TW201431791A - Ito powder and method for manufacturing the same - Google Patents

Abstract

The present invention provides a kind of ITO power which turns into a compaction under low pressure and shows surface modification of high conductivity as well as the manufacturing method thereof, as well as the manufacturing methods of a kind of dispersion liquid and a membrane. When the compaction comprised by the ITO power of the present invention's surface modification is applied a pressure of 0.196 to 29.42MPa and a volume resistivity of the compaction sets to Y, and a relative density of the compaction sets to X, the relationship between the volume resistivity and the relative density are fitted to Y=Alpha Xn, and Alpha is below 5.0*10-3 and n is above -10.

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 In ₂ O ₃ with a compound of tin (Sn) is doped at high carrier concentration with 10 ²⁰ ~ 10 ²¹ cm ^-3, the ITO film forming method of sputtering gas may be Obtain 1 × 10 ^-4 Ω. Low resistivity around cm. 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 obtained by applying a pressure of 0.196 to 29.42 MPa (2 to 300 kgf/cm ² ) to a green compact composed of the ITO powder. When the volume resistivity is Y and the relative density of the green compact is X, the relationship between the volume resistivity and the aforementioned relative density is approximated by the following formula (1), in which the formula (1), a It is 5.0 × 10 ^-3 or less, and n is -10 or more.

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 alkali solution with a mixed aqueous solution of a trivalent indium compound and a tetravalent tin compound to form indium and a step of coprecipitating a hydroxide of tin; a step of washing the coprecipitated hydroxide with pure water or ion-exchanged water; removing a supernatant of the coprecipitated hydroxide to prepare a slurry in which indium tin hydroxide particles are dispersed 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 Up to 5000Ω. 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 the mixture is stirred as described above. 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, and after the baking step, aggregates of the fired ITO powder are pulverized, and the pulverized ITO is pulverized. After the powder is immersed in the surface treatment liquid, it is heated in the 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 according to the second aspect, which is a method for producing an ITO powder: palmitic dimethylethylammonium ethyl sulfate, polyvinyl alcohol or octyldimethyl Ethyl ammonium ethyl sulfate salt.

Further, a fourth 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 alkali solution with a mixed aqueous solution of a trivalent indium compound and a tetravalent tin compound to form indium and a step of coprecipitating a hydroxide of tin; a step of washing the coprecipitated hydroxide with pure water or ion-exchanged water; removing a supernatant of the coprecipitated hydroxide to prepare a slurry in which indium tin hydroxide particles are dispersed a step of drying the slurry; and a step of firing the dried indium tin hydroxide to obtain indium tin oxide. Wherein, in the aforementioned washing step, the resistivity of the supernatant is at least 5000 Ω. 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 the mixture is stirred as described above. 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, and in the drying step, a slurry in which the organic protective agent is added and indium tin hydroxide is dispersed is added. The material 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 after the baking step, the aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is pulverized. After immersing in the surface treatment liquid, it is heated in the range of 200 to 400 ° C for 0.5 to 5 hours in a nitrogen atmosphere.

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

According to a sixth aspect of the present invention, there is provided an invention according to the first aspect, which is characterized in that the method for producing an ITO powder comprises the steps of: mixing an aqueous alkali solution with a mixed aqueous solution of a trivalent indium compound and a tetravalent tin compound to form indium and a step of coprecipitating a hydroxide of tin; a step of washing the coprecipitated hydroxide with pure water or ion-exchanged water; removing a supernatant of the coprecipitated hydroxide to prepare a slurry in which indium tin hydroxide particles are dispersed a step of drying the slurry; and a step of firing the dried indium tin hydroxide to obtain indium tin oxide. Wherein, in the aforementioned washing step, the resistivity of the supernatant is at least 5000 Ω. In the preparation step of the slurry, the slurry from which the supernatant liquid has been removed is diluted with alcohol so that the concentration of the hydroxide particles is in the range of 1 to 5% by mass, and the mixture is stirred as described above. 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, and in the baking step, the inside of the tube furnace heated to a range of 250 to 800 ° C is used. 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 above alcohol and added with the organic protective agent and having indium tin hydroxide particles dispersed therein is sprayed, thereby being sprayed in the tube The furnace is thermally decomposed and fired into indium tin hydroxide particles 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.

Further, the eighth aspect of the present invention is the ITO powder of the first aspect or A method of producing a dispersion by dispersing 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 present invention, when the pressure of 0.196 to 29.42 MPa (2 to 300 kgf/cm ² ) is applied to the green compact comprising the ITO powder, the volume resistivity of the green compact is Y and When the relative density of the green compact is X, it approximates the above formula (1), and since a in the formula (1) is 5.0 × 10 ^-3 or less, and n is -10 or more, the use of the ITO powder can be reduced. The coating method is used to form a resistivity at the time of film formation of the ITO film to obtain high conductivity.

