JPH0737553A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To provide a metal halide lamp in which an emitting characteristic is prevented from worsening to ensure reliability even in the case that a distance between electrodes is shortened to make the electrode approach a point light source. CONSTITUTION:Electrodes 2, 2 connected to molybdenum foils 3 are secured with both end sealed parts of luminous tube tare 1, and its inside is sealed with luminous metal, Hg and argon, to constitute a metal halide lamp. Here is set an area S per lamp power in the both end sealed parts to a relation where 0.04cm<2>/W<=S<=0.06cm<2>/W.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal halide lamp which is composed of only an arc tube without an outer tube and is mainly used as a light source for video equipment or optical equipment.

[0002]

2. Description of the Related Art Conventionally, a short arc type metal halide lamp composed of only an arc tube without an outer tube has been used as a light source for an overhead projector (OHP), a projector, a liquid crystal projector and the like. Such a short arc metal halide lamp is often used in combination with a reflecting mirror for controlling the light emitted from the lamp, depending on its application. In this case, it is easier to control the emitted light by the reflecting mirror if the arc length is shortened so as to be closer to a point light source.

At present, in the case of a short arc metal halide lamp used for a liquid crystal projector, an encapsulating metal (for example, dysprosium or neodymium) having a color temperature close to that of a cathode ray tube of a TV and relatively good color reproducibility is used due to its application. The mainstream is selected and the distance between the electrodes is 5 mm. As mentioned above, this lamp is often constructed by combining with a reflecting mirror. In that case,
When deciding the reflecting surface of the reflector, set the focus to a point (1 point or 2 points).
Point). However, since the actual lamp does not have the light emitting portion as a point, a lamp having a short distance between electrodes and closer to a point light source is considered ideal because of the light distribution efficiency of the emitted light.

[0004]

By the way, in order to bring the lamp closer to the lamp of the point light source, the distance between the electrodes is changed from the current standard of 5 mm to 4 mm.
If the length is shortened to 3 mm or 3 mm, the coldest part of the arc tube (adjacent to the sealing part) becomes more dominant, and satisfactory emission characteristics (color reproducibility, spectral balance, etc.) cannot be obtained. Occurs. In particular, when the enclosed metal is a dysprosium / neodymium-based material, the vapor pressure of dysprosium / neodymium is relatively low, so that the problem is remarkable.

In order to solve this problem, it is conceivable to reduce the shape of the arc tube to increase the load on the wall surface.
The wall load is as high as 60 W / cm ² , and a further large increase in wall load may lead to a shortened lamp life. Moreover, even if the wall load is simply increased, the effect of cooling the temperature of the arc tube by the arc tube sealing portion is increased by the size of the arc tube being reduced, and the effect of increasing the wall load is the only effect on the emission characteristics. There is a problem that it cannot be obtained.

The present invention has been made in order to solve the above-mentioned problems in the conventional short arc metal halide lamp, and it is possible to prevent the deterioration of the light emitting characteristics even when the distance between the electrodes is shortened to bring the light source closer to the point light source. An object of the present invention is to provide a metal halide lamp with high reliability.

[0007]

In order to solve the above problems, the present invention comprises an arc tube only without an outer tube, and at least both ends of the arc tube have a main electrode and the main electrode. In a double-ended metal halide lamp having a sealing portion that supports and seals, the area S per lamp power of the sealing portions at both ends is in the range of 0.04 cm ² /W≦S≦0.06 cm ² / W. To be set to.

As described above, by setting the area S per lamp power of the sealing portion to 0.06 cm ² / W or less, even if the distance between the electrodes is reduced, the coldest portion of the arc tube by the sealing portion can be obtained. The cooling effect can be reduced, and the well-balanced emission characteristics at each wavelength can be maintained. Further, by setting the area S per lamp power of the sealing portion to be 0.04 cm ² / W or more, the temperature rise of the sealing portion can be suppressed, reliability can be secured, and the life can be extended.

