JP5327282B2 - Sintered body target for transparent conductive film production - Google Patents

Description

  The present invention relates to a sintered body target for producing a transparent conductive film used in a sputtering method or an ion plating method, and a transparent electrode or an antistatic function of a display display produced using the same, or a transparent material used for a liquid crystal optical element. The present invention relates to a conductive film and a transparent conductive substrate.

A transparent conductive film having a low electrical resistance and a transparent conductive substrate formed on a transparent substrate are used for applications that require transparency and conductivity, for example, flat panel displays such as liquid crystal displays and EL displays. In addition, it is widely used in various electrical and electronic fields such as display device applications such as transparent electrodes of touch panels, antistatic film applications, and liquid crystal optical element applications. The generally transparent conductive films, film added with tin, i.e. crystal film ITO (I ndium- T in- O xide ) are widely used in the indium oxide. An ITO crystal film is an excellent material having a low specific resistance and good light transmittance in the visible light region. Until now, most applications have responded by controlling the properties of ITO.

However, recently, with the development of new display devices such as organic or inorganic EL and electronic paper, the requirements for transparent conductive films have diversified, and ordinary ITO crystal films can no longer cope with them.
For example, when used as a transparent electrode for organic EL, an amorphous film is preferable instead of a crystalline film. In the crystal film such as ITO, there is a problem in that uniform current display becomes difficult due to local current concentration due to the presence of a protruding structure due to crystal growth. That is, an amorphous film having a very flat film surface is required.
In addition, when used as an anode of an organic EL, it is preferable that the work function is large because holes are more easily injected, but the work function of many transparent conductive films including ITO is less than 5 eV. If it is a value, luminous efficiency can be improved and it is convenient.
Furthermore, a transparent conductive film having a lower refractive index is preferable. By using a transparent conductive film having a refractive index lower than that of an ITO film or the like, there are merits such that the light extraction efficiency from the light emitting layer can be increased and optical design is easy.
As another example, touch panels tend to place importance on visibility. In order not to deteriorate the visibility, a transparent conductive film having a low refractive index is required. Since the refractive index of ITO is as high as about 2.0 to 2.2 and the visibility is not good, a transparent conductive film having a refractive index of about 1.8 is required.

It is also becoming important that the film is an amorphous film, not a crystalline film. In general, an oxide crystal film has a problem that a crystal grain boundary is weak and strength is weak.
As a problem in Patent Document 1, the crystal film is particularly vulnerable to sliding, and cracks and peeling occur in the film, so that it is unsuitable for a touch panel that performs pen input.
As an example other than the above, in an electronic paper application characterized by flexibility, a transparent conductive film that is hard to break against bending is essential. In general, an oxide crystal film has a weak grain boundary and is easily cracked, whereas an amorphous film without a crystal grain boundary is known to be difficult to break. Application of an amorphous transparent conductive film has been proposed. In this application, since a heat-sensitive substrate such as a PET film is used, it is required to form an amorphous transparent conductive film near room temperature. Needless to say, the amorphous transparent conductive film has a low refractive index as in the case of the touch panel.

FIG. 10, 11 and 12 of Non-Patent Document 1 show the work function of each transparent conductive film. According to this, the transparent conductive film having a work function exceeding 5 eV is a (Ga, In) ₂ O ₃ crystal film. , GaInO ₃ crystal film, ZnSnO ₃ crystal film and ZnO crystal film. In other words, there is currently no amorphous film that can be formed at room temperature that has a work function exceeding 5 eV.
In Patent Document 2, in an organic electroluminescence element in which an organic layer including an organic light emitting layer is sandwiched between an anode and a cathode, an electron injection electrode layer, a transparent conductive film, and a resistor are formed from the side where the cathode contacts the organic layer. An organic electroluminescence device has been proposed in which a metal thin film having a rate of 1 × 10 ⁻⁵ Ω · cm or less is laminated in this order, and a transparent thin film layer is formed on the outer side of the cathode. Indium (In), zinc An amorphous transparent conductive film using an oxide composed of (Zn) and oxygen (O) is used.

In Patent Document 3, as a transparent conductive film having high visible light transmittance and low resistance, a composite metal oxide film containing In, Sn, and Zn includes at least one In ₄ Sn ₃ O ₁₂ crystal, Alternatively, a microcrystal composed of In, Sn, and Zn or an amorphous material is formed, and the contained metal component composition has an Sn amount of 40 to 60 atomic% represented by Sn × 100 / (In + Sn), and Zn × A transparent conductive film containing 10 to 90 atomic% of Zn expressed by 100 / (In + Zn) is described.

