JP4047234B2 - Dielectric barrier discharge lamp - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric barrier discharge lamp which is a kind of discharge lamp.
[0002]
[Prior art]
The dielectric barrier discharge lamp is a discharge lamp that forms excimer molecules by dielectric barrier discharge and uses light emitted from the excimer molecules, and is used for, for example, an ultraviolet light source for photochemical reaction. As such a discharge lamp, the one disclosed in Patent Document 1 shown below is known.
[0003]
As shown in FIG. 5, a dielectric barrier discharge lamp 1 disclosed in Patent Document 1 has an elongated straight tubular discharge vessel 2 as a dielectric. A light-transmitting external electrode 3 is provided on the outer peripheral surface of the side surface of the discharge vessel 2, and a linear internal electrode 4 is provided inside the discharge vessel 2. Both end portions 5 of the discharge vessel 2 are sealed with pinch seals, and the end portions of the internal electrodes 4 are held by the pinch seal portions 5. The discharge vessel 2 is filled with a discharge gas that forms excimer molecules by dielectric barrier discharge in contact with the internal electrode 4.
[0004]
As described above, when the end 5 of the discharge vessel 2 is sealed with a pinch seal, the discharge vessel 2 is evacuated using the exhaust pipe 6 provided on the side surface of the discharge vessel 2. Therefore, in the dielectric barrier discharge lamp 1 disclosed in Patent Document 1, the exhaust pipe 6 is used, and the mesh-structured external electrode 3 is engaged with the exhaust pipe 6 and attached to the discharge vessel 2.
[0005]
[Patent Document 1]
[Patent Document 1] Japanese Patent Laid-Open No. 11-265689
[Problems to be solved by the invention]
In the conventional dielectric barrier discharge lamp 1 as described above, a crack may occur at the boundary between the exhaust pipe 6 and the side surface of the discharge vessel 2.
[0007]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve such a conventional technical problem and provide a dielectric barrier discharge lamp having a long lifetime and high reliability.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have made various studies and found that the exhaust pipe is cut and sealed with high heat, so that thermal distortion occurs around the exhaust pipe. In addition, since the mesh-structured external electrode is locked to the exhaust pipe, a discharge is also generated between the end of the exhaust pipe and the internal electrode, and this discharge imposes a load on the heat distortion part of the discharge vessel, causing cracks. It was judged that.
[0009]
The present invention has been made on the basis of such knowledge, and the present invention is a tubular discharge vessel having a sealed exhaust pipe on its side surface, and the axial direction of the discharge vessel disposed inside the discharge vessel. An internal electrode that is fixed at the corresponding sealed end of the discharge vessel, and a plate-like or film-like external electrode provided on the outer peripheral surface of the side surface of the discharge vessel. In the dielectric barrier discharge lamp provided, the external electrode is composed of a conductive film functioning as a reflecting mirror deposited on the outer peripheral surface of the side surface portion of the discharge vessel with a predetermined gap from the exhaust pipe, the conductive film, when viewed in the axial direction of the discharge vessel, an exhaust pipe is formed clockwise and counterclockwise around the, to form a light emitting portion as between the side edges are opened It is characterized by that. In such a configuration, a load due to discharge is not applied to the boundary portion between the exhaust pipe in which thermal distortion occurs and the side surface portion of the discharge vessel, and cracks can be prevented or suppressed.
[0010]
It should be noted that the end of the discharge vessel is sealed with a pinch seal because the operation of enclosing the end of the internal electrode is easy and effective.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent part, and the overlapping description is abbreviate | omitted.
[0012]
FIG. 1 is a side view showing a dielectric barrier discharge lamp according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line II-II in FIG. The illustrated dielectric barrier discharge lamp 10 includes an elongated straight tubular or cylindrical discharge vessel 12. The discharge vessel 12 is sealed and filled with a rare gas for excimer discharge. The discharge vessel 12 constitutes a dielectric in the dielectric barrier discharge and is made of an electrically insulating and light transmissive material so that light emitted from the inside of the vessel 12 can be emitted to the outside. Preferably made from quartz glass. Further, the dimensions of the discharge vessel 12 are appropriately determined. For example, the outer diameter can be about 10 mm, the inner diameter can be about 8 mm, and the length can be about 400 mm.
