JPH04289654A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To prolong a lamp life by restraining the reaction between metal halide and a luminous tube material in a metal halide lamp, in which the metal halide and a rise-aiding rare gas composed of xenon or krypton having 2 atm. or more in a luminous tube. CONSTITUTION:In a metal halide lamp in which rare earth metal bromide and rare earth metal iodide are used as metal halide, the relation of 0.5<=A/B<=5 exists, where A: the mol number of bromine (Br), and B: the mol number of iodine (I). The rare earth metal bromide has more binding energy, enabling restraining the reaction between a rear earth metal and an luminous tube material.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to metal halide lamps used for indoor lighting and the like.

0002

[Prior Art] Metal halide lamps have been widely used as light sources for outdoor lighting because they have excellent luminous efficiency, long life, and excellent color rendering properties, but recently they have been used for indoor lighting such as stores. Applications to automobile headlamps are being studied.

[0003] Metal halide lamps used in such applications are compact because they can be accommodated in limited-sized lamps, and the internal volume of the arc tube is required to be approximately 1 cc or less.

By the way, metal halide lamps generally take time to evaporate the luminescent metal sealed in the arc tube, that is, the metal halide, and even when the power is turned on and started, it takes a predetermined rise time to reach the total luminous flux in a stable lighting state. The disadvantage is that it takes time. Such characteristics are extremely problematic when used for indoor lighting or vehicle lighting.

Recently, an improvement measure has been proposed in which a rare gas such as xenon Xe or krypton Kr is sealed in the arc tube at a high pressure of 2 atmospheres or more. In the case of a lamp filled with such a high-pressure rare gas, when a large current is passed during startup, the rare gas instantly discharges and starts emitting light, making it possible to obtain a light amount close to the total luminous flux during normal operation. During the startup period, the metal halide is heated and evaporated by the discharge of these rare gases, and the metal halide eventually emits light, which has the advantage of shortening the start-up time. Incidentally, this type of small metal halide lamp is often housed in a lamp and lit in a horizontal position.

However, in the case of horizontal lighting, the arc generated between the electrodes may curve upward. This is due to gas convection within the arc tube, and in the case of lamps filled with high-pressure rare gas for startup support as described above, convection is likely to occur due to the large amount of rare gas, and the distance between the electrodes is short. In the case of short-arc lamps, that is, small metal halide lamps, the shape of the discharge space is often spherical or ellipsoidal, and the distance from the lamp center axis passing between the electrodes to the tube wall is smaller than the distance between the electrodes. It is relatively large and therefore convection of rare gas is likely to occur.

The arc-shaped arc generated by such convection approaches the upper tube wall of the arc tube, overheating and deforming the tube wall, and has the disadvantage that metal halides and quartz react with each other, resulting in a shortened lifespan. There is. In particular, small metal halide lamps are given high power to increase light output and are used with high tube wall loads, so the temperature of the arc tube increases significantly.
The disadvantage is that thermal deterioration progresses rapidly. Furthermore, when the arc bends, there is also a problem in that the emitted light color becomes uneven.

[0008]

That is, in metal halide lamps, various selections and combinations of materials are employed as the metal halide sealed in the arc tube. Iodine (I) and bromine (Br) are common halogen substances, and metals used in combination with these halogen substances include sodium (Na).
Alkali metals represented by
) and dysprosium (Dy) are known.

In this case, dysprosium bromide (DyBr3) and dysprosium iodide (Dy) have a high color temperature and excellent color rendering properties.
It is sometimes sealed in the arc tube together with thallium bromide (TlBr) and thallium iodide (TlI) in the form of Dy-Tl (hereinafter referred to as Dy-Tl system).

[0010] Also, sodium (Na) and scandium (
Halides used in combination with Sc) are highly efficient and have rich color rendering properties as their spectral distribution covers the entire visible light spectrum, so sodium bromide (NaBr),
Used in a mixed form of scandium bromide (ScBr3), sodium iodide (NaI) and scandium iodide (ScI3) (hereinafter referred to as Sc-Na system)
.

In the case of the Dy-Tl metal halide lamp described above, when the arc bends as described above, Dy dissociated in the arc reacts with the quartz of the arc tube material, degrading the quartz and destroying the Dy. There is a problem in that the total amount of filler is reduced and the lamp life is shortened.

On the other hand, in the case of an Sc-Na metal halide lamp, if the arc bends as described above, the arc
On the curved side of the arc, the yellowish luminescence of Na becomes stronger, color separation occurs throughout the arc tube, and color unevenness becomes noticeable.

