TWI592383B - Indium oxide-based oxide sintering article and method for producing the same - Google Patents

Description

Indium oxide-based oxide sintered body and method of producing the same

The present invention relates to an indium oxide-based oxide sintered body and a method for producing the same. Further, the present invention relates to a sputtering target using the indium oxide-based oxide sintered body as a target.

Since the transparent conductive oxide film has high conductivity and high transmittance in the visible light region, a transparent electrode such as a solar cell, a liquid crystal display element, or various other light receiving elements can be used. Further, it is also possible to widely use a heat-reflecting film for an anti-fog such as a heat-ray reflecting film such as a window glass of an automobile or a building, various antistatic films, and a frozen display window.

The transparent conductive oxide film is mainly an oxide film of indium oxide (In ₂ O ₃ +α), an oxide film of zinc oxide (ZnO+α), or an oxide film of tin oxide (SnO ₂ +α). It is widely known. Among these, an indium oxide-based oxide film is most often used, but an indium oxide film (In ₂ O ₃ -Sn-based film) containing tin oxide as a dopant is called ITO (Indium Tin). The Oxide film is widely used because it is easy to obtain a low-resistance transparent conductive oxide film.

There are also many effective oxides known optically. A film, a laminate in which the characteristics of each oxide film are surely combined has been applied. Representative examples include an antireflection film of a multilayer structure designed to selectively reflect or penetrate light of a specific wavelength. Further, in addition to the optical characteristics, it is also proposed to add a functional multilayer film (optical film) having an added value such as antistatic or electromagnetic wave shielding.

The reflection preventing property of the multi-layer structure is prevented by the film. The refractive index (n), the extinction coefficient (k), and the film thickness (d) of each layer are determined. That is, the configuration of the laminated body is determined based on the calculation of the data of the refractive index, the extinction coefficient, and the film thickness of each layer constituting the multilayer film. At this time, based on the combination of the high refractive index film and the low refractive index film, a multilayer film (optical film) having more excellent optical characteristics can be realized by incorporating an intermediate refractive index film as necessary.

Generally, as a high refractive index material (n>1.9), it is used. An oxide such as titanium (Ti), cerium (Ce), zirconium (Zr), cerium (Nb), cerium (Ta) or hafnium (Hf), and a low refractive index material is an oxide of cerium (Si).

As a method of forming these oxide films, there are mentioned: Sputtering method, vapor deposition method, ion plating method, and the like. Among these, the sputtering method is known as an effective means when forming a film having a low vapor pressure or when it is necessary to precisely control the film thickness.

Sputtering method can be classified into two according to the method of plasma generation. High-frequency sputtering using high-frequency plasma, or DC sputtering using DC plasma. Among them, the DC sputtering method is widely used industrially because of its relatively rapid film formation speed, low power supply equipment, and simple film formation operation.

When the oxide is formed into a film by DC sputtering, it is necessary to make A sputtering target having conductivity and uniform electrical resistance is used. When DC sputtering is performed using a sputtering target containing a high-resistance substance in a precursor of a conductive material, the high-resistance portion of the target is charged by the irradiation of argon cations, and an arc discharge is generated, so that film formation cannot be performed stably.

Here, an oxide film material having a high refractive index is obtained. Any of the oxides may be inferior in conductivity, and when a sputtering target of such an oxide is used, film formation cannot be performed stably by DC sputtering. Therefore, when a film having a high refractive index is formed by a DC sputtering method, a metal target having conductivity is used, and sputtering is performed while reacting metal particles with oxygen in an environment containing a large amount of oxygen. That is to say, reactive sputtering is used. However, the reactive sputtering method has the disadvantages of extremely low film formation speed and low productivity. For this reason, it is difficult to reduce the manufacturing cost, and the film formation step by the reactive sputtering method has a large problem in the production of an oxide film having a high refractive index.

In Japanese Patent Laid-Open No. Hei 9-176841, it is disclosed that indium oxide (In ₂ O ₃ ) and cerium oxide (Ce ₂ O ₃ ) are contained as a main component, and a trace amount of tin oxide (SnO) is added. / or a sputtering target composed of an oxide sintered body of titanium oxide (TiO ₂ ). The sputtering target system is excellent in electrical conductivity and can be DC-sputtered, and the transparent conductive oxide film obtained from the target has a high refractive index (about 2.3). However, the transparent conductive oxide film has an extinction coefficient on the short-wavelength side of the visible light region of 5.0 × 10 ^-2 or more, and it is difficult to say that the transparency is sufficient as a structural material of the multilayer antireflection film.

Further, in Japanese Laid-Open Patent Publication No. Hei 9-259640 or JP-A-2010-10347, it is disclosed that indium oxide (In ₂ O ₃ ) is used as a main component, and a predetermined amount of gallium (Ga) is added, or further, An oxide sintered body of tin (Sn), titanium (Ti), or zirconium (Zr) is added. By using this oxide sintered body as a film forming material, the light transmittance (extinction coefficient) of the obtained transparent conductive oxide film can be improved. However, such techniques are targeted at touch panels or thin film solar cells, and are not intended to prevent optical films such as reflective films. Further, the amount of gallium added may not provide sufficient penetrability in the transparent conductive oxide film, or the conductivity of the oxide sintered body may be remarkably lowered, and the film formation by DC sputtering may not be performed.

Such prior art is used in manufacturing as a target In the case of an oxide sintered body, there is a problem in that the central portion and the peripheral portion thereof have different color tones (color unevenness) on the surface and the inside thereof. This problem occurs, for example, when a large-sized oxide sintered body having a short side of 5 吋 (12.7 cm) × a long side of 15 吋 (38.1 cm) × a thickness of 0.7 吋 (1.8 cm) or more is produced. There is such a color unevenness target, and the conductivity of different portions of the color tone is different, and the sputtering target system which is required for material uniformity is not good. Therefore, when an oxide sintered body having such a color unevenness is used as a sputtering target, it is necessary to preliminarily remove a portion having color unevenness by mechanical processing or the like, thereby causing an increase in the manufacturing step of the target or accompanying it. The problem of high manufacturing costs.

As a way to prevent color unevenness of the oxide sintered body In the case of producing an indium oxide-zinc oxide sintered body target, the zinc oxide powder which is a raw material thereof is calcined at 400 ° C to 800 ° C, and is subjected to the crucible. The burned zinc oxide powder is mixed with the indium oxide powder, and then the mixed powder is pressure-formed to be 1200 The method of sintering is carried out at a temperature of from °C to 1400 °C. That is, in this document, the color unevenness of the oxide sintered body is considered to be due to the oxygen indefinite ratio of zinc oxide, and the zinc oxide is preliminarily calcined to lower the activity as the zinc oxide powder, thereby suppressing the color. Uneven occurrence.

