JP2003137546A - Method for manufacturing tin oxide powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a tin oxide powder using a jet mill capable of obtaining a sintered compact excellent in densification and in homogeneity of ingredients preferable for forming an ITO thin film. SOLUTION: The method of manufacturing the tin oxide powder using the jet mill is characterized in that at the time of grinding the tin oxide powder in the jet mill, the linear velocity of the tin oxide raw material powder is set at >=300 m/sec, thereby the grains of raw material powder are ground by colliding to each other in an air flow.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing tin oxide powder, which is particularly suitable for producing an ITO sputtering target.

[0002]

2. Description of the Related Art ITO (indium-tin composite oxide)
The film is widely used as a transparent electrode (film) of a display device centering on a liquid crystal display. As a method for forming this ITO film, it is usual to use a method generally called physical vapor deposition, such as vacuum vapor deposition or sputtering. In particular, the magnetron sputtering method is often used in terms of operability and film stability.

The film is formed by the sputtering method, in which positive ions such as Ar ions are physically made to collide with a target placed on the cathode, and the material constituting the target is emitted by the collision energy, and the facing anode side. It is carried out by laminating a film having substantially the same composition as the target material on the substrate. The coating method by the sputtering method is characterized in that a thin film of angstrom unit to a thick film of several tens of μm can be formed at a stable film formation rate by adjusting the processing time, the power supply, and the like.

A particular problem in forming an ITO film is nodules generated during sputtering.
The sputtering target for forming an ITO film is manufactured by sintering a powder in which tin oxide powder and indium oxide powder are mixed in a predetermined ratio, but since they are powders having different component compositions from the beginning, they are already the same at the mixing stage. It is unavoidable that the dispersibility of both is inferior to that of the component powder.

If the particle size of the powder for sintering, especially the particles of tin oxide, is large, it cannot be sufficiently dissolved in the mixed indium oxide to form a solid oxide of tin oxide in the sintered body. Causes pores in the body. In addition, the density of the sintered target becomes low and lacks in denseness, and when forming the ITO sputtering film, nodules (protrusions) frequently occur in the erosion part of the ITO target, which induces irregular sputtering and abnormal discharge. There is a problem that (micro-arcing) or cluster-like (hardened) coating is formed, which causes a short circuit.

In addition, due to nodules and abnormal discharge,
Coarse particles in the sputter chamber
Becomes floating, which causes redeposition on the substrate to short-circuit the thin film circuit, or causes a problem of a thin film protrusion. Commonly known pulverizers include a jet mill that pulverizes materials by mutually colliding or colliding with liners for pulverization, and a bead mill that pulverizes by grinding between media or liners using a pulverizing media. However, in general, in the jet mill method, in order to pulverize a hard and highly cohesive raw material such as tin oxide powder to a particle size in the submicron region, the number of passes is increased and the amount of processing is extremely reduced, resulting in cost reduction. It is said to be disadvantageous to.

For this reason, a media stirring type pulverizer is used for the sintering powder of the ITO target, and the wet type bead mill, which is easy to control the agglomeration of the raw materials, is the most suitable. I was told. This bead mill is performed by inserting hard beads for grinding (such as zirconia beads) and raw material powder made into a slurry. By controlling the particle diameter of the raw material powder and the diameter of the grinding media, the larger the raw material powder particle size, Since it is selectively ground, a sharp particle size distribution with few coarse particles can be obtained. If you increase the grinding power or the number of passes in this bead mill,
It becomes finer, but if it is too strong, it becomes difficult to control the grinding amount, and if it is too weak, the movement of the beads and slurry in the mill deteriorates, and the grinding efficiency decreases significantly, so control it to an appropriate strength. Grinding is required.

