JP3168847B2 - Dielectric barrier discharge lamp device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp device used as an ultraviolet light source for photochemical reactions, for example, which forms excimer molecules by dielectric barrier discharge.
The present invention relates to an improvement in a so-called dielectric barrier discharge lamp device using light emitted from the excimer molecule.

[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. 1-144560.
There, a discharge vessel is filled with a discharge gas for forming excimer molecules, and a dielectric barrier discharge (also known as an ozonizer discharge or a silent discharge) is issued. (See page 263)
A lamp using light emitted from the excimer molecule, i.e., a dielectric barrier discharge lamp, wherein the discharge vessel is cylindrical and at least a part of the discharge vessel is A dielectric barrier discharge lamp is described, which also serves as a dielectric for a dielectric barrier discharge, the dielectric being light transmissive, and a conductive mesh electrode provided on at least a part of the dielectric.

Hereinafter, an outline of a general dielectric barrier discharge will be described with reference to FIG. 1 which is a schematic view of a dielectric barrier discharge lamp. The discharge vessel 1 is made of glass as a dielectric, and has a hollow cylindrical shape in which an inner tube 2 and an outer tube 3 are coaxially arranged. On the outer surface of the outer tube 3, there is provided an electrode 4 for light-transmitting dielectric barrier discharge, and on the outer surface of the inner tube 2, there is provided an electrode 5 for dielectric barrier discharge which also serves as a light reflection film formed by vapor deposition of aluminum. Is provided. In order to mechanically and chemically protect the electrode 5, a protective film 9 made of boron nitride is provided on the electrode 5.

A discharge space 8 is formed between the inner surface of the outer tube 3 facing the electrode 4 and the inner surface of the inner tube 2 facing the electrode 5. The distance between the two inner surfaces is not always uniform at the discharge space 8 depending on the machining accuracy of the discharge vessel 1. Therefore, the discharge gap length of the discharge space 8 is not uniform throughout the discharge space 8. Therefore, of a straight line group that is perpendicular to the central axis of the hollow cylindrical discharge vessel 1 and intersects with the central axis,
A straight line having the same distance from both ends of the discharge vessel 1 is used as a reference line, and a plurality of straight lines equidistant from the reference line in the direction of the central axis are symmetrically centered on the reference line. The average discharge gap length d of the discharge space 8 is obtained by averaging the distances between the inner surfaces at the points where the selected straight lines intersect the two inner surfaces.

When the discharge space 8 is filled with a discharge gas for forming excimer molecules by a dielectric barrier discharge and a voltage is applied to the electrodes 4 and 5 by an AC power supply 10, the dielectric barrier discharge is stably performed in the discharge space 8. Occurs and excimer light is emitted.

In a normal arc discharge generated by an arc discharge lamp at a medium pressure or a high pressure of several tens of torr or more, only one discharge plasma exists in a discharge space, and one small electrode luminescent spot exists on an electrode surface. Has occurred. That is, even if the area of the electrode is increased, the portion that substantially functions as an electrode is a very small portion, and only one discharge plasma exists. On the other hand, as described in the discharge handbook, in a dielectric barrier discharge, a dielectric is inserted in the discharge path. Since this dielectric prevents the discharge plasma from converging into a single line, a very small discharge plasma having a very small plasma diameter and a very short discharge duration (hereinafter referred to as a microplasma) is formed by the discharge. There will be many in space.

The reason why a plurality of dielectric barrier discharge lamps connected in parallel can be turned on by one power supply is that the above-mentioned multiple microplasmas exist.

[0008]

The dielectric barrier discharge lamp as described above is useful because it has various features not found in conventional glow discharge lamps and arc discharge lamps. In particular, the dielectric barrier discharge lamp having the following configuration has various advantages as described below. (1) The discharge vessel is made substantially cylindrical, and the inside of the discharge vessel is
When the internal electrode is provided on the outer surface substantially coaxially with the discharge vessel, a commercially available glass tube, ceramic tube, or the like can be used, and the structure is simplified. The advantage is that a dielectric barrier discharge lamp can be provided. (2) If the total area of the discharge vessel in contact with the conductive mesh electrode of the dielectric barrier discharge lamp connected to one power supply is 160 cm 2 or more, a relatively large device can be used for a compact device. There is an advantage that the object can be irradiated collectively. (3) The value obtained by dividing the electric input to the dielectric barrier discharge lamp by the area expressed in square centimeters of the discharge vessel in contact with the conductive mesh electrode is hereinafter referred to as a tube wall load. When it is 5 W / cm ² or less, there is an advantage that the temperature rise of the discharge vessel is small, and therefore, the object to be irradiated is not excessively heated. Furthermore, since the input of ultraviolet rays to the unit area of the discharge vessel is reduced, there is an advantage that deterioration of the discharge vessel is reduced and a long life is obtained.

