JPH07122238A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To easily obtain a lamp which emits a stable green light even at the initial stage of lighting up during the lifetime period by encapsulating cesium iodide and thallium iodide in the lamp in a specified ratio by weight. CONSTITUTION:Electrodes 2, 3 are furnished at the ends of a light emitting tube 1, and together with rare gas for starting and mercury, thallium iodide (T1I) is encapsulated in an amount of 0.1-2mg/cc. Therein also cesium iodide (CsI) is encapsulated in such a content relative to thallium iodide by weight as 0.05<=CsI/T11<=2. Thus a long life lamp can be obtained easily through the encapsulation of cesium iodide which has a low energizing voltage and presents an effect of stabilizing arcs.

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 containing thallium iodide.

[0002]

2. Description of the Related Art A metal halide lamp is constructed by enclosing a starting rare gas such as metal halide, mercury and argon gas in an arc tube having electrodes at both ends.
Such a metal halide lamp obtains a lamp suitable for the purpose by utilizing the emission spectrum determined by the enclosed metal halide. The life is determined by the reaction between the metal halide in the high temperature and high pressure state during lighting and the quartz glass or alumina ceramics used as the electrode or arc tube material.
000 hours and 9000 hours with vertical lighting are common.
A green lamp using thallium iodide having a strong emission at 535 nm has been commercialized in order to add a light color accent to the above facility lighting.

[0003]

However, when thallium iodide is used alone, the arc tube is blackened at an early stage during its life, for example, within 1000 hours of lighting, and the luminous flux maintenance factor falls below 50%. It cannot be used as a facility lighting lamp. Therefore, Japanese Patent Publication No. 50-31742 discloses a method of encapsulating metal Th in an arc tube to improve lamp characteristics.

However, since the metal Th is a radioactive substance, special care must be taken when handling it. Further, the lamp in which the metal Th is enclosed has a problem that the light green color is light for 1 hour to about 200 hours of lighting, and the characteristic as a green lamp is hard to appear.

[0005]

A metal halide lamp according to the present invention is provided with electrodes at both ends of an arc tube, and a rare gas for starting,
0.1 mg / c of thallium iodide (TlI) with mercury
c to 2 mg / cc, and cesium iodide (C
sI) is encapsulated within the range represented by the following formula in a weight ratio to thallium iodide. (Equation) 0.05 ≦ CsI / TlI ≦ 2 With such a configuration, it is possible to easily obtain a metal halide lamp having a stable green light color from the initial lighting during the life period.

[0006]

The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows a horizontally lit 150 W metal halide lamp according to a first embodiment of the present invention.
In the figure, 1 is an arc tube made of quartz glass and having an inner diameter of 12 mm and an internal volume of about 2.9 cc, and a pair of electrodes 2 and 3 are sealed at both ends. 4 is 20 mm inside diameter, 2 outside diameter
A 3 mm cylindrical quartz glass outer tube has a structure that hermetically holds the arc tube by sealing both ends.

Here, the present inventor, when conducting a study for improving the color of light, immediately after completion, a conventional lamp had a sputter with a diameter of about 5 to 20 mm on the inner surface of the arc tube, and a life test was conducted. It was found that the spatter disappeared in the lamp. This is considered to be a phenomenon that occurred because the metal Th was not completely evaporated immediately after the lamp was completed.
It is thought that this spatter has a bad influence on the initial lamp characteristics, and therefore, a metal-free enclosure, that is, mercury 19
mg, thallium iodide 1 mg, starting argon gas 25
A lamp containing 1 mg of tall and cesium iodide was manufactured. After aging for 1 hour, the characteristics were measured with horizontal lighting. Efficiency was 60 lm / w, color temperature was 7000K,
The chromaticity coordinate (x, y) is (0.242, 0.582), and when the chromaticity is calculated, the color purity is 56% and the dominant wavelength is 531n.
m was a good result. The spectral distribution chart is shown in FIG. 2, and as can be seen from the figure, the light emission at 535 nm appears strongly.

Incidentally, in the conventional example, 0.4 mg of metal Th is enclosed in place of the above cesium iodide, but in the characteristic measurement after aging for 1 hour, the efficiency is 58 lm / w, the color temperature is 7,000 K, and the chromaticity coordinate (x , Y) is (0.260,0.
494), and only color purity of 32% and dominant wavelength of 524 nm were obtained. This spectral distribution diagram is shown in FIG. 3, and although emission at 535 nm appears, a continuous component is seen over the entire visible range, which indicates that there is a problem as a monochromatic light source.

FIG. 4 shows the chromaticity points of the two on chromaticity coordinates. In the figure, A represents an embodiment of the present invention and B represents a conventional example, and the difference between the two is clear from the chromaticity coordinates. Further, when the light color was visually confirmed, it was confirmed that the conventional example had a light green color.

