Optical glass and optical element

Abstract

An optical glass having high refractive index and high dispersion characteristics, and having small specific gravity and good homogeneity. The optical glass contains, in mass%, 20 to 51% of SiO2, 20 to 40% of TiO2, 5 to 28% of Na2O, less than 2.0% of BaO, 8 to 28% of the total content of Li2O, Na2O, K2O and Cs2O (R2O), 0.90 or more of [SiO2 / (SiO2+B2O3+P2O5)], 1.5 to 3.2 of [SiO2 / R2O], 2.6 or less of [(SiO2+R2O) / (TiO2+Nb2O5)], 0.90 or more of [TiO2 / (TiO2+Nb2O5+ZrO2)], 0.90 or more of the mass ratio [(CaO+BaO) / R'O] of (CaO+BaO) to the total content of MgO, CaO, SrO and BaO (R'O), 0.98 or more of [(Na2O+K2O) / R2O], 0.15 or less of [BaO / (Na2O+K2O+CaO)], and 0.12 or less of [BaO / (TiO2+Nb2O5)].

Description

TECHNICAL FIELD

[0001] The present application relates to optical glasses and optical elements. BACKGROUND

[0002] Optical glasses having high refractive index and high dispersion characteristics (low Abbe number) are in great demand as materials for optical elements such as various lenses. For example, by combining with a lens having high refractive index and low dispersion, an optical system for chromatic aberration correction having small volume and high functionality can be constituted. Further, by asphericalizing the optical function surface of a lens having high refractive index and high dispersion characteristics, further high functionality and miniaturization of various optical systems can be achieved.

[0003] High refractive index and high dispersion optical glasses in which components such as Nb2O5, TiO2, etc. that impart high refractive index and high dispersion characteristics are added to SiO2 that is a network-forming component of glass are known. Such high refractive index and high dispersion optical glasses are described in Patent Documents 1 to 3.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2005-097036

[0007] Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No. 2016-521237

[0008] Patent Document 3: Japanese Patent Application Laid-Open (JP-A) No. 2018-168011 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In the SiO2-Nb2O5-TiO2 system like the optical glasses disclosed in Patent Documents 1 and 2, when the content of alkali metal components is large, the bricks (refractory materials) that constitute the melting tank are sometimes eroded by the molten glass at the time of melting the glass. As a result, foreign matter from the refractory material is mixed into the glass, and the glass is contaminated. In addition, the problem of shortening of the life of the melting tank occurs.

[0011] The foreign matter in the glass becomes a scattering source of light, and the quality of the optical glass is reduced. In addition, at the time of heating, softening and shaping the glass, the foreign matter becomes a starting point of crystallization, and the glass becomes apt to devitrify.

[0012] In addition, the SiO2-Nb2O5-TiO2 system high refractive index and high dispersion glass has the problem of large specific gravity because it contains a large amount of Nb2O5. In the optical glass disclosed in Patent Document 3, although the content of Nb2O5 is reduced, the specific gravity cannot be sufficiently reduced because the content of BaO is large.

[0013] An object of the present application is to solve the above-described problems, and to provide an optical glass having high refractive index and high dispersion characteristics, and a small specific gravity, and excellent homogeneity, and an optical element composed of the optical glass.

[0014] Solution to the problem

[0015] (1) An optical glass,

[0016] expressing the content in mass %,

[0017] The content of SiO2 is 20 to 51%,

[0018] The content of TiO2 is 20 to 40%,

[0019] The content of Na2O is 5 to 28%,

[0020] The content of BaO is less than 2.0%,

[0021] The total content of Li2O, Na2O, K2O and Cs2O (R2O) is 8 to 28%,

[0022] The mass ratio of the content of SiO2 to the total content of SiO2, B2O3 and P2O5 (SiO2+B2O3+P2O5) [SiO2 / (SiO2+B2O3+P2O5)] is 0.90 or more,

[0023] The mass ratio of the content of SiO2 to R2O [SiO2 / R2O] is 1.5 to 3.2,

[0024] The mass ratio of the total content of SiO2 and R2O (SiO2+R2O) to the total content of TiO2 and Nb2O5 (TiO2+Nb2O5) [(SiO2+R2O) / (TiO2+Nb2O5)] is 2.6 or less,

[0025] The mass ratio of the content of TiO2 to the total content of TiO2, Nb2O5 and ZrO2 (TiO2+Nb2O5+ZrO2) [TiO2 / (TiO2+Nb2O5+ZrO2)] is 0.90 or more,

[0026] The mass ratio of the total content of CaO and BaO (CaO+BaO) to the total content of MgO, CaO, SrO and BaO (R'O) [(CaO+BaO) / R'O] is 0.90 or more,

[0027] The mass ratio of the total content of Na2O and K2O to R2O [(Na2O+K2O) / R2O] is 0.98 or more,

[0028] the mass ratio of the content of BaO to the total content of Na2O, K2O, and CaO [BaO / (Na2O+K2O+CaO)] is 0.15 or less,

[0029] the mass ratio of the content of BaO to the total content of TiO2and Nb2O5[BaO / (TiO2+Nb2O5)] is 0.12 or less.

[0030] (2) The optical glass according to (1), wherein the refractive index nd is 1.67 to 1.77, and the Abbe number vd is 26 to 33.

[0031] (3) The optical glass according to (1) or (2), wherein the specific gravity is 3.40 or less.

[0032] (4) An optical member composed of the optical glass according to any one of (1) to (3).

[0033] Effects of the Invention

[0034] According to one embodiment of the present application, an optical glass having high refractive index and high dispersion characteristics, a small specific gravity, and good homogeneity can be provided. Further, according to one embodiment of the present application, an optical member composed of the optical glass can be provided. DETAILED DESCRIPTION

[0035] In the present application and the present specification, unless otherwise specified, the glass composition of the optical glass is expressed on an oxide basis. Here, the "glass composition on an oxide basis" means a glass composition obtained by converting the entirety of the glass raw materials into substances existing as oxides in the optical glass upon melting of the glass raw materials, and each glass component is written as SiO2, TiO2, and the like according to the custom. Unless otherwise specified, the content and the total content of the glass components are on a mass basis, and "%" means "mass %".