[0009] The electrical input to the dielectric barrier discharge lamp is:
The Ozonizer Technical Committee of the Institute of Electrical Engineers of Japan, published by Corona “ Ozonizer Handbook”, 1960, No. 232-23
It was determined from the Lissajous figure measurement of the integrated value of the applied voltage and the current flowing through the lamp, that is, the charge amount (symbol Q) described on page 5 . FIG. 2 shows an example of a Lissajous diagram in which the horizontal axis indicates the applied voltage and the vertical axis indicates the charge amount. Straight line AB
And the straight line CD is parallel, and the straight line BC and the straight line AD are parallel. Thus, an electric input to the discharge lamp is calculated from the area of the isosceles quadrilateral. 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.

However, it has been found that the conventional dielectric barrier discharge lamp has the following disadvantages. Commercially available glass tubes, ceramic tubes, and the like have variations in wall thickness, tube diameter, and the like in the axial position of each tube and one tube, and this is the difference in the axial position of each lamp and one lamp. Causes variations in light output. For example,
In FIG. 1, assuming that the thickness of the outer tube 3 is increased at the left end of the figure, the electric input decreases at the left end of the figure, and the light output decreases. That is, while there is a sufficient light output in a portion far from the left end of the figure, the light output decreases as approaching the left end of the figure. This disadvantage is unique to a dielectric barrier discharge lamp in which the tube wall of the discharge vessel is used as a dielectric for a dielectric barrier discharge.

The variation in the light output due to the variation in the wall thickness, the tube diameter and the like naturally increases as the area of the discharge vessel in contact with the conductive mesh electrode of the dielectric barrier discharge lamp increases. Furthermore, it increases as the tube wall load decreases. In particular, when the area is 160 square centimeters or more and the tube wall load is 0.5 W / cm ² or less, the light due to the variation in the thickness and the tube diameter and the variation in the discharge gap length due to the machining accuracy described above. The output variation could not be ignored in practical use. It is obvious that the area is the sum of the areas of the dielectric barrier discharge lamps when a plurality of dielectric barrier discharge lamps connected in parallel are operated by one power supply.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for forming a conductive reticulated electrode of a dielectric barrier discharge lamp connected to one power supply. The sum of the areas of the discharge vessels in contact with each other is 160 square centimeters or more, and the value obtained by dividing the electric input to the dielectric barrier discharge lamp by the area in square centimeters of the discharge vessels in contact with the conductive mesh electrode is: An object of the present invention is to provide a dielectric barrier discharge lamp device having a power output of 0.5 W or less and having no variation in light output depending on each lamp and the axial position of the lamp.

[0013]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention is directed to a light-transmitting discharge vessel having at least a substantially cylindrical outer shape, and at least one of the outer surfaces of the discharge vessel. A conductive mesh electrode provided on the entire periphery of the portion, an internal electrode provided substantially coaxially with the discharge vessel on the outer surface inside the discharge vessel, and a main component comprising xenon and chlorine gas filled in the discharge space. At least one dielectric barrier discharge lamp made of a discharged gas, and at least one power supply for performing a dielectric barrier discharge, wherein the conductivity of the dielectric barrier discharge lamp is connected to one power supply. The total area of the discharge vessel in contact with the conductive reticulated electrode is at least 160 square centimeters, and the electrical input to the dielectric barrier discharge lamp is the square centimeter of the discharge vessel in contact with the conductive reticulated electrode. The value obtained by dividing the area that is 0.5W /
In the dielectric barrier discharge lamp device of not more than cm ² , when the discharge starting voltage in volts is Vs and the voltage applied to the lamp is Vp, the discharge gap, gas pressure, and output voltage of the power supply of the dielectric barrier discharge lamp , The frequency and the like are adjusted so that the value of Vs / Vp is regulated to 0.6 or less.

