glass tube

Abstract

To obtain a glass tube having high transmittance in a deep ultraviolet ray region.SOLUTION: A glass tube of the present invention is a glass tube including a thin portion having a thickness of 0.4 mm or less, wherein when the thickness of the thinnest portion among the thin portions is set to t1 [mm], spectral transmittance at a wavelength 222 nm in terms of the thinnest t1 of the thinnest portion is set to T222[%], an outer diameter of the thinnest part is set to D1 [mm], an inner diameter of the thinnest part is set to d1[mm], and a total amount of iron oxide and titanium oxide contained in the glass is set to Fe2O3+TiO2[mass%], d1 / D1 is 0.76 or more, and the value of (Fe2O3+TiO2)×T222 is 0.2 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a glass tube with high ultraviolet transmittance. [Background technology]

[0002] Light sources with high output in the deep ultraviolet region (e.g., wavelengths of 200-350 nm) have been developed and are used in sterilization UV lamps in medical settings and devices for writing to magnetic recording media.

[0003] A typical example of glass with high transmittance in the deep ultraviolet region is quartz glass. However, because quartz glass has a low coefficient of linear thermal expansion, when sealing it with metal components such as electrodes for use as a light source, the difference in thermal expansion coefficients between the components becomes large, resulting in a problem where the ends of the ultraviolet lamp cannot be sealed.

[0004] For these reasons, the glass described in Patent Documents 1 and 2, for example, is currently used. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2016 / 194780 [Patent Document 2] Patent No. 5847998 [Overview of the project] [Problems that the invention aims to solve]

[0006] The higher the transmittance in the deep ultraviolet range of the glass used to protect the light source, the better the germicidal performance of the light source. For example, the higher the transmittance of the glass tube used in the outer casing of a germicidal ultraviolet lamp, the greater the germicidal power and the shorter the time required for germicidal treatment.

[0007] Conventional glass tubes often used glass containing a high amount of boron oxide to increase transmittance in the deep ultraviolet region. However, these glasses had lower weather resistance compared to common borosilicate glass or soda-lime glass, which led to a shorter lifespan for ultraviolet lamps.

[0008] On the other hand, with highly weather-resistant borosilicate glass and soda-lime glass, ultraviolet light is absorbed by impurities in the glass such as Fe2O3 and TiO2, resulting in a problem of reduced germicidal performance of the light source. Furthermore, the glass described in Patent Documents 1 and 2 also suffers from ultraviolet light absorption due to impurities such as Fe2O3 and TiO2. Therefore, in order to use these materials for the outer casing, it is necessary to reduce impurities by using high-purity raw materials or devising manufacturing methods.

[0009] Therefore, in view of the above circumstances, the technical problem of the present invention is to obtain a glass tube with high transmittance in the deep ultraviolet region. [Means for solving the problem]

[0010] The inventors, after diligent research, have found that the above problems can be solved by providing a thin region in the glass tube used in deep ultraviolet light source devices, and propose this as the present invention. Specifically, the glass tube of the present invention is a glass tube including a thin-walled portion with a thickness of 0.4 mm or less, where the thickness of the thinnest part in the thin-walled portion is t1 [mm], and the spectral transmittance at a wavelength of 222 nm calculated based on the thickness t1 of the thinnest part is T 222 [%], when the outer diameter of the thinnest part is D1 [mm], the inner diameter of the thinnest part is d1 [mm], and the total amount of iron oxide and titanium oxide contained in the glass is Fe2O3 + TiO2 [mass%], then d1 / D1 is 0.76 or greater, and (Fe2O3 + TiO2) × T 222 It is characterized by having a value of 0.2 or higher. By providing a thin-walled section in the glass tube, the absorption of ultraviolet light by impurities such as Fe2O3 and TiO2 is reduced, making it possible to achieve high transmittance in the deep ultraviolet region. (Fe2O3+TiO2)×T 222" means the product of the spectral transmittance of the glass at a wavelength of 222 nm and the total content of iron oxide and titanium oxide contained in the glass. Although Fe2O3 in the glass may include both trivalent iron oxide and divalent iron oxide, here the divalent iron oxide is treated after conversion to trivalent iron oxide.

[0011] In addition, in the glass tube of the present invention, it is preferable that the thickness t1 [mm] of the thinnest part is 0.2 mm or less.

[0012] In addition, in the glass tube of the present invention, it is preferable that the total content of Fe2O3 + TiO2 is 0.002 to 0.1% by mass, the content of Fe2O3 is 0 to 0.05% by mass, and the content of TiO2 is 0 to 0.05% by mass.

[0013] In addition, in the glass tube of the present invention, it is preferable that the spectral transmittance at a wavelength of 222 nm in terms of the thickness t1 of the thinnest part is 30% or more.

[0014] In addition, in the glass tube of the present invention, it is preferable that the spectral transmittance at a wavelength of 230 nm in terms of the thickness t1 of the thinnest part is 40% or more.

[0015] In addition, in the glass tube of the present invention, let the spectral transmittance (%) at a wavelength of 200 nm in terms of the thickness t1 of the thinnest part be T 200 and the spectral transmittance (%) at a wavelength of 260 nm in terms of the thickness t1 of the thinnest part be T 260 When 200 / T 260 it is preferable that it is 0.3 or more.

[0016] In addition, in the glass tube of the present invention, it is preferable that the bend of the glass tube is 6.0 mm or less.

[0017] In addition, in the glass tube of the present invention, it is preferable that the tolerance of the thickness t1 of the thinnest part is 30 μm or less.

[0018] In addition, in the glass tube of the present invention, it is preferable that the ratio D1 / D2 of the outer diameter D1 of the thinnest part to the outer diameter D2 of the end part is 0.8 or more.

[0019] In addition, for the glass tube of the present invention, the ratio d1 / d2 of the inner diameter d1 of the thinnest part to the inner diameter d2 at the end is preferably 0.8 or more.

[0020] In addition, for the glass tube of the present invention, the outer diameter tolerance is preferably 30 μm or less.

[0021] In addition, for the glass tube of the present invention, the inner diameter tolerance is preferably 30 μm or less.

[0022] In addition, for the glass tube of the present invention, the Ra of the outer surface is preferably 0.01 μm or less.

[0023] In addition, for the glass tube of the present invention, the Ra of the inner surface is preferably 0.01 μm or less.

[0024] In addition, for the glass tube of the present invention, the thickness t1 of the thinnest part is preferably less than 0.1 mm.

[0025] In addition, for the glass tube of the present invention, when a highly accelerated stress test (HAST) is performed at a temperature of 121 °C, a relative humidity of 85%, and a test time of 24 hours, the maximum long side of the foreign matter generated on the glass surface is preferably 100 μm or less.

[0026] In addition, for the glass tube of the present invention, the linear thermal expansion coefficient in the temperature range of 20 to 300 °C is 30×10 -7 / °C to 100×10 -7 / °C is preferable. [[ID=A]] [[ID=B]]

[0027] In addition, for the glass tube of the present invention, the temperature at which the high-temperature viscosity becomes 10 4.0 dPa·s is preferably 1300 °C or less.

[0028] In addition, for the glass tube of the present invention, the liquid-phase viscosity is preferably 10 4.8 dPa·s or more.

[0029] Furthermore, in the glass tube of the present invention, it is preferable that the compressive stress value formed on the surface is 200 MPa or more when immersed in a potassium nitrate (KNO3) molten salt heated to 475°C for 7 hours.

