WO2019088509A1 - Surface-treated silver powder and preparation method therefor - Google Patents

Abstract

The present invention relates to a method for surface treating a silver powder and a method for preparing a surface-treated silver powder, and provides a conductive paste having a low thixotropic ratio and comprising a surface-treated silver powder by surface treating a silver powder with a first treatment agent comprising an anionic surfactant and a second treatment agent comprising a fatty acid or a fatty acid salt, and thus a conductive paste is advantageous for high-speed printing and micropattern printing.

Description

Surface-treated silver powder and method for producing the same

The present invention relates to a surface-treated silver powder and a method for producing the same, and more particularly to a silver powder suitable for use in a conductive paste for forming an electrode in an electronic component such as an electrode for a solar cell or an internal electrode of a multilayer capacitor, And a manufacturing method thereof.

The conductive metal paste is a paste in which electricity is applied to a dried or baked coating film having a coating ability capable of forming a coating film and is dispersed with a conductive filler (metal filler) alone or in a glass frit in a vehicle made of a resin- It is widely used for the formation of an electric circuit or the formation of an external electrode of a ceramic capacitor.

In particular, Silver Paste is the most chemically stable and excellent in conductivity among the conductive paste of composite system, and has a wide range of applications in various fields such as conductive bonding and coating and fine circuit formation. In the electronic parts, such as PCBs (Printed Circuit Boards), which are particularly important for reliability, the use of silver paste is used for bonding or coating materials for STH (Silver Through Hole), for internal electrodes in multilayer capacitors, Is widely used as an electrode material.

More specifically, the front electrode of the solar cell is formed by sintering after a conductive paste mainly composed of silver (Ag) powder is printed in a grid pattern on the antireflection film. At this time, the front electrode penetrates the antireflection film in the sintering process through the heat treatment to form an ohmic contact with the N-type silicon layer, thereby lowering the series resistance of the solar cell to increase the conversion efficiency.

The rheology of the conductive paste is a major factor that determines the printing property (application suitability). In order to cope with miniaturization of the electronic parts and high density of the electrode pattern and fine patterning, the conductive paste The rheological properties of the conductive paste are particularly important because screen printed electrodes for solar cells require an increase in the narrow line width and high thickness, that is, the aspect ratio, of the electrodes.

Properties including rheological properties are changed by a network structure formed by the interaction of a filler, a resin binder, a solvent, an additive, etc. constituting the conductive paste. Particularly, the silver powder which occupies the largest amount in the conductive paste is important in determining the shape of the network structure formed by varying the interaction force between the silver powder and the other constituents depending on the kind and content of the surface treatment agent coated on the surface thereof . Therefore, in order to control the printing properties and the rheological properties of the paste, it is necessary to control the surface chemical properties of the silver powder according to the kind and content of the surface treatment agent.

Conventional prior art (Japanese Patent Laid-Open Publication No. 2016-33259) provides a silver powder capable of obtaining a conductive paste having a high consumption ratio (low rpm viscosity / high rpm viscosity) for forming a fine pattern through screen printing and a method for producing the same have.

In recent years, however, the printing speed of a screen printing process for a solar cell has been accelerated and the pattern has become finer, and the slippage of the conductive paste is important. In the case of the conductive paste having high consumption, And the tacky is increased to deteriorate the printing quality.

The present invention provides a surface treatment method for a silver powder used in a conductive paste for solving the above problems, and it is an object of the present invention to provide a method for surface treatment of a silver powder used for a conductive paste, And to provide a conductive paste favorable for high-speed printing and fine pattern printing.

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.

(S41) a first surface treatment step (S41) of dispersing silver powder in a solvent, adding a first treatment agent containing an anionic surfactant, mixing and stirring the silver powder to coat silver powder; And a second surface treatment step (S42) of surface-treating the surface of the silver powder coated with the first treatment agent so as to coat a second treatment agent containing a fatty acid or a fatty acid salt, .

The anionic surfactant may be any one selected from the group consisting of Aromatic alcohol phosphate, Fatty alcohol phosphate, Dialkyl sulfosuccinate, and Polypeptide. Or more.

The fatty acid may be selected from the group consisting of lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linolic acid, And at least one selected from the group consisting of arachidonic acid.

Also, the fatty acid salt may be prepared by dissolving the fatty acid in an aqueous medium such as calcium hydroxide, sodium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, And a fatty acid salt which forms a salt with diethylamine, triethylamine, ethanolamine, diethanolamine, or triethanolamine.

In addition, the first surface treatment step (S41) may be performed by preparing a silver powder dispersion in which silver powder is dispersed in a solvent, adding the first treatment agent to a solvent and stirring to prepare a first coating solution, Adding the first coating liquid, and mixing and stirring.

The first surface treatment step (S41) is a step of mixing the silver powder dispersion and the first coating solution such that the first treating agent is mixed in an amount of 0.1 to 2 parts by weight based on 100 parts by weight of the silver powder.