[0013]
An internal electrode 14 is disposed inside the discharge vessel 12. The internal electrode 14 is a long conductor, and is disposed substantially coaxially with the discharge vessel 12, and its end portions 16 a and 16 b are supported by corresponding sealed ends 18 a and 18 b of the discharge vessel 12. In the illustrated embodiment, the internal electrode 14 is made of a tungsten wire having an outer diameter of 0.18 mm. Further, the internal electrode 14 of the illustrated embodiment is linear over almost the entire length, but a coiled portion 14a is formed on one end side. The coiled portion 14a is provided to apply tension to the linear portion 14b and prevent loosening in a state where the internal electrode 14 is supported in the discharge vessel 12. Another reason is to absorb a difference in thermal expansion between the material of the discharge vessel 12 and the material of the internal electrode 14 when the ambient temperature of the discharge lamp 10 rises or during discharge. The coiled portion 14a is substantially coaxial with the other linear portions 14b, and the outer diameter of the coiled portion 14a is the dimension exemplified above for the discharge vessel, and the inner electrode 14 is formed from a tungsten wire having an outer diameter of 0.18 mm. In this case, for example, the thickness is preferably about 0.8 mm.
[0014]
Metal foils 20a and 20b such as molybdenum foil are connected to both ends 16a and 16b of the internal electrode 14, respectively. In the illustrated embodiment, the metal foils 20a and 20b are rectangular, and the end portions 16a and 16b of the internal electrode 14 are connected to the center of one end on the short side by welding or the like. In addition, a lead wire 22 such as a molybdenum wire is connected to the central portion of the other end of the metal foils 20a and 20b by welding or the like, and the lead wire 2 is connected to an external lighting power source 24. Yes.
[0015]
The end portions 16a and 16b of the internal electrode 14, the metal foils 20a and 20b connected thereto, and the metal foil side ends 26a and 26b of the lead wire 22 are respectively connected to the corresponding sealed end portions 18a and 18a of the discharge vessel 12. The internal electrode 14 is stretched between both end portions 18 a and 18 b of the discharge vessel 12.
[0016]
In the illustrated embodiment, the end portions 18a and 18b of the discharge vessel 12 are sealed with a pinch seal. That is, the end portions 18a and 18b of the discharge vessel 12 are in an open state at the initial stage of manufacture of the discharge lamp 10, but there are end portions 16a and 16b of the internal electrode 14, metal foils 20a and 20b, and end portions of the lead wires 22, respectively. After arranging 26a and 26b, the ends 16a and 16b of the internal electrode 14, the metal foils 20a and 20b, and the ends 26a and 26b of the lead wire 22 are sandwiched by heat-melting and mechanically pressing and adhering from both sides. Sealed in an oval shape.
[0017]
When sealing with this pinch seal, it is difficult to exhaust from the end portions 18a and 18b of the discharge vessel 12, and therefore, an exhaust pipe 30 is formed on the side surface 28 of the discharge vessel 12, and this exhaust tube 30 Exhaust is performed through, and then a rare gas for excimer discharge is sealed. The exhaust pipe 30 is cut and sealed with high heat by a burner after the rare gas is sealed. The exhaust pipe 30 shown in FIGS. 1 and 2 shows a sealed state. In the illustrated embodiment, the exhaust pipe 30 has an outer diameter of about 4 mm, and is provided at the center of the discharge vessel 12 in the axial direction (longitudinal direction).
[0018]
External electrodes 32 (portions indicated by two-dot chain lines in FIG. 1) are provided on the outer peripheral surface of the side surface portion 28 of the discharge vessel 12. In the illustrated first embodiment, the external electrode 32 has a rectangular outer shape in the unfolded state, and passes through the central axis of the discharge vessel 12 and the central axis of the exhaust pipe 30 as understood from FIG. The plane P is symmetrical with respect to the plane P. The external electrode 32 is formed in an angle range of about 120 degrees clockwise and counterclockwise around the exhaust pipe 30, and the side edge of the external electrode 32 (an edge parallel to the central axis of the discharge vessel 12). Between 34a and 34b is opened, and this portion is a light emitting portion 36. The external electrode 32 is a conductive film, preferably a metal film. Specifically, aluminum is deposited on the discharge vessel 12 to a thickness of about 300 nm. The external electrode 32 functions not only as an electrode but also as a reflector. It also has. Therefore, the light generated by the discharge inside the discharge vessel 12 is reflected by the inner surface of the external electrode 32 and is emitted to the outside through the light emitting portion 36 between the side edges 34a and 34b of the external electrode 32. It will be.
[0019]
Further, the end edges 38a and 38b of the external electrode 32 are set at positions separated from the end portions 18a and 18b of the discharge vessel 12 by a predetermined distance in the axial direction. The predetermined distance is about 15 to 20 mm, but the end edge 38b on the coiled portion 14a side of the internal electrode 14 is further about from the inner end portion (end portion on the exhaust pipe 30 side) of the coiled portion 14a. It is preferable to dispose about 15 to 20 mm apart. In other words, the external electrode 32 is formed only in a portion inside the both end portions 18a and 18b of the discharge vessel 12 and surrounding the linear portion 14b of the internal electrode 14, and the coil-shaped portion 14a is formed. It is not formed in the surrounding position.
