WO2020017275A1

WO2020017275A1 - Optical glass, preform and optical element

Info

Publication number: WO2020017275A1
Application number: PCT/JP2019/025752
Authority: WO
Inventors: 浄行桃野
Original assignee: 株式会社オハラ
Priority date: 2018-07-18
Filing date: 2019-06-27
Publication date: 2020-01-23
Also published as: TWI808214B; JP7424978B2; TW202010717A; CN112424135A; JPWO2020017275A1

Abstract

Provided is a stable optical glass which has a refractive index (n_d) and an Abbe number (ν_d) each falling within a desired range and yet from which a preform material or an optical element can be easily produced by polishing processing. The optical glass comprises, in mass%, more than 0% and not more than 35.0% of an SiO₂ component, more than 0% and not more than 35.0% a B₂O₃ component, more than 20.0% and not more than 65.0% of an La₂O₃ component and more than 0% and not more than 30.0% of an Al₂O₃ component, and has a refractive index (n_d) of 1.70 or greater, an Abbe number (ν_d) of 35-55 inclusive, and a chemical durability (acid tolerance) measured by the powder method of class 1-4.

Description

Optical glass, preform and optical element

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

2. Description of the Related Art In recent years, digitalization and high-definition of devices using optical systems have been rapidly progressing, and various optical devices such as photographing devices such as digital cameras and video cameras, and image reproducing (projection) devices such as projectors and projection televisions. In the field of, 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 an optical element, in particular, it has a refractive index ( _nd ) of 1.70 or more, and an Abbe number (ν _d ) of 35 or more and 55 or less, which can reduce the size of the entire optical system. The demand for high refractive index and low dispersion glass having As such a high-refractive-index low-dispersion glass, a glass composition represented by Patent Document 1 is known.

JP-A-11-071129

However, in the glass disclosed in Patent Document 1, the stability of the glass may be insufficient, and it has been demanded to enhance the stability. Furthermore, glass that has been devitrified when the glass is manufactured is liable to be clouded when polishing a glass formed by press using a reheat press or when manufacturing a preform material by polishing the glass. There was a problem. It has been difficult to produce an optical element that controls light in the visible region, in particular, from glass once devitrified or clouded.

The present invention has been made in view of the above-described problems, and has as its object the purpose of polishing by polishing while the refractive index (n _d ) and Abbe number (ν _d ) are within desired ranges. An object of the present invention is to obtain a stable optical glass in which a reforming material and an optical element can be easily manufactured.

Means for Solving the Problems To solve the above-mentioned problems, the inventors of the present invention have conducted intensive tests and studies. As a result, 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 was refracted. while there rate (n _d) and Abbe number ([nu _d) is within a desired range, chemical durability, particularly susceptible perform polishing for high acid resistance, it found that stable glass can be obtained, The present invention has been completed.
Specifically, the present invention provides the following.

(1) In mass%,
SiO ₂ component more than 0% and 35.0% or less,
B ₂ O ₃ component more than 0% and 35.0% or less,
La ₂ O ₃ component more than 20.0% and 65.0% or less,
Al ₂ O ₃ component more than 0% and 30.0% or less,
Contains
Has 1.70 or more of refractive index _{(n d),} has a 35 to 55 following the Abbe number (ν _d),
An optical glass having a chemical durability (acid resistance) of a class 1 to 4 by a powder method.

(2) In mass%,
Y ₂ O ₃ component 0 to less than 25.0%,
Gd ₂ O ₃ component 0 to less than 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 to less than 10.0%,
SrO component 0 to less than 10.0%,
BaO component 0 to less than 10.0%,
Li ₂ O component 0 to 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 components 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 to 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 to less than 3.0%,
Sb ₂ O ₃ component 0 to less than 1.0%;
(1) The optical glass according to (1), wherein the content of F as a fluorine which is partially or entirely substituted with one or more oxides of each of the above elements is 0 to less than 10.0% by mass.

(3) The optical glass according to (1) or (2), wherein the mass sum of 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 of 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) In mass%,
The sum of the contents of Ln ₂ O ₃ components (where Ln is at least one selected from the group consisting of La, Gd, Y, Yb, and Lu) is 40.0% or more and 70.0% or less;
A sum of contents of RO components (where R is at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn) is 0 to less than 10.0%;
Any of (1) to (5), wherein the sum of the contents of Rn ₂ O components (where Rn is at least one selected from the group consisting of Li, Na, and K) is 0 to less than 10.0%; The optical glass of the above.

(7) The optical glass 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 not more than 10.00. , Ln is at least one selected from the group consisting of La, Gd, Y, and Yb).

