Transparent conductive film, transparent conductive film structure, and method for producing transparent conductive film

Abstract

A transparent conductive film comprising a first layer and a second layer, wherein: the second layer is directly laminated on the first layer; the second layer includes an HTB thin film that is a thin film of hexagonal tungsten bronze; and at least a part of the first layer is epitaxially bonded to the HTB thin film of the second layer.

Description

Transparent conductive film, transparent conductive film structure, method for manufacturing a transparent conductive film

[0001] This invention relates to a transparent conductive film, a transparent conductive film structure, and a method for manufacturing a transparent conductive film.

[0002] Transparent conductive films are used in applications such as transparent electrodes for liquid crystal display elements and solar cells, infrared absorption and reflection films, and electromagnetic wave shielding films. For transparent electrodes used in liquid crystal display elements, ITO (Indium Tin Oxide) conductive films are primarily used.

[0003] ITO conductive films excel in high visible light transmittance and low surface resistance, but are expensive due to the use of indium. Therefore, efforts are being made to improve physical properties such as transmittance and conductivity, as well as to reduce costs.

[0004] As one of the novel material candidates for a transparent conductive material to replace ITO, the general formula W ｙ O ｚ Tungsten oxides represented by the general formula M ｘ W ｙ O ｚ A transparent conductive film of composite tungsten oxide represented by has been proposed. (Patent Document 1) However, when thin films of the above tungsten oxide or composite tungsten oxide are formed using sputtering or the like, the electrical resistance is often higher than that of ITO, and further improvement of properties is desired. (Patent Document 2) Patent Document 3 revealed that by removing moisture during film formation, the original hexagonal tungsten bronze can be obtained, resulting in high conductivity.

[0005] However, for industrial use as a transparent conductive film, it is preferable that it has high conductivity.

[0006] Japanese Patent Publication No. 2006-096656, Japanese Patent Publication No. 2020-002459, International Publication No. 2022 / 202640

[0007] Satoshi.Yoshio and Kenji.Adachi Mater.Res.Express 6, (2019) 026548A.Hussain et al. Journal of Alloys and Compounds 246,(1997) 51-61

[0008] 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.

[0009] A transparent conductive film according to one aspect of the present invention comprises a first layer and a second layer, wherein the second layer is directly laminated on the first layer, the second layer includes an HTB thin film which is a thin film of hexagonal tungsten bronze, and at least a portion of the first layer is epitaxially bonded to the HTB thin film of the second layer.

[0010] According to one aspect of the present invention, a transparent conductive film with excellent conductivity can be provided.

[0011] Figure 1 is an explanatory diagram of a transparent conductive film according to one aspect of the present disclosure. Figure 2 is an explanatory diagram of a transparent conductive film according to another aspect of the present disclosure. Figure 3 is an explanatory diagram of a transparent conductive film structure according to one aspect of the present disclosure. Figure 4 is an explanatory diagram of a transparent conductive film structure according to another aspect of the present disclosure. Figure 5 is a flow chart of a method for manufacturing a transparent conductive film according to one aspect of the present disclosure. Figure 6 is the X-ray analysis pattern of the transparent conductive film obtained in Example 1. Figure 7 is the TEM image of the transparent conductive film obtained in Example 1.

[0012] The embodiments for carrying out the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments described below, and various modifications and substitutions can be made to the embodiments described below without departing from the scope of the present invention. [Transparent conductive film] Figures 1 and 2 show explanatory diagrams of the transparent conductive film of this embodiment. Figures 1 and 2 are cross-sectional views of the first and second layers of the transparent conductive film of this embodiment along the lamination direction. Since Figure 2 is another example of the configuration of the transparent conductive film of this embodiment, the explanation will mainly use Figure 1, and use Figure 2 as necessary.

[0013] In this specification, the names of components may be prefixed with "1st," "2nd," etc., such as "1st layer" and "2nd layer." However, this is merely to identify the component being described and to avoid confusion, and does not indicate its arrangement, priority, or anything of the sort.

[0014] As shown in Figure 1, the transparent conductive film 10 of this embodiment has a first layer 11 and a second layer 12. The second layer 12 can be directly laminated on the first layer 11. That is, the transparent conductive film 10 of this embodiment can be laminated in the order of the first layer 11 and the second layer 12.

[0015] The second layer 12 may include a hexagonal tungsten bronze (HTB) thin film. The second layer 12 may also consist only of the HTB thin film, but even in this case, this does not exclude the fact that the second layer 12 may contain unavoidable impurities introduced during the manufacturing process of the second layer 12. (1) For each layer (1-1) First layer At least a portion of the first layer 11 is epitaxially bonded to the HTB thin film of the second layer 12.

[0016] In this specification, epitaxial bonding means that the difference in lattice constants between the bonded layers or thin films is sufficiently small. For example, if the difference between the lattice constant of the material in the first bonded layer and the lattice constant of the material in the second bonded layer is within 20% of the lattice constant of the material in the second bonded layer, then the first and second layers can be epitaxially bonded. Epitaxial bonding can be confirmed by observing a thin section of the bonded layer along the stacking direction using a transmission electron microscope.

[0017] (1-1-1) The material contained in the first layer 11 is not particularly limited in terms of composition, but for example, the first layer 11 may include a crystalline material having a lattice constant within a predetermined range that is the same as the lattice constant of the HTB crystal of the second layer 12, so that it can be epitaxially bonded with the HTB thin film of the second layer 12.

[0018] The second layer 12 can contain, for example, Cs-HTB. Here, Cs-HTB means hexagonal tungsten bronze containing Cs (cesium) as an alkali metal element (hereinafter also referred to as "HTB"). As an example of Cs-HTB, Cs ０．３２ WO ３ can be mentioned. However, the lattice constants of Cs ０．３２ WO ３ are a-axis: 7.4116 Å and c-axis: 7.5981 Å (ICDD 83-1334). Generally, if the difference in lattice constants of the compounds contained in adjacent layers is within 20%, epitaxial bonding can be achieved. Therefore, when the second layer 12 contains Cs ０．３２ WO ３ , crystals with a difference range within 20% from the lattice constants of Cs ０．３２ WO ３ can epitaxially bond with Cs ０．３２ WO ３ in the second layer 12. Specifically, crystals having lattice constants with an a-axis length of 5.92928 Å or more and 8.89392 Å or less and a c-axis length of 6.07848 Å or more and 9.11772 Å or less will have epitaxial properties with the second layer 12. Therefore, when the second layer 12 contains Cs ０．３２ WO ３ , it is preferable that the first layer 11 contains crystals having lattice constants within the above range.

[0019] For the above reasons, it is preferable that the first layer 11 contains a material having a lattice constant with a difference of 20% or less from the lattice constant of the HTB contained in the second layer 12 with respect to the lattice constant of the HTB contained in the second layer 12. The first layer 11 may be composed only of materials having a lattice constant with a difference of 20% or less. More preferably, the difference in the lattice constant of the material contained in the first layer 11 is 20% or less with respect to the {10-10} plane of the HTB contained in the second layer 12.

[0020] By using a material such as a crystalline thin film that has epitaxial bonding properties with the HTB thin film of the second layer 12 as the material for the first layer 11, at least a portion of the first layer 11 can be epitaxially bonded with the HTB thin film of the second layer 12. As a result, the crystal orientation of the HTB thin film of the second layer 12 increases, improving grain boundary bonding properties, reducing the disruption of conductive paths due to microcracks, etc., and improving the conductivity of the transparent conductive film of this embodiment.

[0021] The first layer 11 is, for example, WO ３－ｘ It may also contain tungsten oxide represented by the formula above. Preferably, x in the formula for tungsten oxide satisfies 0 ≤ x ≤ 0.28. The first layer 11 may consist only of tungsten oxide, for example, a thin film of tungsten oxide, but even in this case, it does not exclude the inclusion of unavoidable impurities introduced during the manufacturing process.

[0022] When the first layer 11 contains tungsten oxide, the tungsten oxide is typically tungsten trioxide (WO ３ ) can be used, but it may also be reduced. Among the chemical formulas of tungsten oxide described above, in the range of x from 0 to 0.28, the conductivity improves as the amount of reduction increases, so the conductivity of the transparent conductive film when combined with the second layer 12 can be improved.

[0023] Tungsten oxide WO ３－ｘ Although it can have monoclinic or tetragonal crystal symmetry depending on the manufacturing method, it is approximately a nearly cubic crystal, and WO ６ It has a structure in which octahedrons are arranged in a cubic symmetry.

[0024] The second layer 12 may include an HTB thin film, but HTB is hexagonal tungsten bronze, WO ６ It has a structure in which octahedrons are arranged in hexagonal symmetry.

