JP2023152670A - Optical glass and optical element - Google Patents

Abstract

To provide an optical glass having a high refractive index and excellent thermal stability.SOLUTION: There is provided an optical glass having, on the mass basis, a B2O3 content of 5.0% or more and 30.0% or less, an SiO2 content of 1.0% or more and 15.0% or less, an Nb2O5 content of 15.0% or less, an La2O3 content of 5.0%or more and 70.0% or less, a ZnO content of 0.1% or more, an Li2O content of 0.4% or less and a TiO2 content of 5.0% or less, a mass ratio ((La2O3+Gd2O3+Y2O3+Yb2O3)/(SiO2+B2O3)) of 2.50 or more and 5.30 or less, a mass ratio ((TiO2+Nb2O5+Ta2O5+WO3)/(La2O3+Gd2O3+Y2O3+Yb2O3)) of 0.15 or less, a mass ratio (SiO2/B2O3) of 0.20 or more and 0.60 o less, a mass ratio ((TiO2+Nb2O5+Ta2O5+WO3)/(SiO2+B2O3)) of 0.35 or less, a mass ratio (ZnO/(La2O3+Gd2O3+Y2O3+Yb2O3)) of 0.14 or less, a mass ratio ((Ta2O5+WO3)/(TiO2+W+O3Ta2O5+Nb2O5)) of 0.45 or less, a mass ratio ((La2O3+Gd2O3+Y2O3+Yb2O3+TiO2+Nb2O5+Ta2O5+WO3)/(SiO2+B2O3)) of 3.50 or less and a mass ratio (Gd2O3/(La2O3+Gd2O3+Y2O3+Yb2O3) of 0.10 or more and 0.45 or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to optical glasses and optical elements.

A lens made of optical glass with a high refractive index is disclosed in Patent Document 1, for example.

Japanese Patent Application Publication No. 2002-284542

Optical glass with a high refractive index makes it possible to make an optical system more compact while correcting chromatic aberration by, for example, combining a lens made of this glass with another lens made of glass with a different dispersion property to form a cemented lens. be able to. Therefore, such optical glass is useful as a material for optical elements constituting imaging optical systems and projection optical systems such as projectors.

Glasses with low thermal stability tend to crystallize. Therefore, physical properties desired for optical glass include excellent thermal stability.

In view of the above, an object of one embodiment of the present invention is to provide an optical glass that has a high refractive index and excellent thermal stability.

One embodiment of the present invention has a B ₂ O ₃ content of 5.0% or more and 30.0% or less, a SiO ₂ content of 1.0% or more and 15.0% or less, and a Nb ₂ O ₅ content on a mass basis. amount is 15.0% or less, La ₂ O ₃ content is 5.0% or more and 70.0% or less, ZnO content is 0.1% or more, Li ₂ O content is 0.4% or less, TiO ₂ The content is 5.0% or less, the mass ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and _{Yb 2 O 3} to the total content of SiO ₂ and B 2 O ₃ (( La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )/(SiO ₂ +B ₂ O ₃ )) is 2.50 or more and 5.30 or less, La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O The mass ratio of the total content of TiO _{2 ,} Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ to the total content of Yb ₂ O ₃ and Yb 2 O 3 ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/( La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is 0.15 or less, and the mass ratio of SiO ₂ content to B ₂ O ₃ content (SiO ₂ /B ₂ O ₃ ) is 0. 20 or more and 0.60 or less, the mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ to the total content of SiO ₂ and B ₂ O ₃ ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(SiO ₂ +B ₂ O ₃ )) is 0.35 or less, ZnO content relative to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ The mass ratio (ZnO/(La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ )) is 0.14 or less, Ta 2 O 5 + WO ₃ to TiO ₂ + _{W +} O ₃ Ta ₂ O ₅ + Nb ₂ O ₅ The mass ratio ((Ta ₂ O ₅ + WO ₃ )/(TiO ₂ +W+O ₃ Ta ₂ O ₅ + Nb ₂ O ₅ )) of 0.45 or less, La ₂ O to the total content of SiO ₂ and B ₂ O _{3 3} , the mass ratio of the total content of Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(SiO ₂ +B ₂ O ₃ )) is 3.50 or less, and La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O The mass ratio of the Gd ₂ O ₃ content to the total content of ₃ and Yb ₂ O ₃ (Gd ₂ O ₃ /(La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ )) is 0.10 or more It relates to an optical glass having a particle diameter of 0.45 or less.

According to one aspect of the present invention, it is possible to provide an optical glass that has a high refractive index and excellent thermal stability. Further, according to one aspect of the present invention, an optical element made of such optical glass can also be provided.

[Optical glass]
<Glass composition>
In the present invention and this specification, the glass composition is expressed as an oxide-based glass composition. Here, the term "glass composition based on oxides" refers to a glass composition obtained by calculating the glass raw materials as being completely decomposed during melting and existing as oxides in the glass. Further, unless otherwise specified, the glass composition is expressed on a mass basis (mass %, mass ratio).
The glass composition in the present invention and this specification can be determined, for example, by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Quantitative analysis is performed for each element using ICP-AES. The analytical values are then converted to oxide notation. An analysis value obtained by ICP-AES may include a measurement error of approximately ±5% of the analysis value, for example. Therefore, the value expressed as an oxide converted from the analytical value may similarly include an error of about ±5%.
In addition, in the present invention and this specification, the content of a component of 0.0%, not containing, or not introduced means that this component is not substantially included, and the content of this component is It means that it is below the impurity level. The term "below the impurity level" means, for example, less than 0.01%.

