Optical glass and optical element

Abstract

To provide optical glass exhibiting a low refractive index, high dispersion, and superior thermal stability, as well as an optical element composed of the optical glass.SOLUTION: There is provided optical glass, in which a content of P2O5 is 26.00 mass% or more, a content of B2O3 is 1.00 mass% or less, a content of SiO2 is 5.00 mass% or less, a content of Na2O is 10.00 to 28.00 mass%, a content of TiO2 is 8.00 to 24.00 mass%, a content of Al2O3 is 2.00 to 10.00 mass%, a content of Nb2O5 is 10.00 mass% or less, a mass ratio [B2O3 / Al2O3] of the content of B2O3 to the content of Al2O3 is 0.500 or less, a mass ratio [K2O / (Li2O+Na2O)] of a content of K2O to a total content of Li2O and Na2O is 0.100 or more, a total content [WO3+Bi2O3+ZrO2] of WO3, Bi2O3, and ZrO2 is 5.80 mass% or less, and a total content [TiO2+Nb2O5] of TiO2 and Nb2O5 is 10.00 to 24.00 mass%.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Optical glasses with low refractive index and high dispersion are highly useful in designing optical systems, correcting chromatic aberrations and making optical systems more compact and highly functional. Furthermore, optical glasses with low refractive index and high dispersion are required to have excellent thermal stability, which can suppress the formation of crystals and striae.

[0003] Patent Documents 1 and 2 disclose optical glasses that have a relatively low refractive index and high dispersion. However, in recent years, there has been a demand for optical glasses that have even higher dispersion than the optical glasses disclosed in Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-108395 [Patent Document 2] International Publication No. 2019 / 082419 Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical glass that has a low refractive index, high dispersion, and excellent thermal stability, as well as an optical element made of said optical glass. [Means for solving the problem]

[0006] The gist of the present invention is as follows. (1) The content of P2O5 is 26.00 mass% or more, The content of B2O3 is 1.00 mass% or less, The SiO2 content is 5.00 mass% or less, The NaO content is 10.00 to 28.00 mass%, The TiO2 content is 8.00 to 24.00 mass%; The content of Al2O3 is 2.00 to 10.00 mass%, The content of Nb2O5 is 10.00 mass% or less, The mass ratio of the B2O3 content to the Al2O3 content [B2O3 / Al2O3] is 0.500 or less, the mass ratio of the KO content to the total content of LiO and NaO [KO / (LiO+NaO)] is 0.100 or more; The total content of WO3, Bi2O3, and ZrO2 [WO3 + Bi2O3 + ZrO2] is 5.80 mass% or less, An optical glass having a total content of TiO2 and Nb2O5 [TiO2 + Nb2O5] of 10.00 to 24.00 mass%.

[0007] (2) The optical glass according to (1), wherein the total content of WO3 and Bi2O3 [WO3 + Bi2O3] is 5.80 mass% or less.

[0008] (3) The optical glass according to (1), wherein the total content of ZnO, MgO, CaO, SrO, and BaO [ZnO + MgO + CaO + SrO + BaO] is 3.80 mass % or less.

[0009] (4) The optical glass according to (1), in which the mass ratio of the total content of Li2O, Na2O, K2O, MgO, CaO, SrO, and BaO to the content of Al2O3 [(Li2O + Na2O + K2O + MgO + CaO + SrO + BaO) / Al2O3] is 6.400 or less.

[0010] (5) The optical glass according to (1), having an Abbe number vd of 27.00 to 33.00.

[0011] (6) The optical glass according to (1), having a refractive index nd of 1.600 to 1.660.

[0012] (7) The optical glass according to (1), wherein the Abbe number νd and the refractive index nd satisfy the following formulas: nd<-0.0106×νd+1.950

[0013] (8) An optical element made of the optical glass according to any one of (1) to (7) above. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an optical glass that has a low refractive index, high dispersion, and excellent thermal stability, as well as an optical element made of said optical glass. DETAILED DESCRIPTION OF THE INVENTION

[0015] In this invention and this specification, the glass composition of 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. The content and total content of glass components are expressed on a mass basis unless otherwise specified, and "%" means "mass %."

[0016] The content of glass components can be quantified by known methods, such as inductively coupled plasma atomic emission spectroscopy (ICP-AES), inductively coupled plasma mass spectroscopy (ICP-MS), etc. 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.

[0017] 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).

[0018] The Abbe number νd is used as a value representing the properties related to dispersion and is expressed by the following formula: where nF is the refractive index at the F line (wavelength 486.13 nm) of blue hydrogen, and nC is the refractive index at the C line (656.27 nm) of red hydrogen. νd=(nd-1) / (nF-nC) (1)

[0019] In this specification, the thermal stability of glass refers to the resistance to crystallization when molten glass solidifies. In the present invention, optical glass with excellent thermal stability can be obtained by suppressing an increase in the liquidus temperature LT of the glass.

[0020] The optical glass according to this embodiment will now be described in detail.

[0021] In the optical glass according to this embodiment, the P2O5 content is 26.00% or more. The lower limit of the P2O5 content is preferably 29.00%, and more preferably 32.00%, 35.00%, 36.00%, 37.00%, 38.00%, 39.00%, 40.00%, 41.00%, 42.00%, 43.00%, 43.50%, and 43.68% in that order. The upper limit of the P2O5 content is preferably 55.00%, and more preferably 54.00%, 53.00%, 52.00%, 51.00%, 50.00%, 49.00%, 48.50%, and 48.31% in that order.

