JP2022108395A - Optical glass, and optical element - Google Patents

Abstract

To provide a high dispersion optical glass having a refractive index nd in a range of 1.55-1.68, and an optical element composed of the optical glass.SOLUTION: An optical glass includes: B2O3 and K2O as glass constituents, where the content of P2O5 is 35.0-60.0 mass%, the mass ratio [B2O3/P2O5] of a content of B2O3 to a content of P2O5 is 0.39 or less, the content of Na2O is 5.0-40.0 mass%, the content of BaO is 15.0 mass% or less, the total content [MgO+CaO+SrO+BaO] of MgO, CaO, SrO, and BaO is 18.0 mass% or less, the content of ZnO is 15.0 mass% or less, the content of Nb2O5 is 25.0 mass% or less, the content of WO3 is 5.0 mass% or less, the content of Bi2O3 is 10.0 mass% or less, the total content [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5] of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 is 3.0-30.0 mass%, and the total content [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5+ZnO] of TiO2, Nb2O5, WO3, Bi2O3, Ta2O5, and ZnO is 3.0-33.0 mass%.SELECTED DRAWING: None

Description

The present invention relates to optical glasses and optical elements.

High-dispersion optical glass with a refractive index nd in the range of 1.55 to 1.68 is useful in designing an optical system to correct chromatic aberration and make the optical system highly functional and compact. is high.

Patent Documents 1 to 3 disclose optical glasses having a relatively low Abbe number νd. However, the optical glasses of Patent Documents 1 to 3 have a large refractive index nd. Moreover, when the optical constants of the optical glass disclosed in Patent Document 4 were examined, it was found that the Abbe number νd was relatively low, but the refractive index nd was high. That is, Patent Documents 1 to 4 do not propose an optical glass having a refractive index nd in the range of 1.55 to 1.68 and high dispersion.

JP 2016-74581 A JP 2018-70414 A WO2013/031385 Japanese Patent Publication No. 2020-505311

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical glass having a refractive index nd in the range of 1.55 to 1.68 and high dispersion, and an optical element comprising the optical glass.

The gist of the present invention is as follows.
(1) containing B ₂ O ₃ and K ₂ O as glass components,
The content of P ₂ O ₅ is 35.0 to 60.0% by mass,
mass ratio [B ₂ O ₃ /P ₂ O ₅ ] of the B ₂ O ₃ content and the P ₂ O ₅ content is 0.39 or less;
The content of Na ₂ O is 5.0 to 40.0% by mass,
The content of BaO is 15.0% by mass or less,
The total content of MgO, CaO, SrO and BaO [MgO + CaO + SrO + BaO] is 18.0% by mass or less,
ZnO content is 15.0% by mass or less,
The content of Nb ₂ O ₅ is 25.0% by mass or less,
The content of WO3 is 5.0% by mass or less _,
The content of Bi ₂ O ₃ is 10.0% by mass or less,
The total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O ₅ [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ ] is 3.0 to 30.0 % by mass,
The total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ and ZnO [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ +ZnO] is 3.0 to Optical glass, which is 33.0% by mass.

(2) An optical element made of the optical glass described in (1) above.

According to the present invention, it is possible to provide an optical glass having a refractive index nd in the range of 1.55 to 1.68 and high dispersion, and an optical element made of the optical glass.

In the present invention and in this specification, the glass composition of optical glass is indicated on the oxide basis 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 glass components can be quantified by known methods such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and the like. Moreover, 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.

Also, the Abbe number νd is used as a value representing properties related to dispersion, 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) (1)

The optical glass according to this embodiment will be described in detail.

The optical glass according to this embodiment contains B ₂ O ₃ as a glass component. The lower limit of the B ₂ O ₃ content is preferably 0.3%, more preferably 0.6%, 0.8% and 1.0% in that order. The upper limit of the content of B ₂ O ₃ is preferably 15%, more preferably 13.0%, 11.0% and 10.0% in that order.

B ₂ O ₃ is a network-forming component of glass and has the function of improving the thermal stability of glass. By setting the content of B ₂ O ₃ within the above range, the thermal stability and devitrification resistance of the glass can be improved. On the other hand, if the B ₂ O ₃ content is too high, the thermal stability and devitrification resistance of the glass tend to decrease.

The optical glass according to this embodiment contains K ₂ O as a glass component. The lower limit of the K ₂ O content is preferably 3.0%, more preferably 5.0%, 7.0%, 8.5%, 9.00% and 9.20% in that order. The upper limit of the K ₂ O content is preferably 20.0%, more preferably 17.0%, 15.0% and 14.0% in that order.

K ₂ O works to improve the thermal stability and meltability of the glass. By setting the content of K ₂ O within the above range, an optical glass having excellent thermal stability and meltability can be obtained. On the other hand, if the K ₂ O content is too low, the thermal stability and meltability may deteriorate. Moreover, if the content of K ₂ O is too high, the thermal stability may decrease.

