Optical Glass and Optical Elements

Abstract

To provide an optical glass and an optical element which have a small Abbe's number νd, and a relatively high partial dispersion ratio PC,t in an infrared wavelength region.SOLUTION: In an optical glass, the content of Si4+ is 10 cationic% or more, the content of B3+ is 20 cationic% or more, the total content [Si4++B3+] of Si4+ and B3+ is 50 cationic% or more, a cation ratio between the content of B3+ and the total content of Si4+ and B3+ [B3+ / (Si4++B3+)] is 0.44 or more, a cation ratio between the total content R of Li+, Na+ and K+, and the total amount of the total content R, and the total content R' of Mg2+, Ca2+, Sr2+, Ba2+ and Zn2+ [R / (R+R')] is 0.55 or more, the content of Nb5+ exceeds 0 cationic% and 11.5 cationic% or less, and the glass satisfies one or more of the following (i) and (ii). (i) a cation ratio between the content of Zr4+, the above-described total content R', and the total content of Nb5+, Ti4+, W6+, Bi3+, and Ta5+ [Zr4+ / (R'+Nb5++Ti4++W6++Bi3++Ta5+)] is 0.17 or more. (ii) a cation ratio between the total content of Zr4+ and Ta5+, the above-described total content R', and the total content Nb5+, Ti4+, W6+ and Bi3+ [(Zr4++Ta5+) / (R'+Nb5++Ti4++W6++Bi3+)] is 0.25 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an optical glass and an optical element. [Background technology]

[0002] Many surveillance cameras and security cameras are equipped with night vision capabilities, and their imaging optical systems are required to have imaging performance in the infrared wavelength range in addition to imaging performance in the visible short wavelength range.

[0003] To correct high-order chromatic aberrations from the visible short wavelength region to the infrared wavelength region, two types of lenses may be combined. Examples of two types of lenses include a combination of a convex lens and a concave lens, or a combination of a low-dispersion lens and a high-dispersion lens. It is desirable that these two types of lenses have a large difference in Abbe number, a small difference in the partial dispersion ratio Pg,F in the visible short wavelength region, and a small difference in the partial dispersion ratio PC,t in the infrared wavelength region.

[0004] Of the two types of lenses mentioned above, fluorophosphate glass, which has low dispersion and anomalous dispersion, may be used as one of the lenses. Fluorophosphate glass, which has low dispersion and anomalous dispersion, often has a larger Abbe number νd and PC,t, and a smaller Pg,F, than the lens used in combination with it. Therefore, the glass used as the other lens to be combined with a fluorophosphate glass lens is required to have an Abbe number νd smaller than that of the fluorophosphate glass, and Pg,F and PC,t as close as possible to the values ​​of the fluorophosphate glass.

[0005] In high-dispersion glasses, if the Abbe number νd is reduced by increasing the content of glass components that contribute to high dispersion in the glass composition, Pg,F usually increases and Pc,t decreases. In lenses made from such high-dispersion glasses, the difference in Pc,t from that of the fluorophosphate glass becomes large, making it impossible to sufficiently correct chromatic aberration in the long wavelength range, making them unsuitable for use in night-vision cameras in particular.

[0006] Patent Documents 1 and 2 focus on anomalous partial dispersion and propose optical glasses having dispersion within a predetermined range, but do not pay any attention to the partial dispersion ratio PC,t in the infrared wavelength region.

[0007] Therefore, there is a demand for lenses made of glass with a small Abbe number νd and a relatively high PC,t to be combined with fluorophosphate glass lenses in order to correct high-order chromatic aberrations from the visible short wavelength region to the infrared wavelength region. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 10-130033 [Patent Document 2] Japanese Patent Application Publication No. 2017-095348 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in light of these circumstances, and has as its object the provision of an optical glass and optical element having a small Abbe number vd and a relatively high partial dispersion ratio Pc,t in the infrared wavelength region. With this object in mind, the inventors searched for a glass whose partial dispersion ratio Pc,t does not decrease excessively even when it is made highly dispersed, and as a result, they have completed the present invention. [Means for solving the problem]

[0010] The gist of the present invention is as follows. (1) The SiO2 content is 20 mass% or more, The content of B2O3 is 15% by mass or more, The content of ZrO2 is 5 mass% or more, The content of Nb2O5 exceeds 5% by mass, the mass ratio [(R2O+R'O) / (SiO2+B2O3)] of the total content R2O of Li2O, Na2O, and K2O, and the total content R'O of MgO, CaO, SrO, BaO, and ZnO to the total content R2O of SiO2 and B2O3 is 0.36 or less; the mass ratio of the content of B2O3 to the total content of ZrO2, Nb2O5, TiO2, WO3, Bi2O3, and Ta2O5 [B2O3 / (ZrO2+Nb2O5+TiO2+WO3+Bi2O3+Ta2O5)] is 0.74 or more; The total content of ZrO2, Nb2O5, TiO2, WO3, and Ta2O5 is 22 mass% or more, Optical glass that is substantially Pb-free.

[0011] (2) As a glass component, Contains SiO2, B2O3, ZrO2, and Nb2O5, Contains one or more selected from the group consisting of Li2O, Na2O, and K2O, An optical glass having a ΔPC,t of 0.0250 or more.

[0012] (3) Si 4+ The content of is 10 cation % or more, B 3+ The content of is 20 cation % or more, Si 4+ and B 3+ The total content of [Si 4+ +B 3+ ] is 50 cation % or more, B 3+ and Si content 4+ and B 3+ The total content and cation ratio [B 3+ / (Si 4+ +B 3+ )] is 0.44 or more, Li + , Na + , and K. + The total content R of the above and Mg 2+ , Ca 2+ , Sr 2+ , Ba2+ and Zn 2+ The cation ratio [R / (R+R')] to the total content R' of [R / (R+R')] is 0.55 or more, Nb 5+ The content of is more than 0 cation% and 11.5 cation% or less, An optical glass that satisfies one or more of the following (i) and (ii): (i) Zr 4+ The content of R' and the total content of Nb 5+ , Ti 4+ , W 6+ , Bi 3+ , and Ta 5+ The total content and cation ratio [Zr 4+ / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ +Ta 5+ )] is 0.17 or greater. (ii) Zr 4+ and Ta 5+ The total content of R', Nb 5+ , Ti 4+ , W 6+ , and Bi 3+ The cation ratio [(Zr 4+ +Ta 5+ ) / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ )] is 0.25 or greater.

[0013] (4) Zr 4+ and Ta 5+ The optical glass according to (3), wherein the total content of is 8.5 cation % or less.

[0014] (5) Zr 4+ and Ta 5+ The total content of Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content of R', Nb 5+ , Ti 4+ , W6+ , and Bi 3+ The cation ratio [(Zr 4+ +Ta 5+ ) / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ )] is 3.10 or less.

[0015] (6) As a glass component, Si 4+ , B 3+ , Zr 4+ , and Nb 5+ Contains Li + , Na + , and K. + Contains one or more selected from the group consisting of: An optical glass having a ΔPC,t of 0.0250 or more.

[0016] (7) An optical element made of the optical glass according to any one of (1) to (6) above. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an optical glass and an optical element that have a small Abbe number vd and a relatively high partial dispersion ratio PC,t in the infrared wavelength range. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described. The content of the glass component can be determined by a known method, such as inductively coupled plasma atomic emission spectroscopy (ICP-AES) or inductively coupled plasma mass spectroscopy (ICP-MS).

[0019] In this specification, the thermal stability and reheating stability of glass both refer to the resistance to crystal precipitation in the glass. In particular, the thermal stability refers to the resistance to crystal precipitation when molten glass solidifies, and the reheating stability refers to the resistance to crystal precipitation when solidified glass is reheated, such as during reheat pressing.

[0020] In this specification, unless otherwise specified, the refractive index refers to the refractive index nd at the d line of helium (wavelength 587.56 nm).

[0021] The optical glass of the present invention will be described below as a first embodiment (embodiments 1-1 and 1-2) and a second embodiment (embodiments 2-1 and 2-2).

[0022] First embodiment In the first embodiment (embodiment 1-1 and embodiment 1-2), the glass composition of the optical glass is expressed on an oxide basis unless otherwise specified. Here, "glass composition on an oxide basis" refers to the glass composition obtained by converting the glass raw materials into oxides present in the optical glass after they are all decomposed during melting, and each glass component is conventionally expressed as SiO2, TiO2, etc. In the first embodiment (embodiment 1-1 and embodiment 1-2), the contents and total contents of glass components are on a mass basis unless otherwise specified, and "%" means "mass %." Furthermore, in this specification and the present invention, a content of 0% of a component means that the component is substantially not contained, and it is acceptable for the component to be present at an unavoidable impurity level.

[0023] 1-1 embodiment In embodiment 1-1, the glass composition was designed based on the following guidelines: (1) by incorporating large amounts of SiO2 and B2O3, which are components that increase the partial dispersion ratio Pc,t in the infrared wavelength range; (2) simultaneously substituting a portion of SiO2 with B2O3 as appropriate to achieve high dispersion without significantly decreasing Pc,t; (3) appropriately incorporating alkali metal and alkaline earth metal oxides to further increase dispersion and reduce viscosity, thereby improving meltability and formability; and (4) minimizing the amount of high-dispersion components that are necessary to obtain the desired Abbe number but also decrease Pc,t. Specifically, by actively incorporating Nb2O5, which among the high-dispersion components, can relatively suppress the decrease in Pc,t, and ZrO2, which can simultaneously suppress the decrease in Pc,t and improve the chemical durability of the glass, an optical glass with a small Abbe number νd and a relatively high partial dispersion ratio Pc,t in the infrared wavelength range was completed. The optical glass according to embodiment 1-1 is as follows.

[0024] The optical glass according to the first embodiment is The SiO2 content is 20% or more, The B2O3 content is 15% or more, The ZrO2 content is 5% or more, The content of Nb2O5 exceeds 5%, the mass ratio [(R2O+R'O) / (SiO2+B2O3)] of the total content R2O of Li2O, Na2O, and K2O, and the total content R'O of MgO, CaO, SrO, BaO, and ZnO to the total content R2O of SiO2 and B2O3 is 0.36 or less; the mass ratio of the content of B2O3 to the total content of ZrO2, Nb2O5, TiO2, WO3, Bi2O3, and Ta2O5 [B2O3 / (ZrO2+Nb2O5+TiO2+WO3+Bi2O3+Ta2O5)] is 0.74 or more; The total content of ZrO2, Nb2O5, TiO2, WO3, and Ta2O5 is 22% or more; Substantially free of Pb.

[0025] In the optical glass according to embodiment 1-1, the SiO2 content is 20% or more. The lower limit of the SiO2 content is preferably 24%, with 26% and 28% being more preferred in that order. The upper limit of the SiO2 content is preferably 50%, with 45%, 40%, and 35% being more preferred in that order. SiO2 is a glass network-forming component. By setting the SiO2 content within the above range, the partial dispersion ratio PC,t in the infrared wavelength range can be increased and chemical durability can be improved. If the SiO2 content is too low, the partial dispersion ratio PC,t in the infrared wavelength range can decrease, and the thermal stability and chemical durability of the glass can also decrease. If the SiO2 content is too high, the meltability of the glass can decrease, and the viscosity of the molten glass can increase, potentially worsening moldability.

[0026] In the optical glass according to embodiment 1-1, the B2O3 content is 15% or more. The lower limit of the B2O3 content is preferably 17%, with 19% and 21% being more preferred in that order. The upper limit of the B2O3 content is preferably 50%, with 45%, 40%, and 35% being more preferred in that order. B2O3 is a glass network-forming component. By setting the B2O3 content within the above range, the partial dispersion ratio P C,t in the infrared wavelength range can be increased. If the B2O3 content is too low, the partial dispersion ratio P C,t in the infrared wavelength range will decrease, and the thermal stability of the glass may also decrease. If the B2O3 content is too high, the chemical durability of the glass may decrease.

[0027] In the optical glass according to embodiment 1-1, the ZrO2 content is 5% or more. The lower limit of the ZrO2 content is preferably 6.5%, with 8.0% and 9.5% being more preferred. The upper limit of the ZrO2 content is preferably 30%, with 25%, 20%, and 15% being more preferred in that order. By keeping the ZrO2 content within the above range, the partial dispersion ratio PC,t in the infrared wavelength range can be increased, and chemical durability can be improved. If the ZrO2 content is too low, chemical durability may be reduced. If the ZrO2 content is too high, the liquidus temperature LT may be increased, and stability during reheating may be reduced.

[0028] In the optical glass according to embodiment 1-1, the Nb2O5 content exceeds 5%. The lower limit of the Nb2O5 content is preferably 6.5%, with 8.0% and 9.5% being more preferred. The upper limit of the Nb2O5 content is preferably 30%, with 25%, 20%, and 15% being more preferred in that order. By setting the Nb2O5 content within the above range, high dispersion can be maintained while suppressing a decrease in the partial dispersion ratio P C,t in the infrared wavelength range. If the Nb2O5 content is too low, high dispersion may not be maintained. If the Nb2O5 content is too high, the partial dispersion ratio P C,t in the infrared wavelength range may decrease.

[0029] In the optical glass according to embodiment 1-1, the mass ratio [(R2O + R'O) / (SiO2 + B2O3)] of the total content R2O of Li2O, Na2O, and K2O, and the total content R'O of MgO, CaO, SrO, BaO, and ZnO, to the total content R2O of SiO2 and B2O3 is 0.36 or less. The upper limit of this mass ratio is preferably 0.35, with 0.34 and 0.33 being more preferred in that order. The lower limit of this mass ratio is preferably 0.05, with 0.10, 0.15, and 0.20 being more preferred in that order. By keeping this mass ratio within the above range, the partial dispersion ratio Pc,t in the infrared wavelength region can be increased, thereby improving chemical durability.

[0030] In this specification, the total content of Li2O, Na2O, and K2O may be referred to as R2O, and the total content of MgO, CaO, SrO, BaO, and ZnO may be referred to as R'O.

[0031] In the optical glass according to embodiment 1-1, the mass ratio of the content of B2O3 to the total content of ZrO2, Nb2O5, TiO2, WO3, Bi2O3, and Ta2O5 [B2O3 / (ZrO2+Nb2O5+TiO2+WO3+Bi2O3+Ta2O5)] is 0.74 or greater. The lower limit of this mass ratio is preferably 0.84, with 0.94 and 1.04 being more preferred. The upper limit of this mass ratio is preferably 3.0, with 2.5, 2.0, and 1.5 being more preferred in that order. By keeping this mass ratio within the above range, the partial dispersion ratio P C,t in the infrared wavelength region can be increased.

[0032] In the optical glass according to embodiment 1-1, the total content of ZrO2, Nb2O5, TiO2, WO3, and Ta2O5 [ZrO2 + Nb2O5 + TiO2 + WO3 + Ta2O5] is 22% or more. The lower limit of this total content is preferably 22.5%, with 23.0% and 23.5% being more preferred. The upper limit of this total content is preferably 40%, with 35%, 30%, and 25% being more preferred in that order. By keeping this total content within the above range, the refractive index nd can be increased and the Abbe number νd can be set within a desired range.

[0033] The optical glass according to embodiment 1-1 does not substantially contain Pb, which is a component that poses a concern for its environmental impact. That is, the Pb content is preferably 0% in terms of oxide. Like Pb, As and Th are also components that pose a concern for their environmental impact. Therefore, the As and Th contents are preferably 0 to 0.1% in terms of oxide, and may be 0 to 0.05%, or 0 to 0.01%. The As and Th contents are preferably 0% in terms of oxide. That is, it is preferable that neither As nor Th is substantially contained.

[0034] The preferred contents of the glass components in the optical glass according to embodiment 1-1 are shown below.

[0035] In the optical glass according to embodiment 1-1, the lower limit of the total content of SiO2 and B2O3 [SiO2 + B2O3] is preferably 35%, more preferably 40%, 45%, and 50%, in that order. The upper limit of this total content is preferably 70%, more preferably 65%, 60%, and 57%, in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and maintaining the thermal stability of the glass, it is preferable that the total content be within the above range. If the total content is too low, the partial dispersion ratio PC,t in the infrared wavelength range will decrease, and the thermal stability and chemical durability of the glass may not be maintained. If the total content is too high, the viscosity of the glass melt may increase, potentially worsening moldability. Furthermore, the refractive index may decrease.

[0036] In the optical glass according to embodiment 1-1, the lower limit of the mass ratio [B2O3 / (SiO2+B2O3)] of the B2O3 content to the total content of SiO2 and B2O3 is preferably 0.20, with 0.25, 0.30, and 0.35 being more preferred in this order. The upper limit of this mass ratio is preferably 0.65, with 0.60, 0.55, and 0.50 being more preferred in this order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range, it is preferable that this mass ratio be within the above range. If this mass ratio is too small, the partial dispersion ratio PC,t may decrease. If this mass ratio is too large, the chemical durability of the glass may decrease.

[0037] In the optical glass according to embodiment 1-1, the lower limit of the mass ratio [R2O / (R2O+R2O)] of the total content R2O of Li2O, Na2O, and K2O to the sum of the total content R2O and the total content R'O of MgO, CaO, SrO, BaO, and ZnO is preferably 0.20, and more preferably 0.25, 0.30, and 0.35, in that order. The upper limit of this mass ratio is preferably 1, and more preferably 0.95, 0.90, and 0.85, in that order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that this mass ratio be within the above range. If this mass ratio is too small, the partial dispersion ratio P C,t may decrease. If this mass ratio is too large, the thermal stability of the glass may decrease and the refractive index nd may decrease.

