JP2891997B1 - UV lamp - Google Patents

Abstract

To provide an ultraviolet lamp that can efficiently obtain light in a vacuum ultraviolet region to an ultraviolet region with high radiance, has a high radiant flux maintenance factor, has a long life, and can be used safely. SOLUTION: At least one rare gas of argon, krypton and xenon is sealed in a silica glass discharge vessel at a total pressure of 0.1 × 10 ⁵ Pa or more in terms of 300K,
If necessary, mercury in an amount of 0.7 mg / cc or more and 7 mg / cc or less is sealed, and at least a part of the discharge vessel has an average OH group concentration of 7.8 × at a depth from its inner surface to 200 μm. 10 ²⁴ particles / m ³ or more, and the average OH group concentration in the region from the inner surface to a depth of 20 μm is 1.5 × 1
0 ²⁵ pieces / m ³ or more and 1.2 × 10 ²⁶ pieces / m ³ or less, and the average O between the area deeper than 200 μm from the inner surface and 600 μm deeper from the outer surface of the discharge vessel.
An ultraviolet lamp having an H group concentration of 6.2 × 10 ²⁵ lamps / m ³ or less is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet lamp which emits ultraviolet light, which is used in the photochemical industry and the semiconductor manufacturing field.

[0002]

2. Description of the Related Art Rare gases such as neon, argon, krypton, and xenon are conventionally used as buffer gases for discharge lamps. When the rare gas is excited in the plasma, it emits excimer light. This is described in JP-A-7-50151 and the like. For example, FIG. 1 shows an external view of a short arc xenon lamp. When the material of the discharge vessel 2 of the discharge lamp 1 is synthetic quartz glass, a wide range of radiation from the vacuum ultraviolet region to the infrared region by excimer light can be obtained.
The principle of xenon excimer (Xe ₂ ^* ) emission is the same as that of a dielectric barrier discharge lamp. However, since a xenon lamp can be made into a short arc type, it is compared as a point light source that emits light from the vacuum ultraviolet region to the ultraviolet region. Available.

[0003] The Xe ₂ ^* emission wavelength is in the range of 160 to 200 nm, and a luminescence band is applied to the absorption edge of silica glass. Therefore, in order to extract the vacuum ultraviolet light efficiently, the discharge vessel 2 is made thinner, but the strength of the discharge vessel is reduced,
While the lamp is lit, the exhaust pipe chip 3 (hereinafter, abbreviated as chip) is broken (chip crack) from the root. In addition, when the electric input is set to a high input (high output of light), the time until chip breakage occurs hastened.

[0004] This chip destruction is partly due to a high gas pressure load due to a rise in gas temperature in the discharge vessel when the lamp is turned on, but also partly to glass distortion induced by ultraviolet irradiation. It is considered that the UV-induced distortion causes stress concentration on the chip 3 which is structurally irregular. In particular, when the lighting is performed for a long time, a synergistic effect of the two occurs, and the discharge vessel 2 is broken starting from the vicinity of the mounting portion of the chip 3.

In a mercury lamp, a rare gas of xenon, argon, and krypton, or a rare gas obtained by combining several kinds of rare gases may be sealed in a discharge vessel as a buffer gas. All gases are in excimer state (X
e ₂ ^* , Ar ₂ ^* , Kr ₂ ^* ), the above-mentioned excimer light is generated. When argon and / or krypton are used as the buffer gas, the luminous efficiency, arc stability, and arc concentration of the lamp are improved, but the discharge vessel is likely to become cloudy, which causes a decrease in the illuminance maintenance rate.

[0006] From the study of the inventor, it has been found that the clouding phenomenon of the discharge vessel is caused by the accumulation of silica particles. Ar
₂ ^* and Kr ₂ ^* emit light of higher energy than the absorption edge of silica glass. It is presumed that the Si-O bond is broken by this light irradiation, and the silica glass sublimates and deposits on the inner surface of the discharge vessel.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to efficiently obtain light from the vacuum ultraviolet region to the ultraviolet region with a high radiance, a high radiant flux maintenance factor, a long life, and a safe lighting operation. It is to provide an ultraviolet lamp which can be used.

