JPS6249698B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a metal halide lamp with improved lamp startup and deterioration. In general, metal halide lamps have significantly improved efficiency and color rendering properties of ordinary high-pressure mercury lamps by sealing several types of metal halides in addition to rare gases and mercury inside the arc tube. That is, a rare earth metal halide is used to emit multiple spectra in the visible region, and at least one member selected from the group of sodium, cesium, indium, thallium, and thorium is used to stabilize the arc or slightly modify the emission color. A metal halide is sealed inside an arc tube. In addition, barium oxide-based materials with a low work function cannot be used as the electron-emitting material coated or filled in the main electrode, and in reality, thorium oxide
It uses an electron-emitting material such as metal thorium, which has a higher work function than barium oxide. However, due to the effect of the metal halide on the main electrode, the starting voltage of this type of metal halide lamp is considerably higher than that of a normal high-pressure mercury lamp. Therefore, as a ballast, it was necessary to install an internal circuit that generates high-voltage pulses at the time of starting, or to incorporate a transformer, which had the disadvantage of making the ballast extremely expensive. . In recent years, in order to improve these drawbacks of metal halide lamps, Penning gases such as neon-argon (Ne-Ar) or neon-krypton (Ne-Kr) have been sealed in the arc tube as rare gases for starting aid. Metal halide lamps have been put into practical use that utilize the Penning effect of mixed gases to lower the starting voltage of metal halide lamps, and that can be lit using normal high-pressure mercury lamp ballasts. That is, this metal halide lamp has the configuration as shown in the figure, that is, it is equipped with a quartz arc tube 1 containing a small amount of titanium oxide, main electrodes 2a and 2b are sealed at both ends, and the base 17 side An auxiliary pole 3 for starting is sealed to one end of the starter. Note that quartz containing titanium oxide is used as the material for the arc tube 1 because impurities such as moisture and hydrocarbons remaining on the inner surface of the outer bulb 18 are decomposed by ultraviolet rays from the arc tube 1. This is to prevent the phenomenon of releasing hydrogen and oxygen. The main electrode 2a is connected to the stem lead 1 through the molybdenum foil 4a, the current introduction lead 5a, and the nickel lead 9.
1a, and the main electrode 2b is a molybdenum foil 4b.
- Current introduction lead 5b - Tungsten wire 8
The auxiliary electrode 3 is connected to the stem lead 11b through the molybdenum foil 4c and the current introduction lead 5c.
- Starting resistor 10 - Bimetal 14 - Connected to stem lead 11b through bimetal contact 15. Further, a heat insulating film 6 is coated on the lower end of the arc tube 1 to increase the vapor pressure of the substance enclosed within the arc tube 1. The arc tube 1 includes a holding plate 7 and a support frame 12.
Outer tube 1 through outer tube 18 and stem 16
It is fixed within 8. A mixed gas of neon (Ne) and nitrogen (N ₂ ) is sealed in the outer tube 18 at a predetermined pressure to prevent the neon (Ne) gas from diffusing and flowing out from the arc tube 1 . Further, a zirconium (Nr)-aluminum (Al)-based getter 13 is installed in the outer tube 18 to adsorb impurity gases, especially hydrogen gas, in a gas atmosphere such as nitrogen (N ₂ ). Therefore, in a metal halide lamp having the configuration shown in the figure, 45 mg
of mercury, 2 mg of scandium (Sc) as a rare earth metal, 6 mg of mercury iodide (HgI ₂ ), and 40 mg of sodium iodide as a metal halide.
Manufactured 10 400W metal halide lamps. In addition, because rare earth metal halides are highly hygroscopic, they are sealed in the form of rare earth metals and mercury halides, and the reaction between the earthophilic metals and mercury halides is used in the arc tube 1 when the lamp is lit. This process generates rare earth halides.
In this manufactured metal halide lamp, the starting voltage and total luminous flux were determined at an ambient temperature of -10°C after aging for 16 hours, and when it was lit using a high-pressure mercury lamp ballast, the ambient temperature was -10°C after 6000 hours of lighting.
