Composite tungsten oxide film, film-forming substrate having said film, and article

Abstract

To provide: a composite tungsten film that has the function of reflecting and blocking infrared light, i.e., a thermal radiation blocking function through thermal insulation, and still retains transparency in the visible light region, while ensuring superior film smoothness; and a film formation base material or an article each utilizing these functions.SOLUTION: A composite tungsten oxide film consists of a layer that is primarily composed of the general formula MxWyOz (where M represents one or more elements selected from alkali metals, alkaline-earth metals, Fe, In, Tl, and Sn, W represents tungsten, and O represents oxygen), wherein 0.001≤x / y≤1 and 2.2≤z / y≤3.0 hold, and the composite tungsten oxide film contains substantially no organic matter component, and has a transmittance of 50% or more at a wavelength 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.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a composite tungsten oxide film, and further relates to a film-forming substrate having the composite tungsten oxide film and an article utilizing the functions of the composite tungsten oxide film. [Background technology]

[0002] Various materials have been proposed as light-shielding materials for use in window materials and the like. For example, Patent Document 1 describes a light-shielding material made of a film having a mirror surface formed by vapor deposition of metal such as aluminum as a light-shielding material for window materials and the like. There are also light-shielding materials made of a film formed by sputtering of silver and the like. However, when these light-shielding materials are used, the appearance becomes half-mirror-like, and the reflection is too dazzling for outdoor use, which causes problems in terms of scenery. On the other hand, light-shielding materials using reflection generally have the characteristic of reflecting far-infrared rays and also having heat insulation properties. The reflection of light, including far-infrared rays, by the light-shielding material is brought about by the action of free electrons.

[0003] In response to this, the present applicant has proposed an infrared shielding microparticle dispersion having composite tungsten oxide microparticles described in Patent Document 2. Composite tungsten oxide microparticles efficiently absorb sunlight, particularly light in the near infrared region, and also have high transparency to visible light. In the invention according to Patent Document 2, composite tungsten oxide microparticles are dispersed in an appropriate solvent to form a dispersion, a medium resin is added to the obtained dispersion, and then the dispersion is coated on the surface of a substrate to form a thin film, which has a very high heat shielding property. The infrared shielding microparticle dispersion exhibits high heat shielding property due to its excellent light absorption property, but since it has almost no reflective property, it cannot be expected to have much heat insulation property.

[0004] Patent Document 3 discloses a composite tungsten oxide film produced by applying a solution containing a raw material compound of the composite tungsten oxide to a substrate and then heat treating the substrate. As shown by the broken lines in Figures 2 and 3 of the same document, a part of the film disclosed therein has a reflectance of about 30% at a wavelength of 1400 nm, and is expected to have a certain degree of heat insulation.

[0005] In addition, Patent Document 4 describes a method for forming a composite tungsten oxide film by dropping a solution containing a raw material compound of the composite tungsten oxide onto a rotating substrate, forming a film by centrifugal force, and then firing the film in a reducing atmosphere. x According to Fig. 1 of the document, the film reflects almost all light in the infrared range and is considered to have both shielding and heat insulation properties.

[0006] On the other hand, such composite tungsten oxide films are sometimes optically designed for the purpose of adjusting color tone and preventing reflection, but the thickness of the laminated film is extremely thin, ranging from a few nm to a few hundred 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 of the film to less than 100 nm by the coating method. In addition, the surface roughness of the laminated composite tungsten oxide film is required to be smooth, and if the surface roughness of the film formation surface is large, the desired effect of the optical design cannot be obtained. In the coating and baking method described in Patent Document 3 and Patent Document 4, the surface roughness is likely to become large due to the process in which crystals precipitate from the solution and grow into grains. When the method described in Patent Document 3 was reproduced and the surface roughness was measured with a laser microscope, the arithmetic average height Sa exceeded 60 nm.

[0007] Another method for obtaining a composite tungsten oxide thin film is a physical method such as a vapor deposition method or a sputtering method as shown in the example of Patent Document 1. A thin film formed by a physical film formation method can be a film that excludes elements other than the target composition. In addition, since there is no need to use a dispersant or a medium resin that is not suitable for high-temperature treatment, it can be used in the manufacturing process of tempered glass that is subjected to high-temperature heat treatment. Furthermore, a thin film formed by a physical film formation method is easy to control the film thickness even if it is less than 100 nm, and a very smooth surface with an arithmetic mean roughness of several nm or less can be created, so a laminated structure is easily possible.

[0008] Patent Document 5 proposes a vehicle window glass and a manufacturing method thereof, in which a large in-line sputtering device capable of processing large-area substrates such as vehicle windows is used. If such manufacturing equipment is available, a high-quality, stable film with a uniform thickness can be easily obtained, and the productivity is also high. In addition, the film source in a physical film formation method (for example, a target material in a sputtering method) does not have to be a single compound, and can be, for example, a composition combination of single elements or a mixture of multiple compounds, and the degree of freedom in composition selection is extremely wide.