Indium oxide powder, which is the raw material powder for the ITO target, is easy to pulverize and does not cause any particular problem, but powders that are hard and have a strong cohesive property, such as tin oxide, are pulverized as compared with indium oxide powder. Becomes difficult. Therefore, pulverization of tin oxide is particularly problematic as a raw material powder, and it is necessary to control this. As described above, when pulverizing tin oxide, by increasing the pulverizing power or the number of passes, it is considered that the pulverization can be performed more finely, but in addition to the problem due to increasing the pulverizing power or the number of passes, The liner, hard bead material, etc. in the mill grinder are mixed in the tin oxide powder as contaminants. This is a major problem when using a bead mill grinder. Further, in general, when manufacturing an ITO target sintered body, it is desirable to increase the density because of the problem of nodule and particle generation as described above. For that purpose, it is necessary to strengthen the pulverization to make the particle diameter of the powder finer. Will be needed. However, the problem of densification by sintering using finely divided powder and the problem of contamination of the sintered material due to the refinement of powder are contradictory to each other. The current situation is that it cannot be said that From the above, in order to form an ITO thin film, it was necessary to obtain a sintered compact target having a uniform composition and a high density. However, an optimum tin oxide powder satisfying these requirements can be produced by a stable production method. There was a problem that I could not get it.

[0009]

SUMMARY OF THE INVENTION The present invention provides a jet mill capable of solving the above-mentioned various problems, and in particular, obtaining a sintered body having a high density and excellent component uniformity suitable for forming an ITO thin film. A method for producing a tin oxide powder used is provided.

[0010]

A technical means for solving the above problems is to devise the pulverizing conditions of a jet mill in order to stably and efficiently produce fine tin oxide powder. We obtained the knowledge that it can be obtained.
Based on this finding, the present invention provides 1. 1. When pulverizing tin oxide powder with a jet mill, the linear velocity of the tin oxide raw material powder is set to 300 m / sec or more, and the tin oxide powder is made to collide with each other in an air stream and pulverized. 2. The method for producing tin oxide powder by the jet mill as described in 1 above, wherein the linear velocity of the tin oxide raw material powder is 400 m / sec or more. 3. A method for producing a tin oxide powder by a jet mill, characterized in that, when the tin oxide powder is pulverized by the jet mill, a residence time of the tin oxide raw material powder in the jet mill is 250 seconds or more. 4. The method for producing tin oxide powder by the jet mill as described in 3 above, wherein the residence time in the jet mill is 300 seconds or more. The residence time of the tin oxide raw material powder in the jet mill was set to 25.
5. The method for producing tin oxide powder by the jet mill according to 1 or 2 above, which is set to 0 second or longer. 6. The method for producing tin oxide powder by the jet mill according to the above 1 or 2, wherein the residence time in the jet mill is 300 seconds or more. 90 wt% or more of the particle size obtained from the particle size distribution is 0.1
~ 3.0 μm, the median diameter obtained from the particle size distribution is 0.4
7. A method for producing a tin oxide powder according to each of 1 to 6 above, which comprises pulverizing to a tin oxide having a diameter of 0 to 0.6 μm. 90 wt% or more of the particle size obtained from the particle size distribution is 0.1
To 1.0 μm, and a pulverized into tin oxide having a median diameter of 0.40 to 0.60 μm determined from a particle size distribution, the method for producing tin oxide powder according to each of 1 to 6 above. To do.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a so-called jet mill method in which tin oxide powder obtained by spray pyrolysis method from a solution or slurry of tin chloride is used as a raw material and is crushed by colliding with each other in an air stream. Is used to obtain a tin oxide powder suitable for an ITO sputtering target. As mentioned above, in the jet mill method, in order to pulverize a hard and highly cohesive raw material such as tin oxide powder to a particle size in the submicron range, the number of passes increases and the amount of processing decreases drastically, resulting in cost reduction. However, it was found that the tin oxide powder can be efficiently pulverized by improving the pulverization conditions by the jet mill.

As described above, the jet mill method performs self-pulverization of pulverized products. In order to improve the pulverization efficiency of this jet mill, the oxidization which is a powder introduced into the pulverization chamber of the jet mill. It has been found that this can be achieved by increasing the linear velocity of the tin raw material powder and / or the residence time in the jet mill. That is, when the tin oxide powder was pulverized by the jet mill, the linear velocity of the tin oxide raw material powder was 30%.
By setting the speed to 0 m / sec or more and violently colliding with each other in the air current and pulverizing, it became possible to remarkably enhance the pulverizing efficiency. If the linear velocity is less than 300 m / sec, it cannot be expected to improve the grinding efficiency. In particular, when the linear velocity of the tin oxide raw material powder is 400 m / sec or more, the efficiency becomes higher.

