JPH0334187B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a low-pressure mercury vapor discharge lamp in which the mercury vapor pressure inside the tube is controlled by an amalgam. [Technical background of the invention and its problems] In general, when a low-pressure mercury vapor discharge lamp, such as a fluorescent lamp, is housed in a closed lighting fixture and turned on, mercury is released as the ambient temperature rises. The vapor pressure exceeds the optimum value, causing problems such as a decrease in luminous flux. When operating a fluorescent lamp under such severe temperature conditions, it is recommended to control the mercury vapor pressure in the fluorescent lamp within an appropriate range by using amalgam, which has a lower vapor pressure than pure mercury. It is considered valid. However, this method uses the property that the vapor pressure of amalgam is lower than that of pure mercury to control the mercury vapor pressure. If the ambient temperature of the light lamp is low, the temperature of the amalgam will be slow to reach the temperature most desirable for its operation, and the rate of release of mercury will be slow. Therefore, a problem arises in that the luminous flux does not rise well and takes time to stabilize in a steady state. For this reason, conventionally, for example,
As shown in Publication No. 30387, in addition to the main amalgam that controls the mercury vapor pressure during steady lighting, it also adsorbs floating mercury in the tube when the lights are turned off, and removes the adsorbed mercury during the early stages of lighting, including when starting. It is known that a small amount of auxiliary amalgam to be emitted is placed in a high temperature area near the electrode to improve the rise characteristics of the luminous flux. By the way, conventionally, this auxiliary amalgam is made by coating a thin film of indium, which is a typical amalgam-forming metal, on the surface of a base made of a metal plate such as stainless steel or nickel, in order to efficiently adsorb floating mercury when the lights are turned off. It is often used to wear clothes. The thickness of the indium film has a large effect on the rise characteristics of the luminous flux, and the research of the present inventors has shown that there is a film thickness region of the indium film in which this rise characteristic is the highest. It's becoming clear. On the other hand, in the usual manufacturing technology for fluorescent lamps, a mount with the electrodes, as well as the main amalgam and auxiliary amalgam assembled, is sealed to the openings at both ends of the arc tube. is heated in a furnace to exhaust impurities contained in the electrodes and arc tube, while exhausting the interior of the arc tube. During this evacuation, the temperature at the area where the auxiliary amalgam is installed easily exceeds 400℃. Put it away. in this case,
It was later discovered that indium used in the above-mentioned auxiliary amalgam has a low melting point and is weak against heat, so when stainless steel or nickel is used as the base, it cannot be used in the high temperature range of 400°C or higher as mentioned above. A drawback was found that indium dissolves into the solid from the surface of the base metal, which may result in a thin film or, in extreme cases, be lost from the surface of the base. In other words, since this indium film is deposited in advance at a thickness that maximizes the rise characteristics of the luminous flux as described above, the film thickness of this film is reduced during the lamp manufacturing process. and,
After the lamp was completed, not only the desired start-up characteristics could not be obtained, but also the start-up characteristics became extremely unstable. Similarly, while the lamp is on, the auxiliary amalgam is affected by heat from the electrodes and at least
As the temperature was raised to over 100℃, it was discovered that the indium coating on the surface melted into the substrate over time, and it became clear that the original function of the auxiliary amalgam gradually deteriorated even during the life of the lamp. [Objective of the Invention] The present invention has been made based on the above circumstances, and it is possible to obtain the desired rise characteristics with almost no alloy reaction occurring between the indium film and the substrate, and to maintain the rise characteristics for a long period of time. An object of the present invention is to provide a low-pressure mercury vapor discharge lamp that can last well for a long period of time. [Summary of the invention] That is, in order to achieve the above object, the present invention
The present invention is characterized in that the substrate on which the indium film is deposited is made of a high melting point metal material such as tungsten, molybdenum, or tantalum. [Embodiment of the Invention] An embodiment of the present invention will be described below based on drawings in which the invention is applied to a ball light bulb type lighting device. In the figure, reference numeral 1 denotes a cover made of synthetic resin, and a base 2 is attached to the top of one end of the cover 1. The opening at the other end of the cover 1 is covered with a substantially spherical globe 3, and the cover 1 and the globe 3 form an envelope 4 that approximates a ball-shaped incandescent light bulb.
