Optical glass

Abstract

To provide an optical glass that has light transmittance of a visible region which is required as an optical glass, and has less reduction of light transmittance in a visible region even in the case the glass is irradiated with radiation.SOLUTION: An optical glass contains, in terms of oxide-based mass%, SiO2 component by 0 to 35%, GeO2 component by 0 to 15%, B2O3 component by 0 to 12%, P2O5 component by 0 to 35%, Nb2O5 component by 5 to 60%, TiO2 component by 0 to 35%, Ta2O5 component by 0 to 10%, WO3 component by 0 to 8%, Bi2O3 component by 0 to 5%, ZrO2 component by 0 to 10%, La2O3+Y2O3+Gd2O3 component by 0 to 45%, Sb2O3 component by 0 to 1%, and Rn2O component by 0 to 25% (note that Rn is one or more kinds selected from Li, Na and K). When the glass receives irradiation of cobalt 60 gamma ray such that an absorption dose becomes 100 krad, transmittance reduction at 450 nm and 550 nm before / after the irradiation is 30% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to optical glass. In particular, the present invention relates to optical glass having radiation resistance, in which the decrease in light transmittance in the visible range is small even when exposed to radiation such as gamma rays and X-rays. The present invention relates to an optical glass having radiation resistance, in which the decrease in light transmittance in the visible range is small even when exposed to radiation such as gamma rays and X-rays. 2 The present invention relates to an optical glass that does not contain [Background technology]

[0002] In recent years, there has been an increasing demand for cameras, sensors, and other devices to be used in radiation environments such as outer space. Optical glass is used in these cameras and sensors. However, when conventional optical glass is exposed to radiation, its light transmittance in the visible range decreases and it becomes colored. For this reason, glass containing cerium oxide or the like has been used in radiation environments to impart radiation resistance to optical glass. [Prior art documents] [Patent documents]

[0003] Patent Document 1 describes lead-containing glasses for use in space, d Radiation-resistant optical glasses having a refractive index of 1.52 to 1.65 have been disclosed, but these have a low refractive index for optical applications requiring a variety of optical constants. Furthermore, when considering use in space, lead-containing glasses, which have a high specific gravity, are not preferred from the standpoint of reducing the burden on launch. [Patent Document 1] JP 2018-20959 A Summary of the Invention [Problem to be solved by the invention]

[0004] The problem that the present invention seeks to solve is to obtain optical glass that has a visible light transmittance required of optical glass and that exhibits little decrease in visible light transmittance even when irradiated with radiation, and also to provide glass that has a high refractive index that enables the optical system used to be made compact. [Means for solving the problem]

[0005] As a result of intensive research and testing, the inventors have found that a glass that solves the above problems can be obtained by using a specific composition and specific physical properties as indicators, and have thus completed the present invention. 2 O 5 Due to the effect of (a), the formation of color centers due to irradiation, which occurs conventionally, is suppressed. Specifically, the present invention provides the following.

[0006] (Configuration 1) Mass % based on oxide: SiO 2 Ingredients: 0-35%, GeO 2 Ingredients: 0-15% B 2 O 3 Ingredients: 0-12% P 2 O 5 Ingredients: 0-35%, Nb 2 O 5 Ingredients: 5-60% TiO 2 Ingredients: 0-35%, Ta 2 O 5 Ingredients 0-10%, WO 3 Ingredients: 0-8% Bi 2 O 3 Ingredients: 0-5% ZrO 2 Ingredients 0-10%, La 2 O 3 +Y 2 O 3 +Gd 2 O 3 Ingredients: 0-45%, Sb 2 O 3 Ingredients 0-1%, Rn 2 The composition contains 0-25% O (wherein Rn is one or more selected from Li, Na and K), 0-30% RO (wherein R is one or more selected from Mg, Ca, Sr, Ba and Zn), and 0-8% in total of fluorine (F) of fluorides in which one or more of the above metal elements are partially or completely substituted with oxides thereof, and CeO 2 An optical glass that is substantially free of the PbO component and PbO component, and that, when irradiated with cobalt-60 gamma rays so that the absorbed dose is 100 krad, shows a decrease in transmittance of 30% or less at 450 nm and 550 nm before and after irradiation. (Configuration 2) Mass % based on oxide: SiO 2 Ingredients: 0-5% B 2 O 3 Ingredients: 0-5% P 2 O 5 Ingredients: 20-35% Nb 2 O 5 Ingredients: 35-60% TiO 2 Ingredients: 0-20%, WO 3 Ingredients: 0-8% Bi 2 O 3 Ingredients: 0-5% Sb 2 O 3 Ingredients: 0-0.5%, Rn 2 O component 3 to 25% (wherein Rn is one or more selected from Li, Na and K) RO components: 0-20% (where R is one or more selected from Mg, Ca, Sr, Ba and Zn). 2. The optical glass according to claim 1, further comprising 0 to 8% in total of fluorine (F) in the fluorides which have substituted a part or all of one or more oxides of each of the metal elements. (Configuration 3) Mass % based on oxide: SiO 2 Ingredients: 1-35% GeO 2 Ingredients: 0-15% B 2 O 3 Ingredients: 0-12% La 2 O 3 Ingredients: 0-45% Nb 2 O 5 Ingredients: 5-50% TiO 2 Ingredients: 0-35%, Ta 2 O 5 Ingredients 0-10%, WO 3 Ingredients: 0-5% ZrO 2 Ingredients 0-10%, Sb 2 O 3 Ingredients at 0-1% Rn 2 O component 0-20% (wherein Rn is one or more selected from Li, Na and K) RO components: 0-30% (where R is one or more selected from Mg, Ca, Sr and Ba) 2. The optical glass according to claim 1, further comprising 0 to 8% in total of fluorine (F) in the fluorides which have substituted a part or all of one or more oxides of each of the metal elements. (Configuration 4) When a sample is irradiated with cobalt-60 gamma rays so that the absorbed dose is 100 krad, what is the wavelength [λ] at which the light transmittance of a 10 mm thick sample becomes 70% before and after irradiation? 70 4. The optical glass according to claim 1, wherein the difference between the refractive index and the refractive index of the optical glass is 200 nm or less. (Configuration 5) Refractive index [n d ] is 1.75000 or more and 2.05000 or less, and the Abbe number [ν d 4. The optical glass according to claim 1, wherein the refractive index is 15.00 or more and 35.00 or less. Effect of the Invention

