JP2008034222A - Short arc-type mercury lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure not generating white turbidity on an inner wall of a discharge vessel. <P>SOLUTION: A pair of electrodes are arranged in opposition in a discharge vessel made of quartz glass, in which, 2 to 12 (mg/cm<SP>3</SP>) of mercury, 1 to 8 (atmospheric pressure) of Argon (Ar), krypton (Kr) or their mixture gas are sealed in, with at least ultraviolet rays of wavelengths of 200 to 300 (nm) irradiated. Then, at least either of the electrodes is loaded with tantalum, and at the same time, a volume of hydrogen stored by the tantalum is to be 3×10<SP>16</SP>pcs/cm<SP>3</SP>or less in hydrogen molecule conversion per internal volume of the discharge vessel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a short arc type mercury lamp. In particular, the present invention relates to a short arc type mercury lamp that efficiently emits ultraviolet rays having a wavelength of 250 nm to 350 nm.

  Short arc type mercury lamps are used in various exposure processes such as semiconductors, liquid crystals, and printed circuit boards. In recent years, in exposure of a liquid crystal substrate, a color filter, and the like, an increase in exposure area and an increase in throughput are being demanded. Furthermore, until now, g-line (436 nm), h-line (404 nm), and i-line (365 nm) have been used, but ultraviolet rays with shorter wavelengths are being demanded. That is, the lamp is required to efficiently radiate ultraviolet rays having a shorter wavelength than i-line (365 nm), specifically, ultraviolet rays having a wavelength of 250 nm to 350 nm.

In order to radiate ultraviolet rays efficiently, impurities present in the light emitting portion must be removed. This is because the presence of impurities may contaminate the inner wall of the light emitting portion or promote electrode wear.
For this reason, a technique using tantalum as a getter is known, and is described in, for example, Japanese Patent No. 3077538.
However, even when using a tantalum getter, white turbidity still occurs on the inner wall of the light emitting part. This phenomenon often occurs in a high-power lamp, and is remarkably generated in a lamp that emits ultraviolet light having a wavelength of 250 nm to 350 nm.

  In a short arc type mercury lamp using a tantalum getter, a configuration is provided in which white turbidity is not generated on the inner wall of a light emitting part.

In order to solve the above-described problems, a short arc type mercury lamp according to the present invention has a pair of electrodes opposed to a light emitting portion made of quartz glass, 2-12 (mg / cm ³ ) mercury, 1 Argon (Ar), krypton (Kr), or a mixed gas thereof of ˜8 (atmospheric pressure) is enclosed, and emits ultraviolet rays having a wavelength of at least 200 to 300 (nm). At least one of the electrodes is filled with tantalum, and the amount of hydrogen stored in the tantalum is 3 × 10 ¹⁶ atoms / cm ³ or less in terms of hydrogen molecules per inner volume of the light emitting part. It is characterized by that.

Furthermore, when the internal volume V (cm ³ ) and the internal surface area S (cm ² ) of the light emitting part are satisfied, the relationship of S / V ≦ 0.8 is satisfied.
Further, the light emitting portion is spherical and has an outer diameter D (cm) satisfying a relationship of 7.5 ≦ D.

FIG. 1 shows a schematic configuration of a short arc type mercury lamp according to the present invention.
The mercury lamp includes a discharge vessel 10 made of quartz glass, and the discharge vessel 10 includes a light emitting unit 11 and a rod-shaped sealing unit 12. A light emitting space is formed inside the light emitting unit 11, the cathode 20 and the anode 30 are arranged to face each other with a gap of, for example, 5.0 mm, and an arc bright spot is formed at the tip of the cathode 20. The light emitting portion 11 has a spherical shape or a spindle shape elongated in the tube axis direction.

The cathode 20 is a cylindrical rod made of thorium tungsten, for example, and the tip is formed in a substantially conical shape and is supported by the cathode rod 21.
The anode 30 is made of tungsten, for example, and is a cylindrical rod as a whole, has a substantially bullet shape with a flat surface at the tip, and is supported by the anode rod 31.

