WO2024070341A1 - Metal nanowire production method - Google Patents

Metal nanowire production method Download PDF

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Publication number
WO2024070341A1
WO2024070341A1 PCT/JP2023/030248 JP2023030248W WO2024070341A1 WO 2024070341 A1 WO2024070341 A1 WO 2024070341A1 JP 2023030248 W JP2023030248 W JP 2023030248W WO 2024070341 A1 WO2024070341 A1 WO 2024070341A1
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metal
acid
metal nanowires
crushing
isolated
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PCT/JP2023/030248
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French (fr)
Japanese (ja)
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順二 川口
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富士フイルム株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/04—Wires; Strips; Foils
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/20—Separation of the formed objects from the electrodes with no destruction of said electrodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C25D11/20—Electrolytic after-treatment

Definitions

  • the present invention relates to a method for producing metal nanowires.
  • Patent Document 1 describes a method for obtaining metal nanowires by subjecting an aluminum base to an anodizing treatment, an aluminum base removal treatment, a perforation treatment, a metal filling treatment, and an anodized film removal treatment, in that order ([0025] [ Figure 1]).
  • the inventors have investigated the metal nanowires described in Patent Document 1 and have found that when used as a conductive bonding material (such as a material used to bond a semiconductor chip to a substrate), the bonding strength may not be sufficient.
  • the present invention aims to provide a method for manufacturing metal nanowires that can produce metal nanowires with high bonding strength when bonded.
  • the inventors discovered that by isolating the metal filled into the porous space from the anodized film and the valve metal substrate and then carrying out a crushing process, metal nanowires having high bonding strength when bonded can be obtained, and thus completed the present invention. That is, it has been found that the above object can be achieved by the following configuration.
  • a method for producing metal nanowires. [2] The method for producing metal nanowires according to [1], further comprising a drying step of drying the isolated metal between the isolating step and the crushing step. [3] The method for producing metal nanowires according to [1] or [2], further comprising a step of reducing or removing a surface oxide layer of the isolated metal between the isolation step and the crushing step.
  • [4] The method for producing metal nanowires according to any one of [1] to [3], further comprising a protective layer forming step of forming a protective layer containing a corrosion inhibitor on the isolated metal.
  • [5] The method for producing metal nanowires according to any one of [1] to [4], wherein the valve metal substrate contains aluminum.
  • the metal filling step includes a plating step.
  • the isolation step includes a dissolution step.
  • the present invention provides a method for producing metal nanowires that can produce metal nanowires with high bonding strength when bonded.
  • FIG. 1A is a schematic cross-sectional view of a valve metal substrate prior to an anodization step in a procedure showing an example of a method for producing metal nanowires of the present invention.
  • FIG. 1B is a schematic cross-sectional view of a structure after an anodization step in the procedure showing one example of a method for producing metal nanowires of the present invention.
  • FIG. 1C is a schematic cross-sectional view of a structure after a metal filling step in the procedure showing one example of a method for producing metal nanowires of the present invention.
  • FIG. 1D is a schematic cross-sectional view of the structure after the isolation step in the procedure showing one example of the method for producing metal nanowires of the present invention.
  • FIG. 1E is a schematic cross-sectional view of a structure (metal nanowires) after a crushing step in the procedure showing one example of a method for producing metal nanowires of the present invention.
  • the manufacturing method of metal nanowires of the present invention comprises an anodization process for forming an anodized film having pores on the surface of a valve metal substrate, a metal filling process for filling the pores with metal, an isolation process for isolating the filled metal from the anodized film and the valve metal substrate, and a crushing process for crushing the isolated metal (hereinafter also abbreviated as “isolated metal”) to obtain metal nanowires.
  • a crushing process is carried out after isolating the filled metal from the anodized film and the valve metal substrate (after the isolation process), thereby making it possible to obtain metal nanowires that have high bonding strength when bonded.
  • the reason why metal nanowires having high bonding strength when bonded could be obtained is not clear in detail, but is presumed to be as follows.
  • the surface of a valve metal substrate 1 is anodized to form an anodized film 3 having pores (micropores) 2 on the surface of the valve metal substrate 1.
  • the pores 2 are filled with a metal 4.
  • the isolation step the filled metal 4 is isolated from the anodized film 3 and the valve metal substrate 1.
  • the embodiment shown in Fig. 1D shows the state in which the isolated metal 5 obtained in the isolation step is collected (a part of the isolated metal is adhered).
  • metal nanowires 10 in which the isolated metal 5 is crushed can be obtained.
  • the valve metal substrate used in the manufacturing method of the present invention is not particularly limited as long as it is a substrate containing a valve metal.
  • the valve metal include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc.
  • aluminum is preferable because it has good dimensional stability and is relatively inexpensive. Therefore, in the manufacturing method of the present invention, it is preferable to use a base material containing aluminum (hereinafter, abbreviated as "aluminum base material”) as the valve metal base material.
  • the aluminum substrate is not particularly limited, and specific examples include pure aluminum plates; alloy plates containing aluminum as the main component and trace amounts of other elements; substrates in which high-purity aluminum is vapor-deposited onto low-purity aluminum (e.g., recycled materials); substrates in which the surfaces of silicon wafers, quartz, glass, etc. are coated with high-purity aluminum by methods such as vapor deposition and sputtering; and resin substrates laminated with aluminum.
  • the surface of the valve metal substrate that is anodized in the anodizing process described below preferably has a valve metal purity of 99.5% by mass or more, more preferably 99.9% by mass or more, and even more preferably 99.99% by mass or more.
  • the valve metal purity is within the above range, the arrangement of the through passages is sufficiently regular.
  • the surface of the valve metal base material that is to be anodized in the anodizing step described below is preferably previously subjected to a heat treatment, a degreasing treatment and a mirror finish treatment.
  • the heat treatment, degreasing treatment and mirror finish treatment can be the same as those described in paragraphs [0044] to [0054] of JP-A-2008-270158.
  • the anodizing step is a step of forming a porous anodized film on the surface of the valve metal base by subjecting the surface of the valve metal base to an anodizing treatment.
  • the anodizing treatment carried out in the anodizing step can be a conventionally known method, but it is preferable to use a self-ordering method or a constant voltage treatment because this makes it possible to isolate the filled metal with less variation in diameter in the isolation step described below.
  • the self-ordering method of the anodizing treatment and the constant voltage treatment can be the same as the treatments described in paragraphs [0056] to [0108] and in FIG. 3 of JP-A-2008-270158.
  • the anodizing treatment can be carried out, for example, by passing a current through a valve metal substrate as an anode in a solution having an acid concentration of 1 to 10% by mass.
  • the solution used in the anodizing treatment is preferably an acid solution, more preferably sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, amidosulfonic acid, glycolic acid, tartaric acid, malic acid, citric acid, etc., and among these, sulfuric acid, phosphoric acid, and oxalic acid are further preferable, and oxalic acid is particularly preferable.
  • These acids can be used alone or in combination of two or more kinds.
  • the conditions for the anodizing treatment vary depending on the electrolyte used and cannot be determined in general, but generally, the electrolyte concentration is preferably 0.1 to 20% by mass, the solution temperature is -10 to 30°C, the current density is 0.01 to 20 A/ dm2 , the voltage is 3 to 300 V, and the electrolysis time is 0.5 to 30 hours, more preferably the electrolyte concentration is 0.5 to 15% by mass, the solution temperature is -5 to 25°C, the current density is 0.05 to 15 A/ dm2 , the voltage is 5 to 250 V, and the electrolysis time is 1 to 25 hours, and even more preferably the electrolyte concentration is 1 to 10% by mass, the solution temperature is 0 to 20°C, the current density is 0.1 to 10 A/ dm2 , the voltage is 10 to 200 V, and the electrolysis time is 2 to 20 hours.
  • the anodizing treatment time is preferably 0.5 minutes to 16 hours, more preferably 1 minute to 12 hours, and even more preferably 2 minutes to 8 hours.
  • the thickness of the anodized film formed by the anodization process is not particularly limited, but from the viewpoint of adjusting the length of the metal nanowires, it is preferably 0.3 to 300 ⁇ m, more preferably 0.5 to 120 ⁇ m, and even more preferably 0.5 to 100 ⁇ m.
  • the thickness of the anodic oxide film can be calculated as the average value of measurements taken at 10 points by cutting the anodic oxide film in the thickness direction with a focused ion beam (FIB), taking surface photographs (magnification: 50,000 times) of the cross section with a field emission scanning electron microscope (FE-SEM).
  • the density of the pores formed by the anodization process is not particularly limited, but is preferably 2 million pores/ mm2 or more, more preferably 10 million pores/ mm2 or more, even more preferably 50 million pores/mm2 or more, and particularly preferably 100 million pores/ mm2 or more.
  • the density of the pores can be measured and calculated by the method described in paragraphs [0168] and [0169] of JP-A-2008-270158.
  • the average opening diameter of the pores formed by the above-mentioned anodization process is not particularly limited, but from the viewpoint of adjusting the diameter of the metal nanowires, it is preferably 5 to 500 nm, more preferably 20 to 400 nm, even more preferably 40 to 200 nm, and particularly preferably 50 to 100 nm.
  • the average opening diameter of the pores can be calculated as the average value of measurements taken at 50 points on a surface photograph (magnification: 50,000 times) taken with an FE-SEM.
  • the metal filling step is a step of filling the inside of the pores with a metal after the anodization step.
  • the above metal is preferably a material having an electrical resistivity of 10 3 ⁇ cm or less, and specific examples thereof include gold (Au), silver (Ag), copper (Cu), aluminum (Al), titanium (Ti), nickel (Ni), cobalt (Co), etc.
  • Au gold
  • silver Au
  • Cu copper
  • Al aluminum
  • Ti titanium
  • Ni nickel
  • Co cobalt
  • Examples of the method for filling the interior of the pores with the metal include the methods described in paragraphs [0123] to [0126] and [FIG. 4] of JP-A-2008-270158.
  • the metal filling step includes a plating step, because this makes it difficult for the produced metal nanowires to contain hollow portions.
  • an electrolytic plating method as a method for filling the inside of the pores with the metal, and for example, an electrolytic plating method or an electroless plating method can be used.
  • an electrolytic plating method or an electroless plating method can be used.
  • the manufacturing method of the present invention when filling metal by electrolytic plating, it is necessary to provide a rest period during pulse electrolysis or constant potential electrolysis.
  • the rest period must be 10 seconds or more, and is preferably 30 to 60 seconds. It is also preferable to apply ultrasonic waves to promote stirring of the electrolyte.
  • the electrolysis voltage is usually 20 V or less, and preferably 10 V or less, but it is preferable to measure the deposition potential of the target metal in the electrolyte solution to be used in advance and perform constant-potential electrolysis at a potential within +1 V of that potential.
  • a device that can also be used with cyclic voltammetry, and a potentiostat device manufactured by Solartron, BAS, Hokuto Denko, IVIUM, etc. can be used.
  • the plating solution a conventionally known plating solution can be used. Specifically, when copper is precipitated, an aqueous solution of copper sulfate is generally used, and the concentration of the copper sulfate is preferably 1 to 300 g/L, and more preferably 100 to 200 g/L. Precipitation can be promoted by adding hydrochloric acid to the electrolyte. In this case, the concentration of hydrochloric acid is preferably 10 to 20 g/L. When gold is to be deposited, it is preferable to use a sulfuric acid solution of gold tetrachloride and to perform plating by AC electrolysis.
  • the electrolytic plating method a treatment method in which AC electrolytic plating and DC electrolytic plating are combined in this order.
  • a voltage is applied modulated into a sine wave at a predetermined frequency.
  • the waveform of the voltage modulation is not limited to a sine wave, and may be, for example, a square wave, a triangular wave, a sawtooth wave, or an inverse sawtooth wave.
  • the DC electrolytic plating method can appropriately use the treatment methods in the electrolytic plating method described above.
  • the metal filling step is a process that is performed on the region from the bottom of the hole to halfway through the opening, out of the entire region from the bottom of the hole to the opening.
  • the isolation step is a step of isolating the filled metal from the anodized film and the valve metal substrate after the metal filling step.
  • the method of isolating the filled metal from the anodized film and the valve metal base material is not particularly limited, and for example, the method of removing (for example, dissolving, peeling, etc.) the anodized film and the valve metal base material and isolating the filled metal can be preferably mentioned.
  • the embodiment after the above-mentioned isolation process also includes, for example, the embodiment in which the filled metal is dispersed in an isolated state in the treatment liquid used in the dissolution process (dissolution treatment) described later.
  • the method for removing the anodic oxide film and the valve metal substrate is not particularly limited, and may be, for example, by polishing.
  • the isolation process includes a dissolution process, that is, that at least a portion of the anodic oxide film and the valve metal substrate is removed by a dissolution process.
  • the isolation process includes a one-step removal process of removing the anodic oxide film and the valve metal substrate, and it is more preferable that the removal of the anodic oxide film is a process in which the anodic oxide film is removed by a dissolution treatment.
  • the isolation step may include a two-step removal step of removing the valve metal base material and then removing the anodic oxide film, and in this case, it is more preferable that both of the two removal steps are performed by dissolution treatment.
  • the removal of the valve metal substrate is preferably carried out by a dissolution treatment using a treatment liquid which does not easily dissolve the anodized film but easily dissolves the valve metal.
  • the dissolution rate of such a treatment solution for valve metal is preferably 1 ⁇ m/min or more, more preferably 3 ⁇ m/min or more, and even more preferably 5 ⁇ m/min or more.
  • the dissolution rate of anodized film is preferably 0.1 nm/min or less, more preferably 0.05 nm/min or less, and even more preferably 0.01 nm/min or less.
  • the treatment liquid preferably contains at least one metal compound having a lower ionization tendency than the valve metal, and has a pH of 4 or less or 8 or more, more preferably a pH of 3 or less or 9 or more, and even more preferably a pH of 2 or less or 10 or more.
  • Such a treatment liquid is preferably based on an acid or alkaline aqueous solution and contains, for example, compounds of manganese, zinc, chromium, iron, cadmium, cobalt, nickel, tin, lead, antimony, bismuth, copper, mercury, silver, palladium, platinum, and gold (e.g., chloroplatinic acid), their fluorides, or their chlorides.
  • an acid aqueous solution base is preferred, and a chloride blend is preferred.
  • a treatment solution in which mercury chloride is blended into an aqueous hydrochloric acid solution (hydrochloric acid/mercury chloride) and a treatment solution in which copper chloride is blended into an aqueous hydrochloric acid solution (hydrochloric acid/copper chloride) are preferred from the viewpoint of treatment latitude.
  • the composition of such a treatment liquid is not particularly limited, and for example, a bromine/methanol mixture, a bromine/ethanol mixture, aqua regia, etc. can be used.
  • the acid or alkali concentration of such a treatment solution is preferably from 0.01 to 10 mol/L, and more preferably from 0.05 to 5 mol/L.
  • the processing temperature when using such a processing solution is preferably from -10°C to 80°C, and more preferably from 0°C to 60°C.
  • the valve metal substrate is removed by contacting the valve metal substrate after the metal filling step with the treatment liquid described above.
  • the contact method is not particularly limited, and examples include the immersion method and the spray method. Of these, the immersion method is preferred.
  • the contact time is preferably 10 seconds to 5 hours, and more preferably 1 minute to 3 hours.
  • the anodic oxide film can be removed using a solvent that does not dissolve the metal filled in the pores but selectively dissolves the anodic oxide film, and either an aqueous alkaline solution or an aqueous acid solution can be used.
  • an alkaline aqueous solution When an alkaline aqueous solution is used, it is preferable to use an aqueous solution of at least one alkali selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide, and it is more preferable to use an aqueous solution of potassium hydroxide.
  • the concentration of the alkaline aqueous solution is preferably 1 to 30 mass %.
  • the temperature of the alkaline aqueous solution is preferably 10 to 60°C, more preferably 20 to 60°C, and even more preferably 30 to 60°C.
  • an aqueous acid solution it is preferable to use an aqueous solution of an inorganic acid such as chromic acid, sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, oxalic acid, or a mixture thereof, and it is more preferable to use an aqueous solution of chromic acid.
  • the concentration of the aqueous acid solution is preferably 1 to 30 mass %.
  • the temperature of the aqueous acid solution is preferably 15 to 80°C, more preferably 20 to 60°C, and even more preferably 30 to 50°C.
  • the anodic oxide film is removed by contacting the above-mentioned alkaline aqueous solution and acid aqueous solution after the metal filling step (preferably after the valve metal substrate is removed).
  • the contacting method is not particularly limited, and examples include immersion and spraying. Of these, the immersion method is preferred.
  • the immersion time in the alkaline aqueous solution and acid aqueous solution is preferably 1 to 120 minutes, more preferably 2 to 90 minutes, even more preferably 3 to 60 minutes, and particularly preferably 3 to 30 minutes. Of these, 3 to 20 minutes is preferred, and 3 to 10 minutes is more preferred.
  • the crushing step is a step of crushing the isolated metal after the isolation step.
  • the method for crushing the isolated metal is not particularly limited, but a suitable example is a method in which the isolated metal is crushed by applying an impact to the isolated metal in a liquid.
  • the liquid (solvent) used for disintegration is not particularly limited as long as it does not alter or dissolve the isolated metal, and examples thereof include water, ethanol, methanol, acetone, methyl ethyl ketone, butanol, ethyl acetate, butyl acetate, tetrahydrofuran, toluene, dimethylformamide, cyclohexane, cyclohexanone, etc. Among these, water is preferred from the viewpoint of safety.
