JPH09124364A - Ito sintered compact for forming transparent electroconductive film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject high-density sintered compact having uniform structure by mixing, forming and sintering indium oxide powder having a specified specific surface area with tin oxide powder having a specified specific surface area in production of ITO sintered compact substantially comprising In, Sn and O. SOLUTION: Indium oxide powder used in this method has >=15m<2> /g and <=20m<2> /g specific surface area. Tin oxide powder has >=3m<2> /g and <=50m<2> /g specific surface area. Tin oxide content is preferably >=0.5wt.% and <=20wt.%. Wet type mixing by ball mill, etc., using water, etc., as a dispersing medium is used as a method for mixing these two powders. The wet type mixing is preferable compared with dry type mixing, because aggregation of the powder is released in the wet type method and sintered compact having uniform structure is readily obtainable. The method for forming the mixed powder is not especially limited. The resultant formed article is sintered at 1300-1600 deg.C. Retention time at maximum temperature is preferably <=50hr. It is recommended that sintering atmosphere is not a reductive atmosphere. The resultant sintered compact has <=200μm<2> second phase area and >=95% relative density.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a transparent conductive film forming I
The present invention relates to a TO sintered body, and particularly relates to a limited manufacturing method using indium oxide powder and sodium oxide powder and a sintered body obtained by the method.

[0002]

2. Description of the Related Art In recent years, the demand for transparent conductive films has increased with the development of display devices centered on liquid crystals. For the transparent conductive film, an indium tin oxide film (hereinafter referred to as an ITO film) having low resistance and high transparency is optimal. As a method for obtaining an ITO film, an indium / tin oxide sintered body (hereinafter referred to as an ITO sintered body) obtained by molding and sintering a mixed powder of indium oxide powder and tin oxide powder was used as a target. The sputtering method is widely applied. Particularly in recent years, with the colorization of liquid crystals, the miniaturization of elements, and the adoption of the active matrix system, there has been a demand for an ITO target capable of uniformly forming a high-quality ITO film in a larger area. However, until now, in the ITO film formation using the ITO target, the target cracks,
There is a problem that particles are generated due to abnormal discharge due to the presence of cracks, pores, a phase different from the ITO phase, and the like, and as one of the methods for solving these problems, the densification of targets has been attempted. As a method for obtaining a high-density ITO sintered body that has been proposed so far, JP-A-3-2
18924, JP-A-4-74860, JP-A-6-4.
8816 and JP-A-6-191846, a method for producing by using limited In2O3 powder, JP-A-6-183731, and JP-A-6-18373.
No. 2 proposes a method of manufacturing by using limited SnO2 powder, or limited SnO2 powder and In2O3 powder.

[0003]

By the way, an ITO sintered body is usually manufactured by molding a mixed powder of indium oxide powder and tin oxide powder and sintering the mixture. Therefore, it is very important to select the particle size of the raw material powder used in the production. However, the above-mentioned JP-A-3-218924, JP-A-4-74860, JP-A-6-48816, and JP-A-6-86816
No. 191846, JP-A-6-183731, and JP-A-6-183732 only consider the high density and do not consider the occurrence of cracks or cracks or the state of existence of a phase different from the main phase. The method of using fine powder material powder for densification is not a mistaken method, but when the raw material powder becomes fine powder, the shrinkage rate increases, so shrinkage is constrained during the sintering process, and as a result, There is a problem that cracks and defects that cause the generation of cracks are introduced. Also,
The tin oxide powder corresponding to the additive is preferably uniformly dispersed in the indium oxide powder in order to make the structure of the sintered body uniform, but it is disclosed in JP-A-6-183731 and JP-A-6-183731.
According to the method of No. 183732, it is difficult to uniformly disperse the tin oxide powder because the tin oxide powder has a small specific surface area. Therefore, the obtained sintered body structure cannot be a homogeneous sintered body due to segregation of a phase different from the ITO phase. It is an object of the present invention to provide an ITO sintered body for forming a transparent conductive film having a uniform structure, and a method for producing an ITO sintered body for forming a transparent conductive film having excellent sinterability.

