TWI568675B - ITO powder and its manufacturing method - Google Patents

Description

ITO powder and method of producing the same

The present invention relates to a surface-modified ITO powder which exhibits high electrical conductivity when it is a compact at a low pressure and a method for producing the same. In the present specification, ITO means Indium Tin Oxide.

ITO is a compound doped with tin (Sn) in In ₂ O ₃ , and has a high carrier concentration of 10 ²⁰ to 10 ²¹ cm ^-3 and can be formed by a vapor phase method such as sputtering. A low resistivity of about 1 × 10 ^-4 Ω ‧ cm is obtained. The ITO film made of this ITO has high transparency in the visible light region (for example, refer to Patent Document 1). Therefore, the ITO film is widely used in the field of a transparent electrode of a liquid crystal display (for example, refer to Patent Document 2) or a heat ray mask material having a high heat ray shielding effect (for example, refer to Patent Document 3) and the like which requires excellent optical characteristics. As a film forming method of the ITO film, a film forming method based on simple coating has been studied instead of a physical film forming method such as a vacuum vapor deposition method or a sputtering method which is expensive (for example, refer to Patent Document 4).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-032699 (paragraph [0009])

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2005-054273 (paragraph [0006])

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2011-116623 (paragraph [0002])

[Patent Document 4] Japanese Patent Laid-Open No. 2011-034708 (paragraph [0002])

The coating type film forming method as a method of forming an ITO film has advantages such as high material use efficiency and productivity, excellent bendability, and less restriction on a substrate to be coated. However, compared with the physical film formation method, the conductivity of the particles themselves is low, and the contact resistance between the particles is high, so that there is a disadvantage that the conductivity is low.

An object of the present invention is to provide an ITO powder which can reduce the electrical resistivity when a ITO film is formed by coating, thereby obtaining high conductivity and a method for producing the same.

The first aspect of the present invention is a surface-modified ITO powder which is an ITO powder having a volume resistivity of the green compact when a pressure of 0.98 MPa (10 kgf/cm ² ) is applied to the green compact composed of the ITO powder. 0.50 Ω ‧ cm or less, when the volume resistivity of the green compact when the pressure of 0.196 to 29.42 MPa (2 to 300 kgf/cm ² ) is applied to the green compact is Y and the pressure is X, the pressure is as described above The relationship between the volume resistivities is approximately the following formula (1), in which a is 5.00 or less, and n is -0.500 or less.

Y=aX ⁿ (1)

Further, a second aspect of the present invention is the invention according to the first aspect, which is an improvement of a method for producing an ITO powder comprising the steps of: mixing an aqueous alkaline solution with a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form indium; a step of coprecipitating a hydroxide with tin; a step of washing the coprecipitated hydroxide with pure water or ion-exchanged water; removing the supernatant of the coprecipitated hydroxide to prepare a dispersion of indium tin hydroxide particles a step of slurry; a step of drying the slurry; and a step of firing the dried indium tin hydroxide to obtain indium tin oxide, wherein in the cleaning step, the resist is cleaned to at least a resistivity of the supernatant In the preparation step of the slurry, the slurry from which the supernatant liquid has been removed is diluted with water so that the concentration of the hydroxide particles is in the range of 10 to 30% by mass, and then stirred. At the same time, an organic protective agent in a range of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles is added to the slurry, and after the calcination step, the aggregate of the fired ITO powder is pulverized. After the pulverized ITO powder is immersed in the surface treatment liquid, it is heated in a range of 200 to 400 ° C for 0.5 to 5 hours in a nitrogen atmosphere.

A third aspect of the present invention is the invention based on the second aspect, which is as follows Method for producing ITO powder: The aforementioned organic protective agent is palmityl dimethylethylammonium ethyl sulfate, polyvinyl alcohol or octyldimethylethyl ammonium ethyl sulfate.

Furthermore, the fourth aspect of the present invention is based on the first aspect. The invention is an improvement of a method for producing an ITO powder comprising the steps of: mixing a basic aqueous solution in a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin; Or the step of washing the coprecipitated hydroxide by ion-exchanged water; removing the supernatant of the coprecipitated hydroxide to prepare a slurry in which the indium tin hydroxide particles are dispersed; the step of drying the slurry; and burning The step of obtaining the indium tin oxide by the aforementioned dry indium tin hydroxide. Wherein, in the washing step, the resistivity of the supernatant is at least 5000 Ω ‧ cm, and in the preparation step of the slurry, the slurry from which the supernatant is removed is diluted with water to make the hydrogen After the concentration of the oxide particles is in the range of 10 to 30% by mass, an organic protective agent in an amount of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles is added to the slurry while stirring. In the drying step, the slurry in which the above-mentioned organic protective agent is added and in which indium tin hydroxide is dispersed is dried, and in the baking step, it is heated and fired in a microwave of 2.45 GHz to 28 GHz in the air, and the above-mentioned burning is performed. After the step, the aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is immersed in the surface treatment liquid, and then heated in a range of 200 to 400 ° C for 0.5 to 5 hours in a nitrogen atmosphere.

A fifth aspect of the present invention is the invention according to the fourth aspect, which is the method for producing an ITO powder: the organic protective agent is palmityldimethyl B Alkyl ammonium ethyl sulfate, polyvinyl alcohol or octyl dimethyl ethyl ammonium ethyl sulfate.