[0009]

EXAMPLES Next, examples will be described. FIG. 1 is a plan view showing an embodiment of a metal halide lamp according to the present invention. In the figure, 1 is a quartz glass arc tube tare, having a maximum inner diameter of 8 mm, a maximum outer diameter of 10 mm, and an internal volume of about 0.4 cc. Reference numeral 2 denotes an electrode that is attached to the molybdenum foil 3 at both end sealing portions of the arc tube tare,
The distance between the electrodes 2 and 2 is set to 3 mm. Reference numeral 4 denotes a molybdenum external lead wire welded to the molybdenum foil 3, and 5 denotes a welding point thereof. 6 is the tip-off part of the exhaust pipe, and the total area of the sealing parts on both ends of the arc tube is 7.5 cm.
^{It is 2} .

In the arc tube, dysprosium iodide, neodymium iodide, and cesium iodide are filled as luminous metals, a predetermined amount of mercury is filled as a buffer gas, and 200 torr of argon is filled as a starting auxiliary gas. There is. Although not shown, one end of the arc tube configured in this way is integrally or removably attached to the bottom of a reflecting mirror having a reflecting surface such as a spherical surface, a spheroid, or a paraboloid of revolution. It constitutes a metal halide lamp with a reflector.

Then, the electronic ballast is used to perform AC lighting at a power of 150 W, and the wall load at that time is about
The area S per lamp power of the sealed part is 64 W / cm ² .
It is 05 cm ² / W.

In the present invention, the area S per lamp power of the sealing portion is set to 0.04 cm ² /W≦S≦0.06 cm ² / W. Next, an experiment conducted for this setting Will be described. First, as Experiment 1, a conventional standard arc tube tare with a maximum inner diameter of 9 mm, a maximum outer diameter of 11 mm, and an internal volume of about 0.5 cc was used. Lamps (150 W) having different values of 5 mm, 4 mm, and 3 mm were manufactured, and the emission characteristics were compared. Table 1 shows the relative ratio of background to 546 nmHg peak (546 nmHg peak / background).

[0013]

[Table 1]

As can be seen from Table 1, when only the distance between the electrodes is changed without changing the size of the arc tube, if the distance from the current mainstream is made shorter than 5 mm, the shorter the distance between the electrodes is, the higher the spectral intensity of Hg becomes. And the amount of light emitted by the enclosed halogen metal other than mercury decreases, resulting in a higher relative ratio. Note that this relative ratio is, as a guide, the emission state of the additives other than mercury (emission of R and B from the viewpoint of color reproducibility when light emission is divided into R, G, and B as a light source of a liquid crystal projector, etc. It has been obtained from past experiments that the light emission in the R and B regions is also satisfactory when the relative ratio is 3.0 or less.

The reason why the relative ratio becomes higher as the distance between the electrodes becomes shorter is that the size of the arc tube used in the experiment is optimized when the distance between the electrodes is set to 5 mm.
At a distance between electrodes of 4 mm or 3 mm, the temperature of the arc tube as a whole cannot be made uniform, and the enclosed halogen metal other than Hg gathers in the coldest part, and the vapor of the metal halide expected to emit light cannot be obtained. This is probably because only the emission peak of Hg, which has a high vapor pressure, is intensified.

Next, in Experiment 2, a lamp having a maximum inner diameter of 8 mm, a maximum outer diameter of 10 mm, an inner volume of about 0.4 cc, and the distance between electrodes changed to 5 mm, 4 mm, and 3 mm was prepared as in Experiment 1. When the light emission characteristics (relative ratio) were determined, the results shown in Table 2 were obtained.

[0017]

[Table 2]

As can be seen from Table 2, the distance between the electrodes is 4 mm.
Up to the above lamps, the emission characteristics were improved, but the lamps with an interelectrode distance of 3 mm did not provide satisfactory values. This is considered to be due to the fact that the light emission characteristics are dominated by the coldest part in the lamp with the electrode distance of 3 mm, and the value is not good. The wall load must be increased.

