WO2019244650A1 - Composite tungsten oxide film and production method therefor, and film formation base material and article having said film - Google Patents

Abstract

Provided are: a composite tungsten film that has the function of reflecting and blocking infrared light, i.e., a thermal radiation blocking function achieved by thermal insulation, and still has transparency in the visible light region, and that has high film smoothness; a production method for the composite tungsten film; and a film formation base material or article utilizing these functions. This composite tungsten oxide film comprises, as a main component, a composition represented by 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, 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.

Description

Composite tungsten oxide film and method for producing the same, and film-forming substrate and article having the film

The present invention relates to a composite tungsten oxide film and a method for producing the same, and further relates to a film-forming substrate having the composite tungsten oxide film and an article utilizing the function of the composite tungsten oxide film. This application is based on Japanese Patent Application No. 2018-117340 filed in Japan on June 20, 2018 and Japanese Patent Application No. 2019-24926 filed on February 14, 2019. Which is incorporated herein by reference.

各種 Various materials have been proposed as light shielding members used for window materials and the like. For example, Patent Literature 1 discloses a light-shielding member having a mirror surface state formed by vapor deposition of a metal such as aluminum as a light-shielding member such as a window material. There is also a light-shielding member of a film formed by sputtering silver or the like. However, when these light-shielding members are used, the appearance becomes a half-mirror shape, so that when used outdoors, the reflection is dazzling and there is a problem in view. On the other hand, a light-shielding member using reflection generally has a feature that it reflects far-infrared rays and also has heat insulation. The reflection of the light from the light-shielding member including far-infrared rays is caused by the action of free electrons.

On the other hand, the applicant has proposed an infrared shielding fine particle dispersion having composite tungsten oxide fine particles described in Patent Document 2. The composite tungsten oxide fine particles efficiently absorb sunlight, particularly light in the near infrared region, and have high transparency to visible light. In the invention according to Patent Document 2, composite tungsten oxide fine particles are dispersed in an appropriate solvent to form a dispersion, and after adding a medium resin to the obtained dispersion, a coating is formed on the substrate surface to form a thin film. And has a very high thermal barrier. Although the infrared shielding fine particle dispersion has high heat shielding properties due to its excellent light absorption properties, it has little reflection properties and therefore cannot be expected to have much heat insulating properties.

Patent Document 3 discloses a composite tungsten oxide film manufactured by applying a solution containing a compound compound of a composite tungsten oxide to a substrate and then heat-treating the solution. A part of the film disclosed herein has a reflectance of about 30% at a wavelength of 1400 nm as shown by broken lines in FIGS. 2 and 3 of the document, and is expected to have some heat insulating properties.

Patent Literature 4 discloses a Na _x WO ₃ film in which a solution containing a compound compound of a composite tungsten oxide is dropped on a rotating substrate, formed into a film by centrifugal force, and then fired in a reducing atmosphere. See FIG. According to No. 1, the film almost reflects light in the infrared region, and seems to have both a shielding property and a heat insulating property.

On the other hand, such a composite tungsten oxide film is sometimes optically designed for the purpose of adjusting color tone, preventing reflection, and the like. At this time, the film thickness of the laminated film is extremely several nm to several hundred nm. thin. Therefore, it is necessary to control the thickness of the composite tungsten oxide film to be less than 100 nm, but it is difficult to control a region having a thickness of less than 100 nm by a coating method. Further, 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, a desired optical design effect cannot be obtained. In the coating and baking method described in Patent Documents 3 and 4, the surface roughness tends to increase due to the process of crystal precipitation from the solution and grain growth. The method described in Patent Document 3 was reproduced, and the surface roughness was measured with a laser microscope. As a result, the arithmetic mean height Sa exceeded 60 nm.

別 As another means for obtaining a composite tungsten oxide thin film, there is a physical method such as a vapor deposition method or a sputtering method which is disclosed in the example of Patent Document 1. The thin film formed by the physical film formation method can be a film from which elements other than the target composition are excluded. In addition, since it is not necessary to use a dispersant or a medium resin that is not suitable for high-temperature treatment, it can be provided to, for example, a tempered glass manufacturing process to be subjected to high-temperature heat treatment. Furthermore, the thickness of a thin film formed by a physical film formation method can be easily controlled even when the thickness is less than 100 nm, and a very smooth surface having an arithmetic average roughness of several nm or less can be formed. The structure is easily possible.

Patent Document 5 proposes a window glass for a vehicle and a method for manufacturing the same, and uses a large-size in-line type sputtering apparatus capable of processing a large-area substrate such as a window for a vehicle. If such a manufacturing facility can be used, a high-quality and stable film having a uniform film thickness can be easily obtained, and the productivity is high. Further, the film formation source of the physical film formation method (for example, a target material in the case of the sputtering method) may not be a single compound, but may be, for example, a combination of a single element composition or a mixture of a plurality of compounds. The flexibility of composition selection is extremely wide.