Hereinafter, the glass composition of the above-mentioned optical glass will be explained in more detail.

_B2O3 is a component that works to improve the thermal stability of glass, and _its content is 5.0% or more, preferably 6.0% or more, and 7.0% or more. , 8.0% or more, 9.0% or more, 10.0% or more, 11.0% or more, and 12.0% or more. From the viewpoint of increasing the refractive index, the B ₂ O ₃ content is 30.0% or less, preferably 28.0% or less, 26.0% or less, 24.0% or less, 22.0% or less % or less, 20.0% or less, 18.0% or less, and 16.0% or less, in this order.

_SiO2 is also a component that works to improve the thermal stability of glass, and its content is 1.0% or more, preferably 2.0% or more, 3.0% or more, 4. It is more preferable in the order of .0% or more, 5.0% or more, and 6.0% or more. From the viewpoint of increasing the refractive index, the SiO ₂ content is 15.0% or less, preferably 14.0% or less, 13.0% or less, 12.0% or less, 11.0% or less , 10.0% or less.

The mass ratio of the SiO ₂ content to the B ₂ O ₃ content (SiO ₂ /B ₂ O ₃ ) is 0.20 or more and 0.60 or less from the viewpoint of improving the thermal stability of the glass. From the viewpoint of further improving thermal stability, the mass ratio (SiO ₂ /B ₂ O ₃ ) is preferably 0.35 or more, more preferably 0.40 or more, and 0.50 or more. It is more preferable that From the same viewpoint, the mass ratio (SiO ₂ /B ₂ O ₃ ) is preferably 0.55 or less.

From the viewpoint of low dispersion of high refractive index glass, the Nb ₂ O ₅ content is 15.0% or less, preferably 14.0% or less, 13.0% or less, 12.0% or less , 11.0% or less, 10.0% or less, 9.0% or less, 8.0% or less, and 7.0% or less in this order. The Nb ₂ O ₅ content is, for example, 0.0% or more, more than 0.0%, 1.0% or more, 2.0% or more, 3.0% or more, 4.0% or more, or 5.0%. It can be more than that.

The La ₂ O ₃ content is 5.0% or more and 70.0% or less from the viewpoint of realizing a glass with a high refractive index and low dispersion and excellent thermal stability. From the above viewpoint, the La ₂ O ₃ content is preferably 10.0% or more, 15.0% or more, 20.0% or more, 25.0% or more, 30.0% or more, 35.0% or more. The order of % or higher is more preferable. In addition, from the viewpoint of further improving thermal stability, the La ₂ O ₃ content is preferably 65.0% or less, 60.0% or less, 55.0% or less, 50.0% or less , 45.0% or less.

Mass ratio of Gd ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ (Gd ₂ O ₃ /(La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ +Yb ₂ O ₃ )) is 0.10 or more and 0.45 or less from the viewpoint of increasing the refractive index and improving the thermal stability of the glass. From the viewpoint of further increasing the refractive index, the mass ratio (Gd ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is preferably 0.15 or more, and 0 It is more preferably .18 or more, and even more preferably 0.20 or more. Additionally, from the perspective of further improving thermal stability, the mass ratio (Gd ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) should be 0.40 or less. is preferred.

The mass ratio of the total content of Gd ₂ O ₃ and La 2 O 3 to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ (( _{Gd 2 O 3 +} La ₂ O ₃ )/(La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ )) is preferably 0.40 or more, and preferably 0.50 or more from the viewpoint of increasing the refractive index. is more preferable, and even more preferably 0.60 or more. The mass ratio ((Gd ₂ O ₃ + La ₂ O ₃ )/(La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ )) can be, for example, 1.00 or less or 0.95 or less. .

The mass ratio of the Y ₂ O ₃ content to the La ₂ O ₃ content (Y ₂ O ₃ /La ₂ O ₃ ) is preferably 0.80 or less from the viewpoint of lowering the liquidus temperature described below. , more preferably 0.70 or less, and still more preferably 0.60 or less. For example, it can be 0.00 or more, more than 0.00, or 0.10 or more.

La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ are all components that have the function of increasing the refractive index without increasing dispersion (without decreasing the Abbe number). The La ₂ O ₃ content is as described above.
The Gd ₂ O ₃ content can be, for example, 0.0% or more, more than 0.0%, 1.0% or more, 5.0% or more, or 10.0% or more. Gd ₂ O ₃ is a component that increases specific gravity among glass components, and is also an expensive component. From these viewpoints, the Gd ₂ O ₃ content is preferably 50.0% or less, and in the following order: 45.0% or less, 40.0% or less, 35.0% or less, and 30.0% or less. preferable.
The Y ₂ O ₃ content can be 0.0% or more, more than 0.0%, 1.0% or more or 3.0% or more, and, for example, 10.0% or less, 8.0%. It can be less than or equal to:
The Yb ₂ O ₃ content can be 0.0% or more, more than 0.0%, 1.0% or more or 3.0% or more, and can be, for example, 10.0% or less, 9.0% Below, it can be 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, or 4.0% or less.

Mass ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y 2 O ₃ and Yb ₂ O ₃ to the total content of SiO ₂ and _B 2 O ₃ ((La ₂ O ₃ +Gd _{2 O 3} +Y ₂ O ₃ +Yb ₂ O ₃ )/(SiO ₂ +B ₂ O ₃ )) is 2.50 or more and 5. 30 or less. From the viewpoint of suppressing high dispersion and further improving thermal stability, the mass ratio ((La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ )/(SiO ₂ + B ₂ O ₃ )) is , is preferably 5.00 or less, more preferably 4.50 or less, 4.00 or less, 3.50 or less, and 3.00 or less. In addition, from the viewpoint of further increasing the refractive index, the mass ratio ((La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ )/(SiO ₂ +B ₂ O ₃ )) is 2.60 or more. It is preferably 2.70 or more, and more preferably 2.70 or more.

