JPH08338808A - Method for evaluating photocatalytic activity and film for evaluating photocatalytic activity - Google Patents

Abstract

PURPOSE: To provide a method for evaluating a photocatalytic activity easily without using a gas reaction or a biological reaction. CONSTITUTION: The method includes a process wherein an evaluation reaction substance (halogenated alkali aqueous solution 3) reacting with a hole or electron generated when the light is shed onto a substance having a photocatalytic activity (photocatalytic thin film 2) is applied to a surface to be evaluated, a process of casting ultraviolet, rays to the surface, and a process of determining the reacting amount of the evaluation reaction substance. In these processes, the evaluation reaction substance reacts, e.g. is oxidized or reduced, etc. The reacting amount is determined from a pH or a color change of the evaluation reaction substance, whereby a photocatalytic activity on the surface to be evaluated is quantitatively evaluated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for quantitatively evaluating photocatalytic activity and a film used for the evaluation.
In particular, without going through gas reactions or biological reactions,
The present invention relates to a photocatalytic activity evaluation method capable of simply evaluating photocatalytic activity. Furthermore, the present invention relates to a photocatalytic activity evaluation method that enables easy evaluation of photocatalytic activity in the field even after attaching antibacterial tiles or the like to a building wall or the like.

[0002]

2. Description of the Related Art When a substance is irradiated with ultraviolet rays, the substance sometimes acts to convert light energy into chemical energy and accelerate the reaction of surrounding substances. This property is called photocatalytic activity. For example, when a tile having a TiO ₂ thin film formed thereon (called an antibacterial tile) is stuck on the wall of a toilet or kitchen, it is said that it exerts the effect of deodorizing the indoor atmosphere and the antibacterial effect of the tile surface ( JP-A-5-25354
4 and WO94 / 11092).

As a method for evaluating the activity of the photocatalyst thin film of such an antibacterial tile, conventionally known is a method of monitoring a time-dependent concentration change of a gas decomposed by the photocatalyst thin film (ammonia, methyl mercaptan, etc.) by a gas chromatograph. Has been.

However, the method of monitoring with a gas chromatograph is inefficient because the measuring device is expensive and only one sample can be measured per device. Also, Pt
It is known that the photoactivity is improved by supporting a metal such as TiO ₂ on the TiO _2. However, in the photocatalytic thin film having such a structure, the net photoactivity depends on the gas adsorption by the metal. It is difficult to determine if it is of a degree. Furthermore, once the tile or the like is used as a wall surface, the activity of the photocatalytic thin film formed on the wall cannot be measured by a gas chromatograph.

On the other hand, as a method of evaluating photoactivity without using a gas chromatograph, there is a method of examining the survival rate of bacteria killed by a photocatalyst after light irradiation. In the photocatalytic thin film, the bacteria are killed by the antibacterial activity of the metal itself, so that it is difficult to determine the net photoactivity.

An object of the present invention is to provide a method for evaluating photocatalytic activity, which enables simple evaluation of photocatalytic activity without involving gas reaction or biological reaction.
Furthermore, an object of the present invention is to provide a photocatalytic activity evaluation method that can easily evaluate photocatalytic activity in the field even after pasting antibacterial tiles or the like on the walls of buildings, and a photocatalytic activity evaluation film used therefor. And

[0007]

In order to solve the above problems, the method for evaluating photocatalytic activity of the present invention is a substance which reacts with holes or electrons generated when a substance having photocatalytic activity (active substance) is irradiated with light. The method is characterized by including a step of applying the (evaluation reaction substance) to the surface to be evaluated, a step of irradiating the surface with ultraviolet light, and a step of quantifying the reaction amount of the evaluation reaction substance.

[0008]

First, an evaluation reaction substance showing a change sensitive to the photocatalytic activity phenomenon is applied to the surface to be evaluated. Then, the surface is irradiated with ultraviolet rays through the evaluation reaction substance. Then, the active substance on the surface to be evaluated generates holes and electrons, and acts directly or indirectly on the evaluation reaction substance, causing the evaluation reaction substance to undergo reactions such as oxidation and reduction. The photocatalytic activity of the surface to be evaluated can be quantitatively evaluated by quantifying the amount of this reaction from the change in the pH or color of the evaluation reaction substance.

[0009]

Embodiments of the present invention will be described below. Method using an aqueous solution containing a halogen ion : In the method of this embodiment, an aqueous solution containing a halogen ion is applied to a surface to be evaluated, and then the surface is irradiated with ultraviolet rays to measure a pH change of the aqueous solution before and after irradiation, and a pH change It is characterized in that the photocatalytic activity is evaluated based on the amount.

