JP2014080317A - Optical glass, preform and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical glass having refractive index (n) in a desired range and besides, having small Abbe number (ν), further small partial dispersion ratio (θg,F) and enhanced transparency to visible lights, and to provide a preform and an optical element each obtained by using the optical glass.SOLUTION: The optical glass contains, by mass%, SiOcomponent of 15.0% to 50.0%, BaO component of over 0% to 25.0%, LaOcomponent of over 0% to 35.0%, and NbOcomponent of over 0% to less than 30.0%, and a partial dispersion ratio (θg,F) and an Abbe number (νd) satisfy a relations (-0.00162×νd+0.63822)≤(θg,F)≤(-0.00275×νd+0.68125) in the range of νd≤31 and (-0.00162×νd+0.63822)≤(θg,F)≤(-0.00162×νd+0.64622) in the range of νd>31.

Description

  The present invention relates to an optical glass, a preform, and an optical element.

  Optical systems such as digital cameras and video cameras, although large and small, contain blurs called aberrations. This aberration is classified into monochromatic aberration and chromatic aberration. In particular, the chromatic aberration is strongly dependent on the material characteristics of the lens used in the optical system.

  In general, chromatic aberration is corrected by combining a low-dispersion convex lens and a high-dispersion concave lens. However, this combination can only correct aberrations in the red region and the green region, and remains in the blue region. This blue region aberration that cannot be removed is called a secondary spectrum. In order to correct the secondary spectrum, it is necessary to perform an optical design in consideration of the trend of the g-line (435.835 nm) in the blue region. At this time, the partial dispersion ratio (θg, F) is used as an index of the optical characteristics to be noticed in the optical design. In the optical system combining the low dispersion lens and the high dispersion lens, an optical material having a large partial dispersion ratio (θg, F) is used for the low dispersion side lens, and the partial dispersion ratio ( By using an optical material having a small θg, F), the secondary spectrum is corrected well.

The partial dispersion ratio (θg, F) is expressed by the following equation (1).
θg, F = (n _g −n _F ) / (n _F −n _C ) (1)

In optical glass, there is an approximately linear relationship between a partial dispersion ratio (θg, F) representing partial dispersion in a short wavelength region and an Abbe number (ν _d ). The straight line representing this relationship plots the partial dispersion ratio and Abbe number of NSL7 and PBM2 on the Cartesian coordinates employing the partial dispersion ratio (θg, F) on the vertical axis and the Abbe number (ν _d ) on the horizontal axis. It is represented by a straight line connecting two points and is called a normal line (see FIG. 1). Normal glass, which is the standard for normal lines, differs depending on the optical glass manufacturer, but each company defines it with almost the same slope and intercept. (NSL7 and PBM2 are optical glasses manufactured by OHARA, Inc., and the Abbe number (ν _d ) of PBM2 is 36.3, the partial dispersion ratio (θg, F) is 0.5828, and the Abbe number (ν _d ) of NSL7. Is 60.5, and the partial dispersion ratio (θg, F) is 0.5436.)

  Here, as glass having high dispersion, for example, optical glasses as shown in Patent Documents 1 to 3 are known.

JP 2009-179522 A JP 2009-203134 A JP 2004-161598 A

However, the glasses disclosed in Patent Documents 1 to 3 have a small partial dispersion ratio and are not sufficient for use as a lens for correcting the secondary spectrum. Further, the glasses disclosed in Patent Documents 1 to 3 are not sufficiently transparent to visible light, and are not sufficient for use in applications that transmit visible light. That is, there is a demand for an optical glass having a small Abbe number (ν _d ), high dispersion, a small partial dispersion ratio (θg, F), and high transparency to visible light.

The present invention has been made in view of the above problems, and the object of the present invention is to have a small Abbe number (ν _d ) and a partial dispersion while the refractive index (n _d ) is within a desired range. The object is to obtain an optical glass having a smaller ratio (θg, F) and improved transparency to visible light, and a preform and an optical element using the optical glass.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and studies. As a result, the SiO ₂ component, the BaO component, the La ₂ O ₃ component and the Nb ₂ O ₅ component are used in combination, and the contents thereof are determined in advance. It was found that the partial dispersion ratio (θg, F) of the glass has a desired relationship with the Abbe number (ν _d ) while the refractive index of the glass is increased by making it within this range. . Further, by using the SiO ₂ component, the BaO component and the La ₂ O ₃ component in combination, and making these contents within a predetermined range, the glass coloring is reduced while the stability of the glass is enhanced. As a result, the present invention has been completed. Specifically, the present invention provides the following.

(1) By mass%, the SiO ₂ component is 15.0% to 50.0%, the BaO component is more than 0% to 25.0% or less, the La ₂ O ₃ component is more than 0% to 35.0% or less, and Nb ₂ O ₅ component is contained more than 0% and less than 30.0%, and the partial dispersion ratio (θg, F) is within the range of νd ≦ 31 (−0.00162 × νd + 0. 63822) ≦ (θg, F) ≦ (−0.00275 × νd + 0.68125), and in the range of νd> 31, (−0.00162 × νd + 0.63822) ≦ (θg, F) ≦ (−0 .00162 × νd + 0.64622).

(2) By mass%
Li ₂ O component 0% and 30.0% or less Na ₂ O component from 0 to 25.0%
The optical glass according to (1).

(3) Mass sum _(Li 2 O + _Na 2 O) is less than 20.0% (1) or (2), wherein the optical glass.

(4) the weight ratio _{Na 2 O / (Li 2 O} + Na 2 O) 0.80 or less is (1) to (3) any description of the optical glass.

(5) The optical glass according to any one of (1) to (4), containing, by mass%, a WO ₃ component of more than 0% and 20.0% or less.

(6) The optical glass according to any one of (1) to (5), wherein the content of the TiO ₂ component is 15.0% or less by mass.

(7) The optical glass according to any one of (1) to (6), wherein the content of the B ₂ O ₃ component is 20.0% or less by mass.

(8) mass ratio _B 2 _O 3 / SiO ₂ is less than 1.00 (1) to (7) or the description of the optical glass.

(9) By mass%
MgO component 0 to 15.0%
CaO component 0 to 15.0%
SrO component 0 to 20.0%
ZnO component 0 to 30.0%
The optical glass according to any one of (1) to (8).

