WO2014119791A1 - Novel coated copper fine particles and production method therefor - Google Patents

Novel coated copper fine particles and production method therefor Download PDF

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Publication number
WO2014119791A1
WO2014119791A1 PCT/JP2014/052514 JP2014052514W WO2014119791A1 WO 2014119791 A1 WO2014119791 A1 WO 2014119791A1 JP 2014052514 W JP2014052514 W JP 2014052514W WO 2014119791 A1 WO2014119791 A1 WO 2014119791A1
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copper
fine particles
copper fine
fatty acid
coated copper
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PCT/JP2014/052514
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French (fr)
Japanese (ja)
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正人 栗原
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国立大学法人山形大学
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
    • H01B1/026—Alloys based on copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/102—Metallic powder coated with organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C9/00—Alloys based on copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles

Definitions

  • the present invention relates to coated copper fine particles obtained by reducing fatty acid copper with a reducing compound and a method for producing the same. More specifically, the present invention relates to a method for producing copper fine particles using a reducing agent and fatty acid copper in an alkylamine.
  • a copper precursor compound such as acetylacetonato copper is mixed with an amine-based compound such as oleylamine to prepare a uniform mixture, and then a reducing agent is optionally added, followed by heating to obtain a copper ion species.
  • a method for producing cubic-shaped copper nanoparticles obtained by reducing a metal to a metal oxide state or a metal oxide state (Patent Document 1).
  • 6.5 to 8.5 times the amount of the copper precursor, oleylamine and dodecyl are used in order to make the form of the copper nanoparticles to be formed into a cubic form having a desired size.
  • An amine or the like needs to be used, and a large amount of organic solvent is also required for recovering the obtained copper nanoparticles.
  • a method for producing metallic copper fine particles whose surface is capped with a fatty acid including a step of heating and reacting (Patent Document 2).
  • the reaction solution needs to be heated to 200 ° C. (Example 1), while copper acetate is added with formic acid in the presence of oleic acid and oleylamine.
  • heating is performed at 130 ° C. (Example 2), and it is considered difficult to control the formation reaction of the copper fine particles by this method.
  • the present inventors have so far prepared a process of producing a composite compound by mixing a compound containing copper and a reducing compound, and copper fine particles coated with alkylamine by heating the composite compound in an alkylamine.
  • a process for producing coated copper fine particles without being limited by the supply of substances involved in the reaction see Patent Document 3.
  • a complex compound with a reducing compound is formed in advance, for example, a complex compound such as a complex of copper oxalate and hydrazine.
  • spontaneous decomposition can occur at a relatively low temperature in the coexistence state with the alkylamine, and coated copper fine particles coated with a protective film containing the alkylamine can be produced.
  • coated copper fine particles Although it is possible to produce coated copper fine particles, it is desirable to develop a process for producing coated copper fine particles that can be carried out at a lower temperature and with a simpler and more flexible synthesis process. Then, this invention makes it a subject to provide the manufacturing process of the covering copper fine particle which can be implemented at low temperature.
  • the inventors of the present invention perform the step of producing coated copper fine particles at a lower temperature by using a predetermined fatty acid copper as the copper compound. It became possible to improve the flexibility of the whole process. It has also been found that this process can easily and in large quantities produce fine copper particles that are stable in air, stable in particle size distribution, and stable.
  • the method for producing coated copper fine particles of the present invention includes a step of heating a mixture containing fatty acid copper, a reducing compound, and an alkylamine, and using fatty acid copper having 9 or less carbon atoms as the fatty acid copper.
  • the fatty acid copper may be dissolved or suspended in the presence of an alkylamine, mixed with a reducing compound, heated, or mixed with the fatty acid copper and the reducing compound in advance. It may be added and heated.
  • the production of the fatty acid copper and the mixing of the reducing compound are simultaneously performed by mixing the copper hydroxide, the fatty acid and the reducing compound in an appropriate solvent. Can be done automatically.
  • the solvent used in the method of the present invention is preferably a polar organic solvent such as 1-propanol or 2-propanol.
  • the method of the present invention by using a fatty acid copper having 9 or less carbon atoms as a starting material for producing copper fine particles, in addition to a process for obtaining an intermediate in which a molecule having a reducing action is previously bound to a starting material, even when the starting material is introduced into a mixture of alkylamine, which is a reaction medium and also a coating of copper fine particles, and a molecule having a reducing action, the coated copper fine particles can be produced satisfactorily. Moreover, it becomes possible to produce coated copper fine particles by a reaction at a lower temperature. As a result, according to the method of the present invention, the manufactured coated copper fine particles can be sintered at a lower temperature, and the degree of freedom of the process can be increased.
  • FIG. 2 is a powder X-ray diffraction (XRD) pattern of the coated copper fine particle powder synthesized in Example 1.
  • FIG. 2 It is the transmission electron microscope image and electron beam diffraction in the different magnification of the covering copper fine particle synthesize
  • FIG. 2 is a high-resolution electron microscope image of coated copper fine particles synthesized in Example 1.
  • FIG. 3 is a result of simultaneous thermogravimetric differential thermal analysis of coated copper fine particles synthesized in Example 1.
  • 3 is a powder X-ray diffraction (XRD) pattern of coated copper fine particles synthesized in Example 2.
  • XRD powder X-ray diffraction
  • FIG. 3 is an FE-STEM image of coated copper fine particles synthesized in Example 2.
  • FIG. 3 is an FE-STEM image of coated copper fine particles synthesized in Example 3.
  • FIG. 4 is a powder X-ray diffraction (XRD) pattern of coated copper fine particles synthesized in Example 4.
  • XRD powder X-ray diffraction
  • the reaction conditions such as the starting material, temperature, solvent and the like are adjusted without providing a separate step of forming a complex of such a copper-containing compound and a reducing compound.
  • the fatty acid copper and the reducing compound are mixed in advance in a solvent, preferably dissolved in the solvent, and these complexes are generated more rapidly. It is thought that it is easy to mix more uniformly. That is, in general, the reducing agent is often used in an aqueous medium, and the reduction reaction does not proceed uniformly because it is not uniformly mixed in an organic solvent-based reaction.
  • the reducing agent is often used in an aqueous medium, and the reduction reaction does not proceed uniformly because it is not uniformly mixed in an organic solvent-based reaction.
  • the solvent used in the method of the present invention is preferably a polar solvent in order to promote dissolution of fatty acid copper and the reducing compound.
  • generating a covering copper fine particle can be advanced efficiently at low temperature rather than before. For this reason, it is expected that the sintering temperature of the coated copper fine particles to be produced is further lowered than before.
  • the method for producing coated copper fine particles according to the present invention will be specifically described.
  • fatty acid copper As a raw material of copper used for producing the coated copper fine particles in the present invention, fatty acid copper having 9 or less carbon atoms can be used.
  • the term “fatty acid copper” is a salt compound of a fatty acid having 2 or more carbon atoms and copper, and the fatty acid may be either saturated or unsaturated.
  • select the fatty acid copper to be used because the properties such as solvent dispersibility and sinterability of the coated copper fine particles are affected by the difference in the carbon number of the fatty acid copper used. It is preferable to do.
  • fatty acid copper typically used one selected from the group consisting of copper acetate, copper propionate, copper butyrate, copper valerate, copper caproate, copper enanthate, copper caprylate and copper nonanoate or Two or more types of fatty acid copper.
  • these fatty acid coppers as the raw material for the coated copper fine particles, the degree of freedom of the process for producing the coated copper fine particles is improved, and the coated copper fine particles can be produced at a lower temperature. As a result, it is expected to lower the sintering temperature of the thin film produced using the coated copper fine particles of the present invention.
  • a reducing compound having a reducing action is mixed with the fatty acid copper mainly in an appropriate solvent.
  • a complex compound such as a complex is formed between the two compounds.
  • the reducing compound becomes an electron donor for copper ions in fatty acid copper and tends to cause reduction of copper ions. Therefore, by spontaneous pyrolysis compared to fatty acid copper used. It is thought that copper atoms are likely to be liberated.
  • the reaction is caused to occur within the complex produced in advance, thereby limiting the supply of substances involved in the reaction.
  • the copper atoms are supplied by causing a spontaneous decomposition reaction of a complex or the like by setting conditions such as temperature and pressure, and uniform coated copper fine particles can be produced.
  • the reducing compound used in this case include hydrazine compounds such as hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate, sodium borohydride, and sodium sulfite.
  • Examples include sodium bisulfite, sodium thiosulfate, and sodium hypophosphite, but those having an amino group such as hydrazine and hydrazine compounds are preferred.
  • the reducing agent having an amino group easily forms a coordinate bond with a copper atom in the fatty acid copper, and easily forms a complex with the fatty acid copper while maintaining the structure of the fatty acid copper. This is because a reduction reaction of copper ions occurs.
  • any compound capable of forming a complex or the like that causes reduction / release of a copper atom in a temperature range that does not cause evaporation or decomposition of an alkylamine used as a reaction medium in a subsequent heating step may be used. It is not limited.
  • a high temperature is required for the decomposition, which causes evaporation and decomposition of the alkylamine itself as a reaction medium. For the reason, it becomes difficult to solve the problems of the present invention.
  • a compound selected from the group consisting of hydrazine, hydroxylamine, and derivatives thereof is particularly preferable. It is done. These compounds can form a complex by binding a nitrogen atom constituting a skeleton to a copper atom in a copper-containing compound through a coordination bond.
  • the reducing power is generally stronger than that of alkylamines, the resulting complex undergoes spontaneous decomposition under relatively mild conditions to reduce and release copper atoms, thereby reducing copper fine particles coated with alkylamine. Can be generated.
  • the hydrazine derivative is obtained by substituting one to three hydrogen atoms contained in hydrazine with a predetermined alkyl group, for example, methyl hydrazine, ethyl hydrazine, n-propyl hydrazine, i-propyl hydrazine, n- Butyl hydrazine, i-butyl hydrazine, sec-butyl hydrazine, t-butyl hydrazine, n-pentyl hydrazine, i-pentyl hydrazine, neo-pentyl hydrazine, t-pentyl hydrazine, n-hexyl hydrazine, i-hexyl hydrazine, n- Heptylhydrazine, n-octylhydrazine, n-nonylhydrazine, n-decyl
  • a hydroxylamine derivative is one obtained by substituting one of hydrogens contained in hydroxylamine with a substituent such as a predetermined alkyl group, hydroxyalkyl group, sulfoalkyl group or carboxyalkyl group.
  • a substituent such as a predetermined alkyl group, hydroxyalkyl group, sulfoalkyl group or carboxyalkyl group.
  • N, N-di (sulfoethyl) hydroxylamine, monomethylhydroxylamine, dimethylhydroxylamine, monoethylhydroxylamine, diethylhydroxylamine, N, N-di (carboxyethyl) hydroxylamine are preferred. It is possible to adjust the reactivity with fatty acid copper by using its derivatives instead of hydrazine and hydroxylamine as appropriate, and spontaneous decomposition under appropriate conditions according to the fatty acid copper used.
  • the resulting complex can be produced.
  • it is effective to promote the formation of a composite compound by using an appropriately selected hydrazine derivative.
  • the fatty acid copper and the reducing compound are preferably mixed by cooling to about 10 ° C. or less, more preferably about 5 ° C. or less, and most preferably about 0 ° C. or less.
  • the ratio of the reducing compound mixed with the fatty acid copper for the formation of the complex is equal to the molar ratio (hereinafter referred to as “constant ratio”) of both in the complex formed from the fatty acid copper and the reducing compound, or the like. It is preferable that the ratio is more enriched with reducing compounds. If the ratio of the reducing compound is equal to or less than the constant ratio in the complex or the like, fatty acid copper that does not form a complex or the like is generated, resulting in a metal atom that is not liberated, resulting in a decrease in the yield of copper fine particles.
  • the preferable mixing ratio of the reducing compound is 4 times or less of the ratio in the complex or the like.
  • a good complex or the like can be formed by mixing the reducing compound with fatty acid copper so as to be 1 to 2 times.
  • the reducing compound to be used can be used by mixing two or more kinds of reducing compounds depending on the properties thereof.
  • a reducing compound containing an appropriate additive component for the purpose of assisting the formation of a complex or the like within a range that does not inhibit the properties of the complex or the like to be generated.
  • a fatty acid copper and a reducing compound are mixed, the formation of a complex or the like is promoted by causing a polar solvent capable of dissolving them without causing a reaction with a substance in the system and as a reaction medium.
  • a uniform complex etc. can be produced
  • the polar solvent is preferably one having solubility in water (H 2 O) at room temperature.
  • Alcohols exhibiting solubility in water have a certain polarity, and the use of such alcohols can promote the formation of complexes such as fatty acid copper and a reducing compound. Although the specific action of such an alcohol is not clear, it is considered that complex formation is promoted by promoting contact with a water-soluble reducing compound while dissolving solid state fatty acid copper.
  • Examples of the alcohol showing the solubility in water include linear alkyl alcohols having one OH group, from methanol having 1 carbon atom to octanol having 8 carbon atoms.
  • the number of carbon atoms is 9 or more, it does not substantially dissolve in water, and even if such an alcohol is interposed during the formation of a complex or the like, the formation promoting action of the complex or the like is not observed.
  • phenols or those obtained by substituting hydrogen atoms of appropriate hydrocarbons having an ether bond in the molecule with OH groups can be used.
  • glycols containing two OH groups, glycerin containing three OH groups, Pentaerythritol and the like containing 4 OH groups are preferably used.
  • alcohol compounds examples include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, allyl alcohol, benzyl alcohol, pinacol, propylene glycol, menthol, catechol, hydroquinone, salicyl alcohol, pentaerythritol, sucrose, Examples thereof include glucose, xylitol, methoxyethanol, triethylene glycol monomethyl ether, pentaerythritol, and the like, and polyethylene glycols including ethylene glycol, triethylene glycol, tetraethylene glycol, and pentaethylene glycol.
  • dimethyl (hydroxymethyl) phosphonate, dimethyl (2-hydroxyethyl) phosphonate, or the like can be used as the alcohol compound containing a phosphorus atom.
  • alcohol compounds such as 2- (trimethylsilyl) ethanol, 2- (trimethylsilyl) -1-propanol and triethylsilanol containing silicon atoms can be used.
  • the polar solvent used in a preferred embodiment of the present invention is an alcohol that exhibits extremely high solubility in water, and examples thereof include 1-propanol and 2-propanol. More preferred is 1-propanol.
  • the mixture of fatty acid copper and reducing compound produced above is mixed with a sufficient amount of alkylamine and heated to spontaneously decompose fatty acid copper.
  • Copper fine particles are obtained by the formation and aggregation of copper atoms by the reaction.
  • the coating by the alkylamine used on the surface of the copper fine particle arises in that case, the stable coated copper fine particle which is hard to be oxidized with oxygen in the air can be obtained.
  • the decomposition temperature of the fatty acid copper is desirably about 150 ° C. or lower.
  • the evaporation rate is high when an alkylamine having a high vapor pressure such as butylamine or hexylamine is used as the reaction medium. Therefore, the alkylamine used as a reaction medium is actually limited to a long chain having 8 or more carbon atoms, and the low-temperature sinterability of the coated copper fine particles is hindered.
  • the decomposition temperature of the complex is less than 130 ° C, more preferably 120 ° C, 110 ° C, or 100 ° C.
  • an alkylamine having about 6 carbon atoms can be used stably, and copper particles are generated under relatively mild conditions. It is possible to produce coated copper fine particles that are fine and have a narrow particle size distribution.
  • a low molecular weight alkylamine having a relatively low boiling point can be used, so that the protective coating can be easily removed and coated copper fine particles that can be sintered at a low temperature can be easily produced.
  • Fatty acid copper to be used is different from the reaction to produce a copper atom by a reducing compound, but for example, when nonanoic acid copper is used as the fatty acid copper and hydrazine (or a derivative thereof) is used as the reducing compound, By mixing copper nonanoate and hydrazine and the like, a complex composed of both compounds is produced. By mixing and heating this with alkylamine, copper nonanoate undergoes thermal decomposition even at a low temperature of about 100 ° C. Manufactured.
  • nonanoic acid and alkylamine existing in the system prevent invasion of oxygen existing outside the system, adhere to the reduced copper atoms, and finally coat the copper fine particles, Even when thermal decomposition is performed in the atmosphere, it is considered that oxidation of copper atoms is suppressed and stable coated copper fine particles are produced.
