JP7142118B2 - Optical glasses and optical elements - Google Patents

Description

The present invention relates to optical glasses and optical elements having desired optical constants.

Patent Document 1 discloses an optical glass having a predetermined refractive index nd and Abbe number νd. The optical glass described in Patent Document 1 is characterized in that the inside of the glass does not devitrify in a reheating test. However, in recent years, there has been a demand for higher stability during reheating.

JP 2017-105703 A

In addition to the higher stability during reheating as described above, the optical elements mounted in the autofocus optical system are required to be lightweight in order to reduce the power consumption when driving the autofocus function. It is If the specific gravity of glass can be reduced, the weight of optical elements such as lenses can be reduced. Furthermore, a small partial dispersion ratio Pg,F is required for correction of chromatic aberration.

Accordingly, the present invention provides an optical glass having desired optical constants, a small specific gravity and partial dispersion ratio Pg, F, and excellent stability during reheating, and an optical element comprising the optical glass. With the goal.

The gist of the present invention is as follows.
(1) the content of SiO ₂ is 10 to 50% by mass;
The content of Nb ₂ O ₅ is 10 to 50% by mass,
The total content of TiO ₂ and BaO [TiO ₂ +BaO] is 10% by mass or less,
An optical glass having a mass ratio of B ₂ O ₃ content to SiO ₂ content [B ₂ O ₃ /SiO ₂ ] of 0.15 or less.

(2) The optical glass according to (1), which satisfies at least one of (a) to (g).
(a) The content of La ₂ O ₃ is 15% by mass or less.
_{( b} ) _The mass ratio of the content of ZrO2 to the content of _Nb2O5 [ZrO2/ _Nb2O5 ] is greater _than 0.1.
(c) mass ratio of the _total content of _{Nb2O5 , TiO2} and ZrO2 to the _total content of B2O3 and _SiO2 [ _{( Nb2O5 + TiO2 +} ZrO2)/ ₍ B2O3 ₊ SiO ₂ )] is smaller than 1.7.
(d) The mass ratio [R'O/R ₂ O] of the total content R'O of MgO, CaO, SrO and BaO to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is 5 It is below.
(e) The mass ratio of the content of Ta ₂ O ₅ to the total content of Nb ₂ O ₅ and TiO ₂ [Ta ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ )] is 0.15 or less.
(f) the mass ratio of the content of _TiO2 to the total content of _Nb2O5 , _TiO2 and ZrO2 [ _TiO2 / _{( Nb2O5 + TiO2 +} ZrO2)] is greater than ₀ and less than 0.3; .
(g) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is greater than 0% by mass.

(3) a refractive index nd of 1.69 to 1.77;
The optical glass according to (1) or (2), which has an Abbe number νd of 34-37.

(4) has a specific gravity of 3.45 or less;
The deviation ΔPg,F of the partial dispersion ratio Pg,F is −0.0015 or less,
The liquidus temperature LT is 1250° C. or less,
When heated for 10 minutes at the glass transition temperature Tg and further heated for 10 minutes at a temperature 180 to 200° C. higher than the Tg, the number of crystals observed per 1 g is 20 or less,
The refractive index nd is 1.69 to 1.77,
Optical glass having an Abbe number νd of 34-37.

(5) An optical element made of the optical glass described in any one of (1) to (4) above.

According to the present invention, it is possible to provide an optical glass having desired optical constants, a small specific gravity and partial dispersion ratio Pg,F, and excellent stability during reheating, and an optical element comprising the optical glass. can be done.

Embodiments of the present invention will be described below. In the present invention and this specification, the glass composition of optical glass is indicated on the basis of oxide unless otherwise specified. Here, the term "oxide-based glass composition" refers to a glass composition obtained by conversion assuming that the glass raw materials are all decomposed during melting and exist as oxides in the optical glass, and the notation of each glass component is According to convention, they are described as SiO ₂ , TiO ₂ and the like. The content and total content of glass components are based on mass unless otherwise specified, and "%" means "% by mass."

The content of the glass component can be quantified by known methods such as inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Further, in the present specification and the present invention, the content of a component of 0% means that the component is not substantially contained, and the component is allowed to be contained at the level of unavoidable impurities.

In this specification, the refractive index refers to the refractive index nd at the helium d-line (wavelength 587.56 nm), unless otherwise specified.

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

The partial dispersion ratio Pg, F is expressed as follows using respective refractive indices ng, nF, and nC for g-line, F-line, and c-line.
Pg, F = (ng-nF)/(nF-nC)
In a plane where the horizontal axis is the Abbe number νd and the vertical axis is the partial dispersion ratio Pg, F, the normal line is expressed by the following equation.
Pg,F(0)=0.6483−(0.0018×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)

The optical glass of the present invention will be described below based on the glass composition as a first embodiment, and the optical glass of the present invention will be described based on physical property values as a second embodiment.

First Embodiment The optical glass according to the first embodiment is
The content of SiO ₂ is 10 to 50% by mass,
The content of Nb ₂ O ₅ is 10 to 50% by mass,
The total content of TiO ₂ and BaO [TiO ₂ +BaO] is 10% by mass or less,
The mass ratio [B ₂ O ₃ /SiO ₂ ] of the content of B ₂ O ₃ to the content of SiO ₂ is 0.15 or less.

In the optical glass according to the first embodiment, the content of SiO ₂ is 10-50%. The lower limit of the SiO ₂ content is preferably 15%, more preferably 20%, 25% and 30% in that order. The upper limit of the SiO ₂ content is preferably 47%, more preferably 45% and then 43% in that order. If the _SiO2 content is too low, vitrification becomes difficult. If the _SiO2 content is too high, it is difficult to obtain the desired optical constants.

In the optical glass according to the first embodiment, the content of Nb ₂ O ₅ is 10-50%. The lower limit of the content of Nb ₂ O ₅ is preferably 14%, more preferably 16%, 18% and 20% in that order. The upper limit of the content of Nb ₂ O ₅ is preferably 44%, more preferably 41%, 38% and 35% in that order. If the content of Nb ₂ O ₅ is too small, there is a possibility that the target high refractive index cannot be achieved. If the content of Nb ₂ O ₅ is too high, the thermal stability may deteriorate and the raw material cost of the glass may increase.

