WO2013115339A1 - Silver microparticles, method for producing same, and electronic device, conductive film, and conductive paste containing said silver microparticles - Google Patents

Silver microparticles, method for producing same, and electronic device, conductive film, and conductive paste containing said silver microparticles Download PDF

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Publication number
WO2013115339A1
WO2013115339A1 PCT/JP2013/052273 JP2013052273W WO2013115339A1 WO 2013115339 A1 WO2013115339 A1 WO 2013115339A1 JP 2013052273 W JP2013052273 W JP 2013052273W WO 2013115339 A1 WO2013115339 A1 WO 2013115339A1
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Prior art keywords
fine particles
silver fine
silver
solution
liquid
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PCT/JP2013/052273
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French (fr)
Japanese (ja)
Inventor
石谷　誠治
山本　洋介
岩崎　敬介
峰子 大杉
森井　弘子
林　一之
Original Assignee
戸田工業株式会社
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Publication date
Priority claimed from JP2012021348A external-priority patent/JP5924481B2/en
Priority claimed from JP2012021335A external-priority patent/JP5991459B2/en
Application filed by 戸田工業株式会社 filed Critical 戸田工業株式会社
Priority to CN201380007258.8A priority Critical patent/CN104080561A/en
Priority to KR1020147020950A priority patent/KR20140125366A/en
Publication of WO2013115339A1 publication Critical patent/WO2013115339A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • 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
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/25—Noble metals, i.e. Ag Au, Ir, Os, Pd, Pt, Rh, Ru
    • B22F2301/255—Silver or gold

Definitions

  • the present invention provides silver fine particles having an average particle diameter of 30 to 100 nm, excellent in heat shrinkability and low-temperature sinterability, and excellent in filling properties in electrodes and circuit patterns formed on a substrate, and a method for producing the same.
  • the present invention relates to a conductive paste containing fine particles, a conductive film, and an electronic device.
  • the electrodes and circuit patterns of electronic devices are formed by printing electrodes and circuit patterns on a substrate using a conductive paste containing metal particles, and then baking by heating and sintering the metal particles contained in the conductive paste.
  • the heating and baking temperature tends to be lowered.
  • a polyimide flexible substrate is generally used because it can be heated up to about 300 ° C. and has excellent heat resistance.
  • Inexpensive PET (polyethylene terephthalate) substrates and PEN (polyethylene naphthalate) substrates are being investigated as alternative materials.
  • PET substrates and PEN substrates have lower heat resistance than polyimide flexible substrates, and in particular, PET film substrates used for membrane wiring boards need to be heated and fired at 150 ° C. or lower.
  • heating and firing can be performed at a temperature lower than 200 ° C., it becomes possible to form electrodes and circuit patterns on a substrate such as polycarbonate and paper, and it is expected that the use of various electrode materials will be expanded.
  • silver fine particles of nanometer order are expected.
  • the reason for this is that when the size of the metal particles is on the order of nanometers, the surface activity becomes high and the melting point is much lower than that of the bulk metal, so that it can be sintered at a low temperature.
  • silver fine particles are expensive compared to other conductive particles such as copper, and there is a defect that migration is likely to occur among metal particles, but it is difficult to oxidize compared to copper having the same specific resistance. It is easy to handle.
  • nanometer-order silver fine particles can be sintered at low temperatures, and heat resistance is maintained once sintered, which is also expected as a lead-free solder replacement material using a property not found in conventional solder. Has been.
  • silver fine particles having low crystallinity of the particles tend to have a high thermal shrinkage rate upon heating and firing.
  • fine wiring formed from a conductive paste containing the silver fine particles is the basis.
  • problems such as peeling from the material and high resistance due to thinning of the wiring.
  • problems such as deterioration of the dimensional accuracy of the sintered body occur.
  • metal colloidal particles having a distribution in particle size including metal nanoparticles and a dispersing agent have been proposed as metal colloidal particles including metal nanoparticles that can form a hard film with excellent low-temperature sintering properties.
  • Patent Document 1 metal colloidal particles having a distribution in particle size including metal nanoparticles and a dispersing agent
  • Patent Document 2 metal colloidal particles including metal nanoparticles that can form a hard film with excellent low-temperature sintering properties.
  • silver particles bonded with a straight chain fatty acid having 6 or less carbon atoms as a protective agent Patent Document 2
  • the tap density including at least one crystal grain having a minimum crystal grain size of 0.3 ⁇ m or more is 4 g / cm 3 or more.
  • a silver powder composed of polycrystalline silver particles is known.
  • Patent Document 1 metal colloidal particles having a distribution in particle size including metal nanoparticles and a dispersant are disclosed.
  • the production method described in Patent Document 1 is a mixture of a silver nitrate solution and a reducing agent solution. No particular consideration is given to the temperature control at that time, and the silver colloidal particle aggregates are only recovered by a pressure filter in the drying process. For this reason, the colloidal silver particles obtained by the production method described in Patent Document 1 have a tap density of 3 g / cm 3 or less as shown in a comparative example, and the fine wiring formed by the conductive paste containing the silver colloid particles is It is difficult to increase the filling rate of the silver fine particles, which is disadvantageous for reducing the electric resistance value. Further, since the residual amount of organic matter on the surface of the silver fine particles was 2.5% by weight or more, it is difficult to say that the low-temperature sinterability is excellent.
  • Patent Document 2 discloses silver particles bonded with a straight chain fatty acid having 6 or less carbon atoms as a protective agent. As shown in Comparative Examples, the obtained silver particles have a tap density of 3 g / cm. 3 or less, and since the BET specific surface area value is 7 m 2 / g or more, it is difficult to increase the filling rate of the silver particles in the fine wiring formed by the conductive paste containing the silver particles, This is disadvantageous for reducing the electric resistance value.
  • Patent Document 3 discloses a silver powder composed of polycrystalline silver particles having a tap density of 4 g / cm 3 or more including at least one crystal grain having a minimum crystal grain size of 0.3 ⁇ m or more. Since the minimum particle size is 0.21 ⁇ m or more and the particle size is large, it is disadvantageous for miniaturization of fine electrodes and circuit pattern printing formed on a substrate in recent years. Further, since the particle size is large, it is difficult to say that the low-temperature sinterability is excellent.
  • the present invention has a high tap density of 3.0 g / cm 3 or more while having an average particle size (D SEM ) of 30 to 100 nm and fine particles, and is excellent in heat shrinkability and low temperature sinterability,
  • An object of the present invention is to provide silver fine particles having excellent filling properties in electrodes and circuit patterns formed on a substrate and a method for producing the same.
  • the present invention is a silver fine particle characterized by having an average particle diameter (D SEM ) of 30 to 100 nm and a tap density of 3.0 g / cm 3 or more (Invention 1). Further, the present invention provides the silver fine particles according to claim 1, wherein the BET specific surface area value is 7.0 m 2 / g or less (Invention 2).
  • this invention is a silver microparticle of Claim 1 or Claim 2 whose crystallite diameter ( Dx ) is 30 nm or more (Invention 3).
  • the present invention is the silver fine particles according to any one of claims 1 to 3, wherein the remaining amount of organic matter on the surface of the silver fine particles is 0.5 to 2.0% by weight (Invention 4).
  • the present invention is the silver fine particles according to any one of claims 1 to 4 having a heat shrinkage rate at 240 ° C. of 2.0% or more (Invention 5).
  • the present invention is a conductive paste containing the silver fine particles according to any one of claims 1 to 5 (invention 6).
  • present invention is a conductive film formed using the conductive paste according to claim 6 (present invention 7).
  • present invention is an electronic device having the conductive film according to claim 7 (present invention 8).
  • an aqueous solution is prepared using silver nitrate and a polymer protective agent (liquid A), and separately from the liquid A, an aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved is prepared (liquid B).
  • liquid A aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved
  • liquid B aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved
  • the mixed solution when the B liquid is dropped into the A liquid.
  • This is a silver fine particle production method characterized in that the temperature is controlled to 40 ° C. or lower and the drying step is performed by vacuum freeze-drying (Invention 9).
  • the present invention is the method for producing silver fine particles according to claim 9 , wherein the water content of the water-containing material before vacuum freeze-drying is 30% or more (Invention 10).
  • the present invention is the method for producing silver fine particles according to claim 9 or 10, wherein the obtained silver fine particles are the silver fine particles according to any one of claims 1 to 5 (invention 11).
  • the tap density tends to decrease as the particle size of the silver fine particles decreases.
  • the method for producing silver fine particles according to the present invention has the average particle diameter (D SEM ) of 30 to 100 nm even though the particles are fine particles. Therefore, since silver fine particles having a high tap density of 3.0 g / cm 3 or more can be obtained, it is suitable as a method for producing silver fine particles having excellent low-temperature sintering properties and filling properties in electrodes and circuit patterns.
  • the silver fine particles according to the present invention have a high tap density of 3.0 g / cm 3 or more despite the fine particle having an average particle diameter (D SEM ) of 30 to 100 nm by the above production method. Therefore, it is suitable as a raw material for conductive paste and the like having excellent filling properties in electrodes and circuit patterns formed on a substrate.
  • the silver fine particles according to the present invention are characterized by having an average particle diameter (D SEM ) of 30 to 100 nm and a tap density of 3.0 g / cm 3 or more.
  • D SEM average particle diameter
  • the average particle diameter (D SEM ) of the silver fine particles according to the present invention is 30 to 100 nm, preferably 35 to 95 nm, more preferably 40 to 90 nm.
  • D SEM average particle diameter
  • the average particle diameter (D SEM ) is in the above range, it is easy to refine an electronic device obtained using the average particle diameter (D SEM ).
  • the average particle size (D SEM ) is less than 30 nm, the surface activity of the silver fine particles increases, and it is not preferable because a large amount of organic matter or the like needs to be adhered in order to stably maintain the fine particle size. .
  • the tap density of the silver fine particles according to the present invention is 3.0 g / cm 3 or more, preferably 3.5 g / cm 3 or more, more preferably 4.0 g / cm 3 or more.
  • the upper limit of the tap density of the silver fine particles is about 6.0 g / cm 3 , and more preferably about 5.5 g / cm 3 .
  • the BET specific surface area value of the silver fine particles according to the present invention is preferably 7 m 2 / g or less, more preferably 6 m 2 / g or less. When the BET specific surface area value exceeds 7 m 2 / g, the viscosity of the conductive paste obtained by using this is not preferable.
  • the lower limit of the BET specific surface area value of the silver fine particles is about 1.5 m 2 / g, more preferably about 2.0 m 2 / g.
  • the crystallite diameter (D X ) of the silver fine particles according to the present invention is preferably 30 nm or more, more preferably 35 to 95 nm, and more preferably 40 to 90 nm.
  • the crystallite diameter (D X ) is less than 30 nm, the silver fine particles become unstable and partial sintering and fusion start even at room temperature, which is not preferable.
  • the crystallinity of the silver fine particles according to the present invention is preferably 2.7 or less, more preferably 2.5 or less, still more preferably 2.3 or less. The closer the degree of crystallinity is to 1, the more it is a single crystal. When the degree of crystallinity exceeds 2.7, the heat shrinkage rate of the silver fine particles is high, so that the fine wiring formed from the conductive paste obtained by using this is peeled off from the base material, or the wiring becomes thin. This is not preferable because of the problem of high resistance.
  • the amount of the organic matter remaining on the surface of the silver fine particles according to the present invention is preferably 0.5 to 2.0% by weight, more preferably 0.6 to 1.9% by weight, still more preferably 0.7 to 1.8% by weight.
  • the residual amount of organic matter on the surface of the silver fine particles exceeds 2.0% by weight, the amount of organic matter present on the surface of the silver fine particles is too much, so that the low temperature sinterability is impaired.
  • it is less than 0.5% by weight the wettability to the solvent and the resin is lowered, and the uniform dispersibility of the conductive paste obtained using this is impaired, which is not preferable.
  • the heat shrinkage rate of the silver fine particles according to the present invention is preferably 2.0% or more, more preferably 2.1% or more at 240 ° C.
  • a silver coating film formed from a conductive paste containing silver fine particles has fine gaps between the silver fine particles, and a silver coating having a lower resistance can be obtained by eliminating this gap.
  • the silver fine particles according to the present invention have a high heat shrinkage rate at 240 ° C. of 2.0% or more, so that the gaps between the silver fine particles of the coating film formed from the conductive paste obtained by using this are easily filled. For this reason, the electric resistance value can be further reduced.
  • the particle shape of the silver fine particles according to the present invention is preferably spherical or granular.
  • an aqueous solution is prepared using silver nitrate and a polymer protective agent (liquid A), and separately from the liquid A, an aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved is prepared (B Liquid), in the method for producing silver fine particles, in which the silver fine particles obtained by dropping the B liquid into the A liquid and reducing and depositing the liquid B are separated, washed and dried, the mixing when the B liquid is dropped into the A liquid While controlling the temperature of a solution to 40 degrees C or less, it can obtain by performing a drying process by vacuum freeze-drying.
  • an aqueous solution is prepared using silver nitrate and a polymer protective agent (A liquid).
  • the polymer protective agent in the present invention is preferably water-soluble or water-soluble.
  • the acid value is preferably 1 mgKOH / g or more, more preferably 10 mgKOH / g or more.
  • the upper limit of the acid value can be used without any particular limitation. However, when the acid value is 0 mgKOH / g, silver particles having a large particle size are produced, so that it is difficult to obtain fine silver fine particles of 100 nm or less.
  • the amine value is preferably 0 mgKOH / g.
  • a polymer protective agent having an amine value When a polymer protective agent having an amine value is used, a silver amine complex is formed when mixed with silver nitrate, and the reduction reaction is not completed or requires a very long time. The fine particles are not preferable because they have poor distribution.
  • a polymeric protective agent may be used independently or may use 2 or more types together.
  • the number average molecular weight of the polymer protective agent is preferably 1,000 or more. More preferably, it is 1,000 to 150,000, and still more preferably 5,000 to 100,000.
  • polymer protective agent commercially available products such as acrylic copolymers or polyoxyalkylene resins can be used, and specifically, DISPERBYK-190, DISPERBYK-194, DISPERBYK. -2015, DISPERBYK-2090, DISPERBYK-2091, DISPERBYK-2095 (made by Big Chemie Japan Co., Ltd.); AKM-0531, HKM-50A, AKM-1511-60, AFB-1521 (made by NOF Corporation), etc. Is mentioned. These polymer protective agents may be used alone or in combination of two or more.
  • the addition amount of the polymer protective agent is preferably 1 to 10% by weight, more preferably 1.5 to 8% by weight, based on the silver fine particles.