Patent Document 6 proposes a composite tungsten oxide film formed by a sputtering method. A composite tungsten oxide film made of tungsten and at least one element selected from the group consisting of group IVa, group IIIa, group VIIb, group VIb and group 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 has a problem that its function cannot be exhibited unless it is formed as a multilayer film with another transparent dielectric film.

Japanese Patent Application Laid-Open No. 5-113085 Japanese Patent No. 4096205 JP 2006-096656 A U.S. Pat. No. 3,505,108 JP-A-2002-020142 JP-A-8-12378

の 通 り As described above, the heat ray shielding performance of the composite tungsten oxide film formed by the physical film formation method is not yet sufficient. On the other hand, the film formed by the coating method has a high function of absorbing light and shielding heat rays, but cannot expect much heat insulation. In addition, there is a problem that the smoothness of the film is poor.

Thus, the present invention has been made to solve such a situation, and has a function of reflecting and shielding infrared light, that is, a function of shielding heat rays by heat insulation, while maintaining transparency in a visible light region. In addition, the present invention provides a composite tungsten film having high film smoothness and a method for producing the same, and further provides a film-forming substrate or an article utilizing these functions.

The present inventors have intensively studied a composite tungsten oxide film with respect to the above-mentioned problems, and according to a physical film forming method, have excellent visible light transmittance by optimizing conditions at the time of film formation. While exhibiting the function of reflecting infrared rays to insulate heat while maintaining the above, and in addition, a composite tungsten film having an extremely smooth film was obtained.

That is, one embodiment of the present invention provides a compound represented by 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, and Sn; (W is tungsten, O is oxygen) is a composite tungsten oxide film having a composition represented by the following formula: 0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0 It contains substantially no organic components, 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.

According to one embodiment of the present invention, a composite tungsten oxide film having a function of reflecting and shielding infrared light, that is, a function of shielding heat rays by heat insulation, while maintaining transparency in a visible light region.

At this time, in one embodiment of the present invention, the surface roughness Sa may be 20 nm or less.

を 満 た す By satisfying the above conditions, a composite tungsten film having high film smoothness can be obtained.

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

よ り By setting the sheet resistance within the above range, more preferable heat insulating properties can be obtained.

In one embodiment of the present invention, the composite tungsten oxide film may be derived from sputtering.

(4) By being derived from sputtering film formation, the degree of freedom in selecting a composition is extremely wide, and a composite tungsten oxide film that can be stably formed can be obtained. Further, since an extremely smooth film can be obtained by sputtering, the effect of the optically designed laminated structure can be enhanced.

In one embodiment of the present invention, M is at least one element selected from Cs, Rb, K, Tl, In, Ba, Li, Na, Ca, Sr, Fe, and Sn. Is also good.

By selecting M from the above elements, a composite tungsten oxide film having high smoothness as well as a function of reflecting and blocking higher infrared rays can be obtained.

In one embodiment of the present invention, the composite tungsten oxide film may have a hexagonal crystal structure.

Since the hexagonal phase has a greater reflection in the infrared region, it can be efficiently reflected.

At this time, one embodiment of the present invention provides an 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 I (002) / I (200), I (002) / I (200) is 0.30 or more and 0.50 or less, and the a-axis of hexagonal crystal by X-ray diffraction using CuKα ray is The ratio c / a to the c-axis may be 1.018 to 1.029.

複合 A composite tungsten oxide film that satisfies the above requirements by X-ray diffraction analysis is a composite tungsten oxide film that functions to reflect infrared rays and to insulate heat while maintaining excellent visible light transmittance.

Further, one embodiment of the present invention provides a compound represented by the general formula M _x W _y O _z (where M is one or more elements selected from an alkali metal, an alkaline earth metal, Fe, In, Tl, and Sn; (W is tungsten, O is oxygen) is a composite tungsten oxide film having a composition represented by the following formula: 0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0 The composite tungsten oxide film has a hexagonal crystal structure, and has a diffraction intensity I (002) of a hexagonal (002) plane and a diffraction intensity of a hexagonal (200) plane by X-ray diffraction using CuKα radiation. When the intensity ratio of I (200) is I (002) / I (200), I (002) / I (200) is 0.30 or more and 0.50 or less, and X-ray diffraction using CuKα ray The ratio c / a between the a-axis and the c-axis of the hexagonal crystal is 1.018 to 1.029. You.

複合 A composite tungsten oxide film that satisfies the above requirements by X-ray diffraction analysis is a composite tungsten oxide film that functions to reflect infrared rays and to insulate heat while maintaining excellent visible light transmittance.

