Optical glass and optical elements

Abstract

To provide an optical glass in which the increase in the partial dispersion ratio Pg,F is suppressed and the specific gravity is low, as well as an optical element made of the optical glass. [Solution] The SiO2 content is 10.0 to 40.0 mass%, the Li2O content is greater than 0.0 mass% and 15.0 mass% or less, the Nb2O5 content is 10.0 to 40.0 mass%, the B2O3 content is greater than 0.0 mass% and 7.0 mass% or less, the ZnO content is 5.0 mass% or less, the TiO2 content is 13.0 mass% or less, the mass ratio of the total content of Na2O and K2O to the Li2O content [(Na2O+K2O) / Li2O] is 1.50 or less, and the total content of Li2O, Na2O, and K2O R Optical glass having a total content of La2O3, Gd2O3, Y2O3, and Yb2O3 relative to 2O, with the total mass ratio of Re2O3 to the total content of MgO, CaO, SrO, and BaO, R'O [(Re2O3+R'O) / R2O] being 0.79 or less, a total mass ratio of the above total content of R2O to the total content of ZrO2 relative to the total content of SiO2 and B2O3 [(R2O+ZrO2) / (SiO2+B2O3)] being 0.50 or more, and a total content of BaO and La2O3 [BaO+La2O3] being 5.0% by mass or less.

Description

Technical Field

[0005] ,

[0001] The present invention relates to an optical glass and an optical element having a desired optical constant.

Background Art

[0006] Therefore, the present invention aims to provide an optical glass in which the increase in the partial dispersion ratio Pg,F is suppressed and the specific gravity is low, as well as an optical element made of the optical glass. [Means for solving the problem]

[0007] The gist of this invention is as follows: (1) The SiO2 content is 10.0 to 40.0% by mass, The Li2O content is greater than 0.0% by mass and less than or equal to 15.0% by mass. The Nb2O5 content is 10.0 to 40.0% by mass. The B2O3 content is greater than 0.0% by mass and less than or equal to 7.0% by mass. The ZnO content is 5.0% by mass or less. The TiO2 content is 13.0% by mass or less. The mass ratio of the total content of Na2O and K2O to the content of Li2O [(Na2O+K2O) / Li2O] is 1.50 or less. The mass ratio [(Re2O3+R'O) / R2O] of the total content of La2O3, Gd2O3, Y2O3, and Yb2O3 (Re2O3) and the total content of MgO, CaO, SrO, and BaO (R'O) to the total content of Li2O, Na2O, and K2O (R2O) is 0.79 or less. The mass ratio of the total content of R2O and ZrO2 to the total content of SiO2 and B2O3 [(R2O+ZrO2) / (SiO2+B2O3)] is 0.50 or greater. Optical glass in which the total content of BaO and La2O3 [BaO + La2O3] is 5.0% by mass or less.

[0008] (2) The optical glass according to (1), wherein the mass ratio of the Nb2O5 content to the total content of SiO2 and B2O3 [Nb2O5 / (SiO2+B2O3)] is 0.65 or more.

[0009] (3) The optical glass according to (1), wherein the total content of Re2O3 of La2O3, Gd2O3, Y2O3, and Yb2O3 is 5.0% by mass or less.

[0010] (4) The optical glass according to (1), wherein the total content of Li2O, Na2O, and K2O, the total content of R2O, La2O3, Gd2O3, Y2O3, and Yb2O3, and the total content of Re2O3 and ZrO2 [(R2O+Re2O3+ZrO2) / (TiO2+Nb2O5)] relative to the total content of TiO2 and Nb2O5 is 0.70 or greater.

[0011] (5) The optical glass described in (1) that satisfies one or more of the following conditions (i) to (ii). (i) The total content of MgO, CaO, SrO, and BaO (R'O) is 7.0% by mass or less. (ii) The mass ratio of the Na2O content to the total B2O3 and Nb2O5 content [Na2O / (B2O3+Nb2O5)] is 0.18 or less.

[0012] (6) The optical glass described in (1) that satisfies two or more of the following conditions (iii) to (vii). (iii) The mass ratio of the Nb2O5 content to the total content of SiO2 and B2O3 [Nb2O5 / (SiO2+B2O3)] is 0.65 or higher. (iv) The total content of Re2O3 among La2O3, Gd2O3, Y2O3, and Yb2O3 is 5.0% by mass or less. (v) The mass ratio [(R2O + Re2O3 + ZrO2) / (TiO2 + Nb2O5)] of the total content of Li2O, Na2O, and K2O (R2O), the total content of La2O3, Gd2O3, Y2O3, and Yb2O3 (Re2O3), and the content of ZrO2 to the total content of TiO2 and Nb2O5 is 0.70 or more. (vi) The total content of MgO, CaO, SrO, and BaO (R’O) is 7.0% by mass or less. (vii) The mass ratio [Na2O / (B2O3 + Nb2O5)] of the content of Na2O to the total content of B2O3 and Nb2O5 is 0.18 or less.

[0013] (7) The optical glass according to (1), satisfying one or more of the following (viii) to (xii). (viii) The content of Ta2O5 is 10.0% by mass or less. (ix) The total content of Li2O, Na2O, and K2O (R2O) exceeds 0.0% by mass and is 22.5% by mass or less. (x) The mass ratio [Na2O / Li2O] of the content of Na2O to the content of Li2O is 1.00 or less. (xi) The mass ratio [K2O / Na2O] of the content of K2O to the content of Na2O is 1.00 or less. (xii) The mass ratio [TiO2 / Nb2O5] of the content of TiO2 to the content of Nb2O5 is 0.33 or less.

[0014] (8) An optical element made of the optical glass according to any one of (1) to (7) above.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide an optical glass in which an increase in the partial dispersion ratio Pg,F is suppressed and the specific gravity is small, and an optical element made of the optical glass.

Embodiments for Carrying Out the Invention

[0016] In the present invention and this 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" refers to the glass composition obtained by converting all glass raw materials into oxides existing in the optical glass when melted, and the notation of each glass component follows the convention, such as being described as SiO2, TiO2, etc. The content and total content of the glass components are on a mass basis unless otherwise specified, and "%" means "mass %".

[0017] The content of the glass component can be quantified by known methods, such as methods like inductively coupled plasma atomic emission spectrometry (ICP - AES), inductively coupled plasma mass spectrometry (ICP - MS), etc. Also, in this specification and the present invention, when the content of a constituent component is 0.0%, it means that this constituent component is substantially not contained, and it is allowed that the component is contained at an inevitable impurity level.

[0018] Also, in this specification, unless otherwise specified, the refractive index refers to the refractive index nd at the d - line of helium (wavelength 587.56 nm).

