KR101207363B1 - Composition for Conductive Paste Containing Nanometer-Thick Metal Microplates - Google Patents

Abstract

Disclosed is a composition for conductive paste containing micrometer-scale plate metal particles having a thickness of 200 nm or less. The composition for conductive pastes of the present invention contains silver nanoparticles having an average size of 1 nm to 100 nm and the plate-shaped metal particles. It is preferable to use the said micrometer-scale plate-shaped metal particle whose thickness is 200 nm or less on average, and the average length of a horizontal and a vertical length is 1-20 micrometers. At this time, in addition to the silver nanoparticles may further contain nanoparticles of other metals such as copper, palladium. The composition for a conductive paste of the present invention may further contain carbon nanotubes, and as the carbon nanotubes, those in which metal nanoparticles are modified on the surface may be used. By using the composition for a conductive paste of the present invention, the sintering temperature of the conductive paste can be made lower than 150 ° C, and the thickness of the wiring for achieving the same resistance can be made thinner.

Conductive Paste, Plate Metal, Carbon Nanotube, CNT, Microplate

Description

Composition for Conductive Paste Containing Nanometer-Thick Metal Microplates

The present invention relates to a conductive paste. More specifically, the present invention relates to a conductive paste composition comprising a nanometer-thick plate-shaped metal particles and silver nanoparticles.

Information and communication devices such as liquid crystal display devices are becoming smaller and higher in performance, and efforts have been made to implement such devices in flexible materials. Such devices have usually formed a film by vapor deposition such as chemical vapor deposition (CVD) or sputtering, and unnecessary portions thereof are removed by a method such as optical lithography to form necessary circuit wiring.

However, such a conventional wiring forming method has disadvantages in that the use efficiency of raw materials is poor, waste is generated, manufacturing time is long, and facility cost is high because the film formation and etching are repeated. In addition, even in miniaturizing the wiring for miniaturization of the information communication apparatus, such a prior art wiring forming method becomes more and more problematic.

The recent industry is paying attention to inkjet printing, gravure printing, and screen printing, which are a method of reducing raw material loss, using no harmful components such as lead, and simplifying the wiring forming process. In order to form wiring using inkjet printing, gravure printing, or screen printing, the development of high-performance conductive paste or conductive ink is urgently needed.

The conductive ink for forming the wiring should have a high conductivity with a resistivity of 1 × 10 ⁻⁵ Ω · cm or less. In the prior art, a conductive ink in which continuous metallization has been achieved using a large amount of silver particles of 50-80% of the ink weight is used. However, in order to form a continuous conductor network using only silver particles, the content of silver must be increased to 75% by weight or more to reach the level of pure metal silver (d = 10.5 g / cm 3), which is not only disadvantageous in terms of cost but also in terms of storage stability. Is disadvantageous.

In addition, in order to be able to print the conductive paste on a flexible substrate material, the temperature for sintering (firing) must be sufficiently low in view of the low glass transition temperature (T _g ) such as plastic. The sintering temperature tends to be significantly lower than the original melting point of the metal since the surface energy of the particles increases as the size of the metal particles decreases. The graph of FIG. 1 shows the relationship between the sintering temperature and the metal particle size. Figure 1 records the relationship between the size of silver particles and the lowest sintering temperature that can achieve continuous metallization. In general, the surface energy increases exponentially as the size of the metal particles decreases, so that surface diffusion occurs even when only a small amount of energy (low sintering temperature) is applied than when the large metal particles are sintered. As a result, continuous metallization becomes easy.

However, if the silver particles are made high for conductivity and the particle size is reduced to nanometer level for the sintering temperature as in the prior art, the silver particles promote aggregation. Therefore, additives such as dispersants and stabilizers are inevitably added to the storage stability of the ink or paste, and these additives raise the sintering temperature again, resulting in colorless reduction of the sintering temperature due to the miniaturization of silver particles.

In short, the prior art has a low resistivity value of 1 × 10 ⁻⁵ Ω · cm or less while keeping the content of silver as low as possible, and has not suggested a viable method for lowering the sintering temperature to 150 ° C. or less.

The technical problem of the present invention is to develop a conductive paste capable of low-temperature firing having a higher electrical conductivity by forming a continuous conductive network of silver without requiring high content of silver particles.

The present invention provides a composition for a conductive paste capable of achieving continuous metallization of silver without requiring high content of silver particles and sintering at a temperature of 150 ° C. or less.