The bases of the cathode bar 21 and the anode bar 31 extend toward the sealing part 12, and a molybdenum foil (not shown) is embedded in each sealing part 12 to form an airtight sealing structure. An external lead 13 protrudes from the outer end of the sealing portion 12, and the external lead 13 is connected to a power supply device (not shown) to supply current. The cathode 20 and the anode 30 do not need to be physically separated from the cathode rod 21 and the anode rod 31, respectively. For example, the cathode 20 and the anode 30 may extend with the same outer diameter and have a physically integrated structure. It doesn't matter.
A tantalum getter 40 is attached to the cathode bar 21. The tantalum getter 40 has a plate shape and is attached to the cathode rod 21 so as to be crushed.

  FIG. 2 shows the same structure as the lamp shown in FIG. 1, and shows the length of the light-emitting portion 11 and the length L in the longitudinal direction of the lamp and the length D in the direction perpendicular to the longitudinal direction of the lamp. When the light emitting portion is spherical, the length D and the length L are the same.

The light emitting unit 11 is filled with mercury and a rare gas containing argon or krypton.
The amount of mercury enclosed is in the range of 2 to 12 mg / cc per inner volume of the light emitting space, and is included, for example, 5 mg / cc. The amount of rare gas sealed is 1.0 to 8.0 atm, for example, 3 atm. The total internal pressure during steady lighting of mercury and rare gas is about 18 atmospheres.

  Here, the present inventors not only improve the radiation amount of i-line (365 nm) when argon or krypton is sealed in a positive pressure (1 atm or more) in association with a predetermined amount of mercury, It has been found that the radiation amount of ultraviolet rays having a wavelength of 250 nm to 350 nm is also improved. This is because argon and krypton do not only improve startability but also contribute to an increase in the amount of ultraviolet radiation even during steady lighting. Specifically, the amount of radiation from the arc itself increases. This is based on the two actions of increasing the density of radiant spots in order to contract the arc.

  Of the two effects, the increase in radiation amount will be described. The ionization voltage of the rare gas is 12.1 eV for xenon, 14.0 eV for krypton, and 15.8 eV for argon, and is higher in the order of xenon, krypton, and argon. The gas with a higher ionization voltage has a higher arc temperature than the gas with a lower ionization voltage, and the higher the arc temperature, the more mercury atoms in the excited state in the arc. A gas having a high ionization voltage, that is, argon or krypton has a larger radiation amount than xenon having a low ionization voltage.

  Further, the ionization voltage of mercury is 10.4 eV, which is lower than that of xenon, krypton, and argon. For this reason, when the amount of rare gas enclosed is larger than the amount of mercury enclosed, the arc temperature increases and the amount of ultraviolet radiation increases. Specifically, when the number of moles of rare gas sealed is more than twice the number of moles of mercury sealed, the amount of ultraviolet radiation increases at a practical level.

Since mercury is a luminescent species, a certain amount must be enclosed. This is because if the amount of mercury enclosed becomes too small, the number of excited atoms itself decreases. In the present invention, from the viewpoint of securing excited mercury atoms, mercury needs to be 2.0 mg / cm ³ or more, and the range is desirably 2.0 to 12.0 (mg / cm ³ ). This is because if it exceeds 12.0 mg / cm ³ , the absorption width of the resonance line having a wavelength of 254.7 nm widens, and the amount of radiation at a wavelength longer than 254.7 nm (near 255 to 270 m) decreases.

  Next, of the two actions, the action of arc contraction will be described. Argon and krypton have a property that the arc is more easily contracted than xenon, and the arc contracts, so that the arc becomes dense and the radiation intensity is increased. improves.

  “Positive pressure” means 1 atmosphere or more, and by sealing 1 atmosphere or more in terms of room temperature, the amount of radiation (radiation efficiency) increases in proportion to the enclosed pressure. On the other hand, if argon or krypton exceeds 8 atm, the lamp may burst, which is not desirable.

As described above, in the present invention, a predetermined amount of mercury and a predetermined amount of argon or krypton are inseparably close and integral, and a numerical range is described while having an organic relationship with each other. The radiation amount can be increased by ˜350 nm and the radiation efficiency can be increased by the arc contraction effect. Specifically, the enclosed amount of mercury is 2.0 to 12.0 (mg / cm ³ ), and the enclosed amount of argon or krypton is 1 to 8 atm. The basis for the numerical limitation will be described in an experiment described later.