[0025] WO ３－ｘ The cubic plane ({100} plane) of ¹³¹ and the prism plane ({10-10} plane) of HTB have similar atomic arrangements, making epitaxial bonding easy. ３－ｘThe bonding configuration between the cubic surface of the first layer and the prism surface of the HTB has actually been observed in intergrowth tungsten bronze (Non-Patent Literature 1). Therefore, by including tungsten oxide in the first layer 11, at least a portion of the first layer 11 can be easily epitaxially bonded to the HTB thin film of the second layer 12.

[0026] Layer 11 is WO ３－ｘ The inclusion of tungsten oxide, as represented by [the formula], facilitates epitaxial bonding between the cubic surface of the tungsten oxide in the first layer 11 and the prism surface of the HTB thin film in the second layer.

[0027] In the transparent conductive film of this embodiment, the prism surface ({10-10} surface) of the HTB thin film of the second layer 12 and the cubic surface ({100} surface) of the tungsten oxide of the first layer may be epitaxially bonded.

[0028] The c-axis direction of the HTB thin film in the second layer 12 has higher free electron transport properties compared to the a-axis direction. Therefore, when the first layer 11 is epitaxially joined to the {10-10} plane, which is the prism surface of the HTB thin film in the second layer 12, the c-axis of the second layer 12 is oriented parallel to the film plane direction, which improves the free electron transport properties and further improves the conductivity of the transparent conductive film.

[0029] The optical properties of the second layer 12, such as reflectance and transmittance, may be affected by the refractive index and absorption properties of the first layer 11.

[0030] However, for example, if the first layer 11 contains tungsten oxide and the second layer 12 contains a Cs-HTB thin film, the refractive index of the first layer 11 is smaller than that of the second layer 12, so no attenuation of reflectivity occurs, and the reflective properties of the second layer 12 can be maintained.

[0031] Furthermore, the tungsten oxide contained in the first layer 11 has high transmittance from the visible light region to the near-infrared region, and may have slight absorption in the near-infrared region depending on the degree of reduction.

[0032] On the other hand, the Cs-HTB contained in the second layer 12 has high transmittance in the visible light region and absorption or reflection in the near-infrared region.

[0033] Therefore, by containing tungsten oxide in the first layer 11, the optical properties of the second layer 12 are not inhibited, and the optical properties of the second layer 12 can be maintained even in a two-layer film structure. In other words, by containing tungsten oxide in the first layer 11, the optical properties of the transparent conductive film 10 can be controlled by the optical properties of the second layer 12, and the optical properties of the transparent conductive film 10 can be easily controlled.

[0034] The transparent conductive film of this embodiment can also be arranged on a substrate to form a transparent conductive film structure, as described later. When the transparent conductive film of this embodiment is arranged on a substrate, the first layer 11 functions as a buffer layer between the substrate and the second layer 12. Therefore, the first layer 11 can compensate for the strain caused by the difference in thermal expansion coefficients between the substrate and the second layer 12, thereby easing the stress applied to the HTB thin film.

[0035] Because the first layer 11 functions as a buffer layer, even if there is a large difference in the coefficient of thermal expansion between the substrate and the second layer 12, it is possible to prevent cracks or distortion of the crystal lattice from occurring in the second layer 12 during cooling after the second layer 12 has been formed. Therefore, because the transparent conductive film of this embodiment has the first layer 11, cracks and distortion of the crystal lattice within the second layer 12 can be reduced, thereby improving the conductivity of the second layer 12.

[0036] Furthermore, the first layer 11 functions as a buffer layer, which prevents the transparent conductive film and the second layer 12 from peeling off from the substrate and protects the optical properties of the HTB thin film from the effects of strain. (1-1-2) Regarding film thickness, the film thickness T11 of the first layer 11 is not particularly limited, but for example, the film thickness of the first layer 11 may be 5 nm or more and 1200 nm or less, 10 nm or more and 1200 nm or less, or 30 nm or more and 600 nm or less.

[0037] By making the film thickness of the first layer 11 5 nm or more, the electrical resistance of the transparent conductive film 10 can be reduced, and a highly conductive transparent conductive film can be provided.

[0038] Furthermore, by setting the film thickness of the first layer 11 to 1200 nm or less, the coloration of the first layer 11 and the transparent conductive film 10 can be reduced, and the visible light transmittance can be improved. Also, by setting the film thickness of the first layer 11 to 1200 nm or less, when the first layer 11 is formed by sputtering or the like, the amount of target used during the manufacturing of the first layer 11 can be reduced and the sputtering deposition time can be shortened, thereby increasing productivity. (1-2) Second layer (1-2-1) Composition The HTB thin film contained in the second layer 12 is of general formula A ｘ W ｙ O ｚ It may contain HTB represented by the general formula A. ｘ W ｙ O ｚ It can also be composed of HTB represented by [formula], but even in this case, it does not eliminate the possibility of unavoidable impurities being introduced during the manufacturing process, etc.

[0039] In the above general formula, it is preferable that x, y, and z satisfy the following conditions: 0.2 ≤ x / y ≤ 0.5 and 2.5 ≤ z / y ≤ 3.0.

[0040] Element A may contain one or more alkali metal elements selected from K (potassium), Rb (rubidium), and Cs (cesium). Some of the alkali metal elements contained in element A may be substituted with one or more elements selected from Na (sodium), Tl (thallium), In (indium), Li (lithium), Be (beryllium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium), Al (aluminum), and Ga (gallium).

[0041] In other words, element A includes one or more alkali metal elements selected from K, Rb, and Cs, and may further include one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga as needed. (1-2-2) Regarding the crystal structure, the HTB thin film contained in the second layer 12 has the original crystal structure of hexagonal tungsten bronze, thereby generating free electrons and providing a transparent conductive film with excellent conductivity.

[0042] Therefore, it is preferable that the HTB thin film contained in the second layer 12 exhibits a hexagonal pattern in the X-ray diffraction pattern. Furthermore, the second layer 12 contains Cs, which is normally recognized as a different phase. ４ W １１ O ３５ , Cs ６ W １１ O ３５ , (Cs ２ O) ０．４４ W ２ O ６ , CsW １．６ O ６ It is preferable that there are no trace amounts of crystalline phases such as O, OH, OH, or a pyrochlore phase shift. ２ , H ３ It is preferable that ions such as O are not incorporated into the transparent conductive film (Patent Document 3). However, other phases may be included as long as it is within a range that allows for a transparent conductive film with excellent conductivity.

[0043] The HTB thin film contained in the second layer 12 may have an unoriented polycrystalline structure, but it is more preferable that it has a polycrystalline structure oriented to the {10-10} plane. That is, the diffraction peak intensity of the second layer 12 is increased due to the {10-10} plane of the HTB thin film, and it is more preferable that the HTB thin film has orientation to the prism plane. When the HTB thin film has a polycrystalline structure oriented to the {10-10} plane, free electrons are transported in the c-axis direction of the hexagonal crystal, so the conductivity of the film is further improved.

[0044] The free electrons in HTB have the characteristic that they are bound in the a-axis and b-axis directions (Non-Patent Literature 1). Therefore, the electrical conductivity σ is higher for free electrons parallel to the c-axis (E / / c) than for free electrons perpendicular to the c-axis (E⊥c). For example, K ０．５ WO ３ Then σ / / = 12.7 [×10 ５ For S / m, σ⊥ = 4.0 [×10 ５ A value of S / m has been reported. Also, Cs ０．３ WO ３ Then σ / / = 14.4 [×10 ５ For S / m, σ⊥ = 5.4 [×10 ５A value of S / m has been reported (Non-Patent Document 2). σ / / represents the electrical conductivity parallel to the c-axis, and σ⊥ represents the electrical conductivity perpendicular to the c-axis.

[0045] Therefore, by orienting the HTB thin film contained in the second layer 12 in the {10-10} plane, conductive paths of crystal grains are formed in the direction of high electrical conductivity, thereby increasing conductivity compared to when they are randomly oriented. (1-2-3) Regarding the lattice constant, the lattice constant of the HTB contained in the second layer 12 is not particularly limited, but it is preferable that the lattice constant of the hexagonal c axis is 7.54 Å or less in the general formula for HTB described above when element A is K. When element A is Rb, it is preferable that the lattice constant of the hexagonal c axis is 7.58 Å or less. When element A is Cs, it is preferable that the lattice constant of the hexagonal c axis is 7.64 Å or less. In particular, it is more preferable that the lattice constant of the hexagonal c axis is 7.49 Å or more and 7.54 Å or less when element A is K. When element A is Rb, it is more preferable that the lattice constant of the hexagonal c axis is 7.51 Å or more and 7.58 Å or less. When element A is Cs, it is more preferable that the lattice constant of the hexagonal c axis be 7.56 Å or more and 7.64 Å or less. (1-2-4) Regarding film thickness, the film thickness T12 of the second layer 12 is not particularly limited, but for example, the film thickness of the second layer 12 may be 5 nm or more and 1200 nm or less, 10 nm or more and 1200 nm or less, or 30 nm or more and 600 nm or less.

