WO2024090555A1 - Method for producing cuprous oxide, and cuprous oxide film - Google Patents

Method for producing cuprous oxide, and cuprous oxide film Download PDF

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Publication number
WO2024090555A1
WO2024090555A1 PCT/JP2023/038886 JP2023038886W WO2024090555A1 WO 2024090555 A1 WO2024090555 A1 WO 2024090555A1 JP 2023038886 W JP2023038886 W JP 2023038886W WO 2024090555 A1 WO2024090555 A1 WO 2024090555A1
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copper
cuprous oxide
ink
copper ink
copper particles
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PCT/JP2023/038886
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French (fr)
Japanese (ja)
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隆二 植杉
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三菱マテリアル株式会社
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Publication of WO2024090555A1 publication Critical patent/WO2024090555A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G3/00—Compounds of copper
    • C01G3/02—Oxides; Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D1/00—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/52—Electrically conductive inks

Definitions

  • the present invention relates to a method for producing cuprous oxide and a cuprous oxide film.
  • cuprous oxide (Cu 2 O) is a p-type semiconductor, its application to various applications such as solar cells, thin film transistors, sensors, varistors, and catalysts is being considered.
  • Patent Document 1 describes the production of a cuprous oxide film by attaching a liquid composition containing cuprous oxide powder onto a substrate and heating and sintering the substrate.
  • Patent Document 2 describes the production of a cuprous oxide film by applying a solution in which a copper complex is dissolved onto a substrate surface and heat treating the substrate in an inert gas atmosphere.
  • JP 2008-282913 A Japanese Patent No. 5452196
  • the present invention has been made in consideration of the above, and aims to provide a method for producing cuprous oxide capable of obtaining cuprous oxide with suitable performance, and a cuprous oxide film with suitable performance.
  • the method for producing cuprous oxide disclosed herein includes the steps of obtaining a copper ink, which is a liquid composition containing copper particles; forming a film by applying or printing the copper ink on a substrate; and, after drying the film formed by the copper ink on the substrate, irradiating the film with light having a wavelength in the visible to infrared range and heating the film in an atmosphere having an oxygen concentration of 10% or more and 21% or less, thereby oxidizing and sintering the copper particles in the copper ink to produce cuprous oxide on the substrate.
  • the film of the copper ink formed on the substrate with light having a spectral distribution in which the wavelength of the peak intensity of the irradiated light is 0.6 ⁇ m or more and 10 ⁇ m or less.
  • the film formed by the copper ink on the substrate it is preferable to heat the film formed by the copper ink on the substrate at a heating temperature of 180°C or higher and 500°C or lower.
  • the holding time at the heating temperature is 1 second or more and 600 seconds or less.
  • the rate of temperature rise to the heating temperature is 0.1°C/sec or more and 50°C/sec or less.
  • the copper ink containing copper particles whose particle size is 10 nm or more and 1000 nm or less, and whose surface is coated with an organic substance.
  • the copper ink containing the copper particles, a solvent, an organic solvent having a boiling point of 150°C or higher at atmospheric pressure and miscible with water, and a polyhydric alcohol containing two or more OH groups and soluble in water and ethanol.
  • the cuprous oxide film disclosed herein has an average transmittance of 40% or more and 100% or less for light with wavelengths of 600 nm to 1200 nm when the film thickness is 0.1 ⁇ m.
  • the cuprous oxide film preferably has a ratio (T 2 /T 1 ) of the average transmittance (T 2 ) of light having a wavelength of 600 nm to 1200 nm to the average transmittance (T 1 ) of light having a wavelength of 300 nm to 600 nm when the film thickness is 0.1 ⁇ m, of 3.5 or more.
  • the cuprous oxide film is preferably a sintered body.
  • the present invention makes it possible to obtain cuprous oxide with suitable performance.
  • FIG. 1 is a flow chart illustrating a method for producing cuprous oxide according to the present embodiment.
  • FIG. 2 is a schematic diagram of the copper ink according to this embodiment.
  • FIG. 3 is a flowchart illustrating a method for producing a copper ink according to this embodiment.
  • FIG. 4 is a table showing the components of the copper ink used in each example.
  • FIG. 5A is a table showing the evaluation results of each example.
  • FIG. 5B is a table showing the evaluation results of each example.
  • FIG. 5C is a table showing the evaluation results of each example.
  • FIG. 5D is a table showing the evaluation results of each example.
  • FIG. 5E is a table showing the evaluation results of each example.
  • FIG. 5F is a table showing the evaluation results of each example.
  • FIG. 5A is a table showing the evaluation results of each example.
  • FIG. 5B is a table showing the evaluation results of each example.
  • FIG. 5C is a table showing the evaluation results of each
  • FIG. 5G is a table showing the evaluation results for each example.
  • FIG. 5H is a table showing the evaluation results of each example.
  • FIG. 5I is a table showing the evaluation results of each example.
  • FIG. 5J is a table showing the evaluation results of each example.
  • FIG. 5K is a table showing the evaluation results of each example.
  • FIG. 5L is a table showing the evaluation results of each example.
  • FIG. 5M is a table showing the evaluation results of each example.
  • FIG. 5N is a table showing the evaluation results of each example.
  • FIG. 5O is a table showing the evaluation results of each example.
  • FIG. 5P is a table showing the evaluation results of each example.
  • FIG. 5Q is a table showing the evaluation results of each example.
  • FIG. 5R is a table showing the evaluation results of each example.
  • FIG. 5S is a table showing the evaluation results of each example.
  • FIG. 5T is a table showing the evaluation results of each example.
  • FIG. 5U is a table showing the evaluation results for each example.
  • FIG. 5V is a table showing the evaluation results of each example.
  • FIG. 5W is a table showing the evaluation results of each example.
  • FIG. 5X is a table showing the evaluation results of each example.
  • FIG. 5Y is a table showing the evaluation results of each example.
  • FIG. 5Za is a table showing the evaluation results of each example.
  • FIG. 5Zb is a table showing the evaluation results of each example.
  • FIG. 5Zc is a table showing the evaluation results of each example.
  • FIG. 5D is a table showing the evaluation results of each example.
  • FIG. 5Ze is a table showing the evaluation results of each example.
  • Method for producing cuprous oxide 1 is a flow chart for explaining a method for producing cuprous oxide according to the present embodiment.
  • the production method of the present embodiment produces Cu 2 O (also written as copper(I) oxide, cuprous oxide, copper(I) oxide, or cuprous oxide) as cuprous oxide.
  • a film of cuprous oxide is produced, but the production is not limited to a film-like cuprous oxide, and cuprous oxide of any shape may be produced.
  • a copper ink 10 is obtained (step S10).
  • the copper ink 10 is a liquid composition containing copper particles.
  • the copper ink 10 will be described in detail later.
  • the obtained copper ink 10 is applied or printed on a substrate (step S12) to form a film on the substrate of the copper ink 10.
  • the material, size, thickness, etc. of the substrate on which the copper ink 10 is applied or printed may be arbitrary.
  • the specific heat of the substrate [kJ/(kg ⁇ K)] is preferably 0.1 to 3, more preferably 0.1 to 2, and even more preferably 0.1 to 1.5.
  • the specific heat of the substrate can be measured by a laser flash method, a DSC method, or the like.
  • the material of the substrate is preferably glass, ceramic, heat-resistant organic polymer, resin, or the like.
  • the thickness of the substrate is preferably 0.01 mm or more and 10 mm or less, more preferably 0.05 mm or more and 5 mm or less, and even more preferably 0.05 mm or more and 1 mm or less.
  • the copper ink 10 can be appropriately oxidized and sintered to suitably produce a cuprous oxide film. Any method may be used to apply or print the copper ink 10 onto the substrate.
  • the step of applying or printing the copper ink 10 onto the substrate is not essential, and for example, the copper ink 10 provided at any position may be heated in a subsequent step.
  • the copper ink 10 (in this embodiment, the film of the copper ink 10 formed on the substrate) is dried (step S14).
  • the conditions for drying the copper ink 10 may be arbitrary.
  • the temperature at which the copper ink 10 is dried is preferably 30° C. or higher and 150° C. or lower, more preferably 30° C. or higher and 120° C. or lower, and even more preferably 30° C. or higher and 100° C. or lower.
  • the time for drying the copper ink 10 is preferably 0.1 minutes or more and 60 minutes or less, more preferably 0.5 minutes or more and 60 minutes or less, and even more preferably 0.5 minutes or more and 30 minutes or less.
  • the atmosphere in which the copper ink 10 is dried may be either air or an inert atmosphere, but air is preferable in consideration of workability.
  • the drying conditions as described above, it is possible to properly remove the liquid components in the copper ink 10 and properly oxidize and sinter the copper particles.
  • the step of drying the copper ink 10 is not essential.
  • the copper ink 10 (in this embodiment, a film of copper ink 10 formed on a substrate) is heated in a specified atmosphere with light having a spectral distribution with a peak at a specified wavelength, thereby oxidizing and sintering the copper particles in the copper ink 10 to produce cuprous oxide (step S16).
  • the specified atmosphere in which the copper ink 10 is heated refers to an atmosphere in which the oxygen concentration is 10% or more and 21% or less, preferably 15% or more and 21% or less, and more preferably 18% or more and 21% or less.
  • the copper particles can be appropriately oxidized and cuprous oxide can be appropriately produced.
  • the oxygen concentration can be measured using an oxygen concentration meter such as a galvanic cell type, a zirconia type, or a dumbbell type.
  • Light with a spectral distribution having a peak at a specific wavelength for heating the copper ink 10 refers to light with a spectral distribution having a peak wavelength in the visible to infrared region (light with a spectral distribution having a peak wavelength within the wavelength range from the visible light band to the infrared light band), and more preferably light with a spectral distribution having a wavelength (the wavelength of the peak intensity of the irradiated light) of 0.6 ⁇ m or more and 10 ⁇ m or less, and even more preferably light of 0.6 ⁇ m or more and 5 ⁇ m or less.
  • the heating temperature at which the copper ink 10 is heated is preferably 180°C or higher and 500°C or lower, more preferably 300°C or higher and 500°C or lower, and even more preferably 300°C or higher and 450°C or lower.
  • the heating temperature within this range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be more appropriately produced.
  • the holding time which is the time for which the copper ink 10 is held at the heating temperature, is preferably from 1 second to 600 seconds, more preferably from 10 seconds to 600 seconds, and even more preferably from 10 seconds to 300 seconds.
  • the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be more appropriately produced.
  • the heating rate which is the rate at which the copper ink 10 is heated to the heating temperature, is preferably 0.1°C/sec or more and 50°C/sec or less, more preferably 0.1°C/sec or more and 10°C/sec or less, and even more preferably 0.5°C/sec or more and 10°C/sec or less.
  • the copper ink 10 it is preferable to heat the copper ink 10 by irradiating the copper ink 10 with light from a light irradiating unit that emits light with a spectral distribution having a peak in the visible to infrared wavelengths.
  • the light irradiating unit may be any unit that emits light with a spectral distribution having a peak in the visible to infrared wavelengths, and may be, for example, a light source that emits light in a predetermined wavelength band.
  • the method of heating the copper ink 10 is not limited to irradiation from a light source, and any method or device capable of heating the copper ink 10 within the range of light with a spectral distribution having a peak at the wavelength specified above may be used.
  • steps S12, S14, and S16 may be performed only once to produce cuprous oxide. That is, cuprous oxide may be produced by heating after a single application and drying process. For example, steps S12 and S14 may be repeated multiple times, and then step S16 may be performed. That is, cuprous oxide may be produced by heating after a single application and drying process. For example, steps S12, S14, and S16 may be a series of steps, and the series of steps may be repeated multiple times to produce cuprous oxide. That is, the process of heating after a single application and drying process may be repeated multiple times.
  • cuprous oxide film The characteristics of the cuprous oxide (cuprous oxide film) of this embodiment will be described below. Note that, although the characteristics of the cuprous oxide (cuprous oxide film) manufactured by the manufacturing method of this embodiment will be described below, the cuprous oxide (cuprous oxide film) of this embodiment is not limited to being manufactured by the manufacturing method of this embodiment, and may be manufactured by any manufacturing method as long as it is cuprous oxide (cuprous oxide film) that satisfies at least one of the characteristics described below.
  • the cuprous oxide (cuprous oxide film) of this embodiment is measured by X-ray diffraction (XRD), it is preferable that at least one of the crystal peaks of Cu 2 O having plane indices shown in the following formulas (1) to (12) is detected.
  • the crystal peak here refers to a peak having an intensity equal to or greater than a threshold value
  • the threshold value here is, for example, a relative intensity of 5 when the maximum peak intensity of the measurement result is taken as 100.
  • the X-ray diffraction device used can be a fully automated multipurpose X-ray diffraction device (SmartLab) manufactured by Rigaku.
  • the conditions for the X-ray diffraction method are an X-ray output of 45 kV, 200 mA, a continuous scan mode, a scan speed of 10°/min, a step width of 0.05°, a scan axis of 2 ⁇ , and a scan range of 10 to 100°.
  • the cuprous oxide (cuprous oxide film) of this embodiment can be used in at least one of solar cells, thin film transistors, sensors, varistors, and catalysts.
  • the average transmittance of light (visible light to infrared light) with wavelengths of 600 nm to 1200 nm is preferably 40% to 100%, more preferably 50% to 100%, and even more preferably 60% to 100%.
  • the material can be appropriately used, for example, as a see-through type solar cell or as the top cell (solar cell) of a tandem type solar cell with a crystalline silicon solar cell as the bottom cell (solar cell).
  • the transmittance here can be measured using an ultraviolet-visible-near infrared spectrophotometer.
  • the ratio (transmittance ratio: T 2 /T 1 ) of the average transmittance (T 2 ) of light with a wavelength of 600 nm to 1200 nm to the average transmittance (T 1 ) of light with a wavelength of 300 nm to 600 nm is preferably 3.5 or more, more preferably 4.0 to 20.0, and even more preferably 4.5 to 15.0.
  • the transmittance ratio is in this range, it is possible to obtain a cuprous oxide film that can appropriately transmit light in the infrared range relative to light with a short wavelength and has appropriate performance.
  • it can be suitably used as a top cell (solar cell) of a tandem solar cell in which a see-through type solar cell or a crystalline silicon solar cell is the bottom cell (solar cell).
  • the cuprous oxide (cuprous oxide film) of this embodiment preferably has a thickness of 0.1 ⁇ m or more and 1000 ⁇ m or less, more preferably 0.3 ⁇ m or more and 1000 ⁇ m or less, and even more preferably 0.3 ⁇ m or more and 500 ⁇ m or less. By keeping the thickness within this range, it can be appropriately applied to various applications such as solar cells, thin film transistors, sensors, varistors, and catalysts.
  • the cuprous oxide (cuprous oxide film) of this embodiment is preferably a sintered body.
  • the cuprous oxide of this embodiment preferably has a sintered density of 70% or more, more preferably 80% or more, and even more preferably 85% or more. When the sintered density is in this range, the cuprous oxide can appropriately ensure the characteristics of the solar cell.
  • the sintered density refers to the ratio of the volume of the cuprous oxide excluding the open pores and closed pores to the total volume of the cuprous oxide including the open pores and closed pores.
  • the sintered density was calculated by binarizing the image of the cross section of the cuprous oxide randomly taken at a magnification of 50,000 times with a SEM (Scanning Electron Microscope) using image processing software (ImageJ manufactured by the National Institutes of Health, USA), dividing it into a particle part and a pore part, and calculating the sintered density according to the following formula.
  • Sintered density (%) (total area of particle parts/(total area of particle parts+total area of void parts)) ⁇ 100
  • the method for producing the cuprous oxide (cuprous oxide film) of this embodiment is arbitrary and is not limited to being a sintered body.
  • the copper ink 10 may be any liquid composition containing copper particles as described above, but preferred embodiments of the copper ink 10 used in this embodiment will be described below.
  • FIG. 2 is a schematic diagram of the copper ink according to this embodiment.
  • the copper ink 10 according to this embodiment preferably contains copper particles 12, a polyhydric alcohol 14, a solvent 16, and an organic solvent 18.
  • the copper ink 10 refers to an ink-like substance in which the copper particles 12 do not dissolve in the liquid solvent 16, but rather the solid copper particles 12 are present in the solvent 16.
  • the copper particles 12 may be settled in the solvent 16, or the copper particles 12 may be dispersed.
  • the copper particles 12 are copper particles.
  • the copper particles 12 preferably have a particle size (peak value of particle size distribution (number)) of 10 nm or more and 1000 nm or less.
  • the particle size of the copper particles 12 in the copper ink 10 can be determined as the peak value of the particle size distribution (number) of the copper particles 12 by setting physical property values such as the refractive index of the copper particles and the refractive index and viscosity value of the solvent in the ink using a particle size measuring device (Zetasizer Nano Series ZSP, manufactured by Malvern Instruments), and measuring at 20°C or 25°C according to the temperature conditions of the physical property values.
  • the copper particles 12 may be diluted and dispersed about 10 to 1000 times with the main solvent in the copper ink 10 (water, ethanol, or a high boiling point solvent) and then measured.
  • the main solvent in the copper ink 10 water, ethanol, or a high boiling point solvent
  • the particle size of the copper particles 12 is preferably in the range of 30 nm to 500 nm, and particularly preferably in the range of 30 nm to 300 nm.
  • the BET specific surface area of the copper particles 12 can be determined by measuring the amount of gas adsorption of the copper particles 12 using nitrogen or krypton gas as a measurement gas with a specific surface area measuring device (Quantachrome Instruments, QUANTACROME AUTOSORB-iQ2).
  • the BET specific surface area of the copper particles 12 is preferably in the range of 2.0 m 2 /g to 8.0 m 2 /g, more preferably in the range of 3.5 m 2 /g to 8.0 m 2 /g, and particularly preferably in the range of 4.0 m 2 /g to 8.0 m 2 /g.
  • the shape of the copper particles 12 is not limited to a spherical shape, and may be a needle shape or a flat plate shape.
  • the surfaces of the copper particles 12 are preferably partially or entirely coated with an organic substance.
  • an organic substance By being coated with an organic substance, oxidation of the copper particles 12 is suppressed, and a decrease in sinterability due to oxidation of the copper particles 12 is further prevented.
  • the organic substance coating the copper particles 12 is not formed by the polyhydric alcohol 14 or the solvent 16, and can be said to be not derived from the polyhydric alcohol 14 or the solvent 16. It can also be said that the organic substance coating the copper particles 12 is not a metal oxide (copper oxide) formed by the oxidation of a metal.
  • the fact that the copper particles 12 are coated with an organic substance can be confirmed by analyzing the surface of the copper particles 12 using time-of-flight secondary ion mass spectrometry (TOF-SIMS).
  • TOF-SIMS time-of-flight secondary ion mass spectrometry
  • the ratio of the amount of C 3 H 3 O 3 - ions to the amount of Cu + ions detected by analyzing the surface of the copper particles 12 using time-of-flight secondary ion mass spectrometry is preferably 0.001 or more. It is more preferable that the C 3 H 3 O 3 - / Cu + ratio is in the range of 0.05 to 0.2 .
  • the surface of the copper particles 12 in this analysis does not refer to the surface of the copper particles 12 when the organic substance is removed from the copper particles 12, but refers to the surface of the copper particles 12 containing the organic substance that coats it (i.e., the surface of the organic substance).
  • the copper particles 12 may be subjected to surface analysis using time-of-flight secondary ion mass spectrometry to detect C 3 H 4 O 2 - ions and C 5 or higher ions.
  • the ratio of the amount of C 3 H 4 O 2 - ions to the amount of Cu + ions is preferably 0.001 or more.
  • the ratio of the amount of C 5 or higher ions to the amount of Cu + ions (C 5 or higher ions/Cu + ratio) is preferably less than 0.005.
  • the C 3 H 3 O 3 - ions, C 3 H 4 O 2 - ions, and C 5 or more ions detected by time-of-flight secondary ion mass spectrometry are derived from organic matter coating the surface of the copper particles 12. Therefore, when the C 3 H 3 O 3 - /Cu + ratio and the C 3 H 4 O 2 - /Cu + ratio are each 0.001 or more, the surface of the copper particles 12 is less likely to oxidize and the copper particles 12 are less likely to aggregate.
  • the C 3 H 3 O 3 - /Cu + ratio and the C 3 H 4 O 2 - /Cu + ratio are 0.2 or less, the oxidation and aggregation of the copper particles 12 can be suppressed without excessively reducing the sinterability of the copper particles 12, and further, the generation of decomposition gas of the organic matter during heating can be suppressed, so that cuprous oxide with fewer voids can be formed.
  • the C 3 H 3 O 3 - /Cu + ratio and the C 3 H 4 O 2 - /Cu + ratio are preferably in the range of 0.08 to 0.16.
  • the C 5 or more ion/Cu + ratio is 0.005 times or more, a large amount of organic matter with a relatively high desorption temperature is present on the particle surface, resulting in insufficient sinterability and making it difficult to obtain strong cuprous oxide.
  • the C 5 or more ion/Cu + ratio is preferably less than 0.003 times.
  • the organic matter that coats the copper particles 12 is preferably a carboxylic acid derived from a carboxylic acid metal used in producing the copper particles 12.
  • a method for producing copper particles 12 coated with an organic matter derived from a carboxylic acid will be described later.
  • the amount of the organic matter coated on the copper particles 12 is preferably in the range of 0.5% by mass to 2.0% by mass, more preferably in the range of 0.8% by mass to 1.8% by mass, and even more preferably in the range of 0.8% by mass to 1.5% by mass, relative to 100% by mass of the copper particles.
  • the amount of the organic matter coating can be measured using a commercially available device.
  • the amount of coating can be measured using a differential thermobalance TG8120-SL (manufactured by RIGAKU Corporation).
  • TG8120-SL manufactured by RIGAKU Corporation
  • copper particles from which moisture has been removed by freeze-drying are used as the sample.
  • Measurements are made in nitrogen (G2 grade) gas to suppress oxidation of the copper particles, and the temperature rise rate is set to 10°C/min.
  • the weight loss rate when heated from 250°C to 300°C can be defined as the amount of organic coating.
  • coating amount (sample weight after measurement) / (sample weight before measurement) x 100 (wt%). Measurements are made three times for each of the same lot of copper particles, and the arithmetic mean value can be used as the amount of coating.
  • the copper particles 12 are heated for 30 minutes at 300°C in an inert gas atmosphere such as argon gas, it is preferable that 50% or more by mass of the organic matter is decomposed.
  • an inert gas atmosphere such as argon gas
  • the organic matter derived from carboxylic acid it generates carbon dioxide gas, nitrogen gas, evaporated acetone gas, and water vapor.
  • the polyhydric alcohol 14 preferably contains two or more OH groups and is soluble in water and ethanol.
  • the polyhydric alcohol 14 preferably has a melting point of 30° C. or higher.
  • the polyhydric alcohol 14 may be, for example, at least one of 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2-hydroxymethyl-2-methyl-1,3-propanediol, 1-phenyl-1,2-ethanediol, 1,1,1-tris(hydroxymethyl)propane, erythritol, pentaerythritol, ribitol, resorcinol, (pyro)catechol, 5-methylresorcinol, pyrogallol, 1,2,3-cyclohexanetriol, and 1,3,5-cyclohexanetriol.
  • the polyhydric alcohol 14 is a non-electrolyte, and is present in the copper ink 10 in a state dissolved in the solvent 16 (the molecules of the polyhydric alcohol 14 are dispersed in the solvent 16).
  • the form in which the polyhydric alcohol 14 is present in the copper ink 10 is arbitrary, and it may be in a state in which it is not dissolved in the solvent 16.
  • polyhydric alcohol 14 is coordinated around copper particles 12, and aggregation of copper particles 12 can be appropriately suppressed. In other words, in this embodiment, it is preferable that polyhydric alcohol 14 is coordinated around copper particles 12.
  • the solvent 16 is a liquid (medium) for dispersing the copper particles 12. Details of the solvent 16 will be described later.
  • the organic solvent 18 is an organic solvent having a different component from the polyhydric alcohol 14 and the solvent 16.
