JP7126446B2 - Optical glass, preform materials and optical elements - Google Patents

Description

The present invention relates to optical glass, preform materials and optical elements.

In recent years, the digitization and high-definition of devices that use optical systems are progressing rapidly, and various optical devices such as shooting devices such as digital cameras and video cameras, and image reproduction (projection) devices such as projectors and projection televisions. In the field of optical systems, there is an increasing demand to reduce the number of optical elements such as lenses and prisms used in the optical system, and to reduce the weight and size of the entire optical system.

Among optical glasses for producing optical elements, it has a refractive index (n _d ) of 1.60 or more and 35 or more and 65 or less, which is capable of reducing the weight and size of the entire optical system and correcting chromatic aberration. The demand for medium refractive index low dispersion glasses with Abbe number (ν _d ) is very high.

Glass compositions typified by Patent Documents 1 and 2 are known as such medium-refractive-index, low-dispersion glasses. However, these B ₂ O ₃ —La ₂ O ₃ -based glass compositions are often vulnerable to water and acids due to the characteristics of commonly used glass components, and have insufficient durability. . Therefore, the glass may be deteriorated during the polishing process of the glass, which may cause problems in the manufacturing process.
Surveillance cameras and in-vehicle cameras, for which demand has increased in recent years, are constantly used outdoors, and are often exposed to wind and rain, water vapor in the atmosphere, and the like. When using an image pickup device using a conventional glass composition, if long-term use is assumed in the outside world, the glass composition as described in Patent Documents 1 and 2 has sufficient durability. is not.

JP-A-55-080736 JP-A-11-139844

The present invention has been made in view of the above problems. An object of the present invention is to obtain an optical glass having optical constants within the predetermined range, good chemical durability and low specific gravity.

In order to solve the above problems, the present inventors have conducted extensive research and studies, and as a result, have found that a glass that solves the above problems can be obtained by having a specific composition, and have completed the present invention. rice field. Specifically, the present invention provides the following.

(1) in mole %,
molar sum (SiO ₂ +B ₂ O ₃ ) is 40.0 to 75.0%,
Ln ₂ O ₃ components (wherein Ln is one or more selected from the group consisting of La, Gd, Y and Lu) in a molar sum of 3.0% to 25.0%,
The molar sum of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is more than 0% to 25.0%,
The product of the specific gravity (d) of the glass and the powder method acid resistance grade (RA) multiplied by d × RA is 15.0 or less,
An optical glass having a refractive index (n _d ) of 1.58 or more and 1.80 or less and an Abbe number (ν _d ) of 35 or more and 65 or less.

(2) in mol %,
SiO ₂ component 5.0-60.0%
B ₂ O ₃ components 0-70.0%
Al ₂ O ₃ component 0 to 25.0%,
La ₂ O ₃ component 0 to 25.0%,
Y ₂ O ₃ component 0 to 25.0%,
Gd ₂ O ₃ component 0-25.0%,
Lu ₂ O ₃ component 0-5.0%,
Yb ₂ O ₃ component 0-5.0%,
ZrO ₂ component 0-10.0%,
TiO ₂ component 0-10.0%,
Nb ₂ O ₅ components 0-10.0%,
Ta ₂ O ₅ components 0-5.0%,
WO ₃ components 0 to 5.0%,
ZnO component 0 to 30.0%,
MgO component 0 to 30.0%,
CaO component 0 to 35.0%,
SrO component 0 to 30.0%,
BaO component 0 to 30.0%,
Li ₂ O component 0 to 20.0%,
Na ₂ O component 0 to 15.0%,
K ₂ O component 0-15.0%,
GeO ₂ component 0-10.0%,
Ga ₂ O ₃ component 0 to 10.0%,
P ₂ O ₅ components 0 to 10.0%,
Bi ₂ O ₃ components 0 to 5.0%,
TeO ₂ component 0-5.0%,
SnO ₂ component 0-3.0%,
Sb ₂ O ₃ component 0-1.0%,
The optical glass according to (1).

(3) The optical glass according to (1) or (2), wherein the molar ratio (SiO ₂ +Al ₂ O ₃ )/B ₂ O ₃ is 0.1 or more.

(4) The optical glass according to (1) to (3), wherein the molar sum (SiO ₂ +Al ₂ O ₃ ) is 8.0 to 65.0%.

(5) The optical glass according to any one of (1) to (4), wherein the molar ratio _{( Ln2O3} / _Rn2O ) is 0.3 or more.

(6) The optical glass according to any one of (1) to (5), wherein the molar sum (ZrO ₂ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +TeO ₂ ) is 0 to 20.0%.

(7) The optical glass according to any one of (1) to (6), wherein the molar ratio (Ln ₂ O ₃ +SiO ₂ +Al ₂ O ₃ )/(RO+Rn ₂ O+B ₂ O ₃ ) is 0.2 to 3.0. .

(8) The optical glass according to any one of (1) to (7), which has a molar product (BaO×Gd ₂ O ₃ ) of less than 5.0%.

(9) The optical glass according to any one of (1) to (8), which has grades 1 to 4 in chemical durability (acid resistance) according to the powder method.

(10) The molar sum of RO components (wherein R is one or more selected from the group consisting of Zn, Mg, Ca, Sr, and Ba) is 40.0% or less of (1) to (9) Optical glass according to any one of the above.

(11) A preform material made of the optical glass according to any one of (1) to (10).

(12) An optical element made of the optical glass described in any one of (1) to (10).

(13) An optical instrument comprising the optical element according to (12).

According to the present invention, it is possible to obtain glasses having optical constants within a given range and good chemical durability.

Hereinafter, embodiments of the glass of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all, and can be carried out with appropriate modifications within the scope of the purpose of the present invention. can be done. It should be noted that descriptions of overlapping descriptions may be omitted as appropriate, but the gist of the invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. In this specification, unless otherwise specified, the content of each component is expressed in mol % with respect to the total amount of glass material in terms of oxide composition. Here, the "composition in terms of oxide" refers to all of the oxides, composite salts, metal fluorides, and the like used as raw materials for the constituent components of the glass of the present invention, assuming that they are all decomposed and changed into oxides when melted. It shall be expressed in mol % with respect to the total number of moles of the oxide-equivalent composition.

