JP7086726B2 - Optical glass and optical elements - Google Patents

Description

The present invention relates to optical glass and optical elements.

Patent Document 1 discloses an optical glass having a refractive index nd of 1.674 or more and an Abbe number νd of 30.2 or more. However, the optical glass described in Patent Document 1 has low homogeneity, does not satisfy the conditions of low specific density and low Pg, F. Therefore, an optical glass having a desired optical constant and higher performance is desired.

Japanese Unexamined Patent Publication No. 2017-105702

The optical element mounted on the autofocus type optical system is required to be lightweight in order to reduce the power consumption when driving the autofocus function. If the specific gravity of glass can be reduced, the weight of an optical element such as a lens can be reduced. Further, in order to correct chromatic aberration, it is required that the partial dispersion ratios Pg and F are small.

Therefore, an object of the present invention is to provide an optical glass having a desired optical constant, a relatively small specific gravity, and a small partial dispersion ratios Pg and F, and an optical element made of the optical glass.

The gist of the present invention is as follows.
(1) The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.65. big,
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
Optical glass that satisfies one or more of the following (a) and (b);
(A) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 9% by mass.
(B) Mass of total content R ₂ O with respect to total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.6.

(2) The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.65. big,
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
The mass ratio of the content of Ta ₂ O ₅ to the total content of TiO ₂ and Nb ₂ O ₅ [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] is smaller than 0.3.
Optical glass that satisfies one or more of the following (c) and (d);
(C) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 1.1% by mass.
(D) Total content of Li ₂ O, Na ₂ O and K ₂ O Mass of total content R ₂ O with respect to total content of R ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.05.

(3) The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.65. big,
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
The mass ratio of the ZnO content to the Nb ₂ O ₅ content [ZnO / Nb ₂ O ₅ ] is less than 0.14.
Optical glass that satisfies one or more of the following (e) and (f);
(E) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 1.1% by mass.
(F) Mass of total content R ₂ O with respect to total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.05.

(4) The Abbe number νd is 30 to 36,
The specific density is 3.19 or less,
An optical glass having a partial dispersion ratio Pg and F deviation ΔPg and F of 0.0015 or less.

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

According to the present invention, it is possible to provide an optical glass having a desired optical constant, a relatively small specific gravity, and a small partial dispersion ratios Pg and F, and an optical element made of the optical glass.

Hereinafter, embodiments of the present invention will be described. In addition, in this invention and this specification, the glass composition of an optical glass is shown by an oxide standard unless otherwise specified. Here, the "oxide-based glass composition" refers to a glass composition obtained by converting all glass raw materials into those that are decomposed at the time of melting and exist as oxides in optical glass, and the notation of each glass component is Following the custom, it is described as SiO ₂ , TiO ₂ , and the like. Unless otherwise specified, the content and total content of glass components are based on mass, and "%" means "% by mass".

The content of the glass component can be quantified by a known method, for example, an inductively coupled plasma emission spectroscopic analysis method (ICP-AES), an inductively coupled plasma mass spectrometry method (ICP-MS), or the like. Further, in the present specification and the present invention, the content of the constituent component is 0%, which means that the constituent component is substantially not contained, and the component is allowed to be contained at an unavoidable impurity level.

Further, in the present specification, the refractive index refers to the refractive index nd at the d-line (wavelength 587.56 nm) of helium unless otherwise specified.

The Abbe number νd is used as a value representing the property related to the variance, and is expressed by the following equation. 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 ratios Pg and F are expressed as follows using the refractive indexes ng, nF and nC of the g-line, F-line and c-line.
Pg, F = (ng-nF) / (nF-nC)
The normal line is represented by the following equation in a plane having the Abbe number νd on the horizontal axis and the partial dispersion ratios Pg and F on the vertical axis.
Pg, F (0) = 0.6483- (0.0018 × νd)
Further, the deviations ΔPg and F of the partial dispersion ratios Pg and F from the normal line are expressed as follows.
ΔPg, F = Pg, F-Pg, F (0)

Hereinafter, the optical glass of the present invention will be described as a first embodiment, a second embodiment, a third embodiment, and a fourth embodiment. The actions and effects of each glass component in the second, third, and fourth embodiments are the same as the actions and effects of each glass component in the first embodiment. Therefore, in the second, third, and fourth embodiments, matters that overlap with the description of the first embodiment will be omitted as appropriate.

1st Embodiment The optical glass according to the 1st embodiment is
The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.65. big,
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
Further, one or more of the following (a) and (b) is satisfied.
(A) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 9% by mass.
(B) Mass of total content R ₂ O with respect to total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.6.

In the optical glass according to the first embodiment, the mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05. The lower limit of the mass ratio [SiO ₂ / Nb ₂ O ₅ ] is preferably 1.09, and more preferably 1.11, 1.15, and 1.17 in that order. The upper limit of the mass ratio [SiO ₂ / Nb ₂ O ₅ ] is preferably 2.10, and more preferably 2.05, 2.00, and 1.95 in that order. By setting the mass ratio [SiO ₂ / Nb ₂ O ₅ ] in the above range, it is possible to maintain a desired optical constant (refractive index nd, Abbe number νd) while reducing the specific gravity of the glass.

In the optical glass according to the first embodiment, the mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25. The lower limit of the mass ratio [ZrO ₂ / Nb ₂ O ₅ ] is preferably 0.26, and further 0.27, 0.28, 0.29, 0.30, 0.305, 0.310, 0. It is more preferable in the order of .315. The upper limit of the mass ratio [ZrO ₂ / Nb ₂ O ₅ ] is preferably 0.65, and more preferably 0.61, 0.57, and 0.53 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 ratios Pg and F can be reduced, the raw material cost can be reduced, and the desired optical constant and solubility can be maintained.

In the optical glass according to the first embodiment, the mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B). ₂ O ₃ )] is greater than 0.65. The lower limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 0.66, and further 0.67, 0.70, 0.73, 0.76. , 0.80, 0.83, 0.86, 0.88, in that order. The upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 1.20, and further, in the order of 1.14, 1.12, 1.10. More preferred. By setting the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] in the above range, the thermal stability of the glass can be maintained and a desired optical constant can be obtained.

In the optical glass according to the first embodiment, the total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10%. The upper limit of the total content [TiO ₂ + BaO] is preferably 8.0%, more preferably 7.8%, 7.6%, and 7.4% in that order. The lower limit of the total content [TiO ₂ + BaO] is preferably 0%, more preferably 1%, 2%, and 3%. By setting the upper limit of the total content [TiO ₂ + BaO] to the above range, the partial dispersion ratios Pg and F can be reduced, and the specific gravity of the glass can be reduced.

