Photocatalyst member and method for producing photocatalyst member

Abstract

A photocatalyst member provided with a base material, an underlayer, and a photocatalyst layer formed in contact with the underlayer in this order, the photocatalyst member being characterized in that the underlayer is composed of a composite oxide of cerium and zinc, and the photocatalyst layer contains titanium oxide.

Description

Technical Field

[0001] This invention relates to photocatalyst components and methods for manufacturing photocatalyst components. Background Technology

[0002] Photocatalysts, which catalyze reactions using ultraviolet or visible light, are currently attracting attention due to their various effects. The effects produced by photocatalysts, particularly those observed in the Honda-Fujishima effect, include the photolysis of water to produce hydrogen / oxygen, strong oxidizing properties resulting from the generation of reactive oxygen species on surfaces, and superhydrophilicity resulting from the formation of numerous hydroxyl groups on surfaces. Photocatalysts can be considered for various applications, including sterilization of viruses and pathogens such as coronaviruses, which have become increasingly prevalent in recent years, decomposition of formaldehyde in sick houses, and anti-fog films utilizing superhydrophilic properties.

[0003] Furthermore, when applying photocatalysts to antireflective films, it is expected that they will be effective in decomposing fingerprints adhering to the surface of the antireflective film. In particular, antireflective films based on dielectric multilayer films composed of alternating layers of inorganic materials with different refractive indices and a thickness of less than 1 μm are effective because they utilize light interference. Therefore, even if transparent foreign matter such as fingerprints is slightly adhered to the surface, the interference effect is disrupted, making the transparent foreign matter easily visible. In the past, antireflective films were coated with substances with low surface energy, such as fluorine compounds, to suppress the adhesion of transparent foreign matter such as fingerprints, but the effect was not sufficient, and cleaning such as wiping was still required. To address this issue, if transparent foreign matter, which is an organic substance, can be decomposed by a photocatalyst, cleaning would not be necessary, and therefore, photocatalysts are highly anticipated.

[0004] Titanium oxide is known as a photocatalytic material. Vacuum thin-film formation methods, such as sputtering, are known for forming titanium oxide on the surface of certain substrates. However, to enable titanium oxide to exhibit photocatalytic properties, it needs to be crystallized into anatase or rutile forms, which requires heat treatment at temperatures above 300°C during or after film formation. Therefore, it is difficult to apply photocatalysts to components with low heat resistance, such as plastics. As an alternative method, a method has been proposed that involves coating crystallized titanium oxide micropowder with a binder onto a substrate and then curing it. Since this coating method does not require heating and can be applied to large areas, its applications are very wide, and almost all commercially available photocatalysts are based on this coating method.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2007-308729 Patent Document 2: Japanese Patent Application Publication No. 2007-314835 Patent Document 3: Japanese Patent No. 5217023 Patent Document 4: Japanese Patent Application Publication No. 2000-345320 Patent document 5: Japanese Patent No. 4460537. Summary of the Invention

[0006] The problem that the invention aims to solve However, adhesives used for fixing to the substrate are mostly organic materials, which present problems such as adhesive decomposition due to a phenomenon called chalking caused by contact with the photocatalyst, and the photocatalyst itself also detaching. In addition, when the ratio of adhesive to the substrate is increased to enhance the adhesion between the substrate and the photocatalyst, there is also the problem that the ratio of photocatalyst is relatively reduced, resulting in a decrease in catalytic performance.

[0007] Therefore, it is desirable to form titanium dioxide thin films using a binder-free vacuum thin film formation method, but how to achieve photocatalytic performance in film formation at room temperature is a challenge.

[0008] Patent Document 1 discloses a method for obtaining crystallized titanium oxide at room temperature by using a single or dual cathode to apply a voltage with a duty cycle of a certain value or less. While Patent Document 1 describes that crystallized titanium oxide can be obtained using this method, the inventors were unable to confirm crystallization during reproduction experiments, possibly due to factors such as the configuration of the equipment.

[0009] Furthermore, Patent Documents 2 and 3 disclose methods to promote crystallization by performing the titanium metal film formation and oxidation processes separately. However, these methods require complex equipment configurations and are difficult to implement using general-purpose sputtering devices.

[0010] As an example of using a general sputtering apparatus, as shown in Patent Document 4, a method was attempted to crystallize the film by adding moisture during film formation and performing heat treatment at a relatively low temperature (above 200°C). However, although it is called low-temperature crystallization, it requires heating above 200°C, which causes deformation in many plastic substrates. Therefore, there is a lack of versatility.

[0011] As a method for obtaining photocatalytic performance through room temperature film formation using a common sputtering apparatus, as shown in Patent Document 5, there is a method of forming a film of titanium dioxide after forming a film of zirconium oxide as a substrate. This method can be considered an excellent method for achieving photocatalytic performance without heat treatment of titanium dioxide.

[0012] However, due to the low degree of crystallinity of zirconium oxide, a certain film thickness is required in order for it to function fully as a substrate, resulting in low productivity.

[0013] Furthermore, since zirconium oxide is an insulating material, high-frequency (RF) sputtering is required to form films via sputtering. However, this method is slow and difficult to scale up to large areas, resulting in significantly low productivity. Another approach to achieving photocatalytic performance without high temperatures is to zirconia metallic zirconium via DC reactive sputtering in an inert or reactive gas environment. However, achieving stable production is extremely difficult because sputtering conditions vary considerably depending on the surface oxidation state of the zirconium oxide target.