  • various fatty acids having different carbon numbers are used, or by adjusting the molecular weight of the alkylamine, the particle size of the generated copper fine particles is desired from several nm to about 100 nm. It is possible to adjust the size.
  • the first step of mixing the above-described fatty acid copper and the reducing compound, and the second step of heating the complex in the presence of an alkylamine to produce copper fine particles include 1 It can be carried out simultaneously or sequentially in one container. “Simultaneously” means that copper fine particles are produced by mixing fatty acid copper, a reducing compound, and an alkylamine at the same time, and preferably adding a polar solvent thereto to solubilize, followed by heating at about 100 ° C. Can do.
  • the first step and the second step can be performed sequentially, and the heating temperature at this time may be the same or different. More preferably, the first step is performed by cooling to about 10 ° C. or less, and the second step is performed by heating to about 150 ° C., more preferably about 100 ° C.
  • Alkylamine When a mixture of fatty acid copper and a reducing compound is heated, the alkylamine mixed with the mixture mainly functions as a reaction medium for the decomposition reaction of the complex as described above, and is generated by the reducing action of hydrazine. It is considered that protons are trapped and the reaction solution is inclined to be acidic and copper atoms generated by oxygen in the air are prevented from being oxidized.
  • the alkylamine used in the present invention can be appropriately selected from known alkylamines according to the thermal decomposition conditions of the complex used, the properties expected of the copper fine particles to be produced, and the like. .
  • the alkylamine used in the thermal decomposition of the complex may constitute a coating of copper fine particles together with the fatty acid.
  • the thermal decomposition conditions of the complex to be produced and the coated copper fine particles to be produced are expected.
  • it can be appropriately selected from known alkylamines.
  • the alkylamine used in the thermal decomposition of the mixture is appropriately selected according to the purpose of the coated copper fine particles to be produced as described above.
  • Examples of the alkylamine (monoamine) having one amino group in the molecule include 2-ethoxyethylamine, dipropylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, 3-butoxypropylamine, octylamine, nonylamine Alkylamines such as decylamine, 3-aminopropyltriethoxysilane, dodecylamine, hexadecylamine, octadecylamine, and oleylamine are practical in terms of industrial production and availability.
  • hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine and dodecylamine having 6 to 12 carbon atoms are more preferably used. These may be used alone or in combination of two or more.
  • examples of the alkyldiamine having two amino groups in the molecule include ethylenediamine, N, N-dimethylethylenediamine, N, N′-dimethylethylenediamine, N, N-diethylethylenediamine, N, N′-diethylethylenediamine, 1 , 3-propanediamine, 2,2-dimethyl-1,3-propanediamine, N, N-dimethyl-1,3-diaminopropane, N, N′-dimethyl-1,3-diaminopropane, N, N— Diethyl-1,3-diaminopropane, 1,4-diaminobutane, 1,5-diamino-2-methylpentane, 1,6-diaminohexane, N, N′-dimethyl-1,6-diaminohexane, 1, Examples thereof include, but are not limited to, 7-diaminoheptane and 1,8-d
  • the alkylamine used for the thermal decomposition of the complex one kind of alkylamine may be used, or a plurality of alkylamines may be mixed and used.
  • the alkylamine used as the reaction medium is preferably a liquid at room temperature because it is easy to handle. Therefore, when using an alkylamine that has a large molecular weight and is solid at room temperature, it is mixed with a small molecular weight. It is preferable to use it in a liquid state.
  • the coated copper fine particles according to the present invention typically have an average particle size of 50 nm or less, and further an average particle size of 20 nm or less. Therefore, when the protective film provided on the surface is detached, It is possible to form a copper film by sintering even at an extremely low temperature as compared with the copper powder.
  • a fatty acid contained in fatty acid copper used as a source of copper atoms and an alkylamine used in the thermal decomposition of the complex form a protective film that can be easily detached by using a high vapor pressure. Sintering at a lower temperature is possible.
  • the coated copper fine particles produced are prevented from being oxidized by forming a strong protective film, and can be stored for a long time even in the air.
  • At least a part of the protective film covering the surface of the copper fine particles of the present invention contains the above-mentioned fatty acid copper and / or alkylamine, but the content of the coated copper fine particles relative to the weight, that is, the coverage is 15 wt. % Or less is preferable.
  • the fatty acid and alkylamine forming the protective film are eliminated and the copper fine particles are brought into direct contact with each other, thereby forming a conductor, and at a temperature of about 200 ° C. or less.
  • copper atoms constituting the copper fine particles are diffused and fused with each other, and the conductorization progresses. This phenomenon is because the fatty acids and alkylamines that form the protective film are weakly bonded to the surface of the copper fine particles due to the coordinate bond via the carboxyl group or amino group, and these can be removed relatively easily. It is thought to be because.
  • the ink dispersed in an organic solvent is printed in a desired shape by various methods such as inkjet printing, and heated to a predetermined temperature in an inert atmosphere to remove the protective film, Since the exposed copper fine powders cause sintering, copper wiring and the like can be easily formed by printing. It is also possible to perform the sintering after coating the coated copper fine particles in the form of a paste or powder.
  • the coated copper fine particles according to the present invention are used to form a conductor layer on the non-conductive surface instead of the conventional electroless plating or the like, and the metal layer is pressed between the metals. Therefore, it can be used for an adhesive layer for mechanically and electrically joining metals together.
  • the material and shape of the substrate to which the ink or paste containing the coated copper fine particles is applied are not particularly limited.
  • the material and shape of the substrate to which the ink or paste containing the coated copper fine particles is applied are not particularly limited.
  • thermoplastic resin, thermosetting resin, glass, paper, metal, silicon, ceramics, etc. can be used.
  • thermoplastic resin examples include polyethylene, polyethylene terephthalate, polypropylene, polyvinyl chloride, polystyrene, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer resin, polycarbonate, polyacetal, polybutylene terephthalate, polyphenylene oxide, polyamide, Polyphenylene sulfide, polysulfone, polyethersulfone, polyether-etherketone, polyarylate, aromatic polyester, aromatic polyamide, fluororesin, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetate, polyvinyl formal, polyvinyl butyral, polymethyl methacrylate And cellulose acetate.
  • thermosetting resin examples include phenol resin, urea resin, xylene resin, urea resin, melamine resin, epoxy resin, silicon resin, diallyl phthalate resin, furan resin, aniline resin, acetone-formaldehyde resin, alkyd resin, and the like.
  • the ceramic means inorganic compounds such as oxides, carbides, nitrides, borides and the like. For example, alumina (Al 2 O 3 ), silicon nitride (SiN), silicon carbide (SiC), aluminum nitride (AlN) ), Zirconium boride (ZrB 2 ), and the like.
  • the step of forming a predetermined film or the like on the substrate using ink containing coated copper fine particles is not particularly limited as long as it is a method capable of forming a film with a desired thickness, and general spin coating, spray coating, etc. Can be used.
  • the process of forming a pattern serving as a wiring precursor on a substrate with a film containing coated copper fine particles can use various conventional printing methods such as a screen printing method, an ink jet printing method, and an intaglio. Printing, letterpress printing, lithographic printing, and the like can be used.
  • the use of the metal film obtained by making a film containing coated copper fine particles into a conductor is not limited to electrical wiring, and can be used for mirror surfaces for optical devices, various decorations, and the like.
  • the thickness of the film formed on the substrate with the ink containing the coated copper fine particles can be appropriately set according to the purpose of the metal film obtained by making the conductor. If it is a normal electric wiring etc., a favorable characteristic can be acquired by forming a film
  • Example 1.2 The copper fine particles obtained in Example 1.2 were dispersed in toluene, and this was dropped onto a transmission electron microscope (TEM) substrate (carbon support film) to attach the copper fine particles to the TEM substrate. From the field emission transmission electron microscopic image (FE-TEM image) (JEOL JEM-2100F), it was found that spherical copper fine particles having a particle diameter of 10 nm or less were observed and large particles of 100 to 200 nm were also included. (Fig. 2) High-resolution TEM (HR-TEM) observation was performed on nano-particles of 10 nm or less, which are considered to be susceptible to air oxidation, and the lattice spacing of the observed lattice image is 0.21 nm. This coincided with the lattice spacing of the (111) plane of copper (FIG. 3), so no component derived from copper oxide was observed from the electron microscope.
  • HR-TEM High-resolution TEM
  • thermogravimetric differential thermal analysis In order to examine the content of protective molecules in the copper fine particle powder obtained in Example 1.2, simultaneous thermogravimetric differential thermal analysis (TG-DTA) was performed (FIG. 4).
  • TA instrument SDTQ600 was used, and the temperature was raised at 10 ° C. per minute under a pure nitrogen stream (150 mL per minute). By heating from room temperature to 250 ° C., a two-stage weight reduction was observed. When the temperature exceeds 400 to 500 ° C., the weight reduction becomes constant, and 5.3% by weight of the weight reduction rate at this time is the weight of the organic protective molecule covering the surface of the copper fine particles. From this weight loss, the copper based yield in Example 1.2 was calculated to be 96%.
  • thermogravimetric mass spectrometry Mass spectrometry (TG-Mass) of the desorbed protected molecules was performed using a mass analyzer JEOL (JMS-Q1050GC) while following the thermogravimetric decrease of the copper fine particle powder obtained in Example 1.2. .
  • the ionization method was carried out with EI and PI (photoionization) under a heating condition of 15 ° C. per minute under a helium stream (100 mL per minute). It was found that both the component derived from fatty acids (acetic acid and nonanoic acid) and the protective molecule derived from hexylamine were eliminated by the thermogravimetric decrease in the first stage up to 200 ° C. A component derived from nonanoic acid was detected in the thermogravimetric decrease in the second stage at 200 ° C. or higher.
  • Example 1.2 The copper fine particles obtained in Example 1.2 were dispersed in toluene to prepare a 50% by weight copper fine particle ink. This ink was dropped on a glass substrate and applied using a bar coater (Eiwa Hagi Seisakusho ⁇ 8 ⁇ 300 mm) to prepare a copper-gloss nanoparticle thin film. The obtained copper luster nanoparticle thin film was placed in an electric furnace (KDF S-70), the protective molecules were removed by heat and the particles were sintered together (sintering conditions: under argon, the heating rate was 10 ° C./min. 1 hour at each temperature reached (200, 220, 240, 260 ° C)). As shown in FIG.
  • Example 5 the copper fine particle thin film obtained in Example 1.2 was made into a conductor by heating at 200 ° C., and heated to 260 ° C. to have a volume resistivity (5.0 ⁇ cm, copper bulk resistance (1.7 ⁇ cm)). About 3 times the volume resistance).
  • the volume resistivity is calculated from the surface resistance measured with a four-end needle surface resistance measuring instrument (Kyowa Riken, K-705RS) and the film thickness obtained from a field emission scanning electron microscope (FE-SEM, JEOL JSM-7600F) image. did.
  • Example 2 Synthesis of copper fine particles using copper hydroxide (II) as a starting material
  • Example 2.1 ⁇ Electron microscope observation> The copper fine particles obtained in Example 2.1 were dispersed in toluene, and this was dropped on the TEM substrate, thereby attaching the copper fine particles to the TEM substrate. From the FE-STEM image (JEOL JSM-7600F), copper fine particles having two particle size distributions were observed. The particle size distributions were 7.6 ⁇ 2.3 nm (FIG. 7 (a)) and 24 ⁇ 3.3 nm (FIG. 7 (b)), respectively. In addition to the spherical shape, it was found that there were many prisms and hexagonal plates.
  • thermogravimetric differential thermal analysis In order to examine the content of protective molecules in the copper fine particle powder obtained in Example 2.1, a thermogravimetric differential thermal analysis (TG-DTA) was performed. By heating from room temperature to 250 ° C., a two-stage weight reduction was observed. When the temperature exceeds 400 to 500 ° C., the weight reduction becomes constant, and 9.2% by weight of the weight reduction rate at this time is the weight of the organic protective molecule covering the surface of the copper fine particles. From this weight loss, the copper based yield in Example 2.1 was calculated to be 81%.
  • TG-DTA thermogravimetric differential thermal analysis
  • Example 3 Method in which the order of addition of hexylamine and hydrazine was changed in the method of Example 2.
  • 0.62 g (6.3 mmol) of copper (II) hydroxide, 2.0 g (13 mmol) of nonanoic acid, 1-propanol 0.9 mL was added, and it heated and stirred at 100 degreeC using the aluminum block type heating stirrer.
  • 2.57 g (25.4 mmol) of hexylamine was added and stirred for 6 minutes.
  • This solution was ice-cooled, and 0.628 mL (12.7 mmol) of hydrazine monohydrate dissolved in 1 mL of 1-propanol was added.
  • thermogravimetric differential thermal analysis In order to examine the content of protective molecules contained in the copper fine particle powder obtained above, a thermogravimetric differential thermal analysis (TG-DTA) was performed. By heating from room temperature to 250 ° C., a two-stage weight reduction was observed. When the temperature exceeds 400 to 500 ° C., the weight reduction becomes constant, and 6.4% by weight of the weight reduction rate at this time is the weight of the organic protective molecule covering the surface of the copper fine particles. From this weight loss, the yield based on copper in Example 5 was calculated to be 92%.
  • TG-DTA thermogravimetric differential thermal analysis
  • Example 4 Synthesis of Copper Fine Particles Using One Type of Fatty Acid Copper fine particles were synthesized in the same manner as in Example 2 by replacing nonanoic acid with other fatty acids (3 to 7 carbon atoms).
  • Example 5 Synthesis of copper fine particles using two types of fatty acids In the same manner as in Example 2, two types of fatty acids (1: 1 in molar ratio) were simultaneously added to synthesize copper fine particles.

Abstract

The present invention addresses the issue of providing a coated copper fine particle production process capable of being implemented at low temperatures. Provided is a production method for coated copper fine particles, characterized by including a heating step in which a mixture containing a C9 or lower copper fatty acid, a reducing compound, and an alkyl amine is heated.

Description

新規被覆銅微粒子及びその製造方法Novel coated copper fine particles and method for producing the same
　本発明は、脂肪酸銅を還元性化合物で還元して得られる被覆銅微粒子及びその製造方法に関する。より詳細には、アルキルアミン中で還元剤と脂肪酸銅を用いて銅微粒子を製造する方法に関する。 The present invention relates to coated copper fine particles obtained by reducing fatty acid copper with a reducing compound and a method for producing the same. More specifically, the present invention relates to a method for producing copper fine particles using a reducing agent and fatty acid copper in an alkylamine.
　近年、金属微粒子分散体を用いてインクジェット印刷法や、スクリーン印刷法により所望のパターンを形成し、回路基板における配線等を形成するプリンテッドエレクトロニクス技術が注目されている。例えば、有機ＥＬディスプレイ（ＯＬＥＤ）や電子ペーパー、ＲＦＩＤタグなどへの使用が期待されている。インクジェットプリント用インクとして種々の銀ナノ粒子が開発されており、これらはバルク金属よりも融点が著しく降下し、低い温度で粒子同士の融着が起こる。しかしながら、銀ナノ粒子では、比較的高温高湿度の条件下でエレクトロマイグレーションが起こりやすいことや、銀自体が高価な金属であることから、導電性材料として大量に使用することが難しい。 In recent years, printed electronics technology that forms a desired pattern by using an ink jet printing method or a screen printing method using a metal fine particle dispersion to form wirings on a circuit board has attracted attention. For example, it is expected to be used for organic EL displays (OLED), electronic paper, RFID tags, and the like. Various silver nanoparticles have been developed as inks for ink jet printing, and these have a melting point that is significantly lower than that of bulk metals, and fusion of particles occurs at a low temperature. However, silver nanoparticles are difficult to use in large quantities as a conductive material because electromigration tends to occur under relatively high temperature and high humidity conditions, and silver itself is an expensive metal.