The starting voltage and luminous flux maintenance rate at .degree. C., and the glow discharge duration between the main electrode 2a and the auxiliary electrode 3 at the time of starting the lamp after aging for 16 hours and after 6000 hours of lighting were measured. As a result, the average value of those 10 pieces was 16
The starting voltage after time aging is 174 [V], the glow duration is 1.0 [seconds], the total luminous flux is 33000 [m], and the starting voltage after 6000 hours of lighting is 189 [V], the glow duration is 3.0 [ seconds], luminous flux maintenance rate is 58 [%]
It was hot. As can be seen from these results, it is difficult to transition from glow to arc during startup, and phenomena such as an increase in startup voltage and a decrease in luminous flux due to spatter of the electrode material occur. This is presumed to be due to the following factors. That is, during aging, scandium metal and mercury iodide react as follows: Sc+3/2HgI ₂ →ScI ₃ +3/2Hg to produce scandium iodide and mercury. However, during this aging, a considerable amount of impurity gas such as oxygen (O 2 ) is released from the interior of the arc tube 1, the surface of the arc tube ₁ , or the enclosed material, and oxygen (O ₂ ) intervenes during the above reaction, resulting in ScI ₃
Instead of producing , it produces oxyiodide called ScOI. Since this oxyiodide has a higher vapor pressure than iodide, it evaporates and dissociates into the arc during lamp operation, bringing oxygen into the arc, resulting in an increase in the starting voltage of the lamp,
Acceleration of evaporation of tungsten, which is an electrode component, causes adverse effects such as a decrease in luminous flux. This invention was made in view of the above circumstances, and includes a rare earth metal halide and a metal halide selected from the group of sodium, cesium, indium, thallium, and thorium in addition to rare gas and mercury. Eutectic mixture or composite compound and 1×10 ^-6 to 1× per c.c. volume of arc tube.
Provided is a metal halide lamp that minimizes the adverse effects of impurity gas mixed into the arc tube by enclosing 10 ^-5 g atoms of rare earth metal, thereby making it possible to improve the starting characteristics and deterioration characteristics of the lamp. It is something to do. An embodiment of the present invention will be described below. In a metal halide lamp having the configuration shown in FIG. 1, 47.7 mg of mercury is contained in the arc tube 1.
NaI/ScI ₃ was prepared by mixing and melting sodium iodide (NaI) and scandium iodide (ScI ₃ ) at 780°C in a high vacuum for 6 hours as a eutectic mixture of rare earth metal halides and metal halides. weight ratio of
Scandium iodide (ScI ₃ ) and sodium iodide (NaI) of 10.5 (equivalent to the conventional NaI/ScI ₃ weight ratio)
43.8 mg of eutectic mixture and 1.6 mg of rare earth metals
We manufactured 10 400W metal halide lamps filled with scandium (Sc). Similarly to the conventional example above, this manufactured metal halide lamp was lit using the starting voltage and total luminous flux at an ambient temperature of -10°C after aging for 16 hours, and the high-pressure mercury lamp ballast. Temperature -
The starting voltage and luminous flux maintenance rate at 10°C, and the duration of glow discharge between the main electrode 2a and the auxiliary electrode 3 at the time of starting the lamp after aging for 16 hours and after 6000 hours of lighting were measured. As a result, the average value of those 10 pieces was 16
The starting voltage after time aging is 156 [V], the glow duration is 0.5 [seconds], the total luminous flux is 34500 [m], and the starting voltage after 6000 hours of lighting is 164 [V], the glow duration is 0.5 [ seconds], luminous flux maintenance rate is 70[%]
It was hot.

