Optical glass and optical element

Abstract

To provide an optical glass having a high partial dispersion ratio PC, t, and a low partial dispersion ratio Pg, F.SOLUTION: An optical glass has, on a mass basis, a content of SiO2 of 25.00% or more and 56.00% or less, a content of B2O3 of 16.50% or more and 50.00% or less, a content of Na2O of more than 2.00% and 20.00% or less, a content of ZrO2 of 2.00% or more and 15.00% or less, a content of Nb2O5 of 10.00% or less, a mass ratio (R2O / (SiO2+B2O3+Al2O3)) of a content of an alkali metal oxide R2O to a total content of SiO2, B2O3 and Al2O3 of 0.091 or more and 0.250 or less, a total content (Nb2O5+TiO2+WO3+Ta2O5) of Nb2O5, TiO2, WO3 and Ta2O5 of 14.00% or less, and an external transmittance at a wave length of 400nm to 700nm of 70% or more on a 10.0 mm thickness basis.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Optical glass can be used as a material for optical elements such as lenses (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] CN114907009A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for optical glasses with a high partial dispersion ratio Pc,t, which is an index of anomalous dispersion in the infrared region. For example, lenses made of such optical glasses are suitable as lenses constituting cemented lenses for surveillance cameras, security cameras, etc. Furthermore, to improve the chromatic aberration correction ability of optical elements in the ultraviolet region, it is desirable for the optical glasses to have a low partial dispersion ratio Pg,F.

[0005] In view of the above, an object of one aspect of the present invention is to provide an optical glass having a high partial dispersion ratio PC,t and a low partial dispersion ratio Pg,F. [Means for solving the problem]

[0006] One aspect of the present invention is as follows. [1] By mass, SiO2 content is 25.00% or more and 56.00% or less, B2O3 content is 16.50% or more and 50.00% or less, Na2O content is more than 2.00% and not more than 20.00%; ZrO2 content is 2.00% or more and 15.00% or less, Nb2O5 content is 10.00% or less, a mass ratio of the alkali metal oxide R2O content to the total content of SiO2, B2O3, and Al2O3 (R2O / (SiO2+B2O3+Al2O3)) of 0.091 or more and 0.250 or less; The total content of Nb2O5, TiO2, WO3 and Ta2O5 (Nb2O5 + TiO2 + WO3 + Ta2O5) is 14.00% or less, and Optical glass with an external transmittance of 70% or more at wavelengths of 400nm to 700nm when converted to a thickness of 10.0mm. [2] The optical glass according to [1], in which the mass ratio of the total content of LiO and NaO to the content of alkali metal oxide RO ((LiO + NaO) / RO) is 0.520 or more and 1.000 or less (hereinafter also simply referred to as "optical glass" or "glass"). [3] The optical glass according to [1] or [2], wherein the content of rare earth oxide Ln2O3 is 0.00% or more and 20.00% or less. [4] The optical glass according to any one of [1] to [3], wherein the mass ratio (R'O / R2O) of the alkaline earth metal oxide R'O content to the alkali metal oxide R2O content is 0.000 or more and 1.800 or less. [5] The optical glass according to any one of [1] to [4], wherein the mass ratio (R2O / ZrO2) of the alkali metal oxide R2O content to the ZrO2 content exceeds 0.620. [6] The optical glass according to claim 1, wherein the total content of alkali metal oxide R2O and alkaline earth metal oxide R'O (R2O+R'O) is 5.00% or more and 25.00% or less. [7] The optical glass according to any one of [1] to [5], wherein the mass ratio of the total content of alkali metal oxides R2O and B2O3 to the SiO2 content ((R2O+B2O3) / SiO2) is 0.100 or more and 1.400 or less. [8] The optical glass according to any one of [1] to [7], wherein the total content of SiO2, B2O3 and Al2O3 (SiO2 + B2O3 + Al2O3) is 50.00% or more and 74.00% or less. [9] The optical glass according to any one of [1] to [8], wherein the total content of SiO2 and ZrO2 (SiO2 + ZrO2) is 41.00% or more and 60.00% or less.

[10] The optical glass according to any one of [1] to [9], wherein the mass ratio of the B2O3 content to the total content of SiO2 and B2O3 (B2O3 / (SiO2+B2O3)) is 0.225 or more and 0.495 or less.

[11] The optical glass according to any one of [1] to

[10] , wherein the mass ratio of the total content of BaO and Na2O to the total content of alkali metal oxide R2O, alkaline earth metal oxide R'O, and ZnO ((BaO + Na2O) / (R2O + R'O + ZnO)) is 0.380 or greater.

[12] The optical glass according to any one of [1] to

[11] , wherein the mass ratio of the total content of Nb2O5 and ZrO2 to the total content of SiO2 and B2O3 ((Nb2O5+ZrO2) / (SiO2+B2O3)) is 0.050 or more and 0.350 or less.

[13] The optical glass according to any one of [1] to

[12] , wherein the mass ratio of the alkali metal oxide R2O content to the total content of Nb2O5 and ZrO2 (R2O / (Nb2O5+ZrO2)) is 0.400 or more and 1.700 or less.

[14] The optical glass according to any one of [1] to

[13] , wherein the mass ratio of the Nb2O5 content to the total content of Nb2O5 and ZrO2 (Nb2O5 / (Nb2O5+ZrO2)) is 0.050 or more and 0.550 or less.

[15] The optical glass according to any one of [1] to

[14] , wherein the mass ratio of the B2O3 content to the ZrO2 content (B2O3 / ZrO2) is 1.400 or more.

[16] The optical glass according to any one of [1] to

[15] , wherein the mass ratio of the Na2O content to the total content of SiO2, B2O3, Al2O3 and ZrO2 (Na2O / (SiO2+B2O3+Al2O3+ZrO2)) is 0.100 or more and 0.220 or less.

[17] The optical glass according to any one of [1] to

[16] , wherein the mass ratio of the alkali metal oxide R2O content to the total content of SiO2, B2O3, Al2O3 and Nb2O5 (R2O / (SiO2+B2O3+Al2O3+Nb2O5)) is 0.198 or less.

[18] The optical glass according to any one of [1] to

[17] , wherein the Ta2O5 content is 0.00% or more and 10.00% or less.

[19] An optical element made of the optical glass according to any one of [1] to

[18] . [Effects of the Invention]

[0007] According to one aspect of the present invention, an optical glass having a high partial dispersion ratio Pc,t and a low partial dispersion ratio Pg,F can be provided. Furthermore, according to another aspect of the present invention, an optical element made of such an optical glass can also be provided. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Optical glass] <Glass composition> In the present invention and this specification, the glass composition is expressed as a glass composition based on oxides. Here, "glass composition based on oxides" refers to a glass composition obtained by converting the glass raw materials into oxides that are present in the glass after they are all decomposed during melting. Furthermore, unless otherwise specified, the glass composition is expressed on a mass basis (mass %, mass ratio). The glass composition of the present invention and the present specification can be determined by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Quantitative analysis is performed for each element using ICP-AES. The analytical values ​​are then converted into oxide notation. The analytical values ​​obtained by ICP-AES may contain a measurement error of, for example, about ±5% of the analytical value. Therefore, the oxide notation values ​​converted from the analytical values ​​may also contain an error of about ±5%. In the present invention and this specification, a content of a component of 0.0% or not containing or not incorporating the component means that the component is substantially not contained, and the content of the component is at or below the impurity level, for example, less than 0.01%.

