Excimer lamp for fluid treatment
Patent Information
- Application Number
- PCT/JP2026/003217
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-04-16
- Filing Date
- 2026-01-30
- Publication Date
- 2026-10-22
Smart Images
Figure JP2026003217_22102026_PF_FP_ABST
Abstract
Description
Excimer lamp for fluid treatment
[0001] The present invention relates to an excimer lamp, and particularly to an excimer lamp suitable for use in fluid treatment applications.
[0002] Conventionally, a technique is known in which ultraviolet light with a peak wavelength of 172 nm generated from an arc tube is irradiated to water flowing outside the arc tube to decompose impurities such as organic substances contained in the water (see, for example, Patent Document 1).
[0003] The liquid processing apparatus disclosed in Patent Document 1 is an apparatus that irradiates liquid flowing in a container with 172 nm ultraviolet light generated from a barrier discharge lamp. The container has a tubular shape (more specifically, a cylindrical shape) and is formed of a metal such as stainless steel.
[0004] The container is provided with a recess at one end for supporting one end of the barrier discharge lamp module, and the one end of the barrier discharge lamp module is inserted into this recess. A support plate is attached to the end of the container opposite to the recess, and the other end of the barrier discharge lamp module is supported by this support plate. This support plate is provided with a hole for inserting the barrier discharge lamp module. The barrier discharge lamp module is inserted into the hole of the support plate, and the barrier discharge lamp module is fixed to the support plate by a holder and an O-ring.
[0005] The barrier discharge lamp module includes a barrier discharge lamp including an arc tube, and a protective tube that houses the barrier discharge lamp. The protective tube is provided to prevent the barrier discharge lamp from being exposed to liquid. The arc tube and the protective tube are made of synthetic fused silica glass.
[0006] One end of the protective tube is closed and the other end is open. A support portion made of steatite or aluminum oxide is attached to the end on the opening side. This support portion is provided with a hole for inserting a lead wire electrically connected to an electrode that applies a voltage to the barrier discharge lamp. The support portion and the protective tube are sealed by curing an epoxy adhesive or a silicone adhesive.
[0007] The discharge tube has sealed portions formed using pinch sealing or shrink sealing methods at both ends in the axial direction of the tube. Furthermore, a holder made of steatite or aluminum oxide is attached so that one end is located inside the sealed portion and the other end is located outside the sealed portion. This holder is a different component from the holder used to fix the barrier discharge lamp module to the support plate, as described above, so to avoid confusion, it will be referred to as the "discharge tube holder" below. The discharge tube holder is cylindrical, and lead wires are inserted through its interior. The gap between the lead wires and the discharge tube holder is sealed with a sealing material.
[0008] According to Figure 1 of Patent Document 1, the support portion attached to the open end of the protective tube is in contact with the sealing portion of the discharge tube. The same document also states that "a sealing portion 30b can be provided in the gap between the support portion 30 and the end of the barrier discharge lamp 1." However, considering that the sealing portion 30b is formed by the curing of epoxy adhesive or silicone adhesive according to the same document, this description assumes a minute gap that can be bonded with adhesive, so the support portion and the sealing portion of the discharge tube are in substantial contact. Furthermore, according to Figure 1, the discharge tube holder and the support portion are located outside the support plate through which the barrier discharge lamp module is inserted, with respect to the tube axis direction of the discharge tube.
[0009] Japanese Patent Publication No. 2024-004646
[0010] In the apparatus disclosed in Patent Document 1, the support plate through which the barrier discharge lamp module is inserted also serves the function of suppressing the flow of liquid that has entered through the inlet towards the opposite side of the outlet.
[0011] Here, if there is no support plate to fix the lamp module inside the container, the liquid that flows in through the inlet will also flow to the end of the barrier discharge lamp module, which is located on the opposite side of the outlet. At this time, the liquid comes into contact with a holder made of steatite or aluminum oxide, which is attached to the open end of the protective tube. The material of this holder has high thermal conductivity, and furthermore, as described above, the holder is in substantial contact with the sealing portion of the barrier discharge lamp. The sealing portion of the barrier discharge lamp is formed by a pinch seal or shrink seal method and is therefore connected to the discharge tube of the barrier discharge lamp.
[0012] In other words, if there is no support plate, the holder will be cooled by the incoming liquid, and the barrier discharge lamp will be further cooled through this holder.
[0013] Incidentally, the short-wavelength components of ultraviolet light emitted from barrier discharge lamps, particularly vacuum ultraviolet (VUV) light, are absorbed on the inner surface of the synthetic quartz glass that makes up the discharge tube without passing through it. As a result, the Si-O-Si bonds that make up the quartz glass are broken, causing internal defects. On the other hand, the rate at which Si-O-Si bonds are broken on the outer surface is relatively lower compared to the inner surface of the discharge tube. As a result, the stress balance between the inner and outer surfaces of the discharge tube is disrupted, causing strain to be generated and accumulate. When strain accumulates in the glass of the discharge tube, it can lead to a decrease in ultraviolet light transmittance, and may also cause deformation or cracking of the discharge tube.
