KR20110132282A - Method for fabricating ito paste of transparent electrode and ito paste using the same - Google Patents

Abstract

PURPOSE: A producing method of ITO paste for a transparent electrode, and the ITO paste for the transparent electrode are provided to obtain ITO nanopowder using a low temperature synthesis method. CONSTITUTION: A producing method of ITO paste for a transparent electrode comprises the following steps: synthesizing ITO nanopowder(S1); mixing 5-85wt% of ITO nanopowder with 2-4wt% of dispersant and 11-93wt% of solvent(S2); stirring the mixture(S3); milling the stirred mixture(S4); and filtering the milled mixture(S5).

Description

Method for fabricating ITO paste for transparent electrode and ITO paste for transparent electrode

The present invention relates to a method for preparing a transparent electrode ITO paste and to an ITO paste prepared by the above, and more particularly, to prepare a transparent electrode by coating the ITO paste on the substrate by manufacturing the transparent electrode ITO paste that can be baked at a low temperature The present invention relates to a method for producing an ITO paste for a transparent electrode and to an ITO paste prepared thereby.

Recently, as mobile phones, personal digital assistants (PDAs), game consoles, navigation systems, and digital media broadcasting (DMB) receivers equipped with touch screen functions are rapidly advanced and commercialized, information transmission media are becoming more diverse and multifunctional.

The emergence of next-generation displays, such as electronic paper, curved displays, and electronic devices, means that the electrodes, which had previously only been considered electrical characteristics, have now reached the point where both electrical and optical characteristics should be considered.

When the electrodes used in electronic devices are largely divided into two categories, they can be divided into low resistance metal electrodes for wiring capable of transmitting electrical signals, and oxide electrodes for pixels and common electrodes having optically transparent characteristics.

In general, as the wiring electrode, a metal material having a low specific resistance such as aluminum, molybdenum, copper, etc. is mainly used, and it is preferable to select a material capable of minimizing signal delay due to RC delay rather than an optical function.

In addition, oxide-based indium tin-oxide (ITO), indium-zinc-oxide (IZO), and SnO ₂ are widely used in the industry as optically transparent electrodes having high electrical conductivity.

In addition, there is a method of making a thin metal film such as Ag and Au to use as a transparent electrode, but the metal film has a high electrical conductivity compared to the oxide transparent electrode, but has a disadvantage in that the transmittance in the visible light region is very poor, it is not widely used. I can't.

Conventionally, oxide transparent electrodes such as ITO and IZO form thin films in a vacuum state by using sputtering, e-beam evaporation, and the like. Should be used. And the ITO powder for these methods is a complex process of several steps, which leads to an increase in manufacturing cost. In addition, these methods often use toxic chemicals such as hydrochloric acid or nitric acid, which can result in environmental pollution.

And the above methods are accompanied by a high temperature heat treatment process of about 700 ℃ or more, accordingly, there is a problem that the specific surface area is reduced by coarse particles.

In order to solve the problems of the prior art, it is an object of the present invention to provide a method for producing ITO paste for transparent electrodes that can be fired at a low temperature.

In addition, the present invention has another object to provide a method for producing a transparent electrode ITO paste capable of forming a transparent electrode through a coating.

In addition, another object of the present invention is to provide a method for preparing an ITO paste for a transparent electrode capable of forming a transparent electrode having high light transmittance and electrical conductivity.

In order to achieve the above object, ITO paste manufacturing method for a transparent electrode according to the present invention, the synthesis step of synthesizing ITO nanopowder; A mixing step of making a mixture by mixing a dispersant and a solvent with the ITO nanopowder synthesized through the synthesis step; A stirring step of stirring the mixture formed through the mixing step; Milling step of milling the mixture stirred through the stirring step; And a filtering step of filtering the mixture milled through the milling step.

In the present invention, the mixing step may be mixed in a weight ratio of 5 to 85% by weight of the ITO nanopowder, 2 to 4% by weight of the dispersant and 11 to 93% by weight of the solvent.

In the present invention, the dispersant may be polyvinylpyrrolidone.

In the present invention, the solvent may be composed of ethylene glycol (ethylene glycol) and ethanol (ethanol).

In the present invention, the ethylene glycol and the ethanol may be mixed in a ratio of 4 to 6: 1.

In the present invention, the synthesis step, the process of making an organic solution by mixing In acetate (Acetate) and Sn acetate with an organic solvent, stirring the organic solution, evaporation of the organic solvent in the organic solution ITO precursor It may include a process of making a (precursor) state and the heat treatment of the ITO precursor.