[0019] The Abbe number νd is used as a value representing the property related to dispersion and is expressed by the following formula. Here, nF is the refractive index at the F - line of blue hydrogen (wavelength 486.13 nm), and nC is the refractive index at the C - line of red hydrogen (656.27 nm). νd=(nd - 1) / (nF - nC)

[0020] The partial dispersion ratio Pg,F is expressed as follows using the refractive indices ng, nF, and nC at the g - line, F - line, and c - line. Pg,F=(ng - nF) / (nF - nC) In a plane with the Abbe number νd on the horizontal axis and the partial dispersion ratio Pg,F on the vertical axis, the normal line is expressed by the following formula. Pg,F(0)=0.6483-(0.001802×νd) Furthermore, the deviation ΔPg,F of the partial dispersion ratio Pg,F from the normal line is expressed as follows. ΔPg,F=Pg,F - Pg,F(0)

[0021] In this specification, both the thermal stability and reheating stability of glass refer to the resistance to crystal precipitation within the glass. Specifically, thermal stability refers to the resistance to crystal precipitation when molten glass solidifies, and reheating stability refers to the resistance to crystal precipitation when solidified glass is reheated, such as during reheat pressing.

[0022] Embodiments of the present invention will be described below.

[0023] The optical glass according to this embodiment is The SiO2 content is 10.0-40.0%. The Li2O content is greater than 0.0% and less than or equal to 15.0%. The Nb2O5 content is 10.0-40.0%. The B2O3 content is greater than 0.0% and less than or equal to 7.0%. The ZnO content is 5.0% or less. The TiO2 content is 13.0% or less. The mass ratio of the total content of Na2O and K2O to the content of Li2O [(Na2O+K2O) / Li2O] is 1.50 or less. The mass ratio [(Re2O3+R'O) / R2O] of the total content of La2O3, Gd2O3, Y2O3, and Yb2O3 (Re2O3) and the total content of MgO, CaO, SrO, and BaO (R'O) to the total content of Li2O, Na2O, and K2O (R2O) is 0.79 or less. The mass ratio of the total content of R2O and ZrO2 to the total content of SiO2 and B2O3 [(R2O+ZrO2) / (SiO2+B2O3)] is 0.50 or greater. The total content of BaO and La2O3 [BaO + La2O3] is 5.0% or less.

[0024] In the optical glass according to this embodiment, the SiO2 content is 10.0 to 40.0%. The lower limit of the SiO2 content is preferably 15.0%, and more preferably in the order of 20.0%, 22.0%, 24.0%, 25.0%, 26.0%, 27.0%, 28.0%, 28.5%, 29.0%, and 30.0%. The upper limit of the SiO2 content is preferably 39.5%, and more preferably in the order of 39.0%, 38.5%, 38.0%, 37.5%, 37.0%, 36.5%, and 36.0%. By setting the SiO2 content within the above range, optical glass having the desired optical constants can be obtained. On the other hand, if the SiO2 content is too low, vitrification may become difficult. If the SiO2 content is too high, it may be difficult to obtain the desired optical constants, and the liquidus temperature LT may increase.

[0025] In the optical glass according to this embodiment, the Li2O content is greater than 0.0% and less than or equal to 15.0%. The lower limit of the Li2O content is preferably 0.5%, and more preferably in the order of 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, and 9.0%. The upper limit of the Li2O content is preferably 14.5%, and more preferably in the order of 14.0%, 13.5%, 13.0%, 12.5%, 12.0%, 11.8%, 11.6%, 11.4%, 11.2%, 11.1%, 11.0%, 10.9%, and 10.8%. By setting the Li2O content within the above range, an optical glass can be obtained that has the desired refractive index nd and suppresses an increase in the partial dispersion ratio Pg,F. On the other hand, if the Li2O content is too low, the refractive index nd may decrease and the partial dispersion ratio Pg,F may increase. If the Li2O content is too high, the stability and chemical durability during reheating may decrease.

[0026] In the optical glass according to this embodiment, the Nb2O5 content is 10.0 to 40.0%. The lower limit of the Nb2O5 content is preferably 12.0%, and more preferably in the order of 14.0%, 16.0%, 18.0%, 20.0%, 22.0%, 24.0%, 25.0%, 26.0%, 27.0%, 28.0%, 29.0%, 30.0%, 30.1%, 30.2%, 30.3%, and 30.4%. The upper limit of the Nb2O5 content is preferably 39.0%, and more preferably in the order of 38.0%, 37.0%, 36.0%, 35.0%, 34.5%, 34.0%, 33.5%, 33.0%, 32.8%, and 32.6%. By setting the Nb2O5 content within the above range, optical glass with the desired optical constants can be obtained. On the other hand, if the Nb2O5 content is too low, the refractive index nd will decrease, or the Abbe number νd will increase too much due to low dispersion, and optical glass with the target optical constants may not be obtained. If the Nb2O5 content is too high, the specific gravity will increase, the Abbe number νd will decrease too much due to high dispersion, raw material costs will increase, and the liquidus temperature LT may increase.

[0027] In the optical glass according to this embodiment, the B2O3 content is greater than 0.0% and less than or equal to 7.0%. The lower limit of the B2O3 content is preferably 0.2%, and more preferably in the order of 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, and 1.6%. The upper limit of the B2O3 content is preferably 6.8%, and more preferably in the order of 6.6%, 6.4%, 6.2%, 6.1%, 6.0%, 5.9%, 5.8%, 5.7%, 5.6%, 5.5%, 5.4%, and 5.3%. By setting the B2O3 content within the above range, optical glass having the desired optical constants can be obtained. On the other hand, if the B2O3 content is too low, there is a risk that optical glass having the desired optical constants cannot be obtained. If the B2O3 content is too high, the liquid phase temperature LT may rise, which may worsen the stability during reheating.

[0028] In the optical glass according to this embodiment, the ZnO content is 5.0% or less. The upper limit of the ZnO content is preferably 4.5%, and more preferably in the order of 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, 1.0%, and 0.5%. The lower limit of the ZnO content is preferably 0.0%. By setting the ZnO content within the above range, optical glass with a high refractive index can be obtained. On the other hand, if the ZnO content is too high, the thermal stability of the glass may deteriorate.

[0029] In the optical glass according to this embodiment, the TiO2 content is 13.0% or less. The upper limit of the TiO2 content is preferably 12.0%, and more preferably in the order of 11.0%, 10.0%, 9.0%, 8.0%, 7.0%, 6.0%, 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%. The lower limit of the TiO2 content is preferably 0.0%. By setting the TiO2 content within the above range, optical glass having the desired optical constants can be obtained. On the other hand, if the TiO2 content is too high, the partial dispersion ratio Pg,F may increase.

