KR20030066169A - A method of producing ITO sol by Metal-Organic Decomposition processing - Google Patents

Abstract

PURPOSE: A preparation method of nano-sized indium tin oxide(ITO) sol by metal-organic decomposition(MOD) is provided, which increases stability against moisture and enables produce thin films showing no cracks unlike conventional wet method. CONSTITUTION: The ITO sol is prepared by the following steps of: (S1) dissolving indium acetate and C6H36Sn into 2-ethylhexanoic acid to be a In/Sn molar ratio of 1.86 : 0.14; (S2) heating the mixture at 200deg.C to volatilize a reaction product, acetic acid, and stirring to get a transparent yellow ITO sol from the opaque mixed solution; (S3) adding a hydrophobic solvent, 2-ethyl-1-hexanol, to give stability against moisture; (S4) aging the formed yellow ITO sol over 5hrs to get a concentrated ITO sol.

Description

A method of producing ITO sol by Metal-Organic Decomposition processing

The present invention relates to a method for producing indium tin oxide (ITO) sol using a metal-organic decomposition (MOD) method.

Indium Tin Oxide (ITO) is a light-transmissive conductive thin film that has high light transmittance and high electrical conductivity. It is also used as an electrode for optical materials, heat reflector and anti-static thin film, and the demand for ITO (Indium Tin Oxide) sol, the basic material, is expected to continue to increase. The sol-gel method and the MOD method of the wet chemical thin film manufacturing method are the same in that they use an organometallic compound.However, unlike the sol-gel method using the hydrolysis of a complex metal alkoxide (low molecular weight compound), the MOD method has a high molecular weight. There is a difference that a thin film is produced without using a organometallic compound as a raw material or a solvent without forming a gel. In particular, the sol-gel method dissolves metal alkoxides in a common solvent and prepares raw materials through complex processes such as reflux and distillation. Since these raw materials solutions are very sensitive to moisture, a controlled atmosphere is always required, and problems are likely to occur when the raw materials solution is stored for a long time. In addition, in the sol-gel method, a polymerization reaction occurs through hydrolysis of alkoxide during thin film formation. Therefore, in order to prepare a thin film, a stabilizer for controlling the hydrolysis rate and solvent evaporation must be added to the raw material solution. These processes complicate the sol-gel method, and even though the stabilizer is added, the solvent is evaporated at the same time as the polymerization reaction during the drying process after coating, so that stresses in the vertical and horizontal directions are easily generated and cracks are likely to occur. There is this.

In order to overcome this disadvantage, the present invention applies a metal-organic decomposition (MOD) method to prepare a coating sol. The MOD method is not only capable of uniform mixing from the raw material preparation stage to the molecular unit, which is an advantage of the general wet method, but also has the advantage that the manufacturing cost is low due to the relatively simple equipment and equipment, while being able to manufacture components of complex composition. For this reason, the final product can be obtained stably and it is easy to establish reproducibility. In addition, unlike the sol-gel method, the MOD method uses a hydrophobic solvent with a large molecular weight to increase the stability of the raw material solution to moisture, and the polymerization reaction occurs after all the solvents have evaporated even during the drying process. By rising in parallel with it, a thin film without cracks can be obtained. FIG. 5 is a cross-sectional SEM photograph of a uniform ITO thin film obtained by repeatedly coating an indium tin oxide (ITO) sol prepared by completing a reaction 10 times on a substrate, followed by drying at 300 ° C. and heat treatment at 500 ° C. FIG.

1 is a manufacturing process of the sol according to the present invention.

Figure 2 is a schematic diagram of the ITO sol synthesis apparatus used in the present invention.

3 is an XRD pattern measured after drying and heat treatment at 600 ℃ the ITO sol prepared by the present invention.

4 is an X-ray diffraction pattern result of heat treatment in the range of 500 ~ 700 ℃ of a thin film made of a transparent conductive ITO sol prepared according to a preferred embodiment of the present invention.

5 is a cross-sectional SEM photograph of a transparent conductive ITO thin film prepared by repeated coating 10 times in accordance with a preferred embodiment of the present invention.