Furthermore, the sixth aspect of the present invention is based on the first aspect. The invention is an improvement of a method for producing an ITO powder comprising the steps of: mixing a basic aqueous solution in a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin; Or the step of washing the coprecipitated hydroxide by ion-exchanged water; removing the supernatant of the coprecipitated hydroxide to prepare a slurry in which the indium tin hydroxide particles are dispersed; the step of drying the slurry; and burning The step of obtaining the indium tin oxide by the aforementioned dry indium tin hydroxide. Wherein, in the washing step, the resistivity of the supernatant is at least 5000 Ω ‧ cm, and in the preparation step of the slurry, the slurry from which the supernatant is removed is diluted with alcohol to make the hydrogen After the concentration of the oxide particles is in the range of 1 to 5% by mass, an organic protective agent in an amount of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles is added to the slurry while stirring. In the firing step, the inside of the tube furnace heated to a range of 250 to 800 ° C is diluted with the alcohol and added to the organic state while flowing nitrogen gas at a linear velocity in the range of 0.5 to 5 m/s. The protective agent and the slurry in which the indium tin hydroxide particles are dispersed are sprayed to thermally decompose and calcine the indium tin hydroxide particles in the aforementioned tube furnace to obtain indium tin oxide particles.

A seventh aspect of the invention is the invention according to the sixth aspect, which is a method for producing an ITO powder: the alcohol is ethanol, methanol or propanol, and the organic protective agent is palmityldimethylethylammonium ethyl sulfate Polyvinyl alcohol Or octyl dimethyl ethyl ammonium ethyl sulfate.

Furthermore, the eighth aspect of the present invention is a method for producing a dispersion by dispersing an ITO powder of the first aspect or an ITO powder produced by any one of the second to seventh methods in a solvent.

Further, a ninth aspect of the present invention is the method for producing an ITO film from the dispersion liquid of the eighth aspect.

In the ITO powder according to the first aspect of the invention, the volume resistivity of the green compact of the ITO powder when a pressure of 0.98 MPa (10 kgf/cm ² ) is applied is 0.50 Ω ‧ cm or less, and 0.196 to 29.42 MPa is applied to the green compact ( When the volume resistivity of the green compact at a pressure of 2 to 300 kgf/cm ² ) is Y and the pressure is X, the equation (1) is approximated, and a in the formula (1) is 5.00 or less and n Since it is -0.500 or less, it is possible to reduce the electrical resistivity when the ITO film is formed by coating with the ITO powder to obtain high conductivity.

Further, in the method for producing an ITO powder according to the second aspect of the present invention, in the cleaning step, the resistivity of the supernatant is at least 5,000 Ω·cm, and in the preparation step of the slurry, the supernatant is removed. After the material is diluted with water so that the concentration of the hydroxide particles is in the range of 10 to 30% by mass, the slurry is added to the slurry in an amount of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles. In the range of the organic protective agent, after the firing step, the aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is immersed in the surface treatment liquid, followed by nitrogen gas. Under the atmosphere, it is heated in the range of 200~400 °C for 0.5~5 hours. The hydroxide particles are coated with an organic protective agent having a relatively high decomposition temperature, so that contact between the ITO particles is prevented during the firing process, and particle growth is difficult. The organic protective agent is finally thermally decomposed by firing. Thereby, the surface of the ITO powder is modified, and the electrical resistivity at the time of forming the ITO film by the coating method of the ITO powder can be reduced, and high conductivity can be obtained.

Further, the production of the ITO powder of the fourth aspect of the present invention In the method, in the washing step, the resistivity of the supernatant to the supernatant is at least 5000 Ω ‧ cm, and in the preparation step of the slurry, the slurry from which the supernatant is removed is diluted with water to make the concentration of the hydroxide particles After being in the range of 10 to 30% by mass, an organic protective agent in an amount of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles is added to the slurry while stirring, and in the drying step, the addition is carried out. The slurry having an organic protective agent and in which indium tin hydroxide is dispersed is dried, and in the firing step, it is heated and fired in a microwave of 2.45 GHz to 28 GHz in the air, and after the firing step, the fired is pulverized. The aggregate of the ITO powder is immersed in the surface treatment liquid in the ITO powder, and then heated in the range of 200 to 400 ° C for 0.5 to 5 hours in a nitrogen atmosphere. The hydroxide particles are coated with an organic protective agent having a relatively high decomposition temperature, so that contact between the ITO particles is prevented during the firing process, and particle growth is difficult. The organic protective agent is finally thermally decomposed by firing. Thereby, the surface of the ITO powder is modified, and the electrical resistivity at the time of forming the ITO film by the coating method of the ITO powder can be reduced, and high conductivity can be obtained.