In this method, for example, in the case of an aqueous solution containing iodine ions, the following reactions occur. First, when light (ultraviolet) hits an active substance (TiO ₂ etc.),
The active substance generates holes (h ⁺ ) and electrons (e ⁻ ), and the holes and electrons that have appeared on the surface of the active substance without recombination contribute to the following reaction. This reaction is activated by irradiation with light having a bandgap energy higher than that of the active substance, and the wavelength of ultraviolet rays is suitable for this. The band gap of TiO ₂ differs depending on the crystal system and is 3.2 eV for anatase (wavelength of about 38
7 nm), rutile is 3.0 eV (wavelength: about 414 nm), and in the case of TiO ₂ , ultraviolet rays having a wavelength shorter than about 400 nm are generally absorbed. Due to the holes (h ⁺ ) and the electrons (e ⁻ ), an oxidation reaction: 2I ⁻ + 2h ⁺ → I ₂ reduction reaction: O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ occurs. The pH of the aqueous solution rises due to the OH ⁻ (hydroxy ion) generated here.

In the method of this aspect, the reason why the halogen ion is selected as the ionic species is that the above-mentioned redox reaction is likely to occur. The reason for this is that halogen ions have a high ionization degree, and the amount existing as ions can be increased substantially.

Among the halogen ions, particularly preferred is
It is an iodine ion. The reason is that the energy required for the oxidation reaction to occur is the smallest.

Among the aqueous solutions containing halogen ions, preferred are alkaline halide aqueous solutions. The reason is that the ionization degree is the highest in the compound and the concentration of dissolution in the solution can be increased.

Examples of the alkali halide aqueous solution include:
Iodide; KI, NaI, LiI, chloride; KCl, N
aCl, LiCl, bromide; KBr, NaBr, LiB
An aqueous solution of r, a fluoride; KF, NaF, or LiF can be used.

In the method of this aspect, it is preferable that the aqueous solution further contains a pH indicator. P at the time of ultraviolet irradiation
This is because the H change can be directly measured as the color change of the aqueous solution, and the photocatalytic activity can be evaluated very easily.

As such a pH indicator, a pH of 4 to
An indicator that changes around 8 is preferable, and as an example,
Bromocresol purple; pH range 5.2-6.8,
Chlorophenol red; pH range 5.0 to 6.6, o
-Nitrophenol; pH range 5.0 to 7.0, methyl red; pH range 4.2 to 6.2 and the like can be suitably used.

In the method of the main embodiment, a film containing an aqueous solution containing a halogen ion and a pH indicator, or a film coated with them (a photocatalytic activity evaluation film) is brought into close contact with the surface to be evaluated, and then the film is attached to the surface. The photocatalytic activity can be evaluated based on the amount of color change by irradiating ultraviolet rays through the film, measuring the color change of the film before and after the irradiation.

As such a photocatalytic activity evaluation film, a film formed by adding an aqueous solution containing a halogen ion and a pH indicator to an organic binder and mixing them can be used. Alternatively, it is also possible to use a water-absorbing substance in which an aqueous solution containing a halogen ion and a pH indicator are absorbed.

If such a film is used, the film is attached to the surface to be evaluated, and light is applied to measure the change in color.
That is, the evaluation work can be completed with a simple operation. That is, it is possible to save the trouble of mixing and applying the chemicals. Further, the amount of chemicals used is made uniform, so that measurement error is reduced. Furthermore, it can be easily applied to vertical surfaces such as the surface of tiles already affixed to a wall. The advantage of using this photocatalytic activity evaluation film is common to the photocatalytic activity evaluation methods of other embodiments described later.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a diagram for explaining the method for measuring the activity of a photocatalytic thin film according to the present invention, in which 1 is a substrate such as a tile, and a photocatalytic thin film 2 mainly composed of TiO ₂ is provided on the surface of the substrate 1. Has been formed.

The photocatalyst thin film 2 can be formed by coating Ti sulfate as a coating film and thermally decomposing it, by coating a alkoxide of Ti as a coating film and thermally decomposing it, and after coating a TiO ₂ sol as a coating film. There is a method for obtaining the same by heating, and further, in order to enhance the photoactivation effect, C is uniformly distributed in the TiO ₂ thin film.
Metals such as u, Ag, Fe, Co, Pt, Ni and Pd may be fixed.

To check whether or not the photocatalytic thin film 2 formed as described above is photoactive, the photocatalytic thin film 2
An alkali halide aqueous solution 3 such as potassium iodide or potassium chloride is dropped on the surface, and then the dropped alkali halide aqueous solution 3 is irradiated with ultraviolet rays by an ultraviolet lamp 4 for a predetermined time to adjust the pH of the alkali halide aqueous solution before irradiation. Then, the magnitude of the activity of the photocatalytic thin film 2 is determined from the difference between the pH after irradiation and the pH after irradiation.

