KR102302205B1 - Silver powder manufacturing method - Google Patents

Abstract

The present invention relates to a silver powder having excellent dispersibility and uniform particle distribution, and a method for manufacturing the same.

Description

Silver powder and its manufacturing method {SILVER POWDER MANUFACTURING METHOD}

The present invention relates to a silver powder having a uniform particle size distribution and excellent dispersibility and a method for manufacturing the same.

Silver (Ag) powder has physical properties such as high electrical conductivity, thermal conductivity and oxidation resistance, and is widely applied to various materials such as electronic material pastes, conductive inks, shielding agents, and spacers.

On the other hand, silver powder has a very large surface area because the specific surface area increases in proportion to the square of the change in the powder diameter as the particle size is small. In many cases, desired physical properties cannot be achieved when applied to various fields due to poor fluidity and remarkably poor dispersibility and storage stability.

As a method of manufacturing silver powder, a method of reducing a metal precursor to form a particle, and dispersing it using a dispersant, etc. is known, but it is difficult to control the shape, size, and particle size distribution of the particle, There is a problem that the characteristic change in the state to which acidity and particles are applied is large (Patent Document 1).

Accordingly, research and development on a method for manufacturing silver powder that can have a uniform particle size distribution while increasing process efficiency, can significantly improve dispersibility without agglomeration between powders after manufacturing, and achieve stable and excellent physical properties for a long period of time This is a necessary situation.

Japanese Patent Laid-Open No. 2009-074171 (2009.04.09.)

The present invention has been devised to solve the above problems, and it is an object of the present invention to provide a silver powder having a narrow particle size distribution and capable of preventing agglomeration of particles, thereby remarkably improving dispersibility, and a method for manufacturing the same. do.

Another object of the present invention is to provide a method of manufacturing a silver powder capable of stably implementing excellent physical properties over a long period of time while maximizing manufacturing process efficiency.

Another object of the present invention is to provide a silver powder having excellent conductivity, which can lower electrode resistance and increase battery efficiency.

One aspect of the present invention for achieving the above object is

To provide a method for producing silver powder prepared by reacting an aqueous solution containing a silver precursor, a complexing agent, a polysaccharide-based polymer dispersant having a carboxyl group or a salt thereof, and a hydrazine-based compound.

Another aspect of the present invention is to further include an alkali compound such as an alkali metal salt in the above aspect.

Another aspect of the present invention is

preparing a first aqueous solution containing a silver precursor and a complexing agent;

A second aqueous solution preparation step comprising a polymer dispersant having a carboxyl group or a salt thereof and a hydrazine-based compound;

A precipitation step of preparing silver powder by dropping the first aqueous solution into the second aqueous solution;

It relates to a method for producing a spherical silver powder comprising a.

Another aspect of the present invention is to further include an alkali compound such as an alkali metal salt in the first aqueous solution.

Another aspect of the present invention comprises a post-treatment step further comprising any one or more steps of washing, filtering, drying, and pulverizing the precipitated silver particles after manufacturing by precipitating the silver powder in the above aspects. To provide a method for preparing a spherical silver powder.

In one aspect of the present invention, the polymer-based dispersant containing a carboxyl group or a salt thereof is alginic acid, sodium alginate, potassium alginate, calcium alginate, ammonium alginate, It may be any one or more selected from gum arabic (Arabia gum) and gelatin (Gelatin).

In addition, in one embodiment of the present invention, the polymer-based dispersant may be a carboxymethyl cellulose salt.

In the present invention, the hydrazine-based compound may mean hydrazine, a hydrazine derivative, a hydrazine hydrate, or the like.

In another embodiment of the present invention, the spherical silver powder may have a D50 of 0.5 to 3.0 μm, a D50/Dm of 1.0 to 1.3, and a (D90-D10)/D50 of 0.9 to 1.8. (The cumulative 10% by weight particle diameter measured by laser diffraction is denoted as D10, the cumulative 50% by weight particle diameter is denoted as D50, and the cumulative 90% by weight particle diameter is denoted as D90, and Dm is a scanning electron microscope (SEM) image. It means the average particle size of the primary particles obtained in the analysis.)