[0009] The glass composition of the optical glass will now be described in more detail.

[0010] The SiO content is 25.00% or more, preferably 27.00% or more, and more preferably 29.00% or more, 31.00% or more, and 33.00% or more in that order, from the viewpoints of increasing the partial dispersion ratio PC,t of the glass, improving chemical durability, and maintaining thermal stability. From the viewpoint of maintaining meltability, the SiO2 content is 56.00% or less, preferably 53.00% or less, and more preferably 50.00% or less, 47.00% or less, 44.00% or less, 41.00% or less, 38.00% or less, and 35.00% or less in that order.

[0011] From the viewpoints of further increasing the partial dispersion ratio PC,t of the glass and the deviation ΔPC,t, which will be described in detail later, and maintaining thermal stability, the B2O3 content is 16.50% or more, preferably 18.00% or more, and more preferably 20.00% or more, 22.00% or more, 23.00% or more, and 24.00% or more in that order. From the viewpoint of maintaining chemical durability, the B2O3 content is 50.00% or less, preferably 45.00% or less, and more preferably 40.00% or less, 35.00% or less, 30.00% or less, and 28.00% or less in that order.

[0012] The mass ratio of the B2O3 content to the total content of SiO2 and B2O3 (B2O3 / (SiO2+B2O3)) is preferably 0.225 or more, and more preferably 0.300 or more, 0.350 or more, and 0.400 or more in that order, from the viewpoint of further increasing the partial dispersion ratio PC,t and deviation ΔPC,t of the glass and reducing the viscosity of the melt. From the viewpoint of maintaining the chemical durability of the glass, the mass ratio (B2O3 / (SiO2+B2O3)) is preferably 0.495 or less, and more preferably 0.480 or less, 0.470 or less, 0.460 or less, 0.450 or less, and 0.440 or less in that order.

[0013] From the viewpoints of further increasing the partial dispersion ratio PC,t of the glass, improving the chemical durability, and maintaining the thermal stability of the glass, the total content of SiO2, B2O3, and Al2O3 (SiO2 + B2O3 + Al2O3) is preferably 50.00% or more, more preferably 52.00% or more, and further preferably 54.00% or more, 56.00% or more, and 58.00% or more in that order. From the viewpoint of maintaining the meltability of the glass, the total content (SiO2 + B2O3 + Al2O3) is preferably 74.00% or less, more preferably 72.00% or less, and more preferably 70.00% or less, 68.00% or less, 66.00% or less, 64.00% or less, 62.00% or less, and 60.00% or less in that order.

[0014] The Al2O3 content may be 0.00%, 0.00% or more, or more than 0.00%. From the viewpoint of suppressing phase separation of the glass, the Al2O3 content is preferably 0.10% or more, and more preferably 0.30% or more, 0.50% or more, and 0.70% or more in that order. From the viewpoint of maintaining the thermal stability of the glass, the Al2O3 content is preferably 30.00% or less, and more preferably 25.00% or less, 20.00% or less, 15.00% or less, 10.00% or less, 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, and 1.00% or less, in that order.

[0015] From the viewpoints of increasing the partial dispersion ratio PC,t of the glass, improving the meltability, and reducing the viscosity of the melt, the NaO content is more than 2.00%, preferably 4.00% or more, and more preferably 6.00% or more, 7.00% or more, and 8.00% or more in that order. From the viewpoint of maintaining chemical durability, the Na2O content is 20.00% or less, preferably 15.00% or less, and more preferably 13.00% or less, 11.00% or less, and 9.00% or less in that order.

[0016] The mass ratio of the alkali metal oxide R2O content to the total content of SiO2, B2O3, and Al2O3 (R2O / (SiO2+B2O3+Al2O3)) is, from the viewpoint of improving the meltability of the glass and reducing the viscosity of the melt, 0.091 or more, preferably 0.092 or more, and more preferably 0.125 or more, 0.130 or more, 0.135 or more, 0.138 or more, and 0.140 or more in that order. From the viewpoint of maintaining chemical durability, the mass ratio (R2O / (SiO2+B2O3+Al2O3)) is 0.250 or less, preferably 0.230 or less, and more preferably 0.210 or less, 0.190 or less, 0.170 or less, and 0.150 or less in that order.

[0017] From the viewpoints of improving the meltability of the glass and reducing the viscosity of the melt, the content of the alkali metal oxide R2O is preferably 1.00% or more, and more preferably 2.00% or more, 3.00% or more, 4.00% or more, 5.00% or more, 6.00% or more, 7.00% or more, and 8.00% or more in that order. From the viewpoint of maintaining the chemical durability of the glass, the R2O content is preferably 30.00% or less, and more preferably 25.00% or less, 20.00% or less, 15.00% or less, 13.00% or less, 11.00% or less, 10.00% or less, and 9.00% or less in that order.

[0018] The R2O content can be the total content of Li2O, Na2O and K2O. The optical glass may contain one or more elements selected from the group consisting of Li2O, Na2O, and K2O. The optical glass may contain at least Na2O in the above-mentioned amount, and may contain neither Na2O nor K2O, or only one of them, or both.

[0019] The Li2O content can be 0.00%, 0.00% or more, or more than 0.00%. Li2O is a component that increases the partial dispersion ratio PC,t of the glass and contributes to improving the meltability of the glass and lowering the viscosity of the melt. From the viewpoint of maintaining the chemical durability of the glass, the Li2O content is preferably 20.00% or less, and more preferably 15.00% or less, 10.00% or less, 5.00% or less, 3.00% or less, and 1.00% or less in that order, and may be 0.00%.

[0020] The K2O content can be 0.00%, 0.00% or more, or more than 0.00%. K2O is a component that contributes to improving the meltability of glass and lowering the viscosity of the melt. From the viewpoint of maintaining the chemical durability of the glass, the K2O content is preferably 20.00% or less, and more preferably 15.00% or less, 10.00% or less, 5.00% or less, 3.00% or less, and 1.00% or less in that order, and may be 0.00%.

[0021] The mass ratio of the total content of Li2O and Na2O to the content of alkali metal oxide R2O ((Li2O + Na2O) / R2O) is preferably 0.520 or more, more preferably 0.600 or more, 0.700 or more, 0.800 or more, or 0.900 or more, and even preferably 1.000, from the viewpoint of increasing the partial dispersion ratio PC,t and further increasing the deviation ΔPC,t. The mass ratio ((Li2O + Na2O) / R2O) is preferably 1.000 or less, and as mentioned above, is also preferably 1.000.

[0022] The mass ratio of the total content of alkali metal oxides R2O and B2O3 to the SiO2 content ((R2O+B2O3) / SiO2) is preferably 0.100 or more from the viewpoint of reducing the viscosity of the melt, and is more preferably 0.300 or more, 0.500 or more, 0.700 or more, and 0.900 or more in that order. From the viewpoint of maintaining the chemical durability of the glass, the mass ratio ((R2O+B2O3) / SiO2) is preferably 1.400 or less, more preferably 1.200 or less, and even more preferably 1.000 or less.