[0036] The content of the glass components can be quantified by known methods, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and the like. Further, in the present specification and the present application, the content of the constituent components of 0% means that the constituent component is not actually contained, and the component can be contained to an extent of unavoidable impurities.

[0037] Hereinafter, one embodiment of the present application will be described.

[0038] The optical glass of the present embodiment contains SiO2, TiO2, and Na2O as essential components.

[0039] In the optical glass of the present embodiment, the content of SiO2 is 20 to 51%. The lower limit of the content of SiO2 is preferably 25%, more preferably 30%, and further preferably 33% from the viewpoint of maintaining the refractive index. The upper limit of the content of SiO2 is preferably 50%, more preferably 49%, and further preferably 48% from the viewpoint of maintaining the refractive index.

[0040] SiO2 is a glass network-forming component. When the content of SiO2 is less than 20%, the thermal stability of the glass decreases, and the liquidus temperature increases. In addition, the viscosity of the glass at the time of melting decreases, and the bricks (refractory materials) constituting a melting tank and the like are easily eroded. When the content of SiO2 is more than 51%, the refractive index nd decreases, and it is difficult to produce a glass having a desired optical property. By setting the content of SiO2 in the above range, it is possible to maintain the thermal stability and suppress the erosion of the refractory materials.

[0041] In the optical glass of the present embodiment, the content of TiO2 is 20 to 40%. TiO2 is a component that imparts a high refractive index and a high dispersion property. Although Nb2O5 and ZrO2 also impart a high refractive index and a high dispersion property, TiO2 does not easily increase the specific gravity of the glass as compared with Nb2O5 and ZrO2. When the content of TiO2 is more than 40%, the dispersion is too high, the thermal stability of the glass decreases, and the coloring of the glass is enhanced. On the other hand, when the content of TiO2 is less than 20%, it is difficult to obtain a desired refractive index.

[0042] Therefore, the lower limit of the content of TiO2 is preferably 22%, more preferably 24%, and further preferably 25% from the viewpoint of obtaining a desired refractive index. The upper limit of the content of TiO2 is preferably 38%, more preferably 36%, and further preferably 35% from the viewpoint of maintaining the thermal stability, suppressing the coloring, and achieving a desired dispersion. By setting the content of TiO2 in the above range, it is possible to suppress the increase in the specific gravity and maintain the thermal stability of the glass, and achieve a desired optical property.

[0043] In the optical glass of the present embodiment, the content of Na2O is 5 to 28%. Na2O has a function of improving the melting property of the glass and adjusting the viscosity of the molten glass. When the content of Na2O is less than 5%, the function of adjusting the viscosity becomes insufficient. On the other hand, when the content of Na2O is more than 28%, the refractive index decreases, the viscosity of the molten glass decreases, and the erosion of the molten glass to the refractory materials becomes significant.

[0044] Therefore, from the viewpoint of improving the melting property and making the viscosity of the molten glass appropriate, the lower limit of the content of Na2O is preferably 8%, and further sequentially more preferably 10%, 12%, and 13%. On the other hand, from the viewpoint of suppressing the corrosion of the refractory material at the time of melting the glass and achieving the desired refractive index, the upper limit of the content of Na2O is preferably 25%, and further sequentially more preferably 23%, 21%, and 19%.

[0045] In the optical glass of the present embodiment, the content of BaO is less than 2.0%. BaO is a component that increases the specific gravity. Therefore, the upper limit of the content of BaO is preferably 1.5%, more preferably 1.0%, and further preferably 0.5%. The lower limit of the content of BaO is preferably 0%. The content of BaO can also be 0%. By setting the content of BaO within the above range, the increase in the specific gravity can be suppressed.

[0046] In the optical glass of the present embodiment, the total content of Li2O, Na2O, K2O, and Cs2O (hereinafter, sometimes also referred to as "R2O") is 8 to 28%. Li2O, Na2O, K2O, and Cs2O are components that function to improve the melting property of the glass. When R2O is less than 8%, the melting property decreases, and unmelting raw material residues are likely to occur, the viscosity of the molten glass becomes excessively high, the flowability of the molten glass decreases, and the yield of the glass per unit time decreases. On the other hand, when R2O is more than 28%, the viscosity of the molten glass decreases, and the melting tank made of a refractory material such as a brick is easily corroded by the molten glass.

[0047] Therefore, the lower limit of R2O is preferably 9%, and further sequentially more preferably 10%, 12%, and 13%. From the viewpoint of suppressing the corrosion of the refractory material, the upper limit of R2O is preferably 26%, more preferably 24%, and further preferably 22%. By setting R2O within the above range, the melting property and the productivity of the glass can be maintained.

[0048] In the optical glass of the present embodiment, the mass ratio [SiO2 / (SiO2+B2O3+P2O5)] of the content of SiO2 to the total content of SiO2, B2O3, and P2O5 (SiO2+B2O3+P2O5) is 0.90 or more. In the optical glass of the present embodiment, the network-forming component is mainly SiO2, and the content of SiO2 is particularly large compared to the contents of B2O3 and P2O5, which are network-forming components other than SiO2.

[0049] Therefore, the lower limit of the mass ratio [SiO2 / (SiO2+B2O3+P2O5)] is preferably 0.95, and more preferably 0.98. The upper limit of the mass ratio is preferably 1. The mass ratio can also be 1. By setting the mass ratio within the above range, the above-described desired properties can be obtained.

[0050] In the optical glass of the present embodiment, the mass ratio [Si02 / R20] of the content of Si02to the total content R20of Li20, Na20, K20, and Cs20is 1.5 to 3.2. When the mass ratio is less than 1.5, the erosion of the molten glass against the refractory material becomes strong, and problems such as the mixing of particulate refractory material from the wall surface of the molten tank, which is eroded, into the molten glass and the contamination of the glass, and the shortening of the life of the molten tank, easily occur. On the other hand, when the mass ratio is greater than 3.2, problems such as the reduction of the meltability, the easy remaining of un-melted raw material, the excessive increase of the viscosity of the molten glass, and the reduction of the yield of the glass per unit time easily occur.