According to a second aspect of the present invention, in the first aspect of the present invention, the discharge sustaining voltage expressed in volts is Vm, cm.
Where d is the discharge gap length represented by, and p is the pressure of xenon and chlorine gas in kilopascals, (Vm / d) /
The value of p is changed from 40 V / cm / kPa to 100 V / cm / k.
It is configured to be in the range of Pa.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, a substantially planar light source is constituted by arranging two or more dielectric barrier discharge lamps in parallel. It was done.

[0016]

The light-transmitting discharge vessel having at least a substantially cylindrical outer shape, a conductive mesh electrode provided on at least a part of the outer surface of the discharge vessel, and the discharge vessel inside the discharge vessel. An internal electrode provided substantially coaxially, and at least one dielectric barrier discharge lamp comprising a discharge gas mainly containing xenon and chlorine gas filled in the discharge vessel;
A total of 160 square centimeters of area of the discharge vessel in contact with the conductive mesh electrode of the dielectric barrier discharge lamp connected to one power supply and having at least one power supply for performing a dielectric barrier discharge is provided. The value obtained by dividing the electric input to the dielectric barrier discharge lamp by the area expressed in square centimeters of the conductive mesh electrode is 0.5 W
In the following dielectric barrier discharge lamp device, the following facts have been found.

That is, the variation of the light output at the position in the tube axis direction of each lamp and one lamp is caused by the discharge starting voltage Vs with respect to the voltage Vp applied to the lamp.
Was found to decrease as Vs / Vp became smaller. Note that the above-mentioned discharge starting voltage V
s and the applied voltage Vp are obtained from the Lissajous diagram shown in FIG. 2 and are respectively half the values obtained by projecting D and C on the horizontal axis.

The mechanism by which the variation in light output decreases as the ratio of the firing voltage Vs to the voltage Vp applied to the lamp decreases is presumed to be as follows. In the Lissajous diagram shown in FIG. 2, the period between AD and CB is a period in which the discharge is paused, the discharge starts at D and B, and the generation and extinction of the microplasma are repeated between DC and BA.

When the discharge start voltage Vs varies, the number of times of generation of the microplasma between DC and BA varies. Applied voltage V to discharge start voltage Vs
If p is not sufficiently large, the number of times of generation of the microplasma is small, and therefore, the ratio of the variation of the light output due to the variation of the discharge start voltage Vs increases. However, when the ratio of the discharge start voltage Vs to the applied voltage Vp is small, even if the discharge start voltage Vs varies, the number of occurrences of the microplasma is large, so that the ratio of the variation in the optical output decreases. Conceivable. That is, the variation of the light output at the position in the tube axis direction of each lamp and one lamp tends to decrease as the ratio of the discharge starting voltage Vs to the voltage Vp applied to the lamp decreases, and in particular, Vs / It has been found that when the value of Vp becomes 0.6 or less, the variation in optical output sharply decreases.

According to the first aspect of the present invention, the ratio of the discharge starting voltage Vs to the voltage Vp applied to the lamp,
Since the value of Vs / Vp is limited to 0.6 or less, even if the wall thickness, outer diameter or discharge gap length of the discharge vessel varies, the position of each lamp and one lamp in the direction of the tube axis varies. In this case, it is possible to obtain a dielectric barrier discharge lamp device having a small variation in light output at the time.

According to the second aspect of the present invention, the discharge sustaining voltage in volts is Vm, the discharge gap length in cm is d, and the pressure of xenon and chlorine gas in kilopascals is p. , (Vm / d) / p to 40 V /
Since the range is specified in the range of cm / kPa to 100 V / cm / kPa, it is possible to obtain a high-efficiency dielectric barrier discharge lamp in addition to the advantage that the variation in light output is small.

The mechanism for obtaining high efficiency in the second aspect of the invention is as follows. In a dielectric barrier discharge lamp having a structure similar to that of FIG.
(Cm) and the pressure p (kilopascal) of xenon and chlorine gas were variously changed, and luminous efficiency and discharge stability were examined. The discharge gap length d in the present invention is the distance between the surfaces of the dielectric body 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 xenon and chlorine gas is 25 ° C.
Is the value at.

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. The luminous efficiency is 1 when the converted electric field E / p is smaller than 40.
0%, and the object of increasing the efficiency of the dielectric barrier discharge lamp cannot be obtained. Also, the converted electric field E / p is 1
If it exceeds 00, the luminous efficiency is considerably reduced, and if it exceeds 110, the discharge becomes unstable and the light output becomes unstable. That is, by adjusting the discharge gap length d and the pressure p of xenon and chlorine gas so that the converted electric field E / p is in the range of 40 to 100, the luminous efficiency exceeds 10% and the discharge is stable. A body barrier discharge lamp is obtained.

