Optical glass and optical element

Abstract

The invention relates to high-dispersion optical glass with a refractive index in a range of 1.55-1.68 and an optical element. The optical glass comprises B2O3 and K2O, and is prepared from the following components in percentage by mass: 35.0 to 60.0 percent of P2O5, less than 0.39 percent of [B2O3 / P2O5], 5.0 to 40.0 percent of Na2O, less than 15.0 percent of BaO, less than 18.0 percent of [MgO + CaO + SrO + BaO], less than 15.0 percent of ZnO, less than 25.0 percent of Nb2O5, less than 5.0 percent of WO3, less than 10.0 percent of Bi2O3 and 3.0 to 30.0 percent of [TiO2 + Nb2O5 + WO3 + Bi2O3 + Ta2O5].

Description

[0001] This application is a divisional application of the invention patent application with application number 202210021089.4, the original application being filed on January 10, 2022, and the invention being entitled "Optical Glass and Optical Components". Technical Field

[0002] This invention relates to an optical glass and an optical element. Background Technology

[0003] In optical system design, optical glass with a refractive index (nd) in the range of 1.55 to 1.68 and high dispersion has high application value in correcting chromatic aberration, improving the performance and miniaturization of optical systems.

[0004] Patent documents 1-3 disclose optical glass with a low Abbe number νd. However, the optical glass in patent documents 1-3 has a high refractive index nd. Furthermore, optical constants were measured on the optical glass disclosed in patent document 4, and it was found that although the Abbe number νd is relatively low, the refractive index nd is high. That is, none of the patent documents 1-4 propose an optical glass with a refractive index nd in the range of 1.55-1.68 and high dispersion.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent document 1: Japanese Patent Application Publication No. 2016-74581.

[0008] Patent Document 2: Japanese Patent Application Publication No. 2018-70414.

[0009] Patent document 3: International Publication No. 2013 / 031385.

[0010] Patent document 4: Japanese Patent Publication No. 2020-505311. Summary of the Invention

[0011] The problem the invention aims to solve

[0012] Therefore, the object of the present invention is to provide an optical glass with a refractive index nd in the range of 1.55 to 1.68 and high dispersion, and an optical element formed from the above-mentioned optical glass.

[0013] Solution for solving the problem

[0014] The key points of this invention are as follows.

[0015] (1) An optical glass comprising B2O3 and K2O as glass components.

[0016] The P2O5 content is 35.0–60.0% by mass.

[0017] The mass ratio of B2O3 content to P2O5 content [B2O3 / P2O5] is less than 0.39.

[0018] The Na2O content is 5.0–40.0% by mass.

[0019] The BaO content is less than 15.0% by mass.

[0020] The total content of MgO, CaO, SrO, and BaO [MgO+CaO+SrO+BaO] is less than 18.0% by mass.

[0021] The ZnO content is less than 15.0% by mass.

[0022] The Nb₂O₅ content is below 25.0% by mass.

[0023] The WO3 content is below 5.0% by mass.

[0024] The Bi2O3 content is less than 10.0% by mass.

[0025] The total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5] is 3.0–30.0% by mass.

[0026] The total content of TiO2, Nb2O5, WO3, Bi2O3, Ta2O5 and ZnO [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5+ZnO] is 3.0 to 33.0 by mass.

[0027] (2) An optical element formed from the optical glass described in (1) above.

[0028] Invention Effects

[0029] According to the present invention, it is possible to provide an optical glass with a refractive index nd in the range of 1.55 to 1.68 and high dispersion, and an optical element formed from the above-described optical glass. Detailed Implementation

[0030] In this invention and specification, unless otherwise stated, the glass composition of the optical glass is expressed on an oxide basis. Here, "oxide-based glass composition" refers to the glass composition obtained by completely decomposing the glass raw material during melting and converting it into the form of oxides in the optical glass. The description of each glass component follows convention and is recorded as SiO2, TiO2, etc. Unless otherwise stated, the content and total content of the glass components are on a mass basis, and "%" means "mass %".

[0031] The content of the glass component can be quantified using known methods such as inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Furthermore, in this specification and this invention, a content of 0% for a constituent component means that the constituent component is substantially not present, allowing it to exist at an unavoidable impurity level.

[0032] Furthermore, unless otherwise stated, the refractive index in this specification refers to the refractive index nd at the d line (wavelength 587.56 nm) of helium.

[0033] Furthermore, the Abbe number νd, as a value representing properties related to dispersion, is expressed by the following formula. Here, 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.

[0034]

[0035] The optical glass of this embodiment will be described in detail.

[0036] The optical glass of this embodiment contains B2O3 as a glass component. The lower limit of the B2O3 content is preferably 0.3%, and more preferably 0.6%, 0.8%, and 1.0%. Furthermore, the upper limit of the B2O3 content is preferably 15%, and more preferably 13.0%, 11.0%, and 10.0%.

[0037] B2O3 is a network-forming component of glass and plays a role in improving the thermal stability of glass. By maintaining the B2O3 content within the aforementioned range, the thermal stability and devitrification resistance of the glass can be improved. On the other hand, when the B2O3 content is too high, the thermal stability and devitrification resistance of the glass tend to decrease.

[0038] The optical glass of this embodiment contains K2O as a glass component. The lower limit of the K2O content is preferably 3.0%, and more preferably 5.0%, 7.0%, 8.5%, 9.00%, and 9.20%. Furthermore, the upper limit of the K2O content is preferably 20.0%, and more preferably 17.0%, 15.0%, and 14.0%.

[0039] K₂O improves the thermal stability and solubility of glass. By maintaining the K₂O content within the aforementioned range, optical glass with excellent thermal stability and solubility can be obtained. On the other hand, if the K₂O content is too low, both thermal stability and solubility may decrease. Furthermore, if the K₂O content is too high, thermal stability may decrease.