  (10) The optical glass according to any one of (1) to (9), wherein the mass ratio CaO / BaO is 0.50 or less.

  (11) The mass sum of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, Zn) is 30.0% or less, from (1) to (10) Any one of the optical glasses.

(12)% by weight _{K 2} O component from 0 to 20.0%
Cs ₂ O component 0 to 10.0%
The optical glass according to any one of (1) to (11).

(13) The mass sum of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, K, and Cs) is 25.0% or less, from (1) to (12) Any one of the optical glasses.

(14) Gd ₂ O ₃ component by mass% 0 to 20.0%
Y ₂ O ₃ component 0 to 20.0%
Yb ₂ O ₃ component 0 to 20.0%
Lu ₂ O ₃ component 0-20.0%
P ₂ O ₅ component 0 to 20.0%
GeO ₂ component 0-20.0%
Al ₂ O ₃ component 0 to 20.0%
ZrO ₂ component 0 to 15.0%
Ta ₂ O ₅ component 0 to 15.0%
Bi ₂ O ₃ component 0 to 10.0%
TeO ₂ component 0-20.0%
Sb ₂ O ₃ component 0-3.0%
The optical glass according to any one of (1) to (13).

  (15) The optical glass according to any one of (1) to (14), having a refractive index (nd) of 1.78 to 1.92 and an Abbe number (νd) of 26 to 35.

(16) The optical glass according to any one of (1) to (15), wherein a wavelength (λ ₇₀ ) having a spectral transmittance of 70% is 500 nm or less.

  (17) A preform for polishing and / or precision press molding comprising the optical glass according to any one of (1) to (16).

  (18) An optical element obtained by grinding and / or polishing the optical glass according to any one of (1) to (16).

  (19) An optical element formed by precision press-molding the optical glass according to any one of (1) to (16).

According to the present invention, while the refractive index (n _d ) is within a desired range, the Abbe number (ν _d ) is small, the partial dispersion ratio (θg, F) is smaller, and the transparency to visible light is increased. The obtained optical glass, and a preform and an optical element using the optical glass can be obtained.

It is a figure which shows the normal line by which partial dispersion ratio ((theta) g, F) is represented on the orthogonal coordinate of a vertical axis | shaft and Abbe number ((nu) _d ) on a horizontal axis. It is a figure which shows the relationship between the partial dispersion ratio ((theta) g, F) and the Abbe number ((nu) _d ) about the glass of the Example of this application.

In the optical glass of the present invention, the SiO ₂ component is 15.0% or more and 50.0% or less, the BaO component is more than 0% and 25.0% or less, and the La ₂ O ₃ component is more than 0% and 35.0% by mass. % And Nb ₂ O ₅ component more than 0% and less than 30.0%, the partial dispersion ratio (θg, F) is within the range of νd ≦ 31 (−0. 00162 × νd + 0.63822) ≦ (θg, F) ≦ (−0.00275 × νd + 0.68125), and in the range of νd> 31, (−0.00162 × νd + 0.63822) ≦ (θg, F) The relationship of ≦ (−0.00162 × νd + 0.64622) is satisfied. The La ₂ O ₃ component and the Nb ₂ O ₅ component are used in combination, and the content of these components is set within a predetermined range, thereby increasing the refractive index of the glass. At the same time, the Nb ₂ O ₅ component is used and its content is within a predetermined range, whereby the glass is highly dispersed (lower Abbe number). At the same time, the BaO component, the La ₂ O ₃ component and the Nb ₂ O ₅ component are used in combination, and by setting these contents within a predetermined range, the partial dispersion ratio (θg, F) of the glass becomes the Abbe number (ν _d ) with the desired relationship. At the same time, by using the SiO ₂ component, BaO component, and La ₂ O ₃ component in combination, and making these contents within a predetermined range, the coloration of the glass is reduced while the stability of the glass is enhanced. . Therefore, an optical glass having a low Abbe number (ν _d ), a small partial dispersion ratio (θg, F), and a high transparency to visible light, while the refractive index (n _d ) is within a desired range; A preform and an optical element using the same can be obtained.

  Hereinafter, embodiments of the optical glass of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. . In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the meaning of invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. Unless otherwise specified in the present specification, the contents of the respective components are all expressed in mass% with respect to the total mass of the glass in terms of oxide. Here, the “oxide equivalent composition” means that the oxide, composite salt, metal fluoride, etc. used as a raw material of the glass component of the present invention are all decomposed and changed into an oxide when melted. It is the composition which described each component contained in glass by making the total mass of the said production | generation oxide into 100 mass%.

<About essential and optional components>
The SiO ₂ component is an essential component that reduces devitrification (generation of crystalline substances), which is undesirable as an optical glass, by promoting stable glass formation.
In particular, by containing 15.0% or more of the SiO ₂ component, a stable glass excellent in devitrification resistance can be obtained without increasing the partial dispersion ratio of the glass. Moreover, devitrification and coloring at the time of reheating can be reduced thereby. Therefore, the content of the SiO ₂ component is preferably 15.0%, more preferably more than 18.0%, and even more preferably more than 20.0%.
On the other hand, by making the content of the SiO ₂ component 50.0% or less, a decrease in the refractive index of the glass can be suppressed, and an increase in the partial dispersion ratio can be suppressed. Moreover, the meltability of the glass can be kept good. Accordingly, the upper limit of the content of the SiO ₂ component is preferably 50.0%, more preferably 40.0%, still more preferably 34.0%, and even more preferably 29.0%.
As the SiO ₂ component, SiO ₂ , K ₂ SiF ₆ , Na ₂ SiF ₆ or the like can be used as a raw material.

The BaO component is a component that can increase the refractive index of the glass by containing more than 0%, can reduce the partial dispersion ratio, and can improve the devitrification resistance by appropriate inclusion. Moreover, it is a component which can reduce devitrification and coloring at the time of reheating. Therefore, the content of the BaO component is preferably more than 0%, more preferably 4.0%, and even more preferably 6.0%.
On the other hand, by setting the content of the BaO component to 25.0% or less, it is possible to suppress deterioration in devitrification resistance and chemical durability due to excessive inclusion of the BaO component. Accordingly, the upper limit of the content of the BaO component is preferably 25.0%, more preferably 20.0%, and even more preferably 15.0%.
As the BaO component, BaCO ₃ , Ba (NO ₃ ) ₂ or the like can be used as a raw material.

