JP5347875B2 - Long arc type discharge lamp - Google Patents

Abstract

The invention provides a long arc discharge lamp. A pair of electrodes are oppositely configured in a luminous tube, two ends of which are sealed up by using a foil seal structure so as to achieve the effects of preventing sealed-in materials from intruding sealed-up parts, preventing foil corrosion and inhibiting the leakage of the sealed-in materials from the sealed-up parts. The long arc discharge lamp is characterized in that the potential gradient of the lamp is below 8 V/cm, the input power of the lamp is above 80 W/cm, the emission length is larger than 50 cm, the sealed-in materials are mercury or a combination of metal except mercury and halogen, light with a wavelength shorter than 450 nm is radiated, and the working pressure during the light-up is negative pressure.

Description

  The present invention relates to a long arc type discharge lamp, and more particularly to a long arc type discharge lamp in which mercury or a metal other than mercury and a halogen are enclosed and both ends are sealed by a foil seal structure. is there.

  Conventionally, long arc discharge lamps in which mercury or a metal other than mercury and halogen are enclosed, for example, metal halide lamps, are used as discharge lamps that emit ultraviolet rays, for example, curing resins, adhesives, inks, and photoresists. It is widely used for various processing applications such as drying, melting or softening.

Such a long arc type discharge lamp is composed of an arc tube made of quartz glass and sealed portions at both ends thereof, and a metal foil is embedded in the sealed portion, and an electrode made of tungsten is connected to the metal foil. The one with the structure is common.
There are various types of sealing part structures, and a known one is one in which a plate-like or flat glass member is embedded in the sealing part and sealed using the glass member.
In this structure, the sealing portion side rear end of the electrode is formed flat, and a plate-like or flat glass member is disposed on the rear end side thereof, and the metal foil is provided on the upper and lower surfaces of the flat portion of the electrode. To the upper and lower surfaces of the glass member and joined to the external lead at the rear end.

Japanese Patent Application Laid-Open No. 2006-134710 discloses a long arc type discharge lamp having such a structure. In this lamp, a predetermined amount of rare gas, halogen, mercury, iron, and the like are placed inside the arc tube. Is encapsulated, and can be irradiated mainly with ultraviolet rays having a wavelength of around 365 nm during lighting.
In this patent document, an invention is described in which a small-diameter portion is formed in the body portion of the electrode to prevent the halogen on the sealing portion side from solidifying.

By the way, in such a long arc type discharge lamp, as described above, since the distance from the arc increases in the vicinity of the sealing portion, the temperature is inevitably lower than that of the light emitting portion, and halogen is not easily collected. In addition, this type of lamp generally has an operating pressure higher than atmospheric pressure, and the halogen tends to enter the sealing portion.
The temperature of the molybdenum foil of the sealing part varies depending on the lamp design and cooling conditions, but is at least 500 ° C. or more, and the reaction between molybdenum and halogen proceeds, and the metal foil made of molybdenum of the sealing member is Eventually eroded by halogen, the so-called “foil floating” phenomenon occurs, in which the interface where molybdenum and quartz glass are in close contact with each other is separated from the glass by high pressure. Further, when this foil floating further progresses, the inclusion in the lamp eventually flows out (leaks) to the outside, and an undesired phenomenon occurs such as mercury flowing out.

  The cause of such a leak is mainly due to the operating pressure during lighting. For this type of long arc type discharge lamp having a light emission length of 50 cm or more, the lamp input is 80 W / cm or more, so that it becomes a high input lamp of at least 4 kW or more. For this reason, when the lamp is turned on, the enclosure is completely evaporated and the operation pressure is at least 1 atm or more, which corresponds to what is called a high-pressure discharge lamp. In these lamps, this operating pressure is always applied to the sealing portion during lighting.

JP 2006-134710 A

  In view of the above-mentioned problems of the prior art, the present invention provides a long arc discharge lamp in which a pair of electrodes are disposed opposite to each other in an arc tube, and the arc tube is sealed with a foil seal structure at both ends. An attempt is made to provide a long arc type discharge lamp in which encapsulated halogen does not enter the encapsulated portion to erode the metal foil, or the halogen does not float and the encapsulated material does not flow out to the outside. To do.