　そこで、導電性がよく、低コストでかつエレクトロマイグレーションが生じるおそれが少ない銅微粒子をインク化又はペースト化して配線形成用に用いる技術開発が強く望まれている。これまで、導電性インク用の銅ナノ粒子は、凝集や望ましくない酸化を抑制するための不活性雰囲気中、有機溶媒中にてキャッピング剤を用いて合成されてきた。しかしながら、従来ほとんどの銅ナノ粒子の製造方法は、処理能力が低く、拡張性がなく、そして凝集しやすいため経済的に実現可能でない。さらに、従来の還元方法では、銅塩の還元が反応溶媒中に水が存在するとＣｕ２Ｏの段階で停止してしまうため、純粋な銅ナノ粒子を得ることが極めて困難である。同時に、合成された銅ナノ粒子は空気中で容易に酸化されやすく、酸化銅の存在は銅ナノ粒子の焼結温度を上昇させ、電気伝導性を低下させる。 Therefore, there is a strong demand for technical development that uses copper fine particles, which have good conductivity, low cost, and low risk of electromigration, as an ink or paste for use in wiring formation. So far, copper nanoparticles for conductive inks have been synthesized using a capping agent in an organic solvent in an inert atmosphere to suppress aggregation and undesirable oxidation. However, most conventional methods for producing copper nanoparticles are not economically feasible due to their low throughput, lack of expandability, and easy aggregation. Furthermore, in the conventional reduction method, since the reduction of the copper salt stops at the Cu 2 O stage when water is present in the reaction solvent, it is extremely difficult to obtain pure copper nanoparticles. At the same time, the synthesized copper nanoparticles are easily oxidized in the air, and the presence of copper oxide increases the sintering temperature of the copper nanoparticles and decreases the electrical conductivity.
　例えば、アセチルアセトナト銅などの銅前駆体化合物を、オレイルアミン等のアミン系化合物と混合し、均一な混合物を調製した後、場合により還元剤を添加し、その後、加熱することで、銅イオン種を金属状態又は金属酸化物状態に還元して得られるキュービック形態の銅ナノ粒子の製造方法が提案されている（特許文献１）。しかしながら、特許文献１の方法によれば、生成する銅ナノ粒子の形態を所望の大きさのキュービック形態とするために、銅前駆体量に対して６．５～８．５倍のオレイルアミン、ドデシルアミン等を用いる必要があり、得られた銅ナノ粒子の回収にも多量の有機溶媒を必要とする。 For example, a copper precursor compound such as acetylacetonato copper is mixed with an amine-based compound such as oleylamine to prepare a uniform mixture, and then a reducing agent is optionally added, followed by heating to obtain a copper ion species. There has been proposed a method for producing cubic-shaped copper nanoparticles obtained by reducing a metal to a metal oxide state or a metal oxide state (Patent Document 1). However, according to the method of Patent Document 1, 6.5 to 8.5 times the amount of the copper precursor, oleylamine and dodecyl are used in order to make the form of the copper nanoparticles to be formed into a cubic form having a desired size. An amine or the like needs to be used, and a large amount of organic solvent is also required for recovering the obtained copper nanoparticles.
　また、塩化銅、硝酸銅、硫酸銅、酢酸銅、アセチルアセトナト銅のうち一つの銅塩に、炭素数１０～１８の脂肪酸を混合して解離させて混合物を形成する段階と、上記混合物を加熱して反応させる段階とを含む、脂肪酸で表面がキャッピングされた金属銅微粒子を作製する方法も提案されている（特許文献２）。しかしながら、オレイン酸とブチルアミンとを用いて硝酸銅を解離させる方法では反応溶液を２００℃に加熱する必要があり（実施例１）、一方、酢酸銅をオレイン酸とオレイルアミンの存在下、ギ酸を添加して還元反応を促進する場合には１３０℃で加熱しており（実施例２）、この方法では銅微粒子の生成反応の制御が難しいと考えられる。 A step of mixing a copper salt of one of copper chloride, copper nitrate, copper sulfate, copper acetate, and acetylacetonato copper with a fatty acid having 10 to 18 carbon atoms to dissociate to form a mixture; There has also been proposed a method for producing metallic copper fine particles whose surface is capped with a fatty acid, including a step of heating and reacting (Patent Document 2). However, in the method of dissociating copper nitrate using oleic acid and butylamine, the reaction solution needs to be heated to 200 ° C. (Example 1), while copper acetate is added with formic acid in the presence of oleic acid and oleylamine. When the reduction reaction is promoted, heating is performed at 130 ° C. (Example 2), and it is considered difficult to control the formation reaction of the copper fine particles by this method.
　本発明者らは、これまでに、銅を含む化合物と還元性化合物とを混合して複合化合物を生成する工程と、当該複合化合物をアルキルアミン中で加熱してアルキルアミンで被覆された銅微粒子を生成する工程とを有することにより、反応に関与する物質の供給に律速されることなく被覆銅微粒子を製造する方法を開発した（特許文献３参照）。この方法によれば、自発的な分解を生じることが困難な銅化合物についても、予め還元性の化合物との複合化合物、例えば、シュウ酸銅とヒドラジンとの錯体のような複合化合物を形成させておくことで、アルキルアミンとの共存状態において比較的低い温度で自発的な分解を生じることが可能になり、アルキルアミンを含む保護膜により被覆された被覆銅微粒子を製造することができる。その際、銅微粒子の被覆を形成するためのアルキルアミンとして所定のものを適切に選択することによって、大気中でも長期保存が可能な被覆銅微粒子を提供することができると共に、還元ガスを用いなくとも、不活性ガス雰囲気下、３００℃以下の加熱で良好な導電性を示す導電膜、導電配線を形成させることができることを報告している。 The present inventors have so far prepared a process of producing a composite compound by mixing a compound containing copper and a reducing compound, and copper fine particles coated with alkylamine by heating the composite compound in an alkylamine. A process for producing coated copper fine particles without being limited by the supply of substances involved in the reaction (see Patent Document 3). According to this method, even for a copper compound that is difficult to cause spontaneous decomposition, a complex compound with a reducing compound is formed in advance, for example, a complex compound such as a complex of copper oxalate and hydrazine. Thus, spontaneous decomposition can occur at a relatively low temperature in the coexistence state with the alkylamine, and coated copper fine particles coated with a protective film containing the alkylamine can be produced. At that time, by appropriately selecting a predetermined alkylamine for forming a coating of copper fine particles, it is possible to provide coated copper fine particles that can be stored for a long period of time in the atmosphere, and without using a reducing gas. It has been reported that a conductive film and conductive wiring exhibiting good conductivity can be formed by heating at 300 ° C. or lower in an inert gas atmosphere.
特開２００８－５７０４１号公報JP 2008-57041 A 特開２００８－９５１９５号公報JP 2008-95195 A 特開２０１２－７２４１８号公報JP 2012-72418 A
　しかしながら、被覆銅微粒子の更なる焼結温度の低下を達成するためには、被覆銅微粒子の製造工程において、被覆銅微粒子を生成する際の温度を更に低下することが望まれる。つまり、一般に銅微粒子を製造する段階を高温環境下で行った場合は、銅微粒子の焼結温度も高温になる傾向が見られる。上記特許文献３の方法では、あらかじめ銅化合物に対して還元作用のある分子を結合させ、中間体としての複合化合物を生成させることで、比較的低温（１５０℃程度）でこれを熱分解して被覆銅微粒子を生じさせることができるが、更に合成プロセスが簡便で自由度があり、且つ、より低温で実施することのできる被覆銅微粒子の製造プロセスの開発が望まれる。
　そこで本発明は、低温で実施することが可能な被覆銅微粒子の製造プロセスを提供することを課題とする。 However, in order to achieve further reduction in the sintering temperature of the coated copper fine particles, it is desired to further reduce the temperature at which the coated copper fine particles are produced in the production process of the coated copper fine particles. That is, generally, when the step of producing copper fine particles is performed in a high temperature environment, the sintering temperature of the copper fine particles tends to be high. In the method of the above-mentioned Patent Document 3, a compound having a reducing action is bonded to a copper compound in advance to form a complex compound as an intermediate, which is thermally decomposed at a relatively low temperature (about 150 ° C.). Although it is possible to produce coated copper fine particles, it is desirable to develop a process for producing coated copper fine particles that can be carried out at a lower temperature and with a simpler and more flexible synthesis process.
Then, this invention makes it a subject to provide the manufacturing process of the covering copper fine particle which can be implemented at low temperature.
　本発明者らは、上記特許文献３に記載の方法を基礎としてさらに研究を行った結果、銅化合物として特に所定の脂肪酸銅を用いることにより、被覆銅微粒子を生成する工程をより低温で行うことが可能となると共に、プロセス全体の自由度を向上できることを見出した。また、このプロセスにより、空気中での酸化が抑制され、粒子径分布が均一で安定な銅微粒子を簡便かつ大量に製造しうることを見出した。 As a result of further research based on the method described in Patent Document 3, the inventors of the present invention perform the step of producing coated copper fine particles at a lower temperature by using a predetermined fatty acid copper as the copper compound. It became possible to improve the flexibility of the whole process. It has also been found that this process can easily and in large quantities produce fine copper particles that are stable in air, stable in particle size distribution, and stable.
　すなわち、本発明の被覆銅微粒子の製造方法は、脂肪酸銅、還元性化合物、及びアルキルアミンを含む混合物を加熱する工程を含み、前記脂肪酸銅として炭素原子数９以下の脂肪酸銅を用いることを特徴とする。前記脂肪酸銅は、アルキルアミンの存在下に、これに溶解又は懸濁させて還元性化合物と混合、加熱してもよく、或いはあらかじめ前記脂肪酸銅と還元性化合物とを混合した後に、アルキルアミンを添加して加熱してもよい。なお、当該脂肪酸銅と還元性化合物とを混合する工程は、両者間における還元反応の進行を抑制するため、必要に応じて１０℃以下程度に冷却して行うことが好ましい。
　前記脂肪酸銅と還元性化合物とを混合する工程に代えて、水酸化銅と脂肪酸と還元性化合物を適宜の溶媒中で混合することで、脂肪酸銅の生成と還元性化合物との混合を同時並行的に行うことができる。本発明の方法に用いる溶媒は、１－プロパノール又は２－プロパノールのような極性有機溶媒であることが好ましい。 That is, the method for producing coated copper fine particles of the present invention includes a step of heating a mixture containing fatty acid copper, a reducing compound, and an alkylamine, and using fatty acid copper having 9 or less carbon atoms as the fatty acid copper. And The fatty acid copper may be dissolved or suspended in the presence of an alkylamine, mixed with a reducing compound, heated, or mixed with the fatty acid copper and the reducing compound in advance. It may be added and heated. In addition, it is preferable to perform the process which mixes the said fatty acid copper and a reducing compound, cooling to about 10 degrees C or less as needed, in order to suppress progress of the reductive reaction between both.
Instead of the step of mixing the fatty acid copper and the reducing compound, the production of the fatty acid copper and the mixing of the reducing compound are simultaneously performed by mixing the copper hydroxide, the fatty acid and the reducing compound in an appropriate solvent. Can be done automatically. The solvent used in the method of the present invention is preferably a polar organic solvent such as 1-propanol or 2-propanol.
　本発明の方法によれば、炭素数が９以下の脂肪酸銅を銅微粒子製造の出発原料とすることで、あらかじめ還元作用のある分子を出発原料に結合させた中間体を得るプロセス以外に、単に、反応媒であり銅微粒子の被覆ともなるアルキルアミンと還元作用のある分子の混合物中に当該出発原料を投入した場合であっても、良好に被覆銅微粒子の製造を行うことが可能となる。また、より低温での反応により被覆銅微粒子を生成することが可能となる。その結果、本発明の方法によれば、製造された被覆銅微粒子についてもより低温で焼結させることが可能になると共に、プロセスの自由度を高めることができる。 According to the method of the present invention, by using a fatty acid copper having 9 or less carbon atoms as a starting material for producing copper fine particles, in addition to a process for obtaining an intermediate in which a molecule having a reducing action is previously bound to a starting material, Even when the starting material is introduced into a mixture of alkylamine, which is a reaction medium and also a coating of copper fine particles, and a molecule having a reducing action, the coated copper fine particles can be produced satisfactorily. Moreover, it becomes possible to produce coated copper fine particles by a reaction at a lower temperature. As a result, according to the method of the present invention, the manufactured coated copper fine particles can be sintered at a lower temperature, and the degree of freedom of the process can be increased.
実施例１で合成した被覆銅微粒子粉体の粉末Ｘ線回折（ＸＲＤ）パターンである。2 is a powder X-ray diffraction (XRD) pattern of the coated copper fine particle powder synthesized in Example 1. FIG. 実施例１で合成した被覆銅微粒子の異なる倍率での透過電子顕微鏡像と電子線回折である。It is the transmission electron microscope image and electron beam diffraction in the different magnification of the covering copper fine particle synthesize | combined in Example 1. FIG. 実施例１で合成した被覆銅微粒子の高分解能電子顕微鏡像である。2 is a high-resolution electron microscope image of coated copper fine particles synthesized in Example 1. FIG. 実施例１で合成した被覆銅微粒子の熱重量示差熱同時分析結果である。3 is a result of simultaneous thermogravimetric differential thermal analysis of coated copper fine particles synthesized in Example 1. FIG. 実施例１で合成した被覆銅微粒子を用いて作製した薄膜を各温度で焼結したときの体積低効率を示す。The volume low efficiency when the thin film produced using the covering copper fine particle synthesize | combined in Example 1 is sintered at each temperature is shown. 実施例２で合成した被覆銅微粒子の粉末Ｘ線回折（ＸＲＤ）パターンである。3 is a powder X-ray diffraction (XRD) pattern of coated copper fine particles synthesized in Example 2. FIG. 実施例２で合成した被覆銅微粒子のＦＥ－ＳＴＥＭ像である。3 is an FE-STEM image of coated copper fine particles synthesized in Example 2. FIG. 実施例３で合成した被覆銅微粒子のＦＥ－ＳＴＥＭ像である。3 is an FE-STEM image of coated copper fine particles synthesized in Example 3. FIG. 実施例４で合成した被覆銅微粒子の粉末Ｘ線回折（ＸＲＤ）パターンである。4 is a powder X-ray diffraction (XRD) pattern of coated copper fine particles synthesized in Example 4. FIG.
　以下、本発明に係る被覆銅微粒子の製造方法、及び本発明に係る方法で製造される被覆銅微粒子について説明する。特許文献３に記載されるように、銅を含む化合物と還元性化合物とを混合して錯体等の複合化合物を生成させ、これをアルキルアミンの存在下で加熱して、当該複合化合物を分解して生成する原子状の銅を凝集させることにより、アルキルアミンの保護膜に保護された被覆銅微粒子を製造することができる。このように、還元により分解される含銅化合物の分子に対して、予め還元性化合物を所定の割合で結合させた複合化合物を生成させた場合には、還元性化合物が含銅化合物中の銅イオンに対する電子のドナーとなり銅イオンの還元を生じやすいため、使用した含銅化合物を単に還元剤で処理する場合と比較して自発的な熱分解による銅原子の遊離を生じやすいことが分かっている。これに対して、本発明の方法では、このような含銅化合物と還元性化合物との複合体を生成させる工程を別個に設けなくとも、出発原料や温度、溶媒等の反応条件を調整することで、アルキルアミンの存在下で自発的な分解反応により被覆銅微粒子を製造することが可能であることを見出したものであって、プロセスの自由度を高めることができる。 Hereinafter, the method for producing coated copper fine particles according to the present invention and the coated copper fine particles produced by the method according to the present invention will be described. As described in Patent Document 3, a compound containing copper and a reducing compound are mixed to form a complex compound such as a complex, and this is heated in the presence of an alkylamine to decompose the complex compound. By aggregating the atomic copper produced in this manner, coated copper fine particles protected by an alkylamine protective film can be produced. As described above, when a compound compound in which a reducing compound is bonded in a predetermined ratio to a molecule of a copper-containing compound that is decomposed by reduction in advance, the reducing compound is copper in the copper-containing compound. It is known that it tends to cause liberation of copper atoms due to spontaneous pyrolysis compared to the case where the used copper-containing compound is simply treated with a reducing agent because it becomes an electron donor to ions and tends to cause reduction of copper ions. . On the other hand, in the method of the present invention, the reaction conditions such as the starting material, temperature, solvent and the like are adjusted without providing a separate step of forming a complex of such a copper-containing compound and a reducing compound. Thus, it has been found that coated copper fine particles can be produced by a spontaneous decomposition reaction in the presence of an alkylamine, and the degree of freedom of the process can be increased.
