JPH03215318A - Oxide powder and its production - Google Patents

Abstract

PURPOSE:To make it possible to produce a sintered material having high density by specifying primary granular diameter, BET surface area and specific surface area ratio of indium oxide and indium oxide-tin oxide powder as raw material of the sintered material. CONSTITUTION:Powder of indium oxide and/or indium oxide-tin oxide having high dispersibility thoroughly satisfying the conditions of <=1mu primary granular diameter, >=15m<2>/g BET surface area and >=2m<2>/g specific surface area calcu lated from a granular size distribution is used as raw material of the objective sintered material. By said method, a sintered material inducing a large sintering shrinkage, namely having density of >=75% of theoretical density is obtained. Such a high density ITO-sintered material is used as a target to obtain a trans parent electroconductive film having extremely high quality. The above- mentioned powder is obtained by producing ITO powder having <=1mu primary granular diameter and mechanically crushing using a vibrating crusher having a crushing vessel diameter of <=10 times of vibrating amplitude.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to indium oxide powder, indium oxide/tin oxide (hereinafter referred to as !To'') powder, and a method for producing the same.

[Conventional Technology] In recent years, demand for ITO thin films has rapidly increased as transparent conductive films used in solar cells, transparent electrodes of liquid crystal displays, touch panels, and the like. Methods for forming such an ITO thin film include applying ITO fine particles to a base material, applying an ITO precursor to a base material and then thermally decomposing it, or sputtering an IT alloy target or JT') sintered target. Although methods of forming an ITO film on the surface of a base material are known, currently the most common method is sputtering an ITO sintered body.

The indium oxide and ITO powder according to the present invention can be used as a sputtering target (ITO sintered body) used when creating a transparent conductive film by such sputtering method.
It has extremely excellent performance as a raw material.

Conventionally, indium oxide, tin oxide powder or ITO powder is
A method of heating dehydration or thermal decomposition of each metal hydroxide, oxide hydrate, organic metal salt, or inorganic metal salt powder, or each sol or gel, or a method of heating and decomposing the powder of each metal hydroxide, oxide hydrate, organic metal salt, or inorganic metal salt, or adding a precipitant to a mixed aqueous solution of indium salt and tin salt. to form a precipitate (JP-A-62-7627, JP-A-80-188418),
Or produced by hydrolysis (Japanese Patent Application Laid-Open No. 58-38925)
Methods are known for thermally decomposing L-products. Furthermore, the method of thermally decomposing a mixed organic acid salt obtained from a mixed organic acid aqueous solution of indium and tin (Japanese Unexamined Patent Publication No. 83-195101), which was previously proposed by the present inventors, is also a method for providing high-purity ITO powder. be.

Normally, ITO sintered bodies are manufactured by press-molding CITO powder, a mixed powder of indium oxide and tin oxide obtained by the above method, and then sintering it, but ITO powder has a high density because it is difficult to sinter. It was very difficult to obtain a sintered body. Most of the conventional ITO sintered bodies using powder are low-density sintered bodies with a sintered density of about 65% of the theoretical density (~4.6 g/cm<3>), and also have high electrical resistance.

The sintered density of the JTO sintered body is approximately 7 at 100% theoretical density.
．． 1g/Cm3.

Such a low-density ITO sintered body is easy to break, and has low electrical and thermal conductivity, so when sputtering film formation is performed using it as a target, the amount of power that can be input is significantly reduced, making it difficult to form a film. The drawbacks were that the speed was slow and the discharge state was unstable. Even lower density IT
In O sintered bodies, reducing substances (black substances) are generated on the surface of the sintered body during sputtering, and this substance mixes with the transparent conductive film formed on the surface of the base material and causes a decrease in the quality of the film. Every time a chemical substance was produced, the operation had to be stopped and removed. This has been a significant obstacle in continuous sputtering operation.

Therefore, in order to solve such problems, high-density IT
Several methods have been proposed for producing or processing raw material ITO powder that makes it possible to produce an O sintered body. For example, among indium oxide or tin oxide powder, there is a method in which at least indium oxide powder is calcined to produce indium oxide or tin oxide with an average particle size of 3 to 6 μm (Japanese Patent Application Laid-Open No.
2-21751).