  • the addition amount of the polymer protective agent is less than 1% by weight, the particle size of the obtained silver fine particles is increased, which is not preferable. If it exceeds 10% by weight, the remaining organic matter on the surface of the obtained silver fine particles exceeds 2.0% by weight, which is not preferable because the low-temperature sinterability is impaired.
  • amino alcohols can be preferably used in the present invention, and more preferably N, N-dimethylethanolamine, N, N-diethylethanolamine, N, N-diethylisopropanolamine, N- An amino alcohol having a tertiary amine such as methyldiethanolamine, N-ethyldiethanolamine, Nn-butyldiethanolamine, or Nt-butyldiethanolamine.
  • the amount of the reducing agent added is preferably 2.0 to 5.0 moles, more preferably 2.2 to 4.0 moles per mole of silver nitrate. When the amount of the reducing agent added is less than 2.0 moles with respect to 1 mole of silver nitrate, the reduction reaction does not proceed sufficiently, which is not preferable.
  • an aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved is prepared separately from the liquid A (liquid B).
  • an aqueous solution is prepared by adding a low molecular weight protective agent to an aqueous solution (A solution) containing silver nitrate, the low molecular weight protective agent and silver nitrate react to produce silver carboxylate, which lowers the yield of silver fine particles.
  • the silver fine particles obtained by this are not preferable because of poor distribution.
  • a carboxylic acid having 3 to 7 carbon atoms can be used as the low molecular weight protective agent in the present invention.
  • Propionic acid, hexanoic acid and heptanoic acid are preferable, and hexanoic acid and heptanoic acid are more preferable.
  • the longer the carbon chain of the low molecular protective agent the easier it is to obtain silver fine particles with a higher tap density.
  • a low molecular protective agent may be used independently or may use 2 or more types together.
  • the amount of the low molecular weight protective agent added is preferably 0.05 to 0.4 mole, more preferably 0.1 to 0.35 mole relative to 1 mole of silver nitrate.
  • the addition amount of the low molecular protective agent exceeds 0.4 mol with respect to 1 mol of silver nitrate, the generated silver fine particles tend to aggregate, which is not preferable.
  • aqueous solution (Liquid B) in which a reducing agent and a low molecular protective agent are dissolved is dropped into an aqueous solution (Liquid A) prepared using silver nitrate and a polymeric protective agent, and a mixing reaction is performed.
  • the temperature during the mixing reaction usually rises to 50 ° C. or more unless temperature control is performed, but in the present invention, the temperature is preferably controlled in the range of 25 to 40 ° C., more preferably in the range of 30 to 35 ° C. is there. When the temperature during the mixing reaction exceeds 40 ° C., the distribution of the generated silver fine particles tends to be non-uniform, which is not preferable.
  • the reaction solution After dropping the solution B, the reaction solution is heated to 60 to 80 ° C. and stirred to complete the reduction reaction.
  • the heating temperature of the reaction solution is preferably 65 to 75 ° C.
  • the reduction reaction ends when the pH value of the reaction solution becomes constant.
  • the reduction reaction preferably proceeds as slowly as possible, and from this viewpoint, it is preferable to use a long chain fatty acid as much as possible for the low molecular weight protective agent.
  • the reaction solution after the reduction reaction is repeatedly decanted and washed with water until the supernatant has an electric conductivity of 50 ⁇ S / cm or less, and the resulting hydrated product containing silver fine particles is lyophilized in a vacuum and then pulverized by a conventional method.
  • the silver fine particles of the present invention can be obtained.
  • the silver fine particles can only be taken out as a large lump, and the subsequent pulverization process becomes very complicated, and the silver fine particles share more than necessary. Will take. For this reason, the obtained particles are coarsened and the tap density is lowered, so that the target silver fine particle powder of the present invention cannot be obtained.
  • the water content of the water-containing material containing silver fine particles during vacuum freeze-drying is preferably 30% or more, more preferably 35 to 80%, and still more preferably 40 to 70%.
  • the water content is less than 30%, even if vacuum freeze drying is performed, the silver fine particles can be taken out only as a large lump, as in the case of using the above-mentioned ordinary dryer, and the obtained particles are Since it becomes coarse and the tap density decreases, the silver fine particle powder targeted by the present invention cannot be obtained.
  • the silver fine particles according to the first to fifth aspects of the present invention can be produced by the silver fine particle production method described above. That is, as a preferable method for producing the silver fine particles according to the first to fifth aspects of the present invention, the above-described production methods (the present inventions 9 and 10) can be mentioned.
  • the conductive paste according to the present invention may be in any form of a fired paste and a polymer paste.
  • the conductive paste is composed of the silver fine particles and the glass frit according to the present invention.
  • Other components may be blended.
  • a polymer type paste it consists of silver fine particles and a solvent according to the present invention, and if necessary, other components such as a binder resin, a curing agent, a dispersant, and a rheology modifier may be blended.
  • binder resin those known in the art can be used.
  • cellulose resins such as ethyl cellulose and nitrocellulose
  • various modified materials such as polyester resins, urethane modified polyester resins, epoxy modified polyester resins, and acrylic modified polyesters.
  • These binder resins can be used alone or in combination of two or more.
  • solvent those known in the art can be used, such as tetradecane, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, amylbenzene, p-cymene, tetralin, and petroleum aromatic hydrocarbon mixtures.
  • Hydrocarbon solvents ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-t-butyl ether, diethylene glycol monoethyl ether, diethylene glycol Monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, Ether or glycol ether solvents such as propylene glycol monomethyl ether; glycol ester solvents such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, Ketone solvents such as methyl isobutyl ketone and cyclohexanone; terpen
  • the content of silver fine particles in the conductive paste varies depending on the application, but it is preferably as close to 100% by weight as possible, for example, in the case of wiring formation.
  • the conductive paste according to the present invention is obtained by mixing and dispersing each component using various kneaders and dispersers such as a laika machine, a pot mill, a three roll mill, a rotary mixer, a twin screw mixer, and the like. Can do.
  • the conductive paste according to the present invention can be applied to various coating methods such as screen printing, ink jet method, gravure printing, transfer printing, roll coating, flow coating, spray coating, spin coating, dipping, blade coating, and plating.
  • the conductive paste according to the present invention is used for forming electrodes such as FPD (flat panel display), solar cell, organic EL, wiring for LSI substrates, and wiring for filling fine trenches, via holes, contact holes, etc. It can be used as a material.
  • FPD flat panel display
  • organic EL organic EL
  • wiring for LSI substrates and wiring for filling fine trenches, via holes, contact holes, etc.
  • It can be used as a material.
  • FPD flat panel display
  • organic EL organic EL
  • the important point in the present invention is the fact that the silver fine particles according to the present invention are excellent in heat shrinkability and in filling properties in electrodes and circuit patterns formed on the substrate.
  • the present inventors have described that the average particle size (D SEM ) is 30 to 100 nm and fine particles. Nevertheless, it is thought to be due to having a high tap density of 3.0 g / cm 3 or more. That is, a fine wiring formed of a conductive paste containing silver fine particles having a low tap density is difficult to increase the filling rate of silver fine particles and is disadvantageous in reducing the electric resistance value. Since the tap density tends to decrease as the size decreases, it is difficult to satisfy the characteristics of both the particle size and the tap density.
  • the silver fine particles according to the present invention are fine particles having an average particle diameter (D SEM ) of 30 to 100 nm and have a high tap density of 3.0 g / cm 3 or more, they are formed on the substrate. It is thought that excellent filling properties were obtained in the electrodes and circuit patterns.
  • D SEM average particle diameter
  • the average particle diameter of the silver fine particles was obtained by taking a photograph of the particles using a scanning electron micrograph “S-4800” (manufactured by HITACHI), measuring the particle diameter of 100 or more particles using the photograph, The value was calculated and taken as the average particle size (D SEM ).
  • the specific surface area of the silver fine particles was represented by a value measured by BET method using “Monosorb MS-11” (manufactured by Kantachrome Co., Ltd.).
  • the tap density ( ⁇ t) of the silver fine particles is measured by dropping the powder into a 25 ml tapping cell using a shaking specific gravity measuring instrument (Kurachi Kagaku Kikai Seisakusho Co., Ltd.). Was measured 600 times.
  • the amount of organic matter remaining in the silver fine particles was 10 ° C./min from room temperature (30 ° C.) to 550 ° C. under a condition of flowing dry air at 300 ml / min using a thermal analyzer (EXSTAR 6000 TG / DTA 6300 manufactured by Seiko Instruments Inc.). Shown in the amount obtained by subtracting the sample amount from the sample amount at the beginning of heating (30 ° C) to the point when the reduction is completed (at the start of oxidation of silver fine particles (depending on the sample, 250 to 300 ° C)) It was.
  • the crystallite size (D X ) of the silver fine particles is the peak of the plane index (1,1,1) plane using the K ⁇ ray of Cu as the radiation source using an X-ray diffractometer “RINT 2500” (manufactured by Rigaku Corporation). And the crystallite diameter was calculated from the Scherrer equation.
  • the degree of crystallinity of the silver fine particles was indicated by the ratio of the average particle diameter (D SEM ) to the crystallite diameter (D X ) (D SEM / D X ).
  • the thermal contraction rate of the silver fine particles was determined by using a pellet-shaped silver fine particle sample prepared by applying a load of 125.8 N to silver fine particles placed in a 4 mm diameter mold so as to form a pellet having a height of 5 mm.
  • the length of a sample heated at 30 ° C./min with a temperature increase rate of 10 ° C./min using an analyzer “Thermo Plus2 TMA8310” (manufactured by Rigaku Corporation) is a value calculated according to the following formula 1.
  • the specific resistance of the conductive coating was applied to the polyimide film described later on the polyimide film, preliminarily dried at 120 ° C., heated and cured at 150 ° C. for 10 minutes, and then immersed in 1 mol of HCl aqueous solution for 20 seconds. After washing with water, each conductive film obtained by heating and drying again at 150 ° C. for 1 minute was measured using a four-terminal electrical resistance measuring device “Loresta GP / MCP-T600” (manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The specific resistance was calculated from the sheet resistance and the film thickness.
  • Example 1A-1 Production of silver fine particles> Add 2.8 kg of silver nitrate, 25.2 L of water, and 89 g of polymer protective agent “DISPERBYK-190” (trade name: manufactured by Big Chemie Japan Co., Ltd.) (acid value 10 mgKOH / kg, amine value 0 mgKOH / kg) to a 60 L container.
  • a liquid A was prepared by mixing and stirring. Separately, 4.41 kg of N, N-dimethylethanolamine and 214.5 g of heptanoic acid as a low molecular weight protective agent were added to a 50 L container and mixed and stirred, and then 18.8 L of water was added and mixed and stirred.
  • B liquid was prepared.
  • the B solution was dropped into the A solution, the temperature was raised to 70 ° C., the mixture was stirred for 3 hours, and allowed to stand for 30 minutes to precipitate a solid. After removing the supernatant, it was washed with pure water, and decantation and water washing were repeated until the conductivity of the supernatant was 50 ⁇ S / cm or less.
  • the obtained water-containing material containing silver fine particles was put into a vacuum freeze dryer, and the degree of vacuum was raised to about 10 Pa, and the product temperature was ⁇ 30 ° C. to self-freeze. Thereafter, the temperature was raised to 40 ° C. while maintaining the degree of vacuum at 10 Pa (the product temperature was about 30 ° C.). This state was maintained for 2 hours and then pulverized to obtain silver fine particles of Example 1-1.
  • the obtained silver fine particles are granular, the average particle diameter (D SEM ) is 75 nm, the crystallite diameter (D X ) is 45.2 nm, the crystallinity (D SEM / D X ) is 1.7, and the tap density. ( ⁇ t) was 4.55 g / cm 3 , the BET specific surface area value was 3.1 m 2 / g, the residual amount of organic matter was 1.36% by weight, and the heat shrinkage rate was 2.58%.
  • Example 2A-1 Production of conductive paste>
  • Example 1A-1 100 parts by weight of silver fine particles 11.0 parts by weight of polyester resin and 1.4 parts by weight of hardener, and diethylene glycol monoethyl so that the content of silver fine particles in the conductive paste is 70 wt%.
  • Ether is added and premixed using a rotating / revolving mixer “Awatori Nertaro ARE-310” (registered trademark, manufactured by Sinky Corporation), and then uniformly mixed and dispersed using three rolls. Conductive paste was obtained.
  • the conductive paste obtained above was applied onto a polyimide film having a thickness of 50 ⁇ m, pre-dried at 120 ° C., heat-cured at 150 ° C. for 10 minutes, then immersed in 1 mol HCl aqueous solution for 20 seconds and washed with water. Then, the electroconductive coating film was obtained by heat-drying again at 150 degreeC for 1 minute again.
  • the specific resistance of the obtained conductive coating film was 7.3 ⁇ ⁇ cm.
  • Examples 1A-2 to 1A-3 and Comparative Example 1A-1 Silver fine particles were obtained by variously changing the production conditions of the silver fine particles.
  • Comparative Example 1A-2 JP 2010-229544 A (Further examination of Example 1) 66.8 g of silver nitrate, 10 g of acetic acid as an agglomeration aid having a carboxyl group, 2.0 g of a polymer dispersant “DISPERBYK-190” having a carboxyl group as a polymer dispersant (trade name: manufactured by Big Chemie Japan Co., Ltd.) The mixture was put into 100 g of ion-exchanged water and stirred vigorously. When 100 g of N, N-dimethylethanolamine was gradually added thereto, the reaction solution rose to 60 ° C. When the liquid temperature dropped to 50 ° C., the mixture was heated and stirred in a water bath set at 70 ° C. for 2 hours. After 1 hour, silver colloidal particle aggregates were obtained as gray precipitates.
  • the supernatant of the reaction solution in which the silver colloid particle aggregates were precipitated was removed and diluted with ion-exchanged water. After standing, the supernatant was removed and further diluted with methanol. After standing again, the supernatant was removed and diluted with methanol. Thereafter, the silver colloidal particle aggregates were collected with a pressure filter equipped with a membrane filter (manufactured by Advantech, pore size 0.5 ⁇ m). Various properties of the obtained silver colloidal particle aggregate are shown in Table 2.
  • Comparative Example 1A-3 JP-A-2009-120949 (Additional test of Example 1)
  • 273 g of water was put into a 1 L beaker reaction tank, and after flowing nitrogen at a flow rate of 500 mL / min for 600 seconds from the bottom of the reaction tank, it was supplied at a flow rate of 500 mL / min from the top of the reaction tank.