The second surface treatment step (S42) is a step of dispersing the silver powder coated with the first treatment agent in a solvent, and then adding and stirring the alcohol solution containing the second treatment agent.

The second surface treatment step (S42) is a step of adding an alcohol solution containing a second treatment agent to 100 parts by weight of the silver powder coated with the first treatment agent so that the second treatment agent is mixed with 0.1 to 1.0 part by weight .

In another aspect, the present invention is an ion, ammonia (NH ₃₎ and nitric acid (HNO ₃₎ The first reaction solution and for producing a second reaction solution containing a reducing agent in the reaction mixture prepared step (S21) and the first reaction solution containing the and A silver salt reducing step (S2) including a precipitation step (S22) of reacting the second reaction solution to obtain silver powder; And a surface treatment step (S4) of subjecting the obtained silver powder to a primary treatment using a first treatment agent containing an anionic surfactant and a secondary treatment using a second treatment agent including a fatty acid or a fatty acid salt To a surface of the silver powder.

Also, the present invention is a silver powder having an average particle size (D50) of 1.0 to 3.0 m, wherein the silver powder is subjected to a first surface treatment using a first treatment agent containing an anionic surfactant, And a silver powder for a conductive paste, which is a second surface-treated silver powder using the second treatment agent.

The present invention also relates to a metal powder including the silver powder for the conductive paste; And

A glass vehicle comprising a solvent and an organic binder; And a conductive paste.

The conductive paste is characterized by having a viscosity ratio of 0.8 to 1.5 as measured at 1 rpm to a viscosity measured at 10 rpm when the viscosity (Pa · s) is measured at 25 ° C.

The conductive paste has a viscosity of 350 to 500 Pa · s measured at 10 rpm when the viscosity (Pa · s) is measured at 25 ° C.

A metal powder containing the silver powder for the conductive paste; Glass frit; And an organic vehicle including a solvent and an organic binder.

The present invention relates to a silver paste which is surface-treated with a first treatment agent containing an anionic surfactant and a second treatment agent comprising a fatty acid or a fatty acid salt to provide silver paste and a conductive paste containing the silver paste, It is possible to provide a conductive paste favorable for pattern printing.

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.

The present invention relates to a conductive paste containing a silver powder prepared by surface-treating a silver powder using a first surface treatment agent containing an anionic surfactant and a second surface treatment agent containing a fatty acid or a fatty acid salt in the production process, So as to provide a conductive paste particularly suitable for high speed printing and fine pattern printing.

A method of manufacturing a silver powder according to an embodiment of the present invention includes: a silver salt producing step (S1); Silver salt reduction step (S2); Purification step such as filtration and washing (S3); And a surface treatment step (S4). The method for producing silver powder according to the present invention necessarily includes the surface treatment step (S4), and the other steps can be omitted. That is, the surface treatment step (S4) according to one embodiment of the present invention can be applied not only to the silver powder prepared through the above step but also to silver powder produced by a general method or a conventional method.

The silver salt preparation step S1 according to an embodiment of the present invention is a step of preparing a silver salt solution containing silver ions (Ag ⁺ ) by acid treatment of silver (Ag) in the form of ingots, comprising the steps of manufacturing, but can produce a powder to prepare a salt is passed through the step the solution directly, silver nitrate was purchased commercially (AgNO _3), the salt complex, or can proceed to the later steps, using the intermediate solution have.

The silver salt reducing step S2 according to an embodiment of the present invention is a step of reducing silver ions by adding a reducing agent and ammonia to a silver salt solution to precipitate silver particles, and silver ions, ammonia, and nitric acid (S21) for producing a second reaction solution containing a first reaction solution containing a reducing agent and a precipitation step (S22) for obtaining a silver powder by reacting the first reaction solution and the second reaction solution .

In the reaction solution preparation step (S21) according to an embodiment of the present invention, ammonia and nitric acid are added to a silver salt solution containing silver ions, and the solution is stirred and dissolved to prepare a first reaction solution.

The silver ions are not limited as long as they are contained in the form of silver cations. For example, silver nitrate (AgNO ₃ ), silver salt complex or silver intermediate may be used. It is preferable to use silver nitrate (AgNO ₃ ). Hereinafter, the use of silver nitrate (AgNO ₃ ) containing an ion will be described as an example.

Ammonia (NH ₃ ) can be used in the form of an aqueous solution. When 25% ammonia aqueous solution is used, 100 to 150 parts by weight of silver nitrate (AgNO ₃ ) is added in 100 parts by weight. When the aqueous ammonia solution is added in an amount of less than 100 parts by weight, the reaction pH is low and silver ions are not completely reduced, or there is a problem in forming a uniform particle distribution. When the amount is more than 150 parts by weight, There is a problem that it becomes excessively high. Preferably, a 25% ammonia aqueous solution is added in an amount of 120 to 140 parts by weight based on 100 parts by weight of silver nitrate (AgNO ₃ ). The ammonia includes a derivative thereof.

