JPH0931238A - Electroconductive dispersion, electroconductive coating material and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an electroconductive dispersion, comprising an antimony-doped tin oxide powder in the form of a long-chain aggregate in a dispersion medium and useful for forming an electroconductive film excellent in electroconductivity and transparency. SOLUTION: This electroconductive dispersion comprises an antimony-doped tin oxide powder dispersed into the form of a long-chain aggregate in a dispersion medium. The dispersion can be obtained by regulating a liquid containing a tin and an antimony compounds to pH >=4, preferably pH5-10 and the solid concentration to preferably 20-50wt.%. especially preferably 25-45wt.%, heating the resultant regulated liquid in a pressure-resistant container and thereby carrying out the hydrothermal reaction. Furthermore, a coprecipitate of hydroxides of tin and antimony prepared by adding and reacting an alkaline solution with an aqueous solution or an alcoholic solution of a chloride, a sulfate, etc., of the tin and antimony are preferably used as the tin and antimony compounds which are raw materials. The electroconductive coating material cap be obtained by, as necessary, adding water thereto, regulating the solid concentration to 10-20wt.% and then adding and mixing an aqueous coating material solution with the regulated mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive dispersion liquid, a conductive coating material, and a method for producing the same, which can form a conductive coating film having excellent conductivity and transparency.

[0002]

2. Description of the Related Art In recent years, tin oxide powder containing antimony, that is, antimony-doped tin oxide powder has come to be used as a conductive powder. The antimony-doped tin oxide powder transmits visible light when mixed and blended with media such as plastics, rubbers and paints, so that conductivity can be imparted without impairing the color tone and transparency of these media. .

Conventionally, antimony-doped tin oxide powder has been
Produced by precipitating a tin-antimony hydroxide mixture by adding an alkali to a solution in which a salt of tin and antimony is dissolved and reacting, washing and removing unnecessary salts, collecting by filtration, and further firing. (JP-A-5
6-156606).

A method for producing antimony-doped tin oxide powder by hydrothermally treating a liquid containing an antimony compound and a tin compound has also been proposed (JP-A-2-10587).
5 and JP-A-2-221124).

Particularly, in the case of producing antimony-doped tin oxide powder by hydrothermal treatment, it is possible to avoid particle growth and secondary agglomeration due to heat treatment, so that fine particles can be produced and fine particles are dispersed. With the conductive coating material, a conductive coating film having excellent transparency can be formed.

[0006]

However, since the antimony-doped tin oxide powder produced by the hydrothermal treatment has fine particles, there is little contact between the particles, and therefore, the conductivity required for antistatic treatment is reduced. In order to obtain it, there is a drawback that it is necessary to mix a large amount of antimony-doped tin oxide powder.

That is, in order to form a conductive coating film having good transparency and conductivity, the particles adjacent to each other in the paint or the coating film are often in contact with each other and dispersed with good dispersibility. Therefore, it is desired that the compounding amount of the antimony-doped tin oxide powder for obtaining the necessary conductivity can be reduced, but in the antimony-doped tin oxide powder obtained by the conventional hydrothermal treatment, the particles are There is little contact and the compounding efficiency is poor.

Further, in the conventional hydrothermal treatment, since the solid content concentration in the liquid to be treated is low, the dispersion medium is removed when the conductive dispersion obtained by the hydrothermal treatment is made into a paint. Needs to be concentrated. For example, JP-A-2-105875
According to the method described in the publication, the solid content concentration of the hydrothermally treated liquid is 5
In the method described in JP-A-2-221124, the solid content concentration of the hydrothermally treated liquid is 0.1 to 10% by weight.

On the other hand, since the solid content concentration of the electroconductive dispersion liquid suitable for forming the coating material is about 20% by weight, the electroconductive dispersion liquid obtained by the hydrothermal treatment is formed into the coating material by the evaporation method. Alternatively, it is necessary to remove the dispersion medium by a membrane separation method or the like for concentration. As described above, the conventional method requires a step of concentrating the conductive dispersion liquid, resulting in poor production efficiency. In particular, when the concentration is carried out by the evaporation method, it is disadvantageous in terms of energy cost.

The present invention solves the above-mentioned problems of the prior art, and it is possible to obtain a conductive dispersion liquid having a high contact ratio between antimony-doped tin oxide powders and a high solid content concentration by hydrothermal treatment, which is suitable for coating. Accordingly, it is an object of the present invention to provide a conductive dispersion liquid, a conductive coating material and a method for producing the same, which does not require concentration of the conductive dispersion liquid.