  • the rotating speed of the stirring bar was adjusted to 280 to 320 rpm, and the temperature was adjusted so that the solution temperature in the reaction vessel was 60 ° C.
  • aqueous ammonia containing 30% by mass as ammonia
  • the mixture was stirred for 1 minute to make the solution uniform, and then 7.5 g of hexanoic acid (2% with respect to silver) as a protective agent. (Corresponding to 0.01 mol) and stirred for 10 minutes to dissolve the protective agent. Thereafter, 20.9 g of 50% by weight hydrazine hydrate aqueous solution was added as a reducing agent.
  • an aqueous silver nitrate solution in which 36 g of silver nitrate crystals were dissolved in 175 g of water was prepared, and this was used as a raw material liquid.
  • the temperature of the aqueous silver nitrate solution was adjusted to 60 ° C., the same as the solution in the reaction vessel.
  • Examples 2A-2 to 2A-3 and Comparative Examples 2A-1 to 2A-3 A conductive paint and a conductive film were produced according to the method for producing a conductive paint of Example 2A-1, except that the type of silver fine particles was variously changed.
  • Table 3 shows the manufacturing conditions and various properties of the obtained conductive coating film.
  • Example 1B-1 Production of silver fine particles> To a 60 L container, 2.8 kg of silver nitrate, 25.2 L of water, and a polymer protective agent “DISPERBYK-190” (trade name: manufactured by Big Chemie Japan Co., Ltd.) (acid value 10 mgKOH / kg, amine value 0 mgKOH / kg) 92 g A liquid A was prepared by mixing and stirring. Separately, 4.41 kg of N, N-dimethylethanolamine and 214.5 g of heptanoic acid as a low molecular weight protective agent were added to a 50 L container and mixed and stirred, and then 18.8 L of water was added and mixed and stirred. , B liquid was prepared.
  • the B solution was dropped into the A solution, the temperature was raised to 70 ° C., the mixture was stirred for 3 hours, and allowed to stand for 30 minutes to precipitate a solid. After removing the supernatant, it was washed with pure water, and decantation and water washing were repeated until the conductivity of the supernatant was 50 ⁇ S / cm or less.
  • the obtained water-containing material containing silver fine particles and having a water content of 55% was placed in a vacuum freeze dryer, and the degree of vacuum was raised to about 10 Pa, and the product temperature was ⁇ 30 ° C. to self-freeze. Thereafter, the temperature was raised to 40 ° C. while maintaining the degree of vacuum at 10 Pa (the product temperature was about 30 ° C.). This state was maintained for 2 hours and then pulverized to obtain silver fine particles of Example 1B-1.
  • the obtained silver fine particles are granular, the average particle diameter (D SEM ) is 72 nm, the crystallite diameter (D X ) is 41.8 nm, the crystallinity (D SEM / D X ) is 1.7, and the tap density. ( ⁇ t) was 4.59 g / cm 3 , the BET specific surface area value was 3.5 m 2 / g, the residual amount of organic matter was 1.37% by weight, and the heat shrinkage rate was 2.63%.
  • Example 2B-1 Production of conductive paste>
  • Example 1B-1 100 parts by weight of silver fine particles 11.0 parts by weight of a polyester resin and 1.4 parts by weight of a curing agent, and diethylene glycol monoethyl so that the content of silver fine particles in the conductive paste is 70 wt%.
  • Ether is added and premixed using a rotating / revolving mixer “Awatori Nertaro ARE-310” (registered trademark, manufactured by Sinky Corporation), and then uniformly mixed and dispersed using three rolls. Conductive paste was obtained.
  • the conductive paste obtained above was applied onto a polyimide film having a thickness of 50 ⁇ m, pre-dried at 120 ° C., heat-cured at 150 ° C. for 10 minutes, then immersed in 1 mol HCl aqueous solution for 20 seconds and washed with water. Then, the electroconductive coating film was obtained by heat-drying again at 150 degreeC for 1 minute again.
  • the specific resistance of the obtained conductive coating film was 7.5 ⁇ ⁇ cm.
  • Examples 1B-2 to 1B-3 and Comparative Examples 1B-1 to 1B-2 Silver fine particles were obtained by variously changing the production conditions of the silver fine particles.
  • Comparative Example 1B-3 Same as Comparative Example 1A-2. Table 5 shows various characteristics of the obtained silver colloid particle aggregates.
  • Comparative Example 1B-4 Same as Comparative Example 1A-3. Table 5 shows various characteristics of the obtained fine silver particle block.
  • Examples 2B-2 to 2B-3 and Comparative Examples 2B-1 to 2B-4 A conductive paint and a conductive film were produced according to the method for producing a conductive paint of Example 2B-1, except that the type of silver fine particles was variously changed.
  • Table 6 shows the manufacturing conditions and various characteristics of the obtained conductive coating film.
  • the tap density tends to decrease as the particle size of the silver fine particles decreases.
  • the method for producing silver fine particles according to the present invention has the average particle diameter (D SEM ) of 30 to 100 nm even though the particles are fine particles. Therefore, since silver fine particles having a high tap density of 3.0 g / cm 3 or more can be obtained, it is suitable as a method for producing silver fine particles having excellent low-temperature sintering properties and filling properties in electrodes and circuit patterns.
  • the silver fine particles according to the present invention have a high tap density of 3.0 g / cm 3 or more despite the fine particle having an average particle diameter (D SEM ) of 30 to 100 nm by the above production method. Therefore, it is suitable as a raw material for conductive paste and the like having excellent filling properties in electrodes and circuit patterns formed on a substrate.

Abstract

The present invention pertains to: silver microparticles having superior heat shrinkability and low-temperature sinterability, superior filling properties in a circuit pattern or electrode formed on a substrate, and an average particle size of 30-100 nm; a method for producing the silver microparticles; and an electronic device, conductive film, and conductive paste containing the silver microparticles. In the method for producing silver microparticles by preparing an aqueous solution (solution A) using silver nitrate and a high-molecular-weight protecting agent, preparing an aqueous solution (solution B) separately from solution A and resulting from dissolving a reducing agent and a low-molecular-weight protecting agent, dripping solution B into solution A, and isolating, cleaning, and drying silver microparticles obtained by reductive precipitation, regardless of the fact that the temperature of the mixed solution when dripping solution B into solution A is controlled to no greater than 40°C and the silver microparticles obtained by means of vacuum freeze-drying in the drying step are microparticles having an average particle size of 30-100 nm, the silver microparticles have a high tapped density of at least 3.0 g/cm3, and so have superior filling properties in a circuit pattern or electrode formed on a substrate.

Description

銀微粒子とその製造法並びに該銀微粒子を含有する導電性ペースト、導電性膜及び電子デバイスSilver fine particles, production method thereof, and conductive paste, conductive film and electronic device containing the silver fine particles
　本発明は、熱収縮性及び低温焼結性に優れると共に、基板上に形成された電極や回路パターン中における充填性に優れた平均粒子径３０～１００ｎｍの銀微粒子とその製造法、並びに該銀微粒子を含有する導電性ペースト、導電性膜及び電子デバイスに関する。 The present invention provides silver fine particles having an average particle diameter of 30 to 100 nm, excellent in heat shrinkability and low-temperature sinterability, and excellent in filling properties in electrodes and circuit patterns formed on a substrate, and a method for producing the same. The present invention relates to a conductive paste containing fine particles, a conductive film, and an electronic device.
　電子デバイスの電極や回路パターンの形成は、金属粒子を含む導電性ペーストを用いて基板上に電極や回路パターンを印刷した後、加熱焼成して導電性ペーストに含まれる金属粒子を焼結させることにより行われているが、近年、その加熱焼成温度は低温化する傾向にある。 The electrodes and circuit patterns of electronic devices are formed by printing electrodes and circuit patterns on a substrate using a conductive paste containing metal particles, and then baking by heating and sintering the metal particles contained in the conductive paste. However, in recent years, the heating and baking temperature tends to be lowered.
　例えば、電子デバイスの実装基板としては、一般に、３００℃程度までの加熱が可能であり、耐熱性に優れているためポリイミド製フレキシブル基板が用いられているが、高価であるため、最近では、より安価なＰＥＴ（ポリエチレンテレフタレート）基板やＰＥＮ（ポリエチレンナフタレート）基板が代替材料として検討されている。しかしながら、ＰＥＴ基板やＰＥＮ基板はポリイミド製フレキシブル基板と比較して耐熱性が低く、殊に、メンブレン配線板に用いられるＰＥＴフィルム基板は加熱焼成を１５０℃以下で行う必要がある。 For example, as a mounting substrate for an electronic device, a polyimide flexible substrate is generally used because it can be heated up to about 300 ° C. and has excellent heat resistance. Inexpensive PET (polyethylene terephthalate) substrates and PEN (polyethylene naphthalate) substrates are being investigated as alternative materials. However, PET substrates and PEN substrates have lower heat resistance than polyimide flexible substrates, and in particular, PET film substrates used for membrane wiring boards need to be heated and fired at 150 ° C. or lower.
　また、加熱焼成を２００℃より更に低い温度で行うことができれば、ポリカーボネートや紙等の基板への電極や回路パターンの形成も可能となり、各種電極材等の用途が広がることが期待される。 Also, if heating and firing can be performed at a temperature lower than 200 ° C., it becomes possible to form electrodes and circuit patterns on a substrate such as polycarbonate and paper, and it is expected that the use of various electrode materials will be expanded.
　このような低温焼成が可能な導電性ペーストの原料となる金属粒子として、ナノメートルオーダーの銀微粒子が期待されている。その理由として、金属粒子の大きさがナノメートルオーダーになると表面活性が高くなり、融点が金属のバルクのものよりもはるかに低下するため、低い温度で焼結させることが可能になるためである。また、銅などの他の導電性粒子と比べて銀微粒子は高価であり、金属粒子の中でもマイグレーションを起こしやすいという欠点はあるが、同程度の比抵抗を有する銅に比べて酸化し難いために取り扱いやすいことが挙げられる。 As a metal particle that is a raw material for such a conductive paste that can be fired at a low temperature, silver fine particles of nanometer order are expected. The reason for this is that when the size of the metal particles is on the order of nanometers, the surface activity becomes high and the melting point is much lower than that of the bulk metal, so that it can be sintered at a low temperature. . In addition, silver fine particles are expensive compared to other conductive particles such as copper, and there is a defect that migration is likely to occur among metal particles, but it is difficult to oxidize compared to copper having the same specific resistance. It is easy to handle.
　また、ナノメートルオーダーの銀微粒子は低温で焼結が可能であると共に、一度焼結すると耐熱性が維持されるという、従来のはんだにはない性質を利用した鉛フリーのはんだ代替材料としても期待されている。 In addition, nanometer-order silver fine particles can be sintered at low temperatures, and heat resistance is maintained once sintered, which is also expected as a lead-free solder replacement material using a property not found in conventional solder. Has been.
　一方で、銀微粒子は一般に粒子サイズが小さくなるほどタップ密度が小さくなる傾向にあるため、該銀微粒子を含む導電ペーストにより形成した微細な配線は、銀微粒子の充填率を上げることが困難であり、電気抵抗値の低減には不利である。 On the other hand, since silver fine particles generally tend to have a smaller tap density as the particle size becomes smaller, fine wiring formed with a conductive paste containing the silver fine particles is difficult to increase the filling rate of the silver fine particles, This is disadvantageous for reducing the electric resistance value.
　また、粒子の結晶性が低い銀微粒子は加熱焼成の際の熱収縮率が大きくなる傾向があり、そのため、例えば電子部品の場合は、該銀微粒子を含む導体ペーストより形成した微細な配線が基材から剥離したり、配線が細くなって高抵抗になったりする問題がある。また粉末冶金においては、焼結体の寸法精度を悪化する等の問題が生じる。 In addition, silver fine particles having low crystallinity of the particles tend to have a high thermal shrinkage rate upon heating and firing. For this reason, for example, in the case of electronic components, fine wiring formed from a conductive paste containing the silver fine particles is the basis. There are problems such as peeling from the material and high resistance due to thinning of the wiring. In powder metallurgy, problems such as deterioration of the dimensional accuracy of the sintered body occur.
　これまでに、低温焼結性に優れた硬質な被膜を形成できる金属ナノ粒子を含む金属コロイド粒子として、金属ナノ粒子と分散剤とを含む粒子サイズに分布を有する金属コロイド粒子が提案されている（特許文献１）。また、水を含む極性溶媒中でも安定して存在しうる微小銀粒子として、保護剤として炭素数６以下の直鎖脂肪酸と結合した銀粒子（特許文献２）が提案されている。また、分散性が高く、はんだ濡れ性と耐はんだ性とを兼ね備えた銀粉として、結晶粒径の最小値が０．３μｍ以上である結晶粒を少なくとも１個含むタップ密度が４ｇ／ｃｍ３以上の多結晶の銀粒子からなる銀粉（特許文献３）が知られている。 So far, metal colloidal particles having a distribution in particle size including metal nanoparticles and a dispersing agent have been proposed as metal colloidal particles including metal nanoparticles that can form a hard film with excellent low-temperature sintering properties. (Patent Document 1). Further, as fine silver particles that can exist stably even in a polar solvent containing water, silver particles bonded with a straight chain fatty acid having 6 or less carbon atoms as a protective agent (Patent Document 2) have been proposed. Further, as a silver powder having high dispersibility and having both solder wettability and solder resistance, the tap density including at least one crystal grain having a minimum crystal grain size of 0.3 μm or more is 4 g / cm 3 or more. A silver powder composed of polycrystalline silver particles (Patent Document 3) is known.
特開２０１０－２２９５４４JP 2010-229544 A 特開２００９－１２０９４９号公報JP 2009-120949 A 特開２０１１－１５８１号公報JP 2011-1581 A
　　前出特許文献１には、金属ナノ粒子と分散剤とを含む粒子サイズに分布を有する金属コロイド粒子が開示されているが、特許文献１記載の製造法は硝酸銀溶液と還元剤溶液の混合の際の温度制御についてはなんら考慮されておらず、また、乾燥工程についても加圧ろ過機で銀コロイド粒子凝集体を回収するのみである。そのため、特許文献１記載の製造法で得られた銀コロイド粒子は、後出比較例に示す通りタップ密度が３ｇ／ｃｍ３以下となり、該銀コロイド粒子を含む導電ペーストにより形成した微細な配線は、銀微粒子の充填率を上げることが困難であり、電気抵抗値の低減には不利である。また、銀微粒子表面の有機物残存量が２．５重量％以上であったことから、低温焼結性に優れているとは言い難いものである。 In the aforementioned Patent Document 1, metal colloidal particles having a distribution in particle size including metal nanoparticles and a dispersant are disclosed. However, the production method described in Patent Document 1 is a mixture of a silver nitrate solution and a reducing agent solution. No particular consideration is given to the temperature control at that time, and the silver colloidal particle aggregates are only recovered by a pressure filter in the drying process. For this reason, the colloidal silver particles obtained by the production method described in Patent Document 1 have a tap density of 3 g / cm 3 or less as shown in a comparative example, and the fine wiring formed by the conductive paste containing the silver colloid particles is It is difficult to increase the filling rate of the silver fine particles, which is disadvantageous for reducing the electric resistance value. Further, since the residual amount of organic matter on the surface of the silver fine particles was 2.5% by weight or more, it is difficult to say that the low-temperature sinterability is excellent.