[0009] Patent Document 6 proposes a composite tungsten oxide film produced by a sputtering method. A composite tungsten oxide film consisting 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 oxide film of this composition has an infrared transmittance of 40% or more, and does not have sufficient heat ray shielding performance, and there is a problem that it cannot function unless it is made into a multilayer film with other transparent dielectric films. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 5-113085 [Patent Document 2] Patent No. 4096205 [Patent Document 3] JP 2006-096656 A [Patent Document 4] U.S. Pat. No. 3,505,108 [Patent Document 5] JP 2002-020142 A [Patent Document 6] Japanese Patent Application Publication No. 8-12378 Summary of the Invention [Problem to be solved by the invention]

[0011] As mentioned above, the heat ray shielding performance of the composite tungsten oxide film formed by the physical film forming method is still not sufficient. On the other hand, the film formed by the coating method has a high function of absorbing light and shielding heat rays, but the heat insulation performance cannot be expected to be very good. In addition, there is a problem that the smoothness of the film is poor.

[0012] The present invention has been made to solve this problem, and provides a composite tungsten film that has a function of reflecting and blocking infrared light while retaining transparency in the visible light range, i.e., a heat ray shielding function through insulation, as well as a high film smoothness, and further provides a film-formed substrate or article utilizing these functions. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, the present inventors have conducted extensive research into composite tungsten oxide films, and have succeeded in obtaining a composite tungsten film having an extremely smooth film that retains excellent visible light transmittance by optimizing the conditions during film formation using a physical film formation method, and that exhibits a thermal insulation function by reflecting infrared rays.

[0014] That is, one aspect of the present invention is a compound represented by the general formula M x W y O z (wherein M is one or more elements selected from alkali metals, alkaline earth metals, Fe, In, Tl, and Sn, W is tungsten, and O is oxygen), the composite tungsten oxide film is composed only of a layer having as its main component a composition represented by the formula: 0.001≦x / y≦1, 2.2≦z / y≦3.0, is substantially free of organic components, and has 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. A continuous film containing a hexagonal crystal structure. It is.

[0015] According to one embodiment of the present invention, a composite tungsten oxide film is obtained that has a function of reflecting and shielding infrared light while maintaining transparency in the visible light range, that is, a heat ray shielding function due to heat insulation. In addition, by using a sputtering deposition origin, a composite tungsten oxide film can be obtained that has a very wide degree of freedom in composition selection and can be stably deposited. In addition, since a very smooth film can be obtained by sputtering deposition, the effect of an optically designed laminate structure can be enhanced. Furthermore, the hexagonal phase has a higher reflectance in the infrared range, and therefore can reflect the infrared light efficiently.

[0016] In this case, in one embodiment of the present invention, the surface roughness Sa may be 20 nm or less.

[0017] By satisfying the above conditions, a composite tungsten film with high film smoothness is obtained.

[0018] In one embodiment of the present invention, the sheet resistance is 10 5 It may be less than Ω / □.

[0019] By setting the sheet resistance within the above range, more preferable heat insulation can be obtained.

[0020] In one embodiment 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.

[0021] By selecting M from the above elements, a composite tungsten oxide film can be obtained that has a high infrared ray reflecting and blocking function as well as excellent film smoothness.

[0024] In this case, in one embodiment of the present invention, when the intensity ratio I(002) of the diffraction intensity I(002) of the hexagonal (002) plane and the diffraction intensity I(200) of the hexagonal (200) plane by X-ray diffraction using CuKα radiation is defined as I(002) / I(200), I(002) / I(200) may be 0.30 or more and 0.50 or less, and the ratio c / a of the hexagonal a-axis to the c-axis by X-ray diffraction using CuKα radiation may be 1.018 to 1.029.

[0025] A composite tungsten oxide film that satisfies the above requirements based on X-ray diffraction analysis is a composite tungsten oxide film that exhibits a thermal insulation function by reflecting infrared rays while retaining excellent visible light transmittance.

[0026] Another aspect of the present invention is a film-formed substrate having the above-mentioned composite tungsten oxide film formed on at least one surface of the substrate.

[0027] By forming the above-mentioned composite tungsten oxide film on the film-formed substrate, it is possible to provide a practical form having good mechanical properties, processability, and the like.

[0028] In this case, in another embodiment of the present invention, the substrate on which the film is formed may have a softening point or heat distortion temperature of 400° C. or higher.

[0029] By providing such properties, a film-forming substrate having better functions can be obtained by heat treatment after film formation.