In one aspect of the present invention, the silver powder may have a true specific gravity of 10 to 10.4 g/cm ³ , a BET of 0.1 to 5.0 m ² /g, and a tap density of 2.0 to 6.5 g/cc.

Another aspect of the present invention is a conductive paste including spherical silver powder prepared by the above method.

The present invention can provide a spherical silver powder having a narrow particle size distribution, a low degree of agglomeration between particles, and remarkably improved dispersibility, and a method for manufacturing the same.

Furthermore, it has the advantage of realizing excellent stability of physical properties in the long term and maximizing physical properties when applied to conductive pastes, etc.

In addition, when applied to a conductive paste, etc., dispersibility is significantly improved, fluidity is increased, and electrode resistance can be lowered due to excellent conductivity, thereby maximizing battery efficiency.

In addition, the powder manufacturing process is simple and the process efficiency is high, so it is possible to improve speed and productivity, and there is an advantage in that product reliability can be secured for a long period of time.

Hereinafter, the present invention will be described in more detail through examples including the accompanying drawings. However, the following examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

In the present invention, the unit of % used without special mention means % by weight.

The inventors of the present invention have conducted a lot of research on a method for preparing a silver powder capable of preventing particle binding or agglomeration and implementing excellent dispersibility in providing a silver powder applicable to various material fields, including conductive pastes. .

As a result, when silver powder is prepared by reacting a solution containing a silver precursor, a complexing agent, a polymer dispersing agent having a carboxyl group or a salt thereof, and a hydrazine-based compound, the sphericity of the resulting silver powder is increased, and the silver having an agglomerated structure It was found that the shape of the particles was significantly reduced.

In addition, in the present invention, when an alkali compound such as an alkali metal salt is further added to the solution, it has been found that the physical properties are further increased, thereby completing the present invention.

In addition, the present inventors, when reacting the reactant,

preparing a first aqueous solution containing a silver precursor and a complexing agent;

A second aqueous solution preparation step comprising a polymer dispersing agent having a carboxyl group or a salt thereof and a hydrazine-based compound;

A precipitation step of preparing silver powder by dropping the first aqueous solution into the second aqueous solution;

Specifically, in the case of changing to a manufacturing method comprising

In addition, it was confirmed that when an alkali compound such as an alkali metal salt was added to the first solution and reacted by dropwise addition to the first solution, a better effect was confirmed.

In the above manufacturing method, when silver particles are precipitated by dropping the first aqueous solution into the second aqueous solution at a constant speed, the silver particles grow relatively slowly, the binding or aggregation of the particles is effectively prevented, and the particle size of the silver powder is uniform, the particle size distribution is narrow, and the dispersibility of silver powder is remarkably improved.

The silver powder prepared in this way can be applied to various material fields such as curable electrode materials, low-temperature firing electrode materials, and solar cell electrode materials. properties can be implemented.

Hereinafter, a method for producing a silver powder, a silver powder, and a conductive paste including the same according to the present invention will be described in more detail.

First, the silver precursor of the present invention is not limited as long as the silver precursor can dissociate into silver ions in an aqueous solution. For example, any one or two selected from the group consisting of silver nitrate, silver chloride, silver bromide and silver fluoride. It may include a mixture of the above, more preferably silver nitrate, but is not limited thereto.

In the first aqueous solution, the amount of the silver precursor is 5 to 80% by weight, preferably 10 to 50% by weight, so that it is more effective to improve the reactivity when preparing the silver powder.

The complexing agent of the present invention is not limited as long as it can stably form a complex by combining with a silver precursor, but may be selected from ammonia or ammonium salt as a non-limiting example, and the ammonium salt is ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) Any one or a mixture of two or more selected from the group consisting of a salt, an ammonium nitrate (NH ₄ NO ₃ ) salt and a monobasic ammonium phosphate ((NH ₄ ) ₂ HPO _{4 ) salt may be used, but is not limited thereto} . Preferably, the use of ammonia is effective in producing spherical particles and developing the crystal structure of silver.