At this time, in one embodiment of the present invention, M may be one or more elements selected from Cs, Rb, K, Tl, and Ba.

By selecting M from the above elements, a composite tungsten oxide film having a function of reflecting and blocking higher infrared rays can be obtained.

In one embodiment of the present invention, the composite tungsten oxide film can have a thickness greater than 20 nm.

に よ り With such a film thickness, a composite tungsten oxide film having a high infrared reflection function can be obtained.

の 他 Another embodiment of the present invention is a film-forming substrate having the above-described composite tungsten oxide film formed on at least one surface of a substrate on which a film is to be formed.

こ と By using the film-forming substrate on which the above-described composite tungsten oxide film is formed, it is possible to provide a practical form such as mechanical properties and workability.

At this time, in another embodiment of the present invention, the substrate on which the film is to be formed may have a softening point or a heat distortion temperature of 400 ° C. or higher.

こ と With such characteristics, a film-forming substrate having more excellent functions can be obtained by heat treatment after film formation.

In another embodiment of the present invention, the substrate on which the film is to be formed can be glass.

By using glass as the base material for film formation, it is used in glass windows for vehicle windows and architectural windows, glass fibers, glass for solar power generation, glass for displays, glass for lenses and mirrors, semiconductors and MEMS, and the like. Equipment using glass used in a wide range of fields, such as glass substrates, can be provided with an infrared shielding function.

Another aspect of the present invention is an article having one or more of the composite tungsten oxide film and / or the film-forming substrate described above.

According to another aspect of the present invention, it is possible to provide a large quantity of low-cost and low-environmental articles at the time of energy reduction and manufacturing for various uses.

Further, another aspect of the present invention is a method for producing 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. In the film process, a film is formed in an inert gas, and in the heat treatment process, heat treatment is performed at 400 to 700 ° C. in an inert gas containing an inert gas or a reducing gas.

According to such a manufacturing method, it is possible to easily and stably produce a high-quality composite tungsten oxide film having the above-mentioned characteristics with a uniform thickness using existing general-purpose manufacturing equipment.

According to the present invention, it is possible to obtain a composite tungsten oxide film as an infrared reflecting film having transparency in a visible light region and having reflectivity in an infrared light region. Further, according to the present invention, such a composite tungsten oxide film is widely used industrially, is relatively harmless at the time of film formation, furthermore, the raw material used is excellent in long-term storage, and is useful for storage of dangerous substances and transportation. It can be provided in an unrestricted physical manufacturing method.

FIG. 1 is a diagram showing the difference in optical characteristics (transmittance) between the composite tungsten oxide film of the present invention and the infrared shielding material fine particle dispersion described in Patent Document 2. FIG. 2 is a view showing a difference in optical characteristics (reflectance) between the composite tungsten oxide film of the present invention and the infrared ray shielding material fine particle dispersion described in Patent Document 2. FIG. 3 is a process diagram schematically showing a process in a method for manufacturing a composite tungsten oxide film according to one embodiment of the present invention.

Hereinafter, the composite tungsten oxide film and the method of manufacturing the same according to the present invention will be described in the following order. The present invention is not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention.
1. 1. Composite tungsten oxide film 2. Method for producing composite tungsten oxide film 2-1. Film forming step 2-2. Heat treatment step 3. Film forming base material 4. Goods

<1. Composite Tungsten Oxide Film>
A composite tungsten oxide film according to one embodiment of the present invention will be described. Composite tungsten oxide film according to an embodiment of the present invention have the general formula _M x _W y _{O z} (however, M is selected alkali metal, alkaline earth metal, Fe, an In, Tl, from among Sn One or more elements, W is tungsten, and O is oxygen). The film has a composition represented by the following formula: x: y is 0.001 ≦ x / y ≦ 1, z: y is The configuration is in the range of 2.2 ≦ z / y ≦ 3.0.

Details of the composition range are shown in Patent Document 2 by the present applicant, and the main component of the composite tungsten oxide having this composition range is a film having high transparency and infrared light absorption. It is necessary to make it. The basic optical characteristics of the composite tungsten oxide film originate from the theoretically calculated atomic arrangement of the element M, tungsten W and oxygen O. On the other hand, one embodiment of the present invention is a composite tungsten oxide film having characteristics different from those of the infrared shield described in Patent Literature 2, and will be described in detail below while appropriately comparing with the invention according to Patent Literature 2. I do.

The element M of the composite tungsten oxide film according to one embodiment of the present invention is at least one element selected from alkali metals, alkaline earth metals, Fe, In, Tl, and Sn, and more preferably. , Cs, Rb, K, Tl, In, Ba, Li, Na, Ca, Sr, Fe, and Sn. Although this is a range narrower than the constituent elements described in Patent Document 2, this is only an element whose effect was confirmed according to the Examples, and is not included in the present invention. However, it may have a similar function.

