JPS59101759A - High pressure sodium lamp - Google Patents

Abstract

PURPOSE:To enable the emission color irregularity of a high pressure sodium lamp to be decreased through its life by forming an infrared reflecting film on the surface of the outer tube, in which an emission tube is installed, and burning the lamp at a lamp input of within a specified range per unit surface area of the outer tube. CONSTITUTION:An emission tube 1 is incorporated in the center of an outer quartz tube 8. Over the outer surface of the outer tube 8, an infrared reflecting film 9 is formed which contains a titania-silica multiple interference film having a transmittance of over 95% in the visible range and an infrared reflectivity of over 75% in the wavelength range of 800-1,100nm. In addition, such a high pressure sodium lamp is burned at a lamp input of 1W/cm<3>-3W/cm<3> per unit surface area of the outer tube 8. As a result, most of infrared spectrum discharged from the emission tube 1 is reflected by the reflecting film 9 before being sent back to the emission tube 1, thereby minimizing temperature difference between the discharging emissional portion and the end portion of the emission tube 1. Consequently, the emissional irregularity of the lamp can be greatly decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to high pressure IJ lamps.

Conventional structure and problems Incandescent light bulbs have excellent color rendering properties, high brightness, and easy light distribution control.In addition, they are inexpensive and easy to handle, so they have not been used for indoor lighting until now. It has been used as one of the main light sources.

However, as we enter an era of full-fledged energy conservation, the low efficiency of incandescent light bulbs has recently come to be seen as a problem.

Attempts to improve the efficiency of incandescent light bulbs have been ongoing since daytime, but so far no breakthrough results have been achieved. Therefore, recently there has been a strong demand for the development of a compact, highly efficient, and high-intensity discharge lamp that can replace light bulbs.

As a lamp that has the potential to meet such demands, the applicant has proposed incandescent light bulbs in both light color and color rendering properties in JP-A-57-9046 and JP-A-67-50763. He proposed a high-pressure thorium lamp with a lamp efficiency that is approximately equal to that of the previous one, but whose efficiency is two to three times higher. A small SOW lamp prototyped based on this proposal has a light color similar to that of an incandescent light bulb, and has a lamp efficiency of 3 times that of a light bulb.
(Achieved excellent lamp characteristics of just over f1.

Incidentally, in order to achieve such high efficiency, the design of the arc tube was quite different from that of conventional high-pressure sodium lamps. In other words, the distance between the electrodes is the light emission QQ
It is relatively small compared to the total length of H. In other words, the size of the tube end portion including the electrode is extremely large compared to the discharge light emitting portion. For example, the above soW
In the case of a high-pressure sodium lamp, the total length of the arc tube is 3El
lJl+, whereas the distance between the electrodes is 10MM.

Therefore, the color of the emitted light from the lamp differs depending on the direction from which the lamp is observed. This brings about the inconvenience that the color of the object looks different depending on the lighting direction of the lamp.

OBJECTS OF THE INVENTION The present invention provides a high-pressure sodium lamp in which uneven luminescence of the arc tube is improved.

Structure of the Invention The present invention is characterized in that an arc tube with electrodes at both ends is provided inside the outer bulb, an infrared reflective film is provided on the surface of the outer bulb, and a lamp input voltage of I Vc4 to 5 Vc4 per unit surface area of the outer bulb is provided. It lights up.

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

FIG. 1 shows an overview of the lamp used to conduct experiments regarding the high-pressure sodium lamp of the present invention. In the figure, number 1 has an inner diameter of 5.0 mm at the center and an outer diameter of 6.0 mm.
2HM, an alumina arc tube with a total length of 38 mm,
Electrode conductors 2.3 made of niobium tubes are directly sealed to the inner surfaces of both ends thereof with ceramic cement. Electrodes 4 and 6 are held at the tip of the electrode conductor 2.3, and the shortest distance between these electrodes is 1o. The arc tube 1 has an inner diameter of 5.0 mm at the center, but the inner diameter becomes narrower toward the ends of the arc tube, and the end portion where the electrode conductor 2.3 is sealed. In this case, the outer diameter of the electrode conductors 2 and 3 is approximately the same. Inside the arc tube 1, there is a sodium amalgam 6 with a sodium molar ratio of 78% and a neon gas as a starting rare gas.
Argon mixed gas is sealed at about 40 Torr.

