JPS6034220B2 - metal vapor discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal vapor discharge lamp in which the electron emitting material (emitter) sealed in the arc tube is changed.

Generally, in order to make metal halide lamps easier to start, thorium (Th) or thorium oxide (Tho2) is mixed or coated on the electrodes and sealed in the arc tube as an emitter, and the Q decay of this thorium induces The electrons generated during this process are used as seeds to start the discharge.

In other words, conventional metal halide lamps of the 400W type use thorium oxide coated on the electrodes, and it is known that thorium has a half-life T of 1.4 x 1010 years. In addition, the number of thorium atoms in 9 of thorium oxide 20 is approximately 4.54×1. , and the total decay constant of thorium is 1.6×10-1 ec
-1, it is thought that approximately 72 pieces of thorium in thorium oxide 209 are disintegrated per second on average, and assuming that one electron is created for each Q particle, the initial number of electrons per second is Q will be approximately 72. On the other hand, the average starting time 7 from when a voltage is applied to the lamp until it starts is the probabilistic average time of when the initial electrons are emitted until the start of discharge, and this average starting time 7 is:
By the function of the initial number of electrons Q per second emitted from the electrode and the probability P that one emitted electron starts a discharge,
・ ...[Given in 11.

Therefore, Q in thorium oxide of 9 of 20 is 72, and P is thought to be approximately 0.5, so in this type of lamp? This becomes 0.02 nail sand, and discharge starts instantly after voltage is applied.

On the other hand, in the case of a lamp that does not use thorium at all, the only source that supplies the initial number Q of electrons per second is natural radiation such as cosmic rays, and natural radiation occurs only once every few seconds. It will be about Q30.1, which will be 722 inkstone sand.

In other words, the average starting time for lamps that do not use thorium is about 2 hours, and it will not start unless you wait 2 steps after voltage is applied, and some lamps may take more than 1 minute after voltage is applied. There is a 5% chance that the engine will not start. moreover,
In particular, lamps with a high discharge starting voltage require a pulse voltage at the time of starting, and since such lamps have a probability P of starting discharge only while the pulse voltage is applied, thorium is not used in such lamps. For those that do not, the average value is about P30.01, and therefore it reaches around 3100 sand, so it takes an average of 20 minutes after voltage application.
In some cases, discharge may not start for nearly an hour.

In this way, the use of thorium facilitates the initiation of discharge and contributes to shortening the starting time; however, as mentioned above, thorium has a relatively long half-life of 1.4 x 10 years; Furthermore, in order to ensure reliable startup even at the end of life after 5 years, it is desirable to emit at least one electron during one cycle, so even after 5 years, the number of decays per second - 50~ Therefore, when it is sealed in the form of thorium oxide, an amount of at least about 20.9 is required.

However, 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 light intensity. In addition, the vapor of thorium halide causes an increase in lamp voltage during the life of the lamp. In this way, sodium reacts with halogen and disappears during its life, so if you want to keep this type of lamp reliably and smoothly started even at the end of its life, say 1,000 field hours, an even larger amount is required. Although thorium oxide is required, increasing the amount of thorium oxide has the problem of further decreasing the light output. This invention was made based on these circumstances, and its purpose is to use an emitter with a short half-life that does not cause a chemical reaction with halogen etc. in place of thorium, thereby reducing the amount of emitter used. In addition, it is an object of the present invention to provide a metal vapor discharge lamp in which a sufficient number of initial electrons can be obtained for starting, and a reduction in light intensity during the life of the lamp can be prevented.

An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows the arc tube of a metal halide lamp, where 1 is the arc tube bulb made of quartz glass, 2, 2 are sealing parts formed at both ends, 3, 3 are the main electrodes, and 4 is the auxiliary electrode for starting. , 5
, 5 and 6 are sealing parts, 2 and 2 are sealed metal foil conductors, and 7, 7 and 8 are external lead wires.

The bulb is filled with a starting rare gas such as scandium iodide (Scl), sodium iodide (Nal), mercury, and argon, as well as a radioactive substance. The half-life of radioactive substances is about 0.3 to about 1,000, and the amount of radioactivity per arc tube is regulated to 1 microcurie or less.