Furthermore, in the present invention, in addition to defining the amount of mercury and argon or krypton enclosed, the amount of hydrogen occluded by tantalum is defined. Tantalum is attached to the electrode as a getter, but is defined as 3 × 10 ¹⁶ atoms / cm ³ or less in terms of hydrogen molecules per inner volume of the light emitting part.
The reason for using the getter is adsorption of impurities in the light emitting space. In particular, when hydrogen is present (floating) in the light emitting space, the starting voltage (discharge breakdown voltage) becomes high. For this reason, it is possible to suppress an increase in starting voltage by arranging tantalum so as to be exposed to the discharge space and storing hydrogen floating in the light emission space.

  However, even when tantalum is used, although hydrogen adsorption and starting voltage can be suppressed, there arises a problem that the inner wall of the light emitting part becomes cloudy as the lighting time elapses. This is because as the lighting time elapses, the temperature of the light emitting space rises and hydrogen stored in the tantalum is released, and this hydrogen is intense together with the quartz glass constituting the inner wall of the light emitting part. It is presumed that the irradiated surface is deteriorated by being irradiated with ultraviolet rays.

  In particular, in the case of a lamp that mainly emits light having a wavelength of 350 nm or more, since the wavelength of light that irradiates the inner wall of the light emitting part is large, generation of white turbidity does not occur practically even when irradiated to quartz glass, but the wavelength of 250 nm to 350 nm. In the case of UV rays, since the energy of light is high, the occurrence of white turbidity is not negligible due to irradiation of quartz glass.

  Here, the getter will be described. Although the getter includes zirconium, the reason for using tantalum is that it is suitable as a material that operates in a high temperature region exceeding 1000 ° C. Carbon, oxygen, and nitrogen are released as impurities from the discharge vessel and the electrode. These impurities react with the electrode to form a low melting point compound of tungsten, causing the electrode to evaporate and prematurely discharge vessel blackening, making the getter indispensable.

  In addition, tantalum can irreversibly take in impurities such as carbon, oxygen, and nitrogen, that is, once it is occluded, it will not be released, but it has a reversible property with respect to hydrogen, and at room temperature, tantalum. Even if occludes hydrogen, the hydrogen is released again into the light emitting space when the temperature rises.

As described above, the present invention uses argon or krypton as a rare gas. Since argon and krypton have a higher thermal conductivity of gas than xenon, the temperature of the discharge vessel tends to increase. Moreover, since the irradiance of ultraviolet rays is higher than when xenon is used, the illuminance on the discharge vessel is also high.
Further, since the gas temperature in the discharge vessel is generally high, hydrogen is easily released into the discharge vessel, and the released hydrogen gas is also in a high temperature state.
In other words, when argon or krypton is used as a rare gas, the temperature inside the discharge vessel is higher than when xenon is used, and the degree of tantalum releasing hydrogen is higher, and furthermore, white turbidity occurs on the inner wall of the discharge vessel. It has become easier.

In summary, firstly, a lamp that emits ultraviolet light having a wavelength of 250 to 350 nm has higher radiation energy than a lamp that emits light having a wavelength of 350 nm or more, and therefore the energy applied to quartz glass is also high.
Second, a lamp using argon or krypton as a rare gas has a higher temperature in the discharge vessel than a lamp using xenon as a main component, and hydrogen is not easily released from tantalum.
As a result of having such preconditions, the present invention creates a new problem of causing white turbidity on the inner wall of the discharge vessel, and also finds that the problem occurs at a level that has a practical impact, and its solution, In other words, it is nothing but to reduce the amount of hydrogen originally stored by tantalum.

Furthermore, the present invention focuses on not only hydrogen released from tantalum but also hydrogen released from the discharge vessel, and the volume V (cm ³ ) of the light emitting part and the inner surface area S (cm ² ) of the light emitting part. The relationship is defined numerically.
That is, it is considered that hydrogen that causes white turbidity is released from the quartz glass constituting the discharge vessel into the inside of the light emitting part in addition to the tantalum occluded originally. This regulation can be said to be a numerical regulation that should suppress the occurrence of cloudiness more precisely.