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

{(9)} An optical element comprising 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, the refractive index (n _d) and Abbe number ([nu _d) is while remaining within the desired range, easy to perform the production of a preform or an optical element by grinding, to obtain a stable optical glass Can be.

It is a diagram showing the relationship between the refractive index of the glass of the present embodiment (n _d) and Abbe number (ν _d).

In the optical glass of the present invention, the SiO ₂ component is more than 0% to 35.0% or less, the B ₂ O ₃ component is more than 0% to 35.0% or less, and the La ₂ O ₃ component is more than 20.0% by 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) And has a chemical durability (acid resistance) of 1 to 4 in 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 high Abs number (ν _d ) of 35 or more and 55 or less and high chemical durability, particularly high acid resistance, can be obtained. Therefore, the refractive index (n _d) and Abbe number ([nu _d) is while remaining within the desired range, easy to perform the production of a preform or an optical element according to a high polishing acid resistance, to obtain a stable optical glass Can be.

In addition, the optical glass of the present invention can contribute to weight reduction of an optical element and an optical device due to its low specific gravity.

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 at all, and can be implemented with appropriate modifications within the scope of the present invention. In addition, although the description may be omitted as appropriate for portions where the description is duplicated, the purpose of the invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention will be described below. In the present specification, unless otherwise specified, the content of each component is expressed in terms of% by mass with respect to the total mass of the oxide-converted composition. Here, the `` oxide-equivalent composition '' refers to an oxide, a composite salt, a metal fluoride, and the like used as a raw material of the glass component of the present invention, when it is assumed that all are decomposed at the time of melting and change to an oxide. The composition is a composition in which each component contained in the glass is described, with the total mass of the generated oxide being 100% by mass.

<About essential and optional components>
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 a component that can improve the chemical durability of the glass, especially the acid resistance, and also enhances the stability of the glass to make it easier to obtain a glass that can withstand mass production. Further, 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%, and even more preferably 7.0%. More than, 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%, further preferably less than 27.0%, further preferably less than 24.0%, and still more preferably 21.0%. 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 increased, the devitrification resistance can be increased, 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%, and even more preferably 7. 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 higher 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%, further preferably less than 27.0%, further preferably less than 25.0%, and still more preferably. It is less than 20.0%, more preferably less than 18.0%, and still more preferably less than 15.0%.

The La ₂ O ₃ component is an essential component for increasing the refractive index and Abbe number of glass. Moreover, since the rare earth is relatively inexpensive, the material cost of the 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%, furthermore preferably more than 28.0%, still more preferably more than 30.0%, and still more preferably. The content is more than 35.0%, more preferably more than 37.0%, further preferably more than 40.0%.
On the other hand, by setting the content of the La ₂ O ₃ component to 65.0% or less, destabilization can be reduced by increasing the stability of the glass. Further, the melting property of the glass raw material can be improved. Therefore, the content of the La ₂ O ₃ component is preferably at most 65.0%, more preferably less than 60.0%, further preferably less than 58.0%, further preferably less than 55.0%, further preferably less than 55.0%. It is less than 53.0%, more preferably less than 50.0%.

The Al ₂ O ₃ component is an essential component that can improve the chemical durability of the glass, especially the acid resistance, and the devitrification resistance of the glass. Therefore, the content of the Al ₂ O ₃ component is preferably more than 0%, more preferably more than 1.0%, further preferably more than 2.0%, further preferably more than 3.0%, and still more preferably 5. More than 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 increased. Therefore, the content of the Al ₂ O ₃ component is preferably 30.0% or less, more preferably less than 25.0%, further preferably less than 20.0%, further preferably less than 15.0%, and still more preferably. Is less than 13.0%.

The Y ₂ O ₃ component is an optional component that can suppress the material cost of the glass and reduce the specific gravity of the glass while maintaining a high refractive index and a high Abbe number when containing more than 0%. Therefore, the content of the Y ₂ O ₃ component is preferably more than 0%, more preferably more than 1.0%, further preferably more than 5.0%, further preferably more than 8.0%, and still more preferably 10. It may be more than 0%.
On the other hand, when the content of the Y ₂ O ₃ component is less than 25.0%, a decrease in the refractive index of the glass can be suppressed, and the stability of the glass can be increased. Further, the deterioration of the melting property of the glass raw material can be suppressed. Therefore, the content of the Y ₂ O ₃ component is preferably less than 25.0%, more preferably less than 20.0%, further preferably less than 18.0%, and still 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 glass when containing more than 0%.
However, the raw material price of the Gd ₂ O ₃ component is high, and if the content is high, 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%, further preferably less than 20.0%, and 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 containing more than 0%.
However, the Yb ₂ O ₃ component and the Lu ₂ O ₃ component have a high raw material price, and if the content is large, the production cost increases and the specific gravity of the glass increases. Therefore, the content of each of the Yb ₂ O ₃ component and the Lu ₂ O ₃ component is preferably less than 10.0%, more preferably less than 7.0%, further preferably less than 4.0%, and still more preferably 1. Less than 0%. In particular, from the viewpoint of reducing material costs, it is most preferable not to contain these components.

