JPS6363115B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a metal vapor discharge lamp device in which a radioactive material is sealed within the arc tube to facilitate starting. [Technical background of the invention and its problems] Metal vapor discharge lamp devices, such as metal halide lamps and high-pressure sodium lamps, have excellent luminous efficiency, but on the other hand, their starting voltage is high, so it is necessary to apply a sufficiently high voltage to start them. . however,
Recently, lamps have been developed that are compatible with high-pressure mercury lamps by starting them using low-cost and lightweight mercury lamp ballasts, and these lamps can be started at lower voltages by lowering the starting voltage. A means to enable this is required. Furthermore, due to recent energy saving trends, there is a strong desire to develop small metal vapor discharge lamps that can replace low-efficiency incandescent light bulbs. A problem arises in that it is difficult to install the electrodes in terms of space. As a means of lowering the starting voltage, Japanese Patent Laid-Open Nos. 56-126248 and 57-9047 disclose methods for dispersing and sealing radioactive materials in, for example, ceramic bodies for safety in handling radioactive materials. By enclosing the material inside the arc tube,
Each item is shown to have a significant effect. However, when such measures are taken, the shape may be too large or
Alternatively, when the arc tube is downsized and the height of the electrode is lowered accordingly, there is a possibility that the freely encapsulated radioactive material comes into contact with the electrode, which becomes hot during lamp operation. In such a case,
The radioactive substance reacts with the high melting point metal such as tungsten or molybdenum, which is an electrode constituent material, and scatters on the inner surface of the arc tube, causing early blackening and causing a decrease in luminous flux. For this reason, for example, if the radioactive material-dispersed ceramic body is made very small, it may be possible to prevent contact with the high-temperature part of the electrode, but the amount of radioactive material will inevitably decrease, making it impossible to achieve the original purpose of improving the starting voltage. It becomes difficult. In order to cope with this problem, a method has been proposed in which the arc tube container is provided with a storage section that communicates with the inside of the arc tube, and the radioactive material is stored in this storage section, thereby solving the above-mentioned drawback. However, when such a measure is taken, the coldest part of the arc tube occurs in the gap between the storage part and the radioactive substance, and the luminescent metal, the halide of the same metal, etc., which are the inclusions, accumulate in this gap. As a result, the vapor pressure of the filler material was lowered, resulting in a decrease in luminous flux and luminous flux maintenance rate. As a result of investigating this point, the inventors of the present invention found that the cause has an important relationship with the installation position of the radioactive substance storage section provided in the arc tube container. [Object of the invention] The present invention has been made in consideration of the above circumstances, and
By preventing the radioactive material from coming into contact with the electrodes and preventing the coldest part of the arc tube from forming in the storage area of the radioactive material, the starting voltage can be kept low while the luminous flux and luminous flux maintenance rate can be reduced. The object is to provide an improved metal vapor discharge lamp device. [Summary of the Invention] The present invention provides a metal arc tube container in which a radioactive substance storage section communicating with the interior is provided, and the storage section is installed above a horizontal plane passing through the center of the light emitting section of the arc tube. It is a steam discharge lamp device. [Embodiment of the Invention] The details of the present invention will be described above with reference to an illustrated embodiment. Figure 1 shows the arc tube of a 40W small metal halide lamp, and 1 has an inner diameter of approximately 8.
It is a quartz glass arc tube container formed into a spherical shape of mm in diameter, and inside it is sealed 10 mg of mercury, a total of 2 mg of scandium iodide and sodium iodide, 0.05 mg of scandium metal, and 100 torr of argon. 2
A and 2b are a pair of electrodes placed opposite each other at a distance of 4 mm from each other at both ends of the arc tube container 1, and a molybdenum foil 3 hermetically sealed to the sealing parts 1a and 1b.
It is connected to external lead wires 4a and 4b via wires a and 3b. 5 is the chip that remains after sealing off the exhaust pipe, and 6 is a ceramic body in which promethium- ¹⁴⁷ Pm is dispersed in a radioactive amount of 0.05 microcuries, as shown in the enlarged view in Figure 2. is housed in a storage section 7 formed in a part of the
It also communicates with the interior of the arc tube 8 via an opening 9. The opening 9 is formed to be wide enough to allow radiation from the radioactive substance to enter the interior 8 of the arc tube. In addition, in the case of vertical lighting as shown in the first diagram, the installation position of the radioactive material storage section 7 is as follows:
It is located above the horizontal plane (plane A) passing through the center 0 point of the light emitting part (the center of the distance between the electrode tips). An example of a method for manufacturing such an arc tube is as follows.
First, a part of the tube wall of the arc tube container 1 is heated and melted with a laser beam to form a hole (the opening 9), and then one end of the silica glass tube is welded to surround this hole. A radioactive substance-dispersed ceramic body 6 is inserted into the silica glass capillary from the other end and placed on the hole. Next, the storage portion 7 is formed by heating and melting the silica glass tube at a position where the radioactive substance-dispersed ceramic body 6 remains and sealing it off from the arc tube container 1. At this time, if the sealing part is brought too close to the ceramic body 6, the molten quartz glass will be welded to the ceramic body 6, and cracks will occur in the welded part due to the difference in coefficient of thermal expansion between the two and the temperature change when the lamp flashes. Therefore, it is necessary to seal the two so as to leave a gap between them. After that, form the luminous tube by the usual method,
A lamp is completed by enclosing this arc tube in an outer tube whose interior is vacuumed or filled with nitrogen, inert gas, or the like. This lamp is lit by applying a voltage between the electrodes 2a and 2b from the external lead wires 4a and 4b of the arc tube via a ballast, although the electric circuit is not shown, but the starting voltage is higher than the normal power supply voltage. If the pressure is also high, a high voltage pulse is further applied at startup as necessary. Since the lamp has a radioactive substance-dispersed ceramic body 6 housed in a housing part 7 provided in the tube wall of the arc tube container 1, it is necessary to start discharging from now on.
That is, initial electrons serving as seeds are emitted into the interior 8 of the arc tube through the opening 9, and starting is performed quickly and the starting voltage is also reduced. In other words, the initial electrons emitted from the radioactive substance ionize the argon gas in the vicinity, and when a pulse voltage is applied while a small amount of this ionized gas is present, dielectric breakdown inside the arc tube occurs and the process starts. become. In addition, since the radioactive substance is stored in the storage section 7, it reacts with the electrodes 2a and 2b, which become hot when the light is turned on, and the reaction products scatter on the tube wall, as if they were simply sealed freely in the arc tube. It does not adhere and cause blackening, which does not adversely affect lamp characteristics such as a decrease in luminous flux. Moreover, the radioactive material storage section 7 is installed above the horizontal plane passing through the center of the light emitting part of the arc tube, and the upper part of the arc tube becomes hotter than the lower part due to the convection effect inside the arc tube. The part 7 is never the coldest part of the arc tube, so the luminescent metal or the halide of the luminescent metal, etc., which are the inclusions, do not accumulate in the cavity of the storage part 7, and even if they do, Since the temperature is high when the light is turned on, it is possible to prevent a decrease in luminous flux caused by vaporization and a decrease in the vapor pressure of the luminescent metal. Next, a lamp of the same type as the lamp according to the embodiment of the present invention that does not use radioactive materials (conventional example 1) and a radioactive material are housed in a storage section, and the installation position of the storage section passes through the center of the light emitting section of the arc tube. Table 1 shows the results of a comparison of the characteristics with the lamp (conventional example 2) which was set below the horizontal plane.

