JP7339781B2 - Optical glasses and optical elements - Google Patents

Description

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

Glass softens when heated above the glass transition temperature Tg. Utilizing this property, as a method of molding an optical element, there is a press molding method in which a glass material obtained by heat-melting and molding glass raw materials is reheated to soften and pressed into a desired shape. Are known. At this time, the reheating of the glass may cause crystal formation in the glass or devitrification of the glass. A glass that is excellent in stability during reheating is less likely to crystallize upon reheating, and devitrification is also suppressed. In recent years, a higher degree of stability is required during reheating.

Patent Document 1 discloses an optical glass having a predetermined refractive index nd and Abbe number νd. However, it has been found that the glass of Patent Document 1 does not necessarily satisfy the required stability.

JP 2017-154963 A

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical glass having desired optical constants and excellent stability during reheating, and an optical element comprising the optical glass.

The gist of the present invention is as follows.
(1) Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25 to 55% by mass,
The content of B ₂ O ₃ is 13% by mass or less,
Li ₂ O content is 20% by mass or less,
The content of Na ₂ O is 17% by mass or less,
The content of ZrO ₂ is 2 to 22 % by mass,
The content of Nb ₂ O ₅ is 12 to 42 % by mass,
Mass ratio of _the total content of _SiO2 , _{B2O3 and P2O5} to the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R ₂ O to the sum of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , _ZnO , _TiO2 , _Nb2O5 , _WO3 , _ZrO2 , La the _{total content of 2O3, Gd2O3 and Y2O3 is 93 % by} mass _or more;
The mass ratio of the total content of SiO _{2 ,} B ₂ O ₃ and P ₂ O ₅ to the content of ZrO 2 [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is 5.00 or less. optical glass.

(2) Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25 to 55% by mass,
The content of B ₂ O ₃ is 13% by mass or less,
Li ₂ O content is 20% by mass or less,
The content of Na ₂ O is 17% by mass or less,
The content of ZrO ₂ is 2 to 22 % by mass,
The content of Nb ₂ O ₅ is 12 to 42 % by mass,
_Mass ratio of the total content of _SiO2 , _{B2O3 and P2O5} to _the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R _{2 O} to the sum of the total content R ₂ O of Li 2 O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , _ZnO , _TiO2 , _Nb2O5 , _WO3 , _ZrO2 , La the _{total content of 2O3, Gd2O3 and Y2O3 is 93 % by} mass _or more;
mass ratio of the total content of SiO _{2 ,} B ₂ O ₃ and P ₂ O ₅ to the content of ZrO 2 [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is 5.45 or less;
An optical glass having a mass ratio of _B2O3 content to _SiO2 content [ _B2O3 / _SiO2 ] of _{0.240 or} less.

(3) Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25 to 55% by mass,
The content of B ₂ O ₃ is 13% by mass or less,
Li ₂ O content is 20% by mass or less,
The content of Na ₂ O is 17% by mass or less,
The content of ZrO ₂ is 2 to 22 % by mass,
The content of Nb ₂ O ₅ is 12 to 42 % by mass,
_Mass ratio of the total content of _SiO2 , _{B2O3 and P2O5} to _the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R _{2 O} to the sum of the total content R ₂ O of Li 2 O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , _ZnO , _TiO2 , _Nb2O5 , _WO3 , _ZrO2 , La the _{total content of 2O3, Gd2O3 and Y2O3 is 93 % by} mass _or more;
mass ratio of the total content of SiO _{2 ,} B ₂ O ₃ and P ₂ O ₅ to the content of ZrO 2 [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is 5.45 or less;
An optical glass having a mass ratio of _{B 2 O 3} content to ZrO 2 content [B ₂ O ₃ /ZrO ₂ ] of 1.05 or less.

(4) The mass ratio [Na ₂ O/R ₂ O] of the content of Na ₂ O to the total content R 2 O of _{Li 2} O, Na ₂ O and K ₂ O is 0.80 or less, (1 ) to (3).

(5) mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the total content _of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ , and Li ₂ O and Na ₂ O and the mass ratio of the content of Na ₂ O to the total content of K ₂ O R ₂ O [{R ₂ O/(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )} + (Na ₂ O/R ₂ O)] is 1.30 or less, the optical glass according to any one of (1) to (4).

(6) The mass ratio [ _{R 2 O} /ZrO ₂ ] of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O to the content of ZrO 2 is 2.00 or less. The optical glass according to any one of (5).

(7) An optical element made of the optical glass described in any one of (1) to (6) above.

According to the present invention, it is possible to provide an optical glass having desired optical constants and excellent stability during reheating, and an optical element comprising the optical glass.

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.

Below, the optical glass of the present invention will be described as a first embodiment, a second embodiment, and a third embodiment.

First Embodiment The optical glass according to the first embodiment is
Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25-55%,
The content of B ₂ O ₃ is 13% or less,
Li ₂ O content is 20% or less,
The content of Na ₂ O is 17% or less,
The content of ZrO ₂ is 2-22 % ,
The content of Nb ₂ O ₅ is 12-42 % ,
_Mass ratio of the total content of _SiO2 , _{B2O3 and P2O5} to _the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _{P2O5 )} /( _Nb2O5 + _TiO2 + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R _{2 O} to the sum of the total content R ₂ O of Li 2 O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , ZnO, _TiO2 , _Nb2O5 , _{WO3 , ZrO2} , La the total content _{of 2O3} , _{Gd2O3 and Y2O3} is 93% _or more;
The mass ratio [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the content of ZrO 2 is 5.00 or less.

In the optical glass according to the first embodiment, the Abbe number νd is 36.40 or more. The Abbe number νd may be 36.50 to 45.00, 36.60 to 43.00, 36.70 to 41.00, 36.80 to 40.00, or 36.90 to 39.50. can.

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 , WO ₃ , Bi ₂ O ₃ , 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.

In the optical glass according to the first embodiment, the content of SiO ₂ is 25-55%. The lower limit of the SiO ₂ content is preferably 27%, more preferably 29%, 30%, 31%, 32%, 33% in this order. The upper limit of the SiO ₂ content is preferably 53%, more preferably 50%, 48%, 46%, 44%, 42%, 40% and 38% in that order. _SiO2 is a network-forming component of glass. If the SiO ₂ content is too low, the stability during reheating may decrease. On the other hand, if the content of SiO ₂ is too large, the high dispersion is impaired, it is difficult to obtain desired optical constants, and the partial dispersion ratio Pg,F may increase.

The content of B ₂ O ₃ in the optical glass according to the first embodiment is 13% or less. The upper limit of the content of B ₂ O ₃ is preferably 12%, more preferably 11%, 10%, 9% and 8% in this order. Also, the lower limit of the B ₂ O ₃ content is preferably 0%, more preferably 1%, 2%, and 3% in that order. The content of B ₂ O ₃ may be 0%. It is a network-forming component of B ₂ O ₃ glass. If the content of B ₂ O ₃ is too large, the high dispersion is impaired, it is difficult to obtain desired optical constants, and the partial dispersion ratio Pg,F may increase. If the content of B ₂ O ₃ is too small, the stability during reheating may decrease.

In the glass according to the first embodiment, the content of Li ₂ O is 20% or less. The upper limit of the Li ₂ O content is preferably 18%, more preferably 17%, 16%, 15%, 14%, 13% and 12% in that order. The lower limit of the Li ₂ O content is preferably 0%, and more preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% in that order. Li ₂ O is a component that contributes to low viscosity and low Pg and F contents of the glass. If the content of Li ₂ O is too high, the stability during reheating may decrease. On the other hand, if the content of Li ₂ O is too small, the viscosity of the glass may increase, and Pg and F may increase.

The content of Na ₂ O in the glass according to the first embodiment is 17% or less. The upper limit of the Na ₂ O content is preferably 16%, more preferably 15%, 14%, 13%, 12%, 11%, 10% and 9% in that order. The lower limit of the content of Na ₂ O is preferably 0%, more preferably 1%, 2%, 3%, 4% and 5% in this order. The content of Na ₂ O may be 0%. Na ₂ O, like Li ₂ O, is a component that contributes to low viscosity and low Pg, F content of the glass. If the content of Na ₂ O is too high, the stability during reheating may decrease. On the other hand, if the content of Na ₂ O is too small, the viscosity of the glass may increase and Pg and F may increase.

