JPH0687411B2 - Short arc discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a short arc DC discharge lamp such as a xenon lamp or an ultra-high pressure mercury lamp.

(Prior art) Conventionally, a short arc discharge lamp such as a xenon lamp or an ultra-high pressure mercury lamp is combined with an optical system by taking advantage of the short distance between the tips of the electrodes facing each other at both ends of the hermetic container and being close to a point light source. When used as a light source, the light collection efficiency can be made extremely high, and it is widely used in the fields of projectors, semiconductor exposure apparatuses, and the like. Since these lamps have a common feature of the short arc, the internal pressure of the lamp (xenon gas pressure in the former case, and mercury vapor pressure in the latter case) during lighting is high, and the distance between electrodes, that is, the emission distance is short.

In the case of a projector that uses a xenon lamp as a light source, it is necessary to continuously turn on the lamp, and the light from this lamp must be synchronized by the shutter in synchronization with the frame advance of the film. To reduce the flicker that occurs, a method of increasing the number of blades in the shutter is adopted.

However, in such a method in which the light is chopped by the shutter, there is a problem that the efficiency is poor because the xenon lamp is lit at a constant current even when the shutter is closed.

In order to solve such a problem, a shutterless type has been developed. This one constantly sends the minimum current necessary for the xenon lamp to maintain its discharge (at this current, the lamp substantially stops emitting light) and superimposes a large pulse current periodically. This is a method in which the light is emitted and the lamp is blinked and used. By doing so, an excessive current is passed only when the lamp is desired to emit light, so that the efficiency can be improved.

However, this method has a problem in that the current for maintaining the discharge of the lamp and the current fluctuation when the pulse current is superimposed are large, and thus the electrode deterioration of the xenon lamp is severe and the lamp life is greatly reduced.

In contrast to such a conventional lighting method, the inventors of the present invention have previously proposed an invention relating to a method for lighting a xenon lamp capable of preventing a large decrease in lamp life and improving the lamp efficiency, and a combination of this invention with a shutter, Each of the inventors has filed an invention relating to a lighting method capable of improving the shutter efficiency.

In the former case, when a low base DC current is supplied to the xenon lamp and a pulse current is superposed every period T and a high current is supplied to operate the xenon lamp in that period, the above-mentioned pace current value and high current are applied. The maximum current value and the cumulative time of high current flowing in the cycle T are regulated, and the latter uses the opening and closing operation of the shutter together, and at least the base current is supplied while the shutter is closed. It is something that is done.

Also, in the case of ultra-high pressure mercury lamps, when used in spotty cureers, semiconductor exposure equipment, etc., it is combined with a shutter, and similar efficiency improvement can be achieved by applying the above-mentioned usage of xenon lamps. You can

Although these lighting methods have the effect of improving the lamp life as compared with the shutterless method, they still include the element of blinking lighting, and therefore, it is desirable that the lamp sled itself is strong against blinking lighting. Was there.

FIG. 4 is a vertical cross-sectional view for explaining the schematic structure of a conventional 350 W xenon lamp, (1) is an airtight container made of quartz glass,
It has the shape of a spindle or a sphere as shown in the figure, and a large anode (2) and a smaller cathode (6) are placed opposite to the sealing parts (1a), (1b) at both ends, and lighting is done inside. Xenon gas (Xe), which can reach 10 to 50 atm. The anode (2) has a main part (2a) protruding into the airtight container (1) and a base end part (2c) sealed to the sealing part (1a) of the airtight container (1) as shown in the figure. The main part (2a) and the base end part (2c) have the same diameter, or although not shown, a small diameter part is formed by providing a concave part in the middle of the two parts (2a) and (2c) for the purpose of adiabatic effect. Type is used. Both electrodes (2),
(6) is placed on the outer peripheral surface of the quartz glass body for joint (3),
Moreover, it is connected to the external introduction body (5) through the metal foil (4) hermetically sealed to the sealing parts (1a) and (1b).

In the case of such a lamp structure, according to the usage method in which the number of blinks is large, the repetition of high and low Watts is caused by the electrode (2),
Through (6), heat shock is applied to both sealing parts (1a) and (1b) to increase the strain strength of the quartz glass body of the sealing part, which often leads to cracking or even lamp damage. Ivy. In particular, such a phenomenon was remarkable on the side of the anode (2) where the heat generation of the electrode was large. In order to prevent this, the lamp load can be lowered (enlargement of the airtight container), the size of the electrode can be increased, and the size and length of the sealing part can be increased, but these measures are small and highly efficient. This is contrary to the demands of consumers who expect the lamp.