The optical glass according to the first embodiment satisfies one or more of the following (a) and (b).
(A) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 9%.
(B) Mass of total content R ₂ O with respect to total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.6.

That is, in the optical glass according to the first embodiment, the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O may be larger than 9%. The lower limit of the _total content R2O is preferably 15.0%, more preferably 15.5%, 16.0%, and 16.5% in that order. The upper limit of the _total content R2O is preferably 22.0%, more preferably 21.7%, 21.4%, and 21.1%. By setting the _total content R2O in the above range, the specific gravity of the glass can be reduced and the stability of the glass during reheating can be maintained.

Further, in the optical glass according to the first embodiment, the total content of Li ₂ O, Na ₂ O and K ₂ O is R ₂ O and the total content of MgO, CaO, SrO and BaO is R'O. The mass ratio of the total content R ₂ O to R 2 O [R ₂ O / (R ₂ O + R'O]] may be larger than 0.6. The lower limit of the mass ratio [R ₂ O / (R ₂ O + R'O)] is It is preferably 0.80, more preferably 0.82, 0.84, and 0.86, and the upper limit of the mass ratio [R ₂ O / (R ₂ O + R'O)] is preferable. It is 0.95, more preferably 0.98, 0.99, and 1.00. By setting the mass ratio [R ₂ O / (R ₂ O + R'O)] in the above range, the specific gravity of the glass is set. Can be reduced and the stability of the glass during reheating can be maintained.

In the optical glass according to the first embodiment, the mass ratio of the content of Ta ₂ O ₅ to the total content of TiO ₂ and Nb ₂ O ₅ [Ta ₂ O ₅ / (TIO ₂ + Nb ₂ O ₅ )] is preferable. Is less than 0.3, and the upper limit thereof is more preferably 0.25, 0.25, and 0.15 in that order. The lower limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] is preferably 0, and more preferably 0.05, 0.07, and 0.10. The mass ratio [Ta ₂ O ₅ / (TIO ₂ + Nb ₂ O ₅ )] may be 0. By setting the upper limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] to the above range, the specific gravity of the glass can be reduced and the raw material cost can be reduced.

In the optical glass according to the first embodiment, the mass ratio [ZnO / Nb ₂ O ₅ ] of the ZnO content to the Nb ₂ O ₅ content is preferably less than 0.14, and the upper limit thereof is 0.125. , 0.115, 0.105 are more preferable. The lower limit of the mass ratio [ZnO / Nb _{2O 5} ] is preferably 0, and more preferably 0.02, 0.05, and 0.07. The mass ratio [ZnO / Nb ₂ O ₅ ] may be 0. By setting the upper limit of the mass ratio [ZnO / Nb ₂ O ₅ ] to the above range, the specific gravity of the glass can be reduced and a desired optical constant can be obtained.

The contents and ratios of 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 lower limit of the content of SiO ₂ is preferably 25%, more preferably 28%, 30%, and 32% in that order. The upper limit of the content of SiO ₂ is preferably 45%, more preferably 43%, 41%, and 39% in that order. By setting the content of SiO ₂ in the above range, the specific gravity of the glass can be reduced, the stability of the glass during reheating can be improved, and the desired optical constant can be obtained.

In the optical glass according to the first embodiment, the upper limit of the content of B ₂ O ₃ is preferably 5%, more preferably 4%, 3%, and 2%. The lower limit of the content of B ₂ O ₃ is preferably 0%, more preferably 0.2%, 0.4%, and 0.6% in that order. The content of B ₂ O ₃ may be 0%. By setting the content of B ₂ O ₃ in the above range, the specific gravity of the glass can be reduced and the thermal stability of the glass can be improved.

In the optical glass according to the first embodiment, the upper limit of the total content [SiO ₂ + B ₂ O ₃ ] of SiO ₂ and B ₂ O ₃ is preferably 45%, and further 43%, 41%, 39%. It is more preferable in the order of. The lower limit of the total content [SiO ₂ + B ₂ O ₃ ] is preferably 25%, more preferably 28%, 30%, and 32% in that order. By setting the total content [SiO ₂ + B ₂ O ₃ ] in the above range, the specific gravity of the glass is reduced, the thermal stability of the glass is improved, and the desired optical constant can be obtained.

In the optical glass according to the first embodiment, the upper limit of the content of P2 O ₅ is preferably _1.5 %, more preferably 1.3%, 1.1%, and 0.9% in that order. .. The lower limit of the content of P ₂ O ₅ is preferably 0%, more preferably 0.1%, 0.2%, and 0.3% in that order. The content of P ₂ O ₅ may be 0%. By setting the content of P ₂ O ₅ in the above range, it is possible to suppress an increase in the partial dispersion ratios Pg and F and maintain the thermal stability of the glass.

In the glass according to the first embodiment, the upper limit of the content of Al ₂ O ₃ is preferably 5%, more preferably 4%, 3%, and 2%. The content of Al ₂ O ₃ may be 0%. By setting the content of Al ₂ O ₃ in 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 TiO ₂ content is preferably 10%, more preferably 9.5%, 9.0%, and 8.5% in that order. The lower limit of the TiO ₂ content is preferably 0%. The content of TiO ₂ may be 0%. By setting the content of TiO ₂ in the above range, a desired optical constant can be realized and the raw material cost of glass can be reduced.

In the optical glass according to the first embodiment, the lower limit of the content of Nb ₂ O ₅ is preferably 18%, more preferably 20%, 22%, and 24% in that order. The upper limit of the content of Nb ₂ O ₅ is preferably 38%, more preferably 35%, 33%, and 31% in that order. By setting the content of Nb ₂ O ₅ in the above range, a desired optical constant can be realized, an increase in specific gravity can be suppressed, and partial dispersion ratios Pg and F can be reduced.

In the optical glass according to the first embodiment, the lower limit of the total content [TiO ₂ + Nb ₂ O ₅ ] of TiO ₂ and Nb ₂ O ₅ is preferably 25%, and further 29%, 30%, and 31%. It is more preferable in the order of. The upper limit of the total content [TiO ₂ + Nb ₂ O ₅ ] is preferably 42%, more preferably 40%, 38%, and 36% in that order. By setting the total content [TiO ₂ + Nb ₂ O ₅ ] in the above range, a desired optical constant can be realized.

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%. The content of WO ₃ may be 0%. By setting the upper limit of the content of WO ₃ to the above range, the transmittance can be increased, and the partial dispersion ratios Pg, F and the specific gravity can be reduced.

