JP3738880B2 - Short arc discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a lighting device for a short arc discharge lamp.
[0002]
[Prior art]
Conventionally, a lighting light source of a projector light source device, a stepper light source used for semiconductor manufacturing, and the like have a small ratio of arc length to lamp power and a low lamp voltage. Therefore, the amount of mercury to be enclosed is increased in order to employ a large current or increase the lamp voltage to reduce the current and reduce the electrode burden.
[0003]
For example, a lamp as a light source for a stepper of a large-capacity lamp has an arc length of about 3 mm, 2000 W, an internal volume of 16 ml, an average gas temperature at lighting of 2000 ° C., an operating pressure of about 2.5 atm. Even for the cathode, a mandrel of φ12 mm is used.
[0004]
[Problems to be solved by the invention]
By the way, according to the lamp of the above-mentioned conditions, when it is lit for the first time after the lamp is manufactured, there are some lamps that burst immediately after lighting, so that the operation of turning on for 5 minutes before shipping and turning off for another 5 minutes is performed. Screening was performed by repeating about several times.
[0005]
When a ruptured lamp is observed, discharge starts from the base of the cathode embedded in the lamp seal and discharges from that place for 10 seconds or more, which stabilizes the discharge. It was found that the discharge at the root of the time cathode bursts under thermal stress.
[0006]
On the other hand, the lamp used as a mobile projector light source with a relatively small lamp, with a small ballast, has an arc length of about 1 mm, 120 W, an internal volume of 0.05 ml, an average gas temperature during lighting of 2000 ° C., When calculated, mercury is sealed so that the operation is about 180 atm, and the lamp voltage at the time of stabilization is about 80 volts. Therefore, the stable current is about 1.5A.
[0007]
Even in this type of lamp, as in the case of the light source for steppers, one out of several hundred lamps was ruptured by the first lighting after manufacture. The cause is that the discharge starts from the electrode base embedded in the seal part and lasts for a long time (10 seconds to several tens of seconds). The seal part on the cathode side does not move to the tip of both electrodes. It bursts to continue applying thermal stress to quartz.
[0008]
In determining the voltage and power of the lamp, the large capacity lamp is mainly for industrial use, and because it uses ultraviolet light, it has the value of a light source for steppers. The small capacity lamp is used for ballasting to lighten the device in projectors and the like. The purpose is to make it compact and lightweight.
[0009]
Therefore, the arc length must be shortened in order to increase the optical utilization factor without changing the lamp voltage, the power, and the luminous efficiency.
[0010]
In general illumination lamps, the arc length is about twice the tube diameter, and the total luminous flux is maximized. In the lamp, it is confirmed that an arc is transferred between the electrode tips as soon as the discharge is started, and a phenomenon as seen in a stepper light source or a projector light source is not observed.
[0011]
This is because a radioactive substance is applied to the electrode, and it is difficult for electrons to be emitted from the base of the seal portion, and power is consumed from the beginning in the discharge path, so that the electrode tip temperature is likely to rise.
[0012]
The present invention has been invented in view of the above-described points, and controls the current that flows at the start-up to a phenomenon that a stepper light source as an industrial light source and a projector lamp rupture to some extent upon initial lighting immediately after manufacture. An object of the present invention is to provide a lighting device for a short arc discharge lamp that prevents and has high reliability.
[0013]
[Means for Solving the Problems]
The present invention has the following configuration in order to solve the above problems. That is, the present invention relates to a lighting device for a short arc discharge lamp in which an electrode not coated with an electron discharge substance as an emitter is sealed at both ends of an arc tube, and only an arc tube is used without using an outer tube.
When the lamp power of the discharge lamp is P _L (W), the arc length l (mm) between the electrodes, the stable current of the lamp is I _L (A), and the initial current I _P (A) is l When starting a lamp with / P _L ≦ 1.5 × 10 ⁻² , first, a direct current that is defined as I _P ≧ 1.4 I _L is supplied, and then the current that is subsequently supplied is Is (A). A current defined as Is <I _L and Is ≦ I _P / 2 is allowed to flow for 3 seconds or more, and then the state is shifted to stable lighting.
