Photocatalyst element, method and device for preparing the same

[Technical field] [0001] The present invention relates to a photocatalyst, a method for producing a photocatalyst, and an apparatus for producing a photocatalyst, and in particular, a photocatalyst having a photocatalytic action that promotes the production of active species by irradiation with light, a method for producing a photocatalyst, and a method for producing a photocatalyst. Regarding the device. [Background technology] [0002] In recent years, a photocatalytic thin body using titanium dioxide has attracted attention. A "photocatalyst" is a substance that has semiconducting physical properties and is excited when irradiated with light having an energy larger than the band gap energy of its conduction electron band and valence band, and generates electron-hole pairs. That is. [0003] Titanium dioxide having an anatase-type crystal structure is photoexcited when irradiated with light having a wavelength of 387 nm or less, and simultaneously causes a decomposition reaction based on a redox reaction and a hydrophilization reaction different from the decomposition reaction (activity). At present, titanium oxide, tin oxide and zinc oxide are known as metal oxides that cause these two reactions at the same time, and strontium titanate and ferric oxide are known as metal oxides that cause only the decomposition reaction. , Tungsten trioxide is known as a metal oxide that causes only a hydrophilization reaction. [0004] Therefore, various members and product groups coated with a photocatalyst have been proposed because self-cleaning action, deodorizing action, antibacterial action and the like can be obtained by utilizing these actions. As a method for producing such a photocatalyst, various methods such as a binder method, a sol-gel method, and a vacuum vapor deposition method have been proposed. [0005] The binder method is a method in which fine particles of titanium oxide are dispersed in an adhesive binder, applied on a predetermined substrate, and then heat-dried. However, according to this method, there is a problem that the photocatalytic action is easily impaired because the fine particle titanium oxide is buried between the binders. [0006] The sol-gel method is a method of obtaining a photocatalyst film by applying a liquid agent such as titanium chelate or titanium alkoxide containing titanium on a predetermined substrate, drying it, and then firing it at a high temperature of 500 ° C. or higher. .. However, since a high-temperature firing step of 500 ° C. or higher is required, there is a problem that the materials that can be used as a substrate are extremely limited in terms of heat resistance. [0007] For these forming methods, a forming method using a vacuum vapor deposition method or a sputtering method has been proposed. For example, Japanese Patent No. 2901550 discloses a photocatalyst in which a laminated structure of titanium oxide and silicon oxide is formed by a vacuum vapor deposition method. Further, Japanese Patent Application Laid-Open No. 2000-126613 discloses a method of depositing silicon oxide by using a reactive sputtering method. [0008] On the other hand, the present inventor formed a titanium oxide film under various conditions by a sputtering method and evaluated various physical properties thereof. As a result, the titanium oxide film formed under different conditions from the conventional one is unique. It was found to have the structure of. Then, it was found that the photocatalytic properties of these titanium oxide films are remarkably improved as compared with the conventional ones as described above. [Disclosure of Invention] [Problems to be Solved by the Invention] [0009] The present invention has been made based on such knowledge, and an object of the present invention is to obtain a photocatalyst, a method for producing a photocatalyst, and a photocatalyst, which have excellent photocatalytic properties, can improve productivity, and at the same time have good dark place maintenance characteristics. To provide manufacturing equipment. [Means for solving problems] [0010] The photocatalyst of the present invention is a photocatalyst having a photocatalyst film made of a compound of titanium and oxygen, and the photocatalyst film is an aggregate of a large number of grains, and gaps between the large number of grains are provided on the surface thereof. Is formed in a porous shape with<u style="single">The size of the grains and the size of the gaps are the photocatalytic membranes.</u>The value obtained by dividing the arithmetic mean roughness Ra of the surface by the film thickness is 0.02 or more.<u style="single">In the range that becomes</u>Yes, and its film thickness is 40 nanometers or more and 100 nanometers or less. The intensity ratio of the (101) diffraction peak of the titanium oxide anatase structure to the (215) diffraction peak of the titanium oxide anatase structure when measured by removing background noise using copper (Cu) Kα1 intrinsic X-rays. It is characterized by being 100 or less. [0011] Here, the arithmetic mean roughness Ra of the surface of the photocatalyst film can be assumed to be 1.3 nm or more. [0012] In addition, the intensity of the (101) diffraction peak of the titanium oxide anatase structure relative to the (112) diffraction peak of the titanium oxide anatase structure when measured by removing background noise using copper (Cu) Kα1 intrinsic X-rays. The ratio can be 5 or less. [0013] Further, the film thickness of the photocatalyst film can be 40 nanometers or more and 80 nanometers or less. [0014] Further, a buffer layer made of silicon oxide provided under the photocatalyst film can be further provided. [0015] Further, the refractive index of the photocatalyst film can be 2.7 or less. [0016] Further, it is possible that a silicon oxide film is provided. [0017] In this case, the thickness of the silicon oxide film can be 3 nm or more and 7 nm or less. [0018] On the other hand, the method for producing a photocatalyst of the present invention is a method for producing a photocatalyst having a photocatalyst film composed of a compound of titanium and oxygen, and is 3 pascals or more and 5 pascals or less containing 10% or more and 30% or less of oxygen. When the film formation rate R (nanometer / sec) is 0.2 nanometer / sec or more and 0.6 nanometer / sec or less, and the temperature of the surface on which the photocatalyst film is deposited is T (° C). , The following formula R 2.36 exp (-410 (1 / T)) Is satisfied<u style="single">Heated above room temperature</u>It is characterized in that a porous photocatalyst film is deposited so as to have a film thickness of 40 nanometers or more and 100 nanometers or less by sputtering a target containing titanium at a temperature. [0019] Here, the sputtering can be carried out by the DC sputtering method. [0020] Alternatively, the film thickness of the photocatalyst film can be 40 nanometers or more and 80 nanometers or less. [0021] [0021] In addition, a buffer layer made of silicon oxide can be deposited prior to the deposition of the photocatalyst film. [0022] Further, the step of depositing silicon oxide on the photocatalyst film can be further provided. [0023] On the other hand, the method for producing a photocatalyst of the present invention is a first apparatus for producing a porous photocatalyst having a photocatalyst film made of a compound of titanium and oxygen, which can maintain an atmosphere depressurized from the atmosphere. A film forming chamber, a power source for applying a voltage to a target provided in the first film forming chamber, a heating means for heating the substrate, and a reaction gas containing oxygen are introduced into the first film forming chamber. A photocatalyst film made of a compound of titanium and oxygen is sputtered on the substrate in the first film forming chamber, which comprises a gas introduction mechanism, a heating means, and a controller capable of controlling the gas introduction mechanism. In forming the film, the controller controls the gas introduction mechanism so that the oxygen content in the first film forming chamber is 10% or more and 30% or less and the pressure is 3 pascals or more and 5 pascals or less. Moreover, when the film formation rate R of the photocatalyst film is 0.2 nanometers / second or more and 0.6 nanometers / second or less, the film formation rate R (nanometers / second)<u style="single">Heated above room temperature</u>The temperature T (° C) on the surface of the substrate is expressed by the following equation. R 2.36 exp (-410 (1 / T)) The heating means is controlled so as to satisfy the above, and the film thickness of the photocatalyst film is 40 nanometers or more and 100 nanometers or less. [0024] The power supply may be a DC power supply. [0025] Here, the power supply can be a DC power supply. [0026] Further, a heating chamber having the heating means and a transfer mechanism for transferring the substrate from the heating chamber to the first film forming chamber are further provided, and after heating the substrate in the heating chamber, the transfer mechanism is provided. The substrate may be conveyed to the first film forming chamber to carry out the sputtering of the photocatalyst film. [0027] Further, a second film forming chamber capable of forming a film of silicon oxide may be further provided, and silicon oxide may be formed on the substrate prior to the sputtering of the photocatalyst film. [0028] Further, a third film forming chamber capable of forming a film of silicon oxide may be further provided, and silicon oxide may be formed on the photocatalyst film after the sputtering of the photocatalyst film. [Best mode for carrying out the invention] [0029] This will be described in accordance with the accompanying drawings in order to describe the present invention in more detail. [0030] As a result of an original trial production study, the present inventor has found that when a photocatalyst material such as titanium oxide is formed into a porous form, its activity is dramatically improved. Such a porous photocatalytic material can be obtained by using a reactive sputtering method to significantly increase the film formation rate compared to the conventional method, and at the same time, adjust the film formation parameters such as the sputtering pressure and the substrate temperature within an appropriate range. It has unique physical properties that are different from the conventional ones. [0031] Furthermore, by coating such a porous photocatalytic material with silicon oxide having a predetermined film thickness, the surface can be effectively protected without substantially impairing the photocatalytic action, and at the same time, an excellent dark place. We have found that maintenance characteristics can be obtained. [0032] Hereinafter, embodiments of the present invention will be described in detail with reference to specific examples. [0033] (First Embodiment) First, as the first embodiment of the present invention, a porous photocatalyst membrane and a method for producing the same will be described. [0034] FIG. 1 