JP2005131604A - Photocatalyst body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst body equipped with a photocatalyst membrane capable of obtaining sufficient decomposing activity by ultraviolet light and visible light. <P>SOLUTION: A fluorescent lamp FL is constituted of a fluorescent lamp main body L and the photocatalyst membrane LC. A photocatalyst membrane FC has a thickness of approximately 0.3-4.0 μm, and the photocatalyst membrane LC is constituted of a visible light type photocatalyst particulate 21 and a binder 22. The visible light type photocatalyst particulate 21 is applied with a visible light treatment such as a nitrogen conversion treatment and the average particle diameter of the visible light type photocatalyst particulate 21 is approximately 5-20 nm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photocatalyst having a decomposition activity with respect to ultraviolet light and visible light.

  A fluorescent lamp provided with a photocatalyst film is conventionally known (see, for example, Patent Document 1). A conventional photocatalyst film used in this type of fluorescent lamp uses a photocatalyst exhibiting decomposition activity under ultraviolet light (hereinafter referred to as “ultraviolet light photocatalyst”). As the ultraviolet light type photocatalyst, a structure mainly composed of anatase type titanium oxide is practically used.

  However, a fluorescent lamp provided with a photocatalyst film formed using a conventional ultraviolet light type photocatalyst is not sufficient for the expected decomposition activity. This is because the amount of ultraviolet light having a wavelength effective for activation emitted from the fluorescent lamp to the outside is very small, and the ultraviolet light cannot be effectively used for activating the photocatalyst.

On the other hand, a photocatalyst exhibiting decomposition activity in recent ultraviolet light and visible light (hereinafter referred to as “visible light photocatalyst”) has been developed (for example, see Patent Document 2). The visible light photocatalyst has a structure in which metal ultrafine particles made of at least one of Pt, Au, Pd, Rh, and Ag are supported on the surface of photocatalyst fine particles preferably made of rutile titanium oxide. In addition, a photocatalyst that exhibits decomposition activity with visible light, such as a structure in which lattice defects are formed in titanium oxide, is also known. In addition, as still another structure exhibiting decomposition activity with light similar to the above, a photocatalytic material in which a continuous thin film having rutile and anatase type titanium oxide crystals is formed by using a high-frequency sputtering method is also known ( For example, see Patent Document 3.)
Japanese Patent Application Laid-Open No. 10-072421 Japanese Patent Laid-Open No. 11-047611 JP 2001-063310 A

  Forming a photocatalyst film using visible light type photocatalyst fine particles is expected to provide a photocatalyst film having strong decomposition activity particularly for lighting products such as fluorescent lamps and lighting fixtures. Therefore, the present inventor tried to form a photocatalytic film on a fluorescent lamp using visible light photocatalyst fine particles. However, the expected effect was not obtained.

  The present invention has been made to solve the above problems. That is, it aims at providing the photocatalyst body provided with the photocatalyst film | membrane which can acquire sufficient decomposition | disassembly activity with respect to ultraviolet light and visible light.

  The photocatalyst body according to claim 1 is composed of a substrate; visible light photocatalyst fine particles having an average particle diameter of 5 to 20 nm formed on the substrate and subjected to visible light treatment; A photocatalytic film having a thickness of 0 μm.

  In the present invention and each of the following inventions, the definitions and technical meanings of terms are as follows unless otherwise specified.

  The substrate may have any surface such as a plate shape, a spherical shape, a linear shape, or a fiber shape. Moreover, the base | substrate should just be a solid which can form a photocatalyst film, Glass, ceramics, a metal etc. are mentioned as a suitable example.

  Examples of the substrate include, but are not limited to, electrical products such as lighting products, window glass, window frames, building materials such as tiles, deodorizers, sanitary products, vehicles, and furniture. The “lighting product” is used in a positional relationship that can be a substrate (support) for the photocatalyst film among at least a light source, a lighting fixture, and components of these articles, and can be irradiated with light generated from the light source. It is meant to include a member. Examples of the light source include a fluorescent lamp, a high-pressure discharge lamp, and a halogen bulb, and the photocatalytic film is formed mainly on the outer surface of a member, such as a bulb, that has a relationship to which light generated from the light source is irradiated. Examples of the lighting fixture include indoor lighting fixtures, outdoor lighting fixtures, marker lamps, indicator lamps, and signboard lamps, and the photocatalytic film is a component that is irradiated with light generated from a light source, such as a shade, Such as globes, floodlights, and reflectors.