In the glass according to the first embodiment, the content of ZrO ₂ is 2-22%. The lower limit of the ZrO ₂ content is preferably 4%, more preferably 5%, 6%, 7%, 8%, 9% in that order. The upper limit of the ZrO ₂ content is preferably 20%, more preferably 18%, 16%, 15%, 14% and 13% in that order. ZrO ₂ is a component that contributes to low Pg and F. If the ZrO ₂ content is too high, the liquidus temperature LT may increase. Also, if the content of ZrO ₂ is too small, Pg and F may increase.

In the optical glass according to the first embodiment, the content of Nb ₂ O ₅ is 12-42%. The lower limit of the content of Nb ₂ O ₅ is preferably 14%, more preferably 16%, 18%, 20%, 21%, 22%, 23%, 24% and 25% in that order. The upper limit of the content of Nb ₂ O ₅ is preferably 40%, more preferably 38%, 36%, 34%, 33%, 32%, 31% and 30% in that order. Nb ₂ O ₅ is a component that contributes to achieving both high dispersion and low Pg and F content. If the content of Nb ₂ O ₅ is too high, the stability during reheating may be lowered, and the meltability may be lowered. If the content of Nb ₂ O ₅ is too small, there is a risk of low dispersion.

Total content of SiO ₂ , B 2 O 3 _and P ₂ O _{5 relative} to total content of Nb ₂ O ₅ , TiO ₂ , Bi ₂ O ₃ , WO ₃ and Ta ₂ O ₅ in the optical glass according to the first embodiment The mass ratio [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/(Nb ₂ O ₅ +TiO ₂ +Bi ₂ O ₃ +WO ₃ +Ta ₂ O ₅ )] is 2.00 or less. The upper limit of the mass ratio is preferably 1.95, further 1.90, 1.85, 1.80, 1.75, 1.74, 1.73, 1.72, 1.71, 1 .70 order is more preferred. Further, the lower limit of the mass ratio is preferably 1.00, and further 1.10, 1.20, 1.25, 1.30, 1.32, 1.34, 1.36, 1.38. , 1.40. By setting the mass ratio within the above range, the Abbe number νd can be controlled within a desired range. If the mass ratio is too large, the Abbe number νd may deviate from the desired range. On the other hand, if the mass ratio is too small, the stability during reheating may decrease.

In the optical glass according to the first embodiment, the total content relative to the sum of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO The mass ratio of R ₂ O [R ₂ O/(R ₂ O+RO)] is 0.60 or more. The lower limit of the mass ratio is preferably 0.62, further 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0 .80 order is more preferred. Moreover, the upper limit of the mass ratio is preferably 1, and the mass ratio is more preferably 1. By setting the mass ratio within the above range, the Pg and F of the glass can be reduced. If the mass ratio is too small, there is a risk that ΔPg,F represented by Equation [8], which will be described later, increases.

In the optical glass according to _the first embodiment, _SiO2 , _B2O3 , _P2O5 , Li2O, _Na2O , _K2O , MgO, _CaO , SrO, BaO, ZnO, _{TiO2 , Nb2} The total content _{of O5 , WO3 , ZrO2} , _La2O3 , _Gd2O3 and _Y2O3 is 93% or more. The lower limit of the total content is preferably 94%, more preferably 95%, 96%, 97%, 98% and 99% in that order. Moreover, the upper limit of the total content is preferably 100%, and the total content is more preferably 100%. If the total content is too small, the coloration of the glass may increase, desired optical constants may not be obtained, and stability during reheating may deteriorate. Furthermore, the raw material cost of the glass may increase.

In the optical glass according to the first embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ to the content of ZrO ₂ [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is less than or equal to 5.00. The upper limit of the mass ratio is preferably 4.80, more preferably 4.70, 4.50, 4.40, 4.30, 4.20, 4.10, 4.00 in that order. In addition, the lower limit of the mass ratio is preferably 2.00, further 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.30, 3.40. , 3.50. By setting the mass ratio within the above range, both reduction in Pg and F and improvement in stability during reheating can be achieved. If the mass ratio is too large, Pg, F may increase. If the mass ratio is too small, the liquidus temperature LT may increase, and the stability during reheating may decrease.

In the optical glass according to the first 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 0.240, and more preferably 0.240. 0.238, 0.236, 0.234, 0.232, 0.230 are more preferred. The lower limit of the mass ratio is preferably 0.020, more preferably 0.030, 0.040, 0.050 and 0.060 in that order. By setting the mass ratio within the above range, the specific gravity can be reduced and the transmittance can be improved.

In the optical glass according to the first embodiment, the upper limit of the mass ratio [B ₂ O ₃ /ZrO ₂ ] of the content of B ₂ O ₃ to the content of ZrO 2 is preferably 1.05, more preferably _1.05 . 0.00, 0.95, 0.90, 0.85, 0.80, 0.75 are more preferred. The lower limit of the mass ratio is preferably 0.00, and further 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0 0.18 and 0.20 are more preferred. By setting the mass ratio within the above range, Pg and F can be reduced.

In the optical glass according to the first embodiment, the upper limit of the mass ratio [Na ₂ O/R ₂ O] of the content of Na ₂ O to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is , preferably 0.80, furthermore 0.79, 0.78, 0.77, 0.76, 0.75, 0.70, 0.69, 0.68, 0.67, 0.66 , 0.65. The lower limit of the mass ratio is preferably 0.00, more preferably 0.05, 0.10, 0.15, 0.20, 0.25 in that order. By setting the mass ratio within the above range, a decrease in stability during reheating can be suppressed.

In the optical glass according to the first embodiment, the mass ratio of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O to the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ , The total content of Li ₂ O, Na ₂ O and K ₂ O and the mass ratio of the content of Na ₂ O to the total content of R ₂ O [{R ₂ O/(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )} + (Na ₂ O/R ₂ O)] is preferably 1.30, furthermore 1.28, 1.26, 1.24, 1.22, 1.20, 1.18, 1 .16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04, 1.02, 1.00, in that order. The lower limit of the total is preferably 0.30, more preferably 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65 in that order. By setting the total to the above range, it is possible to suppress a decrease in stability during reheating.

In the optical glass according to the first embodiment, the upper limit of the mass ratio [ _{R 2 O} /ZrO ₂ ] of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O to the content of ZrO 2 is preferably is 2.00 and also 1.95, 1.90, 1.85, 1.80, 1.78, 1.76, 1.74, 1.72, 1.70, 1.68, 1 0.66, 1.64, 1.62, 1.60 are more preferred in that order. The lower limit of the mass ratio is preferably 1.00, further 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1 .45 order is more preferred. By setting the mass ratio within the above range, it is possible to suppress an increase in Pg and F while suppressing a decrease in stability during reheating.

(glass component)
Non-limiting examples of the contents and ratios of glass components other than the above in the optical glass according to the first embodiment are shown below.

In the optical glass according to the first embodiment, the upper limit of the P ₂ O ₅ content is preferably 10.0%, more preferably 9.0%, 8.0%, 7.0% and 6.0%. %, 5.0%, and 4.0% in that order. In addition, the lower limit of the content of P ₂ O ₅ is preferably 0%, further 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, or 3 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 optical glass according to the first embodiment, the upper limit of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ [SiO ₂ +B ₂ O ₃ +P ₂ O ₅ ] is preferably 50.0%. , and further 49.5%, 49.0%, 48.5%, 48.0%, 47.5%, 47.0%, 46.5%, 46.0%, 45.5%, 45.5%. The order of 0% is more preferred. The lower limit of the total content [SiO ₂ +B ₂ O ₃ +P ₂ O ₅ ] is preferably 30.0%, more preferably 31.0%, 32.0%, 33.0% and 34.0%. %, 35.0%, 36.0%, 37.0%, 38.0%, 39.0% and 40.0% in that order.