(Problems to be solved by the invention) When a short arc discharge lamp is lit by the flashing lighting method or the pulse current superposition method including the elements of the flashing lighting method as described above, particularly in this kind of lamp with high internal pressure during lighting, There is a risk that cracks may enter the sealing part on the anode side, where the heat of the electrode is large, and may be damaged. On the other hand, in order to eliminate such defects, there is a problem that the lamp must be upsized.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the related art and to provide a short arc discharge lamp capable of preventing lamp damage without increasing the size.

[Structure of Invention]

In the short arc discharge lamp of the present invention, an anode is formed by a main portion and a shaft portion having a diameter smaller than that of the main portion, and the surface area of the main portion is SA (m
m ² ), the outer diameter is D (mm), the outer diameter of the shaft portion sealed in the sealing portion is d (mm), the length is 1 (mm), and the maximum lamp power is W _L
When a (watt W), configured to _{1.5 ≦ W L /SA≦2.7 0.67 ≦ d} / D + 0.13W L /SA≦0.87 W L / l ≦ 130 so as to satisfy respectively.

(Operation) With such a configuration, the main part of the anode receives the power consumption of the anode, and the surface area of the main part is set large, so that not only is the heat dissipation effect great for maximum power, By reducing the diameter of the shaft part of the anode sealed in the sealing part and regulating the length l of the sealed part,
It is possible to reduce the transmission of heat generated in the main part of the anode through the shaft portion to the quartz glass in the sealing portion as much as possible. Therefore, it is possible to prevent a situation in which the anode, which has the lowest compressive strength, and quartz, which have different thermal expansion coefficients, cause increased strain, cracks, and damage due to heat shock.

Further, such an effect can be obtained not only in a lighting system in which a thermal change occurs in a short time such as a pulse superposition lighting system, but also in a normal DC constant lighting system in an application with a high blinking frequency. ,It is valid.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a vertical cross-sectional view of the sealing part on the anode side of a 350 W xenon lamp which is a short arc discharge lamp of the present invention. (1) is an airtight container made of quartz glass and has a substantially spin-shaped shape. A large tungsten anode (2) is sealed at (1a) on one end side thereof, and is arranged on the outer peripheral surface of the quartz glass body for joint (3) and is hermetically sealed at the sealing portion (1a). The xenon gas, which is electrically connected to the external introduction body (5) via the metal foil (4) and which has a pressure of about 10 to 50 atm during lighting, is enclosed in the airtight container (1). Further, although not shown, a cathode is provided opposite to the other sealing portion of the airtight container (1).

The anode (2) is composed of a main part (2a) and a shaft part (2
b) and the surface area Sa of the main part (2a) is 254 mm ² , diameter D
Is 5.5 lmm, and the diameter (d) of the shaft part (2b) sealed in the airtight container sealing part (1a) is 2.8 mm and the length l is 5.4 mm. Therefore, d / D = 2.8 mm / It is set to 5.5mm = 0.51.

Also, this lamp is lit by pulse superimposition DC with maximum power W _L = 540 W, and therefore W _L / SA = 540 W / 254 (mm ² ) = 2.1 W _L / _l = 540 W / 5.4 mm = 100 is set. Has been done.

The lamp of this embodiment has the same diameter as the main part and the shaft part of the anode, that is, D = d = 4 mm, SA = 175 (mm ² ), l = 4 mm.

That is, for the _{d / D = 1, W L} /SA=3.1,W L / l = 135 of the same type conventionally lamp, a comparison of the initial luminous flux and life characteristics at pulse superimposing DC lighting line Natsuta.

In the pulse superposition DC lighting method, a pulse current having a current waveform shown in FIG. 2 was supplied to the xenon lamp. In the case of FIG. 2, first, a predetermined base current Imin = 7.5A is supplied to the xenon lamp, and then t = 12.5ms at the timing of synchronous T = 20.8msec.
Superimpose the ec pulse current, and the maximum current at this time is Imax = 22A
The maximum power of the lamp is 540W and the average power is 350W.

The test results of 20 lamps each showed that one lamp of the conventional lamp was broken in the middle of 1000 hours, and 3 lamps were peeled off from the sealing part quartz glass on the side where the metal foil of the sealing part was connected to the anode. ， Glass crack had occurred. On the other hand, the above-mentioned defects did not occur in the lamp of the embodiment throughout its life.

In addition, by using an anode in which the main part and the shaft part, which are other conventional lamps, have the same diameter and a recess is formed in the middle part to form a small diameter, the heat generated in the main part of the anode is sealed. The effect of reducing the conduction to the part is small, especially when accompanied by a large thermal change, and the surface area of the main part is small due to the formation of the concave part, and the power consumption of the anode is mainly reduced. It is difficult for some parts to accept it, or the heat dissipation effect of the main part at the maximum power consumption is reduced. Further, in the same average power 350 W lamp as in the above embodiment, the anode D = d = 5.5 mm, that is, the main part and the shaft part have the same diameter, and the diameter is larger, the diameter of the anode shaft part with respect to the sealing part is Is too large, the pressure resistance strength of the sealed portion is lowered, and damage easily occurs. In order to prevent such damage, increasing the distance between the electrodes in order to reduce the high pressure during lighting in the airtight container or lowering the lamp voltage lowers the lamp efficiency, and the sealing part Increasing the size and length of the encapsulation structure in order to increase the pressure resistance of the lamp will result in a reduction in the size of the lamp.