In the present invention, the In acetate and the Sn acetate may have a volume ratio of 8 to 10: 1.

In the present invention, the organic solvent may be acetone or ethanol.

In the present invention, the heat treatment temperature may be 250 ℃ to 350 ℃.

Meanwhile, the transparent electrode ITO paste prepared according to the present invention may be formed on a substrate through a coating process, and may be cured by heat treatment at 250 ° C. to 350 ° C. for 30 minutes to 90 minutes to form a transparent electrode.

According to the present invention, ITO nanopowders can be prepared through low temperature synthesis. The ITO nanopowder can be manufactured using the ITO nanopowder at low temperature, and through this, a transparent electrode can be formed on the substrate through a coating process.

In addition, according to the present invention, it is possible to simplify the transparent electrode forming process through the coating process, thereby reducing the manufacturing cost for the transparent electrode.

In addition, according to the present invention, it is possible to form a transparent electrode having high light transmittance and electrical conductivity by controlling the concentration of the ITO nanopowders used and filtering the ITO paste.

1 is a process flowchart showing step by step a manufacturing method of the transparent electrode ITO paste according to an embodiment of the present invention,
2 is a graph showing the X-ray rotation pattern of the ITO powder synthesized according to the embodiment of the present invention,
3 is a high resolution photograph showing the ITO powder synthesized according to an embodiment of the present invention,
4 is a graph showing the dispersion state according to the concentration of the ITO powder synthesized according to the embodiment of the present invention,
5 is a graph showing the thermal characteristics of the transparent electrode paste prepared according to an embodiment of the present invention,
Figure 6a is a real photo of a transparent electrode paste prepared in accordance with an embodiment of the present invention coated on a substrate and a low temperature heat treatment,
FIG. 6B is a photograph taken by scanning electron microscope of FIG. 6A;
7A to 7D are graphs showing changes in light transmittance of transparent electrode pastes prepared according to embodiments of the present invention.

The objects, features and advantages of the present invention will be more readily understood by reference to the accompanying drawings and the following detailed description.

Specific structural or functional descriptions are merely illustrated for the purpose of describing embodiments in accordance with the concepts of the present invention, and embodiments in accordance with the concepts of the present invention may be embodied in various forms and described in the specification or the application. It should not be construed as limited to these.

The embodiments according to the concept of the present invention can make various changes and have various forms, so that specific embodiments are illustrated in the drawings and described in detail in this specification or application. However, it should be understood that the embodiments according to the concept of the present invention are not intended to limit the present invention to specific modes of operation, but include all changes, equivalents and alternatives included in the spirit and scope of the present invention.

Terms such as first and / or second may be used to describe various components, but the components are not limited to the terms. The terms are for the purpose of distinguishing one component from other components only, for example, without departing from the scope of the rights according to the inventive concept, the first component may be named a second component, Similarly, the second component may also be referred to as the first component.

When a component is referred to as being connected or connected to another component, it should be understood that there may be a direct connection or connection to that other component, but there may be other components in between. On the other hand, when a component is mentioned as being directly connected to or directly connected to another component, it should be understood that there is no other component in between. Other expressions to describe the relationship between components, such as 'between' and 'just between' or 'neighboring to' and 'directly neighboring', should likewise be interpreted.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. The terms 'comprise' or 'having' in this specification are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof that is implemented, and that one or more other features or numbers, It is to be understood that it does not exclude in advance the possibility of the presence or addition of steps, actions, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be interpreted as having meanings consistent with the meanings in the context of the related art, and are not construed in ideal or excessively formal meanings unless expressly defined herein. Do not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

Referring to Figure 1, the method for manufacturing a transparent electrode ITO paste according to an embodiment of the present invention is a method for producing an ITO paste for making a transparent electrode through a coating process and a low temperature baking process, the synthesis step (S1), mixing Step (S2), stirring step (S3), milling step (S4) and filtering step (S5), each step is carried out sequentially.

First, the synthesis step (S1) is a step of synthesizing the ITO nanopowder. This synthesis step (S1) can be subdivided into a series of processes. That is, the synthesis step (S1) is divided into the process of making the organic solution, the process of stirring, the process of making the ITO precursor state and the process of heat treatment. In the process of making an organic solution, In acetate (Acetate) and Sn acetate are mixed with an organic solvent to make an organic solution. In this case, In acetate and the Sn acetate may have a volume ratio of 8 to 10: 1, preferably 9: 1. In an embodiment of the present invention, 18,928 g of Inacetate and 1.571 g of Sn acetate having a purity of 99.99% and 1.571 g of Sn acetate are placed in a 500 ml beaker, and 100 ml of an organic solvent is placed in a beaker to dissolve In acetate and Sn acetate in an organic solvent. Make a solution. In this case, acetone or ethanol may be used as the organic solvent.

