JP3170952B2 - 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 the Electric 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 at least a portion of the discharge vessel also serves as a dielectric for the dielectric barrier discharge, at least a portion of the dielectric radiated from the excimer molecules. A dielectric barrier discharge lamp structure that is light-transmissive to light that passes through, and at least a part of the light-transmissive dielectric is provided with a conductive mesh electrode. It has been mounting. 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. However, the above-described dielectric barrier discharge lamp has a problem that the luminous efficiency is not always sufficient.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dielectric barrier discharge lamp having one electrode made of a conductive mesh and having a high luminous efficiency.

[0004]

The above object of the present invention can be achieved by forming the area of one mesh of the conductive mesh between 6 and 900 mm. The area of the mesh in the present invention is an area surrounded by conductive wires, and does not include the area occupied by the conductive wires.

[0005]

[Function] Dielectric barrier discharge is described in the Discharge Handbook.
The diameter of the discharge is very small, as described in
Moreover, it is a collection of a large number of minute discharge plasmas (hereinafter referred to as microplasma) whose discharge duration is very short. In a dielectric barrier discharge lamp having a structure in which a conductive mesh for electrodes is provided in contact with a light-transmitting dielectric, which is a light extraction window, the stability of light output, that is, temporal fluctuation of light output, And it was experimentally found that the luminous efficiency changes depending on the area of one mesh of the conductive mesh.

The mechanism by which the temporal fluctuation of light output and the luminous efficiency change depending on the area of one mesh of the conductive mesh is not necessarily clear, but is presumed to be as follows. Hereinafter, description will be made with reference to schematic diagrams of FIGS. That is, the discharge vessel is filled with a discharge gas that forms excimer molecules by a dielectric barrier discharge, and at least a part of the discharge vessel also serves as a dielectric of the dielectric barrier discharge, and at least a part of the dielectric Is a dielectric barrier discharge lamp, which is light-transmissive to light emitted from the excimer molecule, and has a conductive mesh electrode in contact with at least a part of the light-transmissive dielectric. In this case, if the area of the mesh of the conductive mesh used as an electrode is between 6 and 900 square millimeters, the following discharge occurs. That is, although the microplasmas 20a, 20b, 20c, and 20d immediately adjacent to the conductive strand 22 are stably generated, the electric charges charged in the dielectric surface area at the center of the mesh due to the relatively large mesh area are generated. Is hardly discharged through the conductive element wire 22 surrounding the mesh, and therefore, the microplasma 21a, 21
b and 21c hardly occur directly. The electric charges charged in the dielectric surface area at the center of the mesh are transferred to the microplasmas 20a, 20b, 20c, and 2 close to the conductive strand 22.
0d is discharged by the electric charge of the portion in contact with the surface of the dielectric material 3 extending to the center of the mesh along the surface of the dielectric material 3, that is, by a creeping discharge-like discharge.
At this time, the microplasmas 20a, 20b, 20c, 2
Od also moves to the center of the mesh slightly later than the creeping discharge. Therefore, not only the creeping discharge, but also the microplasmas 20a, 20b, 20c, 20d
Is also less absorbed by the electrode net 4, resulting in high efficiency.

When the area of one mesh of the conductive net 4, that is, a × b in FIG. 3, is less than 6 mm 2, the following dielectric barrier discharge occurs. That is, the microplasmas 20a, 20b, 20c, and 20d immediately adjacent to the conductive strands 22 that are stably generated.
In addition, since the mesh area is relatively small, microplasmas 21a, 21b, and 21c, which are slightly unstable but close to the center of the mesh, are also generated at the same time. However, the microplasma 20a, 20
b, 20c, and 20d occupy a relatively large proportion, and the proportion of light absorbed by the conductive strand 22 becomes relatively large.
Therefore, the efficiency is not significantly improved.

When the area of one mesh of the conductive net 4, that is, a × b in FIG. 3, exceeds 900 square millimeters, the following dielectric barrier discharge occurs. That is, the microplasmas 20a, 20b, 20c, and 20d in the immediate vicinity of the conductive element wire 22 are stably generated, but the electric charge charged in the dielectric surface area at the center of the mesh plane due to the large area of the mesh is Discharge is less likely to occur through the dielectric surface in contact with the conductive element wire 22 surrounding the mesh, and therefore, the microplasmas 21a, 21b, and 21c near the center of the mesh are less likely to be generated directly. The electric charges charged in the dielectric surface area at the center of the mesh are transferred to the microplasma 20 close to the conductive strand 22.
a, 20b, 20c, and 20d are discharged by the electric charge of the portion in contact with the surface of the dielectric 3 that is developed along the surface of the dielectric 3 toward the center of the mesh, that is, by the discharge in the form of a creeping discharge. Is done. At this time, the microplasma 20
A, 20b, 20c, and 20d also move to the center of the mesh slightly later than the creeping discharge. Since the area of the mesh is large, the surface discharge at this time and the diameter of the microplasmas 20a, 20b, 20c, and 20d are increased, and the duration of the discharge is also increased. As a result, the efficiency of generating excimer molecules is reduced. Then, the luminous efficiency is reduced. In addition, the power injection into the discharge space becomes insufficient,
There is also the disadvantage that the radiation density of the light output is reduced.