[0046] By making the film thickness of the second layer 12 5 nm or more, the electrical resistance of the transparent conductive film 10 can be reduced, and a highly conductive transparent conductive film can be provided.

[0047] Furthermore, by setting the film thickness of the second layer 12 to 1200 nm or less, coloration of the second layer 12 and the transparent conductive film 10 can be suppressed, and visible light transmittance can be improved. Also, by setting the film thickness of the second layer 12 to 1200 nm or less, when the second layer 12 is formed by sputtering, the amount of target used during the manufacturing of the second layer 12 can be suppressed, the sputtering deposition time can be suppressed, and productivity can be increased. (1-3) Protective layer Figure 2 shows a transparent conductive film 20, which is another example of the configuration of this embodiment. The transparent conductive film of this embodiment may further have a protective layer 13 laminated on the second layer 12, as shown in the transparent conductive film 20 in Figure 2. When the transparent conductive film 20 has a protective layer 13, it can be laminated in the order of the first layer 11, the second layer 12, and the protective layer 13, as shown in Figure 2.

[0048] The protective layer 13 may be directly laminated on the second layer 12, or there may be any layer between the second layer 12 and the protective layer 13.

[0049] The presence of the protective layer 13 on the transparent conductive film 20 protects the transparent conductive film 20 from the outside world and prevents damage. Depending on the application of the transparent conductive film 20, the protective layer 13 may also have a function to improve optical properties such as visible light transmittance and infrared region reflectance by adjusting the refractive index.

[0050] The material contained in the protective layer 13 is not particularly limited and can be selected according to the application of the transparent conductive film and the optical properties required for the transparent conductive film. For example, the protective layer 13 may be SiO ２ , TiO ２ WO ３ , Nb ２ O ５ Al ２ O ３ , ZrO ２ Ta ２ O ５ , SnO ２ Si ３ N ４ LaB ６ TiN, MgF ２ , HfO ２ SiO ｘ N ｙ It may contain one or more compounds selected from the group of compounds. The protective layer 13 is, for example, SiO２ , TiO ２ , WO ３ , Nb ２ O ５ , Al ２ O ３ , ZrO ２ , Ta ２ O ５ , SnO ２ , Si ３ N ４ , LaB ６ It may contain one or more selected from the group of compounds of TiN.

[0051] For example, SiO ２ or Nb ２ O ５ etc. have high transparency and high dielectric constant, so when the transparent conductive film 20 is used for an optical device, a display, an electronic device, etc., it can be used as a material for the protective layer 13. For example, ZrO ２ or Si ３ N ４ , Al ２ O ３ etc. can be used as a material for the protective layer 13 when the transparent conductive film 20 is used for a device that requires mechanical strength and heat resistance. Also, for example, SnO ２ or LaB ６ can be used as a material for the protective layer 13 when the transparent conductive film 20 is used for applications that require transparency, chemical stability, and high conductivity.

[0052] The protective film 13 can also be etched when the transparent conductive film is processed into a specific shape or pattern to form a conductive path according to the design of a circuit or device, or when removing the conductivity of unnecessary parts to prevent unintentional electrical shorts and crosstalk.

[0053] The method for etching the protective layer 13 is not particularly limited. For example, the protective layer 13 may be etched by a general etching method. For example, an etching pattern may be printed with a photoresist mask, and the etching of the protective layer 13 may be carried out by spray etching, dip etching, etc. Then, if necessary, through cleaning, removal of the mask, and drying, the protective layer 13 can be etched into a desired pattern. (2) Physical properties, etc. The physical properties of the transparent conductive film 10 of the present embodiment are not particularly limited, but it is preferable to satisfy the characteristics described below, for example. (2-1) Regarding optical properties, the visible light transmittance of the transparent conductive film of the present embodiment is preferably 20% or more and 90% or less, and more preferably 60% or more and 90% or less. (2-2) Regarding electrical properties, the specific resistance value of the transparent conductive film 10 of the present embodiment is preferably －３ Ω·cm or less, and －４ Ω·cm or more and －３ Ω·cm or less is more preferable, and －４ Ω·cm or more and －４ Ω·cm or less is even more preferable.

[0054] Incidentally, the transparent conductive film of the present embodiment may have a protective film. The protective film is a layer provided to protect the first layer and the second layer, and a part of it can be removed by etching or the like as necessary and then used. Therefore, the electrical properties of the transparent conductive film of the present embodiment can be evaluated by the portions of the first layer and the second layer excluding the protective film. When the specific resistance value of the first layer and the second layer is －３ Ω·cm or less, it can be said that it is a transparent conductive film with excellent conductivity. [Manufacturing method of transparent conductive film] Next, a configuration example of the manufacturing method of the transparent conductive film of the present embodiment will be described. According to the manufacturing method of the transparent conductive film of the present embodiment, the transparent conductive film according to one aspect of the present disclosure can be manufactured. Therefore, some descriptions of the matters already described will be omitted. Note that the method for manufacturing the transparent conductive film according to one aspect of the present disclosure is not limited to the following manufacturing method of the transparent conductive film.

[0055] The method for manufacturing a transparent conductive film according to this embodiment may include a film formation step comprising a first layer formation step and a second layer formation step.

[0056] Then, in the second film deposition process, a second layer containing an HTB thin film, which is a thin film of hexagonal tungsten bronze, can be deposited using a target.

[0057] In the first layer deposition process, a first layer can be deposited that forms an epitaxial bond with the HTB thin film.

[0058] The method for manufacturing a transparent conductive film according to this embodiment may further include a heat treatment step in which the film formed in the film formation step is heat-treated.

[0059] The manufacturing process for the transparent conductive film of this embodiment may also include a film deposition process and a heat treatment process for each of the first and second layers. For example, as shown in the flow chart 50 in Figure 5, the manufacturing method for the transparent conductive film of this embodiment may include, for example, a first layer film deposition process S1, a first layer heat treatment process S2, a second layer film deposition process S3, and a second layer heat treatment process S4. However, if the desired transparent conductive film can be formed by omitting any of the above processes, it is not necessary to go through all of the above processes.

[0060] The following describes each process. (1) Film deposition process In the film deposition process, raw material particles can be attached to the substrate by means of a physical film deposition method (dry film deposition method) or a chemical film deposition method to form a thin film. In the film deposition process, the first and second layers can be deposited using one or more methods selected from, for example, vacuum deposition, sputtering, ion plating, ion beam sputtering, pulsed laser deposition (PLD), and chemical vapor deposition (CVD).

[0061] As for the sputtering method, one or more methods selected from high-frequency sputtering, pulsed sputtering, dual magnetron sputtering, etc., may be used. (1-1) The target material used in the target deposition process can be selected according to the composition of the first layer, the second layer, and each of the layers. In addition, multiple targets can be used in the deposition process.

[0062] The raw material for the target used in the first layer deposition process can be a substance containing elements found in the first layer, which forms an epitaxial bond with the second layer's HTB thin film in at least a portion of it.

[0063] Furthermore, the raw material for the target used in the second layer deposition process can be a substance containing elements present in the HTB thin film that the second layer contains.

[0064] The raw materials for the target used in the first layer deposition process and the raw materials for the target used in the second layer deposition process may be materials containing elements common to both the first and second layers.

[0065] For example, the first layer is tungsten oxide WO ３－ｘ If (0 ≤ x ≤ 0.28) is present, the raw material for the target used in the first layer deposition step can be one or more selected from, for example, tungsten and tungsten oxide.

[0066] Furthermore, the hexagonal tungsten bronze (HTB) contained in the second layer is given by general formula A ｘ W ｙ O ｚ When expressed as such, the raw material for the target used in the second layer deposition process can be, for example, a substance containing element A and tungsten. In this case, the raw material for the target used in the second layer deposition process can be selected from various compositions, such as an oxide containing element A and tungsten, a mixture of an oxide of element A and tungsten, or a mixture of element A and a tungsten-containing oxide.

[0067] As described above, when selecting the target raw material, it is preferable to make the ratio of element A to tungsten in the target equivalent to that of the target HTB thin film. Furthermore, if there are differences in the probability of elements A and W reaching the substrate depending on the film deposition conditions, adjusting the ratio of element A to tungsten in the target can make it easier to deposit the target HTB thin film.

[0068] The target for the transparent conductive film in this embodiment can be manufactured, for example, by grinding a compact formed by compressing and molding raw material powder, or a sintered body that has been pressurized at high temperature, through machining.

[0069] In the film deposition process, two targets can be used, for example, a target for the first layer deposition and a target for the second layer deposition. If the amount of sputtering elements can be adjusted by the deposition conditions, a single target consisting of raw materials containing common elements for both the first and second layers may be used.