When the molar sum (SiO ₂ +B ₂ O ₃ ) is 40.0% or more, the effect of improving devitrification resistance is likely to be obtained.
Therefore, the lower limit of the molar sum of (SiO ₂ +B ₂ O ₃ ) is preferably 40.0%, more preferably 45.0%, and still more preferably 50.0%.
On the other hand, by setting the molar sum to 75.0% or less, it is possible to suppress the deterioration of the meltability of glass raw materials and the excessive increase in viscosity. Therefore, the upper limit of the molar sum of (SiO ₂ +B ₂ O ₃ ) is preferably 75.0%, more preferably 70.0%, and even more preferably 65.0%.

The sum of the contents (molar sum) of the _three Ln ₂ O components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Lu) is 3.0% or more and 25.0% or less. is preferred.
In particular, by making this sum 3.0% or more, the refractive index and Abbe number of the glass are increased, so that it is possible to easily obtain glass having a desired refractive index and Abbe number. Therefore, the lower limit of the molar sum of the Ln ₂ O ₃ components is preferably 3.0%, more preferably 6.0%, even more preferably 8.0%, and most preferably 10%.
On the other hand, by setting the sum to 25.0% or less, the liquidus temperature of the glass is lowered, so that devitrification of the glass can be reduced. Therefore, the upper limit of the molar sum of the Ln ₂ O ₃ components is preferably 25.0%, more preferably 20.0%, and still more preferably 18.0%.

The sum (molar sum) of the content of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na and K) is preferably 25.0% or less. As a result, deterioration of chemical durability due to excessive content can be suppressed. Therefore, the total content is preferably 25.0%, more preferably 20.0%, still more preferably 15.0%, still more preferably 10.0%, still more preferably 5.0%, most preferably has an upper limit of 3.0%.
On the other hand, by making this sum more than 0%, deterioration of meltability and excessive increase in viscosity can be suppressed. Therefore, the lower limit of the molar sum of the Rn ₂ O components is preferably more than 0%, more preferably 0.5%, and still more preferably 1.0%.

The _SiO2 component is an essential component for improving devitrification resistance and chemical durability. The lower limit of the content of the _SiO2 component is preferably 5.0%, more preferably 10.0%, and even more preferably 15.0%.
On the other hand, by setting the content of the SiO ₂ component to 60.0% or less, a higher refractive index can be easily obtained, and deterioration of meltability and excessive increase in viscosity can be suppressed. Therefore, the content of _SiO2 component is preferably 60.0% or less, more preferably 50.0%, still more preferably 40.0%, still more preferably 30.0%, most preferably 20.0%. be the upper limit.
_SiO2 component can use _SiO2 , _K2SiF6 , _{Na2SiF6 etc.} as a _raw material.

The B ₂ O ₃ component is an optional component that has the effect of improving meltability and improving devitrification resistance. The content of the B ₂ O ₃ component is preferably greater than 0%, more preferably 5.0%, still more preferably 10.0%, still more preferably 15.0%, still more preferably 20.0%, still more preferably has a lower limit of 30.0%, most preferably 40.0%.
On the other hand, by setting the content of the B ₂ O ₃ component to 70.0% or less, deterioration of the chemical durability of the glass can be suppressed. Therefore, the upper limit of the content of the B ₂ O ₃ component is preferably 70.0%, more preferably 60.0%, still more preferably 55.0%, and most preferably 50.0%.
For 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 and the like can be used as raw materials.

The Al ₂ O ₃ component is an optional component that has the effect of improving devitrification resistance and chemical durability. The lower limit of the content of the Al ₂ O ₃ component is preferably more than 0%, more preferably 0.5%, and still more preferably 1.0%.
In particular, by setting the content of the Al ₂ O ₃ component to 5.0% or more, the chemical durability can be remarkably improved when the Rn ₂ O component is contained in a large amount. Therefore, the lower limit of the Al ₂ O ₃ component content is preferably 5.0%, more preferably 10.0%, and most preferably 15.0%.
On the other hand, by setting the content of the Al ₂ O ₃ component to 25.0% or less, deterioration of devitrification resistance and a decrease in refractive index due to excessive content can be suppressed. Therefore, the upper limit of the Al ₂ O ₃ component content is preferably 25.0%, more preferably 20.0%, and most preferably 18.0%.
_Al2O3 component can use _Al2O3 , Al(OH) _{3 , AlF3, Al(PO3)3 etc. as a raw} material.

The La ₂ O ₃ component is an optional component that increases the refractive index of the glass and increases the Abbe number of the glass. Therefore, the content of La ₂ O ₃ component is preferably more than 0%, more preferably 1.0%, still more preferably 3.0%, still more preferably 5.0%, most preferably 8.0%. be the lower limit.
On the other hand, by setting the content of the La ₂ O ₃ component to 25.0% or less, devitrification can be reduced by increasing the stability of the glass. Therefore, the upper limit of the La ₂ O ₃ component content is preferably 25.0%, more preferably 20.0%, still more preferably 15.0%, and most preferably 12.0%.
La ₂ O ₃ component, La ₂ O ₃ , La(NO ₃ ) ₃ .XH ₂ O (where X is an arbitrary integer), etc. can be used as raw materials.

When the Y ₂ O ₃ component is contained by more than 0%, the material cost of the glass can be suppressed while maintaining a high refractive index and a high Abbe number, and the specific gravity of the glass can be reduced more than other rare earth components. Optional. Therefore, the content of the Y ₂ O ₃ component is preferably more than 0%, more preferably 1.0%, even more preferably 2.5%, and most preferably 3.5% as the lower limit.
On the other hand, by setting the content of the Y ₂ O ₃ component to 25.0% or less, the devitrification resistance of the glass can be enhanced. Therefore, the content of the Y ₂ O ₃ component is preferably 25.0%, more preferably 20.0%, still more preferably 15.0%, still more preferably 10.0%, most preferably 5.0%. is the upper limit.
_{Y2O3 , YF3 ,} etc. can be used as a raw material for the _Y2O3 component.