The MgO component, the CaO component, the SrO component and the BaO component are optional components that can adjust the refractive index, melting property, and devitrification resistance of the glass when containing more than 0%.
On the other hand, when the content of each of the MgO component, CaO component, SrO component and BaO component is less than 10.0%, a decrease in the refractive index can be suppressed, and devitrification due to excessive content of these components. Can be reduced. Therefore, the content of each of the MgO component, the CaO component, the SrO component, and the BaO component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably 3.0% or less, and further preferably 1. Less than 0%. Particularly, from the viewpoint of obtaining a glass having a high refractive index, it is most preferable not to contain these components.

The Li ₂ O component is an optional component that can improve the melting property of the glass and lower the glass transition point when it contains more than 0%.
On the other hand, when the content of the Li ₂ O component is less than 5.0%, the refractive index of the glass is hardly reduced, 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%, further preferably less than 1.0%, further preferably less than 0.5%, and still more preferably 0%. 0.3% or less.

The Na ₂ O component and the K ₂ O component are optional components that can improve the melting property of the glass and lower the glass transition point when containing more than 0%.
On the other hand, when the content of each of the Na ₂ O component and the K ₂ O component is less than 10.0%, the refractive index of the glass is hardly reduced, and the devitrification of the glass can be reduced. Therefore, the content of each of the Na ₂ O component and the K ₂ O component is preferably less than 10.0%, more preferably less than 5.0%, further preferably less than 3.0%, and still more preferably 1.0%. , More preferably less than 0.5%.

The TiO ₂ component is an optional component that increases the refractive index of the glass and lowers the liquidus temperature of the glass to increase the stability. It is also a component that reduces the specific gravity of glass.
On the other hand, when the content of the TiO ₂ component is 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 to visible light (particularly, a wavelength of 500 nm or less) can be reduced. Can be suppressed. In addition, a decrease in the Abbe number can be suppressed. Therefore, the content of the TiO ₂ component is preferably less than 15.0%, more preferably less than 10.0%, further preferably less than 8.0%, still more preferably 5.0% or less, and further preferably 3.0% or less. 0% or less.

The Nb ₂ O ₅ component is an optional component that, when contained more than 0%, can increase the refractive index of the glass and lower the liquidus temperature of the glass to increase the devitrification resistance. 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 setting the content of the Nb ₂ O ₅ component to less than 15.0%, the material cost of the glass can be suppressed, and the decrease in Abbe number can be suppressed. In addition, devitrification due to excessive Nb ₂ O ₅ content can be reduced, and a decrease in transmittance of 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%, and still more preferably less than 10.0%.

The ZrO ₂ component is an optional component that, when contained at more than 0%, can increase the refractive index and Abbe number of the glass and improve the devitrification resistance. Therefore, the content of the ZrO ₂ component may be preferably more than 0%, more preferably more than 1.0%, and still more preferably more than 1.5%.
On the other hand, when the content of the ZrO ₂ component is less than 15.0%, devitrification due to 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%, further preferably less than 10.0%, and still more preferably less than 7.0%.

The Ta ₂ O ₅ component is an optional component that, when contained in more than 0%, can increase the refractive index of the glass and increase the devitrification resistance.
However, the Ta ₂ O ₅ component has a high raw material price, and a high content thereof increases the production cost. 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 production 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%, further preferably less than 3.0%, and still more preferably less than 1.0%. Particularly, from the viewpoint of reducing the material cost, it is most preferable not to contain the Ta ₂ O ₅ component.