The La ₂ O ₃ component is a component that can increase the refractive index of the glass and reduce the partial dispersion ratio by containing more than 0%. Accordingly, the content of the La ₂ O ₃ component is preferably more than 0%, more preferably more than 3.0%, still more preferably more than 5.0%, still more preferably more than 8.0%, and still more preferably 10. Over 0%.
On the other hand, by setting the content of the La ₂ O ₃ component to 35.0% or less, devitrification of the glass due to excessive inclusion of the La ₂ O ₃ component is reduced, and a stable glass can be easily obtained. The increase in the number can be suppressed. Accordingly, the content of the La ₂ O ₃ component is preferably 35.0%, more preferably 34.0%, even more preferably 30.0%, even more preferably 26.0%, and even more preferably 20.0%. Is the upper limit.
As the La ₂ O ₃ component, La ₂ O ₃ , La (NO ₃ ) ₃ .XH ₂ O (X is an arbitrary integer) or the like can be used as a raw material.

The Nb ₂ O ₅ component is a component that can increase the refractive index of the glass, reduce the Abbe number, and reduce the partial dispersion ratio by containing more than 0%. Therefore, the content of the Nb ₂ O ₅ component is preferably more than 0%, more preferably 3.0%, still more preferably 8.5%, and even more preferably 13.0%.
On the other hand, by making the content of the Nb ₂ O ₅ component less than 30.0%, an increase in melting temperature during glass production can be suppressed. Therefore, the content of the Nb ₂ O ₅ component is preferably less than 30.0%, more preferably less than 27.0%, and even more preferably less than 25.0%.
As the Nb ₂ O ₅ component, Nb ₂ O ₅ or the like can be used as a raw material.

Li ₂ O component is an optional component that can increase the melting property of glass, lower the glass transition point, lower the partial dispersion ratio, and reduce devitrification and coloring during reheating by containing more than 0%. is there. Accordingly, the content of the Li ₂ O component is preferably more than 0%, more preferably more than 0.5%, still more preferably 1.3%, still more preferably 1.9%, still more preferably 3.0%. It is good also as a minimum.
On the other hand, by setting the content of the Li ₂ O component to 30.0% or less, it is possible to suppress a decrease in the refractive index and increase the chemical durability of the glass. Moreover, devitrification resistance at the time of glass formation can be improved, and devitrification and coloring at the time of reheating can be reduced. Therefore, the upper limit of the content of the Li ₂ O component is preferably 30.0%, more preferably 15.0%, still more preferably 11.0%, and still more preferably 8.0%.
For the Li ₂ O component, Li ₂ CO ₃ , LiNO ₃ , LiF or the like can be used as a raw material.

The Na ₂ O component is an optional component that can increase the melting property and devitrification resistance of the glass and lower the glass transition point by containing more than 0%.
On the other hand, the partial dispersion ratio can be further reduced by setting the content of the Na ₂ O component to 25.0% or less. Further, it is possible to suppress a decrease in the refractive index and make it difficult to deteriorate the chemical durability. Moreover, devitrification resistance at the time of glass formation can be improved, and devitrification and coloring at the time of reheating can be reduced. Therefore, the content of the Na ₂ O component is preferably 25.0%, more preferably 15.0%, still more preferably 8.0%, and still more preferably 5.0%.
As the Na ₂ O component, Na ₂ CO ₃ , NaNO ₃ , NaF, Na ₂ SiF ₆ or the like can be used as a raw material.

The sum (mass sum) of the contents of the Li ₂ O component and the Na ₂ O component is preferably 20.0% or less. Thereby, the fall of a refractive index can be suppressed and chemical durability can be made hard to deteriorate. Moreover, devitrification resistance at the time of glass formation can be improved, and devitrification and coloring at the time of reheating can be reduced. Therefore, the upper limit of the mass sum (Li ₂ O + Na ₂ O) is preferably 20.0%, more preferably 15.0%, and still more preferably 10.0%.
On the other hand, the mass sum (Li ₂ O + Na ₂ O) may be more than 0%. Thereby, the glass with higher devitrification resistance and stability can be obtained. Accordingly, the mass sum (Li ₂ O + Na ₂ O) is preferably more than 0%, more preferably more than 2.5%, and even more preferably more than 3.0%.

The ratio (mass ratio) of the content of Na ₂ O to the sum of the contents of the Li ₂ O component and the Na ₂ O component is preferably 0.80 or less. Thereby, a glass with a smaller partial dispersion ratio can be obtained. Therefore, Na ₂ O / (Li ₂ O + Na ₂ O) is preferably 0.80, more preferably 0.72, and still more preferably 0.65.

By containing more than 0%, the WO ₃ component is an optional component that can reduce the Abbe number while increasing the refractive index of the glass without increasing the partial dispersion ratio, and can improve devitrification resistance and solubility. Therefore, the content of the WO ₃ component is preferably more than 0%, more preferably 1.1%, still more preferably 2.3%, and even more preferably 3.3%.
On the other hand, by setting the content of the WO ₃ component to 20.0% or less, the partial dispersion ratio of the glass can be hardly increased. Further, by setting the content of the WO ₃ component to 20.0% or less, it is possible to reduce the coloring of the glass and increase the internal transmittance for visible light. Accordingly, the upper limit of the content of the WO ₃ component is preferably 20.0%, more preferably 15.0%, and still more preferably 12.0%.
As the WO ₃ component, WO ₃ or the like can be used as a raw material.

By containing more than 0% of the TiO ₂ component, it is an optional component that can reduce the Abbe number while increasing the refractive index of the glass and can improve the devitrification resistance. Therefore, the content of the TiO ₂ component is preferably more than 0%, more preferably 0.5%, still more preferably 1.0%, and even more preferably 1.4%.
On the other hand, by setting the content of the TiO ₂ component to 15.0% or less, it is possible to reduce the coloring of the glass and increase the internal transmittance for visible light. This also suppresses an increase in the partial dispersion ratio. Therefore, the content of the TiO ₂ component is preferably 15.0% as an upper limit, more preferably less than 13.0%, still more preferably 12.0%, still more preferably 10.0%, still more preferably 8 0.0% is the upper limit.
As the TiO ₂ component, TiO ₂ or the like can be used as a raw material.