is configured. Inside the envelope 4, a fluorescent lamp 5, which is a typical low-pressure mercury vapor discharge lamp, a lighting tube 6 as a starting element of the fluorescent lamp 5, and a chiyoke coil type ballast 7 as a discharge stabilizing element are integrated. is housed in. The arc tube 8 of the fluorescent lamp 5 is made by bending a straight glass bulb into a substantially U-shape at the center between its two ends 9, 9, and connecting the curved part 10 and both ends 9, 9. is curved in a substantially U-shape in a direction substantially orthogonal to the plane containing the U-shape, and both ends 9, 9 and the curved part 10 are located adjacent to each other in the same direction. ing. The inner surface of the arc tube 8 is coated with a phosphor sheath 12, and the flared portions 14 of a mount 13 are sealed to both ends 9, as shown in FIG. An internal lead wire 1 is connected to the stem tube 15 connected to the flare portion 14.
6 and 16 are sealed, and a filament 17 as an electrode is connected between these internal lead wires 16 and 16. Further, a capillary tube 18 led out from the stem tube 15 is opened at the tip of the stem tube 15 close to the filament 17, and through this capillary tube 18, the inside of the arc tube 8 is evacuated and a predetermined amount of inert gas is filled. will be carried out. The fluorescent lamp 5 is housed in the envelope 4 with both end portions 9 and the bent portion 10 facing the base 2, and the lighting tube 6 and ballast 7 are It is connected to the cap 2 via. As shown in FIG. 3, a main amalgam 19 for controlling the mercury vapor pressure inside the tube during steady lighting is accommodated in the thin tube 18 located closer to the tube end than the filament 17. This main amalgam 19 contains indium (In), bismuth (Bi),
Mercury (Hg) is added to tin (Sn), lead (Pb), and an alloy made by mixing these various metals in appropriate proportions.
In the case of this embodiment, it is formed into one substantially spherical lump, and it cannot fall off between the constricted part 18a provided in the middle of the thin tube 18 and the sealed end. is held in This main amalgam 19 has an efficiency of converting the amount of mercury in the arc tube 8 into ultraviolet light when its operating temperature reaches the ambient temperature inside the envelope 4 during steady lighting, that is, approximately 70°C to 90°C. It is designed to be controlled around 6×10 ^-3 mmHg, which is the maximum value. Note that instead of the main amalgam 19, the amalgam-forming metal and mercury may first be separately sealed in the capillary tube 18 and the arc tube 8, and then the amalgam-forming metal may be amalgamated in the capillary tube 18. . Filament 17 than the main amalgam 19 above
An auxiliary amalgam 20 according to the present invention is installed in a high-temperature area close to the filament 17, that is, in this embodiment, located between the filament 17 and the open end of the capillary tube 18. The auxiliary amalgam 20 is made of molybdenum (Mo) foil with a thickness of 20 to 50μ, as shown in FIG.