　また、特許文献２には、保護剤として炭素数６以下の直鎖脂肪酸と結合した銀粒子が開示されているが、後出比較例に示す通り、得られる銀粒子はタップ密度が３ｇ／ｃｍ３以下であり、また、ＢＥＴ比表面積値も７ｍ２／ｇ以上であることから、該銀粒子を含む導電ペーストにより形成した微細な配線は、銀粒子の充填率を上げることが困難であり、電気抵抗値の低減には不利である。 Further, Patent Document 2 discloses silver particles bonded with a straight chain fatty acid having 6 or less carbon atoms as a protective agent. As shown in Comparative Examples, the obtained silver particles have a tap density of 3 g / cm. 3 or less, and since the BET specific surface area value is 7 m 2 / g or more, it is difficult to increase the filling rate of the silver particles in the fine wiring formed by the conductive paste containing the silver particles, This is disadvantageous for reducing the electric resistance value.
　特許文献３には、結晶粒径の最小値が０．３μｍ以上である結晶粒を少なくとも１個含むタップ密度が４ｇ／ｃｍ３以上の多結晶の銀粒子からなる銀粉が開示されているが、最小粒径が０．２１μｍ以上であり、粒子サイズが大きいため、近年の基板上に形成される微細な電極や回路パターン印刷の微細化には不利である。また、粒子サイズが大きいため、低温焼結性に優れているとは言い難いものである。 Patent Document 3 discloses a silver powder composed of polycrystalline silver particles having a tap density of 4 g / cm 3 or more including at least one crystal grain having a minimum crystal grain size of 0.3 μm or more. Since the minimum particle size is 0.21 μm or more and the particle size is large, it is disadvantageous for miniaturization of fine electrodes and circuit pattern printing formed on a substrate in recent years. Further, since the particle size is large, it is difficult to say that the low-temperature sinterability is excellent.
　そこで、本発明は、平均粒子径（ＤＳＥＭ）が３０～１００ｎｍと微粒子でありながら、３．０ｇ／ｃｍ３以上の高いタップ密度を有し、熱収縮性及び低温焼結性に優れると共に、基板上に形成された電極や回路パターン中における充填性に優れた銀微粒子及びその製造法を提供することを技術的課題とする。 Accordingly, the present invention has a high tap density of 3.0 g / cm 3 or more while having an average particle size (D SEM ) of 30 to 100 nm and fine particles, and is excellent in heat shrinkability and low temperature sinterability, An object of the present invention is to provide silver fine particles having excellent filling properties in electrodes and circuit patterns formed on a substrate and a method for producing the same.
　前記技術的課題は、次の通りの本発明によって達成できる。 The technical problem can be achieved by the present invention as follows.
　即ち、本発明は、平均粒子径（ＤＳＥＭ）が３０～１００ｎｍであり、タップ密度が３．０ｇ／ｃｍ３以上であることを特徴とする銀微粒子である（本発明１）。
　また、本発明は、ＢＥＴ比表面積値が７．０ｍ２/ｇ以下である請求項１記載の銀微粒子である（本発明２）。 That is, the present invention is a silver fine particle characterized by having an average particle diameter (D SEM ) of 30 to 100 nm and a tap density of 3.0 g / cm 3 or more (Invention 1).
Further, the present invention provides the silver fine particles according to claim 1, wherein the BET specific surface area value is 7.0 m 2 / g or less (Invention 2).
　また、本発明は、結晶子径（Ｄｘ）が３０ｎｍ以上である請求項１又は請求項２記載の銀微粒子である（本発明３）。 Moreover, this invention is a silver microparticle of Claim 1 or Claim 2 whose crystallite diameter ( Dx ) is 30 nm or more (Invention 3).
　また、本発明は、銀微粒子表面の有機物残存量が０．５～２．０重量％である請求項１から請求項３のいずれかに記載の銀微粒子である（本発明４）。 Further, the present invention is the silver fine particles according to any one of claims 1 to 3, wherein the remaining amount of organic matter on the surface of the silver fine particles is 0.5 to 2.0% by weight (Invention 4).
　また、本発明は、２４０℃における熱収縮率が２．０％以上である請求項１から請求項４のいずれかに記載の銀微粒子である（本発明５）。 Further, the present invention is the silver fine particles according to any one of claims 1 to 4 having a heat shrinkage rate at 240 ° C. of 2.0% or more (Invention 5).
　また、本発明は、請求項１から請求項５のいずれかに記載の銀微粒子を含む導電性ペーストである（本発明６）。 Further, the present invention is a conductive paste containing the silver fine particles according to any one of claims 1 to 5 (invention 6).
　また、本発明は、請求項６記載の導電性ペーストを用いて形成された導電性膜である（本発明７）。 Further, the present invention is a conductive film formed using the conductive paste according to claim 6 (present invention 7).
　また、本発明は、請求項７記載の導電性膜を有する電子デバイスである（本発明８）。 Further, the present invention is an electronic device having the conductive film according to claim 7 (present invention 8).
　また、本発明は、硝酸銀と高分子保護剤とを用いて水溶液を調製し（Ａ液）、前記Ａ液とは別に還元剤と低分子保護剤を溶解させた水溶液を調製し（Ｂ液）、前記Ｂ液を前記Ａ液に滴下して還元析出させて得られた銀微粒子を分離・洗浄・乾燥させる銀微粒子の製造法において、前記Ｂ液を前記Ａ液に滴下した際の混合溶液の温度を４０℃以下に制御すると共に、乾燥工程を真空凍結乾燥により行うことを特徴とする銀微粒子の製造法である（本発明９）。 In the present invention, an aqueous solution is prepared using silver nitrate and a polymer protective agent (liquid A), and separately from the liquid A, an aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved is prepared (liquid B). In the method for producing silver fine particles, in which the silver fine particles obtained by dropping the B liquid into the A liquid and reducing and depositing the B liquid are separated, washed, and dried, the mixed solution when the B liquid is dropped into the A liquid. This is a silver fine particle production method characterized in that the temperature is controlled to 40 ° C. or lower and the drying step is performed by vacuum freeze-drying (Invention 9).
　また、本発明は、真空凍結乾燥前の含水物の含水率が３０％以上である請求項９記載の銀微粒子の製造法である（本発明１０）。 Further, the present invention is the method for producing silver fine particles according to claim 9 , wherein the water content of the water-containing material before vacuum freeze-drying is 30% or more (Invention 10).
　また、本発明は、得られる銀微粒子が請求項１～５の何れかに記載の銀微粒子である請求項９又は１０記載の銀微粒子の製造法である（本発明１１）。 Further, the present invention is the method for producing silver fine particles according to claim 9 or 10, wherein the obtained silver fine particles are the silver fine particles according to any one of claims 1 to 5 (invention 11).
　一般に、銀微粒子の粒子サイズが小さくなるほどタップ密度は小さくなる傾向にあるが、本発明に係る銀微粒子の製造法は、前記平均粒子径（ＤＳＥＭ）が３０～１００ｎｍと微粒子であるにもかかわらず、３．０ｇ／ｃｍ３以上の高いタップ密度を有する銀微粒子を得ることができるため、低温焼結性並びに電極や回路パターン中における充填性に優れた銀微粒子の製造法として好適である。 In general, the tap density tends to decrease as the particle size of the silver fine particles decreases. However, the method for producing silver fine particles according to the present invention has the average particle diameter (D SEM ) of 30 to 100 nm even though the particles are fine particles. Therefore, since silver fine particles having a high tap density of 3.0 g / cm 3 or more can be obtained, it is suitable as a method for producing silver fine particles having excellent low-temperature sintering properties and filling properties in electrodes and circuit patterns.
　また、本発明に係る銀微粒子は、上記製造法により、平均粒子径（ＤＳＥＭ）が３０～１００ｎｍと微粒子であるにもかかわらず、３．０ｇ／ｃｍ３以上の高いタップ密度を有していることから、基板上に形成された電極や回路パターン中における充填性に優れた導電性ペースト等の原料として好適である。 In addition, the silver fine particles according to the present invention have a high tap density of 3.0 g / cm 3 or more despite the fine particle having an average particle diameter (D SEM ) of 30 to 100 nm by the above production method. Therefore, it is suitable as a raw material for conductive paste and the like having excellent filling properties in electrodes and circuit patterns formed on a substrate.
　本発明の構成をより詳しく説明すれば、次の通りである。 The configuration of the present invention will be described in more detail as follows.
　まず、本発明に係る銀微粒子について述べる。 First, the silver fine particles according to the present invention will be described.
　本発明に係る銀微粒子は、平均粒子径（ＤＳＥＭ）が３０～１００ｎｍであり、タップ密度が３．０ｇ／ｃｍ３以上であることを特徴とする。 The silver fine particles according to the present invention are characterized by having an average particle diameter (D SEM ) of 30 to 100 nm and a tap density of 3.0 g / cm 3 or more.
　本発明に係る銀微粒子の平均粒子径（ＤＳＥＭ）は、３０～１００ｎｍであり、好ましくは３５～９５ｎｍ、より好ましくは４０～９０ｎｍである。平均粒子径（ＤＳＥＭ）が上記範囲にあることにより、これを用いて得られる電子デバイスのファイン化が容易となる。平均粒子径（ＤＳＥＭ）が３０ｎｍ未満の場合には、銀微粒子の持つ表面活性が高くなり、その微細な粒子径を安定に維持するために多量の有機物等を付着させる必要があるため好ましくない。 The average particle diameter (D SEM ) of the silver fine particles according to the present invention is 30 to 100 nm, preferably 35 to 95 nm, more preferably 40 to 90 nm. When the average particle diameter (D SEM ) is in the above range, it is easy to refine an electronic device obtained using the average particle diameter (D SEM ). When the average particle size (D SEM ) is less than 30 nm, the surface activity of the silver fine particles increases, and it is not preferable because a large amount of organic matter or the like needs to be adhered in order to stably maintain the fine particle size. .
　本発明に係る銀微粒子のタップ密度は、３．０ｇ／ｃｍ３以上であり、好ましくは３．５ｇ／ｃｍ３以上、より好ましくは４．０ｇ／ｃｍ３以上である。タップ密度が３．０ｇ／ｃｍ３未満の場合、該銀微粒子を含む導電ペーストにより形成した微細な配線は、銀微粒子の充填率を上げることが困難であり、電気抵抗値の低減には不利である。銀微粒子のタップ密度の上限値は６．０ｇ／ｃｍ３程度であり、より好ましくは５．５ｇ／ｃｍ３程度である。 The tap density of the silver fine particles according to the present invention is 3.0 g / cm 3 or more, preferably 3.5 g / cm 3 or more, more preferably 4.0 g / cm 3 or more. When the tap density is less than 3.0 g / cm 3, the fine wiring formed by the conductive paste containing the silver fine particles is difficult to increase the filling rate of the silver fine particles, which is disadvantageous for reducing the electric resistance value. is there. The upper limit of the tap density of the silver fine particles is about 6.0 g / cm 3 , and more preferably about 5.5 g / cm 3 .
本発明に係る銀微粒子のＢＥＴ比表面積値は、７ｍ２／ｇ以下であることが好ましく、より好ましくは６ｍ２／ｇ以下である。ＢＥＴ比表面積値が７ｍ２／ｇを超える場合、これを用いて得られる導電性ペーストの粘度が高くなるため好ましくない。銀微粒子のＢＥＴ比表面積値の下限値は１．５ｍ２／ｇ程度であり、より好ましくは２．０ｍ２／ｇ程度である。 The BET specific surface area value of the silver fine particles according to the present invention is preferably 7 m 2 / g or less, more preferably 6 m 2 / g or less. When the BET specific surface area value exceeds 7 m 2 / g, the viscosity of the conductive paste obtained by using this is not preferable. The lower limit of the BET specific surface area value of the silver fine particles is about 1.5 m 2 / g, more preferably about 2.0 m 2 / g.
　本発明に係る銀微粒子の結晶子径（ＤＸ）は３０ｎｍ以上であることが好ましく、より好ましくは３５～９５ｎｍ、より好ましくは４０～９０ｎｍである。結晶子径（ＤＸ）が３０ｎｍ未満の場合には、銀微粒子が不安定となり、常温においても部分的に焼結・融着が生じ始めるため好ましくない。 The crystallite diameter (D X ) of the silver fine particles according to the present invention is preferably 30 nm or more, more preferably 35 to 95 nm, and more preferably 40 to 90 nm. When the crystallite diameter (D X ) is less than 30 nm, the silver fine particles become unstable and partial sintering and fusion start even at room temperature, which is not preferable.
　本発明に係る銀微粒子の結晶化度［平均粒子径（ＤＳＥＭ）と結晶子径（ＤＸ）の比（ＤＳＥＭ／ＤＸ）］は２．７以下であることが好ましく、より好ましくは２．５以下、更により好ましくは２．３以下である。結晶化度が１に近づくほど、単結晶であることを示す。結晶化度が２．７を超える場合には、銀微粒子の熱収縮率が高いため、これを用いて得られる導電性ペーストより形成した微細な配線が基材から剥離したり、配線が細くなって高抵抗になったりする問題があるため好ましくない。 The crystallinity of the silver fine particles according to the present invention [ratio of average particle diameter (D SEM ) to crystallite diameter (D X ) (D SEM / D X )] is preferably 2.7 or less, more preferably 2.5 or less, still more preferably 2.3 or less. The closer the degree of crystallinity is to 1, the more it is a single crystal. When the degree of crystallinity exceeds 2.7, the heat shrinkage rate of the silver fine particles is high, so that the fine wiring formed from the conductive paste obtained by using this is peeled off from the base material, or the wiring becomes thin. This is not preferable because of the problem of high resistance.
