JPH0877967A - Mercury discharge lamp - Google Patents

Abstract

PURPOSE: To provide a mercury discharge lamp, in which a luminous flux maintaining rate is high and no fusion of a negative electrode tip part occurs, by using a sintered body for the negative electrode in the mercury discharge lamp. CONSTITUTION: A short arc type mercury discharge lamp consists of a bulb 1, a negative electrode 20 and a positive electrode 3 sealed in the bulb 1, and mercury and rare gas sealed in the bulb 1, and in the negative electrode 20, a sintered body composed of high melting point metal powder and emitter powder is arranged in a cylinder part made of high melting point metal provided with a high spreading properly. The tip of the sintered body is formed into a cone. Mercury is sealed in at a rate of 10 to 80mg per 1cc of volume in the bulb, while 2 atm (25 deg.C basis) or more of rare gas is sealed, and the negative electrode 20 is positioned in the lower part so as to be turned on for use.

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 long life and a high luminous flux maintenance rate by improving a cathode and an enclosed gas. It is a thing. This mercury discharge lamp is used as, for example, 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 Mercury discharge lamps have hitherto been widely used as light sources for fiberscopes and light sources for exposure used in the production process of semiconductor devices. As a cathode of this mercury discharge lamp, a thoriated dungsten material containing 2% by weight of thorium oxide is usually used.

The structure of a conventional mercury discharge lamp is shown in FIG. 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 cathode 2 has a conical tip end portion for stable discharge of the arc, and is 2% by weight.
Made of a thoriated dungsten material containing thorium oxide.

In a discharge lamp containing mercury, the arc is lifted by the influence of convection. Therefore, when the mercury discharge lamp is lit horizontally, the lifted arc comes into contact with the bulb tube wall, causing the bulb to be abnormally heated and causing devitrification or rupture, so that the bulb is lit vertically. In order to completely evaporate mercury, the normal usage is to place the high temperature 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, in the conventional mercury discharge lamp, since the cathode is made of a thoriated dungsten material, there is a problem that the cathode tip portion is melted when the lamp is lit for a long time. there were. Then, the molten cathode material evaporates and adheres to the inner surface of the bulb, shields the optical path, attenuates the light flux, and the specified light amount cannot be obtained, resulting in a lifetime.

Further, since the cathode tip portion has the maximum brightness, the focus of the optical system is focused on this tip. However, the tip of the cathode is melted by lighting for a long time, and the position of this maximum brightness is moved, so that the position of the mercury discharge lamp needs to be realigned as the lighting time elapses. Also,
In the conventional optical device, a mechanism for adjusting the position is additionally required, which causes a problem that the device becomes complicated and expensive.

The present invention has been made to solve the above problems, and an object thereof is to use a sintered body cathode as a cathode of a mercury discharge lamp and to obtain a high luminous flux maintenance rate and A mercury discharge lamp that does not melt is provided.

[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 enclosed in the bulb, and a mercury enclosed in the bulb. In a short arc type mercury discharge lamp made of a rare gas, the cathode comprises a sintered body made of a refractory metal powder and an emitter powder arranged in a tubular portion of a refractory metal having a high spreadability, and the tip of the sintered body. Is formed into a conical shape, and the mercury content is 10 per 1 cc of bulb internal volume.
Enclosed from 80 mg to 80 mg, the rare gas is 2 atm (25 ° C
It is characterized by being enclosed more than the standard).

The tubular portion made of a refractory metal having high ductility is
It refers to the cathode body, and the refractory metal is molybdenum, tungsten, tantalum, niobium, or the like.

The sintered body composed of the refractory metal powder of the cathode and the emitter powder is a mixture of the emitter powder having good electron emission and the refractory metal powder of tungsten, nickel, molybdenum or the like at a predetermined ratio. The material is press-molded into a predetermined shape and then sintered. More specifically, this emitter powder is composed of alkaline earth metal (S
r, Ba, Ca) or a compound thereof, thorium oxide,
Or alkaline earth metal oxides and other metals (Ar, Z
r, Be, Th) A composite oxide with an oxide.