In the optical glass according to the first embodiment, the total content of TiO ₂ and BaO [TiO ₂ +BaO] is 10% or less. The upper limit of the total content [TiO ₂ +BaO] is preferably 9%, more preferably 8%, 7% and 6% in that order. The total content [TiO ₂ +BaO] is preferably as small as possible, and its lower limit is preferably 0%. The total content [TiO ₂ +BaO] may be 0%. TiO ₂ is a component that increases the partial dispersion ratio Pg,F, and BaO is a component that increases the specific gravity. Therefore, by setting the total content [TiO ₂ +BaO] within the above range, an increase in the partial dispersion ratio Pg, F and the specific gravity can be suppressed.

In the optical glass according to the first embodiment, the mass ratio [B ₂ O ₃ /SiO ₂ ] of the content of B ₂ O ₃ to the content of SiO ₂ is 0.15 or less. The upper limit of the mass ratio [B ₂ O ₃ /SiO ₂ ] is preferably 0.14, more preferably 0.13, 0.12 and 0.11 in that order. The lower limit of the mass ratio [B ₂ O ₃ /SiO ₂ ] is preferably 0, more preferably 0.01, 0.02 and 0.03 in this order. If the mass ratio [B ₂ O ₃ /SiO ₂ ] is too large, the glass raw material is melted to form a melt, and the glass melt is molded to vitrify. During molding, crystals may precipitate.

In the first embodiment, it is preferable to satisfy at least one of the following (a) to (g).
(a) The content of La ₂ O ₃ is 15% or less.
_{( b} ) _The mass ratio of the content of ZrO2 to the content of _Nb2O5 [ZrO2/ _Nb2O5 ] is greater _than 0.1.
(c) mass ratio of the _total content of _{Nb2O5 , TiO2} and ZrO2 to the _total content of B2O3 and _SiO2 [ _{( Nb2O5 + TiO2 +} ZrO2)/ ₍ B2O3 ₊ SiO ₂ )] is smaller than 1.7.
(d) The mass ratio [R'O/R ₂ O] of the total content R'O of MgO, CaO, SrO and BaO to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is 5 It is below.
(e) The mass ratio of the content of Ta ₂ O ₅ to the total content of Nb ₂ O ₅ and TiO ₂ [Ta ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ )] is 0.15 or less.
(f) the mass ratio of the content of _TiO2 to the total content of _Nb2O5 , _TiO2 and ZrO2 [ _TiO2 / _{( Nb2O5 + TiO2 +} ZrO2)] is greater than ₀ and less than 0.3; .
(g) the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is greater than 0%;
The above (a) to (g) will be described in detail below.

(a) In the optical glass according to the first embodiment, the upper limit of the content of La ₂ O ₃ is preferably 15%, more preferably 13%, 11% and 9% in that order. The lower limit of the La ₂ O ₃ content is preferably 0%, more preferably 0.5%, 1.0% and 1.5% in that order. The content of La ₂ O ₃ may be 0%. By setting the upper limit of the content of La ₂ O ₃ within the above range, an increase in specific gravity can be suppressed.

(b) _In the optical glass according to the _first embodiment, the mass ratio of the content of ZrO2 to the content of _Nb2O5 [ZrO2/ _Nb2O5 ] is preferably greater _than 0.1, _more preferably is greater than 0.3. Also, the upper limit of the mass ratio [ZrO ₂ /Nb ₂ O ₅ ] is preferably 0.8, more preferably 0.7, 0.6 and 0.5 in that order. By setting the lower limit of the mass ratio [ZrO ₂ /Nb ₂ O ₅ ] to the above range, the partial dispersion ratio Pg,F and ΔPg,F can be reduced. By setting the upper limit of the mass ratio [ZrO ₂ /Nb ₂ O ₅ ] within the above range, glass can be stably obtained.

(c) Mass ratio of the total content of Nb ₂ O ₅ , TiO ₂ and ZrO ₂ to the total content of B ₂ O ₃ and SiO ₂ in the optical glass according to the first embodiment [(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )/(B ₂ O ₃ +SiO ₂ )] is preferably less than 1.7, more preferably 1.5 or less, 1.4 or less, and 1.3 or less in that order. Also, the lower limit of the mass ratio [(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )/(B ₂ O ₃ +SiO ₂ )] is preferably 0.5, more preferably 0.6, 0.7, 0.8. is more preferable in that order. By setting the mass ratio [(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )/(B ₂ O ₃ +SiO ₂ )] within the above range, an optical glass having desired optical constants can be obtained.

(d) In the optical glass according to the first embodiment, the mass ratio of the total content R′O of MgO, CaO, SrO and BaO to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O [ R′O/R ₂ O] is preferably 5, more preferably 4.0, 3.5 and 3.0 in this order. The lower limit of the mass ratio [R'O/R ₂ O] is preferably 0, more preferably 0.2, 0.4 and 0.6 in that order. The mass ratio [R'O/R ₂ O] may be zero. By setting the mass ratio [R'O/R ₂ O] within the above range, optical glass with low specific gravity and high dispersion can be obtained.

(e) Mass ratio of the content of Ta ₂ O ₅ to the total content of Nb ₂ O ₅ and TiO ₂ in the optical glass according to the first embodiment [Ta ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ )] is preferably 0.15, more preferably 0.12, 0.10, 0.08 and 0.06 in that order. The mass ratio [Ta ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ )] is preferably as small as possible, and its lower limit is preferably zero. Also, the mass ratio [Ta ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ )] may be zero. By setting [Ta ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ )] within the above range, an increase in specific gravity can be suppressed, and the raw material cost of the glass can be reduced.

