TWI464753B - Method for forming conductive film at room temperature - Google Patents

Description

Method of forming a conductive film at room temperature

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for forming a conductive film at room temperature, and more particularly to a silver nanoparticle precoated on a flexible substrate and having lauric acid as a protective group at room temperature using hydrazine as a reducing agent. A method of chemically reducing a particle film into a conductive silver film.

Low-cost liquid direct printing technology can be applied to various patterning and deposition processes, such as glass substrate circuits or light-emitting diode wafers for integrated circuit (IC), large-size liquid crystal display (LCD). Surface circuits, either used to repair IC breaks, as electronic tags or radio frequency identification (RFID) tags. Conventionally, conductive pattern lines are usually formed by electroplating and etching by a lithography process. However, since the steps required to construct a layer of circuits are extremely complicated, it is relatively time consuming and expensive to process. Therefore, for related industries, there is a need for direct printing technology that simplifies the process and reduces manufacturing costs. This technology rapidly converts nanoparticles into low-resistance metal conductors after solvent removal and heat treatment. To make conductive lines.

Nowadays, one of the direct printing technologies is to use a metal nanoparticle mixed solvent as a printing ink, and then to print a printing ink on a substrate by an inkjet method to form a conductive line, wherein the metal nanoparticle is preferably obtained. Silver, silver is more suitable for this technology than silver, because silver has the highest conductivity among all metals, and the high material cost of gold affects its applicability in the electronics field.

For example, the inventor of the present invention previously published in the Journal of Physical Chemistry Chemical Physics (2009, vol. 11, p. 6269-6275) on May 27, 2009, "Saturated Silver Nanoparticles Protected by Saturated Nitrate" One-step synthesis of uniform silver nanoparticles capped by saturated decanoate: direct spray printing ink to form metallic silver films" reveals the use of silver protected with ortho-rutate Nanoparticles (C ₉ H ₁₉ COO ₂ -Ag) are used as printing inks. However, the operational stability of the silver nanoparticles protected with n-decanoate was only maintained for one day at room temperature due to the desorption of carbon dioxide and other decomposition fragments. Therefore, it is necessary to use other protective agents to stabilize the silver nanoparticles that have been produced, otherwise it will greatly affect the applicability of silver nanoparticles in direct printing technology. Further, the silver nanoparticles coated with the ruthenate as a protective group are coated on a hard ruthenium substrate, and the silver nanoparticle is reduced to a high conductivity by calcination at a temperature higher than 150 ° C. Silver film. However, the above-mentioned high-temperature calcination treatment method also makes the process unsuitable for use on a heat-resistant flexible plastic substrate, and the process takes a long time, and the risk of a hydrogenation reaction at a high temperature is high.

Therefore, it is necessary to provide a method of forming a conductive film at room temperature to solve the problems of the conventional technology.

The main object of the present invention is to provide a method for forming a conductive film at room temperature by first adding silver nitrate to a solution containing lauric acid, and then sequentially dropping n-butylamine as a silver ion ligand and dropping into the joint. Amine diluted aqueous solution reduces silver ions to silver nanoparticles to initially obtain silver nanoparticles with saturated lauric acid as a stable protecting group, and then using cyclohexane as a long-acting solvent to treat the above lauric acid as The silver nanoparticles of the protecting group are spin-coated or sprayed on the surface of the substrate to form a patterned silver nanoparticle film, and finally the substrate is immersed in a high concentration aqueous solution of hydrazine to chemically reduce the silver nanoparticle film into Conductive silver film, this method can not only easily and quickly print on the substrate to form patterned film or circuit, but also the process can be carried out at room temperature, so it can greatly increase the low cost of silver nanoparticles. Application potential on flexible substrates such as PET substrates.