[0040] In the optical glass of this embodiment, the P2O5 content is 35.0% to 60.0%. The lower limit of the P2O5 content is preferably 40.0%, and more preferably 41.0%, 42.0%, 43.0%, 43.5%, and 45.5%. Furthermore, the upper limit of the P2O5 content is preferably 60.0%, and more preferably 58.0%, 56.0%, and 55.0%.

[0041] P2O5 is a network-forming component in glass and is essential for containing more high-dispersion components in the glass. By maintaining the P2O5 content within the aforementioned range, optical glass with excellent thermal stability and desired optical constants can be obtained. On the other hand, if the P2O5 content is too low, it may be impossible to obtain optical glass with the desired optical constants. Furthermore, if the P2O5 content is too high, the thermal stability of the glass may deteriorate.

[0042] In the optical glass of this embodiment, the mass ratio of B2O3 content to P2O5 content [B2O3 / P2O5] is 0.39 or less. The upper limit of this mass ratio is preferably 0.34, and more preferably 0.30, 0.27, or 0.25. Furthermore, the lower limit of this mass ratio is preferably 0.005, and more preferably 0.01, 0.015, or 0.02.

[0043] By maintaining the mass ratio [B2O3 / P2O5] within the aforementioned range, optical glass with excellent thermal stability can be obtained. On the other hand, if this mass ratio is too large, the thermal stability of the glass may deteriorate.

[0044] In the optical glass of this embodiment, the Na2O content is 5.0% to 40.0%. The lower limit of the Na2O content is preferably 10%, and more preferably 12.0%, 13.5%, 15.0%, 16.5%, 17.5%, and 18.0%. Furthermore, the upper limit of the Na2O content is preferably 30.0%, and more preferably 27.0%, 25.0%, and 23.0%.

[0045] Na₂O improves the thermal stability and solubility of glass. By maintaining the Na₂O content within the aforementioned range, optical glass with excellent thermal stability and solubility can be obtained. On the other hand, if the Na₂O content is too low, both thermal stability and solubility may decrease. Furthermore, if the Na₂O content is too high, thermal stability may decrease.

[0046] In the optical glass of this embodiment, the BaO content is 15.0% or less. The upper limit of the BaO content is preferably 13.0%, and more preferably 11.0%, 9.0%, and 7.0%. Furthermore, the BaO content is preferably low, and the lower limit is preferably 0%, and more preferably as low as 1.0%, 2.0%, and 3.0%. The BaO content may also be 0%.

[0047] BaO is also a glass component that improves the thermal stability and devitrification resistance of glass. By maintaining the BaO content within the aforementioned range, optical glass with excellent thermal stability and devitrification resistance can be obtained. On the other hand, when the BaO content is too high, it impairs the high dispersion of the glass, and the thermal stability and devitrification resistance of the glass may decrease.

[0048] In the optical glass of this embodiment, the total content of MgO, CaO, SrO, and BaO [MgO+CaO+SrO+BaO] is 18.0% or less. The upper limit of this total content is preferably 16.0%, and more preferably 14.0%, 12.0%, and 10.0%. Furthermore, this total content is preferably low, with a lower limit preferably 0%, and more preferably as low as 1.0%, 2.0%, and 3.0%. The total content may also be 0%.

[0049] By ensuring the total content [MgO+CaO+SrO+BaO] is within the aforementioned range, thermal stability and devitrification resistance can be maintained without compromising high dispersion. On the other hand, if this total content is too high, it impairs the high dispersion of the glass, and the glass's thermal stability and devitrification resistance may decrease.

[0050] In the optical glass of this embodiment, the ZnO content is 15.0% or less. The upper limit of the ZnO content is preferably 13.0%, and more preferably 11.0%, 9.0%, and 7.0%. Furthermore, the ZnO content is preferably low, and the lower limit is preferably 0%, and more preferably as low as 1.0%, 2.0%, and 3.0%. The ZnO content may also be 0%.

[0051] By maintaining the ZnO content within the aforementioned range, the thermal stability of the glass can be improved, and the increase in the glass's specific gravity can be suppressed. Furthermore, optical glass with desired optical constants can be obtained.

[0052] In the optical glass of this embodiment, the Nb2O5 content is 25.0% or less. The upper limit of the Nb2O5 content is preferably 20.0%, and more preferably 15.0%, 10.0%, 7.0%, and 5.0%. Furthermore, the Nb2O5 content is preferably low, with a lower limit preferably 0%, and more preferably as low as 1.0%, 2.0%, and 3.0%. The Nb2O5 content can also be 0%.

[0053] Nb₂O₅ is a component that contributes to high refractive index and high dispersion. Therefore, by keeping the Nb₂O₅ content within the aforementioned range, optical glass with desired optical constants can be obtained. On the other hand, when the Nb₂O₅ content is too high, the thermal stability of the glass may decrease, and the coloration of the glass may be enhanced.

[0054] In the optical glass of this embodiment, the WO3 content is 5.0% or less. The upper limit of the WO3 content is preferably 4.5%, and more preferably 4.0%, 3.5%, and 3.0%. Furthermore, the WO3 content is preferably low, and the lower limit is preferably 0%, and more preferably as low as 0.5%, 1.0%, and 1.5%. The WO3 content may also be 0%.

[0055] By keeping the WO3 content within the above range, the transmittance of the glass can be improved, and the increase in the specific gravity of the glass can be suppressed.

[0056] In the optical glass of this embodiment, the content of Bi2O3 is 10.0% or less. The upper limit of the Bi2O3 content is preferably 8.0%, and more preferably 7.0%, 6.0%, and 5.0%. Furthermore, the content of Bi2O3 is preferably low, and the lower limit is preferably 0%, and more preferably as low as 1.0%, 1.5%, and 2.0%. The content of Bi2O3 may also be 0%.

[0057] By maintaining the Bi₂O₃ content within the aforementioned range, the thermal stability of the glass can be improved, and the increase in the glass's specific gravity can be suppressed. On the other hand, when the Bi₂O₃ content is excessive, the specific gravity may increase, and the glass's coloration may be enhanced.

