JPH11315398A - Formation of titanium anodically oxidized film for photocatalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a film to exhibit photocatalystic operation even by ultraviolet rays and visible rays and to obtain antibacterial, deodorant and contamination preventive effects by immersing titanium into an electrolytic bath composed of sulfuric acid, phosphoric acid and hydrogen peroxide, increasing the voltage to the prescribed one by a prescribed direct constant current and holding it for a prescribed time to form a titanium anodically oxidized film essentially consisting of an anatase form. SOLUTION: This is a method for forming a titanium anodically oxidized film for a photocatalyst exhibiting photocatalystic operation even by visible rays, in which titanium is immersed into an electrolytic bath composed of sulfuric acid, phosphoric acid, hydrogen peroxide and cobalt sulfate, the voltage is increased to the prescribed one by a prescribed direct constant current, and it is held for a prescribed time to form a TiO2 -CoO series titanium anodically oxidized film. Moreover, titanium is immersed into an electrolytic bath composed of sulfuric acid, phosphoric acid, hydrogen peroxide and zinc sulfate, the voltage is increased to the prescribed one, and it is held for a prescribed time to form a TiO2 -ZnO series titanium anodically oxidized film. The titanium anodically oxidized film to be formed is used for the interior and exterior materials of buildings, apparatus for cooking, tableware or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to various building materials and other equipment and materials, such as interior and exterior materials of buildings, cooking utensils, tableware, sanitary equipment, and other civil engineering materials such as sewer pipes. The present invention relates to a method for forming a titanium anodic oxide film for a photocatalyst used for a photocatalyst.

[0002]

2. Description of the Related Art Titanium has the highest corrosion resistance among practical metals, has a lower specific gravity than steel, and has a very high specific strength. Titanium is used as a building material for factory plants and a medical material. It has been widely used. In recent years, due to its high corrosion resistance, its use in roofing materials and other building materials has been rapidly advancing. In addition, self-cleaning, air cleaning, and disinfection due to the photocatalytic action of titanium oxide discovered in the 1970s have attracted attention with the recent emergence of environmental problems, and have been put to practical use in the field of building materials. Research is progressing. In other words, when ultraviolet light from sunlight or lighting fixtures is applied to titanium oxide, light energy is converted into chemical energy, which exerts a photocatalytic action to decompose organic substances and is a typical allergen generated in offices and residential rooms. In addition to decomposing and removing certain formaldehyde, antibacterial, deodorant and antifouling effects are obtained.

[0003]

However, the conventional photocatalytic action of titanium oxide can be exerted only by irradiation with ultraviolet rays. However, since the amount of ultraviolet rays contained in sunlight, lighting equipment, and the like is very small, sufficient effects may not be obtained in some cases, and applications are limited.

Therefore, the present invention exerts a photocatalytic action not only by ultraviolet light but also by visible light, and provides excellent antibacterial, deodorant,
An object of the present invention is to provide a method for producing a titanium anodic oxide film for a photocatalyst that can obtain an antifouling effect.

[0005]

According to a first aspect of the present invention, there is provided a method for forming a titanium anodic oxide film for a photocatalyst, comprising sulfuric acid, phosphoric acid, and peroxide as main processes of forming the film. Prepare an electrolytic bath composed of hydrogen, immerse titanium in this electrolytic bath, boost the voltage to a predetermined voltage with a predetermined DC constant current, and hold the voltage at the voltage for a predetermined time,
Produces an anodized titanium anodic oxide film. It is a well-known fact that titanium oxide has three crystal forms, anatase, brookite, and rutile, of which anatase crystal has the highest photocatalytic activity.

According to a second aspect of the present invention, as the film forming main process, an electrolytic bath composed of sulfuric acid, phosphoric acid, hydrogen peroxide, and cobalt sulfate is prepared and the first invention is used by using this electrolytic bath. The same electrolytic treatment as in the case of
An O ₂ -CoO-based titanium anodic oxide film is formed.

According to a third aspect of the present invention, as a film forming main process, an electrolytic bath composed of sulfuric acid, phosphoric acid, hydrogen peroxide and zinc sulfate is prepared, and the first electrolytic bath is used by using this electrolytic bath. by performing the same electrolytic treatment as in, TiO ₂
-Generate an anodic oxide film of ZnO-based titanium.