[0022] P2O5 is a glass network-forming component and is essential for containing a large amount of highly dispersible components in the glass. By setting the lower limit of the P2O5 content as described above, an optical glass having excellent thermal stability and the desired optical constants can be obtained. On the other hand, if the P2O5 content is too low, an optical glass having the desired optical constants may not be obtained. Furthermore, if the P2O5 content is too high, the thermal stability of the glass may be impaired.

[0023] In the optical glass according to this embodiment, the B2O3 content is 1.00% or less. The lower limit of the B2O3 content is preferably 0.00%, and may be 0.10% or 0.20%. The upper limit of the B2O3 content is preferably 0.90%, and more preferably 0.80%, 0.70%, 0.60%, 0.50%, 0.40%, 0.32%, and 0.30%, in that order. The B2O3 content may be 0%.

[0024] B2O3 is a glass network-forming component that improves the thermal stability of glass. By setting the upper limit of the B2O3 content as described above, the thermal stability and devitrification resistance of the glass can be improved. On the other hand, if the B2O3 content is too high, the thermal stability and devitrification resistance of the glass may decrease, and the desired dispersion value may not be maintained.

[0025] In the optical glass according to this embodiment, the SiO2 content is 5.00% or less. The upper limit of the SiO2 content is preferably 4.00%, with 3.00%, 2.50%, and 2.22% being more preferable in that order. The lower limit of the SiO2 content is preferably 0.00%, and may be 0.20%, 0.40%, 0.60%, 0.80%, or 1.00%. The SiO2 content may even be 0%.

[0026] SiO2 is a glass network-forming component that improves the thermal stability, chemical durability, and weather resistance of glass, and increases the viscosity of molten glass, making it easier to form molten glass. However, if the SiO2 content is too high, phase separation of the glass may occur, resulting in a deterioration in thermal stability. By setting the upper limit of the SiO2 content as described above, the thermal stability and devitrification resistance of the glass can be improved.

[0027] In the optical glass according to this embodiment, the Na2O content is 10.00 to 28.00%. The lower limit of the Na2O content is preferably 11.00%, and more preferably 12.00%, 13.00%, 14.00%, 15.00%, 16.00%, 16.50%, 17.00%, 17.50%, 17.62%, 18.00%, and 18.50% in that order. The upper limit of the Na2O content is preferably 27.00%, and more preferably 26.00%, 25.00%, 24.00%, 23.00%, 22.00%, 21.50%, 21.00%, 20.50%, and 20.24% in that order.

[0028] Na2O improves the thermal stability and meltability of the glass. Furthermore, Na2O lowers the refractive index while maintaining high dispersion. By setting the Na2O content within the above range, an optical glass can be obtained that has excellent thermal stability and meltability while maintaining high dispersion. On the other hand, if the Na2O content is too low, the thermal stability and meltability may decrease. Furthermore, if the Na2O content is too high, the thermal stability may decrease and the thermal expansion coefficient may increase.

[0029] In the optical glass according to this embodiment, the TiO2 content is 8.00 to 24.00%. The lower limit of the TiO2 content is preferably 10.00%, and more preferably 12.00%, 13.00%, 14.00%, 15.00%, 16.00%, 16.50%, 17.00%, 17.20%, 17.40%, 17.60%, and 17.80% in that order. The upper limit of the TiO2 content is preferably 23.00%, and more preferably 22.00%, 21.00%, 20.50%, 20.00%, 19.50%, 19.00%, and 18.87% in that order.

[0030] TiO2 is a component that significantly contributes to high dispersion and low thermal expansion. However, TiO2 tends to increase the coloration of glass. Furthermore, during the process of forming molten glass and slowly cooling it to obtain optical glass, TiO2 promotes the formation of crystals within the glass, reducing the transparency of the glass (opacity). By setting the TiO2 content within the above range, optical glass with high dispersion, suppressed coloration, and maintained transparency can be obtained.

[0031] In the optical glass according to this embodiment, the Al2O3 content is 2.00 to 10.00%. The lower limit of the Al2O3 content is preferably 3.00%, and more preferably 4.00%, 4.20%, 4.40%, 4.60%, 4.80%, 5.00%, and 5.09%, in that order. The upper limit of the Al2O3 content is preferably 9.00%, and more preferably 8.80%, 8.60%, 8.40%, 8.20%, 8.00%, and 7.95%, in that order.

[0032] Al2O3 improves the thermal stability, chemical durability, and weather resistance of glass, and increases the viscosity of molten glass, making it easier to form the molten glass. On the other hand, Al2O3 is also a component that contributes to low dispersion. By setting the Al2O3 content within the above range, high dispersibility can be maintained, and the viscosity of molten glass can be increased, improving formability.

[0033] In the optical glass according to this embodiment, the Nb2O5 content is 10.00% or less. The upper limit of the Nb2O5 content is preferably 9.00%, and more preferably 8.00%, 7.00%, 6.00%, 5.00%, 4.00%, 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the Nb2O5 content is preferably 0%. The Nb2O5 content may be 0%.