[0051] Therefore, the lower limit of the mass ratio [Si02 / R20] is preferably 1.7, and further sequentially more preferably 1.9, 2.1, and 2.3. Further, the upper limit of the mass ratio is preferably 3.1, and more preferably 3.0. By making the mass ratio within the above range, the erosion of the molten glass against the refractory material can be suppressed, and the reduction of the meltability can also be suppressed.

[0052] In the optical glass of the present embodiment, the mass ratio [(Si02+R20) / (Ti02+Nb205)] of the total content (Si02+R20) of Si02and R20to the total content (Ti02+Nb205) of Ti02and Nb205is 2.6 or less. Among the glass components, Ti02and Nb205have a strong effect of increasing the refractive index, and Si02and alkali metal oxides have a weak effect of increasing the refractive index as compared with Ti02and Nb205.

[0053] Therefore, the upper limit of the mass ratio [(Si02+R20) / (Ti02+Nb205)] is preferably 2.5, and more preferably 2.3, and further preferably 2.1. Further, the lower limit of the mass ratio is preferably 1.4, and more preferably 1.5, and further preferably 1.6. By making the mass ratio within the above range, a glass having a high refractive index can be obtained.

[0054] In the optical glass of the present embodiment, the mass ratio [Ti02 / (Ti02+Nb205+Zr02)] of the content of Ti02to the total content (Ti02+Nb205+Zr02) of Ti02, Nb205, and Zr02is 0.90 or more. The lower limit of the mass ratio is preferably 0.95, and more preferably 0.98. The upper limit of the mass ratio is preferably 1. Among Ti02, Nb205, and Zr02, which have a strong effect of increasing the refractive index, Ti02is a component that is not easily increased in specific gravity. By making the mass ratio within the above range, an increase in specific gravity can be suppressed while a desired refractive index is obtained.

[0055] In the optical glass of the present embodiment, the mass ratio [(CaO+BaO) / R'O] of the total content of CaO and BaO (CaO+BaO) to the total content of MgO, CaO, SrO, and BaO (R'O) is 0.90 or greater. The lower limit of the mass ratio is preferably 0.95, and more preferably 0.98. The upper limit of the mass ratio is preferably 1. The mass ratio can also be 1. Of the alkaline earth metal oxides, CaO and BaO are components that can strongly maintain the thermal stability of the glass by being appropriately introduced. By setting the mass ratio within the above range, the thermal stability of the glass can be maintained. Furthermore, in the optical glass of the present embodiment, by setting the mass ratio within the above range while reducing the content of BaO, the increase in specific gravity can be suppressed.

[0056] In the optical glass of the present embodiment, the mass ratio [(Na2O+K2O) / R2O] of the total content of Na2O and K2O to R2O is 0.98 or greater. The lower limit of the mass ratio is preferably 0.99. The upper limit of the mass ratio is preferably 1. The mass ratio can also be 1. Of the alkali metal oxides, LiO2 has a relatively strong erosive effect on refractory materials, and Cs2O tends to increase the specific gravity compared to other alkali metal oxides. Of the alkali metal oxides, Na2O and K2O have a superior effect of maintaining the thermal stability of the glass. Therefore, by setting the mass ratio within the above range, the erosion of refractory materials and the increase in specific gravity can be suppressed, and the thermal stability of the glass can be maintained.

[0057] In the optical glass of the present embodiment, the mass ratio [BaO / (Na2O+K2O+CaO)] of the content of BaO to the total content of Na2O, K2O, and CaO is 0.15 or less. The upper limit of the mass ratio is preferably 0.12, and more preferably 0.10. The lower limit of the mass ratio is preferably 0. The mass ratio can also be 0. Na2O, K2O, and CaO have an effect of improving the melting property of the glass. Furthermore, BaO is a component that increases the specific gravity. Therefore, by setting the mass ratio within the above range, the melting property can be improved, and the increase in specific gravity can also be suppressed.

[0058] In the optical glass of the present embodiment, the mass ratio [BaO / (TiO2+Nb2O5)] of the content of BaO to the total content of TiO2 and Nb2O5 is 0.12 or less. The upper limit of the mass ratio is preferably 0.10, and more preferably 0.08. The lower limit of the mass ratio is preferably 0. The mass ratio can also be 0. TiO2 and Nb2O5 are components that impart high refractive index and high dispersion characteristics. Furthermore, BaO is a component that increases the specific gravity. Therefore, by setting the mass ratio within the above range, the increase in specific gravity can be suppressed while maintaining the desired high refractive index and high dispersion characteristics.

[0059] Next, non-limiting examples of the content and proportion of glass components other than the above in the optical glass of the present embodiment are shown below.

[0060] In the optical glass of the present embodiment, the upper limit of the mass ratio of the total content of CaO and TiO2 to the content of SiO2 [(CaO + TiO2) / SiO2] is preferably 1.10, more preferably 1.08, and further preferably 1.07. The lower limit of this mass ratio is preferably 0.90, more preferably 0.92, and further preferably 0.93. From the viewpoint of obtaining a glass with good thermal stability, this mass ratio is preferably within the above range.

[0061] In the optical glass of the present embodiment, the upper limit of the total content (R'O) of MgO, CaO, SrO, and BaO is preferably 20%, and further sequentially more preferably 16%, 14%, and 12%. In addition, the lower limit of R'O is preferably 2%, and further sequentially more preferably 4%, 5%, and 6%. From the viewpoint of improving the melting property and suppressing a decrease in thermal stability, R'O is preferably within the above range.

[0062] In the optical glass of the present embodiment, the upper limit of the mass ratio of the content of BaO to the content of CaO [BaO / CaO] is preferably 0.30, and further sequentially more preferably 0.28 and 0.26. In addition, the lower limit of this mass ratio is preferably 0. This mass ratio can also be 0. From the viewpoint of suppressing an increase in specific gravity, this mass ratio is preferably within the above range.

