JP4760964B2 - Short arc type discharge lamp - Google Patents

Description

  The present invention relates to a short arc type discharge lamp applied to a light source for exposure in the field of manufacturing semiconductors and liquid crystals, and a light source for backlight of a projector.

  The short arc type discharge lamp is used as a light source for an exposure apparatus or a backlight of a projector by combining with an optical system because the tip distance between a pair of electrodes arranged opposite to each other in the arc tube is short and close to a point light source. Yes.

Patent Documents 1 and 2 disclose conventional short arc type discharge lamps. As disclosed in Patent Document 1, excimer emission of xenon gas, which is a luminescent gas in xenon short arc lamps, and xenon gas, krypton gas, and argon gas, which are buffer gases in mercury vapor short arc lamps, is made of quartz glass. This caused a problem that white turbidity was generated on the inner surface of the discharge vessel made of the metal. In this document, as a countermeasure for such a problem, the average OH group concentration in the range of 200 μm from the inner surface of the portion where the ultraviolet radiation divergence of the discharge vessel is maximum is 7.8 × 10 ²⁴ / m ³ or more. And the average OH group concentration in the range of 20 μm in depth from the inner surface is specified to be 1.5 × 10 ²⁵ atoms / m ³ or more and 1.2 × 10 ²⁶ atoms / m ³ or less. Thus, in a short arc type discharge lamp, it is a common technique to contain OH groups on the inner surface of the discharge vessel.

On the other hand, in Patent Document 2, if a high concentration OH group exists in a region very close to the inner surface of the arc tube, the arc tube becomes hot at the start of the discharge lamp, and the OH group is removed from the inner surface of the arc tube. It is disclosed that OH groups that have been released and released from the inner surface of the arc tube become H ₂ O and diffuse into the arc tube. As a countermeasure, this document stipulates that the average OH group concentration in the range of 20 μm from the inner surface of the portion where the ultraviolet radiation divergence is maximum is 10 ppm or more and 190 ppm or less.

Thus, it is known that the arc tube contains an OH group, which diffuses as H ₂ O in the luminous space. Further, H ₂ O diffused into the arc tube is thermally decomposed into oxygen and hydrogen by heat from the arc. As a result of intensive studies by the inventors, it has been found that the hydrogen generated in the arc tube in this manner reduces the stability of illuminance. The illuminance stability is caused by a change in the amount of incident light and an incident angle distribution on the optical system as the arc fluctuates. Although the fluctuation period varies depending on the optical system, it causes a so-called flickering in which the illuminance fluctuation becomes large in the range of several milliseconds to several seconds. This decrease in illuminance stability causes a problem of screen flicker in the image projection apparatus, and causes exposure unevenness in the exposure apparatus.

  Patent Document 3 discloses disposing a hydrogen getter that absorbs hydrogen released into the arc tube in the arc tube. FIG. 11 is an explanatory diagram showing an outline of the configuration of the discharge lamp disclosed in the document. FIG. 12 shows a cross-sectional structure of a hydrogen getter included in the discharge lamp shown in FIG.

  The discharge lamp shown in FIG. 11 includes a bulb 201, electrodes 202 and 203, a sealing portion 204, and a metal foil 205. 206 is a quartz cylinder, 207 is a quartz rod, and 210 is a hydrogen getter. As shown in FIG. 12, the hydrogen getter 210 includes a metal shell 213 made of a bottomed cylinder 211 made of a metal such as tantalum and a lid 212, and hydrogen made of cylindrical yttrium sealed inside the metal skin 213. The metal outer skin 213 is hermetically sealed by resistance welding between the flange portion 211A of the bottomed cylinder 211 and the lid 212.

The hydrogen getter 210 is fixed to the valve 201 by welding the other end of a quartz rod 207 provided on the quartz cylinder 206 to the valve 201 as shown in FIG. Has been. Hydrogen in the valve 201 enters the inside of the metal skin 213 through the metal skin 213 having hydrogen permeability such as tantalum and is adsorbed by the getter material 214.
According to the hydrogen getter 210 described in this document, since the hydrogen getter material 214 is sealed inside the metal shell 213, hydrogen can be adsorbed without reacting with other substances in the light emitting space.