is a schematic diagram illustrating the configuration of a photocatalyst according to an embodiment of the present invention. That is, the photocatalyst body of the present invention has a photocatalyst film 10 coated in a thin film on a predetermined substrate 100. Titanium oxide (TiOx) is used as the material of the photocatalyst film 10, and in the present invention, the photocatalyst film 10 made of this titanium oxide is formed in a porous state. [0035] FIG. 2 is a schematic view illustrating the state of the surface of the photocatalyst film 10. That is, the figure shows the surface of a photocatalyst film in which titanium oxide is formed on a substrate to a film thickness of 135 nm. A large number of grains G having a size of 10 nm or less are observed on the surface, but these grains are not densely packed, and a gap S is formed between the grains. [0036] FIG. 3 is a schematic view illustrating the cross-sectional structure of the photocatalyst 10. As shown in the figure, gaps S are formed between the innumerable grains G, and a film structure having a very large surface area is obtained. Such a porous photocatalytic film 10 exhibits a significantly excellent photocatalytic action as compared with the conventional one. Hereinafter, the photocatalytic membrane of the present invention will be described in more detail with reference to the manufacturing method thereof. [0037] The photocatalytic membrane of the present invention can be produced by a reactive sputtering method. FIG. 4 is a schematic diagram showing the main configuration of the sputtering apparatus used in the experiment. That is, a target 102 made of metallic titanium is provided inside the vacuum chamber 101 in connection with the cathode 103. On the other hand, on the anode 104 side, the substrate 100 on which the photocatalyst film is deposited is installed. [0038] At the time of film formation, first, the inside of the chamber 101 is evacuated by the vacuum exhaust pump 106, and argon (Ar) and oxygen (O) are evacuated from the gas supply source 107.₂) Introduce the discharge gas. Then, an electric field is applied between the anode 104 and the cathode 103 by the power supply 110 to start the plasma discharge 108. Then, the surface of the target 102 is sputtered, and metallic titanium and oxygen are bonded on the substrate 100 to form the titanium oxide film 10. Here, the electric power input from the power source 110 may be DC (direct current) electric power or RF (radio frequency) electric power. [0039] In the specific examples described below, unless otherwise specified, a photocatalyst film was formed by a DC sputtering method using a DC power supply. Further, during sputtering, the substrate 100 was placed in a floating state from the chamber 101 (ground potential). [0040] As will be described in detail later, in such a sputtering apparatus, a photocatalytic film having a predetermined film quality can be obtained by adjusting the input power for plasma discharge, the pressure and composition of the atmospheric gas during sputtering, the substrate temperature, and the like. .. The temperature of the substrate 100 was confirmed by attaching a thermolabel 109 on the substrate 100. [0041] FIG. 5 is a graph illustrating a temperature change of the substrate 100 during sputtering. Here, for the film forming conditions A to C, the temperature change when the substrate temperature starts sputtering from room temperature is shown. Each condition is as follows. [0042] Conditions Input DC power Accumulation rate Total pressure Oxygen partial pressure A 2kW 18nm / min 1Pa 30% B 2kW 22nm / min 3.5Pa 30% C 3kW 36nm / min 5Pa 30% As can be seen from FIG. 5, when sputtering is started with the substrate temperature set to room temperature, the temperature of the substrate 100 tends to rise with time due to heat radiation from the sputtering source and reach the saturation temperature according to the input power. Can be seen. The saturation temperature mainly depends on the input power, and when the power is 2 kW, it is about 230 ° C, and when the power is 3 kW, it is about 300 ° C. [0043] However, the deposition of the thin film may end before reaching this saturation temperature. For example, the deposition rate under condition C is 36 nm / min, and the time required to deposit titanium oxide with a film thickness of 135 nm is 3 minutes and 45 seconds. Therefore, the maximum substrate temperature when deposition is started from room temperature is It is about 230 ° C. On the other hand, before sputtering, the substrate may be heated in advance for degassing treatment or the like, and sputtering may be started from a state higher than room temperature. In this case, since the temperature is approached to the saturation temperature from the heated state, the temperature may drop toward the saturation temperature during deposition when the temperature is heated to a high temperature in advance. [0044] 6 and 7 are electron micrographs of the surface of the photocatalyst film obtained by such reactive sputtering. That is, (a) to (d) in these figures are surface photographs of samples A to D of the titanium oxide film, respectively. Fig. 6 and Fig. 7 are photographs obtained at different magnifications for the same sample, and the length of the bar at the lower right of each photograph is 300 nm in Fig. 6 and 119 nm in Fig. 7. Corresponds to. [0045] Further, the sample A was formed under the above-mentioned condition A, the sample B was formed under the above-mentioned condition B, and the samples C and D were formed under the above-mentioned condition C. In addition, in each sample, SiO was placed on the silicon wafer used as the substrate 100.₂Titanium oxide as a photocatalyst film was deposited through the buffer layer, and the film thickness of titanium oxide 10 was 135 nm for samples A to C and 50 nm for samples D. Looking at FIGS. 6 and 7, it can be seen that the surface of sample A has a structure in which fine grains are densely packed, and the grains are densely packed with each other. [0046] On the other hand, on the surface of Samples B to D, innumerable grains having a diameter of about several tens of nm or less are observed, but it can be seen that the grains are not dense and have gaps. That is, it can be seen that it is formed in a porous form. [0047] Here, it is considered that the reason why the grains of sample D are smaller than those of samples B and C is largely due to the difference in film thickness. The photocatalytic action of the photocatalytic film 10 thus obtained was evaluated by a "wax (WAX) decomposition hydrophilic test". This test is a test for evaluating both the "decomposition action" and the "hydrophilic action" of the photocatalytic action of the photocatalytic membrane 10. The "decomposition action" is an action in which an organic material such as wax is decomposed by a hydroxyl radical generated on the surface of a photocatalyst film, an active oxygen species such as superoxide, or the like. Further, the "hydrophilic action" is an action of improving the hydrophilicity on the surface of the photocatalyst film. The contents of the wax decomposition hydrophilic test carried out by the present inventor are as follows. [0048] (1) The surface of the photocatalyst membrane 10 is washed with a neutral detergent to make it hydrophilic. (2) Apply solid wax to the surface of the photocatalyst film 10 and dry it at room temperature for 1 hour. The solid wax used here is a brand name "Hero" manufactured by Shuraster Co., Ltd., and its main component is carnauba wax. (3) After cleaning the surface of the photocatalyst membrane 10 with a neutral detergent, it is dried at 50 ° C. (4) While irradiating with black light (BLB), the contact angle of water droplets formed on the surface of the photocatalyst film 10 is measured periodically. The wax formed on the surface of the photocatalytic film 10 is decomposed by the photocatalytic action of irradiation with black light. When the wax remains on the surface, the contact angle of the water droplet is large, but when the wax is decomposed, the contact angle of the water droplet becomes small. [0049] Therefore, it can be said that the photocatalytic action is more active as the black light is decomposed even if the irradiation intensity is small, or the contact angle of the water droplet after irradiation for a predetermined time is small. [0050] FIG. 8 is a graph showing an example of the results of the wax decomposition hydrophilic test of the photocatalyst film 10 according to the present invention. Here, the data of the sample D described above with respect to FIGS. 5 to 7 is shown. In addition, the irradiation intensity of black light is 500 μW / cm.², 50 μW / cm², 10 μW / cm²The data was plotted. Here, 500 μW / cm²The irradiation intensity is close to the conditions of the wax decomposition hydrophilic test that is usually performed, but it is 50 μW / cm.²The irradiation intensity is a very weak condition, 10 μW / cm.²The irradiation intensity is an ultra-weak condition. [0051] From Fig. 8, the contact angle before irradiating the black light is about 83 degrees, but the irradiation intensity is 500 μW / cm.²And 50 μW / cm²In the case of, the contact angle drops sharply at the same time as the irradiation of black light, and it becomes about 9 degrees after 1 hour, about 5 degrees after 2 hours, and about 3 degrees after 10 hours, and the wax is rapidly decomposed. You can see that there is. [0052] Also noteworthy is the irradiation intensity of 10 μW / cm.²The point is that the photocatalytic action is also obtained by irradiation with ultra-weak light. That is, although the rate of decrease of the contact angle is gradual, it decreases to about 56 degrees after 3 hours, about 22 degrees after 6 hours, and about 4 degrees after 12 hours. As will be described in detail later, it should be noted that the photocatalytic action is obtained even in such ultra-weak light as compared with the conventional photocatalytic film. [0053] The present inventor formed and evaluated photocatalytic films of various film types by variously adjusting the film forming conditions in the reactive sputtering method. Hereinafter, the relationship between the physical characteristics of the photocatalyst film and the film formation parameters will be sequentially described. First, we focused on the "surface roughness" of the photocatalytic membrane as one of the parameters that define the "porousness" of the photocatalytic membrane. [0054] FIG. 9 is a graph showing the relationship between the surface roughness of the photocatalyst film and the contact angle measured by AFM (Atomic Force Microscopy). That is, the horizontal axis in the figure represents the surface roughness Ra of the photocatalyst film made of titanium oxide. The vertical axis of Fig. 9 shows the black light (irradiation intensity 500 μW / cm) in the same wax decomposition hydrophilic test as described above.