B ₂ O ₃ component, by ultra containing 0%, which is an optional component that enhances devitrification resistance and solubility of the glass. Therefore, the content of the B ₂ O ₃ component is preferably more than 0%, more preferably more than 0.5%, even more preferably more than 1.0%, and even more preferably more than 1.5%.
On the other hand, by setting the content of the B ₂ O ₃ component to 20.0% or less, a decrease in refractive index and an increase in partial dispersion ratio can be suppressed. Moreover, devitrification at the time of reheating of glass can be reduced thereby. Therefore, the content of the B ₂ O ₃ component is preferably 20.0%, more preferably 15.0%, more preferably less than 11.0%, still more preferably 8.0%, and even more preferably The upper limit is 6.0%.
As the B ₂ O ₃ component, H ₃ BO ₃ , Na ₂ B ₄ O ₇ , Na ₂ B ₄ O ₇ .10H ₂ O, BPO ₄ or the like can be used as a raw material.

The ratio (mass ratio) of the content of the B ₂ O ₃ component to the content of the SiO ₂ component is preferably less than 1.00. By reducing this ratio, the partial dispersion ratio can be reduced, and chemical durability and resistance to devitrification during reheating can be improved. In addition, the SiO ₂ component is a component that tends to deteriorate the solubility of the glass as compared with the B ₂ O ₃ component. By reducing this ratio, melting at a high temperature can be avoided, so that it is easy to obtain a glass with less coloring. it can. Therefore, the mass ratio (B ₂ O ₃ / SiO ₂ ) is preferably less than 1.00, more preferably 0.80, still more preferably 0.60, still more preferably 0.40, and still more preferably 0.33. Is the upper limit.

The MgO component is an optional component that can lower the melting temperature of the glass by containing more than 0%.
On the other hand, by making the content of the MgO component 15.0% or less, it is possible to suppress a decrease in the refractive index and improve the devitrification resistance of the glass. Moreover, devitrification and coloring at the time of reheating can be reduced thereby. Therefore, the content of the MgO component is preferably 15.0%, more preferably 10.0%, and still more preferably 5.0%.
As the MgO component, MgO, MgCO ₃ , MgF ₂ or the like can be used as a raw material.

The CaO component is an optional component that can reduce the devitrification temperature of the glass by containing more than 0%.
On the other hand, by setting the content of the CaO component to 15.0% or less, it is possible to suppress a decrease in the refractive index and suppress deterioration of the chemical durability of the glass. Moreover, devitrification and coloring at the time of reheating can be reduced thereby. Therefore, the content of the CaO component is preferably 15.0%, more preferably 10.0%, more preferably less than 8.0%, and still more preferably 5.0%.
As the CaO component, CaCO ₃ , CaF ₂ or the like can be used as a raw material.

The SrO component is an optional component that can increase the refractive index of the glass and increase the devitrification resistance by containing more than 0%.
On the other hand, deterioration of the chemical durability of glass can be suppressed by making content of a SrO component into 20.0% or less. Therefore, the content of the SrO component is preferably 20.0%, more preferably 10.0%, and still more preferably 5.0%.
As the SrO component, Sr (NO ₃ ) ₂ , SrF ₂ or the like can be used as a raw material.

The ZnO component is an optional component that can lower the glass transition point while increasing the devitrification resistance of the glass by containing more than 0%.
On the other hand, by setting the content of the ZnO component to 30.0% or less, the chemical durability of the glass can be enhanced while reducing devitrification during reheating of the glass. Moreover, devitrification and coloring at the time of reheating can be reduced thereby. Therefore, the content of the ZnO component is preferably 30.0%, more preferably 20.0%, further preferably 10.0%, and further preferably 5.0%.
As the ZnO component, ZnO, ZnF ₂ or the like can be used as a raw material.

  The ratio (mass ratio) of the content of the CaO component to the total content of the BaO component is preferably 0.50 or less. Thereby, since the content of the BaO component having a large effect of increasing the refractive index by reducing the partial dispersion ratio is increased relative to the CaO component having a small effect, the optical glass having a small partial dispersion ratio and a high refractive index. Can be easily obtained. Therefore, the mass ratio CaO / BaO is preferably 0.50, more preferably 0.30, and still more preferably 0.20.

The total content (mass sum) of RO components (wherein R is one or more selected from the group consisting of Zn, Mg, Ca, Sr, and Ba) is preferably 30.0% or less. Thereby, deterioration of the devitrification resistance and chemical durability of the glass due to excessive inclusion of the RO component can be suppressed. Therefore, the total content of RO components is preferably 30.0%, more preferably 20.0%, and even more preferably less than 15.0%.
On the other hand, the total content of RO components is preferably more than 0%, more preferably more than 2.0%, and even more preferably more than 5.0%, from the viewpoint of increasing the devitrification resistance of the glass.

K 2 _O component and Cs 2 _O component, by ultra containing 0%, which is an optional component that can be lowered glass transition temperature.
On the other hand, by reducing the content of the K ₂ O component to 20.0% or less and / or the content of the Cs ₂ O component to 10.0% or less, the devitrification resistance of the glass is reduced. It can be suppressed. In particular, since the K ₂ O component has an effect of making it difficult to lower the partial dispersion ratio, it is preferable to reduce the content of the K ₂ O component from the viewpoint of obtaining a glass having a particularly low partial dispersion ratio. Therefore, the upper limit of the content of the K ₂ O component is preferably 20.0%, more preferably 10.0%, still more preferably 5.0%, and even more preferably 3.0%. Further, the content of the Cs ₂ O component is preferably 10.0%, more preferably 5.0%, and still more preferably 3.0%.
As the K ₂ O component and the Cs ₂ O component, K ₂ CO ₃ , KNO ₃ , KF, KHF ₂ , K ₂ SiF ₆ , Cs ₂ CO ₃ , CsNO _{3 and the} like can be used as raw materials.

The total content (mass sum) of Rn ₂ O components (wherein Rn is one or more selected from the group consisting of Li, Na, K and Cs) is preferably 25.0% or less. Thereby, a desired high refractive index can be easily obtained, and devitrification of the glass can be reduced. Accordingly, the total content of the Rn ₂ O component is preferably 25.0%, more preferably 18.0%, still more preferably 12.0%, and even more preferably 9.5%.
On the other hand, the total content of the Rn ₂ O component is preferably more than 0%, more preferably from the viewpoint of lowering the viscosity of the glass melt during molding and the glass transition point while enhancing the meltability of the glass. The lower limit is 5%, more preferably 1.0%, and even more preferably more than 3.0%.