　また、本発明に係る方法においては、脂肪酸銅と還元性化合物とをあらかじめ溶媒中で混合して、好ましくは溶媒中に溶解して用いることにより、これらの錯体がより迅速に生じる等、両者をより均一に混合しやすいと考えられる。つまり、一般的に、還元剤は水性媒体中で用いられることが多く、有機溶媒系の反応では均一に混ざらないために還元反応が均一に進行しないことが多い。これに対し、本発明では脂肪酸銅と還元性化合物とをあらかじめ溶媒に溶解して複合化合物の生成等を促進するため、反応媒と還元性化合物との相性に制限されて各成分の混合が進みにくいという問題点が解消される。本発明の方法に用いる溶媒は、脂肪酸銅と還元性化合物との溶解を促進するうえで極性溶媒であることが好ましい。 Further, in the method according to the present invention, the fatty acid copper and the reducing compound are mixed in advance in a solvent, preferably dissolved in the solvent, and these complexes are generated more rapidly. It is thought that it is easy to mix more uniformly. That is, in general, the reducing agent is often used in an aqueous medium, and the reduction reaction does not proceed uniformly because it is not uniformly mixed in an organic solvent-based reaction. On the other hand, in the present invention, since fatty acid copper and a reducing compound are dissolved in a solvent in advance to promote the formation of a composite compound, etc., the mixing of each component proceeds while being limited by the compatibility between the reaction medium and the reducing compound. The problem of difficulty is solved. The solvent used in the method of the present invention is preferably a polar solvent in order to promote dissolution of fatty acid copper and the reducing compound.
　また、本発明の方法では、被覆銅微粒子を生成する工程を、従来よりも低温で効率よく進めることができる。このため、製造される被覆銅微粒子の焼結温度を従来よりも更に低下することが期待される。
　以下、本発明により被覆銅微粒子を製造する方法を具体的に説明する。 Moreover, in the method of this invention, the process of producing | generating a covering copper fine particle can be advanced efficiently at low temperature rather than before. For this reason, it is expected that the sintering temperature of the coated copper fine particles to be produced is further lowered than before.
Hereinafter, the method for producing coated copper fine particles according to the present invention will be specifically described.
（脂肪酸銅）
　本発明で被覆銅微粒子を製造するために用いる銅の原料としては、炭素原子数９以下の脂肪酸銅を用いることができる。本明細書において、用語「脂肪酸銅」とは、炭素数が２以上の脂肪酸と銅との塩化合物であって、当該脂肪酸は、飽和、不飽和のどちらでもよい。使用する脂肪酸銅の炭素数等の違いによって、生成する被覆銅微粒子の溶剤分散性や焼結性などの性質が影響を受けるため、被覆銅微粒子に期待する特性などにより、使用する脂肪酸銅を選択することが好ましい。典型的に使用される脂肪酸銅としては、酢酸銅、プロピオン酸銅、酪酸銅、吉草酸銅、カプロン酸銅、エナント酸銅、カプリル酸銅及びノナン酸銅からなる群より選択される１種又は２種以上の脂肪酸銅である。これらの脂肪酸銅を被覆銅微粒子の原料として用いることにより、被覆銅微粒子を製造するプロセスの自由度が向上すると共に、より低い温度で被覆銅微粒子を製造することが可能になる。この結果、本発明の被覆銅微粒子を用いて作製した薄膜の焼結温度を下げることが期待される。 (Fatty acid copper)
As a raw material of copper used for producing the coated copper fine particles in the present invention, fatty acid copper having 9 or less carbon atoms can be used. In this specification, the term “fatty acid copper” is a salt compound of a fatty acid having 2 or more carbon atoms and copper, and the fatty acid may be either saturated or unsaturated. Depending on the properties of the coated copper fine particles, select the fatty acid copper to be used because the properties such as solvent dispersibility and sinterability of the coated copper fine particles are affected by the difference in the carbon number of the fatty acid copper used. It is preferable to do. As the fatty acid copper typically used, one selected from the group consisting of copper acetate, copper propionate, copper butyrate, copper valerate, copper caproate, copper enanthate, copper caprylate and copper nonanoate or Two or more types of fatty acid copper. By using these fatty acid coppers as the raw material for the coated copper fine particles, the degree of freedom of the process for producing the coated copper fine particles is improved, and the coated copper fine particles can be produced at a lower temperature. As a result, it is expected to lower the sintering temperature of the thin film produced using the coated copper fine particles of the present invention.
（脂肪酸銅と還元性化合物との混合について）
　本発明に係る被覆銅微粒子の製造方法においては、まず上記脂肪酸銅に対して、還元作用を有する還元性化合物を、主に適宜の溶媒中で混合する。脂肪酸銅と還元性化合物とが混合されることにより、両化合物間で錯体等の複合化合物が生成すると考えられる。このような錯体等が形成されることで、還元性化合物が脂肪酸銅中の銅イオンに対する電子のドナーとなり銅イオンの還元を生じ易いため、使用した脂肪酸銅と比較して自発的な熱分解による銅原子の遊離を生じ易くなると考えられる。また、単に脂肪酸銅と還元性化合物との混合により銅イオンの還元反応を生じる場合に比べて、予め生成された錯体等の内部で反応を生じさせることで、反応に関与する物質の供給に律速されることがなく、温度や圧力などの条件の設定により錯体等の自発的な分解反応を生じさせることで銅原子が供給され、均一な被覆銅微粒子を製造することが可能となる。
　この際に使用される還元性化合物としては、例えば、ヒドラジンや塩酸ヒドラジン、硫酸ヒドラジン、抱水ヒドラジン等のヒドラジン化合物、水素化ホウ素ナトリウム、亜硫酸ナトリウム。亜硫酸水素ナトリウム、チオ硫酸ナトリウム、次亜リン酸ナトリウム等が挙げられるが、ヒドラジンやヒドラジン化合物等のアミノ基を有するものが好ましい。アミノ基を有する還元剤は脂肪酸銅中の銅原子等に対して配位結合を形成し易く、脂肪酸銅の構造を維持した状態で容易に脂肪酸銅との錯体等を生成すると共に、脂肪酸銅内の銅イオンの還元反応を生じるためである。 (About mixing of fatty acid copper and reducing compounds)
In the method for producing coated copper fine particles according to the present invention, first, a reducing compound having a reducing action is mixed with the fatty acid copper mainly in an appropriate solvent. By mixing the fatty acid copper and the reducing compound, it is considered that a complex compound such as a complex is formed between the two compounds. By forming such a complex and the like, the reducing compound becomes an electron donor for copper ions in fatty acid copper and tends to cause reduction of copper ions. Therefore, by spontaneous pyrolysis compared to fatty acid copper used. It is thought that copper atoms are likely to be liberated. In addition, compared to the case where the reduction reaction of copper ions is caused simply by mixing fatty acid copper and a reducing compound, the reaction is caused to occur within the complex produced in advance, thereby limiting the supply of substances involved in the reaction. However, the copper atoms are supplied by causing a spontaneous decomposition reaction of a complex or the like by setting conditions such as temperature and pressure, and uniform coated copper fine particles can be produced.
Examples of the reducing compound used in this case include hydrazine compounds such as hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate, sodium borohydride, and sodium sulfite. Examples include sodium bisulfite, sodium thiosulfate, and sodium hypophosphite, but those having an amino group such as hydrazine and hydrazine compounds are preferred. The reducing agent having an amino group easily forms a coordinate bond with a copper atom in the fatty acid copper, and easily forms a complex with the fatty acid copper while maintaining the structure of the fatty acid copper. This is because a reduction reaction of copper ions occurs.
　このような還元性化合物としては、後続する加熱工程で反応媒とするアルキルアミンの蒸発や分解を生じない温度範囲において、銅原子の還元・遊離を生じる錯体等を形成可能なものであれば特に限定されない。一方、還元性化合物と脂肪酸銅とから生成する錯体等の熱的な安定性が高い場合には、その分解に高い温度が必要となり、反応媒とするアルキルアミン自体の蒸発や分解を生じるなどの理由により、本発明の課題の解決が困難となる。 As such a reducing compound, any compound capable of forming a complex or the like that causes reduction / release of a copper atom in a temperature range that does not cause evaporation or decomposition of an alkylamine used as a reaction medium in a subsequent heating step may be used. It is not limited. On the other hand, when the thermal stability of a complex formed from a reducing compound and fatty acid copper is high, a high temperature is required for the decomposition, which causes evaporation and decomposition of the alkylamine itself as a reaction medium. For the reason, it becomes difficult to solve the problems of the present invention.
　約１５０℃以下の低温で分解して銅原子を生成する錯体を形成するための還元性化合物として、典型的には、ヒドラジン、ヒドロキシルアミン及びこれらの誘導体からなる群から選ばれる化合物を特に好ましく挙げられる。これらの化合物は、骨格を成す窒素原子が配位結合により含銅化合物中の銅原子に結合して錯体を生成可能である。また、一般にアルキルアミンと比較して還元力が強いため、生成した錯体が比較的穏和な条件で自発的な分解を生じて銅原子を還元・遊離して、アルキルアミンで被覆された銅微粒子を生成することができる。 As the reducing compound for forming a complex that decomposes at a low temperature of about 150 ° C. or lower to form a copper atom, a compound selected from the group consisting of hydrazine, hydroxylamine, and derivatives thereof is particularly preferable. It is done. These compounds can form a complex by binding a nitrogen atom constituting a skeleton to a copper atom in a copper-containing compound through a coordination bond. In addition, since the reducing power is generally stronger than that of alkylamines, the resulting complex undergoes spontaneous decomposition under relatively mild conditions to reduce and release copper atoms, thereby reducing copper fine particles coated with alkylamine. Can be generated.
　ここで、ヒドラジンの誘導体とは、ヒドラジンに含まれる水素の１～３個を所定のアルキル基等で置換したもの、例えば、メチルヒドラジン、エチルヒドラジン、ｎ－プロピルヒドラジン、ｉ－プロピルヒドラジン、ｎ－ブチルヒドラジン、ｉ－ブチルヒドラジン、ｓｅｃ－ブチルヒドラジン、ｔ－ブチルヒドラジン、ｎ－ペンチルヒドラジン、ｉ－ペンチルヒドラジン、ｎｅｏ－ペンチルヒドラジン、ｔ－ペンチルヒドラジン、ｎ－ヘキシルヒドラジン、ｉ－ヘキシルヒドラジン、ｎ－ヘプチルヒドラジン、ｎ－オクチルヒドラジン、ｎ－ノニルヒドラジン、ｎ－デシルヒドラジン、ｎ－ウンデシルヒドラジン、ｎ－ドデシルヒドラジン、シクロヘキシルヒドラジン、フェニルヒドラジン、４－メチルフェニルヒドラジン、ベンジルヒドラジン、２－フェニルエチルヒドラジン、２－ヒドラジノエタノール、アセトヒドラジン等が例示される。また、ヒドロキシルアミンの誘導体とは、ヒドロキシルアミンに含まれる水素の１個を所定のアルキル基やヒドロキシアルキル基、スルホアルキル基、カルボキシアルキル基などの置換基で置換したものであり、具体的にはＮ，Ｎ－ジ（スルホエチル）ヒドロキルアミン、モノメチルヒドロキシルアミン、ジメチルヒドロキシルアミン、モノエチルヒドロキシルアミン、ジエチルヒドロキルアミン、Ｎ，Ｎ－ジ（カルボキシエチル）ヒドロキルアミンが好ましい。ヒドラジン、ヒドロキシルアミンの使用に代えてその誘導体を適宜選択して使用することで、脂肪酸銅との反応性を調整することが可能であり、使用する脂肪酸銅に応じて適切な条件で自発分解を生じる錯体を生成することができる。特にヒドラジンと混合した際に錯体を生じることなく還元反応を生じやすい脂肪酸銅を用いる際には、適宜選択されるヒドラジン誘導体を使用して複合化合物の生成を促進することが有効である。 Here, the hydrazine derivative is obtained by substituting one to three hydrogen atoms contained in hydrazine with a predetermined alkyl group, for example, methyl hydrazine, ethyl hydrazine, n-propyl hydrazine, i-propyl hydrazine, n- Butyl hydrazine, i-butyl hydrazine, sec-butyl hydrazine, t-butyl hydrazine, n-pentyl hydrazine, i-pentyl hydrazine, neo-pentyl hydrazine, t-pentyl hydrazine, n-hexyl hydrazine, i-hexyl hydrazine, n- Heptylhydrazine, n-octylhydrazine, n-nonylhydrazine, n-decylhydrazine, n-undecylhydrazine, n-dodecylhydrazine, cyclohexylhydrazine, phenylhydrazine, 4-methylphenylhydrazine, benzylhydride Jin, 2-phenylethyl hydrazine, 2-hydrazino ethanol, acetoacetate hydrazine and the like. A hydroxylamine derivative is one obtained by substituting one of hydrogens contained in hydroxylamine with a substituent such as a predetermined alkyl group, hydroxyalkyl group, sulfoalkyl group or carboxyalkyl group. N, N-di (sulfoethyl) hydroxylamine, monomethylhydroxylamine, dimethylhydroxylamine, monoethylhydroxylamine, diethylhydroxylamine, N, N-di (carboxyethyl) hydroxylamine are preferred. It is possible to adjust the reactivity with fatty acid copper by using its derivatives instead of hydrazine and hydroxylamine as appropriate, and spontaneous decomposition under appropriate conditions according to the fatty acid copper used. The resulting complex can be produced. In particular, when using fatty acid copper that easily generates a reduction reaction without forming a complex when mixed with hydrazine, it is effective to promote the formation of a composite compound by using an appropriately selected hydrazine derivative.
　また、脂肪酸銅と還元性化合物とを混合した際に直接的に還元反応を生じる場合には、冷却した環境で混合することで還元反応を抑制することが望ましい。その他、使用する還元性化合物の還元力などの強さ等に応じて、混合の際の温度や圧力等の条件を適宜決定することができる。例えば、脂肪酸銅と還元性化合物とを約１０℃以下に冷却して混合を行うことが好ましく、更に好ましくは約５℃以下、最も好ましくは約０℃以下である。
　錯体の生成のために脂肪酸銅に混合される還元性化合物の比率は、脂肪酸銅と還元性化合物から生成する錯体等における両者のモル比率（以下、「定比」という。）と等しい比率か、それ以上に還元性化合物を富化した比率とすることが好ましい。還元性化合物の比率が錯体等における定比以下であると、錯体等を形成しない脂肪酸銅が生じて遊離しない金属原子を生じる結果、銅微粒子の収率が低下する。また、錯体等を形成しない過剰の還元性化合物は銅原子の還元遊離に関与しないため、好ましい還元性化合物の混合比率は錯体等における定比の４倍以下であり、現実的には定比の１～２倍となるように還元性化合物を脂肪酸銅に混合することで良好な錯体等を形成することができる。使用する還元性化合物は、その性質に応じて２種以上の還元性化合物を混合して用いることが可能である。 In addition, when a reduction reaction is directly generated when fatty acid copper and a reducing compound are mixed, it is desirable to suppress the reduction reaction by mixing in a cooled environment. In addition, conditions such as temperature and pressure during mixing can be appropriately determined according to the strength of the reducing compound used, such as the reducing power. For example, the fatty acid copper and the reducing compound are preferably mixed by cooling to about 10 ° C. or less, more preferably about 5 ° C. or less, and most preferably about 0 ° C. or less.
The ratio of the reducing compound mixed with the fatty acid copper for the formation of the complex is equal to the molar ratio (hereinafter referred to as “constant ratio”) of both in the complex formed from the fatty acid copper and the reducing compound, or the like. It is preferable that the ratio is more enriched with reducing compounds. If the ratio of the reducing compound is equal to or less than the constant ratio in the complex or the like, fatty acid copper that does not form a complex or the like is generated, resulting in a metal atom that is not liberated, resulting in a decrease in the yield of copper fine particles. Moreover, since an excessive reducing compound that does not form a complex or the like does not participate in the reduction and release of a copper atom, the preferable mixing ratio of the reducing compound is 4 times or less of the ratio in the complex or the like. A good complex or the like can be formed by mixing the reducing compound with fatty acid copper so as to be 1 to 2 times. The reducing compound to be used can be used by mixing two or more kinds of reducing compounds depending on the properties thereof.