In order to solve the above problems, in the long arc discharge lamp according to the present invention, the potential gradient is 8 V / cm or less, the lamp input power is 80 W / cm or more, the light emission length is 50 cm or more, Is a combination of mercury and / or a metal other than mercury and halogen, and has a feature that it emits light with a wavelength of 450 nm or less, and the operating pressure during lighting is negative.
More preferably, the gradient of potential is 8 V / cm or less, the operating pressure during lighting is 50 kPa or less, and the foil seal structure is a two-sheet foil. is there.

  According to the present invention, since the operating pressure at the time of lighting becomes a negative pressure of less than 1 atm while being a high input to the long arc type discharge lamp, the inclusion in the arc tube, particularly the halogen, penetrates into the sealing portion. Therefore, there is no corrosion of the metal foil, and there is an effect that the floating of the foil does not occur and the inclusion does not flow out to the outside. As a result, the life of the lamp is extended.

By the way, in order to set the operating pressure to a negative pressure, it is necessary to set a small amount of mercury or the like to be enclosed. As a result, the potential gradient (voltage) is kept low and the current increases. When this lamp current increases, it is necessary to increase the thickness of the foil or increase the width in order to increase the current capacity of the molybdenum foil.
Furthermore, as a method of increasing the current capacity, there is a method of increasing the number of molybdenum foils. However, the method of increasing the number of molybdenum foils increases the number of locations where the molybdenum foil and the electrode are welded, necessitating the insertion of a glass member between the molybdenum foils. It becomes easy to invade and easily causes the foil to float. Therefore, the structure of two or more foils is mainly used in xenon lamps that do not encapsulate halogens or short arc ultra-high pressure mercury lamps, and the lamps that contain halogens are usually sealed with one molybdenum foil.
On the other hand, in the present invention, as described above, because of the advantage that the inside of the arc tube has a negative pressure even when it is lit, it is less likely that the foil floats at the sealing portion than a normal high-pressure discharge lamp. A structure more than a foil can be adopted, and it can accurately cope with an increase in current capacity.

1 is an overall view of a long arc type discharge lamp according to the present invention. The fragmentary sectional view of FIG. Various lamps used for the experiment. The graph showing the illumination intensity maintenance factor of the various lamps of FIG.

FIG. 1 shows a long arc type discharge lamp of the present invention, and FIG. 2 is an enlarged view of a main part thereof.
In the figure, a long arc type lamp 1 is provided with sealing portions 3 at both ends of an arc tube 2 made of quartz glass, and a pair of electrodes 4 and 4 within the arc tube 2 has a predetermined distance, for example, 500 mm. They are arranged opposite to each other.
In this embodiment, the rear end 4a on the non-light-emitting space side of the electrode 4 is formed in a flat shape, and the rear end thereof has a flat shape in accordance with the shape of the electrode rear end 4a. A glass member 6 is disposed.
In the sealing part 3, the two metal foils 5 and 5 joined to the upper and lower surfaces of the flat rear end 4a of the electrode 4 by welding or the like extend along the upper and lower surfaces of the glass member 6, and the rear thereof. The end is connected to the external lead 7. The external lead 7 protrudes outside the arc tube 2 and is connected to a power supply line (not shown).

The arc tube 2 is filled with a predetermined rare gas, halogen, mercury, and iron. In this example, for example, ultraviolet rays having a wavelength of around 365 nm are mainly emitted during lighting.
The inclusions are not limited to the above, and may be A: mercury or all combinations of metals other than mercury + B: halogen.

Examples of these combinations are as follows.
Hg <mercury> + (I <iodine>, Br <bromine>)
Zn (zinc) + (I, Br)
・ Zn + FeI ₂ <Iron iodide>
・ Hg + FeI ₂
Metal α (Bi <bismuth>, Sb <antimony>) + (I, Br)

These luminescent materials are enclosed so that the potential gradient of the lamp is 8 V / cm or less.
Further, for example, xenon is enclosed as a rare gas for improving startability.
The light emission length determined by the distance between the electrodes is 500 mm or more, and the lamp input power is 80 W / cm or more.
The lamp encapsulating the above-mentioned luminescent material mainly emits ultraviolet light having a wavelength of 340 to 450 nm, and its uses include, for example, curing, drying, melting, or softening of resin, adhesive, ink, and photoresist. It is used for various processes.