(f) In the optical glass according to the first embodiment, the mass ratio of the content of _TiO2 to the total content of _Nb2O5 , _TiO2 and ZrO2 [ _TiO2 / _{( Nb2O5 + TiO2 + ZrO2} ) ] is preferably greater than 0, and more preferably 0.01 or more, 0.02 or more, and 0.03 or more in that order. Also, the mass ratio [TiO ₂ /(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )] is preferably less than 0.3, more preferably 0.25 or less, 0.20 or less, and 0.15 or less in that order. By setting the mass ratio [TiO ₂ /(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )] within the above range, an increase in specific gravity can be suppressed and the partial dispersion ratio Pg, F can be reduced. Moreover, the raw material cost of glass can be reduced.

(g) In the glass according to the first embodiment, the total content _R2O [Li2O _{+ Na2O + K2O} ] of Li2O, _Na2O and _K2O is preferably greater than 0%, or even 3 0% or more, 6.0% or more, and 8.0% or more, in that order. Also, the total content R ₂ O is preferably 30% or less, more preferably 25% or less, 23% or less, and 20% or less, in that order. By setting the total content R ₂ O within the above range, the meltability and thermal stability of the glass can be improved, and the liquidus temperature LT can be lowered.

Glass components other than the above in the optical glass according to the first embodiment will be described in detail below.

In the optical glass according to the first embodiment, the upper limit of the content of B ₂ O ₃ is preferably 10%, more preferably 8.0%, 6.0% and 5.0% in that order. Also, the lower limit of the content of B ₂ O ₃ is preferably 0%, more preferably 1.0%, 1.5%, and 2.0% in that order. The content of B ₂ O ₃ may be 0%. By setting the content of B ₂ O ₃ within the above range, the specific gravity of the glass can be lowered and the thermal stability of the glass can be improved.

In the optical glass according to the first embodiment, the upper limit of the content of P ₂ O ₅ is preferably 10%, more preferably 8.0%, 6.0% and 5.0% in that order. Also, the lower limit of the content of P ₂ O ₅ is preferably 0%. The content of _P2O5 may be ₀ %. By setting the content of P ₂ O ₅ within the above range, an increase in the partial dispersion ratio Pg,F can be suppressed and the thermal stability of the glass can be maintained.

In the glass according to the first embodiment, the upper limit of the Al ₂ O ₃ content is preferably 10%, more preferably 8.0%, 6.0% and 5.0% in that order. The content of Al ₂ O ₃ may be 0%. By setting the content of Al ₂ O ₃ within the above range, the devitrification resistance and thermal stability of the glass can be maintained.

In the glass according to the first embodiment, the lower limit of the ZrO ₂ content is preferably 1.0%, more preferably 2.0%, 2.5%, and 3.0% in that order. Also, the upper limit of the content of ZrO ₂ is preferably 15%, more preferably 14%, 13% and 12% in that order. By setting the content of ZrO ₂ within the above range, desired optical constants can be achieved and the partial dispersion ratio Pg,F can be reduced.

In the optical glass according to the first embodiment, the upper limit of the TiO ₂ content is preferably 10%, more preferably 9.0%, 8.0% and 7.0% in that order. The lower limit of the TiO ₂ content is preferably 0.5%, more preferably 1.0%, 1.5% and 2.0% in that order. The content of _TiO2 may be 0%. By setting the content of TiO ₂ within the above range, desired optical constants can be achieved, an increase in specific gravity can be suppressed, and the raw material cost of the glass can be reduced.

In the glass according to the first embodiment, the upper limit of the content of WO ₃ is preferably 5%, more preferably 4%, 3% and 2% in that order. The content of _WO3 may be 0%. By setting the content of WO ₃ within the above range, the transmittance can be increased, and the partial dispersion ratio Pg, F and the specific gravity can be reduced.

In the first embodiment, the upper limit of the Bi ₂ O ₃ content is preferably 5%, more preferably 4%, 3% and 2% in that order. Also, the lower limit of the content of Bi ₂ O ₃ is preferably 0%. By setting the content of Bi ₂ O ₃ within the above range, the thermal stability of the glass can be improved, and the partial dispersion ratio Pg, F and the specific gravity can be reduced.

In the glass according to the first embodiment, the upper limit of the Li ₂ O content is preferably 12%, more preferably 10%, 9.0%, and 8.0% in that order. The lower limit of the Li ₂ O content is preferably 1.0%, more preferably 2.0%, 3.0%, and 4.0% in that order.

In the glass according to the first embodiment, the upper limit of the Na ₂ O content is preferably 20%, more preferably 18%, 16% and 14% in that order. The lower limit of the Na ₂ O content is preferably 0%, more preferably 1.0%, 1.5%, and 2.0% in that order.

In the glass according to the first embodiment, the upper limit of the K ₂ O content is preferably 10%, more preferably 5.0%, 3.0%, and 2.0% in that order. The lower limit of the K ₂ O content is preferably 0%, more preferably 0.2%, 0.4% and 0.6% in that order.

Li ₂ O, Na ₂ O and K ₂ O are components that reduce the partial dispersion ratio Pg,F and have the function of lowering the liquidus temperature and improving the thermal stability of the glass. increases, chemical durability, weather resistance, and reheating stability decrease. Therefore, it is preferable that the respective contents of Li ₂ O, Na ₂ O and K ₂ O are within the above ranges.

In the glass according to the first embodiment, the upper limit of the Cs ₂ O content is preferably 10%, more preferably 5%, 3% and 1% in that order. The lower limit of the Cs ₂ O content is preferably 0%.

Cs ₂ O works to improve the thermal stability of the glass, but if the content is too high, the chemical durability and weather resistance are lowered. Therefore, the content of Cs ₂ O is preferably within the above range.

In the glass according to the first embodiment, the upper limit of the MgO content is preferably 20%, more preferably 10%, 5% and 3% in that order. Also, the lower limit of the MgO content is preferably 0%.

In the glass according to the first embodiment, the upper limit of the CaO content is preferably 20%, more preferably 18%, 16% and 14% in this order. The lower limit of the CaO content is preferably 0%, more preferably 1.0%, 1.5% and 2.0% in that order.