The content of the complexing agent may be 0.1 to 20% by weight, preferably 0.5 to 15% by weight of the total solution in order to improve the stability of the silver-complex produced in the first aqueous solution.

By adjusting the composition ratio of the silver precursor and the complexing agent in the first aqueous solution, the silver-complex formation efficiency may be increased. As an embodiment, it is effective to use 1.1 to 5 moles, preferably 1.5 to 3 moles, of the complexing agent relative to the silver atoms in the silver precursor compound because the silver-complex has high stability.

In the present invention, all of the raw materials for producing the silver particles may be mixed and reacted, but the formation of aggregates is increased, but the prepared first aqueous solution containing a silver precursor, a complexing agent and/or an alkali compound such as an alkali metal salt is mixed with a carboxyl group or its When the reaction is induced while being slowly added dropwise to the second aqueous solution containing the polymer dispersing agent having a salt and the hydrazine-based compound, it is more preferred because it is possible to significantly achieve effects such as better sphericity, excellent dispersibility, and non-generation of aggregates. .

In the present invention, when the first aqueous solution and the second aqueous solution are prepared and reacted, the silver-complex formation efficiency can be increased by adjusting the composition ratio of the silver precursor and the complexing agent in the first aqueous solution. As an embodiment, it is effective to use 1.1 to 5 moles, preferably 1.5 to 3 moles, of the complexing agent relative to the silver atoms in the silver precursor compound because the silver-complex has high stability.

The alkali compound may be, for example, any one or a mixture of two or more selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide, and more preferably sodium hydroxide.

The solution of the alkali compound may be used by adjusting the content so that the pH of the mixed solution becomes 8 to 14, preferably 9 to 13, more preferably 9.5 to 12, in order to improve the stability of the silver-complex.

In the present invention, the polymer-based dispersant having a carboxyl group or a salt thereof is specifically selected from sodium alginate, potassium alginate, and calcium alginate. It is best to achieve the object of the present invention. . However, even when a carboxymethylcellulose salt is used, the object of the present invention can be achieved to some extent, and therefore, it is included in the scope of the present invention.

The content of the polymer-based dispersant may be appropriately adjusted within the range of achieving the object of the present invention, but in the second aqueous solution, 0.01 to 10% by weight, preferably 0.1 to 5% by weight, improves dispersibility and reactivity more effective to make

Next, in one embodiment of the present invention, the hydrazine-based compound refers to, for example, hydrazine, a hydrazine derivative or hydrazine hydrate, and specifically, it is combined with a dispersing agent having a carboxylic acid group or a salt thereof in the present invention, rather than when other reducing agents are used. As a result, it was found that it has an excellent effect of spheroid formation and uniformity of particle size distribution, dispersibility and no agglomeration.

The content of the reducing agent may be 1 to 25 wt%, preferably 2 to 15 wt%, in terms of improving the dispersibility of the silver powder and improving the reactivity with the silver precursor compound, but for the purpose of the present invention The scope is not limited as long as it achieves

The stirring speed can be easily adjusted within the range of achieving the object of the present invention, but it is preferable to stir relatively strongly at 1,000 rpm to 5,000 rpm, and more preferably, it is performed at a stirring speed of 1,500 rpm to 2,500 rpm. it's good

Next, when the method of dropping the first aqueous solution to the second aqueous solution is adopted in the present invention, the input method will be described.

In one aspect of the present invention, when the first aqueous solution is added dropwise to the second aqueous solution, the first aqueous solution may be added simultaneously or dividedly, but for example, it is better to continuously add the first aqueous solution in a uniform amount. For example, it is to be dripped over 30 minutes to 12 hours in a uniform amount.

In the case of continuous and uniform input as described above, the crystal structure of silver is uniformly generated, so that the particle size distribution can be more uniform even after pulverization, and there is an effect of preventing agglomeration between silver powders.

