TW201341087A - Silver fine particles, production process therefor, and conductive paste, conductive membrane and electronic device, containing said silver fine particles - Google Patents

Abstract

The present invention pertains to: silver fine particles with excellent low-temperature sinterability; a production process therefor; and a conductive paste, a conductive membrane and an electronic device, containing the silver fine particles. In a process for producing silver fine particles which comprises preparing an alcoholic solution (A) of a silver nitrate-amine complex prepared using silver nitrate and at least one water-soluble C2-4 aliphatic amine, preparing, separately from the solution (A), an aqueous solution (B) in which either ascorbic acid or erythorbic acid and a halide are dissolved, adding a mixture of the solution (A) with the solution (B) into a vessel in which water has been put, stirring the resulting mixture, and then subjecting the thus obtained silver fine particles to washing and drying, at least 1.610-3 mol of a halide per mol of silver nitrate is added to the solution (B), whereby an aggregate silver fine particle slurry can be obtained to facilitate the subsequent washing. Thus, silver fine particles which have a carbon content of 0.25wt% or less and thus exhibit excellent low-temperature sinterability can be obtained.

Description

Silver microparticles, manufacturing method thereof, and conductive paste, conductive film and electronic device containing the same

The present invention relates to a silver fine particle having an average particle diameter of 30 to 120 nm which is excellent in low-temperature sinterability, a method for producing the same, a conductive paste containing the silver fine particles, a conductive film, and an electronic device.

The electrode or circuit pattern of the electronic device is formed by printing an electrode or a circuit pattern on a substrate using a conductive paste containing metal particles, and then firing the metal particles contained in the conductive paste by heating. However, in recent years, the heating and firing temperature tends to decrease.

For example, the mounting substrate of an electronic device can be generally heated to about 300 ° C, and a flexible substrate made of polyimide is used for excellent heat resistance. However, since it is expensive, PET (polyphenylene terephthalate) has been recently reviewed. A polyethylene dicarboxylate substrate or a PEN (polyethylene naphthalate) substrate is used as an alternative material. However, the PET substrate or the PEN substrate has lower heat resistance than the flexible substrate made of polyimide. In particular, the PET film substrate used in the film wiring board must be heated and fired at 150 ° C or lower.

Further, if the heating and firing can be performed at a temperature lower than 200 ° C, an electrode or a circuit pattern may be formed on a substrate such as polycarbonate or paper. Therefore, it is expected to expand the use of various electrode materials and the like.

As the metal particles of the raw material of such a low-temperature-fireable conductive paste, nano-sized silver fine particles are expected. The reason for this is that the surface activity becomes higher when the size of the metal particles becomes nanometer, and the melting point is compared with the metal block. The body is also reduced, so it can be sintered at a low temperature. Moreover, compared with other conductive particles such as copper, the silver fine particles are expensive, and even if they are easily caused to migrate in the metal particles, they are less susceptible to oxidation than copper having the same specific resistance. Homework is easier.

Further, the nano-sized silver fine particles can be sintered at a low temperature and can maintain heat resistance at the time of primary sintering, and therefore it is expected to use a property which is not possessed by conventional solders as a substitute for lead-free solder.

Heretofore, as a method for stably and efficiently producing fine silver particles having excellent dispersibility, a method of reducing silver ions in the presence of halide ions has been proposed (Patent Document 1), and at a hardening heating temperature of a resin paste. A halogen-containing silver powder having a high shrinkage ratio and a method for producing a silver powder containing the halogen at a simple and low cost (Patent Document 2). Further, as a metal powder which can be sintered at a low temperature (before and after 600 ° C) to produce a sintered member having excellent ductility, it is known that a halogen element or a halide is contained in the surface of the metal powder of 5 to 2,000 ppm (Patent Document) 3).

In addition, all the steps from the reaction to the drying are controlled to 30° C. or less, and the crystal particles having an average particle diameter of 30 to 100 nm of a raw material such as a conductive paste which can be fired at a low temperature (Patent Document 4) ) is known.

Prior technical literature

Patent literature

Patent Document 1: JP-A-2008-274423

Patent Document 2: JP-A-2010-77493

Patent Document 3: JP-A-2005-325411

Patent Document 4: JP-A-2011-80094

In the above-described Patent Document 1, a method of reducing silver ions in the presence of a halide ion is disclosed. However, in the production method described in Patent Document 1, as shown in the comparative example described later, the amount of halide added is small. Since the silver fine particles are dispersed, and the subsequent washing is incomplete, the amount of carbon of the obtained silver fine particles cannot be 0.25 wt% or less, and it is difficult to obtain silver fine particles excellent in low-temperature sintering property.