²) Represents the contact angle of water droplets after irradiation for 1 hour. The four samples A to D plotted in FIG. 9 are the same as the samples A to D described above with respect to FIGS. 5 to 8. [0055] From FIG. 9, it can be seen that in the case of a photocatalytic film (sample A) having a surface roughness Ra of about 0.9 nm, the contact angle is extremely high at about 83 degrees even when irradiated with black light for 1 hour. On the other hand, when the surface roughness Ra is 1.3 nm (sample D), the contact angle under the same conditions drops dramatically to 9 degrees, and when the surface roughness Ra is 3.5 nm (sample B), the contact angle is reduced. When the surface roughness Ra is 3.65 nm (Sample C), the contact angle is reduced to about 8 degrees. [0056] That is, it can be seen that when the surface roughness Ra becomes larger than 1 nm, the photocatalytic action sharply improves. Further, paying attention to the relationship between the film forming condition, the film thickness, and the surface roughness, the following relationship can be obtained. [0057] Sample deposition rate Total pressure Film thickness Surface roughness A 18nm / min 1Pa 135nm 0.9nm B 22nm / min 3.5Pa 135nm 3.5nm C 36nm / min 5Pa 135nm 3.65nm D 36nm / min 5Pa 50nm 1.3nm In other words, it can be seen that the surface roughness Ra increases mainly by increasing the "deposition rate" and "total pressure". From the surface photographs of FIGS. 6 and 7, it can be seen that the larger the surface roughness Ra, the larger the "gap" between the "grains". [0058] [0058] As will be described in detail later with reference to Examples, the deposition rate in Samples B to D is about 10 times or more faster than that in the example of forming the photocatalyst film by the conventional reactive sputtering method.<u style="single"></u>That is, in this way, a porous photocatalyst film can be obtained by adjusting parameters such as total pressure and substrate temperature after significantly increasing the deposition rate as compared with the conventional case. The film thicknesses of Samples B to D are in the range of normal film thicknesses for photocatalyst films. Therefore, if the surface roughness Ra is larger than 1.3 nm, it is considered that a porous thin film having excellent photocatalytic action can be obtained. [0059] By the way, the surface roughness Ra of the sample D is smaller than that of the sample C under the same film forming conditions because the film thickness is different. Therefore, for the data in Fig. 9, we attempted to plot the surface roughness Ra normalized by the film thickness. [0060] FIG. 10 is a graph in which the contact angle is plotted against the value Ra / T obtained by dividing the surface roughness Ra of samples A to D by each film thickness. [0061] As can be seen from the figure, the Ra / T of sample A was about 0.0062, and the Ra / T of samples B to D was about 0.026 to 0.027, and they were divided into two groups. In the case of the former (Sample A), the contact angle after irradiation with black light for 1 hour is as large as about 83 degrees, but the contact angle of the latter (Samples B to D) is dramatically reduced as 7 to 9 degrees. You can see that. [0062] For example, here, if the range in which the contact angle after irradiation with black light for 1 hour is 30 degrees or less is defined as the range of the present invention, the ratio of surface roughness to the film thickness, that is, Ra / T may be 0.02 or more. I understand. Further, similarly, if the range where the contact angle is 10 degrees or less is defined as the range of the present invention, it can be seen that the ratio of the surface roughness to the film thickness, that is, Ra / T should be 0.025 or more. [0063] That is, in the present invention, the deposition rate is significantly increased as compared with the conventional case, and the density of the photocatalyst film formed is reduced by adjusting the total pressure, the substrate temperature, etc. A porous photocatalyst film having gaps formed in the film is formed. Then, it was found that the photocatalytic properties of such a porous photocatalyst film are dramatically improved when the surface roughness exceeds a predetermined value. [0064] The reason why the photocatalytic action is activated by increasing the porosity in this way is that the surface area of the photocatalytic film increases when the porosity is increased, and there are defects near the surface of the grains that effectively act on the photocatalytic action. It is presumed that this is because it is introduced moderately. [0065] Further, according to the present invention, since the film is formed at a significantly faster deposition rate as compared with the conventional one, there is a great merit in that the film forming time can be significantly shortened. For example, in the present invention, the deposition time, which conventionally required 100 minutes, that is, 1 hour and 40 minutes, can be reduced to 10 minutes or less when forming a photocatalyst film having a film thickness of 200 nm. As a result, the manufacturing throughput of the photocatalytic membrane can be dramatically improved and the cost can be reduced. [0066] Furthermore, according to the present invention, since the film can be formed at a substrate temperature lower than that of the conventional one, the requirement for heat resistance of the substrate is significantly relaxed. That is, various materials such as organic materials having low heat resistance, which could not be used in the past, can be used as the substrate, and the range of application of the photocatalyst membrane can be greatly expanded. [0067] Hereinafter, various characteristics of the photocatalyst film of the present invention will be described in relation to the film formation parameters as appropriate. FIG. 11 is a graph showing the X-ray diffraction pattern of the photocatalyst film of sample C described above. Looking at the figure, the background level is quite high, TiO₂It can be seen that the diffraction peak of is quite weak and broad. That is, it is presumed that the crystals are considerably disordered, and the crystal grains are also quite fine and contain a large number of defects. [0068] FIG. 12 is a diffraction pattern after data processing is performed on the diffraction pattern of FIG. 11 to remove background noise. The diffraction peak shown here is a TiO having an "anathase structure".₂It can be seen that it corresponds to the diffraction peak of the above, and even higher-order reflection is obtained. FIG. 13 is a graph in which the X-ray diffraction pattern of the photocatalyst film of Sample A described above was measured in the same manner and the background noise was removed. [0069] Looking at Fig. 13, TiO with an anatase structure is also seen.₂However, when compared with Fig. 12 (Sample C), it can be seen that the height balance of the appearing reflection peaks is different. Specifically, for example, looking at the balance of the intensities of other diffraction peaks with respect to the (101) diffraction peak of anatase appearing near a diffraction angle of 25 degrees, sample A is compared with sample C (Fig. 12). In (Fig. 13), the relative intensity of the main peak is quite high. The intensity ratios of (101) diffraction peaks to other major diffraction peak intensities are summarized below. [0070] Intensity ratio of diffraction peak Sample A Sample C (101) / (112) 10.4 3.8 (101) / (200) 7.5 3.7 (101) / (105) 6.3 2.2 (101) / (204) 10.7 3.9 (101) / (215)> 300 9.6 Looking at the above intensity ratios, it can be seen that in sample A, the intensity ratio of the (101) diffraction peak is overwhelmingly high, and a thin film structure oriented in the [110] direction is obtained. In comparison, in sample C, it can be quantitatively grasped that the intensity ratio of the (101) diffraction peak is very low. That is, it is presumed that in sample C, an aggregate of a large number of crystal grains having such a low orientation and a more disordered orientation relationship is formed. [0071] That is, even from the viewpoint of X-ray diffraction data, in the present invention, a porous thin film containing a large number of defects is formed by depositing the photocatalyst film at a higher speed, higher pressure, and lower temperature than before. I understand. It is considered that the photocatalytic action was dramatically improved due to such a unique porous structure. [0072] Considering the results of the wax decomposition hydrophilization test (Figs. 9 and 10), the photocatalytic film of the present invention has an intensity ratio of (101) diffraction peak to (112) diffraction peak of about 5 or less, or (105). It is considered desirable that the intensity ratio of the (101) diffraction peak to the (101) diffraction peak is approximately 4 or less, or the intensity ratio of the (101) diffraction peak to the (215) diffraction peak is approximately 100 or less. [0073] Next, the dependence of the film quality on the total pressure during sputtering will be described. That is, the DC input power at the time of sputtering was fixed at 2 kW and the oxygen partial pressure was fixed at 30%, a titanium oxide film was deposited, and its refractive index and density ratio were measured. The results are shown below. [0074] Total pressure index of refraction N Density ratio 1Pa 2.73 1 2Pa 2.69 0.94 3Pa 2.63 0.88 5Pa 2.3 0.829 The above refractive index was measured by an ellipsometer using a helium-neon (He-Ne) laser. The density ratio was evaluated by the effective medium approximation method of the spectroscopic ellipsometer. FIG. 14 is a graph in which these refractive indexes and density ratios are plotted against the total pressure. [0075] As can be seen from this graph, when the total pressure at the time of film formation is increased, both the refractive index and the density tend to gradually decrease. This is considered to correspond to the tendency that the film quality of the porous photocatalyst film tends to become coarser as the total pressure increases. [0076] Separately, the absolute values of the composition and density of the photocatalytic film of sample B (filmed at a total pressure of 3.5 Pa) were measured by Rutherford backscatter analysis (RBS). The measurement conditions are as follows.<u style="single">。</u> Energy resolution 24keV Incident energy 2.0MeV Incident angle 0 degrees Incident ion 4He⁺ Incident beam diameter 1.0 mm Sample current 10nA As a result of RBS measurement, the following results were obtained for sample B. [0077] O / Ti 2.02 Density 4.45g / cm³ Here, the measurement accuracy of the O / Ti value is about plus or minus 5%, and the measurement accuracy of the density is also about plus or minus 5%. [0078] In the present invention, it is considered that excellent photocatalytic properties can be obtained as described above by forming the photocatalyst film which is porous, that is, has a lower density than that of sample B. That is, from the above measurement results, in the present invention, the density of the photocatalytic membrane is 4.45 g / cm.