[0034] Nb2O5 improves the thermal stability and meltability of glass. While Nb2O5 is a component that contributes to a high refractive index and high dispersion, its contribution to high dispersion is smaller than that of TiO2. Therefore, by setting the upper limit of the Nb2O5 content as described above, optical glass with the desired optical constants can be obtained.

[0035] In the optical glass according to this embodiment, the mass ratio of the B2O3 content to the Al2O3 content [B2O3 / Al2O3] is 0.500 or less. The upper limit of this mass ratio is preferably 0.400, and more preferably 0.300, 0.275, 0.250, 0.225, 0.200, 0.180, 0.160, 0.140, 0.120, 0.100, 0.080, 0.060, and 0.049, in that order. The lower limit of this mass ratio is preferably 0.00, and may be 0.010, 0.020, 0.030, or 0.040. By setting the upper limit of this mass ratio as described above, the viscosity of the glass melt can be increased while keeping the optical constants within the desired range.

[0036] In the optical glass according to this embodiment, the mass ratio of the content of K2O to the total content of Li2O and Na2O [K2O / (Li2O + Na2O)] is at least 0.100. The lower limit of this mass ratio is preferably 0.150, and more preferably 0.200, 0.220, 0.240, 0.260, 0.280, 0.300, 0.310, 0.320, 0.330, 0.340, 0.350, 0.360, 0.370, 0.380, and 0.388, in that order. The upper limit of the mass ratio is preferably 0.800, and more preferably 0.780, 0.760, 0.740, 0.720, 0.700, 0.690, 0.680, 0.670, 0.660, 0.650, 0.640, and 0.632, in that order. By setting the lower limit of the mass ratio as described above, it is possible to improve the thermal stability and devitrification resistance of the glass while maintaining high dispersibility.

[0037] In the optical glass according to this embodiment, the total content of WO3, Bi2O3, and ZrO2 [WO3 + Bi2O3 + ZrO2] is 5.80% or less. The upper limit of this total content is preferably 5.00%, with 4.00%, 3.00%, 2.00%, and 1.00% being more preferred. The lower limit of this total content is preferably 0.00%, and may be 0.10%, 0.20%, or 0.50%. By setting the upper limit of this total content as described above, the thermal stability of the glass can be improved and high dispersion can be maintained. On the other hand, if the total content is too high, the specific gravity increases and the coloration of the glass may increase.

[0038] In the optical glass according to this embodiment, the total content of TiO2 and Nb2O5 [TiO2 + Nb2O5] is 10.00 to 24.00%. The lower limit of this total content is preferably 12.00%, and more preferably 13.00%, 14.00%, 15.00%, 16.00%, 16.50%, 17.00%, 17.20%, 17.40%, 17.60%, and 17.80%, in that order. The upper limit of this total content is preferably 23.00%, and more preferably 22.00%, 21.00%, 20.50%, 20.00%, 19.50%, 19.00%, and 18.87%, in that order. By keeping this total content within the above range, the thermal stability and meltability of the glass can be maintained while maintaining high dispersibility. On the other hand, if the total content is too high, the refractive index nd increases, and there is a risk that the desired refractive index nd may not be obtained.

[0039] In the optical glass according to this embodiment, the upper limit of the total content of WO3 and Bi2O3 [WO3 + Bi2O3] is preferably 5.80%, and more preferably 5.00%, 4.00%, 3.00%, 2.00%, and 1.00%, in that order. The lower limit of this total content is preferably 0.00%, and may be 0.10%, 0.20%, or 0.50%. From the viewpoints of suppressing an increase in specific gravity and suppressing coloration of the glass, it is preferable that the total content be within the above range.

[0040] In the optical glass according to this embodiment, the upper limit of the total content of ZnO, MgO, CaO, SrO, and BaO [ZnO + MgO + CaO + SrO + BaO] is preferably 3.80%, and more preferably 3.50%, 3.00%, 2.50%, 2.00%, 1.50%, and 1.00%, in that order. The lower limit of this total content is preferably 0.00%, and may be 0.20%, 0.40%, 0.60%, or 0.80%. From the viewpoints of maintaining the high dispersion of the glass and suppressing a decrease in the thermal stability and devitrification resistance of the glass, it is preferable that the total content be within the above range.

[0041] In the optical glass according to this embodiment, the upper limit of the mass ratio of the total content of LiO, NaO, KO, MgO, CaO, SrO, and BaO to the content of AlO, [(LiO + NaO + KO + MgO + CaO + SrO + BaO) / AlO], is preferably 6.400, and more preferably 6.300, 6.200, 6.100, 6.000, 5.900, 5.800, 5.770, and 5.633, in that order. The lower limit of this mass ratio is preferably 3.000, and more preferably 3.100, 3.200, 3.300, 3.400, 3.500, and 3.573, in that order. From the viewpoints of increasing the viscosity of the glass melt while maintaining high dispersibility and facilitating the molding of the glass melt, it is preferable that this mass ratio be within the above range.

[0042] <Abbe number νd> In the optical glass according to this embodiment, the lower limit of the Abbe number vd can be 27.00, or can be 27.50, 28.00, 28.50, or 28.76. The upper limit of the Abbe number vd can be 33.00, or can be 32.50, 32.00, 31.50, 31.10, or 31.00.

