JP3025403B2 - 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 so-called dielectric barrier which forms excimer molecules by a dielectric barrier discharge used as an ultraviolet light source for a photochemical reaction and utilizes light emitted from the excimer molecules. It relates to improvement of a 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, a dielectric barrier discharge lamp, is described. It also describes that xenon gas is used as a discharge gas and light emitted from xenon excimer molecules is used. The dielectric barrier discharge lamp as described above is useful because it has various features not found in conventional low-pressure mercury lamps and high-pressure arc discharge lamps. However, the above-mentioned dielectric barrier discharge lamp does not always have sufficient luminous efficiency,
The luminous efficiency of a conventional dielectric barrier discharge xenon excimer lamp is said to be 5 to 10%, and the discharge is not always sufficiently stable, and the life is short.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dielectric barrier discharge lamp having a high luminous efficiency and a stable discharge and a long life, particularly a xenon excimer lamp for a dielectric barrier discharge.

[0004]

An object of the present invention is to provide an electrode for performing a dielectric barrier discharge, a discharge vessel filled with xenon gas, and xenon excimer molecules generated by the dielectric barrier discharge. In a dielectric barrier discharge lamp having a window member for extracting light, a discharge sustaining voltage expressed in volts is V, a discharge gap length expressed in cm is d, and a pressure of xenon gas expressed in kilopascals is p.
Is solved by defining the value of (V / d) / p in the range of 20 to 70. Further, the object of the present invention can be more effectively solved by providing a getter accommodating chamber accommodating a getter that is electrically connected to the inside of the discharge vessel.

[0005]

We have a dielectric material having an electrode for performing a dielectric barrier discharge, a discharge vessel filled with xenon gas, and a window member for extracting light radiated from xenon excimer molecules generated by the dielectric barrier discharge. In the barrier discharge lamp, the luminous efficiency and the discharge stability were examined by varying the discharge gap length d (cm) and the pressure p (kilopascal) of the xenon gas. The discharge gap length d in the present invention is the distance between the dielectric surfaces sandwiching the discharge space when the discharge space structure is an electrode-dielectric-discharge space-dielectric-electrode. In the case of -dielectric -discharge space -electrode, it is the distance between the inner surface of the dielectric and the inner surface of the electrode facing the discharge space. The pressure p of the xenon gas is a value at 25 ° C.

It is considered that the largest factor governing the luminous efficiency is the energy of electrons in the discharge plasma. Here, V / d is replaced with E, and E / p is called a converted electric field, but the energy of electrons strongly depends on the converted electric field E / p. Therefore, the luminous efficiency eventually depends on E / p. FIG. 2 shows the relationship between the converted electric field E / p and the luminous efficiency. Converted electric field E /
The discharge sustaining voltage V for determining p is the integrated value of the applied voltage and the current flowing through the lamp, described in page 112 of the “Ozonizer Handbook”, published by Corona, edited by the Ozonizer Technical Committee of the Institute of Electrical Engineers of Japan, ie, The charge amount (symbol Q) was determined from measurement of a Lissajous figure. In FIG.
An example of a Lissajous diagram in which the horizontal axis indicates the applied voltage and the vertical axis indicates the charge amount is shown. Straight line AB and straight line CD are parallel, straight line BC
And a straight line AD is obtained in parallel, and a half of the voltage difference between the straight line AB and the straight line CD corresponds to the discharge sustaining voltage V. In some cases, the straight line AB and the straight line CD were slightly deviated from each other and became curved, but in this case, these curves were approximated by straight lines.

The luminous efficiency falls below 10% when the converted electric field E / p is less than 20, and the purpose of increasing the efficiency of the dielectric barrier discharge lamp cannot be obtained. Further, when the converted electric field E / p exceeded 70, the luminous efficiency was considerably reduced, and when it exceeded 80, the discharge became unstable and the light output became unstable. That is, by adjusting the discharge gap length d and the pressure p of the xenon gas, the converted electric field E / p is reduced to 20.
When it is within the range from 70 to 70, a dielectric barrier discharge lamp having a luminous efficiency exceeding 10 and stable discharge can be obtained.