[0007] According to the present invention, it is possible to obtain optical glass that has a visible light transmittance required for optical glass, and that, even when irradiated with radiation, shows little decrease in visible light transmittance compared to before exposure to radiation. [Brief description of the drawings]

[0008] [Figure 1] 1 shows the spectral transmittance curves of the optical glass according to Example 1-3 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 dashed line shows the spectral transmittance after irradiation. [Diagram 2] 1 shows the spectral transmittance curves of the optical glass according to Example 1-7 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 dashed line shows the spectral transmittance after irradiation. [Diagram 3] 2 is a spectral transmittance curve of the optical glass according to Example 2-1 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 dashed line shows the spectral transmittance after irradiation. [Figure 4] 1 shows the spectral transmittance curves of the optical glass according to Example 2-5 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 dashed line shows the spectral transmittance after irradiation. [Diagram 5] 1 shows the spectral transmittance curves 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 dashed line shows the spectral transmittance after irradiation. [Figure 6] 1 shows the spectral transmittance curves 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 dashed line shows the spectral transmittance after irradiation. [Figure 7] 1 shows the spectral transmittance curves of the optical glass according to Comparative Example 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 dashed line shows the spectral transmittance after irradiation. [Figure 8] 1 shows the spectral transmittance curves of the optical glass according to Comparative Example 4 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 dashed line shows the spectral transmittance after irradiation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The optical glass of the present invention will be described in detail below. In this specification, the content of each component is expressed in mass% based on the oxide. This is a method of expressing the composition of each component contained in the optical glass, assuming that the oxides, nitrates, etc., which are the raw materials of the optical glass of the present invention, are all decomposed and converted to oxides when melted. In this method, the total mass of the oxides in the optical glass assumed to be converted and generated is taken as 100 mass%, and the amount of each component contained in the optical glass is expressed.

[0010] The optical glass of the present invention contains, in terms of mass % based on oxide, SiO 2 Ingredients: 0-35%, GeO 2 Ingredients: 0-15%, B 2 O 3 Ingredients: 0-12%, P 2 O 5 Ingredients: 0-35%, Nb 2 O 5 Components: 5-60%, TiO 2 Ingredients: 0-35%, Ta 2 O 5 Ingredients: 0-10%, WO 3 Ingredients: 0-8%, Bi 2 O 3 Ingredients: 0-5%, ZrO 2 Ingredients: 0-10%, La 2 O 3 +Y 2 O 3 +Gd 2 O 3 Ingredients: 0-45%, Sb 2 O 3 Components: 0-1%, Rn 2The composition contains 0-25% O (wherein Rn is one or more selected from Li, Na and K), 0-30% RO (wherein R is one or more selected from Mg, Ca, Sr, Ba and Zn), and 0-8% in total of fluorine (F) of fluorides in which one or more of the above metal elements are partially or completely substituted with oxides thereof, and CeO 2 It is substantially free of the PbO component and the PbO component, and when irradiated with cobalt-60 gamma rays to an absorbed dose of 100 krad, the decrease in transmittance at 450 nm and 550 nm before and after irradiation is 30% or less. By satisfying the above composition and optical indexes, it is possible to obtain optical glass that has a visible light transmittance required of optical glass, and that, even when irradiated with radiation, experiences less decrease in visible light transmittance compared to before exposure to radiation.