In the glass according to the first embodiment, the upper limit of the SrO content is preferably 20%, more preferably 10%, 5% and 3% in that order. Also, the lower limit of the SrO content is preferably 0%.

In the optical glass according to the first embodiment, the upper limit of the BaO content is preferably 10%, more preferably 5.0%, 3.0%, and 2.0% in that order. The lower limit of the BaO content is preferably 0%. By setting the content of BaO within the above range, an increase in specific gravity can be suppressed.

MgO, CaO, SrO, and BaO are all glass components that work to improve the thermal stability and devitrification resistance of glass. However, when the content of these glass components increases, the specific gravity increases, the high dispersibility is impaired, and the thermal stability and devitrification resistance of the glass decrease. Therefore, it is preferable that the content of each of these glass components is within the above range.

Further, in the glass according to the first embodiment, the upper limit of the total content R'O [MgO + CaO + SrO + BaO] of MgO, CaO, SrO and BaO is preferably 20%, and further 18%, 16%, 14%. order is more preferred. Also, the lower limit of the total content R'O is preferably 0%, more preferably 1.0%, 1.5%, and 2.0% in that order. From the viewpoint of suppressing an increase in specific gravity and maintaining thermal stability without hindering high dispersion, the total content R'O is preferably within the above range.

In the glass according to the first embodiment, the upper limit of the ZnO content is preferably 10%, more preferably 5.0%, 3.0%, and 2.0% in that order. Also, the lower limit of the ZnO content is preferably 0%.

ZnO is a glass component that works to improve the thermal stability of glass. However, if the ZnO content is too high, the specific gravity increases. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining desired optical constants, the content of ZnO is preferably within the above range.

In the glass according to the first embodiment, the upper limit of the Ta ₂ O ₅ content is preferably 10%, more preferably 5.0%, 3.0% and 2.0% in that order. Also, the lower limit of the Ta ₂ O ₅ content is preferably 0%.

Ta ₂ O ₅ is a glass component that works to improve the thermal stability of the glass and is a component that lowers the partial dispersion ratio Pg,F. On the other hand, if the Ta ₂ O ₅ content is too high, the thermal stability of the glass is lowered, and unmelted glass raw materials tend to remain unmelted when the glass is melted. Also, the specific gravity increases. Therefore, the content of Ta ₂ O ₅ is preferably within the above range.

In the glass according to the first embodiment, the upper limit of the Y ₂ O ₃ content is preferably 20%, more preferably 10%, 5% and 3% in that order. Moreover, the lower limit of the content of Y ₂ O ₃ is preferably 0%.

If the content of Y ₂ O ₃ is too high, the thermal stability of the glass is lowered, and the glass tends to devitrify during production. Therefore, the content of Y ₂ O ₃ is preferably within the above range from the viewpoint of suppressing deterioration of the thermal stability of the glass.

In the glass according to the first embodiment, the content of Sc ₂ O ₃ is preferably 2% or less. Moreover, the lower limit of the content of Sc ₂ O ₃ is preferably 0%.

In the glass according to the first embodiment, the content of HfO ₂ is preferably 2% or less. Also, the lower limit of the content of HfO ₂ is preferably 0%.

Sc ₂ O ₃ and HfO ₂ work to increase the high dispersibility of glass, but they are expensive components. Therefore, each content of Sc ₂ O ₃ and HfO ₂ is preferably within the above range.

In the glass according to the first embodiment, the content of Lu ₂ O ₃ is preferably 2% or less. Moreover, the lower limit of the content of Lu ₂ O ₃ is preferably 0%.

Lu ₂ O ₃ has a function of increasing the high dispersibility of the glass, but since it has a large molecular weight, it is also a glass component that increases the specific gravity of the glass. Therefore, the content of Lu ₂ O ₃ is preferably within the above range.

In the glass according to the first embodiment, the content of GeO ₂ is preferably 2% or less. Also, the lower limit of the content of GeO ₂ is preferably 0%.

GeO ₂ works to increase the high dispersion of glass, but it is by far the most expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of glass, the content of GeO ₂ is preferably within the above range.

In the glass according to the first embodiment, the content of Gd ₂ O ₃ is preferably 2% or less. Also, the lower limit of the content of Gd ₂ O ₃ is preferably 0%.

If the content of Gd ₂ O ₃ is too high, the thermal stability of the glass will be lowered. Also, if the content of Gd ₂ O ₃ is too high, the specific gravity of the glass increases, which is not preferable. Therefore, the content of Gd ₂ O ₃ is preferably within the above range from the viewpoint of suppressing an increase in specific gravity while maintaining good thermal stability of the glass.

In the glass according to the first embodiment, the content of Yb ₂ O ₃ is preferably 2% or less. Also, the lower limit of the Yb ₂ O ₃ content is preferably 0%.

Yb ₂ O ₃ has a higher molecular weight than La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ and thus increases the specific gravity of the glass. Increasing the specific gravity of the glass increases the mass of the optical element. For example, if a lens with a large mass is incorporated into an autofocus imaging lens, the power required to drive the lens during autofocus increases, resulting in rapid battery consumption. Therefore, it is desirable to reduce the content of Yb ₂ O ₃ to suppress an increase in the specific gravity of the glass.

Also, if the content of Yb ₂ O ₃ is too high, the thermal stability of the glass is lowered. The content of Yb ₂ O ₃ is preferably within the above range from the viewpoint of preventing deterioration of the thermal stability of the glass and suppressing an increase in the specific gravity.

The glass according to the first embodiment mainly includes the glass components described above, that is, SiO ₂ and Nb ₂ O ₅ as essential components, and La ₂ O ₃ , B ₂ O ₃ , P ₂ O ₅ and Al ₂ O ₃ as optional components. , ZrO2, _TiO2 , _{WO3 , Bi2O3} , _{Li2O , Na2O , K2O} , _Cs2O , MgO, _CaO , SrO, BaO, ZnO, _Ta2O5 , _Y2O3 , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ , Gd ₂ O ₃ and Yb ₂ O ₃ , and the total content of the above glass components is more than 95%. More preferably, more than 98%, more preferably more than 99%, even more preferably more than 99.5%.