[0063] K2O, like Na2O, functions to improve the melting property of the glass and adjust the viscosity of the molten glass to an appropriate range. When too much K2O is introduced, the refractive index can decrease, and the corrosiveness of the molten glass can increase. The upper limit of the content of K2O is preferably 7%, more preferably 6%, and further preferably 5%. The lower limit of the content of K2O is preferably 0%. Preferably, the content of K2O in mass% is less than the content of Na2O.

[0064] Li2O is a component that functions to improve the melting property of the glass. However, compared to other alkali metal oxides, Li2O easily corrodes refractory materials. Therefore, the range of the content of Li2O is preferably 0 to 3%, more preferably 0 to 2%, and further preferably 0 to 1%. The content of Li2O can also be 0%.

[0065] Cs2O easily increases the specific gravity compared to other alkali metal oxides. In addition, the raw material cost of Cs2O is high. Therefore, the range of the content of Cs2O is preferably 0 to 5%, more preferably 0 to 3%, and further preferably 0 to 1%. The content of Cs2O can also be 0%.

[0066] CaO has an effect of improving the thermal stability and the melting property of the glass and adjusting the Abbe number. When CaO is excessive, the thermal stability of the glass and the refractive index decrease. The upper limit of the content of CaO is preferably 15%, more preferably 13%, and further preferably 12%. In addition, the lower limit of the content of CaO is preferably 3%, more preferably 5%, and further preferably 6%.

[0067] MgO and SrO have the same effect as CaO and BaO in improving the melting property, but the thermal stability of the glass decreases when the content of either of them is excessive. The content of MgO is preferably in the range of 0 to 10%, more preferably in the range of 0 to 5%, and further preferably in the range of 0 to 3%. The content of MgO can also be 0%. The content of SrO is preferably in the range of 0 to 10%, more preferably in the range of 0 to 5%, and further preferably in the range of 0 to 3%. The content of SrO can also be 0%.

[0068] From the viewpoint of obtaining the above-mentioned properties and characteristics, the total content of SiO2, TiO2, Na2O, K2O, CaO, and BaO is preferably 96% or more, more preferably 99% or more, and further preferably 99.5% or more.

[0069] In the optical glass of the present embodiment, the upper limit of the content of P2O5 is preferably 10%, and further sequentially more preferably 8%, 5%, and 3%, respectively. In addition, the lower limit of the content of P2O5 is preferably 0%. The content of P2O5 can also be 0%. In order to obtain an optical glass having a high refractive index and a small specific gravity, the content of P2O5 is preferably in the above-mentioned range.

[0070] In the optical glass of the present embodiment, the upper limit of the content of B2O3 is preferably 10%, and further sequentially more preferably 8%, 5%, and 3%, respectively. In addition, the lower limit of the content of B2O3 is preferably 0%. The content of B2O3 can also be 0%. Although B2O3 has an effect of improving the thermal stability of the glass, the refractive index decreases when the content of B2O3 is excessive. Therefore, the content of B2O3 is preferably in the above-mentioned range.

[0071] In the optical glass of the present embodiment, the upper limit of the content of Al2O3 is preferably 10%, and further sequentially more preferably 8%, 5%, 3%, 1%, and 0.5%, respectively. The lower limit of the content of Al2O3 is preferably 0%. The content of Al2O3 can also be 0%. Al2O3 has an effect of improving the chemical durability, but the melting property of the glass deteriorates when the content of Al2O3 is excessive. Therefore, the content of Al2O3 is preferably in the above-mentioned range.

[0072] In the optical glass of the present embodiment, the upper limit of the content of Zr02is preferably 10%, further sequentially more preferably 8%, 5%, 3%, 1%, 0.5%. The lower limit of the content of Zr02is preferably 0%. The content of Zr02may also be 0%. Zr02is a component that imparts a high refractive index. On the other hand, when the content of Zr02is too much, the thermal stability decreases, and in addition, the specific gravity increases. Therefore, the content of Zr02is preferably in the above range.

[0073] In the optical glass of the present embodiment, the upper limit of the content of Nb205is preferably 10%, further sequentially more preferably 8%, 5%, 3%. The lower limit of the content of Nb205is preferably 0%. The content of Nb205may also be 0%.

[0074] Nb205is a component that imparts a high refractive index, and has the effect of improving the stability of the glass. On the other hand, when the content of Nb205is too much, the specific gravity increases, and in addition, the thermal stability decreases. Therefore, the content of Nb205is preferably in the above range.

[0075] In the optical glass of the present embodiment, the upper limit of the content of W03is preferably 10%, further sequentially more preferably 8%, 5%, 3%. The lower limit of the content of W03is preferably 0%. The content of W03may also be 0%.

[0076] W03is a component that imparts a high refractive index. On the other hand, when the content of W03is too much, the thermal stability decreases, the specific gravity increases, and in addition, the coloring of the glass increases, and the transmittance decreases. Therefore, the content of W03is preferably in the above range.

[0077] In the optical glass of the present embodiment, the upper limit of the content of Bi203is preferably 10%, further sequentially more preferably 8%, 5%, 3%. In addition, the lower limit of the content of Bi203is preferably 0%. The content of Bi203may also be 0%.

[0078] By containing an appropriate amount of Bi203, the effect of improving the thermal stability of the glass is obtained. In addition, Bi203is a component that achieves a high refractive index. On the other hand, when the content of Bi203is too much, the specific gravity increases. Furthermore, the coloring of the glass increases. Therefore, the content of Bi203is preferably in the above range.

[0079] In the optical glass of the present embodiment, the upper limit of the content of ZnO is preferably 10%, further sequentially more preferably 8%, 5%, 3%. In addition, the lower limit of the content of ZnO is preferably 0%. The content of ZnO may also be 0%.

[0080] ZnO is a glass component having an effect of improving the thermal stability of the glass. However, when the content of ZnO is too much, the specific gravity increases. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining the desired optical properties, the content of ZnO is preferably in the above range.

[0081] In the optical glass of the present embodiment, the upper limit of the content of Ta2O5 is preferably 10%, and further sequentially more preferably 8%, 5%, 3%, respectively. In addition, the lower limit of the content of Ta2O5 is preferably 0%. The content of Ta2O5 can also be 0%.