The visible light type photocatalyst fine particles constituting the photocatalyst film are activated mainly by visible light having a wavelength of 400 nm or more and ultraviolet light having a wavelength of 380 nm or less. The visible light photocatalyst fine particles are made of a metal oxide having a photocatalytic action. Examples of such metal oxides include TiO ₂ , WO ₃ , CdO ₃ , In ₂ O ₃ , Ag ₂ O, MnO ₂ , Cu ₂ O ₃ , Fe ₂ O ₃ , V ₂ O ₅ , ZrO ₂ , RuO _2. , Cr ₂ O ₃ , CoO ₃ , NiO, SnO ₂ , CeO ₂ , Nb ₂ O ₃ , KTaO ₃ , SrTiO ₃ , K ₄ NbO _{17 and the} like can be used in combination. Among these, TiO ₂ , SrTiO _3, and K ₄ NbO ₁₇ are preferable from the viewpoints of generated electron-hole density, superoxide anion, hydroxyl radical density, corrosion resistance as a material, safety, and the like. . However, titanium oxide is most suitable because it has the best photocatalytic action, is available on an industrial scale, is chemically stable, and can be obtained at low cost.

  The visible light photocatalyst fine particles are subjected to a visible light treatment. “Visible light treatment” means a treatment for lowering the band gap energy so that the visible light photocatalyst fine particles exhibit decomposition activity with visible light. For example, titanium oxide includes anatase type, brookite type, and rutile type due to the difference in crystal structure. The anatase type and brookite type titanium oxide has a band gap energy of about 3.20 eV, which is 388 nm in terms of wavelength. Here, when the anatase-type and brookite-type titanium oxide is subjected to a visible light treatment, the band gap energy can be reduced to about 2.8 to 3.0 eV. When this is converted into a wavelength, it becomes about 413 to 443 nm, so that it shows a decomposition activity with visible light.

  Examples of the visible light treatment include nitrogen substitution treatment, sulfur substitution treatment, and oxygen defect formation treatment, and nitrogen substitution treatment and sulfur substitution treatment are preferable from the viewpoint of stability. Whether or not the visible light photocatalyst fine particles are subjected to visible light treatment can be determined by measuring the transmittance of visible light having a wavelength of 400 nm or more.

  The average particle diameter of the visible light photocatalyst fine particles is 5 to 20 nm. The reason why the average particle size is 5 to 20 nm is that if the average particle size is less than 5 nm, the production becomes difficult. Because it disappears.

  The film thickness of the photocatalyst film is 0.3 to 4.0 μm. The reason why the film thickness is 0.3 to 4.0 μm is that sufficient decomposition activity cannot be obtained when the film thickness is less than 0.3 μm, and sufficient mechanical properties are obtained when the film thickness exceeds 4.0 μm. This is because the strength, light transmittance, and decomposition activity cannot be obtained. The film thickness is preferably 0.3 to 2.0 μm, and more preferably 0.3 to 1.0 μm.

In the photocatalyst film, an appropriate amount of an appropriate binder is allowed to be mixed in order to bind the visible light photocatalyst fine particles to increase the mechanical strength of the photocatalyst film. As the binder, for example, one kind or plural kinds such as silicone resin, SiO ₂ , ZrO ₂ , and Al ₂ O ₃ can be used. Although these substances bind well between the fine particles of visible light type photocatalyst fine particles, they have a high transmittance for ultraviolet light and visible light, and therefore do not easily inhibit the decomposition activity of the photocatalyst film.

  If the amount of the binder is too large, the photocatalyst fine particles are embedded in the binder and it becomes difficult to exert the photocatalytic action. If the amount is too small, the required binding force cannot be obtained. . The mixing ratio of the binder is an appropriate amount in the range of 1 to 30% by mass ratio with respect to the visible light type photocatalyst fine particles, and more preferably 7 to 15%.

  The binder may be in an embodiment in which it is melted and solidified to bind between the photocatalyst fine particles and a support such as a lighting product, or in an ultra fine particle state by van der Waals force. Good.

  Thus, by mixing the binder as described above, it is possible to form a photocatalytic film having a mechanical strength with a film thickness of 0.3 to 4.0 μm while maintaining a strong decomposition activity. .