[0013] Such color separation is thought to be due to the weight of Na and Sc; Na has a smaller atomic weight than Sc and easily moves upwards by convection, and in the upper half of the discharge space, N
It is considered that the density of a becomes higher.

[0014] Furthermore, there is a difference in excitation energy between Sc and Na; Na has a low excitation energy, so it emits light well in a medium temperature range, whereas Sc has a high excitation energy, so it emits light in a high temperature range. It is thought that when the arc curvature occurs, a large amount of Na, which has a high density in the upper half, is excited and emits light.

The present invention was made based on the above circumstances, and its first object is to provide a metal halide lamp that can suppress the reaction between the metal halide and the arc tube material and thereby extend the lamp life. That is. A second object of the present invention is to provide a metal halide lamp that can prevent unevenness in emitted light color due to color separation.

[0016]

[Means for Solving the Problems] The first aspect of the present invention is to contain a metal halide, mercury, and xenon or krypton or a mixed gas mainly composed of these at a pressure of 2 atmospheres or more in an arc tube in which a pair of electrodes are sealed. In the metal halide lamp, the number of moles of bromine (Br) is A, and the number of moles of iodine (I) is filled with a rare gas for start-up assistance and containing at least a rare earth metal bromide and a rare earth metal iodide as the metal halide. If B is 0,
．． It is characterized in that 5≦A/B≦5.

[0017] The second aspect of the present invention is a rise assisting gas containing a metal halide, mercury, and xenon or krypton or a mixed gas mainly composed of these at a pressure of 2 atmospheres or more, in the arc tube in which a pair of electrodes are sealed. In a metal halide lamp containing at least bromides and iodides of alkali metals and rare earth metals as the metal halides, the amount of the alkali metal halides charged is C, and the amount of the rare earth metal halides When D, 3≦C/D≦12 and bromine (
It is characterized in that 1.0≦E/F≦5, where E is the number of moles of Br) and F is the number of moles of iodine (I).

[0018]

[Operation] In the first case of the present invention, when rare earth metal bromide and rare earth metal iodide are compared, rare earth metal bromide has a larger binding energy, that is, it is difficult to dissociate. Therefore, by enclosing more rare earth metal bromide than rare earth metal iodide, it is possible to suppress the reaction between the rare earth metal and the arc tube material. From this point of view, bromine (Br)
By defining the optimum ratio between the number of moles A of iodine (I) and the number B of moles of iodine (I), it is possible to improve the life characteristics.

In the second case of the present invention, when alkali metal bromide and alkali metal iodide are compared, alkali metal bromide has a larger binding energy, and therefore more alkali metal bromide is encapsulated than alkali metal iodide. This reduces the alkali metals from gathering upward due to their separation, reduces the light emission of alkali metals such as sodium due to arc bending, and prevents color separation. Based on such consideration, color unevenness can be improved by regulating the inclusion ratio of the inclusion material.

[0020]

Embodiments The present invention will be explained below based on the embodiments shown in FIGS. 1 and 2.

The drawing shows a compact Dy-Tl metal halide lamp that is lit horizontally, and 1 is an arc tube. The arc tube 1 is made of quartz, hard glass, or the like, and has a discharge space formed in the shape of a sphere or an ellipsoid. Collapsed sealing parts 2, 2 are formed at both ends of the arc tube 1 along the lamp axis O-O, and metal foil conductors 3, 3 are sealed to these sealing parts 2, 2, respectively. There is. These metal foil conductors 3, 3 are made of a high melting point metal such as molybdenum, and are connected to electrodes 4, 4 and external lead wires 5, 5. Electrode 4 is 1
A book electrode shaft, for example, a tungsten rod with an electrode coil wound around its tip, may also be used.

The arc tube 1 is filled with a metal halide as a luminescent metal, mercury as a buffer metal, and a rare gas such as xenon or krypton to assist in startup.

[0023] Such a configuration is the same in the case of conventional lamps, and in the conventional small metal halide lamp with a rated input of 35 W, the distance between the electrodes l is 5 mm, and the tube inner diameter, that is, the lamp axis passing through the lamp center point, The diameter of the orthogonal inner surfaces of the arc tubes is 5 mm. And inside the arc tube 1,
3 mg of mercury, 6 atm of xenon, 5 mg of dysprosium iodide (DyI3) as a metal halide,
1 mg of thallium iodide (TlI) is enclosed.

When such a conventional lamp is started, when the power switch is turned on and a current of 3 amperes flows, a luminous flux of 1380 lm, which is about 60% of the total luminous flux at steady state, is obtained one second after the switch is turned on. . Two seconds after the switch was turned on, the current was gradually reduced, and a total luminous flux of 2,300 lm was obtained by lighting at 0.45 amperes during steady lighting.