When the WO ₃ component contains more than 0%, an optional component that can increase the refractive index, lower the glass transition point, and increase the devitrification resistance while reducing coloring of the glass due to other high refractive index components. It is. Therefore, the content of WO ₃ ingredient is preferably 0 percent, more preferably from 0.3%, even more preferably may be 0.5% greater.
On the other hand, by the content of WO ₃ components below 10.0%, it suppressed the material cost of the glass, suppressing a decrease in the Abbe number. Also, it increased visible light transmittance to reduce the coloration of the glass due WO ₃ components. Therefore, the content of WO ₃ component is preferably less than 10.0%, more preferably less than 5.0%, more preferably less than 3.0%, 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 contained in an amount exceeding 0%. It is also a component that can lower the glass transition point and improve chemical durability.
On the other hand, when the content of the ZnO component is less than 30.0%, a decrease in the refractive index of the glass can be suppressed, and devitrification due to an excessive decrease in the viscosity can be reduced. Therefore, the content of the ZnO component is preferably less than 30.0%, more preferably less than 25.0%, further preferably less than 22.0%, further preferably less than 20.0%, and 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 contained in more than 0%, can lower the liquidus temperature of the glass and increase the devitrification resistance.
On the other hand, by reducing the content of the P ₂ O ₅ component to less than 10.0%, a decrease in chemical durability, particularly water resistance, of the glass can be suppressed. Therefore, the content of the P ₂ O ₅ component is preferably less than 10.0%, more preferably less than 5.0%, further preferably less than 3.0%, and still more preferably less than 1.0%.

The GeO ₂ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when contained more than 0%.
However, GeO ₂ has a high raw material price, and a high content thereof increases production costs. Therefore, the content of the GeO ₂ component is preferably less than 10.0%, more preferably less than 5.0%, further preferably less than 3.0%, and still more preferably less than 1.0%. In particular, from the viewpoint of reducing material costs, 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 improve the devitrification resistance of the glass when containing more than 0%.
On the other hand, when the content of the Ga ₂ O ₃ component is less than 10.0%, the liquidus temperature of the glass can be lowered and the devitrification resistance can be increased. Therefore, the content of the Ga ₂ O ₃ component is preferably less than 10.0%, more preferably less than 5.0%, further preferably less than 3.0%, and 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 containing more than 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 increased. Therefore, the content of the Bi ₂ O ₃ component is preferably less than 10.0%, more preferably less than 5.0%, further preferably less than 3.0%, and 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 containing more than 0%.
On the other hand, there is a problem that TeO ₂ can be alloyed with platinum when melting a glass raw material in a platinum crucible or a melting tank in which a portion in contact with the molten glass is formed of platinum. Therefore, the content of the TeO ₂ component is preferably less than 10.0%, more preferably less than 5.0%, further preferably less than 3.0%, and still more preferably less than 1.0%.

The SnO ₂ component is an optional component that, when contained in more than 0%, can reduce the oxidization of the molten glass to clarify it and increase the visible light transmittance of the glass.
On the other hand, when the content of the SnO ₂ component is less than 3.0%, coloring of the glass due to reduction of the molten glass and devitrification of the glass can be reduced. Further, since the alloying of the SnO ₂ component and the melting equipment (particularly, a 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%, further preferably less than 0.5%, and still more preferably less than 0.1%.

The Sb ₂ O ₃ component is an optional component capable of defoaming the molten glass when containing 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 still more preferably less than 0.3%.

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

The F component is an optional component that, when contained at more than 0%, can increase the Abbe number of the glass, lower the glass transition point, and improve the devitrification resistance.
However, when the content of the F component, that is, the total amount of the fluorides substituted with part or all of one or more oxides of the above-described metal elements as F exceeds 10.0%, Since the volatilization amount of the component is large, it is difficult to obtain a stable optical constant, and it is 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%, further preferably less than 3.0%, and 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 from 0.15 to 10.00.
In particular, by setting the ratio SiO ₂ / B ₂ O ₃ to 0.15 or more, the stability of the glass can be enhanced, and the chemical durability, particularly, the acid resistance of the glass can be improved. The glass of the present invention can be vitrified even when the content of the B ₂ O ₃ component is relatively small and the content of the SiO ₂ component is relatively large. Therefore, the mass ratio SiO ₂ / B ₂ O ₃ is preferably at least 0.15, more preferably at least 0.30, further preferably at least 0.50, further preferably at least 0.60, further preferably at least 0.70. The above may be used.
On the other hand, by setting the ratio SiO ₂ / B ₂ O ₃ to 10.00 or less, the rise of the glass transition point can be suppressed, so that molding at a lower temperature can be facilitated. Therefore, the mass ratio SiO ₂ / B ₂ O ₃ is preferably 10.00 or less, more preferably 7.00 or less, further preferably 5.00 or less, and further 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 from 15.0% to 40.0%.
In particular, by setting the sum to 15.0% or more, a glass network structure 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 making this sum 40.0% or less, a decrease in the refractive index due to excessive inclusion of these components can be suppressed. Further, the chemical durability of the glass, particularly the 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%, further preferably less than 35.0%, further preferably less than 32.0%, further preferably less than 32.0%. It is 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 making this sum 15.0% or more, more stable glass can be obtained. Therefore, the mass sum SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ is preferably at least 15.0%, more preferably more than 18.0%, further preferably more than 20.0%, further preferably more than 22.0%. , More preferably more than 25.0%.
On the other hand, when the sum is less than 50.0%, a decrease in the refractive index due to an excessive content of these components can be suppressed. Thus, 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%, even more preferably less than 44.0%, even more preferably less than 42.0%. , More preferably less than 39.0%.

