JPS6343864B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a metal halide lamp in which a metal halide is sealed together with a rare gas and mercury in an arc tube, and is particularly intended to reduce changes in lamp characteristics depending on the lighting direction when the metal halide lamp is lit. Metal halide lamps have significantly improved efficiency and color rendering properties over conventional high-pressure mercury lamps by sealing metal halides together with rare gases and mercury in the arc tube. Usually, metal halide lamps contain a combination of two or more metal halides. For example, a metal halide lamp that combines scandium halide and sodium halide is characterized by excellent efficiency and relatively good color rendering properties. The structure of this type of metal halide lamp will be explained based on the drawings. As shown in FIG.
Translucent outer tube 1 made of hard glass or the like with
A light-transmitting arc tube 1 made of quartz or the like is housed within the chamber 4. Inside the arc tube 1, halides of scandium Sc and sodium Na are sealed together with a rare gas such as argon and mercury. At both ends of the arc tube 1, main electrodes 2a and 2b are installed facing each other, and are made up of a molybdenum foil 3a, a leading wire 4a, a ribbon lead 7, a support frame 9, a stem lead 11, and a molybdenum foil 3b and a leading wire 4b, respectively. - Current supply line 8 - Connected to the base 13 through the stem lead 12. A heat insulating film 5 is provided at both ends of the arc tube 1. The arc tube 1 is fixed to support frames 9 and 10 by a holding plate 6. Many studies have been made to improve the efficiency of metal halide lamps with such a configuration in normal lighting conditions (vertical lighting), for example, as disclosed in Japanese Patent Publication No. 13958-1972 and Publication No. 33359-1973. A method has been used to maintain a balance between the emission intensities of scandium and sodium and increase lamp efficiency by controlling the molar ratio of sodium halide to scandium halide to 11 or less. However, in large metal halide lamps with lamp rated power exceeding 400W, the distance between the electrodes is long, so if the lighting condition is changed from vertical to horizontal, the position and temperature of the coldest point of the arc tube will change. As a result, the vapor density of the fill material introduced into the arc changes, resulting in a significant drop in lamp voltage, luminous efficiency, etc., which often poses a major practical obstacle. This invention was made in view of these conventional drawbacks, and includes the amount of mercury sealed in the arc tube of a metal halide lamp with a lamp rated power exceeding 400W, the scandium atoms in the scandium halide, and the sodium halide for this amount of mercury. By appropriately controlling the atomic ratio of sodium atoms in the lamp, it is possible to minimize the change in characteristics due to the change in lamp lighting angle described above. That is, scandium halide and sodium halide are sealed together with a rare gas and mercury in the arc tube, and the internal volume of the arc tube of mercury 1
The amount enclosed per cc is 2.8 mg or more, and the atomic ratio of scandium atoms to the mercury in the scandium halide is 0.005 to 0.11,
And the atomic ratio of the sodium atoms in the sodium halide to the mercury is 1.2 to 2.0. The details of this invention will be described below based on the drawings. FIG. 2 is a diagram showing changes in lamp efficiency and lamp voltage when the lamp lighting angle of a secondary metal halide lamp having the configuration shown in FIG. 1 is changed from a vertical lighting state to a horizontal lighting state. . The lamp rating is lamp voltage 250V, lamp current 4.5A, lamp power 1000W, arc tube inner diameter 22φ,
Mercury is inside the arc tube with a distance of 11 cm between electrodes and an internal volume of 46 c.c.
160mg, scandium iodide 15mg, sodium iodide
Contains 58mg. When this lamp is lit vertically, it exhibits a high efficiency of 100 lm/h, but when the lighting angle of the lamp is changed horizontally, the lamp efficiency and lamp voltage decrease, and at a lighting angle of 45°, the lamp efficiency and lamp voltage are This decreases to about 82% and 90%, respectively, compared to the lamp voltage and lamp efficiency in the vertical lighting state. At this time, the decrease in luminescence of sodium was most remarkable. Therefore, in order to suppress the changes in lamp characteristics due to changes in the lighting angle mentioned above, the conditions for the inner diameter of the arc tube, the distance between electrodes, and the amount of mercury sealed were adjusted to a rated lamp voltage of 25V.
We made a prototype lamp with the following changes, and measured the vertical efficiency (η0°) and lamp voltage (V0°) at a rated power of 1000W, as well as the lamp efficiency (η45°) and lamp voltage (V45°) at a lighting angle of 45°. ) was measured. The results are shown in the table below.