According to a fourth aspect of the present invention, as the film forming main process, an electrolytic bath composed of sulfuric acid, phosphoric acid, hydrogen peroxide, and ruthenium sulfate is prepared and the first invention is used by using this electrolytic bath. The same electrolytic treatment as in the case of
iO ₂ -RuO generate an anodic oxide film of ₂ system titanium.

According to a fifth aspect of the present invention, there is provided a method for preparing an electrolytic bath comprising sulfuric acid, phosphoric acid, hydrogen peroxide, cobalt sulfate, and zinc sulfate as a main process of forming a film.
Using this electrolytic bath, the same electrolytic treatment as in the first invention is performed to form an anodic oxide film of TiO ₂ —CoO—ZnO-based titanium.

According to a sixth aspect of the present invention, as the film forming main process, an electrolytic bath composed of sulfuric acid, phosphoric acid, hydrogen peroxide, cobalt sulfate, and ruthenium sulfate is prepared as a main process of film formation, and this electrolytic bath is used. By performing the same electrolytic treatment as in the first invention, an anodic oxide film of TiO ₂ —CoO—RuO ₂ titanium is generated.

According to a seventh aspect of the present invention, there is provided a method for preparing an electrolytic bath comprising sulfuric acid, phosphoric acid, hydrogen peroxide, zinc sulfate, and ruthenium sulfate as a main process of forming a film. By performing the same electrolytic treatment as in the first invention, an anodic oxide film of TiO ₂ -ZnO-RuO ₂ titanium is generated.

[0012] A generating method according to an eighth aspect of the present invention.
Is mainly composed of sulfuric acid, phosphoric acid,
Consisting of silicon, cobalt sulfate, zinc sulfate and ruthenium sulfate
An electrolytic bath is prepared, and the electrolytic bath is used in the same manner as in the first invention.
TiO2 by performing the same electrolytic treatment _Two-CoO-ZnO-R
uO_TwoProduces an anodic oxide film of titanium.

The above-described anodic oxide film of titanium formed in the main process of film formation according to the first to eighth inventions, when subjected to a predetermined treatment, exhibits a photocatalytic action not only by ultraviolet light but also by visible light, and is excellent. Antibacterial, deodorant and antifouling effects are obtained. Therefore, the use of the titanium anodic oxide film can be expanded, and the titanium anodic oxide film can be optimally used as an interior and exterior material of a building, cooking utensils, tableware, sanitary equipment, and other civil engineering materials such as sewer pipes.

In a preferred embodiment (first alternative embodiment) of each of these inventions, after an anodic oxide film is formed in the film formation main process of each of the above inventions, the anode and the cathode are exchanged, and the voltage is changed to perform electrolysis. This includes a removal step of removing sulfuric acid and phosphate ions in the anodic oxide film. By removing the sulfuric acid and phosphate ions in the anodic oxide film in this way, the corrosion resistance of the film is enhanced, and the film can be optimally used as an exterior material of a building. In addition, the removal of these impurity ions, which act as recombination centers for the charge carriers generated in the titanium oxide due to light absorption, enhances the photocatalytic action of the titanium anodic oxide film and provides excellent antibacterial, deodorant, and antifouling effects. Can be

In a preferred embodiment (second alternative embodiment), ammonium fluoride is added to the electrolytic bath used in each of the above-described inventions to form a fluorine-containing titanium anodic oxide film. In this way, fluorine or a fluorine compound is formed on the surface of the titanium anodic oxide film, and the strength of the film is strengthened and the weather resistance of the film is improved, so that it is optimally used as an interior or exterior material of a building. Becomes possible. In addition, the photocatalytic action of the titanium anodic oxide film is further enhanced, and more excellent antibacterial, deodorant and antifouling effects can be obtained. Although the cause of the effect of promoting the photocatalytic action of fluorine ions is not clear at present, it seems to be related to promoting anatase crystallization.

Further, in a preferred embodiment (third alternative embodiment), titanium which has been anodized in the main process of film formation of each of the above inventions is immersed in an aqueous solution of a chloride of a noble metal and irradiated with ultraviolet light. Includes a colloid deposition process of reducing and depositing a noble metal colloid on the surface of the anodic oxide film. In this case, the noble metal deposited on the surface of the titanium anodic oxide film exerts a good photocatalytic action, so that more excellent antibacterial, deodorant, and antifouling effects can be obtained. The charge separation of the photocharge carrier is enhanced by the loading of the noble metal, and the photocharge carrier is effectively used for the oxidation / reduction reaction of organic substances. The function of titanium oxide to remove organic substances is derived from the strong oxidizing power of holes generated in the valence band by photoexcitation. RuO ₂ is particularly effective in increasing the oxidation efficiency of organic substances because it helps holes to move to organic substances.