[0014] Therefore, a method of doping quartz glass material with OH groups is known for the purpose of repairing defects caused by broken bonds. OH groups have the effect of migrating to and repairing defects where bonds have been broken. Patent document 1 also describes the introduction of OH groups into the quartz glass that constitutes a discharge tube.
[0015] However, the migration speed of OH groups is affected by temperature. In other words, if the barrier discharge lamp cools down, the migration speed of OH groups decreases, the repair process is not fully effective, and strain accumulates. This point will be discussed later with reference to Figure 7.
[0016] In other words, in the apparatus of Patent Document 1, it is essential to provide a support plate inside the container to prevent liquid from flowing into the holder attached to the open end of the protective tube. This means that the apparatus of Patent Document 1 must be used when attached to a dedicated container and is not suitable for processing liquids using any container.
[0017] Furthermore, in the apparatus of Patent Document 1, the incoming liquid continuously collides with the support plate. As a result, the support plate is cooled by the liquid. Also, as mentioned above, the support plate is fixed to the barrier discharge lamp module by a holder and an O-ring. In other words, the support plate and holder are in contact with the tube wall of the protective tube corresponding to the outer tube of the barrier discharge lamp module. As mentioned above, the protective tube is made of synthetic quartz glass, just like the discharge tube, and the tube wall of the protective tube and the sealing part connected to the discharge tube (barrier discharge lamp) are connected via a holder made of steatite or aluminum oxide. In other words, when the support plate is cooled by the fluid collision, the discharge tube may be cooled by this cooled support plate via the sealing part and holder. In other words, even with the usage method disclosed in Figure 1 of Patent Document 1, there is a concern that the barrier discharge lamp will be cooled, reducing the migration speed of OH groups and causing strain to accumulate.
[0018] In view of the above problems, the present invention aims to provide an excimer lamp that can suppress the accumulation of strain in the glass constituting the discharge tube, even when used for processing fluids.
[0019] The excimer lamp according to the present invention is an excimer lamp for fluid processing, comprising: a discharge tube including a first tube made of quartz glass filled with a light-emitting gas; a first electrode and a second electrode, at least one of which is provided on the outer wall of the first tube and which applies a voltage to the light-emitting gas; and a protective tube including a second tube made of quartz glass that houses the discharge tube, the first electrode, and the second electrode, and in which an inert gas having a lower thermal conductivity than air is sealed in the region outside the discharge tube, wherein the discharge tube has an elongated shape and has a first sealing portion at at least one end that seals the internal space of the first tube; the protective tube has an elongated shape that extends in the same direction as the tube axis of the discharge tube and has a second sealing portion at at least one end that seals the internal space of the second tube; the first sealing portion is located within the internal space of the second tube; and the second sealing portion is located outside the internal space of the second tube.
[0020] According to the above configuration, the first sealing portion that seals the end of the discharge tube, including the first tube body, is located within the internal space of the second tube body that houses the discharge tube. On the other hand, the second sealing portion that seals the end of the protective tube, including the second tube body, is located outside the internal space of the second tube body. In other words, the first sealing portion that seals the end of the discharge tube and the second sealing portion that seals the end of the protective tube are formed at positions spaced apart with respect to the tube axis of the discharge tube.
[0021] Furthermore, within the internal space of the protective tube, an inert gas with lower thermal conductivity than air is sealed around the outside of the discharge tube. In other words, an inert gas with lower thermal conductivity than air is interposed between the first sealing portion that seals the end of the discharge tube and the second sealing portion that seals the end of the protective tube.
[0022] When the excimer lamp described above is exposed to a fluid for use in fluid processing, the outer wall of the protective tube comes into contact with the fluid. The discharge tube is located in the internal space of the second tube that constitutes the protective tube, and this internal space is filled with an inert gas that has a lower thermal conductivity than air. In other words, even if the outer wall of the protective tube (second tube) is cooled by the fluid, the discharge tube is difficult to cool because, in the radial direction of the second tube, there is an inert gas with low thermal conductivity between the tube wall of the second tube and the discharge tube.
[0023] Furthermore, as mentioned above, the second sealing portion located at the end of the protective tube and the first sealing portion located at the end of the discharge tube are spaced apart in the axial direction of the discharge tube, and an inert gas with low thermal conductivity is present at the space between them. In other words, even if the second sealing portion is cooled by the fluid, the first sealing portion is difficult to cool because an inert gas is present between the second sealing portion and the first sealing portion in the axial direction of the discharge tube. Therefore, the discharge tube connected to the first sealing portion is also difficult to cool.
[0024] Therefore, with the excimer lamp described above, by installing it in the region where the fluid to be processed is present, it is possible to achieve the effect of preventing the discharge tube from being cooled by the fluid, without necessarily installing it in a special container that restricts the fluid flow. As a result, it is less likely to cause a decrease in the migration speed of the OH groups introduced into the quartz glass that makes up the discharge tube, and strain accumulation can be suppressed.