[0023] The ZrO content is 2.00% or more, preferably 4.00% or more, and more preferably 6.00% or more, 8.00% or more, and 10.00% or more in that order, from the viewpoints of increasing the partial dispersion ratio Pc,t of the glass, reducing the partial dispersion ratio Pg,F and the deviation ΔPg,F, which will be described in detail later, and improving chemical durability. From the viewpoint of maintaining the meltability and thermal stability of the glass, the ZrO2 content is 15.00% or less, preferably 14.00% or less, and more preferably 13.00% or less and 12.00% or less in that order.

[0024] From the viewpoint of maintaining the chemical durability of the glass, the total content of SiO2 and ZrO2 (SiO2 + ZrO2) is preferably 41.00% or more, and more preferably 42.00% or more, 43.00% or more, 44.00% or more, and 45.00% or more in that order. From the viewpoint of maintaining the meltability of the glass, the total content (SiO2 + ZrO2) is preferably 60.00% or less, and more preferably 58.00% or less, 55.00% or less, 53.00% or less, 50.00% or less, and 48.00% or less in that order.

[0025] From the viewpoint of improving the meltability of the glass and reducing the viscosity of the melt, the mass ratio of the alkali metal oxide R2O content to the ZrO2 content (R2O / ZrO2) is preferably more than 0.620, and more preferably 0.630 or more, 0.650 or more, 0.670 or more, 0.690 or more, 0.710 or more, 0.720 or more, 0.730 or more, and 0.740 or more in that order. From the viewpoint of maintaining the chemical durability of the glass, the mass ratio (R2O / ZrO2) is preferably 5.000 or less, and more preferably 4.500 or less, 4.000 or less, 3.500 or less, 3.000 or less, 2.500 or less, 2.000 or less, 1.500 or less, 1.000 or less, 0.900 or less, and 0.800 or less, in that order.

[0026] From the viewpoints of further increasing the partial dispersion ratio PC,t of the glass and maintaining thermal stability, the mass ratio of the B2O3 content to the ZrO2 content (B2O3 / ZrO2) is preferably 1.400 or more, and more preferably 1.500 or more, 1.600 or more, 1.700 or more, 1.800 or more, 1.900 or more, and 2.000 or more in that order. From the viewpoint of maintaining the thermal stability of the glass, the mass ratio (B2O3 / ZrO2) is preferably 8.000 or less, and more preferably 7.000 or less, 6.000 or less, 5.000 or less, 4.000 or less, 3.000 or less, and 2.500 or less in that order.

[0027] From the viewpoint of reducing the viscosity of the glass melt, the mass ratio of the Na2O content to the total content of SiO2, B2O3, Al2O3, and ZrO2 (Na2O / (SiO2+B2O3+Al2O3+ZrO2)) is preferably 0.100 or more, and more preferably 0.110 or more. From the viewpoint of maintaining the chemical durability of the glass, the mass ratio (Na2O / (SiO2+B2O3+Al2O3+ZrO2)) is preferably 0.220 or less, and more preferably 0.210 or less, 0.200 or less, 0.190 or less, 0.180 or less, 0.170 or less, 0.160 or less, 0.150 or less, 0.140 or less, and 0.130 or less in that order.

[0028] The Nb2O5 content is 10.00% or less, preferably 9.00% or less, and more preferably 8.00% or less and 7.00% or less, in order to maintain the low dispersion, thermal stability, low specific gravity, and low partial dispersion ratio Pg, F of the glass. The Nb2O5 content can be 0.00%, 0.00% or more, or more than 0.00%. From the viewpoint of increasing the refractive index of the glass, the Nb2O5 content is preferably 0.10% or more, and more preferably 1.00% or more, 2.00% or more, 3.00% or more, 4.00% or more, and 5.00% or more in that order.

[0029] The total content of Nb2O5, TiO2, WO3 and Ta2O5 (Nb2O5 + TiO2 + WO3 + Ta2O5) is 14.00% or less, preferably 12.00% or less, and more preferably 10.00% or less, 9.00% or less, 8.00% or less, and 7.00% or less, in that order, from the viewpoint of maintaining low dispersion, thermal stability and low specific gravity of the glass. The total content (Nb2O5+TiO2+WO3+Ta2O5) can be 0.00%, 0.00% or more, or more than 0.00%. From the viewpoint of increasing the refractive index of the glass, the total content (Nb2O5+TiO2+WO3+Ta2O5) is preferably 0.10% or more, and more preferably 1.00% or more, 2.00% or more, 3.00% or more, 4.00% or more, and 5.00% or more in that order.

[0030] From the viewpoint of increasing the refractive index of the glass and improving its chemical durability, the mass ratio of the total content of Nb2O5 and ZrO2 to the total content of SiO2 and B2O3 ((Nb2O5+ZrO2) / (SiO2+B2O3)) is preferably 0.050 or more, and more preferably 0.100 or more, 0.150 or more, 0.200 or more, and 0.250 or more in that order. From the viewpoint of maintaining low dispersion, thermal stability, and a low specific gravity of the glass, the mass ratio ((Nb2O5+ZrO2) / (SiO2+B2O3)) is preferably 0.350 or less, and more preferably 0.340 or less, 0.330 or less, 0.320 or less, 0.310 or less, and 0.300 or less in that order.

[0031] The mass ratio of the alkali metal oxide R2O content to the total content of Nb2O5 and ZrO2 (R2O / (Nb2O5+ZrO2)) is preferably 0.400 or more, and more preferably 0.420 or more, 0.440 or more, 0.460 or more, and 0.480 or more in that order, from the viewpoints of increasing the partial dispersion ratio PC,t of the glass, improving the meltability, and reducing the viscosity of the melt. From the viewpoint of maintaining the chemical durability of the glass, the mass ratio (R2O / (Nb2O5+ZrO2)) is preferably 1.700 or less, and more preferably 1.500 or less, 1.300 or less, 1.000 or less, 0.800 or less, and 0.600 or less in that order.

[0032] From the viewpoint of increasing the refractive index of the glass, the mass ratio of the Nb2O5 content to the total content of Nb2O5 and ZrO2 (Nb2O5 / (Nb2O5+ZrO2)) is preferably 0.050 or more, and more preferably 0.100 or more, 0.150 or more, 0.200 or more, 0.250 or more, 0.300 or more, and 0.330 or more in that order. From the viewpoint of maintaining the low dispersion of the glass, maintaining thermal stability, and maintaining a low deviation ΔPg,F, the mass ratio (Nb2O5 / (Nb2O5+ZrO2)) is preferably 0.550 or less, and more preferably 0.500 or less, 0.450 or less, 0.400 or less, and 0.370 or less in that order.

