JP3043565B2 - Dielectric barrier discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a kind of discharge lamp used as, for example, an ultraviolet light source for a photochemical reaction, in which excimer molecules are formed by dielectric barrier discharge and light emitted from the excimer molecules is used. To improve the so-called dielectric barrier discharge lamp.

[0002]

2. Description of the Related Art As a technique related to the present invention, there is, for example, Japanese Patent Laid-Open Publication No. 2-7353, in which a discharge vessel is filled with a discharge gas for forming excimer molecules, and a dielectric material is filled. Excimer molecules are formed by barrier discharge (also known as ozonizer discharge or silent discharge; see the revised edition of “Discharge Handbook” published by the Institute of Electrical Engineers of Japan, reprinted on June 7, 2001, page 263), and light emitted from the excimer molecules is extracted. A radiator, i.e., a dielectric barrier discharge lamp, is described wherein the discharge vessel is cylindrical, at least a portion of the discharge vessel also serves as a dielectric for the dielectric barrier discharge, and at least a portion of the dielectric A portion is light transmissive to light emitted from the excimer molecule, and at least a part of the light transmissive dielectric is provided with a conductive mesh electrode. Body barrier discharge lamp structure is described. Further, a dielectric barrier discharge lamp device having a light extraction window provided in parallel with a discharge path of the dielectric barrier discharge is described in U.S. Pat. No. 2,943,225. The dielectric barrier discharge lamp as described above is useful because it has various features not found in conventional low-pressure mercury discharge lamps and high-pressure arc discharge lamps. In addition, it has a light extraction window provided parallel to the discharge path, so that the radiance can be increased by increasing the size of the dielectric barrier discharge lamp in the direction perpendicular to the light extraction window. Have. But,
The dielectric barrier discharge lamp as described above has a problem that the stability of light output and the light extraction efficiency are not always sufficient.

[0003]

It is an object of the present invention to provide a dielectric barrier discharge lamp having a stable light output, a high radiance, a high efficiency and a high stability.

[0004]

In order to solve the above problems, a dielectric barrier discharge lamp according to the present invention has a discharge vessel in which a discharge space is formed by arranging an outer tube and an inner tube coaxially. Is filled with a discharge gas for forming excimer molecules by dielectric barrier discharge, and an electrode for dielectric barrier discharge is provided on at least a part of the outer wall of the outer tube and at least a part of the outer wall of the inner tube. In a structure in which a light extraction window is provided at one end, an end on the light extraction window side of the inner tube is separated from the light extraction window to close the airtight. Also, the light of the inner tube
The end on the side closest to the extraction window, which is opposite to the discharge space.
Provide an electrode electrically connected to the inner electrode on the opposite surface
Light-transmitting electrodes on the outer surface of the light extraction window.
Provision of a pole, and furthermore, a light extraction window side of the inner tube
In the gap between the end and the light extraction window, the shortest distance X
Between 50% and 150% of the discharge gap L of the discharge space
The object of the present invention described above is further enhanced by
Can be achieved.

[0005]