The above describes the case of an average lamp power of 350 W.
Result of applying even for those of the results other lamp power, the maximum power W _L surface area of the anode main part of (watt) SA (m
m ² ), the ratio W _L / SA and the ratio d / D of the diameter d of the shaft part to the diameter D of the anode main part have a predetermined relationship, and the thermal gradient W
_If the value of _L / l is restricted to the range shown in the following equation,
It was found that the same effect as in the case of 50 W can be obtained. Its range is _{1.5 ≦ W L /SA≦2.7 ...... (1} ) 0.67 ≦ d / D + 0.13W L /SA≦0.87 ...... (2) W L / l ≦ 130 ...... (3).

Fig. 3 is an explanatory diagram of the above equations (1) and (2). The horizontal axis is W _L / SA and the vertical axis is d / D, and the hatched range is the equations (1) and (2). It is a range that satisfies both and.

That is, when W _L / SA is less than 1.5, the temperature of the anode becomes too high, and the heat conduction to the encapsulation also increases, causing cracking-damage due to repeated heat cycles.
Further, there is a problem that the electrode material is scattered from the anode, the blackening of the airtight container appears, and the luminous flux reduction rate increases. On the other hand, when W _L / SA exceeds 2.7, there are no problems such as thermal problems and life characteristics, but in the case of the metal foil sealing type,
As the weight of the anode increased, the strength of the connection with the metal foil decreased, and excessive force was applied to the sealing glass, causing vibration and problems during transportation. Furthermore, if the anode is too large, problems will occur in light distribution.

Next, within the range of 1.5 ≦ W _L /SA≦2.7, the diameter D of the main anode part
Results of the ratio d / D of the diameter d of the shaft section was variously changed against, W _L /
Despite SA being within the above preferred range, d / D> 0.87
In the case of −0.13W _L / SA, the strength of the sealing part is weakened due to the increase of d, which may cause damage. On the other hand, d / D <
In the case of 0.67-0.13W _L / SA, the anode tends to be easily broken from the shaft, and instead of suppressing heat conduction from the main part, the amount of heat generated by itself increases, resulting in a decrease in the effect.

Furthermore, regarding the thermal gradient, it is necessary that W _L / l does not exceed 130, and if it exceeds 130, the peeling of the metal foil spreads in the latter half of the life, and if the lighting continues, the Expected to lead to leaks and, in some cases, damage. There is no particular restriction on the lower limit of W _L / l, the smaller the better, the better, but considering the miniaturization of the lamp, it is better to keep it at 70th place.

The present invention is not limited to the above xenon lamp, but can be applied to other short arc discharge lamps such as an ultra-high pressure mercury lamp.

〔The invention's effect〕

As described above, according to the configuration of the present invention, even if a lamp of this kind having an extremely high internal pressure during lighting is lit by the flashing lighting method or the pulse current superposition method including the elements of the flashing lighting method, a large amount of heat is generated. Since it is possible to prevent an extreme rise in temperature at the sealing part of the anode to the hermetically sealed part of the airtight container, it is possible to obtain a short arc discharge lamp without causing damage to the sealing part without increasing the size of the lamp.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an anode side sealing portion of a xenon lamp which is an embodiment of the short arc discharge lamp of the present invention, FIG. 2 is a current waveform diagram in a pulse superposition lighting system, and FIG. 3 is an effective range of the present invention. 4 and FIG. 4 are schematic configuration diagrams of a conventional xenon lamp. (1) ... Airtight container, (1a) ... Sealing part, (2) ... Anode, (2a) ... Anode main part, (2b) ... Anode shaft part.

Claims (1)

[Claims] 1. In a short arc DC discharge lamp for direct current lighting, wherein one end is sealed to both ends of a quartz glass airtight container, and an anode and a cathode are provided in opposition to each other. The surface area of the main part is SA
(Mm ² ), the diameter is D (mm), the diameter of the shaft part sealed in the above sealing part is d (mm), the length is 1 (mm), and the maximum lamp power is W _L
When a (watt W), Shiyotoaku discharge lamp, wherein the _{1.5 ≦ W L /SA≦2.7 0.67 ≦ d} / D + 0.13W L /SA≦0.87 W L / l ≦ 130 it has to satisfy respectively.