JP2013016412A - Extra-high pressure mercury lamp and light source device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extra-high pressure mercury lamp capable of achieving high color rendering by increasing mercury density without increasing an arc length and running an excessive lamp current.SOLUTION: The extra-high pressure mercury lamp, including an arc tube and a pair of electrodes protruding in a discharge space of the arc tube, satisfies P/V≥-4.33ρ+5245 and 1500≤P/V≤3100, where ρ is a mercury density [mg/cc] of the discharge space, P is electric power [W] and V is an internal volume [cc], has an average color rendering index Ra of at least 80 and is configured to be turned on by microwave power.

Description

  The present invention relates to an ultra high pressure mercury lamp and a light source device using the same, and more particularly to an ultra high pressure mercury lamp for microwave operation having an average color rendering index Ra of 80 or more and a light source device using the same.

A conventional ultra-high pressure mercury lamp has a mercury density of about 200 to 300 mg / cc, is lit at a tube wall load of about 2700 W / cc (or 1.5 W / mm ² ), and has an average color rendering index Ra of about 60. there were.
As an ultra-high pressure mercury lamp, for example, Patent Document 1 discloses a mercury density of 243 to 357 mg / cc, a tube wall load of 1.30 to 1.36 W / mm ² (2170 to 4290 W / cc), and an arc length of 1.0 to 1. 2 mm is disclosed. Patent Document 2 discloses a mercury density of 160 to 220 mg / cc, a tube wall load of 0.8 to 1.5 W / mm ² , and an arc length of about 1.2 mm.
A pair of electrodes of such an ultra-high pressure mercury lamp is connected to a dedicated power source, and a predetermined current is passed between both electrodes to form a discharge arc.

  As a projector illumination, a light source with high color rendering properties is desirable from the viewpoint of color reproducibility. A xenon lamp can be used to improve the color rendering, but the xenon lamp has a low luminous efficiency of about 30 lm / W. Therefore, it is desired to improve the color rendering with a mercury lamp having a higher efficiency than the xenon lamp.

  In the ultra high pressure mercury lamp, the arc length is set to a very short value of about 1 mm in order to increase the optical efficiency. For this reason, in the case of a conventional ultra-high pressure mercury lamp, that is, in a lighting system in which a dedicated lighting device is connected to both electrodes and a current is passed between both electrodes, the lamp voltage decreases when the arc length is short. In order to obtain a tube wall load necessary for obtaining a desired mercury vapor pressure at this low lamp voltage, it is necessary to increase the lamp current in inverse proportion to the lamp voltage. Thus, when energizing a large current to an electrode, you have to enlarge the cross-sectional area of metal foil which is a sealing member according to the electric current value to energize.

Japanese Patent No. 2829339 Japanese Patent No. 2948200

  Here, in the mercury lamp, it has been found that the color rendering can be improved by increasing the mercury vapor pressure during lighting. In order to increase the mercury vapor pressure, it is necessary to increase the density of mercury sealed in the arc tube and increase the tube wall load. In order to obtain a high tube wall load, it is necessary to increase the lamp power. However, if the lamp current is increased, the consumption of the electrode is accelerated, which is not preferable. Alternatively, the lamp voltage may be increased (ie, the arc length is increased) in order to prevent the lamp current from being increased while increasing the lamp power, but the longer arc for increasing the lamp voltage reduces the optical efficiency. This is not preferable.

  Further, in order to increase the cross-sectional area of the metal foil in order to pass a large current through the electrode, the thickness of the metal foil must be increased or the width must be increased. However, since the metal foil becomes hot and expands during lighting, if its cross-sectional area is increased, the expansion due to heat increases and the arc tube may be damaged. In particular, in an ultra-high pressure mercury lamp, since the pressure in the arc tube during lighting is very high, the possibility of failure due to expansion of the metal foil becomes higher.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ultra-high pressure mercury lamp having an improved color rendering property by increasing the mercury density without increasing the arc length and without passing an excessive lamp current.

  A first aspect of the present invention is an ultrahigh pressure mercury lamp including a light emitting tube and a pair of electrodes protruding into the discharge space of the light emitting tube, wherein the mercury density ρ [mg / cc] in the discharge space and the power P [W ] With respect to the internal volume V [cc], P / V ≧ −4.33ρ + 5245 and 1500 ≦ P / V ≦ 3100 are satisfied, the average color rendering index Ra is 80 or more, and it is turned on by microwave power This is a high-pressure mercury lamp. Here, the distance between the pair of electrodes is preferably 0.5 mm to 3.0 mm, more preferably 0.8 mm to 1.5 mm.