  The photocatalyst film can be applied by using various known film forming methods, for example, spraying, dipping, brushing, electrostatic adsorption, or the like, by room temperature, low temperature heating or high temperature heating baking. .

  According to the photocatalyst of the first aspect, sufficient decomposition activity can be obtained for ultraviolet light and visible light. The photocatalyst of the present invention is effective not only for decomposition of organic gas but also for antifouling. In particular, since the unevenness of the surface of the photocatalyst film is fine, there is an effect that dirt particles are difficult to adhere, which contributes to the antifouling effect.

  The photocatalyst according to claim 2 is the photocatalyst according to claim 1, wherein the visible light photocatalyst fine particles are at least one of anatase type titanium oxide and brookite type titanium oxide, or the anatase type titanium oxide and brookite type. The main component is at least one of titanium oxide, and platinum, gold, chromium, manganese, vanadium, nickel, palladium, vanadium oxide, molybdenum oxide, iron oxide, niobium oxide, tin oxide, zinc oxide, chromium oxide, tungsten oxide, and It is characterized in that at least one of ITO (tin doped indium oxide) is attached or mixed with the titanium oxide. The present invention defines a preferred configuration of fine particles of the visible light photocatalyst. The “titanium oxide” means at least one of anatase type titanium oxide and brookite type titanium oxide.

  When the metal or metal oxide is added or mixed with titanium oxide, electrons appear on the surface of the metal or metal oxide, and holes appear on the surface of the titanium oxide. On the other hand, when no metal or metal oxide is added or mixed with titanium oxide, electrons and holes appear on the surface of titanium oxide. Here, when the metal or metal oxide is added or mixed with titanium oxide, electrons and holes are less likely to recombine than when the metal or metal oxide is not added or mixed with titanium oxide. Thereby, when the said metal and metal oxide are attached or mixed with titanium oxide, an electron and a hole can be made to exist for a longer time, and a decomposition activity can be improved.

  The photocatalyst according to claim 3 is the photocatalyst according to claim 1 or 2, wherein the photocatalyst film has an ultraviolet light transmittance of 20 to 50% at a wavelength of 360 nm and a visible light transmittance of a wavelength of 400 nm. The visible light transmittance at a wavelength of 450 nm is 80 to 95%.

  A photocatalyst according to a fourth aspect is the photocatalyst according to any one of the first to third aspects, wherein the substrate is a fluorescent lamp.

  According to the photocatalyst according to any one of claims 1 to 4, sufficient decomposition activity can be obtained for ultraviolet light and visible light.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view including a cutaway section schematically showing the fluorescent lamp according to the present embodiment, and FIG. 2 is a schematic sectional view of the photocatalyst film according to the present embodiment. In FIG. 1, the fluorescent lamp FL (photocatalyst) is composed of a fluorescent lamp main body L (base) and a photocatalytic film LC formed on the surface of the fluorescent lamp main body L.

  The fluorescent lamp main body L includes a translucent discharge vessel 11, a phosphor layer 12, a pair of electrodes 13 and 13, a discharge medium (not shown) and a base 14.

  The translucent discharge vessel 11 includes an elongated glass bulb 11a and a pair of flare stems 11b. The glass bulb 11a is made of soda lime glass. The flare stem 11b includes an exhaust pipe, a flare, an internal introduction line, and an external introduction line. The exhaust pipe is used to communicate the inside and outside of the translucent discharge vessel 11 to exhaust the inside of the translucent discharge vessel 11 and enclose a discharge medium. The exhaust pipe is cut off after the discharge medium is sealed. The flare is sealed at both ends of the glass bulb 11a to form the translucent discharge vessel 1. The inner lead wire is hermetically embedded in the inside of the flare stem 11b and connected to the outer lead wire. The external lead-in wire has a distal end embedded in the flare stem 11 b and a proximal end led out of the translucent discharge vessel 11.

The phosphor layer 12 is made of a three-wavelength light emitting phosphor and is formed on the inner surface of the translucent discharge vessel 11. The three-wavelength light-emitting phosphor is BaMgAl ₁₆ O ₂₇ : Eu for blue light emission, LaPO ₄ : Ce, Tb for green light emission, and Y ₂ O ₃ : Eu for red light emission.