Y ₂ O ₃ component, _Gd 2 _{O 3} component, _Yb 2 _{O 3} and _Lu 2 _{O 3} component, by ultra containing 0%, which is an optional component that enhances the refractive index of the glass.
On the other _hand, Y 2 _{O 3} component, _Gd 2 _{O 3} component, _Yb 2 _{O 3} and _Lu 2 _{O 3} by the following respectively 20.0% and the content of the component, enhances devitrification resistance of the glass, and It is difficult to increase the Abbe number of glass. Therefore, the content of each of the Y ₂ O ₃ component, Gd ₂ O ₃ component, Yb ₂ O ₃ and Lu ₂ O ₃ component is preferably 20.0%, more preferably 10.0%, and even more preferably 5 0.0% is the upper limit. In particular, the Lu ₂ O ₃ component may be less than 0.5%.
Y ₂ O ₃ component, Gd ₂ O ₃ component, Yb ₂ O ₃ and Lu ₂ O ₃ component are Gd ₂ O ₃ , GdF ₃ , Y ₂ O ₃ , YF ₃ , Yb ₂ O ₃ , Lu ₂ O as raw materials. ₃ etc. can be used.

P ₂ O ₅ component, by ultra containing 0%, which is an optional component to increase the stability of the glass.
On the other _hand, when the content of P 2 _{O 5} component below 20.0% _can be reduced devitrification due to excessive content of P 2 _{O 5} component. Therefore, the content of the P ₂ O ₅ component is preferably 20.0%, more preferably 10.0%, and still more preferably 5.0%.
As the P ₂ O ₅ component, Al (PO ₃ ) ₃ , Ca (PO ₃ ) ₂ , Ba (PO ₃ ) ₂ , BPO ₄ , H ₃ PO ₄ or the like can be used as a raw material.

The GeO ₂ component is an optional component that increases the refractive index of glass and stabilizes the glass to reduce devitrification during molding by containing more than 0%.
On the other hand, when the content of the GeO ₂ component is 20.0% or less, the amount of expensive GeO ₂ component used is reduced, so that the material cost of the glass can be reduced. Accordingly, the content of the GeO ₂ component is preferably 20.0%, more preferably 10.0%, and still more preferably 5.0%.
As the GeO ₂ component, GeO ₂ or the like can be used as a raw material.

The Al ₂ O ₃ component is an optional component that can increase the chemical durability and devitrification resistance of the glass by containing more than 0%.
On the other hand, by making the content of the _Al 2 _{O 3} component below 20.0% can be reduced devitrification due to excessive content of _Al 2 _{O 3} component. Moreover, devitrification and coloring at the time of reheating can be reduced thereby. Accordingly, the upper limit of the content of the Al ₂ O ₃ component is preferably 20.0%, more preferably 10.0%, and even more preferably 5.0%.
As the Al ₂ O ₃ component, Al ₂ O ₃ , Al (OH) ₃ , AlF ₃ or the like can be used as a raw material.

The ZrO ₂ component is an optional component that can reduce the partial dispersion ratio of the glass while increasing the refractive index of the glass and increasing the devitrification resistance by containing more than 0%. Moreover, devitrification and coloring at the time of reheating can be reduced thereby. Accordingly, the content of the ZrO ₂ component is preferably more than 0%, more preferably more than 0.5%, still more preferably more than 1.0%, and even more preferably 2.3%.
On the other hand, by setting the content of the ZrO ₂ component to 15.0% or less, the glass can be easily melted at a lower temperature and a more homogeneous glass can be easily obtained. Therefore, the content of the ZrO ₂ component is preferably 15.0%, more preferably 12.0%, and still more preferably 10.0%.
As the ZrO ₂ component, ZrO ₂ , ZrF ₄ or the like can be used as a raw material.

The Ta ₂ O ₅ component is an optional component that can reduce the partial dispersion ratio and increase the devitrification resistance while increasing the refractive index of the glass by containing more than 0%.
On the other hand, by making the content of Ta ₂ O ₅ component 15.0% or less, the amount of Ta ₂ O ₅ component, which is a rare mineral resource, is reduced, and the glass is easily melted at a lower temperature. Increase in production cost of glass can be suppressed. Therefore, the content of the Ta ₂ O ₅ component is preferably 15.0%, more preferably 10.0%, and still more preferably 5.0%.
As the Ta ₂ O ₅ component, Ta ₂ O ₅ or the like can be used as a raw material.

The Bi ₂ O ₃ component is an optional component that can contain more than 0% to increase the refractive index of the glass, lower the Abbe number, and lower the glass transition point.
On the other hand, by making the content of the Bi ₂ O ₃ component 10.0% or less, it is difficult to increase the partial dispersion ratio of the glass, and the internal transmittance for visible light can be reduced by reducing the coloring of the glass. Enhanced. Therefore, the content of the Bi ₂ O ₃ component is preferably 10.0%, more preferably 5.0%, and still more preferably 3.0%. The Bi ₂ O ₃ component may not be contained.
As the Bi ₂ O ₃ component, Bi ₂ O ₃ or the like can be used as a raw material.

The TeO ₂ component is an optional component that can increase the refractive index of the glass, reduce the partial dispersion ratio of the glass, and lower the glass transition point by containing more than 0%.
On the other hand, by setting the content of the TeO ₂ component to 20.0% or less, the internal transmittance for visible light can be increased by reducing the coloring of the glass. Further, since the use of expensive TeO ₂ component is reduced, glass with lower material cost can be obtained. Therefore, the content of the TeO ₂ component is preferably 20.0% as an upper limit, more preferably less than 10.0%, and still more preferably less than 5.0%. The TeO ₂ component may not be contained.
TeO ₂ component can use TeO ₂ or the like as a raw material.

