JP3269381B2 - Metal halide lamp - Google Patents

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 for a light source such as a color liquid crystal projector.

[0002]

2. Description of the Related Art In a metal halide lamp, a metal halide is sealed as a light emitting metal together with mercury and a rare gas for starting in an arc tube having a pair of electrodes. Scandium, sodium, dysprosium and the like are used as the metal halide. A compound of a metal such as neodymium, tin, thulium, cerium, gadolinium, lutetium and a halogen such as iodine or bromine is used.

[0003] These metal halides are melted during lighting and exist as a liquid on the inner wall of the arc tube, while a part thereof is vaporized and evaporated, and metal atoms and halogen atoms are formed in a high temperature portion at the center of the arc. And the metal element is excited by the arc and emits a spectrum unique to the metal. in this way,
Since metal halide lamps evaporate metal halides, a sufficient vapor pressure can be obtained at a lower temperature than that of a single metal, and the luminous efficiency is superior to that of a high-pressure mercury lamp. Excellent color rendering properties can be obtained, and it is often used for light sources such as color liquid crystal projectors.

The light projecting device of a color liquid crystal projector is
It is composed of a metal halide lamp, which is a light source, and a reflector that reflects the light emitted from this lamp.Reflected light from the reflector is collected by a condenser lens and transmitted through a liquid crystal panel. The metal halide lamp has a distance between the electrodes of 15 mm or less, specifically, 7 to 4
mm short arc type is used.

[0005]

[Problems to be Solved by the Invention] By the way, miniaturization of color liquid crystal projectors is increasingly required, and not only metal halide lamps and reflectors, but also liquid crystal panels are becoming increasingly smaller. It is used. 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 necessary to further shorten the distance between the electrodes of the metal halide lamp and make it as close to the point light source as possible. 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 temperature of the tube wall of the arc tube at an optimum value. And the tube wall load (power consumption / total inner wall area) increases.

When the distance between the electrodes of a metal halide lamp is set to, for example, 3 mm, a high lamp voltage cannot be obtained during operation unless the amount of mercury is increased. For this reason, for example, in a metal halide lamp with a power consumption of 150 W, when trying to secure a lamp voltage of 55 V, the vapor pressure of mercury becomes 30
The mercury spectrum increases when the pressure reaches about 35 atm, and in particular, the mercury ray having a wavelength of 546 nm increases. Therefore, there is a problem that the green component becomes stronger due to the mercury ray, the balance in the entire visible wavelength range is lost, and the color rendering property is reduced.

Next, when the lamp is lit with a high tube wall load, the tube wall temperature becomes, for example, 900 ° C. or more, and there is a problem that the luminous tube becomes cloudy after several hundred hours of lighting. When the arc tube becomes cloudy,
When the light-emitting area of the lamp is equivalently increased and used for a light source such as a color liquid crystal projector, the light-collecting efficiency is reduced, and the luminous flux maintenance rate is reduced, thereby ending the lamp life. The cloudiness of the arc tube is caused by the recombination of halogen with the halogen atoms when the metal atoms at the hot center of the arc approach the tube wall at a lower temperature than the arc center. It is believed that they attach to the quartz tube wall in an atomic state without bonding and cause a change in the crystal structure of silica. The likelihood of metal atoms adhering to the quartz tube wall in an atomic state without recombination with halogen increases as the distance between the arc and the tube wall becomes shorter and the tube wall temperature becomes higher. That is, cloudiness is more likely to occur as the tube wall temperature increases.

Further, when the lamp is lit with a high tube wall load, depending on the characteristics of the halogen used, the base of the electrode is easily corroded, 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 short-time lighting.

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

[0011]

In order to achieve the above object, a metal halide lamp according to the present invention includes a mercury and a rare gas for starting in a light emitting tube having a pair of electrodes having a distance between electrodes of 3.5 mm or less. At least, halogen is a mixture of iodine and bromine, and indium halide and dysprosium halide in which the ratio of bromine is less than 60% in atomic ratio is sealed, and the lamp is lit by DC power.

That is, since the distance between the electrodes is 3.5 mm or less, it is close to a point light source, and when used for a light source such as a color liquid crystal projector, the light collection efficiency is improved. The problem that the green component generated by the intensification causes the balance of the entire visible wavelength range to be disrupted is that by enclosing indium halide that emits blue light strongly and dysprosium halide that emits blue and red light strongly, the balance of the entire visible wavelength range is filled. And good color rendering properties are obtained. In particular, the distance between the electrodes is 2.0 mm
In the following cases, better results can be obtained.

[0013]

Further, indium halide has a large effect of suppressing the clouding of the arc tube. However, since the metal halide lamp of the present invention is lit by DC power, a cataphoresis phenomenon occurs in which metal atoms are attracted toward the cathode. The attracted metal atoms hardly reach the tube wall, and together with the indium halide sealing, cloudiness of the arc tube can be significantly reduced, and the lamp life is extended.

Next, since bromine is more reactive than iodine, it easily reacts with the metal atom at the center of the arc, and the halogen cycle is reliably repeated. On the other hand, since the reactivity is high, it also reacts with tungsten at the base of the electrode. The electrode may be broken at an early stage, but if the ratio of bromine to iodine is less than 60% by atomic ratio, the electrode can be prevented from being broken early and the lamp life is extended.