  However, since the hydrogen getter 210 is attached to the valve 201 as described above, the hydrogen getter 210 may react with silica, which is a component of the valve 201. There was a concern that it would cause a drop or a valve burst.

  In view of the above, in order to eliminate the disadvantages of the prior art, the present inventors have previously provided a hydrogen getter comprising a hydrogen-permeable hollow container and a getter material that adsorbs hydrogen inside the electrode around the electrode axis. Proposes a mounting structure. This is Japanese Patent Application No. 2009-048066.

The structure is shown in FIGS. In FIG. 8, a short arc type discharge lamp 10 includes an arc tube 11 and sealed tube portions 12A and 12B continuous at both ends thereof. Inside the arc tube 11, the main body 2 </ b> B of the cathode 2 and the main body 3 </ b> B of the anode 3 are disposed so as to face each other, and a luminescent substance is enclosed in the discharge space S.
The cathode 2 is composed of a shaft portion 2A and a main body portion 2B having a larger diameter than that, and the anode 3 is composed of a shaft portion 3A and a main body portion 3B having a larger diameter than that.

  8 indicates a place where a hydrogen getter is attached in the discharge space S of the arc tube 11, and the hydrogen getter is fixed to the shaft portion 2 A of the cathode 2.

  FIG. 9 is a partial explanatory view showing a hydrogen getter mounting structure in which the X portion of the short arc type discharge lamp of FIG. 8 is enlarged, and FIG. 10 is a detailed structural view of the hydrogen getter.

10A is a perspective view of a hydrogen getter seen from an oblique direction, and FIG. 10B is a longitudinal sectional view of the hydrogen getter cut along line AA shown in FIG. 10A. 10 (C) is a radial cross-sectional view of the hydrogen getter cut along line BB shown in FIG. 10 (A).
As shown in the figure, the hydrogen getter 30 includes a straight tubular hollow container 31 made of a metal that allows hydrogen to permeate and a getter material 32 that adsorbs hydrogen sealed inside the hollow container 31. . 31A and 31A are both-end sealing portions, which are sealed in a secret manner by pressure-welding both ends of the straight pipe member constituting the hollow container 31, or by welding or welding. This isolates the getter material 32 in the hollow container 31 from the discharge space, prevents direct contact with the gas in the discharge space, and prevents the getter material 32 from leaking outside the hollow container 31. I am doing so.

In addition, the hollow container 31 does not necessarily need to form a sealing part in the both ends, For example, it can also be set as the structure which sealed only the one end side using the bottomed cylindrical member.
The hollow container 31 is made of a metal that allows hydrogen to pass through but hardly reacts with mercury, and is made of, for example, tantalum or niobium. Tantalum and niobium may be simple substances or compounds with other substances.
The hollow container 31 made of these substances efficiently transmits hydrogen, prevents the getter material 32 from reacting with a discharge medium such as mercury in particular, and impure impurities such as hydrogen generated in the arc tube 11. Gas can be removed. The hollow container 31 has, for example, an inner diameter of 3.0 mm and a wall thickness of 0.1 mm.

  The getter material 32 enclosed in the hollow container 31 is, for example, yttrium or zirconium. Substances such as yttrium and zirconium have excellent hydrogen storage capacity. Yttrium and zirconium may be a simple substance or a compound with another substance.

  As shown in FIG. 9, a plurality of hydrogen getters 30 having the above structure are sequentially arranged in the circumferential direction of the shaft portion 2A so as to be separated from each other so as to surround the side surface of the electrode shaft portion 2A. And is fixed to the side surface of the shaft portion 2A in a posture parallel to the axis L of the cathode 2. These hydrogen getters 30 are fixed to the side surface of the shaft portion 2A so that the two fixing members 4A and 4B do not fall from the shaft portion 2A by being wound around each hollow container 31 so as to surround each hollow container 31. Has been.