In the optical glass according to the first embodiment, the upper limit of the Al ₂ O ₃ content is preferably 20.0%, more preferably 15.0%, 10.0%, 5.0% and 3.0%. %, then 1.0%. 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 optical glass according to the first embodiment, the upper limit of the K ₂ O content is preferably 25.0%, more preferably 20.0%, 18.0%, 16.0% and 14.0%. , 12.0%, 10.0%, 5.0%, 2.0%, and 1.0%. The lower limit of the K ₂ O content is preferably 0%, more preferably 0.5%. The content of K ₂ O may be 0%.

K ₂ O is a component that contributes to the reduction of the partial dispersion ratio Pg,F, and has the function of lowering the liquidus temperature and improving the thermal stability of the glass. Durability, weather resistance, and reheat stability decrease. Therefore, the content of K ₂ O is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the total content R ₂ O [Li ₂ O + Na ₂ O + K ₂ O] of Li ₂ O, Na ₂ O and K ₂ O is preferably 25.0%, Furthermore, the order of 24.0%, 23.0%, 22.0%, 21.0% and 20.0% is more preferable. In addition, the lower limit of the total content R ₂ O is preferably 5.0%, and further in the order of 6.0%, 7.0%, 8.0%, 9.0% and 10.0%. preferable. By setting the total content R ₂ O within the above range, the viscosity of the glass can be reduced, and increases in Pg and F can be suppressed.

In the optical 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 optical glass according to the first embodiment, the upper limit of the content of TiO ₂ is preferably 15.0%, further 14.0%, 13.0%, 12.0%, 11.0%, 10.0%, 9.0%, 8.0%, 7.0%, 6.0% and 5.0% are more preferable in that order. In addition, the lower limit of the content of TiO ₂ is preferably 0%, furthermore 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, or 3.0%. %. The content of _TiO2 may be 0%. By setting the content of TiO ₂ within the above range, desired optical constants can be achieved, increases in Pg and F can be suppressed, and increases in specific gravity can be suppressed.

In the optical 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 optical glass according to 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 transmittance can be increased, and the partial dispersion ratio Pg, F and the specific gravity can be reduced.

In the optical glass according to the first embodiment, the mass ratio of the total content of Nb ₂ O ₅ , TiO ₂ and ZrO ₂ to the total content of SiO ₂ and B ₂ O ₃ [(Nb ₂ O ₅ +TiO ₂ +ZrO ₂ )/(SiO ₂ +B ₂ O ₃ )] is preferably 1.50, more preferably 1.45, 1.40, 1.35, 1.30, 1.25, 1.20, 1 0.15, 1.10, 1.05, 1.00 are more preferred. The lower limit of the mass ratio is preferably 0.50, further 0.55, 0.60, 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0 0.74 and 0.76 are more preferred. By setting the mass ratio within the above range, the refractive index can be set within the desired range.

In the optical glass according to the first embodiment, the upper limit of the Ta ₂ O ₅ content is preferably 5.0%, more preferably 4.0%, 3.0%, 2.0% and 1.0%. % order is preferred. 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, when the content of Ta ₂ O ₅ increases, the raw material cost increases. Also, the specific gravity increases. Therefore, the content of Ta ₂ O ₅ is preferably within the above range.

In the optical glass according to _the first embodiment, the total content _{of Nb2O5} , _{TiO2 , Bi2O3 , WO3} and _{Ta2O5 [ Nb2O5} + _TiO2 + _Bi2O3 + _WO3 + _{Ta2O 5} ] is preferably 40.0%, further 39.0%, 38.0%, 37.0%, 36.0%, 35.0%, 34.0%, 33.0% %, 32.0%, 31.0%, and 30.0% in that order. The lower limit of the total content is preferably 15.0%, further 16.0%, 17.0%, 18.0%, 19.0%, 20.0%, 21.0%, 22 0% and 23.0% in that order are more preferable.

In the optical glass according to the first embodiment, the upper limit of the mass ratio [Ta ₂ O ₅ /ZrO ₂ ] of the content of Ta ₂ O ₅ to the content of ZrO ₂ is preferably 0.45, more preferably 0 0.40, 0.35, 0.30, 0.25, 0.20, 0.15, 0.10, 0.05, in that order. The lower limit of the mass ratio is preferably 0, and the mass ratio is more preferably 0. By setting the mass ratio within the above range, the optical constants can be within the desired range, and the raw material cost of the glass can be reduced.

In the optical glass according to _the first embodiment, SiO ₂ , B ₂ O _{3 , P 2 O 5} , Nb ₂ O ₅ , TiO ₂ and The upper limit of the mass ratio of the total content of _WO3 [ _{( SiO2} + _B2O3 + _P2O5 + _Nb2O5 + _{TiO2 + WO3} ) _/ ( _Li2O + _Na2O + _K2O + _ZrO2 )] is preferably 3. 50, and more preferably 3.40, 3.30, 3.20, 3.10, 3.00 in that order. The lower limit of the mass ratio is preferably 1.70, more preferably 1.80, 1.90, 2.00 and 2.10 in that order.

In the optical glass according to the first embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O [( SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/R ₂ O] is preferably 4.00, more preferably 3.80, 3.60 and 3.40 in that order. The lower limit of the mass ratio is preferably 1.50, more preferably 1.60, 1.70, 1.80, 1.90 and 2.00 in that order.

In the optical glass according to the first embodiment, the upper limit of the mass ratio [Nb ₂ O ₅ /ZrO ₂ ] of the content of Nb ₂ O ₅ to the content of ZrO 2 is preferably _3.20 , more preferably 2 .90, 2.70 and 2.50 are more preferred. The lower limit of the mass ratio is preferably 1.20, more preferably 1.40, 1.60 and 1.80 in that order.

In the optical glass according to the first embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O, The mass ratio of the content of Nb ₂ O ₅ to the content of ZrO ₂ and the sum of [{(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/R ₂ O} + (Nb ₂ O ₅ /ZrO ₂ )] The upper limit is preferably 6.20, more preferably 5.80, 5.60, 5.50, 5.10 and 5.00 in that order. The lower limit of the mass ratio is preferably 3.00, further 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.80, 3 0.90, 3.95, 4.00, 4.05, 4.10 are preferred in that order.

In the optical 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 optical glass according to the first embodiment, the upper limit of the CaO content is preferably 20%, more preferably 18%, 16% and 14% in that 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 optical 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%.

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.

In the optical 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 optical glass according to the first embodiment, the upper limit of the total content RO [MgO+CaO+SrO+BaO+ZnO] of MgO, CaO, SrO, BaO and ZnO is preferably 20.0%, more preferably 15.0% and 10.0%. %, 8.0%, 6.0%, 4.0%, and 3.0% in that order. The lower limit of the total content is preferably 0%. By setting the total content within the above range, the refractive index nd can be set within the desired range.

In the optical glass according to the first embodiment, the upper limit of the mass ratio [RO/ZrO ₂ ] of the total content RO of MgO, CaO, SrO, BaO and ZnO to the content of ZrO ₂ is preferably 0.74. , and more preferably 0.70, 0.60, 0.50, 0.40, 0.30, 0.20, 0.10. The lower limit of the mass ratio is preferably zero. By setting the mass ratio within the above range, Pg and F can be reduced, and the refractive index nd can be set within the desired 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. Moreover, there is a possibility that high dispersibility may be impaired. 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 have the function of increasing the high dispersibility of the 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 optical glass according to the first embodiment, the upper limit of the La ₂ O ₃ content is preferably 10.0%, more preferably 9.0%, 8.0%, 7.0% and 6.0%. %, 5.0%, and 4.0% in that order. The lower limit of the La ₂ O ₃ content is preferably 0.1%, more preferably 0.2%, 0.3% and 0.4% 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.