However, this method is applied to the surface of the oxide sintered body. The color is lighter than the color of the peripheral portion, and sometimes white spots (white spots) having a diameter of about 0.5 mm to 5 mm are produced. The white point resistance value is larger than the resistance value of the peripheral portion, and when the oxide sintered body is formed as a sputtering target, the white point becomes a starting point of arc discharge (abnormal discharge) or nodulation.

Further, it is disclosed in Japanese Laid-Open Patent Publication No. 2011-11613 When an indium oxide-zinc oxide-based target is produced, a method of preventing a color unevenness agent composed of a rare earth oxide such as cerium oxide or cerium oxide is added to the raw material powder. According to this method, white spots are not generated, but by preventing the addition of the color unevenness agent, the characteristics of the oxide sintered body or the transparent conductive film formed as a target may be changed.

In response to these, in Japanese Unexamined 2010-150107 In the meantime, a mixed powder of at least one of a zinc compound powder and a compound containing a compound selected from the group consisting of Al, Ga, B, Nb, In, Y, and Sc is filled, and the powder is filled into graphite. A method for producing a zinc oxide-based oxide sintered body which is hot-pressed at a temperature of 1000 ° C to 1400 ° C in a rare gas atmosphere in a mold other than the material. According to this method, the L*a*b* color difference measured by the CIE1976 space of the surface of the fired surface and the center portion is removed: ΔE* is set to 3.0 or less, so that color unevenness is small, and stability of discharge characteristics is obtained. Excellent oxide sintered body.

However, this method must be in a rare gas environment, The hot pressing is not only complicated, but also lacks in productivity, and there is a problem that the purpose of reducing the oxide sintered body can not be obtained at low cost.

[Previous Technical Literature] (Patent Literature)

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 9-176841

Patent Document 2: Japanese Laid-Open Patent Publication No. Hei 9-259640

Patent Document 3: Japanese Patent Laid-Open Publication No. 2010-10347

Patent Document 4: Japanese Patent Laid-Open No. Hei 9-111444

Patent Document 5: Japanese Patent Laid-Open Publication No. 2001-11613

Patent Document 6: JP-A-2010-150107

An object of the present invention is to provide a sputtering target having a high refractive index and capable of stably forming an optical film having a low extinction coefficient on a short-wavelength side of a visible light region while suppressing occurrence of arc discharge, and providing a supply for providing An oxide sintered body in which the color of the sputtering target is less than uniform and the specific resistance is excellent.

The present invention relates to an indium oxide-based oxide sintered body containing indium oxide, gallium oxide, antimony oxide, and tin oxide and/or titanium oxide.

In particular, in the foregoing oxide sintered body, indium oxide, The total content of gallium oxide, cerium oxide, tin oxide, and titanium oxide is 98.5 mol% or more, preferably 99.0 mol% or more, more preferably 99.5 mol% or more.

Moreover, in the oxide sintered body, the total number of atoms of In, Ga, and Ce is: (a) the atomic ratio of In: In/(In+Ga+Ce) is 0.30 to 0.54. Preferably, it is 0.36 to 0.50, more preferably 0.38 to 0.43, and (b) the atomic ratio of Ga: Ga/(In+Ga+Ce) is 0.30 to 0.52, preferably 0.32 to 0.50, more preferably 0.35 to 0.48, (c) the atomic ratio of Ce: Ce / (In + Ga + Ce) is 0.16 to 0.32, preferably 0.16 to 0.30, more preferably 0.17 to 0.28, in the oxide sintered body, relative to In, The total number of atoms of Ga, Ce, Sn, and Ti is (d) the atomic ratio of Sn: Sn / (In + Ga + Ce + Sn + Ti) is 0.04 or less, preferably 0.020 to 0.035, more preferably The ratio of the atomic ratio of (e) Ti is from 0.015 to 0.032, and Ti/(In+Ga+Ce+Sn+Ti) is 0.01 or less, preferably 0.001 to 0.008, more preferably 0.003 to 0.005, and further, Between the surface of the oxide sintered body and the center position in the thickness direction, it is characterized by L*a*b* color difference measured by CIE1976 space: ΔE* is 5.0 or less, preferably 4.0 or less, and more preferably 3.0. the following. Further, between the central portion of the surface in the radial direction and the peripheral portion, the L*a*b* color difference measured by the CIE1976 space: ΔE'* is 5.0 or less, preferably 4.0 or less, more preferably 3.0 or less.

The specific resistance in the surface of the oxide sintered body and the center position in the thickness direction is preferably 1 × 10 ⁵ Ω ‧ cm or less, more preferably 0.5 × 10 ⁵ Ω ‧ cm or less.

The relative density of the foregoing oxide sintered body is 95.0% The above is preferred, preferably 95.5% or more, and more preferably 96.0% or more.

In order to obtain the indium oxide oxide sintered body of the present invention The manufacturing method is characterized in that the indium oxide powder, the gallium oxide powder, the cerium oxide powder, the tin oxide powder, and/or the titanium oxide powder are pulverized and mixed so as to obtain a mixing ratio of the mixed slurry; The mixed slurry is spray-dried to obtain a granulation step of granulating powder, and the granulated powder is pressed to form a molded body, and the molded body is fired in an inert gas atmosphere to obtain an oxide sintered body. The firing step.

The sputtering target of the present invention is characterized by using the aforementioned oxidation The sintered body of the material serves as a target.

According to the present invention, an oxide sintered body having less color unevenness and excellent specific resistance can be obtained. By using such an oxide sintered body as a target, it is possible to provide a sputtering target which has a high refractive index and can suppress the occurrence of arc discharge and can stably form an optical film having a low extinction coefficient on the short-wavelength side of the visible light region. Therefore, the industrial significance of the present invention is enormous.

The present inventors have accumulated in view of the above problems. As a result of careful study, the indium oxide-based oxide sintered body used as a sputtering target material for forming an optical film can be formed by adding a predetermined amount of gallium (Ga) and cerium (Ce). The refractive index and the optical film having a low extinction coefficient can be formed on the short wavelength side of the visible light region.

However, even if it is so zinc-free as an additive element The indium oxide-based oxide sintered body (in-Ga-Ce-based oxide sintered body) was also confirmed to have color unevenness on the surface and inside. As a result of the cumulative study of this viewpoint, the inventors of the present invention added tin (Sn) or titanium (Ti) to an In-Ga-Ce-based oxide sintered body and fired it in an inert gas atmosphere. The insight to solve the above problems. The present invention has been completed in light of such knowledge.