[0038] In the optical glass according to embodiment 1-1, the mass ratio [ZrO2 / (R'O+Nb2O5+TiO2+WO3+Bi2O3+Ta2O5)] of the ZrO2 content to the total content of MgO, CaO, SrO, BaO, and ZnO (R'O, Nb2O5, TiO2, WO3, Bi2O3, and Ta2O5) is preferably 0.20, with 0.25, 0.30, and 0.35 being more preferred. The upper limit of this mass ratio is preferably 1.5, with 1.25, 1.00, and 0.70 being more preferred in this order. From the viewpoints of improving chemical durability, increasing the refractive index nd, and maintaining high dispersion, it is preferable that this mass ratio be within the above range. If this mass ratio is too small, the refractive index nd may decrease, and the chemical durability of the glass may also decrease. If the mass ratio is too large, the liquidus temperature LT may increase, and stability during reheating may decrease.

[0039] In the optical glass according to embodiment 1-1, the mass ratio [(ZrO2 + Ta2O5) / (R'O + Nb2O5 + TiO2 + Bi2O3 + WO3)] of the total content of ZrO2 and Ta2O5 to the total content of MgO, CaO, SrO, BaO, and ZnO, R'O, Nb2O5, TiO2, Bi2O3, and WO3 is preferably 0.1 in lower limit, with 0.2, 0.3, and 0.4 being more preferred in that order. The upper limit of this mass ratio is preferably 1.3, with 1.1, 0.9, and 0.7 being more preferred in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, increasing the refractive index nd, maintaining high dispersion, and maintaining the chemical durability of the glass, it is preferable that this mass ratio be within the above range. If this mass ratio is too small, the refractive index nd may decrease and the chemical durability of the glass may also decrease. If the mass ratio is too large, the thermal stability of the glass may decrease.

[0040] In the optical glass according to embodiment 1-1, the lower limit of the total content of ZrO2 and Ta2O5 [ZrO2 + Ta2O5] is preferably 6%, more preferably 7%, 8%, and 9%, in that order. The upper limit of this total content is preferably 20%, more preferably 18%, 16%, and 14%, in that order. From the viewpoint of maintaining the thermal stability of the glass, it is preferable that this total content be within the above range. If this total content is too low, the chemical durability of the glass may be reduced. If this total content is too high, the thermal stability of the glass may be reduced, and raw material costs may increase.

[0041] Non-limiting examples of the contents and ratios of glass components other than those described above in the optical glass according to embodiment 1-1 are shown below.

[0042] In the optical glass according to embodiment 1-1, the upper limit of the P2O5 content is preferably 20%, and more preferably 15%, 10%, and 5%, in that order. The lower limit of the P2O5 content is preferably 0%, and more preferably 0.1%, 0.5%, and 1%, in that order. The P2O5 content may be 0%. By keeping the P2O5 content within the above range, the thermal stability of the glass can be maintained.

[0043] In the optical glass according to embodiment 1-1, the upper limit of the Al2O3 content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1.75%, 1.50%, and 1.25%, in that order. The lower limit of the Al2O3 content is preferably 0%, and more preferably 0.25%, 0.50%, and 0.75%, in that order. The Al2O3 content may be 0%. When an appropriate amount of Al2O3 is contained, it has the effect of suppressing phase separation in the glass. On the other hand, from the viewpoint of maintaining the thermal stability of the glass, it is preferable that the Al2O3 content be within the above range.

[0044] In the optical glass according to embodiment 1-1, the lower limit of the total content of SiO2, B2O3, and Al2O3 [SiO2 + B2O3 + Al2O3] is preferably 42%, with 45%, 48%, and 51% being more preferred in that order. The upper limit of this total content is preferably 74%, with 71%, 68%, and 65% being more preferred in that order. From the viewpoints of increasing the partial dispersion ratio Pc,t in the infrared wavelength range and maintaining the thermal stability and reheating stability of the glass, it is preferable that the total content be within the above range.

[0045] In the glass according to embodiment 1-1, the upper limit of the Li2O content is preferably 20%, more preferably 15%, 10%, and 6%, in that order. The lower limit of the Li2O content is preferably 0%, more preferably 1%, 2%, and 3%, in that order. The Li2O content may be 0%. Li2O is a component that contributes to lowering the viscosity of the glass, and among alkali metals, it has a relatively large effect of increasing the partial dispersion ratio P C,t in the infrared wavelength range. If the Li2O content is too high, there is a risk that stability during reheating will decrease. If the Li2O content is too low, there is a risk that the viscosity of the glass will increase.

[0046] In the glass according to embodiment 1-1, the upper limit of the Na2O content is preferably 20%, more preferably 18%, 16%, and 14%, in that order. The lower limit of the Na2O content is preferably 0%, more preferably 1%, 2%, and 3%, in that order. Na2O, like Li2O, is a component that contributes to lowering the viscosity of the glass. If the Na2O content is too high, there is a risk that the stability during reheating will decrease. If the Na2O content is too low, there is a risk that the viscosity of the glass will increase.

[0047] In the optical glass according to embodiment 1-1, the upper limit of the K2O content is preferably 20%, and more preferably 18%, 16%, and 14% in that order. The lower limit of the K2O content is preferably 0%, and more preferably 1%, 2%, and 3% in that order. The K2O content may even be 0%.

[0048] K2O has the function of lowering the liquidus temperature and improving the thermal stability of glass. On the other hand, if the K2O content is too high, the chemical durability, weather resistance, and stability during reheating decrease. Therefore, the K2O content is preferably within the above range.

[0049] In the optical glass according to embodiment 1-1, the upper limit of the total content R2O of Li2O, Na2O, and K2O [Li2O + Na2O + K2O] is preferably 25%, with 20%, 15%, and 10% being more preferred in that order. The lower limit of the total content R2O is preferably 1%, with 2.5%, 4.0%, and 5.5% being more preferred in that order. From the viewpoint of preventing a decrease in stability during reheating, it is preferable that the total content R2O be within the above range.

[0050] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [Li2O / R2O] of the content of Li2O to the total content R2O of Li2O, Na2O, and K2O is preferably 1, and more preferably 0.8, 0.6, and 0.4 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.1, 0.2, and 0.3 in that order. This mass ratio may even be 0. From the viewpoint of preventing a decrease in stability during reheating, it is preferable that this mass ratio be within the above range.

[0051] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [Na2O / R2O] of the content of Na2O to the total content R2O of Li2O, Na2O, and K2O is preferably 1, and more preferably 0.9, 0.8, and 0.7 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.1, 0.2, and 0.3 in that order. This mass ratio may even be 0. From the viewpoint of preventing a decrease in stability during reheating, it is preferable that this mass ratio be within the above range.

[0052] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [K2O / R2O] of the content of K2O to the total content R2O of Li2O, Na2O and K2O is preferably 1, and more preferably 0.8, 0.6, and 0.4 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.1, 0.2, and 0.3 in that order. This mass ratio may even be 0. From the viewpoint of preventing a decrease in stability during reheating, it is preferable that this mass ratio be within the above range.

[0053] In the optical glass according to embodiment 1-1, the upper limit of the CsO content is preferably 20%, and more preferably 15%, 10%, and 5%, in that order. The lower limit of the CsO content is preferably 0%. The CsO content may be 0%.

[0054] Cs2O has the function of improving the thermal stability of the glass, but if the content is too high, there is a risk that the chemical durability and weather resistance will decrease. Therefore, the content of Cs2O is preferably within the above range.

[0055] In the optical glass according to embodiment 1-1, the upper limit of the TiO2 content is preferably 30%, and more preferably 15%, 8%, 6%, and 4%, in that order. The lower limit of the TiO2 content is preferably 0%. The TiO2 content may be 0%. By keeping the TiO2 content within the above range, desired optical constants can be achieved and an increase in specific gravity can be suppressed.

[0056] In the optical glass according to embodiment 1-1, the upper limit of the WO3 content is preferably 30%, and more preferably 15%, 8%, 6%, 4%, 2%, and 1%, in that order. The lower limit of the WO3 content is preferably 0%. The WO3 content may be 0%. From the viewpoints of increasing transmittance, suppressing a decrease in the partial dispersion ratio PC,t in the infrared wavelength range, and reducing specific gravity, it is preferable that the WO3 content be within the above range.

[0057] In the optical glass according to embodiment 1-1, the upper limit of the Bi2O3 content is preferably 30%, and more preferably 15%, 10%, and 8%, in that order. The lower limit of the Bi2O3 content is preferably 0%, and more preferably 2%, 4%, and 6%, in that order. The Bi2O3 content may be 0%. From the viewpoints of increasing transmittance and reducing specific gravity, and from the viewpoint of reducing damage to platinum manufacturing equipment, it is preferable that the Bi2O3 content be within the above range.

[0058] In the optical glass according to embodiment 1-1, the upper limit of the Ta2O5 content is preferably 20%, and more preferably 15%, 10%, 8%, 6%, 4%, and 2% in that order. The lower limit of the Ta2O5 content is preferably 0%, and more preferably 0.5%, 1%, and 1.5% in that order. The Ta2O5 content may even be 0%.

[0059] Ta2O5 is a component that imparts high refraction and low dispersion to the glass and increases the partial dispersion ratio P C,t in the infrared wavelength region. However, if the Ta2O5 content increases, the raw material cost increases. There is also a risk of the specific gravity increasing. Therefore, it is preferable that the Ta2O5 content be within the above range.

[0060] In the optical glass according to embodiment 1-1, the upper limit of the total content of Nb2O5, TiO2, WO3, and Bi2O3 [Nb2O5 + TiO2 + WO3 + Bi2O3] is preferably 40%, more preferably 35%, 30%, and 25%, in that order. The lower limit of this total content is preferably 5%, more preferably 7%, 9%, and 11%, in that order. From the viewpoint of maintaining a high refractive index, it is preferable that the total content be within the above range.

[0061] In the optical glass according to embodiment 1-1, the upper limit of the total content of Nb2O5, TiO2, WO3, Bi2O3, and Ta2O5 [Nb2O5 + TiO2 + WO3 + Bi2O3 + Ta2O5] is preferably 40%, and more preferably 35%, 30%, and 25% in that order. The lower limit of this total content is preferably 5%, and more preferably 7%, 9%, and 11% in that order. From the viewpoint of maintaining a high refractive index and a desired Abbe number νd, it is preferable that the total content be within the above range.

[0062] In the optical glass according to embodiment 1-1, the upper limit of the total content of ZrO2, Nb2O5, TiO2, WO3, Bi2O3, and Ta2O5 [ZrO2 + Nb2O5 + TiO2 + WO3 + Bi2O3 + Ta2O5] is preferably 50%, more preferably 45%, 40%, and 37%, in that order. The lower limit of this total content is preferably 10%, more preferably 15%, 20%, and 23%, in that order. From the viewpoint of maintaining a high refractive index, it is preferable that the total content be within the above range.

[0063] In the optical glass according to embodiment 1-1, the upper limit of the total content of ZrO2 and Nb2O5 [ZrO2 + Nb2O5] is preferably 50%, and more preferably 45%, 40%, and 37%, in that order. The lower limit of this total content is preferably 10%, and more preferably 15%, 20%, and 23%, in that order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range and maintaining high dispersion, it is preferable that the total content be within the above range.

[0064] In the optical glass according to embodiment 1-1, the upper limit of the total content of Nb2O5, TiO2, WO3, and Ta2O5 [Nb2O5 + TiO2 + WO3 + Ta2O5] is preferably 40%, and more preferably 35%, 30%, and 25%, in that order. The lower limit of this total content is preferably 5%, and more preferably 7%, 9%, and 11%, in that order. From the viewpoint of maintaining a high refractive index and a desired Abbe number νd, it is preferable that the total content be within the above range.

[0065] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)] of the content of Nb2O5 to the total content of Nb2O5, TiO2, WO3, and Ta2O5 is preferably 1, and more preferably 0.95, 0.90, and 0.85 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.50, 0.60, 0.70, and 0.80 in that order. This mass ratio may be 1. From the viewpoint of maintaining a high refractive index, it is preferable that this mass ratio be within the above range.

[0066] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [Ta2O5 / (Nb2O5+TiO2+WO3+Ta2O5)] of the content of Ta2O5 to the total content of Nb2O5, TiO2, WO3, and Ta2O5 is preferably 1, and more preferably 0.5, 0.3, and 0.1 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.01, 0.03, and 0.05 in that order. This mass ratio may even be 0. From the viewpoint of suppressing increases in the raw material costs of the glass, it is preferable that this mass ratio be within the above range.

[0067] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [TiO2 / (Nb2O5+TiO2+WO3+Ta2O5)] of the content of TiO2 to the total content of Nb2O5, TiO2, WO3, and Ta2O5 is preferably 1, and more preferably 0.5, 0.3, and 0.1 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.01, 0.03, and 0.05 in that order. This mass ratio may even be 0. From the viewpoint of maintaining a high refractive index, it is preferable that this mass ratio be within the above range.

[0068] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [ZrO2 / (ZrO2+Nb2O5+TiO2+WO3+Ta2O5)] of the content of ZrO2 to the total content of ZrO2, Nb2O5, TiO2, WO3, and Ta2O5 is preferably 0.8, with 0.7, 0.6, and 0.5 being more preferred in that order. The lower limit of this mass ratio is preferably 0.10, with 0.20, 0.25, and 0.30 being more preferred in that order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range and maintaining high dispersion, it is preferable that this mass ratio be within the above range.

[0069] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [Nb2O5 / (ZrO2+Nb2O5+TiO2+WO3+Ta2O5)] of the content of Nb2O5 to the total content of ZrO2, Nb2O5, TiO2, WO3, and Ta2O5 is preferably 0.95, with 0.9, 0.8, and 0.7 being more preferred in that order. The lower limit of this mass ratio is preferably 0.1, with 0.2, 0.3, 0.4, and 0.5 being more preferred in that order. The mass ratio may even be 1. From the viewpoint of maintaining high dispersibility, it is preferable that the mass ratio be within the above range.

[0070] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio [Ta2O5 / (ZrO2+Nb2O5+TiO2+WO3+Ta2O5)] of the content of Ta2O5 to the total content of ZrO2, Nb2O5, TiO2, WO3, and Ta2O5 is preferably 0.5, and more preferably 0.4, 0.3, and 0.2 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.05, 0.10, and 0.15 in that order. This mass ratio may even be 0. From the viewpoint of suppressing increases in raw material costs, it is preferable that this mass ratio be within the above range.

[0071] In the optical glass according to embodiment 1-1, the upper limit of the mass ratio of the TiO2 content to the total content of ZrO2, Nb2O5, TiO2, WO3, and Ta2O5 [TiO2 / (ZrO2+Nb2O5+TiO2+WO3+Ta2O5)] is preferably 0.5, and more preferably 0.4, 0.3, and 0.2 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.05, 0.10, and 0.15 in that order. This mass ratio may even be 0. From the viewpoint of maintaining high dispersibility, it is preferable that this mass ratio be within the above range.

[0072] In the optical glass according to embodiment 1-1, the upper limit of the MgO content is preferably 20%, and more preferably 15%, 10%, and 5%, in that order. The lower limit of the MgO content is preferably 0%. The MgO content may be 0%.

[0073] Among alkaline earth metals, MgO is a component that increases the partial dispersion ratio P C,t in the infrared wavelength region. However, if the MgO content is too high, the high dispersion may be impaired and the thermal stability and devitrification resistance of the glass may be reduced. Therefore, the MgO content is preferably within the above range.

[0074] In the optical glass according to embodiment 1-1, the upper limit of the CaO content is preferably 20%, and more preferably 15%, 10%, and 5% in that order. The lower limit of the CaO content is preferably 0%, and more preferably 3.0%, 4.0%, and 4.5% in that order. The CaO content may be 0%.

[0075] Among alkaline earth metals, CaO is a component that increases the partial dispersion ratio PC,t in the infrared wavelength region. However, if the CaO content is too high, the high dispersion may be impaired and the thermal stability and devitrification resistance of the glass may be reduced. Therefore, the CaO content is preferably within the above range.

[0076] In the optical glass according to embodiment 1-1, the upper limit of the SrO content is preferably 30%, and more preferably 20%, 10%, and 5%, in that order. The lower limit of the SrO content is preferably 0%. The SrO content may be 0%.

[0077] Among alkaline earth metals, SrO is a component that increases the refractive index. However, if the SrO content is too high, high dispersion may be impaired and the partial dispersion ratio P C,t in the infrared wavelength region may decrease. Therefore, the SrO content is preferably within the above range.

[0078] In the optical glass according to embodiment 1-1, the upper limit of the BaO content is preferably 30%, and more preferably 25%, 20%, 15%, and 13%, in that order. The lower limit of the BaO content is preferably 0%, and more preferably 5%, 8%, and 10%, in that order. The BaO content may be 0%.

[0079] BaO is a component that increases the refractive index and also lowers the liquidus temperature, thereby improving the thermal stability of the glass. However, if the BaO content is too high, the high dispersion may be impaired and the partial dispersion ratio PC,t in the infrared wavelength range may decrease. If the BaO content is too low, the refractive index nd may decrease and the thermal stability and devitrification resistance of the glass may decrease. Therefore, the BaO content is preferably within the above range.

