JP2021051937A - Barrier discharge lamp and UV irradiation unit - Google Patents

Abstract

To provide a barrier discharge lamp that suppresses a decrease in luminous efficiency.SOLUTION: A barrier discharge lamp 1 includes a cylindrical arc tube 2, an internal electrode 3, and an external electrode 7. The arc tube 2 is filled with gas and transmits ultraviolet light. The internal electrode 3 is arranged inside the arc tube 2 and extends in the tube axial direction of the arc tube 2. The external electrode 7 is provided on the outer surface side of the arc tube 2 so as to face the internal electrode 3. An outer diameter D1 [mm] of the arc tube 2 and the inner diameter D2 [mm] of the external electrode have a relationship of 0.93≤D1/D2≤0.99.SELECTED DRAWING: Figure 2

Description

Embodiments of the present invention relate to barrier discharge lamps and UV irradiation units.

Conventionally, barrier discharge lamps used for the purpose of cleaning and modifying substrates are known. The barrier discharge lamp is a dielectric barrier discharge generated by connecting a spiral internal electrode arranged inside the arc tube, which is a dielectric, and an external electrode arranged outside the arc tube to an AC power source. It emits ultraviolet light having a specific wavelength according to the gas contained inside the arc tube.

Japanese Unexamined Patent Publication No. 2013-21164

In the barrier discharge lamp as described above, the light emitting characteristics may be deteriorated due to, for example, the dimensions of the external electrode and the arc tube.

An object to be solved by the present invention is to provide a barrier discharge lamp and an ultraviolet irradiation unit capable of suppressing a decrease in light emitting characteristics.

The barrier discharge lamp of the embodiment includes a cylindrical arc tube, an internal electrode, and an external electrode. The arc tube is filled with gas and transmits ultraviolet light. The internal electrode is arranged inside the arc tube and extends in the axial direction of the arc tube. The internal electrode is arranged inside the arc tube and extends in the axial direction of the arc tube. The external electrode is provided on the outer surface side of the arc tube so as to face the internal electrode. The outer diameter D1 [mm] of the arc tube and the inner diameter D2 [mm] of the external electrode have a relationship of 0.93 ≦ D1 / D2 ≦ 0.99.

According to the present invention, it is possible to suppress a decrease in light emission characteristics.

It is a figure which shows the ultraviolet irradiation unit which concerns on embodiment. FIG. 1 is a cross-sectional view taken along the line AA of FIG. It is a figure which shows the result of the evaluation test.

The barrier discharge lamp 1 according to the embodiment described below includes a cylindrical arc tube 2, an internal electrode 3, and an external electrode 7. The arc tube 2 is filled with gas and transmits ultraviolet light. The internal electrode 3 is arranged inside the arc tube 2 and extends in the tube axial direction of the arc tube 2. The outer electrode 7 is provided on the outer surface 2b side of the arc tube 2 so as to face the inner electrode 3. The outer diameter D1 [mm] of the arc tube 2 and the inner diameter D2 [mm] of the external electrode 7 have a relationship of 0.93 ≦ D1 / D2 ≦ 0.99.

Further, the ultraviolet irradiation unit 100 according to the embodiment described below includes one or a plurality of barrier discharge lamps 1.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. The embodiments shown below do not limit the techniques disclosed by the present invention.

[Embodiment]
FIG. 1 is a diagram showing an ultraviolet irradiation unit according to an embodiment, and FIG. 2 is a sectional view taken along the line AA of FIG. As shown in FIGS. 1 and 2, the ultraviolet irradiation unit 100 according to the embodiment includes one or more barrier discharge lamps 1, an external electrode 7, and a heat dissipation block 8.

For the sake of clarity, FIGS. 1 and 2 show a three-dimensional Cartesian coordinate system including a Z-axis whose positive direction is the irradiation direction. Further, in FIG. 1, the external electrode 7 and the heat dissipation block 8 are not shown.

The barrier discharge lamp 1 performs barrier discharge with an external electrode 7 provided on the outer surface side of the barrier discharge lamp 1. In the present embodiment, the external electrode 7 is provided on the outer surface side of the barrier discharge lamp 1, but the barrier discharge lamp 1 and the external electrode 7 are combined, and more specifically, the arc tube 2 described later. The form in which the external electrode 7 is combined may be referred to as a "barrier discharge lamp", and the form in which the barrier discharge lamp 1, the external electrode 7 and the heat dissipation block 8 are combined may be referred to as a "barrier discharge lamp". Good. Further, in the present embodiment, the external electrode 7 and the heat radiating block 8 are separately provided, but the morphology in which the heat radiating block 8 also functions as the external electrode 7 without the external electrode 7 is referred to as an “external electrode”. You may call it.

