JP2019147722A - Ultraviolet transmission glass and manufacturing method therefor - Google Patents

Abstract

To provide an ultraviolet transmission glass high in transmission coefficient of an ultraviolet light in deep ultraviolet range, especially with wavelength of 200 to 250 nm.SOLUTION: The ultraviolet transmission glass has thickness of 0.5 mm and T≥75, wherein transmission coefficient (%) at wavelength of 200 nm is T. The manufacturing method of the ultraviolet transmission glass uses synthetic silica as at least a part of glass raw materials.SELECTED DRAWING: Figure 1

Description

    The present invention relates to an ultraviolet transmissive glass and a method for producing the same.

    Currently, a light source having a high output in the deep ultraviolet region (for example, a wavelength region of 200 to 350 nm) has been developed, and is used for an ultraviolet lamp, a writing device for a magnetic recording medium, and the like. In such a light source and an apparatus using the same, ultraviolet transmissive glass (for example, Patent Document 1) having a high deep ultraviolet transmittance is used.

International Publication No. 2017/057375

  The higher the transmittance of the ultraviolet transmissive glass in the deep ultraviolet region, the higher the performance of the light source having a high output in the deep ultraviolet region as described above and the apparatus using the same. For example, in an ultraviolet lamp for sterilization, higher sterilization power can be obtained by using an ultraviolet transmissive glass having a higher transmittance as an outer cylinder. However, the transmittance of conventional ultraviolet transmissive glass, particularly the transmittance in the deep wavelength range of 200 to 250 nm, is still insufficient, and there remains room for improvement.

The ultraviolet transmissive glass of the present invention is characterized in that T ₂₀₀ ≧ 75 when the transmittance (%) at a thickness of 0.5 mm and a wavelength of 200 nm is T ₂₀₀ . Here, the “transmittance at a wavelength of 200 nm” can be measured with a commercially available spectrophotometer (for example, UV-3100 manufactured by Hitachi, Ltd.).

The ultraviolet transmissive glass of the present invention preferably has T ₂₀₀ / T ₂₅₀ ≧ 0.75 or more when the transmittance (%) at a thickness of 0.5 mm and a wavelength of 250 nm is T ₂₅₀ .

The ultraviolet transmissive glass of the present invention preferably has T ₂₂₀ ≧ 80 when the transmittance (%) at a thickness of 0.5 mm and a wavelength of 220 nm is T ₂₂₀ .

  The ultraviolet transmissive glass of the present invention is preferably a plate or tube having a thickness of 0.1 to 3.0 mm.

Ultraviolet transmitting glass of the present invention has a glass composition, in _{mass%, SiO 2 55~75%, Al} 2 O 3 1~10%, B 2 O 3 10~30%, CaO 0~5%, BaO 0~ 5%, Li ₂ O + Na ₂ O + K ₂ O 1.0 to 15%, TiO _{2 0 to} 0.001%, Fe ₂ O _{3 0 to} 0.001% are preferably contained.

  The method for producing an ultraviolet transmissive glass of the present invention is the method for producing an ultraviolet transmissive glass according to any one of the above, wherein synthetic silica is used as at least a part of the glass raw material.

  In the method for producing the ultraviolet light transmitting glass of the present invention, it is preferable that the synthetic silica is a granular silica purified by a gas phase reaction method or a liquid phase reaction method.

  In the method for producing an ultraviolet transmissive glass of the present invention, the synthetic silica preferably has an average particle size of 100 μm or less, and the proportion of the synthetic silica in the total silica source of the glass raw material is preferably 90 to 100% by mass.

  According to the ultraviolet transmissive glass and the method for producing the same of the present invention, it is possible to obtain a glass having a higher transmittance than the conventional product in the deep ultraviolet wavelength region.

It is a graph which shows the transmittance | permeability of sample No. 1-3 of thickness 0.5mm.

In the ultraviolet transmitting glass of the present invention, when T ₂₀₀ is the transmittance (%) at a thickness of 0.5 mm and a wavelength of 200 nm, T ₂₀₀ ≧ 75, preferably T ₂₀₀ ≧ 80, and T ₂₀₀ ≧ 83. If the transmittance at a thickness of 0.5 mm and a wavelength of 200 nm is too low, it is difficult for ultraviolet light to pass through, and the performance of the mounted light source or device tends to be reduced.

