JP2008010359A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To consider a source of ultraviolet light so as to perform a proper measure. <P>SOLUTION: A discharge lamp includes an ultraviolet light generation means generating ultraviolet light; and a valve 1 which is composed of vitreous silica including the ultraviolet light generation means, and has compressive strain SI provided on one inner surface layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discharge lamp with light emission in the ultraviolet region.

  In recent years, ultraviolet lamps such as high-pressure mercury lamps have been used for the purpose of ultraviolet irradiation in semiconductor manufacturing processes and the like, but many of them are broken during use, which is a problem. As one of the causes, ultraviolet distortion generated on the inner surface of the arc tube during lighting is pointed out. This ultraviolet distortion is a problem common to discharge lamps that widely emit light in the ultraviolet region.

  For example, a longitudinal sectional view of a discharge lamp in a state where a cylindrical bulb is horizontally long is as shown in FIG. Inside the quartz glass bulb 101 is an ultraviolet ray generating means such as discharge plasma formed between a pair of electrodes, and the ultraviolet ray UV is radiated as indicated by an arrow. On the inner surface of the bulb that has been irradiated with ultraviolet rays, ultraviolet distortion 102, which is tensile strain indicated by the arrow in FIG. The ultraviolet distortion 102 causes a crack 103, and when the crack 103 extends from the inner surface of the bulb to the outer surface, the lamp is destroyed.

As a countermeasure against the ultraviolet distortion, it is possible to reduce the influence of ultraviolet rays by using ultraviolet cut glass or the like in the discharge tube, but this is not a fundamental solution. On the other hand, Patent Document 1 describes that initial compressive strain is imparted to the outer surface of the arc tube to reduce the lamp breakage rate of the discharge tube that is irradiated with ultraviolet rays. However, the ultraviolet distortion is larger on the side closer to the ultraviolet ray generation source, and the effect of the above configuration is considered to be limited.
JP-A-2-301957

  Conventional UV distortion countermeasures have a problem that measures are not taken according to the distance from the source of ultraviolet rays, and the present invention solves this problem and takes appropriate measures in consideration of the source of ultraviolet rays to break the lamp. An object of the present invention is to provide a discharge lamp capable of greatly reducing the degree of the above.

  The discharge lamp according to the present invention comprises: an ultraviolet ray generating means for generating an ultraviolet ray; and an arc tube composed of quartz glass containing the ultraviolet ray generating means and having at least one inner surface provided with a compressive strain. Features. The ultraviolet ray generating means emits ultraviolet rays when the discharge medium generates plasma. The arc tube made of quartz glass containing the ultraviolet ray generating means is not limited to HID lamps such as mercury high pressure lamps, high pressure sodium lamps and metal halide lamps, as long as they generate ultraviolet rays from the inside of the quartz glass bulb. Allow discharge lamps with UV emission. For applying the compressive strain, either a technique called “cooling strengthening” in which cooling is performed after heating the arc tube, or a chemical technique in which an element or a compound is attached to the surface can be employed.

  In the discharge lamp according to the present invention, the thickness of the arc tube is t, and the layer thickness of the inner surface layer provided with the compressive strain is (1/3) t or less.

  The discharge lamp according to the present invention is characterized in that compressive strain is provided on one outer surface layer of the arc tube.

  In the discharge lamp according to the present invention, the thickness of the arc tube is t, and the layer thickness of the outer surface layer provided with the compressive strain is (1/3) t or less.

  In the discharge lamp according to the present invention, since the compressive strain is provided on the inner surface layer of the arc tube composed of quartz glass containing the ultraviolet ray generating means, the ultraviolet ray is generated and the ultraviolet strain which is the tensile strain is generated on the inner surface. However, it cancels out the compressive strain of the inner surface layer and can prevent the occurrence of cracks from the inner surface of the arc tube, thereby reducing the lamp breakage rate during lighting.

