JP5200749B2 - Excimer lamp - Google Patents

Description

  The present invention relates to an excimer lamp, and more particularly, to an excimer discharge lamp enclosing xenon that efficiently radiates ultraviolet rays by forming an ultraviolet reflecting layer inside a discharge vessel made of silica glass.

  In recent years, for example, by irradiating a vacuum ultraviolet light having a wavelength of 200 nm or less onto a target object made of metal, glass, or other material, the action of the vacuum ultraviolet light and the ozone generated thereby, for example, Technologies for processing objects have been developed and put to practical use, such as cleaning technology that removes organic contaminants attached to the surface and oxide film formation technology that forms an oxide film on the surface of the object. Yes.

  As an apparatus for irradiating vacuum ultraviolet light, for example, there is an apparatus that includes an excimer lamp that forms excimer molecules by excimer discharge and uses light emitted from the excimer molecules as a light source. In this excimer lamp, many attempts have been made to efficiently radiate higher-intensity ultraviolet rays.

  For example, referring to FIG. 6, in an excimer lamp 50 that includes a discharge vessel 51 made of silica glass that transmits ultraviolet rays, and electrodes 55 and 56 are provided on the outer wall of the discharge vessel 51, respectively. It is described that xenon gas is sealed inside as a discharge gas, and an ultraviolet reflection film 58 is formed on the surface exposed to the discharge space S of the discharge vessel 51. As the ultraviolet reflection film, silica particles and alumina are described. What consists of particle | grains is illustrated by the Example (refer patent document 1).

According to the discharge lamp having the above-described configuration, since the ultraviolet reflection film 58 is provided on the inner wall of the discharge vessel 51 and the surface exposed to the discharge space S, the discharge is performed in the region where the ultraviolet reflection film 58 is provided. The ultraviolet rays generated in the space S are reflected by the ultraviolet reflecting film. The reflected ultraviolet rays are transmitted to the outside through the light emitting portion 57 where the ultraviolet reflecting film 58 is not provided.
Therefore, since the ultraviolet rays generated in the discharge space S can be used effectively, the ultraviolet radiation efficiency of the wavelength of 150 to 200 nm emitted from the excimer lamp is 20% or more compared to the excimer lamp having no ultraviolet reflecting film. It is also described that it improves.
JP2007-335350A

However, the above-described excimer lamp has a problem that the illuminance of ultraviolet light having a wavelength of 172 nm gradually decreases with the passage of lighting time. The inventors examined this problem, and in the ultraviolet reflection film of the excimer lamp after lighting for a long time, an absorption band is generated in the ultraviolet region, and a part of the ultraviolet ray is absorbed by the ultraviolet reflection film, thereby causing an illuminance. It was found that there was a decrease.
This absorption is due to the silica particles in the ultraviolet reflective film being exposed to ultraviolet rays and plasma generated by the discharge, resulting in radiation damage and internal defects, and part of the ultraviolet rays being absorbed due to the internal defects. Thus, it was found that the effect of scattering reflection is reduced.
This internal defect is a Si-Si defect having an absorption edge in the vicinity of a wavelength of 163 nm, or an absorption band in the vicinity of a wavelength of 215 nm, caused by exposure of Si—O—Si bonds of silica particles to ultraviolet rays or plasma. It is a certain E'center (Si ·).
In order to solve this problem, the inventors have intensively studied, and by containing OH groups in the silica particles in the ultraviolet reflecting film, the effect of suppressing the generation of internal defects in the silica particles contained in the ultraviolet reflecting film is effective. I found out.
FIG. 2 is a graph showing the relationship between the OH group concentration and the reflection maintenance ratio, which was examined by changing the OH group concentration of the ultraviolet reflecting film made of silica particles of the excimer lamp. The horizontal axis represents the logarithm of the OH group concentration (wt. Ppm), and the vertical axis represents the reflection maintenance ratio (%). The reflection maintenance ratio is obtained by measuring the reflectance of 172 nm vacuum ultraviolet light irradiated from an excimer lamp at the beginning of lighting and after 500 hours, and calculating the maintenance ratio. As shown in FIG. 2, it can be seen that the higher the OH group concentration in the ultraviolet reflective film, the higher the reflection maintenance ratio. As described above, it was possible to prevent the reflection performance of the ultraviolet reflecting film from being deteriorated by sufficiently containing OH groups in the silica particles in the ultraviolet reflecting film.