The discharge sustaining voltage Vm is obtained from the measurement in the Lissajous diagram of FIG. 2, and corresponds to one half of the voltage at the point where the straight line CD intersects the horizontal axis.

According to a third aspect of the present invention, in the first or second aspect of the present invention, two or more of the dielectric barrier discharge lamps are arranged in parallel, so that a spatial variation in light output is obtained. A small and highly efficient substantially planar light source device can be obtained at low cost.

[0026]

1 is a schematic view of a dielectric barrier discharge lamp device according to a first embodiment of the present invention. The discharge vessel 1 is made of quartz glass having a total length of about 300 mm, an outer diameter of 16 mm, and a wall thickness of 1 mm.
The inner tube 2 having a diameter of 2 mm and the outer tube 3 having an outer diameter of about 30 mm and a thickness of 1.5 mm are coaxially arranged to form a hollow cylinder.
The thickness variation of the inner pipe 2 and the outer pipe 3 in the pipe axis direction is ± 0.1 mm. The outer tube 3 also serves as a dielectric barrier for the dielectric barrier discharge and a light extraction window member, and has an electrode 4 made of a metal net that transmits light on its outer surface. The length of the metal net in the tube axis direction is 250 mm. That is, the area of the discharge vessel in contact with the mesh electrode 4 is 23
5 square centimeters. Also, the outer surface of the inner tube 2
An inner electrode 5 for dielectric barrier discharge, which also serves as a light reflection film formed by vapor deposition of aluminum, is provided on the (outer surface inside the discharge vessel) . In order to mechanically and chemically protect the electrode 5, a protective film 9 made of boron nitride is provided on the electrode 5.

A discharge space 8 is formed between the inner surface of the outer tube 3 facing the electrode 4 and the inner surface of the inner tube 2 facing the electrode 5. Therefore, the discharge gap length d in the discharge space 8 is about 0.65 cm.

33 kPa as a discharge gas in the discharge space 8
Xenon and chlorine gas, the frequency is about 13kHz
When the voltage was applied to the lamp with Vp of about 12 kV using the power source 10 of z, the dielectric barrier discharge lamp was turned on. 70V / cm / kP
a, Vm / Vp becomes 0.36, and the ultraviolet ray having the maximum value at the wavelength of 308 nm emitted from the excimer molecule of xenon chlorine is uniformly and efficiently emitted without variation at the position in the lamp axis direction of the lamp. Was.

FIG. 3 is a longitudinal sectional view of a second embodiment of the present invention. Four dielectric barrier discharge lamps 1a, 1b, 1 similar to the coaxial cylindrical dielectric barrier discharge lamp of the first embodiment.
The lamps 1a and 1b are provided with a power supply 10c and 1d in parallel with a cooling block 34 made of aluminum.
a, and the lamps 1 c and 1 d are connected to a power supply 10.
b is connected in parallel. 30a, 30b, 30c, 3
0d is a hole through which a cooling fluid flows. The outer diameter of the dielectric barrier discharge lamps 1a, 1b, 1c, 1d is 26.5 mm,
The discharge gap length is 5 mm, the filling pressure of xenon and chlorine gas is 33 kPa, and the length of the mesh electrode per lamp is 2
50 mm. The total area of the discharge vessel in contact with the mesh electrode of the lamp connected to one power source is 416
Square centimeters.

The dielectric barrier discharge lamps 1a, 1b, 1
c and 1d are sealed by a light extraction window 31, made of quartz glass, a cooling block 34, side plates 35a and 35b, and side plates (not shown) located in the direction of both ends of the lamp. The effective area of the light extraction window 31 is 240m
mx 240 mm. The dielectric barrier discharge lamp 1a,
Light extraction window 3 made of 1b, 1c, 1d and quartz glass
1 is filled with nitrogen gas introduced from the inert gas inlet 32. Reference numeral 33 denotes an inert gas outlet.