[0070] If the target resistivity is a conductor of, for example, 1 Ω·cm or less, it is more preferable because it can be used in a DC sputtering apparatus that has a simple power supply configuration and excellent productivity.

[0071] Even if conductivity cannot be obtained from the target, dry film deposition can be performed using high-frequency sputtering, pulsed sputtering, dual magnetron sputtering, ion beam sputtering, and pulsed laser deposition (PLD) methods.

[0072] In order to efficiently carry out the film deposition process and the heat treatment process, it is preferable that the film deposition apparatus used has a mechanism that can use multiple targets and a mechanism that can heat the inside of the film deposition chamber. (1-2) First layer deposition process The first layer deposition process will be described below.

[0073] For example, when depositing a metal oxide film as the first layer using the sputtering method, oxygen gas can be added to the sputtering gas in a volume ratio of 0% to 30%. It is preferable to precisely adjust the amount of oxygen gas added to the sputtering gas. For example, in addition to setting the flow rate using a mass flow controller and pressure control to maintain a constant pressure, plasma monitor control to maintain a constant plasma emission intensity during sputtering, or impedance control to maintain a constant voltage of the plasma power supply (power control) may also be used.

[0074] For sputtering, argon gas can be used, and if necessary, oxygen gas or nitrogen gas can be used in combination with argon gas as a reactive gas.

[0075] There are no particular limitations on the substrate on which the first layer is deposited, but synthetic quartz or glass may be used because they have excellent transparency and flatness and can withstand the substrate heating temperature. Furthermore, since the transparent conductive film can be used as a standalone unit after removing the substrate, resins, metals, inorganic compounds, etc., can also be used as the substrate material.

[0076] In the first layer deposition process, the substrate temperature during deposition is not particularly limited, and for example, the first layer deposition process may be carried out at room temperature, i.e., without heating. However, depending on the properties required for the first layer or the transparent conductive film, the substrate may be heated during the first layer deposition process. For example, when the substrate is heated and sputtering deposition is performed, the first layer is formed on the substrate while crystal growth occurs. This makes it possible to obtain a first layer thin film with uniform crystal orientation. Note that when the substrate is heated during the first layer deposition process, the substrate temperature is not particularly limited, and the substrate temperature can be selected depending on the composition of the first layer to be deposited, for example. (1-3) Second Layer Deposition Process The second layer deposition process will now be described.

[0077] For example, when depositing a second layer by sputtering, oxygen gas can be added to the sputtering gas in a volume ratio of 0% to 30%. It is preferable to precisely adjust the amount of oxygen gas added to the sputtering gas. For example, in addition to setting the flow rate using a mass flow controller and maintaining a constant pressure, plasma monitor control to maintain a constant plasma emission intensity during sputtering, or impedance control to maintain a constant voltage of the plasma power supply (power control) may also be used.

[0078] For sputtering, argon gas can be used, and if necessary, oxygen gas or nitrogen gas can be used in combination with argon gas as a reactive gas.

[0079] The second layer can use the first layer, which is deposited on a substrate, as the substrate.

[0080] In the second layer deposition process, the substrate temperature during deposition is not particularly limited; for example, the process may be carried out at room temperature, i.e., without heating. However, depending on the characteristics required for the second layer or the transparent conductive film, the substrate may be heated during the second layer deposition process.

[0081] Furthermore, from the viewpoint of improving conductivity, it is preferable to reduce the amount of moisture in the HTB thin film contained in the second layer. For this reason, it is preferable to create a high vacuum inside the chamber before introducing the atmospheric gas in the second layer deposition process. More preferably, the moisture pressure inside the chamber should be 1.01 × 10⁻⁶ －４ The pressure can be reduced to Pa or less. (2) Heat treatment process In the heat treatment process, the first layer and the second layer formed in the first layer formation process and the second layer formation process can be heat treated.

[0082] The atmosphere in the heat treatment process is not particularly limited, but may be selected from, for example, a vacuum atmosphere, an inert gas atmosphere, a reducing gas atmosphere such as hydrogen, and an oxidizing gas atmosphere such as oxygen. In the heat treatment process, the heat treatment can be carried out at a heat treatment temperature of 300°C to 1000°C under the above atmosphere. (2-1) First layer heat treatment process The first layer heat treatment process will now be described.

[0083] The atmosphere for the first layer heat treatment process is not particularly limited, but may be selected from, for example, a vacuum atmosphere, an inert gas atmosphere, a reducing gas atmosphere such as hydrogen, and an oxidizing gas atmosphere such as oxygen.

[0084] For the inert gas, for example, noble gases such as helium or argon, or nitrogen gas can be used, but argon gas is preferable because it is commonly used, readily available, and reduces the generation of by-products.

[0085] To avoid contamination with impurities, the purity of the gas used in the first layer heat treatment step is preferably 99% or higher. Furthermore, it is preferable to select the type and ratio of the gas atmosphere in order to control the degree of oxidation-reduction based on the amount of oxygen deficiency in the target product.

[0086] In the first layer heat treatment process, the heat treatment temperature is not particularly limited, but it is preferable to be 1000°C or lower considering the heat resistance of the substrate. In particular, in order to obtain the desired crystal structure for the material contained in the first layer, it is preferable to perform the heat treatment near the phase transition temperature of the target crystal structure.

[0087] While there are no particular limitations on the heating rate and heat treatment time in the first layer heat treatment process, it is preferable that the heating rate be 1°C / min or more in order to promote crystal growth in the first layer, and furthermore, it is preferable to hold the material at the heat treatment temperature for 30 minutes or more after it has reached the heat treatment temperature.

[0088] In the film formation process, if the substrate heating temperature is high and the crystals of the first layer are growing, this heat treatment step may be omitted. (2-2) Second layer heat treatment step The second layer heat treatment step will now be described.

[0089] The atmosphere in the second heat treatment process is not particularly limited, but may be selected from, for example, a vacuum atmosphere, an inert gas atmosphere, a reducing gas atmosphere such as hydrogen, and an oxidizing gas atmosphere such as oxygen.

[0090] For the inert gas, for example, noble gases such as helium or argon, or nitrogen gas can be used, but argon gas is preferable because it is commonly used, readily available, and reduces the generation of by-products.

[0091] To avoid contamination with impurities, the purity of the gas used in the second heat treatment step is preferably 99% or higher. Furthermore, it is preferable to select the type and ratio of the gas atmosphere in order to control the degree of oxidation-reduction depending on the composition of the target product, the amount of oxygen deficiency, etc.

[0092] In the second layer heat treatment process, the heat treatment temperature is not particularly limited, but it is preferably between 300°C and 1000°C. By setting the heat treatment temperature to 300°C or higher, crystallization can be promoted, improving the transparency and conductivity of the film.

[0093] While there are no particular limitations on the heating rate and heat treatment time in the second layer heat treatment process, it is preferable that the heating rate be 1°C / min or more in order to promote crystal growth in the second layer, and further preferable that the temperature be maintained at the heat treatment temperature for 30 minutes or more after reaching the heat treatment temperature.

[0094] If the desired second layer has already been obtained in the film formation process, this heat treatment step may be omitted. (3) The method for manufacturing the transparent conductive film of this embodiment may also include a protective layer formation step and a protective layer heat treatment step as needed.

[0095] The protective layer deposition process can be carried out under the same conditions as the first layer deposition process, except that a target containing a material corresponding to the material of the protective layer to be deposited is used.

[0096] Furthermore, regarding the protective layer heat treatment process, although the heat treatment conditions can be selected according to the composition of the protective layer, etc., it can be carried out under the same conditions as those described in the first layer heat treatment process, for example. Note that the protective layer does not need to be crystallized, so the protective layer heat treatment process does not need to be performed, and the heat treatment may be carried out at a lower temperature than the first layer heat treatment process, etc.

[0097] Furthermore, if necessary, the method for manufacturing the transparent conductive film of this embodiment may also include a substrate removal step to remove the substrate and obtain the transparent conductive film alone. [Transparent conductive film structure] (1) About the transparent conductive film structure Figure 3 shows an explanatory diagram of the transparent conductive film structure of this embodiment. Figure 3 is a cross-sectional view of the transparent conductive film structure of this embodiment in a plane along the lamination direction.

[0098] As shown in Figure 3, the transparent conductive film structure 30 of this embodiment may have a substrate 14 and a transparent conductive film 10 according to one aspect of the present disclosure disposed on the substrate.

[0099] The transparent conductive film 10 can be arranged on the substrate 14 such that the first layer 11 and the second layer 12 are positioned in order from the position closest to the substrate 14.