Further, the production of the ITO powder of the sixth aspect of the present invention In the method, in the washing step, the resistivity of the supernatant to the supernatant is at least 5000 Ω ‧ cm, and in the preparation step of the slurry, the slurry from which the supernatant is removed is diluted with alcohol to make the concentration of the hydroxide particles After being in the range of 1 to 5% by mass, an organic protective agent in an amount of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles is added to the slurry while stirring, and in the baking step, The inside of the tube furnace heated to a range of 250 to 800 ° C, in which nitrogen gas is circulated at a linear velocity in the range of 0.5 to 5 m/s, diluted with alcohol, and added with an organic protective agent and dispersed with indium tin hydride The slurry of oxide particles is sprayed to thermally decompose and calcine the indium tin hydroxide particles in a tube furnace to obtain indium tin oxide particles. The hydroxide particles are coated with an organic protective agent having a relatively high decomposition temperature, so that contact between the ITO particles is prevented during the firing process, and particle growth is difficult. The organic protective agent is finally thermally decomposed by firing. Thereby, the surface of the ITO powder is modified, and the electrical resistivity at the time of forming the ITO film by the coating method of the ITO powder can be reduced, and high conductivity can be obtained.

Fig. 1 is a schematic view of an apparatus for measuring the electrical resistivity of a green compact of ITO powder.

Fig. 2 is a graph showing the relationship between the applied pressure and the specific resistance of the green compact of the ITO powder.

Next, a specific embodiment will be described.

The electrical resistivity of the ITO powder is an important index when evaluating the characteristics of the ITO film made of the ITO powder. In particular, when an ITO film is used as a conductive sheet or an electrode, high conductivity, that is, low resistivity is required. The electrical resistivity of the ITO powder was determined by measuring the volume resistivity of the ITO powder in the form of a green compact. On the other hand, the volume resistivity of the green compact varies with the applied pressure. Therefore, although the volume resistivity of the green compact under a predetermined pressure is a tentative reference, the volume resistivity is determined by changing the shape and specific surface area of the ITO powder from a low pressure to a high pressure, and this is made into ITO. The resistivity of the powder can be used to determine the electrical resistivity of the ITO powder with better accuracy. The present invention has been completed based on this finding.

The ITO powder of the present invention is a surface-modified ITO powder, and when the pressure of 0.98 MPa (10 kgf/cm ² ) is applied to the green compact composed of the ITO powder, the volume resistivity of the green compact is 0.50 Ω ‧ cm or less, which is correct When the volume resistivity of the green compact when the green compact is applied with a pressure of 0.196 to 29.42 MPa (2 to 300 kgf/cm ² ) is set to Y and the pressure is set to X, the relationship between the pressure and the volume resistivity approximates the following formula (1) ). Here, a of the formula (1) is 5.00 or less, and n is -0.500 or less.

Y=aX ⁿ (1)

This formula is derived from the result of measuring the state of the green compact of the ITO powder whose surface modification is low and the volume resistivity is low. When the above a exceeds 5.00 or n exceeds -0.500, there is a tendency that it is difficult to increase the conductivity even if the applied pressure to the powder is increased, that is, the contact between the reinforcing particles is increased, and there is a problem.

The ITO powder used to manufacture the ITO film of the present invention is The surface-modified ITO powder produced by the following three methods. By performing the surface modification treatment, the conductivity of the ITO film produced using the ITO powder can be improved.

(1) First manufacturing method

An aqueous alkaline solution is mixed with a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin, and the precipitate is dried and fired, and then the obtained indium tin oxide is pulverized to obtain ITO. powder. Examples of the trivalent indium compound include indium trichloride (InCl ₃ ), indium nitrate (In(NO ₃ ) ₃ ), and indium acetate (In(CH ₃ COO) ₃ ). Tin dichloride (SnCl ₂ ‧2H ₂ O), tin sulfate (SnSO ₄ ), tin bromide (SnBr ₂ ), and the like are obtained. Examples of the alkaline aqueous solution include ammonia (NH ₃ ) water, ammonium hydrogencarbonate (NH ₄ HCO ₃ ) water, and the like. The final pH of the reaction solution when the indium and tin hydroxide are coprecipitated is adjusted to 3.5 to 9.3, preferably adjusted to pH 5.0 to 8.0, and the solution temperature is adjusted to 5 ° C or higher, preferably adjusted to the solution temperature. From 10 ° C to 80 ° C, it is possible to precipitate a coprecipitated hydroxide of indium and tin. The alkaline aqueous solution may be mixed while the aqueous alkaline solution is dropped into the mixed aqueous solution to adjust to the above pH range, or the mixed aqueous solution and the alkaline aqueous solution may be simultaneously dropped into water to adjust to the above pH range. At the same time.

After the coprecipitated indium tin hydroxide is formed, the precipitate is washed with pure water or ion-exchanged water, and washed until the resist has a resistivity of at least 5,000 Ω ‧ cm, preferably at least 50,000 Ω ‧ cm. If the supernatant is charged When the resistivity is less than 5,000 Ω ‧ cm, impurities such as chlorine are not sufficiently removed, and high-purity indium tin oxide powder cannot be obtained. The supernatant of the above precipitate having a specific resistance of 5000 Ω ‧ cm or more was removed to obtain a slurry having a high viscosity in which indium tin hydroxide particles were dispersed. The slurry is diluted with pure water or ion-exchanged water so that the concentration of the hydroxide particles is in the range of 10 to 30% by mass, preferably 15 to 25% by mass, and then, while stirring, to the slurry. An organic protective agent for adsorbing on the surface of the hydroxide particles to increase the dispersibility of the particles is added. When the dilution range is less than the lower limit, there is a problem in that the slurry is dried in a time-consuming manner. When the concentration exceeds the upper limit, the organic protective agent is mixed in a state in which the viscosity of the slurry is high. Therefore, the organic protective agent is present. Poorly mixed conditions. The amount of the organic protective agent added is in the range of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles. From the viewpoint of suppressing the sintering of the ITO powder after thermal decomposition of the organic protective agent, the decomposition temperature of the organic protective agent is preferably in the range of 250 to 500 °C. Examples of the organic protective agent include palmityl dimethylethylammonium ethyl sulfate, polyvinyl alcohol, and octyldimethylethylammonium ethyl sulfate. When the amount of the organic protective agent added is less than the lower limit of the above range, the surface of the hydroxide particles is not sufficiently protected, and the dispersibility of the particles is inferior. Further, when the value exceeds the upper limit, a part of the organic substance or a carbon component derived from the organic substance may remain.