　本発明に係る銀微粒子表面の有機物残存量は０．５～２．０重量％であることが好ましく、より好ましくは０．６～１．９重量％であり、更により好ましくは０．７～１．８重量％である。銀微粒子表面の有機物残存量が２．０重量％を超える場合には、銀微粒子表面に存在する有機物が多すぎるため、低温焼結性が損なわれる。また、０．５重量％未満の場合には、溶剤及び樹脂への濡れ性が低下し、これを用いて得られる導電性ペーストの均一分散性が損なわれるため好ましくない。 The amount of the organic matter remaining on the surface of the silver fine particles according to the present invention is preferably 0.5 to 2.0% by weight, more preferably 0.6 to 1.9% by weight, still more preferably 0.7 to 1.8% by weight. When the residual amount of organic matter on the surface of the silver fine particles exceeds 2.0% by weight, the amount of organic matter present on the surface of the silver fine particles is too much, so that the low temperature sinterability is impaired. On the other hand, if it is less than 0.5% by weight, the wettability to the solvent and the resin is lowered, and the uniform dispersibility of the conductive paste obtained using this is impaired, which is not preferable.
　本発明に係る銀微粒子の熱収縮率は、２４０℃における熱収縮率が２．０％以上であることが好ましく、より好ましくは２．１％以上である。一般に、銀微粒子を含む導電性ペーストより形成される銀の塗膜は、銀微粒子間に細かな隙間が生じており、この隙間をなくすことでより低抵抗な銀塗膜を得ることができるが、本発明に係る銀微粒子は、２４０℃における熱収縮率が２．０％以上と高いことにより、これを用いて得られる導電性ペーストより形成した塗膜の銀微粒子間の隙間が容易に埋まるため、より電気抵抗値を低減することが可能となる。 The heat shrinkage rate of the silver fine particles according to the present invention is preferably 2.0% or more, more preferably 2.1% or more at 240 ° C. In general, a silver coating film formed from a conductive paste containing silver fine particles has fine gaps between the silver fine particles, and a silver coating having a lower resistance can be obtained by eliminating this gap. The silver fine particles according to the present invention have a high heat shrinkage rate at 240 ° C. of 2.0% or more, so that the gaps between the silver fine particles of the coating film formed from the conductive paste obtained by using this are easily filled. For this reason, the electric resistance value can be further reduced.
　本発明に係る銀微粒子の粒子形状は、球状もしくは粒状が好ましい。 The particle shape of the silver fine particles according to the present invention is preferably spherical or granular.
　次に、本発明における銀微粒子の製造方法について述べる。 Next, a method for producing silver fine particles in the present invention will be described.
　本発明に係る銀微粒子は、硝酸銀と高分子保護剤とを用いて水溶液を調製し（Ａ液）、前記Ａ液とは別に還元剤と低分子保護剤を溶解させた水溶液を調製し（Ｂ液）、前記Ｂ液を前記Ａ液に滴下して還元析出させて得られた銀微粒子を分離・洗浄・乾燥させる銀微粒子の製造法において、前記Ｂ液を前記Ａ液に滴下した際の混合溶液の温度を４０℃以下に制御すると共に、乾燥工程を真空凍結乾燥により行うことにより得ることができる。 For the silver fine particles according to the present invention, an aqueous solution is prepared using silver nitrate and a polymer protective agent (liquid A), and separately from the liquid A, an aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved is prepared (B Liquid), in the method for producing silver fine particles, in which the silver fine particles obtained by dropping the B liquid into the A liquid and reducing and depositing the liquid B are separated, washed and dried, the mixing when the B liquid is dropped into the A liquid While controlling the temperature of a solution to 40 degrees C or less, it can obtain by performing a drying process by vacuum freeze-drying.
　まず、硝酸銀と高分子保護剤とを用いて水溶液を調製する（Ａ液）。本発明における高分子保護剤は、水溶性あるいは水可溶性であることが好ましい。また、酸価を有することが好ましく、酸価は１ｍｇＫＯＨ／ｇ以上、より好ましくは１０ｍｇＫＯＨ／ｇ以上のものを用いることが好ましい。酸価の上限値については特に制限なく用いることができるが、酸価が０ｍｇＫＯＨ／ｇの場合、粒子サイズの大きな銀粒子が生成するため、１００ｎｍ以下の微細な銀微粒子を得ることが困難となる。また、アミン価は０ｍｇＫＯＨ／ｇであることが好ましい。アミン価を有する高分子保護剤を用いた場合、硝酸銀と混合した際に銀のアミン錯体が生成し、還元反応が完結しないかもしくは還元反応に非常に長い時間を要すると共に、これによって得られる銀微粒子は分布の悪いものであるため好ましくない。なお、高分子保護剤は、単独で使用しても、２種以上を併用してもよい。 First, an aqueous solution is prepared using silver nitrate and a polymer protective agent (A liquid). The polymer protective agent in the present invention is preferably water-soluble or water-soluble. The acid value is preferably 1 mgKOH / g or more, more preferably 10 mgKOH / g or more. The upper limit of the acid value can be used without any particular limitation. However, when the acid value is 0 mgKOH / g, silver particles having a large particle size are produced, so that it is difficult to obtain fine silver fine particles of 100 nm or less. . The amine value is preferably 0 mgKOH / g. When a polymer protective agent having an amine value is used, a silver amine complex is formed when mixed with silver nitrate, and the reduction reaction is not completed or requires a very long time. The fine particles are not preferable because they have poor distribution. In addition, a polymeric protective agent may be used independently or may use 2 or more types together.
　高分子保護剤の数平均分子量は１，０００以上であることが好ましい。より好ましくは、１，０００～１５０，０００、更により好ましくは５，０００～１００，０００である。 The number average molecular weight of the polymer protective agent is preferably 1,000 or more. More preferably, it is 1,000 to 150,000, and still more preferably 5,000 to 100,000.
　また、前記高分子保護剤としては、アクリル系共重合物あるいはポリオキシアルキレン系樹脂等の一般に市販されているものを使用することができ、具体的には、ＤＩＳＰＥＲＢＹＫ－１９０、ＤＩＳＰＥＲＢＹＫ－１９４、ＤＩＳＰＥＲＢＹＫ－２０１５、ＤＩＳＰＥＲＢＹＫ－２０９０、ＤＩＳＰＥＲＢＹＫ－２０９１、ＤＩＳＰＥＲＢＹＫ－２０９５、（ビックケミー・ジャパン株式会社製）；ＡＫＭ－０５３１、ＨＫＭ－５０Ａ、ＡＫＭ－１５１１－６０、ＡＦＢ－１５２１、（日油株式会社製）等が挙げられる。これらの高分子保護剤は、１種類又は２種類以上を組み合わせて使用してもよい。 In addition, as the polymer protective agent, commercially available products such as acrylic copolymers or polyoxyalkylene resins can be used, and specifically, DISPERBYK-190, DISPERBYK-194, DISPERBYK. -2015, DISPERBYK-2090, DISPERBYK-2091, DISPERBYK-2095 (made by Big Chemie Japan Co., Ltd.); AKM-0531, HKM-50A, AKM-1511-60, AFB-1521 (made by NOF Corporation), etc. Is mentioned. These polymer protective agents may be used alone or in combination of two or more.
　高分子保護剤の添加量は、銀微粒子に対して１～１０重量％であることが好ましく、より好ましくは１．５～８重量％である。高分子保護剤の添加量が１重量％未満である場合には、得られる銀微粒子の粒子サイズが大きくなるため好ましくない。１０重量％を超える場合には、得られる銀微粒子表面の有機物残存量が２．０重量％を超えることにより、低温焼結性が損なわれるため好ましくない。 The addition amount of the polymer protective agent is preferably 1 to 10% by weight, more preferably 1.5 to 8% by weight, based on the silver fine particles. When the addition amount of the polymer protective agent is less than 1% by weight, the particle size of the obtained silver fine particles is increased, which is not preferable. If it exceeds 10% by weight, the remaining organic matter on the surface of the obtained silver fine particles exceeds 2.0% by weight, which is not preferable because the low-temperature sinterability is impaired.
　本発明における還元剤としては、水溶性または水可溶性のものを用いることができるが、ヒドラジン、水素化ホウ素アルカリ塩、リチウムアルミニウムハイドライド、アスコルビン酸、エリソルビン酸等は、還元力が強すぎるため好ましくない。還元力の点から、本発明においてはアミノアルコール類を好適に用いることができ、より好ましくはＮ，Ｎ－ジメチルエタノールアミン、Ｎ，Ｎ－ジエチルエタノールアミン、Ｎ，Ｎ－ジエチルイソプロパノールアミン、Ｎ－メチルジエタノールアミン、Ｎ－エチルジエタノールアミン、Ｎ－ｎ－ブチルジエタノールアミン、Ｎ－ｔ－ブチルジエタノールアミン等の第３級アミンを有するアミノアルコールである。 As the reducing agent in the present invention, water-soluble or water-soluble ones can be used, but hydrazine, alkali borohydride, lithium aluminum hydride, ascorbic acid, erythorbic acid and the like are not preferable because the reducing power is too strong. . From the viewpoint of reducing power, amino alcohols can be preferably used in the present invention, and more preferably N, N-dimethylethanolamine, N, N-diethylethanolamine, N, N-diethylisopropanolamine, N- An amino alcohol having a tertiary amine such as methyldiethanolamine, N-ethyldiethanolamine, Nn-butyldiethanolamine, or Nt-butyldiethanolamine.
　還元剤の添加量は、硝酸銀１モルに対して還元剤２．０～５．０モルが好ましく、より好ましくは２．２～４．０モルである。還元剤の添加量が硝酸銀１モルに対して２．０モル未満の場合には、還元反応が十分に進まないため好ましくない。 The amount of the reducing agent added is preferably 2.0 to 5.0 moles, more preferably 2.2 to 4.0 moles per mole of silver nitrate. When the amount of the reducing agent added is less than 2.0 moles with respect to 1 mole of silver nitrate, the reduction reaction does not proceed sufficiently, which is not preferable.
　次いで、前記Ａ液とは別に還元剤と低分子保護剤を溶解させた水溶液を調製する（Ｂ液）。低分子保護剤を、硝酸銀を含有する水溶液（Ａ液）に添加して水溶液を調製した場合、低分子保護剤と硝酸銀が反応し、カルボン酸銀が生成して銀微粒子の収率が低下すると共に、これによって得られる銀微粒子は分布の悪いものであるため好ましくない。 Next, an aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved is prepared separately from the liquid A (liquid B). When an aqueous solution is prepared by adding a low molecular weight protective agent to an aqueous solution (A solution) containing silver nitrate, the low molecular weight protective agent and silver nitrate react to produce silver carboxylate, which lowers the yield of silver fine particles. At the same time, the silver fine particles obtained by this are not preferable because of poor distribution.
　本発明における低分子保護剤としては、炭素数３～７のカルボン酸を用いることができる。好ましくはプロピオン酸、ヘキサン酸及びヘプタン酸であり、より好ましくはヘキサン酸及びヘプタン酸である。低分子保護剤の炭素鎖が長くなるほど、よりタップ密度の高い銀微粒子が得られやすい。低分子保護剤は、単独で使用しても、２種以上を併用してもよい。 As the low molecular weight protective agent in the present invention, a carboxylic acid having 3 to 7 carbon atoms can be used. Propionic acid, hexanoic acid and heptanoic acid are preferable, and hexanoic acid and heptanoic acid are more preferable. The longer the carbon chain of the low molecular protective agent, the easier it is to obtain silver fine particles with a higher tap density. A low molecular protective agent may be used independently or may use 2 or more types together.
　低分子保護剤の添加量は、硝酸銀１モルに対して低分子保護剤０．０５～０．４モルが好ましく、より好ましくは０．１～０．３５モルである。低分子保護剤の添加量が硝酸銀１モルに対して０．４モルを超える場合には、生成した銀微粒子同士が凝集する傾向があるため好ましくない。 The amount of the low molecular weight protective agent added is preferably 0.05 to 0.4 mole, more preferably 0.1 to 0.35 mole relative to 1 mole of silver nitrate. When the addition amount of the low molecular protective agent exceeds 0.4 mol with respect to 1 mol of silver nitrate, the generated silver fine particles tend to aggregate, which is not preferable.
　還元剤と低分子保護剤を溶解させた水溶液（Ｂ液）を、硝酸銀と高分子保護剤とを用いて調製した水溶液（Ａ液）に滴下して混合反応を行う。混合反応時の温度は、通常温度コントロールを行わなければ５０℃以上に上昇するが、本発明においては、２５～４０℃の範囲にコントロールすることが好ましく、より好ましくは３０～３５℃の範囲である。混合反応時の温度が４０℃を超える場合には、生成した銀微粒子の分布が不均一となりやすいため好ましくない。 An aqueous solution (Liquid B) in which a reducing agent and a low molecular protective agent are dissolved is dropped into an aqueous solution (Liquid A) prepared using silver nitrate and a polymeric protective agent, and a mixing reaction is performed. The temperature during the mixing reaction usually rises to 50 ° C. or more unless temperature control is performed, but in the present invention, the temperature is preferably controlled in the range of 25 to 40 ° C., more preferably in the range of 30 to 35 ° C. is there. When the temperature during the mixing reaction exceeds 40 ° C., the distribution of the generated silver fine particles tends to be non-uniform, which is not preferable.
　前記Ｂ液を滴下後、反応溶液を６０～８０℃に加熱し、攪拌を行うことで還元反応を完結させる。反応溶液の加熱温度は、好ましくは６５～７５℃である。反応溶液の加熱温度が６０℃未満の場合には、還元反応が完結するまでに非常に長い時間がかかるため、工業的に不利となる。また、加熱温度が８０℃を超える場合には、生成した銀微粒子同士が凝集する傾向があるため好ましくない。還元反応は、反応溶液のｐＨ値が一定となったところを終点とする。還元反応は可能な限りゆっくり進行することが好ましく、その点からも、低分子保護剤はできるだけ長鎖脂肪酸を用いることが好ましい。 After dropping the solution B, the reaction solution is heated to 60 to 80 ° C. and stirred to complete the reduction reaction. The heating temperature of the reaction solution is preferably 65 to 75 ° C. When the heating temperature of the reaction solution is less than 60 ° C., it takes an extremely long time to complete the reduction reaction, which is industrially disadvantageous. Moreover, when heating temperature exceeds 80 degreeC, since there exists a tendency for the produced | generated silver fine particles to aggregate, it is unpreferable. The reduction reaction ends when the pH value of the reaction solution becomes constant. The reduction reaction preferably proceeds as slowly as possible, and from this viewpoint, it is preferable to use a long chain fatty acid as much as possible for the low molecular weight protective agent.