[0030] Furthermore, in the deep ultraviolet lamp of the present invention, it is preferable that the glass tube described above is used as the outer cylinder. [Brief explanation of the drawing]

[0031] [Figure 1] This is a schematic cross-sectional view in the longitudinal direction showing an example of an embodiment of the present invention. It is also a schematic cross-sectional view in the thickness direction showing the thickness t1 of the thinnest part, the outer diameter D1 of the thinnest part, the inner diameter d1 of the thinnest part, the thickness t2 of the end, the outer diameter D2 of the end, and the inner diameter d2 of the end. [Figure 2] This is a schematic cross-sectional view in the longitudinal direction showing an example of an embodiment of the present invention. In this embodiment, a structure is formed in which the inner diameter increases at an inconsistent incline from near the end toward the thin-walled portion. [Figure 3] This is a schematic cross-sectional view in the longitudinal direction showing an example of an embodiment of the present invention. In this embodiment, a structure is formed in which the inner diameter increases at a constant incline from near the end toward the thin-walled portion. [Figure 4] This is a schematic cross-sectional view in the thickness direction showing an example of an embodiment of the present invention. In this embodiment, structures with different thicknesses are formed on the same circumference. [Figure 5] The data shown are the transmittance curves for wavelengths of 200 nm to 800 nm for Examples 1 and 2. The transmittance curve for a thickness of 0.17 mm is the data for Example 1, and the transmittance curve for a thickness of 0.05 mm is the data for Example 2. [Modes for carrying out the invention]

[0032] The glass tube of the present invention includes a thin-walled section with a thickness of 0.4 mm or less. Preferably, as shown in Figure 1, the entire thickness of the glass tube is 0.4 mm or less, meaning the entire glass tube constitutes a thin-walled section. This increases the transmittance of the glass tube, improving its germicidal performance as an ultraviolet lamp. Furthermore, as shown in Figures 2 and 3, it is also preferable that the glass tube of the present invention has a thicker end and gradually thins towards the thin-walled section, either uniformly or at an irregular rate. This allows for a balance between the germicidal performance of the ultraviolet lamp and ease of sealing components such as electrodes. Moreover, the glass tube of the present invention may have only a portion of its circumference thinned, for example, half of its circumference, as shown in Figure 4. This allows for the extraction and use of ultraviolet light from only a specific region. As a result, the risk of adverse effects on the human body due to unintended irradiation of ultraviolet light can be reduced.

[0033] As shown in Figures 2-4, glass tubes with varying thicknesses can be obtained by, for example, protecting a desired portion of the glass tube with a material that is resistant to erosion by hydrofluoric acid, such as paraffin, resin, or an inorganic film, and then immersing it in hydrofluoric acid. Alternatively, glass tubes with varying thicknesses can also be obtained by immersing a portion of the glass tube in hydrofluoric acid without partially exposing it to the acid.

[0034] In the glass tube of the embodiment shown in Figure 1 of the present invention, the average thickness is preferably 0.4 mm or less, 0.001 to 0.4 mm, more preferably 0.005 to 0.3 mm, more preferably 0.01 to 0.2 mm, even more preferably 0.02 to 0.1 mm, less than 0.03 to 0.1 mm, and most preferably 0.04 to 0.005 mm. If the average thickness is too thick, the transmittance in the deep ultraviolet region tends to decrease. On the other hand, if the average thickness is too thin, the processability decreases significantly.

[0035] In the glass tube of the present invention, it is preferable that the central portion in the longitudinal direction of the glass tube is a thin-walled portion, as shown in Figures 2 and 3. This increases the transmittance in the deep ultraviolet region in the central portion, making it easier to extract and utilize ultraviolet light.

[0036] In the glass tube of the present invention, the thickness t1 of the thinnest part is preferably 0.4 mm or less, 0.001 to 0.4 mm, 0.005 to 0.3 mm, 0.01 to 0.2 mm, 0.02 to 0.1 mm, less than 0.03 to 0.1 mm, and most preferably 0.04 to 0.005 mm. If the thickness t1 of the thinnest part is too thick, the transmittance in the deep ultraviolet region tends to decrease. On the other hand, if the thickness t1 of the thinnest part is too thin, the processability decreases significantly. In order to improve the processability for ultraviolet lamps, the thickness t2 of the end may be 0.4 mm or more.

[0037] Spectral transmittance T at a wavelength of 200 nm, calculated based on the thickness t1 of the thinnest part. 200 The spectral transmittance T is preferably 5% or more, 15% or more, 20% or more, and most preferably 25% or more. 200 If the value is too low, the germicidal performance of ultraviolet lamps that utilize wavelengths in this range tends to decrease.

[0038] Spectral transmittance T at a wavelength of 222 nm, calculated based on the thickness t1 of the thinnest part. 222 The spectral transmittance T is preferably 10% or more, 20% or more, 30% or more, and most preferably 40% or more. 222 If the value is too low, the germicidal performance of ultraviolet lamps that utilize wavelengths in this range tends to decrease.

[0039] Spectral transmittance T at a wavelength of 230 nm, calculated based on the thickness t1 of the thinnest part. 230 The spectral transmittance T is preferably 10% or more, 20% or more, 30% or more, and most preferably 40% or more. 230 If the value is too low, the germicidal performance of ultraviolet lamps that utilize wavelengths in this range tends to decrease.

[0040] Spectral transmittance T at a wavelength of 254 nm, calculated based on the thickness t1 of the thinnest part. 254The spectral transmittance T is preferably 30% or more, 40% or more, 50% or more, and most preferably 60% or more. 254 If the value is too low, the germicidal performance of ultraviolet lamps that utilize wavelengths in this range tends to decrease.

[0041] Spectral transmittance T at a wavelength of 260 nm, calculated based on the thickness t1 of the thinnest part. 260 The spectral transmittance T is preferably 35% or more, 45% or more, 55% or more, and most preferably 65% ​​or more. 260 If the value is too low, the germicidal performance of ultraviolet lamps that utilize wavelengths in this range tends to decrease.

[0042] Spectral transmittance T at a wavelength of 275 nm, calculated based on the thickness t1 of the thinnest part. 275 The spectral transmittance T is preferably 60% or more, 70% or more, 75% or more, and most preferably 80% or more. 275 If the value is too low, the germicidal performance of ultraviolet lamps that utilize wavelengths in this range tends to decrease.

[0043] The spectral transmittance (%) at a wavelength of 200 nm, calculated using the thickness t1 of the thinnest part, is T 200 The spectral transmittance (%) at a wavelength of 260 nm, calculated using the thickness t1 of the thinnest part, is T 260 In that case, T 200 / T 260 Preferably, this value is 0.1 or higher, 0.15 or higher, 0.2 or higher, 0.25 or higher, 0.3 or higher, and most preferably 0.35 or higher. If this value is too small, the change in transmittance at wavelengths of 200 nm to 260 nm becomes large, making it easy for the germicidal performance of the ultraviolet lamp to change depending on the wavelength. On the other hand, if this value is large, the change in transmittance at wavelengths of 200 nm to 260 nm becomes small, so the germicidal performance of the ultraviolet lamp is maintained regardless of the wavelength used. In particular, it is possible to improve the germicidal performance of ultraviolet lamps using short-wavelength ultraviolet light.

[0044] In the glass tube of the present invention, (Fe2O3+TiO2)×T 222The value of (Fe2O3+TiO2)×T is preferably 0.2 or higher, 0.3 or higher, 0.4 or higher, 0.5 or higher, 0.6 or higher, 0.7 or higher, 0.8 or higher, 0.9 or higher, and most preferably 1.0 or higher. 222 A low value indicates that light absorption by iron oxide and titanium oxide is significant, resulting in low transmittance of the glass tube, or that the content of iron oxide and titanium oxide is strictly limited to achieve high transmittance. Glass tubes with low transmittance are unsuitable for UV lamps. Furthermore, strictly limiting the content of iron oxide and titanium oxide to increase transmittance requires the selection of high-purity and expensive glass raw materials, and makes the glass tube difficult to recycle. On the other hand, a high value allows for a balance between transmittance suitable for UV lamps, reduced glass raw material costs, and recyclability.

[0045] TiO2 and Fe2O3 are components that color the glass, so it is preferable not to include them. However, these components are also present as unavoidable impurities in raw materials such as SiO2. Therefore, even if coloring the glass is not intended, TiO2 and Fe2O3 may be included in the glass as unavoidable impurities, taking manufacturing costs into consideration.

[0046] The TiO2 content, in mass%, is preferably 0.1% or less, 0.0001-0.08%, 0.0001-0.05%, 0.0005-0.04%, 0.0008-0.03%, 0.001-0.02%, 0.001-0.01%, and most preferably 0.003-0.005%. If the TiO2 content is too high, the absorption of ultraviolet light increases, impairing transmittance and easily reducing the germicidal performance of the light source. On the other hand, if the TiO2 content is too low, it becomes necessary to reduce the amount of contamination from glass raw materials and manufacturing equipment, which increases production costs. Furthermore, it becomes difficult to recycle waste glass, increasing the environmental burden.

