JP2009203094A - Silica glass tube having high ultraviolet transmission, manufacturing method thereof and ultraviolet lamp using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the decrease in ultraviolet transmission at wavelength of ≤200 nm in a silica glass tube made of a synthetic quartz material ingot. <P>SOLUTION: The silica glass tube is formed by heating and processing the synthetic quartz material ingot at a temperature ranging from its softening point to 2,150°C, preferably at 1,800-2,150°C, more preferably at 1,900-2,150°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a quartz glass tube having a high ultraviolet transmittance made of a synthetic quartz material as a raw material, and more particularly to its manufacturing technology.

  Conventionally, as a technique using ultraviolet light having a wavelength of 200 nm or less, TOC (Total Organic Carbon) in water is oxidized and decomposed with ultraviolet light to produce ultrapure water, or ozone is added to water to be treated and irradiated with ultraviolet light. Accelerated oxidation treatment method that decomposes difficult-to-decompose organic substances such as dioxins, oxygen is irradiated with ultraviolet rays to generate ozone, and active oxygen generated when ozone is decomposed with ultraviolet rays is the organic matter on the surface of the substance There is known a method of cleaning the surface of glass for liquid crystal by utilizing the action of vaporizing and cleaning this.

  An ultraviolet lamp used for such an application is formed by providing discharge electrodes at both ends of an arc tube enclosing mercury and a rare gas (for example, Patent Document 1).

  By the way, as the arc tube used for the ultraviolet lamp, a synthetic quartz glass tube with few metal impurities causing ultraviolet absorption is used. A synthetic quartz glass tube is obtained by forming an ingot of a synthetic quartz material by a manufacturing method such as an MCVD method, a VAD method, or an OCVD method (for example, Patent Document 2).

  As a method for producing a synthetic quartz glass tube, there is known a method in which a synthetic quartz material ingot heated to a predetermined temperature and stably melted is drawn into a tubular shape. (For example, Non-Patent Document 1).

JP-A-4-303448 JP 2000-247649 A Glass Handbook, Asakura Shoten Co., Ltd., issued on June 20, 1979, p. 441-443

  However, in the technique described in Non-Patent Document 1, in a container such as a crucible for heating an ingot to a predetermined temperature, a flow path through which synthetic quartz glass melted by heating flows, a composition constituting them It is conceivable that an object (for example, a ceramic mainly composed of calcia in a container such as a crucible) is mixed as impurities in the synthetic quartz glass.

  When impurities are mixed in synthetic quartz glass, the transmittance of the glass tube may be lowered depending on the wavelength of ultraviolet rays.

  This invention makes it a subject to suppress the fall of the ultraviolet-ray transmittance of the wavelength of 200 nm or less of the quartz glass tube which uses a synthetic quartz raw material ingot as a raw material.

  In order to solve the problem, the present inventors tried an experiment on ultraviolet transmittance of a wavelength of 200 nm or less with respect to a synthetic quartz glass tube formed by heating and melting a synthetic quartz material ingot. As shown in Table 1, it was found that the transmittance decreases as the heating temperature increases. That is, it can be presumed that the composition of a container such as a crucible is mixed as impurities into the synthetic quartz glass, and the mixing rate increases as the melting temperature increases. Accordingly, it has been found that it is desirable to perform the synthetic quartz glass tube at the lowest possible temperature in consideration of the ultraviolet transmittance. However, at a low temperature, the fluidity of the fused synthetic quartz glass decreases and the workability decreases.

  Therefore, the quartz glass tube of the present invention has a transmittance at a wavelength of 200 nm of 80 to 90%, preferably 80 to 90%, considering the workability of quartz glass made from a synthetic quartz material and the transmittance required for practical use. It is characterized by 89%, more preferably 80-88%.

  Further, as a method for producing the synthetic quartz glass tube of the present invention (referred to as a highly permeable quartz glass tube), an ingot of a synthetic quartz material is heated and melted at a softening temperature or higher to 2150 ° C. or lower and processed to produce a quartz glass tube. Is molded. At this time, in consideration of workability, it is preferable to heat at 1800 to 2150 ° C, more preferably 1900 to 2150 ° C.

  In this case, if the heating and melting temperature is lower than 1800 ° C., the fluidity of the fused quartz (quartz melt) is lowered and the workability is deteriorated, so that stable tube forming processing becomes difficult, and the forming yield is also conventionally increased. 70% or less in the case of the above method (heating and melting temperature: 2200 to 2400 ° C.), which is extremely impractical. When the heating and melting temperature is 1800 ° C. or higher, the fluidity is improved and the workability is improved, and the molding process yield is improved. When the heating and melting temperature is 1900 ° C. or higher, the workability is further improved, and the processing yield is 85% or more of the conventional method (heating and melting temperature: 2200 to 2400 ° C.). However, when the heating and melting temperature exceeds 2150 ° C., the molding process yield is improved, but as shown in FIG. 1, the transmittance at a wavelength of 200 nm is less than 80%. No output can be obtained.

  According to the present invention, it is possible to suppress a decrease in ultraviolet transmittance at a wavelength of 200 nm or less of a quartz glass tube made of a synthetic quartz material.

  Hereinafter, the present invention will be described based on embodiments.