  By adopting the above configuration, the disadvantage of the prior art that the hydrogen getter reacts with the arc tube is eliminated, and the hydrogen generated in the discharge space is transmitted through the hollow container 31 and adsorbed by the getter material 32. This makes it possible to fully perform the original functions.

  By the way, according to the subsequent knowledge by the present inventors, in the prior art based on the prior application, the hydrogen getter 30 is disposed with the metal hollow container 31 exposed to the discharge space S. Depending on the structure of the lamp and the lighting conditions, when a starting voltage is applied to the cathode 2 and the anode 3 at the time of starting, abnormal discharge may occur between the anode 3 and the hollow container 31 of the hydrogen getter 30. found.

  When such an abnormal discharge occurs, a hole is formed in the hollow container 31, and a light emitting substance such as mercury sealed in the discharge space S through the hole reacts with the getter material 32, and the original function of the getter material 32 is achieved. A certain hydrogen adsorption capacity is greatly reduced, which sometimes causes malfunction.

  Furthermore, the getter material 32 scatters into the discharge space S through the hole in the hollow container 31 and adheres to the bulb, which may cause a problem that the light transmittance of the bulb is lowered and the emitted light is lowered. there were.

Japanese Patent No. 2891997 Japanese Patent No. 3591470 Japanese Patent Publication No.57-21835

  A problem to be solved by the present invention is a short arc type discharge lamp in which a hydrogen getter formed by enclosing a getter material that adsorbs hydrogen in a hydrogen permeable hollow container is provided in an arc tube, and the hydrogen getter is connected to an electrode shaft. A short arc type discharge lamp that can be attached to the hydrogen getter while adsorbing hydrogen in the discharge space of the arc tube while preventing the hydrogen getter from reacting with the arc tube, and also preventing abnormal discharge between the hollow vessel and the electrode Is intended to provide.

  In order to solve the above problems, a short arc discharge lamp according to the present invention is attached so that the hydrogen getter is wound around an electrode shaft, and a cover made of a high melting point material is provided so as to cover the hydrogen getter, The cover is formed with a communication port that communicates the internal space of the cover with the discharge space in the arc tube.

  The cover includes a tip wall covering the electrode main body side of the hydrogen getter and a side wall covering the side surface of the hydrogen getter following the tip wall, the rear end being open, and the open end being the communication port It is characterized by comprising.

  Further, the cover has a tip wall covering the electrode body side of the hydrogen getter, a side wall covering the side surface of the hydrogen getter following the tip wall, and a side opposite to the electrode body side of the hydrogen getter following the side wall. The communication port is formed in the front end wall and / or the side wall and / or the rear end wall.

According to the short arc type discharge lamp of the present invention, since the hydrogen getter attached to the electrode shaft is covered with a cover made of a high melting point material, even when a high voltage is applied between the electrodes at the start of the discharge lamp, Abnormal discharge does not occur between the hydrogen getter and the electrode, and as a result, the hydrogen getter is not damaged due to the abnormal discharge.
Furthermore, since the cover is formed with a communication port that communicates the discharge space and the internal space of the cover, the hydrogen getter in the cover is in contact with the gas in the discharge space, and the hydrogen present in the discharge space is removed from the hydrogen getter. Can be absorbed reliably.

  In addition, since the cover includes a tip wall that covers the electrode body side of the hydrogen getter and a side wall that covers the side wall of the hydrogen getter following the tip wall, abnormal discharge is most likely to occur between the hydrogen getter and the electrode. It is a structure that covers the portion, and can reliably prevent abnormal discharge and reliably prevent damage to the hydrogen getter.

  The cover further includes a tip wall covering the electrode body side of the hydrogen getter, a side wall covering the side surface of the hydrogen getter following the tip wall portion, and a rear end covering the side wall and the side opposite to the electrode body of the hydrogen getter. Since it consists of walls, it is possible to completely cover the hydrogen getter located in the discharge space, and to reliably prevent abnormal discharge from occurring between the hydrogen getter and the electrode.