In addition, in the stirring process, in order to stir the organic solution, the beaker containing the organic solution is stirred using a stirrer. At this time, the stirring for the organic solution may proceed at a speed of approximately 300rpm, the stirring time is preferably performed within the range of 3 hours to 24 hours. In order to further increase the stirring efficiency, a stirring aid such as a magnetic stirrer may be placed in the beaker and stirring may be performed.

In addition, in the process of making the ITO precursor state, the organic solvent is evaporated at room temperature to make the organic solution in the ITO precursor state.

In the heat treatment process, ITO precursors are made thin and placed in an electric furnace. The ITO precursor is heat treated at 250 ° C. to 350 ° C., preferably at 300 ° C. for 1 hour. At this time, it is preferable to continuously supply air to the electric furnace.

In addition, the heat-treated ITO precursor is, for example, put in a bowl, pulverized and pulverized by a fine sieve (sieve), the step (S1) of synthesizing the ITO nanopowder is completed.

FIG. 2 is a graph showing an X-ray diffraction pattern of ITO nanopowders synthesized according to an embodiment of the present invention. The X axis of the graph is a diffraction angle (2θ) and the Y axis is intensity. As shown in FIG. 2, the ITO nanopowder synthesized according to the embodiment of the present invention had a large peak value in the (222) crystal direction at 30.5 (2θ) and a peak value in the (400) crystal direction at 36.7 (2θ). Since the peak value in the (440) crystal direction was measured at 50.9 (2θ), it can be seen that the crystallinity of the synthesized ITO nanopowder is excellent. And Figure 3 is a high-resolution transmission electron microscopy (HRTEM) analysis of the synthesized ITO nanopowder according to an embodiment of the present invention, it can be seen that the size of the synthesized ITO nanopowder is 10nm class. For reference, the size of the ITO nanopowder can be confirmed to be the same size as the HRTEM analysis photo by calculation through the Scherrer equation, based on the result of XRD (x-ray diffraction) measurement.

In addition, Figure 4 is a graph showing the dispersion state according to the concentration of the ITO nano-powder synthesized according to the embodiment of the present invention, showing the relationship of the retention time according to the concentration of the ITO nano-powder. Referring to Figure 4, it can be seen that the dispersion state is good when using 10% by weight of ITO nanopowder according to an embodiment of the present invention. And it can be seen that the higher the solid content, the shorter the retention period of dispersion.

Next, the mixing step (S2) is a step of making a mixture by mixing a dispersant and a solvent to the ITO nanopowder synthesized through the synthesis step (S1). In this step, 5 to 85% by weight of ITO nanopowder, 2 to 4% by weight of dispersant, and 11 to 93% by weight of solvent can be mixed, using 10% by weight of ITO nanopowder having a relatively good dispersion state. Therefore, it is preferable to mix a dispersing agent by 3 weight% and a solvent by weight ratio of 87 weight%. At this time, the dispersant may be used polyvinylpyrrolidone (polyvinylpyrrolidone). In addition, the solvent may be composed of ethylene glycol (ethylene glycol) and ethanol (ethanol), it may be mixed in a ratio of 4 to 6: 1 preferably 5: 1.

Next, the stirring step (S3) is a step of stirring the mixture mixed through the mixing step (S2). In this step, the mixed mixture is placed in a beaker and stirred using a stirrer. At this time, the stirring speed and time is preferably proceed in consideration of the viscosity of the mixture.

Next, the milling step (S4) is a step of milling the stirred mixture through the stirring step (S3). In this step, the stirred mixture is milled. At this time, the milling is preferably about 4 hours.

Finally, the filtering step (S5) is a step of filtering the mixture milled through the milling step (S4). Filtering the milled mixture through the milling operation, to complete the transparent electrode ITO paste according to an embodiment of the present invention.

The ITO paste for the transparent electrode completed after the filtering step S5 is made of a transparent electrode through low temperature baking. Here, the transparent electrode is made by forming an ITO paste on the substrate through a coating process and then curing through heat treatment at 250 ° C. to 350 ° C. for 30 to 90 minutes. In this case, the coating process may be any one of screen printing, inkjet printing, gravure printing or roll-to-roll printing.