　また、生成する錯体等の性質を阻害しない範囲内で、錯体等の生成を助けること等を目的に、適宜の添加成分を含む還元性化合物を使用することが可能である。特に、脂肪酸銅と還元性化合物を混合する際に、系内の物質と反応を生じることなく、かつこれらを溶解可能な極性溶媒を反応媒として存在させることで、錯体等の生成が促進されて均一な錯体等を速やかに生成することができる。極性溶媒としては、室温において水（Ｈ２Ｏ）に対する溶解度を有するものであることが望ましい。水に対する溶解度を示すアルコールは一定の極性を有し、このようなアルコールを用いることによって脂肪酸銅と還元性化合物等の錯体等の生成を促進することができる。このようなアルコールの示す具体的作用は明らかでないが、固体状態の脂肪酸銅を溶解させながら水溶性の還元性化合物との接触を促進することにより錯体生成を促進するものと考えられる。 In addition, it is possible to use a reducing compound containing an appropriate additive component for the purpose of assisting the formation of a complex or the like within a range that does not inhibit the properties of the complex or the like to be generated. In particular, when a fatty acid copper and a reducing compound are mixed, the formation of a complex or the like is promoted by causing a polar solvent capable of dissolving them without causing a reaction with a substance in the system and as a reaction medium. A uniform complex etc. can be produced | generated rapidly. The polar solvent is preferably one having solubility in water (H 2 O) at room temperature. Alcohols exhibiting solubility in water have a certain polarity, and the use of such alcohols can promote the formation of complexes such as fatty acid copper and a reducing compound. Although the specific action of such an alcohol is not clear, it is considered that complex formation is promoted by promoting contact with a water-soluble reducing compound while dissolving solid state fatty acid copper.
　上記水に対する溶解度を示すアルコールとしては、１個のＯＨ基を有する直鎖のアルキルアルコールとして、炭素数１のメタノールから、炭素数８のオクタノールが挙げられる。一方、炭素数が９以上になると水に対して実質的に溶解せず、このようなアルコールを錯体等の形成の際に介在させても、錯体等の形成促進作用が観察されない。また、アルキルアルコールの他に、フェノールや、分子内にエーテル結合を有する適宜の炭化水素の水素原子をＯＨ基で置換したもの等を用いることができる。 Examples of the alcohol showing the solubility in water include linear alkyl alcohols having one OH group, from methanol having 1 carbon atom to octanol having 8 carbon atoms. On the other hand, when the number of carbon atoms is 9 or more, it does not substantially dissolve in water, and even if such an alcohol is interposed during the formation of a complex or the like, the formation promoting action of the complex or the like is not observed. In addition to alkyl alcohols, phenols or those obtained by substituting hydrogen atoms of appropriate hydrocarbons having an ether bond in the molecule with OH groups can be used.
　アルコールにおいては、一分子内に含まれるＯＨ基の数が増加するに伴って強い極性が発現し、本発明においても２個のＯＨ基を含むグリコール類や、３個のＯＨ基を含むグリセリン、４個のＯＨ基を含むペンタエリトリトール等が好ましく使用される。
　このようなアルコール化合物としては、メタノール、エタノール、プロパノール、ブタノール、ペンタノール、ヘキサノール、ヘプタノール、オクタノール、アリルアルコール、ベンジルアルコール、ピナコール、プロピレングリコール、メントール、カテコール、ヒドロキノン、サリチルアルコール、ペンタエリトリトール、スクロース、グルコース、キシリトール、メトキシエタノール、トリエチレングリコールモノメチルエーテル、ペンタエリトリトール等、及び、エチレングリコール、トリエチレングリコール、テトラエチレングリコール、ペンタエチレングリコールを含むポリエチレングリコール類が挙げられる。
　また、製造される被覆銅微粒子の用途に応じて、硫黄原子を含むアルコールとして、２，２’－チオジエタノール、３－チオフェンエタノール、２－チオフェンエタノール、３－チオフェンメタノール、２－チオフェンメタノール、αーチオグリセロール、２－（メチルチオ）エタノール等が挙げられる。また、リン原子を含むアルコール化合物として、ジメチル（ヒドロキシメチル）ホスホネート、ジメチル（２－ヒドロキシエチル）ホスホネート等を用いることができる。更に、ケイ素原子を含む２－（トリメチルシリル）エタノール、２－（トリメチルシリル）－１－プロパノール、トリエチルシラノール等のアルコール化合物を用いることができる。
　本発明の好ましい実施形態において用いられる極性溶媒は、水に対して極めて大きな溶解度を示すアルコールであり、例えば、１－プロパノール又は２－プロパノールなどが挙げられる。さらに好ましくは、１－プロパノールである。 In alcohol, strong polarity is expressed as the number of OH groups contained in one molecule increases, and in the present invention, glycols containing two OH groups, glycerin containing three OH groups, Pentaerythritol and the like containing 4 OH groups are preferably used.
Examples of such alcohol compounds include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, allyl alcohol, benzyl alcohol, pinacol, propylene glycol, menthol, catechol, hydroquinone, salicyl alcohol, pentaerythritol, sucrose, Examples thereof include glucose, xylitol, methoxyethanol, triethylene glycol monomethyl ether, pentaerythritol, and the like, and polyethylene glycols including ethylene glycol, triethylene glycol, tetraethylene glycol, and pentaethylene glycol.
In addition, depending on the use of the coated copper fine particles to be produced, 2,2′-thiodiethanol, 3-thiopheneethanol, 2-thiopheneethanol, 3-thiophenemethanol, 2-thiophenemethanol, α -Thioglycerol, 2- (methylthio) ethanol and the like. Further, dimethyl (hydroxymethyl) phosphonate, dimethyl (2-hydroxyethyl) phosphonate, or the like can be used as the alcohol compound containing a phosphorus atom. Furthermore, alcohol compounds such as 2- (trimethylsilyl) ethanol, 2- (trimethylsilyl) -1-propanol and triethylsilanol containing silicon atoms can be used.
The polar solvent used in a preferred embodiment of the present invention is an alcohol that exhibits extremely high solubility in water, and examples thereof include 1-propanol and 2-propanol. More preferred is 1-propanol.
（錯体の分解と被覆銅微粒子の製造について）
　次に、本発明に係る被覆銅微粒子の製造方法においては、上記で生成した脂肪酸銅と還元性化合物との混合物を、十分な量のアルキルアミンと混合して加熱し、脂肪酸銅の自発的分解反応により銅原子が生成して凝集することで銅微粒子が得られる。また、その際に銅微粒子の表面に使用したアルキルアミンによる被膜が生じるため、空気中の酸素で酸化され難い、安定な被覆銅微粒子を得ることができる。 (Decomposition of complex and production of coated copper fine particles)
Next, in the method for producing coated copper fine particles according to the present invention, the mixture of fatty acid copper and reducing compound produced above is mixed with a sufficient amount of alkylamine and heated to spontaneously decompose fatty acid copper. Copper fine particles are obtained by the formation and aggregation of copper atoms by the reaction. Moreover, since the coating by the alkylamine used on the surface of the copper fine particle arises in that case, the stable coated copper fine particle which is hard to be oxidized with oxygen in the air can be obtained.
　本発明により製造される被覆銅微粒子における低温焼結性を確保するためには、上記脂肪酸銅の分解温度としては、望ましくは約１５０℃以下の温度が好ましい。錯体の分解に伴う銅原子の還元生成のために１５０℃以上の温度が必要な場合には、ブチルアミンやヘキシルアミンのような蒸気圧の高いアルキルアミンを反応媒に用いた場合に蒸発速度が高くなるため、実際的には反応媒として用いるアルキルアミンが炭素数８以上の長鎖のものに限定され、被覆銅微粒子の低温焼結性が阻害される。錯体の分解温度としてより好ましくは、１３０℃未満、さらに好ましくは１２０℃、１１０℃、又は１００℃である。特に１００℃以下の温度で銅原子の生成が可能であれば、炭素数が６程度のアルキルアミンを安定して使用できると共に、比較的穏和な条件で銅微粒子の生成が行われるため、粒子径が微細であり、粒径分布の狭い被覆銅微粒子を製造することが可能となる。また、比較的沸点の低い低分子のアルキルアミンが使用可能となることで、保護被膜が外れ易く低温焼結が可能な被覆銅微粒子の製造が容易になる点においても好ましい。 In order to ensure low-temperature sinterability in the coated copper fine particles produced according to the present invention, the decomposition temperature of the fatty acid copper is desirably about 150 ° C. or lower. When a temperature of 150 ° C. or higher is required for the reduction of copper atoms accompanying the decomposition of the complex, the evaporation rate is high when an alkylamine having a high vapor pressure such as butylamine or hexylamine is used as the reaction medium. Therefore, the alkylamine used as a reaction medium is actually limited to a long chain having 8 or more carbon atoms, and the low-temperature sinterability of the coated copper fine particles is hindered. More preferably, the decomposition temperature of the complex is less than 130 ° C, more preferably 120 ° C, 110 ° C, or 100 ° C. In particular, if copper atoms can be generated at a temperature of 100 ° C. or lower, an alkylamine having about 6 carbon atoms can be used stably, and copper particles are generated under relatively mild conditions. It is possible to produce coated copper fine particles that are fine and have a narrow particle size distribution. Moreover, it is also preferable in that a low molecular weight alkylamine having a relatively low boiling point can be used, so that the protective coating can be easily removed and coated copper fine particles that can be sintered at a low temperature can be easily produced.
　使用する脂肪酸銅と、還元性化合物によって銅原子を生成する反応は相違するが、例えば、脂肪酸銅としてノナン酸銅を使用し、還元性化合物としてヒドラジン（又はその誘導体）を使用した場合には、ノナン酸銅とヒドラジン等の混合により両化合物からなる錯体が生成し、これをアルキルアミンと混合して加熱することで、ノナン酸銅が１００℃程度の低温においても熱分解を生じて銅微粒子が製造される。このとき、系内に存在するノナン酸やアルキルアミンが系外に存在する酸素の侵入を防止すると共に、還元されて生じた銅原子に付着して、最終的に銅微粒子を被覆することで、大気中で熱分解を行った場合においても銅原子の酸化が抑制され、安定した被覆銅微粒子が製造されると考えられる。また、ノナン酸銅に代えて或いはこれに加えて炭素数の異なる種々の脂肪酸を用いたり、アルキルアミンの分子量を調整することで、生成する銅微粒子の粒子径を数ｎｍから１００ｎｍ程度までの所望の大きさに調節することが可能である。 Fatty acid copper to be used is different from the reaction to produce a copper atom by a reducing compound, but for example, when nonanoic acid copper is used as the fatty acid copper and hydrazine (or a derivative thereof) is used as the reducing compound, By mixing copper nonanoate and hydrazine and the like, a complex composed of both compounds is produced. By mixing and heating this with alkylamine, copper nonanoate undergoes thermal decomposition even at a low temperature of about 100 ° C. Manufactured. At this time, nonanoic acid and alkylamine existing in the system prevent invasion of oxygen existing outside the system, adhere to the reduced copper atoms, and finally coat the copper fine particles, Even when thermal decomposition is performed in the atmosphere, it is considered that oxidation of copper atoms is suppressed and stable coated copper fine particles are produced. In addition, in addition to or in addition to copper nonanoate, various fatty acids having different carbon numbers are used, or by adjusting the molecular weight of the alkylamine, the particle size of the generated copper fine particles is desired from several nm to about 100 nm. It is possible to adjust the size.
　本発明の１つの実施形態において、上述した脂肪酸銅と還元性化合物とを混合する第１工程と、当該錯体をアルキルアミンの存在下に加熱して銅微粒子を生成させる第２工程とを、１つの容器内で同時に又は逐次的に行うことができる。「同時に」とは、脂肪酸銅と還元性化合物とアルキルアミンとを同時に混合し、好ましくはこれに極性溶媒を添加して可溶化した後に、約１００℃で加熱することによって銅微粒子を生成することができる。 In one embodiment of the present invention, the first step of mixing the above-described fatty acid copper and the reducing compound, and the second step of heating the complex in the presence of an alkylamine to produce copper fine particles include 1 It can be carried out simultaneously or sequentially in one container. “Simultaneously” means that copper fine particles are produced by mixing fatty acid copper, a reducing compound, and an alkylamine at the same time, and preferably adding a polar solvent thereto to solubilize, followed by heating at about 100 ° C. Can do.
　本発明の好ましい実施形態では、前記第１工程及び第２工程を逐次的に行うことができ、このときの加熱温度は同一であっても異なる温度であってもよい。さらに好ましくは、前記第１工程が約１０℃以下に冷却して行われ、第２工程が１５０℃程度まで、より好ましくは約１００℃に加熱して行われる。 In a preferred embodiment of the present invention, the first step and the second step can be performed sequentially, and the heating temperature at this time may be the same or different. More preferably, the first step is performed by cooling to about 10 ° C. or less, and the second step is performed by heating to about 150 ° C., more preferably about 100 ° C.
（アルキルアミン）
　脂肪酸銅と還元性化合物との混合物を加熱する際に、当該混合物と混合されるアルキルアミンは、上記のように、主に錯体の分解反応の反応媒として機能すると共に、ヒドラジンの還元作用によって生じるプロトンを捕捉し、反応溶液が酸性に傾いて空気中の酸素によって生じた銅原子が酸化されることを防止していると考えられる。このため、本発明において使用されるアルキルアミンは、使用する錯体の熱分解の条件、製造される銅微粒子に期待される特性等に応じて、公知のアルキルアミンから適宜選択して用いることができる。すなわち、錯体の熱分解の際に使用されるアルキルアミンは、脂肪酸と共に銅微粒子の被膜を構成してもよく、この場合には、生成する錯体の熱分解条件、製造される被覆銅微粒子に期待される特性等に応じて、公知のアルキルアミンから適宜選択して用いることができる。 (Alkylamine)
When a mixture of fatty acid copper and a reducing compound is heated, the alkylamine mixed with the mixture mainly functions as a reaction medium for the decomposition reaction of the complex as described above, and is generated by the reducing action of hydrazine. It is considered that protons are trapped and the reaction solution is inclined to be acidic and copper atoms generated by oxygen in the air are prevented from being oxidized. For this reason, the alkylamine used in the present invention can be appropriately selected from known alkylamines according to the thermal decomposition conditions of the complex used, the properties expected of the copper fine particles to be produced, and the like. . That is, the alkylamine used in the thermal decomposition of the complex may constitute a coating of copper fine particles together with the fatty acid. In this case, the thermal decomposition conditions of the complex to be produced and the coated copper fine particles to be produced are expected. Depending on the properties to be achieved, it can be appropriately selected from known alkylamines.
　上記混合物の熱分解の際に用いるアルキルアミンは、上記のように、製造する被覆銅微粒子の目的等に応じて適宜選択される。分子内に一つのアミノ基を有するアルキルアミン（モノアミン）としては、例えば、２－エトキシエチルアミン、ジプロピルアミン、ジブチルアミン、ヘキシルアミン、シクロヘキシルアミン、ヘプチルアミン、３－ブトキシプロピルアミン、オクチルアミン、ノニルアミン、デシルアミン、３－アミノプロピルトリエトキシシラン、ドデシルアミン、ヘキサデシルアミン、オクタデシルアミン、オレイルアミン等のアルキルアミンは工業的に生産され入手が容易な点で実用的である。
特に、炭素数６～１２のヘキシルアミン、へプチルアミン、オクチルアミン、ノニルアミン、デシルアミン、ウンデシルアミンおよびドデシルアミンがより好適に用いられる。これらは１種でも、あるいは２種以上混合して使用してもよい。 The alkylamine used in the thermal decomposition of the mixture is appropriately selected according to the purpose of the coated copper fine particles to be produced as described above. Examples of the alkylamine (monoamine) having one amino group in the molecule include 2-ethoxyethylamine, dipropylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, 3-butoxypropylamine, octylamine, nonylamine Alkylamines such as decylamine, 3-aminopropyltriethoxysilane, dodecylamine, hexadecylamine, octadecylamine, and oleylamine are practical in terms of industrial production and availability.
In particular, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine and dodecylamine having 6 to 12 carbon atoms are more preferably used. These may be used alone or in combination of two or more.
　一方、分子内に二つのアミノ基を有するアルキルジアミンとして、例えば、エチレンジアミン、Ｎ，Ｎ－ジメチルエチレンジアミン、Ｎ，Ｎ’－ジメチルエチレンジアミン、Ｎ，Ｎ-ジエチルエチレンジアミン、Ｎ，Ｎ’－ジエチルエチレンジアミン、１，３－プロパンジアミン、２，２-ジメチル－１，３－プロパンジアミン、Ｎ，Ｎ－ジメチル－１，３－ジアミノプロパン、Ｎ，Ｎ’－ジメチル－１，３－ジアミノプロパン、Ｎ，Ｎ－ジエチル－１，３－ジアミノプロパン、１，４－ジアミノブタン、１，５－ジアミノ－２－メチルペンタン、１，６－ジアミノヘキサン、Ｎ，Ｎ’－ジメチル－１，６－ジアミノヘキサン、１，７－ジアミノヘプタン、１，８－ジアミノオクタン等が挙げられるが、これらに限定されるものではない。 On the other hand, examples of the alkyldiamine having two amino groups in the molecule include ethylenediamine, N, N-dimethylethylenediamine, N, N′-dimethylethylenediamine, N, N-diethylethylenediamine, N, N′-diethylethylenediamine, 1 , 3-propanediamine, 2,2-dimethyl-1,3-propanediamine, N, N-dimethyl-1,3-diaminopropane, N, N′-dimethyl-1,3-diaminopropane, N, N— Diethyl-1,3-diaminopropane, 1,4-diaminobutane, 1,5-diamino-2-methylpentane, 1,6-diaminohexane, N, N′-dimethyl-1,6-diaminohexane, 1, Examples thereof include, but are not limited to, 7-diaminoheptane and 1,8-diaminooctane.