Further, Patent Document 4 has a band gap of 3.4 eV and a light refractive index of 2.0, which is almost the same as that of a conventional transparent conductive film, and is much higher in conductivity than MgIn ₂ O ₄ and In ₂ O ₃ , that is, As a transparent conductive film having lower resistivity and excellent optical properties, an oxide containing magnesium (Mg), indium (In), or a pseudo binary system represented by MgO—In ₂ O ₃ , In / ( There has been proposed a transparent conductive film containing 70 to 95 atomic percent of In, represented by (Mg + In).
However, many of the conventionally proposed amorphous transparent conductive films represented by Patent Documents 2 to 4 have a work function of less than 5 eV and a refractive index of 2.0 or more. It is not suitable for the above-mentioned use.

Patent Document 5 proposes gallium indium oxide (GaInO ₃ ) doped with a small amount of a heterovalent dopant such as a tetravalent atom. The crystal film of the oxide is excellent in transparency and has a low refractive index of about 1.6. Therefore, the refractive index matching with the glass substrate is improved, and it is about the same as the wide bandgap semiconductor currently used. It is described that the electrical conductivity of can be realized. As described in Non-Patent Document 1, the work function exceeds 5 eV, but it is not an amorphous film required for recent display devices but a crystalline film. In addition, in order to obtain a crystalline film, industrially Since it is disadvantageous and high temperature film formation at a substrate temperature of 250 to 500 ° C. is necessary, it is difficult to use it as it is.

In addition, Patent Document 6 discloses a much higher conductivity than GaInO ₃ and In ₂ O ₃ in a composition range that is considerably different from the conventionally known GaInO ₃ , that is, a lower resistivity and excellent optical characteristics. As a transparent conductive film having a structure, a transparent conductive film containing 15 to 49 atomic% of Ga represented by Ga / (Ga + In) in a pseudo binary system represented by Ga ₂ O ₃ —In ₂ O ₃ has been proposed. Yes. In particular, it is described that the optical refractive index of the transparent conductive film can be changed from about 1.8 to 2.1 by changing the composition. However, the examples do not describe anything about the refractive index and work function. Further details are reported in Non-Patent Document 1 and Non-Patent Document 2 by the inventors of Patent Document 6. As described above, Non-Patent Document 1 only shows the work function of a (Ga, In) ₂ O ₃ crystal film formed at a substrate temperature of 350 ° C., and the work function of an amorphous film is Not shown. Also, FIG. 6 shows the refractive index of a transparent conductive film made of Ga, In, and O that is formed at room temperature. According to this, the refractive index of an In ₂ O ₃ film is about 2.1, and the refractive index of a transparent conductive film containing 5 to 80 atomic% of the Ga amount represented by Ga / (Ga + In) is 1.9 to 2.3. The refractive index of the Ga ₂ O ₃ film is about 1.8, and in particular, it is described that the transparent conductive film containing 50 atomic% of the Ga content represented by Ga / (Ga + In) is about 2.0.
As can be seen from the above, it has been found that a transparent conductive film that can be formed near room temperature, is amorphous, has a work function exceeding 5 eV, and has a low refractive index has not yet been obtained. is there.

  Therefore, there is a need for a transparent conductive film having a high work function and a low refractive index in the above-mentioned organic EL, touch panel and electronic paper applications, a request for an amorphous transparent conductive film that is not easily broken by sliding and bending, and a film surface. However, there is still no well-balanced answer to the need for an extremely flat amorphous transparent conductive film, and the necessity of being able to form a film near room temperature. There is a need for new transparent conductive films. Furthermore, a sintered body target for producing a transparent conductive film for obtaining the transparent conductive film using a sputtering method or an ion plating method is required.

JP 2002-313141 A JP-A-10-294182 JP-A-10-83719 JP-A-8-264023 JP 7-182924 A Japanese Patent Laid-Open No. 9-259640

T.A. Minami et al: J. MoI. Vac. Sci. Technol. A17 (4), Jul / Aug 1999 P1765-1772 T.A. Minami et al: J. MoI. Vac. Sci. Technol. A14 (3), May / Jun 1996 P1689-1693 R. D. Shannon et al: J. Org. inorg. nucl. Chem. , 1968, Vol. 30, pp. 1389-1398

  In view of the technical background of recent display devices as described above, the present invention is amorphous and has a high work function, a low refractive index in the visible region, and peeling and cracking due to sliding and bending. Another object of the present invention is to provide a sintered body target for producing a transparent conductive film suitable for producing a transparent conductive film having a film surface that is extremely flat and capable of forming a film near room temperature.