In the ultraviolet transmitting glass of the present invention, the thickness 0.5 mm, if the transmittance at a wavelength of 220nm (%) was the _{T 220,} is preferably _{T 220} ≧ 80, more preferably _{T 220 ≧ 85, T 220 ≧} 87 is there. If the transmittance at a thickness of 0.5 mm and a wavelength of 220 nm is too low, it is difficult for ultraviolet light to pass through, and the performance of the mounted light source or device is likely to deteriorate.

In the ultraviolet transmitting glass of the present invention, when the thickness 0.5 mm, the transmittance at a wavelength of 250nm (%) was the _{T 250,} preferably _{T 250} ≧ 88, more preferably _{T 250 ≧ 89, T 250 ≧} 89. 5. If the transmittance at a thickness of 0.5 mm and a wavelength of 250 nm is too low, it is difficult for ultraviolet light to pass through, and the performance of the mounted light source or device tends to deteriorate.

Further, the value of T ₂₀₀ / T ₂₅₀ is preferably 0.75 or more, 0.80 or more, 0.85 or more, 0.90 or more, or 0.92 or more. When the value of T ₂₀₀ / T ₂₅₀ is too small, it becomes difficult to transmit ultraviolet light, and the performance of the mounted light source or device tends to be lowered.

  The strain point of the ultraviolet transmissive glass of the present invention is preferably 400 ° C. or higher, 410 ° C. or higher, and 415 ° C. or higher. When the strain point of the ultraviolet transmissive glass is too low, for example, when a functional film is formed on the surface, unintended deformation is likely to occur in the glass in a high-temperature film forming process.

  The softening point of the ultraviolet transmitting glass of the present invention is preferably 850 ° C. or lower, 800 ° C. or lower, 750 ° C. or lower, particularly 700 ° C. or lower. If the softening point is too high, the load on the glass melting furnace becomes large, and the manufacturing cost of the glass tends to increase.

The temperature at a viscosity of 10 ^2.5 dPa · s of the ultraviolet transmissive glass of the present invention is 1540 ° C. or lower, 1520 ° C. or lower, 1500 ° C. or lower, particularly 1480 ° C. or lower. If the temperature at 10 ^2.5 dPa · s is too high, the meltability is lowered, and the production cost of the glass tends to increase. Here, “temperature at 10 ^2.5 dPa · s” can be measured by a platinum ball pulling method.

The average linear thermal expansion coefficient in the temperature range of 30 to 380 ° C. of the ultraviolet transmitting glass of the present invention is preferably 30 × 10 ⁻⁷ / ° C. or higher, particularly 35 × 10 ⁻⁷ / ° C. or higher, and 95 × 10 ^{− 7} / ° C. or less, particularly 80 × 10 ⁻⁷ / ° C. or less. If the average linear thermal expansion coefficient is too low, it becomes difficult to match the thermal expansion coefficient of various members, particularly glass frit. As a result, since it is difficult to lower the melting point of the glass frit, the process temperature of the device is increased, and the performance of the device is easily deteriorated. On the other hand, if the average linear thermal expansion coefficient is too high, the glass tends to break due to thermal shock.

The liquidus temperature of the ultraviolet transmissive glass of the present invention is preferably 1120 ° C. or lower, 1100 ° C. or lower, 1080 ° C. or lower, 1050 ° C. or lower, 1000 ° C. or lower, 950 ° C. or lower, 900 ° C. or lower, particularly 850 ° C. or lower. The viscosity at the liquidus temperature is preferably of ¹⁰ 4.0 dPa · s or ^{more, 10} 4.3 dPa · s or ^{more, 10} 4.5 dPa · s or ^{more, 10} 4.8 dPa · s or ^{more, 10} 5.1 dPa · S or more, 10 ^5.3 dPa · s or more, particularly 10 ^5.5 dPa · s or more. If it does in this way, devitrification resistance will improve and it will become easy to shape | mold by a downdraw method, especially an overflow downdraw method, Therefore It becomes easy to produce glass of a desired shape.

  The Young's modulus of the ultraviolet transmissive glass of the present invention is preferably 40 GPa or more, particularly 45 GPa or more. If the Young's modulus is too low, it is difficult to maintain the rigidity of the glass in the conveying line in the device manufacturing process, and the glass is likely to be deformed, warped, or broken.