The ratio of the sum of the content of the SiO ₂ component and the content of 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 the ratio to be 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, and still more preferably more than 0.90. I do.
On the other hand, by setting this ratio to 10.00 or less, more stable glass can be obtained. Therefore, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is preferably at most 10.00, more preferably at most 10.00, further preferably at most 8.00, further preferably at most 6.00, More preferably, it is set to 5.50 or less.

The sum (mass sum) of the contents of Ln ₂ O ₃ components (where 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 more. % Or less is preferable.
In particular, by setting the sum to 40.0% or more, the refractive index and Abbe number of the glass are increased, so that glass having desired refractive index and Abbe number can be easily obtained. Therefore, the mass sum of the Ln ₂ O ₃ component is preferably 40.0% or more, more preferably more than 43.0%, still more preferably 45.0% or more, and further preferably more than 47.0%.
On the other hand, by setting the sum to 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 component is preferably 70.0% or less, more preferably less than 65.0%, more preferably less than 64.0%, and still more preferably less than 63.0%.

The sum (mass sum) of the content of the RO component (where R is at least one selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably less than 10.0%. Thereby, a decrease in the refractive index can be suppressed, and the stability of the glass can be increased. Therefore, the mass sum of the RO component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably 3.0% or less, and further preferably less than 1.0%.

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

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 at least one selected from the group consisting of La, Gd, Y, and Yb).
In particular, when the mass ratio is 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, further preferably more than 0.80, and still more preferably 1 It is more than 0.000, more preferably 1.27 or more, further preferably 1.35 or more, further preferably 1.50 or more.
On the other hand, by setting the mass ratio to 10.00 or less, the stability 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 10.00 or less, more preferably 5.00 or less, further preferably 3.00 or less, and further preferably 2 or less. .60 or less, more preferably 2.30 or less, and still more preferably 2.10 or less.

SiO ₂ component, Al ₂ O ₃ component and Ln ₂ O _{3 with} respect to a value obtained by adding 10 times the value of the refractive index nd to the sum of the contents of the RO component, Rn ₂ O component, ZnO component and B ₂ O ₃ component The ratio (mass ratio) of the sum of the component contents is preferably 0.80 or more and 6.00 or less (where Ln is at least one selected from the group consisting of La, Gd, Y, and Yb, and R is One or more members selected from the group consisting of Mg, Ca, Sr, Ba and Zn, and Rn one or more members selected from the group consisting of Li, Na and K).
By setting the mass ratio in the range of 0.80 or more and 6.00 or less, the chemical durability, particularly the acid resistance, of the glass can be improved. Accordingly, 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, further preferably 1.20, The lower limit is further preferably 1.50, further preferably 1.80, 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 (where Ln is at least one selected from the group consisting of La, Gd, Y, Yb, and Lu). . Thereby, the effect of improving the devitrification resistance is easily obtained. 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 the mass ratio to 1.00 or less, it is possible to suppress deterioration of the melting property of the glass raw material and excessive rise in viscosity. 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, further preferably 0.0.30 or less, and further more preferably 0.25 or less. , And 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, the effect of improving the devitrification resistance can be easily obtained, and an excessive decrease in Abbe number can be suppressed to easily obtain low dispersion performance. 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, and still more preferably 15% or less. 0.0% or less, more preferably 5.0% or less, and still more preferably 4.0% or less.

The mass ratio (Ln ₂ O ₃ / RO) is preferably 1.0 or more (where Ln is at least one selected from the group consisting of La, Gd, Y, Yb, and Lu). Thereby, the effect of improving the chemical durability of the glass can be easily obtained. Therefore, the mass ratio of (Ln ₂ O ₃ / RO) is preferably 1.0 or more, more preferably 3.0 or more, further preferably 5.0 or more, further preferably 10.0 or more, and further preferably 20 or more. 0.0 or more.
Note that, even when no RO component is contained, the effect of improving the chemical durability can be obtained, and thus 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. Thereby, the effect of improving the chemical durability of the glass can be easily obtained. Therefore, the mass ratio of (Ln ₂ O ₃ / Rn ₂ O) is preferably 3.0 or more, more preferably 5.0 or more, further preferably 8.0 or more, further preferably 10.0 or more, and still more preferably. May be 15.0 or more, more preferably 20.0 or more, further preferably 25.0 or more, and most preferably 30.0 or more.
Note that, even when the Rn ₂ O 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 / Rn ₂ O) is infinite even if it is infinite. Good.

