Composite tungsten oxide film, method for manufacturing the same, and film-formed substrate and article having the same

Abstract

The present invention relates to a composite tungsten oxide film, a method for producing the same, a film-formed substrate and an article having the film. The composite tungsten oxide film is a composite tungsten oxide film having a composition represented by a general formula M x W y O z as a main component, wherein M is one or more elements selected from alkali metals other than Na, alkaline earth metals, Fe, Tl, and Sn, W is tungsten, and O is oxygen, characterized in that 0.001 ≤ x / y ≤ 1, 2.2 ≤ z / y ≤ 3.0, and the film is substantially free of organic components, is a sputtered film and a heat-treated film having a transmittance of 50% or more at a wavelength of 550 nm, a transmittance of 30% or less at a wavelength of 1400 nm, and a reflectance of 35% or more at a wavelength of 1400 nm, and has a sheet resistance of less than 10 5 Ω / □.

Description

[0001] This application is a divisional application of Chinese patent application No. 201980040623.2, filed on June 6, 2019, entitled "Composite tungsten oxide film and method of manufacturing the same, and film forming substrate and article having the film". Technical Field

[0002] This invention relates to composite tungsten oxide films and methods for manufacturing the same, and further to film-forming substrates having the composite tungsten oxide film and articles utilizing the functions of the composite tungsten oxide film. This application is based on and claims priority to Japanese Patent Application No. 2018-117340, filed June 20, 2018, and Japanese Patent Application No. 2019-24926, filed February 14, 2019, which are incorporated herein by reference. Background Technology

[0003] Various materials have been proposed for use as shading components in window materials and the like. For example, Patent Document 1 describes a shading component with a mirror-like film formed from metals such as aluminum by vapor deposition, which is used as a shading component for window materials, etc. Additionally, there are shading components with films formed from materials such as silver by sputtering. However, when using these shading components, because their appearance is semi-reflective, the reflection is too glaring when used outdoors, posing a visual problem. On the other hand, shading components that utilize reflection generally also reflect far-infrared rays, thus possessing the advantage of also providing heat insulation. The reflection of light, including far-infrared rays, by this shading component is caused by the action of free electrons.

[0004] In response, the applicant has proposed an infrared shielding microparticle dispersion containing composite tungsten oxide microparticles, as described in Patent Document 2. The composite tungsten oxide microparticles efficiently absorb sunlight (especially near-infrared light) and exhibit high transparency to visible light. In the invention described in Patent Document 2, the composite tungsten oxide microparticles are dispersed in a suitable solvent to form a dispersion. A medium resin is added to the resulting dispersion, and the dispersion is then coated onto a substrate surface to form a thin film, thereby achieving very high thermal insulation. This infrared shielding microparticle dispersion exhibits high thermal insulation due to its excellent light absorption properties; however, since it has almost no reflective properties, its thermal insulation performance cannot be overly expected.

[0005] Patent document 3 discloses a composite tungsten oxide film manufactured by heat treatment after coating a solution of a raw material compound containing composite tungsten oxide onto a substrate. A portion of the film disclosed herein is as described in that document. Figure 2 and Figure 3 The dashed line indicates a reflectivity of approximately 30% at a wavelength of 1400nm, suggesting some degree of heat insulation.

[0006] Furthermore, Patent Document 4 discloses a method for obtaining Na by dropping a solution of a raw material compound containing composite tungsten oxide onto a rotating substrate, forming a film using centrifugal force, and then calcining it in a reducing atmosphere. x WO3 membrane. According to this literature... Figure 1 The film reflects most of the light in the infrared region, and can be considered to have both shielding and heat insulation properties.

[0007] On the other hand, such composite tungsten oxide films are sometimes used in optical designs for purposes such as color adjustment and anti-reflection. However, in these cases, the thickness of the stacked films is extremely thin, ranging from several nm to hundreds of nm. Therefore, it is necessary to control the thickness of the composite tungsten oxide film to less than 100 nm, but it is difficult to control the thickness to less than 100 nm using coating methods. Furthermore, the surface roughness of the stacked composite tungsten oxide film requires smoothness; if the surface roughness of the film formation surface is large, the desired optical design effect cannot be obtained. In the coating and firing methods described in Patent Documents 3 and 4, crystals precipitate from the solution, and the surface roughness tends to increase during the process known as grain growth. Reproducing the method described in Patent Document 3, the surface roughness was measured using a laser microscope, and the result, calculated as an arithmetic mean height Sa, exceeded 60 nm.

[0008] Other methods for obtaining composite tungsten oxide thin films include physical methods such as vapor deposition and sputtering, as seen in the example of Patent Document 1. Thin films obtained by physical film formation methods can form films that exclude elements other than the target composition. Furthermore, since it eliminates the need for dispersants and dielectric resins unsuitable for high-temperature processing, it can be used in manufacturing processes such as high-temperature heat-treated tempered glass. Moreover, thin films obtained by physical film formation methods are easy to control even at thicknesses less than 100 nm, and can form very smooth surfaces with arithmetic mean roughness count of nm or less, thus facilitating the formation of laminated structures.

[0009] Patent document 5 discloses a method for manufacturing window glass for vehicles, which utilizes a large-scale, continuous sputtering apparatus capable of processing large-area substrates such as those used for vehicle windows. Using such manufacturing equipment, it is easy to obtain films with uniform thickness, high quality, and stability, while also achieving high productivity. Furthermore, the film-forming source in physical film-forming methods (e.g., the target material in sputtering) can be not a single compound, but rather a combination of single-element compositions, a mixture of multiple compounds, etc., offering a high degree of freedom in composition selection.