In order to solve the above-mentioned problems, the inventors of the present application produced various sintered compact targets for producing a transparent conductive film, formed a large number of oxide films on a transparent substrate, the optical characteristics and amorphous properties of the oxide films. We investigated the ease of production of the membrane. As a result, mainly Ga, made of In and O, contains 65 atomic% or less 49.1 atomic% or more based on the total metal atoms of Ga, mainly GaInO ₃ phase and a bixbyite of β-Ga ₂ O ₃ -type structure It is composed of an In ₂ O ₃ phase having a mold structure, is sintered at atmospheric pressure in an oxygen stream at 1350 ° C., has an X-ray diffraction peak intensity ratio defined by the following formula (A) of 15% or less, and a density of 5 Sintered body target for producing a transparent conductive film, characterized in that it is 8 g / cm ³ or more In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) × 100 [%] (A)
As a result, it was found that a suitable transparent conductive film can be obtained by using the present invention.

That is, the sintered compact target for producing a transparent conductive film according to the present invention is mainly composed of Ga, In, and O, contains Ga of 49.1 atomic% or more and 65 atomic% or less with respect to all metal atoms, and is mainly β-. It is composed of a Ga ₂ O ₃ type GaInO ₃ phase and a bixbite type In ₂ O ₃ phase (hereinafter, abbreviated as β-GaInO ₃ phase and In ₂ O ₃ phase unless otherwise specified), and in an oxygen stream It is characterized by being sintered at 1350 ° C. under normal pressure and having an X-ray diffraction peak intensity ratio defined by the following formula (A) of 15% or less and a density of 5.8 g / cm ³ or more.
In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) × 100 [%] (A)

The sintered compact target for producing a transparent conductive film according to the present invention preferably has a specific resistance value of 9.0 × 10 ⁻¹ Ω · cm or less.

  The transparent conductive film produced by using the sintered body target contains Ga of 49.1 atomic% or more and 65 atomic% or less with respect to all metal atoms, and has a work function of 5.1 eV or more. And

  The transparent conductive film preferably has a refractive index of 1.65 to 1.85 at a wavelength of 633 nm.

The transparent conductive film preferably has a specific resistance value of 1.0 × 10 ^{−2 to} 1.0 × 10 ⁺⁸ Ω · cm.

  The transparent conductive film preferably has an arithmetic average height (Ra) of 2.0 nm or less, preferably 1.0 nm or less.

  The transparent conductive substrate using the transparent conductive film is formed by forming any one of the above transparent conductive films on one or both sides of a transparent substrate selected from a glass plate, a quartz plate, a resin plate and a resin film. Features.

  In addition, the transparent conductive substrate is preferably formed by sequentially forming at least one gas barrier film and any one of the above transparent conductive films on one or both surfaces of a transparent substrate selected from a resin plate and a resin film. It is characterized by.

  In addition, the transparent conductive substrate preferably includes any one or more kinds of films selected from silicon nitride, silicon oxynitride, and silicon oxide as a gas barrier film.

The sintered compact target for producing a transparent conductive film of the present invention has a work function of 5.1 eV or more, and is mainly composed of Ga, In, and O in order to obtain a transparent conductive film having suitable optical characteristics and conductivity. Containing 49.1 atomic percent or more and 65 atomic percent or less of Ga with respect to all metal atoms, mainly composed of a GaInO ₃ phase of β-Ga ₂ O ₃ type structure and an In ₂ O ₃ phase of bixbite type structure, Sintered at 1350 ° C. in an oxygen stream and having an X-ray diffraction peak intensity ratio defined by the following formula (A) of 15% or less and a density of 5.8 g / cm ³ or more,
In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) × 100 [%] (A)
Furthermore, the specific resistance value is 9.0 × 10 ⁻¹ Ω · cm or less. Therefore, the sintered compact target for manufacturing the transparent conductive film of the present invention, the transparent conductive film manufactured using the sintered compact target of the present invention, and the transparent conductive base material on which the transparent conductive film is formed will continue to spread widely. It is useful for each application of the display device.

In addition, the transparent conductive film manufactured using the sintered compact target for manufacturing the transparent conductive film of the present invention is an amorphous oxide film transparent conductive film mainly composed of Ga, In and O, and contains all of Ga. 49.1% or more and 65 atomic% or less with respect to the metal atom, the work function is 5.1 eV or more, the refractive index is 1.65 to 1.85 at a wavelength of 633 nm, and the specific resistance is It is a transparent conductive film having a thickness of 1.0 × 10 ^{−2 to} 1.0 × 10 ⁺⁸ Ω · cm.
That is, the transparent conductive film, which has not been obtained conventionally, has a high work function and a low refractive index in the visible region, and is excellent in that it is difficult to crack unique to an amorphous film and has a low arithmetic average height. It has both features. In addition, the film can be formed in the vicinity of room temperature, and the utility value is high industrially.