From the viewpoint of suppressing an increase in glass transition temperature, the ZnO content is 0.1% or more, preferably 0.3% or more, and more preferably 1.0% or more. The ZnO content can be, for example, 10.0% or less, 9.0% or less, 8.0% or less, or 7.0% or less.

Mass ratio of ZnO content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ (ZnO/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is 0.14 or less, preferably 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, from the viewpoint of improving thermal stability. The order of 0.08 or less, 0.07 or less, and 0.06 or less is more preferable. The mass ratio (ZnO/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) can be, for example, 0.00 or more, more than 0.00, or 0.01 or more.

The mass ratio of ZnO content to the total content of SiO ₂ and B ₂ O ₃ (ZnO/(SiO ₂ + B ₂ O ₃ )) is 0.50 from the viewpoint of further improving the thermal stability of the glass. It is preferably at most 0.45, more preferably at most 0.40, even more preferably at most 0.40. The mass ratio (ZnO/(SiO ₂ +B ₂ O ₃ )) can be, for example, 0.00 or more, more than 0.00, 0.01 or more, or 0.02 or more.

From the viewpoint of improving thermal stability, the Li ₂ O content is 0.4% or less, preferably 0.3% or less, more preferably 0.2% or less, and 0.1% or less. % or less is more preferable. The Li ₂ O content can be 0.0% or more than 0.0%. From the viewpoint of further lowering the specific gravity, it is preferable that the Li ₂ O content of the optical glass is 0.0%, that is, the optical glass does not contain Li ₂ O.

Among the alkali metal oxides Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O, the Li ₂ O content is as described above.
The content of each of Na ₂ O, K ₂ O and Cs ₂ O can be, for example, 0.0% or more or more than 0.0%, and can be, for example, 5.0% or less, 4.0% or less. , 3.0% or less, 2.0% or less, 1.0% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less be able to.

The TiO ₂ content is 5.00% or less, preferably 4.0% or less, 3.0% or less, 2.0% or less, 1.0% or less, from the viewpoint of suppressing coloring of the glass. , 0.5% or less, 0.1% or less, and 0.0%, in this order.

Since Ta is a rare element and expensive, it is preferable that the Ta ₂ O ₅ content is small. From the above viewpoint and from the viewpoint of realizing desirable optical constants, the Ta ₂ O ₅ content is preferably 12.0% or less, 11.0% or less, 10.0% or less, 9.0% or less , 8.0% or less, 7.0% or less, 6.0% or less, 5.10.0% or less, 5.0% or less, 4.0% or less, 3.0% or less, 2.0% or less , 1.0% or less, and 0.0% or less are more preferable.

From the viewpoint of suppressing coloration of glass, the WO ₃ content is preferably 1.0% or less, more preferably 0.50% or less, even more preferably 0.1% or less, and 0. More preferably, it is .0%.

Mass ratio of the _total content _{of TiO2} , _{Nb2O5 , Ta2O5} and _WO3 to _the total content of _{La2O3 , Gd2O3} , _Y2O3 and _{Yb2O3 (} ( _TiO2 +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is 0.15 or less from the viewpoint of low dispersion, and 0.14 It is preferably at most 0.13, more preferably at most 0.12, and more preferably at most 0.11. Moreover, the mass ratio ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is, for example, 0.00 or more, 0.00 It can be greater than or equal to 0.01, greater than or equal to 0.02, greater than or equal to 0.03, greater than or equal to 0.04, or greater than or equal to 0.05.

Mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ to the total content of SiO ₂ and B ₂ O ₃ ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ ) /(SiO ₂ +B ₂ O ₃ )) is 0.35 or less, 0.34 or less, 0.33 or less, 0.32 or less, 0.31 or less, from the viewpoint of improving the thermal stability of the glass. The order of 0.30 or less and 0.29 or less is more preferable. The mass ratio ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(SiO ₂ +B ₂ O ₃ )) is, for example, 0.00 or more, more than 0.00, 0.01 or more, 0.03 or more, It can be 0.05 or more, 0.07 or more, or 0.10 or more.

Mass ratio of the total content of _Ta2O5 and _{WO3 to the total content of TiO2, WO3 , Ta2O5 and Nb2O5 ( ( Ta2O5 + WO3} )/( _TiO2 +W+ _{O3 )} Ta ₂ O ₅ +Nb ₂ O ₅ )) is 0.45 or less, preferably 0.40 or less, 0.35 or less, 0.30 or less, from the viewpoint of suppressing coloring of the glass and lowering the specific gravity. , 0.25 or less, 0.20 or less, and 0.15 or less. The mass ratio (( _{Ta2O5 + WO3 )} /( _TiO2 +W+ _O3Ta2O5 + _Nb2O5 )) is, for example, 0.00 or more, more than 0.00, _or 0.01 or _more , 0.02 or more, It can be 0.03 or more, 0.04 or more, or 0.05 or more.

The mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ to the ZnO content ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/ZnO) is the From this point of view, it is preferably 30.00 or less, more preferably 25.00 or less. The mass ratio ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/ZnO) is, for example, 0.00 or more, more than 0.00, 0.50 or more, 1.00 or more, 1.50 or more, or 1. It can be 70 or more.

