JP3156904B2 - Mercury discharge 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 mercury discharge lamp in which mercury contributes to light emission, and more particularly to a mercury discharge lamp having a longer luminous flux maintenance ratio and a longer life by improving a cathode and a filling gas. Things. This mercury discharge lamp is used, for example, as a light source for a fiberscope or an exposure light source used in a semiconductor device production process.

[0002]

2. Description of the Related Art A mercury discharge lamp has been widely used as a light source for a fiberscope or an exposure light source used in a semiconductor device production process. As a cathode of this mercury discharge lamp, a thoriated dangsten material containing usually 2% by weight of thorium oxide is used.

FIG. 3 shows the structure of a conventional mercury discharge lamp. 1 is a bulb, 2 is a cathode, 3 is an anode, 4 is a conductive foil for supplying electricity to the cathode 2 and the anode 3, 5 is a base, and 6 is a light emitting space. The tip of the cathode 2 was cut into a conical shape in order to stably discharge the arc.
Made of a thoriated dungsten material containing thorium oxide.

In a discharge lamp containing mercury, an arc is lifted by the influence of convection. Therefore, when the mercury discharge lamp is turned on horizontally, the lifted arc comes into contact with the bulb tube wall, and the bulb is abnormally heated, causing devitrification or rupture. In order to completely evaporate the mercury, the normal usage is to place a hot anode on the lower side and turn it on. Such a technique is described in Japanese Utility Model Publication No. 5-39564 and Japanese Utility Model Publication No. 5-39568.

[0005]

However, since the conventional mercury discharge lamp uses a toughened dangsten material for the cathode, there is a problem that the tip of the cathode is melted when the lamp is operated for a long time. there were. Then, the molten cathode material evaporates and adheres to the inner surface of the bulb, blocks the light path and attenuates the light beam, and the specified amount of light cannot be obtained, and the life is extended.

Since the tip of the cathode has the maximum brightness, the optical system is focused on this tip. However, when the lamp is operated for a long time, the tip of the cathode is melted, and the position of the maximum luminance is moved, and it is necessary to reposition the mercury discharge lamp as the lighting time elapses. Also,
In the conventional optical device, there is a problem that a mechanism for adjusting the position is separately required, and the device is complicated and expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to use a sintered cathode as a cathode of a mercury discharge lamp, to have a high luminous flux maintenance factor, and to provide a cathode tip. It will provide a mercury discharge lamp without melting.

[0008]

In order to solve the above-mentioned problems, a mercury discharge lamp according to claim 1 comprises a bulb, a cathode and an anode sealed in the bulb, and a mercury sealed in the bulb. In a short arc type mercury discharge lamp composed of a rare gas, the cathode is composed of a high melting point metal powder and an alkaline earth.
Place a sintered body consisting of a emitter powder of the kind based on the cylinder portion of the refractory metal-rich spreadable, which leading end of the sintered body is formed in a conical shape, the cathode tip at the time of lighting Department
The mercury is sealed in an amount of 10 mg to 80 mg per 1 cc volume of the bulb so that the temperature of the mercury becomes 1800 ° C. or less.
2 atmospheres the rare gas so as to evaporate it is sealed (25 ° C. basis) or higher, and an anode within the lamp house Hijikata, characterized by lighting by positioning the cathode downward.

[0009] The cylindrical part of the high-melting-point metal rich in extensibility,
It refers to the cathode body, and the high melting point metal is molybdenum, tungsten, tantalum, niobium, or the like.

The sintered body comprising the high melting point metal powder and the emitter powder of the cathode is obtained by mixing an emitter powder having good electron emission and a high melting point metal powder such as tungsten, nickel and molybdenum at a predetermined ratio. After being press-formed into a predetermined shape, it is sintered. More specifically, the emitter powder is composed of an alkaline earth metal (S
r, Ba, Ca) or a compound thereof, or an alkali
Lithium earth metal oxide and other metal (Ar, Zr, Be) oxidation
Is that of a composite oxide of things.

The rare gas includes xenon, krypton,
Neon means argon.

[0012]

[0013]

According to the mercury discharge lamp of the first aspect, mercury is contained in a bulb having a volume of 1 cc from the relationship between the intensity of ultraviolet rays (to maintain 60% or more of the initial value) and the temperature at the cathode tip (below 1800 ° C.). 10 mg to 80 mg per capsule. The noble gas is 2 atmospheres (25
(Based on ° C). And the cathode tip is
Since it is made of a sintered body composed of the high melting point metal powder and the emitter powder, there is no melting at the tip. That is, the luminous flux maintenance ratio is high.

The use of a sintered body made of an alkaline earth metal and a high melting point metal powder as the cathode requires the work function of the sintered body cathode to be about 1.5 to 1.8 eV, which is equivalent to that of the conventional cathode. It is lower than about 2.6 eV of dangsten. As a result, the operating temperature of the cathode is lowered, so that the tip of the cathode can be prevented from melting, and the movement of the luminescent spot due to the intended lighting time can be prevented.

