JPWO2020017275A1 - Optical glass, preforms and optics - Google Patents

Abstract

Provided is a stable optical glass in which the refractive index (nd) and the Abbe number (νd) are within desired ranges, yet the preform material and the optical element can be easily manufactured by polishing. In the optical glass, the SiO2 component is more than 0% and 35.0% or less, the B2O3 component is more than 0% and 35.0% or less, the La2O3 component is more than 20.0% and 65.0% or less, and the Al2O3 component is 0 in mass%. It contains more than% and 30.0% or less, has a refractive index (nd) of 1.70 or more, has an abbe number (νd) of 35 or more and 55 or less, and has chemical durability (acid resistance) by the powder method. Classes 1 to 4.

Description

The present invention relates to optical glass, preforms and optical elements.

In recent years, the digitization and high definition of devices that use optical systems have been rapidly advancing, and various optical devices such as imaging devices such as digital cameras and video cameras, and image reproduction (projection) devices such as projectors and projection televisions. In this field, there is an increasing demand for reducing the number of optical elements such as lenses and prisms used in an optical system, and reducing the weight and size of the entire optical system.

Among the optical glasses used to make optical elements, _{the Abbe number (ν d} ) _{has a refractive index (nd} ) of 1.70 or more and 35 or more and 55 or less, which enables miniaturization of the entire optical system. The demand for high-refractive-index, low-dispersion glass with high refractive index is very high. As such a high refractive index low dispersion glass, a glass composition as represented by Patent Document 1 is known.

Japanese Unexamined Patent Publication No. 11-071129

However, in the glass disclosed in Patent Document 1, the stability of the glass may be insufficient, and it has been required to improve the stability. Furthermore, the glass that has escaped devitrification during the production of glass is prone to fogging when the glass press-formed by the reheat press is polished or when the glass is polished to produce a preform material. There was a problem. It has been difficult to fabricate an optical element that controls light in the visible region, especially from glass that has once been devitrified or clouded.

The present invention has been made in view of the above problems, and an object of the present invention is _{to perform polishing while the refractive index (nd} ) and Abbe number (ν _d ) are within desired ranges. The purpose is to obtain a stable optical glass that is easy to manufacture a reforming material and an optical element.

As a result of intensive test and research to solve the above problems, the present inventors have refracted the glass containing the _{SiO 2} component, the B ₂ O ₃ component, the La ₂ O ₃ component and the Al ₂ O _{3 component.} We have found that stable glass can be obtained that is easy to polish due to its high chemical durability, especially acid resistance, while the rate ( _nd ) and Abbe number (ν _{d) are within the desired ranges.} The present invention has been completed.
Specifically, the present invention provides the following.

(1) By mass%
SiO ₂ component is more than 0% and 35.0% or less,
B ₂ O ₃ component is more than 0% and less than 35.0%,
La ₂ O ₃ component is more than 20.0% and less than 65.0%,
Al ₂ O ₃ component is more than 0% and less than 30.0%,
Contains,
It has a refractive index ( _nd ) of 1.70 or more, and has an Abbe number (ν _d ) of 35 or more and 55 or less.
Optical glass having chemical durability (acid resistance) of classes 1 to 4 by the powder method.

(2) By mass%
Y ₂ O ₃ component 0 to less than 25.0%,
Gd ₂ O ₃ component 0-40.0%,
Yb ₂ O ₃ component 0 to less than 10.0%,
Lu ₂ O ₃ component 0 to less than 10.0%,
MgO component 0 to less than 10.0%,
CaO component 0-less than 10.0%,
SrO component 0 to less than 10.0%,
BaO component 0-less than 10.0%,
Li ₂ O component 0-less than 5.0%,
Na ₂ O component 0 to less than 10.0%,
K ₂ O component 0 to less than 10.0%,
TiO ₂ component 0 to less than 15.0%,
Nb ₂ O ₅ component 0 to less than 15.0%,
ZrO ₂ component 0 to less than 15.0%,
Ta ₂ O ₅ component 0 to less than 10.0%,
WO ₃ component 0 to less than 10.0%,
ZnO component 0 to less than 30.0%,
P ₂ O ₅ component 0 to less than 10.0%,
GeO ₂ component 0-0 less than 10.0%,
Ga ₂ O ₃ component 0 to less than 10.0%,
Bi ₂ O ₃ component 0 to less than 10.0%,
TeO ₂ component 0 to less than 10.0%,
SnO ₂ component 0-less than 3.0%,
Sb ₂ O ₃ component is less than 0-1.0%,
The optical glass according to (1), wherein the content of fluoride as F, which is substituted with a part or all of one or more oxides of each of the above elements, is less than 0 to 10.0% by mass.

(3) The optical glass according to (1) or (2), wherein the _{mass sum SiO 2} + B ₂ O _{3 is 15.0% or more and 40.0% or less.}

(4) The optical glass according to any one of (1) to (3), wherein the _{mass sum SiO 2} + B ₂ O ₃ + Al ₂ O _{3 is 15.0% or more and less than 50.0%.}

(5) The optical glass according to any one of (1) to (4), wherein the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O _{3 is more than 0.30 and 10.00 or less.}

(6) By mass%
The sum of the contents of the Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is 40.0% or more and 70.0% or less.
The sum of the contents of the RO component (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, Zn) is less than 0 to 10.0%.
Any of (1) to (5) in which the sum of the contents of the Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is less than 0 to 10.0%. The optical glass described.

(7) The optical glass according to any one of (1) to (6) according to any one of (1) to (6), wherein the _{mass ratio Ln 2} O ₃ / (SiO ₂ + B ₂ O ₃ + Al ₂ O _{3) is more than 0.30 and 10.00 or less.} , Ln is one or more selected from the group consisting of La, Gd, Y, and Yb).

(8) A preform made of the optical glass according to any one of (1) to (7).

(9) An optical element made of the optical glass according to any one of (1) to (7).

(10) An optical device including the optical element according to (9).

According to the present invention, it is _{possible to obtain a stable optical glass in which the refractive index (nd} ) and the Abbe number (ν _d ) are within the desired ranges, yet the preform material and the optical element can be easily manufactured by polishing. Can be done.

It is a figure which shows the relationship between _{the refractive index (nd} ) and the Abbe number (ν _d ) about the glass of the Example of this application.