The mass product (BaO × Gd ₂ O ₃ ) is preferably less than 8.0. By reducing this product, the effect of suppressing both the specific gravity of glass and the cost can be easily obtained. 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, and even more preferably 4 or less. 0.0 or less, more preferably 3.0 or less, further preferably 2.0 or less, further preferably 1.0 or less, and still more preferably 0.1 or less.

The mass sum (SiO ₂ + Al ₂ O ₃ ) is preferably 5.0% or more. Thereby, the effect of improving the chemical durability of the glass can be easily obtained. Accordingly, the mass sum of (SiO ₂ + Al ₂ O ₃ ) is preferably at least 5.0%, more preferably at least 7.0%, further preferably at least 9.0%, further preferably at least 10.0%. Is also good.
On the other hand, by setting the mass sum to 40.0% or less, it is possible to suppress the deterioration of the melting property of the glass raw material and the excessive increase in viscosity. Accordingly, 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, and still more preferably 30.0% or less. Good.

<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 preferably contained will be described.

Other components can be added as needed as long as the properties of the glass of the present invention are not impaired. However, each of transition metal components such as Nd, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, is Even if a small amount is contained singly or in combination, the glass is colored and has a property of causing absorption at a specific wavelength in the visible region. Is preferred.

Further, lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components that have a high environmental load, and therefore, should not substantially be contained, that is, should not be contained at all except for unavoidable contamination.

Furthermore, each component of Th, Cd, Tl, Os, Be, and Se tends to refrain from using as harmful chemicals in recent years, and is used not only in the glass manufacturing process but also in the processing process and disposal after commercialization. Environmental measures are required to this extent. Therefore, when importance is placed on environmental influences, it is preferable that these are not substantially contained.

「In this specification,“ substantially not contained ”means that the content is preferably less than 0.1%, and more preferably not contained except for inevitable impurities. Here, the content of components contained as inevitable impurities 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-mentioned 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 is heated at 1100 to 1500 ° C. in an electric furnace according to the melting difficulty of the glass raw materials. The mixture is melted for 2 to 5 hours in the above temperature range, stirred and homogenized, cooled to an appropriate temperature, cast into a mold, and gradually cooled.

[Physical properties]
The optical glass of the present invention preferably has a high refractive index and a high Abbe number (low dispersion). In particular, the lower limit of 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. The upper limit of the refractive index ( _nd ) of the optical glass of the present invention is preferably 2.00, more preferably 1.95, and even more preferably 1.90. In addition, the lower limit of the Abbe number (ν _d ) of the optical glass of the present invention is preferably 35, more preferably 38, further preferably 40, and further preferably 42. The upper limit of 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 light refraction can be obtained even if the optical element is made thin. In addition, by having such a low dispersion, when used as a single lens, a shift in focus (chromatic aberration) due to the wavelength of light can be reduced. Therefore, for example, when an optical system is configured in combination with an optical element having high dispersion (low Abbe number), aberrations can be reduced as a whole of the optical system, and high imaging characteristics can be achieved.
As described above, the optical glass of the present invention is useful in optical design. Particularly, when an optical system is configured, it is possible to reduce the size of the optical system while achieving high imaging characteristics and the like. Can be expanded.

Here, the optical glass of the present invention has a refractive index (n _d ) and an Abbe number (ν _d ) of (−0.01ν _d +2.15) ≦ n _d ≦ (−0.01ν _d +2.35). It is preferable to satisfy the relationship. The glass composition specified in the present invention refractive index (n _d) and Abbe number ([nu _d) is that satisfies this relationship, it is possible to obtain a relatively stable glass.
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, in the optical glass of the present invention, the refractive index (n _d ) and the Abbe number (ν _d ) preferably satisfy the relationship of n _d ≦ (−0.01ν _d +2.35), and n _d ≦ ( It is more preferable to satisfy the relationship of −0.01ν _d +2.30), and it is still more preferable to satisfy the relationship of n _d ≦ (−0.01ν _d +2.28).

