JPH11176385A - Short arc type extra high pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sufficient pressure resistance even if a lamp has extremely high mercury vapor pressure when lighted, by winding a coil around a part of an electrode embedded in a sealing part in a pair of electrodes placed face to face. SOLUTION: A discharge lamp is made of quartz glass, and is composed of a swelled part 20 of a luminous space in a center and a slender sealing part 21 connected to its both ends. A pair of electrodes 3 is placed with a distance of not more than 2.5 mm in the swelled part 20 of the luminous space. A filling quantity of mercury equivalent to a quantity by which vapor pressure becomes not less than 80 atm when stably lighted is calculated and filled. A coil 5 is wound around a part where the electrode 3 is sealed in the sealing part 21. The electrode can be baked in a heating process to form the sealing part 21 by this coil 5, and adhesiveness between metal foil 31 and the quartz glass can be raised. Tungsten, tantalum, molybdenum or the like is used or the coil 5. It is preferable that the coil 5 is embedded only in the sealing part 21 and is not exposed in the luminous space.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Regarding a short arc type ultra-high pressure discharge lamp filled with mercury having a mercury vapor pressure of 80 atm or more when lit at 5 mm or less,
In particular, it relates to a short arc type ultra-high pressure discharge lamp used as a backlight of a liquid crystal display device or the like.

[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. The 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. Such a lamp is disclosed, for example, in Japanese Patent Laid-Open No. 2-1485.
No. 61 and JP-A-6-52830.

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 lamp itself. 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. It is difficult to increase the thickness of this quartz glass part by the so-called pinch seal method, which is generally used frequently,
In a lamp that can withstand lighting under an ultra-high pressure of 0 atm or more, sufficient strength of the sealing portion cannot be obtained. On the other hand, if the quartz glass is baked at an excessively high temperature, the adhesion between the quartz glass and the metal foil can be improved, but cracks are generated at the contact portions between the electrode rods and the quartz glass, and these cracks are generated during lamp operation. Can cause rupture.

[0005]

An object of the present invention is to provide a short arc type ultra-high pressure discharge lamp which has a very high mercury vapor pressure at the time of operation and has a sufficient pressure resistance. Is to do.

[0006]

The short arc type ultra-high pressure discharge lamp according to the present invention has a pair of electrodes of 2.5 m.
m, the mercury vapor pressure at the time of lighting is 80 atm or more, and a coil is wound around a portion of this electrode embedded in the sealing portion. I do.

Further, in the invention according to claim 2, the discharge lamp is characterized in that the remaining portion of the exhaust pipe does not exist on the outer surface of the arc tube. Further, the invention according to claim 3 is characterized in that a metal foil is embedded in the sealing portion.

[0008]

According to the present invention, in order to further realize a point light source, the distance between the electrodes is reduced to 2.5 mm or less, and the sealing portion of the electrodes (electrode bars, hereinafter, "electrodes" includes the electrode bars). Since the coil is wound around the part buried in the glass, cracks between the electrode (electrode rod) and the quartz glass even in the sealing process of bringing the metal foil and quartz glass into close contact, even if it is thermally processed at high temperature Can be favorably prevented. This is because the coil is interposed between the electrode and the quartz glass, so that stress on the quartz glass due to thermal expansion of the electrode can be reduced. In addition, since thermal processing can be performed at a high temperature, the adhesion between the metal foil and the quartz glass can be improved.

In the above-mentioned prior art, the mercury vapor pressure is 2
It is described that the light output is remarkably improved when the pressure is higher than 00 bar (about 197 atm). However, even if the mercury vapor pressure is lower than that, it is found that there is no problem in practical use. However, the problem of the pressure resistance was easily improved by an amount lower than 200 bar. According to the study of the present inventor, it has been confirmed that substantially sufficient light output is obtained when the mercury vapor pressure is 80 atm or more.

[0010]

FIG. 1 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 luminous space bulging portion 20 and elongated sealing portions 21 (21a, 21b) connected to both ends thereof.
A pair of electrodes 3 (3a, 3b) has a size of 2.5 mm
It is arranged with the following gap. Electrode 3 (3a, 3b)
The rear end is embedded in the sealing portion 21 (21a, 21b) and welded to the metal foil 31 (31a, 31b). Metal foil 3
1 (31a, 31b) is connected to an external lead 4 (4a, 4a, 4b).
b) is joined. In the light emitting space, mercury is sealed as a light emitting substance, and a rare gas such as argon or xenon is sealed as a lighting starting gas. The amount of mercury enclosed is calculated by the amount corresponding to a vapor pressure of 80 atm or more during stable lighting.