In the optical glass according to this embodiment, the P ₂ O ₅ content is 35.0 to 60.0%. The lower limit of the content of P ₂ O ₅ is preferably 40.0%, more preferably 41.0%, 42.0%, 43.0%, 43.5%, 45.5% in that order. . The upper limit of the content of P ₂ O ₅ is preferably 60.0%, more preferably 58.0%, 56.0% and 55.0% in that order.

P ₂ O ₅ is a network-forming component of glass, and is an essential component for containing a large amount of highly dispersed components in the glass. By setting the content of P ₂ O ₅ within the above range, an optical glass having excellent thermal stability and desired optical constants can be obtained. On the other hand, if the content of P ₂ O ₅ is too small, there is a possibility that an optical glass having desired optical constants cannot be obtained. Also, if the content of P ₂ O ₅ is too high, the thermal stability of the glass may deteriorate.

In the optical glass according to this embodiment, the mass ratio [B ₂ O ₃ /P ₂ O ₅ ] of the content of B ₂ O ₃ and the content of P ₂ O ₅ is 0.39 or less. The upper limit of the mass ratio is preferably 0.34, more preferably 0.30, 0.27 and 0.25 in that order. The lower limit of the mass ratio is preferably 0.005, more preferably 0.01, 0.015 and 0.02 in that order.

By setting the mass ratio [B ₂ O ₃ /P ₂ O ₅ ] within the above range, an optical glass having excellent thermal stability can be obtained. On the other hand, if the mass ratio is too large, the thermal stability of the glass may deteriorate.

The content of Na ₂ O in the optical glass according to this embodiment is 5.0 to 40.0%. The lower limit of the content of Na ₂ O is preferably 10%, further in the order of 12.0%, 13.5%, 15.0%, 16.5%, 17.5%, 18.0% more preferred. The upper limit of the content of Na ₂ O is preferably 30.0%, more preferably 27.0%, 25.0% and 23.0% in that order.

Na ₂ O works to improve the thermal stability and meltability of the glass. By setting the content of Na ₂ O within the above range, an optical glass having excellent thermal stability and meltability can be obtained. On the other hand, if the content of Na ₂ O is too small, the thermal stability and meltability may deteriorate. Also, if the content of Na ₂ O is too high, the thermal stability may decrease.

In the optical glass according to this embodiment, the content of BaO is 15.0% or less. The upper limit of the BaO content is preferably 13.0%, more preferably 11.0%, 9.0% and 7.0% in that order. The lower limit of the BaO content is preferably 0%, and more preferably 1.0%, 2.0%, and 3.0% in this order. The content of BaO may be 0%.

BaO is also a glass component that works to improve the thermal stability and devitrification resistance of the glass. By setting the content of BaO within the above range, an optical glass having excellent thermal stability and devitrification resistance can be obtained. On the other hand, if the BaO content is too high, the high dispersibility of the glass may be impaired, and the thermal stability and devitrification resistance of the glass may be lowered.

In the optical glass according to this embodiment, the total content of MgO, CaO, SrO and BaO [MgO+CaO+SrO+BaO] is 18.0% or less. The upper limit of the total content is preferably 16.0%, more preferably 14.0%, 12.0% and 10.0% in that order. Also, the lower limit of the total content is preferably 0%, and more preferably 1.0%, 2.0%, and 3.0% in this order. The total content may be 0%.

By setting the total content [MgO+CaO+SrO+BaO] within the above range, thermal stability and devitrification resistance can be maintained without hindering high dispersion. On the other hand, if the total content is too large, the high dispersibility of the glass may be impaired, and the thermal stability and devitrification resistance of the glass may be lowered.

In the optical glass according to this embodiment, the ZnO content is 15.0% or less. The upper limit of the ZnO content is preferably 13.0%, more preferably 11.0%, 9.0% and 7.0% in that order. The lower limit of the ZnO content is preferably 0%, and more preferably 1.0%, 2.0%, and 3.0% in this order. The content of ZnO may be 0%.

By setting the ZnO content within the above range, the thermal stability of the glass can be improved, and an increase in the specific gravity of the glass can be suppressed. Furthermore, an optical glass with desired optical constants is obtained.

In the optical glass according to this embodiment, the content of Nb ₂ O ₅ is 25.0% or less. The upper limit of the content of Nb ₂ O ₅ is preferably 20.0%, more preferably 15.0%, 10.0%, 7.0% and 5.0% in this order. The lower limit of the Nb ₂ O ₅ content is preferably 0%, and more preferably 1.0%, 2.0% and 3.0% in this order. The content of Nb ₂ O ₅ may be 0%.

Nb ₂ O ₅ is a component that contributes to high refractive index and high dispersion. Therefore, by setting the content of Nb ₂ O ₅ within the above range, an optical glass having desired optical constants can be obtained. On the other hand, if the content of Nb ₂ O ₅ is too large, the thermal stability of the glass may be lowered and the coloration of the glass may be enhanced.