However, curvature of the arc was observed due to convection within the discharge space due to horizontal lighting. When we conducted a life test by lighting 10 such lamps, we found that 500
Within hours, the upper wall of the arc tube 1 turned white and its translucency decreased. As a result, it was found that the luminous flux maintenance rate decreased and the lamp life was shortened. In contrast to such conventional lamps,
The present inventors experimented with different metal halides.

That is, the structure and size of the lamp are the same as those of the conventional lamp, and the arc tube 1 contains 3 mg of mercury, 6 atm of xenon, 5 mg of dysprosium bromide (DyBr3), and 5 mg of dysprosium iodide as metal halides. 2 mg of (DyI3), 1 mg of thallium bromide (TlBr), and 1 mg of thallium iodide (TlI) were sealed.

When starting such a lamp, when the power switch is turned on and a current of 3 amperes flows, the luminous flux 1, which is about 60% of the total luminous flux at steady state, will be reduced 1 second after the switch is turned on.
A total luminous flux of 2,300 lm was obtained by gradually reducing the current from 2 seconds after switching on, and lighting at 0.45 amperes during steady lighting. Such characteristics are equivalent to conventional ones.

In the case of the lamps used in this experiment, a life test was conducted by lighting 10 lamps, and even after 2000 hours,
The occurrence of bulges, cracks, etc. was prevented, the reaction between halogen and quartz was prevented, and no deterioration of the upper part of the arc tube 1 was observed.
It was found that the luminous flux maintenance rate was improved.

The reason for this is that dysprosium bromide (DyBr3) was used as the metal halide, that is, bromine was used as the halogen. In other words, dysprosium bromide (DyBr3) has a larger binding energy than dysprosium iodide (DyI3), and 2
In the color temperature range of 000 to 3000 K, the partial pressure of Dy in a gaseous state is about one order of magnitude smaller when dysprosium bromide (DyBr3) is sealed than when dysprosium iodide (DyI3) is sealed. That is, since dysprosium bromide (DyBr3) is difficult to dissociate, it is possible to suppress the reaction between Dy and quartz as the arc tube material.

In this way, dysprosium iodide (Dy
It has been found that life characteristics can be improved by encapsulating dysprosium bromide (DyBr3) rather than I3), and in this case, the encapsulation ratio of dysprosium bromide (DyBr3) becomes a problem.

[0031] Therefore, the present inventors produced a large number of lamps using rare earth metal bromides and rare earth metal iodides with various combinations of filler compositions, and the number of moles of bromine (Br) in the lamps was set to A. , the number of moles of iodine (I) is B
The relationship between the molar ratio A/B and the luminous flux maintenance factor was investigated. The results are shown in FIG. The figure shows lighting at 200.
This is the luminous flux maintenance rate after 0 hours.

From FIG. 2, when the molar ratio A/B is less than 0.5, the reaction between the free Dy and quartz is significant and the luminous flux maintenance rate is poor, and the initial purpose of mixing dysprosium bromide (DyBr3) is Unachievable. If the range is 0.5≦A/B≦5, there is no or little deterioration of quartz, and the luminous flux maintenance rate is also good.

When the molar ratio A/B exceeds 5, the deterioration of quartz is suppressed, but bromine has strong chemical activity, and this property causes a reaction with the electrode, which causes the electrode material tungsten to deteriorate. It evaporates and adheres to the tube wall of the arc tube, causing blackening and reducing the luminous flux. Therefore, in the case of a small Dy-Tl metal halide lamp, the range of 0.5≦A/B≦5 (1) is preferable. Next, a second embodiment of the present invention will be described. This embodiment shows a small Sc--Na metal halide lamp that is lit horizontally, and the structure may be the same as that shown in FIG.

[0034] A lamp using Sc--Na type halogen as the metal halide has a combination of Na halide and Sc-Na type halogen.
Conventionally, the weight ratio of encapsulated with the halide has been regulated in advance. In other words, Sc has the property of constricting the arc, and a thinner arc is likely to cause fluctuations, so if there are many Sc halides, flickering becomes noticeable. In addition, Na exhibits a strong emission spectrum in the yellow wavelength range, so Na
When the amount of halides increases, there is a problem that the color rendering properties deteriorate.