The mass ratio of the Nb ₂ O ₅ content to the total content of TiO ₂ +Nb ₂ O ₅ +Ta 2 O 5 +WO ₃ (Nb ₂ O _{5 /} (TiO _{2 +} Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )) is, for example, It can be less than or equal to 1.00. The mass ratio (Nb ₂ O ₅ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )) can be, for example, 0.00 or more, more than 0.00, 0.10 or more, or 0.50 or more. .

The sum of _{La 2 O 3} , Gd _{2 O 3 ,} Y ₂ O ₃ , _{Yb 2 O 3} , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ relative to the total content of SiO 2 and B 2 O 3 The mass ratio of the content ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(SiO ₂ +B ₂ O ₃ )) is determined by the desired optical From the viewpoint of realizing a constant and improving the thermal stability of the glass, it is 3.50 or less, preferably 3.40 or less, and more preferably 3.30 or less and 3.20 or less, in that order. The mass ratio ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(SiO ₂ +B ₂ O ₃ )) is, for example, more than 0.00. , 0.10 or more, 0.50 or more, 1.50 or more, or 2.00 or more.

From the viewpoint of further improving the thermal stability of the glass, the ZrO ₂ content is preferably 13.0% or less, more preferably 12.0% or less, 11.0% or less, 10 It is more preferable in the order of .0% or less, 9.0% or less, and 8.0% or less. The _ZrO2 content is, for example, 0.0% or more, more than 0.0%, 0.1% or more, 0.5% or more, 1.0% or more, 2.0% or more, 3.0% or more, 4 It can be .0% or more or 5.0% or more.

The optical glass may or may not contain Al ₂ O ₃ . The Al ₂ O ₃ content of the optical glass can be, for example, 0.0% or more, more than 0.0%, 0.1% or more, 0.5% or more, or 1.0% or more. Further, the Al ₂ O ₃ content of the optical glass can be, for example, 5.0% or less, 4.0% or less, or 3.0% or less.

The above optical glass may or may not contain one or more types of alkaline earth metal oxides. In the above optical glass, each content of MgO, CaO, SrO, and BaO is, for example, 0.0% or more, more than 0.0%, 0.1% or more, 0.5% or more, or 1.0% or more. It can also be, for example, 5.0% or less, 4.0% or less, or 3.0% or less.

Sb ₂ O ₃ is a component that can be added as a clarifying agent. Although a small amount of addition can serve to suppress a decrease in light transmittance due to the inclusion of impurities such as Fe, when the amount of Sb ₂ O ₃ added is increased, the coloring of the glass tends to increase. Therefore, the amount of Sb ₂ O ₃ added is preferably 0.00% or more and 0.10% or less, more preferably 0.00% or more and 0.05% or less, and even more preferably 0.00%. % or more and 0.03% or less. The Sb ₂ O ₃ content by external division means the content of Sb ₂ O ₃ expressed in mass % when the total content of glass components other than Sb ₂ O ₃ is 100 mass %.

SnO ₂ can also be added as a fining agent, but if it is added in an amount exceeding 1.00%, the glass may be colored, and when the glass is heated and softened to be remolded by press molding, SnO2 may be added. It becomes a starting point for crystal nucleation and tends to devitrify. Therefore, the amount of SnO ₂ added is preferably 0.00% or more and 1.00% or less, more preferably 0.00% or more and 0.50% or less, and particularly preferably not added. . The SnO ₂ content by external division means the SnO ₂ content expressed in mass % when the total content of glass components other than SnO ₂ is 100 mass %.

The above optical glass can be produced without containing components such as Lu and Hf. Since Lu and Hf are expensive components, it is preferable to suppress the content of Lu ₂ O ₃ and HfO ₂ to 0.00% or more and 2.00% or less, respectively, and 0.00% or more and 1.00% or less, respectively. It is more preferable to suppress it to 0.00% or more and 0.80% or less, each more preferably to suppress it to 0.00% or more and 0.10% or less, and do not introduce Lu ₂ O ₃ . In particular, it is particularly preferable not to introduce HfO ₂ .
Further, in consideration of the environmental impact, it is preferable not to introduce Pb, and it is also preferable not to introduce As, U, Th, Te, or Cd.
Furthermore, from the viewpoint of taking advantage of the excellent light transmittance of glass, it is preferable not to introduce substances that cause coloring, such as Cu, Cr, V, Fe, Ni, and Co.

F is a component that significantly increases the volatility of the glass during melting and causes a decrease in the stability and homogeneity of the optical properties of the glass. The F content can be defined as the content (unit: mass %) of the F element relative to 100 mass % of the total content of the oxide-based glass composition determined as described above. In the above optical glass, the F content defined in this way is preferably less than 0.10%, more preferably less than 0.08%, and even more preferably less than 0.05%. The F content can be 0.00% or more, and may be 0.00%.

<Glass physical properties>
(Refractive index nd)
The optical glass may be a glass with a high refractive index. The refractive index nd of the optical glass is preferably 1.70 or more, more preferably 1.75 or more, 1.80 or more, 1.81 or more, 1.82 or more, 1.83 or more, It is more preferable in the order of 1.84 or more and 1.85 or more. The refractive index nd of the optical glass can be, for example, 1.90 or less, 1.89 or less, or 1.88 or less. In the present invention and this specification, "refractive index" means "refractive index nd."

(Abbe number νd)
The Abbe number νd is a value representing the property related to dispersion, and is expressed as νd = (nd-1)/(nF-nC) using the refractive indexes nd, nF, and nC at the d-line, F-line, and C-line. Ru. From the viewpoint of usefulness as a material for optical elements, the optical glass is preferably a low-dispersion glass. From this viewpoint, the Abbe number νd of the optical glass is preferably 40.0 or more, more preferably 40.5 or more, and even more preferably 41.0 or more. The Abbe number νd of the optical glass can be, for example, 44.0 or less.