　還元反応後の反応溶液を、上澄み液の電導度が５０μＳ／ｃｍ以下になるまでデカンテーションと水洗を繰り返し、得られた銀微粒子を含む含水物を真空凍結乾燥し、その後、常法により粉砕することによって本発明の銀微粒子を得ることができる。真空凍結乾燥を行わず、通常の乾燥機を用いた乾燥を行った場合、銀微粒子を巨大な塊としてしか取り出せず、その後の粉砕処理が非常に煩雑となると共に、銀微粒子に必要以上にシェアがかかることとなる。そのため、得られた粒子は粗大化し、タップ密度が低下するため、本発明の目的とする銀微粒子粉末を得ることができない。 The reaction solution after the reduction reaction is repeatedly decanted and washed with water until the supernatant has an electric conductivity of 50 μS / cm or less, and the resulting hydrated product containing silver fine particles is lyophilized in a vacuum and then pulverized by a conventional method. As a result, the silver fine particles of the present invention can be obtained. When drying using a normal dryer without vacuum freeze-drying, the silver fine particles can only be taken out as a large lump, and the subsequent pulverization process becomes very complicated, and the silver fine particles share more than necessary. Will take. For this reason, the obtained particles are coarsened and the tap density is lowered, so that the target silver fine particle powder of the present invention cannot be obtained.
　真空凍結乾燥は、銀微粒子を含む含水物を乾燥機中に入れた後、品温が－４０～－１０℃になるまで減圧し、その後、４０℃程度まで昇温した後２時間以上保持することによって行う。 In vacuum freeze-drying, a water-containing material containing silver fine particles is placed in a dryer, and then the pressure is reduced until the product temperature reaches −40 to −10 ° C., then the temperature is raised to about 40 ° C. and held for 2 hours or more. By doing.
　真空凍結乾燥を行う際の銀微粒子を含む含水物の含水率は、３０％以上が好ましく、より好ましくは３５～８０％、更により好ましくは４０～７０％である。含水率が３０％未満の場合には、真空凍結乾燥を行ったとしても、上述の通常の乾燥器を用いた場合と同様に、銀微粒子を巨大な塊としてしか取り出せず、得られた粒子は粗大化し、タップ密度が低下するため、本発明の目的とする銀微粒子粉末を得ることができない。 The water content of the water-containing material containing silver fine particles during vacuum freeze-drying is preferably 30% or more, more preferably 35 to 80%, and still more preferably 40 to 70%. When the water content is less than 30%, even if vacuum freeze drying is performed, the silver fine particles can be taken out only as a large lump, as in the case of using the above-mentioned ordinary dryer, and the obtained particles are Since it becomes coarse and the tap density decreases, the silver fine particle powder targeted by the present invention cannot be obtained.
　上記の銀微粒子の製造方法によって、本発明１～５に記載の銀微粒子を製造することができる。すなわち、本発明１～５に記載の銀微粒子の好ましい製造方法として、上記の製造方法（本発明９及び１０）が挙げられる。 The silver fine particles according to the first to fifth aspects of the present invention can be produced by the silver fine particle production method described above. That is, as a preferable method for producing the silver fine particles according to the first to fifth aspects of the present invention, the above-described production methods (the present inventions 9 and 10) can be mentioned.
　次に、本発明に係る銀微粒子を含む導電性ペーストについて述べる。 Next, the conductive paste containing silver fine particles according to the present invention will be described.
　本発明に係る導電性ペーストは、焼成型ペースト及びポリマー型ペーストのいずれの形態でもよく、焼成型ペーストの場合、本発明に係る銀微粒子及びガラスフリットからなり、必要に応じてバインダー樹脂、溶剤等の他の成分を配合してもよい。また、ポリマー型ペーストの場合、本発明に係る銀微粒子及び溶剤からなり、必要に応じて、バインダー樹脂、硬化剤、分散剤、レオロジー調整剤等の他の成分を配合してもよい。 The conductive paste according to the present invention may be in any form of a fired paste and a polymer paste. In the case of a fired paste, the conductive paste is composed of the silver fine particles and the glass frit according to the present invention. Other components may be blended. Moreover, in the case of a polymer type paste, it consists of silver fine particles and a solvent according to the present invention, and if necessary, other components such as a binder resin, a curing agent, a dispersant, and a rheology modifier may be blended.
　バインダー樹脂としては、当該分野において公知のものを使用することができ、例えば、エチルセルロース、ニトロセルロース等のセルロース系樹脂、ポリエステル樹脂、ウレタン変性ポリエステル樹脂、エポキシ変性ポリエステル樹脂、アクリル変性ポリエステル等の各種変性ポリエステル樹脂、ポリウレタン樹脂、塩化ビニル・酢酸ビニル共重合体、アクリル樹脂、エポキシ樹脂、フェノール樹脂、アルキド樹脂、ブチラール樹脂、ポリビニルアルコール、ポリイミド、ポリアミドイミド等が挙げられる。これらバインダー樹脂は、単独でも、又は２種類以上を併用することもできる。 As the binder resin, those known in the art can be used. For example, cellulose resins such as ethyl cellulose and nitrocellulose, various modified materials such as polyester resins, urethane modified polyester resins, epoxy modified polyester resins, and acrylic modified polyesters. Examples include polyester resin, polyurethane resin, vinyl chloride / vinyl acetate copolymer, acrylic resin, epoxy resin, phenol resin, alkyd resin, butyral resin, polyvinyl alcohol, polyimide, and polyamideimide. These binder resins can be used alone or in combination of two or more.
　溶剤としては、当該分野において公知のものを使用することができ、例えば、テトラデカン、トルエン、キシレン、エチルベンゼン、ジエチルベンゼン、イソプロピルベンゼン、アミルベンゼン、ｐ－シメン、テトラリン及び石油系芳香族炭化水素混合物等の炭化水素系溶剤；エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル、プロピレングリコールモノ－ｎ－ブチルエーテル、プロピレングリコールモノ－t－ブチルエーテル、ジエチレングリコールモノエチルエーテル、ジエチレングリコ－ルモノブチルエーテル、ジプロピレングリコールモノメチルエーテル、ジプロピレングリコールモノブチルエーテル、トリプロピレングリコールモノメチルエーテル等のエーテル又はグリコールエーテル系溶剤；エチレングリコールモノメチルエーテルアセテート、エチレングリコールモノエチルエーテルアセテート、エチレングリコールモノブチルエーテルアセテート、プロピレングリコールモノメチルエーテルアセテート、プロピレングリコールモノエチルエーテルアセテート等のグリコールエステル系溶剤；メチルイソブチルケトン、シクロヘキサノン等のケトン系溶剤；テルピネオール、リナロール、ゲラニオール、シトロネロール等のテルペンアルコール；ｎ－ブタノール、ｓ－ブタノール、ｔ－ブタノール等のアルコール系溶剤；エチレングリコール、ジエチレングリコール等のグリコール系溶剤；γ－ブチロラクトン及び水等が挙げられる。溶剤は、単独でも、又は２種類以上を併用することもできる。 As the solvent, those known in the art can be used, such as tetradecane, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, amylbenzene, p-cymene, tetralin, and petroleum aromatic hydrocarbon mixtures. Hydrocarbon solvents: ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-t-butyl ether, diethylene glycol monoethyl ether, diethylene glycol Monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, Ether or glycol ether solvents such as propylene glycol monomethyl ether; glycol ester solvents such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate Ketone solvents such as methyl isobutyl ketone and cyclohexanone; terpene alcohols such as terpineol, linalool, geraniol and citronellol; alcohol solvents such as n-butanol, s-butanol and t-butanol; glycol solvents such as ethylene glycol and diethylene glycol; Γ-butyrolactone and water. Solvents can be used alone or in combination of two or more.
　導電性ペースト中の銀微粒子の含有量は用途に応じて様々であるが、例えば配線形成用途の場合などは可能な限り１００重量％に近いことが好ましい。 The content of silver fine particles in the conductive paste varies depending on the application, but it is preferably as close to 100% by weight as possible, for example, in the case of wiring formation.
　本発明に係る導電性ペーストは、各成分を、ライカイ機、ポットミル、三本ロールミル、回転式混合機、二軸ミキサー等の各種混練機、分散機を用いて、混合・分散させることにより得ることができる。 The conductive paste according to the present invention is obtained by mixing and dispersing each component using various kneaders and dispersers such as a laika machine, a pot mill, a three roll mill, a rotary mixer, a twin screw mixer, and the like. Can do.
　本発明に係る導電性ペーストは、スクリーン印刷、インクジェット法、グラビア印刷、転写印刷、ロールコート、フローコート、スプレー塗装、スピンコート、ディッピング、ブレードコート、めっき等各種塗布方法に適用可能である。 The conductive paste according to the present invention can be applied to various coating methods such as screen printing, ink jet method, gravure printing, transfer printing, roll coating, flow coating, spray coating, spin coating, dipping, blade coating, and plating.
　また、本発明に係る導電性ペーストは、ＦＰＤ（フラットパネルディスプレイ）、太陽電池、有機ＥＬ等の電極形成やＬＳＩ基板の配線形成、更には微細なトレンチ、ビアホール、コンタクトホールの埋め込み等の配線形成材料として用いることができる。また、積層セラミックコンデンサや積層インダクタの内部電極形成用等の高温での焼成用途はもちろん、低温焼成が可能であることからフレキシブル基板やＩＣカード、その他の基板上への配線形成材料及び電極形成材料として好適である。また、導電性被膜として電磁波シールド膜や赤外線反射シールド等にも用いることができる。エレクトロニクス実装においては部品実装用接合材として用いることもできる。 In addition, the conductive paste according to the present invention is used for forming electrodes such as FPD (flat panel display), solar cell, organic EL, wiring for LSI substrates, and wiring for filling fine trenches, via holes, contact holes, etc. It can be used as a material. In addition to firing applications at high temperatures, such as for the formation of internal electrodes for multilayer ceramic capacitors and multilayer inductors, as well as low temperature firing, it is possible to form wiring and materials for wiring on flexible substrates, IC cards, and other substrates. It is suitable as. Moreover, it can also be used for an electromagnetic wave shielding film, an infrared reflection shield, etc. as a conductive film. In electronics mounting, it can also be used as a bonding material for component mounting.
＜作用＞
　本発明において重要な点は、本発明に係る銀微粒子は、熱収縮性に優れると共に、基板上に形成された電極や回路パターン中における充填性に優れるという事実である。 <Action>
The important point in the present invention is the fact that the silver fine particles according to the present invention are excellent in heat shrinkability and in filling properties in electrodes and circuit patterns formed on the substrate.
　本発明に係る銀微粒子が基板上に形成された電極や回路パターン中における充填性に優れている理由について、本発明者らは、平均粒子径（ＤＳＥＭ）が３０～１００ｎｍと微粒子であるにもかかわらず、３．０ｇ／ｃｍ３以上の高いタップ密度を有していることによるものと考えている。即ち、タップ密度の低い銀微粒子を含む導電ペーストにより形成した微細な配線は、銀微粒子の充填率を上げることが困難であり、電気抵抗値の低減には不利であるが、銀微粒子は一般に粒子サイズが小さくなるほどタップ密度が小さくなる傾向にあるため、粒子サイズとタップ密度の両方の特性を満たすことは困難である。しかしながら、本発明に係る銀微粒子は、平均粒子径（ＤＳＥＭ）が３０～１００ｎｍと微粒子でありながら、３．０ｇ／ｃｍ３以上の高いタップ密度を有しているため、基板上に形成された電極や回路パターン中において優れた充填性が得られたものと考えている。 Regarding the reason why the silver fine particles according to the present invention are excellent in filling properties in the electrodes and circuit patterns formed on the substrate, the present inventors have described that the average particle size (D SEM ) is 30 to 100 nm and fine particles. Nevertheless, it is thought to be due to having a high tap density of 3.0 g / cm 3 or more. That is, a fine wiring formed of a conductive paste containing silver fine particles having a low tap density is difficult to increase the filling rate of silver fine particles and is disadvantageous in reducing the electric resistance value. Since the tap density tends to decrease as the size decreases, it is difficult to satisfy the characteristics of both the particle size and the tap density. However, since the silver fine particles according to the present invention are fine particles having an average particle diameter (D SEM ) of 30 to 100 nm and have a high tap density of 3.0 g / cm 3 or more, they are formed on the substrate. It is thought that excellent filling properties were obtained in the electrodes and circuit patterns.
　以下に、本発明における実施例を示し、本発明を具体的に説明するが、本発明は以下の実施例に限定されるものではない。 Hereinafter, examples of the present invention will be shown and the present invention will be specifically described. However, the present invention is not limited to the following examples.
　銀微粒子の平均粒子径は、走査型電子顕微鏡写真「Ｓ－４８００」（ＨＩＴＡＣＨＩ製）を用いて粒子の写真を撮影し、該写真を用いて粒子１００個以上について粒子径を測定し、その平均値を算出し、平均粒子径（ＤＳＥＭ）とした。 The average particle diameter of the silver fine particles was obtained by taking a photograph of the particles using a scanning electron micrograph “S-4800” (manufactured by HITACHI), measuring the particle diameter of 100 or more particles using the photograph, The value was calculated and taken as the average particle size (D SEM ).
　銀微粒子の比表面積は、「モノソーブＭＳ－１１」（カンタクロム株式会社製）を用いて、ＢＥＴ法により測定した値で示した。 The specific surface area of the silver fine particles was represented by a value measured by BET method using “Monosorb MS-11” (manufactured by Kantachrome Co., Ltd.).
　銀微粒子のタップ密度（ρｔ）は、振盪比重測定器（（株）蔵持科学機械製作所）を用い、２５ｍｌのタッピングセルに粉末を落下させ、セルが満杯に充填された後、ストローク長２５ｍｍでタッピングを６００回行って測定した。 The tap density (ρt) of the silver fine particles is measured by dropping the powder into a 25 ml tapping cell using a shaking specific gravity measuring instrument (Kurachi Kagaku Kikai Seisakusho Co., Ltd.). Was measured 600 times.