[0043] The Abbe number vd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that relatively lower the Abbe number vd, i.e., high-dispersion components, include Nb2O5, TiO2, WO3, Bi2O3, Ta2O5, and ZrO2. On the other hand, components that relatively increase the Abbe number vd, i.e., low-dispersion components, include P2O5, SiO2, B2O3, Li2O, Na2O, K2O, La2O3, BaO, CaO, and SrO.

[0044] <Refractive index nd> In the optical glass according to this embodiment, the lower limit of the refractive index nd may be 1.600, or may be 1.605, 1.610, 1.615, or 1.619. The upper limit of the refractive index nd may be 1.660, or may be 1.655, 1.650, 1.645, 1.640, 1.635, or 1.632.

[0045] The refractive index nd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that function to relatively increase the refractive index nd (refractive index increasing components) include Nb2O5, TiO2, WO3, Bi2O3, Ta2O5, ZrO2, and La2O3. On the other hand, components that function to relatively decrease the refractive index nd (refractive index decreasing components) include P2O5, SiO2, B2O3, Li2O, Na2O, and K2O.

[0046] <Relationship between Abbe number νd and refractive index nd> In the optical glass according to this embodiment, the Abbe number vd and the refractive index nd preferably satisfy the following formula (1), more preferably the following formula (2), even more preferably the following formula (3), and particularly preferably the following formula (4): From the viewpoint of obtaining an optical glass with even higher dispersion, it is preferable that the Abbe number vd and the refractive index nd satisfy the following formula: nd<-0.0106×νd+1.950 (1) nd<-0.0106×νd+1.948 (2) nd<-0.0106×νd+1.946 (3) nd<-0.0106×νd+1.944 (4)

[0047] Non-limiting examples of the contents, ratios, and glass properties of glass components other than those described above in the optical glass according to this embodiment are shown below.

[0048] In the optical glass according to this embodiment, the lower limit of the mass ratio of the total content of B2O3 and SiO2 to the content of P2O5 [(B2O3 + SiO2) / P2O5] is preferably 0.00, with 0.01 and 0.02 being more preferred. The upper limit of this mass ratio is preferably 0.06, with 0.05, 0.04, and 0.03 being more preferred in that order. From the viewpoint of obtaining desired optical constants while improving the thermal stability and devitrification resistance of the glass, it is preferable that this mass ratio be within the above range.

[0049] In the optical glass according to this embodiment, the upper limit of the total content of Li2O, Na2O, and K2O [Li2O + Na2O + K2O] is preferably 35.00%, more preferably 34.00%, 33.00%, 32.00%, more preferably 31.00%, 30.50%, 30.00%, and 29.83%, in that order. The lower limit of this total content is preferably 24.00%, more preferably 25.00%, 26.00%, 26.50%, 27.00%, 27.50%, and 27.62%, in that order.

[0050] Li2O, Na2O, and K2O all function to improve the thermal stability of glass. However, if their contents are too high, chemical durability and weather resistance may be reduced. Therefore, it is preferable that the total content of Li2O, Na2O, and K2O [Li2O + Na2O + K2O] be within the above range.

[0051] In the optical glass according to this embodiment, the lower limit of the mass ratio of the TiO2 content to the total content of TiO2, Nb2O5, WO3, Bi2O3, and ZrO2 [TiO2 / (TiO2+Nb2O5+WO3+Bi2O3+ZrO2)] is preferably 0.50, with 0.60, 0.70, 0.80, and 0.90 being more preferable in this order. The upper limit of this mass ratio is preferably 1.00, and may be 0.95 or 0.90. From the viewpoints of suppressing an increase in specific gravity and suppressing coloration of the glass, it is preferable that this mass ratio be within the above range.

[0052] In the optical glass according to this embodiment, the upper limit of the total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is preferably 3.80%, and more preferably 3.50%, 3.00%, 2.50%, 2.00%, 1.50%, 1.00%, and 0.50%, in that order. The lower limit of this total content is preferably 0%, and the total content may even be 0%.

[0053] From the viewpoint of maintaining the thermal stability and devitrification resistance of the glass without impeding high dispersion, it is preferable that the total content [MgO + CaO + SrO + BaO] be within the above range. On the other hand, if the total content is too large, the high dispersibility of the glass may be impaired, and the thermal stability and devitrification resistance of the glass may also be reduced.

[0054] In the optical glass according to this embodiment, the upper limit of the Li2O content is preferably 5%, and more preferably 3%, 2%, and 1%, in that order. The lower limit of the Li2O content is preferably 0%. The Li2O content may be 0%.

[0055] Li2O has the function of lowering the glass transition temperature Tg. On the other hand, if the Li2O content is too high, the acid resistance decreases. Therefore, it is preferable that the Li2O content be in the above range.

[0056] In the optical glass according to this embodiment, the K2O content exceeds 0%, and the lower limit is preferably 2.00%, and more preferably 4.00%, 5.00%, 6.00%, 6.50%, 7.00%, 7.50%, and 7.80% in that order. The upper limit of the K2O content is preferably 15.00%, and more preferably 14.00%, 13.00%, 12.50%, 12.00%, 11.50%, and 11.14% in that order.

[0057] K2O has the function of improving the thermal stability and meltability of glass. From the viewpoint of obtaining an optical glass with excellent thermal stability and meltability, it is preferable that the K2O content be within the above range. On the other hand, if the K2O content is too low, the thermal stability and meltability may decrease. Also, if the K2O content is too high, the thermal stability may decrease.