A secondary object of the present invention is to provide a method for forming a conductive film at room temperature by previously using a cyclohexane containing 0.5 wt% of lauric acid as a solvent to treat silver nanoparticles having lauric acid as a protective group. Formulated as a 30-day long-acting preservation solution of 5.0 to 15.0 wt%, so that the silver nanoparticles are less likely to aggregate and coagulate in the cyclohexane solution containing lauric acid, and maintain the uniformity of the size of the nanoparticles, thereby improving The printing quality of silver nanoparticles used in the printing process.

To achieve the above object, the present invention provides a method of forming a conductive film at room temperature, which comprises the following steps:

(a) adding silver nitrate to a non-polar solvent containing lauric acid to form a first mixed liquid; (b) dropping n-butylamine into the first mixed liquid as a silver ion ligand of silver nitrate, a second mixed liquid; (c), a dilute aqueous solution of hydrazine is dropped into the second mixed liquid to form a third mixed liquid, wherein the hydrazine reduces the silver ions to silver nanoparticles, and at the same time, the lauric acid The acid radical surrounds the silver nanoparticle as a protective group; (d) the silver nanoparticle with lauric acid as a protective group is separated from the third mixed liquid; (e), using cyclohexane as Solvent to prepare the above silver nanoparticle with lauric acid as a protective group as a fourth mixed liquid; (f) applying the fourth mixed liquid to one surface of a substrate to form a lauric acid Protecting the base silver nanoparticle film; and (g) immersing the substrate in an aqueous hydrazine solution to chemically reduce the silver nanoparticle film into a conductive silver film; wherein the steps (a) to (g) are It is carried out at room temperature.

In one embodiment of the invention, in step (a), the molar ratio of silver nitrate silver ions to lauric acid laurate is 1:2.

In an embodiment of the invention, in step (a), the non-polar solvent is toluene.

In one embodiment of the invention, in step (b), the molar ratio of silver ion silver nitrate to n-butylamine is 1:2.

In one embodiment of the invention, in step (c), the molar ratio of the silver nitrate silver ion to the hydrazine in the diamine diluted aqueous solution is 2:1.

In an embodiment of the present invention, in the step (c), the silver nanoparticles having the lauric acid as a protective group have an average particle diameter ranging from 6.20 ± 0.57 nm (nano).

In an embodiment of the present invention, in the step (d), acetone is first added to the third mixed liquid to precipitate the silver nanoparticles having the lauric acid as a protective group, followed by washing with methanol and acetone. The mixture was centrifuged and concentrated under reduced pressure to obtain the above-mentioned silver nanoparticles having lauric acid as a protective group.

In an embodiment of the present invention, in the step (e), the fourth mixed liquid is: the silver nanoparticle of the step (d) is prepared in advance by using cyclohexane containing 0.5 wt% of lauric acid as a solvent. A fourth mixture having 5.0 to 15.0% by weight of silver nanoparticles is prepared, which is a 30-day long-acting preservation solution which preferably has 10.0% by weight of silver nanoparticles.

In an embodiment of the invention, in step (f), the fourth mixture is selected to be applied to the surface of the substrate by spin coating or ink jet printing.

In an embodiment of the invention, in the step (f), the substrate is selected from a flexible plastic substrate, a glass substrate or a germanium wafer substrate, wherein the flexible plastic substrate is preferably polyparaphenylene. A substrate of polyethylene terephthalate (PET).

In an embodiment of the invention, in step (g), the hydrazine aqueous solution has a hydrazine concentration of from 70 to 90% by weight, for example 80% by weight.

In an embodiment of the invention, steps (a) to (g) are carried out at room temperature between 0 and 50 ° C, preferably between 10 and 40 ° C, especially between 20 Between 30 ° C, for example 25 ° C.

The above and other objects, features and advantages of the present invention will become more <RTIgt; Furthermore, the directional terminology referred to in the present invention, such as "upper", "lower", "inside", "outside" or "side", is merely a reference to the direction of the additional drawing. Therefore, the directional terminology used is for the purpose of illustration and understanding of the invention.