[0014] This invention was made to solve the problems involved, and its purpose is to explore a substrate layer different from zirconium oxide to provide a photocatalyst with high industrial productivity.

[0015] Methods for solving problems The inventors conducted in-depth research on the relevant issues, thus completing this invention. The inventors discovered that by using a composite oxide target formed by mixing and sintering cerium oxide (CeO2) and zinc oxide (ZnO), the target becomes conductive. Using this target as a substrate layer for film formation, titanium oxide is then formed into a film. The resulting photocatalyst component exhibits photocatalytic performance without heat treatment.

[0016] Furthermore, it was discovered that by using a target formed by mixing cerium oxide (CeO2) and zinc oxide (ZnO) in a molar ratio (molar ratio) within the range of 3:1 to 3:2, DC sputtering can be performed. After forming a substrate layer using this target, a titanium oxide layer can be formed without heating, thereby creating a photocatalyst component exhibiting particularly good photocatalytic performance.

[0017] The aforementioned substrate layer is preferably a composite oxide of cerium and zinc, but it may also contain other elements. For example, gallium (Ga) or aluminum (Al) may be included to improve the conductivity of zinc oxide. Furthermore, conductivity is only necessary for direct current (DC) sputtering, and the substrate layer may not be conductive. It has been established that even a substrate layer thickness of 10 nm can produce a photocatalyst layer with photocatalytic performance; however, in the case of plastic films, a thickness of 20 nm or more is desirable from the viewpoint of ensuring surface smoothness. While a thickness of 20 nm or more can maintain sufficient crystallinity, film deposition of 100 nm or more not only imposes a thermal load on the substrate but is also inefficient industrially; therefore, a thickness of 100 nm or less is desirable.

[0018] The photocatalyst layer in the photocatalyst component of the present invention has titanium oxide (TiO2) as the main component, but other elements may also be included as long as photocatalytic performance is observed. For example, titanium oxide has a band gap in the ultraviolet region, and ultraviolet light is required for it to function as a photocatalyst; however, there are instances where nitrogen is added to make it responsive in visible light. In the present invention, nitrogen may also be added to produce a visible-light-responsive photocatalyst. Furthermore, a metal element such as niobium may be added to improve the conductivity of the photocatalyst layer. Additionally, in the present invention, titanium oxide may not exhibit crystallinity. The thickness of the photocatalyst layer is sufficient as long as it is thick enough to exhibit photocatalytic performance; for example, it may be 40 nm or more. Furthermore, even if the photocatalyst layer is thick, the effects of the present invention are observed, but industrially, a thickness of 200 nm or less is desirable.

[0019] Furthermore, layers other than the base layer and the photocatalyst layer can also be present on the substrate. For example, to maintain the superhydrophilicity of the photocatalyst, a silicon oxide film can be formed on the surface of the photocatalyst layer. In addition, as seen in the Honda-Fujishima effect, in order to use the present invention as a photocatalyst electrode, a conductive layer can be formed on the substrate before the base layer is formed.

[0020] In all cases, the present invention is accomplished by forming a titanium oxide film on the side opposite to the substrate in the face of a substrate layer composed of a composite oxide of cerium oxide and zinc oxide.

[0021] That is, the present invention provides the following means.

[0022] (1) One aspect of the present invention involves a photocatalyst component comprising a substrate, a base layer and a photocatalyst layer formed in sequence with the base layer, wherein the base layer is a composite oxide of cerium and zinc and the photocatalyst layer comprises titanium oxide.

[0023] (2) In the photocatalyst component of (1) above, the molar ratio of cerium oxide and zinc oxide contained in the substrate layer can be in the range of 3:1 to 1:1.

[0024] (3) In the photocatalyst component of (1) or (2) above, the element ratio of elements other than titanium oxide contained in the photocatalyst layer may be less than 10%.

[0025] (4) In any of the photocatalyst components in (1) to (3) above, the thickness of the substrate layer can be 10 nm or more.

[0026] (5) In the photocatalyst components of (1) to (4) above, the thickness of the photocatalyst layer can be 40 nm or more.

[0027] (6) The photocatalyst components of (1) to (5) above also have a hydrophilic retention layer on the photocatalyst layer, and the hydrophilic retention layer may contain silicon oxide or a composite oxide of silicon and other metals.

[0028] (7) In the photocatalyst components of (1) to (6) above, the substrate may be a transparent substrate.

[0029] (8) In the photocatalyst components of (1) to (7) above, the substrate can be a polymer film.

[0030] (9) In the photocatalyst components of (1) to (8) above, the substrate layer further contains group III elements, and the total amount of group III elements contained in the substrate layer may be less than 10% in molar ratio.

[0031] (10) A method for manufacturing a photocatalyst component according to one aspect of the present invention includes the following steps: a substrate forming step, forming a substrate layer on a substrate; and a photocatalyst layer forming step, forming a photocatalyst layer comprising titanium oxide on the substrate layer, wherein the substrate is sputtered using a composite target of cerium oxide and zinc oxide.

[0032] (11) In the above method for manufacturing the photocatalyst component (10), the mixing ratio of cerium oxide and zinc oxide of the composite target can be in the range of 3:1 to 3:2 in terms of molar ratio.

[0033] (12) In the manufacturing method of the photocatalyst component in (10) or (11) above, the composite target may be conductive.