  • the organic solvent 18 is an organic solvent having a boiling point of 150° C. or higher at atmospheric pressure and miscible with water.
  • the organic solvent 18 more preferably has a boiling point of 200° C. or higher.
  • miscible means that the organic solvent 18 can be mixed with water in any ratio (i.e., they can be completely dissolved in each other at any concentration).
  • the organic solvent 18 is preferably miscible with the solvent 16.
  • the organic solvent 18 is preferably a glycol ether or an aprotic polar solvent. More specifically, the organic solvent 18 may include both a glycol ether and an aprotic polar solvent, in other words, it is preferable that the organic solvent 18 includes at least one of a glycol ether and an aprotic polar solvent.
  • glycol ethers contained in the organic solvent 18 include diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, diethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol isobutyl ether, diethylene glycol monoisobutyl ether, ethylene glycol monoallyl ether, diethylene glycol monobenzyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monopropyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and diethylene glycol diethyl ether.
  • the organic solvent 18 When the organic solvent 18 contains a glycol ether, it may contain at least one selected from the above.
  • Examples of the aprotic polar solvent contained in the organic solvent 18 include N-methylpyrrolidone, dimethylformamide, 2-pyrrolidone, and propylene carbonate.
  • the organic solvent 18 When the organic solvent 18 contains an aprotic polar solvent, it may contain at least one selected from these listed solvents.
  • the content of the polyhydric alcohol 14 in the copper ink 10 is preferably 0.01% or more and 20% or less by mass ratio with respect to the entire copper ink 10.
  • the copper particles 12 can be appropriately dispersed while preventing the concentration of the copper particles 12 from becoming too low.
  • the copper ink 10 preferably contains copper particles 12 in a mass ratio of 1% to 50%, more preferably 5% to 50%, and even more preferably 5% to 30% of the total copper ink 10. Having a copper particle 12 content within this range makes it possible to suppress a decrease in the fluidity of the copper ink 10 while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
  • the content of the solvent 16 in the copper ink 10 is preferably 50% to 99% by mass, more preferably 50% to 95%, and even more preferably 60% to 95% by mass, relative to the total mass of the copper ink 10.
  • the content of organic solvent 18 in copper ink 10 is preferably 0.01% to 20% by mass, and more preferably 0.1% to 20% by mass, relative to the total mass of copper ink 10. By having the content of organic solvent 18 within this range, even if copper ink 10 is left for a long period of time, it has sufficient mold resistance and can be appropriately stored for a long period of time.
  • the copper ink 10 may contain ionized copper particles 12 (ions of the metal that constitutes the copper particles 12).
  • the liquid component of the copper ink 10 may contain ionized copper particles 12. It can be said that the ionized copper particles 12 may be copper ions.
  • the copper ink 10 described above can have a variety of solvent 16 components. Below, we will explain each copper ink 10 with a different solvent 16 component.
  • first copper ink 10A One of the copper inks 10 having different components of the solvent 16 is referred to as a first copper ink 10A.
  • the solvent 16 is water.
  • the polyhydric alcohol 14 and the organic solvent 18 are dissolved in the water, which is the solvent 16, and copper particles 12 are mixed in.
  • the first copper ink 10A is an aqueous solution of the polyhydric alcohol 14 and the organic solvent 18, which contains the copper particles 12.
  • the content of polyhydric alcohol 14 in the first copper ink 10A is preferably 0.1% to 20% by mass, more preferably 0.5% to 20% by mass, and even more preferably 1% to 20% by mass, relative to the entire first copper ink 10A. By having the content of polyhydric alcohol 14 in this range, it is possible to properly disperse the copper particles 12 while preventing the concentration of the copper particles 12 from becoming too low.
  • the content of copper particles 12 in the first copper ink 10A is preferably 1% to 50% by mass, more preferably 5% to 50%, and even more preferably 5% to 30% by mass, relative to the entire first copper ink 10A. Having the content of copper particles 12 within this range makes it possible to suppress a decrease in the fluidity of the first copper ink 10A while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
  • the content of organic solvent 18 in first copper ink 10A is preferably 0.5% to 20% by mass, more preferably 1% to 20%, and even more preferably 2% to 20% by mass, relative to the entire first copper ink 10A. By having the content of organic solvent 18 in this range, the ink can be appropriately stored for a long period of time.
  • the first copper ink 10A does not contain any substances other than the copper particles 12, the polyhydric alcohol 14, the water solvent 16, and the organic solvent 18, except for unavoidable impurities.
  • the first copper ink 10A may contain additives (dispersants, adhesion imparting agents, rheology adjusters, rust inhibitors, etc.) other than the copper particles 12, the polyhydric alcohol 14, the water solvent 16, and the organic solvent 18.
  • the second copper ink 10B contains ethanol as the solvent 16, and more specifically, the main solvent, which is the main component of the solvent 16, is ethanol.
  • the main solvent here refers to a solvent 16 whose content is higher than 50% by mass.
  • the second copper ink 10B may contain a solvent 16 other than ethanol, which is the main solvent, and may contain water in this embodiment.
  • the second copper ink 10B is a mixture of the polyhydric alcohol 14 and the organic solvent 18 dissolved in the solvent 16 and the copper particles 12 mixed therein. That is, for example, the second copper ink 10B is a mixture of the copper particles 12 and an aqueous solution of the polyhydric alcohol 14, the organic solvent 18, and ethanol.
  • the content of polyhydric alcohol 14 in second copper ink 10B is preferably 0.01% to 10% by mass, more preferably 0.1% to 10% by mass, and even more preferably 0.1% to 5% by mass, relative to the entire second copper ink 10B. By having the content of polyhydric alcohol 14 in this range, it is possible to properly disperse copper particles 12 while preventing the concentration of copper particles 12 from becoming too low.
  • the second copper ink 10B preferably contains copper particles 12 in a mass ratio of 1% to 50% relative to the entire second copper ink 10B, more preferably 5% to 50%, and even more preferably 5% to 30%. Having the copper particles 12 content in this range makes it possible to suppress a decrease in the fluidity of the second copper ink 10B while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
  • the ethanol content of the second copper ink 10B is preferably 50% to 99% by mass, more preferably 50% to 95%, and even more preferably 60% to 95% by mass, relative to the entire second copper ink 10B.
  • the content of organic solvent 18 in second copper ink 10B is preferably 0.01% or more and 20% or less, more preferably 0.1% or more and 20% or less, and even more preferably 0.5% or more and 20% or less, by mass ratio relative to the entire second copper ink 10B.
  • the ink can be appropriately stored for a long period of time.
  • the second copper ink 10B preferably does not contain any substances other than the copper particles 12, the polyhydric alcohol 14, the solvent 16 (here, water and ethanol), and the organic solvent 18, except for unavoidable impurities.
  • the second copper ink 10B may contain additives (dispersants, adhesion imparting agents, rheology adjusters, rust inhibitors, etc.) other than the copper particles 12, the polyhydric alcohol 14, the solvent 16, and the organic solvent 18.
  • the second copper ink 10B is mixed with polyhydric alcohol 14, which, for example, coordinates around the copper particles 12, making it possible to suppress aggregation between the copper particles 12.
  • the third copper ink 10C contains a high-boiling point solvent as the solvent 16, and more specifically, the main solvent, which is the main component of the solvent 16, is a high-boiling point solvent.
  • the third copper ink 10C contains copper particles 12 while the polyhydric alcohol 14 and the organic solvent 18 are dissolved in the solvent 16.
  • the third copper ink 10C may contain a solvent 16 other than the high-boiling point solvent, which is the main solvent.
  • the third copper ink 10C may contain at least one of water and ethanol as the solvent 16, and contains both water and ethanol in this embodiment.
  • a high-boiling point solvent is a liquid that contains one or more OH groups, has a boiling point of 150°C or higher, and is poorly soluble or insoluble in water.
  • a high-boiling point solvent that is poorly soluble or insoluble in water is preferably a solvent that is classified as a water-insoluble liquid in Appendix 3 of the Cabinet Order on the Control of Hazardous Materials in the Fire Service Act.
  • the high-boiling point solvent is preferably a so-called organic solvent, and may be, for example, at least one of ⁇ -terpineol and 2-ethyl-1,3-hexanediol. Note that any of the solvents may contain isomers.
  • the content of polyhydric alcohol 14 in third copper ink 10C is preferably 0.01% to 5% by mass, more preferably 0.01% to 5% by mass, and even more preferably 0.01% to 3% by mass, relative to the total mass of third copper ink 10C.
  • the third copper ink 10C preferably contains copper particles 12 in a mass ratio of 1% to 50% relative to the entire third copper ink 10C, more preferably 5% to 50%, and even more preferably 5% to 30%. Having the copper particles 12 content in this range makes it possible to suppress a decrease in the fluidity of the second copper ink 10B while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
  • the content of the high boiling point solvent in the third copper ink 10C is preferably 50% or more and 99% or less, more preferably 50% or more and 95% or less, and even more preferably 60% or more and 95% or less, by mass ratio relative to the entire third copper ink 10C.
  • the content of the high boiling point solvent in this range it is possible to suppress a decrease in the fluidity of the third copper ink 10C while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
  • the content of organic solvent 18 in third copper ink 10C is preferably 0.01% or more and 20% or less, more preferably 0.01% or more and 10% or less, and even more preferably 0.1% or more and 10% or less, by mass ratio relative to the entire third copper ink 10C.
  • the ink can be appropriately stored for a long period of time.
  • the third copper ink 10C preferably contains a dispersant that is a component other than the copper particles 12, the polyhydric alcohol 14, the solvent 16, and the organic solvent 18.
  • dispersants include cationic dispersants, anionic dispersants, nonionic dispersants, and amphoteric dispersants.
  • anionic dispersants include carboxylic acid dispersants, sulfonic acid dispersants, and phosphoric acid dispersants.
  • phosphoric acid ester compounds are preferably used as phosphoric acid dispersants.
  • the molecular weight of the phosphoric acid ester compound used as a dispersant is preferably 200 to 2000, more preferably 200 to 1500, and even more preferably 200 to 1000.
  • a molecular weight of 200 or more provides sufficient hydrophobicity, thereby providing good dispersibility of the copper particles in the high boiling point solvent, and a molecular weight of 2000 or less provides decomposition and reaction at the target heating temperature (approximately 200 to 350°C), so there is no risk of interfering with sintering of the copper particles.
  • the dispersant content of the third copper ink 10C is preferably 0.01% or more and 5% or less, more preferably 0.1% or more and 5% or less, and even more preferably 0.1% or more and 3% or less, by mass ratio relative to the entire third copper ink 10C. By having the dispersant content within this range, aggregation of the copper particles 12 can be appropriately suppressed.
  • the third copper ink 10C preferably does not contain any substances other than the copper particles 12, polyhydric alcohol 14, solvent 16 (here, water, ethanol, and a high boiling point solvent), organic solvent 18, and dispersant, except for unavoidable impurities.
  • the third copper ink 10C may not contain a dispersant, or may contain additives other than the copper particles 12, polyhydric alcohol 14, solvent 16, organic solvent 18, and dispersant (adhesion imparting agents, rheology adjusters, rust inhibitors, etc.).
  • the high-boiling point solvent may cause the copper particles 12 to aggregate.
  • the third copper ink 10C contains a polyhydric alcohol 14, which, for example, coordinates around the copper particles 12, preventing the copper particles 12 from aggregating together.
  • Fig. 3 is a flowchart illustrating a method for manufacturing the copper ink according to this embodiment.
  • a carboxylate copper aqueous dispersion and a reducing agent are mixed to produce copper particles 12 (step S20). Specifically, first, a carboxylate copper aqueous dispersion is prepared, and a pH adjuster is added to the carboxylate copper aqueous dispersion to adjust the pH to 2.0 to 7.5. Next, in an inert gas atmosphere, a hydrazine compound capable of reducing copper ions is added as a reducing agent to the pH-adjusted carboxylate copper aqueous dispersion and mixed. The resulting mixture is heated to a temperature of 60° C. to 80° C.
  • the carboxylic acid used here may be glycolic acid, citric acid, malic acid, maleic acid, malonic acid, fumaric acid, succinic acid, tartaric acid, oxalic acid, phthalic acid, benzoic acid, or a salt thereof, etc.
  • the reducing agent used is a hydrazine compound, but is not limited thereto, and may be hydrazine, ascorbic acid, oxalic acid, formic acid, or a salt thereof, etc.
  • Aqueous dispersions of copper carboxylate can be prepared by adding powdered carboxylate metal to pure water such as distilled water or ion-exchanged water to a concentration of 25% to 40% by mass, and stirring with a stirring blade to disperse the mixture uniformly.
  • pH adjusters include triammonium citrate, ammonium hydrogen citrate, and citric acid. Among these, triammonium citrate is preferred because it is easy to adjust the pH mildly.
  • the pH of the aqueous dispersion of copper carboxylate is set to 2.0 or more in order to increase the elution rate of copper ions eluted from the copper carboxylate, to rapidly advance the generation of copper particles, and to obtain the target fine copper particles.
  • the pH is set to 7.5 or less in order to prevent the eluted metal ions from becoming copper hydroxide (II) and to increase the yield of copper particles.
  • the pH of the aqueous dispersion of copper carboxylate is preferably adjusted to a range of 4 to 6.
  • the reduction of copper carboxylate with hydrazine compounds is carried out in an inert gas atmosphere. This is to prevent oxidation of the copper ions dissolved in the liquid.
  • inert gases include nitrogen gas and argon gas.
  • hydrazine compounds When reducing copper carboxylate under acidic conditions, hydrazine compounds have the advantages of not producing residues after the reduction reaction, being relatively safe, and being easy to handle. Examples of this hydrazine compound include hydrazine monohydrate, hydrazine anhydrous, hydrazine hydrochloride, and hydrazine sulfate. Of these hydrazine compounds, hydrazine monohydrate and hydrazine anhydrous are preferred, as they do not contain components that can become impurities such as sulfur and chlorine.
  • the mixed solution containing the hydrazine compound is heated to a temperature of 60°C or higher and 80°C or lower under an inert gas atmosphere and held for 1.5 to 2.5 hours in order to generate copper particles and to form and coat the surfaces of the generated copper particles with organic matter.
  • the reason for holding the mixture under an inert gas atmosphere is to prevent oxidation of the generated copper particles.
  • the starting material, carboxylate copper usually contains about 35% by mass of copper.
  • a hydrazine compound which is a reducing agent
  • a carboxylate aqueous dispersion containing this amount of copper heating it to the above temperature, and holding it for the above time, the generation of copper particles and the generation of organic matter on the surfaces of the copper particles proceed in a balanced manner, so that copper particles can be obtained with an organic matter coating amount in the range of 0.5% by mass to 2.0% by mass relative to 100% by mass of copper particles. If the heating temperature is less than 60°C and the holding time is less than 1.5 hours, the carboxylate metal is not completely reduced, the generation rate of copper particles becomes too slow, and the amount of organic matter coating the copper particles may become excessive.
  • the heating temperature exceeds 80°C and the holding time exceeds 2.5 hours, the rate at which copper particles are produced may become too fast, resulting in a risk of the amount of organic matter coating the copper particles being too small.
  • the preferred heating temperature is 65°C or higher and 75°C or lower, and the preferred holding time is 2 hours or higher and 2.5 hours or lower.
  • the copper particles produced in the mixed liquid can be separated from the mixed liquid under an inert gas atmosphere, for example using a centrifuge, to obtain an aqueous slurry containing copper particles 12 with a certain solid-liquid ratio (for example, solid-liquid ratio: 50/50 [mass %]).
  • copper particles whose surfaces are coated with an organic substance can be obtained by performing solid-liquid separation and drying using a freeze-drying method or a vacuum drying method. Since the surfaces of these copper particles are coated with an organic substance, they are less likely to oxidize even when stored in the air.
  • the copper particles 12, the polyhydric alcohol 14, the organic solvent 18, and water are mixed to produce the first copper ink 10A (step S22).
  • an aqueous solution of the polyhydric alcohol 14 and the organic solvent 18 containing the polyhydric alcohol 14, the organic solvent 18, and water may be mixed with a metal slurry containing the copper particles 12 and water, or an aqueous solution of the polyhydric alcohol 14 and the organic solvent 18 may be mixed with the copper particles 12 not containing water.
  • the first copper ink 10A is mixed with ethanol to produce the second copper ink 10B (step S24).
  • the first copper ink 10A and ethanol may be mixed in any manner.
  • the first copper ink 10A obtained in step S22 may be left to stand for a predetermined time (for example, about one day) or centrifuged under predetermined conditions, after which a portion of the supernatant liquid is removed, and ethanol may be added to the first copper ink 10A from which the supernatant liquid has been removed.
  • a predetermined time for example, about one day
  • ethanol may be added to the first copper ink 10A from which the supernatant liquid has been removed.
  • the second copper ink 10B is mixed with the high boiling point solvent and the dispersant to produce the third copper ink 10C (step S26).
  • the method of mixing the second copper ink 10B with the high boiling point solvent and the dispersant is arbitrary.
  • the second copper ink 10B obtained in step S24 may be left to stand for a predetermined time (for example, about one day) or centrifuged under predetermined conditions, and then a part of the supernatant may be removed, and the high boiling point solvent may be added to the second copper ink 10B from which the supernatant has been removed.
  • a dispersant is not essential.
  • a solvent water, ethanol, a high boiling point solvent, etc.
  • the third copper ink 10C produced in this manner is used as the copper ink 10.
  • the second copper ink 10B is produced using the first copper ink 10A
  • the third copper ink 10C is produced using the second copper ink 10B.
  • the first copper ink 10A and the second copper ink 10B are intermediate substances for producing the third copper ink 10C.
  • the first copper ink 10A and the second copper ink 10B are not limited to being intermediate substances, and the first copper ink 10A and the second copper ink 10B themselves may be used as the copper ink 10.
  • the above-described method for producing the copper particles 12 and the copper ink 10 is merely an example, and the copper particles 12 and the copper ink 10 may be produced by any method.
  • the method for producing cuprous oxide includes the steps of obtaining the copper ink 10, which is a liquid composition containing copper particles 12; forming a film by applying or printing the copper ink 10 on a substrate; and, after drying the film formed by the copper ink 10 on the substrate, oxidizing and sintering the copper particles 12 in the copper ink 10 by irradiating and heating with light having a wavelength range of visible to infrared in an atmosphere having an oxygen concentration of 10% to 21% to produce cuprous oxide.
  • the copper ink 10 containing the copper particles 12 is heated at the above oxygen concentration and with light in the above wavelength range, so that cuprous oxide having appropriate performance can be obtained.
  • cuprous oxide is not complicated and cuprous oxide can be appropriately produced, so that cuprous oxide can be produced by a simple process. That is, when producing cuprous oxide from a powder of a copper complex or cuprous oxide, the process is complicated, but by using the copper particles 12, cuprous oxide can be appropriately produced by a simple process of, for example, heating with light having the above oxygen concentration and wavelength range.
  • cuprous oxide it is preferable to heat the copper ink 10 with irradiated light having a spectral distribution with a peak in the wavelength range of 0.6 ⁇ m or more and 10 ⁇ m or less.
  • the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be more appropriately produced.
  • cuprous oxide it is preferable to heat the copper ink 10 at a heating temperature of 180°C or more and 500°C or less. By setting the heating temperature within this range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be produced more appropriately.
  • the holding time at the heating temperature is 1 second or more and 600 seconds or less. By keeping the holding time in this range, the copper particles can be properly oxidized and sintered, and cuprous oxide can be produced more appropriately.
  • the rate of temperature rise to the heating temperature is 0.1°C/sec or more and 50°C/sec or less. By keeping the rate of temperature rise within this range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be produced more appropriately.
  • the copper ink 10 In the step of obtaining the copper ink 10, it is preferable to obtain a copper ink 10 that contains copper particles 12 having a particle size of 10 nm or more and 1000 nm or less, and whose surfaces are coated with an organic substance. By using such a copper ink 10, cuprous oxide can be more appropriately produced.
  • copper ink 10 that contains copper particles 12, a solvent 16, an organic solvent 18 that has a boiling point of 150°C or higher at atmospheric pressure and is miscible with water, and a polyhydric alcohol 14 that contains two or more OH groups and is soluble in water and ethanol.
  • a copper ink 10 cuprous oxide can be more appropriately produced.
  • Fig. 4 is a table showing the components of the copper ink used in each example
  • Figs. 5A to 5Ze are tables showing the evaluation results of each example.
  • Copper ink A method for producing copper ink will be described.
  • copper phthalate was prepared as a starting material, copper carboxylate. Copper phthalate was placed in ion-exchanged water at room temperature and stirred with a stirring blade to prepare an aqueous dispersion of copper phthalate with a concentration of 30% by mass. Next, an aqueous solution of ammonium phthalate was added as a pH adjuster to the aqueous dispersion of copper phthalate to adjust the pH of the aqueous dispersion to 3.
  • the pH-adjusted liquid was heated to 50° C., and an aqueous solution of hydrazine monohydrate (diluted 2-fold) with an oxidation-reduction potential of ⁇ 0.5 V, which is 1.2 times the equivalent amount capable of reducing copper ions, was added to the pH-adjusted liquid as a reducing agent in a nitrogen gas atmosphere, and the mixture was mixed uniformly using a stirring blade. Furthermore, in order to synthesize the target copper particles, the mixture of the aqueous dispersion and the reducing agent was heated to a holding temperature of 70° C. under a nitrogen gas atmosphere and held at 70° C. for 2 hours. Furthermore, the mixture was dehydrated and desalted using a centrifuge to obtain an aqueous slurry of copper particles (copper powder concentration: 50% by mass).
  • the resulting aqueous slurry of copper particles (copper powder concentration: 50% by mass) was used to produce copper inks C1 to C12, each containing the components shown in the table in Figure 4, following the steps for producing the first copper ink to the third copper ink described above.
  • Example 1 copper ink C1 was applied to a substrate of 50 mm ⁇ 50 mm, 25 ⁇ m thick PI (polyimide) film by inkjet printing to a size of 30 mm ⁇ 30 mm, and then dried in air at 60° C. for 15 minutes to form an ink film with a thickness of 0.1 ⁇ m.
  • PI polyimide
  • the ink film formed on the PI film was heated under an atmosphere with an oxygen concentration of 10% (the oxygen concentration in the atmosphere was measured using a zirconia oxygen concentration meter LC-860 manufactured by Toray Engineering Co., Ltd.) using a halogen lamp heater as an irradiation source (which mainly radiates light with a spectral distribution having a peak wavelength in the visible to infrared range, more specifically light with a spectral distribution having a peak wavelength of 1 ⁇ m) under conditions of a heating temperature of 250° C., a heating rate up to the heating temperature of 0.1° C./sec, and a holding time at the heating temperature of 1 second, to produce a sintered body on the PI film.
  • a halogen lamp heater which mainly radiates light with a spectral distribution having a peak wavelength in the visible to infrared range, more specifically light with a spectral distribution having a peak wavelength of 1 ⁇ m
  • Examples 2 to 5 In Examples 2 to 5, as shown in FIG. 5A, sintered bodies were produced under the same conditions as in Example 1 except for at least one of the oxygen concentration, heating temperature, heating rate, and holding time.
  • Examples 6 to 19 a sintered body was produced in the same manner as in Example 1, except that a coating method was used in which a printing method using a metal mask was used to coat a substrate having a size of 30 mm x 30 mm, and copper ink C2 or C3 was used, and the film thickness, oxygen concentration, heating temperature, heating rate, and holding time were set as the production conditions shown in Figures 5A and 5B.
  • Example 20 to 34 a sintered body was manufactured in the same manner as in Examples 1 to 19, except that a glass substrate having a size of 50 mm ⁇ 50 mm and a thickness of 0.7 mm was used as the base material, and the type of copper ink, the film thickness, the oxygen concentration, the heating temperature, the heating rate, and the holding time were the manufacturing conditions shown in Figures 5B to 5D.
  • Example 35 to 50 In Examples 35 to 50, a quartz tube heater (which mainly emits light with a spectral distribution having a peak wavelength in the infrared region) was used as the irradiation source, and sintered bodies were manufactured in the same manner as in Examples 1 to 34, except that the type of copper ink, film thickness, oxygen concentration, heating temperature, heating rate, and holding time were manufacturing conditions shown in Figures 5D and 5E.