³From the following, it can be seen that a porous photocatalytic film having an excellent photocatalytic action can be obtained. [0079] Next, the relationship between the film forming conditions at the time of sputtering and the characteristics of the obtained photocatalyst film will be described. The present inventor formed a photocatalyst film under various conditions of reactive sputtering performed using the DC sputtering apparatus described above with respect to FIG. 4, and investigated these characteristics. [0080] [0080] FIG. 15 is a list summarizing the film forming conditions of the photocatalyst film of the example carried out by the present inventor by the DC sputtering method. In addition, FIG. 16 is a list summarizing the film forming conditions of the photocatalyst film of the comparative example carried out by the present inventor by the DC sputtering method. [0081] That is, here, "oxygen partial pressure (%)", "total pressure (Pa)", film formation rate (nm / sec), "temperature (° C)" and "film thickness (nm)" at the time of sputtering. Was used as a parameter, and the relationship with the characteristics of the obtained photocatalyst film was investigated. [0082] Here, the temperature at the time of sputtering is an average temperature during sputtering after heating the substrate in the preliminary chamber in advance and then transporting the substrate to the sputtering chamber. Argon (Ar) was used as the carrier gas during sputtering. [0083] As an evaluation method for the photocatalytic membrane, a wax decomposition hydrophilic test was conducted and the illuminance was 500 μW / cm.²Those with a contact angle of water droplets of 10 degrees or less after irradiation with the black light for 1 hour were regarded as "pass", and those with a contact angle of more than 10 degrees were regarded as "fail". [0084] First, the effect of the oxygen partial pressure during sputtering on the photocatalyst film will be described. FIG. 17 is a graph showing the relationship between the oxygen partial pressure during sputtering and the contact angle of the obtained photocatalyst film. That is, the horizontal axis of the figure represents the oxygen partial pressure in reactive sputtering, and the vertical axis represents black light (500 μm / cm) in the wax decomposition hydrophilic test.²) Represents the contact angle of water droplets after irradiation for 1 hour. [0085] Here, all the samples plotted in Fig. 17 were deposited with a total pressure of 5 Pa during sputtering, a DC input power of 2 kW, a film formation rate of 0.3 nm / sec, a temperature of 330 ° C, and a film thickness of 50 nm. .. [0086] From FIG. 17, it can be seen that the contact angle is very low and an extremely excellent photocatalytic action is obtained in the range where the oxygen partial pressure during sputtering is 10% or more and 30% or less. On the other hand, if the oxygen partial pressure is too low or too high, the contact angle increases. This is because if the oxygen partial pressure during sputtering is too low or too high, it deviates from the proper oxygen composition range in the obtained photocatalyst film, or the bonding state between the metal element and oxygen becomes unstable. Is considered to be. [0087] Further, as a result of the observation by the present inventor, the photocatalyst film formed under the condition that the oxygen partial pressure was 30% or less was not transparent but was in an opaque state having a metallic color. This suggests that the oxygen content of the obtained photocatalytic membrane is insufficient because the oxygen partial pressure is too low. [0088] On the other hand, when the oxygen partial pressure during sputtering is in the range of 10% or more and 30% or less, the obtained photocatalyst film becomes transparent and good photocatalytic characteristics can be obtained. This is because the composition range of oxygen in the photocatalyst film becomes appropriate, the bonding state between the metal element and oxygen becomes stable, and the lifetime of the electron-hole pair excited in the film by light irradiation becomes long, and the photocatalyst It is considered that this is because the action is activated. [0089] Next, the effect of the total pressure during sputtering on the photocatalyst film will be described. FIG. 18 is a graph showing the relationship between the total pressure during sputtering and the contact angle of the obtained photocatalyst film. That is, the horizontal axis in the figure represents the total pressure in reactive sputtering, and the vertical axis is black light (500 μm / cm) in the wax decomposition hydrophilic test.²) Represents the contact angle of water droplets after irradiation for 1 hour. [0090] Here, all the samples plotted in FIG. 18 were deposited with an oxygen partial pressure of 30% during sputtering, a film formation rate of 0.3 to 0.6 nm / sec, a temperature of 330 ° C, and a film thickness of 50 nm. [0091] From Fig. 18, the contact angle of water droplets is about 14 degrees when the total pressure during sputtering is 2 Pa, but when the total pressure is 3 Pa, the contact angle drops to about 4 degrees, and good decomposition hydrophilic characteristics can be obtained. You can see that. It is presumed that this is because if the total pressure is too low, the actual amount of oxygen supplied will decrease, and the film quality of the photocatalyst film will not be "porous" as illustrated in Fig. 2 or Fig. 3. To. [0092] On the other hand, when the total pressure is 5 Pa, the contact angle is as low as about 4 degrees, but when the total pressure rises to 6 Pa, the contact angle rises sharply to about 86 degrees. It is presumed that this is because if the total pressure is too high, the film quality of the photocatalyst film and the bonding state between the metal element and oxygen change. From the above results, it can be seen that good photocatalytic characteristics can be obtained when the total pressure during sputtering is in the range of 3 Pa or more and 5 Pa or less. [0093] Next, the effect of the film formation rate during sputtering on the photocatalyst film will be described. FIG. 19 is a graph showing the relationship between the film formation rate during sputtering and the contact angle of the obtained photocatalyst film. That is, the horizontal axis in the figure represents the film formation rate of the photocatalytic film in reactive sputtering, and the vertical axis represents black light (500 μm / cm) in the wax decomposition hydrophilic test.²) Represents the contact angle of water droplets after irradiation for 1 hour. [0094] Here, the sample plotted in FIG. 19 is deposited with the oxygen partial pressure at the time of sputtering set to 30%, the total pressure set to 3 to 5 Pa, the temperature set to about 330 ° C, and the film thickness set to 40 to 100 nm. [0095] Looking at FIG. 19, it can be seen that when the film formation rate is in the range of 0.2 to 0.6 nm / sec, the contact angle of the water droplet is 10 degrees or less, and good photocatalytic action can be obtained. Then, when the film formation rate increases to 0.7 nm / sec, the contact angle increases to about 17 degrees. It is presumed that this is because if the film formation rate is too high, the film quality of the photocatalyst film and the bonding state between the metal element and oxygen deteriorate. From this result, it can be seen that the film formation rate is preferably at least 0.2 nm / sec or more and 0.6 nm / sec or less. [0096] On the other hand, the film formation rate has a great influence on the "throughput" at the time of manufacturing. For example, when depositing a 50 nm photocatalyst film, if the film formation rate is 0.2 nm / sec, the time required for film formation is 250 seconds, that is, 4 minutes or more. On the other hand, for example, when the film formation rate is 0.4 nm / sec, the time required for film formation is reduced to half of that, that is, 125 seconds (about 2 minutes). As described above, from the viewpoint of production, it is desirable that the film forming speed is high, and it is desirable that the film forming speed is approximately 0.4 nm / sec or more. [0097] Next, the effect of the temperature during sputtering on the photocatalyst film will be described. The present inventor paid attention to the relationship between "temperature" and "deposition rate" at the time of sputtering. Then, from the data shown as a list in FIGS. 15 and 16, "pass", that is, "temperature T" at the time of sputtering for the contact angle of water droplets after irradiation with black light for 1 hour to be 10 degrees or less. The following approximate formula was derived for the relationship between "" and "deposition rate R". R 2.36 exp (-410 (1 / T)) (1) That is, when the photocatalyst film is sputtered under the condition that the "temperature T" is within the range of the above formula with respect to the film formation rate R, the photocatalyst property of "pass" is obtained. The relational expression of (1) above can be qualitatively explained for the following reasons. [0098] That is, in the case of reactive sputtering, the metal element sputtered from the target and the oxygen molecule supplied from the gas atmosphere fly to the deposited surface on the substrate and are adsorbed. After migrating the sedimentary surface, these elements combine and are anchored at a given lattice site. Part of the energy required for these metal elements and oxygen to migrate on the deposited surface is supplied by substrate heating. [0099] When the film formation rate is high, the supply rate of metal elements and oxygen flying to the deposited surface increases, so they tend to be fixed to unstable sites in an incompletely bonded state before being sufficiently migrated on the surface. Will be higher. Therefore, by raising the substrate temperature and promoting migration on the surface, it becomes necessary to fix the site to a stable site in an appropriate bonded state. Therefore, when the film formation rate R is high, it is desirable to raise the substrate temperature T. [0100] In the present invention, a photocatalytic film having a good photocatalytic action can be obtained by setting the temperature so as to satisfy the range of the relational expression (1) described above. [0101] Next, the effect of the film thickness on the photocatalyst film will be described. FIG. 20 is a graph showing the relationship between the film thickness of the photocatalyst film formed by sputtering and the contact angle. That is, the horizontal axis in the figure represents the film thickness of the photocatalyst film, and the vertical axis is black light (500 μm / cm) in the wax decomposition hydrophilic test.