[0030] In the optical glass according to this embodiment, the mass ratio of the total content of Na2O and K2O to the content of Li2O [(Na2O+K2O) / Li2O] is 1.50 or less. The upper limit of this mass ratio is preferably 1.45, and more preferably in the order of 1.40, 1.35, 1.30, 1.25, 1.20, 1.15, 1.10, 1.05, 1.00, 0.95, and 0.90. Furthermore, the mass ratio is preferably greater than 0.00, and the lower limit is preferably 0.10, and more preferably in the order of 0.20, 0.30, 0.40, 0.50, and 0.60.

[0031] Alkali metals Li2O, Na2O, and K2O are glass components that contribute to a decrease in the partial dispersion ratio Pg,F and a decrease in specific gravity. On the other hand, if the content of these glass components is too high, the chemical durability and stability during reheating may decrease, and the specific gravity may increase. Among alkali metals, Li2O > Na2O > K2O has the greatest effect in increasing the refractive index nd. Also, K2O > Na2O > Li2O has the greatest effect in increasing the partial dispersion ratio Pg,F. Furthermore, K2O > Na2O > Li2O has the greatest effect in decreasing stability during reheating. Therefore, by setting the mass ratio [(Na2O + K2O) / Li2O] within the above range, an optical glass with the desired optical constants and stability during reheating in reheat pressing can be obtained.

[0032] In the optical glass according to this embodiment, the mass ratio [(Re2O3+R'O) / R2O] of the total content of La2O3, Gd2O3, Y2O3, and Yb2O3 (Re2O3) and the total content of MgO, CaO, SrO, and BaO (R'O) to the total content of Li2O, Na2O, and K2O (R2O) is 0.79 or less. The upper limit of this mass ratio is preferably 0.78, and more preferably in the order of 0.77, 0.76, 0.75, 0.74, 0.73, 0.72, 0.71, 0.70, 0.67, 0.65, 0.63, 0.60, and 0.58. The lower limit of this mass ratio is preferably 0.00.

[0033] The glass components La2O3, Gd2O3, Y2O3, and Yb2O3 in the total Re2O3 content, and the glass components MgO, CaO, SrO, and BaO in R'O, have the effect of increasing the refractive index nd compared to the glass components Li2O, Na2O, and K2O in R2O. On the other hand, if the total content of Re2O3 and R'O is too high, the specific gravity may increase and the liquidus temperature LT may rise. Therefore, by setting the mass ratio [(Re2O3+R'O) / R2O] within the above range, an optical glass with the desired refractive index nd and reduced specific gravity can be obtained.

[0034] In the optical glass according to this embodiment, the mass ratio of the total content of Li2O, Na2O, and K2O (R2O + ZrO2) to the total content of SiO2 and B2O3 (R2O + ZrO2) [(R2O + ZrO2) / (SiO2 + B2O3)] is 0.50 or higher. The lower limit of this mass ratio is preferably 0.51, and more preferably in the order of 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, and 0.65. Furthermore, the upper limit of the mass ratio is preferably 1.00, and more preferably in the order of 0.95, 0.90, 0.89, 0.88, 0.87, 0.86, 0.85, 0.84, 0.83, 0.82, 0.81, 0.80, 0.79, 0.78, 0.77, 0.76, 0.75, 0.74, and 0.73.

[0035] The glass components Li2O, Na2O, K2O, and ZrO2 in the total R2O content mentioned above have the effect of lowering the partial dispersion ratio Pg,F. On the other hand, if the content of these components is too high, the thermal stability of the glass may decrease. Furthermore, SiO2 and B2O3 have the effect of improving the thermal stability of the glass, but they also have the effect of increasing the partial dispersion ratio Pg,F. Therefore, by setting the mass ratio [(R2O+ZrO2) / (SiO2+B2O3)] within the above range, the increase in the partial dispersion ratio Pg,F is suppressed, and an optical glass with excellent thermal stability can be obtained.

[0036] In the optical glass according to this embodiment, the total content of BaO and La2O3 [BaO + La2O3] is 5.0% or less. The upper limit of the total content is preferably 4.8%, and more preferably in the order of 4.6%, 4.4%, 4.2%, 4.0%, 3.9%, 3.8%, 3.7%, 3.6%, 3.5%, and 3.4%. The lower limit of the total content is preferably 0.0%. By setting the total content within the above range, an optical glass with a low specific gravity can be obtained. On the other hand, if the total content is too high, the specific gravity may increase.

[0037] The following are non-limiting examples of the content and ratio of glass components other than those mentioned above in the optical glass according to this embodiment.

[0038] In the optical glass according to this embodiment, the lower limit of the mass ratio of Nb2O5 content to the total content of SiO2 and B2O3 [Nb2O5 / (SiO2+B2O3)] is preferably 0.65, and more preferably in the order of 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, and 0.80. The upper limit of this mass ratio is preferably 1.50, and more preferably in the order of 1.40, 1.30, 1.20, 1.10, 1.00, 0.99, 0.98, 0.97, 0.96, 0.95, 0.94, 0.93, 0.92, 0.91, and 0.90. If the mass ratio is too large, the specific gravity may increase, the partial dispersion ratio Pg,F may rise, and the thermal stability of the glass may decrease. If the mass ratio is too small, the refractive index nd may decrease, and it may not be possible to obtain optical glass with the desired optical constants.

[0039] In the optical glass according to this embodiment, the upper limit of the total Re2O3 content of La2O3, Gd2O3, Y2O3, and Yb2O3 is preferably 5.0%, and more preferably in the order of 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, and 1.0%. The lower limit of the total Re2O3 content is preferably 0.0%. From the viewpoint of increasing the refractive index nd and decreasing the partial dispersion ratio Pg,F, it is preferable to set the total Re2O3 content within the above range. If the total Re2O3 content is too high, the specific gravity may increase, and the thermal stability of the glass may decrease.

[0040] In the optical glass according to this embodiment, the lower limit of the mass ratio [(R2O+Re2O3+ZrO2) / (TiO2+Nb2O5)] of the total content of Li2O, Na2O, and K2O, the total content of La2O3, Gd2O3, Y2O3, and Yb2O3, and the total content of Re2O3 and ZrO2 to the total content of TiO2 and Nb2O5 is preferably 0.70, and more preferably in the order of 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, and 0.83. Furthermore, the upper limit of the mass ratio is preferably 6.00, and more preferably in the order of 5.50, 5.00, 4.50, 4.00, 3.50, 3.00, 2.50, 2.00, 1.90, 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, 1.20, 1.10, and 1.00. From the viewpoint of reducing the partial dispersion ratio Pg,F, it is preferable to set the mass ratio within the above range. The glass components Li2O, Na2O, and K2O with a total content of R2O, the glass components La2O3, Gd2O3, Y2O3, and Yb2O3 with a total content of Re2O3, and ZrO2 are components that have the effect of reducing the partial dispersion ratio Pg,F more than TiO2 and Nb2O5. Therefore, if the mass ratio is too small, the partial dispersion ratio Pg,F may increase. Furthermore, if the mass ratio is too large, the thermal stability of the glass may decrease.