The glass according to the first embodiment is preferably basically composed of the glass components described above, but may contain other components as long as the effects of the present invention are not impaired. Moreover, in the present invention, inclusion of unavoidable impurities is not excluded.

(other ingredients)
In addition to the above components, the optical glass may contain a small amount of Sb ₂ O ₃ , CeO ₂ or the like as a clarifier. The total amount of the refining agent (additional amount of extra) is preferably 0% or more and less than 1%, more preferably 0% or more and 0.5% or less.

The amount added is the amount of the clarifier added, expressed as a percentage by weight, when the total content of all glass components excluding the clarifier is taken as 100%.

Pb, Cd, As, Th, and the like are components of concern about environmental impact. Therefore, the content of each of PbO, CdO, and ThO ₂ is preferably 0 to 0.1%, more preferably 0 to 0.05%, and 0 to 0.01%. is more preferred, and substantially free of PbO, CdO and ThO ₂ is particularly preferred.

The content of As ₂ O ₃ is preferably ₀ to 0.1%, more preferably 0 to 0.05%, even more preferably 0 to 0.01%. Substantially free of ₃ is particularly preferred.

Furthermore, the optical glass provides high transmittance over a wide visible region. In order to make the most of these features, it is preferable that no coloring element is contained. Examples of coloring elements include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, V, and the like. Any element is preferably 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 preferably not substantially contained.

Moreover, Ga, Te, Tb, etc. are components that do not need to be introduced, and are also expensive components. Therefore, the content ranges of Ga ₂ O ₃ , TeO ₂ , and TbO ₂ expressed in mass% are preferably 0 to 0.1%, more preferably 0 to 0.05%. preferably 0 to 0.01%, more preferably 0 to 0.005%, even more preferably 0 to 0.001%, substantially free of Especially preferred.

(Glass properties)
<Refractive index nd>
In the optical glass according to the first embodiment, the refractive index nd is preferably 1.69-1.77. The refractive index nd can also be between 1.695 and 1.765, or between 1.70 and 1.76. The refractive index nd can be set to a desired value by appropriately adjusting the content of each glass component. Components (refractive index-increasing components) having a function of relatively increasing the refractive index nd include Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , La ₂ O ₃ and the like. On the other hand, the component (refractive index-lowering component) that acts to relatively lower the refractive index nd includes SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O and the like. Also, for example, the total content (Nb ₂ O ₅ +TiO ₂ +ZrO ₂ ) of high refractive index components (Nb ₂ O ₅ , TiO ₂ and ZrO ₂ ) and the total content of low refractive index components B ₂ O ₃ and SiO ₂ The refractive index nd can be increased by increasing the mass ratio [(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )/(B ₂ O ₃ +SiO ₂ )]), and the mass ratio [(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )/(B ₂ O ₃ +SiO ₂ )]) can lower the refractive index nd.

<Abbe number νd>
In the optical glass according to the first embodiment, the Abbe number νd is preferably 34-37. The Abbe number νd can also be 34.3 to 36.7, or 34.5 to 36.5. 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, ie, high-dispersion components, are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ and the like. On the other hand, components that relatively increase the Abbe number νd, ie, low-dispersion components, are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, La ₂ O ₃ , BaO, CaO, SrO. etc. Among the _{high -} dispersion components Nb ₂ O ₅ , TiO ₂ and ZrO ₂ , TiO ₂ has a large function of lowering the Abbe _number ν ₍ function of highly dispersing). and the total content of ZrO ₂ ([TiO ₂ /(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )]), the Abbe number νd can be reduced (highly dispersed), and the mass By decreasing the ratio ([TiO ₂ /(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )]), the Abbe number νd can be increased (lowered).

<Specific gravity of glass>
The specific gravity of the optical glass according to the first embodiment is preferably 3.45 g/cc or less, more preferably 3.40 g/cc or less, and 3.35 g/cc or less in that order.
Components that relatively increase the specific gravity include BaO, La ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and Ta ₂ O ₅ . On the other hand, there are components such as SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O and K ₂ O that relatively lower the specific gravity. The specific gravity can be controlled by appropriately adjusting the contents of these components.

<Partial dispersion ratio Pg, F>
In the optical glass according to the first embodiment, the upper limit of the partial dispersion ratio Pg,F is preferably 0.5870, and more preferably 0.5856, 0.5851 and 0.5846 in that order. By setting the partial dispersion ratio Pg, F within the above range, an optical glass suitable for high-order chromatic aberration correction can be obtained. On the other hand, although the lower limit of the partial dispersion ratio Pg,F is not particularly limited, 0.5717 is used as a guideline.

In the optical glass according to the first embodiment, the upper limit of the deviation ΔPg,F is preferably −0.0015, more preferably −0.0020 and −0.0025 in that order. By setting the deviation ΔPg,F within the above range, an optical glass suitable for high-order chromatic aberration correction can be obtained. On the other hand, the lower limit of the deviation ΔPg,F is not particularly limited, but -0.0080 is used as a guideline.

<Liquid phase temperature LT>
The liquidus temperature LT of the optical glass according to the first embodiment is preferably 1250° C. or lower, more preferably 1220° C. or lower, and 1200° C. or lower in that order. By setting the liquidus temperature LT within the above range, the melting and forming temperature of the glass can be lowered, and the erosion of glass melting equipment (for example, crucibles, molten glass stirring equipment, etc.) in the melting process can be reduced. . The liquidus temperature LT is determined by the content balance of all glass components. Among them, the contents of SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, etc. have a large effect on the liquidus temperature LT.

The liquidus temperature is determined as follows. 10 cc (10 ml) of glass is put into a platinum crucible and melted at 1250° C. to 1350° C. for 20 to 30 minutes, then cooled to a glass transition temperature Tg or less, and the glass is placed in a melting furnace at a predetermined temperature together with the platinum crucible and held for 2 hours. do. The temperature is maintained at 1000° C. or higher in increments of 5° C. or 10° C. After holding for 2 hours, the glass is cooled, and the presence or absence of crystals inside the glass is observed with a 100-fold optical microscope. The liquidus temperature is the lowest temperature at which no crystals precipitate.