When the voltage applied to the lamps of the power supplies 10a and 10b was set to 8.5 kV, the tube wall load was 0.25 W / cm.
² , Vs / Vp is 0.38, E / p is 70 V / cm / k
Pa, and the ultraviolet ray having the maximum value at the wavelength of 308 nm does not vary at the position in the tube axis direction of the lamp, and
It was emitted uniformly and with high efficiency without dispersion by the individual lamps. As a result, uniform irradiance was obtained on the surface of the light extraction window 31, and a substantially planar light source was obtained at low cost.

The third embodiment of the present invention is different from the second embodiment in that the lamps 1a and 1d are connected to the power supply 10a, and the lamps 1b and 1d are connected to the power supply 10b. By adjusting the output of the power supply 10a, the light extraction window 3 can be adjusted.
There is an advantage that the ratio of the irradiance between the central part and the peripheral part can be changed.

The fourth embodiment of the present invention is different from the second embodiment in that the lamps 1a, 1b, 1c and 1d are connected to one power supply. The same effect as that of the second embodiment can be obtained, and further, there is an advantage that the power supply unit is compact.

Although all of the above examples are so-called dielectric barrier discharge ultraviolet radiation lamps having no phosphor, it is obvious that the present invention can be applied to a so-called dielectric barrier discharge fluorescent lamp in which a phosphor is provided in a discharge vessel. It is.

[0035]

As described above, according to the present invention, the following effects can be obtained. According to the first aspect of the present invention, the ratio of the discharge starting voltage Vs to the voltage Vp applied to the lamp and the value of Vs / Vp are limited to 0.6 or less. Even if the diameter or the discharge gap length varies, there is an effect that variations in light output at positions in the tube axis direction of each lamp and one lamp are small. Therefore, since a commercially available material can be used without using a special material for the discharge vessel, there is an advantage that a dielectric barrier discharge lamp device can be obtained at low cost.

According to a second aspect of the present invention, in the first aspect, the discharge sustaining voltage expressed in volts is V
When the discharge gap length in m and cm is d, and the pressure of xenon and chlorine gas in kilopascals is p, (Vm
/ D) / p from 40 V / cm / kPa to 100 V /
Since it is specified in the range of cm / kPa, in addition to the advantage that the variation in light output is small, there is an advantage that a dielectric barrier discharge lamp device with high efficiency can be obtained.

According to the third aspect of the present invention, in the first or second aspect of the present invention, since two or more of the dielectric barrier discharge lamps are arranged in parallel, spatial variations in light output are reduced. A small and highly efficient substantially planar light source device can be obtained at low cost.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a Lissajous figure.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge container 1a, 1b, 1c, 1d Dielectric barrier discharge lamp 2 Inner tube 3 Outer tube 4 Reticulated electrode 5 Inner electrode 31 Light extraction window 34 Cooling block 35a, 35b Side plate

────────────────────────────────────────────────── ─── Continued from the front page Examiner Hiroshi Kojima (56) References JP-A-6-215736 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 65/00

Claims (3)

(57) [Claims] 1. A profile and a light-transmitting discharge vessel which is generally cylindrical, and a conductive mesh electrode provided on the entire circumference of at least a portion of the outer surface of the discharge vessel, the inside of the outer surface of the discharge vessel and internal electrodes arranged in the discharge vessel and schematic coaxial, and at least one dielectric barrier discharge lamp comprising a discharge gas composed mainly of xenon and chlorine gas filled in the discharge space,
A total of 160 square centimeters of area of the discharge vessel in contact with the conductive mesh electrode of the dielectric barrier discharge lamp connected to one power supply and having at least one power supply for performing a dielectric barrier discharge is provided. The dielectric barrier, wherein a value obtained by dividing the electric input to the dielectric barrier discharge lamp by the area expressed in square centimeters of the discharge vessel in contact with the conductive mesh electrode is 0.5 W / cm ² or less. In the discharge lamp device, when the discharge starting voltage in volts is Vs and the voltage applied to the lamp is Vp, Vs / V
A dielectric barrier discharge lamp device, wherein the value of p is specified to be 0.6 or less. 2. The discharge sustaining voltage expressed in volts is Vm, c.
When the discharge gap length in m is d and the pressure of xenon and chlorine gas in kPa is p, (Vm / d)
2. The dielectric barrier discharge lamp device according to claim 1, wherein the value of / p is defined in the range of 40 to 100. 3. The dielectric barrier discharge lamp according to claim 1, wherein two or more dielectric barrier discharge lamps are arranged in parallel to constitute a substantially planar light source. apparatus.