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

Composite tungsten oxide film according to an embodiment of the present invention are the compounds of formula _M x _W y _{O z,} the atomic ratio x / y of the element M and W (tungsten) is at 0.001 ≦ x / y ≦ 1 Yes, the atomic ratio z / y between O (oxygen) and W (tungsten) satisfies 2.2 ≦ z / y ≦ 3.0. When x / y is less than 0.001, a sufficient amount of free electrons is not generated, and an 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, a non-target WO ₂ crystal phase appears in the composite tungsten oxide film. On the other hand, when z / y exceeds 3.0, free electrons for obtaining an infrared ray shielding effect are not generated.

複合 The composite tungsten oxide film according to one embodiment of the present invention does not substantially include an organic component. As described later, since the composite tungsten oxide film according to one embodiment of the present invention is formed by a physical film forming method, a dispersant or a medium resin as disclosed in Patent Documents 2 and 3 is used. Alternatively, there is no need to use surfactants or solvents. Here, “substantially not containing an organic component” means that it does not contain an organic component that is intentionally added, such as a polymer dispersant, in the process of producing the film.

Patent Document 3 describes a method for producing a transparent conductive film using a composite tungsten oxide in paragraph 0060. According to this, the transparent conductive film disclosed in Patent Document 3 is coated with a solution containing a composite tungsten compound as a starting tungsten raw material solution on a substrate, and then coated with an inert gas, an inert gas and a reducing gas, or an atmosphere of a reducing gas. It has been shown that it can be obtained by heat treatment in a medium. 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 chloride of element M to form a solution.

再現 The method described in Patent Document 3 was reproduced, and the surface roughness was measured with a laser microscope. As a result, the arithmetic mean height Sa exceeded 60 nm. On the other hand, since the composite tungsten oxide film according to one embodiment of the present invention is formed by a physical film forming method such as a sputtering method as described later, the surface roughness Sa can be set to 20 nm or less. . Thus, the smoothness of the composite tungsten oxide film according to the embodiment of the present invention is different from that of the transparent conductive film of Patent Document 3.

Further, as described in paragraphs 0050 and 0053 of Patent Document 2, a film composed of a fine particle dispersion containing composite tungsten oxide fine particles of Patent Document 2 absorbs light, particularly in a near infrared region. It has been shown that the absorption in the above serves as an excellent heat ray shielding film.

1 and 2 are diagrams showing a difference in optical characteristics between the composite tungsten oxide film of the present invention and the infrared ray shielding material fine particle dispersion described in Patent Document 2. FIG. FIG. 4 is a diagram showing the reflectance. As shown in FIGS. 1 and 2, the composite tungsten oxide film according to one embodiment of the present invention has optical characteristics different from those of the film made of a fine particle dispersion (fine particle dispersed film) according to 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 or less. The reason for this is presumed to be the difference between the fine particle dispersed film and the continuous film, as described later, but the details have not yet been determined.

複合 The 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.

て も Even if the transmittance at a wavelength of 550 nm, which is an index of transparency, is lower than 50%, it can be used depending on the application. For example, in a window film for a car, a rear window is preferably black or dark gray from the viewpoint of privacy protection, and a pigment or the like may be intentionally used together with the heat ray shielding material.

透明 The transparency index of the present invention indicates the film properties in a state where the above-mentioned intentional pigments and the like are not included. If the index of transparency is lower than the above-mentioned value, lighting becomes poor, which leads to, for example, darkening of an indoor space or making it difficult to see an external scenery.

Similarly, the transmittance at a wavelength of 1400 nm and the reflectance at a wavelength of 1400 nm, which are used as indices of the light shielding performance and the reflection performance, may be configured not to satisfy the above-mentioned values. The penetration increases, and the heat shielding leads to a feeling of skin stiffness and an increase in room temperature, and the light-to-heat conversion leads to a decrease in the amount of heat generated.

反射 Also, since the reflection of the present invention is reflection by free electrons, it reflects light below the plasma frequency. In other words, light having a wavelength equal to or greater than the wavelength corresponding to the plasma frequency is reflected. That is, when the reflectance at a wavelength of 1400 nm is low, the reflectance of far-infrared rays having a longer wavelength is also low, the heat insulation property is low, and the effect of confining heat such as indoor heating is low. In order to obtain effective heat insulating properties, the reflectance at a wavelength of 1400 nm needs to be 35% or more.