In the atmosphere, preferably in an inert gas atmosphere such as nitrogen or argon Next, the indium tin hydroxide having the organic protective agent adsorbed on the surface thereof is dried in the range of 100 to 200 ° C for 2 to 24 hours, and then fired in a baking furnace for 0.5 to 6 hours in the air at a temperature of 250 to 800 ° C. Use a hammer mill or a ball mill Etc., the aggregate formed by the firing is pulverized and decomposed to obtain an ITO powder. The ITO powder is placed in a surface treatment liquid in which 50 to 95% by mass of absolute ethanol and 5 to 50% by mass of distilled water are mixed, and then immersed in a glass dish at 200 to 400 ° C in a nitrogen atmosphere. When the range is heated for 0.5 to 5 hours, an ITO powder subjected to surface modification treatment can be obtained.

(2) Second manufacturing method

The solid-liquid separation method and the heating and firing method of the slurry are different from the first production method. First, the slurry obtained by the first production method and having an organic protective agent added thereto and in which indium tin hydroxide is dispersed is dried. As an example of the drying method, a slurry is pressed into a pressure filter by a pressurizing pump to obtain a mud cake of a hydroxide, and the cake is dried. Next, the dried product was heated and fired in the air at a microwave of 2.45 GHz to 28 GHz. In the microwave heat treatment, for example, the cake is filled in a microwave oven manufactured by CMC Technology Development Co., Ltd., and is subjected to microwave heating treatment of 2.45 GHz of a μ-reactor manufactured by Shikoku Industrial Co., Ltd.

Microwave heating is in the range of 250~800 °C, preferably In the range of 350 to 600 ° C, the temperature is raised at a temperature that reaches the target temperature within 10 minutes, and the firing is carried out by maintaining the target temperature in the range of 5 to 120 minutes, preferably in the range of 10 to 60 minutes. When the heating temperature is less than the lower limit, there is a problem that the hydroxide is not completely decomposed into an oxide, and if it exceeds the upper limit, there is a problem that the ITO particles are coarsened. If the temperature rise time to the target temperature exceeds 10 minutes, there is The problem of rapid warming disappears. If the holding time at the target temperature is less than the lower limit, there is a problem that the hydroxide is not completely decomposed into an oxide, and if it exceeds the upper limit, there is a problem that the ITO particles are coarsened. The ITO powder is obtained by pulverizing and decomposing the fired product by a hammer mill, a ball mill or the like. Hereinafter, the ITO powder subjected to the surface modification treatment was obtained in the same manner as in the first production method.

(3) Third manufacturing method

It is not necessary to pulverize the indium tin oxide after firing the indium tin hydroxide, which is different from the first and second manufacturing methods.

The slurry having a high viscosity in which the indium tin hydroxide particles are dispersed by the first production method is diluted with an alcohol so that the concentration of the hydroxide particles is in the range of 1 to 5% by mass, preferably 1 to 3. A range of mass %, and an organic protective agent for adsorbing on the surface of the hydroxide particles to increase the dispersibility of the particles is added to the slurry while stirring. The amount of the organic protective agent added is in the range of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles. The reason for specifying the lower limit value and each upper limit value of the above-described dilution range and the addition amount range of the above-mentioned organic protective agent is the same as that of the first production method. From the viewpoint of suppressing the sintering of the ITO powder after thermal decomposition of the organic protective agent, the decomposition temperature of the organic protective agent is preferably in the range of 250 to 500 °C. Examples of the alcohol include ethanol, propanol or methanol. Examples of the organic protective agent include palmityl dimethylethylammonium ethyl sulfate, polyvinyl alcohol or octyldimethylethyl ammonium ethyl ester. Sulfate and the like.

Heating to 250~ to the vertical direction of the tube The inside of the tube furnace in the range of 800 ° C is diluted with alcohol in a state in which nitrogen as a carrier gas is circulated at a linear velocity in the range of 0.5 to 5 m/s, preferably at a linear velocity in the range of 1 to 3 m/s. The slurry to which the organic protective agent was added and in which the indium tin hydroxide particles were dispersed was sprayed by a two-fluid nozzle and introduced into a tube furnace together with nitrogen gas. When the linear velocity is less than the lower limit, the amount of ITO powder to be harvested is reduced, and if it exceeds the upper limit, the slurry to be sprayed cannot be sufficiently heated. Thereby, the indium tin hydroxide particles are thermally decomposed and fired in the tube furnace, and the surface-modified ITO powder can be obtained from the discharge port of the tube furnace.