  The pair of electrodes 13, 13 are connected between the distal ends of the pair of internal lead wires that are opposed to each other inside the both ends of the translucent discharge vessel 11. The electrode 13 is made of a tungsten coil filament and an electron radioactive material deposited on the coil filament.

  The discharge medium is made of mercury and argon, and is enclosed in the translucent discharge vessel 11. An appropriate amount of mercury is dripped through the exhaust pipe. Argon is sealed at about 300 Pa.

  The base 14 includes a base body 14a and a pair of base pins 14b and 14b. The base body 14 a has a cap shape and is bonded to both end portions of the translucent discharge vessel 11. The pair of cap pins 14b, 14b are supported in an insulating relationship with each other by the cap body 14a and are connected to external lead-in wires, respectively.

  The photocatalytic film LC is formed so as to have a film thickness of about 0.3 to 4.0 μm. As shown in FIG. 2, the photocatalyst film LC is formed of visible light photocatalyst fine particles 21 and a binder 22.

  The visible light photocatalyst fine particles 21 are subjected to visible light treatment such as nitrogen substitution treatment. Thereby, the visible light type photocatalyst fine particles 21 mainly absorb ultraviolet light having a wavelength of 380 nm or less and visible light having a wavelength of 400 nm or more, and exhibit decomposition activity. In addition, since the visible light photocatalyst fine particles 21 absorb ultraviolet light having a wavelength of 380 nm or less and visible light having a wavelength of 400 nm or more, the photocatalytic film LC is, for example, 20 to 50% by ultraviolet light having a wavelength of 360 nm and visible light having a wavelength of 400 nm. 40 to 80%, visible light having a wavelength of 450 nm shows 80 to 95% light transmittance.

  The visible light photocatalyst fine particles 21 have an average particle diameter of 5 to 20 nm. In the present embodiment, the visible light photocatalyst fine particles 21 are composed of anatase-type titanium oxide fine particles 21a and Pt fine particles 21b attached to the surfaces of the anatase-type titanium oxide fine particles 21a.

The binder 22 is made of melted and solidified SiO ₂ . The mixing ratio of the binder 22 to the visible light photocatalyst fine particles 21 is 10% by mass, and the particles of the visible light photocatalyst fine particles 21 and between the photocatalyst film LC and the translucent discharge vessel 11 are mutually connected. It is bound to.

  In the present embodiment, the photocatalyst film LC including the visible light type photocatalyst fine particles 21 having an average particle diameter of 5 to 20 nm that has been subjected to the visible light treatment and having a film thickness of 0.3 to 4.0 μm is used as the fluorescent lamp body. Since it is formed on the surface of L, it is possible to obtain a strong decomposition activity against ultraviolet light and visible light.

  In the present embodiment, the visible light photocatalyst fine particles 21 are composed of the anatase-type titanium oxide fine particles 21a and the Pt fine particles 21b attached to the surfaces of the anatase-type titanium oxide fine particles 21a. And the degradation activity can be increased.

  Example 1 will be described below. In this example, the relationship between the film thickness of the photocatalyst film and the light transmittance of the photocatalyst film was examined. The measurement conditions will be described. In this example, the fluorescent lamp formed with the photocatalyst film described in the above embodiment was used. The fluorescent lamp was a 20W type three-wavelength type fluorescent lamp. The fluorescent lamp was turned on, and the light transmittance of the photocatalyst film in ultraviolet light having a wavelength of 360 nm was measured.

  The measurement result will be described. FIG. 3 is a graph created based on data obtained by measuring the light transmittance according to this example. In the graph of FIG. 3, the horizontal axis indicates the film thickness of the photocatalyst film, and the vertical axis indicates the light transmittance of the photocatalyst film.

  As can be seen from the graph of FIG. 3, a high light transmittance was obtained when the film thickness of the photocatalyst film was about 0.3 to 4.0 μm. Further, a higher transmittance was obtained when the film thickness was about 0.3 to 2.0 μm, and a higher transmittance was obtained when the film thickness was about 0.3 to 1.0 μm. In this embodiment, the light transmittance of the photocatalyst film is measured using ultraviolet light, but it is considered that the same result can be obtained even when visible light is used.