[0011]

The conductive dispersion liquid of the present invention is characterized in that antimony-doped tin oxide powder is dispersed in a dispersion medium in the form of long chain aggregates.

The method for producing a conductive dispersion according to the present invention is a method for producing a conductive dispersion as described above, which comprises subjecting a liquid containing a tin compound and an antimony compound to hydrothermal treatment. The hydrothermal treatment liquid has a pH of 4 or more and a solid content concentration of 20 to 50% by weight.

The conductive paint of the present invention is characterized in that antimony-doped tin oxide powder is dispersed in the paint in the form of long-chain aggregates.

The method for producing a conductive paint of the present invention is a method for producing the above-mentioned conductive paint, wherein a liquid containing a tin compound and an antimony compound is hydrothermally treated to obtain a conductive dispersion liquid, and the conductive dispersion liquid is obtained. A method for producing a conductive paint by mixing a liquid and a paint solution is characterized in that the hydrothermal treatment liquid has a pH of 4 or more and a solid content concentration of 20 to 50% by weight.

The antimony-doped tin oxide powder produced by the coprecipitation method, which is generally used as a raw material for producing antimony-doped tin oxide powder by hydrothermal treatment, has a pH value in an aqueous solution.
Aggregate and settle around 3 (isoelectric point).

In the present invention, by removing the pH of the hydrothermal treatment system from this isoelectric point and adjusting the pH to 4 or more, the dispersibility of the antimony-doped tin oxide powder is increased and the solid content concentration is 20.
It became possible to perform hydrothermal treatment at a high concentration of ˜50% by weight. Since the hydrothermal treatment is performed at such a high concentration, it is not necessary to concentrate the conductive dispersion liquid when forming a coating,
The conductive paint can be easily prepared simply by diluting it as needed. Needless to say, the dilution is simpler in operation and requires less energy than the concentration.

Further, in the electroconductive dispersion liquid or electroconductive coating material of the present invention thus obtained, fine antimony-doped tin oxide powder particles are uniformly dispersed in the form of long-chain aggregates, and Good contact can be achieved, and therefore a conductive coating film having excellent conductivity and transparency can be formed with a small amount of antimony-doped tin oxide powder blended.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below according to the production method of the present invention.

In the method of the present invention, a liquid containing a tin compound and an antimony compound is adjusted to have a pH of 4 or more and a solid content concentration of 20 to 50% by weight and heated in a pressure vessel to carry out a hydrothermal reaction. As the tin compound and antimony compound of this raw material, in general, a solution of a tin compound and an antimony compound, specifically, an aqueous solution or alcohol solution of tin and antimony chlorides, sulfates, nitrates, etc. is added with an alkaline solution. It is preferable to use a coprecipitate of tin and antimony hydroxide obtained by the reaction.

Therefore, in the present invention, the above coprecipitate is added to water so that the solid content concentration becomes 20 to 50% by weight,
If necessary, ammonia or the like is added to adjust the pH to 4 or more, preferably 5 to 10, and autoclave treatment is preferably performed.

When the pH is less than 4, the solid content concentration is 20.
It is not possible to stably prepare a high-concentration reaction system of ˜50% by weight. If the pH is too high, it may be dangerous to handle.
H is preferably 5-10.

When the solid content concentration is less than 20% by weight,
Concentration is required for making it into a paint, and if it exceeds 50% by weight, the reaction system becomes lumpy and the fluidity deteriorates, which causes trouble in handling. The solid content concentration is particularly preferably 25 to 45% by weight.

The autoclave treatment temperature is 150 to 250.
C. is preferred. If this temperature is lower than 150 ° C., antimony is not doped, and if it exceeds 250 ° C., the pressure becomes high, and sufficient consideration is required for work safety, and the equipment cost as a heat and pressure resistant reactor rises. The reaction time is usually about 1 to 10 hours.

By such an autoclave treatment, a dispersion liquid in which the conductive fine powder of antimony-doped tin oxide is dispersed in the form of a long chain aggregate is obtained.

The obtained conductive dispersion liquid is adjusted to a solid content concentration of 10 to 20% by weight by adding water if necessary, and then,
A conductive paint can be obtained by adding and mixing an aqueous paint solution. Here, an aqueous solution of gelatin, polyvinyl alcohol, a water-soluble acrylic resin or the like can be used as the aqueous coating solution, and the content of the antimony-doped tin oxide powder in the obtained conductive coating is 100 parts by weight of the resin. It is preferably 10 to 300 parts by weight.