[0100] In addition, the transparent conductive film structure 40 may also have a protective layer 13 in the transparent conductor 20. In this case, as shown in Figure 4, the transparent conductive film structure 40 may have a protective layer 13 laminated on the second layer 12.

[0101] Since examples of transparent conductive film configurations have already been explained, we will omit further explanation here.

[0102] The material of the substrate 14 is not particularly limited. For example, synthetic quartz or glass that can withstand the substrate heating temperature may be used. (2) Physical properties, etc. The physical properties of the transparent conductive film structure of this embodiment are not particularly limited, but it is preferable that it satisfies the following characteristics, for example. (2-1) Optical properties The visible light transmittance of the transparent conductive film structure of this embodiment is preferably 20% or more and 90% or less, and more preferably 60% or more and 90% or less. (2-2) Electrical properties The resistivity of the transparent conductive film structure of this embodiment is 1.01 × 10 －３ It is preferable that the ratio be less than or equal to Ωcm, and 1.01 × 10 －４ Ω・cm or more 1.01×10 －３ It is more preferable that it be Ω·cm or less, and 1.01 × 10 －４ Ω・cm or more 2.41×10 －４ It is even more preferable that the value be less than or equal to Ωcm.

[0103] The present invention will be described more specifically below with reference to examples, but the present invention is not limited thereto. 1. Evaluation Method (1) X-ray Diffraction Pattern The powder X-ray diffraction pattern (XRD pattern) of the obtained transparent conductive film structure was measured using Cu-Kα rays with a D2PHASER X-ray diffractometer from BRUKER AXS. (2) Transmission Electron Microscope Observation Using a JEOL JEM-ARM200F (JEOL) from JEOL Corporation, normal magnification observation and atomic image observation were performed at an acceleration voltage of 200 kV. (3) Visible Light Transmittance, Solar Transmittance, and Near-Infrared Reflectance To measure the optical properties of the obtained transparent conductive film structure, the transmittance and 8° incident diffuse reflectance were measured using a V-670 spectrophotometer (manufactured by JASCO Corp.), and the transmittance spectrum and reflectance spectrum were obtained. Using spectral data of transmittance and reflectance, visible light transmittance (VLT) and solar radiation transmittance (ST) at wavelengths of 300 nm to 2500 nm were determined in accordance with JIS R 3106 (2019). (4) Film thickness Film thickness was measured from an SEM image taken at any one location on the cross-section of the sample. (5) Surface resistivity and resistivity The surface resistivity of the obtained transparent conductive film structure was measured using Loresta-GXII manufactured by Nitto Seiko Analytic Co., Ltd., and the resistivity was determined by incorporating the shape factor. 2. Manufacturing conditions and evaluation results of transparent conductive films and transparent conductive film structures in examples and comparative examples [Example 1] In Example 1, the first layer was WO ３－ｘ The following was conducted to fabricate and evaluate transparent conductive films and transparent conductive film structures, with the second layer containing Cs-HTB. (1) Fabrication of transparent conductive films and transparent conductive film structures (1-1) Fabrication of tungsten oxide targets for first layer deposition Tungsten oxide powder was placed in a discharge plasma sintering apparatus (NJS Corporation) under vacuum conditions, temperature 870°C, and pressure 50 MPa to produce a tungsten oxide sintered body. This sintered body was machined to a diameter of 20 mm and a thickness of 4 mm to produce a tungsten oxide target. When using a target containing tungsten oxide, the target type in Table 1 should be "WO ３This is written as "CsHTB". (1-2) Preparation of cesium tungsten oxide target for second layer deposition Cesium tungsten oxide powder (YM-01, manufactured by Sumitomo Metal Mining Co., Ltd.) with a Cs / W atomic ratio of 0.33 was placed in a discharge plasma sintering apparatus (NJS Corporation) under the conditions of a vacuum atmosphere, a temperature of 870°C, and a pressure of 50 MPa to produce a cesium tungsten oxide sintered body. Chemical analysis of the sintered body composition revealed that the Cs / W ratio, which is the ratio of the amount of substance of Cs to W, was 0.32. This oxide sintered body was machined to a diameter of 20 mm and a thickness of 4 mm to produce a CsWO target. When using a target containing cesium tungsten oxide, the type of target in Table 1 is written as "CsHTB".

[0104] Using the above target, a transparent conductive film was deposited according to the flow diagram 50 shown in Figure 5. (1-3) First layer deposition process, first layer heat treatment process The tungsten oxide target was placed in the vacuum chamber of the pulsed laser deposition apparatus (Pascal PAC-LMBE). The maximum vacuum pressure was 1 × 10⁻⁶ －５ The pressure was kept below Pa, and during film deposition, oxygen gas was introduced into the vacuum chamber at a gas pressure of 6.8 Pa to deposit the first layer. In Table 1, the gas pressure of the oxygen gas during film deposition is shown in the "Oxygen Gas Pressure" column.

[0105] During film deposition, a KrF laser (wavelength 248 nm, pulse width 25 ns) was used as the irradiation laser, with a laser power of 225 mJ, a laser frequency of 4 Hz, and a laser irradiation time of 10 minutes, under room temperature deposition conditions (no substrate heating).

[0106] Under the above conditions, a tungsten oxide film was deposited on a synthetic quartz substrate in the first layer deposition process (first layer deposition process).

[0107] After the first layer deposition process was completed, the introduction of oxygen gas was stopped, and the substrate was heated to 545°C at a rate of 20°C / min using a heater inside the vacuum chamber. This heat treatment process was then maintained for 30 minutes, after which the substrate was slowly cooled to room temperature at a rate of 50°C / min (first layer heat treatment process).

[0108] The conditions for the first layer deposition process and the first layer heat treatment process are shown in the "First Layer" row and the "Heat Treatment Process" columns, respectively, in the "Layer" column of the "Manufacturing Conditions" section of Table 1. The same applies to the other examples below. (1-4) Second Layer Deposition Process and Second Layer Heat Treatment Process The target used was replaced with a cesium tungsten oxide target. The maximum vacuum pressure was 1 × 10⁻⁶ －５ The vacuum pressure was kept below Pa, and during film deposition, oxygen gas was introduced into the vacuum chamber to achieve a gas pressure of 6.8 Pa for the deposition of the second layer. During film deposition, a KrF laser (wavelength 248 nm, pulse width 25 ns) was used as the irradiation laser, with a laser power of 225 mJ, a laser frequency of 4 Hz, and a laser irradiation time of 10 minutes. The heater temperature for substrate heating was set to a substrate temperature of 545°C. In the first layer deposition process, a cesium tungsten oxide film was deposited on top of the tungsten oxide film, which was the first layer deposited on the synthetic quartz substrate (second layer deposition process).

[0109] After the second layer deposition process was completed and the substrate was cooled to room temperature, the introduction of oxygen gas was stopped, and the heater for heating the substrate inside the vacuum chamber was raised at 20°C / min until the substrate reached 545°C. After raising the temperature, the substrate was held at that temperature for 30 minutes. Then, it was slowly cooled to room temperature at 50°C / min (second layer heat treatment process).

[0110] The conditions for the second layer deposition process and the second layer heat treatment process are shown in the "Deposition Process" and "Heat Treatment Process" columns, respectively, in the "Second Layer" row of the "Layer" column in the "Manufacturing Conditions" section of Table 1. The same applies to the other examples below. (2) Evaluation Results The transparent conductive film and transparent conductive film structure obtained in Example 1 were evaluated according to the procedure described in "1. Evaluation Method". (2-1) X-ray Diffraction Pattern The XRD patterns of the deposited transparent conductive film and transparent conductive film structure in Example 1 were measured using the measurement method described in "(1) X-ray Diffraction Pattern". The results are shown in Figure 6. In the following explanation of the evaluation results for other examples, the transparent conductive film is used as an example, but the same applies to the transparent conductive film structure.

[0111] The XRD pattern of the transparent conductive film in Example 1 is WO ３－ｘThis can be explained as a mixture of both phases, and hexagonal cesium tungsten bronze. Furthermore, the XRD pattern of the transparent conductive film in Example 1 shows a strong diffraction peak intensity originating from the a-axis (200), confirming that in the first layer, the cubic planes of tungsten oxide are oriented parallel to the film surface.

[0112] Regarding the peaks related to the cesium tungsten oxide contained in the second layer, a characteristic feature is that the diffraction peak intensities at (10-10) and (11-20), which are prism planes perpendicular to the bottom surface of the second layer, are relatively stronger than the diffraction peak at (0002), the bottom surface of the second layer. Therefore, it was shown that hexagonal cesium tungsten bronze strongly oriented on the prism plane was formed.

[0113] The orientation of the second layer was quantitatively evaluated using the following procedure.

