JP2001137661A - Method of manufacturing photocatalytic filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a photocatalytic filter carrying a photocatalyst on a part to be irradiated with excited light and carrying the photocatalyst selectively on a part to be more strongly irradiated with the excited light. SOLUTION: The photocatalytic filter is manufactured by scattering the photocatalyst to carry at least on one surface of a filter base material having air permeability and the photocatalyst is scattered preferably to uniformize the carried quantity of the photocatalyst or to adjust the angle to the angle of the excited light irradiation at the time of using the photocatalytic filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a photocatalyst filter having excellent light receiving ability for excitation light, and more particularly, to a method for manufacturing a photocatalyst filter capable of adjusting a loading amount of a photocatalyst according to a situation irradiated with excitation light. About the method.

[0002]

2. Description of the Related Art Problems of conventional environmental pollution caused by industrially generated odors and harmful chemical substances in factories, and odors caused by wastes in service industries such as restaurants and hotels that discharge a large amount of waste. In addition, with the recent increase in amenity-oriented, the problem of indoor environmental pollution due to odors and harmful chemical substances in general living spaces, for example, indoors and cars, has been increasing, and the need for the removal of these harmful substances has been increasing. It is growing rapidly.

[0003] As a method of removing harmful substances such as odors and harmful chemical substances, porous substances such as activated carbon and zeolite,
A so-called adsorption removal by an adsorbent is common. However, the adsorbent only shows an adsorbing effect on most harmful substances, and when a certain amount of harmful substances is adsorbed, the removal performance is significantly reduced, or harmful substances once adsorbed depending on the ambient temperature and concentration of harmful substances. There is a problem that the substance is detached.

In order to solve such a problem, a method of decomposing and removing harmful substances using a catalyst has been devised.
Various materials having a capability of decomposing and removing harmful substances are known, and among them, a photocatalyst member represented by titanium oxide has recently received a great deal of attention. For example, Cundall et al.
J. Oil. Chem. Assoc. 1978, 61,
In 351, when titanium oxide is irradiated with ultraviolet light,
It is reported that alcohol is decomposed in a mixed system of water and alcohol. Further, JP-A-61-135669 reports that when a photocatalyst member such as zinc oxide is irradiated with ultraviolet light, a sulfur compound as a malodorous substance is decomposed. In the decomposition reaction by these photocatalyst members, the photocatalyst member is not consumed as the reaction proceeds, and its decomposition ability is semi-permanent as long as it is exposed to light. Such a photocatalytic reaction is an interfacial reaction, and the more efficiently the photocatalyst member contacts the decomposition target, the more efficiently it proceeds. Therefore, as the shape of the photocatalyst member,
It is preferable that the powder has a large specific surface area,
It is difficult to use the photocatalyst member as powder, and it is necessary to carry and fix the photocatalyst member on an appropriate support using some method.

[0005] For example, Japanese Patent Application Laid-Open No.
No. 22 and Japanese Utility Model Application Laid-Open No. 2-45130 disclose a method of supporting a photocatalyst on a honeycomb structure having excellent air permeability. However, since the photocatalyst is generally supported on the entire surface thereof, it is practical. In light irradiation, there is a portion that becomes a shadow, and there is a problem that light does not shine on a part or most of the supported photocatalyst and the photocatalyst does not function.

When a photocatalyst is used for deodorization, the photocatalyst may be used in combination with an adsorbent as disclosed in, for example, JP-A-62-53657. Often done. However, when the adsorbent and the photocatalyst are used in combination, the adsorbent and the photocatalyst are present together even in a portion where the light irradiation amount is large, for example, in a portion close to the light source, so that part or most of the light is adsorbed. And light energy is wasted.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to carry a photocatalyst mainly on a portion irradiated with excitation light,
An object of the present invention is to provide a method for manufacturing a photocatalyst filter that supports a photocatalyst mainly in a portion where excitation light is more strongly irradiated.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention.

(1) A method for producing a photocatalyst filter, wherein a photocatalyst is sprayed and carried on at least one surface of a filter substrate having air permeability.

(2) A method for manufacturing a photocatalyst filter according to the invention (1), wherein the photocatalyst is sprayed so that the photocatalyst carrying amount is uniform.

