JPH0766779B2 - Low pressure mercury lamp - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a low-pressure mercury lamp, and more particularly to a high-power low-pressure mercury lamp suitable for improving the maintenance rate.

[Conventional technology]

As described in USP 3679928, the conventional high-power ultraviolet light source has been a high-power type with a lamp current density of 0.5 to 25 A / cm ² at a low pressure of mercury of 10 ^{-3 to} 0.75 Torr. But,
No consideration was given to the prevention of UV output reduction during travel.

(Problems to be Solved by the Invention) In the above-mentioned prior art, no consideration is given to the decrease in light output during the travel, and there is a problem of coloring due to the adhesion of mercury oxide on the inner wall of the tube.

The object of the present invention is to eliminate the adhesion of mercury oxide to the inner wall of the tube,
This is to prevent a reduction in the light output maintenance rate.

[Means for solving problems]

The above object is achieved by setting the temperature of the tube wall during operation to 400 ° C. or higher.

The gist of the present invention is to have a means for cooling the tube end of the discharge tube so that the mercury vapor pressure in the discharge tube when the lamp is lit becomes 1 Pa or less, and the tube of the effective length part of the discharge tube when the lamp is lit. The low-pressure mercury lamp is characterized by having a wall temperature of 400 ° C or higher.

[Action]

When a low-pressure mercury lamp is lit at high output, the evaporation of oxides such as barium, strontium, and calcium, which are the electron emitters that make up the electrodes, increases. Oxygen of this oxide and mercury in the tube are combined to generate mercury oxide, which adheres to the inner wall of the tube and absorbs light. As a result, the maintenance factor of light is greatly reduced with the lighting time.

The present invention operates at a pipe wall temperature of 400 ° C. or higher during operation. As a result, the generated mercury oxide is decomposed, does not adhere to the tube wall, and is not colored, so that the absorption of light is lost and the light output does not decrease during travel.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The light emitting portion is made of a quartz tube 1 (for example, synthetic quartz), and has an electron emitting substance 2 (for example, oxides of Ba, Sr, Ca, etc.) on both ends thereof.
First, the electrode mount portion connected to the tungsten filament 3 coated in the form of carbonate is connected. An exhaust pipe 5 is provided on one side of the stem 4 forming the electrode mount portion. The exhaust pipe 5 is connected to a vacuum exhauster to evacuate the pipe, and then the whole pipe is heated and degassed. Then, a current is passed through the tungsten filament 3 through the lead wire connecting the resistance to the resistance. By heating, the carbonate coated on the tungsten filament is heated and decomposed to release carbon dioxide gas and exhausted, which is an electron emitting substance on the tungsten filament. Form Ba, Sr, Ca oxides. Next, about 400 Pa of neon gas, which is a starting gas, is filled through the exhaust pipe, and about 20 mg of mercury is further filled therein, and then the exhaust pipe is hermetically sealed. Thereafter, the lamp knitted portion is fixed in the base 3 (for example, aluminum) with an adhesive 7 such as cement. The lamp is turned on by connecting to a ballast (not shown). In order to keep the mercury vapor pressure at 1 Pa or less, the mouthpiece 6 is cooled and controlled.

In order to operate the lamp wall temperature above 400 ℃, (1) Operate the tube input above 4W / cm.

(2) A quartz tube 8 for heat insulation is placed on the outside of the light emitting quartz (Fig. 2).

(3) The heating wire 9 is wound around the quartz of the light emitting portion to the extent that the light output is not significantly reduced (FIG. 3).

(4) The top and bottom of the light-emitting quartz is narrowed by a quartz plate 10 to keep it warm (Fig. 4).

Etc., either alone or in combination. Tube wall temperature,
The results of the UV output maintenance rate are shown in FIG. FIG. 5 shows the light output after 2000 hours of lighting, divided by the light output after 100 hours of lighting.

As described above, according to the present invention, a great effect is recognized in improving the maintenance rate of light output.

〔The invention's effect〕

According to the present invention, since light absorption due to the adhesion of mercury oxide to the tube wall is eliminated, there is a great effect in improving the light output maintenance rate as shown in FIG.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a high-power low-pressure mercury lamp showing one example of the present invention, FIG. 2 is a cross-sectional view of a light emitting part of an embodiment using a quartz heat insulation tube, and FIG. FIG. 4 is a side view of the arc tube of the embodiment in which the wire is wound, FIG. 4 is a cross-sectional view of the arc tube portion of the embodiment in which a quartz plate is used for the upper and lower parts, and FIG. 5 is operated at various tube wall temperatures. FIG. 7 is a diagram showing a maintenance ratio with respect to a light output when the lamp is turned on for 2000 hours and then turned on for 100 hours. 1 ... Quartz arc tube, 2 ... Electron emitting material, 3 ... Tungsten filament, 4 ... Stem, 5 ... Exhaust tube, 6
…… Mouthpiece, 7 …… Cement, 8 …… Insulation tube, 9 …… Exothermic line, 10 …… Insulation plate.

Claims (1)

[Claims] 1. The mercury vapor pressure in the discharge tube when the lamp is on is 1 P.
A low-pressure mercury lamp, comprising means for cooling the tube end of the discharge tube so as to be a or less, and the tube wall temperature of the effective length portion of the discharge tube when the lamp is lit is 400 ° C. or higher.