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. Moreover, raw material costs may increase. 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. 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 , ZrO ₂ and Nb ₂ O ₅ as essential components, and B ₂ O ₃ , Li ₂ O, Na ₂ O and P ₂ as optional components. _O5 , _{Al2O3 , K2O} , _{Cs2O , TiO2} , _WO3 , _Bi2O3 , _{Ta2O5 ,} MgO, CaO, SrO, BaO, ZnO, _{Y2O3 , Sc2O 3 , HfO2 , Lu2O3 , GeO2} , _La2O3 , _{Gd2O3 ,} and _Yb2O3 . The total content of the above glass components is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and particularly preferably 99.5% or more.

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.

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

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

Pb, As, Ce, Th, and the like are components of concern about environmental impact. Therefore, the content of each of Pb, As, Ce and Th is preferably 0 to 0.1%, more preferably 0 to 0.05%, more preferably 0 to 0.05% in terms of oxides. 01% is even more preferred. It is particularly preferred that Pb, As, Ce and Th are substantially not contained.

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 1.80 to 1.50. The refractive index nd can also be between 1.75 and 1.55, or between 1.70 and 1.60.

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 has the function of _{relatively lowering the refractive index nd includes SiO2, B2O3 , Li2O , Na2O} , _K2O and the like. Further, for example, the mass ratio of the total content of the high refractive index components Nb ₂ O ₅ , TiO ₂ and ZrO ₂ to the total content of the low refractive index components SiO ₂ and B ₂ O ₃ [(Nb ₂ O ₅ +TiO ₂ + ZrO ₂ )/(SiO ₂ +B ₂ O ₃ )] can increase the refractive index nd, and decreasing the mass ratio can lower the refractive index nd.

<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 0.5850, more preferably 0.5845, 0.5840, 0.5835, 0.5830, 0.5825, 0.5820, 0.5815, 0.5810, 0.5805, 0.5800, 0.5795, 0.5790, 0.5785, 0.5780, 0.5775, 0.5770, 0.5765, 0.5800 5760 order is more preferable. 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, 0.5700 is used as a guideline.

Further, in the optical glass according to the first embodiment, the partial dispersion ratio Pg,F preferably satisfies the following formula [1].
Pg, F≦0.6483−0.001802×νd [1]
The partial dispersion ratio Pg, F more preferably satisfies the following formula [2]. 7] are more preferably satisfied in this order.
Pg, F≦0.6470−0.001802×νd [2]
Pg, F≦0.6460−0.001802×νd [3]
Pg, F≦0.6450−0.001802×νd [4]
Pg, F≦0.6444−0.001802×νd [5]
Pg, F≦0.6439−0.001802×νd [6]
Pg, F≦0.6437−0.001802×νd [7]

When the partial dispersion ratio Pg, F satisfies the above formula, the optical element made of the optical glass according to the first embodiment can satisfactorily correct chromatic aberration in a wide wavelength range.

In the present invention, the Abbe number νd and the partial dispersion ratio Pg,F are calculated as follows. That is, the refractive index at the 12 wavelengths shown in Table A is measured by the Japanese Industrial Standards (JIS) JIS B 7071-1 Refractive index measurement method for optical glasses-Part 1: Minimum deviation method. Next, Japanese Industrial Standards (JIS) JIS B 7071-1 Refractive index measurement method for optical glass-Part 1: Minimum deflection angle method, which is defined in Annex B, was obtained by measurement. The indices of refraction for each line are fitted and the constants of the Schott dispersion equation are determined by the least squares method. Then, the Abbe number νd and the partial dispersion ratio Pg, F are calculated from the value of each line refractive index obtained by using Shot's dispersion formula with a fixed constant.

ショットの分散式： ｎ^２＝ａ_０＋ａ_１λ^２＋ａ_２λ^－２＋ａ_３λ^－４＋ａ_４λ^－６＋ａ_５λ^－８
ここで、ｎは屈折率、λは波長（μｍ）、ａ_０、ａ_１、ａ_２、ａ_３、ａ_４、ａ_５は定数である。

Shot dispersion formula: n ² =a ₀ +a ₁ λ ² +a ₂ λ ⁻² +a ₃ λ ⁻⁴ +a ₄ λ ⁻⁶ +a ₅ λ ⁻⁸
Here, n is the refractive index, λ is the wavelength (μm), and a ₀ , a ₁ , a ₂ , a ₃ , a ₄ and a ₅ are constants.

In the present invention, the partial dispersion ratios Pg and F are obtained by using refractive index values measured at 12 different wavelengths (spectral lines) as described above, and using a formula that relates refractive indices and wavelengths, called Schott's dispersion formula. The coefficients of the wavelength term are obtained by fitting, and after these coefficients are determined, calculation is performed using the dispersion formula. By using the refractive index values measured at 12 different wavelengths, the partial dispersion ratio Pg,F can be calculated with high accuracy. On the other hand, the partial dispersion ratio Pg,F can be calculated by a simplified method by reducing the number of wavelengths for which the refractive indices are measured. The partial dispersion ratio Pg,F calculated by a simple method tends to be a smaller value than the value calculated by In other words, even if the values of the partial dispersion ratios Pg and F are the same, there are cases where superiority or inferiority arises in performance regarding actual correction of chromatic aberration depending on the calculation method. Specifically, since the partial dispersion ratio Pg,F calculated by the simple method as described above is underestimated, the value of Pg,F is calculated using refractive indices measured at 12 different wavelengths. Even with the same value of the dispersion ratio Pg,F, the performance regarding correction of actual chromatic aberration may be inferior.

.DELTA.Pg,F is obtained as the deviation of Pg,F from the normal line by the formula [8].
ΔPg, F=Pg, F−(0.6483−0.001802×νd) [8]
Generally, in optical glass, Pg,F tends to increase as the Abbe number νd decreases, so ΔPg,F is generally used as an index of anomalous dispersion.

<Specific gravity of glass>
The specific gravity of the optical glass according to the first embodiment is preferably 3.30 or less, more preferably 3.20 or less, and even more preferably 3.10 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 . On the other hand, components that relatively lower the specific gravity are _SiO2 , _B2O3 , _Li2O , _Na2O , _K2O and _the like. The specific gravity can be controlled by appropriately adjusting the contents of these components.

<Stability during reheating>
When the optical glass according to the first embodiment is heated at the glass transition temperature Tg for 10 minutes and further heated at a temperature 220° C. higher than the Tg for 10 minutes, the number of crystals observed per 1 g is preferably 25. number or less, more preferably 20 or less, still more preferably 10 or less.

The stability during reheating is evaluated as follows. A glass sample with a size of 1 cm x 1 cm x 1 cm was heated for 10 minutes in a first test furnace set to the glass transition temperature Tg of the glass sample, and further set to a temperature 220°C higher than the glass transition temperature Tg. After heating for 10 minutes in the second test furnace, the presence or absence of crystals is confirmed with an optical microscope (observation magnification: 40 to 100 times). Then, the number of crystals per 1 g is measured. It can be evaluated that the stability is high when the number of crystals is small, and the stability is low when the number of crystals is large.

<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, and further 640°C, 630°C, 620°C, 610°C, 600°C, 590°C, 580°C, 570°C, 560° C. is more preferable in that order. The lower limit of the glass transition temperature Tg is preferably 430°C, more preferably 440°C, 450°C, 460°C and 470°C in that order. The glass transition temperature Tg can be controlled by adjusting the content of each glass component .
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 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 5% is λ5. and

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. λ5 is preferably 370 nm or less, more preferably 360 nm or less, and still 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 glass melt, which is further clarified and homogenized, shaped into a glass melt, 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 optical glass described above, molten glass is poured into a mold and molded 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
Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25-55%,
The content of B ₂ O ₃ is 13% or less,
Li ₂ O content is 20% or less,
The content of Na ₂ O is 17% or less,
The content of ZrO ₂ is 2-22 % ,
The content of Nb ₂ O ₅ is 12-42 % ,
_Mass ratio of the total content of _SiO2 , _{B2O3 and P2O5} to _the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R _{2 O} to the sum of the total content R ₂ O of Li 2 O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , ZnO, _TiO2 , _Nb2O5 , _{WO3 , ZrO2} , La the _total content _{of 2O3} , _Gd2O3 and _Y2O3 is 93% by mass _or more;
mass ratio of the total content of SiO _{2 ,} B ₂ O ₃ and P ₂ O ₅ to the content of ZrO 2 [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is 5.45 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 0.240 or less.