[0010] Patent document 6 discloses a composite tungsten oxide film fabricated by sputtering. A composite tungsten oxide film composed of tungsten and at least one element selected from the group consisting of groups IVa, IIIa, VIIb, VIb, and Vb of the periodic table is formed on a glass substrate. However, the infrared transmittance of this oxide film is over 40%, resulting in insufficient thermal shielding performance. Furthermore, if it is formed into a multilayer film with other transparent dielectric films, it may fail to function properly.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 5-113085

[0014] Patent Document 2: Japanese Patent No. 4096205

[0015] Patent Document 3: Japanese Patent Application Publication No. 2006-096656

[0016] Patent Document 4: US Patent No. 3505108

[0017] Patent Document 5: Japanese Patent Application Publication No. 2002-020142

[0018] Patent Document 6: Japanese Patent Application Publication No. 8-12378 Summary of the Invention

[0019] The problem that the invention aims to solve

[0020] As mentioned above, the heat-shielding performance of composite tungsten oxide films formed by physical film formation methods is not yet sufficient. On the other hand, while films formed by coating methods have a high ability to absorb light and shield heat rays, their thermal insulation performance cannot be expected to be excellent. Furthermore, there is the problem of reduced film smoothness.

[0021] In order to address this situation, the present invention provides a composite tungsten film and its manufacturing method, wherein the composite tungsten film maintains transparency in the visible light region and has the function of reflecting infrared light for shielding, i.e., heat shielding based on heat insulation, and the film has high smoothness; thereby providing a substrate or article formed using the film with these functions.

[0022] Methods for solving problems

[0023] In response to the above-mentioned issues, the inventors conducted a thorough study on composite tungsten oxide films. Based on the physical film formation method, by optimizing the conditions during film formation, they obtained a composite tungsten film that maintains excellent visible light transmittance while reflecting infrared rays to perform heat insulation function, and also has an extremely smooth film.

[0024] That is, one aspect of the present invention is based on the general formula M x W y O z (Where M is one or more elements selected from alkali metals, alkaline earth metals, Fe, In, Tl, Sn, W is tungsten, and O is oxygen) represents a composite tungsten oxide film with the following composition as the main component: 0.001≤x / y≤1, 2.2≤z / y≤3.0. It is essentially free of organic components and is a sputtered film and heat-treated film with a transmittance of more than 50% at a wavelength of 550nm, a transmittance of less than 30% at a wavelength of 1400nm, and a reflectance of more than 35% at a wavelength of 1400nm.

[0025] According to one aspect of the invention, a composite tungsten oxide film is formed that maintains transparency in the visible light region while simultaneously having the function of reflecting infrared light and providing thermal shielding, i.e., a thermally insulating thermal ray shielding function. Furthermore, since the film is obtained by sputtering, the freedom of composition selection is extremely high, enabling the formation of a stable composite tungsten oxide film. Moreover, since an extremely smooth film can be obtained by sputtering, the effect of optically designed laminated structures can be improved.

[0026] In this case, in one aspect of the invention, the surface roughness Sa can be less than 20 nm.

[0027] By meeting the above conditions, a composite tungsten film with high smoothness is formed.

[0028] Furthermore, in one aspect of the present invention, the thin-film resistance can be less than 10. 5 Ω / □.

[0029] By setting the film resistance to the range described above, even better thermal insulation can be obtained.

[0030] Furthermore, in one aspect of the present invention, M may be one or more elements selected from Cs, Rb, K, Tl, In, Ba, Li, Na, Ca, Sr, Fe, and Sn.

[0031] By selecting M from the above elements, a composite tungsten oxide film with higher infrared reflectivity and shielding function and high film smoothness can be obtained.

[0032] Furthermore, in one aspect of the present invention, the composite tungsten oxide film may contain a hexagonal crystal structure.

[0033] Hexagonal crystals reflect infrared light more efficiently.

[0034] In one aspect of the present invention, when the intensity ratio of the diffraction intensity I(002) of the hexagonal crystal (002) plane obtained by X-ray diffraction using CuKα rays to the diffraction intensity I(200) of the hexagonal crystal (200) plane is set as I(002) / I(200), I(002) / I(200) is 0.30 or more and 0.50 or less, and the ratio c / a of the a-axis to the c-axis of the hexagonal crystal obtained by X-ray diffraction using CuKα rays can be 1.018 to 1.029.

[0035] The composite tungsten oxide film that meets the above requirements in X-ray diffraction analysis becomes a composite tungsten oxide film that maintains excellent visible light transmittance while reflecting infrared rays and providing heat insulation.

[0036] Furthermore, one aspect of the present invention is based on the general formula M x W y O z (Where M is one or more elements selected from alkali metals, alkaline earth metals, Fe, In, Tl, Sn, W is tungsten, and O is oxygen) represents a composite tungsten oxide film with the following composition as the main component: 0.001≤x / y≤1, 2.2≤z / y≤3.0. This composite tungsten oxide film contains a hexagonal crystal structure. When the intensity ratio of the diffraction intensity I(002) of the hexagonal crystal (002) plane obtained by X-ray diffraction using CuKα rays is set as I(002) / I(200), I(002) / I(200) is 0.30 or more and 0.50 or less. The ratio of the a-axis to the c-axis of the hexagonal crystal obtained by X-ray diffraction using CuKα rays, c / a, is 1.018 to 1.029.

[0037] The composite tungsten oxide film that meets the above requirements in X-ray diffraction analysis becomes a composite tungsten oxide film that maintains excellent visible light transmittance while reflecting infrared rays and providing heat insulation.

[0038] In this case, in one aspect of the invention, M can be one or more elements selected from Cs, Rb, K, Tl, and Ba.

