KR20170038467A

KR20170038467A - The manufacturing method of flake silver powder using the agglomerated silver powder

Info

Publication number: KR20170038467A
Application number: KR1020150137871A
Authority: KR
Inventors: 강태훈; 이미영; 최재원
Original assignee: 엘에스니꼬동제련 주식회사
Priority date: 2015-09-30
Filing date: 2015-09-30
Publication date: 2017-04-07

Abstract

The present invention provides a method of manufacturing flake silver powder, comprising a flake forming step (S2) of obtaining flake powder by milling agglomerated silver powder as raw material powder through beads. The agglomerated silver powder is formed by agglomerating sliver particles, each having a diameter of 0.5-2.0 m; has an average diameter of particles which is 5.0-20.0 m; and has a specific surface area of 0.1-0.6 m^2/g. Agglomerated powder, not spherical powder, is used as raw material powder such that flake silver powder is able to be manufactured with low manufacturing costs using a generally used milling facility and beads, and compression among particles of the flake silver powder manufactured by controlling the particle-size of agglomerated powder is able to be minimized. Moreover, the flake silver powder allows the particle size thereof to be controlled by a reduced thickness and large average diameter of particles which are highly slender (particle diameter/thickness).

Description

[0001] The present invention relates to a flake-type silver powder,

The present invention relates to a method for producing a powder for a conductive paste, which is used for an electronic component such as an electrode material.

Generally, a well-dispersed silver powder of a uniform size among metal powders can be utilized as an important material for various electronic industries such as conductive ink, pastes, and adhesives.

The flake used as the electrode material is mainly used for the low temperature curing type conductive paste because the contact area between the particles is wide. Particularly, a membrane touch switch (MTS), a printed circuit board (PCB) (5 μm or more), thinner (high aspect ratio, particle diameter / thickness), and low tap density, are used in applications where electrodes are formed with large silver wire widths such as sensor electrodes, Is advantageously used for conductivity.

The flake is composed of a synthesis step of silver powder (referred to as raw material powder) used as a raw material and a processing step of processing raw material powder into a flake shape through mechanical milling using beads. Patent Document No. 4841987, October 14, 2011), Prior Patent Document 2 (Japanese Patent Laid-Open Publication No. 2012-062531, Mar. 29, 2012), and Prior Patent Document 3 (Japanese Patent No. 3341920, Aug. 23, 2002) A spherical shape having a predetermined particle size can be obtained by mixing and milling powder in a bead mill having beads having a predetermined particle size to prepare a flake for use in a conductive paste such as a powder and mixing a spherical powder having a micron size with a ball mill or a mechanical mill For a long period of time to produce a powder that satisfies the above characteristics.

However, the prior art has a problem that the production time is long and the silver concentration in the slurry is low in the flaked processing step, resulting in a high production cost, and agglomeration between flake particles is increased by prolonged milling in order to increase the grain size, It is difficult to control the thickness of the powder.

In order to solve the above-mentioned problems, the present inventors disclose a method for producing flake powder using coagulated powder rather than spherical powder.

1. Japanese Patent No. 4841987 (October 14, 2011) 2. Japanese Patent Laid-Open Publication No. 2012-062531 (March 29, 2012) 3. Japanese Patent No. 3341920 (Aug. 23, 2002)

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method for manufacturing a high- And a flake having a high aspect ratio with an average particle diameter of 5 占 퐉 or more is to provide a method for producing a powder.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention relates to a method for producing a flake powder, which comprises a flaking step (S2) of obtaining a flaky powder by milling through beads using a coagulated silver powder as a raw material powder, The silver flakes, which are 0.5 to 2.0 μm in size, aggregate to provide an average particle size of 5.0 to 20.0 μm and a specific surface area of 0.1 to 0.6 m ² / g.

(S3) the flaking; (S4) for separating the flaked powder from the beads and washing, drying and shredding the flakes to obtain a powder, wherein the average particle diameter (D50) is 5.0 to 15.0 mu m, and the tap density A flake of 2.5 g / cc or less and a thickness of 300 nm or less provides a powder producing method, and the flake provides a powder production method.

(S3) the flaking; Thereafter, the flakes further have an aspect ratio (average particle diameter (D50) / thickness) of 15 or more, further comprising a post-treatment step (S4) of separating the flaked powder from the beads and washing, drying and shredding the flakes to obtain a powder The flakes which obtain the powders provide a method for producing powders.