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

In the glass according to the first embodiment, the lower limit of the content of ZrO ₂ is preferably 5%, more preferably 6%, 7%, and 8% in that order. 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 in the above range, a desired optical constant can be realized and the partial dispersion ratios Pg and F can be reduced.

In the glass according to the first embodiment, the upper limit of the Li ₂ O content is preferably 10%, more preferably 9%, 8%, and 7% in that order. The lower limit of the Li ₂ O content is preferably 2%, more preferably 3%, 4%, and 5%. By setting the Li ₂ O content in the above range, a desired optical constant can be realized, and chemical durability, weather resistance, and stability during reheating can be maintained.

In the glass according to the first embodiment, the upper limit of the Na ₂ O content is preferably 18%, more preferably 15%, 14%, and 13% in that order. The lower limit of the Na ₂ O content is preferably 8%, more preferably 9%, 10%, and 11% in that order.

In the glass according to the first embodiment, the upper limit of the K2O content is preferably 4.0%, more preferably 3.0%, _2.5 %, and 2.0% in that order. The lower limit of the content of K2O is preferably ₀ %, more preferably 0.2%, 0.4%, and 0.6% in that order. The content of K2O may be ₀ %.

Na ₂ O and K ₂ O are components that reduce the partial dispersion ratios Pg and F, and have the function of lowering the liquidus temperature and improving the thermal stability of the glass. Chemical durability and weather resistance are reduced. Therefore, it is preferable that the contents of Na ₂ O and K ₂ O are in the above range.

In the glass according to the first embodiment, the upper limit of the content of Cs ₂ O is preferably 5%, more preferably 3%, 1%, and 0.5% in that order. The lower limit of the content of Cs ₂ O is preferably 0%.

Cs ₂ O has a function of improving the thermal stability of glass, but when the content thereof is increased, the chemical durability and weather resistance are lowered. Therefore, each content of Cs ₂ O is preferably in the above range.

In the glass according to the first embodiment, the upper limit of the MgO content is preferably 10%, more preferably 5%, 3%, and 1%. The lower limit of the MgO content is preferably 0%. The content of MgO may be 0%.

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

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

In the optical glass according to the first embodiment, the upper limit of the BaO content is preferably 10%, more preferably 5%, 3%, and 1%. The lower limit of the BaO content is preferably 0%. The BaO content may be 0%. By setting the BaO content in the above range, an increase in the specific gravity can be suppressed.

MgO, CaO, SrO, and BaO are all glass components having a function of improving the thermal stability and devitrification resistance of the glass. However, when the content of these glass components is increased, the specific gravity is increased, the high dispersibility is impaired, and the thermal stability and devitrification resistance of the glass are lowered. Therefore, the content of each of these glass components is preferably in the above range.

In the glass according to the first embodiment, the upper limit of the total content R'O of MgO, CaO, SrO and BaO is preferably 10%, more preferably 4%, 2% and 1%. The lower limit of the total content R'O is preferably 0%. The total content R'O may be 0%. By setting the total content R'O in the above range, it is possible to suppress an increase in specific gravity and maintain thermal stability without hindering high dispersion.

In the glass according to the first embodiment, the upper limit of the ZnO content is preferably 10%, more preferably 3%, 2.5%, and 2% in that order. The lower limit of the ZnO content is preferably 0%.

ZnO is a glass component having a function of improving the thermal stability of glass. However, if the ZnO content is too high, the specific gravity will increase. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining the desired optical constant, the ZnO content is preferably in the above range.

In the optical glass according to the first embodiment, the upper limit of the content of La ₂ O ₃ is preferably 10%, more preferably 5%, 3%, and 1% in that order. Further, the lower limit of the content of La ₂ O ₃ is preferably 0%, and the content of La ₂ O ₃ may be 0%. By setting the content of La ₂ O ₃ in the above range, a desired optical constant can be realized, an increase in specific gravity can be suppressed, and partial dispersion ratios Pg and F can be reduced.

In the glass according to the first embodiment, the upper limit of the content of Y2O3 is preferably ₁₀ %, more preferably 5%, ₃ %, and 1% in that order. The lower limit of the content of Y ₂ O ₃ is preferably 0%.

If the content of Y2O3 is too _{high ,} the thermal stability of the glass will decrease, and the glass will easily devitrify during production. Therefore _, the content of _Y2O3 is preferably in the above range from the viewpoint of suppressing the decrease in thermal stability of the glass.

In the glass according to the first embodiment, the upper limit of the content of Ta ₂ O ₅ is preferably 20%, more preferably 10%, 5%, 3%, 1%, and 0.5% in that order. The lower limit of the content of Ta ₂ O ₅ is preferably 0%.

Ta ₂ O ₅ is a glass component having a function of improving the thermal stability of glass, and is a component of lowering the partial dispersion ratios Pg and F. On the other hand, when the content of Ta ₂ O ₅ is large, the thermal stability of the glass is lowered, and when the glass is melted, unmelted glass raw materials are likely to occur. In addition, the specific density increases. Therefore, the content of Ta ₂ O ₅ is preferably in the above range.

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

In the glass according to the first embodiment, the content of HfO ₂ is preferably 2% or less. The lower limit of the HfO ₂ content is preferably 0%, more preferably 0.05% and then 0.1%.

Sc ₂ O ₃ and HfO ₂ have a function of enhancing the high dispersibility of glass, but are expensive components. Therefore, the contents of Sc ₂ O ₃ and HfO ₂ are preferably in the above range.

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

Lu ₂ O ₃ has a function of enhancing the high dispersibility of glass, but is also a glass component that increases the specific gravity of glass due to its large molecular weight. Therefore, the content of Lu ₂ O ₃ is preferably in the above range.

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

GeO ₂ has a function of enhancing the high dispersibility of glass, but is a prominently 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 in the above range.

In the glass according to the first embodiment, the content of Gd ₂ O ₃ is preferably 2% or less. 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 decrease. Further, if the content of Gd ₂ O ₃ becomes too large, the specific gravity of the glass increases. Therefore, the content of Gd ₂ O ₃ is preferably in 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. The lower limit of the content of Yb ₂ O ₃ is preferably 0%.

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

Further, if the content of Yb ₂ O ₃ is too large, the thermal stability of the glass is lowered. The content of Yb ₂ O ₃ is preferably in the above range from the viewpoint of preventing a decrease in the thermal stability of the glass and suppressing an increase in the specific gravity.