  • the crushing step is preferably carried out in water or in an aqueous solution having an alkali or acid concentration of less than 1 mass %, from the viewpoint of producing metal nanowires having higher bonding strength when bonded.
  • the crushing treatment include a crushing treatment using cavitation and a crushing treatment using ceramic balls, and devices such as an ultrasonic cleaner, an ultrasonic homogenizer, a jet mill, a wet type micronizer, etc.
  • a crushing treatment using cavitation or a crushing treatment using ceramic balls is preferred, and a crushing treatment using cavitation is more preferred.
  • the concentration of the isolated metal in the liquid during pressure disintegration in the liquid is preferably 0.1 to 50 mass % because this makes the treatment uniform and improves productivity. Furthermore, the concentration of the isolated metal in the liquid when the pressure is released in the liquid is more preferably 0.5 to 30 mass%, and even more preferably 1 to 10 mass%, because this allows for the production of metal nanowires having higher bonding strength upon bonding.
  • the manufacturing method of the present invention preferably further includes a drying step for drying the isolated metal between the isolation step and the crushing step, since this makes apparent the effect of the present invention, that is, the ability to obtain metal nanowires having high bonding strength when bonded.
  • the method for drying the isolated metal is not particularly limited, but after removing the anodized film and the valve metal substrate, the isolated metal can be recovered and dried by performing a separation operation such as filtration using a filter or centrifugation.
  • the manufacturing method of the present invention further includes a step of forming a protective layer containing a corrosion inhibitor on the isolated metal after the isolation step (or after the drying step if the drying step is included).
  • the corrosion inhibitor is not particularly limited, and any known corrosion inhibitor can be used.
  • the corrosion inhibitor include compounds containing at least one of a nitrogen atom, an oxygen atom, and a sulfur atom.
  • the corrosion inhibitor is preferably a heterocyclic compound containing at least one of a nitrogen atom and an oxygen atom, more preferably a compound containing a five-membered ring structure containing one or more nitrogen atoms, and particularly preferably at least one compound selected from the group consisting of a compound containing a triazole structure, a compound containing a benzimidazole structure, and a compound containing a thiadiazole structure.
  • the five-membered ring structure containing one or more nitrogen atoms may be a monocyclic structure or a partial structure constituting a condensed ring.
  • the corrosion inhibitor is preferably a compound containing at least one of a polar group-containing acid and a polar group-containing base, because this makes it easier for the corrosion inhibitor to be adsorbed onto the surface of the isolated metal.
  • the polar group contained in the polar group-containing acid and the polar group-containing base include a carboxylic acid group (carboxy group), a sulfonic acid group (sulfo group), a phosphonic acid group, a phosphoric acid group, a primary to quaternary ammonium base, a carboxylate group, a sulfonate group, a phosphonate group, and a phosphate group.
  • the corrosion inhibitor is preferably a compound containing a carboxy group, because it bonds with metal ions to form complex ions, which makes it easier to protect the surface of the isolated metal.
  • corrosion inhibitors include imidazole, benzimidazole, 1,2,4-triazole, benzotriazole (BTA), tolyltriazole (TTA), butylbenzyltriazole, alkyldithiothiadiazole, alkylthiol, 2-aminopyrimidine, 5,6-dimethylbenzimidazole, 2-amino-5-mercapto-1,3,4-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole (DMTDA), 2-mercaptopyrimidine, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole (MBT), 2-mercaptobenzimidazole, etc.
  • corrosion inhibitors include aliphatic carboxylic acids such as acetic acid, propionic acid, palmitic acid, stearic acid, lauric acid, arachidic acid, terephthalic acid, and oleic acid; carboxylic acids such as glycolic acid, lactic acid, oxalic acid, malic acid, tartaric acid, and citric acid; aminopolycarboxylic acids such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), ethylenediaminediacetic acid (EDDA), and ethylene glycol diethyl ether diaminetetraacetic acid (GEDA); uric acid; and gallic acid.
  • carboxylic acids such as glycolic acid, lactic acid, oxalic acid, malic acid, tartaric acid, and citric acid
  • aminopolycarboxylic acids such as ethylenediaminetetraacetic acid (EDTA), n
  • the corrosion inhibitors may be used alone or in appropriate combination of two or more kinds.
  • the corrosion inhibitor preferably contains a compound containing a nitrogen atom (nitrogen-containing compound), more preferably is a nitrogen-containing compound, and further preferably is a heterocyclic compound containing at least one of a nitrogen atom and a sulfur atom.
  • the method for forming such a protective layer containing a corrosion inhibitor is not particularly limited, and examples include a method in which the isolated metal recovered in the drying process is added to an aqueous solution containing a corrosion inhibitor and stirred; a method in which the corrosion inhibitor is added to a washing solvent that washes the isolated metal recovered in the drying process; etc.
  • the manufacturing method of the present invention further includes a step of reducing or removing the surface oxide layer of the isolated metal between the isolation step and the crushing step (or before the drying step, if the drying step is included).
  • the reduction or removal step may be, for example, a step of carrying out an immersion treatment using an aqueous alkaline solution or an aqueous acid solution as described above in the removal treatment of the anodic oxide film.
  • compositions The metal nanowires produced by the production method of the present invention are preferably used as a composition containing the metal nanowires, and more preferably used as a composition in a paste state.
  • composition of the present invention the composition containing the metal nanowires produced by the production method of the present invention will be formally abbreviated as the "composition of the present invention.”
  • the content (concentration) of the metal nanowires in the composition of the present invention is not particularly limited, but it is preferably 30 to 99 mass %, and more preferably 50 to 90 mass %, relative to the total mass of the composition of the present invention, because this maintains good dispersion stability over time and also provides good uniformity when diluted.
  • the optional solvent contained in the composition of the present invention is mainly an organic solvent.
  • an organic solvent that is miscible with water water can be used in combination with the organic solvent in a proportion of 20% by volume or less.
  • an alcohol-based compound having a boiling point of 50° C. to 250° C., more preferably 55° C. to 200° C. is suitably used.
  • the alcohol-based compound is not particularly limited and can be appropriately selected depending on the purpose. Specific examples thereof include polyethylene glycol, polypropylene glycol, alkylene glycol, glycerol, etc.
  • those having a small number of carbon atoms such as ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2,3-butanediol, which have low viscosity at room temperature, are preferred, but those having a large number of carbon atoms, such as pentanediol, hexanediol, octanediol, and polyethylene glycol, can also be used. Of these, the most preferred solvent is diethylene glycol.
  • surfactant It is preferable to use a surfactant in the composition of the present invention because this provides better dispersion stability.
  • the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and fluorine-based surfactants. These surfactants may be used alone or in combination of two or more.
  • the nonionic surfactant is not particularly limited, and any of the conventionally known surfactants can be used.
  • polyoxyethylene alkyl ethers polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrylphenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, sorbitan fatty acid partial esters, pentaerythritol fatty acid partial esters, propylene glycol mono fatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerin fatty acid partial esters, polyoxyethylated castor oils, polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid
  • the anionic surfactant is not particularly limited, and any of the conventionally known surfactants can be used.
  • fatty acid salts, abietic acid salts, hydroxyalkanesulfonates, alkanesulfonates, dialkylsulfosuccinate salts linear alkylbenzenesulfonates, branched alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylphenoxypolyoxyethylenepropylsulfonates, polyoxyethylenealkylsulfophenylether salts, N-methyl-N-oleyltaurine sodium salt, N-alkylsulfosuccinic acid monoamide disodium salt, petroleum sulfonates, sulfated beef tallow oil, sulfate ester salts of fatty acid alkyl esters, alkane sulfonates, dialkylsulfosuccinate salts, alkylsulfon
  • alkyl sulfate salts examples include polyoxyethylene alkyl ether sulfate salts, fatty acid monoglyceride sulfate salts, polyoxyethylene alkyl phenyl ether sulfate salts, polyoxyethylene styryl phenyl ether sulfate salts, alkyl phosphate salts, polyoxyethylene alkyl ether phosphate salts, polyoxyethylene alkyl phenyl ether phosphate salts, partially saponified products of styrene/maleic anhydride copolymers, partially saponified products of olefin/maleic anhydride copolymers, and naphthalenesulfonate-formaldehyde condensates.
  • the cationic surfactant is not particularly limited, and any conventionally known surfactant can be used. Examples include alkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.
  • amphoteric surfactant is not particularly limited, and any conventionally known surfactant can be used. Examples include carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfuric acid esters, and imitazolines.
  • polyoxyethylene can be read as “polyoxyalkylene” such as polyoxymethylene, polyoxypropylene, polyoxybutylene, etc., and these surfactants can also be used in the present invention.
  • preferred surfactants include fluorine-based surfactants containing a perfluoroalkyl group in the molecule.
  • fluorine-based surfactants include anionic types such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl phosphates; amphoteric types such as perfluoroalkyl betaines; cationic types such as perfluoroalkyl trimethyl ammonium salts; and nonionic types such as perfluoroalkyl amine oxides, perfluoroalkyl ethylene oxide adducts, oligomers containing a perfluoroalkyl group and a hydrophilic group, oligomers containing a perfluoroalkyl group and a lipophilic group, oligomers containing a perfluoroalkyl group, a hydrophilic group, and a lipophilic group, and urethanes containing a
  • the HLB value is a value that indicates the degree of affinity of a surfactant for water and oil (organic compounds insoluble in water).
  • the HLB value ranges from 0 to 20, with the closer to 0 the higher the lipophilicity and the closer to 20 the higher the hydrophilicity.
  • these surfactants may be used alone or in combination of two or more.
  • the content of these surfactants is preferably 0.001 to 10 mass %, and more preferably 0.01 to 5 mass %, based on the total mass of the metal nanowires.
  • the composition of the present invention can use a water-soluble dispersant such as a water-soluble organic molecule having a hydroxyl group, a carboxyl group, a sulfone group, a phosphate group, an amino group, an SH group, or the like at its terminal, for example, succinic acid, polyvinyl alcohol (PVA), or polyvinylpyrrole (PVP).
  • a water-soluble dispersant such as a water-soluble organic molecule having a hydroxyl group, a carboxyl group, a sulfone group, a phosphate group, an amino group, an SH group, or the like at its terminal, for example, succinic acid, polyvinyl alcohol (PVA), or polyvinylpyrrole (PVP).
  • composition of the present invention may further contain conductive particles other than the metal nanowires.
  • the conductive particles preferably contain a metal, and more preferably contain at least one metal selected from the group consisting of gold, silver, copper, aluminum, nickel, zinc and cobalt.
  • the conductive particles may also contain one or more conductive components other than metals.
  • the shape of the conductive particles is not particularly limited, and they may be either solid or hollow.
  • the average major axis of the minimum enclosing ellipsoid of the conductive particle is preferably 0.01 ⁇ m or more and 50 ⁇ m or less.
  • the average major axis of the smallest enclosing ellipsoid of the conductive particle is preferably 1 to 10 times the average minor axis.
  • the minimum enclosing ellipsoid refers to the ellipsoid that has the smallest volume among the ellipsoids that contain the conductive particles therein, and includes an ellipsoid whose major axis and minor axis are the same (i.e., a sphere).
  • the average major axis of the minimum enclosing ellipsoid can be obtained by observing the cross section of the layer formed using the dispersion in the thickness direction with a microscope (e.g., electron microscope), measuring the major axis of 100 arbitrary fine particles, and calculating and averaging them.
  • the average minor axis of the minimum enclosing ellipsoid can be obtained by observing the cross section of the layer formed using the dispersion in the thickness direction with a microscope (e.g., electron microscope), measuring the minor axis of 100 arbitrary fine particles, and calculating and averaging them.
  • the median diameter (D50) described later refers to the median diameter of the conductive particles when the volume of the conductive particles is approximated to that of a sphere, and can be determined by a laser diffraction/scattering method or a dynamic light scattering method.
  • the content of the conductive particles is not particularly limited, but is preferably 5 to 70 parts by mass, and more preferably 10 to 45 parts by mass, per 100 parts by mass of the metal nanowires.
  • the composition of the present invention can be suitably used as a conductive ink for forming a circuit pattern on a wiring substrate.
  • the content (concentration) of the metal nanowires in the composition of the present invention is preferably 10 to 30 mass %, and more preferably 15 to 20 mass %, relative to the total mass of the composition of the present invention, because circuit patterns can be printed using an inkjet system.
  • composition of the present invention described above can be suitably used to form a conductive bonding material.
  • conductive bonding material in the present invention is a concept that includes not only a film formed on the entire surface of a desired substrate, but also the above-mentioned circuit pattern and the like.
  • the substrate on which the conductive film is formed and the method for forming the conductive film are not particularly limited, and for example, the substrate and the method for forming the conductive film described in JP-A-2010-84173 can be used.
  • the conductive bonding material of the present invention can be suitably used as a conductive bonding material for use in, for example, semiconductor bonding members, touch panels, electrode bonding materials for displays, electromagnetic wave shields, sintering materials, electrode materials for thin-layer ceramic capacitors, and various other devices.
  • Example 1 ⁇ Preparation of Aluminum Substrate> A molten metal was prepared using an aluminum alloy containing 0.06 mass% Si, 0.30 mass% Fe, 0.005 mass% Cu, 0.001 mass% Mn, 0.001 mass% Mg, 0.001 mass% Zn, 0.001 mass% Ti, and the remainder being Al and unavoidable impurities. The molten metal was treated and filtered, and an ingot having a thickness of 500 mm and a width of 1,200 mm was produced by a DC (Direct Chill) casting method. Next, the surface was scraped off by an average thickness of 10 mm using a facing machine, and then the plate was soaked at 550°C for about 5 hours.
  • DC Direct Chill
  • the plate When the temperature was lowered to 400°C, the plate was rolled into a 2.7 mm thick plate using a hot rolling machine. Further, the sheet was heat-treated at 500° C. using a continuous annealing machine, and then cold-rolled to a thickness of 1.0 mm to obtain an aluminum substrate of JIS (Japanese Industrial Standards) 1050 material. The aluminum substrate was formed into a wafer having a diameter of 200 mm (8 inches) and then subjected to the following treatments.
  • JIS Japanese Industrial Standards
  • Electrolytic polishing treatment The above-mentioned aluminum substrate was subjected to electrolytic polishing treatment using an electrolytic polishing solution having the following composition under conditions of a voltage of 25 V, a solution temperature of 65° C., and a solution flow rate of 3.0 m/min.
  • the cathode was a carbon electrode
  • the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.)
  • the flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).
  • (Electrolytic polishing solution composition) 85% by weight phosphoric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.) 660 mL ⁇ 160mL of pure water ⁇ 150mL sulfuric acid ⁇ 30mL ethylene glycol
  • the aluminum substrate after the electrolytic polishing treatment was subjected to anodizing treatment by a self-ordering method according to the procedure described in JP-A-2007-204802.
  • the aluminum substrate after electrolytic polishing was subjected to a pre-anodizing treatment for 5 hours in an electrolytic solution of 0.50 mol/L oxalic acid under conditions of a voltage of 40 V, a solution temperature of 16° C., and a solution flow rate of 3.0 m/min.
  • the aluminum substrate after the pre-anodizing treatment was subjected to a coating removal treatment by immersing it in a mixed aqueous solution of 0.2 mol/L chromic anhydride and 0.6 mol/L phosphoric acid (liquid temperature: 50° C.) for 12 hours. Thereafter, re-anodization was performed for 5 hours in an electrolyte of 0.50 mol/L oxalic acid under conditions of a voltage of 40 V, a liquid temperature of 16° C., and a liquid flow rate of 3.0 m/min, to obtain an anodized film with a thickness of 40 ⁇ m.
  • the cathode was a stainless steel electrode, and the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.).
  • the cooling device was NeoCool BD36 (manufactured by Yamato Scientific Co., Ltd.), and the stirring and heating device was Pair Stirrer PS-100 (manufactured by EYELA Tokyo Rikakikai Co., Ltd.).
  • the flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).
  • the surface of the anodized film after the pores were filled with metal was observed with an FE-SEM to determine whether 1,000 pores were sealed with metal.
  • the sealing rate (number of sealed pores/1,000) was calculated to be 96%.
  • the anodized film was cut in the thickness direction using an FIB, and the cross section was photographed with an FE-SEM (magnification 50,000x) to check the inside of the holes. It was found that the filling height from the bottom of the sealed holes was 35 ⁇ m.
  • ⁇ Isolation step> The filled metal was isolated from the anodized film and the aluminum base material by immersing the aluminum base material in an aqueous potassium hydroxide solution (concentration: 5 mol/L) at 60° C. for 300 seconds, to obtain an isolated metal. Specifically, the anodized film was dissolved by immersing the aluminum base material in an aqueous potassium hydroxide solution (concentration: 5 mol/L) at 60° C. for 300 seconds, and the filled metal was isolated by peeling off the aluminum base material at the same time as the anodized film was dissolved (after 300 seconds had elapsed).
