JPS61138448A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To remove hydrogen and free iodine generated in a small sized quartz light emission tube, so as to prevent discontinuance at the start, by enclosing at least either of gold or tellurium in the tube, together with scandium iodide which is a luminescent metal. CONSTITUTION:At least either gold or tellurium is enclosed in a quartz light emission tube valve whose internal capacity is under 1cc, together with mercury, rare gas and metal halide which contains at least scandium iodide. In this way, discontinuance of the lamp at the start can be prevented as hydrogen and free iodine generated in the light emission tube are removed, and a long-lived small metal halide lamp can be got.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to metal halide lamps, and particularly to small metal halide lamps.

[Technical background of the invention and problems with the background art] Conventionally, a metal halide lamp has an arc tube in which a metal halide is sealed together with mercury and a rare gas for starting in a quartz arc tube bulb with electrodes facing each other at both ends. Widely popular.

Furthermore, in recent years, efforts have been made to miniaturize the metal halide lamps for indoor use.

Incidentally, in such lamps, scandium iodide or compounds to which sodium iodide, etc. are added are used as the metal halide because they have high efficiency and high color rendering properties, but they tend to turn off when starting up. This phenomenon occurred.

In other words, although this type of lamp is lit with a ballast with a secondary voltage of 200 ■ class, the above-mentioned fading phenomenon is observed after the power is turned on until the arc tube transitions from glow to arc to a steady state. . Figure 1 shows changes in the voltage waveform of the lamp after lighting. (a) is 5 seconds after lighting, (b) is 10 seconds after lighting, (C) is after 20 seconds, and (d) is 30 seconds after lighting. are shown respectively. About 10 seconds after lighting, a whisker-like thing (first restriking voltage Ps) is seen as shown in (b) K, which increases and then disappears, resulting in the state shown in (c).
After about 30 seconds, as shown in (di), a whisker-like thing (second restriking voltage P2) appears again, which increases once, then decreases again, and disappears during steady lighting. Various experiments have been conducted to investigate this phenomenon. The result is interpreted as follows.

In other words, the first restriking voltage Pl is due to the hydrogen present in the arc tube, and because its vapor pressure is high, it appears early, but disappears as the temperature of the arc tube rises and the mercury vapor pressure rises. . The second restriking voltage P2 that appears after this is due to free iodine, and since its vapor pressure is low, it appears with a delay and is observed until the mercury vapor pressure becomes sufficient.

These restriking voltages have peak values that are proportional to the hydrogen concentration and free iodine concentration in the arc tube, but if the voltage applied to the lamp exceeds 200 V AC in general, the lamp cannot maintain its discharge and the lamp goes out. Causes disappearance.

The generation of impurity gases such as hydrogen and free iodine is mainly due to the reaction between the moisture present in the arc tube and the scandium iodide SC3, which is the enclosed metal halide, as shown in the following equation.

25cIs +3H20→5C20B +3H2+3
I2 In particular, in the case of a small metal halide lamp where the internal volume of the arc tube is less than 1c, c, the amount of encapsulated metal halide 5cIa per unit volume of the arc tube is lower than that of a larger lamp such as a conventional lamp. As a result, the amount of hydrogen and free iodine generated per unit volume of the arc tube becomes larger than in the conventional case, and the phenomenon of lamp extinguishing becomes noticeable.

In order to deal with such an inconvenient phenomenon, there is also a method of sealing scandium (Sc) metal together with 5cIs.

In this case, hydrogen is well adsorbed by the Sc metal, and free iodine reacts with the Sc metal to form 5cIs and is removed, so this is effective. However, it was found that this effect could not be sustained for a long time. The following may be the cause of this.

In other words, S which adsorbed hydrogen as the lamp lighting time elapsed.
c metal reacts with a quartz (SiO2) arc tube bulb to produce scandium oxide 5C203 as shown in the following equation.

At this time, the adsorbed hydrogen is released.

4 Sc + 3510z→2SC203-)-3Si
Also. Since Sc reacts with quartz SiO2 and is consumed, even if free iodine is generated during long-term lamp operation,
It cannot be absorbed. Namely.

Since Sc metal ends up releasing the absorbed hydrogen and iodine into the arc tube, long-term effects cannot be expected. The same can be said for other metals other than Sc if they react with quartz 5i02.

To deal with these drawbacks, for example, Japanese Patent Application Laid-Open No. 57-12
Publication No. 2093 has Cd, Ag, along with Sc.
By enclosing a getter such as B, hydrogen and free iodine generated in the arc tube are adsorbed by Sc at the beginning of the life, and the impurity gases re-released as the life passes are adsorbed by the getter. Disclosed.

However, such a method also has disadvantages, such as the hydrogen adsorption ability of the getter being weaker than that of Sc, and the initial color characteristics changing due to the light emission of the getter metal itself.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances.

To provide a small metal halide lamp with a long life by removing hydrogen and free iodine generated in a small arc tube due to the presence of scandium iodide and preventing the lamp from going out when starting. With the goal.

[Summary of the invention]

The present invention encapsulates at least one of gold, Au, and tellurium Te together with mercury, a rare gas, and a metal tetragenide containing at least scandium iodide in a small quartz arc tube bulb with an internal volume of 1 c, c or less. By doing so, we were able to achieve the above objective.