As shown in FIGS. 1 and 2, the barrier discharge lamp 1 has a light emitting tube 2, an internal electrode 3, a reflective film 4, a base 5, and a lead wire 6. The arc tube 2 is a cylindrical member that transmits ultraviolet light. Examples of the material of the arc tube 2 include synthetic quartz having a wavelength of 200 [nm] or less and a high vacuum ultraviolet transmittance. Specifically, for example, Shinetsu quartz synthetic quartz F-310 can be used as the material for the arc tube 2. Further, the arc tube 2 is hermetically sealed by being held by sealing members having a stem structure at both ends in the tube axis direction (X-axis direction).

Further, gas is sealed inside the arc tube 2. The gas is, for example, 80 to 200 [kPa] xenon gas. Specifically, for example, 93 [kPa] xenon gas is filled inside the arc tube 2. The gas may be composed of, for example, one type of krypton, xenon, argon, neon, etc., or a combination of a plurality of types. Further, the gas may include, for example, a halogen gas, if necessary. The arc tube 2 can emit ultraviolet light (excimer light) having a specific peak wavelength according to the type of the enclosed gas. In the application of cleaning the surface of the glass for a liquid crystal panel, for example, an arc tube 2 that emits vacuum ultraviolet light having a wavelength of 172 [nm] can be used.

The internal electrode 3 is arranged inside the arc tube 2. In the internal electrode 3, a coil portion 3a, which is a spiral conductor, extends in the tube axis direction of the arc tube 2. The internal electrode 3 is formed of, for example, a material containing tungsten. Specifically, the internal electrode 3 contains tungsten as a component of 50 [%] or more of all the components. In particular, when doped tungsten obtained by adding potassium or the like to tungsten is applied as the internal electrode 3, higher dimensional stability can be obtained. Specifically, for example, potassium-doped tungsten WK75 manufactured by Pluse can be used as a material for the internal electrode 3.

Further, the wire diameter φ of the internal electrode 3 can be, for example, 0.5 [mm] or more and 1.0 [mm] or less. Further, for the internal electrode 3, for example, the distance P in the tube axis direction of the coil portion 3a can be set to, for example, 10 [mm] or more and 50 [mm] or less. Specifically, for example, the internal electrode 3 in which the distance P between the coil portions 3a is 30 [mm] can be used.

The reflective film 4 is provided on the inner surface 2a of the arc tube 2 and reflects ultraviolet light into the arc tube 2. Examples of the material of the reflective film 4 include silica. Further, the reflective film 4 is not limited to silica, and may be made of a material containing ultraviolet scattering particles such as alumina. The reflective film 4 is arranged at an angle θ4 of 180 [°] or more, for example, 200 [°] or more and 300 [°] or less in the circumferential direction of the arc tube 2. Further, the length L4 of the reflective film 4 in the tube axis direction is arranged so as to be equal to or longer than the length L3 of the coil portion 3a of the internal electrode 3 in the tube axis direction. As a result, the decrease in luminous efficiency can be suppressed by efficiently irradiating the irradiated body with the ultraviolet light generated in the arc tube 2.

Further, the reflective film 4 is formed so as to have a film thickness of, for example, 100 [μm] or more and 300 [μm] or less from the viewpoint of maintaining good reflectance. The reflective film 4 may be in contact with or separated from the coil portion 3a of the internal electrode 3. However, as the barrier discharge lamp 1 according to the modified example of the embodiment, a mode in which the reflective film 4 is not provided is also allowed.

The external electrode 7 is provided on the outer surface 2b side of the arc tube 2 corresponding to the inner surface 2a of the arc tube 2 provided with the reflective film 4. The external electrode 7 can be made of, for example, stainless steel or aluminum.

The inner diameter D2 [mm] of the external electrode 7 has a relationship of 0.93 ≦ D1 / D2 ≦ 0.99 with respect to the outer diameter D1 [mm] of the arc tube 2. As a result, the adhesion between the arc tube 2 and the external electrode 7 is enhanced, and deterioration of the light emitting characteristics can be suppressed. On the other hand, when D1 / D2 <0.93 or D1 / D2> 0.99, the light emission characteristics deteriorate.