[0080] In the optical glass according to embodiment 1-1, the upper limit of the ZnO content is preferably 20%, and more preferably 15%, 10%, 5%, 4%, 3%, and 2%, in that order. The lower limit of the ZnO content is preferably 0%, and more preferably 0.5%, 0.8%, and 1%, in that order. The ZnO content may even be 0%.

[0081] ZnO is a glass component that improves the thermal stability of glass. However, if the ZnO content is too high, the specific gravity may increase and the partial dispersion ratio PC,t in the infrared wavelength range may decrease. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining the desired optical constants, the ZnO content is preferably within the above range.

[0082] In the optical glass according to embodiment 1-1, the upper limit of the total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is preferably 40%, and more preferably 35%, 30%, 25%, 20%, 15%, and 12%, in that order. The lower limit of this total content is preferably 0%, and more preferably 2%, 4%, 6%, 8%, and 10%, in that order. The total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] may be 0%. If this total content is too high, the high dispersion may be impaired and the partial dispersion ratio PC,t in the infrared wavelength range may decrease. If this total content is too low, the refractive index nd may decrease and the thermal stability and devitrification resistance of the glass may decrease. Therefore, the total content is preferably within the above range.

[0083] In the optical glass according to embodiment 1-1, the upper limit of the total content R'O of MgO, CaO, SrO, BaO, and ZnO [MgO + CaO + SrO + BaO + ZnO] is preferably 40%, and more preferably 35%, 30%, 25%, 20%, 15%, and 12%, in that order. The lower limit of the total content R'O is preferably 0%, and more preferably 2%, 4%, 6%, 8%, and 10%, in that order. R'O may be 0%. If the content of R'O is too high, the high dispersion may be impaired and the partial dispersion ratio PC,t in the infrared wavelength range may decrease. If the content of R'O is too low, the refractive index nd may decrease and the thermal stability and devitrification resistance of the glass may decrease. Therefore, it is preferable that R'O be within the above range.

[0084] In the glass according to embodiment 1-1, the upper limit of the Y2O3 content is preferably 30%, and more preferably 25%, 20%, 15%, 10%, and 5% in that order. The lower limit of the Y2O3 content is preferably 0%, and more preferably 0.5%, 1.0%, and 1.5% in that order. The Y2O3 content may be 0%.

[0085] By incorporating a certain amount of Y2O3, the refractive index nd can be increased. However, if the Y2O3 content is too high, the thermal stability of the glass decreases, making the glass more susceptible to devitrification during production. Furthermore, there is a risk of impairing the high dispersion. Therefore, from the viewpoint of preventing a decrease in the thermal stability of the glass, it is preferable that the Y2O3 content be within the above range.

[0086] In the glass according to embodiment 1-1, the content of Sc2O3 is preferably 2% or less, and the lower limit of the content of Sc2O3 is preferably 0%.

[0087] In the glass according to embodiment 1-1, the content of HfO2 is preferably 2% or less, and the lower limit of the content of HfO2 is preferably 0%.

[0088] Sc2O3 and HfO2 have the function of increasing the dispersibility of the glass, but are expensive components, so the contents of Sc2O3 and HfO2 are preferably within the above ranges.

[0089] In the glass according to embodiment 1-1, the content of Lu2O3 is preferably 2% or less, and the lower limit of the content of Lu2O3 is preferably 0%.

[0090] Lu2O3 has the function of increasing the dispersibility of the glass, but because it has a large molecular weight, it is also a glass component that increases the specific gravity of the glass, so the content of Lu2O3 is preferably in the above range.

[0091] In the glass according to embodiment 1-1, the GeO2 content is preferably 2% or less, and the lower limit of the GeO2 content is preferably 0%.

[0092] GeO2 has the function of increasing the high dispersibility of the glass, but is an extremely expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of the glass, it is preferable that the GeO2 content be in the above range.

[0093] In the optical glass according to embodiment 1-1, the upper limit of the La2O3 content is preferably 30%, with 25%, 20%, 15%, 10%, and 5% being more preferred in that order. The lower limit of the La2O3 content is preferably 0%, with 0.5%, 1.0%, and 1.5% being more preferred in that order. The La2O3 content may be 0%. The refractive index nd can be increased by incorporating a certain amount of La2O3. However, if the La2O3 content is too high, the thermal stability of the glass decreases, making the glass more susceptible to devitrification during manufacturing. Furthermore, there is a risk that the high dispersion may be impaired and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. Therefore, the La2O3 content is preferably within the above range.

[0094] In the glass according to embodiment 1-1, the content of Gd2O3 is preferably 2% or less, and the lower limit of the content of Gd2O3 is preferably 0%.

[0095] If the Gd2O3 content is too high, the thermal stability of the glass decreases. Furthermore, if the Gd2O3 content is too high, the specific gravity of the glass increases, which is undesirable. Furthermore, there is a risk of increasing raw material costs. Therefore, from the viewpoint of suppressing an increase in specific gravity while maintaining good thermal stability of the glass, it is preferable that the Gd2O3 content be within the above range.

[0096] In the glass according to embodiment 1-1, the upper limit of the total content of La2O3, Gd2O3, and Y2O3 [La2O3 + Gd2O3 + Y2O3] is preferably 30%, and more preferably 25%, 20%, 15%, 10%, 5%, 3%, and 1%, in that order. The lower limit of this total content is preferably 0%. From the viewpoints of suppressing a decrease in the thermal stability of the glass and preventing a decrease in the partial dispersion ratio P C,t in the infrared wavelength range, it is preferable that the total content be within the above range.

[0097] In the glass according to embodiment 1-1, the content of Yb2O3 is preferably 2% or less, and the lower limit of the content of Yb2O3 is preferably 0%.

[0098] Yb2O3 has a larger molecular weight than La2O3, Gd2O3, and Y2O3, and therefore increases the specific gravity of the glass. Furthermore, if the Yb2O3 content is too high, the thermal stability of the glass decreases. From the viewpoint of preventing a decrease in the thermal stability of the glass and suppressing an increase in the specific gravity, the Yb2O3 content is preferably within the above range.

[0099] In the glass according to embodiment 1-1, the upper limit of the mass ratio [R2O / (SiO2+B2O3)] of the total content R2O of Li2O, Na2O, and K2O to the total content of SiO2 and B2O3 is preferably 0.50, and more preferably 0.45, 0.40, 0.35, 0.30, and 0.25 in that order. The lower limit of this mass ratio is preferably 0.05, and more preferably 0.07, 0.09, and 0.11 in that order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range and improving chemical durability, it is preferable that this mass ratio be within the above range.

[0100] In the glass according to embodiment 1-1, the upper limit of the mass ratio [(MgO + CaO + SrO + BaO) / (SiO2 + B2O3)] of the total content of MgO, CaO, SrO, and BaO to the total content of SiO2 and B2O3 is preferably 0.50, and more preferably 0.40, 0.35, 0.30, and 0.25 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.05, 0.10, and 0.15 in that order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range and improving chemical durability, it is preferable that this mass ratio be within the above range.

[0101] In the glass according to embodiment 1-1, the upper limit of the mass ratio [R'O / (SiO2+B2O3)] of the total content R'O of MgO, CaO, SrO, BaO, and ZnO to the total content of SiO2 and B2O3 is preferably 0.50, and more preferably 0.40, 0.35, 0.30, and 0.25 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.05, 0.10, and 0.15 in that order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range and improving chemical durability, it is preferable that this mass ratio be within the above range.

[0102] In the glass according to embodiment 1-1, the upper limit of the mass ratio [(La2O3 + Gd2O3 + Y2O3) / (SiO2 + B2O3)] of the total content of La2O3, Gd2O3, and Y2O3 to the total content of SiO2 and B2O3 is preferably 0.50, and more preferably 0.40, 0.35, 0.30, and 0.25 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.05, 0.10, and 0.15 in that order. This mass ratio may even be 0. From the viewpoint of preventing a decrease in the thermal stability of the glass, it is preferable that this mass ratio be within the above range.

[0103] In the glass according to embodiment 1-1, the upper limit of the mass ratio [(Nb2O5 + TiO2 + WO3 + Ta2O5) / (SiO2 + B2O3)] of the total content of Nb2O5, TiO2, WO3, and Ta2O5 to the total content of SiO2 and B2O3 is preferably 0.70, and more preferably 0.65, 0.60, 0.55, 0.50, 0.45, 0.40, 0.35, 0.30, and 0.25, in that order. The lower limit of this mass ratio is preferably 0.05, and more preferably 0.10, 0.14, 0.16, 0.18, and 0.20, in that order. From the viewpoint of maintaining a high refractive index, it is preferable that this mass ratio be within the above range.

[0104] In the glass according to embodiment 1-1, the upper limit of the mass ratio [(MgO + CaO + SrO + BaO) / R2O] of the total content of MgO, CaO, SrO, and BaO to the total content R2O of Li2O, Na2O, and K2O is preferably 5, and more preferably 4.0, 3.0, 2.5, 2.0, 1.8, and 1.6 in this order. The lower limit of this mass ratio is preferably 0, and more preferably 0.20, 0.40, 0.60, 0.80, 1.00, 1.20, and 1.40 in this order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that this mass ratio be within the above range.

[0105] In the glass according to embodiment 1-1, the upper limit of the mass ratio [R'O / R2O] of the total content R'O of MgO, CaO, SrO, BaO, and ZnO to the total content R2O of Li2O, Na2O, and K2O is preferably 5, and more preferably 4.0, 3.0, 2.5, 2.0, 1.8, and 1.6 in this order. The lower limit of this mass ratio is preferably 0, and more preferably 0.20, 0.40, 0.60, 0.80, 1.00, 1.20, and 1.40 in this order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that this mass ratio be within the above range.

[0106] In the glass according to embodiment 1-1, the upper limit of the mass ratio [(La2O3 + Gd2O3 + YO3) / RO] of the total content of La2O3, Gd2O3, and YO3 to the total content of Li2O, Na2O, and KO, RO, is preferably 3.0, and more preferably 2.0, 1.0, 0.8, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1, in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.01, 0.05, and 0.08, in that order. This mass ratio may even be 0. From the viewpoint of preventing a decrease in the thermal stability of the glass, it is preferable that this mass ratio be within the above range.

[0107] In the glass according to embodiment 1-1, the upper limit of the mass ratio [(Nb2O5 + TiO2 + WO3 + Ta2O5) / R2O] of the total content of Nb2O5, TiO2, WO3, and Ta2O5 to the total content of Li2O, Na2O, and K2O, R2O, is preferably 5.0, and more preferably 4.0, 3.5, 3.0, 2.8, 2.6, 2.4, 2.2, 2.0, and 1.8, in that order. The lower limit of this mass ratio is preferably 0.3, and more preferably 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, and 1.7, in that order. From the viewpoints of maintaining a high refractive index, improving the meltability of the glass, and reducing the viscosity of the molten glass to improve formability, it is preferable that this mass ratio be within the above range.

[0108] In the glass according to embodiment 1-1, the upper limit of the mass ratio [R2O / (R2O + MgO + CaO + SrO + BaO)] of the total content R2O of Li2O, Na2O, and K2O to the total content R2O, MgO, CaO, SrO, and BaO is preferably 1, and more preferably 0.9, 0.8, 0.7, 0.6, 0.5, and 0.45 in this order. The lower limit of this mass ratio is preferably 0.10, and more preferably 0.15, 0.20, 0.25, 0.30, and 0.35 in this order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that this mass ratio be within the above range.

[0109] In the glass according to embodiment 1-1, the upper limit of the mass ratio [(R2O + MgO + CaO) / (R2O + R2O)] of the total content R2O of Li2O, Na2O, and K2O, MgO, and CaO, to the sum of the total content R2O and the total content R'O of MgO, CaO, SrO, BaO, and ZnO is preferably 1, and more preferably 0.9, 0.8, 0.7, 0.6, 0.5, and 0.45 in this order. The lower limit of this mass ratio is preferably 0.10, and more preferably 0.15, 0.20, 0.25, 0.30, and 0.35 in this order. From the viewpoints of increasing the partial dispersion ratio P C,t in the infrared wavelength range, improving the meltability of the glass, and reducing the viscosity of the molten glass to improve formability, it is preferable that this mass ratio be within the above range.

[0110] In the glass according to embodiment 1-1, the upper limit of the mass ratio [(La2O3 + Gd2O3 + YO3) / (Nb2O5 + TiO2 + WO3 + Ta2O5)] of the total content of La2O3, Gd2O3, and YO3 to the total content of Nb2O5, TiO2, WO3, and Ta2O5 is preferably 1, and more preferably 0.8, 0.6, 0.4, and 0.2 in that order. The lower limit of this mass ratio is preferably 0, and more preferably 0.05, 0.10, and 0.15 in that order. This mass ratio may even be 0. From the viewpoints of preventing a decrease in the thermal stability of the glass and maintaining a high refractive index, it is preferable that this mass ratio be within the above range.

[0111] The glass according to embodiment 1-1 is preferably composed primarily of the above-mentioned glass components, i.e., essential components of SiO2, B2O3, ZrO2, and Nb2O5, and optional components of P2O5, Al2O3, Li2O, Na2O, K2O, Cs2O, TiO2, WO3, Bi2O3, Ta2O5, MgO, CaO, SrO, BaO, ZnO, Y2O3, Sc2O3, HfO2, Lu2O3, GeO2, La2O3, Gd2O3, and Yb2O3. The total content of the above-mentioned glass components is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and particularly preferably 99.5% or more.

[0112] The glass according to embodiment 1-1 is preferably composed essentially of the above glass components, but may contain other components as long as they do not impair the effects of the present invention. Furthermore, the present invention does not exclude the inclusion of unavoidable impurities.

[0113] In addition to the above components, the optical glass may also contain a small amount of a fining agent such as Sb2O3. The total amount of fining agents (exclusive addition amount) is preferably 0% or more and less than 1%, and more preferably 0% or more and 0.5% or less.

[0114] The total amount added is the amount of fining agent added expressed as a weight percentage when the total content of all glass components excluding the fining agent is taken as 100%.

[0115] Furthermore, the optical glass can achieve high transmittance over a wide range of the visible light region. To make the most of these features, it is preferable that the glass does not contain any coloring elements. Examples of coloring elements include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, V, and Ag. The content of each element is preferably less than 100 ppm by mass, more preferably 0 to 80 ppm by mass, and even more preferably 0 to 50 ppm by mass, and it is particularly preferable that the glass is substantially free of these elements.

[0116] Ga, Te, Tb, etc. are components that do not need to be incorporated and are expensive components, so the range of the content of Ga2O3, TeO2, and TbO2 expressed in mass% is preferably 0 to 0.1%, more preferably 0 to 0.05%, even more preferably 0 to 0.01%, even more preferably 0 to 0.005%, and even more preferably 0 to 0.001%, and it is particularly preferable that they are not substantially contained.

[0117] (glass properties) <Abbe number νd> In the optical glass according to embodiment 1-1, the Abbe number νd is preferably 30-60, and can also be 35-55, 40-50, 41-48, 42-46, 43-45, or 32-50, 34-45, 36-40, or 37-39.

[0118] The Abbe number νd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that relatively lower the Abbe number νd, i.e., highly dispersive components, are Nb2O5, TiO2, ZrO2, WO3, Bi2O3, and Ta2O5 (in terms of cations, Nb 5+ , Ti 4+ , Zr 4+ , W 6+ , Bi 3+ , Ta 5+On the other hand, the components that relatively increase the Abbe number νd, that is, the components that reduce dispersion, are SiO2, B2O3, Li2O, Na2O, K2O, La2O3, BaO, CaO, SrO (in terms of cations, Si 4+ , B 3+ , Li + , Na + , K. + , La 3+ , Ba 2+ , Ca 2+ , Sr 2+ ) etc.

[0119] In the present invention, the Abbe number vd, and the partial dispersion ratios Pc,t and Pg,F (described later) are calculated as follows: Specifically, the refractive index at the 12 wavelengths shown in Table A is measured according to Japanese Industrial Standards (JIS) B 7071-1, Method for Determining the Refractive Index of Optical Glass, Part 1: Minimum Deviation Method. Next, the refractive index of each line obtained by the measurement is applied to Schott's dispersion formula defined in Annex B of JIS B 7071-1, Method for Determining the Refractive Index of Optical Glass, Part 1: Minimum Deviation Method, and the constants of the Schott's dispersion formula are determined by the least squares method. Then, the Abbe number vd, the partial dispersion ratios Pc,t and Pg,F (described later) are calculated from the values ​​of each linear refractive index obtained using the Schott's dispersion formula with the determined constants.

[0120] [Table A] Shot dispersion formula: n 2 =a0+a1λ 2 +a2λ -2 +a3λ -4 +a4λ -6 +a5λ -8 Here, n is the refractive index, λ is the wavelength (μm), and a0, a1, a2, a3, a4, and a5 are constants. The Abbe number νd is expressed as follows using the refractive indices nd, nF, and nC at the d-line, F-line, and C-line, respectively: νd=(nd-1) / (nF-nC)

[0121] <Refractive index nd> In the optical glass according to embodiment 1-1, the refractive index nd is preferably 1.50 to 1.80, and can also be 1.55 to 1.70, 1.58 to 1.65, 1.60 to 1.62, or 1.60 to 1.70, 1.63 to 1.69, or 1.66 to 1.68.