FIG. 4 is a graph showing the relationship between the ultraviolet irradiation time and the amount of change in pH.
The test was conducted with a concentration of 0.1 mo1 / liter, a BLB fluorescent lamp 20W as the ultraviolet lamp 4, a distance between the photocatalytic thin film 2 and the ultraviolet lamp 4 of 20 cm, and an irradiation time of 60 minutes. As can be seen from this figure, in any of the anatase type, metal-supporting type, and rutile type photocatalyst thin films 2, the pH of the alkali halide aqueous solution 3 increases until the ultraviolet irradiation time reaches 30 minutes. .

[0024] The reason why the pH of an aqueous alkali halide solution 3 by the irradiation of ultraviolet rays is increased occurs following oxidation and reduction reactions simultaneously, OH by reduction reaction ^-
This is because (hydroxy ion) is generated. Oxidation reaction: 2I ⁻ + 2h ⁺ → I ₂ reduction reaction: O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ Therefore, when the pH of the alkali halide aqueous solution 3 is increased by the irradiation of ultraviolet rays, the photocatalytic thin film 2 has photoactivity. Can be said to be.

FIG. 5 is a graph showing the relationship between R30 and the amount of change in pH. Here, R30 is the ratio (%) of the gas (methyl mercaptan etc.) that has decreased 30 minutes after the irradiation with ultraviolet rays.
From this figure, it can be seen that there is a positive correlation between R30 and the amount of change in pH. That is, the amount of change in pH serves as an indicator of the presence or absence of photoactivity.

In the above embodiment, the amount of change in pH is p
H meter or pH measurement sheet 5
In the embodiment of FIG.
The mixed solution added with the H indicator is dropped on the surface of the photocatalyst thin film 2, and then the dropped mixed solution is irradiated with ultraviolet rays for a predetermined time, and the magnitude of the activity of the photocatalytic thin film 2 is judged by the change in the color of the mixed solution.

As the pH indicator, bromocresol purple is suitable because the pH of the aqueous solution of alkali halide 3 before irradiation with ultraviolet rays is about 4.5 and the pH after irradiation with ultraviolet rays is 5.5 to 6.5.

In the first and second embodiments, the aqueous solution of alkali halide 3 or the mixed solution of the aqueous solution of alkali halide 3 and the pH indicator added thereto is dropped onto the surface of the photocatalyst thin film 2. The spread of the dropped liquid varies for each case, so that a constant liquid thickness cannot be secured, and the reaction area may differ from substrate to substrate.

The method shown in FIG. 2 solves this problem. In this method, the alkali halide aqueous solution 3 is used.
After dripping, etc. on the surface of the photocatalyst thin film 2, the alkali halide aqueous solution 3 is pressed by a transparent plate 6 such as a glass plate to make it have a constant thickness and prevent it from drying.

Further, the liquid such as the alkali halide aqueous solution 3 is required that the surface of the substrate 1 is horizontal.
It is difficult to determine the activity of the photocatalytic thin film formed on a vertical surface such as an existing wall surface or the ceiling surface.

This is solved by the method shown in FIG. 3. In this method, the activity measuring film 7 is brought into close contact with the surface of the photocatalytic thin film 2 formed on the surface of the substrate 1, and the activity is measured in this state. The film 7 is irradiated with ultraviolet rays, and the magnitude of the activity of the photocatalytic thin film 2 is judged by the color change of the activity measuring film 7. Here, the activity measuring film 7 is obtained by drying a mixed solution of an organic binder to which an aqueous solution of an alkali halide such as potassium iodide or potassium chloride and a pH indicator are dried to form a film. The organic binder used in this example is a water-soluble resin (emulsion), which forms a film when dried and does not dissolve (emulsion) even if it comes into contact with water again. Even after drying, KI, pH indicator and a trace amount of water are dispersed in the film,
Not a little present on the film surface.

As described above, according to the method for measuring the activity of the photocatalyst thin film according to the first embodiment, the aqueous solution of alkali halide is dropped onto the surface of the photocatalyst thin film formed on the surface of the substrate such as the tile, and the dropped halogen. The aqueous alkali chloride solution is irradiated with ultraviolet rays for a predetermined time, and the activity of the photocatalytic thin film is judged from the difference between the pH of the alkali halide solution before irradiation and the pH after irradiation. The presence or absence of the activity of the photocatalytic thin film can be determined more easily and more rapidly than the method described above or the method of measuring the number of dead bacteria.

Further, according to the method for measuring the activity of the photocatalytic thin film according to the second embodiment, since the mixed solution of the pH indicator added to the aqueous solution of alkali halide is dropped on the surface of the photocatalytic thin film, the pH meter and the pH are adjusted. The activity of the photocatalytic thin film can be measured by the change in color of the mixed liquid itself without using a measurement sheet, which is more convenient.