In the optical glass according to this embodiment _, the content of WO3 is 5.0% or less. The upper limit of the WO3 content is preferably 4.5%, more preferably 4.0%, _3.5 % and 3.0% in that order. The lower limit of the WO3 content is preferably 0% _, and more preferably 0.5%, 1.0% and 1.5% in this order. The content of _WO3 can be 0%.

By setting the content of WO ₃ within the above range, the transmittance of the glass can be increased, and an increase in the specific gravity of the glass can be suppressed.

In the optical glass according to this embodiment, the content of Bi ₂ O ₃ is 10.0% or less. The upper limit of Bi ₂ O ₃ is preferably 8.0%, more preferably 7.0%, 6.0% and 5.0% in that order. Also, the content of Bi ₂ O ₃ is preferably as small as possible, and the lower limit thereof is preferably 0%, and more preferably 1.0%, 1.5%, and 2.0% in this order. The content of Bi ₂ O ₃ may be 0%.

By setting the content of Bi ₂ O ₃ within the above range, the thermal stability of the glass can be improved, and an increase in the specific gravity of the glass can be suppressed. On the other hand, if the content of Bi ₂ O ₃ is too high, the specific gravity may increase and the coloration of the glass may increase.

In the optical glass according to the present embodiment, the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O ₅ [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ ] is 3.0 to 30.0%. The lower limit of the total content is preferably 6.0%, more preferably 8.0%, 10.0% and 12.0% in that order. In addition, the upper limit of the total content is preferably 29.0%, further in the order of 27.0%, 25.0%, 22.0%, 20.0% and 18.0% more preferred.

TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O ₅ are components that contribute to high dispersion of the glass. Therefore, by setting the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ ] within the above range, an optical glass having desired optical constants can be obtained. Also, the thermal stability of the glass can be improved. On the other hand, if the total content is too large, an optical glass having desired optical constants may not be obtained, and the thermal stability of the glass may be lowered and the coloration of the glass may be enhanced.

In the optical glass according to the present embodiment, the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ and ZnO [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ +ZnO] is 3.0 to 33.0%. The lower limit of the total content is preferably 6.0%, more preferably 8.0%, 10.0% and 12.0% in that order. In addition, the upper limit of the total content is preferably 29.0%, further in the order of 27.0%, 25.0%, 22.0%, 20.0% and 18.0% more preferred.

By setting the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ +ZnO] within the above range, an optical glass having desired optical constants can be obtained. Also, the thermal stability of the glass can be improved. On the other hand, if the total content is too large, an optical glass having desired optical constants may not be obtained, and the thermal stability of the glass may be lowered and the coloration of the glass may be enhanced.

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

Total content of _TiO2 , _{Nb2O5 , WO3 , Bi2O3} and _Ta2O5 and _P2O5 , _{B2O3 , SiO2} , _{Li2O , Na2O , K2O} and the total content of Cs ₂ O [(TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ + Ta ₂ O ₅ )/(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O)] is preferably 0.45, and more preferably 0.43, 0.40, 0.37, 0.35 and 0.33 in this order. The lower limit of the mass ratio is preferably 0.10, more preferably 0.12, 0.14 and 0.15 in that order.

From the viewpoint of obtaining an optical glass having desired optical constants, the mass ratio [ _{( TiO2 + Nb2O5} +WO3 _{+ Bi2O3} + _Ta2O5 )/ _{( P2O5} + _{B2O3 + SiO2 +} Li2O ₊ Na ₂ O+K ₂ O+Cs ₂ O)] is preferably within the above range.

In the optical glass according to the present embodiment, the lower limit of the mass ratio [TiO ₂ /(P ₂ O ₅ +B ₂ O ₃ )] between the content of TiO ₂ and the total content of P ₂ O ₅ and B ₂ O ₃ is preferably 0.10, and more preferably 0.16, 0.21 and 0.24 in that order. The upper limit of the mass ratio is preferably 0.40, more preferably 0.37, 0.35 and 0.33 in that order.

TiO ₂ is a component having a particularly large effect of increasing dispersion among high refractive index and high dispersion components. However, when the content of TiO ₂ increases, the thermal stability and devitrification resistance may deteriorate. Therefore, the mass ratio [TiO ₂ /(P ₂ O ₅ +B ₂ O ₃ )] is preferably within the above range from the viewpoint of obtaining an optical glass having high dispersion, excellent thermal stability and devitrification resistance. .

Mass ratio of the total content of P ₂ O ₅ , B ₂ O ₃ and SiO ₂ to the total content of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O in the optical glass according to the present embodiment The lower limit of [(P ₂ O ₅ +B ₂ O ₃ +SiO ₂ )/(Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)] is preferably 0.80, furthermore 1.00, 1.20, 1. 30 order is more preferred. The upper limit of the mass ratio is preferably 2.60, more preferably 2.40, 2.20 and 2.10 in that order.