The optical glass of the present invention has a SiO ₂ component of more than 0% and 35.0% or less, a B ₂ O ₃ component of more than 0% and 35.0% or less, and a La ₂ O ₃ component of more than 20.0% in mass%. 65.0% or less, the _Al 2 _{O 3} component contained less 0% and 30.0%, has 1.70 or more of refractive index _{(n d),} 35 or more 55 or less of Abbe number ([nu _d) It has class 1 to 4 in chemical durability (acid resistance) by the powder method. The present inventor has, SiO _{2 component,} the B 2 _{O 3} component and _La 2 _{O 3} component as a base, when it is contained the _Al 2 _{O 3} component to 1.70 or more refractive index _{(n d)} and _{A stable glass having a Abbe number (ν d} ) of 35 or more and 55 or less, which has high chemical durability, particularly acid resistance, can be obtained. Therefore, it is possible to obtain a stable optical glass in which the refractive index ( _nd ) and the Abbe number (ν _d ) are within the desired ranges, but the acid resistance is high and the preform material and the optical element can be easily manufactured by polishing. Can be done.

In addition, the optical glass of the present invention has a small specific gravity, which can contribute to weight reduction of optical elements and optical devices.

Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention. It should be noted that the description may be omitted as appropriate for the parts where the explanations are duplicated, 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 the present specification, the content of each component shall be expressed in mass% with respect to the total mass of the oxide equivalent composition unless otherwise specified. Here, the "oxide-equivalent composition" is used when it is assumed that all the oxides, composite salts, metal fluorides and the like used as raw materials for the glass constituents of the present invention are decomposed into oxides at the time of melting. It is a composition in which each component contained in a glass is described, assuming that the total mass of the produced oxide is 100% by mass.

<About essential ingredients and optional ingredients>
The SiO ₂ component is an essential component as a glass-forming oxide. In particular, by _{containing more than 0% of the SiO 2} component, it is possible to improve the chemical durability of the glass, particularly the acid resistance, and it is a component that enhances the stability of the glass and makes it easy to obtain a glass that can withstand mass production. In addition, the viscosity of the molten glass can be increased and the coloring of the glass can be reduced. Therefore, _{the content of the SiO 2} component is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 3.0%, still more preferably more than 5.0%, still more preferably 7.0%. Super, more preferably more than 10.0%.
On the other hand, by _{setting the content of the SiO 2} component to 35.0% or less, an increase in the glass transition point can be suppressed and a decrease in the refractive index can be suppressed. Therefore, _{the content of the SiO 2} component is preferably 35.0% or less, more preferably less than 30.0%, still more preferably less than 27.0%, still more preferably less than 24.0%, still more preferably 21. It is less than 0%, more preferably less than 18.0%.

The B ₂ O ₃ component is an essential component as a glass-forming oxide. In particular, by _{containing more than 0% of the B 2} O ₃ component, the stability of the glass can be enhanced, the devitrification resistance can be enhanced, and the Abbe number of the glass can be increased. Therefore, _{the content of the B 2} O ₃ component is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 4.0%, still more preferably more than 5.0%, still more preferably 7. It is more than 0%, more preferably more than 10.0%.
On the other hand, by _{setting the content of the B 2} O ₃ component to 35.0% or less, a larger refractive index can be easily obtained, and deterioration of chemical durability, particularly deterioration of acid resistance can be suppressed. Therefore, _{the content of the B 2} O ₃ component is preferably 35.0% or less, more preferably less than 30.0%, still more preferably less than 27.0%, still more preferably less than 25.0%, still more preferably. It is less than 20.0%, more preferably less than 18.0%, still more preferably less than 15.0%.

The La ₂ O ₃ component is an essential component that increases the refractive index and Abbe number of glass. Moreover, since it is relatively inexpensive among rare earths, the material cost of glass can be reduced. Therefore, _{the content of the La 2} O ₃ component is preferably more than 20.0%, more preferably more than 25.0%, still more preferably more than 28.0%, still more preferably more than 30.0%, still more preferably. It is more than 35.0%, more preferably more than 37.0%, still more preferably more than 40.0%.
On the other hand, _{by reducing the content of the La 2} O ₃ component to 65.0% or less, the stability of the glass can be improved and devitrification can be reduced. In addition, the meltability of the glass raw material can be improved. Therefore, _{the content of the La 2} O ₃ component is preferably 65.0% or less, more preferably less than 60.0%, still more preferably less than 58.0%, still more preferably less than 55.0%, still more preferably. It is less than 53.0%, more preferably less than 50.0%.

The Al ₂ O ₃ component is an essential component capable of improving the chemical durability of glass, particularly acid resistance, and the devitrification resistance of glass. Therefore, _{the content of the Al 2} O ₃ component is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 2.0%, still more preferably more than 3.0%, still more preferably 5. It shall be over 0%.
On the other hand, by _{setting the content of the Al 2} O ₃ component to 30.0% or less, the liquidus temperature of the glass can be lowered and the devitrification resistance can be improved. Therefore, _{the content of the Al 2} O ₃ component is preferably 30.0% or less, more preferably less than 25.0%, still more preferably less than 20.0%, still more preferably less than 15.0%, still more preferable. Is less than 13.0%.

The Y ₂ O ₃ component is an optional component capable of suppressing the material cost of glass and reducing the specific gravity of glass while maintaining a high refractive index and a high Abbe number when the content exceeds 0%. _Accordingly, the content of Y 2 _{O 3} component is preferably 0 percent, more preferably 1.0 percent, more preferably 5.0 percent, more preferably 8.0 percent, more preferably 10. It may be more than 0%.
On the other hand, by _{setting the content of the Y 2} O ₃ component to less than 25.0%, the decrease in the refractive index of the glass can be suppressed and the stability of the glass can be improved. In addition, deterioration of the meltability of the glass raw material can be suppressed. _Accordingly, the content of Y 2 _{O 3} component is preferably less than 25.0%, more preferably less than 20.0%, more preferably less than 18.0%, more preferably less than 16.0%.

The Gd ₂ O ₃ component is an optional component that can increase the refractive index and Abbe number of the glass when it is contained in excess of 0%.
However, the _{raw material price of the Gd 2} O ₃ component is high, and if the content of the Gd 2 O 3 component is large, the production cost increases and the specific gravity of the glass increases. Therefore, _{the content of the Gd 2} O ₃ component is preferably less than 40.0%, more preferably less than 30.0%, still more preferably less than 20.0%, still more preferably less than 10.0%.

