JP4706268B2 - ITO granulated powder, ITO sintered body and method for producing the same - Google Patents

Description

  The present invention relates to an ITO granulated powder and an ITO sintered body used for producing a high-density ITO target used for obtaining an ITO transparent conductive film such as a liquid crystal display, and a method for producing them.

  ITO (Indium Tin Oxide) thin film has characteristics such as high conductivity and high transmittance, and since it can be easily processed finely, such as display electrodes for flat panel displays, window materials for solar cells, antistatic films, etc. It is used in a wide range of fields. In particular, in the flat panel display field such as a liquid crystal display device, in recent years, the size and resolution have been increased, and the demand for an ITO thin film serving as a display electrode is also rapidly increasing.

  Such ITO thin film production methods can be broadly divided into chemical film formation methods such as spray pyrolysis and CVD, and physical film formation methods such as electron beam evaporation and sputtering. Among these, the sputtering method is used in various fields because it is a film forming method that can easily increase the area of a thin film and obtain a high-performance film.

  It is well known that in the sputtering method, nodules are generated on the surface of the target as the sputtering proceeds, and a uniform film cannot be stably obtained due to sparks or the like caused by the nodules. As a means for solving this problem, a high-density target is often used. The high-density target here refers to a target having a relative density of 98% or more.

The relative density is a numerical value calculated by dividing the actual density by the true density of the substance. Taking ITO as an example, the true density of ITO is 7.156 g / cm ³ . For example, the relative density of 98% corresponds to 7.013 g / cm ³ in the case of ITO.

  Generally, the granulated powder used for the ITO target is often produced by the following method.

  One is a method of obtaining a granulated powder by mixing an indium oxide powder, a tin oxide powder, water and a binder, preparing a slurry, supplying the obtained slurry to a spray dryer apparatus and spray drying (for example, Patent Document 1).

  In another method, indium oxide powder and tin oxide powder are mixed and stirred and granulated while adding water or a binder (see, for example, Patent Document 2).

  Using these granulated powders, for example, a molded body is produced by a press method or the like, and a sintered body is obtained by sintering the obtained molded body, and shaping, polishing, etc. are performed as necessary. Accordingly, the target is manufactured by sticking to a backing plate made of, for example, oxygen-free copper.

  In the case of the spray drying method, the steps include a step of slurrying indium oxide and tin oxide raw material powder before granulation in a state where an organic binder and water are added, and a step of drying the slurry by a spray drying method. In this production method, there are two steps, and there are many fluctuation factors in granulation, such as the conditions for slurrying and the drying conditions in spray drying, making the process control difficult and cumbersome. As for the yield, there are fine particles that cannot be collected and powder wall adhering to the apparatus. The yield is as low as 80 to 85%, and the economical efficiency of the production is poor due to the concept of man-hours and yield.

  In the case of the stirring granulation method, the steps include a step of mixing and granulating indium oxide and tin oxide while adding water or a binder, and a step of drying the granulated powder. In the case of this production method, in the agitation granulation step, the fine particles fly up and the yield is about 70% due to the powder adhering to the granulator during granulation, resulting in an increase in production cost in target production. And when adding water, a big difference is produced in the granulation characteristics depending on the slurry concentration and the amount of water added, and it is difficult to always produce uniform granulated particles. Therefore, the economy of manufacture is bad from the concept of man-hours and yield.

In addition, when using a powder in which indium oxide and tin oxide powder are intimately mixed and not granulated, the density of the sintered body is as high as 99% or more in relative density, but the light bulk density is 1.3 g / About ³ cm ³ , which is lower than the light dry bulk density of spray dry granulation 1.6 g / cm ^3, and the fluidity of the powder is 40 degrees or more as the angle of repose, and the fluidity is poor. Moreover, when performing a press operation, since fluidity | liquidity is bad and lightly loaded bulk density is low, uniform filling of powder becomes difficult. Furthermore, since the light bulk density is low, the amount of shrinkage at the time of pressure molding is larger than when granulated powder is used, and cracks are likely to occur during molding or sintering.

