JP2021006653A - Article with plating pattern and manufacturing method of the same - Google Patents

Abstract

To provide an inexpensive manufacturing method for manufacturing an article with a plating pattern using a printing technique, and the article manufactured by the method.SOLUTION: A article with a plating pattern comprises a substrate 1, an ink layer 2 including a reducer, a plating layer 4 provided on the ink layer, and a catalyst 3 present on a boundary between the ink layer and the plating layer. The reducer has an ability of reducing an ion of the plating catalyst. The amount of the plating catalyst present on the boundary between the ink layer and the plating layer is more than that present in the ink layer.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to articles with plating patterns and methods of producing articles with plating patterns using printing techniques.

By using printed electronics technology, which makes it possible to manufacture electronic circuits using printing technology, it is possible to reduce manufacturing costs and easily form conductive patterns on flexible materials such as resin films. Become. As one of them, in recent years, a technique for forming a conductive pattern by directly printing an ink containing nanoparticles of silver or copper without going through a photolithography process has become known. For example, Patent Document 1 discloses a method for manufacturing a printed wiring board using a conductive ink containing metal nanoparticles such as silver. Patent Document 2 discloses a method for producing a high-definition conductive pattern by flexographic printing, in which the first pattern is printed by flexographic printing using an ink containing a polymer and a plating catalyst such as a palladium salt. It is described that after curing it, the cured pattern is plated to form a conductive pattern.

Japanese Unexamined Patent Publication No. 2018-074055 Special Table 2015-532779

However, in the conventional method as disclosed in Patent Documents 1 and 2, since the ink used contains a large amount of expensive metal nanoparticles such as silver and palladium, there is a limit in reducing the manufacturing cost. Therefore, there is a demand for printed electronics technology that can be realized at lower cost.

The present inventors have succeeded in developing a technique for forming a plating pattern by printing using an ink composed of a relatively inexpensive material. One embodiment of the present disclosure is an article provided with a plating pattern, wherein the article includes a base material, an ink layer containing a reducing agent, a plating layer provided on the ink layer, and the ink layer. The reducing agent contains a plating catalyst existing at the interface of the plating layer, and the reducing agent has an ability to reduce ions of the plating catalyst, and the plating catalyst existing at the interface between the ink layer and the plating layer. Is greater than the amount of plating catalyst present in the ink layer. In addition, another embodiment of the present disclosure comprises a low valence inorganic metal compound, an amino group-containing polymer, and a solvent, and the molar ratio of the metal ion of the inorganic metal compound to the amino group of the amino group-containing polymer. Is a reducing agent ink having a value of 1.5 or more.

Another embodiment of the present disclosure is a method of forming a plating pattern on a substrate, in which a reducing agent ink containing a low atomic metal compound, an amino group-containing polymer, and a solvent is prepared. Applying the reducing agent ink on the substrate to form an ink layer, contacting the ink layer with a solution containing ions of the plating catalyst to precipitate the plating catalyst on the surface of the ink layer, and the above. Includes contacting the plating catalyst with the plating solution.

According to the embodiment of the present disclosure, it is possible to form a plating pattern by using a printing technique without using an ink containing a large amount of expensive metal nanoparticles, which is required by a conventional method.

It is a figure which showed typically the process of the method in one Embodiment of this disclosure. It is a chart obtained by performing XPS analysis before and after immersing a sample prepared using a reducing agent ink in an activator. It is a figure which showed typically the structure of the line of the roll-to-roll system.

The present disclosure relates to, in one embodiment, a method of forming a plating pattern on a substrate. In the method of the present embodiment, the ink is prepared by preparing the reducing agent ink, applying the reducing agent ink on the substrate to form an ink layer, and contacting the ink layer with a solution containing ions of a plating catalyst. This includes depositing a plating catalyst on the surface of the layer and bringing the plating catalyst into contact with a plating solution. FIG. 1 schematically shows a process of a plating pattern forming method in the present embodiment.