Experimental examples are shown below.
Fig. 3 shows various types of long arc discharge lamps used in the experiment. Each lamp has the same shape and dimensions of the arc tube, sealing structure, light emission length, etc. Are different in voltage and operating pressure.
The lamp shown in Example 1 was sealed using an arc tube having an inner diameter of 22 mm at the center portion and an internal volume of 400 cm ³ so that the sealing pressure of mercury 130 mg, mercury iodide 10 mg and xenon gas was 8 kPa, A discharge lamp in which the electrode 4 is disposed at a distance between electrodes of 000 mm, has a rated point force of 16,000 W and a lamp voltage of 795 V.
The lamp shown in Example 2 was sealed using an arc tube having the same inner diameter and inner volume as in the lamp of Example 1 so that the sealing pressure of mercury 73 mg, mercury iodide 2 mg, and xenon gas was 4 kPa. Although the lamp has the same rated spot force of 16,000 W as that of the first embodiment, the lamp voltage is 585V.
The lamp shown in the conventional example was sealed using an arc tube having the same inner diameter and inner volume as that of the lamp of Example 1 so that the sealing pressure of mercury 825 mg, mercury iodide 2 mg and xenon gas was 4 kPa. The lamp has the same rated spot power of 16,000 W as in Example 1, but the lamp voltage is 1,357V.
The potential gradient of the conventional lamp is 13.6 (V / cm), whereas the lamp of Example 1 of the present invention has a potential gradient of 7.95 (V / cm). The lamp of 2 is as small as 5.85 (V / cm).
Correlating with this, when verifying the operating pressure of each lamp, the respective pressures of mercury, iodine, and xenon when the average gas temperature inside the lamp is 2,000 K,
“Gas equation of state”: P = nRT / V
Where P: operating pressure, n: number of moles, R: gas constant, T: absolute temperature = average gas temperature,
V: Calculated by the lamp internal volume, and summed them to determine the operating pressure.
The operating pressure thus obtained is 1.90 (atm) in the conventional example, whereas it is 0.81 (atm) in the first embodiment of the present invention and 0.41 (atm) in the second embodiment. In any of the lamps according to the present invention, it can be seen that the inside of the lamp has a negative pressure even in the lighting state.

FIG. 4 is a graph in which the life lighting test of each of the lamps is performed and the illuminance maintenance rate is plotted. The vertical axis represents the illuminance maintenance rate (%) with respect to the initial illuminance, and the horizontal axis represents the elapsed lighting time.
From the experimental results, as each lamp was lit, the illuminance decreased in the same manner at the same lighting time. However, although the conventional lamp leaked from the sealing portion at around 4,500 hours of lighting time, the lamps of Examples 1 and 2 continued to be lit while reducing the illuminance. In particular, Example 2 maintained lighting for over 8,000 hours. In the lamp of Example 2, since the internal pressure of the lamp at the time of lighting is lower, it is considered that the progress of the foil floating is delayed. Also, at the time of the leak, the atmosphere flowed into the lamp almost simultaneously with the leak, making it impossible to turn on the lamp, and almost no outflow of the inclusions to the outside was seen.
These are problems caused by the operating pressure at the time of lighting of the lamp enclosing the halogen, regardless of the presence or absence of mercury, and the same tendency can be seen when halogen and other metals are added.

  As described above, even in a lamp having the same arc tube shape and sealing portion structure, the present invention in which the operating pressure is a negative pressure less than the atmospheric pressure compared to the conventional lamp in which the operating pressure in the arc tube is equal to or higher than the atmospheric pressure. In this lamp, the occurrence of leakage of the encapsulated material in the sealing portion is suppressed for a long time, and it can be seen that the lifetime is significantly extended.

DESCRIPTION OF SYMBOLS 1 Long arc type discharge lamp 2 Arc tube 3 Sealing part 4 Electrode 4a Flat electrode rear end 5 Metal foil 6 Glass member 7 External lead

Claims (3)

In a long arc type discharge lamp in which a pair of electrodes are arranged opposite to each other in the arc tube, and the arc tube is sealed with a foil seal structure at both ends,
The potential gradient is 8 V / cm or less, the lamp input power is 80 W / cm or more, the light emission length is 50 cm or more, and the inclusion is a combination of mercury and / or a metal other than mercury and a halogen, A long arc discharge lamp having light emission with a wavelength of 450 nm or less and having a negative operating pressure when lit.
  2. The long arc discharge lamp according to claim 1, wherein an operating pressure at the time of lighting is 50 kPa or less. 2. The long arc discharge lamp according to claim 1, wherein the foil seal structure is a two-sheet foil.

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