Further, in the method for producing an ITO powder according to the second aspect of the present invention, in the washing step, the resistivity of the supernatant until the supernatant is at least 5000 Ω. 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 into the slurry. 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, and after the firing step, an aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is immersed on the surface. After the treatment liquid, it is heated in the range of 200 to 400 ° C for 0.5 to 5 hours in a nitrogen atmosphere. The hydroxide particles are covered by the organic protective agent having a relatively high decomposition temperature, so that the contact of the ITO particles with each other is prevented during the firing, and the growth of the particles 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, in the method for producing an ITO powder according to the fourth aspect of the present invention, in the washing step, the resistivity of the supernatant until the supernatant is at least 5000 Ω. 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 into the slurry. 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, and in the drying step, the slurry to which the organic protective agent is added and in which the indium tin hydroxide is dispersed is dried. In the baking step, the mixture is heated and fired in a microwave of 2.45 GHz to 28 GHz in the air, and after the baking step, the aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is immersed in 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. The hydroxide particles are covered by the organic protective agent having a relatively high decomposition temperature, so that the contact of the ITO particles with each other is prevented during the firing, and the growth of the particles 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, in the method for producing an ITO powder according to the sixth aspect of the present invention, in the washing step, the resistivity of the supernatant until the supernatant is at least 5000 Ω. Cm, in the preparation step of the slurry, the slurry from which the supernatant is removed is diluted with alcohol so that the concentration of the hydroxide particles becomes 1 to 5% by mass. After the addition, 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 while stirring, and heated to 250 to 800 ° C in the baking step. In the inside of the tube furnace of the range, in which the nitrogen gas is circulated at a linear velocity in the range of 0.5 to 5 m/s, the slurry which is diluted with alcohol and added with an organic protective agent and dispersed with indium tin hydroxide particles is used. Spraying is performed to thermally decompose and calcine the indium tin hydroxide particles in a tube furnace to obtain indium tin oxide particles. The hydroxide particles are covered by the organic protective agent having a relatively high decomposition temperature, so that the contact of the ITO particles with each other is prevented during the firing, and the growth of the particles 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 relative density of the green compact of the ITO powder and its specific resistance.

Next, a mode for carrying out the invention 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. Especially in the use of ITO film as conductive In the case of a 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, at a certain pressure, the volume resistivity of the compact becomes a general reference. However, even under the same pressure, the packing density largely changes depending on the particle diameter, shape, and aggregation state of the ITO powder, thereby causing a change in electrical resistivity. Therefore, when the volume resistivity is determined in a state where the relative density of the green compact of the ITO powder is changed from a low pressure to a high pressure, and the resistivity of the ITO powder is determined, an ITO powder having a higher accuracy can be obtained. Resistivity. The present invention has been completed based on this finding.

The ITO powder of the present invention is a surface-modified ITO powder, and the volume resistivity of the green compact when a pressure of 0.196 to 29.42 MPa (2 to 300 kgf/cm ² ) is applied to the green compact composed of the ITO powder is set to Y. When the relative density of the green compact is X, the relationship between the volume resistivity and the relative density is approximated by the following formula (1), and in the formula (1), a is 5.0 × 10 ^-3 or less. And n is -10 or more.

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 5.0 × 10 ^-3 , the conductivity of the coating film is lowered. If n is less than -10, the change in electrical resistance with respect to the relative density is large, and the film is electrically conductive due to rebound of the particles. Sexuality is easy to decline with time.

The ITO powder used for the production of the ITO film of the present invention is an ITO powder subjected to surface modification treatment 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

The aqueous alkali solution is mixed with a mixed aqueous solution of a trivalent indium compound and a tetravalent 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 an 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 ). An aqueous solution of tin tetrachloride (SnCl ₄ ), tin bromide (SnBr ₄ ), or the like is obtained. Examples of the aqueous alkali solution include ammonia (NH ₃ ) water, hydrogencarbonate ammonia (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 mixing of the aqueous alkali solution may be carried out by dropping the aqueous alkali solution into the mixed aqueous solution to adjust the pH range, or may be carried out by simultaneously dropping the mixed aqueous solution and the aqueous alkali solution in water to adjust the pH range.