[0004]

As a result of various studies to solve the above problems, the present inventor found that in order to control the sinterability and the shrinkage ratio, the ratio of the indium oxide powder as the main component was adjusted. By defining the surface area, and by defining the specific surface area of the tin oxide powder, which is an additive in order to obtain a sintered body having a homogeneous structure, a mixed powder of indium oxide powder and tin oxide powder is further prepared. When manufacturing
We have found that the mixing method is important. The present invention relates to a method for producing an ITO sintered body which is substantially composed of In, Sn and O, and has a specific surface area of 15 m ² / g or more, 20
m ² / g or less of indium oxide powder and specific surface area of 3 m ²
/ G or more of tin oxide powder is mixed, molded and sintered, which is a method for producing an ITO sintered body. further,
When mixed, I consisting essentially of In, Sn and O
In the method for manufacturing a TO sintered body, the specific surface area is 15 m ² /
This is a method for producing an ITO sintered body by wet mixing indium oxide powder having a specific surface area of 3 m ² / g or more with indium oxide powder having a specific surface area of 3 m ² / g or more and 20 m ² / g or less. Further, the present invention is an ITO sintered body which is substantially composed of In, Sn and O and has a main phase and a second phase, and the area of the second phase is 200.
It is an ITO sintered body for forming a transparent conductive film having a size of μm ² or less. Furthermore, in the present invention, in an ITO sintered body substantially composed of In, Sn and O, the area of the second phase existing in the sintered body is 200 μm ² or less, and the relative density of the sintered body is The ITO sintered body is 95% or more. In the present invention, the second phase is a phase different from the main phase, and the area of the second phase is 200 μm ² or less means that the second phase having a size of more than 200 μm ² is present in the sintered structure observed by SEM. It means that it does not exist.

The indium oxide powder used in the present invention has a specific surface area of 15 m2 / g or more and 20 m2 / g or less. It is preferably 16 m2 / g or more and 19 m2 / g or less. When the specific surface area of indium oxide is less than 15 m 2 / g, the sinterability is lowered and it is difficult to obtain a high density ITO sintered body. Further, when the specific surface area of indium oxide exceeds 20 m 2 / g, the compacting density is low, and the shrinkage rate of the sintered body during sintering is large, so that a high-density sintered body free from cracks and cracks can be obtained. difficult. Next, the tin oxide powder used in the present invention has a specific surface area of 3 m 2 / g or more. Preferably 4 m2
/ G or more. Specific surface area of tin oxide powder is 3m2 / g
If it is less than the range, it is difficult to obtain a sintered body having a uniform structure. The upper limit of the specific surface area of the tin oxide powder is not particularly limited, but it is practically difficult to produce the tin oxide powder having a specific surface area of more than 50 m2 / g, and therefore it is preferably 50 m2 / g or less. The content of tin oxide powder as an additive is
It is preferably 0.5 wt% or more and 20 wt% or less. If the content of tin oxide is less than 0.5 wt%, a high density ITO sintered body cannot be obtained. If the content of tin oxide is more than 20 wt%, the structure of the sintered body will not be uniform and a high density ITO sintered body will not be obtained.

In the present invention, the indium oxide powder and the tin oxide powder are mixed by wet mixing with a ball mill, an attritor or the like using water as a dispersion medium to obtain a more homogeneous sintered body. be able to. The wet method is preferable as the mixing method because the wet method dissolves the powder agglomerates more easily than the dry method, and a sintered body having a uniform structure is easily obtained. As the molding method of the ITO mixed powder, a mold molding method,
Casting molding method, cold isostatic pressing method (CIP) and the like are mentioned, but not particularly limited. Further, a molded body may be obtained by combining the above-mentioned molding methods. The obtained compact is 1300
Sintering is carried out at a temperature of from 1 ° C to 1600 ° C, preferably from 1350 ° C to 1550 ° C. If the sintering temperature is lower than 1300 ° C,
Alternatively, when the temperature is higher than 1600 ° C, the sintered body has a relative density of less than 95%. The holding time at the maximum temperature is preferably 50 hours or less. When it is longer than 50 hours, tin oxide and indium oxide are dissociated and a high density ITO sintered body cannot be obtained. The sintering atmosphere may be the air, an oxygen atmosphere, an inert gas atmosphere, or the like, and is preferably not a reducing atmosphere.