That is, when the plasma generated by applying a voltage to the barrier discharge lamp 1 comes into contact with the air in the environment that has entered the gap generated between the arc tube 2 and the external electrode 7, nitrifying hydrogen gas is generated. On the other hand, on the surface of the external electrode 7, moisture in the environment condenses. When the nitrifying hydrogen gas dissolves in the condensed water, nitric acid is generated and comes into contact with the outer surface 2b of the arc tube 2, so that the transparency of ultraviolet light is lowered. By repeating such a phenomenon each time the barrier discharge lamp 1 is turned on, the light emitting characteristics are deteriorated. Therefore, the outer diameter D1 [mm] of the arc tube 2 and the inner diameter D2 [mm] of the external electrode 7 have a relationship of 0.93 ≦ D1 / D2 ≦ 0.99.

When 0.99 <D1 / D2 <1.00, when the arc tube 2 is attached to the external electrode 7 or the heat radiating block 8, the attachment is hindered due to dimensional tolerances, twists, and the like. In particular, when D1 / D2> 1.00, the inner diameter D2 [mm] of the external electrode 7 is smaller than the outer diameter D1 [mm] of the arc tube 2, so the external electrode 7 is forcibly expanded and the arc tube 2 is expanded. When the barrier discharge lamp 1 is turned on, pressure is applied to the arc tube 2 from the external electrode 7, leading to early damage to the arc tube 2.

Further, the external electrode 7 is arranged in the circumferential direction of the arc tube 2 at an angle θ7 of, for example, 30 [°] or more and 190 [°] or less. If the angle θ7 is less than 30 [°], the contact area with the arc tube 2 is small, so that the ultraviolet illuminance is reduced and proper emission characteristics may not be obtained. Further, when the angle θ7 exceeds 190 [°], the emitted ultraviolet light may interfere with the external electrode 7 before reaching the irradiated body, and appropriate light emission characteristics may not be obtained. Therefore, the angle θ7 of the external electrode 7 can be set to 30 [°] or more and 190 [°] or less.

Further, the external electrode 7 is arranged so as to face the arc tube 2 and also serves as a heat radiating block for dissipating heat from the generated barrier discharge lamp 1. In addition, a flow path for passing a liquid or gas refrigerant may be provided inside the external electrode 7 to further improve heat dissipation.

The heat dissipation block 8 is arranged so as to face the arc tube 2 with the external electrode 7 interposed therebetween, and dissipates heat from the heat-generating barrier discharge lamp 1. The heat dissipation block 8 can be made of, for example, aluminum or stainless steel. The heat dissipation block 8 may be provided with a flow path for flowing a liquid or gas refrigerant to further improve the heat dissipation. The inner surface 8a of the heat radiating block 8 and the outer surface 7a of the outer electrode 7 may be in contact with each other or separated from each other, but when the heat radiating block 8 and the outer electrode 7 are brought into contact with each other, the heat radiating property can be improved. .. Further, if necessary, the inner surface 8a and / or the end surface 8b of the heat dissipation block 8 may be subjected to an insulating treatment to cut off the conduction with the external electrode 7.

Further, in the example shown in FIG. 2, the angle θ7 of the external electrode 7 and the angle of the heat radiation block 8 that covers the outer surface 7a of the external electrode 7 in the circumferential direction of the arc tube 2 are shown to be the same. It is not limited to, and may be different from each other. In other words, the end faces 7b of the external electrodes 7 located at both ends in the circumferential direction of the arc tube 2 may project from the end faces 8b of the heat dissipation block 8 toward the irradiated body side (Z-axis positive direction side), and the end faces 8b to Z. It may be immersed in the negative axis direction.

The arc tube 2 and the external electrode 7 can be attached to and detached from each other in a direction corresponding to the size of the angle θ7, and can be arranged interchangeably. The arc tube 2 may be attached to and detached from the external electrode 7 from the end surface 7b side of the external electrode 7 along the Z-axis direction, and may be attached to and detached from the external electrode 7 along the tube axis direction of the arc tube 2, that is, along the Y-axis direction. It may be attached and detached. Further, the arc tube 2 and the external electrode 7 may be arranged so as not to be attached and detached.

The base 5 is arranged so as to cover one end side of the lead wire 6 and supports both ends of the arc tube 2 in the tube axial direction. The base 5 is formed using, for example, an insulating steatite. Further, the base 5 may be formed of an insulator such as aluminum oxide. The base 5 may be arranged so as to be in contact with the external electrode 7, or may be arranged apart from the external electrode 7.