[Function] Dielectric barrier discharge is described in the Discharge Handbook.
As described in (1), a large number of minute discharge plasmas (hereinafter referred to as microplasmas) having a very small plasma diameter and a very short discharge duration. We have studied in detail the stability and luminous efficiency of the light output of a dielectric barrier discharge lamp having a light extraction window provided in parallel with the discharge path. It has been found experimentally that it varies greatly depending on the configuration of the electrodes near the light extraction window. FIG. 4 is a schematic diagram of a conventional dielectric barrier discharge lamp. The discharge vessel 8 is made of quartz glass and has a hollow cylindrical shape in which an inner tube 9 and an outer tube 10 are coaxially arranged. On the outer surface of the outer tube 10 and the outer surface of the inner tube 9 are provided electrodes 12 and 11 for dielectric barrier discharge which also serve as a light reflecting film formed by vapor deposition of aluminum.
An annular light extraction window 41 made of synthetic quartz glass is provided at one end of the discharge vessel 8 by welding to the outer tube 10 and the inner tube 9. In the discharge space 15 of the discharge vessel 8,
A discharge gas for forming excimer molecules by dielectric barrier discharge is filled, and electrodes 11 and 12 are supplied by an AC power supply 22.
When a voltage is applied to the micro plasmas 20a, 20a
b, 20c and 20d are generated stably. At the same time,
The surface discharge plasma 7 is generated irregularly along the surface of the light extraction window 41. As a result, the light output becomes unstable. Further, with respect to the radiance obtained from the light extraction window 41, the microplasmas 20a, 20b, 20c,
In addition to the positive column 20d, the surface discharge plasmas 21a, 21b, 21c, 2 generated on the inner surfaces of the dielectrics 9, 10 are formed.
It has been found that the radiated light from 1d greatly contributes, and therefore, when the transmittance of the edge portion 41a of the light extraction window 41 close to the inner tube 9 is reduced, the luminous efficiency is extremely reduced. The above-mentioned problem is caused by a dielectric vessel having a hollow cylindrical discharge space formed by coaxially arranging an outer tube and an inner tube whose outer shapes are substantially cylindrical, that is, a container having a circular cross section. A discharge gas for forming excimer molecules by barrier discharge is filled, and an electrode for the dielectric barrier discharge is provided on at least a part of an outer wall of the outer tube and at least a part of an outer wall of the inner tube. This is unique to a dielectric barrier discharge lamp having a configuration in which a light extraction window is provided at least at one end, that is, a configuration having a light extraction window provided in parallel with a discharge path.
A similar phenomenon is observed in a lamp having a flat cross section.

A discharge gas having excimer molecules formed by a dielectric barrier discharge in a discharge vessel having a hollow cylindrical discharge space formed by coaxially arranging an outer tube and an inner tube each having an approximately cylindrical outer shape. A dielectric barrier electrode is provided on at least a part of the outer surface of the outer tube and at least a part of the outer surface of the inner tube, and a light extraction window is provided on at least one end of the discharge vessel. In the body barrier discharge lamp, when the light extraction window is formed in a substantially disk shape and at least one end of the inner tube that is in close proximity to the light extraction window is airtightly closed, the inner tube and the light are closed. Since there is no need to connect the extraction window, there is little decrease in transmittance of the light extraction window due to connection processing between the inner tube and the light extraction window, for example, welding, bonding, etc. Plasma 21a, 21b, 21
c, a decrease in transmittance of a portion near the inner tube of the light extraction window, which is a place where the light emitted from 21d passes particularly,
Accordingly, a dielectric barrier discharge lamp with high light extraction efficiency and high efficiency can be obtained. In a conventional lamp having a configuration as shown in FIG. 4, a creeping discharge occurs on the inner surface of the light extraction window 41 in the path of the electrode 12, the dielectric 10, the light extraction window 41, the dielectric 9, and the electrode 11. In the characteristic configuration of the present invention, since the light extraction window 41 and the dielectric 9 are separated from each other via the discharge space in the vicinity of the light extraction window 41, the above-described creeping discharge does not occur, and thus the light output is stabilized. The resulting dielectric barrier discharge lamp is obtained. Further, in order to obtain high radiance, it is necessary to discharge stably immediately before the light extraction window 41. For this purpose, for example, in FIG. It is necessary to approach 41. However, in the conventional configuration as shown in FIG. 4, creeping discharge occurs on the outer surface of the light extraction window 41 on the outer surface of the electrode 12, the outer surface of the light extraction window 41 and the path of the electrode 11. On the other hand, in the characteristic configuration of the present invention, in the vicinity of the light extraction window 41, the electrode 12 and the electrode 11 are blocked by the light extraction window 41 and do not form a continuous surface. Even when this is done, no creeping discharge occurs on the outer surface of the light extraction window 41, and therefore, a dielectric barrier discharge lamp with stable light output and high safety can be obtained.

[0007] An end portion of the inner tube, which is close to the light extraction window, is hermetically closed to form a closed portion, and an electrode for a dielectric barrier discharge provided on the outer surface of the inner tube on the outer surface of the closed portion. When a tip electrode electrically connected to the light emitting device is provided, a discharge is generated in a space existing between the closed portion and the external light extraction window, and a dielectric barrier discharge lamp with higher efficiency can be obtained. In addition, when a light transmissive electrode is provided on the outer surface of the light extraction window, a discharge in a space existing between the closed portion and the light extraction window is stronger and stably generated, so that a higher luminance is obtained. A stable dielectric barrier discharge lamp is obtained. Further, in a gap between the light extraction window and the closing portion provided in close proximity to the light extraction window, the shortest distance X between the light exit window and the closing portion provided in close proximity to the light extraction window is defined as: 50% to 150% of the discharge gap L of the hollow cylindrical discharge space
In this case, the discharge in the space existing between the closed portion and the external light extraction window is stronger and more stably generated, so that a more efficient and stable dielectric barrier discharge lamp can be obtained.