The sintered body obtained by the manufacturing method of the present invention has an area of the second phase, which is different from the main phase, of 200 μm.
It has an organization of 2 or less. When a sintered body having a heterogeneous structure in which the second phase exceeds 200 μm 2 is used as a sputtering target, selective sputtering occurs, the film composition changes, and stable film characteristics cannot be obtained. Further, the sintered body obtained by the manufacturing method of the present invention has a second phase area of 2
Is less than 00 μm 2 and the relative density of the sintered body is 95%
It is characterized by the above. The relative density of the sintered body is 95
If it is less than%, when used as a sputtering target, the film formation rate during sputtering gradually decreases, a stable film thickness cannot be obtained, and it is difficult to control the film characteristics.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(Example 1) An indium oxide powder having a predetermined specific surface area and a tin oxide powder having a predetermined specific surface area were mixed in a ball mill with water as a dispersion medium at a slurry solid content of 70%. Using the obtained mixed powder, a molded body was produced by CIP at a pressure of 3 ton and then sintered in an oxygen atmosphere. Amount of SnO2 in the raw material powder, specific surface area of the raw material powder,
Table 1 shows the sintering conditions and the relative density of the obtained sintered body.
In addition, No. 1 to 4 are the present invention, and No. Reference numerals 5 and 6 are comparative examples. From Table 1, No. which is an example of the present invention. 1-4
Is a high density ITO sintered body. No.
In the sample of No. 5, the compacting density was low because the indium oxide powder had a large specific surface area, and the shrinkage was restricted, so that a high-density sintered body could not be obtained. No. In the sample No. 6, a high density sintered body could not be obtained because the indium oxide powder had a small specific surface area and was inferior in sinterability.

[0009]

[Table 1]

(Example 2) Composition of indium oxide powder having a specific surface area of 18 m2 / g and sulphur oxide powder having a specific surface area of 5 m2 / g were prepared by a wet mixing method using a ball mill to obtain a slurry solid content of 72% (10 w).
A mixed powder of t%) SnO2 was prepared. Using the mixed powder, C
After forming a molded body with IP, 1550 ℃ × in an oxygen atmosphere
Sintered for 5 hours (No. 7). Further, as a comparative example, a mixed powder of composition (10 wt%) SnO 2 was prepared by dry mixing of indium oxide powder having a specific surface area of 30 m 2 / g and sulphur oxide powder having a specific surface area of 3 m 2 / g. Using the mixed powder, a molded body was prepared by CIP, and then sintered at 1550 ° C for 5 hours in an oxygen atmosphere (No.
8). No. Sintered body density of No. 7 is 99.5%, No. The sintered body density of No. 8 was 92.5%. In addition, No. 7,8
The sintered body of No. 1 was mirror-finished, and the structure of the sintered body was observed by SEM. FIG. No. 7 of the SEM microstructure photograph of No. 7 is shown in FIG. 8 shows a SEM microstructure photograph of No. 8. In FIGS. 1 and 2, the light gray phase is the main phase and the dark gray phase is the second phase. No. In the sintered body of No. 7, the area of the second phase is all 200 μm
2 or less, but No. The sintered body of No. 8 has a second phase having a size exceeding 200 μm 2 as surrounded by a circle in FIG. The area of the second phase surrounded by circles in Fig. 2 is about 26.
It is 0 μm 2. No. Using the sintered bodies of Nos. 7 and 8 as a sputtering target, changes in the film formation rate with respect to the sputtering time and changes in the amount of SnO2 in the film were evaluated.
Table 2 shows the results. From Table 2, N with a non-uniform structure
o. When the sintered body of No. 8 was used, the film formation rate and the film composition changed with the passage of sputtering time. It can be seen that when the sintered body of No. 7 is used as a target, the film formation rate and the film composition are stable even after the sputtering time of 200 hours.

[0011]

[Table 2]

According to the present invention, an ITO sintered body for forming a transparent conductive film having a uniform structure and a high density can be obtained.

[Brief description of the drawings]

FIG. 1 is a metallographic photograph of an ITO sintered body for forming a transparent conductive film of the present invention.

FIG. 2 is a photograph of a metal structure of a comparative ITO sintered body for forming a transparent conductive film.

Claims (4)

[Claims] 1. A material consisting essentially of In, Sn and O,
In the ITO sintered body having the main phase and the second phase, the second
An ITO sintered body for forming a transparent conductive film, wherein the phase area is 200 μm ² or less. 2. The ITO sintered body for forming a transparent conductive film according to claim 1, wherein the relative density of the sintered body is 95% or more. 3. IT consisting essentially of In, Sn and O
In the method for manufacturing an O-sinter, the specific surface area is 15 m ² / g
As described above, the indium oxide powder having a specific surface area of 20 m ² / g or less and the tin oxide powder having a specific surface area of 3 m ² / g or more are mixed and molded,
A method for producing an ITO sintered body for forming a transparent conductive film, which comprises sintering. 4. The method for producing an ITO sintered body for forming a transparent conductive film according to claim 3, wherein the mixing is wet mixing.