[0030] In another embodiment of the present invention, the substrate on which the film is formed may be glass.

[0031] By using glass as the substrate on which the film is formed, infrared shielding properties can be imparted to glass-based materials 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, glass for lenses and mirrors, and glass substrates used in semiconductors and MEMS.

[0032] Another aspect of the present invention is an article having one or more of the above-mentioned composite tungsten oxide films and / or film-formed substrates.

[0033] According to another aspect of the present invention, it is possible to provide products that reduce energy consumption and have a small environmental impact during production at low cost in large quantities for a variety of uses. Effect of the Invention

[0034] According to the present invention, a composite tungsten oxide film can be obtained as an infrared reflective film having transparency in the visible light region and reflectivity in the infrared light region.Furthermore, according to the present invention, such a composite tungsten oxide film can be provided by a physical manufacturing method that is widely used industrially, is relatively harmless during film formation, and further, uses raw materials that have excellent long-term storage properties and are not subject to restrictions on hazardous material storage or transportation. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is a diagram 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. [Diagram 2] FIG. 1 is a diagram showing the difference in optical properties (reflectance) between the composite tungsten oxide film of the present invention and the infrared shielding material microparticle dispersion described in Patent Document 2. [Diagram 3] FIG. 1 is a process diagram showing an outline of a process in a method for producing a composite tungsten oxide film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The composite tungsten oxide film and the method for producing the same according to the present invention will be described below in the following order. Note that the present invention is not limited to the following examples, and can be modified as desired without departing from the gist of the present invention. 1. Composite tungsten oxide film 2. Manufacturing method of composite tungsten oxide film 2-1. Film formation process 2-2.Heat treatment process 3. Film forming base material 4.Goods

[0037] <1. Composite tungsten oxide film> 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 a tungsten oxide film having a general formula M x W y O z(wherein M is one or more elements selected from alkali metals, alkaline earth metals, Fe, In, Tl, and Sn, W is tungsten, and O is oxygen), and the ratio of x to y is in the range of 0.001≦x / y≦1, and the ratio of z to y is in the range of 2.2≦z / y≦3.0.

[0038] The details of the composition range are shown in Patent Document 2 by the present applicant, and it is necessary to use a composite tungsten oxide in this composition range as the main component in order to obtain a film with high transparency and infrared light absorption. The basic optical properties of the composite tungsten oxide film are derived from the theoretically calculated atomic arrangement of element M, 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 those of the infrared shielding body described in Patent Document 2, and will be described in detail below while appropriately comparing it with the invention according to Patent Document 2.

[0039] The element M of the composite tungsten oxide film according to one embodiment of the present invention is one or more elements selected from alkali metals, alkaline earth metals, Fe, In, Tl, and Sn, and more preferably one or more elements selected 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 this merely indicates elements whose effects have been confirmed by examples, and there is a possibility that the elements described in Patent Document 2, which are not included in the present invention, have at least a similar function.

[0040] More preferably, the element M of the composite tungsten oxide film according to one embodiment of the present invention is one or more elements selected from Cs, Rb, K, Tl, and Ba. By selecting the element M as above, the composite tungsten film can have a crystal structure including a hexagonal crystal, as described below. The element M may have a crystal structure other than a hexagonal crystal depending on the ratio of x / y. For example, K becomes a tetragonal crystal when the ratio of x / y is 0.5 or more. A structure including a hexagonal phase has a higher reflection in the infrared range, and can therefore reflect efficiently.

[0041] The composite tungsten oxide film according to one embodiment of the present invention is represented by the general formula M x W y O z In the above, 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 is not generated, and the infrared shielding effect cannot be obtained. If x / y exceeds 1, an impurity phase is formed in the composite tungsten oxide film. If z / y is less than 2.2, an unintended WO2 crystal phase appears in the composite tungsten oxide film. If z / y exceeds 3.0, free electrons for obtaining the infrared shielding effect are not generated.

[0042] The composite tungsten oxide film according to one embodiment of the present invention does not substantially contain organic components. As described later, the composite tungsten oxide film according to one embodiment of the present invention is formed by a physical film forming method, so there is no need to use a dispersant, a medium resin, or a surfactant or a solvent as in the inventions of Patent Document 2 and Patent Document 3. Here, "substantially not containing organic components" refers to not containing organic components that are intentionally added, such as polymer dispersants, during the film manufacturing process.

[0043] Paragraph 0060 of Patent Document 3 describes a method for producing a transparent conductive film using a composite tungsten oxide. According to this, it is shown that the transparent conductive film of Patent Document 3 is obtained by applying a solution containing a composite tungsten compound as a starting tungsten raw material solution to a substrate, and then heat treating the substrate in an atmosphere of inert gas, inert gas and reducing gas, or reducing gas. According to this method, a surfactant having a polysiloxane skeleton containing an organic component is added to an aqueous solution of ammonium metatungstate and an aqueous solution of a chloride of M element to form a solution.