表面 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), the reflection of a specific wavelength is strengthened or weakened by using interference to obtain a steep transmission profile (adjustment of the color of the film) or reflection in the visible light region. Can be used for prevention. The influence of the surface roughness is that the above optical thin film design (in the case of laminating the films) has a small surface roughness, so that a stable laminated film with little disturbance of the optical path length is possible. Since the composite tungsten oxide film according to one embodiment of the present invention is a film formed by a physical method obtained by film formation by a sputtering method or the like as described later, the surface roughness Sa of the film should be 20 nm or less. Can be. If it is 20 nm or less, there is a low possibility that a problem in designing the optical thin film will occur. When the surface roughness exceeds 20 nm, a uniform lamination state is not obtained, and it is difficult to obtain the effect of optical thin film design (lamination).

複合 In addition, the composite tungsten oxide film according to one embodiment of the present invention is preferably formed with a thickness exceeding 20 nm. The composite tungsten oxide film according to one embodiment of the present invention is a film formed by a physical method obtained by film formation by a sputtering method or the like, as described later, for example, heat-treated after applying a solution described in Patent Document 3. In a film formed by forming a film, components such as a solvent and a resin, which are indispensable for the film formation, are formed by volatilization, so that a residual stress is generated 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 a volatile component, the residual stress of the film accompanying the film formation can be reduced, and the residual volatile component and voids can be reduced. No defects occur. For this reason, a film without cracks or peeling can be formed.

However, when 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%. In the present invention, there is no particular limitation as long as the thickness exceeds the above film thickness. However, when the film thickness is large, the transmittance in the visible light region at a wavelength of 550 nm is less than 50%, so that the visible light transmittance may be deteriorated, or the film may be peeled off due to the residual stress during film formation. . The transmittance of the film can be measured using a spectrophotometer.

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

Further, the composite tungsten oxide film according to one embodiment of the present invention is usually formed as a continuous film, but has a form in which reflection is controlled by patterning, and a form in which irregularities are provided to provide a lens function. The shape of the film, the shape of the unevenness, and the like may be any shape as long as it has the features of the present invention.

複合 The composite tungsten oxide according to one embodiment of the present invention preferably has a hexagonal crystal structure. The inclusion of the hexagonal crystal structure can be known by analyzing the film by X-ray diffraction. The composite tungsten oxide is known to have a crystal structure such as hexagonal, cubic, tetragonal, and orthorhombic, and an amorphous structure, but the composite tungsten oxide film according to one embodiment of the present invention has a hexagonal crystal structure. And a crystal structure other than hexagonal, such as cubic, tetragonal, orthorhombic, or an amorphous structure. By including the hexagonal crystal structure in the composite tungsten oxide film, the hexagonal phase can reflect efficiently since the reflection in the infrared region is larger.

Further, 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 obtained by X-ray diffraction using CuKα ray is 1.018 to 1.029. It is preferable that According to the ICDD reference code 01-081-1244 of the crystal structure database, c / a is 1.028. It is considered that when the number of atoms becomes excessive or insufficient compared with the standard hexagonal structure, the a-axis length and the c-axis length change.

In the composite tungsten oxide film according to one embodiment of the present invention, the diffraction intensity I (002) of the hexagonal (002) plane and the diffraction intensity of the hexagonal (200) plane by X-ray diffraction using CuKα rays When the intensity ratio of I (200) is I (002) / I (200), it is preferable that I (002) / I (200) be 0.30 or more and 0.50 or less. Since the relative intensity of the (002) plane to the (200) plane is described as 26.2% in the above-described ICDD reference code 01-081-1244, 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, but the intensity ratio of the present invention is 0.30 or more and 0.50 or less. Since the intensity ratio is larger than the standard intensity ratio, it is considered that the growth of the hexagonal a and b planes is suppressed and the c-plane orientation tends to occur. If the above-mentioned c / a deviates from 1.018 to 1.029 and the intensity ratio I (002) / I (200) deviates from 0.30 or more to 0.50 or less, the heat ray reflection function decreases.

When the element M is Sn, the crystal structure is trigonal. In the above X-ray diffraction, the ratio c / a between the a-axis length and the c-axis length of the hexagonal crystal is the a-axis length and the c-axis length of the trigonal crystal. It is calculated by the ratio 2c / a.

関係 The relationship between the crystal state different from the standard and the heat ray reflection function is considered to be unique to the sputtering method and the vacuum evaporation method. It is thought to be due to the process of forming a crystal structure by heat treatment after the formation of a non-equilibrium amorphous film, but the details of the mechanism are unknown.

As described above, according to the composite tungsten oxide film according to one embodiment of the present invention, the composite tungsten oxide film has characteristics different from those of the composite tungsten oxide films described in Patent Literature 2 and Patent Literature 3, and exhibits transparency in a visible light region. And a composite tungsten oxide film as an infrared reflecting film having reflectivity in the infrared light region.