The reducing agent ink for forming the ink layer contains at least a reducing agent and a solvent. The reducing agent is a compound having the ability to reduce the ions of the plating catalyst that are later brought into contact with the ink layer. Examples of the reducing agent include low valence inorganic metal compounds, metal hydrides (hydride reducing agents), phosphates, hypophosphates, ascorbates, and oxalates, or their free acids. Examples thereof include formaldehyde, hydrazine and derivatives thereof. Examples of the low valence inorganic metal compound include an inorganic tin (II) compound such as anhydrous tin (II) chloride and tin (II) chloride dihydrate, or an inorganic iron (II) such as potassium hexacyanoferrate (II). Examples include compounds. The "low valence" means a state in which an atom having two or more valences has a relatively low valence and can be oxidized to have a relatively high valence. Examples of the metal hydride include sodium borohydride and the like. The reducing agent preferably has a high affinity with a solvent, and particularly preferably one that easily dissolves in the solvent.

The solvent contained in the reducing agent ink is selected from those capable of dissolving or dispersing at least the reducing agent. The solvent preferably does not erode the substrate on which the plating pattern is formed. Further, it is preferable to select a solvent in which the reducing agent ink does not gel or become highly viscous so that the reducing agent ink can be used in the existing printing technology. From the viewpoint of affinity with the components of the reducing agent ink, a polar solvent may be preferable. Examples of the solvent include methyl ethyl ketone, acetone, methyl isobutyl ketone, ethanol, 2-propanol, water, or a mixture of two or more thereof.

The reducing agent ink preferably further contains a polymer having a functional group capable of coordinating with the reducing agent. Without being bound by theory, such polymers are thought to contribute to improving the bondability between the ink layer and the plating catalyst when the plating catalyst is later deposited on the surface of the ink layer. Examples of the type of polymer include poly (meth) acrylate, polyurethane, polyurethane (meth) acrylate, and polyester. Examples of poly (meth) acrylates include polymethylmethacrylate (MMA), polyhydroxyethylmethacrylate (HEMA), polyethylacrylate (EA), polybutylacrylate (BA), polyacrylonitrile (AN) and the like. Examples of polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and the like. In such polymers, the functional group that can coordinate with the reducing agent may be directly attached to the main chain of the polymer, or may be present on a branched chain (pendant chain) attached to the main chain of the polymer. May be good. The functional group that can be coordinated to the reducing agent is, for example, a functional group that can be coordinated to a metal cation such as Sn ²⁺ ion when the reducing agent is a metal compound (metal salt) such as tin (II) chloride. Means. Examples of functional groups that can be coordinated to the reducing agent include amino groups and carbonyl groups. From the viewpoint of ease of coordination, an amino group, particularly a primary amino group, is preferable. Therefore, the polymer having a functional group that can be coordinated with the reducing agent is preferably an amino group-containing polymer. The amino group-containing polymer preferably contains 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100% of the amino groups contained in the primary amino group. Specific examples of the amino group-containing polymer include poly (meth) acrylate having an aminoalkyl chain in the side chain, for example, aminoethylated poly (meth) acrylate.

When the reducing agent ink contains the above polymer, the reducing agent is preferably present in a sufficient amount with respect to the functional groups of the polymer. If the amount of reducing agent is too small, the reduction of the plating catalyst may be hindered. In the reducing agent ink, the molar ratio of the number of moles of the reducing agent (reducing agent / polymer functional group) to the total number of moles of functional groups contained in all the polymers is 1.5 or more, 1.7 or more, and 1.9. It is preferably 2.1 or more, 2.3 or more, 2.5 or more, 2.7 or more, or 2.9 or more. Further, from the viewpoint of sufficiently obtaining the effect of the polymer on improving the bondability between the ink layer and the plating catalyst, the molar ratios are 20.0 or less, 19.0 or less, 18.0 or less, 17.0 or less, 16.0. It is preferably 15.0 or less, or 15.0 or less. For example, when the molar ratio is 7.0 or less, 6.0 or less, 5.0 or less, 4.0 or less, or 3.0 or less, the reducing agent ink can be transparent without turbidity, and is therefore transparent. More preferred for the purpose of forming a conductive pattern. The number of moles of the reducing agent is, for example, the number of moles of metal ions when the reducing agent is a low valence inorganic metal compound.

