JPH0443965Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to improvements in high-output low-pressure mercury lamps used for surface sterilization of packaging containers, raw water sterilization of chemicals, ultra-precision cleaning of semiconductor devices, and the like.

[Prior art and its problems] Low-pressure mercury lamps conventionally used for various sterilizations, etc. have been improved to efficiently emit ultraviolet rays with wavelengths of 185 nm and 254 nm. A high-output low-pressure mercury lamp has been proposed in which the lamp input is 2 to 8 W per 1 cm distance between the electrodes sealed at both ends of the tube.

Furthermore, since such a lamp is constructed by removing the phosphor coated on a fluorescent lamp for general illumination, its electrode is of a hot cathode type made of a tungsten filament.

As such a low-pressure mercury lamp, the one shown in Japanese Patent Laid-Open No. 60-79663 or No. 60-79664 has been proposed.

The above-mentioned hot cathode is sealed at both ends of the arc tube of this lamp, but based on the demand for higher lamp output, the lamp input is set to about 2 to 8 W per 1 cm of distance between the electrodes of the lamp, which increases the lamp current. The current is about 1 to 10A, which is significantly larger than before, which may cause the tungsten filament to burn out or
The electron radioactive material applied to the filament evaporates,
The particles scatter, turning the wall of the arc tube black and shortening its lifespan. In addition, an attempt is being made to increase the ultraviolet output by filling the arc tube with an inert gas such as argon of about 2 torr as an auxiliary gas for starting, but since the filling pressure is low, the evaporation and scattering of the electron radioactive substance is prevented. It becomes noticeable. This tendency becomes particularly noticeable when the hot cathode temperature increases.

[Purpose of the invention] This invention was made in view of the above points.
A hot cathode is sealed at both ends of a low-pressure mercury lamp, and an anode is provided close to the hot cathode, and the outer surface of the lamp where the electrodes are installed is cooled to maintain the wall temperature of the arc tube at 30 to 50°C. By doing so, the present invention aims to provide a high-output low-pressure mercury lamp that does not cause blackening of the tube wall throughout the life of the lamp, has a large ultraviolet output, and has excellent ultraviolet output maintenance characteristics.

[Structure of the invention] An embodiment of the invention will be described below with reference to FIG.

In the figure, 1 is an arc tube made of a heat-resistant ultraviolet-transparent material such as quartz glass, and hot cathodes 2, 2 made of a tungsten filament coated with an electron radioactive substance are sealed at both ends. Annular anodes 3, 3 made of a high melting point metal such as molybdenum or tungsten are provided adjacent to each other, and these are electrically connected to the hot cathode. The outer surface of the arc tube wall on which the electrodes consisting of the hot cathode and the anode are installed is cooled via the cooling medium 4, thereby forcibly cooling the area around the electrode to 30 to 50°C. I have it too.

In the case of low-pressure mercury lamps, as the lamp input increases, the temperature of the wall of the arc tube increases, the mercury vapor pressure inside the tube increases, and the ultraviolet output decreases, so the cooling means described above is necessary. It's coming.

Further, the anode is made of a high melting point metal such as molybdenum or tungsten, and the dimensions of the anode are set to a thickness of 40 mm.
~200μ and a width of 2 to 10 mm, the temperature of the adjacent hot cathode can be lowered and the scattering of electron radioactive substances can be effectively prevented.

This is because when the thermionic electrons emitted from one hot cathode collide with the opposing anode, the temperature rise in the hot cathode due to the collision of the thermionic electrons of the opposing hot cathode is absorbed by the anode.

Please note that the dimensions of the anode are designed to be less than 40μ thick and 2mm wide.
As shown in curve B in Figure 2, the output of ultraviolet rays after the lighting time of the lamp decreases significantly due to blackening of the tube wall due to the scattering of electron radioactive materials at an early stage before the average life of the lamp has elapsed. Be looked at.

On the other hand, in the case of a lamp with an anode dimension design larger than the above range, the capacity of the anode becomes too large, so the temperature of the hot cathode does not rise to the required range, thermionic emission function is impaired, and eventually It may lead to disadvantages.

As a result, the low-pressure mercury lamp according to the present invention has a lamp input of 2 to 8 W/cm, a tube wall around the electrode of 30 to 50 degrees Celsius, an anode width of 2 to 10 mm, and a width of 2 to 10 mm.
By setting the thickness to 40 to 200 μm, it is possible to obtain a low-pressure mercury lamp that can obtain high ultraviolet output without burning out the electrodes and has a high ultraviolet output maintenance rate.

FIG. 2 shows the dynamic characteristics of the ultraviolet output of the low-pressure mercury lamp according to the present invention and the conventional low-pressure mercury lamp. In the figure, curve A indicates the lamp according to the present invention,
Curve B shows the travel of a lamp with the conventional anode design described above, and curve C shows the travel of a lamp with only a conventional hot cathode.

As is clear from the figure, in the lamp according to the present invention, the UV output remains at about 80% after 6000 hours of lighting.

[Effect of the invention] As is clear from the above explanation, the high-output low-pressure mercury lamp according to the invention prevents electron radioactive materials throughout the life of the lamp by selecting the electrode structure and tube wall temperature within a predetermined range. Since there is little blackening of the wall of the arc tube due to scattering, a lamp with high ultraviolet output and excellent ultraviolet output maintenance characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partially longitudinal side view showing an embodiment of the low-pressure mercury lamp according to the present invention, and FIG. 2 is a movement characteristic curve diagram of the low-pressure mercury lamp according to the present invention and the conventional low-pressure mercury lamp.

Claims (1)

[Claims for Utility Model Registration] A light emitting tube made of heat-resistant glass is sealed with electrodes at both ends, and mercury and rare gas are sealed inside. A low-pressure mercury lamp that emits ultraviolet rays and is lit while maintaining the temperature of the arc tube wall at 30 to 50°C by directly or indirectly cooling the outer surface of the wall of the arc tube in the peripheral area of the lamp. Consisting of a pair of coated hot cathodes and an anode adjacent to them, the anode has a width of 2 to 10 mm and a thickness of 40 to 200 μm.
A high-output low-pressure mercury lamp made of annular heat-resistant metal.