<Stability during reheating>
In the optical glass according to the first embodiment, the number of crystals observed per 1 g when heated at the glass transition temperature Tg for 10 minutes and further at a temperature 180 to 200° C. higher than the Tg for 10 minutes is preferably is 20 or less, more preferably 10 or less.

The stability during reheating is measured as follows. A glass sample with a size of 1 cm × 1 cm × 1 cm is heated for 10 minutes in a first test furnace set to the glass transition temperature Tg of the glass sample, and further heated to a temperature 180 to 200 ° C higher than the glass transition temperature Tg. After heating for 10 minutes in the set second test furnace, the presence or absence of crystals is confirmed with an optical microscope (observation magnification: 10 to 100 times). Then, the number of crystals per 1 g is measured. In addition, the presence or absence of cloudiness of the glass is visually confirmed.

<Glass transition temperature Tg>
The upper limit of the glass transition temperature Tg of the optical glass according to the first embodiment is preferably 650°C, more preferably 620°C, 600°C, and 580°C in that order. The lower limit of the glass transition temperature Tg is preferably 450°C, more preferably 480°C, 500°C and 520°C in that order. The glass transition temperature Tg can be controlled by adjusting each.
Components that relatively lower the glass transition temperature Tg are Li ₂ O, Na ₂ O, K ₂ O and the like. Components that relatively raise the glass transition temperature Tg include La ₂ O ₃ , ZrO ₂ and Nb ₂ O ₅ . The glass transition temperature Tg can be controlled by appropriately adjusting the contents of these components.

<Light transmittance of glass>
The light transmittance of the optical glass according to the first embodiment can be evaluated by coloring degrees λ80, λ70 and λ5.
The spectral transmittance is measured in the wavelength range of 200 to 700 nm for a glass sample with a thickness of 10.0 mm ± 0.1 mm, the wavelength at which the external transmittance is 80% is λ80, and the wavelength at which the external transmittance is 70% is λ70. , the wavelength at which the external transmittance is 5% is λ5.

λ80 of the optical glass according to the first embodiment is preferably 500 nm or less, more preferably 470 nm or less, and even more preferably 450 nm or less. λ70 is preferably 450 nm or less, more preferably 420 nm or less, and even more preferably 400 nm or less. Also, λ5 is preferably 370 nm or less, more preferably 360 nm or less, and even more preferably 350 nm or less.

(Manufacture of optical glass)
The glass according to the first embodiment may be produced by blending glass raw materials so as to have the above-described predetermined composition, and using the blended glass raw materials according to a known glass manufacturing method. For example, a plurality of types of compounds are prepared, sufficiently mixed to form a batch raw material, and the batch raw material is placed in a quartz crucible or a platinum crucible for rough melting (rough melting). A melt obtained by rough melting is rapidly cooled and pulverized to produce cullet. Further, the cullet is placed in a platinum crucible, heated and re-melted to obtain a molten glass, further clarified and homogenized, the molten glass is shaped, and slowly cooled to obtain an optical glass. A known method may be applied to the molding and slow cooling of the molten glass.

The compounds used in preparing the batch raw materials are not particularly limited as long as the desired glass components can be introduced into the glass so as to have the desired content. salts, nitrates, hydroxides, fluorides and the like.

(Manufacture of optical elements, etc.)
A known method may be applied to fabricate an optical element using the optical glass according to the first embodiment. For example, in the production of the above optical glass, molten glass is poured into a mold and formed into a plate shape to produce a glass material comprising the optical glass according to the present invention. The obtained glass material is appropriately cut, ground, and polished to produce a cut piece having a size and shape suitable for press molding. The cut piece is heated, softened, and press-molded (reheat pressed) by a known method to produce an optical element blank that approximates the shape of the optical element. An optical element blank is annealed, ground and polished by a known method to produce an optical element.

The optically functional surface of the manufactured optical element may be coated with an antireflection film, a total reflection film, or the like, depending on the purpose of use.

According to one aspect of the present invention, an optical element made of the above optical glass can be provided. Examples of types of optical elements include lenses such as spherical lenses and aspherical lenses, prisms, and diffraction gratings. Examples of the lens shape include various shapes such as a biconvex lens, a plano-convex lens, a bi-concave lens, a plano-concave lens, a convex meniscus lens, and a concave meniscus lens. An optical element can be manufactured by a method including a step of processing a glass molded body made of the above optical glass. Examples of processing include cutting, cutting, rough grinding, fine grinding, polishing, and the like. By using the above-mentioned glass during such processing, breakage can be reduced, and high-quality optical elements can be stably supplied.

Second Embodiment The optical glass according to the second embodiment is
has a specific gravity of 3.45 or less,
The deviation ΔPg,F of the partial dispersion ratio Pg,F is −0.0015 or less,
The liquidus temperature LT is 1250° C. or less,
When heated for 10 minutes at the glass transition temperature Tg and further heated for 10 minutes at a temperature 180 to 200° C. higher than the Tg, the number of crystals observed per 1 g is 20 or less,
The refractive index nd is 1.69 to 1.77,
The Abbe number νd is 34-37.

The optical glass according to the second embodiment has a refractive index nd of 1.69 to 1.77. The refractive index nd can also be between 1.695 and 1.765, or between 1.70 and 1.76. The refractive index _nd can be controlled by adjusting the mass ratio [ _{( Nb2O5} + _TiO2 +ZrO2)/ ₍ B2O3 _{+ SiO2} )].
Components that relatively increase the refractive index nd are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ and La ₂ O ₃ . Components that relatively lower the refractive index nd are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, and K ₂ O. The refractive index nd can be controlled by appropriately adjusting the content of these components.