　錯体の熱分解の際に用いるアルキルアミンは、１種のアルキルアミンを使用しても良いが、複数のアルキルアミンを混合して使用してもよい。特に、反応媒として使用するアルキルアミンは、室温において液体であることが取扱いの容易な点で好ましいため、分子量が大きく室温では固体であるアルキルアミンを用いる場合には、分子量が小さなものと混合して液状にして用いることが好ましい。特に、長鎖のアルキルアミンのうちで、オレイルアミンが室温で液状であることを利用して、オレイルアミンを主成分として各種のアルキルアミンを混合して用いることが、製造時の取扱いと、製造された被覆銅微粒子の耐酸化性を両立する点で好ましい。また、複数のアルキルアミンを混合して使用することで各アルキルアミンの蒸気圧が減少するため、分子量の小さいアルキルアミンを適宜混合して使用することは好ましい保護膜を得るために有効である。 As the alkylamine used for the thermal decomposition of the complex, one kind of alkylamine may be used, or a plurality of alkylamines may be mixed and used. In particular, the alkylamine used as the reaction medium is preferably a liquid at room temperature because it is easy to handle. Therefore, when using an alkylamine that has a large molecular weight and is solid at room temperature, it is mixed with a small molecular weight. It is preferable to use it in a liquid state. In particular, among long-chain alkylamines, using oleylamine in liquid form at room temperature, it is possible to mix and use various alkylamines based on oleylamine as the main component, and to produce It is preferable at the point which makes the oxidation resistance of a covering copper fine particle compatible. Moreover, since the vapor pressure of each alkylamine decreases when a plurality of alkylamines are mixed and used, it is effective to obtain a preferable protective film by appropriately mixing and using alkylamines having a small molecular weight.
（被覆銅微粒子）
　本発明に係る被覆銅微粒子は、典型的には平均粒径が５０ｎｍ以下であり、さらには平均粒径が２０ｎｍ以下であるため、その表面に設けられた保護膜が脱離することで、通常の銅粉末と比較して極めて低い温度においても焼結して銅被膜を形成することが可能である。特に、銅原子の供給源として用いる脂肪酸銅に含まれる脂肪酸や、錯体の熱分解の際使用されるアルキルアミンとして、蒸気圧の高いものを使用することで脱離が容易な保護膜が形成され、より低温での焼結が可能になる。また、比較的分子量の大きなアルキルアミンを使用した場合には、強固な保護膜が形成されることによって製造した被覆銅微粒子の酸化が防止されて、大気中においても長期間の保存が可能となる。
　本発明の銅微粒子の表面を被覆する保護膜の少なくとも一部には、前記脂肪酸銅及び／又はアルキルアミンを含むものであるが、これらの被覆銅微粒子全体の重量に対する含量、すなわち被覆率は、１５重量％以下であることが好ましい。 (Coated copper fine particles)
The coated copper fine particles according to the present invention typically have an average particle size of 50 nm or less, and further an average particle size of 20 nm or less. Therefore, when the protective film provided on the surface is detached, It is possible to form a copper film by sintering even at an extremely low temperature as compared with the copper powder. In particular, a fatty acid contained in fatty acid copper used as a source of copper atoms and an alkylamine used in the thermal decomposition of the complex form a protective film that can be easily detached by using a high vapor pressure. Sintering at a lower temperature is possible. In addition, when an alkylamine having a relatively large molecular weight is used, the coated copper fine particles produced are prevented from being oxidized by forming a strong protective film, and can be stored for a long time even in the air. .
At least a part of the protective film covering the surface of the copper fine particles of the present invention contains the above-mentioned fatty acid copper and / or alkylamine, but the content of the coated copper fine particles relative to the weight, that is, the coverage is 15 wt. % Or less is preferable.
　一方、当該被覆銅微粒子を適宜の温度に加熱することで、保護膜を形成する脂肪酸やアルキルアミンが脱離して銅微粒子同士が直接接触することにより導体化を生じ、２００℃程度以下の温度においても銅微粒子を構成する銅原子が相互に拡散して融着し、導体化が進展することが確認されている。この現象は、保護膜を形成する脂肪酸やアルキルアミンが、そのカルボキシル基やアミノ基を介した配位結合により銅微粒子の表面に対して弱く結合しており、これらが比較的容易に脱離可能であるためと考えられている。
　この性質を利用して、種々の手法により、主に所望の形態の銅被膜を形成するために使用することが可能であり、特に、耐熱性の低い基板上に銅配線を形成するために有効である。つまり、有機溶媒に分散させてインク状にしたものをインクジェットプリント等の各種の方法で所望の形状に印刷し、不活性雰囲気内で所定の温度に加熱して保護被膜を脱離させることで、露出した銅微粉末同士が焼結を生じるため、容易に銅配線等を印刷により形成することができる。また、被覆銅微粒子をペースト状や粉末状のままで塗布した後に焼結を行うことも可能である。 On the other hand, by heating the coated copper fine particles to an appropriate temperature, the fatty acid and alkylamine forming the protective film are eliminated and the copper fine particles are brought into direct contact with each other, thereby forming a conductor, and at a temperature of about 200 ° C. or less. In addition, it has been confirmed that copper atoms constituting the copper fine particles are diffused and fused with each other, and the conductorization progresses. This phenomenon is because the fatty acids and alkylamines that form the protective film are weakly bonded to the surface of the copper fine particles due to the coordinate bond via the carboxyl group or amino group, and these can be removed relatively easily. It is thought to be because.
Utilizing this property, it can be used mainly to form a copper film of a desired form by various methods, and particularly effective for forming a copper wiring on a substrate having low heat resistance. It is. In other words, the ink dispersed in an organic solvent is printed in a desired shape by various methods such as inkjet printing, and heated to a predetermined temperature in an inert atmosphere to remove the protective film, Since the exposed copper fine powders cause sintering, copper wiring and the like can be easily formed by printing. It is also possible to perform the sintering after coating the coated copper fine particles in the form of a paste or powder.
　その他、被覆銅微粒子の焼結を生じさせる方法としては、紫外線などの電磁波によって保護被膜を脱離させる方法、機械的に圧力を加える方法で保護被膜を脱離させる方法等により保護被膜を脱離させて銅微粒子同士を接触させることで、通常の焼結温度よりも非常に低い温度で焼結を生じさせることができる。また、電気回路を印刷で形成する以外に、本発明に係る被覆銅微粒子を使用して従来の無電解メッキ等に代えて不導体表面に導体層を形成したり、金属間に挟んで押圧することで金属同士を機械的・電気的に接合する接着層とする用途に用いることができる。 Other methods for sintering the coated copper fine particles include removing the protective film by electromagnetic waves such as ultraviolet rays, and removing the protective film by applying mechanical pressure. By allowing the copper fine particles to come into contact with each other, sintering can be caused at a temperature much lower than the normal sintering temperature. In addition to forming the electrical circuit by printing, the coated copper fine particles according to the present invention are used to form a conductor layer on the non-conductive surface instead of the conventional electroless plating or the like, and the metal layer is pressed between the metals. Therefore, it can be used for an adhesive layer for mechanically and electrically joining metals together.
（銅微粒子を含む膜を形成する基体と、膜の形成方法）
　本発明の方法において、被覆銅微粒子を含むインクやペーストを塗布する基体の材質や形状は特に限定されないが、例えば、熱可塑性樹脂、熱硬化性樹脂、ガラス、紙、金属、シリコン及びセラミックス等からなる材料を用いることができる。熱可塑性樹脂としては、例えば、ポリエチレン、ポリエチレンテレフタレート、ポリプロピレン、ポリ塩化ビニル、ポリスチレン、アクリロニトリル－ブタジエン－スチレン共重合樹脂、アクリロニトリル－スチレン共重合樹脂、ポリカーボネート、ポリアセタール、ポリブチレンテレフタレート、ポリフェニレンオキシド、ポリアミド、ポリフェニレンサルファイド、ポリスルホン、ポリエーテルスルホン、ポリエーテル－エーテルケトン、ポリアリレート、アロマティックポリエステル、アロマティックポリアミド、フッ素樹脂、ポリビニリデンクロライド、ポリビニルアルコール、ポリ酢酸ビニル、ポリビニルホルマール、ポリビニルブチラール、ポリメタクリル酸メチル、酢酸セルロース等が挙げられる。 (Substrate for forming a film containing copper fine particles and film forming method)
In the method of the present invention, the material and shape of the substrate to which the ink or paste containing the coated copper fine particles is applied are not particularly limited. For example, from thermoplastic resin, thermosetting resin, glass, paper, metal, silicon, ceramics, etc. Can be used. Examples of the thermoplastic resin include polyethylene, polyethylene terephthalate, polypropylene, polyvinyl chloride, polystyrene, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer resin, polycarbonate, polyacetal, polybutylene terephthalate, polyphenylene oxide, polyamide, Polyphenylene sulfide, polysulfone, polyethersulfone, polyether-etherketone, polyarylate, aromatic polyester, aromatic polyamide, fluororesin, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetate, polyvinyl formal, polyvinyl butyral, polymethyl methacrylate And cellulose acetate.
　前記熱硬化性樹脂としては、例えば、フェノール樹脂、尿素樹脂、キシレン樹脂、ユリア樹脂、メラミン樹脂、エポキシ樹脂、ケイ素樹脂、ジアリルフタレート樹脂、フラン樹脂、アニリン樹脂、アセトン－ホルムアルデヒド樹脂、アルキド樹脂等が挙げられる。前記セラミックスとしては、酸化物、炭化物、窒化物、ホウ化物などの無機化合物を意味し、例えばアルミナ（Ａｌ2Ｏ3）、シリコンナイトライド（ＳｉＮ）、シリコンカーバイド（ＳｉＣ）、アルミナイトライド（ＡｌＮ）、ホウ化ジルコニウム（ＺｒＢ2）等が挙げられる。 Examples of the thermosetting resin include phenol resin, urea resin, xylene resin, urea resin, melamine resin, epoxy resin, silicon resin, diallyl phthalate resin, furan resin, aniline resin, acetone-formaldehyde resin, alkyd resin, and the like. Can be mentioned. The ceramic means inorganic compounds such as oxides, carbides, nitrides, borides and the like. For example, alumina (Al 2 O 3 ), silicon nitride (SiN), silicon carbide (SiC), aluminum nitride (AlN) ), Zirconium boride (ZrB 2 ), and the like.
　被覆銅微粒子を含むインク等を用いて所定の膜等を基体上に形成する工程は、所望の厚みで膜を形成できる方法であれば特に限定されず、一般的なスピンコートやスプレー塗布等を用いることができる。また、特に被覆銅微粒子を含む膜により配線前駆体となるパターンを基体上に形成する工程は、従来の様々な印刷方法を用いることが可能であり、例えば、スクリーン印刷方法、インクジェット印刷方法、凹版印刷、凸版印刷、平板印刷等を用いることができる。また、被覆銅微粒子を含む膜を導体化して得られる金属膜の用途は電気配線に限定されず、光学装置用の鏡面や、各種装飾用等に用いることができる。
　被覆銅微粒子を含むインク等により基体上に形成される膜の厚みは、導体化により得られる金属膜の目的に応じて適宜設定することができる。通常の電気配線等であれば、１μｍ以下程度の金属膜となるように当該インクにより膜を形成し、導体化を行うことで良好な特性を得ることができる。 The step of forming a predetermined film or the like on the substrate using ink containing coated copper fine particles is not particularly limited as long as it is a method capable of forming a film with a desired thickness, and general spin coating, spray coating, etc. Can be used. In particular, the process of forming a pattern serving as a wiring precursor on a substrate with a film containing coated copper fine particles can use various conventional printing methods such as a screen printing method, an ink jet printing method, and an intaglio. Printing, letterpress printing, lithographic printing, and the like can be used. Moreover, the use of the metal film obtained by making a film containing coated copper fine particles into a conductor is not limited to electrical wiring, and can be used for mirror surfaces for optical devices, various decorations, and the like.
The thickness of the film formed on the substrate with the ink containing the coated copper fine particles can be appropriately set according to the purpose of the metal film obtained by making the conductor. If it is a normal electric wiring etc., a favorable characteristic can be acquired by forming a film | membrane with the said ink so that it may become a metal film of about 1 micrometer or less, and making it into a conductor.
　以下、本発明に係る被覆銅微粒子の製造方法について実施例および比較例を挙げて本発明をさらに具体的に説明するが、本発明は以下の実施例に何ら限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the method for producing coated copper fine particles according to the present invention, but the present invention is not limited to the following examples.
［実施例１］ノナン酸銅（ＩＩ）と酢酸銅（ＩＩ）を用いた銅微粒子粉体の合成
[１．１]ノナン酸銅の合成
　水酸化銅（関東化学、特級）２．６g（２６ｍｍｏｌ）に１－プロパノール（関東化学、特級）１０ｍＬを加えて撹拌し、これにノナン酸（関東化学、＞９０％）８．４g（５３ｍｍｏｌ）と１－プロパノール１０ｍＬの混合溶液を加えた。アルミブロック式加熱撹拌機（小池精密機器製作所）中で１００℃で加熱撹拌した。反応は５分以内に終了し、溶液はノナン酸銅溶液の色である緑色を呈色した。放冷した後に生成したノナン酸銅を吸引濾過し、１－プロパノール、水、メタノールの順で洗浄した。その粉体を減圧乾燥した。収量は９．４ｇ（収率９４％）であった。 [Example 1] Synthesis of copper fine particle powder using copper (II) nonanoate and copper (II) acetate
[1.1] Synthesis of copper nonanoate To 2.6 g (26 mmol) of copper hydroxide (Kanto Chemical Co., Ltd.), 10 mL of 1-propanol (Kanto Chemical Co., Ltd.) was added and stirred. > 90%) A mixed solution of 8.4 g (53 mmol) and 1-propanol 10 mL was added. The mixture was heated and stirred at 100 ° C. in an aluminum block heating stirrer (Koike Seimitsu Seisakusho). The reaction was completed within 5 minutes, and the solution turned green, which is the color of the copper nonanoate solution. The copper nonanate produced after cooling was suction filtered and washed with 1-propanol, water, and methanol in this order. The powder was dried under reduced pressure. The yield was 9.4 g (94% yield).
[１．２]銅光沢を放つ銅微粒子の合成
以下の合成は全て大気下で実施した。
　実施例１．１で得られたノナン酸銅（ＩＩ）１．２ｇ（３．２ｍｍｏｌ）と酢酸銅（ＩＩ）一水和物（関東化学、特級）０．６４ｇ（３．２ｍｍｏｌ）を５０ｍＬの遠心ガラス管にいれ、１－プロパノール１ｍＬを添加し、アルミブロック式加熱撹拌機（小池精密機器製作所）中で１００℃で加熱撹拌し溶解させた。ヒドラジン一水和物（関東化学、特級）０．６３１ｍＬ（１２．８ｍｍｏｌ）を１－プロパノール１ｍＬに溶解させ、これを、遠心ガラス管の銅前駆体溶液に加え、氷浴中で撹拌した。ヘキシルアミン（東京化成、純度９９％）２．６ｇ（２５ｍｍｏｌ）（銅：ヘキシルアミン＝１：４（モル比））を加え、さらに撹拌した。アルミブロック式加熱撹拌機中で１００℃で加熱撹拌した。発泡を伴う還元反応が進み、１０分以内で反応が終了した。遠心ガラス管の壁面に銅光沢が現れ、溶液は暗赤色へ変化した。ヘキサン（関東化学、特級）（２ｍＬ）を加え、遠心分離（４０００ｒｐｍ（１分間））により、固体物を得た。その遠心分離した固体物を減圧乾燥すると、銅光沢をもつ銅微粒子粉体（収量０．４１ｇ、収率９６％）が得られた。 [1.2] Synthesis of copper fine particles giving off copper luster The following syntheses were all carried out in the atmosphere.