²) Represents the contact angle of water droplets after irradiation for 1 hour. [0102] Here, the sample plotted in Fig. 20 was deposited with an oxygen partial pressure of 30%, a total pressure of 3 to 5 Pa, a temperature of about 330 ° C, and a film formation rate of 0.34 to 0.4 nm / sec. Is. Looking at FIG. 20, when the film thickness of the photocatalyst film is 20 nm, the contact angle is very high at about 65 degrees, and when the film thickness is 30 nm, the contact angle drops to about 18 degrees. Then, when the film thickness increases to 40 nm, the contact angle decreases to about 6 degrees, and it can be seen that good photocatalytic action can be obtained. On the other hand, regarding the upper limit of the film thickness, in the evaluated range, good photocatalytic action was obtained up to 170 nm. In other words, it was found that the film thickness should be 40 nm or more. [0103] The present inventor conducted a "wet decomposition performance test" in order to further investigate the relationship between the "decomposition action" and the film thickness among the "decomposition action" and the "hydrophilic action" of the photocatalytic film. As a dye to be decomposed, methylene blue (C₁₆H₁₈N₃S · Cl) was used. Methylene blue is a blue organic dye that is hardly decomposed by ultraviolet rays and is irreversibly decomposed by the decomposition activity of the photocatalyst to become colorless. Therefore, methylene blue can be used for evaluation of the decomposability of the photocatalyst film. [0104] FIG. 21 is a flowchart showing the procedure of the wet decomposition performance test. First, as shown in step S1, the test piece of the titanium oxide film is washed with purified water, a surfactant, and if necessary, ultrasonic cleaning. Furthermore, on the test piece after cleaning, the intensity is 1 mW / cm at a wavelength of 360 nm with a black light fluorescent lamp.²By irradiating the above ultraviolet rays for 24 hours or more, stains such as organic substances remaining on the surface even after cleaning are decomposed by photocatalytic action. [0105] Next, as shown in step S2, methylene blue is saturated and adsorbed on the surface of the test piece. That is, in order to cancel the change in the spectrum due to the adsorption of methylene blue on the surface of the test piece, methylene blue is adsorbed on the surface in advance up to the saturation amount. The concentration of methylene blue used as the adsorbent was 0.02 mmol / l. The new adsorbent is brought into contact with the test piece for 12 hours, and the adsorption process is repeated until the absorbance of the adsorbent does not decrease. After saturated adsorption of methylene blue on the surface of the test piece in this way, the initial absorption spectrum is then measured in step S3. At this time, the concentration of the methylene blue test solution was 0.01 mmol / l. [0106] Next, in step S4, the spectrum after light irradiation is measured. That is, 1 mW / cm with the methylene blue test solution in the cell and in contact with the surface of the test piece.²Irradiate with ultraviolet rays for 20 minutes. Immediately after irradiation with light, the absorption spectrum of the methylene blue test solution is measured. Then, the measured test solution is promptly returned to the cell, and in a state of being in contact with the surface of the test piece, it is irradiated with ultraviolet rays again for 20 minutes. [0107] In this way, every 20 minutes, the absorption spectrum of the methylene blue test solution after irradiation with ultraviolet rays is measured, and the measurement is performed 9 times until the total irradiation time reaches 3 hours. The higher the decomposition characteristics of the photocatalyst film, the faster the methylene blue is decomposed and decolorized. That is, the absorption characteristics are lowered. [0108] FIG. 22 is a graph illustrating the results of a wet decomposition performance test. That is, the film thickness of the photocatalyst film in the figure and the vertical axis represent the decomposition activity index (nanomol / liter / minute) converted from the absorbance. As can be seen from the figure, the decomposition activity index of the photocatalyst film increases as the film thickness increases, and becomes almost saturated when the film thickness reaches 100 nm. That is, from the viewpoint of "decomposition action", it can be seen that the decomposition characteristics of the photocatalyst film obtained by the sputtering method are almost saturated in the range of 100 nm or more. [0109] In the wax decomposition hydrophilicity test shown in FIG. 20, good photocatalytic action can be obtained even when the film thickness of the photocatalyst film is 100 nm or less. Therefore, in this film thickness range, the photocatalytic film has "hydrophilization". It is presumed that "characteristics" are working. [0110] On the other hand, as a result of the observation by the present inventor, when the thickness of the photocatalyst film exceeds approximately 80 nm, a double image due to light reflection may be observed by observation with the naked eye. Therefore, from this viewpoint, it is desirable that the film thickness of the photocatalyst film is 40 nm or more and 80 nm or less. From the viewpoint of production throughput, it is desirable to reduce the film thickness of the photocatalyst film. [0111] Next, the action of the "buffer layer" provided between the substrate and the photocatalyst film will be described. FIG. 23 is a schematic view illustrating the cross-sectional structure of the photocatalyst body provided with the buffer layer. [0112] That is, the buffer layer 50 is provided on the predetermined substrate 100, and the photocatalyst film 10 is formed on the buffer layer 50. As the material of the buffer layer 50, for example, silicon oxide can be used. [0113] By providing such a buffer layer 50, it is possible to prevent impurities from being mixed into the photocatalyst film 10 from the substrate 100. Further, it is possible to modify the surface state of the substrate 100 and control the initial stage of deposition of the photocatalyst film 10 to a more ideal state. [0114] For example, when soda lime glass or the like is used as the substrate 100, if an alkaline element such as sodium (Na) contained in the glass diffuses into the photocatalyst film 10, the photocatalyst characteristics may deteriorate. In such a case, by providing the buffer layer 50 made of silicon oxide or the like, it is possible to prevent the diffusion of impurities and prevent the deterioration of the photocatalytic characteristics. [0115] Further, even when the surface of the substrate 100 has micro-concavities and convexities, the irregularities on the surface are alleviated by providing the buffer layer 50 having an appropriate thickness, and the initial stage of deposition of the photocatalyst film 10 is in a more ideal state. Can be approached to. [0116] The present inventor investigated the effect of the buffer layer 50 by using soda lime glass as the substrate 100, silicon oxide as the buffer layer 50, and titanium oxide as the photocatalyst film 10. [0117] FIG. 24 is a graph showing the results of the wax decomposition hydrophilic test. That is, the horizontal axis in the figure is black light (500 μm / cm).²) Represents the irradiation time, and the vertical axis represents the contact angle of water droplets. The figure shows the results of the photocatalyst with the film thickness of the buffer layer 50 set to 0 nm, 20 nm, 50 nm, 100 nm, and 260 nm, respectively. For all samples, the photocatalyst film 10 was deposited by the reactive sputtering method, and the oxygen partial pressure during sputtering was 30%, the total pressure was 5 Pa, the temperature was about 330 ° C, and the film formation rate was 0.5 nm / sec. , The film thickness was set to 50 nm. [0118] From FIG. 24, when the film thickness of the buffer layer 50 is zero to 20 nm, the contact angle of the water droplet after irradiation with black light for 1 hour is 50 degrees or more, whereas the film thickness of the buffer layer 50 is 50 degrees or more. When is set to 50 nm, it can be seen that the contact angle after 1 hour irradiation decreases to about 14 degrees. Furthermore, if the film thickness of the buffer layer 50 is 100 nm, the contact angle at 1 o'clock or after irradiation will be 10 degrees, and if the buffer layer 50 at 260 nm is provided, the contact angle after 1 hour irradiation will be about 4 degrees. Drops to. As described above, it was found that the photocatalytic characteristics are improved when the buffer layer 50 is provided with a certain thickness. [0119] (Second embodiment) Next, as a second embodiment of the present invention, a photocatalyst body in which a coating layer such as silicon oxide is laminated on a photocatalytic film having a photocatalytic action such as titanium oxide will be described. FIG. 25 is a schematic view showing a cross-sectional structure of the photocatalyst of the second embodiment. [0120] That is, the photocatalyst body of the second embodiment has a configuration in which the photocatalyst film 10 is provided on the substrate 100, and the coating layer 20 is further laminated on the photocatalyst film 10. Here, the photocatalyst film 10 is a porous layer similar to the photocatalyst film 10 such as titanium oxide described above with respect to FIGS. 1 to 24. Further, as the coating layer 20, for example, an oxide such as silicon oxide can be used. [0121] The coating layer 20 has an action of appropriately protecting the surface of the photocatalytic film 10 and maintaining hydrophilicity as long as the photocatalytic action is not hindered. That is, in the state of being irradiated with light, as described above with respect to FIGS. 1 to 24, the porous photocatalytic film 10 exerts an active photocatalytic action and decomposes deposits to obtain high hydrophilicity. maintain. However, the photocatalytic action of the photocatalytic membrane 10 cannot be obtained in a state where the light is not irradiated. On the other hand, by maintaining the hydrophilicity of the coating layer 20, the effect of preventing the adhesion of contaminants to the surface thereof is maintained. Therefore, if the film thickness of the coating layer 20 is too thick, the photocatalytic action of the photocatalytic film 10 is hindered, and conversely, if the coating layer 20 is too thin, the hydrophilicity is insufficient. [0122] FIG. 26 is a graph illustrating the results of a wax decomposition hydrophilic test of a photocatalyst film having a laminated structure of FIG. 25. Here, soda lime glass was used as the substrate 100. Further, as the photocatalyst film 10, a titanium oxide film prepared under the same conditions as the above-mentioned sample D with respect to the first embodiment was used. On the other hand, silicon oxide was used as the coating layer 20 deposited on the coating layer 20. The deposition of the coating layer 20 consists of argon (Ar) and oxygen (O).₂) By the reactive sputtering method using the mixed gas, the photocatalyst film 10 was continuously deposited. The DC input power was 300 W, the total pressure was 3.5 Pa, and the oxygen partial pressure was 30%. [0123] In FIG. 26, data are plotted for five types of samples in which the coating layer 20 has a film thickness of 0 nm, 3 nm, 5 nm, 7 nm, and 14 nm. From the figure, it can be seen that the contact angle in the initial state before the black light irradiation is lower in all the samples provided with the coating layer 20 than in the samples without the coating layer 20. That is, it can be seen that the coating layer 20 improves the hydrophilicity of the surface. [0124] On the other hand, looking at the contact angle after black light irradiation, when the film thickness of the coating layer 20 is 3 nm to 7 nm, a sample without a coating layer (SiO).