In the dielectric barrier discharge lamp, when an impurity gas, particularly a molecular gas such as oxygen, hydrogen, carbon monoxide, and water, is present, the rate of decrease in the ultraviolet output is reduced by the conventional arc discharge lamp or glow discharge lamp. It was found to be significantly larger than. Although this mechanism is not always clear, it is considered as follows. One of the features of the dielectric barrier discharge lamp is that it can generate ultraviolet light having a wavelength that cannot be obtained by a conventional arc discharge lamp with high efficiency. 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. Therefore, impurity gases existing in the discharge space, particularly molecular gases such as oxygen, hydrogen, carbon monoxide, and water, not only directly destroy the excimer molecules, but also act on the various collision processes to cause the excimer molecules. And thus the UV output is reduced. That is, the dielectric barrier discharge lamp is more susceptible to the impurity gas than the conventional arc discharge lamp. When a getter is provided in the discharge vessel, an impurity gas such as oxygen, hydrogen, carbon monoxide, and water generated from the discharge vessel, a dielectric or an electrode by the action of discharge plasma or ultraviolet rays is removed as the lighting time elapses. As a result, the dielectric barrier discharge lamp having the above-described influence and therefore, the light output is not reduced, and the luminous efficiency is higher than before, and the discharge is stable and the life characteristics are excellent. Can be obtained.

In a conventional arc discharge lamp, for example, a solid getter made of an alloy of zirconium and aluminum is fixed to a stem or the like provided in a discharge vessel and is in contact with or close to the discharge plasma. Or a thin film getter made of barium or the like deposited on the tube wall of the discharge vessel in contact with or in close proximity to the discharge plasma. As a result of an experimental investigation by the present inventors, it has been found that, in the dielectric barrier discharge lamp, the discharge becomes unstable and the light output becomes unstable with the getter mounting structure as in the conventional arc lamp described above. discovered. That is, since the discharge voltage of the dielectric barrier discharge lamp is as high as several thousand volts, irregular discharge occurs between the conductive getter and the dielectric barrier discharge electrode installed in the vicinity of the discharge plasma. Occurs, and the light output becomes unstable. In particular, in the case of the getter of the metal film deposited on the tube wall of the discharge vessel, creeping discharge is easily generated between the tube wall of the discharge vessel and the metal film getter, and the rate of occurrence of unstable discharge is extremely large. A dielectric barrier discharge lamp having at least a discharge vessel filled with a discharge gas forming excimer molecules by dielectric barrier discharge and a window member for extracting light emitted from the excimer molecules, wherein the discharge vessel is electrically connected to the inside of the discharge vessel. Moreover, if a getter accommodating chamber is provided so that the discharge plasma does not directly enter and the getter is accommodated in the getter accommodating chamber, an irregular discharge generated between the electrode for the dielectric barrier discharge and the conductive getter may occur. It is possible to obtain a dielectric barrier discharge lamp which has a long life and has a stable light output.

[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 with a total length of about 150 mm, an outer diameter of 14 mm,
A hollow cylinder is formed by coaxially arranging an inner tube 2 having a thickness of 1 mm and an outer tube 3 having an inner diameter of about 23 mm and a thickness of 1 mm. The inner tube 2 and the outer tube 3 also serve as a dielectric barrier for a dielectric barrier discharge and a light extraction window member, and are provided on their outer surfaces with electrodes 4 and 5 made of a metal mesh that transmits light. Therefore, the discharge gap length d in the discharge space 6 is 0.45 cm. At one end of the discharge vessel 1, a getter housing chamber 10 is provided which is formed by extending a tube wall of the discharge vessel 1 and providing a disk-shaped partition wall 11 so as to form a space t. A barium getter 12 made of a barium alloy was housed in the getter housing chamber 10, and the barium getter 12 was heated at a high frequency to form a barium thin film in the getter housing chamber.
The discharge space 6 was filled with xenon gas of 300 Torr as a discharge gas, and the high frequency power supply 20 was used to light the dielectric barrier discharge lamp at an input power of 0.2 Watt per square centimeter of surface area. The voltage V becomes 800 V, that is, the reduced electric field E / p becomes 44, and 172 nm emitted from the excimer molecule of xenon.
Vacuum ultraviolet rays having a maximum value in the range of 160 nm to 180 nm were emitted with a high efficiency of 12% or more. There was no unwanted discharge between the getter and the discharge was stable. Further, the impurity gas generated even after long-time operation is removed by the getter, and a dielectric barrier discharge lamp having excellent life characteristics can be obtained. Life time is 7
At 0%, this lamp maintains a high efficiency of about 8.4% even after 1,000 hours of use.