In one aspect of the present invention, the conductive paste composition is a plate-like metal having an average size of 1 nm to 100 nm of silver nanoparticles of 3 to 20 wt%, an average thickness of 200 nm or less, and silver particles perpendicular to the thickness direction. It contains 40 to 70% by weight of a metal microplate having a micrometer scale of width and length of the plate.

In another aspect of the present invention, the composition for the conductive paste containing 1 to 10% by weight of the silver nanoparticles, 40 to 60% by weight of the metal microplate, and 0.01 to 2% by weight of carbon nanotubes having an average diameter of 2 to 40 nm. Initiate.

In another aspect of the present invention, the carbon nanotubes may be modified metal nanoparticles on the surface.

In the composition for a conductive paste of the present invention, the width and length of the metal microplate are preferably 1-20 μm in average length.

In one embodiment of the invention the compositions for paste are copper, tin, gold. It may further contain metal nanoparticles selected from platinum and palladium.

The conductive paste composition of the present invention may further include a solvent or a solvent and other additives in addition to the above components.

The present invention also provides a conductive substrate having a wiring formed on the substrate using such a conductive paste.

The conductive paste according to the present invention can be sintered at a temperature of 150 ° C. or less, and can be printed on substrates of various materials. In addition, low resistivity of less than 10 ⁻⁵ Ω · cm can be realized, and the wiring thickness can be made thinner than that of the prior art. Furthermore, even with this level of conductivity and low temperature sintering, the required amount of silver can be significantly reduced compared to the prior art, so the economy is excellent.

Since the conductive paste of the present invention is excellent in rheological properties, it can be widely used in the formation of wirings using printing methods, especially screen printing, and displays such as printed circuit board wirings, liquid crystal display devices, plasma display panels, and organic light emitting diodes. It can be used for wiring material of devices, antenna formation of radio wave propagation identification (RFID) system, production of solar cell electrodes and reflective films, and electrode wiring for gold wiring replacement of semiconductor chips.

Hereinafter, the configuration of the present invention will be described in detail. The present invention relates to a composition for a conductive paste containing micrometer-scale plate-shaped silver particles having a nanometer-scale thickness and silver nanoparticles. Using the composition for a conductive paste of the present invention can achieve a high conductivity and low sintering temperature even using less silver nanoparticles than the prior art.

In one aspect of the present invention, a composition for a conductive paste containing 3 to 20% by weight of silver nanoparticles and 40 to 70% by weight of a metal microplate is disclosed.

In the present invention, the silver nanoparticles may be spherical or other forms such as flake shape. And it is preferable to use the thing whose average size is 1 nm-100 nm. The use of nanoparticles with an average size of less than 1 nm can make the viscosity of the paste so low that it is difficult to form a wire over a certain thickness. The use of silver particles larger than 100 nm is undesirable because most of the beneficial effects, such as low temperature sintering, that come from the nanometer scale, are lost. However, it is not necessary to use silver nanoparticles having an average size of 20 nm or less for high conductivity and low sintering temperature as in the prior art. This is because the low sintering temperature and the high electrical conductivity can be achieved by adding a metal microplate and / or carbon nanotube as described below. As the size of nanoparticles increases, cost and storage stability increase, so that the average diameter of silver nanoparticles exceeds 20 nm. On the one hand, the use of silver nanoparticles on the 5-40 nm scale is desirable in terms of synthetic yield, workability and conductive network formation.

The nanoparticles used in the conductive paste of the present invention may be silver particles which are not coated or surface modified, and the silver nanoparticles whose surface is coated with a coating material such as hydrophilic or hydrophobic or a protective colloid forming material may be used. It may be.

It is preferable that the composition for the conductive paste according to the present invention does not contain carbon nanotubes, containing 3 to 20 wt% of silver nanoparticles in the total weight of the composition. This range is a range that can implement high electrical conductivity with a low content compared to the silver nanoparticle content of the prior art. If the content of the silver nanoparticles is less than 3% by weight, the electrical contact between the silver particles is poor and the resistance of the paste is increased. Even if the content exceeds 20% by weight, the effect of improving the conductivity is insignificant compared to the increase in cost, which is not preferable.

In one embodiment of the present invention, the silver nanoparticles and nanoparticles composed of one or more other metals may be mixed in the composition without sacrificing conductivity and low temperature sintering properties. Other metals that can be used include copper, tin, gold, platinum, and palladium, which do not inhibit low-temperature firing and have good conductivity. Such other metal nanoparticles have an average size of 1 nm to 100 nm, and are suitably contained in 0.5 to 5% by weight in the composition containing the silver nanoparticles and the metal microplate. When the silver nanoparticles are mixed with the appropriate metal nanoparticles, the cost can be reduced and the welding between the particle interfaces can be improved while maintaining high conductivity and low temperature sinterability.