However, if OH groups are sufficiently contained in the silica particles in the ultraviolet reflecting film, when a predetermined time elapses after the lamp is turned on, green light emission near the wavelength of 550 nm appears strongly, and further, the wavelength of 172 nm. Decrease in illuminance of ultraviolet rays occurred.
When the above green emission was analyzed, it was confirmed to be molecular emission by xenon oxide (hereinafter referred to as XeO). When this light emission became strong, the illuminance of ultraviolet light having a wavelength of 172 nm also decreased. Therefore, the inventors considered that the cause of the problem was related to XeO as follows.

As described above, in order to suppress internal defects, the OH group contained in the silica particles in the ultraviolet reflecting film is dissociated when the silica particles are exposed to the discharge or the ultraviolet rays are emitted, so that the discharge space May be released.
The excimer lamp is filled with xenon (hereinafter referred to as Xe) as a discharge gas. The OH groups released into the discharge space are decomposed by plasma into O (oxygen atoms) and react with Xe enclosed in the lamp to become XeO, thereby substantially reducing the xenon atoms from the beginning of lighting. End up.
That is, when the OH group concentration is appropriate, the OH group can satisfactorily suppress the generation of internal defects and maintain the reflection performance of the ultraviolet reflecting film. However, if the OH group concentration is excessive, It is discharged into the discharge space and causes Xe gas to substantially decrease.
FIG. 3 is a graph showing the relationship between the OH group concentration in the silica particles in the ultraviolet reflecting film and the illuminance of vacuum ultraviolet light having a wavelength of 172 nm by Xe excimer. The horizontal axis is a logarithmic display of the OH group concentration (wt. Ppm) in the silica particles in the ultraviolet reflecting film, and the vertical axis is the illuminance of light having a wavelength of 172 nm. As a measurement sample, an ultraviolet reflecting film made only of silica particles was prepared on an excimer lamp, and the illuminance at 172 nm irradiated from the excimer lamp after 500 hours was measured.
As shown in FIG. 3, the illuminance of light having a wavelength of 172 nm decreases as the OH group concentration in the ultraviolet reflective film increases.
That is, OH is gradually released and XeO is generated every time a predetermined time has elapsed since the start of the excimer lamp, and the proportion of molecular luminescence with a wavelength of 550 nm emitted by the excitation of XeO is the initial stage of lighting. More than. Along with this, Xe substantially decreases, and it is considered that the proportion of ultraviolet rays having a wavelength of 172 nm emitted by Xe excimer molecular light emission is smaller than in the initial stage of lighting.

  As described above, the present invention provides an excimer lamp in which an ultraviolet reflecting film is provided on the inner wall of a discharge vessel in which a discharge gas containing xenon gas is sealed, and silica particles that constitute the ultraviolet reflecting film contain OH groups. An object of the present invention is to provide an excimer lamp in which the illuminance of ultraviolet rays does not decrease as the lighting time elapses.

The present invention provides an excimer in which an inner wall of a discharge vessel made of silica glass has an ultraviolet reflecting film formed of silica particles and ultraviolet scattering particles made of alumina particles not containing OH groups , and a gas containing xenon is enclosed. In the lamp, the alumina concentration Y (vol%) of the ultraviolet reflecting film and the OH group concentration X (wt. Ppm) in the silica particles of the ultraviolet reflecting film satisfy Y ≧ 13.7 log _e (X) +1.2. It is characterized by satisfying the relationship.

  Further, the present invention is characterized in that the center particle size RS (μm) of silica particles of the ultraviolet reflecting film and the center particle size RA (μm) of alumina particles satisfy a relationship of RA / RS ≧ 1.

