WO2007105636A1

WO2007105636A1 - Process for production of ultrafine silver particles and ultrafine silver particles produced by the process

Info

Publication number: WO2007105636A1
Application number: PCT/JP2007/054682
Authority: WO
Inventors: Takashi Mukuno; Taku Fujimoto; Takuya Sasaki
Original assignee: Mitsui Mining & Smelting Co., Ltd.
Priority date: 2006-03-10
Filing date: 2007-03-09
Publication date: 2007-09-20
Also published as: JP5065607B2; CN101384388A; JP2007239077A; KR20080100365A; TW200734090A

Abstract

The invention aims at providing ultrafine silver particles having diameters of nanometer order which exhibit low-temperature sinterability free from the influence of a dispersant and are reduced in the content of impurities to thereby attain lower electrical resistance and which are excellent in dispersibility. The aim is attained by a process for the production of ultrafine silver particles by a wet reduction method which is characterized by mixing a silver salt solution containing a silver salt, a chelating agent, and gelatin with a reducing agent solution containing a reducing agent and subjecting the obtained mixture to reduction to form ultrafine silver particles. The obtained ultrafine silver particles have a mean primary particle diameter of 100nm or below and are excellent in dispersibility.

Description

Specification

Technical field of fine silver particle production method and fine silver particle obtained by the production method

The invention according to the present application relates to a method for producing fine silver particles and fine silver particles obtained by the production method. In particular, an object is to provide fine silver particles suitable as a conductive paste or conductive filler for conductive ink used for forming fine wiring.

Background art

Conventionally, silver pastes and silver inks containing conductive fillers such as metal powders have been used for relatively high temperature firing such as simultaneous firing with a ceramic substrate to form a circuit. As disclosed in No. 1, there are applications in which it is mixed with various resin components such as printed circuit board wiring circuits, via hole filling, and component mounting adhesives and cured. In applications such as the latter, it has been common to obtain electrical conductivity only by contacting the powder particles without sintering the powder particles of the silver powder as the conductive filler.

However, in recent years, there has been a demand for reduction in electrical resistance and high connection reliability with respect to conductors formed using silver powder. As the resin component hardens, the filler silver powder itself is also sintered to become conductive. There is a growing demand for silver inks or silver pastes that exhibit the same. In general, in order to meet such requirements, efforts have been made to refine the particles of silver powder, which is a conductive filler, in consideration of lowering the sintering temperature.

[0004] As disclosed in Patent Document 2, conventional silver powder production uses a wet reduction process in which a silver ammine complex aqueous solution is produced with a silver nitrate solution and ammonia water, and an organic reducing agent is added thereto. It has been. In order to ensure low-temperature sinterability exceeding that of silver powder, silver ink containing silver nanoparticles has been proposed as disclosed in Patent Document 3.

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-107101

Patent Document 2: Japanese Patent Laid-Open No. 2002-334618

Patent Document 3: Japanese Patent Laid-Open No. 2002-324966

Disclosure of the invention Problems to be solved by the invention

[0006] However, with metal powders such as silver powder, it is difficult to achieve both atomization of particles and good particle dispersibility. For example, as disclosed in Patent Document 1 above, in the case of a silver ink containing silver nanoparticles, it is common to add a large amount of a dispersant as a protective colloid in order to ensure the dispersibility of the nanoparticles. Is. The dispersing agent used in such a case is generally a dispersing agent having a decomposition temperature higher than the sintering temperature of the silver nanoparticles, and the low temperature sintering characteristics of the silver nanoparticles themselves are sufficiently obtained. There are drawbacks such as

[0007] Further, it has been demanded that silver powder has a small amount of impurities. That is, the above-described wet reduction process is used for the production of silver powder, and the reducing agent, dispersant, etc. used in the process remain on the surface and inside of the silver powder particles. Therefore, it was an inevitable problem as long as the conventional manufacturing method was adopted. As the amount of impurities in the silver powder increases, the electrical resistance of the conductor formed using the conductive paste containing the silver powder increases.

[0008] From the above, in the field, fine silver particles having a primary particle diameter on the order of nm showing good particle dispersibility, exhibiting low-temperature sinterability that is not affected by the dispersant, and There has been a demand for products with low impurity content to achieve low resistance. Means for solving the problem

[0009] Therefore, as a result of intensive research, the inventors of the present invention have obtained fine silver particles having a particle size of nm level with excellent particle dispersibility by adopting the following production method. I came up with the idea of coming. Moreover, although a dispersant is used in this production method, the dispersant adhering to the silver particles can be easily removed afterwards.