The Yb ₂ O ₃ component and the Lu ₂ O ₃ component are optional components that can increase the refractive index and Abbe number of the glass when the content exceeds 0%.
However, the _{raw material prices of the Yb 2} O ₃ component and the Lu ₂ O ₃ component are high, and if the raw material price is high, the production cost increases and the specific gravity of the glass increases. Therefore, _{the contents of the Yb 2} O ₃ component and the Lu ₂ O ₃ component are preferably less than 10.0%, more preferably less than 7.0%, still more preferably less than 4.0%, still more preferably 1. It shall be less than 0%. In particular, from the viewpoint of reducing the material cost, it is most preferable not to contain these components.

The MgO component, CaO component, SrO component and BaO component are optional components that can adjust the refractive index, meltability and devitrification resistance of the glass when they are contained in excess of 0%.
On the other hand, by setting the contents of the MgO component, the CaO component, the SrO component and the BaO component to less than 10.0%, the decrease in the refractive index can be suppressed, and devitrification due to the excessive content of these components can be suppressed. Can be reduced. Therefore, the contents of the MgO component, the CaO component, the SrO component and the BaO component are preferably less than 10.0%, more preferably less than 5.0%, still more preferably 3.0% or less, still more preferably 1. It shall be less than 0%. In particular, from the viewpoint of obtaining glass having a high refractive index, it is most preferable that these components are not contained.

The Li ₂ O component is an optional component that can improve the meltability of the glass and lower the glass transition point when it is contained in excess of 0%.
On the other hand, by _{setting the content of the Li 2} O component to less than 5.0%, it is difficult to reduce the refractive index of the glass and the devitrification of the glass can be reduced. Therefore, _{the content of the Li 2} O component is preferably less than 5.0%, more preferably less than 3.0%, still more preferably less than 1.0%, still more preferably less than 0.5%, still more preferably 0. . Less than 3%.

The Na ₂ O component and the K ₂ O component are optional components that can improve the meltability of the glass and lower the glass transition point when the content exceeds 0%.
On the other hand, by _{setting the contents of the Na 2} O component and the K ₂ O component to less than 10.0%, it is possible to make it difficult to reduce the refractive index of the glass and reduce the devitrification of the glass. Therefore, _{the contents of the Na 2} O component and the K ₂ O component are preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably 1.0%, respectively. Less than, more preferably less than 0.5%.

The TiO ₂ component is an optional component whose stability can be enhanced by increasing the refractive index of the glass and lowering the liquidus temperature of the glass. It is also a component that reduces the specific gravity of glass.
On the other hand, by _{setting the content of the TiO 2} component to less than 15.0%, the _{devitrification due to the excessive content of the TiO 2} component can be reduced, and the transmittance of the glass with respect to visible light (particularly the wavelength of 500 nm or less) can be reduced. It can be suppressed. Further, this can suppress a decrease in the Abbe number. Therefore, _{the content of the TiO 2} component is preferably less than 15.0%, more preferably less than 10.0%, still more preferably less than 8.0%, still more preferably 5.0% or less, still more preferably 3. It shall be 0% or less.

The Nb ₂ O ₅ component is an optional component whose devitrification resistance can be enhanced by increasing the refractive index of the glass and lowering the liquidus temperature of the glass when the content exceeds 0%. Therefore, _{the content of the Nb 2} O ₅ component may be preferably more than 0%, more preferably more than 1.0%, and even more preferably more than 2.0%.
On the other hand, by making _{the content of the Nb 2} O ₅ component less than 15.0%, the material cost of the glass can be suppressed and the decrease in the Abbe number can be suppressed. In addition, _{devitrification due to excessive inclusion of the Nb 2} O ₅ component can be reduced, and a decrease in the transmittance of the glass with respect to visible light (particularly, a wavelength of 500 nm or less) can be suppressed. Therefore, _{the content of the Nb 2} O ₅ component is preferably less than 15.0%, more preferably less than 12.0%, still more preferably less than 10.0%.

ZrO ₂ component, when 0% ultra-containing, elevated refractive index of the glass and the Abbe number, which is an optional component that can and improving the devitrification resistance. Accordingly, the content of the ZrO ₂ component is preferably 0 percent, more preferably from 1.0%, even more preferably may be 1.5% greater.
On the other hand, by _{setting the content of the ZrO 2} component to less than 15.0%, devitrification due to the excessive content _{of the ZrO 2 component can be reduced.} Therefore, the content of the ZrO ₂ component is preferably less than 15.0%, more preferably less than 12.0 percent, more preferably less than 10.0%, more preferably less than 7.0%.

The Ta ₂ O ₅ component is an optional component that can increase the refractive index of the glass and enhance the devitrification resistance when it is contained in excess of 0%.
However, the _{raw material price of the Ta 2} O ₅ component is high, and if the content is high, the production cost increases. Further, by _{setting the content of the Ta 2} O ₅ component to less than 10.0%, the melting temperature of the raw material is lowered, and the energy required for melting the raw material is reduced, so that the manufacturing cost of the optical glass can be reduced. Therefore, _{the content of the Ta 2} O ₅ component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost, it is most preferable that _{the Ta 2} O _{5 component is not contained.}

When the WO ₃ component is contained in excess of 0%, it is an optional component that can increase the refractive index, lower the glass transition point, and enhance the devitrification resistance while reducing the coloring of the glass due to other high refractive index components. Is. Therefore, _{the content of the WO 3} component may be preferably more than 0%, more preferably more than 0.3%, and even more preferably more than 0.5%.
On the other hand, by making _{the content of the WO 3} component less than 10.0%, the material cost of the glass can be suppressed and the decrease in the Abbe number can be suppressed. Also, it increased visible light transmittance to reduce the coloration of the glass due WO ₃ components. Therefore, _{the content of the WO 3} component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

The ZnO component is an optional component that can enhance the stability of the glass and reduce the coloring when it is contained in excess of 0%. It is also a component that can lower the glass transition point and improve chemical durability.
On the other hand, by setting the content of the ZnO component to less than 30.0%, it is possible to suppress a decrease in the refractive index of the glass and reduce devitrification due to an excessive decrease in viscosity. Therefore, the content of the ZnO component is preferably less than 30.0%, more preferably less than 25.0%, still more preferably less than 22.0%, still more preferably less than 20.0%, still more preferably 15.0. %, More preferably less than 10.0%.

