JP3275772B2 - Metal halide lamp - Google Patents

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 enclosing a sealed radiation source.

[0002]

2. Description of the Related Art Conventionally, an arc tube having a pair of electrodes inside and a metal halide, mercury, and a rare gas sealed in the outer tube, and a quartz tube surrounding the arc tube are conventionally provided. There is known a metal halide lamp having a transparent tube.

[0003] Usually, in such a metal halide lamp, the arc tube may be damaged at the end of its life, and the outer tube may be damaged due to the scattering of the arc tube material due to the damage, and the outer tube material may be scattered. Was. For this reason,
The light-emitting tube is surrounded by a light-transmitting tube in the outer tube, and the light-transmitting tube prevents the light-emitting tube material from scattering and colliding with the outer tube in the event of damage to the light-emitting tube.

However, in such a metal halide lamp, since the arc tube is surrounded by the light-transmitting tube, the temperature of the light-emitting tube during lighting is higher than that without the light-transmitting tube. There is a problem that the subsequent lamp restart time becomes longer, and it has been desired to reduce the restart time.

[0005]

To shorten the restart time, it is conceivable to enclose a radioactive substance. However, many attempts have been made to enclose a radioactive substance in an arc tube. JP-A-3-171546 and JP-A-4-3
No. 42950 discloses a quartz arc tube in which a carrier made of quartz is coated with a radiation source, and a thin film made of quartz is applied on the radiation source so as to have a radiation dose of 0.1 to 1.0 kBq. A metal halide lamp enclosing a radiation source is disclosed.

However, the relationship between the restart time and the encapsulated radiation dose is not mentioned, and it is not easy to predict the optimum radiation dose for shortening the restart time of the arc tube surrounded by the translucent cylinder. Was.

When translucent alumina having a melting point higher than that of quartz is used as the arc tube material, the load on the arc tube can be increased as compared with that of a quartz arc tube, and the lamp efficiency and the like can be significantly increased. Can be.

However, when such an arc tube made of translucent alumina is used, the temperature of the inner wall of the arc tube is higher than that of a quartz arc tube, and a light transmission for preventing damage to the outer tube. If a sex cylinder is used, the temperature will be even higher.
This not only greatly affects the restart time, but also causes a problem in that the use of a sealed radiation source made of quartz causes a reaction with the inner wall of the arc tube, causing a sharp rise in the lamp voltage and a decrease in the luminous flux maintenance factor. Was.

On the other hand, it is disclosed in Japanese Patent Publication No. 60-34222 or the like that a sealed radiation source containing alumina as a main component as a carrier is sealed in an arc tube made of quartz. When it is sealed in the tube, it reacts with quartz of the arc tube material at a high temperature, and has a problem that lamp characteristics, color characteristics, and luminous flux maintenance rate are greatly affected.
Therefore, a lamp in which such a sealed radiation source of a carrier containing alumina as a main component is enclosed in an arc tube made of quartz has not been put to practical use.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a metal halide lamp having an arc tube made of alumina and a light-transmitting tube surrounding the arc tube. It is an object of the present invention to obtain a metal halide lamp capable of achieving stable lamp characteristics during lighting and improving restart characteristics.

[0011]

A metal halide lamp according to the present invention has a pair of electrodes inside an outer tube and a metal halide, mercury, a rare gas, and a radiation source sealed inside. A metal halide lamp comprising a light-emitting tube made of transparent alumina and a light-transmitting tube surrounding the light-emitting tube, wherein the radiation source has an average crystal grain size of 15 μm or less.
The above-mentioned carrier made of alumina is coated with a radioactive substance,
In addition, non-radioactive material consisting of alumina on the radioactive material
It has a configuration in which a thin film is coated .