In the optical glass according to the second embodiment, the Abbe number νd is 34-37. The Abbe number νd can also be 34.3 to 36.7, or 34.5 to 36.5. The Abbe number νd can be controlled by adjusting the mass ratio [TiO ₂ /(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )].
Components that relatively lower the Abbe number νd are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ and Ta ₂ O ₅ . Components that relatively increase the Abbe number νd are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, La ₂ O ₃ , BaO, CaO, and SrO. The Abbe number νd can be controlled by appropriately adjusting the contents of these components.

The optical glass according to the second embodiment has a specific gravity of 3.45 or less, preferably 3.40 or less, and more preferably 3.35 or less.
Components that relatively increase the specific gravity include BaO, La ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and Ta ₂ O ₅ . Components that relatively lower the specific gravity include SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O and the like. The specific gravity can be controlled by adjusting the content of these components.

In the optical glass according to the second embodiment, the deviation ΔPg,F is −0.0015 or less, preferably −0.0020 or less, more preferably −0.0025 or less. Also, the lower limit of the deviation ΔPg,F is preferably −0.0100, more preferably −0.0080, −0.0060, −0.0050 in this order. By setting the deviation ΔPg,F within the above range, an optical glass suitable for high-order chromatic aberration correction can be obtained. The deviation ΔPg,F can be calculated by the same method as in the first embodiment.

In the optical glass according to the second embodiment, the liquidus temperature LT is 1250° C. or lower, preferably 1220° C. or lower, more preferably 1200° C. or lower. By setting the liquidus temperature LT within the above range, the melting and forming temperature of the glass can be lowered, and the erosion of glass melting equipment (for example, crucibles, molten glass stirring equipment, etc.) in the melting process can be reduced. . The liquidus temperature LT is determined by the content balance of all glass components. Among them, the contents of SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, etc. have a large effect on the liquidus temperature LT. Note that the liquidus temperature LT can be measured by the same method as in the first embodiment.

When the optical glass according to the second embodiment is heated at the glass transition temperature Tg for 10 minutes and further heated at a temperature 180 to 200° C. higher than the Tg for 10 minutes, the number of crystals observed per 1 g is 20. or less, preferably 10 or less.
The number of crystals can be measured by the same method as for the stability during reheating in the first embodiment.

In the second embodiment, the partial dispersion ratio Pg, F, the glass transition temperature Tg, and the light transmittance of the glass can be the same as in the first embodiment.

(glass component)
In the optical glass according to the second embodiment, the lower limit of the SiO ₂ content is preferably 10%, more preferably 15%, 20%, 25% and 30% in this order. The upper limit of the SiO ₂ content is preferably 50%, more preferably 48%, 46%, 44% and 43% in that order. If the _SiO2 content is too low, vitrification becomes difficult. If the _SiO2 content is too high, it is difficult to obtain the desired optical constants.

In the optical glass according to the second embodiment, the lower limit of the content of Nb ₂ O ₅ is preferably 10%, more preferably 14%, 16%, 18% and 20% in that order. The upper limit of the content of Nb ₂ O ₅ is preferably 50%, more preferably 44%, 41%, 38% and 35% in that order. If the content of Nb ₂ O ₅ is too small, the increase in the refractive index of the glass is suppressed. If the content of Nb ₂ O ₅ is too high, the thermal stability may deteriorate and the raw material cost of the glass may increase.

In the optical glass according to the second embodiment, the upper limit of the total content of TiO ₂ and BaO [TiO ₂ +BaO] is preferably 10%, more preferably 9%, 8%, 7%, 6% in that order. preferable. The total content [TiO ₂ +BaO] is preferably as small as possible, and its lower limit is preferably 0%. The total content [TiO ₂ +BaO] may be 0%. TiO ₂ is a component that increases the partial dispersion ratio Pg,F, and BaO is a component that increases the specific gravity. Therefore, by setting the total content [TiO ₂ +BaO] within the above range, an increase in the partial dispersion ratio Pg, F and the specific gravity can be suppressed.

In the optical glass according to the second embodiment, the upper limit of the mass ratio [B ₂ O ₃ /SiO ₂ ] of the content of B ₂ O ₃ to the content of SiO ₂ is preferably 0.15, more preferably 0. 0.14, 0.13, 0.12, 0.11 are more preferred. The lower limit of the mass ratio [B ₂ O ₃ /SiO ₂ ] is preferably 0, more preferably 0.01, 0.02 and 0.03 in this order. If the mass ratio [B ₂ O ₃ /SiO ₂ ] is too large, the glass raw material is melted to form a melt, and the glass melt is molded to vitrify. During molding, crystals may precipitate.

In the optical glass according to the second embodiment, glass components and composition ratios other than those described above may be the same as those in the first embodiment.

Also, the manufacture of the optical glass and the manufacture of the optical element etc. according to the second embodiment can be the same as in the first embodiment.

EXAMPLES 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.

(Example 1)
Glass samples having the glass compositions shown in Tables 1-1 to 1-2 and Tables 2-1 to 2-2 were produced by the following procedure and subjected to various evaluations.

[Manufacture of optical glass]
First, oxides, hydroxides, carbonates, and nitrates corresponding to the components of the glass are prepared as raw materials, and the glass compositions of the obtained optical glasses are shown in Tables 1-1 and 1-2. The above raw materials were weighed and mixed as above, and the raw materials were thoroughly mixed. The prepared raw material (batch raw material) thus obtained is charged into a platinum crucible, heated at 1350° C. to 1400° C. for 2 to 4 hours to form a glass melt, stirred for homogenization, clarified, and then melted into a glass melt. was cast into a mold preheated to a suitable temperature. The cast glass was heat-treated for 30 minutes at any temperature between the glass transition temperature Tg and 100° C. lower than Tg, and allowed to cool to room temperature in a furnace to obtain a glass sample.

[Confirmation of glass component composition]
The obtained glass samples were measured for the content of each glass component by inductively coupled plasma-atomic emission spectrometry (ICP-AES), and confirmed to have the respective compositions shown in Tables 1-1 and 1-2. .