【table】

[Table] Test number 1 in the table is the conventional example described above. As is clear from the table, Na/
The values of η45°/η0° and V45°/V0° tend to increase as the atomic ratio of Hg increases and as the atomic ratio of Sc/Hg decreases. This is thought to be due to the fact that by increasing the atomic ratio of Na/Hg, sufficient Na vapor is brought into the arc and contributes to light emission even when the lamp is lit vertically and when the lighting angle is changed.
According to a detailed study, the amount of mercury per 1 c.c. of arc tube internal volume is 2.8 mg or more, and the atomic ratio of Sc/Hg is
The Na/Hg atomic ratio should be in the range 0.005 to 0.11 and the Na/Hg atomic ratio should be in the range 1.2 to 2.0. That is, in a metal halide lamp with a lamp rated power exceeding 400 W, the distance between the electrodes is long, so when the Hg amount exceeds 2.8 mg/cc, the effect of increasing the Na vapor density in the arc due to activation of convection becomes noticeable. Since Na has a low ionization voltage, the temperature gradient in the radial direction of the arc becomes gentle, allowing for sufficient diffusion and a stable arc. Therefore, even when the lighting is tilted, there is little bending of the arc, and it is possible to suppress the decrease in Na vapor density as much as possible, and η45° /
The improvement effect of η0° and V45°/V0° becomes greater. Na／
When Hg is less than 1.2, even if the above convection is activated, the increase in Na vapor density in the arc is insufficient.
If the value exceeds 20, the increase in Na vapor density due to activation of convection will be too large, and the arc temperature will drop significantly.
The luminescence of Sc decreases, the luminescent color of the lamp becomes reddish, and the color rendering properties deteriorate. Also, Sc/Hg is 0.005
If Suemitsu is used, sufficient Sc light emission cannot be obtained, resulting in a decrease in both efficiency and color rendering. When the above value exceeds 0.11, the Sc vapor density in the arc increases and the arc constricts, canceling out the effect of the increase in Na vapor density mentioned above, and as the lighting angle changes, the emission of Sc and Na also decreases significantly. η45°/η0° and
The improvement effect of V45°/V0° becomes smaller. Furthermore, when the amount of Hg is less than 2.8 mg/cc, there is no improvement effect even if the atomic ratios of Na/Hg and Sc/Hg are controlled. In this way, under conditions where the amount of mercury enclosed per 1 c.c. of arc tube internal volume is 2.8 mg or more, the smaller the Sc/Hg and the larger the Na/Hg, the greater the lamp efficiency when changing the lighting angle. The reason why the characteristic change in lamp voltage is small is thought to be as follows. That is,
In general, in metal halide lamps containing scandium halides and sodium halides, the vapor pressure of sodium halides is lower than that of scandium halides, and the vapor pressure of sodium halides tends to be biased towards the lower part when lit, so the lamp When the lighting direction is changed from vertical to horizontal, the coldest part of the arc tube changes from the sealed area around the electrode to the lower part of the center of the arc tube, and the area of the coldest part becomes larger than when the lighting is vertical. As the temperature increases, the coldest spot temperature substantially decreases, and the area where sodium halide is unevenly distributed substantially increases, so that the attenuation of light emission from sodium halide becomes most significant. The excitation voltage of sodium is sufficiently lower than that of mercury and scandium, so by tilting the lighting as described above, the vapor pressure of sodium halide decreases and the uneven distribution effect increases, narrowing the arc and separating the arc center and the arc periphery (tube). The temperature difference between the arc and the arc near the wall becomes large, causing the arc to bend upward in an arched shape and float, thereby further accelerating the attenuation of the luminescence of the sodium halide described above. This invention was made in view of these drawbacks, and focused particularly on the relationship between the above-mentioned uneven distribution phenomenon of sodium halide and mercury density.
By reducing Sc/Hg and increasing Na/Hg under conditions of mg/cc or less, mercury activates convection, which alleviates the uneven distribution of sodium halide and causes it to spread above and below the arc in the arc tube. Sodium halide is uniformly distributed and
Because the inclusion ratio of Na to mercury is high,
By minimizing the drop in vapor pressure of sodium halide due to tilted lighting, and further reducing the inclusion ratio of Sc to mercury, we are able to reduce arc squeezing.
This makes it possible to suppress the influence of Sc as much as possible, thereby minimizing changes in characteristics when lighting is tilted. From this point of view, the lower limit of the amount of encapsulated mercury,
Regulates the upper limit of Sc/Hg and the lower limit of Na/Hg,
Further, for Sc/Hg, a lower limit value is regulated to obtain the required luminescence of Sc, and for Na/Hg, an upper limit value is regulated to prevent the luminescence of Na from becoming excessively preferential. FIG. 3 shows changes in lamp efficiency and lamp voltage due to changes in lighting direction of a metal halide lamp equipped with an example of the present invention (test number 13 in the table). As is clear from the figure, the improvement effect achieved by the present invention is remarkable. In the above embodiments, Sc and Na were sealed in the form of halides in the arc tube, but in the case of Sc, they may be sealed in the form of Sc metal and mercury halide to generate scandium halide within the tube. As mentioned above, in the metal halide using scandium halide and sodium halide, the amount of mercury per 1 c.c. of the internal volume of the arc tube is set to 2.8 mg or more, and the atomic ratio of Na/Hg is made larger than before,
Furthermore, by appropriately selecting the atomic ratio of Sc/Hg, even if the lighting angle changes, changes in the lamp's luminous efficiency and lamp voltage can be suppressed to a relatively small value, resulting in a metal halide lamp that is superior to conventional lamps. Further, even if a small amount of at least one halide of sodium, thallium, cesium, indium, lithium, or a rare earth metal of the lanthanide series is added to the arc tube, the above-described effects of the present invention can be obtained.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a metal halide lamp, Figure 2
FIG. 3 is a diagram showing a characteristic change depending on the lighting direction of a conventional metal halide lamp, and FIG. 3 is a diagram showing a characteristic change depending on the lighting direction of a metal halide lamp according to a preferred embodiment of the present invention. In the figure, numeral 1 is an arc tube, 2a and 2b are electrodes, and 4
a and 4b are lead-in wires, 6 is a holding plate, 8 is a current supply line, 9 and 10 are support frames, 11 and 12 are stem leads, 13 is a cap, and 14 is an outer tube.

Claims (1)

[Claims] 1 Lamp in which scandium halide and sodium halide are sealed together with rare gas and mercury in the arc tube.In a metal halide lamp whose rated power exceeds 400W and is lit at an angle, the amount of mercury filled per 1 c.c. of the inner volume of the arc tube is 2.8. mg or more, and the atomic ratio of scandium atoms to the mercury in the scandium halide is 0.005.
0.11 to 0.11, and the atomic ratio of sodium atoms to the mercury in the sodium halide is 1.2 to 2.0.