The nitric acid (HNO ₃ ) can be used in the form of an aqueous solution. When 60% nitric acid aqueous solution is used, 40 to 120 parts by weight are added to 100 parts by weight of silver nitrate (AgNO ₃ ). When the amount of the nitric acid (HNO ₃ ) is less than 40 parts by weight, it is difficult to control the size of the powder. When the amount of the nitric acid (HNO ₃ ) is more than 120 parts by weight, have. Preferably, a 60% nitric acid aqueous solution is added in an amount of 80 to 100 parts by weight based on 100 parts by weight of silver nitrate (AgNO ₃ ). The nitric acid includes a derivative thereof.

The first reaction solution containing silver ions, ammonia and nitric acid can be prepared in an aqueous solution state by adding a silver ion, an aqueous ammonia solution and an aqueous nitric acid solution to a solvent such as water and dissolving them by stirring to form a slurry form .

The reaction solution preparation step (S21) according to an embodiment of the present invention also produces a second reaction solution containing a reducing agent.

The reducing agent may be at least one member selected from the group consisting of ascorbic acid, alkanolamine, hydroquinone, hydrazine and formalin, and among them, hydroquinone can be preferably selected. The content of the reducing agent is preferably 10 to 20 parts by weight based on 100 parts by weight of silver nitrate (AgNO ₃ ) contained in the first reaction solution. If less than 10 parts by weight is used, silver ions may not be reduced at all, and when used in excess of 20 parts by weight, organic matter content increases. Preferably, the second reaction liquid is prepared by using 14 to 16 parts by weight of a reducing agent per 100 parts by weight of silver nitrate.

The second reaction solution containing a reducing agent can be prepared in an aqueous solution state by adding a reducing agent to a solvent such as water and dissolving it by stirring.

The precipitation step (S22) according to an embodiment of the present invention is a step of reacting the first reaction solution and the second reaction solution to obtain a silver powder, wherein the first reaction solution produced by the reaction solution production step (S21) The second reaction solution may be slowly added dropwise or the reaction may be carried out in a batch. Preferably, the particles are added in a batch and further stirred for 5 minutes to 10 minutes to grow the particles in the mixed solution, so that the reduction reaction can be terminated in a short period of time to prevent agglomeration of the particles and increase dispersibility.

In the refining step S3 according to an embodiment of the present invention, the silver powder dispersed in the aqueous solution or slurry is separated and washed by filtration after completing the silver particle precipitation reaction through the silver salt reducing step S2 Step S31. More specifically, after precipitating silver particles in the silver powder dispersion, the supernatant of the dispersion is discarded, filtered using a centrifugal separator, and the filter material is washed with pure water. The process of washing is done by completely removing the washing water from which the powder is washed. It is also possible to prevent agglomeration of the silver powder by optionally adding the above-mentioned dispersant to the reaction-completed solution before filtration.

Further, the purification step S3 according to an embodiment of the present invention may further include a post-cleaning drying and decoloring step (S34).

The surface treatment step S4 according to an embodiment of the present invention is a method that can be generally applied to the silver powder produced by the general method or the conventional method as well as the silver powder prepared through the above step. The surface treatment step S4 is a step of treating the rheological properties of the conductive paste including the silver powder prepared by surface treatment of the silver powder using the first treatment agent containing the anionic surfactant and the second treatment agent containing the fatty acid or the fatty acid salt Can be controlled.

The surface treatment step S4 includes a first surface treatment step S41 using the first treatment agent and a second surface treatment step S42 using the second treatment agent.

The first surface treatment step (S41) is a step of hydrophobizing the hydrophilic surface of the silver powder. The silver powder is dispersed in a solvent, and a first treatment agent containing an anionic surfactant is added and mixed and stirred to coat the silver powder.

The first treatment agent includes at least one selected from the group consisting of aromatic alcohol phosphate, fatty alcohol phosphate, dialkyl sulfosuccinate, and a polypeptide. do. Preferably an aliphatic alcohol phosphate.

As the solvent, water, ethanol, isopropyl alcohol, ethylene glycol hexyl ether, diethylene glycol, butyl ether, propylene glycol, propyl ether and the like can be used, and water is preferably used.

The first surface treatment step (S41) is a step of first treating the surface of the silver powder with the first treatment agent so as to coat the second treatment agent more effectively. The silver powder dispersion is prepared by dispersing silver powder in a solvent, A first treatment agent is added to a solvent and stirred to prepare a first coating solution, and then the first coating solution is added to the silver powder dispersion, followed by mixing and stirring.

Silver powder is obtained by adding silver powder to a solvent having a mass of 2 to 5 times the mass of the silver powder and agitating the powder at 2000 to 5000 rpm for 10 to 30 minutes using a stirrer. Preferably 3000 to 4000 rpm, for 15 to 25 minutes to obtain a silver powder dispersion.

