JP7305317B2 - Optical glasses, optical element blanks and optical elements - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical glass, an optical element blank, and an optical element having excellent acid resistance.

2. Description of the Related Art In recent years, with the improvement of image quality and resolution of digital cameras and the like, low-dispersion optical glasses have been demanded. Such low-dispersion optical glasses have hitherto had poor acid resistance. For this reason, further improvements are required in applications where high durability is required, such as for in-vehicle use.

Although the optical glass disclosed in Patent Document 1 has low dispersion, no attention is paid to its acid resistance. In addition, since 4% or more of fluorine (F) is contained as a glass component, the glass component tends to volatilize during melting of the glass, and the composition of the molten glass may not be stable.

JP 2014-214082 A

An object of the present invention is to provide an optical glass, an optical element blank, and an optical element that are excellent in acid resistance.

As a result of intensive research to achieve the above object, the present inventors have found that the object can be achieved by adjusting the content ratio of various glass constituent components (hereinafter referred to as glass components) that constitute glass. and completed the present invention based on this finding.

That is, the gist of the present invention is as follows.
(1) a refractive index nd of 1.70 to 1.85;
The content of B ₂ O ₃ is 5 to 35% by mass,
The content of La ₂ O ₃ is 25 to 50% by mass,
The content of Al ₂ O ₃ is 1 to 20% by mass,
Optical glass satisfying the following (a) or (b);
(a) the Abbe number νd is 42 or more and less than 50, and the acid resistance based on JOGIS is grade 1 to 2;
(b) The Abbe number νd is 50 or more and 55 or less, and the acid resistance is grade 1 to 3 according to JOGIS.

(2) a refractive index nd of 1.70 to 1.85;
Abbe number νd is 42 to 55,
The content of SiO ₂ is 5 to 20% by mass,
The content of B ₂ O ₃ is 5 to 35% by mass,
The content of La ₂ O ₃ is 25 to 50% by mass,
The content of Al ₂ O ₃ is 1 to 20% by mass,
The mass ratio of the B ₂ O ₃ content to the Al ₂ O ₃ content [B ₂ O ₃ /Al ₂ O ₃ ] is 8 or less,
An optical glass having an F content of 2% by mass or less.

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

(4) An optical element comprising the optical element blank according to (3) above.

ADVANTAGE OF THE INVENTION According to this invention, the optical glass, optical element blank, and optical element which are excellent in acid resistance can be provided.

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

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

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

The Abbe number νd is used as a value representing properties related to dispersion, and is expressed by the following 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)

Below, the optical glass of the present invention will be described separately for a first embodiment and a second embodiment. The action and effect of each glass component in the second embodiment are the same as the action and effect of each glass component in the first embodiment. Therefore, in the second embodiment, matters overlapping with the description of the first embodiment will be omitted as appropriate.

First Embodiment The optical glass according to the first embodiment of the present invention is
The refractive index nd is 1.70 to 1.85,
The content of B ₂ O ₃ is 5 to 35%,
La ₂ O ₃ content is 25 to 50%,
The content of Al ₂ O ₃ is 1 to 20%,
satisfy (a) or (b) of the following;
(a) the Abbe number νd is 42 or more and less than 50, and the acid resistance based on JOGIS is grade 1 to 2;
(b) Abbe number νd is 50 or more and 55 or less, and the acid resistance is grade 1 to 3 according to JOGIS.

The optical glass according to the first embodiment will be described in detail below.

The optical glass according to the first embodiment has a refractive index nd of 1.70 to 1.85. The refractive index nd can also be between 1.71 and 1.84, or between 1.72 and 1.83.

The refractive index nd can be controlled by adjusting the composition of the glass component. For example, components that relatively increase the refractive index nd are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ . Components _that relatively lower the refractive index nd are _SiO2 , _B2O3 , _Li2O , _Na2O and _K2O . The refractive index nd can be controlled by appropriately adjusting the content of these components.

In the optical glass according to the first embodiment, the content of B ₂ O ₃ is 5-35%. The upper limit of the content of B ₂ O ₃ is preferably 31%, more preferably 29%, 27% and 25% in that order. Also, the lower limit of the content of B ₂ O ₃ is preferably 7%, more preferably 8%, 9% and 10% in that order.