JP 2004-277836 A JP-A-4-293707

  The object of the present invention is a conventional powder granulation method of a sintered body for a target, which is more economical than spray-dry granulation and stirring granulation, and has a light bulk density and fluidity compared to a compacted mixed powder. To improve the efficiency at the time of pressure molding by improving the powder, and to obtain a powder that can maintain or improve the sintered body density of the sintered compact for the target compared to the compacted mixed powder, the powder It is to stably obtain a high-density sintered body by using and to establish a production method thereof.

  As a result of intensive investigations on the improvement of sinterability, light bulk density and fluidity, the present inventors have conducted granulation by rolling granulation, which is simpler and less process than spray-dry granulation. It is possible to improve the light bulk density and fluidity of the powder in comparison with the compacted mixed powder, and further to improve the sintered body density in the same manner as when the compacted mixed powder is used or without further aggregation. I found.

  That is, the method for producing ITO granulated powder of the present invention is a method for producing ITO granulated powder, characterized in that raw material powder containing indium oxide and tin oxide is granulated by rolling granulation. The raw material powder containing indium oxide and tin oxide may contain water or a binder, but the binder content in the raw material powder is preferably 5 wt% or less, and the water content in the raw material powder is 5 wt%. The following is preferable.

  The ITO granulated powder of the present invention is an ITO granulated powder produced by the above production method. Furthermore, the manufacturing method of the ITO sintered body of the present invention is a manufacturing method of an ITO sintered body characterized in that the ITO granulated powder is sintered after being pressure-molded, and the ITO sintered body of the present invention is sintered. The body is an ITO sintered body manufactured by the above manufacturing method.

  In addition, the raw material powder containing indium oxide and tin oxide in the present invention may be a mixed powder of indium oxide powder and tin oxide powder, indium oxide and tin oxide, as long as it can be granulated by rolling granulation. Co-precipitated powder, raw powder or re-pulverized powder after sintering, etc. can be used, and if necessary, a metal element compound other than indium and tin is added. May be. The content ratio of indium oxide and tin oxide may be appropriately determined according to required characteristics. For example, the weight ratio of indium oxide powder and tin oxide powder is about 95: 5 to 80:20. Can do.

  Furthermore, in the production method of the ITO granulated powder of the present invention, before rolling rolling granulation, the raw powder is subjected to consolidation treatment or consolidation by ball mill or the like to increase the light bulk density. It is preferable to keep it. In addition, by removing the coarse components from the raw material powder, or the powder that has been subjected to consolidation treatment or consolidation, the fluidity and yield of the resulting granulated powder can be improved. It is preferable to adjust the particle size distribution. The adjustment of the particle size distribution can be performed, for example, by sieving with a sieve. As the sieve, a 500 μm sieve is preferable, and a 300 μm sieve is more preferable.

  Further, in order to facilitate granulation, this raw material powder may contain a binder made of water, organic matter, or the like, but the content of water or binder in the raw material powder is preferably 5 wt% or less. In particular, it is preferable that the raw material powder containing indium oxide and tin oxide does not contain a binder made of an organic substance other than water and the water content is 5 wt% or less.

  By the ITO granulated powder production method of the present invention, an ITO granulated powder having an average particle size of 50 μm to 300 μm with good fluidity and a large light bulk density is obtained without impairing the sinterability of the raw material powder. The yield can be obtained. In addition, in the manufacturing method of ITO granulated powder of this invention, the fluctuation | variation of the light-packed bulk density resulting from the fluctuation | variation of raw material powder etc. can also be suppressed.

  Hereinafter, the present invention will be described in detail.

  The present invention uses a rolling granulation method, is a more economical process than spray-dry granulation and agitation granulation, and is compacted by improving light bulk density and fluidity compared to compacted mixed powder. In addition to improving the efficiency of the time, the sintered compact density of the target sintered compact is compared with the compacted mixed powder, and the powder that maintains or improves the density, and the sintered compact sintered using the powder, and their production A method is provided.

  In normal rolling granulation, after filling powder in a drum or bread container, add 5% or more of moisture or binder, and rotate the container itself, moisture, binder cohesive force, powder self-weight and adhesion force This is a technology for granulating powder. However, in this granulation method, the granulated particles are increased to 1 mm or more, and the raw material powder is agglomerated by the cohesive force of water or the binder, so that the sinterability of the powder is lowered. Further, when molding and sintering with this powder, it is difficult to adjust the amount of water added during granulation, and it is difficult to always prepare an equivalent powder with respect to molding and sintering properties. In addition, a drying step is required before molding, and a degreasing step is required at the time of sintering, which increases the number of steps and complexity, and makes process management difficult.