The reducing agent ink may further contain other components. Other components include, for example, additional polymers that allow the reducing agent ink to be cured by chemical rays, heat, etc., fillers such as fumed silica, dispersants, viscosity modifiers, and the like. The filler may improve the bondability between the plating layer and the ink layer to be formed later by making the surface of the ink layer to be formed a rough surface. However, from the viewpoint of obtaining a transparent reducing agent ink, the filler may not be contained. Further, the reducing agent ink may not substantially contain components other than the reducing agent, the above-mentioned polymer, and the solvent. In a preferred embodiment, the reducing agent ink is free of metal nanoparticles, except those derived from the reducing agent.

The application of the reducing agent ink on the substrate can be performed using ordinary printing techniques. Available printing techniques include inkjet printing, gravure printing, screen printing, flexographic printing, reverse offset printing and the like. By such a printing technique, the ink layer can be formed in a desired pattern. Therefore, in theory, any fine pattern possible by printing technology can be formed. For example, it is possible to form a fine pattern in which the width of the narrowest portion is 10 μm or less, 5 μm or less, or 1 μm or less.

The base material to which the reducing agent ink is applied is not particularly limited as long as the ink can be applied on the base material, and for example, a general plastic film can be used. As the material of the plastic film, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polymethylmethacrylate and polyacrylic acid. Examples thereof include poly (meth) acrylate, polyurethane (PU), polyimide (PI), polybutylene terephthalide (PVDF), ABS resin, ETFE resin and the like. It is preferable that the surface of the base material is subjected to surface treatment such as corona treatment or plasma treatment from the viewpoint of adhesiveness between the base material and the ink layer. When the method of the present disclosure is carried out by a roll-to-roll method, the thickness of the base material is preferably 500 μm or less, or 400 μm or less so as to facilitate unwinding and winding.

The reducing agent ink applied on the substrate becomes an ink layer by drying and volatilizing the solvent, or by curing with chemical rays or heat. Therefore, the ink layer contains at least a reducing agent and, optionally, a polymer having a functional group capable of coordinating with the above-mentioned reducing agent. The thickness of the ink layer can be, for example, 20 μm or less, 15 μm or less, 10 μm or less, 8 μm or less, or 6 μm or less, depending on the amount and composition of the reducing agent ink to be applied. The ink layer thus formed is washed and dried as necessary, and then brought into contact with a solution containing plating catalyst ions. The contact between the ink layer and the solution can be performed, for example, by immersing the base material on which the ink layer is formed in the solution. Alternatively, the solution may be applied on the ink layer by coating or the like. Upon contact, a redox reaction occurs between the reducing agent contained in the ink layer and the plating catalyst ions, and the plating catalyst is deposited on the surface of the ink layer. The contact between the ink layer and the solution containing the plating catalyst ions is carried out for a sufficient time for metal precipitation, for example, 1 minute or more, 2 minutes or more, or 3 minutes or more. The solution may be heated if desired.

Examples of plating catalysts include palladium, silver, and copper. As the solution containing the ions of the plating catalyst, for example, a solution known as a so-called activator used in the conventional electroless plating technique can be used. Examples of the solution containing ions of the plating catalyst include a solution containing palladium (II) chloride, silver (I) nitrate, or copper (II) acetate. The solvent of the solution is not particularly limited as long as it does not erode the substrate or dissolve the ink layer. When the reducing agent contained in the ink layer is a tin (II) compound and the plating catalyst is palladium, palladium is deposited on the surface of the ink layer by the following redox reaction.
Sn ²⁺ + Pd ²⁺ → Sn ⁴⁺ + Pd
Although it depends on the state of the ink layer and the contact time with the solution, the plating catalyst precipitated on the surface of the ink layer is, for example, in the form of nano-sized metal particles, and the particles make the surface of the ink layer very thin. A layer of covered plating catalyst can be formed. The thickness of the plating catalyst layer is substantially equal to the diameter of the plating catalyst particles, and there may be one primary particle of the plating catalyst existing in the thickness direction. Although referred to as a "plating catalyst layer" in the present specification for convenience, the surface of the ink layer does not have to be completely covered with the plating catalyst, and there is a portion where the plating catalyst does not exist and the ink layer is exposed. You may. The thickness of the plating catalyst layer is 1.0 μm or less, 0.9 μm or less, 0.8 μm or less, 0.7 μm or less, 0.6 μm or less, 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, 0. It can be .2 μm or less, 0.1 μm or less, or 0.05 μm or less.