However, the density of the ITO sintered body obtained from such a raw material having a relatively large particle size is at most 5 g/cm1, which cannot be called a sufficiently high density, as can be seen from the examples described in the publication. In addition, a method has been proposed in which coprecipitated JTO powder using a precipitant is used as a raw material for a sintered body (Japanese Patent Application Laid-Open No. 1983-1999-
12009). However, the sintered density of the sintered body obtained by this method is about 70% (5 g/cm') of the theoretical density, which cannot be said to be sufficiently high density.

[Problems to be Solved by the Invention] As explained above, the current situation is that no indium oxide powder or JTO powder capable of producing a high-density sintered body has been obtained by an industrial method. The object of the present invention is to achieve a density of 75% or more of the theoretical density, that is, 5-3g1
The object of the present invention is to provide an indium oxide powder or an ITO powder capable of producing a high-density ITO sintered body having a density of cm' or more, more preferably 85% or more of the theoretical density, that is, 6glcII13 or more, and a method for manufacturing the same.

[Means for Solving the Problems] As a result of extensive research into the raw material fTO powder for manufacturing high-density ITO sintered bodies, the inventors have found that the primary particle size is fine with a diameter of 1 μm or less, and the BET surface area is small. 15In”/g
As mentioned above, highly dispersible ITO powder with a specific surface area of 2+a2/g or more determined from the particle size distribution has a sintered density of 75% or more of the theoretical density, that is, a sintered density of 5.3 g/cm3 or more, and even more. 85% or more of the theoretical density, i.e. 8g/
A high-density sintered body of cm3 or more can be obtained, and such powder can be produced by vibrating ITO powder with a primary particle size of 1 μm or less, which satisfies the condition that the diameter of the crushing container is less than 10 times the vibration amplitude. They have discovered that it can be obtained by pulverizing using a vessel, and have completed the present invention.

In the case of ITO powder in the powder of the present invention, the ratio of indium oxide to tin oxide in the powder is indium oxide/tin oxide -98:2 to 80:20 by weight, particularly 92:8 to 8.
A range of 5:15 is preferred. If the content of tin oxide is less than 2% or more than 20%, a sintered body using the tin oxide will not have high conductivity. The primary particle size of the indium oxide powder or ITO powder of the present invention must be at least 1 μm or less, especially 0.0 μm or less.
Preferably, the thickness is in the range of 5 μι to 0.03 μι. If the primary particle size is 0.5μ1 or more, the sinterability does not improve much even if the dispersibility is high; Below the OSμ layer, it is extremely difficult to suppress agglomeration and it is difficult to obtain a powder with good sinterability.

Although powders satisfying the above primary particle size can be obtained using conventional techniques, they are agglomerated and do not have good sinterability. The indium oxide powder and ITO powder of the present invention have such a primary particle size and are characterized by being highly dispersed, that is, not agglomerated. Common means for evaluating the dispersibility of powders include BET surface area and particle size distribution, but the powder of the present invention has a specific surface area of 15 m2/g or more calculated from BET surface area, and a ratio calculated from particle size distribution. The surface area is 2IIl2/g or more, more preferably 3IIl2/g or more. BET surface area is 15
Powder of less than m2/g is agglomerated powder and has poor sinterability. On the other hand, a powder with too large a BET surface area is porous or has a rough surface, which results in poor sinterability, so the BET surface area is preferably 50 s2/g or less.

Until now, no ITO powder has been proposed that satisfies all of the above conditions, and even if any of these conditions is not met, the sinterability of the powder is insufficient.

As a method for producing ITO powder that satisfies all of the above conditions, the present invention uses IT powder with a primary particle size of 1 μm or less.
A method is proposed in which O powder is mechanically crushed after it is produced. Mechanical pulverization is generally known as a method for improving the sinterability of ceramic powders, but especially in the case of indium oxide and ITO powders, no pulverization method improves the sinterability.

Mechanical methods for pulverizing oxide powder generally include ball mills, dyno mills, sand mills, homogenizers, vibration mills, etc., but methods for pulverizing powder that can achieve the effects of the present invention include pulverizers with high pulverization efficiency, For example, it is necessary to pulverize using a vibrating mill or the like. A product that satisfies the conditions of the present invention cannot be obtained using a product with low pulverization efficiency, such as a rotary ball mill.

