JP2008088021A - Glass composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass composition exhibiting high radiation shielding performance in a glass system consisting essentially of a B<SB>2</SB>O<SB>3</SB>component and La<SB>2</SB>O<SB>3</SB>component. <P>SOLUTION: The glass composition contains 20-35% B<SB>2</SB>O<SB>3</SB>, 16-50% La<SB>2</SB>O<SB>3</SB>, 0-30% WO<SB>3</SB>, 0-25% Gd<SB>2</SB>O<SB>3</SB>and/or Dy<SB>2</SB>O<SB>3</SB>and/or Lu<SB>2</SB>O<SB>3</SB>, 0-5% M<SB>2</SB>O<SB>3</SB>(M is one or more kinds selected from a group of Al, Ga and In) and 0-10% BaO by mass expressed in terms of oxide and has ≥0.05 mmPb/mm lead equivalent to X-ray of 150 kV. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a glass composition, and more particularly to a glass composition having an ability to shield radiation such as X-rays and γ-rays.

  In facilities that handle radiation such as X-rays and γ-rays, radiation shielding glass is used to facilitate work and to protect people engaged in work from radiation. Such glass is required to have high transparency in the visible region and excellent shielding ability (absorption ability) against radiation. Since shielding ability is proportional to the mass absorption coefficient and density of glass, lead glass with high density has been used for a long time.

  However, because the lead component is a harmful substance, radiation shielding glass containing a large amount of the lead component is required to take measures for environmental measures when manufacturing, processing, and disposing of it. Had a problem. In addition, radiation shielding glass containing a large amount of lead component has low chemical durability, so it easily reacts with water and detergent adhering to the glass surface to remove dirt, and `` burns '' occur on the glass surface. It has also been a problem that the transparency of the glass is significantly lowered due to the “yake”.

  Further, since the surface hardness is low, the surface is easily scratched in processing steps such as polishing and cutting, and the glass may be broken due to the scratch.

Accordingly, a radiation shielding glass containing no lead component has been developed. Patent Document 1 below is an SiO ₂ —BaO-based glass that essentially does not contain a lead component and has a density of 3.01 g. Radiation shielding glass that is greater than / cm ³ is disclosed. Patent Document 2 below essentially contains no lead component, contains SiO ₂ and Al ₂ O _{3, and} has a lead equivalent to 100 kV X-rays of 0.03 mmPb / mm or more. A radiation shielding glass is disclosed.
Japanese Patent Laid-Open No. 6-127773 Japanese Patent Laid-Open No. 2003-315489

  However, since the radiation shielding glasses of Patent Documents 1 and 2 have considerably lower shielding ability than lead glass, their use is limited mainly to places where radiation with low energy is handled.

The present invention has been made in view of the problems described above, B ₂ O ₃ component in the glass system with La ₂ O ₃ component as essential components, to provide a glass composition having a high radiation shielding performance.

As a result of intensive studies to solve the above problems, the present inventors made B ₂ O ₃ component and La ₂ O ₃ component as essential components, more preferably WO ₃ , M ₂ O ₃ (M is Al, 1 or more selected from the group consisting of Ga and In.), Gd ₂ O ₃ and / or Dy ₂ O ₃ and / or Lu ₂ O ₃ , and a glass composition containing any one of BaO components Was found to have excellent radiation shielding ability similar to that of lead glass, and higher surface hardness and transparency than lead glass, thereby completing the present invention. More specifically, the present invention provides the following.

(1)% by mass on the oxide _basis, B 2 _{O 3} and 20~35%, _La 2 _{O 3} and 16 to 50%, WO ₃ and 0~30%, _Gd 2 _{O 3} and / or _Dy 2 _{O 3} And / or Lu ₂ O ₃ is 0 to 25%, M ₂ O ₃ (M is one or more selected from the group consisting of Al, Ga and In) is 0 to 5%, and BaO is 0 to 10%. %, A glass composition having a lead equivalent to 150 kV X-rays of 0.05 mmPb / mm or more.