[0058] In the optical glass according to this embodiment, the upper limit of the CsO content is preferably 5%, and more preferably 3%, 2%, and 1%, in that order. The lower limit of the CsO content is preferably 0%. The CsO content may even be 0%.

[0059] CsO has the function of improving the thermal stability of glass, but if the content is too high, the thermal stability, chemical durability, and weather resistance of the glass will decrease. Therefore, it is preferable that the content of CsO be within the above range.

[0060] In the optical glass according to this embodiment, the upper limit of the MgO content is preferably 3.80%, and more preferably 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the MgO content is preferably 0%, and the MgO content may be 0%.

[0061] In the optical glass according to this embodiment, the upper limit of the CaO content is preferably 3.80%, and more preferably 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the CaO content is preferably 0%, and the CaO content may be 0%.

[0062] In the optical glass according to this embodiment, the upper limit of the SrO content is preferably 3.80%, and more preferably 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the SrO content is preferably 0%. The SrO content may be 0%.

[0063] In the optical glass according to this embodiment, the upper limit of the BaO content is preferably 3.80%, and more preferably 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the BaO content is preferably 0%, and the BaO content may be 0%.

[0064] MgO, CaO, SrO, and BaO are all glass components that improve the thermal stability and devitrification resistance of the glass. However, if the content of these glass components increases, the high dispersibility of the glass is impaired and the thermal stability and devitrification resistance of the glass are reduced. Therefore, it is preferable that the content of each of these glass components be within the above-mentioned range.

[0065] In the optical glass according to this embodiment, the upper limit of the ZnO content is preferably 3.80%, and more preferably 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the ZnO content is preferably 0%, and the ZnO content may be 0%.

[0066] It is preferable that the ZnO content be within the above range, from the viewpoints of improving the thermal stability of the glass, suppressing an increase in the specific gravity of the glass, and obtaining an optical glass having desired optical constants.

[0067] In the optical glass according to this embodiment, the upper limit of the ZrO2 content is preferably 5.80%, and more preferably 4.00%, 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the ZrO2 content is preferably 0%. The ZrO2 content may be 0%.

[0068] ZrO2 is a glass component that functions to improve the thermal stability and devitrification resistance of glass. However, if the ZrO2 content is too high, the thermal stability tends to decrease. Furthermore, ZrO2 contributes less to high dispersion than TiO2. Therefore, from the viewpoint of maintaining good thermal stability and devitrification resistance of the glass while obtaining the desired optical constants, it is preferable to set the ZrO2 content within the above range.

[0069] In the optical glass according to this embodiment, the upper limit of the WO3 content is preferably 5.80%, and more preferably 4.00%, 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the WO3 content is preferably 0%. The WO3 content may be 0%.

[0070] Although WO3 is a component that contributes to high dispersion, its contribution to high dispersion is smaller than that of TiO2. From the viewpoints of increasing the transmittance of the glass while obtaining the desired optical constants and suppressing an increase in the specific gravity of the glass, it is preferable that the WO3 content be within the above range.

[0071] In the optical glass according to this embodiment, the upper limit of Bi2O3 is preferably 5.80%, and more preferably 4.00%, 3.00%, 2.00%, and 1.00%, in that order. The lower limit of the Bi2O3 content is preferably 0%. The Bi2O3 content may be 0%.

[0072] Although Bi2O3 is a component that contributes to high dispersion, its contribution to high dispersion is smaller than that of TiO2. From the viewpoints of improving the thermal stability of the glass and suppressing an increase in the specific gravity of the glass while obtaining the desired optical constants, it is preferable to set the Bi2O3 content within the above range. On the other hand, if the Bi2O3 content is too high, the specific gravity increases and there is a risk of the glass becoming more colored.

[0073] In the optical glass according to this embodiment, the upper limit of the Ta2O5 content is preferably 10.0%, and more preferably 5.0%, 3.0%, and 1.0%, in that order. The lower limit of the Ta2O5 content is preferably 0%. The Ta2O5 content may be 0%.

[0074] Ta2O5 is a glass component that improves the thermal stability and devitrification resistance of glass. On the other hand, Ta2O5 increases the refractive index and makes the glass highly dispersible. Furthermore, as the Ta2O5 content increases, the thermal stability of the glass decreases, making it more likely that glass raw materials will remain unmelted when melting the glass. Therefore, it is preferable to keep the Ta2O5 content within the above range. Furthermore, Ta2O5 is an extremely expensive component compared to other glass components, and increasing the Ta2O5 content increases the glass production cost. Furthermore, because Ta2O5 has a larger molecular weight than other glass components, it increases the specific gravity of the glass, which may result in an increase in the weight of the optical element.

[0075] In the optical glass according to this embodiment, the upper limit of the Sc2O3 content is preferably 2%, and the lower limit of the Sc2O3 content is preferably 0%.

[0076] In the optical glass according to this embodiment, the upper limit of the HfO2 content is preferably 2%, and the lower limit of the HfO2 content is preferably 0%.

[0077] Both Sc2O3 and HfO2 have the function of increasing the refractive index nd and are expensive components, so it is preferable that the contents of Sc2O3 and HfO2 are within the above ranges.

[0078] In the optical glass according to this embodiment, the upper limit of the Lu2O3 content is preferably 2%, and the lower limit of the Lu2O3 content is preferably 0%.

