JPH11228218A - Manufacturing method of ITO sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high-density ITO sintered body having a small amount of impurities mixed into a slurry used in a slurry casting method for an ITO sintered body. SOLUTION: Ion-exchanged water and an organic additive are added to indium oxide powder and tin oxide powder, and the mixture is pulverized and mixed by a ball mill to prepare a slurry. In the method for producing an ITO sintered body, the tin oxide powder is adjusted to have a specific surface area of 1 to 4 m ² / g and an average particle diameter of 1 μm or less in advance. Low-density IT
A method for producing an O sintered body. Further, a compact formed from the slurry is fired in an oxygen atmosphere.
A method for producing an O sintered body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an ITO sintered body suitable for use as a high-density ITO target used for forming a transparent conductive film by a sputtering method.

[0002]

2. Description of the Related Art Conventionally, when preparing a mixed slurry of indium oxide and tin oxide for preparing an ITO sintered body, a pulverized mixing medium is heavier than the specific gravity of the slurry, and has poor impact resistance and abrasion resistance. Excellent zirconia balls are commonly used.

However, although zirconia balls are very excellent in impact resistance and abrasion resistance, zirconia (ZrO ₂ ) is contained as an impurity in a slurry in the order of several hundred ppm when wet ball milling is performed for a long time. Will be mixed.
The use of iron core-containing resin balls or the like as the pulverization / mixing medium can prevent impurities from being mixed, but under such conditions, the efficiency of slurry pulverization is low and the density of the finally obtained ITO sintered body is not sufficient. There is a problem that does not go up. If the impurities from the ball mill pulverized mixed media increase in the ITO slurry, the film forming characteristics and film characteristics of the ITO transparent conductive film formed by sputtering using such an ITO sintered body are adversely affected, which is not preferable. .

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to provide an IT
An object of the present invention is to provide a method for producing a high-density ITO sintered body in which the amount of impurities mixed from a pulverized mixed medium into a slurry used in a slurry casting method for producing an O sintered body is small.

[0005]

Means for Solving the Problems The present inventors put indium oxide powder and tin oxide powder and ion-exchanged water into a resin pot and performed ball milling using zirconia balls to measure the amount of zirconia impurities. Using the same indium oxide powder and tin oxide powder having different specific surface area and average particle size conditions, the relationship between tin oxide and the amount of mixed zirconia impurities was investigated. As a result, it was found that when tin oxide having a small specific surface area and a large average particle diameter was used, the amount of mixed zirconia impurities increased. Here, the average particle diameter of the tin oxide powder is a value measured by a particle size distribution analyzer using a laser scattering method. The specific surface area is
This is a value measured by the BET method.

Therefore, the present inventors have found that if the agglomeration of tin oxide powder is pulverized in advance to reduce the average particle diameter and increase the specific surface area, the amount of impurities mixed from the pulverized mixed media can be reduced. I paid attention. By adjusting the specific surface area and average particle diameter of the tin oxide powder to specific ranges, it was found that a high-density ITO sintered body in which the amount of impurities mixed from the pulverized mixed media was effectively suppressed could be obtained. The invention has been completed.

The present invention is as follows. Ion-exchanged water and an organic additive are added to indium oxide powder and tin oxide powder to prepare a slurry by ball mill pulverization and mixing, and this slurry is cast into a slurry, and the obtained compact is sintered to form an ITO sintered body. A high-density ITO containing less impurities from the pulverized mixed media, wherein the tin oxide powder is adjusted to have a specific surface area of 1 to 4 m ² / g and an average particle diameter of 1 μm or less in advance. A method for manufacturing a sintered body. In addition, a method for producing a high-density ITO sintered body having a small amount of impurities mixed from a pulverizing medium, comprising firing a molded body produced from the slurry in an oxygen atmosphere.