In the present specification, the metal microplate is a flat plate-shaped metal particle having a thickness of 200 nm or less and having a flat surface on a micrometer scale in a direction substantially perpendicular to the thickness direction. The flattening of "roughly vertical" or "roughly vertical" is an expression taking into account that the shape of the metal microplate particles is in the shape of a plate but not an exact cuboid shape. If it is a plate-shaped particle, those skilled in the art will have no difficulty understanding the shape of the microplate. In the present invention, the metal microplate helps to achieve high electrical conductivity while minimizing the content of silver nanoparticles, supports low temperature sintering, and on the other hand, serves to reduce cost and increase storage stability since the particles are micrometer sized. The use of flat plate-shaped micrometer scale particles has the effect of making the low temperature sinterability much better than using other readily available micrometer scale metal particles. Examples of the micrometer scale metal particles according to the prior art include flake particles which can be easily obtained by using an attrition mill. When the flake particles are mixed with the conductive metal nanoparticles, the amount of the metal nanoparticles can be reduced while forming a relatively good conductive network, thereby reducing the cost. However, these micrometer scale metal flakes do not support low temperature sintering. For example, the melting point of metallic silver is about 960 ° C, and the sintering temperature of the micrometer-sized silver flake is at a temperature of 750 ° C or higher, so that the effect of lowering the sintering temperature due to the reduction of particle size is not so great.

On the contrary, when the metal microplate of the present invention is used in combination with silver nanoparticles at the rate specified in the following claims, there is an advantage that it can be quickly sintered at a minimum of 120 ° C., and high conductivity can be realized while greatly reducing the amount of silver nanoparticles used. Due to the plate-like polygonal shape, the packing ratio is superior to any other particles. For this reason, when the electrically conductive paste of this invention using a metal microplate is used, even if wiring thickness is about 1-2 micrometers, sufficient electrical conductivity can be obtained. Considering that the wiring thickness is 4 to 8 μm when using conventional micrometer scale flake particles, the conductive paste of the present invention can naturally bring down the manufacturing cost. While not wishing to be bound by any particular theory, it may be explained that plate metal microparticles exhibit excellent low temperature sinterability unlike other metal particles such as flake particles of the same micrometer scale because they are thinner than 200 nm in thickness.

In the present invention, metals such as silver, copper, tin, gold, platinum, palladium, and aluminum may be used as the material of the metal microplate. These may be used alone or in combination of several metals, as well as a mixture of individual pure metal particles, as well as a composite metal microplate such as, for example, coating a surface of plate-shaped copper micrometer particles with silver.

In the present invention, the scale of the plate substantially perpendicular to the thickness direction of the metal microplate may be approximately 1 μm to 20 μm in the horizontal and vertical sides forming the plane. Preferably, the length and width are in the average length of 1 m to 8 m. If the scale of the plate is in the above range, since only a small amount of the polymer binder is used to wet the particles, it is preferable to the electrical conductivity and the dispersibility is good. If the horizontal or vertical scale of the plate is less than 1 μm, the tap density decreases, which requires a large amount of binder, which hinders electrical conductivity. Not only is it necessary for the particles of, but also it is not good because it will interfere with the resolution of the wiring electrode.

The thickness of the metal microplate is preferably 200 nm or less, more preferably 50 nm or less. If the thickness exceeds 200 nm, it is not preferable because the firing temperature increases and the packing ratio decreases to increase the thickness of the wiring. On the other hand, if it is 50 nm or less, the firing temperature is lowered, which is advantageous. The lower limit of the thickness of the metal microplate is not really important in practice. Theoretically, the lower limit will be the thickness of a single metal atom, but considering the economical efficiency of metal microplates and the ease of manufacture and acquisition, all thicknesses obtained as 200 nm or less and 50 nm or less may be used.

In another aspect of the present invention by adding carbon nanotubes (CNT) to the silver nanoparticles, the metal microplate to reinforce the conductive network in the paste composition, to further reduce the content of silver nanoparticles The composition is disclosed.