According to this aspect, since B ₂ O ₃ , La ₂ O ₃ and WO ₃ are contained as glass components, the glass composition is excellent in glass melting property, stability and devitrification resistance, and has a high density. It becomes. Moreover, by further containing Gd ₂ O ₃ , Dy ₂ O ₃ , Lu ₂ O ₃ and BaO in addition to La ₂ O ₃ , the density of the glass is increased and the surface strength (surface hardness) is further improved. And higher radiation shielding ability can be easily obtained. Moreover, (the _M Al, Ga, indicating one or more members selected from the group consisting of In.) M 2 _{O 3} by containing, chemical durability and surface strength (surface hardness) is improved . For this reason, in addition to the essential components of B ₂ O ₃ and La ₂ O ₃ , the glass composition of the present invention is more excellent in meltability and stability and has high radiation by containing an appropriate amount of the above components as optional components. It has shielding ability and high surface hardness. Moreover, since the lead equivalent with respect to the 150-kV X-ray is 0.05 mmPb / mm or more, it can be used suitably also when handling high energy radiation.

(2) The glass composition according to (1), wherein the content of WO ₃ is 0.5% to 30% by mass% based on an oxide.

Since the WO ₃ component is a component that is effective in improving the radiation shielding ability, it is more excellent in the radiation shielding effect.

(3) The glass composition according to (1) or (2), wherein the density is 4.0 g / cm ³ or more.

According to this aspect, since the density is 4.0 g / cm ³ or more, high radiation shielding ability can be easily obtained.

  (4) The glass composition according to any one of (1) to (3), wherein the transmittance at a wavelength of 400 nm is 40% or more and the transmittance at a wavelength of 550 nm is 80% or more in the glass composition having a thickness of 10 mm. object.

  According to this aspect, since the transmittance at a wavelength of 400 nm is 40% or more and the transmittance at a wavelength of 550 nm is 80% or more, a glass composition that is highly transparent in the visible region and easy to observe inside can be easily obtained. Can be provided.

(5) The glass composition according to any one of (1) to (4), wherein the Knoop hardness of the glass is 500 N / mm ² or more.

According to this aspect, since the Knoop hardness (HK) is 500 N / mm ² or more, the glass surface is hardly damaged and a glass composition having high mechanical strength can be easily provided.

(6)% by mass on the oxide basis, of SiO ₂ 0%, the total amount of GeO ₂ and / or _P 2 O5 0%, 0 to _30% of _ZnO, Y 2 _{O 3} and / or Yb ₂ O ₃ and / or _Tb 2 _{O 3} and _0~25%, Rn 2 O (Rn is Li, Na, K, indicating one or more members selected from the group consisting of Cs.) 0-10% RO (R represents one or more selected from the group consisting of Sr, Ca and Mg) is 0 to 10%, TiO ₂ is 0 to 10%, ZrO ₂ is 0 to 10%, SnO ₂ is 0 to 0%. 10%, Nb ₂ O ₅ from 0 to 20%, Ta ₂ O ₅ from 0 to 30%, Ce ₂ O ₃ from 0 to 5%, the total amount of Sb ₂ O ₃ and As ₂ O ₃ from 0 to 5% The glass composition according to any one of (1) to (5), which contains each component in the range of.

SiO ₂ and / or GeO ₂ , P ₂ O ₅ , ZnO, Y ₂ O ₃ and / or Yb ₂ O ₃ and / or Tb ₂ O ₃ , RO (R is selected from the group consisting of Sr, Ca, Mg) By including a component such as one or more), it is possible to easily produce a stable glass composition having further excellent devitrification resistance. _Further, Rn 2 O (Rn represents Li, Na, K, one or more selected from the group consisting of Cs.), By containing components such as _Ce 2 _{O 3,} coloration can be prevented by irradiation . _Further, by containing a component of TiO 2, ZrO ₂ or the like, and more further improve the hardness of the surface of the glass. _Further, by containing a component such as _{SnO 2, Nb 2 O 5,} Ta 2 O 5, it is improved even more radiation shielding capability.

