JPS5937643A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To provide a small lamp having practical light efficiency and minimized going out by forming a luminous tube having an inner volume of 1cc or less with an infrared absorption quartz, and making lamp power 70W or less, tube wall load A 12-26W/cm<2>, and limiting the L of projecting length Lmm. of an electrode to a specified length to the A. CONSTITUTION:An infrared absorption quartz luminous tube is formed by sealing electrodes at its both sides, and enclosing a rare gas for starting, mercury, and at least scandium halide as metal halides. In this tube, the inner volume is made 1cc or less, the lamp power to 70W or less, the tube wall load A to 12- 26W/cm<2>, and the projecting length Lmm. of the electrodes is limited as follows; 1/14A-5/14<=L<=1/28A+11/7.

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] High-efficiency metal halide lamps, in which a metal halide is sealed together with a rare starting gas and mercury in a quartz arc tube with opposing electrodes sealed at both ends, have been widely used. It is widespread.

Furthermore, in recent years, compact lamps with low lamp power have been actively developed for the purpose of using the above-mentioned metalnolide lamps as light sources for indoor lighting in shops, offices, and the like. By the way, the characteristics of metal halide lamps, such as light efficiency and color rendering, depend on the temperature of the coldest part of the arc tube, and the temperature of the cooling part does not depend on the tube wall load, the protrusion length of the electrode into the arc tube, etc. well known. However, 9
In order to raise the temperature of the coldest part of the arc tube, the load on the tube wall is increased,
1! Shortening the pole protrusion length has a negative effect on the life characteristics, and this effect is particularly significant in small metal halide lamps with small arc tube volumes. In other words, the temperature of the electrode bright spot remains the same regardless of the volume of the arc tube.

This is because in a small lamp, the distance between the electrode and the wall of the arc tube becomes shorter, and the temperature of the wall of the arc tube increases significantly. If the tube wall temperature rises significantly, the reaction between the encapsulated metal halide and the quartz tube will be rapidly accelerated and free halogens, such as free iodine, will be released into the tube, resulting in a whisker-like restriking in the lamp voltage waveform. A voltage is generated, and if this value exceeds the power supply voltage, the lamp goes out, an undesirable phenomenon. In order to avoid such a phenomenon, if the protruding length of the electrode is increased or the diameter of the arc tube is increased, there is a problem that practical light efficiency as a light source for indoor lighting cannot be obtained.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a small metal halide lamp that has practical light efficiency as a light source for indoor lighting and does not turn off.

[Summary of the invention]

In the present invention, electrodes are sealed at both ends, and a rare gas for starting is contained inside.
An arc tube with an internal volume of 1 c or less, filled with mercury and at least a scandium halide as a metal halide, is formed of infrared absorbing quartz, the lamp electric cuff is 0 W or less, and the tube wall load A is 12 to 26 W/cm2. , when the electrode protrusion length is Lmm.

This metal halide lamp is characterized in that TTA 14≦1≦28”7.

[Embodiments of the invention]

The details of the present invention will be explained below based on experimental examples. First, in a small lamp with a lamp cuff of 0 W or less and an arc tube internal volume of 1 c or less, the tube wall load A of one arc tube, that is, the lamp power (watts)/inner tube surface area (cm") is 12~
It is necessary to set it to 26W/cm2. If this upper limit is exceeded, the temperature of the tube wall will reach a high temperature of 1000°C or higher, which will cause the quartz to deteriorate, and furthermore, the encapsulated metal halide, especially scandium S
When a rare earth metal halide such as C is used, it reacts with quartz at high temperatures, resulting in a significant decrease in life characteristics. On the other hand, below the lower limit, the light emitted from the arc tube is only mercury emission, and no metal emission from the encapsulated halide is observed, resulting in a significant decrease in both light efficiency and color rendering.

Figure 1 shows a front view of the arc tube for a metal halide lamp with a lamp power of 40 W used in this experiment.