However, if the size of the arc tube is further reduced, the temperature of the entire arc tube can be increased, but the highest temperature part in the arc tube is also increased, which may cause early deformation of the arc tube, which affects the life of the arc tube. Probability is high.

Therefore, in Experiment 3, the area of the sealing portion, which is considered to affect temperature uniformity in the arc tube, was examined without changing the size of the arc tube used in Experiment 2. That is, the arc tube size was the same as in Experiment 2, the distance between the electrodes was 3 mm, and only the surface area of the sealing part was changed to change the area S per lamp power of the sealing part (150
W) was prepared and the emission characteristics (relative ratio) were determined. The results shown in Table 3 were obtained.

[0021]

[Table 3]

[0022] As can be seen from Table 3, the area S per lamp power of the sealing portion 0.058 cm ² / W (about 0.06 cm ² /
When it is W) or less, the emission characteristics are improved and well-balanced emission is obtained in each wavelength range. When the area of the sealing portion is reduced, the temperature rise of the sealing portion affects the reliability of the lamp. Therefore, in order to confirm the reliability, the temperature at the welding connection point between the molybdenum foil and the external lead wire was measured, and the results shown in Table 4 were obtained.

[0023]

[Table 4]

Assuming that the welding point temperature is 350 ° C. or lower based on past reliability confirmation results, etc., from Table 4, the area S per lamp power of the sealing portion is about 0.04 cm ² / W.
It can be seen that reliability can be obtained by the above.

Table 3 of Experiment 3 shows the experimental results for the electrode distance of 3 mm, and the relative ratios shown in Table 3 for the electrode distance of 4 mm or 5 mm. It is clear that it becomes even better, and even when the distance between the electrodes is shortened to 3 mm and the area is closer to a point light source, if the area S of the sealing portion is about 0.06 cm ² / W or less, it is good. It shows that a relative ratio can be obtained.

In Table 3 of Experiment 3, the arc tube size is maximum inner diameter 8 mm, maximum outer diameter 10 mm, and internal volume about 0.4 cc.
The experimental results are shown for a wall load of about 64 W / cm ² , but the wall load was changed to about 40-
Similar experimental results were obtained for the lamp with 100 W / cm ² .

From the above experimental results, according to the present invention, the area S per lamp power of the sealing portion is 0.04 cm ² /W≦S≦0.06.
It is set within the range of cm ² / W.

Further, the present invention is applied to a metal halide lamp generally called a short arc type, but the short arc type metal halide lamp is usually used.
When the maximum inner diameter is D and the distance between the electrodes is L, L / D is 1.
It is set to 0 or less.

[0029]

As described above on the basis of the embodiments,
According to the present invention, by setting the area per lamp power of the sealing portion in a specific range, even if the distance between the electrodes is shortened to approach a point light source, a highly reliable light emission characteristic with well-balanced emission characteristics at each wavelength is obtained. The metal halide lamp can be realized.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a metal halide lamp according to the present invention.

[Explanation of symbols]

 1 Tare of arc tube 2 Electrode 3 Molybdenum foil 4 Molybdenum external lead wire 5 Welding part 6 Tip off part

Claims (3)

[Claims] 1. A double-ended metal halide lamp comprising an arc tube alone without an outer tube, and having at least both ends of the arc tube at least a main electrode and a sealing portion for supporting and sealing the main electrode. In, the area S per lamp power of the sealing portion at both ends
Is set to 0.04 cm ² /W≦S≦0.06 cm ² / W, the metal halide lamp. 2. The metal halide lamp according to claim 1, wherein L / D is 1.0 or less, where D is a maximum inner diameter of the arc tube and L is a distance between electrodes. 3. The reflecting mirror having a reflecting surface such as a spherical surface, a spheroidal surface, or a paraboloid of revolution is integrally or detachably attached to one end of the arc tube. Metal halide lamp.