[0008]

Therefore, in order to solve the above-mentioned problems, according to the first aspect of the present invention, the discharge vessel is made of silica glass, and the discharge vessel is made of argon, krypton, or xenon. An ultraviolet lamp in which at least one kind of rare gas is filled at 0.1 × 10 ⁵ Pa or more at a total pressure in terms of 300K, and mercury in a quantity of 0.7 mg / cc to 7 mg / cc as needed. So,
At least a portion of the discharge vessel where the ultraviolet radiation emission degree is maximum has an average OH group concentration of 7.8 × 10 ²⁴ / m ³ or more at a depth from the inner surface up to 200 μm, and The average OH group concentration in a region from to a depth of 20 μm is 1.5 × 10 ²⁵ / m ³ or more and 1.2 × 10 ²⁶ / m ³ or less, and a depth deeper than 200 μm from the inner surface. An ultraviolet lamp having an average OH group concentration of not more than 6.2 × 10 ²⁵ / m ^{3 in} a region from the outer surface of the discharge vessel to a depth of 600 μm from the outer surface of the discharge vessel.

Here, the portion where the ultraviolet radiation emission degree is maximum is the portion where the amount of ultraviolet radiation radiated from the outer surface of the discharge vessel is maximum, and in a discharge lamp in which a pair of electrodes are opposed to each other, the discharge vessel Of the container wall at the substantially central portion of FIG.

In the ultraviolet lamp, the reason why at least one rare gas of argon, krypton, and xenon is sealed in the discharge vessel at 0.1 × 10 ⁵ Pa or more at a total pressure of 300K in terms of the sealed rare gas Pressure is 300
If the total pressure is less than 0.1 × 10 ⁵ Pa in terms of K, it is not possible to obtain sufficient ultraviolet light emission efficiency by the rare gas.

The amount of mercury enclosed is 0.7 mg /
The reason that the concentration is between cc and 7 mg / cc is 0.7 mg / cc.
If it is less than cc, it is impossible to effectively obtain an ultraviolet intensity at a wavelength of 365 nm, and if it is more than 7 mg / cc, the spectrum width of light emission at a wavelength of 365 nm is widened.

According to a second aspect of the present invention, the discharge vessel is made of silica glass, and the discharge vessel has a partial pressure of argon (PA) and a partial pressure of krypton (PK).
(Pa), PA + PK ≧ 1.0 × 10
Argon and krypton are sealed under the condition of ⁵ (Pa),
In addition, xenon has a partial pressure of 0.13 × 1
Encapsulated in a range of not less than 0 ⁵ Pa and not more than 2.0 × 10 ⁵ Pa,
An ultraviolet lamp filled with a predetermined amount of mercury, wherein at least a portion of the discharge vessel having the maximum emission of ultraviolet radiation has an average O 2 at a depth of 200 μm from its inner surface.
The H group concentration is 1.5 × 10 ²⁵ / m ³ or more, and the average OH group concentration in the region from the inner surface to a depth of 20 μm is 1.5 × 10 ²⁵ / m ³ or more and 1.2 × The average OH group concentration is 7.8 × 10 ²³ between a region of not more than 10 ²⁶ / m ³ and a depth of more than 200 μm from the inner surface to a depth of 600 μm from the outer surface of the discharge vessel. 1.5 ×
The ultraviolet lamp is 10 ²⁵ lamps / m ³ or less.

In the ultraviolet lamp, the partial pressure of argon PA and the partial pressure of krypton are defined as PK + PK ≧ 1.0 by PK.
X10 ⁵ (Pa) and, in addition, xenon is encapsulated in the range of 0.13 × 10 ⁵ Pa or more and 2.0 × 10 ⁵ Pa or less because PA + PK <1.0 × 10 ⁵ (P
In the case of a), the intensity of ultraviolet light having a wavelength of 365 nm cannot be increased, and when the partial pressure of xenon in addition to krypton and argon is less than 0.13 × 10 ⁵ Pa, clouding of the discharge vessel occurs. While 2.0 × 1
If it is 0 ⁵ Pa or more intensity of ultraviolet light having a wavelength of 365nm is not achieved effectively.

It is known that silica glass contains an OH group to be less susceptible to distortion by ultraviolet rays (for example, Japanese Patent Application Laid-Open No. 7-50151). However, the effect when a large amount of OH groups are contained and the concentration distribution of OH groups suitable for silica glass for a discharge vessel of an ultraviolet lamp have not been known. In this study, it was estimated that, if a large amount of OH groups were contained in the entire bulk of the silica glass, compressive strain was generated at the center of the thickness of the discharge vessel wall by ultraviolet irradiation, and tensile strain was generated on the inner and outer surfaces. .