If the content of B ₂ O ₃ is too high, the acid resistance may deteriorate. On the other hand, if the content of B ₂ O ₃ is too small, the thermal stability of the glass may deteriorate.

In the optical glass according to the first embodiment, the content of La ₂ O ₃ is 25-50%. The upper limit of the La ₂ O ₃ content is preferably 48%, more preferably 46%, 44% and 42% in that order. The lower limit of the La ₂ O ₃ content is preferably 27%, more preferably 28%, 29% and 30% in that order.

By setting the content of La ₂ O ₃ within the above range, the acid resistance of the glass can be improved and desired optical constants can be achieved.

In the optical glass according to the first embodiment, the content of Al ₂ O ₃ is 1-20%. The upper limit of the content of Al ₂ O ₃ is preferably 18%, more preferably 16%, 15% and 14% in that order. Also, the lower limit of the content of Al ₂ O ₃ is preferably 2%, more preferably 3%, 4% and 5% in that order.

If the content of Al ₂ O ₃ is too high, the liquidus temperature LT may increase, and the dispersibility may become high, making it impossible to obtain an optical glass having desired optical constants. Moreover, when the content of Al ₂ O ₃ is too small, the acid resistance may be lowered.

The optical glass according to the first embodiment satisfies the following (a) or (b).
(a) The Abbe number νd is 42 or more and less than 50, and the acid resistance is grade 1 to 2 based on JOGIS.
(b) The Abbe number νd is 50 or more and 55 or less, and the acid resistance is grade 1 to 3 according to JOGIS.

In the case of (a) above, the Abbe number νd is 42 or more and less than 50. The Abbe number νd can also be 43 or more and less than 50, or 44 or more and less than 50.

The Abbe number νd can be controlled by adjusting the composition of the glass component. Components that relatively lower the Abbe number νd are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ and Ta ₂ O ₅ . Components that relatively increase the Abbe number νd are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , BaO, and CaO. , SrO. The Abbe number νd can be controlled by appropriately adjusting the contents of these components.

In the case of (a) above, the acid resistance based on JOGIS is grade 1 or 2, preferably grade 1. Acid resistance can be enhanced by appropriately adjusting the contents of B ₂ O ₃ and Al ₂ O ₃ .

The acid resistance is evaluated in accordance with the Japanese Optical Glass Industry Standard JOGIS06-2009. Specifically, a weight of powdered glass (particle size 425 to 600 μm) corresponding to the specific gravity was placed in a platinum cage, which was immersed in a quartz glass round-bottomed flask containing a 0.01 mol/L nitric acid aqueous solution, and then placed in a boiling water bath. for 60 minutes, and the weight reduction rate Da (%) before and after the treatment is measured. Table 1 shows the grade according to the acid resistance weight loss rate Da.

In the case of (b) above, the Abbe number νd is 50 or more and 55 or less. The Abbe number νd can also be 50 or more and 54.5 or less, or 50 or more and 54 or less. The glass components involved in controlling the Abbe number νd are the same as in the case of (a) above.

In the case of (b) above, the acid resistance based on JOGIS is grades 1 to 3, preferably grades 1 to 2, and more preferably grade 1. The glass components involved in acid resistance control are the same as in the case of (a) above. Moreover, the method for evaluating the acid resistance is also the same as in the case of (a) above.

In the optical glass according to the first embodiment, the upper limit of the SiO ₂ content is preferably 20%, more preferably 17%, 14% and 12% in that order. The lower limit of the SiO ₂ content is preferably 5%, more preferably 6%, 7% and 8% in that order. By setting the content of SiO ₂ within the above range, deterioration of the acid resistance, devitrification resistance and chemical durability of the glass can be suppressed.

In the optical glass according to the first embodiment, the upper limit of the mass ratio [B ₂ O ₃ /Al 2 O _{3 ] of the content of B 2 O 3 to the content} of Al ₂ O ₃ is preferably 8, and is more preferred in the order of 5, 4, 3. Also, the lower limit of the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is preferably 0.5, more preferably 0.6, 0.7 and 0.8 in that order. By setting the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] within the above range, it is possible to suppress deterioration in acid resistance and obtain an optical glass having desired optical constants.