[0047] The Fe2O3 content is preferably 0-0.1%, 0-0.08%, 0-0.05%, 0.0001-0.04%, 0.0005-0.03%, 0.0008-0.02%, 0.001-0.01%, and most preferably 0.002-0.005% by mass. If the Fe2O3 content is too high, the absorption of ultraviolet light increases, impairing transmittance and easily reducing the germicidal performance of the light source. On the other hand, if the Fe2O3 content is too low, it becomes necessary to reduce the amount of contamination from glass raw materials and manufacturing equipment, which increases production costs. Furthermore, it becomes difficult to recycle waste glass, increasing the environmental burden.

[0048] Iron absorbs different wavelengths of light depending on its valency. In particular, trivalent iron readily absorbs light with wavelengths of 300 nm or less. When prioritizing increased transmittance in this range, it is preferable to add reducing agents such as wood powder, carbon, or metallic aluminum to the glass raw material, or to increase the content of divalent iron oxide by making the molten atmosphere reducing. Therefore, the mass ratio of divalent iron oxide to total iron oxide is preferably 0.05 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, and most preferably 0.5 or more.

[0049] To color glass, TiO2 and Fe2O3 can be added to the batch raw materials. In this case, the total and individual content of TiO2 and Fe2O3 are preferably 7% or less, 6% or less, greater than 0% to 5%, 0.001% to 1%, 0.002% to 1%, and most preferably 0.1% to 0.5% by mass.

[0050] The outer diameter D1 at the thinnest part, thickness t1, can be appropriately selected depending on the size of the UV lamp, but is preferably 4-70 mm, 10-50 mm, 15-40 mm, 15.5-38 mm, and most preferably 16-35 mm. If the outer diameter D1 is too small, it becomes difficult to manufacture the UV lamp. On the other hand, if the outer diameter D1 is too large, it becomes difficult to handle as a UV lamp.

[0051] The inner diameter d1 at the thinnest part thickness t1 is preferably 3.2 to 69.9 mm, 9.2 to 49.9 mm, 14.2 to 39.9 mm, and most preferably 15.2 to 34.9 mm. If the inner diameter d1 is too small compared to the outer diameter D1, the glass thickness increases, which reduces the transmittance of the thin-walled part and decreases the germicidal performance of the ultraviolet lamp. On the other hand, if the inner diameter d1 is too large, the glass tube thickness decreases, which improves transmittance, but also increases the possibility of breakage.

[0052] In ultraviolet lamps, it is necessary to seal components containing metal, such as electrodes, into a glass tube. It is necessary to achieve both an outer diameter suitable for manufacturing ultraviolet lamps and a thin thickness to obtain high transmittance. The ratio of inner diameter d1 to outer diameter D1 is preferably 0.76 or higher, 0.8 or higher, 0.85 or higher, 0.9 or higher, 0.91 or higher, 0.92 or higher, 0.93 or higher, 0.94 or higher, 0.95 or higher, 0.96 or higher, 0.97 or higher, 0.98 or higher, and most preferably 0.99 or higher. Therefore, if the ratio of inner diameter d1 to outer diameter D1 is too small, the thickness will be too large or the outer diameter too small, making it unsuitable for manufacturing ultraviolet lamps. On the other hand, since the inner diameter d1 cannot be greater than or equal to the outer diameter D1, the ratio of inner diameter d1 to outer diameter D1 is always less than 1.

[0053] When manufacturing ultraviolet lamps, glass tubes require processing such as sealing in metal components like electrodes. This processing is difficult with thin glass tubes. Therefore, if processability for ultraviolet lamps is prioritized, the thickness t2 of the end of the glass tube may be increased. In this case, the end thickness t2 is preferably 0.4 mm or more, 0.5 mm or more, 0.6 mm or more, 0.7 mm or more, and most preferably 0.8 mm or more. Increasing the end thickness t2 allows for a balance between processability and germicidal performance as an ultraviolet lamp. On the other hand, if germicidal performance as an ultraviolet lamp is prioritized, the end thickness t2 of the glass tube may be the same as the rest of the tube. In this case, the end thickness t2 is preferably 0.4 mm or less, 0.3 mm or less, 0.2 mm or less, 0.1 mm or less, 0.09 mm or less, 0.08 mm or less, 0.07 mm or less, 0.06 mm or less, and most preferably 0.05 mm or less. If the thickness t2 at the end is thin, the transmittance of the glass tube can be improved, which can enhance the germicidal performance of the ultraviolet lamp.

[0054] The outer diameter D2 at the end thickness t2 is preferably 4-70 mm, 10-50 mm, 15-40 mm, 15.5-38 mm, and most preferably 16-35 mm. The outer diameter D2 can be appropriately selected depending on the size of the UV lamp, but if the outer diameter D2 is too small, it becomes difficult to manufacture the UV lamp. On the other hand, if the outer diameter D2 is too large, it becomes difficult to handle as a UV lamp.

[0055] The inner diameter d2 at the end thickness t2 is preferably 3.2 to 69.9 mm, 8 to 49.9 mm, 13 to 39.9 mm, and most preferably 14 to 34.9 mm. The inner diameter d2 depends on the outer diameter D2 and the thickness. When prioritizing the processability of the UV lamp, it is preferable for the inner diameter d2 to be moderately small. However, if the inner diameter d2 is too small, the processability will decrease, and the germicidal performance of the UV lamp will tend to decrease. On the other hand, if the inner diameter d2 is too large, the thickness of the glass tube will decrease, which will improve the transmittance, but the processability of the UV lamp will decrease, and the possibility of breakage will also increase.

[0056] If there are parts of the glass tube with drastically different outer diameters, the processability for making ultraviolet lamps may be impaired. Therefore, it is preferable that the outer diameters of the glass tubes be relatively close in size. In the glass tube of the present invention, the ratio D1 / D2, which is the ratio of the outer diameter D1 at the thinnest part thickness t1 to the outer diameter D2 at the end thickness t2, is preferably 0.8~1.2, 0.85~1.15, 0.9~1.1, 0.91~1.09, 0.92~1.08, 0.93~1.07, 0.94~1.06, 0.95~1.05, 0.96~1.04, and most preferably 0.97~1.03. If this value deviates too far from 1, there will be parts of the glass tube with drastically different outer diameters, which may not only impair the processability for making ultraviolet lamps but also make the ultraviolet lamps difficult to handle.

[0057] In order to facilitate sealing of metal components such as electrodes, when the end of the glass tube is pre-processed to match the outer and inner diameters of the electrode components, the ratio D1 / D2 of the glass tube of the present invention, which is the ratio of the outer diameter D1 at the thinnest part thickness t1 to the outer diameter D2 at the end thickness t2, is preferably 0.5 to 2.0, 0.6 to 1.9, 0.7 to 1.8, 0.8 to 1.7, 0.9 to 1.6, and most preferably 1.0 to 1.5.

[0058] If there are parts of the glass tube with extremely different inner diameters, the processability for making ultraviolet lamps may be impaired. Therefore, it is preferable that the inner diameters of the glass tubes be relatively close in size. In the glass tube of the present invention, the ratio d1 / d2 of the inner diameter d1 at the thinnest part thickness t1 to the inner diameter d2 at the end thickness t2 is preferably 0.8 or more, 0.85 or more, 0.9 or more, 0.95 or more, 0.96 or more, 0.97 or more, 0.98 or more, 0.99 or more, and most preferably 1.00 or more. If this value is too small, the thickness at the end will be too thin, which will easily reduce the processability for making ultraviolet lamps. On the other hand, if this value is too large, the thickness at the end will be too thick, which will take a long time to produce the thin-walled section.

[0059] In order to facilitate sealing of metal components such as electrodes, when the end of the glass tube is pre-processed to match the outer and inner diameters of the electrode components, the ratio d1 / d2 of the glass tube of the present invention, which is the ratio of the inner diameter d1 at the thinnest part thickness t1 to the inner diameter d2 at the end thickness t2, is preferably 0.5 to 2.0, 0.6 to 1.9, 0.7 to 1.8, 0.8 to 1.7, 0.9 to 1.6, and most preferably 1.0 to 1.5.