The optical glass according to the second embodiment has an Abbe number νd of 36.40 or more. The Abbe number νd may be 36.50 to 45.00, 36.60 to 43.00, 36.70 to 41.00, 36.80 to 40.00, or 36.90 to 39.50. can.

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 , WO ₃ , Bi ₂ O ₃ , 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.

In the optical glass according to the second embodiment, the content of SiO ₂ is 25-55%. The lower limit of the SiO ₂ content is preferably 27%, more preferably 29%, 30%, 31%, 32%, 33% in this order. The upper limit of the SiO ₂ content is preferably 53%, more preferably 50%, 48%, 46%, 44%, 42%, 40% and 38% in that order. _SiO2 is a network-forming component of glass. If the SiO ₂ content is too low, the stability during reheating may decrease. On the other hand, if the content of SiO ₂ is too large, the high dispersion is impaired, it is difficult to obtain desired optical constants, and the partial dispersion ratio Pg,F may increase.

The content of B ₂ O ₃ in the optical glass according to the second embodiment is 13% or less. The upper limit of the content of B ₂ O ₃ is preferably 12%, more preferably 11%, 10%, 9% and 8% in this order. Also, the lower limit of the B ₂ O ₃ content is preferably 0%, more preferably 1%, 2%, and 3% in that order. The content of B ₂ O ₃ may be 0%. It is a network-forming component of B ₂ O ₃ glass. If the content of B ₂ O ₃ is too large, the high dispersion is impaired, it is difficult to obtain desired optical constants, and the partial dispersion ratio Pg,F may increase. If the content of B ₂ O ₃ is too small, the stability during reheating may decrease.

In the glass according to the second embodiment, the content of Li ₂ O is 20% or less. The upper limit of the Li ₂ O content is preferably 18%, more preferably 17%, 16%, 15%, 14%, 13% and 12% in that order. The lower limit of the Li ₂ O content is preferably 0%, more preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% in that order. Li ₂ O is a component that contributes to low viscosity and low Pg and F contents of the glass. If the content of Li ₂ O is too high, the stability during reheating may decrease. On the other hand, if the content of Li ₂ O is too small, the viscosity of the glass may increase and Pg and F may increase.

In the glass according to the second embodiment, the content of Na ₂ O is 17% or less. The upper limit of the Na ₂ O content is preferably 16%, more preferably 15%, 14%, 13%, 12%, 11%, 10% and 9% in that order. The lower limit of the Na ₂ O content is preferably 0%, more preferably 1%, 2%, 3%, 4% and 5% in this order. The content of Na ₂ O may be 0%. Na ₂ O, like Li ₂ O, is a component that contributes to low viscosity and low Pg, F content of the glass. If the content of Na ₂ O is too high, the stability during reheating may decrease. On the other hand, if the content of Na ₂ O is too small, the viscosity of the glass may increase, and Pg and F may increase.

In the glass according to the second embodiment, the content of ZrO ₂ is 2-22%. The lower limit of the ZrO ₂ content is preferably 4%, more preferably 5%, 6%, 7%, 8%, 9% in that order. The upper limit of the ZrO ₂ content is preferably 20%, more preferably 18%, 16%, 15%, 14% and 13% in that order. ZrO ₂ is a component that contributes to low Pg and F. If the ZrO ₂ content is too high, the liquidus temperature LT may increase. Also, if the content of ZrO ₂ is too small, Pg and F may increase.

In the optical glass according to the second embodiment, the content of Nb ₂ O ₅ is 12-42%. The lower limit of the content of Nb ₂ O ₅ is preferably 14%, more preferably 16%, 18%, 20%, 21%, 22%, 23%, 24% and 25% in that order. The upper limit of the content of Nb ₂ O ₅ is preferably 40%, more preferably 38%, 36%, 34%, 33%, 32%, 31% and 30% in that order. Nb ₂ O ₅ is a component that contributes to achieving both high dispersion and low Pg and F content. If the content of Nb ₂ O ₅ is too high, the stability during reheating may be lowered, and the meltability may be lowered. If the content of Nb ₂ O ₅ is too small, there is a risk of low dispersion.

Total content of SiO ₂ , B 2 O 3 _and P ₂ O ₅ relative to total content of Nb ₂ O ₅ , TiO ₂ , Bi ₂ O ₃ , WO ₃ and Ta ₂ O ₅ in the optical glass according to _the second embodiment The mass ratio [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/(Nb ₂ O ₅ +TiO ₂ +Bi ₂ O ₃ +WO ₃ +Ta ₂ O ₅ )] is 2.00 or less. The upper limit of the mass ratio is preferably 1.95, further 1.90, 1.85, 1.80, 1.75, 1.74, 1.73, 1.72, 1.71, 1 .70 order is more preferred. Further, the lower limit of the mass ratio is preferably 1.00, and further 1.10, 1.20, 1.25, 1.30, 1.32, 1.34, 1.36, 1.38. , 1.40. By setting the mass ratio within the above range, the Abbe number νd can be controlled within a desired range. If the mass ratio is too large, the Abbe number νd may deviate from the desired range. On the other hand, if the mass ratio is too small, the stability during reheating may decrease.

In the optical glass according to the second embodiment, the total content relative to the sum of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO The mass ratio of R ₂ O [R ₂ O/(R ₂ O+RO)] is 0.60 or more. The lower limit of the mass ratio is preferably 0.62, further 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0 .80 order is more preferred. Moreover, the upper limit of the mass ratio is preferably 1, and the mass ratio is more preferably 1. By setting the mass ratio within the above range, the Pg and F of the glass can be reduced. If the mass ratio is too small, ΔPg,F shown in formula [8] may increase.

In the optical glass according to _the second embodiment, _SiO2 , _B2O3 , _P2O5 , Li2O, _Na2O , _K2O , MgO, _CaO , SrO, BaO, ZnO, _{TiO2 , Nb2} The total content _{of O5 , WO3 , ZrO2} , _La2O3 , _Gd2O3 and _Y2O3 is 93% or more. The lower limit of the total content is preferably 94%, more preferably 95%, 96%, 97%, 98% and 99% in that order. Moreover, the upper limit of the total content is preferably 100%, and the total content is more preferably 100%. If the total content is too small, the coloration of the glass may increase, desired optical constants may not be obtained, and stability during reheating may deteriorate. Furthermore, the raw material cost of the glass may increase.

In the optical glass according to the second embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ to the content of ZrO ₂ [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is less than or equal to 5.45. The upper limit of the mass ratio is preferably 5.30, further 5.20, 5.10, 5.00, 4.90, 4.80, 4.70, 4.50, 4.40, 4 .30, 4.20, 4.10, 4.00 are more preferred. In addition, the lower limit of the mass ratio is preferably 2.00, further 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.30, 3.40. , 3.50. By setting the mass ratio within the above range, both reduction in Pg and F and improvement in stability during reheating can be achieved. If the mass ratio is too large, Pg, F may increase. If the mass ratio is too small, the stability during reheating may decrease.

In the optical glass according to the second 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 0.240 or less. The upper limit of the mass ratio is preferably 0.238, more preferably 0.236, 0.234, 0.232, 0.230 in that order. The lower limit of the mass ratio is preferably 0.020, more preferably 0.030, 0.040, 0.050 and 0.060 in that order. By setting the mass ratio within the above range, the specific gravity can be reduced and the transmittance can be improved. If the mass ratio is too large, the transmittance may deteriorate.

