JP6670570B2 - Excimer discharge unit - Google Patents

Description

  The present invention relates to an excimer lamp that irradiates deep ultraviolet light or vacuum ultraviolet light by dielectric barrier discharge, and more particularly, to an excimer lamp used for air cleaning that performs a purification process by photocatalysis.

2. Description of the Related Art In recent years, air purifiers using photocatalysis have been developed. For example, a titanium oxide photocatalyst generates OH radicals and the like from oxygen and moisture in the air by catalytic action when absorbing ultraviolet light. These OH radicals and the like decompose organic compounds in the air by a strong oxidizing power to exhibit an air purifying function and the like.
BACKGROUND ART Conventionally, an air purifier in which a photocatalyst is set with an excitation light source, which is an ultraviolet lamp, has been known. Ultraviolet lamps are mainly those in which mercury is sealed or coated with a phosphor, and considering environmental regulations in recent years, mercury lamps cannot be used as an excitation light source at present. Therefore, a mercury-free excitation light source is required.

  For example, Patent Document 1 discloses an excimer lamp having such a function. As shown in FIG. 5, in the conventional excimer lamp 5, one electrode (internal electrode) 52 is disposed inside a cylindrical discharge vessel 51, and a photocatalyst is coated on a conductive mesh on the outer periphery of the discharge vessel 51. The supported corrugated external electrodes 53 are arranged in line contact. In the invention of this conventional example, it is said that light utilization efficiency is high by supporting a photocatalyst on a conductive mesh.

Patent No. 5705599

However, the external electrode having the conventional structure has a complicated manufacturing process due to its structure and material, and is not economical from the viewpoint of manufacturing cost. Further, when the external electrode is made of a metal such as titanium, there is a possibility that the external electrode is corroded by a strong oxidizing power such as OH radical and cannot be used for a long time.
In view of the above, an object of the present invention is to provide an excimer lamp in which no electrode is provided outside a cylindrical discharge vessel as a light source for exciting a photocatalyst.

In order to solve the above-described problems, the present invention provides a first discharge cell in which a gas that generates excimer discharge is sealed in a first tubular container made of glass, and a first discharge cell provided inside the first discharge cell. An internal electrode, a second discharge cell in which a gas that generates excimer discharge is sealed in a second tubular container made of glass, and a second internal electrode provided inside the second discharge cell. , In an excimer discharge unit in which the first discharge cell and the second discharge cell are in contact with each other in such a direction that their tube axes are parallel, discharge of at least one of the first discharge cell and the second discharge cell is performed. A photocatalyst layer is formed on the outer surface of the container.
Further, the present invention may emit excimer light having a wavelength of 230 nm or less by applying an AC voltage between the first internal electrode and the second internal electrode.
Further, in the present invention, the excimer discharge unit may have a non-film-forming region where the photocatalytic layer is not formed in a region where the first tubular container and the second tubular container are in contact with each other.
In the present invention, the first tubular container and the second tubular container may have a circular cross section perpendicular to the pipe axis.
Further, in the present invention, the first tubular container and the second tubular container may have a rectangular cross section perpendicular to the pipe axis.

  According to the present invention, since electrodes for generating excimer discharge do not exist outside the tubular container, these electrodes are not exposed to OH radicals and the like generated by vacuum ultraviolet light, and the electrodes are not corroded. Absent.

FIG. 1 is a schematic configuration diagram of a cross-sectional view of an excimer discharge unit according to a first embodiment of the present invention, taken along a tube axis direction. FIG. 2 is a schematic cross-sectional view of the excimer discharge unit cut along a plane perpendicular to the tube axis. FIG. 6 is a schematic cross-sectional view of an excimer discharge unit according to a second embodiment of the present invention, taken along a plane perpendicular to the tube axis direction. FIG. 9 is a schematic cross-sectional view of an excimer discharge unit according to a third embodiment of the present invention, taken along a plane perpendicular to the tube axis direction. FIG. 4 is a diagram showing an excimer discharge unit according to a conventional example.

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a cross-sectional view along the tube axis direction of an excimer discharge unit according to a first embodiment of the present invention.
The excimer discharge unit 1 includes a pair of first discharge cells 10 and second discharge cells 20. The first discharge cell 10 has a first internal electrode 12 inside a first tubular container 11, and the second discharge cell 20 has a second internal electrode 12 inside a second tubular container 21. 22. That is, the excimer discharge unit has no electrodes outside the tubular container.