The rare gas is xenon, krypton,
It is neon and argon.

The mercury discharge lamp according to claim 2 is
In the lamp house, the anode is positioned above and the cathode is positioned below to be used for lighting.

[0013]

In the mercury discharge lamp according to claim 1, mercury has a bulb internal volume of 1 cc due to the relationship between the ultraviolet intensity (to maintain 60% or more of the initial value) and the temperature of the cathode tip (to 1800 ° C. or less). Enclose 10 to 80 mg per package. The noble gas is 2 atm (25 atm to accelerate evaporation of mercury.
Enclosed above (° C standard). And the cathode tip is
Since it is made of a sintered body composed of a high melting point metal powder and an emitter powder, there is no melting at the tip. That is, the luminous flux maintenance factor is high.

When a sintered body using an alkaline earth metal and a high melting point metal powder is used for the cathode, the work function of the sintered body cathode is about 1.5 to 1.8 eV, which is a triated of the conventional cathode. It is low compared with about 2.6 eV of Dangsten. As a result, the operating temperature of the cathode is lowered, the melting of the cathode tip can be prevented, and the movement of the bright spot due to the intended lighting time can be prevented.

In the mercury discharge lamp according to claim 2,
In the lamp house, since the cathode is positioned below and used for lighting, it is possible to prevent the temperature of the cathode from rising more than necessary. That is, it is possible to prevent melting of the sintered body at the tip of the cathode.
Further, even if the arc is lifted due to the effect of convection, the arc does not come into contact with the bulb. In other words, the problem of devitrification or rupture due to abnormal heating of the valve locally does not occur.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. The cathode material is evaporated in the mercury discharge lamp because the cathode temperature is higher than that in the xenon gas discharge lamp.
Therefore, the inventors examined a method for lowering the temperature of the cathode. First, in a proven xenon gas discharge lamp using a sintered body cathode, the temperature of the sintered body was 1200 to 1800 ° C near the tip, and various experiments were conducted with this value as the target.

[Experiment 1] Barium oxide was used as the emitter of the sintered body, and tungsten was used as the refractory metal powder. The amount of enclosed mercury is 100m per 1cc of internal volume of the bulb.
g and xenon gas were sealed at 0.3 atm (25 ° C. standard). In order to completely evaporate the mercury, as in the case of the conventional mercury discharge lamp, as shown in FIG. 3, vertical lighting was performed so that the anode was on the lower side and the cathode was on the upper side. FIG. 4 is data showing a change in ultraviolet illuminance attenuation with the passage of lighting time. As shown in FIG. 4, the evaporation from the cathode was severe, and the light flux was about 50% of the initial value due to the blackening on the inner surface of the bulb in about 100 hours, which was unusable. The mercury discharge lamp used in this experiment had an electric rating of 40 V, a current of 6.25 A, a power consumption of 250 W, and a sintered body temperature of 2000 to 2300 ° C. Therefore, the experiment was conducted by changing the volume and the tip angle of the sintered body, but it was not effective.

[Experiment 2] As shown in FIG. 1, when the cathode containing the same sintered body as in Experiment 1 was placed in the bulb so as to be on the lower side of the lower temperature and turned on, mercury was not completely evaporated and the rated value was obtained. Was 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 envelope. Usually, since the anode having a high temperature is located on the lower side, mercury evaporates, the internal pressure rises, the voltage rises, and the specified power consumption is reached. However, when 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 is not reached, so the temperature of the discharge lamp does not rise and mercury does not evaporate. It becomes a vicious circle. Therefore, when the power consumption immediately after lighting is forcibly increased, mercury evaporates, but due to overcurrent, the conductive foil melts and the tips of the cathode and anode melt. Alternatively, the lamp was forcibly heated from the outside to evaporate the mercury and the lamp was lit at a specified power consumption, but no effect of extending the life was seen.

