JP2003323863A - Low-pressure mercury discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a life-prolongation of a lamp by suppressing the start voltage lower and by suppressing the sublimation rate of the electrode lower. <P>SOLUTION: In a low-pressure mercury discharge lamp, a gas sealed in the discharging lamp is made to have two kinds of mixed inert gases. These mixed gases are preferably a mixed gas of Ar gas and Ne gas, a composition molar ratio of the Ar gas and the Ne gas is set within a range of Ar:Ne=5:5 to 1:9, and preferably the composition molar ratio of the Ar gas and the Ne gas is set to be Ar:Ne=7:3. By this, the start voltage of the discharging lamp can be suppressed lower, and the life-prolongation of the lamp can be realized by also suppressing the sublimation rate of the electrode lower. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low pressure mercury discharge lamp, and more particularly to a low pressure mercury discharge lamp capable of reducing the starting voltage.

[0002]

2. Description of the Related Art Generally, a mercury lamp has a structure in which a rare gas such as argon and a metal are enclosed in a pipe-shaped quartz glass and a voltage is applied to both ends to cause a discharge. It is generally called a mercury lamp because the metal contained in it is mercury. Mercury lamps are divided into low-pressure mercury lamps and high-pressure mercury lamps because of the difference in the vapor pressure of mercury contained in them. Especially, in low-pressure mercury lamps, the density of mercury inside is low, so there is little energy exchange between atoms, Efficiently generates light of a wavelength that is peculiar to and can easily transfer energy. This is a germicidal ray (UV
It is called C).

Conventionally, low-pressure mercury discharge lamps have been rare gas (A
r, Kr, Ne, Xe) or the like is used. Atoms belonging to Group 8A of the Periodic Table have characteristics that they are difficult to ionize and that they are difficult to combine with other atoms. Since they are in a stable state by a single atom, they are generally called inert gas. . The discharge light emission performed in a state in which this inert gas is enclosed, ionizes this inert gas, a Group 2 element called alkaline earth metal, and a Group 2B element to form a streamer of electrons and It is a mechanism that emits the outermost electron outside the inner orbit of the electron, builds an excited state that repeats trapping infinitely, and emits light when transiting to the ground state (stabilization).

By the way, mercury is ionized in a temperature range around 330 ° C. where it vaporizes inside the tube, and mercury is ionized at a low pressure (760 Tor).
The emission line of the mercury atom (r or less) is the triplet excited state 6 ³
It occurs when the transition from P ₁ to the ground state 6 ¹ S is repeated. The mercury pressure inside the tube at the time of this excitation is in the state of several Torr, and the luminous efficiency is 253.7 nm (254 nm).
The bright line emits the strongest. At this time, the luminous intensity of mercury maintains about 30% of the total intensity.

Further, the increase of the pressure of the enclosed gas inside the discharge lamp is caused by the repeated collision of discontinuity between the streamer of electrons (electrons emitted from the electrode) and the mercury ion due to the increase of the applied current value. Mercury ion self-absorption occurs, the relative intensity of the resonance emission line decreases, and the continuous emission intensity on the long wavelength side is amplified instead. At this time, the internal pressure of the tube is about 2 atm (1500 Torr), and the emission bright lines 302, 313, 365, 40 are also changed depending on the pressure.
5, 436 nm, etc.

[0006]

In such a low pressure mercury discharge lamp, it is desirable to keep the starting voltage low.
Generally, a size of 64 inches has an approximate target voltage of 600 to 700V. When this starting voltage rises,
Since the pressure inside the tube is different, the lamp voltage during discharge tends to rise. As the lamp voltage rises, the current decreases, sputtering occurs, the electrodes are sputtered, and eventually the wire may be broken. Therefore, lowering the starting voltage to reduce the sublimation rate of the electrodes leads to an improvement in life. However, in order to lower the starting voltage, it is necessary to lower the filling pressure of an inert gas such as Ar. For example, in order to reduce the starting voltage by about 40%, it is necessary to set the Ar gas filling pressure to 0.1 Torr or less. However, when the gas pressure is lowered, the sublimation rate of the electrode increases, which causes a defect such as a shortened lamp life.