The Gd ₂ O ₃ component is an optional component that can increase the refractive index of the glass and increase the Abbe number when it is contained in an amount exceeding 0%.
On the other hand, by setting the Gd ₂ O ₃ component, which is expensive among rare earth elements, to 25.0% or less, the increase in specific gravity is suppressed and the material cost of the glass is reduced, so that optical glass can be produced at a lower cost. Therefore, the content of the Gd ₂ O ₃ component is preferably 25.0%, more preferably 20.0%, still more preferably 15.0%, still more preferably 10.0%, still more preferably 5.0%. , and most preferably up to 1.0%. From the viewpoint of reducing material cost and suppressing increase in specific gravity, the Gd ₂ O ₃ component may not be contained.
For the Gd ₂ O ₃ component, Gd ₂ O ₃ , GdF ₃ and the like can be used as raw materials.

The Lu ₂ O ₃ component is an optional component that can increase the refractive index of the glass and increase the Abbe number when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of each of the Lu ₂ O ₃ components to 5.0% or less, the material cost of the glass is reduced, so that the optical glass can be manufactured at a lower cost. Moreover, the devitrification resistance of glass can be improved by this. Therefore, the upper limit of the content of the Lu ₂ O ₃ component is preferably 5.0%, more preferably 3.0%, even more preferably 1.0%, and most preferably 0.1%. From the viewpoint of reducing material costs, the Lu ₂ O ₃ component may not be contained.
Lu ₂ O ₃ and the like can be used as raw materials for the Lu ₂ O ₃ component.

The Yb ₂ O ₃ component is an optional component that can increase the refractive index of the glass and increase the Abbe number when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the Yb ₂ O ₃ component to 5.0% or less, the material cost of the glass is reduced, so that the optical glass can be produced at a lower cost. Moreover, the devitrification resistance of glass can be improved by this. Therefore, the upper limit of the content of the Yb ₂ O ₃ component is preferably 5.0%, more preferably 3.0%, still more preferably 1.0%, and most preferably 0.1%. From the viewpoint of reducing material costs, the Yb ₂ O ₃ component may not be contained.
Yb ₂ O ₃ or the like can be used as a raw material for the Yb ₂ O ₃ component.

The ZrO ₂ component is an optional component that can increase the refractive index and Abbe number of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the ZrO ₂ component to 10.0% or less, it is possible to reduce devitrification due to the excessive content of the ZrO ₂ component. Therefore, the upper limit of the ZrO ₂ component content is preferably 10.0%, more preferably 5.0%, even more preferably 3.0%, and most preferably 1.0%.
For the ZrO ₂ component, ZrO ₂ , ZrF ₄ and the like can be used as raw materials.

The TiO ₂ component is an optional component that can increase the refractive index of the glass when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the TiO ₂ component to 10.0% or less, devitrification due to excessive content of the TiO ₂ component can be reduced, and the decrease in the transmittance of the glass to visible light (especially wavelengths of 500 nm or less) can be suppressed. suppressed. Therefore, the upper limit of the content of the TiO ₂ component is preferably 10.0%, more preferably 5.0%, even more preferably 3.0%, and most preferably 1.0%.

The Nb ₂ O ₅ component is an optional component that can increase the refractive index of the glass when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the Nb ₂ O ₅ component to 10.0% or less, devitrification due to excessive content of the Nb ₂ O ₅ component can be reduced, and visible light of the glass (especially wavelength of 500 nm or less) It is possible to suppress the decrease in transmittance for Therefore, the upper limit of the content of the Nb ₂ O ₅ component is preferably 10.0%, more preferably 5.0%, still more preferably 3.0%, and most preferably 1.0%.
_{Nb2O5 etc.} can be used as a raw material for the _{Nb2O5 component} .

The Ta ₂ O ₅ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%.
On the other hand, by reducing the expensive Ta ₂ O ₅ component to 5.0% or less, the material cost of the glass is reduced, so that optical glass can be manufactured at a lower cost. Therefore, the upper limit of the Ta ₂ O ₅ component content is preferably 5.0%, more preferably 3.0%, still more preferably 1.0%, and most preferably 0.1%. From the viewpoint of reducing material costs, the Ta ₂ O ₅ component may not be contained.
For the Ta ₂ O ₅ component, Ta ₂ O ₅ or the like can be used as a raw material.

The WO ₃ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the WO ₃ components to 5.0% or less, it is possible to reduce the coloring of the glass due to the WO ₃ components and increase the visible light transmittance. Therefore, the upper limit of the content of the _three WO components is preferably 5.0%, more preferably 3.0%, and still more preferably 1.0%.
_WO3 etc. can be used as a raw material for the _WO3 component.

The ZnO component is an optional component that improves the low-temperature meltability when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the ZnO component to 30.0% or less, a decrease in Abbe number and a decrease in devitrification resistance due to excessive content can be suppressed. Therefore, the content of the ZnO component is preferably 30.0%, more preferably 20.0%, still more preferably 15.0%, still more preferably 10.0%, still more preferably 5.0%, still more preferably is up to 3.0%, most preferably 1.0%.
ZnO, _ZnF2 , etc. can be used as raw materials for the ZnO component.

The MgO component is an optional component that improves low-temperature meltability when contained in an amount exceeding 0%.
On the other hand, by setting the content of the MgO component to 30.0% or less, deterioration of chemical durability and deterioration of devitrification resistance due to excessive content of the MgO component can be suppressed. Therefore, the content of the MgO component is preferably 30.0%, more preferably 20.0%, still more preferably 10.0%, still more preferably 5.0%, still more preferably 3.0%, most preferably has an upper limit of 1.0%.
MgCO ₃ , MgF ₂ and the like can be used as raw materials for the MgO component.