By the amount of Ga of the sintered body obtained by ICP emission spectroscopic analysis of the sintered body, the density calculated by the Archimedes method using pure water, the specific resistance measured by the four probe method, and X-ray diffraction (using CuKα rays) resulting in ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) peak intensity ratio is a table summarizing. It is the figure which showed the X-ray-diffraction pattern by the CuK alpha ray of the sintered compact of sintering temperature 1350 degreeC. It is an X-ray diffraction pattern of the thin film formed into a film using the target sintered at 1350 degreeC.

Next, although embodiment of this invention is shown, this invention is not limited to the following example.
The sintered compact target for producing a transparent conductive film of the present invention is mainly composed of Ga, In and O, contains Ga of 49.1 atomic% or more and 65 atomic% or less with respect to all metal atoms, and is mainly β-Ga _2. X-ray diffraction peak intensity composed of an O ₃ type GaInO ₃ phase and a bixbite type In ₂ O ₃ phase, sintered at 1350 ° C. in an oxygen stream, and defined by the following formula (A) The ratio is 15% or less, and the density is 5.8 g / cm ³ or more.
In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) × 100 [%] (A)

Moreover, the sintered compact target for producing a transparent conductive film of the present invention preferably has a specific resistance value of 9.0 × 10 ⁻¹ Ω · cm or less.

Here, the In ₂ O ₃ phase may be one in which oxygen deficiency is introduced, or a portion in which Ga is substituted for In. Further, the Ga / In atomic ratio may be slightly deviated from the stoichiometric composition, and the β-GaInO ₃ phase may be introduced with oxygen deficiency.
Outside the Ga composition range as described above, when the formed amorphous film has the same composition as the target, a high work function and a low refractive index cannot be realized. However, this is not the case when the target composition and the amorphous composition are not substantially equal depending on the film formation conditions.

The target of the present invention preferably has a smaller proportion of the In ₂ O ₃ phase. That is, the peak intensity ratio (area intensity ratio of diffraction peaks) of the (111) reflection of the β-GaInO ₃ phase and the (400) reflection of the In ₂ O ₃ phase in X-ray diffraction defined by the above formula (A) is It is preferably 45% or less. Furthermore, it is more preferable that it is 15% or less. When this peak intensity ratio exceeds 45%, even within the above composition range, the influence of the In ₂ O ₃ phase exhibiting a high refractive index of 2.0 to 2.2 becomes large, and the peak intensity ratio is as high as 5.1 eV or higher. A work function and a low refractive index of 1.65 or more and 1.85 or less cannot be realized.

Note that according to JCPDS card (ASTM card), the main peak of the beta-GaInO _3-phase and In ₂ O ₃ phase in X-ray diffraction, respectively (111) depending on the reflection and (222) reflections, In ₂ O ₃ phase Since the (222) reflection overlaps with the β-GaInO ₃ phase (002) reflection, the In ₂ O ₃ phase is evaluated with the next highest intensity (400) reflection.

Non-Patent Document 3 describes that an unreacted In ₂ O ₃ phase tends to remain particularly when a β-GaInO ₃ phase of Ga ₂ O ₃ : In ₂ O ₃ = 1: 1 is prepared. Yes. Since the In ₂ O ₃ phase has a low work function of 4.8 to 4.9 eV and a high refractive index of 2.0 to 2.2, when it is included in a sintered body target for producing a transparent conductive film, As a result, the work function of the film formed by using this becomes low, and the refractive index becomes high.

In the present invention, the raw material powder, the mixing conditions, and the sintering conditions were examined in order to suppress the formation of this unreacted In ₂ O ₃ phase in the sintered body target for producing the transparent conductive film. .
That is, when the atmospheric pressure sintering method is used, the raw material powder preferably has a purity of 3N or more, and the average particle size is preferably adjusted to 3 μm or less by crushing. It is preferable to mix the blended powder, the organic binder, the dispersant, and the like until a uniform state is obtained. For the molding, it is preferable to use an isostatic press capable of applying a uniform stress. The sintering temperature is preferably 1250 ° C. or more and 1400 ° C. or less, and the sintering time is preferably 12 hours or more, and more preferably sintered in an oxygen stream. In addition, said conditions are conditions preferable in the case of atmospheric pressure sintering, and when using pressure sintering methods, such as a hot press method, it is not the limitation.

Further, in the transparent conductive film manufacturing process of manufacturing sintered target of the present invention, by including the average particle diameter and sintering conditions of the disintegrated raw material powder differs from GaInO ₃ phase (Ga, In) ₂ O ₃ In some cases, a Ga ₂ O ₃ phase that is a phase or an inevitable generation phase is generated. The sintered target of the present invention mainly comprises a β-GaInO ₃ phase and an In ₂ O ₃ phase, but the above (Ga, In) ₂ O ₃ phase is defined by the following formula (B). If the intensity ratio is 70% or less, it may be contained.
Reflection by (Ga, In) ₂ O ₃ phase (2θ = around 28 °) / {In ₂ O ₃ phase (400)
+ Β-GaInO ₃ phase (111)} × 100 [%] (B)
Here, it is described as reflection by the (Ga, In) ₂ O ₃ phase (around 2θ = 28 °). According to the JCPDS card (ASTM card), it is a crystal of the (Ga, In) ₂ O ₃ phase. This is because the structure and the plane index are not specified, and only the plane spacing and the X-ray diffraction relative intensity ratio are specified.

