JP5023977B2 - Ink jet ink for forming metal pattern and method for forming metal pattern - Google Patents

Description

  The present invention relates to an ink-jet ink for forming a metal pattern and a metal pattern forming method using the same. More specifically, the present invention relates to a metal pattern forming inkjet ink used in a circuit and a metal pattern forming method using the same.

  Formation of a metal pattern used for a circuit has been conventionally performed by a forming method using a resist material. In other words, a resist material is applied on a thin metal layer, a required pattern is exposed to light, an unnecessary resist is removed by development, an exposed thin metal is removed by etching, and a remaining resist portion is peeled off. The metal thin film on which the metal pattern was recorded was formed.

  However, this method requires many processes and takes time, and is unnecessary in terms of production time, energy and raw material use efficiency, such as removing unnecessary resist and thin metal, and has been required to be improved.

  In recent years, attention has been focused on a metal pattern forming method in which a metal pattern is directly drawn by screen printing, ink jet printing or the like using an ink containing a so-called metal nanoparticle having a particle size of 100 nm or less (see Patent Document 1).

  This is a method of forming a circuit by firing at a relatively low temperature of about 200 to 300 ° C. by utilizing the fact that the melting point is lowered by minimizing the particle size. Although this technology certainly has advantages such as reduced man-hours and improved utilization efficiency of raw materials, it is difficult to completely fuse metal particles, and the electrical resistance does not decrease to the equivalent of bulk metal in the fired metal pattern The problem remained unresolved.

  Further, a metal ion solution and a solution containing a reducing agent are separately attached to the substrate and reacted to form a conductive metal region (see Patent Document 2). When these solutions are contacted almost simultaneously on the substrate, accurate landing accuracy is required, and each droplet on the substrate is wet-on-wet (the next droplet in a wet state before drying and solidifying after landing). There was a defect such as disturbance of landing due to the landing on the top). In the case where one of the solutions is landed and the next solution is landed after drying, it is not preferable because it takes more than double the time for pattern formation. Furthermore, the technique for reducing metal ions is a pattern forming method based on the premise that a catalyst such as palladium acetate is applied to the substrate in advance, and this catalyst application step is a drawback.

Although it is disclosed that a catalyst (or physical development nucleus) in such a reduction reaction is not used, a conductive pattern is formed from a solution containing a metal salt and a reducing agent that is reducible under heating. No complexing agent that stabilizes and stabilizes is used (see Patent Document 3). For this reason, the reduction reaction of the metal salt is likely to proceed and the liquid storage stability is poor.
JP 2002-299833 A JP-T-2006-516818 JP 2004-214236 A

  The present invention has been made in view of the above problems and circumstances, and the first solution is to select a reduction condition for the copper ion complex, so that the formation of metallic copper proceeds in a preferable state, and is dense. An object of the present invention is to provide a metal pattern forming ink-jet ink capable of forming a metal film having a good resistance value and a metal pattern forming method using the same.

  A second problem to be solved is to provide a metal pattern forming ink-jet ink that can be reduced to metallic copper without using a catalyst (or physical development nucleus), and a metal pattern forming method using the same.

  The above-mentioned problem according to the present invention is solved by the following means.

1. An ink-jet ink for forming a metal pattern, comprising a copper metal salt, a complexing agent and a reducing agent, wherein the reducing agent is a boron compound and satisfies the following relational expression (1) relating to the oxidation-reduction potential: An ink-jet ink for forming a metal pattern, characterized by being adjusted with a salt, a complexing agent and a reducing agent.
Relational expression (1): E ₁ −E ₂ = 1.00 to 1.40 (V)
Here, E ₁ : redox potential of the copper ion complex formed by the complexing agent and copper ions, E ₂ : redox potential of the reducing agent, where the redox potential is 25 ° C. and for forming the metal pattern The measured value is the same pH value as that of the inkjet ink.

  2. 2. The inkjet ink for forming a metal pattern according to 1, wherein the inkjet ink for forming a metal pattern has a pH value of 11.0 to 14.0 at 25 ° C.

