JPH0535544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrodeless metal vapor discharge lamp used for photochemical reactions, curing of paints and inks, and the like.

[Prior art and its problems]

Ultraviolet rays are often used to cause photochemical reactions and to harden paints and inks, but for these purposes, ultraviolet rays with a wavelength range of 280
Ultraviolet light of ~400nm is effective.

Conventionally, a high-pressure mercury lamp that discharges between electrodes has been used as a source of ultraviolet rays, but recently,
Enough mercury and rare gas to maintain a discharge are sealed in an arc tube that has no electrodes, and high-frequency waves or microwaves of several + MHz or higher are projected from the outside to excite the mixture sealed inside, causing the discharge to emit light. Electrode high pressure mercury lamps are known.

By the way, the light emitted from this electrodeless high-pressure mercury lamp consists of a large number of bright line spectra, and each spectrum is dispersed over a fairly wide wavelength range. There are efficiency problems in using electrodeless high-pressure mercury lamps for curing, etc. For this reason, an electrodeless metal vapor discharge lamp has been reported in which a metal halide is sealed as a luminescent substance in the arc tube of an electrodeless high-pressure mercury lamp to increase the amount of light emitted in the effective wavelength range. In particular, electrodeless metal vapor discharge lamps containing iron are 350~
Since it emits light continuously in the 400 nm wavelength range, it is convenient for purposes such as photochemical reactions and curing of paints.

However, when an electrodeless metal vapor discharge lamp filled with iron is lit for a long time, iron adheres to the inner wall of the arc tube and forms a thin film. Therefore, there is a problem that the amount of iron that contributes to light emission decreases, and the formed thin film obstructs the transmission of ultraviolet rays, resulting in a decrease in the output of ultraviolet rays.

[Purpose of the invention]

Therefore, an object of the present invention is to provide an electrodeless metal vapor discharge lamp that prevents iron from adhering to the inner wall of the arc tube and maintains ultraviolet output for a long time without adversely affecting the emission spectrum of mercury and iron. That is.

[Structure of the invention]

The structure of the present invention is an electrodeless metal vapor discharge lamp in which high frequency waves or microwaves are projected from the outside of the arc tube, and a mixture sealed inside the arc tube is excited to discharge and emit light. Along with sufficient amounts of mercury and rare gas to maintain the
2/3 is characterized in that iron is prevented from adhering to the inner wall of the arc tube and forming a thin film.

That is, the inventors discovered that magnesium halides were effective in achieving the above object, and completed the present invention after conducting various experiments. The above-mentioned range is appropriate for the amount of magnesium added, but if the amount added is less than 1/40 in terms of gram atomic ratio to iron, it will not be sufficient to maintain the ultraviolet output, and conversely, if it exceeds 2/3 of iron, A problem occurs in which the emission spectrum becomes slightly weaker due to

〔Example〕

The present invention will be specifically described below based on embodiments shown in the drawings.

FIG. 1 shows a light source device for photochemical reactions. Magnetron 2 has a rated output of 1.5KW and oscillates microwaves with a frequency of 2450MHz. This microwave is guided into a reflecting mirror 4 by a waveguide 3, but inside the reflecting mirror 4 is a spherical quartz glass arc tube 1.
An electrodeless metal vapor discharge lamp consisting of an arc tube 1 is held, and microwaves are projected onto this arc tube 1. Note that the frequency of the microwave is not limited to those mentioned above, and any high frequency of several + MHz or more may be used.

The inner diameter of arc tube 1 is 22 mm, so the internal volume is approximately 5.6 mm.
cc, and the interior contains 6 mg of metallic mercury, 2.6 mg of mercury iodide, 1 mg of iron, 0.04 mg of magnesium, and 10 mmHg of argon gas.
The amount of magnesium added is 1/11 in terms of gram atomic ratio to iron.

However, when microwaves are projected onto the arc tube 1, the mixture sealed inside is excited and discharges light, resulting in lighting, but even if the light is on for up to 1000 hours, there is no iron on the inner wall of the arc tube 1. There is no adhesion and no thin film of iron is formed. At this time, we measured the change in the output of ultraviolet rays in the wavelength range of 280 to 400 nm, and as shown by characteristic curve A in Figure 2, the output maintenance rate was 97 after 1000 hours.
It was %.

Incidentally, when we lit up the same electrodeless metal vapor discharge lamp as in this example, but without the addition of magnesium, iron began to adhere to the inner wall of the arc tube after several tens of hours. A thin film was formed. The output maintenance rate decreased to 30% after 1000 hours, as shown by characteristic curve B in FIG.

Next, we investigated the effect of adding and enclosing magnesium on the output of the bright line spectrum of mercury and the output of the iron spectrum. In comparison, the spectral output of mercury is 3%
The spectral power of iron decreased by 5%, and the decrease was small.

In this example, metallic iron and metallic magnesium were added, but they may be added as iron halides or magnesium halides, or a mixture of both may be added to obtain the same effect.

〔Effect of the invention〕

As explained above, in the present invention, magnesium is added to an electrodeless metal vapor discharge lamp filled with iron at a gram atomic ratio of 1/40 to 2/3 to that of iron. Magnesium has almost no negative effect on the emission spectrum output of mercury and iron, and the properties of mercury and iron can be utilized as they are. This also prevents iron from adhering to the inner wall of the arc tube.
Since no thin film is formed, the output of ultraviolet rays in the wavelength range of 280 to 400 nm does not decrease even if the lamp is turned on for a long time.
Therefore, the electrodeless metal vapor discharge lamp can be suitable as an ultraviolet source for causing photochemical reactions and curing paints, inks, and the like.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the light source device, and FIG. 2 is a characteristic diagram of the output maintenance rate. 1... Arc tube (electrodeless metal vapor discharge lamp), 2...
...Magnetron, 3...Waveguide, 4...Reflector.

Claims (1)

[Scope of Claims] 1. In an electrodeless metal vapor discharge lamp in which high frequency waves, microwaves, etc. are projected from the outside of the arc tube and a mixture sealed inside the arc tube is excited to discharge and emit light, Adequate amounts of iron and halogens, along with sufficient amounts of mercury and noble gases to sustain the discharge.
Furthermore, metal magnesium or magnesium halide is sealed, and the gram atomic ratio of magnesium to iron is set to 1/40 to 2/3 to prevent iron from adhering to the inner wall of the arc tube and forming a thin film. Electrodeless metal vapor discharge lamp.