JP2002003961A - Method for recovering indium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove impurities, particularly zinc in the scrap of an IXO (multiple oxide of indium oxide and zinc oxide) sputtering target used for depositing a transparent electroconductive film or the like or an IXO scrap such as abrasive powder generated at the time of producing an IXO sputtering target with high efficiency, and to recover indium having high purity. SOLUTION: This method for recovering indium in which indium is recovered from the scrap of an IXO sputtering target or IXO scrap such as abrasive powder is composed of a stage in which IXO scrap is pulverized and is mixed with carbon powder, a stage in which this powdery mixture is charged to a reducing furnace and is heated and reduced, and simultaneously, zinc is exhausted to the outside of the system as vapor and a stage in which the obtained coarse indium is electrolytically refined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scrap of an IXO (indium oxide-zinc oxide composite oxide) sputtering target used for forming a transparent conductive film or the like, a polishing powder generated at the time of manufacturing an IXO sputtering target, and the like. And a method for efficiently recovering high-purity indium from IXO scrap.

[0002]

2. Description of the Related Art In recent years, since a transparent conductive film made of IXO has high conductivity and visible light transmittance, a liquid crystal display device, a thin film electroluminescence display device, a radiation detection device, a transparent tablet of a terminal device, It is used in a wide variety of applications, such as heat-generating films for anti-condensation devices on windowpanes, antistatic films or permselective films for solar collectors, and electrodes for touch panels. It is used to form a film on a substrate or the like. Although this sputtering method is an excellent method for forming a thin film, when a sputtering target is used to produce a transparent conductive thin film, for example, the target is not consumed uniformly.

[0003] A part of the target which is particularly depleted is generally called an erosion portion. The erosion portion is depleted, and the sputtering operation is continued until just before the backing plate supporting the target is exposed. But then exchanged for a new target. Therefore, many non-erosion portions, that is, unused target portions remain in the used sputtering target, and all of them become scrap. In addition, there are IXO scraps such as polishing powder generated during the manufacture of the IXO sputtering target.

[0004] Since a high-purity material is used for the IXO sputtering target material and its price is high, indium is generally recovered from such scrap material. As this indium recovery method, a method combining wet purification such as an acid dissolution method, an ion exchange method, and a solvent extraction method has been conventionally used. For example, IXO scrap is washed and pulverized, dissolved in nitric acid, hydrogen sulfide is passed through the solution to precipitate and remove impurities such as zinc, tin, lead, and copper as sulfide, and then neutralized by adding ammonia thereto. And indium hydroxide. However, indium hydroxide obtained by this method has poor filterability and requires a long time for operation, has many impurities such as Si and Al, and indium hydroxide to be generated depends on its neutralizing conditions and aging conditions. Because the particle size and particle size distribution fluctuate,
Thereafter, when manufacturing the IXO target, there is a problem that the characteristics of the IXO target cannot be stably maintained.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an IXO (indium oxide-zinc oxide composite oxide) sputtering target scrap used for forming a transparent conductive film or the like. The present invention relates to a method for efficiently removing impurities, particularly zinc, in IXO scrap such as polishing powder generated during the production of an IXO sputtering target and recovering high-purity indium.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for producing an IXO sputtering target or an abrasive powder.
A method of recovering indium from XO scrap, comprising a step of pulverizing IXO scrap and mixing it with carbon powder, a step of charging the mixed powder into a reduction furnace and reducing by heating, and simultaneously discharging zinc as vapor out of the system. 2. A method for recovering indium, which comprises a step of electrolytically refining the crude indium thus obtained. 4. The method for recovering indium as described in 1 or 2 above, wherein the reduction is performed in a nitrogen atmosphere.
3. The method for recovering indium described in each of No. 3 is provided.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, IXO scrap such as IXO sputtering target scrap used for forming a transparent conductive film or the like and polishing powder generated during the production of the IXO sputtering target is ground. Next, carbon powder is mixed with the crushed IXO scrap. In this case, it is preferable to mix 15 to 30% of carbon powder. If it is less than 15%, the amount is not sufficient to reduce IXO scrap, and if it is added in excess of 30%, the reduction efficiency is saturated and there is no economic significance. further,
This mixed powder is put into a reduction furnace and reduced by heating. At this time, zinc is discharged out of the system as vapor. The reduction temperature is 800 ~
1300 ° C. If the temperature is lower than 800 ° C., the reduction of IXO scrap is not sufficient, and if the temperature exceeds 1300 ° C., the suboxide of indium becomes vapor and escapes from the system, and the loss of indium increases. The reducing atmosphere is a nitrogen atmosphere to prevent oxygen from entering the reducing furnace.

Next, electrolytic purification is performed using the reduced crude indium as an anode to obtain high-purity indium. During the electrolytic refining of indium, the electrodeposits may be deposited in a dendritic manner with the progress of the electrodeposition, causing a short circuit between the electrodes, resulting in a decrease in current efficiency. As a countermeasure, ions (hydrochloric acid or alkali metal chlorides such as sodium chloride and potassium chloride and indium chloride) are added to the electrolytic solution. The chlorine ion concentration in the electrolytically purified solution is preferably adjusted to 10 to 40 g / L. Preferably, the chlorine ion concentration is 20 to 35 g /
Adjust to L. At the time of electrolysis, the concentration of indium in the electrolytic solution is adjusted to 30 to 80 g / L. If it is less than 30 g / L, the current efficiency becomes poor and the generation of hydrogen increases, which is not preferable. Further, even if it exceeds 80 g / L, there is no problem in electrolysis, but it is not preferable because residual in the system increases. More preferably, the indium concentration range in the electrolyte is 40 to 60 g / L.
It is.