In order to achieve the above object, the present invention,

Mixing the raw materials in a common solvent at a predetermined ratio (S1);

Heating and stirring the mixture mixed in the step (S1) (S2);

Synthesizing the reactants with sol in a reactor (S3);

Adding a hydrophobic solvent 2-Ethyl-1-hexanol to the reactant (S4); And

It provides a method for producing indium tin oxide (ITO) sol comprising the step (S5) of aging the product made in the step (S4) in a reactor for a certain time.

Preferably, the purity of the product is at least 99.99%.

As mentioned above, in the manufacturing method of indium tin oxide (ITO) sol according to the present invention, the sol is manufactured using the MOD method. Hereinafter, a manufacturing process of an indium tin oxide (ITO) sol according to the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 2 is a diagram of a synthesis reactor used to carry out the present invention. Referring to FIG. 2, the synthesis reactor is composed of a heating mantle capable of maintaining a constant temperature, a stirer, and a vessel equipped with a thermocouple and a hermetic seal.

On the other hand, Figure 1 is a process diagram showing an example of the ITO sol manufacturing process according to the present invention. The manufacturing process of ITO sol by MOD method is demonstrated with reference to FIG. 1 and FIG.

The present invention is a method of preparing a sol after dissolving the raw material in a solvent at a molar ratio of In: Sn = 1.86: 0.14, which is the best molar ratio in consideration of the solid solution limit (20%) of Indium and Tin, the material ratio, and the characteristics of the thin film after coating. . ITO sol prepared through the present invention is preferably at least 99.99% purity.

Hereinafter, a preferred embodiment of the present invention will be briefly described.

Example

A certain amount of indium acetate is dissolved in a common solvent, 2-Ethylhexanoic acid, and C ₁₆ H ₃₆ Sn is dissolved in 2-Ethylhexanoic acid to prepare an aqueous solution so that the molar ratio of Indium and Tin is 1.86: 0.14. Subsequently, the aqueous solution is charged into a vessel maintained at 200 ° C., which is a temperature higher than the volatilization temperature of Acetic acid 118 ° C. to remove Acetic acid, the main reaction product, and the solution is stirred for a certain period of time. Transparent ITO sol is synthesized. In order to give this sol stability to water, it is yellow to reddish brown when hydrophobic solvent 2-Ethyl-1-hexanol is added and aged for 5 hours at the same temperature to intensify the homogeneous mixing and reaction of ions. Is a concentrated sol.

FIG. 3 shows the XRD pattern of the powder obtained by preparing ITO sol through the reactor shown in FIG. 2 and drying and heat-treating at 600 ° C. FIG. From this result, it can be seen that the pure ITO powder was synthesized, and ITO sol was successfully synthesized in the previous step. 4 is an X-ray diffraction pattern result of heat treatment in the range of 500 ~ 700 ℃ of a thin film made of a transparent conductive ITO sol prepared according to a preferred embodiment of the present invention. As a result, the intrinsic ITO peak was confirmed in the thin film heat-treated at 500 ° C. or higher, and the ITO thin film was successfully coated on the substrate.

As mentioned above, the manufacturing method of the ITO sol by the MOD method according to the present invention has a simpler process than the other manufacturing method, high stability of the prepared sol, simple equipment, and relatively low manufacturing cost. In addition, uniform mixing from the preparation stage of the raw material to the molecular unit is possible, and it is easy to prepare complex components. In addition, compared to the sol-gel method, the stability to moisture is higher and there is an advantage that a uniform thin film can be obtained when manufacturing the thin film.

In particular, ITO sol is a basic material used to manufacture transparent conductive thin films, and is mainly used as an electrode for electro-optic materials such as PDP LCD and EL, and its application and demand are expected to continue to increase. Therefore, by manufacturing ITO sol using this MOD method, it can greatly contribute to the national economic development as well as to strengthen international competitiveness in the display sector.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (3)

Mixing the raw materials in a common solvent at a predetermined ratio (S1); Heating and stirring the mixture mixed in the step (S1) (S2); Synthesizing the reactants with sol in a reactor (S3); Adding a hydrophobic solvent 2-Ethyl-1-hexanol to the reactant (S4); And Method for producing an indium tin oxide (ITO) sol comprising the step (S5) of aging the product made in the step (S4) in a reactor for a certain time The method of claim 1, wherein the hydrophobic solvent 2-Ethyl-1-hexanol is added to the prepared sol to increase the stability against moisture. The method of claim 1, wherein the raw material is prepared so that the molar ratio of Indium and Tin is 1.86: 0.14.