The P ₂ O ₅ component is an optional component that can act as a glass forming component, and when it is contained in excess of 0%, it can lower the liquidus temperature of the glass and enhance the devitrification resistance.
On the other hand, by _{setting the content of the P 2} O ₅ component to less than 10.0%, it is possible to suppress a decrease in the chemical durability of the glass, particularly the water resistance. Therefore, _{the content of the P 2} O ₅ component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

The GeO ₂ component is an optional component capable of increasing the refractive index of the glass and improving the devitrification resistance when it is contained in excess of 0%.
However, the _{raw material price of Geo 2} is high, and if the content of GeO 2 is high, the production cost increases. Therefore, _{the content of the GeO 2} component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost, it is not necessary to contain _{the GeO 2 component.}

The Ga ₂ O ₃ component is an optional component that can improve the chemical durability of the glass and the devitrification resistance of the glass when it is contained in excess of 0%.
On the other hand, by _{setting the content of the Ga 2} O ₃ component to less than 10.0%, the liquidus temperature of the glass can be lowered and the devitrification resistance can be improved. Therefore, _{the content of the Ga 2} O ₃ component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

The Bi ₂ O ₃ component is an optional component that can increase the refractive index and lower the glass transition point when it is contained in excess of 0%.
On the other hand, by _{setting the content of the Bi 2} O ₃ component to less than 10.0%, the liquidus temperature of the glass can be lowered and the devitrification resistance can be improved. Therefore, _{the content of the Bi 2} O ₃ component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

The TeO ₂ component is an optional component that can increase the refractive index and lower the glass transition point when the content exceeds 0%.
On the other hand, TeO ₂ has a problem that it can be alloyed with platinum when the glass raw material is melted in a platinum crucible or a melting tank in which the portion in contact with the molten glass is made of platinum. Therefore, _{the content of the TeO 2} component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

The SnO ₂ component is an optional component that can reduce the oxidation of the molten glass to make it clear and increase the visible light transmittance of the glass when it is contained in an amount of more than 0%.
On the other hand, by _{setting the content of the SnO 2} component to less than 3.0%, it is possible to reduce the coloring of the glass and the devitrification of the glass due to the reduction of the molten glass. Further, since _{the alloying of the SnO 2} component and the melting equipment (particularly noble metal such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, _{the content of the SnO 2} component is preferably less than 3.0%, more preferably less than 1.0%, still more preferably less than 0.5%, still more preferably less than 0.1%.

The Sb ₂ O ₃ component is an optional component capable of defoaming the molten glass when it contains more than 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 becomes poor. Therefore, _{the content of the Sb 2} O ₃ component is preferably less than 1.0%, more preferably less than 0.5%, and even more preferably less than 0.3%.

The component that clarifies and defoams the _{glass is not limited to the above Sb 2} O ₃ component, and a clarifying agent, a defoaming agent, or a combination thereof known in the field of glass production can be used.

The F component is an optional component capable of increasing the Abbe number of the glass, lowering the glass transition point, and improving the devitrification resistance when the content exceeds 0%.
However, when the content of the F component, that is, the total amount of fluoride substituted with a part or all of one or more oxides of each of the above-mentioned metal elements exceeds 10.0%, F Since the amount of volatilization of the components increases, it becomes difficult to obtain a stable optical constant, and it becomes difficult to obtain a homogeneous glass.
Therefore, the content of the F component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

The ratio (mass ratio) of the content of the SiO ₂ component to the content of the B ₂ O ₃ component is preferably 0.15 or more and 10.00 or less.
In particular, by _{setting this ratio SiO 2} / B ₂ O ₃ to 0.15 or more, the stability of the glass can be enhanced, and the chemical durability of the glass, particularly the acid resistance, can be improved. The glass of the present invention can be vitrified even if _{the content of the B 2} O ₃ component is relatively low and _{the content of the SiO 2} component is relatively high. Therefore, the mass ratio SiO ₂ / B ₂ O ₃ is preferably 0.15 or more, more preferably 0.30 or more, still more preferably 0.50 or more, still more preferably 0.60 or more, still more preferably 0.70. The above may be done.
On the other hand, by _{setting this ratio SiO 2} / B ₂ O ₃ to 10.00 or less, an increase in the glass transition point can be suppressed, so that molding can be facilitated at a lower temperature. Therefore, the mass ratio SiO ₂ / B ₂ O ₃ is preferably 10.00 or less, more preferably 7.00 or less, still more preferably 5.00 or less, still more preferably 4.65 or less.

The sum (mass sum) of the contents of the B ₂ O ₃ component and the SiO ₂ component is preferably 15.0% or more and 40.0% or less.
In particular, when the sum is 15.0% or more, a network structure of glass is formed, so that stable glass can be formed. Therefore, the mass sum B ₂ O ₃ + SiO ₂ is preferably 15.0% or more, more preferably more than 18.0%, and further preferably 20.0% or more.
On the other hand, by setting the sum to 40.0% or less, it is possible to suppress a decrease in the refractive index due to excessive inclusion of these components. In addition, the chemical durability of glass, particularly acid resistance, can be improved. Therefore, the mass sum B ₂ O ₃ + SiO ₂ is preferably 40.0% or less, more preferably less than 38.0%, still more preferably less than 35.0%, still more preferably less than 32.0%, still more preferably. It shall be less than 30.0%.

The sum (mass sum) of the contents of the B ₂ O ₃ component, the SiO ₂ component and the Al ₂ O ₃ component is preferably 15.0% or more and less than 50.0%.
In particular, by setting this sum to 15.0% or more, a more stable glass can be obtained. Therefore, the mass sum SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ is preferably 15.0% or more, more preferably more than 18.0%, still more preferably more than 20.0%, still more preferably more than 22.0%. , More preferably more than 25.0%.
On the other hand, by setting the sum to less than 50.0%, it is possible to suppress a decrease in the refractive index due to excessive inclusion of these components. Therefore, the mass sum SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ is preferably less than 50.0%, more preferably less than 47.0%, still more preferably less than 44.0%, still more preferably less than 42.0%. , More preferably less than 39.0%.

The ratio of the sum of the contents of the SiO ₂ component and the Al ₂ O ₃ component to the content of the B ₂ O _{3 component is preferably more than 0.30 and 10.00 or less.}
In particular, by setting this ratio to more than 0.30, the chemical durability of the glass, particularly the acid resistance, can be improved. Therefore, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is preferably more than 0.30, more preferably more than 0.45, still more preferably more than 0.60, still more preferably more than 0.90. do.
On the other hand, by setting this ratio to 10.00 or less, a more stable glass can be obtained. Therefore, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is preferably 10.00 or less, more preferably 10.00 or less, still more preferably 8.00 or less, still more preferably 6.00 or less. More preferably, it is 5.50 or less.

