JPH0340463B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a metal halide lamp in which a radioactive substance is sealed in the arc tube to improve starting characteristics.

[Technical background of the invention and its problems]

It has been known to use thorium (Th) or thorium oxide (ThO ₂ ) as an emitter in metal halide lamps in order to facilitate their starting. In addition, these thorium reacts with the halogen of the metal halide sealed in the arc tube to form thorium halide, which emits light and suppresses the light emission of other highly efficient fillers, causing a decrease in luminous flux. In order to address the drawbacks such as an increase in lamp voltage, there is also a proposal (Japanese Patent Application Laid-Open No. 126248/1983) to use an emitter (radioactive substance) with a short half-life that does not react with halogen etc. in place of thorium. Furthermore, in order to make it easier to handle radioactive substances with short half-lives from the viewpoint of safety, a ceramic body in which radioactive substances are dispersed has been proposed (Japanese Patent Laid-Open No. 56-126248). However, the ceramic body that disperses radioactive materials is
Normally, discharge lamps contain components such as alkali metals and alkaline earth metals such as sodium oxide and calcium oxide that are harmful to discharge lamps, and when a ceramic body is enclosed in an arc tube, it may cause damage due to long-term lighting. The alkali metals and alkaline earth metals undergo a substitution reaction with halides of rare earth metals such as scandium Sc and disprosium Dy, and the luminescent metals such as Sc and Dy, whose oxides are stable, are
Sodium oxide _Na2O , calcium oxide CaO
Sc 2 O 3 , which is a stable oxide that can be substituted with Na and Ca, such as Sc ₂ O ₃ ,
This resulted in disadvantages such as generation of Dy ₂ O ₃ and the like, resulting in a decrease in its effective amount and a decrease in luminous efficiency.

[Purpose of the invention]

The present invention has been made to address the above-mentioned drawbacks.
An object of the present invention is to provide a metal halide lamp which is easy to start and has little reduction in luminous efficiency by enclosing a radioactive substance-dispersed ceramic body in an arc tube.

[Summary of the invention]

The present invention is characterized in that the ceramic body in which a radioactive substance is dispersed and supported in the arc tube along with a starting rare gas, mercury, and a luminescent metal has impurities contained therein replaced with the luminescent metal.

[Embodiments of the invention]

Hereinafter, details of the present invention will be described with reference to Examples.

When naturally occurring zeolite is fired into granules with a diameter of about 1 to 3 mm, it has the general formula M ₂ / _o O.
Al ₂ O ₃・xSiO ₂・yH ₂ O (where M is a metal cation, n is a valence, x and y
For example, a ceramic such as Na ₁₂ (AlO ₂ ) ₁₂ (SiO ₂ ) ₁₂ ]·27H ₂ O is obtained.

Next, when this material is washed in an ammonium chloride NH ₄ Cl solution, Na ions are replaced with NH ₄ ions, resulting in (NH ₄ ) ₁₂ [(AlO ₂ ) ₁₂ (SiO ₂ ) ₁₂ ]・27H ₂ O. .

When this material is calcined at about 800° C., NH ₃ is scattered and H-type zeolite H ₁₂ [(AlO ₂ ) ₁₂ (SiO ₂ ) ₁₂ ]·27H ₂ O is formed. However, since some Na ions still remain in this product, it is further immersed in the vapor of a luminescent metal halide, such as scandium iodide ScI ₃ , which is sealed in the arc tube.

That is, the H-type zeolite is placed in, for example, a quartz container, evacuated, and then ScI ₃ is sealed,
By heating at around 1000°C for several hours, the remaining Na ions can be sufficiently replaced with Sc ions to the extent that they do not adversely affect the characteristics of the arc tube.

In this way, the zeolite whose components harmful to the arc tube have been replaced with luminescent metals is then immersed in, for example, a ¹⁴⁷ pm hydrochloric acid solution, which is a type of radioactive substance, and the hydrogen ions contained in the zeolite are replaced with ¹⁴⁷ pm ions. Alternatively, the ¹⁴⁷ pm atoms can penetrate between the zeolite particles and become trapped. The zeolite impregnated with the radioactive substance in this way is then fired again at around 800°C for about 20 minutes to scatter off the chlorine ions and obtain a radioactive substance-dispersed zeolite body.

This material can be further treated with alumina, for example, as required.
Immersed in a water-soluble paste mainly composed of silica, etc.
After drying, it can be fired at around 1,000°C to form a surface layer that does not contain radioactive substances, making it even safer to handle.

The zeolite impregnated with the radioactive substance ¹⁴⁷ pm thus formed was mixed with 50 mg of mercury, 25 torr of argon gas, and each of the luminescent metals scandium and sodium in an amount such that ¹⁴⁷ pm was 5 × 10 ^-6 mg (5 microcuries as the amount of radioactivity). A total of 30 mg of iodide is sealed in a quartz arc tube with an inner diameter of 20 mm and a distance between main electrodes of 42 mm, and this arc tube is sealed inside an outer tube filled with vacuum or inert gas to make a 400 W metal halide lamp.