  Here, hydrogen existing inside the discharge vessel is mixed in a step of forming the discharge vessel or a sealing step with a mixed gas burner of oxygen and hydrogen. For this reason, hydrogen from the mixed gas burner dissolves in the quartz glass constituting the discharge vessel, and is released into the discharge vessel during lighting. Further, even if quartz glass is released into the discharge space in the form of water instead of hydrogen, it is changed to hydrogen when it is decomposed by an arc. Therefore, it has been derived that the generation of white turbidity can be prevented by defining the amount of hydrogen contained in quartz glass.

  Here, for the sake of simplicity, assuming that the amount of impurities released from the discharge vessel per unit volume is ρ, the thickness of the discharge vessel is t, and the inner surface area is S, all impurities are released into the discharge vessel. The amount is given by ρtS. The average concentration n of impurities in the discharge vessel is given by n = ρtS / V, where V is the discharge vessel volume, and can be approximated by S / V. Thereby, when the internal volume of the discharge vessel becomes relatively larger than the internal surface area of the discharge vessel, the hydrogen gas concentration in the discharge vessel decreases. In the present invention, assuming that the inner surface area of the discharge vessel and the inner volume of the discharge vessel affect the amount of hydrogen released into the light emitting space, the discharge vessel inner surface area (S) ÷ the discharge vessel inner volume (V) is defined. It is.

Next, an experiment regarding a numerical range related to the present invention will be described.
First, an experiment was conducted on the relationship between the amount of mercury enclosed in the discharge vessel and the radiation amount of the mercury lamp.
(Experiment A)
Five types of lamps with different mercury contents (Lamp A1 to Lamp A5) are prepared, and 1 mg / cm ³ , 2 mg / cm ³ , 5 mg / cm ³ , 12 mg / cm ³ , and 13 mg / cm ³ are enclosed in each lamp. did. The other lamp specifications and lighting conditions are basically the same, the electrode distance is 4.5 mm, the tube wall load is 20 W / cm ² , the discharge vessel is 3 mm thick, the noble gas is sealed at 1 atm, and the input power is 2 KW. Direct current was turned on. For the measurement, a spectroscope was placed at a position 1 m from the lamp, and the integral amount from a wavelength of 250 nm to a wavelength of 300 nm was measured.

FIG. 3 shows the result of Experiment A. In the experiment, the radiation amount of each lamp when the radiation amount of the lamp A4 was set to 100 was expressed as a relative value, and the case where the relative value exceeded 100 was judged as acceptable, and the case where the relative value was less than 100 was judged as unacceptable.
From the results shown in the figure, the lamp A2 of mercury filling amount 2 mg / cm ^3, the lamp A3 of mercury filling amount 5 mg / cm ^3, the lamp A4 of mercury filling amount 12 mg / cm ³ is passed a large amount of radiation, lamp A1 of mercury filling amount 1 mg / cm ^3, the amount of enclosed mercury lamp A5 of 13 mg / cm ³ had failed small amount of radiation. That is, it can be seen that the radiation amount is at least large when the amount of enclosed mercury is 2 to 13 mg / cm ³ . In addition, as described above, when the amount of enclosed mercury is 1 mg / cm ³ , it is considered that the amount of mercury is too small in the sense of luminescent species, and that the radiation amount is reduced, and when the amount of enclosed mercury is 13 mg / cm ³ , the wavelength The absorption width of the resonance line of 254.7 nm is considered to be the cause of the decrease in radiation amount.

Here, in the resonance absorption at a wavelength of 254.7 nm, the wavelength width for resonance absorption greatly depends on the distance from the arc to the inner wall of the discharge vessel and the amount of mercury existing therebetween. That is, when the discharge vessel becomes larger in dimension, the distance from the arc to the inner wall of the discharge vessel increases, and the resonance absorption of ultraviolet rays tends to occur. Furthermore, when the density of mercury present on the optical path is high, it is natural that resonance absorption is likely to occur. In the present invention, when the maximum inner diameter of the discharge vessel (the inner diameter of the discharge vessel at the position of the arc and indicated by L in FIG. 1) is 40 mm to 140 mm, which is the inner diameter value of a commonly used mercury lamp, If the mercury amount is 12 mg / cm ³ or less, it means that it is not affected by resonance absorption.