In particular, if a transparent plate such as a glass plate is placed on the surface of the substrate after dropping the above-mentioned alkali halide aqueous solution or a mixed solution of the alkali halide aqueous solution and the pH indicator, the alkali halide aqueous solution, etc. Since the thickness of the product becomes constant and it becomes difficult to dry, it is possible to make a more accurate judgment.

Further, the organic binder is an aqueous solution of an alkali halide such as potassium iodide or potassium chloride, and pH.
By measuring the activity of the photocatalyst thin film with the photocatalyst thin film activity measurement film formed by drying the mixed solution containing the indicator and forming it into a film, the tiles after the implementation, specifically the ceiling surface or It is possible to easily measure the activity of the photocatalytic thin film formed on the tile on which it is difficult to drop the measurement liquid because the vertical surface is formed.

Those who use a solution containing colored metal ions
Method : The photocatalytic activity evaluation method of this embodiment is a method in which a solution containing colored metal ions is applied to the surface to be evaluated (the surface of the active substance (TiO ₂ ) or the like), and then the surface is irradiated with ultraviolet rays, before and after irradiation. It is characterized in that the change in color of the surface is measured and the photocatalytic activity is evaluated based on the amount of change in color.

In the method of this embodiment, for example, when the colored metal is silver, the following reactions occur. Ag ⁺ + e ⁻ → Ag ↓ Here, e ⁻ is an electron generated by photocatalytically active substance (TiO ₂ or the like) irradiated with ultraviolet rays. By the reaction of the above formula,
Ag is deposited on the surface to be evaluated (such as the TiO ₂ surface) and the surface turns brown or black. The photocatalytic activity is evaluated by this change in color.

Examples of preferred colored metals used in this method are Ag, Cu, Au, Pb, Ni, Co and F.
e, Sn, Pd, Ge, Mo, V, Tl, In, Cr,
Cd etc. can be mentioned.

Examples of such solutions include silver nitrate, silver lactate, silver sulfate, silver chlorate, silver fluoride, platinum sulfate, palladium rhodanide, palladium sulfate, gold (I) chloride, gold (II) chloride, and gold (II) sulfate. Cuprous acetate, cuprous acetate, cupric acetate, cupric sulfate, cupric chloride, cupric bromide, cupric nitrate, cupric chlorate, cupric rhodanide, ferrous chloride , Ferric chloride, ferrous sulfate, ferric sulfate, ferrous iodide, ferrous bromide, ferric bromide, ferric oxalate, ferrous acetate, ferric acetate, Ferrous chlorate, ferric chlorate, ferrous nitrate, ferric nitrate, ferrous thiosulfate, ferrous rhodanide, ferric rhodanide, cobalt chloride, cobalt sulfate, cobalt iodide, Cobalt bromide, cobalt acetate, cobalt chlorate, cobalt nitrate, nickel chloride, nickel sulfate, nickel iodide, nickel bromide, nickel acetate Chlorine acid nickel, nickel nitrate,
Examples thereof include nickel rhodanide.

An experiment for evaluating the photocatalytic activity using the Ag coloration amount as an index was conducted under the following conditions. Surface to be evaluated: TiO ₂ sol was formed into a coating film on a matte wall tile (substrate: ceramic wall tile, surface: glaze layer), and after heating, Cu was immobilized by photoreduction to a thickness of 0. A 5 μm TiO ₂ layer (supporting Cu) was formed (antibacterial tile). For details of the manufacturing method of this antibacterial tile, refer to Japanese Patent Application No. 5-313061.

Colored metal ion aqueous solution: silver nitrate (AgN
An aqueous solution containing 1 wt% of O ₃ ) was used. Aqueous solution application: The tile was dipped in the aqueous solution. It is also possible to use brush coating or spraying.

Light irradiation: Using a BLB fluorescent lamp (black light fluorescent lamp, main wavelength 365 mm), the tile was irradiated with light for 90 seconds. Aqueous solution wiping: The aqueous solution on the tile surface was wiped off with a Kim towel.

Color difference ΔE measurement: The amount of Ag coloration of the tile was measured and the difference from the amount of coloration before irradiation (before coating) was determined. The measurement was performed using a color difference meter ND300A manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS
Z8729 (1980) and Z8730 (1980)
Based on. E. coli viability test: An E. coli viability test was performed on the same antibacterial tile surface prepared above. For the details of the test, the method described in Japanese Patent Application No. 05-313061 was adopted.

At the stage of forming the TiO ₂ layer, the degree of photocatalytic activity was changed in several stages by manipulating the amount of Cu immobilized, and the above test was conducted several times. In addition, when the amount of Cu immobilized is changed, the photocatalytic activity can be changed by the electron-trapping effect of Cu. FIG. 6 is a graph showing the relationship between Ag coloration amount (horizontal axis) and Escherichia coli viability (antibacterial activity).

