KR20160146240A - Manufacturing process of silver oxide nanoparticle and silver nanoparticle - Google Patents

Abstract

Printed electronics is growing as nano technology and materials technology have developed continuously. Printed electronics is a technology of making electroconductive or thermoconductive patterns by directly making ink with metal or metal oxide particles and directly printing as much as a manufacturer needs unlike an existing metal thin film etching process. The prevent invention relates to a raw material composition and a process to efficiently manufacture silver ink which is most used in printed electronics. The present invention provides an economic manufacturing method further proper in printed electronics by improving productivity and product quality of silver oxide nanoparticles and silver nanoparticles. For this, the manufacturing method is capable of uniformly making small particles with high economic feasibility by finding optimal combination of silver salts, a basic material, a surfactant, and a solvent.

Description

Technical Field [0001] The present invention relates to a silver oxide nanoparticle and a silver nanoparticle,

This technique is a method for efficiently producing silver nanoparticles useful for electronic printing.

Printing electronics refers to the production of electronic devices and components through printing technology. That is, a conductive or functional ink is printed on a substrate such as a plastic, a paper, or a cloth to produce a desired function product. Semiconductors, transistors, resistors, insulating layers, etc. are drawn in a pre-designed form. Printed electronics are organic electronics (organic electronics) based on organic materials rather than inorganic materials such as silicones, flexible electronics that make products based on bendable films that can break away from rigid and regular devices and components, Together. The printing electronics make it possible to convert the existing silicon-based batch-type manufacturing process into a continuous process (roll-to-roll). In the roll-to-roll process based on printing, only necessary materials are added on a film or a substrate, and complicated processes by conventional photolithography can be greatly reduced. Existing processes usually involve large-scale facility investments. On the other hand, the printing electron can be rolled up on a rotating roll using a flexible material such as a film. Compared with existing device manufacturing processes, it has advantages of low precision but low production cost. Because of the roll-to-roll continuous process, the manufacturing speed can be greatly increased. Depending on the product, it is possible to reduce production costs by 40% or more by 90% or more through the printing method. In addition, the use of materials and toxic materials used in conventional silicon-based processes and energy consumption can be significantly reduced, which is also environmentally friendly. It is possible to plant functional devices, circuits, and memories on a wide variety of flexible substrates or substrates, so that printing electronics can meet new customer and consumer design needs while creating new demand. Printed electronics have been limitedly applied in some areas, such as circuits in past printed circuit boards, photomasks in semiconductors, and color filters in displays. It is not a whole new area. Since the mid-2000s, however, various ink and substrate materials and fine printing technologies have been developing and converging, attracting attention as a new growth area. This is because related technologies such as nanotechnology and materials technology are continuously developing.

The silver nano, which is most commonly used for printing electronics, has a low sintering temperature due to its nano size and is used as an electrode material that is most suitable for a film substrate having flexibility because a thin electrode can be formed. Already, silver nano ink and electrodes have been commercialized and used as a flexible circuit board, a micro-electrode pattern circuit board having a few um, an RFID antenna, a solar cell fine wiring, and a conductive additive. When silver nano-oxide is also 100 nm or less, it can be converted into silver oxide even at 150 degrees or less, and it is partially used for printing electrons. 150 ° C is the highest temperature at which no shrinkage deformation such as PET and nylon occurs, and is treated as a suitable temperature for heat treatment in printing electronics.

 There are many techniques for manufacturing silver nano, which are divided into physical and chemical methods. The physical method is typically used to decompose micro-sized silver into nano-sized using high-density plasma, and is often used when high-purity nano-nano is required. A chemical method is a method of producing silver nano in solution by adding a solvent and a reducing agent as a raw material of silver salt in the scope of the present invention.

In the liquid phase synthesis method using chemical methods, silver salts such as silver nitrate are reduced to silver in a mixture of an expensive reducing agent and a low concentration to form silver nanoparticles . In Korean Patent No. 10-2007-0079072, silver nitrate is produced using a well-known surfactant while reducing the silver salt using high temperature reductive power of -OH group by the polyol process. Since this method produces silver nano at a high temperature of 100 degrees or higher, the silver nanoparticles grow and grow together. It is necessary to stop the growth with surfactant, but since the activity of surfactant decreases at the reduction temperature, a burden is imposed on the process of adding a large amount. As a result, there is a disadvantage that the amount of waste increases. In Korean Patent No. 10-2007-0086884, a new type of silver salt capable of low-temperature decomposition is manufactured and a low-temperature decomposition furnace nano is manufactured at a temperature of about 150 ° C. It is known that the manufacturing cost of the low-temperature decomposition silver nitrate produced in this process is high.

