Transparent conductive film, method for manufacturing a transparent conductive film, transparent conductive component, electronic display device, and solar cell

Abstract

Provided is a transparent conductive film containing an alkali tungsten bronze. In a powder X-ray diffraction pattern, the alkali tungsten bronze shows a hexagonal crystal pattern, and there is no orthorhombic, trigonal, or pyrochlore phase shift.

Description

[Technical Field]

[0001] The present invention relates to a transparent conductive film, a method for manufacturing a transparent conductive film, a transparent conductive member, an electronic display device, and a solar cell. [Background technology]

[0002] Transparent conductive films are used in applications such as liquid crystal display elements, transparent electrodes for solar cells, infrared absorption and reflection films, and electromagnetic wave shielding films. Liquid crystal display elements, in particular, are being actively adopted in office automation equipment such as personal computers and word processors, and the demand for transparent electrodes is increasing accordingly. For transparent electrodes used in liquid crystal display elements, ITO (Indium-Tin-Oxide), which is indium oxide doped with several mole percent tin, is mainly used because it contains many conduction electrons (free electrons) in the material, has high conductivity, and is relatively easy to pattern by etching (see Patent Documents 1 and 2, and Non-Patent Document 1).

[0003] In2O3, the base material for ITO, is an oxide semiconductor that exhibits conductivity by supplying carrier electrons through the introduction of oxygen vacancies in its crystal structure. It is believed that adding Sn to In2O3 further increases the number of carrier electrons by replacing the trivalent In sites with tetravalent Sn, resulting in high conductivity.

[0004] Incidentally, recent liquid crystal display devices are trending toward larger area, more pixels, higher resolution, and lower costs. In order to obtain high-quality liquid crystal display elements without display defects, the performance of transparent electrodes, particularly the reduction of visible light transmittance and the surface resistance of the film (also called sheet resistance), and the improvement of visible light transmittance are desired, making cost reduction of the transparent electrodes themselves an extremely important issue.

[0005] ITO conductive films offer excellent visible light transmittance and surface resistance, but they are expensive due to the use of indium. Therefore, improvements in ITO deposition technology and sputtering targets have been pursued to enhance the properties of transparent conductive films and reduce costs. However, there are limitations to the properties of ITO, making it increasingly difficult to meet the more advanced needs of recent times.

[0006] One candidate for a transparent conductive material to replace ITO is zinc oxide (AZO, GZO) doped with several mole percent of Al or Ga. In AZO and GZO, carrier electrons are supplied by the substitution of divalent Zn sites with trivalent Al or Ga, resulting in a highly conductive transparent material. Because AZO and GZO can achieve transparency and conductivity close to that of ITO, they have been considered leading candidates for ITO replacement materials. However, AZO and GZO have drawbacks, such as narrow conditions for achieving conductivity and significantly inferior heat resistance and weather resistance compared to ITO (Non-Patent Literature 1).

[0007] Tin oxide is a material that has long been known as a transparent conductive material that can replace ITO. Because tin oxide has better chemical and thermal stability and visible light transmittance (visible light transparency) than ITO, it is used in electrodes for solar cells, etc. However, even when tin oxide has reduced resistivity by antimond doping or partial fluorine substitution of oxygen, its conductivity is considerably lower than ITO, and it is also inferior in etching properties. For this reason, tin oxide is not used as an electrode for displays (Non-Patent Literature 1).

[0008] As a novel candidate material for a transparent conductive material to replace ITO, the applicant has proposed a material with the general formula W y O z Tungsten oxides represented by (2.2 ≤ z / y ≤ 2.999), and the general formula M x W y O zA transparent conductive film of a composite tungsten oxide represented by has been proposed (see Patent Document 3). The M element of the composite tungsten oxide is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, other transition metals, etc., and satisfies 0.001≦x / y≦1 and 2.2≦z / y≦3.0.

[0009] Patent Document 3 also discloses a method for producing a transparent conductive film, wherein a solution containing a raw material compound of tungsten oxide and / or composite tungsten oxide and / or composite oxide is applied onto a substrate, followed by heat treatment in an atmosphere of reducing gas and / or inert gas to produce the transparent conductive film.

[0010] Patent Document 4 discloses a technique of an infrared shielding film using a composite tungsten oxide film formed by a sputtering method.

[0011] However, when the above-mentioned tungsten oxide or composite tungsten oxide conductive film is formed by a sputtering method, many of the films have extremely high electric resistance values, and the specific resistance is usually 10 2 Ωcm or more, and even the film with the lowest resistance value has a resistance value on the order of 10 -2 Ωcm. For this reason, transparent conductive films of tungsten oxide and composite tungsten oxide formed by a sputtering method have overwhelmingly insufficient conductivity required for a transparent conductive film.

[0012] Cs having a hexagonal tungsten bronze structure 0.32 For WO3, a room temperature specific resistance of 5.5×10 -5 Ωcm has been reported for single crystals (Non-Patent Document 2). However, this potential high conductivity has not been realized as a dry thin film.

[0013] As described above, transparent conductive films of tungsten oxide and composite tungsten oxide have been proposed as one of the candidates for transparent conductive films replacing ITO. However, in general dry continuous film production methods including the sputtering method, the specific resistance is 5.2×10 -2No transparent conductive film with high conductivity below Ωcm had been found.

[0014] Therefore, a new transparent conductive film with high conductivity was needed. [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] Japanese Patent Application Publication No. 2003-249125 [Patent Document 2] Japanese Patent Application Publication No. 2004-026554 [Patent Document 3] Japanese Patent Publication No. 2006-096656 [Patent Document 4] Japanese Patent Publication No. 2019-196521 [Non-patent literature]

[0016] [Non-Patent Document 1] Japan Society for the Promotion of Science (ed.), "Technology of Transparent Conductive Films," Ohmsha, 2006 revised 2nd edition (pp. 153-173). [Non-Patent Document 2] MR Skokan, WG Moulton, and RC Morris, Normal and superconducting properties of CsxWO3, Phys. Rev. B 20 (1979) 3670 -3677 [Non-Patent Document 3] S. Oshio, M. Yamamoto, J. Kuwata, and T. Matsuoka, Interaction of reactively sputtered TaOx thin films with In-Sn-O thin films and properties of TaOx thin films, J. Appl. Phys. 71, 3471 (1992). [Overview of the project] [Problems that the invention aims to solve]

[0017] In view of the problems of the prior art described above, one aspect of the present invention aims to provide a transparent conductive film with excellent conductivity. [Means for solving the problem]

[0018] In one aspect of the present invention, the present invention includes alkali tungsten bronze. 、 The aforementioned alkali tungsten bronze exhibits a hexagonal pattern in powder X-ray diffraction patterns, and does not exhibit orthorhombic, trigonal, or pyrochlore phase shifts. Ku, The aforementioned alkali tungsten bronze is subject to general formula A x W y O z (0.2 ≤ x / y ≤ 0.5, 2.5 ≤ z / y ≤ 3.0, element A is one or more alkali metal elements selected from K, Rb, and Cs) The alkali tungsten bronze has a lattice constant of 7.54 Å or less along the hexagonal c axis when element A is K, 7.58 Å or less when element A is Rb, and 7.64 Å or less when element A is Cs. To provide a transparent conductive film. [Effects of the Invention]

[0019] One aspect of the present invention is that it is possible to provide a transparent conductive film with excellent conductivity. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 shows the powder X-ray diffraction pattern of the transparent conductive film obtained in Example 1. [Figure 2] Figure 2 shows the powder X-ray diffraction pattern of the film obtained in Comparative Example 3. [Modes for carrying out the invention]

[0021] Specific examples of a transparent conductive film, a method for manufacturing a transparent conductive film, a transparent conductive member, an electronic display device, and a solar cell according to one embodiment of this disclosure (hereinafter referred to as "this embodiment") will be described below with reference to the drawings. However, the present invention is not limited to these examples and is intended to be shown in the claims, with all modifications within the meaning and scope equivalent to the claims being included.