  3. 3. The metal as described in 1 or 2 above, wherein the amount of the complexing agent added in preparing the ink jet ink for forming a metal pattern is 0.8 to 3.0 in terms of a molar ratio to the copper metal salt. Ink-jet ink for pattern formation.

  4). The inkjet ink for forming a metal pattern according to any one of 1 to 3, wherein the complexing agent is ammonia or a polyamine compound.

5. 5. The ink for forming a metal pattern according to any one of 1 to 4, wherein the relational expression related to the oxidation-reduction potential is expressed by the following relational expression (2).
Relational expression (2): E ₁ −E ₂ = 1.10 to 1.30 (V)
Here, the meanings of E ₁ and E ₂ and the conditions for measuring the oxidation-reduction potential are the same as those in the relational expression (1).

  6). A metal pattern forming method, comprising: forming a metal pattern on a substrate using the metal pattern forming inkjet ink according to any one of 1 to 5 above.

  7). 7. The method for forming a metal pattern according to 6 above, wherein when forming a copper metal by reducing a copper ion complex by a reduction reaction, a compound having a catalytic action for the reduction reaction is not used. Method.

  By selecting the reduction conditions of the copper ion complex by the above means of the present invention, the formation of metallic copper proceeds in a preferable state, and a metal film forming inkjet ink capable of forming a dense metal film with good resistance value And the metal pattern formation method using the same can be provided. Further, it is possible to provide a metal pattern forming inkjet ink that can be reduced to metallic copper without using a catalyst (or physical development nucleus) and a metal pattern forming method using the same.

  The inkjet ink for forming a metal pattern of the present invention (hereinafter also simply referred to as “inkjet ink” or “ink”) is an inkjet ink for forming a metal pattern containing a copper metal salt, a complexing agent and a reducing agent, The reducing agent is a boron-based compound and is adjusted with the copper metal salt, the complexing agent, and the reducing agent so as to satisfy the relational expression (1) relating to the oxidation-reduction potential. This feature is a technical feature common to the inventions according to claims 1 to 7.

  In the present application, “adjusted with a copper metal salt, a complexing agent and a reducing agent so as to satisfy the relational expression (1) relating to the oxidation-reduction potential” means that each of the copper metal salt, the complexing agent and the reducing agent is used. It means that the compound has been adjusted to satisfy a predetermined redox potential relational expression through selection experiments of compounds belonging to it and optimization experiments such as the use amount (addition amount), use ratio, and concentration thereof.

As a preferred embodiment of the present invention, the relational expression relating to the oxidation-reduction potential is an aspect represented by the following relational expression (2).
(Relational expression 2): E ₁ −E ₂ = 1.10 to 1.30 (V)
The meanings of E ₁ and E ₂ and the measurement conditions for the oxidation-reduction potential are the same as those in the relational expression 1.

  Moreover, in this invention, the pH value in 25 degreeC of the said inkjet ink for metal pattern formation is 11.0-14.0, and the addition amount of the said complexing agent at the time of preparing the inkjet ink for metal pattern formation However, it is preferable that the molar ratio with respect to the copper metal salt is 0.8 to 3.0 and that the complexing agent is ammonia or a polyamine compound.

  The inkjet ink for forming a metal pattern of the present invention can be suitably used in a metal pattern forming method for forming a metal pattern on a substrate. In addition, in the said metal pattern formation method, when reducing a copper ion complex by a reduction reaction and forming metallic copper, it is also preferable to set it as the embodiment which does not use the compound which has a catalytic action with respect to the said reduction reaction.

  Hereinafter, the present invention, its components, and the best mode and mode for carrying out the present invention will be described in detail.

<Metal formation by reduction reaction of metal ions>
Electrons released by oxidation of the reducing agent are supplied (reduced) to metal ions (copper ions in the present invention) in the solution and generated as metals.

R (reducing agent) + H ₂ O → Ox (oxide) + H ⁺ + e ⁻
M ^{n +} + ne ⁻ → M ⁰ (metal)
Since this reaction is a redox reaction, it does not proceed or is affected by the redox potential of the reducing agent and the metal ion. Moreover, since this electric potential changes also with pH values, it demonstrates using a potential-pH diagram (refer FIG. 1).