This metal halide lamp, for example,
It is used by the lighting circuit as shown in the figure. That is, a series circuit consisting of a resistor 6, a bimetallic switch 7, and a glow lighting tube 8 is connected in parallel with the luminous tube 2 in the discharge lamp outer bulb 1 shown by a dotted line, and from the midpoint between the lighting tube 8 and the bimetallic switch 7, It is connected to the starting auxiliary electrode 5 via a resistor 9. The arc tube 2 has a pair of main electrodes 4a, 4b, which are ultimately connected to a power source 11 via a ballast 10. In such a lighting circuit, when a voltage is applied to the lamp, a current first flows through the resistor 6, the bimetallic switch 7, and the glow lighting tube 8.
The glow lighting tube 8 operates to interrupt the circuit. This intermittent current generates a kick voltage from the ballast 10.

On the other hand, charged particles with strong energy are generated from the radioactive substance-dispersed ceramic body 3 sealed in the arc tube 2 and ionize the starting rare gas.

As a result, a minute current flows between the starting auxiliary electrode 5 and one of the main electrodes 4a when a pulse is applied, and grows to start the arc tube and light it up.

The starting time at this time was almost instantaneous and required only a very short time.

In particular, the rate of decrease in luminous efficiency is about 20% even after 5000 hours of lighting, which is the same lighting time as a conventional lamp in which the impurity sodium contained in zeolite, which is a ceramic body that disperses radioactive substances, is not replaced with luminescent metal. Luminous efficiency decreases after 50%
It was much better than that.

Although zeolite was used as the ceramic body in the above embodiment, the present invention is not limited to this, and the main component may be zeolite.
Mullite, which is 3Al ₂ O ₃ 2SiO ₂ , the main component is Al ₄
Kaolinite, whose main component is (OH) ₈・Si ₄ O ₁₀
Halloysite, which is Al ₄ (OH) ₈ · Si ₄ O ₁₀ · nH ₂ O, etc., can be similarly applied if its main component is harmless when it is enclosed in the arc tube of a metal halide lamp. In addition, in the present invention, impurities contained in the ceramic body itself refer to impurities that, when the ceramic body is sealed and used in an arc tube, replace luminescent metals and allow the formation of more stable oxides of luminescent metals.
This refers to substances that reduce the effective amount of luminescent metal in the arc tube and reduce luminous efficiency.The range of impurities differs depending on the type of luminescent metal, but in general, alkali metals and Often alkaline earth metals. On the other hand, as a luminescent metal
Rare earth metals including Sc, Al, Sn, etc. are particularly suitable, and halides are preferable for sealing in the arc tube.

Furthermore, the radioactive substances are not limited to the above ¹⁴⁷ pm, but include ¹⁴ C, ²² NA, ⁶⁰ Co, ⁵⁵ Fe, ⁴⁵ Ca, ⁶⁰ Ni,
⁶⁵ Zn, ⁵⁴ Mn, ⁹⁰ Sr, ¹⁰⁶ Ru, ¹¹⁰ Ag, ¹²⁵ Sb, ¹³⁴ Cs, ¹³⁷ C
s,
¹³³ Ba, ¹⁴⁴ Ce, ¹⁵⁴ Eu, ¹⁵⁵ Eu, ¹⁹⁵ Au, ²⁴⁰ Tl, ²²⁷ Ac,
²⁴¹ Am, ²⁴² Cm, ²⁴⁴ Cm, ²⁵² Cf, ²¹⁰ Pb, ²²⁶ Ra, ²²⁸ Ra,
Those with a half-life of 0.5 to 10 years, such as ²²⁸ Th, are preferable.

This is because if the half-life is less than 0.5 years, the decay will be rapid and the lamp will complete its decay over the course of its life, resulting in a significant drop in starting performance.

On the other hand, if the half-life is too long, exceeding 10 years,
This is because the attenuation of radiation progresses slowly, which can be harmful in terms of safety.

〔Effect of the invention〕

As detailed above, in the metal halide lamp of the present invention, the impurities contained in the ceramic body dispersively supporting the radioactive substance are replaced with a luminescent metal, so that it is easy to start, and
Decrease in luminous efficiency can also be reduced.

[Brief explanation of drawings]

The figure shows a lighting circuit for a metal halide lamp, which is an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Outer tube, 2... Arc tube, 3... Radioactive substance dispersed ceramic body, 4a, 4b... Main electrode, 5...
... Starting auxiliary electrode, 6 ... Resistor, 7 ... Bimetal switch, 8 ... Glow lighting tube, 9 ... Resistor, 1
0... Stabilizer.

Claims (1)

[Scope of Claims] 1. A metal halide lamp in which a radioactive substance-dispersed ceramic body is enclosed in an arc tube together with a starting rare gas, mercury, and a luminescent metal, wherein a part of the components of the ceramic body are replaced with the luminescent metal. A metal halide lamp characterized by: 2. The metal halide lamp according to claim 1, wherein the luminescent metal contains at least one of a rare earth metal, aluminum, and tin.