Referring to Figures 1 to 3, the method for forming a conductive film at room temperature according to the first embodiment of the present invention mainly comprises the following steps: (a) adding silver nitrate (AgNO ₃ ) to decanoic acid (C) ₁₁ H ₂₃ COOH, also known as n-dodecanoic acid or n-dodecanoic acid, is a first mixed solution; (b) n-butylamine (also known as n-butylamine) butylamine) was added dropwise to the first mixture of silver nitrate as silver ions ligand (ligand), into a second mixture; (c), the hydrazine _{(hydrazine, N 2 H 4 ‧H} 2 O, and A diluted aqueous solution called hydrazine is added to the second mixed solution to form a third mixed liquid in which the hydrazine reduces the silver ions to silver nanoparticles (NPs), while the lauric acid lauric acid is used as a protection. a capping ligand surrounding the silver nanoparticle; (d) separating silver nanoparticles (Ag-C ₁₁ H ₂₃ CO ₂ ) using lauric acid as a protecting group from the third mixture; (e) using cyclohexane as a solvent to blend the above silver nanoparticles with lauric acid as a protective group into a fourth mixture (f) spin coating the surface of one of the substrates to form a silver nanoparticle film having lauric acid as a protective group; and (g) The substrate is immersed in an aqueous hydrazine solution to chemically reduce the silver nanoparticle film into a conductive silver film; wherein the above steps (a) to (g) are carried out at room temperature. DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to Figures 1 through 3, and the details of the implementation of the above-described steps of the first and second embodiments and their reaction principles will be explained in detail.

Referring to FIG. 1 , the method for forming a conductive film at room temperature according to the first embodiment of the present invention first performs the step (a) of adding silver nitrate to a non-polar solvent containing lauric acid to form a first mixture. liquid. In this step, the present invention takes 31.69 ml of toluene as a non-polar solvent, and adds 3.3387 g (16.67 mmol) of dodecanoic acid to toluene, and after stirring until dissolved, 1.4156 g (8.33 mmol) is added. Silver nitrate (AgNO ₃ ) containing 0.25 molar concentration of silver ions, wherein silver nitrate in the first mixture is used as a silver ion precursor, and lauric acid in the first mixture is as follows In step (c), it will serve as a protecting ligand for silver nanoparticles, but in this step, lauric acid has not reacted with silver nitrate. Further, in the step (a), the molar ratio of the silver nitrate silver ion to the lauric acid laurate is maintained substantially at 1:2. The non-polar solvent is preferably selected from toluene, but may be selected from other equivalent non-polar solvents as desired.

Referring to FIG. 1, the method for forming a conductive film at room temperature according to the first embodiment of the present invention is followed by the step (b) of dropping n-butylamine into the first mixed liquid as silver nitrate. The ionic ligand becomes a second mixed solution. In this step, the present invention adds 1.6473 ml (16.67 mmol) of n-butylamine in one drop per second, and after the dropwise addition in 2.5 minutes, the reaction is continued for 3.5 minutes. The second mixture gradually turns into a milky white turbid suspension, that is, n-butylamine is used as a ligand for silver ions, so that silver ions and silver nitrate are separated first, and the milky white turbid suspension is suspended. The aspect shows that the second mixture contains a complex formed by the coordination of silver ions with n-butylamine. In step (b), the molar ratio of silver ion silver nitrate to n-butylamine is substantially maintained at 1:2.

Referring to FIG. 1, the method for forming a conductive film at room temperature according to the first embodiment of the present invention is followed by the step (c) of dropping a dilute aqueous solution of hydrazine (N ₂ H ₄ ‧H ₂ O) In the second mixed liquid, it becomes a third mixed liquid. In this step, the present invention preliminarily dilutes 80 wt% hydrazine (N ₂ H ₄ ‧H ₂ O) solution into 25 ml of deionized water to prepare a hydrazine diluted aqueous solution as a chemical reducing solution, which comprises 0.2607 g (4.17 mmol) of hydrazine. Then, after the reaction of the n-butylamine in the above step (b) for 3.5 minutes, the pre-formed aqueous solution of the hydrazine diluted into the second mixture is added to the second mixture in a drop per second to become a third mixed solution. The titration takes 15 minutes. After completion of the titration, the reaction is further carried out for 3 hours, wherein the hydrazine is used to reduce the silver ion having the n-butylamine as a temporary ligand to a metallic silver atom, and further reaggregate into silver nanoparticles, while The lauric acid laurate is used as a protective group around the silver nanoparticle. In the step (c), the molar ratio of the silver nitrate silver ion to the hydrazine in the diamine diluted aqueous solution is maintained substantially at 2:1.