  According to a second aspect of the present invention, there is provided the ultrahigh pressure mercury lamp of the first aspect, an antenna for propagating microwave power to the ultrahigh pressure mercury lamp, and a resonator in which the antenna and the ultrahigh pressure mercury lamp are disposed. It is a light source device.

It is a figure of the ultrahigh pressure mercury lamp of the present invention. It is a figure of the light source device of this invention. It is a figure which shows the relationship between the mercury density in a super high pressure mercury lamp, electric power, and Ra. It is a figure which shows the relationship between the mercury density and tube wall load in an ultra-high pressure mercury lamp. It is a figure which shows the emission spectrum in the conventional super-high pressure mercury lamp. It is a figure which shows the emission spectrum in the ultra-high pressure mercury lamp by one Example of this invention. It is a figure which shows the emission spectrum in the ultra-high pressure mercury lamp by the other Example of this invention.

  In order to increase mercury density and lamp power (tube wall load) without increasing the arc length, the ultra-high pressure mercury lamp of the present invention is not a lighting system in which a large current is directly passed between electrodes, but an electric field around the electrodes. A microwave lighting method is used. That is, in the lamp of the present invention, microwave power is coupled to the electrodes in the discharge space to evaporate and excite the luminescent material, thereby performing arc discharge between the electrodes. Therefore, a large current does not flow through the electrode. In the following examples, “tube wall load” refers to a value obtained by dividing the lamp power [W] by the internal volume [cc] of the discharge space.

  FIG. 1 shows an ultrahigh pressure mercury lamp 1 (hereinafter referred to as “lamp 1”) of the present invention. The lamp 1 includes an arc tube 2 made of quartz glass, electrodes 3a and 3b projecting from the discharge space 21 of the arc tube 2, and metal foils (molybdenum foils) 4a and 4b joined to the electrodes 3a and 3b, respectively. Prepare. The electrodes 3 a and 3 b and the molybdenum foils 4 a and 4 b are sealed in the arc tube 2. Note that the pair of electrodes 3a and 3b may protrude into the discharge space 20 with different lengths as long as discharge by microwave power is possible, and may not have the same shape. In consideration of productivity, the lamp 1 has a symmetric shape with respect to the light emitting portion 21. However, the effects of the present invention can be obtained even with an asymmetric shape. The drawings are not to scale.

  Since the ultra-high pressure mercury lamp of the present invention is lit by microwaves, unlike a lamp that is lit by passing a current through a metal foil (molybdenum foil) that is a sealing member, a current that flows through the molybdenum foil when increasing the lighting power Need not be increased, that is, it is not necessary to increase the cross-sectional area of the molybdenum foil. Therefore, the expansion of the sealing member is small, and the possibility of failure is reduced as compared with the conventional lighting method. In other words, since the cross-sectional area of the metal foil can be reduced as compared with the case of the conventional lighting method, the probability of failure can be further reduced.

  FIG. 2 shows a light source device of the present invention. The light source device includes the lamp 1, the antenna 5 for supporting the lamp 1 and propagating the microwave power, the resonator 6 including a metal cylindrical casing in which the lamp 1 and the antenna 5 are disposed, the lamp Reflector 9 for reflecting light from 1 and guiding it to a desired region, and connector 7 (for example, a coaxial connector) for propagating microwave power from a microwave power source (not shown) outside resonator 6 to antenna 5 ). The light from the lamp 1 is reflected by the inner surface of the reflecting mirror 9 and taken out from the light outlet 8. The light extraction port 8 is made of a metal mesh or the like, and prevents leakage of microwaves from the resonator 6 to the outside. The impedance matching of the light source device composed of the above members is not an object of the present invention, and thus the description thereof is omitted. However, the impedance matching is appropriately performed. Also, the drawings are not to scale.

  As dimensions of one embodiment of the lamp 1, the outer diameter of the light emitting section 20 (maximum diameter of the cross section perpendicular to the optical axis) is 9.4 mm, and the inner diameter of the discharge space 21 (maximum diameter of the cross section perpendicular to the optical axis) is 4. 0.2 mm and the internal volume is 0.055 cc. The total length of the lamp is 32 mm, and the arc length (interelectrode distance) is 0.9 mm. In addition, each dimension is not restricted above, For example, the distance between electrodes should just be about 0.5-3.0 mm, More preferably, it may be about 0.8-1.5 mm.