The first coating liquid is prepared by placing the first treating agent in a solvent having a mass of 5 to 20 times the mass of the first treating agent, and then stirring the mixture with ultrasonic waves for 5 to 20 minutes.

The first coating liquid is added to the silver powder dispersion prepared above, and the mixture is stirred at 2000 to 5000 rpm for 10 to 30 minutes using a stirrer to perform a first surface treatment. At this time, the silver powder dispersion and the first coating solution are added so that the first treating agent is treated with 0.1 to 2 parts by weight per 100 parts by weight of the powder. When the amount of the first surface treatment agent is less than 0.1 part by weight, the amount of the first surface treatment agent adsorbed on the surface of the powder is so small that there is a problem in that it is difficult to produce a conductive paste having a low consumption, Excessive bubbles are generated in the surface treatment process and the workability is poor and there is a problem that the electrical conductivity of the electrode manufactured by adsorbing an excessive amount of the surface treatment agent on the surface of the silver powder may be deteriorated. Preferably, 0.5 to 1.5 parts by weight of the first treatment agent is applied to 100 parts by weight of the silver powder.

The second surface treatment step (S42) is a step of secondary treatment with the second treatment agent so that the surface of the silver powder coated with the first treatment agent is coated with the second treatment agent, 5-fold mass of a solvent, adding an alcohol solution containing a second treatment agent, stirring the solution, filtering, washing and drying to obtain a second surface-treated silver powder.

In the second surface treatment step (S42), silver powder is added to an alcohol solution containing a fatty acid or a fatty acid salt as a second treatment agent and stirred. At this time, an alcohol solution in which a fatty acid or a fatty acid salt is dissolved in an amount of 5 to 20 wt% based on the total weight of the solution is used. The alcohol may be methanol, ethanol, n-propanol, benzyl alcohol, terpineol or the like, preferably ethanol.

The alcohol solution containing the second treatment agent is added to the solution in which the primary surface-treated silver powder is dispersed, and the mixture is stirred at 2000 to 5000 rpm for 10 to 30 minutes using a stirrer to perform the second surface treatment. At this time, 0.1 to 1.0 part by weight of the second treating agent is mixed with 100 parts by weight of the silver powder coated with the first treating agent. When the second treating agent is mixed at less than 0.1 part by weight, the amount of the second treating agent adsorbed on the surface of the powder is small and aggregation occurs between the powders, and the dispersibility of the paste is lowered due to low compatibility with the vehicle during the production of the conductive paste There is a problem that it is difficult to obtain the desired rheological characteristics of the paste. When the silver powder is mixed in an amount exceeding 1.0 part by weight, excessive electrical conductivity of the electrode, which is produced by adsorbing excess surface treatment agent on the silver powder surface, There is a problem. Preferably, 0.1 to 0.5 parts by weight of the second treating agent is mixed with 100 parts by weight of the silver powder.

The fatty acid may be selected from the group consisting of lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linolic acid, And arachidonic acid. The term " arachidonic acid " It is preferable to use stearic acid or oleic acid.

The fatty acid may be at least one selected from the group consisting of calcium hydroxide, sodium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, And a fatty acid salt which forms a salt with diethylamine, triethylamine, ethanolamine, diethanolamine or triethanolamine. Preferably, stearic acid or ammonium stearate or ammonium oleate in which oleic acid forms a salt with ammonia water is preferably used.

After the surface treatment step (S4), the silver powder finally surface-treated through the purification step (S3) once more can be obtained.

The silver powder produced by the silver powder production method according to an embodiment of the present invention has an average particle size (D50) of 0.5 to 5.0 mu m, more specifically 1.0 to 3.0 mu m. The adsorption amount of the first treatment agent, which is measured as the difference between the organic matter content (%) of the silver powder after the first surface treatment and the organic matter content (%) of the powder before the first surface treatment, is 0.05 to 0.2% (%) Of the silver powder after the secondary surface treatment and the adsorption amount of the second treating agent measured by the difference of the organic matter content (%) of the powder before the secondary surface treatment (after the primary surface treatment) Is at least 0.05%.

[Formula 1]

Amount of adsorbed amount of first treating agent (%) = amount of powdered organic matter (%) after first surface treatment Powder organic matter content (%) before first surface treatment

[Formula 2]

(%) = The amount of powdered organic matter (%) after the second surface treatment The content (%) of the powdered organic matter before the second surface treatment

The present invention also provides a conductive paste comprising silver powder prepared according to an embodiment of the present invention. The conductive paste includes a metal powder and an organic vehicle.

As the metal powder, a surface-treated silver powder is used according to an embodiment of the present invention. The content of the metal powder is preferably 85 to 95 wt% based on the total weight of the conductive paste composition, considering the thickness of the electrode formed during printing and the line resistance of the electrode.

The organic vehicle preferably contains 5 to 15% by weight, based on the total weight of the conductive paste composition, of an organic binder mixed with 5 to 15% by weight of a solvent.