　銀微粒子の有機物残存量は、熱分析装置（Ｓｅｉｋｏ　Ｉｎｓｔｒｕｍｅｎｔｓ　Ｉｎｃ．製　ＥＸＳＴＡＲ　６０００　ＴＧ／ＤＴＡ６３００）を用い、乾燥空気を３００ｍｌ／ｍｉｎフローした条件下、室温（３０℃）から５５０℃まで１０℃／ｍｉｎで昇温加熱し、加熱始め（３０℃）のサンプル量から減量が終了した時点（銀微粒子の酸化開始時点（サンプルによって異なるが、２５０～３００℃））までのサンプル量を差し引いた量で示した。 The amount of organic matter remaining in the silver fine particles was 10 ° C./min from room temperature (30 ° C.) to 550 ° C. under a condition of flowing dry air at 300 ml / min using a thermal analyzer (EXSTAR 6000 TG / DTA 6300 manufactured by Seiko Instruments Inc.). Shown in the amount obtained by subtracting the sample amount from the sample amount at the beginning of heating (30 ° C) to the point when the reduction is completed (at the start of oxidation of silver fine particles (depending on the sample, 250 to 300 ° C)) It was.
　銀微粒子の結晶子径（ＤＸ）は、Ｘ線回折装置「ＲＩＮＴ２５００」（株式会社リガク製）を用いて、ＣｕのＫα線を線源とした面指数（１，１，１）面のピークの半値幅を求め、Ｓｃｈｅｒｒｅｒの式より結晶子径を計算した。 The crystallite size (D X ) of the silver fine particles is the peak of the plane index (1,1,1) plane using the Kα ray of Cu as the radiation source using an X-ray diffractometer “RINT 2500” (manufactured by Rigaku Corporation). And the crystallite diameter was calculated from the Scherrer equation.
　銀微粒子の結晶化度は、平均粒子径（ＤＳＥＭ）と結晶子径（ＤＸ）の比（ＤＳＥＭ／ＤＸ）で示した。 The degree of crystallinity of the silver fine particles was indicated by the ratio of the average particle diameter (D SEM ) to the crystallite diameter (D X ) (D SEM / D X ).
　銀微粒子の熱収縮率は、直径４ｍｍの金型に高さ５ｍｍのペレットになるように入れた銀微粒子に１，２２５．８Ｎの荷重をかけて作製したペレット状の銀微粒子試料を、熱機械分析装置「Ｔｈｅｒｍｏ　Ｐｌｕｓ２　ＴＭＡ８３１０」（株式会社リガク製）を用いて、３０～３００℃まで昇温速度１０℃／分で加熱した試料の長さを測定し、下記数１に従って算出した値である。 The thermal contraction rate of the silver fine particles was determined by using a pellet-shaped silver fine particle sample prepared by applying a load of 125.8 N to silver fine particles placed in a 4 mm diameter mold so as to form a pellet having a height of 5 mm. The length of a sample heated at 30 ° C./min with a temperature increase rate of 10 ° C./min using an analyzer “Thermo Plus2 TMA8310” (manufactured by Rigaku Corporation) is a value calculated according to the following formula 1.
＜数１＞
　２４０℃における熱収縮率（％）＝｛（３０℃における試料の長さ－２４０℃における試料の長さ）／３０℃における試料の長さ｝×１００ <Equation 1>
Thermal contraction rate (%) at 240 ° C. = {(Sample length at 30 ° C.−sample length at 240 ° C.) / Sample length at 30 ° C.} × 100
　導電性塗膜の比抵抗は、後述する導電性ペーストをポリイミドフィルム上に塗布し、１２０℃で予備乾燥後、１５０℃において１０分間加熱硬化させた後、１ｍｏｌのＨＣｌ水溶液に２０秒間浸漬し、水洗した後、再度１５０℃で１分間加熱乾燥して得られた導電性膜それぞれについて、４端子電気抵抗測定装置「ロレスタＧＰ／ＭＣＰ－Ｔ６００」（株式会社三菱化学アナリテック製）を用いて測定し、シート抵抗と膜厚より比抵抗を算出した。 The specific resistance of the conductive coating was applied to the polyimide film described later on the polyimide film, preliminarily dried at 120 ° C., heated and cured at 150 ° C. for 10 minutes, and then immersed in 1 mol of HCl aqueous solution for 20 seconds. After washing with water, each conductive film obtained by heating and drying again at 150 ° C. for 1 minute was measured using a four-terminal electrical resistance measuring device “Loresta GP / MCP-T600” (manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The specific resistance was calculated from the sheet resistance and the film thickness.
＜実施例１Ａ－１：銀微粒子の製造＞
　６０Ｌの容器に硝酸銀２．８ｋｇと水２５．２Ｌと高分子保護剤「ＤＩＳＰＥＲＢＹＫ－１９０」（商品名：ビックケミー・ジャパン株式会社製）（酸価１０ｍｇＫＯＨ／ｋｇ、アミン価０ｍｇＫＯＨ／ｋｇ）８９ｇを加えて混合・攪拌してＡ液を調製した。別に、５０Ｌの容器にＮ，Ｎ－ジメチルエタノールアミン４．４１ｋｇと低分子保護剤としてヘプタン酸２１４．５ｇを加えて混合・攪拌を行った後、水１８．８Ｌを加えて混合・攪拌を行い、Ｂ液を調製した。 <Example 1A-1: Production of silver fine particles>
Add 2.8 kg of silver nitrate, 25.2 L of water, and 89 g of polymer protective agent “DISPERBYK-190” (trade name: manufactured by Big Chemie Japan Co., Ltd.) (acid value 10 mgKOH / kg, amine value 0 mgKOH / kg) to a 60 L container. A liquid A was prepared by mixing and stirring. Separately, 4.41 kg of N, N-dimethylethanolamine and 214.5 g of heptanoic acid as a low molecular weight protective agent were added to a 50 L container and mixed and stirred, and then 18.8 L of water was added and mixed and stirred. , B liquid was prepared.
　次いで、混合溶液の温度が３２℃以下になるようコントロールしつつＡ液にＢ液を滴下し、７０℃まで昇温した後３時間攪拌し、３０分間静置して固形物を沈降させた。上澄み液を取り除いた後、純水を用いて洗浄し、上澄み液の電導度が５０μＳ／ｃｍ以下になるまでデカンテーション・水洗を繰り返した。 Next, while controlling the temperature of the mixed solution to be 32 ° C. or lower, the B solution was dropped into the A solution, the temperature was raised to 70 ° C., the mixture was stirred for 3 hours, and allowed to stand for 30 minutes to precipitate a solid. After removing the supernatant, it was washed with pure water, and decantation and water washing were repeated until the conductivity of the supernatant was 50 μS / cm or less.
　得られた銀微粒子を含む含水物を真空凍結乾燥機に入れ、真空度を１０Ｐａ程度まであげて品温を－３０℃にして自己凍結させた。その後、真空度を１０Ｐａに維持したまま４０℃まで昇温し（品温は３０℃程度）、その状態を２時間保持した後、粉砕して実施例１－１の銀微粒子を得た。 The obtained water-containing material containing silver fine particles was put into a vacuum freeze dryer, and the degree of vacuum was raised to about 10 Pa, and the product temperature was −30 ° C. to self-freeze. Thereafter, the temperature was raised to 40 ° C. while maintaining the degree of vacuum at 10 Pa (the product temperature was about 30 ° C.). This state was maintained for 2 hours and then pulverized to obtain silver fine particles of Example 1-1.
　得られた銀微粒子の粒子形状は粒状、平均粒子径（ＤＳＥＭ）は７５ｎｍ、結晶子径（ＤＸ）は４５．２ｎｍ、結晶化度（ＤＳＥＭ／ＤＸ）は１．７、タップ密度（ρｔ）は４．５５ｇ／ｃｍ３、ＢＥＴ比表面積値は３．１ｍ２／ｇであり、有機物残存量は１．３６重量％、熱収縮率は２．５８％であった。 The obtained silver fine particles are granular, the average particle diameter (D SEM ) is 75 nm, the crystallite diameter (D X ) is 45.2 nm, the crystallinity (D SEM / D X ) is 1.7, and the tap density. (Ρt) was 4.55 g / cm 3 , the BET specific surface area value was 3.1 m 2 / g, the residual amount of organic matter was 1.36% by weight, and the heat shrinkage rate was 2.58%.
＜実施例２Ａ－１：導電性ペーストの製造＞
　実施例１Ａ－１の銀微粒子１００重量部に対してポリエステル樹脂１１．０重量部及び硬化剤１．４重量部と、導電性ペーストにおける銀微粒子の含有量が７０ｗｔ％となるようにジエチレングリコールモノエチルエーテルを加え、自転・公転ミキサー「あわとり練太郎　ＡＲＥ－３１０」（株式会社シンキー社製、登録商標）を用いてプレミックスを行った後、３本ロールを用いて均一に混練・分散処理を行い、導電性ペーストを得た。 <Example 2A-1: Production of conductive paste>
Example 1A-1 100 parts by weight of silver fine particles 11.0 parts by weight of polyester resin and 1.4 parts by weight of hardener, and diethylene glycol monoethyl so that the content of silver fine particles in the conductive paste is 70 wt%. Ether is added and premixed using a rotating / revolving mixer “Awatori Nertaro ARE-310” (registered trademark, manufactured by Sinky Corporation), and then uniformly mixed and dispersed using three rolls. Conductive paste was obtained.
　上記で得られた導電性ペーストを膜厚５０μｍのポリイミドフィルム上に塗布し、１２０℃で予備乾燥後、１５０℃において１０分間加熱硬化させた後、１ｍｏｌのＨＣｌ水溶液に２０秒間浸漬し、水洗した後、再度１５０℃で１分間加熱乾燥することにより導電性塗膜を得た。 The conductive paste obtained above was applied onto a polyimide film having a thickness of 50 μm, pre-dried at 120 ° C., heat-cured at 150 ° C. for 10 minutes, then immersed in 1 mol HCl aqueous solution for 20 seconds and washed with water. Then, the electroconductive coating film was obtained by heat-drying again at 150 degreeC for 1 minute again.
　得られた導電性塗膜の比抵抗は、７．３μΩ・ｃｍであった。 The specific resistance of the obtained conductive coating film was 7.3 μΩ · cm.
　実施例１Ａ－２～１Ａ－３及び比較例１Ａ－１：
　銀微粒子の生成条件を種々変更することにより、銀微粒子を得た。 Examples 1A-2 to 1A-3 and Comparative Example 1A-1:
Silver fine particles were obtained by variously changing the production conditions of the silver fine particles.
　このときの製造条件を表１に、得られた銀微粒子の諸特性を表２に示す。 The production conditions at this time are shown in Table 1, and the various characteristics of the obtained silver fine particles are shown in Table 2.
　比較例１Ａ－２：特開２０１０－２２９５４４（実施例１の追試）
　硝酸銀６６．８ｇ、カルボキシル基を有する凝集助剤として酢酸１０ｇ、高分子分散剤としてカルボキシル基を有する高分子分散剤「ＤＩＳＰＥＲＢＹＫ－１９０」（商品名：ビックケミー・ジャパン株式会社製）２．０ｇを、イオン交換水１００ｇに投入し、激しく撹拌した。これにＮ，Ｎ－ジメチルエタノールアミン１００ｇを徐々に加えたところ、反応溶液が６０℃まで上昇した。液温が５０℃に下がったところで７０℃に設定されたウォーターバス中で２時間加熱撹拌した。１時間後、銀コロイド粒子凝集体が灰色の沈殿物として得られた。 Comparative Example 1A-2: JP 2010-229544 A (Further examination of Example 1)
66.8 g of silver nitrate, 10 g of acetic acid as an agglomeration aid having a carboxyl group, 2.0 g of a polymer dispersant “DISPERBYK-190” having a carboxyl group as a polymer dispersant (trade name: manufactured by Big Chemie Japan Co., Ltd.) The mixture was put into 100 g of ion-exchanged water and stirred vigorously. When 100 g of N, N-dimethylethanolamine was gradually added thereto, the reaction solution rose to 60 ° C. When the liquid temperature dropped to 50 ° C., the mixture was heated and stirred in a water bath set at 70 ° C. for 2 hours. After 1 hour, silver colloidal particle aggregates were obtained as gray precipitates.
　次いで、銀コロイド粒子凝集体が沈殿した反応溶液の上澄み液を除去し、イオン交換水で希釈した。静置した後、上澄み液を除去し、メタノールでさらに希釈した。再度、静置後、上澄み液を除去し、メタノールで希釈した。その後、メンブレンフィルタ（アドバンテック社製、ポアサイズ０．５μｍ）を付けた加圧ろ過機で銀コロイド粒子凝集体を回収した。得られた銀コロイド粒子凝集体の諸特性を表２に示す。 Next, the supernatant of the reaction solution in which the silver colloid particle aggregates were precipitated was removed and diluted with ion-exchanged water. After standing, the supernatant was removed and further diluted with methanol. After standing again, the supernatant was removed and diluted with methanol. Thereafter, the silver colloidal particle aggregates were collected with a pressure filter equipped with a membrane filter (manufactured by Advantech, pore size 0.5 μm). Various properties of the obtained silver colloidal particle aggregate are shown in Table 2.
比較例１Ａ－３：特開２００９－１２０９４９（実施例１の追試）
　１Ｌビーカーの反応槽に水２７３ｇを入れ、残存酸素を除くため反応槽下部から窒素を５００ｍＬ／分の流量で６００秒間流した後、反応槽上部から５００ｍＬ／分の流量で供給し、反応槽中を窒素雰囲気とした。攪拌棒の回転速度が２８０から３２０ｒｐｍになるように調整し、反応槽内の溶液温度が６０℃になるように温度調整を行なった。 Comparative Example 1A-3: JP-A-2009-120949 (Additional test of Example 1)
In order to remove residual oxygen, 273 g of water was put into a 1 L beaker reaction tank, and after flowing nitrogen at a flow rate of 500 mL / min for 600 seconds from the bottom of the reaction tank, it was supplied at a flow rate of 500 mL / min from the top of the reaction tank. Was a nitrogen atmosphere. The rotating speed of the stirring bar was adjusted to 280 to 320 rpm, and the temperature was adjusted so that the solution temperature in the reaction vessel was 60 ° C.
　アンモニア水（アンモニアとして３０質量％含有する）７．５ｇを反応槽に投入した後、液を均一にするために１分間攪拌し、次いで、保護剤としてヘキサン酸７．５ｇ（銀に対して２．０１ｍｏｌに相当する）を添加し、保護剤を溶解するため１０分間攪拌した。その後、還元剤として５０重量％のヒドラジン水和物水溶液を２０．９ｇ添加した。 After adding 7.5 g of aqueous ammonia (containing 30% by mass as ammonia) to the reaction vessel, the mixture was stirred for 1 minute to make the solution uniform, and then 7.5 g of hexanoic acid (2% with respect to silver) as a protective agent. (Corresponding to 0.01 mol) and stirred for 10 minutes to dissolve the protective agent. Thereafter, 20.9 g of 50% by weight hydrazine hydrate aqueous solution was added as a reducing agent.