[0058] In the optical glass of this embodiment, the total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5] is 3.0% to 30.0%. The lower limit of this total content is preferably 6.0%, and more preferably 8.0%, 10.0%, and 12.0%. Furthermore, the upper limit of this total content is preferably 29.0%, and more preferably 27.0%, 25.0%, 22.0%, 20.0%, and 18.0%.

[0059] TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 are components that contribute to the high dispersion of glass. Therefore, by keeping the total content [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5] within the above-mentioned range, optical glass with desired optical constants can be obtained. Furthermore, the thermal stability of the glass can be improved. On the other hand, if the total content is too high, it may be impossible to obtain optical glass with desired optical constants, and the thermal stability of the glass may decrease, while the coloration of the glass may be enhanced.

[0060] In the optical glass of this embodiment, the total content of TiO2, Nb2O5, WO3, Bi2O3, Ta2O5, and ZnO [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5+ZnO] is 3.0% to 33.0%. The lower limit of this total content is preferably 6.0%, and more preferably 8.0%, 10.0%, and 12.0%. Furthermore, the upper limit of this total content is preferably 29.0%, and more preferably 27.0%, 25.0%, 22.0%, 20.0%, and 18.0%.

[0061] By ensuring the total content [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5+ZnO] is within the aforementioned range, optical glass with desired optical constants can be obtained. Furthermore, the thermal stability of the glass can be improved. On the other hand, if the total content is excessive, it may be impossible to obtain optical glass with the desired optical constants, and the thermal stability of the glass may decrease, while the coloration of the glass may be enhanced.

[0062] Regarding the content and ratio of glass components other than those described above in the optical glass of this embodiment, non-limiting examples are shown below.

[0063] The upper limit of the mass ratio of the total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 to the total content of P2O5, B2O3, SiO2, Li2O, Na2O, K2O, and Cs2O [(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5) / (P2O5+B2O3+SiO2+Li2O+Na2O+K2O+Cs2O)] is preferably 0.45, and more preferably 0.43, 0.40, 0.37, 0.35, and 0.33. Furthermore, the lower limit of this mass ratio is preferably 0.10, and more preferably 0.12, 0.14, and 0.15.

[0064] From the viewpoint of obtaining optical glass with desired optical constants, the preferred mass ratio [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5) / (P2O5+B2O3+SiO2+Li2O+Na2O+K2O+Cs2O)] is within the range described above.

[0065] In the optical glass of this embodiment, the lower limit of the mass ratio of TiO2 content to the total content of P2O5 and B2O3 [TiO2 / (P2O5+B2O3)] is preferably 0.10, and more preferably 0.16, 0.21, and 0.24. Furthermore, the upper limit of this mass ratio is preferably 0.40, and more preferably 0.37, 0.35, and 0.33.

[0066] TiO2 plays a particularly significant role in high dispersion in high-refractive-index, high-dispersion compositions. However, excessive TiO2 content may decrease thermal stability and devitrification resistance. Therefore, from the viewpoint of obtaining optical glass with high dispersion, excellent thermal stability, and superior devitrification resistance, a mass ratio [TiO2 / (P2O5+B2O3)] within the aforementioned range is preferred.

[0067] In the optical glass of this embodiment, the lower limit of the mass ratio of the total content of P2O5, B2O3, and SiO2 to the total content of Li2O, Na2O, K2O, and Cs2O [(P2O5+B2O3+SiO2) / (Li2O+Na2O+K2O+Cs2O)] is preferably 0.80, and more preferably 1.00, 1.20, and 1.30. Furthermore, the upper limit of this mass ratio is preferably 2.60, and more preferably 2.40, 2.20, and 2.10.

[0068] From the viewpoint of obtaining optical glass with excellent thermal stability, the preferred mass ratio [(P2O5+B2O3+SiO2) / (Li2O+Na2O+K2O+Cs2O)] is within the range mentioned above.

[0069] In the optical glass of this embodiment, the lower limit of the mass ratio of TiO2 content to the total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 [TiO2 / (TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)] is preferably 0.20, and more preferably 0.30, 0.40, and 0.50. Furthermore, the upper limit of this mass ratio is preferably 0.90, and more preferably 0.80, 0.70, and 0.60. This mass ratio can also be 1.00.

[0070] TiO2 is a component with a particularly large effect on high dispersion in high refractive index and high dispersion components. Therefore, from the viewpoint of obtaining optical glass with desired optical constants and excellent thermal stability and devitrification resistance, the mass ratio [TiO2 / (TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)] is preferably in the above range.

[0071] In the optical glass of this embodiment, the lower limit of the mass ratio of Na2O content to K2O content [Na2O / K2O] is preferably 0.80, and more preferably 1.00, 1.20, and 1.30. Furthermore, the upper limit of this mass ratio is preferably 2.70, and more preferably 2.50, 2.30, and 2.20.

[0072] From the viewpoint of improving the thermal stability and devitrification resistance of glass, a mass ratio [Na₂O / K₂O] within the above-mentioned range is preferred. In particular, from the viewpoint of suppressing excessive decrease in refractive index and decrease in chemical durability, a lower limit of this mass ratio within the above-mentioned range is preferred.

[0073] In the optical glass of this embodiment, the upper limit of the Al2O3 content is preferably 15.0%, and more preferably 11.0%, 8.0%, and 6.0%. Furthermore, the lower limit of the Al2O3 content is preferably 0%, and more preferably 0.5%, 1.0%, and 1.5%. The Al2O3 content may also be 0%.

[0074] From the viewpoint of suppressing the decline in the glass's anti-devitrification properties, the Al2O3 content is preferably within the above-mentioned range.

[0075] In the optical glass of this embodiment, the upper limit of the SiO2 content is preferably 5.0%, and more preferably 4.0%, 3.0%, and 2.0%. The lower limit of the SiO2 content is preferably 0%. The SiO2 content may also be 0%.