In one form, the optical glass can be a high refractive index, low dispersion glass having a refractive index nd of 1.70 or more and 1.90 or less, and an Abbe number νd of 40.0 or more and 44.0 or less.

Further, from the viewpoint of usefulness as a material for optical elements, it is preferable that the refractive index nd and Abbe number νd of the optical glass satisfy the following formula (1).
Formula (1):
nd>-0.05*νd+3.94

(specific gravity)
The refractive power of an optical element that makes up an optical system is determined by the refractive index of the glass that makes up the optical element and the curvature of the optically functional surface of the optical element (the surface on which the light beam to be controlled enters and exits). Increasing the curvature of the optical functional surface also increases the thickness of the optical element. As a result, the optical element becomes heavier. On the other hand, if glass with a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optically functional surface.
From the above, if the refractive index can be increased while suppressing an increase in the specific gravity of glass, it is possible to reduce the weight of an optical element having a certain refractive power.
From the above viewpoint, the specific gravity of the optical glass is preferably 5.20 or less, more preferably 5.15 or less, and 5.10 or less in that order. Since the lower the specific gravity is, the more preferable it is from the viewpoint of reducing the weight of the optical element, the lower limit of the specific gravity of the optical glass is not particularly limited. In one form, the specific gravity can be 4.40 or higher, 4.50 or higher, or 4.60 or higher.

(Coloring degree λ5, λ70, λ80)
Regarding suppression of coloration of glass, the light transmittance of glass, specifically, suppression of the increase in wavelength of the light absorption edge on the short wavelength side can be evaluated by one or more of the degree of coloration λ5, λ70, and λ80. can. The degree of coloring λ5 represents a wavelength at which the spectral transmittance (including surface reflection loss) of a 10 mm thick glass is 5% from the ultraviolet region to the visible region. λ70 represents a wavelength at which the spectral transmittance measured by the method described for λ5 is 70%. λ80 represents a wavelength at which the spectral transmittance measured by the method described for λ5 is 80%. λ5, λ70, and λ80 shown in the Examples section below are values measured in the wavelength range of 250 to 700 nm. Note that the spectral transmittance T (%) of glass in the present invention and this specification refers to the spectral transmittance T (%) of light that is perpendicularly incident on one of the two optically polished planes of the glass sample that is parallel to each other. When the intensity is I _in and the intensity of the light transmitted through the glass sample and emitted from the other side is I _out ,
T (%) = I _out / I _in ×100
It is expressed as
According to the coloring degrees λ5, λ70, and λ80, the absorption edge of the spectral transmittance on the short wavelength side can be quantitatively evaluated. When joining lenses together using an ultraviolet curable adhesive to produce a cemented lens, the adhesive is cured by irradiating the adhesive with ultraviolet rays through an optical element. From the viewpoint of efficiently curing the ultraviolet curable adhesive, it is preferable that the absorption edge on the short wavelength side of the spectral transmittance is in a short wavelength range. As an index for quantitatively evaluating the absorption edge on the short wavelength side, one or more of the degree of coloration λ5, λ70, and λ80 can be used.
The above optical glass can preferably exhibit λ5 of 340 nm or less, more preferably 335 nm or less. Further, the above-mentioned optical glass can preferably exhibit a λ70 of 400 nm or less, and more preferably can exhibit a λ70 of 390 nm or less. λ80 is preferably 480 nm or less, more preferably 475 nm or less. The lower λ5, λ70, and λ80 are, the more preferable they are, and the lower limit is not particularly limited.

(Glass transition temperature Tg)
From the viewpoint of reducing the burden on the annealing furnace and mold, the glass transition temperature Tg of the optical glass is preferably 800°C or lower, such as 790°C or lower, 780°C or lower, 770°C or lower, 760°C or lower, or 750°C or lower. It is more preferable that the temperature is lower than or equal to ℃. On the other hand, from the viewpoint of machinability (specifically, from the viewpoint that it is difficult to break when performing glass machining such as cutting, cutting, grinding, polishing, etc.), the glass transition temperature Tg of the above optical glass is 640°C or higher. The temperature is preferably 650°C or higher, more preferably 660°C or higher. The glass transition temperature Tg is determined by the method described below.

(Thermal stability)
Thermal stability of glass includes resistance to devitrification during molding of a glass melt and resistance to devitrification when glass once solidified is reheated.

Liquidus temperature LT
The liquidus temperature (LT) can be used as a guideline for devitrification resistance when molding a glass melt. A glass having a lower liquidus temperature can be said to have better devitrification resistance. For glasses with a high liquidus temperature, in order to prevent devitrification, the temperature of the glass melt, that is, the molten glass, must be maintained at a high temperature, which causes volatilization of easily volatile components and promotes corrosion of the crucible. In particular, in the case of noble metal crucibles, phenomena such as noble metal ions dissolving into the glass melt and coloring the glass, and lower viscosity during molding making it difficult to mold highly homogeneous glass may occur. . Therefore, the liquidus temperature LT of the optical glass is preferably 1320°C or less, more preferably 1310°C or less, 1300°C or less, 1290°C or less, 1280°C or less, 1270°C or less, and 1260°C or less. The liquidus temperature LT can be, for example, 1000° C. or higher or 1100° C. or higher, but since it is preferable that the liquidus temperature LT is low, it can also exceed the values exemplified here.

The "liquidus temperature" in the present invention and this specification is determined by the following method.
A platinum crucible containing 5 cc of glass was placed with a lid and held in a furnace heated to a predetermined temperature for 2 hours. After cooling, the inside of the glass was observed with an optical microscope (magnification: 100x) to determine the presence or absence of crystals. From this, determine the liquidus temperature. The temperature was changed in 10°C increments.

Tx-Tg
Regarding the devitrification resistance when a glass that has been solidified is reheated, it is considered that the larger the difference between the crystallization peak temperature Tx and the glass transition temperature Tg (Tx - Tg), the better the devitrification resistance. I can do it.
The glass transition temperature Tg and the crystallization peak temperature Tx are determined as follows. In differential scanning calorimetry, when a glass sample is heated, an endothermic behavior occurs due to a change in specific heat, that is, an endothermic peak appears, and when the temperature is further increased, an exothermic peak appears. In differential scanning calorimetry analysis, a differential scanning calorimetry curve (DSC curve) is obtained in which the horizontal axis is temperature and the vertical axis is a quantity corresponding to exothermic endotherm of the sample. In this curve, the intersection of the tangent at the point where the slope is maximum when the endothermic peak appears from the baseline and the above baseline is defined as the glass transition temperature Tg, and the tangent at the point where the slope is maximum when the exothermic peak appears and the above base line. The intersection of the lines is defined as the crystallization peak temperature Tx. The glass transition temperature Tg and crystallization temperature Tx are measured by using a sample of glass that has been thoroughly crushed in a mortar or the like, using a platinum cell as a sample container, and using a differential scanning calorimeter at a heating rate of 10°C/10°C. It can be done in minutes.
Since devitrification occurs when the temperature of the glass during molding reaches the crystallization temperature range, a glass with a small (Tx-Tg) is disadvantageous in performing molding while preventing devitrification. On the other hand, glass with a large value (Tx-Tg) is advantageous in that it can be reheated, softened, and molded without devitrification. For the above reasons, the difference between the crystallization peak temperature Tx and the glass transition temperature Tg (Tx - Tg) is preferably 70°C or more. (Tx-Tg) can be, for example, 300°C or less, 280°C or less, 260°C or less, 240°C or less, 220°C or less, or 200°C or less, but it is preferable that (Tx-Tg) is large. , it is also possible to exceed the values exemplified here.

<Method for manufacturing optical glass>
The above-mentioned optical glass is produced by weighing and preparing raw materials such as oxides, carbonates, sulfates, nitrates, hydroxides, etc., and thoroughly mixing them to form a mixed batch so as to obtain the desired glass composition. It can be obtained by heating, melting, degassing, and stirring a homogeneous molten glass that does not contain bubbles, and then molding the molten glass. Specifically, it can be made using a known melting method.

[Glass material for press molding, optical element blank, and manufacturing method thereof]
Another aspect of the present invention is
Glass material for press molding made of the above optical glass;
An optical element blank made of the above optical glass,
Regarding.

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

An optical element blank is a blank that approximates the shape of the intended optical element, and must be polished to the shape of the optical element (surface layer to be removed by polishing), or ground as necessary (to be removed by grinding). It is an optical element base material with a surface layer) added. The optical element is finished by grinding and polishing the surface of the optical element blank. In one form, an optical element blank can be produced by a method of press-molding a molten glass obtained by melting an appropriate amount of the glass (referred to as a direct press method). In another form, an optical element blank can also be produced by melting an appropriate amount of the glass and solidifying a molten glass.

In another embodiment, an optical element blank can be produced by producing a press-molding glass material and press-molding the produced press-molding glass material.

Press molding of the glass material for press molding can be performed by a known method of pressing the glass material for press molding that has been heated and softened using a press mold. Both heating and press molding can be performed in the atmosphere. By annealing the glass after press molding to reduce distortion inside the glass, a homogeneous optical element blank can be obtained.

Press-molding glass materials are used in their original state as press-molding glass gobs, which are used for press-molding to produce optical element blanks, and in addition to press-molding glass gobs that are subjected to mechanical processing such as cutting, grinding, and polishing. It also includes those that are subjected to press molding after passing through the process. The cutting method is to form grooves on the surface of the glass plate where you want to cut using a method called scribing, and then apply local pressure to the grooved area from the back side of the surface where the groove was formed, so that the glass plate is cut in the grooved area. There are methods such as breaking the glass plate and cutting the glass plate with a cutting blade. Furthermore, examples of grinding and polishing methods include barrel polishing and the like.

The glass material for press molding can be produced, for example, by casting molten glass into a mold to form a glass plate, and cutting the glass plate into a plurality of glass pieces. Alternatively, a glass gob for press molding can also be produced by molding an appropriate amount of molten glass. An optical element blank can also be produced by reheating, softening, and press-molding a glass gob for press molding. The method of producing an optical element blank by reheating and softening glass and press-molding it is called a reheat press method, as opposed to a direct press method.

[Optical element and its manufacturing method]
Another aspect of the present invention is
The present invention relates to an optical element made of the optical glass described above.
The optical element is manufactured using the optical glass. In the above optical element, one or more coatings such as a multilayer film such as an antireflection film may be formed on the glass surface.

Further, according to one aspect of the present invention,
A method for manufacturing an optical element, comprising a step of manufacturing an optical element by grinding and/or polishing the optical element blank,
is also provided.

In the above method for manufacturing an optical element, mechanical processing such as grinding and polishing can be performed by applying a known method, and by thoroughly cleaning and drying the surface of the optical element after processing, internal quality and surface quality can be improved. A high quality optical element can be obtained. In this way, an optical element made of the above optical glass can be obtained. Examples of optical elements include various lenses such as spherical lenses, aspherical lenses, and microlenses, prisms, and the like.

Further, the optical element made of the above optical glass is also suitable as a lens constituting a cemented optical element. Examples of the cemented optical element include one in which lenses are cemented together (a cemented lens), a lens and a prism in one cemented together, and the like. For example, a bonded optical element is manufactured by precisely processing (e.g., spherical polishing) the bonding surfaces of two optical elements to be bonded so that the shape is inverted, and using an ultraviolet curing adhesive used to bond the bonded lens. It can be manufactured by coating the adhesive, bonding it together, and then irradiating it with ultraviolet light through a lens to harden the adhesive. In order to produce a bonded optical element in this way, the above-mentioned optical glass is preferable. By manufacturing a plurality of optical elements to be bonded using a plurality of types of glass having different Abbe numbers νd and bonding them, an element suitable for correcting chromatic aberration can be obtained.

EXAMPLES Below, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to the embodiments shown in Examples.

(Example 1)
<Example No. 1-156>
In order to obtain the glass composition shown in the table below, we weighed the raw materials using corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. as raw materials for introducing each component, and The mixture was thoroughly mixed and used as a raw material for preparation.
This mixed raw material was placed in a platinum crucible, heated in a furnace set at 1400°C, and melted for 2 hours. After stirring and homogenizing the molten glass, the molten glass is poured into a preheated mold, allowed to cool to around the glass transition temperature, and then immediately placed in an annealing furnace and held at a temperature around the glass transition temperature for about 30 minutes. By slow cooling at a slow cooling rate of -30°C/hour for 4 hours and then cooling to room temperature in the furnace, No. 1 shown in the table below was obtained. Optical glasses Nos. 1 to 122 were obtained.
The physical properties of the optical glass thus obtained are shown in the table below.
Various physical properties of the optical glass were measured by the methods shown below.

<Evaluation of physical properties of optical glass>
(1) Refractive index nd Abbe number νd
The refractive index nd and Abbe number νd of the obtained glass were measured by the refractive index measurement method specified by the Japan Optical Glass Industry Association.

(2) Glass transition temperature Tg, crystallization temperature Tx
The glass transition temperature was determined by thoroughly crushing glass in a mortar and using a platinum cell as the sample container using a differential scanning calorimeter (DSC8270) manufactured by Rigaku at a heating rate of 10°C/min. Tg and crystallization temperature Tx were measured.
"Tg-Tx" was calculated from the measured Tg and Tx.

(3) Specific gravity Specific gravity was measured by the Archimedes method.

(4) Coloring degree λ5, λ70, λ80
Using a glass sample with a thickness of 10±0.1 mm having two optically polished planes facing each other, the spectral transmittance T (%) was measured using a spectrophotometer. The wavelength (nm) at which T becomes 5% is defined as λ5, the wavelength (nm) at which T becomes 70% is defined as λ70, and the wavelength (nm) at which T becomes 80% is defined as λ80.

(5) Liquidus temperature LT
The liquidus temperature LT was determined by the method described above.

(Example 2)
Using the various glasses obtained in Example 1, glass gobs for press molding were produced. This glass gob was heated and softened in the atmosphere, and press-molded using a press mold to produce a lens blank (optical element blank). The produced lens blank was taken out from the press mold, annealed, and machined including polishing to produce spherical lenses made of the various glasses produced in Example 1.

(Example 3)
A desired amount of the molten glass produced in Example 1 was press-molded using a press mold to produce a lens blank (optical element blank). The produced lens blank was taken out from the press mold, annealed, and machined including polishing to produce spherical lenses made of the various glasses produced in Example 1.

(Example 4)
A glass lump (optical element blank) produced by solidifying the molten glass produced in Example 1 was annealed and machined including polishing to produce spherical lenses made of the various glasses produced in Example 1.

(Example 5)
The spherical lenses produced in Examples 2 to 4 were bonded to spherical lenses made of other types of glass to produce cemented lenses. The cemented surfaces of the spherical lenses produced in Examples 2 to 4 were convex, and the cemented surfaces of the spherical lenses made of other types of glass were concave. The two bonding surfaces were fabricated so that the absolute values of their radii of curvature were equal to each other. An ultraviolet curing adhesive for bonding optical elements was applied to the bonding surfaces, and the two lenses were bonded together. Thereafter, the adhesive applied to the joint surface was irradiated with ultraviolet rays through the spherical lenses prepared in Examples 2 to 4 to solidify the adhesive.
A cemented lens was produced as described above. The bonding strength of the cemented lens was sufficiently high, and the optical performance was also at a sufficient level.

Finally, the above-mentioned aspects will be summarized.