[0044] When the method described in Patent Document 3 was reproduced and the surface roughness was measured with a laser microscope, the arithmetic mean height Sa exceeded 60 nm. On the other hand, the composite tungsten oxide film according to one embodiment of the present invention is formed by a physical film formation method such as a sputtering method, as described later, and therefore the surface roughness Sa can be made 20 nm or less. Thus, the composite tungsten oxide film according to one embodiment of the present invention differs in smoothness from the transparent conductive film of Patent Document 3.

[0045] Furthermore, as described in paragraphs 0050 and 0053 of Patent Document 2, a film (particle-dispersed film) made of a microparticle dispersion containing the composite tungsten oxide microparticles of Patent Document 2 is shown to function as a heat ray shielding film that absorbs light, particularly has excellent absorption in the near-infrared region.

[0046] 1 and 2 are diagrams 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, where FIG. 1 shows the transmittance and FIG. 2 shows the reflectance. As shown in FIGS. 1 and 2, the composite tungsten oxide film according to one embodiment of the present invention shows optical properties different from those of the film (microparticle-dispersed film) made of the microparticle dispersion described in Patent Document 2. In particular, as shown in FIG. 2, the composite tungsten oxide film according to the present invention largely reflects light in the infrared region of 1400 nm and above. The reason for this is presumed to be the difference between the microparticle-dispersed film and the continuous film, as described below, but the details are not yet known.

[0047] A composite tungsten oxide film according to one embodiment of the present invention has 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.

[0048] Even if the transmittance at a wavelength of 550 nm, which is an index of transparency, is less than 50%, it can be used depending on the application. For example, in the case of windshield films for cars, black or dark gray is preferred for rear seat windows from the viewpoint of privacy protection, and pigments are sometimes intentionally used at the same time as heat shielding materials.

[0049] The transparency index of the present invention refers to the film properties in a state in which the above-mentioned intentional pigments, etc. are not included. If the transparency index is lower than the above-mentioned value, lighting will be poor, leading to, for example, a dark interior and difficulty in viewing the outside scenery.

[0050] Similarly, it is possible to configure the transmittance at a wavelength of 1400 nm and the reflectance at a wavelength of 1400 nm, which are used as indicators of light blocking performance and reflective performance, so as not to satisfy the above values. In such cases, however, the transmittance of infrared light will be high, which in the case of heat blocking will lead to a tingling sensation on the skin and an increase in room temperature, and in the case of photothermal conversion, a decrease in the amount of heat generated.

[0051] In addition, since the reflection of the present invention is due to free electrons, it reflects light below the plasma frequency. In other words, it reflects light with a wavelength equal to or greater than the wavelength corresponding to the plasma frequency. In other words, if the reflectance at a wavelength of 1400 nm is low, the reflectance at a wavelength of longer wavelengths, far infrared rays, is also low, resulting in low thermal insulation and low effect of trapping heat from indoor heating. To obtain effective thermal insulation, it is necessary for the reflectance at a wavelength of 1400 nm to be 35% or more.

[0052] The surface roughness Sa of the composite tungsten oxide film according to one embodiment of the present invention is 20 nm or less. In optical thin film design (when laminating films), interference can be used to strengthen or weaken the reflection of a specific wavelength, making it possible to create a steep transmission profile (adjusting the color of the film) and to prevent reflection in the visible light range. In the above optical thin film design (when laminating films), the surface roughness is small, so that a stable laminated film with little disturbance in the optical path length can be formed. As described later, the composite tungsten oxide film according to one embodiment of the present invention is a film obtained by a physical method such as sputtering, so the surface roughness Sa of the film can be 20 nm or less. If it is 20 nm or less, there is a low possibility that problems will occur in the optical thin film design. If the surface roughness exceeds 20 nm, the laminated state is not uniform, and it is difficult to obtain the effect of the optical thin film design (lamination).

[0053] Moreover, the composite tungsten oxide film according to one embodiment of the present invention is preferably formed with a film thickness of more than 20 nm. As described later, the composite tungsten oxide film according to one embodiment of the present invention is a film obtained by a physical method obtained by film formation by a sputtering method or the like. For example, in a film formed by applying a solution described in Patent Document 3 and then heat treating it, the film is formed by volatilizing components such as solvents and resins that are essential for film formation, and therefore residual stress occurs in the film. In addition, defects such as residual volatile components and voids may be present. Since the composite tungsten oxide film according to one embodiment of the present invention is formed without containing volatile components, the residual stress of the film due to film formation can be reduced, and defects such as residual volatile components and voids do not occur. Therefore, a film without cracks or peeling can be formed.