The glass according to the first embodiment mainly has the above-mentioned glass components, that is, SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , Al ₂ O ₃ , TIO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ . , ZrO ₂ , Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O, MgO, CaO, SrO, BaO, ZnO, La ₂ O ₃ , Y ₂ O ₃ , Ta ₂ O ₅ , Sc ₂ O ₃ , It is preferably composed of HfO ₂ , Lu ₂ O ₃ , GeO ₂ , Gd ₂ O ₃ and Yb ₂ O ₃ , and the total content of the above-mentioned glass components is preferably more than 95%, 98. It is more preferably more than%, more preferably more than 99%, and even more preferably more than 99.5%.

It is preferable that the glass according to the present embodiment is basically composed of the above glass components, but other components may be contained as long as the effects of the present invention are not impaired. Further, in the present invention, the inclusion of unavoidable impurities is not excluded.

(Other ingredients)
In addition to the above components, the above optical glass may also contain a small amount of Sb ₂ O ₃ , CeO ₂ , etc. as a clarifying agent. The total amount of the clarifying agent (the amount added to the external split) is preferably 0% or more and less than 1%, and more preferably 0% or more and 0.5% or less.

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

Pb, Cd, As, Th and the like are components that are concerned about environmental load. Therefore, the contents of PbO, CdO, and ThO ₂ , respectively, are preferably 0 to 0.1%, more preferably 0 to 0.05%, and 0 to 0.01%, respectively. Is more preferable, and it is particularly preferable that PbO, CdO, and ThO ₂ are not substantially contained.

The content of As ₂ O ₃ is preferably 0 to 0.1%, more preferably 0 to 0.05%, further preferably 0 to 0.01%, and As ₂ O. It is particularly preferable that ₃ is not substantially contained.

Further, the optical glass can obtain high transmittance over a wide range of the visible region. In order to take advantage of these features, it is preferable that they do not contain coloring elements. Examples of the coloring element include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, and V. Each element is preferably less than 100 mass ppm, more preferably 0 to 80 mass ppm, further preferably 0 to 50 mass ppm, and particularly preferably not substantially contained.

Further, Ga, Te, Tb and the like are components that do not need to be introduced and are also expensive components. Therefore, the range of the contents of Ga ₂ O ₃ , TeO ₂ , and TbO ₂ in terms of mass% is preferably 0 to 0.1%, and more preferably 0 to 0.05%, respectively. It is preferable that it is 0 to 0.01%, more preferably 0 to 0.005%, further preferably 0 to 0.001%, and substantially not contained. Especially preferable.

(Glass characteristics)
<Refractive index nd>
In the optical glass according to the first embodiment, the refractive index nd is preferably 1.69 to 1.76. The refractive index nd can also be 1.695 to 1.755, or 1.70 to 1.75. The 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 . The 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.

<Abbe number νd>
In the optical glass according to the first embodiment, the Abbe number νd is preferably 30 to 36. The Abbe number νd can also be 30.5 to 35.8, or 31 to 35.5. The components that relatively lower the Abbe number νd are Nb ₂ O ₅ , TIO ₂ , ZrO ₂ , and Ta ₂ O ₅ . The 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 content of these components.

<Specific gravity of glass>
The specific gravity of the optical glass according to the first embodiment is preferably 3.19 or less, more preferably 3.18 or less, 3.17 or less, and 3.16 or less in that order. The smaller the specific density is, the more preferable it is, and the lower limit is not particularly limited, but it is generally about 3.05. The components having a relatively high specific gravity are BaO, La ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and the like. The components that relatively lower the specific gravity are 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.

<Partial dispersion ratio Pg, F>
The upper limit of the partial dispersion ratios Pg and F of the optical glass according to the first embodiment is preferably 0.5950, and more preferably 0.5945, 0.5940, and 0.5935 in that order. The lower limit of the partial dispersion ratios Pg and F is preferably 0.5780, and more preferably 0.5785, 0.5790, 0.5795, 0.5805, 0.5815, and 0.5830. By setting the partial dispersion ratios Pg and F in the above range, optical glass suitable for high-order chromatic aberration correction can be obtained.

Further, the upper limit of the deviation ΔPg, F of the partial dispersion ratio Pg, F of the optical glass according to the first embodiment is preferably 0.0015, and further, in the order of 0.0012, 0.0010, 0.0008. preferable. The lower limit of the deviation ΔPg, F is preferably -0.0060, and further, -0.0048, -0.0045, -0.0042, -0.0040, -0.0035, -0.0025. Is more preferable in the order of.

<Liquid phase temperature>
The liquidus temperature LT of the optical glass according to the first embodiment is preferably 1200 ° C. or lower, more preferably 1190 ° C. or lower, 1180 ° C. or lower, and 1170 ° C. or lower. By setting the liquid phase temperature within the above range, the melting and molding temperature of the glass can be lowered, and as a result, the corrosion of the glass melting device (for example, a pit, a stirring device for the molten glass, etc.) in the melting step can be reduced. .. The lower limit of the liquidus temperature LT is not particularly limited, but is generally about 1000 ° C. The liquidus temperature LT is determined by the balance of the contents of all glass components. Among them, the content of SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, etc. has a large influence on the liquid phase temperature LT.

The liquidus temperature is determined as follows. 10 cc (10 ml) of glass is put into a platinum crucible, melted at 1250 ° C to 1400 ° C for 15 to 30 minutes, cooled to a glass transition temperature of 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 holding temperature is 1000 ° C. or higher in 5 ° C. or 10 ° C. increments, and after holding for 2 hours, the glass is cooled and the presence or absence of crystals inside the glass is observed with a 100x optical microscope. The lowest temperature at which crystals do not precipitate is defined as the liquidus temperature.

<Glass transition temperature Tg>
The upper limit of the glass transition temperature Tg of the optical glass according to the first embodiment is preferably 580 ° C, more preferably 575 ° C, 570 ° C, and 565 ° C. The lower limit of the glass transition temperature Tg is preferably 510 ° C, more preferably 515 ° C, 520 ° C, and 525 ° C. The components that relatively lower the glass transition temperature Tg are Li ₂ O, Na ₂ O, K ₂ O, and the like. The components that relatively increase the glass transition temperature Tg are La ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , and the like. The glass transition temperature Tg can be controlled by appropriately adjusting the content of these components.

<Stability during reheating>
In the optical glass according to the first embodiment, the number of crystals observed per gram when heated at a glass transition temperature Tg for 10 minutes and further heated at a temperature 140 to 250 ° C. higher than the Tg for 10 minutes is preferable. Is 20 or less, more preferably 10 or less.

The stability during reheating is measured as follows. A glass sample having a size of 1 cm × 1 cm × 0.8 cm is heated for 10 minutes in a first test furnace set to a glass transition temperature Tg of the glass sample, and further 140 to 250 ° C. higher than the glass transition temperature Tg. After heating for 10 minutes in a second test furnace set to a temperature, 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. Also, visually check for cloudiness of the glass.