Hereinafter, regarding the present invention, the separation is "1. Oxide sintering The body, the "2. method for producing an oxide sintered body", and "3. an optical film" will be described in detail. Further, although the oxide sintered body of the present invention is not limited in size, it is mainly a short side 5 吋 (12.7 cm) × a long side 15 吋 (38.1 cm) × thickness which is problematic in the production of color unevenness. The case of a large flat oxide sintered body of 0.7 吋 (1.8 cm) or more is taken as an example. However, the present invention is not limited to the application of such a large flat oxide sintered body, and can be applied to flat-sized, disk-shaped, and cylindrical oxide sintered bodies of various sizes and sputtering using the same. target. Among them, a large-sized cylindrical oxide sintered body having an outer diameter of 4 吋 (10.2 cm) or more and a thickness of 0.7 吋 (1.8 cm) or more and a total length of 2 吋 (5.0 cm) or more is suitable for use in the present invention. .

Oxide sintered body

The present invention relates to an indium oxide-based oxide sintered body (hereinafter referred to as "oxide sintered body") containing indium oxide, gallium oxide, antimony oxide, and tin oxide and/or titanium oxide.

The oxide sintered body is characterized in that the total content of indium oxide, gallium oxide, cerium oxide, tin oxide, and titanium oxide is 98.5 mol% or more.

Further, in the oxide sintered body, the atomic ratio of (a) In is in the total of the number of atoms of indium (In), gallium (Ga), and cerium (Ce): In / (In + Ga + Ce) 0.30 to 0.54, (b) atomic ratio of Ga: Ga / (In + Ga + Ce) is 0.30 to 0.52, (c) atomic ratio of Ce: Ce / (In + Ga + Ce) is 0.16 to 0.32 In the oxide sintered body, the atomic ratio of (d)Sn is the sum of the atomic numbers of In, Ga, Ce, tin (Sn), and titanium (Ti): Sn / (In + Ga + Ce + Sn +Ti) is 0.04 or less, and the atomic ratio of (e) Ti: Ti/(In+Ga+Ce+Sn+Ti) is 0.01 or less, and these constituent components are uniformly dispersed.

Further, the oxide sintered body of the present invention is characterized in that the L*a*b* color difference measured by the CIE1976 space in the surface and the center portion is ΔE* of 5.0 or less.

In such an oxide sintered body, there is little variation in electric resistance between the surface and the center portion. Therefore, using this oxide sintered body When it is a target, a transparent conductive film can be formed by a DC sputtering method.

(1) Composition

The oxide sintered body of the present invention is composed of indium oxide, gallium oxide, cerium oxide, and tin oxide and/or titanium oxide. In addition, components (addition components and unavoidable impurities) other than the constituent components may be contained, but in this case, indium oxide, gallium oxide, cerium oxide, tin oxide, and oxidation contained in the oxide sintered body. The total content of titanium must be 98.5 mol% or more, preferably 99.0 mol% or more, more preferably 99.5 mol% or more. The total content of indium oxide, gallium oxide, cerium oxide, tin oxide, and titanium oxide is less than 98.5 mol%, that is, when the content of the additive component exceeds 1.5 mol%, the desired effect cannot be obtained.

[In content]

In the oxide sintered body, the atomic ratio of In is equal to the number of atoms of In, Ga, and Ce constituting the oxide sintered body: In / (In + Ga + Ce) (hereinafter, The "In/(In + Ga + Ce) atomic ratio") must be 0.30 to 0.54, preferably 0.36 to 0.50, more preferably 0.38 to 0.43. When the In/(In+Ga+Ce) atomic ratio is less than 0.36, the conductivity of the oxide sintered body is remarkably lowered, and it is impossible to form a film by a DC sputtering method. On the other hand, when the In/(In+Ga+Ce) atomic ratio exceeds 0.54, the desired effect cannot be obtained in relation to the content of other constituent components.

[Ga content]

Ga is added to reduce the extinction coefficient on the short-wavelength side of the visible light region of the optical film obtained by forming an oxide sintered body as a sputtering target. element. The content of Ga is equal to the number of atoms of In, Ga, and Ce constituting the oxide sintered body, and the atomic ratio of Ga is Ga/(In+Ga+Ce) (hereinafter, referred to as "Ga/(In+) The Ga + Ce) atomic ratio ") must be 0.30 to 0.52, preferably 0.32 to 0.50, more preferably 0.35 to 0.48. When the atomic ratio of Ga/(In+Ga+Ce) is less than 0.30, the effect of reducing the extinction coefficient cannot be sufficiently obtained. On the other hand, when the atomic ratio of Ga/(In+Ga+Ce) exceeds 0.48, the extinction coefficient can be lowered, but the desired effect cannot be obtained in relation to the content of other constituent components.

[Ce content]

In order to increase the refractive index of the optical film obtained by forming an oxide sintered body as a sputtering target, the Ce is added. The content of Ce is a total number of atoms of In, Ga, and Ce constituting the oxide sintered body: Ce/(In+Ga+Ce) (hereinafter, referred to as "Ce/(In+) The Ga + Ce) atomic ratio ") must be from 0.16 to 0.32, preferably from 0.16 to 0.30, more preferably from 0.17 to 0.28. When the atomic ratio of Ce/(In+Ga+Ce) is less than 0.16, it is impossible to sufficiently increase the refractive index. On the other hand, when the Ce/(In+Ga+Ce) atomic ratio is more than 0.32, the refractive index can be increased, but the desired effect cannot be obtained in relation to the content of other constituent components.

[Sn and Ti content]

Sn and Ti are elements which are added in order to increase the relative density of the oxide sintered body and reduce the specific resistance. It is only necessary to add at least either Sn and Ti, and it is not necessary to add both Sn and Ti.

The content of Sn is a total of the atomic ratio of Sn with respect to the total number of atoms of In, Ga, Ce, Sn, and Ti constituting the oxide sintered body: Sn/(In+Ga+Ce+Sn+Ti) (hereinafter referred to as "Sn/(In+Ga+Ce+Sn+Ti) atomic ratio") is 0.040 or less, preferably 0.035 or less. More preferably, it is 0.032 or less.

Moreover, the content of Ti is relative to the sintering of the oxide In total, the atomic numbers of In, Ga, Ce, Sn, and Ti, the atomic ratio of Ti: Ti/(In+Ga+Ce+Sn+Ti) (hereinafter, referred to as "Ti/(In+Ga+Ce) The +Sn+Ti) atomic ratio ") is preferably 0.010 or less, more preferably 0.008 or less, still more preferably 0.005 or less. When the atomic ratio of Sn/(In+Ga+Ce+Sn+Ti) exceeds 0.040, or when the atomic ratio of Ti/(In+Ga+Ce+Sn+Ti) exceeds 0.010, the contents of In, Ga, and Ce are even Within the above range, it is also impossible to obtain the desired effect.