〔Effect of the invention〕

As described in detail above, according to the present invention, the starting voltage can be lowered and reactions caused by contact between radioactive substances and electrodes can be avoided, thereby preventing blackening of the wall of the arc tube, and moreover, it is possible to prevent the blackening of the wall of the arc tube. Since the coldest part does not occur, the luminescent metal sealed in the luminous tube or the halide of the same metal does not accumulate in the cavity of the housing, and therefore a decrease in luminous flux due to a decrease in the vapor pressure of the luminescent metal can be prevented. .

[Brief explanation of drawings]

Fig. 1 is a perspective view of an arc tube for a small metal halide lamp which is an embodiment of the present invention, Fig. 2 is a sectional view of a radioactive substance storage section, and Figs. 3 and 4 are perspective views of other embodiments. are shown respectively. 1... Arc tube container, 2a, 2b... Electrode, 6...
...radioactive substance dispersed ceramic body, 7...radioactive substance dispersed ceramic body housing section, 4...horizontal plane passing through the center of the light emitting part of the arc tube.

Claims (1)

[Claims] 1. An arc tube container is provided with a pair of electrodes facing each other, and is equipped with an arc tube in which mercury or at least one of a metal and a metal halide is sealed together with a starting rare gas, and a radioactive material that communicates with the interior of the arc tube container is provided. A metal vapor discharge lamp device provided with a substance storage section, characterized in that the installation position of the radioactive substance storage section is above a horizontal plane passing through the center of the light emitting section of the arc tube. Device.