[0039] By selecting M from the above elements, a composite tungsten oxide film with higher infrared reflectivity and shielding function can be obtained.

[0040] Furthermore, in one aspect of the present invention, the composite tungsten oxide film may have a film thickness greater than 20 nm.

[0041] By setting the film thickness to this level, a composite tungsten oxide film with high infrared reflectivity can be obtained.

[0042] Another aspect of the invention is a film forming substrate on which the above-described composite tungsten oxide film is formed on at least one surface of the substrate to be film-formed.

[0043] By obtaining a film-forming substrate on which the above-mentioned composite tungsten oxide film is formed, it is possible to obtain a form that is practical in terms of mechanical properties, processability, etc.

[0044] In other aspects of the present invention, the substrate to which the film is formed may have a softening point or heat distortion temperature of 400°C or higher.

[0045] By possessing such characteristics, it is possible to obtain film-forming substrates that impart superior functionality during post-film heat treatment.

[0046] Furthermore, in other aspects of the present invention, the substrate to which the film is formed may be glass.

[0047] By using glass as the substrate for film formation, infrared shielding functions can be applied to glass substrates used in a wide range of fields, such as glass windows for vehicles and buildings, glass fibers, glass for solar power generation, glass for displays, lenses, mirrors, and glass substrates used in semiconductors and MEMS.

[0048] Furthermore, another aspect of the present invention is an article characterized by having one or more of the aforementioned composite tungsten oxide films and / or film-forming substrates.

[0049] According to other aspects of the invention, it is possible to provide energy-efficient articles with low environmental impact during manufacturing in large quantities and at low cost for a variety of applications.

[0050] Furthermore, another aspect of the present invention is a method for manufacturing a composite tungsten oxide film, comprising: a film-forming step of forming a film by a physical film-forming method, and a heat treatment step of heat-treating the film, wherein the film-forming step is performed in an inactive gas, and the heat treatment step is performed in an inactive gas or an inactive gas containing a reducing gas at 400 to 700°C.

[0051] According to this manufacturing method, composite tungsten oxide films with the above-mentioned characteristics can be easily and stably manufactured with high productivity using existing general-purpose manufacturing equipment, exhibiting uniform thickness and high quality.

[0052] Invention Effects

[0053] According to the present invention, a composite tungsten oxide film that is transparent in the visible light region and reflective in the infrared light region can be obtained. Furthermore, according to the present invention, such a composite tungsten oxide film can be provided by a physical manufacturing method that is widely used in industry and is relatively harmless during film formation, thereby utilizing the excellent long-term preservation properties of the raw materials and not being limited by the storage and transportation of hazardous materials. Attached Figure Description

[0054] Figure 1 This is a graph showing the difference in optical properties (transmittance) between the composite tungsten oxide film of the present invention and the infrared shielding material microparticle dispersion described in Patent Document 2.

[0055] Figure 2 This is a graph showing the difference in optical properties (reflectivity) between the composite tungsten oxide film of the present invention and the infrared shielding material microparticle dispersion described in Patent Document 2.

[0056] Figure 3 This is a process diagram illustrating a general process of manufacturing a composite tungsten oxide film according to one embodiment of the present invention. Detailed Implementation

[0057] The composite tungsten oxide film and its manufacturing method according to the present invention will be described below in the following order. It should be noted that the present invention is not limited to the following examples, and any modifications can be made without departing from the spirit of the invention.

[0058] 1. Composite tungsten oxide film

[0059] 2. Manufacturing method of composite tungsten oxide film

[0060] 2-1. Film Forming Process

[0061] 2-2. Heat treatment process

[0062] 3. Film forming substrate

[0063] 4. Items

[0064] <1. Composite tungsten oxide film>

[0065] A composite tungsten oxide film according to one embodiment of the present invention will be described. The composite tungsten oxide film according to one embodiment of the present invention is based on the general formula M... x W y O z (Where M is one or more elements selected from alkali metals, alkaline earth metals, Fe, In, Tl, Sn, W is tungsten, and O is oxygen) represents a membrane whose main components are in the range where the ratio of x to y is 0.001 ≤ x / y ≤ 1 and the ratio of z to y is 2.2 ≤ z / y ≤ 3.0.

[0066] The detailed composition range is disclosed in Patent Document 2 of the applicant. Using a composite tungsten oxide as the main component within this composition range is necessary to obtain a film with high transparency and infrared light absorption. The basic optical properties of the composite tungsten oxide film originate from the theoretically calculated atomic configuration of element M with tungsten W and oxygen O. On the other hand, one embodiment of the present invention is a composite tungsten oxide film having properties different from the infrared shielding body described in Patent Document 2. Hereinafter, a detailed description will be provided while appropriately comparing it with the invention involved in Patent Document 2.

[0067] In one embodiment of the present invention, the element M of the composite tungsten oxide film is selected from one or more elements chosen from alkali metals, alkaline earth metals, Fe, In, Tl, and Sn, more preferably from one or more elements chosen from Cs, Rb, K, Tl, In, Ba, Li, Na, Ca, Sr, Fe, and Sn. This is a narrower range than the constituent elements described in Patent Document 2, but it only shows elements whose effects can be confirmed according to the embodiments. Even elements described in Patent Document 2 that are not included in the present invention may have many of the same functions.

[0068] In one embodiment of the present invention, the element M of the composite tungsten oxide film is further preferably one or more elements selected from Cs, Rb, K, Tl, and Ba. By selecting element M as described above, the composite tungsten film can form a crystal structure containing hexagonal crystals as described below. It should be noted that, depending on the x / y ratio, the aforementioned element M may sometimes form crystal structures other than hexagonal crystals. For example, K is tetragonal when the x / y ratio is 0.5 or higher. Structures containing hexagonal crystal phases have greater reflectivity in the infrared region, thus enabling efficient reflection.