An example of a potential-pH diagram of metal ions (salt ions and complex ions) and a reducing agent is shown. In general, when the pH is increased, the oxidation-reduction potential becomes lower (smaller). Considering a combination of a metal ion and a reducing agent, the reduction reaction proceeds when the potential (E ₀ ) of the metal ion is noble (larger) than the potential (E ₂ ) of the reducing agent. In order to proceed further quantitatively, E ₀ and E ₂ need to be separated to some extent. However, even if it is too far away, the reduction reaction proceeds rapidly and the generated metal particles become coarse particles. For wiring applications such as circuits, it is preferable for conductivity and adhesion, and is within a certain range. is necessary.

Further, the potential (E ₁ ) of the complex formed of the metal salt and the complexing agent is less likely to be reduced because the potential is lower (smaller) than the potential (E ₀ ) of the metal ion. However, the redox potential is constant with respect to fluctuations in pH value, and the reduction proceeds stably. In addition, the ink storage stability under various conditions is also excellent.

Various reducing agents capable of reducing copper metal ions are known, and the type can be selected. However, it has been found that the effect of the present invention can be obtained with a boron-based compound as a reducing agent from the magnitude and reduction rate of the redox potential (E ₂ ) of the reducing agent and the metal film quality obtained.

  The ink of the present invention is characterized by containing a copper metal salt and a complexing agent that forms a complex with the copper metal salt. Furthermore, when the difference between these oxidation-reduction potentials is within a certain range, the reduction reaction proceeds quantitatively, and the generated metal particles become fine and dense, and the conductivity and adhesion to the substrate are good.

When the redox potential of the copper ion complex formed by the complexing agent and copper ion is E ₁ and the redox potential of the reducing agent is E2, E ₁ -E ₂ is 1.00 to 1.40 (V). It is necessary, and it is preferable that it is 01.10-1.30 (V). However, the oxidation-reduction potential is a measured value at 25 ° C. and the same pH value as that of the metal pattern forming inkjet ink.

  In addition, as the reduction reaction proceeds, the pH value of the reaction system also decreases, often affecting the denseness of the copper film that is not equivalent to the reaction in the initial state. As a means for eliminating these drawbacks, the pH value of the initial ink at 25 ° C. is preferably in the range of 11.0 to 14.0.

<Determination method of redox potential>
"Measuring method of the oxidation-reduction potential E ₁ copper ion complex formed by the complexing agent and copper ions"
An aqueous solution containing 0.1% by mass of a copper metal salt and an equimolar amount of a complexing agent is adjusted to a desired value at 25 ° C. using sodium hydroxide or hydrochloric acid (the pH value is 7 Prepare 8 types of -14 range.)

Next, the ORP value (V) is measured at 25 ° C. with an oxidation-reduction potential (ORP) meter. In addition, when there are multiple types of copper ion complexes formed of a complexing agent and copper ions, the redox potential of the copper ion complex species with the maximum concentration is E ₁ .

"Method of measuring the oxidation-reduction potential E ₂ of the reducing agent"
An aqueous solution containing 0.1% by mass of a reducing agent is adjusted to a desired pH value at 25 ° C. using sodium hydroxide or hydrochloric acid (pH values in the range of 7 to 14 are 8 types). prepare.).

  Next, the ORP value (V) is measured at 25 ° C. with an oxidation-reduction potential (ORP) meter.

The measured values are plotted on a graph of horizontal axis: pH value, vertical axis: oxidation-reduction potential, and E ₁ and E ₂ are connected by a line.

The pH value of the ink of the present invention is measured, E ₁ and E ₂ corresponding to the pH value are obtained on the graph, and the relational expression (E ₁ -E ₂ ) is calculated.