[0011] SiO 2 The SiO component is an important component as a glass-forming oxide, but if the content is too high, the desired optical performance cannot be obtained, and on the contrary, the devitrification resistance and melting property tend to deteriorate. 2 The upper limit of the content of the component is preferably 35% or less, more preferably 33% or less, and most preferably 30% or less.

[0012] GeO 2 The component is SiO 2 Similarly, GeO is an important component as a glass-forming oxide, and if its content is too high, the desired optical performance cannot be obtained, and on the contrary, devitrification resistance and melting property tend to deteriorate. In addition, it is expensive in terms of raw material cost, so it is not preferable to use a large amount. Therefore, GeO 2 The upper limit of the content of the component is preferably 15% or less, more preferably 14% or less, and most preferably 13% or less.

[0013] B 2 O 3 The component is an optional component that can be included as a glass-forming oxide. 2 O 3 If the content of the component is too high, the chemical durability and devitrification resistance of the optical glass tend to decrease. 2 O3 The upper limit of the component is preferably 12% or less, more preferably 10% or less, and most preferably 8% or less.

[0014] P 2 O 5 The component is an optional component that can be included as a glass-forming oxide. 2 O 5 If the content of the component is too high, the chemical durability and devitrification resistance of the optical glass tend to decrease. 2 O 5 The upper limit of the component is preferably 35% or less, more preferably 30% or less, and most preferably 26% or less.

[0015] Nb 2 O 5 The component is an essential component that can be contained as a glass component, and has a large effect of increasing the refractive index and dispersion. 2 O 5 Nb has the effect of suppressing the decrease in the visible light transmittance of optical glass caused by irradiation with radiation and preventing coloration due to the various valences it can take. 2 O 5 The lower limit of the content of the element is preferably 5% or more, more preferably 7% or more, and most preferably 8% or more. 2 O 5 The upper limit of the content of the component is preferably 60% or less, more preferably 58% or less, and most preferably 55% or less.

[0016] TiO 2 The TiO component is an optional component that has the effect of increasing the chemical durability and mechanical strength of optical glass, and has a large effect of increasing the refractive index. 2 If the content of the component is too high, the glass becomes easily devitrified and the transmittance of the glass decreases. 2 The upper limit of the content of the component is preferably 35% or less, more preferably 32% or less, and most preferably 29% or less.

[0017] Ta 2 O 5The component is an optional component and has a large effect of increasing the refractive index. 2 O 5 If the content of the component is too high, the glass is likely to devitrify, and is also undesirable from the standpoint of cost. 2 O 5 The upper limit of the content of the component is preferably 10% or less, more preferably 9% or less, and most preferably 8% or less.

[0018] WO 3 The component is an optional component and has a large effect of increasing the refractive index. 3 If the content of the component is too high, the glass becomes easily devitrified, resulting in a decrease in transmittance. 3 The upper limit of the content of the component is preferably 8% or less, more preferably 7% or less, and most preferably 6% or less.

[0019] Bi 2 O 3 The component is an optional component and is used as a glass component to increase the refractive index. However, Bi 2 O 3 If the content of the component is too high, the glass becomes easily devitrified and the transmittance decreases. 2 O 3 The upper limit of the content of the component is preferably 5% or less, more preferably 3% or less, and most preferably 2% or less.

[0020] ZrO 2 The component is an optional component that contributes to improving the chemical durability of the glass. However, ZrO 2 If the content of the component is too high, the glass is prone to devitrification. 2 The upper limit of the content of the component is preferably 10% or less, more preferably 9% or less, and most preferably 8% or less.

[0021] La 2 O 3 , Y 2 O 3 , Gd 2 O 3The component contributes to improving the chemical durability and refractive index of the glass. 2 O 3 are used as glass constituents. However, if the content of these components is too high, the glass is prone to devitrification. Therefore, the upper limit of the total content of these components is preferably 45% or less, more preferably 40% or less, and most preferably 37% or less.

[0022] Sb 2 O 3 This component is effective as a glass clarifier and in suppressing discoloration during production, but a content of 1% or less is sufficient.

[0023] Rn 2 The O component (wherein Rn is one or more selected from Li, Na and K) is an optional component that has the effect of promoting the melting of glass raw materials. 2 If the content of the O component is too high, the chemical durability of the optical glass tends to decrease. 2 The upper limit of the O component is preferably 25% or less, more preferably 18% or less, and most preferably 16% or less.

[0024] Li 2 The O component is an optional component that has the effect of promoting the melting of glass raw materials. However, Li 2 If the O content is too high, the chemical durability of the optical glass is likely to decrease. 2 The upper limit of the O component is preferably 5% or less, more preferably 4% or less, and most preferably 3% or less.

[0025] Na 2 The O component is an optional component that has the effect of promoting the melting of glass raw materials. However, Na 2 If the O content is too high, the chemical durability of the optical glass is likely to decrease. 2 The upper limit of the O component is preferably less than 20%, more preferably 18% or less, and most preferably 16% or less.