The gas generating an excimer discharge sealed in the first tubular container 11 and the second tubular container 21 is, for example, a rare gas such as xenon gas (Xe), argon gas (Ar), and krypton gas (Kr). Is mentioned. If necessary, a halogen gas such as a fluorine gas (F), a chlorine gas (CI), an iodine gas (1), or a bromine gas (Br) can be used together with the rare gas.
For example, when xenon gas is used as the luminescent gas, vacuum ultraviolet light with a wavelength of 172 nm is obtained, and when a mixed gas of argon gas and chlorine gas is used as the luminescent gas, vacuum ultraviolet light with a wavelength of 175 nm is obtained. When a mixed gas of krypton gas and iodine gas is used as a luminescent gas, vacuum ultraviolet light having a wavelength of 191 nm is obtained, and when a mixed gas of argon gas and fluorine gas is used as a luminescent gas, a wavelength of 193 nm is obtained. Vacuum ultraviolet light was obtained, and when a mixed gas of krypton gas and bromine gas was used as a luminescent gas, vacuum ultraviolet light having a wavelength of 207 nm was obtained, and a mixed gas of krypton gas and chlorine gas was used as a luminescent gas. In this case, vacuum ultraviolet light having a wavelength of 222 nm is obtained.
Therefore, in the excimer discharge unit according to the present invention, the rare gas or the mixed gas of the rare gas and the halogen gas is sealed in order to emit excimer light having a wavelength of 230 nm or less.

  The gas pressure of the gas causing the excimer discharge is preferably low, for example, 10 kPa to 45 kPa in static pressure.

  As a material for forming the first tubular container 11 and the second tubular container 21, glass is used because it is required to have a property as a dielectric and a property to transmit ultraviolet light. Specifically, for example, quartz glass having a good transmittance at a wavelength of 230 nm to 160 nm is suitably used.

  For the first internal electrode 12 and the second internal electrode 22, for example, a metal wire such as tungsten is used. A metal wire such as tungsten or molybdenum may be formed into a coil shape or a straight line shape. The space in which the internal electrodes are arranged is filled with a luminescent gas, so that the electrodes do not corrode.

The internal electrodes 12 and 22 are usually sealed by some means so as to be electrically connected to the outside. Here, a pinch seal will be described as an example of the sealing method. In a so-called pinch seal, the end of a glass tubular container is heated by a burner or the like to apply pressure, and both the metal foil and the internal lead connected thereto are crushed and sealed. Of course, the structure of the sealing portion is not limited to this structure, but can be easily manufactured.
As shown in FIG. 1, one end of each of the internal electrodes 12 and 22, that is, one end having the same electric circuit potential as the internal electrodes is provided at a tube axial end of each of the tubular containers 11 and 21. It is embedded in the stoppers 111 and 211 and is electrically connected to conductive members such as the metal foils 141 and 241 by welding or the like.
Outer leads 122 and 222 that are led out of the tubular container are connected to the other ends of the metal foils 141 and 241 to which the internal electrodes are connected. With such a structure, electric power can be supplied from outside to inside of the glass tubular containers 11 and 22.

In FIG. 1, the sealing portions 111, 112, 211, and 212 are formed at both ends of each of the tubular containers 11 and 21, but the sealing portion may be formed at one location. In order to physically hold the wire-shaped or coil-shaped internal electrode, a sealing portion is provided at the other end of the tubular container for the sake of convenience, and a similar pinch seal structure is used, and the internal electrode is suspended. I'm just there.
The two discharge cells can be fixed by inserting the end of the tubular container into a member such as a socket.

FIG. 2 is a schematic cross-sectional view of the excimer discharge unit cut along a plane perpendicular to the tube axis. This figure is a cross-sectional view taken along the line AA 'of FIG.
The first discharge cell 10 and the second discharge cell 20 are arranged such that the outer surface of the first tubular container 11 and the outer surface of the second tubular container 21 are in contact with each other. However, strictly speaking, a foil film layer made of a photocatalyst described later is sandwiched.
As described above, the first internal electrode 12 is disposed in the discharge space formed hollow inside the first tubular container 11, and the second internal electrode 22 is similarly placed in the second tubular container 21. It is located inside.