[0034] (13) In the manufacturing method of the photocatalyst component in (10) to (12) above, DC discharge sputtering or AC discharge sputtering can be performed in the substrate layer formation process.

[0035] (14) In the manufacturing method of the photocatalyst component in (10) to (13) above, the photocatalyst layer can be formed by sputtering a target containing any one of titanium, titanium alloy and oxygen-deficient titanium oxide in the photocatalyst layer formation step.

[0036] (15) In the manufacturing method of the photocatalyst component in (10) to (14) above, the substrate can be a polymer film.

[0037] Invention Effects According to the present invention, a photocatalyst with high industrial productivity can be provided. For example, a photocatalyst component that exhibits photocatalytic performance without high-temperature heat treatment and a method for manufacturing the photocatalyst component can be provided. This manufacturing method can use a substrate with low heat resistance, can improve the film formation rate, and can manufacture a photocatalyst component that exhibits photocatalytic performance. Attached Figure Description

[0038] [ Figure 1 [This is a cross-sectional view showing an example of the structure of a photocatalyst component according to one embodiment of the present invention.]

[0039] [ Figure 2 ] is the display Figure 1 A cross-sectional view of the structure of the photocatalyst component involved in the modified example.

[0040] [ Figure 3 [ ] is a graph showing the XRD spectrum of the substrate layer formed on the alkali-free glass substrate in Example 1. Detailed Implementation

[0041] In the accompanying drawings used in the following description, for ease of understanding of the features of the invention, sometimes the parts that will become features are shown enlarged for convenience, and the size ratios of the constituent elements may differ from the actual dimensions. The materials, dimensions, etc., exemplified in the following description are examples, and the invention is not limited to these; it can be implemented by appropriate modifications within the scope of its effects. Furthermore, the upper and / or lower limits of the numerical ranges described in this specification can be arbitrarily combined to define preferred ranges. For example, the upper and lower limits of the numerical ranges can be arbitrarily combined to define preferred ranges.

[0042] [Photocatalyst components] Figure 1 This is a cross-sectional view showing an example of the structure of a photocatalyst component according to one embodiment of the present invention. Figure 1 The photocatalyst component 1 shown sequentially comprises a substrate 2, a base layer 3, and a photocatalyst layer 4 formed in contact with the base layer 3. The base layer 3 is composed of a composite oxide of cerium and zinc, and the photocatalyst layer 4 comprises titanium oxide. In this embodiment, the number of layers of the base layer 3 and the photocatalyst layer 4 is typically one each. Figure 1 In the example shown, the photocatalyst layer 4 is the outermost layer of the stack.

[0043] <Substrate> The substrate 2 can be made of any material. Examples of materials for the substrate 2 include glass, metal, resin, and ceramic. Resin films, such as polymer films, can be used as examples of resins suitable for the substrate 2. In particular, resin films with reduced resin thickness offer numerous advantages, such as being lightweight and adaptable to various applications. Furthermore, for industrial reasons, they offer the advantage of continuous film formation using roll-to-roll sputtering equipment for mass production. Additionally, transparent resin (polymer) films are sometimes used in applications requiring light transmission, such as window glass or displays.

[0044] There are no particular limitations on the materials used for transparent resin films. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyarylamide, polyimide, polycarbonate, polyethylene, polypropylene, triacetyl cellulose (TAC), polycyclic olefins (COC, COP), etc. can be used.

[0045] Substrate 2 is preferably a transparent substrate. The transparent substrate can be formed of any transparent material that can transmit light in the visible light region. For example, the transmittance of the transparent substrate to light in the visible light region is 80% or more.

[0046] There is no particular limitation on the thickness of the substrate 2. When the substrate 2 is a resin film, considering ease of manufacturing and the thinness of the component, a thickness of 20 μm or more and 200 μm or less is desirable. It should be noted that, from the viewpoint of improving the scratch resistance of the substrate 2, a film based on, for example, acrylic resin can also be formed on at least one surface of the substrate 2 by solution coating. Furthermore, to improve haze and film travel, a resin in which organic or inorganic particles are dispersed within the aforementioned acrylic resin can also be used.

[0047] <Basal layer> The substrate 3 is a composite oxide of cerium and zinc. The content of cerium and zinc in the substrate 3, for example, is in a molar ratio of Ce:Zn = 9:1 to 1:1. That is, the content of cerium and zinc in the substrate 3, for example, is in a molar ratio of Ce:Zn between 9:1 and 1:1. The molar ratio of cerium and zinc in the substrate 3 is preferably in the range of Ce:Zn between 3:1 and 13:12, but can be in the range of 3:1 to 1:1, 7:3 to 3:2, 2:1 to 3:2, or 62:38 to 52:48. By maintaining the molar ratio of cerium and zinc in the substrate 3 within this range, the photocatalyst layer 4 formed directly above exhibits particularly good photocatalytic performance.