The Sb ₂ O ₃ component is an optional component that promotes the defoaming of the glass and can clarify the glass by containing more than 0%.
On the other hand, by setting the content of the Sb ₂ O ₃ component to 3.0% or less, excessive foaming during glass melting can be made difficult to occur, and the Sb ₂ O ₃ component can be dissolved in a melting facility (particularly Pt Alloying with noble metals such as Therefore, the content of the Sb ₂ O ₃ component is preferably 3.0%, more preferably 1.0%, and still more preferably 0.5%. However, when importance is attached to the environmental impact of the optical glass, it is preferable not to contain the Sb ₂ O ₃ component.
As the Sb ₂ O ₃ component, Sb ₂ O ₃ , Sb ₂ O ₅ , Na ₂ H ₂ Sb ₂ O ₇ .5H ₂ O, or the like can be used as a raw material.

Incidentally, components of the fining defoaming of glass is not limited to the above Sb ₂ O ₃ ingredients may be used known refining agents and defoamers in the field of glass production, or a combination thereof .

<About ingredients that should not be included>
Next, components that should not be contained in the optical glass of the present invention and components that are not preferably contained will be described.

  Other components can be added as necessary within the range not impairing the properties of the glass of the present invention. However, each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, Ce, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, Even when a small amount is contained alone or in combination, the glass is colored and has the property of causing absorption at a specific wavelength in the visible range. Is preferred.

Moreover, since lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components with high environmental loads, it is desirable that they are not substantially contained, that is, not contained at all except for inevitable mixing.

  Furthermore, each component of Th, Cd, Tl, Os, Be, and Se has tended to be refrained from being used as a harmful chemical material in recent years, and not only in the glass manufacturing process, but also in the processing process and disposal after commercialization. Until then, environmental measures are required. Therefore, when importance is placed on the environmental impact, it is preferable that these are not substantially contained.

The glass composition of the present invention cannot be expressed directly in the description of mol% because the composition is expressed by mass% with respect to the total mass of the glass of oxide conversion composition, but various properties required in the present invention. The composition expressed by mol% of each component present in the glass composition satisfying the above conditions generally takes the following values in terms of oxide conversion.
SiO ₂ component 25.0-70.0 mol%,
BaO component more than 0% to 15.0 mol%,
La ₂ O ₃ component over 0% to 12.0 mol% and _Nb 2 _{O 5} component 0% and 10.0 mol%
And Li ₂ O component 0 to 50.0 mol%
Na ₂ O component from 0 to 40.0 mol%
WO ₃ component 0-10.0 mol%
TiO ₂ component 0 to 20.0 mol%
B ₂ O ₃ component 0 to 30.0 mol%
MgO component 0-40.0 mol%
CaO component 0 to 30.0 mol%
SrO component 0 to 30.0 mol%
ZnO component 0 to 40.0 mol%
K ₂ O component from 0 to 30.0 mol%
Cs ₂ O components 0 to 3.0 mol%
Gd ₂ O ₃ component 0 to 7.0 mol%
Y ₂ O ₃ component 0 to 10.0 mol%
Yb ₂ O ₃ component from 0 to 7.0 mol%
Lu ₂ O ₃ component 0-7.0 mol%
P ₂ O ₅ component from 0 to 15.0 mol%
GeO ₂ component 0-15.0 mol%
Al ₂ O ₃ component 0 to 30.0 mol%
ZrO ₂ component 0 to 15.0 mol%
Ta ₂ O ₅ component 0-5.0 mol%
Bi ₂ O ₃ component 0-3.0 mol%
TeO ₂ component 0 to 10.0 mol%
Sb ₂ O ₃ component 0 to 1.0 mol%

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is put into a platinum crucible, a quartz crucible or an alumina crucible and roughly melted, then a gold crucible, a platinum crucible In a platinum alloy crucible or iridium crucible, melt in a temperature range of 1100 to 1400 ° C. for 3 to 5 hours, stir to homogenize, blow out bubbles, etc., and then finish at a temperature of 1000 to 1400 ° C. It is manufactured by removing the striae, casting into a mold and slow cooling.

<Physical properties>
The optical glass of the present invention preferably has a predetermined refractive index and dispersion (Abbe number). More specifically, the refractive index (n _d ) of the optical glass of the present invention is preferably 1.78, more preferably 1.79, and still more preferably 1.80. On the other hand, the upper limit of the refractive index (n _d ) of the optical glass of the present invention is not particularly limited, but is generally 1.92 or less, more specifically 1.90 or less, and more specifically 1.87 or less. Also good. The Abbe number (ν _d ) of the optical glass of the present invention is preferably 35, more preferably 34.5, and more preferably 34. On the other hand, the lower limit of the Abbe number (ν _d ) of the optical glass of the present invention is not particularly limited, but may be approximately 26 or more, more specifically 27 or more, and more specifically 30 or more. As a result, the degree of freedom in optical design is increased, and a large amount of light refraction can be obtained even if the device is made thinner.

Moreover, the optical glass of the present invention has a low partial dispersion ratio (θg, F). More specifically, the partial dispersion ratio (θg, F) of the optical glass of the present invention is (−0.00162 × νd + 0.63822) in the range of ν _d ≦ 31 with respect to the Abbe number (ν _d ). ≦ (θg, F) ≦ (−0.00275 × νd + 0.68125) is satisfied, and (−0.00162 × νd + 0.63822) ≦ (θg, F) ≦ (− in the range of ν _d > 31 0.00162 × νd + 0.64622). As a result, an optical glass having a partial dispersion ratio (θg, F) close to the normal line can be obtained, so that chromatic aberration of an optical element formed from the optical glass can be reduced. Here, the lower limit of the partial dispersion ratio (θg, F) of the optical glass at ν _d ≦ 31 is preferably (−0.00162 × νd + 0.63822), more preferably (−0.00162 × νd + 0.63922), More preferably, it is (−0.00162 × νd + 0.64022). On the other hand, the upper limit of the partial dispersion ratio (θg, F) of the optical glass at ν _d ≦ 31 is preferably (−0.00275 × νd + 0.68125), more preferably (−0.00275 × νd + 0.68025). More preferably, (−0.00275 × νd + 0.67925). Further, the lower limit of the partial dispersion ratio (θg, F) of the optical glass at ν _d > 31 is preferably (−0.00162 × νd + 0.63822), more preferably (−0.00162 × νd + 0.63922), Preferably, it is (−0.00162 × νd + 0.64022). On the other hand, the upper limit of the partial dispersion ratio (θg, F) of the optical glass at ν _d > 31 is preferably (−0.00162 × νd + 0.64622), more preferably (−0.00162 × νd + 0.64522). More preferably, it is (−0.00162 × νd + 0.64422). In particular, in a region where the Abbe number (ν _d ) is small, the partial dispersion ratio (θg, F) of general glass is higher than that of the normal line, and the partial dispersion ratio (θg, F) of general glass is high. And the Abbe number (ν _d ) are represented by curves. However, since it is difficult to approximate this curve, the present invention uses a straight line having a different slope from ν _d = 31 as a partial dispersion ratio (θg, F) lower than that of general glass. Expressed.