[0041] In the optical glass according to this embodiment, the upper limit of the total content R'O of MgO, CaO, SrO, and BaO is preferably 7.0%, and more preferably in the order of 6.8%, 6.6%, 6.4%, 6.2%, 6.0%, 5.8%, 5.6%, 5.4%, 5.2%, 5.0%, 4.9%, 4.8%, 4.7%, 4.6%, 4.5%, 4.4%, 4.3%, 4.2%, and 4.1%. The lower limit of the total content R'O is preferably 0.0%. From the viewpoint of increasing the refractive index nd and decreasing the partial dispersion ratio Pg,F, it is preferable to set the total content R'O within the above range. If the total content R'O is too high, the specific gravity may increase, and the thermal stability of the glass may decrease. In glass components with a total R'O content, CaO > SrO > BaO have the greatest effect in reducing the partial dispersion ratios of Pg and F. Therefore, it is preferable to keep the total R'O content within the above range while adjusting the content of each glass component so that CaO ≥ SrO ≥ BaO.

[0042] In the optical glass according to this embodiment, the upper limit of the mass ratio of the Na2O content to the total content of B2O3 and Nb2O5 [Na2O / (B2O3+Nb2O5)] is preferably 0.18, and more preferably in the order of 0.17, 0.16, 0.15, 0.14, and 0.13. Furthermore, the mass ratio is preferably 0.00 or higher, and may exceed 0.00. Furthermore, the lower limit of the mass ratio is preferably in the order of 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, and 0.08. If the mass ratio is too high, the thermal stability of the glass may deteriorate, and the stability during reheating may decrease. If the mass ratio is too low, the partial dispersion ratio Pg,F may increase.

[0043] In the optical glass according to this embodiment, the upper limit of the Ta2O5 content is preferably 10.0%, and more preferably in the order of 9.0%, 8.0%, 7.0%, 6.0%, 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%. The lower limit of the Ta2O5 content is preferably 0.0%. Ta2O5 has the function of increasing the refractive index nd. On the other hand, if the Ta2O5 content is too high, the specific gravity may increase, and the raw material cost may also increase. For this reason, it is preferable to keep the Ta2O5 content within the above range.

[0044] In the optical glass according to this embodiment, the total content R2O of Li2O, Na2O, and K2O is preferably greater than 0.0%. Furthermore, the lower limit of the total content R2O is more preferably in the order of 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, and 12.0%. The upper limit of the total content R2O is preferably 22.5%, and further preferably in the order of 22.0%, 21.5%, 21.0%, 20.5%, 20.0%, 19.5%, 19.0%, 18.5%, 18.4%, 18.3%, 18.2%, 18.1%, 18.0%, 17.9%, 17.8%, and 17.7%. From the viewpoint of reducing the partial dispersion ratio Pg,F and the specific gravity, it is preferable to keep the total R2O content within the above range. If the total R2O content is too high, the chemical durability and stability during reheating may decrease. Among the glass components of the total R2O content, Li2O > Na2O > K2O have the greatest effect in increasing the refractive index nd in that order. Also, K2O > Na2O > Li2O have the greatest effect in increasing the partial dispersion ratio Pg,F in that order. Furthermore, K2O > Na2O > Li2O have the greatest effect in decreasing stability during reheating in that order. Therefore, it is preferable to keep the total R2O content within the above range while adjusting the content of each glass component so that Li2O ≥ Na2O ≥ K2O.

[0045] In the optical glass according to this embodiment, the upper limit of the mass ratio of Na2O content to Li2O content [Na2O / Li2O] is preferably 1.00, and more preferably in the order of 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, and 0.50. Furthermore, the mass ratio is preferably 0.00 or higher, and may exceed 0.00. Furthermore, the lower limit of the mass ratio is preferably in the order of 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40. Both Li2O and Na2O have the effect of lowering the partial dispersion ratio Pg,F and lowering the specific gravity, but if the content is too high, the chemical durability and thermal stability may decrease. Li2O > Na2O has a greater effect in increasing the refractive index nd, Na2O > Li2O has a greater effect in increasing the partial dispersion ratio Pg,F, Na2O > Li2O has a greater effect in reducing stability during reheating, and Na2O > Li2O has a greater effect in increasing the liquidus temperature LT. From the viewpoint of obtaining optical glass having the desired optical constants while ensuring a certain level of productivity, it is preferable to set the mass ratio within the above range.

[0046] In the optical glass according to this embodiment, the upper limit of the mass ratio of K2O content to Na2O content [K2O / Na2O] is preferably 1.00, and more preferably in the order of 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, and 0.50. Furthermore, the mass ratio is preferably 0.00 or higher, and may exceed 0.00. Furthermore, the lower limit of the mass ratio is more preferably in the order of 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40. Both Na2O and K2O have the effect of lowering the partial dispersion ratio Pg,F and reducing the specific gravity, but Na2O has a greater effect of increasing the refractive index nd in the order of Na2O > K2O, K2O has a greater effect of increasing the partial dispersion ratio Pg,F in the order of K2O > Na2O, and K2O has a greater effect of decreasing the stability during reheating in the order of K2O > Na2O. Therefore, from the viewpoint of obtaining optical glass that has the desired optical constants and excellent stability during reheating in reheat pressing, it is preferable to set the mass ratio within the above range. If the mass ratio is too large, the chemical durability and stability during reheating may decrease.

[0047] In the optical glass according to this embodiment, the upper limit of the mass ratio of TiO2 content to Nb2O5 content [TiO2 / Nb2O5] is preferably 0.33, and more preferably in the order of 0.30, 0.28, 0.26, 0.24, 0.22, 0.20, 0.18, 0.16, 0.14, 0.12, and 0.10. The lower limit of this mass ratio is preferably 0.00. Both TiO2 and Nb2O5 are components that contribute to high refractive index and high dispersion of the glass, but Nb2O5 has a greater effect in reducing the partial dispersion ratio Pg,F. Therefore, it is preferable to set the mass ratio within the above range.

[0048] In the optical glass according to this embodiment, the upper limit of the mass ratio [(R'O+Re2O3) / Nb2O5] of the total content of MgO, CaO, SrO, and BaO (R'O) and the total content of La2O3, Gd2O3, Y2O3, and Yb2O3 (Re2O3) to the content of Nb2O5 is preferably 0.30, and more preferably in the order of 0.29, 0.28, 0.27, 0.26, 0.25, and 0.24. The lower limit of this mass ratio is preferably 0.00. If the mass ratio is too large, the glass may become less dispersed, and it may not be possible to obtain optical glass having the desired optical constants. Also, the liquidus temperature LT may rise. For this reason, it is preferable to keep the mass ratio within the above range.