₂Wax decomposition characteristics similar to those of the sample with a film thickness of 0 nm) are observed, and it can be seen that the photocatalytic action is hardly inhibited. The irradiation intensity of the black light used here is 50 μm / cm.²Therefore, considering that the strength is lower than that used in the wax decomposition hydrophilic test generally performed as described above, it is said that the coating layer in the above film thickness range does not substantially inhibit the photocatalytic action. I can say. [0125] However, when the film thickness of the silicon oxide layer 20 is 14 nm, the amount of decrease in the contact angle is small, and it can be seen that the photocatalytic action is inhibited. That is, from the results of FIG. 26, it can be said that it is desirable that the layer thickness of the coating layer 20 is 3 nm or more and 7 nm or less. [0126] FIGS. 27 to 29 are graphs illustrating the results of the wax decomposition hydrophilic test of the photocatalyst film of the second embodiment. As the photocatalyst film used here, the same titanium oxide film as that of sample D described above with respect to the first embodiment was used as the photocatalyst film 10, and a silicon oxide film having a thickness of 7 nm was used as the coating layer 20. In addition, as Comparative Example 34, the data of the sample without the coating layer 20 is also shown. [0127] Fig. 27 shows the irradiation intensity of black light of 500 μm / cm.²In this irradiation intensity, it can be seen that the photocatalyst film of the second embodiment provided with the coating layer 20 shows superior hydrophilicity before and after irradiation. [0128] In addition, Fig. 28 shows the irradiation intensity of black light of 50 μm / cm.²In this irradiation intensity, the photocatalyst film of the second embodiment is more hydrophilic before irradiation, and after irradiation, it shows almost the same hydrophilicity as that of Comparative Example 34. You can see that. [0129] On the other hand, Fig. 29 shows the irradiation intensity of black light of 10 μm / cm.²It is the data in the case of ultra-weak light, and it can be seen that the photocatalyst film of the second embodiment is more hydrophilic in this irradiation intensity up to about 7 hours after irradiation. It is considered that this is because the hydrophilicity of the coating layer 20 is superior to the photocatalytic action of the photocatalytic film 10 under ultra-weak light. [0130] As described above, according to the second embodiment, it is possible to maintain excellent hydrophilicity before light irradiation or when the light intensity is low. [0131] FIG. 30 is a graph showing a change in the contact angle when the photocatalyst film of the second embodiment is maintained in a dark place. That is, here, it is the result of measuring the change in the contact angle when the contact angle is kept in a dark place by blocking the light after first irradiating the black light to make the contact angle almost zero. [0132] From the figure, when the coating layer 20 is not provided, the contact angle increases in a relatively short time due to the blocking of light, and increases to about 45 degrees after 8 days. On the other hand, in the sample of the second embodiment provided with the coating layer 20, the increase in the contact angle is gradual, and it can be seen that the increase is suppressed as the film thickness of the coating layer 20 becomes thicker. That is, it was confirmed that the thicker the coating layer 20, the better the hydrophilicity maintaining property in a dark place. [0133] As described above, according to the second embodiment, by providing the coating layer 20 in a predetermined film thickness range on the photocatalytic film 10 such as titanium oxide, the photocatalytic action is not substantially impaired and is excellent. It is possible to obtain the characteristics of maintaining a dark place. As a result, it is possible to maintain a high level of hydrophilicity on the surface even when the light is irradiated or when the light is weak or blocked. [0134] Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples. (Example 32) First, as Example 32 of the present invention, a photocatalyst according to the first embodiment of the present invention was prepared and compared with a comparative example prepared by a conventional method. FIG. 31 is a graph showing the photocatalytic action of the photocatalysts of Example 32 and Comparative Example. That is, the figure shows the result of the wax decomposition hydrophilic test, where the irradiation intensity of black light is 500 μW / cm.²And said. [0135] The photocatalyst body of the present invention represented here is the same as that of Sample D described above as the photocatalyst film of the first embodiment of the present invention. In addition, Comparative Example 35 and Comparative Example 36 were prototyped by the reactive sputtering method, and their characteristics were also plotted. Each film formation condition is summarized below. [0136] Sample D Comparative Example 35 Comparative Example 36 Film formation method DC sputtering RF sputtering RF sputtering Input power 3kW 220W 220W Sedimentation rate 36nm / min 3.5nm / min 3.5nm / min Total pressure 5Pa 2.7Pa 2.7Pa Oxygen partial pressure 30% 11% 50% Substrate temperature 280 ° C or less 300 ° C 400 ° C Since the sample D was heat degassed once in the preliminary chamber before the sputtering deposition, the initial temperature at the time of deposition was higher than room temperature. However, the sedimentation was carried out under the condition that the maximum temperature during deposition did not exceed 280 ° C. In addition, the background pressure of the vacuum chamber before film formation was 8 × 10 for all of the above samples.^-4Exhaust until it was below Pa. [0137] From FIG. 31, the contact angle before irradiation with black light was 75 degrees in the present invention (Sample D), 85 degrees in Comparative Example 35, and 90 degrees in Comparative Example 36. When this is irradiated with black light, the contact angle of the photocatalyst film of the present invention drops sharply, and after 1 hour, it drops to about 9 degrees. On the other hand, the rate of decrease of Comparative Examples 35 and 36 was slow, and the contact angles of Comparative Examples 35 and 36 after 1 hour remained at 36 degrees and 51 degrees, respectively. As described above, it was confirmed that the photocatalytic film of the present invention exhibits a remarkable photocatalytic action as compared with the photocatalytic film obtained by the conventional sputtering method. [0138] In addition, the surfaces of Comparative Examples 35 and 36 have a structure in which grains that are about 10 times larger than those shown in FIGS. 6 (a) and 7 (a) are densely assembled, and are porous. There wasn't. [0139] Next, the X-ray diffraction pattern was measured for these. FIG. 32 is a graph showing the X-ray diffraction pattern of sample D. Further, FIG. 33 is a graph showing the X-ray diffraction pattern of Comparative Example 35. The diffraction peaks appearing in these are TiO of the "anathase structure".₂Corresponds to the diffraction peak of. [0140] Comparing Fig. 32 (Sample D) and Fig. 33 (Comparative Example 35), it is found that the intensity of the diffraction peaks with respect to the background level and the balance between the peaks are significantly different even though the measurements were made under the same conditions. I understand. That is, in Comparative Example 35 (Fig. 33), the intensity of the diffraction peak is extremely high with respect to the background intensity, and a sharp and strong diffraction peak appears. Moreover, almost no diffraction peaks appear except for the low-order (101) and (200) diffraction peaks. [0141] On the other hand, in sample C (FIG. 32) of the present invention, the intensity of the diffraction peak with respect to the background level is generally low, and a weak and broad diffraction peak is obtained. Moreover, a large number of higher-order diffraction peaks appear. [0142] Examining the balance of the intensities of the other diffraction peaks with respect to the anatase (101) diffraction peak, in the case of Comparative Example 35 (Fig. 33), the intensities of the (101) and (200) diffraction peaks were overwhelmingly high, and these were low-order. It can be seen that a structure strongly oriented in the plane orientation of is obtained. [0143] On the other hand, in the case of sample D (Fig. 32) of the present invention, the intensity balance of the (101) diffraction peak is considerably low, and many high-order diffraction peaks are observed. That is, in the sample D of the present invention, it is presumed that a large number of fine crystal streams having a low orientation and a disordered plane orientation are aggregated. [0144] The intensity ratios of (101) diffraction peaks to other major diffraction peak intensities are summarized below. Intensity ratio of diffraction peak Sample D Comparative Example 35 (101) / (112) 3.7> 1000 (101) / (105) 6.3 ~ 270 Looking at the above intensity ratios, it can be seen that in Comparative Example 35, the intensity ratio of the (101) diffraction peak is overwhelmingly high, and a strongly oriented thin film structure is obtained. Compared to this , in sample D, it can be quantitatively grasped that the intensity ratio of the (101) diffraction peak is very low. [0145] That is, from these results, the photocatalyst film of Comparative Example 35 has considerably good crystallinity, whereas in the sample D of the present invention, it is an aggregate of fine particles which are porous and contain many crystal defects. You can see that it is. [0146] Comparing the film forming conditions of the present invention and the comparative example, it can be seen that the deposition rate of the present invention is 10 times or more faster, the total pressure is high, and the substrate temperature is low. Conversely, in these comparative examples, the film is formed at a higher temperature, a lower pressure, and a low speed. In general, when a thin film is deposited at such a high temperature and low speed, its crystallinity tends to be good and the film quality tends to be dense. This is in agreement with the surface structure and the results of X-ray diffraction. On the other hand, in the present invention, the deposition rate is significantly faster than before, and the photocatalytic film is formed into a unique porous state by forming a film at a higher pressure and a lower temperature, and the photocatalytic action is remarkable. I was able to improve. [0147] (Example 33) Next, as Example 33 of the present invention, the photocatalytic action of the photocatalyst of the second embodiment of the present invention and the conventional photocatalyst under weak light was compared and examined. [0148] First, as the photocatalyst of the present invention, the one shown in FIG. 25 was prototyped. Here, soda lime glass was used as the substrate 100, and a silicon oxide buffer layer having a thickness of 50 nm was deposited, and then the photocatalyst film 10 and the coating layer 20 were continuously deposited. As the photocatalyst film 10, the same photocatalyst film 10 as the sample B described above with respect to the first embodiment was deposited. Further, as the coating layer 20, silicon oxide having a film thickness of 7 nm was deposited by reactive sputtering. [0149] On the other hand, as Comparative Example 37, a titanium oxide film having a light film thickness of 100 nm was deposited on the same substrate and buffer layer by a vacuum deposition method, and a silicon oxide film having a film thickness of 15 nm was further deposited on the same substrate by a vacuum deposition method. did. Ti as an evaporation source when depositing titanium oxide₂O₃Partial pressure of oxygen in the vacuum chamber 1.3 × 10^-2The electron beam was vapor-deposited while being introduced so as to be Pa. The deposition rate of titanium oxide was 18 nm / min, and the substrate temperature was 200 ° C. [0150] In addition, when silicon oxide is deposited, SiO is used as an evaporation source.