The present invention has been made by paying attention to the above-mentioned conventional problems, and it is possible to achieve a long lamp life by suppressing the starting voltage and the sublimation rate of the electrodes to be low. An object is to provide a low pressure mercury discharge lamp.

[0008]

In order to achieve the above object, in the low-pressure mercury discharge lamp according to the present invention, the gas sealed in the discharge lamp is a mixed gas of at least two kinds in an inert gas. Is characterized by. This mixed gas is A
A mixed gas of r gas and Ne gas may be used, and the composition molar ratio of Ar gas and Ne gas is Ar: Ne = 5: 5-1: 1.
The composition molar ratio of the Ar gas and the Ne gas may be set to Ar: Ne = 7: 3.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of a low-pressure mercury discharge lamp according to the present invention will be described below with reference to the drawings.
The details will be described. The low-pressure mercury discharge lamp according to the embodiment has an arc tube 1 made of quartz glass that transmits ultraviolet rays.
0 is provided with a pair of electrodes 12a and 12b at both ends, and an AC voltage is applied to the electrodes 12a and 12b to enclose a gas in which at least two kinds of inert gases are mixed together with mercury, and the discharge is performed inside the arc tube 10. The vaporization of mercury produces ultraviolet rays.

1 and 2 are block diagrams of the discharge lamp according to the present embodiment. The electrodes 12a and 12b are composed of a filament 14 which is a discharging member and a current conducting portion 18 which connects the filament 14 and the internal pin 16 which is a voltage applying portion. The electrical conducting portion 18 is formed of two molybdenum foils 22 embedded in a pinch seal 20 that seals the ends of the arc tube 10 and a high melting point substance such as tantalum material. And a pair of internal stem shafts 24 that are respectively connected to the parts and penetrate the inside of the pinch seal 20 to project inside the arc tube and an external stem shaft 26 that projects outside the arc tube 10.
And a nickel lead wire 28 connecting the outer stem shaft 26 and the inner pin 16.

Both ends of a filament 14 formed of a refractory material such as tungsten are joined to the upper ends of two internal stem shafts 24 arranged so as to project from the upper portion of the pinch seal 20 into the arc tube 10. Has been done. By adjusting the wire diameter and the number of windings, the filament 14 has an optimum color temperature range (70) when a voltage is applied to the electrodes.
The cold resistance value is set to be 0 to 800 Kelvin). The joint portion between the filament 14 and the inner stem shaft 24 is annealed by hydrogen gas to remove impurities of a high melting point material such as a tungsten material or a tantalum material and suppress oxidation, so that the inside of the arc tube is oxidized at the start of discharge. Prevents the release of ionic ions.

Nickel lead wires 28 are connected to the ends of two external stem shafts 26 connected so as to project from the ends of the arc tube 10. This nickel lead wire 28
Are joined to each other at positions equidistant from the ends of the two external stem shafts 26. In this way, the resistance between the two is made equal by joining the both at positions where the distance is equal. Thereby, the color temperatures at both ends of the filament 14 can be equalized. The joint portion of the two nickel lead wires 28 is joined by using spiral spot welding in which another nickel wire 30 is wound around the two nickel lead wires 28 and joined together, so that the joining strength is enhanced. ing. Then, the nickel lead wire 28 is spot-bonded to the internal pin 16 of the socket 32 to enable electrical conduction with a power source (not shown).