At the time of the dropwise addition, it is better to stir the aqueous solution to improve dispersion and produce uniform particles. The stirring speed can be easily adjusted within the range of achieving the object of the present invention, but it is preferable to stir relatively strongly at 1,000 rpm to 5,000 rpm, and more preferably, it is performed at a stirring speed of 1,500 rpm to 2,500 rpm. it's good

In one aspect of the present invention, the silver particle precipitation reaction temperature is not particularly limited, but may be, for example, carried out in a temperature range of 5 to 80 °C. The temperature range of the reducing aqueous solution is preferably 10 to 70 ° C, more preferably 20 to 50 ° C. It is good to increase dispersibility and reactivity, and in particular, it is more effective for sphericity and uniform particle size distribution of the powder.

Next, the post-processing of the present invention will be described.

In one aspect of the present invention, one or more post-treatment processes selected from washing, filtering, drying and pulverizing the precipitated silver particles may be employed.

The washing step may be washing the silver powder several times using distilled water. For washing, room temperature water of 10 to 30° C. or washing water of 30 to 50° C. may be used for more effective organic removal. In addition, it is also possible to prevent aggregation and oxidation during drying by mixing fatty acids with the washing water.

The filtration step may be performed using a known filtration method in order to remove impurities in the silver powder, but preferably, filtration is performed by decantation, a filter, or the like, but is not limited thereto.

The silver powder obtained from the silver powder manufacturing step may be dried. At this time, the drying is not significantly limited within the scope of achieving the object of the present invention, but preferably carried out in a temperature range of 60 to 130 ℃, more preferably carried out in a temperature range of 70 to 80 ℃ Better yet, you can use a vacuum oven.

The pulverizing step may be pulverizing the obtained silver powder using a mixer. The mixer is not limited as long as it is a mixer that can be pulverized by mechanical collision, and specifically, an intensive mixer, a food mixer, or the like may be used.

In addition, the processing sequence of the steps consisting of grinding, washing, filtration and drying is not limited.

In one aspect of the present invention, after the silver powder manufacturing step, a lubricant may be applied to the obtained powder. The lubricant may be at least one selected from the group consisting of a wax-based compound and a surfactant-based compound. The wax-based compound may include any one or more of a natural wax-based compound and a synthetic wax-based compound, and may be, for example, a polyolefin-based wax. The surfactant-based compound may be at least one selected from the group consisting of a fatty acid metal salt, a fatty acid ester compound, an alkyl sulfate-based surfactant, and a polyoxyethylene alkyl sulfate-based surfactant. In this case, the fatty acid may be more specifically, oleic acid, stearic acid, palmitic acid, etc., but is not limited thereto. Such lubricant application not only ensures long-term stability of the physical properties of the final silver powder product, but also improves dispersibility and compatibility when mixed with other components.

In one embodiment of the present invention, the silver powder obtained by the method as described above may have a D50 of 0.5 to 3.0 μm, a D50/Dm of 1.0 to 1.3, and a (D90-D10)/D50 of 0.9 to 1.8. The meaning of the parameters used above is the characteristic of the particles measured by the laser diffraction method, where D50 is the cumulative 50% by weight particle diameter measured by the laser diffraction method, and D90 and D10 are the cumulative 90% by weight particle diameter and the cumulative 10, respectively. It is a particle size by weight, and the D50 is a cumulative 50% by weight particle size. In addition, the Dm is a primary particle average particle size (Mean size) obtained by image analysis of a scanning electron microscope.

The closer the D50/Dm value to 1, the smaller the degree of aggregation of the primary particles. In addition, (D90-D10)/D50 is a measure indicating the uniformity of the particle size of the silver powder, and the closer to 1, the more uniform the particle size distribution.

When the above range is satisfied, the sphericity of the silver powder is increased, the particle size distribution is uniform, and the fluidity is remarkably increased, which is preferable because of the advantages of excellent conductivity.

Specifically, D50 is 0.7 to 2.5 μm, D50/Dm is 1.0 to 1.6 and (D90-D10)/D50 is 0.95 to 1.7, more specifically D50 is 0.9 to 2.5 μm, D50/Dm is 1.0 to 1.4 and (D90- D10)/D50 may be 0.95 to 1.3, but is not limited thereto.