[0015] Silica glass is weak in tension and strong in compression, but by distributing OH groups at a higher concentration especially on the inner surface than at the center of the thickness of the discharge vessel wall, it is possible to reduce the tensile strain generated on the inner surface. It can suppress the sublimation of silica glass due to vacuum ultraviolet light, absorb the vacuum ultraviolet light that changes the silica glass, and surprisingly suppress the generation of absorption centers and white turbidity occurring below 300 nm. I found that.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The relationship between the magnitude of OH group concentration and the magnitude of distortion of glass in a discharge vessel induced by ultraviolet irradiation and glass turbidity of the inner wall of the discharge vessel caused by sublimation of silica glass were actually produced by producing an ultraviolet lamp. Was examined.
The present invention is not limited to the short arc type ultraviolet lamp, but may be a long arc type ultraviolet lamp, a dielectric barrier discharge lamp having no electrode in the discharge vessel, or an ultraviolet ray that emits light in the vacuum ultraviolet region to the ultraviolet region. Applies to lamps.

Example 1 A short arc xenon lamp having an output of 2 kW was manufactured. The filling gas is Xe, the pressure is 3 × 10 ⁵ Pa in terms of 300K, and the distance between the electrodes is a short arc type lamp having a distance of 4.5 mm. The original silica glass used as the material for the discharge vessel includes (1) average O
An H group concentration of 4.0 × 10 ²³ / m ³ ;
(2) an average OH group concentration of 6.0 × 10 ²⁵ / m ³ and (3) an average OH group concentration of 9.4 × 10 ²⁵ / m 3
^The one that was ³ was used. And (1),
The original tubes of (2) and (3) are used, and as shown in the table of FIG. Xenon lamps using five types of discharge vessels A5 were produced.

A1 was prepared by processing the discharge vessel as it was in (1), A2 was obtained by simply introducing an OH group into the (1) raw tube, and A3 was prepared by adding an OH group to the (2) raw tube. Introduced and heated in a vacuum, A4 is only the OH group introduced into the original tube of (2), and A5 is only the OH group introduced into the original tube of (3). The introduction of OH groups was carried out by introducing water vapor into a silica glass raw tube and then heating the silica glass from the outside.

The measurement of the OH group concentration was performed as follows.
An absorption measurement in an IR (infrared) region was performed, and a wavelength of 3673 was measured.
The OH group concentration was determined from the infrared absorption intensity at cm ^-1 . The concentration of a certain region in the depth direction of the glass is obtained by chemically polishing (etching with HF / H ₂ SO ₄ ) the silica glass as a sample in the thickness direction and comparing the degree of IR absorption before and after the polishing. The average OH group concentration contained in the polished area was calculated.

In this embodiment, the glass distortion induced in the discharge vessel by the irradiation of ultraviolet light after the lighting time of 400 hours was measured. The glass distortion is measured by a method of arranging a glass plate and a polarizing plate as a sample in a crossed Nicols relationship and irradiating diffused light to obtain the intensity of light transmitted through the sample by birefringence (photoelasticity measurement). The measurement was performed on the glass portion of the discharge vessel (the portion where the degree of emission of ultraviolet radiation becomes maximum) which is located substantially in the horizontal direction at the tip of the cathode when the discharge lamp is vertical.

As can be seen from the evaluation results shown in FIG.
3. Even after the A4 discharge lamp was operated for 400 hours, the distortion of the discharge vessel induced by ultraviolet rays was small.

In the case of a long arc lamp or a dielectric barrier discharge lamp, the measurement site when the strain is measured in the same manner is the discharge vessel glass portion located at the center in the longitudinal direction of the discharge vessel. In addition, some types of dielectric barrier discharge lamps emit ultraviolet light from a flat glass surface, in which case the maximum emission of ultraviolet radiation is at the center of the flat glass surface. Become.

Example 2 Next, a mercury lamp having an output of 2 kW was manufactured. Ar and Kr are 1 in total in the discharge vessel.
× 10 ⁵ Pa, Xe 1 × 10 ⁵ Pa sealed, mercury 4
mg / cc. 100 wtp of titanium (Ti) is used for the silica glass of the original tube, which is a material for the discharge vessel.
Silica glass containing pm was used. (4) an average OH group concentration of 4.0 × 10 ²³ / m ³ and (5) an average O
An H-group concentration of 1.56 × 10 ²⁵ particles / m ³ was used. As shown in the table of FIG. A mercury lamp was manufactured using four different discharge vessels B1 to B4 shown below.