  (6) A radiation shielding glass comprising the glass composition according to any one of (1) to (5).

  According to this aspect, the glass composition has a radiation shielding ability of 0.05 mm Pb / mm or more with a lead equivalent to 150 kV of X-rays, high transparency in the visible range, excellent transparency, and surface hardness. Since it is high, it is more suitable as a radiation shielding glass.

The glass composition of the present invention contains B ₂ O ₃ and La ₂ O ₃ as essential components, and has good melting and stability of glass and resistance to devitrification. Therefore, it is possible to provide a glass composition having a radiation shielding ability comparable to that of a glass containing a lead component even without containing a lead component. Thereby, the glass composition of this invention can be used as radiation shielding glass.

  Next, specific embodiments of the glass composition of the present invention will be described.

[Glass component]
The composition range of each component which comprises the glass composition of this invention is described below. In the present specification, the content of each component is expressed in mass% unless otherwise specified. In addition, all the glass compositions represented by% in this-application specification are represented by the mass% on the basis of an oxide. Here, the “oxide standard” means that the oxide, nitrate, etc. used as a raw material of the glass component of the present invention are all decomposed and changed into oxides when melted, and the mass of the generated oxide Is a composition in which each component contained in the glass is described with the total of 100% by mass.

<About essential and optional components>
The B ₂ O ₃ component is an essential component for obtaining highly transparent glass without devitrification in the glass composition of the present invention containing a large amount of rare earth oxides such as La ₂ O _3. If the amount is too large, the radiation shielding ability and chemical durability of the glass tend to be lowered, and if too small, the stability of the glass tends to be lowered. Therefore, the lower limit is 20%, preferably 21%, and the upper limit is 35%, preferably 30%, and most preferably 28%.

The SiO ₂ component is a glass-forming oxide, and is an optional component that has the effect of improving the stability against devitrification and improving the chemical durability and surface hardness of the glass. The upper limit of the amount is 10%, preferably 9%, most preferably 8%.

Both the B ₂ O ₃ component and the SiO ₂ component are glass-forming oxides. Therefore, even if B ₂ O ₃ alone is introduced into the glass, the object of the present invention can be achieved. However, the simultaneous use of SiO ₂ improves the meltability, stability and chemical durability of the glass. Therefore, it is preferable to use them simultaneously.

The La ₂ O ₃ component is an essential component for achieving the object of the present invention in order to increase the density of the glass and impart high radiation shielding ability to the glass. It also has the effect of improving chemical durability and surface hardness. In particular, in terms of improving chemical durability, La ₂ O ₃ is more effective than Gd ₂ O ₃ , Dy ₂ O ₃ , and Lu ₂ O ₃ described later, and is effective in a smaller amount. Therefore, it is preferable to use La ₂ O ₃ with priority. In particular, when the amount is less than 16%, the radiation shielding ability and chemical durability of the glass tend to be insufficient. Moreover, when it exceeds 50%, devitrification resistance will worsen. Accordingly, the lower limit is 16%, preferably 20%, most preferably 25%, and the upper limit is 50%, preferably 45%, most preferably 40%.

Gd ₂ O ₃ and / or Dy ₂ O ₃ and / or Lu ₂ O ₃ , Y ₂ O ₃ and / or Yb ₂ O ₃ and / or Tb ₂ O ₃ component is not essential, but La ₂ O ₃ component It is a useful component for achieving the object of the present invention because it increases the density of the glass and imparts high radiation shielding ability to the glass. However, in addition to La ₂ O ₃ , rare earth oxidation of Gd ₂ O ₃ and / or Dy ₂ O ₃ and / or Lu ₂ O ₃ , Y ₂ O ₃ and / or Yb ₂ O ₃ and / or Tb ₂ O ₃ If an excessive amount is contained, the stability of the glass tends to be impaired, and if it is too small, it becomes difficult to satisfy the object of the present invention. Thus, the amount of Gd ₂ O ₃ and / or Dy ₂ O ₃ and / or Lu ₂ O ₃ , Y ₂ O ₃ and / or Yb ₂ O ₃ and / or Tb ₂ O ₃ is 25%, preferably 23%, Most preferably, the upper limit is 20%. Of these components, Gd ₂ O ₃ and Lu ₂ O ₃ are particularly effective, and therefore it is preferable to include one or both of them.