[0122] The refractive index nd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that have the effect of relatively increasing the refractive index nd (high refractive index components) are Nb2O5, TiO2, ZrO2, Ta2O5, and La2O3 (in terms of cations, Nb 5+ , Ti 4+ , Zr 4+ , Ta 5+ , La 3+ On the other hand, the components that act to relatively lower the refractive index nd (low refractive index components) are SiO2, B2O3, Li2O, Na2O, K2O (in cationic form, Si 4+ , B 3+ , Li + , Na + , K. + ) etc.

[0123] <Partial dispersion ratio PC,t> In the optical glass according to embodiment 1-1, the lower limit of the partial dispersion ratio PC,t in the infrared wavelength region is preferably 0.7300, and more preferably 0.7400, 0.7500, 0.7600, 0.7700, 0.7750, 0.7800, 0.7850, 0.7860, 0.7870, 0.7880, 0.7890, 0.7900, 0.7910, 0.7920, 0.7930, 0.7940, and 0.7950, in that order. By setting the partial dispersion ratio PC,t within the above range, an optical glass suitable for correcting high-order chromatic aberrations can be obtained. On the other hand, the upper limit of the partial dispersion ratio PC,t is not particularly limited, but is usually 0.9000, preferably 0.8700, and even more preferably 0.8500 and 0.8400, in that order.

[0124] In the optical glass according to the 1-1 embodiment, the partial dispersion ratio PC,t preferably satisfies the following formula (1). PC,t≧0.5711+0.004667×νd···[1] It is more preferable that the partial dispersion ratio PC,t satisfies the following formula [2], and more preferably satisfies the following formula [3], the following formula [4], the following formula [5], the following formula [6], and the following formula [7] in this order. PC,t≧0.5731+0.004667×νd···[2] PC,t≧0.5751+0.004667×νd···[3] PC,t≧0.5771+0.004667×νd···[4] PC,t≧0.5791+0.004667×νd···[5] PC,t≧0.5811+0.004667×νd···[6] PC,t≧0.5831+0.004667×νd···[7]

[0125] When the partial dispersion ratio PC,t satisfies the above formula, the optical element made of the optical glass according to the 1-1 embodiment can satisfactorily correct chromatic aberration over a wide wavelength range.

[0126] In the optical glass according to embodiment 1-1, the lower limit of the deviation ΔP C,t is preferably 0.0250, and more preferably 0.0270, 0.0290, 0.0310, 0.0330, 0.0350, and 0.0370, in that order. By setting the deviation ΔP C,t within the above range, an optical glass suitable for correcting high-order chromatic aberrations can be obtained. On the other hand, the upper limit of the deviation ΔP C,t is not particularly limited, but is usually 0.0900, and preferably 0.0800.

[0127] The partial dispersion ratio PC,t is calculated using the above shot dispersion formula. The partial dispersion ratio PC,t is expressed as follows using the refractive indices nt, nF, and nC at the t-line, F-line, and C-line, respectively: PC,t = (nC-nt) / (nF-nC) In addition, in a plane in which the horizontal axis represents the Abbe number νd and the vertical axis represents the partial dispersion ratio PC,t, the normal line is expressed by the following equation. PC,t(0)=0.5461-(0.004667×νd) Furthermore, the deviation ΔPC,t of the partial dispersion ratio PC,t from the normal line is expressed as follows: ΔPC,t = PC,t - PC,t(0)

[0128] The partial dispersion ratio PC,t can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that have the effect of relatively increasing the partial dispersion ratio PC,t are SiO2, B2O3, Al2O3, and Li2O (in terms of cations, Si 4+ , B 3+ , Al 3+ , Li + On the other hand, the components that act to relatively lower the partial dispersion ratio PC,t are (SrO, BaO, ZnO, La2O3, TiO2, Nb2O5, WO3, (in cation expression, Sr 2+ , Ba 2+ , Zn 2+ , La 3+ , Ti 4+ , Nb 5+ , W 6+ In this embodiment, in particular, SiO2 and B2O3 (in cation expression, Si) which are components that increase <1> PC,t 4+ and B 3+ ) and (2) at the same time, SiO2 (Si 4+ ) to B2O3(B 3+ ) to achieve high dispersion without significantly decreasing PC,t, (3) to further improve formability by further increasing dispersion and reducing viscosity, by appropriately introducing alkali metal and alkaline earth metal oxides, (4) to minimize the amount of highly dispersible components that are necessary to obtain the desired Abbe number but that decrease PC,t, and by minimizing the amount of highly dispersible components that decrease PC,t, Nb2O5(Nb 5+ ), and ZrO2 (Zr 4+ By actively incorporating ), it is possible to obtain an optical glass having a small Abbe number νd and a relatively high partial dispersion ratio PC,t.

[0129] <Partial dispersion ratio Pg,F> In the optical glass according to embodiment 1-1, the upper limit of the partial dispersion ratio Pg,F in the visible short wavelength region is preferably 0.5800, and more preferably 0.5750, 0.5720, 0.5690, 0.5660, 0.5640, 0.5630, 0.5620, 0.5610, and 0.5600, in that order. By setting the partial dispersion ratio Pg,F within the above range, an optical glass suitable for correcting high-order chromatic aberrations can be obtained. On the other hand, the lower limit of the partial dispersion ratio Pg,F is not particularly limited, but is usually 0.5500, and preferably 0.5550.

[0130] In the optical glass according to the 1-1 embodiment, the partial dispersion ratio Pg,F preferably satisfies the following formula [8]. Pg,F≦0.6483-0.001802×νd···[8] It is more preferable that the partial dispersion ratio Pg,F satisfies the following formula [9], and it is further more preferable that the following formulas

[10] ,

[11] ,

[12] ,

[13] , and

[14] are satisfied in this order. Pg,F≦0.6470-0.001802×νd···[9] Pg,F≦0.6460-0.001802×νd···

[10] Pg,F≦0.6450-0.001802×νd···

[11] Pg,F≦0.6444-0.001802×νd···

[12] Pg,F≦0.6439-0.001802×νd···

[13] Pg,F≦0.6433-0.001802×νd···

[14]

[0131] When the partial dispersion ratio Pg,F satisfies the above formula, the optical element made of the optical glass according to the 1-1 embodiment can satisfactorily correct chromatic aberration over a wide wavelength range.

[0132] In the optical glass according to embodiment 1-1, the lower limit of the deviation ΔPg,F is preferably 0, and more preferably -0.0013, -0.0023, -0.0033, -0.0039, -0.0044, and -0.0050, in that order. By setting the deviation ΔPg,F within the above range, an optical glass suitable for correcting high-order chromatic aberrations can be obtained. On the other hand, the upper limit of the deviation ΔPg,F is not particularly limited, but is usually -0.0300, and preferably -0.0250.

[0133] The partial dispersion ratio Pg,F is calculated using the above shot dispersion formula. The partial dispersion ratio Pg,F is expressed as follows using the refractive indices ng, nF, and nC for the g-line, F-line, and c-line: Pg,F=(ng-nF) / (nF-nC) In addition, in a plane in which the horizontal axis represents the Abbe number νd and the vertical axis represents the partial dispersion ratio Pg,F, the normal line is expressed by the following formula. Pg,F(0)=0.6483-(0.001802×νd) Furthermore, the deviation ΔPg,F of the partial dispersion ratio Pg,F from the normal line is expressed as follows: ΔPg,F=Pg,F-Pg,F(0)

[0134] <Specific gravity of glass> The specific gravity of the optical glass according to embodiment 1-1 is preferably 4.00 or less, more preferably 3.50 or less, and even more preferably 3.10 or less. The components that increase the relative density are BaO, La2O3, ZrO2, Nb2O5, Ta2O5 (in cation notation, Ba 2+ , La 3+ , Zr 4+ , Nb 5+ , Ta 5+ On the other hand, the components that relatively lower the specific gravity are SiO2, B2O3, Li2O, Na2O, K2O (in cation notation, Si 4+ , B 3+ , Li + , Na + , K. +) etc. The specific gravity can be controlled by appropriately adjusting the content of these components.

[0135] <Liquidus temperature LT> The upper limit of the liquidus temperature LT of the optical glass according to embodiment 1-1 is preferably 1300°C, and more preferably 1270°C, 1240°C, 1210°C, 1180°C, 1150°C, and 1100°C in that order. By keeping the liquidus temperature within the above range, the glass melting and forming temperatures can be lowered, thereby reducing corrosion of glass melting equipment (e.g., crucibles, molten glass stirring equipment, etc.) during the melting process and the occurrence of striae due to volatilization of the glass components themselves. The lower limit of the liquidus temperature LT is not particularly limited, but is usually 1000°C, preferably 1050°C. The liquidus temperature LT is determined by the balance of the contents of all the glass components. Among these, the following elements are important for the liquidus temperature LT: SiO2, B2O3, Li2O, Na2O, and K2O (in terms of cations, Si 4+ , B 3+ , Li + , Na + , K. + ) content is also affected. 4+ , Al 3+ ) content is high, the liquidus temperature rises.

[0136] The liquidus temperature is determined as follows: 10 cc (10 ml) of glass is placed in a platinum crucible and melted at 1250°C to 1400°C for 15 to 30 minutes, then cooled to below the glass transition temperature Tg. The glass, together with the platinum crucible, is placed in a furnace at the specified temperature and held there for two hours. The temperature is held at 1000°C or above in 5°C or 10°C increments, and after two hours, the glass is cooled and the presence or absence of crystals inside the glass is observed under a 100x optical microscope. The lowest temperature at which no crystals precipitate is taken as the liquidus temperature.

[0137] <Glass transition temperature Tg> The lower limit of the glass transition temperature Tg of the optical glass according to embodiment 1-1 is preferably 400°C, and more preferably 450°C, 470°C, and 490°C in that order. The upper limit of the glass transition temperature Tg is preferably 600°C, and more preferably 580°C, 560°C, and 550°C in that order. The components that relatively lower the glass transition temperature Tg are Li2O, Na2O, and K2O (in terms of cations, Li + , Na + , K. + ) etc. The components that relatively increase the glass transition temperature Tg are La2O3, ZrO2, Nb2O5 (in cation expression, La 3+ , Zr 4+ , Nb 5+ The glass transition temperature Tg can be controlled by appropriately adjusting the content of these components.

[0138] <Light transmittance of glass> The light transmittance of the optical glass according to the 1-1 embodiment can be evaluated by the coloring degrees λ80 and λ5. The spectral transmittance of a glass sample with a thickness of 10.0 mm±0.1 mm is measured in the wavelength range of 200 to 700 nm, and the wavelength at which the external transmittance is 80% is defined as λ80, and the wavelength at which the external transmittance is 5% is defined as λ5.

[0139] The λ80 of the optical glass according to embodiment 1-1 is preferably 450 nm or less, more preferably 430 nm or less, and even more preferably 410 nm or less. The λ5 is preferably 400 nm or less, more preferably 380 nm or less, and even more preferably 360 nm or less.

[0140] <Chemical durability Water resistance Dw> In the optical glass according to embodiment 1-1, the water resistance Dw is preferably grade 5 or higher, more preferably grade 4 or higher, and even more preferably grade 3 or higher.

[0141] Water resistance Dw is evaluated by placing a mass of powdered glass (particle size 425-600 μm) equivalent to the specific gravity in a platinum cage, immersing it in a quartz glass round-bottom flask containing 80 mL of pure water (pH = 6.5-7.5), and treating it in a boiling water bath for 60 minutes. The weight loss rate (%) is then classified into the grades in Table B and evaluated. [Table B]

[0142] <Chemical durability Acid resistance Da> In the optical glass according to embodiment 1-1, the acid resistance Da is preferably grade 5 or higher, more preferably grade 4 or higher, and even more preferably grade 3 or higher.

[0143] Acid resistance Da is evaluated by placing a mass of powdered glass (particle size 425-600μm) equivalent to the specific gravity in a platinum cage, immersing it in a quartz glass round-bottom flask containing 80mL of 0.01mol / L nitric acid solution for 60 minutes, and classifying it into the grades in Table C according to the weight loss rate (%). [Table C]

[0144] <Chemical durability Latent scratch resistance D NaOH > In the optical glass according to the first embodiment, the latent scratch resistance D NaOH is preferably 4th grade or higher, more preferably 3rd grade or higher, and even more preferably 2nd grade or higher.

[0145] Latent scratch resistance D NaOH diameter 43.7mm (30cm on both sides) 2 ), and the mass loss per unit area [mg / (cm ] when a glass sample with a thickness of approximately 5 mm and polished on both sides is immersed in a well-stirred 0.01 mol / L NaOH aqueous solution at 50°C for 15 hours. 2 15h) and classify and evaluate in Table D. [Table D]

[0146] <Chemical durability Latent scratch resistance D STPP > In the optical glass according to the first embodiment, the latent scratch resistance D STPP is preferably 4th grade or higher, more preferably 3rd grade or higher, and even more preferably 2nd grade or higher.

[0147] Latent scratch resistance D STPP diameter 43.7mm (30cm on both sides) 2 ), a polished glass sample with a thickness of approximately 5 mm was placed in a well-stirred solution of 0.01 mol / L Na5P3O 10 Mass loss per unit area [mg / (cm2) when immersed in (STPP) aqueous solution for 1 hour 2 ·h)) and classify and evaluate according to the grade in Table E. [Table E]

[0148] <Chemical durability Chemical durability D0> In the optical glass according to embodiment 1-1, the chemical durability D0 is preferably grade 4 or higher, more preferably grade 3 or higher, and even more preferably grade 2 or higher.

[0149] Chemical durability D0 is 43.7 mm diameter (30 cm on both sides) 2 ), the mass loss per unit area when a glass sample with a thickness of approximately 5 mm and polished on both sides is immersed in pure water that is circulated through an ion exchange resin bed at a rate of 1 L per minute and is kept at 50°C and pH = 7.0 ± 0.2 and is well stirred [10 -3 mg / (cm 2 ·h)) and classify and evaluate them into grades according to Table F. [Table F]

[0150] (Optical glass manufacturing) The glass according to embodiment 1-1 may be produced by blending glass raw materials to obtain the above-described predetermined composition and using the blended glass raw materials in accordance with a known glass manufacturing method. For example, a plurality of compounds may be blended and thoroughly mixed to form batch raw materials, which are then placed in a quartz crucible or platinum crucible for rough melting. The molten material obtained by rough melting is then quenched and crushed to produce cullet. The cullet is then placed in a platinum crucible, heated, and remelted to form a glass melt, which is then refined and homogenized, and then formed and slowly cooled to obtain an optical glass. Known methods may be used to form and slowly cool the glass melt.

[0151] The compounds used when preparing the batch raw materials are not particularly limited as long as they can introduce desired glass components into the glass to achieve desired contents. Examples of such compounds include oxides, carbonates, nitrates, hydroxides, and fluorides.

[0152] (Manufacturing of optical elements, etc.) To produce an optical element using the optical glass according to embodiment 1-1, a known method may be applied. For example, in the production of the optical glass, molten glass is poured into a mold and formed into a plate to produce a glass material made of the optical glass according to the present invention. The obtained glass material is cut, ground, and polished as appropriate to produce cut pieces of a size and shape suitable for press molding. The cut pieces are heated and softened, and press-molded (reheat pressed) by a known method to produce an optical element blank that approximates the shape of the optical element. The optical element blank is annealed, and then ground and polished by a known method to produce an optical element.

[0153] The optically functional surface of the fabricated optical element may be coated with an anti-reflection film, a total reflection film, or the like depending on the intended use.

[0154] According to one aspect of the present invention, an optical element made of the above optical glass can be provided. Examples of types of optical elements include lenses such as spherical lenses and aspherical lenses, prisms, and diffraction gratings. Examples of lens shapes include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, and concave meniscus lenses. The optical element can be manufactured by a method including a step of processing a glass molded body made of the above optical glass. Examples of processing include cutting, milling, rough grinding, fine grinding, and polishing. By using the above glass during such processing, breakage can be reduced, enabling a stable supply of high-quality optical elements.

[0155] 1-2 Embodiment The optical glass according to the first and second embodiments is As a glass component, Contains SiO2, B2O3, ZrO2, and Nb2O5, Contains one or more selected from the group consisting of Li2O, Na2O, and K2O, ΔPC,t is 0.0250 or more.

[0156] The optical glass according to the first and second embodiments contains SiO2 as a glass component. The lower limit of the SiO2 content is preferably 20%, and more preferably 24%, 26%, and 28%, in that order. The upper limit of the SiO2 content is preferably 50%, and more preferably 45%, 40%, and 35%, in that order. SiO2 is a glass network-forming component. By including SiO2 as a glass component, the partial dispersion ratio PC,t in the infrared wavelength range can be increased, and chemical durability can be improved. From the viewpoints of suppressing a decrease in the partial dispersion ratio PC,t in the infrared wavelength range and suppressing a decrease in the thermal stability and chemical durability of the glass, the lower limit of the SiO2 content is preferably as described above. From the viewpoints of suppressing a decrease in the meltability of the glass and preventing an increase in the viscosity of the molten glass, which would deteriorate the formability, the upper limit of the SiO2 content is preferably as described above.