[0060] In the glass tube of the present invention, when the thickness in the circumferential direction is the same, the tolerance of the outer diameter on the same circumference is preferably 30 μm or less, 25 μm or less, 20 μm or less, and most preferably 15 μm or less. If the roundness of the outer surface is too high, when the glass tube is rotated for processing by heating it with a burner flame, the position of the glass tube is unstable, resulting in uneven heating. Then, while the parts that are difficult to heat rise to a temperature suitable for processing, the parts that are easily heated remain at a high temperature. As a result, the amount of evaporation of easily evaporable components in the glass composition, such as B2O3 and Na2O, increases, and the quality of the product deteriorates. Also, the processing time is longer, so the processing efficiency decreases. On the other hand, when the thickness in the circumferential direction differs in parts, the tolerance of the outer diameter on the same circumference is preferably 1.5 mm or less, 1 mm or less, 0.5 mm or less, 0.1 mm or less, and most preferably 0.03 mm or less.

[0061] When the thickness in the circumferential direction is the same, the tolerance of the inner diameter on the same circumference is preferably 30 μm or less, 25 μm or less, 20 μm or less, and most preferably 15 μm or less. If the roundness of the inner surface is too high, it is easy for defects to occur in sealing with metal-containing parts such as electrodes when processing into an ultraviolet lamp, and efficiency decreases. On the other hand, when the thickness in the circumferential direction differs in parts, the tolerance of the outer diameter on the same circumference is preferably 1.5 mm or less, 1 mm or less, 0.5 mm or less, 0.1 mm or less, and most preferably 0.03 mm or less.

[0062] In the glass tube of the present invention, the Ra of the outer surface is preferably 0.01 μm or less, 0.005 μm or less, 0.003 μm or less, 0.001 μm or less, 0.0008 μm or less, and most preferably 0.0005 μm or less. If the Ra of the outer surface is too high, the light emitted from the ultraviolet lamp will be easily scattered. This will reduce the transmittance of the glass tube and decrease the germicidal performance of the ultraviolet lamp.

[0063] The Ra of the inner surface is preferably 0.01 μm or less, 0.005 μm or less, 0.003 μm or less, 0.001 μm or less, 0.0008 μm or less, and most preferably 0.0005 μm or less. If the Ra of the inner surface is too high, the light emitted from the ultraviolet lamp will be easily scattered. This will reduce the transmittance of the glass tube and decrease the germicidal performance of the ultraviolet lamp.

[0064] In the glass tube of the present invention, the curvature of the tube is preferably 6.0 mm or less, more preferably 5.0 mm or less, and even more preferably 4.0 mm or less. If the curvature of the tube is too large, the position of the glass tube will not be stable when it is rotated for processing by heating it with a burner flame, resulting in uneven heating. Furthermore, while the parts that are difficult to heat rise to a temperature suitable for processing, the parts that are easily heated will remain at a high temperature. As a result, the amount of evaporation of easily evaporable components in the glass composition, such as B2O3 and Na2O, will increase, and the quality of the product will deteriorate. In addition, the processing time will be longer, reducing processing efficiency. In particular, glass tubes with a thickness of 0.1 mm or less are prone to shrinkage due to surface tension when softened, so the curvature of the glass tube greatly affects processing efficiency.

[0065] In embodiments where the circumferential thickness is uniform, the tolerance for thickness on the same circumference is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. If the tolerance for thickness on the same circumference is too large, the difference in heat capacity between different parts of the glass tube becomes large, and the temperature does not rise uniformly when heated and processed by a burner flame. While the thicker, larger heat capacity parts are heated to a temperature suitable for processing, the thinner, smaller heat capacity parts remain at a high temperature, increasing the evaporation of easily evaporable components in the glass composition, such as B2O3 and Na2O, thus degrading the quality of the product. Furthermore, the processing time also increases, reducing processing efficiency. In particular, glass tubes with a thickness of 0.1 mm or less are prone to shrinkage due to surface tension when softened, so the tolerance for the thickness of the glass tube greatly affects processing efficiency. On the other hand, in embodiments where the thickness in the circumferential direction is partially different, the tolerance of the thickness on the same circumference is preferably 1.5 mm or less, 1 mm or less, 0.5 mm or less, 0.1 mm or less, and particularly preferably 0.03 mm or less.

[0066] The glass tube of the present invention is preferably made of soda-lime glass. Soda-lime glass is a glass composition used in window panes of buildings, vehicles, etc., and has the advantage of being weather-resistant and relatively easy to manufacture.

[0067] Furthermore, the glass tube of the present invention preferably contains, in mass%, SiO2 50-85% by mass, Al2O 30-20% by mass, B2O 30-10%, Li2O+Na2O+K2O 5-30%, and MgO+CaO+SrO+BaO 5-30%. "MgO+CaO+SrO+BaO" refers to the combined amounts of MgO, CaO, SrO, and BaO. The reasons for limiting the content range of each component will be explained below. In the following explanation, unless otherwise specified, "%" means "mass%".

[0068] SiO2 is one of the components that make up the network structure of glass. The lower the SiO2 content, the better the processability. However, if the content is too low, weather resistance tends to decrease, vitrification becomes difficult, and the coefficient of thermal expansion increases, leading to a decrease in thermal shock resistance. On the other hand, the higher the SiO2 content, the better the weather resistance. However, if the content is too high, the viscosity of the glass increases, making it difficult to process, and the liquidus temperature rises, making it prone to devitrification. Therefore, the SiO2 content is preferably 50-85%, 55-84%, 60-83%, 65-82%, 68-81%, 69-80%, and particularly 70-79%.

[0069] Al2O3 is one of the components that make up the network structure of glass and also has the effect of improving weather resistance. If the Al2O3 content is too low, weather resistance tends to decrease. On the other hand, if the Al2O3 content is too high, the viscosity of the glass increases. Therefore, the Al2O3 content is preferably 0-20%, 0.5-15%, 0.6-10%, 0.7-8%, 0.8-7%, 0.9-6%, and especially 1.0-5%.

[0070] B2O3 has the effect of lowering the viscosity of glass and improving its meltability and processability. If the B2O3 content is too high, the glass becomes more prone to phase separation, and its weather resistance tends to decrease. Therefore, the B2O3 content is preferably 0-10%, 0.01-9%, 0.02-8%, 0.03-7%, 0.04-6%, 0.04-5%, and especially 0.05-4%.

[0071] Alkali metal oxides (R2O), namely Li2O, Na2O, and K2O, are components that break the network structure of glass, reducing its viscosity and improving its processability and meltability. The lower limit of the Li2O+Na2O+K2O content is preferably 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 12.5% ​​or more, and particularly 13% or more. On the other hand, if the Li2O+Na2O+K2O content is too high, weather resistance decreases, and the coefficient of thermal expansion increases, reducing thermal shock resistance. Therefore, the upper limit of the Li2O+Na2O+K2O content is preferably 30% or less, 25% or less, 23% or less, 20% or less, 19.5% or less, 19% or less, 18.5% or less, and particularly 18% or less.

[0072] As previously mentioned, Li2O has the effect of reducing the viscosity of glass, thereby improving its processability and meltability. Among alkali metal oxides, Li2O is the most effective at reducing the viscosity of glass, followed by Na2O and then K2O. However, if the Li2O content is too high, the weather resistance tends to decrease. Therefore, the upper limit of the Li2O content is preferably 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, and especially 5% or less. Furthermore, when the Li2O content is 6% or less, devitrification becomes less likely to occur.

[0073] When processability is a priority, the lower limit of the Li2O content is preferably 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, and especially 1.0% or more.

[0074] When weather resistance is a priority, the upper limit of the Li2O content is preferably 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, 0.05% or less, 0.01% or less, or preferably no Li2O content at all.