Contents, ratios, and glass properties 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 total content of SiO ₂ and Al ₂ O ₃ [SiO ₂ +Al ₂ O ₃ ] is preferably 14.5%, more preferably 14.8%. %, then 15.1%. The upper limit of the total content [SiO ₂ +Al ₂ O ₃ ] is preferably 30%, more preferably 28%, 27% and 26% in that order. By setting the total content [SiO ₂ +Al ₂ O ₃ ] within the above range, both desired acid resistance and devitrification resistance can be achieved.

In the optical glass according to the first embodiment, the lower limit of the total content of SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ [SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ] is preferably 31.0%. , and more preferably 31.5%, 32%, and 32.5% in that order. The upper limit of the total content [SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ] is preferably 45%, more preferably 44%, 43% and 42% in that order. By setting the total content [SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ] within the above range, both desired acid resistance and devitrification resistance can be achieved.

In the optical glass according to the first embodiment, the lower limit of the mass ratio [SiO ₂ /La ₂ O ₃ ] of the content of SiO ₂ to the content of La ₂ O ₃ is preferably 0.19, more preferably 0 0.20, 0.21, 0.22 are more preferred. Also, the upper limit of the mass ratio [SiO ₂ /La ₂ O ₃ ] is preferably 0.34, more preferably 0.32, 0.31 and 0.30 in that order. By setting the mass ratio [SiO ₂ /La ₂ O ₃ ] within the above range, both desired acid resistance and devitrification resistance can be achieved.

In the optical glass according to the first embodiment, the lower limit of the mass ratio [Al _{2 O 3 /} La ₂ O ₃ ] _of the content of Al ₂ O ₃ to the content of La 2 O 3 is preferably 0.15. , and more preferably 0.16, 0.17 and 0.18 in that order. Also, the upper limit of the mass ratio [Al ₂ O ₃ /La ₂ O ₃ ] is preferably 0.40, more preferably 0.39, 0.38 and 0.37 in that order. By setting the mass ratio [Al ₂ O ₃ /La ₂ O ₃ ] within the above range, both desired acid resistance and devitrification resistance can be achieved.

In the optical glass according to the first embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ to the content of La ₂ O ₃ [(SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ) /La ₂ O ₃ ] is preferably 0.68, and more preferably 0.70, 0.72 and 0.74 in this order. In addition, the upper limit of the mass ratio [(SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ )/La ₂ O ₃ ] is preferably 1.10, and further in the order of 1.08, 1.06 and 1.04. more preferred. By setting the mass ratio [(SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ )/La ₂ O ₃ ] within the above range, desired acid resistance and devitrification resistance can both be achieved.

In the optical glass according to the first embodiment, the upper limit of the content of P ₂ O ₅ is preferably 5%, more preferably 4%, 3% and 2% in that order. Also, the content of P ₂ O ₅ is preferably as small as possible, and the lower limit thereof is preferably 0%. The content _{of P2O5} may be 0%. By setting the content of P ₂ O ₅ within the above range, deterioration of devitrification resistance and chemical weather resistance of the glass can be suppressed.

In the optical glass according to the first embodiment, the upper limit of the Li ₂ O content is preferably 5%, more preferably 4%, 3% and 2% in that order. The Li ₂ O content is preferably as low as possible, and the lower limit is preferably 0%. The content of Li ₂ O may be 0%.

In the optical glass according to the first embodiment, the upper limit of the Na ₂ O content is preferably 5%, more preferably 4%, 3% and 2% in that order. A lower Na ₂ O content is preferable, and the lower limit thereof is preferably 0%. The content of Na ₂ O may be 0%.

In the optical glass according to the first embodiment, the upper limit of the K ₂ O content is preferably 5%, more preferably 4%, 3% and 2% in that order. The K ₂ O content is preferably as low as possible, and its lower limit is preferably 0%. The content of K ₂ O may be 0%.

In the optical glass according to the first 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 10%, more preferably 5%, The order of 4% and 3% is more preferable. The lower limit of the total content [Li ₂ O+Na ₂ O+K ₂ O] is preferably 0%.

Li ₂ O, Na ₂ O and K ₂ O have the function of lowering the liquidus temperature and improving the thermal stability of the glass. do. Therefore, it is preferable that each content of Li ₂ O, Na ₂ O and K ₂ O and the total content thereof are within the ranges described above.

