JPH07122234A - High pressure discharge lamp - Google Patents

Abstract

PURPOSE:To provide a high pressure discharge lamp having a long lifetime and capable of being manufactured relatively easily by preventing the sputter of electrode while the lamp is being lighted, and reducing the blackening of a light emitting tube. CONSTITUTION:The light emission part 1 of a light emitting tube includes a pair of electrodes 2, 3, and mercury, rare gas for starting, and metal halide are encapsulated in this part 1. The tips 2a, 3a of these electrodes 2, 3 on the discharge side are made of a material chiefly containing hafnium carbide, tantalum carbide, zirconium carbide, or a composite of the former two, and the electrode bars 2b, 3b on the seal side are made of a material chiefly containing tungsten, and the electrodes 2, 3 are constructed by joining them together. Equipment of such electrodes allows the accomplishment of a long lifetime of lamp and enhancing of the yield of the connecting workmanship of the tube seal parts 4, 5 with metal foil conductors 6, 7 of molybdenum to lead to easier manufacturing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode of a high pressure discharge lamp having at least one pinch seal portion applied to a metal halide lamp or the like, and more particularly to an improvement thereof.

[0002]

2. Description of the Related Art In recent years, high pressure discharge lamps such as metal halide lamps, sodium lamps and xenon lamps have been installed on roads,
In addition to wide area lighting such as open spaces and stadiums, there is an increasing demand for indoor lighting in stores and the like. In particular, metal halide lamps are widely used and being widely used as light sources for overhead projectors, overhead type liquid crystal projection televisions, projectors, etc., in addition to lighting for display products, because of their high color rendering properties and high efficiency.

A conventional high pressure discharge lamp will be described below by using an example of a metal halide lamp with reference to the drawings. FIG. 3 is a front view showing a metal halide lamp which is a type of conventional high pressure discharge lamp. In FIG. 3, reference numeral 11 denotes an elliptical arc tube made of quartz glass,
Metal foil conductors 14 and 15 connected to a pair of electrodes 12 and 13 containing tungsten (W) as a main component are sealed at both ends, and external leads are connected to the other ends of these metal foil conductors 14 and 15. Lines 16 and 17 are connected. Arc tube 1
Mercury, a metal halide, and a rare gas for starting are added to the inside of 1. When the lamp is turned on, the metal halide melts, and the metal halide transported to the high temperature part at the electrode tip evaporates violently. Therefore, the density of the metal halide in the arc becomes extremely high, the emission spectrum peculiar to the metal halide increases, and a highly efficient and high color rendering lamp can be obtained.

[0004]

However, in general, a high pressure discharge lamp such as a metal halide lamp has a problem that the luminous flux maintenance rate is greatly reduced during its life. That is, the decrease in the luminous flux maintenance factor during the lifetime is caused by the excessive temperature rise of the electrode tip during lighting, which causes tungsten (W), which is the main constituent material of the electrode, to scatter, and is transported by convection in the arc tube and adheres to the tube wall. The blackening phenomenon occurs, and the blackening of the tube wall blocks the transmission of visible light generated in the arc tube.

Further, in place of the tungsten electrode, hafnium carbide, tantalum carbide, zirconium carbide, or a compound compound of hafnium carbide and tantalum carbide has been investigated as an electrode material, but these materials are fragile and molybdenum of a metal foil conductor is used. The lamp is very difficult to manufacture as it breaks when it is welded to the foil.

In view of the above problems, it is an object of the present invention to provide a high pressure discharge lamp that suppresses electrode scattering at the electrode tip, prolongs the life of the electrode, and is easy to manufacture.

[0007]

In order to solve the above problems, a high pressure discharge lamp according to the present invention comprises a hafnium carbide (TaC),
Tantalum Carbide (TaC), Zirconium Carbide (Zr
C), or an electrode formed by joining a material containing a composite compound of hafnium carbide and tantalum carbide as a main material and a material containing tungsten (W) as a main material, and wherein the hafnium carbide, tantalum carbide, A material mainly made of zirconium carbide or a composite compound of hafnium carbide and tantalum carbide is arranged on the discharge side, and a material mainly made of tungsten is arranged on the sealing portion side.

[0008]

According to the present invention, with the above-described structure, compared with the conventional lamp, the blackening of the light emission amount is reduced, the luminous flux maintenance rate during the life of the lamp becomes extremely high, and the life can be prolonged. It is possible to provide a high-pressure discharge lamp in which the yield at the time of connection with a conductor is improved and the lamp manufacturing can be simplified.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A metal halide lamp which is a kind of high pressure discharge lamp will be described below as an embodiment of the present invention with reference to the drawings. FIG. 1 shows a horizontally lit 250 W metal halide lamp arc tube according to an embodiment of the present invention.
This arc tube has a single tube structure not housed in the outer bulb. In FIG. 1, reference numeral 1 denotes an arc tube light emitting portion having an inner volume of 1.0 cc and formed in an elliptical shape made of quartz glass.
A pair of electrodes 2 and 3 are sealed at both ends. The distance between the electrodes is 6.0 mm. 2a is HfC,
A spherical electrode tip composed mainly of a complex compound of TaC, ZrC, or HfC / TaC,
Reference numeral 2b is an electrode rod composed mainly of tungsten, and these electrodes 2 and 3 are formed. Arc tube sealing parts 4, 5
Are sealed with metal foil conductors 6 and 7 made of molybdenum, and the electrode rods 2b and 3b of the electrodes 2 and 3 are connected to these metal foil conductors 6 and 7, respectively. The other ends of 6, 7 are connected to external lead wires 8, 9. Reference numeral 10 is a heat insulating film applied to the outer surface of the tube around the electrodes. Then, the light emission tube emitting portion 1, mercury 35 mg, as an argon gas 250Torr and metal halides as starting rare gas, DyI ₃ 1 mg, TlI
1 mg, NdI ₃ 0.25 mg, and CsI ₂ mg are sealed.