[0022] Note that in Miller indices, negative indices are supposed to have a bar (-) above the number, but in the following explanation, the negative sign (-) is placed before the number. When an indice has two digits, a comma "," is placed between the numbers of the indices. Also, the subscripts H for hexagonal, O for orthorhombic, R for trigonal, and P for pyrochlore phase. Two planes whose reflections overlap at the same diffraction angle are indicated by a " / " between the Miller indices representing each plane. [Transparent conductive film] The inventors of this invention focused on tungsten bronze, a material that generates conduction electrons by reducing the oxygen content and adding cations, utilizing the skeletal structure of tungsten trioxide, a wide-bandgap material that transmits light in the visible light region, as a material for transparent conductive films. As a result of diligent research, they predicted that among tungsten bronzes, alkali tungsten bronze (alkali composite tungsten oxide), which has a hexagonal crystal structure as a composite tungsten oxide, has high visible light transmittance and is the most promising as a transparent conductive film.

[0023] However, according to the inventors' research, when a film was dry-deposited using a film deposition source such as a sputtering target containing alkali metal elements and tungsten under conventional conditions, the formed film was often amorphous. Even when crystallized by heat treatment, it did not form a hexagonal tungsten bronze structure. Similarly, even when crystallization occurred immediately after deposition by raising the substrate temperature, it did not form a hexagonal tungsten bronze structure. Furthermore, although the formed film had high visible light transmittance, it did not possess the conductivity required for a transparent conductive film.

[0024] Analysis of the structure of the thin film deposited by the dry deposition method described above revealed that the thin film is a polytungstate in which water, oxygen, OH ions, etc., partially penetrate the voids of the orthorhombic, trigonal, or cubic pyrochlore structure. In other words, it was found that the alkali composite tungsten oxide thin film deposited by the dry deposition method described above does not have the usual hexagonal tungsten bronze structure.

[0025] Conventionally, when measuring the powder X-ray diffraction pattern of alkali-composite tungsten oxide thin films, it was observed to belong to a hexagonal pattern. However, in the powder X-ray diffraction patterns of alkali-composite tungsten oxide thin films, diffraction patterns that are slightly shifted towards orthorhombic, trigonal, or pyrochlore phases are also observed to belong to a hexagonal pattern.

[0026] The orthorhombic crystal structure described above is one in which stacking faults occur on the hexagonal prism plane, and the structure in which defects are regularly inserted is called orthorhombic Cs4W. 11 O 35 The trigonal and cubic pyrochlore phases are formed when stacking faults occur at the hexagonal base plane, and the trigonal Cs6W is a structure in which defects are regularly inserted. 11 O 36 or trigonal Cs 8.5 W 15 O 48 , pyrochlore phase (Cs2O) 0.44 The result is W2O6.

[0027] In typical hexagonal tungsten bronze films, the maximum intensity of the powder X-ray diffraction pattern is around the diffraction angle 2θ = 27.5° (20-20). H Diffraction peaks and (10-12) H Diffraction peaks appear. However, in many actual thin films, detailed observation of the pattern reveals that weak diffraction lines originating from orthorhombic, trigonal, or cubic pyrochlore phases are interspersed on the low-angle and / or high-angle sides of these two peaks. That is, hexagonal Cs 0.32 In WO3, surface defects are prone to occur on the basal surface and prism surface. And, in relation to surface defects on the prism surface, orthorhombic Cs4W 11 O 35However, trigonal Cs6W is associated with surface defects on the base. 11 O 36 Cs 8.5 W 15 O 48 , pyrochlore phase (Cs2O) 0.44 W2O6 appears.

[0028] Figures 1 and 2 show the main diffraction peaks from 2θ = 25° to 35°. The top row of Figure 1 shows the powder X-ray diffraction pattern of the hexagonal tungsten bronze film obtained in Example 1, which will be described later.

[0029] Figures (A) to (C) in Figure 1 show data from a database of powder X-ray diffraction patterns. Figure (A) in Figure 1 shows hexagonal Cs 0.32 (B) of WO3 is orthorhombic Cs4W 11 O 35 (C) is trigonal Cs6W 11 O 36 This will be the profile.

[0030] Furthermore, the top row of Figure 2 shows the powder X-ray diffraction pattern of the pyrochlore-shifted film obtained in Comparative Example 3, which will be described later. (A) in Figure 2 represents hexagonal Cs 0.32 In WO3, (B) is the pyrochlore phase (Cs2O). 0.44 This will be the W2O6 profile.

[0031] Hexagonal orthorhombic Cs4W 11 O 35 If shifting in the direction of (0,16,0), then O (480) O (10-12) H (20-20) H Increase the peak width. Also, (20-20) H (252) on the lower angle side O (082) O (232) O This causes weak peaks such as those mentioned above.

[0032] Hexagonal crystal structure is trigonal (Cs6W) 11 O 36If shifting in the direction of (024) R , / (1,1,18) R (0,2,10) R / (0,1,32) R (202) R (0,0,36) R The diffraction line is (20-20) H It appears weakly on the higher angle side.

[0033] Hexagonal crystal structure transforms into cubic pyrochlore phase (Cs2O) 0.44 If the shift is in the direction of W2O6, (311) P , (222) P The weak diffraction line is (20-20) H It appears on the higher angle side.

[0034] However, the intensity distribution and location of these excess diffraction lines may differ from the location and intensity of the diffraction lines for the orthorhombic, trigonal, and pyrochlore phases. This suggests that the orthorhombic, trigonal, and pyrochlore phases, which appear to be mixed within the hexagonal crystal, are not simply a mixture of separate crystalline phases, but rather that the powder X-ray diffraction pattern is altered by changes in the insertion planes and amounts of stacking faults within a single hexagonal crystal.

[0035] Thus, hexagonal crystal (10-12) H (20-20) H The inventors discovered that the fundamental cause of the phenomenon in which excess peaks originating from orthorhombic, trigonal, and pyrochlore phases appear at low and high angles of diffraction peaks is the presence of water introduced into the film during vacuum deposition.

[0036] In conventional dry deposition, a significant amount of moisture is present in the supply gases such as Ar and O2, as well as in the inner walls of the vacuum deposition chamber and the target itself. Therefore, during the surface condensation process of molecules and atoms flying onto the substrate during deposition, a large amount of water molecules and water-derived O2 are deposited. 2- , OH - H3O + H +Ions such as are incorporated into the membrane (Non-Patent Literature 3). Hydrogen derived from water combines with oxygen in the crystal, but Cs in the crystal + Alkali metal element ions and W 6+ Because of the competition, the charge neutrality condition causes W defects and Cs defects, which are defects of cationic elements, to be generated on the basal plane and prism plane of the hexagonal crystal. The inventors of this invention discovered that local ionic repulsion occurs on the planes where W defects and Cs defects are generated, causing a slight expansion of the interplanar spacing. Due to this expansion, the hexagonal symmetry of the crystal is broken, and it becomes orthorhombic, trigonal, or cubic.

[0037] Various molecules derived from water, such as O, OH, OH2, and H3O, remain in orthorhombic polytung states, trigonal polytung states, and alkali pyrochlore structures. They are then incorporated into relatively large voids within the crystal, such as hexagonal cavities, hexagonal windows, and pyrochlore cavities.

[0038] In the conventional dry deposition of composite tungsten oxide thin films under the usual conditions described above, the oxygen forming the WO6 octahedral framework is reduced by reducing heat treatment after film formation. Then, bound electrons W are introduced into the W cation by these oxygen vacancies. 5+ The material absorbs near-infrared light significantly due to hopping motion within the crystal. Research by the inventors of this invention has revealed that there are very few free electrons, or all of them are bound electrons, resulting in extremely low conductivity. Therefore, by removing the moisture during film formation, which is the cause of all these issues, the original hexagonal tungsten bronze can be obtained, and the electrical conductivity and near-infrared free electron reflection due to the abundant free electrons in this material can be acquired.

[0039] Therefore, the transparent conductive film of this embodiment contains alkali tungsten bronze, which exhibits a hexagonal pattern in powder X-ray diffraction patterns and can have a structure without orthorhombic, trigonal, or pyrochlore phase shifts. In other words, it is preferable that ions such as O, OH, OH2, and H3O are not incorporated into the transparent conductive film.