[0079] Lu2O3 has the function of increasing the refractive index nd. In addition, because of its large molecular weight, it is also a glass component that increases the specific gravity of the glass. Therefore, it is preferable that the content of Lu2O3 be within the above range.

[0080] In the optical glass according to this embodiment, the upper limit of the GeO2 content is preferably 2%, and the lower limit of the GeO2 content is preferably 0%.

[0081] GeO2 has the function of increasing the refractive index nd and 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 within the above range.

[0082] In the optical glass according to this embodiment, the upper limit of the La2O3 content is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0%, in that order. The lower limit of the La2O3 content is preferably 0%. The La2O3 content may be 0%.

[0083] If the La2O3 content is large, the thermal stability and devitrification resistance of the glass decrease, and the glass becomes more susceptible to devitrification during production. Therefore, from the viewpoint of suppressing the decrease in thermal stability and devitrification resistance, it is preferable to set the La2O3 content within the above range.

[0084] In the optical glass according to this embodiment, the upper limit of the Gd2O3 content is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0%, in that order. The lower limit of the Gd2O3 content is preferably 0%.

[0085] If the Gd2O3 content is too high, the thermal stability and devitrification resistance of the glass will decrease, making the glass more susceptible to devitrification during production. Furthermore, if the Gd2O3 content is too high, the specific gravity of the glass will increase, which is undesirable. Therefore, from the viewpoint of suppressing an increase in specific gravity while maintaining good thermal stability and devitrification resistance of the glass, it is preferable to set the Gd2O3 content within the above range.

[0086] In the optical glass according to this embodiment, the upper limit of the Y2O3 content is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0%, in that order. The lower limit of the Y2O3 content is preferably 0%. The Y2O3 content may be 0%.

[0087] If the Y2O3 content is too high, the thermal stability and devitrification resistance of the glass will decrease. Therefore, from the viewpoint of suppressing the decrease in thermal stability and devitrification resistance, it is preferable to set the Y2O3 content within the above range.

[0088] In the optical glass according to this embodiment, the upper limit of the Yb2O3 content is preferably 2%, and the lower limit of the Yb2O3 content is preferably 0%.

[0089] Yb2O3 has a larger molecular weight than La2O3, Gd2O3, and Y2O3, and therefore increases the specific gravity of the glass. An increase in the specific gravity of the glass increases the mass of the optical element. For example, if a heavy lens is incorporated into an autofocus imaging lens, the power required to drive the lens during autofocusing increases, resulting in rapid battery drain. Therefore, it is desirable to reduce the Yb2O3 content and prevent the increase in the specific gravity of the glass.

[0090] Furthermore, if the Yb2O3 content is too high, the thermal stability and devitrification resistance of the glass will decrease. From the viewpoint of preventing a decrease in the thermal stability of the glass and suppressing an increase in specific gravity, it is preferable that the Yb2O3 content be within the above range.

[0091] The optical glass according to this embodiment is preferably composed primarily of the above-mentioned glass components, namely, P2O5, B2O3, SiO2, Na2O, TiO2, Al2O3, Nb2O5, Li2O, K2O, Cs2O, MgO, CaO, SrO, BaO, ZnO, ZrO2, WO3, Bi2O3, Ta2O5, Sc2O3, HfO2, Lu2O3, GeO2, La2O3, Gd2O3, Y2O3, and Yb2O3, and 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 even more preferably 99.5% or more.

[0092] The optical glass according to this embodiment 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.

[0093] <Other ingredient composition> In the optical glass according to this embodiment, the upper limit of the TeO2 content is preferably 2%. The lower limit of the TeO2 content is preferably 0%. Since TeO2 is toxic, it is preferable to reduce the TeO2 content.

[0094] Pb, As, Cd, Tl, Be, and Se are all toxic, so it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0095] U, Th, and Ra are all radioactive elements, so it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0096] V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm increase the coloration of the glass and can be sources of fluorescence, so it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0097] Sb2O3, SnO2, and CeO2 are optional elements that function as fining agents. Of these, Sb2O3 has a significant fining effect. However, Sb2O3 is highly oxidizing, and adding large amounts of Sb2O3 oxidizes the molding surfaces of the press mold during precision press molding. As a result, the molding surfaces deteriorate significantly over repeated precision press molding, making precision press molding impossible. This also reduces the surface quality of the molded optical elements. Furthermore, SnO2 and CeO2 have a weaker fining effect than Sb2O3. Furthermore, adding large amounts of CeO2 intensifies the coloring of the glass. Therefore, when adding fining agents, it is preferable to add Sb2O3, SnO2, and CeO2 while paying careful attention to the amount added.

[0098] The Sb2O3 content is expressed as an exclusive percentage. That is, when the total content of all glass components other than Sb2O3, SnO2, and CeO2 is taken as 100 mass%, the Sb2O3 content is preferably 1 mass% or less, and more preferably 0.2 mass% or less, 0.05 mass% or less, 0.02 mass% or less, and 0.01 mass% or less, in that order. The Sb2O3 content may be 0 mass%.

[0099] The SnO2 content is also expressed as an exclusive percentage. That is, when the total content of all glass components other than SnO2, Sb2O3, and CeO2 is taken as 100 mass%, the SnO2 content is preferably 1 mass% or less, more preferably 0.2 mass% or less, and even more preferably 0.02 mass% or less. The SnO2 content may be 0 mass%, and it is preferable that SnO2 is substantially not contained. By keeping the SnO2 content within the above range, the clarity of the glass can be improved.