  Further, in the discharge lamp according to the present invention, the thickness of the arc tube is t, and the layer thickness of the inner surface layer provided with the compressive strain is set to (1/3) t or less, so that the lamp breakage rate is sufficiently reduced. The effect is seen.

  In addition, in the discharge lamp according to the present invention, since compressive strain is provided on the outer surface layer of the arc tube, in addition to the effect of preventing the occurrence of cracks from the inner surface of the arc tube, temporary cracks are generated from the inner surface of the arc tube. Even if there is a crack, it is expected that the progress of the crack will remain before the outer surface layer having the compressive strain, which has the effect of reducing the lamp breakage rate during lighting.

  Further, in the discharge lamp according to the present invention, the thickness of the arc tube is t, and the layer thickness of the outer surface layer provided with the compressive strain is set to (1/3) t or less, so that the lamp breakage rate is sufficiently reduced. The effect is seen.

  In the present invention, the compressive strain is appropriately provided on the inner surface of the arc tube composed of quartz glass containing the ultraviolet ray generating means, thereby appropriately dealing with the phenomenon that the ultraviolet ray strain increases toward the side closer to the ultraviolet ray generation source. This achieves the purpose of greatly reducing the degree of lamp breakage.

  Embodiments of a discharge lamp according to the present invention will be described below with reference to the accompanying drawings. In each figure, the same components are denoted by the same reference numerals, and redundant description is omitted. FIG. 1 is a partially cutaway view of a high-pressure mercury lamp according to an embodiment of the present invention. This high-pressure mercury lamp has a bulb 1 made of quartz glass which is an arc tube, electrode shafts 2 and 3, anode 4, cathode 5, refractory metal foil 6, quartz glass cylindrical member 7 constituting ultraviolet generating means. The sealing part 8 is provided. An anode terminal 9 and a cathode terminal 10 are provided at both ends of the bulb 1.

  The bulb 1 has, for example, an axial dimension of 60 mm and a radial dimension of 50 mm. The bulb 1 communicates with the discharge space portion 1 a and the discharge space portion 1 a having a substantially elliptical shape with a thickness of 3 mm, and is integrally formed at both ends thereof. A pair of branch pipes 1b and 1b made of quartz glass is provided. The electrode shaft 2 is a tungsten rod having a diameter of 5 mm, and an anode 4 is supported at the tip thereof. The anode 4 is made of tungsten, has a diameter of 10 mm, and a weight of 34 g.

  The electrode shaft 3 is a tungsten rod having a diameter of 5 mm, and its tip is shaped into a conical shape to form the cathode 5. The distance between the electrodes formed between the anode 4 and the cathode 5 is set to about 5 mm.

  The base ends of the electrode shafts 2 and 3 are housed in the branch pipe 1 b of the valve 1. The electrode shafts 2 and 3 are fixed at predetermined positions by a refractory metal foil 6 and a quartz glass cylindrical member 7 described later in the branch pipe 1b.

  The sealing part 8 has a so-called foil seal structure. A disk 8a made of tungsten having a diameter of 10 mm is connected to the base end surfaces of the electrode shafts 2 and 3, and one end of a quartz glass rod 8b having the same thickness as the disk 8a is disposed in contact with the disk 8a. An outer well 8c made of molybdenum is disposed in contact with the other end of the quartz glass rod 8b. Further, around the quartz glass rod 8b, three sealing ribbons 8d made of an elongated molybdenum foil having a width of 8 mm are arranged at equal intervals along the longitudinal direction of the quartz glass rod 8b, and one end thereof is attached to the disk 8a. The other ends are connected to the outer wells 8c. Further, the branch pipe 1b is welded to the seal ribbon 8d and the quartz glass rod 8b by baking to form a foil seal structure.

  In the discharge space 1a of the bulb 1 sealed as described above, 800 mg of mercury and argon as a discharge medium are sealed at 67 KPa to constitute a short arc type high-pressure mercury lamp for DC lighting.