According to a twelfth aspect of the present invention, there is provided a method for producing a titanium anodic oxide film for a photocatalyst according to the ninth aspect of the present invention, comprising forming an anodic oxide film on titanium by primary anodic oxidation, and then removing the lower titanium oxide from the anodic oxide film. And a method of adding a small amount of fluorine to the film. The method of removing the low order titanium oxide and adding a small amount of fluorine to the film can be specifically performed by the method of the following tenth invention. Claim 13
The method for producing a titanium anodic oxide film for a photocatalyst according to the tenth aspect of the present invention comprises, after producing an anodic oxide film by primary anodic oxidation on titanium, converting the titanium produced with this film to ammonium hydrogen fluoride, hydrofluoric acid, or This is a method of immersing in an electrolytic bath containing a fluoride ion such as ammonium fluoride, or an electrolytic bath containing hydrogen peroxide, and performing anodization again. When metal titanium is treated at a high voltage in a phosphoric acid-sulfuric acid-hydrogen peroxide aqueous bath, a thick-film anodic oxide film containing anatase-type titanium oxide as a main component is obtained. However, this film contains anatase-type titanium oxide as a main component, but does not show photocatalytic activity as it is. The cause is considered to be due to the lower titanium oxide present in the coating. Therefore, we decided to remove this. In addition, as a method for removing the film, re-anodization of the film was examined. The bath used for the re-anodizing process contains F ions because it is necessary to dissolve low-order titanium oxide. As a result of the experiment, it was found that the photocatalytic activity can be imparted to the anodized film by performing anodization in an ammonium hydrogen fluoride bath as a secondary treatment. For this purpose, it is considered effective to dope fluorine into the film at the same time as removing the lower titanium oxide in the film. This is clear from the fact that the sample of the immersion experiment did not show catalytic activity, and the sample obtained by secondary anodic oxidation showed catalytic activity. That is, during the secondary anodic oxidation, the fluoride ions of ammonium hydrogen fluoride used to remove low-order titanium oxide penetrate into the titanium oxide film by electrophoresis and create impurity levels, resulting in improved photocatalytic activity. Can be considered.

In the ninth and tenth inventions, the anodic oxide film formed by primary anodic oxidation may be a thick-film anodic oxide film containing anatase-type titanium oxide as a main component.

In the ninth aspect, the anodic oxide film formed by the primary anodic oxidation may be any one of the first to eighth anodic oxide films.
Or the film formed in the main process of forming the film in the method for forming a titanium anodic oxide film for a photocatalyst in the second alternative embodiment. That is, the film formed in the main process of film formation in each of the above inventions is used as an intermediate product. Further, in the tenth aspect, the anodic oxide film formed by the primary anodic oxidation is formed in the main step of film formation in the method for producing a titanium anodic oxide film for a photocatalyst according to any one of the first to eighth aspects. It may be a coated film. In the ninth and tenth inventions, the anodic oxide film formed by the primary anodic oxidation is a film after the removal process of the first alternative embodiment,
Alternatively, it may be a film after the colloid deposition process of the third alternative embodiment.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to specific examples. Example 1 First, 1.5 mol / L (L is liter) sulfuric acid (H ₂ SO ₄ ) and 0.3 mol / L phosphoric acid (H ₃ P)
An electrolytic bath (hereinafter, referred to as a “basic bath”) composed of O ₄ ) and 0.3 mol / L hydrogen peroxide solution (H ₂ O ₂ ) is prepared.
Then, titanium is immersed in the electrolytic bath, and the bath temperature is set at 20 ° C.
℃, DC up to 200V at a constant DC current of 1A / dm ² ,
After boosting, anodizing treatment is performed while maintaining the same voltage for 5 minutes.
As a result, an anatase-type titanium anodic oxide film (TiO ₂ ) of a partly rutile type was obtained.

[0021] 0.02~0.1m of in the basic bath is an electrolytic bath used in Example 1, further cobalt sulfate (CoSO ₄ · 7H ₂ O)
ol / L. Then, in the electrolytic bath thus prepared, the temperature is raised to 150 V at a bath temperature of 30 ° C. and a DC constant current of 3 A / dm ² , and after the pressure is raised, the voltage is maintained for 5 minutes to perform anodizing treatment. As a result, a TiO ₂ —CoO-based titanium anodic oxide film mainly composed of an anatase type and partly rutile was obtained.