Such radioactive substances include sodium (22N
a), Calcium 45 (45Ca), Manganese 54 (5
4Mn), iron 55 ($Fe), cobalt 60 (Co)
, zinc 65 (65Zn), ruthenium 106 (1$Ru
), silver 110 (110Ag), antimony 125 (12
5Sb), barium-133 (13Ba), cesium-13
4 (134Cs), cerium 144 (144Ce), promethium 147 (147Pm), eurobium 155
(1 South Eu), gold 195 (195Au), thallium 20
4 (2o4TI) and curium 242 (242Cm).

At least one of these radioactive substances is sealed within the arc tube bulb. We will now discuss the reason why the half-life of radioactive substances is more than about 0.5 years and less than about 1 year.

Generally, the lifespan of metal vapor discharge lamps, including metal halide lamps, is about 1000 field hours, and if it is assumed that they are used for 5 hours a day, they will operate normally for about 5 years. In this respect, if a radioactive substance has a half-life of about 0.3K or more, after 5 years it will be (1/2) = 1/1000, so the decay of the radioactivity will not be completed completely, so the starting function will be maintained. can. On the other hand, if the radioactive substance has a half-life of 0.5 at the end of the year, the attenuation is rapid and will be completed during the life of the lamp, resulting in a significant drop in starting performance at the end of the life of the lamp. On the other hand, if the half-life is too long, it takes time for the radiation to decay, resulting in poor startability, and it becomes necessary to encapsulate a large amount of radioactive material.

It is desirable for radioactive substances to decay to the extent that they do not have a negative impact on the living environment in about 10 kings, and if we use the idea that they decay to 1/100 in 10 kings as a rough guide, their half-life is approximately 1 Become the mountain king. Furthermore, even if radioactive materials are handled in the form of a sealed source, the amount of radioactivity per arc tube is selected to be 1 microcurie or less.

However, the purpose of the present invention is to reduce the amount of such radioactive substances enclosed as much as possible, and therefore, we have considered how much of the above-mentioned radioactive substances are required. View.

As mentioned above, assuming that at least one radiation is emitted during one cycle, 50 to 60 decays are required per second, and considering the safety factor, it is assumed that one decay per second is required. Then, in the case of a radioactive element with a half-life of 0.5K, approximately 2.3 x 1 elements will be required after 5 years.

This means that 2.3 x 1 and 2 pieces are required at the beginning of packaging. In addition, in the case of a radioactive element with a half-life of 1, approximately 4.5 x 10 elements will be required after 5 years.
The original size was also 4.5 x 1. Requires pcs. The number of these elements is the number of elements of the subordinate thorium, which is 4.54 x 1 and 9.
The amount of the radioactive substance of the present invention can be reduced by 1/107 to 1/1 compared to the case of a secondary vessel. 40 again
In the case of a 0W metal halide lamp, about 30 units of luminescent metals, Sc and Na, are enclosed in the form of iodides, and the number of elements of Sc and Na in this weight is about 1 unit. According to experiments by the present inventors, if the number of elements in the radioactive substance is less than 1/1000 of the number of elements in the luminescent metal, the chemical influence of the radioactive element, that is, the formation of halogenated substances, can be ignored and black Therefore, if it is a radioactive substance with a half-life of about 0.5 years or more and until the end of about 10 years, the amount of encapsulation is small, so it will not create a substance that reacts with halogen. It also makes it difficult for light to deteriorate over a long service life. Next, a method of enclosing such a radioactive substance in an arc tube will be explained.

The above-mentioned radioactive substances are dangerous if the radioactivity scatters during handling, so it is necessary to prevent the radioactivity from scattering during the encapsulation process.

Therefore, as shown in FIG. 2, the radioactive material 10 is covered with a coating 11 made of a non-radioactive material to form a capsule-shaped sealed radiation source. This coating 11 is preferably a luminescent metal sealed in the arc tube, an oxide thereof, a halide of the luminescent metal injected into the arc tube, or a non-radioactive isotope of a radioactive element or an oxide thereof. The easiest way to handle it is to enclose it as the central core of a pellet-shaped capsule of luminescent metal halide. After completing the assembly of the arc tube, such a sealed radiation source is introduced into the bulb through the exhaust pipe 12 while the exhaust pipe 12 is not yet sealed, as shown by the imaginary line in FIG. do. In this case, it does not matter whether it is before the exhaust inside the valve is completed or after the exhaust is completed. Thereafter, the exhaust pipe 12 is sealed off and a voltage is applied between the electrodes 3 to perform flushing. Then, the coating 11 is broken and scattered by the heat of this flashing discharge or the impact of the charged particles, so that the radioactive substance 10 appears on the surface and spreads into the arc tube. Therefore, the effect of initial electron emission is fully exhibited. Furthermore, as radioactive substances, elements that emit 7-rays are undesirable because their diagonals pass through the wall of the arc tube, which has a negative effect on the human body, and substances that emit Q-rays and 8-rays are more desirable. be.