As shown in FIG. 6, the color difference ΔE
It was found that the larger the ratio, the lower the survival rate of E. coli, that is, the higher the antibacterial activity. From this, it was found that the Ag coloration amount is a good index for quantitatively evaluating the photocatalytic activity.

Using an aqueous solution containing an easily reducing metal ion
The method for evaluating the photocatalytic activity of this embodiment is to apply an aqueous solution containing a readily reducible metal ion to the surface to be evaluated, and then irradiate the surface with ultraviolet rays to adjust the pH of the aqueous solution before and after irradiation.
It is characterized in that the change is measured and the photocatalytic activity is evaluated based on the pH change amount.

In the method of this aspect, for example, when the aqueous solution is an AgNO ₃ aqueous solution, the following reaction occurs. _{AgNO 3 + H 2 O → Ag} + + NO 3 - + H 2 O 2H 2 O + 4h + → O 2 + 4H + ( ^{oxidation) Ag + + e - → Ag} ↓ ( reduction) produced in the above reaction H ⁺ is in an aqueous solution system Since it increases, the pH of the aqueous solution decreases. The photocatalytic activity of the surface to be evaluated is evaluated by this pH decrease.

In the method of the present embodiment, it is preferable that the metal ion used is easily reducible when the standard electrode potential of the metal is more positive than the potential at the lower end of the conduction band of the photocatalyst. Examples of such metals include Ag, Cu, Au, Pb, Ni, Co, Fe, Sn and P when the photocatalyst is TiO _2.
Examples thereof include d, Ge, Mo, V, Tl, In, Cr and Cd.

Under the following conditions, an experiment of a method for evaluating the photocatalytic activity was carried out using the pH change of the aqueous solution containing the easily reducing metal ion as an index. Surface to be evaluated: An antibacterial tile prepared by the same method as in the case of the Ag coloration amount described above was prepared. However, the thickness of the TiO ₂ thin film was 0.3 μm. The supporting metal was Ag. Aqueous solution containing easily reducing metal ions: Silver nitrate (AgN
An aqueous solution containing 1 wt% of O ₃ ) was used.

Drop of aqueous solution: 0.15 ml of the above aqueous solution was dropped onto the surface of the tile. Light irradiation BLB fluorescent lamp (black light fluorescent lamp, main wavelength 365 mm) is used, and the UV illuminance is about 10 W / cm ^2.
Lighted for minutes.

Recovery of aqueous solution: After irradiation with light, the aqueous solution was recovered with a water absorbing sheet. pH measurement: The pH of the collected aqueous solution was measured with a pH meter (manufactured by Horiba, compact pH meter B-212) to determine the difference from the pH of the original aqueous solution.

E. coli viability test: An E. coli viability test was performed on the same antibacterial tile surface prepared above. At the stage of forming the TiO ₂ layer, the degree of photocatalytic activity was changed in several stages by manipulating the fixed amount of Ag, and the above test was performed several times.

FIG. 7 shows the pH change of the silver nitrate aqueous solution (vertical axis).
It is a graph showing the relationship between and antibacterial activity (horizontal axis). In the antibacterial activity on the horizontal axis, “+++” means that the survival rate of E. coli is 10% when the sample is contacted with the tile for 30 minutes.
It shows that it was the following. Similarly, the survival rate of "++" is 10 to 30%, "+" is 30 to 70%, and "-" is 70%.
The above is shown.

As shown in FIG. 7, there is a clear correlation between pH change and antibacterial activity.
From this, it was found that the pH change of the aqueous silver nitrate solution is a good index for quantitatively evaluating the photocatalytic activity. In the case of an aqueous solution of silver nitrate, it is possible to perform the double evaluation of the discoloration due to the above-described silver precipitation and the pH change of the aqueous solution at the same time, and there is also an advantage that the evaluation becomes more reliable.

Method using a substance having a double bond ; The photocatalytic activity evaluation method of this embodiment is such that a substance having a double bond is applied to a surface to be evaluated, and then the surface is irradiated with ultraviolet rays,
The photocatalytic activity of the surface to be evaluated is evaluated by observing a change due to the cleavage reaction of the substance at that time.

Here, the types of changes based on the cleavage reaction of the substance having a double bond include, for example, changes in color, changes in contact angle at the time of dropping a solvent, changes in specific gravity, and the like. Of these, it is color that is easy to measure quantitatively.

Examples of the substance having such a double bond include polymers such as elastomers, polyenes and ABS. Of these, substances containing elastomers such as rubber and gum arabic are preferable because they have appropriate reactivity.