[0010] The method for producing fine silver particles according to the present invention: The method for producing fine silver particles according to the present invention is a method for producing fine silver particles by a wet reduction method, wherein each component of silver salt, chelating agent, and gelatin is used. A silver salt-containing solution containing a reducing agent-containing solution containing a reducing agent is mixed to cause a reduction reaction to obtain fine silver particles.

[0011] In the method for producing fine silver particles according to the present invention, the silver salt is preferably silver nitrate. [0012] In the method for producing fine silver particles according to the present invention, the chelating agent comprises one or more selected from ethylenediamine complex, darconic acid, dalconate, pyrophosphate, pyrophosphate. It is preferable to use in combination.

[0013] In the method for producing fine silver particles according to the present invention, the reducing agent is a sulfite, formalin, hydroquinone, hydrazine, borohydride compound, or a combination of one or more selected. It is preferable to use it.

[0014] The silver salt-containing solution used in the method for producing fine silver particles according to the present invention preferably includes a gelatin content of 0.oigZi to i.oogZi with respect to a silver content of lgZi.

[0015] The silver salt-containing solution used in the method for producing fine silver particles according to the present invention preferably contains 0.lgZl to 50. OgZl as a silver content.

[0016] The reducing agent-containing solution used in the method for producing fine silver particles according to the present invention preferably has a reducing agent concentration of 0.1 molZl to 10. OmolZl.

[0017] Fine silver particles according to the present invention: The fine silver particles according to the present invention are fine silver particles obtained by the fine silver particle production method described in the above production method, and the average primary particle diameter thereof is It is characterized by being less than lOOnm.

The invention's effect

[0018] By employing the method for producing fine silver particles according to the present invention, fine silver particles exhibiting good particle dispersibility and having a primary particle diameter of lOOnm or less can be produced. In addition, by using gelatin in this production method, it is easy to remove the gelatin component adhering to the surface of the particles after the production of the fine silver particles, and it is easy to remove the original silver fine particles without being affected by the dispersant. Low temperature sinterability can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the method for producing fine silver particles and the best form of fine silver particles according to the present invention will be described.

Production form of fine silver particles according to the present invention: The fine silver particles according to the present invention are produced by a method of producing fine silver particles by a wet reduction method. That is, a silver salt-containing solution containing silver salt, a chelating agent and gelatin is brought into contact with a reducing agent-containing solution containing a reducing agent to cause a reduction reaction to obtain fine silver particles. The present invention is to be described later It has a great feature in that it uses a combination of a salt agent and gelatin. And this gelatin is described as a concept including glue. This gelatin remains adhered to the particle surface of the resulting fine silver particles, but can be easily peeled off from the particle surface by chemical treatment afterwards.

In the silver salt-containing solution, the gelatin content is preferably 0.oigZi to i.oogZi with respect to the silver content lg / 1. This is because when the gelatin content is less than 0. oigZi, it cannot function as a steric hindrance to prevent the reductive precipitation of fine silver particles and does not serve as a protective colloid. On the other hand, when the gelatin content exceeds 1.00 g, 1, the viscosity of the silver salt-containing solution will be affected, and the reduction precipitation rate of fine silver particles will be slowed, leading to a decrease in productivity. It is. In order to obtain an appropriate reduction deposition rate and to obtain stable particle dispersibility of the precipitated particles, it is more preferable to set the gelatin content in the range of 0.1 lgZl to 0.5 gZl. preferable. In addition, if it is planned to reduce the amount of gelatin remaining on the particle surface and exfoliate it later, it is preferable to dilute the gelatin concentration as much as possible.

[0022] Silver nitrate is preferably used as the silver salt in the silver salt-containing solution used in the method for producing fine silver particles according to the present invention. The use of silver nitrate as the silver supply source is excellent in solubility in water and ionization characteristics in water, so that the reaction with the chelating agent described later can be carried out smoothly. Regarding the silver concentration in the silver salt-containing solution, it is preferable to contain 0.lgZl to 50.OgZl as silver. If the silver concentration here exceeds 50. OgZl, fine particles with high particle dispersibility with a sharp particle size distribution tend to form coarse particles in the precipitated silver particles or tend to form agglomerated particles. Unable to get particles

. On the other hand, when the silver concentration is less than 0.1 lgZi, good power can be obtained as fine silver particles. The particle size resulting from reduction and precipitation easily varies, and the required industrial productivity is not satisfied. Become a thing. And the viewpoint power to make the particle size distribution more stable

More preferably, the force is in the range of 0.lgZl to 30.OgZl.