[0048] The substrate 3 is preferably composed of a composite oxide containing only cerium and zinc as metallic elements. That is, the content of the third element (described later) in the substrate 3 is preferably 0%. On the other hand, the substrate 3 may contain one or more other elements besides cerium, zinc, and oxygen. In this embodiment, the metallic elements contained in the substrate 3 other than cerium and zinc are referred to as the third element. The third element is, for example, gallium (Ga), aluminum (Al), or indium (In) added to improve the conductivity of zinc oxide. Thus, the third element is, for example, a group III element. The content of the third element in the substrate 3 other than cerium, zinc, and oxygen is preferably 10% or less. The composition of the substrate 3 corresponds to the composition of the composite target used in the manufacturing process described later. The elements contained in the substrate 3 can be determined by, for example, X-ray microanalyzer (XMA) or X-ray photoelectron spectroscopy (ESCA). By this determination, the molar ratio of the cerium and zinc contents can also be determined. In the base layer 3, the total amount of the third element, which is an element other than cerium and zinc, is, for example, 10% or less in terms of elemental ratio (molar ratio), preferably 5% or less, and more preferably 2% or less. Alternatively, the total amount of the third element can be 0, or it can be 0.5% or more, or 1% or more.

[0049] Regarding the resistance value of the target to which the substrate layer 3 is formed, when DC sputtering is performed during its manufacturing process, it is preferably 100 Ω·cm or less, more preferably 1 Ω·cm or less. In this embodiment, when DC sputtering is performed during its manufacturing process, the target material needs to be conductive, but the substrate layer 3 sputtered to form the film may not be conductive.

[0050] The thickness of the substrate layer 3 is, for example, 8 nm or more, preferably 10 nm or more. When the substrate 2 is a plastic film or the like, the surface may be uneven. Therefore, from the viewpoint of ensuring a sufficient amount of composite oxide in any part in the in-plane direction, 20 nm or more is more preferable. Furthermore, it can be said that sufficient crystallinity can be maintained as long as the thickness of the substrate layer 3 is 20 nm or more. From the viewpoint of suppressing the thermal load on the substrate 2 during manufacturing, and from the viewpoint that the crystallinity improvement required to enable the photocatalyst layer 4 to exhibit sufficient catalytic performance would become saturated when the substrate layer 3 is sufficiently thick, the thickness of the substrate layer 3 is preferably 100 nm or less, and the thickness of the substrate layer 3 can be 50 nm or less. The thickness of the substrate layer 3 can be measured, for example, by preparing a cross-sectional section of the sample using a microtomy method and measuring it using a transmission electron microscope.

[0051] <Photocatalyst layer> Photocatalyst layer 4 is the layer that functions as a photocatalyst. Photocatalyst layer 4 contains titanium oxide as a photocatalyst. More specifically, photocatalyst layer 4 is composed solely of titanium oxide, or of titanium oxide and at least one other element whose combined percentage of titanium is less than 10 atomic percent. Titanium oxide has a band gap in the ultraviolet region, and ultraviolet light is typically required for it to function as a photocatalyst; however, by adding nitrogen, it can be made responsive in visible light. The present invention can also produce a visible-light-responsive photocatalyst by adding nitrogen to titanium oxide in photocatalyst layer 4. Even in this case, the nitrogen content in photocatalyst layer 4 is less than 10 atomic percent relative to the total titanium oxide and titanium. Furthermore, to improve the electrical conductivity of the photocatalyst layer, a metallic element, such as niobium (Nb), may be included.

[0052] However, this configuration is only one example; it is sufficient to include titanium oxide in the photocatalyst layer 4 to achieve the effects of this embodiment. The elements contained in the photocatalyst layer 4 can be determined, for example, by X-ray microanalysis (XMA) or X-ray fluorescence analysis (XRF).

[0053] To ensure that photocatalyst layer 4 functions as a photocatalyst, its thickness is ideally at least 40 nm. While a thicker layer is preferable, it also slows down the deposition rate of titanium dioxide. From an industrial productivity perspective, a thickness of less than 200 nm is desirable. The thickness of photocatalyst layer 4 can be measured, for example, by preparing cross-sectional slices of the sample using a slicing method and then measuring them using a transmission electron microscope.

[0054] Furthermore, in the evaluation of photodecomposition performance, even when the thickness of titanium oxide was set to be greater than 200 nm, no further improvement in decomposition performance was observed.

[0055] The photocatalyst component involved in this embodiment is not limited to, for example... Figure 1 The component shown, consisting of a substrate 2, a base layer 3, and a photocatalyst layer 4, may also have other layers between the substrate 2 and the base layer 3, or on the photocatalyst layer 4.

[0056] For example, to make the photocatalyst component 1 conductive, one or more layers of conductive material may be laminated between the substrate 2 and the base layer 3. Examples of such conductive materials include indium tin oxide (ITO) or aluminum-zinc oxide (AZO). Alternatively, metallic materials may be laminated. Furthermore, to suppress oxidation caused by plasma during the deposition of the base layer 3 on the metallic material, different oxides may be laminated. Moreover, to ensure the adhesion between the substrate 2 and the base layer 3, an adhesion layer may be formed. Furthermore, if the substrate 2 is a transparent substrate, a transparent material may be deposited to improve the transparency of the photocatalyst component 1. Moreover, to smooth the surface of the substrate 2, a smoothing layer may be formed.

[0057] Alternatively, a transparent material can be formed on the surface of the photocatalyst layer 4. In particular, a hydrophilic retention layer comprising silicon oxide, or a composite oxide of silicon oxide and other metals, can be formed on the photocatalyst layer 4 to maintain the superhydrophilicity for a long time, even in the dark. Figure 2 It displays like this Figure 1 A cross-sectional view of the structure of the photocatalyst component involved in the modified example. Figure 2 In the photocatalyst component 1A shown, in Figure 1 The photocatalyst layer 4 of the photocatalyst component 1 shown further has a hydrophilic retention layer 5. When the hydrophilic retention layer 5 contains a composite oxide, the metal contained therein is, for example, Na or Al.