From the viewpoint of obtaining optical glass with excellent thermal stability, the mass ratio [(P ₂ O ₅ +B ₂ O ₃ +SiO ₂ )/(Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O)] is preferably within the above range.

_In the optical glass according to the present embodiment _, the _{mass ratio [ TiO 2 / ( TiO 2} +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )] is preferably 0.20, more preferably 0.30, 0.40 and 0.50 in that order. The upper limit of the mass ratio is preferably 0.90, more preferably 0.80, 0.70 and 0.60 in that order. The mass ratio may be 1.00.

TiO ₂ is a component having a particularly large effect of increasing dispersion among high refractive index and high dispersion components. Therefore, from the viewpoint of obtaining an optical glass having desired optical constants and excellent thermal stability and devitrification resistance, the mass ratio [TiO ₂ /(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )] is preferably within the above range.

In the optical glass according to the present embodiment, the lower limit of the mass ratio [Na ₂ O/K ₂ O] between the content of Na ₂ O and the content of K ₂ O is preferably 0.80, more preferably 1 0.00, 1.20 and 1.30 are more preferred. The upper limit of the mass ratio is preferably 2.70, more preferably 2.50, 2.30 and 2.20 in that order.

From the viewpoint of improving the thermal stability and devitrification resistance of the glass, the mass ratio [Na ₂ O/K ₂ O] is preferably within the above range. In particular, from the viewpoint of suppressing an excessive decrease in refractive index and a decrease in chemical durability, the lower limit of the mass ratio is preferably within the above range.

In the optical glass according to this embodiment, the upper limit of the content of Al ₂ O ₃ is preferably 15.0%, more preferably 11.0%, 8.0% and 6.0% in that order. The lower limit of the Al ₂ O ₃ content is preferably 0%, more preferably 0.5%, 1.0% and 1.5% in that order. The content of Al ₂ O ₃ may be 0%.

From the viewpoint of suppressing a decrease in the devitrification resistance of the glass, the content of Al ₂ O ₃ is preferably within the above range.

In the optical glass according to the present embodiment, the upper limit of the SiO ₂ content is preferably 5.0%, more preferably 4.0%, 3.0% and 2.0% in that order. The lower limit of the _SiO2 content is preferably 0%. The content of _SiO2 may be 0%.

SiO ₂ is a network-forming component of glass, and has the functions of improving the thermal stability, chemical durability, and weather resistance of glass, increasing the viscosity of glass melt, and making the glass melt easier to shape. On the other hand, when the _SiO2 content is high, the devitrification resistance of the glass tends to decrease. Therefore, from the viewpoint of improving the thermal stability and devitrification resistance of the glass, the upper limit of the SiO ₂ content is preferably within the above range.

A quartz glass melting device such as a quartz glass crucible may be used to melt the glass. In this case, a small amount of SiO ₂ dissolves into the glass melt from the melting device, so that the glass produced contains a small amount of SiO ₂ even if the frit does not contain SiO ₂ . The amount of SiO ₂ mixed into the glass from the quartz glass melting device depends on the melting conditions, but is, for example, about 0.5 to 1% by mass with respect to the total content of all glass components. The amount of SiO ₂ increases by about 0.5 to 1% by mass while the content ratio of glass components other than SiO ₂ remains constant. Note that the above amount may be increased or decreased depending on the melting conditions. Since optical properties such as refractive index and Abbe's number change depending on the content of SiO ₂ , optical glass having desired optical properties is obtained by finely adjusting the content of glass components other than SiO ₂ .

In the optical glass according to the present embodiment, the lower limit of the TiO ₂ content is preferably 0%, more preferably 5.0%, 9.0% and 12.0% in that order. The content of _TiO2 may be 0%. The upper limit of the TiO ₂ content is preferably 30.0%, more preferably 25.0%, 21.0% and 18.0% in that order.

_TiO2 greatly contributes to high dispersion. On the other hand, TiO ₂ tends to increase the coloration of glass relatively easily. In addition, TiO ₂ promotes the formation of crystals in the glass during the process of forming and slowly cooling the molten glass to obtain an optical glass, and reduces the transparency of the glass (white turbidity). Therefore, the content of TiO ₂ is preferably within the above range.

In the optical glass according to this embodiment, the upper limit of the Ta ₂ O ₅ content is preferably 10.0%, more preferably 5.0%, 3.0%, and 1.0% in that order. Also, the lower limit of the Ta ₂ O ₅ content is preferably 0%. The content of Ta ₂ O ₅ may be 0%.