In the present invention, carbon nanotubes (CNT) are located in the space between the silver particles, and electrically connected between the silver particles or attached to the surface of the silver particles to substantially increase the surface area of the silver particles, thereby facilitating the formation of a conductive network. Play a role. Figure 2 is a schematic diagram showing the effect of improving the conductivity of the carbon nanotubes. Therefore, using carbon nanotubes reduces the amount of silver needed to achieve the same conductivity.

On the other hand, the adhesion between the substrate material and the paste is improved thanks to the carbon nanotubes, and there is an advantageous effect that the viscosity of the paste can be easily adjusted to a level suitable for printing. Conventional carbon nanotubes are not perfect graphene sheets but have some degree of surface defects. In the manufacturing process, functional groups such as carboxyl groups protrude from the surface. While not intending to be bound by a particular theory, it is believed that the carbon nanotubes have such surface functional groups that can enhance the adhesion of the conductive paste to the substrate surface.

As the (anhydrous) carbon nanotubes used in the composition for a conductive paste of the present invention, all single-walled, double-walled, multi-walled carbon nanotubes can be used, and those whose surfaces are modified with various functional groups can also be used. The diameter of the (anhydrous) carbon nanotube used in the composition of the present invention is suitable 2 ~ 40 nm, the length can range from several micrometers to several tens of micrometers.

Using such carbon nanotubes can significantly reduce the amount of silver nanoparticles required to achieve a resistivity of less than 10 ⁻⁵ Ω · cm. The composition for pastes of the present invention containing (anhydrous) carbon nanotubes comprises 1 to 10% by weight of silver nanoparticles having an average size of 1 nm to 100 nm, 40 to 60% by weight of a metal microplate, and an average diameter of 2 to 40 Containing 0.01 to 2% by weight of carbon nanotubes in nm can achieve low temperature sintering and high conductivity. If the carbon nanotube is less than 0.01% by weight, there is no conductivity improvement effect, and even if it exceeds 2% by weight, further improvement in conductivity is insignificant, and it is not preferable because it may lead to a decrease in dispersibility and rheological properties of the paste described below. .

Carbon nanotubes without special metal particles modification on the surface are good conductive reinforcements, but because they have a very large aspect ratio of 10,000 or more, they can be twisted together like threads in the conductive paste composition to cause entanglement. When this entanglement occurs, the carbon nanotubes are not evenly dispersed in the conductive ink tissue and are biased to one side, making it difficult to effectively connect the silver particles. In addition, when the carbon nanotubes are unevenly dispersed in the paste composition, the mechanical properties between the portions with and without the nanotubes are changed to form a non-uniform film during printing, or the smoothness is inhibited, thereby reducing the reliability of the final product.

In another aspect of the present invention, a composition for a conductive paste containing silver nanoparticles, metal microplates, and metal-modified carbon nanotubes is disclosed. All.

In the present invention, the metal-modified carbon nanotubes refer to carbon nanotubes on which metal nanoparticles are modified. 3 illustrates silver modified CNTs as examples of such metal modified carbon nanotubes. As depicted in the schematic diagram of FIG. 3, the silver-modified carbon nanotubes have silver atoms or silver ions attached to the surfaces of the carbon nanotubes, thereby reducing the high aspect ratio of the nanotubes and preventing the nanotubes from intertwining with each other. For this reason, there is an advantage that a separate process for dispersing the carbon nanotubes can be omitted. Since the silver-modified carbon nanotubes are smoothly dispersed, rheological properties such as repeatability, smoothness, and storage stability of the ink may be improved. In addition, since silver particles are present on the surface, the surface area of the conductor is increased, and the conductivity is higher than that of carbon nanotubes without silver particles.

Examples of the metal for modification in the metal modified carbon nanotubes of the present invention include nanoparticles of silver, tin, platinum, gold, and palladium. In such modified nanoparticles, these metals may be in a reduced state or may be in an ionic state that forms a complex. When the metal for modification is in an ionic state in the complex, the dispersing agent or the solvent may act as a reducing agent in the sintering process, and a separate reducing agent may be added to the paste. Can function as

In the composition for a paste for a conductive paste of the present invention containing a metal-modified carbon nanotube, the content of the silver-modified carbon nanotube is preferably 0.01 to 2% by weight of the total paste weight. This is because conductive inks containing silver-modified carbon nanotubes in this range have high electrical conductivity, low firing temperature, and mechanical and rheological properties suitable for screen printing. If the content of the silver-modified nanotube is less than 0.01% by weight, the electrical contact between the silver particles is poor and the resistance of the paste is increased. Even if the content exceeds 2% by weight, the effect of improving the conductivity is insignificant due to the increase in cost and the decrease in dispersibility, and it is not preferable to increase the firing temperature because it requires the addition of a large amount of polymer binder.