[0114] Cs ０．３２ WO ３ In the powder XRD pattern (ICDD 83-1334), the XRD peak intensity ratios of the prism planes (10-10) and (11-20) relative to the base plane (0002) were set to 1. Hereinafter, the XRD peak intensity ratio of the prism plane (10-10) relative to the base plane (0002) will be denoted as "P(10-10) / B". Similarly, the XRD peak intensity ratio of the prism plane (11-20) relative to the base plane (0002) will be denoted as "P(11-20) / B".

[0115] And Cs ０．３２ WO ３ The values ​​of "P(10-10) / B" and "P(11-20) / B" in the XRD pattern of the transparent conductive film of Example 1 were calculated, with "P(10-10) / B" and "P(11-20) / B" set to 1 in the powder XRD pattern.

[0116] From the above definition, it can be seen that the larger the values ​​of P(10-10) / B and P(11-20) / B, the stronger the orientation towards the prism surface.

[0117] The transparent conductive film of Example 1 showed large values ​​of P(10-10) / B = 4.48 and P(11-20) / B = 16.49, quantitatively confirming that it has a strong orientation on the prism surface.

[0118] The above P(10-10) / B and P(11-20) / B are shown in the "P(10-10) / B" and "P(11-20) / B" columns of the XRD column in Table 1, respectively. (2-2) Transmission electron microscopy observation A transmission electron microscope was performed on a sample that had been thinned so that the plane along the layer stacking direction was exposed. An example of atomic image observation of a part of the cross section of a two-layer film is shown in Figure 7. The observation orientation is the c-axis orientation of Cs-HTB contained in the second layer 12, and at the same time the WO contained in the first layer 11 ３－ｘ This is the

[010] M direction. WO ３－ｘ The atomic arrangement clearly confirmed that the Cs-HTB interface is epitaxially bonded with (10-10)H and (200)M planes.

[0119] Note that in Figure 7, for convenience, the first layer 11 is shown as WO ３ Regarding the second layer 12, Cs ０．３３ WO ３ It states that.

[0120] In other words, it was confirmed that at least a portion of the first layer and the HTB thin film of the second layer were epitaxially bonded. (2-3) Visible light transmittance, solar transmittance, and near-infrared reflectance were measured using a spectrophotometer (UH-4150, Hitachi High-Tech Group) to measure the transmittance and 8° incident diffuse reflectance of the transparent conductive film according to Example 1. Using the obtained spectral data, the visible light transmittance (VLT) and solar transmittance (ST) at wavelengths of 300 nm to 2500 nm were determined in accordance with JIS R 3106 (2019).

[0121] As a result, the VLT showed a value of 59.7% and the ST showed a value of 28.7%, confirming that it has high visible light transmission characteristics. Solar radiation shielding characteristics due to near-infrared reflection were also observed, which suggests high conductivity of the film.

[0122] VLT and ST are shown in the "Optical Properties" column of Table 1, respectively. (2-4) When the transparent conductive film obtained in Example 1 was evaluated from a cross-sectional SEM image, the film thickness of the first layer was 94 nm and the film thickness of the second layer was 91 nm.

[0123] The film thickness of each layer, and the sum of the film thicknesses of the first and second layers, are shown in the "Film Thickness" column of Table 1. (2-5) Surface resistivity, resistivity The surface resistivity of the transparent conductive film obtained in Example 1 is 2.56 × 10 (Ω / □), and the resistivity is 4.7 × 10 from the film thickness and sample shape. －４ It was (Ω・cm).

[0124] From these results, it was confirmed that the transparent conductive film and transparent conductive film structure of Example 1 are useful materials that possess both high transparency and conductivity.

[0125] Surface resistivity and resistivity are shown in the "Electrical Properties" column of Table 1. [Example 2] (1) Fabrication of transparent conductive film and transparent conductive film structure For the cesium tungsten oxide target for second layer deposition, a target with a Cs / W ratio of 0.15 (the ratio of the amount of substance of Cs to W) was used. Except for the above, the transparent conductive film and transparent conductive film structure were fabricated under the same conditions and procedures as in Example 1. (2) Evaluation results The transparent conductive film and transparent conductive film structure of Example 2 were evaluated using the same procedure as in Example 1. (2-1) X-ray diffraction pattern From the XRD pattern measured for the transparent conductive film of Example 2, WO ３－ｘ The existence of hexagonal cesium tungsten bronze was also confirmed.

[0126] In the second layer, the diffraction peak intensities of the (10-10) and (11-20) prism planes perpendicular to the bottom surface were relatively strong, indicating the formation of hexagonal cesium tungsten bronze strongly oriented toward the prism plane. Values ​​of P(10-10) / B = 2.98 and P(11-20) / B = 25.16 were observed, numerically confirming the strong orientation toward the prism plane. (2-2) Transmission electron microscopy observation A sample thinned along the stacking direction of the layers was observed using a transmission electron microscope. As a result, it was clearly confirmed from the atomic arrangement observed by locally magnifying the atomic image according to the

[0001] orientation of the second layer that at least a portion of the first layer and the HTB thin film of the second layer are epitaxially bonded. (2-3) Measurement of visible light transmittance, solar transmittance, and near-infrared reflectance From the spectral data of the transparent conductive film according to Example 2, the VLT was 56.8% and the ST was 30.2%, confirming that it has high visible light transmission characteristics. (2-4) Film thickness When the transparent conductive film obtained in Example 2 was evaluated from a cross-sectional SEM image, the film thickness of the first layer was 92 nm and the film thickness of the second layer was 88 nm. (2-5) Surface resistivity and resistivity The surface resistivity of the transparent conductive film obtained in Example 2 was 2.31 × 10 (Ω / □), and the resistivity was 4.2 × 10 based on the film thickness and sample shape. －４ It was (Ω・cm).

[0127] From the above results, it was confirmed that the transparent conductive film and transparent conductive film structure of Example 2 are useful materials that possess both high transparency and conductivity. [Example 3] (1) Fabrication of transparent conductive film and transparent conductive film structure In the first layer deposition process, the deposition time (laser irradiation time) was set to 5 minutes, and in the second layer deposition process, the deposition time (laser irradiation time) was set to 5 minutes. Except for the above, the transparent conductive film and transparent conductive film structure were fabricated under the same conditions and procedures as in Example 1. (2) Evaluation results The transparent conductive film and transparent conductive film structure of Example 3 were evaluated using the same procedure as in Example 1. (2-1) X-ray diffraction pattern From the XRD pattern measured for the transparent conductive film of Example 3, WO ３－ｘ The existence of hexagonal cesium tungsten bronze was also confirmed.

[0128] Furthermore, the strong diffraction peak intensity originating from the a-axis (200) in the first layer confirmed the formation of a-axis oriented tungsten oxide.

[0129] In the second layer, the diffraction peak intensities of the (10-10) and (11-20) prism planes perpendicular to the bottom surface were relatively strong, indicating the formation of hexagonal cesium tungsten bronze strongly oriented toward the prism plane. Values ​​of P(10-10) / B = 3.44 and P(11-20) / B = 15.69 were observed, numerically confirming the strong orientation toward the prism plane. (2-2) Transmission electron microscopy observation A sample thinned along the stacking direction of the layers was observed using a transmission electron microscope. As a result, it was clearly confirmed from the atomic arrangement observed by locally magnifying the atomic image according to the

[0001] orientation of the second layer that at least a portion of the first layer and the HTB thin film of the second layer are epitaxially bonded. (2-3) Measurement of visible light transmittance, solar transmittance, and near-infrared reflectance From the spectral data of the transparent conductive film according to Example 3, the VLT was 75.5% and the ST was 45.6%, confirming that it has high visible light transmission characteristics. (2-4) Film thickness When the transparent conductive film obtained in Example 2 was evaluated from a cross-sectional SEM image, the film thickness of the first layer was 48 nm and the film thickness of the second layer was 45 nm. (2-5) Surface resistivity and resistivity The surface resistivity of the transparent conductive film obtained in Example 1 was 1.85 × 10 (Ω / □), and the resistivity was 1.7 × 10 from the film thickness and sample shape. －４ It was (Ω・cm).

[0130] From the above results, it was confirmed that the transparent conductive film and transparent conductive film structure of Example 3 are useful materials that possess both high transparency and conductivity. [Example 4] (1) Fabrication of transparent conductive film and transparent conductive film structure (1-1) Deposition of the first and second layers Under the same conditions as in Example 1, the first layer deposition process, the first layer heat treatment process, the second layer deposition process, and the second layer heat treatment process were carried out to deposit the first and second layers on a synthetic quartz substrate. (1-2) Fabrication of a target for protective layer deposition LaB ６ The powder (Nippon Shinkinzoku Co., Ltd.) was placed into a discharge plasma sintering apparatus (NJS Co., Ltd.) under the conditions of a vacuum atmosphere, a temperature of 1000°C, and a pressure of 50 MPa, and LaB ６A sintered body was fabricated. This LaB ６ The sintered body was machined to a diameter of 20 mm and a thickness of 4 mm using LaB. ６ The target was fabricated. (1-3) Protective layer deposition process, protective layer heat treatment process LaB ６ The target was placed inside the vacuum chamber of a pulsed laser deposition system (Pascal PAC-LMBE). The maximum vacuum pressure was 1 × 10⁻¹⁶. －５ A protective layer was deposited at a pH of Pa or less.