[Embodiments of the invention]

As a result of careful consideration of the above-mentioned conventional problems, the present inventor found that
It has been found that the above object can be achieved by encapsulating a metal satisfying all of the following conditions in a quartz arc tube together with a metal halide containing at least scandium iodide.

Namely.

l) It must be a metal that does not react with quartz or does not react easily with quartz. In other words, the impure gas that has been adsorbed must not be released again through reaction with quartz.

It is a metal that can react with iodine and capture free iodine. In other words, the impurity of the metal must be stable.

111) It has the ability to adsorb hydrogen well.

lv) The metal must not emit strong visible light when the lamp is lit. In other words, it must be a metal that does not cause large fluctuations in the color characteristics of the Sc-containing lamp.

It is required that the metal has the following properties.

An embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows a front view of a small 40W arc tube for a metal halide lamp, (1) has an inner diameter of about 8mm and an internal volume of 0.3mm.
c, c, approximately spherical quartz arc tube bulb, (21,(
2+ is an electrode sealed to both ends of the quartz arc tube bulb (1), and is formed by winding a coil (2b) made of tungsten doped with, for example, an oxide of AI, K, or Si.

Furthermore, a scandium oxide emitter is deposited if necessary. In addition, 9 quartz arc tube bulbs (1) contain 100 tons of argon and 151 tons of mercury as rare gases for starting.
g.

Scandium iodide 0.41n9 as metal halide
2Tng of sodium iodide and 0.05μ of either gold Au or tellurium Te are sealed.

The table below shows the lamp of the present invention using such an arc tube, the conventional lamp (■) of the lamp of the present invention without the added metals Au and Te, and the conventional lamp (■) of the lamp of the present invention using Su metal instead of the conventional lamp. About the one with added 2
The results of an investigation into the occurrence of failure to turn off during startup at each time point of 300 hours and 3,000 hours of lighting in the initial stage 2 of lighting are shown.

As can be seen from the table, some conventional lamps may go out from the beginning of lighting, and conventional lamps with Sc metal added are effective in the early stages of lighting, but as the lighting time progresses, this effect is maintained. come. In contrast, none of the lamps of the present invention went out even after 3,000 hours.

The reason why the lamp of the present invention was able to achieve such remarkable effects is considered to be due to the following reasons.

That is, as mentioned above, there are four essential conditions for the metal to be sealed in the quartz arc tube together with the iodide of Sc, which is a luminescent metal. First, we will discuss what happens thermodynamically regarding condition 1).

If we consider the respective reactions of Au and Sc to quartz Si02 as a bowl.

Au+3/4Sj02→3/4Si+1/2Aus+0
3-・-・-・-(1) Sc +3/4 S io2→
3/4 S i + 1/2 Sc 20:1...
・・・・・・・・・・・・In (2), the standard free energies of reactions (1) and (21) are expressed as ΔF(1) and Δ
Assuming F(2), the more negative this value is, the more the reaction progresses to the right, and the more positive this value is, the less the reaction progresses (the reaction does not occur). In the temperature range from 800 to 1,600, which includes the tube wall temperature of the quartz arc tube during normal lamp lighting, ΔF(1) is a positive value, whereas ΔF(2
) was a negative value. That is, Au is quartz 5iOz
It can be seen that Sc does not react, but Sc reacts.

Results of similarly calculating ΔF for other metals.

Tellurium Te, rhodium Rh, indium In, lithium Li, cobalt Co, iron Fe, nickel Ni
, thallium TI, lead Pb, cadmium CD, zinc Zn, copper Cu.

It has been found that silver Ag, manganese seeds, tin Sn, etc. do not react with quartz 5in2 similarly to the above-mentioned Au.

Next, as a result of considering the remaining three conditions for each metal that satisfies the condition 1) above, Rh does not satisfy the condition 11), and Co, Fe, Ni, Cu, Ag
, Mn, Sn (111), and Li, TI, Pb, Cd, Zn.

It was found that In does not satisfy the condition lv).

Therefore, in the end, only Au and Te remained as metals satisfying the four conditions. Moreover, Au, T
The iodide of e is very stable and has excellent iodine adsorption ability, and also has an excellent hydrogen adsorption ability comparable to that of Sc.
The remarkable effects shown in the above embodiments can be obtained.

Note that Au and Te may not be used alone, but may be used in combination.

〔Effect of the invention〕

As described in detail above, the present invention includes Au and Sc iodide, which is a luminescent metal, in a quartz arc tube having an internal volume of 1 c or less.
Since at least one type of Te is sealed, hydrogen and free iodine generated within the arc tube are removed.
It is possible to prevent the lamp from turning off during startup throughout its life.

[Brief explanation of the drawing]

FIG. 1 is a front view of the arc tube of a 40W metal halide lamp which is an embodiment of the present invention, and FIGS. 2(a-d) are diagrams showing changes in the voltage waveform of a conventional lamp. Pl......First restriking voltage. P2... Second restriking voltage. 1......Quartz arc tube bulb. 2... Electrode agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 (a) (b)

Claims (1)

[Claims] Internal volume 1c. A metal halide lamp comprising an arc tube in which at least one of gold and tellurium is sealed together with mercury, a rare gas, and a metal halide containing at least scandium iodide in a quartz arc tube bulb of c or less.