Among those that are present in our daily lives, cellophane adhesive tape (so-called cellophane tape) is preferable as the photocatalytic activity evaluation film used in the photocatalytic activity evaluation method of this embodiment. That is, the evaluation reaction substance (rubber or the like) can be easily attached to the surface to be evaluated with a substantially uniform thickness. In addition, since the cloth and the adhesive substance are transparent, the light is almost completely transmitted to the surface to be evaluated upon irradiation, and the color measurement of the adhesive layer is not disturbed.

The mechanism of discoloration is considered as follows. Rubber-based materials are mainly used as adhesives for cellophane tape. Even if rubber bands are naturally left unattended, they are oxidized by oxygen in the air to lose elasticity and become tattered, that is, rubber is relatively easily decomposed. Rubber generally exhibits elasticity because it has many double bonds. The double bond was destroyed by the oxidation reaction, and the elasticity was lost. It is considered that the rubber used in the cellophane tape was oxidized and deteriorated by accelerating the oxidation reaction using a photocatalyst, and thus the adhesive was discolored. Although the above-mentioned reaction proceeds slowly only by irradiating it with ultraviolet rays, it will occur even in a short time of about 30 minutes by adding a photocatalyst. Therefore, the photocatalytic activity can be evaluated by quantifying the degree of discoloration by light irradiation for a relatively short time.

In order to realize functions such as deodorization, sterilization and antifouling utilizing photocatalytic reaction in everyday space, a wall or ceiling of the space is constructed by using a building material having a thin film of photocatalyst on its surface, such as tile. It is possible to construct it. In that case, according to the method using this cellophane tape, it is possible to easily visually judge that the photocatalytic reaction is working at the site where the construction is performed.

Under the following conditions, an experiment for evaluating the photocatalytic activity using the color change of cellophane tape as an index was conducted. Surface to be evaluated: Ordinary bright wall tile (base: ceramic tile, surface: glaze layer) as it is, on which a photocatalytically active thin film made of anatase TiO ₂ was formed (thickness: about 1 μm, 780 ° C) (Fired), and a rutile type TiO ₂ thin film formed on the tile and a photocatalytically active thin film carrying Cu (thickness: about 1 μm, 9
Three samples (fired at 00 ° C) were prepared. Regarding the method of forming a thin film and the method of supporting Cu, Japanese Patent Application No. 5-3130
See 61.

Cellotape: Cellotape (trade name) manufactured by Nichiban Pharmaceutical Co., Ltd. was used. This cellophane tape was attached to the surface to be evaluated. Light irradiation: Using a BLB fluorescent lamp (black light fluorescent lamp, main wavelength 365 mm), light was applied for 30 minutes at an ultraviolet illuminance of about 1.0 mW / cm ² . At this time, the illuminance meter UIT101-365PD manufactured by Ushio Inc. is used to measure the ultraviolet illuminance.
Was used. For comparison, a non-irradiated (light-shielded) one was also prepared.

Color difference ΔE measurement: The chromaticity of the cellophane tape before and after irradiation was measured to determine the color difference between the two. As the color difference meter, ND-300A manufactured by Nippon Denshoku Co., Ltd. was used, the L ^* a ^* b ^* color system was selected, and the color difference ΔE ^* was calculated by the following formula. ΔE ^* = ((ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* )
² ) ^1/2

The test results obtained are shown in Table 1.

[0065]

[Table 1]

FIG. 8 is a summary of the results of Table 1 and is a graph showing the color difference of the cellophane tape adhesive stuck on the tile surface.

As shown in Table 1 and FIG. 8, almost no color difference is observed in the case of ordinary tiles or when light is shielded, whereas in the case of irradiation of anatase type thin film and rutile type thin film, , A large color difference is observed. From this, it was found that the color change of the cellophane tape is a good index for quantitatively evaluating the photocatalytic activity.

The photocatalytic activity evaluation film of one embodiment of the present invention is substantially transparent and is characterized by containing a halogen ion-containing aqueous solution and a pH indicator. The photocatalytic activity evaluation film according to another aspect of the present invention is substantially transparent and is characterized by containing a solution containing ions of a colored metal. The production method and use method of these films are as described above.

[0069]

As is apparent from the above description, the present invention exhibits the following effects. The photocatalytic activity can be evaluated more easily and rapidly compared to the conventional method of monitoring with a gas chromatograph and the method of measuring the number of dead bacteria. It is also possible to measure a tilted surface to be evaluated or the surface of a tile that has already been pasted on site.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method for measuring the activity of a photocatalytic thin film according to an example of the present invention.

FIG. 2 is a diagram illustrating a method for measuring activity of a photocatalytic thin film according to an example in which a transparent member is placed on an evaluation reaction substance.

FIG. 3 is a diagram illustrating a method for measuring activity of a photocatalytic thin film according to an example using an activity measuring film.