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

Therefore, an experiment was conducted to find the optimum amount of mercury. The result is shown in FIG. FIG. 5 shows the valve internal volume 1c.
It is a dader showing the relationship between the amount of enclosed mercury per c, the cathode temperature, and the relative illuminance. As shown in FIG. 5, it was found that when the amount of enclosed mercury exceeds 80 mg per bulb inner volume, the temperature of the cathode becomes 1800 ° C. or higher and cannot be used.
Further, when it was less than 10 mg, the intensity of ultraviolet rays became 60% or less, which was not practical.

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

FIG. 7 is data showing the state of attenuation of ultraviolet illuminance with lighting time. The mercury discharge lamp of the present invention used in this experiment is one in which 28 mg of mercury per 1 cc of the internal volume of the bulb and 6 atm of xenon gas are filled using a sintered cathode, and the electric rating of the lamp is 40 V, current is 6. 25A and power consumption 250W. The conventional mercury discharge lamp used in this experiment is one in which 50 mg of mercury per 1 cc of internal volume of the bulb and 0.3 atm of xenon gas are enclosed. In the conventional mercury discharge lamp, thoriated tungsten is used 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, in the conventional mercury discharge lamp, the intensity of ultraviolet rays is 7 at the initial level.
Although attenuated to 0%, the intensity of ultraviolet rays of the mercury discharge lamp of the present invention was maintained at 90% of the initial value. Furthermore, as a result of measuring the cathode, the temperature did not exceed 1700 ° C. Further, in the conventional mercury discharge lamp, the illuminance is rapidly attenuated in the first 100 hours of lighting, but in the mercury discharge lamp of the present invention, such a phenomenon did not occur. Therefore,
Even after the lighting time of 1000 hours, the mercury discharge lamp of the present invention has no movement of the cathode bright spot due to melting of the cathode tip portion, no adhesion of the cathode material to the inner surface of the bulb, and the intensity of ultraviolet rays. The initial value of 90% 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 the noble gas, but similar results were obtained with noble gases such as krypton, neon, and argon.

[0024]

As described above, in the mercury discharge lamp having the structure according to the first aspect, the ultraviolet intensity (to maintain 60% or more of the initial value) and the temperature of the cathode tip (to 1800 ° C. or less) Therefore, 10 to 80 mg of mercury is enclosed per 1 cc of the internal volume of the bulb. The rare gas is filled at 2 atm (25 ° C. standard) or more in order to promote evaporation of mercury. Since the cathode tip portion is made of a sintered body composed of a high melting point metal powder and an emitter powder, the tip portion does not melt. That is, the luminous flux maintenance factor is high.

According to another aspect of the mercury discharge lamp of the present invention,
In the lamp house, since the cathode is positioned below and used for lighting, it is possible to prevent the temperature of the cathode from rising more than necessary. That is, it is possible to prevent melting of the sintered body at the tip of the cathode.
Further, even if the arc is lifted due to the effect of convection, the arc does not come into contact with the bulb. In other words, the problem of devitrification or rupture due to abnormal heating of the valve locally does not occur.

[Brief description of drawings]

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

FIG. 2 is a sectional view for explaining a sintered body cathode.

FIG. 3 is an explanatory diagram 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 dader showing the relationship between the amount of enclosed mercury per 1 cc of bulb volume, the cathode temperature, and the temperature of relative illuminance.

FIG. 6 is a dader showing the relationship between the enclosed xenon gas pressure (25 ° C. standard) and power consumption.

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

[Explanation of symbols]

 1 Valve 2 Cathode 20 Cathode 21 Cathode Main Body 22 Sintered Body 3 Anode 4 Conductive Foil 5 Base 6 Luminous Space

Claims (2)

[Claims] 1. A short arc type mercury discharge lamp comprising a bulb, a cathode and an anode enclosed in the bulb, and mercury and a rare gas enclosed in the bulb, wherein the cathode is a refractory metal powder and an emitter. A sintered body composed of a powder is placed in a cylindrical portion of a high-melting-point metal having a high spreadability, and the tip of the sintered body is formed in a conical shape. 80 mg
A mercury discharge lamp in which the rare gas is filled in at least 2 atm (25 ° C. standard). 2. The mercury discharge lamp according to claim 1, wherein the mercury discharge lamp is used in a lamp house with the anode positioned above and the cathode positioned below.