JP2021073163A - Optical glass - Google Patents

Abstract

To obtain an optical glass having a ray transmittance in a visible range required for an optical glass and showing little reduction in the ray transmittance in the visible range even when irradiated with radiation.SOLUTION: A glass having the following properties is provided: the glass comprises, by mass% on an oxide basis, SiO2 component by 30 to 75%, CeO2 component by over 0% and 5% or less, Al2O3 component by 0 to 8%, B2O3 component by 0 to 18%, R2O component by 0 to 20% (where R represents at least one element selected from Li, Na and K), and MO component by 0 to 50% (where M represents at least one element selected from Mg, Ca, Sr, Ba and Zn); a wavelength [λ80] where the ray transmittance of a 10-mm thick sample of the glass is 80% is 390 nm or more; and when a 10-mm thick sample of the glass is irradiated with cobalt 60 gamma rays to have an absorption dose of 0.5 MGy, changes [Δλ5] in a wavelength [λ5] where the ray transmittance of the sample is 5%, due to the irradiation, is 20 nm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to optical glass. In particular, the present invention relates to a radiation-resistant optical glass having a small decrease in light transmittance in the visible region even when exposed to irradiation with radiation such as γ-rays and X-rays.

In recent years, there has been an increasing demand for the use of cameras, sensors, etc. in spaces with high radiation doses, such as in outer space and nuclear facilities. Optical glass is used for these cameras and sensors. However, when the conventional optical glass is exposed to radiation, the light transmittance in the visible region is lowered and the conventional optical glass is colored. Therefore, a camera or sensor using conventional optical glass can perform its function only for a short time in a space where the irradiation dose of radiation is high.

Patent Document 1 discloses a glass for medical containers whose coloring is suppressed even when sterilized by irradiation, but even before irradiation, light transmittance in the visible region required for optical glass is disclosed. Has no rate.
Japanese Unexamined Patent Publication No. 2014-55092

The problem to be solved by the present invention is to obtain an optical glass having a light transmittance in the visible region required as an optical glass and having a small decrease in the light transmittance in the visible region even when irradiated with radiation. That is.

As a result of intensive test and research, the present inventor has found that a glass having a specific composition and using a specific physical property as an index can obtain a glass that solves the above problems, and has completed the present invention. It was. Specifically, the present invention provides the following.

(Structure 1)
By mass% based on oxide,
SiO ₂ component 30-75%,
CeO ₂ component more than 0% and less than 5%,
Al ₂ O ₃ component 0-8%,
B ₂ O ₃ component 0-18%,
The R ₂ O component 0-20% (wherein, R represents Li, 1 or more selected from Na and K.),
Contains 0 to 50% of MO component (however, M is one or more selected from Mg, Ca, Sr, Ba and Zn).
When a sample with a thickness of 10 mm _{is irradiated with cobalt 60 gamma rays so that the wavelength [λ 80} ] at which the light transmittance is 80% is 390 nm or more and the absorbed dose is 0.5 MGy, before and after the irradiation, An optical glass in which the change [Δλ _{5 ] of the wavelength [λ 5} ] at which the light transmittance of a sample having a thickness of 10 mm is 5% is 20 nm or less.
(Structure 2)
By mass% based on oxide,
SiO ₂ component 30-45%,
CeO ₂ component 0.5-3%,
Al ₂ O ₃ component 1-8%,
B ₂ O ₃ component 3-18%,
The R ₂ O component 0-10% (wherein, R represents Li, 1 or more selected from Na and K.),
The optical glass according to configuration 1, which contains 35 to 50% of the MO component (where M is one or more selected from Mg, Ca, Sr, Ba and Zn).
(Structure 3)
By mass% based on oxide,
SiO ₂ component 65-75%,
CeO ₂ component 0.5-3%,
B ₂ O ₃ component 7 to 15%,
The R ₂ O component 10-20% (where, R represents Li, 1 or more selected from Na and K.),
The optical glass according to configuration 1, which contains 0 to 5% of an MO component (where M is one or more selected from Mg, Ca, Sr, Ba and Zn).
(Structure 4)
By mass% based on oxide,
40-58% of SiO _{2 component,}
CeO ₂ component 0.5-3%,
B ₂ O ₃ component 0-3%,
The R ₂ O component 5-15% (wherein, R represents Li, 1 or more selected from Na and K.),
The optical glass according to configuration 1, which contains 30 to 50% of a PbO component.
(Structure 5)
The optical glass according to any one of configurations 1 to 4, wherein the wavelength [[λ80]] at which the light transmittance of a sample having a thickness of 10 mm is 80% is 490 nm or less.
(Structure 6)
The optical glass according to any one of configurations 1 to 5, wherein the refractive index [nd] is 1.50 or more and 1.65 or less, and the Abbe number [νd] is 35 or more and 65 or less.

According to the present invention, it has the light transmittance in the visible region required for optical glass, and even when it is irradiated with radiation, it transmits light in the visible region as compared with before it is exposed to radiation. It is possible to obtain an optical glass with a small decrease in rate.