In one embodiment of the present invention, the silver powder has a true specific gravity of 9.0 to 10.4 g/cm³, BET specific surface area 0.1 to 5.0 m²/g, and a tap density of 2.0 to 6.5 g/cc.

The BET is a parameter that can obtain a specific surface area of a material by adsorbing and desorbing a specific gas on the surface of a solid sample and measuring the adsorption amount for each partial pressure.

The true specific gravity is the specific gravity of only the material constituting the particle, which does not take into account the voids inside and outside the particle, unlike the apparent density, regardless of the size or shape of the particle, and includes the type of material and the inside and outside of the particle It is determined by the content of other ingredients such as organic matter.

The tap density is a mass per volume of powder, and it means a density in which the voids between particles are filled by constant tapping or vibration. Factors affecting the tap density include particle size distribution, moisture content, particle formation, cohesiveness, and the like, and the packing density of the material may be predicted through the tap density.

When the above range is satisfied, when the silver powder is used in a field such as a conductive paste, the viscosity is appropriate and the conductive conductivity is improved.

Specifically, the silver powder may have a true specific gravity of 9 to 10.4 g/cm ³ _, BET of 0.1 to 3 m ² /g, more preferably 0.35 to 1.20 m ² /g, and a tap density of 2.0 to 6.5 g/cc. and, more specifically, the true specific gravity is 10 to 10.4 g/cm ³ , BET is 0.1 to 1.5 m ² /g, and the tap density is 2 to 6.5 g/cc, preferably 3.5 to 6.5 g/cc, but is not limited thereto. does not

In addition, D50/Dm of 1.0 to 1.4, (D90-D10)/D50 of 0.95 to 1.05 may have uniform particles without agglomeration.

The silver powder according to the present invention can be applied to various electronic materials. In one aspect of the present invention, there is provided a conductive paste including the silver powder. In addition, the conductive paste containing the silver powder may be applied as a hardening or low-temperature firing type due to characteristics such as particle characteristics and physical stability, or preferably used as a battery electrode paste capable of realizing excellent resistance characteristics at a relatively low temperature. can

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following Examples and Comparative Examples are merely examples for explaining the present invention in more detail, and the present invention is not limited by the following Examples and Comparative Examples.

[Method of measuring physical properties]

1) Measurement of particle size distribution

0.3 g of silver powder was put into 30 mL of isopropyl alcohol, it was made to disperse|distribute for 5 minutes with the ultrasonic cleaner of output 50W, and it measured using the Microtrac particle size distribution analyzer (Fritz, Analysette22).

2) BET measurement

After degassing at 100 degreeC for 60 minutes, it measured using the specific surface area measuring apparatus (BELSORP-miniII manufactured by MicrotracBEL).

3) True specific gravity measurement

10 g of silver powder was measured using an Accupyc II 1340 from Micromeritics.

4) Tap density measurement

Using a tap specific gravity meter (Autotap by Quantachrome), weigh 15 g of silver powder, put it in a container (20 mL test tube), and tap 2,000 times with a drop of 20 mm, tap density = sample mass (15 g) / sample volume after tapping (cm ³ ) was calculated.

[Example 1]

To 185 g of silver nitrate aqueous solution containing 40 g of silver, 60 g of 25% aqueous ammonia was added and stirred to prepare a first aqueous solution.

After heating 420 g of water to 50° C., 1.2 g of sodium carboxymethyl cellulose (Sigma-Aldrich, average molecular weight 90,000 g/mol) was added and stirred for one hour to prepare an aqueous solution, 40 g of 25% aqueous ammonia was added thereto, and then hydrazine hydrate 45 g was added and stirred to prepare a second aqueous solution.

The first aqueous solution maintained at 25° C. was uniformly added to the second aqueous solution for 6 hours to perform the reaction, and then the precipitated silver particles were washed three times with 200 g of ion-exchanged water, filtered with a solution containing oleic acid, and 75 After drying at ℃ for 12 hours, it was pulverized with a food mixer (manufacturer: Hanil, model name: HMF-3000S) to obtain silver powder.