When the CaO component is contained in an amount of more than 0%, it is possible to improve the low-temperature meltability and easily obtain the effect of suppressing an excessive increase in viscosity. Therefore, the lower limit of the content of the CaO component is preferably more than 0%, more preferably 0.5%, and still more preferably 1.0%. In particular, if the Al ₂ O ₃ component is less than 5.0%, the devitrification resistance is not sufficient. can be improved. Therefore, the lower limit of the CaO content is preferably 2.0%, more preferably 3.0%, and even more preferably 5.0%.
On the other hand, by setting the content of the CaO component to 35.0% or less, deterioration of chemical durability and deterioration of devitrification resistance due to an excessive content of the CaO component can be suppressed. Therefore, the content of the CaO component is preferably 35.0%, more preferably 25.0%, still more preferably 15.0%, still more preferably 10.0%, still more preferably 5.0%. do.
CaCO ₃ , CaF ₂ and the like can be used as raw materials for the CaO component.

When the content of the SrO component exceeds 0%, the effect of improving the low-temperature meltability and suppressing an excessive increase in viscosity can be easily obtained. Therefore, the lower limit of the content of the SrO component is preferably more than 0%, more preferably 0.5%, and still more preferably 1.0%.
In particular, if the Al ₂ O ₃ component is less than 8.0%, the devitrification resistance is not sufficient. can be improved. Therefore, the lower limit of the SrO content is preferably 2.0%, more preferably 3.0%, and still more preferably 5.0%.
On the other hand, by setting the content of the SrO component to 30.0% or less, deterioration of chemical durability and deterioration of devitrification resistance due to excessive SrO component content can be suppressed. Therefore, the upper limit of the SrO component content is preferably 30.0%, more preferably 20.0%, still more preferably 10.0%, and still more preferably 5.0%.
SrO component can use Sr( _NO3 ) ₂ , _SrF2 , etc. as a raw material.

When the BaO component is contained in an amount exceeding 0%, it is possible to easily obtain the effect of improving the low-temperature meltability and suppressing an excessive increase in viscosity. Therefore, the lower limit of the content of the BaO component is preferably more than 0%, more preferably 0.5%, and still more preferably 1.0%. In particular, when the Al ₂ O ₃ component is less than 8.0%, the devitrification resistance is not sufficient. can be improved. Therefore, the lower limit of the BaO content is preferably 2.0%, more preferably 3.0%, and still more preferably 5.0%.
On the other hand, by setting the content of the BaO component to 30.0% or less, deterioration of chemical durability and deterioration of devitrification resistance due to excessive content of the BaO component can be suppressed. Therefore, the upper limit of the BaO component content is preferably 30.0%, more preferably 20.0%, still more preferably 10.0%, and still more preferably 5.0%.
BaO component can use _{BaCO3, Ba(NO3)2 , BaF2 etc.} as a raw material.

The Li ₂ O component is an optional component that improves the low-temperature meltability and moldability of the glass when it is contained in an amount exceeding 0%. Therefore, the lower limit of the Li ₂ O component content is preferably more than 0%, more preferably more than 0.1%, and still more preferably 0.5%.
On the other hand, by setting the content of the Li ₂ O component to 20.0% or less, deterioration of chemical durability due to excessive content of the Li ₂ O component can be suppressed. Therefore, the content of the Li ₂ O component is preferably 20.0%, more preferably 15.0%, still more preferably 10.0%, still more preferably 5.0%, still more preferably 3.0%, Most preferably, the upper limit is 1.0%.
Li ₂ CO ₃ , LiNO ₃ , Li ₂ CO ₃ and the like can be used as raw materials for the Li ₂ O component.

The Na ₂ O component is an optional component that improves the low-temperature meltability and formability of the glass when it is contained in an amount exceeding 0%. Therefore, the lower limit of the Na ₂ O component content is preferably more than 0%, more preferably more than 0.1%, and still more preferably 0.5%.
On the other hand, by setting the content of the Na ₂ O component to 15.0% or less, deterioration of chemical durability due to excessive content of the Na ₂ O component can be suppressed. Therefore, the content of the Na ₂ O component is preferably 15.0%, more preferably 10.0%, still more preferably 5.0%, still more preferably 3.0%, most preferably 1.0%. be the upper limit.
_Na2O component can use _{Na2CO3 , NaNO3} , _NaF , _Na2SiF6 etc. as a raw material.

The K ₂ O component is an optional component that improves the low-temperature meltability and moldability of the glass when it is contained in an amount exceeding 0%. Therefore, the lower limit of the K ₂ O component content is preferably more than 0%, more preferably more than 0.1%, and still more preferably 0.5%.
On the other hand, by setting the content of the K ₂ O component to 15.0% or less, deterioration of chemical durability due to excessive content of the K ₂ O component can be suppressed. Therefore, the content of the K ₂ O component is preferably 15.0%, more preferably 10.0%, still more preferably 5.0%, still more preferably 3.0%, most preferably 1.0%. be the upper limit.
_K2O component can use _{K2CO3 , KNO3} , KF, _{KHF2 , K2SiF6} etc. as a raw material.

The GeO ₂ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%.
However, since the raw material price of GeO ₂ is high, a high content of GeO 2 results in high production costs. Therefore, the content of the GeO ₂ component is preferably 10.0%, more preferably 5.0%, still more preferably 3.0%, still more preferably 1.0%, still more preferably 0.1%. and From the viewpoint of reducing the material cost, the GeO ₂ component may not be included.
The _GeO2 component can use _GeO2 or the like as a raw material.

The Ga ₂ O ₃ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%.
However, since Ga ₂ O ₃ is expensive as a raw material, a large content of Ga 2 O 3 results in an increase in production cost. Therefore, the content of the Ga ₂ O ₃ component is preferably 10.0%, more preferably 5.0%, still more preferably 3.0%, still more preferably 1.0%, still more preferably 0.1% is the upper limit. From the viewpoint of reducing material costs, the Ga ₂ O ₃ component may not be contained.
_{Ga2O3 etc.} can be used as a _raw material for the _Ga2O3 component.

The P ₂ O ₅ component is an optional component that can lower the liquidus temperature of the glass to improve devitrification resistance when contained in an amount exceeding 0%.
On the other hand, by setting the content of the P ₂ O ₅ component to 10.0% or less, it is possible to suppress the deterioration of the chemical durability of the glass, particularly the water resistance. Therefore, the upper limit of the content of the P ₂ O ₅ component is preferably 10.0%, more preferably 5.0%, and most preferably 1.0%.
Al(PO3) ₃ , Ca _{( PO3)2, Ba(PO3)2 , BPO4 , H3PO4 , etc. can be} used as raw materials for the P2O5 component.

