JPH0684500A - Metallic vapor electric discharge lamp and projector provided therewith - Google Patents

Abstract

PURPOSE:To provide a metallic vapor electric discharge lamp, in which clouding of quartz due to devitrification is prevented while biasing of luminous colors due to cataphoresis and blackening of an arc tube are prevented, and a projector. CONSTITUTION:A lamp, having electrodes 21 sealed at both ends of an arc tube 20 made from quartz glass with a luminescent material, mercury and a rare gas sealed in the arc tube, is turned on by supply of low-frequency power of 0.01 to 10Hz between both of the electrodes. Since the lamp is turned on at frequencies as low as 0.01 to 10Hz, metal ions are attracted to the plus electrode of a longer reversal period and separated from quartz and is thereby prevented from reacting with the quartz. Furthermore, both of the electrodes have their polarities reversed every 0.05 to 50 seconds and therefore alternately function as a cathode, so preventing cataphoresis from taking place and the light-emitting tube from being blackened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor discharge lamp such as a short arc metal halide lamp and a floodlight device using the same.

[0002]

2. Description of the Related Art A metal halide lamp having a short arc length is used as a light source of a color liquid crystal projector as one of typical applications.

The basic principle of a color liquid crystal projector is
As shown in FIG. 3, a light source 1, a reflector 2 that reflects the light emitted from the light source, and a condenser lens 3 that condenses the reflected light are provided.

The light radiated forward from the condenser lens 3 is reflected by a dichroic mirror (wavelength selective reflecting mirror) 4 which reflects blue light, and this blue light is reflected by a mirror 5 and liquid crystal. Illuminate the panel (LCD) 6,
The image on the liquid crystal panel 6 is colored blue and projected on the screen 10 via the other dichroic mirrors 7 and 8 and the projection lens 9.

Of the light projected from the condenser lens 3, the red and green lights pass through the dichroic mirror 4 which reflects the blue light, and the red light is reflected by the other dichroic mirror 11. LCD panel 1
2, the image on the liquid crystal panel 12 is colored red, and the red image is reflected by the dichroic mirror 7 and transmitted through the other dichroic mirrors 8 and the projection lens 9
The image is projected on the screen 10 via.

Further, the green light transmitted through the dichroic mirror 11 for reflecting the red light irradiates the liquid crystal panel 13 to color the image on the liquid crystal panel 13 green, and the green image is reflected by the mirror 14 and the dichroic mirror. It is reflected by 8 and projected on the screen 10 via the projection lens 9.

Therefore, by controlling the images of the three liquid crystal panels 6, 12 and 13, images of three colors are superimposed and projected on the front surface of the screen 10, and a color image is displayed.

As a light source for such a color liquid crystal projector, the light source has a shape close to that of a point light source, and a large amount of light can be obtained for low power consumption. The red, blue, and green components are efficiently radiated, and mirrors and lenses are used. It is necessary to have a lamp that can send abundant three primary colors of light to the necessary area when used in combination with an optical system such as, and can satisfy the condition that heat generation is small. A short arc metal halide lamp is used as the lamp.

This kind of short arc metal halide lamp 1
The structure of is as shown in FIG.
Reference numeral 0 is an arc tube made of quartz glass. This arc tube 20
Has electrodes 21 and 21 sealed at both ends thereof, and the pair of electrodes 21 and 21 are connected to metal foil conductors 23 and 23 sealed to the sealing portions 22 and 22, respectively. One of the metal foil conductors 23 is electrically connected to a base 24 attached to the end portion via an external lead wire (not shown), and the other metal foil conductor 23 is connected to an external lead wire 25. Has been done. The arc tube 20 is filled with mercury as a buffer metal, a metal halide as a light emitting metal, and a rare gas such as argon.

Such a lamp 1 is attached to a reflector 2. The reflector 2 is provided with a support cylinder portion 32 at the inner part of the reflecting surface 31 formed of a rotating curved surface, and the base 24 portion of the lamp 1 is fixed to the support cylinder portion 32 with an adhesive 33 such as insulating cement. is there. A small hole 34 is formed in the reflector 2, and the external lead wire 25 of the lamp 1 penetrates through the small hole 34 and is guided to the back side.

As the metal halide enclosed in the arc tube 20 of the short arc metal halide lamp 1, the luminous efficiency is improved, the color temperature is high, and the correlated color temperature is 6000K.
The halides of rare earth metals such as scandium Sc, dysprosium Dy, neodymium Nd, holmium Ho, and thulium Tm which are suitable for efficiently emitting the three primary colors of light can be used, and sodium Na is further used. Alkali metal halides typified by lithium Li are used together. In addition, scandium Sc
Is not a rare earth metal in terms of classification, but its physical and chemical properties are very similar to those of rare earth metals, and its ability to devitrify quartz is also very similar to that described later, so scandium Sc is also used here. It is treated in the same way as rare earth metals.