In more detail, in the step (c), the silver ion having n-butylamine as a temporary ligand may be further reduced by the hydrazine into a metallic silver atom, and the silver atoms of the plurality of metal states may aggregate with each other (cluster) ) becomes a nanometer-sized silver nanoparticle. After aggregation, the average particle diameter of the above-mentioned silver nanoparticle particles is approximately 6.20±0.57 nm (nano), wherein each silver nanoparticle is actually counted Ten to hundreds of silver atoms are aggregated, and the outermost layer of silver nanoparticles will react with laurate to form an ionic complex, in which the outermost silver atoms will be converted into positively charged silver ions to bond a negatively charged laurate (as shown at the far right of Figure 1), which is used as a protective group and surrounds the silver nanoparticles (Ag-C ₁₁ H ₂₃ CO ₂ ). This can avoid the problem that the adjacent silver nanoparticles are further aggregated and then aggregated to expand the particle size, thereby effectively limiting the total number of silver atoms accumulated inside the silver nanoparticles to no longer increase, so as to stably maintain the silver nanoparticles. Particle size, the advantage of this is that it is Yinnai. The particle size of the particle to obtain a stable control, can effectively prevent the subsequent steps of conductive lines affected by the quality of the conductive particles are too large when forming a patterned circuit.

Referring to FIG. 1, the method for forming a conductive film at room temperature according to the first embodiment of the present invention is followed by the step (d) of separating the lauric acid as a protective group from the third mixed solution. Silver nanoparticles (Ag-C ₁₁ H ₂₃ CO ₂ ). In this step, after the hydrazine reaction is completed, 200 ml of acetone is first added to the third mixture to precipitate the silver nanoparticles having the lauric acid as a protective group, followed by a solution of methanol and acetone. The cleaning, centrifugation, and concentration under vacuum are carried out, so that a silver nanoparticle powder having a dark blue color and a lauric acid as a protective group can be obtained. However, the separation method of the present invention is not limited thereto, and the present invention may also use other existing separation techniques or other solvents to separate silver nanoparticles having lauric acid as a protective group from the third mixed liquid.

Referring to FIG. 2, the method for forming a conductive film at room temperature according to the first embodiment of the present invention is followed by the step (e) of using the above-mentioned lauric acid as a protecting group using cyclohexane as a solvent. The silver nanoparticles are blended to form a fourth mixed liquid 10. In this step, the present invention preliminarily uses cyclohexane having 0.5 wt% of lauric acid as a solvent, and adding silver nanoparticles of the step (d) to the solvent to prepare 5.0 to 15.0 wt%. a fourth mixed liquid 10 of silver nanoparticles, wherein the fourth mixed liquid 10 is a long-acting preservation suspension, which preferably has 10.0 wt% of silver nanoparticles, and the fourth mixed liquid 10 contains 0.5 wt% % lauric acid and cyclohexane, thus facilitating stable storage of silver nanoparticles with lauric acid as a protective group for at least about 30 days or more, and silver nanoparticles with lauric acid as a protective group can be stably suspended in It contains 0.5 wt% of lauric acid in cyclohexane solvent, so the fourth mixed liquid 10 can be used not only for storage purposes, but also to avoid the problem that the silver nanoparticles are enlarged due to further aggregation during storage. .