After the above-mentioned coprecipitated indium tin hydroxide is formed, the precipitate is washed with pure water or ion-exchanged water, and washed until the resistivity of the supernatant reaches at least 5000 Ω. Cm, preferably at least 50,000 Ω. Cm. If the supernatant is charged The resistivity is less than 5000Ω. In the case of cm, impurities such as chlorine are not sufficiently removed, and high-purity indium tin oxide powder cannot be obtained. Remove the resistivity to 5000Ω. The supernatant of the above precipitate of cm or more was obtained as 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, if it exceeds the upper limit value, a part of the organic substance or a problem that the carbon content of the organic substance remains may be left.

In the atmosphere, it is preferred to dry the indium tin hydroxide adsorbing the organic protective agent on the surface in an inert gas atmosphere such as nitrogen or argon for 2 to 24 hours in the range of 100 to 200 ° C, and then in the atmosphere at 250 to 800. The range of °C is fired in a firing furnace for 0.5 to 6 hours. Using a hammer mill or ball A mill or the like pulverizes and decomposes the aggregate formed by the firing to obtain an ITO powder. The ITO powder is placed in a surface treatment liquid mixed with 50 to 95% by mass of absolute ethanol and 5 to 50% by mass of distilled water, and then immersed in a glass petri dish under a nitrogen atmosphere at 200 to 400. When the range of °C 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.

The microwave heating is carried out in the range of 250 to 800 ° C, preferably in the range of 350 to 600 ° C, and the temperature is raised at a target temperature within 10 minutes, and the firing is maintained at a target temperature for 5 to 120 minutes. Preferably, it is maintained in a 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 fired product is pulverized and decomposed by a hammer mill or a ball mill or the like to obtain an ITO powder. 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 and added with an organic protective agent and dispersed with indium tin hydroxide in a state where nitrogen as a carrier gas is circulated at a linear velocity in the range of 0.5 to 5 m/s. The slurry of particles was sprayed using a two-fluid nozzle and introduced into a tube furnace together with nitrogen. 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]

To 230.7 g of an indium chloride (InCl ₃ ) aqueous solution having a concentration of In metal of 24% by mass, 25.4 g of an aqueous solution of tin tetrachloride (SnCl ₄ ) having a concentration of 55% by mass was added and stirred to prepare a raw material solution. The above raw material solution and a 25% by mass aqueous solution of ammonia (NH ₃ ) were added dropwise together with 1000 ml of pure water heated to 60 ° C while adjusting the pH. 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 oblique washing by ion-exchanged water. The resistivity in the supernatant reaches 5000 Ω. When it is cm or more, the supernatant of the above precipitate is removed to obtain a slurry having a high viscosity in which indium tin hydroxide particles are dispersed.

While stirring the slurry, the slurry was diluted with ion-exchanged water so that the concentration of the hydroxide particles became 20% by mass, and then 3.0 g of an organic protective agent, that is, polyvinyl alcohol, was added. The amount of the organic protective agent added was 2.5% by mass based on the indium tin hydroxide. The slurry was dried at 110 ° C for 10 hours in the atmosphere, and then fired at 800 ° C for 3 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 petri dish. The ITO powder subjected to the surface modification treatment was obtained by heating at 400 ° C for 2 hours under a nitrogen atmosphere.

[Manufacture of ITO film]

To 100 parts by mass of the ITO powder obtained as described above, 300 parts by mass of ethanol was added, and the mixture was dispersed by a homogenizer. The obtained coating liquid was applied by a bar coating method to a PET film having a width of 100 mm and a thickness of 50 μm, and dried by blowing with a warm air of 50 °C. The thickness of the obtained film, that is, the ITO coating film, was 0.2 μm.

Next, the ITO film was compressed by a roll press equipped with a pair of metal rolls having a diameter of 140 mm at a pressure of 1000 N/mm per unit length in the film width direction and a roll rotation speed of 5 m/min to prepare an ITO film.

<Example 2>

To 237.6 g of an indium chloride (InCl ₃ ) aqueous solution having a concentration of In metal of 24% by mass, 19.1 g of an aqueous solution of tin tetrachloride (SnCl ₄ ) having a concentration of 55% by mass was added and stirred, and then all the amounts were added. 1000 ml of pure water was used as a raw material solution. A 25% by mass aqueous solution of ammonia (NH ₃ ) was dropped into the raw material solution for 60 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 oblique washing by ion-exchanged water. The resistivity in the supernatant reaches 5000 Ω. When it is cm or more, the supernatant of the above precipitate is removed to obtain a slurry having a high viscosity in which indium tin hydroxide particles are dispersed. An aqueous solution of 4.5 g of palmityl dimethylethylammonium ethyl sulfate (70% by mass) dissolved in 100 g of pure water was added to the slurry, and the mixture was sufficiently stirred. The amount of the organic protective agent added was 3.0% by mass based on the indium tin hydroxide.