[Examples]

Next, an embodiment of the present invention will be described in detail together with a comparative example.

<Example 1> [Method of Manufacturing Surface-Modified ITO Powder]

4 g of mixed tin dichloride powder (SnCl ₂ ‧2H ₂ O powder) was added to 163 g of an indium chloride (InCl ₃ ) aqueous solution having a concentration of In metal of 24% by mass, and the mixture was stirred until all the tin dichloride powder was dissolved. All amounts were added to 1000 ml of pure water as a raw material solution. A 25% by mass aqueous solution of ammonia (NH ₃ ) was dropped into the raw material solution for 90 minutes. At this time, the reaction temperature was adjusted to 80 ° C, and the pH of the final reaction solution was adjusted to 8.0. The formed indium tin coprecipitated hydroxide, that is, the precipitate, was repeatedly subjected to gradient washing by ion-exchanged water. When the resistivity of the supernatant reaches 5000 Ω‧cm or more, the supernatant of the above precipitate is removed to obtain a slurry having a high viscosity in which the indium tin hydroxide particles are dispersed.

While stirring the slurry, the slurry is diluted with pure water. After the concentration of the hydroxide particles was 20% by mass, 1.3 g of an organic protective agent, that is, polyvinyl alcohol was added. The amount of the organic protective agent added was 1.0% by mass based on the indium tin hydroxide. The slurry was dried in the air at 110 ° C for 10 hours, and then fired at 700 ° C for 2 hours in the atmosphere, and the aggregate was pulverized and decomposed to obtain about 70 g of ITO powder. 70 g of the ITO powder was placed in a surface treatment liquid (mixing ratio of 95% by mass of ethanol and 5% by mass of distilled water) mixed with anhydrous ethanol and distilled water, and then immersed in a glass dish. The ITO powder subjected to the surface modification treatment was obtained by heating at 330 ° C for 2 hours under a nitrogen atmosphere.

[Manufacture of ITO film]

20 g of the surface-modified ITO powder was placed in distilled water (0.020 g), di(2-ethylhexanoic acid) triethylene glycol ester [3G] (23.8 g), absolute ethanol (2.1 g), and phosphoric acid. A mixture of an ester (1.0 g), 2-ethylhexanoic acid (2.0 g) and 2,4-pentanedione (0.5 g) was dispersed. The prepared dispersion was diluted with absolute ethanol to a solid content, that is, the content of the ITO powder was 10% by mass. The diluted dispersion was applied onto a quartz glass plate by spin coating to form a film, thereby obtaining an ITO film having a thickness of 0.2 μm.

<Example 2>

16 g of mixed tin dichloride powder (SnCl ₂ ‧2H ₂ O powder) was added to 135 g of an indium chloride (InCl ₃ ) aqueous solution having a concentration of In metal of 24% by mass, and the mixture was stirred until all the tin dichloride powder was dissolved. All amounts were added to 1000 ml of pure water as a raw material solution. A 25% by mass aqueous solution of ammonia (NH ₃ ) was dropped into the raw material solution for 90 minutes. At this time, the reaction temperature was adjusted to 60 ° C, and the pH of the final reaction solution was adjusted to 5.0. The formed indium tin coprecipitated hydroxide, that is, the precipitate, was repeatedly subjected to gradient washing by ion-exchanged water. When the resistivity of the supernatant reaches 5000 Ω‧cm or more, the supernatant of the above precipitate is removed, thereby obtaining a slurry having a high viscosity in which the indium tin hydroxide particles are dispersed. While stirring the slurry, the slurry was diluted with pure water so that the concentration of the hydroxide particles became 15% by mass, and then an organic protective agent, palmitoyldimethylethylammonium ethyl sulfate (70 mass) was added. %) 4.5g. The amount of the organic protective agent added was 3.0% by mass based on the indium tin hydroxide.

After the slurry was dried at 110 ° C for 10 hours in the atmosphere, It was baked at 800 ° C for 3 hours in the atmosphere, and the aggregate was pulverized and decomposed to obtain about 75 g of ITO powder. 75 g of ITO powder was placed in a surface treatment liquid (mixing ratio: 95% by mass relative to ethanol and 5% by mass of distilled water) mixed with anhydrous ethanol and distilled water, and then immersed in a glass dish in a nitrogen atmosphere. Next, it was heated at 330 ° C for 2 hours to obtain an ITO powder subjected to surface modification treatment. Further, an ITO film was produced in the same manner as in Example 1 using this ITO powder.

<Example 3>

8 g of mixed tin dichloride powder (SnCl ₂ ‧2H ₂ O powder) was added to 154 g of an indium chloride (InCl ₃ ) aqueous solution having an In metal concentration of 24% by mass, and the mixture was stirred until all the tin dichloride powder was dissolved. All amounts were added to 1000 ml of pure water as a raw material solution. A 25% by mass aqueous solution of ammonia (NH ₃ ) was dropped into the raw material solution for 90 minutes. At this time, the reaction temperature was adjusted to 20 ° C, and the pH of the final reaction solution was adjusted to 7.0. The formed indium tin coprecipitated hydroxide, that is, the precipitate, was repeatedly subjected to gradient washing by ion-exchanged water. When the resistivity of the supernatant reaches 5000 Ω‧cm or more, the supernatant of the above precipitate is removed, thereby obtaining a slurry having a high viscosity in which the indium tin hydroxide particles are dispersed. While stirring the slurry, the slurry was diluted with ethanol so that the concentration of the hydroxide particles became 1.0% by mass, and then an organic protective agent, octyldimethylethylammonium ethyl sulfate (50% by mass) was added. ) 10g. The amount of the organic protective agent added was 5.0% by mass based on the indium tin hydroxide.