The arc tube is normally housed within an outer tube (not shown). Arc tube (
The electrodes (2+, (2+) are sealed to both ends of the electrode (21) facing each other, and the base end of the electrode (21, (2) is sealed to the sealing part (31).
, (metal foil such as molybdenum (4) hermetically sealed in (37)
1, (41) are connected to the external conductors (5), (5).The interior of the arc tube (1) contains Ar100) as a starting rare gas.

The halogen containing at least scandium Sc, for example, scandium 8 iodide.
cI3o, 5rrllg and sodium iodide NaI
2.51 T1 g and mercury in an amount such that the run:j voltage is about 70 V are each sealed.

Further, one arc tube (1) was formed into a substantially spherical shape, and its materials were used to compare ordinary quartz and infrared absorbing quartz. Infrared absorbing quartz.

For example, it is a mixture of ordinary quartz and iron or iron and aluminum.For example, it is manufactured by mixing quartz powder (8i02) with fine iron oxide (FeO) and melting it and crystallizing it. , heat is accumulated inside due to infrared absorption, and the temperature itself becomes high.

Since the inner surface area of such a 40W spherical arc tube is πR2, the V tank load A, that is, the lamp power W (watts)/tube inner surface area (cm2) is 40W/πR2, and this value is converted to 12 to 26 W/as described above. R to be within the range of cm2
(diameter of the spherical arc tube) was set in a range of approximately 7 to 10 mm.

Next, for a lamp that combines the above-mentioned various requirements, the protrusion length of the electrode (2) into the arc tube should be set to 0.2 to 3.5.
Producing lamps with various changes within the range of mm,
FIG. 2 shows the results of experiments regarding the light efficiency and extinction of each type. In the figure, the vertical axis is the electrode protrusion length Lmm
The horizontal axis represents the pipe wall load A, and lines 1, 11, 28''7 are shown, respectively.

In the area below the control 2X, that is, the area where the electrode protrusion length is small, the luminous efficiency is 60 gm/W or more for those using ordinary quartz as the arc tube material, and 755 m/W or more for those using infrared absorbing quartz. Although it is possible to achieve the desired light efficiency of 60#1/W, which is practical as a target indoor lighting light source, the lamp goes out when it is started, which is not preferable. On the other hand, in the region E above the line Y where the protruding length of the stain pole is large, the light efficiency is 60 W/W, not to mention those using ordinary quartz, and even those using infrared absorbing quartz.
It was found that the target value could not be achieved. On the other hand, in the region F between lines , and there were no disappearances.

Therefore, the region F in which the object of the present invention can be achieved is a range in which the tube wall load A is 12 to 26 W/c, m2, and the relationship between the electrode protrusion length Lmm and the tube wall load.

IA-1st base 1<, t, <-! -A +-LL14
14 -- -- 28 It can be seen that it is within the range that satisfies 7.

Note that although the above example describes the case of 40W, the same effect can be obtained at 70W or less.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to obtain a small metal halide lamp which has a practical light efficiency as a light source for indoor lighting and which does not turn off or go out.

[Brief explanation of the drawing]

FIG. 1 is a front view of an arc tube for a small-sized metalno-ride lamp, and FIG. 2 is a graph showing the relationship between tube wall load and electrode protrusion length in a small-sized metalno-ride lamp according to the present invention. (1)... Arc tube, (2)... Electrode, (3)...
Arc tube sealing part. (4)...Metal foil, (5)...External conductor. Agent: Patent attorney Kensuke Chika (and 1 other person)

Claims (1)

[Claims] Electrodes are sealed at both ends, and a rare gas for starting is contained inside. The internal volume of an infrared absorbing quartz arc tube filled with mercury and at least scandium halide as a metal halide is l c, c or less, lamp electric cuff 0 W or less,
The tube wall load A is 12 to 26 W/cm2. When the above electrode protrusion length is Lmm. 1 5 J 11 - A-1 ≦ L ≦ 7 < A + 14 14 A metal halide lamp characterized by 4.