[0008]

1 is a schematic view of a dielectric barrier discharge lamp according to a first embodiment of the present invention. The hollow cylindrical discharge vessel 8 is made of synthetic quartz glass having a total length of about 150 mm, and has an outer diameter of 1 mm.
This is a configuration in which a hollow cylindrical discharge space 15 is formed by coaxially disposing a 4 mm inner tube 9 and an outer tube 10 having a thickness of 1 mm and an inner diameter of about 25 mm. The outer tube 10 and the inner tube 9 also serve as dielectrics for dielectric barrier discharge. At one end of the outer tube 10 made of a quartz glass tube having a hydroxyl content of about 3 ppm by weight, the hydroxyl content is about 700 p by weight.
A light extraction window 41 made of a disc made of synthetic quartz glass having a thickness of pm was provided by welding. A light reflecting plate 13 was provided at the other end 8a for sealing the outer tube 10 and the inner tube 9. One end portion of the inner tube 10 made of a quartz glass tube having a hydroxyl group content of about 3 ppm, which was close to the light extraction window 41, was airtightly closed to form a closed portion 16. The shortest distance X between the closed portion and the light extraction window was set to 5.5 mm, which is the same as the discharge gap L of the hollow cylindrical discharge space. Outer tube 10
The electrode 12 serving also as a light reflecting plate was provided by evaporating aluminum on the outer surface of the substrate. The electrode 12 is provided so as to extend until it comes into contact with the light extraction window 41. Inner tube 9
The electrode 11 also serving as a light reflection plate and the tip electrode 17 electrically connected to the electrode 11 are provided by evaporating aluminum on the outer surface of the above and the outer surface of the closed portion opposite to the discharge space 8b. Was. Although not shown, the aluminum electrode was covered with a protective film of boron nitride to mechanically and chemically protect the aluminum electrode. The discharge space 15 of the discharge vessel was filled with xenon gas at 300 Torr as a discharge gas.

When the dielectric barrier discharge lamp is turned on using a high-frequency, high-voltage power supply 22, first, even though the electrode 12 is extended until it comes into contact with the light extraction window 41, Regardless, no creeping discharge occurs on the inner surface and the outer surface of the light extraction window 41, and therefore, the light output is stable. Secondly, by providing the tip electrode 17, the closing portion 16 and the light extraction A stable discharge is generated in the space 8b existing between the windows 41, so that the radiance is increased. Thirdly, since the light extraction window 41 is disk-shaped, the radiated light from the plasma generated on the inner surface of the inner tube 9 is obtained. Could be taken out efficiently. As a result, the wavelength was 172 nm.
Thus, a dielectric barrier discharge lamp with high efficiency, vacuum ultraviolet rays having a central wavelength, high radiance, stable light output, and high safety was obtained.

FIG. 2 shows a dielectric barrier discharge lamp according to a second embodiment of the present invention. In this embodiment, a metal mesh electrode 19 through which light electrically connected to the electrode 12 can pass is provided on the outer surface of the light extraction window 41. Further, a getter chamber 18 for accommodating a getter was provided at one end of the discharge vessel 8 so as to penetrate the discharge space 15 and accommodate a barium getter. In this embodiment, the tip electrode 17 and the electrode 1
2 and the tip electrode 17 and the metal mesh electrode 19
A stable discharge was generated between the two, and the radiance was further increased. Further, by setting the electrode 12 and the metal mesh electrode 19 to the ground potential, there is no danger of electric shock even when approaching the light extraction window 41, radiation of electromagnetic noise is reduced, and a more stable dielectric barrier discharge is achieved. A lamp was obtained. Further, since the barium getter was provided, the impurity gas generated during the operation was removed, so that a long-life dielectric barrier discharge lamp was obtained.