[0049] In the optical glass according to this embodiment, the upper limit of the P2O5 content is preferably 10.0%, and more preferably in the order of 8.0%, 6.0%, 4.0%, 3.0%, and 2.0%. The lower limit of the P2O5 content is preferably 0.0%. From the viewpoint of suppressing an increase in the partial dispersion ratio Pg,F and maintaining the thermal stability of the glass, it is preferable to set the P2O5 content within the above range.

[0050] In the optical glass according to this embodiment, the upper limit of the Al2O3 content is preferably 10.0%, and more preferably in the order of 8.0%, 6.0%, 4.0%, 3.0%, and 2.0%. The lower limit of the Al2O3 content is 0.0%. It is preferable to set the Al2O3 content within the above range from the viewpoint of suppressing an increase in the partial dispersion ratio Pg,F, suppressing an increase in specific gravity, suppressing an increase in liquidus temperature LT, and further maintaining the thermal stability of the glass.

[0051] In the optical glass according to this embodiment, the upper limit of the Na2O content is preferably 15.0%, and more preferably in the order of 14.0%, 13.0%, 12.0%, 11.0%, 10.0%, 9.0%, 8.0%, 7.5%, 7.0%, 6.5%, 6.0%, 5.5%, 5.0%, 4.8%, and 4.6%. Furthermore, the Na2O content is preferably greater than 0.0%, and the lower limit is more preferably in the order of 0.5%, 1.0%, 1.5%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, and 3.2%. If the Na2O content is too low, the refractive index nd may decrease, and the partial dispersion ratio Pg,F may increase. If the Na2O content is too high, the stability during reheating and chemical durability may decrease.

[0052] In the optical glass according to this embodiment, the upper limit of the K2O content is preferably 15.0%, and more preferably in the order of 14.0%, 13.0%, 12.0%, 11.0%, 10.0%, 9.0%, 8.0%, 7.0%, 6.0%, 5.0%, 4.5%, 4.0%, 3.5%, 3.0%, 2.8%, 2.6%, 2.4%, and 2.2%. Furthermore, the K2O content is preferably 0.0% or more, and may exceed 0.0%. The lower limit is more preferably in the order of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, and 1.6%. If the K2O content is too low, the refractive index nd may decrease, and the partial dispersion ratio Pg,F may increase. If the K2O content is too high, the stability during reheating and chemical durability may decrease.

[0053] In the optical glass according to this embodiment, the upper limit of the MgO content is preferably 7.0%, and more preferably in the order of 6.0%, 5.0%, 4.0%, 3.0%, and 2.0%. The lower limit of the MgO content is preferably 0.0%. From the viewpoint of suppressing an increase in the partial dispersion ratio Pg,F and lowering the specific gravity, it is preferable to set the MgO content within the above range.

[0054] In the optical glass according to this embodiment, the upper limit of the CaO content is preferably 7.0%, and more preferably in the order of 6.0%, 5.0%, 4.0%, 3.0%, and 2.0%. The lower limit of the CaO content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having the desired optical constants, it is preferable to set the CaO content within the above range.

[0055] In the optical glass according to this embodiment, the upper limit of the SrO content is preferably 7.0%, and more preferably in the order of 6.0%, 5.0%, 4.0%, 3.0%, and 2.0%. The lower limit of the SrO content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having the desired optical constants, it is preferable to set the SrO content within the above range.

[0056] In the optical glass according to this embodiment, the upper limit of the BaO content is preferably 7.0%, and more preferably in the order of 6.0%, 5.0%, 4.0%, 3.0%, and 2.0%. The lower limit of the BaO content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having the desired optical constants, it is preferable to set the BaO content within the above range.

[0057] In the optical glass according to this embodiment, the upper limit of the La2O3 content is preferably 5.0%, and more preferably in the order of 4.8%, 4.6%, 4.4%, 4.2%, 4.0%, 3.8%, and 3.7%. The lower limit of the La2O3 content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having a desired optical constant, it is preferable to set the La2O3 content within the above range.

[0058] In the optical glass according to this embodiment, the upper limit of the Y2O3 content is preferably 5.0%, and more preferably in the order of 4.8%, 4.6%, 4.4%, 4.2%, 4.0%, 3.8%, and 3.7%. The lower limit of the Y2O3 content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having the desired optical constants, it is preferable to set the Y2O3 content within the above range.

[0059] In the optical glass according to this embodiment, the upper limit of the Gd2O3 content is preferably 5.0%, and more preferably in the order of 4.8%, 4.6%, 4.4%, 4.2%, 4.0%, 3.8%, and 3.7%. The lower limit of the Gd2O3 content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having a desired optical constant, it is preferable to set the Gd2O3 content within the above range.

[0060] In the optical glass according to this embodiment, the upper limit of the Yb2O3 content is preferably 5.0%, and more preferably in the order of 4.8%, 4.6%, 4.4%, 4.2%, 4.0%, 3.8%, and 3.7%. The lower limit of the Yb2O3 content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having the desired optical constants, it is preferable to set the Yb2O3 content within the above range.

[0061] In the optical glass according to this embodiment, the ZrO2 content is preferably 0.0% or more, and may exceed 0.0%. Furthermore, the lower limit of the ZrO2 content is more preferably 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 5.5%, 6.0%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, and 9.5%, in that order. The upper limit of the ZrO2 content is preferably 16.0%, and further preferably 15.5%, 15.0%, 14.5%, 14.0%, 13.5%, 13.0%, 12.5%, 12.0%, and 11.5%, in that order. ZrO2 is a component that has the function of lowering the partial dispersion ratio Pg,F, but it is also a component that increases the specific gravity. If the ZrO2 content is too low, the desired partial dispersion ratio Pg,F may not be obtained. On the other hand, if the ZrO2 content is too high, the specific gravity will increase, which may worsen the stability during reheating and cause the liquid phase temperature LT to rise. Therefore, it is preferable to keep the ZrO2 content within the above range.

[0062] In the optical glass according to this embodiment, the upper limit of the WO3 content is preferably 10.0%, and more preferably in the order of 8.0%, 6.0%, 4.0%, 3.0%, and 2.0%. The lower limit of the WO3 content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having the desired optical constants, it is preferable to set the WO3 content within the above range.

[0063] In the optical glass according to this embodiment, the upper limit of the Bi2O3 content is preferably 10.0%, and more preferably in the order of 8.0%, 6.0%, 4.0%, 3.0%, and 2.0%. The lower limit of the Bi2O3 content is preferably 0.0%. From the viewpoint of suppressing the increase in specific gravity and obtaining optical glass having the desired optical constants, it is preferable to set the Bi2O3 content within the above range.