  • Example 1 ⁇ Cleaning/Protective Layer Forming Step/Reduction or Removal Step> Next, the isolated metal recovered on the membrane was washed for 1 minute using the washing solvent shown below. In Example 1, since a corrosion inhibitor was added to the washing solvent, a protective layer was formed at the same time as washing. In Example 1, since citric acid was used as the corrosion inhibitor, the surface oxide layer of the isolated metal was also removed at the same time as the protective layer was formed. The isolated metals on the membrane were then collected. (Washing Solvent) An aqueous solution containing 1% by weight of citric acid
  • Example 2 The steps from “preparation of aluminum substrate” to “cleaning/protective layer formation step/reduction or removal step” in Example 1 were repeated twice, and twice the amount of isolated metal as in Example 1 was recovered. Thereafter, metal nanowires were produced in the same manner as in Example 1, except that the concentration of the isolated metal during the crushing treatment was changed to 40 mass %.
  • Example 3 Metal nanowires were produced in the same manner as in Example 1, except that the concentration of the isolated metal during the crushing treatment was changed to 0.5 mass %.
  • Example 4 Metal nanowires were produced in the same manner as in Example 1, except that the washing solvent in the washing/protective layer forming step/reduction or removal step was changed to water. That is, in Example 4, no protective layer was formed.
  • Example 5 Metal nanowires were produced in the same manner as in Example 1, except that the cleaning solvent in the cleaning/protective layer formation step/reduction or removal step was changed to an aqueous solution containing 1 mass % each of citric acid and benzotriazole.
  • Example 6 Metal nanowires were produced in the same manner as in Example 1, except that in the isolation step, the aluminum substrate was dissolved and removed by immersing the aluminum substrate in a 0.5 mass % Cu-12% HCl aqueous solution at 10°C for 1 hour before immersing the aluminum substrate in the potassium hydroxide aqueous solution.
  • Example 7 Metal nanowires were produced in the same manner as in Example 1, except that the liquid used in the crushing step was changed from water to a 1 mass % aqueous citric acid solution.
  • Example 8 Metal nanowires were produced in the same manner as in Example 1, except that the type of metal used in the metal filling step was changed to Ni.
  • Example 9 Metal nanowires were produced in the same manner as in Example 1, except that electroless Au plating was performed after the crushing step.
  • Example 10 Metal nanowires were produced in the same manner as in Example 1, except that the cleaning solvent in the cleaning/protective layer formation step/reduction or removal step was changed to an aqueous solution containing 1 mass % each of citric acid and 2-mercaptobenzothiazole.
  • Example 11 Metal nanowires were produced in the same manner as in Example 1, except that the metal filling height in the metal filling step was set to 15 ⁇ m.
  • Example 12 Metal nanowires were produced in the same manner as in Example 1, except that the surface oxide layer of the metal nanowires was reduced or removed by immersing them in a 10% by mass aqueous solution of sulfuric acid at 35°C for 15 seconds prior to the cleaning/protective layer formation process/reduction or removal process.
  • the prepared composition was applied to a Cu plate (10 mm ⁇ 10 mm ⁇ 0.5 mm) with a squeegee using a metal mask (opening: 1 ⁇ 1 mm ⁇ 0.2 mm), and a Cu plate (5 mm ⁇ 5 mm ⁇ 0.5 mm) was placed on the applied composition. Thereafter, using a bonding device (WP-100, manufactured by PMT), the atmosphere inside the device was replaced with reducing gas (N2: 85%, formic acid: 15%), and then the pieces were bonded by heating and compression at 250°C, 1 minute, and 5 MPa.
  • WP-100 manufactured by PMT
  • Example 1 shows that when the crushing step is not carried out, the bonding strength of the produced metal nanowires (isolated metal) is low (Comparative Example 1). In contrast, it was found that when the crushing step was not carried out, the bonding strength of the produced metal nanowires was high (Examples 1 to 12). In particular, a comparison of Examples 1 to 3 reveals that when the concentration of the isolated metal during the crushing treatment is 0.5 to 30 mass %, metal nanowires having higher bonding strength when bonded can be produced. Furthermore, a comparison between Example 1 and Example 7 revealed that disintegration in an aqueous solution with an alkali or acid concentration of less than 1 mass % made it possible to produce metal nanowires with higher bonding strength when bonded.
  • Valve metal substrate Porous (micropore) 3 Anodic oxide film 4 Metal 5 Isolated metal 10 Metal nanowire

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Abstract

The present invention addresses the problem of providing a metal nanowire production method that makes it possible to obtain a metal nanowire having high joining strength at the time of joining. A metal nanowire production method according to the present invention comprises: an anodization step for forming an anodization film that has pores on a surface of a valve metal substrate; a metal filling step for filling a metal into the pores; an isolation step for isolating the metal used for filling from the anodization film and the valve metal substrate; and a crushing step for crushing the isolated metal to obtain a metal nanowire.

Description

金属ナノワイヤの製造方法Method for producing metal nanowires
　本発明は、金属ナノワイヤの製造方法に関する。 The present invention relates to a method for producing metal nanowires.
　近年、金属ナノワイヤや金属ナノピラーを用いた導電性材料について種々の検討が試みられている。
　このような導電性材料として、ポーラスアルミナをナノ材料製作におけるテンプレートとすることは既に知られており、例えば、特許文献１には、アルミニウム基材に対して、陽極酸化処理、アルミニウム基材除去処理、貫通化処理、金属充填処理および陽極酸化膜除去処理をこの順に施して金属ナノワイヤを得る方法が記載されている（［００２５］［図１］）。 In recent years, various studies have been conducted on conductive materials using metal nanowires and metal nanopillars.
It is already known that porous alumina, one such conductive material, can be used as a template in the production of nanomaterials. For example, Patent Document 1 describes a method for obtaining metal nanowires by subjecting an aluminum base to an anodizing treatment, an aluminum base removal treatment, a perforation treatment, a metal filling treatment, and an anodized film removal treatment, in that order ([0025] [Figure 1]).
特開２０１２－２３８５９２号公報JP 2012-238592 A
　本発明者らは、特許文献１に記載された金属ナノワイヤについて検討を行った結果、導電性接合材料（例えば、半導体チップと基材との接合に用いる材料など）に用いた場合、接合強度が十分でない場合があることを明らかとした。 The inventors have investigated the metal nanowires described in Patent Document 1 and have found that when used as a conductive bonding material (such as a material used to bond a semiconductor chip to a substrate), the bonding strength may not be sufficient.
　そこで、本発明は、接合時に高い接合強度を有する金属ナノワイヤを得ることができる金属ナノワイヤの製造方法を提供することを課題とする。 The present invention aims to provide a method for manufacturing metal nanowires that can produce metal nanowires with high bonding strength when bonded.
　本発明者らは、上記課題を達成すべく鋭意研究した結果、ポーラスに充填した金属を陽極酸化膜およびバルブ金属基材から単離した後に、解砕工程を行うことにより、接合時に高い接合強度を有する金属ナノワイヤを得ることができることを見出し、本発明を完成させた。
　すなわち、以下の構成により上記課題を達成することができることを見出した。 As a result of intensive research to achieve the above-mentioned object, the inventors discovered that by isolating the metal filled into the porous space from the anodized film and the valve metal substrate and then carrying out a crushing process, metal nanowires having high bonding strength when bonded can be obtained, and thus completed the present invention.
That is, it has been found that the above object can be achieved by the following configuration.
　［１］　ポーラスを有する陽極酸化膜をバルブ金属基材の表面に形成する陽極酸化工程と、
　ポーラスに金属を充填する金属充填工程と、
　充填した金属を陽極酸化膜およびバルブ金属基材から単離する単離工程と、
　単離した金属を解砕して金属ナノワイヤを得る解砕工程とを有する、
　金属ナノワイヤの製造方法。
　［２］　単離工程と解砕工程との間に、更に、単離した金属を乾燥する乾燥工程を有する、［１］に記載の金属ナノワイヤの製造方法。
　［３］　単離工程と解砕工程との間に、更に、単離した金属の表面酸化層を還元または除去する工程を有する、［１］または［２］に記載の金属ナノワイヤの製造方法。
　［４］　更に、単離した金属に腐食防止剤を含有する保護層を形成する保護層形成工程を有する、［１］～［３］のいずれかに記載の金属ナノワイヤの製造方法。
　［５］　バルブ金属基材がアルミニウムを含む、［１］～［４］のいずれかに記載の金属ナノワイヤの製造方法。
　［６］　金属充填工程がめっき工程を含む、［１］～［５］のいずれかに記載の金属ナノワイヤの製造方法。
　［７］　単離工程が溶解工程を含む、［１］～［６］のいずれかに記載の金属ナノワイヤの製造方法。
　［８］　解砕工程が、水中、または、アルカリもしくは酸の濃度が１質量％未満となる水溶液中で行われる、［１］～［７］のいずれかに記載の金属ナノワイヤの製造方法。 [1] An anodizing step of forming a porous anodized film on a surface of a valve metal substrate;
a metal filling step of filling the pores with metal;
isolating the filled metal from the anodized film and the valve metal substrate;
and a crushing step of crushing the isolated metal to obtain metal nanowires.
A method for producing metal nanowires.
[2] The method for producing metal nanowires according to [1], further comprising a drying step of drying the isolated metal between the isolating step and the crushing step.
[3] The method for producing metal nanowires according to [1] or [2], further comprising a step of reducing or removing a surface oxide layer of the isolated metal between the isolation step and the crushing step.
[4] The method for producing metal nanowires according to any one of [1] to [3], further comprising a protective layer forming step of forming a protective layer containing a corrosion inhibitor on the isolated metal.
[5] The method for producing metal nanowires according to any one of [1] to [4], wherein the valve metal substrate contains aluminum.
[6] The method for producing metal nanowires according to any one of [1] to [5], wherein the metal filling step includes a plating step.
[7] The method for producing metal nanowires according to any one of [1] to [6], wherein the isolation step includes a dissolution step.
[8] The method for producing metal nanowires according to any one of [1] to [7], wherein the crushing step is carried out in water or in an aqueous solution having an alkali or acid concentration of less than 1 mass %.
　本発明によれば、接合時に高い接合強度を有する金属ナノワイヤを得ることができる金属ナノワイヤの製造方法を提供することができる。 The present invention provides a method for producing metal nanowires that can produce metal nanowires with high bonding strength when bonded.
図１Ａは、本発明の金属ナノワイヤの製造方法の一例を示す手順のうち、陽極酸化工程前のバルブ金属基材の模式的断面図である。FIG. 1A is a schematic cross-sectional view of a valve metal substrate prior to an anodization step in a procedure showing an example of a method for producing metal nanowires of the present invention. 図１Ｂは、本発明の金属ナノワイヤの製造方法の一例を示す手順のうち、陽極酸化工程後の構造体の模式的断面図である。FIG. 1B is a schematic cross-sectional view of a structure after an anodization step in the procedure showing one example of a method for producing metal nanowires of the present invention. 図１Ｃは、本発明の金属ナノワイヤの製造方法の一例を示す手順のうち、金属充填工程後の構造体の模式的断面図である。FIG. 1C is a schematic cross-sectional view of a structure after a metal filling step in the procedure showing one example of a method for producing metal nanowires of the present invention. 図１Ｄは、本発明の金属ナノワイヤの製造方法の一例を示す手順のうち、単離工程後の構造体の模式的断面図である。FIG. 1D is a schematic cross-sectional view of the structure after the isolation step in the procedure showing one example of the method for producing metal nanowires of the present invention. 図１Ｅは、本発明の金属ナノワイヤの製造方法の一例を示す手順のうち、解砕工程後の構造体（金属ナノワイヤ）の模式的断面図である。FIG. 1E is a schematic cross-sectional view of a structure (metal nanowires) after a crushing step in the procedure showing one example of a method for producing metal nanowires of the present invention.
　以下、本発明について詳細に説明する。
　以下に記載する構成要件の説明は、本発明の代表的な実施態様に基づいてなされることがあるが、本発明はそのような実施態様に限定されるものではない。
　なお、本明細書において、「～」を用いて表される数値範囲は、「～」の前後に記載される数値を下限値および上限値として含む範囲を意味する。 The present invention will be described in detail below.
The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.
In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
［金属ナノワイヤの製造方法］
　本発明の金属ナノワイヤの製造方法（以下、「本発明の製造方法」とも略す。）は、ポーラスを有する陽極酸化膜をバルブ金属基材の表面に形成する陽極酸化工程と、ポーラスに金属を充填する金属充填工程と、充填した金属を陽極酸化膜およびバルブ金属基材から単離する単離工程と、単離した金属（以下、「単離金属」とも略す。）を解砕して金属ナノワイヤを得る解砕工程とを有する。 [Metal Nanowire Manufacturing Method]
The manufacturing method of metal nanowires of the present invention (hereinafter also abbreviated as "the manufacturing method of the present invention") comprises an anodization process for forming an anodized film having pores on the surface of a valve metal substrate, a metal filling process for filling the pores with metal, an isolation process for isolating the filled metal from the anodized film and the valve metal substrate, and a crushing process for crushing the isolated metal (hereinafter also abbreviated as "isolated metal") to obtain metal nanowires.
　本発明においては、上述した通り、充填した金属を陽極酸化膜およびバルブ金属基材から単離した後（単離工程後）に、解砕工程を行うことにより、接合時に高い接合強度を有する金属ナノワイヤを得ることができる。
　ここで、接合時に高い接合強度を有する金属ナノワイヤを得ることができた理由は、詳細には明らかではないが、およそ以下のとおりと推測される。
　すなわち、単離金属に解砕処理を施すことにより、解砕処理を施さない場合と比較して、金属ナノワイヤが凝着した状態（例えば、束のような状態）で存在する割合が減少し、金属ナノワイヤの向きがランダムの状態で存在する割合が増加したことにより、接合材料として用いた際に柔軟性が向上したため、接合強度が向上したと考えられる。 In the present invention, as described above, a crushing process is carried out after isolating the filled metal from the anodized film and the valve metal substrate (after the isolation process), thereby making it possible to obtain metal nanowires that have high bonding strength when bonded.
The reason why metal nanowires having high bonding strength when bonded could be obtained is not clear in detail, but is presumed to be as follows.
In other words, by subjecting the isolated metal to a crushing treatment, the proportion of metal nanowires that exist in an adhered state (e.g., in a bundle-like state) decreased and the proportion of metal nanowires that exist in a randomly oriented state increased, compared to when the crushing treatment was not performed.This is thought to have improved the flexibility when used as a bonding material, and therefore the bonding strength.
　次に、図１Ａ～図１Ｅを用いて、本発明の製造方法における各工程の概要を説明した後に、各処理工程について詳述する。 Next, we will use Figures 1A to 1E to provide an overview of each step in the manufacturing method of the present invention, and then provide a detailed description of each processing step.
　図１Ａおよび図１Ｂに示すように、陽極酸化工程において、バルブ金属基材１の表面に陽極酸化処理を施し、バルブ金属基材１の表面に、ポーラス（マイクロポア）２を有する陽極酸化膜３を形成する。
　次いで、図１Ｃに示す通り、金属充填工程において、ポーラス２に金属４を充填する。
　次いで、図１Ｄに示す通り、単離工程において、充填した金属４を陽極酸化膜３およびバルブ金属基材１から単離する。なお、図１Ｄに示す態様は、単離工程によって得られた単離金属５を回収した状態（単離金属の一部が凝着している状態）を示すものである。
　次いで、図１Ｅに示す通り、解砕工程において、単離金属５が解砕された金属ナノワイヤ１０を得ることができる。 As shown in FIGS. 1A and 1B, in the anodizing step, the surface of a valve metal substrate 1 is anodized to form an anodized film 3 having pores (micropores) 2 on the surface of the valve metal substrate 1.
Next, as shown in FIG. 1C, in a metal filling step, the pores 2 are filled with a metal 4.
Next, as shown in Fig. 1D, in the isolation step, the filled metal 4 is isolated from the anodized film 3 and the valve metal substrate 1. The embodiment shown in Fig. 1D shows the state in which the isolated metal 5 obtained in the isolation step is collected (a part of the isolated metal is adhered).
Next, as shown in FIG. 1E, in a crushing step, metal nanowires 10 in which the isolated metal 5 is crushed can be obtained.
 〔バルブ金属基材〕
　本発明の製造方法に用いられるバルブ金属基材は、バルブ金属を含有する基材であれば特に限定されない。
　ここで、バルブ金属としては、具体的には、例えば、アルミニウム、タンタル、ニオブ、チタン、ハフニウム、ジルコニウム、亜鉛、タングステン、ビスマス、アンチモン等が挙げられる。これらのうち、寸法安定性がよく、比較的安価であることからアルミニウムであることが好ましい。
　そのため、本発明の製造方法においては、バルブ金属基材としてアルミニウムを含む基材（以下、「アルミニウム基材」と略す。）を用いることが好ましい。 [Valve metal substrate]
The valve metal substrate used in the manufacturing method of the present invention is not particularly limited as long as it is a substrate containing a valve metal.
Specific examples of the valve metal include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc. Among these, aluminum is preferable because it has good dimensional stability and is relatively inexpensive.
Therefore, in the manufacturing method of the present invention, it is preferable to use a base material containing aluminum (hereinafter, abbreviated as "aluminum base material") as the valve metal base material.