Or indium (In) is coated in a thin film form by plating or vapor deposition on the surface of the base 21 made of high melting point metal foil such as tantalum (Ta) foil or niobium (Nb) foil of similar thickness. The entire surface is covered with an indium film 22. The thickness of the indium film 22 is preferably 2 to 5 μm, which maximizes the rise of the luminous flux. One end of the base body 21 of the auxiliary amalgam 20 is welded to one of the internal lead wires 16, and when the temperature inside the arc tube 8 is low, such as when the light is turned off, it adsorbs floating mercury inside the tube. Conversely, when the lamp is turned on, the mercury that has been absorbed is released. In such a configuration, when the cap 2 is inserted into the socket on the power supply side and the power supply voltage is applied to the arc tube 8 to start it, a trace amount of mercury vapor and inert gas remaining in the arc tube 8 will be released. A discharge is started between the filaments 17, 17. At this time, since mercury has not yet been adsorbed to the auxiliary amalgam 20 in the lamp immediately after manufacture, as the temperature of the wall of the arc tube 8 increases due to the discharge, the temperature of the main amalgam 19 in the thin tube 18 gradually increases. , an amount of mercury vapor corresponding to this temperature is released into the arc tube 8 through the thin tube 18. After the light output reaches a steady state, the mercury vapor pressure inside the tube is controlled to a vapor pressure determined by the temperature of the part where the main amalgam 19 is installed. On the other hand, when the fluorescent lamp 5 in such an operating state is turned off, the temperature of the area where the arc tube 8 and the main amalgam 19 are installed decreases, so the arc tube 8
The floating mercury inside begins to be adsorbed by the main amalgam 19 within the capillary tube 18. In this case, since the opening of the capillary tube 18 is relatively small, the rate at which the main amalgam 19 adsorbs floating mercury is slow, and since this floating mercury flows toward the opening of the capillary tube 18, the auxiliary amalgam located near the opening 20 indium coatings 22 adsorb most of the floating mercury. Therefore, when the fluorescent lamp 5 is restarted by applying a power supply voltage to the arc tube 8 after being turned off, the auxiliary amalgam 20 that has adsorbed mercury is affected by heat from the adjacent filament 17, and
Receives ion bombardment due to discharge. As a result, the temperature of the auxiliary amalgam 20 rises rapidly and mercury is actively released, so that a sufficient amount of mercury is supplied into the arc tube 8 in a short period of time, and the light output is increased almost instantly. can be set. By the way, in the usual lamp manufacturing technology,
After sealing the mount 13, the interior of the arc tube 8 is evacuated while being heated in a furnace, so if a metal such as aluminum is used as the base 21 of the auxiliary amalgam 20 as described above, the base 21 and its An alloy reaction occurs with the indium film 22 deposited on the surface. Therefore, the inventors of the present invention attempted to use a high melting point metal material such as molybdenum or tantalum instead of the metal such as aluminum, and conducted the following experiments. In other words, in this experiment, the total luminous flux at the first lighting immediately after completion of the lamp was determined in the case where a conventional nickel or stainless steel plate was used as the material of the base 21, and in the case where a molybdenum, tantalum foil and a tungsten plate were used. I checked the value. The total luminous flux value in this experiment was evaluated based on the value 30 seconds after starting, and the experimental results are shown in Table 1 below.

〔Effect of the invention〕

According to the present invention described in detail above, since the base itself has a high melting point, even if the auxiliary amalgam is heated to a high temperature due to the influence of heat from the electrodes during the lamp manufacturing process or during lamp lighting, the base It is maintained in a stable state with respect to the indium coating on the surface, and almost no alloying reaction occurs with the indium coating, thereby suppressing reduction in thickness and deterioration of the indium coating. Therefore, there is an advantage that a desired luminous flux rise characteristic can be obtained at the initial stage of lighting, and that this rise characteristic can be satisfactorily maintained until the end of the lamp life.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a cross-sectional view of a lighting device, FIG. 2 is a partially cross-sectional perspective view of a fluorescent lamp, FIG. 3 is a cross-sectional view of a tube end, and FIG. 4 is a cross-sectional view of a lighting device. is a cross-sectional view of the auxiliary amalgam, and FIG. 5 is a characteristic diagram. 8... Arc tube, 17... Electrode (filament), 1
9...Main amalgam, 20...Auxiliary amalgam, 21
...Substrate, 22...Indium coating.

Claims (1)

[Scope of Claims] 1. In an arc tube having electrodes at both ends and enclosing an ionizable medium containing a predetermined amount of mercury, the mercury inside the tube is located closer to the end of the tube than the electrodes, and the mercury inside the tube during steady lighting. In addition to providing a main amalgam to control vapor pressure,
In a low-pressure mercury vapor discharge lamp equipped with an auxiliary amalgam that is located in a higher temperature area near the electrode than the main amalgam and that adsorbs floating mercury in the arc tube when the lamp is turned off and releases the adsorbed mercury when the lamp is started, the auxiliary amalgam is a low-pressure mercury vapor discharge lamp characterized by having an indium coating applied to the surface of a base made of a high-melting point metal material. 2. The low-pressure mercury vapor discharge lamp according to claim 1, wherein the main amalgam is installed in a thin tube led out from the end of the arc tube.