  In addition, although the wavelength range which this invention calculates | requires is 250 nm-350 nm, in the said experiment, the radiation amount of wavelength 250nm-300nm is evaluated as a measuring object. This is because the transmittance of quartz glass (discharge vessel) greatly changes in the wavelength range of 250 to 300 nm, so if sufficient radiation is obtained up to the wavelength of 300 nm, naturally sufficient radiation is also obtained at the wavelength of 300 to 350 nm. Experimenting on the premise.

Next, experiments were conducted on the relationship between the rare gas sealed in the discharge vessel, the amount of the sealed rare gas, and the radiation amount of the mercury lamp.
(Experiment B)
Nine types of lamps (lamps B0 to B8) with different kinds of rare gases and different amounts of filling were prepared. Specifically, as the type of rare gas, the lamp B0 encloses xenon, the lamps B1 to B4 enclose argon, and the lamps B5 to B8 enclose krypton. Among the lamps B1 to B4 enclosing argon, the lamp B1 is 0.5 atm, the lamp B2 is 1.0 atm, the lamp B3 is 3.0 atm, the lamp B4 is 8.0 atm, and the lamps B5 to B8 are encapsulated with krypton. Among them, lamp B5 encloses 0.5 atm, lamp B6 encloses 1.0 atm, lamp B7 encloses 3.0 atm, and lamp B8 encloses 8.0 atm. The lamp B0 has the same specifications as the lamp A3 of Experiment A. The lamp specifications and lighting conditions other than the above are basically the same, and the distance between the electrodes is 4.5 mm, the mercury amount is 5 mg / cm ³ , the discharge vessel is 3 mm thick, and the direct current is input with the tube wall load of 16 w / cm ^2. The amount of radiation was measured after lighting. The measurement was performed by placing a spectroscope at a position 1 m from the lamp.

FIG. 4 shows the result of Experiment B. In the experiment, the radiation amount of each lamp when the radiation amount of the reference lamp B0 is set to 100 is expressed as a relative value, and when the relative value exceeds 102, it is judged as acceptable, and when the relative value is less than 102, it is judged as unacceptable. .
From the results shown in the figure, in the lamp filled with argon, the lamp B1 with an enclosed gas pressure of 1.0 atm, the lamp B3 with an enclosed gas pressure of 3.0 atm, and the lamp B4 with an enclosed gas pressure of 8.0 atm have a large radiation amount and pass. Of the lamps in which krypton was sealed, lamp B6 with a sealed gas pressure of 1.0 atm, lamp B7 with a sealed gas pressure of 3.0 atm, and lamp B8 with a sealed gas pressure of 8.0 atm passed the large radiation amount. The lamp B1 having an argon sealing gas pressure of 0.5 atm and the lamp B5 having a krypton sealing gas pressure of 0.5 atm failed in the same manner as in the case of xenon radiation.
That is, it is understood that the rare gas to be sealed is not xenon but argon or krypton, and the radiation amount is large when the sealed gas pressure is 1 to 8 atmospheres. As described above, when the sealed gas pressure is 1 atm, it is considered that the cause of the failure is that the sealed amount is too small and the radiation amount from the arc is not increased sufficiently.
In this experiment, since the ellipsoidal mirror is not used to focus on the arc bright spot, the effect of increasing the radiation amount due to arc contraction cannot be achieved.

As described above, Experiment A can explain that the amount of ultraviolet radiation with a wavelength of 250 to 350 nm can be improved by setting the mercury encapsulation amount to 2.0 to 12.0 (mg / cm ³ ). It can be explained that the radiation amount of ultraviolet rays having a wavelength of 250 to 350 nm can be improved by setting the amount of encapsulation to 1 to 8 atmospheres.