[0008] Although in the manufacturing method of the ITO sintered body of the present invention used to precondition the specific surface area of the tin oxide powder in the range of 1 to 4 m ² / g, which is a specific surface area of 4m ² / g This is because cracking occurs in the obtained ITO sintered body if it exceeds the above. When the specific surface area of the tin oxide powder is 1 m ² / g or less, the particle diameter is increased by grain growth or sintering. This makes it difficult to reduce the average particle diameter, which may result in an increase in the amount of ZrO ₂ mixed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Commercially available indium oxide powder is used. As the tin oxide powder, a commercially available tin oxide powder is used. The specific surface area of the tin oxide is set to ¹ to 4 m ² / g by using a means such as a ball mill pulverization using a resin ball containing an iron core in advance without a risk of impurities being mixed in from the pulverization media. The average particle diameter is adjusted to a range of 1 μm or less.

Although there is no particular lower limit for the average particle diameter, the average particle diameter of the tin oxide powder obtained by using such means does not generally fall below 0.1 μm. The tin oxide powder, the indium oxide powder, and the zirconia balls are put into a resin pot and pulverized and mixed by a dry ball mill. The composition of tin oxide is 5
-10% by weight is preferred. At this time, deionized water 1-5
If the weight% is added, the effect of reducing the adhesion of the raw material powder to the pot wall and sufficiently performing the pulverization and mixing can be expected. It is preferable to use a resin pot as a ball mill pot from the viewpoint of preventing impurities from being mixed.

Next, 10 to 25% by weight of ion-exchanged water is added to the ball mill pot, and an organic additive (dispersant) is added.
Is added and pulverized and mixed by a wet ball mill to disperse the raw material powder. As the dispersant, a polycarboxylic acid-based dispersant can be used, and the addition amount is preferably 0.2 to 1.0% by weight.

Further, an organic additive (binder) was added and mixed to form a slurry. As the binder, a wax emulsion-based binder can be used, and the addition amount is preferably 0.3 to 1.0% by weight. It is preferable to prepare a slurry having a slurry viscosity of 100 cps or less. If the slurry viscosity is high, deaeration becomes difficult, and the slurry recovery rate decreases due to adhesion to containers and balls.
Finally, an organic additive (antifoaming agent) is added to the slurry, and the slurry is degassed under reduced pressure. As the defoaming agent, an amide-based defoaming agent can be used, and the addition amount is preferably 0.01 to 0.5% by weight.

[0013] A slurry is cast into a porous mold, and a molded body is obtained by removing moisture in the slurry. After the molded body is naturally dried, it is preferable that degreasing is performed at 400 to 600 ° C. to remove residual moisture and a binder in the molded body. Thereafter, the formed body is fired to obtain an ITO sintered body. The firing temperature is preferably from 1400 to 1600 ° C. In order to obtain a higher density ITO sintered body, firing in an oxygen atmosphere is preferable.

[0014]

The present invention will be further described below with reference to examples and comparative examples. Example 1 A resin ball containing a tin oxide powder having a specific surface area of 2.64 m ² / g and an average particle diameter of 8.4 μm and an iron core having a diameter of 20 mm was placed in a resin pot, and subjected to dry ball mill pulverization for 72 hours. The powder was pulverized to 8 m ² / g and the average particle diameter was 0.59 μm. Table 1 shows changes in the pulverizing time, the specific surface area and the average particle diameter at this time.

[0015]

[Table 1]

A resin pot was charged with 7200 g of indium oxide powder, 800 g of tin oxide powder having the above specific surface area, 240 g of ion-exchanged water, and zirconia balls having a diameter of 10 mm.
The ball mill was crushed and mixed for 20 hours. Next, 1440 g of ion-exchanged water and polycarboxylic acid-based dispersant 56 were added to the pot.
g was added and mixed for 1 hour with a ball mill. One hour later, 80 g of a wax-based binder was added, and the mixture was pulverized and mixed by a ball mill for 9 hours.