According to the present invention, in an excimer lamp having an ultraviolet reflecting film formed of ultraviolet scattering particles including silica particles and alumina particles on the inner wall of a discharge vessel made of silica glass, By satisfying the relationship of Y ≧ 13.7ln (X) +1.2, the alumina volume concentration Y (vol product%) and the OH group concentration X (wt. Ppm) in the reflective film satisfy the relationship OH in the ultraviolet reflective film. Depending on the concentration, alumina particles having a sufficient volume concentration are contained.
This makes it easier for the alumina particles to be exposed on the surface of the ultraviolet reflective film exposed to the discharge. Since the alumina particles do not contain OH groups, OH released from the ultraviolet reflecting film is reduced, and generation of XeO can be suppressed. In addition, since silica particles containing an appropriate amount of OH groups are used in the ultraviolet reflection film, the reflection performance of the ultraviolet reflection film can be maintained without lowering the ultraviolet illuminance due to Xe excimer emission.

  Moreover, the average particle diameter RS of the silica particles in the ultraviolet reflective film and the average particle diameter RA of the alumina particles satisfy the relationship of the formula: RA / RS ≧ 1, so that the silica particles have a gap between the alumina particles and the alumina particles. It penetrates and partly melts and contributes to adhesion, and is difficult to be exposed on the surface of the ultraviolet reflective film exposed to electric discharge. For this reason, the silica particles are not exposed to electric discharge to release OH, and the generation of XeO can be suppressed. Therefore, the ultraviolet illuminance due to Xe excimer emission does not decrease.

FIG. 1 is a cross-sectional view showing an outline of the configuration of an example of an excimer lamp 10 according to the present invention. FIG. 1A is a cross-sectional view of a discharge vessel 11 cut along a tube axis direction (longitudinal direction). FIG.1 (b) is the sectional view on the AA 'line in Fig.1 (a).
The excimer lamp 10 includes a discharge vessel 11 having a rectangular cross section and a long hollow shape, both ends of which are hermetically sealed and a discharge space S is formed therein. Xenon (Xe) gas is sealed as the gas.
The discharge vessel 11 is made of silica glass, for example, silica glass made of synthetic quartz, and has a function as a dielectric.

  The discharge vessel 11 is disposed such that the long side surfaces 12a and 12b face each other along the tube axis AX, and the short side surface 13a and the long side surface 12a that are continuous with each other at a right angle to the long side surface 12b, A tube having a rectangular cross section is formed by 13b. Both ends in the tube axis direction are closed by end faces 14a and 14b, and the inside of the discharge vessel is used as an airtight space.

A pair of grid-like or mesh-like electrodes 15 and 16 are formed along the tube axis direction on the outer walls of the long side surfaces 12 a and 12 b in the discharge vessel 11 and face each other with the discharge vessel 11 in between. One electrode 15 that functions as a high-voltage power supply electrode is disposed on the outer wall of the long side surface 12a, and the other electrode 16 that functions as a ground electrode is disposed on the outer wall of the long side surface 12b.
A high frequency power source (not shown) is connected to each of the electrodes 15 and 16. As a result, the discharge vessel 11 functioning as a dielectric is interposed between the pair of electrodes 15 and 16. Such electrodes 15 and 16 can be formed, for example, by applying an electrode material made of a metal such as aluminum, nickel, or gold to the discharge vessel 11 or by printing.

The excimer lamp 10 is provided with an ultraviolet reflecting film 18 made of a particle deposit described later on the inner wall on the discharge space S side of the discharge vessel 11 in order to efficiently use vacuum ultraviolet light generated by excimer light emission. .
The ultraviolet reflecting film 18 is formed, for example, over the inner wall region of the long side surface 12a where the high-voltage side electrode 15 is provided and the inner wall regions of the short side surfaces 13a and 13b continuous with this region. Further, in order to further increase the amount of reflected light, the ultraviolet reflecting film 18 may be formed in other regions such as the inner walls of both end faces 14a and 14b.
On the other hand, in the inner wall region of the long side surface 12b corresponding to the ground-side electrode 16, the ultraviolet reflective film 18 is not formed, but the region of the gap on the long side surface 12b where the electrode 16 is not formed is exposed to ultraviolet rays. The light emitting portion 17 that emits light is used.