The slurry was dried at 110 ° C for 10 hours in the atmosphere, and then fired at 700 ° C for 2 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 petri dish in nitrogen. The ITO powder subjected to the surface modification treatment was obtained by heating at 400 ° C for 2 hours under an atmosphere. Further, an ITO film was produced in the same manner as in Example 1 using this ITO powder.

<Example 3>

In a solution of 244.5 g of an indium chloride (InCl ₃ ) aqueous solution having an In metal concentration of 24% by mass, 12.7 g of a sodium tin tetrachloride (SnCl ₄ ) aqueous solution having a concentration of 55% by mass was added and stirred to prepare a raw material solution. The above raw material solution and a 25% by mass aqueous solution of ammonia (NH ₃ ) were added dropwise together with 1000 ml of pure water heated to 60 ° C while adjusting the pH. 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 oblique washing by ion-exchanged water. The resistivity in the supernatant reaches 5000 Ω. When it is cm or more, the supernatant of the above precipitate is removed to obtain a slurry having a high viscosity in which 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. ) 6.0 g, and sufficiently stirred to obtain a slurry. The amount of the organic protective agent added was 3.0% by mass based on the indium tin hydroxide.

In the inside of the tube furnace heated to 500° C., which is disposed vertically in the longitudinal direction of the tube, the slurry is passed through a two-fluid nozzle while the nitrogen gas as the carrier gas is allowed to flow at a linear velocity in the range of 1 m/s. Spraying was carried out and introduced into the tube furnace together with nitrogen. 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. While stirring, all the amounts of the above mixed solution of InCl ₃ -SnCl ₄ were dropped into the aqueous solution over about 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 4.5. The precipitate is recovered as indium tin hydroxide, dehydrated by a centrifuge, and then ion-exchanged water is added for cleaning while centrifugal filtration, and the resistivity of the filtrate reaches 5000 Ω. Centrifugal filtration is completed when it is above cm. 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.

75 g of 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 petri dish. The ITO powder subjected to the surface modification treatment was obtained by heating at 400 ° C for 2 hours under a nitrogen atmosphere. Further, an ITO film was produced in the same manner as in Example 1 using this ITO powder.

<Comparative Example 2>

The indium tin hydroxide produced in the same manner as in Comparative Example 1 was fired at 1000 ° C for 5 hours, and the same surface treatment as in Comparative Example 1 was carried out to obtain 70 g of ITO powder. Further, the surface treatment of the ITO powder was carried out in the same manner as in Comparative Example 1, to obtain an ITO powder. Use this ITO powder and real In the same manner as in Example 1, an ITO film was produced.

<Comparative test> [Evaluation of ITO Powder]

The volume resistivity of each of the ITO powders obtained in 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 measurement of the volume resistivity of each ITO powder was carried out as follows: the inner diameter shown in FIG. 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.

Dividing the filling mass of the sample, ie the ITO powder, by the thickness of the sample and the inner diameter of the cylinder The obtained volume is used to determine the actual density, and the actual density is divided by the theoretical density to determine the relative density. The relationship between the relative density (horizontal axis) and the volume resistivity (vertical axis) of the green compact of the ITO powder is shown in FIG. 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 system 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 Examples 1 and 2. Y is the volume resistivity of the compact, and X is the relative density.

Y=aX ⁿ (1)

The surface resistivity (Ω/□) of each of the ITO films obtained in Examples 1 to 3 and Comparative Examples 1 and 2 was measured by a resistivity measuring device (MCP-T400 manufactured by Mitsubishi Petrochemical Co., Ltd.). Further, after one day (24 hours) of film formation, the same measurement was carried out to calculate the ratio with the measured value after film formation. The results are shown in Table 1.

<evaluation>

As is clear from Table 1, the surface resistivity of the ITO film of the ITO powders of Examples 1 to 3 in which a of the formula (1) was 5.0 × 10 ^-3 or less and n was -10 or more was 1.0 × 10 ⁴ Ω. /□ below. On the other hand, the surface resistivity of the ITO film of the ITO powder of Comparative Example 1 in which a of the formula (1) exceeds 5.0 × 10 ^-3 exceeds 1.0 × 10 ⁴ Ω / □. Further, the surface resistivity of the ITO film made of the ITO powder of n of Comparative Example 2 of less than -10 exceeded 1.0 × 10 ⁴ Ω/□, and the surface resistivity after one day of film formation was 1.7 times, which was more than 1.5 times. Thus, Examples 1 to 3 having a relationship similar to the formula (1) were verified, and the electrical resistivity at the time of film formation of the ITO film by coating was reduced to obtain high conductivity.