<Copper metal salt>
Examples of the copper metal salt according to the present invention include copper (I) chloride, copper (II) chloride, copper (I) bromide, copper (II) bromide, copper (I) iodide, and potassium (II) chloride. , Copper perchlorate (II), copper nitrate (II), copper sulfate (II), copper sulfate (II) ammonium, copper carbonate (II), copper formate (II), copper acetate (II), 2-ethylhexane Copper (II) oxide, copper (II) stearate, copper (II) trifluoromethanesulfonate, copper (II) oxalate, copper (II) tartrate, copper (II) benzoate, copper naphthenate, copper citrate ( II), copper (II) acetylacetonate, copper (II) hexafluoroacetylacetonate, copper (II) benzoylacetonate, dicopper ethylenediaminetetraacetate, copper (II) oxide, copper hydroxide and the like. From the viewpoints of solubility and cost, copper (II) sulfate, copper (II) formate, and copper (II) acetate are preferred.

  The amount of copper metal salt added to the ink is preferably in the range of 1% by mass to 30% by mass.

<Complexing agent>
Examples of the complexing agent according to the present invention include polyamine compounds such as ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, amine alkanol compounds such as diethanolamine and triethanolamine, and amino acid compounds such as glycine and alanine. And aminocarboxylic acid compounds such as ethylenediaminetetraacetic acid and salts thereof, tartaric acid and salts thereof, citric acid and salts, oxycarboxylic acid compounds such as glycolic acid and salts thereof, and the like. Of these, ammonia and polyamine compounds are preferred.

  When the complexing agent is coordinated with the copper metal salt, the absorption spectrum of the copper metal salt solution changes. This can be confirmed by visual observation because color variation of the solution occurs, but it can also be confirmed by measuring a UV absorption spectrum.

  The addition amount of the complexing agent is preferably 0.8 to 5.0 in terms of a molar ratio with respect to the copper metal salt because of coordination to the copper metal salt and the need for stabilization.

<Reducing agent>
Examples of the boron compound used as the reducing agent according to the present invention include sodium borohydride, trimethylamine borane, dimethylamine borane, and sodium tetrahydroborate.

  The addition amount of the reducing agent is preferably 0.8 to 10 in terms of a molar ratio to the copper metal salt.

<solvent>
As the solvent according to the present invention, an aqueous liquid medium is preferably used, and as the aqueous liquid medium, a mixed solvent such as water and a water-soluble organic solvent is further preferably used. Examples of water-soluble organic solvents that are preferably used include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, Triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol), polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene Glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol Nomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol Monophenyl ether, propylene glycol monophenyl ether), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetra) , Tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2 -Pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) and the like.

<Surfactant>
Surfactants preferably used in the ink of the present invention include alkyl sulfates, alkyl ester sulfates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, fatty acids. Anionic surfactants such as salts, nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyalkylene alkyl phenyl ethers, acetylene glycols, polyoxyethylene-polyoxypropylene block copolymers, glycerin esters, sorbitan Activators such as esters, polyoxyethylene fatty acid amides and amine oxides, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. These surfactants can also be used as pigment dispersants, and in particular, anionic and nonionic surfactants can be preferably used.

<Various additives>
In the present invention, other conventionally known additives can be contained. For example, optical brighteners, antifoaming agents, lubricants, preservatives, thickeners, antistatic agents, matting agents, water-soluble polyvalent metal salts, acid bases, pH adjusters such as buffer solutions, antioxidants, surface tension It is a regulator, a non-resistance modifier, a rust inhibitor, an inorganic pigment, and the like.

<substrate>
As the substrate used in the present invention, any substrate may be used as long as it is insulative. For example, it is composed of a material having high rigidity such as glass or ceramics, or a resin such as polyethylene terephthalate (PET) or polyimide. The film-like thing to be used is mentioned.

  The substrate used in the present invention may be subjected to so-called primer treatment or plasma treatment for improving adhesion. Similarly, an undercoat layer may be provided on the substrate. Examples of the material for the undercoat layer include thermoplastic resins such as acrylic resins, coupling agents such as silane coupling agents, and inorganic pigment fine particles such as colloidal silica.

<Method for producing metallic copper>
Metallic copper in the present invention is produced by reducing a copper ion complex coordinated with a complexing agent with a reducing agent. In this case, the reduction easily proceeds by heating. The heating temperature is preferably in the range of 50 ° C. to 150 ° C. from the reaction rate and damage to the substrate. Heating may be performed on the entire substrate or only on the patterned portion.