The Bi ₂ O ₃ component is an optional component that can increase the refractive index and lower the glass transition point when contained in an amount exceeding 0%.
On the other hand, by setting the content of the Bi ₂ O ₃ component to 5.0% or less, the coloration of the glass can be suppressed and the devitrification resistance can be enhanced. Therefore, the upper limit of the content of the Bi ₂ O ₃ component is preferably 5.0%, more preferably 3.0%, still more preferably 1.0%, and most preferably 0.1%.
_{Bi2O3 etc.} can be used as a _raw material for the _Bi2O3 component.

The TeO ₂ component is an optional component that can increase the refractive index and lower the glass transition point when contained in excess of 0%.
On the other hand, TeO ₂ has a problem that it can be alloyed with platinum when frit is melted in a crucible made of platinum or in a melting tank in which the portion in contact with the molten glass is made of platinum. Therefore, the upper limit of the content of the TeO ₂ component is preferably 5.0%, more preferably 3.0%, even more preferably 1.0%, and most preferably 0.1%.
_The TeO2 component can use _TeO2 or the like as a raw material.

The SnO ₂ component is an optional component that, when contained in excess of 0%, can reduce oxidation of the glass melt to refine it and increase the visible light transmittance of the glass.
On the other hand, by setting the SnO ₂ component content to 3.0% or less, it is possible to reduce the coloring of the glass due to the reduction of the molten glass and the devitrification of the glass. In addition, since alloying of SnO ₂ and melting equipment (especially precious metals such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the upper limit of the SnO2 component content is preferably 3.0%, _more preferably 1.0%, even more preferably 0.5%, and most preferably 0.1%.
SnO ₂ component can use SnO, SnO ₂ , SnF ₂ , SnF ₄ etc. as raw materials.

The Sb ₂ O ₃ component is an optional component capable of defoaming the glass melt when it is contained in an amount exceeding 0%.
On the other hand, if the amount of Sb ₂ O ₃ is too large, the transmittance in the short wavelength region of the visible light region will deteriorate. Therefore, the content of the Sb ₂ O ₃ component is preferably 1.0%, more preferably 0.7%, still more preferably 0.5%, still more preferably 0.2%, most preferably 0.1%. is the upper limit.
For 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, etc. can be used as raw materials.

The component for fining and defoaming the glass is not limited to the above Sb ₂ O ₃ component, and any known fining agent, defoaming agent or combination thereof in the field of glass production can be used.

The F component is an optional component that can increase the Abbe number of the glass, lower the glass transition point, and improve the devitrification resistance when contained in an amount exceeding 0%.
However, when the content of the F component, that is, the total amount as F of the fluoride substituted with part or all of one or more oxides of each metal element described above exceeds 15.0%, F Since the amount of volatilization of the components increases, it becomes difficult to obtain stable optical constants, making it difficult to obtain a homogeneous glass.
Therefore, the content of the F component is preferably 15.0%, more preferably 12.0%, still more preferably 10.0%, still more preferably 5.0%, still more preferably 3.0%,
Most preferably, the upper limit is 1.0%.
The F component can be contained in the glass by using ZrF ₄ , AlF ₃ , NaF, CaF ₂ or the like as raw materials.

The sum of the contents (molar sum) of the RO components (wherein R is one or more selected from the group consisting of Zn, Mg, Ca, Sr and Ba) is preferably 40.0% or less. As a result, deterioration of chemical durability and deterioration of devitrification resistance due to excessive content can be suppressed. Therefore, the molar sum of the RO components is preferably 40.0%, more preferably 30.0%, still more preferably 25.0%, still more preferably 20.0%, still more preferably 15.0%, still more preferably is limited to 10.0%, most preferably 5.0%.
On the other hand, if it exceeds 0%, it is possible to easily obtain the effect of improving the meltability of the glass raw material and the effect of suppressing an excessive increase in viscosity. Therefore, the lower limit of the molar sum of RO components is preferably more than 0%, more preferably 0.5%, and still more preferably 1.0%.
In particular, when the Al ₂ O ₃ component is less than 8.0%, the devitrification resistance is not sufficient. can be improved. Therefore, the lower limit of the RO component is preferably 2.0%, more preferably 3.0%, and even more preferably 5.0%.

When the molar ratio (SiO ₂ +Al ₂ O ₃ )/(B ₂ O ₃ ) is 0.1 or more, the effect of improving the chemical durability of the glass is likely to be obtained. Therefore, the molar ratio of (SiO ₂ +Al ₂ O ₃ )/(B ₂ O ₃ ) is preferably 0.1, more preferably 0.2, more preferably 0.3, even more preferably 0.4, most preferably Let 0.5 be the lower limit.
On the other hand, by setting this molar ratio to 10.0 or less, it is possible to suppress the deterioration of the meltability of the glass raw material and the excessive increase in viscosity. Therefore, the molar ratio of (SiO ₂ +Al ₂ O ₃ )/(B ₂ O ₃ ) is preferably 10.0, more preferably 8.0, still more preferably 6.0, still more preferably 4.0, still more preferably may have an upper limit of 3.0.
When the B ₂ O ₃ component is not contained, the value of (SiO ₂ +Al ₂ O ₃ )/(B ₂ O ₃ ) is infinite.

When the molar sum (SiO ₂ +Al ₂ O ₃ ) is 8.0% or more, the effect of improving the chemical durability of the glass is likely to be obtained. Therefore, the molar sum of (SiO ₂ +Al ₂ O ₃ ) is preferably 8.0%, more preferably 10.0%, still more preferably 15.0%, still more preferably 20.0%, most preferably 25.0%. % as the lower limit.
On the other hand, by setting the molar sum to 65.0% or less, it is possible to suppress the deterioration of the meltability of glass raw materials and the excessive increase in viscosity. Therefore, the molar sum of (SiO ₂ +Al ₂ O ₃ ) is preferably 65.0%, more preferably 60.0%, more preferably 50.0%, even more preferably 45.0%, most preferably 40%. The upper limit is 0%.