The electroconductive dispersion or electroconductive coating material of the present invention obtained by the above method usually contains 10 to 1 fine particles of antimony-doped tin oxide powder having a secondary particle diameter of about 2 to 10 nm.
Agglomerated about 00 pieces, width 2 to 10 nm, length 50 to 20
It is a conductive dispersion liquid or a conductive coating material dispersed in the form of a long chain aggregate having a long chain portion of about 0 nm.

The conductive coating material of the present invention can be applied to a substrate to be treated by a conventional method to form a conductive coating film having excellent conductivity and transparency.

[0028]

The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 In 5 L (liter) of pure water at 80 ° C., 390 g of 60 wt% tin chloride aqueous solution and 60 wt% antimony chloride aqueous solution 3
A mixed solution with 6 g and a 3N sodium hydroxide aqueous solution were simultaneously added over 60 minutes so that the pH of the reaction system was maintained at 6 to 7 to form a coprecipitate composed of a hydrate of tin oxide and antimony oxide. Was generated. Next, hydrochloric acid was added to adjust the pH of the reaction system to 3, and then the coprecipitate was filtered and washed until the electric conductivity of the filtrate became 50 μS or less, and the pH was adjusted to 3.
A sol of 0 was obtained.

Pure water and aqueous ammonia were added to the obtained sol to have a pH of 6.0 and a solid content concentration of 30% by weight, which was placed in an autoclave and hydrothermally treated at 200 ° C. for 10 hours with stirring. The obtained antimony-doped tin oxide dispersion liquid was taken out, and pure water was added thereto to obtain a solid content concentration of 18.
The amount of the slurry was adjusted to 5% by weight, and 100 g of this slurry was mixed with 100 g of a 13.2% by weight gelatin aqueous solution at 40 ° C. to prepare an aqueous conductive paint. The content of the antimony-doped tin oxide powder in the paint was 140 parts by weight per 100 parts by weight of the gelatin solid content of the binder.

This paint was applied to a polyester film (thickness 100 μm, haze 2.0%) with a # 3 wire bar, and left to dry to obtain a conductive coating film.
Surface resistance (using a surface resistance meter "Hiresta Model HT-210" manufactured by Mitsubishi Petrochemical Co., Ltd.) and haze (Haze computer "HGM-3 manufactured by Suga Test Instruments Co., Ltd.")
D ”. ) Was measured, the surface resistance was 8.7 ^log
Ω / □ and haze 0.1%.

The dispersion state of the antimony-doped tin oxide powder in the conductive coating material obtained in this example was examined by an electron micrograph, and as shown in FIG. 1, antimony-doped tin oxide having a primary particle diameter of about 2 to 5 nm was observed. About 10 to 50 fine particles of tin oxide powder are aggregated, and the width is 5 to 10 nm.
It was confirmed that they were dispersed in the form of a long chain aggregate having a long chain portion having a length of 50 to 100 nm.

Examples 2 to 4 In the same manner as in Example 1, except that the solid content concentration during the hydrothermal treatment was set to the value shown in Table 1, the dispersion state of the antimony-doped tin oxide powder in the conductive coating material, The surface resistance and haze of the obtained conductive coating film were examined, and the results are shown in Table 1.

Further, the dispersion state of the antimony-doped tin oxide powder in the conductive paints obtained in Examples 2 and 3 was examined by an electron micrograph, and as shown in FIGS. 2 and 3, the primary particle diameter was 2 to 5 nm. Approximately 10 to 50 fine particles of antimony-doped tin oxide powder are aggregated and the width is 5 to 1
It was confirmed that they were dispersed in the form of a long chain aggregate having a long chain portion of 0 nm and a length of 50 to 100 nm.

Example 5 The same procedure as in Example 1 was carried out except that the hydrothermal treatment was carried out at 250 ° C. for 5 hours, and the dispersion state of the antimony-doped tin oxide powder in the conductive coating material and the conductive coating film obtained were obtained. The surface resistance and haze were examined and the results are shown in Table 1.

Comparative Example 1 Pure water was added to the sol obtained in Example 1 to adjust the solid content to 5
% By weight. The pH of this liquid was 3.2. This solution was subjected to hydrothermal treatment while stirring in an autoclave at 200 ° C. for 10 hours. Take out the produced antimony-doped tin oxide dispersion, concentrate it with an evaporator,
The solid content was adjusted to a concentration of 18.5% by weight.

Using this slurry, a coating material was formed in the same manner as in Example 1 to form a conductive coating film, and the surface resistance and haze thereof were examined. The results are shown in Table 1.

When the dispersion state of the antimony-doped tin oxide powder was examined by an electron micrograph of the conductive coating material of this comparative example, it was found to be a primary fine particle dispersion state without aggregation, as shown in FIG.