Next, an experiment was conducted on the relationship between the amount of hydrogen stored in tantalum and the occurrence of cloudiness.
(Experiment C)
Five types of lamps (lamp C1 to lamp C5) having different amounts of hydrogen stored by tantalum were prepared. Specifically, regarding the amount of hydrogen stored in tantalum, the converted pressure in the light emission space of the lamp is 533 Pa for the lamp C1, 266 Pa for the lamp C2, 133 Pa for the lamp C3, 13 Pa for the lamp C4, and 2. 7 Pa. The other lamp specifications and lighting conditions are basically the same. The distance between the electrodes is 4.5 mm, the mercury amount is 5 mg / cm ³ , the discharge vessel is 3 mm thick, and the tube wall load is 16 w / cm ² . The amount of radiation was measured after lighting. In the measurement, the occurrence of white turbidity on the inner surface of the discharge vessel after lighting for 200 hours was visually observed.

  In the five types of lamps, hydrogen is removed from the components of the lamp except for the getter. Specifically, first, a lamp including an electrode is subjected to a high-temperature treatment during evacuation to release all hydrogen contained in quartz glass, electrodes, and getters constituting the arc tube. This is because in the step of molding and sealing the light emitting part and the sealing part, hydrogen enters the inside of the quartz glass or the light emitting space from the oxygen-hydrogen burner. Next, a predetermined amount of hydrogen is mixed in the arc tube while being heated to about 600 ° C. At this time, most of the hydrogen is adsorbed by the getter. Therefore, by adjusting the amount of hydrogen, getters having different occlusion amounts can be made for each lamp.

FIG. 5 shows the result of Experiment C. In the experiment, “x” was given when white turbidity was observed, and “◯” was given when no white turbidity was visually observed.
From the results shown in the figure, the lamp C1 having a hydrogen pressure of 533 Pa and the lamp C2 having a hydrogen pressure of 266 Pa are rejected due to the occurrence of white turbidity, the lamp C3 having a hydrogen pressure of 133 Pa, and a lamp C4 having a hydrogen pressure of 13 Pa. Then, the lamp C5 having a hydrogen pressure of 2.7 Pa passed the white turbidity without being visually observed. The lamp C1 was observed to be heavily clouded, and the lamp C2 was confirmed to be clouded although not as much as the lamp C1.
That is, when the amount of hydrogen occluded by tantalum is 0.05 mol / m ³ (= 3 × 10 ¹⁶ pieces / cm ³ ) or less in terms of hydrogen molecules per inner volume of the discharge vessel, generation of white turbidity can be suppressed. Recognize.

Here, the hydrogen pressure P (Pa) and the number of hydrogen molecules are enclosed by volume V (m ³ ), pressure P (Pa), gas constant R (= 8.314 J / K), room temperature T (= 298 K). and that the number of moles n of the hydrogen (mol), the number n (number ^{/ m} 3) of hydrogen molecules and the Avogadro constant _n a (= 6.0 × 10 ²³ pieces / mol), "PV = nRT" from the state equation of gas Given in. Since the number of moles n of hydrogen is “N / N _A ”, when the number of moles of hydrogen n is 0.05 (mol / m ³ ), the number of hydrogen molecules can be expressed as “N = n × N _A ” 0.05 × 6.0 × 10 ²³ ”(pieces / m ³ ), and“ 3.0 × 10 ¹⁶ ”(pieces / cm ³ ).
Next, when the number of moles of hydrogen molecules (n = 0.05 (mol / m ³ )) is converted into pressure, the gas equation of state “PV = nRT” is changed to “P × 1 = 0.05 × 8.314 × 298”. = 1.3 × 10 ² ”(Pa).

In this way, the hydrogen pressures of the lamps C1 to C5 are expressed by the number of moles of hydrogen molecules and the number of hydrogen molecules as follows.
Lamp C1: Hydrogen pressure “533 Pa” is the number of moles of hydrogen molecules “0.22 mol / m ³ ”, the number of hydrogen molecules “1.3 × 10 ¹⁷ / cm ³ ”,
Lamp C2: “266 Pa” of hydrogen pressure indicates that the number of hydrogen molecules is “0.11 mol / m ³ ”, the number of hydrogen molecules is “6.4 × 10 ¹⁶ / cm ³ ”,
Lamp C3: Hydrogen pressure “133 Pa” indicates that the number of hydrogen molecules is “0.54 × 10 ⁻¹ mol / m ³ ”, the number of hydrogen molecules is “3.2 × 10 ¹⁶ molecules / cm ³ ”,
Lamp C4: Hydrogen pressure “13 Pa” is the number of hydrogen molecules “0.52 × 10 ⁻² mol / m ³ ”, the number of hydrogen molecules “3.1 × 10 ¹⁵ / cm ³ ”,
Lamp C5: Hydrogen pressure “2.7 Pa” is the number of hydrogen molecules “1.08 × 10 ⁻³ mol / m ³ ” and the number of hydrogen molecules “6.5 × 10 ¹⁴ / cm ³ ”.