[0058] Furthermore, since titanium dioxide used in the photocatalyst layer is a high-refractive-index material, a layer of low-refractive-index material such as silicon dioxide can be stacked on top of the photocatalyst layer to reduce surface reflectivity. For example, it is also possible to... Figure 2 The hydrophilic retention layer 5 can be replaced by a low-refractive-index material layer. Alternatively, a low-refractive-index material layer can be formed between the photocatalyst layer 4 and the hydrophilic retention layer 5.

[0059] [Manufacturing method of photocatalyst components] Figure 1 and Figure 2 The photocatalyst components 1 and 1A shown can be manufactured, for example, by the method described below. One embodiment of the invention involves a method for manufacturing photocatalyst components 1 and 1A, comprising the following steps: a substrate layer forming step, in which a substrate layer 3 is formed on a substrate 2; and a photocatalyst layer forming step, in which a photocatalyst layer 4 comprising titanium oxide is formed on the substrate layer 3; in the substrate layer forming step, the substrate 2 is sputtered using a composite target containing a mixture of cerium oxide and zinc oxide. In the case of manufacturing the photocatalyst components by roll-to-roll, firstly, the substrate 2 wound on the unwinding roller is unwound.

[0060] (Base layer formation process) Next, a substrate layer 3 is formed on the unwound and properly treated substrate 2. The substrate layer 3 can be formed by any method. However, sputtering is effective from the viewpoint of stacking different types of materials used to form multilayer films. Various sputtering methods exist, including high-frequency (RF) sputtering, alternating current (AC) sputtering, and direct current (DC) sputtering. However, AC or DC sputtering is primarily used for high-speed, large-area film formation and for long strip film formation using continuous roll-up devices. While RF sputtering offers virtually no restrictions on target materials and can sputter various substances, it is not suitable for high-speed, large-area, long strip film formation, as mentioned above. AC or DC sputtering requires conductive target materials but is suitable for high-speed, large-area, long strip film formation. In the substrate layer formation process, for example, the chamber containing the substrate and composite target is set to an oxygen and inert gas atmosphere and the process is carried out under reduced pressure.

[0061] From the viewpoint of fabricating photocatalyst components that exhibit photocatalytic performance without high-temperature heat treatment, the substrate formation process is preferably performed by DC sputtering or AC sputtering as described above. When forming the substrate by DC sputtering or AC sputtering, a conductive composite target is used. In this embodiment, conductivity means, for example, a resistivity of 100 Ω·cm or less. The resistivity of the composite target is preferably 100 Ω·cm or less.

[0062] The composite target used in the substrate formation process is a composite target containing a mixture of cerium oxide and zinc oxide. The composition of the substrate 3 formed in the substrate formation process depends on the composition of the composite target. Therefore, by studying the correlation between the molar ratio of cerium and zinc in the composite target and the molar ratio of cerium and zinc in the substrate 3 in advance, a substrate with any composition can be manufactured. That is, in order to form a substrate with a molar ratio of cerium oxide and zinc oxide within a specified range as described above, the content of cerium and zinc in the composite target, for example, is in the range of Ce (cerium):Zn (zinc) = 9:1 to 1:1 in molar ratio. From the viewpoint of film formation by DC sputtering, it is preferably in the range of 3:1 to 3:2, more preferably in the range of 18:7 to 13:7, and can be in the range of 7:3 to 13:7. In addition, when forming a substrate 3 containing a third element other than cerium, zinc, and oxygen, the composite target also contains the corresponding third element. That is, the composite target may contain the same third element as the substrate 3. For example, the composite target may contain gallium, aluminum, indium, or other elements added as a third element to improve the conductivity of zinc oxide. If the target material does not contain this third element, the composition of the resulting substrate layer 3 is approximately the same as that of the target material. Regarding the target's resistance, the third element acts as a dopant for zinc oxide, reducing the resistance and accelerating the film formation rate of the composite target. However, since the rate of increase for zinc oxide is greater than that for cerium oxide, it is speculated that a compositional deviation will occur.

[0063] In the substrate formation process, for example, a pressure (reaching a vacuum level) of 10 -2 Sputtering can be performed under conditions of Pa. Alternatively, it can be performed at sputtering power, for example, 50 to 300 W.

[0064] For composite targets used in the substrate forming process, the aforementioned raw material powders can be weighed and mixed, and then manufactured by sintering, powder forming, or similar methods. When manufacturing a composite target by sintering after mixing the raw material powders, the heating temperature can be, for example, 1000~1400°C, and the heating time can be, for example, 2~6 hours. When manufacturing a composite target by powder forming, the raw material powders are contained in a die, and pressure is applied through an upper punch and a lower punch, thereby forming the composite target.

[0065] (Photocatalyst layer formation process) Next, a photocatalyst layer 4 is formed on the substrate layer 3. The method for preparing the photocatalyst layer 4 can be any method. However, from the viewpoint of stacking different types of materials used to form multilayer films, sputtering is effective.

[0066] When the photocatalyst layer 4 is formed on the substrate layer 3 by sputtering, the target can be any of titanium, titanium alloys, oxygen-deficient titanium oxide, and composite oxides containing oxygen-deficient titanium oxide. As a titanium alloy, titanium alloys containing niobium, copper, tungsten, etc., in addition to titanium can be used. Oxygen-deficient titanium oxide is a titanium oxide represented by the general formula TiOx, where x is a value less than 2.