[0025] The first and second sealing portions may be formed by foil seals. A foil seal refers to a sealing portion in which the lamp electrodes and lead wires are connected by a metal foil (typically molybdenum foil), and this metal foil is embedded inside the lamp tube and sealed. Typically, a pinch seal method is used for this sealing, but a shrink seal method may also be used.
[0026] The fluid to be processed can be either a liquid or a gas.
[0027] As the inert gas, one or more gases selected from the group consisting of Ar, Kr, Xe, and N2 can be used.
[0028] The main component of the luminescent gas is Xe, and the first and second tubes may be made of synthetic quartz glass. In this case, ultraviolet light with a peak wavelength of around 172 nm is emitted from the luminescent tube.
[0029] The use of the term "near" in the description of the peak wavelength of ultraviolet light emitted from the lamp is intended to include individual variations in the lamp product. For example, the statement that the peak wavelength is "near 172 nm" means that a wavelength deviation within ±2.0 nm from 172.0 nm is acceptable, in addition to the absolute value of 172.0 nm.
[0030] The excimer lamp described above includes a first connection portion that extends from the outside of the protective tube, through the second sealing portion, and connects to the first electrode located in the internal space of the second tube, and a second connection portion that extends from the outside of the protective tube, through the second sealing portion, and connects to the second electrode located in the internal space of the second tube, wherein the first connection portion and the second connection portion are spaced apart within the second tube between the first sealing portion and the second sealing portion, and the inert gas may be sealed at a gas pressure of 1.3 kPa or more and atmospheric pressure or less.
[0031] The first connection typically includes a wire (lead wire) connected to the first electrode of the excimer lamp, and the second connection typically includes a wire (lead wire) connected to the second electrode of the excimer lamp. These first and second connection parts extend to the outside of the protective tube. A voltage is applied between the first and second connection parts from a power circuit installed outside the protective tube, thereby applying a voltage between the first and second electrodes, causing the light-emitting gas sealed inside the discharge tube to undergo a dielectric barrier discharge and emit light.
[0032] The first and second connection sections, which extend from the outside of the protective tube through the second sealing section, pass through the inside of the protective tube before connecting to the first and second electrodes of the discharge tube. In other words, both the first and second connection sections pass through a region that is located inside the protective tube (second tube body) and outside the discharge tube.
[0033] If a voltage is applied between the first and second connection points, dielectric breakdown may occur in the internal space of the second tube and in the region located outside the light-emitting tube. If this phenomenon occurs, voltage will not be applied to the light-emitting gas, and the excimer lamp will not light up. However, with the above configuration, since the inert gas sealed in the space is sealed at a gas pressure of 1.3 kPa (10 Torr) or more, dielectric breakdown in the internal space of the second tube is suppressed. The gas pressure of the inert gas is preferably 6.7 kPa (50 Torr) or more, and more preferably 13.3 kPa (100 Torr) or more.
[0034] On the other hand, if the gas pressure of the inert gas sealed in the internal space of the second tube is higher than atmospheric pressure, there is a possibility that the second tube may rupture. From this viewpoint, it is preferable that the gas pressure of the inert gas be atmospheric pressure, i.e., 101 kPa (760 Torr) or less. Furthermore, considering a safety margin, it is more preferable that the gas pressure of the inert gas be 93.3 kPa (700 Torr) or less, and particularly preferable that it be 86.7 kPa (650 Torr) or less.
[0035] The first electrode may be provided in the internal space of the first tube, and the second electrode may be provided on the outer wall of the first tube. In this case, the excimer lamp may be provided with a support member that contacts both the region of the outer wall of the first tube that is further from the first sealing portion with respect to the extending direction of the first tube and is outside the first electrode, and the inner wall of the second tube, within the internal space of the second tube.
[0036] According to the above configuration, the outer wall of the first tube and the inner wall of the second tube are connected via a support member. As a result, even if the excimer lamp vibrates (oscillates) due to the flow of the fluid being processed, for example, the distance between the outer wall of the first tube and the inner wall of the second tube is maintained within the internal space of the second tube. Therefore, even if the second tube is cooled by the fluid, the first tube remains less susceptible to cooling.
[0037] According to the present invention, an excimer lamp is realized that can suppress the accumulation of strain in the glass constituting the discharge tube, even when used for processing fluids.
[0038] This is a schematic plan view showing the structure of one embodiment of an excimer lamp. This is a schematic plan view showing the structure of one embodiment of an excimer lamp, and the viewing direction is different from that of Figure 1. This is a schematic cross-sectional view of the excimer lamp when it is cut along the line A1-A1 in Figure 2. This is a schematic cross-sectional view of the excimer lamp when it is cut along the line A2-A2 in Figure 2. This is a graph showing the transmission spectrum of synthetic quartz glass. This is a graph that superimposes the ultraviolet spectrum inside the first tube and the ultraviolet spectrum extracted to the outside of the first tube. This is a graph showing the relationship between the lighting time and strain intensity when the excimer lamp is continuously lit with the protective tube removed, and the results are shown as they were measured at different temperatures of the discharge tube. This is a schematic cross-sectional view of the excimer lamp when it is cut along the Y-Z plane near the +X side end of the first tube.
