JPH09213267A - Discharge lamp - Google Patents

Abstract

(57) An object of the present invention is to provide a discharge lamp which effectively suppresses the blackening phenomenon of a sealed body even after long-term use and has a long service life. A getter in a discharge lamp comprising a glass envelope, an electrode arranged in the envelope and having a temperature of 1000 ° C. or higher in a lighting state, and a getter arranged in the envelope. As the material, a tantalum material having a total weight concentration of iron, nickel and titanium of 50 ppm or less is used. The tantalum material preferably has a total weight concentration of iron, nickel and titanium of 30 ppm or less, and further has a weight concentration of iron of 10 ppm or less and a weight concentration of nickel of 10 ppm.
It is preferable that the weight concentration of titanium is 10 ppm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp such as a short arc discharge lamp, and more particularly to a discharge lamp having a getter.

[0002]

2. Description of the Related Art For example, a photolithography method is used for exposing a minute image in a manufacturing process of a semiconductor exposure apparatus or a liquid crystal display element exposure apparatus. In the photolithography method, a short arc type light source is used as a light source. A discharge lamp is used.

The short arc type discharge lamp used in the photolithography method is arranged such that an anode and a cathode are opposed to each other in a glass enclosure, and necessary discharge light emitting substances such as mercury are sealed therein. Radiates. Further, in the discharge lamp, a getter made of, for example, a tantalum material may be provided in order to adsorb an impure gas or the like in the sealed body.

The service life of a certain kind of short arc type discharge lamp, that is, the effective lighting time is, for example, about 750 hours. However, recently, there has been a demand for a discharge lamp having a particularly long service life, and specifically, a lamp having a long service life of, for example, 1500 hours or more is required.

Generally, the service life of a discharge lamp is determined by the time during which the desired irradiance is maintained when the discharge lamp is lit under its rated lighting conditions. Therefore, the inventors of the present invention have studied the cause of the discharge lamp reaching the end of its useful life. As a result, except for the case of an accident such as damage to the envelope during lighting, many discharge lamps have a glass envelope. It was found that the desired irradiance could not be maintained due to the blackening phenomenon that the wall blackened.

[0006]

The present invention has been completed as a result of further research on the cause of the blackening phenomenon based on the above findings. An object of the present invention is to provide a discharge lamp that effectively suppresses the blackening phenomenon of the envelope even after long-term use and has a long service life.

[0007]

DISCLOSURE OF THE INVENTION The discharge lamp of the present invention comprises:
The getter includes a glass envelope, an electrode that is placed in the envelope and has a temperature of 1000 ° C. or higher in a lighting state, and a getter that is placed in the envelope.
It is characterized by being made of a tantalum material having a total weight concentration of iron, nickel and titanium contained of 50 ppm or less.

The tantalum material forming the getter preferably has a total weight concentration of iron, nickel and titanium contained therein of 30 ppm or less. Further, it is preferable that the tantalum material has a weight concentration of iron of 10 ppm or less, a weight concentration of nickel of 10 ppm or less, and a weight concentration of titanium of 10 ppm or less.

In the discharge lamp of the present invention, since the getter made of the specific tantalum material as described above is used, the concentration of iron, nickel and titanium, which are the main causative substances causing the blackening phenomenon, is small. Since the absolute amount of iron, nickel and titanium evaporated from the getter when the discharge lamp is turned on is small and the blackening phenomenon occurs at a significantly low speed, a long service life can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The discharge lamp of the present invention will be described in detail below. FIG. 1 is an explanatory diagram showing an example of the configuration of a short arc type discharge lamp 10 used as a light source for a photolithography method, for example. The discharge lamp 10 comprises a glass bulb 14 having a central bulb portion 11 and stem portions 12 and 13 linearly extending from the bulb portion 11 on both sides. The cathodes 16 are arranged opposite each other, the bases of which are supported by the stem portions 12, 13 of the envelope 14.

The outer ends of the stem portions 12 and 13 of the sealing body 14 are provided with bases 17 and 18, respectively.
5 is electrically connected to a lead wire 21 extending outwardly from the base 17 and having a crimp terminal 20 at the tip via a metal foil 19 arranged in the stem portion 12, while the cathode 16 is It is electrically connected to a terminal 24 extending outward from the base 18 through a metal foil 23 arranged in the stem portion 13. Reference numerals 25 and 26 are reflection films made of a metal vapor deposition film, and 27 is the remaining portion of the exhaust pipe.

A getter is provided in the envelope 14 of the discharge lamp 10 so as to be located in the bulb portion 11. Specifically, as shown in FIG. 2, the anode 15 is a columnar electrode body 30 having a truncated cone-shaped head portion.
And a rod-shaped support rod portion 31 extending from the base of the electrode body 30, a small-diameter rod portion 32 is formed on the outer end side of the support rod portion 31 for sealing. One end of the metal foil 19 is connected to the outer peripheral surface.

A neck portion 33 having a small diameter is formed at a portion of the support rod portion 31 adjacent to the electrode body 30, and a wire getter 35 made of a tantalum material is wound around the outer periphery of the neck portion 33. It is arranged.