[0022] in Example 3 the base bath, further zinc sulfate (ZnSO ₄ · 7H
0.02 to 0.3 mol / L of ₂ O) is added. And, immersing titanium in the electrolytic bath prepared in this way,
The temperature is raised to 200 V at a bath temperature of 25 ° C. and a DC constant current of 1 A / dm ² , and after the pressure is raised, the voltage is maintained for 5 minutes to perform an anodizing treatment. As a result, an anatase-type titanium anodic oxide film of a TiO ₂ —ZnO-based titanium oxide partially rutile was obtained.

Example 4 In the basic bath, ruthenium sulfate (Ru (S
Add 0.01 mol / L of O ₄ ) ₂ ). Then, the titanium was immersed in the electrolytic bath prepared as described above, and the bath temperature was set at 2 ° C.
The voltage is raised to 200 V at 5 ° C. and a constant DC current of 1 A / dm ^2. After the voltage is raised, the voltage is maintained for 5 minutes to perform anodizing treatment. As a result, an anatase-type titanium anodic oxide film of TiO ₂ -RuO ₂ -based, which was partly rutile, was obtained.

EXAMPLE 5 0.02 to 0.1 mol of cobalt sulfate was added to the basic bath.
1 / L and 0.02-0.3 mol / L of zinc sulfate are added. Then, titanium is immersed in the electrolytic bath prepared as described above, and the temperature is raised to 150 V at a bath temperature of 30 ° C. and a constant DC current of 3 A / dm ^2. I do. As a result, a TiO ₂ —CoO—ZnO-based titanium anodic oxide film mainly composed of anatase and partially rutile was obtained.

Example 6 In the above-mentioned basic bath, 0.02-0.
1 mol / L and 0.01 mol / L of ruthenium sulfate
And. Then, the titanium was immersed in the electrolytic bath thus prepared, and the bath temperature was 30 ° C., and the DC constant current was 3 A / dm.
^The pressure is raised to 150 V in step ² , and after the pressure is raised, the voltage is maintained for 5 minutes to perform anodizing treatment. As a result, a titanium anodic oxide film of a TiO ₂ —CoO—RuO ₂ system mainly composed of anatase and partially rutile was obtained.

Example 7 In the basic bath, 0.02 to 0.3 m of zinc sulfate was further added.
ol / L and 0.01 mol / L of ruthenium sulfate are added. Then, titanium is immersed in the electrolytic bath prepared as described above, and the temperature is raised to 200 V at a bath temperature of 25 ° C. and a DC constant current of 1 A / dm ^2. I do. As a result, a titanium anodic oxide film of a TiO ₂ —ZnO—RuO ₂ system mainly composed of anatase and partially rutile was obtained.

Example 8 In the above-mentioned basic bath, 0.02 to 0.
1 mol / L and 0.02-0.3 mol /
L and 0.01 mol / L of ruthenium sulfate are added. Then, the titanium is immersed in the electrolytic bath prepared in this manner, and the bath temperature is 30 ° C., the DC constant current is 3 A / dm ² , and
The voltage is raised to V, and after the pressure is raised, the voltage is maintained at the same voltage for 5 minutes to perform anodizing treatment. As a result, a titanium anodic oxide film of a TiO ₂ —CoO—ZnO—RuO ₂ system mainly composed of anatase and partially rutile was obtained. The crystal form of the anodic oxide film according to each of the above embodiments is based on the result of detection by the XRD method.

Example 9 After the anodic oxide film was formed in the above Examples 1 to 8, the anode and the cathode were exchanged, and the voltage was changed in the range of 100 to 200 V to carry out electrolysis. Sulfate ions (SO ₄ ²⁻ ) and phosphate ions (PO ₄ 3 ⁻ ) were removed.

Example 10 0.01 mol / L of ammonium fluoride (NH ₄ F) was added to the electrolytic baths used in Examples 1 to 8 above, and anodizing treatment was performed under the same electrolysis conditions as in each Example. To produce an anodized film of fluorine-containing titanium.

Example 11 The titanium anodized in Examples 1 to 8 was replaced with A
It was immersed in an aqueous solution of u, Ag, Pd, and Pt chlorides, and irradiated with ultraviolet rays to reduce and precipitate various noble metal colloids on the surface of the anodic oxide film.