[0069] The composite tungsten oxide film according to one embodiment of the present invention, in general formula M x W y O z In this process, the atomic ratio (x / y) of element M to W (tungsten) is 0.001 ≤ x / y ≤ 1, and the atomic ratio (z / y) of O (oxygen) to W (tungsten) is 2.2 ≤ z / y ≤ 3.0. If x / y is less than 0.001, a sufficient amount of free electrons cannot be generated, and an infrared shielding effect cannot be obtained. Furthermore, if x / y exceeds 1, an impurity phase will form in the composite tungsten oxide film. If z / y is less than 2.2, a crystalline phase of WO2, unrelated to the target, will appear in the composite tungsten oxide film. Moreover, if z / y exceeds 3.0, no free electrons necessary for achieving an infrared shielding effect will be generated.

[0070] One embodiment of the present invention relates to a composite tungsten oxide film that is substantially free of organic components. As described below, the composite tungsten oxide film of one embodiment of the present invention is formed by a physical film-forming method, and therefore does not require the use of dispersants, mediating resins, surfactants, or solvents as described in Patent Documents 2 and 3. Here, "substantially free of organic components" means that no intentionally added organic components, such as polymeric dispersants, are present during the film manufacturing process.

[0071] Patent Document 3, in paragraph 0060, discloses a method for manufacturing a transparent conductive film using a composite tungsten oxide. Accordingly, the transparent conductive film disclosed in Patent Document 3 is obtained by coating a solution containing a composite tungsten compound as an initial tungsten raw material solution onto a substrate and then subjecting it to heat treatment in any of the following atmospheres: an inactive gas, an inactive gas and a reducing gas, or a reducing gas. According to this method, a solution is prepared by adding a surfactant containing an organic component and having a polysiloxane backbone to an aqueous solution of ammonium metatungstate and an aqueous solution of chloride of element M.

[0072] The method described in Patent Document 3 is reproduced, and the surface roughness is measured using a laser microscope, resulting in an arithmetic mean height Sa exceeding 60 nm. On the other hand, an embodiment of the present invention relates to a composite tungsten oxide film formed by a physical film-forming method such as sputtering, as described later, thus achieving a surface roughness Sa of 20 nm or less. Therefore, the smoothness of the composite tungsten oxide film according to an embodiment of the present invention differs from that of the transparent conductive film in Patent Document 3.

[0073] Furthermore, the membrane (microparticle dispersion membrane) formed from a microparticle dispersion containing composite tungsten oxide microparticles in Patent Document 2, as described in paragraphs 0050 and 0053 of Patent Document 2, demonstrates its function as a thermal ray shielding membrane with excellent absorption of light, especially in the near-infrared region.

[0074] Figure 1 , Figure 2 This is a graph showing the difference in optical properties between the composite tungsten oxide film of the present invention and the infrared shielding material microparticle dispersion described in Patent Document 2. Figure 1 It's a graph showing transmittance. Figure 2 This is a graph showing reflectance. For example... Figure 1 , Figure 2 As shown, one embodiment of the present invention relates to a composite tungsten oxide film exhibiting different optical properties than the film formed from a microparticle dispersion (microparticle dispersion film) disclosed in Patent Document 2. In particular, as Figure 2 As shown, the composite tungsten oxide film of the present invention reflects a large amount of light in the infrared region below 1400 nm. The reason for this, as will be explained later, is presumably due to the difference between particulate dispersed films and continuous films, but the detailed reason is not yet clear.

[0075] One embodiment of the present invention relates to a composite tungsten oxide film having a transmittance of 50% or more at a wavelength of 550 nm, a transmittance of 30% or less at a wavelength of 1400 nm, and a reflectance of 35% or more at a wavelength of 1400 nm.

[0076] Even if the transmittance at a wavelength of 550nm, which is an indicator of transparency, is lower than 50%, it can still be used depending on the application. For example, in automotive window films, from the perspective of protecting privacy, black or dark gray is preferred for rear window films, and sometimes pigments are intentionally used together with heat shielding materials.

[0077] The transparency index of this invention refers to the film properties in a state free of intentional pigments or the like described above. If the transparency index is lower than the above value, it will lead to poor light transmission, such as darkening of the room and obstruction of the outside view.

[0078] Similarly, it is also possible to make a configuration in which the transmittance and reflectance at a wavelength of 1400nm, which are indicators of light shielding and reflection performance, do not meet the above values. In this case, the transmittance of infrared light increases, and due to heat insulation, it will cause skin irritation, room temperature rise, and heat generated during photothermal conversion decrease.

[0079] Furthermore, since the reflection of this invention is performed by free electrons, it reflects light below the plasma frequency. In other words, it reflects light with wavelengths above the plasma frequency. That is, if the reflectivity at a wavelength of 1400 nm is low, the reflectivity of far-infrared rays with longer wavelengths will also be low, resulting in reduced heat insulation and a lower effectiveness in retaining heat from indoor heating equipment, etc. To obtain effective heat insulation, the reflectivity at a wavelength of 1400 nm needs to be 35% or higher.