6 is a spectral transmittance curve of the optical glass according to Example 1-2 before and after irradiation with cobalt-60 gamma rays. The thickness of the sample is 10 mm. The solid line shows the spectral transmittance before irradiation, and the broken line shows the spectral transmittance after irradiation. It is a spectral transmittance curve of the optical glass which concerns on Example 1-3 before and after irradiation with cobalt-60 gamma ray. The thickness of the sample is 10 mm. The solid line shows the spectral transmittance before irradiation, and the broken line shows the spectral transmittance after irradiation. 3 is a spectral transmittance curve of the optical glass according to Example 2-2 before and after irradiation with cobalt-60 gamma rays. The thickness of the sample is 10 mm. The solid line shows the spectral transmittance before irradiation, and the broken line shows the spectral transmittance after irradiation. 3 is a spectral transmittance curve of the optical glass according to Example 3-2 before and after irradiation with cobalt-60 gamma rays. The thickness of the sample is 10 mm. The solid line shows the spectral transmittance before irradiation, and the broken line shows the spectral transmittance after irradiation. 6 is a spectral transmittance curve of the optical glass according to Example 3-3 before and after irradiation with cobalt-60 gamma rays. The thickness of the sample is 10 mm. The solid line shows the spectral transmittance before irradiation, and the broken line shows the spectral transmittance after irradiation. 6 is a spectral transmittance curve of the optical glass according to Comparative Example 1 before and after irradiation with cobalt-60 gamma rays. The thickness of the sample is 10 mm. The solid line shows the spectral transmittance before irradiation, and the broken line shows the spectral transmittance after irradiation. 6 is a spectral transmittance curve of the optical glass according to Comparative Example 2 before and after irradiation with cobalt-60 gamma rays. The thickness of the sample is 10 mm. The solid line shows the spectral transmittance before irradiation, and the broken line shows the spectral transmittance after irradiation.

Hereinafter, the optical glass of the present invention will be described in detail. In this specification, the content of each component is expressed in mass% based on the oxide. This is a method of describing the composition of each component contained in the optical glass, assuming that all the oxides, nitrates, etc., which are the raw materials of the optical glass of the present invention, are decomposed into oxides at the time of melting. .. In this method, the total mass of oxides in the optical glass, which is assumed to be changed and generated, is taken as 100% by mass, and the amount of each component contained in the optical glass is expressed.

The optical glass of the present invention, in mass percent on the oxide basis, of SiO ₂ component from 30 to 75%, the CeO ₂ component than 5% greater than 0% 0 to 8% of _Al 2 _{O 3 component, B} 2 O ₃ components are 0 to 18%, R ₂ O components are 0 to 20% (however, R is one or more selected from Li, Na and K), and MO components are 0 to 50% (however, M is Mg, One or more selected from Ca, Sr, Ba and Zn.) The wavelength [λ ₈₀ ] at which the light transmittance of a sample having a thickness of 10 mm is 80% is 390 nm or more. By satisfying the above composition and the optical index, it has the light transmittance in the visible region required for optical glass, and even when it is irradiated with radiation, it is compared with that before it is exposed to radiation. , It is possible to obtain an optical glass with a small decrease in light transmittance in the visible region.

The SiO ₂ component is an essential component that is indispensable as a glass-forming oxide, and the inclusion of this component reduces the coloring of the glass. However, if the content is too large, the devitrification resistance and meltability tend to deteriorate. Therefore, _{the lower limit of the content of the SiO 2} component is preferably 30%, more preferably 32%, and most preferably 34%, and _{the upper limit of the content of the SiO 2} component is preferably 75%, more preferably 73. %, Most preferably 72.5%.

The CeO ₂ component has an effect of suppressing a decrease in light transmittance in the visible region of the optical glass due to irradiation with radiation and preventing coloring. However, if the content is too large, the optical glass will be colored yellow. Therefore, _{the lower limit of the content of the CeO 2} component is preferably more than 0%, more preferably 0.5%, and most preferably 0.6%, and the upper limit of the content of the _{CeO 2 component is preferably 5%.} , More preferably 2%, most preferably 1.9%.

In the glass of the present invention, when _{the value of SiO 2} / CeO _{2 which} is the ratio of the content of the SiO _{2 component to the content of the CeO 2} component expressed in mass% based on the oxide is 30 or more, the glass is irradiated with radiation. This is preferable because it is easy to obtain a high light transmittance in the visible region while suppressing a decrease in the light transmittance in the visible region of the optical glass. The lower limit of the value of SiO ₂ / CeO ₂ is more preferably 31 and most preferably 32.
On the other hand, when _{the value of SiO 2} / CeO ₂ exceeds 60, the light transmittance in the visible region of the optical glass tends to decrease when irradiated with radiation. Therefore, _{the upper limit of the value of SiO 2} / CeO ₂ is preferably 60, more preferably 59, and most preferably 58.

The Al ₂ O ₃ component is an optional component having an effect of increasing the chemical durability and mechanical strength of the optical glass. However, _{if the content of the Al 2} O ₃ component is too large, the light transmittance in the visible region of the optical glass tends to decrease due to the irradiation with radiation. Therefore, _{the upper limit of the content of the Al 2} O ₃ component is preferably 8%, more preferably 7%, and most preferably 6%.