In the optical glass according to the second embodiment, the upper limit of the mass ratio [B ₂ O ₃ /ZrO ₂ ] of the content of B ₂ O ₃ to the content of ZrO 2 is preferably 1.05, more preferably 1.05 _. 0.00, 0.95, 0.90, 0.85, 0.80, 0.75 are more preferred. The lower limit of the mass ratio is preferably 0.00, and further 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0 0.18 and 0.20 are more preferred. By setting the mass ratio within the above range, Pg and F can be reduced.

In the optical glass according to the second embodiment, the upper limit of the mass ratio [Na ₂ O/R ₂ O] of the content of Na ₂ O to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is , preferably 0.80, furthermore 0.79, 0.78, 0.77, 0.76, 0.75, 0.70, 0.69, 0.68, 0.67, 0.66 , 0.65. The lower limit of the mass ratio is preferably 0.00, more preferably 0.05, 0.10, 0.15, 0.20, 0.25 in that order. By setting the mass ratio within the above range, a decrease in stability during reheating can be suppressed.

In the optical glass according to the second embodiment, the mass ratio of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O to the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ , The total content of Li ₂ O, Na ₂ O and K ₂ O and the mass ratio of the content of Na ₂ O to the total content of R ₂ O [{R ₂ O/(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )} + (Na ₂ O/R ₂ O)] is preferably 1.30, furthermore 1.28, 1.26, 1.24, 1.22, 1.20, 1.18, 1 .16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04, 1.02, 1.00, in that order. The lower limit of the total is preferably 0.30, more preferably 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65 in that order. By setting the total to the above range, it is possible to suppress deterioration in stability during reheating.

In the optical glass according to the second embodiment, the upper limit of the mass ratio [ _{R 2 O} /ZrO ₂ ] of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O to the content of ZrO 2 is preferably is 2.00 and also 1.95, 1.90, 1.85, 1.80, 1.78, 1.76, 1.74, 1.72, 1.70, 1.68, 1 0.66, 1.64, 1.62, 1.60 are more preferred. The lower limit of the mass ratio is preferably 1.00, further 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1 .45 order is more preferred. By setting the mass ratio within the above range, it is possible to suppress an increase in Pg and F while suppressing a decrease in stability during reheating.

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

Further, in the optical glass according to the second embodiment, glass properties other than those described above can be the same as those in the first embodiment.

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

Third Embodiment The optical glass according to the third embodiment is
Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25-55%,
The content of B ₂ O ₃ is 13% or less,
Li ₂ O content is 20% or less,
The content of Na ₂ O is 17% or less,
The content of ZrO ₂ is 2-22 % ,
The content of Nb ₂ O ₅ is 12-42 % ,
_Mass ratio of the total content of _SiO2 , _{B2O3 and P2O5} to _the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
The sum of Li ₂ O, Na ₂ O and K ₂ O with respect to the sum of the total content of Li ₂ O, Na 2 O and K ₂ O and the total content of MgO _, CaO, SrO, BaO _and ZnO RO mass ratio [R ₂ O/(R ₂ O+RO)] of content R 2 O is 0.60 or _more ;
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , _ZnO , _TiO2 , _Nb2O5 , _WO3 , _ZrO2 , La the _{total content of 2O3, Gd2O3 and Y2O3 is 93 % by} mass _or more;
The mass ratio of the total content of SiO _{2 ,} B ₂ O ₃ and P ₂ O ₅ to the content of ZrO 2 [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is 5.45 or less,
The mass ratio [B ₂ O ₃ /ZrO ₂ ] of the B ₂ O ₃ content to the ZrO 2 content is 1.05 or _less .

The optical glass according to the third embodiment has an Abbe number νd of 36.40 or more. The Abbe number νd may be 36.50 to 45.00, 36.60 to 43.00, 36.70 to 41.00, 36.80 to 40.00, or 36.90 to 39.50. can.

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 , WO ₃ , Bi ₂ O ₃ , 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.

In the optical glass according to the third embodiment, the content of SiO ₂ is 25-55%. The lower limit of the SiO ₂ content is preferably 27%, more preferably 29%, 30%, 31%, 32%, 33% in this order. The upper limit of the SiO ₂ content is preferably 53%, more preferably 50%, 48%, 46%, 44%, 42%, 40% and 38% in that order. _SiO2 is a network-forming component of glass. If the SiO ₂ content is too low, the stability during reheating may decrease. On the other hand, if the content of SiO ₂ is too large, the high dispersion is impaired, it is difficult to obtain the desired optical constants, and the partial dispersion ratio Pg,F may increase.

The content of B ₂ O ₃ in the optical glass according to the third embodiment is 13% or less. The upper limit of the content of B ₂ O ₃ is preferably 12%, more preferably 11%, 10%, 9% and 8% in this order. Also, the lower limit of the B ₂ O ₃ content is preferably 0%, more preferably 1%, 2%, and 3% in that order. The content of B ₂ O ₃ may be 0%. It is a network-forming component of B ₂ O ₃ glass. If the content of B ₂ O ₃ is too large, the high dispersion is impaired, it is difficult to obtain desired optical constants, and the partial dispersion ratio Pg,F may increase. If the content of B ₂ O ₃ is too small, the stability during reheating may decrease.

In the glass according to the third embodiment, the content of Li ₂ O is 20% or less. The upper limit of the Li ₂ O content is preferably 18%, more preferably 17%, 16%, 15%, 14%, 13% and 12% in that order. The lower limit of the Li ₂ O content is preferably 0%, more preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% in that order. Li ₂ O is a component that contributes to low viscosity and low Pg and F contents of the glass. If the content of Li ₂ O is too high, the stability during reheating may decrease. On the other hand, if the content of Li ₂ O is too small, the viscosity of the glass may increase and Pg and F may increase.

In the glass according to the third embodiment, the content of Na ₂ O is 17% or less. The upper limit of the Na ₂ O content is preferably 16%, more preferably 15%, 14%, 13%, 12%, 11%, 10% and 9% in that order. The lower limit of the content of Na ₂ O is preferably 0%, more preferably 1%, 2%, 3%, 4% and 5% in this order. The content of Na ₂ O may be 0%. Na ₂ O, like Li ₂ O, is a component that contributes to low viscosity and low Pg, F content of the glass. If the content of Na ₂ O is too high, the stability during reheating may decrease. On the other hand, if the content of Na ₂ O is too small, the viscosity of the glass may increase and Pg and F may increase.

In the glass according to the third embodiment, the content of ZrO ₂ is 2-22%. The lower limit of the ZrO ₂ content is preferably 4%, more preferably 5%, 6%, 7%, 8%, 9% in that order. The upper limit of the ZrO ₂ content is preferably 20%, more preferably 18%, 16%, 15%, 14% and 13% in that order. ZrO ₂ is a component that contributes to low Pg and F. If the ZrO ₂ content is too high, the liquidus temperature LT may increase. Also, if the content of ZrO ₂ is too small, Pg and F may increase.

In the optical glass according to the third embodiment, the content of Nb ₂ O ₅ is 12-42%. The lower limit of the content of Nb ₂ O ₅ is preferably 14%, more preferably 16%, 18%, 20%, 21%, 22%, 23%, 24% and 25% in that order. The upper limit of the content of Nb ₂ O ₅ is preferably 40%, more preferably 38%, 36%, 34%, 33%, 32%, 31% and 30% in that order. Nb ₂ O ₅ is a component that contributes to achieving both high dispersion and low Pg and F content. If the content of Nb ₂ O ₅ is too high, the stability during reheating may be lowered, and the meltability may be lowered. If the content of Nb ₂ O ₅ is too small, there is a risk of low dispersion.

Total content of SiO ₂ , B 2 O 3 _and P ₂ O ₅ relative to total content of Nb ₂ O ₅ , TiO ₂ , Bi ₂ O ₃ , WO ₃ and Ta ₂ O ₅ in _the optical glass according to the third embodiment The mass ratio [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/(Nb ₂ O ₅ +TiO ₂ +Bi ₂ O ₃ +WO ₃ +Ta ₂ O ₅ )] is 2.00 or less. The upper limit of the mass ratio is preferably 1.95, further 1.90, 1.85, 1.80, 1.75, 1.74, 1.73, 1.72, 1.71, 1 .70 order is more preferred. Further, the lower limit of the mass ratio is preferably 1.00, and further 1.10, 1.20, 1.25, 1.30, 1.32, 1.34, 1.36, 1.38. , 1.40. By setting the mass ratio within the above range, the Abbe number νd can be controlled within a desired range. If the mass ratio is too large, the Abbe number νd may deviate from the desired range. On the other hand, if the mass ratio is too small, the stability during reheating may decrease.