In this type of lamp, the arc length, that is, the distance L between the electrodes is 12 mm or less, preferably 4 to 7.
mm, and the power of 150 W to 250 W is supplied during lighting, for example, by a commercial power cycle of 50 to 60 Hertz or a power cycle of 250 to 400 Hertz by an electronic ballast, so that the wall load Z (input power W is emitted. Inner surface area S of the pipe
cm ² Value divided by, Z = W / S) is 40 to 60 W / cm ² It is used under a large load condition such that

However, in the short arc metal halide lamp 1 used with such a high tube wall load, the tube wall temperature at the time of lighting rises to a level close to the limit of the quartz glass, which is the material of the arc tube, and the enclosed metal halide vapor Due to the action, devitrification starts around the tube wall of the highest temperature part from the lighting time of about 100 hours. Then, with the passage of the lighting time, this devitrification eventually spreads over the entire inner surface of the tube, and the thickness of the devitrification increased, and after about 1000 hours of lighting, it was as if the entire inner surface of the lamp had turned into a cloudy refractory, The transparency of the glass is lost, and what was originally a point light source seems to emit light from the entire arc tube due to the diffusion effect of the lamp surface, the function of the point light source is impaired, and the condensing property by the mirror Will be significantly impaired. Further, as the devitrification of the inner surface of the arc tube progresses, the mechanical strength of the quartz glass decreases, and there is a concern that the arc tube may be damaged.

[0014]

The devitrification phenomenon of quartz will be described in more detail physically.

[0015] Analysis of the devitrification phenomenon as described above, this is what kind of crystal of SiO ₂ that cristobalite silica in the surface occurs, the reticulated SiO ₂ and elemental composition ratio of normal quartz glass Although the same, the arrangement of Si and O ₂ is changed from an amorphous to a regularly arranged crystal. This cristobalite crystal has a coefficient of thermal expansion different from that of quartz glass, and occurs when glassy quartz is left in the air at a high temperature of 1200 ° C. or higher for a long time.
If there is dirt on the surface, it is likely to occur even at a lower temperature than that. In particular, the cristobalite crystal is more likely to be generated when exposed to metal vapor, and the temperature and time for devitrification generation are greatly affected by the type of vapor, vapor concentration, and temperature at that time. Therefore, in the short arc metal halide lamp 1 using the vapor of a metal having a large ionization tendency such as alkali metal or rare earth metal, the vapor of the rare earth metal or the like and quartz strongly react to devitrify the arc tube in a short time. .

On the other hand, in the case of a metal halide lamp, D
Although iodide and bromide of rare earth metals such as y and Nd, mercury and rare gas are enclosed, the arc temperature becomes high at about 4000 to 6000 ° C near the center of the arc, and the enclosed metal halide is the arc. At the center, most of the vapor is decomposed into a rare earth metal and a halogen by the above high temperature, and further ionized, so that a so-called ionic state is exhibited. The rare earth metal and halogen thus decomposed combine with each other in the vicinity of the wall of the tube to form a metal halide, which is decomposed in the high temperature part and the so-called halogen cycle is repeated. Further, the vapor of the rare earth metal vapor has a larger ability to devitrify quartz than the vapor of the metal halide, and the ions of the rare earth metal are even larger.

Therefore, in order to prevent the turbidity of the quartz glass due to devitrification, a metal encapsulated as a luminescent substance,
For example, it is considered effective to keep the rare earth metal ions away from the high temperature wall of the arc tube.

Considering the metal ion, one metal ion has the same weight as a metal atom of the same kind,
It has a positive charge according to its number of charges, and due to the force of diffusion and gas convection due to gravity and concentration gradients like metal atoms, it moves from the central part of the arc tube to the wall direction, from the bottom to the top. And move. However, in the case of metal ions, it is strongly affected by the electric field in the arc tube created by both electrodes, and for example, in the case of direct current lighting, it moves toward the cathode.

From this phenomenon, when the short arc metal halide lamp is lit by direct current, the ions of the rare earth metal can be attracted to the cathode side, so that the metal ions can be kept away from the high temperature quartz glass tube wall. Therefore, it is presumed that the reaction between the rare earth metal and quartz can be reduced. That is, it is considered that devitrification can be prevented by keeping the ions of the luminescent metal, which causes devitrification of quartz, from approaching the tube wall of quartz.