[0075] Na2O, like Li2O, has the effect of lowering the viscosity of glass, thereby improving processability and meltability. However, if the Na2O content is too low, the devitrification resistance may decrease. On the other hand, if the Na2O content is too high, the weather resistance tends to decrease. Therefore, the upper limit of the Na2O content is preferably 30% or less, 25% or less, 20% or less, 19% or less, 18.5% or less, 18.3% or less, 18% or less, 17.9% or less, 17.5% or less, 17% or less, 16.5% or less, and especially 16% or less.

[0076] When processability is a priority, the lower limit of the Na2O content is preferably 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, 4% or more, 4.5% or more, 5% or more, 5.5% or more, and especially 6% or more.

[0077] K2O, though not as effective as Li2O and Na2O, reduces the viscosity of glass, improving processability and meltability. However, too much K2O can easily reduce weather resistance. On the other hand, too little K2O can reduce devitrification resistance. Therefore, the upper limit of the K2O content is preferably 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5.5% or less, and especially 5% or less.

[0078] When processability is a priority, the lower limit of the K2O content is preferably 0.01% to 0.05%, 0.1%, 0.3%, 0.5%, 0.6% or more, 0.7% to 0.8% or more, 0.9% or more, and especially 1.0% or more.

[0079] Alkaline earth metal oxides (R’O) such as MgO, CaO, SrO, and BaO are, like alkali metal oxides (R2O), one of the components that break the glass network structure and have the effect of reducing the viscosity of the glass. They are also components that affect weather resistance. If the content of MgO + CaO + SrO + BaO is too high, not only the devitrification resistance is likely to decrease, but the weather resistance is also likely to decrease. Therefore, the content of MgO + CaO + SrO + BaO is preferably 5 - 30%, 5.5 - 25%, 5.3 - 20%, 5.5 - 15%, 5.8 - 13%, 6.5 - 12%, 6.6 - 11%, 6.7 - 10.8%, 6.8 - 10.5%, 6.9 - 10.3%, particularly 7 - 10%.

[0080] The effect of reducing the viscosity of the glass is highest for BaO, followed by SrO, CaO, and MgO in that order. Therefore, when focusing on processability, the relationship between the contents of alkaline earth metal oxides is preferably MgO ≤ CaO (particularly MgO < CaO), MgO ≤ SrO (particularly MgO < SrO), MgO ≤ BaO (particularly MgO < BaO), CaO ≤ SrO (particularly CaO < SrO), CaO ≤ BaO (particularly CaO < BaO), SrO ≤ BaO (particularly SrO < BaO), more preferably MgO ≤ CaO ≤ SrO ≤ BaO, and even more preferably MgO < CaO < SrO < BaO.

[0081] As described above, MgO is a component that has the effect of reducing the viscosity of the glass. If the content of MgO is too low, the viscosity of the glass becomes high, and if the content of MgO is too high, not only does the devitrification resistance decrease, but the weather resistance is also likely to decrease. Therefore, the content of MgO is preferably 0 - 30%, over - 0 to 25%, 0.001 - 20%, 0.005 - 15%, 0.01 - 10%, 0.05 - 9%, 0.08 - 8%, 0.1 - 7%, 0.2 - 6%, 0.3 - 5%, 0.4 - 4.5%, particularly 0.5 - 4%.

[0082] CaO, like MgO, is a component that reduces the viscosity of glass, and as previously mentioned, its viscosity-reducing effect is greater than that of MgO. If the CaO content is too low, the viscosity of the glass will increase, and if the CaO content is too high, not only will the devitrification resistance decrease, but the weather resistance will also tend to decrease. Therefore, the CaO content is preferably 0-30%, greater than 0-25%, 0.001-20%, 0.005-15%, 0.01-13%, 0.05-12%, 0.1-11%, 0.5-10%, 0.6-9%, 0.7-8%, 0.8-7%, 0.9-6%, and especially 1.0-5%.

[0083] SrO, like MgO and CaO, is a component that reduces the viscosity of glass, and as previously mentioned, its viscosity-reducing effect is greater than that of MgO and CaO. If the SrO content is too low, the viscosity of the glass will increase, and if the SrO content is too high, not only will the devitrification resistance decrease, but the weather resistance will also tend to decrease. Therefore, the SrO content is preferably 0-30%, greater than 0-25%, 0.001-20%, 0.005-15%, 0.01-13%, 0.05-12%, 0.1-11%, 0.5-10%, 0.6-9%, 0.7-8%, 0.8-7%, 0.9-6%, and especially 1.0-5%.

[0084] BaO, like MgO, CaO, and SrO, is a component that reduces the viscosity of glass, and as previously mentioned, its viscosity-reducing effect is greater than that of MgO, CaO, and SrO. If the BaO content is too low, the viscosity of the glass will increase, and if the BaO content is too high, not only will the devitrification resistance decrease, but the weather resistance will also tend to decrease. In addition, if the BaO content is too high, carbonates or sulfates will precipitate more easily, and the hydrolysis resistance will tend to decrease. Therefore, the BaO content is preferably 0-30%, 0-1%, 0-0.9%, 0-0.8%, 0-0.7%, 0-0.6%, 0-0.5%, 0-0.4%, 0-0.3%, 0-0.2%, 0-0.1%, 0-0.01%, less than 0-0.01%, and especially 0-0.001%.

[0085] The preferred content of TiO2 and Fe2O3 is as previously described.

[0086] Other ingredients may be introduced in addition to those listed above.

[0087] ZrO2 is an ingredient that enhances alkali resistance. However, if the ZrO2 content is too high, the viscosity of the glass increases and its devitrification resistance tends to decrease. Therefore, the ZrO2 content is preferably 0-3%, 0-2.5%, 0-2%, 0-1.5%, 0.1-0.8%, and particularly 0.2-0.6%.

[0088] ZnO has the effect of reducing the viscosity of glass. However, if the ZnO content is too high, it will reduce the weather resistance. Therefore, the ZnO content is preferably 0-4%, 0-1%, and especially 0-0.01%.

[0089] One or more fining agents such as F, Cl, Sb2O3, SnO2, SO3, etc., may be introduced. The total content and individual content of these fining agents are preferably 5% or less, 1% or less, 0.5% or less, and particularly 0.3% or less. Note that even if Cl is not added as a fining agent, Cl may be present in the glass as an impurity in the batch raw materials. If the Cl content is too high, white defects are likely to occur during heat processing. Therefore, the Cl content is preferably 0.1% or less, 0.05% or less, 0.01% or less, 0.005% or less, and particularly 0.04% or less.

[0090] To improve chemical durability, high-temperature viscosity, etc., P2O5, Cr2O3, PbO, La2O3, WO3, Nb2O3, Y2O3, etc. may be introduced at concentrations of 3% or less, 2% or less, 1% or less, less than 1%, and 0.5% or less, respectively.

[0091] Impurities such as H2, CO2, CO, H2O, He, Ne, Ar, and N2 may be introduced up to 0.1% each. Furthermore, the amount of noble metal elements such as Pt, Rh, and Au is preferably 500 ppm or less, and more preferably 300 ppm or less, each.

[0092] Furthermore, the glass tube of the present invention is preferably made of borosilicate glass. Borosilicate glass is a glass composition system used for laboratory and pharmaceutical containers, and although its productivity is lower than that of soda-lime glass, it has excellent weather resistance. The glass tube of the present invention preferably contains, in mass%, SiO2 60-85%, Al2O 30-15%, B2O 33-20%, Li2O+Na2O+K2O 3-15%, and MgO+CaO+SrO+BaO 0-10%. The reasons for limiting the content range of each component will be explained below. In the following explanation, unless otherwise specified, "%" means "mass%".

[0093] SiO2 is one of the components that make up the network structure of glass. The lower the SiO2 content, the better the processability. However, if the content is too low, hydrolysis resistance tends to decrease, vitrification becomes difficult, and the coefficient of thermal expansion increases, leading to a decrease in thermal shock resistance. On the other hand, the higher the SiO2 content, the better the weather resistance. However, if the content is too high, the viscosity of the glass increases, processability tends to decrease, the liquidus temperature rises, and devitrification becomes more likely. Therefore, the SiO2 content is preferably 60-85%, 65-80%, 66-79%, 67-78%, 68-77%, 69-76%, and particularly 70-75%.