Examples of the organic binder include a cellulose ester compound such as cellulose acetate and cellulose acetate butyrate. Examples of the cellulose ether compound include ethyl cellulose, methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose , And hydroxyethyl methyl cellulose. Examples of the acrylic compound include polyacrylamide, polymethacrylate, polymethylmethacrylate, and polyethylmethacrylate. Examples of the vinyl compound include polyvinyl butyrate Polyvinyl acetate, polyvinyl alcohol, and the like. At least one or more organic binders may be selected and used.

Examples of the solvent used for diluting the composition include alcohols such as methanol, ethanol, n-propanol, benzyl alcohol and terpineol; Ketones such as acetone, methyl ethyl ketone, cyclohexanone, isophorone, and acetylacetone; Amides such as N, N-dimethylformamide and N, N-dimethylacetamide; Ethers such as tetrahydrofuran, dioxane, methyl cellosolve, diglyme and butyl carbitol; Esters such as methyl acetate, ethyl acetate, diethyl carbonate, TXIB (1-isopropyl-2,2-dimethyltrimethylene diisobutyrate), acetic acid carbitol and acetic acid butyl carbitol; Sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane; Aliphatic halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, and 1,1,2-trichloroethane; It is preferable to use at least one compound selected from aromatic compounds such as benzene, toluene, o-xylene, p-xylene, m-xylene, monochlorobenzene and dichlorobenzene.

Also, when used for forming a solar cell electrode, the conductive paste according to the present invention comprises a metal powder, a glass frit, and an organic vehicle.

As the metal powder, a surface-treated silver powder is used according to an embodiment of the present invention. The content of the metal powder is preferably 85 to 95% by weight based on the total weight of the conductive paste composition, taking into account the electrode thickness formed during printing and the line resistance of the electrode.

The composition, particle diameter and shape of the glass frit are not particularly limited. It is possible to use not only flexible glass frit but also lead-free glass frit. Preferably, the content and content of the glass frit are 5 to 29 mol% of PbO, 20 to 34 mol% of TeO ₂ , 3 to 20 mol% of Bi ₂ O ₃ , 20 mol% or less of SiO ₂ , 10 mol% or less of B ₂ O ₃ , 10 to 20 mol% of an alkali metal (Li, Na, K, etc.) and an alkaline earth metal (Ca, Mg, etc.) By combining the organic components of the above components, it is possible to prevent an increase in the line width of the electrode, to improve the contact resistance in the high-surface resistance, and to improve the short-circuit current characteristic.

The average particle diameter of the glass frit is not limited, but it may have a particle diameter in the range of 0.5 to 10 mu m, and a mixture of various particles having different average particle diameters may be used. Preferably, at least one kind of glass frit has an average particle diameter (D50) of not less than 2 mu m and not more than 10 mu m. As a result, the reactivity at the time of firing can be improved, the damage of the n-layer at the high temperature can be minimized, the adhesion can be improved, and the open-circuit voltage (Voc) can be improved. Also, the increase in the line width of the electrode during firing can be reduced.

The content of the glass frit is preferably 1 to 5% by weight based on the total weight of the conductive paste composition. If the amount is less than 1% by weight, incomplete firing may occur to increase electrical resistivity. If the amount exceeds 5% by weight, There is a possibility that the electrical resistivity becomes too high due to too much component.

The organic vehicle is not limited, but organic binders, solvents, and the like may be included. Solvents may sometimes be omitted. The organic vehicle is not limited, but is preferably 1 to 10% by weight based on the total weight of the conductive paste composition.

The organic vehicle is required to have a property of keeping the metal powder and the glass frit uniformly mixed. For example, when the conductive paste is applied to the substrate by screen printing, the conductive paste becomes homogeneous, And a property to suppress the flow and to improve the discharging property and the plate separability of the conductive paste from the screen plate.

The organic binder contained in the organic vehicle is not limited, but examples of the cellulose ester compound include cellulose acetate and cellulose acetate butyrate. Examples of the cellulose ether compound include ethylcellulose, methylcellulose, hydroxypropylcellulose, hydroxyethylcellulose Examples of the acrylic compound include polyacrylamide, polymethacrylate, polymethylmethacrylate, and polyethylmethacrylate, and the like. Examples of the acrylic compound include polyacrylamide, polymethacrylate, polymethylmethacrylate, and polyethylmethacrylate And examples of vinyl based ones include polyvinyl butyral, polyvinyl acetate, polyvinyl alcohol, and the like. At least one or more organic binders may be selected and used.

Examples of the solvent used for diluting the composition include alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol monobutyl ether, ethylene Glycol monobutyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and the like.

The conductive paste composition according to the present invention may further contain additives commonly known in the art, for example, dispersants, plasticizers, viscosity regulators, surfactants, oxidizing agents, metal oxides, metal organic compounds and the like.