  Therefore, in the granulation method of the present invention, by performing rolling granulation without adding excessive moisture and binder, the powder is granulated by making the powder's own weight and adhesive force a basic granulation action. ing. That is, the granulation method of the present invention is to granulate by filling powder in a container and rotating the container. The number of steps is only one step for granulation. Furthermore, this process is also a simple granulation method, and since it is a simple granulation mechanism, process management is further simple. And in this granulation method, since the powder is only flowed, the yield of the granulated powder is 90% or higher, which is higher than other granulation methods. Therefore, it is superior to other granulation methods in view of economy and workability.

  The granulation mechanism of this manufacturing method allows the powder to flow by using the rotational force, so that the powder surface is first smoothed by the weight of the powder, thereby regulating the size. Further, it is considered that granulation is caused by causing powder particles to lightly agglomerate and grow due to collision between powders by further flowing the powder.

  By using this method, it is possible to suppress the aggregation of powder because the amount of water added is small, and since the aggregation of powder is suppressed, the density of the sintered body due to the powder aggregation during granulation is reduced. There is no decline. Furthermore, by adjusting the degree of granulation, improving the fluidity while weakening the agglomeration of the granules allows the powder to flow at the time of molding. The pores at the micron level at the time of molding due to the absence of the powder can be reduced, and the density of the sintered body can be improved as compared with the sintered body of the compacted mixed powder.

  With respect to the manufacturing process, this manufacturing method is based on the concept of granulating that the powder flows and adheres by its own weight, so that it can be performed with a simple granulator. That is, regarding this granulation, the powder is put into a granulator and granulation is performed only by the process of promoting powder flow by its own weight due to rotation or the like. In addition, since no moisture is added excessively, no drying process is required and no degreasing process is required. In addition, since the yield is not particularly applied to the powder, the powder hardly adheres to the outer wall, resulting in a high yield of 90% or more.

  Although it is a raw material powder before granulation, it is not particularly limited, but in this rolling granulation, the ability to stir and mix is low, so it is desirable that each substance is uniformly mixed. Examples of the powder include a powder that is compacted and mixed, or a powder obtained by sintering a raw material powder after sintering or molding and sintering. This is because the rolling granulation method is granulated by adhesion force and its own weight, and the state after granulation is determined to some extent by the initial powder state. In the case of using the compacted powder, the powder is compressed by the compaction and the powder surface is activated so that the powder is more easily granulated.

  Moreover, although it is the particle diameter of raw material powder, since it granulates by self-weight and adhesive force, the larger particle | grains are granulated more aggregated particle | grains. In other words, if there are too many large particles (for example, 1 mm or more), the cohesive force of the powder increases, and there is a possibility that the particles become hard granulated particles. In addition, when there are many large particles, adhesion to the container wall increases due to the weight of the particles, and the yield of the granulated powder decreases. Therefore, it is desirable to control the powder particle size of the raw material powder before granulation. The method for controlling the particle size of the powder is not particularly limited, but as means for adjusting the particle size, methods such as sieving and controlling the particle size of the powder during raw material synthesis are conceivable. As another method, it is possible to adjust the particle size of a granulated powder without adjusting the particle size before granulation. However, in this case, the sieved large particles may have strong aggregation as described above, and it is difficult to reuse the granulated particles. In addition, since larger particles are likely to produce larger granulated particles, the yield of the sieve is lowered when it is sieved after granulation than when it is sieved before granulation. Therefore, there is also an aspect of making it easy to reuse the sieved particles by passing the powder before aggregation through a sieve. Specifically, it is preferable to adjust the average particle diameter of the raw material powder to 50 to 200 μm. Moreover, the yield can be improved from 90% without adjusting the particle size to 95% or more simply by removing coarse particles of 500 μm or more with a sieve, and it is also effective in improving sinterability. is there.

