JPS6037648A - Metal halide lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a metal halide lamp containing scandium halide as a metal halide.

[Technical background of the invention and its problems]

Demand for halide lamps is increasing further. In particular, those using scandium halide as the gold halide have good color rendering properties, and are now the mainstream of metal halide lamps for general lighting.

However, lamps using scandium halides often have a problem in that cracks occur in the sealing portion of the arc tube, causing leaks and shortening the lamp life.

As a result of investigating this problem, the inventors of the present invention found that the cause of the problem was that the scandium halide contained in the arc tube and the thoria ThO2 applied to the main electrode as an emitter invaded the main electrode sealing part of the sealing part. It was presumed that a white precipitate was produced, causing a devitrification phenomenon, which caused strain in the sealing part and caused cracks. As a result of analysis, the above white precipitate was found to contain silicon 811 scandium Sc,) lium Th
, oxygen 02, etc. were detected in large quantities, and this is thought to be caused by the reaction of three components: scandium chloride, ThO2 of the emitter, and quartz glass of the arc tube pulp.

The 3 rock π Tsui elbow + Funi 5 scandium halide and quartz glass arc tube bulk are essential for the construction of this kind of lamp, and what remains is the emitter ThO2 coated on the main electrode. It is. However, it is impossible to use alkaline earth metal oxides, which are well known as emitters in the 20s, because they react with nitrogen oxides.
On the other hand, if ThO2 is not applied, the starting voltage of the lamp will be high, resulting in problems such as blackening during its life and an increase in the lamp voltage and turn-off voltage.

[Purpose of the invention]

The present invention provides a metal halide lamp equipped with an arc tube in which scandium 7.logogenide is sealed in a quartz arc tube.
It is an object of the present invention to provide a lamp with a long life by preventing the occurrence of cracks in the sealed portion of the arc tube without deteriorating the lamp characteristics.

[Summary of the invention]

The present invention comprises forming a main electrode sealed in a sealed portion of an arc tube in which at least scandium tetragenide is sealed as a metal halide, an electrode shaft and one or more layers of coils wound around the electrode shaft. and a layer of the coil that is in contact with at least the electrode axis are formed of thorium tungsten.

[Embodiments of the invention]

The details of the present invention will be explained below with reference to the drawings.

(Example I) FIG. 1 is a front view of a 1 kW type metal halide lamp arc tube, and FIG. 2 is an enlarged front view of its main electrode. In the figure, (1) is a quartz glass arc tube, and (2) is an arc tube made of quartz glass.

(2) is sealed to the sealing part (3), (3) formed by heating and crushing the end of the arc tube (1) with the main electrode, and is sealed to the sealing part (3), (3) through the metal foil (4,), (4). External lead wire (5)
I (5) respectively. Further, (6) is an auxiliary electrode. The main electrodes (2) and <2) each have a coil (8) wound around the tip of the electrode shaft (7).
Tungsten toe containing hO2; 9) Made of lithium tungsten. In addition, 25 torr of argon gas was contained in the arc tube (1) as a starting rare gas.

Contains 180mg of mercury and a total of 30mg of scandium iodide and sodium iodide as metal halides.

Such an arc tube (1) is usually sealed in an outer tube (not shown) with a cap attached to one end to form a metal halide lamp. This lamp can keep the starting voltage low as described below.

No cracks occurred in the arc tube sealing part (3), and a long life was achieved.

(Example ■) FIG. 3 shows only the main electrode (12) of another embodiment.

The rest of the structure is the same as that described above (Example 2), and the same parts are designated by the same reference numerals.

The main electrode (work 2) is made by winding a two-layer coil (18) around the electrode shaft (7). , shi, electrode shaft (7) of two-layer coil (18)
The first layer (18a) to be treated is made of thorium tungsten.
The 2N1 (18b) wound around the outside 1j is made of tungsten.

Further, the electrode shaft (7) is made of thorium tungsten.

As shown in the table below, the same effects as in (Example I) were obtained in this example as well. In I), both the electrode shaft and coil are made of pure tungsten, and the emitter is not coated +1. +7'1.
/ #-*All 1π）纾宕t*きょうIT）The one in which thoria TbO2 is applied by applying TbO2, (conventional example ■), the electrode shaft is made of thorium tungsten, and the film is made of pure tungsten and is emic. I'll use the one without.

Table n = 10 As is clear from the table, (Conventional Example I) has an extremely high starting voltage, and (Conventional Example ■) uses ThO2 as the emitter.
Although the starting voltage is lower due to the use of , there are many cases where cracks occur in the sealing part.

I don't like either of them. Furthermore, although thorium tungsten is used only for the electrode shaft (conventional example (2)), it is effective in preventing the occurrence of glue buildup at the sealing part, but it is still not sufficient in terms of obtaining a low starting voltage. On the other hand, in each of the examples, a sufficiently low starting voltage was obtained,
In addition, there were no cases where two cracks occurred at the sealed portion of the arc tube, and the effect was remarkable.

That is, in each example, ThO□, which is an electron radioactive substance that facilitates starting, is present in the electrode material as thorium tungsten, and as in the conventional case, T
Since the hO2 emitter does not exist in a free state as a single unit, it does not generate white precipitates that can cause cracks in the main electrode sealing area, and on the other hand, the main electrode made of tungsten can be heated sufficiently. Since it emits hot electrons, a low starting voltage can be obtained. Furthermore, in the case of (Example ■), the outside of the first layer of the coil made of thorium tungsten is covered with the second layer coil made of pure tungsten, so the arc spot does not occur on the coil but on the tip of the electrode shaft. Since the arc can be generated reliably, it also has the advantage of stabilizing the arc.

Note that the present invention is not limited to the above embodiments.

For example, the coil may be multilayered with more than two layers, and each layer of coils may be made entirely of thorium tungsten.

〔Effect of the invention〕

As detailed above, according to the present invention, a metal halide lamp can be obtained which has a low starting voltage similar to that of conventional lamps in which a ThO2 emitter is applied to the main electrode, and which has a long life without cracking in the sealed part of the arc tube. It will be done.

[Brief explanation of the drawing]

Fig. 1 is a front view of the arc tube of a metal halide lamp which is an embodiment of the present invention, Fig. 2 is an enlarged front view of the main electrode thereof, and Fig. 3 is an enlarged front view of the main electrode of another embodiment. They are shown below. (1)... Arc tube, (2), (12)...
...Main electrode. (3)...Sealing part, (7)......
electrode axis. (8)...Coil (18)...Two-layer coil.

Claims (1)

[Claims] A pair of main electrodes are sealed in the sealing part, and rare gas for starting,
In a metal halide lamp equipped with a quartz glass arc tube filled with mercury and at least scandium halide as a metal halide, the main electrode has one or more coils wound around the electrode shaft, and the electrode shaft and the coil A metal halide lamp characterized in that at least the first layer in contact with the electrode shaft is made of thorium tungsten.