[0040] The alkali tungsten bronze in the transparent conductive film of this embodiment exhibits a hexagonal pattern in the powder X-ray diffraction pattern and has a structure without orthorhombic, trigonal, or pyrochlore phase shifts. As a result, the alkali tungsten bronze has the original hexagonal tungsten bronze structure. Consequently, it generates free electrons, making it possible to create a transparent conductive film with excellent conductivity.

[0041] Furthermore, the transparent conductive film of this embodiment may also be made from the above-mentioned alkali tungsten bronze. However, even in this case, this does not eliminate the possibility that the transparent conductive film of this embodiment may contain unavoidable impurities from the manufacturing process.

[0042] The transparent conductive film of this embodiment has an alkali tungsten bronze powder X-ray diffraction pattern that is hexagonal (10-12). H (20-20) H It is preferable that the diffraction peaks do not have excess peaks originating from orthorhombic, trigonal, or pyrochlore phases on the low-angle and high-angle sides.

[0043] Since excess peaks usually overlap with the peaks of hexagonal alkali tungsten bronze, it is preferable to perform peak separation before analysis.

[0044] Furthermore, the absence of excess peaks means that, after peak separation, for example, (252) described above... O (082) O (232) O (024) R / (1,1,18) R (0,2,10) R / (0,1,32) R (202) R (0,0,36) R (311) P , (222) P This means that it does not have peaks originating from such sources.

[0045] Still, the transparent conductive film of the present embodiment may contain a trace amount of heterogeneous phases, as long as it can be a transparent conductive film excellent in conductivity. Therefore, the criteria for determining an excessive peak are not particularly limited. For example, (20-20), which is the peak of maximum intensity of hexagonal alkali tungsten bronze H when the intensity of this peak is taken as 1, it can be determined that there is no excessive peak if the maximum intensity peak derived from the orthorhombic phase, trigonal phase, or pyrochlore phase is 0.25 or less.

[0046] The alkali tungsten bronze contained in the transparent conductive film of the present embodiment is represented by the general formula A x W y O z (0.2≦x / y≦0.5, 2.5≦z / y≦3.0, wherein element A is one or more alkali metal elements selected from K, Rb and Cs), which is preferable.

[0047] A part of element A may be substituted with an element other than alkali metal elements. Therefore, the alkali tungsten bronze contained in the transparent conductive film of the present embodiment is represented by the general formula A x W y O z (0.2≦x / y≦0.5, 2.5≦z / y≦3.0, wherein element A is one or more alkali metal elements selected from K, Rb and Cs), and a part of element A may be substituted with one or more elements selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al and Ga. In the case where the alkali tungsten bronze is substituted with the aforementioned substituting element, when said substituting element is referred to as substituting element M, the alkali tungsten bronze contained in the transparent conductive film of the present embodiment is represented by the general formula A x-a M a W y O z It can also be expressed as . In the above general formula, M is the aforementioned substituting element M, a corresponds to the substitution amount of element A by substituting element M, and satisfies 0≦a<x. Descriptions of element A, x, y, and z are omitted since they have already been described. The degree and proportion of substitution of element A with the aforementioned substituting elements are not particularly limited, and can be arbitrarily selected according to required properties and the like.

[0048] The lattice constant of the alkali tungsten bronze contained in the transparent conductive film of the present embodiment is not particularly limited. However, it is preferable that the lattice constant of the hexagonal c-axis is 7.54 Å or less when the element A is K, 7.58 Å or less when the element A is Rb, and 7.64 Å or less when the element A is Cs. More preferably, the lattice constant of the hexagonal c-axis is 7.49 Å or more and 7.54 Å or less when the element A is K, 7.51 Å or more and 7.58 Å or less when the element A is Rb, and 7.56 Å or more and 7.64 Å or less when the element A is Cs.

[0049] Setting the lattice constant of the alkali tungsten bronze within the above range means that the alkali tungsten bronze more reliably forms a hexagonal crystal structure, and does not have the aforementioned orthorhombic phase, trigonal phase or pyrochlore phase shift.

[0050] The film thickness of the transparent conductive film of the present embodiment is not particularly limited, but is preferably 30 nm or more and 1200 nm or less. As will be described later, the transparent conductive film of the present embodiment is a film obtained by sputtering film formation or the like, so there is no need to use a dispersant or a medium resin, and the film can be formed thinly and uniformly.

[0051] By setting the film thickness of the transparent conductive film of the present embodiment to 30 nm or more, a transparent conductive film having a particularly low resistance value can be obtained.

[0052] In addition, by setting the film thickness of the transparent conductive film of the present embodiment to 1200 nm or less, coloration of the film can be suppressed. Furthermore, the amount of target used during manufacturing can be reduced, the sputtering film formation time can be shortened, and productivity can be improved.

[0053] The specific resistance of the transparent conductive film of the present embodiment is, for example, 1.0×10 -2 Ωcm or less, more preferably 5.0×10 -3 Ωcm or less.

[0054] In addition, the transparent conductive film of the present embodiment preferably has a visible light transmittance of 50% or more. [Method for manufacturing transparent conductive film] Next, an example of the configuration for the manufacturing method of the transparent conductive film according to this embodiment will be described. According to the manufacturing method of the transparent conductive film according to this embodiment, the transparent conductive film described above can be manufactured. Therefore, some of the matters already explained will be omitted.

[0055] The method for manufacturing the transparent conductive film of this embodiment may include the following film formation step and heat treatment step.

[0056] In the film formation process, an unheated film containing the elements that make up alkali tungsten bronze can be formed on the surface of the substrate.

[0057] Furthermore, the heat treatment process allows for the heat treatment of untreated films.

[0058] Furthermore, it is preferable that the film formation process be carried out under film formation conditions that prevent moisture from penetrating the unheat-treated film.

[0059] The following describes each step. (1) Film formation process (1-1) About raw materials and targets In the film deposition process, an unheat-treated film can be deposited, for example, by a dry method. As raw materials used to deposit the unheat-treated film in the film deposition process, for example, a tungsten source and an alkali metal element source that can constitute alkali tungsten bronze can be used. Furthermore, a composite tungsten oxide of a specific composition can also be used as the raw material.

[0060] As a tungsten source, one or more types selected from tungsten and tungsten compounds can be used.

[0061] As the alkali metal element source, one or more selected from alkali metal element compounds and hydrates of alkali metal element compounds can be used.

[0062] For example, tungstic acid (H2WO4) is one of the commonly used raw materials for tungsten sources. Tungstic acid can be calcined to produce tungsten trioxide powder, which can then be used as a raw material for tungsten, or commercially available tungsten trioxide powder can be used.

[0063] As a tungsten source, tungsten oxides and composite tungsten oxides can also be used. As for the tungsten oxide, W y O z (wherein W is tungsten, O is oxygen, and 2.2 ≤ z / y ≤ 3.0) Tungsten oxide powder represented by this formula may also be used. Furthermore, as the composite tungsten oxide, for example, general formula A x W y O z (However, a powder of a composite tungsten oxide represented as follows: A is element A, W is tungsten, O is oxygen, 0.001≦x / y≦1, 2.2≦z / y≦3.0) can also be used.

[0064] As raw materials used to form an unheat-treated film, it is preferable to use a raw material prepared by mixing a tungsten source and an alkali metal element source so that the formed unheat-treated film has the desired composition.

[0065] As raw materials, for example, a mixed powder obtained by mixing tungstic acid (H2WO4) with one or more selected alkali metal element oxides and hydroxides, or a mixed powder obtained by mixing tungsten trioxide with one or more selected alkali metal element oxides and hydroxides, can be used. Alternatively, a mixed powder obtained by mixing a mixture of tungstic acid (H2WO4) and tungsten trioxide particles with one or more selected alkali metal element oxides and hydroxides, or a dried powder obtained by mixing one or more selected from tungstic acid (H2WO4) and tungsten trioxide powder with one or more selected from aqueous solutions of alkali metal element salts, colloidal solutions of metal oxides, and alkoxy solutions, and then calcining the dried powder in an inert gas atmosphere or a mixed gas atmosphere of inert gas and reducing gas, can also be used. When using a dried powder prepared by mixing one or more selected from tungstic acid (H2WO4) and tungsten trioxide powder with one or more selected from aqueous solutions of metal salts containing alkali metal elements, colloidal solutions of metal oxides, and alkoxy solutions, the ions used to form the salt are not particularly limited and include, for example, nitrate ions, sulfate ions, chloride ions, and carbonate ions. The drying temperature and time are not particularly limited.