(Manufacturing of optical glass)
The optical glass according to the first embodiment may be produced by blending a glass raw material so as to have the above-mentioned predetermined composition and using the blended glass raw material according to a known glass manufacturing method. For example, a plurality of kinds of compounds are mixed and sufficiently mixed to obtain a batch raw material, and the batch raw material is placed in a quartz crucible or a platinum crucible for rough melting. The melt obtained by crude melting is rapidly cooled and crushed to prepare a cullet. Further, the cullet is placed in a platinum crucible, heated and remelted to obtain molten glass, and after further clarification and homogenization, the molten glass is formed and slowly cooled to obtain an optical glass. A known method may be applied to the molding and slow cooling of the molten glass.

As long as a desired glass component can be introduced into the glass so as to have a desired content, the compound used when formulating the batch raw material is not particularly limited, but as such a compound, oxides and carbonates are used. Examples thereof include salts, nitrates, hydroxides and fluorides.

(Manufacturing of optical elements, etc.)
In order to manufacture an optical element using the optical glass according to the first embodiment, a known method may be applied. For example, in the production of the above optical glass, the molten glass is poured into a mold and formed into a plate shape to produce a glass material made of 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 and 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, and the optical element is manufactured by grinding and polishing by a known method.

The optical 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, it is possible to provide an optical element made of the above optical glass. Examples of the type of optical element include a spherical lens, a lens such as an aspherical lens, a prism, a diffraction grating, and the like. As the shape of the lens, various shapes such as a biconvex lens, a plano-convex lens, a biconcave lens, a plano-concave lens, a convex meniscus lens, and a concave meniscus lens can be exemplified. The 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, and polishing. By using the above glass during such processing, damage can be reduced and high-quality optical elements can be stably supplied.

2nd Embodiment The optical glass according to the 2nd embodiment is
The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.65. big,
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
The mass ratio of the content of Ta ₂ O ₅ to the total content of TiO ₂ and Nb ₂ O ₅ [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] is smaller than 0.3.
Further, one or more of the following (c) and (d) is satisfied.
(C) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 1.1% by mass.
(D) Total content of Li ₂ O, Na ₂ O and K ₂ O Mass of total content R ₂ O with respect to total content of R ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.05.

In the optical glass according to the second embodiment, the mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05. The lower limit of the mass ratio [SiO ₂ / Nb ₂ O ₅ ] is preferably 1.09, and more preferably 1.11, 1.15, and 1.17 in that order. The upper limit of the mass ratio [SiO ₂ / Nb ₂ O ₅ ] is preferably 2.10, and more preferably 2.05, 2.00, and 1.95 in that order. By setting the mass ratio [SiO ₂ / Nb ₂ O ₅ ] in the above range, it is possible to maintain a desired optical constant (refractive index nd, Abbe number νd) while reducing the specific gravity of the glass.

In the optical glass according to the second embodiment, the mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25. The lower limit of the mass ratio [ZrO ₂ / Nb ₂ O ₅ ] is preferably 0.26, and further 0.27, 0.28, 0.29, 0.30, 0.305, 0.310, 0. It is more preferable in the order of .315. The upper limit of the mass ratio [ZrO ₂ / Nb ₂ O ₅ ] is preferably 0.65, and more preferably 0.61, 0.57, and 0.53 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 ratios Pg and F can be reduced, the raw material cost can be reduced, and the desired optical constant and solubility can be maintained.

In the optical glass according to the second embodiment, the mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B). ₂ O ₃ )] is greater than 0.65. The lower limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 0.66, and further 0.67, 0.70, 0.73, 0.76. , 0.80, 0.83, 0.86, 0.88, in that order. The upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 1.20, and further, in the order of 1.14, 1.12, 1.10. More preferred. By setting the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] in the above range, the thermal stability of the glass can be maintained and a desired optical constant can be obtained.

In the optical glass according to the second embodiment, the total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10%. The upper limit of the total content [TiO ₂ + BaO] is preferably 8.0%, more preferably 7.8%, 7.6%, and 7.4% in that order. The lower limit of the total content [TiO ₂ + BaO] is preferably 0%, more preferably 1%, 2%, and 3%. By setting the upper limit of the total content [TiO ₂ + BaO] to the above range, the partial dispersion ratios Pg and F can be reduced, and the specific gravity of the glass can be reduced.

In the optical glass according to the second embodiment, the mass ratio of the content of Ta ₂ O ₅ to the total content of TiO ₂ and Nb ₂ O ₅ [Ta ₂ O ₅ / (TIO ₂ + Nb ₂ O ₅ )] is 0. Less than 3. The upper limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] is preferably 0.25, and more preferably 0.20 and 0.15. The lower limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] is preferably 0, and more preferably 0.05, 0.07, and 0.10. The mass ratio [Ta ₂ O ₅ / (TIO ₂ + Nb ₂ O ₅ )] may be 0. By setting the upper limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] to the above range, the specific gravity of the glass can be reduced and the raw material cost can be reduced.

The optical glass according to the second embodiment satisfies one or more of the following (c) and (d).
(C) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 1.1%.
(D) Total content of Li ₂ O, Na ₂ O and K ₂ O Mass of total content R ₂ O with respect to total content of R ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.05.

That is, in the optical glass according to the second embodiment, the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O can be made larger than 1.1%. The _total content R2O is preferably larger than 9%, and the lower limit thereof is more preferably 15.0%, 15.5%, 16.0%, and 16.5% in that order. The upper limit of the _total content R2O is preferably 22.0%, more preferably 21.7%, 21.4%, and 21.1%. By setting the _total content R2O in the above range, the specific gravity of the glass can be reduced and the stability of the glass during reheating can be maintained.

Further, in the optical glass according to the second embodiment, the total content of Li ₂ O, Na ₂ O and K ₂ O is R ₂ O and the total content of MgO, CaO, SrO and BaO is R'O. The mass ratio of total content R ₂ O to R 2 O [R ₂ O / (R ₂ O + R'O)] can be made larger than 0.05. The mass ratio [R ₂ O / (R ₂ O + R'O)] is preferably larger than 0.6, and the lower limit thereof is more preferably 0.80, 0.82, 0.84, 0.86 in that order. The upper limit of the mass ratio [R ₂ O / (R ₂ O + R'O)] is preferably 1.00, and more preferably 0.99, 0.98, 0.95 in that order. By setting the mass ratio [R ₂ O / (R ₂ O + R'O)] to the above range, the specific gravity of the glass can be reduced and the stability of the glass during reheating can be maintained.

