KR20170038465A

KR20170038465A - The manufacturing method of flake silver powder using the agglomerated silver powder

Info

Publication number: KR20170038465A
Application number: KR1020150137869A
Authority: KR
Inventors: 이미영; 최재원; 강태훈
Original assignee: 엘에스니꼬동제련 주식회사
Priority date: 2015-09-30
Filing date: 2015-09-30
Publication date: 2017-04-07

Abstract

The present invention includes a flaking step (S2) of obtaining a flaked powder by milling through beads by using agglomerated silver powder as a raw material powder, wherein the agglomerated silver powder has a primary particle diameter of 0.1 to 0.8 占 퐉, A flake which is a powder having an average particle diameter of 2.0 to 10.0 mu m and a specific surface area of 1.0 to 2.5 m < ² > / g is used as a raw material powder, The use of milling equipment and beads can provide a method for producing powders that does not cause agglomeration between powders at low manufacturing costs and which has a good electrical conductivity with a wide inter-particle contact area and a fine flake.

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 low temperature curable conductive paste should exhibit the required conductivity at a low drying temperature of 250 ° C or less. Therefore, the powder is mainly used as a conductive filler in a flake having a larger contact area between particles than a sphere.

As the electrode pattern is miniaturized such as a touch screen panel (TSP), a flexible printed circuit board (FPCB), an RFID antenna, and a metal mesh for a transparent electrode, the silver powder used for the conductive paste A fine powder having a small particle diameter is required.

The flake is made by a process of synthesizing silver powder (referred to as raw material powder) used as a raw material and a process of processing raw material powder into a flake form through mechanical milling using beads. Spherical powder of micron size was used as the powder.

However, as the spherical raw material powder is deformed into the flake shape in the flake processing step, the particle size thereof increases as shown in FIG. 1, and when the plastic deformation of the silver powder is excessive, There is a problem that one flake is difficult to produce powder.

On the other hand, when the mechanical force is decreased to reduce the particle size increase, the size of the powder is fine, but the contact area between the partially flaked spherical powder particles is small, which lowers the conductivity of the electrode.

That is, when a micron-sized spherical powder is used as a raw material powder, a fine, uniform flake is difficult to produce powder, or when a fine powder is used, spherical powder or partially flaked powder exists so that the contact area between particles is small The conductivity of the electrode is not good.

In addition, when fine nano powder having a small particle size is used as a raw material powder for producing powder, the surface energy of the particles is increased and the tendency of the particles to agglomerate is increased, which causes the dispersibility of the powder to be lowered And the production cost also increases with the use of the nano powder.

In addition, even if a spherical powder having a micron size is used as in the conventional patent (Korean Patent No. 1327973), plastic deformation stress at the time of collision between silver particles and beads is appropriately adjusted by using beads of small size (0.2 mm) Although fine flakes can be obtained without causing agglomeration, expensive milling equipment (Super Apex Mill) and beads (0.2 mm) are required to be used, resulting in an increase in manufacturing cost and lower workability due to the use of small beads.

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

1. Korean Registered Patent No. 1327973 (Nov. 2. Japanese Patent No. 4841987 (Apr. 4, 2007) 3. Japanese Patent Laid-Open Publication No. 2012-062531 (March 29, 2012)

Disclosure of Invention Technical Problem [8] 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 of manufacturing a flake, which uses coagulated powder as a raw material powder, , Microflakes which are easily controlled in particle size and have a large contact area between particles and are excellent in conductivity, provide a method for producing powders.

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, comprising a flaking step (S2) of obtaining a powder flaked by milling through beads by using agglomerated silver powder as raw material powder, wherein the agglomerated silver powder has a primary particle diameter in the range of 0.1 to 0.8㎛ are particle aggregates, the average particle diameter of 2.0 to 10.0㎛, the flake powder having a specific surface area of 1.0 to 2.5m ² / g provides a method for producing the powder.