[0012] Thus, restarting can be performed in substantially the same time as a metal halide lamp that does not use a light-transmitting tube. Further, since the sealed arc radiation source is made of alumina of the same material as the arc tube, the reaction between the radiation source and the inner wall of the arc tube can be suppressed, and stable lamp characteristics can be obtained during lighting. Furthermore, the reaction between the encapsulated halide and the radiation source can be made smaller.

[0013]

[0014]

[0015]

[0016]

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment 15 of the present invention will be described.
As shown in FIG. 1, the 0 W metal halide lamp includes a light-emitting tube 2 made of a light-transmitting alumina having a pair of electrodes 1 inside an outer tube 3, and a light-transmitting lamp provided to surround the light-emitting tube 2. A cylinder 4 is provided. One end of the electrode 1 is provided with an electrode coil, and one end of each of the pair of electrodes 1 is provided in the arc tube 2. The other end of the electrode 1 is led out of the arc tube 2 to form external lead wires 1a and 1b.

The external lead wires 1a and 1b pass through metal plates 5 provided so as to close the openings at both ends of the translucent cylinder 4, respectively. One end of the outer tube 3 is sealed by a stem 6. Of the stem wires 6a and 6b derived from the stem 6, one of the stem wires 6b is connected to the external lead wire 1b of the arc tube 2, and the other of the stem wires 6a.
Is connected to the external lead wire 1 of the arc tube 2 via a power supply line 7.
a is connected.

In the arc tube 2, a sealed radiation source 8 described later, a predetermined amount of mercury, and argon as a starting rare gas are sealed, and dysprosium, holmium, thulium, thallium, sodium, lithium as a metal halide. Of iodide is enclosed. The inside of the outer tube 3 is filled with nitrogen. The outer tube 3 sealed by the stem 6
Is provided with a base 9 at one end thereof.

Next, the relationship between the radiation dose of the sealed radiation source and the restart time in the metal halide lamp of the present embodiment was measured and is shown in FIG.

As shown in FIG.
At Bq, the restart time was 25 minutes.
It was 15 minutes at 0 kBq and 8 minutes at 15 kBq. The pulse voltage applied at this time is 2.5 kV (width at 90% peak voltage is 1 μsec).

As is apparent from FIG. 2, a radiation dose of at least 1.0 kBq is required to make the restart time of the lamp within 15 minutes (the value in many existing metal halide lamps). Also, when the radioactive substance has a half-life of 0.5 years or more and is handled in the form of a sealed radiation source,
It is regulated to be 37 MBq or less.

The radioactive substance used here is ¹⁴⁷ Pm (promethium 147), and its half-life is 2.62.
Year. When ¹⁴⁷ Pm is used as the radiation source to be encapsulated, the radiation dose to be enclosed is 3.7 kBq to 37 MBq.
It is preferable that Also, other radiation sources may be used.

As shown in FIG. 3, the sealed radiation source 8 according to the present embodiment has a carrier 10 made of alumina covered with a radiation layer 11 made of alumina containing a radioactive substance.
Further, a thin film of the non-radiation layer 12 of alumina is coated thereon. The radiation dose of this radiation source 8 is 15 kBq
It is.

Next, a lamp in which a radiation source is coated on a carrier made of quartz in an arc tube 2 made of translucent alumina, and a sealed radiation source in which a thin film made of quartz is applied on the radiation source, is enclosed in a lamp. Similarly, an average crystal grain size of 10 μm, 15 μm, 20 μm, 30 μ
A lamp in which a radiation source containing alumina as a carrier was sealed was used, and a change in lamp voltage and a luminous flux maintenance ratio during 6000 hours of operation of the lamps were examined. FIG. 4 shows the results.
In FIG. 4, the sealed radiation source made of quartz is denoted by the symbol A, and the average crystal grain size of the sealed radiation source made of alumina is 10%.
The symbol of B is denoted by B, the symbol of 15 μm in average crystal diameter is denoted by C, the symbol of 20 μm in average is denoted by D, and the symbol of 30 μm in average is denoted by E.