5 to 6b illustrate the results of evaluating the characteristics of the transparent electrode made of the ITO paste and the characteristics of the transparent electrode prepared according to the embodiment of the present invention.

Figure 5 is a graph showing the thermal properties of the transparent electrode paste prepared in accordance with an embodiment of the present invention, shows that the solvent and the additives are pyrolyzed at low temperatures. That is, the ITO paste for the transparent electrode according to the embodiment of the present invention can implement the transparent electrode in the heat treatment below 300 ℃.

In addition, Figure 6a is a real photo of the transparent electrode paste prepared in accordance with an embodiment of the present invention coated on the substrate and the low-temperature heat treatment, Figure 6b is a photograph measured by a scanning electron microscope in Figure 6a, cured through the naked eye You can check the degree and transparency.

The following tests were performed on the ITO paste according to the embodiment of the present invention.

ITO POWDER
(w%)
PVP (w%)
Ethylene Glycol (w%)
Ethanol (w%)
Resistance
Transmittance (%) Save
stability
(term) Example 1       5     1.5    77.9     15.6 More than 10 ⁷      91 45 days Example 2      10      3    75     15    2400      90 30 days Example 3      15     4.5    70.8     14.2    1800      90 15th Example 4      20      6    66.7     13.3    1300      89 10 days Example 5      25     7.5    62.5     12.5    818      88 7 days Example 6      30      9    58.3     11.7    456      87 5 days

As can be seen through Examples 1 to 6 above, it can be seen that the resistance value is lowered as the solid content of the ITO powder is increased. Examples 1 to 6 were carried out under the same conditions (1000 rpm, 600 ° C.).

In the case of the above embodiments, it can be seen that each of the solids content is different. If the solids content is changed through this, the thickness is all different under a certain rpm (spin coating speed) when coating the substrate, that is, a constant speed when the solid content is high. As the coating amount increases under the following conditions, the resistance value is lowered, and on the contrary, the transmittance is lowered (in the case of a low temperature condition).

On the other hand, since the transmittance and the resistance value may also vary depending on the firing conditions, in the test according to the embodiment of the present invention as described above, the solid content in a fixed state such as the firing temperature, coating speed, dispersant, content of the dispersion medium, etc. The property comparison was performed only by the change of content.

7A to 7D are graphs showing changes in the light transmittance of the transparent electrode paste prepared according to the embodiment of the present invention for the case where the solid content is 10%, 15%, 25%, and 30%, respectively.

7A to 7D, it can be seen that the ITO paste according to the embodiment of the present invention exhibits a light transmittance of about 90% on average under various conditions, and the transmittance difference according to the concentration of the ITO nanopowders used at this time. It is not large and it can be seen that there is a difference in light transmittance depending on whether or not the filtering step (S5).

In addition, the sheet resistance of the transparent electrode produced by low-temperature firing the ITO paste prepared according to the embodiment of the present invention shows an average of 2100 ± 300 kW / □ (ohm / sq). In other words, when the transparent electrode was coated with a thickness of 660 nm, the sheet resistance was 2400 Ω / □ (ohm / sq), and when the transparent electrode was coated with the 750 nm thickness, the sheet resistance was 1800 Ω / □ (ohm / sq). It was. Through this, it can be seen that the higher the coating thickness, the lower the resistance value. And it can be inferred that the higher the concentration of ITO nanopowder and the further the filtering step (S5), the lower the resistance value.

In addition, the specific surface area of the transparent electrode was measured to be 80 m 2 / g or more through the ITO paste prepared according to the embodiment of the present invention. This is implemented through low temperature firing, which increases the specific surface area by more than 10 times compared to the conventional high temperature heat treatment.

ITO POWDER
(w%)
Dispersant Ethylene Glycol (w%)
Ethanol (w%)
Resistance Dispersion stability (period) Example 7      25     PVP    62.5     12.5    818     7 days Example 8      25   CMC salt    62.5     12.5    1400     5 days Example 9      25    HPMC    62.5     12.5    830     7 days Example 10      25 Ester type dispersant    62.5     12.5  Not measurable     20 days Example 11      25 Amine type
Dispersant
62.5
12.5
Not measurable
22 days

In Examples 7 to 11 of the present invention as shown in the above table, the dispersant was selected from the content ratio of the optimum degree of dispersion through the respective tests, the results of the test using the pvp and hpmc In this case, the resistance was relatively low.