[0026] K 2The O component is an optional component that has the effect of promoting the melting of glass raw materials. 2 If the content of the O component is too high, the chemical durability of the optical glass tends to decrease. 2 The upper limit of the O component is preferably 10% or less, more preferably 9% or less, and most preferably 8% or less.

[0027] The RO component (wherein R 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 constants to desired values. However, if the content of the RO component is too high, the devitrification resistance of the optical glass is likely to deteriorate. Therefore, the upper limit of the RO component is preferably 30% or less, more preferably 29% or less, and most preferably 28% or less.

[0028] The MgO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the MgO component is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MgO component is preferably 5% or less, more preferably 3% or less, and most preferably 1% or less.

[0029] The CaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the CaO content is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably 10% or less, more preferably 8% or less, and most preferably 6% or less.

[0030] The SrO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the SrO component is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the SrO component is preferably 5%, more preferably 4%, and most preferably 3%.

[0031] The BaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the BaO component is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the BaO component is preferably 30% or less, more preferably 29% or less, and most preferably 28% or less.

[0032] ZnO is an optional component that has the effect of lowering the liquidus temperature of glass and adjusting optical constants to desired values. However, if the content of ZnO is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the ZnO content is preferably 5% or less, more preferably 4% or less, and most preferably 3% or less.

[0033] Furthermore, fluoride which replaces part or all of one or more oxides of the above metal elements can be introduced as fluorine (F) of the fluoride component up to about 1% in order to adjust the refractive index of the glass.

[0034] The PbO component has the effect of increasing the refractive index of optical glass, but is harmful to the human body and the environment. In addition, since it has a large specific gravity, it increases the weight when used in space applications, which is not preferable. The glass of the present invention does not substantially contain the PbO component.

[0035] CEO 2 The TiO component has the effect of suppressing the decrease in the light transmittance in the visible region of optical glass caused by exposure to radiation and preventing coloration. However, especially in the region with a high refractive index, the glass becomes significantly colored, and the transmittance of the optical glass itself is greatly deteriorated. 2 In the optical glass of the present invention, the color development is emphasized in the presence of CeO 2 Even without the inclusion of any of the CeO components, the decrease in the visible light transmittance of the optical glass caused by irradiation with radiation can be suppressed, and a desired transmittance can be obtained. 2 Contains no ingredients.

[0036] The optical glass of the present invention shows little loss in light transmittance in the visible region even when irradiated with radiation. The optical glass of the present invention preferably shows a loss in light transmittance including reflection loss in a parallel plate sample of 10 mm thickness before and after irradiation with cobalt-60 gamma rays of wavelengths 450 nm and 550 nm at a dose rate of 100 krad of 30% or less, more preferably 28% or less, and most preferably 25% or less.

[0037] The optical glass of the present invention shows little decrease in light transmittance in the visible region when irradiated with radiation. Thus, the change [Δλ70] after exposure to gamma rays relative to [λ70] before exposure to gamma rays is 200 nm or less. In a more preferred embodiment, it is 180 nm or less, and in the most preferred embodiment, it is 150 nm or less.

[0038] The refractive index [n d The lower limit of the Abbe number [ν d ] has a lower limit of 15.00 and an upper limit of 35.00.

[0039] More specifically, the optical glass of the present invention can take two embodiments. Two embodiments will be described below. [First embodiment]

[0040] A first embodiment of the optical glass of the present invention will now be described.

[0041] SiO 2 The SiO component is an important component as a glass-forming oxide, but in this embodiment, if the content is too high, the desired optical performance cannot be obtained, and on the contrary, the devitrification resistance and melting property tend to deteriorate. 2 The upper limit of the content of the component is preferably 5% or less, more preferably 3% or less, and most preferably 2% or less.

[0042] B 2 O 3The component is an optional component that can be included as a glass-forming oxide. 2 O 3 If the content of the component is too high, the chemical durability and devitrification resistance of the optical glass tend to decrease. 2 O 3 The upper limit of the component is preferably 5% or less, more preferably 3% or less, and most preferably 2% or less.

[0043] P 2 O 5 The component is an important essential component as a glass-forming oxide. However, P 2 O 5 If the content of the component is too high, the chemical durability and devitrification resistance of the optical glass tend to decrease. 2 O 5 The lower limit of the content of the component is preferably 20% or more, more preferably 22% or more, and most preferably 24% or more. 2 O 5 The upper limit of the content of the component is preferably 35% or less, more preferably 30% or less, and most preferably 28% or less.

[0044] Nb 2 O 5 The component is an essential component that can be vitrified over a wide range as a glass component and has a great effect on increasing the refractive index and dispersion. 2 O 5 Nb has the effect of suppressing the decrease in the visible light transmittance of optical glass caused by irradiation with radiation and preventing coloration due to the various valences it can take. 2 O 5 The lower limit of the content of the element is preferably 35% or more, more preferably 38% or more, and most preferably 40% or more. 2 O 5 The upper limit of the content of the component is preferably 60% or less, more preferably 58% or less, and most preferably 55% or less.