[0014]
According to the lighting device for a short arc discharge lamp according to claim 1, when the lamp is lit, a time zone in which the current is smaller than the current at the start is provided immediately after the start, thereby preventing the initial lamp from bursting and reliability. High lamp can be obtained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 1 denotes a 1500 W light source (light emitting tube) for a stepper used for manufacturing a semiconductor, which has a bulging portion 2 at the center, and has a maximum outer diameter φ50 mm and a maximum inner diameter φ45 mm. Reference numeral 3 denotes an anode sealed in a seal portion 4 at one end of the light source, which is made of tungsten and is configured to taper toward the center. The anode 3 has a maximum diameter φ18 mm of 20 mm in length, and is inserted into a quartz material as a discharge vessel, so that the portion embedded in the seal portion 4 is cut to φ8 mm. Further, in order to prevent cracks from being generated in the quartz when embedded in quartz, the anode embedded portion is wound with a 0.1 mm thick molybdenum foil 5, and a molybdenum ribbon provided with several knife edges is provided. The molybdenum lead is electrically connected to the outside. In this configuration, the arc length is 3 mm.
[0016]
On the other hand, a cathode 11 is inserted into the seal portion 10 at the other end of the light source 1 and is drawn at an angle of about 30 degrees toward the center of the light source. A tungsten wire with a diameter of φ1.2 mm is closely attached and wound for 5 turns from a position about 10 mm away. Mercury is enclosed as a buffer gas so that the starting volume of xenon is about 1 atm and the stable lamp voltage is 25 V in a discharge vessel internal volume of about 62 ml.
[0017]
When the lamp is turned on, an initial current (primary current) of about 1.5 times the steady-state current is passed for 5 seconds, and then about 70% of the steady-state current is passed for 5 seconds. When a DC current substantially equal to the stable current is passed, even if the discharge is started from the cathode portion embedded in the seal portion, the current at the start only flows for a maximum of 5 seconds, and then becomes about 1.4 times the current. Immediately after it becomes 4 times, an arc is generated between the electrode tips, and it is difficult for thermal stress to be applied to the seal quartz. For this reason, 30 sets of the same lamp and the same ballast were combined, and the test was performed 1000 times in a flashing cycle of 10 minutes ON and 10 minutes OFF.
[0018]
Next, a specific example of the lamp is configured such that, for example, the lamp power P _L is 1500 W, the initial current I _P is 90 A, the current Is flowing after starting is 40 A, and the stable current I _L is 60 A.
[0019]
Next, the projector light source device will be described with reference to FIG. The lamp 20 (arc tube) shown in FIG. 2 is a lamp having a rating of 120 W, a discharge space having a maximum outer diameter of 9.4 mm and a maximum inner diameter of 5.0 mm, and an internal volume of about 0.05 ml at the center of the lamp. Argon gas is 10 ⁴ Pa, average gas temperature is 2000 ° C., and about 15 mg of mercury is sealed so that the internal pressure at the time of stability becomes 230 atm. Further, a small amount of bromide is added to prevent the progress of blackening during the lifetime. Enclosed.
[0020]
In FIG. 2, reference numerals 21 and 22 denote electrodes embedded in the seal portion 23 of the lamp 20 and are configured to have the same size. Further, both electrodes 21 and 22 are arranged to face each other, and the distance between the electrodes is 1.0 mm. Further, both electrodes are constructed by winding a core rod diameter φ0.3 mm made of tungsten and a coil 24 of φ0.22 mm made of tungsten as a double winding and winding four turns. The total length of the electrode is 9 mm, the length embedded in the seal part is about 4 mm, the welding scale is about 1.5 mm, the width is 1.5 mm, the length is 19 mm and the molybdenum foil with a knife edge. 25 (thickness 20 μm) is connected, and the other end of the molybdenum foil 25 is connected to a φ0.5 mm molybdenum lead 26 with a 2 mm welding shell, and further connected to a base or a metal terminal. It is. The lamp constructed in this way can be connected to an electronic ballast and lit.