[0100] The CeO2 content is also expressed as an exclusive percentage. That is, when the total content of all glass components other than CeO2, Sb2O3, and SnO2 is taken as 100 mass%, the CeO2 content is preferably 1 mass% or less, more preferably 0.2 mass% or less, and even more preferably 0.02 mass% or less. The CeO2 content may be 0 mass%, and it is preferable that CeO2 is substantially not contained. By setting the CeO2 content within the above range, the clarity of the glass can be improved.

[0101] (glass properties) <Specific gravity of glass> In the optical glass according to this embodiment, the specific gravity is preferably 2.90 or less, with 2.80 or less and 2.77 or less being more preferred. There are no particular restrictions on the lower limit of the specific gravity, but it is usually 2.50. If the specific gravity of the glass can be reduced, the weight of the lens can be reduced. As a result, the power consumption of the autofocus drive of the camera lens equipped with the lens can be reduced.

[0102] <Glass transition temperature Tg> The glass transition temperature Tg of the optical glass according to this embodiment is preferably 480°C or lower, and more preferably 470°C or lower, 465°C or lower, and 462°C or lower in that order. The lower limit of the glass transition temperature Tg is usually 400°C, and preferably 447°C.

[0103] By ensuring that the upper limit of the glass transition temperature Tg satisfies the above range, increases in the molding temperature and annealing temperature of the glass can be suppressed, thereby reducing thermal damage to press molding equipment and annealing equipment. Furthermore, by ensuring that the lower limit of the glass transition temperature Tg satisfies the above range, it becomes easier to maintain good thermal stability of the glass while maintaining the desired Abbe number and refractive index.

[0104] <Average linear expansion coefficient α 100-300 > In the optical glass according to this embodiment, the average linear expansion coefficient α 100-300 The lower limit is preferably 150 × 10 -7 °C -1and 153×10 -7 °C -1 , 155×10 -7 °C -1 , 157×10 -7 °C -1 In addition, the average linear expansion coefficient α 100-300 The upper limit of is preferably 175×10 from the viewpoint of maintaining the thermal stability of the glass and obtaining the desired optical properties. -7 °C -1 and 172 × 10 -7 °C -1 , 170×10 -7 °C -1 , 168×10 -7 °C -1 The order of preference is:

[0105] Average linear expansion coefficient α 100-300 The average linear expansion coefficient α is measured in accordance with the JOGIS08-2019 standard. The sample is a round bar with a length of 20 mm ± 0.5 mm and a diameter of 5 mm ± 0.5 mm. With a load of 98 mN applied to the sample, it is heated at a constant rate of 4°C per minute, and the temperature and sample elongation are measured every second. 100-300 is the average value of the linear expansion coefficient at 100 to 300°C. In this specification, the average linear expansion coefficient α is expressed as [°C -1 ], but the unit is [K -1 ], the value of the average linear expansion coefficient α is the same.

[0106] <Liquidus temperature LT> In the optical glass according to this embodiment, the upper limit of the liquidus temperature LT is preferably 1000°C, and more preferably 990°C, 980°C, and 970°C in that order. The lower limit of the liquidus temperature LT is preferably 920°C, and more preferably 930°C, 940°C, and 950°C in that order. From the viewpoint of improving the thermal stability of the glass, it is preferable that the liquidus temperature LT be within the above range.

[0107] The liquidus temperature LT is determined as follows: 10 cc (10 ml) of glass is placed in a platinum crucible and melted at 1100°C to 1250°C for 15 to 20 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 holding temperature is 900°C or higher in 5°C or 10°C increments, and after holding for 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 LT.

[0108] (Optical glass manufacturing) The optical glass according to this embodiment may be produced by blending glass raw materials to obtain the above-described predetermined composition, and then 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 a batch raw material, which is then placed in a quartz crucible or platinum crucible and roughly melted (rough melted). The molten material obtained by rough melting is then rapidly cooled and pulverized to produce cullet. The cullet is then placed in a platinum crucible, heated, and remelted (remelted) to produce a glass melt, which is then refined and homogenized, and then formed and slowly cooled to obtain the optical glass. Known methods may be used to form and slowly cool the glass melt.

[0109] 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.

[0110] (Manufacturing of optical elements, etc.) To produce an optical element using the optical glass according to this embodiment, a known method may be applied. For example, glass raw materials are melted to form a glass melt, which is then 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.

[0111] 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.

[0112] Examples of optical elements include various lenses such as spherical lenses, prisms, and diffraction gratings.

[0113] (Example) 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.

[0114] Glass samples having the glass compositions shown in Tables 1(1)-(2), 2(1)-(2), and 3(1)-(2) were prepared by the following procedure, and various evaluations were performed. Comparative Example 1 is a comparative example with a high B2O3 content, and has the same composition as Sample No. 5 in the examples of JP 2022-108395 A. Comparative Example 2 is a comparative example with a low Al2O3 content and a high B2O3 content, and has the same composition as Sample No. 31 in the examples of JP 2022-108395 A.