[0076] SiO2 is a network-forming component of glass, which improves the thermal stability, chemical durability, and weather resistance of glass, increases the viscosity of molten glass, and facilitates the molding of molten glass. On the other hand, when the SiO2 content is high, the glass tends to have reduced devitrification resistance. Therefore, from the viewpoint of improving the thermal stability and devitrification resistance of glass, the upper limit of the SiO2 content is preferably within the range described above.

[0077] Furthermore, when melting glass, quartz glass melting vessels, such as quartz glass crucibles, are sometimes used. In this case, because a small amount of SiO2 dissolves into the molten glass from the melting vessel, the resulting glass will contain a small amount of SiO2 even if the glass raw material does not contain SiO2. The amount of SiO2 mixed into the glass from the quartz glass melting vessel also depends on the melting conditions, but it is approximately 0.5 to 1% by mass relative to, for example, the total content of all glass components. Compared to keeping the content of glass components other than SiO2 constant, the amount of SiO2 increases by approximately 0.5 to 1% by mass. Furthermore, the above amount increases or decreases depending on the melting conditions. Due to the SiO2 content, optical properties such as refractive index and Abbe number change; therefore, by fine-tuning the content of glass components other than SiO2, optical glass with desired optical properties can be obtained.

[0078] In the optical glass of this embodiment, the lower limit of the TiO2 content is preferably 0%, and more preferably 5.0%, 9.0%, and 12.0%. The TiO2 content may also be 0%. Furthermore, the upper limit of the TiO2 content is preferably 30.0%, and more preferably 25.0%, 21.0%, and 18.0%.

[0079] TiO2 greatly contributes to high dispersion. On the other hand, TiO2 readily increases the coloration of glass. Furthermore, during the process of forming and slowly cooling molten glass to obtain optical glass, TiO2 promotes crystal formation within the glass, causing a decrease in transparency (cloudiness). Therefore, the TiO2 content is preferably within the range described above.

[0080] In the optical glass of this embodiment, the upper limit of the Ta2O5 content is preferably 10.0%, and more preferably 5.0%, 3.0%, and 1.0%. The lower limit of the Ta2O5 content is preferably 0%. The Ta2O5 content may also be 0%.

[0081] Ta₂O₅ is a glass component that improves the thermal stability and anti-devitrification properties of glass. However, Ta₂O₅ increases the refractive index and causes high dispersion in the glass. Furthermore, a high Ta₂O₅ content decreases the thermal stability of the glass and easily leads to molten residue from the glass raw material during molten glass production. Therefore, the Ta₂O₅ content is preferably within the aforementioned range. Moreover, compared to other glass components, Ta₂O₅ is an extremely expensive component; increasing its content increases the production cost of the glass. Furthermore, since Ta₂O₅ has a larger molecular weight than other glass components, it may increase the specific gravity of the glass, resulting in an increase in the weight of the optical element.

[0082] In the optical glass of this embodiment, the upper limit of the Li2O content is preferably 5%, and more preferably 3%, 2%, and 1%. The lower limit of the Li2O content is preferably 0%. The Li2O content may also be 0%.

[0083] Li₂O has the effect of lowering the glass transition temperature (Tg). On the other hand, as the Li₂O content increases, the acid resistance decreases. Therefore, the Li₂O content is preferably within the range described above.

[0084] In the optical glass of this embodiment, the upper limit of the total content of Li2O, Na2O and K2O [Li2O+Na2O+K2O] is preferably 45.0%, and more preferably 42.0%, 39.0% and 37.0% respectively. Furthermore, the lower limit of this total content is preferably 10.0%, and more preferably 15.0%, 19.0% and 22.0% respectively.

[0085] Li₂O, Na₂O, and K₂O all improve the thermal stability of glass. However, as their content increases, chemical durability and weather resistance decrease. Therefore, the preferred total content of Li₂O, Na₂O, and K₂O [Li₂O + Na₂O + K₂O] is within the range mentioned above.

[0086] In the optical glass of this embodiment, the upper limit of the Cs2O content is preferably 5%, and more preferably 3%, 2%, and 1%. Furthermore, the lower limit of the Cs2O content is preferably 0%. The Cs2O content may also be 0%.

[0087] Although Cs₂O improves the thermal stability of glass, its thermal stability, chemical durability, and weather resistance decrease as its content increases. Therefore, the preferred Cs₂O content is within the range described above.

[0088] In the optical glass of this embodiment, the upper limit of the MgO content is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0%. Furthermore, the lower limit of the MgO content is preferably 0%. The MgO content may also be 0%.

[0089] In the optical glass of this embodiment, the upper limit of the CaO content is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5%. Furthermore, the lower limit of the CaO content is preferably 0%. The CaO content may also be 0%.

[0090] In the optical glass of this embodiment, the upper limit of the SrO content is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0%. Furthermore, the lower limit of the SrO content is preferably 0%. The SrO content may also be 0%.

[0091] MgO, CaO, SrO, and BaO are all glass components that improve the thermal stability and devitrification resistance of glass. However, as the content of these glass components increases, high dispersion is impaired, and the thermal stability and devitrification resistance of the glass decrease. Therefore, it is preferable that the contents of these glass components are respectively within the ranges mentioned above.

[0092] In the optical glass of this embodiment, the upper limit of the ZrO2 content is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0%. Furthermore, the lower limit of the ZrO2 content is preferably 0%. The ZrO2 content may also be 0%.

[0093] ZrO2 is a glass component that improves the thermal stability and devitrification resistance of glass. However, when the ZrO2 content is too high, it tends to decrease thermal stability. Therefore, from the viewpoint of maintaining the thermal stability and devitrification resistance of glass well, the ZrO2 content is preferably within the range mentioned above.

[0094] In the optical glass of this embodiment, the upper limit of the Sc2O3 content is preferably 2%. Furthermore, the lower limit of the Sc2O3 content is preferably 0%.