  The anode terminal 9 is attached to the end of the branch pipe 1b with a base cement and connected to the outer wells 7c. Furthermore, the anode terminal 9 includes an external lead wire 9a and a crimp terminal 9b connected to the tip of the external lead wire 9a.

  The cathode terminal 10 is attached to the end of the branch pipe 1b by a base cement and is connected to the outer well 7c on the cathode side. The cathode terminal 9 includes a mounting bolt 9a.

  Particularly in the discharge space 1a in the bulb 1, a compressive strain is provided on the inner surface layer. This compressive strain is a strain in which a force acts in the direction of the arrow as shown by SI in FIG. 2A in which the inside is omitted in the AA cross section of FIG.

  For example, the compressive strain is obtained by inserting a heater made of a rod-shaped nichrome wire into the valve 1 existing as a single valve, and then drawing out the nichrome wire so that cold air released from a refrigerant such as liquid nitrogen is introduced into the valve 1. A technique called air cooling strengthening (cooling strengthening) by feeding and cooling can be used. Further, for example, a chemical method in which a required element or compound is deposited (doping) in the valve 1 existing as a single valve and burned and reacted with glass can be employed.

Here, when the thickness of the bulb 1 is t, the layer thickness of the inner surface layer provided with the compressive strain is set to t / 3 or less, and the strain value is set to 50 kg / cm ² . In addition, the valve 1 existing as a single valve is processed into a shape in which the outer wells 8c made of molybdenum can be arranged in the vicinity of the anode terminal 9 and the cathode terminal 10, and the compression strain previously applied to this portion is in an initial state. However, since the ultraviolet ray distortion is larger on the side closer to the ultraviolet ray source, the inner surface having a compressive strain is formed in the bulb 1 in the discharge space portion 1a having an almost elliptical shape near the ultraviolet ray source. One layer has the effect of reducing the lamp breakage rate during lighting as described below by maintaining the initial state.

  In the high-pressure mercury lamp having such a configuration, arc discharge occurs in the bulb during lighting, and ultraviolet rays (i-rays) are emitted. This ultraviolet ray is irradiated to the inner surface layer provided with the compressive strain to generate the ultraviolet strain, but it cancels out the compressive strain of the inner surface layer, and the force due to the compressive strain as shown as SIa in FIG. Although it becomes smaller as indicated by the size of the arrow, it is possible to prevent the occurrence of tensile strain, to prevent the occurrence of cracks from the inner surface of the arc tube, and to reduce the lamp breakage rate during lighting.

  Particularly in the discharge space 1a in the bulb 1 according to the second embodiment, the inner surface layer and the outer surface layer have compressive strain. This compression strain is indicated by an arrow in FIG. 3A in which the inside is omitted in the AA cross section of FIG. 1 so that the compression strain of the inner surface layer is shown as SI and the compression strain of the outer surface layer is shown as SO. A strain that exerts a force in the direction.

  Also for the compressive strain of the outer surface layer, a technique called air cooling strengthening can be used for the outer surface of the bulb 1. It is also possible to apply compressive strain to the outer surface of the valve 1 by a chemical method.

  When the thickness of the bulb 1 is t, the layer thickness of the outer surface layer provided with the compressive strain is set to t / 3 or less, and the strain value is 50 kg / cm 2. Further, since the outer wells 8c are processed in the vicinity of the anode terminal 9 and the cathode terminal 10, the compressive strain is different in the initial state in this portion, but the ultraviolet strain is a source of ultraviolet rays. In the bulb 1 in the portion of the discharge space 1a, which is almost elliptical and close to the ultraviolet ray generation source, the closer to the near side, the lighting is as described below by keeping the outer surface layer provided with compressive strain in the initial state. It has the effect of reducing the lamp breakage rate.