　アルミニウム基材は、特に限定されず、その具体例としては、純アルミニウム板；アルミニウムを主成分とし微量の異元素を含む合金板；低純度のアルミニウム（例えば、リサイクル材料）に高純度アルミニウムを蒸着させた基材；シリコンウエハ、石英、ガラス等の表面に蒸着、スパッタ等の方法により高純度アルミニウムを被覆させた基材；アルミニウムをラミネートした樹脂基材；等が挙げられる。 The aluminum substrate is not particularly limited, and specific examples include pure aluminum plates; alloy plates containing aluminum as the main component and trace amounts of other elements; substrates in which high-purity aluminum is vapor-deposited onto low-purity aluminum (e.g., recycled materials); substrates in which the surfaces of silicon wafers, quartz, glass, etc. are coated with high-purity aluminum by methods such as vapor deposition and sputtering; and resin substrates laminated with aluminum.
　バルブ金属基材のうち、後述する陽極酸化工程において陽極酸化処理を施す側の表面は、バルブ金属純度が、９９．５質量％以上であることが好ましく、９９．９質量％以上であることがより好ましく、９９．９９質量％以上であることが更に好ましい。バルブ金属純度が上述の範囲であると、貫通路の配列の規則性が十分となる。 The surface of the valve metal substrate that is anodized in the anodizing process described below preferably has a valve metal purity of 99.5% by mass or more, more preferably 99.9% by mass or more, and even more preferably 99.99% by mass or more. When the valve metal purity is within the above range, the arrangement of the through passages is sufficiently regular.
　また、バルブ金属基材のうち、後述する陽極酸化工程において陽極酸化処理を施す側の表面は、あらかじめ熱処理、脱脂処理および鏡面仕上げ処理が施されることが好ましい。
　ここで、熱処理、脱脂処理および鏡面仕上げ処理については、特開２００８－２７０１５８号公報の段落［００４４］～［００５４］に記載された各処理と同様の処理を施すことができる。 In addition, the surface of the valve metal base material that is to be anodized in the anodizing step described below is preferably previously subjected to a heat treatment, a degreasing treatment and a mirror finish treatment.
Here, the heat treatment, degreasing treatment and mirror finish treatment can be the same as those described in paragraphs [0044] to [0054] of JP-A-2008-270158.
 〔陽極酸化工程〕
　上記陽極酸化工程は、上記バルブ金属基材の表面に陽極酸化処理を施すことにより、上記バルブ金属基材の表面に、ポーラスを有する陽極酸化膜を形成する工程である。 [Anodizing process]
The anodizing step is a step of forming a porous anodized film on the surface of the valve metal base by subjecting the surface of the valve metal base to an anodizing treatment.
　上記陽極酸化工程で行う陽極酸化処理は、従来公知の方法を用いることができるが、後述する単離工程において、直径にバラツキの少ない充填した金属を単離することができる理由から、自己規則化法や定電圧処理を用いるのが好ましい。
　ここで、陽極酸化処理の自己規則化法や定電圧処理については、特開２００８－２７０１５８号公報の［００５６］～［０１０８］段落および［図３］に記載された各処理と同様の処理を施すことができる。 The anodizing treatment carried out in the anodizing step can be a conventionally known method, but it is preferable to use a self-ordering method or a constant voltage treatment because this makes it possible to isolate the filled metal with less variation in diameter in the isolation step described below.
Here, the self-ordering method of the anodizing treatment and the constant voltage treatment can be the same as the treatments described in paragraphs [0056] to [0108] and in FIG. 3 of JP-A-2008-270158.
　陽極酸化処理は、例えば、酸濃度１～１０質量％の溶液中で、バルブ金属基材を陽極として通電する方法を用いることができる。
　陽極酸化処理に用いられる溶液としては、酸溶液であることが好ましく、硫酸、リン酸、クロム酸、シュウ酸、スルファミン酸、ベンゼンスルホン酸、アミドスルホン酸、グリコール酸、酒石酸、りんご酸、クエン酸等がより好ましく、中でも硫酸、リン酸、シュウ酸が更に好ましく、シュウ酸が特に好ましい。これらの酸は単独でまたは２種以上を組み合わせて用いることができる。 The anodizing treatment can be carried out, for example, by passing a current through a valve metal substrate as an anode in a solution having an acid concentration of 1 to 10% by mass.
The solution used in the anodizing treatment is preferably an acid solution, more preferably sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, amidosulfonic acid, glycolic acid, tartaric acid, malic acid, citric acid, etc., and among these, sulfuric acid, phosphoric acid, and oxalic acid are further preferable, and oxalic acid is particularly preferable. These acids can be used alone or in combination of two or more kinds.
　極酸化処理の条件は、使用される電解液によって種々変化するので一概に決定され得ないが、一般的には電解液濃度０．１～２０質量％、液温－１０～３０℃、電流密度０．０１～２０Ａ／ｄｍ２、電圧３～３００Ｖ、電解時間０．５～３０時間であるのが好ましく、電解液濃度０．５～１５質量％、液温－５～２５℃、電流密度０．０５～１５Ａ／ｄｍ２、電圧５～２５０Ｖ、電解時間１～２５時間であるのがより好ましく、電解液濃度１～１０質量％、液温０～２０℃、電流密度０．１～１０Ａ／ｄｍ２、電圧１０～２００Ｖ、電解時間２～２０時間であるのが更に好ましい。 The conditions for the anodizing treatment vary depending on the electrolyte used and cannot be determined in general, but generally, the electrolyte concentration is preferably 0.1 to 20% by mass, the solution temperature is -10 to 30°C, the current density is 0.01 to 20 A/ dm2 , the voltage is 3 to 300 V, and the electrolysis time is 0.5 to 30 hours, more preferably the electrolyte concentration is 0.5 to 15% by mass, the solution temperature is -5 to 25°C, the current density is 0.05 to 15 A/ dm2 , the voltage is 5 to 250 V, and the electrolysis time is 1 to 25 hours, and even more preferably the electrolyte concentration is 1 to 10% by mass, the solution temperature is 0 to 20°C, the current density is 0.1 to 10 A/ dm2 , the voltage is 10 to 200 V, and the electrolysis time is 2 to 20 hours.
　陽極酸化処理の処理時間は、０．５分～１６時間であるのが好ましく、１分～１２時間であるのがより好ましく、２分～８時間であるのが更に好ましい。 The anodizing treatment time is preferably 0.5 minutes to 16 hours, more preferably 1 minute to 12 hours, and even more preferably 2 minutes to 8 hours.
　上記陽極酸化工程により形成される陽極酸化膜の厚みは特に限定されないが、金属ナノワイヤの長さを調整する観点から、０．３～３００μｍであることが好ましく、０．５～１２０μｍであることがより好ましく、０．５～１００μｍであることが更に好ましい。
　なお、陽極酸化膜の厚みは、陽極酸化膜を厚さ方向に対して集束イオンビーム（ＦＩＢ）で切削加工し、その断面を電界放射型走査電子顕微鏡（ＦＥ－ＳＥＭ）により表面写真（倍率５万倍）を撮影し、１０点測定した平均値として算出することができる。 The thickness of the anodized film formed by the anodization process is not particularly limited, but from the viewpoint of adjusting the length of the metal nanowires, it is preferably 0.3 to 300 μm, more preferably 0.5 to 120 μm, and even more preferably 0.5 to 100 μm.
The thickness of the anodic oxide film can be calculated as the average value of measurements taken at 10 points by cutting the anodic oxide film in the thickness direction with a focused ion beam (FIB), taking surface photographs (magnification: 50,000 times) of the cross section with a field emission scanning electron microscope (FE-SEM).
　上記陽極酸化工程により形成されるポーラスの密度は特に限定されないが、２００万個／ｍｍ２以上であることが好ましく、１０００万個／ｍｍ２以上であるのことがより好ましく、５０００万個／ｍｍ２以上であるのが更に好ましく、１億個／ｍｍ２以上であるのが特に好ましい。
　なお、ポーラスの密度は、特開２００８－２７０１５８号公報の［０１６８］および［０１６９］段落に記載された方法で測定し、算出することができる。 The density of the pores formed by the anodization process is not particularly limited, but is preferably 2 million pores/ mm2 or more, more preferably 10 million pores/ mm2 or more, even more preferably 50 million pores/mm2 or more, and particularly preferably 100 million pores/ mm2 or more.
The density of the pores can be measured and calculated by the method described in paragraphs [0168] and [0169] of JP-A-2008-270158.
　上記陽極酸化工程により形成されるポーラスの平均開口径は特に限定されないが、金属ナノワイヤの直径を調整する観点から、５～５００ｎｍであることが好ましく、２０～４００ｎｍであることがより好ましく、４０～２００ｎｍであることが更に好ましく、５０～１００ｎｍであることが特に好ましい。
　なお、ポーラスの平均開口径は、ＦＥ－ＳＥＭにより表面写真（倍率５００００倍）を撮影し、５０点測定した平均値として算出することができる。 The average opening diameter of the pores formed by the above-mentioned anodization process is not particularly limited, but from the viewpoint of adjusting the diameter of the metal nanowires, it is preferably 5 to 500 nm, more preferably 20 to 400 nm, even more preferably 40 to 200 nm, and particularly preferably 50 to 100 nm.
The average opening diameter of the pores can be calculated as the average value of measurements taken at 50 points on a surface photograph (magnification: 50,000 times) taken with an FE-SEM.
 〔金属充填工程〕
　上記金属充填工程は、上記陽極酸化工程の後に、ポーラスの内部に金属を充填する工程である。 [Metal filling process]
The metal filling step is a step of filling the inside of the pores with a metal after the anodization step.
　＜金属＞
　上記金属は、電気抵抗率が１０３Ω・ｃｍ以下の材料であるのが好ましく、その具体例としては、金（Ａｕ）、銀（Ａｇ）、銅（Ｃｕ）、アルミニウム（Ａｌ）、チタン（Ｔｉ）、ニッケル（Ｎｉ）、コバルト（Ｃｏ）等が好適に例示される。
　中でも、電気伝導性の観点から、Ｃｕ、Ａｕ、Ａｌ、Ｎｉ、Ｃｏが好ましく、Ｃｕ、Ｎｉ、Ｃｏがより好ましく、Ｃｕが更に好ましい。 <Metal>
The above metal is preferably a material having an electrical resistivity of 10 3 Ω·cm or less, and specific examples thereof include gold (Au), silver (Ag), copper (Cu), aluminum (Al), titanium (Ti), nickel (Ni), cobalt (Co), etc.
Among these, from the viewpoint of electrical conductivity, Cu, Au, Al, Ni, and Co are preferable, Cu, Ni, and Co are more preferable, and Cu is even more preferable.
　＜充填方法＞
　上記金属をポーラスの内部に充填する方法としては、例えば、特開２００８－２７０１５８号公報の段落［０１２３］～［０１２６］および［図４］に記載された各方法と同様の方法等が挙げられる。 <Filling method>
Examples of the method for filling the interior of the pores with the metal include the methods described in paragraphs [0123] to [0126] and [FIG. 4] of JP-A-2008-270158.
　本発明の製造方法においては、作製される金属ナノワイヤに空洞部分が含まれ難くなる理由から、上記金属充填工程がめっき工程を含むことが好ましい。
　具体的には、上記金属をポーラスの内部に充填する方法として、電解めっき処理方法を用いることが好ましく、例えば、電解めっき法または無電解めっき法を用いることができる。
　ここで、着色などに用いられる従来公知の電解めっき法では、選択的に孔中に金属を高アスペクトで析出（成長）させることは困難である。これは、析出金属が孔内で消費され一定時間以上電解を行なってもめっきが成長しないためと考えられる。
　そのため、本発明の製造方法においては、電解めっき法により金属を充填する場合は、パルス電解または定電位電解の際に休止時間をもうける必要がある。休止時間は、１０秒以上必要で、３０～６０秒あることが好ましい。
　また、電解液のかくはんを促進するため、超音波を加えることも望ましい。
　更に、電解電圧は、通常２０Ｖ以下であって望ましくは１０Ｖ以下であるが、使用する電解液における目的金属の析出電位を予め測定し、その電位＋１Ｖ以内で定電位電解を行なうことが好ましい。なお、定電位電解を行なう際には、サイクリックボルタンメトリを併用できるものが望ましく、Ｓｏｌａｒｔｒｏｎ社、ＢＡＳ社、北斗電工社、ＩＶＩＵＭ社等のポテンショスタット装置を用いることができる。 In the manufacturing method of the present invention, it is preferable that the metal filling step includes a plating step, because this makes it difficult for the produced metal nanowires to contain hollow portions.
Specifically, it is preferable to use an electrolytic plating method as a method for filling the inside of the pores with the metal, and for example, an electrolytic plating method or an electroless plating method can be used.
Here, it is difficult to selectively deposit (grow) a metal in a hole with a high aspect ratio using a conventional electrolytic plating method used for coloring, etc. This is thought to be because the deposited metal is consumed in the hole and the plating does not grow even if electrolysis is performed for a certain period of time or more.
Therefore, in the manufacturing method of the present invention, when filling metal by electrolytic plating, it is necessary to provide a rest period during pulse electrolysis or constant potential electrolysis. The rest period must be 10 seconds or more, and is preferably 30 to 60 seconds.
It is also preferable to apply ultrasonic waves to promote stirring of the electrolyte.
Furthermore, the electrolysis voltage is usually 20 V or less, and preferably 10 V or less, but it is preferable to measure the deposition potential of the target metal in the electrolyte solution to be used in advance and perform constant-potential electrolysis at a potential within +1 V of that potential. When performing constant-potential electrolysis, it is preferable to use a device that can also be used with cyclic voltammetry, and a potentiostat device manufactured by Solartron, BAS, Hokuto Denko, IVIUM, etc. can be used.
　めっき液は、従来公知のめっき液を用いることができる。
　具体的には、銅を析出させる場合には硫酸銅水溶液が一般的に用いられるが、硫酸銅の濃度は、１～３００ｇ／Ｌであるのが好ましく、１００～２００ｇ／Ｌであるのがより好ましい。また、電解液中に塩酸を添加すると析出を促進することができる。この場合、塩酸濃度は１０～２０ｇ／Ｌであるのが好ましい。
　また、金を析出させる場合、テトラクロロ金の硫酸溶液を用い、交流電解でめっきを行なうのが望ましい。 As the plating solution, a conventionally known plating solution can be used.
Specifically, when copper is precipitated, an aqueous solution of copper sulfate is generally used, and the concentration of the copper sulfate is preferably 1 to 300 g/L, and more preferably 100 to 200 g/L. Precipitation can be promoted by adding hydrochloric acid to the electrolyte. In this case, the concentration of hydrochloric acid is preferably 10 to 20 g/L.
When gold is to be deposited, it is preferable to use a sulfuric acid solution of gold tetrachloride and to perform plating by AC electrolysis.
　なお、無電解めっき法では、アスペクトの高いポーラスからなる孔中に金属を完全に充填には長時間を要するので、本発明の製造方法においては、電解めっき法により金属を充填するのが望ましい。 In addition, since it takes a long time to completely fill the pores of high aspect ratio pores with metal using electroless plating, it is preferable to fill the metal using electrolytic plating in the manufacturing method of the present invention.
　本発明の製造方法においては、電解めっき処理方法として、交流電解めっき法と直流電解めっき法とをこの順で組み合わせた処理方法を用いることが好ましい。
　ここで、交流電解めっき法は、例えば、電圧を予め定めた周波数で正弦波状に変調させて印加する。なお、電圧の変調の際の波形は正弦波に限定されるものではなく、例えば、矩形波、三角波、のこぎり波、または逆のこぎり波とすることもできる。
　また、直流電解めっき法は、上述した電解めっき法における処理方法を適宜用いることができる。 In the manufacturing method of the present invention, it is preferable to use, as the electrolytic plating method, a treatment method in which AC electrolytic plating and DC electrolytic plating are combined in this order.
Here, in the AC electrolytic plating method, for example, a voltage is applied modulated into a sine wave at a predetermined frequency. Note that the waveform of the voltage modulation is not limited to a sine wave, and may be, for example, a square wave, a triangular wave, a sawtooth wave, or an inverse sawtooth wave.
In addition, the DC electrolytic plating method can appropriately use the treatment methods in the electrolytic plating method described above.
　本発明の製造方法においては、金属ナノワイヤを製造する時間を短縮できる理由から、図１Ｃにも示す通り、上記金属充填工程における金属の充填が、ポーラスの底部から開口部までの全領域のうち、ポーラスの底部から開口部の途中までの領域に対して施される処理であることが好ましい。 In the manufacturing method of the present invention, because it is possible to shorten the time required to manufacture metal nanowires, as shown in FIG. 1C, it is preferable that the metal filling step is a process that is performed on the region from the bottom of the hole to halfway through the opening, out of the entire region from the bottom of the hole to the opening.
 〔単離工程〕
　上記単離工程は、上記金属充填工程の後に、充填した金属を上記陽極酸化膜および上記バルブ金属基材から単離する工程である。
　ここで、充填した金属を上記陽極酸化膜および上記バルブ金属基材から単離する方法は特に限定されず、例えば、上記陽極酸化膜および上記バルブ金属基材を除去（例えば、溶解、剥離など）し、充填した金属を単離する方法が好適に挙げられる。そのため、上記単離工程後の態様としては、例えば、後述する溶解工程（溶解処理）に用いた処理液中に、充填した金属が単離された状態で分散している態様も含まれる。 [Isolation step]
The isolation step is a step of isolating the filled metal from the anodized film and the valve metal substrate after the metal filling step.
