JPH0475623B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a 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, high-pressure mercury lamps have been used as sources of ultraviolet light, but the light emitted by high-pressure mercury lamps consists of many bright line spectra, and each spectrum is dispersed over a fairly wide wavelength range.
There is a problem in terms of efficiency when using a high-pressure mercury lamp for photochemical reactions, curing of paint, etc. whose effective wavelength range is within the above-mentioned range. For this reason, metal vapor discharge lamps are often used in which a metal halide is sealed as a luminescent substance in the arc tube of a high-pressure mercury lamp to increase the amount of light emitted in an effective wavelength range. In particular, metal vapor discharge lamps containing iron emit light continuously in the wavelength range of 350 to 400 nm, making them convenient for purposes such as photochemical reactions and curing paints.

However, when a metal vapor discharge lamp containing iron is left on 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.

In order to improve this problem, it has been reported that lead is further added to the metal vapor discharge lamp filled with iron. (Publication No. 54-15503) However,
When lead is added, the original purpose of inhibiting the formation of a thin iron film and maintaining ultraviolet output can be achieved, but at the same time, lead can inhibit the formation of mercury's 302, 313,
Because the output of the large emission line at 365 nm is extremely weakened, it is not often used for purposes such as photochemical reactions or curing paints.

It is also known to add tin, but this also has the problem that, together with lead, the output of the bright line spectrum of mercury is significantly reduced.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a 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. It is something.

[Structure of the invention]

The structure of the present invention is to place a metal vapor discharge lamp in which sufficient amounts of mercury and rare gas to maintain arc discharge as well as appropriate amounts of iron and halogen are placed inside an arc tube equipped with electrodes. Magnesium or magnesium halide is sealed in such a way that the gram atomic ratio of magnesium to iron is 1/40 to 2/3 to prevent iron from adhering to the inner wall of the arc tube and forming a thin film. shall be.

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, This causes a problem in which the emission spectrum becomes slightly weaker.

〔Example〕

Embodiments of the present invention will be specifically described below based on the drawings.

Figure 1 shows a metal vapor discharge lamp with a rating of 4KW used as a light source for photochemical reactions, with an inner diameter of 22
A pair of electrodes 2 are placed inside the arc tube 1 made of quartz with mmφ.
2 are arranged facing each other, and the distance between the electrodes is 250 mm.
Both ends of the arc tube 1 are sealed portions 11, a molybdenum foil 3 is sealed in the seal portion 11, and the outer conductor 4 and the electrode 2 are electrically connected via the molybdenum foil 3. Inside the arc tube 1, 120 mg of metallic mercury, 13 mg of iodine mercury, 5 mg of iron, 0.2 mg of magnesium, and 15 mmHg of argon gas are sealed. The amount of magnesium added is 1/11 in gram atomic ratio to iron.

When this metal vapor discharge lamp was lit, the lamp current was 12.3A and the lamp voltage was 362V when the lamp power was 4KW. Although the light was lit for up to 1000 hours, no iron adhered to the inner wall of the arc tube.
No thin film of iron is formed. At this time, the wavelength range is 280
Changes in the output of ultraviolet rays of ~400 nm were measured, and as shown by characteristic curve A in FIG. 2, the output maintenance rate was 90% after 1000 hours.

Incidentally, when a metal vapor discharge lamp similar to that used in this example but without magnesium added was lit for comparison, iron began to adhere to the inner wall of the arc tube after several tens of hours, and a thin film formed. Been formed. The output maintenance rate decreased to 50% after 1000 hours, as shown by characteristic curve B in FIG.

Next, we investigated the effect of adding magnesium on the mercury emission line spectrum output and the iron spectrum output, and found that the metal vapor discharge lamp of this example was significantly better than the one without the addition of magnesium. , the spectral output of mercury decreased by 3%, and the spectral output of iron decreased by 5%, which was a small decrease. On the other hand, in this example, in which lead and tin were added and encapsulated instead of magnesium, the spectral output of mercury decreased by 35% due to the addition of lead.
The addition of tin resulted in a 28% reduction, confirming that magnesium has almost no negative effect on the spectral output of mercury.

Further, the addition of magnesium has almost no effect on electrical characteristics such as starting voltage and restriking voltage.

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 a metal vapor discharge lamp filled with iron so that the gram atomic ratio to iron is 1/40 to 2/3, so that the added magnesium is It 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 prevents iron from adhering to the inner wall of the arc tube and prevents the formation of a thin film, so the wavelength range remains unchanged even when the lamp is turned on for long periods of time.
The output of ultraviolet light between 280 and 400 nm does not decrease. Therefore, the 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 cross-sectional view of a metal vapor discharge lamp, and FIG. 2 is an explanatory diagram of the characteristics of the output maintenance rate. DESCRIPTION OF SYMBOLS 1... Arc tube, 2... Electrode, 3... Molybdenum foil, 4... Outer conductor, 11... Seal part.

Claims (1)

[Claims] 1. In a metal vapor discharge lamp in which an appropriate amount of iron and halogen is sealed together with sufficient amounts of mercury and rare gas to maintain arc discharge inside an arc tube equipped with electrodes, magnesium metal or magnesium halide is A metal vapor discharge lamp characterized in that magnesium is enclosed in a gram atomic ratio of 1/40 to 2/3 to iron to prevent iron from adhering to the inner wall of the arc tube and forming a thin film.