[0064] In the optical glass according to this embodiment, the Sc2O3 content is preferably 2.0% or less. Furthermore, the lower limit of the Sc2O3 content is preferably 0.0%.

[0065] In the optical glass according to this embodiment, the HfO2 content is preferably 2.0% or less. Furthermore, the lower limit of the HfO2 content is preferably 0.0%.

[0066] Sc2O3 and HfO2 enhance the dispersibility of glass, but they are expensive components. Therefore, it is preferable to keep the respective contents of Sc2O3 and HfO2 within the above ranges.

[0067] In the optical glass according to this embodiment, the Lu2O3 content is preferably 2.0% or less. Furthermore, the lower limit of the Lu2O3 content is preferably 0.0%.

[0068] Lu2O3 enhances the dispersibility of glass, but due to its large molecular weight, it also increases the specific gravity of the glass. Therefore, it is preferable to keep the Lu2O3 content within the above range.

[0069] In the optical glass according to this embodiment, the GeO2 content is preferably 2.0% or less. Furthermore, the lower limit of the GeO2 content is preferably 0.0%.

[0070] GeO2 enhances the high dispersion properties of glass, but it is by far the most expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the cost of glass manufacturing, it is preferable to keep the GeO2 content within the above range.

[0071] The optical glass according to this embodiment is preferably composed mainly of the above-mentioned glass components, namely, SiO2, Li2O, Nb2O5, and B2O3 as essential components, and ZnO, TiO2, Ta2O5, P2O5, Al2O3, Na2O, K2O, Cs2O, MgO, CaO, SrO, BaO, La2O3, Y2O3, Gd2O3, Yb2O3, ZrO2, WO3, Bi2O3, Sc2O3, HfO2, Lu2O3, and GeO2 as optional components, and the total content of the above-mentioned glass components is preferably 95.0% or more, more preferably 98.0% or more, even more preferably 99.0% or more, and particularly preferably 99.5% or more.

[0072] While the optical glass according to this embodiment is preferably composed of the above-mentioned glass components, it may also contain other components as long as they do not hinder the effects of the present invention. Furthermore, the present invention does not exclude the inclusion of unavoidable impurities.

[0073] (Other ingredients) In addition to the above components, the optical glass may also contain small amounts of clarifying agents such as Sb2O3 and CeO2. The total amount of clarifying agents (amount added separately) is preferably 0.0% or more and less than 1.0%, and more preferably 0.0% or more and 0.5% or less.

[0074] External addition amount refers to the amount of fining agent added as a mass percentage, where the total content of all glass components excluding the fining agent is considered to be 100%.

[0075] Pb, Cd, As, Th, etc., are components that raise environmental concerns. Therefore, the content of PbO, CdO, As2O3, and ThO2 is preferably 0.0 to 0.1%, more preferably 0.0 to 0.05%, even more preferably 0.0 to 0.01%, and particularly preferably substantially free of PbO, CdO, As2O3, and ThO2.

[0076] Furthermore, the above optical glass provides high transmittance over a wide range of the visible spectrum. To take advantage of these features, it is preferable that the glass does not contain coloring elements. Examples of coloring elements include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, and V. It is preferable that the amount of any of these elements be less than 100 ppm by mass, more preferably 0 to 80 ppm by mass, even more preferably 0 to 50 ppm by mass, and particularly preferable that they be substantially absent.

[0077] Furthermore, Ga, Te, Tb, etc., are components that do not need to be introduced and are also expensive components. Therefore, the range of Ga2O3, TeO2, and TbO2 content expressed in mass percent is preferably 0.0 to 0.1%, more preferably 0.0 to 0.05%, even more preferably 0.0 to 0.01%, even more preferably 0.0 to 0.005%, even more preferably 0.0 to 0.001%, and particularly preferably substantially absent.

[0078] (Glass properties) <refractive index nd> In the optical glass according to this embodiment, the lower limit of the refractive index nd is preferably 1.690, but can also be 1.695, 1.700, 1.702, 1.704, 1.706, 1.708, or 1.710. The upper limit of the refractive index nd is preferably 1.770, but can also be 1.765, 1.760, 1.755, or 1.750. The refractive index nd can be set to a desired value by appropriately adjusting the content of each glass component. Components that relatively increase the refractive index nd (high refractive index components) include Nb2O5, TiO2, ZrO2, Ta2O5, La2O3, etc. On the other hand, components that relatively decrease the refractive index nd (low refractive index components) include SiO2, B2O3, Li2O, Na2O, K2O, etc.

[0079] <Abbe number νd> In the optical glass according to this embodiment, the lower limit of the Abbe number νd is preferably 33.5, but can also be 33.6, 33.7, 33.8, 33.9, 34.0, 34.1, 34.2, 34.3, 34.4, 34.5, 34.6, or 34.7. The upper limit of the Abbe number νd is preferably 37.0, but can also be 36.9, 36.8, 36.7, 36.6, 36.5, 36.4, 36.3, 36.2, 36.1, 36.0, 35.9, or 35.8. The Abbe number νd can be set to a desired value by appropriately adjusting the content of each glass component. Components that relatively lower the Abbe number νd, i.e., highly dispersible components, are Nb2O5, TiO2, ZrO2, Ta2O5, etc. On the other hand, components that relatively increase the Abbe number νd, i.e., low-dispersion components, include SiO2, B2O3, Li2O, Na2O, K2O, La2O3, BaO, CaO, SrO, etc.

[0080] <Specific gravity of glass> The specific gravity of the optical glass according to this embodiment is preferably 3.50 or less, and more preferably in the order of 3.48 or less, 3.46 or less, 3.44 or less, 3.42 or less, 3.40 or less, 3.38 or less, 3.36 or less, 3.35 or less, 3.34 or less, 3.33 or less, 3.32 or less, 3.31 or less, 3.30 or less, 3.29 or less, and 3.28 or less. Components that relatively increase the specific gravity include BaO, La2O3, ZrO2, Nb2O5, Ta2O5, etc. On the other hand, components that relatively decrease the specific gravity include SiO2, B2O3, Li2O, Na2O, K2O, etc. The specific gravity can be controlled by appropriately adjusting the content of these components.

[0081] <Partial dispersion ratio Pg,F> In the optical glass according to this embodiment, the upper limit of the partial dispersion ratio Pg,F is preferably 0.5859, and more preferably in the order of 0.5855, 0.5850, 0.5845, 0.5840, 0.5835, 0.5830, 0.5825, and 0.5820. By setting the partial dispersion ratio Pg,F within the above range, an optical glass suitable for correcting higher-order chromatic aberration can be obtained. The lower limit of the partial dispersion ratio Pg,F is not particularly limited, but 0.5757 is used as a guideline.