The sum (mass sum) of the contents of the Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is 40.0% or more and 70.0. % Or less is preferable.
In particular, when the sum is 40.0% or more, the refractive index and Abbe number of the glass are increased, so that it is possible to easily obtain a glass having a desired refractive index and Abbe number. Therefore, _{the mass sum of the Ln 2} O ₃ components is preferably 40.0% or more, more preferably more than 43.0%, still more preferably 45.0% or more, still more preferably more than 47.0%.
On the other hand, when the sum is 70.0% or less, the liquidus temperature of the glass is lowered, so that the devitrification of the glass can be reduced. Therefore, _{the mass sum of the Ln 2} O ₃ components is preferably 70.0% or less, more preferably less than 65.0%, more preferably less than 64.0%, still more preferably less than 63.0%.

The sum (mass sum) of the contents of the RO component (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably less than 10.0%. As a result, a decrease in the refractive index can be suppressed, and the stability of the glass can be improved. Therefore, the mass sum of the RO components is preferably less than 10.0%, more preferably less than 5.0%, still more preferably 3.0% or less, still more preferably less than 1.0%.

The sum (mass sum) of the contents of the Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is preferably less than 10.0%. As a result, the decrease in the viscosity of the molten glass can be suppressed, the refractive index of the glass can hardly be decreased, and the devitrification of the glass can be reduced. Therefore, _{the mass sum of the Rn 2} O components is preferably less than 10.0%, more preferably less than 6.0%, still more preferably less than 4.0%, still more preferably less than 2.0%, still more preferably 1. It shall be less than 0.0%.

The ratio (mass ratio) of the sum of the Ln ₂ O ₃ components to the sum of the contents of the B ₂ O ₃ component, the SiO ₂ component and the Al ₂ O ₃ component is preferably more than 0.30 and 10.00 or less (in the formula). , Ln is one or more selected from the group consisting of La, Gd, Y, and Yb).
In particular, by setting this mass ratio to more than 0.30, the refractive index and Abbe number of the glass can be increased. Therefore, the mass ratio Ln ₂ O ₃ / (SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ ) is preferably more than 0.30, more preferably more than 0.50, still more preferably more than 0.80, still more preferably 1. It is more than .00, more preferably 1.27 or more, still more preferably 1.35 or more, still more preferably 1.50 or more.
On the other hand, by setting this mass ratio to 10.00 or less, the stability of the glass can be improved. Therefore, the mass ratio Ln ₂ O ₃ / (SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ ) is preferably 10.00 or less, more preferably 5.00 or less, still more preferably 3.00 or less, still more preferably 2. It is .60 or less, more preferably 2.30 or less, still more preferably 2.10 or less.

_{SiO 2} component, Al ₂ O ₃ component and Ln ₂ O _{3 with} respect to the sum of the contents of the RO component, Rn ₂ O component, Zn O component and B ₂ O ₃ component plus 10 times the value of the refractive index nd. The ratio (mass ratio) of the sum of the contents of the components is preferably 0.80 or more and 6.00 or less (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, and Yb, and R is One or more selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and Rn is one or more selected from the group consisting of Li, Na, and K).
By setting this mass ratio within the range of 0.80 or more and 6.00 or less, the chemical durability of the glass, particularly the acid resistance, can be improved. Therefore, the mass ratio (SiO ₂ + Al ₂ O ₃ + Ln ₂ O ₃ ) / (RO + Rn ₂ O + ZnO + B ₂ O ₃ + nd × 10) is preferably 0.80, more preferably 1.00, still more preferably 1.20. The lower limit is more preferably 1.50, still more preferably 1.80, and the upper limit is preferably 6.00, more preferably 5.50, and even more preferably 5.00.

The mass ratio (Al ₂ O ₃ / Ln ₂ O ₃ ) is preferably 0.01 or more (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu). .. This makes it easier to obtain the effect of improving the devitrification resistance. Therefore, _{the mass ratio of (Al 2} O ₃ / Ln ₂ O ₃ ) may be preferably 0.01 or more, more preferably 0.03 or more, and further preferably 0.05 or more.
On the other hand, by setting this mass ratio to 1.00 or less, deterioration of the meltability of the glass raw material and an excessive increase in viscosity can be suppressed. Therefore, _{the mass ratio of (Al 2} O ₃ / Ln ₂ O ₃ ) is preferably 1.00 or less, more preferably 0.50 or less, still more preferably 0.0.30 or less, still more preferably 0.25 or less. , More preferably 0.20 or less.

The mass sum (ZrO ₂ + TiO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ + WO ₃ + Bi ₂ O ₃ + TeO ₂ ) is preferably 20.0% or less. As a result, it is possible to easily obtain the effect of improving the devitrification resistance, and it is possible to easily obtain low dispersion performance by suppressing an excessive decrease in the Abbe number. Therefore, _{the mass 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% or less, more preferably 18.0% or less, still more preferably 15. It is 0.0% or less, more preferably 5.0% or less, still more preferably 4.0% or less.

The mass ratio (Ln ₂ O ₃ / RO) is preferably 1.0 or more (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu). This makes it easier to obtain the effect of improving the chemical durability of the glass. Therefore, _{the mass ratio of (Ln 2} O ₃ / RO) is preferably 1.0 or more, more preferably 3.0 or more, still more preferably 5.0 or more, still more preferably 10.0 or more, still more preferably 20. It may be 0.0 or more.
Even when the RO component is not contained, the effect of improving the chemical durability can be obtained, so that the upper limit of the mass ratio of _{(Ln 2} O _{3 / RO) may be infinite.}

The mass ratio (Ln ₂ O ₃ / Rn ₂ O) is preferably 3.0 or more. This makes it easier to obtain the effect of improving the chemical durability of the glass. Therefore, _{the mass ratio of (Ln 2} O ₃ / Rn ₂ O) is preferably 3.0 or more, more preferably 5.0 or more, still more preferably 8.0 or more, still more preferably 10.0 or more, still more preferable. May be 15.0 or more, more preferably 20.0 or more, still more preferably 25.0 or more, and most preferably 30.0 or more.
Even when the Rn ₂ O component is not contained, the effect of improving the chemical durability can be obtained. Therefore, the upper limit of the mass ratio of _{(Ln 2} O ₃ / Rn _{2 O) may be infinite.} good.