The B ₂ O ₃ component is an optional component that can be contained as a glass-forming oxide. However, _{if the content of the B 2} O ₃ component is too large, the chemical durability and devitrification resistance of the optical glass tend to decrease. Therefore, _{the upper limit of the B 2} O ₃ component is preferably 18%, more preferably 16%, and most preferably 15%.

The R ₂ O component (where R is one or more selected from Li, Na and K) is an optional component having an effect of promoting melting of the glass raw material. However, when the content of R 2 _O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 20%, more preferably 18%, and most preferably 17%.

The Li ₂ O component is an optional component that has the effect of promoting the melting of the glass raw material. However, _{if the content of the Li 2} O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 8%, more preferably 6%, most preferably 5%.

The Na ₂ O component is an optional component that has the effect of promoting the melting of the glass raw material. However, _{if the content of the Na 2} O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, _{the upper limit of the Na 2} O component is preferably less than 12%, more preferably 11%, and most preferably 10%.

K 2 _O component is an optional component having an effect of promoting the melting of glass raw materials. However, when the content of K 2 _O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 13%, more preferably 11%, most preferably 10%.

The MO component (where M is one or more selected from Mg, Ca, Sr, Ba and Zn) is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. is there. However, if the content of the MO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MO component is preferably 50%, more preferably 46%, and most preferably 43%.

The MgO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the MgO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MgO component is preferably 10%, more preferably 5%, and most preferably 3%.

The CaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the CaO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably 22%, more preferably 20%, and most preferably 18%.

The SrO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the SrO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably 10%, more preferably 5%, and most preferably 3%.

The BaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the SrO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably 50%, more preferably 46%, and most preferably 43%.

In the glass of the present invention, when _{the value of SiO 2} / CeO _{2 which} is the ratio of the content of the SiO _{2 component to the content of the CeO 2} component expressed in mass% based on the oxide is 30 or more, the glass is irradiated with radiation. This is preferable because it is easy to obtain a high light transmittance in the visible region while suppressing a decrease in the light transmittance in the visible region of the optical glass. The lower limit of the value of SiO ₂ / CeO ₂ is more preferably 31 and most preferably 32.
On the other hand, when _{the value of SiO 2} / CeO ₂ exceeds 60, the light transmittance in the visible region of the optical glass tends to decrease when irradiated with radiation. Therefore, _{the upper limit of the value of SiO 2} / CeO ₂ is preferably 60, more preferably 59, and most preferably 58.

Since the TiO ₂ component enhances _{the coloring caused by the CeO 2} component and causes a decrease in the light transmittance in the visible region, the content thereof is preferably less than 1%, more preferably 0.3% or less, and substantially. Most preferably, it is not contained in.

The transition metal components of V, Cr, Mn, Fe, Co, Ni, Cu, and Mo are colored because they have absorption at a specific wavelength in the visible region even when a small amount is added. Therefore, in order to obtain the light transmittance required for optical glass, these components should not be substantially contained.

The Sb ₂ O ₃ component has a defoaming effect in the glass melting step, but when irradiated with radiation, the decrease in light transmittance in the visible region becomes large. In the optical glass of the present invention, defoaming effect can be obtained by containing the CeO ₂ component. Therefore, _{the content of the Sb 2} O ₃ component is preferably less than 1%, more preferably 0.3% or less, and most preferably substantially not contained.

The As ₂ O ₃ component has a defoaming effect in the glass melting process, but is harmful to the human body and the environment. In the optical glass of the present invention, defoaming effect can be obtained by containing the CeO ₂ component. Therefore, _{the content of the As 2} O ₃ component is preferably less than 1%, more preferably 0.3% or less, and most preferably substantially not contained.

_{The optical glass of the present invention has a wavelength [λ 80} ] of 390 nm or more at which the light transmittance including reflection loss in a parallel plate sample having a thickness of 10 mm is 390 nm or more. This is preferable because the decrease in light transmittance in the visible region is small as compared with before exposure to irradiation. More preferably, [λ ₈₀ ] is 395 nm or more, and most preferably [λ ₈₀ ] is 400 nm or more.
On the other hand, in the optical glass of the present invention, in order to secure the light transmittance in the visible region required for the optical glass, [λ ₈₀ ] is preferably 490 nm or less, more preferably 485 nm or less, and most preferably 480 nm or less. preferable.

_{The optical glass of the present invention has a wavelength [λ 5} ] at which the light transmittance including reflection loss is 5% in a parallel plate sample having a thickness of 10 mm, which is 425 nm or less and 350 nm or more. In a more preferred embodiment, λ ₅ is 420 nm or less, and in the most preferred embodiment, λ ₅ is 415 nm or less.

The optical glass of the present invention has little decrease in light transmittance in the visible region even when irradiated with radiation. Therefore, when the absorbed dose due to the irradiation of cobalt-60 gamma rays is 0.5 MGy, the change [Δλ _{5 ] of λ 5} after the irradiation of gamma rays with respect to _{λ 5} before the irradiation of the gamma rays is 20 nm or less. is there. In a more preferred embodiment, Δλ ₅ is 18 nm or less, and in the most preferred embodiment, Δλ ₅ is 16 nm or less.