Comparative Example 2 Pure water and ammonia were added to the sol obtained in Example 1 to obtain p.
H was adjusted to 6.0 and the solid content concentration was adjusted to 5% by weight, and hydrothermal treatment was performed in an autoclave at 200 ° C. for 10 hours with stirring. The produced antimony-doped tin oxide dispersion was taken out and concentrated with an evaporator to obtain a solid content of 18.5.
The concentration was adjusted to%.

Using this slurry, a coating film was formed in the same manner as in Example 1 to form a conductive coating film, and the surface resistance and haze thereof were examined. The results are shown in Table 1.

When the dispersion state of the antimony-doped tin oxide powder was examined by an electron micrograph of the conductive coating material of this comparative example, a good aggregation state was not obtained as shown in FIG.

Comparative Example 3 Pure water was added to the sol obtained in Example 1 to obtain a solid content concentration of 30.
Attempting to adjust it to a weight percentage made it impossible to perform hydrothermal treatment by an autoclave because it could not be made into a slurry and became a lump.

Comparative Example 4 The sol obtained in Example 1 was filtered, dried and then heated in an electric furnace at 55 ° C.
It was baked at 0 ° C. for 3 hours and pulverized with a mill to obtain a conductive fine powder. This powder was suspended in water to adjust the pH to 7, and treated with a bead mill for 30 minutes to obtain a conductive aqueous dispersion, which was adjusted to a solid content concentration of 18.5% by weight.

Using this slurry, a coating film was formed in the same manner as in Example 1 to form a conductive coating film, and the surface resistance and haze thereof were examined. The results are shown in Table 1.

When the dispersion state of the antimony-doped tin oxide powder was examined by an electron micrograph of the conductive coating material of this comparative example, the particles were aggregated as shown in FIG.

[0046]

[Table 1]

As is clear from Table 1, according to the present invention, the antimony-doped tin oxide powder is dispersed in the form of a long-chain aggregate, and the particles are in good contact with each other. A conductive coating film having excellent properties and transparency can be formed. Further, according to the hydrothermal treatment in the high-concentration reaction system according to the present invention, it is possible to efficiently produce the conductive coating material without concentrating it when forming the coating material.

[0048]

As described in detail above, in the conductive dispersion liquid of claim 1 and the conductive coating material of claim 2, fine particles of antimony-doped tin oxide powder are uniformly dispersed, and
The contact ratio between the particles of the contained antimony-doped tin oxide powder is high, and therefore a conductive coating film having excellent conductivity and transparency can be formed with a small amount of the antimony-doped tin oxide powder blended.

Such a conductive dispersion and a conductive coating material of the present invention can be easily manufactured by the manufacturing methods of claims 3 and 4. Moreover, according to the methods of claims 3 and 4, it is possible to prepare a conductive dispersion liquid having a high solid content concentration, and to eliminate the step of concentrating the conductive dispersion liquid at the time of forming a coating material. And energy costs can be reduced.

[Brief description of drawings]

FIG. 1 is an electron micrograph (200,000 times) of the conductive coating material obtained in Example 1.

FIG. 2 is an electron micrograph (200,000 times) of the conductive coating material obtained in Example 2.

FIG. 3 is an electron micrograph (200,000 times) of the conductive coating material obtained in Example 3.

FIG. 4 is an electron micrograph (200,000 times) of the conductive coating material obtained in Comparative Example 1.

FIG. 5 is an electron micrograph (200,000 times) of the conductive coating material obtained in Comparative Example 2.

6 is an electron micrograph (200,000 times) of the conductive coating material obtained in Comparative Example 4. FIG.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location C09D 201/00 PDC C09D 201/00 PDC

Claims (4)

[Claims] 1. A conductive dispersion liquid, wherein antimony-doped tin oxide powder is dispersed in a dispersion medium in the form of long-chain aggregates. 2. A conductive coating material, wherein antimony-doped tin oxide powder is dispersed in the coating material in the form of long-chain aggregates. 3. A method for producing a conductive dispersion by hydrothermally treating a liquid containing a tin compound and an antimony compound, wherein the pH of the hydrothermally treated liquid is 4 or more and the solid content concentration is 20 to 50% by weight. The method for producing a conductive dispersion according to claim 1, wherein: 4. A method for producing a conductive paint by subjecting a liquid containing a tin compound and an antimony compound to a hydrothermal treatment to obtain a conductive dispersion, and mixing the conductive dispersion with a coating solution to produce a conductive coating, the hydrothermal treatment being performed. The method for producing a conductive paint according to claim 2, wherein the liquid has a pH of 4 or more and a solid content concentration of 20 to 50% by weight.