[0080] One embodiment of the present invention relates to a composite tungsten oxide film with a surface roughness Sa of 20 nm or less. In optical thin film design (when stacking films), by utilizing interference to intensify or weaken reflection at specific wavelengths, a steep transmission spectrum is established (adjusting the film's hue), thereby preventing reflection in the visible light region. Regarding the effect of surface roughness, in the aforementioned optical thin film design (when stacking films), due to the small surface roughness, there is less disturbance in the optical path length, and a stable stacked film can be formed. The composite tungsten oxide film according to one embodiment of the present invention, as described below, is a film formed by a physical method using film deposition methods such as sputtering, thus enabling the film's surface roughness Sa to be 20 nm or less. If it is 20 nm or less, the possibility of problems arising in optical thin film design is low. If the surface roughness exceeds 20 nm, a uniform stacked state cannot be obtained, making it difficult to achieve the desired optical thin film design (stacking) effect.

[0081] Furthermore, the composite tungsten oxide film according to one embodiment of the present invention is preferably formed with a film thickness exceeding 20 nm. As described below, the composite tungsten oxide film according to one embodiment of the present invention is a film formed by a physical method, such as sputtering. For example, in the film formed by heat treatment after coating the solution as described in Patent Document 3, residual stress is generated in the film due to the evaporation of essential components such as solvents and resins used in film formation. Moreover, defects such as residual volatile components and porosity may sometimes exist internally. The composite tungsten oxide film according to one embodiment of the present invention is formed without volatile components, thus reducing the residual stress accompanying film formation and preventing defects such as residual volatile components and porosity. Therefore, a film free of cracks and peeling can be formed.

[0082] However, when the film thickness is below 20 nm, sufficient reflectivity is not achieved in the infrared region, and the infrared transmittance at 1400 nm exceeds 30%. In this invention, there are no particular limitations on the film thickness as long as it exceeds the aforementioned limit. However, if the film thickness increases, the transmittance in the visible light region at 550 nm will be less than 50%, resulting in poor visible light transmittance. Sometimes, film peeling may occur due to residual stress from film formation. The film transmittance can be measured using a spectrophotometer.

[0083] One embodiment of the present invention relates to a composite tungsten oxide film with a thin film resistivity of less than 1.0 × 10⁻⁶. 5 Ω / □ (read as ohms per unit area), more preferably less than 1.0 × 10 3 Ω / □. If the film resistivity is higher than the above value, the reflection by free electrons will be weaker, and it will not be able to reflect far-infrared rays in the longer wavelength region, thus failing to achieve heat insulation. The film resistivity can be adjusted by the film formation conditions and heat treatment conditions described later. The film resistivity can be measured, for example, using a resistivity meter.

[0084] Furthermore, the composite tungsten oxide film according to one embodiment of the present invention is generally formed as a continuous film. Even if the film has a shape or shape such as a reflection control form for patterning or a lens function form with concave and convex features, it can be any form as long as it has the features of the present invention.

[0085] One embodiment of the present invention relates to a composite tungsten oxide that preferably contains a hexagonal crystal structure. The hexagonal crystal structure can be determined by X-ray diffraction analysis of the film. Composite tungsten oxides are known to have hexagonal, cubic, tetragonal, orthorhombic, and other crystalline and amorphous structures. The composite tungsten oxide film of one embodiment of the present invention has a hexagonal crystal structure, but may also contain cubic, tetragonal, orthorhombic, or other crystalline and amorphous structures. By including a hexagonal crystal structure in the composite tungsten oxide film, the hexagonal phase reflects more light in the infrared region, thus enabling efficient reflection.

[0086] Furthermore, in one embodiment of the composite tungsten oxide film, the ratio of the a-axis length to the c-axis length of the hexagonal crystal obtained by X-ray diffraction using CuKα rays, c / a, is preferably 1.018 to 1.029. According to ICDD reference code 01-081-1244 in the crystal structure database, c / a is 1.028. If there is an excess or deficiency of atoms compared to the standard hexagonal crystal structure, it is assumed that the a-axis length and c-axis length will change.

[0087] Furthermore, in a composite tungsten oxide film according to one embodiment of the present invention, when the intensity ratio of the diffraction intensity I(002) of the hexagonal (002) plane obtained by X-ray diffraction using CuKα rays to the diffraction intensity I(200) of the hexagonal (200) plane is set as I(002) / I(200), it is preferable that I(002) / I(200) is 0.30 or more and 0.50 or less. In the aforementioned ICDD reference code 01-081-1244, the relative intensity of the (002) plane to the (200) plane is described as 26.2%, therefore the standard intensity ratio I(002) / I(200) is 0.26. The intensity ratio of the composite tungsten oxide film produced by the coating and firing method is this standard value, while the intensity ratio of the present invention is 0.30 or more and 0.50 or less. Since the intensity ratio is greater than the standard, it is considered that the growth of the a and b planes of the hexagonal crystal is suppressed, and there is a tendency for the c plane orientation. If the above c / a does not fall within 1.018 to 1.029 and the intensity ratio I(002) / I(200) does not fall between 0.30 and 0.50, the heat reflection function will decrease.

[0088] It should be noted that when element M is Sn, the crystal structure is trigonal. In the above X-ray diffraction, the ratio of the a-axis length to the c-axis length of the hexagonal crystal, c / a, is calculated by the ratio of the a-axis length to the c-axis length of the trigonal crystal, 2c / a.

[0089] The relationship between this unusual crystallization state and thermal reflectivity is considered unique to sputtering and vacuum evaporation methods. It can be attributed to the process of forming a crystalline structure through heat treatment after the formation of a non-equilibrium amorphous film, but the detailed mechanism remains unclear.

[0090] As described above, the composite tungsten oxide film according to one embodiment of the present invention can form a composite tungsten oxide film having properties different from those described in Patent Documents 2 and 3, being transparent in the visible light region and reflective in the infrared light region, thus serving as an infrared reflective film.