[0033] The alkaline earth metal oxide R'O content can be 0.00%, 0.00% or more, or more than 0.00%. From the viewpoints of further increasing the partial dispersion ratio PC,t of the glass, maintaining thermal stability, and lowering the liquidus temperature, the R'O content is preferably 1.00% or more, and more preferably 2.00% or more, 3.00% or more, 4.00% or more, and 5.00% or more in that order. From the viewpoint of maintaining a high partial dispersion ratio P C,t of the glass and maintaining a low specific gravity, the R′O content is preferably 40.00% or less, and more preferably 35.00% or less, 30.00% or less, 25.00% or less, 20.00% or less, 18.00% or less, 16.00% or less, 14.00% or less, 12.00% or less, 10.00% or less, 8.00% or less, and 6.00% or less in that order.

[0034] The R'O content can be the total content of MgO, CaO, SrO and BaO. The alkaline earth metal oxides are components that contribute to increasing the partial dispersion ratio PC,t of the glass. The optical glass may contain, for example, one or more types selected from the group consisting of MgO, CaO, SrO, and BaO, or may contain only one type, or two to four types.

[0035] The MgO content can be 0.00%, greater than or equal to 0.00% or greater than 0.00%. From the viewpoint of maintaining a high partial dispersion ratio P C,t of the glass and maintaining thermal stability, the MgO content is preferably 20.00% or less, and is more preferably 15.00% or less, 10.00% or less, 5.00% or less, 3.00% or less, 1.50% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0036] The CaO content can be 0.00%, 0.00% or more or greater than 0.00%. From the viewpoint of maintaining a high partial dispersion ratio PC,t of the glass and maintaining a low specific gravity, the CaO content is preferably 20.00% or less, and is more preferably 15.00% or less, 10.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0037] The SrO content can be 0.00%, 0.00% or more, or greater than 0.00%. From the viewpoint of maintaining a high partial dispersion ratio P C,t of the glass and maintaining a low specific gravity, the SrO content is preferably 30.00% or less, and is more preferably 25.00% or less, 20.00% or less, 15.00% or less, 10.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may even be 0.00%.

[0038] The BaO content may be 0.00%, 0.00% or more, or more than 0.00%. From the viewpoint of maintaining thermal stability and lowering the liquidus temperature, the BaO content is preferably 0.10% or more, and more preferably 1.00% or more, 3.00% or more, 5.00% or more, 7.00% or more, 9.00% or more, 11.00% or more, and 12.00% or more in that order. From the viewpoint of maintaining a high partial dispersion ratio PC,t of the glass and maintaining a low specific gravity, the BaO content is preferably 30.00% or less, and more preferably 25.00% or less, 20.00% or less, 18.00% or less, 16.00% or less, and 14.00% or less in that order.

[0039] The mass ratio (R'O / R2O) of the alkaline earth metal oxide R'O content to the alkali metal oxide R2O content can be 0.000, 0.000 or more, or more than 0.000. From the viewpoint of lowering the liquidus temperature of the glass, the mass ratio (R'O / R2O) is preferably 0.100 or more, more preferably 0.200 or more, 0.300 or more, 0.400 or more, 0.500 or more, or 0.600 or more. From the viewpoint of maintaining a low specific gravity of the glass and maintaining a high deviation ΔP C,t, the mass ratio (R′O / R O) is preferably 1.800 or less, and more preferably 1.700 or less, 1.600 or less, 1.500 or less, 1.400 or less, 1.300 or less, 1.200 or less, 1.100 or less, 1.000 or less, 0.900 or less, 0.800 or less, and 0.700 or less, in that order.

[0040] From the viewpoints of maintaining a high partial dispersion ratio P C,t of the glass, maintaining thermal stability, and lowering the liquidus temperature, the total content of alkali metal oxide R O and alkaline earth metal oxide R′ O (R O + R′ O) is preferably 5.00% or more, and more preferably 7.00% or more, 9.00% or more, 11.00% or more, 12.00% or more, and 13.00% or more in that order. From the viewpoint of maintaining a high partial dispersion ratio P C,t of the glass and maintaining a low specific gravity, the total content (R O + R' O) is preferably 25.00% or less, and more preferably 23.00% or less, 21.00% or less, 19.00% or less, 17.00% or less, and 15.00% or less in that order.

[0041] From the viewpoint of maintaining the chemical durability of the glass, the mass ratio of the alkali metal oxide R2O content to the total content of SiO2, B2O3, Al2O3 and Nb2O5 (R2O / (SiO2+B2O3+Al2O3+Nb2O5)) is preferably 0.198 or less, and more preferably 0.190 or less, 0.180 or less, 0.170 or less, 0.160 or less, 0.150 or less, and 0.140 or less in that order. The mass ratio (R2O / (SiO2+B2O3+Al2O3+Nb2O5)) can be greater than 0.000, and from the viewpoint of reducing the viscosity of the glass melt, it is preferably 0.100 or greater, and more preferably 0.110 or greater.

[0042] The ZnO content can be 0.00%, greater than or equal to 0.00%, or greater than 0.00%. From the viewpoint of maintaining a high partial dispersion ratio P C,t of the glass and maintaining a low specific gravity, the ZnO content is preferably 30.00% or less, and is more preferably 25.00% or less, 20.00% or less, 15.00% or less, 10.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0043] From the viewpoint of lowering the liquidus temperature of the glass and suppressing phase separation of the glass, the mass ratio of the total content of BaO and NaO to the total content of alkali metal oxide R2O, alkaline earth metal oxide R'O, and ZnO ((BaO + Na2O) / (R2O + R'O + ZnO)) is preferably 0.380 or more, more preferably 0.390 or more, 0.400 or more, 0.450 or more, 0.500 or more, 0.540 or more, 0.580 or more, 0.600 or more, 0.700 or more, 0.800 or more, or 0.900 or more, and may even be 1.000.

[0044] The content of the rare earth oxide Ln2O3 can be 0.00%, 0.00% or more, or more than 0.00%. From the viewpoint of increasing the refractive index of the glass, decreasing the partial dispersion ratio Pg,F, and decreasing the deviation ΔPg,F, the Ln2O3 content is preferably 1.00% or more, and more preferably 2.00% or more, 3.00% or more, 4.00% or more, 5.00% or more, 6.00% or more, 7.00% or more, 8.00% or more, and 9.00% or more in that order. From the viewpoint of maintaining the thermal stability of the glass and maintaining a low specific gravity, the Ln2O3 content is preferably 20.00% or less, and more preferably 18.00% or less, 16.00% or less, 14.00% or less, 12.00% or less, and 10.00% or less in that order.

[0045] The content of rare earth oxide Ln2O3 can be the total content of La2O3, Gd2O3, Y2O3, and Yb2O3. Rare earth oxides are components that contribute to increasing the refractive index of the glass, lowering the partial dispersion ratio Pg,F, and reducing the deviation ΔPg,F. The optical glass may contain, for example, one or more selected from the group consisting of La2O3, Gd2O3, Y2O3 and Yb2O3, or may contain only one type or two to four types.