Ultraviolet transmitting glass of the present invention has a glass composition, in _{mass%, SiO 2 55~75%, Al} 2 O 3 1~10%, B 2 O 3 10~30%, CaO 0~5%, BaO 0~ 5%, Li ₂ O + Na ₂ O + K ₂ O 1.0-15%, TiO ₂ 0-0.001%, Fe ₂ O ₃ 0-0.001%, F 0.5-2.0% Is preferred.

  The reason for limiting the content of each component as described above will be described below. In addition, in description of content of each component,% display represents the mass% unless there is particular notice.

SiO ₂ is a main component that forms a glass skeleton. The content of SiO ₂ is preferably 50 to 80%, 55 to 75%, 58 to 70%, particularly 65 to 69%. When the content of SiO ₂ is too small, the Young's modulus, acid resistance tends to decrease. On the other hand, if the SiO ₂ content is too large, the high-temperature viscosity becomes high and the meltability tends to be lowered, and devitrified crystals such as cristobalite are likely to precipitate, and the liquidus temperature is likely to rise. Become.

Al ₂ O ₃ and B ₂ O ₃ are components that enhance devitrification resistance. The content of Al ₂ O ₃ + B ₂ O ₃ is preferably 2 to 40%, 5 to 35%, 10 to 30%, particularly 20 to 28%. When the content of _{Al 2 O 3 + B 2 O} 3 is too small, easily glass devitrified. On the other hand, when the content of _{Al 2 O 3 + B 2 O} 3 is too large, is impaired balance of components glass composition, the glass is liable to devitrify reversed.

Al ₂ O ₃ is a component that enhances the Young's modulus and a component that suppresses phase separation and devitrification. The content of Al ₂ O ₃ is preferably 1 to 20%, 2 to 15%, particularly 3 to 10%. When the content of Al ₂ O ₃ is too small, easily Young's modulus is lowered and also the glass phase separation, easily devitrified. On the other hand, when the content of Al ₂ O ₃ is too large, the higher the viscosity at high temperature melting property tends to decrease.

B ₂ O ₃ is a component that enhances meltability and devitrification resistance, and is a component that improves the ease of scratching and increases strength. The content of B ₂ O ₃ is preferably 10 to 25%, 13 to 28%, 15 to 25%. When the content of B ₂ O ₃ is too small, meltability, devitrification resistance is liable to lower, also resistance tends to decrease with respect to hydrofluoric acid chemical. On the other hand, when the content of B ₂ O ₃ is too large, the Young's modulus, acid resistance tends to decrease.

Li ₂ O, Na ₂ O, and K ₂ O are alkali metal oxide components that contribute to the initial melting of the glass raw material while lowering the high-temperature viscosity to significantly increase the meltability. The content of Li ₂ O + Na ₂ O + K ₂ O is preferably 1.5 to 15%, 2 to 10%, in particular 3 to 6%. When li ₂ O ₊ content of Na 2 O + _{K 2} O is too small, the melting property tends to decrease. On the other hand, if the content of the alkali metal oxide is too large, the thermal expansion coefficient may be unduly high.

Li ₂ O is a component that contributes to the initial melting of the glass raw material while lowering the high-temperature viscosity to significantly increase the meltability. The content of Li ₂ O is preferably 0 to 5%, 0 to 3%, particularly 0 to 1.2%. If the content of Li ₂ O is too small, the meltability tends to decrease, and the thermal expansion coefficient may be unduly lowered. On the other hand, when the content of Li 2 _O is too large, easily glass phase separation.

Na ₂ O is a component that contributes to the initial melting of the glass raw material while lowering the high-temperature viscosity to significantly increase the meltability. It is a component for adjusting the thermal expansion coefficient. The content of Na ₂ O is preferably 0 to 10%, 0 to 8%, 1 to 5%, particularly 1 to 3%. If the content of Na ₂ O is too small, the meltability tends to be lowered, and the thermal expansion coefficient may be unduly lowered. On the other hand, when the content of Na 2 _O is too large, there is a concern that the thermal expansion coefficient becomes unduly high.

K ₂ O is a component that contributes to the initial melting of the glass raw material while lowering the high-temperature viscosity to significantly increase the meltability. It is a component for adjusting the thermal expansion coefficient. The content of K ₂ O is preferably 0.1 to 10%, 0.5 to 5%, particularly 1 to 3%. When the content of K 2 _O is too large, there is a concern that the thermal expansion coefficient becomes unduly high.

  CaO, SrO, and BaO are components that lower the high-temperature viscosity and increase the meltability. The content of CaO + SrO + BaO is preferably 0 to 8% and 0.1 to 5%. When there is too much content of CaO + SrO + BaO, it will become easy to devitrify glass.