Heating to 500 ° C in the direction of the long side of the tube In the inside of the tube furnace, the slurry was sprayed by a two-fluid nozzle while flowing nitrogen gas as a carrier gas at a linear velocity of 1 m/s, and introduced into a tube furnace together with nitrogen gas. Thereby, the indium tin hydroxide particles were thermally decomposed and fired in a tube furnace, and the surface-modified ITO powder was obtained from the discharge port of the tube furnace. Further, an ITO film was produced in the same manner as in Example 1 using this ITO powder.

<Comparative Example 1>

To 245 g of an indium chloride (InCl ₃ ) aqueous solution having a concentration of In metal of 24% by mass, 11.5 g of an aqueous solution of tin tetrachloride (SnCl ₄ ) mixed at a concentration of 55% by mass was added to prepare a mixed solution of InCl ₃ -SnCl ₄ . Next, 500 g of ammonium hydrogencarbonate (NH ₄ HCO ₃ ) water was dissolved in ion-exchanged water to prepare a total amount of 1000 ml and a temperature of 70 °C. In the aqueous solution, all the amounts of the above-mentioned mixed solution of InCl ₃ -SnCl ₄ were stirred while being dropped for 20 minutes to form an indium tin coprecipitated hydroxide. Stirring was continued for 30 minutes in this state. The final pH of the reaction solution at this time was 9.0. The indium tin hydroxide is recovered as a precipitate, and after dehydration by a centrifuge, centrifugal filtration is carried out while adding ion-exchanged water to wash, and centrifugation is terminated when the resistivity of the filtrate reaches 5000 Ω·cm or more. Then, the precipitate was dried at 100 ° C overnight, and then fired at 600 ° C for 3 hours, and the aggregate was pulverized and decomposed to obtain 75 g of ITO powder.

The 75 g of ITO powder was mixed with anhydrous ethanol and The surface treatment liquid of distilled water (mixing ratio: 95% by mass of ethanol and 5% by mass of distilled water) was immersed, placed in a glass dish, and heated at 330 ° C for 3 hours in a nitrogen atmosphere to obtain a progress. Surface modified ITO powder. Further, an ITO film was produced in the same manner as in Example 1 using this ITO powder.

<Comparative test> [Evaluation of ITO Powder]

The volume resistivity of the green compact when a pressure of 0.98 MPa (10 kgf/cm ² ) was applied to the green compact composed of each of the ITO powders obtained in Examples 1 to 3 and Comparative Example 1 is shown in Table 1 below. The volume resistivity of each of the ITO powders obtained in the above Examples 1 to 3 and Comparative Example 1 was measured by a measuring apparatus (MCP-PD51 manufactured by Mitsubishi Chemical Analytech Co., Ltd.) shown in Fig. 1 . Specifically, the inner diameter shown in Figure 1 The cylinder 1 of 25 mm was filled with 2.00 g of ITO powder, and the pressure was changed in the range of 0.196 to 29.42 MPa (2 to 300 kgf/cm ² ), and the obtained in Examples 1 to 3 and Comparative Example 1 were simultaneously measured. The resistivity of 10 points or more in the ITO powder and the thickness of the sample. The pressure was measured by a pressure sensor (not shown), and the specific resistance was measured by a DC four-terminal method. In Fig. 1, 2 is a green compact of ITO powder.

FIG. 2 shows the relationship between the pressure (horizontal axis) converted to a force per unit area of the sample powder and the volume resistivity (vertical axis) of the green compact of the ITO powder. This relationship is approximated by the least squares method to the formula (1) of the following power. Further, the volume resistivity of the powder is calculated by multiplying the correction coefficient attached to the measurement system by the measured value. Table 1 shows the values of a and n of the approximate formula (1) obtained in Examples 1 to 3 and Comparative Example 1.

Y=aX ⁿ (1)

The surface resistivity (Ω/□) of each of the ITO films obtained in Examples 1 to 3 and Comparative Example 1 was measured by a resistivity measuring device (MCP-T400 manufactured by Mitsubishi Petrochemical Co., Ltd.). The results are shown in Table 1.

<evaluation>

As can be seen from Table 1, when a pressure of 0.98 MPa (10 kgf/cm ² ) is applied to the green compact composed of the ITO powders of Examples 1 to 3 in which a of the formula (1) is 5.00 or less and n is -0.500 or less. The volume resistivity of the green compact is 0.500 Ω ‧ cm or less. Further, the surface resistivity of the ITO film made of these ITO powders was 1.0 × 10 ⁶ Ω/□ or less. On the other hand, when the pressure of 0.98 MPa (10 kgf/cm ² ) was applied to the green compact composed of the ITO powder of Comparative Example 1 in which a of the formula (1) was 5.00 or less but n exceeded -0.500, the volume resistivity of the green compact was applied. The rate is over 0.5 Ω ‧ cm. Further, the surface resistivity of the ITO film made of the ITO powder of Comparative Example 1 exceeded 1.0 × 10 ⁶ Ω/□. As described above, Examples 1 to 3 having a relationship similar to the formula (1) were examined, and the electrical resistivity at the time of film formation of the ITO film by coating was reduced to obtain high conductivity.