The ultraviolet reflecting film 18 is a particle volume in which ultraviolet scattering particles composed of silica (silicon oxide: SiO ₂ ) particles and alumina (aluminum oxide: Al ₂ O ₃ ) particles are deposited.
The silica particles may be in a glass state or a crystalline state, but are preferably in a glass state with good adhesion to the discharge vessel.
Although the definition of the particle size of the ultraviolet scattering particles will be described later, the silica particles preferably have a particle size of 0.01 to 20 μm, and the center particle size of 0.1 to 10 μm. .

Alumina particles are usually in a crystalline state because alumina is easily crystallized and difficult to be in a glass state. Since the alumina particles have a higher refractive index and a higher reflectance than silica particles, ultraviolet rays are used together with silica particles. By configuring the reflective film 18, an excellent ultraviolet reflectivity can be obtained.
The particle diameter of the alumina particles is preferably 0.1 to 3 μm, and the center particle diameter is preferably 0.3 to 1 μm.

According to the ultraviolet reflecting film 18 on which such particles are deposited, a part of the incident vacuum ultraviolet light is reflected by the surface of the ultraviolet scattering particles, and a part thereof is refracted and transmitted through the inside of the particles. Reflect or refract on another surface again. The opportunity of repeated reflection and refraction is increased by the grain boundaries of these many fine particles, so that the vacuum ultraviolet light is efficiently diffusely reflected.
Accordingly, the ultraviolet reflection film 18 is formed in the range of 10 to 1000 μm because the amount of reflected light is small even if the film as the particle layer is too thin, and the film itself is easy to peel off if it is too thick. Preferably

The term “particle size” as used herein refers to an approximately intermediate position in the thickness direction of the fractured surface when the ultraviolet reflective film is fractured in the direction perpendicular to the surface, and is observed by a scanning electron microscope (SEM). It refers to the Feret diameter, which is the interval between parallel lines obtained when an enlarged projection image is acquired and arbitrary particles in the enlarged projection image are sandwiched between two parallel lines in a fixed direction.
Further, the “center particle size” is a range of the maximum value and the minimum value for the particle size of each particle obtained as described above, for example, divided into a plurality of, for example, about 15 categories, with a 0.1 μm category, The particle size is the median value of the category in which the number (frequency) of particles belonging to each category is the maximum.

The silica particles and alumina particles constituting the ultraviolet reflecting film have the following role in addition to the function of reflecting ultraviolet rays, and will be described.
The silica particles have the same thermal expansion coefficient as that of the silica glass that is the material of the discharge vessel 11, and have high adhesiveness. The adhesion between the ultraviolet reflective film 18 and the discharge vessel 11 is the silica contained in the ultraviolet reflective film. It is obtained by partially melting the particles. In general, those having the same or close thermal expansion coefficient have the property of being easily bonded. Therefore, the silica particles adhere well to the discharge vessel 11 and can prevent the ultraviolet reflective film from peeling off.

In this excimer lamp 10, when lighting power is supplied to one electrode 15, a voltage is applied between the electrodes 15 and 16 through the wall of the discharge vessel 11, which is a dielectric, and a discharge is generated in the discharge space S. Arise. As a result, excimer molecules are formed, and excimer molecule emission in which vacuum ultraviolet light is emitted from the excimer molecules occurs.
Depending on the type of gas used for the discharge, the center wavelength of the emitted excimer emission differs. For example, an excimer lamp enclosing xenon (Xe) emits excimer light having a center wavelength of 172 nm as described above. The vacuum ultraviolet light generated by the excimer emission is reflected without passing through the wall (silica glass) of the discharge vessel 11 other than the light emitting part 17 and is irradiated in a desired direction, so that the vacuum ultraviolet light is efficiently used. I can do it.

Silica particles contain OH groups in order to suppress the generation of internal defects due to ultraviolet radiation damage. In order to contain the OH group, for example, the ultraviolet reflective film is heated to a high temperature while being exposed to the atmosphere, or a silicon compound (for example, silicon tetrachloride) is hydrolyzed in an oxyhydrogen flame. When such a production method is used, OH groups are contained in the silica particles.
The ultraviolet reflective film can suppress the generation of internal defects and increase the reflection maintenance rate of the ultraviolet reflective film as the concentration of the OH group thus contained is higher.