In Nanoscale Research Letters, 8: 318, 2013, we show how to make silver nano by using epicatechin and epicatechin gallate, a type of polyphenol, as a reducing agent. In the International Journal of Chemical and Biomolecular Engineering, 2: 3, 2009, sodium dodecyl sulphate is used to block the growth of particles and to reduce hydrazine. Journal of Chemical Education, Vol. 84, No. 2, 2007, we are producing nano-silver by low-concentration reduction in water with sodium borohydride. All are manufactured using expensive and toxic reducing agents. These methods were common methods of manufacturing silver nano. So the silver nano was expensive.

We are trying to improve the low productivity of silver nano-silver and silver nano suitable for printing electronics and to improve the quality so that the printing electronics can be used in a wider and wider range.

The present invention relates to a process for producing silver oxide nanoparticles by mixing a silver salt, a basic substance, a surfactant and a solvent,

The first stage consists of two stages of heating the mixture to change the silver oxide to silver nano.

Here, silver salt refers to a salt form formed by binding of silver (Ag) to an acid, and silver nitrate, silver chloride, sulfuric acid, silver acetate, silver oxalate, and carbonyl silver are typical examples. Or a metal salt compound containing the same.

The basic substance includes at least one substance selected from the group consisting of KOH, NaOH, NH ₄ OH, Ca (OH) ₂ , Ba (OH) ₂ and LiOH and binds to an acid functional group of silver, It converts to silver oxide.

Surfactants are molecules that are divided into hydrophilic and hydrophobic groups in water, and include those referred to collectively as solubilizers and emulsifiers. It is well known that surfactants are useful for making sub-nanoscale materials. The concentration of the nanodispersion and the particle size of the nanodispersion are determined according to the performance of the surfactant.

A feature of the present invention is that a basic substance is used, so that when an acidic or neutral surfactant is used, it will react with a basic substance or lose its function. Therefore, the surfactant should have a high basicity compared to other surfactants, and should not lose its ability to meet a strong basic solution of pH 11 or higher. We have tested a variety of surfactants that meet these requirements and have tested various types of surfactants. Cocamide diethanolamine (DEA), Cocamide monoethanolamine (MEA), Decyl glucoside, Decyl polyglucoside, Lauryl glucoside, Octyl glucoside . These surfactants are non-ionic surfactants. When they are made into 1wt% aqueous solution, water molecules are ionized and pH 8.0 ~ 11.5 is produced. This makes it possible to make small, homogeneous and high concentration of silver oxide in basic environment.

As the solvent, a solvent having a reducing property is suitable. Representative solvents include ethylene glycol, diethylene glycol, glycerol, propylene glycol, and polyethylene glycol. As the temperature increases, these solvents become more highly reducible. At a certain temperature, silver oxide particles are reduced to silver nanoparticles. This is called a polyol process. However, as the temperature rises, the silver nanoparticles aggregate with each other and the particles become larger. The present invention finds such surfactants suitable for this process and optimizes the process. The above-mentioned reducing agent solvent has an optimal combination of -OH groups at the end similar to the ends of the basic surfactant. Therefore, the surfactant exhibits high ability even in a high-temperature reducing solvent, thereby effectively preventing nanoparticle aggregation. The solvent may be used alone, mixed, or mixed with water or other organic solvent. Mixing can lower the viscosity and increase the dispersibility of the particles. It is also possible to produce silver oxide by preparing silver nano-particles using water having no reducing ability or other polar solvent, adding the above-mentioned chelating solvent, and heating the silver nanoparticles.

The mixing method of the silver salt, the basic substance, the surfactant, and the solvent may be various. Silver salts and basic substances dissolve separately in the solvent, but surfactants can enter anywhere on both sides. In the easiest way, the metal salt is dissolved in a small amount of solvent, and the basic substance and the surfactant are dissolved in the remaining solvent. Stir the basic solution and slowly add the metal salt solution. At this time, the particle size may change depending on the temperature. Since this reaction is an exothermic reaction, it is preferable to cool the mixture to below room temperature. It is also possible to lower or raise the temperature below room temperature depending on the degree of particle size required.