Ta ₂ O ₅ is a glass component that works to improve the thermal stability and devitrification resistance of glass. On the other hand, Ta ₂ O ₅ increases the refractive index and makes the glass highly dispersed. In addition, when the content of Ta ₂ O ₅ increases, the thermal stability of the glass decreases, and when the glass is melted, unmelted glass raw materials tend to remain unmelted. Therefore, the content of Ta ₂ O ₅ is preferably within the above range. Furthermore, Ta ₂ O ₅ is a very expensive component compared to other glass components, and the higher the Ta ₂ O ₅ content, the higher the production cost of the glass. Furthermore, since Ta ₂ O ₅ has a higher molecular weight than other glass components, it may increase the specific gravity of the glass, resulting in an increase in the weight of the optical element.

In the optical glass according to this embodiment, the upper limit of the Li ₂ O content is preferably 5%, more preferably 3%, 2%, and 1% in that order. The lower limit of the Li ₂ O content is preferably 0%. The content of Li ₂ O may be 0%.

Li ₂ O has the function of lowering the glass transition temperature Tg. On the other hand, when the content of Li ₂ O increases, the acid resistance decreases. Therefore, the content of Li ₂ O is preferably within the above range.

In the optical glass according to this embodiment, the upper limit of the total content of Li ₂ O, Na ₂ O and K ₂ O [Li ₂ O+Na ₂ O+K ₂ O] is preferably 45.0%, more preferably 42.0%. The order of 0%, 39.0%, 37.0% is more preferred. The lower limit of the total content is preferably 10.0%, more preferably 15.0%, 19.0% and 22.0% in that order.

Li ₂ O, Na ₂ O and K ₂ O all work to improve the thermal stability of the glass. However, when the content of these elements increases, chemical durability and weather resistance decrease. Therefore, the total content of Li ₂ O, Na ₂ O and K ₂ O [Li ₂ O+Na ₂ O+K ₂ O] is preferably within the above range.

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

Cs ₂ O works to improve the thermal stability of the glass, but when the content is too large, the thermal stability, chemical durability and weather resistance of the glass deteriorate. Therefore, the content of Cs ₂ O is preferably within the above range.

In the optical glass according to the present embodiment, the upper limit of the MgO content is preferably 10.0%, and further in the order of 8.0%, 7.0%, 6.0% and 5.0%. preferable. Also, the lower limit of the MgO content is preferably 0%. The content of MgO may be 0%.

In the optical glass according to the present embodiment, the upper limit of the CaO content is preferably 10.0%, more preferably 8.0%, 7.0%, 6.0% and 5% in this order. Also, the lower limit of the CaO content is preferably 0%. The content of CaO may be 0%.

In the optical glass according to the present embodiment, the upper limit of the SrO content is preferably 10.0%, and further in the order of 8.0%, 7.0%, 6.0%, and 5.0%. preferable. Also, the lower limit of the SrO content is preferably 0%. The content of SrO may be 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 high dispersibility is impaired, and the thermal stability and devitrification resistance of the glass are lowered. 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 present embodiment, the upper limit of the ZrO2 content is preferably 10.0%, and further in the order of 8.0%, 7.0%, 6.0% and 5.0%. more preferred. Also, the lower limit of the ZrO ₂ content is preferably 0%. The content of ZrO ₂ can be 0%.

_ZrO2 is a glass component that works to improve the thermal stability and devitrification resistance of the glass. However, if the content of ZrO ₂ is too high, it tends to decrease thermal stability. Therefore, from the viewpoint of maintaining good thermal stability and devitrification resistance of the glass, the content of ZrO ₂ is preferably within the above range.

In the optical glass according to this embodiment, the upper limit of the Sc ₂ O ₃ content is preferably 2%. Moreover, the lower limit of the content of Sc ₂ O ₃ is preferably 0%.

In the optical glass according to this embodiment, the upper limit of the HfO ₂ content is preferably 2%. Also, the lower limit of the content of HfO ₂ is preferably 0%.

Both Sc ₂ O ₃ and HfO ₂ work to increase the refractive index nd and are expensive components. Therefore, each content of Sc ₂ O ₃ and HfO ₂ is preferably within the above range.

In the optical glass according to this embodiment, the upper limit of the content of Lu ₂ O ₃ is preferably 2%. 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 refractive index nd. Moreover, 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 optical glass according to this embodiment, the upper limit of the GeO ₂ content is preferably 2%. Also, the lower limit of the content of GeO ₂ is preferably 0%.

GeO ₂ has the function of increasing the refractive index nd, and 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 present embodiment, the upper limit of the content of La ₂ O ₃ is preferably 10.0%, and further 8.0%, 7.0%, 6.0% and 5.0%. is more preferable in that order. Also, the lower limit of the content of La ₂ O ₃ is preferably 0%. The content of La ₂ O ₃ may be 0%.

When the content of La ₂ O ₃ increases, the thermal stability and resistance to devitrification of the glass deteriorate, and the glass tends to devitrify during production. Therefore, from the viewpoint of suppressing deterioration of thermal stability and devitrification resistance, the content of La ₂ O ₃ is preferably within the above range.