  When a metal is produced by reducing a metal salt, a compound that catalyzes the reduction reaction is often used in a process for producing copper metal for the purpose of facilitating the progress of the reduction reaction. For example, physical development nuclei (colloidal noble metal particles and colloidal heavy metal sulfide compounds) are used in the case of silver halide, and palladium / tin catalysts are used in electroless metal plating. However, it is preferable not to use these reduction catalytic compounds in the metal pattern formation of the present invention. When a catalyst compound is used, a reduced metal is generated around the catalyst compound and the catalytic action is lowered, so that the metal film thickness is reduced. On the other hand, when the catalytic action is not used as in the present invention, the metal film thickness can be increased and the film uniformity is improved.

<Metal pattern formation method>
The ink of the present invention is ejected from an ink jet head onto a substrate, a pattern is formed on the substrate, and is reduced to metallic copper on the substrate to be used as wiring for a circuit or the like. The size of the droplets to be discharged is not particularly limited, but in the case of circuit wiring or the like, it is necessary to form fine lines, so the droplet amount is set to 50 pl or less, preferably 20 pl or less.

  There is no restriction | limiting in particular as an inkjet head, A piezo-type or a thermal-type head can be used.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In the examples, “%” represents mass% unless otherwise specified.

(Ink adjustment)
Copper (II) acetate monohydrate (2.0% by mass) was dissolved in glycerin (20% by mass) and water (residual amount%). When 1.5% by mass of ethylenediamine was added thereto, the color of the solution changed from bright blue to dark blue, and it was confirmed that a complex was formed with the complexing agent and copper acetate. To this, 3.0% by mass of dimethylamine borane as a reducing agent was added. Finally, at 25 ° C., ink 1 was prepared by adding sodium hydroxide or hydrochloric acid so that the pH values shown in Table 1 were obtained. The remaining inks were prepared as described in Table 1 and Table 2. In addition to ink 7, when the complexing agent was added to the copper metal salt solution, the color of the solution changed, so that it was confirmed that the complexing agent was coordinated.

  The pH was measured at a liquid temperature of 25 ° C. using a pH meter HM-20 (manufactured by Toa DKK) equipped with a pH composite electrode GST-5711C (manufactured by Toa DKK).

(Measurement of redox potential)
<Redox potential of metal ion formed by complexing agent and copper ion>
In the inks shown in Tables 1 and 2, solutions were prepared in which only the reducing agent was not added. Further, the solution was adjusted with sodium hydroxide or hydrochloric acid at 25 ° C. so that the pH values shown in Table 2 were obtained. This solution was measured using an oxidation-reduction potentiometer HM-20 (manufactured by Toa DKK) equipped with an ORP composite electrode PST-5721C (manufactured by Toa DKK).

<Redox potential of reducing agent>
In the inks shown in Tables 1 and 2, a solution was prepared by removing the copper metal salt and the complexing agent. Further, the solution was adjusted with sodium hydroxide or hydrochloric acid at 25 ° C. so that the pH values shown in Table 2 were obtained. This solution was measured using an oxidation-reduction potentiometer HM-20 (manufactured by Toa DKK) equipped with an ORP composite electrode PST-5721C (manufactured by Toa DKK).

(Metal pattern forming method)
The surface of the polyimide film (thickness 140 μm) was subjected to plasma treatment. An ink jet head KM256Aq aqueous head was attached to an ink jet head evaluation apparatus EB100 (manufactured by Konica Minolta IJ Co., Ltd.) attached to the transport system option XY100 so that the ink produced above could be ejected. The polyimide film was attached to the stage, and the metal film was formed by discharging ink from the ink onto the polyimide film while heating the surface of the polyimide film to 100 ° C.

  In the case of ink 6 and ink 7, a metal pattern was formed on a polyimide film provided with a Pd catalyst. As a method for applying the Pd catalyst, a polyimide film was immersed in a solution of Alcup activator MAT (A liquid + B liquid: manufactured by Uemura Kogyo Co., Ltd.) at a specified temperature and time.