And the flaking step S2 is a step of slurrying the coagulated silver powder and milling the powder at a speed of 300 to 700 rpm for 3 to 6 hours using beads of 1 to 5 mm. &Lt; / RTI >

The flaking step (S2); (S1) a raw material powder preparation step (S1) of adding a reducing solution containing a reducing agent to a silver source solution containing silver (Ag) to prepare a coagulated silver powder, Wherein the solution is a solution containing 0.4 to 0.7 equivalents of ammonia relative to the content of silver (Ag).

The reducing solution may contain a single kind of reducing agent or two or more kinds of reducing agents having different reducing rates to control the particle size of the coagulated silver powder to be produced.

Further, the present invention relates to a method for producing silver flakes by agglomerating silver particles having a particle diameter of 0.5 to 2.0 탆 and using agglomerated silver powder having an average particle diameter of 5.0 to 20.0 탆 and a specific surface area of 0.1 to 0.6 m ² / g The flake, which is a powder, provides a powder.

The flakes of the flakes have a mean particle size (D50) of 5.0 to 15.0 mu m, a tap density of 2.5 g / cc or less, and a thickness of 300 nm or less to provide a powder.

The flakes are also characterized in that the powder has an aspect ratio (average particle diameter (D50) / thickness) of at least 15, providing a powder.

The present invention also relates to a flake comprising a powder; And a binder resin.

The present invention can reduce the production cost by reducing the production time, and it is possible to reduce the production cost. The flake produced by controlling the particle size of the coagulated powder has a small thickness and a large average particle size, That is, a flake having a high aspect ratio (particle size / thickness) can provide a method for producing powder.

More specifically, a coarse powder having a primary particle size of 0.5 to 2.0 탆, an average particle size of 5.0 to 20.0 탆 and a specific surface area of 0.1 to 0.6 m ² / g is used as a raw material powder at a low manufacturing cost of 5.0 To 15.0 占 퐉 average particle diameter (D50), a thickness of 300 nm or less, a tap density of 2.5 g / cc or less, and an aspect ratio of 15 or more can provide a method for producing a powder.

FIG. 1 is a SEM photograph of raw material powder according to Example 1 of the present invention.
FIG. 2 is a SEM photograph of the raw material powder according to Example 2 of the present invention.
3 is a SEM photograph of the raw material powder according to Comparative Example 1 of the present invention.
4 is a SEM photograph of the raw material powder according to Comparative Example 2 of the present invention.
5 is a SEM photograph of the raw material powder according to Comparative Example 3 of the present invention.
6 is a SEM photograph of the flake powder according to Example 1 of the present invention.
7 is a SEM photograph of the flake powder according to Example 2 of the present invention.
8 is a SEM photograph of the flake powder according to Comparative Example 1 of the present invention.
9 is a SEM photograph of the flake powder according to Comparative Example 2 of the present invention.
10 shows SEM photographs of the flake powder according to Comparative Example 3 of the present invention.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.

Throughout this specification and claims, the word "comprise", "comprises", "comprising" means including a stated article, step or group of articles, and steps, , Step, or group of objects, or a group of steps.

On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. Any feature that is specifically or advantageously indicated as being advantageous may be combined with any other feature or feature that is indicated as being preferred or advantageous. Hereinafter, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.

A flake according to an embodiment of the present invention includes a raw material powder production step (S1), a flaking step (S2), and a post-treatment step (S3). Other steps that necessarily include the flaking step S2 according to the present invention and which may unnecessarily obscure the gist of the invention may be omitted.

The raw material powder preparation step (S1) according to an embodiment of the present invention is a step of producing a coagulated silver powder, and a specific method is as follows.

Silver solution is added to the source solution to reduce silver (Ag) to precipitate silver particles. That is, after preparing a silver source solution containing silver (Ag), a reducing solution containing a reducing agent is added to reduce silver to obtain a silver powder. Can be slowly added to the reducing solution under the condition that the source solution is stirred, or can be supplied at a time.

The silver source solution containing silver (Ag) is not limited as long as it is a solution in which silver particles can be precipitated by a reducing agent, and silver nitrate solution, silver oxide solution, silver salt complex or silver intermediate solution . Hereinafter, a salt complex will be described as an example.

The pH in the source solution can be adjusted using ammonia, and ammonia is used in an amount of 0.4 to 0.7 equivalents based on the silver ion content. When the content of ammonia is less than 0.4 equivalent, the pH in the silver source solution is low, so that the reduction rate due to the reducing agent introduced during the precipitation of the silver particles is slowed to cause unreacted reaction, There is a problem that it is difficult to obtain the agglomerated powder required in the present patent because the Ag0 reduced in the particle is refined and spheronized through rapid nucleation. Further, nitric acid may be further mixed and used as a method of adjusting the pH.