Further, since the mercury discharge lamp of the present invention is used for lighting with the cathode positioned downward in the lamp house, it is possible to prevent the temperature of the cathode from rising more than necessary.
That is, melting of the sintered body at the tip of the cathode can be prevented. Further, even if the arc is lifted by the influence of convection, the arc does not contact the bulb. That is, the problem of devitrification or rupture due to the local abnormal heating of the valve does not occur.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. The reason why the cathode material evaporates in the mercury discharge lamp is that the temperature of the cathode is higher than that of the xenon gas discharge lamp.
Then, the inventors studied a method for lowering the temperature of the cathode. First, in a xenon gas discharge lamp that has been used by using a sintered body cathode, the temperature of the sintered body is 1200 to 1800 ° C. in the vicinity of the tip, and various experiments were conducted with this value as a target.

[Experiment 1] Barium oxide was used as the emitter of the sintered body, and tungsten was used as the high melting point metal powder. The amount of enclosed mercury is 100m per 1cc volume of the bulb.
g, xenon gas was sealed at 0.3 atm (based on 25 ° C.). In order to completely evaporate mercury, vertical lighting was performed with the anode on the lower side and the cathode on the upper side as in the conventional mercury discharge lamp as shown in FIG. FIG. 4 is data showing a change in ultraviolet illuminance attenuation with the elapse of the lighting time. As shown in FIG. 4, the evaporation from the cathode was intense, and the luminous flux was reduced to about 50% of the initial value due to blackening of the inner surface of the bulb in about 100 hours. The mercury discharge lamp used in this experiment had an electrical rating of 40 V, a current of 6.25 A, a power consumption of 250 W, and a temperature of the sintered body of 2000 to 2300 ° C. Thus, experiments were conducted with various changes in the volume and tip angle of the sintered body, but no effect was obtained.

[Experiment 2] As shown in FIG. 1, when the cathode including the same sintered body as that of Experiment 1 was placed in the bulb so as to be on the lower side with a low temperature, the lamp was turned on. Did not output. This is because, in the case of a mercury discharge lamp, the temperature does not rise immediately after lighting, and mercury condenses on the lower side of the low-temperature enclosure. Usually, mercury evaporates because the high temperature anode is on the lower side, the internal pressure rises, and the voltage rises to reach the specified power consumption. However, if the cathode is placed on the lower side, the temperature of the cathode is low, so mercury does not evaporate forever, so the voltage does not rise and the specified power consumption does not reach, so the temperature of the discharge lamp does not rise and mercury does not evaporate A vicious cycle. Therefore, if the power consumption immediately after the lighting is increased, the mercury evaporates, but the overcurrent causes the conductive foil to melt or the tips of the cathode and anode to melt. Alternatively, mercury was evaporated by forcible heating from the outside to turn on the lamp with a specified power consumption, but the effect of extending the life was not observed.

[Experiment 3] FIG. 1 is an explanatory view of a mercury discharge lamp of the present invention. Reference numeral 20 denotes a sintered body cathode;
Is positioned on the lower side, and the anode 3 is positioned on the upper side. The same reference numerals as those in FIG. 3 denote the same parts. Note that xenon gas was used as a rare gas. FIG. 2 is a sectional view for explaining the sintered compact cathode 20. Reference numeral 21 denotes a molybdenum electrode body having a diameter of 3.5 mm. Reference numeral 22 denotes a sintered body obtained by sintering a high melting point metal powder of tungsten and an emitter powder of alkaline earth metal (Sr, Ba, Ca). The mercury discharge lamp has no effect, although it has a track record with a xenon gas discharge lamp lit with the cathode facing down, due to the difference in the enclosed gas. Since the atomic weight of mercury is 200, xenon is 131, and mercury is about 1.5 times as heavy as xenon, the ion impact on the cathode is larger for mercury. for that reason,
The temperature of the cathode was about 600 ° C. higher for the lamp containing 100 mg / cc of mercury than for the lamp containing only xenon.

Therefore, an experiment for obtaining an optimum amount of mercury was performed. The result is shown in FIG. FIG. 5 shows the valve internal volume 1c.
It is a data which shows the relationship between the amount of enclosed mercury per c, the cathode temperature, and relative illuminance. As shown in FIG. 5, it was found that when the amount of enclosed mercury exceeded 80 mg per bulb internal volume, the temperature of the cathode became 1800 ° C. or more, and the cathode could not be used.
On the other hand, when the amount is less than 10 mg, the intensity of ultraviolet rays becomes 60% or less, which is not practical.