  • a quartz tube heater which mainly emits light with a spectral distribution having a peak wavelength in the infrared region
  • Example 51 to 54 In Examples 51 to 54, a ceramic heater (which mainly emits light with a spectral distribution having a peak wavelength in the infrared region) was used as the irradiation source, and sintered bodies were manufactured in the same manner as in Examples 1 to 34, except that the type of copper ink, film thickness, oxygen concentration, heating temperature, heating rate, and holding time were manufacturing conditions shown in FIG. 5E.
  • a ceramic heater which mainly emits light with a spectral distribution having a peak wavelength in the infrared region
  • Example 55 to 216 sintered bodies were manufactured in the same manner as in Examples 1 to 34, except that the irradiation source, type of copper ink, film thickness, oxygen concentration, heating temperature, heating rate, and holding time were as shown in Figures 5E to 5T.
  • Comparative Examples 1 to 6 sintered bodies were produced in the same manner as in Examples 1 to 34 under the production conditions shown in FIG. 5U, except that heating was performed using a xenon flash lamp (which mainly radiates light in the ultraviolet to infrared range) as an irradiation source.
  • a xenon flash lamp which mainly radiates light in the ultraviolet to infrared range
  • Comparative Examples 7 to 12 sintered bodies were produced in the same manner as in Examples 1 to 34 under the production conditions shown in Figures 5U and 5V, except that heating was performed using a gyrotron (mainly emitting light in the microwave region of 24 GHz) as an irradiation source.
  • a gyrotron mainly emitting light in the microwave region of 24 GHz
  • Comparative Examples 13 to 48 sintered bodies were manufactured in the same manner as in Examples 1 to 34, except that the irradiation source, type of copper ink, film thickness, oxygen concentration, heating temperature, heating rate, and holding time were as shown in Figures 5V to 5Y.
  • Comparative Examples 49 to 53 sintered bodies were produced in the same manner as in Examples 1 to 5 under the production conditions shown in FIG. 5Za, except that the oxygen concentration was adjusted to less than 10% in the atmosphere.
  • Comparative Examples 54 to 67 sintered bodies were produced in the same manner as in Examples 6 to 19 under the production conditions shown in Figures 5Za and 5Zb, except that the oxygen concentration was adjusted to be less than 10% in the atmosphere.
  • Comparative Examples 68 to 82 sintered bodies were produced in the same manner as Examples 20 to 34 under the production conditions shown in Figures 5Zb to 5Zd, except that the oxygen concentration was adjusted to an atmosphere of less than 10%.
  • Comparative Examples 83 to 98 sintered bodies were manufactured in the same manner as Examples 35 to 50 under the manufacturing conditions shown in Figures 5Zd and 5Ze, except that the oxygen concentration was adjusted to an atmosphere of less than 10%.
  • the sintered bodies of Examples 1 to 216 which were obtained by irradiating copper ink, a liquid composition containing copper particles, with light having a wavelength in the visible to infrared range and heating it under conditions of an oxygen concentration of 10% to 21%, have a peak in any one of the formulas (1) to (12) that indicate the peak of cuprous oxide in XRD measurement, and have no peaks other than those in formulas (1) to (12), and therefore it is understood that cuprous oxide can be appropriately produced.
  • the sintered bodies of Comparative Examples 1 to 48 which were heated by irradiating light having a spectral distribution with a peak at a wavelength outside the visible to infrared range
  • the sintered bodies of Comparative Examples 49 to 102 which were heated in an atmosphere with an oxygen concentration of less than 10%, have peaks other than those in formulas (1) to (12) that indicate the peak of cuprous oxide in XRD measurement, which indicates the presence of copper or copper compounds other than cuprous oxide, and therefore it is understood that cuprous oxide cannot be appropriately produced.
  • the transmittance of the sintered body to light in the visible to infrared region was evaluated.
  • the transmittance of the sintered body was measured by a Hitachi High-Tech Science ultraviolet-visible near-infrared spectrophotometer (UH4150) as a visible infrared spectrophotometer, with the data mode set to transmittance measurement (%T), the start wavelength set to 1200 nm, the end wavelength set to 300 nm, the scan speed set to 600 nm/min, and the sampling interval set to 1.00 nm.
  • the sintered bodies of Comparative Examples 1 to 48 which were heated by irradiating light with a spectral distribution having a peak wavelength outside the visible to infrared region
  • the sintered bodies of Comparative Examples 49 to 102 which were heated in an atmosphere with an oxygen concentration of less than 10%, contain copper or copper compounds other than cuprous oxide, and therefore cannot appropriately transmit light with a wavelength of 600 nm to 1200 nm, resulting in no light transmission.
  • the transmittance of the sintered body was measured using a Hitachi High-Tech Science ultraviolet-visible near-infrared spectrophotometer (UH4150) as a visible infrared spectrophotometer, with the data mode set to transmittance measurement (%T), the start wavelength set to 300 nm, the end wavelength set to 1200 nm, the scan speed set to 600 nm/min, and the sampling interval set to 1.00 nm.
  • the absorption coefficient ( ⁇ ( ⁇ )) at each wavelength was calculated from the transmittance and film thickness of the obtained sintered body using formula (13).
  • the average transmittance (T 1 ) of light with a wavelength of 300 nm or more and less than 600 nm and the average transmittance (T 2 ) of light with a wavelength of 600 nm to 1200 nm at a film thickness of 0.1 ⁇ m were calculated using formula (13).
  • the ratio of the average transmittance ( T2 ) of light having a wavelength of 600 nm to 1200 nm to the average transmittance ( T1 ) of light having a wavelength of 300 nm or more and less than 600 nm was defined as the transmittance ratio ( T2 / T1 ).
  • the embodiment of the present invention has been described above, the embodiment is not limited to the contents of this embodiment.
  • the above-mentioned components include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range.
  • the above-mentioned components can be combined as appropriate.
  • various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-mentioned embodiment.

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Abstract

The present invention produces cuprous oxide having adequate performance. This method for producing cuprous oxide comprises a step in which a copper ink that is a liquid composition containing copper particles is obtained, a step in which the copper ink is applied or printed on a substrate to form a film, and a step in which the film of the copper ink formed on the substrate is dried and then heated in an atmosphere having an oxygen concentration of 10-21% by irradiation with light having wavelengths in a range of from visible to infrared regions to thereby oxidize and sinter the copper particles contained in the copper ink, thereby producing a sintered object made of cuprous oxide.

Description

亜酸化銅の製造方法及び亜酸化銅膜Method for producing cuprous oxide and cuprous oxide film
　本発明は、亜酸化銅の製造方法及び亜酸化銅膜に関する。 The present invention relates to a method for producing cuprous oxide and a cuprous oxide film.
　亜酸化銅（Ｃｕ２Ｏ）は、ｐ型半導体となるため、太陽電池、薄膜トランジスタ、センサ、バリスタ、触媒など、様々な用途への適用が検討されている。特許文献１には、亜酸化銅粉末を含有する液状組成物を基板上に付着させて、加熱焼結することで、亜酸化銅膜を製造する旨が記載されている。また特許文献２には、銅錯体が溶解した溶液を基板表面に塗布して、不活性ガス雰囲気下で熱処理することで、亜酸化銅膜を製造する旨が記載されている。 Since cuprous oxide (Cu 2 O) is a p-type semiconductor, its application to various applications such as solar cells, thin film transistors, sensors, varistors, and catalysts is being considered. Patent Document 1 describes the production of a cuprous oxide film by attaching a liquid composition containing cuprous oxide powder onto a substrate and heating and sintering the substrate. Patent Document 2 describes the production of a cuprous oxide film by applying a solution in which a copper complex is dissolved onto a substrate surface and heat treating the substrate in an inert gas atmosphere.
特開２００８－２８２９１３号公報JP 2008-282913 A 特許第５４５２１９６号公報Japanese Patent No. 5452196
　しかしながら、特許文献１の製法だと、亜酸化銅粉末を焼成するため、焼成中や焼成後に特定の雰囲気下にする必要があり、プロセスが複雑となる。また、特許文献２の製法だと、銅錯体を用いて亜酸化銅を製造するため、プロセスが複雑になる。従って、適切な性能を有する亜酸化銅を得ることが求められている。 However, in the manufacturing method of Patent Document 1, since the cuprous oxide powder is calcined, a specific atmosphere must be maintained during and after the calcination, making the process complicated. In addition, in the manufacturing method of Patent Document 2, since cuprous oxide is produced using a copper complex, the process is also complicated. Therefore, there is a demand for obtaining cuprous oxide with appropriate performance.
　本発明は、上記に鑑みてなされたものであって、適切な性能を有する亜酸化銅を得ることが可能な亜酸化銅の製造方法及び適切な性能を有する亜酸化銅膜を提供することを目的とする。 The present invention has been made in consideration of the above, and aims to provide a method for producing cuprous oxide capable of obtaining cuprous oxide with suitable performance, and a cuprous oxide film with suitable performance.
　上記の課題を解決するために、本開示の亜酸化銅の製造方法は、銅粒子を含む液状の組成物である銅インクを得るステップと、前記銅インクを、基材上に塗布もしくは印刷することにより膜を形成するステップと、前記銅インクが基材上に形成された膜を乾燥した後、酸素濃度が１０％以上２１％以下の雰囲気下で、波長の範囲が可視～赤外領域の光を照射して加熱することで、前記銅インク中の前記銅粒子を酸化及び焼結して、前記基材上に亜酸化銅を製造するステップと、を含む。 In order to solve the above problems, the method for producing cuprous oxide disclosed herein includes the steps of obtaining a copper ink, which is a liquid composition containing copper particles; forming a film by applying or printing the copper ink on a substrate; and, after drying the film formed by the copper ink on the substrate, irradiating the film with light having a wavelength in the visible to infrared range and heating the film in an atmosphere having an oxygen concentration of 10% or more and 21% or less, thereby oxidizing and sintering the copper particles in the copper ink to produce cuprous oxide on the substrate.
　前記亜酸化銅を製造するステップにおいては、照射する光のピークとなる強度の波長が、０．６μｍ以上１０μｍ以下である分光分布を有する光により、前記銅インクが基材上に形成された膜を加熱することが好ましい。 In the step of producing the cuprous oxide, it is preferable to heat the film of the copper ink formed on the substrate with light having a spectral distribution in which the wavelength of the peak intensity of the irradiated light is 0.6 μm or more and 10 μm or less.
　前記亜酸化銅を製造するステップにおいては、１８０℃以上５００℃以下の加熱温度で、前記銅インクが基材上に形成された膜を加熱することが好ましい。 In the step of producing the cuprous oxide, it is preferable to heat the film formed by the copper ink on the substrate at a heating temperature of 180°C or higher and 500°C or lower.
　前記亜酸化銅を製造するステップにおいては、前記加熱温度での保持時間を、１秒以上６００秒以下とすることが好ましい。 In the step of producing the cuprous oxide, it is preferable that the holding time at the heating temperature is 1 second or more and 600 seconds or less.
　前記亜酸化銅を製造するステップにおいては、前記加熱温度までの昇温速度を、０．１℃／秒以上５０℃／秒以下とすることが好ましい。 In the step of producing the cuprous oxide, it is preferable that the rate of temperature rise to the heating temperature is 0.1°C/sec or more and 50°C/sec or less.
　前記銅インクを得るステップにおいては、粒径が１０ｎｍ以上１０００ｎｍ以下であり、かつ、表面が有機物で被覆されている前記銅粒子を含む前記銅インクを得ることが好ましい。 In the step of obtaining the copper ink, it is preferable to obtain the copper ink containing copper particles whose particle size is 10 nm or more and 1000 nm or less, and whose surface is coated with an organic substance.
　前記銅インクを得るステップにおいては、前記銅粒子と、溶媒と、大気圧における沸点が１５０℃以上であり、水と混和可能な有機溶媒と、ＯＨ基を２つ以上含み、水及びエタノールに溶解可能な多価アルコールと、を含む前記銅インクを得ることが好ましい。 In the step of obtaining the copper ink, it is preferable to obtain the copper ink containing the copper particles, a solvent, an organic solvent having a boiling point of 150°C or higher at atmospheric pressure and miscible with water, and a polyhydric alcohol containing two or more OH groups and soluble in water and ethanol.
　本開示の亜酸化銅膜は、膜厚を０．１μｍとした際の、波長６００ｎｍ～１２００ｎｍの光の平均透過率が、４０％以上１００％以下である。 The cuprous oxide film disclosed herein has an average transmittance of 40% or more and 100% or less for light with wavelengths of 600 nm to 1200 nm when the film thickness is 0.1 μm.
　前記亜酸化銅膜は、膜厚を０．１μｍとした際の、波長３００ｎｍ～６００ｎｍの光の平均透過率（Ｔ１）に対する、波長６００ｎｍ～１２００ｎｍの光の平均透過率（Ｔ２）の比率（Ｔ２／Ｔ１）が、３．５以上であることが好ましい。 The cuprous oxide film preferably has a ratio (T 2 /T 1 ) of the average transmittance (T 2 ) of light having a wavelength of 600 nm to 1200 nm to the average transmittance (T 1 ) of light having a wavelength of 300 nm to 600 nm when the film thickness is 0.1 μm, of 3.5 or more.
　前記亜酸化銅膜は、焼結体であることが好ましい。 The cuprous oxide film is preferably a sintered body.
　本発明によれば、適切な性能を有する亜酸化銅を得ることが可能となる。 The present invention makes it possible to obtain cuprous oxide with suitable performance.
図１は、本実施形態に係る亜酸化銅の製造方法を説明するフローチャートである。FIG. 1 is a flow chart illustrating a method for producing cuprous oxide according to the present embodiment. 図２は、本実施形態に係る銅インクの模式図である。FIG. 2 is a schematic diagram of the copper ink according to this embodiment. 図３は、本実施形態に係る銅インクの製造方法を説明するフローチャートである。FIG. 3 is a flowchart illustrating a method for producing a copper ink according to this embodiment. 図４は、各例で用いた銅インクの成分を示す表である。FIG. 4 is a table showing the components of the copper ink used in each example. 図５Ａは、各例の評価結果を示す表である。FIG. 5A is a table showing the evaluation results of each example. 図５Ｂは、各例の評価結果を示す表である。FIG. 5B is a table showing the evaluation results of each example. 図５Ｃは、各例の評価結果を示す表である。FIG. 5C is a table showing the evaluation results of each example. 図５Ｄは、各例の評価結果を示す表である。FIG. 5D is a table showing the evaluation results of each example. 図５Ｅは、各例の評価結果を示す表である。FIG. 5E is a table showing the evaluation results of each example. 図５Ｆは、各例の評価結果を示す表である。FIG. 5F is a table showing the evaluation results of each example. 図５Ｇは、各例の評価結果を示す表である。FIG. 5G is a table showing the evaluation results for each example. 図５Ｈは、各例の評価結果を示す表である。FIG. 5H is a table showing the evaluation results of each example. 図５Ｉは、各例の評価結果を示す表である。FIG. 5I is a table showing the evaluation results of each example. 図５Ｊは、各例の評価結果を示す表である。FIG. 5J is a table showing the evaluation results of each example. 図５Ｋは、各例の評価結果を示す表である。FIG. 5K is a table showing the evaluation results of each example. 図５Ｌは、各例の評価結果を示す表である。FIG. 5L is a table showing the evaluation results of each example. 図５Ｍは、各例の評価結果を示す表である。FIG. 5M is a table showing the evaluation results of each example. 図５Ｎは、各例の評価結果を示す表である。FIG. 5N is a table showing the evaluation results of each example. 図５Ｏは、各例の評価結果を示す表である。FIG. 5O is a table showing the evaluation results of each example. 図５Ｐは、各例の評価結果を示す表である。FIG. 5P is a table showing the evaluation results of each example. 図５Ｑは、各例の評価結果を示す表である。FIG. 5Q is a table showing the evaluation results of each example. 図５Ｒは、各例の評価結果を示す表である。FIG. 5R is a table showing the evaluation results of each example. 図５Ｓは、各例の評価結果を示す表である。FIG. 5S is a table showing the evaluation results of each example. 図５Ｔは、各例の評価結果を示す表である。FIG. 5T is a table showing the evaluation results of each example. 図５Ｕは、各例の評価結果を示す表である。FIG. 5U is a table showing the evaluation results for each example. 図５Ｖは、各例の評価結果を示す表である。FIG. 5V is a table showing the evaluation results of each example. 図５Ｗは、各例の評価結果を示す表である。FIG. 5W is a table showing the evaluation results of each example. 図５Ｘは、各例の評価結果を示す表である。FIG. 5X is a table showing the evaluation results of each example. 図５Ｙは、各例の評価結果を示す表である。FIG. 5Y is a table showing the evaluation results of each example. 図５Ｚａは、各例の評価結果を示す表である。FIG. 5Za is a table showing the evaluation results of each example. 図５Ｚｂは、各例の評価結果を示す表である。FIG. 5Zb is a table showing the evaluation results of each example. 図５Ｚｃは、各例の評価結果を示す表である。FIG. 5Zc is a table showing the evaluation results of each example. 図５Ｚｄは、各例の評価結果を示す表である。FIG. 5D is a table showing the evaluation results of each example. 図５Ｚｅは、各例の評価結果を示す表である。FIG. 5Ze is a table showing the evaluation results of each example.
　以下、本発明につき図面を参照しつつ詳細に説明する。なお、下記の発明を実施するための形態（以下、実施形態という）により本発明が限定されるものではない。また、下記実施形態における構成要素には、当業者が容易に想定できるもの、実質的に同一のもの、いわゆる均等の範囲のものが含まれる。さらに、下記実施形態で開示した構成要素は適宜組み合わせることが可能である。また、数値については四捨五入の範囲が含まれる。 The present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the following modes for carrying out the invention (hereinafter referred to as embodiments). Furthermore, the components in the following embodiments include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate. Also, the numerical values include the range of rounding.
　（亜酸化銅の製造方法）
　図１は、本実施形態に係る亜酸化銅の製造方法を説明するフローチャートである。本実施形態の製造方法は、亜酸化銅として、Ｃｕ２Ｏ、（酸化銅（Ｉ）、酸化第一銅、ｃｏｐｐｅｒ（Ｉ）　ｏｘｉｄｅ、又はｃｕｐｒｏｕｓ　ｏｘｉｄｅとも表記される）を製造する。本実施形態においては、亜酸化銅の膜を製造するが、膜状の亜酸化銅を製造することに限られず、任意の形状の亜酸化銅を製造してよい。 (Method for producing cuprous oxide)
1 is a flow chart for explaining a method for producing cuprous oxide according to the present embodiment. The production method of the present embodiment produces Cu 2 O (also written as copper(I) oxide, cuprous oxide, copper(I) oxide, or cuprous oxide) as cuprous oxide. In the present embodiment, a film of cuprous oxide is produced, but the production is not limited to a film-like cuprous oxide, and cuprous oxide of any shape may be produced.
　（銅インクを得るステップ）
　図１に示すように、本製造方法においては、最初に、銅インク１０を得る（ステップＳ１０）。銅インク１０は、銅粒子を含む液状の組成物である。銅インク１０の詳細については後述する。 (Step of Obtaining Copper Ink)
1, in this manufacturing method, first, a copper ink 10 is obtained (step S10). The copper ink 10 is a liquid composition containing copper particles. The copper ink 10 will be described in detail later.
　（塗布するステップ）
　次に、得られた銅インク１０を、基板に塗布又は印刷して（ステップＳ１２）、基板上に銅インク１０の膜を形成する。銅インク１０を塗布又は印刷する基板の材料、大きさ、厚みなどは、任意であってよい。
　例えば、基板の比熱［ｋＪ/（ｋｇ・Ｋ）］は、０．１以上３以下であることが好ましく、０．１以上２以下であることがより好ましく、０．１以上１．５以下であることが更に好ましい。基板の比熱は、レーザーフラッシュ法やＤＳＣ法などにより測定できる。
　また例えば、基板の材料は、ガラス、セラミック及び耐熱性を有する有機高分子・ポリマー、樹脂等であることが好ましい。
　また例えば、基板の厚みは、０．０１ｍｍ以上１０ｍｍ以下が好ましく、０．０５ｍｍ以上５ｍｍ以下がより好ましく、０．０５ｍｍ以上１ｍｍ以下が更に好ましい。
　基板の熱容量や材料や厚みがこの範囲となることで、銅インク１０を適切に酸化及び焼結して、亜酸化銅の膜を好適に製造できる。また、基板上に銅インク１０を塗布又は印刷する方法は任意であってよい。さらに言えば、銅インク１０を基板に塗布又は印刷する工程は必須ではなく、例えば任意の位置に設けられた銅インク１０を後段の工程で加熱してもよい。 (Applying Step)
Next, the obtained copper ink 10 is applied or printed on a substrate (step S12) to form a film on the substrate of the copper ink 10. The material, size, thickness, etc. of the substrate on which the copper ink 10 is applied or printed may be arbitrary.
For example, the specific heat of the substrate [kJ/(kg·K)] is preferably 0.1 to 3, more preferably 0.1 to 2, and even more preferably 0.1 to 1.5. The specific heat of the substrate can be measured by a laser flash method, a DSC method, or the like.
Furthermore, for example, the material of the substrate is preferably glass, ceramic, heat-resistant organic polymer, resin, or the like.
For example, the thickness of the substrate is preferably 0.01 mm or more and 10 mm or less, more preferably 0.05 mm or more and 5 mm or less, and even more preferably 0.05 mm or more and 1 mm or less.
By setting the heat capacity, material, and thickness of the substrate within these ranges, the copper ink 10 can be appropriately oxidized and sintered to suitably produce a cuprous oxide film. Any method may be used to apply or print the copper ink 10 onto the substrate. Furthermore, the step of applying or printing the copper ink 10 onto the substrate is not essential, and for example, the copper ink 10 provided at any position may be heated in a subsequent step.
　（乾燥するステップ）
　次に、銅インク１０を（本実施形態の例では基板上に形成された銅インク１０の膜を）、乾燥させる（ステップＳ１４）。銅インク１０を乾燥させる条件は任意であってよい。
　例えば、銅インク１０を乾燥させる際の温度は、３０℃以上１５０℃以下であることが好ましく、３０℃以上１２０℃以下であることがより好ましく、３０℃以上１００℃以下であることが更に好ましい。
　例えば、銅インク１０を乾燥させる時間は、０．１分以上６０分以下であることが好ましく、０．５分以上６０分以下であることがより好ましく、０．５分以上３０分以下であることが更に好ましい。
　また例えば、銅インク１０を乾燥させる際の雰囲気は、大気および不活性などいずれの雰囲気でも問題無いが、作業性などを考慮すると大気雰囲気であることが好ましい。
　乾燥条件を上記のようにすることで、銅インク１０中の液体成分を適切に除去して、銅粒子を適切に酸化及び焼結できる。ただし、銅インク１０を乾燥させる工程は必須ではない。 (Drying step)
Next, the copper ink 10 (in this embodiment, the film of the copper ink 10 formed on the substrate) is dried (step S14). The conditions for drying the copper ink 10 may be arbitrary.
For example, the temperature at which the copper ink 10 is dried is preferably 30° C. or higher and 150° C. or lower, more preferably 30° C. or higher and 120° C. or lower, and even more preferably 30° C. or higher and 100° C. or lower.
For example, the time for drying the copper ink 10 is preferably 0.1 minutes or more and 60 minutes or less, more preferably 0.5 minutes or more and 60 minutes or less, and even more preferably 0.5 minutes or more and 30 minutes or less.
For example, the atmosphere in which the copper ink 10 is dried may be either air or an inert atmosphere, but air is preferable in consideration of workability.
By setting the drying conditions as described above, it is possible to properly remove the liquid components in the copper ink 10 and properly oxidize and sinter the copper particles. However, the step of drying the copper ink 10 is not essential.