Next, an experiment was conducted on the relationship between the discharge vessel internal volume and the discharge vessel internal surface area.
(Experiment D)
Five types of lamps (Lamp D1 to Lamp D5) with different discharge vessel sizes were prepared. A lamp was manufactured under the same conditions as in Experiment C. Here, the lamps were kept lit until white turbidity occurred for each lamp. Of the five lamps, the lamp D1 has a discharge vessel diameter of 12 cm, the discharge vessel inner surface area S is 502 cm ² , the discharge vessel inner volume V is 1043 cm ³ , and the ratio S / V is 0.5, and the lamp D2 has a discharge vessel diameter of 9.4. The discharge vessel inner surface area S is 335 cm ² , the discharge vessel inner volume V is 580 cm ³ , the ratio S / V is 0.6, the lamp D3 has a discharge vessel diameter of 8 cm, the discharge vessel inner surface area S is 186 cm ² , and the discharge vessel inner volume. V is 241 cm ³ , the ratio S / V is 0.8, the lamp D4 has a discharge vessel diameter of 6.2 cm, a discharge vessel internal surface area S of 121 cm ² , a discharge vessel internal volume V of 124 cm ³ , and a ratio S / V of 1.0, The lamp D5 has a discharge vessel diameter of 5 cm, a discharge vessel internal surface area S of 77 cm ² , a discharge vessel internal volume V of 63 cm ³ , and a ratio S / V of 1.2. Here, the inner volume of the light emitting part is a volume excluding the volume of the electrode part in the light emitting part. The other lamp specifications and lighting conditions are basically the same. The distance between the electrodes is 4.5 mm, the mercury amount is 5 mg / cm ³ , the discharge vessel is 3 mm thick, and the wall load is 16 w / cm ² . The amount of radiation was measured after lighting. Note that none of the lamps contains hydrogen in the getter.

FIG. 6 shows the result of Experiment D.
From the results shown in the figure, the lamp D1, the lamp D2, and the lamp D3 have white turbidity generation times as long as 800 hours, 700 hours, and 600 hours, respectively, whereas the lamp D4 and the lamp D5 have white turbidity occurrence times of 300 hours, It can be seen that 200 hours is short.
That is, it can be seen that the occurrence of white turbidity is suppressed when the ratio S / V between the discharge vessel inner surface area S and the discharge vessel inner volume V is 0.8 or less.

Here, consider a case where the light emitting portion is spherical. Assuming that the outer diameter L (cm) of the discharge vessel and the wall thickness t (cm) of the discharge vessel, the inner surface area S of the discharge vessel is “4π ((L / 2) −t) ² ”. Further, the internal volume V of the discharge vessel when no electrode is present is “(4π ((L / 2) −t) ³ ) ÷ 3”. Since the wall thickness t is extremely smaller than the outer diameter L, the ratio S / V is “3 ÷ ((L / 2) −t)”, which can be approximated to “6 / L”. That is, “S / V <0.8” becomes “7.5 <L”.