In the optical glass according to the first embodiment, the upper limit of the Cs ₂ O content is preferably 5%, more preferably 3%, 1% and 0.5% in that order. The lower limit of the Cs ₂ O content is preferably 0%.
Cs ₂ O has the function of improving the thermal stability of glass, but when the content of these elements increases, the chemical durability and weather resistance decrease. Therefore, the content of Cs ₂ O is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the MgO content is preferably 5%, more preferably 4%, 3% and 2% in that order. The MgO content is preferably as low as possible, and its lower limit is preferably 0%. The content of MgO may be 0%.

In the optical glass according to the first embodiment, the upper limit of the CaO content is preferably 5%, more preferably 4%, 3% and 2% in that order. The CaO content is preferably as low as possible, and its lower limit is preferably 0%. The content of CaO may be 0%.

In the optical glass according to the first embodiment, the upper limit of the SrO content is preferably 5%, more preferably 4%, 3% and 2% in that order. The SrO content is preferably as low as possible, and its lower limit 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 5%, more preferably 4%, 3% and 2% in that order. The BaO content is preferably as low as possible, and its lower limit is preferably 0%. The content of BaO may be 0%.

In the optical glass according to the first embodiment, the upper limit of the total content of MgO, CaO, SrO and BaO [MgO + CaO + SrO + BaO] is preferably 10%, more preferably 5%, 4%, and 3% in that order. Also, the lower limit of the total content [MgO+CaO+SrO+BaO] is preferably 0%.

MgO, CaO, SrO, and BaO are all glass components that work to improve the thermal stability and devitrification resistance of glass. However, when the content of these glass components increases, the acid resistance, thermal stability and devitrification resistance of the glass are lowered. Therefore, it is preferable that each content of MgO, CaO, SrO and BaO and the total content thereof are within the above range.

In the optical glass according to the first embodiment, the upper limit of the ZnO content is preferably 20%, more preferably 15%, 10% and 6% in that order. The content of ZnO is preferably as small as possible, and its lower limit is preferably 0%. The content of ZnO may be 0%. By setting the upper limit of the ZnO content within the above range, the acid resistance and meltability of the glass can be improved.

In the optical glass according to the first embodiment, the upper limit of the content of Gd ₂ O ₃ is preferably 20%, more preferably 18%, 16% and 15% in that order. The lower limit of the content of Gd ₂ O ₃ is preferably 0%, more preferably 1%, 2% and 3% in that order. By setting the content of Gd ₂ O ₃ within the above range, an increase in raw material cost can be suppressed and desired optical constants can be achieved.

In the optical glass according to the first embodiment, the upper limit of the Y ₂ O ₃ content is preferably 20%, more preferably 18%, 15% and 13% in that order. The lower limit of the Y ₂ O ₃ content is preferably 2%, more preferably 4%, 5% and 6% in that order. Desired optical constants can be achieved by setting the content of Y ₂ O ₃ within the above range.

In the optical glass according to the first embodiment, the upper limit of the ZrO ₂ content is preferably 12%, more preferably 10%, 9% and 8% in that order. Also, the lower limit of the ZrO ₂ content is preferably 0%, and more preferably 1%, 2%, and 3% in that order. The content of ZrO ₂ can be 0%. By setting the content of ZrO ₂ within the above range, the acid resistance of the glass can be improved and desired optical constants can be achieved.

In the optical glass according to the first embodiment, the upper limit of the TiO ₂ content is preferably 10%, more preferably 8%, 7% and 6% in that order. In addition, it is preferable that the content of TiO ₂ is small, and the lower limit thereof is preferably 0%. The content of _TiO2 may be 0%. By setting the content of TiO ₂ within the above range, the acid resistance of the glass can be improved and desired optical constants can be achieved.

In the optical glass according to the first embodiment, the upper limit of the content of Nb ₂ O ₅ is preferably 20%, more preferably 15%, 12% and 10% in that order. Also, the lower limit of the content of Nb ₂ O ₅ is preferably 0%, more preferably 1%, 2% and 3% in that order. The content of Nb ₂ O ₅ may be 0%. By setting the content of Nb ₂ O ₅ within the above range, the acid resistance of the glass can be improved and desired optical constants can be achieved.