[0131] During film deposition, a KrF laser (wavelength 248 nm, pulse width 25 ns) was used as the irradiation laser, with a laser power of 225 mJ, a laser frequency of 4 Hz, and a laser irradiation time of 5 minutes, under room temperature deposition conditions (no substrate heating).

[0132] Under the above conditions, LaB is placed on the second layer. ６ A protective film was formed (protective layer formation process).

[0133] After the protective layer deposition process, the substrate heating heater inside the vacuum chamber was raised at a rate of 20°C / min until the substrate reached 545°C. After raising the temperature, the substrate was held at that temperature for 30 minutes in a protective layer heat treatment process, and then slowly cooled to room temperature at a rate of 50°C / min.

[0134] The conditions for the protective layer deposition process and the protective layer heat treatment process are shown in the "Deposition Process" and "Heat Treatment Process" columns, respectively, in the "Protective Layer" row in the "Layer" column of the "Manufacturing Conditions" section of Table 1. The same applies to Example 5 below. (2) Evaluation Results The transparent conductive film and transparent conductive film structure of Example 4 were evaluated using the same procedure as in Example 1. (2-1) X-ray Diffraction Pattern From the XRD pattern measured for the transparent conductive film of Example 4, WO ３－ｘ The presence of hexagonal cesium tungsten bronze was confirmed. Additionally, LaB was found around 2θ = 21.4°. ６ A diffraction peak originating from [the source of the signal] was detected.

[0135] Other evaluation results are shown in Table 1. (2-2) Transmission electron microscopy observation A sample thinned along the layer stacking direction was observed using a transmission electron microscope. As a result, it was clearly confirmed from the atomic arrangement observed by locally magnifying the atomic image in line with the

[0001] orientation of the second layer that at least a portion of the first layer and the HTB thin film of the second layer are epitaxially bonded. (2-3) Measurement of visible light transmittance, solar transmittance, and near-infrared reflectance Spectroscopic data of the transparent conductive film according to Example 4 showed a VLT of 56.7% and an ST of 26.3%, confirming that it has high visible light transmission characteristics. From these results, LaB ６ It was confirmed that it has high transparency and functions as a protective layer without impairing the transparency of the first and second layers. (2-4) Film Thickness When the transparent conductive film obtained in Example 4 was evaluated from a cross-sectional SEM image, the film thickness of the first layer was 93 nm, the film thickness of the second layer was 90 nm, and the film thickness of the protective layer was 41 nm. (2-5) Surface Resistivity and Resistivity The surface resistivity of the transparent conductive film obtained in Example 4 was 2.05 × 10⁻⁶. ４ (Ω / □) and, given the film thickness and sample shape, the resistivity is 4.6 × 10⁻⁶. －１ The result was (Ω・cm). This result is for the protective layer LaB ６ This is due to the conductivity of the layer.

[0136] The transparent conductive film and transparent conductive film structure obtained in Example 4 can be made into a transparent conductive film having the same electrical properties as in Example 1 by removing at least a portion of the protective layer by etching, for example. Therefore, it was confirmed that the transparent conductive film and transparent conductive film structure of Example 4 are useful materials that combine high transparency and conductivity. [Example 5] (1) Fabrication of transparent conductive film and transparent conductive film structure (1-1) Deposition of the first and second layers Under the same conditions as in Example 1, the first layer deposition process, the first layer heat treatment process, the second layer deposition process, and the second layer heat treatment process were carried out to deposit the first and second layers on a synthetic quartz substrate. (1-2) Fabrication of a target for protective layer deposition Si ３ N ４ The powder (Nippon Shinkinzoku Co., Ltd.) is placed into a discharge plasma sintering apparatus (NJS Co., Ltd.) under the conditions of a vacuum atmosphere, a temperature of 1500°C, and a pressure of 50 MPa, and Si ３ N ４A sintered body was fabricated. This Si ３ N ４ The sintered body is machined to a diameter of 20 mm and a thickness of 4 mm and then ground down to Si ３ N ４ The target was fabricated. (1-3) Protective layer deposition process, protective layer heat treatment process Si ３ N ４ The target was placed inside the vacuum chamber of a pulsed laser deposition system (Pascal PAC-LMBE). The maximum vacuum pressure was 1 × 10⁻¹⁶. －５ A protective layer was deposited at a pH of Pa or less.

[0137] During film deposition, a KrF laser (wavelength 248 nm, pulse width 25 ns) was used as the irradiation laser, with a laser power of 225 mJ, a laser frequency of 4 Hz, and a laser irradiation time of 5 minutes, under room temperature deposition conditions (no substrate heating).

[0138] Under the above conditions, Si is placed on the second layer. ３ N ４ A protective film was formed (protective layer formation process).

[0139] After the protective layer deposition process, the substrate heating heater inside the vacuum chamber was raised at 20°C / min until the substrate reached 545°C, and after raising the temperature, a protective layer heat treatment process was performed in which the temperature was maintained for 30 minutes, followed by slow cooling to room temperature at 50°C / min. (2) Evaluation results The transparent conductive film and transparent conductive film structure of Example 5 were evaluated using the same procedure as in Example 1. (2) X-ray diffraction pattern From the XRD pattern measured for the transparent conductive film of Example 5, WO ３－ｘ The presence of hexagonal cesium tungsten bronze was confirmed. Also, Si was found around 2θ = 20.55°. ３ N ４ A diffraction peak originating from [the source of the signal] was detected.

[0140] Other evaluation results are shown in Table 1. (2-2) Transmission electron microscopy observation A sample thinned along the layer stacking direction was observed using a transmission electron microscope. As a result, it was clearly confirmed from the atomic arrangement observed by locally magnifying the atomic image in line with the

[0001] orientation of the second layer that at least a portion of the first layer and the HTB thin film of the second layer are epitaxially bonded. (2-3) Measurement of visible light transmittance, solar transmittance, and near-infrared reflectance Spectroscopic data of the transparent conductive film according to Example 5 showed values ​​of 60.1% for VLT and 27.8% for ST25, confirming that it has high visible light transmission characteristics. From these results Si ３ N ４ It was confirmed that it has high transparency and functions as a protective layer without impairing the transparency of the first and second layers. (2-4) Film Thickness When the transparent conductive film obtained in Example 5 was evaluated from a cross-sectional SEM image, the film thickness of the first layer was 94 nm, the film thickness of the second layer was 90 nm, and the film thickness of the protective layer was 51 nm. (2-5) Surface Resistivity and Resistivity The surface resistivity of the transparent conductive film obtained in Example 5 was 5.35 × 10⁻⁶. ９ (Ω / □) and, given the film thickness and sample shape, the resistivity is 1.3 × 10⁻⁶. ５ The result was (Ω·cm). This result indicates that the protective layer is Si ３ N ４ This is due to the conductivity of the film, Si ３ N ４ Because it is a highly insulating material, it was confirmed that it functions as a protective layer without affecting the electrical properties of the first or second layer.

[0141] The transparent conductive film and transparent conductive film structure obtained in Example 5 can be made into a transparent conductive film having the same electrical properties as in Example 1 by removing at least a part of the protective layer by etching, for example. Therefore, it was confirmed that the transparent conductive film and transparent conductive film structure of Example 5 are useful materials that combine high transparency and conductivity. [Comparative Example 1] (1) Preparation of transparent conductive film and transparent conductive film structure In Comparative Example 1, only the first layer deposition process and the first layer heat treatment process were performed, and the second layer deposition process and the second layer heat treatment process were not performed. The first layer deposition process and the first layer heat treatment process were performed under the same conditions and procedures as in Example 1. (2) Evaluation results The transparent conductive film and transparent conductive film structure of Comparative Example 1 were evaluated using the same procedure as in Example 1. (2-1) X-ray diffraction pattern From the XRD pattern of the obtained thin film, WO ３ and WO ３－ｘ The presence of was confirmed. In addition, the strong diffraction peak intensity originating from the a-axis (200) indicates that the WO is a-axis oriented. ３ It was confirmed that it was being generated. (2-2) Measurement of visible light transmittance, solar transmittance, and near-infrared reflectance From the spectral data of the transparent conductive film related to Comparative Example 1, the VLT was 76.6% and the ST was 54.3%, confirming that it has high visible light transmission characteristics. (2-3) Film thickness When the transparent conductive film obtained in Comparative Example 1 was evaluated from a cross-sectional SEM image, the film thickness was 101 nm. (2-4) Surface resistivity and resistivity The surface resistivity of the transparent conductive film obtained in Comparative Example 1 was 2.98 × 10⁻⁶. ２ (Ω / □) and, given the film thickness and sample shape, the resistivity is 3.0 × 10⁻⁶ －３ It was (Ω・cm).