Further, although Patent Document 2 discloses a silver powder containing a halogen, the period of adding a halide is after the reduction reaction of silver, so that the halogen contained is easily desorbed compared to the case where silver chloride is formed during the reduction reaction. Or an ionizer, in particular, silver fine particles used for the use of the conductive paste and the conductive film used in the formation of the electrode or circuit pattern of the present invention, since the halogen is simply attached to the particle surface in an ionized state, good.

Patent Document 3 discloses that the metal powder contains 5 to 2,000 ppm of a halogen element or a halide on the surface of the metal powder. However, the metal powder described in Patent Document 3 press-forms a metal powder to produce a green compact and is sintered at 500 to 900 ° C. On the other hand, since the purpose of adding halogen is for the ductility and dimensional shrinkage of the sintered member, it is used in particular as the conductive paste and the conductive film used for forming the electrode or circuit pattern of the present invention. The silver fine particles are not preferable because the halogen is simply attached to the surface of the particles in an ionized state.

In Patent Document 4, it is disclosed that all the steps of the reaction to drying are controlled to 30° C. or less, and a plurality of crystallized silver particles having an average particle diameter of 30 to 100 nm which is a raw material of a conductive paste which can be fired at a low temperature are obtained. However, as shown in the comparative example described later, since the silver fine particles formed without adding a halide are dispersed, the subsequent washing may be incomplete, so that the amount of carbon of the obtained silver fine particles cannot be 0.25 wt% or less, and it is difficult to obtain low-temperature sinterability. Excellent silver particles. In addition, since the drying temperature needs to be controlled below 30 ° C, it is industrially disadvantageous.

Here, the technical problem of the present invention is to provide a silver fine particle having an average particle diameter of 30 to 120 nm which is excellent in low-temperature sinterability and a method for efficiently producing the silver fine particle.

The above technical problems can be achieved by the present invention as described below.

That is, the present invention is a method for producing silver microparticles, which is characterized in that an alcohol solution of silver nitrate amine complex prepared by using silver nitrate or more than one water-soluble or water-soluble aliphatic amine having 2 to 4 carbon atoms is prepared. (A liquid), an aqueous solution (B liquid) obtained by dissolving ascorbic acid or erythorbic acid and a halide is prepared separately from the liquid A, and the liquid A and the liquid B are mixed by using a static mixer. After being added to a container that has been placed in water and stirred, the obtained silver particles are washed. A method for producing dry silver fine particles, wherein a halide of 1.6 × 10 ^-3 mol or more is added to the liquid B of the silver nitrate (the present invention 1).

Further, the present invention is a method of obtaining silver fine particles by the method of the present invention, The amount of carbon of the silver fine particles is 0.25 wt% or less (Invention 2).

Further, the present invention is the silver fine particles of the invention 2, wherein the surface of the particles of the silver fine particles is coated with a polymer compound having a molecular weight of 10,000 or more (Invention 3).

Further, the present invention is the silver fine particles according to the invention 2 or the invention 3, which has an average particle diameter (D _SEM ) of 30 nm or more and 120 nm or less (Invention 4).

Further, the present invention is a conductive paste comprising the silver fine particles of any one of Invention 2 to Invention 4 (Invention 5).

Further, the present invention is a conductive film formed using the conductive paste of the present invention 5 (Invention 6).

Further, the present invention is an electronic device comprising the conductive film of the present invention 6 (Invention 7).

Since the silver fine particles of the present invention have a low carbon content after the reduction reaction, they are suitable as a raw material for a conductive paste which can be fired at a low temperature.

Further, the method for producing silver fine particles of the present invention can reduce the carbon content of the silver fine particles after the reduction reaction and obtain silver fine particles in a high yield. Therefore, it is suitable as a method for producing silver fine particles excellent in low-temperature sintering property.

The structure of the present invention will be described in more detail below.

First, a method of producing the silver fine particles of the present invention will be described.

The silver microparticles of the invention can be prepared by using silver nitrate and more than one kind of water. An alcohol solution (solution A) of a silver nitrate amine complex prepared by a soluble or water-soluble aliphatic amine having 2 to 4 carbon atoms, which is additionally prepared by dissolving ascorbic acid or isoascorbic acid and a halide. The aqueous solution (solution B) is obtained by mixing the liquid A and the liquid B with a static mixer, and adding the mixture to the container in which the water has been placed, and stirring, and then the obtained silver fine particles are washed. Obtained by drying.