In the silver-modified carbon nanotubes used in the present invention, the average length of the carbon nanotube portions excluding the silver-modified portion is preferably 5 to 50 µm.

Metal-modified carbon nanotubes used in the conductive paste of the present invention can be obtained by various methods. For example, carbon nanotubes may be prepared by modifying silver on carbon nanotubes manufactured by thermochemical vapor deposition, laser ablation, arc discharge, or the like. Since a method of modifying a metal such as silver in such carbon nanotubes is well known in the art, it will not be described in detail in the present specification. Some examples are:

1) chemical reduction (eg NaBH ₄ Metal coating such as silver on the surface of the carbon nanotubes by treatment, reduction in hydrogen atmosphere) or thermal reduction

2) adding carbon nanotubes in the process of reducing metal complexes to metal particles,

3) a method of adding a functional group to the surface of the carbon nanotube to form a metal ion complex intermediate on the surface of the carbon nanotube, and then reducing it.

The case of 3) is illustrated in FIG. 4 with silver as an example.

The conductive paste of the present invention may further include a binder resin and a solvent in addition to the metal conductive component including the silver nanoparticles. In addition, it may further include an additive as an optional component. Some examples of binders include nitrocellulose, acrylic resins, vinyl resins, ethylcellulose and modified resins thereof. Solvents and additives include all solvents or additives commonly used in the art and are not described here as those skilled in the art may appropriately select according to the desired final properties with reference to the prior art. Some examples of the solvent may include ketones such as butyl carbitol acetate and butyl acetate, alpha-terpineol, glycol and alcohol solvents. The additive is selected from the group consisting of stabilizers, dispersants, reducing agents, surfactants, wetting agents, thixotropic agents, surface leveling agents, defoamers, coupling agents, surface tension modifiers and thickeners. It is preferable to contain 0.1 to 10% by weight of at least one additive.

As described above, a conductive ink may be manufactured using the composition for a conductive paste of the present invention containing silver nanoparticles and a metal microplate. Methods for producing such conductive inks are well known in the art and will not be discussed. The conductive ink according to the present invention has a specific resistance in the range of 2 × 10 ⁻⁶ to 10 × 10 ⁻⁶ Ω · cm and a low sintering temperature of 120 to 150 ° C., which satisfies both high conductivity and low temperature sintering.

In still another aspect of the present invention, there is provided a conductive substrate on which wiring is formed using the conductive paste. An example of a method of forming a conductive substrate is as follows. The conductive paste may be printed on a substrate of metal, glass, plastic, or the like by inkjet, spin coating, screen printing, or the like to form wiring. In this case, the substrate surface on which the wiring is to be formed is a substrate on which a base film is formed, and a substrate on which a pre-designed wiring pattern is transferred onto a base film using an optical lithography method or a screen printing method may be used. The paste is sprayed along the transferred wiring pattern to form a film including a conductive filler. Subsequently, the paste-printed substrate is sintered to remove the solvent and the like, and the silver particles are fused. Subsequently, if necessary, lamination, film formation, plating, and the like for forming the multilayer substrate may be followed.

Hereinafter, the present invention will be described in more detail with reference to Examples and Preparation Examples. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. It should not be construed as an intention to limit the scope to example.

In order to compare the performance of the conductive paste of the present invention with the pastes of the prior art, an example and a comparative paste composition were prepared. In the example paste according to the present invention, silver microplates were used as metal microplates, silver-modified carbon nanotubes were used as metal-modified carbon nanotubes, and acrylic resins were used as binders. As a solvent, a mixture of tetradecane, terpineol, and butylcarbitol acetate used to disperse the silver nanoparticles, the silver microplate, and the binder were used. Examples and Comparative Examples The composition of the paste is shown in Table 1 below.

Example No. Comparative example number One 2 3 4 5 One 2 3  Silver Nanoparticles (%) 14 7 7 7 7 63 ━ 14  Silver Microplate (%) 50 50 50 50 50 ━ ━ ━  Anhydrous Carbon Nanotubes (%) ━ One ━ ━ ━ ━ ━ ━  Silver Modified Carbon Nanotubes (%) ━ ━ One One One ━ ━ ━  Flake silver microparticles (%) ━ ━ ━ ━ ━ ━ 78 50  bookbinder(%) 3 3.6 3.6 3.6 3.6 3 3 3  Solvent (%) 33 38.4 38.4 38.4 38.4 34 19 33  Sintering temperature (℃) 130 130 130 120 110 130 130 130  Sintering time (minutes) 2

Example and Comparative Example The method for producing a paste is as follows.