50 mL of 1.2 g (3.2 mmol) of nonanoate copper (II) obtained in Example 1.1 and 0.64 g (3.2 mmol) of copper (II) acetate monohydrate (Kanto Chemical Co., Ltd.) 1 mL of 1-propanol was added to a centrifuge glass tube, and dissolved by heating and stirring at 100 ° C. in an aluminum block heating stirrer (Koike Seimitsu Seisakusho). Hydrazine monohydrate (Kanto Chemical Co., Ltd.) 0.631 mL (12.8 mmol) was dissolved in 1 mL of 1-propanol, and this was added to the copper precursor solution in a centrifuge glass tube and stirred in an ice bath. 2.6 g (25 mmol) (copper: hexylamine = 1: 4 (molar ratio)) of hexylamine (Tokyo Kasei, purity 99%) was added and further stirred. The mixture was heated and stirred at 100 ° C. in an aluminum block type heating stirrer. The reduction reaction accompanied with foaming progressed, and the reaction was completed within 10 minutes. Copper luster appeared on the wall of the centrifuge glass tube, and the solution turned dark red. Hexane (Kanto Chemical Co., Ltd., special grade) (2 mL) was added, and a solid was obtained by centrifugation (4000 rpm (1 minute)). The centrifugally separated solid was dried under reduced pressure to obtain a copper fine particle powder (yield 0.41 g, yield 96%) having copper luster.
[１．３]上記工程で合成した酢酸銅（ＩＩ）とノナン酸銅（ＩＩ）を用いた銅微粒子の評価
＜粉末Ｘ線回折＞
　実施例１．２で得られた銅微粒子粉体は大気下合成でありながら銅光沢を放っており、大気中の酸素に対して安定であり、その表面酸化が抑制されていることが分かる。銅微粒子粉体の粉末Ｘ線回折（ＸＲＤ）パターン（理学 ＭｉｎｉＦｌｅｘＩＩ）から、金属銅に帰属される三つのシグナルが観測されたが、顕著な酸化銅成分に由来するシグナルは見られなかった（図１）。また、そのシグナルの半値幅から計算された金属銅微粒子の単結晶子サイズは、シェラーの式から１０±５ｎｍであった。 [1.3] Evaluation of copper fine particles using copper (II) acetate and nonanoate (II) synthesized in the above steps <Powder X-ray diffraction>
It can be seen that the copper fine particle powder obtained in Example 1.2 has a copper luster while being synthesized in the atmosphere, is stable to oxygen in the atmosphere, and its surface oxidation is suppressed. From the powder X-ray diffraction (XRD) pattern (Science MiniFlexII) of the copper fine particle powder, three signals attributed to metallic copper were observed, but no signal derived from a significant copper oxide component was observed (Fig. 1). The single crystallite size of the metal copper fine particles calculated from the half width of the signal was 10 ± 5 nm from Scherrer's equation.
＜電子顕微鏡観察＞
　実施例１．２で得られた銅微粒子をトルエンに分散させ、これを透過電子顕微鏡（ＴＥＭ）基板（カーボン支持膜）に滴下することで、ＴＥＭ基板に銅微粒子を付着させた。その（フィールドエミッション透過電子顕微鏡像（ＦＥ－ＴＥＭ像）（ＪＥＯＬ ＪＥＭ－２１００Ｆ）から、粒子径１０ｎｍ以下の球状銅微粒子が観察されるほか、１００～２００ｎｍの大きな粒子も含まれていることが分かった（図２）。空気酸化を受けやすいと考えられる１０ｎｍ以下のナノ微粒子に対して高分解能ＴＥＭ（ＨＲ－ＴＥＭ）観察を行った。観察できた格子像の格子間隔である０．２１ｎｍは金属銅の（１１１）面の面格子間隔と一致した（図３）。従って、電子顕微鏡からは、酸化銅に由来する成分は観察されなかった。 <Electron microscope observation>
The copper fine particles obtained in Example 1.2 were dispersed in toluene, and this was dropped onto a transmission electron microscope (TEM) substrate (carbon support film) to attach the copper fine particles to the TEM substrate. From the field emission transmission electron microscopic image (FE-TEM image) (JEOL JEM-2100F), it was found that spherical copper fine particles having a particle diameter of 10 nm or less were observed and large particles of 100 to 200 nm were also included. (Fig. 2) High-resolution TEM (HR-TEM) observation was performed on nano-particles of 10 nm or less, which are considered to be susceptible to air oxidation, and the lattice spacing of the observed lattice image is 0.21 nm. This coincided with the lattice spacing of the (111) plane of copper (FIG. 3), so no component derived from copper oxide was observed from the electron microscope.
＜熱重量示差熱同時分析＞
　実施例１．２で得られた銅微粒子粉体の保護分子の含有重量を調べるため、熱重量示差熱同時分析（ＴＧ－ＤＴＡ）を行った（図４）。ＴＡインスツルメント ＳＤＴＱ６００を用いて、昇温条件１０℃毎分、純窒素気流下（１５０ｍＬ毎分）で行った。室温から２５０℃の加熱により、２段階の重量減少が見られた。４００～５００℃を超えると重量減少は一定となり、このときの重量減少率の５．３重量％が銅微粒子の表面を覆っている有機保護分子の重量となる。この重量減少から実施例１．２における銅基準の収率は９６％と計算された。 <Simultaneous thermogravimetric differential thermal analysis>
In order to examine the content of protective molecules in the copper fine particle powder obtained in Example 1.2, simultaneous thermogravimetric differential thermal analysis (TG-DTA) was performed (FIG. 4). TA instrument SDTQ600 was used, and the temperature was raised at 10 ° C. per minute under a pure nitrogen stream (150 mL per minute). By heating from room temperature to 250 ° C., a two-stage weight reduction was observed. When the temperature exceeds 400 to 500 ° C., the weight reduction becomes constant, and 5.3% by weight of the weight reduction rate at this time is the weight of the organic protective molecule covering the surface of the copper fine particles. From this weight loss, the copper based yield in Example 1.2 was calculated to be 96%.
＜熱重量同時質量分析＞
　実施例１．２で得られた銅微粒子粉体の熱重量減少を追跡しながら質量分析器ＪＥＯＬ（ＪＭＳ－Ｑ１０５０ＧＣ）を用いて、脱離した保護分子の質量分析（ＴＧ－Ｍａｓｓ）を行った。昇温条件１５℃毎分、ヘリウム気流下（１００ｍＬ毎分）で、イオン化方法はＥＩとＰＩ（光イオン化）で実施した。２００℃までの第一段階目の熱重量減少で、脂肪酸（酢酸とノナン酸）の由来する成分とヘキシルアミンに由来する保護分子の両方が脱離していることが分かった。２００℃以上の第二段階目の熱重量減少ではノナン酸に由来の成分が検出された。 <Simultaneous thermogravimetric mass spectrometry>
Mass spectrometry (TG-Mass) of the desorbed protected molecules was performed using a mass analyzer JEOL (JMS-Q1050GC) while following the thermogravimetric decrease of the copper fine particle powder obtained in Example 1.2. . The ionization method was carried out with EI and PI (photoionization) under a heating condition of 15 ° C. per minute under a helium stream (100 mL per minute). It was found that both the component derived from fatty acids (acetic acid and nonanoic acid) and the protective molecule derived from hexylamine were eliminated by the thermogravimetric decrease in the first stage up to 200 ° C. A component derived from nonanoic acid was detected in the thermogravimetric decrease in the second stage at 200 ° C. or higher.
＜焼結性＞
　実施例１．２で得られた銅微粒子をトルエンに分散させ、５０重量％の銅微粒子インクを調製した。このインクをガラス基板上に垂らし、バーコーター（栄和発條製作所 φ８×３００ｍｍ）を用いて塗布し、銅光沢ナノ微粒子薄膜を作製した。得られた銅光沢ナノ微粒子薄膜を電気炉（ＫＤＦ　Ｓ－７０）に入れ、保護分子を熱除去並びに粒子同士を焼結させた（焼結条件：アルゴン下、昇温速度は１０℃／分、各到達温度（２００、２２０、２４０、２６０℃）で１時間維持）。図５に示すように、実施例１．２で得られた銅微粒子薄膜は２００℃加熱で導体化し、２６０℃加熱で、体積抵抗率（５．０μΩｃｍ、銅のバルク抵抗（１．７μΩｃｍ）の約３倍の体積抵抗）を示した。体積抵抗率は４端針面抵抗測定器（共和理研、Ｋ－７０５ＲＳ）で測定した面抵抗値と、フィールドエミッション走査電子顕微鏡（ＦＥ－ＳＥＭ、ＪＥＯＬ ＪＳＭ－７６００Ｆ）像から求めた膜厚から算出した。 <Sinterability>
The copper fine particles obtained in Example 1.2 were dispersed in toluene to prepare a 50% by weight copper fine particle ink. This ink was dropped on a glass substrate and applied using a bar coater (Eiwa Hagi Seisakusho φ8 × 300 mm) to prepare a copper-gloss nanoparticle thin film. The obtained copper luster nanoparticle thin film was placed in an electric furnace (KDF S-70), the protective molecules were removed by heat and the particles were sintered together (sintering conditions: under argon, the heating rate was 10 ° C./min. 1 hour at each temperature reached (200, 220, 240, 260 ° C)). As shown in FIG. 5, the copper fine particle thin film obtained in Example 1.2 was made into a conductor by heating at 200 ° C., and heated to 260 ° C. to have a volume resistivity (5.0 μΩcm, copper bulk resistance (1.7 μΩcm)). About 3 times the volume resistance). The volume resistivity is calculated from the surface resistance measured with a four-end needle surface resistance measuring instrument (Kyowa Riken, K-705RS) and the film thickness obtained from a field emission scanning electron microscope (FE-SEM, JEOL JSM-7600F) image. did.
[実施例２]水酸化銅（ＩＩ）を出発物質とする銅微粒子の合成
[２．１]水酸化銅（ＩＩ）を用いた銅微粒子の簡便合成
　５０ｍＬの遠心ガラス管に水酸化銅（ＩＩ）０．６２ｇ（６．３ｍｍｏｌ）とノナン酸２．０ｇ（１３ｍｍｏｌ）、１－プロパノール０．９ｍＬを加え、アルミブロック式加熱撹拌機を用いて１００℃で加熱・撹拌した。この加熱撹拌により、水酸化銅とノナン酸が反応することでノナン酸銅プロパノール溶液が得られる（反応式：Ｃｕ（ＯＨ）２＋２Ｃ８Ｈ１７ＣＯＯＨ → Ｃｕ（Ｃ８Ｈ１７ＣＯＯ）２＋２Ｈ２Ｏ）この溶液を氷冷し、１－プロパノール１ｍＬに溶かしたヒドラジン一水和物０．６２８ｍＬ（１２．７ｍｍｏｌ）を加えた。その後、ヘキシルアミン２．５７ｇ（２５．４ｍｍｏｌ）を加え、さらに数分撹拌した。１００℃で加熱・撹拌することで、発泡を伴う還元反応が進み、１０分以内で反応が終了した。遠心ガラス管の壁面に銅光沢が現れ、溶液は暗赤色へ変化した。ヘキサン（２ｍＬ）を加え、遠心分離（４０００ｒｐｍ（１分間））により、固体物を得た。その遠心分離した固体物を減圧乾燥すると、銅光沢をもつ銅微粒子粉体（収量０．３６ｇ、収率８１％）が得られた。 [Example 2] Synthesis of copper fine particles using copper hydroxide (II) as a starting material
[2.1] Simple synthesis of copper fine particles using copper (II) hydroxide In a 50 mL centrifugal glass tube, 0.62 g (6.3 mmol) of copper (II) hydroxide and 2.0 g (13 mmol) of nonanoic acid, 1 -0.9 mL of propanol was added, and the mixture was heated and stirred at 100 ° C using an aluminum block heating stirrer. By this heating and stirring, copper hydroxide and nonanoic acid react to obtain a copper propanol solution of nonanoate (reaction formula: Cu (OH) 2 + 2C 8 H 17 COOH → Cu (C 8 H 17 COO) 2 + 2H 2 O) This solution was ice-cooled, and 0.628 mL (12.7 mmol) of hydrazine monohydrate dissolved in 1 mL of 1-propanol was added. Thereafter, 2.57 g (25.4 mmol) of hexylamine was added, and the mixture was further stirred for several minutes. By heating and stirring at 100 ° C., the reduction reaction accompanied with foaming progressed, and the reaction was completed within 10 minutes. Copper luster appeared on the wall of the centrifuge glass tube, and the solution turned dark red. Hexane (2 mL) was added, and a solid was obtained by centrifugation (4000 rpm (1 minute)). The centrifuged solid was dried under reduced pressure to obtain a copper fine particle powder (yield 0.36 g, yield 81%) having copper luster.
[２．２]水酸化銅（ＩＩ）を用いた銅微粒子の評価
＜粉末Ｘ線回折＞
　実施例２．１で得られた銅微粒子粉体の粉末Ｘ線回折ＸＲＤパターンから、金属銅に帰属される三つのシグナルが観測された。また、酸化銅成分に由来するシグナルも弱い強度であるが観測された（図６）。また、そのシグナルの半値幅から計算された金属銅微粒子の単結晶子サイズは、９±４ｎｍであり、実施例１で得られた金属銅微粒子の比べて単結晶子サイズが小さいことが分かった。 [2.2] Evaluation of copper fine particles using copper (II) hydroxide <Powder X-ray diffraction>
From the powder X-ray diffraction XRD pattern of the copper fine particle powder obtained in Example 2.1, three signals attributed to metallic copper were observed. Further, a signal derived from the copper oxide component was also observed with a weak intensity (FIG. 6). Moreover, the single crystallite size of the metal copper fine particles calculated from the half width of the signal was 9 ± 4 nm, and it was found that the single crystallite size was smaller than that of the metal copper fine particles obtained in Example 1. .
＜電子顕微鏡観察＞
　実施例２．１で得られた銅微粒子をトルエンに分散させ、これをＴＥＭ基板に滴下することで、ＴＥＭ基板に銅微粒子を付着させた。ＦＥ－ＳＴＥＭ像（ＪＥＯＬ ＪＳＭ－７６００Ｆ）からは２つの粒子径分布を示す銅微粒子が観察された。その粒子径分布はそれぞれ７．６±２．３ｎｍ（図７(ａ)）と２４±３．３ｎｍ（図７(ｂ)）であった。また、粒子形状は球状の他に、プリズムやヘキサゴナルプレートが多く存在していること分かった。 <Electron microscope observation>
The copper fine particles obtained in Example 2.1 were dispersed in toluene, and this was dropped on the TEM substrate, thereby attaching the copper fine particles to the TEM substrate. From the FE-STEM image (JEOL JSM-7600F), copper fine particles having two particle size distributions were observed. The particle size distributions were 7.6 ± 2.3 nm (FIG. 7 (a)) and 24 ± 3.3 nm (FIG. 7 (b)), respectively. In addition to the spherical shape, it was found that there were many prisms and hexagonal plates.
＜熱重量示差熱同時分析＞
　実施例２．１で得られた銅微粒子粉体の保護分子の含有重量を調べるため、熱重量示差熱同時分析（ＴＧ－ＤＴＡ）を行った。室温から２５０℃の加熱により、２段階の重量減少が見られた。４００～５００℃を超えると重量減少は一定となり、このときの重量減少率の９．２重量％が銅微粒子の表面を覆っている有機保護分子の重量となる。この重量減少から実施例２．１における銅基準の収率は８１％と計算された。 <Simultaneous thermogravimetric differential thermal analysis>
In order to examine the content of protective molecules in the copper fine particle powder obtained in Example 2.1, a thermogravimetric differential thermal analysis (TG-DTA) was performed. By heating from room temperature to 250 ° C., a two-stage weight reduction was observed. When the temperature exceeds 400 to 500 ° C., the weight reduction becomes constant, and 9.2% by weight of the weight reduction rate at this time is the weight of the organic protective molecule covering the surface of the copper fine particles. From this weight loss, the copper based yield in Example 2.1 was calculated to be 81%.