FIG. 3 is a partial cross-sectional perspective view showing a hydrogen getter mounting structure of a short arc discharge lamp according to the present invention. Sectional drawing of FIG. Sectional drawing of another Example. Sectional drawing of another Example. Sectional drawing of another Example. Explanatory drawing of another Example. Illustration of another embodiment The whole figure showing the prior art concerning a prior application. The principal part perspective view of FIG. FIG. 10 is a detailed view of the hydrogen getter of FIG. 9. The fragmentary sectional view of a prior art. FIG. 12 is an essential part cross-sectional view of FIG. 11.

FIG. 1 is a partial cross-sectional perspective view showing the structure of a hydrogen getter 30 and a cover 50 fixed to the electrode shaft 2A of the electrode 2 (FIG. 8), and FIG. 2 is a cross-sectional view in the electrode shaft direction.
In the figure, the hydrogen getter 30 has the same structure as that of the prior art described above, and is attached to the electrode shaft 2A by the fixing members 4A and 4B.
A cover 50 is provided so as to cover the hydrogen getter 30. The cover 50 is made of a high melting point material such as tungsten, molybdenum, or tantalum.

The cover 50 includes a tip wall 51 that covers the electrode body side of the hydrogen getter 30, and a side wall 52 that covers the side surface of the hydrogen getter 30 following the tip wall 51, and its rear end 52A is open.
A part of the tip wall 51 is joined to the electrode shaft 2A by welding, and the cover 50 is fixed to the electrode shaft 2A.
The open rear end 52A of the cover 50 forms a communication port 7 that connects the discharge space and the internal space of the cover.

An example of the cover 5 is as follows.
The tip wall 51 of the cover 50 has a disk shape with a diameter of 6 to 40 mm, and has a hole through which the electrode shaft 2A passes in the center. The side wall 52 is a cylindrical body, has a length exceeding the rear end side of the hollow container 31 of the hydrogen getter 30, and has a length of 5 to 50 mm in the electrode axis direction.
The thickness of the tip wall 51 and the side wall 52 is 0.3 to 5 mm.

FIG. 3 is a modified example of the cover 50.
The cover 50 includes a tip wall 51 covering the electrode body side of the hydrogen getter 30, a side wall 52 covering the side surface of the hydrogen getter 30 following the tip wall 51, and an electrode body direction of the hydrogen getter 30 following the side wall 52. Has a rear end wall 53 covering the opposite side, and a gap is formed between the rear end wall 53 and the electrode shaft 2 </ b> A, and the gap constitutes the communication port 7.
A part of the tip wall 51 is joined to the electrode shaft 2A by welding, and the cover 50 is fixed to the electrode shaft 2A.

FIG. 4 is another modification of the cover 50.
The cover 50 includes a tip wall 51 covering the electrode tip direction side of the hydrogen getter 30, a side wall 52 covering the side surface of the hydrogen getter 30 following the tip wall 51, and an electrode body of the hydrogen getter 30 following the side wall 52. Has a rear end wall 53 covering the opposite side.
A gap is formed between the tip wall 51 and the electrode shaft 2 </ b> A, and this gap serves as a communication port 7.
In addition, a part of the rear end wall 53 is joined to the electrode shaft 2A by welding, and the cover 50 is fixed to the shaft portion.

  In the embodiment shown in FIG. 3 and FIG. 4 described above, the gap formed between the front end wall 51 or the rear end wall 53 of the cover 50 and the electrode shaft 2A constitutes the communication port 7. However, the communication port 7 is not limited to this, and an opening may be formed in the front end wall 51 or the rear end wall 53 to form a communication port.

FIG. 5 shows still another modification of the cover 50.
The cover 50 has the front end wall 51, the side wall 52, and the rear end wall 53, as in FIGS. In this example, a plurality of openings are formed in the side wall 52 to form the communication ports 7 and 7.

3 to 5, the communication port 7 is described as being formed in the rear end wall 53, the front end wall 51, and the side wall 52. However, the present invention is not limited to this, and one of these walls or You may make it provide in two or three.
That is, the communication port 7 may be formed in the front wall 51 and / or the side wall 52 and / or the rear wall 53.