FIG. 7 shows a schematic configuration of a hydrogen detection method.
One method for detecting hydrogen absorbed by the getter is described. A quadrupole mass spectrometer calibrated quantitatively for the quantitative detection of hydrogen is used. The detection device is composed of a vacuum sample chamber 70, a quadrupole mass spectrometer 71 that follows the vacuum sample chamber 70, a vacuum pump system 72, and a vacuum vessel 73. The vacuum sample chamber 70 is heated from outside by an electric furnace 701.
Now, the getter attached to the electrode in the lamp is taken out, the getter sample is inserted into the preliminary exhaust vacuum sample chamber 721, and heated to around 100 ° C. to remove mercury attached to the sample. Next, the sample is taken out from the preliminary exhaust vacuum sample chamber 721 and inserted into the vacuum sample chamber 70 of the hydrogen detection system. Here, the temperature of the sample is raised by the operation of the electric furnace 701 for heating. While monitoring the sample temperature, the hydrogen release amount is measured by the quadrupole mass. In the case of tantalum (Ta), the solubility of hydrogen is large up to 600 ° C. and hardly released. However, at 1000 ° C., the stored hydrogen is rapidly released until the ambient hydrogen equilibrium vapor pressure is reached. By heating for 2 hours, it can be considered that all the dissolved hydrogen is exhaled because the surroundings are vacuum. As a result, the amount of hydrogen released per hour can be obtained, and the total amount of occluded hydrogen (total dissolved amount) can be obtained by integrating over time.

A simple method for measuring the amount of hydrogen will be described. Tantalum (Ta) to be measured is placed in the sample container. Sample container is evacuated and connected to a vacuum vessel having a vacuum evacuation stand found the volume V _2. When the internal pressure of the sample container becomes less than 10 ⁻³ Pa, the evacuation is stopped. Then, the sample container is heated to a high temperature, for example, up to 1000 ° C. with a high-temperature heater such as an electric furnace, and the pressure value P (Pa) in the vacuum container is read. From these measurements, using the gas equation of state, the total number of moles n of hydrogen released from tantalum (Ta) is expressed as n≈PV ₂ / (RT)
Can be calculated as Here, T is the temperature of the vacuum vessel.

In this specification, “discharge vessel” means a container including a sealing portion, that is, quartz glass, and “light emitting portion” is a portion of the discharge vessel where a light emitting space exists and includes a portion including the light emitting space. means.

As described above, the radiation amount of ultraviolet rays having a wavelength of 250 to 350 nm can be improved by setting the mercury encapsulation amount to 2.0 to 12.0 (mg / cm ³ ) and the argon or krypton encapsulation amount to 1 to 8 atmospheres. Further, the amount of hydrogen tantalum is occluded, the internal volume of hydrogen per molecule converted at 0.05 mol / m 3 of the discharge vessel ⁽⁼ 3 × 10 ¹⁶ atoms / cm ³⁾ the occurrence of white turbidity by the following can be suppressed.

1 shows the overall configuration of a short arc type mercury lamp according to the present invention. The parameter of each part of the short arc type mercury lamp concerning the present invention is shown. The result of the evaluation experiment regarding the amount of mercury and the amount of radiation of the present invention is shown. The result of the evaluation experiment regarding the rare gas amount and radiation amount of the present invention is shown. The result of the evaluation experiment regarding the amount of hydrogen and cloudiness of the present invention is shown. The result of the evaluation experiment regarding the ratio of the discharge container internal volume of this invention and an internal surface area is represented. 1 shows a hydrogen detector according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Discharge container 11 Light emission part 12 Sealing part 20 Cathode 21 Cathode stick 30 Anode 31 Anode stick 40 Tantalum

Claims (3)

A pair of electrodes are arranged opposite to each other in a light emitting part of a discharge vessel made of quartz glass, and mercury is 2 to 12 (mg / cm ³ ), and at least argon (Ar) or krypton (Kr) is contained in the light emitting part. In a short arc type mercury lamp sealed with 1 to 8 atmospheres,
At least one of the electrodes is attached with tantalum,
A short arc type mercury lamp characterized in that the amount of hydrogen occluded by the tantalum is 3 × 10 ¹⁶ pieces / cm ³ or less in terms of hydrogen molecules per inner volume of the light emitting part. ^2. The short arc type mercury lamp according to claim 1, wherein the relationship of S / V ≦ 0.8 is satisfied when the inner volume V (cm ³ ) and the light emitting portion S (cm ² ) of the light emitting portion are satisfied. When the light emitting part is spherical and the outer diameter is D (cm),
7.5 ≦ D
The short arc type mercury lamp according to claim 2, wherein:

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