In the optical glass according to the third embodiment, the total content relative to the sum of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO The mass ratio of R ₂ O [R ₂ O/(R ₂ O+RO)] is 0.60 or more. The lower limit of the mass ratio is preferably 0.62, further 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0 .80 order is more preferred. Moreover, the upper limit of the mass ratio is preferably 1, and the mass ratio is more preferably 1. By setting the mass ratio within the above range, the Pg and F of the glass can be reduced. If the mass ratio is too small, ΔPg,F shown in formula [8] may increase.

In the optical glass according to _the third embodiment, _SiO2 , _B2O3 , _P2O5 , Li2O, _Na2O , _K2O , MgO, _CaO , SrO, BaO, ZnO, _{TiO2 , Nb2} The total content _{of O5 , WO3 , ZrO2} , _La2O3 , _Gd2O3 and _Y2O3 is 93% or more. The lower limit of the total content is preferably 94%, more preferably 95%, 96%, 97%, 98% and 99% in that order. Moreover, the upper limit of the total content is preferably 100%, and the total content is more preferably 100%. If the total content is too small, the coloration of the glass may increase, desired optical constants may not be obtained, and stability during reheating may deteriorate. Furthermore, the raw material cost of the glass may increase.

In the optical glass according to the third embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ to the content of ZrO ₂ [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is less than or equal to 5.45. The upper limit of the mass ratio is preferably 5.30, further 5.20, 5.10, 5.00, 4.90, 4.80, 4.70, 4.50, 4.40, 4 .30, 4.20, 4.10, 4.00 are more preferred. In addition, the lower limit of the mass ratio is preferably 2.00, further 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.30, 3.40. , 3.50. By setting the mass ratio within the above range, both reduction in Pg and F and improvement in stability during reheating can be achieved. If the mass ratio is too large, Pg, F may increase. If the mass ratio is too small, the stability during reheating may decrease.

In the optical glass according to the third embodiment, the mass ratio [B ₂ O ₃ /ZrO ₂ ] of the content of B ₂ O ₃ to the content of ZrO ₂ is 1.05 or less. The upper limit of the mass ratio is more preferably 1.00, 0.95, 0.90, 0.85, 0.80 and 0.75 in that order. The lower limit of the mass ratio is preferably 0.00, and further 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0 0.18 and 0.20 are more preferred. By setting the mass ratio within the above range, Pg and F can be reduced. If the mass ratio is too large, Pg, F may increase. On the other hand, if the mass ratio is too small, the stability during reheating may decrease.

In the optical glass according to the third 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 0.240, more preferably 0.240. 0.238, 0.236, 0.234, 0.232, 0.230 are more preferred. The lower limit of the mass ratio is preferably 0.020, more preferably 0.030, 0.040, 0.050 and 0.060 in that order. By setting the mass ratio within the above range, the specific gravity can be reduced and the transmittance can be improved.

In the optical glass according to the third embodiment, the upper limit of the mass ratio [Na ₂ O/R ₂ O] of the content of Na ₂ O to the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is , preferably 0.80, furthermore 0.79, 0.78, 0.77, 0.76, 0.75, 0.70, 0.69, 0.68, 0.67, 0.66 , 0.65. The lower limit of the mass ratio is preferably 0.00, more preferably 0.05, 0.10, 0.15, 0.20, 0.25 in that order. By setting the mass ratio within the above range, a decrease in stability during reheating can be suppressed.

In the optical glass according to the third embodiment, the mass ratio of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O to the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ , The total content of Li ₂ O, Na ₂ O and K ₂ O and the mass ratio of the content of Na ₂ O to the total content of R ₂ O [{R ₂ O/(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )} + (Na ₂ O/R ₂ O)] is preferably 1.30, furthermore 1.28, 1.26, 1.24, 1.22, 1.20, 1.18, 1 .16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04, 1.02, 1.00, in that order. The lower limit of the total is preferably 0.30, more preferably 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65 in that order. By setting the total to the above range, it is possible to suppress deterioration in stability during reheating.

In the optical glass according to the third embodiment, the upper limit of the mass ratio [ _{R 2 O} /ZrO ₂ ] of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O to the content of ZrO 2 is preferably is 2.00 and also 1.95, 1.90, 1.85, 1.80, 1.78, 1.76, 1.74, 1.72, 1.70, 1.68, 1 0.66, 1.64, 1.62, 1.60 are more preferred in that order. The lower limit of the mass ratio is preferably 1.00, further 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1 .45 order is more preferred. By setting the mass ratio within the above range, it is possible to suppress an increase in Pg and F while suppressing a decrease in stability during reheating.

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

Further, in the optical glass according to the third embodiment, glass properties other than those described above can be the same as those in the first embodiment.

Furthermore, the manufacture of the optical glass and the manufacture of the optical element etc. according to the third embodiment can also 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 Table 1 were produced by the following procedure, and various evaluations were performed.

[Manufacture of optical glass]
First, oxides, hydroxides, carbonates, and nitrates corresponding to the components of glass are prepared as raw materials, and the raw materials are weighed so that the resulting optical glass has the glass composition shown in Table 1. , to mix the raw materials thoroughly. 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 to homogenize, clarified, and then the 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 content of each glass component in the resulting glass sample was measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES), and it was confirmed that each composition shown in Table 1 was obtained.

[Reheating test (stability during reheating)]
The obtained glass sample was cut into a size of 1 cm × 1 cm × 1 cm, heated for 10 minutes in the first test furnace set to the glass transition temperature Tg of the glass sample, and further heated to 220 ° C. above the glass transition temperature Tg. Heated for 10 minutes in a second test oven set at a higher temperature. After that, the presence or absence of crystals was confirmed with an optical microscope (observation magnification: 40 to 100 times). Then, the number of crystals (the number of foreign matter) per 1 g was measured.

[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 refractive index, Abbe number νd, partial dispersion ratio Pg, F, specific gravity, glass transition temperature Tg, λ80 and λ5 were measured for the obtained annealed sample. Table 1 shows the results.

(i) refractive index and Abbe number νd and partial dispersion ratio Pg, F
For the annealed sample, the refractive index at 12 wavelengths shown in Table A was measured according to Japanese Industrial Standards (JIS) JIS B 7071-1 Refractive index measurement method for optical glasses-Part 1: Minimum deflection angle method.
Next, the Japanese Industrial Standards (JIS) JIS B 7071-1 Refractive index measurement method for optical glasses - Part 1: Minimum deviation method, each line obtained by measurement in the Schott dispersion formula specified in Annex B was applied, and the constants of Schott's dispersion equation were obtained by the method of least squares. Then, the Abbe number νd and the partial dispersion ratio Pg,F were calculated using the shot dispersion formula with a fixed constant.

ショットの分散式： ｎ^２＝ａ_０＋ａ_１λ^２＋ａ_２λ^－２＋ａ_３λ^－４＋ａ_４λ^－６＋ａ_５λ^－８
ここで、ｎは屈折率、λは波長（μｍ）、ａ_０、ａ_１、ａ_２、ａ_３、ａ_４、ａ_５は定数である。
なお、屈折ｎｄとは、波長５８７．５６ｎｍにおける屈折率である。

Shot dispersion formula: n ² =a ₀ +a ₁ λ ² +a ₂ λ ⁻² +a ₃ λ ⁻⁴ +a ₄ λ ⁻⁶ +a ₅ λ ⁻⁸
Here, n is the refractive index, λ is the wavelength (μm), and a ₀ , a ₁ , a ₂ , a ₃ , a ₄ and a ₅ are constants.
The refractive index nd is the refractive index at a wavelength of 587.56 nm.