Also, the lower limit of the content of Sn and Ti should not be special Limitation, but in order to achieve the effect of increasing the relative density stably, the atomic ratio of Sn/(In+Ga+Ce+Sn+Ti) is set to 0.020 or more, and Ti/(In+Ga+Ce+Sn+Ti) atoms are used. The number ratio is preferably 0.001 or more, and the atomic ratio of Sn/(In+Ga+Ce+Sn+Ti) is set to 0.025 or more, and the atomic ratio of Ti/(In+Ga+Ce+Sn+Ti) is set to 0.003. The above is better.

(2) Chromatic aberration

[L*a*b* color difference between the surface and the center position in the thickness direction: ΔE*]

The oxide sintered body of the present invention is characterized in that the L* value measured by the CIE1976 space between the surface after removing the calcined surface and the center position in the thickness direction of the oxide sintered body is based on the a* value and b* value, L*a*b* color difference obtained by the following formula (1): ΔE* value is 5.0 Preferably, it is 4.5 or less, more preferably 4.0 or less, and still more preferably 3.0 or less.

△E *=√(△L ² +Δa ² +Δb ² )‧‧‧(1)

Here, L*a*b* refers to the color space according to the xyz color system set by the International Commission on Illumination (CIE), the L* value indicates brightness (lightness), and the a*b* value indicates hue and chroma. The L* value is a value from L=0 (黒) to L=100 (white), meaning that the larger the value, the more obvious white. On the other hand, the a* value indicates the position of red/magenta and green (a*<0: position of greenish, a*>0: position of positive magenta). Further, the b* value indicates the position of yellow and blue (b*<0: position in bluish blue, b*>0: position in yellowish). The L* value, the a* value, and the b* value can be determined by a spectrophotometer.

When the ΔE* value exceeds 3.0, the color unevenness of the surface of the oxide sintered body and the center position in the thickness direction becomes visually recognized, and when the ΔE* value exceeds 5.0, the color unevenness is clearly recognized. When there is such a clear color unevenness portion, since the volume resistance becomes uneven, abnormal discharge (arc discharge) occurs, and the quality of the obtained transparent conductive film deteriorates. Further, the smaller the ΔE* value, the better, and the lower limit is not limited.

The obtained oxide sintered body is fired in an electric furnace or an electromagnetic wave heating furnace to form a fired surface on the surface. The surface of the fired noodle is rough, and in such a state, it is difficult to accurately measure the L* value, the a* value, and the b* value. Therefore, in the present invention, after firing, the fired surface is ground by an oxide sintered body to remove 0.05 mm to 0.1 mm, preferably After the average roughness Ra (JIS B 0601) was set to a surface of 0.9 μm or less, the L* value, the a* value, and the b* value were measured. Moreover, this surface becomes a sputter surface at the time of sputtering.

Further, the L* value, the a* value, and the center position in the thickness direction are And the b* value is measured by cutting the sample of the oxide sintered body in the thickness direction, and similarly, the cross section is ground and removed by 0.05 mm to 0.1 mm, preferably by arithmetic mean roughness Ra (JIS B 0601). After the surface of 0.9 μm or less is set, the L* value, the a* value, and the b* value are measured at the center position in the thickness direction of the cross section.

Also, between the surface and the center position in the thickness direction * a * b * color difference: ΔE *, preferably in the case of a flat oxide sintered body, measured at the center of the plane and in the vicinity of each corner, and in the case of a disk-shaped oxide sintered body, in a plane In the radial direction center portion and the outer peripheral portion, the circumferential direction is measured at four, and in the cylindrical oxide sintered body, at least in the axial direction at the central portion and the axial direction in the circumferential direction 4 of the outer peripheral surface. The vicinity of both ends is measured, and the maximum value is adopted.

[L*a*b* color difference between the central portion and the peripheral portion of the surface in the radial direction: ΔE' *]

In the oxide sintered body of the present invention, the L*a*b* color difference between the central portion in the radial direction and the peripheral portion of the surface of the sputtering surface at the time of sputtering is ΔE'*, preferably 5.0 or less, and 4.0. The following is preferable, and it is more preferably 3.0 or less. Not only the L*a*b* color difference in the center of the surface and the thickness direction: ΔE*, by the L*a*b* color difference in the central portion and the peripheral portion of the surface in the radial direction: ΔE'* is controlled in such a range , can make the volume resistance of the oxide sintered body It becomes more uniform and can surely prevent the occurrence of arc discharge.

Further, the central portion and the peripheral portion of the surface in the radial direction L*a*b* color difference: ΔE'*, preferably in the case of a flat oxide sintered body, measured and compared in the vicinity of the center of the plane and in the vicinity of each corner, and in the case of a disk-shaped oxide sintered body In the circumferential direction of the center portion and the outer peripheral portion of the plane in the radial direction of the plane, the cylindrical oxide sintered body is in the circumferential direction of the outer peripheral surface at 4, and the central portion and the shaft in the axial direction. The vicinity of both ends of the direction were measured and compared, and the maximum value was used.

(3) Uniformity of specific resistance

As described above, in the oxide sintered body of the present invention, there is almost no color unevenness between the surface of the sputtering surface and the center position in the thickness direction at the time of sputtering, and further preferably, the center portion of the surface in the radial direction is Since there is almost no color unevenness between the peripheral portions, there is no portion (high-resistance portion) in which the resistance value is extremely high, and it is excellent in uniformity of resistance. Therefore, when the oxide sintered body of the present invention is used as a target to form a film by a sputtering method, the occurrence of arc discharge can be effectively suppressed, and an optical film can be efficiently formed in industrial scale production.

More specifically, in the oxide sintered body of the present invention, the specific resistance measured by the four-terminal method in the center position in the surface direction and the thickness direction is preferably 1 × 10 ⁵ Ω ‧ cm or less. It is more preferably 0.5 × 10 ⁵ Ω ‧ cm or less.

Also, the ratio of the surface to the center of the thickness direction When the flat-plate oxide sintered body is preferably used, it is measured in the center portion of the plane and in the vicinity of each corner portion, and in the case of a disk-shaped oxide sintered body, In the circumferential direction of the center portion and the outer peripheral portion of the surface, the measurement is performed at the fourth direction in the circumferential direction, and in the circumferential direction of the outer peripheral surface, at least in the axial direction at the center portion and the shaft. The measurement was performed in the vicinity of both ends of the direction, and the maximum value was used.