However, when an attempt was made to actually perform direct current lighting on this type of short arc metal halide lamp, a good tendency was obtained in terms of preventing white turbidity due to devitrification of quartz, but the light color of the arc was positive. The light is reddish on the negative side, and the light is bluish on the positive side. This phenomenon is because the rare earth metal ions generated in the arc are continuously attracted to the negative electrode, and as a result, strong emission of the rare earth metal is observed near the negative electrode, but the opposite positive electrode. In the vicinity of, strong emission of mercury can be seen due to lack of vapor of rare earth metal. That is, when this type of short arc metal halide lamp is lit by direct current, a so-called catalysis phenomenon occurs.

Further, when DC lighting is performed, electrons collide with the positive electrode, and the tip of the electrode is severely damaged.
After about 500 hours, the tip of the electrode almost disappears and scatters, resulting in a blackening of the valve early.

In order to prevent such a problem, it is preferable to use AC lighting rather than DC lighting. However, conventional AC lighting causes a problem of clouding due to devitrification of quartz as described above. There is.

The present invention has been made in view of such circumstances, and an object thereof is to prevent clouding due to devitrification of quartz, and to prevent deviation of light color and blackening of arc tube due to catalysis phenomenon. An object of the present invention is to provide a metal vapor discharge lamp that can be prevented and a floodlighting device including the same.

[0024]

In the metal vapor discharge lamp of the present invention, electrodes are sealed at both ends of an arc tube, and the arc tube is filled with a luminescent substance, mercury and a rare gas. It is characterized in that a low frequency electric power having a frequency of 0.01 to 10 Hertz is supplied to turn on.

Further, the floodlighting device of the present invention is characterized by using a metal vapor discharge lamp as a light source, which is lit by supplying low frequency power having a frequency of 0.01 to 10 Hz between both electrodes. .

[0026]

According to the present invention, since the lamp is ignited at an extremely low frequency of 0.01 to 10 Hertz, the metal ions are attracted to the positive side electrode having a long inversion period and move away from the quartz. The reaction is prevented. In other words, when the frequency is high, the polarity is reversed before the metal ions are attracted to one of the electrodes and move, and there is no time margin for the metal ions to be attracted to the minus side electrode, and the metal ions are high. The temperature approaches the tube wall at the center of the arc.
Both electrodes can be surely put into a direct current lighting state for 05 to 50 seconds, the metal ions are surely attracted to the minus side electrode, diffusion to the tube wall direction is prevented, and devitrification can be prevented. it can.

Moreover, although both electrodes have an extremely low frequency, the polarity is reversed to alternately act as the cathode, and the metal ions are prevented from concentrating only on one electrode. It is possible to prevent the deviation of the emission color, that is, the occurrence of the catalysis phenomenon, and also to prevent the arc tube from blackening.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

This embodiment is based on FIGS. 1 and 3 described above.
The present invention is applied to the color liquid crystal projector shown in FIG. 2 and the contents already explained in the above drawings are duplicated, and the explanation thereof will be omitted.

The short arc metal halide lamp 1 shown in FIG. 1 has a rated input of 250 W, and the light emitting portion of the arc tube 20 is a substantially elliptical rotator made of quartz glass having a thickness of 1.4 mm. Is about 15 mm and the minor axis is about 10
mm, resulting in an internal surface area of approximately 4.7 cm ² The internal volume is about 0.9 CC. The electrodes 21, 21 sealed at both ends of the arc tube 20 are 2
% -Thickness electrode shaft 211 made of a tungsten-thorium alloy containing 10% by weight thorium oxide
In addition, it has an electrode coil 212 in which a tungsten wire with a wire diameter of 0.5 mm is tightly wound 3 turns.
The distance L between the electrodes 1 and 21 is 6 mm.

Further, the metal foil conductors 23, 23 sealed to the sealing portions 22, 22 are Mo foils, and have a width of 3 mm and a thickness of 30.
It is said to be μm. The outer lead wire 25 is made of a 0.8 mm diameter Mo metal rod.

The arc tube 20 contains 22 mg of mercury, 3.0 mg of a rare earth metal such as iodide and bromide such as Dy, Nd, Tl, In, Sn and Cs, and Ar as a rare gas. Enclosed at 300 Torr.

In such a lamp 1, the frequency of the commercial power source 51 is set to 0.01 to 0.01 through the base 24 and the external lead wire 25.
It is connected to a low frequency oscillating device 50 for converting into a rectangular wave of 10 hertz.