(S3) the flaking; (D50) of 0.5 to 3.0 占 퐉, a specific surface area of 1.0 to 3.0 占 퐉, and a specific surface area of 1.0 to 3.0 占 퐉, and further comprising a post-treatment step (S4) of separating the flaked powder from the beads and washing, 3.0 m ² / g, and the tap density is 2.5 to 4.5 g / cc. The flakes obtained from the powders provide a powder production method.

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 previously adding a reducing solution containing a reducing agent to a silver source solution containing silver (Ag) at a feeding rate to produce a coagulated silver powder; and the flakes &Lt; / RTI >

In addition, the raw material powder producing step (S1) may include adding the reducing solution so that the reducing agent in the reducing solution is charged at a rate of 1 to 100 g / min per kg of silver (Ag) in the silver source solution to produce a coagulated silver powder Wherein the flakes provide a powder production method.

In addition to milling of the present invention is a primary particle diameter of 0.1 to 0.8㎛ is agglomerated particles, and the average particle diameter of 2.0 to 10.0㎛, and a specific surface area of 1.0 to 2.5m ² / g of the powder through the aggregation type is used Beads Flakes, which are flaked powders, provide a powder.

The flakes are characterized in that the powder has an average particle diameter (D50) of 0.5 to 3.0 μm, a specific surface area of 1.0 to 3.0 m ² / g, and a tap density of 2.5 to 4.5 g / cc.

The flak comprises a powder; And a binder resin.

The present invention uses general-purpose milling equipment such as an attrition mill and general-purpose beads of 1 to 5 mm by using agglomerated powder having a primary particle size of 0.1 to 0.8 μm and an average particle size of 2.0 to 10.0 μm as a raw material powder Uniform and fine flakes having excellent electrical conductivity at a wide contact area between particles without causing agglomeration between powders at a low production cost can provide a method for producing powder.

Also, by controlling the particle size of the coagulated powder as the raw material powder through the manufacturing method of the present invention, uniform and fine flakes can control the particle size of the powder without causing agglomeration between the powders.

More specifically, a coarse powder having a primary particle size of 0.1 to 0.8 탆, an average particle size of 2.0 to 10.0 탆 and a specific surface area of 1.0 to 2.5 m ² / g is used as a raw material powder in general milling equipment and 0.5 The flakes having an average particle size (D50) of 3.0 μm, a specific surface area of 1.0-3.0 m ² / g, and a tap density of 2.5-4.5 g / cc can provide a method for producing powders.

The micro flakes manufactured according to an exemplary embodiment of the present invention may be fabricated by using a touch screen panel (TSP), a flexible printed circuit board (FPCB), an RFID An antenna, a metal mesh for a transparent electrode, and the like.

Fig. 1 shows a schematic diagram in which a spherical powder is flaked with a raw material powder.
2 shows SEM photographs of the coagulated silver powder according to Example 1 of the present invention.
FIG. 3 is a SEM photograph of a powder according to Example 1 of the present invention.
4 shows SEM photographs of the coagulated silver powder according to Example 2 of the present invention.
5 shows SEM photographs of the flakes according to Example 2 of the present invention.
6 shows SEM photographs of the coagulated silver powder according to Example 3 of the present invention.
FIG. 7 is a SEM photograph of a powder according to Example 3 of the present invention.
8 is a SEM photograph of spherical silver powder according to Comparative Example 1 of the present invention.
9 is a SEM photograph of the flakes according to Comparative Example 1 of the present invention.
10, SEM photographs of the flakes according to Comparative Example 2 of the present invention are shown.
11 shows a SEM photograph of the powder according to Comparative Example 3 of the present invention.
12 shows SEM photographs of the coagulated silver powder according to Comparative Example 4 of the present invention.
13 is a SEM photograph of the coagulated silver powder according to Comparative Example 5 of the present invention.
14 is a SEM photograph of the powder according to Comparative Example 6 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.

A reducing solution is added to a silver (Ag) 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 Ag 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 oxide solution, silver nitrate solution, silver salt complex or silver intermediate solution . Hereinafter, an oxidized silver solution will be described as an example.