FIG. 4 is a graph showing a relationship between an ultraviolet irradiation time and a change amount of pH.

FIG. 5 is a graph showing the relationship between R30 and the amount of change in pH.

FIG. 6 Ag coloration amount (horizontal axis) and Escherichia coli viability (antibacterial activity)
It is a graph showing the relationship with.

FIG. 7 is a graph showing the relationship between pH change (vertical axis) and antibacterial activity (horizontal axis) of an aqueous silver nitrate solution.

FIG. 8 is a graph showing the color difference of a cellophane tape adhesive attached to the surface of a tile.

[Explanation of symbols]

1 substrate 2 photocatalytic thin film 3 alkali halide aqueous solution 4 ultraviolet lamp 5 pH measurement sheet 6 glass plate 7
Activity measurement film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichiro Norimoto, 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture Totoki Kikai Co., Ltd. (72) Shin Hayakawa, Nakajima, Kitakyushu, Kitakyushu 2-1-1 1-1 Totoki Co., Ltd. (72) Inventor Tatsuhiko Kuga 2-1-1 1-1 Nakajima, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture Totoki Co., Ltd.

Claims (36)

[Claims] 1. A step of applying a substance (evaluation reaction substance) that reacts with holes or electrons generated when a substance having photocatalytic activity (active substance) is irradiated to the surface to be evaluated, and irradiating the surface with ultraviolet rays. And a step of quantifying the reaction amount of the reaction substance to be evaluated, the method for evaluating photocatalytic activity. 2. The photocatalytic activity evaluation method according to claim 1, wherein the reaction of the evaluation reaction substance is an oxidation or reduction reaction. 3. The photocatalytic activity evaluation method according to claim 1, wherein the reaction amount is quantified by measuring the pH change of the evaluation reaction substance. 4. The method for evaluating photocatalytic activity according to claim 1, wherein the reaction amount is quantified by measuring the change in color of the evaluation reaction substance. 5. The method for evaluating photocatalytic activity according to claim 1, wherein the evaluation reaction substance is applied to the surface to be evaluated by bringing a transparent member coated with the evaluation reaction substance into close contact with the surface to be evaluated. 6. A film containing an evaluation reaction substance or a film coated with an evaluation reaction substance (photocatalytic activity evaluation film)
The method for evaluating photocatalytic activity according to any one of claims 1 to 4, wherein the reaction substance for evaluation is applied to the surface to be evaluated by sticking to the surface to be evaluated. 7. A film containing an evaluation reaction substance and an indicator for quantifying the reaction amount of the evaluation reaction product, or a film (photocatalytic activity evaluation film) coated with the film is attached to the surface to be evaluated so as to cover the evaluation reaction product. The photocatalytic activity evaluation method according to claim 1, which is applied to an evaluation surface. 8. An aqueous solution containing halogen ions is applied to a surface to be evaluated, and then the surface is irradiated with ultraviolet rays to measure the pH change of the aqueous solution before and after irradiation, and the photocatalytic activity is evaluated based on the pH change amount. A method for evaluating photocatalytic activity, comprising: 9. A photocatalyst is prepared by applying an aqueous solution containing halogen ions and a pH indicator to a surface to be evaluated, and then irradiating the surface with ultraviolet rays to measure the change in color of the aqueous solution before and after irradiation, and based on the amount of change in color. A method for evaluating photocatalytic activity, which comprises evaluating the activity. 10. The method for evaluating photocatalytic activity according to claim 8, wherein after the aqueous solution is applied to the surface to be evaluated, a transparent member is placed on the application part and ultraviolet rays are radiated through the transparent member. 11. A film containing an aqueous solution containing a halogen ion and a pH indicator, or a film coated with them (a photocatalytic activity evaluation film) is brought into close contact with the surface to be evaluated, and then the surface is irradiated with ultraviolet rays through the film. A method for evaluating photocatalytic activity, which comprises measuring the color change of the film before and after irradiation and evaluating the photocatalytic activity based on the amount of color change. 12. The method for evaluating photocatalytic activity according to claim 11, wherein the photocatalytic activity evaluation film is formed into a film after adding and mixing an aqueous solution containing a halogen ion and a pH indicator to an organic binder. 13. The method for evaluating photocatalytic activity according to claim 11, wherein the photocatalytic activity evaluation film is obtained by absorbing an aqueous solution containing a halogen ion and a pH indicator in a water-absorbing substance. 14. The method for evaluating photocatalytic activity according to claim 8, wherein the aqueous solution containing halogen ions is an aqueous alkali halide solution. 15. A solution containing colored metal ions is applied to a surface to be evaluated, and then the surface is irradiated with ultraviolet rays to measure the change in color of the surface before and after irradiation, and the photocatalyst is based on the amount of change in color. A method for evaluating photocatalytic activity, which comprises evaluating the activity. 