In the structure of the conductive net 4, the conductive wires 22 do not need to be perpendicular to each other, but only need to intersect. When the longer distance between the conductive strands 22 of the conductive net 4 is a, and the shorter distance is b, the ratio of a to b (a / b)
Is less than or equal to 2.5, there is an advantage that the conductive net 4 can be easily attached to the lamp. The conductive strand 22
May have a circular or rectangular cross section, or may be a thin film formed by screen printing, sputtering, or the like. Further, the above effect is further optimized when the electrode net 4 is configured so that the area of one mesh of the conductive net 4 is between 10 and 100 square millimeters.

[0010]

FIG. 1 is a schematic view of a coaxial cylindrical dielectric barrier discharge lamp according to a first embodiment of the present invention. Discharge vessel 1
Is made of quartz glass having a total length of about 300 mm, and has an outer diameter D ₁ of 24.
An inner tube 2 having a diameter of ₂ mm and an outer tube 3 having an inner diameter D2 of about 34 mm are coaxially arranged to form a hollow cylinder. The outer tube 3 also serves as a dielectric barrier for the dielectric barrier discharge and a light extraction window, and a metal net 4 for transmitting light is provided on the outer surface. One of the electrodes is the mesh 4 described above, and the strand 22 is a stainless steel wire having a diameter c of 0.1 mm, which is woven at a right angle at a constant pitch, and a and b in FIG.
mm, so that the mesh area was about 16 square millimeters. On the outer surface of the inner tube 2, another electrode 5 formed by aluminum evaporation is provided. Dielectric thin films 11 and 12 of MgF ₂ having a thickness of about 900 nm are provided on the surfaces of the outer tube 3 and the inner tube 2 facing the discharge space 13. A getter 6 is provided at one end of the discharge vessel 1 by compressing a mixture of alumina powder and silica powder into a ring shape in a porous state. In addition, the getter 6 is only prevented from moving into the discharge space by the protrusion 7 provided on the outer tube 3 and is not fixed to the discharge vessel 1. 450 g of a mixed gas of chlorine and xenon is used as a discharge gas in the discharge space 13.
Torr sealed and turned on with power supply 14 308n
m and ultraviolet rays in the vicinity thereof were emitted with high efficiency. further,
The dielectric thin film made of MgF ₂ prevents the quartz glass from being damaged by chlorine, and the porous oxide is used as the getter, so that the getter is not attacked by chlorine in the discharge gas, and therefore has excellent life characteristics. The resulting dielectric barrier discharge lamp was obtained. In this example,
The luminous efficiency is 10 times higher than that of the conventional dielectric barrier discharge lamp.
%.

In the second embodiment of the present invention, the net 4 in the first embodiment is formed by knitting a stainless wire having a diameter of 0.15 mm at a right angle and at a constant pitch.
And b are equal to 6 mm, so that the mesh area is about 36 square millimeters, and the discharge gas is 30 mm.
The dielectric thin film 12 which is made of xenon of 0 Torr and is provided on the inner surface of the inner tube 2 which is a single layer in the first embodiment,
25 layers of MgF ₂ and LaF ₃ are alternately laminated, and 172 n
It is characterized in that it is a multilayer dielectric reflection film that reflects ultraviolet rays of m. Further, the last layer of the multilayer dielectric reflection film, that is, the layer in contact with the discharge space 13 was made of MgF ₂ . In this example, ultraviolet rays of 172 nm generated in the discharge space could be taken out more efficiently, and high efficiency was obtained. In addition, since the layer that comes into contact with air is made of MgF ₂ when the lamp is manufactured, LaF _{3, which} is relatively easily degraded in air, does not come into direct contact with air, so that the dielectric surface becomes uniform, and a dielectric barrier discharge of more stable quality is achieved. A lamp was obtained. Also in this example, the luminous efficiency was increased by about 10% as compared with the conventional dielectric barrier discharge lamp.

[0012]

As described above, according to the present invention, a high-efficiency dielectric barrier discharge lamp can be provided in a dielectric barrier discharge lamp in which one electrode is a conductive net.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a microplasma.

FIG. 3 is an explanatory diagram of a conductive net.

[Explanation of symbols]

 Reference Signs List 1 discharge vessel 2 inner tube 3 outer tube 4 conductive net 5 electrode 6 getter 11 dielectric thin film 12 dielectric thin film

────────────────────────────────────────────────── ─── Continuing from the front page Examiner Katsumi Enari (56) References JP-A-4-223039 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 65/04

Claims (1)

(57) [Claims] A discharge vessel is filled with a discharge gas for forming excimer molecules by a dielectric barrier discharge. At least a part of the discharge vessel also serves as a dielectric of the dielectric barrier discharge. At least a part is light-transmissive to light emitted from the excimer molecule, and in a dielectric barrier discharge lamp provided with a conductive mesh electrode in contact with at least a part of the light-transmitting dielectric, A dielectric barrier discharge lamp, wherein the area of one mesh of the conductive mesh is between 6 and 900 square millimeters.