Through such adjustment, it is possible to manufacture silver nano-silver oxide and silver nano-oxide generally having an average of 300 nm or less. It is also possible to produce particles of larger size, but it is difficult to see the effect of nano more prominently.

The concentration of oxidized silver nano-silver or silver nano-dispersion of the present invention is at a level of 0.5 mol / liter or more, which is considerably higher than that of the reference and patent. Being able to make it at a high concentration is a technology that greatly enhances industrial availability because it secures high economic efficiency. Applying the technique of the present invention minimizes the solvent and optimizes the respective concentrations, it is possible to produce at least 1 mol of oxidized silver nano or silver nano dispersion per liter.

Generally, a few tens of micro-oxidation silver particles without a surfactant require more than 120 degrees of conversion of the particles to silver by heat. However, nano-sized silver oxide particles can be converted to silver even at temperatures ranging from 100 ° C to room temperature, depending on their size. In this case also, the reducing solvent is necessary. Silver oxide particles of 30 nm or less are converted into silver only at a temperature of 30 ° C in glycerin, but they have a disadvantage of requiring a long time. Accordingly, the present invention has also found a method of preventing the growth of silver nano with the help of a surfactant and converting the silver oxide into silver oxide in a short time by raising the temperature. The range of the temperature rise is determined by the size of the silver oxide, but it is generally found that the temperature of the silver oxide is at least 10 degrees at the manufacturing temperature, more preferably at least 30 degrees is the effective range. This allows the conversion of silver oxide to silver within 24 hours.

The basic reaction of the present invention is well known in the art, but so far it has not been widely used for making nano. Because conventional known surfactants did not function well in basic solutions and thus did not obtain homogeneous particles that were industrially available. However, in the present invention, a surfactant suitable for the present process was specifically found among the surfactants used in shampoos and cosmetics, and the process was optimized to improve the result, thereby completing the present invention.

The low productivity of silver nano-silver and silver nano are improved and the uniformity is improved, making it possible to manufacture an electrode material which is more suitable for printing electrons and is economical.

Fig. SEM photograph of the silver oxide nanoparticles according to Example 1
Fig. SEM photograph of silver nanoparticles according to Example 1
3. SEM photograph of the silver oxide nanoparticles according to Example 2
FIG. SEM photograph of silver nanoparticles according to Example 2
Figure 5. SEM photograph of silver oxide according to Comparative Example 1
6. SEM photograph of silver particles according to Comparative Example 1

The details of the invention will be described with reference to the embodiments. The scope of the invention has been supported in detail by means of solving the above problems.

Example 1

170 g of silver nitrate having a purity of 99.9% is dissolved in 300 g of glycerin, and a solution of 1 at room temperature is prepared. 40 g of sodium hydroxide was dissolved in 500 g of water, and 10 g of a 50% solution of decyl polyglucoside was added thereto to prepare a solution of 2 times. The solution No. 2 was placed in a constant temperature circulation tank at 20 ° C., and the solution of No. 1 was mixed little by little over 10 minutes. The entire solution turned black. Samples were taken, diluted with distilled water and sedimented by centrifugation five times, and the powder was recovered. The particle size was confirmed by electron microscope.

The temperature of the circulating bath was raised to 60 ° C. and maintained for 24 hours. The sample was again sampled, diluted with distilled water and settled five times by centrifugation, and the powder was recovered. The particle size was confirmed with an electron microscope, and a 2 μm thick printed electrode was formed on the PET film. After the heat treatment at 150 ° C., the electric conductivity was confirmed. The electrical conductivity is 3 × 10 ^-5 Ω.Cm.

As a result of electron microscopic observation, the silver oxide of FIG. 1 was found to be in the range of 20 to 30 nm, and the reduced silver nano of FIG. 2 was found to be in the range of 50 to 100 nm. This is enough to make high-capacity electronic printing silver nano inks such as gravure, offset, flexographic printing. As in the above examples, the use of glycerin only as needed and the remainder of water can be economically improved and the amount of industrial wastes can be reduced, and the viscosity can be lowered to improve the dispersibility of the particles, There is also the advantage of being able to raise the castle. Of course, it is also possible to use only a reducing organic solvent such as glycerin or ethylene glycol.

In FIGS. 1 and 2, it can be seen that a part of silver oxide is converted into silver from silver oxide, and 20 to 30 nm particles are grown to about 50 to 100 nm.