[0066] As a raw material used to form an unheat-treated film, General formula A x W y O z When using the composite tungsten oxide represented by , as described above, element A can be one or more alkali metal elements selected from K, Rb, and Cs. However, element A may be partially substituted with one or more elements selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0067] Untreated films can be formed, for example, using pellets molded from the above raw materials or a sintered target.

[0068] In the film deposition process, vacuum deposition or sputtering is preferred as the method for depositing the unheat-treated film. More preferably, the method for depositing the unheat-treated film is sputtering using a sputtering target. In particular, DC sputtering, in which a DC voltage is applied to the target, is more preferred because it has a simple power supply configuration and excellent productivity.

[0069] When an unheat-treated film is deposited by sputtering, the sputtering target can contain alkali metal elements and tungsten that constitute alkali tungsten bronze.

[0070] In this case, it is preferable that the sputtering target is either a sputtering target made of alkali tungsten bronze or a sputtering target made of a precursor containing an alkali metal element and tungsten. For example, it is preferable to use a sputtering target made of the raw materials described above.

[0071] When using a sintered body of alkali tungsten bronze, i.e., a sintered body of alkali composite tungsten oxide, as a sputtering target, its composition is not particularly limited. However, the A / W ratio, which is the composition ratio of the amount of substance of element A (A) to tungsten (W) contained in the sputtering target, is preferably 0.2 or more and 0.7 or less, and more preferably 0.2 or more and 0.5 or less. This is because it is reflected in the A / W ratio, which is the amount of substance of element A to tungsten contained in the resulting unheat-treated film. For example, the polytungstate target described in Patent Document 4 above may be used. However, the crystal structure of the target is not particularly limited as it does not directly affect the crystal structure of the film.

[0072] The sputtering target preferably has a relative density of 70% or more and a resistivity of 1 Ω·cm or less. Such a sputtering target can be manufactured, for example, by hot-press sintering composite tungsten oxide powder in a vacuum or inert atmosphere. The sintered body manufactured in this way has the strength to withstand the machining in target manufacturing and the brazing temperature during bonding, and has the conductivity to enable DC sputtering.

[0073] The method for forming the unheat-treated film is not limited to using the above-mentioned composite tungsten oxide sintered body as the target. For example, an alkali metal oxide A x O z The target and W, a tungsten oxide. y O z An unheat-treated film may be formed by a binary sputtering method using a target. For example, by adjusting the sputtering applied power so that the A / W ratio, which is the composition ratio of the amount of substance of element A (A) to element W in the obtained unheat-treated film, is 0.2 or more and 0.7 or less, an unheat-treated film similar to that obtained when using a composite tungsten oxide target can be obtained. The above A / W ratio is preferably 0.2 or more and 0.5 or less.

[0074] Depending on the target manufacturing method, the target's conductivity may decrease, making DC sputtering using a DC power supply impossible. In this case, the problem can be solved by using a pulse power supply, MF (medium frequency) power supply, or RF (radio frequency) power supply. (1-2) Operation of the film deposition process There are no particular limitations on the substrate (substrate) on which the unheat-treated film is deposited, but glass is preferred. This is because glass is transparent in the visible light region and is less prone to degradation and deformation in the subsequent heat treatment process. When using glass as the substrate, the thickness of the glass is preferably 0.1 mm to 10 mm. However, there are no particular limitations as long as the thickness is one that is commonly used in architectural window glass, automotive glass, or display equipment.

[0075] In sputtering equipment used in the film deposition process, it is preferable to employ a load-lock type sputtering equipment in order to minimize the incorporation of moisture into the sputtered film, which is an unheat-treated film. Furthermore, while a turbomolecular pump can be used to exhaust the sputtering equipment, it is even more preferable to add means for coagulating and exhausting moisture, such as a cryocoil or cryopanel, in order to exhaust moisture more efficiently.

[0076] In the film formation process, it is preferable that the film formation conditions for the unheat-treated film are such that moisture does not penetrate into the unheat-treated film.

[0077] Specifically, when depositing an unheat-treated film, the moisture pressure inside the chamber is 1 × 10⁻⁶. -4 It is preferable that the moisture pressure be less than Pa. The moisture pressure referred to here means the moisture pressure in the atmosphere immediately before sputtering gas is introduced to deposit the unheat-treated film after exhausting the chamber.

[0078] Furthermore, in the film deposition process, the achievable vacuum level in the chamber where the unheat-treated film is deposited is 1 × 10⁻⁶. -4 It is preferable that the vacuum level be less than Pa. The ultimate vacuum level referred to here means the vacuum level achieved immediately after the chamber has been evacuated and before the sputtering gas is introduced to deposit the unheat-treated film.

[0079] To achieve the above-mentioned moisture pressure and ultimate vacuum, it is preferable to place the target and substrate inside the chamber and then exhaust the chamber using the turbomolecular pump or the like while heating the inside of the chamber. Alternatively, before placing the target and substrate inside the chamber, the inside of the chamber can be purged with a gas such as nitrogen gas while heating it to reduce any moisture adhering to the inner surface of the chamber (preheating and degassing). After the chamber reaches a sufficient ultimate vacuum, sputtering gas can be supplied into the chamber.

[0080] If necessary, dummy sputtering may be performed with the shutter between the substrate and the target closed to remove moisture adhering to the target, and then the chamber may be evacuated again. In this case, it is preferable that the moisture pressure and the ultimate vacuum level are satisfied even after evacuating after dummy sputtering. After evacuating, it is preferable to supply sputtering gas into the chamber and perform film deposition.

[0081] Therefore, it is preferable to perform a moisture removal step to remove moisture from inside the chamber before performing film formation in the film formation process.

[0082] In the moisture removal process, specifically, for example, a preheating degassing process in which moisture in the chamber is purged with an inert gas, a first exhaust process in which the chamber is evacuated after a target or substrate is placed inside the chamber, and a first sputtering gas supply process in which sputtering gas is supplied into the chamber can be carried out.

[0083] In the moisture removal process, a dummy sputtering process may be performed after the first sputtering gas supply process, if necessary, and a second exhaust process may be performed after the dummy sputtering process to exhaust the chamber again. Then, after the second exhaust process, a second sputtering gas supply process is performed to supply sputtering gas into the chamber, and then a film formation process is performed to form an unheat-treated film on the substrate surface.

[0084] In both the first and second exhaust processes, the ultimate vacuum level is 1 × 10⁻⁶. -4 It is preferable that the Pa level be less than Pa.

[0085] The sputtering gas used when forming the unheat-treated film is not particularly limited, but it is preferable to use, for example, argon gas or a mixture of argon gas and oxygen. Nitrogen gas can also be used instead of argon gas, but argon gas is more preferable.

[0086] Whether argon gas or a mixture of argon and oxygen gas is used when depositing an unheat-treated film depends on the subsequent heat treatment process.

[0087] When depositing an unheat-treated film using a mixed gas, a high oxygen concentration in the mixed gas can reduce the deposition rate and decrease productivity. Therefore, the oxygen concentration in the mixed gas is preferably less than 20% by volume, and more preferably between 3% and 10% by volume. The optimal oxygen concentration depends largely on the time it takes for oxygen to be incorporated into the unheat-treated sputtered film, i.e., the deposition rate, and can be selected according to the deposition conditions.

[0088] The purity of the sputtering gas used in the film deposition process, that is, for example, supplied in the second sputtering gas supply process described above, is preferably high. The purity of the sputtering gas is preferably 3N or higher, more preferably 4N or higher, and even more preferably 5N or higher. This is because increasing the purity of the sputtering gas suppresses the moisture pressure in the chamber during the film deposition process, thereby suppressing the inclusion of impurities such as moisture in the unheat-treated film.

[0089] As described above, when performing a dummy sputtering process, it is preferable that the sputtering gas in the dummy sputtering process, i.e., the sputtering gas supplied in the first sputtering gas supply process, also has high purity. The sputtering gas purity is preferably 3N or higher, more preferably 4N or higher, and even more preferably 5N or higher.