Claims (9)

A surface-modified ITO powder characterized in that a volume resistivity of the green compact when a pressure of 0.196 to 29.42 MPa is applied to a green compact composed of the ITO powder is set to Y and a relative density of the green compact is set. In the case of X, the relationship between the volume resistivity and the aforementioned relative density is approximated by the following formula (1), in which a is 5.0 × 10 ^-3 or less, and n is -10 or more and Y = aX ⁿ (1). A method for producing an ITO powder, which is the method for producing an ITO powder according to claim 1, which comprises the steps of: mixing an aqueous alkali solution in a mixed aqueous solution of a trivalent indium compound and a tetravalent tin compound to form a coprecipitate of indium and tin; a step of hydroxide; washing the coprecipitated hydroxide with pure water or ion-exchanged water; removing the supernatant of the coprecipitated hydroxide to prepare a slurry in which indium tin hydroxide particles are dispersed; a step of drying the slurry; and a step of firing the dried indium tin oxide to obtain indium tin oxide, characterized in that in the step of cleaning, the resistivity of the supernatant is at least 5000 Ω. 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 the mixture is stirred as described above. 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. After the calcination 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. The method of claim 2, wherein the organic protective agent is palmityldimethylethylammonium ethyl sulfate, polyvinyl alcohol or octyldimethylethylammonium ethyl sulfate. A method for producing an ITO powder, which is the method for producing an ITO powder according to claim 1, which comprises the steps of: mixing an aqueous alkali solution in a mixed aqueous solution of a trivalent indium compound and a tetravalent tin compound to form a coprecipitate of indium and tin; a step of hydroxide; washing the coprecipitated hydroxide with pure water or ion-exchanged water; removing the supernatant of the coprecipitated hydroxide to prepare a slurry in which indium tin hydroxide particles are dispersed; a step of drying the slurry; and a step of firing the dried indium tin oxide to obtain indium tin oxide, characterized in that in the step of cleaning, the resistivity of the supernatant is at least 5000 Ω. 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 the mixture is stirred as described above. 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, and in the step of drying, the organic protective agent is added and indium tin hydroxide is dispersed. The slurry is dried, In the step of baking, the film is heated and fired in a microwave of 2.45 GHz to 28 GHz in the air, and after the baking step, the aggregate of the fired ITO powder is pulverized, and the pulverized ITO powder is immersed in After the surface treatment liquid is heated, it is heated in the range of 200 to 400 ° C for 0.5 to 5 hours in a nitrogen atmosphere. The method of claim 4, wherein the organic protective agent is palmityl dimethylethylammonium ethyl sulfate, polyvinyl alcohol or octyldimethylethyl ammonium ethyl sulfate. A method for producing an ITO powder, which is the method for producing an ITO powder according to claim 1, which comprises the steps of: mixing an aqueous alkali solution in a mixed aqueous solution of a trivalent indium compound and a tetravalent tin compound to form a coprecipitate of indium and tin; a step of hydroxide; washing the coprecipitated hydroxide with pure water or ion-exchanged water; removing the supernatant of the coprecipitated hydroxide to prepare a slurry in which indium tin hydroxide particles are dispersed; a step of drying the slurry; and a step of firing the dried indium tin oxide to obtain indium tin oxide, wherein in the step of cleaning, the resistivity of the supernatant is at least 5000 Ω . In the preparation step of the slurry, the slurry from which the supernatant liquid has been removed is diluted with alcohol so that the concentration of the hydroxide particles is in the range of 1 to 5% by mass, and the mixture is stirred as described above. 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. In the step of firing, the inside of the tube furnace heated to a range of 250 to 800 ° C is diluted with the alcohol in a state where nitrogen gas is allowed to flow at a linear velocity in the range of 0.5 to 5 m/s. The slurry having the aforementioned organic protective agent and dispersed with indium tin hydroxide particles is sprayed to thermally decompose and calcine the indium tin hydroxide particles in the above-mentioned tube furnace to obtain indium tin oxide particles. The method of claim 6, wherein the alcohol is ethanol, methanol or propanol, and the organic protective agent is palmityldimethylethylammonium ethyl sulfate, polyvinyl alcohol or octyldimethylethyl ammonium. Ethyl sulfate. A method of producing a dispersion in which an ITO powder as claimed in claim 1 or an ITO powder produced by the method according to any one of claims 2 to 7 is dispersed in a solvent to prepare a dispersion. A method of producing an ITO film, wherein an ITO film is produced from the dispersion as claimed in claim 8.