Referring to FIG. 2, the method for forming a conductive film at room temperature according to the first embodiment of the present invention is followed by the step (f) of spin coating the fourth mixed solution 10 on a substrate. On one of the surfaces 20, a silver nanoparticle film 11 having lauric acid as a protective group is formed. In this embodiment, the fourth mixed liquid 10 is selected to be applied to one surface of the substrate 20 via a spin-on liquid dispenser 30 in a spin coating manner, wherein the substrate 20 may be selected from a flexible type. a plastic substrate, a glass substrate or a wafer substrate, wherein the substrate is preferably selected from a flexible plastic substrate, for example, made of a low-temperature polyethylene terephthalate (PET) material. The substrate. In this step, the present invention performs a spin coating operation with a fourth mixed liquid 10 containing 10 wt% of silver nanoparticles (Ag-C ₁₁ H ₂₃ CO ₂ ) having a lauric acid as a protective group, wherein the substrate 20 was placed on a turntable and it was spin coated at 2000 rpm for 15 seconds to be evenly applied to the substrate 20 (e.g., a PET substrate). After the nitrogen is blown dry (or air-dried) to completely volatilize the cyclohexane in the fourth mixed solution 10, a silver nanoparticle film 11 having lauric acid as a protective group can be formed on the surface of the substrate 20. .

Referring to FIG. 2, the method for forming a conductive film at room temperature according to the first embodiment of the present invention is followed by the step (g) of immersing the substrate 20 in an aqueous hydrazine solution to form the silver nanoparticle. The film 11 is chemically reduced into a conductive silver film 12. In this step, the hydrazine concentration of the aqueous hydrazine solution is significantly higher than the hydrazine concentration of the aqueous hydrazine solution used in the step (c), wherein the hydrazine concentration of the aqueous hydrazine solution in this step is between 70 and 90 wt. %, for example, is preferably 80 wt%. In the present embodiment, the present invention is to soak the silver nanoparticle film 11 coated in the step (f) with a commercially available 80 wt% aqueous solution of hydrazine (N ₂ H ₄ ) at room temperature 25 ° C for one hour. Chemically, a conductive silver film 12 is obtained, and finally the surface of the conductive silver film 12 is washed with deionized water and blown dry (or air dried) with nitrogen. More specifically, the above hydrazine can also reduce the silver ions on the outer surface of the silver nanoparticles in the silver nanoparticle film 11 into a metallic silver atom, and simultaneously desorb the lauric acid from the silver lining. After the rice particles are reduced and desorbed, the silver nanoparticles contain only metallic silver atoms and can be tightly bonded to the upper surface of the substrate 20.

It should be noted that the above steps (a) to (g) are all carried out at room temperature, and the room temperature of the present invention means a normal temperature between 0 and 50 ° C, preferably between 10 and 40 ° C. In particular, it is between 20 and 30 ° C, for example 21, 23, 25, 27, 29 ° C. Furthermore, the conductive silver film 12 made by the above steps (a) to (g) is particularly suitable for use in a transparent conductive layer of an integrated circuit (IC) or a thin film transistor liquid crystal display (TFT-LCD) on a wafer. The line is fabricated or applied to the repair of its minor breakage defects.

Referring to FIG. 3, the method for forming a conductive film at room temperature according to the second embodiment of the present invention is similar to the first embodiment of the present invention, and substantially uses the same component name and figure number, but compared to the first In a preferred embodiment, the second embodiment comprises the steps of: (a) adding silver nitrate (AgNO ₃ ) to a non-polar solvent containing lauric acid (C ₁₁ H ₂₃ COOH) to form a first mixed liquid; (b) adding n-butylamine to the first mixed liquid as a silver ion ligand of silver nitrate to form a second mixed liquid; (c), hydrazine (N ₂ H ₄ ‧H ₂ O) The diluted aqueous solution is dropped into the second mixed liquid to form a third mixed liquid, wherein the hydrazine reduces the silver ions to silver nanoparticles, and the lauric acid lauric acid surrounds the silver nanoparticles as a protective group; (d) separating silver nanoparticles (Ag-C ₁₁ H ₂₃ CO ₂ ) having lauric acid as a protective group from the third mixed liquid; (e) using cyclohexane as a solvent The silver nanoparticle with lauric acid as a protecting group is formulated into a fourth mixed liquid; (f) the inkjet printing of the fourth mixed liquid (inkje t printing) on one surface of a substrate to form a silver nanoparticle film with lauric acid as a protective group; and (g) immersing the substrate in an aqueous hydrazine solution to coat the silver nanoparticle film Chemically reducing to a conductive silver film; wherein the above steps (a) to (g) are carried out at room temperature.