  However, as described above, when the OH group concentration in the silica particles is excessive, the OH groups are dissociated and released into the discharge space when the silica particles are exposed to plasma or irradiated with ultraviolet rays. Sometimes. OH released into the discharge space S is decomposed by plasma into O, and further combined with Xe to become XeO. This series of phenomena substantially reduces Xe in the discharge space.

If the volume concentration of the alumina particles in the ultraviolet reflection film is increased, the alumina particles are mainly exposed on the surface of the ultraviolet reflection film exposed to the discharge. Since OH groups are not included in the alumina particles, OH is not released, OH can be prevented from being released into the discharge space, and XeO production can be suppressed. Further, since the ultraviolet reflecting film is composed of alumina particles and silica particles, if the volume concentration of the alumina particles increases, the volume concentration of the silica particles naturally decreases, and the OH release amount also decreases.
That is, by increasing the volume concentration of alumina particles, an ultraviolet reflective film can be produced using silica particles containing OH and alumina particles, and the amount of OH released from the silica particles can be reduced. From the above, it is necessary to define the volume concentration of alumina particles in the ultraviolet reflecting film.
Specifically, the volume concentration Y (vol%) of the alumina particles is defined as follows with respect to the OH concentration X (wt. Ppm) in the ultraviolet reflecting film.
Formula (1): Y ≧ 13.7ln (X) +1.2
Here, the volume concentration is the ratio of the volume of the alumina particles to the total volume of the silica particles and the alumina particles constituting the ultraviolet reflecting film.
By satisfy | filling the above formula | equation, it can suppress that OH is discharge | released from the ultraviolet reflective film to discharge space.

Furthermore, when the alumina particles are contained so as to satisfy the above regulations, the following effects can be obtained.
In the excimer lamp, it is known that plasma is generated. However, in the excimer lamp according to the present embodiment, the plasma is incident on the ultraviolet reflection film at a substantially right angle, so that the ultraviolet reflection occurs. In some cases, the temperature of the film rapidly rises locally, and the heat of the plasma causes the silica particles to melt and the grain boundaries to disappear, making it impossible to diffusely reflect vacuum ultraviolet light and lower the reflectivity.
Since the alumina particles have a higher melting point than the silica particles, even if the silica particles are melted by being exposed to the discharge plasma, they do not melt to the alumina particles. For this reason, the silica particles can be prevented from chain melting by mixing a large amount of alumina particles between the silica particles and the silica particles. That is, the particles can be prevented from being fused and integrated, the shape of the particles can be maintained, and the reflection function can be maintained.
As a result, even after a long time has elapsed since the start of lighting, the ratio of xenon gas existing alone in the discharge space is maintained at substantially the same level as in the initial lighting, and the emission intensity at a wavelength of 172 nm can be maintained. .

The center particle size of the silica particles is preferably smaller than the center particle size of the alumina particles. Thereby, OH discharge | release amount can be reduced and the illumination intensity fall of wavelength 172nm can be suppressed. Specifically, the average particle size RA of alumina particles and the average particle size RS of silica particles in the ultraviolet reflecting film satisfy the relationship of the following formula.
Formula (2): RA / RS ≧ 1
In the ultraviolet reflecting film satisfying the relationship of the above formula, the average particle size of the silica particles is smaller than the average particle size of the alumina particles. Therefore, when the coating liquid mixed with these ultraviolet particles is applied in the discharge vessel in the production of the reflective film, the small silica particles enter the gaps between the large alumina particles, so the silica particles are exposed to the surface. It becomes difficult to be exposed. Therefore, the effect of mixing an appropriate amount of alumina particles can be made more reliable.
In addition, if the particle size of the silica particles is small, it becomes easy to enter between the alumina particles and the alumina particles or between the alumina particles and the discharge vessel, and by melting part of the ultraviolet reflective film during baking, the adhesion is improved. It can be strengthened.

