JPH09274886A - Metal halide lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal halide lamp having excellent converging efficiency, good balance of the whole of visible wave length area and excellent color rendering property and a long life, by setting a distance between electrodes at the specified value or less, and sealing halogenated indium and halogenated dysprosium as the light, emitting metal for direct current lighting. SOLUTION: A negative electrode 21 and a positive electrode 22 are arranged in a light emitting tube 10 opposite to each other, and a distance between the negative electrode 21 and the positive electrode 22 is set at a specified value or less. As the light emitting metal, halogenated indium and halogenated dysprosium are sealed with the buffer gas and the starting auxiliary gas in the light emitting tube 10 in a range at 1-5 micro mole/cm<3> , 0.3-2 micro mole/cm<3> per unit light emitting tube inside volume. A metal halide lamp, of which converging efficiency is improved by shortening the distance between the electrodes and in which a good balance of the whole of the visible wave length area is taken and the excellent color rendering property is obtained by sealing halogenated indium and halogenated dysprosium and which has long life, can be thereby obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal halide lamp used as a light source for a color liquid crystal projector or the like.

[0002]

2. Description of the Related Art In a metal halide lamp, a metal halide is enclosed as a light emitting metal together with mercury and a rare gas for starting in an arc tube having a pair of electrodes. The metal halides are scandium, sodium, and dysprosium. Compounds of metals such as neodymium, tin, thulium, cerium, gadolinium and lutetium and halogens such as iodine or bromine are used.

While these metal halides are melted during lighting and exist as a liquid on the inner wall of the arc tube, some of them are vaporized and vaporized, and metal atoms and halogen atoms are generated at a high temperature part at the center of the arc. The metal element is excited by the arc and emits a spectrum peculiar to the metal. in this way,
Since metal halide lamps evaporate metal halides, sufficient vapor pressure can be obtained at a lower temperature than in the case of metal alone, and luminous efficiency is superior to high pressure mercury lamps. It has excellent color rendering properties and is often used for light sources such as color liquid crystal projectors.

The projector of the color liquid crystal projector is
It consists of a metal halide lamp that is a light source and a reflector that reflects the light emitted from this lamp, and the reflected light of the reflector is condensed by a condenser lens and transmitted through the liquid crystal panel, but in order to improve the condenser efficiency, The metal halide lamp has an electrode distance of 15 mm or less, specifically, 7 to 4
mm short arc type is used.

[0005]

By the way, miniaturization of color liquid crystal projectors is more and more demanded, and not only metal halide lamps and reflectors but also liquid crystal panels are further miniaturized. in use. Therefore, in order to collect the reflected light of the reflector on this small liquid crystal panel, it is necessary to increase the light collection efficiency more than ever, and it is possible to further shorten the distance between the electrodes of the metal halide lamp and bring it closer to the point light source. Requested.

However, when the distance between the electrodes of the metal halide lamp is set to a small value of, for example, 4 mm or less, it is necessary to reduce the inner volume of the arc tube in order to maintain the coldest point temperature of the tube wall of the arc tube at the optimum value. Therefore, the pipe wall load (power consumption / total inner wall area) increases.

When the distance between the electrodes of the metal halide lamp is set to 3 mm, for example, a high lamp voltage cannot be obtained at the time of lighting unless the amount of mercury is increased. Therefore, for example, in a metal halide lamp with a power consumption of 150 W, if an attempt is made to secure a lamp voltage of 55 V, the vapor pressure of mercury will be 30
At about 35 atm, the spectrum of mercury increases, especially the mercury line with a wavelength of 546 nm becomes large. Therefore, there is a problem that the green component is strengthened by this mercury ray, the balance in the entire visible wavelength region is lost, and the color rendering property is deteriorated.

Next, when the lamp is lit with a high tube wall load, the tube wall temperature becomes 900 ° C. or more, for example, and there is a problem that the arc tube becomes cloudy after being lit for several hundred hours. When the arc tube becomes cloudy,
When the light emitting area of the lamp is equivalently increased and the light emitting device is used for a light source such as a color liquid crystal projector, the light collection efficiency is reduced, and the luminous flux maintenance factor is reduced, resulting in exhaustion of the lamp life. The cloudiness of the arc tube recombines with the halogen and repeats the halogen cycle when the metal atom at the high-temperature arc center approaches the tube wall at a temperature lower than the arc center. It is thought that they are attached to the quartz tube wall in the atomic state without being bonded, and change the crystal structure of silica. The possibility of metal atoms adhering to the quartz tube wall in the atomic state without recombining with the halogen increases as the distance between the arc and the tube wall decreases and the tube wall temperature increases. That is, cloudiness is more likely to occur as the tube wall temperature increases.

Further, when lighting with a high tube wall load, the base of the electrode is easily corroded depending on the characteristics of the halogen used, and the corroded compound is scattered by electron impact and adheres to the tube wall. Since the arc tube is blackened, the lamp life may be exhausted by a short lighting time.