After contacting the ink layer with the solution containing the plating catalyst ions, if necessary, the ink layer is washed and dried, and then the plating catalyst precipitated on the surface of the ink layer is brought into contact with the plating solution. The contact can be performed, for example, by immersing the entire base material provided with the ink layer having the plating catalyst deposited on the surface in the plating solution. Alternatively, the plating solution may be applied on the ink layer by coating or the like. By contact, a plating layer is formed on the plating catalyst on the surface of the ink layer. The contact between the plating catalyst and the plating solution is carried out for a sufficient time for precipitation of plating, for example, 1 minute or more, 2 minutes or more, or 3 minutes or more. The plating solution may be heated if necessary. As the plating solution, a known electroless plating solution can be used, and is not particularly limited as long as it does not erode the base material or dissolve the ink layer. Examples of the type of plating include nickel (Ni), copper (Cu), silver (Ag), gold (Au), and palladium (Pd). Therefore, the plating layer contains nickel (Ni), copper (Cu), silver (Ag), gold (Au), or palladium (Pd). Further, electroless plating may be followed by further electroplating. In electroless plating and subsequent electroplating, the metal type of plating may be the same or different. Examples of the type of electrolytic plating include nickel (Ni), copper (Cu), silver (Ag), gold (Au), and palladium (Pd). The thickness of the plating layer depends on the state of the ink layer and the contact time with the plating solution, but is, for example, 0.1 μm or more, 0.5 μm or more, 1.0 μm or more, 5.0 μm or more, or 10 μm or more. obtain. In some cases, the thickness can be 100 μm or more, 300 μm or more, or 500 μm or more.

The present disclosure relates to an article with a plating pattern that, in another embodiment, can be made by the methods described above. The article of the present embodiment includes a base material, an ink layer containing a reducing agent, a plating layer provided on the ink layer, and a plating catalyst existing at an interface between the ink layer and the plating layer. The ink layer may further contain a polymer having a functional group that can be coordinated with the reducing agent. However, the ink layer preferably does not contain metal nanoparticles other than the metal derived from the plating catalyst and the reducing agent. In the present specification, the interface between the ink layer and the plating layer is the concentration of the metal constituting the plating layer as an index when the surface analysis is carried out in the thickness direction from the surface of the plating layer to the ink layer. It includes a region of ± 2 μm, ± 1.5 μm, or ± 1 μm in the thickness direction from the point where the gradient changes most. The amount of the plating catalyst present at the interface between the ink layer and the plating layer is larger than the amount of the plating catalyst present in the ink layer. The reducing agent, the ink layer, the plating catalyst, the plating layer, the polymer having a functional group capable of coordinating with the reducing agent, and the like are as described above.

The present disclosure relates to reducing agent inks used in the methods described above in another embodiment. The reducing agent ink of the present embodiment contains at least a reducing agent and a solvent, and preferably further contains a polymer having a functional group capable of coordinating with the reducing agent. When the reducing agent ink contains the above-mentioned polymer, the molar ratio of the number of moles of the reducing agent to the total number of moles of the functional groups of all the polymers contained in the reducing agent ink (reducing agent / polymer functional group) is 1. It is preferably 5 or more, 1.7 or more, 1.9 or more, 2.1 or more, 2.3 or more, 2.5 or more, 2.7 or more, or 2.9 or more. The reducing agent, the solvent, the polymer having a functional group coordinating to the reducing agent, and the like are as described above.

The present disclosure uses, in one embodiment, a reducing agent, an amino group-containing polymer as a polymer having a functional group coordinating to the reducing agent, a reducing agent ink containing a solvent, and a reducing agent ink thereof. It relates to a method of forming a plating pattern on the top. In one embodiment, when the reducing agent is a low valence inorganic metal compound, the molar ratio of the metal ion to the amino group of the amino group-containing polymer of the reducing agent ink is 1.5 or more.