16. The photocatalytic activity according to claim 15, wherein a solution containing the colored metal ions is applied to the surface to be evaluated, a transparent member is placed on the application portion, and ultraviolet rays are radiated through the transparent member. Evaluation method. 17. A film containing a solution containing colored metal ions, or a film coated with the solution (a photocatalytic activity evaluation film) is brought into close contact with the surface to be evaluated, and then the surface is irradiated with ultraviolet rays through the film, A method for evaluating photocatalytic activity, which comprises measuring a change in color of the surface to be evaluated or the film before and after irradiation and evaluating the photocatalytic activity based on the amount of change in color. 18. The photocatalytic activity evaluation method according to claim 17, wherein the photocatalytic activity evaluation film is formed into a film after adding and mixing a solution containing colored metal ions to an organic binder. 19. The photocatalytic activity evaluation method according to claim 17, wherein the photocatalytic activity evaluation film is obtained by absorbing a solution containing a colored metal ion in a water-absorbing substance. 20. The method according to claim 15, wherein the colored metal is silver.
19. The method for evaluating photocatalytic activity according to any one of 19 above. 21. An aqueous solution containing an easily reducing metal ion is applied to a surface to be evaluated, and then the surface is irradiated with ultraviolet rays,
A method for evaluating photocatalytic activity, which comprises measuring the pH change of the aqueous solution before and after irradiation and evaluating the photocatalytic activity based on the pH change amount. 22. An aqueous solution containing a readily reducible metal ion and a pH indicator is applied to the surface to be evaluated, and then the surface is irradiated with ultraviolet rays to measure the change in color of the aqueous solution before and after irradiation,
A method for evaluating photocatalytic activity, which comprises evaluating photocatalytic activity based on the amount of color change. 23. The method for evaluating photocatalytic activity according to claim 21, wherein the aqueous solution is dropped onto the surface to be evaluated, a transparent member is placed on the dropping portion, and ultraviolet rays are radiated through the transparent member. 24. An aqueous solution containing an easily reducing metal ion and a film containing a pH indicator, or a film coated with them (a film for evaluating photocatalytic activity) is adhered to a surface to be evaluated, and then the film is passed through the surface to emit ultraviolet light. And a change in color of the surface to be evaluated or the film before and after irradiation, and the photocatalytic activity is evaluated based on the amount of change in color. 25. The photocatalytic activity evaluation film, wherein the organic binder contains an easily reducing metal ion in an aqueous solution and p.
25. The photocatalytic activity evaluation method according to claim 24, which is formed into a film after adding and mixing the H indicator. 26. The photocatalytic activity evaluation method according to claim 24, wherein the photocatalytic activity evaluation film is obtained by absorbing an aqueous solution containing a readily reducing metal ion and a pH indicator in a water-absorbing substance. 27. An aqueous solution containing a colored and easily reducing metal ion is applied to a surface to be evaluated, and then the surface is irradiated with ultraviolet rays to change the color of the surface before and after irradiation and the pH change of the aqueous solution. A method for evaluating photocatalytic activity, which comprises measuring and evaluating photocatalytic activity based on the amount of color change and the amount of pH change. 28. The photocatalytic activity evaluation method according to claim 21, wherein the aqueous solution is an aqueous silver nitrate solution. 29. A photocatalytic activity of a surface to be evaluated is obtained by applying a substance having a double bond to the surface to be evaluated, irradiating the surface with ultraviolet rays, and observing a change due to the cleavage reaction of the substance at that time. A method for evaluating photocatalytic activity, which comprises: 30. A film containing a substance having a double bond or a film coated with a substance having a double bond (photocatalytic activity evaluation film) is brought into close contact with the surface to be evaluated, and then the surface is irradiated with ultraviolet rays, A method for evaluating a photocatalytic activity, which comprises evaluating a photocatalytic activity of a surface to be evaluated by observing a change due to a cleavage reaction of the substance at the time. 31. The change in color is a change in color.
Or the method for evaluating photocatalytic activity according to item 30. 32. The method for evaluating photocatalytic activity according to claim 29, wherein the substance having a double bond is a substance containing an elastomer. 33. The photocatalytic activity evaluation method according to claim 29, wherein the substance having a double bond is a substance containing gum arabic. 34. The photocatalytic activity evaluation method according to claim 30, wherein the photocatalytic activity evaluation film is a cellophane adhesive tape. 35. A photocatalytic activity evaluation film, which is substantially transparent and contains an aqueous solution containing a halogen ion and a pH indicator. 36. A photocatalytic activity evaluation film, which is substantially transparent and contains a solution containing ions of a colored metal.