The WO ₃ component is preferably added because it is highly effective in improving the stability and chemical durability of the glass and the radiation shielding ability that is the object of the present invention. However, if the amount is too large, the stability of the glass is improved. It tends to decline. In order to obtain a good effect, the upper limit is 30%, preferably 25%, most preferably 20%, and the lower limit is 0.5%, more preferably 2%, most preferably 3%.

M ₂ O ₃ (M represents at least one selected from the group consisting of Al, Ga, and In) is not essential, but 5 components are used to improve the meltability and stability of the glass. % May be contained. If it exceeds 5%, the stability of the glass tends to deteriorate. Preferably it is 3% or less.

  The BaO component is effective in improving the meltability, stability and radiation shielding ability of glass. Although it is a component that can be arbitrarily added, if the amount is too large, the stability of the glass tends to be lowered. Therefore, the upper limit of the content is 10%, preferably 8%, and most preferably 5%.

The components of GeO ₂ and P ₂ O ₅ are glass-forming oxides and are particularly useful for obtaining a highly transparent glass without devitrification. Although it is a component that can be arbitrarily added, if the amount is too large, the radiation shielding ability of the glass tends to be lowered, and if too small, the stability of the glass tends to be lowered. Therefore, the upper limit of the total amount of these components is preferably 10%, more preferably 5%.

Particularly GeO ₂ component, since the same function as the SiO ₂ component, and it is possible to replace some or all of the SiO ₂ component, because it is expensive, more than 10% the upper limit of the content of Preferably, it is 5% or less, more preferably 3% or less.

The _P 2 _{O 5} component, since the same function as SiO ₂ or _B 2 _{O 3} component, it is possible to replace some or all of the SiO ₂ or _B 2 _{O 3} component. However, if the amount is too large, the stability of the glass is deteriorated. Therefore, the upper limit of the content is preferably 10%, more preferably 5%, and most preferably 3%.

  The ZnO component is an effective component for improving the meltability of glass. Although it is a component that can be arbitrarily added, if the amount is too large, devitrification tends to occur, and the radiation shielding ability tends to be lowered. Therefore, the upper limit of the content is preferably 30%, more preferably 25%, and most preferably 20%.

  The RO component (R represents one or more selected from the group consisting of Sr, Ca, and Mg) is a component that is effective in improving the meltability and stability of the glass. Although it is a component that can be optionally added, if the amount is too large, the stability of the glass is easily lowered. Therefore, the upper limit of the content is preferably 10%, more preferably 8%, and most preferably 5%.

  The SrO component is effective in improving the meltability, stability and radiation shielding ability of the glass, but if the amount is too large, the stability of the glass will be lowered. Therefore, the upper limit of the content is preferably 10%, more preferably 8%, and most preferably 5%.

  The CaO component is an effective component for improving the meltability of the glass. However, if the amount is too large, devitrification tends to occur, and the radiation shielding ability tends to be lowered. Therefore, the upper limit of the content is preferably 10%, more preferably 8%, and most preferably 5%.

  The MgO component is an effective component for improving the meltability of the glass. However, if the amount is too large, devitrification is likely to occur, and the radiation shielding ability tends to be lowered. Therefore, the upper limit of the content is preferably 10%, more preferably 5%, and most preferably 3%.

The Rn ₂ O component (Rn represents one or more selected from the group consisting of Li, Na, K, and Cs) is effective in improving the meltability and stability of the glass and is colored by irradiation. It is a component that is also effective for prevention. Although it is a component that can be added arbitrarily, if the amount is too large, the stability of the glass tends to deteriorate, and the radiation shielding ability tends to decrease greatly. Therefore, the upper limit of the total amount is preferably 10%, more preferably 5%, and most preferably 3%. Further, when two or more Rn ₂ O components are combined, a large effect can be easily obtained by preventing coloring due to radiation irradiation.