[0067] In the photocatalyst layer formation process, for example, oxygen and argon are sealed in a chamber containing a substrate 2 on which a base layer 3 is formed and a target, and sputtering is performed under reduced pressure.

[0068] According to the manufacturing method and the photocatalyst component described in the above embodiments, a photocatalyst with high industrial productivity can be achieved by using a composite oxide of cerium and zinc in the substrate layer 3. For example, after the photocatalyst layer 4 is formed, it can function as a photocatalyst even without heating.

[0069] Cerium oxide and zirconium oxide are insulators. Therefore, high-frequency (RF) sputtering can be used for film formation, but conventional direct current (DC) sputtering is not feasible. RF sputtering is superior in that it can form films even on insulators, but its deposition rate is significantly slower than DC sputtering. Furthermore, because it uses the same frequency band as radio waves, leakage during high-power film formation can potentially cause severe radio interference in the surrounding environment, making it unsuitable for critical high-speed, large-area production in industrial applications. While roll-to-roll sputtering, which continuously deposits the substrate and photocatalyst layers onto the film, can be considered, methods such as vapor deposition are preferable, as both the substrate and photocatalyst layers are ideally formed using sputtering.

[0070] In the above embodiments, the composite target of cerium oxide and zinc oxide used when forming the composite oxide of cerium and zinc on the substrate layer exhibits conductivity not found in cerium oxide. Therefore, the substrate layer can be formed by DC sputtering even without RF sputtering.

[0071] Therefore, according to the above embodiments, a photocatalyst component that exhibits photocatalytic performance without high-temperature heat treatment and a method for manufacturing the photocatalyst component can be provided. This manufacturing method can use a substrate with low heat resistance, can increase the film formation rate, and can manufacture a photocatalyst component that exhibits photocatalytic performance. In addition, since the sputtering conditions do not change significantly due to the surface oxidation state of the target, stable production can be easily achieved.

[0072] Furthermore, it is believed that in the photocatalyst components 1 and 1A involved in the above embodiments, a lattice is formed through the substrate layer 3, and titanium oxide is grown in a manner consistent with the microcrystals, thereby exhibiting good photocatalytic performance.

[0073] Furthermore, it is believed that the formation of the substrate layer 3 is difficult because, in the sol-gel method, it is particularly difficult to uniformly form a thin film of about 100 nm on the film, thus making it difficult to form a photocatalyst layer 4 that can exert good photocatalytic performance without heating. Example

[0074] The present invention will be specifically described below with examples and comparative examples, but the present invention is not limited to the following examples.

[0075] [Example 1] First, as a preparatory step, cerium oxide (CeO2) powder and gallium-doped zinc oxide (GZO) powder were weighed and mixed at a molar ratio of 7:3, and then heated at 1400°C for 4 hours to fabricate a sintered substrate target (composite target). Furthermore, the resistivity of the fabricated composite target was measured using a LORESTA-GP MCP-T610 (Nittoseiko Analytech Co., Ltd.).

[0076] Next, alkali-free glass (NECEL OA-10G) was prepared as the substrate. After washing the substrate with a neutral detergent, it was ultrasonically washed in pure water for 10 minutes. Upon removal from the liquid, droplets were immediately removed with an air gun and the substrate was dried. The substrate was placed in a quaternary sputtering apparatus (Toei Scientific Industries Co., Ltd., model: SPV-420), and film formation was performed after venting. The sputtering apparatus used can employ both DC discharge and RF discharge via a switch. In Example 1, the substrate layer formation process was performed using DC discharge.

[0077] The following details the conditions for the substrate formation process.

[0078] (Splash conditions) • Target size: 2 inches in diameter, 4 mm in thickness • Distance between target and substrate: 80mm • Achieved vacuum level: <1×10 -3 Pa • Substrate temperature: room temperature Sputtering power: DC100W As described above, the substrate layer is deposited with a thickness of 50 nm by DC sputtering.

[0079] Subsequently, a 150 nm titanium oxide (TiO2) layer was deposited on top of this layer as a photocatalyst under the following film formation conditions, and then removed to prepare a sample. The photocatalyst layer was formed using oxygen-deficient titanium oxide (TiOx) as the target.

[0080] (Splash conditions) • Target size: 2 inches in diameter, 4 mm in thickness • Distance between target and substrate: 80mm • Achieved vacuum level: <1×10 -3 Pa • Substrate temperature: room temperature Sputtering power: RF 200W.

[0081] [Example 2] When fabricating the composite target used in the substrate formation process, the sample was prepared under the same conditions as in Example 1, except that cerium oxide (CeO2) powder and gallium-doped zinc oxide (GZO) powder were mixed at a molar ratio of 3:1.

[0082] [Example 3] When fabricating the composite target used in the substrate formation process, the sample was prepared under the same conditions as in Example 1, except that cerium oxide (CeO2) powder and gallium-doped zinc oxide (GZO) powder were mixed at a molar ratio of 3:2.

[0083] [Example 4] Except that the thickness of the substrate layer was set to 10 nm, the sample was prepared under the same conditions as in Example 1.

[0084] [Example 5] Except that the thickness of the photocatalyst layer was set to 40 nm, the sample was prepared under the same conditions as in Example 1.