The mass product (BaO × Gd ₂ O ₃ ) is preferably less than 8.0. By reducing this product, it is possible to easily obtain the effect of suppressing both the specific gravity and the cost of the glass. Therefore, the mass product of (BaO × Gd ₂ O ₃ ) is preferably less than 8.0, more preferably 7.0 or less, still more preferably 6.0 or less, still more preferably 5.0 or less, still more preferably 4. It may be 0.0 or less, more preferably 3.0 or less, still more preferably 2.0 or less, still more preferably 1.0 or less, still more preferably 0.1 or less.

The mass sum (SiO ₂ + Al ₂ O ₃ ) is preferably 5.0% or more. This makes it easier to obtain the effect of improving the chemical durability of the glass. Therefore, _{the mass sum of (SiO 2} + Al ₂ O ₃ ) is preferably 5.0% or more, more preferably 7.0% or more, still more preferably 9.0% or more, still more preferably 10.0% or more. May be good.
On the other hand, by setting the sum of mass to 40.0% or less, deterioration of the meltability of the glass raw material and an excessive increase in viscosity can be suppressed. Therefore, _{the mass sum of (SiO 2} + Al ₂ O ₃ ) is preferably 40.0% or less, more preferably 45.0% or less, more preferably 35.0% or less, still more preferably 30.0% or less. good.

<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 preferable to be contained will be described.

Other components can be added as needed within a range that does not impair the characteristics of the glass of the present invention. However, each transition metal component such as Nd, V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo except Ti, Zr, Nb, W, La, Gd, Y, Yb and Lu is each. Even if a small amount of the above is contained alone or in combination, the glass is colored and has the property of causing absorption at a specific wavelength in the visible region. Is preferable.

Further, since lead compounds such as PbO and _{arsenic compounds such as As 2} O ₃ are components having a high environmental load, it is desirable that they are not substantially contained, that is, they are not contained at all except for unavoidable contamination.

Furthermore, each component of Th, Cd, Tl, Os, Be, and Se has tended to refrain from being used as a harmful chemical substance in recent years, and is used not only in the glass manufacturing process but also in the processing process and disposal after commercialization. Up to this point, environmental measures are required. Therefore, when the environmental impact is emphasized, it is preferable that these are not substantially contained.

In the present specification, "substantially free" means that the content is preferably less than 0.1%, and more preferably it is not contained except for unavoidable impurities. Here, the content of the component contained as an unavoidable impurity is, for example, less than 0.01% or less than 0.001%, but is not limited thereto.

[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 the temperature is 1500 to 1500 ° C. in an electric furnace according to the difficulty of melting the glass raw material. It is produced by melting in the temperature range of 2 to 5 hours, stirring and homogenizing, lowering the temperature to an appropriate temperature, casting into a mold, and slowly cooling.

[Physical characteristics]
The optical glass of the present invention preferably has a high refractive index and a high Abbe number (low dispersion). In particular, the refractive index ( _nd ) of the optical glass of the present invention is preferably 1.70, more preferably 1.73, and even more preferably 1.75 as the lower limit. _{The refractive index (nd} ) of the optical glass of the present invention may be preferably 2.00, more preferably 1.95, and even more preferably 1.90 as the upper limit. Further, 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 42 as the lower limit. _{The Abbe number (ν d} ) of the optical glass of the present invention is preferably 55, more preferably 53, and even more preferably 51.
By having such a high refractive index, a large amount of refraction of light can be obtained even if the optical element is made thinner. Further, by having such a low dispersion, it is possible to reduce the focus shift (chromatic aberration) due to the wavelength of light when used as a single lens. Therefore, for example, when an optical system is configured by combining with an optical element having a high dispersion (low Abbe number), it is possible to reduce aberrations as a whole of the optical system and achieve high imaging characteristics and the like.
As described above, the optical glass of the present invention is useful in optical design, and particularly when the optical system is configured, the optical system can be miniaturized while achieving high imaging characteristics and the like, and the optical design can be achieved. The degree of freedom can be expanded.

Here, the optical glass of the present invention is a refractive index _{(n d)} and Abbe number ([nu _d) is, - the _{(0.01ν d +2.15) ≦ n d} ≦ (-0.01ν d +2.35) It is preferable to satisfy the relationship. In the glass having the composition specified in the present invention, a more stable glass can be obtained by satisfying this relationship between _{the refractive index (nd} ) and the Abbe number (ν _d).
Accordingly, in the optical glass of the present invention refractive index _{(n d)} and Abbe number ([nu _d) is, it is preferable to satisfy the relation of _{n d ≧ (-0.01ν d +2.15)} , n d ≧ (- it is more preferable to satisfy the relationship 0.01ν _d +2.20), it is more preferable to satisfy the relation of _{n d ≧ (-0.01ν d +2.22)} .
On the other hand, the optical glass of the present invention refractive index _{(n d)} and Abbe number ([nu _d) is, it is preferable to satisfy the relation of _{n d ≦ (-0.01ν d +2.35)} , n d ≦ ( it is more preferable to satisfy the relationship -0.01ν _d +2.30), it is more preferable to satisfy the relation of _{n d ≦ (-0.01ν d +2.28)} .

The optical glass of the present invention has high acid resistance. In particular, the chemical durability (acid resistance) of the glass powder method according to JOBIS06-2006 is preferably class 1 to 4, more preferably class 1 to 3, further preferably class 1 to 2, and most preferably class. It is 1. As a result, when the optical glass is polished, fogging of the glass due to the acidic polishing liquid or cleaning liquid is reduced, so that the polishing process can be made easier. Here, "acid resistance" is the durability against erosion of glass by acid, and this acid resistance is measured according to the Japan Optical Glass Industry Association standard "Method for measuring chemical durability of optical glass" JOBIS06-2006. Can be done. Further, "the chemical durability (acid resistance) by the powder method is class 1 to 4" means that the chemical durability (acid resistance) performed according to JOBIS06-2006 is the mass of the sample before and after the measurement. It means that the weight loss rate is less than 1.20% by mass. In "Class 1" of chemical durability (acid resistance), the weight loss rate of the sample before and after measurement is less than 0.20 mass%, and in "Class 2", the weight loss of the sample before and after measurement is reduced. The rate is 0.20% by mass or more and less than 0.35% by mass, and in "Class 3", the weight loss rate of the sample before and after the measurement is 0.35% by mass or more and less than 0.65% by mass, and "Class 3". In "4", the weight loss rate of the sample before and after the measurement is 0.65% by mass or more and less than 1.20% by mass, and in "Class 5", the weight loss rate of the sample before and after the measurement is 1.20% by mass%. The above is less than 2.20% by mass, and in "Class 6", 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, and more specifically, has a low liquidus temperature. That is, the liquidus temperature of the optical glass of the present invention is preferably 1300 ° C., more preferably 1280 ° C., and even more preferably 1250 ° C. As a result, even if the molten glass flows out at a lower temperature, the crystallization of the produced glass is reduced, so that devitrification when the glass is formed from the molten state can be reduced, and optics using the glass can be reduced. The influence on the optical characteristics of the element can be reduced. Further, since the glass can be formed even if the melting temperature of the glass is lowered, the manufacturing cost of the glass can be reduced by suppressing the energy consumed at the time of forming 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, but the liquidus temperature of the glass obtained by the present invention is approximately 800 ° C. or higher, specifically 850 ° C. or higher, and more specifically 900. Often above ° C. The term "liquid phase temperature" as used herein refers to a 5 cc cullet-shaped glass sample placed in a platinum crucible having a capacity of 50 ml and completely melted at 1400 ° C., and the temperature is lowered to a predetermined temperature. When the temperature is maintained for 1 hour, taken out of the furnace, cooled, and immediately observed on the glass surface and the presence or absence of crystals in the glass, it represents the lowest temperature at which no crystals are observed. Here, the predetermined temperature at the time of lowering the temperature is a temperature in increments of 10 ° C. between 1300 ° C. and 800 ° C.