A coaxial cylindrical dielectric barrier discharge lamp according to a second embodiment of the present invention has a structure in which the electrode 4 in the first embodiment is changed to an aluminum foil formed by vapor deposition.
The aluminum foil has a maximum at 172 nm emitted from the xenon excimer molecule from 160 nm to 180 n.
m and efficiently reflects vacuum ultraviolet rays in the range of m, and the luminous efficiency is 8 even when used for 1,000 hours, like the lamp of Example 1.
% Is obtained.

A third embodiment of the present invention is a lamp having a configuration in which light is extracted in a direction perpendicular to the discharge direction, and a schematic diagram thereof is shown in FIG. Two rectangular synthetic quartz glass plates each having a long side of 150 mm and a short side of 30 mm are used as dielectrics 13 and 14.
14, ie, the discharge gap length d is 0.5
cm and the light extraction window member 31
, Side plate 36, and dielectrics 13, 1 (not shown)
The discharge vessel was formed by providing two side plates on the long side of No. 4.
The light extraction window member 31 is provided on one short side of the dielectrics 13 and 14, and the length H parallel to the discharge direction is set to 1 cm so as to exceed the discharge gap length d of 0.5 cm.
With such a configuration, light generated immediately near the inner surfaces of the dielectrics 13 and 14 can be efficiently extracted. On the inner surfaces of the dielectrics 13 and 14, there were provided multilayer dielectric reflection films 37a and 37b that alternately laminate 25 layers of MgF ₂ and LaF ₃ and reflect ultraviolet light of 172 nm. This reflective film is
This is unnecessary when the electrodes 15 and 16 are made of an aluminum metal film, but since the quartz glass is not irradiated with ultraviolet rays, there is also an effect of preventing generation of impurity gas.

The length L parallel to the discharge direction of the side plate 36 facing the light extraction window member 31 is also set to 1 cm so as to exceed the discharge gap length d. Side plate 36 as described above
The light from the plasma generated immediately near the inner surfaces of the dielectrics 13 and 14 is also well reflected by the light reflecting film 38 provided on the outside of the side plate 36 and emitted from the light extraction window member 31. Xenon as a discharge gas is sealed in the discharge space 6 at 350 Torr, and the electrodes 15 and 1 are supplied by the power supply 20.
As a result of applying a voltage to No. 6, the converted electric field E / p becomes 52, and 172 nm emitted from the excimer molecule of xenon.
Vacuum ultraviolet rays having a maximum value in the range of 160 nm to 180 nm are radiated with high efficiency of 11% or more.
A dielectric barrier discharge lamp having stable discharge and stable light output even after use for 00 hours was obtained.

Although all of the above examples are so-called dielectric barrier discharge ultraviolet light emitting lamps having no fluorescent material, the present invention can also be applied to so-called dielectric barrier discharge fluorescent lamps in which a fluorescent material is provided in a discharge vessel. It is obvious.

[0015]

As described above, according to the present invention, a long-life dielectric barrier discharge lamp having high luminous efficiency and stable light output can be provided.

[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 diagram of luminous efficiency.

FIG. 3 is an explanatory diagram of a Lissajous figure.

FIG. 4 is an explanatory view of another embodiment of the dielectric barrier discharge lamp of the present invention.

[Description of Signs] 1 Discharge vessel 2 Inner tube 3 Outer tube 4, 5 Transparent electrode 10 Getter storage chamber 11 Partition wall 12 Getter 31 Light extraction window 36 Side plate 37Aa, 37b Light reflection film 38 Light reflection film

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuo Onishi 1194, Sado, Bessho-cho, Himeji-shi, Hyogo Ushio Electric Co., Ltd. Examiner in a corporation Shinichi Omori (56) References JP-A-2-7353 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 65/00 H01J 65/04

Claims (2)

(57) [Claims] An electrode for performing a dielectric barrier discharge;
In a dielectric barrier discharge lamp having a discharge vessel filled with xenon gas and a window member for extracting light emitted from xenon excimer molecules generated by the dielectric barrier discharge, a discharge sustaining voltage expressed in volts is expressed as V or cm. When the discharge gap length expressed as d and the pressure of xenon gas expressed in kilopascals as p, the value of (V / d) / p is 20.
A dielectric barrier discharge lamp defined in the range of from 70 to 70. 2. The dielectric barrier discharge lamp according to claim 1, wherein a metal boride film that reflects ultraviolet rays is formed on the inner surface of the discharge vessel.