In the case of the test as well, the results were different for each condition, so the dispersion content of each dispersion was selected based on the solid content ratio of 25%, which is inferior in dispersion stability. For example, in the case of PVP, more than 3w% Since the dispersion stability was good, the minimum amount was set to 3w% and other dispersants were similarly set after the test. The remaining conditions are the same as those of the first to sixth embodiments.

ITO POWDER
(w%) Dispersant
(PVP)  Dispersion medium 1   Dispersion medium 2 Resistance Dispersion stability (period) Example 12      15     4.5    PEG300     Ethanol  Not measurable    45 days Example 13      15     4.5    PEG200     Ethanol  Not measurable    30 days Example 14      15     4.5    PEG100     Ethanol 10 ¹¹    20 days Example 15      15     4.5 Ethylene Glycol     Ethanol    1800    15th Example 16      15     4.5    MEK     Ethanol  Not measurable   3 hours Example 17      15     4.5   ACETONE     Ethanol  Not measurable   4 hours

In Examples 12 to 17 of the present invention as shown in the above table, as a result of confirming the dispersion medium showing the optimum dispersion stability for each dispersion medium, in the case of Example 12, the dispersion stability was optimal, but the resistance was relatively Increasing results were obtained (not measured), and in the case of Example 16 and Example 17, it was confirmed that a result of very low dispersion was obtained.

Therefore, as a result of the experiment, the case of Example 15 is compared with the resistance value compared to the dispersion stability, it is determined that the most preferable data (condition: 1000rpm, 300-400 ℃).

As described above, the present invention can produce ITO nanopowders through a low temperature synthesis method, it is possible to prevent the coarse ITO nanopowders. And using the ITO nano-powder can be prepared ITO paste that can be baked at a low temperature. In addition, since the transparent electrode can be formed using the low temperature calcinable ITO paste, it is possible to coat the ITO paste on the substrate through a simple coating process, thereby simplifying the overall process, thereby reducing manufacturing costs. Can be.

In addition, it is possible to form a transparent electrode having high light transmittance and electrical conductivity by controlling the concentration of the ITO nanopowder used and filtering the ITO paste.

As described above, with reference to the preferred embodiment of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated that it can be changed.

Claims (11)

Synthesis step of synthesizing ITO nanopowder;
A mixing step of making a mixture by mixing a dispersant and a solvent with the ITO nanopowder synthesized through the synthesis step;
A stirring step of stirring the mixture formed through the mixing step;
Milling step of milling the mixture stirred through the stirring step; And
ITO paste manufacturing method for a transparent electrode comprising a filtering step of filtering the mixture milled through the milling step.
The method of claim 1,
The mixing step, ITO nano-powder ITO paste manufacturing method characterized in that the mixing in a weight ratio of 5 to 85% by weight, 2 to 4% by weight of the dispersant and 11 to 93% by weight of the solvent.
The method of claim 1,
The dispersing agent is a polyvinylpyrrolidone (polyvinylpyrrolidone) characterized in that the manufacturing method for the transparent electrode ITO paste.
The method of claim 1,
The solvent is a method for producing a transparent electrode ITO paste, characterized in that consisting of ethylene glycol (ethylene glycol) and ethanol (ethanol).
The method of claim 4, wherein
The ethylene glycol and the ethanol is a method for producing a transparent electrode ITO paste, characterized in that the mixture of 4 to 6: 1 ratio.
The method of claim 1,
The synthesis step,
A process of mixing In acetate and Sn acetate with an organic solvent to form an organic solution,
Stirring the organic solution,
Making the ITO precursor by evaporating the organic solvent in the organic solution, and
ITO paste manufacturing method for a transparent electrode comprising the step of heat-treating the ITO precursor.
The method of claim 6,
The In acetate and the Sn acetate have a volume ratio of 8 to 10: 1 ITO paste manufacturing method for a transparent electrode.
The method of claim 6,
The organic solvent is acetone or ethanol for producing a transparent electrode ITO paste, characterized in that.
The method of claim 6,
The heat treatment temperature is 250 ℃ to 350 ℃ ITO paste manufacturing method for a transparent electrode, characterized in that.
A transparent electrode ITO paste prepared according to any one of claims 1 to 9.
The method of claim 10,
The transparent electrode ITO paste,
It is formed on the substrate through a coating process, the transparent electrode ITO paste, characterized in that formed by curing through heat treatment for 30 to 90 minutes at 250 ℃ to 350 ℃.

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