[0039] Embodiments of the excimer lamp according to the present invention will be described below with reference to the drawings as appropriate. Note that the following drawings are schematic representations, and the dimensional ratios and number of elements shown in the drawings do not necessarily correspond to the actual dimensional ratios and number of elements.
[0040] Figures 1 and 2 are schematic plan views illustrating the structure of one embodiment of an excimer lamp, with different viewing directions. Figure 1 corresponds to a view of the excimer lamp 1 in the Z direction, and Figure 2 corresponds to a view of the excimer lamp 1 in the Y direction.
[0041] In the following descriptions, when expressing direction, positive and negative directions are distinguished, and these are indicated with a sign, such as "+X direction" and "-X direction". When expressing direction without distinguishing between positive and negative directions, it is simply written as "X direction". In other words, in this specification, when simply written as "X direction", it includes both "+X direction" and "-X direction". The same applies to the Y direction and Z direction.
[0042] FIG. 3 is a schematic cross-sectional view of the excimer lamp 1 taken along line A1-A1 in FIG. 2. FIG. 4 is a schematic cross-sectional view of the excimer lamp 1 taken along line A2-A2 in FIG. 2. Note that in FIG. 4, illustration of some elements is omitted for the sake of clarity of understanding.
[0043] As shown in FIG. 1 to FIG. 3, the excimer lamp 1 includes an arc tube 3 and a protective tube 9. The arc tube 3 is accommodated in the inner space of the protective tube 9.
[0044] The arc tube 3 includes a first tubular body 5 having an elongated shape extending in the X direction, and a first sealing portion 7 that seals the inner space of the first tubular body 5 at an end portion of the first tubular body 5. In the examples shown in FIG. 1 to FIG. 2, the X direction corresponds to the tube axis direction of the arc tube 3.
[0045] In the excimer lamp 1 shown in FIG. 1 to FIG. 2, the end portion on the -X side of the first tubular body 5 is sealed by the first sealing portion 7.
[0046] A light-emitting gas G1 is enclosed in the inner space of the first tubular body 5. In the present embodiment, the main component of the light-emitting gas G1 is Xe. The type of the light-emitting gas G1 is selected according to the wavelength of ultraviolet light L1 (see FIG. 3) that is desired to be utilized by the excimer lamp 1. When it is desired that the ultraviolet light L1 is ultraviolet light having a peak wavelength near 172 nm, the main component of the light-emitting gas G1 is set to Xe.
[0047] The excimer lamp 1 of the present embodiment is used in an application of irradiating a fluid to be treated Q1 (see FIG. 3) with the ultraviolet light L1 emitted from the excimer lamp 1 to treat the fluid to be treated Q1. Therefore, the peak wavelength of the ultraviolet light L1 can be appropriately selected according to the type of the fluid to be treated Q1 and the treatment purpose.
[0048] The gas pressure of the light-emitting gas G1 enclosed inside the first tubular body 5 is preferably 1.3 kPa (10 Torr) to 101.3 kPa (760 Torr), more preferably 6.7 kPa (50 Torr) to 80.0 kPa (600 Torr), and particularly preferably 13.3 kPa (100 Torr) to 40.0 kPa (300 Torr).
[0049] The excimer lamp 1 comprises a first electrode 21 and a second electrode 22. As shown in Figures 1 to 3, in the excimer lamp 1 of this embodiment, the first electrode 21 is arranged in the internal space of the discharge tube 3, and the second electrode 22 is arranged on the outer wall of the discharge tube 3. From the viewpoint of extracting ultraviolet light L1 generated inside the discharge tube 3 to the outside of the discharge tube 3, the second electrode 22 has a mesh-like structure. However, the second electrode 22 may also be linear.
[0050] As shown in Figures 1 to 3, the protective tube 9 has an elongated shape that extends in the same direction as the tube axis direction (X direction) of the discharge tube 3, and houses the discharge tube 3 inside. The protective tube 9 comprises a second tube body 11 that extends in the X direction, and a second sealing portion 13 that seals the internal space of the second tube body 11 at its end. In the excimer lamp 1 shown in Figures 1 to 2, the -X side end of the second tube body 11 is sealed by the second sealing portion 13. Also, similar to the discharge tube 3, in the protective tube 9, the X direction corresponds to the tube axis direction.
[0051] The second tube 11 is sealed with an inert gas G2. The inert gas G2 sealed inside the second tube 11 is a gas with a lower thermal conductivity than air. Specifically, the inert gas G2 can be one or more gases selected from the group consisting of Ar, Kr, Xe, and N2.
[0052] The gas pressure of the inert gas G2 sealed inside the second tube 11 is preferably 1.3 kPa (10 Torr) to 101 kPa (760 Torr: atmospheric pressure), more preferably 6.7 kPa (50 Torr) to 93.3 kPa (700 Torr), and particularly preferably 13.3 kPa (100 Torr) to 86.7 kPa (650 Torr).