The reducing agent may be at least one selected from the group consisting of ascorbic acid, hydrazine, hydroquinone, and formalin, either singly or in combination. The use of a reducing agent in an amount of 1/3 to 2/3 equivalents based on the amount of the silver ion can react all the ions. When the amount of the reducing agent is insufficient, an unreacted reaction occurs. Preferably, 0.5 equivalents relative to the silver ion content is used. Particularly, the coagulation type produced according to the type of reducing agent can control the primary particle size of the powder. When a reducing agent having a high reducing power is used, the coagulation type silver powder having a primary particle size smaller than that of the silver Can be obtained. Therefore, the reducing solution may contain a single kind of reducing agent or may include two or more kinds of reducing agents having different reducing rates, thereby controlling the particle size of the coagulated silver powder to be produced.

And then washed and dried with pure water to obtain a raw material powder. Thus, an agglomerated type having a primary particle size of 0.5 to 2.0 탆, an average particle size of 5.0 to 20.0 탆 and a specific surface area of 0.1 to 0.6 m ² / g Powder is obtained.

In the flaking step S2 according to an embodiment of the present invention, the coagulated powder is made into a slurry and flakes through mechanical milling through the beads. The concrete method is as follows. The agglomerated silver powder may be agglomerated silver powder prepared through the raw material powder production step (S1), but is not limited thereto. The primary silver particles having a particle diameter of 0.5 to 2.0 탆 may aggregate to have an average particle diameter of 5.0 - 20.0 mu m, and a specific surface area of 0.1 to 0.6 m < ² > / g.

The coagulated type slurries the powder. The lubricant is added to the solvent, the mixture is stirred until the lubricant is dissolved, and the coagulated powder is dispersed in the solvent to form a slurry. The characteristics of the powder are largely dependent on the flakes obtained according to the characteristics of the raw material powder. As the coagulation-type solvent in which the powder is dispersed, water, an organic solvent, a mixed solvent of water and an organic solvent can be used. Considering the residual solvent component as a contaminant component on the particle surface, it is preferable to use a solvent having a composition close to that of water. Or an agglomerated type in a slurry, it is preferable to use an organic solvent solely in consideration of stabilizing the quality when the powder is made flaky by increasing the dispersibility of the powder. As an organic solvent, alcohol such as methanol, ethanol, ethylene glycol or the like is highly volatile, and the flakes are less likely to remain on the particle surface during drying of the powder. Considering the production efficiency and milling efficiency through flaking, the coagulation type for the solvent properly determines the blending amount of the powder.

The solvent is used in an amount of 25 to 50 parts by weight based on 100 parts by weight of the powder, and the lubricant is used in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the powder.

The agglomerated type slurry containing powder is milled by impact of the ball using an impact mill. The impact mill is a milling apparatus in which a vertical alumina shaft is filled with a shaft and a zirconia ball. The detailed milling process is shown in Table 1 below.

Powder loading 500 ~ 800g Ball material Zirconia Ball size 1 to 5 mm Ball input 250 to 500 wt.% Of Ag powder, Milling time 3 ~ 6hrs Milling speed 300 to 700 rpm slush Fatty acid group menstruum Alcohol group

When a spherical powder is used to obtain a powder having a large particle diameter and a high aspect ratio, the manufacturing time is long in the flaking process and the silver concentration in the slurry is low, so that the manufacturing cost is increased. In order to increase the particle diameter, There is a problem that it is difficult to obtain a high aspect ratio due to an increase in cohesion between particles. On the other hand, in the case of using agglomerated powder, since the silver powder concentration in the slurry can be increased, the production amount per batch is high and the manufacturing time can be reduced in the same Ag slurry concentration, thereby reducing the manufacturing cost. Also, the flakes produced by controlling the particle size of the agglomerated powder have a small thickness and a large average particle diameter (that is, having a high aspect ratio (particle diameter / thickness)) capable of minimizing the squeezing between powders and controlling the particle size, Can be provided.