  In the high-pressure mercury lamp having such a configuration, arc discharge occurs in the bulb during lighting, and ultraviolet rays (i-rays) are emitted. This ultraviolet ray is irradiated to the inner surface layer where the compressive strain is provided, and ultraviolet strain is generated. As described above, the force due to the compressive strain is shown as SIa in the inner surface layer shown in FIG. Is small as shown by the size of the arrow, but it can prevent the occurrence of cracks from the inner surface of the arc tube and reduce the lamp breakage rate during lighting.

  On the other hand, the emitted ultraviolet light hardly affects the outer surface layer farther than the inner surface layer, and the compressive strain in the outer surface layer is indicated as SOa in the outer surface layer shown in FIG. It does not change significantly before UV radiation. However, even if a large ultraviolet ray strain is generated in the inner surface layer shown in FIG. 3B and a crack is generated from the inner surface to the outer surface exceeding the compressive strain, the outer surface layer Due to the presence of the compressive strain, the progress of the crack stops without reaching the compressive strain portion on the outer surface layer, so that the lamp breakage rate during lighting is less likely to occur. That is, the lamp breakage rate during lighting can also be reduced by the configuration according to the second embodiment.

  Next, a prototype of the high-pressure mercury lamp according to Example 1 and Example 2 and a prototype having a compressive strain only on one outer surface layer were prepared and compared with a conventional product having no compressive strain. The comparison results are shown in Table 1.

  The discharge lamps used in the tests of Table 1 are high pressure mercury lamps having a bulb thickness of 1 mm and an electric power of 10 KW. In the test, the lamp temperature during lighting was 800 ° C., and lighting was continuously performed for 10,000 hours. The layer thickness of the inner surface layer and the outer surface layer layer provided with compressive strain were both 0.3 mm as measured by a strain gauge.

  As is apparent from Table 1, the conventional product having no compression strain was broken in 1000 hours. After 10,000 hours of continuous lighting, in Prototype 1 having compressive strain only on one outer surface layer, it was visually confirmed that a crack was generated in a mesh form from the inside of the bulb. Neither destruction nor crack generation was observed in the prototype 2 in which the compressive strain was provided on the inner surface layer and the prototype 3 in which the compressive strain was provided on the inner surface layer and the outer surface layer.

  Regarding the layer thickness of the inner surface layer and the outer layer layer provided with compressive strain, there is no difference in the effect of the test even if the thickness of the valve is 0.4 mm or more when the thickness of the valve is 1.0 mm. On the other hand, cracks are more likely to occur due to the reaction, which is not preferable. In addition, when the compressive strain layer thickness is less than 1/10 of the bulb thickness, a sufficient effect is not exhibited, and when the thickness is 1/10 or more to 1/3 or less of the bulb thickness, a sufficient lamp breakage rate is obtained. A reduction effect was seen.

Sectional drawing of the high pressure mercury lamp which concerns on the Example of this invention. The figure which shows the structure of the 1st Example which abbreviate | omitted the inside in the AA cross section of FIG. The figure which shows the structure of the 1st Example which abbreviate | omitted the inside in the AA cross section of FIG. Sectional drawing for demonstrating the ultraviolet distortion in a discharge lamp. The principal part enlarged view of FIG.

Explanation of symbols

1 Valve
1a Discharge space
2, 3 electrode shaft
4 Anode
5 Cathode
6 High melting point metal foil
7 Quartz glass cylindrical member
8 Sealing part
SI, SO Compression strain

Claims (4)

Ultraviolet ray generating means for generating ultraviolet rays;
An arc tube made of quartz glass containing ultraviolet ray generating means and having a compressive strain on at least one inner surface;
A discharge lamp comprising: The discharge lamp according to claim 1, wherein the thickness of the arc tube is t, and the thickness of the inner surface layer provided with the compressive strain is (1/3) t or less. 3. The discharge lamp according to claim 1, wherein a compression strain is provided on one outer surface layer of the arc tube. The discharge lamp according to claim 3, wherein the thickness of the arc tube is t, and the thickness of the outer surface layer provided with the compressive strain is (1/3) t or less.

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