[0053] The first tube 5 and the second tube 11 are both made of a material that is transparent to ultraviolet light L1. Here, being transparent to ultraviolet light L1 means that the transmittance to the peak wavelength of ultraviolet light L1 is 50% or more, preferably 60% or more, more preferably 70% or more, and particularly preferably 80% or more. When the main component of the light-emitting gas G1 is Xe and the peak wavelength of ultraviolet light L1 is around 172 nm, the first tube 5 and the second tube 11 are preferably made of synthetic quartz glass. As another example, the first tube 5 and the second tube 11 are made of fused quartz glass.
[0054] Of the first tube 5 and the second tube 11, at least the quartz glass constituting the first tube 5 is doped with OH groups. The quartz glass constituting the second tube 11 may or may not be doped with OH groups.
[0055] As shown in Figure 1, the excimer lamp 1 has a first connection part 31 and a second connection part 32.
[0056] The first connecting portion 31 is inserted into the protective tube 9 from the outside, passing through the second sealing portion 13, and is connected to the first electrode 21 located in the internal space of the first tube body 5. More specifically, the first connecting portion 31 passes through the inside of the second sealing portion 13, the internal space of the second tube body 11 and the external space of the discharge tube 3, and the inside of the first sealing portion 7 before being connected to the first electrode 21.
[0057] The second connecting portion 32 is inserted into the protective tube 9 from the outside, passing through the second sealing portion 13, and is connected to the second electrode 22 located on the outer wall of the first tube 5. More specifically, the second connecting portion 32 passes through the inside of the second sealing portion 13, the internal space of the second tube 11 and the external space of the discharge tube 3, and the outer surface of the first sealing portion 7 before being connected to the second electrode 22.
[0058] The first sealing portion 7 and the second sealing portion 13 may both be sealed with foil. By using foil sealing, the tubes (first tube 5, second tube 11) are sealed while ensuring electrical connection between the connecting portions (31, 32) and the electrodes (21, 22). Note that either a pinch seal method or a shrink seal method may be used for foil sealing. However, the present invention does not exclude cases where the first sealing portion 7 and the second sealing portion 13 use sealing methods other than foil sealing.
[0059] As described above, the discharge tube 3 is housed in the internal space of the second tube 11 that constitutes the protective tube 9. More specifically, the first tube 5 and the first sealing part 7 are housed in the internal space of the second tube 11. On the other hand, the second sealing part 13 that seals the second tube 11 is located outside the internal space of the second tube 11. As a result, there is a gap dx1 in the X direction between the first sealing part 7 and the second sealing part 13 (see Figure 1). This region of gap dx1 is the internal space of the second tube 11 and the external space of the discharge tube 3, and therefore, as described above, there is an inert gas G2 with a lower thermal conductivity than air present in this region.
[0060] When a voltage is applied between the first connection part 31 and the second connection part 32 through a power supply circuit (not shown), a voltage is applied between the first electrode 21 and the second electrode 22 provided on the discharge tube 3. That is, a voltage is applied through the tube wall of the discharge tube 3 to the internal space (luminescence space) of the first tube body 5 in which the luminescent gas G1 is sealed. As a result, atoms contained in the luminescent gas G1 are excited and enter an excimer state, and when these atoms transition to the ground state, they emit ultraviolet light L1 through excimer emission.
[0061] Figure 3 is a schematic diagram showing how the treatment is performed by irradiating the fluid to be treated Q1 with ultraviolet light L1. As shown in Figure 3, the fluid to be treated Q1 is located outside the second tube 11 that constitutes the protective tube 9, and ultraviolet light L1 generated from the light-emitting gas G1 passes through the first tube 5 and the second tube 11 and irradiates the fluid to be treated Q1. When the fluid to be treated Q1 is irradiated with ultraviolet light L1, the chemical bonds of the organic matter contained in the fluid to be treated Q1 are broken, and the organic matter is decomposed. The fluid to be treated Q1 may be a liquid such as water, or a gas such as air. Typically, the fluid to be treated Q1 is a liquid or gas containing impurities composed of organic matter, and the excimer lamp 1 is used to irradiate the fluid to be treated Q1 with ultraviolet light L1 to decompose the organic matter contained in the fluid to be treated Q1 and perform impurity treatment. In this invention, "fluid treatment" is a general concept that includes all treatments involving the irradiation of a fluid with ultraviolet light, such as treatments that decompose organic matter contained in the fluid with ultraviolet light, and treatments that generate active species such as ozone and radicals by irradiating the fluid with ultraviolet light.
[0062] Of the ultraviolet light L1 propagating from the internal space of the first tube 5 toward the outside, the short-wavelength components are absorbed by the inner wall of the first tube 5. Figure 5 is a graph showing the transmission spectrum of synthetic quartz glass. In Figure 5, the horizontal axis represents wavelength and the vertical axis represents transmittance.
