JP2000340174A - Metal halide lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a luminous flux maintenance factor and to suppress a lamp voltage rise to prevent flame failure from being generated. SOLUTION: This metal halide lamp is provided with an arc tube 1 provided with an electrode 1a on both sides thereof. Inside the arc tube, predetermined amounts of a mercury, a gas mixed with a neon and argon, a scandium iodide and a sodium iodide are sealed. Also sealed are 3-5 wt.% of the thorium iodide with respect to the total amount of a metal iodide and a metal to be a metal iodide having free energy higher than that of the sodium iodide and lower than that of the thorium iodide so as to have a molar ratio of 1.4-20 with respect to the thorium iodide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal halide lamp used for high ceiling lighting and the like.

[0002]

2. Description of the Related Art Conventionally, such a metal halide lamp has electrodes made of tungsten at both ends and a scandium iodide in order to prevent a significant decrease in luminous flux maintenance factor, that is, blackening of the inner surface of the arc tube. , Sodium iodide, and thorium iodide or metal thorium.

[0003] As described above, by enclosing thorium iodide or metal thorium in the arc tube, metal thorium adheres to the tip of the electrode during lamp operation, and the work function of the electrode is reduced. As a result, the temperature at the tip of the electrode is lowered, the evaporation of tungsten is suppressed, and blackening of the arc tube can be prevented.

[0004]

However, in the prior art, when excessive thorium iodide or metal thorium is sealed in the arc tube, the lamp voltage increases due to the high vapor pressure of metal thorium, and the lamp disappears. There was a problem of getting up.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a metal halide lamp having an improved luminous flux maintenance ratio and preventing the lamp from going out due to an increase in lamp voltage.

[0006]

The metal halide lamp of the present invention has electrodes at both ends and has at least scandium iodide, sodium iodide, thorium iodide, and free energy of its iodide. An arc tube filled with a metal higher than sodium and lower than thorium iodide is provided, wherein the thorium iodide is 3 wt% with respect to the total amount of metal iodides sealed in the arc tube.
-5 wt%, and the amount of the metal to be sealed is in a molar ratio of 1.4 to 20 with respect to the thorium iodide.

As a result, it is possible to reduce a decrease in the luminous flux maintenance factor and prevent the light from going out due to an increase in the lamp voltage.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

A rated power 700 according to an embodiment of the present invention.
As shown in FIG. 1, a W metal halide lamp has a length 1 having electrodes 1a made of tungsten at both ends.
A quartz arc tube 1 having a length of 30 mm and a maximum outer diameter of 30 mm is supported and fixed by metal plates 3 and 4 in a hard glass outer tube 2 having a total length of 360 mm and a maximum outer diameter of 140 mm. The distance between the electrodes 1a is 66 mm.

In the arc tube 1, the free energy of mercury, a mixed gas of neon and argon, scandium iodide, sodium iodide, thorium iodide, and their iodides is higher than that of sodium iodide. For example, scandium (hereinafter, referred to as metal scandium) is sealed in a predetermined amount as a lower metal.

A mixed gas of neon and nitrogen is sealed in the outer tube 2.

In FIG. 1, reference numeral 5 denotes a base.

Next, a method of lighting such a metal halide lamp will be described.

First, when the power is turned on, the bimetal 6 is in a closed state, and a current flows to the lighting tube 7. Therefore, the lighting tube 7 and about 470
A secondary voltage is applied to the low resistance 8 of Ω, and a pulse voltage is generated in the lighting tube 7. This pulse voltage generates a discharge between the electrode 1a and the auxiliary electrode 10 through the high resistance 9 of about 10 kΩ, and then generates an arc discharge between the electrodes 1a to turn on the lamp.

Such a metal halide lamp (hereinafter, referred to as "metal halide lamp")
Thiadium iodide in the arc tube 1)
3 wt% to the total amount of metal iodide enclosed in
It is preferable to seal the inside of the arc tube 1 so as to be 5 wt%. The reason will be described as follows.

In the product of the present invention, 10 mg of scandium iodide, 50 mg of sodium iodide,
Lamps in which metal scandium is sealed in various amounts of thorium iodide in a range of 2 to 6% by weight with respect to the total amount of metal iodides so that the molar ratio is 1.4 with respect to thorium halide described below. Was manufactured, and the luminous flux maintenance ratio of each lamp after the lapse of 9000 hours of rated life was examined. The results shown in Table 1 were obtained.

The default value of the lamp voltage is 130
V.