　（焼結するステップ）
　次に、銅インク１０を（本実施形態の例では基板上に形成された銅インク１０の膜を）、所定雰囲気下、かつ所定の波長をピークに有する分光分布の光で加熱することで、銅インク１０中の銅粒子を酸化及び焼結して、亜酸化銅を製造する（ステップＳ１６）。 (Sintering step)
Next, the copper ink 10 (in this embodiment, a film of copper ink 10 formed on a substrate) is heated in a specified atmosphere with light having a spectral distribution with a peak at a specified wavelength, thereby oxidizing and sintering the copper particles in the copper ink 10 to produce cuprous oxide (step S16).
　銅インク１０を加熱する所定雰囲気下とは、酸素濃度が１０％以上２１％以下の雰囲気を指し、酸素濃度が１５％以上２１％以下であることが好ましく、酸素濃度が１８％以上２１％以下であることがより好ましい。このような雰囲気下で銅インク１０を加熱することで、銅粒子を適切に酸化して、亜酸化銅を適切に製造できる。酸素濃度は、ガルバニ電池式、ジルコニア式、ダンベル式等の酸素濃度計で測定できる。 The specified atmosphere in which the copper ink 10 is heated refers to an atmosphere in which the oxygen concentration is 10% or more and 21% or less, preferably 15% or more and 21% or less, and more preferably 18% or more and 21% or less. By heating the copper ink 10 in such an atmosphere, the copper particles can be appropriately oxidized and cuprous oxide can be appropriately produced. The oxygen concentration can be measured using an oxygen concentration meter such as a galvanic cell type, a zirconia type, or a dumbbell type.
　銅インク１０を加熱する所定の波長をピークに有する分光分布の光とは、可視～赤外線領域の波長をピークに有する分光分布の光（可視光帯域から赤外光帯域までの波長帯範囲内の波長をピークに有する分光分布の光）を指し、波長（照射する光のピークとなる強度の波長）が０．６μｍ以上１０μｍ以下の分光分布を有する光であることがより好ましく、０．６μｍ以上５μｍ以下の光であることが更に好ましい。このような波長をピークに有する分光分布の光で銅インク１０を加熱することで、基材ではなく、銅インク１０を効果的に加熱することが可能となり、銅粒子を適切に酸化して、亜酸化銅を適切に、もしくはより適切に製造できる。 Light with a spectral distribution having a peak at a specific wavelength for heating the copper ink 10 refers to light with a spectral distribution having a peak wavelength in the visible to infrared region (light with a spectral distribution having a peak wavelength within the wavelength range from the visible light band to the infrared light band), and more preferably light with a spectral distribution having a wavelength (the wavelength of the peak intensity of the irradiated light) of 0.6 μm or more and 10 μm or less, and even more preferably light of 0.6 μm or more and 5 μm or less. By heating the copper ink 10 with light with a spectral distribution having a peak at such a wavelength, it becomes possible to effectively heat the copper ink 10 rather than the substrate, and the copper particles can be appropriately oxidized to appropriately or more appropriately produce cuprous oxide.
　銅インク１０を加熱する温度である加熱温度は、１８０℃以上５００℃以下であることが好ましく、３００℃以上５００℃以下であることがより好ましく、３００℃以上４５０℃以下であることが更に好ましい。加熱温度をこの範囲とすることで、銅粒子を適切に酸化及び焼結して、亜酸化銅をより適切に製造できる。 The heating temperature at which the copper ink 10 is heated is preferably 180°C or higher and 500°C or lower, more preferably 300°C or higher and 500°C or lower, and even more preferably 300°C or higher and 450°C or lower. By setting the heating temperature within this range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be more appropriately produced.
　銅インク１０を加熱温度で保持する時間である保持時間は、１秒以上６００秒以下であることが好ましく、１０秒以上６００秒以下であることがより好ましく、１０秒以上３００秒以下であることが更に好ましい。保持時間をこの範囲とすることで、銅粒子を適切に酸化及び焼結して、亜酸化銅をより適切に製造できる。 The holding time, which is the time for which the copper ink 10 is held at the heating temperature, is preferably from 1 second to 600 seconds, more preferably from 10 seconds to 600 seconds, and even more preferably from 10 seconds to 300 seconds. By setting the holding time within this range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be more appropriately produced.
　銅インク１０を加熱温度まで昇温する速度である昇温速度は、０．１℃／秒以上５０℃／秒以下であることが好ましく、０．１℃／秒以上１０℃／秒以下であることがより好ましく、０．５℃／秒以上１０℃／秒以下であることが更に好ましい。昇温速度をこの範囲とすることで、銅粒子を適切に酸化及び焼結して、亜酸化銅をより適切に製造できる。 The heating rate, which is the rate at which the copper ink 10 is heated to the heating temperature, is preferably 0.1°C/sec or more and 50°C/sec or less, more preferably 0.1°C/sec or more and 10°C/sec or less, and even more preferably 0.5°C/sec or more and 10°C/sec or less. By keeping the heating rate within this range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be more appropriately produced.
　本実施形態においては、可視～赤外線の波長をピークに有する分光分布の光を出射する光照射部から、銅インク１０に向けて光を照射させることで、銅インク１０を加熱することが好ましい。光照射部としては、可視～赤外線の波長をピークに有する分光分布の光を出射する任意のものを用いてよく、例えば所定の波長帯の光を出射する光源であってよい。このような光源から光を照射することで、銅インク１０を適切に加熱して、亜酸化銅を適切に、もしくはより適切に製造できる。
　ただし、銅インク１０を加熱する方法は、光源からの照射に限られず、例えば、上述で規定した波長をピークに有する分光分布の光の範囲で銅インク１０を加熱可能な任意の手法もしくは装置等を用いてよい。 In the present embodiment, it is preferable to heat the copper ink 10 by irradiating the copper ink 10 with light from a light irradiating unit that emits light with a spectral distribution having a peak in the visible to infrared wavelengths. The light irradiating unit may be any unit that emits light with a spectral distribution having a peak in the visible to infrared wavelengths, and may be, for example, a light source that emits light in a predetermined wavelength band. By irradiating the copper ink 10 with light from such a light source, it is possible to appropriately heat the copper ink 10 and appropriately or more appropriately produce cuprous oxide.
However, the method of heating the copper ink 10 is not limited to irradiation from a light source, and any method or device capable of heating the copper ink 10 within the range of light with a spectral distribution having a peak at the wavelength specified above may be used.
　本実施形態においては、ステップＳ１２、Ｓ１４、Ｓ１６を、一度のみ実施して、亜酸化銅を製造してもよい。すなわち、一回の塗布及び乾燥工程を経て、加熱することで、亜酸化銅を製造してもよい。また例えば、ステップＳ１２、Ｓ１４を複数回繰り返した後、ステップＳ１６を実施してよい。すなわち、塗布及び乾燥工程を複数回繰り返した後、加熱することで、亜酸化銅を製造してもよい。また例えば、ステップＳ１２、Ｓ１４、Ｓ１６を一連の工程として、その一連の工程を複数回繰り返して、亜酸化銅を製造してよい。すなわち、一回の塗布及び乾燥工程を経て加熱する工程を、複数回繰り返してもよい。 In this embodiment, steps S12, S14, and S16 may be performed only once to produce cuprous oxide. That is, cuprous oxide may be produced by heating after a single application and drying process. For example, steps S12 and S14 may be repeated multiple times, and then step S16 may be performed. That is, cuprous oxide may be produced by heating after a single application and drying process. For example, steps S12, S14, and S16 may be a series of steps, and the series of steps may be repeated multiple times to produce cuprous oxide. That is, the process of heating after a single application and drying process may be repeated multiple times.
　（亜酸化銅膜）
　以降で、本実施形態の亜酸化銅（亜酸化銅膜）の特性について説明する。なお、以降においては、本実施形態の製造方法で製造された亜酸化銅（亜酸化銅膜）の特性を説明しているが、本実施形態の亜酸化銅（亜酸化銅膜）は、本実施形態の製造方法で製造されることに限られず、以降で説明する特性の少なくとも１つを満たす亜酸化銅（亜酸化銅膜）であれば、任意の製造方法で製造されたものであってもよい。 (Cuprous oxide film)
The characteristics of the cuprous oxide (cuprous oxide film) of this embodiment will be described below. Note that, although the characteristics of the cuprous oxide (cuprous oxide film) manufactured by the manufacturing method of this embodiment will be described below, the cuprous oxide (cuprous oxide film) of this embodiment is not limited to being manufactured by the manufacturing method of this embodiment, and may be manufactured by any manufacturing method as long as it is cuprous oxide (cuprous oxide film) that satisfies at least one of the characteristics described below.
　本実施形態の亜酸化銅（亜酸化銅膜）は、Ｘ線回折法（ＸＲＤ）で測定した場合に、以下の式（１）から式（１２）に示す、面指数のＣｕ２Ｏの結晶ピークの少なくとも１つが検出されることが好ましい。なお、ここでの結晶ピークとは、強度が閾値以上のピークを指し、ここでの閾値は、例えば測定結果の最大ピーク強度を１００とした場合の相対強度５である。 When the cuprous oxide (cuprous oxide film) of this embodiment is measured by X-ray diffraction (XRD), it is preferable that at least one of the crystal peaks of Cu 2 O having plane indices shown in the following formulas (1) to (12) is detected. Note that the crystal peak here refers to a peak having an intensity equal to or greater than a threshold value, and the threshold value here is, for example, a relative intensity of 5 when the maximum peak intensity of the measurement result is taken as 100.
　２θ＝３３．３５°±１．０°［１１０］　・・・（１）
　２θ＝３６．３７°±１．０°［００２］　・・・（２）
　２θ＝３６．４８°±１．０°［１１－１］　・・・（３）
　２θ＝３９．７２°±１．０°［１１１］　・・・（４）
　２θ＝３９．９７°±１．０°［２００］　・・・（５）
　２θ＝４７．５１°±１．０°［１１－２］　・・・（６）
　２θ＝５０．１０°±１．０°［２０－２］　・・・（７）
　２θ＝５２．７３°±１．０°［１１２］　・・・（８）
　２θ＝５４．９１°±１．０°［０２０］　・・・（９）
　２θ＝５８．２５°±１．０°［０２０］　・・・（１０）
　２θ＝５９．８８°±１．０°［２０２］　・・・（１１）
　２θ＝６３．３０°±１．０°［１１－３］　・・・（１２） 2θ=33.35°±1.0°[110] (1)
2θ=36.37°±1.0°[002] (2)
2θ=36.48°±1.0°[11-1] ... (3)
2θ=39.72°±1.0°[111] (4)
2θ=39.97°±1.0°[200] (5)
2θ=47.51°±1.0°[11-2] ... (6)
2θ=50.10°±1.0°[20-2] ... (7)
2θ=52.73°±1.0°[112] (8)
2θ=54.91°±1.0°[020] (9)
2θ=58.25°±1.0°[020] (10)
2θ=59.88°±1.0°[202] (11)
2θ=63.30°±1.0°[11-3] ... (12)
　なお、Ｘ線回折装置は、リガク社の全自動多目的Ｘ線回折装置（ＳｍａｒｔＬａｂ）を使用できる。Ｘ線回折法の条件は、Ｘ線出力が４５ｋＶ、２００ｍＡで、スキャンモードが連続で、スキャンスピードが１０°／分で、ステップ幅が０．０５°で、スキャン軸が２θで、スキャン範囲が１０～１００°である。 The X-ray diffraction device used can be a fully automated multipurpose X-ray diffraction device (SmartLab) manufactured by Rigaku. The conditions for the X-ray diffraction method are an X-ray output of 45 kV, 200 mA, a continuous scan mode, a scan speed of 10°/min, a step width of 0.05°, a scan axis of 2θ, and a scan range of 10 to 100°.
　本実施形態の亜酸化銅（亜酸化銅膜）は、太陽電池、薄膜トランジスタ、センサ、バリスタ及び触媒の少なくとも１つの用途に適用できる。本実施形態の亜酸化銅は、例えば、膜厚を０．１μｍとした場合において、波長６００ｎｍ～１２００ｎｍの光（可視光～赤外線）の平均の透過率が、４０％以上１００％以下であることが好ましく、５０％以上１００％以下であることがより好ましく、６０％以上１００％以下であることが更に好ましい。可視光の透過率がこの範囲となることで、例えばシースルータイプの太陽電池や結晶シリコン太陽電池をボトムセル（太陽電池）としたタンデム型の太陽電池のトップセル（太陽電池）として適切に利用できる。ここでの透過率は、紫外可視近赤外分光光度計により測定できる。 The cuprous oxide (cuprous oxide film) of this embodiment can be used in at least one of solar cells, thin film transistors, sensors, varistors, and catalysts. When the cuprous oxide of this embodiment has a film thickness of, for example, 0.1 μm, the average transmittance of light (visible light to infrared light) with wavelengths of 600 nm to 1200 nm is preferably 40% to 100%, more preferably 50% to 100%, and even more preferably 60% to 100%. When the visible light transmittance is within this range, the material can be appropriately used, for example, as a see-through type solar cell or as the top cell (solar cell) of a tandem type solar cell with a crystalline silicon solar cell as the bottom cell (solar cell). The transmittance here can be measured using an ultraviolet-visible-near infrared spectrophotometer.
　本実施形態の亜酸化銅（亜酸化銅膜）は、膜厚を０．１μｍとした場合において、波長３００ｎｍ～６００ｎｍの光の平均の透過率（Ｔ１）に対する、波長６００ｎｍ～１２００ｎｍの光の平均の透過率（Ｔ２）の比率（透過率比率：Ｔ２／Ｔ１）が、３．５以上であることが好ましく、４．０以上２０．０以下であることがより好ましく、４．５以上１５．０以下であることが更に好ましい。透過率比率がこの範囲となることで、短波長の光に対して赤外域の光を適切に透過でき、適切な性能を有する亜酸化銅膜にできる。例えばシースルータイプの太陽電池や結晶シリコン太陽電池をボトムセル（太陽電池）としたタンデム型の太陽電池のトップセル（太陽電池）として好適に利用できる。 In the cuprous oxide (cuprous oxide film) of this embodiment, when the film thickness is 0.1 μm, the ratio (transmittance ratio: T 2 /T 1 ) of the average transmittance (T 2 ) of light with a wavelength of 600 nm to 1200 nm to the average transmittance (T 1 ) of light with a wavelength of 300 nm to 600 nm is preferably 3.5 or more, more preferably 4.0 to 20.0, and even more preferably 4.5 to 15.0. When the transmittance ratio is in this range, it is possible to obtain a cuprous oxide film that can appropriately transmit light in the infrared range relative to light with a short wavelength and has appropriate performance. For example, it can be suitably used as a top cell (solar cell) of a tandem solar cell in which a see-through type solar cell or a crystalline silicon solar cell is the bottom cell (solar cell).
　本実施形態の亜酸化銅（亜酸化銅膜）は、厚みが０．１μｍ以上１０００μｍ以下であることが好ましく、０．３μｍ以上１０００μｍ以下であることがより好ましく、０．３μｍ以上５００μｍ以下であることが更に好ましい。厚みをこの範囲とすることで、太陽電池、薄膜トランジスタ、センサ、バリスタ、触媒など、様々な用途へ適切に適用できる。 The cuprous oxide (cuprous oxide film) of this embodiment preferably has a thickness of 0.1 μm or more and 1000 μm or less, more preferably 0.3 μm or more and 1000 μm or less, and even more preferably 0.3 μm or more and 500 μm or less. By keeping the thickness within this range, it can be appropriately applied to various applications such as solar cells, thin film transistors, sensors, varistors, and catalysts.
　本実施形態の亜酸化銅（亜酸化銅膜）は、焼結体であることが好ましい。例えば、本実施形態の亜酸化銅は、焼結密度が、７０％以上であることが好ましく、８０％以上であることがより好ましく、８５％以上であることがさらに好ましい。焼結密度がこの範囲となることで、亜酸化銅は、太陽電池の特性を適切に担保できる。なお、焼結密度とは、開気孔及び閉気孔を含んだ亜酸化銅の体積全体に対する、開気孔及び閉気孔を除いた亜酸化銅の体積の比率を指す。焼結密度は、亜酸化銅の断面をＳＥＭ（Scanning　Electron　Microscope）で倍率５００００倍にて無作為に取得した画像を画像処理ソフト（米国国立衛生研究所製ＩｍａｇｅＪ）を用いて２値化して、粒子部と空孔部とに分け、下記の式より焼結密度を算出した。
　焼結密度（％）＝（粒子部の総面積／（粒子部の総面積＋空孔部の総面積））×１００ The cuprous oxide (cuprous oxide film) of this embodiment is preferably a sintered body. For example, the cuprous oxide of this embodiment preferably has a sintered density of 70% or more, more preferably 80% or more, and even more preferably 85% or more. When the sintered density is in this range, the cuprous oxide can appropriately ensure the characteristics of the solar cell. The sintered density refers to the ratio of the volume of the cuprous oxide excluding the open pores and closed pores to the total volume of the cuprous oxide including the open pores and closed pores. The sintered density was calculated by binarizing the image of the cross section of the cuprous oxide randomly taken at a magnification of 50,000 times with a SEM (Scanning Electron Microscope) using image processing software (ImageJ manufactured by the National Institutes of Health, USA), dividing it into a particle part and a pore part, and calculating the sintered density according to the following formula.
Sintered density (%)=(total area of particle parts/(total area of particle parts+total area of void parts))×100
　ただし上述のように、本実施形態の亜酸化銅（亜酸化銅膜）の製造方法は任意であり、焼結体であることに限られない。 However, as mentioned above, the method for producing the cuprous oxide (cuprous oxide film) of this embodiment is arbitrary and is not limited to being a sintered body.
　（銅インク）
　本実施形態に係る銅インク１０は、上述のように銅粒子を含む液状の組成物であれば、任意の組成物であってよいが、以下に、本実施形態に用いる銅インク１０の好ましい態様を説明する。 (Copper ink)
The copper ink 10 according to this embodiment may be any liquid composition containing copper particles as described above, but preferred embodiments of the copper ink 10 used in this embodiment will be described below.
　図２は、本実施形態に係る銅インクの模式図である。図２に示すように、本実施形態に係る銅インク１０は、銅粒子１２と、多価アルコール１４と、溶媒１６と、有機溶媒１８とを含むことが好ましい。銅インク１０は、液体である溶媒１６中に銅粒子１２が溶解せずに、固体状の銅粒子１２が溶媒１６中に存在しているインク状の物質を指す。銅インク１０においては、溶媒１６中に銅粒子１２が沈降していてもよいし、銅粒子１２が分散していてもよい。 FIG. 2 is a schematic diagram of the copper ink according to this embodiment. As shown in FIG. 2, the copper ink 10 according to this embodiment preferably contains copper particles 12, a polyhydric alcohol 14, a solvent 16, and an organic solvent 18. The copper ink 10 refers to an ink-like substance in which the copper particles 12 do not dissolve in the liquid solvent 16, but rather the solid copper particles 12 are present in the solvent 16. In the copper ink 10, the copper particles 12 may be settled in the solvent 16, or the copper particles 12 may be dispersed.
　（銅粒子）
　銅粒子１２は、銅の粒子である。銅粒子１２は、粒径（粒度分布（個数）のＰｅａｋ値）が１０ｎｍ以上１０００ｎｍ以下であることが好ましい。銅インク１０中の銅粒子１２の粒径は、粒子径測定装置（マルバーン社製、ゼータサイザーナノシリーズ　ＺＳＰ）を用いて、銅粒子の屈折率及び、インク中の溶媒の屈折率、粘度値等の物性値を設定し、測定温度を物性値の温度条件に合わせて、２０℃や２５℃にて測定を行い、銅粒子１２の粒度分布（個数）のＰｅａｋ値として求めることができる。尚、粒度分布の測定において、銅インク１０中の銅粒子１２の濃度が高いことにより、十分な測定品質が得られない場合は、銅インク１０中の主な溶媒（水、エタノールや高沸点溶媒）で１０～１０００倍程度に希釈・分散させた後に測定してもよい。 (Copper particles)
The copper particles 12 are copper particles. The copper particles 12 preferably have a particle size (peak value of particle size distribution (number)) of 10 nm or more and 1000 nm or less. The particle size of the copper particles 12 in the copper ink 10 can be determined as the peak value of the particle size distribution (number) of the copper particles 12 by setting physical property values such as the refractive index of the copper particles and the refractive index and viscosity value of the solvent in the ink using a particle size measuring device (Zetasizer Nano Series ZSP, manufactured by Malvern Instruments), and measuring at 20°C or 25°C according to the temperature conditions of the physical property values. In addition, when the concentration of the copper particles 12 in the copper ink 10 is high and sufficient measurement quality cannot be obtained in the measurement of the particle size distribution, the copper particles 12 may be diluted and dispersed about 10 to 1000 times with the main solvent in the copper ink 10 (water, ethanol, or a high boiling point solvent) and then measured.
　粒径が１０ｎｍ以下であると、粒径に反比例して比表面積が大きくなるため、表面酸化の影響が大きくなり、銅粒子１２を用いて得られた塗膜の焼結性が低下する恐れがある。一方、銅粒子１２の粒径が１０００ｎｍ以上であると、粒径が大きくなりすぎるため、溶媒中に分散したインクにおいて、銅粒子１２が沈降分離し易くなる恐れがある。銅粒子１２の粒径は、３０ｎｍ以上５００ｎｍ以下の範囲内にあることが好ましく、３０ｎｍ以上３００ｎｍ以下の範囲内にあることが特に好ましい。 If the particle size is 10 nm or less, the specific surface area increases inversely proportional to the particle size, which increases the effect of surface oxidation and may reduce the sinterability of the coating film obtained using the copper particles 12. On the other hand, if the particle size of the copper particles 12 is 1000 nm or more, the particle size becomes too large and there is a risk that the copper particles 12 may easily settle out and separate in the ink dispersed in the solvent. The particle size of the copper particles 12 is preferably in the range of 30 nm to 500 nm, and particularly preferably in the range of 30 nm to 300 nm.
　銅粒子１２のＢＥＴ比表面積は、比表面積測定装置（カンタクローム・インスツルメンツ社製、ＱＵＡＮＴＡＣＨＲＯＭＥ　ＡＵＴＯＳＯＲＢ－ｉＱ２）にて、測定ガスとして窒素又はクリプトンガスを用いて、銅粒子１２のガスの吸着量を測定することにより求めることができる。銅粒子１２のＢＥＴ比表面積は、２．０ｍ２／ｇ以上８．０ｍ２／ｇ以下の範囲内にあることが好ましく、３．５ｍ２／ｇ以上８．０ｍ２／ｇ以下の範囲内にあることがより好ましく、４．０ｍ２／ｇ以上８．０ｍ２／ｇ以下の範囲内にあることが特に好ましい。また、銅粒子１２の形状は、球状に限らず、針状、扁平な板状でもよい。 The BET specific surface area of the copper particles 12 can be determined by measuring the amount of gas adsorption of the copper particles 12 using nitrogen or krypton gas as a measurement gas with a specific surface area measuring device (Quantachrome Instruments, QUANTACROME AUTOSORB-iQ2). The BET specific surface area of the copper particles 12 is preferably in the range of 2.0 m 2 /g to 8.0 m 2 /g, more preferably in the range of 3.5 m 2 /g to 8.0 m 2 /g, and particularly preferably in the range of 4.0 m 2 /g to 8.0 m 2 /g. The shape of the copper particles 12 is not limited to a spherical shape, and may be a needle shape or a flat plate shape.
　銅粒子１２は、表面が、有機物で一部または全面を被覆されていることが好ましい。有機物で被覆されていることにより、銅粒子１２の酸化が抑制され、銅粒子１２の酸化による焼結性の低下がさらに起こりにくくなる。なお、銅粒子１２を被覆する有機物は、多価アルコール１４や溶媒１６によって形成されるものでなく、多価アルコール１４や溶媒１６由来のものでないといえる。また、銅粒子１２を被覆する有機物は、金属の酸化により形成される酸化金属（酸化銅）ではないともいえる。 The surfaces of the copper particles 12 are preferably partially or entirely coated with an organic substance. By being coated with an organic substance, oxidation of the copper particles 12 is suppressed, and a decrease in sinterability due to oxidation of the copper particles 12 is further prevented. The organic substance coating the copper particles 12 is not formed by the polyhydric alcohol 14 or the solvent 16, and can be said to be not derived from the polyhydric alcohol 14 or the solvent 16. It can also be said that the organic substance coating the copper particles 12 is not a metal oxide (copper oxide) formed by the oxidation of a metal.