光学 The optical glass of the present invention has high acid resistance. In particular, the chemical durability (acid resistance) of the glass by the powder method according to JOGIS06-2006 is preferably Class 1-4, more preferably Class 1-3, further preferably Class 1-2, and most preferably Class 1-2. It is one. Accordingly, when the optical glass is polished, the fogging of the glass due to an acidic polishing liquid or a cleaning liquid is reduced, so that the polishing processing can be performed more easily. Here, "acid resistance" refers to the durability against erosion of glass by an acid, and the acid resistance is measured by JOGIS06-2006, "Method for measuring the chemical durability of optical glass" specified by Japan Optical Glass Industrial Association. Can be. Further, “the chemical durability (acid resistance) by powder method is class 1 to class 4” means that the chemical durability (acid resistance) performed according to JOGIS06-2006 is the mass of the sample before and after the measurement. It means that the weight loss is less than 1.20% by mass. In addition, "class 1" of chemical durability (acid resistance) means that the weight loss of the sample before and after the measurement is less than 0.20% by mass, and "class 2" means the weight loss of the sample before and after the measurement. "Class 3" means that the weight loss rate of the sample before and after the measurement is 0.35 mass% or more and less than 0.65 mass%. "4" indicates that 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 weight, and "Class 5" indicates that the weight loss rate of the sample before and after the measurement is 1.20% by weight. It 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.

光学 It is preferable that the optical glass of the present invention has high devitrification resistance, and more specifically, has a low liquidus temperature. That is, the upper limit of the liquidus temperature of the optical glass of the present invention is preferably 1300 ° C, more preferably 1280 ° C, and further preferably 1250 ° C. As a result, even if the melted glass flows out at a lower temperature, the crystallization of the produced glass is reduced, so that the devitrification when the glass is formed from the molten state can be reduced, and the 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 when 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 generally 800 ° C or higher, specifically 850 ° C or higher, more specifically 900 ° C or higher. Often above ° C. In this specification, "liquid phase temperature" refers to a 5 ml cullet-shaped glass sample placed in a platinum crucible having a capacity of 50 ml, completely melted at 1400 ° C., and cooled to a predetermined temperature. The temperature was maintained for 1 hour, taken out of the furnace, cooled, and immediately observed, and the lowest temperature at which no crystal was observed when the surface of the glass and the presence or absence of crystals in the glass were observed. Here, the predetermined temperature at the time of cooling is a temperature between 1300 ° C. and 800 ° C. in steps of 10 ° C.

The upper limit of 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 reducing the weight of the optical element and the optical device. On the other hand, the specific gravity of the optical glass of the present invention is generally about 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 JOGIS05-1975 “Method for measuring specific gravity of optical glass” specified by Japan Optical Glass Industrial Association.

The optical glass of the present invention preferably has both high acid resistance and light weight. That is, the optical glass of the present invention preferably has a value of d × RA of 18.0 or less, where d is a specific gravity and RA is a series of chemical durability (acid resistance) by a powder method. In such an optical glass, both acid resistance and specific gravity are low values, so that both high acid resistance and weight reduction can be achieved, and further improvement in workability by polishing and reduction in the weight of optical elements and optical devices. Can be compatible. Therefore, the value of d × RA in the optical glass of the present invention is preferably 18.0, more preferably 15.0, further preferably 13.0, further preferably 10.0, and still more preferably 9.0. And
On the other hand, the lower limit of d × RA is often about 2.0 or more, more specifically 3.0 or more, and more specifically 4.0 or more.

[Preform and optical element]
From the produced optical glass, a glass molded body can be produced, for example, by means of polishing or by means of mold press molding such as reheat press molding or precision press molding. That is, mechanical processing such as grinding and polishing is performed on the optical glass to produce a glass molded body, or a preform for mold press molding is produced from the optical glass, and reheat press molding is performed on the preform. After that, a glass molded body is manufactured by performing a polishing process, or a preform manufactured by performing a polishing process or a preform formed by a known floating molding or the like is subjected to precision press molding to perform 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 or precision press molding using the preform to produce an optical element such as a lens or a prism. This makes it possible to form a preform having a large diameter, so that the size of the optical element can be increased, and when used in an optical device such as a camera or a projector, high-definition and high-precision imaging and projection characteristics can be achieved. Can be realized.

Compositions of Examples (No.1 ~ No.43) of the present invention and comparative examples (No. A), and the refractive index of these glasses _(n d), Abbe number ([nu _d), a chemical by a powder method Tables 1 to 6 show the results of durability (acid resistance), liquidus temperature and specific gravity. The following embodiments are for illustrative purposes only, and are not limited to these embodiments.

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

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

(4) The acid resistance of the glasses of Examples and Comparative Examples was measured according to JOGIS06-2006, "Method for Measuring Chemical Durability of Optical Glass", Japan Optical Glass Industry Association Standard. 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 nitric acid aqueous solution and treated in a boiling water bath for 60 minutes. Calculate the weight loss rate (% by mass) of the glass sample after the treatment, and class 1 when the weight loss rate is less than 0.20, and class 1 when 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 Class 4 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.