Photocatalyst layers 13 and 23 are formed on the outer surfaces of the tubular containers 11 and 21. Photocatalytic material, typically a titanium dioxide (TiO _2).
In addition, metal oxides such as zinc oxide (ZnO), nickel oxide (NiO), copper oxide (Cu ₂ O), and tungsten oxide (W ₃ O); zinc sulfide (ZnS); cadmium sulfide (CdS); Metal sulfides such as mercury (HgS), and metal selenides such as cadmium selenide (CdSe), and those obtained by adding a metal to these photocatalyst materials and adding properties can also be used.
As a method for forming the photocatalyst layer, the powder can be fired as a paste, but it is preferable that the powder does not contain a binder. A sol-gel method, a sputtering method, or the like can be employed, and when forming on the outer surface of the glass tubular container, it is particularly desirable to form by a thermal spraying method from the viewpoint of improving the degree of adhesion.
The photocatalyst layer exerts its function even if it is provided in at least one of the tubular containers 11 and 21, and thus may be formed on only one of the tubular containers.

  In addition, between the first tubular container 11 and the second tubular container 12, a dielectric having a predetermined dielectric constant and a predetermined thickness may be disposed as a spacer. This can play a role of adjusting the impedance between the first internal electrode 12 and the second internal electrode 22 through capacitive coupling in addition to a role of adjusting the physical interval. Glass or ceramic is used as the material of the spacer.

  As shown in FIG. 1, each of the first discharge cell 10 and the second discharge cell 20 is connected to an AC power supply 30, and by applying a predetermined AC voltage, an excimer is formed inside each discharge cell. Discharge occurs. This excimer discharge is visible to the naked eye from the second internal electrode to the first internal electrode, from the first internal electrode toward the second internal electrode, to the inner surface of the first tubular container, as shown in FIG. Thus, the discharge column P is observed up to the inner surface of the second tubular container. That is, the dielectric barrier discharge is performed as a pair of cells is capacitively coupled by the tube wall of the glass tubular container, and no electrode exists outside the tubular container.

  The applied AC voltage is, for example, a high frequency voltage having a frequency of 5 to 100 kHz and an applied voltage of 1 kV to 20 kV. Although not shown, it can be supplied by a known AC power supply for excimer lamps.

The air cleaning action of the present invention will be described. When an AC voltage is applied to the excimer discharge unit 1, excimer discharge is generated, and deep ultraviolet light having a wavelength of 230 nm or less and vacuum ultraviolet light are generated. These vacuum ultraviolet lights have higher energy than visible light and are excellent as excitation light for photocatalysts, but they attenuate significantly in air to be cleaned, that is, in an atmosphere containing oxygen. Having.
That is, for titanium dioxide, which is currently the most widely used material as a photocatalyst, ultraviolet light is more advantageous than visible light as excitation light, but it is difficult to handle.

However, in the present invention, the vacuum ultraviolet light generated by the excimer discharge can reach the photocatalyst layer without being attenuated. That is, the vacuum ultraviolet light first propagates through the internal space of the tubular containers 11 and 21 in which a rare gas or the like is sealed and oxygen is basically absent, and then reaches the material constituting the tubular containers 11 and 21 such as quartz glass. . Then, the light propagates inside the tubular containers 11 and 21 and is released to the outside. Since the photocatalyst layers 13 and 13 are formed directly on the outer surface of the tubular container, the photocatalyst layers 13 and 13 hardly come into contact with oxygen. 13 is reached.
Although the energy is reduced, the phosphor layer that shifts the vacuum ultraviolet light to a longer wavelength side, for example, around 400 nm, is used to adjust the excitation energy of each photocatalyst to the outer surface of the tubular container and the photocatalyst layer. And on the inner wall surface of the tubular container.

  When the vacuum ultraviolet light reaches the photocatalyst layer (titanium dioxide), the electrons in the titanium dioxide are excited to exhibit air cleaning ability. This process is known, so the description will be simplified.However, when oxygen molecules existing in the atmosphere around titanium dioxide are adsorbed on the surface of titanium dioxide, a reduction reaction and an oxidation reaction occur, and finally OH radicals are generated. Active oxygen such as (hydroxyl radical) is generated. The air is purified by decomposing organic substances in the air by oxidizing power such as OH radicals.

Since electrodes for generating excimer discharge do not exist outside the tubular container, these electrodes are not exposed to OH radicals or the like generated by vacuum ultraviolet light, and the electrodes do not corrode.
In other words, the present invention uses an excimer lamp when utilizing vacuum ultraviolet light as excitation light for the photocatalyst. Then, the problem of corrosion of the discharge electrode, which is a main problem at that time, and furthermore, the problem of attenuation of vacuum ultraviolet light in an oxygen atmosphere can be solved.

FIG. 3 is a schematic sectional view of an excimer discharge unit according to a second embodiment of the present invention, taken along a plane perpendicular to the tube axis direction.
The present embodiment is basically the same as the first embodiment shown in FIG.
The first tubular container 11 of the first discharge cell 10 and the second tubular container 21 of the second discharge cell 20 are in direct contact. The photocatalyst layer 13 is not formed in a portion where the first tubular container 11 and the second tubular container 21 are in direct contact.