[0157] The optical glass according to the first and second embodiments contains B2O3 as a glass component. The lower limit of the B2O3 content is preferably 15%, and more preferably 17%, 19%, and 21%, in that order. The upper limit of the B2O3 content is preferably 50%, and more preferably 45%, 40%, and 35%, in that order. B2O3 is a glass network-forming component. By including B2O3 as a glass component, the partial dispersion ratio P C,t in the infrared wavelength range can be increased. From the viewpoints of suppressing a decrease in the partial dispersion ratio P C,t in the infrared wavelength range and suppressing a decrease in the thermal stability of the glass, it is preferable that the lower limit of the B2O3 content be as described above. From the viewpoint of suppressing a decrease in the chemical durability of the glass, it is preferable that the upper limit of the B2O3 content be as described above.

[0158] The optical glass according to the first and second embodiments contains ZrO2 as a glass component. The lower limit of the ZrO2 content is preferably 5.0%, and more preferably 6.5%, 8.0%, and 9.5%, in that order. The upper limit of the ZrO2 content is preferably 30%, and more preferably 25%, 20%, and 15%, in that order. By including ZrO2 as a glass component, the partial dispersion ratio PC,t in the infrared wavelength range can be increased, and chemical durability can be improved. From the viewpoint of suppressing a decrease in chemical durability, the lower limit of the ZrO2 content is preferably as described above. From the viewpoint of suppressing an increase in the liquidus temperature LT and a decrease in stability during reheating, the upper limit of the ZrO2 content is preferably as described above.

[0159] The optical glass according to the first and second embodiments contains Nb2O5 as a glass component. The content of Nb2O5 is preferably greater than 5.0%, with the lower limit being 6.5%, 8.0%, and 9.5%, in that order being more preferable. The upper limit of the Nb2O5 content is preferably 30%, with 25%, 20%, and 15%, in that order being more preferable. By containing Nb2O5 as a glass component, high dispersion can be maintained while suppressing a decrease in the partial dispersion ratio PC,t in the infrared wavelength range. From the viewpoint of maintaining high dispersion, the lower limit of the Nb2O5 content is preferably set as described above. From the viewpoint of suppressing a decrease in the partial dispersion ratio PC,t in the infrared wavelength range, the lower limit of the Nb2O5 content is preferably set as described above.

[0160] The optical glass according to the first and second embodiments contains, as a glass component, one or more selected from the group consisting of Li2O, Na2O, and K2O. Preferably, it contains Na2O, but it may contain Li2O and Na2O, or Na2O and K2O, or Li2O and K2O, or it may contain Li2O, Na2O, and K2O. By containing, as a glass component, one or more selected from the group consisting of Li2O, Na2O, and K2O, it is possible to increase the partial dispersion ratio P C,t in the infrared wavelength range and improve chemical durability.

[0161] In the optical glass according to the first-second embodiment, the upper limit of the mass ratio [(R2O + R'O) / (SiO2 + B2O3)] of the total content R2O of Li2O, Na2O, and K2O, and the total content R'O of MgO, CaO, SrO, BaO, and ZnO, to the total content R2O of SiO2 and B2O3 is preferably 0.36, with 0.35, 0.34, and 0.33 being more preferred in this order. The lower limit of this mass ratio is preferably 0.05, with 0.10, 0.15, and 0.20 being more preferred in this order. From the viewpoints of increasing the partial dispersion ratio Pc,t in the infrared wavelength range and improving chemical durability, it is preferable that this mass ratio be within the above range.

[0162] In the optical glass according to the first-second embodiment, the lower limit of the mass ratio [B2O3 / (ZrO2+Nb2O5+TiO2+WO3+Bi2O3+Ta2O5)] of the content of B2O3 to the total content of ZrO2, Nb2O5, TiO2, WO3, Bi2O3, and Ta2O5 is preferably 0.74, with 0.84, 0.94, and 1.04 being more preferred in that order. The upper limit of this mass ratio is preferably 3.0, with 2.5, 2.0, and 1.5 being more preferred in that order. From the viewpoint of increasing the partial dispersion ratio P C,t in the infrared wavelength range, it is preferable that this mass ratio be within the above range.

[0163] In the optical glass according to the first and second embodiments, the lower limit of the total content of ZrO2, Nb2O5, TiO2, WO3, and Ta2O5 [ZrO2 + Nb2O5 + TiO2 + WO3 + Ta2O5] is preferably 22%, and more preferably 22.5%, 23.0%, and 23.5% in that order. The upper limit of this total content is preferably 40%, and more preferably 35%, 30%, and 25% in that order. From the viewpoints of increasing the refractive index nd and setting the Abbe number νd within a desired range, it is preferable that the total content be within the above range.

[0164] The optical glass according to the first and second embodiments preferably does not substantially contain Pb, which is a component that poses a concern for its environmental impact. That is, the Pb content is preferably 0% in terms of oxide. Like Pb, As and Th are also components that pose a concern for their environmental impact. Therefore, the As and Th contents are preferably 0 to 0.1% in terms of oxide, and may be 0 to 0.05%, or 0 to 0.01%. The As and Th contents are preferably 0% in terms of oxide. That is, it is preferable that neither As nor Th is substantially contained.

[0165] In the optical glass according to the 1-2 embodiment, the contents and ratios of glass components other than those mentioned above can be the same as those in the 1-1 embodiment.

[0166] In the optical glass according to the first embodiment, the deviation ΔP C,t is 0.0250 or more. The lower limit of the deviation ΔP C,t is preferably 0.0270, with 0.0290, 0.0310, 0.0330, 0.0350, and 0.0370 being more preferable in this order. By setting the deviation ΔP C,t within the above range, an optical glass suitable for correcting high-order chromatic aberrations can be obtained. On the other hand, the upper limit of the deviation ΔP C,t is not particularly limited, but is usually 0.0900, preferably 0.0800. The method for calculating the deviation ΔP C,t is as described in the first embodiment.

[0167] In the optical glass according to the 1-2 embodiment, the glass properties other than those mentioned above can be the same as those of the 1-1 embodiment.

[0168] The optical glass according to the 1-2 embodiment and the optical elements and the like can be manufactured in the same manner as in the 1-1 embodiment.

[0169] Second embodiment In the second embodiment (embodiment 2-1 and embodiment 2-2), the glass composition of the optical glass is expressed in cation % unless otherwise specified. Cation % is the molar percentage when the total content of all cationic components is 100%. In the second embodiment (embodiment 2-1 and embodiment 2-2), the content and total content of the glass components are based on cation %, unless otherwise specified, and "%" means "cation %." Furthermore, in this specification and the present invention, a content of 0% of a constituent component means that the constituent component is substantially not contained, and it is acceptable for the constituent component to be present at an unavoidable impurity level.

[0170] The anion % is a molar percentage when the total content of all anion components is taken as 100%.

[0171] The valence of the cationic component (e.g., B 3+ The valence of is +3, Si 4+ The valence of is +4, La 3+The valence of the anion component (e.g., O) is a value established by convention, similar to the way that the glass components B, Si, and La are expressed on an oxide basis as B2O3, SiO2, and La2O3. Therefore, when analyzing glass composition, it is not necessary to analyze the valence of the cation component. Also, the valence of the anion component (e.g., O 2- The valence of an anion (-2) is also a value determined by convention, similar to the way glass components based on oxides are expressed as B2O3, SiO2, La2O3, etc. Therefore, when analyzing glass composition, it is not necessary to analyze the valence of the anion components. 2-1 Embodiment

[0172] In the second embodiment, the glass composition was designed based on the following guidelines: <1> Si, which is a component that increases the partial dispersion ratio PC,t in the infrared wavelength range. 4+ and B 3+ While containing a large amount of Si, 4+ Part of B 3+ (3) To improve formability by further increasing dispersion and reducing viscosity, alkali metal and alkaline earth metal oxides are appropriately introduced. (4) By minimizing the amount of highly dispersible components, which are necessary to obtain the desired Abbe number but which also reduce PC,t, Nb, which is particularly capable of relatively suppressing the decrease in PC,t among highly dispersible components, is used. 5+ , and Zr, which can simultaneously suppress the decrease in PC,t and improve the chemical durability of the glass. 4+ By actively incorporating these factors, they have been able to complete an optical glass that has a small Abbe number vd and a relatively high partial dispersion ratio PC,t in the infrared wavelength range. The optical glass according to embodiment 2-1 is as follows.

[0173] The optical glass according to the second embodiment is Si 4+ The content is 10% or more, B 3+ The content is 20% or more, Si 4+ and B 3+The total content of [Si 4+ +B 3+ ] is 50% or more, B 3+ and Si content 4+ and B 3+ The total content and cation ratio [B 3+ / (Si 4+ +B 3+ )] is 0.44 or more, Li + , Na + , and K. + The total content R of the above and Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The cation ratio [R / (R+R')] to the total content R' of [R / (R+R')] is 0.55 or more, Nb 5+ The content is more than 0% and 11.5% or less, Satisfy one or more of the following (i) and (ii): (i) Zr 4+ The content of R' and the total content of Nb 5+ , Ti 4+ , W 6+ , Bi 3+ , and Ta 5+ The total content and cation ratio [Zr 4+ / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ +Ta 5+ )] is 0.17 or greater. (ii) Zr 4+ and Ta 5+ The total content of R', Nb 5+ , Ti 4+ , W 6+ , and Bi 3+ The cation ratio [(Zr 4+ +Ta 5+ ) / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ )] is 0.25 or greater.

[0174] In the optical glass according to the second embodiment, Si 4+ The Si content is 10% or more. 4+ The lower limit of the Si content is preferably 12%, and more preferably 14%, 16%, 18%, 20%, 22%, 23%, and 24% in that order. 4+ The upper limit of the Si content is preferably 50%, and more preferably 43%, 40%, 38%, 36%, 34%, 32%, and 30% in that order. 4+ is a glass network forming component. 4+ By setting the content of Si in the above range, the partial dispersion ratio P C,t in the infrared wavelength region can be increased, and chemical durability can be improved. 4+ If the Si content is too low, the partial dispersion ratio PC,t in the infrared wavelength region decreases, and the thermal stability and chemical durability of the glass may decrease. 4+ If the content is too high, the meltability of the glass may decrease, and the viscosity of the molten glass may increase, resulting in poor formability.

[0175] In the optical glass according to the second embodiment, B 3+ The content of is 20% or more. 3+ The lower limit of the content of B is preferably 25%, and more preferably 28%, 29%, 30%, 31%, and 32% in that order. 3+ The upper limit of the content of B is preferably 60%, and more preferably 55%, 50%, 48%, 46%, and 44% in that order. 3+ is a glass network forming component. 3+ By setting the content of B in the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased. 3+ If the content of B is too small, the partial dispersion ratio PC,t in the infrared wavelength region decreases, and the thermal stability of the glass may decrease. 3+ If the content is too high, the chemical durability of the glass may decrease.

[0176] In the optical glass according to the second embodiment, Si4+ and B 3+ The total content of [Si 4+ +B 3+ ] is 50% or more. The lower limit of the total content is preferably 52%, and more preferably 54%, 56%, and 57%, in that order. The upper limit of the total content is preferably 80%, and more preferably 78%, 76%, 74%, 72%, and 71%, in that order. By setting the total content within the above range, the partial dispersion ratio PC,t in the infrared wavelength range can be increased and the thermal stability of the glass can be maintained. If the total content is too low, the partial dispersion ratio PC,t in the infrared wavelength range decreases, and the thermal stability and chemical durability of the glass may not be maintained. If the total content is too high, the viscosity of the molten glass may increase, which may deteriorate the moldability. In addition, the refractive index may decrease.

[0177] In the optical glass according to the second embodiment, B 3+ and Si content 4+ and B 3+ The total content and cation ratio [B 3+ / (Si 4+ +B 3+ )] is 0.44 or more. The lower limit of the cation ratio is preferably 0.47, and more preferably 0.50, 0.53, and 0.56 in that order. The upper limit of the cation ratio is preferably 0.80, and more preferably 0.75, 0.71, 0.67, 0.63, and 0.61 in that order. By setting the cation ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the chemical durability of the glass may decrease.

[0178] In the optical glass according to the second embodiment, Li + , Na + , and K. + The total content R of the above and Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+The cation ratio [R / (R+R')] of the total content of R and the total content of R' is 0.55 or more. The lower limit of the cation ratio is preferably 0.60, with 0.65, 0.70, and 0.75 being more preferable in this order. The upper limit of the cation ratio is preferably 1.00, with 0.95, 0.90, and 0.85 being more preferable in this order. By setting the cation ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength range can be increased, the meltability of the glass can be improved, and the viscosity of the molten glass can be reduced, thereby improving moldability. If the cation ratio is too small, the partial dispersion ratio PC,t may be reduced. If the cation ratio is too large, the thermal stability of the glass may be reduced and the refractive index nd may be reduced.

[0179] In this specification, Li + , Na + , and K. + The total content of Mg is sometimes referred to as R. 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content of these may be referred to as R'.

[0180] In the optical glass according to the second embodiment, Nb 5+ The Nb content is greater than 0% and less than 11.5%. 5+ The lower limit of the Nb content is preferably 2.0%, and more preferably 3.0%, 3.5%, 4.0%, 4.5%, and 5.0% in that order. 5+ The upper limit of the Nb content is preferably 10%, and more preferably 9.5%, 9.0%, 8.5%, 8.0%, 7.5%, 7.0%, 6.5%, and 6.0% in that order. 5+ By setting the content of Nb in the above range, it is possible to maintain high dispersion while suppressing a decrease in the partial dispersion ratio PC,t in the infrared wavelength region. 5+ If the Nb content is too low, high dispersion may not be maintained. 5+ If the content is too large, the partial dispersion ratio PC,t in the infrared wavelength region may decrease.

[0181] The optical glass according to the 2-1 embodiment satisfies one or more of the following (i) and (ii).

[0182] (i) In the optical glass according to the second embodiment, Zr 4+ and Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content of R', Nb 5+ , Ti 4+ , W 6+ , Bi 3+ , and Ta 5+ The total content and cation ratio [Zr 4+ / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ +Ta 5+ The lower limit of the cation ratio ( ) is preferably 0.17, and more preferably 0.20, 0.25, 0.30, 0.35, 0.37, 0.39, and 0.40, in that order. The upper limit of the cation ratio is preferably 2.00, and more preferably 1.80, 1.60, 1.40, 1.20, 1.00, 0.80, and 0.60, in that order. From the viewpoints of improving chemical durability, increasing the refractive index nd, and maintaining high dispersibility, it is preferable that the cation ratio be within the above range. If the cation ratio is too small, the refractive index nd may decrease and the chemical durability of the glass may decrease. If the cation ratio is too large, the liquidus temperature LT may increase and stability during reheating may decrease.

[0183] (ii) In the optical glass according to the second embodiment, Zr 4+ and Ta 5+ The total content of Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content of R', Nb 5+ , Ti 4+ , W 6+ , and Bi 3+ The cation ratio [(Zr4+ +Ta 5+ ) / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ The lower limit of the cation ratio (Pc,t) is preferably 0.25, and more preferably 0.30, 0.35, 0.37, 0.39, and 0.40, in that order. The upper limit of the cation ratio is preferably 3.10, and more preferably 2.80, 2.60, 2.40, 2.20, 2.00, 1.80, 1.60, 1.40, 1.20, 1.00, 0.80, and 0.60, in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, increasing the refractive index nd, maintaining high dispersion, and maintaining the chemical durability of the glass, it is preferable that the cation ratio be within the above range. If the cation ratio is too small, the refractive index nd may decrease and the chemical durability of the glass may also decrease. If the cation ratio is too large, the thermal stability of the glass may decrease.

[0184] The preferred contents of the glass components in the optical glass according to embodiment 2-1 are shown below.

[0185] In the optical glass according to the second embodiment, Zr 4+ and Ta 5+ The total content of [Zr 4+ +Ta 5+ The upper limit of [% by weight] is preferably 8.5%, and more preferably 8.0%, 7.5%, 7.0%, 6.5%, 6.0%, and 5.5% in that order. The lower limit of the total content is preferably 1.0%, and more preferably 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, and 4.5% in that order. From the viewpoint of maintaining the thermal stability of the glass, it is preferable that the total content be within the above range. If the total content is too low, the chemical durability of the glass may be reduced. If the total content is too high, the thermal stability of the glass may be reduced and the raw material costs may increase.

[0186] In the optical glass according to the second embodiment, Zr 4+The lower limit of the content of Zr is preferably 1.0%, and more preferably 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, and 4.5% in that order. 4+ The upper limit of the content of Zr is preferably 8.5%, and more preferably 8.0%, 7.5%, 7.0%, 6.5%, 6.0%, and 5.5% in that order. 4+ It is preferable that the content of Zr is within the above range. 4+ If the content is too low, chemical durability may decrease. 4+ If the content is too large, the liquidus temperature LT may increase and the stability during reheating may decrease.

[0187] In the optical glass according to the second embodiment, Li + , Na + , and K. + The total content of R and Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content R' of Si 4+ and B 3+ The total content and cation ratio [(R+R') / (Si 4+ +B 3+ The upper limit of the cation ratio is preferably 1.00, and more preferably 0.90, 0.80, 0.70, 0.60, and 0.50 in that order. The lower limit of the cation ratio is preferably 0.10, and more preferably 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, and 0.24 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio be in the above range.