In the discharge lamp having the above structure, the rare gas is enclosed in the arc tube 10. In the present embodiment, the gas enclosed in the arc tube 10 is a mixture of at least two kinds of inert gas. Gas, and in particular, the mixed gas is a mixed gas of Ar gas and Ne gas. And
The composition molar ratio of the Ar gas and the Ne gas is Ar: Ne =
It is set in the range of 5: 5 to 1: 9, and preferably, the composition molar ratio of the Ar gas and the Ne gas is Ar: Ne.
= 7: 3.

The noble gas (group 8A), which should be an insulator, becomes conductive because the particles emitted by thermoelectrons collide with the atoms constituting the noble gas and are ionized to generate high energy particles and momentum. It is exchanged and released into the space. Since the particles discharged into the discharge space have an electric charge, they are accelerated by the electric field,
It collides with the cathode (heater coil), emits secondary electrons again and is accelerated toward the anode. The accelerated secondary electron repeats spin motion in space, amplifies energy, collides with gas molecules having a certain density or more to be ionized, and an avalanche phenomenon in which ions and electrons are generated one after another occurs. This phenomenon recombines inside the discharge space and reaches a steady state.
That is, by mixing a rare gas atom having a low ionization probability with a high metastable excitation voltage in order to increase the ionization property (ionization), the ionization steady value can be obtained with a relatively low energy.

When a small amount of Ar is mixed in the rare gas Ne, the metastable excitation voltage Vm of Ne is 16.6 eV, so that a large amount of Ne metastable atoms Ne ¹⁰ are generated, which is slightly lower. Ar atoms having an ionization voltage of 15.8 eV can be easily ionized and ionized with a relatively low energy. Since Ne ¹⁰ has the same mass as Ne ^+, it has many opportunities to collide with Ar, and the probability of ionizing Ar is almost “1”.

When a trace amount of Hg is mixed in Ar, Ar ¹⁸ is similarly generated at 11.5 eV, which is close to 10.4.
Easily ionize Hg having an ionization voltage of eV. A low-pressure mercury lamp is 1 × 1 which is determined by Ar at a pressure of several Torr and vapor pressure.
Discharge with a mixed gas of Hg of about 0 ^-3 Torr. The Hg light ionized at that time is a mercury resonance line.

The composition molar ratio of Ar gas and Ne gas is Ar:
The mixed gas changed within the range of Ne = 5: 5 to 1: 9 was used. The rare gas having the same filling ratio is filled with 1 Torr of the rare gas having an improved mixing ratio of 2 Torr. After getter mercury excess amount or vacuum evacuation, 100 mg of cold mercury trapped is filled. Washing in the exhaust process is performed three times with the improved rare gas of about 100 Torr. The results are shown in the table below.

[Table 1]

In this experiment, according to an example, when the ratio of Ar in the mixed gas of Ne and Ar was increased, the luminous efficiency of the mercury resonance emission line (254 nm) was increased by the molar ratio Ne + Ar.
(7: 3) with 100% as a peak, Ne + Ar (5:
In 5), it decreased to 70%, and in Ne + Ar (3: 7), it decreased to 5%.
It fell to 5%. Similarly, when the ratio of Ar is extremely reduced, the emission efficiency was 70% when the ratio was Ne + Ar (9: 1), which was the same as when the ratio was 5: 5. The composition is Ne: Ar =
It was judged that 7: 3 was appropriate. FIG. 3 shows changes in luminous efficiency and the molar ratio of the mixed gas.

As a result of repeated experiments, it was found that the control temperature at which the radiation efficiency of the mercury resonance line having a wavelength of 254 nm reaches the maximum value is about 40 ° C. (see FIG. 4). When the current value flowing through the heater coil is 4.6 A to 4.75 Amp, the color temperature of the heater reaches a temperature of 750 Kelvin to 800 Kelvin steady value. At this time, electrons are emitted from the crystal of the electron emitter doped into the heater coil, and the enclosed rare gas is ionized and ionized. When Ne and Ar were selected as the rare gases and they were mixed and used at a composition molar ratio of Ne + Ar (1: 9), they were easily affected by the ambient atmospheric temperature, and a sufficient mercury resonance line could not be obtained.