<2. Manufacturing method of composite tungsten oxide film>
Next, a method for manufacturing a composite tungsten oxide film will be described. FIG. 3 is a process diagram schematically showing 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 producing a composite tungsten oxide film containing the element M, tungsten W, and oxygen O as main components, and a film forming step S1 for forming a film using a physical film forming method. And a heat treatment step S2 for heat treating the film. Hereinafter, each step will be described in detail.

<2-1. Film forming process>
In the film forming step S1, a film is formed using a physical film forming method. Examples of the physical film forming method of the composite tungsten oxide film according to one embodiment of the present invention include a vacuum deposition method, a sputtering method, an ion plating method, and an ion beam method. Among them, the sputtering method has a large energy of a film-forming particle, a strong adhesive force, a dense film and a strong film quality, a stable film-forming process, and high-precision control of the film quality and the film thickness. In addition, the sputtering method has the advantages that films of high melting point metals, alloys and compounds can be formed, oxides and nitrides can be formed by introducing a reactive gas, and composition adjustment is relatively easy. It is preferable because it 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 wind films and mirrors, and has many manufacturing devices.

The sputtering target for forming the composite tungsten oxide film represented by the general formula M _x W _y O _z is, for example, a sputtering target including the element M and the element W, and a sputtering target including the element M and the compound of the element W and the element O. , A sputtering target composed of a compound of the element M and the element O, and a sputtering target composed of a compound of the element M, the element W, and the element O. Preferably, a sputtering target formed in advance as a compound phase is used. If the sputtering target is formed as a compound phase in advance, the dependence of the film composition on the difference in vapor pressure of each element can be reduced, and stable film formation can be achieved.

The sputtering target may be used in the form of, for example, a compact formed by compacting powder composed of particles of the sputtering target composition or a sintered body formed by sintering the sputtering target composition.

In addition, since the sputtering target is formed of a compact or a sintered body as described above, it does not substantially include an organic component, and a film formed using the target does not substantially include an organic component. . Here, “substantially not contained” means that it does not contain intentionally added components such as a polymer dispersant.

と If the sputtering target is a conductor having a specific resistance of, for example, 1 Ω · cm or less, a DC sputtering apparatus with high productivity can be used. Further, when the sputtering target is a sintered body having a relative density of 70% or more, for example, cracks due to vibration during transportation are reduced, and it is not necessary to take extreme care in handling such as mounting to an apparatus. It is a form suitable for general production.

雰 囲 気 The atmosphere in the film forming step is variously selected, but preferably in an inert gas atmosphere. As the inert gas, for example, a rare gas such as a helium gas or an argon gas, a nitrogen gas, or the like may be used. In the case of a nitrogen gas, a nitride may be formed depending on the selected element M. Argon gas which is used and easily available is more preferable. The purity of the gas used is preferably 99% or more, and the mixing of oxidizing gas such as oxygen is preferably less than 1%. Although details are unclear, a composite tungsten oxide film having a high reflectance can be obtained by forming a film in an inert atmosphere and performing a heat treatment under the conditions described later. On the other hand, if the ratio of the oxidizing gas exceeds 1%, the reflectance of the composite tungsten oxide film after the heat treatment decreases.

(4) Although the film after film formation is usually amorphous, a diffraction peak based on crystals may appear when subjected to X-ray diffraction analysis.

<2-2. Heat treatment process>
Next, in a 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 performed in an inert or reducing atmosphere.

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 when crystallized, the hexagonal diffraction peak in X-ray diffraction is extremely weak, and the heat shielding properties in the infrared region are low. Further, even if the heat treatment temperature is higher than 700 ° C., the characteristics of the film of the present invention can be obtained. However, practically, the film reacts with the substrate, the film peels off from the substrate, and the surface roughness increases. Will occur.

At any of the above-mentioned heat treatment temperatures, the heat treatment time may be sufficient to complete the crystallization of the composite tungsten oxide, and depends on the balance between the heat conduction of the base material and the productivity. It may be adjusted appropriately in about a minute.

の 通 り As described above, the heat treatment is performed 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.

As described above, according to the method for manufacturing a composite tungsten oxide film according to one embodiment of the present invention, a composite tungsten oxide film having the above-described characteristics is widely used industrially and is relatively harmless during film formation. In addition, the raw material can be provided by a physical production method that is excellent in long-term storage of the raw material and has no restrictions during transportation.

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

(4) Since the heat treatment temperature of the film after the film formation is 400 ° C. or higher, the substrate on which the film is to be formed is preferably a substrate having a softening point or heat deformation temperature of 400 ° C. or higher. When a substrate having a softening point or a heat deformation temperature of less than 400 ° C. is used, problems such as peeling of the film from the substrate on which the film is to be formed and cracking of the film occur during the heat treatment. Preferably, the thermal expansion coefficient of the film-forming substrate is closer to the thermal expansion coefficient of the film. However, when the film is used after being peeled off from the base material, the above conditions need not necessarily be satisfied, and for example, a base material that melts at 400 ° C. or lower may be used.