[0054] However, if the film thickness is 20 nm or less, sufficient reflection performance in the infrared region cannot be obtained, and the infrared transmittance at 1400 nm exceeds 30%. There is no particular limitation on the thickness of the present invention as long as it exceeds the above film thickness. However, if the film thickness is large, the transmittance in the visible light region at a wavelength of 550 nm falls below 50%, and visible light transmittance may deteriorate, or the film may peel off due to the influence of residual stress during film formation. The transmittance of the film can be measured using a spectrophotometer.

[0055] The composite tungsten oxide film according to one embodiment of the present invention has a sheet resistance of 1.0×10 5 Less than Ω / □ (read as ohms per square), preferably less than 1.0×10 3 It is less than Ω / □. If the sheet resistance of the film is higher than the above value, the reflection by free electrons is weakened, and the far infrared rays in the longer wavelength range cannot be reflected, so that heat insulation cannot be obtained. The sheet resistance can be adjusted by the film formation conditions and heat treatment conditions described later. The sheet resistance can be measured, for example, using a resistivity meter.

[0056] Furthermore, the composite tungsten oxide film according to one embodiment of the present invention is usually formed as a continuous film, but may be in any form, such as a form in which reflection control is imparted by patterning, or a form in which irregularities are provided to impart a lens function, or the like, and may have any shape or irregularity in the film as long as it has the characteristics of the present invention.

[0057] The composite tungsten oxide according to one embodiment of the present invention preferably includes a hexagonal crystal structure. The inclusion of a hexagonal crystal structure can be confirmed by X-ray diffraction analysis of the film. Composite tungsten oxide is known to have crystal structures such as hexagonal, cubic, tetragonal, and orthorhombic, and amorphous structures, but the composite tungsten oxide film according to one embodiment of the present invention has a hexagonal crystal structure and may include crystal structures such as cubic, tetragonal, and orthorhombic other than hexagonal, and amorphous structures. By including a hexagonal crystal structure in the composite tungsten oxide film, the hexagonal phase has a higher reflection in the infrared range, so that it can be efficiently reflected.

[0058] In addition, in the composite tungsten oxide film according to one embodiment of the present invention, the ratio c / a of the a-axis length to the c-axis length of the hexagonal crystal by X-ray diffraction using CuKα radiation is preferably 1.018 to 1.029. According to the crystal structure database ICDD reference code 01-081-1244, c / a is 1.028. It is believed that the a-axis length and c-axis length change when there is an excess or shortage of atoms compared to the standard hexagonal crystal structure.

[0059] In addition, in the 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 and the diffraction intensity I(200) of the hexagonal (200) plane by X-ray diffraction using CuKα rays is I(002) / I(200), it is preferable that I(002) / I(200) is 0.30 or more and 0.50 or less. The above-mentioned ICDD reference code 01-081-1244 states that the relative intensity of the (002) plane to the (200) plane is 26.2%, so 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 baking method is this standard value, but the intensity ratio of the present invention is 0.30 or more and 0.50 or less. Since it is larger than the standard intensity ratio, 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 aforementioned c / a is out of the range of 1.018 to 1.029 and the intensity ratio I(002) / I(200) is out of the range of 0.30 or more and 0.50 or less, the heat ray reflection function decreases.

[0060] When the element M is Sn, the crystal structure is trigonal, and in the above X-ray diffraction, the ratio c / a of the a-axis length to the c-axis length of the hexagonal crystal is calculated as the ratio 2c / a of the a-axis length to the c-axis length of the trigonal crystal.

[0061] This relationship between the crystal state and the heat reflection function that differs from the standard is thought to be unique to the sputtering and vacuum deposition methods. It is thought to be due to the process in which a crystal structure is formed by heat treatment after the formation of a non-equilibrium amorphous film, but the details of this mechanism are unknown.

[0062] As described above, the composite tungsten oxide film according to one embodiment of the present invention has properties different from those of the composite tungsten oxide films described in Patent Documents 2 and 3, and can be used as an infrared reflective film that has transparency in the visible light range and reflectivity in the infrared light range.

[0063] <2. Method for producing composite tungsten oxide film> Next, a method for producing a composite tungsten oxide film will be described. Fig. 3 is a process diagram showing an outline of a method for producing a composite tungsten oxide film according to one embodiment of the present invention. One embodiment of the present invention is a method for producing a composite tungsten oxide film mainly composed of element M, tungsten W, and oxygen O, and includes a film formation step S1 for forming a film using a physical film formation method, and a heat treatment step S2 for heat treating the film. Each step will be described in detail below.