When the molar ratio (Ln ₂ O ₃ /Rn ₂ O) is 0.3 or more, the effect of improving the chemical durability of the glass is likely to be obtained. Therefore, the molar ratio of (Ln ₂ O ₃ /Rn ₂ O) is preferably 0.3, more preferably 0.5, and most preferably 0.7 as the lower limit.
In particular, by setting the molar ratio (Ln ₂ O ₃ /Rn ₂ O) to 8.0 or less, it is possible to suppress the deterioration of the meltability of the raw material for glass and the excessive increase in viscosity. Therefore, the upper limit is preferably 8.0, more preferably 5.0, still more preferably 3.0.
When the Rn ₂ O component is not contained, the value of (Ln ₂ O ₃ /Rn ₂ O) is assumed to be infinite.

When the molar sum (ZrO ₂ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +TeO ₂ ) is 20.0% or less, the effect of improving devitrification resistance is likely to be obtained, and the Abbe number Excessive decrease is suppressed and low dispersion performance is easily obtained. Therefore, the molar sum of (ZrO ₂ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +TeO ₂ ) is preferably 20.0%, more preferably 15.0%, still more preferably 10.0%. , more preferably 5.0%, more preferably 3.0%, still more preferably 1.0%, most preferably 0.1%.

When the molar ratio (Ln ₂ O ₃ +SiO ₂ +Al ₂ O ₃ )/(RO+Rn ₂ O+B ₂ O ₃ ) is 0.2 or more, the effect of improving the chemical durability of the glass is likely to be obtained. Therefore _, the molar ratio of ( _Ln2O3 + _{SiO2 + Al2O3} )/(RO+ _{Rn2O + B2O3} ) is preferably 0.2, more preferably 0.3, even more preferably 0.4, most preferably Let 0.5 be the lower limit.
On the other hand, by setting this molar ratio to 3.0 or less, it is possible to suppress the deterioration of the meltability of the raw material for glass and the excessive increase in viscosity. Therefore, the molar ratio of (Ln ₂ O ₃ +SiO ₂ +Al ₂ O ₃ )/(RO + Rn ₂ O + B ₂ O ₃ ) is preferably 3.0, more preferably 2.0, and still more preferably 1.5. do.
When the _three components RO, Rn ₂ O and B ₂ O are not contained, the value of (Ln ₂ O ₃ +SiO ₂ +Al ₂ O ₃ )/(RO+Rn ₂ O+B ₂ O ₃ ) is infinite.

When the molar ratio (Ln ₂ O ₃ /RO) is 0.1 or more, the effect of improving the chemical durability of the glass is likely to be obtained. Therefore, the lower limit of the (Ln ₂ O ₃ /RO) molar ratio is preferably 0.1, more preferably 0.2, and still more preferably 0.3.
In addition, when the RO component is not contained, the value of (Ln ₂ O ₃ /RO) is assumed to be infinite.

When the molar product (BaO×Gd ₂ O ₃ ) is less than 5.0, the effect of reducing both the specific gravity and cost of the glass is likely to be obtained. Therefore, the molar product of (BaO×Gd ₂ O ₃ ) is preferably less than 5.0, more preferably 3.0, even more preferably 2.0, even more preferably 1.0, most preferably 0.1. and

<Ingredients that should not be contained>
Next, components that should not be contained in the optical glass of the present invention and components that are not preferable to be contained will be described.

Other components can be added as necessary within a range that does not impair the properties of the glass of the present invention. However, each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb and Lu, is Or even if it is combined and contained in a small amount, the glass is colored and has the property of causing absorption at a specific wavelength in the visible region. .

Since the Nd ₂ O ₃ component has a strong coloring effect on the glass, it is desirable that it is not substantially contained, that is, it is not contained at all except for unavoidable contamination.

Since the Er ₂ O ₃ component has a strong coloring effect on the glass, it is desirable that it is not substantially contained, that is, it is not contained at all except for unavoidable contamination.

In addition, since lead compounds such as PbO and the like are components with a high environmental load, it is desirable not to substantially contain them, that is, not to contain them at all except for unavoidable contamination.

Moreover, since arsenic compounds such as As ₂ O ₃ are components with a high environmental load, it is desirable not to substantially contain them, that is, not to contain them at all except for unavoidable contamination.

Furthermore, Th, Cd, Tl, Os, Be, and Se components have recently tended to refrain from being used as harmful chemical substances, and are not only used in the glass manufacturing process, but also in the processing process and disposal after manufacturing. Environmental measures are required up to the present. Therefore, it is preferable not to contain these substantially when environmental influence is emphasized.

[Physical properties]
The optical glass of the present invention preferably has a medium refractive index and a high Abbe number (low dispersion). In particular, the refractive index (n _d ) of the optical glass of the present invention is preferably 1.58, more preferably 1.60, still more preferably 1.62, still more preferably 1.63, most preferably 1.64. be the lower limit. The upper limit of the refractive index (n _d ) is preferably 1.80, more preferably 1.75, even more preferably 1.70, and most preferably 1.68.
The Abbe number (ν _d ) of the optical glass of the present invention is preferably 35, more preferably 38, still more preferably 40, still more preferably 45, most preferably 50 as the lower limit. The upper limit of the Abbe number (ν _d ) is preferably 65, preferably 64, more preferably 63, still more preferably 62, still more preferably 61, and most preferably 60.
By having such a medium refractive index, it is possible to obtain a large amount of light refraction even if the thickness of the optical element is reduced. In addition, by having such low dispersion, it is possible to reduce defocus (chromatic aberration) caused by the wavelength of light when used as a single lens. Therefore, when an optical system is configured by combining an optical element having high dispersion (low Abbe number), for example, aberration can be reduced in the optical system as a whole, and high imaging characteristics can be achieved.
As described above, the optical glass of the present invention is useful in optical design, and in particular, when an optical system is constructed, it is possible to reduce the size of the optical system while achieving high image-forming characteristics. degree of freedom can be expanded.