In the optical glass according to the second embodiment, the mass ratio [ZnO / Nb ₂ O ₅ ] of the ZnO content to the Nb ₂ O ₅ content is preferably less than 0.14, and the upper limit thereof is 0.125. , 0.115, 0.105 are more preferable. The lower limit of the mass ratio [ZnO / Nb _{2O 5} ] is preferably 0, and more preferably 0.02, 0.05, and 0.07. The mass ratio [ZnO / Nb ₂ O ₅ ] may be 0. By setting the upper limit of the mass ratio [ZnO / Nb ₂ O ₅ ] to the above range, the specific gravity of the glass can be reduced and a desired optical constant can be obtained.

In the optical glass according to the second embodiment, the content and ratio of glass components other than the above can be the same as those in the first embodiment. Further, the glass characteristics, the production of the optical glass, the production of the optical element and the like in the second embodiment can be the same as those in the first embodiment.

Third Embodiment The optical glass according to the third embodiment is
The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.65. big,
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
The mass ratio of the ZnO content to the Nb ₂ O ₅ content [ZnO / Nb ₂ O ₅ ] is less than 0.14.
Further, one or more of the following (e) and (f) is satisfied.
(E) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 1.1% by mass.
(F) Mass of total content R ₂ O with respect to total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.05.

In the optical glass according to the third embodiment, the mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05. The lower limit of the mass ratio [SiO ₂ / Nb ₂ O ₅ ] is preferably 1.09, and more preferably 1.11, 1.15, and 1.17 in that order. The upper limit of the mass ratio [SiO ₂ / Nb ₂ O ₅ ] is preferably 2.10, and more preferably 2.05, 2.00, and 1.95 in that order. By setting the mass ratio [SiO ₂ / Nb ₂ O ₅ ] in the above range, it is possible to maintain a desired optical constant (refractive index nd, Abbe number νd) while reducing the specific gravity of the glass.

In the optical glass according to the third embodiment, the mass ratio [ZrO ₂ / Nb ₂ O ₅ ] of the content of ZrO ₂ to the content of Nb ₂ O ₅ is larger than 0.25. The lower limit of the mass ratio [ZrO ₂ / Nb ₂ O ₅ ] is preferably 0.26, and further 0.27, 0.28, 0.29, 0.30, 0.305, 0.310, 0. It is more preferable in the order of .315. The upper limit of the mass ratio [ZrO ₂ / Nb ₂ O ₅ ] is preferably 0.65, and more preferably 0.61, 0.57, and 0.53 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 ratios Pg and F can be reduced, the raw material cost can be reduced, and the desired optical constant and solubility can be maintained.

In the optical glass according to the third embodiment, the mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B). ₂ O ₃ )] is greater than 0.65. The lower limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 0.66, and further 0.67, 0.70, 0.73, 0.76. , 0.80, 0.83, 0.86, 0.88, in that order. The upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 1.20, and further, in the order of 1.14, 1.12, 1.10. More preferred. By setting the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] in the above range, the thermal stability of the glass can be maintained and a desired optical constant can be obtained.

In the optical glass according to the third embodiment, the total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10%. The upper limit of the total content [TiO ₂ + BaO] is preferably 8.0%, more preferably 7.8%, 7.6%, and 7.4% in that order. The lower limit of the total content [TiO ₂ + BaO] is preferably 0%, more preferably 1%, 2%, and 3%. By setting the upper limit of the total content [TiO ₂ + BaO] to the above range, the partial dispersion ratios Pg and F can be reduced, and the specific gravity of the glass can be reduced.

In the optical glass according to the third embodiment, the mass ratio [ZnO / Nb ₂ O ₅ ] of the ZnO content to the Nb ₂ O ₅ content is smaller than 0.14. The upper limit of Nb ₂ O ₅ is preferably 0.125, and more preferably 0.115 and 0.105 in that order. The lower limit of the mass ratio [ZnO / Nb _{2O 5} ] is preferably 0, and more preferably 0.02, 0.05, and 0.07. The mass ratio [ZnO / Nb ₂ O ₅ ] may be 0. By setting the upper limit of the mass ratio [ZnO / Nb ₂ O ₅ ] to the above range, the specific gravity of the glass can be reduced and a desired optical constant can be obtained.

The optical glass according to the third embodiment satisfies one or more of the following (e) and (f).
(E) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 1.1%.
(F) Mass of total content R ₂ O with respect to total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.05.

That is, in the optical glass according to the third embodiment, the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O can be made larger than 1.1%. The _total content R2O is preferably larger than 9%, and the lower limit thereof is more preferably 15.0%, 15.5%, 16.0%, and 16.5% in that order. The upper limit of the _total content R2O is preferably 22.0%, more preferably 21.7%, 21.4%, and 21.1%. By setting the _total content R2O in the above range, the specific gravity of the glass can be reduced and the stability of the glass during reheating can be maintained.

Further, in the optical glass according to the third embodiment, the total content of Li ₂ O, Na ₂ O and K ₂ O is R ₂ O and the total content of MgO, CaO, SrO and BaO is R'O. The mass ratio of total content R ₂ O to R 2 O [R ₂ O / (R ₂ O + R'O)] can be made larger than 0.05. The mass ratio [R ₂ O / (R ₂ O + R'O)] is preferably larger than 0.6, and the lower limit thereof is more preferably 0.80, 0.82, 0.84, 0.86 in that order. The upper limit of the mass ratio [R ₂ O / (R ₂ O + R'O)] is preferably 0.95, and more preferably 0.98, 0.99, and 1.00 in that order. By setting the mass ratio [R ₂ O / (R ₂ O + R'O)] to the above range, the specific gravity of the glass can be reduced and the stability of the glass during reheating can be maintained.

In the optical glass according to the third embodiment, the mass ratio of the content of Ta ₂ O ₅ to the total content of TiO ₂ and Nb ₂ O ₅ [Ta ₂ O ₅ / (TIO ₂ + Nb ₂ O ₅ )] is preferable. Is less than 0.3, and the upper limit thereof is more preferably 0.25, 0.25, and 0.15 in that order. The lower limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] is preferably 0, and more preferably 0.05, 0.07, and 0.10. The mass ratio [Ta ₂ O ₅ / (TIO ₂ + Nb ₂ O ₅ )] may be 0. By setting the upper limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] to the above range, the specific gravity of the glass can be reduced and the raw material cost can be reduced.