[0063] For example, if the main component of the luminescent gas G1 is Xe, ultraviolet light L1 with a peak wavelength of around 172 nm is generated in the internal space of the first tube 5, but this ultraviolet light L1 also contains extremely short wavelength components of 160 nm or less. These short wavelength components contained in ultraviolet light L1 are absorbed by the inner wall of the first tube 5, resulting in a spectrum of ultraviolet light L1 passing through the first tube 5 with reduced intensity of the extremely short wavelength components of 160 nm or less. Figure 6 is a graph that superimposes the ultraviolet light spectrum inside the first tube 5 and the ultraviolet light spectrum extracted to the outside of the first tube 5. In Figure 6, the horizontal axis represents wavelength, and the vertical axis represents light intensity. In Figure 6, the spectrum of ultraviolet light L1 inside the first tube 5 (a) is shown by a solid line, and the spectrum of ultraviolet light L1 extracted to the outside of the first tube 5 (b) is shown by a dashed line. Note that the graph in Figure 6 is expressed based on relative values with the peak intensity in spectrum (a) as the reference value.
[0064] As shown in Figure 5, the synthetic quartz glass constituting the first tube 5 has low transmittance in the extremely short wavelength region of 160 nm or less. On the other hand, as shown in Figure 6, the ultraviolet light L1 emitted within the first tube 5 also contains components with wavelengths of 160 nm or less. Therefore, when this ultraviolet light L1 is irradiated onto the tube wall of the first tube 5, the components with wavelengths of 160 nm or less are absorbed by the inner wall, while the components with longer wavelengths pass through the tube wall of the first tube 5 and propagate into the internal space of the second tube 11. This is also evident in Figure 6, where the intensity of the spectrum (b) with wavelengths of 160 nm or less is significantly lower than the intensity of the spectrum (a) with wavelengths of 160 nm or less.
[0065] In this way, the inner wall of the first tube 5 absorbs light with extremely short wavelengths contained in ultraviolet light L1. If this condition continues, the bonds in the quartz glass that makes up the first tube 5 will break, and internal defects will occur. However, as mentioned above, the first tube 5 is doped with OH groups, so these OH groups move to the internal defects caused by the broken bonds, and the defects are repaired.
[0066] Incidentally, the second tube 11, like the first tube 5, is also made of quartz glass, but since the short-wavelength components of ultraviolet light L1 with wavelengths of 160 nm or less have already been absorbed by the inner wall of the first tube 5, the ultraviolet light L1 passing through the internal space of the second tube 11 contains almost no wavelength components with low transmittance to the second tube 11. Furthermore, as mentioned above, the region of the internal space of the second tube 11 that is located outside the first tube 5 is sealed with inert gas G2, and this inert gas G2 has high transmittance to ultraviolet light L1. Therefore, the ultraviolet light L1 that has passed through the first tube 5 passes directly through the internal space and wall of the second tube 11 and irradiates the fluid to be treated Q1 located outside of it. As a result, in the second tube 11, the phenomenon of absorption of short-wavelength components with wavelengths of 160 nm or less and the breaking of bonds in the quartz glass, as in the first tube 5, is less likely to occur, and therefore internal defects are less likely to occur. Therefore, the quartz glass constituting the second tube 11 does not necessarily have to be doped with OH groups, as described above.
[0067] Incidentally, under the light emission of the excimer lamp 1, the light-emitting space, i.e., the internal space of the first tube 5, is heated due to the light emission and exhibits a temperature higher than room temperature. For example, the internal space of the first tube 5 exhibits a temperature of 150°C to 200°C. On the other hand, unless special pretreatment such as heating the fluid to be processed Q1 is performed before introducing it near the excimer lamp 1, the fluid to be processed Q1 exhibits a temperature lower than the internal space of the first tube 5.
[0068] Since the fluid Q1 being treated is in contact with the outer wall of the second pipe 11, the temperature of the outer wall of the second pipe 11 is similar to the temperature of the fluid Q1 being treated. However, an inert gas G2 is sealed between the first pipe 5 and the second pipe 11, and this inert gas G2 is a type of gas with a lower thermal conductivity than air. Therefore, the cooling effect of the fluid Q1 being treated does not easily reach the first pipe 5, and as a result, the temperature of the first pipe 5 does not easily decrease.
[0069] Figure 7 is a graph showing the intensity of strain generated in the discharge tube 3 when an excimer lamp 1 with the protective tube 9 removed was continuously lit as a sample. This verification was performed under different temperatures of the discharge tube 3. More specifically, the verification was performed under four different temperatures: when the discharge tube 3 was not cooled (temperature 188°C), when the discharge tube 3 was air-cooled (temperatures 60°C and 32°C), and when the discharge tube 3 was water-cooled (temperature 20°C). In Figure 7, the horizontal axis represents the lighting time, and the vertical axis represents the strain intensity. The strain intensity was calculated using the birefringence method. More specifically, when laser light is incident on the discharge tube 3, if no strain is generated in the discharge tube 3, there is no phase difference between the incident light and the transmitted light. However, if strain is generated in the discharge tube 3, the refractive index of the discharge tube 3 changes, and a phase difference occurs. This phase difference is proportional to the stress (strain intensity), and the proportionality constant is based on the photoelastic coefficient derived from the material of the discharge tube 3 and the optical path length (thickness of the discharge tube 3) that traveled through the discharge tube 3. Therefore, the strain intensity can be derived from the phase difference.