[0082] Ta2O5 is a component that contributes to high refractive index. In addition, Ta2O5 is a glass component having an effect of improving the thermal stability of the glass. On the other hand, when the content of Ta2O5 is too much, the thermal stability of the glass decreases, and un-melted glass raw materials are easily left over when the molten glass is produced. In addition, the specific gravity increases. Therefore, the content of Ta2O5 is preferably in the above range.

[0083] In the optical glass of the present embodiment, the upper limit of the content of La2O3 is preferably 10%, and further sequentially more preferably 8%, 5%, 3%, respectively. In addition, the lower limit of the content of La2O3 is preferably 0%. The content of La2O3 can also be 0%.

[0084] La2O3 is a component that contributes to high refractive index. On the other hand, when the content of La2O3 is too much, the specific gravity increases, and the thermal stability of the glass decreases. Therefore, from the viewpoint of suppressing the increase in the specific gravity and the decrease in the thermal stability of the glass, the content of La2O3 is preferably in the above range.

[0085] In the optical glass of the present embodiment, the upper limit of the content of Y2O3 is preferably 10%, and further sequentially more preferably 8%, 5%, 3%, respectively. In addition, the lower limit of the content of Y2O3 is preferably 0%. The content of Y2O3 can also be 0%.

[0086] Y2O3 is a component that contributes to high refractive index. On the other hand, when the content of Y2O3 is too much, the thermal stability of the glass decreases, and the glass is easily devitrified during the manufacturing process. Therefore, from the viewpoint of suppressing the decrease in the thermal stability of the glass, the content of Y2O3 is preferably in the above range.

[0087] In the optical glass of the present embodiment, the content of Sc2O3 is preferably 2% or less. In addition, the lower limit of the content of Sc2O3 is preferably 0%. The content of Sc2O3 can also be 0%.

[0088] In the optical glass of the present embodiment, the content of HfO2 is preferably 2% or less. In addition, the lower limit of the content of HfO2 is preferably 0%. The content of HfO2 can also be 0%.

[0089] Sc203, Hf02, although having an effect of increasing the high dispersion of the glass, are expensive components. Therefore, the content of each of Sc203, Hf02is preferably in the above range.

[0090] In the optical glass of the present embodiment, the content of Lu203is preferably 2% or less. Further, the lower limit of the content of Lu203is preferably 0%. The content of Lu203may also be 0%.

[0091] Lu203, although having an effect of increasing the high dispersion of the glass, is a glass component that increases the specific gravity of the glass because of its large molecular weight. Therefore, the content of Lu203is preferably in the above range.

[0092] In the optical glass of the present embodiment, the content of Ge02is preferably 2% or less. Further, the lower limit of the content of Ge02is preferably 0%. The content of Ge02may also be 0%.

[0093] Ge02, although having an effect of increasing the high dispersion of the glass, is a very expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of the glass, the content of Ge02is preferably in the above range.

[0094] In the optical glass of the present embodiment, the upper limit of the content of Gd203is preferably 3.0%, more preferably 2.0%. Further, the lower limit of the content of Gd203is preferably 0%. The content of Gd203may also be 0%.

[0095] Gd203is a component that contributes to high refractive index. On the other hand, when the content of Gd203is too much, the thermal stability of the glass decreases. Further, when the content of Gd203is too much, the specific gravity of the glass increases, so it is not preferable. Therefore, from the viewpoint of maintaining the thermal stability of the glass to be good and suppressing the increase in the specific gravity, the content of Gd203is preferably in the above range.

[0096] In the optical glass of the present embodiment, the content of Yb203is preferably 2% or less. Further, the lower limit of the content of Yb203is preferably 0%. The content of Yb203may also be 0%.

[0097] Yb203is a component that increases the specific gravity of the glass. Further, when the content of Yb203is too much, the thermal stability of the glass decreases. From the viewpoint of preventing the decrease in the thermal stability of the glass and suppressing the increase in the specific gravity, the content of Yb203is preferably in the above range.

[0098] The optical glass of the present embodiment is preferably composed mainly of the above glass components, i.e., SiO2, TiO2, Na2O as essential components, and BaO, K2O, Li2O, Cs2O, CaO, MgO, SrO, P2O5, B2O3, Al2O3, ZrO2, Nb2O5, WO3, Bi2O3, ZnO, Ta2O5, La2O3, Y2O3, Sc2O3, HfO2, Lu2O3, GeO2, Gd2O3, and Yb2O3 as optional components, and the total content of the above glass components is preferably 95% or more, more preferably 98% or more, further preferably 99% or more, and still further preferably 99.5% or more.

[0099] The optical glass of the present embodiment is preferably composed mainly of the above glass components, i.e., SiO2, TiO2, Na2O as essential components, and BaO, K2O, Li2O, Cs2O, CaO, MgO, SrO, P2O5, B2O3, Al2O3, ZrO2, Nb2O5, WO3, Bi2O3, ZnO, Ta2O5, La2O3, Y2O3, Sc2O3, HfO2, Lu2O3, GeO2, Gd2O3, and Yb2O3 as optional components, and the total content of the above glass components is preferably 95% or more, more preferably 98% or more, further preferably 99% or more, and still further preferably 99.5% or more.

[0100] (Other Components)

[0101] The optical glass of the present embodiment can contain a small amount of Sb2O3, CeO2, etc. as a fining agent in addition to the above components. In the present specification, the content of the fining agent is expressed as a percentage excluding the total content of all glass components expressed on an oxide basis. Therefore, when the total content of all glass components excluding the fining agent is set to 100 mass%, the total amount of the fining agent is preferably 1 mass% or less, further preferably 0.5 mass% or less, and still further preferably 0.1 mass% or less. The content of the fining agent can also be 0%.

[0102] Pb, Cd, As, Th, etc. are components that affect the environment.

[0103] Therefore, the content of each of PbO, CdO, and ThO2 is preferably 0 to 0.1%, more preferably 0 to 0.05%, further preferably 0 to 0.01%, and particularly preferably substantially none of PbO, CdO, and ThO2 is contained.