In the optical glass according to the third embodiment, the content and ratio of the glass components other than the above can be the same as those of the first embodiment. Further, the glass characteristics, the production of the optical glass, the production of the optical element and the like in the third embodiment can be the same as those in the first embodiment.

Fourth Embodiment The optical glass according to the fourth embodiment is
The Abbe number νd is 30 to 36,
The specific density is 3.19 or less,
The deviations ΔPg and F of the partial dispersion ratios Pg and F are 0.0015 or less.

In the optical glass according to the fourth embodiment, the Abbe number νd is 30 to 36. The Abbe number νd can also be 30.5 to 35.8, or 31 to 35.5. The components that relatively lower the Abbe number νd are Nb ₂ O ₅ , TIO ₂ , ZrO ₂ , and Ta ₂ O ₅ . The 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 content of these components.

In the optical glass according to the fourth embodiment, the specific gravity is 3.19 or less. The specific gravity is preferably 3.18 or less, more preferably 3.17 or less, and more preferably 3.16 or less. The smaller the specific density is, the more preferable it is, and the lower limit is not particularly limited, but it is generally about 3.05.

In the optical glass according to the fourth embodiment, the deviations ΔPg and F of the partial dispersion ratios Pg and F are 0.0015 or less. The upper limit of the deviations ΔPg and F is preferably 0.0012, and more preferably 0.0010 and 0.0008 in that order. Further, the lower limit of the deviation ΔPg, F is preferably -0.0060, and further, -0.0048, -0.0045, -0.0042, -0.0040, -0.0035, -0.0025. Is more preferable in the order of.

In general, the partial dispersion ratios Pg and F tend to decrease as the Abbe number νd increases. Therefore, in the fourth embodiment, the partial dispersion ratios Pg and F are defined by using the ΔPg and F described above instead of the partial dispersion ratios Pg and F themselves. By setting ΔPg and F to 0.0015 or less in the Abbe number νd, it is possible to provide an optical glass suitable for high-order chromatic aberration correction. Further, when the specific gravity is 3.19 or less, the weight of the optical element can be reduced.

Next, preferred embodiments of the content and ratio of the glass component in the optical glass according to the fourth embodiment will be described in detail below.

In the optical glass according to the fourth embodiment, the mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is preferably larger than 1.05, and the lower limit thereof is 1. The order of 09, 1.11, 1.15, 1.17 is more preferable. The upper limit of the mass ratio [SiO ₂ / Nb ₂ O ₅ ] is preferably 1.50, and more preferably 1.48, 1.46, and 1.44 in that order. By setting the mass ratio [SiO ₂ / Nb ₂ O ₅ ] in the above range, it is possible to maintain a desired optical constant (refractive index nd, Abbe number νd) while reducing the specific gravity of the glass.

In the optical glass according to the fourth embodiment, the mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is preferably larger than 0.25, and the lower limit thereof is 0. 26, 0.27, 0.28, 0.29, 0.30, 0.305, 0.310, 0.315 are more preferable in this order. The upper limit of the mass ratio [ZrO ₂ / Nb ₂ O ₅ ] is preferably 0.50, and more preferably 0.47, 0.44, and 0.41 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 ratios Pg and F can be reduced, the raw material cost can be reduced, and the desired optical constant and solubility can be maintained.

In the optical glass according to the fourth embodiment, the mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B). ₂ O ₃ )] is preferably larger than 0.65, and its lower limit is 0.66, 0.67, 0.69, 0.71, 0.73, 0.76, 0.80, 0.83, The order of 0.86 and 0.88 is more preferable. The upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 1.20, and further, in the order of 1.14, 1.12, 1.10. More preferred. By setting the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] in the above range, the thermal stability of the glass can be maintained and a desired optical constant can be obtained.

In the optical glass according to the fourth embodiment, the total content of TiO ₂ and BaO [TiO ₂ + BaO] is preferably less than 10%, and the upper limit thereof is 8.0%, 7.8%, and 7.6%. , 7.4%, which is more preferable. The lower limit of the total content [TiO ₂ + BaO] is preferably 0%, more preferably 1%, 2%, and 3%. By setting the upper limit of the total content [TiO ₂ + BaO] to the above range, the partial dispersion ratios Pg and F can be reduced, and the specific gravity of the glass can be reduced.

In the optical glass according to the fourth embodiment, the mass ratio of the content of Ta ₂ O ₅ to the total content of TiO ₂ and Nb ₂ O ₅ [Ta ₂ O ₅ / (TIO ₂ + Nb ₂ O ₅ )] is preferable. Is less than 0.3, and the upper limit thereof is more preferably 0.25, 0.25, and 0.15 in that order. The lower limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] is preferably 0, and more preferably 0.05, 0.07, and 0.10. The mass ratio [Ta ₂ O ₅ / (TIO ₂ + Nb ₂ O ₅ )] may be 0. By setting the upper limit of the mass ratio [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] to the above range, the specific gravity of the glass can be reduced and the raw material cost can be reduced.

In the optical glass according to the fourth embodiment, the mass ratio [ZnO / Nb ₂ O ₅ ] of the ZnO content to the Nb ₂ O ₅ content is preferably less than 0.14, and the upper limit thereof is 0.125. , 0.115, 0.105 are more preferable. The lower limit of the mass ratio [ZnO / Nb _{2O 5} ] is preferably 0, and more preferably 0.02, 0.05, and 0.07. The mass ratio [ZnO / Nb ₂ O ₅ ] may be 0. By setting the upper limit of the mass ratio [ZnO / Nb ₂ O ₅ ] to the above range, the specific gravity of the glass can be reduced and a desired optical constant can be obtained.

The optical glass according to the fourth embodiment preferably satisfies one or more of the following (g) and (h).
(G) The total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O is larger than 1.1%.
(H) Mass of total content R ₂ O with respect to total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is greater than 0.05.

That is, in the optical glass according to the fourth embodiment, the total content R ₂ O of Li ₂ O, Na ₂ O and K ₂ O can be made larger than 1.1%. The _total content R2O is preferably larger than 9%, and the lower limit thereof is more preferably 15.0%, 15.5%, 16.0%, and 16.5% in that order. The upper limit of the _total content R2O is preferably 22.0%, more preferably 21.7%, 21.4%, and 21.1%. By setting the _total content R2O in the above range, the specific gravity of the glass can be reduced and the stability of the glass during reheating can be maintained.