The optical glass of the present invention has little decrease in light transmittance in the visible region even when irradiated with radiation. Therefore, when the absorbed dose due to the irradiation of cobalt-60 gamma rays is 0.5 MGy, the change [Δλ ₈₀ ] _{of [λ 80} ] after the irradiation of gamma rays with respect to _{[λ 80] before the irradiation of the gamma rays is} , 230 nm or less. In a more preferred embodiment, [Δλ ₈₀ ] is 60 nm or less, and in the most preferable embodiment, [Δλ ₈₀ ] is 20 nm or less.

The lower limit of the refractive index [nd] of the optical glass of the present invention is 1.50, and the upper limit is 1.65. The lower limit of the Abbe number [νd] of the optical glass of the present invention is 35, and the upper limit is 65.

More specifically, the optical glass of the present invention can take three embodiments.
Hereinafter, three embodiments will be described.

[First Embodiment]
The first embodiment of the optical glass of the present invention will be described.

The SiO ₂ component is an essential component that is indispensable as a glass-forming oxide, and the inclusion of this component reduces the coloring of the glass. However, if the content is too large, the devitrification resistance and meltability tend to deteriorate. Therefore, _{the lower limit of the content of the SiO 2} component is preferably 30%, more preferably 32%, most preferably 34%, and _{the upper limit of the content of the SiO 2} component is preferably 45%, more preferably 43. %, Most preferably 42%.

The CeO ₂ component has an effect of suppressing a decrease in light transmittance in the visible region of the optical glass due to irradiation with radiation and preventing coloring. However, if the content is too large, the optical glass will be colored yellow. Therefore, _{the lower limit of the content of the CeO 2} component is preferably 0.4%, more preferably 0.5%, and most preferably 0.6%, and the upper limit of the content of the _{CeO 2 component is preferably 3.} %, More preferably 2%, most preferably 1.5%.

The Al ₂ O ₃ component has the effect of increasing the chemical durability and mechanical strength of the optical glass. However, _{if the content of the Al 2} O ₃ component is too large, the light transmittance in the visible region of the optical glass tends to decrease due to the irradiation with radiation. Therefore, _{the lower limit of the content of the Al 2} O ₃ component is preferably 1%, more preferably 2%, and most preferably 3%, and the upper limit of the content of the _{Al 2} O _{3 component is preferably 8%.} It is more preferably 7% and most preferably 6%.

The B ₂ O ₃ component is a component contained as a glass-forming oxide. However, _{if the content of the B 2} O ₃ component is too large, the chemical durability and devitrification resistance of the optical glass tend to decrease. Therefore, _{the lower limit of the B 2} O ₃ component is preferably 3%, more preferably 3.5%, most preferably 4%, and _{the upper limit of the B 2} O ₃ component is preferably 18%, more preferably 16%. %, Most preferably 15%

The R ₂ O component (where R is one or more selected from Li, Na and K) is an optional component having an effect of promoting melting of the glass raw material. However, when the content of R 2 _O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 10%, more preferably 9%, and most preferably 8%.

The Li ₂ O component is an optional component that has the effect of promoting the melting of the glass raw material. However, _{if the content of the Li 2} O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 5%, more preferably 4%, and most preferably 3%.

The Na ₂ O component is an optional component that has the effect of promoting the melting of the glass raw material. However, _{if the content of the Na 2} O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, _{the upper limit of the Na 2} O component is preferably 10%, more preferably 6%, and most preferably 4%.

K 2 _O component is an optional component having an effect of promoting the melting of glass raw materials. However, when the content of K 2 _O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of _{K 2} O component is preferably 10%, more preferably 6%, and most preferably 4%.

The MO component (where M is one or more selected from Mg, Ca, Sr, Ba and Zn) is a component having the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. .. However, if the content of the MO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the lower limit of the MO component is preferably 34%, more preferably 35%, most preferably 36%, and the upper limit of the MO component is preferably 50%, more preferably 46%, most preferably 43%. is there.

The MgO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the MgO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MgO component is preferably 10%, more preferably 5%, and most preferably 3%.

The CaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the CaO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably 22%, more preferably 20%, and most preferably 18%.

The SrO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the SrO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably 10%, more preferably 5%, and most preferably 3%.

The BaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. In order to obtain this effect, the BaO component can be contained in an amount of 15.5% or more, more preferably 20% or more, and most preferably 23% or more. However, if the content of the BaO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the BaO component is preferably 50%, more preferably 46%, and most preferably 43%.

The ZnO component is an optional component that has the effect of lowering the viscosity of the glass and improving the devitrification resistance. However, if the content of the ZnO component is too large, the devitrification resistance tends to deteriorate. Therefore, the upper limit of the ZnO component is preferably 10%, more preferably 5%, and most preferably 3%.