Tests for the photocatalysis according to Examples 1 to 11 above were performed. However, it has been found that these anodic oxide films do not show sufficient photocatalytic activity as they are. That is, as described above, when the metal titanium is treated at a high voltage in a phosphoric acid-sulfuric acid-hydrogen peroxide water bath, a thick-film anodic oxide film containing anatase-type titanium oxide as a main component is obtained. However, although this film contains anatase-type titanium oxide as a main component, it does not show photocatalytic activity.

The cause is considered to be based on the lower titanium oxide which is considered to be present in the film, and as a method of removing the same, re-anodization (secondary anodic oxidation) of the film is performed.
Was considered. The bath used for the re-anodizing process contains F ions because it is necessary to dissolve low-order titanium oxide.

Example 12 An example in which this secondary anodic oxidation was performed will be described together with a comparative example. The titanium used for the experiment was a plate of industrial quasi-titanium as specified by JISH4600 (width 30 mm, length 50 m)
m, thickness 0.4 mm), and used for pre-treatment was immersed in n-hexane for surface degreasing. In Example 12, the following primary anodic oxidation and secondary anodic oxidation were performed on the titanium formed from the plate pieces. In the comparative example,
After the same primary anodic oxidation as in Example 12, the following immersion treatment was performed.

(1) Primary anodic oxidation In this anodic oxidation, phosphoric acid (H ₃ PO ₄ ) contains 0.3 mol /
L (L is liter) and sulfuric acid (H ₂ SO ₄ )
5 mol / L, hydrogen peroxide (H ₂ O ₂ ) 0.3 mol / L
Titanium was immersed in an electrolyte solution consisting of a composition (20 to 50 ° C.), with complete smooth direct current, 20 3.0A / dm ²
The voltage was increased to 0 V, and after the voltage increase, the voltage was maintained for 30 minutes to perform electrolysis. This treatment is referred to as primary anodic oxidation. (2) Secondary anodic oxidation (Example) and immersion treatment (Comparative example) In Example 12, the sample prepared by primary anodic oxidation was subjected to anodic oxidation (secondary anodic oxidation) again, and the We tried to remove low order titanium oxide.
In the comparative example, the lower titanium oxide in the film is removed by immersing the sample prepared by the primary anodic oxidation under the same conditions as in Example 12 in an aqueous solution of hydrogen peroxide and ammonium hydrogen fluoride. Tried that. In the above secondary anodic oxidation, the concentration of ammonium hydrogen fluoride is adjusted to 0.01.
０．３0.3 mol / L, the bath temperature was changed from 20 ° C. to 40 ° C., and the electrolysis time was changed between 5 and 30 minutes to examine the optimum conditions. In the above immersion treatment, the concentration of ammonium hydrogen fluoride was adjusted to 0.0
1 to 0.5 mol / L, bath temperature was 20 to 50 ° C, and immersion time was 5 to 90 minutes.

[Measurement] Embodiment 12 created in this way
For the coatings of Comparative Examples, the crystallization of the coating was confirmed by X-ray diffraction measurement, SEM image observation, cross-sectional analysis of the coating by EPMA, and surface analysis by XPS were performed.

[Test Results] (Appearance of Coating) Samples prepared by primary anodic oxidation are all gray. This suggests that the coating contains titanium dioxide, which is a white component called lower titanium oxide, which is a black component, whereas the sample after the secondary treatment contains fluorine in the bath. Concentration of ammonium hydride,
Although there is a difference depending on various conditions of time and temperature, the titanium oxide is surely whiter than that after the primary anodic oxidation, and it is considered that the lower titanium oxide in the film is removed by the secondary treatment.

(Secondary anodic oxidation)
Tables 1 to 3 show the state of the film according to the electrolysis time and the concentration of ammonium hydrogen fluoride, and the photocatalytic activity of the film.
From these tables, it is found that when secondary anodic oxidation is performed in a high-concentration bath, the coating is destroyed in a very short time. Also,
The concentration of ammonium hydrogen fluoride is 0.1 M (M = mol /
L) It can be seen that a stable film could not be obtained unless it was below. As a general tendency, a good film was obtained by anodizing in a short period of 10 minutes or 5 minutes using a low concentration bath.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

Next, Tables 4 and 5 show the state of the film when immersed in ammonium hydrogen fluoride. From these tables, it is understood that a film having photocatalytic activity cannot be produced in the experiment by immersion.