The specific gravity of the optical glass of the present invention is preferably 5.50, more preferably 5.00, and preferably 4.80 from the viewpoint of contributing to weight reduction of optical elements and optical instruments. On the other hand, the specific gravity of the optical glass of the present invention is often 3.00 or more, more specifically 3.50 or more, and more specifically 4.00 or more.
The specific gravity of the optical glass of the present invention is measured based on the Japan Optical Glass Industry Association standard JOBIS05-1975 “Method for measuring the specific gravity of optical glass”.

The optical glass of the present invention preferably has both high acid resistance and weight reduction. That is, the optical glass of the present invention preferably has a value of d × RA of 18.0 or less, where d is the specific gravity and RA is the series of chemical durability (acid resistance) by the powder method. Since both such optical glass has low acid resistance and specific gravity, it is possible to achieve both high acid resistance and weight reduction, which in turn improves workability by polishing and reduces the weight of optical elements and optical instruments. It is possible to make it compatible with the conversion. Therefore, the value of d × RA in the optical glass of the present invention is preferably 18.0, more preferably 15.0, still more preferably 13.0, still more preferably 10.0, still more preferably 9.0. And.
On the other hand, the lower limit of d × RA is often 2.0 or more, more specifically 3.0 or more, and more specifically 4.0 or more.

[Preforms and optics]
From the produced optical glass, a glass molded body can be produced by using, for example, polishing means or mold press molding means such as reheat press molding or precision press molding. That is, a glass molded body is produced by performing machining such as grinding and polishing on optical glass, or a preform for mold press molding is produced from optical glass, and reheat press molding is performed on this preform. After that, a glass molded body is produced by polishing, a preform produced by polishing, or a preform formed by a known levitation molding or the like is subjected to precision press molding to produce a glass molded body. Can be produced. The means for producing the glass molded body is not limited to these means.

As described above, the optical glass of the present invention is useful for various optical elements and optical designs. Among them, it is particularly preferable to form a preform from the optical glass of the present invention and perform reheat press molding, precision press molding, or the like using this preform to produce an optical element such as a lens or a prism. This makes it possible to form a preform with a large diameter, so that while increasing the size of the optical element, it has high-definition and high-precision imaging characteristics and projection characteristics when used in optical equipment such as cameras and projectors. Can be realized.

The compositions of Examples (No. 1 to No. 43) and Comparative Examples (No. A) of the present invention, as well as the refractive index ( _nd ), Abbe number (ν _d ) of these glasses, and chemistry by the powder method. The results of durability (acid resistance), liquidus temperature and specific gravity are shown in Tables 1 to 6. The following examples are for purposes of illustration only, and are not limited to these examples.

The glasses of Examples and Comparative Examples of the present invention are used for ordinary optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds corresponding to each component as raw materials. High-purity raw materials are selected, weighed so as to have the composition ratio of each example shown in the table, mixed uniformly, then put into a platinum crucible, and 1100 in an electric furnace according to the difficulty of melting the glass raw material. After melting in a temperature range of ~ 1500 ° C. for 2 to 5 hours, the mixture was homogenized by stirring, cast into a mold or the like, and slowly cooled to prepare the mixture.

The refractive index of the glass of the Examples and Comparative Examples _{(n d)} is, JIS B 7071-2: according to the V block method specified in 2018, indicated by measured values for helium lamp d line (587.56 nm) .. The Abbe number (ν _d ) is the refractive index of the d line, the refractive index of the hydrogen lamp with respect to the F line (486.13 nm) (n _F ), and the refractive index of the hydrogen lamp with respect to the C line (656.27 nm) (n _C ). It was calculated from the formula of Abbe number (ν _d ) = [(n _d -1) / (n _F −n _{C)] using the value of.} Then, from the obtained values of the refractive index ( _nd ) and the Abbe number (ν _d ), the intercept b in the relational expression n _d = −a × ν _d + b when the slope a is 0.01 was obtained.

The acid resistance of the glasses of Examples and Comparative Examples was measured according to the Japan Optical Glass Industry Association standard "Method for measuring chemical durability of optical glass" JOBIS06-2006. That is, a glass sample crushed to a particle size of 425 to 600 μm was placed in a specific gravity bottle and placed in a platinum basket. The platinum basket was placed in a quartz glass round bottom flask containing a 0.01 N aqueous nitric acid solution and treated in a boiling water bath for 60 minutes. Calculate the weight loss rate (mass%) of the treated glass sample, and class 1 if the weight loss rate (mass%) is less than 0.20, and class 1 if the weight loss rate is less than 0.20 to 0.35. 2. Class 3 when the weight loss rate is less than 0.35 to 0.65, Class 4 when the weight loss rate is less than 0.65 to 1.20, and when the weight loss rate is less than 1.20 to 2.20. Class 5 and the case where the weight loss rate was 2.20 or more were classified as class 6. At this time, the smaller the number of classes (series RA), the better the acid resistance of the glass.

The specific gravity d of the glass of Examples and Comparative Examples was measured based on the Japan Optical Glass Industry Association standard JOGIS05-1975 “Method for measuring the specific density of optical glass”. Further, the value of d × RA, which is the product of these, was obtained from the measured value of the specific gravity d and the value of the acid resistance series RA.