B1 was prepared by processing the discharge vessel as it was in (4), B2 was obtained by simply introducing OH groups into (1), and B3 was prepared by adding OH groups to (2). Introduced and vacuum-heated, B4 was processed into a discharge vessel with the original tube of (2). The introduction of OH groups was carried out in the same manner as in Example 1, by introducing water vapor into the silica glass raw tube and then heating from the outside.

As shown in FIG. 3, the degree of white turbidity of the discharge vessel after lighting for 300 hours was significant in B1, not white turbid in B2 and B4, and slightly turbid in B3. Then, the change in the illuminance maintenance rate due to the progress of the clouding of the discharge vessel due to the sublimation of the silica glass was confirmed by lighting up to 1500 hours. Wavelength 36
FIG. 4 shows the measurement results obtained by normalizing the 5 nm ultraviolet illuminance maintenance factor to 1 at the initial stage of lighting. Even after lighting for 1500 hours in B2 and B4, the discharge vessel did not become cloudy, and the illuminance maintenance ratio was 90% of the initial lighting. In B1, the illuminance maintenance rate deteriorated drastically, halving to 50% of the initial lighting in 300 hours, and B3 was also reduced to 15%.
After lighting for 00 hours, the illuminance decreased to about 45% of the initial lighting.

[0026]

As described above, according to the first aspect of the present invention, the tensile strain generated on the inner surface of the discharge vessel can be reduced, the stress concentration on the exhaust pipe tip of the discharge vessel can be suppressed, and the exhaust gas can be exhausted. A safe ultraviolet lamp with little risk of rupture at the tube tip can be provided.

According to the first aspect of the present invention, it is possible to suppress sublimation of silica glass due to vacuum ultraviolet light and absorb vacuum ultraviolet light that changes the quality of the silica glass.
It is possible to surprisingly suppress the generation of absorption centers and white turbidity occurring at a wavelength of 00 nm or less, and to provide an ultraviolet lamp having a high radiant flux maintenance factor and a long life.

[Brief description of the drawings]

FIG. 1 shows an external view of a short arc type xenon lamp.

FIG. 2 is a table showing the relationship between OH group concentration and ultraviolet distortion of a discharge vessel.

FIG. 3 is a table showing the relationship between the OH group concentration and the degree of cloudiness of the discharge vessel.

FIG. 4 shows a measurement result of an illuminance maintenance ratio.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Discharge vessel 3 Exhaust pipe tip

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01J 61/30 H01J 61/16 H01J 61/20

Claims (2)

(57) [Claims] 1. A discharge vessel is made of silica glass, and at least one rare gas of argon, krypton, and xenon is filled in the discharge vessel at a pressure of 300 K at a total pressure of 0.1 × 10 ⁵ Pa or more. 0.7 if necessary
An ultraviolet lamp filled with mercury in an amount of not less than 7 mg / cc and not more than 7 mg / cc, wherein at least a portion of the discharge vessel having the maximum emission of ultraviolet radiation has a depth from its inner surface up to 200 μm. The average OH group concentration is 7.8 × 10 ²⁴ / m ³ or more, and the average OH group concentration in a region from the inner surface to a depth of 20 μm is 1.5 × 10 ²⁵ / m ³ or more. × 10 ²⁶ / m ³ or less, and the average OH group concentration in a region from a depth of more than 200 μm from the inner surface to a depth of 600 μm from the outer surface of the discharge vessel is 6.2 × 10 6 An ultraviolet lamp characterized by being at most ²⁵ lamps / m ³ . 2. The discharge vessel is made of silica glass. When the partial pressure of argon is PA (Pa) and the partial pressure of krypton is PK (Pa), PA + P
Argon and krypton are sealed under the condition of K ≧ 1.0 × 10 ⁵ (Pa), and in addition, xenon is a partial pressure of 0.13 × 10 ⁵ Pa or more and 2.0 × 10 ⁵ Pa or less. And mercury is 0.7mg / cc or more and 7mg / cc
cc or less of the enclosed ultraviolet lamp, wherein at least the portion of the discharge vessel where the ultraviolet radiation emission degree is maximum has an average OH group concentration at a depth from its inner surface up to 200 μm of 1.5 × 10 ²⁵ is the / m ³ or more, and an average OH group concentration in the region to a depth of 20μm from the inner surface of 1.5 × 10 ²⁵ / m ³ or more 1.2 × 10 ²⁶ atoms / m ³ or less And the average OH group concentration between a region deeper than 200 μm from the inner surface and a region deeper than 600 μm from the outer surface of the discharge vessel is 7.8 × 10 ^{23 to} 1.5.
× 10 ²⁵ lamps / m ³ or less.