[0046] The La2O3 content can be 0.00%, 0.00% or more, or greater than 0.00%. From the viewpoint of maintaining the thermal stability of the glass and maintaining a low specific gravity, the La2O3 content is preferably 20.00% or less, and is more preferably 15.00% or less, 10.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0047] The Gd2O3 content can be 0.00%, greater than or equal to 0.00%, or greater than 0.00%. From the viewpoint of maintaining the thermal stability of the glass and maintaining a low specific gravity, the Gd2O3 content is preferably 20.00% or less, and is more preferably 15.00% or less, 10.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0048] The Y2O3 content may be 0.00%, 0.00% or more, or more than 0.00%. From the viewpoint of increasing the refractive index of the glass and decreasing the partial dispersion ratio Pg,F, the Y2O3 content is preferably 1.00% or more, and more preferably 3.00% or more, 5.00% or more, 7.00% or more, 8.00% or more, and 9.00% or more in that order. From the viewpoint of maintaining the thermal stability of the glass and maintaining a low specific gravity, the Y2O3 content is preferably 20.00% or less, and more preferably 18.00% or less, 16.00% or less, 14.00% or less, 12.00% or less, and 10.00% or less in that order.

[0049] The Yb2O3 content can be 0.00%, 0.00% or greater, or greater than 0.00%. From the viewpoint of maintaining the thermal stability of the glass and maintaining a low specific gravity, the Yb2O3 content is preferably 20.00% or less, and is more preferably 15.00% or less, 10.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0050] The TiO2 content can be 0.00%, 0.00% or more, or more than 0.00%. TiO2 is a component that contributes to increasing the refractive index of the glass. From the viewpoint of maintaining the low dispersibility, thermal stability, and low specific gravity of the glass, the TiO content is preferably 20.00% or less, and is more preferably 15.00% or less, 10.00% or less, 8.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0051] The WO3 content can be 0.00%, 0.00% or more, or more than 0.00%. WO3 is a component that contributes to increasing the refractive index of the glass. From the viewpoint of maintaining the low dispersibility, thermal stability, and low specific gravity of the glass, the WO content is preferably 20.00% or less, and is more preferably 15.00% or less, 10.00% or less, 8.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may even be 0.00%.

[0052] The Ta2O5 content can be 0.00%, 0.00% or more, or more than 0.00%. Ta2O5 is a component that contributes to increasing the refractive index of the glass. From the viewpoint of maintaining the low dispersibility, thermal stability, and low specific gravity of the glass, the Ta2O5 content is preferably 10.00% or less, and is more preferably 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0053] The P2O5 content can be 0.00%, greater than or equal to 0.00%, or greater than 0.00%. From the viewpoint of maintaining a high refractive index of the glass, the P2O5 content is preferably 20.00% or less, and is more preferably 18.00% or less, 16.00% or less, 14.00% or less, 12.00% or less, 10.00% or less, 8.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.50% or less, 1.00% or less, and 0.50% or less, in that order, and may even be 0.00%.

[0054] Sb2O3 is a component that can be added as a fining agent. Addition of a small amount can suppress a decrease in light transmittance due to the inclusion of impurities such as Fe, but increasing the amount of Sb2O3 tends to increase the coloration of the glass. Therefore, from the viewpoint of maintaining high transmittance, the amount of Sb2O3 added is preferably 0.00% or more and 5.00% or less, more preferably 0.00% or more and 0.05% or less, and even more preferably 0.00% or more and 0.03% or less. The Sb2O3 content by external percentage refers to the Sb2O3 content expressed in mass % when the total content of glass components other than Sb2O3 is taken as 100 mass %.

[0055] SnO2 can also be added as a fining agent, but if it is added in excess of 1.00% by weight, the glass will become discolored, and when the glass is heated, softened, and reshaped by press molding or other methods, the Sn can act as a starting point for crystal nucleation, leading to a tendency for devitrification. Therefore, the amount of SnO2 added is preferably between 0.00% and 1.00%, more preferably between 0.00% and 0.50%, and particularly preferably none is added. The SnO2 content by weight refers to the SnO2 content expressed in mass% when the total content of glass components other than SnO2 is taken as 100% by weight.

[0056] The optical glass can be produced without containing components such as Lu and Hf. Because Lu and Hf are expensive components, the contents of Lu2O3 and HfO2 are preferably kept to between 0.00% and 2.00%, more preferably between 0.00% and 1.00%, even more preferably between 0.00% and 0.80%, and even more preferably between 0.00% and 0.10%. It is particularly preferred that no Lu2O3 or no HfO2 is incorporated. Furthermore, in consideration of the environmental impact, it is preferable not to incorporate Pb, and it is also preferable not to incorporate As, U, Th, Te, or Cd. Furthermore, from the viewpoint of making the most of the excellent light transmittance of the glass, it is preferable not to incorporate substances that cause coloration, such as Cu, Cr, V, Fe, Ni, and Co.

[0057] F is a component that significantly increases the volatility of glass during melting, reducing the stability and homogeneity of the glass's optical properties. The F content can be defined as the content (unit: mass%) of F element as an external ratio relative to 100 mass% of the total content of the glass composition based on oxides, as determined above. In the above optical glass, the F content defined in this way is preferably less than 10.00%, more preferably less than 5.00%, and even more preferably less than 2.50%. The F content can be 0.00% or more, and may be 0.00%.

[0058] <Glass properties> (Transmittance characteristics) The optical glass has an external transmittance of 70% or more at wavelengths of 400 nm to 700 nm, calculated as a thickness of 10.0 mm. "An external transmittance of 70% or more at wavelengths of 400 nm to 700 nm, calculated as a thickness of 10.0 mm" means that the external transmittance is 70% or more at a thickness of 10.0 mm over the entire wavelength range of 400 nm to 700 nm. The optical glass can have an external transmittance of 70% or more and 100% or less at a wavelength of 400 nm to 700 nm, calculated as a thickness of 10.0 mm. Optical glass having such transmittance characteristics is useful as a material for optical elements.

[0059] The transmittance characteristics of the above glass are determined by the following method. The glass sample is processed to have parallel, optically polished flat surfaces, and the external transmittance at wavelengths of 400 to 700 nm is measured. The external transmittance includes the reflection loss of light rays on the sample surface. If the glass being measured is not 10.0 mm thick, the thickness of the glass being measured is taken as d0, and the transmittance at each wavelength λ is converted using the following formula A to determine the transmittance characteristics converted to a 10.0 mm thickness.

[0060] Formula A: T(λ)=(1-R(λ))2×exp(loge((T0(λ) / 100) / (1-R(λ))2)×d / d0)×100

[0061] In formula A, T(λ): converted transmittance (%) at wavelength λ, T0(λ): measured transmittance (%) at wavelength λ, d: converted thickness (mm), d0: glass thickness (mm), R(λ) = ((n(λ)-1) / (n(λ)+1)) 2 The reflectance at wavelength λ is expressed as n(λ), where n(λ) is the refractive index at wavelength λ. The refractive index at wavelength λ, n(λ), is measured at each wavelength in accordance with the Japanese Industrial Standards (JIS) JIS B 7071-1 "Method for measuring the refractive index of optical glass - Part 1: Minimum deviation angle method."