The present invention also provides a method of forming an electrode of a solar cell and a solar cell electrode produced by the method, wherein the conductive paste is applied on a substrate, followed by drying and firing. In the method for forming a solar cell electrode of the present invention, the methods used for producing substrates, printing, drying, and firing can be generally those used for manufacturing solar cells, except that conductive pastes containing silver powder having the above- to be. For example, the substrate may be a silicon wafer.

Production Example 1 is a step for preparing powder

9950 g of silver nitrate, 1225 g of ammonia (concentration 25%), and 983 g of nitric acid (concentration 60%) were added to 5150 g of pure water at room temperature and dissolved by stirring to prepare a first aqueous solution. Meanwhile, 156 g of pure water at room temperature and 156 g of hydroquinone were added and dissolved by stirring to prepare a second aqueous solution. Subsequently, the first aqueous solution was stirred, and the second aqueous solution was added all at once to the first aqueous solution, and the mixture was further stirred for 5 minutes from the completion of the addition to grow 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, the mixed solution was filtered using a centrifugal separator, and the filter material was washed with pure water to obtain a silver powder having an average particle size (D50) .

Examples and comparative examples show that the surface treatment of powders

(1) Example 1

2 L of De-Mineralized Water (DMW) and 500 g of the silver powder prepared in the above Preparation Example were placed in a 5 L beaker, and silver powder was dispersed in a homo-mixer at 4000 rpm for 20 minutes to prepare silver slurry. Meanwhile, 30 ml of pure water was added to a 50 ml beaker, 5 g of PS-810E (ADEKA) (Fatty alcohol phosphate) was added thereto, and the mixture was stirred with ultrasonic waves for 10 minutes to prepare a first coating solution. The first coating solution was added to the silver slurry and agitated at 4000 rpm for 20 minutes to perform primary surface treatment of the silver powder, followed by further washing with pure water through centrifugation to prepare a primary coated silver powder.

Next, the silver powder was dispersed again in 2 L of pure water, and then a second coating solution of ammonium stearate solution dissolved in 15 ml of ethanol was added and stirred at 4000 rpm for 20 minutes to subject the silver powder to a second surface treatment, The surface-treated silver powder was prepared by washing with the same process.

Then, it was hot-air dried at 80 DEG C for 12 hours and was shredded through a jet mill to complete a silver powder.

(2) Examples 2 to 15 and Comparative Examples 1 to 13

The surface-treated silver powder was prepared in the same manner as in Example 1 except that the composition of the surface-treated coating liquid was changed as shown in Table 1 below.

Comparative Examples 2 to 13, which were surface-treated silver powders, were prepared in the same manner as in Example 1 except that the surface treatment was not carried out in Comparative Example 1 and the composition of the surface-treated coating liquid was changed as shown in Table 1 below.

	Silver powder (g)	The first treatment agent		The second treatment agent
		ingredient	Content (g)	ingredient	Content (g)
Example 1	500	Fatty alcohol phosphate	5	Ammonium stearate	1.5
Example 2	500	Aromatic alcohol phosphate	5	Ammonium stearate	1.5
Example 3	500	Dialkyl sulfosuccinate	5	Ammonium stearate	1.5
Example 4	500	Polypeptide	5	Ammonium stearate	1.5
Example 5	500	Fatty alcohol phosphate	5	Stearic acid	1.5
Example 6	500	Fatty alcohol phosphate	5	Oleic acid	1.5
Example 7	500	Fatty alcohol phosphate	5	Ammonium oleate	1.5
Example 8	500	Fatty alcohol phosphate	5	Triethanolamine myristate	1.5
Example 9	500	Fatty alcohol phosphate	0.5	Ammonium stearate	1.5
Example 10	500	Fatty alcohol phosphate	2.5	Ammonium stearate	1.5
Example 11	500	Fatty alcohol phosphate	7.5	Ammonium stearate	1.5
Example 12	500	Fatty alcohol phosphate	10	Ammonium stearate	1.5
Example 13	500	Fatty alcohol phosphate	5	Ammonium stearate	0.5
Example 14	500	Fatty alcohol phosphate	5	Ammonium stearate	2.5
Example 15	500	Fatty alcohol phosphate	5	Ammonium stearate	5
Comparative Example 1	500	-	-	-	-
Comparative Example 2	500	Polyoxyethylenequaternary ammonium	0.045	Stearic acid	3.8
Comparative Example 3	500	Stearic acid	8	Hexadecylamine	1.8
Comparative Example 4	500	Fatty alcohol phosphate	5	-	-
Comparative Example 5	500	oleic acid	5	-	-
Comparative Example 6	500	-	-	Sodium myristate	2.5
Comparative Example 7	500	-	-	Ammonium stearate	0.3
Comparative Example 8	500	Quaternary ammonium salt (Cirrasol G-265)	0.5	Ammonium stearate	0.3
Comparative Example 9	500	Polyvinyl Pyrrolidone	0.5	Ammonium stearate	0.3
Comparative Example 10	500	Fatty alcohol phosphate	0.25	Ammonium stearate	1.5
Comparative Example 11	500	Fatty alcohol phosphate	12	Ammonium stearate	1.5
Comparative Example 12	500	Fatty alcohol phosphate	5	Ammonium stearate	0.1
Comparative Example 13	500	Fatty alcohol phosphate	5	Ammonium stearate	7

Experimental Example  ( 1)  Measurement of organic substance adsorption amount of powder

The surface-treated silver powder was measured for weight loss at room temperature and 500 ° C at a temperature rising rate of 10 ° C / min in the air using a Seiko Instrument TG / DTA EXART 6600 to determine the ignition loss Respectively.