The most important point in pulverization using a vibratory pulverizer in the present invention is to use a pulverizer whose diameter is less than lθ times the vibration amplitude of the vibratory pulverizer. When the diameter of the crushing vessel is larger than lO times the amplitude of the vibratory crusher,
Not only is the movement of the grinding media inside the grinding container irregular, but most of the grinding media even undergoes small vibrations or sliding movements at the bottom of the grinding container during grinding, which significantly reduces the grinding efficiency. This phenomenon is particularly noticeable when the grinding medium is small, for example, when a grinding medium with a diameter of about 21 mm is used for fine grinding. Furthermore, if the powder is pulverized in such a state, the amorphization of the powder, that is, the destruction of the crystals will proceed more selectively than the dispersion, so that the pulverization process will actually reduce the sinterability of the powder.

On the other hand, when the crushing process is performed using a crushing container whose diameter is less than 10 times the vibration amplitude of the vibration crusher, the movement of the crushing media inside the crushing container is extremely uniform, and the agglomerates of the powder can be broken up efficiently. It will be resolved in In addition, in this kind of crushing process,
Crystal destruction of the powder due to crushing is also suppressed. In addition, such efficient grinding significantly reduces wear of the grinding media, making it possible to maintain a high purity of the treated powder.

Further, the grinding medium used for grinding is important, and from the viewpoint of grinding efficiency, it is preferable to use one with a high specific gravity. In addition, since the contamination of impurities into the powder during the pulverization process causes a decrease in the conductivity of the JTO sintered body using the impurity, the pulverizing medium used in the present invention must have a high specific gravity and wear resistance. It is preferable to use an excellent one. Examples of excellent dispersion media with high specific gravity and excellent wear resistance include zirconia beads, hard carbon coated beads, and diamond coated beads. In particular, even if hard carbon-coated beads and diamond-coated beads are worn out, no problem occurs because impurity carbon is removed as carbon dioxide gas at the sintering temperature of ITO powder. On the other hand, with alumina beads and glass beads, impurities due to abrasion are a problem, and resin beads are too light to achieve a crushing effect. The size of the grinding media used in the present invention is 5 cm in diameter.
Hereinafter, it is particularly desirable to use a material with a diameter of 2 mm or less that can be pulverized. Furthermore, in order to improve the pulverization efficiency and the dispersibility of the powder, it is preferable to add a liquid to the powder to be pulverized to form a slurry. As the liquid to be added here, it is possible to use water or various organic solvents, but it is particularly preferable to use water in view of the abrasion resistance of the dispersion medium. Furthermore, it is also effective to add various dispersants to the slurry. The amount of water added to make the above slurry is determined from the viewpoint of pulverization efficiency when the viscosity of the slurry is 5 oepS.
It is preferable to add it in a range from 5000 cps to 5000 cps. If the viscosity of this slurry is higher or lower than that, the pulverization efficiency will decrease. The amount of water added to prepare such a slurry varies depending on the properties of the powder to be treated, such as particle size, and the grinding medium used for grinding, but is generally in the range of 80:20 to 10:90 of powder/water. . Further, the crushing time is about 1 hour to 100 hours, particularly preferably in the range of 5 hours to 3 hours.

By performing the above-mentioned pulverization process, the ITO powder becomes highly dispersed, and the ITO powder satisfies the conditions specified in the present invention.
TO powder is obtained. That is, the primary particle size is 1μ1 or less,
The BET surface area is 15 m2/g or more, and the specific surface area determined from the particle size distribution is 2IQ2/g or more.

[Effects of the invention] When such ITO powder is used as a raw material for a sintered body, the pores inside the sintered body are reduced during sintering, and the sintered body has a large sintering shrinkage, that is, 75% or more of the theoretical density (sintered body). Condensation density 54g/
cm3 or more), and in many cases it is possible to form a sintered body with a theoretical density of 85% or more (sintered density of 6 g/cImm or more). In sintered bodies obtained from conventional ITO powder, sintering progresses unevenly between the agglomerated and non-agglomerated parts of the JTO powder secondary particles, so the sintered particles are irregularly shaped, and the sintering process is uneven. Although there are many pores between the particles, it is thought that the sintered body made of the ITO powder of the present invention is sintered uniformly, resulting in the formation of densely packed sintered particles, resulting in high density. It will be done.

When such a high-density JTO sintered body is used as a target, the resulting transparent conductive film will also be of extremely high quality.
Extremely excellent performance can be expected as a sintered raw material powder for sputtering targets.

Furthermore, especially in the case of coprecipitated ITO, since the distribution of tin in the sintered body is uniform, a uniform transparent conductive film can be obtained over a wide range.