In the second embodiment of the present invention, the difference is characterized in that, as shown in FIG. 3, the step (f) of the second embodiment is further changed to an inkjet printing method instead of a spin coating. The way. In the second embodiment of the present invention, the fourth mixed liquid 10 is selected to be applied to one of the upper surfaces of the substrate 20 via an inkjet liquid dispenser 40 in a spin coating manner, wherein the substrate 20 may be selected from the group consisting of A flexible plastic substrate, a glass substrate or a wafer substrate, preferably selected from a flexible plastic substrate, such as a substrate made of a low-cost PET material that is not resistant to high temperatures.

In the present step (f), the present invention performs a printing operation by using a fourth mixed liquid 10 containing 10 wt% of silver nanoparticles (Ag-C ₁₁ H ₂₃ CO ₂ ) having a lauric acid as a protective group. Wherein the substrate 20 is fixed on a working platform or a moving platform, and then the inkjet liquid distributor 40 is used to perform an inkjet operation on the upper surface of the substrate 20 to uniformly spray the fourth mixed liquid 10 It is printed on the substrate 20 (for example, a PET substrate). After the nitrogen is blown dry (or air-dried) to completely volatilize the cyclohexane in the fourth mixed solution 10, a silver nanoparticle film 13 having lauric acid as a protective group can be formed on the surface of the substrate 20. It can be a patterned line shape. Next, in the step (g), the substrate 20 is immersed in an aqueous hydrazine solution to chemically reduce the silver nanoparticle film 13 into a conductive silver film 14. Steps (a) to (e) and (g) of the second embodiment are substantially the same as those of the first embodiment, and thus the description thereof will not be repeated.

As described above, compared with the prior art method of forming a conductive film, the silver nanoparticles protected with orthosilicate have poor stability of the nano particles at room temperature and need to be calcined at a temperature higher than 150 ° C. The silver nanoparticle coating is reduced on the hard crucible substrate to form a highly conductive silver film, which is not suitable for the heat-resistant flexible plastic substrate, and has the disadvantages of time-consuming and high-risk process, and the first to third figures In the present invention, silver nitrate is first added to a solution containing lauric acid, and then n-butylamine is added as a silver ion ligand in sequence, and the silver ion is reduced to silver nanoparticles by dropwise addition of a diamine diluted aqueous solution to obtain a preliminary Saturated lauric acid as a stable protective group of silver nanoparticles, and then using cyclohexane as a long-acting solvent to spin or spray the above-mentioned silver nanoparticles with lauric acid as a protective group on the surface of the substrate. In order to form a patterned silver nanoparticle film, and finally immersing the substrate in a high concentration aqueous solution of hydrazine to chemically reduce the silver nanoparticle film into a conductive silver film, the method can be printed on the substrate simply and quickly. Forming a patterned thin film or a line, but the whole process may be carried out at room temperature, the applied potential can be greatly increased the cost of silver nanoparticles in the flexible substrate (e.g., PET substrate) is not of high temperature.

Furthermore, the present invention preliminarily preserves a silver nanoparticle having lauric acid as a protective group by using cyclohexane containing 0.5 wt% of lauric acid as a solvent for a period of 30 to 15.0 wt% for 30 days. The solution makes the silver nanoparticles not easily aggregate and coagulate in the cyclohexane-containing cyclohexane solution, and maintains the uniformity of the size of the nanoparticles, thereby improving the printing quality of the silver nanoparticles applied in the printing process.