In the optical glass according to the first embodiment, the upper limit of the content of WO ₃ is preferably 10%, more preferably 8%, 7% and 6% in that order. The lower the content of _WO3 , the better, and the lower limit is preferably 0%. The content of _WO3 may be 0%. By setting the content of WO ₃ within the above range, the acid resistance of the glass can be improved and desired optical constants can be achieved.

In the optical glass according to the first embodiment, the upper limit of the Bi ₂ O ₃ content is preferably 10%, more preferably 8%, 7% and 6% 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%. The content of Bi ₂ O ₃ may be 0%. By setting the content of Bi ₂ O ₃ within the above range, corrosion of the melting vessel (Pt) can be suppressed and desired optical constants can be achieved.

In the optical glass according to the first embodiment, the upper limit of the Ta ₂ O ₅ content is preferably 20%, more preferably 15%, 12% and 10% in that order. The lower limit of the Ta ₂ O ₅ content is preferably 0%, more preferably 1%, 2% and 3% in that order. is. The content of Ta ₂ O ₅ may be 0%. By setting the content of Ta ₂ O ₅ within the above range, the acid resistance of the glass can be improved and desired optical constants can be achieved.

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

In the optical 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 0.1% in that order.

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

In the optical glass according to the first embodiment, the content of Lu ₂ O ₃ is preferably 2% or less. Moreover, the lower limit of the content of Lu ₂ O ₃ is preferably 0%.
Lu ₂ O ₃ has a function of increasing the high dispersibility of the glass, but since it has a large molecular weight, it is also a glass component that increases the specific gravity of the glass. Therefore, the content of Lu ₂ O ₃ is preferably within the above range.

In the optical glass according to the first embodiment, the content of GeO ₂ is preferably 2% or less. Also, the lower limit of the content of GeO ₂ is preferably 0%.
GeO ₂ works to increase the high dispersion of glass, but it is by far the most expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of glass, the content of GeO ₂ is preferably within the above range.

In the optical glass according to the first embodiment, the content of Yb ₂ O ₃ is preferably 2% or less. Also, the lower limit of the Yb ₂ O ₃ content is preferably 0%.
When the content of Yb ₂ O ₃ increases, the specific gravity of the glass increases, possibly deteriorating the thermal stability of the glass. Therefore, the content of Yb ₂ O ₃ is preferably within the above range.

The optical glass according to the first embodiment mainly includes the glass components described above, that is, B ₂ O ₃ , La ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , P ₂ O ₅ , Li ₂ O, Na ₂ O, K _2O , _{Cs2O ,} MgO, CaO, SrO, BaO, _ZnO , _Gd2O3 , _{Y2O3 , ZrO2} , _TiO2 , _Nb2O5 , _{WO3 , Bi2O3 , Ta2O5} , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ and Yb ₂ O ₃ , the total content of the above glass components is preferably greater than 95%, It is more preferably greater than 98%, even more preferably greater than 99%, and even more preferably greater than 99.5%.

Further, the optical glass according to the first embodiment is oxide glass, and the main component in the anion component is O (oxygen). The upper limit of the F (fluorine) content in terms of the total mass on the oxide basis is preferably 2%, more preferably 1.5%, 1% and 0.5% in this order. The F content is preferably as small as possible, and may be 0%. If the content of F is too high, the glass component tends to volatilize during glass melting, and the composition of the glass melt may not be stable.

In the present invention and this specification, the content of F (fluorine) is determined based on the assumption that all the cationic components constituting the glass are made of oxides bonded with oxygen to balance the charge. Taking the mass of the entire glass as 100%, the mass of F is represented by mass % (% by mass relative to the mass based on oxide).

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

The addition amount of the fining agent is expressed in % by mass when the total content of all glass components excluding the fining agent is taken as 100%.

Pb, Cd, As, Th, and the like are components of concern about environmental impact. Therefore, the content of PbO, CdO, As ₂ O ₃ and ThO ₂ is preferably 0 to 0.1%, more preferably 0 to 0.05%, and more preferably 0 to 0.01%. % is more preferable. PbO, CdO, As ₂ O ₃ and ThO ₂ are particularly preferably substantially free.

