JP3170932B2 - 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 an improvement of a so-called dielectric barrier discharge lamp in which excimer molecules are formed by, for example, a dielectric barrier discharge, and light emitted from the excimer molecules is used as an ultraviolet light source for a photochemical reaction. About.

[0002]

2. Description of the Related Art As a technique related to the present invention, for example, Japanese Unexamined Patent Publication No. 2-7353 discloses a technique in which a discharge vessel is filled with a discharge gas for forming excimer molecules, and a dielectric barrier discharge (also known as a dielectric barrier discharge). Ozonizer discharge or silent discharge.
New edition published by the Institute of Electrical Engineers of Japan (Discharge Handbook) June 2001
A description is given of a radiator for forming excimer molecules by a reprint of the seventh edition of the moon, page 263) and extracting light emitted from the excimer molecules, that is, a dielectric barrier discharge lamp. Also, Japanese Unexamined Patent Publication No. Hei 2-
No. 7353 describes a radiator (for example, a fluorescent lamp) provided with a luminescence (for example, a phosphor) for converting ultraviolet light into light of another wavelength in a discharge vessel of a dielectric barrier discharge lamp. 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 dielectric barrier discharge lamp as described above has a problem that the light output decreases as the lighting time elapses.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dielectric barrier discharge lamp having a sufficient life characteristic in which the light output does not decrease as the lighting time elapses.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to fill a discharge vessel with a discharge gas for forming excimer molecules by a dielectric barrier discharge, and radiate from the excimer molecules generated by the dielectric barrier discharge. In a dielectric barrier discharge lamp having a window member for extracting light, the content of OH groups in quartz glass used for the window member is set to 10% by weight.
The problem can be solved by setting the content to less than ppm.

[0005]

We have found that in the dielectric barrier discharge, compared to the conventional arc discharge lamp, the presence of impurity gases, especially oxygen, hydrogen and other molecular gases, reduces the rate of UV output reduction in the conventional arc discharge lamp. It was found to be significantly larger than the lamp. Although this mechanism is not always clear, it is considered as follows. The dielectric barrier discharge is capable of efficiently generating ultraviolet light having a wavelength that cannot be obtained by a conventional arc discharge. Generation of the characteristic ultraviolet rays is based on the following mechanism. That is, first, high-energy plasma that is not present in the conventional arc discharge lamp is generated by the dielectric barrier discharge. This plasma generates excimer molecules through various collision processes, and the excimer molecules emit characteristic ultraviolet rays with high efficiency. Therefore, the impurity gas present in the discharge space, especially the molecular gas such as oxygen, hydrogen and water, not only directly destroys the excimer molecule, but also
The various collision processes also act to reduce the excimer molecules, ie, reduce the density of the excimer molecules, and thus reduce the UV output. In particular, when halogen is contained in the discharge gas, when oxygen, water, and the like are released, the erosion of the halogen into the quartz glass occurs, and the decrease in the ultraviolet output becomes large. That is, in the dielectric barrier discharge lamp, the ratio of the decrease in the ultraviolet output due to the impurity gas is remarkably large as compared with the conventional arc discharge lamp.

[0006] We have investigated the origin of the impure gases and found that the main source of emission is quartz glass used for dielectrics or extraction windows. In particular, when the OH group concentration in quartz is high, water is released more. UV-induced {Si-OH bond (結合
Represents a bond to oxygen), which is released and released as H ₂ O. We investigated various quartz glasses and found that O
It has been found that by using quartz having an H group concentration of 10 ppm or less, a decrease in the density of excimer molecules can be prevented, and thus a decrease in light output can be prevented.

FIG. 1 is a schematic view of a coaxial cylindrical dielectric barrier discharge lamp according to an embodiment of the present invention. The discharge vessel 1 is one in which the outer diameter D ₁ is the inner tube 2 of 6mm of quartz glass length about 300 mm, an inside diameter D ₂ has a hollow cylindrical shape by arranging the outer tube 3 of 8mm coaxially. The inner tube 2 and the outer tube 3 also serve as a dielectric and discharge window member of the dielectric barrier discharge, and are made of quartz glass having an OH group containing 10 ppm or less by weight. Electrodes 4 and 5 made of a metal net that transmits light are provided on the outer surfaces of the inner tube 2 and the outer tube 3. The discharge space 6 is filled with xenon and chlorine as a discharge gas. When the dielectric barrier discharge lamp is turned on by the AC power supply 7, as described above, the amount of impurity gas released from the quartz glass is small, and therefore, the erosion of the quartz glass by chlorine is small, and the excimer molecules in the discharge space are not eroded. Since the density can be maintained high, a dielectric barrier discharge lamp with a small decrease in light output can be obtained.

Next, a lamp is manufactured from quartz glass having different OH group contents, and the light output value 100 hours after lighting is reduced to 10%.
The result of measuring the excimer light attenuation rate from the time of 0 to 1000 hours will be described. The lamp used was the dielectric barrier discharge lamp shown in FIG. As a result, when the OH group concentration in quartz was 10 ppm or more, the light attenuation rate was as large as 30% to 60%, and when it was 10 ppm or less, the light attenuation was as small as 20% or less.

[0009]

As described above, according to the present invention, as the lighting time elapses, the quartz glass forming the window member from which light is extracted is eroded by the halogen, so that the deterioration of the light output due to the deterioration is small. It is possible to provide a dielectric barrier discharge lamp capable of preventing a decrease in the density of excimer molecules containing the same.

[Brief description of the drawings]

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

[Explanation of symbols]

 2 inner tube 3 outer tube 4,5 electrode 6 discharge space 7 AC power supply

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-7353 (JP, A) JP-A-3-247522 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 65/04 G21K 5/00 H01J 61/30

Claims (2)

(57) [Claims] 1. A dielectric barrier discharge lamp having a window member filled with a discharge gas for forming excimer molecules by dielectric barrier discharge in a discharge vessel and taking out light emitted from the excimer molecules. A dielectric barrier discharge lamp characterized in that at least a part thereof is made of quartz glass, and the OH group content of the quartz glass is 10 ppm or less by weight. 2. The dielectric barrier discharge lamp according to claim 1, comprising a halogen as a discharge gas.