In the optical glass according to this embodiment, the upper limit of the content of Gd ₂ O ₃ is preferably 10.0%, and further 8.0%, 7.0%, 6.0% and 5.0%. is more preferable in that order. 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 and devitrification resistance of the glass are lowered, and the glass tends to be devitrified during production. Also, if the content of Gd ₂ O ₃ is too high, the specific gravity of the glass increases, which is not preferable. Therefore, the content of Gd ₂ O ₃ is preferably within the above range from the viewpoint of suppressing an increase in specific gravity while maintaining good thermal stability and devitrification resistance of the glass.

In the optical glass according to the present embodiment, the upper limit of the Y ₂ O ₃ content is preferably 10.0%, and further 8.0%, 7.0%, 6.0% and 5.0%. is more preferable in that order. Moreover, the lower limit of the content of Y ₂ O ₃ is preferably 0%. The content of Y ₂ O ₃ may be 0%.

If the Y ₂ O ₃ content is too high, the thermal stability and devitrification resistance of the glass are lowered. Therefore, from the viewpoint of suppressing deterioration of thermal stability and devitrification resistance, the content of Y ₂ O ₃ is preferably within the above range.

In the optical glass according to this embodiment, the upper limit of the Yb ₂ O ₃ content is preferably 2%. Also, the lower limit of the Yb ₂ O ₃ content is preferably 0%.

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

On the other hand, if the Yb ₂ O ₃ content is too high, the thermal stability and devitrification resistance of the glass are 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 optical glass according to the present embodiment mainly includes the glass components described above, that is, B ₂ O ₃ , K ₂ O, P ₂ O ₅ and Na ₂ O as essential components, and ZnO, Nb ₂ O ₅ and WO ₃ as optional components. , _Bi2O3 , _{Al2O3 , SiO2} , _TiO2 , _Ta2O5 , _Li2O , _Cs2O , MgO, CaO, _SrO , _BaO , _ZrO2 , _{Sc2O3 , HfO2} , Lu ₂ O ₃ , GeO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ , and the total content of the above glass components is 95% or more. It is preferably 98% or more, more preferably 99% or more, and even more preferably 99.5% or more.

In the optical glass according to this embodiment, the upper limit of the TeO ₂ content is preferably 2%. Also, the lower limit of the TeO ₂ content is preferably 0%.

Since _TeO2 is toxic, it is preferable to reduce the _TeO2 content. Therefore, the content of TeO ₂ is preferably within the above range.

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

<Other component compositions>
Pb, As, Cd, Tl, Be and Se are all toxic. Therefore, it is preferable that the optical glass according to the present embodiment does not contain these elements as glass components.

All of U, Th, and Ra are radioactive elements. Therefore, it is preferable that the optical glass according to the present embodiment does not contain these elements as glass components.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm can increase the coloration of glass and become a source of fluorescence. Therefore, it is preferable that the optical glass according to the present embodiment does not contain these elements as glass components.

Sb (Sb ₂ O ₃ ), Sn (SnO ₂ ), and Ce (CeO ₂ ) are optional elements that function as refining agents. Among these, Sb (Sb ₂ O ₃ ) is a refining agent having a large refining effect. However _, Sb _{( Sb 2} O ₃ ) has a strong oxidizing property _. oxidizes the molding surface of the press mold. Therefore, as precision press molding is repeated, the molding surface is significantly deteriorated, and precision press molding becomes impossible. Also, the surface quality of the molded optical element is degraded. Also, Sn(SnO ₂ ) and Ce(CeO ₂ ) have a smaller refining effect than Sb(Sb ₂ O ₃ ). Furthermore, when Ce(CeO ₂ ) is added in a large amount, the coloration of the glass is enhanced. Therefore, when adding a clarifier, it is preferable to add Sb (Sb ₂ O ₃ ) while paying attention to the amount added.

Contents of the refining agents shown below are values converted to oxides.
The content of Sb ₂ O ₃ is expressed as an outside ratio. That is, when the total content of all glass components other than Sb ₂ O ₃ , SnO ₂ and CeO ₂ is 100% by mass, the content of Sb ₂ O ₃ is preferably 1% by mass or less, more preferably 0% by mass. 0.2% by mass or less, 0.05% by mass or less, 0.02% by mass or less, and 0.01% by mass or less are preferred in that order. The content of Sb ₂ O ₃ may be 0 mass %.

The content of SnO ₂ is also expressed as an external weighting. That is, when the total content of all glass components other than SnO ₂ , Sb ₂ O ₃ and CeO ₂ is 100% by mass, the content of SnO ₂ is preferably 1% by mass or less, more preferably 0.2% by mass. % or less, more preferably 0.02 mass % or less. The SnO ₂ content may be 0% by mass, preferably substantially free of SnO ₂ . By setting the SnO ₂ content within the above range, the clarity of the glass can be improved.