(Evaluation)
<Film thickness>
The film thickness of the metal pattern formed on the polyimide film was determined by determining the height difference between the metal pattern and the substrate using a non-contact type three-dimensional surface analyzer (RST / PLUS, WYKO).
○: Average value of film thickness is 0.3 μm or more Δ: Average value of film thickness is 0.1 μm or more and less than 0.3 μm ×: Average value of film thickness is less than 0.1 μm <Resistivity>
A four-probe probe PSP was connected to a resistivity meter Loresta GP (manufactured by Dia Instruments Co., Ltd.), and the resistivity of the metal pattern portion was measured.
○: The average value of resistivity is less than 10 μΩ · cm Δ: The average value of resistivity is 10 μΩ · cm or more and less than 50 μΩ · cm ×: The average value of resistivity is 50 μΩ · cm or more <Adhesiveness>
The sample was subjected to a tape peeling test in accordance with JIS D0202-1988. The drawing pattern of the evaluation sample was separated by 10 mm in total, using cellophane tape (“CT24”, manufactured by Nichiban Co., Ltd.), and adhered to the film with the belly of the finger and then peeled. Judgment was evaluated according to the following criteria from the number of squares not peeled out of 10 squares.

○: The peeled square is 1 square or less Δ: The peeled square is 4 to 2 squares ×: 5 squares or more are peeled off.

  The evaluation results are summarized in Table 3.

  As is apparent from the results shown in Table 3, in the examples according to the present invention, it can be seen that the average film thickness is moderately large, the resistance value is good, and the adhesion (peeling resistance) is excellent. .

  That is, by selecting the reducing conditions for the copper ion complex by the above-described means of the present invention, the formation of metallic copper proceeds in a preferable state, and a metal film for forming a dense metal film with good resistance can be formed. It can be seen that an inkjet ink and a metal pattern forming method using the same can be provided. It can also be seen that a metal pattern forming ink-jet ink that can be reduced to metallic copper without using a catalyst (or physical development nucleus) and a metal pattern forming method using the same.

The figure which shows the relationship between the oxidation reduction potential in 25 degreeC, and the pH value of an ink.

Explanation of symbols

E ₀ Redox potential of copper ion E ₁ Redox potential of copper ion complex E ₂ Redox potential of reductant

Claims (7)

An ink-jet ink for forming a metal pattern, comprising a copper metal salt, a complexing agent and a reducing agent, wherein the reducing agent is a boron compound and satisfies the following relational expression (1) relating to the oxidation-reduction potential: An ink-jet ink for forming a metal pattern, characterized by being adjusted with a salt, a complexing agent and a reducing agent.
Relational expression (1): E ₁ −E ₂ = 1.00 to 1.40 (V)
Here, E ₁ : redox potential of the copper ion complex formed by the complexing agent and copper ions, E ₂ : redox potential of the reducing agent, where the redox potential is 25 ° C. and for forming the metal pattern The measured value is the same pH value as that of the inkjet ink. The inkjet ink for forming a metal pattern according to claim 1, wherein the inkjet ink for forming a metal pattern has a pH value of 11.0 to 14.0 at 25 ° C. The amount of the complexing agent added when preparing the ink jet ink for forming a metal pattern is 0.8 to 3.0 in terms of a molar ratio to the copper metal salt. Ink-jet ink for forming a metal pattern. The inkjet ink for forming a metal pattern according to any one of claims 1 to 3, wherein the complexing agent is ammonia or a polyamine compound. 5. The inkjet ink for forming a metal pattern according to claim 1, wherein the relational expression relating to the oxidation-reduction potential is expressed by the following relational expression (2).
Relational expression (2): E ₁ −E ₂ = 1.10 to 1.30 (V)
Here, the meanings of E ₁ and E ₂ and the conditions for measuring the oxidation-reduction potential are the same as those in the relational expression (1). A metal pattern forming method, comprising: forming a metal pattern on a substrate with the ink jet ink for forming a metal pattern according to claim 1. 7. The metal pattern forming method according to claim 6, wherein when forming a copper metal by reducing a copper ion complex by a reduction reaction, a compound having a catalytic action for the reduction reaction is not used. Forming method.

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