[0035] For this reason, in the conventional Sc-
When using a Na-based small metal halide lamp as a light source for illumination, if the amount of Na halide is C and the amount of Sc halide is D, the weight ratio of these is C.
/D is 3≦C/D≦12 (2). If the enclosed weight ratio C/D is less than 3, as mentioned above, the arc is constricted, causing arc fluctuation, and C/D is less than 3.
When /D exceeds 12, color rendering properties are extremely degraded. Therefore, when using an Sc-Na-based small metal halide lamp as an illumination light source, the enclosed weight ratio C/D should be as specified in (2) above.
The premise is that it is regulated within the range of the formula.

Under this premise, the conventional Sc-N
In the case of an A-series small metal halide lamp with a rated input of 35 W, the distance between the electrodes l is 5 mm, and the tube inner diameter is 5 mm. Inside the arc tube 1, 3 mg of mercury, 6 atm of xenon, 2 mg of scandium iodide (ScI3),
10 mg of sodium iodide (NaI) is enclosed.

[0037] In such a conventional lamp, when the power was turned on and a current of 3 amperes was applied, a luminous flux of 1680 lm, which is about 60% of the total luminous flux in a steady state, was obtained one second after the switch was turned on. Two seconds after the switch was turned on, the current was gradually reduced, and during steady lighting, a total luminous flux of 2800 lm was obtained by lighting at 0.45 ampere. However, curvature of the arc was observed due to convection within the discharge space due to horizontal lighting.

FIG. 3 shows the measured relationship between the upward distance x (mm) from the center of the lamp (see FIG. 1) and the emission correlated color temperature at a point halfway there. The above conventional lamp has a spectral distribution as shown in characteristic (a), and scandium (Sc) and sodium (Na) emit light in a well-balanced manner up to about 1 mm from the center of the lamp, and the color temperature is 42.
00K white light, but when the distance x reaches 2mm, Na
The yellow and red lights become more intense.

That is, when the spectral distribution at the center of the lamp was measured, as shown in FIG. 5, the emission intensity was distributed in a well-balanced manner over the entire visible light range, and the color rendering property was also extremely high. On the other hand, when the spectral distribution at a point where x is 2 mm was measured, as shown in FIG. 6, the luminescence of sodium was extremely strong, yellow was dominant, and the color rendering property was low.

[0040] Such color separation is thought to be due to the weight of Na and Sc; Na has a smaller atomic weight than Sc and easily moves upward by convection, and in the upper half of the discharge space, N
It is considered that the density of a becomes higher.

[0041] Furthermore, there is a difference in excitation energy between Sc and Na. Na has a low excitation energy and therefore emits light well in a medium temperature range, whereas Sc has a high excitation energy and therefore emits light in a high temperature range. It is thought that when the arc curvature occurs, a large amount of Na, which has a high density in the upper half, is excited and emits light. Therefore, the present inventors experimented with different metal halides.

That is, the structure and size of the lamp are the same as those of the conventional lamp, and the arc tube 1 contains 3 mg of mercury, 6 atm of xenon, and scandium bromide (metal halide).
2 mg of scandium iodide (ScBr3), 2 mg of scandium iodide (ScI
3) 1mg, sodium bromide (NaBr) 10m
g, 5 mg of sodium iodide (NaI) was enclosed. In this case, the molar ratio of bromine (Br) to iodine (I) is 3/1. If you start such a lamp,
The rise characteristic was the same as that of the conventional one, and a total luminous flux of 2800 lm was obtained during steady lighting.

When the emission correlated color temperature of this lamp was measured, as shown in characteristic (b) in FIG. 3, there was no noticeable difference in color depending on the location in the x direction, indicating that color separation was greatly improved. It turned out that there was.

The cause of this is scandium bromide (ScBr3) and sodium bromide (ScBr3) as metal halides.
In other words, this is due to the use of bromine as the halogen. That is, scandium bromide (
ScBr3) and sodium bromide (NaBr) are
Each has a higher binding energy than scandium iodide (ScI3) and sodium iodide (NaI). For example, in the medium temperature range around the color temperature of 3000K, Na
The partial pressure of the gas is about one order of magnitude smaller when sodium bromide (NaBr) is sealed than when sodium iodide (NaI) is sealed. As a result, it is thought that when bromide is encapsulated, it binds strongly to sodium and reduces dissociation, thereby reducing the concentration of sodium above the arc tube and the increase in density.

Thus, sodium iodide (NaI)
It has been found that color unevenness can be improved by enclosing sodium bromide (NaBr) compared to when enclosing sodium bromide (NaBr), and in this case, the inclusion ratio of bromide becomes a problem.

The present inventors prototyped a large number of lamps combining various filling compositions, and determined the molar ratio E, where the number of moles of bromine (Br) was E and the number of moles of iodine (I) was F. We investigated the relationship between /F and color unevenness. For evaluation of color unevenness, the color temperature at the arc center (TA) and x is 2m.
Difference ΔT (=TA − TB) from the color temperature (TB) of point m
)It was adopted.