Here, the method of isolating the filled metal from the anodized film and the valve metal base material is not particularly limited, and for example, the method of removing (for example, dissolving, peeling, etc.) the anodized film and the valve metal base material and isolating the filled metal can be preferably mentioned.Therefore, the embodiment after the above-mentioned isolation process also includes, for example, the embodiment in which the filled metal is dispersed in an isolated state in the treatment liquid used in the dissolution process (dissolution treatment) described later.
　本発明の製造方法においては、上記陽極酸化膜および上記バルブ金属基材を除去する方法は特に限定されず、例えば、研摩により除去する態様であってもよいが、作製される金属ナノワイヤの長さが均一になる理由から、上記単離工程が溶解工程を含むこと、すなわち、溶解処理によって上記陽極酸化膜および上記バルブ金属基材の少なくとも一部を除去することが好ましい。 In the manufacturing method of the present invention, the method for removing the anodic oxide film and the valve metal substrate is not particularly limited, and may be, for example, by polishing. However, in order to ensure that the length of the produced metal nanowires is uniform, it is preferable that the isolation process includes a dissolution process, that is, that at least a portion of the anodic oxide film and the valve metal substrate is removed by a dissolution process.
　本発明の製造方法においては、作製される金属ナノワイヤの形状やサイズが維持される理由から、上記単離工程が、上記陽極酸化膜を除去するとともに、上記バルブ金属基材を除去する１段階の除去工程を含むことが好ましく、上記陽極酸化膜の除去が溶解処理によって除去される工程であることがより好ましい。
　また、同様の理由から、上記単離工程が、上記バルブ金属基材を除去し、その後に上記陽極酸化膜を除去する２段階の除去工程を含む工程であってもよく、この場合、２段階の除去工程がいずれも溶解処理によって除去される工程であることがより好ましい。 In the manufacturing method of the present invention, in order to maintain the shape and size of the metal nanowires produced, it is preferable that the isolation process includes a one-step removal process of removing the anodic oxide film and the valve metal substrate, and it is more preferable that the removal of the anodic oxide film is a process in which the anodic oxide film is removed by a dissolution treatment.
For the same reason, the isolation step may include a two-step removal step of removing the valve metal base material and then removing the anodic oxide film, and in this case, it is more preferable that both of the two removal steps are performed by dissolution treatment.
　＜バルブ金属基材の除去＞
　上記バルブ金属基材の除去は、陽極酸化膜を溶解しにくく、バルブ金属を溶解しやすい処理液を用いた溶解処理が好ましい。
　このような処理液は、バルブ金属に対する溶解速度が、１μｍ／分以上であるのが好ましく、３μｍ／分以上であるのがより好ましく、５μｍ／分以上であるのが更に好ましい。同様に、陽極酸化膜に対する溶解速度が、０．１ｎｍ／分以下となるのが好ましく、０．０５ｎｍ／分以下となるのがより好ましく、０．０１ｎｍ／分以下となるのが更に好ましい。
　具体的には、バルブ金属よりもイオン化傾向の低い金属化合物を少なくとも１種含み、かつ、ｐＨが４以下または８以上となる処理液であるのが好ましく、そのｐＨが３以下または９以上であるのがより好ましく、２以下または１０以上であるのが更に好ましい。 <Removal of valve metal substrate>
The removal of the valve metal substrate is preferably carried out by a dissolution treatment using a treatment liquid which does not easily dissolve the anodized film but easily dissolves the valve metal.
The dissolution rate of such a treatment solution for valve metal is preferably 1 μm/min or more, more preferably 3 μm/min or more, and even more preferably 5 μm/min or more.Similarly, the dissolution rate of anodized film is preferably 0.1 nm/min or less, more preferably 0.05 nm/min or less, and even more preferably 0.01 nm/min or less.
Specifically, the treatment liquid preferably contains at least one metal compound having a lower ionization tendency than the valve metal, and has a pH of 4 or less or 8 or more, more preferably a pH of 3 or less or 9 or more, and even more preferably a pH of 2 or less or 10 or more.
　このような処理液としては、酸またはアルカリ水溶液をベースとし、例えば、マンガン、亜鉛、クロム、鉄、カドミウム、コバルト、ニッケル、スズ、鉛、アンチモン、ビスマス、銅、水銀、銀、パラジウム、白金、金の化合物（例えば、塩化白金酸）、これらのフッ化物、これらの塩化物等を配合したものであるのが好ましい。
　中でも、酸水溶液ベースが好ましく、塩化物をブレンドするのが好ましい。
　特に、塩酸水溶液に塩化水銀をブレンドした処理液（塩酸／塩化水銀）、塩酸水溶液に塩化銅をブレンドした処理液（塩酸／塩化銅）が、処理ラチチュードの観点から好ましい。
　なお、このような処理液の組成は特に限定されず、例えば、臭素／メタノール混合物、臭素／エタノール混合物、王水等を用いることができる。 Such a treatment liquid is preferably based on an acid or alkaline aqueous solution and contains, for example, compounds of manganese, zinc, chromium, iron, cadmium, cobalt, nickel, tin, lead, antimony, bismuth, copper, mercury, silver, palladium, platinum, and gold (e.g., chloroplatinic acid), their fluorides, or their chlorides.
Among these, an acid aqueous solution base is preferred, and a chloride blend is preferred.
In particular, a treatment solution in which mercury chloride is blended into an aqueous hydrochloric acid solution (hydrochloric acid/mercury chloride) and a treatment solution in which copper chloride is blended into an aqueous hydrochloric acid solution (hydrochloric acid/copper chloride) are preferred from the viewpoint of treatment latitude.
The composition of such a treatment liquid is not particularly limited, and for example, a bromine/methanol mixture, a bromine/ethanol mixture, aqua regia, etc. can be used.
　また、このような処理液の酸またはアルカリ濃度は、０．０１～１０ｍｏｌ／Ｌが好ましく、０．０５～５ｍｏｌ／Ｌがより好ましい。
　更に、このような処理液を用いた処理温度は、－１０℃～８０℃が好ましく、０℃～６０℃が好ましい。 The acid or alkali concentration of such a treatment solution is preferably from 0.01 to 10 mol/L, and more preferably from 0.05 to 5 mol/L.
Furthermore, the processing temperature when using such a processing solution is preferably from -10°C to 80°C, and more preferably from 0°C to 60°C.
　また、上記バルブ金属基材の除去は、上記金属充填工程後のバルブ金属基材を上述した処理液に接触させることにより行う。接触させる方法は、特に限定されず、例えば、浸せき法、スプレー法が挙げられる。中でも、浸せき法が好ましい。このときの接触時間としては、１０秒～５時間が好ましく、１分～３時間がより好ましい。 The valve metal substrate is removed by contacting the valve metal substrate after the metal filling step with the treatment liquid described above. The contact method is not particularly limited, and examples include the immersion method and the spray method. Of these, the immersion method is preferred. The contact time is preferably 10 seconds to 5 hours, and more preferably 1 minute to 3 hours.
　＜陽極酸化膜の除去＞
　上記陽極酸化膜の除去は、ポーラスに充填した金属を溶解せず、陽極酸化膜を選択的に溶解する溶媒を用いることができ、アルカリ水溶液および酸水溶液のいずれも用いることができる。 <Removal of anodic oxide film>
The anodic oxide film can be removed using a solvent that does not dissolve the metal filled in the pores but selectively dissolves the anodic oxide film, and either an aqueous alkaline solution or an aqueous acid solution can be used.
　ここで、アルカリ水溶液を用いる場合は、水酸化ナトリウム、水酸化カリウムおよび水酸化リチウムからなる群から選ばれる少なくとも１つのアルカリの水溶液を用いることが好ましく、水酸化カリウムの水溶液を用いることがより好ましい。また、アルカリ水溶液の濃度は１～３０質量％であるのが好ましい。アルカリ水溶液の温度は、１０～６０℃が好ましく、２０～６０℃がより好ましく、３０～６０℃であるのが更に好ましい。
　一方、酸水溶液を用いる場合は、クロム酸、硫酸、リン酸、硝酸、塩酸、シュウ酸等の無機酸またはこれらの混合物の水溶液を用いることが好ましく、クロム酸の水溶液を用いることがより好ましい。また、酸水溶液の濃度は１～３０質量％であるのが好ましい。酸水溶液の温度は、１５～８０℃が好ましく、２０～６０℃がより好ましく、３０～５０℃が更に好ましい。 When an alkaline aqueous solution is used, it is preferable to use an aqueous solution of at least one alkali selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide, and it is more preferable to use an aqueous solution of potassium hydroxide. The concentration of the alkaline aqueous solution is preferably 1 to 30 mass %. The temperature of the alkaline aqueous solution is preferably 10 to 60°C, more preferably 20 to 60°C, and even more preferably 30 to 60°C.
On the other hand, when an aqueous acid solution is used, it is preferable to use an aqueous solution of an inorganic acid such as chromic acid, sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, oxalic acid, or a mixture thereof, and it is more preferable to use an aqueous solution of chromic acid. The concentration of the aqueous acid solution is preferably 1 to 30 mass %. The temperature of the aqueous acid solution is preferably 15 to 80°C, more preferably 20 to 60°C, and even more preferably 30 to 50°C.
　また、上記陽極酸化膜の除去は、上記金属充填工程後（好ましくはバルブ金属基材を除去した後）に上述したアルカリ水溶液および酸水溶液に接触させることにより行う。接触させる方法は、特に限定されず、例えば、浸せき法、スプレー法が挙げられる。中でも、浸せき法が好ましい。アルカリ水溶液および酸水溶液への浸せき時間は、１～１２０分であるのが好ましく、２～９０分であるのがより好ましく、３～６０分であるのが更に好ましく、３～３０分であるのが特に好ましい。なかでも、３～２０分であるのが好ましく、３～１０分であるのがより好ましい。 The anodic oxide film is removed by contacting the above-mentioned alkaline aqueous solution and acid aqueous solution after the metal filling step (preferably after the valve metal substrate is removed). The contacting method is not particularly limited, and examples include immersion and spraying. Of these, the immersion method is preferred. The immersion time in the alkaline aqueous solution and acid aqueous solution is preferably 1 to 120 minutes, more preferably 2 to 90 minutes, even more preferably 3 to 60 minutes, and particularly preferably 3 to 30 minutes. Of these, 3 to 20 minutes is preferred, and 3 to 10 minutes is more preferred.
 〔解砕工程〕
　上記解砕工程は、上記単離工程の後に、単離金属を解砕する工程である。
　単離金属を解砕する方法は特に限定されないが、例えば、液中で単離金属に衝撃与えて解砕する方法が好適に挙げられる。
　解砕に用いる液体（溶媒）としては、単離金属を変質および溶解させなければ特に限定されないが、例えば、水、エタノール、メタノール、アセトン、メチルエチルケトン、ブタノール、酢酸エチル、酢酸ブチル、テトラヒドロフラン、トルエン、ジメチルホルムアミド、シクロヘキサン、シクロヘキサノンなどが挙げられる。これらのうち、安全性の観点から水であることが好ましい。
　また、上記解砕工程は、接合時により高い接合強度を有する金属ナノワイヤを作製できる観点から、水中、または、アルカリもしくは酸の濃度が１質量％未満となる水溶液中で行われることが好ましい。
　解砕処理としては、例えば、キャビテーションを利用した解砕処理や、セラミックスボールを衝突させた解砕処理などが挙げられ、超音波洗浄機、超音波ホモジナイザー、ジェットミル、湿式微粒化装置などの装置を用いることができる。これらのうち、キャビテーションを利用した解砕処理、または、セラミックスボールを衝突させた解砕処理が好ましく、キャビテーションを利用した解砕処理がより好ましい。 [Crushing process]
The crushing step is a step of crushing the isolated metal after the isolation step.
The method for crushing the isolated metal is not particularly limited, but a suitable example is a method in which the isolated metal is crushed by applying an impact to the isolated metal in a liquid.
The liquid (solvent) used for disintegration is not particularly limited as long as it does not alter or dissolve the isolated metal, and examples thereof include water, ethanol, methanol, acetone, methyl ethyl ketone, butanol, ethyl acetate, butyl acetate, tetrahydrofuran, toluene, dimethylformamide, cyclohexane, cyclohexanone, etc. Among these, water is preferred from the viewpoint of safety.
In addition, the crushing step is preferably carried out in water or in an aqueous solution having an alkali or acid concentration of less than 1 mass %, from the viewpoint of producing metal nanowires having higher bonding strength when bonded.
Examples of the crushing treatment include a crushing treatment using cavitation and a crushing treatment using ceramic balls, and devices such as an ultrasonic cleaner, an ultrasonic homogenizer, a jet mill, a wet type micronizer, etc. Among these, a crushing treatment using cavitation or a crushing treatment using ceramic balls is preferred, and a crushing treatment using cavitation is more preferred.
　本発明においては、液中で圧力を解砕する際の液中での単離金属の濃度は、処理が均一となり、生産性が向上する理由から、０．１～５０質量％が好ましい。
　また、液中で圧力を解砕する際の液中での単離金属の濃度は、接合時により高い接合強度を有する金属ナノワイヤを得ることができる理由から、０．５～３０質量％がより好ましく、１～１０質量％が更に好ましい。 In the present invention, the concentration of the isolated metal in the liquid during pressure disintegration in the liquid is preferably 0.1 to 50 mass % because this makes the treatment uniform and improves productivity.
Furthermore, the concentration of the isolated metal in the liquid when the pressure is released in the liquid is more preferably 0.5 to 30 mass%, and even more preferably 1 to 10 mass%, because this allows for the production of metal nanowires having higher bonding strength upon bonding.
 〔乾燥工程〕
　本発明の製造方法は、接合時に高い接合強度を有する金属ナノワイヤを得ることができるという本発明の効果が顕在化する理由から、上記単離工程と上記解砕工程との間に、更に、単離金属を乾燥する乾燥工程を有していることが好ましい。
　ここで、単離金属を乾燥する方法は特に限定されないが、上記陽極酸化膜および上記バルブ金属基材を除去した後に、フィルター等を用いた濾過、遠心分離などの分離操作を行うことにより、単離金属を回収することにより乾燥することができる。 [Drying process]
The manufacturing method of the present invention preferably further includes a drying step for drying the isolated metal between the isolation step and the crushing step, since this makes apparent the effect of the present invention, that is, the ability to obtain metal nanowires having high bonding strength when bonded.
Here, the method for drying the isolated metal is not particularly limited, but after removing the anodized film and the valve metal substrate, the isolated metal can be recovered and dried by performing a separation operation such as filtration using a filter or centrifugation.
 〔保護層形成工程〕
　本発明の製造方法は、接続抵抗の低い金属ナノワイヤを得ることができる理由から、上記単離工程の後（上記乾燥工程を有している場合には上記乾燥工程の後）に、更に、上記単離金属に腐食防止剤を含有する保護層を形成する工程を有していることが好ましい。 [Protective layer forming process]
Because the manufacturing method of the present invention can obtain metal nanowires with low connection resistance, it is preferable that the manufacturing method of the present invention further includes a step of forming a protective layer containing a corrosion inhibitor on the isolated metal after the isolation step (or after the drying step if the drying step is included).
　上記腐食防止剤は特に限定されず、公知の腐食防止剤を適用できる。
　腐食防止剤としては、例えば、窒素原子、酸素原子および硫黄原子の少なくとも１つを含有する化合物等が挙げられる。
　腐食防止剤は、耐久性の観点から、窒素原子および酸素原子の少なくとも１つを含有する複素環式化合物であることが好ましく、１つ以上の窒素原子を含有する５員環構造を含む化合物であることがより好ましく、トリアゾール構造を含む化合物、ベンゾイミダゾール構造を含む化合物、および、チアジアゾール構造を含む化合物からなる群より選択される少なくとも１種の化合物であることが特に好ましい。１つ以上の窒素原子を含有する５員環構造は、単環の構造であってもよく、縮合環を構成する部分構造であってもよい。 The corrosion inhibitor is not particularly limited, and any known corrosion inhibitor can be used.
Examples of the corrosion inhibitor include compounds containing at least one of a nitrogen atom, an oxygen atom, and a sulfur atom.
From the viewpoint of durability, the corrosion inhibitor is preferably a heterocyclic compound containing at least one of a nitrogen atom and an oxygen atom, more preferably a compound containing a five-membered ring structure containing one or more nitrogen atoms, and particularly preferably at least one compound selected from the group consisting of a compound containing a triazole structure, a compound containing a benzimidazole structure, and a compound containing a thiadiazole structure. The five-membered ring structure containing one or more nitrogen atoms may be a monocyclic structure or a partial structure constituting a condensed ring.
　また、腐食防止剤は、単離金属の表面に吸着しやすくなる理由から、極性基含有酸および極性基含有塩基の少なくとも一方を含む化合物であることが好ましい。
　極性基含有酸および極性基含有塩基が有する極性基としては、例えば、カルボン酸基（カルボキシ基）、スルホン酸基（スルホ基）、ホスホン酸基、リン酸基、第一級～第四級アンモニウム塩基、カルボン酸塩基、スルホン酸塩基、ホスホン酸塩基、リン酸塩基などが挙げられる。 In addition, the corrosion inhibitor is preferably a compound containing at least one of a polar group-containing acid and a polar group-containing base, because this makes it easier for the corrosion inhibitor to be adsorbed onto the surface of the isolated metal.