Even when the sintered body target for producing a transparent conductive film containing (Ga, In) ₂ O ₃ phase exceeding 70% in the above formula (B) is used, the formed amorphous transparent conductive film is 5.1 eV or more. A high work function and a low refractive index of 1.65 or more and 1.85 or less. However, since the sintered body of (Ga, In) ₂ O ₃ single phase exhibits a high specific resistance of about 5 to 10 Ω · cm, the amount exceeding 70% in the above formula in the sintered body target for producing a transparent conductive film When the (Ga, In) ₂ O ₃ phase is contained, the film forming rate is lowered, and the productivity is deteriorated. Therefore, the content of the (Ga, In) ₂ O ₃ phase in the above formula is preferably 70% or less. In addition, inevitable impurities such as unreacted substances such as Ga ₂ O ₃ may be included as long as no peak is observed by X-ray diffraction.

Moreover, it is preferable that the sintered compact target for transparent conductive film manufacture of this invention is a density of a sintered compact is 5.8 g / cm < ³ > or more. When the density of the sintered body is less than 5.8 g / cm ³ , the frequency of occurrence of abnormal discharge in sputtering increases, and as a result, a high-quality low refractive index amorphous transparent conductive film cannot be obtained.

In addition, the sintered compact target for producing a transparent conductive film of the present invention preferably has a specific resistance value of 9.0 × 10 ⁻¹ Ω · cm or less. When the specific resistance value exceeds the above value, even if DC magnetron sputtering is possible, the film formation rate is reduced, and thus the productivity is lowered.

When film formation is performed using a sintered compact target for producing a transparent conductive film that does not satisfy these conditions, an amorphous transparent conductive film having a high work function exceeding 5.0 eV cannot be obtained. Furthermore, as described in Patent Document 6 and Non-Patent Document 2, only an amorphous film having a high refractive index exceeding 1.85 can be obtained except for a Ga ₂ O ₃ film that hardly exhibits conductivity. Moreover, productivity is also lowered.

  Furthermore, when the refractive index at a wavelength of 633 nm exceeds 1.85, the reflectance increases and the light transmittance decreases. Further, it is preferable that the refractive index is less than 1.65 because it can be said that the light transmittance is excellent, but such a low refractive index is not obtained in the present invention.

  The transparent conductive film manufactured using the sintered compact target for manufacturing the transparent conductive film of the present invention is mainly composed of Ga, In and O, is an amorphous oxide film transparent conductive film, and Ga is an all-metal atom. It is preferable to contain 49.1 atomic% or more and 65 atomic% or less. If the Ga content is less than 49.1 atomic%, the work function is low and the refractive index is high, which is equivalent to the conventional transparent conductive film. On the other hand, if the Ga content exceeds 65 atomic%, sufficient conductivity necessary for use as a transparent electrode cannot be obtained.

Further, the work function and the refractive index are influenced by the constituent phase of the sintered compact target that is the thin film forming source even if they have the same composition. When the In ₂ O ₃ phase (400) peak intensity ratio represented by the formula (A) is higher than 45%, the work function of the transparent conductive film is lower than 5.1 eV, and the refractive index exceeds 1.85. Therefore, it becomes equivalent to a conventional transparent conductive film.

The specific resistance value depends on the amount of oxygen introduced into the amorphous film during film formation, but the specific resistance value is in the range of 1.0 × 10 ^{−2 to} 1.0 × 10 ⁺⁸ Ω · cm. Control is possible. Furthermore, if a large amount of oxygen is introduced, an insulating film can be obtained. If it is the said range, a wide range application, such as a transparent electrode and an antistatic film, is possible, but if it removes from this range, it will be restricted to a special use.

  The transparent conductive film preferably has an arithmetic average height (Ra) of 2.0 nm or less. Here, the arithmetic average height (Ra) is based on the definition of JIS B0601-2001. If the arithmetic average height (Ra) exceeds 2.0 nm, it is not preferable in applications where flatness of the film surface is required, such as organic EL.

Examples of a method for forming the transparent conductive film include a sputtering method and an ion plating method. Considering reasons such as productivity, the magnetron sputtering method using DC plasma (DC magnetron sputtering method) is preferable.
In the case of the ion plating method, a transparent conductive film can be obtained by using, as an evaporation source, pellets obtained by the same manufacturing method as the sintered conductive target for manufacturing a transparent conductive film of the present invention.