ZrO ₂ component is an optional component having an effect of increasing the refractive index of the glass, increasing the chemical durability. However, when the content of the ZrO ₂ component is too large, stability of the glass tends to decrease. Therefore, the upper limit of the content of the ZrO ₂ component is preferably 10%, more preferably 8%, and most preferably 6%.

The PbO component has the effect of increasing the refractive index of the optical glass, but is harmful to the human body and the environment, so its content is preferably less than 5%. In the optical glass of the first embodiment of the present invention, a desired refractive index can be obtained even if the PbO component is not contained. Therefore, the glass of the first embodiment of the present invention does not have to contain the PbO component substantially.

_{In the optical glass of the first embodiment, when the wavelength [λ 80} ] at which the light transmittance including the reflection loss in the parallel plate sample having a thickness of 10 mm is 80% is 440 nm or more, even when irradiated with radiation, This is preferable because the decrease in light transmittance in the visible region is small as compared with before exposure to radiation. More preferably, [λ ₈₀ ] is 445 nm or more, and most preferably [λ ₈₀ ] is 446 nm or more.
On the other hand, in the optical glass of the present invention, in order to secure the light transmittance in the visible region required for the optical glass, [λ ₈₀ ] is preferably 490 nm or less, more preferably 485 nm or less, and more preferably 480 nm or less. Most preferred.

_{The optical glass of the first embodiment has a wavelength [λ 5} ] at which the light transmittance including reflection loss is 5% in a parallel plate sample having a thickness of 10 mm, which is 425 nm or less and 370 nm or more. In a more preferred embodiment, λ ₅ is 420 nm or less, and in the most preferred embodiment, λ ₅ is 415 nm or less.

The optical glass of the first embodiment has little decrease in light transmittance in the visible region even when irradiated with radiation. Therefore, when the absorbed dose due to the irradiation of cobalt-60 gamma rays is 0.5 MGy, the change [Δλ _{5 ] of λ 5} after the irradiation of gamma rays with respect to _{λ 5} before the irradiation of the gamma rays is 20 nm or less. is there. In a more preferred embodiment, Δλ ₅ is 18 nm or less, and in the most preferred embodiment, Δλ ₅ is 16 nm or less.

The optical glass of the first embodiment has little decrease in light transmittance in the visible region even when irradiated with radiation. Therefore, when the absorbed dose due to the irradiation of cobalt-60 gamma rays is 0.5 MGy, _{the change [Δλ 80} ] _{of [λ 80} ] after the irradiation of gamma rays with respect to [λ 80] before the irradiation of the gamma rays is It is 230 nm or less. In a more preferred embodiment, [Δλ ₈₀ ] is 60 nm or less.

The lower limit of the refractive index [nd] of the optical glass of the first embodiment is 1.55, and the upper limit is 1.65. The lower limit of the Abbe number [νd] of the optical glass of the present invention is 48, and the upper limit is 65.

[Second Embodiment]
A second embodiment of the optical glass of the present invention will be described.

The SiO ₂ component is an essential component that is indispensable as a glass-forming oxide, and the inclusion of this component reduces the coloring of the glass. However, if the content is too large, the devitrification resistance and meltability tend to deteriorate. Therefore, _{the lower limit of the content of the SiO 2} component is preferably 55%, more preferably 60%, most preferably 65%, and _{the upper limit of the content of the SiO 2} component is preferably 78%, more preferably 75%. %, Most preferably 73%.

The CeO ₂ component has an effect of suppressing a decrease in light transmittance in the visible region of the optical glass due to irradiation with radiation and preventing coloring. However, if the content is too large, the optical glass will be colored yellow. Therefore, _{the lower limit of the content of the CeO 2} component is preferably 0.5%, more preferably 0.6%, and most preferably 0.7%, and the upper limit of the content of the _{CeO 2 component is preferably 3.} %, More preferably 2%, most preferably 1.8%.

The Al ₂ O ₃ component is an optional component having an effect of increasing the chemical durability and mechanical strength of the optical glass. However, _{if the content of the Al 2} O ₃ component is too large, the light transmittance in the visible region of the optical glass tends to decrease due to the irradiation with radiation. The upper limit of the content of the Al ₂ O ₃ component is preferably 5%, more preferably 4%, and most preferably 3.5%.

The B ₂ O ₃ component is a component contained as a glass-forming oxide. However, _{if the content of the B 2} O ₃ component is too large, the chemical durability and devitrification resistance of the optical glass tend to decrease. Therefore, _{the lower limit of the B 2} O ₃ component is preferably 3%, more preferably 3.5%, most preferably 4%, and _{the upper limit of the B 2} O ₃ component is preferably 15%, more preferably 14 %, Most preferably 13%

The R ₂ O component (where R is one or more selected from Li, Na and K) is an optional component having an effect of promoting melting of the glass raw material. However, when the content of R 2 _O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 23%, more preferably 20%, and most preferably 18%.

The Li ₂ O component is an optional component that has the effect of promoting the melting of the glass raw material. However, _{if the content of the Li 2} O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, _{the upper limit of the Li 2} O component is preferably 5%, more preferably 4%, and most preferably 3%.