  CaO is a component that lowers the high-temperature viscosity and increases the meltability. Further, among the alkaline earth metal oxides, since the introduced raw material is relatively inexpensive, it is a component that lowers the raw material cost. The content of CaO is preferably 0 to 8%, 0 to 5%, 0.01 to 1%, and 0.1 to 0.8%. When there is too much content of CaO, it will become easy to devitrify glass. In addition, when there is too little content of CaO, it will become difficult to receive the said effect.

  SrO is a component that improves devitrification resistance. The content of SrO is preferably 0 to 7%, 0 to 5%, 0 to 3%, particularly 0 to 1%. When there is too much content of SrO, it will become easy to devitrify glass.

  BaO is a component that increases devitrification resistance. The content of BaO is preferably 0 to 7%, 0.1 to 5%, 0.5 to 3%, and 1 to 1.5%. When there is too much content of BaO, it will become easy to devitrify glass.

  In addition to the above components, any other component may be introduced in a range that does not decrease the transmittance in a wavelength band of 250 nm or less. In addition, the content of other components other than the above components is preferably 10% or less, 5% or less, particularly 3% or less as a combined amount from the viewpoint of accurately enjoying the effects of the present invention.

ZrO ₂ is a component that enhances acid resistance, but if it is contained in a large amount in the glass composition, the glass tends to devitrify. Therefore, the content of ZrO ₂ is preferably 0.1% or less, more preferably 0.001 to 0.02%, and particularly preferably 0.0001 to 0.01%.

Fe ₂ O ₃ and TiO ₂ are components that reduce the transmittance in the deep ultraviolet region. The content of Fe ₂ O ₃ + TiO ₂ is preferably 0.0010% (10 ppm) or less and 0.00001 to 0.0007% (0.1 to 7 ppm). When the content of Fe _{2 O} 3 ₊ TiO 2 is too large, the glass is colored, the transmittance in the deep ultraviolet region is likely to decrease.

Fe ₂ O ₃ is a component that reduces the transmittance in the deep ultraviolet region. The content of Fe ₂ O ₃ is preferably 0.0010% (10 ppm) or less, 0.00001 to 0.0009% (0.1 to 9 ppm), 0.00001 to 0.0007% (0.1 to 7 ppm) ). When the content of Fe ₂ O ₃ is too large, the glass is colored, the transmittance in the deep ultraviolet region is likely to decrease.

Fe ions in iron oxide exist in the state of Fe ²⁺ or Fe ³⁺ . If the proportion of Fe ²⁺ is too small, the transmittance with deep ultraviolet rays tends to decrease. Therefore, the mass ratio of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) in the iron oxide contained in the ultraviolet ray transmitting glass of the present invention is preferably 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more. In particular, it is 0.5 or more.

TiO ₂ is a component that reduces the transmittance in the deep ultraviolet region. The content of TiO ₂ is preferably 0.0010% (10 ppm) or less, 0.00030% (3 ppm) or less, and 0.00001 to 0.00015% (0.1 to 1.5 ppm). When the content of TiO ₂ is too large, the glass is colored, the transmittance in the deep ultraviolet region is likely to decrease.

  F is a component that lowers the viscosity and increases the meltability. The content of F is preferably 0 to 2%, 0.1 to 1.5%, and 0.5 to 1.5%.

  As a clarifying agent, Cl may be added to 2000 ppm or less, preferably 1000 ppm.

  The shape of the ultraviolet transmissive glass of the present invention can be arbitrarily set. The shape of the ultraviolet ray transmitting glass of the present invention can be, for example, a flat plate shape, a curved plate shape, a straight tubular shape, a curved tubular shape, a rod shape, a spherical shape, a container shape, or a block shape.

  When the ultraviolet transmissive glass of the present invention is formed into a flat plate shape, for example, the main plane dimensions are preferably 100 mm × 100 mm or more, 200 mm × 200 mm or more, 400 mm × 400 mm or more, 1000 mm × 1000 mm or more, particularly 2000 mm × 2000 mm or more.