The lamp voltage of the lamp in which the sealed radiation source made of quartz is sealed rises sharply by 2000 hours of operation, and the luminous flux maintenance factor also drops to about 70%.
At 0 hours, it is 50%. In addition, the particle size is 10 μm
Lamp sealed with a sealed radiation source made of alumina
As compared with a sealed radiation source made of quartz, the lamp exhibited higher characteristics, but had a lamp voltage rise of 15 V and a luminous flux maintenance rate of 65% after 6000 hours of operation. In contrast, the lamp in which the sealed radiation source made of alumina having a particle size of 15 μm was sealed had a lamp voltage rise of 13 V and a luminous flux maintenance rate of 70% after 6000 hours of operation. The lamp in which a sealed radiation source made of alumina having a particle size of 20 μm was sealed had a lamp voltage rise of 10 V and a luminous flux maintenance factor of 75% after 6000 hours of operation. Further, the lamp in which a sealed radiation source made of alumina having a particle size of 30 μm was sealed had a lamp voltage rise of 7 V and a luminous flux maintenance ratio of 78% during 6000 hours of operation.

Next, FIG. 5 shows the relationship between the luminous flux maintenance factor and the crystal grain size after the lamp has been operated for 6000 hours in which a radiation source containing alumina having a different crystal grain size as a carrier is sealed.

As is apparent from FIG. 5, a luminous flux maintenance factor of 70% or more is secured by setting the crystal grain size of alumina to 15 μm or more. Conventionally, the luminous flux maintenance rate of a metal halide lamp having an arc tube made of quartz is 70% in about 6000 hours.
In order to obtain a luminous flux maintenance factor equal to or higher than that of the conventional lamp, it is preferable that the crystal grain size of alumina is 15 μm or more. Therefore, it was confirmed that stable lamp characteristics can be obtained by using alumina as the carrier of the radiation source and setting the crystal grain size to 15 μm or more.

[0029]

As described above, the present invention can provide a metal halide lamp capable of shortening the restart time and obtaining stable lamp characteristics during lamp operation.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional front view of a metal halide lamp according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the encapsulated radiation dose and the restart time.

FIG. 3 also shows a sealed radiation source.

FIG. 4 is a diagram showing lamp characteristics during lighting;

FIG. 5 is a diagram showing lamp characteristics during lighting;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrode 2 arc tube 3 outer tube 4 translucent cylinder 5 metal plate 6 stem 7 power supply line 8 sealed radiation source 9 base 10 carrier 11 radiation layer 12 non-radiation layer

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuo Takeda 1-1, Kochi-cho, Takatsuki-shi, Osaka Prefecture Inside Matsushita Electronics Corporation (72) Inventor Yoshiharu Nishiura 1-1-1, Kochi-cho, Takatsuki-shi, Osaka Matsushita Electronics Inside Kogyo Co., Ltd. (72) Inventor Koichi Sugimoto 1-1, Yukicho, Takatsuki-shi, Osaka Prefecture Inside Matsushita Electronics Co., Ltd. (72) Inventor Shigefumi Oda 1-1-1, Kochicho, Takatsuki-shi, Osaka Matsushita Electronics (56) References JP-A-4-167350 (JP, A) JP-A-57-134858 (JP, A) JP-A-2-201862 (JP, A) (58) Fields surveyed (Int .Cl. ⁷ , DB name) H01J 61/54

Claims (1)

(57) [Claims] 1. An outer tube having a pair of electrodes inside, and a metal halide, mercury, a rare gas, and radiation inside.
A metal halide lamp including an arc tube made of a translucent alumina in which a radiation source is enclosed, and a translucent tube surrounding the arc tube, wherein the radiation source has an average crystal grain size of 15 μm.
m or more of alumina is coated with radioactive material.
And non-radiation comprising alumina on the radioactive material
Metal halide lamp characterized by being coated with a conductive thin film .