[0104] The content of As2O3 is preferably 0 to 0.1%, more preferably 0 to 0.05%, further preferably 0 to 0.01%, and particularly preferably substantially none of As2O3 is contained.

[0105] Furthermore, the optical glass of the present embodiment can achieve high transmittance in a wide range of the visible region. In order to exhibit this characteristic, it is preferable that coloring elements are not contained. As the coloring elements, Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, etc. can be exemplified. Regardless of which element, it is preferable that each of the elements is less than 100 mass ppm, more preferably 0 to 80 mass ppm, further preferably 0 to 50 mass ppm or less, and particularly preferably substantially none of these elements is contained.

[0106] Further, Ga, Te, Tb, and the like are components that need not be introduced, and are also expensive components. Therefore, the content of each of Ga2O3, TeO2, and TbO2, expressed in mass%, is preferably 0 to 0.1%, more preferably 0 to 0.05%, further preferably 0 to 0.01%, still further preferably 0 to 0.005%, yet further preferably 0 to 0.001%, and particularly preferably substantially does not contain these components.

[0107] (Glass properties)

[0108] [Abbe number νd, refractive index nd]

[0109] In the optical glass of the present embodiment, the Abbe number νd is preferably 26 or higher, more preferably 26.5 or higher, and further preferably 27 or higher, from the viewpoint of correcting chromatic aberration in combination with a lens made of a glass having other optical properties. The upper limit of the Abbe number νd is preferably 33, more preferably 32.5, and further preferably 32.

[0110] An optical glass having a high refractive index nd is desirable because it can have the same light condensing ability and can reduce the absolute value of the curvature of the optical functional surface of the lens (slow down the curve of the optical functional surface of the lens). In the optical glass of the present embodiment, the lower limit of the refractive index nd is preferably 1.67, more preferably 1.675, and further preferably 1.68.

[0111] On the other hand, when the refractive index is too high, the relative proportion of the high refractive index component becomes high, and the specific gravity of the glass increases. From the viewpoint of suppressing an increase in the specific gravity, in the optical glass of the present embodiment, the upper limit of the refractive index nd is preferably 1.77, more preferably 1.765, and further preferably 1.76.

[0112] [Transmittance]

[0113] The optical glass of the present embodiment can be an optical glass having little coloration. This optical glass is suitable as a material for an optical element for imaging, such as a camera lens, and an optical element for projection, such as a projector.

[0114] The degree of coloration of a general optical glass is indicated by λ80, λ70, λ5, and the like. The spectral transmittance of a glass sample having a thickness of 10.0 mm ± 0.1 mm is measured in the wavelength range of 200 to 700, and the wavelength at which the external transmittance is 80% is set as λ80, the wavelength at which the external transmittance is 70% is set as λ70, and the wavelength at which the external transmittance is 5% is set as λ5.

[0115] The λ80 of the optical glass of the present embodiment is preferably 480 nm or lower, the λ70 is preferably 440 nm or lower, and the λ5 is preferably 380 nm or lower.

[0116] [Glass transition temperature Tg]

[0117] The glass transition temperature Tg of the optical glass of the present embodiment is preferably 640°C or lower. When the glass transition temperature is low, the heating temperature at the time of reheating, softening, and press molding of the glass can be reduced. As a result, fusion of the glass and the press molding mold can be easily suppressed. Furthermore, since the heating temperature can be reduced, the heat consumption of the heating device, the press molding mold, and the like of the glass can be reduced. Furthermore, since the annealing temperature of the glass can also be reduced, the life of the annealing furnace can be extended. The glass transition temperature is more preferably 635°C or lower, and further preferably 630°C or lower.

[0118] [Specific gravity]

[0119] The specific gravity of the optical glass of the present embodiment is preferably 3.40 or lower. The specific gravity is more preferably 3.20 or lower, further preferably 3.10 or lower, and particularly preferably 3.00 or lower.

[0120] [Use]

[0121] The optical glass of the present embodiment is preferably an optical lens optical glass or a prism optical glass.

[0122] [Manufacturing method]

[0123] The optical glass of the present embodiment can be obtained, for example, by blending, melting, and molding a glass raw material to obtain the desired properties. As the glass raw material, oxides, carbonates, nitrates, sulfates, and the like can be used. As the melting method and the molding method of the glass, known methods can be used.

[0124] [Glass raw material for press molding, manufacturing method thereof, and manufacturing method of glass molded body]

[0125] According to one embodiment of the present application, a glass raw material for press molding composed of the optical glass of the present embodiment, a glass molded body composed of the optical glass of the present embodiment, and a manufacturing method thereof can be provided.

[0126] Press molding of the glass raw material for press molding can be performed by using a press molding mold to press the glass raw material for press molding that is in a softened state by heating. Both the heating and the press molding can be performed in an atmospheric environment. By uniformly applying a powder-like releasing agent such as boron nitride to the surface of the glass raw material for press molding and performing heating and press molding, fusion of the glass and the molding mold can be reliably prevented, and the glass can be smoothly stretched along the molding surface of the press molding mold. By performing annealing after press molding to reduce the strain in the glass, a homogeneous optical element blank can be obtained.

[0127] As examples of the glass raw material for press molding, there are a preform for precision press molding, a glass raw material for press molding an optical element blank (a press molding glass gob), and the like, and a glass block having a mass equivalent to that of a target press molded product.

[0128] Further, the glass raw material for press molding is also referred to as a preform, and includes, in addition to those directly supplied to press molding, those supplied to press molding by machining such as cutting, grinding, and polishing. As a cutting method, there are a method in which a groove is formed on a part to be cut on the surface of a glass sheet by a scribe method, and a part of the groove on the back surface of the face on which the groove is formed is subjected to local pressure to cut the glass sheet at the part of the groove, or a method in which a glass sheet is cut with a cutting blade. Further, as a grinding method, there are spherical machining using a curve generator, smooth machining, and the like. As a polishing method, there is a method in which polishing is performed using abrasive grains such as ceria and zirconia.