　銅粒子１２が有機物で被覆されていることは、飛行時間型二次イオン質量分析法（ＴＯＦ－ＳＩＭＳ）を用いて、銅粒子１２の表面を分析することに確認することができる。銅粒子１２は、飛行時間型二次イオン質量分析法を用いて、表面を分析することによって検出されるＣｕ＋イオンの検出量に対するＣ３Ｈ３Ｏ３ －イオンの検出量の比（Ｃ３Ｈ３Ｏ３ －／Ｃｕ＋比）が０．００１以上であることが好ましい。Ｃ３Ｈ３Ｏ３ －／Ｃｕ＋比は、０．０５以上０．２以下の範囲内にあることがさらに好ましい。なお、本分析における銅粒子１２の表面とは、銅粒子１２から有機物を除去した際の銅粒子１２の表面でなく、被覆している有機物を含んだ銅粒子１２の表面（すなわち有機物の表面）を指す。 The fact that the copper particles 12 are coated with an organic substance can be confirmed by analyzing the surface of the copper particles 12 using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The ratio of the amount of C 3 H 3 O 3 - ions to the amount of Cu + ions detected by analyzing the surface of the copper particles 12 using time-of-flight secondary ion mass spectrometry (C 3 H 3 O 3 - /Cu + ratio) is preferably 0.001 or more. It is more preferable that the C 3 H 3 O 3 - / Cu + ratio is in the range of 0.05 to 0.2 . Note that the surface of the copper particles 12 in this analysis does not refer to the surface of the copper particles 12 when the organic substance is removed from the copper particles 12, but refers to the surface of the copper particles 12 containing the organic substance that coats it (i.e., the surface of the organic substance).
　銅粒子１２は、飛行時間型二次イオン質量分析法を用いて、表面を分析することによってＣ３Ｈ４Ｏ２ －イオンやＣ５以上のイオンが検出されてもよい。Ｃｕ＋イオンの検出量に対するＣ３Ｈ４Ｏ２ －イオンの検出量の比（Ｃ３Ｈ４Ｏ２ －／Ｃｕ＋比）は０．００１以上であることが好ましい。また、Ｃｕ＋イオンの検出量に対するＣ５以上のイオンの検出量の比（Ｃ５以上のイオン／Ｃｕ＋比）は０．００５未満であることが好ましい。 The copper particles 12 may be subjected to surface analysis using time-of-flight secondary ion mass spectrometry to detect C 3 H 4 O 2 - ions and C 5 or higher ions. The ratio of the amount of C 3 H 4 O 2 - ions to the amount of Cu + ions (C 3 H 4 O 2 - /Cu + ratio) is preferably 0.001 or more. In addition, the ratio of the amount of C 5 or higher ions to the amount of Cu + ions (C 5 or higher ions/Cu + ratio) is preferably less than 0.005.
　飛行時間型二次イオン質量分析法において検出されるＣ３Ｈ３Ｏ３ －イオンとＣ３Ｈ４Ｏ２ －イオンとＣ５以上のイオンは、銅粒子１２の表面を被覆している有機物に由来する。このためＣ３Ｈ３Ｏ３ －／Ｃｕ＋比とＣ３Ｈ４Ｏ２ －／Ｃｕ＋比のそれぞれが０．００１以上であると、銅粒子１２の表面が酸化しにくくなり、かつ銅粒子１２が凝集しにくくなる。また、Ｃ３Ｈ３Ｏ３ －／Ｃｕ＋比及びＣ３Ｈ４Ｏ２ －／Ｃｕ＋比が０．２以下であると、銅粒子１２の焼結性を過度に低下させずに銅粒子１２の酸化と凝集を抑制でき、さらに加熱時における有機物の分解ガスの発生を抑えることができるので、ボイドが少ない亜酸化銅を形成することができる。銅粒子１２の保存中の耐酸化性をより一層向上し、かつ低温度での焼結性をより一層向上させるために、Ｃ３Ｈ３Ｏ３ －／Ｃｕ＋比及びＣ３Ｈ４Ｏ２ －／Ｃｕ＋比は０．０８以上０．１６以下の範囲内にあることが好ましい。また、Ｃ５以上のイオン／Ｃｕ＋比が０．００５倍以上であると、粒子表面に脱離温度が比較的高い有機物が多く存在するため、結果として焼結性が十分に発現せず強固な亜酸化銅が得られにくい。Ｃ５以上のイオン／Ｃｕ＋比は０．００３倍未満であることが好ましい。 The C 3 H 3 O 3 - ions, C 3 H 4 O 2 - ions, and C 5 or more ions detected by time-of-flight secondary ion mass spectrometry are derived from organic matter coating the surface of the copper particles 12. Therefore, when the C 3 H 3 O 3 - /Cu + ratio and the C 3 H 4 O 2 - /Cu + ratio are each 0.001 or more, the surface of the copper particles 12 is less likely to oxidize and the copper particles 12 are less likely to aggregate. Furthermore, when the C 3 H 3 O 3 - /Cu + ratio and the C 3 H 4 O 2 - /Cu + ratio are 0.2 or less, the oxidation and aggregation of the copper particles 12 can be suppressed without excessively reducing the sinterability of the copper particles 12, and further, the generation of decomposition gas of the organic matter during heating can be suppressed, so that cuprous oxide with fewer voids can be formed. In order to further improve the oxidation resistance during storage of the copper particles 12 and further improve the sinterability at low temperatures, the C 3 H 3 O 3 - /Cu + ratio and the C 3 H 4 O 2 - /Cu + ratio are preferably in the range of 0.08 to 0.16. Furthermore, if the C 5 or more ion/Cu + ratio is 0.005 times or more, a large amount of organic matter with a relatively high desorption temperature is present on the particle surface, resulting in insufficient sinterability and making it difficult to obtain strong cuprous oxide. The C 5 or more ion/Cu + ratio is preferably less than 0.003 times.
　銅粒子１２を被覆する有機物は、銅粒子１２を製造する時に用いられるカルボン酸金属に由来するカルボン酸であることが好ましい。カルボン酸由来の有機物で被覆された銅粒子１２の製造方法は後述する。銅粒子１２の有機物の被覆量は、銅粒子１００質量％に対して０．５質量％以上２．０質量％以下の範囲内にあることが好ましく、０．８質量％以上１．８質量％以下の範囲内にあることがより好ましく、０．８質量％以上１．５質量％以下の範囲内にあることがさらに好ましい。有機物の被覆量が０．５質量％以上であることによって、銅粒子１２を有機物により均一に被覆することができ、銅粒子１２の酸化をより確実に抑制することができる。また、有機物の被覆量が２．０質量％以下であることによって、加熱による有機物の分解によって発生するガスにより、銅粒子の焼結体（接合層）にボイドが発生することを抑制することができる。有機物の被覆量は、市販の装置を用いて測定することができる。例えば、差動型示差熱天秤ＴＧ８１２０－ＳＬ（ＲＩＧＡＫＵ社製）を用いて、被覆量を測定できる。この場合例えば、試料は、凍結乾燥により水分を除去した銅粒子を用いる。銅粒子の酸化を抑制するため窒素(Ｇ２グレード)ガス中で測定し、昇温速度は１０℃／ｍｉｎとし、２５０℃から３００℃まで加熱したときの重量減少率を、有機物の被覆量と定義できる。すなわち、被覆量＝(測定後の試料重量)／(測定前の試料重量)×１００(ｗｔ％)である。測定は同一ロットの銅粒子で各々３回行い、相加平均値を被覆量としてよい。 The organic matter that coats the copper particles 12 is preferably a carboxylic acid derived from a carboxylic acid metal used in producing the copper particles 12. A method for producing copper particles 12 coated with an organic matter derived from a carboxylic acid will be described later. The amount of the organic matter coated on the copper particles 12 is preferably in the range of 0.5% by mass to 2.0% by mass, more preferably in the range of 0.8% by mass to 1.8% by mass, and even more preferably in the range of 0.8% by mass to 1.5% by mass, relative to 100% by mass of the copper particles. By having an organic matter coating amount of 0.5% by mass or more, the copper particles 12 can be uniformly coated with the organic matter, and oxidation of the copper particles 12 can be more reliably suppressed. In addition, by having an organic matter coating amount of 2.0% by mass or less, it is possible to suppress the generation of voids in the sintered body (bonding layer) of the copper particles due to gas generated by decomposition of the organic matter by heating. The amount of the organic matter coating can be measured using a commercially available device. For example, the amount of coating can be measured using a differential thermobalance TG8120-SL (manufactured by RIGAKU Corporation). In this case, for example, copper particles from which moisture has been removed by freeze-drying are used as the sample. Measurements are made in nitrogen (G2 grade) gas to suppress oxidation of the copper particles, and the temperature rise rate is set to 10°C/min. The weight loss rate when heated from 250°C to 300°C can be defined as the amount of organic coating. In other words, coating amount = (sample weight after measurement) / (sample weight before measurement) x 100 (wt%). Measurements are made three times for each of the same lot of copper particles, and the arithmetic mean value can be used as the amount of coating.
　銅粒子１２は、アルゴンガスなどの不活性ガス雰囲気下、３００℃の温度で３０分加熱したときに、有機物の５０質量％以上が分解することが好ましい。カルボン酸由来の有機物は、分解時に二酸化炭素ガス、窒素ガス、アセトンの蒸発ガス及び水蒸気を発生する。 When the copper particles 12 are heated for 30 minutes at 300°C in an inert gas atmosphere such as argon gas, it is preferable that 50% or more by mass of the organic matter is decomposed. When the organic matter derived from carboxylic acid is decomposed, it generates carbon dioxide gas, nitrogen gas, evaporated acetone gas, and water vapor.
　（多価アルコール）
　多価アルコール１４は、ＯＨ基を２つ以上含み、水及びエタノールに溶解可能なアルコールであることが好ましい。また、多価アルコール１４は、融点が３０℃以上であることが好ましい。 (Polyhydric alcohol)
The polyhydric alcohol 14 preferably contains two or more OH groups and is soluble in water and ethanol. The polyhydric alcohol 14 preferably has a melting point of 30° C. or higher.
　多価アルコール１４は、例えば、２，２－ジメチル－１，３－プロパンジオール、２，５－ジメチル－２，５－ヘキサンジオール、２－ヒドロキシメチル－２－メチル－１，３－プロパンジオール、１－フェニル－１，２－エタンジオール、１，１，１－トリス（ヒドロキシメチル）プロパン、エリトリトール、ペンタエリトリトール、リビトール、レソルシノール、（ピロ）カテコール、５－メチルレソルシノール、ピロガロール、１，２，３－シクロヘキサントリオール、及び１，３，５－シクロヘキサントリオールのうちの、少なくとも１つであってよい。 The polyhydric alcohol 14 may be, for example, at least one of 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2-hydroxymethyl-2-methyl-1,3-propanediol, 1-phenyl-1,2-ethanediol, 1,1,1-tris(hydroxymethyl)propane, erythritol, pentaerythritol, ribitol, resorcinol, (pyro)catechol, 5-methylresorcinol, pyrogallol, 1,2,3-cyclohexanetriol, and 1,3,5-cyclohexanetriol.
　多価アルコール１４は、非電解質であり、溶媒１６に溶解した状態で（多価アルコール１４の分子が溶媒１６中に分散した状態で）、銅インク１０中に存在している。ただし、多価アルコール１４の銅インク１０中での存在形態は任意であり、溶媒１６に溶解しない状態であってもよい。 The polyhydric alcohol 14 is a non-electrolyte, and is present in the copper ink 10 in a state dissolved in the solvent 16 (the molecules of the polyhydric alcohol 14 are dispersed in the solvent 16). However, the form in which the polyhydric alcohol 14 is present in the copper ink 10 is arbitrary, and it may be in a state in which it is not dissolved in the solvent 16.
　多価アルコール１４が銅インク１０に含まれることで、銅粒子１２の周囲に多価アルコール１４が配位して、銅粒子１２の凝集を適切に抑制できる。すなわち、本実施形態においては、多価アルコール１４が、銅粒子１２の周囲に配位していることが好ましいといえる。 By including polyhydric alcohol 14 in copper ink 10, polyhydric alcohol 14 is coordinated around copper particles 12, and aggregation of copper particles 12 can be appropriately suppressed. In other words, in this embodiment, it is preferable that polyhydric alcohol 14 is coordinated around copper particles 12.
　（溶媒）
　溶媒１６は、銅粒子１２を分散させるための液体（媒体）である。溶媒１６の詳細については後述する。 (solvent)
The solvent 16 is a liquid (medium) for dispersing the copper particles 12. Details of the solvent 16 will be described later.
　（有機溶媒）
　有機溶媒１８は、多価アルコール１４及び溶媒１６とは異なる成分の有機溶媒である。有機溶媒１８は、大気圧における沸点が１５０℃以上であり、水と混和可能な有機溶媒である。有機溶媒１８は、沸点が２００℃以上であることがより好ましい。ここでの混和可能とは、有機溶媒１８が、あらゆる比率で水に混ぜ合せ可能（すなわち、お互い任意の濃度で完全に溶解可能）であることを指している。本実施形態では、有機溶媒１８は、溶媒１６と混和可能であることが好ましい。 (Organic solvent)
The organic solvent 18 is an organic solvent having a different component from the polyhydric alcohol 14 and the solvent 16. The organic solvent 18 is an organic solvent having a boiling point of 150° C. or higher at atmospheric pressure and miscible with water. The organic solvent 18 more preferably has a boiling point of 200° C. or higher. Here, miscible means that the organic solvent 18 can be mixed with water in any ratio (i.e., they can be completely dissolved in each other at any concentration). In this embodiment, the organic solvent 18 is preferably miscible with the solvent 16.
　有機溶媒１８は、グリコールエーテル又は非プロトン性極性溶媒であることが好ましい。さらに言えば、有機溶媒１８は、グリコールエーテル及び非プロトン性極性溶媒の両方を含んでいてよく、言い換えれば、グリコールエーテル及び非プロトン性極性溶媒の少なくとも１つを含むことが好ましいといえる。
　有機溶媒１８が含むグリコールエーテルとしては、例えば、ジエチレングリコールモノメチルエーテル、トリエチレングリコールモノメチルエーテル、ポリエチレングリコールモノメチルエーテル、ジエチレングリコールモノイソプロピルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノブチルエーテル、トリエチレングリコールモノブチルエーテル、エチレングリコールイソブチルエーテル、ジエチレングリコールモノイソブチルエーテル、エチレングリコールモノアリルエーテル、ジエチレングリコールモノベンジルエーテル、ジプロピレングリコールモノメチルエーテル、トリプロピレングリコールモノメチルエーテル、プロピレングリコールモノプロピルエーテル、ジエチレングリコールジメチルエーテル、トリエチレングリコールジメチルエーテル、ジエチレングリコールメチルエチルエーテル、及びジエチレングリコールジエチルエーテルが挙げられる。有機溶媒１８がグリコールエーテルを含む場合には、これらの列挙したものから選択された少なくとも１つを含んでよい。
　有機溶媒１８が含む非プロトン性極性溶媒としては、例えば、Ｎ－メチルピロリドン、ジメチルホルムアミド、２－ピロリドン、及び炭酸プロピレンが挙げられる。有機溶媒１８が非プロトン性極性溶媒を含む場合には、これらの列挙したものから選択された少なくとも１つを含んでよい。 The organic solvent 18 is preferably a glycol ether or an aprotic polar solvent. More specifically, the organic solvent 18 may include both a glycol ether and an aprotic polar solvent, in other words, it is preferable that the organic solvent 18 includes at least one of a glycol ether and an aprotic polar solvent.
Examples of glycol ethers contained in the organic solvent 18 include diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, diethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol isobutyl ether, diethylene glycol monoisobutyl ether, ethylene glycol monoallyl ether, diethylene glycol monobenzyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monopropyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and diethylene glycol diethyl ether. When the organic solvent 18 contains a glycol ether, it may contain at least one selected from the above.
Examples of the aprotic polar solvent contained in the organic solvent 18 include N-methylpyrrolidone, dimethylformamide, 2-pyrrolidone, and propylene carbonate. When the organic solvent 18 contains an aprotic polar solvent, it may contain at least one selected from these listed solvents.
　（銅インク）
　銅インク１０は、多価アルコール１４の含有量が、銅インク１０の全体に対して、質量比で、０．０１％以上２０％以下であることが好ましい。多価アルコール１４の含有量がこの範囲となることで、銅粒子１２を適切に分散させつつ、銅粒子１２の濃度が低くなり過ぎることを抑制できる。 (Copper ink)
The content of the polyhydric alcohol 14 in the copper ink 10 is preferably 0.01% or more and 20% or less by mass ratio with respect to the entire copper ink 10. When the content of the polyhydric alcohol 14 is in this range, the copper particles 12 can be appropriately dispersed while preventing the concentration of the copper particles 12 from becoming too low.
　銅インク１０は、銅粒子１２の含有量が、銅インク１０の全体に対して、質量比で、１％以上５０％以下であることが好ましく、５％以上５０％以下であることがより好ましく、５％以上３０％以下であることがさらに好ましい。銅粒子１２の含有量がこの範囲となることで、銅粒子１２の濃度を十分に保ちつつ、銅インク１０の流動性の低下を抑制できるため、例えばノズルによる噴射性を向上させるなど、製造面でも有利となる。 The copper ink 10 preferably contains copper particles 12 in a mass ratio of 1% to 50%, more preferably 5% to 50%, and even more preferably 5% to 30% of the total copper ink 10. Having a copper particle 12 content within this range makes it possible to suppress a decrease in the fluidity of the copper ink 10 while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
　銅インク１０は、溶媒１６の含有量が、銅インク１０の全体に対して、質量比で、５０％以上９９％以下であることが好ましく、５０％以上９５％以下であることがより好ましく、６０％以上９５％以下であることがさらに好ましい。溶媒１６の含有量がこの範囲となることで、銅粒子１２の濃度を十分に保ちつつ、銅インク１０の流動性の低下を抑制できるため、例えばノズルによる噴射性を向上させるなど、製造面でも有利となる。 The content of the solvent 16 in the copper ink 10 is preferably 50% to 99% by mass, more preferably 50% to 95%, and even more preferably 60% to 95% by mass, relative to the total mass of the copper ink 10. By having the content of the solvent 16 within this range, it is possible to suppress a decrease in the fluidity of the copper ink 10 while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
　銅インク１０は、有機溶媒１８の含有量が、銅インク１０の全体に対して、質量比で、０．０１％以上２０％以下であることが好ましく、０．１％以上２０％以下であることがさらに好ましい。有機溶媒１８の含有量がこの範囲となることで、銅インク１０を長期間放置した場合でも、防黴性が十分となり、長期間適切に保存できる。 The content of organic solvent 18 in copper ink 10 is preferably 0.01% to 20% by mass, and more preferably 0.1% to 20% by mass, relative to the total mass of copper ink 10. By having the content of organic solvent 18 within this range, even if copper ink 10 is left for a long period of time, it has sufficient mold resistance and can be appropriately stored for a long period of time.
　銅インク１０は、イオン化した銅粒子１２（銅粒子１２を構成する金属のイオン）を含んでよい。すなわち、銅インク１０の液体成分中に、イオン化した銅粒子１２が含まれていてもよい。イオン化した銅粒子１２は、銅イオンであってよいといえる。 The copper ink 10 may contain ionized copper particles 12 (ions of the metal that constitutes the copper particles 12). In other words, the liquid component of the copper ink 10 may contain ionized copper particles 12. It can be said that the ionized copper particles 12 may be copper ions.
　以上説明した銅インク１０は、溶媒１６の成分にバリエーションを持たせることができる。以下、溶媒１６の成分が異なるそれぞれの銅インク１０について説明する。 The copper ink 10 described above can have a variety of solvent 16 components. Below, we will explain each copper ink 10 with a different solvent 16 component.
　（第１銅インク）
　溶媒１６の成分が異なるそれぞれの銅インク１０のうちの１つを、第１銅インク１０Ａとする。第１銅インク１０Ａは、溶媒１６が水である。第１銅インク１０Ａは、溶媒１６である水に多価アルコール１４及び有機溶媒１８が溶解しつつ、銅粒子１２が混合されたものとなる。すなわち、第１銅インク１０Ａは、多価アルコール１４及び有機溶媒１８の水溶液に、銅粒子１２が含まれたものとなる。 (First copper ink)
One of the copper inks 10 having different components of the solvent 16 is referred to as a first copper ink 10A. In the first copper ink 10A, the solvent 16 is water. In the first copper ink 10A, the polyhydric alcohol 14 and the organic solvent 18 are dissolved in the water, which is the solvent 16, and copper particles 12 are mixed in. In other words, the first copper ink 10A is an aqueous solution of the polyhydric alcohol 14 and the organic solvent 18, which contains the copper particles 12.
　第１銅インク１０Ａは、多価アルコール１４の含有量が、第１銅インク１０Ａの全体に対して、質量比で、０．１％以上２０％以下であることが好ましく、０．５％以上２０％以下であることがより好ましく、１％以上２０％以下であることがさらに好ましい。多価アルコール１４の含有量がこの範囲となることで、銅粒子１２を適切に分散させつつ、銅粒子１２の濃度が低くなり過ぎることを抑制できる。 The content of polyhydric alcohol 14 in the first copper ink 10A is preferably 0.1% to 20% by mass, more preferably 0.5% to 20% by mass, and even more preferably 1% to 20% by mass, relative to the entire first copper ink 10A. By having the content of polyhydric alcohol 14 in this range, it is possible to properly disperse the copper particles 12 while preventing the concentration of the copper particles 12 from becoming too low.
　第１銅インク１０Ａは、銅粒子１２の含有量が、第１銅インク１０Ａの全体に対して、質量比で、１％以上５０％以下であることが好ましく、５％以上５０％以下であることがより好ましく、５％以上３０％以下であることがさらに好ましい。銅粒子１２の含有量がこの範囲となることで、銅粒子１２の濃度を十分に保ちつつ、第１銅インク１０Ａの流動性の低下を抑制できるため、例えばノズルによる噴射性を向上させるなど、製造面でも有利となる。 The content of copper particles 12 in the first copper ink 10A is preferably 1% to 50% by mass, more preferably 5% to 50%, and even more preferably 5% to 30% by mass, relative to the entire first copper ink 10A. Having the content of copper particles 12 within this range makes it possible to suppress a decrease in the fluidity of the first copper ink 10A while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
　第１銅インク１０Ａは、有機溶媒１８の含有量が、第１銅インク１０Ａの全体に対して、質量比で、０．５％以上２０％以下であることが好ましく、１％以上２０％以下であることがより好ましく、２％以上２０％以下であることがさらに好ましい。有機溶媒１８の含有量がこの範囲となることで、長期間適切に保存できる。 The content of organic solvent 18 in first copper ink 10A is preferably 0.5% to 20% by mass, more preferably 1% to 20%, and even more preferably 2% to 20% by mass, relative to the entire first copper ink 10A. By having the content of organic solvent 18 in this range, the ink can be appropriately stored for a long period of time.
　本実施形態では、第１銅インク１０Ａは、不可避的不純物を除き、銅粒子１２、多価アルコール１４、水である溶媒１６、及び有機溶媒１８以外の物質を含まないことが好ましい。ただしそれに限られず、第１銅インク１０Ａは、銅粒子１２、多価アルコール１４、水である溶媒１６及び有機溶媒１８以外の添加剤（分散剤、密着性付与剤、レオロジー調整剤、防錆剤等）を含むものであってもよい。 In this embodiment, it is preferable that the first copper ink 10A does not contain any substances other than the copper particles 12, the polyhydric alcohol 14, the water solvent 16, and the organic solvent 18, except for unavoidable impurities. However, without being limited thereto, the first copper ink 10A may contain additives (dispersants, adhesion imparting agents, rheology adjusters, rust inhibitors, etc.) other than the copper particles 12, the polyhydric alcohol 14, the water solvent 16, and the organic solvent 18.