[0188] In the optical glass according to the second embodiment, B 3+ and Zr 4+ , Nb 5+ , Ti 4+ , W 6+ , Bi 3+ , and Ta5+ The total content and cation ratio [B 3+ / (Zr 4+ +Nb 5+ +Ti 4+ +W 6+ +Bi 3+ +Ta 5+ The upper limit of the cation ratio is preferably 7.0, and more preferably 6.0, 5.5, 5.0, 4.5, and 4.0 in that order. The lower limit of the cation ratio is preferably 1.0, and more preferably 1.2, 1.4, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, and 2.2 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable that the cation ratio be in the above range.

[0189] In the optical glass according to the second embodiment, Zr 4+ , Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content of [Zr 4+ +Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The lower limit of [% by weight] is preferably 5.0%, and more preferably 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, and 10%, in that order. The upper limit of the total content is preferably 20%, and more preferably 19%, 18%, 17%, 16%, and 15%, in that order. From the viewpoint of increasing the refractive index nd and adjusting the Abbe number νd, it is preferable that the total content be within the above range.

[0190] The optical glass according to the second embodiment is Pb 2+ It is preferable that the material does not substantially contain Pb. 2+The content of As is preferably 0%. Furthermore, like Pb, As and Th are components that pose a concern for their environmental impact. Therefore, the content of each of As and Th is preferably 0 to 0.1% in terms of oxide, and may be 0 to 0.05%, or 0 to 0.01%. The content of each of As and Th is preferably 0% in terms of oxide. In other words, it is preferable that neither As nor Th is substantially contained.

[0191] Non-limiting examples of the contents and ratios of glass components other than those described above in the optical glass according to embodiment 2-1 are shown below.

[0192] In the optical glass according to the second embodiment, P 5+ The upper limit of the content of P is preferably 20%, and more preferably 10%, 5%, and 3% in that order. 5+ The lower limit of the content of P is preferably 0.1%, and more preferably 0.5%, 0.8%, and 1% in that order. 5+ The content of P may be 0%. 5+ By setting the content within the above range, the thermal stability of the glass can be maintained.

[0193] In the optical glass according to the second embodiment, Al 3+ The upper limit of the Al content is preferably 10%, and more preferably 8%, 6%, 4%, and 2% in that order. 3+ The lower limit of the Al content is preferably 0%, and more preferably 0.01%, 0.05%, 0.10%, 0.15%, and 0.20%, in that order. 3+ The content of Al may be 0%. 3+ The inclusion of an appropriate amount of Al has the effect of suppressing phase separation of glass. On the other hand, from the viewpoint of maintaining the thermal stability of glass, Al 3+ It is preferable that the content of is within the above range.

[0194] In the optical glass according to the second embodiment, Si 4+ , B 3+ , and Al 3+ The total content of [Si4+ +B 3+ +Al 3+ The lower limit of

[0049] is preferably 50%, and more preferably 52%, 54%, 56%, and 57% in that order. The upper limit of the total content is preferably 80%, and more preferably 78%, 76%, 74%, and 72% in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range and maintaining the thermal stability and stability during reheating of the glass, it is preferable that the total content be set within the above range.

[0195] In the glass according to embodiment 2-1, Li + The upper limit of the content of Li is preferably 50%, and more preferably 45%, 40%, 35%, 30%, 25%, 20%, 18%, and 16% in that order. + The lower limit of the content of Li is preferably 0%, and more preferably 5%, 10%, and 15% in that order. + The content of Li may be 0%. + Li is a component that contributes to lowering the viscosity of glass, and among alkali metals, it has a relatively large effect of increasing the partial dispersion ratio PC,t in the infrared wavelength region. + If the content is too high, the stability may decrease when reheated. + If the content is too low, the viscosity of the glass may increase.

[0196] In the glass according to embodiment 2-1, Na + The upper limit of the content of Na is preferably 50%, and more preferably 45%, 40%, 35%, 30%, 25%, 20%, 18%, and 16% in that order. + The lower limit of the Na content is preferably 0%, and more preferably 5%, 10%, and 12% in that order. + Li + Like Na, it is a component that contributes to lowering the viscosity of glass. + If the content is too high, the stability may decrease when reheated. + If the content is too low, the viscosity of the glass may increase.

[0197] In the optical glass according to the second embodiment, K + The upper limit of the content of K is preferably 20%, and more preferably 15%, 10%, and 5% in that order. + The lower limit of the content of K is preferably 0%, and more preferably 1%, 2%, and 3% in that order. + The content may be 0%.

[0198] K + has the function of lowering the liquidus temperature and improving the thermal stability of the glass. + If the content of K increases, chemical durability, weather resistance, and stability during reheating decrease. + The content is preferably in the above range.

[0199] In the optical glass according to the second embodiment, Li + , Na + , and K. + The total content of R[Li + +Na + +K + The upper limit of [R] is preferably 50%, and more preferably 45%, 40%, 35%, 30%, and 27% in that order. The lower limit of the total content R is preferably 5%, and more preferably 8%, 11%, and 13% in that order. From the viewpoint of suppressing a decrease in stability during reheating, it is preferable that the total content R be within the above range.

[0200] In the optical glass according to the second embodiment, Li + and Li + , Na + , and K. + The total content R and the cation ratio [Li +The upper limit of [(R / R)] is preferably 1, and more preferably 0.95, 0.90, 0.85, 0.80, 0.75, and 0.70 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, and 0.60 in this order. The cation ratio may be 0. From the viewpoint of suppressing a decrease in stability during reheating, it is preferable that the cation ratio be within the above range.

[0201] In the optical glass according to the second embodiment, Na + and Li content + , Na + , and K. + The total content R and the cation ratio [Na + The upper limit of [(R / R)] is preferably 1, and more preferably 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, and 0.35 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.05, 0.10, 0.15, 0.20, and 0.25 in that order. The cation ratio may be 0. From the viewpoint of suppressing a decrease in stability during reheating, it is preferable that the cation ratio be within the above range.

[0202] In the optical glass according to the second embodiment, K + and Li content + , Na + , and K. + The total content R and the cation ratio [K + The upper limit of [(R / R)] is preferably 1, and more preferably 0.95, 0.90, 0.85, 0.80, 0.75, and 0.70 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, and 0.60 in this order. The cation ratio may be 0. From the viewpoint of suppressing a decrease in stability during reheating, it is preferable that the cation ratio be within the above range.

[0203] In the optical glass according to the second embodiment, Cs+ The upper limit of the content of Cs is preferably 20%, and more preferably 15%, 10%, and 5% in that order. + The lower limit of the content of Cs is preferably 0%. + The content may be 0%.

[0204] Cs + Although Cs has the function of improving the thermal stability of glass, if its content is too high, it may reduce chemical durability and weather resistance. + The content is preferably in the above range.

[0205] In the optical glass according to the second embodiment, Ti 4+ The upper limit of the Ti content is preferably 20%, and more preferably 15%, 10%, 8%, 6%, and 4% in that order. 4+ The lower limit of the Ti content is preferably 0%. 4+ The content of Ti may be 0%. 4+ By setting the content within the above range, desired optical constants can be achieved and an increase in specific gravity can be suppressed.

[0206] In the optical glass according to the second embodiment, W 6+ The upper limit of the content of W is preferably 20%, and more preferably 15%, 10%, 8%, 6%, 4%, 2%, 1%, 0.5%, and 0.1% in that order. 6+ The lower limit of the content of W is preferably 0%. 6+ The content of W may be 0%. From the viewpoint of increasing the transmittance, suppressing the decrease in the partial dispersion ratio PC,t in the infrared wavelength region, and reducing the specific gravity, 6+ It is preferable that the content of is within the above range.

[0207] In the optical glass according to the second embodiment, Bi 3+ The upper limit of the content of Bi is preferably 20%, and more preferably 15%, 10%, 8%, and 6% in that order. 3+The lower limit of the content of Bi is preferably 0%, and more preferably 1%, 2%, 3%, 4%, and 5% in that order. 3+ The content of Bi may be 0%. From the viewpoint of increasing the transmittance, reducing the specific gravity, and reducing damage to the platinum manufacturing equipment, 3+ It is preferable that the content of is within the above range.

[0208] In the optical glass according to the second embodiment, Ta 5+ The upper limit of the content of Ta is preferably 20%, and more preferably 15%, 10%, 9%, 8%, and 6% in that order. 5+ The lower limit of the content of Ta is preferably 0%, and more preferably 1%, 2%, 3%, and 4% in that order. 5+ The content may be 0%.

[0209] Ta 5+ is a component that gives the glass high refractive index and low dispersion, and increases the partial dispersion ratio PC,t in the infrared wavelength range. 5+ If the content of Ta is high, the raw material cost will increase. In addition, there is a risk of the specific gravity increasing. 5+ The content is preferably in the above range.

[0210] In the optical glass according to the second embodiment, Nb 5+ , Ti 4+ , W 6+ , and Bi 3+ The total content of [Nb 5+ +Ti 4+ +W 6+ +Bi 3+ The upper limit of the total content is preferably 20%, and more preferably 15%, 14%, 13%, 12%, 11%, and 10% in that order. The lower limit of the total content is preferably 0.5%, and more preferably 1%, 2%, 3%, and 4% in that order. From the viewpoint of maintaining a high refractive index and a desired Abbe number νd, it is preferable that the total content be within the above range.

[0211] In the optical glass according to the second embodiment, Nb 5+ , Ti4+ , W 6+ , Bi 3+ , and Ta 5+ The total content of [Nb 5+ +Ti 4+ +W 6+ +Bi 3+ +Ta 5+ The upper limit of the total content is preferably 20%, and more preferably 15%, 14%, 13%, 12%, 11%, and 10% in that order. The lower limit of the total content is preferably 0.5%, and more preferably 1%, 2%, 3%, and 4% in that order. From the viewpoint of maintaining a high refractive index and a desired Abbe number νd, it is preferable that the total content be within the above range.

[0212] In the optical glass according to the second embodiment, Zr 4+ , Nb 5+ , Ti 4+ , W 6+ , Bi 3+ , and Ta 5+ The total content of [Zr 4+ +Nb 5+ +Ti 4+ +W 6+ +Bi 3+ +Ta 5+ The upper limit of the total content is preferably 20%, and more preferably 19%, 18%, 17%, 16%, and 15% in that order. The lower limit of the total content is preferably 5%, and more preferably 6%, 7%, 8%, 9%, and 10% in that order. From the viewpoint of maintaining a high refractive index, it is preferable that the total content be within the above range.

[0213] In the optical glass according to the second embodiment, Zr 4+ and Nb 5+ The total content of [Zr 4+ +Nb 5+ The upper limit of

[0045] is preferably 20%, and more preferably 19%, 18%, 17%, 16%, and 15% in that order. The lower limit of the total content is preferably 5%, and more preferably 6%, 7%, 8%, 9%, and 10% in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region and maintaining high dispersibility, it is preferable that the total content be within the above range.

[0214] In the optical glass according to the second embodiment, Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content of [Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of the total content is preferably 20%, and more preferably 15%, 14%, 13%, 12%, 11%, and 10% in that order. The lower limit of the total content is preferably 0.5%, and more preferably 1%, 2%, 3%, and 4% in that order. From the viewpoint of maintaining a high refractive index and a desired Abbe number νd, it is preferable that the total content be within the above range.

[0215] In the optical glass according to the second embodiment, Nb 5+ and Nb content 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content and cation ratio [Nb 5+ / (Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of the cation ratio is preferably 1, and more preferably 0.99, 0.98, 0.97, 0.96, 0.95, 0.94, 0.93, 0.92, and 0.91 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.5, 0.6, 0.7, 0.8, and 0.9 in that order. The cation ratio may be 1. From the viewpoint of maintaining a high refractive index, it is preferable that the cation ratio be in the above range.

[0216] In the optical glass according to the second embodiment, Ta 5+ and Nb content 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content and cation ratio [Ta 5+ / (Nb 5+ +Ti 4+ +W 6+ +Ta 5+The upper limit of the cation ratio is preferably 0.5, and more preferably 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.03, 0.05, and 0.07 in this order. The cation ratio may be 0. From the viewpoint of suppressing an increase in raw material costs, it is preferable that the cation ratio be in the above range.

[0217] In the optical glass according to the second embodiment, Ti 4+ and Nb content 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content and cation ratio [Ti 4+ / (Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of the cation ratio is preferably 0.5, and more preferably 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.03, 0.05, and 0.07 in this order. The cation ratio may be 0. From the viewpoint of maintaining a high refractive index, it is preferable that the cation ratio be in the above range.

[0218] In the optical glass according to the second embodiment, Zr 4+ and Zr 4+ , Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content and cation ratio [Zr 4+ / (Zr 4+ +Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of the cation ratio is preferably 0.9, and more preferably 0.8, 0.7, 0.6, and 0.55 in this order. The lower limit of the cation ratio is preferably 0.01, and more preferably 0.10, 0.15, 0.20, 0.25, and 0.30 in this order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region and maintaining high dispersibility, it is preferable that the cation ratio be within the above range.

[0219] In the optical glass according to the second embodiment, Nb 5+ and Zr 4+ , Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content and cation ratio [Nb 5+ / (Zr 4+ +Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of the cation ratio is preferably 0.9, and more preferably 0.8, 0.75, and 0.7 in that order. The lower limit of the cation ratio is preferably 0.1, and more preferably 0.2, 0.3, 0.4, and 0.45 in that order. From the viewpoint of maintaining high dispersibility, it is preferable that the cation ratio be within the above range.

[0220] In the optical glass according to the second embodiment, Ta 5+ and Zr 4+ , Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content and cation ratio [Ta 5+ / (Zr 4+ +Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of the cation ratio is preferably 0.5, and more preferably 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.03, 0.05, and 0.07 in this order. The cation ratio may be 0. From the viewpoint of suppressing an increase in raw material costs, it is preferable that the cation ratio be in the above range.

[0221] In the optical glass according to the second embodiment, Ti 4+ and Zr 4+ , Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content and cation ratio [Ti4+ / (Zr 4+ +Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of the cation ratio is preferably 0.5, and more preferably 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.03, 0.05, and 0.07 in this order. The cation ratio may be 0. From the viewpoint of maintaining high dispersibility, it is preferable that the cation ratio be in the above range.

[0222] In the optical glass according to the second embodiment, Mg 2+ The upper limit of the content of Mg is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1% in that order. 2+ The lower limit of the content of Mg is preferably 0%. 2+ The content may be 0%.

[0223] Mg 2+ Among alkaline earth metals, Mg is a component that increases the partial dispersion ratio PC,t in the infrared wavelength range. 2+ If the content of Mg is too high, the high dispersion may be impaired, and the thermal stability and devitrification resistance of the glass may be reduced. 2+ The content is preferably in the above range.

[0224] In the optical glass according to the second embodiment, Ca 2+ The upper limit of the Ca content is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1% in that order. 2+ The lower limit of the content of Ca is preferably 0%. 2+ The content may be 0%.

[0225] Ca 2+ Among alkaline earth metals, Ca is a component that increases the partial dispersion ratio PC,t in the infrared wavelength range. 2+If the content of Ca is too high, the high dispersion may be impaired, and the thermal stability and devitrification resistance of the glass may be reduced. 2+ The content is preferably in the above range.

[0226] In the optical glass according to the second embodiment, Sr 2+ The upper limit of the Sr content is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1% in that order. 2+ The lower limit of the Sr content is preferably 0%. 2+ The content may be 0%.

[0227] Sr 2+ is a component that increases the refractive index among alkaline earth metals. 2+ If the content of Sr is too high, the high dispersion may be impaired and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. 2+ The content is preferably in the above range.

[0228] In the optical glass according to the second embodiment, Ba 2+ The upper limit of the Ba content is preferably 20%, and more preferably 10%, 9%, 8%, 7%, 6%, 5%, and 4.5% in that order. 2+ The lower limit of the Ba content is preferably 0%, and more preferably 1.0%, 1.5%, and 2.0% in that order. 2+ The content may be 0%.

[0229] Ba 2+ is a component that increases the refractive index and at the same time lowers the liquidus temperature and improves the stability of the glass. 2+ If the content of Ba is too high, the high dispersion may be impaired, and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. 2+ If the content of Ba is too small, the refractive index nd may decrease, and the thermal stability and devitrification resistance of the glass may also decrease. 2+ The content is preferably in the above range.

[0230] In the optical glass according to the second embodiment, Zn 2+ The upper limit of the content of Zn is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1% in that order. 2+ The lower limit of the Zn content is preferably 0%, and more preferably 0.1%, 0.5%, and 0.7% in that order. 2+ The content may be 0%.

[0231] Zn 2+ is a glass component that improves the thermal stability of glass. 2+ If the content of Zn is too high, the specific gravity may increase and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining the desired optical constants, Zn 2+ The content is preferably in the above range.

[0232] In the optical glass according to the second embodiment, Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ The total content of [Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ The upper limit of the total content is preferably 20%, and more preferably 15%, 10%, 9%, 8%, 7%, 6%, 5%, and 4% in that order. The lower limit of the total content is preferably 0%, and more preferably 0.3%, 0.6%, 0.9%, 1.0%, 1.2%, 1.5%, 1.7%, and 1.9% in that order. Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ The total content of [Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+] may be 0%. If the total content is too high, high dispersion may be impaired and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. If the total content is too low, the refractive index nd may decrease and the thermal stability and devitrification resistance of the glass may decrease. Therefore, the total content is preferably within the above range.