[0095] In the optical glass of this embodiment, the upper limit of the HfO2 content is preferably 2%. Furthermore, the lower limit of the HfO2 content is preferably 0%.

[0096] Sc2O3 and HfO2 are both components that can increase the refractive index (nd) and are expensive. Therefore, the preferred contents of Sc2O3 and HfO2 are within the ranges mentioned above.

[0097] In the optical glass of this embodiment, the upper limit of the Lu2O3 content is preferably 2%. Furthermore, the lower limit of the Lu2O3 content is preferably 0%.

[0098] Lu₂O₃ has the effect of increasing the refractive index (nd). Furthermore, due to its large molecular weight, it is also a glass component that increases the specific gravity of the glass. Therefore, the preferred Lu₂O₃ content is within the range described above.

[0099] In the optical glass of this embodiment, the upper limit of the GeO2 content is preferably 2%. Furthermore, the lower limit of the GeO2 content is preferably 0%.

[0100] GeO2 is a component that increases the refractive index (nd) and is extremely expensive in commonly used glass compositions. Therefore, from the viewpoint of reducing glass manufacturing costs, the GeO2 content is preferably within the range described above.

[0101] In the optical glass of 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%. Furthermore, the lower limit of the La2O3 content is preferably 0%. The La2O3 content may also be 0%.

[0102] As the La2O3 content increases, the thermal stability and devitrification resistance of the glass decrease, making it prone to devitrification during manufacturing. Therefore, from the viewpoint of suppressing the decrease in thermal stability and devitrification resistance, the La2O3 content is preferably within the range described above.

[0103] In the optical glass of 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%. Furthermore, the lower limit of the Gd2O3 content is preferably 0%.

[0104] When the Gd₂O₃ content is too high, the thermal stability and devitrification resistance of the glass decrease, making it prone to devitrification during manufacturing. Furthermore, an excessive Gd₂O₃ content increases the specific gravity of the glass, which is undesirable. Therefore, from the viewpoint of maintaining good thermal stability and devitrification resistance while suppressing an increase in specific gravity, the Gd₂O₃ content within the aforementioned range is preferred.

[0105] In the optical glass of 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%. Furthermore, the lower limit of the Y2O3 content is preferably 0%. The Y2O3 content may also be 0%.

[0106] On the other hand, when the Y2O3 content is too high, the thermal stability and devitrification resistance of the glass decrease. Therefore, from the viewpoint of suppressing the decrease in thermal stability and devitrification resistance, the Y2O3 content is preferably within the above-mentioned range.

[0107] In the optical glass of this embodiment, the upper limit of the Yb2O3 content is preferably 2%. Furthermore, the lower limit of the Yb2O3 content is preferably 0%.

[0108] Because Yb₂O₃ has a larger molecular weight compared to La₂O₃, Gd₂O₃, and Y₂O₃, it increases the specific gravity of the glass. As the specific gravity of the glass increases, the mass of the optical components also increases. For example, when a heavy lens is fitted into an autofocus camera lens, the power required to drive the lens during autofocus increases, leading to increased battery consumption. Therefore, it is desirable to reduce the Yb₂O₃ content to suppress the increase in the specific gravity of the glass.

[0109] Furthermore, when the Yb₂O₃ content is too high, the thermal stability and devitrification resistance of the glass decrease. From the viewpoint of preventing a decrease in the thermal stability of the glass and suppressing an increase in specific gravity, the Yb₂O₃ content within the above-mentioned range is preferred.

[0110] The optical glass of this embodiment is preferably mainly composed of the glass components described above, that is, it includes B2O3, K2O, P2O5, and Na2O as essential components, and ZnO, Nb2O5, WO3, Bi2O3, Al2O3, SiO2, TiO2, Ta2O5, Li2O, Cs2O, MgO, CaO, SrO, BaO, ZrO2, Sc2O3, HfO2, Lu2O3, GeO2, La2O3, Gd2O3, Y2O3, and Yb2O3 as optional components. The total content of the above glass components is preferably 95% or more, more preferably 98% or more, further preferably 99% or more, and even more preferably 99.5% or more.

[0111] In the optical glass of this embodiment, the upper limit of the TeO2 content is preferably 2%. Furthermore, the lower limit of the TeO2 content is preferably 0%.

[0112] Because TeO2 is toxic, it is preferable to reduce its content. Therefore, the TeO2 content is preferably within the range described above.

[0113] Furthermore, although the optical glass of this embodiment is preferably composed essentially of the above-described glass components, it is also permissible to contain other components within a range that does not affect the effectiveness of the present invention. In addition, the presence of unavoidable impurities is not excluded in the present invention.

[0114] <Other Components>

[0115] Pb, As, Cd, Tl, Be, and Se are all toxic. Therefore, the optical glass of this embodiment preferably does not contain these elements as glass components.

[0116] U, Th, and Ra are all radioactive elements. Therefore, the optical glass of this embodiment preferably does not contain these elements as glass components.

[0117] The presence of V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm increases the coloration of the glass, making it a source of fluorescence. Therefore, the optical glass of this embodiment preferably does not contain these elements as glass components.

[0118] Sb(Sb₂O₃), Sn(SnO₂), and Ce(CeO₂) are elements that can be added arbitrarily as clarifying agents. Among them, Sb(Sb₂O₃) has the strongest clarifying effect. However, Sb(Sb₂O₃) has strong oxidizing properties. When a large amount of Sb(Sb₂O₃) is added, the Sb(Sb₂O₃) contained in the glass will oxidize the forming surface of the pressing mold during precision pressing. Therefore, with repeated precision pressing, the forming surface deteriorates significantly, making precision pressing impossible. Furthermore, the surface quality of the formed optical components decreases. In addition, compared with Sb(Sb₂O₃), Sn(SnO₂) and Ce(CeO₂) have a smaller clarifying effect. Consequently, when a large amount of Ce(CeO₂) is added, the coloration of the glass is enhanced. Therefore, when adding clarifying agents, the amount added should be carefully considered, and Sb(Sb₂O₃) is preferred.