₂Partial pressure of oxygen in the vacuum chamber 2.6 × 10^-2The electron beam was vapor-deposited while being introduced so as to be Pa. The deposition rate of silicon oxide was 30 nm / min, and the substrate temperature was 200 ° C. [0151] FIG. 34 is a graph showing a comparison of the photocatalytic action of the photocatalysts of Example 33 and Comparative Example 37. That is, the figure shows the result of the wax decomposition hydrophilic test, where the irradiation intensity of black light is 50 μW / cm.²It was a faint light. Looking at FIG. 34, it can be seen that the contact angle in the initial state is the same at about 17.4 degrees in both the present invention and the comparative example, but the rate of decrease after irradiation with black light is different. That is, in the photocatalyst of the present invention, the contact angle after irradiation for 1 hour is reduced to about 4 degrees, whereas in the case of Comparative Example 37, it is only about 11 degrees. [0152] That is, the photocatalyst of the present invention is 50 μW / cm.²It can be seen that even in the presence of such weak light, the photocatalytic action is higher than that of the conventional photocatalyst having a laminated structure. It is considered that this is a combination of the excellent photocatalytic action of the photocatalytic film 10 and the effect of setting the layer thickness of the coating layer 20 in a suitable range. [0153] (Example 34) Next, as Example 34 of the present invention, the photocatalyst of the second embodiment of the present invention and the conventional photocatalyst were compared and examined for their photocatalytic action under ultra-weak light. In Example 34 as well, as the photocatalyst of the present invention, the one shown in FIG. 25 was prototyped. That is, soda lime glass was used as the substrate 100, and the silicon oxide buffer layer was deposited with a thickness of 50 nm, and the photocatalyst film 10 and the coating layer 20 were continuously deposited. The photocatalyst film 10 was deposited with the same sample D as described above for the first embodiment. Further, as the coating layer 20, silicon oxide having a film thickness of 7 nm was deposited by reactive sputtering. On the other hand, as Comparative Example 38, the same sample as Comparative Example 37 described above was prepared for Example 33. [0154] FIG. 35 is a graph showing a comparison of the photocatalytic action of the photocatalysts of Example 34 and Comparative Example 38. That is, the figure shows the result of the wax decomposition hydrophilic test, where the irradiation intensity of black light is 10 μW / cm.²The light was very weak. Looking at FIG. 35, it can be seen that in the sample of Comparative Example 38, the contact angle hardly decreased even when irradiated with black light, and only slightly increased and decreased. This is 10 μW / cm²It means that almost no photocatalytic action occurs with respect to the ultra-weak light. [0155] On the other hand, in the sample of the present invention, it can be seen that the contact angle is surely lowered by the irradiation with black light, and the photocatalytic action is generated. That is, the photocatalyst of the present invention is 10 μW / cm.²It can be seen that the photocatalytic action is obtained even in the presence of the ultra-weak light, and the photocatalytic action is more active than that of the conventional photocatalyst having a laminated structure. It is considered that this is also a combination of the excellent photocatalytic action of the photocatalytic film 10 and the effect of setting the layer thickness of the coating layer 20 in a suitable range. [0156] (Example 35) Next, as Example 35 of the present invention, a manufacturing apparatus suitable for manufacturing the photocatalyst of the present invention will be described. FIG. 36 is a conceptual diagram illustrating the main configuration of the photocatalyst manufacturing apparatus of the present invention. That is, the figure (a) shows the plane structure, and the figure (b) shows the cross-sectional structure. [0157] In the manufacturing apparatus of this specific example, SiO is placed above the main chamber 200 capable of vacuum exhaust.₂Film formation chamber 210, heating chamber 220, TiO₂Film formation chamber 230, TiO₂Film formation chamber 240, SiO₂The film forming chamber 250 and the load lock portion 260 have a structure provided in this order. [0158] A transfer table 400 is provided in the main chamber 200, and the substrate 100 can be rotationally transferred to the bottom of each chamber while being placed on the transfer table 400. As shown in FIG. 36 (b), when the substrate 100 is conveyed to the bottom of each chamber by the transfer table 400, it is appropriately pushed up by the elevating mechanism 600. For example, as shown in Fig. 36 (b), TiO₂When the substrate 100 is transported to the bottom of the film forming chamber 230, it is lifted together with the substrate holder 420 by the elevating mechanism 600 and transferred into the space of the film forming chamber 230. [0159] In the case of the manufacturing apparatus of this specific example, the substrate 100 introduced into the chamber from the load lock portion 260 is sequentially conveyed by the transfer table 400, and SiO₂The buffer layer 50 is formed in the film forming chamber 210, heated to a predetermined temperature in the heating chamber 220, and TiO.₂TiO with a predetermined film thickness in the film forming chambers 230 and 240₂A film (photocatalyst film) 10 is formed, and SiO₂SiO in the film formation chamber 250₂The coating layer 20 is formed, and after that, it is taken out from the load lock portion 260. In the heating chamber 220, the substrate 100 can be heated to a predetermined temperature by lamp heating using, for example, a quartz lamp. [0160] Figure 37 shows TiO₂It is a conceptual diagram which illustrates the main part structure of the film forming chamber 230 (or 240). A titanium (Ti) target 102 is provided in the film forming chamber, and reaction gases such as argon and oxygen can be introduced via mass flow controllers (MFC) 600 and 610, respectively. [0161] Further, the substrate holder 420 does not completely seal the film forming chamber 230, and an opening (not shown) is appropriately provided between them. That is, the film forming chamber 230 is exhausted by the vacuum exhaust system connected to the main chamber 200 through this opening. [0162] Then, reactive DC sputtering is performed by introducing oxygen-containing reaction gases such as argon and oxygen into the film forming chamber 230 via the MFC 600 and 610, and applying a voltage to the target by the DC power supply 510. can do. [0163] Then, in the 35th embodiment, the operation of the heating mechanism such as the lamp provided in the heating chamber 220 can be controlled by the controller 500. Specifically, as described above with respect to FIGS. 15 and 16, control is performed so that the following relational expression is satisfied as a condition between the film formation rate R and the substrate temperature T. Will be done. R 2.36 exp (-410 (1 / T)) (1) For example, when manufacturing a photocatalyst, a predetermined film formation rate is input to the controller 500. Then, the controller 500 calculates the temperature range for satisfying the above equation (1) at this film forming rate, and preliminarily sets the heating conditions in the heating chamber so that this temperature range is maintained at the time of film forming. Determine and perform preheating. [0164] Further, as described above with respect to FIGS. 15 and 16, in order to produce an excellent photocatalyst, the total pressure should be in the range of 3 pascals to 5 pascals, and the oxygen partial pressure should be 10% or more and 30% or less. Is desirable. Therefore, the controller 500 may be configured to control the MFC 600 and 610 so that these conditions are also satisfied at the same time. [0165] In addition, the film formation speed is mainly determined by the input power from the DC power supply 510, but it also depends on the total pressure and oxygen partial pressure, so the controller 500 considers this point as well. The 610 may be controlled. [0166] Further, since the change in the substrate temperature during film formation differs depending on the input power from the DC power supply 510, the controller 500 controls the heating mechanism provided in the heating chamber 220 in consideration of this point as appropriate. It is possible to do. [0167] Furthermore, the controller 500 may also control the DC power supply 510. That is, the power applied to the target from the DC power supply 510 may be controlled so that a predetermined film forming speed can be obtained. [0168] Further, the film formation temperature may be determined first instead of determining and inputting the film formation rate first. That is, the film formation temperature may be specified in advance, and the controller 500 may control the DC power supply 510 by calculating the film formation rate so that the above equation (1) is satisfied at this film formation temperature. .. [0169] Alternatively, the film forming speed and the film forming temperature may not be set in advance, and the controller may appropriately determine these to perform the film forming. In this case as well, the controller 500 determines the film formation rate and the film formation temperature within the range in which the above equation (1) is satisfied, and the film formation is performed. [0170] As described above, according to the 35th embodiment, the controller 500 appropriately determines and controls the relationship between the substrate heating conditions and the film formation rate, thereby stabilizing the photocatalyst having excellent photocatalytic properties with good reproducibility. Can be manufactured. [0171] FIG. 38 is a conceptual diagram showing a modified example of the photocatalyst manufacturing apparatus of the present invention. That is, the figure shows the planar configuration of the manufacturing equipment, centering on the transport mechanism 700, and around it, a vertical SiO.