[0062] (Abbe number νd, partial dispersion ratio PC,t, deviation ΔPC,t, partial dispersion ratio Pg,F, deviation ΔPg,F) The Abbe number vd, partial dispersion ratio PC,t, and partial dispersion ratio Pg,F in the present invention and this specification are determined by the following methods. Measure the refractive index at the 12 wavelengths in the table below according to JIS (Japanese Industrial Standards) B 7071-1:2015, "Measurement of refractive index of optical glass - Part 1: Minimum deviation method." Next, apply the measured refractive index for each line to the Schott dispersion formula defined in Appendix B of the above JIS, and determine the constants of the Schott dispersion formula using the least squares method. Then, calculate the Abbe number νd, partial dispersion ratio PC,t, and partial dispersion ratio Pg,F from the values ​​of each linear refractive index obtained using the Schott dispersion formula with the determined constants.

[0063] [Table 1]

[0064] Abbe number νd 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)

[0065] The Abbe number vd is a value that represents a property related to dispersion. From the viewpoint of usefulness as a material for optical elements, the above optical glass is preferably a low-dispersion glass. From this viewpoint, the Abbe number vd of the above optical glass is preferably 47.00 or more, with 47.50, 48.00, 48.50, 49.00, and 49.50 being more preferred in that order. The Abbe number vd of the optical glass can be, for example, 65.00 or less, 64.00 or less, 63.00 or less, 62.00 or less, 61.00 or less, 60.00 or less, 59.00 or less, 58.00 or less, 57.00 or less, 56.00 or less, 55.50 or less, or 55.00 or less.

[0066] Partial dispersion ratio PC,t, deviation ΔPC,t 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)

[0067] The lower limit of the partial dispersion ratio PC,t 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. Optical glasses having a partial dispersion ratio PC,t in the above range are suitable for correcting high-order chromatic aberrations. The upper limit of the partial dispersion ratio PC,t is not particularly limited, but can be, for example, 0.9000, 0.8900, 0.8800, 0.8700, 0.8600, 0.8500, or 0.8400. The lower limit of the deviation ΔPC,t is preferably 0.0100, and more preferably 0.0150, 0.0200, 0.0210, 0.0220, 0.0230, 0.0240, 0.0250, 0.0260, 0.0270, 0.0280, 0.0290, and 0.0300, in that order. Glasses with a deviation ΔPC,t in the above range are suitable for correcting high-order chromatic aberrations. The upper limit of the deviation ΔPC,t is not particularly limited, but can be, for example, 0.0900 or 0.0800.

[0068] Partial dispersion ratio Pg,F, deviation ΔPg,F 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)

[0069] The upper limit of the partial dispersion ratio Pg,F is preferably 0.5800, and more preferably 0.5750, 0.5720, 0.5690, 0.5660, 0.5640, 0.5630, 0.5620, 0.5610, 0.5600, 0.5550, and 0.5500, in that order. Optical glasses having a partial dispersion ratio Pg,F in the above range are suitable for correcting high-order chromatic aberrations. The lower limit of the partial dispersion ratio Pg,F is not particularly limited, but can be, for example, 0.5300, or preferably 0.5400. The upper limit of the deviation ΔPg,F is preferably 0, and more preferably -0.0005, -0.0010, -0.0013, -0.0023, -0.0033, -0.0039, -0.0044, and -0.0050, in that order. Optical glasses with a deviation ΔPg,F in the above range are suitable for correcting high-order chromatic aberrations. The lower limit of the deviation ΔPg,F is not particularly limited, but can be, for example, -0.0300 or -0.0150.

[0070] The "lower limit" mentioned above means equal to or greater than the stated value, and the "upper limit" mentioned above means equal to or less than the stated value.

[0071] (refractive index nd) The optical glass may be a glass with a high refractive index. The refractive index nd of the optical glass is preferably 1.51000 or more, and more preferably 1.52000 or more, 1.53000 or more, 1.54000 or more, 1.55000 or more, 1.56000 or more, 1.57000 or more, and 1.58000 or more in that order. The refractive index nd of the optical glass can be, for example, 1.65000 or less, 1.64000 or less, 1.63000 or less, 1.62000 or less, 1.61500 or less, 1.61000 or less, or 1.60500 or less. In the present invention and in this specification, "refractive index" means "refractive index nd."

[0072] (specific gravity) The refractive power of the optical elements that make up an optical system is determined by the refractive index of the glass that makes up the optical element and the curvature of the optically functional surface of the optical element (the surface through which the light rays to be controlled enter and exit). Increasing the curvature of the optically functional surface also increases the thickness of the optical element. As a result, the optical element becomes heavier. In contrast, if glass with a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optically functional surface. From the above, if the refractive index can be increased while suppressing an increase in the specific gravity of the glass, it will be possible to reduce the weight of an optical element having a certain refractive power. From the above viewpoints, the specific gravity of the optical glass is preferably 3.50 or less, and more preferably 3.40 or less, 3.30 or less, 3.20 or less, 3.10 or less, and 3.00 or less in that order. Since a lower specific gravity is preferable from the viewpoint of reducing the weight of optical elements, there is no particular lower limit for the specific gravity of the optical glass. In one embodiment, the specific gravity can be 2.40 or more or 2.50 or more. In this specification, "specific gravity" is also abbreviated as "sg" (specific gravity).

[0073] (glass transition temperature Tg) From the viewpoint of reducing the burden on the annealing furnace and the molding die, the glass transition temperature Tg of the optical glass is preferably 620°C or lower, and more preferably 610°C or lower, 605°C or lower, 600°C or lower, 595°C or lower, and 590°C or lower. On the other hand, from the viewpoint of machinability (more specifically, from the viewpoint of being less susceptible to breakage during mechanical processing of the glass such as cutting, milling, grinding, polishing, etc.), the glass transition temperature Tg of the optical glass is preferably 500°C or higher, and more preferably 510°C or higher, 520°C or higher, 530°C or higher, 540°C or higher, and 545°C or higher. The glass transition temperature Tg is determined by the method described below.

[0074] <Optical glass manufacturing method> The above optical glass can be obtained, for example, by the following method. Raw materials such as oxides, carbonates, sulfates, nitrates, and hydroxides are weighed, blended, and thoroughly mixed to obtain the desired glass composition. This mixed batch is heated and melted in a melting vessel, degassed, and stirred to produce a homogeneous, bubble-free glass melt. Specifically, the glass melt can be produced using a known melting method. The above optical glass can be obtained by molding the glass melt thus obtained.

[0075] [Glass materials for press molding, optical element blanks, and their manufacturing methods] Another aspect of the present invention is a glass material for press molding comprising the optical glass; an optical element blank made of the optical glass; Regarding.

[0076] According to another aspect of the present invention, a method for producing a glass material for press molding, comprising a step of molding the optical glass into a glass material for press molding; a method for producing an optical element blank, comprising a step of press-molding the glass material for optical glass press molding using a press mold to produce an optical element blank; a method for manufacturing an optical element blank, comprising a step of molding the optical glass into an optical element blank; is also provided.