Examples of the base material having a softening point or heat distortion temperature of 400 ° C. or higher include glass, ceramics, and single crystals. The substrate on which the film is to be formed is not necessarily required to be transparent. However, when the composite tungsten oxide film of the present invention is used together with the substrate, a transparent substrate is required. Examples of the transparent substrate include glass, transparent ceramics such as YAG and Y ₂ O _3, and single crystals such as sapphire. Above all, it is preferable to use a glass having a softening point of 400 ° C. or higher as a substrate on which a film is to be formed, from the viewpoints of easy availability, low cost, weather resistance, chemical resistance and the like.

(4) The substrate is not limited to a flat surface but may have a curved surface or an uneven surface without deteriorating the features of the present invention.

As described above, according to the film-forming substrate of one embodiment of the present invention, the film-forming substrate has transparency in the visible light region, and has an infrared reflective film having reflectivity in the infrared light region. be able to.

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

In addition, even if the composite tungsten oxide film and / or the film-forming substrate of the present invention is used together with, for example, a film or a particle having another function, the composite tungsten oxide film and / or the film-forming substrate is included in an article utilizing the function described in the present invention. .

The composite tungsten oxide film of the present invention is an infrared reflective film having reflectivity in an infrared light region. Examples of the article having a function of reflecting and shielding light include heat-insulating glass.
The heat insulating and insulating glass has a feature of shielding and insulating heat while being transparent, and reduces a rise in indoor temperature and a rise in vehicle temperature due to sunlight in summer. In addition, the heat of the heating in winter can be reflected and kept indoors.

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 region and having reflectivity in the infrared light region, and the formation of such a film. The article can be provided with a substrate.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples.

(Example 1)
In Example 1, a cesium tungsten oxide powder having a Cs / W atomic ratio of 0.33 (YM-01 manufactured by Sumitomo Metal Mining Co., Ltd.) was charged into a hot press apparatus, and a vacuum atmosphere, a temperature of 950 ° C., and a pressing pressure of 250 kgf / It was sintered under the condition of cm ² to produce a cesium tungsten oxide sintered body. As a result of chemical analysis of the sintered body composition, Cs / W was 0.33. This oxide sintered body was ground by machining to a diameter of 153 mm and a thickness of 5 mm, and joined to a stainless steel backing plate using a metal indium brazing material, to produce a cesium tungsten oxide sputtering target.

Next, this sputtering target was attached to a DC sputtering apparatus (SBH2306 manufactured by ULVAC, Inc.), the ultimate vacuum was 5 × 10 ⁻³ Pa or less, the atmosphere during film formation was an argon gas atmosphere, and the gas pressure was 0.6 Pa. At a power of 600 W DC, a cesium tungsten oxide film was formed on a glass substrate (EXG manufactured by Corning, thickness 0.7 mm). 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 diffractometer (X'Pert-PRO (manufactured by PANalytical).) The film after film formation was an amorphous film having no diffraction peak derived from the crystal structure. It was a structure.

(4) The formed film was put into a lamp heating furnace (HP-2-9, manufactured by Yonekura Seisakusho Co., Ltd.) and heat-treated at 500 ° C. for 30 minutes in a nitrogen atmosphere (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.

With respect to the structure of the film after the heat treatment, the crystal structure, the X-ray diffraction intensity ratio, and the ratio c / a between the a-axis and the c-axis were examined using an X-ray diffractometer (X'Pert-PRO, manufactured by PANalytical). The transmittance and the reflectance were measured using a spectrophotometer (manufactured by Hitachi, model number V-670).

膜 The crystal structure of the film after heat treatment was a structure containing hexagonal crystals. The X-ray diffraction intensity ratio was 0.401, and the ratio c / a between the a-axis and the c-axis was 1.028. 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%.

The sheet resistance of the film after the heat treatment was 3.0 × 10 ³ Ω / □ as a result of measurement using a resistivity meter (manufactured by Mitsubishi Chemical Corporation, Loresta), and the film after the heat treatment had high conductivity and low resistance. (The resistance was measured using Mitsubishi Chemical Loresta or Hiresta according to the resistivity).

{Circle around (4)} The surface roughness of the film after the heat treatment was measured using a laser microscope (OLS4100, manufactured by Olympus), and the arithmetic average height (surface roughness) Sa was 8 nm.