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

(iii) 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.

(iv) λ80, λ5
The annealed sample was processed so as to have parallel and optically polished flat surfaces 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 of the light incident perpendicularly to one of the optically polished planes as the intensity A and the intensity of the light emitted from the other plane as the intensity B. The wavelength at which the spectral transmittance is 80% is λ80, 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.
Secondary chromatic aberration could be satisfactorily corrected by combining various lenses with lenses made of other types of optical glass.

In addition, since glass has a relatively low specific gravity, each lens is lighter in weight than lenses with similar optical characteristics and sizes. preferred. 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 scope and meaning 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 composition 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 (14)

Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25 to 55% by mass,
The content of B ₂ O ₃ is 13% by mass or less,
Li ₂ O content is 20% by mass or less,
The content of Na ₂ O is 17% by mass or less,
The content of ZrO ₂ is 6 to 22% by mass,
The content of Nb ₂ O ₅ is 12 to 42% by mass,
Mass ratio of _the total content of _SiO2 , _{B2O3 and P2O5} to the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R ₂ O to the sum of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , ZnO, _TiO2 , _Nb2O5 , _{WO3 , ZrO2} , La the _{total content of 2O3, Gd2O3 and Y2O3 is 93 % by} mass _or more;
The mass ratio of the total content of SiO _{2 ,} B ₂ O ₃ and P ₂ O ₅ to the content of ZrO 2 [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is 4.30 or less. optical glass. Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25 to 55% by mass,
The content of B ₂ O ₃ is 13% by mass or less,
Li ₂ O content is 20% by mass or less,
The content of Na ₂ O is 17% by mass or less,
The content of ZrO ₂ is 6 to 22% by mass,
The content of Nb ₂ O ₅ is 12 to 42% by mass,
Mass ratio of _the total content of _SiO2 , _{B2O3 and P2O5} to the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R ₂ O to the sum of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , ZnO, _TiO2 , _Nb2O5 , _{WO3 , ZrO2} , La the _total content _{of 2O3} , _Gd2O3 and _Y2O3 is 93% by mass _or more;
mass ratio of the total content of SiO _{2 ,} B ₂ O ₃ and P ₂ O ₅ to the content of ZrO 2 [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is 4.30 or less;
An optical glass having a mass ratio of _B2O3 content to _SiO2 content [ _B2O3 / _SiO2 ] of _{0.240 or} less. Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25 to 55% by mass,
The content of B ₂ O ₃ is 13% by mass or less,
Li ₂ O content is 20% by mass or less,
The content of Na ₂ O is 17% by mass or less,
The content of ZrO ₂ is 6 to 22% by mass,
The content of Nb ₂ O ₅ is 12 to 42% by mass,
_Mass ratio of the total content of _SiO2 , _{B2O3 and P2O5} to _the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R _{2 O} to the sum of the total content R ₂ O of Li 2 O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , ZnO, _TiO2 , _Nb2O5 , _{WO3 , ZrO2} , La the _{total content of 2O3, Gd2O3 and Y2O3 is 93 % by} mass _or more;
mass ratio of the total content of SiO _{2 ,} B ₂ O ₃ and P ₂ O ₅ to the content of ZrO 2 [(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )/ZrO ₂ ] is 4.30 or less;
An optical glass having a mass ratio of _{B 2 O 3} content to ZrO 2 content [B ₂ O ₃ /ZrO ₂ ] of 1.05 or less. Abbe number νd is 36.40 or more,
The content of SiO ₂ is 25 to 55% by mass,
The content of B ₂ O ₃ is 3% by mass or more and 13% by mass or less,
Li ₂ O content is 20% by mass or less,
The content of Na ₂ O is 17% by mass or less,
The content of ZrO ₂ is 5 to 22% by mass,
The content of Nb ₂ O ₅ is 12 to 42% by mass,
Mass ratio of _the total content of _SiO2 , _{B2O3 and P2O5} to the total content _of Nb2O5 _{, TiO2 , Bi2O3 , WO3} and _Ta2O5 [( _SiO2 + _{B2 O3} + _P2O5 )/( _{Nb2O5 + TiO2} + _Bi2O3 + _WO3 + _Ta2O5 )] is _{2.00 or} less _,
Mass ratio of the total content R _{2 O} to the sum of the total content R ₂ O of Li 2 O, Na ₂ O and K ₂ O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R ₂ O /(R ₂ O+RO)] is 0.60 or more,
_SiO2 , _B2O3 , _P2O5 , Li2O _{, Na2O} , _K2O , _MgO , CaO, SrO, _BaO , _ZnO , _TiO2 , _Nb2O5 , _WO3 , _ZrO2 , La the total content _{of 2O3 , Gd2O3} and _Y2O3 is 93% by mass _or more;
mass ratio _[ ( _SiO2 + _B2O3 + _P2O5 )/ _ZrO2 ] of the total content of _{SiO2 , B2O3} and _P2O5 to the content of _ZrO2 is 5.00 _or less _; ,
Mass _ratio of the total content of Nb2O5 , TiO2 _and ZrO2 _{to the total content} of SiO2 _{and B2O3} [ ₍ Nb2O5 ₊ TiO2 + ZrO2 ₎ / ( _SiO2 + _{B2O3 )} ] is 1.00 or less . SiO ₂ The optical glass according to claim 4, wherein the content of is 31% by mass or more. Nb ₂ O. _Five The optical glass according to claim 4 or 5, wherein the content of is 31% by mass or less. Nb ₂ O. _Five , TiO ₂ , Bi ₂ O. ₃ , WO ₃ and Ta ₂ O. _Five SiO relative to the total content of ₂ , B ₂ O. ₃ and P ₂ O. _Five The mass ratio of the total content of [(SiO ₂ +B ₂ O. ₃ +P ₂ O. _Five )/(Nb ₂ O. _Five +TiO ₂ +Bi ₂ O. ₃ +WO ₃ +Ta ₂ O. _Five )] is 1.20 or more, the optical glass according to any one of claims 4 to 6. SiO ₂ , B ₂ O. ₃ and P ₂ O. _Five total content of [SiO ₂ +B ₂ O. ₃ +P ₂ O. _Five ] is 39.0% by mass or more, the optical glass according to any one of claims 4 to 7. Li ₂ O, Na ₂ O and K ₂ Total content of O R ₂ SiO to O ₂ , B ₂ O. ₃ and P ₂ O. _Five and the mass ratio of the total content of ZrO ₂ Nb for the content of ₂ O. _Five and the mass ratio of the content [{(SiO ₂ +B ₂ O. ₃ +P ₂ O. _Five )/R ₂ O} + (Nb ₂ O. _Five /ZrO ₂ )] is 6.20 or less, the optical glass according to any one of claims 4 to 8. Nb ₂ O. _Five , TiO ₂ , Bi ₂ O. ₃ , WO ₃ and Ta ₂ O. _Five total content [Nb ₂ O. _Five +TiO ₂ +Bi ₂ O. ₃ +WO ₃ +Ta ₂ O. _Five ] is 31.0 mass % or less, the optical glass according to any one of claims 4 to 9. Claims 1 to 10 , wherein the mass ratio [Na ₂ O/R ₂ O] of the content of Na ₂ O to the total content R ₂ O of Li ₂ O, Na 2 O and K 2 O _is 0.80 or _less . The optical glass according to any one of 1. Mass ratio of the total content _{R2O of Li2O} , _Na2O and _{K2O to the total content of SiO2, B2O3 and P2O5 , and Li2O , Na2O and K2} Sum of mass ratios of Na ₂ O content to total O content R ₂ O [{R ₂ O/(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )} + (Na ₂ O/R ₂ O) ] is 1.30 or less, the optical glass according to any one of claims 1 to 11 . The mass ratio [R ₂ O/ZrO ₂ ] of the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O to the content of ZrO 2 _is 2.00 or less. The optical glass according to 1. An optical element comprising the optical glass according to any one of claims 1 to 13 .