The optical glass of the present invention preferably has a small specific gravity. More specifically, the specific gravity of the optical glass of the present invention is 5.00 or less. As a result, the mass of the optical element and the optical equipment using the optical element is reduced, so that it is possible to contribute to the weight reduction of the optical equipment. Therefore, the upper limit of the specific gravity of the optical glass of the present invention is preferably 5.00, more preferably 4.70, and preferably 4.50. The specific gravity of the optical glass of the present invention is generally 2.80 or higher, more specifically 3.00 or higher, and still more specifically 3.20 or higher in many cases.
The specific gravity of the optical glass of the present invention is measured based on the Japan Optical Glass Industry Standard JOGIS05-1975 "Method for measuring specific gravity of optical glass".

It is desirable that the product of the specific gravity (d) of the glass and the powder method acid resistance grade (RA) multiplied (d x RA) be low. More specifically, the multiplication value of (d×RA) in the present invention is 15.0 or less.
As a result, it is possible to produce a lens with excellent acid resistance and low specific gravity, which makes it easier to produce optical elements that are lightweight and resistant to acid rain and the like, suitable for use in vehicles and surveillance cameras. .
Therefore, the multiplication value of (d × RA) of the present invention is preferably 15.0, more preferably 14.0, still more preferably 13.0, still more preferably 12.0, still more preferably 11.0, more preferably is limited to 10.5, most preferably 10.0.
The lower limit of the multiplication value of (d×RA) of the optical glass of the present invention is not particularly limited, but is generally 3.0 or more, more specifically 5.0 or more, and more specifically 6 0.5 or more.

The optical glass of the present invention preferably has high acid resistance. In particular, the chemical durability (acid resistance) of the glass according to JOGIS06-1999 by powder method is preferably grades 1 to 4, more preferably grades 1 to 3.
As a result, the workability of the optical glass is improved, and fogging of the glass due to acid rain or the like is reduced when the glass is used for in-vehicle applications, etc., making it easier to manufacture optical elements from the glass.

Here, "acid resistance" is the resistance to corrosion of glass by acid, and this acid resistance is measured according to the Japan Optical Glass Industry Standard "Method for Measuring Chemical Durability of Optical Glass" JOGIS06-1999. can be done. In addition, "the chemical durability (acid resistance) by the powder method is grade 1 to 3" means that the chemical durability (acid resistance) performed according to JOGIS06-1999 is the mass of the sample before and after the measurement. It means that the weight loss rate is less than 0.65% by mass.
In addition, the chemical durability (acid resistance) "first grade" is less than 0.20% by mass of the sample before and after the measurement, and "second grade" is the weight loss of the sample before and after the measurement. rate is 0.20% by mass or more and less than 0.35% by mass, and "class 3" means that the mass loss rate of the sample before and after measurement is 0.35% by mass or more and less than 0.65% by mass, and "4 "Grade" means that the weight loss rate of the sample before and after measurement is 0.65% by mass or more and less than 1.20% by weight, and "Grade 5" means that the weight loss rate of the sample before and after measurement is 1.20% by mass. It is not less than 2.20% by mass, and "Class 6" means that the weight loss rate of the sample before and after the measurement is 2.20% by mass or more.

The optical glass of the present invention preferably has high devitrification resistance, more specifically, a low liquidus temperature.
That is, the upper limit of the liquidus temperature of the optical glass of the present invention is preferably 1200°C, more preferably 1150°C, and still more preferably 1100°C. As a result, even if the melted glass flows out at a lower temperature, the crystallization of the manufactured glass is reduced, so devitrification when the glass is formed from the molten state can be reduced. The influence on the optical properties of the element can be reduced. Further, since the glass can be molded even if the melting temperature of the glass is lowered, the energy consumed in molding the glass can be suppressed, thereby reducing the manufacturing cost of the glass.
On the other hand, the lower limit of the liquidus temperature of the optical glass of the present invention is not particularly limited. °C or higher in many cases. In this specification, the "liquidus temperature" is held in a temperature gradient furnace with a temperature gradient of 1000 ° C. to 1150 ° C. for 30 minutes, taken out of the furnace and cooled, and then examined with a microscope at a magnification of 100 times. This is the lowest temperature at which crystals are not observed when observing the presence or absence of crystals.

[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, the prepared mixture is put into a platinum crucible, and an electric furnace is used at 1100 to 1340 ° C. depending on the melting difficulty of the glass composition. for 2 to 6 hours, stirred and homogenized, lowered to an appropriate temperature, cast into a mold, and slowly cooled.

[Glass molding]
The glass of the present invention can be melt-molded by a known method. In addition, the means to shape|mold a glass melt is not limited.

[Glass molding and optical element]
The glass of the present invention can be produced into a glass molded body by using, for example, grinding and polishing means. That is, the glass molding can be produced by subjecting the glass to mechanical processing such as grinding and polishing. In addition, the means for producing the glass molded body is not limited to these means.

As described above, the glass molded body formed from the glass of the present invention is excellent in durability and processability, and is less likely to be deteriorated by acid rain or the like, so that it can be used for vehicle applications.

The compositions of Examples and Comparative Examples of the glass of the present invention, the refractive index (n _d ), the Abbe number (ν _d ), the specific gravity (d), the powder method acid resistance grade (RA), and the liquidus temperature of these glasses Shown in Tables 1 to 10. It should be noted that the following examples are for the purpose of illustration only, and are not limited only to these examples.

The glass of the examples of the present invention and the comparative example both contain ordinary optical glasses such as corresponding oxides, hydroxides, carbonates, nitrates, fluorides, hydroxides, metaphosphate compounds, etc. as raw materials for each component. After selecting the high-purity raw materials used for, weighing and mixing uniformly so that the composition ratio of each example shown in the table is obtained, it is put into a platinum crucible, and depending on the melting difficulty of the glass composition After melting in an electric furnace at a temperature range of 1100 to 1350° C. for 2 to 5 hours, the mixture was stirred and homogenized, cast into a mold or the like, and slowly cooled to prepare a glass.

Here, the refractive index and Abbe number of the glasses of Examples and Comparative Examples were measured based on the Japan Optical Glass Industry Association Standard JOGIS01-2003. Here, the refractive index and Abbe's number were obtained by measuring the glass obtained by setting the slow cooling rate to −25° C./hr.