The alcohol solution (solution A) of the silver nitrate amine complex in the present invention can be obtained by mixing silver nitrate with one or more water-soluble or water-soluble aliphatic amines having 2 to 4 carbon atoms in an alcohol solution. The amount of the aliphatic amine added is preferably from 2.0 to 2.5 mol, more preferably from 2.0 to 2.3 mol, based on 1 mol of silver nitrate. When the amount of the aliphatic amine is less than 2.0 mol per mol of silver nitrate, there is a tendency that large particles are easily formed.

The aliphatic amine having 2 to 4 carbon atoms of the present invention is important to use water-soluble or water-soluble ones, specifically ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutyl. An amine or the like is preferable to n-propylamine and n-butylamine in consideration of low-temperature sinterability and handleability of silver fine particles.

The alcohol of the present invention can be used in accordance with water. Specifically, methanol, ethanol, propanol, isopropanol or the like can be used, and methanol and ethanol are preferred. These alcohols may be used singly or in combination.

In the present invention, an aqueous solution (solution B) obtained by dissolving ascorbic acid or erythorbic acid and a halide is prepared separately from the liquid A. The amount of silver nitrate 1 mol ascorbic acid or isoascorbic acid added in the liquid A to be mixed is preferably 1.0 to 2.0 mol, more preferably 1.0 to 1.8 mol. When compared to silver nitrate 1 mol ascorbic acid or isoascorbic acid exceeding 2.0 mol, The tendency of the generated silver particles to agglomerate with each other is less preferred.

The halide of the present invention can be used from potassium chloride (KCl), sodium chloride (NaCl), ammonium chloride (NH ₄ Cl), potassium bromide (KBr), sodium bromide (NaBr), ammonium bromide (NH). One or more selected from ₄ Br), potassium iodide (KI), sodium iodide (NaI) and ammonium iodide (NH ₄ I), but preferably potassium chloride (KCl) or sodium chloride (NaCl) Etc. chloride.

The amount of the halide added is preferably from 1.6 × 10 ^-3 to 8.0 × 10 ^-3 mol, more preferably from 1.7 × 10 ^-3 to 6.0 ×, relative to the silver nitrate in the liquid A to be mixed. 10 ^{- 3} moles, more preferably 1.8 × 10 ^-3 ~ 4.0 × 10 ^-3 moles, the amount of halide added is more than 8.0 × 10 ^-3 moles relative to silver nitrate 1 mole, by adding halogenation When the effect of the slurry of the silver fine particles obtained by the material is saturated, and the halide of the necessary amount or more is present, the silver fine particles used in the use of the conductive paste and the conductive film used for forming the electrode or the circuit pattern are compared. not good. Further, when the amount of the halide added is less than 1.6 × 10 ^-3 mol with respect to 1 mol of silver nitrate, since the amount of the halide is too small, the slurry of the obtained silver fine particles becomes dispersed, and the subsequent washing is not performed. Since it is complete, it is difficult to make the amount of carbon of the silver fine particles 0.25 wt% or less.

An alcohol solution of the silver nitrate amine complex (liquid A) and an aqueous solution (solution B) obtained by dissolving ascorbic acid or iso-hydro-humic acid and a halide are mixed using a static mixer, and added to the water which has been placed. Stir in the container. a method of adding an aqueous solution (solution B) of dissolved ascorbic acid or erythorbic acid and a halide to an alcohol solution (solution A) of silver nitrate, or an alcohol solution of an amine complex of silver nitrate (solution A) ) added to the dissolved isoascorbic acid In the method of the aqueous solution of the halide (solution B), since the mixed concentration of the liquid A and the liquid B produced by the initial reduction reaction is constant, it is easy to obtain a uniform particle size distribution of the obtained silver fine particles.

Mixing an alcohol solution of the silver nitrate amine complex (liquid A) with an aqueous solution of the ascorbic acid or erythorbic acid and the halide (solution B) using a static mixer, and adding the obtained reaction solution to the container which has been placed in the water, The concentration of silver is adjusted to a range of 0.1 to 1.0 mol/L, and after stirring for 30 minutes or more, the obtained silver fine particles are filtered by a conventional method using an alcohol and water. Washed. At this time, washing was performed until the conductivity of the filtrate became 60 μS/cm or less.

The filter cake of the washed silver fine particles is redispersed in a hydrophilic organic solvent, and the water on the surface of the silver fine particles is replaced with a hydrophilic organic solvent, and then the silver fine particles filtered by a conventional method are preferably at a temperature of 40 ° C or lower. After drying at 30 ° C or lower, or by vacuum drying, it is pulverized by a conventional method to obtain silver fine particles of the present invention. By replacing the moisture on the surface of the silver microparticles with a hydrophilic organic solvent, it is possible to prevent the silver microparticles after drying from being in a state of solid agglomeration with each other, so that the subsequent pulverization treatment or surface treatment. The pulverization process and the like become easy.