Moreover, as for the thickness of the ultraviolet transmissive glass of this invention, 0.1-3.0 mm is preferable, for example. With such a thickness, it can be suitably used for an ultraviolet lamp, a writing device for a magnetic recording medium, etc. Especially, in the precision instrument application, the thickness of the ultraviolet transmissive glass of the present invention is 0.2 to 1.0 mm. More preferably, the thickness is 0.3 to 0.6 mm. On the other hand, in the use of a large apparatus, the thickness of the ultraviolet light transmitting glass of the present invention is preferably 0.5 mm or more, more preferably 0.5 to 2.0 mm from the viewpoint of ensuring strength rigidity. In general, the ultraviolet transmittance decreases as the glass thickness increases. However, since the ultraviolet transmitting glass of the present invention has a high transmittance in a wavelength region of 250 nm or less, even if the thickness is increased compared to the conventional product. High transmittance can be maintained in the same wavelength region.

  The surface roughness Ra of the ultraviolet transmissive glass of the present invention is preferably 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, 2 nm or less, particularly 1 nm or less. If the surface roughness Ra of the surface is too large, the transmittance at deep ultraviolet rays tends to decrease.

  The ultraviolet transmissive glass of the present invention is prepared by, for example, preparing various glass raw materials to obtain a glass batch, melting the glass batch, clarifying and homogenizing the obtained molten glass, and molding the glass into a predetermined shape. Can be produced.

  In the manufacturing method of the ultraviolet transmissive glass of this invention, synthetic silica is used as at least one part of a glass raw material. In particular, it is preferable to use granular synthetic silica produced by a gas phase reaction method or a liquid phase reaction method. The average particle size of the synthetic silica is preferably 100 μm or less, more preferably 5 to 90 μm. The synthetic silica is, for example, amorphous silica, spherical silica, or a mixture thereof. Moreover, it is preferable that the ratio of the said synthetic silica to the whole silica source of a glass raw material is 90-100 mass%. By using such a raw material, the ultraviolet transmittance of the glass can be improved.

In the method for producing an ultraviolet transmitting glass of the present invention, it is preferable to use a reducing agent as a part of the glass raw material. If it does in this way, Fe3 ⁺ contained in glass will be reduced and the transmittance in deep ultraviolet rays will improve. As the reducing agent, materials such as wood powder, carbon powder, metallic aluminum, metallic silicon, and aluminum fluoride can be used, among which metallic silicon and aluminum fluoride are preferable.

In the manufacturing method of the ultraviolet transmissive glass of this invention, it is preferable to use metallic silicon as a part of glass raw material, The addition amount is 0.001-3 mass% with respect to the total mass of a glass batch, 0.005. ~ 2 mass%, 0.01-1 mass%, especially 0.03-0.1 mass% is preferable. When there is too little addition amount of a metal silicon, Fe3 ⁺ contained in glass will not be reduced, but the transmittance | permeability in deep ultraviolet rays will fall easily. On the other hand, when there is too much addition amount of metal silicon, there exists a tendency for glass to color brown.

It is also preferable to use aluminum fluoride (AlF ₃ ) as a part of the glass raw material, and the addition amount is 0.01 to 2% by mass, 0.05 to 1 in terms of F with respect to the total mass of the glass batch. 0.5 mass% and 0.3-1.5 mass% are preferable. On the other hand, when there is too much addition amount of aluminum fluoride, there exists a possibility that F gas may remain as a bubble in glass. If the amount of aluminum fluoride added is too small, Fe ³⁺ contained in the glass is not reduced, and the transmittance at deep ultraviolet rays tends to decrease.

  In the method for producing an ultraviolet light transmitting glass of the present invention, when the ultraviolet light transmitting glass is formed into a flat plate shape, it is preferably formed using a down draw method or an overflow down draw method. In the overflow down draw method, molten glass overflows from both sides of the heat-resistant bowl-shaped structure, and the overflowed molten glass is merged at the lower top end of the bowl-like structure, and then stretched downward to form a glass plate. It is a method to do. In the overflow down draw method, the surface to be the surface of the glass plate is not in contact with the bowl-shaped refractory and is molded in a free surface state. For this reason, it becomes easy to produce a thin glass plate, and variation in plate thickness can be reduced without polishing the surface. As a result, the manufacturing cost of the glass plate can be reduced. In addition, the structure and material of a bowl-shaped structure will not be specifically limited if a desired dimension and surface accuracy are realizable. In addition, the method of applying a force when performing downward stretch molding is not particularly limited. For example, a method may be adopted in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with glass, or a plurality of pairs of heat-resistant rolls are contacted only near the end face of the glass. It is also possible to adopt a method of stretching by stretching.