[0082] <ΔPg,F> In the optical glass according to this embodiment, the upper limit of the deviation ΔPg,F is preferably -0.0020, and more preferably in the order of -0.0025, -0.0030, -0.0032, -0.0034, -0.0035, -0.0036, -0.0037, -0.0038, -0.0039, and -0.0040. By setting the deviation ΔPg,F within the above range, optical glass suitable for correcting higher-order chromatic aberration can be obtained. The lower limit of the deviation ΔPg,F is not particularly limited, but -0.0065 is used as a guideline.

[0083] <Relationship between specific gravity and ΔPg,F> In the optical glass according to this embodiment, the specific gravity ρ and the deviation ΔPg,F preferably satisfy the following relationship. ΔPg,F ≤ -0.0035 and ΔPg,F ≤ 0.0127 - 0.0051 × ρ however, ΔPg,F=Pg,F-(0.6483-0.001802×νd) Let's assume that.

[0084] <Glass transition temperature Tg> The upper limit of the glass transition temperature Tg of the optical glass according to this embodiment is preferably 580°C, and more preferably in the order of 575°C, 570°C, 565°C, 560°C, 555°C, 550°C, 545°C, and 540°C. The lower limit of the glass transition temperature Tg is preferably 470°C, and more preferably in the order of 475°C, 480°C, 485°C, 490°C, 495°C, 500°C, and 505°C. Components that relatively lower the glass transition temperature Tg include Li2O, Na2O, and K2O. Components that relatively raise the glass transition temperature Tg include La2O3, ZrO2, and Nb2O5. The glass transition temperature Tg can be controlled by appropriately adjusting the content of these components.

[0085] <Light transmittance of glass> The light transmittance of the optical glass according to this embodiment can be evaluated by the degree of coloration λ80 and λ5. For a glass sample with a thickness of 10.0 mm ± 0.1 mm, the spectral transmittance is measured in the wavelength range of 200 to 700 nm, and the wavelength at which the external transmittance is 80% is defined as λ80, and the wavelength at which the external transmittance is 5% is defined as λ5.

[0086] In this embodiment, the λ80 of the optical glass is preferably 430 nm or less, and more preferably in the order of 425 nm or less, 420 nm or less, 415 nm or less, and 410 nm or less. Furthermore, the λ5 is preferably 340 nm or less, and more preferably in the order of 335 nm or less, 330 nm or less, and 325 nm or less.

[0087] (Manufacturing of optical glass) The glass according to this embodiment can be produced by blending glass raw materials to achieve the predetermined composition described above, and then manufacturing the blended glass raw materials according to a known glass manufacturing method. For example, several types of compounds can be blended and thoroughly mixed to form a batch raw material, and the batch raw material can be roughly melted in a quartz crucible or a platinum crucible. The molten material obtained by rough melting can be rapidly cooled and pulverized to produce cullet. The cullet can then be heated in a platinum crucible and remelted to produce molten glass, which can then be clarified and homogenized before being molded and slowly cooled to obtain optical glass. Known methods can be applied to mold and slowly cool the molten glass.

[0088] Furthermore, the compounds used when preparing the batch raw materials are not particularly limited, as long as the desired glass components can be introduced into the glass in the desired amounts. Examples of such compounds include oxides, carbonates, nitrates, hydroxides, and fluorides.

[0089] (Manufacturing of optical elements, etc.) To manufacture an optical element using the optical glass according to this embodiment, known methods can be applied. For example, in the manufacture of the optical glass described above, molten glass is poured into a mold and formed into a plate to produce a glass material made of the optical glass according to the present invention. The obtained glass material is cut, ground, and polished as appropriate to produce cut pieces of a size and shape suitable for press molding. The cut pieces are heated and softened, and then press-molded (reheat-pressed) using a known method to produce an optical element blank that approximates the shape of the optical element. The optical element blank is annealed, and then ground and polished using a known method to produce an optical element.

[0090] Depending on the intended use, the optical functional surface of the fabricated optical element may be coated with an anti-reflective coating, a total reflection coating, or the like.

[0091] According to one aspect of the present invention, an optical element made of the above-mentioned optical glass can be provided. Examples of types of optical elements include lenses such as spherical lenses and aspherical lenses, prisms, diffraction gratings, etc. Examples of lens shapes include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, concave meniscus lenses, etc. The optical element can be manufactured by a method that includes a process of processing a glass molded body made of the above-mentioned optical glass. Examples of processing include cutting, machining, rough grinding, fine grinding, polishing, etc. When performing such processing, using the above-mentioned glass can reduce breakage and enable the stable supply of high-quality optical elements. [Examples]

[0092] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

[0093] (Example 1) Glass samples having the glass compositions shown in Tables 1(1) and (2), and Tables 2(1) and (2), were prepared using the following procedure and evaluated in various ways.

[0094] [Manufacturing of optical glass] First, oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of glass were prepared as raw materials. These raw materials were weighed and blended so that the glass composition of the resulting optical glass would be as shown in Tables 1(1) and (2), and the raw materials were thoroughly mixed. The resulting blended raw materials (batch raw materials) were placed in a platinum crucible and heated at 1100°C to 1400°C for 2 to 4 hours to form molten glass. The mixture was then stirred to homogenize it, clarified, and the molten glass was cast into a mold preheated to an appropriate temperature. The cast glass was heat-treated at an arbitrary temperature between the glass transition temperature Tg and 100°C below Tg for 30 minutes, and then allowed to cool to room temperature in the furnace to obtain a glass sample.

[0095] [Confirmation of glass component composition] The content of each glass component was measured in the obtained glass samples using inductively coupled plasma atomic emission spectroscopy (ICP-AES), and it was confirmed that the compositions were as shown in Tables 1(1) and (2).

[0096] [Measurement of optical properties] The obtained glass samples were further annealed at approximately 30 minutes to 2 hours near the glass transition temperature Tg, and then cooled to room temperature in a furnace at a cooling rate of -30°C / hour to obtain annealed samples. For the obtained annealed samples, the refractive index nd, ng, nF and nC, Abbe number νd, partial dispersion ratio Pg,F, specific gravity, glass transition temperature Tg, λ80, and λ5 were measured. The results are shown in Tables 2(1) and (2). (i) Refractive index nd, ng, nF, nC and Abbe number νd For the above annealed samples, the refractive indices nd, ng, nF, and nC were measured according to the refractive index measurement method of JIS standard JIS B 7071-1, and the Abbe number νd was calculated based on the following formula. νd=(nd-1) / (nF-nC)

[0097] (ii) Partial dispersion ratio Pg,F The partial dispersion ratios Pg and F were calculated using the refractive indices ng, nF, and nC for the g, F, and c lines, respectively, based on the following formula. Pg,F=(ng-nF) / (nF-nC)

[0098] (iii) Deviation ΔPg,F The calculation was performed using the partial variance ratios Pg,F and Abbe number νd, based on the following formula. ΔPg,F=Pg,F-(0.6483-0.001802×νd)

[0099] (iv) Specific gravity The specific gravity was measured using the Archimedes method.