The specific gravity of the glass of Examples and Comparative Examples was measured based on the Japan Optical Glass Industry Standard JOGIS05-1975 "Method for measuring specific gravity of optical glass".

The acid resistance of the glass of Examples and Comparative Examples was measured according to the Japan Optical Glass Industry Standard "Method for measuring chemical durability of optical glass" JOGIS06-1999. Specifically, a glass sample crushed to a particle size of 425 to 600 μm was placed in a pycnometer and placed in a platinum basket. The platinum cage was placed in a quartz glass round-bottomed flask containing a 0.01 N nitric acid aqueous solution and treated in a boiling water bath for 60 minutes. Calculate the weight loss rate (mass%) of the glass sample after treatment, and class 1 if the weight loss rate (mass%) is less than 0.20, and 2 if the weight loss rate is less than 0.20 to 0.35. Grade 3 if the weight loss rate is less than 0.35 to 0.65, Grade 4 if the weight loss rate is 0.65 to less than 1.20, and if the weight loss rate is less than 1.20 to 2.20 Grade 5, and Grade 6 when the weight loss rate was 2.20 or more. At this time, the smaller the class number, the better the acid resistance of the glass.

The liquidus temperatures of the glasses of Examples and Comparative Examples were determined by holding them in a temperature gradient furnace with a temperature gradient of 1000° C. to 1150° C. for 30 minutes, taking them out of the furnace and cooling them, and then examining the crystals with a microscope at a magnification of 100. The lowest temperature at which no crystals were observed was determined.
The description "1000°C or lower" means that no crystals are observed at least at 1000°C.

As shown in the table, the optical glasses of the examples of the present invention have a molar sum (SiO ₂ +B ₂ O ₃ ) of 40.0 to 75.0%, Ln ₂ O ₃ components (wherein Ln is La , Gd, Y, one or more selected from the group consisting of Lu) is 3.0% to 25.0%, Rn ₂ O component (wherein Rn is Li, Na, from the group consisting of K The molar sum of selected one or more kinds) is more than 0% to 25.0%, it is possible to obtain an optical glass having excellent durability and desired optical constants.

Further, the optical glasses of the examples of the present invention all have a refractive index (n _d ) of 1.60 or more, more specifically 1.64 or more, and this refractive index (n _d ) is 1.80 or less. , which was within the desired range.

Further, the optical glasses of the examples of the present invention all have an Abbe number (ν _d ) of 65 or less, and an Abbe number (ν _d ) of 35 or more, more specifically 40 or more. was inside.

In addition, the optical glass of the present invention formed a stable glass, and devitrification was less likely to occur during glass production. This is inferred from the fact that the liquidus temperature of the optical glass of the present invention is 1150° C. or lower, more specifically 1100° C. or lower.

Further, the optical glasses of the examples of the present invention all had a specific gravity of 4.00 or less, more specifically 3.60 or less. Therefore, it has been clarified that the optical glasses of the examples of the present invention have a small specific gravity.

In addition, the optical glasses of the examples of the present invention all had chemical durability (acid resistance) by the powder method of grades 1 to 4, which was within the desired range.

Furthermore, in the optical glasses of the examples of the present invention, the value of d×RA, which is the product of the specific gravity (d) of the glass and the acid resistance class (RA) of the powder method, was 15.0 or less.

Therefore, the optical glass of the example of the present invention has a specific gravity of 5.00 or less while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges, and the powder The chemical durability (acid resistance) according to the method was grades 1 to 4, and the product of the specific gravity (d) of the glass and the powder method acid resistance grade (RA) multiplied by d×RA was within the desired range. Therefore, it was found that the optical glasses of the examples of the present invention are excellent in both weight reduction and chemical durability.

On the other hand, in the optical glass of the comparative example, the molar sum of Ln ₂ O ₃ components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Lu) is less than 3.0%, Since the product of the specific gravity (d) of the glass and the acid resistance grade (RA) of the powder method (d×RA) exceeds 15.0, a glass material having a low specific gravity and excellent chemical durability cannot be obtained.

Furthermore, using the optical glass of the example of the present invention, a glass block was formed, and this glass block was ground and polished to be processed into the shapes of lenses and prisms. As a result, various lens and prism shapes could be stably processed.

Although the invention has been described in detail for purposes of illustration, the examples are for illustration only and many modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. be understood.

Claims (7)

in mol %,
SiO ₂ component 0-30.0%
B ₂ O ₃ component 43.90-60.0%
molar sum (SiO ₂ +B ₂ O ₃ ) is 50.0 to 75.0%,
the molar sum of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y and Lu) is 6.0 to 18.0%;
the molar sum of Rn ₂ O components (wherein Rn is one or more selected from the group consisting of Li, Na and K) of 0.5 to 6.53 %;
The sum of the contents (molar sum) of RO components (wherein R is one or more selected from the group consisting of Zn, Mg, Ca, Sr, and Ba) is 20.0% or less,
ZnO component 0-3.0%,
a molar ratio (SiO ₂ +Al ₂ O ₃ )/B ₂ O ₃ of 0.3 or more;
The product of the specific gravity (d) of the glass and the powder method acid resistance grade (RA) multiplied by d × RA is 15.0 or less,
An optical glass having a refractive index (n _d ) of 1.58 or more and 1.75 or less and an Abbe number (ν _d ) of 50 or more and 65 or less. _2. The optical glass according to claim 1, wherein the molar ratio ( _Ln2O3 / _Rn2O ) is 1.39 or more . 3. The optical glass according to claim 1, wherein the molar sum (ZrO ₂ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +TeO ₂ ) is 0 to 20.0%. 4. The optical glass according to claim 1, wherein the molar ratio (Ln ₂ O ₃ +SiO ₂ +Al ₂ O ₃ )/(RO+Rn ₂ O+B ₂ O ₃ ) is 0.2 to 3.0. 5. The optical glass according to any one of claims 1 to 4, which has a chemical durability (acid resistance) of grades 1 to 4 as determined by the powder method. An optical element comprising the optical glass according to any one of claims 1 to 5. An optical instrument comprising the optical element according to claim 6 .