[0020]
Further, the external electrode 32 is not provided in a region from the central axis of the exhaust pipe 30 to a predetermined distance D, for example, about 6 mm, along the outer peripheral surface of the side surface portion 28 of the discharge vessel 12. That is, an opening 40 is formed at the center of the external electrode 32, and a gap is formed between the exhaust pipe 30 protruding from the opening 40 and the inner peripheral edge of the external electrode 32 that defines the opening 40. .
[0021]
In the dielectric barrier discharge lamp 10 having the above configuration, when the lighting power source 24 is connected to the external electrode 32 and the lead wire 22 and an AC voltage is applied between the external electrode 32 and the internal electrode 14, the inside of the discharge vessel 12 The rare gas causes dielectric barrier discharge and is irradiated with ultraviolet rays. Since the internal electrode 14 is exposed to a rare gas, the AC voltage applied between the external electrode 32 and the internal electrode 14 may be a low value of about 2 kV. A part of the ultraviolet rays is directly radiated from the light emitting portion 36 where the external electrode 32 is not formed, and the remaining ultraviolet rays are reflected by the inner surface of the external electrode 32 and then emitted from the light emitting portion 36 to the outside.
[0022]
At this time, since a gap is formed between the exhaust tube 30 and the external electrode 32, no discharge occurs at the boundary portion 42 between the exhaust tube 30 and the side surface portion 28 of the discharge vessel 12. The boundary portion 42 between the exhaust tube 30 and the side surface portion 28 of the discharge vessel 12 is distorted by the heat applied when the exhaust tube 30 is formed, and when it is cut and sealed. As a result, no load due to discharge is applied to the thermally strained portion, and the generation of cracks can be suppressed or prevented. As a comparison, a discharge lamp having an external electrode 32 provided to the exhaust pipe 30 was actually prepared and turned on. In such a case, however, the boundary 42 between the exhaust pipe 30 and the discharge vessel 12 was cracked after lighting for about 1000 hours. Became easier to enter. On the other hand, in the discharge lamp 10 of the present embodiment, no cracks occurred and no signs of cracking were observed even after lighting for 1000 hours or more.
[0023]
Further, the boundary portion 42 between the exhaust pipe 30 and the side surface portion 28 of the discharge vessel 12 has a larger curvature change than the other portions of the discharge vessel 12. For this reason, even if a discharge is generated in the part, the discharge becomes unstable. On the other hand, in this embodiment, since no discharge occurs in the part, the discharge is stabilized as a whole of the discharge lamp 10.
[0024]
In the present embodiment, the external electrode 32 is separated from the pinch-sealed end portions 18a and 18b of the discharge vessel 12, so that the influence of the pinch seal is avoided. That is, the pinch seal causes silica to adhere to the vicinity of the end portions 18a and 18b of the discharge vessel 12 to reduce the amount of light transmission and cause thermal distortion, but it is not affected.
[0025]
Furthermore, since the coil-shaped part 14a is formed in the internal electrode 14 and the external electrode 32 is disposed so as to surround only the linear part 14b of the internal electrode 14, the emission intensity fluctuation from the discharge plasma is changed. Is also prevented. The internal electrode 14 is thermally expanded / contracted due to an increase in the ambient temperature of the electrode during discharge or a change in the ambient temperature of the discharge lamp. However, since the expansion / contraction is absorbed by the coiled portion 14a, the linear portion The distance between 14b and the external electrode 32 is kept substantially constant. Accordingly, the light emission intensity from the discharge plasma is also substantially constant.
[0026]
FIG. 3 shows a dielectric barrier discharge lamp 110 according to the second embodiment of the present invention. The discharge lamp 110 is different from the discharge lamp 10 according to the first embodiment in that the external electrode is divided into two. These external electrodes 132a and 132b are formed with a predetermined gap 2D (for example, about 12 mm) between them. The external electrodes 132a and 132b are formed so that the exhaust pipe 30 is disposed in the center between them. In this case as well, as in the first embodiment, a gap of 6 mm or more is secured from the central axis of the exhaust pipe 30 to the external electrodes 132a and 132b, and the same effect as described above can be obtained. Since other parts are the same as those in the first embodiment, the same or corresponding parts are denoted by the same reference numerals, and detailed description thereof is omitted.