  The substrate is preferably a transparent substrate selected from a glass plate, a quartz plate, a resin plate, and a resin film, but is not limited to this as long as it is a substrate for a display device.

  When producing a transparent conductive film by using a sputtering method or an ion plating method, it is important to use the target of the present invention in order to obtain an amorphous transparent conductive film having a high work function and a low refractive index. .

  A transparent conductive base material forms the transparent conductive film manufactured using the sintered compact target for transparent conductive film manufacture of this invention on the single side | surface or both surfaces of a transparent substrate.

  When the display device requires gas barrier properties, it is preferable to form at least one gas barrier film between the transparent substrate and the transparent conductive film in order to impart a gas barrier function to the transparent conductive substrate. The gas barrier film preferably contains one or more of silicon nitride, silicon oxynitride, and silicon oxide. Further, the gas barrier film is not limited to an inorganic film, and may include an organic film.

  The transparent conductive film has a work function exceeding 5.1 eV and a low refractive index of 1.65 or more and 1.85 or less at a wavelength of 633 nm. Applications other than electrodes are also possible. For example, the present invention can be applied as an antistatic film that may have a high electric resistance or a simple optical thin film that may be an insulating film.

(Example 2 and Comparative Examples 8-9)
4N purity Ga ₂ O ₃ powder and In ₂ O ₃ powder were each adjusted by ball milling to an average particle size of 3 μm or less. Then, it mix | blended so that Ga represented by Ga / (Ga + In) might be 50 atomic%, and it mixed by the ball mill for 48 hours with the organic binder, the dispersing agent, and the plasticizer, and produced the slurry. Subsequently, the obtained slurry was spray-dried by a spray dryer to produce a granulated powder.

  Next, the obtained granulated powder was put in a rubber mold, and a molded body having a thickness of about 191 mmφ and a thickness of about 6 mm was produced by an isostatic press. The molded bodies obtained in the same manner were sintered under normal pressure at 1250 ° C. (Comparative Example 8), 1350 ° C. (Example 2) and 1400 ° C. (Comparative Example 9) for 20 hours in an oxygen stream. . Each sintered body was subjected to circumferential processing and surface grinding processing to obtain a shape with a diameter of about 6 inches and a thickness of about 5 mm.

Density measured by the Archimedes method (using a high-precision automatic hydrometer manufactured by Toyo Seiki Seisakusho) using pure water and the Ga content of the sintered body obtained by ICP emission spectroscopic analysis (using SPS4000 manufactured by Seiko Instruments), four-terminal method ( In ₂ O ₃ phase (400) / β-GaInO ₃ phase obtained by specific resistance measured by LORESTA-IP manufactured by Mitsubishi Chemical Co., Ltd. and MCP-T250) and X-ray diffraction (manufactured by Rigaku Corporation, using CuKα ray) The (111) peak intensity ratio is summarized in the table shown in FIG. FIG. 2 shows an X-ray diffraction pattern of the sintered body obtained in Example 2 at a sintering temperature of 1350 ° C. by CuKα rays.

Next, these sintered bodies were bonded to a cooled copper plate and used as a sintered body target for producing a transparent conductive film. As the sputtering apparatus, SPEC-530H made by Anelva was used. As a substrate, a Corning 7059 substrate and a Si substrate for refractive index measurement (manufactured by Komatsu Electronic Metal) were used and arranged so as to be parallel to the target surface. The distance between the substrate and the target was 60 mm. The sputtering gas was a mixed gas composed of Ar and O ₂ , the oxygen ratio was set to 1.5%, and the total gas pressure was set to 0.5 Pa. The input power was 200W. Room temperature film formation was performed by DC magnetron sputtering under the above conditions. The discharge was stable and no abnormalities such as arc discharge were found. The film formation time was adjusted to obtain a 200 nm thick transparent conductive film.

  FIG. 3 shows an X-ray diffraction pattern of a thin film formed using the target sintered at 1350 ° C. in Example 2. There was no clear peak, and it was confirmed to be an amorphous film. Films formed with other targets were similarly amorphous. FIG. 1 shows the composition, refractive index (using an ellipsometer: DHA-XA manufactured by Mizoji Optical Co., Ltd.), specific resistance, arithmetic average height (Ra) (atom) of a film formed on each target. Measurement results of an atomic force microscope: using Nanoscope III manufactured by Digital Instruments, and a work function (using photoelectron spectrometer: AC-2 manufactured by Riken Keiki Co., Ltd.) are shown.