  The shape of the granulating apparatus is not particularly limited as long as it is an apparatus capable of rolling granulation. For example, it may be granulated by rotating a plastic container or the like on a rotating mount. If possible, it is preferable to mix relics in the container and the powder does not rise, and considering the amount of granulation, granulation using a sealed container is desirable, and it is desirable to use a drum-type rolling granulator. The drum-type rolling granulator mentioned here is an apparatus for granulating by rotating powder in a container by rotating a sealed cylindrical container in the circumferential direction. However, it does not matter if the device rotates in any direction.

  In the granulation method, the amount is small in the granulation container, but since the powder adheres, the yield is reduced and the fragments of the powder adhering to the wall may be mixed, which may hinder fluidity and sinterability. . As a countermeasure against this, it is desirable that there is a mechanism for giving an impact to the granulation container from the outside. A mechanism that gives impact to the container is installed, and by applying impact or vibration to the container, the powder adhering to the outer periphery of the container is peeled off at an early stage to promote granulation and increase the yield.

  The material of the container to be granulated is not particularly limited, but it is intended to prevent contamination from the container, and it is desirable to use a material that does not easily adhere powder to the wall of the container during granulation.

  The actual rolling granulation conditions include the capacity of the container, the amount of powder input, the rotational speed of the container, and the rolling granulation time.

  Although there is no particular limitation on the amount charged into the container, if the amount is too small, the amount is small and the amount of container adhering to the amount is increased and the yield of the granulated powder is lowered. In addition, if the input amount is too large, granulated powder having strong cohesiveness is prepared due to poor powder flow and the self-weight of the powder.

  When the container rotates at a very high speed, for example, at a peripheral speed of 1.5 m / s or more, the aggregation of the powder becomes strong and the density of the sintered body obtained by sintering decreases.

  The amount of water or binder added to the raw material powder is preferably as small as possible. If a large amount of moisture is added, for example, if it is added in an amount of more than 5 wt%, the degree of aggregation of the granulated particles increases, and the particle size of the granulated particles also increases. The density of the aggregate also tends to be lower than before granulation. Therefore, it is not suitable as a powder for forming and sintering. In addition, adding a large amount of water and binder requires a drying step before molding, which complicates work. When the moisture content is smaller, granulated particles do not grow and agglomerate loosely, so that improvement of light bulk density and fluidity is desired.

The rolling granulation time has a high light bulk density and fluidity compared to before the granulation from a very short time. For example, in the case of a compacted mixed powder, the light loading bulk density may be improved for a certain period of time or more, for example, 60 hours or more, and the light loading bulk density and fluidity may be improved, but the sintering characteristics may gradually deteriorate. is there. This is because granulation for a long time increases the aggregation of the particles, which impairs the sinterability. For example, when a compacted mixed powder of ITO powder is granulated, the light bulk density is desirably about 1.4 to 2.0 g / cm ³ . When the lightly loaded bulk density is less than 1.4 g / cm ³ , granulation is hardly performed and the fluidity is not improved, so that the granulation effect cannot be expected. Further, when the light bulk density is 2.0 g / cm ³ or more, the aggregation of particles is large and the density of the sintered body is lowered. Regarding the fluidity, when the angle of repose exceeds 40 °, the effect of granulation is thin, and the effect of moldability and workability does not appear. Therefore, the angle of repose is preferably 40 ° or less.

  In molding, pressure molding is generally well known. However, in pressure molding, it is desirable that the light-packed bulk density is high because it is suitable for pressure molding as the compression distance is shorter. Moreover, when producing a plate-shaped molded body, it is necessary to reduce unevenness due to powder filling as much as possible. If the powder filling is uneven, problems such as cracks in the molded body or unevenness in the thickness after sintering occur.

  Since the granulated powder of the present invention has a high light bulk density and fluidity compared to a compacted mixed powder, the compression distance is shortened during pressurization, so that cracks are less likely to occur when a thick molded body of 15 mm or more is produced. . Furthermore, since the fluidity is high, the powder can be uniformly filled, and the productivity and economy can be further improved by preventing cracks in the molded body and reducing the thickness unevenness in the sintered body.

  As mentioned above, various desirable conditions in rolling granulation were mentioned, but since these are independent factors, ITO granulated powder further improved by combining each condition, that is, granulated powder for ITO target sintered body It is possible to manufacture.