(3) The method for producing a photocatalyst filter according to the invention (1), wherein the photocatalyst is sprayed at the same angle as the irradiation of the excitation light when the photocatalyst filter is used.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a method for producing a photocatalyst filter, wherein a photocatalyst is dispersed and supported on at least one surface of a filter substrate having air permeability, and preferably the photocatalyst loading amount is uniform. Or a method for producing a photocatalyst filter, which comprises spraying a photocatalyst at an angle with irradiation of excitation light when a photocatalyst filter is used. According to the present invention, the photocatalyst is optimally supported in accordance with the state of irradiation of the excitation light, so that a photocatalyst filter that functions efficiently with a minimum loss of the photocatalyst and the excitation light can be obtained.

The photocatalyst according to the present invention is 0.5 to 5 e
V, preferably a photoreactive semiconductor that has a bandgap of 1 to 4 eV and provides a photocatalytic reaction, and exhibits functions such as antibacterial, antiviral, antifungal, deodorizing, and antifouling by irradiating with excitation light. It is a material to do. In particular, its antibacterial properties are excellent, and it not only suppresses the growth of bacteria, but also decomposes toxins generated when bacteria die and detoxifies them, and also decomposes dead bacteria. It is said that it does not deteriorate in a short period of time unlike conventional inorganic antibacterial agents and is permanent.

The photocatalyst according to the present invention includes metal oxide particles such as zinc oxide, tungsten oxide, titanium oxide, and cerium oxide. Among them, titanium oxide is most suitable for use in a living space because of its structural stability, ability to remove photoreactive harmful substances, and safety in handling, and is advantageously used as the photocatalyst of the present invention.
The titanium oxide according to the present invention may be a general-purpose titanium dioxide used as a white pigment (provided that the weathering treatment is completely or only partially performed), metatitanic acid, orthotitanic acid, hydrous titanium oxide, hydrated titanium oxide, and the like. Titanium oxides and hydroxides such as titanium oxide, titanium hydroxide and titanium peroxide are exemplified.

Among them, fine particle titanium oxide having a primary particle size of about several tens nm and having an anatase crystal structure is a relatively inexpensive and excellent photocatalyst. However, the titanium oxide according to the present invention is not limited to an anatase crystal structure, and may have a crystal structure such as rutile or brookite or an amorphous titanium oxide as long as it has a photocatalytic ability. . Examples of the shape of the titanium oxide include a cube, a sphere, a true sphere, a flake, and a nanocluster.

In addition to the above titanium compounds, organic titanates such as titanium alkoxides and titanium chelates may be used, so that a highly uniform and highly transparent photocatalyst layer can be formed.

Pt, Au, Ag, Cu, Pd, Ni, C
o, Fe, Zn, Mo, Ir, Bi, W, Os, Rh,
Compounds such as various metals such as Nb, Zr, Sn, V, Cr, and Ru, and compounds such as ions or oxides thereof may be supported or doped to form a composite.

The photocatalyst according to the present invention may be a microencapsulated photocatalyst coated with a porous substance such as silica or alumina-silica. It is preferable because it is excellent.

The filter substrate according to the present invention has air permeability, and is made of non-woven fabric, woven fabric, knitted fabric, net, net,
Mesh, cage, foam, sponge, honeycomb, felt and the like, the material is metal, glass, ceramics, inorganic substances such as carbon and cellulose, chitin,
Organic substances such as various synthetic resins can be used.

The filter substrate according to the present invention preferably has a deodorizing property, and may contain a deodorant. The deodorant according to the present invention is a chemical used mainly for the purpose of removing offensive odors, and specifically, an adsorbent as exemplified below, iron ascorbic acid, iron, metal phthalocyanine derivatives such as cobalt or manganese, and the like. Enzymatic deodorant, catechin, tannin, which are compounds contained in plant extract components,
Examples include deodorants using flavonoids and the like, oxidation catalysts such as manganese dioxide, vanadium pentoxide, osmium tetroxide, and bismuth trioxide, and far-infrared ceramics such as silicon carbide, silicon nitride, and barley stone. If necessary, a plurality of these deodorants may be used in combination, or a hybrid deodorant obtained by combining these deodorants may be used.