(Examples 5 to 6 and Comparative Example 10)
The amount of Ga represented by Ga / (Ga + In) was changed to 49.5 (Comparative Example 10), 55 (Example 5), 65 (Example 6) atomic%, and under the same conditions as in Example 2. A target was prepared and a film was formed.
As in Example 2, abnormal discharge was not confirmed. FIG. 1 shows the results of examining the target and the thin film in the same manner as in Example 2. Further, when the structure of the obtained thin film was examined by X-ray diffraction, it was found to be an amorphous film as in Example 2.

(Example 7)
The substrate temperature was changed to 200 ° C., and the same film formation as in Example 2 was performed. Despite raising the substrate temperature to 200 ° C., it was confirmed by X-ray diffraction that the obtained film was an amorphous film as in Examples 2 and 5-6. FIG. 1 shows the characteristics of this film.

(Examples 8 and 9)
The same film formation as in Example 6 was performed by changing the oxygen ratio in the sputtering gas to 3.0% and 5.0%. As in Examples 2 and 5 to 7, it was confirmed by X-ray diffraction that the obtained film was an amorphous film. FIG. 1 shows the characteristics of this film.

(Example 10)
A film having a thickness of 50 nm was formed on a PET film having a thickness of 125 μm with a single-side hard coat at room temperature under the same conditions as in Example 2, and evaluated by a pen sliding durability test. A polyacetal pen (tip shape: 0.8 mmR) was subjected to a load of 5.0 N, and a linear sliding test was conducted 100,000 times (50,000 reciprocations) on the PET film substrate with the transparent conductive film. The sliding distance at this time was 30 mm, and the sliding speed was 60 mm / second. After this sliding durability test, it was observed visually and with a stereomicroscope, but no whitening of the sliding portion, peeling of the film, and cracking were observed.

(Comparative Examples 1-3)
The sintered compact target for transparent conductive film manufacture was produced on the same conditions as Example 2 except having changed Ga represented by Ga / (Ga + In) into 40.0, 49.0, and 66 atomic%. FIG. 1 shows the density, specific resistance, and peak intensity ratio of the In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) obtained by X-ray diffraction.
Next, a film was formed in the same manner as in Example 2 using these sintered compact targets. No abnormal discharge occurred during film formation. When the structures of the obtained films were examined by X-ray diffraction, they were all amorphous. FIG. 1 shows the characteristics of these films.

(Comparative Examples 4 and 5)
The sintered compact target similar to Example 2 was produced by changing the sintering temperature to 1100 and 1200 ° C. FIG. 1 shows the relative density and specific resistance of the sintered body. When structural analysis was performed by X-ray diffraction, when the sintering temperature was 1100 ° C., the β-GaInO ₃ phase was hardly generated, and only the (Ga, In) ₂ O ₃ phase and the In ₂ O ₃ phase were present. It was generated. Therefore, the In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) peak intensity ratio could not be obtained. Note that the peak intensity of the In ₂ O ₃ phase (400) was higher than that in Example 2, and it was clear that a large amount of In ₂ O ₃ phase was generated. Also, the sintering temperature 1200 ° C, β-GaInO _{3 phase, (Ga, In) 2 O} 3 phase and three-phase In ₂ O ₃ phase was formed. FIG. 1 shows only the peak intensity ratio of 1200 ° C. In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111).
When a film was formed using a target having a sintering temperature of 1100 ° C., arc discharge occurred frequently during the film formation. Even when a target having a sintering temperature of 1200 ° C. was used, arc discharge occurred frequently, although not as much as 1100 ° C. That is, when using a target sintered at 1100 ° C. and 1200 ° C. and having a density of less than 5.8 g / cm ³ , arcing frequently occurs during sputter film formation, resulting in film breakage and film formation speed. There was a problem that stable film formation was not possible, such as problems such as large fluctuations. As a result of structural analysis by X-ray diffraction, all of the obtained films were amorphous films. FIG. 1 shows the characteristics of these films.

(Comparative Example 6)
Film formation was performed in the same manner as in Examples 8 and 9, except that the oxygen ratio in the sputtering gas was changed to 6.0%. As in Examples 8 and 9, it was confirmed by X-ray diffraction that the obtained film was an amorphous film. FIG. 1 shows the characteristics of this film.

(Comparative Example 7)
A film was formed on the same substrate as in Example 10 at room temperature in the same manner as in Example 2, except that the oxygen ratio was changed to 2.0% using an ITO (10 wt% SnO ₂ ) target. When the surface of the film was observed by AFM (Atomic Force Microscope: Nanoscope III manufactured by Digital Instruments), a projection-like crystal phase of about 10 nm was observed in the amorphous material. The same linear sliding test as in Example 10 was performed on this ITO film-coated film substrate. After the test, when observed visually and with a stereomicroscope, whitening of the sliding portion and peeling and cracking of the film were observed.