Next, in order to investigate the relationship between the lighting time and the color characteristics, five of each were manufactured. The result is shown in FIG.
In the figure, A shows an embodiment of the present invention and B shows a conventional example. As can be seen from the figure, when the present invention is used, color purity is 5 after 1 hour of lighting
5% and does not change within 200 hours. on the other hand,
In the conventional example, the color purity is only 28% in one hour of lighting, and it takes about 170 hours to saturate the color purity to 55%. For this reason, the metal Th reacts with iodine in the arc in the arc tube to become thorium iodide with continuous light emission, and part of it becomes a thin metal thin film with a heat retaining effect to cover the inner surface of the arc tube, resulting in a spectrum. The distribution shows a spread. As the reaction of the Th metal progressed, the metal thin film also disappeared, and it took about 170 hours for the heat retention effect to decrease and the emission of thorium iodide, which has a lower vapor pressure than thallium iodide, to decrease. During that time, it is considered that the spectral distribution shifted from the continuous light component to the monochromatic light component, and as a result, the color characteristics were saturated.

Further, according to the present invention, since cesium iodide which does not cause the reaction as described above is used, it is considered that the color characteristics are sufficiently stable and saturated even after aging for 1 hour.

Further, in order to investigate the relationship between the enclosure ratio of cesium iodide to thallium iodide and the lamp characteristics,
Using the arc tube of FIG. 1, 1 mg of thallium iodide, 19 mg of mercury and 25 Torr of argon gas were charged and CsI /
A total of 35 lamps with TlI changed from 0 to 4.0
I made a lamp. Table 1 shows the measurement results after aging for 1 hour.

[0013]

[Table 1] In Table 1, the efficiency and color purity decrease with the increase of the filling amount ratio. This means that cesium iodide has a lower excitation voltage than thallium iodide, and iodide with lower luminous efficiency with the increase of the filling amount ratio. This is because the emission of cesium is dominant, and it was found that the practical range is 2.0 or less.

On the other hand, the enclosed amount of thallium iodide is 535 nm.
When it is too small, the light emission of mercury becomes strong, and when it is too large, the light emission of 535 nm causes self-absorption, and the color purity is lowered, which is not preferable as a green lamp.

Therefore, an appropriate range of the amount of thallium iodide enclosed is 0.1 mg / cc≤TlI≤2.0 mg / cc.

Next, in order to investigate the life characteristics of the product of the present invention,
Among the lamps in Table 1, CsI / TlI having a CsI / TlI of 0 to 2.0 were horizontally lit at 150 W, and the relationship between the lighting time and the luminous flux maintenance factor was examined. The result is shown in FIG. As can be seen from the figure, the higher the encapsulation ratio of cesium iodide, the higher the luminous flux maintenance factor. This is because cesium iodide stabilizes the arc and suppresses the reaction between the encapsulation and quartz glass. It seems to be because. Lighting time 600
Considering a luminous flux maintenance factor of 60% or more at 0 hours as a practical level, 0.05 ≦ CsI / TlI is required. Therefore,
A suitable CsI / TlI encapsulation ratio is 0.05 ≦ CsI / TlI ≦ 2.0.

In the above embodiment, a horizontal lighting lamp having a quartz glass outer bulb is described.
The lighting direction and outer spherical shape to which the present invention can be applied are not limited to these.

[0018]

As described above, according to the present invention, in addition to thallium iodide, cesium iodide, which has a low excitation voltage and has an effect of stabilizing the arc, is enclosed. It is possible to easily obtain a long-lived metal halide lamp having a green light color.
Further, since the metal Th, which is a radioactive substance, is not used, its special handling becomes unnecessary.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a metal halide lamp according to the present invention.

FIG. 2 is a spectral distribution diagram of an example according to the present invention.

FIG. 3 is a spectral distribution chart of a conventional example.

FIG. 4 is a chromaticity diagram of an example according to the present invention and a conventional example.

FIG. 5 is a diagram showing a relationship between lighting time and color purity.

FIG. 6 is a diagram showing a relationship between a lighting time and a luminous flux maintenance factor.

[Explanation of symbols]

 1 Quartz glass 2 Electrode 3 Electrode 4 Quartz glass outer tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinfumi Taniguchi No. 1 Inobaba-cho, Nishinosho, Kichijoin, Minami-ku, Kyoto

Claims (1)

[Claims] 1. Thallium iodide (TlI) is added together with a rare gas for starting and mercury in an arc tube having electrodes at both ends in an amount of 0.1.
A metal halide lamp filled with mg / cc to 2 mg / cc, wherein cesium iodide (CsI) is filled in a weight ratio with respect to the thallium iodide in a range of 0.05 ≦ CsI / TlI ≦ 2. A metal halide lamp that is characterized by