First, in a region where the first tubular container 11 and the second tubular container 21 contact each other, strictly speaking, even if a gap in units of μm is generated due to irregularities on the surface of the glass, This is because there is no reason to form the photocatalyst layer 13 in this part, considering that the photocatalyst layer 13 has almost no area in contact with the atmosphere.
Secondly, the presence of the photocatalyst layer 13 with a small thickness causes a material having a dielectric constant different from that of the tubular container to intervene as a foreign substance, so that the first inner electrode 12 and the second inner electrode 22 This is to prevent unstable discharge or undesired discharge from occurring outside the container due to a change in the electric capacity between them.
Third, even if the photocatalyst layer 13 is firmly adhered to the tubular container by a thermal spraying method or the like, if the photocatalyst layer 13 is rubbed or peeled off due to contact, there is a possibility that the photocatalyst layer 13 may be peeled to other regions. Because there is.
Such a non-formation region of the photocatalyst layer can be provided by forming a film by masking the portion in advance, depending on a film formation method.

FIG. 4 is a schematic cross-sectional view of an excimer discharge unit according to a third embodiment of the present invention, taken along a plane perpendicular to the tube axis direction.
This embodiment is basically the same as the first embodiment shown in FIG. 2 except for matters relating to the shape of the tubular container, and therefore, the description is omitted.
As shown in this figure, the shape of the tubular containers 11 and 21 is rectangular when cut along a plane perpendicular to the tube axis direction. The example of the rectangle is not limited to a rectangle, but may be a square. In the case of a rectangle, it is preferable that the long sides abut on each other as described below.

This is because, when the first tubular container 11 and the second tubular container 21 are first brought into contact with each other, there is an effect that the first tubular container 11 and the second tubular container 21 come into contact stably in shape. In that sense, it is not necessary to make the entire tubular container rectangular, and it is also possible to provide a flat portion only at the contact portion and bring the flat portions into contact with each other. When the flat portions are in contact with each other, the contact surface also becomes flat and the discharge is stabilized.
Second, the photocatalytic layer is easily formed if the tubular container has a portion constituting a flat portion. Forming a strongly adhered photocatalyst layer on a curved surface is technically difficult, so if it has such a flat portion, it can be used as a conventional photocatalyst layer formation technology for a substrate. The number of options that can be applied to form a film increases. Third, in the case of a rectangular shape, it is easy to provide a non-film formation region separately.

DESCRIPTION OF SYMBOLS 1 Excimer discharge unit 10 1st discharge cell 11 1st tubular container 111 Sealing part 112 Sealing part 12 First internal electrode 122 External lead 141 Metal foil 13 Photocatalytic layer 20 Second discharge cell 21 Second tube Container 211 Sealing part 212 Sealing part 12 First internal electrode 222 External lead 241 Metal foil 23 Photocatalytic layer 30 AC power supply P Discharge column NDA Non-film formation area 5 Excimer lamp 51 Discharge container 52 Internal electrode 53 External electrode

Claims (4)

A first discharge cell in which a gas that generates excimer discharge is sealed in a first tubular container made of glass, a first internal electrode provided inside the first discharge cell, and a first electrode made of glass. A second discharge cell in which a gas generating an excimer discharge is sealed in a second tubular container; and a second internal electrode provided inside the second discharge cell, wherein the first discharge cell and the second discharge cell are provided. In an excimer discharge unit used for air cleaning in which the cells and the respective tube axes are in contact with each other in a parallel direction,
By applying an AC voltage between the first internal electrode and the second internal electrode, excimer emission having a wavelength of 230 nm or less is emitted,
An air characterized in that a purification process is performed by irradiating excimer light having a wavelength of 230 nm or less to a photocatalytic layer formed on an outer surface of at least one of the first discharge cell and the second discharge cell. Excimer discharge unit used for cleaning . The excimer discharge unit,
2. The excimer discharge unit according to claim 1, wherein a non-film formation region where the photocatalytic layer is not formed is provided in a region where the first tubular container and the second tubular container are in contact with each other.   3. The excimer discharge unit according to claim 1, wherein each of the first tubular container and the second tubular container has a circular cross section perpendicular to the tube axis. 4.   3. The excimer discharge unit according to claim 1, wherein the first tubular container and the second tubular container have a rectangular cross section orthogonal to a tube axis. 4.

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