JPH0539571Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a short arc type high-pressure mercury lamp in which mercury and a rare gas are sealed in a bulb and a pair of electrodes are disposed facing each other.

[Prior art and its problems]

A short arc type high-pressure mercury lamp has a short distance between the tips of a pair of electrodes placed opposite each other in the bulb, making it almost like a point light source, so when used in combination with an optical system, the light collection efficiency can be extremely high.
It is widely used in semiconductor exposure equipment, etc. In such lamps, while the lamp is lit, the gas pressure inside the bulb increases from around 1 atm to several tens of atm, and the electrodes also become hot, but there is little damage to the electrodes and arc stability is good, and the scattered electrode constituent materials are scattered on the inner wall of the bulb. It is required that there is little blackening phenomenon caused by adhesion to the surface, that is, that the amount of light can be maintained well and that it has a long life. In response to this requirement, various studies have been made on electrode design and manufacturing methods, but it is also important for lamp performance to reliably absorb and capture impure gases generated within the bulb during lighting. .

By the way, getters (impure gas absorbing members) are attached to electrodes to absorb impure gases, and the typical getter metals currently used are zirconium and tantalum, which are used in the form of wire or plate materials. has been done. Here, to explain how to use the getter using zirconium wire based on Fig. 1, the arc support part 1 at the tip
A coil 3 is wound around the electrode body 2 following the coil 3, and a thin zirconium wire 4 is wound in a small approximately V-shaped groove formed between the pitches of the coil 3. This zirconium wire 4 is well held in the approximately V-shaped groove,
Although it can be used as it is, in order to ensure further retention, it is heated to weld the coil 3 to the electrode body 2, and the zirconium wire 4 is melted so that the zirconium layer covers the coil 3. do. Although this results in a lamp having an excellent getter function, if the usage conditions of the lamp become severe or the power consumption increases, the temperature of the electrode body also rises excessively. Furthermore, when the lamp is lit vertically, the temperature conditions of the upper electrode are significantly different from those of the lower electrode, and the temperature is extremely high. Therefore, the evaporation of zirconium is promoted and the blackening phenomenon of the lamp tends to appear quickly.In such a case, it is presumed that tantalum, which has a low vapor pressure, is preferable in place of zirconium.

Here, tantalum is generally used in the form of a plate material, and as shown in FIG. 2, a tantalum metal plate 5 is wound around the electrode body 2 at the rear of the coil 3.
Although this tantalum metal plate also has an excellent getter function, it is necessary to maintain the tantalum metal plate at an appropriate temperature in order to function effectively as a getter. However, although the tantalum metal plate wrapped around the electrode body comes into surface contact with the electrode body, the tantalum metal plate inevitably separates partially from the electrode body, so the effective contact area varies widely due to production control. Therefore, there is a problem that variations occur in the temperature of the tantalum metal plate, and variations in lamp performance also increase.

[Purpose of invention]

Therefore, the object of the present invention is to provide a short arc type high-pressure mercury lamp in which when a tantalum metal plate is used as a getter material, the temperature of the tantalum metal plate is stable, the getter function is excellent, and the lamp performance has less variation. .

[Means to achieve the purpose]

In order to achieve the above object, the lamp in the present invention is configured as follows.

That is, in a short arc type high-pressure mercury lamp in which mercury and rare gas are sealed in the bulb and a pair of electrodes are arranged facing each other, at least one electrode has tantalum metal for getter in the electrode body following the arc support at the tip. When the plate is wrapped tightly and turned on, the edge of the tantalum metal plate on the side of the arc support part is 1 inch in the direction of the arc support part.
The difference between the temperature of the electrode body at a distance of mm and the temperature of the tantalum metal plate at a distance of 1 mm in the opposite direction from this edge should be within 200°C.

[Effect]

Although it is generally difficult to accurately evaluate the effective contact area in surface contact, such as when a tantalum metal plate is wrapped around the electrode body, the inventor of the present invention The present invention was completed by discovering that the effective contact area can be accurately evaluated by measuring the temperature difference between the two. That is, a tantalum metal plate is tightly wrapped around the electrode body, and the temperature of the electrode body at a position 1 mm away from the edge of the tantalum metal plate on the arc support side toward the arc support, and 1 mm in the opposite direction from this edge. If the difference between the temperature of the tantalum metal plate at a distant position is within 200℃, the effective contact area in surface contact will be large and the variation will be small.
The tantalum metal plate is maintained at the proper temperature to stabilize lamp performance.