　別の容器に硝酸銀結晶３６ｇを水１７５ｇに溶解した硝酸銀水溶液を用意し、これを原料液とした。なお、硝酸銀水溶液は反応槽内の溶液と同じ６０℃に温度調整を行なった。 In another container, an aqueous silver nitrate solution in which 36 g of silver nitrate crystals were dissolved in 175 g of water was prepared, and this was used as a raw material liquid. The temperature of the aqueous silver nitrate solution was adjusted to 60 ° C., the same as the solution in the reaction vessel.
　その後、原料液を還元液に一挙添加により加え、還元反応を行った。攪拌は連続して行い、その状態のまま１０分間熟成させた。その後、攪拌を止め、濾過・洗浄工程、乾燥工程を経て、微小銀粒子塊を得た。得られた微小銀粒子塊の諸特性を表２に示す。 Thereafter, the raw material solution was added to the reducing solution at once and a reduction reaction was performed. Stirring was performed continuously and aged for 10 minutes in that state. Thereafter, stirring was stopped, and a fine silver particle mass was obtained through a filtration / washing step and a drying step. Table 2 shows various characteristics of the obtained fine silver particle block.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　＜導電性塗料の製造＞
　実施例２Ａ－２～２Ａ－３及び比較例２Ａ－１～２Ａ－３：
　銀微粒子の種類を種々変化させた以外は、前記実施例２Ａ－１の導電性塗料の作製方法に従って導電性塗料及び導電性膜を製造した。 <Manufacture of conductive paint>
Examples 2A-2 to 2A-3 and Comparative Examples 2A-1 to 2A-3:
A conductive paint and a conductive film were produced according to the method for producing a conductive paint of Example 2A-1, except that the type of silver fine particles was variously changed.
　このときの製造条件及び得られた導電性塗膜の諸特性を表３に示す。 Table 3 shows the manufacturing conditions and various properties of the obtained conductive coating film.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　＜実施例１Ｂ－１：銀微粒子の製造＞
　６０Ｌの容器に硝酸銀２．８ｋｇと水２５．２Ｌと高分子保護剤「ＤＩＳＰＥＲＢＹＫ－１９０」（商品名：ビックケミー・ジャパン株式会社製）（酸価１０ｍｇＫＯＨ／ｋｇ、アミン価０ｍｇＫＯＨ／ｋｇ）９２ｇを加えて混合・攪拌してＡ液を調製した。別に、５０Ｌの容器にＮ，Ｎ－ジメチルエタノールアミン４．４１ｋｇと低分子保護剤としてヘプタン酸２１４．５ｇを加えて混合・攪拌を行った後、水１８．８Ｌを加えて混合・攪拌を行い、Ｂ液を調製した。 <Example 1B-1: Production of silver fine particles>
To a 60 L container, 2.8 kg of silver nitrate, 25.2 L of water, and a polymer protective agent “DISPERBYK-190” (trade name: manufactured by Big Chemie Japan Co., Ltd.) (acid value 10 mgKOH / kg, amine value 0 mgKOH / kg) 92 g A liquid A was prepared by mixing and stirring. Separately, 4.41 kg of N, N-dimethylethanolamine and 214.5 g of heptanoic acid as a low molecular weight protective agent were added to a 50 L container and mixed and stirred, and then 18.8 L of water was added and mixed and stirred. , B liquid was prepared.
　次いで、混合溶液の温度が３５℃以下になるようコントロールしつつＡ液にＢ液を滴下し、７０℃まで昇温した後３時間攪拌し、３０分間静置して固形物を沈降させた。上澄み液を取り除いた後、純水を用いて洗浄し、上澄み液の電導度が５０μＳ／ｃｍ以下になるまでデカンテーション・水洗を繰り返した。 Next, while controlling the temperature of the mixed solution to be 35 ° C. or lower, the B solution was dropped into the A solution, the temperature was raised to 70 ° C., the mixture was stirred for 3 hours, and allowed to stand for 30 minutes to precipitate a solid. After removing the supernatant, it was washed with pure water, and decantation and water washing were repeated until the conductivity of the supernatant was 50 μS / cm or less.
　得られた銀微粒子を含む含水率５５％の含水物を真空凍結乾燥機に入れ、真空度を１０Ｐａ程度まであげて品温を－３０℃にして自己凍結させた。その後、真空度を１０Ｐａに維持したまま４０℃まで昇温し（品温は３０℃程度）、その状態を２時間保持した後、粉砕して実施例１Ｂ－１の銀微粒子を得た。 The obtained water-containing material containing silver fine particles and having a water content of 55% was placed in a vacuum freeze dryer, and the degree of vacuum was raised to about 10 Pa, and the product temperature was −30 ° C. to self-freeze. Thereafter, the temperature was raised to 40 ° C. while maintaining the degree of vacuum at 10 Pa (the product temperature was about 30 ° C.). This state was maintained for 2 hours and then pulverized to obtain silver fine particles of Example 1B-1.
　得られた銀微粒子の粒子形状は粒状、平均粒子径（ＤＳＥＭ）は７２ｎｍ、結晶子径（ＤＸ）は４１．８ｎｍ、結晶化度（ＤＳＥＭ／ＤＸ）は１．７、タップ密度（ρｔ）は４．５９ｇ／ｃｍ３、ＢＥＴ比表面積値は３．５ｍ２／ｇであり、有機物残存量は１．３７重量％、熱収縮率は２．６３％であった。 The obtained silver fine particles are granular, the average particle diameter (D SEM ) is 72 nm, the crystallite diameter (D X ) is 41.8 nm, the crystallinity (D SEM / D X ) is 1.7, and the tap density. (Ρt) was 4.59 g / cm 3 , the BET specific surface area value was 3.5 m 2 / g, the residual amount of organic matter was 1.37% by weight, and the heat shrinkage rate was 2.63%.
　＜実施例２Ｂ－１：導電性ペーストの製造＞
　実施例１Ｂ－１の銀微粒子１００重量部に対してポリエステル樹脂１１．０重量部及び硬化剤１．４重量部と、導電性ペーストにおける銀微粒子の含有量が７０ｗｔ％となるようにジエチレングリコールモノエチルエーテルを加え、自転・公転ミキサー「あわとり練太郎　ＡＲＥ－３１０」（株式会社シンキー社製、登録商標）を用いてプレミックスを行った後、３本ロールを用いて均一に混練・分散処理を行い、導電性ペーストを得た。 <Example 2B-1: Production of conductive paste>
Example 1B-1 100 parts by weight of silver fine particles 11.0 parts by weight of a polyester resin and 1.4 parts by weight of a curing agent, and diethylene glycol monoethyl so that the content of silver fine particles in the conductive paste is 70 wt%. Ether is added and premixed using a rotating / revolving mixer “Awatori Nertaro ARE-310” (registered trademark, manufactured by Sinky Corporation), and then uniformly mixed and dispersed using three rolls. Conductive paste was obtained.
　上記で得られた導電性ペーストを膜厚５０μｍのポリイミドフィルム上に塗布し、１２０℃で予備乾燥後、１５０℃において１０分間加熱硬化させた後、１ｍｏｌのＨＣｌ水溶液に２０秒間浸漬し、水洗した後、再度１５０℃で１分間加熱乾燥することにより導電性塗膜を得た。 The conductive paste obtained above was applied onto a polyimide film having a thickness of 50 μm, pre-dried at 120 ° C., heat-cured at 150 ° C. for 10 minutes, then immersed in 1 mol HCl aqueous solution for 20 seconds and washed with water. Then, the electroconductive coating film was obtained by heat-drying again at 150 degreeC for 1 minute again.
　得られた導電性塗膜の比抵抗は、７．５μΩ・ｃｍであった。 The specific resistance of the obtained conductive coating film was 7.5 μΩ · cm.
　実施例１Ｂ－２～１Ｂ－３及び比較例１Ｂ－１～１Ｂ－２：
　銀微粒子の生成条件を種々変更することにより、銀微粒子を得た。 Examples 1B-2 to 1B-3 and Comparative Examples 1B-1 to 1B-2:
Silver fine particles were obtained by variously changing the production conditions of the silver fine particles.
　このときの製造条件を表４に、得られた銀微粒子の諸特性を表５に示す。 The production conditions at this time are shown in Table 4, and the characteristics of the obtained silver fine particles are shown in Table 5.
　比較例１Ｂ－３：
　上記比較例１Ａ－２と同じである。得られた銀コロイド粒子凝集体の諸特性を表５に示す。 Comparative Example 1B-3:
Same as Comparative Example 1A-2. Table 5 shows various characteristics of the obtained silver colloid particle aggregates.
　比較例１Ｂ－４：
　上記比較例１Ａ－３と同じである。得られた微小銀粒子塊の諸特性を表５に示す。 Comparative Example 1B-4:
Same as Comparative Example 1A-3. Table 5 shows various characteristics of the obtained fine silver particle block.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
＜導電性塗料の製造＞
実施例２Ｂ－２～２Ｂ－３及び比較例２Ｂ－１～２Ｂ－４：
　銀微粒子の種類を種々変化させた以外は、前記実施例２Ｂ－１の導電性塗料の作製方法に従って導電性塗料及び導電性膜を製造した。 <Manufacture of conductive paint>
Examples 2B-2 to 2B-3 and Comparative Examples 2B-1 to 2B-4:
A conductive paint and a conductive film were produced according to the method for producing a conductive paint of Example 2B-1, except that the type of silver fine particles was variously changed.
　このときの製造条件及び得られた導電性塗膜の諸特性を表６に示す。 Table 6 shows the manufacturing conditions and various characteristics of the obtained conductive coating film.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　一般に、銀微粒子の粒子サイズが小さくなるほどタップ密度は小さくなる傾向にあるが、本発明に係る銀微粒子の製造法は、前記平均粒子径（ＤＳＥＭ）が３０～１００ｎｍと微粒子であるにもかかわらず、３．０ｇ／ｃｍ３以上の高いタップ密度を有する銀微粒子を得ることができるため、低温焼結性並びに電極や回路パターン中における充填性に優れた銀微粒子の製造法として好適である。 In general, the tap density tends to decrease as the particle size of the silver fine particles decreases. However, the method for producing silver fine particles according to the present invention has the average particle diameter (D SEM ) of 30 to 100 nm even though the particles are fine particles. Therefore, since silver fine particles having a high tap density of 3.0 g / cm 3 or more can be obtained, it is suitable as a method for producing silver fine particles having excellent low-temperature sintering properties and filling properties in electrodes and circuit patterns.
　また、本発明に係る銀微粒子は、上記製造法により、平均粒子径（ＤＳＥＭ）が３０～１００ｎｍと微粒子であるにもかかわらず、３．０ｇ／ｃｍ３以上の高いタップ密度を有していることから、基板上に形成された電極や回路パターン中における充填性に優れた導電性ペースト等の原料として好適である。 In addition, the silver fine particles according to the present invention have a high tap density of 3.0 g / cm 3 or more despite the fine particle having an average particle diameter (D SEM ) of 30 to 100 nm by the above production method. Therefore, it is suitable as a raw material for conductive paste and the like having excellent filling properties in electrodes and circuit patterns formed on a substrate.

Claims (11)

  1. 　平均粒子径（ＤＳＥＭ）が３０～１００ｎｍであり、タップ密度が３．０ｇ／ｃｍ３以上であることを特徴とする銀微粒子。 Silver fine particles having an average particle diameter (D SEM ) of 30 to 100 nm and a tap density of 3.0 g / cm 3 or more.
  2. 　ＢＥＴ比表面積値が７．０ｍ２/ｇ以下である請求項１記載の銀微粒子。 The silver fine particles according to claim 1, which have a BET specific surface area value of 7.0 m 2 / g or less.
  3. 　結晶子径（Ｄｘ）が３０ｎｍ以上である請求項１又は請求項２記載の銀微粒子。 The silver fine particles according to claim 1 or 2, wherein the crystallite diameter ( Dx ) is 30 nm or more.
  4. 　銀微粒子表面の有機物残存量が０．５～２．０重量％である請求項１から請求項３のいずれかに記載の銀微粒子。 The silver fine particles according to any one of claims 1 to 3, wherein the amount of organic matter remaining on the surface of the silver fine particles is 0.5 to 2.0% by weight.
  5. 　２４０℃における熱収縮率が２．０％以上である請求項１から請求項４のいずれかに記載の銀微粒子。 The silver fine particles according to any one of claims 1 to 4, wherein a heat shrinkage rate at 240 ° C is 2.0% or more.
  6. 　請求項１から請求項５のいずれかに記載の銀微粒子を含む導電性ペースト。 A conductive paste containing the silver fine particles according to any one of claims 1 to 5.
  7. 　請求項６記載の導電性ペーストを用いて形成された導電性膜。 A conductive film formed using the conductive paste according to claim 6.
  8. 　請求項７記載の導電性膜を有する電子デバイス。 An electronic device having the conductive film according to claim 7.
  9. 　硝酸銀と高分子保護剤とを用いて水溶液を調製し（Ａ液）、前記Ａ液とは別に還元剤と低分子保護剤を溶解させた水溶液を調製し（Ｂ液）、前記Ｂ液を前記Ａ液に滴下して還元析出させて得られた銀微粒子を分離・洗浄・乾燥させる銀微粒子の製造法において、前記Ｂ液を前記Ａ液に滴下した際の混合溶液の温度を４０℃以下に制御すると共に、乾燥工程を真空凍結乾燥により行うことを特徴とする銀微粒子の製造法。 An aqueous solution is prepared using silver nitrate and a polymer protective agent (liquid A), and an aqueous solution in which a reducing agent and a low molecular weight protective agent are dissolved separately from liquid A (liquid B). In the method for producing silver fine particles in which the silver fine particles obtained by dropping into the A liquid and reducing and depositing are separated, washed and dried, the temperature of the mixed solution when the B liquid is dropped into the A liquid is 40 ° C. or lower. A method for producing silver fine particles, characterized in that the drying step is performed by vacuum freeze-drying while controlling.
  10. 　真空凍結乾燥前の含水物の含水率が３０％以上である請求項９記載の銀微粒子の製造法。 The method for producing silver fine particles according to claim 9 , wherein the water content of the water-containing material before vacuum freeze-drying is 30% or more.
  11. 　得られる銀微粒子が請求項１～５の何れかに記載の銀微粒子である請求項９又は１０記載の銀微粒子の製造法。 The method for producing silver fine particles according to claim 9 or 10, wherein the obtained silver fine particles are the silver fine particles according to any one of claims 1 to 5.
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