The getter 35 is substantially made of tantalum metal, and is made of a high-purity tantalum material having a total weight concentration of iron, nickel and titanium of 50 ppm or less, preferably 30 ppm or less. is there. It is preferable that the tantalum material has a weight concentration of iron of 10 ppm or less, a weight concentration of nickel of 10 ppm or less, and a weight concentration of titanium of 10 ppm or less.

Generally, metallic tantalum is obtained by refining a raw material ore, but normally obtained tantalum materials are nonmetals such as carbon, hydrogen, nitrogen and oxygen unless special purification treatment or refining treatment is applied. It contains the components and other metal components such as iron, molybdenum, nickel, niobium, titanium and tungsten as impurities or trace components. In addition, the total weight concentration of iron, nickel and titanium among other metal components is usually 200 ppm or more in a normal tantalum material.

Therefore, as the tantalum material for the getter 35 in the present invention, metal tantalum which is usually obtained is used as a raw material and iron, nickel and titanium are obtained by subjecting the metal tantalum to a refining treatment such as repeating refining operation. Of the three metal components, the total weight concentration of which is reduced to 50 ppm or less, preferably 30 ppm or less, and more preferably the weight concentration of each of the three metal components is reduced to 10 ppm or less. You can use it.

For refining the raw metal tantalum, conventional tantalum refining means can be used.
According to this, the concentration of metal components other than iron, nickel and titanium is also reduced, but this does not reduce the getter action. Further, the purification treatment may be a treatment for reducing the concentration of any one or two metal components of iron, nickel and titanium.

In the present invention, the rated specifications such as the rated power consumption of the discharge lamp 10 are such that the maximum temperature portion of the electrode body 30 of the anode 15, specifically the temperature of the tip, is 1000 ° C. or more in the lit state. Is set to. Under such conditions, the emission of light by the discharge light-emitting substance such as mercury enclosed in the bulb portion 11 is sufficient, and the desired irradiance can be reliably realized.

In the discharge lamp 10 having the above-mentioned structure, the getter 35 made of a tantalum material has a total weight concentration of iron, nickel and titanium of 50 ppm or less. In addition, the occurrence of the blackening phenomenon in the valve portion 11 of the envelope 14 is effectively suppressed, and as a result, a long service life can be obtained.

That is, in the discharge lamp 10 of the present invention, the tantalum material forming the getter 35 is heated and activated in the bulb portion 11 due to a high temperature of the anode 15 due to a discharge phenomenon, and is unique to metal tantalum. By the action of, the molecules or atoms such as hydrogen, oxygen and water existing in the space inside the bulb portion 11 are adsorbed and their concentration is kept low, thereby contributing to the continuation of the original discharge phenomenon of the discharge lamp 10. Although it effectively exerts the getter action, when the amount of iron, nickel and titanium contained in the tantalum material is large, a large amount of those metal components evaporate due to the high temperature of the getter itself, which is As a result of adhering to the inner surface of the tube wall of the valve portion 11, a blackening phenomenon occurs early.

However, as in the present invention, when the total weight concentration of iron, nickel, and titanium contained in the getter 35 is 50 ppm or less, even if they are evaporated, that tantalum material is used. Since the absolute amount is small, the blackening phenomenon is not actually observed in the envelope for a long time, and as a result, the desired irradiance is maintained for a long time, and eventually a discharge lamp with a long service life is obtained. be able to.

When the total weight concentration of iron, nickel and titanium in the tantalum material is 50 ppm or less, the blackening phenomenon is remarkably suppressed, but this value is 50 pp.
If it exceeds m, the blackening phenomenon may occur early depending on the lighting conditions. Further, in order to reliably obtain a discharge lamp having a sufficiently long service life, the total weight concentration of the above-mentioned three metal components in the tantalum material forming the getter is preferably 30 ppm or less,
In particular, the weight concentrations of these three metal components are all 10
It is desirable that the content is ppm or less.

The effects of the present invention can be effectively obtained as long as the discharge lamp has a temperature of the electrode body of the anode of 1000 ° C. or higher in the lighting state. That is, in such a discharge lamp, the evaporation of trace components consisting of iron, nickel and titanium from the getter made of a tantalum material becomes remarkable, which causes an early blackening phenomenon. Therefore, the effect of the present invention is not essentially affected by the type of discharge lamp, the shape of the sealing body, the size of the rated power consumption, the discharge luminescent substance to be sealed, the type of sealing gas, and the like.

Further, metal components other than iron, nickel, and titanium, such as molybdenum, tungsten, and niobium, which have a low vapor pressure even at high temperatures, do not cause an early blackening phenomenon. Similarly, carbon,
Non-metal elements such as hydrogen, nitrogen and oxygen also do not cause an early blackening phenomenon.

In the lighting state, the temperature of the anode is 10
In a discharge lamp that does not reach 00 ° C., even if the tantalum material forming the getter contains a large amount of iron, nickel, and titanium, the amount of those metals evaporating is small because the temperature is low. The degree of the blackening phenomenon does not change depending on the proportion of the content concentration of the tantalum material.