[0094] Al2O3 is one of the components that make up the network structure of glass and also has the effect of improving hydrolysis resistance. If the Al2O3 content is too low, hydrolysis resistance tends to decrease. On the other hand, if the Al2O3 content is too high, the viscosity of the glass increases. Therefore, the Al2O3 content is preferably 0-15%, 1-12%, 2-11%, 3-10%, 3.5-9%, 3.9-8.5%, 4-8%, 4.1-7.9%, 4.2-7.8%, 4.3-7.7%, 4.4-7.6%, and especially 4.5-7.5%.

[0095] B2O3 has the effect of lowering the viscosity of glass and improving its meltability and processability. If the B2O3 content is too high, the glass becomes more prone to phase separation, and its weather resistance tends to decrease. Therefore, the B2O3 content is preferably 3-20%, 5-18%, 6-16%, 7-15%, 8-14%, 9-13%, and especially 10-12%.

[0096] Alkali metal oxides (R2O), namely Li2O, Na2O, and K2O, are components that break the network structure of glass, reducing its viscosity and improving its processability and meltability. On the other hand, if the content of Li2O + Na2O + K2O is too high, weather resistance decreases, and the coefficient of thermal expansion increases, reducing thermal shock resistance. Therefore, the content of Li2O + Na2O + K2O is preferably 3-15%, preferably 3.5-14%, 4-13%, 4.5-12.5%, 5-12%, 5.5-11.5%, 5.6-11% or more, 5.7-10.5%, 5.8-10%, 5.9-9.5%, 6-9%, 6.1-8.9%, 6.2-8.8%, 6.3-8.7%, 6.4-8.6%, and particularly 6.5-8.5%.

[0097] Among alkali metal oxides (R2O), Li2O has the greatest effect in reducing the viscosity of glass, followed by Na2O and then K2O. Therefore, from the viewpoint of reducing the viscosity of glass, the relationship of alkali metal oxide content is preferably Li2O≧Na2O≧K2O, Li2O≧Na2O>K2O, or Li2O>Na2O≧K2O, and especially Li2O>Na2O>K2O. Furthermore, if the proportion of K2O among the alkali metal oxides is too high, it becomes difficult to achieve both weather resistance and workability. Therefore, from the viewpoint of achieving both weather resistance and workability, Na2O>K2O is preferable.

[0098] If the proportion of Li2O in the alkali metal oxide is too high, the devitrification resistance tends to decrease. Therefore, from the viewpoint of devitrification resistance, the relationship of alkali metal oxide content is preferably Na2O > Li2O. Furthermore, K2O has the greatest effect in improving devitrification resistance, followed by Na2O, and then Li2O. From the viewpoint of prioritizing both weather resistance and devitrification resistance, it is preferable that Li2O ≥ Na2O ≥ K2O, Li2O ≥ K2O > Na2O, or Li2O > Na2O ≥ K2O, and especially Li2O > K2O > Na2O.

[0099] As previously mentioned, Li2O has the effect of reducing the viscosity of glass, thereby improving its processability and meltability. Among alkali metal oxides, Li2O is the most effective at reducing the viscosity of glass, followed by Na2O and then K2O. However, if the Li2O content is too high, the weather resistance tends to decrease. Therefore, the Li2O content is preferably 0-6%, 0-5.5%, 0-5%, 0-4.5%, 0-4%, 0-3.5%, 0-3.4%, 0-3.3%, 0-3.2%, 0-3.1%, 0-3%, 0-2.9%, 0-2.8%, and especially 0-2.7%. Furthermore, when the Li2O content is 3% or less, devitrification is less likely to occur.

[0100] Na2O, like Li2O, has the effect of lowering the viscosity of glass, thereby improving processability and meltability. However, if the Na2O content is too low, the devitrification resistance may decrease. On the other hand, if the Na2O content is too high, the weather resistance tends to decrease. Therefore, the Na2O content is preferably 0-12%, 0-10%, 0-9%, 0-8.5%, 0-8.3%, 0-8.2%, 0-8.1%, 0-8%, 0-7.9%, 0-7.8%, 0-7.7%, 0-7.6%, and especially 0-7.5%.

[0101] Although K₂O does not have as great an effect as Li₂O and Na₂O, it has the effect of reducing the viscosity of glass and enhancing workability and fusibility. However, if the content of K₂O is too high, the weather resistance is likely to decrease. On the other hand, if the content of K₂O is too low, the devitrification resistance may decrease. Therefore, the content of K₂O is preferably 0 - 5%, 0 - 4%, 0 - 3.8%, 0 - 3.7%, 0 - 3.6%, 0 - 3.5%, 0 - 3.3%, 0 - 3.1%, 0 - 3%, particularly less than 0 - 3%.

[0102] MgO, CaO, SrO, and BaO, which are alkaline earth metal oxides (R’O), like alkali metal oxides, are one of the components that break the network structure of glass and also have the effect of reducing the viscosity of glass. They are also components that affect weather resistance. If the content of MgO + CaO + SrO + BaO is too high, not only is the weather resistance likely to decrease, but the devitrification resistance is also likely to decrease. Therefore, the content of MgO + CaO + SrO + BaO is preferably 0 - 10%, more than 0 - 9%, 0.01 - 8%, 0.05 - 7%, 0.1 - 6%, 0.15 - 5%, 0.2 - 4%, 0.25 - 3%, 0.3 - 2.9%, 0.35 - 2.8%, 0.4 - 2.7%, 0.45 - 2.6%, particularly 0.5 - 2.5%.

[0103] The effect of reducing the viscosity of glass is highest for BaO, followed by SrO, CaO, and MgO in that order. Therefore, when focusing on workability, the relationship between the contents of alkaline earth metal oxides is preferably MgO ≤ CaO (particularly MgO < CaO), MgO ≤ SrO (particularly MgO < SrO), MgO ≤ BaO (particularly MgO < BaO), CaO ≤ SrO (particularly CaO < SrO), CaO ≤ BaO (particularly CaO < BaO), SrO ≤ BaO (particularly SrO < BaO), more preferably MgO ≤ CaO ≤ SrO ≤ BaO, and even more preferably MgO < CaO < SrO < BaO.

[0104] MgO is a component that breaks the network structure of glass and reduces its viscosity. Furthermore, if the MgO content is too high, weather resistance and devitrification resistance tend to decrease. Therefore, the MgO content is preferably 0-10%, 0-8%, 0-5%, 0-3%, 0-1%, 0-0.9%, 0-0.8%, 0-0.7%, 0-0.6%, 0-0.5%, 0-0.4%, 0-0.3%, 0-0.2%, and particularly 0-0.1%. If processability is a priority, MgO of 0.01% or more may be introduced.

[0105] CaO, like MgO, is a component that reduces the viscosity of glass. However, if the CaO content is too high, the weather resistance and devitrification resistance tend to decrease. Therefore, the CaO content is preferably between 0 and 10%, 0.01 and 10%, 0.05 and 9%, 0.1 and 8%, 0.15 and 7%, 0.2 and 6%, 0.25 and 5%, 0.3 and 4.5%, 0.35 and 4%, 0.4 and 3.5%, 0.45 and 3%, and especially between 0.5 and 2.5%.

[0106] The SrO content is preferably 0-5%, 0-4%, 0-3%, 0-2%, 0-1%, 0-0.5%, 0-0.4%, 0-0.3%, 0-0.2%, 0-0.1%, 0-0.01%, less than 0-0.01%, and particularly 0-0.001%. If the SrO content is too high, weather resistance and devitrification resistance tend to decrease.

[0107] The BaO content is preferably 0-5%, 0-4.5%, 0-4%, 0-3.5%, 0-3%, 0-2.5%, 0-2%, 0-1.9%, 0-1.8%, 0-1.7%, 0-1.6%, and especially 0-1.5%. If the BaO content is too high, weather resistance and devitrification resistance tend to decrease.

[0108] Other ingredients may be introduced in addition to those listed above.

[0109] ZrO2 is a component that enhances weather resistance. However, if the ZrO2 content is too high, the viscosity of the glass increases and its resistance to devitrification tends to decrease. Therefore, the ZrO2 content is preferably 0-3%, 0-2.5%, 0-2%, 0-1.5%, 0.1-0.8%, and particularly 0.2-0.6%.