As the adsorbent according to the present invention, activated carbon,
Activated carbon impregnated, activated carbon fiber, natural and synthetic zeolites, activated alumina, activated clay, sepiolite, iron compounds such as iron oxide, zinc oxide, magnesium oxide, silica, silica-zinc oxide composite, silica-alumina-zinc oxide composite Products, composite phyllosilicates, ion exchange resins, or mixtures thereof. Among the adsorbents, a porous substance having a large surface area sometimes functions as a carrier for the photocatalyst, and thus is preferable.

The adsorbent according to the present invention is mainly composed of physical adsorption, in particular, the heat of adsorption of the odorous substance to be decomposed by the photocatalyst is preferably 11 kcal / mol or less, and the deodorizing property is saturated by the odorous substance. It is regenerated by the photocatalyst without any problems.

The adsorbent according to the present invention is preferably an aldehyde adsorbent, and an example of the aldehyde adsorbent is high silica zeolite. The high silica zeolite is chemically a crystal of an aluminosilicate metal salt like a normal zeolite, but particularly has a high ratio of silica to alumina in the crystal, and oxygen atoms in the silica structure have almost no basicity.

Such a high-silica zeolite does not participate in the formation of hydrogen bonds due to the Si—O—Si bond on the surface, exhibits hydrophobicity and does not adsorb water molecules, and thus can be used in a high humidity environment and a high temperature environment. It is also possible to efficiently adsorb aldehydes. Therefore, the high silica zeolite is sometimes called a hydrophobic zeolite.

Further, the high silica zeolite can adsorb not only aldehydes but also a wide range of odorous substances, for example, organic acids, ammonia, amines, ketones, sulfur-containing compounds such as hydrogen sulfide and mercaptans, and indoles. The adsorbent according to the present invention is particularly preferred.

The filter substrate according to the present invention may contain a substance having an affinity for microorganisms such as bacteria. As a substance having an affinity for the microorganisms according to the present invention, calcium phosphate compounds, chitin and chitosan,
Examples thereof include a polymer substance having an amino group such as polygalactosamine and polyethyleneimine, and lysozyme contained in egg white and the like, and a calcium phosphate compound is particularly preferable. Examples of the calcium phosphate compound include hydroxyapatite, fluorapatite, apatite compounds such as apatite antibacterial agents in which calcium of hydroxyapatite is replaced with silver, copper or zinc, and tricalcium phosphate, tetracalcium phosphate, and calcium hydrogen phosphate. No.

The deodorant, particularly the adsorbent and the substance having an affinity for microorganisms, may be contained in the filter base material in advance as described above, but the photocatalyst may be used without departing from the gist of the present invention. You may carry together using when carrying by spraying.

The photocatalyst of the present invention can be sprayed by dry spraying of a powdery photocatalyst as it is, or by wet spraying of a photocatalyst coating liquid dispersed in a liquid such as water or a liquid photocatalyst such as an organic titanate. Is also good.

Examples of the method of dry spraying include a spraying method by spraying, a spraying method by blowing air dispersed in the air, and a spraying method by free fall from the lower part of the hopper. The wet spraying methods include spray coating and curtain. Coating and die coating may be mentioned, but the method is not particularly limited to these methods.

In the wet spraying method, as a method for fixing the photocatalyst, for example, the photocatalyst can be sprayed after imparting adhesiveness to the filter substrate in advance. On the other hand, in wet spraying, a binder may be used in combination when the film forming property of the photocatalyst is not sufficient. Further, heat treatment such as drying or baking may be performed so that the fixing is sufficiently performed.

In the wet spraying, it is preferable that the photocatalyst liquid applied to the substrate has an appropriate viscosity so as not to flow, or is fixed promptly. In order to obtain an appropriate viscosity, for example, a chemical such as a viscosity modifier can be added, and in order to quickly fix it, for example, a relatively strong heat treatment can be performed while applying.

The kind of the binder used in the present invention is not particularly limited, and various binders such as a natural polymer such as starch, a modified polymer such as carboxymethyl cellulose, and a synthetic polymer such as polyvinyl alcohol may be used. Although it is possible, a thermoplastic polymer emulsion is preferable as a binder which can obtain sufficient adhesiveness without covering the surface of a photocatalyst or the like.