When the tin oxide powder is pulverized by the jet mill, the retention time of the tin oxide raw material powder in the jet mill is set to 250 seconds or more to increase the chances of collision in the air flow, thereby improving the pulverization efficiency. Can be significantly increased. Especially, the residence time in the jet mill is 30
By setting the time to 0 seconds or more, the pulverization efficiency can be further increased. By simultaneously adjusting the linear velocity of the tin oxide raw material powder and the residence time in the jet mill, the grinding efficiency can be significantly increased.

A conceptual explanatory view of the jet mill is shown in FIG.
The basic structure of the jet mill has a crushing chamber 1, a grinding nozzle 2 having an ejection port in the tangential direction of the inner wall of the crushing chamber 1, and a jet nozzle in the tangential direction of the inner wall of the crushing chamber 1 as well. It comprises a Venturi nozzle 3 for supplying raw materials. A swirling airflow 5 is formed in the crushing chamber 1 by jetting grinding air 10 from the grinding nozzle 2 and the venturi nozzle 3. As a result, the tin oxide raw material powders violently collide with each other and are ground.
The crushed material 9 is continuously or semi-continuously extracted from the crushed material outlet 4 at the center of the crushing chamber 1. Venturi nozzle 3
Has a pusher nozzle 7 for injecting pusher air 6, and has a structure for injecting the powder raw material supplied from the raw material inlet 8 into the crushing chamber 1 from the tip of the venturi nozzle 3.

Generally, the linear velocity of the tin oxide raw material powder can be increased by narrowing the diameter of the Venturi nozzle 3 which is a raw material introducing portion into the crushing chamber 1 of the jet mill. However, only by reducing the diameter of the Venturi nozzle 3, although the linear velocity increases, the amount of air supplied into the crushing chamber 1 decreases. As a result, the problem of backflow from the crushing chamber occurs. In order to prevent this, it is necessary to keep the throughput of the raw material powder constant. However, in this case, it means that the residence time in the crushing chamber 1 cannot be increased correspondingly and the crushing efficiency cannot be increased. For this reason, measures were taken to increase the diameter of the pusher nozzle 7 of the jet mill, increase the amount of air supplied, and prevent backflow from the grinding chamber. As a result, the amount of powder to be treated can be reduced even when the linear velocity is increased, the residence time can be increased, and the pulverization efficiency can be increased.

By crushing tin oxide by the above jet mill, suitable for manufacturing an ITO sputtering target,
90 wt% or more of the particle size obtained from the particle size distribution is 0.1
3.0 μm, the median diameter obtained from the particle size distribution is 0.40
Tin oxide having a thickness of up to 0.6 μm can be stably obtained with high efficiency. In particular, 90 wt% of the particle size obtained from the particle size distribution
It is possible to produce a tin oxide powder in which the above is 0.1 to 1.0 μm and the median diameter determined from the particle size distribution is 0.40 to 0.60 μm.

[0017]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of the present invention will be described. It should be noted that this embodiment is merely an example, and the present invention is not limited to this example. That is, it includes all aspects or modifications other than the examples within the scope of the technical idea of the present invention.

(Example 1) Tin oxide raw material powders obtained by the spraying / pyrolysis method were made to collide with each other in an air stream by a jet mill to obtain tin oxide fine powders. The raw material powder of tin oxide used had a median diameter of 2.5 μm. Air of the same pressure is supplied from the compressor to the grinding nozzle (2 mmφ x 6) and the pusher nozzle of the jet mill. The amount of air supplied to the entire jet mill is 2.7 m
³ / min. The amount of air in the pusher nozzle is determined by the ratio with the cross-sectional area of the grinding nozzle. The pusher nozzle diameter was 4.2 mmφ and the air amount was 1.5 m ³ / min. The linear velocity of the powder raw material can be obtained from the amount of air from the pusher nozzle and the venturi diameter. The venturi nozzle diameter was 8 mmφ. The linear velocity at this time was 497 m / sec. When the treatment amount was 3.0 kg / hr, the median diameter obtained from the particle size distribution was 0.55 μm, and when the treatment amount was 1.0 kg / hr, the median diameter obtained from the particle size distribution was 0. It became 38 μm.