[Example 2]

In Example 1, the second aqueous solution

After heating 420 g of water to 50°C, 40 g of 25% aqueous ammonia and 0.4 g of caustic soda were added, 1.2 g of sodium alginate was added and stirred for 1 hour to prepare an aqueous solution, and 45 g of hydrazine hydrate was added and stirred. The same procedure was performed except that

[Example 3]

It was carried out in the same manner as in Example 1, except that 0.8 g of alginic acid was used instead of sodium carboxymethyl cellulose and the input time of the first aqueous solution was 3 hours.

[Example 4]

The same procedure was carried out in Example 4, except that the input time of the first aqueous solution was 8 hours.

[Example 5]

The same procedure was carried out in Example 1, except that 1.0 g of sodium carboxymethyl cellulose was used and the input time of the first aqueous solution was 0.5 hours.

[Comparative Example 1]

A silver powder was prepared in the same manner as in Example 1 except that sodium carboxymethyl cellulose was removed from the mixed solution B and reacted.

[Comparative Example 2]

A silver powder was prepared in the same manner as in Example 1 except that the amount of sodium carboxymethyl cellulose was 0.8 g and hydrazine was changed to hydroquinone.

division second aqueous solution input time
(hr) dispersant (g) reducing agent (g) Sodium Carboxymethyl Cellulose sodium alginate alginic acid hydrazine hydrate hydroquinone Example 1 1.2 - - 45 - 6 Example 2 - 1.2 - 45 - 6 Example 3 - - 0.8 45 - 3 Example 4 - - 0.8 45 - 8 Example 5 1.0 - - 45 - 0.5 Comparative Example 1 - - - 45 - 6 Comparative Example 2 0.8 - - - 32 3

[Physical properties of the obtained powder]

division Dm
(μm) D10 (μm) D50
(μm) D90
(μm) D50/Dm (D90-D10)
/D50 BET
(m ² /g) Jin Bi-jung
(g/cm ³ ) tap density
(g/cc) Example 1 1.05 0.626 1.069 1.685 1.02 0.99 0.712 10.03 3.63 Example 2 1.13 0.629 1.228 1.842 1.09 0.99 0.701 10.21 5.56 Example 3 1.57 0.871 1.633 2.458 1.04 0.97 0.484 10.38 6.21 Example 4 1.05 0.664 1.063 1.720 1.01 0.99 0.732 10.01 3.52 Example 5 0.74 0.389 0.959 1.521 1.30 1.18 1.159 10.12 4.67 Comparative Example 1 0.93 8.512 56.735 6.55 0.07 3.12 Comparative Example 2 1.36 0.756 1.831 3.659 1.35 1.59 0.361 9.52 4.82

In Example 1, using sodium carboxymethyl cellulose as a dispersant, the BET specific surface area was remarkably high, and the (D90-D10)/D50 value was very close to 1, so the sphericity and uniformity of the particles were good. In Example 2, sodium alginate was used as the dispersing agent, and it was confirmed that the (D90-D10)/D50 value was very close to 1, and the particle size distribution was uniform. In addition, the BET was also high, and the sphericity of the silver powder was improved. In addition, in Example 3, alginic acid was used as a dispersant, and it was confirmed that the dispersibility was remarkably good as the D50/Dm value was close to 1.

In Example 4, it can be seen that, when the input time of the first aqueous solution is increased in Example 3, the effect of more excellent particle size distribution and non-generation of aggregates is obtained. In Example 5, it was confirmed that silver powder having relatively good dispersibility and high true specific gravity was formed even when the addition amount of sodium carboxymethylcellulose as a dispersing agent was reduced and the input time was reduced as compared with Comparative Examples.

Looking at the D50/Dm values of the Examples, as shown in Table 2 above, it was confirmed that the silver powders of Examples 1 to 5 had a small degree of agglomeration and high dispersibility, with an aggregation degree of 1.0 or more and 1.4 or less. In addition, since the value of (D90-D10)/D50 was close to 1, it was confirmed that the particle size distribution of the generated silver powder was uniform. The BET specific surface area also ^{satisfies the range of 0.35 to 1.20 m 2} /g, confirming that the sphericity of the silver powder is improved as shown in FIG. 1 below. The true specific gravity also showed a high value of 10 or more, and thus the sphericity and fluidity were remarkably good. In addition, it was confirmed that the tap density value satisfies the range of 2 to 6.5 g/cc, the particle size distribution is uniform, the particles are more well formed, the cohesiveness is small, and the fluidity is remarkably good.

