JP2001160374A - Short-arc ultra-pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a short-arc ultra-high pressure discharge lamp having extremely high mercury vapor pressure when the lamp is on, and which is capable of forming sealing region having sufficient pressure withstanding property. SOLUTION: In this short-arc ultra-high pressure discharge lamp with a pair of electrodes 2 arranged in a luminance tube 10 that are connected to a metal foil 3 embedded in a sealing region 11, the metal foil 3 is connected to the electrodes 2, such that it is positioned at a cross-sectional canter X of the electrode 2, and a the coil member 4 with its one and cones in contact with an end of the metal boil 3, is wound around the electrodes 2 and embedded in the sealing region 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short arc type ultra-high pressure discharge lamp containing mercury having a mercury vapor pressure of 80 atm or more when turned on. Ultra-high pressure discharge lamp.

[0002]

2. Description of the Related Art A projection-type liquid crystal display device is required to uniformly illuminate an image on a rectangular screen with sufficient color rendering properties. Therefore, mercury or a metal halide is used as a light source. An enclosed metal halide lamp is used. In recent years, such metal halide lamps have been further reduced in size and made into point light sources, and those having extremely small distances between electrodes have been put to practical use.

[0003] Against this background, in recent years, instead of metal halide lamps, lamps having an unprecedented high mercury vapor pressure, for example, 200 bar (about 197 atm) or more have been proposed. This means that by increasing the mercury vapor pressure, the spread of the arc is suppressed (narrowed down) and the light output is further improved.

In general, an ultra-high pressure discharge lamp needs to form a sealing portion by bringing quartz glass and metal foil into close contact with each other. This is because if the adhesion is poor, a high internal pressure is applied from a minute gap between the electrode (rod) and the quartz glass, which may cause damage to the sealing portion. For this reason, in the manufacturing process for forming the sealing portion, the thick quartz glass is gradually shrunk by heating at a high temperature of, for example, 2000 ° C., so as to increase the adhesion of the portion.

[0005] It is difficult to increase the thickness of quartz glass in a sealing portion by a so-called pinch seal method, which is widely used. It cannot be adopted, and a sealing method of gradually shrinking thick quartz glass is adopted. However, when the quartz glass is baked and shrunk at an excessively high temperature, the adhesion between the quartz glass and the metal foil can be improved, but after the sealing step, the temperature of the electrode and the quartz glass is reduced at a stage where the temperature of the sealing portion is lowered. There is a problem that cracks occur in the contact portions due to the difference in the expansion coefficient, and the sealing portion is damaged.

In order to solve such a problem, as shown in FIG. 1, a coil member 4 is wound around an electrode 2 embedded in a sealing portion 11, and the coil member 4 is
Embedded therein to reduce stress on the quartz glass due to thermal expansion of the electrode 2. Such a technique is described in JP-A-11-176385.

[0007] However, as shown in FIG.
The metal foil 3 is directly welded to the outer peripheral surface of the electrode 2, that is, the metal foil 3 is disposed at a position shifted from the cross-sectional center X of the electrode 2, so that the coil member 4 wound around the electrode 2 near the metal foil 3
Move in the direction of the metal foil 3 during the sealing process,
May be deformed and sealed in a state in which the end portion leans on the metal foil 3. When the sealing portion 11 is formed in such a state, the temperature of the sealing portion 11 decreases after the sealing step. At this stage, the stress on the quartz glass due to the heat shrinkage of the electrode 2 cannot be sufficiently reduced, and further, the accumulation of the stress due to the deformation of the coil member 4 causes a crack to occur in the sealing portion 11 so that the sealing is performed. There was a problem that the stop was damaged.

Further, as shown in FIG. 2, which is a cross-sectional view taken along line AA of FIG. 1, the metal foil 3 is located at a position shifted from the center X of the cross section of the electrode 2. Stop 11
Is no longer symmetric, and the metal foil 3 and quartz glass (sealing part 1
The contact portion C1 with 1) became small, and the metal foil 3 and the quartz glass (sealing portion 11) could not be sufficiently adhered.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can form a sealing portion having a sufficient pressure resistance. Another object of the present invention is to provide a short arc type ultra-high pressure discharge lamp having a very high mercury vapor pressure.

[0010]

According to a first aspect of the present invention, there is provided a short arc type ultra-high pressure discharge lamp in which a pair of electrodes disposed in an arc tube are connected to a metal foil embedded in a sealing portion. In the ultra high pressure discharge lamp, the metal foil is connected to the electrode so as to be located at the center of the cross section of the electrode, and a coil member is wound around the electrode, and one end of the coil member is connected to an end of the metal foil. And the coil member is embedded in the sealing portion.

[0011]

FIG. 3 shows a short arc type ultra-high pressure discharge lamp according to the present invention. The discharge lamp 1 is made of quartz glass and includes a central arc tube 10 and elongated sealing portions 11 connected to both ends thereof.

In the arc tube 10, a pair of electrodes 2 is provided.
The rear end of the electrode 2 is embedded in the sealing portion 11 and welded to the metal foil 3. An external lead 5 is joined to the other end of the metal foil 3.

The arc tube 10 is filled with mercury as a light-emitting substance and a rare gas such as argon or xenon as a starting gas for lighting. The amount of mercury enclosed is calculated by the amount corresponding to a vapor pressure of 80 atm or more during stable lighting.