[0100] (v) Glass transition temperature Tg The glass transition temperature (Tg) was measured using a Rigaku differential scanning calorimetry analyzer (DSC8271) at a heating rate of 10°C / min.

[0101] (vi)λ80, λ5 The above annealed sample was processed to have a thickness of 10 mm and two parallel, optically polished planes, and its spectral transmittance was measured in the wavelength range from 200 nm to 700 nm. The intensity of light rays incident perpendicularly to one of the optically polished planes was defined as intensity A, and the intensity of light rays emanating from the other plane was defined as intensity B, and the spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance was 80% was defined as λ80, and the wavelength at which the spectral transmittance was 5% was defined as λ5. Note that the spectral transmittance includes the reflection loss of light rays at the sample surface.

[0102] [Table 1(1)]

[0103] [Table 1(2)]

[0104] [Table 2(1)]

[0105] [Table 2(2)]

[0106] (Example 2) Using the optical glass prepared in Example 1, lens blanks were fabricated by known methods, and various lenses were manufactured by processing the lens blanks by known methods such as polishing. The optical lenses fabricated include various types such as biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses, and convex meniscus lenses. By combining various lenses with lenses made of other types of optical glass, secondary chromatic aberration could be effectively corrected.

[0107] Furthermore, because the glass has a low specific gravity, each lens is lighter than lenses with equivalent optical properties and size, making them suitable for various imaging devices, especially autofocus imaging devices, due to their energy-saving properties. Similarly, prisms were fabricated using the various optical glasses prepared in Example 1.

[0108] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended.

[0109] For example, by adjusting the composition described in the specification with respect to the glass composition exemplified above, an optical glass according to one aspect of the present invention can be produced. Furthermore, it is certainly possible to arbitrarily combine two or more items described as examples or preferred scopes in the specification.

Claims

1. SiO 2 The content is 10.0 to 40.0% by mass, Li 2 The O content is greater than 0.0% by mass and less than or equal to 15.0% by mass. Nb 2 O 5 The content is 10.0 to 40.0% by mass, B 2 O 3 The content is greater than 0.0% by mass and less than or equal to 7.0% by mass. The ZnO content is 5.0% by mass or less. TiO 2 The content is 13.0% by mass or less. Li 2 The mass ratio of Na 2 O and K 2 O to the total content of O [(Na 2 O + K 2 O) / Li 2 O] is 1.50 or less, Li 2 O, Na 2 O, and K 2 Total content of O R 2 La for O 2 O 3 , Gd 2 O 3 , Y 2 O 3 , and Yb 2 O 3 Total content Re 2 O 3 The total mass ratio of the total content of MgO, CaO, SrO, and BaO to the total mass ratio of R'O [(Re 2 O 3 +R'O) / R 2 O] is 0.79 or less, SiO 2 and B 2 O 3 The total content R 2 O and ZrO 2 The total mass ratio of the content of [(R 2 O+ZrO 2 ) / (SiO 2 +B 2 O 3 ) ] is 0.50 or higher, BaO and La 2 O 3 Total content [BaO + La 2 O 3 Optical glass in which the content of 5.0% by mass or less.

2. SiO 2 and B 2 O 3 Nb relative to the total content 2 O 5 Mass ratio of the content [Nb 2 O 5 / (SiO 2 +B 2 O 3 The optical glass according to claim 1, wherein the ratio of ) is 0.65 or greater.

3. La 2 O 3 , Gd 2 O 3 , Y 2 O 3 , and Yb 2 O 3 Total content Re 2 O 3 The optical glass according to claim 1, wherein the amount is 5.0% by mass or less.

4. TiO 2 and Nb 2 O 5 Li 2 O, Na 2 O, and K 2 Total content of O R 2 O and La 2 O 3 , Gd 2 O 3 , Y 2 O 3 , and Yb 2 O 3 Total content Re 2 O 3 and ZrO 2 The total mass ratio of the content of [(R 2 O+Re 2 O 3 +ZrO 2 ) / (TiO 2 +Nb 2 O 5 The optical glass according to claim 1, wherein the ratio of ) is 0.70 or higher.

5. The optical glass according to claim 1, satisfying one or more of the following conditions (i) to (ii). (i) The total content of MgO, CaO, SrO, and BaO, R'O, is 7.0% by mass or less. (ii) B 2 O 3 and Nb 2 O 5 The mass ratio [Na 2 O / (B 2 O 2 O 3 + Nb 2 O 5 )] of the content of Na 2 O to the total content of B 2 O and Nb 3 O is 0.18 or less.

6. The optical glass according to claim 1, satisfying two or more of the following conditions (iii) to (vii). (iii) SiO 2 and B 2 O 3 Nb relative to the total content 2 O 5 Mass ratio of the content [Nb 2 O 5 / (SiO 2 +B 2 O 3 The value of ) is 0.65 or higher. (iv) La 2 O 3 , Gd 2 O 3 , Y 2 O 3 , and Yb 2 O 3 Total content Re 2 O 3 It is 5.0% by mass or less. (v) TiO 2 and Nb 2 O 5 Li 2 O, Na 2 O, and K 2 Total content of O R 2 O and La 2 O 3 , Gd 2 O 3 , Y 2 O 3 , and Yb 2 O 3 Total content Re 2 O 3 and ZrO 2 The total mass ratio of the content of [(R 2 O+Re 2 O 3 +ZrO 2 ) / (TiO 2 +Nb 2 O 5 The value of ) is 0.70 or higher. (vi) The total content of MgO, CaO, SrO, and BaO, R'O, is 7.0% by mass or less. (vii) B 2 O 3 and Nb 2 O 5 Na relative to the total content 2 Mass ratio of O content [Na 2 O / (B 2 O 3 +Nb 2 O 5 The value of ) is 0.18 or less.

7. The optical glass according to claim 1, satisfying one or more of the following conditions (viii) to (xii). (viii) Ta 2 O 5 The content is 10.0% by mass or less. (ix) Li 2 O, Na 2 O, and K 2 Total content of O R 2 The oxygen content is greater than 0.0% by mass and less than or equal to 22.5% by mass. (x) Li 2 Na in relation to O content 2 Mass ratio of O content [Na 2 O / Li 2 O is 1.00 or less. (xi)Na 2 K relative to O content 2 Mass ratio of O content [K 2 O / Na 2 O is 1.00 or less. (xii) Nb 2 O 5 TiO content 2 Mass ratio of the content [TiO 2 / Nb 2 O 5 The value of ] is 0.33 or less.

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

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