Example 2 will be described below. In this example, the relationship between the film thickness of the photocatalyst film and the gas decomposition activity index was examined. Experimental conditions will be described. FIG. 4 is a conceptual diagram showing equipment for measuring the gas decomposition effect of the fluorescent lamp according to the present embodiment. As shown in FIG. 4, the facility for measuring the gas decomposition effect includes a fan 32, a gas source 33 and a heater 34 in a stainless steel sealed tank 31 having an internal volume of 1 m ³ . A multi-gas monitor 35 for monitoring the gas is provided. The fan 32 circulates the gas in the sealed tank 21 and the gas source 33 supplies formaldehyde gas. The heater 34 heats the gas source 33 to generate formaldehyde gas, and the multi-gas monitor 35 measures the formaldehyde gas concentration in the sealed tank 31.

The four fluorescent lamps FL described in the above embodiment are installed in the ceiling portion of the sealed tank 31 and the gas source 33 is supplied by the heater 34 in a state where the sealed tank 31 is filled with N ₂ gas mixed with Kr. Then, 2 ppm of formaldehyde gas was generated, and the decay slope after 3 hours was measured while circulating the gas in the tank by the fan 32.

  The measurement results are described. FIG. 5 is a graph created based on the data obtained by measuring the gas decomposition activity index according to this example. In the graph of FIG. 5, the horizontal axis indicates the film thickness of the photocatalytic film, and the vertical axis indicates the gas decomposition activity index, which indicates the decay slope after 3 hours after introducing 2 ppm of formaldehyde gas as a relative value. .

  As can be seen from the graph of FIG. 5, high light transmittance was obtained when the film thickness of the photocatalyst film was about 0.3 to 4.0 μm. Here, when the film thickness of the photocatalyst film exceeds 2.0 μm, the decomposition activity decreases. This is considered to be due to the following reason. That is, since the decomposition reaction occurs near the surface of the photocatalyst film, ultraviolet light and visible light must reach the vicinity of the surface of the photocatalyst film. However, when the film thickness of the photocatalyst film exceeds 2.0 μm, ultraviolet light and visible light are absorbed by the photocatalyst film before reaching the surface of the photocatalyst film. For this reason, it is considered that the ultraviolet light and visible light that reach the vicinity of the surface of the photocatalytic film are reduced, and the decomposition activity is lowered.

  The present invention is not limited to the description of the above embodiment, and the structure, material, arrangement of each member, and the like can be appropriately changed without departing from the gist of the present invention. In the above embodiment, the Pt fine particles 21b are attached to the surface of the anatase-type titanium oxide fine particles 21a. However, the Pt fine particles 21b need not be attached.

FIG. 1 is a front view including a cutaway section schematically showing a fluorescent lamp according to an embodiment. FIG. 2 is a schematic cross-sectional view of the photocatalytic film according to the embodiment. FIG. 3 is a graph created based on the data obtained by measuring the light transmittance according to the first embodiment. FIG. 4 is a conceptual diagram illustrating equipment for measuring the gas decomposition effect of the fluorescent lamp according to the second embodiment. FIG. 5 is a graph created based on data obtained by measuring the gas decomposition activity index according to Example 2.

Explanation of symbols

  FL: fluorescent lamp, F: fluorescent lamp body, FC: photocatalytic film, 21: visible light type photocatalyst fine particles, 21a: anatase type titanium oxide fine particles, 21b: Pt fine particles.

Claims (4)

A substrate;
A photocatalyst film formed of visible light photocatalyst fine particles having an average particle diameter of 5 to 20 nm formed on the substrate and subjected to visible light treatment, and having a film thickness of 0.3 to 4.0 μm;
Comprising a photocatalyst body.   The visible light photocatalyst fine particles are mainly composed of at least one of anatase-type titanium oxide and brookite-type titanium oxide, or at least one of the anatase-type titanium oxide and brookite-type titanium oxide, and platinum, gold, chromium, manganese, vanadium. Nickel, palladium, vanadium oxide, molybdenum oxide, iron oxide, niobium oxide, tin oxide, zinc oxide, chromium oxide, tungsten oxide, and ITO are attached or mixed with the titanium oxide. The photocatalyst body according to claim 1, wherein   The photocatalyst film has an ultraviolet light transmittance of 20 to 50% at a wavelength of 360 nm, a visible light transmittance of a wavelength of 400 nm is 40 to 80%, and a visible light transmittance of a wavelength of 450 nm is 80 to 95%. The photocatalyst body according to claim 1 or 2.   The photocatalyst according to any one of claims 1 to 3, wherein the substrate is a fluorescent lamp.

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