  In the method for producing an ultraviolet light transmitting glass of the present invention, when the ultraviolet light transmitting glass is formed into a tubular shape, it is preferably formed using a downdraw method, a bellow method, a Dunner method, or the like. The Danner method is a method of forming a glass tube by flowing and winding molten glass around the upper end side of a heat-resistant sleeve-like structure arranged in an inclined manner, and drawing the molten glass flowing down to the lower end side.

  As a forming method, in addition to the above, for example, a slot down method, a redraw method, a float method or the like can be adopted.

  Hereinafter, the present invention will be described based on examples. The following examples are merely illustrative. The present invention is not limited to the following examples.

  Table 1 shows examples of the present invention (sample Nos. 1-2) and comparative examples (samples Nos. 3-4).

  First, the glass batch which prepared the glass raw material shown to a table | surface so that it might become the glass composition in a table | surface was put into the platinum crucible, and it melted at 1550 degreeC for 4 hours. As synthetic silica, synthetic silica having an average particle diameter of 30 μm produced by a gas phase reaction method is used. As natural raw materials, natural silica raw materials having an average particle diameter of 100 to 120 μm, which have been refined and are generally used for glass production, are used. It was.

  About the obtained molten glass, it stirred using the platinum stirrer and homogenized. Next, the molten glass was poured onto a carbon plate and formed into a flat plate shape, and then slowly cooled from a temperature about 20 ° C. higher than the annealing point to room temperature at a rate of 3 ° C./min.

  The transmittance of each obtained sample was measured. The transmittance is a value obtained by measuring the spectral transmittance in the thickness direction using a double beam spectrophotometer. As a measurement sample, one having both thicknesses shown in Table 1 polished to an optically polished surface (mirror surface) was used. In addition, when surface roughness Ra of the surface of these measurement samples was measured by AFM, it was 0.5 to 1.0 nm in a measurement region of 10 μm × 10 μm.

  FIG. 1 shows a sample No. 5 having a thickness of 0.5 mm at a wavelength of 200 to 400 nm. It is the transmittance | permeability curve of 1-3. As is clear from Table 1 and FIG. 1, the glass of the example had a higher ultraviolet transmittance in the wavelength region of 250 nm or less than the glass of the comparative example.

  In the above embodiment, molten glass was poured out and formed into a flat plate shape. However, when produced on an industrial scale, it was formed into a flat plate shape by an overflow down draw method or the like, and both surfaces were unpolished. It is preferable to use. Moreover, when forming in a tubular shape, it is preferable to form the tubular shape by a downdraw method, a Dunner method, or the like.

  The ultraviolet transmissive glass of the present invention is suitable, for example, as a glass provided in a germicidal lamp, a magnetic recording medium read / write device, and other devices using ultraviolet rays.

Claims (8)

An ultraviolet transmissive glass characterized by T ₂₀₀ ≧ 75, where T ₂₀₀ is a transmittance (%) at a thickness of 0.5 mm and a wavelength of 200 nm. When the thickness 0.5 mm, the transmittance at a wavelength of 250nm (%) was the _{T 250,}
The ultraviolet transmissive glass according to claim 1, wherein T ₂₀₀ / T ₂₅₀ ≧ 0.75 or more. The ultraviolet ray transmitting glass according to claim 1, wherein T ₂₂₀ ≧ 80 when the transmittance (%) at a thickness of 0.5 mm and a wavelength of 220 nm is T ₂₂₀ .   The ultraviolet ray transmitting glass according to any one of claims 1 to 3, which is a plate or tube having a thickness of 0.1 to 3.0 mm. As a glass composition, in _{mass%, SiO 2 55~75%, Al} 2 O 3 1~10%, B 2 O 3 10~30%, CaO 0~5%, BaO 0~5%, Li 2 O + Na 2 O + K _{2 O 1.0~15%, TiO 2 0~0.001} %, containing _Fe 2 O 3 _0~0.001%, UV transmittance glass according to claim 1.   6. The method for producing an ultraviolet transmissive glass according to claim 1, wherein synthetic silica is used as at least a part of the glass raw material.   The method for producing an ultraviolet transmissive glass according to claim 6, wherein the synthetic silica is granular silica produced by a gas phase reaction method or a liquid phase reaction method. The synthetic silica has an average particle size of 100 μm or less,
The manufacturing method of the ultraviolet transmissive glass of Claim 6 or 7 whose ratio of the said synthetic silica to the total silica source of the said glass raw material is 90-100 mass%.