The Na ₂ O component is an optional component that has the effect of promoting the melting of the glass raw material. However, _{if the content of the Na 2} O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, _{the upper limit of the Na 2} O component is preferably less than 12%, more preferably 11%, and most preferably 10%.

K 2 _O component is an optional component having an effect of promoting the melting of glass raw materials. However, when the content of K 2 _O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 18%, more preferably 16%, and most preferably 15%.

The MO component (where M is one or more selected from Mg, Ca, Sr, Ba and Zn) is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. is there. However, if the content of the MO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MO content is preferably 10%, more preferably 8%, and most preferably 6%.

The MgO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the MgO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MgO component is preferably less than 5%, more preferably 3%, and most preferably 1%.

The CaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the CaO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably less than 5%, more preferably 3%, and most preferably 1%.

The SrO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the SrO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably less than 5%, more preferably 3%, and most preferably 1%.

The BaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the BaO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the BaO component is preferably less than 5%, more preferably 4%, and most preferably 3%.

The ZnO component is an optional component that has the effect of lowering the viscosity of the glass and improving the devitrification resistance. However, if the content of the ZnO component is too large, the devitrification resistance tends to deteriorate. Therefore, the upper limit of the ZnO component is preferably less than 5%, more preferably 3%, and most preferably 1%.

ZrO ₂ component is an optional component having an effect of increasing the refractive index of the glass, increasing the chemical durability. However, when the content of the ZrO ₂ component is too large, stability of the glass tends to decrease. Therefore, the upper limit of the content of the ZrO ₂ component is preferably 5%, more preferably 3%, and most preferably 1%.

The PbO component has the effect of increasing the refractive index of the optical glass, but is harmful to the human body and the environment, so its content is preferably less than 5%. In the optical glass of the second embodiment of the present invention, a desired refractive index can be obtained even if the PbO component is not contained. Therefore, the glass of the second embodiment of the present invention does not have to contain the PbO component substantially.

_{In the optical glass of the second embodiment, when the wavelength [λ 80} ] at which the light transmittance including the reflection loss in the parallel plate sample having a thickness of 10 mm is 80% is 390 nm or more, even when irradiated with radiation, This is preferable because the decrease in light transmittance in the visible region is small as compared with before exposure to radiation. More preferably, [λ ₈₀ ] is 395 nm or more, and most preferably [λ ₈₀ ] is 400 nm or more.
On the other hand, in the optical glass of the present invention, in order to secure the light transmittance in the visible region required for the optical glass, [λ ₈₀ ] is preferably 470 nm or less, more preferably 460 nm or less, and most preferably 455 nm or less. preferable.

_{The optical glass of the second embodiment has a wavelength [λ 5} ] at which the light transmittance including reflection loss is 5% in a parallel plate sample having a thickness of 10 mm, which is 400 nm or less and 355 nm or more. In a more preferred embodiment, [λ ₅ ] is 395 nm or less, and in the most preferable embodiment, [λ ₅ ] is 390 nm or less.

The optical glass of the second embodiment has little decrease in light transmittance in the visible region even when irradiated with radiation. Therefore, when the absorbed dose due to the irradiation of cobalt-60 gamma rays is 0.5 MGy, the change [Δλ ₅ ] _{of [λ 5} ] after the irradiation of gamma rays with respect to _{[λ 5] before the irradiation of the gamma rays is} , 20 nm or less. In a more preferred embodiment, [Δλ ₅ ] is 18 nm or less, and in the most preferable embodiment, [Δλ ₅ ] is 15 nm or less.

The optical glass of the second embodiment has little decrease in light transmittance in the visible region even when irradiated with radiation. Therefore, when the absorbed dose due to the irradiation of cobalt-60 gamma rays is 0.5 MGy, _{the change [Δλ 80} ] _{of [λ 80} ] after the irradiation of gamma rays with respect to [λ 80] before the irradiation of the gamma rays is It is 70 nm or less. In a more preferred embodiment, [Δλ ₈₀ ] is 60 nm or less.

The lower limit of the refractive index [nd] of the optical glass of the second embodiment is 1.50, and the upper limit is 1.60. The lower limit of the Abbe number [νd] of the optical glass of the present invention is 50, and the upper limit is 65.
[Third Embodiment]
A third embodiment of the optical glass of the present invention will be described.

The SiO ₂ component is an essential component that is indispensable as a glass-forming oxide, and the inclusion of this component reduces the coloring of the glass. However, if the content is too large, the devitrification resistance and meltability tend to deteriorate. Therefore, _{the lower limit of the content of the SiO 2} component is preferably 35%, more preferably 37%, most preferably 40%, and _{the upper limit of the content of the SiO 2} component is preferably 56%, more preferably 54. %, Most preferably 52%.

The CeO ₂ component has an effect of suppressing a decrease in light transmittance in the visible region of the optical glass due to irradiation with radiation and preventing coloring. However, if the content is too large, the optical glass will be colored yellow. Therefore, _{the lower limit of the content of the CeO 2} component is preferably 0.4%, more preferably 0.5%, and most preferably 0.6%, and the upper limit of the content of the _{CeO 2 component is preferably 3.} %, More preferably 2%, most preferably 1.5%.