 Example 2

170 g of silver nitrate having a purity of 99.9% is dissolved in 300 g of ethylene glycol to prepare a first solution at room temperature. 40 g of sodium hydroxide was dissolved in 500 g of water, and 10 g of a 95% purity cocamide DEA solution was added thereto. The solution No. 2 was placed in a constant temperature circulation tank at 20 ° C., and the solution of No. 1 was mixed little by little over 10 minutes. The entire solution turned black. Samples were taken, diluted with distilled water and sedimented by centrifugation five times, and the powder was recovered. The particle size was confirmed by electron microscope.

The temperature of the circulating bath was raised by 80 ° C. and maintained for 12 hours. The sample was again sampled, diluted with distilled water and settled five times by centrifugation, and the powder was recovered. The particle size was confirmed with an electron microscope, and a 2 μm thick printed electrode was formed on the PET film. After the heat treatment at 150 ° C., the electric conductivity was confirmed. Electrical conductivity was 5 × 10 ^-5 Ω.Cm.

As a result of the electron microscopic observation, the silver nanooxide shown in FIG. 3 is about 50 nm, and the reduced silver nano of FIG. 4 is about 50 nm. This is enough to make high-capacity electronic printing silver nano inks such as gravure, offset, flexographic printing. The use of nanoparticles that are too small may not be suitable if lower electrical conductivity is desired for some purposes. Since the solvent is present between the nanoparticles, the amount of shrinkage upon drying after coating increases. As a result, cracks occur in too thick electrodes, making it difficult to make thick electrodes beyond a few um. In addition, since a small amount of surfactant and dispersing agent remains between the nanoparticles, too small particles cause a slight deterioration of the electric conductivity even after sintering.

Comparative Example 1

170 g of silver nitrate having a purity of 99.9% is dissolved in 300 g of diethylene glycol, and a solution at room temperature is prepared. 40 g of sodium hydroxide was dissolved in 500 g of water to prepare two solutions without surfactant. The solution No. 2 was placed in a constant-temperature circulation bath, stirred at 20 ° C, and the solution of No. 1 was mixed little by little over 10 minutes. The entire solution turned black. Samples were taken, diluted with distilled water and sedimented by centrifugation five times, and the powder was recovered. The particle size was confirmed by electron microscope.

The temperature of the circulating bath was raised to 60 ° C. and maintained for 24 hours. The sample was again sampled, diluted with distilled water and settled five times by centrifugation, and the powder was recovered. The particle size was confirmed with an electron microscope, and a 2 μm thick printed electrode was made on the PET film. Uniform electrodes could not be obtained due to interference of large particles. On the other hand, a 5-μm-thick printed electrode could be obtained, but the economical efficiency was lost and no further testing was performed.

5 is an SEM photograph of the silver oxide particle produced by Comparative Example 1. Fig. It can be seen that small particles of 50 nm or less and large particles of about 1 μm are mixed. Because there is no surfactant, the reason is that the particle size varies greatly depending on the agitation state of the solution. 6 is an SEM photograph of silver particles produced by Comparative Example 1. Fig. It can be seen that the particles that are smaller in silver oxide grow slightly larger, and still come out mixed with nano and microparticles.

Oxidized silver nanoparticles and silver nanoparticles produced by the present invention are useful in industry as thin film electrode materials. However, there are many price differences according to the manufacturing method, and the method of the present invention is a method of making silver nano-silver oxide and nano-silver at least inexpensively than any other methods, and therefore, it will be usefully used in the electronic printing industry.

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Claims (6)

Cocamide DEA , Cocamide MEA , Decyl glucoside , Decyl polyglucoside , Lauryl glucoside , Octyl glucoside , a silver salt, a basic substance and a solvent to prepare silver oxide nanoparticles and a dispersion thereof
The method according to claim 1, wherein the average size of the oxidized silver nanoparticles is 300 nm or less
The method of claim 1, wherein the silver oxide nanoparticle dispersion is a silver oxide nanoparticle dispersion preparation method comprising 0.5 mol or more silver oxide per liter
The method of claim 1, wherein the silver oxide nanoparticle dispersion is a silver oxide nanoparticle dispersion preparation method comprising 1 mol or more of silver oxide per liter
The method for producing silver oxide nanoparticles according to claim 1, wherein the solvent is at least one selected from the group consisting of ethylene glycol, diethylene glycol, glycerol, propylene glycol, and polyethylene glycol
The silver nano-particles according to claim 1, wherein the resultant silver oxide nanoparticle dispersion is heated to convert silver oxide nanoparticles into silver nanoparticles,

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