[0119] The following values ​​for the content of clarifying agents are shown after oxide conversion.

[0120] The Sb₂O₃ content is expressed as the addition rate. That is, when the total content of all glass components other than Sb₂O₃, SnO₂, and CeO₂ is set to 100% by mass, the Sb₂O₃ content is preferably 1% by mass or less, and more preferably 0.2% by mass or less, 0.05% by mass or less, 0.02% by mass or less, and 0.01% by mass or less. The Sb₂O₃ content can also be 0% by mass.

[0121] The SnO2 content is also expressed as the addition rate. That is, when the total content of all glass components other than SnO2, Sb2O3, and CeO2 is set to 100% by mass, the SnO2 content is preferably 1% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.02% by mass or less. The SnO2 content can also be 0% by mass, preferably substantially free of SnO2. By setting the SnO2 content within the above range, the clarity of the glass can be improved.

[0122] The CeO2 content is also expressed as the addition rate. That is, when the total content of all glass components other than CeO2, Sb2O3, and SnO2 is set to 100% by mass, the CeO2 content is preferably 1% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.02% by mass or less. The CeO2 content can also be 0% by mass, preferably substantially free of CeO2. By setting the CeO2 content within the above range, the clarity of the glass can be improved.

[0123] (Glass properties)

[0124] <Refractive index nd>

[0125] In the optical glass of this embodiment, the refractive index nd is preferably 1.55 to 1.68, and more preferably in the range of 1.55 to 1.65 or 1.57 to 1.64.

[0126] By appropriately adjusting the content of each glass component, the refractive index (nd) can be made to a desired value. Components that relatively increase the refractive index (nd) (high refractive index components) include Nb₂O₅, TiO₂, WO₃, Bi₂O₃, Ta₂O₅, ZrO₂, and La₂O₃. On the other hand, components that relatively decrease the refractive index (nd) (low refractive index components) include P₂O₅, SiO₂, B₂O₃, Li₂O, Na₂O, and K₂O. Therefore, by increasing the mass ratio of the total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 relative to the total content of P2O5, B2O3, SiO2, Li2O, Na2O, K2O, and Cs2O [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5) / (P2O5+B2O3+SiO2+Li2O+Na2O+K2O+Cs2O)], the refractive index nd can be increased, and by decreasing this mass ratio, the refractive index nd can be decreased.

[0127] <Abbe number>

[0128] In the optical glass of this embodiment, the Abbe number νd is preferably 25 to 50, and more preferably 28 to 45.

[0129] By appropriately adjusting the content of each glass component, the Abbe number νd can be made to the desired value. Components with relatively low Abbe number νd, i.e., high dispersion components, include Nb₂O₅, TiO₂, WO₃, Bi₂O₃, Ta₂O₅, ZrO₂, etc. On the other hand, components with relatively high Abbe number νd, i.e., low dispersion components, include P₂O₅, SiO₂, B₂O₃, Li₂O, Na₂O, K₂O, La₂O₃, BaO, CaO, SrO, etc.

[0130] <Specific gravity of glass>

[0131] In the optical glass of this embodiment, the specific gravity is preferably 3.20 or less, and more preferably 3.10 or less, and 2.95 or less. The lower limit of the specific gravity is not particularly limited, and is typically 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 consumed by the camera lens to drive autofocus can be reduced.

[0132] <Glass transition temperature Tg>

[0133] The glass transition temperature (Tg) of the optical glass in this embodiment is preferably 520°C or lower, and more preferably 500°C or lower, 480°C or lower, and 470°C or lower. The lower limit of the glass transition temperature (Tg) is typically 300°C, and preferably 350°C.

[0134] By satisfying the upper limit of the glass transition temperature (Tg) within the aforementioned range, the rise in glass forming and annealing temperatures can be suppressed, thus reducing thermal damage to the pressing and forming equipment and the annealing equipment. Furthermore, by satisfying the lower limit of the glass transition temperature (Tg) within the aforementioned range, the desired Abbe number and refractive index can be maintained, and the thermal stability of the glass can be easily and well maintained.

[0135] <Light transmittance of glass>

[0136] The light transmittance of the optical glass in this embodiment can be evaluated by the tinting degree λ5.

[0137] For glass samples with a thickness of 10.0 mm ± 0.1 mm, the spectral transmittance was measured in the wavelength range of 200 to 700 nm, and the wavelength with an external transmittance of 5% was set as λ5.

[0138] In this embodiment, the λ5 of the optical glass is preferably 390 nm or less, more preferably 380 nm or less, and even more preferably 375 nm or less.

[0139] By using optical glass with a short wavelength of λ5, it is possible to provide optical elements that can achieve proper color reproduction.

[0140] Average linear expansion coefficient α 100-300 >

[0141] In the optical glass of this embodiment, the average coefficient of linear expansion α at 100–300°C 100-300 The lower limit is preferably 100×10 -7 ℃ -1 Furthermore, it is more preferably 120×10 -7 ℃ -1 130×10 -7 ℃ -1 140×10 -7 ℃ -1 Furthermore, from the viewpoint of maintaining the stability of the glass and obtaining the desired optical properties, the average linear expansion coefficient α... 100-300 The upper limit can be exemplified as 210×10 -7 ℃ -1 Preferably 205×10 -7 ℃ -1 Furthermore, it is more preferably 200×10 -7 ℃ -1 195×10-7 ℃ -1 190×10 -7 ℃ -1 .

[0142] The average linear expansion coefficient α is measured according to the JOGIS08-2019 standard. 100-300 The specimen was a round bar with a length of 20 mm ± 0.5 mm and a diameter of 5 mm ± 0.5 mm. Under a load of 98 mN, the specimen was heated at a fixed rate of 4 °C per minute, and the temperature and elongation were measured every second. The average coefficient of linear expansion α... 100-300 It is the average value of the linear expansion coefficient from 100 to 300℃.