[0110] ZnO has the effect of reducing the viscosity of glass. However, if the ZnO content is too high, it will negatively affect the weather resistance. Therefore, the ZnO content is preferably 0-4%, 0-1%, and especially 0-0.01%.

[0111] One or more fining agents such as F, Cl, Sb2O3, SnO2, SO3, etc., may be introduced. The total content and individual content of these fining agents are preferably 5% or less, 1% or less, 0.5% or less, and particularly 0.3% or less. Note that even if Cl is not added as a fining agent, Cl may be present in the glass as an impurity in the batch raw materials. If the Cl content is too high, white defects are likely to occur during heat processing. Therefore, the Cl content is preferably 0.1% or less, 0.05% or less, 0.01% or less, 0.005% or less, and particularly 0.04% or less.

[0112] To improve chemical durability, high-temperature viscosity, etc., P2O5, Cr2O3, PbO, La2O3, WO3, Nb2O3, Y2O3, etc. may be introduced at concentrations of 3% or less, 2% or less, 1% or less, less than 1%, and 0.5% or less, respectively.

[0113] Impurities such as H2, CO2, CO, H2O, He, Ne, Ar, and N2 may be introduced up to 0.1% each. Furthermore, the amount of noble metal elements such as Pt, Rh, and Au is preferably 500 ppm or less, and more preferably 300 ppm or less, each.

[0114] In a high-speed accelerated life test (HAST) conducted at a temperature of 121°C, relative humidity of 85%, and for a test period of 24 hours, the glass tube of the present invention preferably has a maximum long side of 100 μm or less for foreign matter generated on the glass surface after the test, more preferably 50 μm or less, 30 μm or less, and particularly 10 μm or less.

[0115] The term "High-Speed ​​Accelerated Life Test (HAST)" refers to the following tests: (1) Surface area is 16 cm 2 Prepare a glass tube that has been cut to the specified dimensions and the cut surface has been mirror-polished, or a glass sample of the same composition as a glass tube that has been processed to the dimensions of 20mm x 35mm x 2.00mm and mirror-polished. (2) An accelerated test will be conducted using a test apparatus manufactured by Hirayama Seisakusho Co., Ltd., at a temperature of 121°C, relative humidity of 85%, and for a test period of 24 hours. (3) After the accelerated test, the sample is observed using a Keyence digital microscope, and the longest side of any foreign matter generated on the glass surface is measured.

[0116] In the glass tube of the present invention, the working point is preferably 1300°C or lower, 1260°C or lower, 1240°C or lower, 1220°C or lower, 1200°C or lower, and particularly 1180°C or lower. If the working point is high, the processing temperature when processing the glass tube into an ultraviolet lamp becomes higher, and the evaporation of alkaline components contained in the glass increases significantly. Since the evaporated alkaline components adhere to the inner wall of the glass tube, this may cause defects in the processed ultraviolet lamp. Here, the "working point" is defined as the viscosity of the glass being 10 4.0 This refers to the temperature at which the temperature becomes dPa·s.

[0117] The glass tube of the present invention can form a compressive stress layer on its surface by subjecting it to a chemical strengthening treatment (ion exchange treatment). When the glass tube of the present invention is subjected to a chemical strengthening treatment by immersion in a molten KNO3 salt at 475°C for 7 hours, the compressive stress value of the compressive stress layer formed is preferably 100 MPa or more, more preferably 200 MPa or more, and particularly preferably 300 MPa or more.

[0118] The compressive stress value and stress depth of the compressive stress layer can be measured as follows. First, both surfaces of the sample are mirror-polished, and then chemically strengthened by immersion in molten KNO3 at 475°C for 7 hours. Next, the surface of the sample is cleaned, and the compressive stress value and stress depth are calculated from the number and spacing of interference fringes observed using a surface stress meter (FSM-6000, manufactured by Orihara Seisakusho Co., Ltd.). For the calculation, the refractive index of the sample is assumed to be 1.50 and the photoelastic constant is assumed to be 29.5 [(nm / cm) / MPa]. Although the glass composition on the glass surface differs microscopically before and after the chemical strengthening treatment, the glass composition as a whole is substantially the same.

[0119] Next, the method for manufacturing the glass tube of the present invention will be described using the Danner process.

[0120] First, glass raw materials are mixed to create a batch with the desired glass composition. Next, this batch is continuously fed into a melting furnace at 1550-1700°C for melting and clarification. Then, the resulting molten glass is wrapped around a rotating refractory material, and air is blown from the tip of the refractory material, drawing the glass out in a tubular shape from the tip of the refractory material.

[0121] Next, the extracted tubular glass is cut to a predetermined length to obtain glass tubes. The glass tubes thus obtained are used in the manufacture of ultraviolet lamps.

[0122] Furthermore, the glass tubes of the present invention may be manufactured not only by the Dannah process but also by other methods (for example, the Bellows process, the downdraw process, or the redraw process).

[0123] Furthermore, the glass tube of the present invention may be pre-processed to match the outer and inner diameters of the electrode components in order to facilitate sealing of metal components such as electrodes. The processing method is not particularly limited, but for example, a glass tube suitable for sealing can be obtained by heating the part to be processed with a burner flame, applying a shaping jig to the softened glass to achieve the desired outer and inner diameters, cutting off the unnecessary parts with a cutter, and then shaping the end with a burner flame. This processing and the processing to reduce the thickness of the glass tube, which will be described later, can be performed in any order.

[0124] Next, we will explain how to manufacture glass tubes used in deep ultraviolet light source devices. The following describes a manufacturing method in which glass tubes are processed to reduce their thickness by etching with hydrofluoric acid, but this method is just one example, and other methods (for example, etching with acids other than hydrofluoric acid or mixed acids, the Danner method, the Bellow method, the downdraw method, or the redraw method) may also be used.

[0125] First, prepare a glass tube and immerse it in a mixed solution of hydrofluoric acid and an acid selected from hydrochloric acid, sulfuric acid, nitric acid, etc., at a desired concentration. At this time, a portion of the glass tube may be masked to form a thin-walled section. Once the glass tube reaches the desired thickness, remove it from the mixed solution and wash off any remaining solution from the glass surface to obtain the glass tube. The immersion time should be appropriately selected according to the glass composition and the concentration of the mixed solution.

[0126] If necessary, chemically strengthened glass tubes can be obtained by immersing the glass tubes in a molten KNO3 salt and performing ion exchange.

[0127] The glass tube of the present invention may have a coating on its inner and / or outer surface. Examples of coatings include inorganic coatings such as fluorine, silicon, and surfactants, and organic coatings. [Examples]

[0128] The present invention will be described below based on examples. Note that the following examples are merely illustrative and do not limit the present invention in any way.

[0129] Table 1 shows Examples 1 and 2 and a comparative example of the present invention. In the table, "NA" indicates that the measurement was not taken.

[0130] [Table 1]

[0131] Each sample was prepared as follows. First, glass tubes prepared by the Danner method to have the glass composition shown in the table were immersed in a mixed solution. In Example 1, the tubes were immersed for 130 minutes in a mixed solution prepared to have a hydrofluoric acid concentration of 5 mol / L and a hydrochloric acid concentration of 2 mol / L. In Example 2, the tubes were immersed for 70 minutes in a mixed solution prepared to have a hydrofluoric acid concentration of 7.5 mol / L and a hydrochloric acid concentration of 3 mol / L. After that, the tubes were processed into the shape necessary for measurement and subjected to various evaluations. The results are shown in the table.

[0132] Various pipe dimensions (outer diameter, inner diameter, thickness) can be measured using calipers, micrometers, dial gauges, lasers, or other measuring methods with appropriate accuracy. In the table, the outer diameter is shown as the average value obtained by measuring three points on the same circumference using calipers. The thickness is shown as the average value obtained by measuring three different points on the same sample using a dial gauge. The inner diameter is shown as the average value of the outer diameter minus twice the average value of the thickness.