[0233] In the optical glass according to the second embodiment, Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content of R'[Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ +Zn 2+ The upper limit of [R'] is preferably 20%, and more preferably 15%, 10%, 9%, 8%, 7%, 6%, 5%, and 4% in that order. The lower limit of the total content R' is preferably 0%, and more preferably 0.3%, 0.6%, 0.9%, 1.0%, 1.2%, 1.5%, 1.7%, and 1.9% in that order. The total content R' may be 0%. If the total content R' is too high, the high dispersion may be impaired and the partial dispersion ratio PC,t in the infrared wavelength range may decrease. If the total content R' is too low, the refractive index nd may decrease and the thermal stability and devitrification resistance of the glass may decrease. Therefore, the total content R' is preferably within the above range.

[0234] In the glass according to embodiment 2-1, Y 3+ The upper limit of the content of Y is preferably 20%, and more preferably 10%, 5%, 4%, and 3% in that order. 3+ The lower limit of the content of Y is preferably 0%, and more preferably 1% and 2% in that order. 3+ The content may be 0%.

[0235] Y 3+ By introducing a certain amount of Y, the refractive index nd can be increased. 3+If the content of Y is too high, the thermal stability of the glass decreases, and the glass is likely to devitrify during production. In addition, there is a risk that the high dispersion properties may be impaired. Therefore, from the viewpoint of suppressing the decrease in the thermal stability of the glass, it is preferable to limit the content of Y. 3+ The content is preferably in the above range.

[0236] In the glass according to embodiment 2-1, Sc 3+ The content of Sc is preferably 2% or less. 3+ The lower limit of the content is preferably 0%.

[0237] In the glass according to embodiment 2-1, Hf 4+ The content of Hf is preferably 2% or less. 4+ The lower limit of the content is preferably 0%.

[0238] Sc 3+ , Hf 4+ Although Sc has the effect of increasing the dispersibility of the glass, it is an expensive component. 3+ , Hf 4+ The content of each of the above is preferably within the above range.

[0239] In the glass according to embodiment 2-1, Lu 3+ The content of Lu is preferably 2% or less. 3+ The lower limit of the content is preferably 0%.

[0240] Lu 3+ Although Lu has the function of increasing the dispersibility of glass, it is also a glass component that increases the specific gravity of glass due to its large molecular weight. 3+ The content is preferably in the above range.

[0241] In the glass according to embodiment 2-1, Ge 4+ The content of Ge is preferably 2% or less. 4+ The lower limit of the content is preferably 0%.

[0242] Ge4+ Although Ge has the function of enhancing the high dispersibility of glass, it is an extremely expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of glass, Ge 4+ The content is preferably in the above range.

[0243] In the optical glass according to the second embodiment, La 3+ The upper limit of the content of Y is preferably 20%, and more preferably 10%, 5%, 4%, and 3% in that order. 3+ The lower limit of the content of La is preferably 0%, and more preferably 1% and 2% in that order. 3+ The content of La may be 0%. 3+ The refractive index nd can be increased by introducing a certain amount of La. 3+ If the content of La is too high, the thermal stability of the glass decreases, and the glass becomes more susceptible to devitrification during manufacturing. In addition, there is a risk that the high dispersion may be impaired and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. Therefore, La 3+ The content is preferably in the above range.

[0244] In the glass according to the second embodiment, Gd 3+ The content of Gd is preferably 2% or less. 3+ The lower limit of the content is preferably 0%.

[0245] Gd 3+ If the content is too high, the thermal stability of the glass will decrease. 3+ If the content of Gd is too high, the specific gravity of the glass increases, which is undesirable. In addition, there is a risk of an increase in the raw material cost. Therefore, from the viewpoint of suppressing an increase in the specific gravity while maintaining good thermal stability of the glass, it is preferable to use a Gd content of 100%. 3+ The content is preferably in the above range.

[0246] In the glass according to embodiment 2-1, La 3+ , Gd 3+ , and Y 3+ The total content of [La3+ +Gd 3+ +Y 3+ The upper limit of

[0045] is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1% in that order. The lower limit of the total content is preferably 0%. From the viewpoint of suppressing a decrease in the thermal stability of the glass and preventing a decrease in the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable that the total content be set within the above range.

[0247] In the glass according to embodiment 2-1, Yb 3+ The content of Yb is preferably 2% or less. 3+ The lower limit of the content is preferably 0%.

[0248] Yb 3+ La 3+ , Gd 3+ , Y 3+ Its molecular weight is larger than that of Yb, which increases the specific gravity of the glass. 3+ If the content of Yb is too high, the thermal stability of the glass will decrease. 3+ The content is preferably in the above range.

[0249] In the glass according to embodiment 2-1, Li + , Na + , and K. + The total content of R and Si 4+ and B 3+ The total content and cation ratio [R / (Si 4+ +B 3+ The upper limit of the cation ratio is preferably 2.0, and more preferably 1.5, 1.0, 0.9, 0.8, 0.7, 0.6, and 0.5 in that order. The lower limit of the cation ratio is preferably 0.01, and more preferably 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, and 0.14 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio be in the above range.

[0250] In the glass according to embodiment 2-1, Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ and the total content of Si 4+ and B 3+ The cation ratio [(Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ ) / (Si 4+ +B 3+ The upper limit of the cation ratio is preferably 0.5, and more preferably 0.4, 0.3, 0.2, 0.1, and 0.08 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.01, 0.02, and 0.03 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio be in the above range.

[0251] In the glass according to embodiment 2-1, Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content R' and Si 4+ and B 3+ The total content and cation ratio [R' / (Si 4+ +B 3+ The upper limit of the cation ratio is preferably 0.5, and more preferably 0.4, 0.3, 0.2, 0.1, and 0.08 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.01, 0.02, and 0.03 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio be in the above range.

[0252] In the glass according to embodiment 2-1, La 3+ , Gd 3+ , and Y 3+ and the total content of Si 4+ and B 3+ The cation ratio [(La 3+ +Gd 3+ +Y 3+) / (Si 4+ +B 3+ The upper limit of the cation ratio is preferably 0.5, and more preferably 0.4, 0.3, 0.2, 0.1, and 0.08 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.01, 0.02, and 0.03 in that order. The cation ratio may be 0. From the viewpoint of suppressing a decrease in the thermal stability of the glass, it is preferable that the cation ratio be within the above range.

[0253] In the glass according to embodiment 2-1, Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ and the total content of Si 4+ and B 3+ The cation ratio [(Nb 5+ +Ti 4+ +W 6+ +Ta 5+ ) / (Si 4+ +B 3+ The upper limit of the cation ratio is preferably 0.50, and more preferably 0.40, 0.35, 0.30, 0.25, and 0.20 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.02, 0.04, and 0.06 in that order. From the viewpoint of maintaining a high refractive index and a desired Abbe number νd, it is preferable that the cation ratio be within the above range.

[0254] In the glass according to embodiment 2-1, Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ The total content of Li + , Na + , and K. + The total content R and the cation ratio [(Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+The upper limit of the cation ratio [(R / R)] is preferably 0.6, and more preferably 0.5, 0.4, and 0.35 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.02, 0.04, and 0.06 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that the cation ratio be within the above range.

[0255] In the glass according to embodiment 2-1, Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content R' and Li + , Na + , and K. + The upper limit of the cation ratio [R' / R] to the total content R of [R] is preferably 0.6, and more preferably 0.5, 0.4, and 0.35 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.02, 0.04, and 0.06 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that the cation ratio be within the above range.

[0256] In the glass according to embodiment 2-1, La 3+ , Gd 3+ , and Y 3+ The total content of Li + , Na + , and K. + The total content R and the cation ratio [(La 3+ +Gd 3+ +Y 3+ The upper limit of [(R) / R] is preferably 0.5, and more preferably 0.4, 0.3, and 0.2 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.01, 0.03, and 0.05 in this order. The cation ratio may be 0. From the viewpoint of suppressing a decrease in the thermal stability of the glass, it is preferable that the cation ratio be within the above range.

[0257] In the glass according to embodiment 2-1, Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ The total content of Li + , Na + , and K. + The total content R and the cation ratio [(Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of [(R / R)] is preferably 0.60, and more preferably 0.55, 0.50, 0.45, and 0.40 in this order. The lower limit of the cation ratio is preferably 0.05, and more preferably 0.10, 0.15, and 0.17 in this order. From the viewpoints of maintaining a high refractive index, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve moldability, it is preferable that the cation ratio be within the above range.

[0258] In the glass according to embodiment 2-1, Li + , Na + , and K. + The total content R of the above, Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ The total content and cation ratio [R / (R+Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ The upper limit of the cation ratio is preferably 1, and more preferably 0.99, 0.98, 0.97, 0.96, 0.95, and 0.94 in this order. The lower limit of the cation ratio is preferably 0.50, and more preferably 0.55, 0.60, 0.65, 0.70, and 0.75 in this order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that the cation ratio be within the above range.

[0259] In the glass according to embodiment 2-1, Li + , Na + , and K.+ The total content of R, Mg 2+ , and Ca 2+ The total content of R and Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content of R' and the cation ratio [(R + Mg 2+ +Ca 2+ The upper limit of the cation ratio (R+R') / (R+R') is preferably 1, and more preferably 0.99, 0.98, 0.97, 0.96, 0.95, and 0.94 in this order. The lower limit of the cation ratio is preferably 0.50, and more preferably 0.55, 0.60, 0.65, 0.70, and 0.75 in this order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that the cation ratio be within the above range.

[0260] In the glass according to embodiment 2-1, La 3+ , Gd 3+ , and Y 3+ and the total content of Nb 5+ , Ti 4+ , W 6+ , and Ta 5+ The cation ratio [(La 3+ +Gd 3+ +Y 3+ ) / (Nb 5+ +Ti 4+ +W 6+ +Ta 5+ The upper limit of the cation ratio is preferably 1, and more preferably 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1 in that order. The lower limit of the cation ratio is preferably 0, and more preferably 0.01, 0.02, 0.03, 0.04, and 0.05 in that order. The cation ratio may be 0. From the viewpoints of preventing a decrease in the thermal stability of the glass and maintaining a high refractive index, it is preferable that the cation ratio be within the above range.

[0261] The glass according to the second embodiment mainly contains the above-mentioned glass components, that is, Si as an essential component. 4+ , B 3+ , Zr 4+ , and Nb 5+ , and optionally P 5+ , Al 3+ , Li + , Na + , K. + , Cs + , Ti 4+ , W 6+ , Bi 3+ , Ta 5+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Zn 2+ , Y 3+ ,Sc. 3+ , Hf 4+ , Lu 3+ , Ge 4+ , La 3+ , Gd 3+ , and Yb 3+ The total content of the above glass components is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and particularly preferably 99.5% or more.

[0262] The optical glass according to the second embodiment contains O as an anion component. 2- Includes: O 2- The content is preferably 90 to 100 anion %, more preferably 95 to 100 anion %.

[0263] The optical glass according to the second embodiment contains F as an anion component. - It can contain F - The content is preferably 0 to 10 anion %, more preferably 0 to 5 anion %.

[0264] The optical glass according to the second embodiment contains O as an anion component. 2- and F - It may contain ingredients other than those listed above. 2- and F- Other anion components include Cl - , Br - , I - However, Cl - , Br - , I - All of these components are prone to volatilization during glass melting. The volatilization of these components causes problems such as fluctuations in the glass properties, a decrease in the homogeneity of the glass, and significant wear on the melting equipment. - The content of is preferably less than 5 anion %, more preferably less than 3 anion %, even more preferably less than 1 anion %, particularly preferably less than 0.5 anion %, and even more preferably The anion content is less than 0.25%. - and I - The total content is preferably less than 5 anion %, more preferably less than 3 anion %, even more preferably less than 1 anion %, particularly preferably less than 0.5 anion %, even more preferably less than 0.1 anion %, and even more preferably 0 anion %.

[0265] The glass according to embodiment 2-1 is preferably composed essentially of the above glass components, but may contain other components as long as they do not impair the effects of the present invention. Furthermore, the present invention does not exclude the inclusion of unavoidable impurities.

[0266] In addition to the above components, the optical glass contains Sb as a fining agent. 3+ It is also possible to contain small amounts of Sb2O3, etc. The total amount of fining agents (exclusive addition amount) is preferably 0% or more and less than 1%, and more preferably 0% or more and 0.5% or less, 0% or more and 0.3% or less, 0% or more and 0.2% or less, 0% or more and 0.1% or less, 0% or more and 0.05% or less, or 0% or more and 0.03% or less.

[0267] The total amount added is the amount of fining agent added expressed as a weight percentage when the total content of all glass components excluding the fining agent is taken as 100%.

[0268] Furthermore, the optical glass can achieve high transmittance over a wide range of the visible light region. To make the most of these features, it is preferable that the glass does not contain any coloring elements. Examples of coloring elements include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, V, and Ag. The content of each element is preferably less than 100 ppm by mass, more preferably 0 to 80 ppm by mass, and even more preferably 0 to 50 ppm by mass, and it is particularly preferable that the glass is substantially free of these elements.

[0269] Ga, Te, Tb, etc. are components that do not need to be incorporated and are expensive components, so the range of the content of Ga2O3, TeO2, and TbO2 expressed in mass% is preferably 0 to 0.1%, more preferably 0 to 0.05%, even more preferably 0 to 0.01%, even more preferably 0 to 0.005%, and even more preferably 0 to 0.001%, and it is particularly preferable that they are not substantially contained.

[0270] In the optical glass according to the 2-1 embodiment, the glass properties can be the same as those of the 1-1 embodiment.

[0271] The optical glass and optical elements according to the second embodiment can be manufactured in the same manner as in the first embodiment.

[0272] 2-2 embodiment The optical glass according to the second embodiment is As a glass component, Si 4+ , B 3+ , Zr 4+ , and Nb 5+ Contains Li + , Na + , and K. + Contains one or more selected from the group consisting of: ΔPC,t is 0.0250 or more.

[0273] The optical glass according to the second embodiment contains Si as a glass component.4+ Contains Si 4+ The lower limit of the content of Si is preferably 10%, and more preferably 12%, 14%, 16%, 18%, 20%, 22%, 23%, and 24% in that order. 4+ The upper limit of the Si content is preferably 50%, and more preferably 43%, 40%, 38%, 36%, 34%, 32%, and 30% in that order. 4+ is a glass network forming component. 4+ By containing SiO2, the partial dispersion ratio P C,t in the infrared wavelength range can be increased, and chemical durability can be improved. From the viewpoints of suppressing a decrease in the partial dispersion ratio P C,t in the infrared wavelength range and suppressing a decrease in the thermal stability and chemical durability of the glass, it is preferable that the lower limit of the SiO2 content be as described above. From the viewpoints of suppressing a decrease in the meltability of the glass and preventing an increase in the viscosity of the molten glass, which would deteriorate its formability, it is preferable that the upper limit of the SiO2 content be as described above.

[0274] The optical glass according to the second embodiment contains B as a glass component. 3+ Contains B 3+ The lower limit of the content of B is preferably 20%, and more preferably 25%, 28%, 29%, 30%, 31%, and 32% in that order. 3+ The upper limit of the content of B is preferably 60%, and more preferably 55%, 50%, 48%, 46%, and 44% in that order. 3+ is a glass network forming component. B is a glass component. 3+ By containing B, the partial dispersion ratio PC,t in the infrared wavelength region can be increased. From the viewpoint of suppressing a decrease in the partial dispersion ratio PC,t in the infrared wavelength region and suppressing a decrease in the thermal stability of the glass, 3+ The lower limit of the content of B is preferably as described above. 3+ The upper limit of the content is preferably as described above.

[0275] The optical glass according to the second embodiment contains Zr as a glass component. 4+ Contains Zr4+ The lower limit of the content of Zr is preferably 1.0%, and more preferably 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, and 4.5% in that order. 4+ The upper limit of the content of Zr is preferably 8.5%, and more preferably 8.0%, 7.5%, 7.0%, 6.5%, 6.0%, and 5.5% in that order. 4+ By containing Zr, the partial dispersion ratio PC,t in the infrared wavelength range can be increased, and chemical durability can be improved. 4+ The lower limit of the content of Zr is preferably set as described above. From the viewpoint of suppressing the rise in the liquidus temperature LT and suppressing the deterioration of stability during reheating, 4+ The upper limit of the content is preferably as described above.

[0276] The optical glass according to the second embodiment contains Nb 5+ Contains Nb 5+ The content of Nb is preferably more than 0%, and the lower limit is more preferably 2.0%, 3.0%, 3.5%, 4.0%, 4.5%, and 5.0%, in that order. 5+ The upper limit of the Nb content is preferably 11.5%, and more preferably 10%, 9.5%, 9.0%, 8.5%, 8.0%, 7.5%, 7.0%, 6.5%, and 6.0% in that order. 5+ By containing Nb, it is possible to maintain high dispersion while suppressing the decrease in the partial dispersion ratio PC,t in the infrared wavelength region. 5+ The lower limit of the content of Nb is preferably as described above. 5+ The upper limit of the content is preferably as described above.