Furthermore, the optical glass provides high transmittance over a wide visible region. In order to make the most of these features, it is preferable that no coloring element is contained. Examples of coloring elements include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, V, and the like. Any element is preferably less than 100 ppm by mass, more preferably 0 to 80 ppm by mass, even more preferably 0 to 50 ppm by mass, and particularly preferably not substantially contained.

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

(Glass properties)
<Specific gravity of glass>
The specific gravity of the optical glass according to the first embodiment is preferably 5.00 or less, more preferably 4.90 or less, 4.80 or less, and 4.70 or less in that order. The lower the specific gravity, the better, and although the lower limit is not particularly limited, it is generally about 4.00. Components that relatively increase the specific gravity include BaO, La ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and Ta ₂ O ₅ . Components that relatively lower the specific gravity include SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O and the like. The specific gravity can be controlled by adjusting the content of these components.

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

λ80 of the optical glass according to the first embodiment is preferably 500 nm or less, more preferably 470 nm or less, and even more preferably 450 nm or less.
Also, λ70 is preferably 400 nm or less, more preferably 395 nm or less, and even more preferably 390 nm or less.
λ5 is preferably 350 nm or less, more preferably 345 nm or less, and still more preferably 340 nm or less.

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

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

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

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

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

Second Embodiment An optical glass according to a second embodiment of the present invention is
The refractive index nd is 1.70 to 1.85,
Abbe number νd is 42 to 55,
The content of SiO ₂ is 5-20%,
The content of B ₂ O ₃ is 5 to 35%,
La ₂ O ₃ content is 25 to 50%,
The content of Al ₂ O ₃ is 1 to 20%,
The mass ratio of the B ₂ O ₃ content to the Al ₂ O ₃ content [B ₂ O ₃ /Al ₂ O ₃ ] is 8 or less,
It is characterized in that the content of F is 2% or less in terms of outside ratio.

The optical glass according to the second embodiment will be described in detail below.

The optical glass according to the second embodiment has a refractive index nd of 1.70 to 1.85. The refractive index nd can also be between 1.71 and 1.84, or between 1.72 and 1.83.

The optical glass according to the second embodiment has an Abbe number νd of 42-55. The Abbe number νd can also be 43-54.5, or 44-54.

In the optical glass according to the second embodiment, the content of SiO ₂ is 5-20%. The upper limit of the SiO ₂ content is preferably 17%, more preferably 14% and then 12%. The lower limit of the SiO ₂ content is preferably 6%, more preferably 7% and then 8%.

If the _SiO2 content is too high, the acid resistance, devitrification resistance and chemical durability may decrease. On the other hand, if the content of SiO ₂ is too low, unmelted glass raw materials tend to remain unmelted when the glass is melted.

In the optical glass according to the second embodiment, the content of B ₂ O ₃ is 5-35%. The upper limit of the content of B ₂ O ₃ is preferably 31%, more preferably 29%, 27% and 25% in that order. Also, the lower limit of the content of B ₂ O ₃ is preferably 7%, more preferably 8%, 9% and 10% in that order.

If the content of B ₂ O ₃ is too high, the acid resistance may deteriorate. On the other hand, if the content of B ₂ O ₃ is too small, the thermal stability of the glass may deteriorate.

In the optical glass according to the second embodiment, the content of La ₂ O ₃ is 25-50%. The upper limit of the La ₂ O ₃ content is preferably 48%, more preferably 46%, 44% and 42% in that order. The lower limit of the La ₂ O ₃ content is preferably 27%, more preferably 28%, 29% and 30% in that order.

By setting the content of La ₂ O ₃ within the above range, the acid resistance of the glass can be improved and desired optical constants can be achieved.

In the optical glass according to the second embodiment, the content of Al ₂ O ₃ is 1-20%. The upper limit of the content of Al ₂ O ₃ is preferably 18%, more preferably 16%, 15% and 14% in that order. Also, the lower limit of the content of Al ₂ O ₃ is preferably 2%, more preferably 3%, 4% and 5% in that order.

If the content of Al ₂ O ₃ is too high, the liquidus temperature LT may increase, and the dispersibility will be high, making it impossible to obtain an optical glass having desired optical constants. Moreover, when the content of Al ₂ O ₃ is too small, the acid resistance may be lowered.