[Examples] The present invention will be described below based on Examples, but the present invention is not limited thereto.

Example 1 An acetic acid aqueous solution containing these at an indium/tin ratio of 90,710 was concentrated to obtain an indium/tin mixed acetate, and this acetate was thermally decomposed to prepare ITO powder. Water was added to this powder to make a 50% slurry, and the diameter was 2
Vibration mill using n+a+ hard carbon coated metal beads as a grinding medium (vibration amplitude 10I1 grinding container diameter 50mm)
) for 20 hours. The powder after the treatment has a primary particle size of about 0.3μ■ as observed by electron microscopy, and a BET surface area of 17IIl2lg1 and a specific surface area of 3.
5n2/g, satisfying all the conditions set forth in claim 1 of the present invention.

Pressure mold the powder with a metal mold; 3. /g/cm3, and then sintered at 1400"c in normal pressure atmosphere.

The temperature increase rate during sintering is 100"C/hour, 1400'
In C, the temperature was maintained for 10 hours and the temperature decrease rate was 10'' CI time.

Under these sintering conditions, the sintered density was 5. /g/ em'
, a sintered body with a specific resistance of 3 XIO-'Ω·cfll was obtained.

FIG. 1 shows a scanning electron micrograph (2000x magnification) showing the grain structure of the surface of the sintered body.

Example 2 Using the sintered body obtained in Example 1, film formation was performed by DC magnetron sputtering (conditions were input power =
(4v/cIIl2, pressure: 0.6 Pa (5xlO torr), substrate temperature: 350°C) As a result, as shown in Table 1, a transparent conductive film with extremely low resistance was obtained.

Example 3 Indium acetate and tin acetate were each thermally decomposed to prepare indium oxide and tin oxide, respectively, and then mixed so that the ratio of indium oxide to tin oxide was 90/10. Thereafter, a sintered body was prepared under the same conditions as in Example 1, and the sintered body had a sintered density of 5.
A sintered body with a specific resistance of 4 g/cm3 and a specific resistance of 9×10-'Ω·CI1 was obtained.

The primary particle size of the mixed powder observed under an electron microscope is 0.3.
The μm s BET surface area was ty ts2/gs The specific surface area determined from the particle size distribution was 3.51 Il2/g.

Example 4 Using the sintered body obtained in Example 3, film formation was performed by DC magnetron sputtering (under the same conditions as in Example 2). A transparent conductive film with low resistance was obtained.

Comparative Example 1 Commercially available indium oxide powder and tin oxide powder (reagent))9
After mixing at a ratio of 0:10, molding and sintering were performed under the same conditions as in Example 1, resulting in a sintered density of 4. /g/cm' A sintered body with a specific resistance of 2X 10-'Ω·crn was obtained.

The primary particle size of the mixed powder observed under an electron microscope is 0.0.
5 μm satisfies the conditions of the present invention, but the specific surface area determined from the particle size distribution is 2 m2/gSBET surface area is 8 m2/
It was g.

Comparative Example 2 Using the sintered body obtained in Comparative Example 1, film formation was performed by DC magnetron sputtering under the same conditions as in Example 2. Table 1 shows the specific resistance of the produced film. As shown in Table 1, a low-resistance transparent conductive film like the example was not obtained.

Table 1 Specific resistance (X 10-'Ω・cl) Example 22.1 Example 42.2 Comparative example 33.5

[Brief explanation of drawings]

FIG. 1 is a scanning electron micrograph (2000x magnification) used as a drawing showing the grain structure of the surface of the sintered body obtained in Example 1.

Claims (1)

[Claims] 1) Primary particle size is 1 μm or less, BET surface area is 15 m^2
/g or more, specific surface area determined from particle size distribution is 2m^2/g
An indium oxide and/or indium oxide/tin oxide powder that satisfies all of the above conditions. 2) The powder according to claim 1, wherein the indium oxide/tin oxide powder is prepared by a coprecipitation method. 3) Grind indium oxide/tin oxide powder or indium oxide powder with a primary particle size of 1 μm or less in a container with a diameter of 1 μm or less of vibration amplitude.
A method for pulverizing indium oxide or indium oxide/tin oxide powder, the method comprising mechanically pulverizing indium oxide or indium oxide/tin oxide powder using a vibration type pulverizer of less than 0 times.