(Example 2) Using the same tin oxide raw material powder with a median diameter of 2.5 µm as in the above example, the same jet mill was used to pulverize under the same pulverization conditions. The residence time was determined from the amount of treatment at this time. When the treatment amount was 1 kg / hr, the amount of powder in the crushing chamber was 97 g, and the residence time was 348 seconds.
The linear velocity at this time was 42.8 m / sec, and the residence time was 3
48 seconds and the median diameter obtained from the particle size distribution is 0.3.
It was 8 μm.

Comparative Example 1 Tin oxide raw material powder having a median diameter of 2.5 μm similar to that in the above example was used, and was pulverized by the same jet mill under the same pulverization conditions. The residence time was determined from the amount of treatment at this time. When the treatment amount was 3 kg / hr, the amount of powder in the crushing chamber was 176 g, and the residence time was 211 seconds. The linear velocity at this time was 122 m / sec, the residence time was 211 seconds, and the median diameter determined from the particle size distribution was 0.
It was 70 μm.

As is clear from Examples 1 and 2, when the tin oxide powder is pulverized by the jet mill, the linear velocity of the tin oxide raw material powder is set to 30 m / sec or more.
The median diameter obtained from the particle size distribution is 0.40 to 0.6 μm
Can be crushed to tin oxide in the range. Further, by setting the residence time in the jet mill to 300 seconds or more, the median diameter similarly obtained from the particle size distribution is 0.40 to 0.40.
It can be ground to tin oxide in the range of 0.6 μm. On the other hand, in Comparative Example 1 in which the linear velocity is 122 m / sec and the residence time is 211 seconds, the median diameter obtained from the particle size distribution is 0.70 μm, and sufficient particle size is not obtained.

[0022]

When the tin oxide powder is pulverized by the jet mill, the tin oxide raw material powder is crushed by violently colliding with each other in an air stream with a linear velocity of 300 m / sec or more, particularly a linear velocity of 400 m / sec or more. This has an excellent effect that the pulverization efficiency can be remarkably increased. In addition, when the tin oxide powder is pulverized by the jet mill, the residence time of the tin oxide raw material powder in the jet mill is set to 250 seconds or longer, particularly 300 seconds or longer, thereby increasing the chances of collision in the air flow and pulverizing efficiency. Has a remarkable effect that can significantly increase. In particular, it is possible to significantly increase the grinding efficiency by simultaneously adjusting the linear velocity of the tin oxide raw material powder and the residence time in the jet mill.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory view of a jet mill.

[Explanation of symbols]

1 crushing room 2 grinding nozzle 3 Venturi nozzle 4 crushed material outlet 5 swirling airflow 6 pusher air 7 pusher nozzle 8 Raw material inlet 9 crushed objects 10 grinding air

Claims (8)

[Claims] 1. A tin oxide powder produced by a jet mill, characterized in that when a tin oxide powder is pulverized by a jet mill, the linear velocity of the tin oxide raw material powder is 300 m / sec or more, and the tin oxide powder is pulverized by colliding with each other in an air stream. Manufacturing method. 2. The linear velocity of the tin oxide raw material powder is 400 m / s.
ec or more, The manufacturing method of the tin oxide powder by the jet mill of Claim 1 characterized by the above-mentioned. 3. When the tin oxide powder is ground by a jet mill, the residence time of the tin oxide raw material powder in the jet mill is set to 2
A method for producing tin oxide powder by a jet mill, which is characterized in that the time is 50 seconds or more. 4. The method for producing tin oxide powder by a jet mill according to claim 3, wherein the residence time in the jet mill is 300 seconds or more. 5. The method for producing tin oxide powder by a jet mill according to claim 1, wherein the residence time of the tin oxide raw material powder in the jet mill is 250 seconds or more. 6. The method for producing tin oxide powder by a jet mill according to claim 1, wherein the residence time in the jet mill is 300 seconds or more. 7. A tin oxide having a particle size of 90 wt% or more determined from a particle size distribution of 0.1 to 3.0 μm and a median diameter determined from a particle size distribution of 0.40 to 0.6 μm. The method for producing the tin oxide powder according to each of claims 1 to 6. 8. A pulverized product into tin oxide having 90 wt% or more of the particle size determined from the particle size distribution of 0.1 to 1.0 μm and a median diameter determined from the particle size distribution of 0.40 to 0.60 μm. The method for producing a tin oxide powder according to claim 1, wherein the tin oxide powder is produced.