Examples of the polar group contained in the polar group-containing acid and the polar group-containing base include a carboxylic acid group (carboxy group), a sulfonic acid group (sulfo group), a phosphonic acid group, a phosphoric acid group, a primary to quaternary ammonium base, a carboxylate group, a sulfonate group, a phosphonate group, and a phosphate group.
　また、腐食防止剤は、金属イオンと結合して錯イオンを形成し、単離金属の表面が保護されやすくなる理由から、カルボキシ基を含む化合物であることが好ましい。 In addition, the corrosion inhibitor is preferably a compound containing a carboxy group, because it bonds with metal ions to form complex ions, which makes it easier to protect the surface of the isolated metal.
　上記腐食防止剤の具体例としては、イミダゾール、ベンゾイミダゾール、１，２，４－トリアゾール、ベンゾトリアゾール（ＢＴＡ）、トリルトリアゾール（ＴＴＡ）、ブチルベンジルトリアゾール、アルキルジチオチアジアゾール、アルキルチオール、２－アミノピリミジン、５，６－ジメチルベンゾイミダゾール、２－アミノ－５－メルカプト－１，３，４－チアジアゾール、２，５－ジメルカプト－１，３，４－チアジアゾール（ＤＭＴＤＡ）、２－メルカプトピリミジン、２－メルカプトベンゾオキサゾール、２－メルカプトベンゾチアゾール（ＭＢＴ）、２－メルカプトベンゾイミダゾール等が挙げられる。 Specific examples of the corrosion inhibitors include imidazole, benzimidazole, 1,2,4-triazole, benzotriazole (BTA), tolyltriazole (TTA), butylbenzyltriazole, alkyldithiothiadiazole, alkylthiol, 2-aminopyrimidine, 5,6-dimethylbenzimidazole, 2-amino-5-mercapto-1,3,4-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole (DMTDA), 2-mercaptopyrimidine, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole (MBT), 2-mercaptobenzimidazole, etc.
　上記腐食防止剤の他の具体例としては、酢酸、プロピオン酸、パルミチン酸、ステアリン酸、ラウリン酸、アラキジン酸、テレフタル酸、オレイン酸などの脂肪族カルボン酸；グリコール酸、乳酸、シュウ酸、リンゴ酸、酒石酸、クエン酸などのカルボン酸；エチレンジアミン四酢酸（ＥＤＴＡ）、ニトリロ三酢酸（ＮＴＡ）、イミノジ酢酸（ＩＤＡ）、エチレンジアミンジ酢酸（ＥＤＤＡ）、エチレングリコールジエチルエーテルジアミン四酢酸（ＧＥＤＡ）などのアミノポリカルボン酸；尿酸；没食子酸；などが挙げられる。 Other specific examples of the corrosion inhibitors include aliphatic carboxylic acids such as acetic acid, propionic acid, palmitic acid, stearic acid, lauric acid, arachidic acid, terephthalic acid, and oleic acid; carboxylic acids such as glycolic acid, lactic acid, oxalic acid, malic acid, tartaric acid, and citric acid; aminopolycarboxylic acids such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), ethylenediaminediacetic acid (EDDA), and ethylene glycol diethyl ether diaminetetraacetic acid (GEDA); uric acid; and gallic acid.
　腐食防止剤は、１種単独でも２種類以上適宜組み合わせて用いてもよい。
　また、経時安定性が良好となる理由から、上記腐食防止剤が窒素原子を含有する化合物（窒素含有化合物）を含むことが好ましく、窒素含有化合物であることがより好ましく、窒素原子および硫黄原子の少なくとも１つを含有する複素環式化合物であることが更に好ましい。 The corrosion inhibitors may be used alone or in appropriate combination of two or more kinds.
In addition, for the reason that the stability over time is good, the corrosion inhibitor preferably contains a compound containing a nitrogen atom (nitrogen-containing compound), more preferably is a nitrogen-containing compound, and further preferably is a heterocyclic compound containing at least one of a nitrogen atom and a sulfur atom.
　このような腐食防止剤を含有する保護層を形成する方法は特に限定されず、例えば、腐食防止剤を含有する水溶液に、上記乾燥工程で回収された単離金属を添加し、撹拌する方法；上記乾燥工程で回収された単離金属を洗浄する洗浄溶媒に腐食防止剤を添加する方法；などが挙げられる。 The method for forming such a protective layer containing a corrosion inhibitor is not particularly limited, and examples include a method in which the isolated metal recovered in the drying process is added to an aqueous solution containing a corrosion inhibitor and stirred; a method in which the corrosion inhibitor is added to a washing solvent that washes the isolated metal recovered in the drying process; etc.
 〔還元または除去する工程〕
　本発明の製造方法は、接続抵抗の低い金属ナノワイヤを得ることができる理由から、上記単離工程と上記解砕工程との間（上記乾燥工程を有している場合には上記乾燥工程の前）に、更に、上記単離金属の表面酸化層を還元または除去する工程を有していることが好ましい。
　還元または除去する工程としては、例えば、上述した陽極酸化膜の除去処理に記載したアルカリ水溶液および酸水溶液を用いた浸漬処理を施す工程などが挙げられる。 [Reduction or removal step]
Because the manufacturing method of the present invention can obtain metal nanowires with low connection resistance, it is preferable that the manufacturing method of the present invention further includes a step of reducing or removing the surface oxide layer of the isolated metal between the isolation step and the crushing step (or before the drying step, if the drying step is included).
The reduction or removal step may be, for example, a step of carrying out an immersion treatment using an aqueous alkaline solution or an aqueous acid solution as described above in the removal treatment of the anodic oxide film.
［組成物］
　本発明の製造方法で製造される金属ナノワイヤは、金属ナノワイヤを含有する組成物として用いることが好ましく、ペースト状態の組成物として用いることがより好ましい。なお、以下の説明においては、形式的に、本発明の製造方法で製造される金属ナノワイヤを含有する組成物を「本発明の組成物」と略す。
　ここで、本発明の組成物における金属ナノワイヤの含有量（濃度）は特に限定されないが、経時での分散安定性が良好に維持され、希釈時の均一性も良好となる理由から、本発明の組成物の総質量に対して、３０～９９質量％であるのが好ましく、５０～９０質量％であるのがより好ましい。 [Composition]
The metal nanowires produced by the production method of the present invention are preferably used as a composition containing the metal nanowires, and more preferably used as a composition in a paste state. In the following description, the composition containing the metal nanowires produced by the production method of the present invention will be formally abbreviated as the "composition of the present invention."
Here, the content (concentration) of the metal nanowires in the composition of the present invention is not particularly limited, but it is preferably 30 to 99 mass %, and more preferably 50 to 90 mass %, relative to the total mass of the composition of the present invention, because this maintains good dispersion stability over time and also provides good uniformity when diluted.
 〔溶媒〕
　本発明の組成物に含まれる任意の溶媒としては、主として有機溶媒が用いられ、水と混和する有機溶媒を用いる場合には、有機溶媒とともに水を２０容量％以下の割合で併用することができる。
　上記有機溶媒としては、例えば、沸点が５０℃～２５０℃、より好ましくは５５℃～２００℃のアルコール系化合物が好適に用いられる。このようなアルコール系化合物を併用することにより、導電膜の形成時の塗布工程での塗り付け良化、乾燥負荷の低減をすることができる。
　上記アルコール系化合物は、特に限定はなく、目的に応じて適宜選択することができ、その具体例としては、ポリエチレングリコール、ポリプロピレングリコール、アルキレングリコール、グリセロール等が挙げられる、これらを１種単独で用いてもよく、２種以上を併用してもよい。
　具体的には、室温において粘度の低いエチレングリコール、ジエチレングリコール、１，２－プロパンジオール、１，３－プロパンジオール、１，２－ブタンジオール、１，３－ブタンジオール、１，４－ブタンジオール、２，３－ブタンジオール等の炭素数の小さなものが好ましいが、ペンタンジオール、ヘキサンジオール、オクタンジオール、ポリエチレングリコール等の炭素数の大きなものも使用可能である。
　これらのうち、最も好ましい溶媒はジエチレングリコールである。 〔solvent〕
The optional solvent contained in the composition of the present invention is mainly an organic solvent. When an organic solvent that is miscible with water is used, water can be used in combination with the organic solvent in a proportion of 20% by volume or less.
As the organic solvent, for example, an alcohol-based compound having a boiling point of 50° C. to 250° C., more preferably 55° C. to 200° C., is suitably used. By using such an alcohol-based compound in combination, it is possible to improve the application and reduce the drying load in the coating step when forming the conductive film.
The alcohol-based compound is not particularly limited and can be appropriately selected depending on the purpose. Specific examples thereof include polyethylene glycol, polypropylene glycol, alkylene glycol, glycerol, etc. These may be used alone or in combination of two or more kinds.
Specifically, those having a small number of carbon atoms, such as ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2,3-butanediol, which have low viscosity at room temperature, are preferred, but those having a large number of carbon atoms, such as pentanediol, hexanediol, octanediol, and polyethylene glycol, can also be used.
Of these, the most preferred solvent is diethylene glycol.
 〔界面活性剤〕
　本発明の組成物は、分散安定性がより良好となる理由から、界面活性剤を用いるのが好ましい。
　上記界面活性剤としては、例えば、ノニオン界面活性剤、アニオン界面活性剤、カチオン界面活性剤、両性界面活性剤、フッ素系界面活性剤等が挙げられ、こられを１種単独で用いてもよく、２種以上を組み合わせて用いてもよい。 [Surfactant]
It is preferable to use a surfactant in the composition of the present invention because this provides better dispersion stability.
Examples of the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and fluorine-based surfactants. These surfactants may be used alone or in combination of two or more.
　上記ノニオン界面活性剤は、特に限定されず、従来公知のものを用いることができる。
　例えば、ポリオキシエチレンアルキルエーテル類、ポリオキシエチレンアルキルフェニルエーテル類、ポリオキシエチレンポリスチリルフェニルエーテル類、ポリオキシエチレンポリオキシプロピレンアルキルエーテル類、グリセリン脂肪酸部分エステル類、ソルビタン脂肪酸部分エステル類、ペンタエリスリトール脂肪酸部分エステル類、プロピレングリコールモノ脂肪酸エステル類、ショ糖脂肪酸部分エステル類、ポリオキシエチレンソルビタン脂肪酸部分エステル類、ポリオキシエチレンソルビトール脂肪酸部分エステル類、ポリエチレングリコール脂肪酸エステル類、ポリグリセリン脂肪酸部分エステル類、ポリオキシエチレン化ひまし油類、ポリオキシエチレングリセリン脂肪酸部分エステル類、脂肪酸ジエタノールアミド類、Ｎ，Ｎ－ビス－２－ヒドロキシアルキルアミン類、ポリオキシエチレンアルキルアミン、トリエタノールアミン脂肪酸エステル、トリアルキルアミンオキシド、ポリエチレングリコール（例えば、モノステアリン酸ポリエチレングリコール等）、ポリエチレングリコールとポリプロピレングリコールの共重合体が挙げられる。 The nonionic surfactant is not particularly limited, and any of the conventionally known surfactants can be used.
For example, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrylphenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, sorbitan fatty acid partial esters, pentaerythritol fatty acid partial esters, propylene glycol mono fatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerin fatty acid partial esters, polyoxyethylated castor oils, polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides, polyethylene glycol (e.g., polyethylene glycol monostearate, etc.), and copolymers of polyethylene glycol and polypropylene glycol.
　上記アニオン界面活性剤は、特に限定されず、従来公知のものを用いることができる。
　例えば、脂肪酸塩類、アビエチン酸塩類、ヒドロキシアルカンスルホン酸塩類、アルカンスルホン酸塩類、ジアルキルスルホ琥珀酸エステル塩類、直鎖アルキルベンゼンスルホン酸塩類、分岐鎖アルキルベンゼンスルホン酸塩類、アルキルナフタレンスルホン酸塩類、アルキルフェノキシポリオキシエチレンプロピルスルホン酸塩類、ポリオキシエチレンアルキルスルホフェニルエーテル塩類、Ｎ－メチル－Ｎ－オレイルタウリンナトリウム塩、Ｎ－アルキルスルホコハク酸モノアミド二ナトリウム塩、石油スルホン酸塩類、硫酸化牛脂油、脂肪酸アルキルエステルの硫酸エステル塩類、アルキル硫酸エステル塩類、ポリオキシエチレンアルキルエーテル硫酸エステル塩類、脂肪酸モノグリセリド硫酸エステル塩類、ポリオキシエチレンアルキルフェニルエーテル硫酸エステル塩類、ポリオキシエチレンスチリルフェニルエーテル硫酸エステル塩類、アルキルリン酸エステル塩類、ポリオキシエチレンアルキルエーテルリン酸エステル塩類、ポリオキシエチレンアルキルフェニルエーテルリン酸エステル塩類、スチレン／無水マレイン酸共重合物の部分けん化物類、オレフィン／無水マレイン酸共重合物の部分けん化物類、ナフタレンスルホン酸塩ホルマリン縮合物類が挙げられる。 The anionic surfactant is not particularly limited, and any of the conventionally known surfactants can be used.
For example, fatty acid salts, abietic acid salts, hydroxyalkanesulfonates, alkanesulfonates, dialkylsulfosuccinate salts, linear alkylbenzenesulfonates, branched alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylphenoxypolyoxyethylenepropylsulfonates, polyoxyethylenealkylsulfophenylether salts, N-methyl-N-oleyltaurine sodium salt, N-alkylsulfosuccinic acid monoamide disodium salt, petroleum sulfonates, sulfated beef tallow oil, sulfate ester salts of fatty acid alkyl esters, alkane sulfonates, dialkylsulfosuccinate salts, alkylsulfonates ... Examples of the alkyl sulfate salts include polyoxyethylene alkyl ether sulfate salts, fatty acid monoglyceride sulfate salts, polyoxyethylene alkyl phenyl ether sulfate salts, polyoxyethylene styryl phenyl ether sulfate salts, alkyl phosphate salts, polyoxyethylene alkyl ether phosphate salts, polyoxyethylene alkyl phenyl ether phosphate salts, partially saponified products of styrene/maleic anhydride copolymers, partially saponified products of olefin/maleic anhydride copolymers, and naphthalenesulfonate-formaldehyde condensates.
　上記カチオン界面活性剤は、特に限定されず、従来公知のものを用いることができる。例えば、アルキルアミン塩類、第四級アンモニウム塩類、ポリオキシエチレンアルキルアミン塩類、ポリエチレンポリアミン誘導体が挙げられる。 The cationic surfactant is not particularly limited, and any conventionally known surfactant can be used. Examples include alkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.
　上記両性界面活性剤は、特に限定されず、従来公知のものを用いることができる。例えば、カルボキシベタイン類、アミノカルボン酸類、スルホベタイン類、アミノ硫酸エステル類、イミタゾリン類が挙げられる。 The amphoteric surfactant is not particularly limited, and any conventionally known surfactant can be used. Examples include carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfuric acid esters, and imitazolines.
　なお、上記界面活性剤の中で、「ポリオキシエチレン」とあるものは、ポリオキシメチレン、ポリオキシプロピレン、ポリオキシブチレン等の「ポリオキシアルキレン」に読み替えることもでき、本発明においては、それらの界面活性剤も用いることができる。 In addition, among the above surfactants, "polyoxyethylene" can be read as "polyoxyalkylene" such as polyoxymethylene, polyoxypropylene, polyoxybutylene, etc., and these surfactants can also be used in the present invention.
　本発明においては、好ましい界面活性剤として、分子内にパーフルオロアルキル基を含有するフッ素系界面活性剤が挙げられる。
　このようなフッ素系界面活性剤としては、例えば、パーフルオロアルキルカルボン酸塩、パーフルオロアルキルスルホン酸塩、パーフルオロアルキルリン酸エステル等のアニオン型；パーフルオロアルキルベタイン等の両性型；パーフルオロアルキルトリメチルアンモニウム塩等のカチオン型；パーフルオロアルキルアミンオキサイド、パーフルオロアルキルエチレンオキシド付加物、パーフルオロアルキル基および親水性基を含有するオリゴマー、パーフルオロアルキル基および親油性基を含有するオリゴマー、パーフルオロアルキル基、親水性基および親油性基を含有するオリゴマー、パーフルオロアルキル基および親油性基を含有するウレタン等のノニオン型が挙げられる。また、特開昭６２－１７０９５０号、同６２－２２６１４３号および同６０－１６８１４４号の各公報に記載されているフッ素系界面活性剤も好適に挙げられる。 In the present invention, preferred surfactants include fluorine-based surfactants containing a perfluoroalkyl group in the molecule.
Examples of such fluorine-based surfactants include anionic types such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl phosphates; amphoteric types such as perfluoroalkyl betaines; cationic types such as perfluoroalkyl trimethyl ammonium salts; and nonionic types such as perfluoroalkyl amine oxides, perfluoroalkyl ethylene oxide adducts, oligomers containing a perfluoroalkyl group and a hydrophilic group, oligomers containing a perfluoroalkyl group and a lipophilic group, oligomers containing a perfluoroalkyl group, a hydrophilic group, and a lipophilic group, and urethanes containing a perfluoroalkyl group and a lipophilic group. In addition, fluorine-based surfactants described in JP-A-62-170950, JP-A-62-226143, and JP-A-60-168144 are also suitable.