[0064] <2-1. Film formation process> In the film forming step S1, a film is formed using a physical film forming method. Examples of physical film forming methods for the composite tungsten oxide film according to one embodiment of the present invention include vacuum deposition, sputtering, ion plating, and ion beam methods. Among these, the sputtering method has high energy of film forming particles and strong adhesion, dense film and strong film quality, and the film forming process is stable, allowing high-precision control of film quality and film thickness. Furthermore, the sputtering method has features such as the ability to form films of high-melting-point metals, alloys, and compounds, the ability to form films of oxides and nitrides by introducing reactive gases, and the relative ease of composition adjustment, and is widely used in a wide range of fields such as electronic devices such as liquid crystal display elements and hard disks, and general-purpose products such as window films and mirrors, and is preferred because of the large number of manufacturing devices.

[0065] General formula M x W y O z The sputtering target for forming the composite tungsten oxide film represented by the formula (I) can be selected from various configurations, such as a sputtering target consisting of element M and element W, a sputtering target consisting of a compound of element M, element W, and element O, a sputtering target consisting of a compound of element M, element O, and element W, and a sputtering target consisting of a compound of element M, element W, and element O. It is preferable to use a sputtering target formed in advance as a compound phase. If the sputtering target is formed in advance as a compound phase, the dependency of the film composition due to the difference in vapor pressure of each element can be reduced, and stable film formation can be achieved.

[0066] The sputtering target may be used in the form of, for example, a green compact formed by compressing a powder consisting of particles of the sputtering target composition, or a sintered body formed by sintering the sputtering target composition.

[0067] In addition, since the sputtering target is formed of a compressed powder or a sintered body as described above, it does not substantially contain organic components, and the film formed using the target also does not substantially contain organic components. Here, "substantially free" means that it does not contain any intentionally added components, such as polymer dispersants.

[0068] If the sputtering target is, for example, a conductor with a resistivity of 1 Ω·cm or less, a highly productive DC sputtering device can be used. Also, if the sputtering target is, for example, a sintered body with a relative density of 70% or more, it is less likely to crack due to vibration during transportation, and there is no need to be extremely careful when handling it when installing it in the device, making it more suitable for industrial production.

[0069] The atmosphere for the film formation process may be selected from a variety of types, but an inert gas atmosphere is preferred. As the inert gas, for example, rare gases such as helium gas and argon gas, nitrogen gas, etc. may be used. In the case of nitrogen gas, nitrides may be formed depending on the selected element M, so argon gas, which is commonly used and easily available, is more preferred. The purity of the gas used is preferably 99% or more, and the mixture of oxidizing gas such as oxygen is preferably less than 1%. Although some details are unclear, a composite tungsten oxide film with high reflectivity can be obtained by forming the film in an inert atmosphere and heat-treating it under the conditions described later. On the other hand, if the proportion of oxidizing gas exceeds 1%, the reflectivity of the composite tungsten oxide film after heat treatment decreases.

[0070] The film after deposition is usually amorphous, but it is acceptable if diffraction peaks due to crystals appear when subjected to X-ray diffraction analysis.

[0071] <2-2. Heat treatment process> Next, in the heat treatment step S2, the film obtained in the film formation step S1 is heat treated. In order to obtain the film characteristics of the composite tungsten oxide film according to one embodiment of the present invention, the heat treatment step S2 is carried out in an inert or reducing atmosphere.

[0072] In the heat treatment step S2, the heat treatment temperature is preferably 400 to 700°C. If the heat treatment temperature is lower than 400°C, the film remains amorphous and does not crystallize, or even if it crystallizes, the hexagonal diffraction peak in X-ray diffraction is extremely weak, and the heat shielding properties in the infrared region are low. Even if the heat treatment temperature is higher than 700°C, the characteristics of the film of the present invention can be obtained, but practical problems such as reaction between the film and the substrate, peeling of the film from the substrate, and increased surface roughness occur.

[0073] At any of the above heat treatment temperatures, the heat treatment time should be long enough to complete the crystallization of the composite tungsten oxide, and may be appropriately adjusted to about 5 to 60 minutes, depending on the balance between the thermal conductivity of the substrate and productivity.

[0074] As described above, the heat treatment is carried out in an inert atmosphere or a reducing atmosphere. Examples of the inert atmosphere include nitrogen and argon, and examples of the reducing atmosphere include a mixed gas of nitrogen and hydrogen, and a mixed gas of argon and hydrogen.

[0075] As described above, according to the method for producing a composite tungsten oxide film according to one embodiment of the present invention, a composite tungsten oxide film having the above-mentioned characteristics can be provided by a physical production method that is widely used industrially, is relatively harmless when formed, has excellent long-term storage properties for the raw materials used, and has no restrictions on transportation.