The post-treatment step S3 according to an embodiment of the present invention is a purification step including washing, drying and crushing steps. The ball / slurry is separated using a screen, and a solvent is further added thereto, The powder is washed, dried and crushed. More specifically, the prepared flake may be a step of gravity settling the powder, removing the solution containing the organic matter such as lubricant in the upper layer, and drying the slurry at 80 ° C for 10 hours. The washing method is not particularly limited, but a flake which has been solid-liquid separated from the slurry can be obtained by charging the powder into a washing liquid, stirring the mixture using a stirrer or an ultrasonic cleaner, and then separating the solid and liquid again to recover the powder . Further, in order to sufficiently remove the surface adsorbed material, it is preferable to perform the operation including the introduction into the cleaning liquid, the stirring cleaning, and the solid-liquid separation several times. Water may be used as the cleaning liquid, but an aqueous alkaline solution or an aqueous ethanol solution is preferably used to efficiently remove the lubricant and the organic material.

The resulting flakes have an average particle diameter (D50) of 5.0 to 15.0 m, a thickness of 300 nm or less, a tap density of 2.5 g / cc or less and an aspect ratio (average particle diameter (D50) / thickness) of 15 or more.

A flake according to an embodiment of the present invention may be manufactured by a powder manufacturing method, and the powder may include a wire such as a membrane touch switch (MTS), a printed circuit board (PCB), an LED light, These large and low silver powders are best suited for use in conductive pastes for electronic components that form electrodes.

Examples and Experimental Examples

(1) Example 1

160 g of silver nitrate solution, 50 ml of ammonia water (concentration 25 to 40%) and 15 ml of nitric acid (40 to 60%) were added to 1,765 g of pure water at normal temperature and dissolved with stirring to prepare a silver source solution having a pH of 6.5 to 7.0. On the other hand, 50 g of hydroquinone and 0.5 g of hydrazine were added to 2000 g of pure water at room temperature and dissolved by stirring to prepare a reducing solution.

Subsequently, the silver source solution was stirred, the reducing solution was added to the silver source solution in a batch, and the stirring was continued for 5 minutes from the completion of the addition, thereby growing the particles in the mixed solution. Thereafter, the stirring was stopped, and the silver particles and the reaction solution were separated by solid-liquid separation using a centrifuge, washed with pure water and dried to prepare a raw material powder. An SEM photograph of the powder of the coagulated silver powder obtained by the above process is shown in Fig. 1. As shown in Table 2, the primary particle diameter was 0.5 to 1.5 占 퐉, the D50 was 8.0 占 퐉 by PSA, and the specific surface area was 0.45 m ² / g .

6 g of a lubricant was added to 180 g of ethanol and stirred until the lubricant dissolved. Then, 600 g of the prepared coagulated powder was added and stirred to prepare a silver slurry solution. 3.0 kg of zirconia beads having a diameter of 1 mm were filled in an attrition mill under the same conditions as those shown in Table 1, and then a silver slurry solution was added thereto and subjected to mechanical impact at a rotating speed of 700 rpm for flaking.

At this time, flaking was carried out for 6 hours. Thereafter, the beads / slurry were separated through a screen, and then the powder was washed using ethanol. After the gravity settling, the supernatant containing organic substances such as lubricant was removed and dried at 80 ° C for 12 hours.

The flakes obtained as above were sieved and powdered to obtain the following characteristics. SEM photographs are shown in Fig. As shown in Table 3, D10 of 2.9 占 퐉, D50 of 8.3 占 퐉, D90 of 17.7 占 퐉 by PSA, tap density of 2.5 g / cc, thickness of 0.22 占 퐉 and aspect ratio of 37.72.

(2) Example 2

160 g of silver nitrate solution, 70 ml of ammonia water (concentration 25%) and 25 ml of nitric acid (40 to 60%) were added to 1,765 g of pure water at normal temperature and dissolved with stirring to prepare a silver source solution having a pH of 6.5 to 7.0. Meanwhile, 50 g of hydroquinone was added to 2000 g of pure water at room temperature and dissolved by stirring to prepare a reducing solution.

Subsequently, the silver source solution was stirred, the reducing solution was added to the silver source solution in a batch, and the stirring was continued for 5 minutes from the completion of the addition, thereby growing the particles in the mixed solution. Thereafter, the stirring was stopped, and the silver particles and the reaction solution were separated by solid-liquid separation using a centrifuge, washed with pure water and dried to prepare a raw material powder. SEM photographs of the coagulated silver powder obtained by the above process are shown in Fig. As shown in Table 2, the primary particle diameter was 0.8 to 2.0 占 퐉, the D50 was 16.9 占 퐉 by PSA, and the specific surface area was 0.25 m ² / g.