According to the embodiment of the present disclosure, the plating pattern can be formed by a printing technique by a method different from the conventional technique using an ink containing a large amount of expensive metal nanoparticles. For example, as compared with the method using an ink containing a palladium compound as disclosed in Patent Document 2, according to the technique of the present disclosure, the manufacturing cost per unit area can be suppressed to a few hundredths. It is possible. Further, the method of the present disclosure can be easily applied to a so-called roll-to-roll method in which ink loss tends to increase due to the low cost of ink used for printing. Further, the method of the present disclosure can be carried out only by repeating immersion in various solutions after printing on a substrate, and washing and drying as necessary, to a roll-to-roll method. Suitable for application. FIG. 3 is a diagram schematically showing a line configuration when the method of the present disclosure is applied to a roll-to-roll method. As shown, the unwound base material is printed with a reducing agent ink (not shown) and then immersed in a tank containing each solution or cleaning solution according to the method of the embodiment of the present disclosure in order. The line is configured as follows. The immersion time in each solution or the like can be appropriately adjusted, and can be, for example, 2 minutes, 3 minutes, or 5 minutes. The line configuration can be changed or adjusted as needed.

In the method of the embodiment of the present disclosure, it is not necessary to go through a sintering step at a high temperature, which is often required in the conventional method using an ink containing a large amount of metal nanoparticles. Therefore, the base material to which the plating pattern is applied can be selected without considering the glass transition temperature (Tg). Further, in the method of the embodiment of the present disclosure, in the prior art, there is a concern in the process of printing and firing the ink containing metal nanoparticles, that is, the generation of bubbles and the defect of the pattern due to the voids of the fired film (void). Occurrence can be suppressed. According to the embodiment of the present disclosure, by adjusting the composition of the reducing agent ink or the like, it is possible to produce a transparent conductive pattern that cannot be confirmed with the naked eye.

Articles provided with plating patterns according to the embodiments of the present disclosure include, for example, solar panels, lighting equipment, display panels, disposable electronic devices, smart cards, smart packaging, thin film transistors (TFTs), flexible substrates, flexible sensors, flexible displays, etc. It can be applied as a component of a transparent antenna, a transparent heater, a wearable sensor, an interactive wall, or the like.

The present disclosure includes the following embodiments.
(1) An article with a plating pattern
With the base material
An ink layer containing a reducing agent and
The plating layer provided on the ink layer and
The plating catalyst existing at the interface between the ink layer and the plating layer,
Including
The reducing agent has the ability to reduce the ions of the plating catalyst.
An article in which the amount of plating catalyst present at the interface between the ink layer and the plating layer is larger than the amount of plating catalyst present in the ink layer.
(2) The article according to (1), wherein the ink layer further contains a polymer having a functional group capable of coordinating with a reducing agent.
(3) The article according to (2), wherein the functional group that can be coordinated with the reducing agent is an amino group.
(4) The article according to any one of (1) to (3), wherein the ink layer does not contain metal nanoparticles other than the metal derived from the reducing agent and the plating catalyst.
(5) The article according to any one of (1) to (4), wherein the reducing agent is a low valence inorganic metal compound.

(6) The article according to any one of (1) to (5), wherein the plating catalyst is palladium, silver, or copper.
(7) The article according to any one of (1) to (6), wherein the plating layer contains nickel, copper, silver, gold, or palladium.
(8) It contains a low valence inorganic metal compound, an amino group-containing polymer, and a solvent, and the molar ratio of the metal ion of the inorganic metal compound to the amino group of the amino group-containing polymer is 1.5 or more. Reducing agent ink.
(9) A method of forming a plating pattern on a base material.
Preparing a reducing agent ink containing a low valence inorganic metal compound, an amino group-containing polymer, and a solvent,
Applying the reducing agent ink on a base material to form an ink layer,
A method comprising contacting an ink layer with a solution containing ions of a plating catalyst to precipitate a plating catalyst on the surface of the ink layer, and contacting the plating catalyst with a plating solution.

Hereinafter, the present disclosure will be described in more detail with reference to Examples, but the present disclosure is not limited to these Examples.

(material)
NK-380: Polyment NK-380 (Nippon Shokubai), aminoethylated acrylic polymer, amine value 0.7-1.3 mmol / g-solid
NK-350: Polyment NK-350 (Nippon Catalyst), aminoethylated acrylic polymer, amine value 0.6-1.0 mmol / g-solid
STD45: ETHOCEL STD45 (Dow Chemical), Ethyl Cellulose