In the surface of the oxide sintered body and the center in the thickness direction, it is preferable that the L*a*b* color difference between the central portion and the peripheral portion of the surface in the radial direction is ΔE* of 5.0 or less, and the oxide When the surface of the sintered body and the specific resistance at the center position in the thickness direction are both 1 × 10 ⁵ Ω ‧ cm or less, the oxide sintered system does not have a high resistance portion, and it can be evaluated that the electric resistance is uniform.

(4) Relative density

The relative density of the oxide sintered body of the present invention is preferably 95.0% or more, more preferably 95.5% or more, still more preferably 96.0% or more. Thereby, the strength and conductivity of the oxide sintered body can be improved, and when the oxide sintered body is formed as a target material, it is possible to effectively prevent cracking of the target material and occurrence of arc discharge.

Further, the relative density of the oxide sintered body, system (indium oxide according to the density of the respective constituent components: 7.18g / cm ^3, gallium oxide: 6.16g / cm ^3, cerium oxide: 7.18g / cm ^3, tin oxide: 6.91 g/cm ³ , titanium oxide: 4.26 g/cm ³ ), and the density (solid density) of the indium oxide-based oxide sintered body measured by the Archimedes method or the like after calculating the weighted average density (theoretical density) , divided by the theoretical density.

(5) size and shape

The invention can be adapted to any size and shape (flat shape, disk shape, Or a cylindrical oxide sintered body. However, the present invention is particularly suitable for a large flat oxide sintered body or a cylindrical oxide sintered body, and the effect can be obtained. In the case of a flat oxide sintered body, the present invention is particularly suitable for use in an oxide sintered body having a short side of 5 吋 (12.7 cm) × a long side of 15 吋 (38.1 cm) × a thickness of 0.7 吋 (1.8 cm) or more. In the case of the cylindrical oxide sintered body, the present invention is an oxide sintered body having an outer diameter of 4 吋 (10.2 cm) or more, a thickness of 0.7 吋 (1.8 cm) or more, and a total length of 2 吋 (5.0 cm) or more. It is especially suitable for use.

2. Method for producing oxide sintered body

The method for producing an oxide sintered body of the present invention is not particularly limited as long as the above-described oxide sintered body can be produced. However, in the case of industrial scale production, it is preferable to produce by the following production method: the raw material powder is pulverized at a specific ratio to obtain a mixing step of the mixed slurry; and the mixed slurry is spray-dried to obtain a granulated powder. The granulation step; the granulation powder is press-formed to obtain a molding step of the molded body; and the molded body is fired in an inert gas atmosphere to obtain a firing step of the oxide sintered body.

(1) Raw material powder

As the raw material powder of the oxide sintered body of the present invention, indium oxide powder, gallium oxide powder, cerium oxide powder, and tin oxide powder and/or titanium oxide powder can be used. Further, these raw material powders are not limited by the oxidation number of the metal oxide or the like.

The average particle diameter of these raw material powders is preferably from 0.1 μm to 3.0 μm, more preferably from 0.4 μm to 2.0 μm. Especially for indium oxide powder, gallium oxide powder, and cerium oxide powder, It is preferred that the average particle diameter is from 0.4 μm to 1.0 μm. When the average particle diameter of the raw material powder is less than 0.1 μm, the raw material powder is aggregated during mixing, and a uniform mixed slurry cannot be formed. On the other hand, when the average particle diameter exceeds 3.0 μm, it is difficult to set the relative density to 95.0% or more in the obtained oxide sintered body. Further, in the present invention, the average particle diameter of the raw material powder means an intermediate diameter, which can be measured by a particle size distribution meter.

(2) mixing step

In the mixing step, the indium oxide powder, the gallium oxide powder, the cerium oxide powder, and the tin oxide powder and/or the titanium oxide powder are weighed so as to have a composition ratio of the oxide sintered body described above, and the raw material powders are The water or the binder is placed together in a resin pot, and pulverized and mixed to obtain a step of mixing the slurry.

In the present invention, the mixing method is not limited, and a known means such as a ball mill or a bead mill can be used. However, from the viewpoint of improving work efficiency and quality, it is preferred to pulverize and mix by a bead mill. In this case, it is preferable to use a hard zirconia (ZrO ₂ ) as a bead or a ball.

Further, as the binder, it is only required to be debonded as described later. In the step of the agent, the loss or gasification may be carried out without limitation. For example, a water-soluble binder such as polyvinyl alcohol (PVA) may be suitably used. Further, the amount of the binder added is preferably 0.5% by mass to 1.5% by mass based on the total amount of the raw material powder.

In the mixing step of the present invention, it is necessary to mix the slurry The average particle size of some raw material powders must be 0.50 μm or less, preferably 0.48 μm or less, more preferably 0.45 μm or less, and continuous pulverization and mixing. Thereby, the relative density of the obtained oxide sintered body can be easily made 95.0% or more.

Also, the mixing time should be in accordance with the mixing method or use The characteristics of the apparatus are appropriately adjusted so long as the average particle diameter of the raw material powder can be set to the above range, and is not particularly limited. For example, in the case of a ball mill, it is preferably from about 15 hours to about 28 hours, and in the case of a bead mill, it is preferably from about 3 Pa (pa; pascal) to about 7 Pa. Even if any one of the operations is insufficient, the mixing time is insufficient, and in the obtained oxide sintered body, the respective constituent components cannot be uniformly dispersed. On the other hand, when the mixing time is too long, not only the productivity is deteriorated, but also the fine powder caused by the ball or the beads may be mixed as a sundries.

(3) Granulation step

The granulation step is a step of spray-drying the mixed slurry obtained in the mixing step to obtain a granulated powder. In this case, the method of spray-drying the mixed slurry is not particularly limited, and for example, a known means such as a spray dryer can be used.

Also, the conditions in the granulation step must be It is suitably selected by the characteristics of the apparatus, etc., but generally, after adjusting the slurry concentration to 55% to 70%, it is preferred to spray dry at a drying temperature (hot air temperature) of 140 ° C to 160 ° C.

Granulated powder obtained in such a granulation step, It is preferable that the average particle diameter is controlled to be 10 μm to 80 μm to be controlled at 30 μm to 60 μm. Thereby, the relative density of the obtained oxide sintered body can be easily made 95.0% or more.

(4) Forming step

The forming step is a step of filling the granulated powder into a molding die and obtaining a molded body by press molding. The method of press molding is not particularly limited, but from the viewpoint of productivity, it is preferably formed by cold hydrostatic pressure (CIP) press molding. At this time, the pressing force is preferably about 250 MPa to 350 MPa.