FIG. 6 is still another modification of the cover 50.
The cover 50 has a front end wall 51, a side wall 52, and a rear end wall 53.
Gaps are formed between the front end wall 51 and the rear end wall 52 and the electrode shaft 2 </ b> A, and the gaps form communication ports 7 and 7.
Fixing members 9A and 9B made of a coil spring or the like for preventing the movement of the cover 50 are provided on the electrode body side of the front end wall 51 and on the opposite side of the electrode body of the rear end wall 53, respectively.

In addition, the shape of the hollow container 31 of the hydrogen getter 30 is not limited to a straight tube shape as in the above embodiment, and may be a hollow ring shape as shown in FIG.
What is shown in this figure is a hollow ring shape with a flat cross section as shown in FIG. 7A, and as shown in FIGS. It is attached so as to be wound around the electrode shaft 2A.
Furthermore, although not shown, the ring-shaped hollow container may have a circular cross section.
The attachment to the electrode shaft may be performed by winding an elongated hollow container around the electrode shaft in a coil shape.
That is, various forms can be adopted for the shape of the hollow container 31 of the hydrogen getter 30 and the way to attach it to the electrode shaft.

The cover 50 has a tria or lanthanoid oxide content of 1 W% or less, preferably 0.1 W%, so that the surface of the cover 50 does not become a starting point of abnormal discharge.
3 to 6 has a structure having a front end wall 51, a side wall 52, and a rear end wall 53, the hollow container 31 of the hydrogen getter 30 is positioned in the cover, and the cover 50 is hollow. Depending on the dimensional relationship between the container 31 and the cover 50, the hollow container 30 is not necessarily fixed to the electrode shaft 2A by the fixing members 4A and 4B.

In addition, although the electrode comprised what comprised the electrode main body and the electrode shaft of a smaller diameter than this in the figure, it is not necessarily restricted to this, The thing of the same diameter may be sufficient.
Further, although the hydrogen getter is attached to the cathode shaft, it may be attached to the anode shaft.

  As described above, the short arc discharge lamp according to the present invention has a hydrogen getter composed of a sealed hollow container and a getter material enclosed in the sealed hollow container attached to the electrode shaft, and a cover is provided so as to cover the hydrogen getter. Therefore, abnormal discharge is not generated between the hollow container and the electrode of the hydrogen getter, the hollow container is not damaged, and the safety is maintained.

2, 3 Electrode 2A, 3A Electrode shaft 2B, 3B Electrode body 4A, 4B Fixing member 30 Hydrogen getter 31 Hollow container 50 Cover 51 Front end wall 52 Side wall 53 Rear end wall 7 Communication port

Claims (3)

An arc tube that forms a discharge space, and a pair of electrodes that are composed of an electrode body and an electrode shaft that is connected to the electrode body are disposed in the arc tube, and in the arc tube, a sealed hollow container made of a hydrogen-permeable material In a short arc type discharge lamp provided with a hydrogen getter formed by enclosing a getter material that adsorbs hydrogen inside,
The hydrogen getter is attached to the electrode shaft;
The hydrogen getter is covered with a cover made of a high-melting-point material, and the cover is formed with a communication port that connects the internal space of the cover and the discharge space.   The cover is composed of a tip wall that covers the electrode body side of the hydrogen getter and a side wall that covers the side surface of the hydrogen getter following the tip wall, the rear end is open, and the open end serves as the communication port. The short arc type discharge lamp according to claim 1, wherein the short arc type discharge lamp is configured. The cover includes a tip wall covering the electrode body side of the hydrogen getter, a side wall covering the side surface of the hydrogen getter following the tip wall, and a side opposite to the electrode body side of the hydrogen getter following the side wall. It consists of the rear end wall that covers it,
The short arc type discharge lamp according to claim 1, wherein the communication port is formed in the front end wall and / or the side wall and / or the rear end wall.

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