The pH of the source solution can be adjusted by using an alkali solution. In the step of preparing the raw material powder according to the present invention, an alkali solution, preferably a sodium hydroxide (NaOH) solution, is added to a silver nitrate solution A silver source solution containing silver oxide is prepared and used. When the pH of the source solution is less than 10, the reduction rate due to the reducing agent introduced during the precipitation of the silver particles may become slow, resulting in an unreacted reaction that does not terminate the reaction.

The alkali solution (sodium hydroxide (NaOH, 45% concentration)) is added in an amount of 20 to 50 parts by weight based on 100 parts by weight of the silver nitrate solution (20 to 50% concentration) to adjust the pH of the silver source solution to 10 to 14.

The reducing agent may be selected from the group consisting of glucose, ascorbic acid, hydrazine, hydroquinone, and formalin, either singly or in combination. The use of 0.1 to 1.5 equivalents of the reducing agent in relation to the silver ion content can react all the ions. When the amount of the reducing agent is insufficient, the irreversible reaction occurs, and the organic matter remaining in the powder may be deposited upon the addition.

Can adjust the primary particle size of the agglomerated silver powder prepared by adjusting the rate of the reducing solution to the source solution. The charging rate of the reducing solution can be represented by the charging rate of the reducing agent in terms of the mass (solid content) into which the reducing agent is charged in the reducing solution, relative to 1 kg of silver (Ag) in the silver source solution. Is fed at a rate of 1 to 100 g / min. When the powder is added at a rate close to 100 g / min in the above-mentioned feed rate range, a relatively fine coagulated silver powder having a primary particle diameter of close to 0.1 m is produced. When the powder is fed at a rate close to 1 g / min, relatively coarse agglomerated silver powder is produced. When the charging rate is less than 1 g / min or more than 100 g / min, the coagulation type produced has only a small effect of controlling the primary inclination of the powder. That is, even if a reducing agent is added at a rate exceeding 100 g / min, the primary particle size of the powder in the coagulated form does not become smaller than 0.1 μm, and even if the reducing agent is added at a rate of less than 1 g / min, μm. That is, when controlling the rate of feeding the reducing solution within the above range, the agglomerated silver powder whose primary particle size can be controlled within the range of 0.1 to 0.8 μm can be produced.

The reducing solution is introduced into the silver source solution at the above-mentioned content ratio and at the charging rate, and precipitation reaction is caused to precipitate the coagulated silver powder.

Thereafter, the raw powder is produced by washing with pure water and then dried to obtain a coagulated product having a primary particle size of 0.1 to 0.8 탆, an average particle size of 2.0 to 10.0 탆 and a specific surface area of 1.0 to 2.5 m ² / g Of silver powder.

In the flaking step S2 according to an embodiment of the present invention, the coagulated powder is made into a slurry and flakes through milling through the beads. The concrete method is as follows. The agglomerated silver powder may be agglomerated silver powder produced through the raw material powder production step (S1), but is not limited thereto. The primary silver particles having a particle diameter of 0.1 to 0.8 탆 may be agglomerated, 10.0 mu m and a specific surface area of 1.0 to 2.5 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 30 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 the powder is milled by the impact of the beads using an induction 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 5 ~ 8kg 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

Microflakes are partially flaked when a spherical powder is used to obtain a powder, and the contact area between the powders is small, so that the conductivity is deteriorated. Accordingly, when the mechanical impact force is increased to increase the conductivity, flaking is strengthened, But it is difficult to obtain a fine powder.

On the other hand, fine flakes are partially flaked in the same manner as in the case of using spherical powders in the case of using coagulated powders to obtain powders, but the contact area between coagulated powders is wide, so that the fine powders and the flakes having excellent conductivity can be obtained. Further, by controlling the particle size of the coagulated powder as the raw material powder, it is easy to control the particle size of the powder.