₂Film formation chamber 210, heating chamber 220, TiO₂Film formation chamber 230, TiO₂Film formation chamber 240, SiO₂The film forming chamber 250 and the load lock portion 260 have a structure provided in this order. The transport mechanism 700 has holders 720 on which a substrate can be placed radially, rotates in the direction of arrow A, and is capable of further transporting in the direction of arrow B. [0172] Figure 39 shows TiO₂It is sectional drawing in the vertical direction of the film forming chambers 230, 240. In FIG. 37, the same elements as those described above with respect to FIG. 37 are designated by the same reference numerals, and detailed description thereof will be omitted. [0173] The substrate 100 mounted on the substrate holder 720 is rotationally conveyed to the front surface of the chamber by the conveying mechanism 700, and further transferred in the direction of the chamber to form a sealed state in the chamber by the holder 720. In this state, the inside of the film forming chamber 230 (240) can be evacuated by the turbo molecular pump (TMP) 110. The transport space provided by the transport mechanism 700 is also maintained in a vacuum state by a vacuum exhaust system (not shown). [0174] In the film forming chamber 230 (240), reactive sputtering is carried out by introducing argon and oxygen. At this time, in the same manner as described above with respect to FIG. 37, the film formation rate and the film formation temperature are controlled by the controller 500 so that the above equation (1) is satisfied. For example, when the film formation rate is specified in advance, the controller 500 calculates the heating conditions of the substrate so that the above equation (1) is satisfied at the film formation rate, and the heating mechanism provided in the heating chamber 220. The substrate is heated by controlling the operation of. Also in the case of this modification, the controller 500 may be able to control not only the heating mechanism but also the DC power supply 510. In this case, the controller 500 controls the DC power supply 510 and TiO₂The film is formed. [0175] Further, as described above with respect to FIGS. 15 and 16, in order to produce an excellent photocatalyst, the total pressure should be in the range of 3 pascals to 5 pascals, and the oxygen partial pressure should be 10% or more and 30% or less. Is desirable. Therefore, the controller 500 may perform control so that these conditions are also satisfied at the same time. The manufacturing apparatus of this modified example can also stably manufacture a photocatalyst having excellent photocatalytic characteristics with good reproducibility by appropriately determining and controlling the relationship between the substrate heating conditions and the film formation rate by the controller 500. .. [0176] In addition, in FIGS. 36 to 39, a specific example in which the substrate 100 is preheated in the heating chamber 220 provided separately from the film forming chamber is given. [0177] However, the present invention is not limited to this. For example, the same effect can be obtained by applying the present invention in the same manner to the manufacturing apparatus provided with the substrate heating mechanism in the film forming chambers 230 and 240. That is, even in the case of such a manufacturing apparatus, the controller 500 can control the substrate heating mechanism to carry out the film formation so that the above equation (1) is satisfied. [0178] Embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, the photocatalytic membrane in the present invention includes titanium oxide (TiO).₂), But the same effect can be obtained by using titanium oxide to which a predetermined element is added, and these are also included in the scope of the present invention. [0179] Further, when the photocatalyst film of the present invention is formed by sputtering, the reaction gas to be introduced into the chamber is not limited to argon and oxygen, and other, for example, a mixed gas of a gas other than argon and oxygen. It may be a mixed gas of argon, oxygen and other gases. [Industrial applicability] [0180] As described in detail above, according to the present invention, it is possible to provide a photocatalyst having excellent photocatalytic action by forming a unique porous photocatalyst film different from the conventional one. By depositing a silicon oxide film having a predetermined film thickness, this photocatalyst can maintain a high level of hydrophilicity even in a dark place without impairing the photocatalytic action. Moreover, according to the present invention, since the photocatalyst film is formed at a significantly higher deposition rate than before, the production throughput can be significantly improved, the productivity can be improved, and the cost can be significantly reduced. [0181] Further, the photocatalyst coating material of the present invention may be any one in which the above-mentioned photocatalyst material of the present invention is coated on the surface, for example, a rearview mirror for an automobile, a body or a window glass, and other bathrooms. Includes various mirrors, exterior wall materials for buildings, interior wall materials for bathrooms, toilet bowls, sinks, road signs, exterior materials for various indicators, etc. When applied to a rear-view mirror for automobiles, a clear view can be obtained due to the drip action and anti-fog action of the photocatalyst film, and safety is ensured. In addition, when applied to automobile bodies, road signs, building exterior wall materials, etc., a self-cleaning effect due to rainfall can be obtained. [0182] That is, according to the present invention, it is possible to provide a high-performance photocatalyst at a low cost, and various coatings using the photocatalyst can be supplied to the market, which is a great industrial merit. [Simple explanation of drawings] [0183] FIG. 1 is a schematic view illustrating the configuration of a photocatalyst according to an embodiment of the present invention. FIG. 2 is a schematic view showing the surface of the photocatalyst film 10. FIG. 3 is a schematic view illustrating the cross-sectional structure of the photocatalyst 10. FIG. 4 is a schematic diagram showing the main configuration of the sputtering apparatus used in the experiment. FIG. 5 is a graph illustrating a temperature change of the substrate 100 during sputtering. FIG. 6 is an electron micrograph of the surface of the photocatalyst film obtained by reactive sputtering. FIG. 7 is an electron micrograph of the surface of the photocatalyst film obtained by reactive sputtering. FIG. 8 is a graph showing an example of the results of the wax decomposition hydrophilic test of the photocatalyst film 10 according to the present invention. FIG. 9 is a graph showing the relationship between the surface roughness of the photocatalyst film and the contact angle measured by AFM (Atomic Force Microscopy). FIG. 10 is a graph in which the contact angle is plotted against the value Ra / T obtained by dividing the surface roughness Ra of samples A to D by each film thickness. FIG. 11 is a graph showing the X-ray diffraction pattern of the photocatalyst film of sample C. FIG. 12 is a diffraction pattern after data processing is performed on the diffraction pattern of FIG. 10 to remove background noise. FIG. 13 is a graph in which the X-ray diffraction pattern of the photocatalyst film of sample A was measured in the same manner and the background noise was removed. FIG. 14 is a graph in which the refractive index and the density ratio are plotted against the total pressure, respectively. FIG. 15 is a list summarizing the film forming conditions of the photocatalyst film of the examples carried out by the present inventor by the DC sputtering method. FIG. 16 is a list summarizing the film forming conditions of the photocatalyst film of the comparative example carried out by the present inventor by the DC sputtering method. FIG. 17 is a graph showing the relationship between the oxygen partial pressure during sputtering and the contact angle of the obtained photocatalyst film. FIG. 18 is a graph showing the relationship between the total pressure during sputtering and the contact angle of the obtained photocatalyst film. FIG. 19 is a graph showing the relationship between the film formation rate during sputtering and the contact angle of the obtained photocatalyst film. FIG. 20 is a graph showing the relationship between the film thickness of the photocatalyst film formed by sputtering and the contact angle. FIG. 21 is a flowchart showing the procedure of the wet decomposition performance test. FIG. 22 is a graph illustrating the results of the wet decomposition performance test. FIG. 23 is a schematic view illustrating the cross-sectional structure of the photocatalyst body provided with the buffer layer. FIG. 24 is a graph showing the results of the wax decomposition hydrophilic test. FIG. 25 is a schematic view showing the cross-sectional structure of the photocatalyst according to the second embodiment of the present invention. FIG. 26 is a graph illustrating the results of the wax decomposition hydrophilic test of the photocatalyst film having the laminated structure of FIG. 25. FIG. 27 is a graph illustrating the results of the wax decomposition hydrophilic test of the photocatalyst film of the second embodiment of the present invention. FIG. 28 is a graph illustrating the results of the wax decomposition hydrophilic test of the photocatalyst film of the second embodiment of the present invention. FIG. 29 is a graph illustrating the results of the wax decomposition hydrophilic test of the photocatalyst film of the second embodiment of the present invention. FIG. 30 is a graph showing a change in contact angle when the photocatalyst film of the second embodiment of the present invention is maintained in a dark place. FIG. 31 is a graph showing the photocatalytic action of the photocatalyst of the present invention and the comparative example. FIG. 32 is a graph showing the X-ray diffraction pattern of sample D. FIG. 33 is a graph showing the X-ray diffraction pattern of Comparative Example 35. FIG. 34 is a graph showing a comparison of the photocatalytic action of the photocatalysts of Example 33 and Comparative Example 37. FIG. 35 is a graph showing a comparison of the photocatalytic action of the photocatalysts of Example 34 and Comparative Example 38. FIG. 36 is a conceptual diagram illustrating the main configuration of the photocatalyst manufacturing apparatus of the present invention. Figure 37 shows TiO₂It is a conceptual diagram which illustrates the main part structure of the film forming chamber 230 (or 240), and is FIG. 38 is a conceptual diagram showing a modified example of the photocatalyst manufacturing apparatus of the present invention. Figure 39 shows TiO₂It is sectional drawing in the vertical direction of the film forming chambers 230, 240.