"Evaluation"
From the results of Examples 2 to 5 to 9 in FIG. 1, the present invention is mainly composed of Ga, In, and O and contains Ga of 49.1 atomic% or more and 65 atomic% or less represented by Ga / (Ga + In). The characteristic of the transparent conductive film manufactured using the sintered compact target for transparent conductive film manufacture is understood. That is, the film had a work function as high as 5.1 eV or higher, a refractive index at a wavelength of 633 nm as low as 1.65 or more and 1.85 or less, and a specific resistance value of 9.0 × 10 ⁻¹ Ω · cm or less. Thus, the film surface having an arithmetic average height (Ra) of 2.0 nm or less is extremely flat and has a necessary and sufficient characteristic as a display device.

Similarly, from the results of Examples 2 to 5-9, the present invention is mainly composed of Ga, In and O and contains Ga of 49.1 atomic% or more and 65 atomic% or less represented by Ga / (Ga + In). The characteristic of the sintered compact target for transparent conductive film manufacture is understood. That is, the X-ray diffraction peak intensity ratio defined by the following formula (A) is 15% or less, the density is 5.8 g / cm ³ or more, and the specific resistance value is 9.0 × 10 ⁻¹ Ω · cm or less. And it has sufficient characteristics necessary to obtain the transparent conductive film.
In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) × 100 [%] (A)

In particular, when a room temperature film formation was performed from Examples 2 to 5-6 using a transparent conductive film production target having a density of 6.2 g / cm ³ or more, the work function was 5.2 eV or more, and It can be seen that the refractive index at a wavelength of 633 nm is in the range of 1.7 to 1.8.

  When the composition range of the transparent conductive film of the present invention in which Ga represented by Ga / (Ga + In) is 49.1 atomic% or more and 65 atomic% or less is deviated from Comparative Examples 1 to 3, the original characteristics are not exhibited. I understand that. That is, when Ga is less than 49.1 atomic% or exceeds 65 atomic%, the work function is less than 5.1 eV, and the refractive index exceeds 1.85.

  Moreover, from Comparative Examples 4 and 5, when the X-ray peak intensity ratio of the sintered body target for transparent conductive film production defined above exceeds 45%, the film produced using the target falls within the above composition range. Even if it exists, a work function will be less than 5.1 eV and a refractive index will exceed 1.85.

When a film is formed by introducing excess oxygen from Comparative Example 6, the specific resistance value becomes high resistance exceeding the range of 1.0 × 10 ^{−2 to} 1.0 × 10 ⁺⁸ Ω · cm. . However, this film is useful when it does not require electrical conductivity and is used only in optical applications.

  From the comparison between Example 10 and Comparative Example 7, the transparent conductive film produced using the sintered conductive target for producing the transparent conductive film of the present invention has a mechanical action from the outside as compared with the conventional ITO film. On the other hand, it was proved that the film hardly deteriorates. That is, it became clear that the transparent conductive film produced using the sintered compact target for manufacturing a transparent conductive film according to the present invention has sufficient characteristics necessary for a display device such as a touch panel or electronic paper.

Claims (3)

It is mainly composed of Ga, In, and O, contains 49.1 atomic% or more and 65 atomic% or less of Ga with respect to all metal atoms, and mainly has a β-Ga ₂ O ₃ type GaInO ₃ phase and a bixbite type structure. It is composed of an In ₂ O ₃ phase , is sintered under atmospheric pressure at 1350 ° C. in an oxygen stream, has an X-ray diffraction peak intensity ratio defined by the following formula (A) of 15% or less, and a density of 5.8 g / A sintered compact target for producing a transparent conductive film, characterized in that it is cm ³ or more.
In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) × 100 [%] (A) It is mainly composed of Ga, In, and O, contains 49.1 atomic% or more and 65 atomic% or less of Ga with respect to all metal atoms, and mainly has a β-Ga ₂ O ₃ type GaInO ₃ phase and a bixbite type structure. It is composed of an In ₂ O ₃ phase and a (Ga, In) ₂ O ₃ phase , is sintered at 1350 ° C. in an oxygen stream, and has an X-ray diffraction peak intensity ratio defined by the following formula (A) of 15%. The X-ray diffraction peak intensity ratio defined by the following formula (B) is 70% or less, and the density is 5.8 g / cm ³ or more. Consolidation target.
In ₂ O ₃ phase (400) / β-GaInO ₃ phase (111) × 100 [%] (A)

Reflection by (Ga, In) ₂ O ₃ phase (2θ = around 28 °) / {In ₂ O ₃ phase (400)
+ Β-GaInO ₃ phase (111)} × 100 [%] (B) The sintered compact target for producing a transparent conductive film according to claim 1, wherein the specific resistance value is 9.0 × 10 ⁻¹ Ω · cm or less.

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