Claims (9)

An ITO powder obtained by mixing an alkaline aqueous solution in a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin, and washing the precipitate to the upper portion with pure water or ion-exchanged water. The resistivity of the supernatant is at least 5000 Ω ‧ cm, the supernatant of the precipitate is removed to prepare a slurry in which the indium tin hydroxide particles are dispersed, and the slurry from which the supernatant is removed is diluted with water to make the aforementioned After the concentration of the hydroxide particles is in the range of 10 to 30% by mass, an organic protective agent in an amount of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles is added to the slurry while stirring. The organic protective agent is palm dimethyl dimethyl ammonium ethyl sulphate, polyvinyl alcohol or octyl dimethyl ethyl ammonium ethyl sulphate, and the indium tin hydroxide adsorbing the organic protective agent on the surface is dried. After that, it is fired in a baking furnace for 0.5 to 6 hours in the atmosphere at 250 to 800 ° C, and the aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is impregnated with 50 to 95. % by mass of absolute ethanol and 5 to 50% by mass of steamed The surface treatment liquid of the distilled water is heated in the range of 200 to 400 ° C for 0.5 to 5 hours in a nitrogen atmosphere, and the surface-modified ITO powder is characterized in that 0.98 is applied to the green compact composed of the ITO powder. The volume resistivity of the green compact at a pressure of MPa is 0.50 Ω ‧ cm or less, and when the pressure of 0.196 to 29.42 MPa is applied to the green compact, the volume resistivity of the green compact is Y and the pressure is X. The relationship between the aforementioned pressure and the volume resistivity is approximated by the least squares method (1), in which a is 5.00 or less, and n is -0.500 or less, Y = aX ⁿ (1). A method for producing an ITO powder according to claim 1, comprising the steps of: mixing an aqueous alkaline solution in a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin; a step of washing the precipitate by pure water or ion-exchanged water; a step of removing the supernatant of the precipitate to prepare a slurry in which the indium tin hydroxide particles are dispersed; a step of drying the slurry; and baking the aforementioned dried a step of obtaining indium tin oxide by indium tin oxide, characterized in that in the cleaning step, the resistivity of the supernatant is at least 5000 Ω ‧ cm, and in the preparation step of the slurry, the removal is performed After the slurry of the supernatant liquid is diluted with water so that the concentration of the hydroxide particles is in the range of 10 to 30% by mass, 100% by mass of the hydroxide particles are added to the slurry while stirring. Is an organic protective agent in the range of 0.1 to 5% by mass, and the organic protective agent is palmityl dimethylethyl ammonium ethyl sulfate, polyvinyl alcohol or octyl dimethyl ethyl ammonium ethyl sulfate, table After the indium tin hydroxide adsorbing the organic protective agent is dried, it is fired in a firing furnace at a temperature of 250 to 800 ° C for 0.5 to 6 hours in the baking step, and is pulverized after the baking step. An aggregate of the fired ITO powder, the immersed ITO powder is impregnated with a surface treatment liquid mixed with 50 to 95% by mass of absolute ethanol and 5 to 50% by mass of distilled water Thereafter, it was heated in the range of 200 to 400 ° C for 0.5 to 5 hours under a nitrogen atmosphere. An ITO powder obtained by mixing an alkaline aqueous solution in a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin, and washing the precipitate to the upper portion with pure water or ion-exchanged water. The resistivity of the supernatant is at least 5000 Ω ‧ cm, the supernatant of the precipitate is removed to prepare a slurry in which the indium tin hydroxide particles are dispersed, and the slurry from which the supernatant is removed is diluted with water to make the aforementioned After the concentration of the hydroxide particles is in the range of 10 to 30% by mass, an organic protective agent in an amount of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles is added to the slurry while stirring. The organic protective agent is palm dimethyl dimethyl ammonium ethyl sulphate, polyvinyl alcohol or octyl dimethyl ethyl ammonium ethyl sulphate, which is added with an organic protective agent and is dispersed with indium tin hydroxide. After the slurry is dried, it is heated in the atmosphere at a temperature of 250 to 800 ° C in a microwave of 2.45 GHz to 28 GHz in a range of 50 to 800 ° C, and then maintained at a target temperature of 5 to 120 minutes. Heated and burned The aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is impregnated with a surface treatment liquid in which 50 to 95% by mass of absolute ethanol and 5 to 50% by mass of distilled water are mixed, in a nitrogen atmosphere. The surface-modified ITO powder is heated in the range of 200 to 400 ° C for 0.5 to 5 hours, and is characterized in that the volume resistivity of the green compact is applied to a green compact composed of the ITO powder at a pressure of 0.98 MPa. When the volume resistivity of the green compact is set to Y and the pressure is X, the relationship between the pressure and the volume resistivity is 0.50 Ω ‧ cm or less when the pressure of 0.196 to 29.42 MPa is applied to the green compact. The following formula (1) is approximated by the least square method, in which a is 5.00 or less, and n is -0.500 or less Y = aX ⁿ (1). A method for producing an ITO powder according to claim 3, which comprises the steps