[0277] The optical glass according to the second embodiment contains Li as a glass component. + , Na + , and K. + Preferably, the compound contains one or more selected from the group consisting of Na + Contains Li +and Na + may contain Na + and K. + may contain Li + and K. + may contain Li + , Na + and K. + As a glass component, Li may be contained. + , Na + , and K. + By containing one or more selected from the group consisting of: the partial dispersion ratio PC,t in the infrared wavelength range can be increased, and chemical durability can be improved.

[0278] In the optical glass according to the second embodiment, Si 4+ and B 3+ The total content of [Si 4+ +B 3+ The lower limit of [0.01% by weight] is preferably 50%, and more preferably 52%, 54%, 56%, and 57% in that order. The upper limit of the total content is preferably 80%, and more preferably 78%, 76%, 74%, 72%, and 71% in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and maintaining the thermal stability of the glass, it is preferable that the total content be within the above range. If the total content is too low, the partial dispersion ratio PC,t in the infrared wavelength range will decrease, and the thermal stability and chemical durability of the glass may not be maintained. If the total content is too high, the viscosity of the molten glass may increase, which may deteriorate its moldability. In addition, the refractive index may decrease.

[0279] In the optical glass according to the second embodiment, B 3+ and Si content 4+ and B 3+ The total content and cation ratio [B 3+ / (Si 4+ +B 3+The lower limit of the cation ratio is preferably 0.44, and more preferably 0.47, 0.50, 0.53, and 0.56 in that order. The upper limit of the cation ratio is preferably 0.80, and more preferably 0.75, 0.71, 0.67, 0.63, and 0.61 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable that the cation ratio be within the above range. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the chemical durability of the glass may decrease.

[0280] In the optical glass according to the second embodiment, Li + , Na + , and K. + The total content R of the above and Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The lower limit of the cation ratio [R / (R+R')] to the total content R' of R is preferably 0.55, and more preferably 0.60, 0.65, 0.70, and 0.75 in that order. The upper limit of the cation ratio is preferably 1.00, and more preferably 0.95, 0.90, and 0.85 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that the cation ratio be within the above range. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the thermal stability of the glass may decrease and the refractive index nd may decrease.

[0281] The optical glass according to the 2-2 embodiment preferably satisfies one or more of the following (i) and (ii).

[0282] (i) In the optical glass according to the second embodiment, Zr 4+ and Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn2+ The total content of R', Nb 5+ , Ti 4+ , W 6+ , Bi 3+ , and Ta 5+ The total content and cation ratio [Zr 4+ / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ +Ta 5+ The lower limit of the cation ratio ( ) is preferably 0.17, and more preferably 0.20, 0.25, 0.30, 0.35, 0.37, 0.39, and 0.40, in that order. The upper limit of the cation ratio is preferably 2.00, and more preferably 1.80, 1.60, 1.40, 1.20, 1.00, 0.80, and 0.60, in that order. From the viewpoints of improving chemical durability, increasing the refractive index nd, and maintaining high dispersibility, it is preferable that the cation ratio be within the above range. If the cation ratio is too small, the refractive index nd may decrease and the chemical durability of the glass may decrease. If the cation ratio is too large, the liquidus temperature LT may increase and stability during reheating may decrease.

[0283] (ii) In the optical glass according to the second embodiment, Zr 4+ and Ta 5+ The total content of Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content of R', Nb 5+ , Ti 4+ , W 6+ , and Bi 3+ The cation ratio [(Zr 4+ +Ta 5+ ) / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+The lower limit of the cation ratio (Pc,t) is preferably 0.25, and more preferably 0.30, 0.35, 0.37, 0.39, and 0.40, in that order. The upper limit of the cation ratio is preferably 3.10, and more preferably 2.80, 2.60, 2.40, 2.20, 2.00, 1.80, 1.60, 1.40, 1.20, 1.00, 0.80, and 0.60, in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, increasing the refractive index nd, maintaining high dispersion, and maintaining the chemical durability of the glass, it is preferable that the cation ratio be within the above range. If the cation ratio is too small, the refractive index nd may decrease and the chemical durability of the glass may also decrease. If the cation ratio is too large, the thermal stability of the glass may decrease.

[0284] In the optical glass according to embodiment 2-2, the contents and ratios of glass components other than those mentioned above can be the same as those in embodiment 2-1.

[0285] In the optical glass according to the 2-2 embodiment, the deviation ΔP C,t is 0.0250 or more. The lower limit of the deviation ΔP C,t is preferably 0.0270, with 0.0290, 0.0310, 0.0330, 0.0350, and 0.0370 being more preferable in this order. By setting the deviation ΔP C,t within the above range, an optical glass suitable for correcting high-order chromatic aberrations can be obtained. On the other hand, the upper limit of the deviation ΔP C,t is not particularly limited, but is usually 0.0900, preferably 0.0800. The method for calculating the deviation ΔP C,t is as described in the 1-1 embodiment.

[0286] In the optical glass according to the 2-2 embodiment, the glass properties other than those mentioned above can be the same as those of the 1-1 embodiment.

[0287] The optical glass according to the 2-2 embodiment and the optical elements and the like can be manufactured in the same manner as in the 1-1 embodiment. [Example]

[0288] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the embodiments shown in the examples.

[0289] Example 1 Glass samples having the glass compositions shown in Table 1 (Table 1-1(1), Table 1-1(2), Table 1-2(1), Table 1-2(2), Table 1-3(1), Table 1-3(2), Table 1-4(1), Table 1-4(2), Table 1-5(1), Table 1-5(2)) and Table 2 (Table 2-1(1), Table 2-1(2), Table 2-2(1), Table 2-2(2), Table 2-3(1), Table 2-3(2), Table 2-4(1), Table 2-4(2), Table 2-5(1), Table 2-5(2), Table 2-6(1), Table 2-6(2)) were prepared by the following procedure, and various evaluations were performed.

[0290] Here, Table 1 shows the glass composition in mass %, and Table 2 shows it in cation %. That is, although the glass composition is shown in different ways in Tables 1 and 2, optical glasses with the same sample number represent the same optical glasses having the same composition. Therefore, Tables 1 and 2 show substantially the same optical glasses and their results.

[0291] In Table 2, the glass composition is shown in cation %. 2- That is, all of the compositions listed in Table 2 are O 2- The content is 100% anion.

[0292] The compositions in Table 1 expressed in mass % are converted from the compositions in Table 2 expressed in cation %.

[0293] [Optical glass manufacturing] First, oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of the glass were prepared as raw materials. These raw materials were weighed, blended, and thoroughly mixed so that the resulting optical glass would have the glass composition shown in Tables 1 and 2. The blended raw materials (batch raw materials) obtained in this way were placed in a platinum crucible and heated at 1350°C to 1400°C for 2 to 4 hours to form a molten glass. The mixture was stirred to homogenize it, and after clarification, the molten glass was cast into a mold preheated to an appropriate temperature. The cast glass was heat-treated for 30 minutes at a temperature near the glass transition temperature Tg and then allowed to cool to room temperature in a furnace, yielding a glass sample.

[0294] [Confirmation of glass composition] The content of each glass component in the obtained glass sample was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and it was confirmed that each composition was as shown in Tables 1 and 2.

[0295] [Optical property measurement] The resulting glass sample was further annealed at a temperature near the glass transition temperature Tg for approximately 30 minutes to approximately 2 hours, and then cooled to room temperature in a furnace at a rate of -30°C / hour to obtain an annealed sample. The refractive index, Abbe number νd, partial dispersion ratio Pg,F, deviation ΔPg,F, partial dispersion ratio PC,t, deviation ΔPC,t, specific gravity, glass transition temperature Tg, liquidus temperature LT, λ80, and λ5 were measured for the resulting annealed sample. The results are shown in Tables 1 and 2.

[0296] (i) Refractive index nd, ng, nF, nC, Abbe number νd, partial dispersion ratio PC,t, and partial dispersion ratio Pg,F The refractive index of the annealed sample was measured at the 12 wavelengths shown in Table A according to JIS B 7071-1, Method for measuring refractive index of optical glass, Part 1: Minimum deviation angle method. Next, the refractive index of each line obtained by measurement was applied to Schott's dispersion formula defined in JIS B 7071-1, Measurement of refractive index of optical glass - Part 1: Minimum deviation angle method, Appendix B, and the constants of the Schott dispersion formula were determined by the least squares method.The Abbe number νd, partial dispersion ratio PC,t, and partial dispersion ratio Pg,F were then calculated using the Schott dispersion formula with the determined constants.

[0297] [Table A] Shot dispersion formula: n 2 =a0+a1λ 2 +a2λ -2 +a3λ -4 +a4λ -6 +a5λ -8 Here, n is the refractive index, λ is the wavelength (μm), and a0, a1, a2, a3, a4, and a5 are constants. The refraction nd is the refractive index at a wavelength of 587.56 nm. The Abbe number νd is expressed as follows using the refractive indices nd, nF, and nC at the d-line, F-line, and C-line, respectively: νd=(nd-1) / (nF-nC) The partial dispersion ratio PC,t is expressed as follows using the refractive indices nt, nF, and nC at the t-line, F-line, and C-line, respectively: PC,t = (nC-nt) / (nF-nC) The partial dispersion ratio Pg,F is expressed as follows using the refractive indices ng, nF, and nC for the g-line, F-line, and c-line: Pg,F=(ng-nF) / (nF-nC)

[0298] (ii) Deviation ΔPC,t, deviation ΔPg,F In a plane where the horizontal axis represents the Abbe number νd and the vertical axis represents the partial dispersion ratio PC,t, the normal line PC,t(0) is expressed by the following equation. PC,t(0)=0.5461-(0.004667×νd) The deviation of the partial dispersion ratio PC,t from the normal line, ΔPC,t, was calculated based on the following formula. ΔPC,t = PC,t - PC,t(0) In addition, in a plane in which the horizontal axis represents the Abbe number νd and the vertical axis represents the partial dispersion ratio Pg,F, the normal line Pg,F(0) is expressed by the following equation. Pg,F(0)=0.6483-(0.001802×νd) Pg,F, which is the deviation Δ of the partial dispersion ratio Pg,F from the normal line, was calculated based on the following formula. ΔPg,F=Pg,F-Pg,F(0)

[0299] (iii) Specific gravity The specific gravity was measured by the Archimedes method.

[0300] (iv) Glass transition temperature Tg The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN at a temperature rise rate of 10°C / min.

[0301] (v) Liquidus temperature LT The glass was placed in a furnace heated to a predetermined temperature and held for about 2 hours. After cooling, the interior of the glass was observed under an optical microscope at 40 to 100 magnifications, and the liquidus temperature was measured based on the presence or absence of crystals.

[0302] (vi) λ80, λ5 The above annealed sample was processed to a thickness of 10 mm so that it had parallel, optically polished flat surfaces, and its spectral transmittance was measured in the wavelength range from 280 nm to 700 nm. The intensity of the light beam incident perpendicularly on one of the optically polished flat surfaces was defined as intensity A, and the intensity of the light beam emerging from the other flat surface was defined as intensity B, and the spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance was 80% was defined as λ80, and the wavelength at which the spectral transmittance was 5% was defined as λ5. Note that the spectral transmittance also includes the reflection loss of the light beam on the sample surface.

[0303] [Chemical durability Water resistance Dw] The obtained glass sample was made into powdered glass (particle size 425-600μm), and the powdered glass of a mass equivalent to the specific gravity was placed in a platinum cage, which was then immersed in a quartz glass round-bottom flask containing 80mL of pure water (pH = 6.5-7.5) and treated in a boiling water bath for 60 minutes. The weight loss rate (%) was classified and evaluated according to the grades in Table B. [Table B]

[0304] [Chemical durability Acid resistance Da] The obtained glass sample was made into powdered glass (particle size 425-600μm), and the powdered glass of a mass equivalent to the specific gravity was placed in a platinum cage, which was then immersed in a quartz glass round-bottom flask containing 80mL of 0.01mol / L nitric acid aqueous solution for 60 minutes. The weight loss rate (%) was then classified and evaluated according to the grades shown in Table C. [Table C]

[0305] [Chemical durability Latent scratch resistance D NaOH ] The obtained glass sample was placed in a glass tube with a diameter of 43.7 mm (30 cm on both sides). 2 The specimens were polished on both sides and were approximately 5 mm thick. The mass loss per unit area [mg / (cm 2 15h) and classified and evaluated into grades in Table D. [Table D]

[0306] [Chemical durability Latent scratch resistance D STPP ] The obtained glass sample was placed in a glass tube with a diameter of 43.7 mm (30 cm on both sides). 2 ), and processed into a surface-polished sample approximately 5 mm thick. This was placed in a well-stirred solution of 0.01 mol / L Na5P3O 10Mass loss per unit area [mg / (cm2) when immersed in (STPP) aqueous solution for 1 hour 2 The samples were classified and evaluated according to the grades in Table E based on the following criteria: [Table E]

[0307] [Chemical durability Chemical durability D0] The obtained glass sample was placed in a glass tube with a diameter of 43.7 mm (30 cm on both sides). 2 The specimen was processed into a polished specimen with a thickness of approximately 5 mm. The specimen was immersed in well-stirred pure water maintained at 50°C and pH 7.0±0.2, which was circulated through an ion-exchange resin bed at a rate of 1 L per minute. The mass loss per unit area [10 -3 mg / (cm 2 The samples were classified and evaluated according to the grades in Table F based on the following criteria: [Table F]

[0308] [Table 1-1(1)]

[0309] [Table 1-1(2)]

[0310] [Table 1-2(1)]

[0311] [Table 1-2(2)]

[0312] [Table 1-3(1)]

[0313]

Table 1-3(2)

[0314]

Table 1-4(1)

[0315]

Table 1-4(2)

[0316]

Table 1-5(1)

[0317]

Table 1-5(2)

[0318] Table 2-1(1)

[0319]

Table 2-1(2)

[0320]

Table 2-2(1)

[0321]

Table 2-2(2)

[0322]

Table 2-3(1)

[0323]

Table 2-3(2)

[0324]

Table 2-4(1)

[0325]

Table 2-4(2)

[0326] Table 2-5(1)

[0327]

Table 2-5(2)

[0328]

Table 2-6(1)

[0329]

Table 2-6(2)

[0330]

Table 2-7(1)

[0331]

Table 2-7(2)

[0332]

Table 2-8(1)

[0333] [Table 2-8(2)]

[0334] [Table 2-9(1)]

[0335] [Table 2-9(2)]

[0336] [Table 2-10(1)]

[0337] [Table 2-10(2)]

[0338] [Table 2-11(1)]

[0339] [Table 2-11(2)]

[0340] [Table 2-12(1)]

[0341] [Table 2-12(2)]

[0342] Example 2 Lens blanks were prepared by known methods using the optical glasses prepared in Example 1, and the lens blanks were processed by known methods such as polishing to prepare various lenses. The optical lenses produced include various lenses such as biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses, and convex meniscus lenses. By combining various lenses with lenses made of low-dispersion glass with an Abbe number of 65 or more, such as fluorophosphate glass, it was possible to effectively correct high-order chromatic aberrations in the infrared region.

[0343] Furthermore, because glass has a relatively low specific gravity, each lens is lighter than lenses with equivalent optical properties and size, making it suitable for use in various imaging devices, particularly autofocus imaging devices, due to its energy-saving properties. Similarly, prisms were made using the various optical glasses made in Example 1.

[0344] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0345] For example, by adjusting the composition described in the specification to the glass compositions exemplified above, an optical glass according to one aspect of the present invention can be produced. Furthermore, it is of course possible to arbitrarily combine two or more of the items described in the specification as examples or preferred ranges.

Claims

1. Si 4+ The content of is 10 cation % or more, B 3+ The content is 20 to 60 cation %, Si 4+ and B 3+ The total content [Si 4+ +B 3+ ] is 50 cation % or more, B 3+ and the content of Si 4+ and B 3+ The total content of the cation ratio [B 3+ / (Si 4+ +B 3+ ) )] is 0.44 or more, Li + , Na + , and K + The total content R of the above and Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The cation ratio [R / (R+R')] to the total content R' of Nb 5+ The content of is more than 0 cation % and 11.5 cation % or less, The content of La 3+ is 5 cation % or less, The content of Zr 4+ is 2.0 cation % or more, the total content of Zr 4+ and Ta 5+ is 8.5 cation % or less; An optical glass that satisfies one or more of the following (i) and (ii): (i) Zr 4+ and the total content R', Nb 5+ , Ti 4+ , W 6+ , Bi 3+ , and Ta 5+ The cation ratio [Zr 4+ / (R'+Nb 5+ +Ti 4+ +W 6+ +Bi 3+ +Ta 5+ ) )] is 0.17 or more. (ii) Zr 4+ and Ta 5+ and the total content of R′, Nb 5+ , Ti 4+ , W 6+ , and Bi 3+ The cation ratio [(Zr 4+ +Ta 5+ ) / (R' + Nb 5+ +Ti 4+ +W 6+ +Bi 3+ ) )] is 0.25 or more.

2. Zr 4+ and Ta 5+ and the total content of Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ The total content of R', Nb 5+ , Ti 4+ , W 6+ , and Bi 3+ The cation ratio [(Zr 4+ +Ta 5+ ) / (R' + Nb 5+ +Ti 4+ +W 6+ +Bi 3+ 2. The optical glass according to claim 1, wherein the refractive index (μm) of the optical glass is 3.10 or less.

3. 3. An optical element comprising the optical glass according to claim 1.

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