[0143] In addition, the unit "℃" is used in this instruction manual. -1 "" represents the average linear expansion coefficient α, however, using "K" -1 "When used as a unit, the value of the average linear expansion coefficient α is also the same."

[0144] (Manufacturing of optical glass)

[0145] For the optical glass of the embodiments of the present invention, it is sufficient to prepare the glass raw materials in the manner specified above, and then manufacture the glass using the prepared glass raw materials according to a known glass manufacturing method. For example, multiple compounds are prepared and thoroughly mixed to form a batch raw material, which is then placed in a quartz crucible or a platinum crucible for rough melting. The melt obtained through rough melting is then rapidly cooled and pulverized to produce crushed glass. The crushed glass is then added to a platinum crucible, heated, and remelted to form molten glass. After clarification and homogenization, the molten glass is shaped and slowly cooled to obtain the optical glass. The shaping and slow cooling of the molten glass can be performed using known methods.

[0146] Furthermore, as long as the desired glass components are introduced into the glass to achieve the desired content, there are no particular limitations on the compounds used when preparing batch raw materials. Examples of such compounds include oxides, carbonates, nitrates, hydroxides, and fluorides.

[0147] (Manufacturing of optical components, etc.)

[0148] For manufacturing optical elements using the optical glass of the embodiments of the present invention, any known method can be used. For example, glass raw materials are melted to form molten glass, which is then poured into a mold and shaped into a plate to produce a glass material formed from the optical glass of the present invention. The obtained glass material is appropriately cut, ground, and polished to produce slices of suitable size and shape for pressing. The slices are heated and softened, and then pressed (re-pressed) using a known method to produce an optical element blank with a shape similar to that of the optical element. The optical element blank is annealed, ground, and polished using a known method to manufacture the optical element.

[0149] Depending on the intended use, anti-reflective coatings, total reflection coatings, etc., can also be applied to the optical functional surfaces of the manufactured optical components.

[0150] As optical elements, examples include various lenses such as spherical lenses, prisms, and gratings.

[0151] The present invention will be described below through embodiments; however, the present invention is not limited to the following embodiments.

[0152] (Example)

[0153] [Preparation of glass samples]

[0154] Weigh the corresponding compound raw materials, such as phosphates, carbonates, and oxides, to form glass with the compositions shown in Tables 1(1) and (2), and mix them thoroughly to obtain a blending raw material. Place the blending raw material into a platinum crucible and heat it to 900–1350 °C in an atmospheric atmosphere to melt it. Homogenize and clarify it by stirring to obtain molten glass. Pour the molten glass into a molding die to form it and allow it to cool slowly to obtain a block glass sample.

[0155] Alternatively, the raw materials can be added to a quartz glass crucible for melting, then transferred to a platinum crucible for further heating and melting. The mixture is then homogenized and clarified by stirring to obtain molten glass. The molten glass is then poured into a molding die for shaping and slow cooling.

[0156] [Evaluation of Glass Samples]

[0157] For the obtained glass samples, the glass composition, specific gravity, refractive index nd, Abbe number νd, λ5, glass transition temperature Tg, and average coefficient of linear expansion α are measured using the methods shown below. 100-300 Furthermore, the resistance to depermeability was evaluated. The results are shown in Tables 2(1) and (2).

[0158] {1} Glass composition

[0159] The content of each glass component in the obtained glass samples was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0160] {2} Specific gravity

[0161] Measurements were performed based on the Japan Optical Glass Manufacturers Association standard JOGIS-05.

[0162] {3} Refractive index nd and Abbe number νd

[0163] Measurements were performed based on the Japan Optical Glass Manufacturers Association standard JOGIS-01.

[0164] {4}λ5

[0165] A glass sample was processed to have a thickness of 10 mm and two parallel, optically polished planes. The spectral transmittance in the wavelength range of 280 nm to 700 nm was measured. The intensity of light incident perpendicularly to one side of the optically polished plane was defined as intensity A, and the intensity of light emanating from the other side was defined as intensity B. The spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance is 5% was defined as λ5. Furthermore, the spectral transmittance also includes the light reflection loss from the sample surface.

[0166] {5} Glass transition temperature Tg

[0167] The glass transition temperature Tg was determined based on the DSC plot of a solid glass heated using a differential scanning calorimeter DSC3300SA (NETZSCH Japan Co., Ltd.).

[0168] {6} Average linear expansion coefficient α 100-300

[0169] For the obtained glass samples, the average coefficient of linear expansion was measured according to the standard JOGIS08-2019. The average coefficient of linear expansion was measured using a thermomechanical analysis apparatus TMA4000SE (NETZSCH Japan Co., Ltd.). The specimens were round bars with a length of 20 mm ± 0.5 mm and a diameter of 5 mm ± 0.5 mm. During the measurement, the specimens were heated at a fixed rate of 4 °C per minute under a load of 98 mN, and the temperature and elongation of the specimens were measured every second. The average coefficient of linear expansion from 100 to 300 °C was taken as the average coefficient of linear expansion α. 100-300 .

[0170] {7} Resistance to devitrification

[0171] For the obtained glass samples, the presence or absence of crystals or cloudiness was confirmed using an optical microscope. The magnification of the optical microscope ranged from 10 to 100 times. A glass sample without crystals or cloudiness was judged as "good," while a sample containing at least one of crystals or cloudiness was judged as "poor." Samples No. 1 to 32 of the examples were all judged as "good." Samples No. 1 to 32 of the examples were confirmed to be glasses with excellent devitrification resistance.

[0172] Table 1(1)

[0173]

[0174]

Table 1(2)

[0175]

[0176] Table 2(1)

[0177]

[0178]

Table 2(2)

[0179]

[0180] (Example 2)

[0181] The glass sample obtained in Example 1 was cut and ground to produce slices. The slices were then pressed and shaped using reheating to produce optical element blanks. The optical element blanks were precision annealed to precisely adjust the refractive index to the desired value. Then, they were 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.