In addition, all types of luminescent substances can be used to fill the arc tube, except for thorium, but scandium (Sc), yttrium (Y), rare earth elements, aluminum (AI), and sodium (Na) have particularly excellent luminous efficiency. It is suitable for metal vapor discharge lamps containing at least one of , thallium (TI), indium (ln), and tin (Sn), which has excellent color rendering properties. See you again ha. Among the genifying substances, AI is known to be more efficient when using bromide or chloride than iodide, and since thorium cannot be used for this, the present invention is particularly effective. Note that specific experimental examples of the present invention will be explained. In a quartz arc tube with an inner diameter of 20 Yanagi and an electrode distance of 42 Yanagi, scandium sodium iodide was encapsulated in 30 9, - iodide with 10-6 9 promethium 147 (147Pm) as a central core. Formed and put into the valve through the exhaust pipe, and filled with 50 parts of mercury and 25 tons of argon gas to 400
Make a W metal halide lamp. After performing glow discharge for 3 minutes, the voltage was changed to AC 200V at a height of 1500V.
When we measured the starting time by applying a pulse voltage of 25〃S to the car, we found that it started instantaneously over several times, to the extent that it could not be measured with a stopwatch. 1.25 compared to the one used
It was double that. The half-life of 147Pm is 2.7 years with 8 decays, and the amount of radioactivity is 1 microcurie, or 3 per second.
．． It emits 7×1 electrons.

With this many initial electrons, 460 electrons will be emitted per second even after 8 years, so startability is reliable. In addition, in the above experiment, the amount of radioactivity was changed to 0.7 microCurie, 0.5 microCurie, and 0.1 microCurie instead of 1 microCurie, and metal halide lamps made under the same conditions were also used. It was confirmed that the engine also exhibited excellent starting performance and light performance.

The invention described in detail above is characterized in that a half-reducing machine uses a radioactive substance of about 0.3 to about 1K or less at a concentration of 1 microCurie or less per arc tube as an emitter. According to this, the amount of filling does not impair the starting characteristics at least until the end of the life, and since chemical reactions do not occur as the amount of filling decreases, it is possible to prevent a decrease in light power.

Furthermore, when enclosing radioactive substances such as those mentioned above in an arc tube, if the source is sealed with a non-radioactive substance and the coating is removed by the heat or electron impact caused by the discharge between the electrodes, the radioactive substance Not only is it safe to handle, but the coating inside the arc tube can be easily peeled off, making the sealing work easier.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a front view of an arc tube, and FIG. 2 is a sectional view of a sealed source of radioactive material. 1... Arc tube bulb, 3, 3... Main electrode, 4... Auxiliary electrode, 10... Radioactive substance, 11... Covering. Figure 2 Figure 1

Claims (1)

[Claims] 1. In the arc tube, a compound having a half-life of about 0.5 years or more and about 10
1. A metal vapor discharge lamp characterized in that a radioactive substance of less than 1 year is encapsulated in an amount of radioactivity of 1 microkyrie or less per arc tube. 2 The above radioactive substances are ^2^2Na, ^4^5Ca,
^5^4Mn, ^5^5Fe, ^6^9Co, ^6^5
Zn, ^1^0^6Ru, ^1^1^0Ag, ^1^2
^5Sb, ^1^3^3Ba, ^1^3^4Cs, ^1
^4^4Ce, ^1^4^7Pm, ^1^5^5Eu,
^1^9^5Au,^2^0^4Tl,^2^4^2C
The metal vapor discharge lamp according to claim 1, characterized in that the metal vapor discharge lamp is at least one of m. 3 The above discharge lamp has Sc, Y, rare earth metals, and A inside the arc tube.
Claim 1, characterized in that the lamp is a metal halide lamp in which a luminescent metal halide consisting of at least one of l, Sn, Na, Tl, and In is enclosed.
Metal vapor discharge lamps specified in Section 2 or Section 2. 4. The metal according to claim 1, 2, or 3, wherein the radioactive substance is coated with a non-radioactive substance to form a sealed radiation source, and the sealed radiation source is enclosed in an arc tube. Steam discharge lamp.