[0045] TiO 2The TiO component is an optional component that has the effect of increasing the chemical durability and mechanical strength of optical glass, and has a large effect of increasing the refractive index. 2 If the content of the component is too high, the glass becomes easily devitrified and the transmittance of the glass decreases. 2 The upper limit of the content of the component is preferably 20% or less, more preferably 18% or less, and most preferably 17% or less.

[0046] WO 3 The component is an optional component and has a large effect of increasing the refractive index. 3 If the content of the component is too high, the glass becomes easily devitrified, resulting in a decrease in transmittance. 3 The upper limit of the content of the component is preferably 8% or less, more preferably 7% or less, and most preferably 6% or less.

[0047] Bi 2 O 3 The component is an optional component and is used as a glass component to increase the refractive index. However, Bi 2 O 3 If the content of the component is too high, the glass becomes easily devitrified and the transmittance decreases. 2 O 3 The upper limit of the content of the component is preferably 5% or less, more preferably 3% or less, and most preferably 2% or less.

[0048] Sb 2 O 3 This component is effective as a glass clarifier and in suppressing discoloration during production, and a content of 0.5% or less is sufficient.

[0049] Rn 2 The O component (wherein Rn is one or more selected from Li, Na and K) is an optional component that has the effect of promoting the melting of glass raw materials. 2 If the content of the O component is too high, the chemical durability of the optical glass tends to decrease. 2 The lower limit of the content of the O component is preferably 3% or more, more preferably 4% or more, and most preferably 5% or more.2 The upper limit of the O component is preferably 25% or less, more preferably 18% or less, and most preferably 16% or less.

[0050] Li 2 The O component is an optional component that has the effect of promoting the melting of glass raw materials. However, Li 2 If the O content is too high, the chemical durability of the optical glass is likely to decrease. 2 The upper limit of the O component is preferably 2% or less, more preferably 1% or less, and most preferably 0.5% or less.

[0051] Na 2 The O component is an optional component that has the effect of promoting the melting of glass raw materials. However, Na 2 If the O content is too high, the chemical durability of the optical glass is likely to decrease. 2 The upper limit of the O component is preferably less than 20%, more preferably 18% or less, and most preferably 16% or less.

[0052] K 2 The O component is an optional component that has the effect of promoting the melting of glass raw materials. 2 If the O content is too high, the chemical durability of the optical glass is likely to decrease. 2 The upper limit of the O component is preferably 10% or less, more preferably 9% or less, and most preferably 8% or less.

[0053] The RO component (wherein R is one or more selected from Mg, Ca, Ba, Sr, and Zn) is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the RO component is too high, the devitrification resistance of the optical glass is likely to deteriorate. Therefore, the upper limit of the RO component is preferably 20% or less, more preferably 18% or less, and most preferably 15% or less.

[0054] The MgO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the MgO component is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MgO component is preferably 5% or less, more preferably 4% or less, and most preferably 3% or less.

[0055] The CaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the CaO content is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably 5% or less, more preferably 4% or less, and most preferably 3% or less.

[0056] The BaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the BaO component is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the BaO component is preferably 20% or less, more preferably 15% or less, and most preferably 12% or less.

[0057] ZnO is an optional component that has the effect of lowering the liquidus temperature of glass and adjusting optical constants to desired values. However, if the content of ZnO is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the ZnO content is preferably 5% or less, more preferably 4% or less, and most preferably 3% or less.

[0058] Furthermore, fluoride which replaces part or all of one or more oxides of the above metal elements can be introduced as fluorine (F) of the fluoride component up to about 1% in order to adjust the refractive index of the glass.

[0059] The PbO component has the effect of increasing the refractive index of optical glass, but is harmful to the human body and the environment. In addition, since it has a large specific gravity, it increases the weight when used in space applications, which is not preferable. The glass of the present invention does not substantially contain the PbO component.

[0060] CEO 2 The TiO component has the effect of suppressing the decrease in the light transmittance in the visible region of optical glass caused by exposure to radiation and preventing coloration. However, especially in the region with a high refractive index, the glass becomes significantly colored, and the transmittance of the optical glass itself is greatly deteriorated. 2 In the optical glass of the present invention, the color development is emphasized in the presence of CeO 2 Even without the inclusion of any of the CeO components, the decrease in the visible light transmittance of the optical glass caused by irradiation with radiation can be suppressed, and a desired transmittance can be obtained. 2 Contains no ingredients.

[0061] The optical glass of the first embodiment shows little loss in light transmittance in the visible range even when irradiated with radiation. The optical glass of the present invention preferably shows a loss in light transmittance including reflection loss in a parallel plate sample of 10 mm thickness before and after irradiation with cobalt-60 gamma rays of wavelengths 450 nm and 550 nm at a dose rate of 100 krad of 30% or less, more preferably 28% or less, and most preferably 25% or less.