[0042]

[Table 4]

[0043]

[Table 5]

(Photocatalytic Activity) FIGS. 1 to 3 show the acetaldehyde decomposability of the sample after secondary anodic oxidation by irradiation with visible light. It is the amount of decomposition per 0.15 dm ^{2 of} titanium plate. FIG.
Thus, at a bath temperature of 20 ° C., the resolution is as low as about 10% at the maximum. Therefore, it is presumed that the solubility of the low order titanium oxide is small at this bath temperature. The sample with the highest resolution was anodized for 5 min in a solution containing 0.1 M ammonium hydrogen fluoride and 1 M hydrogen peroxide, but this sample had a fairly brittle coating, and overall Samples anodized for 10 min or 5 min in a solution containing 0.05M ammonium hydrogen fluoride and hydrogen peroxide were found to be superior. The experiment of the photocatalytic activity was performed by irradiating visible light using a xenon lamp as a light source. At this time, a cut filter for blocking ultraviolet rays of 400 nm or less was attached in front of the light source.

XRD Measurement (X-ray Diffraction Measurement) FIG. 4 shows the change in the crystallinity of the film depending on the bath temperature during the primary anodic oxidation. From this figure, it is confirmed that when the temperature at the time of the primary anodic oxidation increases, an anatase peak at 25 ° C. grows. However, when a secondary treatment is performed on a film that has been subjected to primary anodic oxidation in a bath at 40 ° C. or 50 ° C., the time at which the film is destroyed becomes extremely short as compared with a sample treated at 30 ° C. or lower. Therefore, the bath temperature of the primary anodizing treatment is 30
° C was set. Although not shown in the figure, no change was observed in the XRD pattern even after secondary anodic oxidation and after immersion.

EPMA Measurement (Electron Prog X-ray Microanalyzer Measurement) FIG. 5 shows the EPM after primary anodic oxidation, and FIG. 6 shows the EPM after secondary anodic oxidation.
The result of A measurement is shown. From these figures, in both cases, a considerable amount of phosphorus and sulfur, which are considered to be caused by phosphoric acid and sulfuric acid, as well as titanium and oxygen were confirmed over the entire film. It is considered that these anions were taken into the film by electrophoresis. Fluorine was not detected from the film after the secondary anodic oxidation, which is presumed to be due to the low concentration.

XPS Measurement (Measurement by X-ray Photoelectron Spectroscopy) When the sample subjected to the secondary anodic oxidation was analyzed in the depth direction by XPS measurement, it was confirmed that fluorine was present in the film. It was confirmed that fluorine was also incorporated into the film by electrophoresis like phosphate ions and sulfur ions.

SEM Image Observation (Scanning Electron Microscope Image Observation) FIG. 7 shows S after the primary anodic oxidation and after the respective secondary treatments.
3 shows an EM image. These SEM images show that all the films have the same shape.

[Consideration of Experimental Results] From the above results, it was found that photocatalytic activity can be imparted to the anodized film by performing anodization in an ammonium hydrogen fluoride bath as a secondary treatment. For this purpose, it is considered effective to dope fluorine into the film at the same time as removing the lower titanium oxide in the film. This is clear from the fact that the sample of the immersion experiment did not show catalytic activity, and the sample obtained by secondary anodic oxidation showed catalytic activity. That is, during the secondary anodic oxidation, the fluoride ions of ammonium hydrogen fluoride used for the removal of low order titanium oxide penetrate into the titanium oxide film by electrophoresis and create impurity levels, resulting in improved photocatalytic activity. Can be considered.

Next, Table 6 shows the results of tests of the photocatalytic action on visible light of the titanium anodic oxide films obtained in Examples 2 to 8, which were re-anodized. As shown in the same table, it was confirmed that the titanium anodized films obtained in Examples 2 to 8 could also decompose acetaldehyde with visible light by re-anodizing.

[0051]

[Table 6]

The titanium anodic oxide film which has been subjected to each of the above reanodization treatments is subjected to the treatment performed in any of the first, second and third alternative embodiments. It is presumed that an even more favorable antibacterial, deodorant and antifouling effect can be obtained. For example, one of the following processes is performed. After the re-anodized titanium anodic oxide film is formed, the anode and the cathode are exchanged, the voltage is changed, and electrolysis is performed to remove sulfuric acid and phosphate ions in the anodic oxide film. The re-anodized titanium is immersed in an aqueous solution of a chloride of a noble metal, and irradiated with ultraviolet rays to perform a colloid deposition process of reducing and depositing a noble metal colloid on the surface of the anodized film. Re-anodized titanium to be subjected to these treatments may have been re-anodized by any of the aforementioned methods.