The Li ₂ O component is a component that improves the meltability of the glass. However, if the amount is too large, devitrification is likely to occur, and the radiation shielding ability is also likely to be reduced. Therefore, the upper limit of the content is preferably 10%, more preferably 5%, and most preferably 3%.

The Na ₂ O component is a component that improves the meltability of the glass. However, if the amount is too large, devitrification tends to occur, and the radiation shielding ability tends to decrease. Therefore, the upper limit of the content is preferably 10%, more preferably 5%, and most preferably 3%.

The K ₂ O component is a component that improves the meltability of the glass. However, if the amount is too large, devitrification tends to occur, and the radiation shielding ability tends to decrease. Therefore, the upper limit of the content is preferably 10%, more preferably 8%, and most preferably 5%.

The Cs ₂ O component is a component that improves the meltability of the glass and further contributes to the improvement of the radiation shielding ability. However, if the amount is too large, devitrification is likely to occur. Therefore, the upper limit of the content is preferably 10%, more preferably 8%, and most preferably 5%.

The TiO ₂ component is a component that is effective in improving the stability of the glass and the hardness of the surface. Although it is a component that can be optionally added, if the amount is too large, the stability of the glass tends to be low. Therefore, the upper limit of the content is preferably 10%, more preferably 8%, and most preferably 5%.

The ZrO ₂ component is a component that is effective in improving the radiation shielding ability and the hardness of the glass surface. Although it is a component that can be optionally added, if the amount is too large, the stability of the glass is easily lowered. Therefore, the upper limit of the content is preferably 10%, more preferably 8%, and most preferably 5%.

The SnO ₂ component is a component that is effective in improving the radiation shielding ability. Although it is a component that can be optionally added, if the amount is too large, the stability of the glass tends to be lowered. Therefore, the upper limit of the content is preferably 10%, more preferably 5%, and most preferably 3%.

The Nb ₂ O ₅ component is a component that is effective in improving the radiation shielding ability. Although it is a component that can be arbitrarily added, if the amount is too large, the stability of the glass tends to decrease. Therefore, the upper limit of the content is preferably 20%, more preferably 15%, and most preferably 10%.

The Ta ₂ O ₅ component is a component that is effective in improving the radiation shielding ability. Although it is a component that can be optionally added, if the amount is too large, the stability of the glass tends to be lowered. Therefore, the upper limit of the content is preferably 30%, more preferably 20%, and most preferably 10%.

The Ce ₂ O ₃ component is a component having an effect of preventing coloring due to radiation irradiation. Although it is a component that can be added arbitrarily, if the amount is too large, the absorption edge of the glass shifts to the longer wavelength side, and the transparency in the visible region may be reduced. Therefore, the upper limit of the content is preferably 5% or less, more preferably 3% or less, and most preferably 1% or less.

Sb ₂ O ₃ and As ₂ O ₃ components are components that can be optionally added for defoaming of glass melting. The total amount of Sb ₂ O ₃ and As ₂ O ₃ is sufficiently effective at 5% or less. Moreover, As ₂ O ₃ needs to take measures for environmental measures when manufacturing, processing, and discarding glass. Therefore, the upper limit of the total amount of Sb ₂ O ₃ and As ₂ O ₃ is preferably 5%, more preferably 3%, and most preferably 1%.

<About ingredients that should not be included>
Other components can be added as needed within a range not impairing the properties of the glass composition of the present invention. However, even when each transition metal component excluding Ti, such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, is contained alone or in combination with a small amount, the glass is colored and visible. Causes absorption at specific wavelengths in the region. Therefore, it is preferable that the glass composition of the present invention does not contain substantially.