　（第２銅インク）
　溶媒１６の成分が異なるそれぞれの銅インク１０のうちの１つを、第２銅インク１０Ｂとする。第２銅インク１０Ｂは、溶媒１６としてエタノールを含み、さらに言えば、溶媒１６のうちの主要成分である主溶媒がエタノールである。ここでの主溶媒は、溶媒１６の全体のうちで、含有量が質量比で５０％より高いものを指す。第２銅インク１０Ｂは、溶媒１６として、主溶媒であるエタノール以外を含んでもよく、本実施形態では、水を含んでよい。第２銅インク１０Ｂは、溶媒１６に多価アルコール１４及び有機溶媒１８が溶解しつつ、銅粒子１２が混合されたものとなる。すなわち例えば、第２銅インク１０Ｂは、多価アルコール１４、有機溶媒１８及びエタノールの水溶液に、銅粒子１２が含まれたものとなる。 (Second copper ink)
One of the copper inks 10 having different components of the solvent 16 is referred to as the second copper ink 10B. The second copper ink 10B contains ethanol as the solvent 16, and more specifically, the main solvent, which is the main component of the solvent 16, is ethanol. The main solvent here refers to a solvent 16 whose content is higher than 50% by mass. The second copper ink 10B may contain a solvent 16 other than ethanol, which is the main solvent, and may contain water in this embodiment. The second copper ink 10B is a mixture of the polyhydric alcohol 14 and the organic solvent 18 dissolved in the solvent 16 and the copper particles 12 mixed therein. That is, for example, the second copper ink 10B is a mixture of the copper particles 12 and an aqueous solution of the polyhydric alcohol 14, the organic solvent 18, and ethanol.
　第２銅インク１０Ｂは、多価アルコール１４の含有量が、第２銅インク１０Ｂの全体に対して、質量比で、０．０１％以上１０％以下であることが好ましく、０．１％以上１０％以下であることがより好ましく、０．１％以上５％以下であることがさらに好ましい。多価アルコール１４の含有量がこの範囲となることで、銅粒子１２を適切に分散させつつ、銅粒子１２の濃度が低くなり過ぎることを抑制できる。 The content of polyhydric alcohol 14 in second copper ink 10B is preferably 0.01% to 10% by mass, more preferably 0.1% to 10% by mass, and even more preferably 0.1% to 5% by mass, relative to the entire second copper ink 10B. By having the content of polyhydric alcohol 14 in this range, it is possible to properly disperse copper particles 12 while preventing the concentration of copper particles 12 from becoming too low.
　第２銅インク１０Ｂは、銅粒子１２の含有量が、第２銅インク１０Ｂの全体に対して、質量比で、１％以上５０％以下であることが好ましく、５％以上５０％以下であることがより好ましく、５％以上３０％以下であることがさらに好ましい。銅粒子１２の含有量がこの範囲となることで、銅粒子１２の濃度を十分に保ちつつ、第２銅インク１０Ｂの流動性の低下を抑制できるため、例えばノズルによる噴射性を向上させるなど、製造面でも有利となる。 The second copper ink 10B preferably contains copper particles 12 in a mass ratio of 1% to 50% relative to the entire second copper ink 10B, more preferably 5% to 50%, and even more preferably 5% to 30%. Having the copper particles 12 content in this range makes it possible to suppress a decrease in the fluidity of the second copper ink 10B while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
　第２銅インク１０Ｂは、エタノールの含有量が、第２銅インク１０Ｂの全体に対して、質量比で、５０％以上９９％以下であることが好ましく、５０％以上９５％以下であることがより好ましく、６０％以上９５％以下であることがさらに好ましい。エタノールの含有量がこの範囲となることで、銅粒子１２の濃度を十分に保ちつつ、第２銅インク１０Ｂの流動性の低下を抑制できるため、例えばノズルによる噴射性を向上させるなど、製造面でも有利となる。 The ethanol content of the second copper ink 10B is preferably 50% to 99% by mass, more preferably 50% to 95%, and even more preferably 60% to 95% by mass, relative to the entire second copper ink 10B. By having the ethanol content within this range, it is possible to suppress a decrease in the fluidity of the second copper ink 10B while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the sprayability from a nozzle.
　第２銅インク１０Ｂは、有機溶媒１８の含有量が、第２銅インク１０Ｂの全体に対して、質量比で、０．０１％以上２０％以下であることが好ましく、０．１％以上２０％以下であることがより好ましく、０．５％以上２０％以下であることがさらに好ましい。有機溶媒１８の含有量がこの範囲となることで、長期間適切に保存できる。 The content of organic solvent 18 in second copper ink 10B is preferably 0.01% or more and 20% or less, more preferably 0.1% or more and 20% or less, and even more preferably 0.5% or more and 20% or less, by mass ratio relative to the entire second copper ink 10B. By having the content of organic solvent 18 in this range, the ink can be appropriately stored for a long period of time.
　本実施形態では、第２銅インク１０Ｂは、不可避的不純物を除き、銅粒子１２、多価アルコール１４、溶媒１６（ここでは水及びエタノール）、及び有機溶媒１８以外の物質を含まないことが好ましい。ただしそれに限られず、第２銅インク１０Ｂは、銅粒子１２、多価アルコール１４、溶媒１６、及び有機溶媒１８以外の添加剤（分散剤、密着性付与剤、レオロジー調整剤、防錆剤等）を含むものであってもよい。 In this embodiment, the second copper ink 10B preferably does not contain any substances other than the copper particles 12, the polyhydric alcohol 14, the solvent 16 (here, water and ethanol), and the organic solvent 18, except for unavoidable impurities. However, without being limited thereto, the second copper ink 10B may contain additives (dispersants, adhesion imparting agents, rheology adjusters, rust inhibitors, etc.) other than the copper particles 12, the polyhydric alcohol 14, the solvent 16, and the organic solvent 18.
　エタノールを主溶媒とする銅インクは、エタノールにより銅粒子が凝集するおそれがある。それに対し、第２銅インク１０Ｂは、多価アルコール１４が混合されることで、例えば銅粒子１２の周囲に多価アルコール１４が配位して、銅粒子１２同士の凝集を抑制できる。 In copper inks that use ethanol as the main solvent, there is a risk that the copper particles will aggregate due to the ethanol. In contrast, the second copper ink 10B is mixed with polyhydric alcohol 14, which, for example, coordinates around the copper particles 12, making it possible to suppress aggregation between the copper particles 12.
　（第３銅インク）
　溶媒１６の成分が異なるそれぞれの銅インク１０のうちの１つを、第３銅インク１０Ｃとする。第３銅インク１０Ｃは、溶媒１６として高沸点溶媒を含み、さらに言えば、溶媒１６のうちの主要成分である主溶媒が高沸点溶媒である。例えば、第３銅インク１０Ｃは、溶媒１６に多価アルコール１４及び有機溶媒１８が溶解しつつ、銅粒子１２が含まれたものとなる。なお、第３銅インク１０Ｃは、溶媒１６として、主溶媒である高沸点溶媒以外を含んでもよい。第３銅インク１０Ｃは、溶媒１６として、水及びエタノールの少なくとも１つを含んでよく、本実施形態では水及びエタノールの両方を含む。 (Third copper ink)
One of the copper inks 10 having different components of the solvent 16 is referred to as a third copper ink 10C. The third copper ink 10C contains a high-boiling point solvent as the solvent 16, and more specifically, the main solvent, which is the main component of the solvent 16, is a high-boiling point solvent. For example, the third copper ink 10C contains copper particles 12 while the polyhydric alcohol 14 and the organic solvent 18 are dissolved in the solvent 16. Note that the third copper ink 10C may contain a solvent 16 other than the high-boiling point solvent, which is the main solvent. The third copper ink 10C may contain at least one of water and ethanol as the solvent 16, and contains both water and ethanol in this embodiment.
　高沸点溶媒は、ＯＨ基を１つ以上含み、沸点が１５０℃以上であり、水に難溶又は不溶な液体である。水に難溶又は不溶な高沸点溶媒とは、消防法における危険物の規制に関する政令、別表３において、非水溶性液体に分類される溶媒であることが好ましい。高沸点溶媒は、いわゆる有機溶媒であることが好ましく、例えば、α－テルピネオール、及び、２－エチル－１，３－ヘキサンジオールのうちの、少なくとも１つであってよい。なお、いずれの溶媒も、異性体を含んでよい。 A high-boiling point solvent is a liquid that contains one or more OH groups, has a boiling point of 150°C or higher, and is poorly soluble or insoluble in water. A high-boiling point solvent that is poorly soluble or insoluble in water is preferably a solvent that is classified as a water-insoluble liquid in Appendix 3 of the Cabinet Order on the Control of Hazardous Materials in the Fire Service Act. The high-boiling point solvent is preferably a so-called organic solvent, and may be, for example, at least one of α-terpineol and 2-ethyl-1,3-hexanediol. Note that any of the solvents may contain isomers.
　第３銅インク１０Ｃは、多価アルコール１４の含有量が、第３銅インク１０Ｃの全体に対して、質量比で、０．０１％以上５％以下であることが好ましく、０．０１％以上５％以下であることがより好ましく、０．０１％以上３％以下であることがさらに好ましい。多価アルコール１４の含有量がこの範囲となることで、銅粒子１２を適切に分散させつつ、銅粒子１２の濃度が低くなり過ぎることを抑制できる。 The content of polyhydric alcohol 14 in third copper ink 10C is preferably 0.01% to 5% by mass, more preferably 0.01% to 5% by mass, and even more preferably 0.01% to 3% by mass, relative to the total mass of third copper ink 10C. By having the content of polyhydric alcohol 14 in this range, it is possible to properly disperse copper particles 12 while preventing the concentration of copper particles 12 from becoming too low.
　第３銅インク１０Ｃは、銅粒子１２の含有量が、第３銅インク１０Ｃの全体に対して、質量比で、１％以上５０％以下であることが好ましく、５％以上５０％以下であることがより好ましく、５％以上３０％以下であることがさらに好ましい。銅粒子１２の含有量がこの範囲となることで、銅粒子１２の濃度を十分に保ちつつ、第２銅インク１０Ｂの流動性の低下を抑制できるため、例えばノズルによる噴射性を向上させるなど、製造面でも有利となる。 The third copper ink 10C preferably contains copper particles 12 in a mass ratio of 1% to 50% relative to the entire third copper ink 10C, more preferably 5% to 50%, and even more preferably 5% to 30%. Having the copper particles 12 content in this range makes it possible to suppress a decrease in the fluidity of the second copper ink 10B while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
　第３銅インク１０Ｃは、高沸点溶媒の含有量が、第３銅インク１０Ｃの全体に対して、質量比で、５０％以上９９％以下であることが好ましく、５０％以上９５％以下であることがより好ましく、６０％以上９５％以下であることがさらに好ましい。高沸点溶媒の含有量がこの範囲となることで、銅粒子１２の濃度を十分に保ちつつ、第３銅インク１０Ｃの流動性の低下を抑制できるため、例えばノズルによる噴射性を向上させるなど、製造面でも有利となる。 The content of the high boiling point solvent in the third copper ink 10C is preferably 50% or more and 99% or less, more preferably 50% or more and 95% or less, and even more preferably 60% or more and 95% or less, by mass ratio relative to the entire third copper ink 10C. By having the content of the high boiling point solvent in this range, it is possible to suppress a decrease in the fluidity of the third copper ink 10C while maintaining a sufficient concentration of the copper particles 12, which is advantageous in terms of manufacturing, for example by improving the jetting ability from a nozzle.
　第３銅インク１０Ｃは、有機溶媒１８の含有量が、第３銅インク１０Ｃの全体に対して、質量比で、０．０１％以上２０％以下であることが好ましく、０．０１％以上１０％以下であることがより好ましく、０．１％以上１０％以下であることがさらに好ましい。有機溶媒１８の含有量がこの範囲となることで、長期間適切に保存できる。 The content of organic solvent 18 in third copper ink 10C is preferably 0.01% or more and 20% or less, more preferably 0.01% or more and 10% or less, and even more preferably 0.1% or more and 10% or less, by mass ratio relative to the entire third copper ink 10C. By having the content of organic solvent 18 within this range, the ink can be appropriately stored for a long period of time.
　第３銅インク１０Ｃは、銅粒子１２、多価アルコール１４、溶媒１６及び有機溶媒１８以外の成分である分散剤を含むことが好ましい。分散剤としては、例えば、カチオン系分散剤、アニオン系分散剤、ノニオン系分散剤、両性分散剤等が挙げられ、中でも、アニオン系分散剤として、カルボン酸系分散剤、スルホン酸系分散剤、リン酸系分散剤が挙げられ、特にリン酸系分散剤として、リン酸エステル化合物が好適に用いられる。分散剤として用いるリン酸エステル化合物の分子量としては、２００以上２０００以下であることが好ましく、２００以上１５００以下であることがより好ましく、２００以上１０００以下であることがさらに好ましい。分子量が２００以上となることで十分な疎水性が得られるため、高沸点溶媒中への銅粒子の良好な分散性が得られ、分子量が２０００以下となることで狙いの加熱温度（２００～３５０℃程度）での分解、反応が可能となるため、銅粒子同士の焼結等を妨げる恐れがない。分散剤に用いるリン酸エステル化合物は任意のものであってよいが、例えば、ポリオキシエチレンアルキルエーテルリン酸エステルとして、ラウレス－ｎリン酸、オレス－ｎリン酸、ステアレス－ｎリン酸（ｎ＝２～１０）などやアルキルリン酸エステルなどが挙げられる。分散剤として、これらのうちの１種を用いてよいし、２種以上を用いてもよい。 The third copper ink 10C preferably contains a dispersant that is a component other than the copper particles 12, the polyhydric alcohol 14, the solvent 16, and the organic solvent 18. Examples of dispersants include cationic dispersants, anionic dispersants, nonionic dispersants, and amphoteric dispersants. Among these, examples of anionic dispersants include carboxylic acid dispersants, sulfonic acid dispersants, and phosphoric acid dispersants. In particular, phosphoric acid ester compounds are preferably used as phosphoric acid dispersants. The molecular weight of the phosphoric acid ester compound used as a dispersant is preferably 200 to 2000, more preferably 200 to 1500, and even more preferably 200 to 1000. A molecular weight of 200 or more provides sufficient hydrophobicity, thereby providing good dispersibility of the copper particles in the high boiling point solvent, and a molecular weight of 2000 or less provides decomposition and reaction at the target heating temperature (approximately 200 to 350°C), so there is no risk of interfering with sintering of the copper particles. Any phosphate ester compound may be used as the dispersant, but examples include polyoxyethylene alkyl ether phosphate esters such as laureth-n phosphate, oleth-n phosphate, steareth-n phosphate (n = 2 to 10), and alkyl phosphate esters. One of these may be used as the dispersant, or two or more may be used.
　第３銅インク１０Ｃは、分散剤の含有量が、第３銅インク１０Ｃの全体に対して、質量比で、０．０１％以上５％以下であることが好ましく、０．１％以上５％以下であることがより好ましく、０．１％以上３％以下であることがさらに好ましい。分散剤の含有量がこの範囲となることで、銅粒子１２の凝集を適切に抑制できる。 The dispersant content of the third copper ink 10C is preferably 0.01% or more and 5% or less, more preferably 0.1% or more and 5% or less, and even more preferably 0.1% or more and 3% or less, by mass ratio relative to the entire third copper ink 10C. By having the dispersant content within this range, aggregation of the copper particles 12 can be appropriately suppressed.
　本実施形態では、第３銅インク１０Ｃは、不可避的不純物を除き、銅粒子１２、多価アルコール１４、溶媒１６（ここでは水、エタノール及び高沸点溶媒）、有機溶媒１８及び分散剤以外の物質を含まないことが好ましい。ただしそれに限られず、第３銅インク１０Ｃは、分散剤を含まなくてもよいし、銅粒子１２、多価アルコール１４、溶媒１６、有機溶媒１８及び分散剤以外の添加剤（密着性付与剤、レオロジー調整剤、防錆剤等）を含むものであってもよい。 In this embodiment, the third copper ink 10C preferably does not contain any substances other than the copper particles 12, polyhydric alcohol 14, solvent 16 (here, water, ethanol, and a high boiling point solvent), organic solvent 18, and dispersant, except for unavoidable impurities. However, without being limited thereto, the third copper ink 10C may not contain a dispersant, or may contain additives other than the copper particles 12, polyhydric alcohol 14, solvent 16, organic solvent 18, and dispersant (adhesion imparting agents, rheology adjusters, rust inhibitors, etc.).
　高沸点溶媒を主溶媒とする銅インクは、高沸点溶媒により、銅粒子１２が凝集するおそれがある。それに対し、第３銅インク１０Ｃは、多価アルコール１４が混合されることで、例えば銅粒子１２の周囲に多価アルコール１４が配位して、銅粒子１２同士の凝集を抑制できる。 In copper inks that use a high-boiling point solvent as the main solvent, the high-boiling point solvent may cause the copper particles 12 to aggregate. In contrast, the third copper ink 10C contains a polyhydric alcohol 14, which, for example, coordinates around the copper particles 12, preventing the copper particles 12 from aggregating together.
　（銅インクの製造方法）
　次に、以上説明した銅インク１０の製造方法の一例について説明する。図３は、本実施形態に係る銅インクの製造方法を説明するフローチャートである。 (Method of manufacturing copper ink)
Next, a description will be given of an example of a method for manufacturing the above-described copper ink 10. Fig. 3 is a flowchart illustrating a method for manufacturing the copper ink according to this embodiment.
　（銅粒子の製造）
　図３に示すように、本製造方法においては、カルボン酸銅水分散液と還元剤とを混合して、銅粒子１２を生成する（ステップＳ２０）。具体的には、先ず、カルボン酸銅の水分散液を用意し、このカルボン酸銅水分散液にｐＨ調整剤を加えてｐＨを２．０以上７．５以下に調整する。次に、不活性ガス雰囲気下でこのｐＨ調整したカルボン酸銅水分散液に、還元剤として、銅イオンを還元できる１．０倍当量分以上１．２倍当量分以下のヒドラジン化合物を添加して混合する。得られた混合液を、不活性ガス雰囲気下で、得られた混合液を６０℃以上８０℃以下の温度に加熱し１．５時間以上２．５時間以下保持する。これにより、カルボン酸銅から溶出した銅イオンを還元して銅粒子１２を生成させると共に、この銅粒子１２の表面にカルボン酸銅由来の有機物を形成させる。なお、ここでのカルボン酸としては、グリコール酸、クエン酸、リンゴ酸、マレイン酸、マロン酸、フマル酸、コハク酸、酒石酸、シュウ酸、フタル酸、安息香酸およびこれらの塩などが用いられる。また、還元剤としては、ヒドラジン化合物を用いたが、それに限られず、ヒドラジン、アスコルビン酸、シュウ酸、ギ酸及びこれらの塩などを用いてよい。 (Production of copper particles)
As shown in FIG. 3, in this manufacturing method, a carboxylate copper aqueous dispersion and a reducing agent are mixed to produce copper particles 12 (step S20). Specifically, first, a carboxylate copper aqueous dispersion is prepared, and a pH adjuster is added to the carboxylate copper aqueous dispersion to adjust the pH to 2.0 to 7.5. Next, in an inert gas atmosphere, a hydrazine compound capable of reducing copper ions is added as a reducing agent to the pH-adjusted carboxylate copper aqueous dispersion and mixed. The resulting mixture is heated to a temperature of 60° C. to 80° C. in an inert gas atmosphere and held for 1.5 hours to 2.5 hours. As a result, the copper ions eluted from the carboxylate copper are reduced to produce copper particles 12, and an organic substance derived from the carboxylate copper is formed on the surface of the copper particles 12. The carboxylic acid used here may be glycolic acid, citric acid, malic acid, maleic acid, malonic acid, fumaric acid, succinic acid, tartaric acid, oxalic acid, phthalic acid, benzoic acid, or a salt thereof, etc. The reducing agent used is a hydrazine compound, but is not limited thereto, and may be hydrazine, ascorbic acid, oxalic acid, formic acid, or a salt thereof, etc.
　カルボン酸銅の水分散液は、蒸留水、イオン交換水のような純水に、粉末状のカルボン酸金属を２５質量％以上４０質量％以下の濃度となるように添加し、撹拌羽を用いて撹拌し、均一に分散させることによって調製できる。ｐＨ調整剤としては、クエン酸三アンモニウム、クエン酸水素アンモニウム、クエン酸などが挙げられる。この中でマイルドにｐＨ調整しやすいことからクエン酸三アンモニウムが好ましい。カルボン酸銅水分散液のｐＨを２．０以上とするのは、カルボン酸銅から溶出した銅イオンの溶出速度を速くして、銅粒子の生成を速やかに進行させ、目標とする微細な銅粒子を得られるようにするためである。また、ｐＨを７．５以下とするのは、溶出した金属イオンが水酸化銅（ＩＩ）となることを抑制して、銅粒子の収率を高くするためである。また、ｐＨを７．５以下とすることによって、ヒドラジン化合物の還元力が過度に高くなることを抑制でき、目標とする銅粒子が得られやすくなる。カルボン酸銅水分散液のｐＨは４以上６以下の範囲内に調整することが好ましい。 Aqueous dispersions of copper carboxylate can be prepared by adding powdered carboxylate metal to pure water such as distilled water or ion-exchanged water to a concentration of 25% to 40% by mass, and stirring with a stirring blade to disperse the mixture uniformly. Examples of pH adjusters include triammonium citrate, ammonium hydrogen citrate, and citric acid. Among these, triammonium citrate is preferred because it is easy to adjust the pH mildly. The pH of the aqueous dispersion of copper carboxylate is set to 2.0 or more in order to increase the elution rate of copper ions eluted from the copper carboxylate, to rapidly advance the generation of copper particles, and to obtain the target fine copper particles. The pH is set to 7.5 or less in order to prevent the eluted metal ions from becoming copper hydroxide (II) and to increase the yield of copper particles. In addition, by setting the pH to 7.5 or less, the reducing power of the hydrazine compound can be prevented from becoming excessively high, making it easier to obtain the target copper particles. The pH of the aqueous dispersion of copper carboxylate is preferably adjusted to a range of 4 to 6.
　ヒドラジン化合物によるカルボン酸銅の還元は不活性ガス雰囲気下で行われる。液中に溶出した銅イオンの酸化を防止するためである。不活性ガスの例としては、窒素ガス、アルゴンガスなどが挙げられる。ヒドラジン化合物は、酸性下でカルボン酸銅を還元するときに、還元反応後に残渣を生じないこと、安全性が比較的高いこと及び取扱いが容易であることなどの利点がある。このヒドラジン化合物としては、ヒドラジン一水和物、無水ヒドラジン、塩酸ヒドラジン、硫酸ヒドラジンなどが挙げられる。これらのヒドラジン化合物の中では、硫黄や塩素といった不純物となり得る成分を含まないヒドラジン一水和物、無水ヒドラジンが好ましい。 The reduction of copper carboxylate with hydrazine compounds is carried out in an inert gas atmosphere. This is to prevent oxidation of the copper ions dissolved in the liquid. Examples of inert gases include nitrogen gas and argon gas. When reducing copper carboxylate under acidic conditions, hydrazine compounds have the advantages of not producing residues after the reduction reaction, being relatively safe, and being easy to handle. Examples of this hydrazine compound include hydrazine monohydrate, hydrazine anhydrous, hydrazine hydrochloride, and hydrazine sulfate. Of these hydrazine compounds, hydrazine monohydrate and hydrazine anhydrous are preferred, as they do not contain components that can become impurities such as sulfur and chlorine.