With the power source 51 and the low-frequency oscillator 50, the lamp 1 is supplied with a voltage having a substantially rectangular waveform as shown in FIG.
A rectangular wave voltage of 0 V is applied. By applying such a voltage, the lamp current is 2.7 A, the lamp voltage is 92 V, and the lamp power is 247 W during the lighting of the lamp. The operation of such a short arc metal halide lamp will be described.

In the short arc metal halide lamp under the above conditions, the tube wall load calculated from the surface area of the arc tube and the lamp power is 53 W / cm ^2. In the case of horizontal lighting, a maximum temperature part is generated above the arc tube of the lamp, and the maximum tube wall temperature reaches as high as 1050 ° C.

In the case of a conventional lamp, the lamp is lit by a power supply circuit having a frequency of about 400 Hz, the lamp current is 2.7 A, the lamp voltage is 92 V, and the lamp power is 247 W.
, The total luminous flux is 20000 lm and the correlated color temperature is 69
It showed 00K.

When the lamp is continuously lit for a long time in such a situation, devitrification occurs on the inner wall of the upper part of the arc tube in the high temperature part for about 100 hours, and this devitrification causes clouding with the progress of lighting time. The white turbidity gradually expands in area and darkness, and by the time it reaches 1000 hours, the performance as a point light source will be lost due to the diffused light from the wall surface of the lamp.

On the other hand, in the waveform similar to the rectangular wave shown in FIG. 2, when the frequency is gradually lowered, the values of the lamp voltage, the lamp current and the lamp power do not change, but they are the largest in the life characteristics. It was found that the devitrification-white turbidity, which was a problem, was affected.

That is, even if the lighting frequency is lowered to 50 to 60 Hertz, that is, even if the direction of the electric field in the arc is changed every 0.01 seconds, as in the case of lighting at 400 Hertz, 100 hours is left above the lamp. The devitrification occurred.

However, in a rectangular wave of the same waveform, 10
If the frequency is lowered to Hertz, in other words, if direct current lighting for 0.05 seconds is performed alternately between both electrodes, even after 100 hours have passed, a slight white strip with a width of about 1 mm is located above the arc tube on the mirror side. No white turbidity occurred. And 1
Even after 000 hours, only a slight white turbid devitrification was observed in the upper part of the arc tube, which was 70% of the initial characteristic in the screen illuminance ratio. I was able to maintain the illuminance.

As the lighting frequency of the rectangular wave is further lowered, the effect on the devitrification resistance of the lamp increases, and when the lighting frequency is around 1 hertz, a clear cloudy substance is obtained even after 1000 hours of lighting. Was not observed, and the screen illuminance maintenance rate could be maintained at 83%.

When the frequency was further lowered to 0.1 Hertz, good results were obtained with respect to white turbidity due to devitrification, but the scattering from both electrodes 21 and 21 caused blackening of the inner surface of the arc tube. Has come to be recognized. After 1000 hours, two ring-shaped black oxides were clearly recognized on the inner surface of the arc tube at the tip of the electrode. Therefore, although the performance as a point light source was maintained, the screen illuminance maintenance rate was 68%.
Fell to%.

Further, when it is turned on by direct current, devitrification-white turbidity is good, but the electrode tip corresponding to the positive electrode side is severely damaged, and the electrode tip scatters after 200 to 500 hours, and the screen The illuminance has dropped significantly.

From the above, since the short arc metal halide lamp of the above-mentioned embodiment is lit at an extremely low frequency of 0.01 to 10 Hertz, metal ions are attracted to the negative side electrode having a long inversion period. The diffusion toward the tube wall is reduced, and the reaction with quartz is prevented. That is, both electrodes can be surely brought into a direct current lighting state every 0.05 to 50 seconds, the metal ions can be reliably attracted to the negative electrode, and the metal ions can be kept away from the quartz. In addition, devitrification can be prevented, and the occurrence of clouding can be reduced.

Moreover, since the polarities of both electrodes are inverted every 0.05 to 50 seconds, they act as cathodes alternately, and metal ions are prevented from concentrating only on one electrode. As a result, it is possible to prevent the occurrence of the bias of light emission, that is, the catalysis phenomenon in which the density of the light emitting metal increases near the negative pole, the light emitting material emits light intensively, and the positive pole emits mercury. It is also possible to prevent the anode from being subjected to electron impact and being scattered in a concentrated manner to blacken the arc tube. The present invention is not limited to the short arc metal halide lamp of the above embodiment.

That is, in the short arc metal halide lamp of the above embodiment, the light emitting substance is a halide of a rare earth metal containing scandium, but an alkali metal halide typified by sodium Na or lithium Li may be used together. .