  As described above, the ultraviolet reflecting film provided in the excimer lamp according to the present invention is preferably configured by mixing both alumina particles and silica particles and satisfying the above relationship. Thereby, it is possible to suppress the release of OH groups from the ultraviolet reflective film, reduce the generation of XeO, and prevent the illuminance decrease of light having a wavelength of 172 nm.

The matter concerning the manufacturing method of these ultraviolet reflective films is demonstrated below.
Silica particles and alumina particles can be produced, for example, by chemical vapor deposition (CVD). Specifically, silica particles are synthesized by reacting silicon tetrachloride and oxygen at 900 to 1000 ° C., and alumina particles are synthesized by reacting raw material aluminum chloride and oxygen at 1000 to 1200 ° C. by heating. can do. The particle size of the particles can be adjusted by controlling the raw material concentration, the pressure in the reaction field, and the reaction temperature.

Formation of the ultraviolet reflecting film on the discharge vessel can be performed, for example, by the “flow-down method” shown below.
A dispersion liquid is prepared by mixing fine silica particles and alumina particles in a solvent having a viscosity obtained by combining water and PEO resin (polyethylene oxide), and this dispersion station is poured into the discharge vessel forming material. And after attaching a dispersion station to the predetermined | prescribed area | region in the inner wall of a discharge vessel formation material, water and PEO resin are evaporated by drying and baking, Thereby, a particle deposit can be formed. The firing temperature is, for example, 500 ° C to 1100 ° C.

Next, an embodiment relating to the excimer lamp of the present invention will be described.
In accordance with the configuration shown in FIGS. 1A and 1B, an excimer lamp having an ultraviolet reflecting film according to an embodiment of the present invention was produced.
The discharge vessel is made of silica glass and has dimensions of 15 mm × 43 mm × 350 mm and a wall thickness of 2.5 mm. The dimensions of the high voltage supply electrode and the ground electrode are 30 mm × 300 mm.
The ultraviolet reflecting film was composed of alumina particles and silica particles, each formed by a flow-down method, and baked at 1000 ° C.

[Example 1]
According to the OH group concentration contained in the silica particles of the ultraviolet reflective film, in order to define an appropriate volume concentration by mixing the alumina particles, the OH group concentration and the alumina concentration in the silica particles are changed, The relationship with XeO emission was investigated.
As a measurement object, several lamps having an ultraviolet reflection film formed of mixed particles of silica particles and alumina particles and having different alumina concentrations and OH group concentrations in the silica particles were prepared. For each of the prepared lamps, green light emitted from the lamps was observed with a spectrometer after 500 hours had elapsed since the start of lighting.
As for the OH group concentration, only the OH group concentration contained in the silica particles can be measured by using a Fourier transform infrared spectrophotometer (FT-IR). As the measurement sample, a lamp was crushed and the ultraviolet reflective film was scraped off from the crushed piece to obtain a powder.
As for the alumina concentration, the volume concentration (vol%) converted by specific gravity was calculated based on the weight ratio of silica particles and alumina particles to be mixed when producing the ultraviolet reflective film. The specific gravity of the silica particles is 2.15 (g / cm ³ ), and the specific gravity of the alumina particles is 3.99 (g / cm ³ ). For example, when the silica concentration by weight is 90 (wt%), the silica concentration by volume is such that the volume of silica particles is 90 (wt%) ÷ 2.15 (g / cm ³ ) = 41.9 ( vol), and the volume of alumina particles is 10 (wt%) ÷ 3.99 = 2.51 (Vol), so 41.9 ÷ (41.9 + 2.51) × 100 = 94.3 (Vol) %) .
Further, in the spectrum obtained by measuring each lamp, the XeO emission intensity (550 nm) is divided by the reference Xe (980 nm) emission intensity to obtain a light intensity ratio of XeO to Xe: XeO / Xe was determined.
FIG. 4 shows the relationship between the OH group concentration and the alumina concentration in the silica particles. The horizontal axis represents the logarithm of the OH group concentration (wt. Ppm), and the vertical axis represents the alumina concentration (vol%).
Light intensity ratio: XeO / Xe means that the higher the value, the more dominant the XeO emission, and the lower Xe is bound to oxygen. In each sample, XeO / Xe intensity ratio of 0.5 or higher is marked as “x” (failed) because the ratio of XeO is high and Xe is decreased, and “○” (passed) when XeO is less than 0.5. ) And less than 0.3 were plotted on the graph as “◎” (pass).
In FIG. 4, when the OH group concentration in the silica particles is constant, the higher the alumina concentration, the smaller the XeO / Xe ratio. It can also be seen that as the OH group concentration in the silica particles increases, the alumina concentration must be increased in order to keep the XeO / Xe ratio below the specified value. Thus, it is preferable to increase the alumina concentration in accordance with the OH group concentration contained in the silica particles of the ultraviolet reflecting film.
Also, an approximate line was drawn based on each sample for which the determination was “◯” in FIG. At the same OH group concentration, the higher the alumina concentration, the lower the proportion of XeO. Therefore, at the point where “◯” is plotted, if the OH group concentration is constant, the higher the alumina concentration, the higher the O concentration. H release can be suppressed. In other words, it means that XeO is hardly generated in the region above this approximate line (the alumina concentration is high).
From the above, the alumina concentration Y (vol%) of the ultraviolet reflecting film and the OH group concentration X (wt. Ppm) in the silica particles of the ultraviolet reflecting film have a relationship of Y ≧ 13.7 log _e (X) +1.2. By satisfying the above, the illuminance of 172 nm can be maintained.