Therefore, the present invention provides a metal halide lamp having excellent light-collecting efficiency, good balance in the entire visible wavelength range, excellent color rendering properties, and long lamp life when used for a light source such as a color liquid crystal projector. The purpose is to

[0011]

In order to achieve the above object, the metal halide lamp of the present invention, in an arc tube having a pair of electrodes with an interelectrode distance of 3.5 mm or less, together with mercury and a rare gas for starting. , At least indium halide and dysprosium halide are sealed, and the lamp is turned on with DC power.

That is, since the distance between the electrodes is 3.5 mm or less, it becomes closer to a point light source, and when used in a light source such as a color liquid crystal projector, the light collection efficiency is improved, but the distance between the electrodes should be shortened. The problem is that the green component caused by the increase in the balance of the entire visible wavelength range is lost, and the balance of the entire visible wavelength range is achieved by encapsulating indium halide that strongly emits blue light and dysprosium halide that strongly emits blue and red light. Is excellent and excellent color rendering is obtained. Especially, the distance between electrodes is 2.0 mm
Even better results are obtained in the following cases.

[0013] In particular, indium halide and halide enclosed amount of dysprosium unit arc tube volume per each 1 to 5 micromole / cm ^3, when the 0.3 to 2 micromoles / cm ^3, the entire visible wavelength region The balance is extremely good.

Further, indium halide has a great effect of suppressing clouding of the arc tube, but since the metal halide lamp of the present invention is turned on by direct current power, a catalysis phenomenon occurs in which metal atoms are attracted toward the cathode, but at the cathode. It becomes difficult for the attracted metal atoms to reach the tube wall, and in combination with encapsulation of indium halide, the cloudiness of the arc tube can be significantly reduced, and the lamp life is extended.

Next, since bromine has a higher reactivity than iodine, it easily reacts with the metal atom in the center of the arc and the halogen cycle is surely repeated. On the other hand, since it has a high reactivity, it also reacts with tungsten at the base of the electrode. The electrode may be broken at an early stage, but if the proportion of bromine is less than 60% in terms of the number of atoms with respect to iodine, it is possible to prevent the electrode from being broken at an early stage and prolong the lamp life.

[0016]

EXAMPLE FIG. 1 is a side view of a short arc type metal halide lamp, in which a quartz glass arc tube 10 is
It is almost spherical, for example, the maximum inner diameter is 10.5 mm
φ, the internal volume is 0.7 cm ³ . Molybdenum foils 31 and 32 are embedded in the sealing portions 11 and 12 at both ends of the arc tube 10, and a cathode 21 and an anode 22 respectively connected to the molybdenum foils 31 and 32 are arranged to face each other in the arc tube 10. There is. The distance between the cathode 21 and the anode 22 is 3.
It is 5 mm or less, for example 2.0 mm. The distance between the electrodes is extremely shorter than that of a conventional metal halide lamp and is close to that of a point light source, and when used for a light source such as a color liquid crystal projector, excellent condensing efficiency can be obtained.

In the arc tube 10, 30 is used as a buffer gas.
mg of mercury and 300 Torr of argon gas as a starting auxiliary gas are enclosed. Indium halide (for example, In
Br) and dysprosium halide (eg Dy ₂ Cs
I ₇₎ 1 to 5 each per unit arc tube volume micromoles / cm ^3, is encapsulated in a range of 0.3 to 2 micromolar / cm ^3. Halogen is iodine or a mixture of iodine and bromine, and the proportion of bromine is less than 60% in terms of the number of atoms. The reason why the proportion of bromine is less than 60% in terms of the number of atoms is to suppress the corrosion of the base of the electrode as described above.

The luminescent metal may be encapsulated, if necessary, in addition to the halides of indium and dysprosium. For example, a halogen such as holmium, erbium, gadolinium, thulium, cerium, praseodymium, or neodymium is sealed in order to improve color rendering. Also,
Halides of lutetium and other rare earth metals are enclosed for the purpose of improving color unevenness.

The metal halide lamp is lit with DC power, the tube wall load is set to 60 to 80 W / cm ² , the lamp voltage is 45 to 60 V, and the power consumption is 250 W.
It is. At this time, the color temperature is about 6500 to 7500.
K, the efficiency is about 50 to 60 lm / W, and excellent color rendering properties can be obtained.

Next, description will be made on an example in which the emission characteristics were tested by changing the amount of indium halide and dysprosium halide enclosed. First, the amount of halide of a luminescent metal other than indium halide is kept constant, and the amount of InBr enclosed as indium halide (micromol / c
We made 5 lamps with different m ³ ). And
The luminous flux (lm), the ratio of the blue range energy output B to the green range energy output G (B / G), and the ratio of the red range energy output R to the green range energy output G (R / G) were measured. Table 1 shows the results. In addition, 410-500n
m is the blue range, 500-570 nm is the green range, 580-7
00nm was made into the red region.