Reference numeral 7 denotes a 5oWO high pressure sodium lamp with a high color rendering property, in which an arc tube 1 is built into an outer tube 8 made of quartz. The outer surface of the outer tube 8 is made of titania (TiOz), which has a transmittance in the visible range of 95% or more and an average value of infrared reflectance in the wavelength range of aoonm to 1l100n of 75% or more.
) - An infrared reflecting film 9 including a silica (Si02) multiple interference film is formed, and visible light emitted from the arc tube 1 during operation is transmitted, but most of the infrared light is reflected by this interference film. , and returns it to the arc tube 1 again. The arc tube 1 has strut wires 10, 11 within the outer tube 8,
It is held by an arc tube support plate 12.13. The strut wire 1o is connected to an arc tube support plate 12, and an electrode conductor 2 is welded to this arc tube support plate. Similarly, strut line 11
is connected to the arc tube support plate 13, and this arc tube support plate 13
The electrode conductor 3 is welded to.

The strut wire 10.11 is connected to the stem 14 and connected to the lamp lighting circuit.

In the high-pressure sodium lamp 7 having such a configuration, the lamp was lit with various dimensions of the outer bulb 8, and the color of the lamp light was observed from two directions: the X direction of the central portion of the arc tube 1 and the direction of the central axis 2 of the arc tube 1. The outer tube 8 actually has an outer diameter of 8 silk to 50 mm.
Several cylindrical tubes with a total length of about 60 ff were formed using available quartz glass tubes. That is, the lamp input per unit surface area of the outer tube 8 is 3-3 W/c.
The lamp light color was observed in the range of a-0, aW/, 1°. As a result, as the tube wall load on the outer tube 8 increases, as shown in FIG. I definitely hoped that it would be smaller. According to the figure, it is clear that the color temperature difference is below 10oK, which is not a problem in practice, when the lamp input per 80 unit surface area of the outer bulb is 1"/cA or more. However,
If the temperature exceeds 3 degrees, the temperature of the outer surface of the arc tube 1 will rise to 4111 degrees, and the evaporation of alumina will become significant, shortening the lamp life, so it is best to avoid this.

The uneven light emission of the arc tube can be improved by forming an infrared reflective film on the surface of the lamp outer bulb and increasing the lamp input per unit surface area of the outer bulb for the following reasons. be. Sodium atoms originally have an emission line spectrum with a high transition probability in the near-infrared region. The representative Mononoke is 8201m. Therefore, as in this embodiment, an infrared reflective film having a large reflectance in the near-infrared region of 80 onm or more is formed on the surface of the outer tube, and the surface area of the outer tube is relatively reduced to form a wall of the tube. In a high-pressure sodium lamp with a high load, most of the near-infrared spectrum of the IJ um atoms emitted from the -1-+- arc tube will be reflected by the infrared reflective film and returned to the arc tube by 11 f. . As a result, the non-light emitting parts of the arc tube, especially the sodium atomic layer near the electrodes, are heated and the temperature rises. Therefore, the temperature difference between the sodium atom population at the center of the arc tube, the discharge light emitting section, and the ends is reduced, and the unevenness of the emitted light color is significantly reduced.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention includes a light emitting tube provided with electrodes at both ends within the outer tube, an infrared reflective film provided on the surface of the outer tube, and a unit surface fj? of the outer tube. per I W/ca
It is possible to provide a high-pressure sodium lamp that can reduce the unevenness of luminescent color to a level that does not pose a practical problem throughout its life because it is lit with a lamp input of ~3W/7.

[Brief explanation of drawings]

FIG. 1 is a partial 1,2J partial diagram of a high-pressure sodium lamp according to an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between color temperature and lamp power per unit surface area of the outer bulb. 1... Arc tube, 2, 3... Electrode rod,
4, 6...electrode, 6...sodium amalgam, finished...high pressure sodium lamp, 8...
...outer tube, 9...infrared rays JiQ dimension jmo. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 1''' Fig. 2/) t/l group shortage 1d result, 62 riunbu input (W
/、ssu

Claims (1)

[Claims] An arc tube with electrodes at both ends is provided within the outer bulb, an infrared reflective film is formed on the surface of the outer bulb, and a lamp input of 1 w/c$ to 3 W/clr per unit surface area of the outer bulb. A high-pressure sodium lamp that is characterized by being lit at