(5) firing step

The firing step is constituted by a process of removing the formed body obtained in the forming step at a relatively low temperature to remove the organic component (adhesive) debonding agent contained in the formed body; The firing of the oxide sintered body is obtained by firing at a higher temperature than the debonding process.

Further, the sintering furnace used in the firing step is not particularly limited, and an electric furnace, an electromagnetic wave heating furnace, or the like can be used.

[debonding process]

In the process of removing the binder, the range in which the organic component in the formed body can be easily removed, for example, from room temperature to 500 ° C at which the organic component is completely removed, is preferably set to 15 hours to 25 hours. The hour is preferably from 18 hours to 23 hours, more preferably about 20 hours. Further, the ambient gas in the process of removing the binder is not particularly limited and may be any one of an oxidizing atmosphere or a vacuum environment. However, from the viewpoint of production cost, it is preferable to set it as an atmospheric environment.

[firing process]

a) firing temperature

The temperature during the firing (burning temperature) is set to 1400 ° C to 1500 °C, preferably 1400 ° C to 1450 ° C. When the firing temperature is less than 1400 ° C, the relative density of the obtained oxide sintered body is lowered. On the other hand, when the baking temperature exceeds 1500 ° C, the relative density of the obtained oxide sintered body is lowered or the composition is shifted by volatilization of the raw material component. Further, in the firing process, the raw material component may be melted, and the molded body may be deformed, and the oxide of a desired shape may not be obtained.

b) firing time

The holding time (firing time) of the firing temperature is set to 15 hours to 30 hours, preferably 15 hours to 20 hours. When the firing time is within this range, the amount of energy (electric power) used can be suppressed, and high productivity can be obtained, and a high-quality oxide sintered body can be obtained.

c) firing environment

The indium oxide-based oxide sintered body of the present invention, more specifically, in the In-Ga-Ce-Sn/Ti-based oxide sintered body, the reason why the color unevenness occurs regardless of whether or not zinc is contained as an additive component is not necessarily clear . However, according to the knowledge of the inventors of the present invention, one of the reasons is considered to be related to the oxygen indefinite ratio of cerium oxide contained in the oxide sintered body.

That is, in the past, an oxide used as a sputtering target was burned. The structure is required to have a high density from the viewpoint of preventing cracking or arc discharge at the time of film formation. For this reason, in the manufacturing stage, the formed body must be fired in an oxidizing gas atmosphere. However, in the In-Ga-Ce-based oxide sintered body, the oxygen indefinite ratio due to the ruthenium oxide constituting the ruthenium is considered, and the molded body is considered to be molded when the molded body is fired in an oxidizing atmosphere in the production stage. The surface of the surface and the oxygen in and out of it will become very intense, thereby causing color Evenly.

For this, in the present invention, in the composition, adding a specific At the same time as the amount of Sn and/or Ti, as the ambient gas in the firing step, an inert gas atmosphere is employed. It is considered that oxygen ingress and egress at the surface of the molded body at the time of firing and the vicinity thereof are alleviated, and the oxygen indefinite ratio of the cerium oxide disappears. Moreover, even if it is a thick-walled oxide sintered body having a thickness of more than 20 mm, the relative density is not lowered, and color unevenness at the center of the surface and the thickness direction can be suppressed.

As an inert gas for forming an inert gas atmosphere A rare gas or a nitrogen gas or a mixed gas of these may be used. As a rare gas, helium gas, helium gas, argon gas or the like can be used, but a relatively inexpensive argon gas is preferred. Further, the concentration of the inert gas in the inert gas atmosphere is not necessarily 100% by volume, and may be any degree as long as it causes color unevenness in the oxide sintered body. Specifically, in an inert gas atmosphere, oxygen containing less than 10 ppm by volume is allowed.

Such an inert gas environment, at the end of the debinding agent After the process, for example, it can be formed by replacing the environment in the firing furnace with an inert gas atmosphere or by flowing an inert gas in the firing furnace.

3. Optical film

(1) Optical film

The optical film of the present invention is formed by sputtering using the above-described oxide sintered body as a target. This optical film can have a high refractive index while making the extinction coefficient on the short wavelength side of the visible light region low.

Specifically, when visible light of 300 nm to 1000 nm measured by a visible light spectrophotometer is used, when measured by a spectroscopic ellipsometer, the refractive index at a wavelength of 500 nm can be 2.1 or more, and preferably 2.15 or more. Further, the extinction coefficient at a wavelength of 380 nm can be made 4.08 × 10 ^-2 or less, preferably 3.5 × 10 ^-2 or less, more preferably 3.0 × 10 ^-2 or less.

Moreover, the composition of the optical film also depends on the film formation conditions. In the case of the film formation, it is possible to use a composition of an oxide sintered body which is used as a sputtering target as long as it is formed under appropriate conditions as described below.

(2) Film formation method

The film formation method of the optical film described above is not particularly limited, except that the oxide sintered body of the present invention is used as a sputtering target, and a known means can be used. However, from the viewpoint of mass productivity, the DC sputtering method is particularly preferably performed by using a DC magnetron sputtering apparatus.

Further, the film formation conditions are not particularly limited, and can be set as general conditions. For example, when forming a film by a DC magnetron sputtering apparatus, the target-substrate distance is set to 35 mm to 120 mm, the substrate temperature is set to room temperature to 300 ° C, and the vacuum degree is set to 1 × 10 ^-3 Pa or less. , may contain 10% by volume of oxygen as a sputtering gas of argon gas, the pressure became 0.1Pa so introduced to 1.0 Pa, input power to 0.5W / cm ² to 5.50W / cm ² to form a film.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples. Further, in the following examples and comparative examples, (a) relative density, (b) chromatic aberration, (c) specific resistance, (d) discharge characteristics, and oxides of the obtained oxide sintered body Sintered body as a sputtering target The (e) refractive index and extinction coefficient of the film were evaluated by the following method.

(a) Relative density

The actual density of the oxide sintered bodies obtained in Examples 1 to 9 and Comparative Examples 1 to 13 was measured by the Archimedes method, and the composition ratio of each sample and the density of its constituent components (oxidation) indium: 7.18g / cm ^3, gallium oxide: 6.16g / cm ^3, cerium oxide: 7.18g / cm ^3, tin oxide: 6.91g / cm ^3, titanium oxide: 4.26g / cm ^3), calculates the average density increased ( Theoretical density), the relative density is obtained by dividing the actual density by the theoretical density.