[0182] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is indicated by the scope of the claims, not by the foregoing description, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

[0183] For example, with the glass composition exemplified above, by adjusting the composition as described in the specification, an optical glass according to one aspect of the present invention can be manufactured.

[0184] Furthermore, two or more items may be combined as examples or preferred items described in the specification.

Claims

1. An optical glass comprising B2O3 and K2O as glass components, The P2O5 content is 35.0–60.0% by mass. The mass ratio of B2O3 content to P2O5 content [B2O3 / P2O5] is less than 0.

39. The Na2O content is 5.0–40.0% by mass. The BaO content is less than 15.0% by mass. The total content of MgO, CaO, SrO, and BaO [MgO+CaO+SrO+BaO] is less than 18.0% by mass. The ZnO content is less than 15.0% by mass. The Nb₂O₅ content is below 25.0% by mass. The WO3 content is below 5.0% by mass. The Bi2O3 content is less than 10.0% by mass. The total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5] is 3.0–30.0% by mass. The total content of TiO2, Nb2O5, WO3, Bi2O3, Ta2O5, and ZnO [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5+ZnO] is 3.0–33.0% by mass. The mass ratio of the total content of P2O5, B2O3, and SiO2 to the total content of Li2O, Na2O, K2O, and Cs2O [(P2O5+B2O3+SiO2) / (Li2O+Na2O+K2O+Cs2O)] is greater than 1.

82. The mass ratio of TiO2 content to the total content of P2O5 and B2O3 [TiO2 / (P2O5+B2O3)] is less than 0.

29.

2. The optical glass according to claim 1, wherein, The B2O3 content is 0.3% by mass or more. The K2O content is 3.0–20.0% by mass. The mass ratio of B2O3 content to P2O5 content [B2O3 / P2O5] is greater than 0.

005. The mass ratio of the total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 to the total content of P2O5, B2O3, SiO2, Li2O, Na2O, K2O, and Cs2O [(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5) / (P2O5+B2O3+SiO2+Li2O+Na2O+K2O+Cs2O)] is 0.10–0.

45. The mass ratio of TiO2 content to the total content of P2O5 and B2O3 [TiO2 / (P2O5+B2O3)] is greater than 0.

10. The mass ratio of the total content of P2O5, B2O3, and SiO2 to the total content of Li2O, Na2O, K2O, and Cs2O [(P2O5+B2O3+SiO2) / (Li2O+Na2O+K2O+Cs2O)] is less than 2.

60. The mass ratio of TiO2 content to the total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 [TiO2 / (TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)] is greater than 0.

20. The mass ratio of Na₂O to K₂O [Na₂O / K₂O] is 0.80–2.

70. The Al2O3 content is below 15.0% by mass. The SiO2 content is below 5.0% by mass. The TiO2 content is below 30.0% by mass. The Ta2O5 content is less than 10.0% by mass. The Li2O content is less than 5% by mass. The total content of Li₂O, Na₂O, and K₂O [Li₂O + Na₂O + K₂O] is 10.0–45.0% by mass. The Cs2O content is less than 5% by mass. The MgO content is less than 10.0% by mass. The CaO content is less than 10.0% by mass. The SrO content is less than 10.0% by mass. The ZrO2 content is below 10.0% by mass. The Sc2O3 content is less than 2% by mass. The HfO2 content is less than 2% by mass. The Lu2O3 content is less than 2% by mass. The GeO2 content is less than 2% by mass. The La2O3 content is less than 10.0% by mass. The Gd2O3 content is less than 10.0% by mass. The Y2O3 content is below 10.0% by mass. The Yb₂O₃ content is less than 2% by mass. The TeO2 content is less than 2% by mass. Expressed as the external addition rate, the Sb₂O₃ content is less than 1% by mass. Expressed as the external addition rate, the SnO2 content is less than 1% by mass. Expressed as the external addition rate, the CeO2 content is less than 1% by mass.

3. The optical glass according to claim 1, wherein, The Al2O3 content is less than 6.0% by mass. The Ta2O5 content is less than 1.0% by mass. The Li2O content is less than 2% by mass. The Cs2O content is less than 1% by mass. The MgO content is less than 5.0% by mass. The CaO content is less than 5% by mass. The SrO content is below 8.0% by mass. The ZrO2 content is less than 5.0% by mass. The La2O3 content is less than 5.0% by mass. The Gd2O3 content is less than 5.0% by mass. The Y2O3 content is less than 5.0% by mass. Expressed as the external addition rate, the Sb₂O₃ content is less than 0.05% by mass. Expressed as the external addition rate, the SnO2 content is less than 0.2% by mass. The CeO2 content, expressed as an external addition rate, is less than 0.02% by mass.

4. The optical glass according to claim 1, wherein, The total content of B2O3, K2O, P2O5, Na2O, ZnO, Nb2O5, WO3, Bi2O3, Al2O3, SiO2, TiO2, Ta2O5, Li2O, Cs2O, MgO, CaO, SrO, BaO, ZrO2, Sc2O3, HfO2, Lu2O3, GeO2, La2O3, Gd2O3, Y2O3, and Yb2O3 is above 95% by mass.

5. The optical glass according to claim 1, wherein, It does not contain Pb, As, Cd, Tl, Be, or Se as glass components. It does not contain U, Th, or Ra as glass components. It does not contain V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, or Tm as glass components.

6. The optical glass according to claim 1, wherein, The refractive index nd is 1.55–1.

68. The Abbe number νd is 25–50. Specific gravity below 3.20 The glass transition temperature (Tg) is below 520℃. λ5 is below 390nm. The average linear expansion coefficient α between 100 and 300℃ 100-300 100×10 -7 ℃ -1 Above and 210×10 -7 ℃ -1 the following.

7. An optical element formed from the optical glass according to any one of claims 1 to 6.

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