  Although it is a shaping | molding method of granulated powder, it is not limited to a shaping | molding method in particular, It is desirable to shape | mold the produced powder as it is from the place where the powder was granulated. Furthermore, it is desirable to fill a mold or the like and press-mold. By using pressure molding, the effect of more granulated powder appears. The pressure molding referred to here is a method in which powder is filled into a mold, a container, and the like, and the mold, the container, etc. are uniaxially or isotropically pressed to form a fixed shape.

  The sintering method is not particularly limited, however, it is desirable that the temperature raising program and the sintering temperature be performed under the condition that the compacted mixed powder is sintered at a high density. The gas atmosphere at the time of sintering is not particularly limited, but in order to sinter at higher density, it is desirable to carry out in an oxygen atmosphere.

The ITO granulated powder of the present invention, that is, the granulated powder for a transparent conductive film target, and the production method thereof have the following effects.
1) The method of the present invention can obtain an ITO granulated powder and an ITO sintered body with improved light bulk density and fluidity by a simpler manufacturing process that is less than other granulation methods.
2) The ITO granulated powder produced by the granulation method of the present invention has improved light bulk density and fluidity, and can produce a higher density ITO sintered body with good stability.
3) The method of the present invention can provide ITO granulated powder with improved moldability as compared with powders produced by other granulation methods.
4) The ITO granulated powder produced by the granulation method of the present invention has an improved powder uniform filling property, and can improve workability during pressure molding.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited only to these Examples.

Example 1
After indium oxide powder and tin oxide powder are put into a cylindrical container at a weight ratio of 90:10, an appropriate amount of pulverized balls are put and rotated to perform compaction, mixing, and dispersion treatment of indium oxide powder and tin oxide powder. went. The powdered bulk density and angle of repose of the powder after the consolidation process (hereinafter, this powder is referred to as a compacted mixed powder) were determined. The bulked bulk density was 1.3 g / cm ³ and the angle of repose was 41 degrees. .

The mixed powder (consolidated mixed powder) subjected to this compaction was sieved with a 500 μm sieve mesh to produce a powder excluding particles of 500 μm or more. This powder was put into the cylindrical container again, and rolling granulation was performed by rotating the cylindrical container for 2 hours at a peripheral speed of 0.5 m / s on a rotating base. When the light-packed bulk density and repose angle of the obtained ITO granulated powder were determined, the light-packed bulk density was 1.70 g / cm ³ and the repose angle was improved to 36 degrees. Moreover, the average particle diameter of the obtained ITO granulated powder was 150 μm. Furthermore, the weight of the obtained ITO granulated powder was 98% of the compacted mixed powder used as a raw material.

The obtained ITO granulated powder was press-molded at 300 kgf / cm ² to obtain three types of molded bodies having a size of 60 mm square, a thickness of about 13 mm, about 18 mm, and about 23 mm. The molded body was subjected to CIP treatment at 3 t / cm ² , and the produced molded body was baked at 1600 ° C. in an oxygen atmosphere in an atmosphere furnace to obtain an ITO sintered body. The thickness of the obtained ITO sintered body was about 10 mm, about 15 mm and about 19 mm, and a good sintered body was obtained with no particular cracks. The relative density of each sintered body was 99.81% when the thickness was 10 mm, 99.75% when the thickness was 15 mm, and 99.58% when the thickness was 19 mm.

Comparative Example 1
An ITO sintered body was obtained from the compacted mixed powder produced by the same method as in Example 1 by the same molding and sintering method. The thickness of the obtained ITO sintered body was about 10 mm, about 15 mm, and about 19 mm. The sintered body having a thickness of 19 mm was cracked during sintering. The relative density of each sintered body was 99.82% when the thickness was 10 mm, and 99.72% when the thickness was 15 mm.

  When the thickness was 15 mm or less, the density of the obtained ITO sintered body was the same as or slightly lower than that of Example 1, but when the thickness was 19 mm, cracks occurred during sintering. The powder was insufficient as a powder for producing the ITO sintered body.

Comparative Example 2
The compacted mixed powder prepared in the same manner as in Example 1 and water were charged into a stirring granulator (manufactured by Nara Machinery) at a weight ratio of 100: 20, and stirring granulation was performed for 30 minutes. After the granulation, drying was performed overnight, and the light weight bulk density and angle of repose of the obtained ITO granulated powder were determined. The light weight bulk density was improved to 2.29 g / cm ³ and the angle of repose was improved to 34 degrees. It was. Moreover, the weight of the obtained ITO granulated powder was 70% of the compacted mixed powder used as a raw material.

