JPH066447Y2 - Short arc type mercury vapor discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a short arc type mercury vapor discharge lamp that is preferably used for printing semiconductors and printed circuit boards.

[Prior art and its problems]

For example, ultraviolet rays are used for baking semiconductors and printed circuit boards, and as a light source for generating the ultraviolet rays, a short arc type ultra-high pressure mercury vapor discharge lamp is usually used.
The quartz glass arc tube of such a discharge lamp is composed of a central substantially spherical luminous space bulging portion and sealing tube portions extending from both sides thereof, and a cathode and an anode made of tungsten are arranged to face each other in the luminous space bulging portion. ing. The metal foil embedded in the sealing tube is connected to the cathode and the anode, respectively. Also,
A certain amount of mercury and an inert gas are filled in the arc tube.The anode, which becomes extremely hot during lighting, is brought closer to the mercury staying in the lower part of the arc tube to accelerate the evaporation of mercury. It will be lit in the vertical position.

By the way, the lighting life of the discharge lamp used for such a purpose was conventionally designed to be about 400 to 600 hours,
Recently, a lighting life of 1000 hours or more may be required. There are various causes of the discharge lamp's lighting life, but the three main causes are as follows.

First, the tongue ten of the electrode evaporates and adheres to the inner wall of the bulging portion of the emission space to turn black, so that the amount of transmitted ultraviolet rays may decrease and the amount of light emitted may decrease. The evaporated tungsten rises along with the ascending air current, adheres from the upper inner wall of the light emitting space bulging portion, and gradually adheres to the central inner wall of the light emitting space bulging portion as the lighting time increases. Of the light emitted from the discharge lamp when baking semiconductors,
Only light emitted from an angle range of 40 ° above and 35 ° below the arc center is actually used. In other words, blackening in a range of 40 ° or more above the center of the arc does not have much effect, but if the lamp is lit for a long time, the part below this is also blackened, and the amount of light emitted is reduced. When the amount of emitted light used reaches about 70% of that at the start of use, it becomes unusable.

In addition, a phenomenon called “foil float” in which the quartz glass and the metal foil of the sealing tube portion on the cathode side, which is located on the upper side and has a high temperature, peels off from each other, which may cause lighting failure. This is because the metal cations of the impurities contained in the quartz glass are thermally excited and a negative potential is applied to the metal foil, so that a large electric field is generated in the direction toward the metal foil, and the cations of the impurities are generated. Concentrate near the interface of the metal foil. For this reason, the metal foil oxidizes and peels off from the quartz glass, creating a gap, but if the lamp is on for a long time, the gap gradually progresses due to the high pressure of the arc tube and communicates with the outside. It is thought that the airtightness of the part is destroyed.

Furthermore, since the anode also becomes extremely hot, it is melted and the shape is deformed, and a normal arc is not formed, resulting in a decrease in output.

As described above, when the lighting time has passed about 600 hours, these phenomena become remarkable remarkably, and it is very difficult to obtain a lighting life of 1000 hours or more.

[Purpose of device]

Therefore, an object of the present invention is to provide a short arc type mercury vapor discharge lamp in which blackening of an arc tube, floating of a foil, and melting damage of an anode are suppressed and which has a long lighting life.

[Constitution of the device and its action]

The short arc type mercury vapor discharge lamp of the present invention is located in the center of the arc tube, and the maximum diameter portion is displaced upward from the arc center and has a vertically asymmetrical substantially egg-shaped emission space bulging portion,
A sealing tube portion extending vertically above the emission space bulging portion, a cathode disposed above the emission space bulging portion, and a cathode disposed inside the emission space bulging portion facing the cathode. An anode provided with a heat radiation layer, a metal foil embedded in the sealing tube portion and connected to the cathode and the anode, respectively, and an electrical surface of the cathode provided on the outer surface of the sealing tube portion on the cathode side. And a conductive layer connected thereto.

In such a discharge lamp, the light emission space bulging portion has a substantially upper and lower asymmetrical egg shape in which the maximum diameter portion is displaced upward from the center of the arc and thus has a large volume on the upper side. In other words, the surface area of the upper inner wall of the light emitting space bulging portion that does not affect the light to be used even if blackened is large, and since blackening occurs from this portion, the central portion of the light emitting space bulging portion that affects is blackened. You can extend the time until. In addition, since the conductive layer applied to the outer surface of the sealing tube portion on the cathode side is electrically connected to the cathode and has the same potential, the electric field strength of the quartz glass and the metal foil becomes substantially zero, and the quartz Impurity metal cations in the glass do not move toward the metal foil. Therefore, the metal foil is less likely to be oxidized and the foil floating phenomenon can be prevented. Furthermore, since the heat radiating layer is provided on the outer surface of the body of the anode, the heat is well dissipated from the anode and is not overheated, so that thermal melting loss is suppressed.

That is, since it is attempted to prevent the blackening of the main part of the arc tube, the floating of the foil, and the melting damage of the anode, which are the main causes of the exhaust lamp's lighting life being exhausted, the lighting life is dramatically extended to 1000
A lighting life of more than an hour can be achieved.