As the thermoplastic polymer emulsion, acrylic resins such as polyacrylonitrile and polyacrylate, styrene-acryl copolymer, styrene
Butadiene copolymer, ethylene-vinyl acetate copolymer,
Various copolymer resins such as vinyl chloride-vinyl acetate copolymer and ethylene-vinyl acetate-vinyl chloride copolymer, polypropylene, polyester, phenoxy resin, phenol resin, and butyral resin are exemplified.

The binder used in the present invention has high oxidation resistance and is resistant to photocatalysis, such as a fluororesin-based or silicon-resin-based antioxidant binder such as polytetrafluoroethylene, or a metal oxide. It is preferable to use an inorganic-organic composite binder such as a compound composite thermoplastic polymer emulsion, an inorganic binder, and an appropriate combination thereof. Among them, inorganic binders are preferred.Specific examples include saponite, hectorite, smectite group such as montmorillonite, vermiculite group, kaolinite, kaolinite such as halloysite-serpentine group, and other natural clay minerals such as sepiolite, and colloidal silica. , Colloidal alumina, modified products thereof, and synthetic inorganic polymer compounds.

The photocatalyst filter obtained according to the present invention can be used as an antibacterial agent, without departing from the spirit of the present invention.
Fungicide, antiviral agent, insect repellent, pest repellent, fragrance,
Various agents such as a hygroscopic agent, a humectant or a desiccant may be used in combination. As such antibacterial agents or fungicides, antiviral agents, inorganic antibacterial agents containing silver, zinc or calcium phosphate as main components, organic antibacterial agents such as benzimidazole, isothiazoline, pyrithione, chlorohexidine and the like. , High-molecular antibacterial agents such as chitin and chitosan, catechin and Meng Song bamboo extract extracted from tea and persimmon,
An antibacterial agent derived from a natural product such as hinokitiol, and a hybrid antibacterial agent obtained by combining these agents are exemplified.

It is preferable that the photocatalyst filter obtained by the present invention can be washed with water so that sulfate ions and nitrate ions which lower the photocatalytic performance can be washed and removed. In order to obtain washability, materials such as a filter substrate and a binder preferably have appropriate water resistance, and various chemicals such as a photocatalyst and a deodorant are preferably supported so as not to flow out into water. .

The photocatalyst filter obtained by the present invention may be subjected to various processings, and the processing contents which can be performed vary depending on the type of the filter base material. However, cutting processing, pleating processing, roll winding processing, honeycomb processing,
Framing and the like. The photocatalytic filter obtained by the present invention can be used in combination with a dust removing filter such as an electret filter, an antibacterial filter, a deodorizing filter, and the like. These various filters may be, for example, laminated or integrated at the time of framing to form a composite filter. At this time, it is preferable that light irradiation to the photocatalytic filter obtained by the present invention is not hindered. .

The photocatalyst filter obtained by the present invention has a suitable air permeability, so that it can be ventilated as desired, and the chance of removing odorous substances and harmful substances such as bacteria is preferably increased. Means for ventilating the photocatalytic filter obtained by the present invention is not particularly limited,
Methods using blowers such as sirocco type, axial flow type, propeller type, turbo type, radial type, cross flow type and other fan motors, natural wind or wind generated by exhaust fans such as ventilation fans and air conditioners such as air conditioners A method using heat convection, a method using an air current generated by movement of a passenger car, and the like.

As a method for irradiating the photocatalytic filter according to the present invention with excitation light, black light, insect trap, health lamp, germicidal lamp, fluorescent lamp for general lighting, high pressure mercury lamp, metal halide lamp, high pressure sodium lamp, etc. In addition to irradiating by providing a light source, irradiation of indirect light such as direct light and reflected light emitted from a light source incorporated in a photocatalytic air purifying device, leakage light leaking from a porous member, etc., fluorescent light Irradiation with indoor illumination light and irradiation with sunlight outdoors or near a window can be used. Irradiation of photocatalytic excitation light can be either continuous or intermittent,
In particular, there is a means which is installed inside a device having no light source and is irradiated with sunlight or room illumination light temporarily when the device is not used and the excitation light is not irradiated.