[0062] The optical glass of the first embodiment shows little loss in visible light transmittance when irradiated with radiation. Thus, the change [Δλ70] after exposure to gamma rays relative to [λ70] before exposure to gamma rays is 200 nm or less. In a more preferred embodiment, it is 180 nm or less, and in the most preferred embodiment, it is 150 nm or less.

[0063] The refractive index [n d The lower limit of the Abbe number [ν d ] has a lower limit of 15.00 or more and an upper limit of 35.00 or less. [Second embodiment]

[0064] A second embodiment of the optical glass of the present invention will now be described.

[0065] SiO 2 The SiO component is an essential component that is indispensable as a glass-forming oxide, and the inclusion of this component reduces coloration of the glass. However, if the content of this component is too high, the glass tends to have poor resistance to devitrification and melting properties. Therefore, SiO 2 The lower limit of the content of the component is preferably 1% or more, more preferably 2% or more, and most preferably 3% or more. 2 The upper limit of the content of the component is preferably 35% or less, more preferably 30% or less, and most preferably 27% or less.

[0066] GeO 2 The component is SiO 2 Similarly, GeO is an important component as a glass-forming oxide, and if its content is too high, the desired optical performance cannot be obtained, and on the contrary, devitrification resistance and melting property tend to deteriorate. In addition, it is expensive in terms of raw material cost, so it is not preferable to use a large amount. Therefore, GeO 2 The upper limit of the content of the component is preferably 15% or less, more preferably 14% or less, and most preferably 13% or less.

[0067] B 2 O 3 The component is an optional component that can be included as a glass-forming oxide. 2 O 3 If the content of the component is too high, the chemical durability and devitrification resistance of the optical glass tend to decrease. 2 O 3 The upper limit of the component is preferably 12% or less, more preferably 10% or less, and most preferably 9% or less.

[0068] La 2 O 3 The component contributes to improving the chemical durability and refractive index of the glass. However, if the content of the component is too high, the glass becomes easily devitrified. Therefore, La 2 O 3 The upper limit of the content of the component is preferably 45% or less, more preferably 40% or less, and most preferably 37% or less.

[0069] Nb 2 O 5 The component is an essential component that can be vitrified over a wide range as a glass component and has a great effect on increasing the refractive index and dispersion. 2 O 5 Nb has the effect of suppressing the decrease in the visible light transmittance of optical glass caused by irradiation with radiation and preventing coloration due to the various valences it can take. 2 O 5 The lower limit of the content of the element is preferably 5%, more preferably 6%, and most preferably 7%. 2 O 5 The upper limit of the content of the component is preferably 50% or less, more preferably 49% or less, and most preferably 48% or less.

[0070] TiO 2 The TiO component is an optional component that has the effect of increasing the chemical durability and mechanical strength of optical glass, and has a large effect of increasing the refractive index. 2 If the content of the component is too high, the glass becomes easily devitrified and the transmittance of the glass decreases. 2 The upper limit of the content of the component is preferably 35% or less, more preferably 32% or less, and most preferably 29% or less.

[0071] Ta 2 O 5 The component is an optional component and has a large effect of increasing the refractive index. 2 O 5 If the content of the component is too high, the glass is likely to devitrify, and is also undesirable from the standpoint of cost. 2 O 5 The upper limit of the content of the component is preferably 10% or less, more preferably 9% or less, and most preferably 8% or less.

[0072] WO 3 The component is an optional component and has a large effect of increasing the refractive index. 3 If the content of the component is too high, the glass becomes easily devitrified, resulting in a decrease in transmittance. 3The upper limit of the content of the component is preferably 5% or less, more preferably 3% or less, and most preferably 2% or less.

[0073] ZrO 2 The component is an optional component that contributes to improving the chemical durability of the glass. However, ZrO 2 If the content of the component is too high, the glass is prone to devitrification. 2 The upper limit of the content of the component is preferably 10% or less, more preferably 9% or less, and most preferably 8% or less.

[0074] Sb 2 O 3 The component can be used as a fining agent for glass, and a content of 1% or less is sufficient.

[0075] Rn 2 The O component (wherein Rn is one or more selected from Li, Na and K) is an optional component that has the effect of promoting the melting of glass raw materials. 2 If the content of the O component is too high, the chemical durability of the optical glass tends to decrease. 2 The upper limit of the O component is preferably 20% or less, more preferably 15% or less, and most preferably 12% or less.

[0076] Li 2 The O component is an optional component that has the effect of promoting the melting of glass raw materials. However, Li 2 If the O content is too high, the chemical durability of the optical glass is likely to decrease. 2 The upper limit of the O component is preferably 5% or less, more preferably 4% or less, and most preferably 3% or less.