[0077] An optical element blank is an optical element base material that approximates the shape of the desired optical element, with polishing allowances (surface layers to be removed by polishing) and, if necessary, grinding allowances (surface layers to be removed by grinding) added to the shape of the optical element. The optical element is finished by grinding and polishing the surface of the optical element blank. In one embodiment, the optical element blank can be produced by a method (called a direct press method) in which a molten glass obtained by melting an appropriate amount of the above glass is press-molded. In another embodiment, the optical element blank can also be produced by solidifying a molten glass obtained by melting an appropriate amount of the above glass.

[0078] In another embodiment, an optical element blank can be produced by preparing a glass material for press molding and press-molding the prepared glass material for press molding.

[0079] Press molding of a glass material for press molding can be carried out by a known method in which a glass material for press molding in a heated and softened state is pressed in a press mold. Both heating and press molding can be carried out in the atmosphere. After press molding, the glass is annealed to reduce internal strain, thereby obtaining a homogeneous optical element blank.

[0080] Glass materials for press molding include not only glass gobs for press molding that are used for press molding as they are to produce optical element blanks, but also glass gobs for press molding that are machined by cutting, grinding, polishing, etc. and then used for press molding. Cutting methods include forming a groove in the area of ​​the surface of the glass plate to be cut by a method called scribing, applying local pressure to the grooved area from the back side of the surface where the groove was formed, thereby breaking the glass plate at the grooved area, and cutting the glass plate with a cutting blade. Grinding and polishing methods include barrel polishing, etc.

[0081] A glass material for press molding can be produced, for example, by casting molten glass into a mold to form a glass plate, and then cutting this glass plate into a plurality of glass pieces. Alternatively, a suitable amount of molten glass can be molded to produce a glass gob for press molding. An optical element blank can also be produced by reheating, softening, and press-molding a glass gob for press molding. The method of producing an optical element blank by reheating, softening, and press-molding glass is called a reheat press method, as opposed to a direct press method.

[0082] [Optical element and its manufacturing method] Another aspect of the present invention is Optical elements made of the above optical glass Regarding. The optical element is manufactured using the optical glass. In the optical element, the glass surface may be coated with one or more layers, such as a multilayer film including an anti-reflection film.

[0083] According to another aspect of the present invention, a method for manufacturing an optical element, comprising a step of manufacturing an optical element by grinding and / or polishing the optical element blank described above; is also provided.

[0084] In the method for manufacturing the optical element, known methods can be used for mechanical processing such as grinding and polishing, and by thoroughly cleaning and drying the surface of the optical element after processing, an optical element with high internal and surface quality can be obtained. In this way, an optical element made of the optical glass can be obtained. Examples of optical elements include various lenses such as spherical lenses, aspherical lenses, and microlenses, as well as prisms.

[0085] Optical elements made of the above optical glass are also suitable as lenses constituting cemented optical elements. Examples of cemented optical elements include those in which lenses are cemented together (cemented lenses) and those in which a lens and a prism are cemented together. For example, a cemented optical element can be produced by precisely machining (e.g., spherical polishing) the cementing surfaces of two optical elements to be cemented so that their shapes are inverted, applying an ultraviolet-curing adhesive used for bonding cemented lenses, bonding them together, and then irradiating ultraviolet light through the lenses to cure the adhesive. The above optical glass is preferable for producing such cemented optical elements. By producing multiple optical elements to be cemented using multiple types of glass with different Abbe numbers νd and partial dispersion ratios and cementing them together, an element suitable for correcting chromatic aberration can be obtained. [Example]

[0086] 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.

[0087] Example 1 <Examples Nos. 1 to 92> To obtain the glass compositions shown in the tables below, the corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials for introducing the respective components, and the raw materials were weighed and thoroughly mixed to obtain blended raw materials. This blended raw material was placed in a platinum crucible and heated and melted for two hours in a furnace set at 1400°C to 1450°C. The molten glass was stirred to homogenize it, then poured into a preheated mold and allowed to cool to near the glass transition temperature. It was then immediately placed in an annealing furnace and held at a temperature near the glass transition temperature for about 30 minutes, after which it was slowly cooled at a rate of -30°C / hour for four hours, and then allowed to cool to room temperature in the furnace to obtain the optical glasses Nos. 1 to 92 shown in the table below. The physical properties of the optical glass thus obtained are shown in the table below. The physical properties of the optical glass were measured by the following methods.

[0088] <Evaluation of the physical properties of optical glass> (Refractive index nd, Abbe number νd, partial dispersion ratio PC,t, deviation ΔPC,t, partial dispersion ratio Pg,F, deviation ΔPg,F) The refractive index of the obtained glass was measured at the 12 wavelengths shown in the table above in accordance with JIS (Japanese Industrial Standards) B 7071-1:2015, Measurement of refractive index of optical glass - Part 1: Minimum deviation angle method. The refractive index nd was also calculated in this way. Next, the refractive index of each line obtained by measurement was applied to the dispersion formula of Schottky defined in Appendix B of the above-mentioned JIS, and the constants of the dispersion formula of Schottky were determined by the least squares method. Then, the Abbe number νd, partial dispersion ratio PC,t, and partial dispersion ratio Pg,F were calculated from the values ​​of each linear refractive index obtained using the dispersion formula of Schottky defined in the above-mentioned JIS. The details of the calculation method are as described above. Furthermore, the deviation ΔPC,t and deviation ΔPg,F were calculated using the calculation method described above.

[0089] (Transmittance characteristics) A test piece was cut out from the obtained glass, and both surfaces were mirror-polished to have parallel, optically polished flat surfaces to a thickness of 10.0 mm. The external transmittance at wavelengths of 400 to 700 nm was then measured using a spectrophotometer. It was confirmed that for all of Samples Nos. 1 to 92, the external transmittance at wavelengths of 400 nm to 700 nm was 70% or more and 100% or less at a thickness of 10.0 mm.

[0090] (specific gravity sg) The specific gravity was measured by the Archimedes method.

[0091] (glass transition temperature Tg) The glass was thoroughly crushed in a mortar and used as a sample. A platinum cell was used as the sample container, and the glass transition temperature Tg was measured at a heating rate of 10°C / min using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN.

[0092] (Chemical durability (water resistance Dw)) The resulting glass samples were powdered (particle size: 425-600 μm). A mass of powdered glass equivalent to the specific gravity was placed in a platinum cage, which was then immersed in a quartz glass round-bottom flask containing 80 mL of pure water (pH = 6.5-7.5) and treated in a boiling water bath for 60 minutes. The samples were classified into grades in the table below based on the weight loss rate (in the table below, "mass loss") (%), and water resistance (Dw) was evaluated. The smaller the weight loss rate, the higher the chemical durability, which is preferable.

[0093] [Table 2]

[0094] The results are shown in the table below, where "R2O" represents the total content of Li2O, Na2O, and K2O, "R'O" represents the total content of MgO, CaO, SrO, and BaO, "Ln2O3" represents the total content of La2O3, Gd2O3, YO3, and Yb2O3, and "wt.%" represents mass %.