Further, in the optical glass according to the fourth embodiment, the total content of Li ₂ O, Na ₂ O and K ₂ O is R ₂ O and the total content of MgO, CaO, SrO and BaO is R'O. The mass ratio of total content R ₂ O to R 2 O [R ₂ O / (R ₂ O + R'O)] can be made larger than 0.05. The mass ratio [R ₂ O / (R ₂ O + R'O)] is preferably larger than 0.6, and the lower limit thereof is more preferably 0.80, 0.82, 0.84, 0.86 in that order. The upper limit of the mass ratio [R ₂ O / (R ₂ O + R'O)] is preferably 0.95, and more preferably 0.98, 0.99, and 1.00 in that order. By setting the mass ratio [R ₂ O / (R ₂ O + R'O)] to the above range, the specific gravity of the glass can be reduced and the stability of the glass during reheating can be maintained.

In the optical glass according to the fourth embodiment, the content and ratio of the glass components other than the above can be the same as those of the first embodiment. Further, the glass characteristics other than the above, the production of the optical glass, the production of the optical element and the like in the fourth embodiment can be the same as those in the first embodiment.
Further, in the fourth embodiment, any of the configurations of the first to third embodiments may be adopted.

Hereinafter, the present invention will be described in more detail by way of 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 and 2-1 to 2-2 were prepared by the following procedure and evaluated in various ways.

[Manufacturing of optical glass]
First, oxides, hydroxides, carbonates, and nitrates corresponding to the constituents of the glass are prepared as raw materials, and the above raw materials are weighed so that the glass composition of the obtained optical glass has each composition shown in Table 1. , Formulated and mixed the raw materials well. The compounding raw material (batch raw material) thus obtained is put into a platinum crucible and heated at 1350 ° C. to 1400 ° C. for 2 hours to form molten glass. It was cast into a mold preheated to a normal temperature. The cast glass was heat-treated at a temperature 100 ° C. lower than the glass transition temperature Tg for 30 minutes 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 of the obtained glass sample was measured by inductively coupled plasma emission spectroscopy (ICP-AES), and it was confirmed that the composition was as shown in Table 1.

[Stability during reheating]
The obtained glass sample is cut into a size of 1 cm × 1 cm × 0.8 cm, heated in a first test furnace set to a glass transition temperature Tg of the glass sample for 10 minutes, and further heated above the glass transition temperature Tg. It was heated for 10 minutes in a second test furnace set at a temperature higher than 140 to 250 ° C. Then, 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 of the glass was visually confirmed. If the number of crystals per 1 g was 20 or less and no cloudiness was confirmed, it was judged as "OK", and if the number of crystals per 1 g was more than 20 or at least one of the white turbidity was confirmed, it was judged as "impossible". .. The results are shown in Tables 3-1 to 3-2.

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

(Ii) Partial dispersion ratio Pg, F
The partial dispersion ratios Pg and F were calculated based on the following formulas using the refractive indexes ng, nF and nC of the g-line, F-line and c-line.
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 ratios Pg, F and Abbe number νd.
ΔPg, F = Pg, F + (0.0018 × νd) -0.6483

(Iv) Relative density Relative density was measured by the Archimedes method.

(V) Liquid phase temperature LT
The glass was placed in a furnace heated to a predetermined temperature and held for about 2 hours, and after cooling, the inside of the glass was observed with an optical microscope of 40 to 100 times, 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 at a heating rate of 10 ° C./min using a differential scanning calorimetry device (DSC3300SA) manufactured by NETZSCH JAPAN.

(Vii) λ80, λ70, λ5
The annealed sample was processed to have a thickness of 10 mm and having planes parallel to each other and optically polished, and the spectral transmittance in the wavelength range from 280 nm to 700 nm was measured. The spectral transmittance B / A was calculated with the intensity A of the light beam perpendicularly incident on one of the optically polished planes as the intensity A and the intensity of the light rays emitted from the other plane as the intensity B. The spectral transmittance B / A was calculated by setting the wavelength at which the spectral transmittance is 80% to λ80. The wavelength at which the spectral transmittance is 70% is λ70, and the wavelength at which the spectral transmittance is 5% is λ5. The spectral transmittance also includes the reflection loss of light rays 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 glass has a low specific density, each lens is lighter in weight than a lens having the same optical characteristics and size, and is suitable for various imaging devices, especially for autofocus type imaging devices because it can save energy. be. Similarly, a prism was produced using various optical glasses produced in Example 1.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of 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 items described in the specification as an example or a preferable range.

Claims (6)

The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is 0.80 or more . And
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
The content of Ta ₂ O ₅ is 3% by mass or less,
The Abbe number νd is 35.8 or less,
Optical glass that satisfies the following (b) ;
(B) Mass of total content R ₂ O relative to total content of Li ₂ O, Na ₂ O and K ₂ O total content R ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is 0.80 or more . The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is 0.80 or more . And
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
The mass ratio of the content of Ta ₂ O ₅ to the total content of TiO ₂ and Nb ₂ O ₅ [Ta ₂ O ₅ / (TiO ₂ + Nb ₂ O ₅ )] is smaller than 0.3.
The content of Ta ₂ O ₅ is 3% by mass or less,
The Abbe number νd is 35.8 or less,
Optical glass that satisfies the following (d) ;
(D) Total content of Li ₂ O, Na ₂ O and K ₂ O Mass of total content R ₂ O with respect to total content of R ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is 0.80 or more . The mass ratio of the content of SiO ₂ to the content of Nb ₂ O ₅ [SiO ₂ / Nb ₂ O ₅ ] is larger than 1.05.
The mass ratio of the content of ZrO ₂ to the content of Nb ₂ O ₅ [ZrO ₂ / Nb ₂ O ₅ ] is larger than 0.25.
The mass ratio of the total content of TiO ₂ and Nb ₂ O ₅ to the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is 0.80 or more . And
The total content of TiO ₂ and BaO [TiO ₂ + BaO] is less than 10% by mass,
The mass ratio of the ZnO content to the Nb ₂ O ₅ content [ZnO / Nb ₂ O ₅ ] is less than 0.14.
The content of Ta ₂ O ₅ is 3% by mass or less,
The Abbe number νd is 35.8 or less,
Optical glass satisfying the following (f) ;
(F) Mass of total content R ₂ O relative to total content of Li ₂ O, Na ₂ O and K ₂ O total content R ₂ O and total content R'O of MgO, CaO, SrO and BaO The ratio [R ₂ O / (R ₂ O + R'O)] is 0.80 or more . Li ₂ O, Na ₂ O and K ₂ Total content of O R ₂ The optical glass according to claim 1, wherein O is larger than 9% by mass. Li ₂ O, Na ₂ O and K ₂ Total content of O R ₂ The optical glass according to claim 2 or 3, wherein O is greater than 1.1% by mass. The optical element made of the optical glass according to any one of claims 1 to 5 .