When a discharge lamp in which a rare gas having a mixed molar ratio of Ne: Ar = 1: 9 is filled at about 1 Torr and about 90 mg of G / Hg is turned on, a discharge lamp of a comparative example (L5 manufactured by GS, L5) is produced.
00US type), the starting voltage is higher and the peeling property of the electron emission material doped in the heater coil is also higher. Judging from the theoretical discharge value, it was confirmed that the starting voltage of the fixed volume containing the rare gas 3 Torr with the Ar + Ne mixture ratio (5: 5) was lower than the starting voltage of the Ar gas 1 Torr. Further, in order to obtain the same level of radiation efficiency of the mercury resonance line as that of the rare gas of Ar + Ne (7: 3), the lamp of the same shape containing Ar gas needs to have a pressure of 0.1 Torr or less.

Specifically, the discharge voltage and the radiation efficiency of a lamp of the same shape in which Ar gas was filled at 3 Torr were mixed at a preset composition molar ratio, and Ar + Ne gas (3: 7) was filled at the same pressure for comparison. The results of the experiments are shown in the table below. Radiation efficiency is 100 compared to Ar gas only
%, The starting voltage was 40% lower.
The following table is a comparative table of measured data when used for photooxidative decomposition lamps.

[Table 2]

As can be seen from this table, the starting voltage (discharge starting voltage) could be lowered to 450 V by using Ar + Ne gas (3: 7). Quasi-resonance emission intensity (254 nm) due to self-absorption in mercury gas due to increase in mercury vapor pressure inside the tube and increase in internal temperature.
Decreases, the relative intensity of the long-side emission line increases, and the emission line width increases (transition from triplet excited state 6 ³ P ₁ to ground state 6 ¹ S, resonance emission 7 ¹ P ₁ → 6 ¹ S , At 185 nm).

[0023]

As described above, the present invention is characterized in that the gas enclosed in the discharge lamp is a mixed gas of at least two kinds of inert gas. This mixed gas may be a mixed gas of Ar gas and Ne gas.
The composition molar ratio of r gas and Ne gas is Ar: Ne = 5: 5.
It is set in the range of 1: 9, preferably Ar gas and Ne.
Since the discharge lamp has a composition molar ratio of gas set to Ar: Ne = 7: 3, it is possible to maintain the discharge efficiency while keeping the starting voltage low and the sublimation rate of the electrode low. The effect that the life can be extended was obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a low pressure mercury discharge lamp according to an embodiment.

FIG. 2 is an enlarged sectional view of an electrode part of the lamp.

FIG. 3 is a graph showing the relationship between rare gas mixture molar ratio and luminous efficiency.

FIG. 4 is a graph showing changes in relative illuminance with respect to temperatures of 184 nm and 254 nm of mercury emission lines.

[Explanation of symbols]

10 ... Arc tube, 12a, 12b ... Electrode, 14 ...
...... Filament, 16 ………… Internal pin, 18 ………… Current conducting part, 20 ………… Pinch seal, 22 ………… Molybdenum foil, 24 ………… Internal stem shaft, 26 ………… External stem shaft, 28 … Nickel lead wire, 30… Nickel wire, 32… Socket.

Claims (4)

[Claims] 1. A low-pressure mercury discharge lamp, characterized in that the gas enclosed in the discharge lamp is a mixed gas of at least two kinds in an inert gas. 2. A low-pressure mercury discharge lamp, wherein the mixed gas is a mixed gas of Ar gas and Ne gas. 3. The low-pressure mercury discharge lamp according to claim 1, wherein the composition molar ratio of the Ar gas and the Ne gas is set in the range of Ar: Ne = 5: 5 to 1: 9. 4. The low pressure mercury discharge lamp according to claim 1, wherein the composition molar ratio of the Ar gas and the Ne gas is set to Ar: Ne = 7: 3.