The prepared coagulated silver powder was flaked and post-treated in the same manner as in Example 1, and the SEM photograph of the obtained flakes was shown in FIG. As shown in Table 3, the PSA had a D10 of 4.9 m, a D50 of 11.4 m, a D90 of 19.4 m, a tap density of 2.2 g / cc, a thickness of 0.181 m and an aspect ratio of 62.98.

(3) Comparative Example 1

22 ml of silver nitrate solution and 18 ml of ammonia (concentration 25%) were added to 960 g of pure water at normal temperature and dissolved by stirring to prepare a silver source solution. On the other hand, 5.5 g of hydroquinone was added to 1000 g of pure water at room temperature and dissolved by stirring to prepare a reducing solution.

Subsequently, the silver source solution was stirred, the reducing solution was added to the silver source solution in a batch, and the stirring was continued for 5 minutes from the completion of the addition, thereby growing the particles in the mixed solution. Thereafter, stirring was stopped, and the particles in the mixed solution were settled. Then, the supernatant of the mixed solution was discarded and the mixed solution was filtered using a centrifugal separator. The filter medium was washed with pure water and dried to obtain spherical silver powder. SEM photographs of spherical silver powders obtained by the above process are shown in Fig. 3, and their characteristics are as shown in Table 2. The D50 was 1.13 mu m and the specific surface area was 0.9 m < ² > / g.

The spherical silver powder was flaked in the same manner as in Example 1 to obtain a powder, and an SEM photograph of the obtained flake powder was shown in FIG. As shown in Table 3, the D10 of 1.3 μm, the D50 of 4.5 μm, the D90 of 11.2 μm, the tap density of 3.3 g / cc, the thickness of the powder of 0.42 μm and the aspect ratio of 10.71 were determined by PSA.

(4) Comparative Example 2

22 ml of silver nitrate solution and 30 ml of ammonia (concentration 25%) were added to 960 g of pure water at room temperature, and 45 ml of nitric acid (40 to 60%) was added and dissolved by stirring to prepare a silver source solution. On the other hand, 5.5 g of hydroquinone was added to 1000 g of pure water at room temperature and dissolved by stirring to prepare a reducing solution.

Subsequently, the silver source solution was stirred, the reducing solution was added to the silver source solution in a batch, and the stirring was continued for 5 minutes from the completion of the addition, thereby growing the particles in the mixed solution. Thereafter, stirring was stopped, and the particles in the mixed solution were settled. Then, the supernatant of the mixed solution was discarded and the mixed solution was filtered using a centrifugal separator. The filter medium was washed with pure water and dried to obtain spherical silver powder. The SEM photograph of the spherical silver powder obtained by the above process is shown in FIG. 4, and its characteristics are as shown in Table 2. The D50 was 2.13 mu m and the specific surface area was 0.3 m ² / g.

The spherical silver powder was flaked in the same manner as in Examples 1 and 2 using a powder to obtain a powder, and an SEM photograph of the obtained flake powder was shown in FIG. As shown in Table 3, D10 of 2.7 μm, D50 of 6.2 μm, D90 of 13.1 μm, the tap density of 3.0 g / cc, the thickness of 0.45 μm and the aspect ratio of 13.77.

(5) Comparative Example 3

First, 900 g of silver nitrate solution was dissolved in 900 ml of pure water to prepare an aqueous solution of silver nitrate. 370 g of a 45% NaOH solution was added at once to the solution and stirred to obtain an oxidized silver solution of pH 10. Then, 350 g of a reducing solution of 15% concentration was added to the silver oxide solution at a rate of 80 ml / min and stirred to reduce the coagulated silver powder. The reducing agent used was glucose, and the reaction temperature was maintained at 25 ° C.

The coagulated-type powdery solution thus obtained was filtered using Nutsche, washed with 5 L of pure water, and further dried at 80 ° C for 10 hours to obtain a coagulated silver powder. Aggregation type obtained by the process as described above are exhibited in the SEM photograph of the powder 5, the characteristic is the primary particle size of 0.2 ~ 0.5μm, D50 as shown in Table 2 4.8μm, a specific surface area of 1.5 m ² / g.

The coagulated mold was flaked in the same manner as in Example 1 using a powder to obtain a powder, and an SEM photograph of the obtained flake was shown in FIG. As shown in Table 3, D10 of 1.4 μm, D50 of 4.7 μm, D90 of 13.3 μm, tap density of 3.5 g / cc, thickness of 0.38 μm and aspect ratio of 12.37 were determined by PSA.