[0129] [Optical element blank and method for manufacturing the same]

[0130] According to one embodiment of the present application, an optical element blank can be provided, which is composed of the optical glass of the present embodiment. The optical element blank is a glass formed body having a shape similar to that of an optical element to be manufactured. The optical element blank can be manufactured by a method of forming a shape which is the shape of the optical element to be manufactured plus a processing allowance to be removed at the time of processing, or the like. For example, the optical element blank can be produced by a method of heating, softening, and press molding a glass raw material for press molding (reheat press method), a method of supplying a molten glass block to a press molding mold by a known method to press mold (direct press method), or the like.

[0131] [Optical element and method for manufacturing the same]

[0132] According to one embodiment of the present application, an optical element can be provided, which is composed of the optical glass of the present embodiment. As a kind of the optical element, there are a lens such as a spherical lens and an aspherical lens, a prism, a diffraction grating, and the like. As a shape of the lens, there are various shapes such as a double convex lens, a plano-convex lens, a double concave lens, a plano-concave lens, a convex meniscus lens, a concave meniscus lens, and the like. The optical element can be manufactured by a method including a step of processing a glass formed body composed of the optical glass of the present embodiment. As the processing, there are cutting, dicing, rough grinding, fine grinding, polishing, and the like. By using the above glass at the time of performing such processing, damage can be reduced and a high-quality optical element can be stably provided.

[0133] [Embodiment]

[0134] Hereinafter, the present application will be described in detail further by way of examples. However, the present application is not limited to the modes shown in the examples.

[0135] (Example 1)

[0136] In order to form the glass compositions shown in Table 1 (1) to (3), respective oxides and the like corresponding to each component were used as raw materials for introducing each component, and the raw materials were weighed and mixed sufficiently to prepare a mixed raw material.

[0137] The mixed raw material was put in a platinum crucible and heated and melted. After melting, the molten glass was introduced into a mold, and immediately after cooling to around the glass transition temperature, the glass was put in an annealing furnace and annealed at around the glass transition temperature for about 1 hour, and then cooled to room temperature in the furnace, whereby an optical glass having the composition shown in Table 1 (1) to (3) was obtained.

[0138] When the obtained optical glass was observed under a light microscope with magnification, no crystallization, no foreign matter such as platinum particles from the platinum crucible, no bubbles, and no streaks were observed.

[0139] Each property of the obtained optical glass was measured by the following method. The results are shown in Table 2.

[0140] (i) Refractive indices nd, ng, nF, nC, and Abbe number vd

[0141] For the glass obtained by lowering the temperature at a rate of -30°C / hour, the refractive indices nd, ng, nF, nC were measured according to the refractive index measurement method of the Japan Optical Glass Industry Association standard, and the Abbe number vd was calculated based on Equation (1).

[0142] vd = (nd - l) / (nF - nC)... (1)

[0143] (ii) Transmittance (λ80, λ70, and λ5)

[0144] The spectral transmittance of a sample having a thickness of 10.0 mm ± 0.1 mm was measured in the range of wavelengths from 200 to 700 nm. The wavelength at which the external transmittance was 80% was set as λ80, the wavelength at which the external transmittance was 70% was set as λ70, and the wavelength at which the external transmittance was 5% was set as λ5.

[0145] (iii) Glass transition temperature Tg

[0146] A differential scanning calorimeter (DSC3300) manufactured by NETZSCH was used, and the measurement was performed at a temperature increase rate of 10°C / minute.

[0147] (iv) Specific gravity

[0148] The measurement was performed according to the Archimedes method.

[0149] [Table 1 (1)]

[0150]

[0151] [Table 1 (2)]

[0152]

[0153] [Table 1 (3)]

[0154]

[0155] [Table 2]

[0156]

[0157] (Example 2)

[0158] Using a glass melting furnace having a melting tank made of a refractory material, a refining tank made of platinum alloy, and a working tank (stirring tank), a batch material prepared in a manner that each optical glass prepared in Example 1 can be obtained was charged into the melting tank, and the glass was melted.

[0159] The batch material was melted into a molten glass in the melting tank, and the molten glass was flowed from the melting tank into the refining tank through a pipe connecting the melting tank and the refining tank, and from the refining tank into the working tank through a pipe connecting the refining tank and the working tank, and in this process, refining and homogenization were performed, and the glass was flowed into a mold for molding through a discharge pipe installed at the bottom of the working tank.

[0160] The glass was molded in the mold, and the molded glass was annealed to obtain an optical glass. The obtained optical glass was observed, and it was confirmed that there were no unmelted residues of the raw material, no mixing of the refractory material, and no crystallization.

[0161] Each optical glass obtained in Example 1 was produced using a continuous-type glass melting furnace in this way. In addition, the above glass melting furnace has a publicly known structure.

[0162] (Example 3)

[0163] Using each optical glass prepared in Example 2, a lens blank was prepared by a known method, and the lens blank was processed by a known method such as polishing, and various lenses were prepared.

[0164] The prepared optical lenses were various lenses such as a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, a concave meniscus lens, and a convex meniscus lens.

[0165] Since the specific gravity of the glass is low, each lens has a small weight compared to a lens having the same optical characteristics and size, and is suitable for various image pickup devices, particularly, an automatic focusing type image pickup device since energy can be saved. Similarly, a prism is produced using each optical glass produced in Example 2.

[0166] It should be understood that the embodiments disclosed herein are exemplary in all points, and are not intended to limit the present application. The scope of the present application is represented by the scope of the claims rather than the above description, and is intended to include all modifications having equivalent meanings and within the scope of the claims.

[0167] For example, for the glass composition shown above, an optical glass of one embodiment of the present application can be produced by performing the component adjustment described in the specification.

[0168] Further, of course, two or more of the matters described in the specification as examples or preferred ranges can be arbitrarily combined.

Claims

1. An optical glass, Expressed as a percentage of mass, The SiO2 content is 20-51%. The TiO2 content is 20-40%. The Na2O content is 5-28%. The BaO content is less than 2.0%. The CaO content is above 6%. The total content of Li2O, Na2O, K2O and Cs2O (R2O) is 8-28%. The mass ratio of SiO2 content to the total content of SiO2, B2O3, and P2O5 (SiO2+B2O3+P2O5) [SiO2 / (SiO2+B2O3+P2O5)] is 0.90 or higher. The mass ratio of SiO2 to R2O [SiO2 / R2O] is 1.5~3.