FIG. 3 shows the dielectric barrier discharge lamp according to the third embodiment of the present invention. When the effective diameter D of the light extraction window 41 is configured to exceed the inner diameter of the outer tube 10 as in the present embodiment, the depression 23 is formed, and the creeping discharge plasma generated on the inner surface of the outer tube 10 is formed. Synchrotron radiation can be efficiently extracted, and thus high efficiency can be obtained.

In the above description of the embodiment of the present invention, the discharge gas is xenon. However, other discharge gases such as a mixed gas of chlorine and xenon and a mixed gas of chlorine and krypton are used as the discharge gas. It is self-evident that it is effective even if you do.

In the lamp of the above embodiment, the sectional shape of the obtained light beam is circular, but the present invention is also applied to a lamp structure in which the sectional shape of the beam is formed in a square or linear shape. There is a problem, and the problem can be solved by the technique of the present invention. Diverting Figure 1,
This point will be additionally described. In the lamp shown in FIG. 1, assuming that the discharge spaces 15 and 8b extend in a direction perpendicular to the plane of the paper, the outer tube and the inner tube have flat outer shapes, and the electrodes for the dielectric barrier discharge also include: It can be seen that the flat tube should be provided so as to cover it, and the shape of the window should be rectangular. In other words, the technique of the present invention uses excimer molecules by a dielectric barrier discharge in a discharge vessel having a hollow flat discharge space formed by coaxially arranging an outer tube and an inner tube whose outer shapes are substantially flat. A discharge gas to be formed is filled, electrodes for the dielectric barrier discharge are provided on at least a part of the outer surface of the outer tube and at least a part of the outer surface of the inner tube, and light is extracted from at least one end of the discharge vessel. In a dielectric barrier discharge lamp provided with a window, the light extraction window has a substantially rectangular shape, and at least one end of the inner tube in the immediate vicinity of the light extraction window is hermetically closed. It can also be applied to the characteristic dielectric barrier discharge lamp.

[0014]

As described above, according to the present invention, it is possible to provide a dielectric barrier discharge lamp having stable light output, high radiance, high efficiency, and high stability.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of a dielectric barrier discharge lamp of the present invention.

FIG. 2 is an explanatory view of another embodiment of the dielectric barrier discharge lamp of the present invention.

FIG. 3 is an explanatory view of another embodiment of the dielectric barrier discharge lamp of the present invention.

FIG. 4 is an explanatory view of a conventional dielectric barrier discharge lamp.

[Explanation of symbols]

 Reference Signs List 8 discharge vessel 9 inner tube 10 outer tube 11, 12 electrode 15 discharge space 16 closing part 17 tip electrode 18 getter room 19 mesh electrode 41 light extraction window

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noriyoshi Hishinuma, 1194, Sado, Bessho-cho, Himeji-shi, Hyogo Ushio Electric Co., Ltd. (72) Inventor Yasuhiko Wakahata Inspector Katsumi Enari, Ushio Electric Co., Ltd. 1194, Sado Bessho-cho, Himeji-shi, Hyogo (56) References JP-A-5-2666863 (JP, A) (58) ) Field surveyed (Int. Cl. ⁷ , DB name) H01J 65/04 G21K 5/00

Claims (4)

(57) [Claims] An outer tube and an inner tube are coaxially arranged, and a discharge vessel having a discharge space formed therebetween is filled with a discharge gas for forming excimer molecules by dielectric barrier discharge. An electrode for the dielectric barrier discharge is provided on at least a part and at least a part of an outer surface of the inner tube, and a dielectric barrier discharge lamp provided with a light extraction window at one end of the discharge vessel; The end near the light extraction window is
A dielectric barrier discharge lamp, which is hermetically closed away from the light extraction window. 2. The dielectric barrier discharge according to claim 1, wherein an end of the inner tube on the side immediately adjacent to the light extraction window has a tip electrode connected to the inner electrode on an outer surface thereof. lamp. 3. An end portion of the inner tube on the side immediately adjacent to the light extraction window and a shortest distance X between the light extraction window and the end portion are defined to be between 50% and 150% of the discharge gap L of the discharge space. 3. The dielectric barrier discharge lamp according to claim 1, wherein said discharge lamp is a discharge lamp. 4. The light extraction window has a light transmissive electrode on an outer surface thereof.
3. The dielectric barrier discharge lamp according to 1.