[0095]

Table 3-1

[0096]

Table 3-2

[0097]

Table 3-3

[0098]

Table 3-4

[0099]

Table 3-5

[0100]

Table 3-6

[0101]

Table 3-7

[0102]

Table 3-8

[0103]

Table 3-9

[0104]

Table 3-10

[0105]

Table 4-1

[0106] [Table 4-2]

[0107] [Table 4-3]

[0108] [Table 4-4]

[0109] [Table 4-5]

[0110] [Table 4-6]

[0111] [Table 4-7]

[0112] [Table 4-8]

[0113] [Table 4-9]

[0114] [Table 4-10]

[0115] Example 2 Glass gobs for press molding (glass gobs) were prepared using the various glasses obtained in Example 1. These glass gobs were heated and softened in the atmosphere and press-molded in a press mold to produce lens blanks (optical element blanks). The produced lens blanks were removed from the press mold, annealed, and subjected to machining including polishing to produce spherical lenses made from the various glasses produced in Example 1.

[0116] Example 3 A desired amount of the molten glass produced in Example 1 was press-molded in a press mold to produce a lens blank (optical element blank). The produced lens blank was removed from the press mold, annealed, and subjected to machining including polishing to produce spherical lenses made of the various glasses produced in Example 1.

[0117] Example 4 The glass molten glass produced in Example 1 was solidified to produce a glass lump (optical element blank), which was then annealed and subjected to machining including polishing to produce spherical lenses made of the various glasses produced in Example 1.

[0118] Example 5 Lens blanks were prepared by known methods using the various glasses obtained 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 νd of 65 or more, such as fluorophosphate glass, it was possible to effectively correct high-order chromatic aberrations in the infrared region.

[0119] The various glasses obtained in Example 1 have a low specific gravity, so each lens is lighter than a lens with equivalent optical properties and size, and is therefore suitable for use in various imaging devices, particularly autofocus imaging devices, due to the energy savings that can be achieved. Similarly, prisms were made using the various optical glasses produced in Example 1.

[0120] 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. For example, by adjusting the composition as described in the specification for the glass compositions exemplified above, an optical glass according to one aspect of the present invention can be obtained. 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. By mass, SiO ２ The content is 25.00% or more and 56.00% or less, B ２ O ３ The content is 16.50% or more and 50.00% or less, Na ２ O content is more than 2.00% and not more than 20.00%; ZrO ２ The content is 2.00% or more and 15.00% or less, Nb ２ O ５ The content is 10.00% or less, SiO ２ , B ２ O ３ and Al ２ O ３ Alkali metal oxide R relative to the total content ２ Mass ratio of O content (R ２ O / (SiO ２ +B ２ O ３ +Al ２ O ３ ) is 0.091 or more and 0.250 or less, Nb ２ O ５ , TiO ２ , W.O. ３ and Ta ２ O ５ The total content (Nb ２ O ５ + TiO ２ +WO ３ +Ta ２ O ５ ) is 14.00% or less, and An optical glass having an external transmittance of 70% or more at wavelengths of 400 nm to 700 nm when converted to a thickness of 10.0 mm.

2. Alkali metal oxide R ２ Li relative to O content ２ O and Na ２ The mass ratio of the total content of Li and O ((Li ２ O + Na ２ O) / R ２ 2. The optical glass according to claim 1, wherein .DELTA.O) is 0.520 or more and 1.000 or less.

3. Rare earth oxide Ln ２ O ３ 2. The optical glass according to claim 1, wherein the content is 0.00% or more and 20.00% or less.

4. Alkali metal oxide R ２ The mass ratio of the alkaline earth metal oxide R′O content to the O content (R′O / R ２ 2. The optical glass according to claim 1, wherein .DELTA.O) is 0.000 or more and 1.800 or less.

5. ZrO ２ Alkali metal oxide R content ２ Mass ratio of O content (R ２ O / ZrO ２ 2. The optical glass of claim 1 , wherein σ is greater than 0.

620.

6. Alkali metal oxide R ２ The total content of O and alkaline earth metal oxide R′O (R ２ 2. The optical glass according to claim 1, wherein the content of O+R'O) is 5.00% or more and 25.00% or less.

7. SiO ２ Alkali metal oxide R content ２ O and B ２ O ３ The mass ratio of the total content of (R ２ O+B ２ O ３ ) / SiO ２ 2. The optical glass according to claim 1, wherein σ is 0.100 or more and 1.400 or less.

8. SiO ２ , B ２ O ３ and Al ２ O ３ The total content (SiO ２ +B ２ O ３ +Al ２ O ３ 2. The optical glass according to claim 1, wherein the ratio of Cr to Cu is 50.00% or more and 74.00% or less.

9. SiO ２ and ZrO ２ and the total content (SiO ２ + ZrO ２ 2. The optical glass according to claim 1, wherein the content of Cr is 41.00% or more and 60.00% or less.

10. SiO ２ and B ２ O ３ B relative to the total content of ２ O ３ Mass ratio of content (B ２ O ３ / (SiO ２ +B ２ O ３ 2. The optical glass according to claim 1, wherein σ is 0.225 or greater and 0.495 or less.

11. Alkali metal oxide R ２ The ratio of BaO and Na to the total content of O, alkaline earth metal oxides R'O and ZnO ２ The mass ratio of the total content of BaO and Na ２ O) / (R ２ 2. The optical glass according to claim 1, wherein (O+R'O+ZnO)) is 0.380 or greater.

12. SiO ２ and B ２ O ３ Nb relative to the total content of ２ O ５ and ZrO ２ The mass ratio of the total content of (Nb ２ O ５ + ZrO ２ ) / (SiO ２ +B ２ O ３ 2. The optical glass according to claim 1, wherein σ is 0.050 or more and 0.350 or less.

13. Nb ２ O ５ and ZrO ２ The total content of alkali metal oxide R ２ Mass ratio of O content (R ２ O / (Nb ２ O ５ + ZrO ２ 2. The optical glass according to claim 1, wherein σ is 0.400 or greater and 1.700 or less.

14. Nb ２ O ５ and ZrO ２ Nb relative to the total content of ２ O ５ Mass ratio of content (Nb ２ O ５ / (Nb ２ O ５ + ZrO ２ 2. The optical glass according to claim 1, wherein σ is 0.050 or more and 0.550 or less.

15. ZrO ２ B relative to content ２ O ３ Mass ratio of content (B ２ O ３ / ZrO ２ 2. The optical glass according to claim 1, wherein σ is 1.400 or greater.

16. SiO ２ , B ２ O ３ , Al ２ O ３ and ZrO ２ Na relative to the total content ２ Mass ratio of O content (Na ２ O / (SiO ２ +B ２ O ３ +Al ２ O ３ + ZrO ２ 2. The optical glass according to claim 1, wherein σ is 0.100 or more and 0.220 or less.

17. SiO ２ , B ２ O ３ , Al ２ O ３ and Nb ２ O ５ Alkali metal oxide R relative to the total content ２ Mass ratio of O content (R ２ O / (SiO ２ +B ２ O ３ +Al ２ O ３ +Nb ２ O ５ 2. The optical glass according to claim 1, wherein σ is 0.198 or less.

18. Ta ２ O ５ 2. The optical glass according to claim 1, wherein the content is 0.00% or more and 10.00% or less.

19. An optical element made of the optical glass according to any one of claims 1 to 18.

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