　また、本発明においては、これらの界面活性剤のうち、分散安定性が更に良好となる理由から、ＨＬＢ値が１０以上のものを用いるのが望ましい。
　ここで、ＨＬＢ値（エイチエルビー値：Ｈｙｄｒｏｐｈｉｌｅ－Ｌｉｐｏｐｈｉｌｅ　Ｂａｌａｎｃｅ）とは、界面活性剤の水と油（水に不溶性の有機化合物）への親和性の程度を表す値である。ＨＬＢ値は０から２０までの値を取り、０に近いほど親油性が高く２０に近いほど親水性が高くなる。 In the present invention, it is preferable to use, among these surfactants, those having an HLB value of 10 or more, because this further improves the dispersion stability.
Here, the HLB value (Hydrophile-Lipophile Balance) is a value that indicates the degree of affinity of a surfactant for water and oil (organic compounds insoluble in water). The HLB value ranges from 0 to 20, with the closer to 0 the higher the lipophilicity and the closer to 20 the higher the hydrophilicity.
　本発明においては、これらの界面活性剤は、１種単独で用いてもよく、２種以上を併用してもよい。
　また、これらの界面活性剤の含有量は、上記金属ナノワイヤの全質量に対して、０．００１～１０質量％であるのが好ましく、０．０１～５質量％であるのがより好ましい。 In the present invention, these surfactants may be used alone or in combination of two or more.
The content of these surfactants is preferably 0.001 to 10 mass %, and more preferably 0.01 to 5 mass %, based on the total mass of the metal nanowires.
 〔水溶性分散剤〕
　本発明の組成物は、水酸基やカルボキシル基、スルホン基、リン酸基、アミノ基、ＳＨ基等を末端に有する水溶性の有機分子、例えば、コハク酸、ポリビニルアルコール（ＰＶＡ）、ポリビニールピロール（ＰＶＰ）等の水溶性分散剤を用いることができる。 [Water-soluble dispersant]
The composition of the present invention can use a water-soluble dispersant such as a water-soluble organic molecule having a hydroxyl group, a carboxyl group, a sulfone group, a phosphate group, an amino group, an SH group, or the like at its terminal, for example, succinic acid, polyvinyl alcohol (PVA), or polyvinylpyrrole (PVP).
 〔導電性粒子〕
　本発明の組成物は、金属ナノワイヤ以外の導電性粒子を更に含有していてもよい。
　ここで、導電性粒子は、金属を含むことが好ましく、金、銀、銅、アルミニウム、ニッケル、亜鉛およびコバルトからなる群から選択される少なくとも１種の金属を含むことがより好ましい。
　また、導電性粒子は、金属以外の導電成分を１種または２種以上含んでもよい。 [Conductive particles]
The composition of the present invention may further contain conductive particles other than the metal nanowires.
Here, the conductive particles preferably contain a metal, and more preferably contain at least one metal selected from the group consisting of gold, silver, copper, aluminum, nickel, zinc and cobalt.
The conductive particles may also contain one or more conductive components other than metals.
　本発明においては、導電性粒子の形状は特に限定されず、中実および中空のいずれであってもよい。
　また、導電性粒子の最小包囲楕円体における平均長径は、０．０１μｍ以上５０μｍ以下であることが好ましい。
　また、導電性粒子の最小包囲楕円体における平均長径は、平均短径に対して１～１０倍であることが好ましい。
　ここで、最小包囲楕円体とは、導電性粒子を内部に包含する楕円体の中で体積が最少となるものをいい、長径と短径とが一致する楕円体（すなわち球体）も含むものである。
　また、最小包囲楕円体における平均長径は、分散液を用いて形成した層の厚み方向の断面を顕微鏡（例えば、電子顕微鏡）にて観察し、１００個の任意の微粒子の長径を測定して、それらを算出平均して求めることができる。同様に、最小包囲楕円体における平均短径は、分散液を用いて形成した層の厚み方向の断面を顕微鏡（例えば、電子顕微鏡）にて観察し、１００個の任意の微粒子の短径を測定して、それらを算出平均して求めることができる。
　更に、後述するメジアン径（Ｄ５０）は、導電性粒子の体積を球に近似した場合の直径のメジアン径のことをいい、レーザー回折・散乱法または動的光散乱法により求めることができる。 In the present invention, the shape of the conductive particles is not particularly limited, and they may be either solid or hollow.
The average major axis of the minimum enclosing ellipsoid of the conductive particle is preferably 0.01 μm or more and 50 μm or less.
The average major axis of the smallest enclosing ellipsoid of the conductive particle is preferably 1 to 10 times the average minor axis.
Here, the minimum enclosing ellipsoid refers to the ellipsoid that has the smallest volume among the ellipsoids that contain the conductive particles therein, and includes an ellipsoid whose major axis and minor axis are the same (i.e., a sphere).
The average major axis of the minimum enclosing ellipsoid can be obtained by observing the cross section of the layer formed using the dispersion in the thickness direction with a microscope (e.g., electron microscope), measuring the major axis of 100 arbitrary fine particles, and calculating and averaging them. Similarly, the average minor axis of the minimum enclosing ellipsoid can be obtained by observing the cross section of the layer formed using the dispersion in the thickness direction with a microscope (e.g., electron microscope), measuring the minor axis of 100 arbitrary fine particles, and calculating and averaging them.
Furthermore, the median diameter (D50) described later refers to the median diameter of the conductive particles when the volume of the conductive particles is approximated to that of a sphere, and can be determined by a laser diffraction/scattering method or a dynamic light scattering method.
　本発明においては、導電性粒子を含有する場合の導電性粒子の含有量は特に限定されないが、金属ナノワイヤ１００質量部に対して５～７０質量部であることが好ましく、１０～４５質量部であることがより好ましい。 In the present invention, when conductive particles are contained, the content of the conductive particles is not particularly limited, but is preferably 5 to 70 parts by mass, and more preferably 10 to 45 parts by mass, per 100 parts by mass of the metal nanowires.
　本発明の組成物は、配線基材の回路パターンを形成する導電性インクとして好適に用いることができる。
　導電性インクとして用いる場合、本発明の組成物における上記金属ナノワイヤの含有量（濃度）は、インクジェット方式を利用して回路パターンを印刷できる理由から、本発明の組成物の総質量に対して、１０～３０質量％であるのが好ましく、１５～２０質量％であるのがより好ましい。 The composition of the present invention can be suitably used as a conductive ink for forming a circuit pattern on a wiring substrate.
When used as a conductive ink, the content (concentration) of the metal nanowires in the composition of the present invention is preferably 10 to 30 mass %, and more preferably 15 to 20 mass %, relative to the total mass of the composition of the present invention, because circuit patterns can be printed using an inkjet system.
［導電性接合材］
　上述した本発明の組成物は、導電性接合材の形成に好適に用いることができる。
　ここで、導電性接合材とは、本発明においては所望の基材表面の全面に形成される膜だけでなく、上述した回路パターン等も含む概念である。
　また、導電膜を形成する基材や導電膜の形成方法は特に限定されず、例えば、特開２０１０－８４１７３号公報に記載された基材や形成方法を採用することができる。
　本発明の導電性接合材は、例えば、半導体接合部材、タッチパネル、ディスプレイ用電極接合材、電磁波シールド、シンタリング材、薄層セラミックコンデンサ用電極材、その他の各種デバイス等に利用される導電性接合材として好適に用いることができる。 [Conductive bonding material]
The composition of the present invention described above can be suitably used to form a conductive bonding material.
Here, the term "conductive bonding material" in the present invention is a concept that includes not only a film formed on the entire surface of a desired substrate, but also the above-mentioned circuit pattern and the like.
Furthermore, the substrate on which the conductive film is formed and the method for forming the conductive film are not particularly limited, and for example, the substrate and the method for forming the conductive film described in JP-A-2010-84173 can be used.
The conductive bonding material of the present invention can be suitably used as a conductive bonding material for use in, for example, semiconductor bonding members, touch panels, electrode bonding materials for displays, electromagnetic wave shields, sintering materials, electrode materials for thin-layer ceramic capacitors, and various other devices.
　以下に実施例に基づいて本発明を更に詳細に説明する。以下の実施例に示す材料、使用量、割合、処理内容、処理手順等は、本発明の趣旨を逸脱しない限り適宜変更することができる。したがって、本発明の範囲は以下に示す実施例により限定的に解釈されるべきものではない。 The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below.
［実施例１］
　＜アルミニウム基材の作製＞
　Ｓｉ：０．０６質量％、Ｆｅ：０．３０質量％、Ｃｕ：０．００５質量％、Ｍｎ：０．００１質量％、Ｍｇ：０．００１質量％、Ｚｎ：０．００１質量％、Ｔｉ：０．０３質量％を含有し、残部はＡｌと不可避不純物のアルミニウム合金を用いて溶湯を調製し、溶湯処理およびろ過を行った上で、厚さ５００ｍｍ、幅１２００ｍｍの鋳塊をＤＣ（Direct Chill）鋳造法で作製した。
　次いで、表面を平均１０ｍｍの厚さで面削機により削り取った後、５５０℃で、約５時間均熱保持し、温度４００℃に下がったところで、熱間圧延機を用いて厚さ２．７ｍｍの圧延板とした。
　更に、連続焼鈍機を用いて熱処理を５００℃で行った後、冷間圧延で、厚さ１．０ｍｍに仕上げ、ＪＩＳ（日本工業規格） １０５０材のアルミニウム基材を得た。
　アルミニウム基材を、直径２００ｍｍ（８インチ）のウエハ状に形成した後、以下に示す各処理を施した。 [Example 1]
<Preparation of Aluminum Substrate>
A molten metal was prepared using an aluminum alloy containing 0.06 mass% Si, 0.30 mass% Fe, 0.005 mass% Cu, 0.001 mass% Mn, 0.001 mass% Mg, 0.001 mass% Zn, 0.001 mass% Ti, and the remainder being Al and unavoidable impurities. The molten metal was treated and filtered, and an ingot having a thickness of 500 mm and a width of 1,200 mm was produced by a DC (Direct Chill) casting method.
Next, the surface was scraped off by an average thickness of 10 mm using a facing machine, and then the plate was soaked at 550°C for about 5 hours. When the temperature was lowered to 400°C, the plate was rolled into a 2.7 mm thick plate using a hot rolling machine.
Further, the sheet was heat-treated at 500° C. using a continuous annealing machine, and then cold-rolled to a thickness of 1.0 mm to obtain an aluminum substrate of JIS (Japanese Industrial Standards) 1050 material.
The aluminum substrate was formed into a wafer having a diameter of 200 mm (8 inches) and then subjected to the following treatments.
　＜電解研磨処理＞
　上述のアルミニウム基材に対して、以下組成の電解研磨液を用いて、電圧２５Ｖ、液温度６５℃、液流速３．０ｍ／分の条件で電解研磨処理を施した。
　陰極はカーボン電極とし、電源は、ＧＰ０１１０－３０Ｒ（株式会社高砂製作所社製）を用いた。また、電解液の流速は渦式フローモニターＦＬＭ２２－１０ＰＣＷ（アズワン株式会社製）を用いて計測した。
　（電解研磨液組成）
　・８５質量％リン酸（和光純薬社製試薬）　　６６０ｍＬ
　・純水　　１６０ｍＬ
　・硫酸　　１５０ｍＬ
　・エチレングリコール　　３０ｍＬ <Electrolytic polishing treatment>
The above-mentioned aluminum substrate was subjected to electrolytic polishing treatment using an electrolytic polishing solution having the following composition under conditions of a voltage of 25 V, a solution temperature of 65° C., and a solution flow rate of 3.0 m/min.
The cathode was a carbon electrode, and the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.) The flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).
(Electrolytic polishing solution composition)
85% by weight phosphoric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.) 660 mL
・160mL of pure water
・150mL sulfuric acid
・30mL ethylene glycol
　＜陽極酸化工程＞
　次いで、電解研磨処理後のアルミニウム基材に、特開２００７－２０４８０２号公報に記載の手順にしたがって自己規則化法による陽極酸化処理を施した。
　電解研磨処理後のアルミニウム基材に、０．５０ｍｏｌ／Ｌシュウ酸の電解液で、電圧４０Ｖ、液温度１６℃、液流速３．０ｍ／分の条件で、５時間のプレ陽極酸化処理を施した。
　その後、プレ陽極酸化処理後のアルミニウム基材を、０．２ｍｏｌ／Ｌ無水クロム酸、０．６ｍｏｌ／Ｌリン酸の混合水溶液（液温：５０℃）に１２時間浸漬させる脱膜処理を施した。
　その後、０．５０ｍｏｌ／Ｌシュウ酸の電解液で、電圧４０Ｖ、液温度１６℃、液流速３．０ｍ／分の条件で、５時間の再陽極酸化処理を施し、膜厚４０μｍの陽極酸化膜を得た。
　なお、プレ陽極酸化処理および再陽極酸化処理は、いずれも陰極はステンレス電極とし、電源はＧＰ０１１０－３０Ｒ（株式会社高砂製作所製）を用いた。また、冷却装置にはＮｅｏＣｏｏｌ　ＢＤ３６（ヤマト科学株式会社製）、かくはん加温装置にはペアスターラー　ＰＳ－１００（ＥＹＥＬＡ東京理化器械株式会社製）を用いた。更に、電解液の流速は渦式フローモニターＦＬＭ２２－１０ＰＣＷ（アズワン株式会社製）を用いて計測した。 <Anodizing process>
Next, the aluminum substrate after the electrolytic polishing treatment was subjected to anodizing treatment by a self-ordering method according to the procedure described in JP-A-2007-204802.
The aluminum substrate after electrolytic polishing was subjected to a pre-anodizing treatment for 5 hours in an electrolytic solution of 0.50 mol/L oxalic acid under conditions of a voltage of 40 V, a solution temperature of 16° C., and a solution flow rate of 3.0 m/min.
Thereafter, the aluminum substrate after the pre-anodizing treatment was subjected to a coating removal treatment by immersing it in a mixed aqueous solution of 0.2 mol/L chromic anhydride and 0.6 mol/L phosphoric acid (liquid temperature: 50° C.) for 12 hours.
Thereafter, re-anodization was performed for 5 hours in an electrolyte of 0.50 mol/L oxalic acid under conditions of a voltage of 40 V, a liquid temperature of 16° C., and a liquid flow rate of 3.0 m/min, to obtain an anodized film with a thickness of 40 μm.
In both the pre-anodizing treatment and the re-anodizing treatment, the cathode was a stainless steel electrode, and the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.). The cooling device was NeoCool BD36 (manufactured by Yamato Scientific Co., Ltd.), and the stirring and heating device was Pair Stirrer PS-100 (manufactured by EYELA Tokyo Rikakikai Co., Ltd.). Furthermore, the flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).
　＜金属充填工程＞
　次いで、アルミニウム基材を陰極にし、白金を正極にして電解めっき処理を施した。
　具体的には、以下に示す組成の銅めっき液を使用し、定電流電解を施すことにより、ポーラス（マイクロポア）の内部に銅が充填された金属充填微細構造体を作製した。
　ここで、定電流電解は、株式会社山本鍍金試験器社製のめっき装置を用い、北斗電工株式会社製の電源（ＨＺ－３０００）を用い、めっき液中でサイクリックボルタンメトリを行って析出電位を確認した後に、以下に示す条件で処理を施した。
　（銅めっき液組成および条件）
　・硫酸銅　１００ｇ／Ｌ
　・硫酸　５０ｇ／Ｌ
　・塩酸　１５ｇ／Ｌ
　・温度　２５℃
　・電流密度　１０Ａ／ｄｍ２ <Metal filling process>
Next, electrolytic plating was carried out using the aluminum substrate as the cathode and platinum as the anode.
Specifically, a copper plating solution having the composition shown below was used and constant current electrolysis was carried out to produce a metal-filled microstructure in which the inside of the pores (micropores) was filled with copper.
Here, the constant current electrolysis was performed using a plating device manufactured by Yamamoto Plating Tester Co., Ltd. and a power supply (HZ-3000) manufactured by Hokuto Denko Corporation. After confirming the deposition potential by carrying out cyclic voltammetry in the plating solution, the treatment was performed under the conditions shown below.
(Copper plating solution composition and conditions)
・Copper sulfate 100g/L
Sulfuric acid 50g/L
Hydrochloric acid 15g/L
Temperature: 25℃
Current density 10A/ dm2
　ポーラスに金属を充填した後の陽極酸化膜の表面をＦＥ－ＳＥＭで観察し、１０００個のポーラスにおける金属による封孔の有無を観察して封孔率（封孔ポーラスの個数／１０００個）を算出したところ、９６％であった。
　また、ポーラスに金属を充填した後の陽極酸化膜を厚さ方向に対してＦＩＢで切削加工し、その断面をＦＥ－ＳＥＭにより表面写真（倍率５００００倍）を撮影し、ポーラスの内部を確認したところ、封孔されたポーラスにおいては、ポーラスの底部からの充填高さが３５μｍであることが分かった。 The surface of the anodized film after the pores were filled with metal was observed with an FE-SEM to determine whether 1,000 pores were sealed with metal. The sealing rate (number of sealed pores/1,000) was calculated to be 96%.
In addition, after filling the holes with metal, the anodized film was cut in the thickness direction using an FIB, and the cross section was photographed with an FE-SEM (magnification 50,000x) to check the inside of the holes. It was found that the filling height from the bottom of the sealed holes was 35 μm.