[0091] <2. Manufacturing method of composite tungsten oxide film>

[0092] Next, the manufacturing method of the composite tungsten oxide film will be explained. Figure 3 This is a schematic process diagram illustrating a method for manufacturing a composite tungsten oxide film according to one embodiment of the present invention. One embodiment of the present invention is a method for manufacturing a composite tungsten oxide film with element M, tungsten W, and oxygen O as the main components, comprising a film-forming step S1 using a physical film-forming method and a heat treatment step S2 for heat-treating the film. Each step will be described in detail below.

[0093] <2-1. Film Formation Process>

[0094] In film formation step S1, a physical film formation method is used to form the film. As one embodiment of the present invention, the physical film formation method for the composite tungsten oxide film includes vacuum evaporation, sputtering, ion plating, and ion beam methods. Among these, sputtering offers advantages such as high particle energy, strong adhesion, dense film formation, strong film quality, and stable film formation process, allowing for high-precision control of film quality and thickness. Furthermore, sputtering can form films of high-melting-point metals, alloys, and compounds, and can form films of oxides, nitrides, etc., by introducing reactive gases. It has advantages such as easy composition adjustment and is widely used in a wide range of fields, including liquid crystal display elements, hard disks and other electronic devices, automotive window films, mirrors, and other general-purpose products. It also has many manufacturing apparatuses available, making it a preferred method.

[0095] Used to form the general formula M x W y O z The sputtering target for the composite tungsten oxide film can be selected from various configurations, such as a sputtering target formed from elements M and W, a sputtering target formed from a compound of elements M, W, and O, a sputtering target formed from a compound of elements M and O and element W, and a sputtering target formed from a compound of elements M, W, and O. It is preferable to use a sputtering target pre-formed as a compound phase. If the sputtering target is pre-formed as a compound phase, the dependence of the vapor pressure difference of each element on the film composition can be reduced, enabling stable film formation.

[0096] The sputtering target can be used in the form of, for example, a pressed powder body formed by pressing powder formed from particles of the above-mentioned sputtering target composition, or a sintered body formed by sintering the above-mentioned sputtering target composition.

[0097] Furthermore, as mentioned above, since the sputtering target is formed from pressed powder and sintered material, it is substantially free of organic components, and the film formed using this target is also substantially free of organic components. Here, "substantially free" means that it does not contain intentionally added components such as polymeric dispersants.

[0098] If the sputtering target is, for example, a conductive material with a resistivity of less than 1 Ω·cm, a high-productivity DC sputtering apparatus can be used. Furthermore, if the sputtering target is, for example, a sintered body with a relative density of 70% or more, cracking caused by vibration during transport will be reduced, and extreme care will not be required during operation such as installation in the apparatus, making it a more suitable form for industrial manufacturing.

[0099] The atmosphere for the film-forming process can be varied, but a non-reactive gas atmosphere is preferred. For example, rare gases such as helium and argon, or nitrogen, can be used. In the case of nitrogen, depending on the selected element M, nitrides may sometimes form; argon, which is commonly used and readily available, is more preferred. The purity of the gas used is preferably 99% or higher, and the mixing of oxidizing gases such as oxygen is preferably less than 1%. Although some details are still unclear, if the film is formed in a non-reactive atmosphere and heat-treated under the conditions described later, a composite tungsten oxide film with high reflectivity can be obtained. On the other hand, if the proportion of oxidizing gases exceeds 1%, the reflectivity of the heat-treated composite tungsten oxide film will decrease.

[0100] The film after deposition is usually amorphous, but it is also possible for diffraction peaks based on crystallization to appear during X-ray diffraction analysis.

[0101] <2-2. Heat Treatment Process>

[0102] Next, in the heat treatment step S2, the film obtained from the film formation step S1 is heat-treated. In order to obtain the film properties of the composite tungsten oxide film according to one embodiment of the present invention, the heat treatment step S2 is carried out in an inactive or reducing atmosphere.

[0103] In the heat treatment step S2, the heat treatment temperature is preferably 400–700°C. If the heat treatment temperature is lower than 400°C, the film will remain amorphous and will not crystallize; or, even if it crystallizes, the hexagonal diffraction peaks in X-ray diffraction will become extremely weak, and the thermal insulation properties in the infrared region will be low. Furthermore, although the characteristics of the film of the present invention can be obtained even at heat treatment temperatures higher than 700°C, practical problems such as film-substrate reaction, film peeling from the substrate, and increased surface roughness will occur.

[0104] At any of the above heat treatment temperatures, the heat treatment time is sufficient to ensure the completion of the crystallization of the composite tungsten oxide. Although it also depends on the balance between the thermal conductivity of the substrate and the productivity, it is preferable to adjust it appropriately within the range of 5 to 60 minutes.

[0105] As mentioned above, the heat treatment atmosphere is either an inactive atmosphere or a reducing atmosphere. Examples of inactive atmospheres include nitrogen and argon, while examples of reducing atmospheres include mixtures of nitrogen and hydrogen, and mixtures of argon and hydrogen.

[0106] As described above, the method for manufacturing a composite tungsten oxide film according to one embodiment of the present invention can provide a composite tungsten oxide film with the above-mentioned properties by means of a physical manufacturing method. This physical manufacturing method is widely used in industry and is relatively harmless during film formation. Furthermore, it provides excellent long-term preservation of raw materials and has no limitations during transportation.

[0107] <3. Film Forming Substrate>

[0108] One embodiment of the present invention relates to a film-forming substrate obtained by forming the aforementioned composite tungsten oxide film on at least one surface of a substrate to be film-formed. The substrate to be film-formed is not particularly limited as long as it is capable of forming the composite tungsten oxide film according to one embodiment of the present invention.