  FIG. 3 shows the relationship of the average color rendering index Ra to the lamp power P for each mercury density ρ sealed in the discharge space 21 in the lamp 1 having the above dimensions. As can be seen from FIG. 3, the higher the mercury density, the higher Ra can be achieved even with a low lamp power (tube wall load). If the mercury density is 280 mg / cc, Ra of 80 or more cannot be realized unless the lamp power is made very high. When the mercury density is 400 mg / cc, the lamp power is about 200 W or more, 550 mg / cc is about 147 W or more, and 800 mg / cc is about 102 W or more.

  FIG. 4 shows the tube wall load P / V with respect to the mercury density ρ based on the result of FIG. The approximate line is based on the result of FIG. 3 above, and (x, y) = (ρ [mg / cc], P / V [W / cc]) = (400, 200 / 0.055), (550, 147 / 0.055) and (800, 102 / 0.055), and P / V = −4.33ρ + 5245. And the area | region of the upper right of an approximate straight line is a range with which Ra80 or more is satisfy | filled.

  In this embodiment, approximation is performed using linear approximation, but curve approximation such as a multi-order function, an exponential function, or the like may be performed. Actually, the function P / V (ρ) of Ra 80 or more is considered to be a lower chord curve as shown by the broken line in FIG. 3, but as shown below, the range of the pipe wall load P / V in actual use is as follows. Since it is limited, there is no problem with linear approximation within the limited range.

  However, when the tube wall load P / V is less than 1500 (that is, when the lamp power is too low), the arc tube temperature does not rise to the design temperature, so the internal pressure does not increase (the enclosed material does not evaporate sufficiently), In reality, it is difficult to realize Ra80. Further, it has been found that when the tube wall load P / V exceeds 3100, the lamp life is adversely affected, for example, devitrification occurs due to excessive power with respect to the internal volume. Therefore, it is desirable that the tube wall load is 1500 ≦ P / V ≦ 3100 (see the thick line in FIG. 4). Note that the upper limit of the mercury density is about 1000 mg / cc in consideration of the fact that when the encapsulation density is too high, unevaporated mercury blocks light from the arc and brightness decreases.

  From the above, in the ultra-high pressure mercury lamp of the lighting system using microwave power, by setting P / V ≧ −4.33ρ + 5245 and 1500 ≦ P / V ≦ 3100, a conventional arc length (for example, 0.9 mm) Degree) and lamp power (ie, lamp current), mercury density can be increased to improve color rendering and Ra80 can be achieved.

5A to 5C show emission spectra in the lamps of the conventional example, Example 1 and Example 2, respectively. Each lamp has the dimensions described above, and the mercury density, tube wall load (lamp power), and average color rendering index Ra are as shown in Table 1.

  As shown in FIG. 5A, the emission spectrum of the conventional example mainly consists of mercury emission lines, but as shown in FIGS. 5B and 5C, the emission spectra of Examples 1 and 2 are emission of the base portion other than the mercury emission lines. It can be seen that light is emitted over the entire visible range (380 to 780 nm). Ra is improved by improving the emission spectrum.

  As described above, in the ultrahigh pressure mercury lamp, Ra80 can be achieved by improving the color rendering by increasing the mercury density without increasing the arc length and without flowing an excessive lamp current. In both Examples 1 and 2, the luminous efficiency is about 70 lm / W, which is much higher than when a xenon lamp is used (about 30 lm / W). By applying the lamp of the embodiment to a light source device as shown in FIG. 2, a suitable light source for a projector can be obtained.

1. Lamp 2. Arc tube 3a, 3b. Electrodes 4a, 4b. 4. Molybdenum foil Antenna 6. Resonator 7. Connector 8. 8. Light outlet 9 Reflector 20. Light emitting unit 21. Discharge space

Claims (3)

An ultra-high pressure mercury lamp comprising an arc tube and a pair of electrodes protruding into the discharge space of the arc tube,
Regarding the mercury density ρ [mg / cc], power P [W], and internal volume V [cc] in the discharge space,
P / V ≧ −4.33ρ + 5245, and 1500 ≦ P / V ≦ 3100
And an average color rendering index Ra of 80 or more, and an ultra-high pressure mercury lamp that is lit by microwave power.   The ultra-high pressure mercury lamp according to claim 1, wherein the distance between the pair of electrodes is 0.5 mm or more and 3.0 mm or less. The ultra-high pressure mercury lamp according to claim 1 or 2,
A light source device comprising: an antenna for propagating microwave power to the ultra high pressure mercury lamp; and a resonator in which the antenna and the ultra high pressure mercury lamp are disposed.

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