　一般的にｐＨ７未満の酸性液中で生成した銅は溶解してしまう。しかし本実施形態では、ｐＨ７未満の酸性液に還元剤であるヒドラジン化合物を添加混合し、得られた混合液中に銅粒子を生成させる。このため、カルボン酸銅から生成したカルボン酸由来の成分が銅粒子の表面を速やかに被覆するので、銅粒の溶解が抑制される。ｐＨを調整した後のカルボン酸銅の水分散液は、温度５０℃以上７０℃以下にして、還元反応を進行しやすくすることが好ましい。 Generally, copper produced in an acidic solution with a pH of less than 7 dissolves. However, in this embodiment, a hydrazine compound, which is a reducing agent, is added and mixed with an acidic solution with a pH of less than 7, and copper particles are produced in the resulting mixed solution. As a result, the components derived from the carboxylic acid produced from the copper carboxylate quickly coat the surfaces of the copper particles, suppressing dissolution of the copper particles. After adjusting the pH, it is preferable to keep the temperature of the aqueous dispersion of copper carboxylate at 50°C or higher and 70°C or lower to facilitate the progress of the reduction reaction.
　不活性ガス雰囲気下でヒドラジン化合物を混合した混合液を６０℃以上８０℃以下の温度に加熱し１．５時間以上２．５時間以下保持するのは、銅粒子を生成させると共に、生成した銅粒子の表面に有機物を形成し被覆するためである。不活性ガス雰囲気下で加熱保持するのは、生成した銅粒子の酸化を防止するためである。出発原料であるカルボン酸銅は通常３５質量％程度の銅成分を含む。この程度の銅成分を含むカルボン酸水分散液に還元剤であるヒドラジン化合物を添加して、上記の温度で昇温加熱し、上記の時間で保持することにより、銅粒子の生成と、銅粒子の表面での有機物の生成とがバランスよく進行するので、銅粒子１００質量％に対して、有機物の被覆量が０．５質量％以上２．０質量％以下の範囲内にある銅粒子を得ることができる。加熱温度が６０℃未満で保持時間が１．５時間未満では、カルボン酸金属が完全に還元せずに、銅粒子の生成速度が遅くなりすぎて、銅粒子を被覆する有機物の量が過剰となるおそれがある。また加熱温度が８０℃を超えかつ保持時間が２．５時間を超えると、銅粒子の生成速度が速くなりすぎて、銅粒子を被覆する有機物の量が少なりすぎるおそれがある。好ましい加熱温度は６５℃以上７５℃以下であり、好ましい保持時間は２時間以上２．５時間以下である。 The mixed solution containing the hydrazine compound is heated to a temperature of 60°C or higher and 80°C or lower under an inert gas atmosphere and held for 1.5 to 2.5 hours in order to generate copper particles and to form and coat the surfaces of the generated copper particles with organic matter. The reason for holding the mixture under an inert gas atmosphere is to prevent oxidation of the generated copper particles. The starting material, carboxylate copper, usually contains about 35% by mass of copper. By adding a hydrazine compound, which is a reducing agent, to a carboxylate aqueous dispersion containing this amount of copper, heating it to the above temperature, and holding it for the above time, the generation of copper particles and the generation of organic matter on the surfaces of the copper particles proceed in a balanced manner, so that copper particles can be obtained with an organic matter coating amount in the range of 0.5% by mass to 2.0% by mass relative to 100% by mass of copper particles. If the heating temperature is less than 60°C and the holding time is less than 1.5 hours, the carboxylate metal is not completely reduced, the generation rate of copper particles becomes too slow, and the amount of organic matter coating the copper particles may become excessive. Furthermore, if the heating temperature exceeds 80°C and the holding time exceeds 2.5 hours, the rate at which copper particles are produced may become too fast, resulting in a risk of the amount of organic matter coating the copper particles being too small. The preferred heating temperature is 65°C or higher and 75°C or lower, and the preferred holding time is 2 hours or higher and 2.5 hours or lower.
　混合液で生成された銅粒子を、不活性ガス雰囲気下で混合液から、例えば遠心分離機を用いて、一定の割合の固液比（例えば、固液比：５０／５０[質量％]）とした銅粒子１２を含む水スラリーを得ることが出来る。また、場合によっては固液分離して、凍結乾燥法、減圧乾燥法で乾燥することにより、表面が有機物で被覆された銅粒子を得ることができる。この銅粒子は、表面が有機物で被覆されているため、大気中に保存しても酸化しにくくなる。 The copper particles produced in the mixed liquid can be separated from the mixed liquid under an inert gas atmosphere, for example using a centrifuge, to obtain an aqueous slurry containing copper particles 12 with a certain solid-liquid ratio (for example, solid-liquid ratio: 50/50 [mass %]). In some cases, copper particles whose surfaces are coated with an organic substance can be obtained by performing solid-liquid separation and drying using a freeze-drying method or a vacuum drying method. Since the surfaces of these copper particles are coated with an organic substance, they are less likely to oxidize even when stored in the air.
　（第１銅インクの製造）
　次に、銅粒子１２と、多価アルコール１４と、有機溶媒１８と、水とを混合して、第１銅インク１０Ａを生成する（ステップＳ２２）。ここでは、銅粒子１２や多価アルコール１４や有機溶媒１８の含有量が、上述で説明した数値範囲となるように、銅粒子１２と多価アルコール１４と有機溶媒１８と水とを混合して、第１銅インク１０Ａを製造することが好ましい。なお、銅粒子１２と多価アルコール１４と有機溶媒１８と水との混合方法は任意である。例えば、銅粒子１２に水が含まれた金属スラリーに、多価アルコール１４と有機溶媒１８と水とを含む多価アルコール１４及び有機溶媒１８の水溶液を混合してもよいし、水が含まれない銅粒子１２に、多価アルコール１４及び有機溶媒１８の水溶液を混合してもよい。 (Production of First Copper Ink)
Next, the copper particles 12, the polyhydric alcohol 14, the organic solvent 18, and water are mixed to produce the first copper ink 10A (step S22). Here, it is preferable to produce the first copper ink 10A by mixing the copper particles 12, the polyhydric alcohol 14, the organic solvent 18, and water so that the contents of the copper particles 12, the polyhydric alcohol 14, and the organic solvent 18 are within the numerical ranges described above. Note that the method of mixing the copper particles 12, the polyhydric alcohol 14, the organic solvent 18, and the water is arbitrary. For example, an aqueous solution of the polyhydric alcohol 14 and the organic solvent 18 containing the polyhydric alcohol 14, the organic solvent 18, and water may be mixed with a metal slurry containing the copper particles 12 and water, or an aqueous solution of the polyhydric alcohol 14 and the organic solvent 18 may be mixed with the copper particles 12 not containing water.
　（第２銅インクの製造）
　次に、第１銅インク１０Ａとエタノールとを混合して、第２銅インク１０Ｂを生成する（ステップＳ２４）。ここでは、銅粒子１２や多価アルコール１４やエタノールや有機溶媒１８の含有量が、上述で説明した数値範囲となるように、第１銅インク１０Ａとエタノールとを混合して、第２銅インク１０Ｂを製造することが好ましい。なお、第１銅インク１０Ａとエタノールの混合方法は任意である。例えば、ステップＳ２２で得られた第１銅インク１０Ａを所定時間（例えば１日程度）静置もしくは所定の条件で遠心分離した後、一部の上澄み液を除去して、上澄み液が除去された第１銅インク１０Ａに対して、エタノールを添加してよい。 (Production of Copper II Ink)
Next, the first copper ink 10A is mixed with ethanol to produce the second copper ink 10B (step S24). Here, it is preferable to produce the second copper ink 10B by mixing the first copper ink 10A with ethanol so that the contents of the copper particles 12, the polyhydric alcohol 14, the ethanol, and the organic solvent 18 are within the numerical ranges described above. The first copper ink 10A and ethanol may be mixed in any manner. For example, the first copper ink 10A obtained in step S22 may be left to stand for a predetermined time (for example, about one day) or centrifuged under predetermined conditions, after which a portion of the supernatant liquid is removed, and ethanol may be added to the first copper ink 10A from which the supernatant liquid has been removed.
　（第３銅インクの製造）
　次に、第２銅インク１０Ｂと高沸点溶媒と分散剤とを混合して、第３銅インク１０Ｃを生成する（ステップＳ２６）。ここでは、銅粒子１２や多価アルコール１４や高沸点溶媒や分散剤や有機溶媒１８の含有量が、上述で説明した数値範囲となるように、第２銅インク１０Ｂと高沸点溶媒と分散剤とを混合して、第３銅インク１０Ｃを製造することが好ましい。なお、第２銅インク１０Ｂと高沸点溶媒と分散剤の混合方法は任意である。例えば、ステップＳ２４で得られた第２銅インク１０Ｂを所定時間（例えば１日程度）静置もしくは所定の条件で遠心分離した後、一部の上澄み液を除去して、上澄み液が除去された第２銅インク１０Ｂに対して、高沸点溶剤を添加してもよい。また、分散剤の添加は必須ではない。
　また、第３銅インク１０Ｃから、更に、上述で説明した数値範囲となるように、溶媒（水、エタノール、高沸点溶剤等）を除去もしくは添加してもよい。 (Production of tertiary copper ink)
Next, the second copper ink 10B is mixed with the high boiling point solvent and the dispersant to produce the third copper ink 10C (step S26). Here, it is preferable to manufacture the third copper ink 10C by mixing the second copper ink 10B with the high boiling point solvent and the dispersant so that the contents of the copper particles 12, the polyhydric alcohol 14, the high boiling point solvent, the dispersant and the organic solvent 18 are in the numerical ranges described above. The method of mixing the second copper ink 10B with the high boiling point solvent and the dispersant is arbitrary. For example, the second copper ink 10B obtained in step S24 may be left to stand for a predetermined time (for example, about one day) or centrifuged under predetermined conditions, and then a part of the supernatant may be removed, and the high boiling point solvent may be added to the second copper ink 10B from which the supernatant has been removed. In addition, the addition of a dispersant is not essential.
Furthermore, a solvent (water, ethanol, a high boiling point solvent, etc.) may be removed from or added to the third copper ink 10C so as to fall within the numerical range described above.
　このようにして生成された第３銅インク１０Ｃは、銅インク１０として使用される。なお、以上の説明では、第１銅インク１０Ａを用いて第２銅インク１０Ｂを生成し、第２銅インク１０Ｂを用いて第３銅インク１０Ｃを生成していた。すなわち、第１銅インク１０Ａ及び第２銅インク１０Ｂは、第３銅インク１０Ｃを製造するための中間物質であった。ただし、第１銅インク１０Ａ及び第２銅インク１０Ｂは、中間物質であることに限られず、第１銅インク１０Ａ及び第２銅インク１０Ｂそのものを、銅インク１０として使用してもよい。 The third copper ink 10C produced in this manner is used as the copper ink 10. In the above explanation, the second copper ink 10B is produced using the first copper ink 10A, and the third copper ink 10C is produced using the second copper ink 10B. In other words, the first copper ink 10A and the second copper ink 10B are intermediate substances for producing the third copper ink 10C. However, the first copper ink 10A and the second copper ink 10B are not limited to being intermediate substances, and the first copper ink 10A and the second copper ink 10B themselves may be used as the copper ink 10.
　なお、以上説明した銅粒子１２及び銅インク１０の製造方法は、一例であり、任意の方法で、銅粒子１２や銅インク１０を製造してよい。 The above-described method for producing the copper particles 12 and the copper ink 10 is merely an example, and the copper particles 12 and the copper ink 10 may be produced by any method.
　（効果）
　以上説明したように、本実施形態に係る亜酸化銅の製造方法は、銅粒子１２を含む液状の組成物である銅インク１０を得るステップと、銅インク１０を、基材上に塗布もしくは印刷することにより膜を形成するステップと、銅インク１０が基材上に形成された膜を乾燥した後、酸素濃度が１０％以上２１％以下の雰囲気下で、波長の範囲が可視～赤外領域の光を照射して加熱することで、銅インク１０中の銅粒子１２を酸化及び焼結して、亜酸化銅を製造するステップと、を含む。本実施形態においては、銅粒子１２を含む銅インク１０を、上記酸素濃度で、かつ上記の波長の範囲の光で加熱するため、適切な性能を有する亜酸化銅を得ることができる。より詳しくは、このような製造方法を用いることで、亜酸化銅を得るためのプロセスが複雑とならず、かつ亜酸化銅を適切に製造できるため、簡単なプロセスで亜酸化銅を製造できる。すなわち、銅錯体や亜酸化銅を粉末から亜酸化銅を製造する場合には、プロセスが複雑となるが、銅粒子１２を用いることで、例えば上記の酸素濃度と波長の範囲の光で加熱するだけの簡単なプロセスで、亜酸化銅を適切に製造できる。 (effect)
As described above, the method for producing cuprous oxide according to the present embodiment includes the steps of obtaining the copper ink 10, which is a liquid composition containing copper particles 12; forming a film by applying or printing the copper ink 10 on a substrate; and, after drying the film formed by the copper ink 10 on the substrate, oxidizing and sintering the copper particles 12 in the copper ink 10 by irradiating and heating with light having a wavelength range of visible to infrared in an atmosphere having an oxygen concentration of 10% to 21% to produce cuprous oxide. In this embodiment, the copper ink 10 containing the copper particles 12 is heated at the above oxygen concentration and with light in the above wavelength range, so that cuprous oxide having appropriate performance can be obtained. More specifically, by using such a production method, the process for obtaining cuprous oxide is not complicated and cuprous oxide can be appropriately produced, so that cuprous oxide can be produced by a simple process. That is, when producing cuprous oxide from a powder of a copper complex or cuprous oxide, the process is complicated, but by using the copper particles 12, cuprous oxide can be appropriately produced by a simple process of, for example, heating with light having the above oxygen concentration and wavelength range.
　亜酸化銅の製造するステップにおいては、照射する光が、０．６μｍ以上１０μｍ以下の波長の範囲をピークに有する分光分布の光で、銅インク１０を加熱することが好ましい。照射する光の波長の範囲をこの範囲とすることで、銅粒子を適切に酸化及び焼結して、亜酸化銅をより適切に製造できる。 In the step of producing cuprous oxide, it is preferable to heat the copper ink 10 with irradiated light having a spectral distribution with a peak in the wavelength range of 0.6 μm or more and 10 μm or less. By irradiating light with this wavelength range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be more appropriately produced.
　亜酸化銅を製造するステップにおいては、１８０℃以上５００℃以下の加熱温度で、銅インク１０を加熱することが好ましい。加熱温度をこの範囲とすることで、銅粒子を適切に酸化及び焼結して、亜酸化銅をより適切に製造できる。 In the step of producing cuprous oxide, it is preferable to heat the copper ink 10 at a heating temperature of 180°C or more and 500°C or less. By setting the heating temperature within this range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be produced more appropriately.
　亜酸化銅を製造するステップにおいては、加熱温度での保持時間を、１秒以上６００秒以下とすることが好ましい。保持時間をこの範囲とすることで、銅粒子を適切に酸化及び焼結して、亜酸化銅をより適切に製造できる。 In the step of producing cuprous oxide, it is preferable that the holding time at the heating temperature is 1 second or more and 600 seconds or less. By keeping the holding time in this range, the copper particles can be properly oxidized and sintered, and cuprous oxide can be produced more appropriately.
　亜酸化銅を製造するステップにおいては、加熱温度までの昇温速度を、０．１℃／秒以上５０℃／秒以下とすることが好ましい。昇温速度をこの範囲とすることで、銅粒子を適切に酸化及び焼結して、亜酸化銅をより適切に製造できる。 In the step of producing cuprous oxide, it is preferable that the rate of temperature rise to the heating temperature is 0.1°C/sec or more and 50°C/sec or less. By keeping the rate of temperature rise within this range, the copper particles can be appropriately oxidized and sintered, and cuprous oxide can be produced more appropriately.
　銅インク１０を得るステップにおいては、粒径が１０ｎｍ以上１０００ｎｍ以下であり、かつ、表面が有機物で被覆されている銅粒子１２を含む銅インク１０を得ることが好ましい。このような銅インク１０を用いることで、亜酸化銅をより適切に製造できる。 In the step of obtaining the copper ink 10, it is preferable to obtain a copper ink 10 that contains copper particles 12 having a particle size of 10 nm or more and 1000 nm or less, and whose surfaces are coated with an organic substance. By using such a copper ink 10, cuprous oxide can be more appropriately produced.
　銅インク１０を得るステップにおいては、銅粒子１２と、溶媒１６と、大気圧における沸点が１５０℃以上であり、水と混和可能な有機溶媒１８と、ＯＨ基を２つ以上含み、水及びエタノールに溶解可能な多価アルコール１４と、を含む銅インク１０を得ることが好ましい。このような銅インク１０を用いることで、亜酸化銅をより適切に製造できる。 In the step of obtaining copper ink 10, it is preferable to obtain copper ink 10 that contains copper particles 12, a solvent 16, an organic solvent 18 that has a boiling point of 150°C or higher at atmospheric pressure and is miscible with water, and a polyhydric alcohol 14 that contains two or more OH groups and is soluble in water and ethanol. By using such a copper ink 10, cuprous oxide can be more appropriately produced.
　（実施例）
　次に、実施例について説明する。図４は、各例で用いた銅インクの成分を示す表であり、図５Ａ～図５Ｚｅは、各例の評価結果を示す表である。 (Example)
Next, examples will be described. Fig. 4 is a table showing the components of the copper ink used in each example, and Figs. 5A to 5Ze are tables showing the evaluation results of each example.
　（銅インク）
　銅インクの製造方法を説明する。銅インクの製造においては、出発原料であるカルボン酸銅として、フタル酸銅を用意した。フタル酸銅を室温のイオン交換水に入れ、撹拌羽根を用いて撹拌し、濃度３０質量％のフタル酸銅の水分散液を調製した。次いで、このフタル酸銅の水分散液にｐＨ調整剤としてのフタル酸アンモニウム水溶液を加えて、上記水分散液のｐＨが３になるように調整した。次に、ｐＨ調整した液を５０℃の温度にし、窒素ガス雰囲気下で、ｐＨ調整した液に還元剤として、銅イオンを還元できる１．２倍当量分である酸化還元電位が－０．５Ｖのヒドラジン一水和物水溶液（２倍希釈）を一気に添加し、撹拌羽を用いて均一に混合した。更に、目標とする銅粒子を合成するために、上記水分散液と上記還元剤との混合液を窒素ガス雰囲気下で保持温度の７０℃まで昇温し、７０℃で２時間保持した。更に、遠心分離機を用いて、脱水及び脱塩することにより銅粒子の水スラリー（銅粉末濃度：５０質量％）を得た。 (Copper ink)
A method for producing copper ink will be described. In the production of copper ink, copper phthalate was prepared as a starting material, copper carboxylate. Copper phthalate was placed in ion-exchanged water at room temperature and stirred with a stirring blade to prepare an aqueous dispersion of copper phthalate with a concentration of 30% by mass. Next, an aqueous solution of ammonium phthalate was added as a pH adjuster to the aqueous dispersion of copper phthalate to adjust the pH of the aqueous dispersion to 3. Next, the pH-adjusted liquid was heated to 50° C., and an aqueous solution of hydrazine monohydrate (diluted 2-fold) with an oxidation-reduction potential of −0.5 V, which is 1.2 times the equivalent amount capable of reducing copper ions, was added to the pH-adjusted liquid as a reducing agent in a nitrogen gas atmosphere, and the mixture was mixed uniformly using a stirring blade. Furthermore, in order to synthesize the target copper particles, the mixture of the aqueous dispersion and the reducing agent was heated to a holding temperature of 70° C. under a nitrogen gas atmosphere and held at 70° C. for 2 hours. Furthermore, the mixture was dehydrated and desalted using a centrifuge to obtain an aqueous slurry of copper particles (copper powder concentration: 50% by mass).
　得られた銅粒子の水スラリー（銅粉末濃度：５０質量％）より、前記、第１銅インクの製造から第３銅インクの製造にしたがって、図４の表に示す、各成分を含有した銅インクＣ１～Ｃ１２を各々作製した。 The resulting aqueous slurry of copper particles (copper powder concentration: 50% by mass) was used to produce copper inks C1 to C12, each containing the components shown in the table in Figure 4, following the steps for producing the first copper ink to the third copper ink described above.
　（実施例１）
　実施例１においては、インクとして銅インクＣ１を、基材として５０ｍｍ×５０ｍｍ、厚さ２５μｍのＰＩ（ポリイミド）フィルム上に、インクジェット法を用いて、３０ｍｍ×３０ｍｍのサイズに塗布した後、大気中、６０℃、１５分の条件で乾燥することにより、膜厚０．１μｍのインクの膜を形成させた。ＰＩフィルム上に形成されたインクの膜を、酸素濃度１０％の雰囲気下（東レエンジニアリング社製ジルコニア式酸素濃度計ＬＣ－８６０を用いて雰囲気中の酸素濃度を測定）に調整した状態で、照射源としてハロゲンランプヒーター（主に、可視～赤外領域の波長をピークに有する分光分布の光、より詳しくは１μｍの波長をピークに有する分光分布の光を放射）を用いて、加熱温度が２５０℃、加熱温度までの昇温速度が０．１℃／秒、加熱温度での保持時間が１秒の条件で加熱することにより、ＰＩフィルム上に焼結体を製造した。 Example 1
In Example 1, copper ink C1 was applied to a substrate of 50 mm×50 mm, 25 μm thick PI (polyimide) film by inkjet printing to a size of 30 mm×30 mm, and then dried in air at 60° C. for 15 minutes to form an ink film with a thickness of 0.1 μm. The ink film formed on the PI film was heated under an atmosphere with an oxygen concentration of 10% (the oxygen concentration in the atmosphere was measured using a zirconia oxygen concentration meter LC-860 manufactured by Toray Engineering Co., Ltd.) using a halogen lamp heater as an irradiation source (which mainly radiates light with a spectral distribution having a peak wavelength in the visible to infrared range, more specifically light with a spectral distribution having a peak wavelength of 1 μm) under conditions of a heating temperature of 250° C., a heating rate up to the heating temperature of 0.1° C./sec, and a holding time at the heating temperature of 1 second, to produce a sintered body on the PI film.
　（実施例２～５）
　実施例２～５においては、図５Ａに示すように、酸素濃度、加熱温度、昇温速度、及び保持時間の少なくとも１つ以外の条件を実施例１と同様の方法として、焼結体を製造した。 (Examples 2 to 5)
In Examples 2 to 5, as shown in FIG. 5A, sintered bodies were produced under the same conditions as in Example 1 except for at least one of the oxygen concentration, heating temperature, heating rate, and holding time.
　（実施例６～１９）
　実施例６～１９においては、塗布方法としてメタルマスクを用いた印刷法により、３０ｍｍ×３０ｍｍのサイズの基板に塗布し、銅インクＣ２又はＣ３を用いつつ、膜厚、酸素濃度、加熱温度、昇温速度、及び保持時間を図５Ａ、図５Ｂに示す製造条件とした以外は、実施例１と同様の方法で、焼結体を製造した。 (Examples 6 to 19)
In Examples 6 to 19, a sintered body was produced in the same manner as in Example 1, except that a coating method was used in which a printing method using a metal mask was used to coat a substrate having a size of 30 mm x 30 mm, and copper ink C2 or C3 was used, and the film thickness, oxygen concentration, heating temperature, heating rate, and holding time were set as the production conditions shown in Figures 5A and 5B.
　（実施例２０～３４）
　実施例２０～３４においては、基材として５０ｍｍ×５０ｍｍ、厚さ０．７ｍｍのガラス基板を用いつつ、銅インクの種類、膜厚、酸素濃度、加熱温度、昇温速度、及び保持時間を図５Ｂ～図５Ｄに示す製造条件とした以外は、実施例１～１９と同様の方法で、焼結体を製造した。 (Examples 20 to 34)
In Examples 20 to 34, a sintered body was manufactured in the same manner as in Examples 1 to 19, except that a glass substrate having a size of 50 mm × 50 mm and a thickness of 0.7 mm was used as the base material, and the type of copper ink, the film thickness, the oxygen concentration, the heating temperature, the heating rate, and the holding time were the manufacturing conditions shown in Figures 5B to 5D.