[Stability during reheating]
The obtained glass sample was cut into a size of 1 cm × 1 cm × 1 cm, heated for 10 minutes in a first test furnace set to the glass transition temperature Tg of the glass sample, and further 180 to 180 from the glass transition temperature Tg. Heated for 10 minutes in a second test oven set at 200°C higher. After that, the presence or absence of crystals was confirmed with an optical microscope (observation magnification: 10 to 100 times). Then, the number of crystals per 1 g was measured. The presence or absence of cloudiness in the glass was visually confirmed. When the number of crystals per 1 g was 20 or less and no white turbidity was observed, it was evaluated as ◯.

[Measurement of optical properties]
The obtained glass sample was further annealed at about the glass transition temperature Tg for about 30 minutes to about 2 hours, and then cooled to room temperature at a cooling rate of −30° C./hour in a furnace to obtain an annealed sample. The annealed samples obtained were measured for refractive indices nd, ng, nF and nC, Abbe number νd, partial dispersion ratio Pg, F, specific gravity, liquidus temperature LT, glass transition temperature Tg, λ80, λ70 and λ5. The results are shown in Tables 3-1 and 3-2.
(i) refractive indices nd, ng, nF, nC and Abbe number νd
The refractive indices nd, ng, nF, and nC of the annealed sample were measured by the refractive index measurement method of JIS standard JIS B 7071-1, and the Abbe number νd was calculated based on the following equation.
νd = (nd-1)/(nF-nC)

(ii) Partial dispersion ratio Pg,F
Using the respective refractive indices ng, nF, and nC for the g-line, F-line, and c-line, the partial dispersion ratios Pg, F were calculated according to the following equations.
Pg, F = (ng-nF)/(nF-nC)

(iii) Deviation ΔPg,F of partial dispersion ratio Pg,F
It was calculated based on the following formula using the partial dispersion ratio Pg, F and the Abbe number νd.
ΔPg,F=Pg,F+(0.0018×νd)−0.6483

(iv) Specific Gravity Specific gravity was measured by the Archimedes method.

(v) liquidus temperature LT
The glass was placed in a furnace heated to a predetermined temperature and held for about 2 hours. After cooling, the inside of the glass was observed with an optical microscope at a magnification of 40 to 100, and the liquidus temperature was determined from the presence or absence of crystals.

(vi) glass transition temperature Tg
The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN at a heating rate of 10°C/min.

(vii) λ80, 70, λ5
The annealed sample was processed so as to have parallel and optically polished planes with a thickness of 10 mm, and the spectral transmittance in the wavelength range from 280 nm to 700 nm was measured. The spectral transmittance B/A was calculated by setting the intensity A to the intensity of light incident perpendicularly to one optically polished plane and the intensity B to the intensity of light emitted from the other plane. The wavelength at which the spectral transmittance is 80% is λ80, the wavelength at which the spectral transmittance is 70% is λ70, and the wavelength at which the spectral transmittance is 5% is λ5. Note that the spectral transmittance also includes the reflection loss of light on the sample surface.

(Example 2)
Using each optical glass produced in Example 1, a lens blank was produced by a known method, and the lens blank was processed by a known method such as polishing to produce various lenses.
The manufactured optical lenses are various lenses such as a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, a concave meniscus lens, and a convex meniscus lens.
By combining various lenses with lenses made of other types of optical glass, secondary chromatic aberration could be satisfactorily corrected.

In addition, since the glass has a low specific gravity, each lens is lighter in weight than a lens having the same optical characteristics and size, and is suitable for various imaging equipment, especially autofocus imaging equipment for the reason that it can save energy. be. Similarly, prisms were produced using the various optical glasses produced in Example 1.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

For example, the optical glass according to one aspect of the present invention can be produced by adjusting the composition described in the specification with respect to the glass compositions exemplified above.
In addition, it is of course possible to arbitrarily combine two or more of the matters described as examples or preferred ranges in the specification.

Claims (3)

has a specific gravity of 3.45 or less,
The deviation ΔPg,F of the partial dispersion ratio Pg,F is −0.0015 or less,
The liquidus temperature LT is 1250° C. or less,
When heated for 10 minutes at the glass transition temperature Tg and further heated for 10 minutes at a temperature 180 to 200° C. higher than the Tg, the number of crystals observed per 1 g is 20 or less,
The refractive index nd is 1.69 to 1.77,
Abbe number νd is 34 to 37,
The content of Nb ₂ O ₅ is 10 to 35% by mass,
The content of B ₂ O ₃ is 1.0% by mass or more,
ZnO content is 2.0% by mass or less,
La ₂ O ₃ content is 4.70% by mass or less,
The mass ratio [R'O/R ₂ O] of the total content R'O of MgO, CaO, SrO and BaO to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is 0.6 or more and
Optical glass that satisfies (1) or (2).
(1) the content of BaO is 5.0% by mass or less,
The content of Ta ₂ O ₅ is 2.0% by mass or less,
Mass ratio of the _total content of _Nb2O5 , _TiO2 and ZrO2 to the _total content of B2O3 and _SiO2 [ _{( Nb2O5 + TiO2 +} ZrO2)/ _{( B2O3 + SiO2} )] is greater than or equal to 0.92 and less than 1.7.
(2) the content of BaO is 5.0% by mass or less,
The content of Ta ₂ O ₅ is 2.0% by mass or less,
Mass ratio of the _total content of _Nb2O5 , _TiO2 and ZrO2 to the _total content of B2O3 and _SiO2 [ _{( Nb2O5 + TiO2 +} ZrO2)/ _{( B2O3 + SiO2} )] is 0.8 or more and less than 1.7,
The mass ratio [ _TiO2 / _{( Nb2O5 + TiO2 +} ZrO2)] of the content of _TiO2 to the _total content of _Nb2O5 , _TiO2 and ZrO2 is greater than 0 and less than 0.3. 2. The optical glass according to claim 1, wherein the total content of _TiO2 and BaO [ _TiO2 +BaO] is 6% by mass or less. An optical element comprising the optical glass according to claim 1 or 2.