FIG. 6 is data showing the relationship between the xenon gas pressure (based on 25 ° C.) and power consumption. As shown in FIG. 6, when the xenon gas was 2 atm or less, power was not supplied after lighting, and mercury did not evaporate. That is, it was found that xenon gas was required to be at least 2 atm.

FIG. 7 is data showing the decay state of the ultraviolet illuminance with the lighting time. The mercury discharge lamp of the present invention used in this experiment was a sintered compact cathode in which 28 mg of mercury was filled per 1 cc of bulb volume and 6 atm of xenon gas was charged. 25 A and power consumption 250 W. The conventional mercury discharge lamp used in this experiment was filled with 50 mg of mercury per 1 cc bulb volume and 0.3 atm of xenon gas. The conventional mercury discharge lamp used thoriated tungsten for the cathode.

As shown in FIG. 7, in the mercury discharge lamp of the present invention, mercury evaporates immediately after lighting, and after 1000 hours of lighting, the intensity of ultraviolet light in the conventional mercury discharge lamp is 7 in the initial stage.
Although attenuated to 0%, the intensity of the ultraviolet light of the mercury discharge lamp of the present invention was maintained at the initial 90%. Furthermore, as a result of measuring the cathode, the temperature did not exceed 1700 ° C. Further, in the conventional mercury discharge lamp, the illuminance sharply decreases in the first 100 hours of operation, but such a phenomenon does not occur in the mercury discharge lamp of the present invention. Therefore,
Even when the lighting time has passed 1000 hours, the mercury discharge lamp of the present invention has no movement of the cathode luminescent spot due to melting of the cathode tip, no attachment of the cathode material to the inner surface of the bulb, and an intensity of ultraviolet rays. 90% of the initial mercury discharge lamp was maintained, and a mercury discharge lamp having a longer life than the conventional mercury discharge lamp could be completed. In each experiment, xenon gas was shown as a rare gas, but similar results were obtained with rare gases such as krypton, neon, and argon.

[0024]

As described above, the mercury discharge lamp according to the first aspect of the present invention has an ultraviolet intensity (to maintain 60% or more of the initial value) and a temperature at the tip of the cathode (below 1800 ° C.). Therefore, 10 to 80 mg of mercury is enclosed per 1 cc of the bulb volume. The rare gas is sealed at 2 atm (at 25 ° C.) or more to promote the evaporation of mercury. Since the tip of the cathode is made of a sintered body composed of the high melting point metal powder and the emitter powder, there is no melting of the tip. That is, the luminous flux maintenance ratio is high.

Further, since the mercury discharge lamp of the present invention is used for lighting with the cathode positioned downward in the lamp house, it is possible to prevent the temperature of the cathode from rising more than necessary.
That is, melting of the sintered body at the tip of the cathode can be prevented. Further, even if the arc is lifted by the influence of convection, the arc does not contact the bulb. That is, the problem of devitrification or rupture due to the local abnormal heating of the valve does not occur.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a mercury discharge lamp of the present invention.

FIG. 2 is an explanatory cross-sectional view of a sintered compact cathode.

FIG. 3 is an explanatory view of a conventional mercury discharge lamp.

FIG. 4 is data showing a change in ultraviolet illuminance attenuation with the passage of lighting time.

FIG. 5 is a data showing the relationship between the amount of enclosed mercury per 1 cc of bulb internal volume, the cathode temperature, and the temperature of relative illuminance.

FIG. 6 is a dasher showing the relationship between the sealed xenon gas pressure (based on 25 ° C.) and power consumption.

FIG. 7 is data showing the state of attenuation of ultraviolet illuminance with lighting time.

[Explanation of symbols]

 Reference Signs List 1 bulb 2 cathode 20 cathode 21 cathode body 22 sintered body 3 anode 4 conductive foil 5 base 6 light emitting space

 ──────────────────────────────────────────────────続 き Continuing on the front page Judge Koichi Itsubo Judge Chieko Goto Judge Hidehiro Sumita (56) References JP-A-62-241253 (JP, A) JP-A-3-8255 (JP, A) Open 4-4-554 (JP, A) Open 2-4-75555 (JP, U)

Claims (1)

(57) [Claims] And 1. A valve, a cathode and an anode that Fu設within the valve, the short arc mercury discharge lamp comprising a mercury and a rare gas enclosed in the bulb, the cathode is a refractory metal powder and alkali place a sintered body consisting of a emitter powder earth system in the cylinder portion of the refractory metal-rich spreadable, which leading end of the sintered body is formed in a conical shape, at the time of lighting the cathode The temperature at the tip falls below 1800 ° C
The aqueous silver as made to 80mg sealed from 10mg per the volume 1cc valves, 2 the rare gas as the mercury evaporates
It is sealed pressure (25 ° C. basis) or higher, and mercury discharge lamp for causing the anode in the lamp house upper, lit by positioning the cathode downward.