[0023] The chelating agent in the silver salt-containing solution used in the method for producing fine silver particles according to the present invention is one or two selected from ethylenediamine complex salt, darconic acid, dalconate, pyrophosphate, pyrophosphate. It is preferable to use a combination of species or more. This chelating agent In addition, silver ions supplied with silver salt strength in a silver salt-containing solution are stabilized as chelate complexes. By using a combination of the chelating agent listed here and the above gelatin, it becomes possible for the first time to efficiently produce fine silver particles having a particle size of nm order.

[0024] The chelating agent referred to here is that the addition amount is appropriately adjusted according to the amount of silver ions on the premise that it is in the range of the above-mentioned silver content, so that there is no particular limitation. I don't think so. However, in the case of the present invention, the silver salt-containing solution is preferably contained at a concentration of 0.01 molZl to 5. OOmolZl. The chelating agent described here is in a range that efficiently forms a chelate complex with silver ions ionized in a solution such as a silver salt source as a silver ion supply source. Among them, ethylenediamine tetraacetic acid tetrasodium salt forms the most stable silver chelate complex, suppresses the growth of silver particles, and promotes the formation of silver precipitation nuclei. It becomes easy to generate. Here, the addition amount of the chelating agent is originally determined according to the type of the chelating agent and the amount of silver in the solution. However, even if any of the above-mentioned chelate complexes is used, the chelating agent concentration is in the range of 0.01 molZl to 5.00 mol / 1, and therefore the general notation is adopted. When two or more chelating agents are used in combination, the total concentration of the two or more chelating agents may be in the range of 0.01 molZl to 5. OOmolZl. When the chelating agent concentration is less than 0. Olmol / 1, the aggregation of particles with slow particle growth tends to be remarkable. On the other hand, if the chelating agent concentration exceeds 5.OOmolZl, the silver particles grow faster and become larger silver particles.

[0025] In the method for producing fine silver particles according to the present invention, the reducing agent contained in the reducing agent-containing solution is selected from sulfites, formalin, hydroquinone, hydrazine, and borohydride compounds 1 It is preferable to use a species or a combination of two or more species. The sulfite referred to here is preferably one or more of sodium sulfite and potassium sulfite. In addition, it is preferable to use sodium borohydride (SBH) or potassium borohydride as the borohydride compound. The reducing agent-containing solution mentioned here is preferably a solution containing 0.1 to 10. OmolZl of a reducing agent. The reducing agent is used according to the amount of silver in the silver-containing solution, and the concentration of the reducing agent is 0. If it is less than ImolZl, the reduction of the existing silver ions becomes insufficient, the industrial economy is not satisfied, the amount of the solution for causing the reduction reaction increases, and the waste liquid treatment load increases. On the other hand, if the concentration of the reducing agent exceeds 10. OmolZl, the reducing agent concentration becomes too high, and no matter how the solution is stirred during the reduction reaction, there is a local heterogeneity of the reduction reaction. There is a tendency that the particle size distribution of fine silver particles becomes broad, and that connected particles are easily formed. In addition, the progress of particle agglomeration resulting in reduction precipitation becomes remarkable, and when an organic reducing agent is used, the amount of impurities contained in the particles (in this specification, the amount of impurities is regarded as the carbon content) is rapidly increased. Begin to become. In order to cause a more stable reduction precipitation reaction and stably produce fine silver particles having an excellent particle size distribution, it is more preferable to use a reducing agent as a solution containing 1.0 molZl to 5. OmolZl. .

[0026] From the above, when the silver salt-containing solution and the reducing agent-containing solution containing the reducing agent are mixed to cause a reduction reaction to obtain fine silver particles, the silver concentration (silver As) lgZi

Maintaining the reducing agent concentration at 1. OmolZl to 5. OmolZl in the range of ˜30 gZl is the most suitable condition for obtaining fine silver particles according to the present invention with good yield.

[0027] The liquid temperature of the mixed solution obtained by mixing the silver salt-containing solution and the reducing agent-containing solution during the reduction reaction is preferably 40 ° C to 80 ° C. Therefore, it is preferable to prepare both the liquid temperature of the silver salt-containing solution before mixing and the liquid temperature of the reducing agent-containing solution so that the liquid temperature is 40 ° C to 80 ° C after mixing. If the temperature of the mixture is less than 40 ° C, appropriate industrial productivity with a slow reduction reaction cannot be obtained. On the other hand, when the liquid temperature of the mixed liquid exceeds 80 ° C, the reduction reaction rate increases, and at the same time, the evaporation of moisture becomes remarkable, and the concentration fluctuation during the reduction reaction increases, so that the obtained fine silver particles The particle size distribution is broad.