[Table] Thus, it can be seen that the above example is superior to the conventional example in all characteristics. In this way, the difference in lamp characteristics between the above embodiment and the conventional example is as follows:
There is a close relationship with the glow discharge duration between the main pole 2a and the auxiliary pole 3 at the time of starting, and a lamp with a long glow discharge duration between the main pole 2a and the auxiliary pole 3 has a long main pole 2a-
It is believed that impure gas such as oxygen (O ₂ ) is mixed into the discharge path of the main electrode 2b and prevents the discharge from starting normally. However, in the above example, scandium iodide (ScI ₃ ) forms a stable eutectic mixture with sodium iodide (NaI) even if impurity gases such as oxygen (O ₂ ) are released during aging. , oxygen (O ₂ ) does not react with scandium iodide, but reacts with scandium (Sc) to form a stable compound scandium oxide (Sc ₂ O ₃ ), so oxygen is brought into the arc. This prevents the lamp characteristics from being adversely affected. In the above examples, a eutectic mixture of scandium iodide and sodium iodide has been described, but at least one rare earth metal halide and at least one selected from the group of sodium, cesium, indium, thallium, and thorium are used. Any eutectic mixture or composite compound with a metal halide may be used. In addition, regarding the amount of enclosed rare earth metal, we created a 400W metal halide lamp similar to the previous example, changed only the amount of rare earth metal, and turned it on.
After 6000 hours, we investigated the starting voltage and luminous flux maintenance rate at an ambient temperature of -10°C, as well as the glow connection time when starting the lamp. The results are shown in FIG. The arc tube used in the example had an internal volume of 15.5 cc, and the amount of Sc metal sealed in Fig. 2 is Ss per 1 c.c. of arc tube internal volume.
Expressed in g atoms of metal. In FIG. 2, △ indicates the glow connection time, ◎ indicates the starting voltage, and × indicates the luminous flux maintenance rate. As can be seen from Figure 2,
If the amount of Sc enclosed is less than 1×10 ^-6 atoms/cc, the glow connection time will be long and the starting voltage will exceed 180V, causing practical problems. On the other hand, the amount of Sc included is 1×10 ^-5 g atom/
If it exceeds cc, the luminous flux maintenance factor will decrease significantly, which poses a practical problem. Therefore, the amount of rare earth metal enclosed is 1×10 ^-6 to 1× per 1 c.c. of arc tube internal volume.
Good results were obtained with approximately 10 ^-5 g atoms. Furthermore, it has been discovered that the metal halide lamp produced by implementing the present invention has a new effect in that the color characteristics change extremely little during its life. That is, FIG. 3 shows the measurement results of the change in color temperature during lighting of the lamp when the amount of Sc metal sealed per 1 c.c. of the internal volume of the arc tube was changed based on the example shown in Table 1. In Fig. 3, ○・ is the conventional example, △・ is the amount of Sc metal filled in is 2×10 ^-5 g atoms/cc, ・ is the amount of Sc metal filled in is 2×10 ^-6 g atoms/cc, ▲ is Sc indicates the case where the amount of metal enclosed is 8 x 10 ^-6 g atoms/cc, × indicates the case where the amount of Sc metal enclosed is 5 x 10 ^-7 g atoms/cc, the horizontal axis is the lighting time, and the vertical axis is the color temperature It shows. As can be seen from FIG. 3, in the conventional example, the color temperature changes significantly from 0 hours to 100 hours at the beginning of life and during life. On the other hand, when a eutectic mixture is formed, the change in color temperature of the lamp at the beginning of its life is small regardless of the amount of Sc metal filled in, but the color temperature change after long-term lighting depends on the amount of Sc metal filled in. In particular, when the amount of inclusion is 2×10 ^-5 g atoms/cc or more, the change in color temperature during life becomes particularly large. Further, it was also observed that when the above-mentioned amount of inclusion was less than 2 x 10-7 g atoms, the color temperature tended to change significantly during the life. In particular, the amount of the above-mentioned Sc metal enclosed is 1×10 ^-6 ~
In the range of 1×10 ⁻⁵ g atoms, the change in color temperature of the lamp during its lifetime was particularly small. These experimental results are considered to be due to the following factors. In the eutectic mixture in the above experiment,