[0090] When using argon gas as the sputtering gas, it is preferable that the argon gas purity is 99.9% or higher, the oxygen concentration is less than 0.1%, and the hydrogen concentration is less than 1 ppm. More preferably, the argon gas purity is 99.999% or higher, the oxygen concentration is less than 0.2 ppm, and the hydrogen concentration is less than 0.5 ppm.

[0091] Films deposited by sputtering at room temperature without heating the substrate are usually amorphous, but it is acceptable if diffraction peaks based on crystal structure appear during X-ray diffraction analysis. This is because a hexagonal crystal structure will be formed again during the subsequent heat treatment process. (2) Heat treatment process Next, in the heat treatment process, the untreated film obtained in the film formation process can be heat-treated to form a hexagonal crystal structure. In the heat treatment process, the untreated film can be heat-treated at a temperature of 400°C to less than 1000°C in an atmosphere selected according to the oxygen content of the untreated film, specifically in an inert atmosphere, a reducing atmosphere, or an oxidizing atmosphere.

[0092] The purpose of the heat treatment can be, for example, the formation of hexagonal crystals and the reduction of octahedral oxygen. Therefore, in the heat treatment process, the untreated film may be heat-treated in, for example, an inert atmosphere or a reducing atmosphere at, for example, 400°C to less than 1000°C. By heat-treating the untreated film obtained in the film formation process, alkali tungsten bronze with a highly crystalline hexagonal structure can be formed.

[0093] In the heat treatment process, it is preferable to select an atmosphere according to the gas used during sputtering deposition so that the oxygen concentration of the resulting film is within an appropriate range. Either the deposition process or the heat treatment process may be carried out in an atmosphere containing oxygen.

[0094] When a film is formed using a mixed gas of argon and oxygen as the sputtering gas in the film deposition process, the heat treatment of the unheated film in the heat treatment process is preferably carried out in an inert gas atmosphere or a reducing atmosphere at a temperature of 400°C to less than 1000°C, and more preferably at a temperature of 400°C to 950°C. As the inert gas atmosphere or reducing atmosphere, nitrogen gas, argon gas, a mixed gas of hydrogen and nitrogen, a mixed gas of hydrogen and argon, etc., can be used.

[0095] If the film deposition process is carried out in an oxygen-containing atmosphere, and the heat treatment process is performed in an oxidizing atmosphere such as air or oxygen, the oxidation of the untreated film may proceed excessively. As a result, the alkali tungsten bronze contained in the resulting film may have reduced oxygen vacancies, altering the crystal structure and resulting in an orthorhombic crystal with many alkali metal element vacancies such as W vacancies and Cs vacancies. This can lead to an insulator with deficient conduction electrons and potentially low conductivity.

[0096] As mentioned above, the heat treatment temperature is preferably between 400°C and 1000°C. By setting the heat treatment temperature to 400°C or higher, the alkali tungsten bronze contained in the transparent conductive film can be crystallized and various defects can be suppressed. As a result, a transparent conductive film with an appropriate electronic structure and particularly excellent conductivity can be obtained.

[0097] Furthermore, by keeping the heat treatment temperature below 1000°C, the reaction between the transparent conductive film and the substrate can be suppressed, thereby preventing deformation of the substrate and peeling of the transparent conductive film.

[0098] Since the formation of hexagonal crystals and the reduction of oxygen proceed rapidly, the heat treatment time is not particularly limited, but it can be, for example, between 10 minutes and 60 minutes.

[0099] On the other hand, when a film is deposited using only argon gas as the sputtering gas in the film deposition process, the oxygen concentration of the unheat-treated film is considered to be moderate or insufficient.

[0100] Therefore, conductivity can be obtained even when heat treatment is performed with an inert gas such as nitrogen gas that does not contain oxygen. Heat treatment with an inert gas such as nitrogen gas that does not contain oxygen allows conductivity to be obtained over a wide temperature range. In this case, the heat treatment process may also be performed in an oxidizing atmosphere that contains oxygen. Heat treatment in an oxidizing atmosphere that contains oxygen allows the oxygen concentration in the film to be maintained within a more appropriate range, thereby further improving conductivity.

[0101] Therefore, in this case, it is preferable to perform the heat treatment process in an atmosphere of air or an atmosphere with an oxygen concentration of 5% to 20% by volume.

[0102] When the heat treatment atmosphere is an air atmosphere, the heat treatment furnace does not need to have a special sealed structure. The heat treatment temperature is preferably 400°C or higher and less than 1000°C, and more preferably 400°C or higher and 950°C or lower.

[0103] By setting the heat treatment temperature to 400°C or higher, the alkali tungsten bronze contained in the transparent conductive film can be sufficiently crystallized, and various defects can be suppressed. As a result, a transparent conductive film with an appropriate electronic structure and particularly excellent conductivity can be obtained.

[0104] Furthermore, by keeping the heat treatment temperature below 1000°C, excessive oxidation can be suppressed, resulting in a transparent conductive film with particularly excellent conductivity. Additionally, the reaction between the transparent conductive film and the substrate can be suppressed, preventing deformation of the substrate and peeling of the transparent conductive film.

[0105] The heat treatment time is not particularly limited, but can be, for example, 10 minutes or more and 60 minutes or less.

[0106] Furthermore, when using a resin substrate or similar material that cannot withstand heat treatment processes above 400°C, it may be possible to achieve a similar effect to heat treatment by irradiating the substrate with an ion beam or plasma during sputtering at room temperature. This can promote crystallization through the collision energy of ions. [Transparent conductive materials, electronic display devices, solar cells] The transparent conductive member of this embodiment may have a substrate and a transparent conductive film described above disposed on the surface of the substrate.

[0107] Because the transparent conductive film described above has excellent conductivity, it can be used in various applications such as transparent electrodes for displays and transparent electrodes for solar cells.

[0108] Therefore, this embodiment can be used to create electronic display devices equipped with the transparent conductive member, or solar cells equipped with the transparent conductive member. [Examples]

[0109] The present invention will be described with specific examples below, but it is not limited to these examples. (1) Evaluation method (1-1) Specific resistance The resistivity of the film was measured using Loresta-GX and Hiresta-UX manufactured by Mitsubishi Chemical Corporation. (1-2) Film thickness The film thickness was measured using a step gauge (Alpha-Step IQ, manufactured by KLA-Tencor). (1-3) Powder X-ray diffraction pattern measurement, lattice constant The powder X-ray diffraction pattern (XRD pattern) of the obtained film was measured using Cu-Kα rays with a D2PHASERX diffractometer from BRUKER AXS.

[0110] The lattice constants of the crystalline phase were determined using the Pawley method, assuming a space group P63 / mcm, with the computational software DIFFRAC TOPAS from BRUKER AXS. (1-4) Visible light transmittance, solar radiation transmittance, near-infrared reflectance The optical properties of the obtained film were measured using a V-670 spectrophotometer (manufactured by JASCO Corp.) by determining its transmittance and 8° incident diffuse reflectance.

[0111] Using spectral data of transmittance and reflectance, visible light transmittance (VLT) and solar radiation transmittance (ST25) between 300 nm and 2500 nm were determined in accordance with JIS R 3106 (2019). Furthermore, near-infrared reflectance (η) between 780 nm and 2500 nm was calculated in accordance with JIS K 5602 (2008). (1-5) Composition The composition of the alkali tungsten bronze in the obtained film was determined by chemical analysis. Alkali metal elements and tungsten were analyzed using an ICP emission spectrometer (Shimadzu Corporation, Model: ICPE-9000). Oxygen was analyzed by melting the sample in He gas using a light element analyzer (LECO Corporation, Model: ON-836) and measuring the CO gas produced by the reaction with carbon in the analytical crucible using IR absorption spectroscopy. [Example 1] (Target fabrication process) A precursor was prepared by mixing and kneading an aqueous solution of cesium carbonate and hydrated tungsten trioxide in a ratio of cesium (Cs) to tungsten (W) such that the molar ratio was Cs / W = 0.35, and then drying the mixture in air at 100°C for 12 hours.

[0112] The precursor was heated to 800°C in a 5 vol% H2-95 vol% N2 gas stream and held for 1 hour, then slowly cooled to room temperature. A dark blue composite tungsten oxide powder (hereinafter referred to as CsWO powder) was obtained.