The Al ₂ O ₃ component is an optional component having an effect of increasing the chemical durability and mechanical strength of the optical glass. However, _{if the content of the Al 2} O ₃ component is too large, the light transmittance in the visible region of the optical glass tends to decrease due to the irradiation with radiation. Therefore, _{the upper limit of the content of the Al 2} O ₃ component is preferably 5%, more preferably 4%, and most preferably 3%.

The B ₂ O ₃ component is an optional component that can be contained as a glass-forming oxide. However, _{if the content of the B 2} O ₃ component is too large, the chemical durability and devitrification resistance of the optical glass tend to decrease. Therefore, _{the upper limit of the B 2} O ₃ component is preferably 5%, more preferably 4%, and most preferably 3%.

The R ₂ O component (where R is one or more selected from Li, Na and K) is an optional component having an effect of promoting melting of the glass raw material. However, when the content of R 2 _O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 16%, more preferably 15%, and most preferably 13%.

The Li ₂ O component is an optional component that has the effect of promoting the melting of the glass raw material. However, _{if the content of the Li 2} O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of the _{R 2} O component is preferably 5%, more preferably 4%, and most preferably 3%.

The Na ₂ O component is an optional component that has the effect of promoting the melting of the glass raw material. However, _{if the content of the Na 2} O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, _{the upper limit of the Na 2} O component is preferably 11%, more preferably 9%, and most preferably 7%.

K 2 _O component is an optional component having an effect of promoting the melting of glass raw materials. However, when the content of K 2 _O component is too large, the chemical durability of the optical glass tends to decrease. Therefore, the upper limit of _{K 2} O component is preferably 11%, more preferably 9%, and most preferably 7%.

The MO component (where M is one or more selected from Mg, Ca, Sr, Ba and Zn) is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. is there. However, if the content of the MO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MO component is preferably less than 5%, more preferably 4%, and most preferably 3%.

The MgO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the MgO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MgO component is preferably less than 5%, more preferably 4%, and most preferably 3%.

The CaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the CaO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably less than 5%, more preferably 4%, and most preferably 3%.

The SrO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the SrO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the SrO component is preferably less than 5%, more preferably 4%, and most preferably 3%.

The BaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constant to a desired value. However, if the content of the BaO component is too large, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the BaO component is preferably less than 5%, more preferably 4%, and most preferably 3%.

The ZnO component is an optional component that has the effect of lowering the viscosity of the glass and improving the devitrification resistance. However, if the content of the ZnO component is too large, the devitrification resistance tends to deteriorate. Therefore, the upper limit of the ZnO component is preferably less than 5%, more preferably 4%, and most preferably 3%.

ZrO ₂ component is an optional component having an effect of increasing the refractive index of the glass, increasing the chemical durability. However, when the content of the ZrO ₂ component is too large, stability of the glass tends to decrease. Therefore, the upper limit of the content of the ZrO ₂ component is preferably less than 5%, more preferably 4%, and most preferably 3%.

The PbO component is a component having the effect of increasing the refractive index of the optical glass and increasing the light transmittance in the visible region. However, if the content of the PbO component is too large, the light transmittance in the short wavelength region is lowered. Therefore, the lower limit of the PbO component is preferably 30%, more preferably 32%, most preferably 35%, and the upper limit of the PbO component is preferably 52%, more preferably 49%, and most preferably 47%.

_{In the optical glass of the third embodiment, when the wavelength [λ 80} ] at which the light transmittance including the reflection loss in the parallel plate sample having a thickness of 10 mm is 80% is 410 nm or more, even when irradiated with radiation, This is preferable because the decrease in light transmittance in the visible region is small as compared with before exposure to radiation. More preferably, [λ ₈₀ ] is 415 nm or more, and most preferably [λ ₈₀ ] is 420 nm or more.
On the other hand, in the optical glass of the present invention, in order to secure the light transmittance in the visible region required for the optical glass, [λ ₈₀ ] is preferably 460 nm or less, more preferably 455 nm or less, and 450 nm or less. Most preferred.

_{The optical glass of the third embodiment has a wavelength [λ 5} ] at which the light transmittance including reflection loss is 5% in a parallel plate sample having a thickness of 10 mm, which is 400 nm or less and 350 nm or more. In a more preferred embodiment, [λ ₅ ] is 395 nm or less, and in the most preferable embodiment, [λ ₅ ] is 390 nm or less.

The optical glass of the third embodiment has little decrease in light transmittance in the visible region even when irradiated with radiation. Therefore, when the absorbed dose due to the irradiation of cobalt-60 gamma rays is 0.5 MGy, the change [Δλ _{5 ] of λ 5} after the irradiation of gamma rays with respect to _{λ 5} before the irradiation of the gamma rays is 18 nm or less. is there. In a more preferred embodiment, [Δλ ₅ ] is 17 nm or less, and in the most preferable embodiment, [Δλ ₅ ] is 16 nm or less.