The results are shown in FIG. From the same figure, when the molar ratio E/F is less than 1.0, the released color separation is significant;
Since the color distribution of the irradiated surface is noticeable, the initial purpose cannot be achieved.

When the molar ratio E/F exceeds 5, color unevenness is improved, but due to the strong chemical activity of bromine, a reaction occurs with the electrode, and the wall of the arc tube becomes black due to evaporation of the electrode material. , the luminous flux decreases. Therefore, in a small Sc-Na metal halide lamp, the range of 1.0≦E/F≦5 (3) is preferable.

As explained above, the enclosed weight ratio C/D between the enclosed amount C of Na halide and the enclosed amount D of Sc halide needs to satisfy the relationship 3≦C/D≦12. When using a small Sc-Na metal halide lamp as an illumination light source as in this example, the above (
2) and (3) must be satisfied at the same time. Note that formulas (1) and (3) both represent bromine (Br).
The reason why the values are different even though the molar ratios of iodine and iodine (I) are different is due to the difference in the composition of the encapsulated substances.

Note that the present invention is not limited to horizontal lighting. In other words, even if the lamp is lit diagonally or vertically, if the lamp is filled with a rare gas at high pressure (2 atmospheres or more) to assist in startup, convection will occur more significantly than in a lamp with low pressure. Applicable. Further, as explained above, the present invention is particularly effective when applied to a small lamp with an internal volume of 1 cc or less, but the same can be said for a lamp with an internal volume of 1 cc or more.

[0051]

As explained above, according to the first aspect of the present invention, in a metal halide lamp filled with rare earth metal bromide and rare earth metal iodide, by filling more rare earth metal bromide than the rare earth metal bromide, the rare earth metal and arc tube Reactions with materials can be suppressed and lamp life can be improved.

According to the second aspect of the present invention, in the case of a metal halide lamp containing an alkali metal bromide and an alkali metal iodide, the alkali metal bromide has a larger binding energy than the alkali metal iodide. By enclosing a large amount of the alkali metal, it is possible to reduce the alkali metal from gathering upward due to its separation, thereby reducing the light emission of the alkali metal and preventing color separation.

[Brief explanation of the drawing]

FIG. 1 is a side view of a small metal halide lamp according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the molar ratio of halogen and the luminous flux maintenance rate during 2000 hours of lighting.

FIG. 3 is a characteristic diagram showing the relationship between distance from the lamp center and correlated color temperature.

FIG. 4 is a characteristic diagram showing the relationship between halogen molar ratio and color temperature difference.

FIG. 5 is a spectral distribution characteristic diagram at the center of the lamp.

FIG. 6 is a spectral distribution characteristic diagram at a position 2 mm away from the center of the lamp.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Arc tube, 2... Crushing sealing part, 3... Metal foil conductor, 4... Electrode.

Claims (4)

[Claims] Claim 1: A metal halide, mercury, and a rare gas for supporting startup consisting of xenon or krypton or a mixed gas mainly composed of these at a pressure of 2 atmospheres or more are sealed in an arc tube in which a pair of electrodes are sealed, In the metal halide lamp containing at least rare earth metal bromide and rare earth metal iodide as the metal halide, when the number of moles of bromine (Br) is A and the number of moles of iodine (I) is B, 0.5≦A. /B≦5…(1) A metal halide lamp. 2. The rare earth metal bromide and the rare earth metal iodide are each dysprosium bromide (DyBr3
) and dysprosium iodide (DyI3). 3. A metal halide, mercury, and a rare gas for supporting startup consisting of xenon or krypton or a mixed gas mainly composed of these at a pressure of 2 atmospheres or more is sealed in an arc tube in which a pair of electrodes are sealed, In the metal halide lamp containing at least bromides and iodides of alkali metals and rare earth metals as the metal halide, the amount of the alkali metal halide enclosed is C,
When the amount of rare earth metal halide enclosed is D, 3≦
If C/D≦12...(2), and the number of moles of bromine (Br) is E and the number of moles of iodine (I) is F, then 1.0≦E/F≦5...(3) A metal halide lamp characterized by: 4. The alkali metal and rare earth metal bromides are sodium bromide (NaBr) and scandium bromide (ScBr3), respectively, and the alkali metal and rare earth metal iodides are sodium iodide (NaI) and iodide, respectively. Scandium oxide (ScI3)
The metal halide lamp according to claim 3, characterized in that: