JP3267153B2 - Metal vapor discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor discharge lamp utilizing luminescence of cadmium and / or zinc atoms and ions.

[0002]

2. Description of the Related Art Ultraviolet rays are widely used in industries such as surface modification of plastics, photo-CVD, photo-ashing, and UV curing, but discharge lamps having a high ultraviolet output particularly in a short wavelength ultraviolet region of 200 to 250 nm. Is required. Conventionally, a high-pressure mercury lamp or a xenon lamp has been used as a discharge lamp that emits ultraviolet rays in the short wavelength range, but these discharge lamps have low luminous efficiency (up to several percent).
That was the problem. In addition, a KrF excimer laser is a light source having a large output in this wavelength range, but this laser has a problem that it requires a lot of cost and labor for maintenance.

[0003] Discharge lamps utilizing cadmium and zinc luminescence, so-called low-pressure discharge cadmium lamps with a tube wall load of several W / cm ² and a partial pressure of cadmium vapor or zinc vapor of 10 Pa or less during operation, and low pressure Discharge zinc lamps have been put to practical use for optical experiments. These discharge lamps utilize the emission of resonance lines emitted when the cadmium and zinc atoms in the short wavelength region of 200 to 250 nm transition to the excited state, but the partial pressure of cadmium and zinc inside the discharge lamp is reduced. Due to its low resonance line emitted inside the arc is emitted inside the arc with little absorption by ground state atoms. However, since the emission light of these discharge lamps in the 200 to 250 nm region has only a line spectrum, the output is weak, only about several percent of the lamp input, and the lamp input is small. It was not suitable for use as a light source.

[0004]

SUMMARY OF THE INVENTION As described above, the present invention has a higher energy conversion efficiency in a short wavelength region of 200 to 250 nm than an existing discharge lamp such as an existing high-pressure mercury lamp or a xenon lamp. Another object of the present invention is to provide a discharge lamp which is inexpensive, easy to maintain and has no problem as the industrial light source and has a high energy conversion efficiency.

[0005]

In order to solve the above-mentioned problems, a pair of electrodes are arranged opposite to each other in a quartz glass arc tube having both ends sealed, and X is used as a buffer gas in the arc tube.
e gas is sealed, cadmium and / or zinc is sealed, and the distance between the electrodes is defined as x, and the arc tube inner diameter is defined as x / y ≧ 2, where the arc tube inner diameter y is 2 ≦ 2.
y ≦ 25 (unit: mm), no mercury is enclosed in the arc tube, cadmium and / or zinc are enclosed in a total amount of 0.001 to 10 mg / cm ^3, and a tube wall load of 10 W
A metal vapor discharge lamp characterized in that the lamp is turned on at / cm ² or more.

In the above metal vapor discharge lamp, the molar ratio to cadmium and / or zinc is 1/100 to 10 in terms of a diatomic molecule halogen element.
The present invention provides a metal vapor discharge lamp filled with at least one of iodine, bromine and chlorine.

And, as the quartz glass arc tube,
Either fused quartz glass produced by melting natural quartz or synthetic quartz glass produced by chemically synthesizing and melting silicon tetrachloride or an artificial silicon compound is selected and used. Also, sapphire or translucent alumina ceramic
Used as an arc tube.

Further, the above quartz glass or sapphire
It is preferable that the wall thickness of the arc tube made of a transparent alumina ceramic be 0.3 to 5 mm.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The metal vapor discharge lamp of the present invention
A long quartz glass or sapphire
A pair of electrodes are arranged opposite to each other in an arc tube made of translucent alumina ceramic , mercury is not sealed in the arc tube, Xe is sealed as a buffer gas, and cadmium and / or zinc are sealed in the arc tube. When the distance is x and the inner diameter of the arc tube is y, x / y ≧ 2, and the inner diameter y of the arc tube is 2 ≦ y ≦ 25 (unit: mm), and the total amount of cadmium and / or zinc is 0.001 to 10
mg / cm ^3, and the sealing pressure of the Xe gas is set to 0.6 to 300 kPa at 25 ° C.

More preferably, the molar ratio to cadmium and zinc is 1/1 in terms of a diatomic molecule halogen element.
One or more of iodine, bromine, and chlorine in an amount of 00 to 10 are sealed, and the lamp is turned on by a lamp input that causes the tube wall load to be 10 W / cm ² or more.

According to the above configuration, the vapor pressure of cadmium or zinc increases with the lighting of the discharge lamp, and arc discharge occurs. In such a discharge, the temperature distribution has a distribution in the direction of the tube diameter of the discharge lamp, the excited atoms are distributed in the center of the arc, and the atoms in the ground state are distributed closer to the tube wall.

For this reason, the emission spectrum of the resonance line of the cadmium or zinc atom becomes a self-inversion spectrum because absorption occurs at the center wavelength of the emission. On the other hand, when the vapor pressure is high, the mean free path of atoms is short, and the collision width of cadmium and zinc atoms widens the spectrum width of the cadmium and zinc resonance lines, and emits light at wavelengths far from the center wavelength. Can avoid absorption by ground state atoms distributed around the tube wall. With such a mechanism, in a state where the vapor pressure is high, the emission at wavelengths around the center wavelength increases despite the absorption at the center wavelength, and high emission efficiency can be achieved.

However, when the amount of cadmium or zinc is less than 0.001 mg / cm ^{3, the} number density of excited state atoms involved in light emission is reduced.
When the relative output efficiency of ultraviolet rays in a short wavelength range of 0 to 250 nm is small, and the amount of encapsulation exceeds 10 mg / cm ³ , the reaction between cadmium or zinc and tungsten which is a material of the electrode becomes intense, and the useful life is reduced. I can't achieve it.

In order to further improve the luminous efficiency of such a discharge lamp, it is important to reduce self-absorption in the ground state. This is to make the temperature distribution of the plasma in the tube diameter direction close to a constant, and can be achieved by making the tube diameter narrow and increasing the current.

Further, by increasing the current density, ionization of cadmium and zinc proceeds, and light emission of these ions also appears. The emission wavelength of monovalent cadmium ion is 214.
4, 219.4, and 226.5 nm, and monovalent zinc ions have two wavelengths, 202.6 and 206.2 nm. These emissions increase the emission intensity in the wavelength range of 200 to 250 nm.

The smaller the inner diameter of the arc tube, the higher the current density and the larger the output of the ion resonance line.
m or less, the electrons and ions inside the discharge lamp are likely to be lost by diffusion as the arc and the tube wall become close to each other. The percentage of energy increases,
Light emitted to the outside of the discharge lamp is weakened. On the other hand, if the inner diameter of the arc tube exceeds 25 mm, self-absorption by cadmium and zinc atoms increases, and the light emission intensity decreases.

By optimizing the buffer gas pressure, the gas temperature inside the discharge lamp can be sufficiently increased, and the atomic number density in an excited state involved in light emission can be increased. This result appears remarkably as the gas pressure increases.

When the filling gas pressure is 0.6 kPa or less, the effect of increasing the gas temperature of the arc is poor, and the internal pressure of the discharge lamp during operation is low, so that the tungsten of the electrode material evaporates violently and the arc tube becomes black. Is accelerated. As the filling gas pressure is increased, the emission intensity increases with an increase in the gas temperature. However, when the distance between the electrodes is x and the inside diameter of the arc tube is y, x / y ≧ 2. In the long arc type metal vapor discharge lamp described above, since the emission length is long, an excessively high filling gas pressure causes a large practical problem of an increase in breakdown voltage.

In fact, before reaching this problem, the long arc type metal vapor discharge lamp of the present application causes a bias in the emission in the longitudinal direction of the arc, and the effective emission length with respect to the emission length is reduced. A phenomenon occurs in which the amount of light emitted from the entire lamp also decreases. This phenomenon can be seen from the vicinity where the filling gas pressure exceeds 100 kPa. At 300 kPa, light emission of cadmium or zinc can be seen only in the vicinity of one electrode.

When fused silica glass is used as the arc tube, if the lamp is turned on by enclosing metal cadmium or metal zinc at a high current density, the arc tube devitrifies within several hours. The cause of the devitrification is considered to be that cadmium and zinc ions and metastable cadmium and zinc atoms contained in the arc plasma collide with the inner surface of the arc tube and react with the fused silica glass. As a countermeasure, there is addition of a halogen element such as iodine. Iodine is in a molecular state at a low temperature, and has a characteristic of being distributed near a tube wall in a lamp.

For this reason, ions of cadmium and zinc and atoms of cadmium and zinc in a metastable state that have entered in the radial direction of the tube react with iodine and do not reach the wall of the arc tube, so that the inner surface of the arc tube wall is protected. This effect is remarkable when the amount of halogen is 1/100 or more in terms of the molar ratio to the metal to be sealed. This effect is increased by further increasing the amount of enclosed halogen. However, when the molar ratio with respect to the enclosed metal exceeds 10, the halogen element released during lighting reacts with the tungsten of the electrode material, and the tungsten evaporates due to evaporation of the tungsten. Is blackened, and light is absorbed by the halogen element.
The light output in the wavelength range of 00 to 250 nm decreases.

In a conventional mercury discharge lamp or the like, a halogen element is added to prevent devitrification caused by blackening of an arc tube caused by tungsten scattered from an electrode. A halogen element is sealed in order to prevent the reaction between the glass and quartz glass. The transmittance of synthetic quartz glass in the wavelength range of 200 to 250 nm is about 1.2 times that of fused silica glass. Therefore, if synthetic quartz glass is used as the arc tube, the luminous efficiency is improved.
Since sapphire hardly reacts to metal vapor, using sapphire for the arc tube can prevent devitrification of the arc tube. The temperature of the arc tube surface is 900
° C and around 20 ° C when fused silica glass is used.
The transmittance in the wavelength range of 0 to 250 nm decreases with increasing temperature. On the other hand, in the sapphire arc tube, even at such an operating temperature, the transmittance is about 60%, and a high transmittance is maintained. Therefore, if sapphire is used as an arc tube, a lamp with high luminous efficiency can be realized.
Further, although the luminous efficiency is lower than that of sapphire, translucent alumina ceramics can be used as the arc tube.

Quartz glass or sapphire or translucent
When the thickness of the alumina ceramic arc tube is 0.3 mm or less, the arc tube is easily deformed by the heat of electric discharge, and when the thickness of the arc tube is 5 mm or more, the arc tube has a thickness of 200 to 250 mm.
The thickness of the arc tube is preferably 0.3 to 5 mm because the transmittance in the wavelength region of nm decreases and light emitted from the inside of the lamp cannot be effectively extracted.

[0024]

EXAMPLES Hereinafter, specific experimental examples of the present invention will be described, but the present invention is not limited to the lamps shown in these experimental examples.

FIG. 1 is a sectional view for explaining an embodiment of a metal vapor discharge lamp according to the present invention. Inner diameter 12mm, inner volume 25c
A pair of electrodes 2 and 2 made of tungsten are opposed to each other in an arc tube 1 made of m ³ fused silica glass, and the distance between the electrodes is 250 mm. Both ends of the arc tube 1 are seal portions 5, and the external lead bar 4 and the electrode 2 are electrically connected to the seal portion 5 via the molybdenum foil 3.

[Experiment 1] A discharge lamp in which xenon gas of 80 kPa is sealed and cadmium is sealed, a discharge lamp in which zinc is sealed, a discharge lamp in which zinc is sealed, cadmium and zinc are put together in an arc tube 1 constructed in the same manner as in FIG. The enclosed discharge lamps were prototyped as long arc type discharge lamps A to C having a rated input of 3 kW. Further, a low-pressure discharge cadmium lamp (lamp D) using the same arc tube was prototyped and 200 to 250 n.
The relative luminous efficiency with respect to the lamp input in the wavelength range of m was compared. The results are shown in Table 1, and the spectral distribution diagrams are shown in FIGS. From this, it is understood that ultraviolet rays are emitted with a considerably high intensity in the wavelength range of 200 to 250 nm.

[0027]

[Table 1]

[Experiment 2] Using a metal vapor discharge lamp configured in the same manner as in FIG. 1, an experiment was conducted in which the relative output efficiency in the wavelength region of 200 to 250 nm was examined by changing the amount of cadmium enclosed. The experimental results are shown in FIG. FIG. 6 shows the relationship between the amount of cadmium enclosed and the relative output efficiency in the wavelength range of 200 to 250 nm. As can be seen from FIG. 6, when the cadmium encapsulation amount is less than 0.001 mg / cm ³ , the relative number efficiency of the excited state of cadmium involved in light emission decreases, so that the relative output efficiency in the wavelength region of 200 to 250 nm becomes extremely high. It became clear that it became weak. The relative output efficiency is almost constant when the cadmium filling amount is 0.1 mg / cm ³ or more, but when the cadmium filling amount exceeds 10 mg / cm ³ , the reaction with tungsten of the electrode material becomes violent, and the lamp is turned on for about one hour. As a result, the arc tube was blackened and became unsuitable for practical use.

[Experiment 3] A metal vapor discharge lamp having a rated input of 3 kW, which is constructed in the same manner as in FIG. 1 and in which 1.6 mg of cadmium and 2 mg of zinc are sealed in an arc tube and the type of gas to be sealed and the sealing pressure are changed. An experiment was conducted to determine the relative output efficiency between 200 and 250 nm. FIG. 7 shows the relationship between the sealing pressure and the relative UV output efficiency as experimental results. As apparent from FIG .
The kind of gas to be sealed is Xe compared to Ar or Kr.
It can be seen that the relative output efficiency of ultraviolet light improves when gas is used.
Call When the filling pressure is about 100 kPa, 200
The relative output efficiency at ２５０250 nm showed a maximum value. This is because when the filling pressure of the buffer gas is increased, the gas temperature of the arc is increased and the relative luminous efficiency is increased.
When the distance exceeds a, the light emission of cadmium and zinc gradually becomes uneven in the longitudinal direction of the arc tube, and the light emission is partially biased toward a part of the lamp. It is considered that the relative output efficiency decreases because the effective radiation length with respect to the length decreases.

When the filling gas pressure was 0.6 kPa or less, the internal pressure of the lamp during operation was low, and the evaporation of tungsten in the electrodes became intense, resulting in blackening of the arc tube.

[Experiment 4] 1.6 mg of cadmium, 2 mg of zinc, and X as a buffer gas
e was sealed at a sealing pressure of 80 kPa, and a cadmium discharge lamp having a luminous length of 250 mm and a rated input of 3 kW having a different inner diameter of the arc tube was prototyped, and an experiment was conducted to examine the relationship between the inner diameter of the arc tube and the relative output efficiency. FIG. 8 shows the experimental results. FIG. 8 shows the relative output efficiency (%) on the vertical axis and the arc tube inner diameter (m) on the horizontal axis.
m). The smaller the inner diameter of the arc tube, the higher the current density and the greater the resonance line output of the ions. However, when the inner diameter is 2 mm, the arc and the tube wall become closer, causing electrons and ions inside the lamp to be lost to the tube wall. And the relative output efficiency decreased.

When the inner diameter of the arc tube was 4 mm, the relative output efficiency was highest. However, as the inner diameter of the arc tube increased, self-absorption by atoms increased and the relative output efficiency decreased. And a relative luminous efficiency of 10% or more was confirmed.

[Experiment 5] In a lamp constructed in the same manner as in FIG. 1, 1.6 mg of cadmium, 2 mg of zinc and 80 kPa of Xe as a buffer gas were sealed, and the amount of iodine as a halogen element to be sealed was changed to 200 to 250 nm. An experiment was conducted to examine the light output maintenance ratio of the ultraviolet light output after lighting for 1500 hours. FIG. 9 shows the experimental results. FIG. 9 shows data on the relationship between the amount of enclosed iodine and the relative maintenance ratio after lighting for 1000 hours. The vertical axis indicates the relative maintenance ratio (%), and the horizontal axis indicates the lighting time (%).
h).

As is apparent from FIG. 9, when the ratio of iodine to the total amount of cadmium and zinc is 1, the relative maintenance ratio is 9
0%. Assuming that the amount of iodine to be enclosed is 1/100 in molar ratio, the reaction between cadmium and zinc and the quartz glass of the arc tube starts to be observed after about 500 hours. It shows a maintenance rate and can be used industrially enough.

When the iodine ratio is set to 10 or more, no reaction between cadmium and zinc and quartz glass is observed, but the reaction between iodine and tungsten as an electrode material becomes violent, and the tungsten vaporized from the electrode causes an arc tube to emit. It turned black. However, after 1000 hours, 200
The relative maintenance ratio of the emission intensity in the wavelength range of ~ 250 nm is 75%
It became fully practical.

In the above experiment, iodine was encapsulated as a halogen element. However, the same effect as iodine can be obtained by enclosing not only iodine but also bromine and chlorine.