No special electrolytic device is required. For example, electrolysis may be performed using crude indium to be purified as an anode and a titanium plate or the like as a cathode mother plate. Of the impurities in the anode, those noble than indium, such as tin, precipitate as slime, and those nobler than indium dissolve in the electrolytic solution and do not precipitate on the cathode. In this case, it is desirable to provide a diaphragm between the anode and the cathode in order to avoid mixing of slime into the precipitate.
Surfactants such as glue, gelatin, and PEG can be added to the electrolyte to further reduce the amount of dendritic precipitates. The pH of the electrolyte is preferably adjusted to 0.5 to 2.5. When the pH is less than 0.5, generation of hydrogen is increased and current efficiency is lowered, which is not preferable. Also, PH
Exceeds 2.5, indium forms hydroxide and precipitates, which is not preferable. A more preferred range is PH 1.0 to
2.0.

It is desirable to adjust the current density to 0.1 to 2.0 A / dm ² . If the current density is less than 0.1 A / dm ² , the production efficiency decreases. On the other hand, when the current density exceeds 2.0 A / dm ² , the generation of hydrogen gas increases, and electrodeposition is not performed, which is not preferable. The electrolysis temperature is 10 to 75 °.
It is desirable to perform electrolysis while adjusting to C. Electrolysis temperature 10 °
If it is less than C, the current efficiency decreases, which is not preferable. Conversely, when the electrolysis temperature exceeds 75 ° C, the evaporation of the electrolyte increases,
It is not preferable because the indium concentration in the electrolytic solution fluctuates. A more preferred electrolysis temperature is 25 to 50 ° C. Under the above electrolysis conditions, indium can be efficiently recovered.

[0011]

Next, an embodiment will be described. It should be noted that the present embodiment is merely an example of the present invention, and the present invention is not limited to these embodiments. That is, it includes other aspects and modifications included in the technical idea of the present invention. IXO scrap such as abrasive powder generated during the production of the IXO sputtering target was pulverized to obtain a raw material powder. This raw material powder contained 73.6% by weight of indium and 8.6% by weight of zinc. Next, 9.7 g of carbon powder was added to and mixed with 100 g of the raw material powder, and the mixture was placed in a reduction furnace (crucible) and reduced by heating at 1250 ° C. for 20 hours in a nitrogen atmosphere. After reduction, the crude indium was dissolved with nitric acid for quantitative analysis, and then filtered to separate the indium solution. As a result of analyzing the filtrate (1000 ml), the indium content in the filtrate was 65.2 g / L, and the zinc content was 10 mg.
/ L or less. The recovery of indium was 88.6%. As a result of the reduction, there is almost no zinc as described above,
It is considered to have evaporated. It is also considered that some indium was evaporated, but the amount was small. This resulted in efficient removal of zinc. FIG. 1 shows an outline of a process for purifying crude indium from IXO scrap by a dry method.

Next, the crude indium subjected to the carbon reduction treatment is electrolytically purified. This material contains Fe as an impurity.
It contained 19 ppm. Using this sample, the electrolytic solution and conditions were adjusted to an indium concentration of 56.2 g / L and a pH of 1.8 to
2.0, current density 0.7 A / dm ² , liquid temperature 35-40 °
C, amount of chloride ion 24-30g / L, glue 3-4mg
/ L and the gap between the electrodes were adjusted to 40 to 60 mm to perform electrolysis. As a result, high-purity indium having a purity of 99.99% was obtained.

[0013]

The present invention relates to an IXO (indium oxide-zinc oxide composite oxide) sputtering target scrap or IX used for forming a transparent conductive film or the like.
IXO scraps such as abrasive powder generated during the production of O sputtering targets are heated and reduced using carbon powder to efficiently remove zinc and further electrolytically purify the zinc to efficiently recover high-purity indium. It has an excellent effect of being able to.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a step of purifying crude indium from IXO scrap by a dry method.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22B 5/16 B09B 3/00 ZAB 7/00 304J C25C 1/22 5/00 CF Term (Reference) 4D004 AA21 AB03 BA05 CA04 CA15 CA24 CA35 CA36 CA41 CA44 CB04 CC11 DA03 DA06 4K001 AA15 AA30 BA22 CA01 DA05 DA06 HA01 4K058 AA11 AA23 BA07 BB03 CA05 CA08 CA09 CA12 CA17 CA22 EB02 EB16 FA22

Claims (4)

[Claims] 1. A method for recovering indium from an IXO scrap such as an IXO sputtering target or a polishing powder, comprising the steps of: pulverizing the IXO scrap and mixing it with carbon powder; A method for recovering indium, comprising: a step of discharging zinc as vapor out of the system; and a step of electrolytically refining the obtained crude indium. 2. The method for recovering indium according to claim 1, wherein the reduction is performed at 800 to 1300 ° C. 3. The method for recovering indium according to claim 1, wherein 15 to 30% of carbon powder is mixed. 4. The method for recovering indium according to claim 1, wherein the reduction is performed in a nitrogen atmosphere.