The method for producing a photocatalyst filter of the present invention comprises:
It is preferable to spray the photocatalyst at the same angle as the irradiation of the excitation light when using the photocatalyst filter so as to increase the density of the photocatalyst carried in the portion to be irradiated with the excitation light. As a method of dispersing the photocatalyst at the same angle as the excitation light irradiation, a dispersion method having the same spread as the excitation light irradiation (FIG. 1) as illustrated in FIG. 2 and a small spread as illustrated in FIG. A method of shaking the angle using a spraying method, and the like can be given.

The method for producing a photocatalyst filter of the present invention comprises:
The photocatalyst may be sprayed so that the photocatalyst carrying amount is uniform, and it is particularly preferable that the excitation light is a parallel ray such as sunlight, since the light irradiation on the photocatalyst filter is uniform.

According to the present invention, it is possible to manufacture a photocatalytic filter having excellent light receiving properties for excitation light. Above all, the photocatalyst filter obtained by the third invention of the present invention, as illustrated in FIG. 5, sprays the photocatalyst at an angle with the irradiation of the excitation light to reduce the amount of the photocatalyst carried in the portion irradiated with the excitation light. Since the density can be increased, the light receiving property of the excitation light is particularly excellent. Further, according to the present invention, the obtained photocatalyst filter has no or little photocatalyst in the shaded portion where the excitation light is difficult to be irradiated as illustrated in FIG. 5, so that the loss of the photocatalyst can be minimized. It is possible.

[0043]

EXAMPLES The present invention will be described below with reference to examples, but it should not be construed that the invention is limited thereto without departing from the spirit of the present invention.

Preparation Example 1 50% by weight of a commercially available titanium oxide as a photocatalyst and 50% by weight of a commercially available Na-montmorillonite as a binder were dispersed in water, mixed and stirred to prepare a coating solution. A photocatalyst coating liquid was used.

Preparation Example 2 A single-sided corrugated cardboard corresponding to the E-corrugated cardboard described in JIS-Z-0104 using a commercially available activated carbon sheet for the inner lining and the liner in accordance with the “corrugated cardboard for exterior” described in JIS-Z-1516 Then, a plurality of the single-faced cardboards were laminated to produce a corrugated honeycomb, which was used as a filter substrate of Preparation Example 2.

Example 1 The photocatalyst coating solution of Preparation Example 1 was applied to the filter base material of Preparation Example 2 by the spraying method shown in FIG.
The composition was spray-coated so as to be a weight% to produce a photocatalytic filter. This was used as the method for manufacturing the photocatalytic filter of Example 1.

Example 2 The photocatalyst coating solution of Preparation Example 1 was applied to the filter base material of Preparation Example 2 by the spraying method shown in FIG.
The composition was spray-coated so as to be a weight% to produce a photocatalytic filter. This was used as the method for manufacturing the photocatalyst filter of Example 2.

Example 3 The photocatalyst coating solution of Preparation Example 1 was uniformly spray-coated on the filter base material of Preparation Example 2 by the spraying method shown in FIG. A filter was manufactured. This was used as the method for manufacturing the photocatalytic filter of Example 3.

Comparative Example 1 The photocatalyst coating liquid of Preparation Example 1 was impregnated and applied to the filter substrate of Preparation Example 2 so as to be 10% by weight of the filter substrate on a dry weight basis to produce a photocatalyst filter. This was used as the method for manufacturing the photocatalytic filter of Comparative Example 1.

Comparative Example 2 In Preparation Example 2, instead of a commercially available activated carbon sheet, a commercially available activated carbon sheet was impregnated and coated with the photocatalyst coating solution of Preparation Example 1 so that the dry weight averaged 10% by weight of the activated carbon sheet. A photocatalyst filter was manufactured in the same manner as in Preparation Example 5 except that a photocatalyst sheet was used. This was used as the method for manufacturing the photocatalytic filter of Comparative Example 2.

The following performance tests were performed on the photocatalyst filters obtained by the production methods of the examples and the comparative examples.