The distance L between the electrodes is not limited to 6 mm,
A short arc type lamp having a length of 15 mm or less has a high tube wall load, and therefore the arc tube temperature during lighting rises, which is suitable for a lamp in such a situation.

In the case of a short arc metal halide lamp, the tube wall load is 40 W / cm ² When it is used over the range, devitrification of the quartz glass is likely to occur, which is effective for such a lamp.

Furthermore, according to the experiments by the present inventors,
If the distance between the electrodes is L (cm) and the lamp voltage (voltage between both electrodes in the stable lighting state) is V volts, between the potential gradient G (= V / L) and devitrification. It was found to be correlated.

That is, when the potential gradient G is reduced with the tube wall load kept constant, it is preferable from the viewpoint of devitrification that lighting is performed in a region where the lighting frequency is small. When the potential gradient G ≦ 30, the lighting frequency is set to 1 hertz or less. It was confirmed that it is preferable to This is presumed to be due to the fact that when the potential gradient G becomes smaller, the concentration of metal ions on the electrode weakens, so that the metal ions are stably captured and concentrated on the electrode by lighting in a region where the lighting frequency is small. It Therefore, when the potential gradient G is 30 or less, it is more effective to set the lighting frequency to 0.1 to 1 hertz.

Further, when the potential gradient G is large, the metal ions are stably captured by the electrode. Therefore, in order to reduce the excessive temperature rise of the electrode and prevent its scattering, it is set to 0.1 Hz or more. It is preferable that the lighting frequency is 0. Therefore, when the potential gradient G is 30 or more, the lighting frequency is 0.
A convenient setting is 1 to 10 hertz.

[0052]

As described above, according to the present invention, by direct-current lighting in which the discharge between both electrodes is reversed every 0.05 to 50 seconds, the ions of the luminescent metal are attracted to the electrode side. , It is possible to prevent white turbidity caused by the reaction of the luminescent metal with quartz, and inevitably if DC lighting is used, the deviation of the luminescent color due to the bias of the enclosed metal toward the cathode side, that is, the cataphoresis phenomenon At the same time, it is possible to prevent blackening of the arc tube.

Therefore, it becomes possible to improve the life characteristics of the conventional high load type discharge lamp which has been considered as a short life lamp because the arc tube becomes high temperature, and the projector is provided with such effective characteristics. be able to.

[Brief description of drawings]

FIG. 1 is a sectional view showing a short arc metal halide lamp together with a reflector.

FIG. 2 is a characteristic diagram of a rectangular wave supplied when the lamp is turned on.

FIG. 3 is an explanatory diagram showing the principle of a color liquid crystal projector.

[Explanation of symbols]

1 ... Short arc metal halide lamp, 2 ... Reflector,
20 ... Arc tube, 21 ... Electrode, 22 ... Sealing part, 23 ... Metal foil conductor, 24 ... Base, 25 ... External lead wire, 50 ... Low frequency oscillator, 51 ... Commercial power supply.

Claims (6)

[Claims] 1. A metal vapor discharge lamp in which electrodes are sealed at both ends of an arc tube made of quartz glass, and a luminous substance, mercury, and a rare gas are sealed in the arc tube. A metal vapor discharge lamp characterized by being supplied with low frequency electric power of 01 to 10 Hertz to be lit. 2. The metal vapor discharge lamp is a metal halide lamp containing at least one of a rare earth metal halide containing scandium and an alkali metal halide as a luminescent material. Metal vapor discharge lamp according to. 3. The metal vapor discharge lamp according to claim 2, wherein the metal halide lamp is a short arc metal halide lamp having a distance between electrodes of 15 mm or less. 4. The metal halide lamp as described above has a tube wall load of 40 W / cm ^2. The metal vapor discharge lamp according to claim 2 or 3, wherein the metal vapor discharge lamp is used in excess of the above. 5. The potential gradient G of the metal halide lamp when the distance between electrodes of the metal halide lamp is L (cm) and the lamp voltage (voltage between both electrodes when in stable lighting state, unit is volt) is V. 3. When (= V / L) is 30 or less, the frequency is set to 0.01 to 1 hertz, and when G is more than 30, the frequency is set to 0.1 to 10 hertz and the lighting is performed. Metal vapor discharge lamp. 6. An electrode is sealed on each end of the arc tube,
A luminous substance, mercury and a rare gas are enclosed in this arc tube,
A floodlighting device comprising a metal vapor discharge lamp which is lit by supplying low-frequency power having a frequency of 0.01 to 10 Hertz between the electrodes.