〔Example〕

Figure 3 A and B show the method of measuring temperature. In FIG. 3A, E is the edge of the tantalum metal plate 5 on the arc support side, and Q and R indicate the positions of the electrode body and the tantalum metal plate, respectively, 1 mm apart from the edge E. Then, the temperature at position Q and position R is measured, but as shown in Figure 3B, for position R, any four point-symmetric points
Measure R ₁ , R ₂ , R ₃ , and R ₄ and find the average temperature ΤR. Next, the four points are translated in the longitudinal direction of the electrode body and the points Q ₁ , Q ₂ , Q ₃ , and Q ₄ that intersect with Q are measured to determine the average temperature TQ. In addition, in the short arc type high pressure mercury lamp to which this invention is applied, when the power consumption is about 500 to 1000 W, the diameter of the cathode body is about 1.5 to 3 mm, and the diameter of the anode body is about 4 to 8 mm. Therefore, in order to obtain the average temperatures TR and TQ, it is sufficient to measure at four points each.

Next, we will show examples of lamps and measured temperatures that were actually measured.

Lamp specifications Power consumption 1KW Rated current 19A Rated voltage 53V Distance between electrodes 2.9mm Diameter of anode body 8mm Edge position 6mm from the tip of the anode Measured temperature Q ₁ = 2060℃, Q ₂ = 2060℃, Q ₃ = 2040℃, Q ₄ = 2050°C ΤQ = 2050°C R ₁ = 1850°C, R ₂ = 1890°C R ₃ = 1870°C, R ₄ = 1880°C ΤR = 1870°C ΤQ−ΤR = 180°C The position R where the temperature was measured is Since it is located 1 mm away from the edge on the support side, it is the hottest part of the tantalum metal plate. Due to the temperature gradient in the electrode body, the temperature of the tantalum metal plate decreases as it moves away from the edge on the arc support side, but the area below 700°C absorbs H ₂ and H ₂ O as impure gases. However, the part between 700 and 1200℃ absorbs O ₂ and CO ₂ well. In other words, in order for the tantalum metal plate to function effectively as a getter material, it needs to be maintained at a temperature ranging from 1200°C to 700°C or less. Therefore, if the tantalum metal plate is tightly wrapped around the electrode body so that the temperature difference between position Q and position R is within 200℃, the tantalum metal plate will rise to 1200℃ according to the temperature gradient of the electrode body.
The lamp performance is maintained within a temperature range of 700°C or below, ensuring stable lamp performance.

If the temperature difference between position Q and position R is 200°C or more, the way the tantalum metal plate is wound is loose, and as a result, the heat in the electrode body will be accurately directed to the tantalum metal plate according to the temperature gradient. As a result, the temperature of the tantalum metal plate cannot be accurately maintained within the above temperature range, resulting in large variations in lamp performance.

[Effect of idea]

As explained above, when the short arc type high pressure mercury lamp of the present invention is lit, the tantalum metal plate used as the getter material is tightly wrapped around the electrode body, and an arc is generated from the edge of the tantalum metal plate on the arc support side. The temperature difference between the temperature of the electrode body at a position 1 mm away from the support and the temperature of the tantalum metal plate at a position 1 mm away from this edge in the opposite direction should be within 200°C.
The tantalum metal plate is maintained within a predetermined temperature range according to the temperature gradient of the electrode body, effectively exhibiting its getter function, and stabilizing lamp performance.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of the electrodes, and FIGS. 3A and 3B are explanatory diagrams of the temperature measuring method. 1... Arc support part, 2... Electrode body part, 3...
...Coil, 4...Zirconium wire, 5...
Tantalum metal plate.

Claims (1)

[Claims for Utility Model Registration] In a short-arc high-pressure mercury lamp in which mercury and rare gas are sealed in a bulb and a pair of electrodes are arranged facing each other, at least one of the electrodes has an electrode body that continues to the arc supporting portion at the tip. A tantalum metal plate for a getter is tightly wound around the electrode body, and during lighting, the temperature of the electrode body at a position 1 mm away from the edge of the tantalum metal plate on the arc support side in the direction of the arc support, and this edge. A short arc type high pressure mercury lamp characterized in that the temperature difference between the temperature of the tantalum metal plate and the tantalum metal plate located 1 mm apart in the opposite direction is within 200°C.