Furthermore, the time required for the reduction reaction (hereinafter referred to as “reduction reaction time”) is preferably in the range of 20 minutes to 2 hours. When the reduction reaction time is less than 20 minutes, even if the upper limit of the above liquid temperature is adopted, sufficient reduction reaction does not proceed. On the other hand, even if the reduction reaction time exceeds 2 hours, the reduction of silver ions existing within 2 hours is usually almost complete. Even if silver ions are present in the solution at this stage, Originally precipitated silver particles grow and fine silver particles having a particle size of lOOnm or less cannot be obtained.

[0029] The fine silver particles obtained as described above are filtered, washed, dehydrated and dried to obtain fine silver particles.

It can be collected as (fine silver powder). However, it is preferable to store in a slurry state in order to maintain a very fine particle and a good dispersion state. In the case of storing in a slurry state, it is preferable to store the slurry in a silver particle slurry state using water as a solvent by washing by a conventional method. In order to obtain the fine silver particles according to the present invention in a dry state, various methods can be used, and the method and conditions are not particularly limited.

[0030] Fine silver particles according to the present invention: The fine silver particles according to the present invention are fine silver particles obtained by the fine silver particle production method described in the above production method, and have an average primary particle diameter force. It is less than SlOOnm. The average primary particle size referred to here is the average primary particle size (hereinafter referred to as `` D

Referred to as “IA”. ). Here, in the case of fine silver particles according to the present invention, the average particle diameter obtained by image analysis of particles in an observed image obtained by employing a magnification of 30000 times or more. In addition, the image analysis of fine silver powder observed using a scanning electron microscope (SEM) in this specification is performed using IP-1000PC manufactured by Asahi Engineering Co., Ltd., with a circularity threshold of 10 and an overlap of 20. Perform circular particle analysis to determine the average primary particle size D

IA

It is a thing. The average primary particle diameter D obtained by image processing of the observation image of this fine silver powder is obtained directly from the SEM observation image power.

IA

It will be caught. The D of the fine silver particles referred to in the present invention is observed by the present inventors.

IA

As far as we can see, the force almost falls within the range of 15 nm to 100 nm. In reality, a finer particle size may be confirmed, and the lower limit is not clearly stated.

[0031] Hereinafter, the powder characteristics capable of specifying the fine silver particles according to the present invention will be described. Furthermore, as an effect having the above-mentioned powder characteristics, the film density of the conductive film obtained by the silver paste using the fine silver powder according to the present invention is as high as 4. OgZcm ³ or more. The film density here refers to a silver paste with a composition of 70 wt% fine silver particles, 5 wt% ethyl cellulose, and 25 wt% turbeneol. Create it on film and put it at 80 ° C The film density was measured after drying. Considering that the film density of the silver powder composed of conventional nanoparticles is less than 4. Og / cm ³ , the fine silver particles according to the present invention are excellent in dispersibility and packing property as nanoparticles. It is supported that Hereinafter, examples will be described.

Example 1

[0032] In this example, lOOg of silver nitrate as silver salt, 150g of ethylenediaminetetraacetic acid / 4sodium salt as chelating agent, and 15g of gelatin were dissolved in 2.0 liters of pure water by stirring. A silver salt-containing solution having a liquid temperature of 50 ° C. was prepared. Silver concentration 31.8gZl (as silver) in the silver salt-containing solution at this time, chelating agent concentration 75gZl (l. 66molZD, gelatin concentration 7.5g

Zi.

On the other hand, 150 g of potassium sulfite as a reducing agent was dissolved in 2.0 liters of pure water with stirring to prepare a reducing agent-containing solution having a liquid temperature of 50 ° C. The reducing agent concentration of the reducing agent-containing solution at this time is 75 gZl (0.47 molZD).

[0034] Next, the reducing agent-containing solution was added all at once to the silver salt-containing solution to obtain a mixed solution. Then, while maintaining the liquid temperature of this mixed liquid at 50 ° C., stirring was performed for 1 hour to carry out a reduction reaction, thereby generating fine silver particles in the mixed liquid.

[0035] The fine silver particles obtained as described above were washed by an ultrafiltration method to remove excess impurities, and collected as a fine silver particle slurry using pure water as a solvent.