[Example 2]
The relationship between the center particle size ratio of alumina particles and silica particles constituting the ultraviolet reflection film and the illuminance of light having a wavelength of 172 nm was examined.
An excimer lamp having an ultraviolet reflective film prepared by mixing silica particles having a center particle diameter of 1.0 μm mixed with silica particles having a center particle diameter changed to 0.1 to 3.0 μm is manufactured. The illuminance of light having a wavelength of 172 nm after 500 hours from lighting was measured.
The alumina volume concentration in the ultraviolet reflecting film is constant at a certain value.
As shown in FIG. 5, it can be seen that the illuminance at a wavelength of 172 nm does not decrease as the alumina center particle size / silica center particle size decreases, that is, the alumina particle size increases. In particular, it can be seen that the illuminance of 172 nm is maintained when alumina average particle size RA / silica average particle size RS ≧ 1.

It is sectional drawing for description which shows the outline of the structure in an example of the excimer lamp of this invention, Comprising: (a) Sectional drawing which shows the cross section along the tube-axis direction of a discharge vessel, (b) AA 'in (a) It is line sectional drawing. It is sectional drawing for description concerning the manufacturing method of the excimer lamp of this invention. It is an experimental result of an excimer lamp. It is an experimental result of an excimer lamp. It is an experimental result of an excimer lamp. It is sectional drawing for description which shows the outline of a structure of the conventional excimer lamp, Comprising: (a) Sectional drawing which shows the cross section along the tube-axis direction of a discharge vessel, (b) BB 'sectional view taken on the line in (a) It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Excimer lamp 11 Discharge vessel 12a Long side surface 12b Long side surface 13a Short side surface 13b Short side surface 14a End surface 14b End surface 15 Electrode 16 Electrode 17 Light-emitting part 18 Ultraviolet reflective film AX Tube axis S Discharge space 50 Excimer lamp 51 Discharge vessel 52 Outer tube 53 Inner tube 54 End face 55 Electrode 56 Electrode 57 Light emitting portion 58 Ultraviolet reflective film S Discharge space

Claims (2)

In an excimer lamp having an ultraviolet reflecting film formed of silica particles and ultraviolet scattering particles made of alumina particles not containing OH groups on the inner wall of a discharge vessel made of silica glass, and containing a gas containing xenon,
The alumina concentration Y (vol%) of the ultraviolet reflecting film and the OH group concentration X (wt. Ppm) in the silica particles of the ultraviolet reflecting film satisfy the relationship of Y ≧ 13.7 log _e (X) +1.2. Excimer lamp characterized by that. 2. The excimer according to claim 1, wherein a center particle size RS (μm) of silica particles of the ultraviolet reflecting film and a center particle size RA (μm) of alumina particles satisfy a relationship of RA / RS ≧ 1. lamp.

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