The content of CeO ₂ is also expressed as an external weighting. That is, when the total content of all glass components other than CeO ₂ , Sb ₂ O ₃ and SnO ₂ is 100% by mass, the content of CeO ₂ is preferably 1% by mass or less, more preferably 0.2% by mass. % or less, more preferably 0.02 mass % or less. _The content of CeO2 may be ₀ % by weight, preferably substantially free of CeO2. By setting the content of CeO ₂ within the above range, the clarity of the glass can be improved.

(Glass properties)
<Refractive index nd>
In the optical glass according to this embodiment, the refractive index nd is preferably 1.55 to 1.68, and may be in the range of 1.55 to 1.65 or 1.57 to 1.64.

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 , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , La ₂ O ₃ and the like. is. On the other hand, the component (refractive index lowering component) that has the function of relatively lowering the refractive index nd is P ₂ O ₅ , SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, or the like. be. Therefore, _TiO2 , _Nb2O5 , _{WO3 , Bi2O3} relative to the _total content of _P2O5 , _{B2O3 , SiO2} , _Li2O , _{Na2O , K2O} and _Cs2O and the mass ratio of the total content of Ta ₂ O ₅ [(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )/(P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Li ₂ O +Na ₂ O +K ₂ O +Cs ₂ O)] can increase the refractive index nd, and decreasing the mass ratio can lower the refractive index nd.

<Abbe number νd>
In the optical glass according to this embodiment, the Abbe number νd is preferably 25-50, more preferably 28-45.

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 , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ and the like. On the other hand, components that relatively increase the Abbe number νd, ie, low-dispersion components, are P ₂ O ₅ , SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, La ₂ O ₃ , BaO, CaO, SrO and the like.

<Specific gravity of glass>
In the optical glass according to this embodiment, the specific gravity is preferably 3.20 or less, more preferably 3.10 or less, and 2.95 or less, in that order. Although the lower limit of the specific gravity is not particularly limited, it is usually 2.50. If the specific gravity of the glass can be reduced, the weight of the lens can be reduced. As a result, it is possible to reduce power consumption for autofocus driving of a camera lens equipped with the lens.

<Glass transition temperature Tg>
The glass transition temperature Tg of the optical glass according to this embodiment is preferably 520° C. or lower, more preferably 500° C. or lower, 480° C. or lower, and 470° C. or lower in that order. The lower limit of the glass transition temperature Tg is usually 300°C, preferably 350°C.

When the upper limit of the glass transition temperature Tg satisfies the above range, it is possible to suppress an increase in the molding temperature and annealing temperature of the glass, and to reduce thermal damage to press molding equipment and annealing equipment. Moreover, when the lower limit of the glass transition temperature Tg satisfies the above range, it becomes easier to maintain good thermal stability of the glass while maintaining the desired Abbe number and refractive index.

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

λ5 of the optical glass according to this embodiment is preferably 390 nm or less, more preferably 380 nm or less, and still more preferably 375 nm or less.

By using an optical glass with a shortened wavelength λ5, it is possible to provide an optical element that enables suitable color reproduction.

<Average linear expansion coefficient α _100-300 >
In the optical glass according to the present embodiment, the lower limit of the average coefficient of linear expansion α _100-300 at 100 to 300° C. is preferably 100×10 ⁻⁷ ° C. ⁻¹ , more preferably 120×10 ⁻⁷ ° C. ⁻¹ , 130×10 ⁻⁷ ° C. ⁻¹ and 140×10 ⁻⁷⁵ ° C. ⁻¹ are preferred in that order. Further, the upper limit of the average linear expansion coefficient α _100-300 can be exemplified by 210×10 ⁻⁷ ° C. ⁻¹ , preferably 205×10 ⁻⁷ ° C., from the viewpoint of maintaining the stability of the glass and obtaining desired optical properties. ⁻¹ , and more preferably 200×10 ⁻⁷ ° C. ⁻¹ , 195×10 ⁻⁷ ° C. ⁻¹ , 190×10 ⁻⁷ ° C. ⁻¹ in that order.

The average coefficient of linear expansion α _100-300 is measured according to JOGIS08-2019. The sample is a round bar with a length of 20 mm±0.5 mm and a diameter of 5 mm±0.5 mm. With a load of 98 mN applied to the sample, the sample is heated so as to increase at a constant rate of 4° C. per minute, and the temperature and elongation of the sample are measured in increments of 1 second. The average linear expansion coefficient α _100-300 is the average value of linear expansion coefficients at 100 to 300°C.
In this specification, the average coefficient of linear expansion α is expressed in units of [° C. ⁻¹ ], but the value of the average coefficient of linear expansion α is the same even when [K ⁻¹ ] is used as the unit.

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

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

(Manufacture of optical elements, etc.)
A known method may be applied to produce an optical element using the optical glass according to the embodiment of the present invention. For example, a glass raw material is melted to form a glass melt, and the glass melt is poured into a mold and formed into a plate to produce a glass material comprising the optical glass of 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.