[0053]

As described above, according to the present invention, not only ultraviolet light but also visible light can exert a photocatalytic action,
Excellent antibacterial, deodorant and antifouling effects can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the acetaldehyde resolution (in the case of a secondary bath temperature of 20 ° C.) of a sample after secondary anodic oxidation according to an embodiment of the present invention, which is irradiated with visible light.

FIG. 2 is a graph showing the acetaldehyde resolution (in the case of a secondary bath temperature of 30 ° C.) of the sample after the secondary anodic oxidation according to the embodiment of the present invention by irradiation with visible light.

FIG. 3 is a graph showing acetaldehyde decomposability (in the case of a secondary bath temperature of 40 ° C.) of a sample after secondary anodic oxidation according to an example of the present invention by irradiation with visible light.

FIG. 4 is a graph showing a change in crystallinity of a film depending on a bath temperature during primary anodic oxidation.

FIG. 5 is a graph showing the results of EPMA measurement after primary anodization.

FIG. 6 is a graph showing the results of EPMA measurement after secondary anodic oxidation.

FIGS. 7A and 7B are photographs showing SEM images after primary anodic oxidation of a titanium anode coating and after secondary treatment, respectively.

Claims (15)

[Claims] 1. A method for producing a titanium anodic oxide film for a photocatalyst that exhibits a photocatalytic action even with visible light, comprising preparing an electrolytic bath composed of sulfuric acid, phosphoric acid, and hydrogen peroxide, and immersing titanium in the electrolytic bath. Then, the voltage is boosted to a predetermined voltage with a predetermined DC constant current, and after the boosting, the voltage is held for a predetermined time,
A method for producing a titanium anodic oxide film for a photocatalyst, comprising a main step of forming a anodic oxide film of titanium mainly comprising an anatase type. 2. A method for producing a titanium anodic oxide film for a photocatalyst which exhibits a photocatalytic action even with visible light, comprising preparing an electrolytic bath comprising sulfuric acid, phosphoric acid, hydrogen peroxide and cobalt sulfate, and applying the electrolytic bath to the electrolytic bath. Titanium is immersed, the voltage is raised to a predetermined voltage with a predetermined DC constant current, and after the boosting, the voltage is maintained for a predetermined time to form a TiO ₂ —CoO-based titanium anodic oxide film. A method for producing a titanium anodic oxide film for a photocatalyst, including a process. 3. A method for producing a titanium anodic oxide film for a photocatalyst that exhibits a photocatalytic action even with visible light, comprising preparing an electrolytic bath composed of sulfuric acid, phosphoric acid, hydrogen peroxide, and zinc sulfate. A film forming process comprising the steps of immersing titanium, raising the voltage to a predetermined voltage with a predetermined DC constant current, holding the voltage and holding the voltage for a predetermined time, and forming a TiO ₂ -ZnO-based titanium anodic oxide film. A method for producing a titanium anodic oxide film for a photocatalyst, including a process. 4. A method for producing a titanium anodic oxide film for a photocatalyst that exhibits a photocatalytic action even with visible light, comprising preparing an electrolytic bath comprising sulfuric acid, phosphoric acid, hydrogen peroxide and ruthenium sulfate, and applying the electrolytic bath to the electrolytic bath. A film formation process of immersing titanium, raising the voltage to a predetermined voltage with a predetermined DC constant current, holding the voltage for a predetermined time after the boost, and forming an anodic oxide film of TiO ₂ -RuO ₂ titanium. A method for producing a titanium anodic oxide film for a photocatalyst including a main process. 5. A method for producing a titanium anodic oxide film for a photocatalyst which exhibits a photocatalytic action even with visible light, comprising preparing an electrolytic bath comprising sulfuric acid, phosphoric acid, hydrogen peroxide, cobalt sulfate and zinc sulfate. Immerse titanium in the electrolytic bath,
A photocatalyst including a film forming main process including a process of forming a TiO ₂ —CoO—ZnO-based titanium anodic oxide film by boosting a voltage to a predetermined voltage with a predetermined direct current and holding the voltage at the voltage for a predetermined time. Method of forming titanium anodic oxide film for use. 6. A method for producing a titanium anodic oxide film for a photocatalyst that exhibits a photocatalytic action even with visible light, comprising preparing an electrolytic bath comprising sulfuric acid, phosphoric acid, hydrogen peroxide, cobalt sulfate, and ruthenium sulfate. Titanium is immersed in the electrolytic bath, the pressure is raised to a predetermined voltage with a predetermined DC constant current, and after the pressure is raised, the voltage is held for a predetermined time to obtain TiO ₂ —CoO—R.