In the optical glass according to the second embodiment, the mass ratio [B _{2 O 3 /} Al 2 O ₃ ] of the content of B ₂ O ₃ to the content of Al ₂ O 3 _is 8 or less. The upper limit of the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is preferably 5, more preferably 4 and 3 in that order. Also, the lower limit of the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is preferably 0.5, more preferably 0.6, 0.7 and 0.8 in that order.

If the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is too large, the acid resistance may deteriorate. Also, if the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is too small, an optical glass having desired optical constants may not be obtained.

The optical glass according to the second embodiment is oxide glass, and the main component in the anion component is O (oxygen). Further, the upper limit of the content of F (fluorine) in terms of the total mass on the oxide basis is 2%. The upper limit of the F (fluorine) content is preferably 1.5%, more preferably 1% and then 0.5%. The F content is preferably as small as possible, and may be 0%. If the content of F is too high, the glass component tends to volatilize during melting of the glass, and the composition of the glass may not be stable.

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

(Glass properties)
<Acid resistance>
In the optical glass according to the second embodiment, when the Abbe number νd is 42 or more and less than 50, the acid resistance based on JOGIS is preferably grade 1 or 2, more preferably grade 1. When the Abbe number νd is 50 or more and 55 or less, the acid resistance based on JOGIS is preferably grade 1 to 3, more preferably grade 1 to grade 2, and still more preferably grade 1. Acid resistance based on JOGIS can be evaluated in the same manner as in the first embodiment.

The specific gravity of the optical glass and the light transmittance of the glass according to the second embodiment can be the same as those of the first embodiment.

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

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
Glass samples having the glass compositions shown in Table 2 were produced by the following procedure, and various evaluations were performed.

[Manufacture of optical glass]
First, oxides, hydroxides, carbonates, and nitrates corresponding to the components of glass are prepared as raw materials, and the raw materials are weighed so that the resulting optical glass has the glass composition shown in Table 2. , to mix the raw materials thoroughly. The prepared raw material (batch raw material) thus obtained is charged into a platinum crucible, heated at 1200° C. to 1450° C. for 2 to 5 hours to form a glass melt, stirred for homogenization, clarified, and then melted into a glass melt. was cast into a mold preheated to a suitable temperature. The cast glass is heat-treated for 30 to 120 minutes at any temperature between 100 ° C. lower than the glass transition temperature Tg (Tg-100 ° C.) and 30 ° C. higher than Tg (Tg + 30 ° C.). A glass sample was obtained by standing to cool to.

[Confirmation of glass component composition]
The content of each glass component in the obtained glass sample was measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES), and it was confirmed that each composition shown in Table 2 was obtained.

[Measurement of acid resistance weight loss rate Da]
In accordance with the provisions of the Japan Optical Glass Industry Association Standard JOGIS06-2009, the obtained glass sample is made into powdered glass (particle size 425 to 600 μm) with a weight corresponding to the specific gravity, placed in a platinum cage, and 0.01 mol / L nitric acid aqueous solution. It was immersed in a quartz glass round-bottomed flask containing the sample, treated in a boiling water bath for 60 minutes, and the weight reduction rate (%) before and after the treatment was measured. Also, the weight reduction rate was evaluated by grade. Table 3 shows the results.

[Measurement of optical properties]
The obtained glass sample was further annealed at about the glass transition temperature Tg for about 30 minutes to about 2 hours, and then cooled to room temperature at a cooling rate of −30° C./hour in a furnace to obtain an annealed sample. The refractive index nd, Abbe number νd, specific gravity, λ80, λ70 and λ5 of the obtained annealed sample were measured. Table 3 shows the results.

(i) refractive index nd and Abbe number νd
The refractive indices nd, ng, nF, and nC of the annealed sample were measured by the refractive index measurement method of JIS standard JIS B 7071-1, and the Abbe number νd was calculated based on the following equation.
νd = (nd-1)/(nF-nC)

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

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

(Example 2)
Using the glass sample obtained in Example 1, a preform for precision press molding was produced by a known method. The obtained preform was heated and softened in a nitrogen atmosphere, and precision press-molded with a press mold to mold the optical glass into the shape of an aspherical lens. Thereafter, the molded optical glass was removed from the press mold, annealed, and centered to obtain an aspherical lens.