The obtained ITO granulated powder was press-molded at 300 kgf / cm ² to obtain two types of molded bodies having a size of 30 mm square, a thickness of about 9.5 mm, a size of 60 mm square, a thickness of about 18 mm, and about 23 mm. . The molded body was subjected to CIP treatment at 3 t / cm ² , and the produced molded body was baked at 1600 ° C. in an oxygen atmosphere in an atmosphere furnace to obtain an ITO sintered body. The thickness of the obtained ITO sintered body was about 9 mm, about 15 mm, and about 19 mm, but the 19 mm sintered body was cracked during sintering. The density of the sintered body having a thickness of 9 mm was 99.40% in terms of relative density, and 98.71% in the case of having a thickness of 15 mm. Thus, the sintered body density was lower than that of the ITO sintered body of Example 1. The thicker the sintered body, the lower the density of the sintered body, and the lower the density of the 9 mm and 15 mm sintered bodies, the lower the density is expected in the case of 19 mm thickness.

  In this granulation method, by adding water, the primary particles of the submicron level of the raw material powder are agglomerated, and as a result, the density of the sintered body obtained by sintering this granulated powder is equal to that of the compacted mixed powder. It is presumed that it has decreased compared to the case of concluding.

Comparative Example 3
Water was added to the compacted mixed powder produced by the same method as in Example 1 to form a slurry, and then granulated by spray dry granulation. When the light-packed bulk density and repose angle of the obtained ITO granulated powder were determined, the light-packed bulk density was 1.55 g / cm ³ and the repose angle was improved to 29 degrees. Moreover, the weight of the obtained ITO granulated powder was 80% of the compacted mixed powder used as a raw material.

The obtained ITO granulated powder was subjected to press molding of 300 kgf / cm ² to obtain molded bodies of 60 mm square, thickness of about 15 mm and about 20 mm. The molded body was subjected to CIP treatment at 3 t / cm ² , and the produced molded body was baked at 1600 ° C. in an oxygen atmosphere in an atmosphere furnace to obtain an ITO sintered body. The thickness of the obtained ITO sintered body was about 13 mm and about 17 mm, but the 17 mm sintered body was cracked during sintering. The density of the sintered body having a thickness of 13 mm was 99.66% as a relative density, which was lower than that of the ITO sintered body of Example 1. The thicker the sintered body, the lower the density of the sintered body, and the lower the density of the 13 mm-thick sintered body, the lower the density expected at 19 mm.

  In this granulation method, by adding moisture, the primary particles at the submicron level of the raw material powder are agglomerated, and as a result, the density of the sintered body of the granulated powder is lower than when the compacted mixed powder is sintered. I guess it was.

  Light weight bulk density and angle of repose of ITO granulated powder of Example 1 and Comparative Examples 1 to 3, yield, and sintered body density of ITO sintered body obtained using those ITO granulated powder, Table 1 shows the presence or absence of cracks during production. Moreover, the thickness dependence of the sintered compact density of the ITO sintered compact obtained above is shown in FIG.

  In the production method of the ITO granulated powder of the present invention, the yield is high, and by using the ITO granulated powder of the present invention, a high-density ITO sintered body can be produced without generating cracks during sintering. It turns out that it becomes possible to manufacture stably.

It is a figure which shows the comparison of the sinterability by various granulation methods.

Claims (2)

The content of water or binder in the raw material powder containing indium oxide and tin oxide is 5 wt% or less, the raw material powder is granulated by rolling granulation, and the light bulk density is 1.4 g / cm ³ or more 2 A method for producing an ITO granulated powder, comprising producing an ITO granulated powder having an angle of repose of less than 0.0 g / cm ³ and an angle of repose of 40 ° or less . The content of water or binder in the raw material powder containing indium oxide and tin oxide is 5 wt% or less, the raw material powder is granulated by rolling granulation, and the light bulk density is 1.4 g / cm ³ or more 2 A method for producing an ITO sintered body comprising producing an ITO granulated powder having an angle of repose of less than 0.0 g / cm ³ and an angle of repose of 40 ° or less, and pressurizing and molding the obtained ITO granulated powder. .

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