of: mixing an aqueous alkaline solution in a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin; a step of washing the precipitate by pure water or ion-exchanged water; a step of removing the supernatant of the precipitate to prepare a slurry in which the indium tin hydroxide particles are dispersed; a step of drying the slurry; and baking the foregoing dried The indium tin oxide is used to obtain indium tin oxide, characterized in that in the cleaning step, the resistivity of the supernatant is at least 5000 Ω ‧ cm, and in the preparation step of the slurry After the slurry of the supernatant liquid is diluted with water so that the concentration of the hydroxide particles is in the range of 10 to 30% by mass, 100 masses of the hydroxide particles are added to the slurry while stirring. % is an organic protective agent in the range of 0.1 to 5% by mass, and the organic protective agent is palm dimethyl dimethyl ammonium ethyl sulfate, polyvinyl alcohol or octyl dimethyl ethyl ammonium ethyl sulfate. The drying step, the organic protective agent is added and dispersed indium tin hydroxide slurry was dried, In the calcination step, the microwave is heated from 2.45 GHz to 28 GHz in the atmosphere at a temperature of 250 to 800 ° C, and the temperature is raised to a target temperature within 10 minutes, and then maintained at the target temperature for 5 to 120 minutes. The range is heated and fired, and after the calcination step, the aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is impregnated with 50 to 95% by mass of absolute ethanol and 5 to 50% by mass of distilled water. After the surface treatment liquid, it is heated in the range of 200 to 400 ° C for 0.5 to 5 hours under a nitrogen atmosphere. An ITO powder obtained by mixing an alkaline aqueous solution in a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin, and washing the precipitate to the upper portion with pure water or ion-exchanged water. The resistivity of the supernatant is at least 5000 Ω ‧ cm, the supernatant of the precipitate is removed to prepare a slurry in which the indium tin hydroxide particles are dispersed, and the slurry from which the supernatant is removed is diluted with alcohol to make the aforementioned After the concentration of the hydroxide particles is in the range of 1 to 5% by mass, an organic protective agent in an amount of 0.1 to 5% by mass based on 100% by mass of the hydroxide particles is added to the slurry while stirring. The organic protective agent is palm dimethyl dimethyl ammonium ethyl sulphate, polyvinyl alcohol or octyl dimethyl ethyl ammonium ethyl sulphate, and is heated inside the tube furnace in the range of 250 to 800 ° C In a state where nitrogen gas is allowed to flow at a linear velocity in the range of 0.5 to 5 m/s, a slurry diluted with the alcohol and added with the organic protective agent and dispersed with indium tin hydroxide particles is sprayed, thereby Thermal decomposition in a tube furnace The ITO powder which is surface-modified with indium tin hydroxide particles is characterized in that the volume resistivity of the green compact when a pressure of 0.98 MPa is applied to the green compact composed of the ITO powder is 0.50 Ω·cm or less. When the volume resistivity of the green compact when the pressure of 0.196 to 29.42 MPa is applied to the green compact is Y and the pressure is X, the relationship between the pressure and the volume resistivity is approximated by the least squares method. In the formula (1), a is 5.00 or less, and n is -0.500 or less Y = aX ⁿ (1). A method for producing an ITO powder according to claim 5, which comprises the steps of: mixing an aqueous alkaline solution in a mixed aqueous solution of a trivalent indium compound and a divalent tin compound to form a coprecipitated hydroxide of indium and tin; a step of washing the precipitate by pure water or ion-exchanged water; a step of removing the supernatant of the precipitate to prepare a slurry in which indium tin hydroxide particles are dispersed; and baking a slurry in which the indium tin hydroxide is dispersed The step of obtaining indium tin oxide, characterized in that in the cleaning step, the resistivity of the supernatant is at least 5000 Ω ‧ cm, and in the preparation step of the slurry, the supernatant is removed The slurry of the liquid is diluted with an alcohol so that the concentration of the hydroxide particles is in the range of 1 to 5% by mass, and then 100% by mass of the hydroxide particles are added to the slurry while stirring. An organic protective agent in the range of 5 mass%, and the aforementioned organic protective agent is palmityldimethylethylammonium ethyl Sulfate, polyvinyl alcohol or octyldimethylethylammonium ethyl sulfate, in the above-mentioned baking step, to the inside of the tube furnace heated to a range of 250 to 800 ° C, and nitrogen gas is made 0.5 to 5 m In a state in which the linear velocity of the range of /s is in a state in which the slurry is diluted with the aforementioned alcohol and the organic protective agent is added and the indium tin hydroxide particles are dispersed, the mixture is thermally decomposed and fired in the tube furnace. Indium tin hydroxide particles are used to obtain indium tin oxide particles. The production method of claim 5 or 6, wherein the aforementioned alcohol is ethanol, methanol or propanol. A method of producing a dispersion, characterized in that the ITO powder of any one of claims 1, 3 or 5 or the ITO powder produced by the method of any one of claims 2, 4 or 6 is dispersed in The dispersion is prepared in a solvent. A method of producing an ITO film, characterized in that an ITO film is produced from the dispersion liquid of claim 8.