Since NaI and ScI ₃ are melted for a long time and a stable eutectic mixture is formed, part of NaI reacts with ScI ₃ , and the above mixture forms a uniform eutectic mixed salt of NaScI ₄ + NaI. . Therefore, this mixed salt is
Since the vapor pressure during lamp operation is controlled by the mole fraction of NaScI ₄ in the mixed salt, the vapor pressure tends to be stable even when the adhesion state of the enclosed halide tends to become unstable at the beginning of life. However, if a large amount of Sc metal is enclosed at the same time as the mixed salt, the Sc metal will gradually melt into the mixed salt during lighting, react with NaScI ₄ , and convert this compound into two single compounds [NaI + ScI ₃ ]. As a result of dissociation, the vapor pressure of NaI is more than two orders of magnitude lower than that of NaScI ₄ , so the luminescence of Na decreases, and the vapor pressure increases over time. On the other hand, if the amount of enclosed Sc metal is small, the oxygen present in the arc tube during lighting will react with NaScI ₄ in the eutectic salt, and the reaction products such as oxygen Sc ₂ O ₃ will gradually light up and melt. The oxide layer covers the surface of the eutectic salt and obstructs the evaporation of the eutectic salt as the lighting time passes. Therefore, the vapor pressure of the halogen substance decreases with lighting time, and the color temperature increases. Considering the starting characteristics, life characteristics, and color characteristics mentioned above of Sc metal, the amount of inclusion should be 1×10 ^-6
It is necessary to regulate it to ~1×10 ^-5 g atoms/cc. In addition, this invention encapsulates the metal halide in the form of a eutectic mixture or a composite compound,
Moreover, by simultaneously encapsulating 1×10 ⁻⁶ to 1×10 ⁻⁵ g atoms/cc of rare earth metal, it is possible to realize good characteristics during the life that could not be obtained conventionally. Therefore, the type and amount of the encapsulated metal halide may be determined depending on the target performance (luminous efficiency, luminous characteristics, life characteristics, etc.) of the metal halide lamp. In addition, the rare earth metal to be sealed in the above example is
For example, in Hg-Dy-Tl-I, Dy
In Ho-Tm-Tl-Na-I, the metal is Ho or
A similar effect can be obtained by encapsulating Tm. In addition, although the above example was conducted on a metal halide lamp that can be lit with a normal high-pressure mercury lamp ballast filled with Pennine gas, it is also effective in improving the starting characteristics and deterioration characteristics of a general metal halide lamp that is lit with a dedicated ballast. It goes without saying that there is. As described above, this invention comprises, in addition to a rare gas and mercury, at least one rare earth metal halide and at least one metal halide selected from the group of sodium, cesium, indium, thallium, and thorium. The eutectic mixture or composite compound and at least one rare earth metal in an amount of 1 x 10 ^-6 to 1 x 10 ^-5 g per 1 c.c. of the internal volume of the arc tube.
Since it is sealed inside the atomic arc tube, it is possible to prevent the lamp from being adversely affected by impurity gases such as oxygen remaining in the arc tube, and to reduce the initial starting voltage of the lamp.
Lamp characteristics such as initial luminous flux, starting voltage, and luminous flux maintenance rate during the life of the lamp can be significantly improved, and furthermore, there is an effect that the change in color characteristics of the lamp during the life of the lamp is extremely small.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the configuration of a metal halide lamp, FIG. 2 is a diagram showing experimental results of starting voltage, glow connection time, and luminous flux maintenance rate in this invention,
FIG. 3 is a diagram showing experimental results regarding the relationship between lighting time and color temperature. In the figure, 1 is an arc tube, 2a and 2b are main electrodes, and 18 is an outer tube.

Claims (1)

[Claims] 1. A stable eutectic mixture or composite compound of a rare gas, mercury, and at least one rare earth metal halide and at least one metal halide selected from the group of sodium, cesium, indium, thallium, and thorium in the arc tube. and at least one kind of rare earth metal that reacts with the impure gas generated during lighting, and the amount of rare earth metal sealed per 1 c.c. of volume in the arc tube is 1×10 ^-6
A metal halide lamp characterized by having ~1×10 ^-5 g atoms.