[0109] Since the heat treatment temperature of the film after film formation is above 400°C, the substrate for film formation is preferably a substrate with a softening point or heat distortion temperature of 400°C or higher. When using a substrate with a softening point or heat distortion temperature below 400°C, problems such as film peeling from the substrate and cracking in the film may occur during the aforementioned heat treatment. Preferably, the closer the coefficient of thermal expansion of the substrate is to the coefficient of thermal expansion of the film, the better. However, when the film is peeled from the substrate for use, the above conditions do not necessarily need to be met; for example, a substrate that dissolves below 400°C can also be used.

[0110] Substrates for film formation that have a softening point or heat distortion temperature of 400°C or higher include glass, ceramics, and single crystals. The substrate for film formation does not necessarily need to be transparent, but a transparent substrate is required when using the composite tungsten oxide film of this invention with a substrate. Transparent substrates include, for example, transparent ceramics such as glass, YAG, and Y2O3, and single crystals such as sapphire. From the viewpoints of availability, low cost, weather resistance, and chemical resistance, glass with a softening point of 400°C or higher is preferred as the substrate for film formation.

[0111] The substrate may not be flat but may have curved or uneven surfaces; any choice can be made as long as it does not compromise the advantages of the present invention.

[0112] As described above, the film-forming substrate according to one embodiment of the present invention can be fabricated to have an infrared reflective film that is transparent in the visible light region and reflective in the infrared light region.

[0113] <4. Items>

[0114] One embodiment of the present invention relates to an article having one or more of the aforementioned composite tungsten oxide films and / or film-forming substrates. Any article can be any article as long as the composite tungsten oxide film has the function of reflecting light.

[0115] Furthermore, even if the composite tungsten oxide film and / or film forming substrate of the present invention are used together with, for example, films, particles, etc. having other functions, they are included in articles that utilize the functions described in the present invention.

[0116] The composite tungsten oxide film of the present invention is an infrared reflective film that is reflective in the infrared light region. Among articles that have the function of reflecting light and shielding, there are, for example, heat-insulating glass.

[0117] Insulated glass has the advantages of being transparent and blocking heat, which can reduce the rise in indoor and vehicle interior temperatures caused by sunlight in summer. In addition, it can reflect the heat from heating systems in winter and keep it indoors.

[0118] As described above, according to one embodiment of the present invention, a film-forming substrate can be used to make a composite tungsten oxide film that is transparent in the visible light region and reflective in the infrared light region, and articles having such a film-forming substrate.

[0119] Example

[0120] The present invention will now be described in more detail with reference to embodiments, but the present invention is not limited to any of the embodiments described below.

[0121] (Example 1)

[0122] In Example 1, cesium tungsten oxide powder (manufactured by Sumitomo Metal Mining Co., Ltd., YM-01) with a Cs / W atomic ratio of 0.33 was fed into a hot pressing apparatus and pressed under vacuum at a temperature of 950°C and a pressure of 250 kgf / cm³. 2 Cesium tungsten oxide sintered bodies were fabricated under specific conditions. Chemical analysis of the sintered body revealed a Cs / W ratio of 0.33. The oxide sintered body was then machined to a diameter of 153 mm and a thickness of 5 mm, and bonded to a stainless steel backing plate using indium wax to fabricate a cesium tungsten oxide sputtering target.

[0123] Next, the sputtering target was installed in a DC sputtering apparatus (ULVAC SBH2306), and the vacuum level was set to 5 × 10⁻⁶. -3 Below Pa, the atmosphere during film formation was set to argon. A cesium tungsten oxide film was formed on a glass substrate (Corning EXG, 0.7 mm thick) under conditions of 0.6 Pa pressure and 600 W DC power. The film thickness was 100 nm (film formation step S1). The film structure was analyzed using an X-ray diffraction apparatus (X'Pert-PRO (PANalytical)). The film was found to be an amorphous structure with no identified diffraction peaks originating from a crystal structure.

[0124] The film after deposition was placed in a lamp heating furnace (HP-2-9 manufactured by Yonekura Manufacturing Co., Ltd.) and heat-treated at 500°C for 30 minutes in a nitrogen atmosphere (heat treatment step S2). Chemical analysis of the heat-treated film showed that the Cs / W atomic ratio x / y was 0.33.

[0125] The structure of the heat-treated film was analyzed using an X-ray diffraction apparatus (X'Pert-PRO, manufactured by PANalytical) to determine the crystal structure, X-ray diffraction intensity ratio, and the a-axis to c-axis ratio (c / a). Furthermore, transmittance and reflectance were measured using a spectrophotometer (Hitachi, model V-670).

[0126] The heat-treated film has a hexagonal crystal structure. The X-ray diffraction intensity ratio is 0.401, and the a-axis to c-axis ratio (c / a) is 1.028. Furthermore, the transmittance at 550 nm is 71.3%, at 1400 nm it is 11.3%, and the reflectance at 1400 nm is 44.5%.

[0127] The thin-film resistance of the heat-treated film was measured using a resistivity meter (Loresta, Mitsubishi Chemical Corporation), and the result was 3.0 × 10⁻⁶. 3 Ω / □, the heat-treated film is a low-resistivity film with high conductivity (resistivity is measured using Mitsubishi Chemical's Loresta or Hiresta).

[0128] In addition, the surface roughness of the heat-treated film was measured using a laser microscope (Olympus, OLS4100), and the arithmetic mean height (surface roughness) Sa was 8 nm.