(Test Example 1)
A reducing agent ink was prepared according to the composition shown in Table 1, and the aspect of the obtained ink was visually observed. From the composition, the molar ratio of Sn ²⁺ / amine was calculated. The median amine values of NK-380 and NK-350 were used in the calculation. Next, using the obtained ink, printing was performed on a PET film subjected to corona treatment, and the ink was dried by heating. A 50 mm × 50 mm size test piece was cut out from a PET film on which the reducing agent ink was printed, washed by immersing it in water, and then a 100 mL activator (Red Schumer (aqueous solution containing PdCl ₂ , Japan Kanigen)). Was immersed in the water for 3 minutes. Then, the test piece was washed with water again and dried at room temperature. The obtained test piece was subjected to inductively coupled high frequency plasma emission spectroscopy (ICP-AES) to measure the amount of Pd contained in the test piece. As a comparative example, the amount of Pd was also measured for a test piece in which an unprinted PET film was immersed in an activator. Further, an ink containing palladium acetate was separately prepared with reference to Patent Document 2, and the amount of Pd per unit area when the ink of Patent Document 2 was printed in the same manner was obtained by calculation. When the obtained brown ink was applied onto the PET film, the PET film was colored yellow.

No. in Table 1 Cross-section AFM / XPS analysis was performed on the sample using the reducing agent ink according to the composition of No. 2 before and after being immersed in the activator. Based on the cross-sectional observation of AFM, the correlation between the XPS sputtering time and the depth from the outermost layer was taken. The obtained XPS chart is shown in FIG. Prior to immersion in the activator, the presence of metallic palladium was virtually unconfirmed. On the other hand, in the measurement after immersion in the activator, it was confirmed from the observation result of AFM that the surface was scraped by about 1 μm per minute by sputtering, and by evaluating the XPS chart, it was on the ink layer. It was confirmed that metallic palladium was present at a depth of at least about 1 μm from the surface of the ink.

(Test Example 2)
A reducing agent ink was prepared according to the composition shown in Table 2, and the aspect of the obtained ink was visually observed. Next, using the obtained ink, printing was performed on a corona-treated PET film in the same manner as in Test Example 1 to obtain a test piece immersed in an activator. The obtained test piece was immersed in a non-electrolytic nickel plating solution (SC-93-0, Nippon Kanizen) for 3 minutes and subjected to a plating treatment. With respect to the obtained sample, it was visually confirmed whether or not plating was formed on the printed portion and the properties of the plating. Further, the adhesion of the formed plating was evaluated on the plated surface which had been cross-cut in advance according to the "peeling test method" specified in JIS H 8504: 1999. It was confirmed that the same result can be obtained even when the plating solution is changed to an electroless copper plating solution (OPC Copper MIC, Okuno Pharmaceutical Industry Co., Ltd.).

1 Base material 2 Ink layer 3 Plating catalyst 4 Plating layer

Claims (9)

An article with a plating pattern
With the base material
An ink layer containing a reducing agent and
The plating layer provided on the ink layer and
The plating catalyst existing at the interface between the ink layer and the plating layer,
Including
The reducing agent has the ability to reduce the ions of the plating catalyst.
An article in which the amount of plating catalyst present at the interface between the ink layer and the plating layer is larger than the amount of plating catalyst present in the ink layer. The article according to claim 1, wherein the ink layer further contains a polymer having a functional group capable of coordinating with a reducing agent. The article according to claim 2, wherein the functional group that can be coordinated to the reducing agent is an amino group. The article according to any one of claims 1 to 3, wherein the ink layer does not contain metal nanoparticles other than the metal derived from the reducing agent and the plating catalyst. The article according to any one of claims 1 to 4, wherein the reducing agent is an inorganic metal compound having a low valence. The article according to any one of claims 1 to 5, wherein the plating catalyst is palladium, silver, or copper. The article according to any one of claims 1 to 6, wherein the plating layer contains nickel, copper, silver, gold, or palladium. A reducing agent ink containing a low valence inorganic metal compound, an amino group-containing polymer, and a solvent, wherein the molar ratio of the metal of the inorganic metal compound to the amino group of the amino group-containing polymer is 1.5 or more. A method of forming a plating pattern on a base material.
Preparing a reducing agent ink containing a low valence inorganic metal compound, an amino group-containing polymer, and a solvent,
Applying the reducing agent ink on a base material to form an ink layer,
A method comprising contacting an ink layer with a solution containing ions of a plating catalyst to precipitate a plating catalyst on the surface of the ink layer, and contacting the plating catalyst with a plating solution.

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