Production Example 2 [

According to the examples and the comparative examples, by using a three roll roll after mixing the surface-treated silver powder with 89.5 wt%, glass frit with 1.92 wt%, organic vehicle with 5.20 wt%, and additive with 3.38 wt% Thereby obtaining a conductive paste.

Experimental Example (2) Measurement of Rheological Property (Viscosity) of Conductive Paste

The conductive paste prepared in Preparation Example 2 was measured for viscosity at 25 ° C by a Brookfield viscometer (HBDVII + Pro) at a shear rate of 1 rpm at 10 rpm, as shown in Table 2 below. Rick consumption means the ratio of 1 rpm viscosity (low rpm) to 10 rpm viscosity (high rpm).

	The amount of adsorption of the first surface treating agent (%)	Adsorption amount (%) of second surface treating agent	Viscosity (Pas)
			1 rpm (Pas)	10 rpm (Pas)	Chick consumption
Example 1	0.16	0.06	380	369	1.03
Example 2	0.19	0.08	370	320	1.16
Example 3	0.08	0.19	540	377	1.43
Example 4	0.1	0.19	470	457	1.03
Example 5	0.19	0.17	380	443	0.86
Example 6	0.08	0.12	310	322	0.96
Example 7	0.08	0.05	380	410	0.93
Example 8	0.12	0.11	390	400	0.98
Example 9	0.06	0.14	530	358	1.48
Example 10	0.09	0.11	400	354	1.13
Example 11	0.17	0.16	430	464	0.93
Example 12	0.06	0.2	480	410	1.17
Example 13	0.2	0.17	370	319	1.16
Example 14	0.13	0.17	410	498	0.82
Example 15	0.08	0.2	490	412	1.19
Comparative Example 1	-	-	720	326	2.21
Comparative Example 2	0.01	0.17	780	433	1.80
Comparative Example 3	0.18	0.03	600	340	1.76
Comparative Example 4	0.07	-	820	442	1.86
Comparative Example 5	0.08	-	740	295	2.51
Comparative Example 6	-	0.19	620	300	2.07
Comparative Example 7	-	0.09	730	297	2.46
Comparative Example 8	0.11	0.05	660	294	2.24
Comparative Example 9	0.07	0.08	840	334	2.51
Comparative Example 10	0.02	0.2	610	362	1.69
Comparative Example 11	0.3	0.17	760	439	1.73
Comparative Example 12	0.12	0.01	780	253	3.08
Comparative Example 13	0.11	0.45	790	431	1.83

As shown in Table 2, the conductive paste containing the silver powder surface-treated according to the embodiment of the present invention had a viscosity of 300 to 550 Pa · s at 1 rpm and a viscosity of 350 to 500 Pa · s at 10 rpm, ≪ / RTI > to < RTI ID = 0.0 > 1.5, < / RTI > Conductive paste with low consumption is advantageous for high-speed printing and fine pattern printing, which is supported by the results of line width spreading rate measurement of the fine electrode pattern described later.

In the case of the comparative example, the viscosity at 1 rpm is 600 to 850 Pa · s and the viscosity at 10 rpm is 250 to 450 Pa · s. In the case of the conductive paste having high consumption, the slip property of the paste is decreased and the tacky is increased, so that the print quality may be deteriorated.

Experimental Example (3) Measurement of printed electrode pattern of conductive paste

The electroconductive paste prepared in Preparation Example 2 was applied on an alumina substrate using a 360 mesh screen manufactured by Murakami Co., Ltd. with a screen distance of 1.5 mm, a squeegee pressure of 75 N, and a printing speed of 300 mm / The line width pattern was screen printed and dried at 100 DEG C for 30 minutes. The line width of the dried electrode pattern was measured using an optical microscope.