[0036] The powder properties of the fine silver particles obtained as described above are listed in Table 1 in the same manner as in the other Examples and Comparative Examples. The fine silver particles obtained in Example 1 are referred to as fine silver particles A. FIG. 1 shows an electron microscope observation image (observation magnification: 100,000 times) of the fine silver particles A. As for the fine silver particles A, the particles were observed with a transmission electron microscope as shown in FIG. 2, and it was confirmed that a gelatin coating was formed on the surface of the particles. It can be seen that the transparent layer around the grain in Fig. 2 is a gelatin coating, in which fine silver particles are present.

Example 2

[0037] This Example 2 is different only in that the amount of the ethylenediamine tetraacetic acid-4sodium salt, which is the chelating agent of Example 1, was changed and a silver salt-containing solution was prepared as follows. The

[0038] In this example, 100 g of silver nitrate as a silver salt, 300 g of ethylenediaminetetraacetic acid, tetrasodium salt, and 15 g of gelatin as a chelating agent were stirred and dissolved in 2.0 liters of pure water. A silver salt-containing solution having a liquid temperature of 50 ° C. was prepared. The silver concentration in the silver salt-containing solution at this time is 31.8 gZl (as silver), the chelating agent concentration is 150 gZl, and the gelatin concentration is 7.5 gZl.

Hereinafter, fine silver particles were produced in the same manner as in Example 1, and collected as a fine silver particle slurry state using pure water as a solvent.

[0040] The powder characteristics of the fine silver particles obtained as described above are listed in Table 1 in the same manner as in the other Examples and Comparative Examples. The fine silver particles obtained in Example 2 are referred to as fine silver particles B. FIG. 3 shows a transmission electron microscope image (observation magnification: 500 000 times) of the fine silver particles B.

Comparative example

[0041] [Comparative Example 1]

This Comparative Example 1 is different in that the silver salt-containing solution was prepared as follows by omitting the ethylenediamine tetraacetic acid · 4 sodium salt which is the chelating agent of Example 1. That is, there is no chelating agent to see the state of the case.

[0042] In this comparative example, 100 g of silver nitrate and 15 g of gelatin as silver salts were dissolved in 2.0 liters of pure water with stirring to prepare a silver salt-containing solution having a liquid temperature of 50 ° C. At this time, the silver concentration in the silver salt-containing solution was 31.8 gZl (as silver), and the gelatin concentration was 7.5 gZl.

[0043] Hereinafter, fine silver particles were produced in the same manner as in Example 1, and collected as a fine silver particle slurry state using pure water as a solvent.

[0044] The powder characteristics of the fine silver particles obtained as described above are listed in Table 1 in the same manner as in the other Examples and Comparative Examples. The fine silver particles obtained in this comparative example are referred to as fine silver particles C. FIG. 5 shows an electron microscope observation image (observation magnification: 50000 times) of the fine silver particles C.

[0045] [Comparative Example 2]

In Comparative Example 2, a silver salt-containing solution was prepared in the following manner by using quenoic acid monohydrate instead of ethylenediamine tetraacetic acid-4 sodium salt, which is the chelating agent of Example 1. Only the point is different.

[0046] In this example, lOOg of silver nitrate as a silver salt, 150 g of citrate '1 hydrate as a chelating agent, and 15 g of gelatin as a dispersing agent were dissolved in 2.0 liters of pure water by stirring. Then, a silver salt-containing solution having a liquid temperature of 50 ° C. was prepared. The silver concentration in the silver salt-containing solution at this time is 31.8 gZl (as silver), the chelating agent concentration is 75 gZl, and the gelatin concentration is 7.5 gZl.

[0047] Hereinafter, fine silver particles were produced in the same manner as in Example 1, and collected as a fine silver particle slurry state using pure water as a solvent.

[0048] The powder characteristics of the fine silver particles obtained as described above are listed in Table 1 in the same manner as in the other Examples and Comparative Examples. The fine silver particles obtained in Comparative Example 1 are referred to as fine silver particles D. FIG. 4 shows an electron microscope observation image (observation magnification: 100,000 times) of the fine silver particles D.

<Consideration between Example and Comparative Example> The above-described Examples and Comparative Examples will be compared with reference to Table 1.