Moreover, it is preferable that the optical glass of this invention has little coloring. In particular, when the optical glass of the present invention is represented by the transmittance of the glass, the wavelength (λ ₇₀ ) indicating a spectral transmittance of 70% in a sample having a thickness of 10 mm is 500 nm or less, more preferably 470 nm or less, and still more preferably. Is 450 nm or less, more preferably 410 nm or less. In the optical glass of the present invention, the wavelength (λ ₅ ) showing a spectral transmittance of 5% in a sample having a thickness of 10 mm is 420 nm or less, more preferably 400 nm or less, and further preferably 390 nm or less. Thereby, the absorption edge of the glass is positioned in the vicinity of the ultraviolet region, and the transparency of the glass in the visible region is enhanced. Therefore, this optical glass can be preferably used as a material for an optical element such as a lens.

The optical glass of the present invention preferably has good press formability. That is, the optical glass of the present invention divides the transmittance of light (d-line) having a wavelength of 587.56 nm of the test piece after the reheating test (ii) by the transmittance of d-line of the test piece before the reheating test. The measured value is preferably 0.95 or more. Also, a lambda ₇₀ is a wavelength at which the transmittance of the reheating test (a) before the specimen is 70% and the difference between the lambda ₇₀ of the test piece after the reheating test is 20nm or less. This makes it difficult for devitrification and coloring to occur even in a reheating test assuming reheat press processing, so that the light transmittance of the glass is less likely to be lost. Processing can be facilitated. That is, since an optical element having a complicated shape can be produced by press molding, it is possible to realize optical element production with low manufacturing cost and high productivity.

Here, the value obtained by dividing the transmittance of the light beam (d-line) having a wavelength of 587.56 nm of the test piece after the reheating test (ii) by the transmittance of the d-line of the test piece before the reheating test (ii) is The lower limit is preferably 0.95, more preferably 0.96, and still more preferably 0.97. Further, the difference between the lambda ₇₀ of the test piece after the reheating test and lambda ₇₀ of reheating test (a) prior to the test piece (b) is preferably 20 nm, more preferably 18 nm, more preferably the upper limit of the 16nm To do.

  In the reheating test (A), a test piece 15 mm × 15 mm × 30 mm is reheated, and the temperature is raised from room temperature to a temperature 80 ° C. higher than the transition temperature (Tg) of each sample in 150 minutes. The temperature can be kept at 30 ° C. higher than the transition temperature (Tg) for 30 minutes, then naturally cooled to room temperature, and the two opposing surfaces of the test piece are polished to a thickness of 10 mm and visually observed.

The optical glass of the present invention preferably has a yield point (At) of 750 ° C. or lower. Like the glass transition point, the yield point is one of the indices indicating the low temperature softening property of the glass, but is an index indicating a temperature closer to the press molding temperature. Therefore, by lowering the yield point, the press molding temperature can be further lowered and the press molding can be easily performed. Accordingly, the upper limit of the yield point of the optical glass of the present invention is preferably 750 ° C., more preferably 700 ° C., and most preferably 650 ° C.
The lower limit of the yield point of the optical glass of the present invention is not particularly limited, but the yield point of the glass obtained by the present invention is generally 300 ° C. or higher, specifically 400 ° C. or higher, more specifically 500 ° C. or higher. More specifically, it may be higher than 580 ° C.

[Preforms and optical elements]
A glass molded body can be produced from the produced optical glass by means of mold press molding such as reheat press molding or precision press molding. That is, a preform for mold press molding is prepared from optical glass, and after performing reheat press molding on the preform, polishing is performed to prepare a glass molded body, or for example, polishing is performed. The preform can be precision press-molded to produce a glass molded body. In addition, the means for producing the glass molded body is not limited to these means.

  The glass molded body thus produced is useful for various optical elements, and among them, it is particularly preferable to use it for applications of optical elements such as lenses and prisms. As a result, color bleeding due to chromatic aberration in the transmitted light of the optical system provided with the optical element is reduced. Therefore, when this optical element is used in a camera, a photographing object can be expressed more accurately, and when this optical element is used in a projector, a desired image can be projected with higher definition.

Composition of Examples (No. 1 to No. 37) and Comparative Examples (No. A to No. C) of the present invention, refractive index (n _d ), Abbe number (ν _d ), partial dispersion ratio (θg) , F) and wavelengths (λ ₅ , λ ₇₀ ) at which the spectral transmittance is 5% and 70% are shown in Tables 1 to 5. The following examples are merely for illustrative purposes, and are not limited to these examples.

  The glasses of the examples and comparative examples of the present invention are ordinary optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, hydroxides, and metaphosphate compounds corresponding to the raw materials of the respective components. After selecting the high-purity raw materials to be used in the above, weighing them so as to have the composition ratios of the examples and comparative examples shown in the table, mixing them uniformly, and then putting them into a platinum crucible, making it easy to melt the glass composition Depending on the degree, melt in a temperature range of 1100 to 1400 ° C in an electric furnace for 3 to 5 hours, stir and homogenize to eliminate bubbles, etc., then lower the temperature to 1000 to 1400 ° C and homogenize with stirring, then mold The glass was produced by casting and slowly cooling.

Here, the refractive index (n _d ), Abbe number (ν _d ), and partial dispersion ratio (θg, F) of the glasses of Examples and Comparative Examples were measured based on Japan Optical Glass Industry Association Standard JOGIS01-2003. Then, regarding the values of the obtained Abbe number (ν _d ) and partial dispersion ratio (θg, F), the slope a in the relational expression (θg, F) = − a × ν _d + b is 0.00162 and 0.00275. The intercept b at that time was determined. In addition, the glass used for this measurement used what was processed in the slow cooling furnace by making slow cooling temperature-fall rate into -25 degrees C / hr.