[0070] Figure 7 clearly shows that the higher the temperature of the discharge tube 3, the smaller the tendency for strain intensity to increase in response to continuous lighting time. Conversely, the lower the temperature of the discharge tube 3, the faster the rate of increase in strain intensity. This result suggests that when the temperature of the discharge tube 3 is low, the migration speed of OH groups decreases, resulting in a slower repair rate by OH groups than the rate of defect generation, which makes it easier for the strain intensity of the discharge tube 3 to increase.
[0071] In other words, when the excimer lamp 1 is used to process the fluid Q1 to be processed, it is expected that as the temperature of the discharge tube 3 (first tube body 5) decreases depending on the temperature of the fluid Q1 to be processed, the migration speed of the OH groups will decrease, the repair function will decrease, and strain will be more likely to accumulate in the discharge tube 3.
[0072] However, as shown in Figure 3, in the excimer lamp 1 of this embodiment, the fluid to be processed Q1 is in contact with the outer wall of the protective tube 9 (second tube 11), and an inert gas G2 with low thermal conductivity is sealed between the second tube 11 and the first tube 5. Therefore, the first tube 5 is not easily cooled by the fluid to be processed Q1, which makes it less likely to cause a decrease in the repair rate by OH groups and less likely to cause strain to accumulate.
[0073] Furthermore, as shown in Figures 1 and 2, the excimer lamp 1 has a gap dx1 between the first sealing portion 7 and the second sealing portion 13, and an inert gas G2 is sealed within this gap dx1. Therefore, even if the second sealing portion 13, which is located outside the internal space of the second tube 11, is cooled by the passage of the fluid to be treated Q1, the first sealing portion 7 is not easily cooled because an inert gas G2 with low thermal conductivity exists between the second sealing portion 13 and the first sealing portion 7. As a result, it is unlikely that the first tube 5 will be cooled through the first sealing portion 7.
[0074] Therefore, with the excimer lamp 1 of this embodiment, it is sufficient to simply install the excimer lamp 1 itself within the region where the fluid to be processed Q1 exists, and it is not necessarily required to take any special measures to suppress the cooling of the second sealing portion 13.
[0075] As shown in Figures 1 and 2, the first tube 5 may have an exhaust pipe remainder 41. The exhaust pipe remainder 41 is formed during the manufacturing process of the light-emitting tube 3 and is the remainder formed when the exhaust pipe (tip pipe) provided for exhausting impurity gas from inside the first tube 5 or for introducing light-emitting gas G1 into the first tube 5 is removed while being melt-sealed. Similarly, the second tube 11 may have an exhaust pipe remainder 42. The exhaust pipe remainder 42 is formed during the manufacturing process of the protective tube 9 and is the remainder formed when the exhaust pipe (tip pipe) provided for exhausting impurity gas from inside the second tube 11 or for introducing inert gas G2 into the second tube 11 is removed while being melt-sealed. In Figures 1 and 2, the exhaust pipe remainder 41 is formed at the +X side end of the first tube 5, but the installation position of the exhaust pipe remainder 41 is not limited. The same applies to the exhaust pipe remainder 42.
[0076] The excimer lamp 1 preferably has a support member 45. In the example shown in Figures 1 and 2, the support member 45 is installed near the +X side end of the first pipe 5. Figure 8 is a schematic cross-sectional view of the excimer lamp 1 when cut along the Y-Z plane near the +X side end of the first pipe 5. In this example, the support member 45 is a coil-shaped member that connects the vicinity of the outer circumference of the remaining exhaust pipe portion 41 of the first pipe 5 to the inner wall of the second pipe 11. The support member 45 has the function of preventing the second pipe 11 from coming close to the outer wall of the first pipe 5. With the presence of this support member 45, when ultraviolet light L1 from the excimer lamp 1 is irradiated onto the fluid to be treated Q1 in flow to treat the fluid to be treated Q1, even if the second pipe 11 oscillates due to the flow of the fluid to be treated Q1, a separation is maintained between the outer wall of the first pipe 5 and the inner wall of the second pipe 11, so that an inert gas G2 with low thermal conductivity can be positioned in the separated portion. This ensures that the first pipe 5 is not easily cooled by the fluid Q1 being processed. The support member 45 is preferably made of a material that is not easily degraded even when irradiated with ultraviolet light L1 emitted from the first pipe 5, and can be made of a metal material such as stainless steel or titanium.
[0077] The support member 45 only needs to be positioned outside the region where the first electrode 21 and the second electrode 22 face each other in the X direction. In the example shown in Figures 1 and 2, the support member 45 is installed further to the +X side than the +X side end of the first electrode 21. That is, the installation position of the support member 45 is outside the region where the first electrode 21 and the second electrode 22 face each other.