[0077] Na 2 The O component is an optional component that has the effect of promoting the melting of glass raw materials. However, Na 2 If the O content is too high, the chemical durability of the optical glass is likely to decrease. 2 The upper limit of the O component is preferably less than 20%, more preferably 15% or less, and most preferably 12% or less.

[0078] K 2 The O component is an optional component that has the effect of promoting the melting of glass raw materials. 2 If the O content is too high, the chemical durability of the optical glass is likely to decrease. 2 The upper limit of the O component is preferably 5% or less, more preferably 3% or less, and most preferably 1% or less.

[0079] The RO component (wherein R 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 constants to desired values. However, if the content of the RO component is too high, the devitrification resistance of the optical glass is likely to deteriorate. Therefore, the upper limit of the RO component is preferably 30% or less, more preferably 29% or less, and most preferably 28% or less.

[0080] The MgO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the MgO component is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the MgO component is preferably 10% or less, more preferably 8% or less, and most preferably 6% or less.

[0081] The CaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the CaO content is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the CaO component is preferably 10% or less, more preferably 8% or less, and most preferably 6% or less.

[0082] The SrO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the SrO component is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the SrO component is preferably 5% or less, more preferably 4% or less, and most preferably 3% or less.

[0083] The BaO component is an optional component that has the effect of lowering the liquidus temperature of the glass and adjusting the optical constants to desired values. However, if the content of the BaO component is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the BaO component is preferably 30% or less, more preferably 29% or less, and most preferably 28% or less.

[0084] ZnO is an optional component that has the effect of lowering the liquidus temperature of glass and adjusting optical constants to desired values. However, if the content of ZnO is too high, the devitrification resistance of the optical glass tends to deteriorate. Therefore, the upper limit of the ZnO component is preferably 30% or less, more preferably 29% or less, and most preferably 28% or less.

[0085] Furthermore, fluoride which replaces part or all of one or more oxides of the above metal elements can be introduced as fluorine (F) of the fluoride component up to about 1% in order to adjust the refractive index of the glass.

[0086] The PbO component has the effect of increasing the refractive index of optical glass, but is harmful to the human body and the environment. In addition, since it has a large specific gravity, it increases the weight when used in space applications, which is not preferable. The glass of the present invention does not substantially contain the PbO component.

[0087] CEO 2 The TiO component has the effect of suppressing the decrease in the light transmittance in the visible region of optical glass caused by exposure to radiation and preventing coloration. However, especially in the region with a high refractive index, the glass becomes significantly colored, and the transmittance of the optical glass itself is greatly deteriorated. 2 In the optical glass of the present invention, the color development is emphasized in the presence of CeO 2 Even without the inclusion of any of the CeO components, the decrease in the visible light transmittance of the optical glass caused by irradiation with radiation can be suppressed, and a desired transmittance can be obtained. 2 Contains no ingredients.

[0088] The optical glass of the second embodiment shows little loss in light transmittance in the visible range even when irradiated with radiation. The optical glass of the present invention preferably shows a loss in light transmittance including reflection loss in a parallel plate sample of 10 mm thickness before and after irradiation with cobalt-60 gamma rays of wavelengths 450 nm and 550 nm at a dose rate of 100 krad of 30% or less, more preferably 28% or less, and most preferably 25% or less.

[0089] The optical glass of the second embodiment has a small decrease in light transmittance in the visible range when irradiated with radiation. 70 ] after exposure to gamma rays [Δλ 70 In a more preferred embodiment, it is 180 nm or less, and in a most preferred embodiment, it is 150 nm or less.

[0090] The refractive index [n d The lower limit of the Abbe number [ν d ] has a lower limit of 15.00 or more and an upper limit of 35.00 or less. EXAMPLES

[0091] Examples of optical glass according to the present invention are shown below. The optical glass according to the examples of the present invention was produced as follows. First, normal raw materials for optical glass, such as oxides, hydroxides, carbonates, and nitrates, were mixed to obtain the composition of each example shown in Table 1. Next, the mixed raw materials were placed in a platinum crucible and melted at 1100 to 1350°C for 2 to 5 hours depending on the melting property of the composition, and then clarified and stirred to homogenize the molten glass. Finally, the molten glass was cast into a stainless steel mold and molded, and then slowly cooled. In addition, the comparative examples include the Nb 2 O 5 Glasses outside the above range were similarly prepared and shown as comparative examples.