[0018]

[Table 1]

As is evident from Table 1, in a lamp in which thorium iodide is filled in an amount of 3 wt% to 5 wt% with respect to the total amount of metal iodide, a luminous flux maintenance factor of 55% which is practically sufficient was obtained. . On the other hand, when the amount of thorium iodide is 2 wt% based on the total amount of metal iodides, the luminous flux maintenance factor is 5%.
0% or less, which was not practically sufficient. When the amount of thorium iodide was 6 wt% with respect to the total amount of the metal iodides, the lamp voltage increased by 24 V, and after lighting for 7000 hours, the lamp went out and turned off.

As described above, by enclosing the thorium iodide in the arc tube 1 with 3 wt% to 5 wt% of the total amount of metal iodide, the amount of thorium iodide can be optimized, that is, the electrode 1 a Can be prevented from excessively increasing the vapor pressure of the metal thorium in the arc tube 1 while the temperature of the light-emitting element is lowered, so that the luminous flux maintenance factor can be improved and the extinction can be prevented.

Here, the reason why a metal that becomes a metal iodide that is higher than the free energy of sodium iodide and lower than the free energy of thorium iodide is enclosed will be described.

In the metal halide lamp of the present invention, in order to attach metal thorium to the electrode 1a, it is necessary to decompose the enclosed thorium iodide and take out the metal thorium. Therefore, the free energy of the iodide is higher than sodium iodide, and, for example, by enclosing metal scandium as a metal lower than thorium iodide, thorium iodide and metal scandium react with each other, and scandium iodide is formed. Once formed, metal thorium can be removed. However, as is conventionally known, when metal scandium is excessively encapsulated, it reacts with quartz and reduces the luminous flux maintenance factor.

In order to improve the luminous flux maintenance factor,
It is preferable that the metal whose free energy is higher than that of sodium iodide and lower than that of thorium iodide is specified to have a molar ratio of 1.4 to 20 with respect to thorium iodide. The reason will be described as follows.

In the invention, 10 mg of scandium iodide, 50 mg of sodium iodide, and 3 wt% of thorium iodide are contained in the arc tube 1 with respect to the total amount of metal iodide.
The molar ratio of scandium metal to thorium iodide is 0.1.
Various sealed lamps were prepared with various changes in the range of 5 to 22, and the luminous flux maintenance factor after the lapse of 9000 hours of rated life of each lamp was examined. The results shown in Table 2 were obtained.

[0025]

[Table 2]

As is apparent from Table 2, in the lamp in which scandium metal was sealed in 1.4 to 20 with thorium iodide, a luminous flux maintenance factor of 55% which was practically sufficient was obtained. On the other hand, for example, when the scandium metal has a molar ratio of 0.5 to thorium iodide, the luminous flux maintenance factor is 45%.
%, Which was not practically sufficient. Further, for example, when the scandium metal has a molar ratio of 22 to thorium iodide, the luminous flux maintenance factor is 50%, which is not practically sufficient.

As described above, by encapsulating metal scandium in the arc tube 1 at a molar ratio of 1.4 to 20 with respect to thorium iodide, the amount of metal scandium to be encapsulated can be optimized, and the luminous flux maintenance rate can be improved. Can be improved.
Further, in order to further improve the luminous flux maintenance rate, it is preferable to encapsulate metal scandium in a molar ratio of 6 to 17 with respect to thorium iodide.

In the above-described embodiment, the case where scandium is used as a metal which is a metal iodide higher than the free energy of sodium iodide and lower than the free energy of thorium iodide has been described, but dysprosium, The same effect as described above can be obtained by using thulium metal.

In the above embodiment, the rated power 70
Although the description has been given of the case of the metal halide lamp of 0 W, the same effect as described above can be obtained also with the metal halide lamp of the rated power of 100 W or 1000 W.

[0030]

As described above, the present invention provides a metal halide lamp capable of improving the luminous flux maintenance factor and suppressing an increase in the lamp voltage to prevent the lamp from going out. Can be done.

[Brief description of the drawings]

FIG. 1 is a perspective view of a metal halide lamp having a rated power of 700 W according to an embodiment of the present invention.

[Description of Signs] 1 Arc tube 1a Electrode

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Akiyoshi 1-1, Saimachi, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. F-term (reference) 5C015 QQ03 QQ14 QQ20 QQ35 RR05

Claims (3)

[Claims] 1. An electrode at both ends, and at least scandium iodide, sodium iodide, thorium iodide, and the free energy of iodide thereof higher than sodium iodide and lower than thorium iodide An arc tube filled with metal is provided, wherein the thorium iodide is 3w with respect to the total amount of metal iodide sealed in the arc tube.
a metal halide lamp having a molar ratio of 1.4 to 20 with respect to the thorium iodide; 2. The metal halide lamp according to claim 1, wherein the metal has a molar ratio of 6 to 17 with respect to the thorium iodide. 3. The metal halide lamp according to claim 1, wherein the metal is scandium.