FIG. 4 is an enlarged view of a boundary portion between the arc tube 10 and the sealing portion 11, and FIG. 5 is an enlarged view showing only the electrode 2, the metal foil 3, and the coil member 4. As shown in FIGS. 4 and 5, the metal foil 3 is welded to the electrode 2 so as to be located at the cross-sectional center X of the electrode 2. Specifically, a step 2a having a semicircular cross section is formed on one end side of the electrode 2 embedded in the sealing portion 11, and the metal foil 3 is formed on the flat surface M of the step 2a. Joined by welding. That is,
One surface 31 of the metal foil 3 is welded to the electrode 2 so as to be located at the cross-sectional center X of the electrode 2. The coil member 4 is wound around the electrode 2 so as to contact the end 3a of the metal foil 3. The coil member 4 is made of, for example, tungsten, tantalum, molybdenum, or the like, and has a diameter of 0.1 m.
m are wound 7 to 8 times.

As a result, as shown in FIG. 4, the metal foil 3 is arranged at a position coinciding with the center X of the cross section of the electrode 2, and the end 3a of the metal foil 3 comes into contact with the center of the coil diameter of the coil member 4. Therefore, even if the coil member 4 moves during the sealing process, the end of the coil member 4 does not tilt and ride on the metal foil 3, and therefore, without deformation of the coil member 4,
The coil member 4 can be embedded in the sealing portion 11.

As a result, the stress caused by the difference in the expansion coefficient between the electrode 2 and the quartz glass can be reliably alleviated by the undeformed coil member 4 when the temperature of the sealing portion is lowered after the sealing step. In addition, since no deformation stress is accumulated by the coil member 4 itself, no crack occurs in the sealing portion 11 and the sealing portion is not damaged.

As shown in FIG. 6, which is a cross-sectional view taken along the line BB of FIG. 4, the metal foil 3 is located at the cross-sectional center X of the electrode 2. Since it is substantially symmetric, the contact portion C2 between the metal foil 3 and the quartz glass (sealing portion 11) becomes large, and the metal foil 3 and the quartz glass (sealing portion 11) can be sufficiently adhered. Therefore, a short arc type ultra-high pressure discharge lamp with a very high mercury vapor pressure during operation is provided by using a sealing method that gradually shrinks the thick quartz glass to improve the adhesion between the quartz glass and the metal foil. It is possible to do.

FIG. 7 shows a modification of the electrodes used in the short arc type ultra-high pressure discharge lamp of the present invention. The electrode 2 of FIG. 7 has a slit S formed at the position of the cross-sectional center X of the electrode 2. By inserting the metal foil 3 into this slit, the metal foil 3 can be positioned at the cross-sectional center X of the electrode 2. Things.

[0019]

According to the short arc type ultra-high pressure discharge lamp of the present invention, the metal foil embedded in the sealing portion is connected to the electrode so as to be located at the center of the cross section of the electrode. Since the member is wound, one end of the coil member abuts against the end of the metal foil, and the coil member is embedded in the sealing portion, the end of the coil member tilts during the sealing process. Therefore, the coil member can be embedded in the sealing portion without deformation of the coil member, so that a sealing method in which the thick quartz glass is gradually shrunk is adopted, and the sealing is performed. After the process, when the temperature of the sealing portion is lowered, the stress caused by the difference in the expansion coefficient between the electrode and the quartz glass can be reliably reduced by the coil member, and the deformation stress due to the coil member itself is also accumulated. Since there is no Rack does not occur, the sealing portion is not damaged. In addition, since the metal foil is located at the center of the cross section of the electrode, the sealing portion is formed substantially symmetrically with respect to the foil. It is possible to provide a short arc type ultra-high pressure discharge lamp in which the adhesion to glass can be improved and the mercury vapor pressure during operation is extremely high.

[Brief description of the drawings]

FIG. 1 is a partially enlarged description of a conventional short arc type ultra-high pressure discharge lamp.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is an explanatory view of a short arc type ultra-high pressure discharge lamp according to the present invention.

FIG. 4 is an enlarged view of a boundary portion between an arc tube and a sealing portion of the short arc type ultra-high pressure discharge lamp according to the present invention.

FIG. 5 is an enlarged view showing only the electrode, metal foil, and coil member of FIG. 4;

FIG. 6 is a sectional view taken along line BB in FIG. 4;

FIG. 7 is an explanatory view showing a modification of the electrode used in the short arc type ultra-high pressure discharge lamp of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge lamp 10 Arc tube 11 Sealing part 2 Electrode 2a Step of electrode 3 Metal foil 31 Metal foil surface 4 Coil member 5 External lead

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C015 JJ01 5C043 AA14 AA20 BB09 CC01 CC02 CD01 DD12 EA09

Claims (1)

[Claims] 1. A short arc type ultra-high pressure discharge lamp in which a pair of electrodes arranged in an arc tube are connected to a metal foil embedded in a sealing portion, wherein the metal foil is located at a center of a cross section of the electrode. A coil member is wound around the electrode, one end of the coil member is in contact with an end of the metal foil, and the coil member is embedded in the sealing portion. Characterized by a short arc type ultra-high pressure discharge lamp.