Of silver nanoparticles Manufacturing example

LS Cable & System Co., Ltd. manufactured itself as follows. Silver nitrate was reacted with tertiary fatty acid to prepare a silver complex, which was synthesized by dissolving the silver complex in toluene solvent and adding triethylamine as a reducing agent. The obtained nano silver particles were spherical and 5-20 nm in size. Ultraviolet-visible spectroscopic analysis showed a characteristic peak of silver on the nanometer scale at 427 nm. As a result of differential scanning calorimetry (DSC), it was found that the region where silver nanoparticles were sintered was 80 to 140 ° C (see FIG. 9 and the following experimental example). A transmission electron microscope (TEM) photograph of the silver nanoparticles obtained in the preparation example is shown in FIG. 5.

silver Microplate Manufacturing example

M27-SA (horizontal, plate-shaped silver particles having a vertical scale of 2 to 7 μm) from Tokusen, Japan, was used. M27-SA is a plate with a thickness of 200 nm or less, and a polygonal plate like a triangle, hexagon, octagon, etc., having a width of 2-7 μm in length and width, and a microplate. A scanning electron microscope (SEM) photograph of this silver microplate particle is shown in FIG.

Silver formula CNT of Manufacturing example

In 10% aqueous sodium hydroxide solution Multi-walled carbon nanotubes (diameter 10 nm, several tens of micrometers in length, liquid phase modification and high temperature heat treatment, manufactured by LS Cable, Inc.) were dispersed at 50 g / L. 50 g of silver nitrate (Mw = 169.89 g / mol) was dissolved in 1 L of an aqueous solution of CNT-sodium hydroxide, and then 12 g of sodium borohydride (NaBH ₄ , Mw = 40 g / mol) was added to reduce silver ions. A nanotube product with modified particles was obtained. The product was filtered and then placed in a hydrogen atmosphere at 500 ° C. for heat treatment for 1 hour to obtain a silver modified CNT in which silver adhered more stably to the nanotube surface. An electron micrograph of the silver modified CNT is shown in FIG. 7.

Example  1: Silver Nanoparticle-Silver Microplate Hybrid Paste

Silver nanoparticles, silver microplates and binders were prepared as shown below a) ~ c).

A) 20 g of a tetradecane dispersion containing 70% by weight of spherical silver nanoparticles having an average size of 5-20 nm

B) 50 g of silver microplate obtained according to the preparation example dispersed in 20 g of butyl carbitol acetate solvent

C) 10 g of terpinol solution of acrylic resin as a binder (resin solid content is 30% by weight)

The a) to c) were premixed and then stirred in a 3-roll mill until the contents were evenly dispersed. The paste was then printed onto a PET substrate with a uniform film of 6 × 6 cm size by Sus 325 (350 mesh) screen printing and then the substrate was sintered at 130 ° C. for 2 minutes in a convection oven to complete the sample. The surface photograph of the electrode wiring obtained in Example 1 is shown in FIG.

Example  2: silver nanoparticles-silver microplate- CNT  Hybrid paste

A sample was prepared in the same manner as in Example 1. 12 g of binder resin solution and 27 g of butylcarbitol acetate solvent were used as the unmodified carbon nanotube furnace when premixed.

D) 1 g of multi-walled carbon nanotubes with an average diameter of 10 nm and an average length of several tens of micrometers

In addition to the above a) to c) there is a difference in mixing.

Example  3: silver nanoparticles-silver microplate-silver formula CNT  Hybrid paste

A sample was prepared in the same manner as in Example 2, except that when premixing instead of the anhydrous CNT of (d)

(ㅁ) 1 g of the spherical silver modified carbon nanotube having an average size of 5-20 nm of the preparation example

In addition to the above a) to c) there is a difference in mixing.

Example  4: silver nanoparticles-silver microplate-silver formula CNT  Hybrid paste

Samples were prepared in the same manner as in Example 3, but the sintering conditions were different at 120 ° C. for 2 minutes.

Example  5: silver nanoparticles-silver microplate-silver formula CNT  Hybrid paste

Samples were prepared in the same manner as in Example 3, but the sintering conditions were different at 110 ° C. for 2 minutes.