<Photolysis Deodorization Performance 1> The photocatalyst filters of Examples and Comparative Examples were placed on the bottom of a 5.6 liter closed vessel equipped with a 6 W black lamp in the same manner as in FIG. Was placed. Acetaldehyde was injected into the container to adjust the concentration of acetaldehyde when the adsorption equilibrium was reached to 15 ppm. Then, the black lamp was turned on to irradiate ultraviolet rays, and the concentration of acetaldehyde (ppm) in the container 5 minutes after the start of irradiation was measured. It was measured by gas chromatography to determine the acetaldehyde removal rate (% / min).

<Photodecomposable and deodorizable 2> The photocatalyst filters of the examples and comparative examples were allowed to stand in a 5.6 liter closed container made of a near-ultraviolet transparent acrylic plate. Acetaldehyde was injected into the vessel to adjust the concentration of acetaldehyde when the adsorption equilibrium was reached to 15 ppm. Then, the sun was irradiated outdoors on a sunny day, and the acetaldehyde concentration in the vessel 5 minutes after the start of irradiation (ppm ) Was measured by gas chromatography to determine the acetaldehyde removal rate (% / min).

Table 1 shows the results of the tests performed according to the above method and the evaluation of the performance.

[0055]

[Table 1]

From the results shown in Table 1, it can be seen that the photocatalytic filter obtained by the present invention has high photocatalytic performance and excellent ability to remove harmful substances such as deodorization. Above all, to increase the density of the photocatalyst carried in the portion where the excitation light is irradiated,
The photocatalyst filter obtained by the present invention when the photocatalyst is sprayed at the same angle as the irradiation of the excitation light when using the photocatalyst filter, particularly excellent photocatalytic performance is obtained by irradiating the excitation light at a predetermined angle, On the other hand, the photocatalyst filter obtained by the present invention when the photocatalyst is sprayed so that the photocatalyst carrying amount becomes uniform can obtain excellent photocatalytic performance by irradiating relatively uniform and parallel excitation light such as sunlight. You can see that.

[0057]

According to the present invention, a photocatalyst is supported mainly on a portion to be irradiated with excitation light, and a photocatalyst filter is manufactured by mainly supporting a photocatalyst on a portion to be more strongly irradiated with excitation light. It is possible to obtain a photocatalyst filter with small photocatalyst and excitation light loss and excellent photocatalytic performance. The photocatalyst filter obtained by the present invention is particularly used as a deodorizing filter mounted on various air conditioners such as an air purifier, a deodorizer, an air conditioner, a ventilation device, a humidifier or a dehumidifier, and a filter for removing harmful substances such as antibacterial or antiviral. It is useful.

[Brief description of the drawings]

FIG. 1 is a plan view showing excitation light irradiation on a photocatalytic filter obtained by one embodiment of the present invention.

FIG. 2 is a plan view showing a method for dispersing a photocatalyst according to one embodiment (Example 1) of the present invention.

FIG. 3 is a plan view showing a method for dispersing a photocatalyst according to one embodiment (Example 2) of the present invention.

FIG. 4 is a plan view showing a method for dispersing a photocatalyst according to one embodiment (Example 3) of the present invention.

FIG. 5 is a diagram for explaining a relationship between a photocatalyst supported on a photocatalyst filter obtained by one embodiment of the present invention and excitation light irradiation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photocatalyst filter 2 Photocatalyst excitation light lamp 3 Filter base material 4 Spray coater 5 Boundary line showing spread range of coating liquid 6 Spray coating liquid 7 Line showing movement range (angle of swing) of spray coater 8 Movement of spray coater Line indicating the range (horizontal movement distance in the vertical direction) 9 Partially enlarged cross-sectional view of a filter substrate composed of two meshes 10 Photocatalyst 11 Arrows indicating directions of scattering of the photocatalyst and excitation light irradiation

Claims (3)

[Claims] 1. A method for producing a photocatalyst filter, wherein a photocatalyst is dispersed and carried on at least one surface of a filter substrate having air permeability. 2. The method for producing a photocatalyst filter according to claim 1, wherein the photocatalyst is sprayed so that the photocatalyst carrying amount is uniform. 3. The method according to claim 1, wherein the photocatalyst is sprayed at the same angle as the irradiation of the excitation light when the photocatalyst filter is used so as to increase the density of the photocatalyst carried in the portion to be irradiated with the excitation light. 2. The method for producing the photocatalytic filter according to 1.