The lead wire 6 is electrically connected to the internal electrode 3. Further, the lead wire 6 is drawn from a base 5 that supports both ends of the arc tube 2 in the tube axial direction, and is electrically connected to the external electrode 7 via a lighting device (not shown) connected to an AC power supply. A predetermined voltage can be applied between the electrodes to cause the arc tube 2 to emit light. The lighting device includes an inverter capable of outputting high voltage and high frequency, and is configured to be able to supply electric power from an AC power source to the barrier discharge lamp 1. The lighting device can, for example, apply a sine wave having a frequency of 37 kHz to light the barrier discharge lamp 1 with a lamp power of about 2.4 kW. The lead wire 6 is not limited to the configuration provided only on one end side of the arc tube 2 as shown in FIG. 1, and may be provided on both ends of the arc tube 2, for example.

[Evaluation test]
A lighting test was performed using a prototype of a barrier discharge lamp, and the ratio (D1 / D2) of the outer diameter D1 [mm] of the arc tube 2 to the inner diameter D2 [mm] of the external electrode 7 was from 0.85 to 1.06. The effect on the nitric acid generation rate [%] from the arc tube 2 was evaluated by changing the value every 0.1. FIG. 3 shows the results of the evaluation test. The nitric acid generation rate [%] is the area ratio between the area where nitric acid is generated on the external electrode discharge surface and the area on the external electrode discharge surface when the barrier discharge lamp 1 is turned on for 100 hours. Here, the "area where nitric acid is generated on the surface of the discharge of the external electrode" is calculated by measuring the area of the portion that becomes cloudy when the external electrode 7 is visually observed with a metal scale or the like. In FIG. 3, the angle θ7 of the external electrode 7 is set to 180 [°].

As shown in FIG. 3, the nitric acid generation rate [%] became 0 in the range of D1 / D2 of 0.93 or more and 0.99 or less, and it was confirmed that the deterioration of the light emitting characteristics could be suppressed. On the other hand, in the range of D1 / D2 <0.93 and D1 / D2> 1.00, nitric acid was generated, suggesting that the luminescence characteristics deteriorated with time. When D1 / D2 exceeds 0.99, the outer diameter D1 [mm] of the arc tube 2 becomes larger than the inner diameter D2 [mm] of the external electrode 7, and the arc tube 2 becomes the external electrode 7 and the heat radiation block 8. Even if the arc tube 2 can be attached to the external electrode 7 or the heat radiation block 8, the arc tube 2 is tightened due to the difference in the dimensions of the external electrode 7 or the heat radiation block 8. Therefore, the arc tube 2 is likely to be damaged at an early stage. From these results, the conditions of D1 / D2 that can suppress the deterioration of the light emitting characteristics were confirmed. In particular, when D1 / D2 is 0.93 or more and 0.98 or less, the arc tube 2 can be smoothly attached to the external electrode 7 or the heat radiation block 8, so that the more preferable range of D1 / D2 is 0.93 or more. It is 0.98 or less.

As described above, the barrier discharge lamp 1 according to the embodiment includes a cylindrical arc tube 2, an internal electrode 3, and an external electrode 7. The arc tube 2 is filled with gas and transmits ultraviolet light. The internal electrode 3 is arranged inside the arc tube 2 and extends in the tube axial direction of the arc tube 2. The outer electrode 7 is provided on the outer surface 2b side of the arc tube 2 so as to face the inner electrode 3. The outer diameter D1 [mm] of the arc tube 2 and the inner diameter D2 [mm] of the external electrode 7 have a relationship of 0.93 ≦ D1 / D2 ≦ 0.99. As a result, it is possible to suppress a decrease in light emission characteristics.

Further, the ultraviolet irradiation unit 100 according to the embodiment includes one or a plurality of barrier discharge lamps 1. As a result, heat dissipation can be ensured without separately providing a heat dissipation member.

Although embodiments of the present invention have been described, the embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. The embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

1 Barrier discharge lamp 2 Light emitting tube 3 Internal electrode 4 Reflective film 7 External electrode 8 Heat dissipation block 100 Ultraviolet irradiation unit

Claims (2)

With a cylindrical arc tube filled with gas and transmitting ultraviolet light;
With an internal electrode arranged inside the arc tube and extending in the tube axis direction of the arc tube;
With an external electrode provided on the outer surface side of the arc tube so as to face the internal electrode;
Equipped with
A barrier discharge lamp in which the outer diameter D1 [mm] of the arc tube and the inner diameter D2 [mm] of the outer electrode have a relationship of 0.93 ≦ D1 / D2 ≦ 0.99. An ultraviolet irradiation unit including one or a plurality of barrier discharge lamps according to claim 1.

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