[0113] This CsWO powder is placed in a hot press machine under a vacuum atmosphere, at a temperature of 950°C and a pressing pressure of 250 kgf / cm. 2 A CsWO sintered body was prepared by sintering under the specified conditions. Chemical analysis of the sintered body composition revealed that the ratio of Cs to W (Cs / W) was 0.32. This oxide sintered body was machined to a diameter of 153 mm and a thickness of 5 mm, and then joined to a stainless steel backing plate using indium metal brazing material to prepare a CsWO target. (Film forming process) In the film deposition process, a sputtering system (ULVAC, model SBH2306) was used. The sputtering system's chamber opening and closing is a load-lock type, and exhaust from the chamber is performed by a turbomolecular pump. First, to minimize the adsorption of water molecules onto the inner wall of the chamber when the sputtering system is opened to the atmosphere, 60°C hot water was introduced into water-cooling pipes that ran along the entire outer wall of the chamber to heat it. Then, nitrogen gas was introduced into the chamber, and the chamber was opened to the atmosphere while exhausting moisture (preheating and degassing).

[0114] Next, the previously described CsWO target and Ti target were mounted in the sputtering apparatus. A glass substrate (Corning EXG, 0.7 mm thick) was also attached to the sputtering apparatus. Then, after closing the chamber, a dry pump, turbo molecules, and a cryocoil (moisture condensation) were used to achieve a vacuum of 10°C inside the chamber. -3 After exhausting until the pressure reaches Pa, the sheath heater and substrate heating heater inside the chamber are kept at 300°C, and then 10 -5 The exhaust was vented until it reached the Pa level.

[0115] Then, with the shutter between the glass substrate and the target closed, dummy sputtering was performed for 20 minutes using 5N pure argon gas and applying a DC power of 600W to the Ti target to remove any residual moisture in the chamber.

[0116] Furthermore, with the shutter between the glass substrate and the target closed, dummy sputtering was performed for 20 minutes using 5N pure argon gas and applying a DC current of 600W to the CsWO target in order to remove moisture adsorbed near the surface of the CsWO target.

[0117] Subsequently, the moisture pressure inside the chamber was 2.0 × 10⁻⁶. -5 The vacuum was evacuated until it reached Pa. The achieved vacuum level is shown in Table 1. Then, using a 5N purity 5 vol% oxygen / 95 vol% argon mixed gas, a CsWO film with a thickness of 40 nm was deposited with the shutter between the glass substrate and the target open, under conditions of a sputtering gas pressure of 0.6 Pa and an input power of 600 W DC. A quadrupole mass spectrometer was used to measure the moisture content. (Heat treatment process) This film was placed in a lamp heating furnace (manufactured by Yonekura Seisakusho Co., Ltd., model number HP-2-9) and heat-treated at a temperature of 600°C for 30 minutes in a 3 vol.% H2-97 vol.% N2 atmosphere. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the atomic ratio of Cs:W:O was 7.76:24.19:68.05 (Cs / W = 0.32).

[0118] The powder X-ray diffraction pattern of the transparent conductive film obtained after the heat treatment process was measured, and as shown in Figure 1, hexagonal Cs 0.32 A diffraction peak originating from CsWO in WO3 was observed as a single phase.

[0119] The powder X-ray diffraction pattern of the obtained transparent conductive film showed no shift from the hexagonal pattern. That is, the obtained transparent conductive film contained alkali tungsten bronze, and the alkali tungsten bronze exhibited a hexagonal pattern in the powder X-ray diffraction pattern, with no orthorhombic, trigonal, or pyrochlore phase shifts. Furthermore, the powder X-ray diffraction pattern of the alkali tungsten bronze showed a hexagonal (10-12) pattern. H (20-20) H It was confirmed that there were no excess peaks originating from orthorhombic, trigonal, or pyrochlore phases on the low-angle and high-angle sides of the diffraction peak.

[0120] The lattice constants of the alkali tungsten bronze crystalline phase contained in the obtained transparent conductive film were a = 7.390 Å and c = 7.626 Å.

[0121] The thickness of the obtained transparent conductive film was 39.6 nm. Surface resistance was measured, and the resistivity was found to be 2.5 × 10⁻⁶. -4 A value of Ωcm was obtained, confirming that it possesses high conductivity.

[0122] Spectral characteristics measurements of the transparent conductive film revealed significant transmission in the main visible light region between 400 nm and 780 nm, while large near-infrared reflection was observed in the near-infrared region at wavelengths above 800 nm.

[0123] A visible light transmittance of 68.1% and a near-infrared reflectance of 61.2% were obtained. Therefore, while maintaining sufficient transparency in the visible light region with VLT ≥ 50%, the resistivity ρ was 1.0 × 10⁻⁶. -2 It was confirmed that the transparent conductive film possesses metallic conductivity of less than Ωcm and reflects light in the near-infrared region, resulting in high heat shielding performance.

[0124] Table 1 shows the conditions for fabricating the transparent conductive film, and Table 2 shows the evaluation results of the obtained transparent conductive film.

[0125] [Table 1]

[0126] [Table 2] [Example 2] In the target preparation process, a dark blue CsWO powder and a CsWO target were prepared in the same manner as in Example 1, except that an aqueous cesium carbonate solution and tungsten trioxide hydrate were mixed and kneaded in a ratio of cesium (Cs) to tungsten (W) such that the molar ratio was Cs / W = 0.45.

[0127] Then, the film deposition process and heat treatment process were carried out in the same manner as in Example 1, except that the CsWO target was used. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the atomic ratio of Cs:W:O was 9.68:24.07:66.25 (Cs / W = 0.40). This indicates that the film is Cs-rich.

[0128] The powder X-ray diffraction pattern of the obtained transparent conductive film showed no shift from the hexagonal pattern. That is, the obtained transparent conductive film contained alkali tungsten bronze, and the alkali tungsten bronze exhibited a hexagonal pattern in the powder X-ray diffraction pattern, with no orthorhombic, trigonal, or pyrochlore phase shifts. Furthermore, the powder X-ray diffraction pattern of the alkali tungsten bronze showed a hexagonal (10-12) pattern. H (20-20) H It was confirmed that there were no excess peaks originating from orthorhombic, trigonal, or pyrochlore phases on the low-angle and high-angle sides of the diffraction peak.

[0129] As shown in Table 2, the obtained transparent conductive film has a visible light transmittance of 67.5% and a resistivity of 5.4 × 10⁻⁶. -4 It was found to be a transparent conductive film with metallic conductivity of Ωcm and heat ray reflectivity of 48.4% near-infrared reflectance. [Example 3] In the target preparation process, a dark blue CsWO powder and a CsWO target were prepared in the same manner as in Example 1, except that an aqueous cesium carbonate solution and tungsten trioxide hydrate were mixed and kneaded in a ratio of cesium (Cs) to tungsten (W) such that the molar ratio was Cs / W = 0.30.

[0130] Then, the film deposition process and heat treatment process were carried out in the same manner as in Example 1, except that the CsWO target was used. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the atomic ratio of Cs:W:O was 6.57:25.43:68.00 (Cs / W = 0.26).

[0131] The powder X-ray diffraction pattern of the obtained transparent conductive film showed no shift from the hexagonal pattern. That is, the obtained transparent conductive film contained alkali tungsten bronze, and the alkali tungsten bronze exhibited a hexagonal pattern in the powder X-ray diffraction pattern, with no orthorhombic, trigonal, or pyrochlore phase shifts. Furthermore, the powder X-ray diffraction pattern of the alkali tungsten bronze showed a hexagonal (10-12) pattern. H (20-20) H It was confirmed that there were no excess peaks originating from orthorhombic, trigonal, or pyrochlore phases on the low-angle and high-angle sides of the diffraction peak.