As the hydrophilic organic solvent, an alcohol such as methanol, ethanol or propanol, acetone or the like can be used. If it is considered to remove the solvent by drying, methanol and ethanol are preferred.

The silver fine particles of the present invention are preferably surface-treated with a polymer compound having a molecular weight of 10,000 or more before the pulverization treatment. The coating amount of the polymer compound having a molecular weight of 10,000 or more is preferably 0.2 to 4% by weight, more preferably 0.3 to 3% by weight based on the silver fine particles. By making high scores The amount of the sub-compound treated falls within the above range, and a sufficient treatment effect by the pulverization treatment can be obtained. By subjecting the surface treatment with a polymer compound in advance, a high pulverization treatment effect can be obtained in the subsequent pulverization treatment, and the pulverization treatment can be more uniform. On the other hand, when a polymer compound is added to the reduction precipitation reaction of silver fine particles, there is a problem in the uniformity of the treatment amount and the treatment effect, and aggregation occurs in the subsequent pulverization treatment, so that the obtained silver fine particles are The dispersibility in the conductive paste becomes difficult, which is less preferred.

The surface treatment of the silver microparticles by the polymer compound is replaced by a hydrophilic organic solvent. The dried silver fine particles are redispersed in a polymer compound solution obtained by dissolving the polymer compound in an organic solvent, and the mixture is slowly stirred for 30 to 300 minutes, and then the organic solvent is removed and dried.

The pulverization of the silver fine particles surface-treated with the polymer compound is preferably carried out using a jet mill.

Next, the silver fine particles of the present invention will be described.

The silver microparticles of the present invention are silver microparticles obtained by the above-mentioned manufacturing method, which are characterized in that the silver microparticle slurry after the reduction reaction is washed. The amount of carbon of the silver fine particles after drying is 0.25 wt% or less.

Wash the silver microparticle slurry after the reduction reaction. When the amount of carbon of the dried silver fine particles exceeds 0.25% by weight, it is less preferable because the low-temperature sintering property is impaired. Further, the lower limit is usually 0.15% by weight, and when it is less than the lower limit, the wettability to the solvent and the resin tends to be lowered. More preferably, it is 0.15 to 0.24% by weight, more preferably 0.16 to 0.23% by weight.

The average particle diameter (D _SEM ) of the silver fine particles of the present invention is preferably 30 nm or more and 120 nm or less, more preferably 35 nm or more and 110 nm or less, and still more preferably 40 nm or more and 100 nm or less. By setting the average particle diameter (D _SEM ) to the above range, it is easy to refine the electronic device obtained by the above. When the average particle diameter (D _SEM ) is less than 30 nm, the surface activity of the silver fine particles is high, and it is not preferable to adhere a large amount of organic substances in order to maintain the fine particle diameter stably.

The crystal diameter (D _X ) of the silver fine particles of the present invention is preferably 30 nm or less, more preferably 10 to 29 nm, still more preferably 10 to 28 nm. When the crystal diameter (D _X ) exceeds 30 nm, the reactivity in the silver fine particles is lowered, and the low-temperature sintering property is impaired, which is not preferable. Moreover, when the crystal diameter (D _X ) is less than 10 nm, the silver fine particles become unstable, and partial sintering starts to occur even at normal temperature. It is not good to melt.

The present invention as much as the silver microparticles degree of crystallinity [average particle diameter (D _SEM) and a crystalline diameter (D _X) ratio (D _SEM / D _X) is 2.8 or more, preferably 3.0 or more, more preferably 3.2 or more. When the degree of polycrystallization is less than 2.8, the crystal diameter in the silver fine particles becomes large, and the reactivity in the silver fine particles is lowered as it is close to the single crystal, which is disadvantageous in that the low-temperature sintering property is impaired. The upper limit of the degree of polycrystallization is about 10, more preferably about 8.

The low-temperature sinterability of the silver fine particles of the present invention is a rate of change of the crystal diameter (D _X ) by heating described later [(the crystal diameter (D _x ) of the silver fine particles after heating at 150 ° C for 30 minutes / before heating The crystal diameter (D _X ) of the silver fine particles × 100] was evaluated, and the rate of change of the crystal diameter (D _X ) by heating at 150 ° C was preferably 130% or more, more preferably 135% or more. When the rate of change of the crystal diameter (D _X ) is less than 130%, it cannot be said that it is excellent in low-temperature sinterability. In the present invention, when heated at 210 ° C for 30 minutes, the rate of change of the crystal diameter (D _X ) is preferably 140% or more, more preferably 150% or more.