Comparative example  1: Paste only for silver nanoparticles

Silver nanoparticles and a binder were prepared as shown below a) ~ b).

A) 90 g of a tetradecane dispersion containing 70% by weight of spherical silver nanoparticles having an average size of 5-20 nm

B) 10 g of terpinol solution of acrylic resin as a binder (30% by weight of resin solids)

C) Butylcarbitol acetate 34 g

The a) and b) were premixed and then stirred until the contents were evenly dispersed in a 3-roll mill. The paste was then printed onto a PET substrate with a uniform film of 6 × 6 cm size by Sus 325 (350 mesh) screen printing and then the substrate was sintered at 130 ° C. for 2 minutes in a convection oven to complete the sample.

Comparative example  2: Flakes  Silver microparticle paste

When manufacturing paste

A) 78 g of silver flake microparticles with an average size of 2 to 7 µm

B) 10 g of an acrylic resin dissolved in a terpineol solvent as a binder (30% by weight of a resin solid content)

C) butyl carbitol acetate 19 g

It was prepared in the same manner as in Comparative Example 1 except for premixing.

Comparative example  3: silver nanoparticles- Flakes  Hybrid Paste of Silver Microparticles

When prepared in the same manner as in Comparative Example 1, but premixed

A) 20 g of a tetradecane dispersion containing 70% by weight of spherical silver nanoparticles having an average size of 5-20 nm

B) 50 g of flake silver microparticles with an average size of 2-7 μm

C) Butylcarbitol acetate 33 g

D) 10 g of terpinol solution (30% by weight of resin solid content) of acrylic resin was mixed as a binder.

The scanning electron micrograph of the particle | grains of the wiring electrode manufactured by the comparative example 3 is shown in FIG.

Experimental Example : Sintering Temperature of Silver Nanoparticles

Differential scanning thermal analysis (DSC) experiments were conducted to determine the possible sintering temperature ranges of the silver nanoparticles obtained in the above preparation. The temperature increase rate was measured at 10 ℃ per minute melting range of silver, it can be seen that the sintering is completed between 80 ~ 140 ℃ from the experimental result graph shown in FIG.

The thickness of the wiring was measured and the specific resistance was evaluated on the PET substrate on which the Example and Comparative Example pastes thus obtained were printed. The resistivity was measured according to ASTM D 991 standard using a 4-probe tester (LORESTA-GP from Mitsubishi Chemical, Japan). Surface resistance was measured and the thickness of the printed film was measured. The specific resistance was obtained by multiplying the sheet resistance by the thickness. The measurement results are summarized in Table 2 below.

Example No. Comparative example number One 2 3 4 5 One 2 3  Thickness of the wiring (㎛) 1.8 1.8 1.8 1.8 1.8 2.5 3.3 3.2  Resistivity (Ω? Cm) 7 × 10 ^-6 7 × 10 ^-6 5 × 10 ^-6 6 × 10 ^-6 6 × 10 ^-6 7 × 10 ^-6 800 × 10 ^-6 10 × 10 ^-6

Looking at Examples 1 to 5, the specific resistance values are comparable to each other, and it can be seen that they are less than 10 ⁻⁵ μm · cm, which is a suitable range for the antenna for RFID. Among the comparative examples, showing such high conductivity is Comparative Example 1, which used only silver nanoparticles at high content (63%). However, the example pastes according to the present invention achieve this level of conductivity with only much lower silver nanoparticle content. Thanks to the use of the metal microplate of the present invention, the content of silver nanoparticles required to reach a desired specific resistance can be reduced to the fifth level of Comparative Example 1 (Example 1), and 10 minutes when carbon nanotubes are added. It can be seen that it can be reduced to one level (Examples 2 to 4). This not only reduces the cost, but also has the advantage of supporting the miniaturization of the circuit wiring because the thickness of the wiring required for the same target specific resistance can be made thin as is apparent in Table 2.

In addition, in Examples 4 and 5, the sintering temperature required for such wiring thinning and high conductivity can be further lowered, and the sintering can be performed quickly (~ 2 minutes), thereby improving the productivity of the manufacturing process.

The advantageous effects resulting from the use of metal microplates according to the invention can be seen more clearly in Comparative Examples 2 and 3. Comparative Example 2 contains a large amount of flake-like silver particles on the same micrometer scale, but has very low conductivity. In the case of Comparative Example 3, the sintering temperature and the specific resistance are comparable with those of the present invention, but since the wiring thickness for achieving such a specific resistance is much thicker, the manufacturing cost of the wiring electrode using the paste of Comparative Example 3 is inevitably high. .