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 0.5 to 3.0 mu m, a specific surface area of 1.0 to 3.0 m < ² > / g, and a tap density of 2.5 to 4.5 g / cc.

According to one embodiment of the present invention, a flake manufactured by the method for manufacturing a powder includes fine particles having a line width of 80 m or less such as a touch screen panel (TSP), a flexible printed circuit board (FPCB) It is most suitable for use in a conductive paste for electronic parts in which an electrode pattern is required.

Examples and Experimental Examples

(1) Example 1

First, 9 kg of silver nitrate solution was dissolved in 9 L of purified water to prepare an aqueous solution of silver nitrate. 3.7 kg of 45% NaOH solution was added at once to the solution and stirred to obtain an oxidized silver solution of pH 10. Then, 3.5 kg of a reducing solution of 15% concentration was added to the silver oxide solution at a rate of 300 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 thus obtained coagulated-type powdery solution was filtered using Nutsche, washed with 50 L of pure water, and further dried at 80 캜 for 10 hours to obtain a coagulated silver powder. An SEM photograph of the powder of the coagulated powder obtained by the above process is shown in Fig. 2. The characteristics are as shown in Table 2, in which the primary particle diameter is 0.1 to 0.3 mu m, the average particle diameter is 3.5 mu m, the specific surface area is 2.3 m ² / g.

0.06 kg of lubricant was added to 3.0 kg of ethanol and stirred until the lubricant was dissolved. Then, 6 kg of the prepared agglomerated silver powder was added and stirred well to prepare a silver slurry solution. 30 kg of zirconia beads having a diameter of 1.0 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 500 rpm for flaking.

At this time, flaking was carried out for 3 hours. Then, the slurry was transferred from the attrition mill to the washing tank by using a pump, and the flakes were settled for a certain period of time, and the supernatant was discarded. 10 L of ethanol was further added for washing the powder, and the mixture was stirred for a certain time. After repeating the above steps, a silver slurry with a high concentration was obtained and dried at 80 DEG C for 10 hours to obtain a flake powder.

The flakes thus obtained were crushed and sieved to obtain fine flake powder. SEM photographs are shown in Fig. As shown in Table 3, D10 of 0.6 μm, D50 of 1.0 μm, D90 of 2.1 μm, Dmax of 4.4 μm, tap density of 3.8 g / cc and specific surface area of 2.2 m ² / g.

(2) Example 2

A coagulated silver powder was prepared in the same manner as in Example 1 except that the reducing agent solution was added at a rate of 80 ml / min. An SEM photograph of the coagulated silver powder obtained by the above process is shown in Fig. 4. The characteristics are as shown in Table 2, in which the primary particle diameter is 0.2 to 0.5 mu m, the average particle diameter is 4.8 mu m, the specific surface area is 1.5 m ² / g.

The coagulated silver powder thus prepared was flaked and post-treated in the same manner as in Example 1, and an SEM photograph of the obtained fine flake powder was shown in Fig. By PSA as shown in Table 3 D10 0.8μm, D50 1.7μm, D90 3.9μm Dmax 10.0μm, tap density was 4.2g / cc, a specific surface area of 1.6m was ² / g.

(3) Example 3

A coagulated silver powder was prepared in the same manner as in Example 1 except that the reducing agent solution was added at a rate of 10 ml / min. An SEM photograph of the coagulated silver powder obtained by the above process is shown in Fig. 6, and its characteristics are shown in Table 2, in which the primary particle diameter is 0.4 to 0.7 mu m, the average particle diameter is 8.5 mu m, the specific surface area is 1.1 m ² / g.

The prepared coagulated silver powder was flaked and post-treated in the same manner as in Example 1, and an SEM photograph of the obtained fine flake powder was shown in Fig. As shown in Table 3, D10 of 1.0 μm, D50 of 2.5 μm, D90 of 5.4 μm, Dmax of 12.0 μm, PSA of 4.3 g / cc, and specific surface area of 1.2 m ² / g.