[0078] Note that the configuration of the support member 45 shown in Figure 8 is merely an example. The shape and structure of the support member 45 are not limited as long as it functions to connect the outer wall of the first pipe 5 and the inner wall of the second pipe 11 and maintain the distance between them.
[0079] [Alternative Embodiments] Alternative embodiments will be described below.
[0080] <1> In the excimer lamp 1 of the embodiment described above, the first electrode 21 was arranged in the internal space of the first tube 5, and the second electrode 22 was arranged on the outer wall of the first tube 5. However, both the first electrode 21 and the second electrode 22 may be arranged on the outer wall of the first tube 5. For example, the first tube 5 may have a shape having two planes along the X-Y plane that are opposite to each other in the Z direction, with the first electrode 21 arranged on one face and the second electrode 22 on the other face, so that both electrodes (21, 22) face each other in the Z direction via the light-emitting gas G1 sealed inside the first tube 5. Typically, the first tube 5 has a substantially rectangular shape when viewed in the X direction.
[0081] In this case, the shape of the second tube 11 may also correspond to the shape of the first tube 5, for example, it may be substantially rectangular when viewed in the X direction. In other words, the shapes of the first tube 5 and the second tube 11 do not necessarily have to be circular when viewed in the X direction, and any shape can be adopted.
[0082] <2> In the above embodiment, the main component of the luminescent gas G1 was Xe, but the present invention does not exclude the case in which other gas species are used for the luminescent gas G1. For example, by making ArBr the main component of the luminescent gas G1, ultraviolet light L1 with a peak wavelength of around 165 nm can be obtained. Other examples of combinations of the main component of the luminescent gas G1 and the peak wavelength of ultraviolet light L1 include ArF (around 193 nm), ArCl (around 175 nm), KrBr (around 207 nm), etc. These ultraviolet light sources may also contain extremely short wavelength components that break the bonds of quartz glass, so the same discussion as in the case where the main component of the luminescent gas G1 is Xe is possible.
[0083] <3> As described in the above embodiment, the excimer lamp 1 is used to perform processing on the fluid to be processed Q1 by irradiating the fluid to be processed Q1 with ultraviolet light L1 emitted from the discharge tube 3, as described above with reference to Figure 3. At this time, the fluid to be processed Q1 may be in a flowing state or in a stored state (stationary state).
[0084] (4) The present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail for a better understanding of the present invention and are not necessarily limited to all configurations described. The scope of the present invention is indicated by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included.
[0085] 1: Excimer lamp 3: Light-emitting tube 5: First tube body 7: First sealing part 9: Protective tube 11: Second tube body 13: Second sealing part 21: First electrode 22: Second electrode 31: First connection part 32: Second connection part 41: Remaining exhaust pipe 42: Remaining exhaust pipe 45: Support member G1: Light-emitting gas G2: Inert gas L1: Ultraviolet light Q1: Fluid to be processed
Claims
1. An excimer lamp for fluid processing comprising: a discharge tube including a first quartz glass tube filled with a luminescent gas; a first electrode and a second electrode, at least one of which is provided on the outer wall of the first tube and for applying a voltage to the luminescent gas; and a protective tube including a second quartz glass tube that houses the discharge tube, the first electrode, and the second electrode, and in which an inert gas with a lower thermal conductivity than air is sealed in the region outside the discharge tube; wherein the discharge tube has an elongated shape and has a first sealing portion at at least one end that seals the internal space of the first tube; the protective tube has an elongated shape extending in the same direction as the tube axis of the discharge tube and has a second sealing portion at at least one end that seals the internal space of the second tube; the first sealing portion is located within the internal space of the second tube; and the second sealing portion is located outside the internal space of the second tube.
2. An excimer lamp for fluid processing according to claim 1, comprising: a first connecting portion that extends from the outside of the protective tube, through the second sealing portion, and is connected to the first electrode located in the internal space of the second tube; and a second connecting portion that extends from the outside of the protective tube, through the second sealing portion, and is connected to the second electrode located in the internal space of the second tube, wherein the first connecting portion and the second connecting portion are spaced apart within the second tube between the first sealing portion and the second sealing portion, and the inert gas is sealed at a gas pressure of 1.3 kPa or more and atmospheric pressure or less.
3. The excimer lamp for fluid processing according to claim 1 or 2, characterized in that the first electrode is provided in the internal space of the first tube, the second electrode is provided on the outer wall of the first tube, and the second tube has a support member that contacts both the region of the outer wall of the first tube that is further from the first sealing portion with respect to the extending direction of the first tube and is outside the first electrode, and the inner wall of the second tube, within the internal space of the second tube.
4. The excimer lamp for fluid processing according to claim 1 or 2, characterized in that the inert gas consists of one or more gases selected from the group consisting of Ar, Kr, Xe, and N2.
5. The excimer lamp for fluid processing according to claim 1 or 2, characterized in that the main component of the luminescent gas is Xe, and the first tube and the second tube are made of synthetic quartz glass.