[0132] As shown in Table 2, the obtained transparent conductive film has a visible light transmittance of 63.8% and a resistivity of 9.6 × 10⁻⁶. -4 It was found to be a transparent conductive film with metallic conductivity of Ωcm and heat ray reflectivity of 58.8% near-infrared reflectance. [Example 4] In the target preparation process, a cesium carbonate aqueous solution and tungsten trioxide hydrate were mixed and kneaded in a ratio of cesium (Cs) to tungsten (W) such that Cs / W = 0.33. Except for this difference, a CsWO powder and a CsWO target were prepared in the same manner as in Example 1. The obtained CsWO target was used in the film deposition process. In the heat treatment process, the film was heat-treated at 550°C for 30 minutes in a 3 vol.% H2-97 vol.% N2 atmosphere. A transparent conductive film was prepared in the same manner as in Example 1, except for the differences described above. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the atomic ratio of Cs:W:O was 7.41:24.42:68.17 (Cs / W = 0.30).

[0133] The powder X-ray diffraction pattern of the obtained transparent conductive film showed no shift from the hexagonal pattern. That is, the obtained transparent conductive film contained alkali tungsten bronze, and the alkali tungsten bronze exhibited a hexagonal pattern in the powder X-ray diffraction pattern, with no orthorhombic, trigonal, or pyrochlore phase shifts. Furthermore, the powder X-ray diffraction pattern of the alkali tungsten bronze showed a hexagonal (10-12) pattern. H (20-20) H It was confirmed that there were no excess peaks originating from orthorhombic, trigonal, or pyrochlore phases on the low-angle and high-angle sides of the diffraction peak.

[0134] As shown in Table 2, the obtained transparent conductive film has a visible light transmittance of 65.4% and a resistivity of 6.9 × 10⁻⁶. -4 It was found to be a transparent conductive film with metallic conductivity of Ωcm and heat ray reflectivity of 45.2% near-infrared reflectance. [Example 5] In the target preparation process, a cesium carbonate aqueous solution and tungsten trioxide hydrate were mixed and kneaded in a ratio of cesium (Cs) to tungsten (W) such that Cs / W = 0.33. Except for this difference, a CsWO powder and a CsWO target were prepared in the same manner as in Example 1. The obtained CsWO target was used in the film deposition process. In the heat treatment process, the film was heat-treated at 500°C for 30 minutes in a 3 vol.% H2-97 vol.% N2 atmosphere. A transparent conductive film was prepared in the same manner as in Example 1, except for the differences described above. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the atomic ratio of Cs:W:O was 7.37:24.18:68.45 (Cs / W = 0.30).

[0135] The powder X-ray diffraction pattern of the obtained transparent conductive film showed no shift from the hexagonal pattern. That is, the obtained transparent conductive film contained alkali tungsten bronze, and the alkali tungsten bronze exhibited a hexagonal pattern in the powder X-ray diffraction pattern, with no orthorhombic, trigonal, or pyrochlore phase shifts. Furthermore, the powder X-ray diffraction pattern of the alkali tungsten bronze showed a hexagonal (10-12) pattern. H (20-20) H It was confirmed that there were no excess peaks originating from orthorhombic, trigonal, or pyrochlore phases on the low-angle and high-angle sides of the diffraction peak.

[0136] As shown in Table 2, the obtained transparent conductive film has a visible light transmittance of 69.6% and a resistivity of 1.3 × 10⁻⁶. -3 It was found to be a transparent conductive film with metallic conductivity of Ωcm and heat ray reflectivity of 40.9% near-infrared reflectance. [Example 6] In the target fabrication process, the raw material composition is Rb 0.33 The formula was WO3(RbWO). Except for the points mentioned above, the blue RbWO powder and RbWO target were prepared in the same manner as in Example 1.

[0137] Then, the film deposition process and heat treatment process were carried out in the same manner as in Example 1, except that the RbWO target was used and the gas purity was as shown in Table 1. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the atomic ratio of Rb:W:O was 7.39:23.86:68.75 (Rb / W = 0.31).

[0138] The powder X-ray diffraction pattern of the obtained transparent conductive film showed no shift from the hexagonal pattern. That is, the obtained transparent conductive film contained alkali tungsten bronze, and the alkali tungsten bronze exhibited a hexagonal pattern in the powder X-ray diffraction pattern, with no orthorhombic, trigonal, or pyrochlore phase shifts. Furthermore, the powder X-ray diffraction pattern of the alkali tungsten bronze showed a hexagonal (10-12) pattern. H (20-20) H It was confirmed that there were no excess peaks originating from orthorhombic, trigonal, or pyrochlore phases on the low-angle and high-angle sides of the diffraction peak.

[0139] As shown in Table 2, the obtained transparent conductive film has a visible light transmittance of 70.7% and a resistivity of 3.1 × 10⁻⁶. -4 It was found to be a transparent conductive film with metallic conductivity of Ωcm and heat ray reflectivity of 55.3% near-infrared reflectance. [Example 7] In the target manufacturing process, the raw material composition is K 0.33 The material was WO3(KWO). Except for the points mentioned above, sky-blue KWO powder and KWO targets were prepared in the same manner as in Example 1.

[0140] Then, the film deposition process and heat treatment process were carried out in the same manner as in Example 1, except that the KWO target was used. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the ratio of K:W:O was 7.27:23.45:69.28 (atomic ratio) (K / W = 0.31).

[0141] The powder X-ray diffraction pattern of the obtained transparent conductive film showed no shift from the hexagonal pattern. That is, the obtained transparent conductive film contained alkali tungsten bronze, and the alkali tungsten bronze exhibited a hexagonal pattern in the powder X-ray diffraction pattern, with no orthorhombic, trigonal, or pyrochlore phase shifts. Furthermore, the powder X-ray diffraction pattern of the alkali tungsten bronze showed a hexagonal (10-12) pattern. H (20-20) H It was confirmed that there were no excess peaks originating from orthorhombic, trigonal, or pyrochlore phases on the low-angle and high-angle sides of the diffraction peak.

[0142] As shown in Table 2, the obtained transparent conductive film has a visible light transmittance of 74.1% and a resistivity of 2.6 × 10⁻⁶. -3 It was found to be a transparent conductive film with metallic conductivity of Ωcm and heat ray reflectivity of 36.7% near-infrared reflectance. [Comparative Example 1] In the target preparation process, an aqueous cesium carbonate solution and tungsten trioxide hydrate were mixed and kneaded in a ratio of cesium (Cs) to tungsten (W) such that Cs / W = 0.33. Then, the resulting CsWO target was used in the film deposition process.

[0143] Furthermore, in the film deposition process, the measures taken to remove moisture as in Example 1 were eliminated, and the process was carried out using a normal sputtering method. Except for the points mentioned above, a transparent conductive film was deposited in the same manner as in Example 1.

[0144] Specifically, first, the water cooling pipes on the outer wall of the sputtering apparatus chamber were opened to the atmosphere without preheating with hot water. Next, after installing only the CsWO target and glass substrate (Corning EXG, 0.7 mm thick) into the sputtering apparatus without using a Ti target, the chamber was evacuated at room temperature without heating the sheath heater and substrate heating heater inside the chamber, resulting in a vacuum of 6.5 × 10⁻⁶. -4 Pa and 10 -5 It did not reach the Pa level.

[0145] Next, the moisture pressure inside the chamber, measured without dummy sputtering, was 5.0 × 10⁻⁶. -4 The pressure was Pa. Using a 4N purity 5 vol% oxygen / 95 vol% argon mixed gas, the shutter between the glass substrate and the target was opened, and a CsWO film with a thickness of 400 nm was deposited under conditions of a sputtering gas pressure of 0.6 Pa and an input power of 600 W DC.

[0146] Subsequently, the heat treatment process was carried out in the same manner as in Example 1. (evaluation) Quantitative analysis of the film obtained after the heat treatment process using XPS revealed that the atomic ratio of Cs:W:O was 7.03:24.58:68.39 (Cs / W = 0.29).

[0147] The powder X-ray diffraction pattern of the obtained film showed a characteristic orthorhombic shift from a hexagonal pattern.

[0148] As shown in Table 2, the obtained film was a near-infrared absorbing film with a visible light transmittance of 69.7% and a low solar radiation transmittance of 46.3%, but its resistivity was 1.9 × 10⁻⁶. 4 Because the density is orders of magnitude higher (Ωcm), it was determined that it does not possess metallic conductivity or infrared reflectivity, and therefore cannot be considered a transparent conductive film. [Comparative Example 2] In the target preparation process, a blue (dark blue) CsWO powder and a CsWO target were prepared in the same manner as in Example 1, except that an aqueous cesium carbonate solution and tungsten trioxide hydrate were mixed and kneaded in a ratio of cesium (Cs) to tungsten (W) such that the molar ratio was Cs / W = 0.20.