(Example 3)
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 of equivalents of the scope of the claims.

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

Claims (6)

The refractive index nd is 1.70 to 1.85,
The content of SiO ₂ is 5 to 14% by mass,
The content of B ₂ O ₃ is 8 to 35% by mass,
The content of La ₂ O ₃ is 25 to 42% by mass,
The content of Al ₂ O ₃ is 3 to 20% by mass,
ZnO content is 10% by mass or less,
The content of Gd ₂ O ₃ is 20% by mass or less,
mass ratio of B ₂ O ₃ content to Al ₂ O ₃ content [B ₂ O ₃ /Al ₂ O ₃ ] is 5 or less,
the total content of SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ [SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ] is 44% by mass or less;
The mass ratio of _the total content of _{SiO2 , B2O3} and _{Al2O3 to} the content _{of La2O3 [} ( _SiO2 + _B2O3 + _Al2O3 )/ _La2O3 ] is _0.68 . ~ 1.04;
The total content of SiO ₂ and Al ₂ O ₃ [SiO ₂ +Al ₂ O ₃ ] is 28% by mass or less,
Yb ₂ O ₃ content is 2% by mass or less,
The mass ratio of the content of Al ₂ O ₃ to the content of La 2 O 3 [Al ₂ O _{3 /} La ₂ O ₃ ] _is 0.15 or more,
Optical glass that satisfies the following (a ) ;
(a) The Abbe number νd is 42 or more and less than 50, and the acid resistance is grade 1 to 2 based on JOGIS. The refractive index nd is 1.70 to 1.85,
The content of SiO ₂ is 5 to 14% by mass,
The content of B ₂ O ₃ is 8 to 35% by mass,
The content of La ₂ O ₃ is 25 to 42% by mass,
The content of Al ₂ O ₃ is 3 to 20% by mass,
ZnO content is 10% by mass or less,
The content of Gd ₂ O ₃ is 20% by mass or less,
The mass ratio of the B ₂ O ₃ content to the Al ₂ O ₃ content [B ₂ O ₃ /Al ₂ O ₃ ] is 3.40 or less,
the total content of SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ [SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ] is 44% by mass or less;
The mass ratio of _the total content _{of SiO2 , B2O3} and _Al2O3 to the content _{of La2O3} [( _SiO2 + _B2O3 + _Al2O3 )/ _La2O3 ] is _{0.68 .} ~ 1.04;
the total content of SiO ₂ and Al ₂ O ₃ [SiO ₂ +Al ₂ O ₃ ] is 28% by mass or less;
The content of Yb ₂ O ₃ is 2% by mass or less,
Optical glass that satisfies the following ( b);
(b) The Abbe number νd is 50 or more and 55 or less, and the acid resistance is grade 1 to 3 according to JOGIS. The refractive index nd is 1.70 to 1.85,
Abbe number νd is 42 to 55,
The content of SiO ₂ is 5 to 14% by mass,
The content of B ₂ O ₃ is 8 to 35% by mass,
The content of La ₂ O ₃ is 25 to 42% by mass,
The content of Al ₂ O ₃ is 3 to 20% by mass,
ZnO content is 10% by mass or less,
The content of Gd ₂ O ₃ is 20% by mass or less,
The mass ratio of the B ₂ O ₃ content to the Al ₂ O ₃ content [B ₂ O ₃ /Al ₂ O ₃ ] is 3.40 or less,
the total content of SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ [SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ] is 44% by mass or less;
The mass ratio of _the total content _{of SiO2 , B2O3} and _{Al2O3 to the content of La2O3 [ ( SiO2} + _B2O3 + _Al2O3 )/ _La2O3 ] is _{0.68 .} ~ 1.04;
the total content of SiO ₂ and Al ₂ O ₃ [SiO ₂ +Al ₂ O ₃ ] is 28% by mass or less;
The content of Yb ₂ O ₃ is 2% by mass or less,
An optical glass having an F content of 2% by mass or less. 4. The optical glass according to claim 1, wherein the total content of SiO ₂ and Al ₂ O ₃ [SiO ₂ +Al ₂ O ₃ ] is 26 mass % or less. An optical element blank comprising the optical glass according to any one of claims 1 to 4 . An optical element comprising an optical element blank according to claim 5 .