A method for producing a titanium anodic oxide film for a photocatalyst, comprising a main step of producing a anodic oxide film of uO ₂ -based titanium. 7. A method for producing a titanium anodic oxide film for a photocatalyst that exhibits a photocatalytic action even with visible light, comprising preparing an electrolytic bath comprising sulfuric acid, phosphoric acid, hydrogen peroxide, zinc sulfate, and ruthenium sulfate. Titanium is immersed in the electrolytic bath, the pressure is raised to a predetermined voltage with a predetermined DC constant current, and after the pressure is raised, the voltage is maintained for a predetermined time to obtain TiO ₂ -ZnO-Ru.
A method for producing a titanium anodic oxide film for a photocatalyst, comprising a main process of producing a film comprising an anodic oxide film of O ₂ -based titanium. 8. A method for producing a titanium anodic oxide film for a photocatalyst which exhibits a photocatalytic action even with visible light, comprising preparing an electrolytic bath comprising sulfuric acid, phosphoric acid, hydrogen peroxide, cobalt sulfate, zinc sulfate, and ruthenium sulfate. Then, titanium is immersed in the electrolytic bath, the pressure is raised to a predetermined voltage by a predetermined DC constant current, and after the pressure is raised, the voltage is maintained for a predetermined time to obtain TiO ₂ −
Method of generating a photocatalytic titanium anodized film including the film generation main process consisting of process of producing an anodic oxide film of titanium CoO-ZnO-RuO ₂ system. 9. The method for producing a titanium anodic oxide film for a photocatalyst according to any one of claims 1 to 8,
After forming the anodic oxide film by the main process of film formation,
A method for producing a titanium anodic oxide film for a photocatalyst, comprising a removal step of removing sulfuric acid and phosphate ions in an anodic oxide film by exchanging an anode and a cathode and changing a voltage to perform electrolysis. 10. The method for producing a titanium anodic oxide film for a photocatalyst according to any one of claims 1 to 8, wherein ammonium fluoride is added to an electrolytic bath in the main process of forming the film to contain fluorine. For producing a titanium anodic oxide film for photocatalyst which produces an anodic oxide film of titanium. 11. The method for producing a titanium anodic oxide film for a photocatalyst according to any one of claims 1 to 8, wherein the titanium anodized in the main process of forming the film is placed in an aqueous solution of a chloride of a noble metal. A method for producing a titanium anodic oxide film for a photocatalyst, comprising a colloid deposition process in which a colloid of a noble metal is reduced and deposited on the surface of the anodic oxide film by immersion and irradiation with ultraviolet light. 12. A method for producing a titanium anodic oxide film for photocatalyst, which exhibits a photocatalytic action even with visible light,
A method for producing a titanium anodic oxide film for a photocatalyst, comprising forming an anodic oxide film on titanium by primary anodic oxidation, removing low order titanium oxide from the anodic oxide film, and adding a small amount of fluorine to the film. 13. A method for producing a titanium anodic oxide film for a photocatalyst that exhibits a photocatalytic action even with visible light,
After forming an anodic oxide film on the titanium by primary anodic oxidation, the formed titanium film is transferred to an electrolytic bath containing fluoride ions such as ammonium hydrogen fluoride, hydrofluoric acid, or ammonium fluoride, or to an electrolytic bath containing the same. A method for forming a titanium anodic oxide film for a photocatalyst, wherein the titanium anodic oxide film is immersed in an electrolytic bath containing hydrogen oxide and re-anodized. 14. The titanium anodic oxide film for a photocatalyst according to claim 12, wherein the anodic oxide film formed by primary anodic oxidation is a thick-film anodic oxide film containing anatase-type titanium oxide as a main component. Generation method. 15. The anodic oxide film formed by the primary anodic oxidation is a film forming main process in the method for producing a titanium anodic oxide film for a photocatalyst according to any one of claims 1 to 8 or claim 10. The method for producing a titanium anodic oxide film for a photocatalyst according to claim 12 or 13, which is a formed film.