比 The specific gravity d of the glasses of the examples and comparative examples was measured based on JOGIS05-1975 “Method for measuring the specific gravity of optical glass” specified by Japan Optical Glass Industrial Association. From the value of the measured specific gravity d and the value of the acid resistance series RA, the value of d × RA, which is the product of these, was determined.

The liquidus temperature of the glass of the example and the comparative example is such that a 5 ml cullet-shaped glass sample is put into a platinum crucible having a capacity of 50 ml and completely melted at 1400 ° C. in a platinum crucible. The temperature was lowered to any temperature set in units of ° C, held for 1 hour, taken out of the furnace and cooled, and immediately after observation of the glass surface and the presence or absence of crystals in the glass, the lowest value where no crystals were observed The temperature was determined.

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, within the desired range.

Further, the optical glasses of the examples of the present invention each have an Abbe number (ν _d ) of 35 or more, more specifically 38 or more, and an Abbe number (ν _d ) of 55 or less, more specifically 54 And within the desired range.

光学 Further, the optical glasses of Examples of the present invention all had chemical durability (acid resistance) according to 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 chemical durability (acid resistance) of class 5 by the powder method. For this reason, it became clear that the optical glasses of the examples of the present invention had better acid resistance than the glasses of the comparative examples.

光学 Further, the optical glass of the present invention formed a stable glass, and devitrification hardly occurred during glass production. This is inferred from the fact that the liquidus temperature of the optical glass of the present invention is 1300 ° C. or lower, 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 ) Was satisfied, and more specifically, the relationship (−0.02ν _d +2.22) ≦ n _d ≦ (−0.02ν _d +2.28) was satisfied. The relationship between the refractive index of the glass of the present embodiment (n _d) and Abbe number ([nu _d) became as shown in Figure 1.

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

In the optical glass of the example of the present invention, the value of d × RA when the specific gravity is d and the series of chemical durability (acid resistance) by the powder method is RA is 18.0 or less. In detail, it was 4.0 or more and 13.0 or less. On the other hand, the optical glass of the comparative example had a value of d × RA of 19.10, and was not compatible with the suitability for polishing and the reduction in weight.

Accordingly, the optical glasses of Examples of the present invention, while remaining refractive index (n _d) and Abbe number ([nu _d) is within the desired range, high acid resistance, and clear that the hard watermarks stable and lost Became. Therefore, it is presumed that the optical glass of the example of the present invention can easily produce a preform material and an optical element by polishing.

Furthermore, using the optical glass of the example of the present invention, a glass block was formed, and the glass block was ground and polished to form lenses and prisms. As a result, it was possible to stably process into various lens and prism shapes.

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

Claims

In mass%,
SiO 2 component more than 0% and 35.0% or less,
B 2 O 3 component more than 0% and 35.0% or less,
La 2 O 3 component more than 20.0% and 65.0% or less,
Containing more than 0% and not more than 30.0% of an Al 2 O 3 component,
Has 1.70 or more of refractive index (n d), has a 35 to 55 following the Abbe number (ν d),
An optical glass having a chemical durability (acid resistance) of a class 1 to 4 by a powder method.
In mass%,
Y 2 O 3 component 0 to less than 25.0%,
Gd 2 O 3 component 0 to less than 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 to less than 10.0%,
SrO component 0 to less than 10.0%,
BaO component 0 to less than 10.0%,
Li 2 O component 0 to 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 components 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 to 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 to less than 3.0%,
Sb 2 O 3 component 0 to less than 1.0%;
2. The optical glass according to claim 1, wherein the content of F as a F, which is substituted with part or all of one or more kinds of oxides of each element, as F is 0 to less than 10.0% by mass.
The optical glass according to claim 1, 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%.
Mass ratio (SiO 2 + Al 2 O 3 ) / B 2 O 3 is 0.30 ultra 10.00 any description of the optical glass of claims 1 to 4, which is.
In mass%,
The sum of the contents of Ln 2 O 3 components (where Ln is at least one selected from the group consisting of La, Gd, Y, Yb, and Lu) is 40.0% or more and 70.0% or less;
A sum of contents of RO components (where R is at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn) is 0 to less than 10.0%;
6. The method according to claim 1, wherein the sum of the contents of Rn 2 O components (where Rn is at least one selected from the group consisting of Li, Na, and K) is 0 to less than 10.0%. 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 not more than 10.00. One or more selected from the group consisting of Gd, Y, and Yb).
(8) A preform comprising the optical glass according to any one of (1) to (7).
An optical element comprising the optical glass according to any one of claims 1 to 7.
An optical device comprising the optical element according to claim 9.