(4) Comparative Example 1

220 ml of silver nitrate solution and 180 ml of ammonia (concentration 25%) were added to 9.6 kg of pure water at normal temperature and dissolved by stirring to prepare a silver source solution. Meanwhile, 55 g of hydroquinone was added to 10 kg 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. An SEM photograph of the spherical silver powder obtained by the above process is shown in FIG. 8, and its characteristics are as shown in Table 2, with an average particle diameter of 1.1 μm and a specific surface area of 0.9 m ² / g.

The spherical silver powder was flaked in the same manner as in Example 1 to obtain fine flake powder, and an SEM photograph of the obtained fine flake powder was shown in FIG. As shown in Table 3, D10 of 0.8 μm, D50 of 1.4 μm, D90 of 2.7 μm, Dmax of 5.8 μm, tap density of 3.4 g / cc and specific surface area of 1.2 m ² / g.

(5) Comparative Example 2

A spherical silver powder was produced in the same manner as in Comparative Example 1.

The spherical silver powder was flaked and post-treated in the same manner as in Example 1 except that the milling time was changed to 6 hours. SEM photograph of the obtained fine flake powder was shown in FIG. As shown in Table 3, D10 of 0.9 μm, D50 of 1.8 μm, D90 of 4.5 μm, Dmax of 13.2 μm, tap density of 3.1 g / cc and specific surface area of 1.6 m ² / g.

(6) Comparative Example 3

The spherical silver powder was flaked and post-treated in the same manner as in Example 1 except that the powder was used at a rotation speed of 700 rpm and a milling time of 6 hours. SEM photographs of the obtained flakes were shown in Fig. As shown in Table 3, D10 of 1.3 μm, D50 of 4.5 μm, D90 of 11.2 μm, Dmax of 30.2 μm by PSA, tap density of 2.0 g / cc and specific surface area of 2.4 m ² / g.

(7) Comparative Example 4

An silver oxide solution was prepared in the same manner as in Example 1. Then, 3.0 kg of a reducing solution of 50% concentration was added to the silver oxide solution by the dumping method to reduce the coagulated silver powder. The reducing agent used was hydroquinone, and the reaction temperature was maintained at 25 ° C. Thereafter, the resultant was washed and dried in the same manner as in Example 1 to obtain a coagulated silver powder.

Or more and cohesive type such as obtained by the process showed in the SEM photograph of the powder 12, its characteristics are the primary particle size of 0.1μm or less, an average particle size as shown in Table 2 1.5μm, a specific surface area of 3.2 m ² / g.

The obtained coagulated silver powder was flaked and post-treated in the same manner as in Example 1, and the resulting fine flakes had a D10 of 0.5 μm, a D50 of 0.8 μm, a D90 of 1.3 μm Dmax A tap density of 2.8 g / cc, and a specific surface area of 3.1 m ² / g.

(8) Comparative Example 5

160 g of silver nitrate solution and 50 ml of ammonia water (concentration 25%) were added to 1,765 g of pure water at normal temperature and dissolved by 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 1 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 coagulated silver powder. An SEM photograph of the powder of the coagulated silver powder obtained by the above process is shown in Fig. 13, and its characteristics are shown in Table 2, in which the primary particle diameter is 0.8 to 1.1 탆, the average particle diameter is 8.0 탆, the specific surface area is 0.4 m ² / g.

Using the prepared coagulated powder, flaking and post-treatment were carried out in the same manner as in Example 1. SEM photographs of the obtained flakes were shown in Fig. As shown in Table 3, D10 of 2.4 μm, D50 of 6.6 μm, D90 of 14.7 μm, Dmax of 34.7 μm, tap density of 2.9 g / cc and specific surface area of 1.0 m ² / g.