The present invention has been disclosed in its preferred embodiments, and is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

10‧‧‧ fourth mixture

11‧‧‧Silver Nanoparticle Film

12‧‧‧ Conductive silver film

13‧‧‧Silver Nanoparticle Film

14‧‧‧ Conductive silver film

20‧‧‧Substrate

30‧‧‧Spin coating dispenser

40‧‧‧Inkjet Dispenser

Fig. 1 is a view showing the steps (a) to (d) of the method for forming a conductive film at room temperature according to the first embodiment of the present invention.

Fig. 2 is a view showing the steps (e) to (g) of the method of forming a conductive film at room temperature in the first embodiment of the present invention.

Fig. 3 is a view showing the steps (e) to (g) of the method of forming a conductive film at room temperature in the second embodiment of the present invention.

10. . . Fourth mixture

11. . . Silver nanoparticle film

12. . . Conductive silver film

20. . . Substrate

30. . . Spin coating dispenser

Claims (12)

A method for forming a conductive film at room temperature, comprising: (a) adding silver nitrate to a non-polar solvent containing lauric acid to form a first mixed liquid; (b) dropping n-butylamine into the first a silver ion ligand as a silver nitrate ion in a mixed solution; (c), a dilute aqueous solution of hydrazine is dropped into the second mixed liquid to form a third mixed liquid, wherein the hydrazine is silver The ions are reduced to silver nanoparticles, and the lauric acid of lauric acid is used as a protective group around the silver nanoparticles; (d) the silver with the lauric acid as a protective group is separated from the third mixture Nanoparticles; (e), using 0.5% by weight of cyclohexane of lauric acid as a solvent to prepare the silver nanoparticles of step (d) into a fourth mixture; (f), the fourth mixture Applying a liquid to a surface of a substrate to form a silver nanoparticle film having lauric acid as a protective group; and (g) immersing the substrate in an aqueous solution of hydrazine having a concentration of 70 to 90% by weight, Chemically reducing the silver nanoparticle film into a conductive silver film; wherein the above steps (a) to (g) are at room temperature Go on. A method of forming a conductive film at room temperature as described in claim 1, wherein in step (a), the molar ratio of silver nitrate silver ions to lauric acid laurate is 1:2. Forming a thin conductive film at room temperature as described in claim 1 A method of film, wherein in step (a), the non-polar solvent is toluene. A method of forming a conductive film at room temperature as described in claim 1, wherein in step (b), the molar ratio of silver ion silver nitrate to n-butylamine is 1:2. The method for forming a conductive film at room temperature according to claim 1, wherein in the step (c), the molar ratio of the silver nitrate silver ion to the hydrazine diluted aqueous solution in the aqueous solution is 2:1. . The method for forming a conductive film at room temperature according to claim 1, wherein in the step (c), the average particle diameter of the silver nanoparticles having the lauric acid as a protective group is 6.20±0.57. Nano. The method for forming a conductive film at room temperature according to claim 1, wherein in the step (d), acetone is first added to the third mixture to make the lauric acid as a protective base. The nanoparticles were precipitated, followed by washing with methanol and acetone, centrifugation, and concentration under reduced pressure to obtain the above-mentioned silver nanoparticles having lauric acid as a protective group. A method of forming a conductive film at room temperature as described in claim 1, wherein in the step (e), the fourth mixture has 5.0 to 15.0% by weight of silver nanoparticles. A method of forming a conductive film at room temperature as described in claim 1, wherein in the step (f), the fourth mixture is selected to be applied to the surface of the substrate by spin coating or ink jet printing. on. Forming a thin conductive film at room temperature as described in claim 1 The method of the film, wherein in the step (f), the substrate is selected from a flexible plastic substrate, a glass substrate or a wafer substrate. The method for forming a conductive film at room temperature according to claim 10, wherein the flexible plastic substrate is a polyethylene terephthalate substrate. A method of forming a conductive film at room temperature as described in claim 1, wherein steps (a) to (g) are carried out at room temperature between 20 and 30 °C.