Although the embodiment of the discharge lamp of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be added. Specifically, in the present invention, the cause of the blackening phenomenon is surely achieved only by the condition that the total weight concentration of the three metal components of iron, nickel and titanium is 50 ppm or less in the tantalum material forming the getter. Since the getter can be suppressed, the form of the getter itself, the arrangement position, the mode of support, etc. are not limited. However, it is not preferable to arrange the getter in a place where it is heated to a too high temperature.

[0027]

EXAMPLES Examples of the discharge lamp of the present invention will be described below, but the present invention is not limited thereto.

Example 1 A short arc type discharge lamp of the present invention having the following specifications was produced according to the configuration shown in FIG. Rated current 21.3A Rated voltage 47V Rated power consumption 1.0kW Anode material Tungsten Cathode material Thoriated tungsten electrode distance 3mm Anode temperature during lighting 2300 ℃ (tip part) Getter is shown in Table 1. Made of tantalum material A with a certain impurity concentration, diameter 0.5 mm, total length 5
A 0 mm wire (weight 0.17 mg) was used.

Control Example A control discharge lamp was produced in the same manner as in Example 1 except that a getter made of tantalum material B was used.

The impurity component concentrations of the tantalum material A and the tantalum material B are as shown in Table 1. In Table 1, "three-way total" means the total of iron, nickel, and titanium.

[0031]

[Table 1]

Experimental Example The discharge lamps produced in Example 1 and the control example were continuously lit for 2000 hours according to the rated conditions, and the change in irradiance with the lapse of lighting time was measured. The results shown in FIG. was gotten. In this figure, curve A shows the result of the discharge lamp of Example 1, and curve B shows the result of the discharge lamp of the control example. The irradiance is shown as a relative value (%) when the initial value is 100.

From the result of the curve A in FIG. 3, according to the discharge lamp of Example 1, since the degree of blackening phenomenon of the sealing body is very small, the lighting time reaches 2000 hours. The irradiance of 93% or more is maintained, and a long service life of 2000 hours or more can be obtained. On the other hand, according to the discharge lamp of the comparative example, as shown by the curve B, the irradiance becomes smaller than 92% at the time when the lighting time of about 800 hours has elapsed, and the blackening phenomenon occurs early. It is understood that the resulting service life is short. From the above, it is clear that the discharge lamp of the present invention can obtain a long service life of about twice or more.

Further, with respect to each discharge lamp after the experiment was completed, the adhered substance on the inner surface of the portion where the blackening phenomenon occurred in the bulb portion of the envelope was sampled and subjected to elemental analysis. The total content of iron, nickel and titanium was 70% by weight or more, but the total content of iron, nickel and titanium was 40% by weight or less in the discharge lamp of Example 1. From this,
It is understood that iron, nickel, and titanium are the main causes of the blackening phenomenon, and molybdenum, niobium, and tungsten have a small influence on the occurrence of the blackening phenomenon, because the reasons are molybdenum, niobium, and tungsten. Is thought to be because the vapor pressure is extremely low.

From the above, in the discharge lamp of the comparative example, a large amount of iron from the tantalum material B constituting the getter,
The blackening phenomenon occurs early because nickel and titanium evaporate and adhere to the bulb portion of the sealing body, and in the discharge lamp of Example 1, the blackening phenomenon occurs due to the small evaporation amount of the three. It is understood that it is slow to develop and has a very long service life.

[0036]

According to the discharge lamp of the present invention, the use of a tantalum material having a total weight concentration of iron, nickel and titanium contained in a getter at a specific ratio or less as a getter causes a blackening phenomenon to occur. Is extremely small,
As a result, it is possible to effectively suppress the occurrence of the blackening phenomenon in the sealed body even after long-term use, and to obtain a long service life.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an example of a short arc type discharge lamp.

FIG. 2 is an explanatory diagram showing an anode in a state where a getter is arranged.

FIG. 3 is a curve diagram showing irradiance maintenance characteristics when a continuous lighting experiment is performed on a discharge lamp according to an example of the present invention and a discharge lamp according to a comparative example.

[Explanation of symbols]

 10 Short Arc Discharge Lamp 11 Bulb Part 12, 13 Stem Part 14 Enclosure 15 Anode 16 Cathode 17, 18 Base 19, 23 Metal Foil 20 Crimp Terminal 21 Lead Wire 24 Terminal 25, 26 Reflective Film 27 Exhaust Pipe Remaining 30 Electrode Body 31 Support Rod Part 32 Small Diameter Rod Part 33 Neck Part 35 Getter

Claims (3)

[Claims] 1. A glass envelope, an electrode arranged in the envelope and having a temperature of 1000 ° C. or higher in a lighting state, and a getter arranged in the envelope. A discharge lamp comprising a tantalum material having a total weight concentration of iron, nickel and titanium of 50 ppm or less. 2. The discharge lamp according to claim 1, wherein the total weight concentration of iron, nickel and titanium contained in the tantalum material forming the getter is 30 ppm or less. 3. The tantalum material constituting the getter has a weight concentration of iron of 10 ppm or less, a weight concentration of nickel of 10 ppm or less, and a titanium concentration of 10 ppm or less. Discharge lamp.