The liquidus temperature of the glass of Examples and Comparative Examples is 10 from 1350 ° C. to 800 ° C. by putting a 5 cc cullet-shaped glass sample in a platinum crucible having a capacity of 50 ml and putting it in a platinum crucible to completely melt it at 1400 ° C. When the temperature was lowered to one of the temperatures set in ℃ increments, held for 1 hour, taken out of the furnace, cooled, and immediately observed for the presence or absence of crystals on the glass surface and in the glass, no crystals were observed. The temperature was calculated.

As represented in the table, the optical glasses of Examples of the present invention are both refractive index (n _d) of 1.70 or more, with more detail is 1.71 or more, the refractive index (n _d ) Was 2.10 or less, more specifically 1.87 or less, which was within the desired range.

Further, all of the optical glasses of the examples of the present invention have an Abbe number (ν _d ) of 35 or more, more specifically 38 or more, and this Abbe number (ν _d ) is 55 or less, more specifically 54. It was below and was within the desired range.

Further, all of the optical glasses of the examples of the present invention had chemical durability (acid resistance) by the powder method of classes 1 to 4, and more specifically, classes 1 to 3. On the other hand, the glass of the comparative example had a class 5 chemical durability (acid resistance) by the powder method. Therefore, it was clarified that the optical glass of the example of the present invention is superior in acid resistance to the glass of the comparative example.

Further, the optical glass of the present invention forms a stable glass, and devitrification is unlikely to occur during glass production. This can be inferred from the fact that the liquidus temperature of the optical glass of the present invention is 1300 ° C. or lower, and more specifically, 1250 ° C. or lower.

The optical glasses of Examples of the present invention is a refractive index _{(n d)} and Abbe number ([nu _{d) is, (- 0.01ν d +2.15) ≦} n d ≦ (-0.01ν d +2.35 ), And more specifically, the relationship of (−0.02ν _d + 2.22) ≦ n _d ≦ (−0.02ν _d +2.28) was satisfied. _{The relationship between the refractive index (nd} ) and the Abbe number (ν _d ) for the glass of the examples of the present application is shown in FIG.

Further, all of the optical glasses of the examples of the present invention had a specific gravity of 5.50 or less, and more specifically, 4.80 or less.

The optical glass of the embodiment of the present invention has a d × RA value of 18.0 or less when the specific gravity is d and the series of chemical durability (acid resistance) by the powder method is RA. Specifically, it was 4.0 or more and 13.0 or less. On the other hand, the optical glass of the comparative example had a d × RA value of 19.10, and was unable to achieve both suitability for polishing and weight reduction.

Therefore, it is clear that the optical glass of the embodiment of the present invention has high acid resistance, is stable, and is difficult to devitrify, while _{having a refractive index (nd} ) and an Abbe number (ν _{d) within desired ranges.} Became. Therefore, it is presumed that the optical glass of the embodiment of the present invention can easily produce a preform material and an optical element by polishing.

Further, a glass block was formed using the optical glass of the embodiment of the present invention, and the glass block was ground and polished to be processed into the shape of a lens and a prism. As a result, it was possible to stably process various lens and prism shapes.

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

Claims (10)

By mass%
SiO ₂ component is more than 0% and 35.0% or less,
B ₂ O ₃ component is more than 0% and less than 35.0%,
La ₂ O ₃ component is more than 20.0% and less than 65.0%,
Contains Al ₂ O ₃ component more than 0% and 30.0% or less,
It has a refractive index ( _nd ) of 1.70 or more, and has an Abbe number (ν _d ) of 35 or more and 55 or less.
Optical glass having chemical durability (acid resistance) of classes 1 to 4 by the powder method. By mass%
Y ₂ O ₃ component 0 to less than 25.0%,
Gd ₂ O ₃ component 0-40.0%,
Yb ₂ O ₃ component 0 to less than 10.0%,
Lu ₂ O ₃ component 0 to less than 10.0%,
MgO component 0 to less than 10.0%,
CaO component 0-less than 10.0%,
SrO component 0 to less than 10.0%,
BaO component 0-less than 10.0%,
Li ₂ O component 0-less than 5.0%,
Na ₂ O component 0 to less than 10.0%,
K ₂ O component 0 to less than 10.0%,
TiO ₂ component 0 to less than 15.0%,
Nb ₂ O ₅ component 0 to less than 15.0%,
ZrO ₂ component 0 to less than 15.0%,
Ta ₂ O ₅ component 0 to less than 10.0%,
WO ₃ component 0 to less than 10.0%,
ZnO component 0 to less than 30.0%,
P ₂ O ₅ component 0 to less than 10.0%,
GeO ₂ component 0-0 less than 10.0%,
Ga ₂ O ₃ component 0 to less than 10.0%,
Bi ₂ O ₃ component 0 to less than 10.0%,
TeO ₂ component 0 to less than 10.0%,
SnO ₂ component 0-less than 3.0%,
Sb ₂ O ₃ component is less than 0-1.0%,
The optical glass according to claim 1, wherein the content of fluoride as F, which is substituted with a part or all of one or more oxides of each of the above elements, is less than 0 to 10.0% by mass. The optical glass according to claim 1 or 2, wherein the mass sum SiO ₂ + B ₂ O _{3 is 15.0% or more and 40.0% or less.} The optical glass according to any one of claims 1 to 3, wherein the mass sum SiO ₂ + B ₂ O ₃ + Al ₂ O _{3 is 15.0% or more and less than 50.0%.} The optical glass according to any one of claims 1 to 4, wherein the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O _{3 is more than 0.30 and 10.00 or less.} By mass%
The sum of the contents of the Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is 40.0% or more and 70.0% or less.
The sum of the contents of the RO component (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, Zn) is less than 0 to 10.0%.
Rn ₂ O component (wherein, Rn is Li, Na, 1 or more selected from the group consisting of K) according to any one of claims 1 sum of the contents is less than 0 to 10.0% of 5 Optical glass. The optical glass according to any one of claims 1 to 6, wherein the mass ratio Ln ₂ O ₃ / (SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ ) is more than 0.30 and 10.00 or less (in the formula, Ln is La, One or more selected from the group consisting of Gd, Y, and Yb). A preform made of optical glass according to any one of claims 1 to 7. An optical element made of the optical glass according to any one of claims 1 to 7. An optical device including the optical element according to claim 9.

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