Moreover, the transmittance | permeability of the glass of an Example and a comparative example was measured according to Japan Optical Glass Industry Association standard JOGIS02. In the present invention, the presence / absence and degree of coloration of the glass were determined by measuring the transmittance of the glass. More specifically, a face parallel polished product having a thickness of 10 ± 0.1 mm is measured for a spectral transmittance of 200 to 800 nm in accordance with JISZ8722, and λ ₅ (wavelength when the transmittance is 5%) and λ ₇₀ (transmittance). Wavelength at 70%).

As shown in Tables 1 to 5, the optical glasses of the examples of the present invention all have ν _d > 31, and the partial dispersion ratio (θg, F) is (−0.00162 × νd + 0. 64622) or less, more specifically, (−0.00162 × νd + 0.64310) or less. On the other hand, the optical glass of the example of the present invention has a partial dispersion ratio (θg, F) of (−0.00162 × νd + 0.63822) or more, more specifically (−0.00162 × νd + 0.64033) or more. Met. That is, the relationship between the partial dispersion ratio (θg, F) and the Abbe number (ν _d ) for the glass of the example of the present application is as shown in FIG. Therefore, it was found that these partial dispersion ratios (θg, F) are within a desired range. On the other hand, the glass of the comparative example of the present invention had ν _d > 31, and the partial dispersion ratio (θg, F) exceeded (−0.00162 × νd + 0.64622). Therefore, it was revealed that the optical glass of the example of the present invention has a small partial dispersion ratio (θg, F) as compared with the glass of the comparative example.

The optical glasses of the examples of the present invention all have a refractive index (n _d ) of 1.78 or more, more specifically 1.80 or more, while this refractive index (n _d ) is 2.20. And within the desired range.

Further, in the optical glass of the example of the present invention, this Abbe number (ν _d ) is 35 or less, more specifically 34 or less, while each has an Abbe number (ν _d ) of 26 or more. It was within the range.

In addition, in the optical glass of the example of the present invention, each of λ ₇₀ (wavelength at 70% transmittance) was 500 nm or less, more specifically, 406 nm or less. In addition, in the optical glasses of the examples of the present invention, each of λ ₅ (wavelength at 5% transmittance) was 420 nm or less, more specifically, 389 nm or less. For this reason, it became clear that the optical glass of the Example of this invention has the high transmittance | permeability with respect to visible light, and is hard to be colored.

Therefore, it is clear that the optical glass of the example of the present invention has a high transmittance for visible light and a small chromatic aberration, while the refractive index (n _d ) and the Abbe number (ν _d ) are within the desired ranges. became.

  Although the present invention has been described in detail for the purpose of illustration, this embodiment is only for the purpose of illustration, and many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention. Will be understood.

Claims (19)

In terms of mass%, the SiO ₂ component is 15.0% to 50.0%, the BaO component is more than 0% to 25.0%, the La ₂ O ₃ component is more than 0% to 35.0%, and Nb ₂ O ₅ components are contained more than 0% and less than 30.0%, and the partial dispersion ratio (θg, F) is within the range of νd ≦ 31 with respect to the Abbe number (νd) (−0.00162 × νd + 0.63822) ≦ The relationship (θg, F) ≦ (−0.00275 × νd + 0.68125) is satisfied, and in the range of νd> 31, (−0.00162 × νd + 0.63822) ≦ (θg, F) ≦ (−0.00162 × Optical glass satisfying the relationship of νd + 0.64622). % By mass
Li ₂ O component 0% and 30.0% or less Na ₂ O component from 0 to 25.0%
The optical glass according to claim 1. The optical glass according to claim 1 or 2, wherein a mass sum (Li ₂ O + Na ₂ O) is 20.0% or less. The optical glass according to claim 1, wherein a mass ratio Na ₂ O / (Li ₂ O + Na ₂ O) is 0.80 or less. The optical glass according to any one of claims 1 to 4, wherein the optical glass contains more than 0% and not more than 20.0% of WO ₃ component by mass%. The optical glass according to any one of claims 1 to 5, wherein the content of the TiO ₂ component is 15.0% by mass or less. The optical glass according to any one of claims 1 to 6, wherein the content of the B ₂ O ₃ component is 20.0% or less in terms of mass%. The optical glass according to any one of claims 1 to 7, wherein the mass ratio B ₂ O ₃ / SiO ₂ is less than 1.00. % By mass
MgO component 0 to 15.0%
CaO component 0 to 15.0%
SrO component 0 to 20.0%
ZnO component 0 to 30.0%
The optical glass according to any one of claims 1 to 8.   The optical glass according to claim 1, wherein the mass ratio CaO / BaO is 0.50 or less.   The optical component according to any one of claims 1 to 10, wherein a mass sum of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, and Zn) is 30.0% or less. Glass. K ₂ O component in mass% 0 to 20.0%
Cs ₂ O component 0 to 10.0%
The optical glass according to any one of claims 1 to 11. The optical sum as defined in any one of claims 1 to 12, wherein the Rn ₂ O component (wherein Rn is at least one selected from the group consisting of Li, Na, K, and Cs) is 25.0% or less. Glass. Gd ₂ O ₃ component by mass% 0 to 20.0%
Y ₂ O ₃ component 0 to 20.0%
Yb ₂ O ₃ component 0 to 20.0%
Lu ₂ O ₃ component 0-20.0%
P ₂ O ₅ component 0 to 20.0%
GeO ₂ component 0-20.0%
Al ₂ O ₃ component 0 to 20.0%
ZrO ₂ component 0 to 15.0%
Ta ₂ O ₅ component 0 to 15.0%
Bi ₂ O ₃ component 0 to 10.0%
TeO ₂ component 0-20.0%
Sb ₂ O ₃ component 0-3.0%
The optical glass according to any one of claims 1 to 13.   The optical glass according to claim 1, having a refractive index (nd) of 1.78 or more and 1.92 or less and an Abbe number (νd) of 26 or more and 35 or less. The optical glass according to claim 1, wherein the wavelength (λ ₇₀ ) at which the spectral transmittance shows 70% is 500 nm or less.   A preform for polishing and / or precision press molding comprising the optical glass according to any one of claims 1 to 16.   An optical element obtained by grinding and / or polishing the optical glass according to claim 1.   An optical element formed by precision press-molding the optical glass according to claim 1.

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