[実施例３]
実施例２の方法においてヘキシルアミンとヒドラジンの添加順序を入れ替えた方法
　５０ｍＬの遠心ガラス管に水酸化銅（ＩＩ）０．６２ｇ（６．３ｍｍｏｌ）とノナン酸２．０ｇ（１３ｍｍｏｌ）、１－プロパノール０．９ｍＬを加え、アルミブロック式加熱撹拌機を用いて１００℃で加熱・撹拌した。この溶液にヘキシルアミン２．５７ｇ（２５．４ｍｍｏｌ）を加え、６分間撹拌した。この溶液を氷冷し、１－プロパノール１ｍＬに溶かしたヒドラジン一水和物０．６２８ｍＬ（１２．７ｍｍｏｌ）を加えた。その後、１００℃で加熱・撹拌することで、発泡を伴う還元反応が進み、１０分以内で反応が終了した。遠心ガラス管の壁面に銅光沢が現れ、溶液は暗赤色へ変化した。ヘキサン（２ｍＬ）を加え、遠心分離（４０００ｒｐｍ（１分間））により、固体物を得た。その遠心分離した固体物を減圧乾燥すると、銅光沢をもつ銅微粒子粉体（収量０．４０ｇ、収率９２％）が得られた。 [Example 3]
Method in which the order of addition of hexylamine and hydrazine was changed in the method of Example 2. In a 50 mL centrifuge glass tube, 0.62 g (6.3 mmol) of copper (II) hydroxide, 2.0 g (13 mmol) of nonanoic acid, 1-propanol 0.9 mL was added, and it heated and stirred at 100 degreeC using the aluminum block type heating stirrer. To this solution, 2.57 g (25.4 mmol) of hexylamine was added and stirred for 6 minutes. This solution was ice-cooled, and 0.628 mL (12.7 mmol) of hydrazine monohydrate dissolved in 1 mL of 1-propanol was added. Then, the reduction reaction accompanied by foaming progressed by heating and stirring at 100 ° C., and the reaction was completed within 10 minutes. Copper luster appeared on the wall of the centrifuge glass tube, and the solution turned dark red. Hexane (2 mL) was added, and a solid was obtained by centrifugation (4000 rpm (1 minute)). The centrifuged solid was dried under reduced pressure to obtain a copper fine particle powder (yield 0.40 g, yield 92%) having copper luster.
＜粉末Ｘ線回折＞
上記で得られた銅微粒子粉体の粉末Ｘ線回折ＸＲＤパターンから、金属銅に帰属される三つのシグナルが観測された。また、酸化銅成分に由来するシグナルもごく弱い強度であるが観測された。また、そのシグナルの半値幅から計算された金属銅微粒子の単結晶子サイズは、１０±３ｎｍであった。 <Powder X-ray diffraction>
From the powder X-ray diffraction XRD pattern of the copper fine particle powder obtained above, three signals attributable to metallic copper were observed. In addition, a signal derived from the copper oxide component was also observed with a very weak intensity. The single crystallite size of the metal copper fine particles calculated from the half width of the signal was 10 ± 3 nm.
＜電子顕微鏡観察＞
ＦＥ－ＳＴＥＭ像からは２つの粒子径分布を示す銅微粒子が観察された。その粒子径分布はそれぞれ５．７±１．７ｎｍと２７±７．９ｎｍであった。また、実施例２で合成した銅微粒子と同様に、粒子形状は球状の他に、プリズムやヘキサゴナルプレートが多く存在していること分かった（図８）。 <Electron microscope observation>
From the FE-STEM image, copper fine particles having two particle size distributions were observed. The particle size distributions were 5.7 ± 1.7 nm and 27 ± 7.9 nm, respectively. Moreover, it turned out that there are many prisms and hexagonal plates in addition to the spherical shape as in the case of the copper fine particles synthesized in Example 2 (FIG. 8).
＜熱重量示差熱同時分析＞
　上記で得られた銅微粒子粉体の保護分子の含有重量を調べるため、熱重量示差熱同時分析（ＴＧ－ＤＴＡ）を行った。室温から２５０℃の加熱により、２段階の重量減少が見られた。４００～５００℃を超えると重量減少は一定となり、このときの重量減少率の６．４重量％が銅微粒子の表面を覆っている有機保護分子の重量となる。この重量減少から実施例５における銅基準の収率は９２％と計算された。 <Simultaneous thermogravimetric differential thermal analysis>
In order to examine the content of protective molecules contained in the copper fine particle powder obtained above, a thermogravimetric differential thermal analysis (TG-DTA) was performed. By heating from room temperature to 250 ° C., a two-stage weight reduction was observed. When the temperature exceeds 400 to 500 ° C., the weight reduction becomes constant, and 6.4% by weight of the weight reduction rate at this time is the weight of the organic protective molecule covering the surface of the copper fine particles. From this weight loss, the yield based on copper in Example 5 was calculated to be 92%.
[実施例４]　１種類の脂肪酸を用いた銅微粒子の合成
　実施例２と同様な方法で、ノナン酸を他の脂肪酸（炭素数３～７）に置き換えて、銅微粒子を合成した。 Example 4 Synthesis of Copper Fine Particles Using One Type of Fatty Acid Copper fine particles were synthesized in the same manner as in Example 2 by replacing nonanoic acid with other fatty acids (3 to 7 carbon atoms).
[４．１]　銅微粒子の評価
　ＸＲＤ測定結果（図９）から、いずれの脂肪酸銅を用いた合成でも、酸化銅由来のピークは強度的にはごくわずかで、主に金属銅のシグナルが観測された。
　図９のＸＲＤパターンのシグナルの半値幅から計算した金属銅微粒子の単結晶子サイズとＴＧ－ＤＴＡから計算した有機保護分子の重量％を表１にまとめた（この重量減少から求めた銅基準の銅微粒子の収率はいずれの脂肪酸を用いた合成でも８０％以上であった）。用いた脂肪酸の炭素鎖が短い方が、ＸＲＤのシグナルがよりシャープであり（シグナル半値幅が小さい）、表１の得られた銅微粒子の単結晶子サイズは大きくなる傾向がみられた。その結晶子サイズが大きい方が、混在する酸化銅に由来するシグナル強度が減少し、酸化が抑制される傾向があることが分かった。 [4.1] Evaluation of copper fine particles From the XRD measurement results (Fig. 9), the peak derived from copper oxide was very small in intensity in any synthesis using fatty acid copper, and the signal of metal copper was mainly observed. It was done.
The single crystallite size of the metal copper fine particles calculated from the half-value width of the signal of the XRD pattern in FIG. 9 and the weight percentage of the organic protective molecule calculated from TG-DTA are summarized in Table 1 (on the basis of copper based on this weight reduction). The yield of copper fine particles was 80% or more in any fatty acid synthesis). The shorter the carbon chain of the fatty acid used, the sharper the XRD signal (the signal half width is smaller), and the single crystallite size of the obtained copper fine particles in Table 1 tended to increase. It was found that when the crystallite size is larger, the signal intensity derived from the mixed copper oxide decreases, and the oxidation tends to be suppressed.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
[実施例５]　２種類の脂肪酸を用いた銅微粒子の合成
　実施例２と同様な方法で、２種類の脂肪酸（モル比で１：１）を同時に加えて、銅微粒子を合成した。 [Example 5] Synthesis of copper fine particles using two types of fatty acids In the same manner as in Example 2, two types of fatty acids (1: 1 in molar ratio) were simultaneously added to synthesize copper fine particles.
[５．１]　銅微粒子の評価
　ＸＲＤパターンのシグナルの半値幅から計算した金属銅微粒子の単結晶子サイズとＴＧ－ＤＴＡから計算した有機保護分子の重量％を表２にまとめた（この重量減少から求めた銅基準の銅微粒子の収率はいずれの脂肪酸を用いた合成でも８０％以上であった）。
　実施例４で得られた銅微粒子と同様に、表２で結晶子サイズが大きい方が、混在する酸化銅に由来するシグナル強度が減少し、酸化が抑制される傾向があることが分かった。 [5.1] Evaluation of copper fine particles The single crystallite size of the metal copper fine particles calculated from the half-value width of the XRD pattern signal and the weight percentage of the organic protective molecules calculated from TG-DTA are summarized in Table 2 (this weight reduction). The yield of copper-based copper fine particles obtained from the above was 80% or more in any fatty acid synthesis).
As with the copper fine particles obtained in Example 4, it was found that the larger the crystallite size in Table 2, the lower the signal intensity derived from the mixed copper oxide, and the tendency to suppress oxidation.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
[比較例１]　アルキルアミンを用いない場合
　５０ｍＬの遠心ガラス管に水酸化銅（ＩＩ）０．６２ｇ（６．３ｍｍｏｌ）とノナン酸１．０ｇ（６．３ｍｍｏｌ）と酢酸０．３８１ｇ（６．３ｍｍｏｌ）、１－プロパノール０．９ｍＬを加え、アルミブロック式加熱撹拌機を用いて１００℃で加熱・撹拌した。この溶液を氷冷し、１－プロパノール１ｍＬに溶かしたヒドラジン一水和物０．６２８ｍＬ（１２．７ｍｍｏｌ）を加えた。その後、１００℃で加熱・撹拌することで、発泡を伴う還元反応が進み、５分以内で反応が終了した。遠心ガラス管の壁面に銅光沢が現れ、溶液は暗赤色へ変化した。ヘキサン（１～３ｍＬ）を加え、遠心分離（４０００ｒｐｍ（１分間））により、固体物を得た。その遠心分離した固体物を減圧乾燥すると、銅光沢をもつ銅微粒子粉体が得られた。 [Comparative Example 1] When alkylamine is not used In a 50 mL centrifuge glass tube, 0.62 g (6.3 mmol) of copper (II) hydroxide, 1.0 g (6.3 mmol) of nonanoic acid, and 0.381 g of acetic acid (6. 3 mmol) and 0.9 mL of 1-propanol were added, and the mixture was heated and stirred at 100 ° C. using an aluminum block heating stirrer. This solution was ice-cooled, and 0.628 mL (12.7 mmol) of hydrazine monohydrate dissolved in 1 mL of 1-propanol was added. Then, the reduction reaction accompanied by foaming progressed by heating and stirring at 100 ° C., and the reaction was completed within 5 minutes. Copper luster appeared on the wall of the centrifuge glass tube, and the solution turned dark red. Hexane (1-3 mL) was added, and the solid was obtained by centrifugation (4000 rpm (1 minute)). The centrifuged solid was dried under reduced pressure to obtain a copper fine particle powder having copper luster.
銅微粒子の評価
＜粉末Ｘ線回折＞
　ヘキシルアミンが存在する場合には、酸化物がほとんど出ないのに対して、本比較例では酸化銅に由来するピークが検出された。
＜電子顕微鏡像＞
　トルエンに銅粉体を溶解させたインクをマイクロチューブに取り、トルエンで希釈した。その後、希釈したインクをマイクログリッドの上に滴下し、アセトンで洗浄、ＦＥ－ＳＥＭの透過像により粒子を観察した。ヘキシルアミンが存在する場合と比べて、凝集が顕著に起こっていることが分かった。この時、超音波などの操作を行ったが、２次粒子の離散はできなかった。
　これらの結果より、アルキルアミンの非存在下では、銅の酸化を抑制することができず、かつ分散した銅微粒子の合成はできないことが分かった。 Evaluation of copper fine particles <Powder X-ray diffraction>
When hexylamine is present, almost no oxide appears, whereas in this comparative example, a peak derived from copper oxide was detected.
<Electron microscope image>
Ink in which copper powder was dissolved in toluene was placed in a microtube and diluted with toluene. Thereafter, the diluted ink was dropped on the microgrid, washed with acetone, and the particles were observed with a transmission image of FE-SEM. It was found that agglomeration was conspicuous compared to the case where hexylamine was present. At this time, although operations such as ultrasonic waves were performed, secondary particles could not be dispersed.
From these results, it was found that in the absence of alkylamine, copper oxidation could not be suppressed and dispersed copper fine particles could not be synthesized.

Claims (15)

  1. 　炭素原子数９以下の脂肪酸銅、還元性化合物及びアルキルアミンを含む混合物を加熱する加熱工程を含むことを特徴とする被覆銅微粒子の製造方法。 A method for producing coated copper fine particles, comprising a heating step of heating a mixture containing fatty acid copper having 9 or less carbon atoms, a reducing compound and an alkylamine.
  2. 　前記混合物が、更に少なくとも１種の極性溶媒を含むことを特徴とする請求項１に記載の被覆銅微粒子の製造方法。 The method for producing coated copper fine particles according to claim 1, wherein the mixture further contains at least one polar solvent.
  3. 　前記混合物が、１０℃以下の温度で混合する工程を含む工程により調製されたものであることを特徴とする請求項１又は２に記載の被覆銅微粒子の製造方法。 The method for producing coated copper fine particles according to claim 1 or 2, wherein the mixture is prepared by a process including a process of mixing at a temperature of 10 ° C or lower.
  4. 　前記加熱工程が、１５０℃以下の温度で行われることを特徴とする請求項１～３のいずれかに記載の被覆銅微粒子の製造方法。 The method for producing coated copper fine particles according to any one of claims 1 to 3, wherein the heating step is performed at a temperature of 150 ° C or lower.
  5. 　前記脂肪酸銅が、水酸化銅と、炭素原子数が９以下の脂肪酸と、極性溶媒の混合物を加熱して生成させたものであることを特徴とする請求項１～４のいずれかに記載の被覆銅微粒子の製造方法。 5. The fatty acid copper according to claim 1, wherein the fatty acid copper is produced by heating a mixture of copper hydroxide, a fatty acid having 9 or less carbon atoms, and a polar solvent. A method for producing coated copper fine particles.
  6. 　前記極性溶媒が、１－プロパノール又２－プロパノールを含むことを特徴とする請求項２～５のいずれかに記載の被覆銅微粒子の製造方法。 6. The method for producing coated copper fine particles according to claim 2, wherein the polar solvent contains 1-propanol or 2-propanol.
  7. 　前記脂肪酸銅が、酢酸銅、プロピオン酸銅、酪酸銅、吉草酸銅、カプロン酸銅、エナント酸銅、カプリル酸銅及びノナン酸銅からなる群より選択される１種又は２種以上の脂肪酸銅を含むことを特徴とする請求項１～６のいずれかに記載の被覆銅微粒子の製造方法。 The fatty acid copper is one or more fatty acid copper selected from the group consisting of copper acetate, copper propionate, copper butyrate, copper valerate, copper caproate, copper enanthate, copper caprylate and copper nonanoate The method for producing coated copper fine particles according to any one of claims 1 to 6, comprising:
  8. 　前記還元性化合物が、ヒドラジン、ヒドロキシルアミン又はそれらの誘導体を含むことを特徴とする請求項１～７のいずれかに記載の被覆銅微粒子の製造方法。 The method for producing coated copper fine particles according to any one of claims 1 to 7, wherein the reducing compound contains hydrazine, hydroxylamine or a derivative thereof.
  9. 　銅微粒子が、アルキルアミンと脂肪酸とを含む膜で被覆されている被覆銅微粒子であって、当該銅微粒子は実質的に銅の酸化物相を含まないことを特徴とする被覆銅微粒子。 A coated copper fine particle, wherein the copper fine particle is coated with a film containing an alkylamine and a fatty acid, and the copper fine particle does not substantially contain a copper oxide phase.
  10. 　前記銅微粒子は銅の結晶相を含むことを特徴とする請求項９に記載の被覆銅微粒子。 The coated copper fine particles according to claim 9, wherein the copper fine particles contain a crystalline phase of copper.
  11. 　前記被覆銅微粒子は、不活性雰囲気で相互に焼結して導電性の被膜を形成可能であることを特徴とする請求項９又は１０に記載の被覆銅微粒子。 The coated copper fine particles according to claim 9 or 10, wherein the coated copper fine particles can be sintered together in an inert atmosphere to form a conductive film.
  12. 　請求項９～１１のいずれか一項に記載の被覆銅微粒子を有機溶媒に分散させたことを特徴とする分散液。 A dispersion characterized in that the coated copper fine particles according to any one of claims 9 to 11 are dispersed in an organic solvent.
  13. 　前記有機溶媒は、非極性溶媒を含むことを特徴とする請求項１２に記載の分散液。 The dispersion according to claim 12, wherein the organic solvent contains a nonpolar solvent.
  14. 　前記有機溶媒は、極性溶媒を含むことを特徴とする請求項１２に記載の分散液。 The dispersion according to claim 12, wherein the organic solvent contains a polar solvent.
  15. 　請求項９～１１のいずれか一項に記載の被覆銅微粒子を含むことを特徴とするペースト。 A paste comprising the coated copper fine particles according to any one of claims 9 to 11.
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