[0092] The refractive index [n d], Abbe number [ν d ], the spectral transmittance before exposure to radiation, and the spectral transmittance after exposure to radiation were measured. The refractive index and Abbe number of the examples and comparative examples were measured based on the Japan Optical Glass Industry Association standard JOGIS01-2019. Here, the refractive index and Abbe number were measured in accordance with the V-block method defined in JIS B 7071-2:2018. Here, the refractive index (n d ) is shown as a measurement value for the d line (587.56 nm) of a helium lamp. d ) is the refractive index for the d line of the helium lamp (n d ) and the refractive index (n F ), and the refractive index for the C line (656.27 nm) (n C ) value, the Abbe number (ν d )=[(n d -1) / (n F -n C The refractive indexes (n d ), Abbe number (ν d ) was determined by measuring the glass obtained by cooling at a rate of -25°C / hr. In addition, the spectral transmittance of the examples and comparative examples was measured in accordance with the Japan Optical Glass Industry Association standard JOGIS02-2019. Specifically, the spectral transmittance was obtained by measuring the transmittance of light having a wavelength of 200 to 800 nm for a 10±0.1 mm thick parallel polished product in accordance with JIS Z 8722. From the obtained spectral transmittance, the transmittance at 450 nm and 550 nm and the wavelength [λ] at which the light transmittance becomes 70% were calculated. 70 The optical glass thus produced was irradiated with radiation using a cobalt-60 gamma ray irradiation facility. Specifically, the optical glass was irradiated with cobalt-60 gamma rays so that the absorbed dose was 100 krad. The transmittance at 450 nm and 550 nm after exposure to gamma rays, and the wavelength at which the light transmittance becomes 70% [λ 70 ] and the transmittance at 450 nm and 550 nm before exposure to gamma rays, and the wavelength at which the light transmittance becomes 70% [λ 70] were calculated and designated as Δ450, Δ550, and Δ70. The measured nd, νd, λ70, Δ450, Δ550, and Δ70 are shown in the table.

[0093] [Table 1]

[0094] [Table 2]

[0095] [Table 3]

[0096] [Table 4]

[0097] From the above examples, it is clear that the optical glass of the present invention has a visible light transmittance required for optical glass, and even when irradiated with radiation, there is little decrease in the visible light transmittance compared to before exposure to radiation.

Claims

1. In mass% based on oxide, SiO ２ Ingredients: 0-35%, GeO ２ Ingredients: 0-15% B ２ O ３ Ingredients: 0-12% P ２ O ５ Ingredients: 0-35%, Nb ２ O ５ Ingredients: 5-60% TiO ２ Ingredients: 0-35%, T ２ O ５ Ingredients: 0-10% WO ３ Ingredients: 0-8% Bi ２ O ３ Ingredients: 0-5% ZrO ２ Ingredients: 0-10% La ２ O ３ +Y ２ O ３ +Gd ２ O ３ The content of the component is 0 to 45%, Sb ２ O ３ Ingredients: 0-1% Rn ２ The oxides of the above metal elements are substituted in whole or in part with fluorine (F) of the fluoride, and the oxides of the above metal elements are substituted in a total amount of 0 to 8%. ２ and PbO, and when irradiated with cobalt-60 gamma rays so as to achieve an absorbed dose of 100 krad, the decrease in transmittance at 450 nm and 550 nm before and after irradiation is 30% or less.

2. In mass% based on oxide, SiO ２ Ingredients: 0-5% B ２ O ３ Ingredients: 0-5% P ２ O ５ Ingredients: 20-35% Nb ２ O ５ Ingredients: 35-60%, TiO ２ Ingredients: 0-20%, WO ３ Ingredients: 0-8% Bi ２ O ３ Ingredients: 0-5% Sb ２ O ３ Ingredients: 0-0.5%, Rn ２ O component is 3 to 25% (wherein Rn is one or more selected from Li, Na and K). RO component: 0 to 20% (wherein R is one or more selected from Mg, Ca, Sr, Ba and Zn). and the optical glass according to claim 1, containing 0 to 8% in total of fluorine (F) in fluorides which have substituted a part or all of an oxide of one or more of the above metal elements.

3. In mass% based on oxide, SiO ２ Ingredients: 1-35%, GeO ２ Ingredients: 0-15% B ２ O ３ Ingredients: 0-12% La ２ O ３ Ingredients: 0-45% Nb ２ O ５ Ingredients: 5-50% TiO ２ Ingredients: 0-35%, T ２ O ５ Ingredients: 0-10% WO ３ Ingredients: 0-5% ZrO ２ Ingredients: 0-10% Sb ２ O ３ Ingredients: 0-1% Rn ２ O component is 0 to 20% (wherein Rn is one or more selected from Li, Na and K). RO component: 0 to 30% (wherein R is one or more selected from Mg, Ca, Sr and Ba). and the optical glass according to claim 1, containing 0 to 8% in total of fluorine (F) in fluorides which have substituted a part or all of an oxide of one or more of the above metal elements.

4. When a sample is irradiated with cobalt 60 gamma rays so that the absorbed dose is 100 krad, the wavelength [λ] at which the light transmittance of a sample with a thickness of 10 mm becomes 70% before and after the irradiation is ７０ 4. The optical glass according to claim 1, wherein the difference between the refractive index and the refractive index of the optical fiber is 200 nm or less.

5. Refractive index [n ｄ ] is 1.75000 or more and 2.05000 or less, and the Abbe number [ν ｄ 4. The optical glass according to claim 1, wherein the refractive index is 15.00 or more and 35.00 or less.

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