram illustrating an embodiment of a nozzle plate forming step constituting the present invention.
FIG. 7 is a diagram illustrating a conventional method for manufacturing a nozzle plate.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 non-conductive transparent substrate 2 conductive film 3 resist layer 6 first electroformed layer 8 resist layer 11 second electroformed layer 12 release layer 13 water-repellent layer 14 pore structure

Claims (6)

A conductive film forming step of forming a conductive film on one surface of a non-conductive transparent substrate,
The resist material on the conductive film is applied to form a resist layer, the resist layer is subjected to proximity exposure and development processing, the exposed conductive film is subjected to electroforming as an electrode, and then the resist remaining after development is developed. A first electroformed layer forming step of separating a layer and a conductive film formed on the surface thereof to form a first electroformed layer on the conductive film;
A negative resist material is applied from the surface of the non-conductive transparent substrate on which the first electroformed layer is formed to form a resist layer, and the non-conductive transparent substrate is formed from the other surface of the non-conductive transparent substrate. Exposing and developing the resist layer through the transparent conductive substrate, performing electroforming using the exposed first electroformed layer as an electrode, and forming a second electroformed layer on the first electroformed layer A second electroformed layer forming step;
Separating the first electroformed layer, the resist layer remaining after the exposure and development treatment, and the non-conductive transparent substrate from the laminate obtained in the second electroformed layer forming step, A method for manufacturing a nozzle plate for an inkjet head, comprising: a nozzle plate forming step of forming a nozzle plate. The method according to claim 1, wherein in the second electroformed layer forming step, after exposing and developing the resist layer, a release layer is formed on the exposed surface of the first electroformed layer. The method according to claim 2, wherein the release layer is an oxide film obtained by performing an oxide film treatment on a surface of the first electroformed layer. The method according to any one of claims 1 to 3, wherein in the second electroformed layer forming step, a water-repellent layer is formed on the exposed surface before the electroforming process. The method according to claim 4, wherein the water repellent layer is obtained by eutectoid plating a material having water repellency and a material forming the first electroformed layer. 4. The method according to claim 1, wherein in the second electroformed layer forming step, the electroforming process is performed by eutectoid plating with a material having water repellency. 5.

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