[0050] [Table 1]

[0051] As can be seen from Table 1, the fine silver particles A and fine silver particles B according to the present invention described in Example 1 and Example 2 have a mean primary particle size of lOOnm or less. In addition, the film density measurement of the conductive film formed by the silver paste using the fine silver particles shows a good filling property exceeding 4. Og / cm ³ . Therefore, when the fine silver particles of each Example are used as a conductive base or a conductive filler of a conductive ink to form a conductor, it is possible to obtain a conductive film having a high film density and a low electric resistance. Become. In addition, there is little aggregation of particles and particle content It is also clear from the scanning or transmission electron microscope images in Fig. 1 or Fig. 3 that the powder has excellent dispersibility. Therefore, it can be expected that the surface shape of the formed conductor film will be smooth.

[0052] In contrast, the fine silver particles of Comparative Example 1 returned silver particles in a reaction system that did not contain the chelating agent, ethylenediamine tetraacetic acid / 4 sodium salt, even when gelatin was contained in the silver salt-containing solution. This is a result demonstrating that when the original precipitation is performed, the particle dispersibility deteriorates. That is, from the scanning electron microscope observation image in FIG. 5, it is clear that the particles are agglomerated and the particle dispersibility is poor. Furthermore, the film density is 3.7 gZcm ^3, which is lower than 4. OgZcm ³ . Therefore, using the fine silver particles of this comparative example as a conductive paste for conductive paste or conductive ink and forming a conductor, a conductive film having a high film density and a low electrical resistance cannot be obtained. The membrane can be expected to have a porous structure.

[0053] Further, in Comparative Example 2, fine silver particles D are obtained by using citrate monohydrate instead of ethylenediamine tetraacetic acid / 4 sodium salt as a chelating agent. The film density measurement using these fine silver particles D also showed good packing properties exceeding 4. OgZcm ^3, and the fact that there was little aggregation of particles and excellent particle dispersibility was also observed from the scanning electron microscope image of FIG. it is obvious. However, it can be understood that the average primary particle size exceeds lOOnm, and it is impossible to stably produce an average primary particle size of lOOnm or less.

Industrial applicability

[0054] The method for producing fine silver particles according to the present invention can utilize a conventional silver particle production apparatus by a wet method as it is, and does not require new production equipment. Therefore, it is possible to efficiently produce fine silver particles having a primary particle diameter on the order of _nm showing good particle dispersibility without causing an increase in production cost. The fine silver particle silver powder according to the present invention can easily remove the gelatin component adhering to the particle surface later by using gelatin in the production process, and is not affected by the dispersant. It becomes possible to obtain the original low temperature sinterability of fine silver particles.

Brief Description of Drawings

FIG. 1 is a scanning electron microscope image of fine silver particles according to Example 1.

FIG. 2 is a transmission electron microscope image of fine silver particles according to Example 1.

FIG. 3 is a scanning electron microscope observation image of fine silver particles according to Example 2. IV] Scanning electron microscope image of fine silver particles according to Comparative Example 1.圆 5] Scanning electron microscope image of fine silver particles according to Comparative Example 2.

Claims

The scope of the claims

[1] A method for producing fine silver particles by a wet reduction method,

Fine particles characterized in that a silver salt-containing solution containing silver salt, a chelating agent, and gelatin components and a reducing agent-containing solution containing a reducing agent are mixed to cause a reduction reaction to obtain fine silver particles. Silver particle manufacturing method.

2. The method for producing fine silver particles according to claim 1, wherein the silver salt uses silver nitrate.

[3] The chelating agent according to claim 1 or 2, wherein the chelating agent is one or a combination of two or more selected from ethylenediamine complex, darconic acid, dalconate, pyrophosphate, and pyrophosphate. A method for producing fine silver particles.

[4] The fine-grained silver according to any one of claims 1 to 3, wherein the reducing agent is a sulfite, formalin, hydroquinone, hydrazine, borohydride compound, or one selected from a combination of two or more. Particle manufacturing method.

[5] The silver salt-containing solution has a gelatin content of 0.01 g / l to l.l with respect to a silver content of lg / 1.

The method for producing fine silver particles according to any one of claims 1 to 4, comprising OOgZl.

[6] The method for producing fine silver particles according to any one of [1] to [5], wherein the silver salt-containing solution contains 0.1 lgZl to 50. OgZl as silver.

7. The reducing agent-containing solution has a reducing agent concentration of 0.1 molZl to 10. OmolZl.

The method for producing fine silver particles according to claim 6.

[8] Fine silver particles obtained by the method for producing fine silver particles according to any one of claims 1 to 7, wherein the average primary particle diameter is lOOnm or less. particle.