The lamp assembled as described above was horizontally lit, and it was examined how the luminous flux maintenance factor changed with the lapse of lighting time, and the results shown in FIG. 2 were obtained. In FIG. 2, the characteristic A has a tip whose main component is HfC (9
9% by weight or more), the characteristic B is a lamp having an electrode whose tip is TaC as a main component (99% by weight or more), and the characteristic C is a tip having ZrC as a main component (99% by weight).
The lamp has an electrode with a weight ratio of at least 0.5%, and the characteristic D is that the tip has a molar ratio of HfC and TaC of 0.5 ≦ TaC / HfC
A lamp having an electrode made of a HfC / TaC composite compound having a range of ≦ 5, and a characteristic E is a lamp having an electrode containing W as a main component (99% by weight or more). As can be seen from FIG. 2, HfC and HfC · T according to the present embodiment.
A lamp equipped with an electrode composed of aC complex compound is 800
The luminous flux maintenance factor after lighting for 0 hours is about 90%, about 85% for lamps equipped with TaC-based electrodes, and about 75% for lamps equipped with ZrC-based electrodes. The luminous flux maintenance factor was much higher than that of the lamp as the component.

Next, the yield at the time of welding the electrode rod and the molybdenum foil is shown in (Table 1). As can be seen from (Table 1), the electrode rod is HfC, TaC, ZrC or HfC.
In the case of TaC composite compound, the electrode is almost broken during welding with the molybdenum foil. Therefore, it is desirable that the material of the end of the electrode portion joined to the molybdenum foil is tungsten that can withstand high temperatures and is relatively easy to weld.

[0012]

[Table 1]

In the above embodiment, no additive was added to the tip electrode, but HfC, TaC, Zr containing electron emitting substances such as thorium oxide and cerium oxide were added.
Excellent effects were also obtained with electrodes of C and HfC / TaC composite compounds.

The electrode of the present embodiment is more effective than the conventional electrode containing W as the main component as the electrode operating temperature is higher, and the electrode distance is 10 mm or less. Suitable for use in high high watt lamps.

Further, although a lamp having a single tube structure is used in the above-mentioned embodiment, it can be used for a high pressure discharge lamp such as a lamp having a double tube structure, and the same effect as above can be obtained.

[0016]

As described above, according to the present invention, hafnium carbide (TaC), tantalum carbide (TaC), zirconium carbide (ZrC), or a material mainly containing a composite compound of hafnium carbide and tantalum carbide and tungsten. By including an electrode formed by joining a material mainly composed of (W), scattering of the electrode can be prevented, blackening of the arc tube can be reduced, and further, the hafnium carbide, tantalum carbide, By arranging the material containing zirconium carbide or the composite compound of hafnium carbide and tantalum carbide as the main material on the discharge side and the material containing tungsten as the main material on the sealing part side, the connection with the molybdenum metal foil conductor can be achieved. It is possible to obtain a high-pressure discharge lamp which has a long yield and is easy to manufacture because of improved yield.

[Brief description of drawings]

FIG. 1 is a front view of a kind of metal halide lamp of a high pressure discharge lamp according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the rate of change in the luminous flux maintenance factor with the passage of lighting time.

FIG. 3 is a front view of a type of metal halide lamp of a conventional high pressure discharge lamp.

[Explanation of symbols]

 1 Quartz glass arc tube light emitting part 2,3 Electrode 2a, 3a Electrode tip part 2b, 3b Electrode rod 4,5 Arc tube sealing part 6,7 Molybdenum metal foil conductor 8,9 External lead wire 10 Thermal insulation film

 ─────────────────────────────────────────────────── ─── Continued front page (72) Hideaki Omura Inventor Hideaki Omura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kazutaka Koyama 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A high pressure discharge lamp comprising an arc tube having at least one pinch seal portion, wherein the electrode is made of a material mainly composed of hafnium carbide (HfC) and a material mainly composed of tungsten (W). A high-pressure discharge lamp, characterized in that a material mainly composed of hafnium carbide is arranged on the discharge side, and a material mainly composed of tungsten is arranged on the sealing part side. 2. A high pressure discharge lamp comprising an arc tube having at least one pinch seal portion, wherein the electrodes are made of a material mainly made of tantalum carbide (TaC) and a material mainly made of tungsten (W). And a material mainly made of the above-mentioned tantalum carbide is arranged on the discharge side, and a material mainly made of tungsten is arranged on the sealing portion side. 3. A high pressure discharge lamp comprising an arc tube having at least one pinch seal portion, wherein the electrode is made of a material composed mainly of zirconium carbide (ZrC) and a material composed mainly of tungsten (W). And a material mainly made of zirconium carbide on the discharge side and a material mainly made of tungsten on the sealing portion side. 4. A high pressure discharge lamp comprising an arc tube having at least one pinch seal portion, wherein the electrode is made of a composite compound of hafnium carbide (HfC) and tantalum carbide (TaC) and tungsten (W). The main material is formed by joining, and the composite material of hafnium carbide (HfC) and tantalum carbide (TaC) is the main material on the discharge side, and the main material is tungsten. High-pressure discharge lamp, which is characterized in that it is placed on the side.