(Examples 2 to 17 and Comparative Examples 1 to 13)
Using the same apparatus as in Example 1, the composite tungsten oxide film was changed by changing the element M, the composition ratio, the film thickness, the film formation atmosphere, the heat treatment atmosphere, the temperature, and the time as described in Tables 1 and 2. Was prepared and the characteristics of the film were examined. Tables 1 and 2 show the results of the examples together with the results of the comparative examples.

From Tables 1 and 2, in Examples 1 to 17 included in the method for producing a composite tungsten oxide film according to the present invention, the transmittance at a wavelength of 550 nm is 50% or more, the transmittance at a wavelength of 1400 nm is 30% or less, and the wavelength is It was confirmed that the film had a characteristic that the reflectance at 1400 nm was 35% or more. Further, in Examples 1 to 17 included in the present invention, the sheet resistance was less than 1.0 × 10 ⁵ Ω / □, and the surface roughness Sa was 20 nm or less. On the other hand, in Comparative Examples 1 to 13 which are not included in the method for manufacturing a composite tungsten oxide film according to the present invention, the optical characteristics do not satisfy the above requirements, and the sheet resistance is 1.0 × 10 ⁵ Ω / □. That's all.

Although one embodiment and each example of the present invention have been described in detail as described above, it is understood by those skilled in the art that many modifications that do not substantially depart from the novel matter and effects of the present invention are possible. , Will be easy to understand. Therefore, such modified examples are all included in the scope of the present invention.

For example, in the specification or the drawings, a term described at least once together with a broader or synonymous different term can be replaced with the different term in any part of the specification or the drawing. Further, the configuration of the composite tungsten oxide film and the method of manufacturing the same are not limited to those described in the embodiment and each example of the present invention, and various modifications can be made.

Since the composite tungsten oxide film according to the present invention has high transparency in the visible light region, excellent light reflectivity in the infrared region, and high film smoothness, it is used for a wide range of applications utilizing the function of reflecting light. Have the potential to do so.

Claims (15)

A general formula M _x W _y O _z (where M is at least one element selected from alkali metals, alkaline earth metals, Fe, In, Tl, and Sn, W is tungsten, and O is oxygen). A composite tungsten oxide film having a composition represented by the main component,
0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0,
Contains substantially no organic components,
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. The composite tungsten oxide film according to claim 1, wherein the surface roughness Sa is 20 nm or less. The composite tungsten oxide film according to claim 1, wherein a sheet resistance is less than 10 ⁵ Ω / □. The composite tungsten oxide film according to any one of claims 1 to 3, wherein the composite tungsten oxide film is derived from sputtering film formation. The M is one or more elements selected from Cs, Rb, K, Tl, In, Ba, Li, Na, Ca, Sr, Fe, and Sn. The composite tungsten oxide film according to claim 4. The composite tungsten oxide film according to any one of claims 1 to 5, wherein the composite tungsten oxide film has a hexagonal crystal structure. The intensity ratio between 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). And I (002) / I (200) is 0.30 or more and 0.50 or less,
7. The composite tungsten oxide film according to claim 6, wherein a ratio c / a of a-axis to c-axis of hexagonal crystal determined by X-ray diffraction using CuKα ray is 1.018 to 1.029. A general formula M _x W _y O _z (where M is at least one element selected from alkali metals, alkaline earth metals, Fe, In, Tl, and Sn, W is tungsten, and O is oxygen). A composite tungsten oxide film having a composition represented by the main component,
0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0,
The composite tungsten oxide film has a hexagonal crystal structure,
The intensity ratio between 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). Where I (002) / I (200) is 0.30 or more and 0.50 or less,
A composite tungsten oxide film having a hexagonal a-axis to c-axis ratio c / a of 1.018 to 1.029 by X-ray diffraction using CuKα rays. The composite tungsten oxide film according to claim 8, wherein M is at least one element selected from Cs, Rb, K, Tl, and Ba. The composite tungsten oxide film according to any one of claims 1 to 9, wherein the composite tungsten oxide film has a thickness greater than $ 20 nm. A film-forming substrate, wherein the composite tungsten oxide film according to any one of claims 1 to 10 is formed on at least one surface of the film-forming substrate. The film-forming substrate according to claim 11, wherein the film-forming substrate has a softening point or a heat distortion temperature of 400 ° C or higher. The film-forming substrate according to claim 11 or 12, wherein the film-forming substrate is glass. A composite tungsten oxide film according to any one of claims 1 to 10 and / or one or more film-forming substrates according to any one of claims 11 to 13. Goods to be. A method for producing a composite tungsten oxide film, comprising:
A film forming step of forming a film by a physical film forming method,
A heat treatment step of heat treating the film,
Forming a film in an inert gas in the film forming step and performing a heat treatment in an inert gas containing an inert gas or a reducing gas at 400 to 700 ° C. in the heat treatment step; Production method of material film.

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