[0037]

As described above in detail, in the metal vapor discharge lamp of the present invention, the vapor partial pressure at the time of lighting cadmium and / or zinc inside the discharge lamp is increased.
By increasing the power supplied to the discharge lamp, the output of the resonance line of ions at the center of the arc is improved, and by further increasing the temperature at the periphery of the arc, the emission of atoms at the periphery of the arc is increased. Alternative to low-pressure discharge cadmium lamps, low-pressure discharge zinc lamps, high-pressure mercury lamps, etc.
A strong light output is obtained in the range of 00 to 250 nm, and ultraviolet light which can be sufficiently used in industry can be taken out for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view for explaining an embodiment of a metal vapor discharge lamp of the present invention.

FIG. 2 shows a prototype 200 of a metal vapor discharge lamp A of the present invention.
FIG. 4 is a spectral distribution diagram in a wavelength range of ２５０250 nm.

FIG. 3 shows a prototype 200 of a metal vapor discharge lamp B of the present invention.
FIG. 4 is a spectral distribution diagram in a wavelength range of ２５０250 nm.

FIG. 4 shows a prototype 200 of a metal vapor discharge lamp C of the present invention.
FIG. 4 is a spectral distribution diagram in a wavelength range of ２５０250 nm.

FIG. 5 is a spectral distribution diagram in a wavelength range of 200 to 250 nm of a discharge lamp D prototyped as a conventional metal vapor discharge lamp.

FIG. 6 is a diagram showing the relationship between the amount of cadmium enclosed and the relative output efficiency in the wavelength range of 200 to 250 nm in the metal vapor discharge lamp of the present invention.

FIG. 7 is a diagram showing a relationship between a filling pressure of a buffer gas and a relative output efficiency in a wavelength range of 200 to 250 nm in the metal vapor discharge lamp of the present invention.

FIG. 8 is a diagram showing the relationship between the inner diameter of the arc tube and the relative output efficiency in the wavelength range of 200 to 250 nm in the metal vapor discharge lamp of the present invention.

FIG. 9 is a diagram showing the relationship between the ratio of iodine to the total amount of cadmium and zinc in the metal vapor discharge lamp of the present invention (iodine ratio) and the relative output efficiency in the wavelength range of 200 to 250 nm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc tube 2 Electrode 3 Molybdenum foil 4 External lead rod 5 Seal part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-57693 (JP, A) JP-A-8-45479 (JP, A) JP-A-7-21980 (JP, A) 187944 (JP, A) JP-A-9-45287 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 61/16 H01J 61/073 H01J 61/30

Claims (5)

(57) [Claims] A pair of electrodes are opposed to each other in a quartz glass arc tube having both ends sealed, Xe gas is sealed in the arc tube as a buffer gas, and cadmium and / or zinc are sealed in the arc tube. When the distance is x and the inner diameter of the arc tube is y, x / y ≧ 2, and the inner diameter y of the arc tube is 2 ≦ y ≦
25 (unit: mm), no mercury was sealed in the arc tube, and cadmium and / or zinc were added in a total amount of 0.2.
001-10mg / cm ³ sealed, tube wall load 10W / c
metal vapor discharge lamp, characterized in that an illuminated m ² or more. 2. A molar ratio to cadmium and / or zinc of 1/10 in terms of a diatomic molecule of a halogen element.
The metal vapor discharge lamp according to claim 1, wherein one or more of iodine, bromine, and chlorine are sealed in an amount of 0 to 10. 3. A metal vapor discharge lamp according to claim 1 or 2, characterized in that the synthetic quartz glass the quartz glass. 4. A sapphire or light-transmitting material having both ends sealed.
A pair of electrodes are arranged opposite to each other in a luminous ceramic arc tube, and Xe gas is sealed in the arc tube as a buffer gas.
And cadmium and / or zinc are sealed, and the distance between the electrodes is defined as x, and the inner diameter of the arc tube is defined as y, where x / y ≧ 2, and the inner diameter y of the arc tube is 2 ≦ y ≦ 25.
(Unit: mm), wherein mercury is not sealed in the arc tube, and cadmium and / or zinc are added in a total amount of 0.00.
1 to 10 mg / cm ³ sealed, tube wall load 10 W / cm ²
A metal vapor discharge lamp characterized by being turned on as described above. 5. The quartz glass or sapphire or
Thickness of translucent alumina ceramic arc tube is 0.3 ~
The metal vapor discharge lamp according to any one of claims 1 to 4 , wherein the distance is 5 mm.