As described above, an embodiment according to the present invention has been disclosed. The terminology used in the description and examples herein is for the purpose of describing the invention in detail to the average person skilled in the art, and is not intended to limit the scope of the invention described in the claims or any particular meaning. It was not intended.

1 is a graph showing the relationship between the size of silver particles and the lowest possible sintering temperature.

2 is a schematic diagram comparing the conductivity of a conductive paste containing only silver nanoparticles and a paste to which carbon nanotubes (CNT) are added.

3 is a schematic diagram of silver-modified carbon nanotubes whose surface is modified with silver nanoparticles.

4 is a schematic diagram showing one embodiment of producing silver-modified carbon nanotubes from silver ions and carbon nanotubes.

5 is a transmission electron microscope (TEM) photograph of silver nanoparticles obtained in Preparation Example.

Figure 6 is an average thickness of 200 nm obtained in the preparation example, the average width, width 2-7 It is a scanning electron microscope (SEM) photograph of silver microplate particle which is micrometer. (a) is a top view, (b) shows a side view.

7 is a scanning electron micrograph of silver modified multi-walled carbon nanotubes synthesized according to the preparation example method of the present specification.

Fig. 8 is a scanning electron micrograph of the wiring electrode surface produced by Example 1 of the present invention.

9 is a graph showing the results of differential scanning calorimetry to determine the sintering temperature range of silver nanoparticles obtained in the preparation example.

10 is a scanning electron micrograph of a paste obtained according to Comparative Example 3. FIG.

Claims (13)

delete delete As a composition for conductive pastes, 1-10% by weight of silver nanoparticles with an average size of 1 nm-100 nm; 40 to 60% by weight of a metal microplate having an average thickness of 200 nm or less and having an average length of 1 to 20 μm in the length and width of the plane in the direction perpendicular to the thickness direction; 0.01 to 2% by weight of metal-modified carbon nanotubes in which at least one metal nanoparticle selected from the group consisting of silver, tin, platinum, gold, palladium and ionic complexes of these metals is modified on a surface thereof; 0.5 to 5% by weight of metal nanoparticles having an average size of 1 nm to 100 nm as at least one metal selected from the group of metals consisting of copper, tin, gold, platinum and palladium; And A conductive paste composition comprising a binder selected from the group consisting of acryl, vinyl, nitrocellulose, ethyl cellulose and modified resins of these resins and a solvent selected from ketones, alpha-terpineol, glycol and alcohols. delete The method of claim 3, The silver nanoparticles are a composition for a conductive paste, characterized in that the average size is 5 ~ 40 nm. The method of claim 3, The metal of the metal microplate is a composition for a conductive paste, characterized in that at least one metal selected from the group consisting of silver, copper, tin, gold, platinum, palladium and aluminum. delete The method according to claim 3 or 6, wherein At least one selected from the group consisting of stabilizers, dispersants, reducing agents, surfactants, wetting agents, thixotropic agents, surface leveling agents, antifoaming agents, coupling agents, surface tension modifiers and thickeners The conductive paste composition, characterized in that it further comprises 0.1 to 10% by weight of the additive. delete The method of claim 3, The conductive ink prepared from the conductive paste composition has a specific resistance of 2 x 10 ^-6 to 10 x 10 ^-6 Ω cm. The method of claim 3, The conductive ink prepared by the conductive paste composition is a conductive paste composition, characterized in that the sintering temperature is 110 ~ 150 ℃. delete 1-10 wt% of silver nanoparticles having an average size of 1 nm to 100 nm, a thickness of 200 nm or less, and a metal having an average length of 1 μm to 20 μm in the length and width of the plane in the direction perpendicular to the thickness direction 40 to 60 wt% of the microplate, 0.01 to 2 wt% of metal-modified carbon nanotubes modified on the surface of at least one metal nanoparticle selected from the group consisting of silver, tin, platinum, gold, palladium and ion complexes of these metals, At least one metal selected from the group of metals consisting of copper, tin, gold, platinum and palladium, 0.5-5% by weight of metal nanoparticles with an average size of 1 nm to 100 nm and acrylic, vinyl, nitrocellulose, ethylcellulose and Before the wiring is formed with a conductive paste composition comprising a binder selected from the group consisting of modified resins of these resins and a solvent selected from ketones, alpha-terpineol, glycols and alcohols Conductive substrate.

Images