  Since each component of Pb, Th, Cd, Tl, and Os has tended to refrain from being used as a harmful chemical material in recent years, not only the glass manufacturing process, but also the processing measures and environmental measures from disposal to commercialization. The above measures are required. Therefore, it is preferable not to include substantially when importance is attached to environmental influences.

  The fluorine component has a problem of volatilizing when the glass is melted, and further causes the occurrence of striae. Therefore, it is preferable that the fluorine composition is not substantially contained in the glass composition of the present invention.

The glass composition of the present invention containing the above composition can have a density of 4.0 g / cm ³ or more. A more preferable density range is 4.5 g / cm ³ or more. For this reason, it is excellent in radiation shielding ability.

  Further, the glass composition of the present invention has high transparency in the visible region, and the transmittance at 400 nm is 40% or more and the transmittance at 550 nm is 80% or more in a glass composition having a thickness of 10 mm. For this reason, when used as a shielding window, it is easy to observe the inside.

The glass composition of the present invention has a Knoop hardness (HK) of 500 N / mm ² or more, more preferably 550 N / mm ² or more, and most preferably 600 N / mm ² or more. For this reason, the surface is not easily damaged when the glass composition is processed and polished. Here, Knoop hardness is a kind of hardness indication, which is measured using a diamond indenter with diamond-shaped compression marks (marks) on the test piece. It measures the hardness of metals, glass, ceramics, etc. Used to do. This Knoop hardness is calculated by the following formula 1 when a diamond rhombus indenter (diagonal angles 172 ° 30 'and 130 °) is pressed with a load of 0.98 N for 15 seconds and a dent is made on the flat polished surface of the sample. Is done.

  In the present invention, the radiation shielding ability is expressed in terms of lead equivalent. The lead equivalent is represented by the thickness of the lead plate having the same X-ray shielding ability, and the larger this value, the better the radiation shielding ability. About the glass composition of this invention, the lead equivalent with respect to 150-kV X-rays calculated | required by converting the lead equivalent measured by the method according to JISZ4501 into thickness 1mm. The lead equivalent of the glass composition of the present invention is preferably 0.03 mmPb / mm or more, and more preferably 0.05 mmPb / mm or more.

As described above, the glass composition of the present invention has a lead equivalent to 150 kV X-ray of 0.05 mmPb / mm or more, and a glass composition having a thickness of 10 mm has a transmittance of 40% or more at 400 nm and a transmission at 550 nm. The rate is 80% or more, and the Knoop hardness is 500 N / mm ² or more, and the transparency in the visible range is high, so the radiation shielding ability is high, and the surface strength (surface hardness) and transparency are excellent. Suitable as radiation shielding glass.

[Production method]
Although the glass composition of this invention will not be specifically limited if it is a method of manufacturing a normal glass, For example, it can manufacture with the following method. A predetermined amount of each starting material (oxide, carbonate, nitrate, phosphate, sulfate, fluoride salt, etc.) is weighed and mixed uniformly. The mixed raw materials are put into a quartz crucible, alumina crucible, platinum crucible, platinum alloy crucible or iridium crucible and melted at 1100 to 1550 ° C. for 1 to 10 hours in a melting furnace. Then, after stirring and homogenizing, the temperature is lowered to an appropriate temperature and cast into a mold or the like to produce glass.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example and a comparative example, this invention is not limited to a following example.

[Examples 1 to 10]
The starting materials were weighed in the compositions of Examples 1 to 10 shown in Table 1 (unit: mass%), mixed uniformly, and then melted at 1250 to 1400 ° C. for 2 to 4 hours using a platinum crucible. The glass was produced.

[Comparative Example 1]
As Comparative Example 1, a lead-containing glass used as a radiation shielding glass was produced as follows.

  The starting materials were weighed so as to have the composition of Comparative Example 1 shown in Table 1, mixed uniformly, and then first melted at 1300 ° C. for 1 hour and 20 minutes using a quartz crucible to prepare cullet. Thereafter, the cullet was put in a platinum crucible and melted at 1320 ° C. for 2 hours and 30 minutes, and then cast into a mold to produce glass.