FIG. 2 is an enlarged view of a boundary portion between the light emitting space bulging portion 20 and the sealing portion 21. A coil 5 is wound around a portion where the electrode 3 is embedded in the sealing portion 21. With this coil 5, it can be baked at a high temperature in the heating step of forming the sealing portion 21, and the adhesion between the metal foil 31 and the quartz glass can be improved. To further explain this point, in the case where the coil is not wound around the portion as in the prior art, if thermal processing is performed at a high temperature as described above, the portion to prevent the contact portion between the electrode and the quartz glass from cracking is used. Tended to be insufficiently heated. That is, in the portion of the metal foil 31 far from the electrode, thermal processing can be performed without any particular problem, but in the portion close to the electrode, sufficient heating cannot be performed. Therefore, the portion of the metal foil 21 close to the electrode is insufficiently heated, and the metal foil 31 in the portion is not sufficiently heated.
There was a problem in the adhesion between the glass and the quartz glass. In the present invention,
Such a problem, that is, sufficient thermal processing can be performed without generating cracks between the electrode and the quartz glass, so that the adhesion between the metal foil and the quartz glass can be improved, and a discharge lamp with extremely high withstand voltage is provided. It is possible to do.

The coil is made of, for example, tungsten, tantalum, molybdenum, etc.
Winded up to 8 times. Preferably, the coil 5 is buried only in the sealing portion and is not exposed to the light emitting space. The reason for this is that a discharge occurs immediately after the start of lighting between the coil and the opposite electrode opposite to the coil, which may cause blackening or bursting of the arc tube.

A method for manufacturing such a discharge lamp will be described. First, a coil is inserted into a predetermined portion of the electrode. Then, two assemblies of the electrode, the metal foil, and the external lead are formed. The method of inserting the coil into the predetermined portion of the electrode is not particularly limited, but may be a method of manually inserting the coil. Then, the assembly is arranged in a portion to be one of the sealing portions of the quartz glass molded roughly in the shape of a discharge lamp. Seal. Next, a light emitting substance such as mercury is sealed in the light emitting space through the other opening, and another assembly is disposed in a portion to be the other sealing portion, and an inert gas of 1 atm or less is provided therein. And shrink-sealed while heating at a high temperature in the same manner. At this time, it is necessary to cool the light emitting space so that the sealed substance does not evaporate. The discharge lamp according to this manufacturing method is of a so-called "chipless type" in which the remainder of the exhaust pipe does not exist on the outer surface of the arc tube.

The discharge lamp of the present invention is, for example, as follows. Lamp power: 150 W Lamp voltage: 70 V Distance between electrodes: 1.25 mm Luminous efficiency: 56 lm / W Tube wall load: 80 W / cm ² Emission wavelength: 400 to 600 nm

In the above-described embodiment, a discharge lamp of a DC lighting type has been described, but the present invention can be applied to an AC lighting discharge lamp. Further, in the above embodiment, the so-called “chipless type” discharge lamp having no exhaust pipe residue on the outer surface of the arc tube has been described. However, the present invention is not limited to this. Can be applied even if the exhaust pipe has the rest. The light emitting metal may be a metal halide lamp by enclosing other light emitting metal, for example, dysprosium halide, in addition to encapsulating mercury.

[Brief description of the drawings]

FIG. 1 shows a short arc type ultra-high pressure discharge lamp according to the present invention.

FIG. 2 is a partially enlarged view of a short arc type ultra-high pressure discharge lamp according to the present invention.

[Explanation of symbols]

 1: Discharge lamp 20: Light emitting space bulging part 21: Sealing part 3: Electrode 31: Metal foil 4: External lead 5: Coil

Claims (3)

[Claims] 1. A pair of electrodes are opposed to each other at an interval of 2.5 mm or less, a mercury vapor pressure at the time of lighting is 80 atm or more, and a portion of the electrodes embedded in a sealing portion is A short arc type ultra-high pressure discharge lamp having a coil wound thereon. 2. The ultra-high pressure discharge lamp according to claim 1, wherein the discharge lamp has no remaining portion of the exhaust pipe on the outer surface of the arc tube. 3. The short arc type ultra-high pressure discharge lamp according to claim 1, wherein a metal foil is buried in the sealing portion.