1.6 g of an amide-based antifoaming agent was added to the slurry thus prepared, and deaeration was performed under reduced pressure. The average particle size of this slurry was 0.5 μm. This slurry was cast into a casting mold having a molding size of 300 mm × 700 mm to obtain a molded body. After the molded body was naturally dried, it was degreased at 600 ° C. After that, firing at 1550 ° C. in an oxygen atmosphere,
A crack-free ITO sintered body was obtained. ITO at this time
The dimensions of the sintered body were 245 mm × 572 mm × 7.3 mm, and the density was 98.7% (7.05 g / cm ³ ). At this time, the zirconia impurity amount was 30 ppm.

Comparative Example 1 Indium oxide powder 7200 g and specific surface area 2.6 m ² / g
Then, 800 g of tin oxide powder having an average particle diameter of 8.4 μm, 240 g of ion-exchanged water, and zirconia balls having a diameter of 10 mm were placed in a resin pot, and ball milled and mixed for 20 hours. Next, 1440 g of ion-exchanged water and 56 g of a polycarboxylic acid-based dispersant were placed in the pot, and mixed by ball milling for 1 hour. After 1 hour, 80g of wax-based binder
The mixture was added and ball milled and mixed for 19 hours. 1.6 g of the amide-based antifoaming agent was added to the slurry thus prepared, and deaeration was performed under reduced pressure. The average particle size of this slurry was 0.5 μm.

The slurry was formed into a mold having a size of 300 mm × 7.
It was cast into a casting mold having a thickness of 00 mm used in Example 1 to obtain a molded body. After the molded body was naturally dried, it was degreased at 600 ° C.
Then, it was baked at 1550 ° C. in an oxygen atmosphere to obtain a crack-free ITO sintered body. At this time, the dimensions of the ITO sintered body were 247 mm × 578 mm × 7.3 mm, and the density was 98.1% (7.01 g / cm ³ ). The zirconia impurity amount was 220 ppm.

Comparative Example 2 900 g of indium oxide powder, 100 g of tin oxide powder having a specific surface area of 9.5 m ² / g and an average particle diameter of 1.5 μm, 30 g of ion-exchanged water and zirconia balls having a diameter of 10 mm were put into a resin pot. The ball mill was crushed and mixed for 20 hours. Next, 177 g of ion-exchanged water and 8 g of a polycarboxylic acid-based dispersant were placed in the pot, and mixed by ball milling for 1 hour. After 1 hour, 10 g of a wax-based binder is added,
Ball milling and mixing were performed for 19 hours. 0.2 g of the amide-based antifoaming agent was added to the slurry thus prepared,
Vacuum deaeration was performed. The average particle size of this slurry is 0.5
μm.

This slurry was cast into a casting mold having a forming size of 190 mmφ to obtain a formed body. After the molded body was naturally dried, it was degreased at 600 ° C. Then, in an oxygen atmosphere,
It was fired at 50 ° C. to obtain an ITO sintered body. IT at this time
The size of the O sintered body was 157 mmφ × 5.8 mm, and the density was 98.3% (7.03 g / cm ³ ). This sintered body had a crack having a length of 10 mm. The zirconia impurity content at this time was 90 ppm.

[0022]

According to the present invention, when preparing the ITO slurry used in the slurry casting method, the specific surface area and the average particle diameter of the tin oxide powder are selected within an appropriate range, so that the amount of impurities mixed from the pulverized media is reduced. And a high-density ITO sintered body having a low density can be obtained.

Claims (2)

[Claims] 1. A slurry is prepared by adding ion-exchanged water and an organic additive to indium oxide powder and tin oxide powder and pulverizing and mixing them in a ball mill to perform slurry casting and sintering the obtained compact. A tin oxide powder having a specific surface area of 1 to 4 m ² / g and an average particle diameter of 1 μm or less in a method for producing an ITO sintered body by using a high-density mixture with a small amount of impurities mixed from a pulverized mixed medium. Manufacturing method of ITO sintered body. 2. A high-density ITO sintered body having a small amount of impurities mixed from a pulverized mixed medium, wherein the molded body manufactured by using the slurry according to claim 1 is fired in an oxygen atmosphere. Manufacturing method.