[0021]
The ultra high pressure mercury lamp configured as described above has a rated lamp power of 120 W and a stable lamp voltage of about 80V. Also, let the lamp flow for 3 seconds as the DC current of the initial current 3A at the start, then the current of the rectangular wave 400HZ for 1A and 5 seconds, then flow the rectangular wave current of 3A of the same frequency, and decrease the current as the lamp voltage increases It was configured to be 1.5 amperes at the time of stability, and when 100 sets of the same device were tested 4000 times with a flashing cycle of 15 minutes ON and 15 minutes OFF, no abnormality was found and good life characteristics were shown. . The light source 20 shown in FIG. 2 is fixed to a glass mirror 27 as shown in FIG.
[0022]
In the short arc discharge lamp described above, as a condition for starting the lamp, the relationship between the lamp power P _L (W) and the arc length l (mm) is 1 / P _L ≦ 1.5 × 10 ⁻² .
Further, assuming that the current when the lamp is stable is I _L (A) and the current I _P (A) at the time of initial inrush is set as a condition for flowing a direct current, I _P ≧ 1.4 I _L.
Further, when Is (A) (secondary current) is a current to be subsequently supplied, Is <I _L and Is ≦ I _P / 2 are supplied for 3 seconds or more.
[0023]
As described above, if a time zone in which the current is smaller than the initial current is provided immediately after starting, the initial lamp burst does not occur.
It has been confirmed that, for example, when a current substantially equal to the stable current is supplied immediately after the start-up current is supplied in the early stage of lighting, there is a discharge from the seal portion, which may cause a burst. If the initial current I _P is less than 1.4 times the stable current I _L , the lamp does not start and cannot be implemented. When the current Is subsequently passed is larger than the stable current I _L and exceeds the current value of I _P / 2 of the initial current, not only the arc does not move to the electrode tip but also initial sputtering occurs. Furthermore, it was confirmed that if the current flow time is less than 3 seconds, then the arc does not move to the tip of the electrode, but the cathode coil discharges and spatters, resulting in early blackening. Yes. It is practical that this time is 3 to 10 seconds.
[0024]
【The invention's effect】
As described above, according to the present invention, by providing a time zone in which the current is smaller than the initial current immediately after starting, the initial lamp can be prevented from bursting and a highly reliable lamp can be obtained. As a light source for a projector or a lamp for a projector, there is a special effect that has great utility value.
[Brief description of the drawings]
FIG. 1 is a side view of a lamp used in a lighting device for a short arc discharge lamp according to the present invention.
FIG. 2 is a side view of another lamp used in the lighting device for a short arc discharge lamp according to the present invention.
FIG. 3 is a side view when the short arc discharge lamp of FIG. 2 is fixed to a mirror.
[Explanation of symbols]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF SYMBOLS 1 Light source 2 Expansion part 3 Anode 4 Seal part 5 Molybdenum foil 10 Seal part 11 Cathode 20 Lamp 21, 22 Electrode 23 Seal part 24 Coil 25 Molybdenum foil 26 Molybdenum lead 27 Glass mirror

Claims (1)

In a lighting device for a short arc discharge lamp in which an electrode not coated with an electron discharge material as an emitter is sealed at both ends of an arc tube, and only the arc tube is used without using an outer tube, the lamp power of the discharge lamp is expressed as P _L (W ), _L / P _L ≦ 1.5 × 10 ⁻² , ^{assuming that} the arc length between the electrodes is l (mm), the lamp stable current is I _L (A), and the initial current I _P (A) is the same. In starting the lamp, first, when a direct current that prescribes I _P ≧ 1.4 I _L is passed, and then the current to be subsequently supplied is Is (A), Is <I _L and Is ≦ I _P / 2 A lighting device for a short arc discharge lamp, characterized in that a current specified by

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