2. The mass ratio of the total content of SiO2 and R2O (SiO2+R2O) to the total content of TiO2 and Nb2O5 (TiO2+Nb2O5) [(SiO2+R2O) / (TiO2+Nb2O5)] is less than 2.

6. The mass ratio of TiO2 content to the total content of TiO2, Nb2O5, and ZrO2 (TiO2+Nb2O5+ZrO2) [TiO2 / (TiO2+Nb2O5+ZrO2)] is 0.90 or higher. The mass ratio of the total content of CaO and BaO (CaO+BaO) to the total content of MgO, CaO, SrO and BaO (R'O) [(CaO+BaO) / R'O] is 0.90 or higher. The total content of Na2O and K2O to the mass ratio of R2O [(Na2O+K2O) / R2O] is greater than 0.

98. The mass ratio of BaO content to the total content of Na2O, K2O, and CaO [BaO / (Na2O+K2O+CaO)] is less than 0.

15. The mass ratio of BaO content to the total content of TiO2 and Nb2O5 [BaO / (TiO2+Nb2O5)] is less than 0.

12.

2. The optical glass according to claim 1, wherein the refractive index nd is 1.67~1.77 and the Abbe number νd is 26~33.

3. The optical glass according to claim 1, wherein the specific gravity is 3.40 or less.

4. The optical glass according to claim 2 has a specific gravity of 3.40 or less.

5. The optical glass according to any one of claims 1 to 4, wherein, The SiO2 content is above 25%.

6. The optical glass according to any one of claims 1 to 4, wherein, The SiO2 content is above 30%.

7. The optical glass according to any one of claims 1 to 4, wherein, The SiO2 content is above 33%.

8. The optical glass according to any one of claims 1 to 4, wherein, The SiO2 content is below 50%.

9. The optical glass according to any one of claims 1 to 4, wherein, The SiO2 content is below 49%.

10. The optical glass according to any one of claims 1 to 4, wherein, The SiO2 content is below 48%.

11. The optical glass according to any one of claims 1 to 4, wherein, The TiO2 content is above 22%.

12. The optical glass according to any one of claims 1 to 4, wherein, The TiO2 content is above 24%.

13. The optical glass according to any one of claims 1 to 4, wherein, The TiO2 content is above 25%.

14. The optical glass according to any one of claims 1 to 4, wherein, The TiO2 content is below 38%.

15. The optical glass according to any one of claims 1 to 4, wherein, The TiO2 content is below 36%.

16. The optical glass according to any one of claims 1 to 4, wherein, The TiO2 content is below 35%.

17. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is above 8%.

18. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is above 10%.

19. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is above 12%.

20. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is above 13%.

21. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is below 25%.

22. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is below 23%.

23. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is below 21%.

24. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is below 19%.

25. The optical glass according to any one of claims 1 to 4, wherein, The Na2O content is below 17%.

26. The optical glass according to any one of claims 1 to 4, wherein, The BaO content is less than 1.5%.

27. The optical glass according to any one of claims 1 to 4, wherein, The BaO content is less than 1.0%.

28. The optical glass according to any one of claims 1 to 4, wherein, The BaO content is less than 0.5%.

29. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [SiO2 / (SiO2+B2O3+P2O5)] is 0.95 or higher.

30. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [SiO2 / (SiO2+B2O3+P2O5)] is 0.98 or higher.

31. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [SiO2 / R2O] is 1.7 or higher.

32. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [SiO2 / R2O] is 1.9 or higher.

33. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [SiO2 / R2O] is 2.1 or higher.

34. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [SiO2 / R2O] is 2.3 or higher.

35. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [SiO2 / R2O] is 3.1 or less.

36. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [SiO2 / R2O] is 3.0 or less.

37. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(SiO2+R2O) / (TiO2+Nb2O5)] is 2.5 or less.

38. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(SiO2+R2O) / (TiO2+Nb2O5)] is 2.3 or less.

39. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(SiO2+R2O) / (TiO2+Nb2O5)] is 2.1 or less.

40. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(SiO2+R2O) / (TiO2+Nb2O5)] is 1.4 or higher.

41. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(SiO2+R2O) / (TiO2+Nb2O5)] is 1.5 or higher.

42. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(SiO2+R2O) / (TiO2+Nb2O5)] is 1.6 or higher.

43. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [TiO2 / (TiO2+Nb2O5+ZrO2)] is 0.95 or higher.

44. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [TiO2 / (TiO2+Nb2O5+ZrO2)] is 0.98 or higher.

45. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(CaO+BaO) / R'O] is 0.95 or higher.

46. ​​The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(CaO+BaO) / R'O] is 0.98 or higher.

47. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [(Na2O+K2O) / R2O] is 0.99 or higher.

48. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [BaO / (Na2O+K2O+CaO)] is 0.12 or less.

49. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio [BaO / (Na2O+K2O+CaO)] is less than 0.

10.

50. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio of the total content of CaO and TiO2 to the content of SiO2 [(CaO+TiO2) / SiO2] is less than 1.

10.

51. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio of the total content of CaO and TiO2 to the content of SiO2 [(CaO+TiO2) / SiO2] is less than 1.

08.

52. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio of the total content of CaO and TiO2 to the content of SiO2 [(CaO+TiO2) / SiO2] is less than 1.

07.

53. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio of the total content of CaO and TiO2 to the content of SiO2 [(CaO+TiO2) / SiO2] is greater than 0.

90.

54. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio of the total content of CaO and TiO2 to the content of SiO2 [(CaO+TiO2) / SiO2] is greater than 0.

92.

55. The optical glass according to any one of claims 1 to 4, wherein, The mass ratio of the total content of CaO and TiO2 to the content of SiO2 [(CaO+TiO2) / SiO2] is greater than 0.

93.

56. An optical element comprising the optical glass of any one of claims 1 to 55.

Images