〔Example〕

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows a short arc type ultra-high pressure mercury vapor discharge lamp having a power consumption of 1 kW and used for printing semiconductors and printed circuit boards. The center of the arc tube 1 made of quartz glass is a luminescent space bulging portion 11, and the sealing tube portion 12 is provided above and below the bulging portion 11.
Is growing. Then, the cathode 3 and the anode 4 made of tungsten are arranged to face each other in the light emitting space bulging portion 11, and the distance between the electrodes is 2.9 mm. A getter 31 for absorbing impure gas generated during lighting is wound around the cathode 3. A cap 5 is attached to each end of the sealing tube portion 12, and a metal foil 2 made of molybdenum foil having a plate thickness of about 0.02 mm is embedded in the sealing tube portion 12. Is connected to the cathode 3 to the anode 4. Then, the arc tube 1 is filled with mercury and an inert gas, for example, which have a pressure of 40 atm during lighting, and are lit in a vertical posture with the cathode 3 facing upward.

Here, the maximum diameter portion 11a of the light emitting space bulging portion 11 is located above the arc center C. That is, the normal light emitting space bulge is spherical or elliptical spherical and is vertically symmetrical, but the light emitting space bulge 11 of the present invention is a combination of two semi-elliptical spheres having different focal lengths. , Which is vertically asymmetrical and has a large egg-shaped shape with a large upper side. Here, what effectively uses the light emitted from the arc is the light that passes through 40 ° above the arc center C and 35 ° below the arc center (effective use range shown in FIG. 1). Therefore, the inner surface of the light emitting space bulging portion 11 above the effective use range is large. However, when the position of the maximum diameter portion 11a is greatly separated from the arc center C and the inner surface above the effective use range is made too large, the quartz glass in that portion does not reach a sufficiently high temperature during lighting and contacts the quartz glass. This must be avoided as mercury vapor will condense. For this reason,
The maximum diameter portion 11a is preferably provided at a position where the length of the light emitting space bulging portion 11 in the vertical direction is proportionally divided into 1: 2 or 2: 3.

Next, the sealing tube portion 12 on the side of the cathode 3 located on the upper side and having a high temperature 12
A conductive layer 6 is provided on the outer surface of the, and the conductive layer 6 is electrically connected to the cathode 3 by a connection line 61. The conductive layer 6 is, for example, a conductive paint applied to a length of about 20 mm and baked, but a thin copper plate may be wound or a thin copper wire may be wound in a dense spiral shape.

The anode 4 has a trapezoidal tip and is formed of a body portion following the body portion, and the heat radiation layer 41 is formed on the surface of the body portion. The heat radiation layer 41 is formed by applying a metal carbide such as tantalum carbide, zirconium carbide, and halfnium carbide in a paste form to a thickness of several tens of μm and baking the paste. Since these metal carbides have a high heat resistance temperature and a large heat radiation characteristic, the heat of the anode 4 radiates well from the heat radiation layer 41.

Then, when the discharge lamp having such a configuration is lit, the tungsten evaporated from the cathode 3 rides on the rising air current and adheres to the inner surface of the upper part of the emission space bulging portion 11 to be blackened. The part gradually goes down. However, since the inner surface above the effective use range is wide, it takes time to blacken this part, and the effective use range is 100%.
No blackening even after lighting for more than 0 hours. By the way, when the maximum diameter portion 11a is provided at a position where the vertical length of the light emitting space bulging portion 11 is proportionally divided into 1: 2 and the inner surface of the upper half of the light emitting space bulging portion 11 is enlarged by about 10%. When the lighting time was 1500 hours, the amount of light passing through the effective range was attenuated to 70%, and the lighting life was exhausted.

Then, the conductive layer 6 is provided on the outer surface of the sealing tube portion 12 on the cathode 3 side, and since the conductive layer 6 has the same potential as the cathode 3, the quartz glass of the sealing tube portion 12 and the metal foil 2 are provided. Since the electric field strength of is substantially zero and the metal cations of impurities contained in the quartz glass do not move to the metal foil 2 side as described above, the oxidation of the metal foil 2 is suppressed, and the lighting time is 1500 hours. Even then, the airtightness of the sealing tube portion 12 was not destroyed.
Further, since the heat of the anode 4 is well radiated from the heat radiation layer 41 and is not overheated, the anode 4 is in a good state with almost no melting damage even after the lighting time of 1500 hours.

[Effect of device]

As explained above, the short arc type mercury vapor discharge lamp of the present invention is the main cause of the discharge lamp's lighting life being blackened, the blackening of the effective use range of the arc tube, and the foil floating of the cathode side sealing tube part. Further, since the anode is prevented from being melted and damaged, the lighting life can be remarkably extended and a lighting life of 1000 hours or more can be achieved, and it can be suitably used as a light source for printing semiconductors or printed boards.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of the present invention. 1 ... Arc tube, 11 ... Luminous space bulging portion, 11a ... Maximum diameter portion, 1
2 ... Sealing tube part, 2 ... Metal foil, 3 ... Anode, 31 ... Getter,
4 ... Anode, 41 ... Heat emitting layer, 5 ... Base, 6 ... Conductive layer, 61 ...
Connection line, C ... Center of arc.

Claims (1)

[Scope of utility model registration request] 1. A light emitting space bulging portion located in the center of the arc tube, the maximum diameter portion of which is displaced upward from the center of the arc, and which has a substantially asymmetrical vertical egg shape, and an upper and lower portion of the light emitting space bulging portion, respectively. An extending sealing tube portion, a cathode disposed on the upper side in the emission space bulging portion, an anode disposed opposite to the cathode in the emission space bulging portion, and having a heat radiation layer provided on the outer surface of the body portion thereof. A metal foil embedded in the sealing tube and connected to the cathode and the anode, respectively, and a conductive layer provided on the outer surface of the sealing tube on the cathode side and electrically connected to the cathode. A short arc type mercury vapor discharge lamp.