The flakes prepared according to Examples and Comparative Examples were prepared by mixing and dispersing 75% by weight of powder, 3% by weight of ethylcellulose binder and 22% by weight of butylcabinetol acetate, thereby preparing a conductive paste. Then, using a applicator, And dried at 130 ° C. for 10 minutes. The conductivity of the electrode film was measured and shown in Table 3.

shape Primary
Drop size
(μm) Average
Particle size
(μm) Specific surface area (m ² / g) Example 1 Cohesive type 0.1 to 0.3 3.5 2.3 Example 2 Cohesive type 0.2 to 0.5 4.8 1.5 Example 3 Cohesive type 0.4 to 0.6 8.5 1.1 Comparative Example 1 rectangle - 1.1 0.9 Comparative Example 2 rectangle - 1.1 0.9 Comparative Example 3 rectangle - 1.1 0.9 Comparative Example 4 Cohesive type &Lt; 0.1 1.5 3.2 Comparative Example 5 Cohesive type 0.8-1.1 8.0 0.4

PSA (um) Specific surface area
(m ² / g) Tap density
(g / cc) Coat
Electrical conductivity (m? / Cm) D10 D50 D90 Dmax Example 1 0.6 1.0 2.1 4.4 2.2 3.8 20 ~ 22 Example 2 0.8 1.7 3.9 10.0 1.6 4.2 16-18 Example 3 1.0 2.5 5.4 12.0 1.2 4.3 13-14 Comparative Example 1 0.8 1.4 2.7 5.8 1.2 3.4 750 to 880 Comparative Example 2 0.9 1.8 4.5 13.2 1.6 3.1 95-110 Comparative Example 3 1.3 4.5 11.2 30.2 2.4 2.0 53 to 60 Comparative Example 4 0.5 0.8 1.3 3.2 3.1 2.8 72 ~ 85 Comparative Example 5 2.4 6.6 14.7 34.7 1.0 2.9 8 ~ 9

As shown in Table 3, it can be seen that the particle size of the powder can be controlled by controlling the particle size of the coagulated powder as the raw material powder through Examples 1 to 3 and Comparative Examples 4 and 5, and the particle size of the raw powder is small The micro flakes were found to be advantageous for preparing powders, but the electrical conductivity was not good. The larger the particle diameter, the better the electrical conductivity, but the micro flakes were hard to obtain the powder.

Also, it can be seen from the comparison example 1 that the fine flakes can be produced by using the spherical powder, but the powder is partially flaked to show poor conductivity. In comparison example 2, the mechanical impact force is increased by increasing the milling time The conductivity was slightly improved by increasing the mechanical impact force by increasing the rotation speed as well as the milling time through the comparative example 3, but the cohesion between the particles was improved It can be seen that the micro flakes are hard to obtain the powder.

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 powder having an average particle diameter of 2.0 to 10.0 mu m and a specific surface area of 1.0 to 2.5 m < ² > / g, the silver particles having a primary particle diameter of 0.1 to 0.8 mu m aggregated to form a powder.

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 having a mean particle size (D50) of 0.5 to 3.0 占 퐉, a specific surface area of 1.0 to 3.0 m ² / g, and a tap density of 2.5 to 4.5 g / cc.

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) a raw material powder preparation step (S1) of adding a reducing solution containing a reducing agent to a silver source solution containing silver (Ag) at a feeding rate to produce a coagulated silver powder.

5. The method of claim 4,
In the step (S1) of producing the raw material powder, the reducing solution in the reducing solution is charged at a rate of 1 to 100 g / min per kg of silver (Ag) in the silver source solution to prepare a coagulated silver powder &Lt; / RTI >

Particle diameter of 0.1 to 0.8㎛ the primary particles are the aggregate and the average particle diameter of 2.0 to 10.0㎛, and a specific surface area of from 1.0 to to 2.5m ² / g of aggregation type is used as a powder, flakes, milled through a bead powdered In flakes are powder.

The method according to claim 6,
Wherein the flakes have a mean particle size (D50) of 0.5 to 3.0 mu m, a specific surface area of 1.0 to 3.0 m < ² > / g, and a tap density of 2.5 to 4.5 g / cc.

The flake of claim 6 is a powder; And a binder resin.