(b) Chromatic aberration

First, the samples obtained in Examples 1 to 9 and Comparative Examples 1 to 13 were cut in the thickness direction, and the surface roughness and the cross-section were polished to about 0.07 mm, and the surface roughness was attempted to be 0.9 μm with arithmetic mean roughness. The following ways to adjust. Next, the L* value, the a* value, and the b* value of the surface of each sample and the center position in the thickness direction (the position in the thickness direction from the surface to 1/2 of the thickness of the oxide sintered body) are for the center portion in the radial direction. Four places in the circumferential direction of the outer peripheral portion were measured using a portable spectrophotometer (Gardner spectro-guide, manufactured by BYK Japan Co., Ltd.), and the following formula (1) The L*a*b* color difference between the surface and the center in the thickness direction was calculated: ΔE*, and its evaluation was performed by using its maximum value.

△E *=√(△L ² +Δa ² +Δb ² ) (1)

Further, in the other samples obtained in Examples 1 to 9 and Comparative Examples 1 to 13, the surface was polished to a thickness of about 0.07 mm. The surface roughness was adjusted so that the arithmetic mean roughness was 0.9 μm or less. Next, for the center of the radial direction of the surface of each sample (the center position in the radial direction) and the circumferential direction of the outer peripheral portion, a portable spectrophotometer (BYK Chemical Japan Co., Ltd., Garners Pike-Guide) was used. The L* value, the a* value, and the b* value are respectively measured, and in the same manner as in the formula (1), the L*a*b* color difference between the central portion and the peripheral portion in the radial direction of the surface is calculated: ΔE '*, conduct its evaluation by taking its maximum value.

(c) specific resistance

Similarly, the samples obtained in Examples 1 to 9 and Comparative Examples 1 to 13 were cut in the thickness direction, and the specific resistance of the center portion in the surface and thickness direction was measured in addition to the surface and the cross section. The center portion and the outer peripheral portion were measured at four places in the circumferential direction using a four-terminal method resistance meter (manufactured by Mitsubishi Chemical Analysis Co., Ltd., Loresta GP MCP-T610 type). As a result, the specific resistance of the surface of the sample in the radial direction and the center of the sample in the circumferential direction of the outer peripheral portion and the center portion in the thickness direction were evaluated as "excellent (◎) in any case of 5 × 10 ⁴ Ω ‧ cm or less In the case of more than 5 × 10 ⁴ Ω ‧ cm and less than 1 × 10 ⁵ Ω ‧ cm, it was evaluated as "good (○)", and those exceeding 1 × 10 ⁵ Ω ‧ cm were evaluated as "bad (×)".

(d) Discharge characteristics

When the oxide sintered bodies obtained in Examples 1 to 9 and Comparative Examples 1 to 13 were formed as a target by a DC sputtering method, the presence or absence of an arc discharge or the like was observed by visual observation, and the discharge characteristics were evaluated. Specifically, when an arc discharge or the like is not generated and the film formation can be stably performed, it is evaluated as "excellent (◎)", and a certain amount of arc discharge is generated. However, if there is no problem in practical use, it is evaluated as "good (○)", and an arc is generated. Those who have discharged and have problems in practical use are evaluated as "bad (×)".

(e) refractive index and extinction coefficient

For the optical films obtained in Examples 1 to 9 and Comparative Examples 1 to 13, visible light measured by a visible light spectrophotometer (Ubest V-570iRM/DS, manufactured by JASCO Corporation) was used, and a spectroscopic ellipsometer device was used. (VASR, manufactured by JA Woollam Co., Ltd.), which was evaluated by measuring the refractive index at a wavelength of 550 nm and the extinction coefficient at a wavelength of 380 nm. Specifically, those who have a refractive index of 2.1 or higher are evaluated as "good (○)", and those who have not reached 2.1 are evaluated as "bad (x)". In addition, those who have an extinction coefficient of 4.08×10 ⁻² or less are evaluated as “good (○)”, and those who exceed 4.08×10 ⁻² are evaluated as “bad (×)”.

(Example 1)

[Production of oxide sintered body and sputtering target]

Preparation of indium oxide powder as a raw material powder (average particle diameter: 0.4 μm, specific surface area: 11.2 m ² /g), gallium oxide powder (average particle diameter: 0.5 μm, specific surface area: 13.3 m ² /g), cerium oxide powder (average particle diameter: 0.9 μm, specific surface area: 12.5 m ² /g), tin oxide powder (average particle diameter: 1.7 μm, specific surface area: 11.1 m ² /g), and titanium oxide powder (average particle diameter: 0.9 μm, Specific surface area: 6.6 m ² /g).

These raw material powders are made into Ga/(In+Ga+Ce) The atomic ratio is 0.311, the Ce/(In+Ga+Ce) atomic ratio is 0.174, and the Sn/(In+Ga+Ce+Sn+Ti) atomic ratio is 0.031, Ti/(In+Ga+Ce+Sn +Ti) The amount of atomic ratio was weighed to 0.005, and the water-soluble binder (PVA) weighed at 1.4% by mass and pure water were placed in a resin pot together with the total amount of the raw material powder. Further, input The hard zirconia ball is sealed on the lid of the resin pot and placed on the rack of the ball mill. It takes 24 hours to pulverize and mix to prepare the raw material powder with an average particle diameter of 0.5 μm or less and a slurry concentration of 55% to 70. % mixed slurry.

This mixed slurry was spray-dried under the following conditions using a spray dryer (CNK-P-SDD-2, manufactured by Chubu Thermal Industries Co., Ltd.) to obtain a granulated powder having an average particle diameter of 50 μm.

(spray drying conditions)

Slurry concentration: 1.95g/cm ³

Slurry supply: 250ml / minute

Exhaust air volume: 8Nm ³ / minute

Drying temperature: 170 ° C

Then, this granulated powder was filled in a molding die (rubber die) having a diameter of 216 mm and a thickness of 10 mm, and press-molded by cold hydrostatic pressure under a pressure of 294 MPa (3 ton/cm ² ) to obtain a molded body.

This molded body was fired using an electric furnace (manufactured by Benyama Co., Ltd.). Specifically, in an atmospheric environment, the temperature was raised from room temperature to 500 ° C for 20 hours. Next, argon gas was introduced until the argon gas concentration in the furnace became 100% by volume, and the temperature was raised to 1400 ° C, and the temperature was maintained for 20 hours. The oxide sintered body obtained in this manner was cooled to room temperature, and the oxide sintered body was taken out from the electric furnace, and then subjected to a grinding process to obtain a sample of a sputtering target having a diameter of 6 吋 (152.4 mm) and a thickness of 5 mm.