[0016]

FIG. 1 is a side view of a short arc type metal halide lamp.
Almost spherical, for example, the maximum inner diameter is 10.5mm
φ, the inner 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 connected to the molybdenum foils 31 and 32 are arranged to face each other in the arc tube 10. I have. 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 a point light source, so that when used for a light source such as a color liquid crystal projector, excellent light-collecting efficiency can be obtained.

In the arc tube 10, 30 is used as a buffer gas.
mg of mercury and argon gas of 300 Torr as a starting auxiliary gas are sealed. In addition, as indispensable luminescent metals for the present invention, indium halide (eg, InBr) and dysprosium halide (eg, Dy ₂
CsI ₇ ) is 1 to 5 micromol / cm ³ and 0.3 to 2 micromol / cm per unit arc tube volume, respectively.
³ is enclosed. Halogen is a mixture of iodine and bromine, and the proportion of bromine is less than 60% in atomic ratio. The ratio of bromine is 60
% Is to suppress corrosion at the base of the electrode as described above.

The luminescent metal is encapsulated as required 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,
Lutetium and other rare earth metal halides are sealed for the purpose of improving color unevenness.

Such a metal halide lamp is lit by 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 6500-7500.
K, the efficiency is about 50-60 lm / W, and excellent color rendering properties can be obtained.

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

[0021]

[Table 1]

As the light source for the projector, the ratio of the blue region energy output B to the green region energy output G (B /
G) is 1.1 <(B / G) <1.5, and the ratio (R / G) of the red energy output R and the green energy output G is 1.0 <(R / G) <1.4. Is desired to obtain good on-screen chromaticity, but InBr
Lamp 1 with 0.72 micromol / cm ³ of encapsulation lacks blue component and lamp 5 with 5.86 micromol / cm ³ has insufficient red component to obtain good on-screen chromaticity. Could not. In contrast, InB
The lamp 2 with an encapsulation amount of 1.45 μmol / cm ³ , the lamp ³ with 2.93 μmol / cm ³ , 4.4
The lamp 4 of 1 μmol / cm ³ was able to obtain good chromaticity on the screen. 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 the arc tends to flicker. Therefore, from the viewpoints of emission chromaticity and lamp efficiency, the amount of indium halide to be charged is preferably 1 to 5 micromol / cm ³ per unit arc tube volume.

Next, the enclosed amount of luminescent metal other than halogenated dysprosium constant charging amount of DyI ₂ halogenated dysprosium (micromoles / cm ³⁾ is also to manufacture the five different lamps luminous flux (lm ) And blue range / green range (B / G) and red range / green range (R / G). Table 2 shows the results.

[0024]

[Table 2]

As can be seen from Table 2, the lamp 6 containing 0.26 μmol / cm ³ of DyI ₂ does not have sufficient chromaticity on the screen due to lack of red component, and has a light flux and That is, the lamp efficiency is low. Further, the lamp 10 of 2.36 μmol / cm ³ has insufficient blue component and excess red component, and the color temperature is too low. On the other hand, a lamp 7 of 0.53 μmol / cm ^3, a lamp 8 of 1.05 μmol / cm ³ , 1.5
The 8 μmol / cm ³ lamp 9 provides good chromaticity on the screen and high lamp efficiency. Therefore, it is preferable that the amount of dysprosium halide to be enclosed is 0.3 to 2 micromol / cm ³ per unit arc tube volume.

When a part of InBr of the lamps 1 to 5 was replaced with InI and actually tested, the ratio of bromine to bromine and iodine added as halogen exceeded 60% in atomic ratio. In particular, it was found that the lamp efficiency was significantly reduced. This is presumed to be due to the formation of rare earth bromide having a low vapor pressure.

Next, the result of the lamp life test of the present invention will be described. In the used lamp, a cathode and an anode were arranged in a quartz glass arc tube having an inner diameter of 10.5 mm with a distance between the electrodes of 1.8 mm, and 0.3 mg of dysprosium iodide was added together with an appropriate amount of argon gas and mercury. 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 ratio of bromine to bromine and iodine added as halogen was 55.5% in terms of the number of atoms. This lamp is connected to input power 2
The lighting mode in which the light was turned on at 50 W for 2 hours and 45 minutes and then turned off for 15 minutes was repeated, and the luminous flux maintenance ratio was measured. The results are shown in FIG. 2. The maintenance rate of the screen luminous flux after 3000 hours was about 70%, and an extremely long lamp life was obtained. As a comparative example, the luminous flux maintenance factor of a lamp having an arc length of 3 mm and operated by alternating current is also shown, but the luminous flux maintenance factor becomes 70% in 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, the halogen is a mixture of iodine and bromine as the luminescent metal, and the proportion of bromine is small. Since indium halide and dysprosium halide, which are less than 60% in atomic number ratio, are sealed and illuminated with DC power, when used in a light source such as a color liquid crystal projector, the light collection efficiency is excellent and the entire visible wavelength range is improved. A metal halide lamp having a good balance, excellent color rendering properties and a long lamp life can be obtained.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 10 arc tube 21 cathode 22 anode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-191846 (JP, A) JP-A-6-310095 (JP, A) JP-A-6-342641 (JP, A) JP-A-6-342641 338284 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 61/20

Claims (1)

(57) [Claims] An arc tube provided with a pair of electrodes having a distance between electrodes of 3.5 mm or less contains at least indium halide and dysprosium halide together with mercury and a starting rare gas, and the halogen contains iodine and bromine. A metal halide lamp, which is a mixture, wherein the proportion of bromine is less than 60% in atomic ratio, and which is operated by DC power.