[1] Based on mass,
B ₂ O ₃ content is 5.0% or more and 30.0% or less,
_SiO2 content is 1.0% or more and 15.0% or less,
Nb ₂ O ₅ content is 15.0% or less,
La ₂ O ₃ content is 5.0% or more and 70.0% or less,
ZnO content is 0.1% or more,
Li ₂ O content is 0.4% or less,
_TiO2 content is 5.0% or less,
Mass ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y 2 O ₃ and Yb ₂ O ₃ to the total content of SiO ₂ and _B 2 O ₃ ((La ₂ O ₃ +Gd _{2 O 3} +Y ₂ O ₃ + Yb ₂ O ₃ )/(SiO ₂ + B ₂ O ₃ )) is 2.50 or more and 5.30 or less,
Mass ratio of the _total content _{of TiO2} , _{Nb2O5 , Ta2O5} and _WO3 to _the total content of _{La2O3 , Gd2O3} , _Y2O3 and _{Yb2O3 (} ( _TiO2 +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is 0.15 or less,
The mass ratio of SiO ₂ content to B ₂ O ₃ content (SiO ₂ /B ₂ O ₃ ) is 0.20 or more and 0.60 or less,
Mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ to the total content of SiO ₂ and B ₂ O ₃ ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ ) /(SiO ₂ +B ₂ O ₃ )) is 0.35 or less,
Mass ratio of ZnO content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ (ZnO/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is 0.14 or less,
Mass ratio of the total content of _Ta2O5 and _{WO3 to the total content of TiO2, WO3 , Ta2O5 and Nb2O5 ( ( Ta2O5 + WO3} )/( _TiO2 +W+ _{O3 )} Ta ₂ O ₅ + Nb ₂ O ₅ )) is 0.45 or less,
The sum of _{La 2 O 3} , Gd _{2 O 3 ,} Y ₂ O ₃ , _{Yb 2 O 3} , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ relative to the total content of SiO 2 and B 2 O 3 The mass ratio of the content ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(SiO ₂ +B ₂ O ₃ )) is 3.50. Below, and the mass ratio of Gd ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ (Gd ₂ O ₃ /(La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ )) is 0.10 or more and 0.45 or less.
[2] The optical glass according to [1], which has a refractive index nd of 1.70 or more and 1.90 or less.
[3] The optical glass according to [1] or [2], which has an Abbe number νd of 40.0 or more and 44.0 or less.
[4] The optical glass according to any one of [1] to [3], wherein the Yb ₂ O ₃ content is 10.0% by mass or less.
[5] The optical glass according to any one of [1] to [4], wherein the Ta ₂ O ₅ content is 12.0% by mass or less.
[6] The optical glass according to any one of [1] to [5], which does not contain Pb.
[7] The optical glass according to any one of [1] to [6], wherein the refractive index nd and the Abbe number νd satisfy the following formula (1).
Formula (1):
nd>-0.05*νd+3.94
[8] An optical element made of the optical glass according to any one of [1] to [7].

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.
For example, an optical glass according to one embodiment of the present invention can be obtained by adjusting the composition described in the specification with respect to the glass composition exemplified above.
Furthermore, it is of course possible to arbitrarily combine two or more of the items described as examples or preferred ranges in the specification.

Claims (9)

Based on mass,
B ₂ O ₃ content is 5.0% or more and 30.0% or less,
_SiO2 content is 1.0% or more and 15.0% or less,
Nb ₂ O ₅ content is 15.0% or less,
La ₂ O ₃ content is 5.0% or more and 70.0% or less,
ZnO content is 0.1% or more,
Li ₂ O content is 0.4% or less,
_TiO2 content is 5.0% or less,
Mass ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y 2 O ₃ and Yb ₂ O ₃ to the total content of SiO ₂ and _B 2 O ₃ ((La ₂ O ₃ +Gd _{2 O 3} +Y ₂ O ₃ + Yb ₂ O ₃ )/(SiO ₂ + B ₂ O ₃ )) is 2.50 or more and 5.30 or less,
Mass ratio of the _total content _{of TiO2} , _{Nb2O5 , Ta2O5} and _WO3 to _the total content of _{La2O3 , Gd2O3} , _Y2O3 and _Yb2O3 ( _{( TiO2} +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is 0.15 or less,
The mass ratio of SiO ₂ content to B ₂ O ₃ content (SiO ₂ /B ₂ O ₃ ) is 0.20 or more and 0.60 or less,
Mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ to the total content of SiO ₂ and B ₂ O ₃ ((TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ ) /(SiO ₂ +B ₂ O ₃ )) is 0.35 or less,
Mass ratio of ZnO content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ (ZnO/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ )) is 0.14 or less,
Mass ratio of the total content of _Ta2O5 and _{WO3 to the total content of TiO2, WO3 , Ta2O5 and Nb2O5 ( ( Ta2O5 + WO3} )/( _TiO2 +W+ _{O3 )} Ta ₂ O ₅ + Nb ₂ O ₅ )) is 0.45 or less,
The sum of _{La 2 O 3} , Gd _{2 O 3 ,} Y ₂ O ₃ , _{Yb 2 O 3} , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ relative to the total content of SiO 2 and B 2 O 3 The mass ratio of the content ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(SiO ₂ +B ₂ O ₃ )) is 3.50. Below, and the mass ratio of Gd ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ (Gd ₂ O ₃ /(La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ )) is 0.10 or more and 0.45 or less. The optical glass according to claim 1, having a refractive index nd of 1.70 or more and 1.90 or less. The optical glass according to claim 1, having an Abbe number νd of 40.0 or more and 44.0 or less. The optical glass according to claim 1, wherein the _Yb2O3 content is 10.0% by mass _or less. The optical glass according to claim 1, wherein _{the Ta2O5} content is 12.0% by mass or less. The optical glass according to claim 1, which does not contain Pb. The optical glass according to claim 1, wherein the refractive index nd and the Abbe number νd satisfy the following formula (1).
Formula (1):
nd>-0.05*νd+3.94 Yb ₂ O ₃ content is 10.0% by mass or less,
Ta ₂ O ₅ content is 12.0% by mass or less,
Does not contain Pb,
the refractive index nd is 1.70 or more and 1.90 or less,
The optical glass according to claim 1, wherein the Abbe number νd is 40.0 or more and 44.0 or less, and the refractive index nd and the Abbe number νd satisfy the following formula (1).
Formula (1):
nd>-0.05*νd+3.94 An optical element made of the optical glass according to any one of claims 1 to 8.