The optical glass of the third embodiment has little decrease in light transmittance in the visible region even when irradiated with radiation. Therefore, when the absorbed dose due to the irradiation of cobalt-60 gamma rays is 0.5 MGy, the change [Δλ ₈₀ ] _{of [λ 80} ] after the irradiation of gamma rays with respect to _{[λ 80] before the irradiation of the gamma rays is} , 60 nm or less. In a more preferred embodiment, [Δλ ₈₀ ] is 55 nm or less.

The lower limit of the refractive index [nd] of the optical glass of the third embodiment is 1.55, and the upper limit is 1.65. The lower limit of the Abbe number [νd] of the optical glass of the present invention is 32, and the upper limit is 45.

Hereinafter, examples of the optical glass according to the present invention will be shown. The optical glass of the example of the present invention was produced as follows. First, ordinary raw materials for optical glass such as oxides, hydroxides, carbonates, and nitrates were prepared so as to have the compositions of each of the examples shown in Tables 1 to 3. Next, the prepared raw material was put into a platinum crucible and melted at 1100 to 1350 ° C. for 2 to 5 hours depending on the meltability according to the composition, and then clarified and stirred to homogenize the molten glass. Finally, the molten glass was cast into a stainless steel mold to form it, and then slowly cooled.
A comparative example was also prepared in the same manner.

For the prepared optical glasses of Examples and Comparative Examples, the refractive index [nd], Abbe number [νd], spectral transmittance before exposure to radiation, and spectral transmittance after irradiation were measured. did.
The refractive index and Abbe number were measured based on the Japan Optical Glass Industry Association standard JOBIS01-2003. Here, the refractive index and the Abbe number were determined by measuring the glass obtained by slowly cooling the cooling rate at −25 ° C./hr.
The spectral transmittance was measured according to the Japan Optical Glass Industry Association standard JOBIS02-2003. Specifically, the spectral transmittance was obtained by measuring the transmittance of a face-to-face parallel polished product having a thickness of 10 ± 0.1 mm for light rays having a wavelength of 200 to 800 nm according to JISZ8722. From the obtained spectral transmittance, the wavelength [λ _{80 ] at which the light transmittance is 80% and the wavelength [λ 5} ] at which the light transmittance is 5% were determined.
The produced optical glass was irradiated with radiation using a gamma ray irradiation facility of Cobalt-60 of the Japan Atomic Energy Agency. Specifically, cobalt-60 gamma rays were irradiated toward the optical glass so that the absorbed dose was 0.5 MGy.
Determined after receiving the irradiation of gamma [lambda _80] and [lambda _5] and before being exposed to gamma irradiation [λ80] and lambda ₅ differences of each, [Δλ _80], and the [[Delta] [lambda] _5] ..
The measured [nd], [νd], [λ ₈₀ ], [λ ₅ ], [Δλ ₈₀ ] and [Δλ ₅ ] are shown in the table.

From the above examples, the optical glass of the present invention has a light transmittance in the visible region required as an optical glass, and even when it is irradiated with radiation, it is compared with that before it is exposed to radiation. Therefore, it can be seen that the decrease in light transmittance in the visible region is small.
On the other hand, the glass of the comparative example was colored black by being irradiated with radiation, and the light transmittance was significantly reduced.

Claims (4)

By mass% based on oxide,
SiO ₂ component 30-50.11%,
CeO ₂ component more than 0% and less than 5%,
Al ₂ O ₃ component 0-8%,
B ₂ O ₃ component 0-18%,
The R ₂ O component from 0 to 11.70% (wherein, R represents Li, 1 or more selected from Na and K.),
Contains 0 to 50% of MO component (however, M is one or more selected from Mg, Ca, Sr, Ba and Zn).
Ratio of content of SiO ₂ component to content of _{CeO 2} component expressed in mass% based on oxide _{SiO 2} / CeO ₂ is 36.83 or more and 60 or less.
When a sample with a thickness of 10 mm is irradiated with cobalt 60 gamma rays so that the wavelength [λ80] at which the light transmittance is 80% is 390 nm or more and the absorbed dose is 0.5 MGy, the thickness before and after the irradiation. An optical glass in which the change [Δλ5] of the wavelength [λ5] at which the light transmittance of a 10 mm sample is 5% is 20 nm or less. By mass% based on oxide,
SiO ₂ component 30-45%,
CeO ₂ component 0.5-3%,
Al ₂ O ₃ component 1-8%,
B ₂ O ₃ component 3-18%,
The R ₂ O component 0-10% (wherein, R represents Li, 1 or more selected from Na and K.),
The optical glass according to claim 1, which contains 35 to 50% of the MO component (where M is one or more selected from Mg, Ca, Sr, Ba and Zn). By mass% based on oxide,
CeO ₂ component 0.5-3%,
B ₂ O ₃ component 0-3%,
Contains 30-50% of PbO component,
The optical glass according to claim 1 or 2, wherein the wavelength [λ80] at which the light transmittance of a sample having a thickness of 10 mm is 80% is 490 nm or less. The optical glass according to any one of claims 1 to 3, wherein the refractive index [nd] is 1.50 or more and 1.65 or less, and the Abbe number [νd] is 35 or more and 65 or less.

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