[0115] [Preparation of glass samples] The compound raw materials corresponding to each component, i.e., raw materials such as phosphates, carbonates, and oxides, were weighed and thoroughly mixed to prepare blended raw materials so that the resulting optical glass would have the glass composition shown in Tables 1(1) and 1(2). The blended raw materials were placed in a platinum crucible, heated to 900 to 1350°C in an air atmosphere to melt, and then homogenized and refined by stirring to obtain a molten glass. The molten glass was cast into a mold and molded, and then slowly cooled to obtain a block-shaped glass sample.

[0116] [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 Table 1(1) to (2).

[0117] [Glass sample evaluation] The obtained glass samples were measured for refractive index nd, Abbe number νd, specific gravity, glass transition temperature Tg, and average linear expansion coefficient α by the following methods. 100-300 The liquidus temperature LT was measured, and the results are shown in Table 4 (1) and (2).

[0118] [1] Refractive index nd and Abbe number νd Measurements were made based on the Japan Optical Glass Industry Association standard JOGIS-01.

[0119] [2] Specific gravity Measurements were made based on the Japan Optical Glass Industry Association standard JOGIS-05.

[0120] [3] Glass transition temperature Tg The glass transition temperature Tg was determined based on a DSC chart obtained by heating the solid glass using a differential scanning calorimeter DSC3300SA (NETZSCH Japan).

[0121] [4] Average linear expansion coefficient α 100-300 The average linear expansion coefficient of the obtained glass samples was measured in accordance with the provisions of JOGIS08-2019. The average linear expansion coefficient was measured using a thermomechanical analyzer TMA4000SE (NETZSCH Japan). The sample was a round bar with a length of 20 mm ± 0.5 mm and a diameter of 5 mm ± 0.5 mm. During the measurement, a load of 98 mN was applied to the sample, and the temperature was raised at a constant rate of 4°C per minute, while the temperature and sample elongation were measured in 1-second intervals. The average value of the linear expansion coefficients from 100 to 300°C was taken as the average linear expansion coefficient α 100-300 It was decided.

[0122] [5] Liquidus temperature LT 10 cc (10 ml) of glass was placed in a platinum crucible and melted at 1100-1250°C for 15-20 minutes, then cooled to below the glass transition temperature Tg. The glass, together with the platinum crucible, was placed in a furnace at the specified temperature and held there for 2 hours. The temperature was 900°C or higher in 5- or 10-degree increments, and after 2 hours, the glass was cooled and the presence or absence of crystals inside the glass was observed under a 100x optical microscope. The lowest temperature at which no crystals precipitated was taken as the liquidus temperature LT.

[0123] [Table 1(1)]

[0124] [Table 1(2)]

[0125] [Table 2(1)]

[0126] [Table 2(2)]

[0127] [Table 3(1)]

[0128] [Table 3(2)]

[0129] [Table 4(1)]

[0130] [Table 4(2)]

[0131] Example 2 The glass sample obtained in Example 1 was cut and ground to prepare cut pieces. The cut pieces were press-molded using a reheat press to prepare optical element blanks. The optical element blanks were precision annealed to precisely adjust the refractive index to the required value, and then ground and polished using known methods to obtain various lenses, such as biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses, and convex meniscus lenses.

[0132] 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.

[0133] 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 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. P 2 O 5 The content is 26.00% by mass or more, B 2 O 3 The content is 1.00% by mass or less, SiO 2 The content is 5.00% by mass or less, Na 2 The O content is 10.00 to 28.00 mass%; TiO 2 The content is 8.00 to 24.00 mass%; Al 2 O 3 The content is 2.00 to 10.00 mass %, Nb 2 O 5 The content is 10.00% by mass or less, Al 2 O 3 B relative to the content of 2 O 3 The mass ratio of the content [B 2 O 3 / Al 2 O 3 ] is 0.500 or less, Li 2 O and Na 2 K relative to the total content of O 2 Mass ratio of the content of O [K 2 O / (Li 2 O + Na 2 O)] is 0.100 or more, WO 3 , Bi 2 O 3 , and ZrO 2 The total content [WO 3 +Bi 2 O 3 + ZrO 2 ] is 5.80% by mass or less, TiO 2 and Nb 2 O 5 The total content [TiO 2 +Nb 2 O 5 ] is 10.00 to 24.00 mass %.

2. WO 3 and Bi 2 O 3 The total content [WO 3 +Bi 2 O 3 2. The optical glass according to claim 1, wherein the content of ZnO is 5.80 mass % or less.

3. 2. The optical glass according to claim 1, wherein the total content of ZnO, MgO, CaO, SrO, and BaO [ZnO + MgO + CaO + SrO + BaO] is 3.80 mass % or less.

4. Al 2 O 3 Li relative to the content of 2 O, Na 2 O.K. 2 The mass ratio of the total content of O, MgO, CaO, SrO, and BaO [(Li 2 O + Na 2 O+K 2 O+MgO+CaO+SrO+BaO) / Al 2 O 3 2. The optical glass according to claim 1, wherein the refractive index is 6.400 or less.

5. 2. The optical glass according to claim 1, wherein the Abbe number vd is 27.00 to 33.

00.

6. 2. The optical glass according to claim 1, wherein the refractive index nd is 1.600 to 1.

660.

7. 2. The optical glass according to claim 1, wherein the Abbe number vd and the refractive index nd satisfy the following formula: nd<-0.0106×νd+1.950

8. An optical element made of the optical glass according to any one of claims 1 to 7.

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