[0133] The thickness of the thinnest part of a thin-walled section, i.e., the thickness t1 of the thinnest part, can be measured as follows. For example, when using a dial gauge, in the case shown in Figures 1-3, the glass tube is cut lengthwise, and the minimum thickness measured while moving the dial gauge from one end to the other is t1. In the case of the glass tube shown in Figure 4, the minimum thickness measured while rotating the glass tube circumferentially is t1. Any instrument or device with appropriate accuracy can be used to measure the thickness.

[0134] The bend was measured by placing a 1000mm long glass tube on two rollers spaced 1000mm apart, and reading the maximum and minimum values ​​during one rotation of the tube using a dial gauge. Half the difference between the maximum and minimum values ​​was taken as the bend of the glass tube.

[0135] The outer diameter tolerance is measured using the following procedure: Place the glass tube on a flat table or stand and measure the outer diameter at any one point. Then, without moving the measuring instrument or device, rotate the glass tube so that the position of the end of the tube does not shift, and measure the outer diameter again. The difference between the maximum and minimum values ​​measured at at least three points is taken as the tolerance.

[0136] The tolerance for the inner diameter is measured using the following procedure: Place the glass tube on a flat table or stand and measure the inner diameter at any one point. Then, without moving the measuring instrument or device, rotate the glass tube so that the position of the end of the tube does not shift, and measure the inner diameter again. The difference between the maximum and minimum values ​​measured at at least three points is taken as the tolerance.

[0137] The thickness tolerance is measured using the following procedure: Place the glass tube on a flat table or stand and measure the thickness at any one point. Then, without moving the measuring instrument or device, rotate the glass tube so that the position of the ends of the tube does not shift, and measure the thickness again. The difference between the maximum and minimum values ​​measured at at least three points is defined as the tolerance.

[0138] The Ra of the outer surface can be measured using a surfcoder that scans a stylus, a laser microscope, a white light interferometer, or an AFM. A measurement distance of approximately 5 μm is preferred.

[0139] The Ra of the inner surface can be measured using a surfcoder that scans a stylus, a laser microscope, a white light interferometer, or an AFM. A measurement distance of approximately 5 μm is preferred.

[0140] The strain point Ps was determined by the fiber stretching method in accordance with ASTM C336. The slow cooling point Ta and softening point Ts were determined by the fiber stretching method in accordance with ASTM C388.

[0141] Working point (when the viscosity of the glass is 10 4.0 (Temperature at which it becomes dPa·s) and high-temperature viscosity 10 3.0 The temperature at which the pressure reaches dPa·s was determined using the platinum sphere pulling method.

[0142] The weathering test was conducted using a method similar to the High-Speed ​​Accelerated Life Test (HAST). The detailed test procedure is as described above.

[0143] Spectral transmittance was evaluated using a JASCO V-670. The measurement conditions were as follows: Measurement range: 200 nm to 800 nm, data acquisition interval: 1 nm, UV-Vis bandwidth: 5.0 nm, near-infrared bandwidth: 20.0 nm, response: Medium, scanning speed: 200 nm / min, and an integrating sphere unit was used. The glass tube was cut in half for measurement.

[0144] The linear thermal expansion coefficient was measured using a Deilartometer at a temperature range of 20 to 300°C, with glass molded into a rod shape of approximately 5 mm in diameter and 20 mm in length as the measurement sample.

[0145] Figure 5 shows the transmittance curves for wavelengths of 200 nm to 800 nm for Examples 1 and 2. The transmittance curve for a thickness of 0.17 mm is the data for Example 1, and the transmittance curve for a thickness of 0.05 mm is the data for Example 2.

[0146] As is clear from the table and figures, Examples 1 and 2 had high transmittance in the deep ultraviolet region because T222×(Fe2O3+TiO2) was large. On the other hand, the comparative example had low transmittance in the deep ultraviolet region because T222×(Fe2O3+TiO2) was small. [Industrial applicability]

[0147] The glass tube of the present invention is suitable as a protective material for deep ultraviolet light source devices. It can also be used as a storage container for solids, liquids, gases, and the like.

Claims

1. A glass tube including a thin-walled portion with a thickness of 0.4 mm or less, The thickness of the thinnest part within the thin-walled section is t1 [mm], and the spectral transmittance at a wavelength of 222 nm is calculated based on the thickness t1 of the thinnest part. ２２２ [%], outer diameter of the thinnest part is D1 [mm], inner diameter of the thinnest part is d1 [mm], and the total amount of iron oxide and titanium oxide contained in the glass is Fe ２ O ３ +TiO ２ When expressed as [mass%], d1 / D1 is 0.76 or more, the spectral transmittance at a wavelength of 222 nm calculated as the thickness t1 of the thinnest part is 30% or more, the outer diameter D1 at the thickness t1 of the thinnest part is 10 to 70 mm, and (Fe ２ O ３ +TiO ２ ) × T ２２２ A glass tube characterized in that the value of is 0.2 or greater.

2. The glass tube according to claim 1, characterized in that the thickness t1 [mm] of the thinnest part is 0.2 mm or less.

3. Fe ２ O ３ +TiO ２ The total content of which is 0.002 to 0.1% by mass, Fe ２ O ３ The content of which is 0 to 0.05% by mass, TiO ２ The glass tube according to claim 1 or 2, characterized in that the content of is 0 to 0.05% by mass.

4. A glass tube according to any one of claims 1 to 3, characterized in that the spectral transmittance at a wavelength of 230 nm, calculated based on the thickness t1 of the thinnest part, is 40% or more.

5. The spectral transmittance (%) at a wavelength of 200 nm, calculated using the thickness t1 of the thinnest part, is T ２００ The spectral transmittance (%) at a wavelength of 260 nm, calculated using the thickness t1 of the thinnest part, is T ２６０ In that case, T ２００ / T ２６０ A glass tube according to any one of claims 1 to 4, characterized in that the ratio is 0.3 or greater.

6. A glass tube according to any one of claims 1 to 5, characterized in that the bend of the glass tube is 6.0 mm or less.

7. A glass tube according to any one of claims 1 to 6, characterized in that the tolerance of the thickness t1 of the thinnest part is 30 μm or less.

8. A glass tube according to any one of claims 1 to 7, characterized in that the ratio D1 / D2 of the outer diameter D1 of the thinnest part to the outer diameter D2 of the end part is 0.8 to 1.

2.

9. A glass tube according to any one of claims 1 to 8, characterized in that the ratio d1 / d2 of the inner diameter d1 of the thinnest part to the inner diameter d2 of the end is 0.8 or more.

10. A glass tube according to any one of claims 1 to 9, characterized in that the tolerance of the outer diameter is 30 μm or less.

11. A glass tube according to any one of claims 1 to 10, characterized in that the tolerance of the inner diameter is 30 μm or less.

12. A glass tube according to any one of claims 1 to 11, characterized in that the Ra of the outer surface is 0.01 μm or less.

13. A glass tube according to any one of claims 1 to 12, characterized in that the Ra of the inner surface is 0.01 μm or less.

14. A glass tube according to any one of claims 1 to 13, characterized in that the thickness t1 of the thinnest part is less than 0.1 mm.

15. A glass tube according to any one of claims 1 to 14, characterized in that when a rapid accelerated life test (HAST) is performed at a temperature of 121°C, relative humidity of 85%, and test time of 24 hours, the longest side of any foreign matter generated on the glass surface is 100 μm or less.

16. The coefficient of linear thermal expansion in the temperature range of 20 to 300°C is 30 × 10⁻⁶. －７ / ℃~100×10 －７ A glass tube according to any one of claims 1 to 15, characterized in that it is / ℃.

17. High temperature viscosity 10 ４．０ A glass tube according to any one of claims 1 to 16, characterized in that the temperature at which it becomes dPa·s is 1300°C or lower.

18. Liquid phase viscosity is 10 ４．８ A glass tube according to any one of claims 1 to 17, characterized in that it has a pressure of dPa·s or higher.

19. Potassium nitrate (KNO) heated to 475°C ３ A glass tube according to any one of claims 1 to 18, characterized in that when immersed in molten salt for 7 hours, the compressive stress value formed on the surface is 200 MPa or more.

20. A deep ultraviolet lamp characterized in that the outer cylinder is a glass tube as described in any of claims 1 to 19.

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