[assessment]

First, a sputtering target (oxide sintered body) obtained as described above The composition of the sample was analyzed using an ICP emission spectrometer (manufactured by Shimadzu Corporation, ICPS8100). As a result, the composition of the sample of the sputtering target was confirmed to be the same as the mixing ratio of the raw material powder. Further, in the oxide sintered body, the total content of indium oxide, gallium oxide, cerium oxide, tin oxide, and titanium oxide is 99.2 mol%.

Further, for the sample of the sputtering target, evaluations regarding (a) relative density, (b) chromatic aberration, and (c) specific resistance were performed.

Next, the sample of the sputtering target was metal-bonded to a pad made of oxygen-free copper, and mounted on a magnetron sputtering apparatus (manufactured by Tokki Co., Ltd.) using a DC power source, under the following conditions, on a glass substrate. While the optical film having a thickness of 200 nm was formed thereon, the evaluation of (d) discharge characteristics was performed on the sample of the sputtering target.

(sputter condition)

Target-substrate distance: 60mm

Substrate temperature: 200 ° C

The degree of vacuum reached: 1 × 10 ^-3 Pa or less

Sputtering gas: Ar gas containing 10% or less of O ₂ gas

Gas pressure: 0.5Pa

Input power: DC 200W/cm ²

Further, the composition of the composition was analyzed by an ICP emission spectrometer, and it was confirmed that the composition ratio of the obtained optical film to the raw material powder was the same.

Finally, with respect to the optical film thus obtained, evaluation of (e) refractive index and extinction coefficient was performed. Representing the results of these In 1 and Table 2.

(Examples 2 to 9 and Comparative Examples 1 to 13)

As shown in Table 1, in the same manner as in Example 1, except that the mixing ratio of the raw material powder (the composition ratio in the oxide sintered body), the firing environment, and the firing temperature were changed, indium oxide sputtering was obtained. A sample of the target was simultaneously evaluated for (a) relative density, (b) color difference, and (c) specific resistance for the sample of the sputtering target.

Next, using the sample of the sputtering target, and Example 1 The same operation was carried out to produce an optical film. At this time, for the sample of the sputtering target, (d) evaluation of the discharge characteristics was performed, and (e) the refractive index and the extinction coefficient were evaluated for the obtained optical film. The results of these and the like are shown in Tables 1 and 2.

Further, for the sputtering target sample obtained as described above As a result of composition analysis by an ICP emission spectrometry apparatus, it was confirmed that the optical film was the same as the mixing ratio of the raw material powder.

[Comprehensive Evaluation]

From Table 1 and Table 2, it was confirmed that any of the oxide sintered bodies of Examples 1 to 9 which are within the scope of the present invention has L*a*b* measured in the CIE1976 space at the center portion in the surface and thickness direction. Color difference: ΔE* is 5.0 or less, L*a*b* color difference: ΔE'* is 5.0 or less, specific resistance is 1 × 10 ⁵ Ω‧cm or less, and relative density is 95.0% or more. Further, when these oxide sintered bodies were used as targets, when a film was formed by a DC sputtering method, it was confirmed that arc discharge hardly occurred during discharge. Moreover, the optical film in the examples was found to have a refractive index of 2.1 or more and an extinction coefficient of 4.08 × 10 ^-2 or less, and is applicable to applications such as an antireflection film.

In contrast, the oxide sintered bodies of Comparative Examples 1 to 13 Any one or more of the composition, the firing environment, and the firing temperature deviate from the scope of the present invention. Therefore, these comparative examples are L*a*b* color difference: ΔE*, L*a*b*color difference: ΔE'* or a value such as a specific resistance is not within a predetermined range, and film formation cannot be continued stably.

[Industrial availability]

The oxide sintering system of the present invention has less color unevenness, excellent uniformity of specific resistance, and high relative density. Therefore, this oxide sintered body is used as a target, and an optical film having a high refractive index and a low extinction coefficient on the short-wavelength side in the visible light region is produced by DC sputtering without causing arc discharge or the like. . Such an optical film is widely used as a high refractive index film used for preventing refractive index control of a reflective film or a functional multilayer film (optical film).

Claims (6)

An indium oxide-based oxide sintered body comprising an indium oxide-based oxide sintered body containing indium oxide, gallium oxide, antimony oxide, and tin oxide and/or titanium oxide, wherein in the oxide sintered body, The total content of indium oxide, gallium oxide, cerium oxide, tin oxide, and titanium oxide is 98.5 mol% or more. In the oxide sintered body, the atom of (a) In is the total of the number of atoms of In, Ga, and Ce. The ratio of the number: In / (In + Ga + Ce) is 0.30 to 0.54, (b) the ratio of the number of atoms of Ga: Ga / (In + Ga + Ce) is 0.30 to 0.52, (c) the number of atoms of Ce Ratio: Ce / (In + Ga + Ce) is 0.16 to 0.32; in the oxide sintered body, the ratio of the atomic number of (d) Sn to the total number of atoms of In, Ga, Ce, Sn, and Ti: Sn/(In+Ga+Ce+Sn+Ti) is 0.04 or less, and (e) the ratio of the atomic number of Ti: Ti/(In+Ga+Ce+Sn+Ti) is 0.01 or less, and the oxide is Between the surface of the sintered body and the center position in the thickness direction, L*a*b* color difference measured by CIE1976 space: ΔE* is 5.0 or less. The indium oxide-based oxide sintered body according to the first aspect of the invention, wherein L*a*b measured by the CIE1976 space between the central portion and the peripheral portion in the radial direction of the surface of the oxide sintered body * Color difference: ΔE'* is 5.0 or less. The indium oxide-based oxide sintered body according to the first or second aspect of the invention, wherein the specific resistance of the surface of the oxide sintered body and the center in the thickness direction is 1 × 10 ⁵ Ω. Below cm. The indium oxide-based oxide sintered body according to claim 1 or 2, which has a relative density of 95.0% or more. A method for producing an indium oxide-based oxide sintered body, which is a method for producing an indium oxide-based oxide sintered body according to any one of claims 1 to 4, which comprises: oxidizing indium oxide powder The gallium powder, the cerium oxide powder, and the tin oxide powder and/or the titanium oxide powder are pulverized and mixed so as to have the composition ratio, thereby obtaining a mixing step of mixing the slurry; and the mixed slurry is spray-dried to obtain a granulated powder. a granule step; a step of molding the granulated powder by pressure molding to obtain a molded body; and firing the formed body in an inert gas atmosphere to obtain a firing step of the oxide sintered body. An indium oxide-based sputtering target is obtained by using the oxide sintered body according to any one of claims 1 to 4.