[0142] From the above results, the WO contained in the transparent conductive film and transparent conductive film structure of Comparative Example 1 ３－ｘIt was found that the thin film was a Magneli phase with high conductivity. This film is made of a conventionally known material and, from the viewpoint of both conductivity and transparency, did not surpass the properties of the transparent conductive films and transparent conductive film structures of Examples 1 to 5. [Comparative Example 2] (1) Fabrication of transparent conductive film and transparent conductive film structure In Comparative Example 2, only the second layer deposition process was performed, and the first layer deposition process, first layer heat treatment process, and second layer heat treatment process were not performed. The second layer deposition process was performed under the same conditions and procedure as in Example 1. (2) Evaluation results The transparent conductive film and transparent conductive film structure of Comparative Example 2 were evaluated using the same procedure as in Example 1. (2-1) X-ray diffraction pattern The XRD pattern of the obtained thin film showed an amorphous pattern, and the presence of hexagonal cesium tungsten bronze was not confirmed. (2-2) Measurement of visible light transmittance, solar transmittance, and near-infrared reflectance From the spectral data of the transparent conductive film related to Comparative Example 2, the VLT was 70.1% and the ST was 36.9%, confirming that it has high visible light transmission characteristics. (2-3) Film thickness When the transparent conductive film obtained in Comparative Example 2 was evaluated from a cross-sectional SEM image, the film thickness was 106 nm. (2-4) Surface resistivity and resistivity The surface resistivity of the transparent conductive film obtained in Comparative Example 2 was 1.13 × 10⁻⁶. ２ (Ω / □) and, given the film thickness and sample shape, the resistivity is 1.2 × 10⁻⁶. －３ It was (Ω・cm).

[0143] From the above results, it was confirmed that the CsHTB monolayer film contained in the transparent conductive film and transparent conductive film structure of Comparative Example 2 has low conductivity and high visible light transmittance, but its properties as a transparent conductive film and transparent conductive film structure are inferior.

[0144]

[0145] Examples of embodiments of the present disclosure are as follows:

[0146] <1> A transparent conductive film having a first layer and a second layer, wherein the second layer is directly laminated on the first layer, the second layer includes an HTB thin film which is a thin film of hexagonal tungsten bronze, and at least a portion of the first layer is epitaxially bonded to the HTB thin film of the second layer.

[0147] <2> The first layer is WO ３－ｘ A transparent conductive film according to <1>, comprising tungsten oxide represented by (0 ≤ x ≤ 0.28).

[0148] <3> The transparent conductive film according to <2>, wherein the prism surface of the second layer HTB thin film and the cubic surface of the first layer tungsten oxide are epitaxially joined.

[0149] <4> The transparent conductive film according to any one of <1> to <3>, wherein the film thickness of the first layer is 5 nm or more and 1200 nm or less, and the film thickness of the second layer is 5 nm or more and 1200 nm or less.

[0150] <5> The transparent conductive film according to any one of <1> to <4>, further comprising a protective layer laminated on the second layer.

[0151] <6> The protective layer is SiO ２ , TiO ２ WO ３ , Nb ２ O ５ Al ２ O ３ , ZrO ２ Ta ２ O ５ , SnO ２ Si ３ N ４ LaB ６ The transparent conductive film according to <5>, comprising one or more compounds selected from the group of TiN compounds.

[0152] <7> A transparent conductive film structure comprising a substrate and a transparent conductive film according to any one of <1> to <6> disposed on the substrate, wherein the transparent conductive film is disposed on the substrate such that the first layer and the second layer are located in order from a position close to the substrate.

[0153] <8> The transparent conductive film structure described in <7>, wherein the visible light transmittance is 20% or more and 90% or less.

[0154] <9> The resistivity is 1.01 × 10 －４ Ω・cm or more 1.01×10 －３ A transparent conductive film structure as described in <7> or <8>, having a density of Ω·cm or less.

[0155] <10> A method for manufacturing a transparent conductive film, comprising a film deposition step including a first layer deposition step and a second layer deposition step, wherein in the second layer deposition step, a second layer including an HTB thin film which is a thin film of hexagonal tungsten bronze is deposited using a target, and in the first layer deposition step, a first layer which is epitaxially bonded to the HTB thin film is deposited.

[0156] <11> The method for manufacturing a transparent conductive film according to <10>, wherein in the film formation step, the first layer and the second layer are formed using one or more methods selected from vacuum deposition, sputtering, ion plating, ion beam sputtering, pulsed laser deposition (PLD), and chemical vapor deposition (CVD).

[0157] <12> A method for manufacturing a transparent conductive film according to <10> or <11>, further comprising a heat treatment step of heat-treating the film formed in the film formation step.

[0158] <13> The method for manufacturing a transparent conductive film according to <12>, wherein the heat treatment step is performed in an atmosphere selected from a vacuum atmosphere, an inert gas atmosphere, a reducing gas atmosphere, or an oxidizing gas atmosphere, at a heat treatment temperature of 300°C or more and 1000°C or less.

[0159] This application claims priority based on Japanese Patent Application No. 2024-184468, filed with the Japan Patent Office on 18 October 2024, and the entire contents of Japanese Patent Application No. 2024-184468 are incorporated herein by reference.

[0160] 10 Transparent conductive film 11 First layer T11 Film thickness 12 Second layer T12 Film thickness 20 Transparent conductive film 13 Protective layer 30 Transparent conductive film structure 14 Substrate 40 Transparent conductive film structure 50 Flow diagram S1 First layer deposition process S2 First layer heat treatment process S3 Second layer deposition process S4 Second layer heat treatment process

Claims

1. A transparent conductive film comprising a first layer and a second layer, wherein the second layer is directly laminated on the first layer, the second layer includes an HTB thin film which is a thin film of hexagonal tungsten bronze, and at least a portion of the first layer is epitaxially bonded to the HTB thin film of the second layer.

2. The first layer is WO ３－ｘ The transparent conductive film according to claim 1, comprising tungsten oxide represented by (0 ≤ x ≤ 0.28).

3. The transparent conductive film according to claim 2, wherein the prism surface of the second layer HTB thin film and the cubic surface of the first layer tungsten oxide are epitaxially bonded.

4. The transparent conductive film according to any one of claims 1 to 3, wherein the film thickness of the first layer is 5 nm or more and 1200 nm or less, and the film thickness of the second layer is 5 nm or more and 1200 nm or less.

5. The transparent conductive film according to any one of claims 1 to 4, further comprising a protective layer laminated on the second layer.

6. The protective layer is SiO ２ , TiO ２ , WO ３ , Nb ２ O ５ , Al ２ O ３ , ZrO ２ , Ta ２ O ５ , SnO ２ , Si ３ N ４ , LaB ６ , the transparent conductive film according to claim 5, comprising one or more selected from the group of compounds of TiN.

7. A transparent conductive film structure comprising a substrate and a transparent conductive film according to any one of claims 1 to 6 disposed on the substrate, wherein the transparent conductive film is disposed on the substrate such that the first layer and the second layer are located in order from the position closest to the substrate.

8. The transparent conductive film structure according to claim 7, wherein the visible light transmittance is 20% or more and 90% or less.

9. The resistivity is 1.01 × 10⁻⁶. －４ Ω・cm or more 1.01×10 －３ A transparent conductive film structure according to claim 7 or claim 8, wherein the density is Ω·cm or less.

10. A method for manufacturing a transparent conductive film, comprising a film deposition step including a first layer deposition step and a second layer deposition step, wherein in the second layer deposition step, a second layer including an HTB thin film, which is a thin film of hexagonal tungsten bronze, is deposited using a target, and in the first layer deposition step, a first layer is deposited that is epitaxially bonded to the HTB thin film.

11. The method for manufacturing a transparent conductive film according to claim 10, wherein in the film formation step, the first layer and the second layer are formed using one or more methods selected from vacuum deposition, sputtering, ion plating, ion beam sputtering, pulsed laser deposition (PLD), and chemical vapor deposition (CVD).

12. A method for manufacturing a transparent conductive film according to claim 10 or claim 11, further comprising a heat treatment step of heat treating the film formed in the film formation step.

13. The method for manufacturing a transparent conductive film according to claim 12, wherein the heat treatment step is performed in an atmosphere selected from a vacuum atmosphere, an inert gas atmosphere, a reducing gas atmosphere, or an oxidizing gas atmosphere, at a heat treatment temperature of 300°C to 1000°C.

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