In Comparative Example 1, no dispersing agent was mixed, and silver agglomerated in bulk was similarly produced, and the particle size could not be measured. In Comparative Example 2, hydroquinone was used as a reducing agent, and as a result, it was confirmed that the dispersibility of the silver powder was lower and the particle size distribution was not uniform.

[Test Example 1]

A conductive paste was prepared by uniformly mixing 90% by weight of the silver particles prepared in Example 1, 7.8% by weight of an organic binder, and 2.2% by weight of a glass frit in a 3-roll mill, and then it was prepared on a single crystal silicon wafer with a thickness of 20㎛. , the screen printing pattern was screen-printed with a line width of 38 μm, the peak temperature was set to 810° C. in a belt-type firing furnace, and then fired at the same time under conditions of in-out 1 minute to prepare a substrate containing silver particles.

In this case, the organic binder is cellulose ester (CAB-382-20, EASTMAN): ethyl cellulose resin (ECN-50, AQUALON): butylcarbitol: texanol (Dow Chemical) in a weight ratio of 1:1:3.5:1.5 was used, and the glass frit had a softening temperature of 410 ° C, a particle size of 2.0 μm, 80.0 wt % PbO, 6.0 wt % B ₂ O ₅ , 12.0 wt % SiO ₂ , 1.0 wt % % of Li ₂ O and 1.0 wt% of K ₂ O was used.

[Test Examples 2 to 5]

It was carried out in the same manner as in Test Example 1 except that the silver particles prepared in Examples 2 to 5 were used.

[Comparative test example]

It was carried out in the same manner as in Test Example 1, except that the silver particles prepared in Comparative Example 2 were used.

The photoelectric conversion efficiency and resistance of the substrates prepared in Test Examples 1 to 5 and Comparative Test Example were measured using a solar simulator (Sol3A, Oriel Corporation), and are shown in Table 3.

Photoelectric conversion efficiency (%) Resistance (mΩ) Test Example 1 18.566 4.50 Test Example 2 18.643 4.35 Test Example 3 18.616 4.29 Test Example 4 18.580 4.78 Test Example 5 18.644 4.95 Comparative test example 17.159 5.80

From Table 3, when the silver particles prepared by the present invention are used in the electrode paste, it is possible to realize excellent electrical properties in photoelectric conversion efficiency and resistance due to the characteristics of the powder having a uniform particle size distribution and narrow dispersibility. can be checked

Claims (9)

A first aqueous solution containing a silver precursor and a complexing agent and a second aqueous solution containing a polysaccharide-based polymer dispersant having a carboxyl group or a salt thereof and a hydrazine-based compound are prepared, and the first aqueous solution is added to the second aqueous solution in a uniform amount continuously adding dropwise to precipitate silver particles; and
and washing the precipitated silver particles using washing water containing fatty acids and drying them to obtain a silver powder coated with fatty acids;
D50 is 0.5 to 3 μm, D50/Dm is 1.0 to 1.3, (D90-D10)/D50 is 0.85 to 1.3, BET specific surface area is 0.1 to 3.0 m ² /g, true specific gravity is 10 to 10.5 g/cm ³ , and a method for producing a spherical silver powder having a tap density of 2 to 6.5 g/cc.
The method of claim 1, wherein the dispersant is a dispersant selected from sodium alginate, potassium alginate, calcium alginate and carboxymethyl cellulose salt.
delete According to claim 1,
The complexing agent is any one or more selected from ammonia, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) salt, ammonium nitrate (NH ₄ NO ₃ ) salt, and monoammonium phosphate ((NH ₄ ) ₂ HPO _{4 ) salt} Method for producing silver powder.
delete A silver powder produced by the method of claim 1 .
The electrically conductive paste containing the silver powder of Claim 6.
delete delete