The flakes prepared in Table 3 also show particle size analysis (D10, D50, D90), thickness and tap density, aspect ratio, and specific surface area characteristic measurement data of powders. The flakes showed FE-SEM photographs of the powder.

division shape Primary particle size
(μm) Average particle size (D50)
(μm) Specific surface area
(m ² / g) Example 1 Cohesive type 0.5 to 1.5 8.0 0.45 Example 2 Cohesive type 0.8 to 2.0 16.9 0.25 Comparative Example 1 rectangle - 1.13 0.9 Comparative Example 2 rectangle - 2.13 0.3 Comparative Example 3 Cohesive type 0.2 to 0.5 4.8 1.5

division PSA (탆) Thickness (㎛) Tap density (g / cc) Aspect ratio
(Particle size / thickness) D10 D50 D90 Example 1 2.9 8.3 17.7 0.22 2.5 37.72 Example 2 4.9 11.4 19.4 0.181 2.2 62.98 Comparative Example 1 1.3 4.5 11.2 0.42 3.3 10.71 Comparative Example 2 2.7 6.2 13.1 0.45 3.0 13.77 Comparative Example 3 1.4 4.7 13.3 0.38 3.5 12.37

As shown in Table 3, it can be seen from Examples 1 and 2 that the flakes prepared according to the size of the powder in the coagulated form are capable of controlling the particle size of the powder, It is found that the aspect ratio of the particle diameter / thickness is as high as 15 or more because of the thinness, the low tap density and the large average particle diameter.

On the other hand, in the comparative example, it can be seen that the thickness of the flakes due to the mutual squeezing of powders is thick, and the tab density and the average particle diameter are low. Although not shown as a comparative example, when a flake is produced by using an agglomerated silver powder having a primary particle size of 2 μm or more in diameter, the flake has a too large particle size of the powder and the binding property by the vehicle is poor, As a result, there is a problem that the dispersibility of the paste is deteriorated, the printing property is deteriorated and the electric conductivity is decreased.

The features, structures, effects, and the like illustrated in the above-described embodiments can be combined and modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

Claims

Flakes are a method for producing powders,
And a flaking step (S2) of obtaining a flaked powder by milling through beads using an agglomerated silver powder as a raw material powder,
Wherein the coagulated silver powder is a silver powder having an average particle diameter of 5.0 to 20.0 mu m and a specific surface area of 0.1 to 0.6 m < ² > / g by aggregation of silver particles having a particle diameter of 0.5 to 2.0 mu m.

The method according to claim 1,
The flaking (S3); Since the,
Further comprising a post-treatment step (S4) of separating the flaked powder from the beads, washing, drying and shredding the flakes to obtain a powder,
A flake for obtaining a powder having an average particle diameter (D50) of 5.0 to 15.0 占 퐉, a tap density of 2.5 g / cc or less, and a thickness of 300 nm or less.

3. The method of claim 2,
The flaking (S3); Since the,
Further comprising a post-treatment step (S4) of separating the flaked powder from the beads, washing, drying and shredding the flakes to obtain a powder,
A flake having an aspect ratio (average particle diameter (D50) / thickness) of 15 or more is obtained by obtaining a powder.

The method according to claim 1,
Wherein the flaking step S2 is a step of slurrying the coagulated silver powder and milling the powder at a speed of 300 to 700 rpm for 3 to 6 hours using beads of 1 to 5 mm. .

The method according to claim 1,
The flaking step (S2); Before,
(S1) for preparing a coagulated silver powder by adding a reducing solution containing a reducing agent to a silver source solution containing silver (Ag)
Wherein the silver source solution is a solution containing 0.4 to 0.7 equivalents of ammonia relative to the silver (Ag) content.

6. The method of claim 5,
Wherein the reducing solution comprises a single kind of reducing agent or comprises two or more kinds of reducing agents having different reducing rates to adjust the particle size of the coagulated silver powder to be produced.

The particle diameter of 0.5 to 2.0μm which is agglomerated particle, average particle diameter of 5.0 to 20.0μm, a specific surface area of 0.1 to 0.6m ² / g of aggregation type is used as a powder, flakes, milled through a bead of powdered flakes Silver powder.

8. The method of claim 7,
The flake has a powder average particle diameter (D50) of 5.0 to 15.0 m, a tap density of 2.5 g / cc or less, and a thickness of 300 nm or less.

9. The method of claim 8,
The flakes are characterized in that the powder has an aspect ratio (average particle size (D50) / thickness) of at least 15.

The flak of claim 7 is a powder; And a binder resin.