[0076] <3. Film forming base material> The film-forming substrate according to one embodiment of the present invention is a substrate on which the above-mentioned composite tungsten oxide film is formed on at least one surface. The substrate on which the film is formed is not particularly limited as long as the composite tungsten oxide film according to one embodiment of the present invention can be formed.

[0077] Since the heat treatment temperature of the film after the film formation is 400°C or higher, the substrate to be film-formed is preferably a substrate having a softening point or heat distortion temperature of 400°C or higher. If a substrate having a softening point or heat distortion temperature of less than 400°C is used, problems such as the film peeling off from the substrate to be film-formed during the heat treatment, or cracks occurring in the film, occur. It is preferable that the thermal expansion coefficient of the substrate to be film-formed is close to the thermal expansion coefficient of the film. However, when the film is peeled off from the substrate and used, the above conditions are not necessarily required, and for example, a substrate that melts at 400°C or lower may be used.

[0078] The substrate to be coated with a film having a softening point or heat distortion temperature of 400°C or more includes glass, ceramics, single crystals, etc. The substrate to be coated with a film does not necessarily need to be transparent, but when the composite tungsten oxide film of the present invention is used together with a substrate, a transparent substrate is required. Examples of transparent substrates include glass, transparent ceramics such as YAG and Y2O3, and single crystals such as sapphire. Among them, it is preferable to use glass with a softening point of 400°C or more as the substrate to be coated with a film, from the viewpoints of availability, low cost, weather resistance, chemical resistance, etc.

[0079] The substrate may be selected from various types, not only flat but also curved or uneven, without impairing the features of the present invention.

[0080] As described above, according to the film-forming substrate of one embodiment of the present invention, a film-forming substrate having an infrared reflective film that has transparency in the visible light range and reflectivity in the infrared light range can be obtained.

[0081] <4. Goods> An article according to one embodiment of the present invention has one or more of the above-mentioned composite tungsten oxide films and / or film-forming substrates. The article according to one embodiment of the present invention may be any article as long as the composite tungsten oxide film has the function of reflecting light.

[0082] In addition, even if the composite tungsten oxide film and / or film-formed substrate of the present invention is used together with, for example, films or particles having other functions, they are also included in the articles utilizing the functions described in the present invention.

[0083] The composite tungsten oxide film of the present invention is an infrared reflective film having reflectivity in the infrared light region, and examples of articles having the function of reflecting and blocking light include heat insulating glass. Heat-insulating glass is transparent yet has the characteristic of blocking and insulating heat, reducing the rise in indoor temperature caused by sunlight in the summer and the rise in temperature inside a car. It can also reflect the heat from heating in the winter and keep it inside the room.

[0084] As described above, according to the film-forming substrate of one embodiment of the present invention, a composite tungsten oxide film having transparency in the visible light range and reflectivity in the infrared light range, and an article including such a film-forming substrate can be obtained. EXAMPLES

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0086] Example 1 In Example 1, cesium tungsten oxide powder (YM-01 manufactured by Sumitomo Metal Mining Co., Ltd.) having a Cs / W atomic ratio of 0.33 was placed in a hot press apparatus and subjected to a vacuum atmosphere, a temperature of 950°C, and a pressure of 250 kgf / cm. 2 A cesium tungsten oxide sintered body was produced by sintering under the above conditions. Chemical analysis of the sintered body composition revealed that the Cs / W ratio was 0.33. This oxide sintered body was machined to a diameter of 153 mm and a thickness of 5 mm, and bonded to a stainless steel backing plate using metallic indium brazing material to produce a cesium tungsten oxide sputtering target.

[0087] Next, this sputtering target was attached to a DC sputtering device (ULVAC SBH2306) and the ultimate vacuum was 5×10 -3A cesium tungsten oxide film was formed on a glass substrate (EXG manufactured by Corning, thickness 0.7 mm) under the conditions of argon gas atmosphere at a gas pressure of 0.6 Pa or less and a DC power of 600 W. The film thickness after film formation was 100 nm (film formation step S1). The structure of the film after film formation was examined using an X-ray diffraction device (X'Pert-PRO (manufactured by PANalytical)). The film after film formation had an amorphous structure with no diffraction peaks derived from a crystalline structure.

[0088] The film after deposition was placed in a lamp heating furnace (HP-2-9 manufactured by Yonekura Manufacturing Co., Ltd.) and heat-treated in a nitrogen atmosphere at a temperature of 500°C for 30 minutes (heat treatment step S2). As a result of chemical analysis of the film after this heat treatment, the Cs / W atomic ratio x / y was 0.33.

[0089] The crystal structure, X-ray diffraction intensity ratio, and a-axis to c-axis ratio c / a of the heat-treated film were examined using an X-ray diffraction device (X'Pert-PRO (PANalytical)). In addition, the transmittance and reflectance were measured using a spectrophotometer (Hitachi, model number V-670).