First, the manufacturing method of the synthetic quartz glass tube of one Embodiment of this invention is demonstrated. An ingot made of a synthetic quartz material is manufactured by a VAD method (Vapor Phase Axial Deposition Method) using silicon halide (for example, SiCl ₄ ) and hydrogen, oxygen, and nitrogen as raw materials. Next, using a crucible with a ceramic material containing calcia as a main component, an ingot of a synthetic quartz material is heated and melted to a predetermined temperature, processed and formed into a tubular shape. The heating and melting temperature of the synthetic quartz material at this time is determined in consideration of the workability of the quartz material and the practically required ultraviolet transmittance.

  Next, the relationship between the heating and melting temperature of the synthetic quartz material ingot and the transmittance of ultraviolet light having a wavelength of 200 nm, which is a feature of the present embodiment, will be described. First, using the above manufacturing method, a quartz glass tube made of a synthetic quartz material having an outer diameter of 14 mm and a wall thickness of 0.5 mm at 11 heating and melting temperatures in the range of 1600 to 2600 ° C. is used. It created and cut | disconnected so that it might become length 50mm. Next, the transmittance of each prepared quartz glass tube at a wavelength of 200 nm was measured with a spectrophotometer (measurement wavelength range: 200 nm to 2000 nm) (Table 1). Further, using the data in Table 1, FIG. 1 shows the relationship between the heating and melting temperature of a quartz glass tube made of a synthetic quartz material and the transmittance at a wavelength of 200 nm. Note that, since the wavelength mainly used in the accelerated oxidation method is usually 185 nm, it is desirable to measure at a wavelength of 185 nm. However, the commercially available spectrophotometer used for the evaluation of transmittance is the shortest measurable wavelength. Is 200 nm, the wavelength 185 nm cannot be measured. However, since the transmittances at wavelengths of 185 nm and 200 nm are almost the same, in this embodiment, evaluation was performed at a wavelength of 200 nm.

  As shown in FIG. 1 and Table 1, it was found that the transmittance at a wavelength of 200 nm decreases as the heating and melting temperature of the synthetic quartz material increases. Further, it was found that the transmittance was 86% when the heating and melting temperature was 2000 ° C., and the transmittance rapidly decreased when the heating temperature was further increased. That is, it can be inferred that the composition of the crucible was mixed in the synthetic quartz glass as an impurity. Accordingly, it was found that it is desirable to perform the glass tube from the synthetic quartz material ingot at a temperature as low as possible in consideration of the ultraviolet transmittance.

  Usually, the transmittance of the quartz glass tube at the wavelength of 200 nm when used as an actual ultraviolet lamp is required to be 80% or more. Therefore, FIG. 1 shows that the upper limit of the heating temperature is preferably 2150 ° C. or less. At this time, considering the workability of quartz glass and the transmittance required for practical use, about 2150 ° C. is suitable. Therefore, the heating and melting temperature is preferably 1800 to 2150 ° C. (transmittance 80 to 89%), more preferably. It shall be 1900-2150 degreeC (transmittance 80-88%).

  In this manner, when the synthetic quartz material ingot is heated and melted and formed into a tubular shape, it is possible to prevent impurities from being mixed into the finished quartz glass tube by controlling the heating and melting temperature. As a result, it is possible to suppress a decrease in transmittance of the finished quartz glass tube with a wavelength of 200 nm or less. Further, conventionally, since the heat melting temperature of the synthetic quartz material ingot was heated and melted at 2200-2400 ° C. based on the heat resistance temperature of the crucible (2630 ° C. in the case of a ceramic material mainly composed of calcia), The material was mixed in the finished quartz glass, and the transmittance at a wavelength of 200 nm or less was remarkably lowered. However, according to the present embodiment, such a problem does not occur, and the short wavelength ultraviolet region (280 nm or less) It is possible to manufacture a highly transmissive quartz glass tube (highly transmissive quartz tube) having a high transmittance with a wavelength of 200 nm or less. Also, by producing a low-pressure mercury lamp using this highly transmissive quartz tube, an ultraviolet lamp having a high output of 185 nm, which is the resonance emission of mercury, can be produced.

  Further, the highly permeable quartz glass tube can be mounted as a light-emitting tube of a low-pressure mercury lamp. Note that the highly transmissive quartz glass tube of the present embodiment is not limited to a low-pressure mercury lamp, and can be appropriately used for a lamp using a quartz glass tube such as a nonpolar discharge lamp (Japanese Patent Laid-Open No. 10-13479).

  The synthetic quartz material ingot of the present embodiment uses a material prepared by the VAD method, but is not limited to this as long as it is a method for producing a synthetic quartz material that is a high-purity quartz material. For example, the MCVD method, VAD, etc. Method, OCVD method, or the like can be used.

  Moreover, as a method for forming the synthetic quartz material into a tubular shape, a known method for forming a quartz glass tube by drawing or extruding can be used.

  Further, the high-transmittance quartz glass tube is not limited to the ultraviolet lamp, but for example, a lamp protective tube for storing an ultraviolet lamp of an ultraviolet irradiation device (Japanese Patent Laid-Open No. 2007-155546) or an illuminometer protective tube for storing an illuminometer. Can be applied.

It is a figure which shows the relationship between the heat melting temperature of the synthetic quartz raw material ingot by this invention, and the transmittance | permeability with a wavelength of 200 nm.

Claims (3)

  A quartz glass tube having a transmittance at a wavelength of 200 nm of 80 to 90%, preferably 80 to 89%, more preferably 80 to 88%.   An ultraviolet lamp using the quartz glass tube according to claim 1.   A method for producing a quartz glass tube, in which a synthetic quartz material ingot is processed and molded by heating at a softening temperature to 2150 ° C., preferably 1800 to 2150 ° C., more preferably 1900 to 2150 ° C.

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