[0027]
FIG. 4 shows a dielectric barrier discharge lamp 210 according to the third embodiment of the present invention. In the discharge lamp 210, the exhaust pipe 230 is provided not on the central portion of the discharge vessel 12 but on one end side. In the present embodiment, the exhaust pipe 230 is disposed on the side where the coiled portion 14a of the internal electrode 14 is formed, and is disposed on the inner side (closer to the other end 18a) than the coiled portion 14a of the internal electrode 14. ing. The coiled portion 14a of the internal electrode 14 may be disposed on the opposite side of the exhaust pipe 230, that is, between the end edge 238a of the external electrode 232 and the sealed end portion 18a.
[0028]
In the dielectric barrier discharge lamp 210 in which the exhaust pipe 230 is formed at such a position, the external electrode 232 is disposed between the exhaust pipe 230 and the end 18 a of the discharge vessel 12 on the opposite side of the exhaust pipe 230. It is characterized by being provided. In this case, the end edge 238 b of the external electrode 232 on the exhaust tube 230 side is separated from the center line of the exhaust tube 230 by a certain distance D, for example, about 6 mm, and the other end 238 a is the end portion 18 a of the discharge vessel 12. Is about 10 to 15 mm away. Therefore, the effect of preventing and suppressing the adverse effect of cracks occurring at the boundary between the exhaust pipe 230 and the side surface portion 28 of the discharge vessel 12 and the discharge stabilization effect are the same as those in the first and second embodiments. It is the same.
[0029]
In the third embodiment, it is not necessary to provide an opening in the external electrode 232 or to divide it into two parts in order to form a gap between the exhaust pipe 230 and the external electrode 232. In this case, it becomes one large plane without an opening. Therefore, the dielectric barrier discharge lamp 210 according to the third embodiment is different from the discharge lamps 10 and 110 according to the first embodiment and the second embodiment, in which no discharge is partially generated in the central portion in the axial direction of the discharge vessel 12. Thus, there is an effect that uniform light intensity can be obtained over almost the entire length of the discharge lamp 210.
[0030]
In FIG. 4, the same or corresponding parts as those of the discharge lamps 10 and 110 of the first embodiment and the second embodiment are denoted by the same reference numerals, and redundant description is omitted.
[0031]
As mentioned above, although preferred embodiment of this invention was described in detail, it cannot be overemphasized that this invention is not limited to the said embodiment. For example, the numerical values and shapes given in the description of the above embodiments are merely examples, and can be changed as appropriate.
[0032]
【The invention's effect】
As described above, according to the present invention, in the dielectric barrier discharge lamp having the exhaust pipe on the side surface portion and the external electrode formed on the side surface portion, the boundary between the exhaust pipe and the side surface portion is cracked. It can be prevented or suppressed from entering. In addition, since the discharge is stabilized, a dielectric barrier discharge lamp having high reliability over a long period of time can be obtained.
[Brief description of the drawings]
FIG. 1 is a side view showing a dielectric barrier discharge lamp according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a side view showing a dielectric barrier discharge lamp according to a second embodiment of the present invention.
FIG. 4 is a side view showing a dielectric barrier discharge lamp according to a third embodiment of the present invention.
FIG. 5 is a side view showing a conventional dielectric barrier discharge lamp.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10,110,210 ... Dielectric barrier discharge lamp, 12 ... Discharge container, 14 ... Internal electrode, 18a, 18b ... Sealed end part, 28 ... Side part, 30, 230 ... Exhaust pipe, 32, 132a, 132b, 232 ... external electrode.

Claims (4)

A tubular discharge vessel having a sealed exhaust pipe on its side surface;
An internal electrode disposed within the discharge vessel and extending along the axial direction of the discharge vessel, each end being fixed at a corresponding sealed end of the discharge vessel;
A dielectric barrier discharge lamp comprising an external electrode provided on an outer peripheral surface of the side surface portion of the discharge vessel,
The external electrode is a conductive film functioning as a reflecting mirror formed by vapor deposition on the outer peripheral surface of the side surface portion of the discharge vessel with a predetermined gap from the exhaust pipe,
When the conductive film is viewed along the axial direction of the discharge vessel, it is formed clockwise and counterclockwise around the exhaust pipe, and the light emitting portion is opened between both side edges. A dielectric barrier discharge lamp formed.   The dielectric barrier discharge lamp according to claim 1, wherein the sealed end portion of the discharge vessel is sealed with a pinch seal.   The internal electrode includes a linear part and a coiled part formed on one end side of the linear part, and the external electrode is not formed at a position surrounding the coiled part of the internal electrode. The dielectric barrier discharge lamp according to claim 1, wherein the dielectric barrier discharge lamp is provided.   4. The dielectric barrier discharge lamp according to claim 3, wherein the exhaust pipe is disposed on a side of the internal electrode where the coiled portion is formed.

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