  Table 1 shows the density, Knoop hardness (HK), transparency, and lead equivalent of Examples 1 to 6 and Comparative Example 1. The density was measured by the Archimedes method. About the transmittance | permeability measurement, it carried out according to Japan Optical Glass Industry Association standard JOGIS02. In the present invention, the transmittance is shown not the degree of coloring. Specifically, a face-to-face parallel polished product having a thickness of 10 ± 0.1 mm was measured for a spectral transmittance of 200 to 800 nm in accordance with JIS Z 8722. The transmittance at wavelengths of 400 nm and 550 nm was determined and used as an index representing the transparency of the present invention. Knoop hardness (HK) was measured according to the Japan Optical Glass Industry Association Standard JOGIS09. The lead equivalent was measured at a tube voltage of 150 kV according to JIS Z 4501.

  FIG. 1 shows the spectral transmittance curves of Examples 1 and 2. The horizontal axis represents wavelength (nm) and the vertical axis represents spectral transmittance (%). These transmittances include reflection loss.

  As shown in FIG. 1, it can be seen that the glass of the present invention has high transparency over the entire visible range.

According to Table 1, the Knoop hardness (HK) of the glass of the present invention is 610 N / mm ² or more, and it can be seen that the surface hardness is superior to the comparative example.

Also shows the change due to the content of WO ₃ of Namarito amount in FIG.

As shown in FIG. 2, it can be seen that the lead equivalent increases with increasing WO ₃ content. From this, it can be seen that WO ₃ is effective in improving radiation shielding. Moreover, according to Table 1, it can be seen that the glass of the present invention has a high lead equivalent, 0.19 mm Pb / mm or more, and has a radiation shielding ability comparable to the lead glass of Comparative Example 1.

It is a figure which shows the spectral transmittance curve in the glass of Example 1 and 2. Is a diagram showing a change by WO ₃ content of lead equivalent.

Claims (7)

% By mass on the oxide _basis, B 2 _{O 3} and 20~35%, _La 2 _{O 3} and 16 to 50%, WO ₃ and 0~30%, _Gd 2 _{O 3} and / or _Dy 2 _{O 3} and / or Lu ₂ O ₃ is 0 to 25%, M ₂ O ₃ (M is at least one selected from the group consisting of Al, Ga and In) is 0 to 5%, and BaO is 0 to 10%. And a glass composition having a lead equivalent with respect to 150 kV X-rays of 0.05 mmPb / mm or more. The glass composition according to claim 1, wherein the content of WO ₃ is 0.5% to 30% by mass% based on an oxide. The glass composition according to claim 1, wherein the density is 4.0 g / cm ³ or more.   The glass composition according to any one of claims 1 to 3, wherein in the glass composition having a thickness of 10 mm, the transmittance at a wavelength of 400 nm is 40% or more and the transmittance at a wavelength of 550 nm is 80% or more. The glass composition according to any one of claims 1 to 4, wherein the glass has a Knoop hardness of 500 N / mm ² or more. SiO ₂ 0-10%, GeO ₂ and / or P ₂ O ₅ total amount 0-10%, ZnO 0-30%, Y ₂ O ₃ and / or Yb ₂ in mass% on oxide basis. 0 to 25% of O ₃ and / or Tb ₂ O ₃ , Rn ₂ O (Rn represents one or more selected from the group consisting of Li, Na, K and Cs) 0 to 10%, RO ( R represents one or more selected from the group consisting of Sr, Ca and Mg.) 0-10%, TiO ₂ 0-10%, ZrO ₂ 0-10%, SnO ₂ 0-10% Nb ₂ O ₅ is 0 to 20%, Ta ₂ O ₅ is 0 to 30%, Ce ₂ O ₃ is 0 to 5%, and the total amount of Sb ₂ O ₃ and As ₂ O ₃ is 0 to 5%. The glass composition according to claim 1, comprising each component.   A radiation shielding glass comprising the glass composition according to claim 1.

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