　＜単離工程＞
　６０℃の水酸化カリウムの水溶液（濃度：５ｍｏｌ／Ｌ）に３００秒浸漬させることにより、充填した金属を陽極酸化膜およびアルミニウム基材から単離し、単離金属を得た。具体的には、６０℃の水酸化カリウムの水溶液（濃度：５ｍｏｌ／Ｌ）に３００秒浸漬させることにより、陽極酸化膜を溶解し、陽極酸化膜の溶解と同時に（３００秒経過した時点で）アルミニウム基材を剥離することにより、充填した金属を単離した。 <Isolation step>
The filled metal was isolated from the anodized film and the aluminum base material by immersing the aluminum base material in an aqueous potassium hydroxide solution (concentration: 5 mol/L) at 60° C. for 300 seconds, to obtain an isolated metal. Specifically, the anodized film was dissolved by immersing the aluminum base material in an aqueous potassium hydroxide solution (concentration: 5 mol/L) at 60° C. for 300 seconds, and the filled metal was isolated by peeling off the aluminum base material at the same time as the anodized film was dissolved (after 300 seconds had elapsed).
　＜乾燥工程＞
　次いで、メンブレン（０．４μｍ、ＰＴＦＥ、Ｏｍｎｉｐｏｒｅ社製）を用いた吸引ろ過により、単離金属を回収し、単離金属を乾燥させた。 <Drying process>
Next, the isolated metal was recovered by suction filtration using a membrane (0.4 μm, PTFE, manufactured by Omnipore), and the isolated metal was dried.
　＜洗浄／保護層形成工程／還元または除去する工程＞
　次いで、メンブレン上に回収された単離金属に対して、以下に示す洗浄溶媒を用いて１分間洗浄した。なお、実施例１においては、洗浄溶媒に防食防止剤を添加しているため、洗浄と同時に、保護層の形成を行っている。また、実施例１においては、腐食防止剤としてクエン酸を用いているため、保護層の形成と同時に、単離金属の表面酸化層の除去も行っている。
　その後、メンブレン上の単離金属を回収した。
　（洗浄溶媒）
　クエン酸を１質量％含有する水溶液 <Cleaning/Protective Layer Forming Step/Reduction or Removal Step>
Next, the isolated metal recovered on the membrane was washed for 1 minute using the washing solvent shown below. In Example 1, since a corrosion inhibitor was added to the washing solvent, a protective layer was formed at the same time as washing. In Example 1, since citric acid was used as the corrosion inhibitor, the surface oxide layer of the isolated metal was also removed at the same time as the protective layer was formed.
The isolated metals on the membrane were then collected.
(Washing Solvent)
An aqueous solution containing 1% by weight of citric acid
　＜解砕工程＞
　次いで、回収した単離金属を水中に１質量％添加し、スギノマシン社製スターバーストミニを使用し、キャビテーションによる解砕処理を施した。
　その後、メンブレン（０．４μｍ、ＰＴＦＥ、Ｏｍｎｉｐｏｒｅ社製）を用いた吸引ろ過により、解砕処理を施した単離金属を回収し、１２時間、減圧乾燥させることにより、金属ナノワイヤを製造した。 <Crushing process>
Next, the recovered isolated metal was added to water at 1% by mass, and the mixture was subjected to a crushing treatment by cavitation using a Starburst Mini manufactured by Sugino Machine Ltd.
Thereafter, the crushed isolated metal was collected by suction filtration using a membrane (0.4 μm, PTFE, manufactured by Omnipore Corporation) and dried under reduced pressure for 12 hours to produce metal nanowires.
［実施例２］
　実施例１における「アルミニウム基材の作製」から「洗浄／保護層形成工程／還元または除去する工程」までを２回行い、実施例１の２倍量の単離金属を回収した。
　その後、解砕処理時の単離金属の濃度を４０質量％に変更した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 2]
The steps from "preparation of aluminum substrate" to "cleaning/protective layer formation step/reduction or removal step" in Example 1 were repeated twice, and twice the amount of isolated metal as in Example 1 was recovered.
Thereafter, metal nanowires were produced in the same manner as in Example 1, except that the concentration of the isolated metal during the crushing treatment was changed to 40 mass %.
［実施例３］
　解砕処理時の単離金属の濃度を０．５質量％に変更した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 3]
Metal nanowires were produced in the same manner as in Example 1, except that the concentration of the isolated metal during the crushing treatment was changed to 0.5 mass %.
［実施例４］
　洗浄／保護層形成工程／還元または除去する工程時の洗浄溶媒を水に変更した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。すなわち、実施例４においては、保護層の形成を行っていない。 [Example 4]
Metal nanowires were produced in the same manner as in Example 1, except that the washing solvent in the washing/protective layer forming step/reduction or removal step was changed to water. That is, in Example 4, no protective layer was formed.
［実施例５］
　洗浄／保護層形成工程／還元または除去する工程時の洗浄溶媒をクエン酸およびベンゾトリアゾールをそれぞれ１質量％含有する水溶液に変更した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 5]
Metal nanowires were produced in the same manner as in Example 1, except that the cleaning solvent in the cleaning/protective layer formation step/reduction or removal step was changed to an aqueous solution containing 1 mass % each of citric acid and benzotriazole.
［実施例６］
　単離工程において、水酸化カリウムの水溶液に浸漬させる前に、１０℃の０．５質量％Ｃｕ－１２％ＨＣｌ水溶液に１時間浸漬させることによりアルミニウム基材を溶解して除去した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 6]
Metal nanowires were produced in the same manner as in Example 1, except that in the isolation step, the aluminum substrate was dissolved and removed by immersing the aluminum substrate in a 0.5 mass % Cu-12% HCl aqueous solution at 10°C for 1 hour before immersing the aluminum substrate in the potassium hydroxide aqueous solution.
［実施例７］
　解砕工程で用いる液体を水に代えて、１質量％のクエン酸水溶液を用いた以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 7]
Metal nanowires were produced in the same manner as in Example 1, except that the liquid used in the crushing step was changed from water to a 1 mass % aqueous citric acid solution.
［実施例８］
　金属充填工程で用いる金属の種類をＮｉに変更した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 8]
Metal nanowires were produced in the same manner as in Example 1, except that the type of metal used in the metal filling step was changed to Ni.
［実施例９］
　解砕工程後に無電解Ａｕめっき処理を施した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 9]
Metal nanowires were produced in the same manner as in Example 1, except that electroless Au plating was performed after the crushing step.
［実施例１０］
　洗浄／保護層形成工程／還元または除去する工程時の洗浄溶媒をクエン酸および２－メルカプトベンゾチアゾールをそれぞれ１質量％含有する水溶液に変更した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 10]
Metal nanowires were produced in the same manner as in Example 1, except that the cleaning solvent in the cleaning/protective layer formation step/reduction or removal step was changed to an aqueous solution containing 1 mass % each of citric acid and 2-mercaptobenzothiazole.
［実施例１１］
　金属充填工程での金属の充填高さを１５μｍとした以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 11]
Metal nanowires were produced in the same manner as in Example 1, except that the metal filling height in the metal filling step was set to 15 μm.
［実施例１２］
　洗浄／保護層形成工程／還元または除去する工程の前に、３５℃の硫酸１０質量％水溶液に１５秒間浸漬させることにより、金属ナノワイヤの表面酸化層を還元または除去を実施した以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Example 12]
Metal nanowires were produced in the same manner as in Example 1, except that the surface oxide layer of the metal nanowires was reduced or removed by immersing them in a 10% by mass aqueous solution of sulfuric acid at 35°C for 15 seconds prior to the cleaning/protective layer formation process/reduction or removal process.
［比較例１］
　解砕工程を実施しないこと以外は、実施例１と同様の方法で、金属ナノワイヤを製造した。 [Comparative Example 1]
Metal nanowires were produced in the same manner as in Example 1, except that the crushing step was not carried out.
［評価］
 〔組成物の調製〕
　回収した金属ナノワイヤをポリエチレングリコール（分子量２００）中に、８０ｗｔ％となるよう添加し、あわとり練太郎（ＡＲＥ－４００ＴＷＩＮ、シンキー社製）を用い遠心攪拌により組成物を調製した。なお、調製した組成物はいずれもペースト状であった。 [evaluation]
[Preparation of Composition]
The collected metal nanowires were added to polyethylene glycol (molecular weight 200) to give a concentration of 80 wt %, and a composition was prepared by centrifugal stirring using a Thinky Mixer (ARE-400TWIN, manufactured by Thinky Corporation). All of the compositions prepared were in the form of a paste.
 〔接続抵抗〕
　調製した組成物を、メタルマスク（開口部：１×１ｍｍ×０．２ｍｍ）を用いて、Ｃｕ板（１０ｍｍ×１０ｍｍ×０．５ｍｍ）にスキージ塗布し、塗布された組成物上にＣｕ板（５ｍｍ×５ｍｍ×０．５ｍｍ）を設置した。
　その後、接合装置（ＷＰ－１００、ＰＭＴ社製）を用いて、還元ガス（Ｎ２：８５％，ギ酸：１５％）を用い、装置内の雰囲気を還元ガスで置換した後、２５０℃、１分間、５ＭＰａの条件で加熱圧着をし、接合した。
　次いで、ダイヤインスツルメンツ製ロレスタＧＰを用い、測定端子（ピン）間を３ｍｍとし、上下の銅板に測定端子をあて、測定端子の押し付け圧（ばね圧）を２００ｇとし、接続抵抗を測定し、以下の基準で評価した。結果を下記表１に示す。
　＜評価基準＞
　Ａ：銅の抵抗に対して１２０％以下
　Ｂ：銅の抵抗に対して１２０％超１５０％以下
　Ｃ：銅の抵抗に対して１５０％超 [Connection resistance]
The prepared composition was applied to a Cu plate (10 mm×10 mm×0.5 mm) with a squeegee using a metal mask (opening: 1×1 mm×0.2 mm), and a Cu plate (5 mm×5 mm×0.5 mm) was placed on the applied composition.
Thereafter, using a bonding device (WP-100, manufactured by PMT), the atmosphere inside the device was replaced with reducing gas (N2: 85%, formic acid: 15%), and then the pieces were bonded by heating and compression at 250°C, 1 minute, and 5 MPa.
Next, using a Loresta GP made by Dia Instruments, the distance between the measuring terminals (pins) was set to 3 mm, the measuring terminals were placed on the upper and lower copper plates, and the pressing pressure (spring pressure) of the measuring terminals was set to 200 g, and the connection resistance was measured and evaluated according to the following criteria. The results are shown in Table 1 below.
<Evaluation criteria>
A: 120% or less against copper resistance B: 120% or more against copper resistance and 150% or less C: 150% or more against copper resistance
 〔接合強度〕
　接続抵抗を測定したサンプルでＮｏｒｄｓｏｎ社製４０００万能型ボンドテスターを用いダイシェア強度を測定し、以下の基準で評価した。結果を下記表１に示す。
　＜評価基準＞
　Ａ：１５ＭＰａ以上
　Ｂ：１０ＭＰａ以上１５ＭＰａ未満
　Ｃ：１０ＭＰａ未満 [Bonding strength]
The samples for which the connection resistance had been measured were subjected to measurement of die shear strength using a Nordson 4000 universal bond tester, and were evaluated according to the following criteria. The results are shown in Table 1 below.
<Evaluation criteria>
A: 15 MPa or more B: 10 MPa or more but less than 15 MPa C: less than 10 MPa
　表１に示す結果から、解砕工程を実施しない場合には、作製される金属ナノワイヤ（単離金属）の接合強度が低くなることが分かった（比較例１）。
　これに対し、解砕工程を実施しない場合には、作製される金属ナノワイヤの接合強度が高くなることが分かった（実施例１～１２）。
　特に、実施例１～３の対比から、解砕処理時の単離金属の濃度が０．５～３０質量％であると、接合時により高い接合強度を有する金属ナノワイヤを作製できることが分かった。
　また、実施例１と実施例７との対比から、アルカリもしくは酸の濃度が１質量％未満となる水溶液で解砕すると、接合時により高い接合強度を有する金属ナノワイヤを作製できることが分かった。 The results shown in Table 1 show that when the crushing step is not carried out, the bonding strength of the produced metal nanowires (isolated metal) is low (Comparative Example 1).
In contrast, it was found that when the crushing step was not carried out, the bonding strength of the produced metal nanowires was high (Examples 1 to 12).
In particular, a comparison of Examples 1 to 3 reveals that when the concentration of the isolated metal during the crushing treatment is 0.5 to 30 mass %, metal nanowires having higher bonding strength when bonded can be produced.
Furthermore, a comparison between Example 1 and Example 7 revealed that disintegration in an aqueous solution with an alkali or acid concentration of less than 1 mass % made it possible to produce metal nanowires with higher bonding strength when bonded.
　１　バルブ金属基材
　２　ポーラス（マイクロポア）
　３　陽極酸化膜
　４　金属
　５　単離金属
　１０　金属ナノワイヤ 1 Valve metal substrate 2 Porous (micropore)
3 Anodic oxide film 4 Metal 5 Isolated metal 10 Metal nanowire

Claims (8)

  1. 　ポーラスを有する陽極酸化膜をバルブ金属基材の表面に形成する陽極酸化工程と、
    　前記ポーラスに金属を充填する金属充填工程と、
    　充填した前記金属を前記陽極酸化膜および前記バルブ金属基材から単離する単離工程と、
    　単離した前記金属を解砕して金属ナノワイヤを得る解砕工程とを有する、
    　金属ナノワイヤの製造方法。     an anodizing step of forming a porous anodized film on the surface of a valve metal substrate;
    a metal filling step of filling the pores with a metal;
    isolating the filled metal from the anodized film and the valve metal substrate;
    and a crushing step of crushing the isolated metal to obtain metal nanowires.
    A method for producing metal nanowires.
  2. 　前記単離工程と前記解砕工程との間に、更に、単離した前記金属を乾燥する乾燥工程を有する、請求項１に記載の金属ナノワイヤの製造方法。 The method for producing metal nanowires according to claim 1, further comprising a drying step between the isolation step and the crushing step for drying the isolated metal.
  3. 　前記単離工程と前記解砕工程との間に、更に、単離した前記金属の表面酸化層を還元または除去する工程を有する、請求項１または２に記載の金属ナノワイヤの製造方法。 The method for producing metal nanowires according to claim 1 or 2, further comprising a step of reducing or removing a surface oxide layer of the isolated metal between the isolation step and the crushing step.
  4. 　更に、単離した前記金属に腐食防止剤を含有する保護層を形成する保護層形成工程を有する、請求項１または２に記載の金属ナノワイヤの製造方法。 The method for producing metal nanowires according to claim 1 or 2 further comprises a protective layer forming step of forming a protective layer containing a corrosion inhibitor on the isolated metal.
  5. 　前記バルブ金属基材がアルミニウムを含む、請求項１または２に記載の金属ナノワイヤの製造方法。 The method for producing metal nanowires according to claim 1 or 2, wherein the valve metal substrate contains aluminum.
  6. 　前記金属充填工程がめっき工程を含む、請求項１または２に記載の金属ナノワイヤの製造方法。 The method for producing metal nanowires according to claim 1 or 2, wherein the metal filling step includes a plating step.
  7. 　前記単離工程が溶解工程を含む、請求項１または２に記載の金属ナノワイヤの製造方法。 The method for producing metal nanowires according to claim 1 or 2, wherein the isolation step includes a dissolution step.
  8. 　前記解砕工程が、水中、または、アルカリもしくは酸の濃度が１質量％未満となる水溶液中で行われる、請求項１または２に記載の金属ナノワイヤの製造方法。 The method for producing metal nanowires according to claim 1 or 2, wherein the crushing step is carried out in water or in an aqueous solution having an alkali or acid concentration of less than 1% by mass.
PCT/JP2023/030248 2022-09-30 2023-08-23 Metal nanowire production method WO2024070341A1 (en)

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* Cited by examiner, † Cited by third party
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CN101886283A (en) * 2010-06-24 2010-11-17 浙江大学 Preparation method and application of magnetically encoded nano-wire
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US20190085478A1 (en) * 2015-11-30 2019-03-21 The Regents Of The University Of California Low-density interconnected ionic material foams and methods of manufacture
JP2020046506A (en) * 2018-09-18 2020-03-26 住友金属鉱山株式会社 Metal nanorod-containing resin, near-infrared ray shielding lens, near-infrared ray shielding spectacle, protection tool, near-infrared ray shielding window material, near-infrared ray shielding device, near-infrared ray film, near-infrared ray shielding glass, and method for manufacturing metal nanorod assembly

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050274833A1 (en) * 2002-01-03 2005-12-15 Tapesh Yadav Shape engineering of nanoparticles
CN101886283A (en) * 2010-06-24 2010-11-17 浙江大学 Preparation method and application of magnetically encoded nano-wire
WO2012147964A1 (en) * 2011-04-28 2012-11-01 富士フイルム株式会社 Dispersion liquid containing metal nanowires, and conductive film
US20190085478A1 (en) * 2015-11-30 2019-03-21 The Regents Of The University Of California Low-density interconnected ionic material foams and methods of manufacture
JP2020046506A (en) * 2018-09-18 2020-03-26 住友金属鉱山株式会社 Metal nanorod-containing resin, near-infrared ray shielding lens, near-infrared ray shielding spectacle, protection tool, near-infrared ray shielding window material, near-infrared ray shielding device, near-infrared ray film, near-infrared ray shielding glass, and method for manufacturing metal nanorod assembly

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