[0129] (Examples 2-17 and Comparative Examples 1-13)

[0130] Using the same apparatus as in Example 1, composite tungsten oxide films were fabricated by varying element M, composition ratio, film thickness, film-forming atmosphere, heat treatment atmosphere, temperature, and time as described in Tables 1 and 2, and the film properties were analyzed. Tables 1 and 2 show the results of both the examples and comparative examples.

[0131] [Table 1]

[0132]

[0133] [Table 2]

[0134]

[0135] As can be confirmed from Tables 1 and 2, Examples 1 to 17 of the method for manufacturing the composite tungsten oxide film included in this invention form a film having the characteristics of a transmittance of 50% or more at a wavelength of 550 nm, a transmittance of 30% or less at a wavelength of 1400 nm, and a reflectance of 35% or more at a wavelength of 1400 nm. Furthermore, in Examples 1 to 17 of this invention, the thin film resistance is less than 1.0 × 10⁻⁶. 5 The surface roughness Sa is 20 nm or less. On the other hand, in Comparative Examples 1 to 13, which are not included in the method for manufacturing the composite tungsten oxide film of the present invention, the optical properties do not meet the above requirements, and the thin film resistance is 1.0 × 10⁻⁶. 5 Ω / □ and above.

[0136] It should be noted that while one embodiment and various embodiments of the present invention have been described in detail above, those skilled in the art will readily understand that various modifications can be made without substantially departing from the novel aspects and effects of the present invention. Therefore, all such modifications are included within the scope of the present invention.

[0137] For example, in the specification or drawings, a term that is recorded at least once, or a term that is recorded together with a different term that is more general or synonymous, can be replaced with its different terminology, regardless of where it appears in the specification or drawings. Furthermore, the composition of the composite tungsten oxide film and its manufacturing method is not limited to the content described in one embodiment and various embodiments of the present invention, and various modifications can be implemented.

[0138] Industrial availability

[0139] The composite tungsten oxide film of the present invention has the potential to be used in a wide range of applications that utilize the function of reflected light due to its high transparency in the visible light region, excellent light reflectivity in the infrared region, and high film smoothness.

Claims

1. A composite tungsten oxide film, which is based on the general formula M x W y O z The composite tungsten oxide film represented is mainly composed of [a specific component]. M is one or more elements selected from alkali metals other than Na, alkaline earth metals, Fe, Tl, and Sn; W is tungsten; and O is oxygen. The composite tungsten oxide film is characterized by forming a continuous film with a hexagonal crystal structure, where 0.001 ≤ x / y ≤ 1 and 2.2 ≤ z / y ≤ 3.

0. It does not actually contain any organic components. It refers to sputtered films and heat-treated films with a transmittance of over 50% at a wavelength of 550nm, a transmittance of less than 30% at a wavelength of 1400nm, and a reflectance of over 35% at a wavelength of 1400nm. Thin film resistance less than 10 5 Ω / □.

2. The composite tungsten oxide film as described in claim 1, characterized in that, The surface roughness Sa is below 20 nm.

3. The composite tungsten oxide film as described in claim 1 or claim 2, characterized in that, The M is one or more elements selected from Cs, Rb, K, Tl, Ba, Li, Ca, Sr, Fe, and Sn.

4. The composite tungsten oxide film as described in claim 1, When the intensity ratio of the diffraction intensity I(002) of the hexagonal (002) plane obtained by X-ray diffraction using CuKα rays is set as I(002) / I(200), then I(002) / I(200) is 0.30 or more and 0.50 or less. The ratio of the a-axis to the c-axis of the hexagonal crystal obtained by X-ray diffraction using CuKα rays is c / a = 1.018~1.

029.

5. The composite tungsten oxide film as described in claim 1 or claim 2, characterized in that, It has a film thickness of more than 20 nm.

6. A film-forming substrate, characterized in that, A composite tungsten oxide film according to any one of claims 1 to 5 is formed on at least one surface of the substrate to be film-formed.

7. The film-forming substrate as claimed in claim 6, characterized in that, The substrate to be film-formed has a softening point or heat distortion temperature of 400°C or higher.

8. The film-forming substrate as claimed in claim 6 or claim 7, characterized in that, The substrate to which the film is formed is glass.

9. An article characterized in that, A composite tungsten oxide film having one or more of the claims 1 to 5 and / or a film forming substrate having one of the claims 6 to 8.

10. A method for manufacturing a composite tungsten oxide film, characterized in that, The composite tungsten oxide film is based on the general formula M x W y O z The composite tungsten oxide film represented by this designation is a composite film with M as the main component, where M is one or more elements selected from alkali metals other than Na, alkaline earth metals, Fe, Tl, and Sn; W is tungsten; and O is oxygen. The composite tungsten oxide film forms a continuous film with a hexagonal crystal structure, where 0.001 ≤ x / y ≤ 1 and 2.2 ≤ z / y ≤ 3.

0. The composite tungsten oxide film is essentially free of organic components. The composite tungsten oxide film is a sputtered film and a heat-treated film with a transmittance of 50% or more at a wavelength of 550 nm, a transmittance of 30% or less at a wavelength of 1400 nm, and a reflectance of 35% or more at a wavelength of 1400 nm, and a thin film resistance of less than 10 Ω·cm. 5 Ω / □ The method for manufacturing the composite tungsten oxide film includes: a film-forming step of forming the film by a physical film-forming method, and a heat treatment step of heat-treating the film. In the film-forming process, film formation is carried out in an inactive gas, and in the heat treatment process, heat treatment is carried out in an inactive gas or an inactive gas containing reducing gas at a temperature greater than 400°C and less than 700°C, thereby forming a continuous film containing a hexagonal crystal structure.

Images