Examples of optical elements include various lenses such as spherical lenses, prisms, and diffraction gratings.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited only to the following examples.

(Example)
[Preparation of glass sample]
Sample Nos. shown in Tables 1 (1) and (2). Compound raw materials corresponding to each component, that is, raw materials such as phosphates, carbonates, oxides, etc., were weighed and thoroughly mixed to obtain a glass having a composition of 1 to 32 to obtain a raw material preparation. The prepared raw material was placed in a platinum crucible, heated to 900 to 1350° C. in an air atmosphere, melted, homogenized by stirring, and refined to obtain a glass melt. The molten glass was cast into a mold, molded, and slowly cooled to obtain a block-shaped glass sample.
In addition, after the raw material to be prepared is put into a quartz glass crucible and melted, it is transferred to a platinum crucible and further heated and melted, homogenized by stirring, clarified, and the resulting molten glass is cast into a mold and molded. , may be slowly cooled.

[Glass sample evaluation]
The obtained glass samples were measured for glass composition, specific gravity, refractive index nd, Abbe number νd, λ5, glass transition temperature Tg, and average linear expansion coefficient α _100-300 by the methods described below. Permeability was evaluated. The results are shown in Tables 2 (1) and (2).

[1] Glass composition The content of each glass component in the obtained glass sample was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[2] Specific Gravity Measured based on the Japan Optical Glass Industry Standard JOGIS-05.

[3] Refractive index nd and Abbe number νd
It was measured based on the Japan Optical Glass Industry Association Standard JOGIS-01.

[4] λ5
A glass sample having a thickness of 10 mm was processed so as to have parallel and optically polished flat surfaces, and the spectral transmittance in the wavelength range from 280 nm to 700 nm was measured. The spectral transmittance B/A was calculated by setting the intensity A to the intensity of light incident perpendicularly to one optically polished plane and the intensity B to the intensity of light emitted from the other plane. The wavelength at which the spectral transmittance becomes 5% was defined as λ5. Note that the spectral transmittance also includes the reflection loss of light on the sample surface.

[5] Glass transition temperature Tg
The glass transition temperature Tg was obtained based on a DSC chart obtained when the temperature of the solid state glass was increased using a differential scanning calorimeter DSC3300SA (NETZSCH Japan).

[6] Average linear expansion coefficient α _100-300
The average coefficient of linear expansion of the obtained glass samples was measured with reference to the specifications of JOGIS08-2019. The average coefficient of linear expansion was measured using a thermomechanical analyzer TMA4000SE (NETZSCH Japan). The sample was a round bar with a length of 20 mm±0.5 mm and a diameter of 5 mm±0.5 mm. During the measurement, a load of 98 mN was applied to the sample, and the temperature and elongation of the sample were measured in increments of 1 second while increasing the temperature at a constant rate of 4°C per minute. The average value of linear expansion coefficients at 100 to 300° C. was defined as average linear expansion coefficient α _100-300 .

[7] Devitrification resistance The presence or absence of crystals or white turbidity in the obtained glass samples was confirmed with an optical microscope. The observation magnification of the optical microscope was 10 to 100 times. When neither crystals nor white turbidity was found inside the glass, it was judged as "good", and when at least one of crystals and white turbidity was found inside the glass, it was judged as "bad". Example sample no. All of 1 to 32 were judged as "good". Example sample no. It was confirmed that Nos. 1 to 32 are glasses excellent in devitrification resistance.

(Example 2)
The glass sample obtained in Example 1 was cut and ground to produce a cut piece. The cut piece was press-molded by reheat press to produce an optical element blank. An optical element blank is precisely annealed, the refractive index is precisely adjusted to a desired refractive index, and then ground and polished by a known method to obtain a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, and a concave meniscus lens. , a convex meniscus lens, etc. were obtained.

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 equivalent to the scope of the claims.

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

Claims (2)

containing B ₂ O ₃ and K ₂ O as glass components,
The content of P ₂ O ₅ is 35.0 to 60.0% by mass,
mass ratio [B ₂ O ₃ /P ₂ O ₅ ] of the B ₂ O ₃ content and the P ₂ O ₅ content is 0.39 or less;
The content of Na ₂ O is 5.0 to 40.0% by mass,
The content of BaO is 15.0% by mass or less,
The total content of MgO, CaO, SrO and BaO [MgO + CaO + SrO + BaO] is 18.0% by mass or less,
ZnO content is 15.0% by mass or less,
The content of Nb ₂ O ₅ is 25.0% by mass or less,
The content of WO3 is 5.0% by mass or less _,
The content of Bi ₂ O ₃ is 10.0% by mass or less,
The total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O ₅ [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ ] is 3.0 to 30.0 % by mass,
The total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ and ZnO [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ +ZnO] is 3.0 to Optical glass, which is 33.0% by mass. An optical element comprising the optical glass according to claim 1 .