	Line width (μm)	Line width spreading rate (%)
Example 1	48.5	21.3
Example 2	52.9	32.3
Example 3	54.7	36.8
Example 4	52.7	31.8
Example 5	50.6	26.5
Example 6	52.4	31.0
Example 7	51.6	29.0
Example 8	49.2	23.0
Example 9	54.4	36.0
Example 10	51.3	28.3
Example 11	51.1	27.8
Example 12	53.8	34.5
Example 13	53.1	32.8
Example 14	49.5	23.8
Example 15	54.2	35.5
Comparative Example 1	65.4	63.5
Comparative Example 2	59.2	48.0
Comparative Example 3	58.6	46.5
Comparative Example 4	63.8	59.5
Comparative Example 5	66.8	67.0
Comparative Example 6	66.8	67.0
Comparative Example 7	65.7	64.3
Comparative Example 8	63.5	58.8
Comparative Example 9	60.7	51.8
Comparative Example 10	57.8	44.5
Comparative Example 11	55.6	39.0
Comparative Example 12	71.1	77.8
Comparative Example 13	61.8	54.5

As shown in Table 3, when the fine electrode pattern was formed from the conductive paste containing the silver powder surface-treated according to the present invention, the line width spreading ratio was at least 21.3% and the maximum was 36.8%, and the line width spreading ratio of the comparative example was at least 44.5% It can be seen that the fine pattern formation is excellent. In particular, it can be seen that, in Examples 1, 7, 8, 10, and 11, the line width spreading rate is 30% or less and the fine pattern formation is further superior.

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 (14)

1. A first surface treatment step (S41) of dispersing silver powder in a solvent, adding a first treatment agent containing an anionic surfactant, mixing and stirring to coat silver powder; And

   And a second surface treatment step (S42) of surface-treating the surface of the silver powder coated with the first treatment agent so as to coat a second treatment agent containing a fatty acid or a fatty acid salt.

   Silver powder.
2. The method according to claim 1,

   The anionic surfactant may be at least one selected from the group consisting of Aromatic alcohol phosphate, Fatty alcohol phosphate, Dialkyl sulfosuccinate, and Polypeptide / RTI >

   Silver powder.
3. The method according to claim 1,

   The fatty acid may be selected from the group consisting of lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linolic acid, And at least one member selected from the group consisting of arachidonic acid,

   Silver powder.
4. The method according to claim 1,

   The fatty acid salt may be prepared by dissolving the fatty acid in a solvent selected from the group consisting of calcium hydroxide, sodium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, Which comprises a fatty acid salt forming a salt with diethylamine, triethylamine, ethanolamine, diethanolamine or triethanolamine,

   Silver powder.
5. The method according to claim 1,

   In the first surface treatment step (S41), a silver powder dispersion in which silver powder is dispersed in a solvent is prepared, the first treatment agent is added to a solvent and stirred to prepare a first coating solution, 1 coating solution, and mixing and stirring,

   Silver powder.
6. 6. The method of claim 5,

   Wherein the first surface treatment step (S41) is a step of mixing the silver powder dispersion and the first coating solution so that the first treating agent is mixed with 0.1 to 2 parts by weight with respect to 100 parts by weight of the silver powder,

   Silver powder.
7. The method according to claim 1,

   The second surface treatment step (S42) is a step of dispersing the silver powder coated with the first treatment agent in a solvent, and then adding and stirring an alcohol solution containing a second treatment agent,

   Silver powder.
8. 8. The method of claim 7,

   Wherein the second surface treatment step (S42) is a step of adding an alcohol solution containing a second treatment agent to 100 parts by weight of the silver powder coated with the first treatment agent so that the second treatment agent is mixed with 0.1 to 1.0 part by weight,

   Silver powder.
9. Silver ions, ammonia (NH ₃₎ and nitric first reaction solution and for producing a second reaction solution containing a reducing agent in the reaction mixture prepared step (S21) and the first reaction solution containing the (HNO ₃₎ and a second reaction mixture A silver salt reducing step (S2) including a precipitation step (S22) for obtaining a silver powder by reacting the silver powder; And

   And a surface treatment step (S4) of subjecting the obtained silver powder to a primary treatment using a first treatment agent containing an anionic surfactant and a secondary treatment using a second treatment agent including a fatty acid or a fatty acid salt ,

   A method for producing a silver powder for producing surface-treated silver powder.
10. As a silver powder having an average particle size (D50) of 1.0 to 3.0 占 퐉,

    The silver powder is a first surface-treated silver powder using a first treatment agent containing an anionic surfactant, and a second surface-treated silver powder using a second treatment agent containing a fatty acid or a fatty acid salt.

    Silver powder for conductive paste.
11. A metal powder comprising the silver powder for conductive paste according to claim 10; And

    A glass vehicle comprising a solvent and an organic binder; / RTI >

    Conductive paste.
12. 12. The method of claim 11,

    When the viscosity (Pa · s) of the conductive paste is measured at 25 ° C,

    The ratio of the viscosity measured at 1 rpm to the viscosity measured at 10 rpm is 0.8 to 1.5,

    Conductive paste.
13. 12. The method of claim 11,

    When the viscosity (Pa · s) of the conductive paste is measured at 25 ° C,

    A viscosity measured at 10 rpm of 350 to 500 Pa · s,

    Conductive paste.
14. A metal powder comprising the silver powder for conductive paste according to claim 10;

    Glass frit; And

    1. A conductive paste for a solar cell electrode, comprising an organic vehicle comprising a solvent and an organic binder.