[0149] In the next film deposition process, sputter film deposition was performed, retaining some of the moisture removal techniques used in Example 1 above, while also eliminating some of them.

[0150] Specifically, 60°C hot water was introduced into water-cooling pipes that ran along the entire outer wall of the sputtering machine (ULVAC, model SBH2306) chamber to heat it up, then nitrogen gas was introduced into the chamber, and the chamber was opened to the atmosphere while exhausting the moisture (preheating and degassing).

[0151] Next, the CsWO target and glass substrate (Corning EXG, 0.7 mm thick) are mounted in the sputtering apparatus. After closing the chamber, the sputtering is performed using a dry pump, turbo molecules, and cryocoil (moisture condensation) for 10 minutes. -3 After evacuating to the Pa level, the sheath heater and substrate heating heater inside the chamber were maintained at 300°C while the vacuum was evacuated. As a result, the ultimate vacuum level was 5.0 × 10⁻⁶. -4 Pa and 10 -5 It did not reach the Pa level.

[0152] Next, the moisture pressure inside the chamber, measured without dummy sputtering, was 4.0 × 10⁻⁶. -4 The pressure was Pa. Using a 4N purity 5 vol% oxygen / 95 vol% argon mixed gas, the shutter between the glass substrate and the target was opened, and a CsWO film with a thickness of 400 nm was deposited under conditions of a sputtering gas pressure of 0.6 Pa and an input power of 600 W DC.

[0153] Subsequently, the heat treatment process was carried out in the same manner as in Example 1. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the atomic ratio of Cs:W:O was 4.03:24.28:71.69 (Cs / W = 0.17).

[0154] The powder X-ray diffraction pattern of the obtained transparent conductive film showed a characteristic orthorhombic shift from a hexagonal pattern.

[0155] As shown in Table 2, the obtained transparent conductive film had a visible light transmittance of 73.2% and was a near-infrared absorbing film with a low solar transmittance of 46.4%. However, its near-infrared reflectance was low at 10.4%, and its resistivity was 4.6 × 10⁻⁶. 6Because the density is orders of magnitude higher (Ωcm), it was determined that it does not possess metallic conductivity or infrared reflectivity, and therefore cannot be considered a transparent conductive film. [Comparative Example 3] In the target preparation process, a blue (dark blue) CsWO powder and a CsWO target were prepared in the same manner as in Example 1, except that an aqueous cesium carbonate solution and tungsten trioxide hydrate were mixed and kneaded in a ratio of cesium (Cs) to tungsten (W) such that the molar ratio was Cs / W = 0.33.

[0156] In the next film deposition step, the measures taken to remove moisture as in Example 1 were eliminated, and the process was carried out using a normal sputtering film deposition method.

[0157] Specifically, the water cooling pipes on the outer wall of the sputtering chamber were not preheated with hot water and were instead vented to the atmosphere. Next, without using a Ti target, only a CsWO target and a glass substrate (Corning EXG, 0.7 mm thick) were installed in the sputtering apparatus. Then, without heating the sheath heater and substrate heating heater inside the chamber, the chamber was evacuated at room temperature, and the resulting vacuum was 7.0 × 10⁻⁶. -4 Pa and 10 -5 It did not reach the Pa level.

[0158] Next, the moisture pressure inside the chamber, measured without dummy sputtering, was 6.0 × 10⁻⁶. -4 The pressure was Pa. Using a 4N purity 5 vol% oxygen / 95 vol% argon mixed gas, the shutter between the glass substrate and the target was opened, and a CsWO film with a thickness of 400 nm was deposited under conditions of a sputtering gas pressure of 0.6 Pa and an input power of 600 W DC.

[0159] Subsequently, the heat treatment process was carried out in the same manner as in Example 1, except that it was performed in an atmospheric environment. (evaluation) Quantitative analysis of the transparent conductive film obtained after the heat treatment process using XPS revealed that the atomic ratio of Cs:W:O was 7.03:23.19:69.78 (Cs / W = 0.30).

[0160] As shown in Figure 2, the powder X-ray diffraction pattern of the obtained transparent conductive film showed a characteristic pyrochlore phase shift from the hexagonal pattern.

[0161] This film was a near-infrared absorbing film with a visible light transmittance of 62.5% and a low solar radiation transmittance of 33.8%, but its near-infrared reflectance was low at 8.6%, while its resistivity was 8.3 × 10⁻⁶. 6 Because the density is orders of magnitude higher (Ωcm), it was determined that it does not possess metallic conductivity or infrared reflectivity, and therefore cannot be considered a transparent conductive film.

[0162] This application claims priority based on Japanese Patent Application No. 2021-047555, filed with the Japan Patent Office on March 22, 2021, and the entire contents of Japanese Patent Application No. 2021-047555 are incorporated herein by reference.

Claims

1. Contains alkali tungsten bronze, The aforementioned alkali tungsten bronze exhibits a hexagonal pattern in powder X-ray diffraction patterns and lacks orthorhombic, trigonal, and pyrochlore phase shifts. The aforementioned alkali tungsten bronze is subject to general formula A ｘ W ｙ O ｚ (0.2 ≤ x / y ≤ 0.5, 2.5 ≤ z / y ≤ 3.0, element A is one or more alkali metal elements selected from K, Rb, and Cs) The alkali tungsten bronze is a transparent conductive film in which the lattice constant of the hexagonal c axis is 7.54 Å or less when element A is K, 7.58 Å or less when element A is Rb, and 7.64 Å or less when element A is Cs.

2. The powder X-ray diffraction pattern of the alkali tungsten bronze is hexagonal (10-12). Ｈ (20-20) Ｈ The transparent conductive film according to claim 1, wherein the diffraction peaks on the low-angle and high-angle sides do not have excess peaks originating from orthorhombic, trigonal, or pyrochlore phases.

3. The transparent conductive film according to claim 1 or claim 2, wherein a portion of element A is replaced by one or more elements selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

4. A film formation process in which an unheat-treated film containing elements that constitute alkali tungsten bronze is formed on the surface of the substrate, The process includes a heat treatment step for heat-treating the aforementioned unheat-treated film, The aforementioned film formation process is carried out under film formation conditions that prevent moisture from penetrating the unheat-treated film. If a film is formed using a mixed gas of argon and oxygen in the aforementioned film formation process, the heat treatment process is carried out in an inert gas atmosphere or a reducing atmosphere. In the aforementioned film formation step, if only argon gas is used for film formation, the heat treatment step is performed in an inert gas atmosphere, or in an atmosphere of air or oxygen with an oxygen concentration of 5% to 20% by volume.

5. The aforementioned film deposition process is a film deposition method using a sputtering target, The method for producing a transparent conductive film according to claim 4, wherein the sputtering target contains an alkali metal element and tungsten that constitute the alkali tungsten bronze.

6. The method for manufacturing a transparent conductive film according to claim 5, wherein the sputtering target is either a sputtering target composed of alkali tungsten bronze or a sputtering target composed of a precursor containing an alkali metal element and tungsten.

7. During the film formation process described above, the moisture pressure is 1 × 10⁻⁶ －４ A method for producing a transparent conductive film according to any one of claims 4 to 6, wherein the pressure is less than Pa.

8. The vacuum level achieved in the aforementioned film formation process is 1 × 10 －４ A method for producing a transparent conductive film according to any one of claims 4 to 7, wherein the pressure is less than Pa.

9. A method for manufacturing a transparent conductive film according to any one of claims 4 to 8, wherein the purity of the sputtering gas in the film formation step is 5N or higher.

10. A method for manufacturing a transparent conductive film according to any one of claims 4 to 9, wherein the heat treatment step is carried out in an inert atmosphere or a reducing atmosphere at a heat treatment temperature of 400°C or more and less than 1000°C.

11. Substrate and A transparent conductive member having a transparent conductive film according to any one of claims 1 to 3 disposed on the surface of the substrate.

12. An electronic display device comprising a transparent conductive member as described in claim 11.

13. A solar cell comprising the transparent conductive member according to claim 11.

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