[0021]

[Table 1]

As a light source for a projector, a ratio (B /
G) is 1.1 <(B / G) <1.5, and the ratio (R / G) of the red range energy output R and the green range energy output G is 1.0 <(R / G) <1.4. Is desired to obtain good on-screen chromaticity, but InBr
The lamp 1 having an encapsulation amount of 0.72 μmol / cm ³ lacks the blue component, and the lamp 5 having 5.86 μmol / cm ³ lacks the red component to obtain good chromaticity on the screen. I couldn't. On the other hand, InB
Lamp 2 with an enclosed amount of r of 1.45 μmol / cm ³ ; Lamp ³ with 2.93 μmol / cm ³ ; 4.4
Lamp 4 at 1 micromol / cm ³ was able to obtain good on-screen chromaticity. Also, the lamp 5 has a luminous flux,
That is, there is a problem that the lamp efficiency (luminous flux / input power) is low, and the lamp 1 has a problem that an arc flickers easily. Therefore, from the viewpoint of emission chromaticity and lamp efficiency, the amount of indium halide enclosed is preferably 1 to 5 μmol / cm ³ per unit inner volume of the arc tube.

Next, the amount of luminescent metal other than dysprosium halide enclosed was kept constant, and five lamps having different amounts of DyI ₂ (micromol / cm ³ ) enclosed as dysprosium halide were manufactured to produce the same luminous flux (lm). ) And the blue / green range (B / G) and the red / green range (R / G) were measured. The results are shown in Table 2.

[0024]

[Table 2]

As can be seen from Table 2, in the lamp 6 containing 0.26 μmol / cm ³ of DyI ₂ , the chromaticity on the screen cannot be obtained because the red component is insufficient, and the luminous flux, That is, the lamp efficiency is low. Further, in the lamp 10 having 2.36 μmol / cm ³ , the blue component is insufficient and the red component is excessive, and the color temperature is too low. On the other hand, 0.53 μmol / cm ³ lamp 7, 1.05 μmol / cm ³ lamp 8, 1.5
A lamp 9 of 8 μmol / cm ³ has good screen chromaticity and high lamp efficiency. Therefore, the enclosed amount of dysprosium halide is preferably 0.3 to 2 μmol / cm ³ per unit inner volume of the arc tube.

When a part of InBr of the above-mentioned lamps 1 to 5 was replaced with InI and actually tested, the proportion of bromine in the bromine and iodine added as halogens exceeded 60% in atomic number ratio. It was found that the decrease in lamp efficiency was particularly remarkable. It is speculated that this is due to the formation of rare earth bromide with a low vapor pressure.

Next, the results of testing the lamp life of the present invention will be described. The lamp used had a cathode and an anode placed in a quartz glass arc tube with an inner diameter of 10.5 mm with an interelectrode distance of 1.8 mm, and together with an appropriate amount of argon gas and mercury, 0.3 mg of dysprosium iodide ( 0.553
Micromol / cm ³ ), cesium iodide 0.1 mg
(0.385 μmol / cm ³ ) and 0.5 mg (2.56 μmol / cm ³ ) of indium bromide. In this lamp, the proportion of bromine in bromine and iodine added as halogens is 55.5%. Input power to this lamp 2
The lighting mode of lighting at 50 W for 2 hours and 45 minutes and then extinguishing for 15 minutes was repeated to measure the maintenance factor of the luminous flux. The results are shown in FIG. 2. The maintenance factor of the screen luminous flux at 3000 hours was about 70%, and an extremely long lamp life could be obtained. As a comparative example, the luminous flux maintenance factor of a lamp with an arc length of 3 mm and AC lighting is also shown, but the luminous flux maintenance factor becomes 70% after about 500 hours.

[0028]

As described above, in the metal halide lamp of the present invention, the distance between the electrodes is set to 3.5 mm or less, and indium halide and dysprosium halide are enclosed as the light emitting metal, so that it can be used in a color liquid crystal projector or the like. When used as a light source, the metal halide lamp has excellent light-collecting efficiency, good balance in the entire visible wavelength range, excellent color rendering properties, and long lamp life. Further, indium halide 1-5 respectively per unit arc tube volume inclusion of the halogenated dysprosium micromoles / cm ^3, by this to 0.3 to 2 micromoles / cm ^3, to obtain better results You can Furthermore, when a mixture of iodine and bromine is used as the halogen, the proportion of bromine is preferably less than 60% in terms of the number of atoms.

[Brief description of drawings]

FIG. 1 is a side view of a metal halide lamp.

FIG. 2 is a data explanatory diagram of a luminous flux maintenance factor.

[Explanation of symbols]

 10 arc tube 21 cathode 22 anode

Claims (3)

[Claims] 1. An arc tube provided with a pair of electrodes having an inter-electrode distance of 3.5 mm or less contains at least indium halide and dysprosium halide together with mercury and a rare gas for starting, and is lit by direct current power. A metal halide lamp featuring. Wherein said indium halide and amount of halogen of dysprosium unit arc tube volume per each 1 to 5 micromole / cm ^3, wherein, characterized in that 0.3 to 2 micromoles / cm ³ Item 1. A metal halide lamp according to item 1. 3. The halogen is iodine or a mixture of iodine and bromine, and the proportion of bromine in the atomic number ratio is 60.
The metal halide lamp according to claim 1, wherein the content is less than%.