The silver fine particles of the present invention preferably have a BET specific surface area value of 10 m ² /g or less, more preferably 8 m ² /g or less. When the BET specific surface area value exceeds 10 m ² /g, the viscosity of the conductive paste obtained by using it becomes high, which is not preferable.

The halogen content of the silver fine particles of the present invention is preferably from 1.6 × 10 ^-3 to 8.0 × 10 ^-3 mol, more preferably from 1.7 × 10 ^-3 to 6.0 × 10 ^-3 mol, relative to the silver 1 molar. More preferably 1.8 x 10 ^-3 ~ 4.0 x 10 ^-3 mol. When the content of the halogen exceeds 8.0 × 10 ^-3 mol with respect to the silver 1 mol, the halogen content is too large, so the silver paste used for the use of the conductive paste and the conductive film for forming an electrode or a circuit pattern is not preferable. .

The particle shape of the silver fine particles of the present invention is preferably spherical or granular.

The silver microparticles of the present invention are preferably washed after the above-mentioned reduction reaction of the silver microparticle slurry. The surface of the particles of the dried silver fine particles is coated with a polymer compound having a molecular weight of 10,000 or more. When the molecular weight is less than 10,000, agglomerates are generated in the subsequent pulverization treatment, and the dispersion of the obtained silver fine particles in the conductive paste becomes difficult, which is not preferable. Further, the upper limit of the molecular weight of the polymer compound is about 100,000, and if the molecular weight is increased to be higher than the above, the viscosity is increased, and uniform treatment of the surface of the silver fine particles becomes difficult. When considering the treatment uniformity and treatment effect of the polymer compound on the surface of the silver fine particles, it is preferably a dispersing agent having two functional groups of an acidic functional group and a basic functional group, or a dispersing agent having an acid value and having Amine valence dispersant.

As the above-mentioned polymer-based dispersant, those generally commercially available as a pigment dispersant can be used, and specifically, they are listed as ANTI-TERRA-U, ANTI-TERRA- 205, DISPERBYK-101, DISPERBYK-102, DISPERBYK-106, DISPERBYK-108, DISPERBYK-109, DISPERBYK-110, DISPERBYK-111, DISPERBYK-112, DISPERBYK-116, DISPERBYK-130, DISPERBYK-140, DISPERBYK-142, DISPERBYK-145, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-168, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, DISPERBYK-180, DISPERBYK- 182, DISPERBYK-183, DISPERBYK-184, DISPERBYK-185, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2008, DISPERBYK-2009, DISPERBYK-2022, DISPERBYK-2025, DISPERBYK-2050, DISPERBYK-2070, DISPERBYK-2096, DISPERBYK-2150, DISPERBYK-2155, DISPERBYK-2163, DISPERBYK-2164, BYK-P104, BYK-P104S, BYK-P105, BYK-9076, BYK-9077, BYK-220S (made by BYK Chemical Co., Ltd.); EFKA 4008, EFKA 4009, EFKA 4046, EFKA 4047, EFKA 4010, EFKA 4015, EFKA 4020, EFKA 4050, EFKA 4055, EFKA 4060, EFKA 4080, EFKA 4300, EFKA 4330, EFKA 4400, EFKA 4401, EFKA 4402, EFKA 4403, EFKA 4406, E FKA 4800, EFKA 5010, EFKA 5044, EFKA 5244, EFKA 5054, EFKA 5055, EFKA 5063, EFKA 5064, EFKA 5065, EFKA 5066, EFKA 5070 (manufactured by BASF, Japan); SOLSPERSE 3000, SOLSPERSE 13240, SOLSPERSE 13940, SOLSPERSE 16000, SOLSPERSE 17000, SOLSPERSE 18000, SOLSPERSE 20000, SOLSPERSE 21000, SOLSPERSE 24000SC, SOLSPERSE 24000GR, SOLSPERSE 26000, SOLSPERSE 27000, SOLSPERSE 28000, SOLSPERSE 31845, SOLSPERSE 32000, SOLSPERSE 32500, SOLSPERSE 32550, SOLSPERSE 34750, SOLSPERSE 35100, SOLSPERSE 35200, SOLSPERSE 36000, SOLSPERSE 36600, SOLSPERSE 37500, SOLSPERSE 38500, SOLSPERSE 39000, SOLSPERSE 41000 (manufactured by LUBRIZOL Co., Ltd.); AJISUPER PB821, AJISUPER PB822, AJISUPER PB881, AJISUPER PN-411, AJISUPER PA-111 (Ajinomoto Fine-Techno Co., Inc.); DISPARLON KS-860, DISPARLON KS-873N, DISPARLON 7004, DISPARLON 1831, DISPARLON 1850, DISPARLON 1860, DISPARLON DA-7301, DISPARLON DA-325, DISPARLON DA-375, DISPARLON DA-234 (manufactured by Nanben Chemical Co., Ltd.); FLOREN DOPA-15B, FLOREN DOPA-17HF, FLOREN DOPA-22, FLOREN DOPA-33, FLOREN G-700, FLOREN G-820, FLOREN G-900 Chemical Co., Ltd.) and so on. These pigment dispersants may be used alone or in combination of two or more.

Next, the conductive paste containing the silver fine particles of the present invention will be described.

The conductive paste of the present invention may be a fire-forming paste and a polymer paste. In any case, in the case of a baked paste, the silver fine particles and the glassy material of the present invention are used, and other components such as a binder resin and a solvent may be blended as needed. Further, in the case of the polymer type paste, it is composed of the silver fine particles and the solvent of the present invention, and other components such as a binder resin, a curing agent, a dispersing agent, and a rheology adjusting agent may be blended as needed.

As the binder resin, those known in the art can be used, and are exemplified by cellulose resins such as ethyl cellulose and nitrocellulose, polyester resins, urethane-modified polyester resins, and epoxy resins. Various polyester resin, acrylic modified polyester and other modified polyester resin, polyurethane resin, vinyl chloride. Vinyl acetate copolymer, acrylic resin, epoxy resin, phenol resin, alkyd resin, butyral resin, polyvinyl alcohol, polyimide, polyamidimide, and the like. These binder resins may be used alone or in combination of two or more.

As the solvent, those skilled in the art can be used, for example, tetradecane, toluene, xylene, ethylbenzene, diethylbenzene, cumene, pentylbenzene, p-isopropyltoluene (cymene). Hydrocarbon solvent such as tetrahydronaphthalene and petroleum aromatic hydrocarbon mixture; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl Ethers such as ether, propylene glycol mono-tert-butyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether Class, or glycol ether solvent; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate a glycol ester solvent such as propylene glycol monoethyl ether acetate; a ketone solvent such as methyl isobutyl ketone or cyclohexanone; terpineol, linalool, geraniol ( Geraniol), citronellol a terpene alcohol such as (citronellol); an alcohol solvent such as n-butanol, a second butanol or a third butanol; a glycol solvent such as ethylene glycol or diethylene glycol; and γ-butyl Lactone and water. The solvent may be used singly or in combination of two or more.

The content of the silver fine particles in the conductive paste varies depending on the application, but it is preferably as close as possible to 100% by weight, for example, in the case of wiring formation.

The conductive paste of the present invention can be mixed by using various kneading machines and dispersing machines such as a detonator, a can grinder, a triaxial roll grinder, a rotary mixer, and a two-axis kneading machine. Obtained by dispersion.

The conductive paste of the present invention can be used for screen printing, inkjet printing, gravure printing, transfer printing, roll coating, flow coating, spray coating, spin coating, dipping, blade coating, plating, etc. Among various coating methods.

Further, the conductive paste of the present invention can be formed as an electrode formation of an FPD (flat panel display), a solar cell, an organic EL or the like, or a wiring of an LSI substrate, in particular, wiring of fine grooves, through holes, and buried holes of contact holes. Forming materials used. Moreover, it can be suitably used for high-temperature baking applications for forming an internal electrode of a laminated ceramic capacitor or a laminated inductor, and of course, it can be suitably used as a flexible substrate or an IC card because it can be fired at a low temperature. And wiring forming materials and electrode forming materials on other substrates. Further, it can be used as a conductive film for an electromagnetic wave protective film or infrared reflection shielding. It is also possible to use a bonding material for component mounting in electronic mounting.

<effect>

The present invention is directed to preparing an alcohol solvent (solution A) using silver nitrate and an amine complex of silver nitrate prepared by one or more kinds of water-soluble or water-soluble aliphatic amines having 2 to 4 carbon atoms, and the above-mentioned liquid A An aqueous solution (B liquid) obtained by dissolving ascorbic acid or isoascorbic acid and a halide is prepared, and the liquid A and the liquid B are mixed by using a static mixer, and are added to a container in which water has been placed and stirred. , the silver particles obtained are washed. The fact that the silver fine particles of the present invention obtained by drying have excellent low-temperature sinterability.

The reason why the silver fine particles of the present invention obtained by the above-mentioned production method are excellent in the low-temperature sinterability is considered to be a reduction of 1.6 × 10 ^-3 mol of a halide to silver nitrate 1 mol. In the reaction solution, the slurry of the obtained silver fine particles is agglomerated, and subsequent washing is facilitated, so that the amount of carbon of the silver fine particles can be made 0.25% by weight or less. Further, according to the above production method, even if the drying temperature exceeds 30 ° C, the obtained silver fine particles have a crystallinity of 2.8 or more.

Example

The invention is specifically illustrated by the following examples of the invention.

The average particle diameter of the silver particles was photographed using a scanning electron micrograph "S-4800" (manufactured by HITACHI), and the particle size of the ball was measured for 100 or more particles using the photograph, and the average value was calculated as an average. Particle size (D _SEM ).

The specific surface area of the silver particles is determined by the BET method using "Monosorb MS-11" (manufactured by Quantachrome Co., Ltd.). Show.

The silver microparticle slurry after the reduction reaction is washed. The amount of the carbon of the dried silver granules was determined by using the "Essence Metal Carbon and Sulfur Analyzer EMIA-2200" (manufactured by Horiba, Ltd.).

The crystal diameter (D _X ) of the silver fine particles was obtained by using an X-ray diffraction device "RINT 2500" (manufactured by RIGAKU Co., Ltd.), and the peak of the surface index (1, 1, 1) was obtained by using the Kα line of Cu as a line source. The half value is wide and the crystal diameter is calculated by Scherrer's formula.

The degree of crystallinity of the silver fine particles is expressed by the ratio of the average particle diameter (D _SEM ) to the crystal diameter (D _X ) (D _SEM /D _X ).

The halogen content in the silver fine particles was measured by burning 20 mg of the sample at 1100 ° C in a combustion tube, and the generated gas was collected and determined by ion chromatography using a combustion tube type oxycombustion/ion chromatography.

(%) Caused by heating of the silver particles to crystallize the rate of change in the crystal diameter of the silver fine particles using the system before the silver crystal particles 150 heating deg.] C after 30 minutes of the diameter (D _X) is heated with a diameter (D _X), according to the The value calculated by the number 1 is described. Further, the heating condition was changed to a rate of change in crystal diameter in the same manner at 210 ° C for 30 minutes.

<Number 1> Rate of change of crystal diameter (%) = crystal diameter (D _X ) of silver fine particles after heating / crystal seed diameter (D _X ) of the silver fine particles before heating × 100

The specific resistance of the conductive coating film is applied to a conductive paste to be described later. After pre-drying at 120 ° C on a polyimide film, each conductive coating film obtained by heat-hardening at 150 ° C, 210 ° C, and 300 ° C for 30 minutes was used as a 4-terminal resistance measuring device "ROLESTA". GP/MCP-T600" (manufactured by Mitsubishi Chemical Corporation) measured the specific resistance from the sheet resistance and the film thickness.

<Example 1-1: Production of silver fine particles>

Add 5.16 kg of silver nitrate to 25.8 L of methanol and 4.89 kg of n-butylamine in a 50 L vessel, and then mix while cooling to 15 ° C or less. Stir and prepare solution A. In addition, 27.8 L of water and 8.03 kg of isoascorbic acid were weighed and dissolved in a 50 L vessel, and then 3.78 g of sodium chloride was added and the mixture was cooled to 15 ° C or lower. Stir and prepare solution B.

Then, while mixing the liquid A and the liquid B with a static mixer, the mixture was stirred in a vessel having a water of 7 L, and the reaction system was cooled to 25 ° C or lower and stirred for 5 hours, and then allowed to stand for 30 minutes to settle the solid components. . After the supernatant was removed by decantation, it was suction-filtered using a filter paper, followed by washing with methanol and pure water, and filtering.

One part of the solid content of the obtained silver fine particles was dried in a dryer at 40 ° C for 6 hours, and then pulverized to obtain silver fine particles of Example 1-1.

The particle shape of the obtained silver fine particles was granular, the carbon amount was 0.20% by weight, the average particle diameter (D _SEM ) was 81.7 nm, the crystal diameter D _X was 23.8 nm, and the degree of polycrystallization (D _SEM /D _X ) was 3.4. The BET specific surface area was 5.3 m ² /g, the halogen content was 690 ppm, the rate of change in crystal diameter (150 ° C × 30 minutes) was 138%, and the rate of change in crystal diameter (210 ° C × 30 minutes) was 161%.

<Example 2-1: Production of Conductive Paste>

To 100 parts by weight of the silver fine particles of Example 1-1, 11.0 parts by weight of a polyester resin and 1.4 parts by weight of a curing agent were added, and diethylene glycol monoethyl ether was added so that the content of silver fine particles in the conductive paste became 70% by weight. , use rotation. The remixing machine "AWATORY ritaro ARE-310" (manufactured by THINKY Co., Ltd., registered trademark) is premixed and then uniformly kneaded using a triaxial roller. Dispersion treatment to obtain a conductive paste.

The conductive paste obtained above was applied onto a polyimide film having a thickness of 50 μm, and heated at 120 ° C, 210 ° C, and 300 ° C for 30 minutes to obtain a conductive coating film.

The specific resistance of the obtained conductive coating film after heat treatment at 120 ° C for 30 minutes is 9.5 × 10 ^-6 Ω. Cm, the specific resistance at a temperature of 210 ° C for 30 minutes is 4.1 × 10 ^-6 Ω. Cm, the specific resistance is 2.6×10 ^-6 Ω when heat treated at 300 ° C for 30 minutes. Cm.

Silver fine particles and a conductive paste were produced in accordance with the above Examples 1-1 and 2-1. The properties of each of the production conditions and the obtained silver fine particles and the conductive paste are listed.

Examples 1-2 to 1-3 and comparative particles 1-1 to 1-2:

Silver fine particles are obtained by changing various generation conditions of silver fine particles, respectively.

The manufacturing conditions at this time are shown in Table 1, and the characteristics of the obtained silver fine particles are shown in Table 3.

<Example 1-4: Production of silver fine particles>

60 g of a polymer compound "DISPERBYK-106" (trade name: manufactured by BYK Chemical Co., Ltd., Japan) was placed in a container in which 5.17 kg of a mixed solution of methanol and water (methanol: water = 10:1) was placed. Next, the washing obtained in Example 1-1 was measured. The concentration of the silver fine particles in the solid content of the filtered silver fine particles is measured in a manner of 3 kg in terms of silver fine particles. After adding the solid component of the aforementioned silver microparticles, it is stirred. After mixing for 100 minutes, methanol was distilled off, and dried in a vacuum dryer at 30 ° C for 7 hours, and then pulverized by a jet mill to obtain silver fine particles of Example 1-4.

Examples 1-5~1-6:

Silver fine particles are obtained by changing the type of the polymer compound and the processing conditions, respectively.

The manufacturing conditions at this time are shown in Table 2, and the characteristics of the obtained silver fine particles are shown in Table 3.

<Manufacture of Conductive Coatings> Examples 2-2 to 2-6 and Comparative Examples 2-1 to 2-2:

In addition to the type of the silver fine particles, the conductive paint and the conductive film were produced in accordance with the method for producing the conductive paint of the above-described Example 2-1.

The production conditions at this time and the properties of the obtained conductive coating film are shown in Table 4.

Industrial availability

Since the silver fine particle system of the present invention has a low carbon content after the reduction reaction, it is suitable as a raw material for a conductive paste which can be fired at a low temperature.

In addition, since the method for producing silver fine particles of the present invention can reduce the carbon content of the silver fine particles after the reduction reaction and obtain silver fine particles in a high yield, it is suitable as a method for producing silver fine particles excellent in low-temperature sinterability.

Claims (7)

A method for producing silver microparticles, which comprises preparing an alcohol solution (solution A) of silver nitrate amine complex prepared by using silver nitrate or more than one water-soluble or water-soluble aliphatic amine having 2 to 4 carbon atoms, and preparing An aqueous solution (solution B) obtained by dissolving ascorbic acid or erythorbic acid and a halide different from the above-mentioned liquid A, and mixing the liquid A and the liquid B with a static mixer to add water. After stirring in the container, the obtained silver particles are washed. The drying is carried out by adding a halide of 1.6 × 10 ^-3 mol or more to silver nitrate 1 mol in the liquid B described above. A silver fine particle obtained by the production method of claim 1, characterized in that the amount of carbon of the silver fine particles is 0.25 wt% or less. The silver fine particles of claim 2, wherein the surface of the particles of the silver fine particles is coated with a polymer compound having a molecular weight of 10,000 or more. The silver fine particles of claim 2 or 3, wherein the average particle diameter (D _SEM ) is 30 nm or more and 120 nm or less. A conductive paste containing the silver fine particles according to any one of claims 2 to 4. A conductive film formed using the conductive paste of claim 5. An electronic device having the conductive film of claim 6.