　（実施例３５～５０）
　実施例３５～５０においては、照射源として石英管ヒーター（主に、赤外領域の波長をピークに有する分光分布の光を放射）を用いつつ、銅インクの種類、膜厚、酸素濃度、加熱温度、昇温速度、及び保持時間を図５Ｄ、図５Ｅに示す製造条件とした以外は、実施例１～３４と同様の方法で、焼結体を製造した。 (Examples 35 to 50)
In Examples 35 to 50, a quartz tube heater (which mainly emits light with a spectral distribution having a peak wavelength in the infrared region) was used as the irradiation source, and sintered bodies were manufactured in the same manner as in Examples 1 to 34, except that the type of copper ink, film thickness, oxygen concentration, heating temperature, heating rate, and holding time were manufacturing conditions shown in Figures 5D and 5E.
　（実施例５１～５４）
　実施例５１～５４においては、照射源としてセラミックヒーター（主に、赤外領域の波長をピークに有する分光分布の光を放射）を用いつつ、銅インクの種類、膜厚、酸素濃度、加熱温度、昇温速度、及び保持時間を図５Ｅに示す製造条件とした以外は、実施例１～３４と同様の方法で、焼結体を製造した。 (Examples 51 to 54)
In Examples 51 to 54, a ceramic heater (which mainly emits light with a spectral distribution having a peak wavelength in the infrared region) was used as the irradiation source, and sintered bodies were manufactured in the same manner as in Examples 1 to 34, except that the type of copper ink, film thickness, oxygen concentration, heating temperature, heating rate, and holding time were manufacturing conditions shown in FIG. 5E.
　（実施例５５～２１６）
　実施例５５～２１６については、照射源、銅インクの種類、膜厚、酸素濃度、加熱温度、昇温速度、及び保持時間を図５Ｅ～図５Ｔに示したものとした以外は、実施例１～３４と同様の方法で、焼結体を製造した。 (Examples 55 to 216)
For Examples 55 to 216, sintered bodies were manufactured in the same manner as in Examples 1 to 34, except that the irradiation source, type of copper ink, film thickness, oxygen concentration, heating temperature, heating rate, and holding time were as shown in Figures 5E to 5T.
　（比較例１～６）
　比較例１～６においては、照射源としてキセノンフラッシュランプ（主に、紫外～赤外領域の光を放射）を用いて加熱した以外は、図５Ｕに示す製造条件で、実施例１～３４と同様の方法で、焼結体を製造した。 (Comparative Examples 1 to 6)
In Comparative Examples 1 to 6, sintered bodies were produced in the same manner as in Examples 1 to 34 under the production conditions shown in FIG. 5U, except that heating was performed using a xenon flash lamp (which mainly radiates light in the ultraviolet to infrared range) as an irradiation source.
　（比較例７～１２）
　比較例７～１２においては、照射源としてジャイロトロン（主に、２４ＧＨｚのマイクロ波領域の光を放射）を用いて加熱した以外は、図５Ｕ、図５Ｖに示す製造条件で、実施例１～３４と同様の方法で、焼結体を製造した。 (Comparative Examples 7 to 12)
In Comparative Examples 7 to 12, sintered bodies were produced in the same manner as in Examples 1 to 34 under the production conditions shown in Figures 5U and 5V, except that heating was performed using a gyrotron (mainly emitting light in the microwave region of 24 GHz) as an irradiation source.
　（比較例１３～４８）
　比較例１３～４８については、照射源、銅インクの種類、膜厚、酸素濃度、加熱温度、昇温速度、及び保持時間を図５Ｖ～図５Ｙに示したものとした以外は、実施例１～３４と同様の方法で、焼結体を製造した。 (Comparative Examples 13 to 48)
For Comparative Examples 13 to 48, sintered bodies were manufactured in the same manner as in Examples 1 to 34, except that the irradiation source, type of copper ink, film thickness, oxygen concentration, heating temperature, heating rate, and holding time were as shown in Figures 5V to 5Y.
　（比較例４９～５３）
　比較例４９～５３については、酸素濃度を１０％未満の雰囲気下に調整した状態とした以外は、図５Ｚａに示す製造条件で、実施例１～５と同様の方法で、焼結体を製造した。 (Comparative Examples 49 to 53)
For Comparative Examples 49 to 53, sintered bodies were produced in the same manner as in Examples 1 to 5 under the production conditions shown in FIG. 5Za, except that the oxygen concentration was adjusted to less than 10% in the atmosphere.
　（比較例５４～６７）
　比較例５４～６７については、酸素濃度を１０％未満の雰囲気下に調整した状態とした以外は、図５Ｚａ、図５Ｚｂに示す製造条件で、実施例６～１９と同様の方法で、焼結体を製造した。 (Comparative Examples 54 to 67)
For Comparative Examples 54 to 67, sintered bodies were produced in the same manner as in Examples 6 to 19 under the production conditions shown in Figures 5Za and 5Zb, except that the oxygen concentration was adjusted to be less than 10% in the atmosphere.
　（比較例６８～８２）
　比較例６８～８２については、酸素濃度を１０％未満の雰囲気下に調整した状態とした以外は、図５Ｚｂ～図５Ｚｄに示す製造条件で、実施例２０～３４と同様の方法で、焼結体を製造した。 (Comparative Examples 68 to 82)
For Comparative Examples 68 to 82, sintered bodies were produced in the same manner as Examples 20 to 34 under the production conditions shown in Figures 5Zb to 5Zd, except that the oxygen concentration was adjusted to an atmosphere of less than 10%.
　（比較例８３～９８）
　比較例８３～９８については、酸素濃度を１０％未満の雰囲気下に調整した状態とした以外は、図５Ｚｄ、図５Ｚｅに示す製造条件で、実施例３５～５０と同様の方法で、焼結体を製造した。 (Comparative Examples 83 to 98)
For Comparative Examples 83 to 98, sintered bodies were manufactured in the same manner as Examples 35 to 50 under the manufacturing conditions shown in Figures 5Zd and 5Ze, except that the oxygen concentration was adjusted to an atmosphere of less than 10%.
　（比較例９９～１０２）
　比較例９９～１０２については、酸素濃度を１０％未満の雰囲気下に調整した状態とした以外は、図５Ｚｅに示す製造条件で、実施例５１～５４と同様の方法で、焼結体を製造した。 (Comparative Examples 99 to 102)
For Comparative Examples 99 to 102, sintered bodies were produced in the same manner as in Examples 51 to 54 under the production conditions shown in FIG. 5Ze, except that the oxygen concentration was adjusted to less than 10% in the atmosphere.
　（評価）
　評価においては、各例の焼結体に対して、Ｘ線回折装置としてリガク社の全自動多目的Ｘ線回折装置（ＳｍａｒｔＬａｂ）を使用した。Ｘ線回折法の条件は、Ｘ線出力が４５ｋＶ、２００ｍＡで、スキャンモードが連続で、スキャンスピードが１０°／分で、ステップ幅が０．０５°で、スキャン軸が２θで、スキャン範囲が１０～１００°で測定を行った。ＸＲＤの測定において、式（１）～式（１２）のいずれかにピークがあって、式（１）～式（１２）以外のピークがない場合に、同定結果を合格とした。一方、ＸＲＤの測定において、式（１）～式（１２）以外のピークがある場合に、同定結果を不合格とした。尚、ＰＩフィルムやガラス基板の基材に由来するピークについては評価から除外した。各例の評価結果を図５Ａ～図５Ｚｅに示す。 (evaluation)
In the evaluation, a fully automatic multipurpose X-ray diffraction apparatus (SmartLab) manufactured by Rigaku Corporation was used as the X-ray diffraction apparatus for the sintered bodies of each example. The conditions of the X-ray diffraction method were an X-ray output of 45 kV and 200 mA, a scan mode of continuous, a scan speed of 10°/min, a step width of 0.05°, a scan axis of 2θ, and a scan range of 10 to 100°. In the XRD measurement, if there is a peak in any of the formulas (1) to (12) and there is no peak other than the formulas (1) to (12), the identification result was deemed to be passed. On the other hand, in the XRD measurement, if there is a peak other than the formulas (1) to (12), the identification result was deemed to be failed. Note that peaks derived from the base material of the PI film and the glass substrate were excluded from the evaluation. The evaluation results of each example are shown in Figures 5A to 5Ze.
　図５Ａ～図５Ｔに示すように、銅粒子を含む液状の組成物である銅インクを、酸素濃度が１０％以上２１％以下の条件で、波長の範囲が可視～赤外領域の光を照射して加熱した実施例１～２１６の焼結体は、ＸＲＤの測定において、亜酸化銅のピークを示す式（１）～式（１２）のいずれかにピークがあって、式（１）～式（１２）以外のピークがないことから、適切に亜酸化銅を製造できることが分かる。一方、波長の範囲が可視～赤外領域を外れた波長をピークに有する分光分布の光を照射して加熱した比較例１～４８の焼結体、及び、酸素濃度が１０％未満の雰囲気下で加熱した比較例４９～１０２の焼結体は、ＸＲＤの測定において、亜酸化銅のピークを示す式（１）～式（１２）以外のピークがあることから、亜酸化銅以外の銅もしくは銅化合物が存在していることを示しており、適切に亜酸化銅を製造できないことが分かる。 As shown in Figures 5A to 5T, the sintered bodies of Examples 1 to 216, which were obtained by irradiating copper ink, a liquid composition containing copper particles, with light having a wavelength in the visible to infrared range and heating it under conditions of an oxygen concentration of 10% to 21%, have a peak in any one of the formulas (1) to (12) that indicate the peak of cuprous oxide in XRD measurement, and have no peaks other than those in formulas (1) to (12), and therefore it is understood that cuprous oxide can be appropriately produced. On the other hand, the sintered bodies of Comparative Examples 1 to 48, which were heated by irradiating light having a spectral distribution with a peak at a wavelength outside the visible to infrared range, and the sintered bodies of Comparative Examples 49 to 102, which were heated in an atmosphere with an oxygen concentration of less than 10%, have peaks other than those in formulas (1) to (12) that indicate the peak of cuprous oxide in XRD measurement, which indicates the presence of copper or copper compounds other than cuprous oxide, and therefore it is understood that cuprous oxide cannot be appropriately produced.
　（オプションの評価）
　オプションの評価として、焼結体の可視～赤外領域の光に対する透過度合いを評価した。透過度合いの評価においては、焼結体に対して、可視赤外分光光度計として、日立ハイテクサイエンス社の紫外可視近赤外分光光度計（ＵＨ４１５０）により、データモードを透過率測定（％Ｔ）とし、開始波長１２００ｎｍ、終了波長３００ｎｍとし、スキャンスピードを６００ｎｍ／ｍｉｎとし、サンプリング間隔を１．００ｎｍとして、焼結体の透過率を測定した。このとき、ランベルト・ベールの法則では、透過率（Ｉ１／Ｉ０、Ｉ1：透過光強度、Ｉ０：入射光強度）、被測定物の厚さ（Ｌ）、吸収係数（α）との間に、関係式：Ｉ１／Ｉ０＝ｅｘｐ（－α・Ｌ）（式（１３））が成り立つことが知られている。各実施例、比較例について、得られた焼結体の透過率と膜厚より、式（１３）より各波長における吸収係数（α（λ））を求めた。この吸収係数（α（λ））を元に、膜厚が０．１μｍでの、波長が６００ｎｍ～１２００ｎｍにおける平均透過率を、式（１３）より算出した。平均透過率（図における「可視・赤外透過率」）が４０％以上を、透過有とし、平均透過率が４０％未満を、透過無とした。図５Ａ～図５Ｚｅに示すように、実施例１～２１６においては、適切な製造条件とすることで、波長が６００ｎｍ～１２００ｎｍの光を適切に透過するため、例えば結晶Ｓｉ太陽電池と組み合わせたタンデム型太陽電池などに適切に適用できるため、より好ましいことが分かる。一方、波長の範囲が可視～赤外領域を外れた波長をピークに有する分光分布の光を照射して加熱した比較例１～４８の焼結体、及び、酸素濃度が１０％未満の雰囲気下で加熱した比較例４９～１０２の焼結体は、亜酸化銅以外の銅もしくは銅化合物が存在していることから、波長が６００ｎｍ～１２００ｎｍの光を適切に透過することができず、光透過無となることが分かる。 (optional evaluation)
As an optional evaluation, the transmittance of the sintered body to light in the visible to infrared region was evaluated. In the evaluation of the transmittance, the transmittance of the sintered body was measured by a Hitachi High-Tech Science ultraviolet-visible near-infrared spectrophotometer (UH4150) as a visible infrared spectrophotometer, with the data mode set to transmittance measurement (%T), the start wavelength set to 1200 nm, the end wavelength set to 300 nm, the scan speed set to 600 nm/min, and the sampling interval set to 1.00 nm. At this time, according to the Lambert-Beer law, it is known that the relational formula: I 1 /I 0 =exp(-α·L) (formula (13)) holds between the transmittance (I 1 /I 0 , I 1 : transmitted light intensity, I 0 : incident light intensity), the thickness (L) of the measured object, and the absorption coefficient (α). For each example and comparative example, the absorption coefficient (α(λ)) at each wavelength was calculated from the transmittance and film thickness of the obtained sintered body according to formula (13). Based on this absorption coefficient (α(λ)), the average transmittance at a film thickness of 0.1 μm and a wavelength of 600 nm to 1200 nm was calculated from formula (13). An average transmittance ("visible/infrared transmittance" in the figure) of 40% or more was considered to be transmitted, and an average transmittance of less than 40% was considered to be non-transmitted. As shown in Figures 5A to 5Ze, in Examples 1 to 216, by setting appropriate manufacturing conditions, light with a wavelength of 600 nm to 1200 nm is appropriately transmitted, and it can be suitably applied to, for example, a tandem solar cell combined with a crystalline Si solar cell, and is therefore more preferable. On the other hand, the sintered bodies of Comparative Examples 1 to 48, which were heated by irradiating light with a spectral distribution having a peak wavelength outside the visible to infrared region, and the sintered bodies of Comparative Examples 49 to 102, which were heated in an atmosphere with an oxygen concentration of less than 10%, contain copper or copper compounds other than cuprous oxide, and therefore cannot appropriately transmit light with a wavelength of 600 nm to 1200 nm, resulting in no light transmission.
　また、オプションの評価として、焼結体に対して、可視赤外分光光度計として、日立ハイテクサイエンス社の紫外可視近赤外分光光度計（ＵＨ４１５０）により、データモードを透過率測定（％Ｔ）とし、開始波長３００ｎｍ、終了波長１２００ｎｍとし、スキャンスピードを６００ｎｍ／ｍｉｎとし、サンプリング間隔を１．００ｎｍとして、焼結体の透過率を測定した。各実施例、比較例について、得られた焼結体の透過率と膜厚より、式（１３）より各波長における吸収係数（α（λ））を求めた。この吸収係数（α（λ））を元に、膜厚が０．１μｍでの、波長３００ｎｍ以上６００ｎｍ未満の光の平均透過率（Ｔ１）および、波長６００ｎｍ～１２００ｎｍの光の平均透過率（Ｔ２）を、式（１３）より算出した。波長３００ｎｍ以上６００ｎｍ未満の光の平均透過率（Ｔ１）に対する、波長６００ｎｍ～１２００ｎｍの光の平均透過率（Ｔ２）の比率を、透過率比率（Ｔ２／Ｔ１）とした。透過率比率の判定結果として、３．５以上の場合を合格とし、３．５未満の場合を不合格とした。各例の透過率比率の判定結果を、図５Ａ～図５Ｚｅに示す。 In addition, as an optional evaluation, the transmittance of the sintered body was measured using a Hitachi High-Tech Science ultraviolet-visible near-infrared spectrophotometer (UH4150) as a visible infrared spectrophotometer, with the data mode set to transmittance measurement (%T), the start wavelength set to 300 nm, the end wavelength set to 1200 nm, the scan speed set to 600 nm/min, and the sampling interval set to 1.00 nm. For each example and comparative example, the absorption coefficient (α(λ)) at each wavelength was calculated from the transmittance and film thickness of the obtained sintered body using formula (13). Based on this absorption coefficient (α(λ)), the average transmittance (T 1 ) of light with a wavelength of 300 nm or more and less than 600 nm and the average transmittance (T 2 ) of light with a wavelength of 600 nm to 1200 nm at a film thickness of 0.1 μm were calculated using formula (13). The ratio of the average transmittance ( T2 ) of light having a wavelength of 600 nm to 1200 nm to the average transmittance ( T1 ) of light having a wavelength of 300 nm or more and less than 600 nm was defined as the transmittance ratio ( T2 / T1 ). As a result of the transmittance ratio judgment, a value of 3.5 or more was deemed to be pass, and a value of less than 3.5 was deemed to be fail. The judgment results of the transmittance ratio for each example are shown in Figures 5A to 5Ze.
　以上、本発明の実施形態を説明したが、この実施形態の内容により実施形態が限定されるものではない。また、前述した構成要素には、当業者が容易に想定できるもの、実質的に同一のもの、いわゆる均等の範囲のものが含まれる。さらに、前述した構成要素は適宜組み合わせることが可能である。さらに、前述した実施形態の要旨を逸脱しない範囲で構成要素の種々の省略、置換又は変更を行うことができる。 　Although the embodiment of the present invention has been described above, the embodiment is not limited to the contents of this embodiment. Furthermore, the above-mentioned components include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-mentioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-mentioned embodiment.
　１０　銅インク
　１２　銅粒子
　１４　多価アルコール
　１６　溶媒
　１８　有機溶媒 10 Copper ink 12 Copper particles 14 Polyhydric alcohol 16 Solvent 18 Organic solvent

Claims (10)

  1. 　銅粒子を含む液状の組成物である銅インクを得るステップと、
    　前記銅インクを、基材上に塗布もしくは印刷することにより膜を形成するステップと、
    　前記銅インクが基材上に形成された膜を乾燥した後、酸素濃度が１０％以上２１％以下の雰囲気下で、波長の範囲が可視～赤外領域の光を照射して加熱することで、前記銅インク中の前記銅粒子を酸化及び焼結して、前記基材上に亜酸化銅を製造するステップと、
    　を含む、
    　亜酸化銅の製造方法。     Obtaining a copper ink, which is a liquid composition including copper particles;
    forming a film by applying or printing the copper ink onto a substrate;
    a step of drying the film formed by the copper ink on the substrate, and then irradiating the film with light having a wavelength in the visible to infrared range in an atmosphere having an oxygen concentration of 10% to 21% and heating the film to oxidize and sinter the copper particles in the copper ink, thereby producing cuprous oxide on the substrate;
    including,
    How to make cuprous oxide.
  2. 　前記亜酸化銅を製造するステップにおいては、照射する光のピークとなる強度の波長が、０．６μｍ以上１０μｍ以下である分光分布を有する光により、前記銅インクが基材上に形成された膜を加熱する、請求項１に記載の亜酸化銅の製造方法。 The method for producing cuprous oxide according to claim 1, wherein in the step of producing the cuprous oxide, the film formed by the copper ink on the substrate is heated by light having a spectral distribution in which the wavelength of the peak intensity of the irradiated light is 0.6 μm or more and 10 μm or less.
  3. 　前記亜酸化銅を製造するステップにおいては、１８０℃以上５００℃以下の加熱温度で、前記銅インクが基材上に形成された膜を加熱する、請求項１又は請求項２に記載の亜酸化銅の製造方法。 The method for producing cuprous oxide according to claim 1 or 2, wherein in the step of producing the cuprous oxide, the film formed by the copper ink on the substrate is heated at a heating temperature of 180°C or higher and 500°C or lower.
  4. 　前記亜酸化銅を製造するステップにおいては、前記加熱温度での保持時間を、１秒以上６００秒以下とする、請求項３に記載の亜酸化銅の製造方法。 The method for producing cuprous oxide according to claim 3, wherein in the step of producing the cuprous oxide, the holding time at the heating temperature is 1 second or more and 600 seconds or less.
  5. 　前記亜酸化銅を製造するステップにおいては、前記加熱温度までの昇温速度を、０．１℃／秒以上５０℃／秒以下とする、請求項３に記載の亜酸化銅の製造方法。 The method for producing cuprous oxide according to claim 3, wherein in the step of producing the cuprous oxide, the rate of temperature rise to the heating temperature is 0.1°C/sec or more and 50°C/sec or less.
  6. 　前記銅インクを得るステップにおいては、粒径が１０ｎｍ以上１０００ｎｍ以下であり、かつ、表面が有機物で被覆されている前記銅粒子を含む前記銅インクを得る、請求項１又は請求項２に記載の亜酸化銅の製造方法。 The method for producing cuprous oxide according to claim 1 or 2, wherein in the step of obtaining the copper ink, the copper ink is obtained, the copper particles having a particle size of 10 nm or more and 1000 nm or less, and the surface of which is coated with an organic substance.
  7. 　前記銅インクを得るステップにおいては、前記銅粒子と、溶媒と、大気圧における沸点が１５０℃以上であり、水と混和可能な有機溶媒と、ＯＨ基を２つ以上含み、水及びエタノールに溶解可能な多価アルコールと、を含む前記銅インクを得る、請求項１又は請求項２に記載の亜酸化銅の製造方法。 The method for producing cuprous oxide according to claim 1 or 2, wherein in the step of obtaining the copper ink, the copper ink is obtained, the copper ink containing the copper particles, a solvent, an organic solvent having a boiling point of 150°C or higher at atmospheric pressure and miscible with water, and a polyhydric alcohol containing two or more OH groups and soluble in water and ethanol.
  8. 　膜厚を０．１μｍとした際の、波長６００ｎｍ～１２００ｎｍの光の平均透過率が、４０％以上１００％以下である、亜酸化銅膜。 A cuprous oxide film that has an average transmittance of 40% or more and 100% or less for light with wavelengths between 600 nm and 1200 nm when the film thickness is 0.1 μm.
  9. 　膜厚を０．１μｍとした際の、波長３００ｎｍ～６００ｎｍの光の平均透過率（Ｔ１）に対する、波長６００ｎｍ～１２００ｎｍの光の平均透過率（Ｔ２）の比率（Ｔ２／Ｔ１）が、３．５以上である、請求項８に記載の亜酸化銅膜。 9. The cuprous oxide film according to claim 8, wherein, when the film thickness is set to 0.1 μm, a ratio (T 2 /T 1 ) of an average transmittance (T 2 ) of light having a wavelength of 600 nm to 1200 nm to an average transmittance (T 1 ) of light having a wavelength of 300 nm to 600 nm is 3.5 or more.
  10. 　焼結体である、請求項８又は請求項９に記載の亜酸化銅膜。 The cuprous oxide film according to claim 8 or claim 9, which is a sintered body.
PCT/JP2023/038886 2022-10-28 2023-10-27 Method for producing cuprous oxide, and cuprous oxide film WO2024090555A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10265960A (en) * 1997-03-27 1998-10-06 Star Micronics Co Ltd Production of cuprous oxide film
JP2011119454A (en) * 2009-12-03 2011-06-16 Tftech:Kk Manufacturing method of copper-oxide (i) film having performance of p-type semiconductor and method of manufacturing solution for creating the film
JP2015044705A (en) * 2013-08-28 2015-03-12 国立大学法人 岡山大学 Manufacturing method of nanoparticle of cuprous oxide
CN111748804A (en) * 2020-07-14 2020-10-09 济南大学 Preparation of cubic cuprous oxide based on photo-assisted reduction method
JP2021009958A (en) * 2019-07-02 2021-01-28 株式会社東芝 Solar cell, laminate, multi-junction solar cell, solar cell module and photovoltaic power generation system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10265960A (en) * 1997-03-27 1998-10-06 Star Micronics Co Ltd Production of cuprous oxide film
JP2011119454A (en) * 2009-12-03 2011-06-16 Tftech:Kk Manufacturing method of copper-oxide (i) film having performance of p-type semiconductor and method of manufacturing solution for creating the film
JP2015044705A (en) * 2013-08-28 2015-03-12 国立大学法人 岡山大学 Manufacturing method of nanoparticle of cuprous oxide
JP2021009958A (en) * 2019-07-02 2021-01-28 株式会社東芝 Solar cell, laminate, multi-junction solar cell, solar cell module and photovoltaic power generation system
CN111748804A (en) * 2020-07-14 2020-10-09 济南大学 Preparation of cubic cuprous oxide based on photo-assisted reduction method

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