[0085] [Example 6] When preparing the composite target used in the substrate formation process, the sample was prepared under the same conditions as in Example 1, except that cerium oxide (CeO2) powder and zinc oxide (ZnO) powder were mixed in a molar ratio of 7:3.

[0086] [Example 7] When fabricating the composite target used in the substrate formation process, the sample was prepared under the same conditions as in Example 1, except that cerium oxide (CeO2) powder and aluminum-doped zinc oxide (AZO) powder were mixed at a molar ratio of 7:3.

[0087] (Splash conditions) • Target size: 2 inches in diameter, 4 mm in thickness • Distance between target and substrate: 80mm • Achieved vacuum level: <1×10 -3 Pa • Substrate temperature: room temperature Sputtering power: RF 200W.

[0088] [Comparative Example 1] A sample was prepared by stacking 150 nm titanium oxide as a photocatalyst layer without forming a substrate layer. That is, in Comparative Example 1, TiO2 was directly formed as a photocatalyst layer on an alkali-free glass substrate. The TiO2 layer was formed by sputtering using the same target as in Example 1.

[0089] [Comparative Example 2] Except that the oxygen-deficient niobium pentoxide (NbOx) was used as the target for the substrate, the sample was prepared under the same conditions as in Example 1.

[0090] [Reference Example 1] As a composite target, cerium oxide (CeO2) powder and gallium-doped zinc oxide (GZO) powder were mixed at a molar ratio of 4:1 and sintered under the same conditions as in Example 1 to prepare a target for the substrate layer. Using this composite target, DC sputtering was attempted on an alkali-free glass substrate under the same conditions as in Example 1. It was found that the DC sputtering device could not discharge, and it was impossible to prepare a sample with a substrate layer formed on the substrate.

[0091] [evaluate] The photocatalytic performance of the prepared samples was evaluated. The evaluation of photocatalytic performance was carried out in accordance with JIS R1703-1 (Fine ceramics - Self-cleaning test method for photocatalyst materials - Part 1: Determination of water contact angle).

[0092] Specifically, under black light, the sample was placed in an environment where the irradiance was adjusted to 2.0 mW / cm². 2 Place the mixture in the desired location and let it stand for at least 24 hours. Afterward, apply a thin and even layer of oleic acid to each 100cm² area. 2 The value is 2.0 mg. The contact angle at this moment is taken as the initial contact angle.

[0093] After measuring the initial contact angle, under black light with an irradiance of 2.0 mW / cm², 2 The sample was left stationary for 24 hours, then removed and the contact angle was measured again to determine the contact angle after UV irradiation.

[0094] According to the photocatalytic performance evaluation criteria of the Photocatalyst Industry Association, a contact angle of less than 30° after UV irradiation can be said to have good photocatalytic performance.

[0095] In addition, the thickness of the substrate layer immediately after the substrate layer formation process was evaluated using a spectroscopic ellipsometer (M-2000 JA Woollam). In the ellipsometer, the amplitude ratio Ψ and phase difference Δ of p-polarized and s-polarized light were obtained for each wavelength. When these were fitted using an appropriate optical model, including the film thickness as a parameter, the film thickness could be obtained simultaneously with the optical constants. The film thickness was recorded based on the measurement results at the center of the substrate.

[0096] Table 1 summarizes the evaluation results regarding sample preparation conditions, the resistivity of the composite target used in substrate preparation, and the aforementioned photocatalytic performance. In Table 1, "OK" in the "Discharge" column of the substrate indicates that discharge can be performed under the same sputtering conditions as in Example 1 above using a DC sputtering device, while "NG" indicates that discharge is not possible. Samples marked "infinite" in the target resistance column are those exceeding the detection limit.

[0097] [Table 1] [Evaluation Results] <Examples 1-3> As shown in Table 1, discharge is possible if the molar ratio of CeO2 to GZO is in the range of 3:1 to 3:2. Furthermore, the prepared samples, after being coated with oleic acid and irradiated with UV light for 24 hours, exhibited a contact angle of less than 30°, demonstrating sufficient self-cleaning properties and thus good photocatalytic performance.

[0098] <Example 4> Compared to Example 1, even when the substrate layer is formed with a thickness of 10 nm, the contact angle is less than 30° after 24 hours of UV light irradiation following oleic acid coating, demonstrating sufficient self-cleaning performance and good photocatalytic performance.

[0099] <Example 5> Compared to Example 1, even when the titanium dioxide photocatalyst layer is formed with a thickness of 40 nm, the contact angle is less than 30° after 24 hours of UV light irradiation following oleic acid coating, demonstrating sufficient self-cleaning performance and indicating good photocatalytic performance.

[0100] <Example 6> Compared to Example 1, discharge was still possible even when zinc oxide (ZnO) was used instead of GZO to fabricate the composite target for the substrate. Furthermore, when the fabricated sample was coated with oleic acid and irradiated with UV light for 24 hours, the contact angle was less than 30°, demonstrating excellent self-cleaning properties and indicating good photocatalytic performance.

[0101] <Example 7> Compared to Example 1, discharge was still possible even when aluminum-doped zinc oxide (AZO) was used instead of GZO to fabricate the composite target for the substrate. Furthermore, when the fabricated sample was coated with oleic acid and irradiated with UV light for 24 hours, the contact angle was less than 30°, demonstrating excellent self-cleaning properties and indicating good photocatalytic performance.