[0090] The crystal structure of the film after heat treatment was a structure including hexagonal crystals. The X-ray diffraction intensity ratio was 0.401, and the ratio of the a-axis to the c-axis, c / a, was 1.028. In addition, the transmittance at a wavelength of 550 nm was 71.3%, the transmittance at a wavelength of 1400 nm was 11.3%, and the reflectance at a wavelength of 1400 nm was 44.5%.

[0091] The sheet resistance of the film after heat treatment was measured using a resistivity meter (Loresta, manufactured by Mitsubishi Chemical Corporation) and found to be 3.0×10 3 The resistivity was Ω / □, and the film after heat treatment was a film with high conductivity and low resistance (resistance was measured using Loresta or Hiresta manufactured by Mitsubishi Chemical depending on the resistivity).

[0092] In addition, the surface roughness of the film after the heat treatment was measured using a laser microscope (OLS4100, manufactured by Olympus), and the arithmetic mean height (surface roughness) Sa was 8 nm.

[0093] (Examples 2 to 17 and Comparative Examples 1 to 13) Using the same apparatus as in Example 1, composite tungsten oxide films were produced and the properties of the films were investigated by changing the element M, composition ratio, film thickness, film formation atmosphere, heat treatment atmosphere, temperature and time as shown in Tables 1 and 2. Tables 1 and 2 show the results of the examples and the comparative examples.

[0094] [Table 1]

[0095] [Table 2]

[0096] From Tables 1 and 2, it was confirmed that in Examples 1 to 17 included in the method for producing a composite tungsten oxide film according to the present invention, a 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 was obtained. In addition, in Examples 1 to 17 included in the present invention, the sheet resistance was 1.0×10 5 On the other hand, in Comparative Examples 1 to 13, which are not included in the method for producing a composite tungsten oxide film according to the present invention, the optical properties did not satisfy the above requirements, and the sheet resistance was 1.0×10 5 It became more than Ω / □.

[0097] Although one embodiment of the present invention and each example have been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel features and effects of the present invention. Therefore, all such modifications are intended to be included within the scope of the present invention.

[0098] For example, a term described at least once in the specification or drawings together with a different term having a broader or similar meaning can be replaced with that different term anywhere in the specification or drawings. In addition, the configuration of the composite tungsten oxide film and the manufacturing method thereof are not limited to those described in the embodiment and each example of the present invention, and various modifications are possible. [Industrial Applicability]

[0099] The composite tungsten oxide film according to the present invention has high transparency in the visible light range, excellent light reflectivity in the infrared range, and high film smoothness, and therefore has the potential to be used in a wide range of applications that utilize its light reflecting function.

Claims

1. General formula M ｘ W ｙ O ｚ (wherein M is one or more elements selected from alkali metals, alkaline earth metals, Fe, In, Tl, and Sn, W is tungsten, and O is oxygen), 0.001≦x / y≦1, 2.2≦z / y≦3.0, Substantially free of organic components A composite tungsten oxide film, characterized in that it has 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 is a continuous film containing a hexagonal crystal structure.

2. 2. The composite tungsten oxide film according to claim 1, characterized in that the surface roughness Sa is 20 nm or less.

3. Sheet resistance is 10 ５ 3. The composite tungsten oxide film according to claim 1, wherein the resistivity is less than Ω / □.

4. 4. The composite tungsten oxide film according to claim 1, wherein M is one or more elements selected from the group consisting of Cs, Rb, K, Tl, In, Ba, Li, Na, Ca, Sr, Fe, and Sn.

5. When the intensity ratio of the diffraction intensity I(002) of the hexagonal (002) plane to the diffraction intensity I(200) of the hexagonal (200) plane by X-ray diffraction using CuKα radiation is defined as I(002) / I(200), I(002) / I(200) is 0.30 or more and 0.50 or less, 2. The composite tungsten oxide film according to claim 1, wherein the ratio c / a of the a-axis to the c-axis of the hexagonal crystal, as determined by X-ray diffraction using CuKα radiation, is 1.018 to 1.

029.

6. A substrate on which a film is to be formed, the composite tungsten oxide film according to any one of claims 1 to 5 being formed on at least one surface of the substrate.

7. The substrate for film formation according to claim 6, wherein the substrate for film formation has a softening point or a heat distortion temperature of 400°C or higher.

8. 8. The film-forming substrate according to claim 6, wherein the substrate on which the film is formed is made of glass.

9. 9. An article comprising one or more composite tungsten oxide films according to any one of claims 1 to 5 and / or one or more film-formed substrates according to any one of claims 6 to 8.

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