[0102] <Comparative Examples 1 and 2> In the case where titanium oxide is formed directly on the substrate without forming a substrate layer (Comparative Example 1), or in the case where a metal oxide other than a composite oxide of cerium and zinc is formed as a substrate layer and titanium oxide is formed thereon (Comparative Example 2), it was confirmed that the contact angle after irradiation with UV light for 24 hours after oleic acid coating could not reach below 30°, no self-cleaning performance was observed, and no photocatalytic performance was observed. Thus, the titanium oxide layer formed without a substrate layer, or the layer formed directly on top of the substrate layer 3 with a layer other than a composite oxide of cerium and zinc as the substrate layer, does not have photocatalytic performance.

[0103] [Composition of the basal layer] To investigate the composition of the substrate layer, substrate layers were formed using their respective targets under the same conditions as in the Examples, Reference Examples, and Comparative Examples. The substrates were then removed without forming a photocatalyst layer, and the elemental ratio of Ce to Zn was evaluated by X-ray photoelectrochemical spectrometry (ESA). The results are shown in Table 1.

[0104] [Evaluation of Crystallinity] In Example 1, an XRD-based evaluation was performed on the sample immediately after the substrate layer was formed. XRD was performed using an X'PertPRO MPD (manufactured by PANalytical), with Cuα as the X-ray source, and at an incident angle of 1°. The XRD results are shown below. Figure 3 middle. Figure 3 The XRD patterns of zinc oxide, cerium oxide, and zirconium oxide are also shown for comparison.

[0105] The XRD spectra of zinc oxide, cerium oxide and zirconium oxide are shown, with a film thickness of 50 nm formed by RF sputtering on the same alkali-free glass substrate as in Example 1.

[0106] like Figure 3 As shown, a cerium oxide peak can be identified near the zirconia peak. Its narrow half-width suggests the presence of crystallites larger than zirconia crystallites. This indicates that cerium oxide is more readily crystallizable. In contrast, the film formed from a composite target of cerium oxide and gallium-doped zinc oxide shows a similar XRD pattern to cerium oxide, suggesting that the crystallite size is also similar to that of cerium oxide. The XRD pattern of zinc oxide is also shown in the figure, and based on the comparison of peak positions, the crystals identified in the cerium oxide-gallium-doped zinc oxide combination are considered to be cerium oxide crystallites.

[0107] The formation of a substrate layer composed of a composite oxide of cerium and zinc is considered a major factor in the photocatalytic performance of titanium oxide formed on the substrate layer, and is believed to be partly heteroepitaxial growth. It is thought that titanium oxide crystallizes in a manner consistent with the crystallite formed by the substrate layer. Therefore, it is believed that if the substrate layer undergoes significant crystallization with a thin film thickness, the titanium oxide in the subsequent photocatalyst layer will also promote crystallization.

[0108] Symbol Explanation 1, 1A: Photocatalyst component, 2: Substrate, 3: Base layer, 4: Photocatalyst layer, 5: Hydrophilic retention layer.

Claims

1. A photocatalyst component, comprising a substrate, a base layer, and a photocatalyst layer formed in contact with the base layer, characterized in that, The base layer is a composite oxide of cerium and zinc. The photocatalyst layer contains titanium oxide.

2. The photocatalyst component according to claim 1, wherein, The molar ratio of cerium oxide to zinc oxide contained in the base layer is in the range of 3:1 to 1:

1.

3. The photocatalyst component according to claim 1, characterized in that, The elemental ratio of the photocatalyst layer, excluding titanium oxide, is less than 10%.

4. The photocatalyst component according to claim 1, characterized in that, The thickness of the substrate layer is 10 nm or more.

5. The photocatalyst component according to claim 1, characterized in that, The thickness of the photocatalyst layer is 40 nm or more.

6. The photocatalyst component according to claim 1, wherein, The photocatalyst layer also has a hydrophilic retention layer. The hydrophilic retaining layer comprises silicon oxide, or a composite oxide of silicon and other metals.

7. The photocatalyst component according to claim 1, characterized in that, The substrate is a transparent substrate.

8. The photocatalyst component according to claim 1, characterized in that, The substrate is a polymer film.

9. The photocatalyst component according to claim 1, characterized in that, The substrate layer also contains group III elements, and the total amount of group III elements contained in the substrate layer is less than 10% in molar ratio.

10. A method for manufacturing a photocatalyst component, characterized in that, It has the following processes: The substrate formation process involves forming a substrate layer on a substrate, and The photocatalyst layer formation process involves forming a photocatalyst layer containing titanium oxide on the substrate layer; In the substrate formation process, the substrate is sputtered using a composite target consisting of a mixture of cerium oxide and zinc oxide.

11. The method for manufacturing the photocatalyst component according to claim 10, characterized in that, The mixing ratio of cerium oxide and zinc oxide in the composite target is in the range of 3:1 to 3:2 in molar ratio.

12. The method for manufacturing the photocatalyst component according to claim 10, characterized in that, The composite target is conductive.

13. The method for manufacturing the photocatalyst component according to claim 10, characterized in that, In the substrate layer formation process, DC discharge sputtering or AC discharge sputtering is performed.

14. The method for manufacturing the photocatalyst component according to claim 10, characterized in that, In the photocatalyst layer formation process, the photocatalyst layer is formed by sputtering a target comprising any one of titanium, titanium alloy, and oxygen-deficient titanium oxide.

15. The method for manufacturing the photocatalyst component according to claim 10, characterized in that, The substrate is a polymer film.

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