TW202010717A - Optical glass, preform and optical element - Google Patents

Abstract

Provided is a stable optical glass which has a refractive index (nd) and an Abbe number ([nu]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 (nd) of 1.70 or greater, an Abbe number ([nu]d) of 35-55 inclusive, and a chemical durability (acid tolerance) measured by the powder method of class 1-4.

Description

Optical glass, preforms and optical components

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

In recent years, digitalization and high-definition of equipment using optical systems are rapidly developing. Various optical equipment such as digital cameras and video cameras, or video playback (projection) equipment such as projectors and projection TVs. In the field, the number of lenses used in optical systems, such as lenses and 珜鏡, is reduced, and there is an increasing demand for lightening and miniaturization of the entire optical system.

Among the optical glass for manufacturing optical elements, in particular, it is possible to achieve miniaturization of the entire optical system, which has a refractive index (n _d ) of 1.70 or more and a high refractive index of Abbe number (ν _d ) of 35 or more and 55 or less The demand for low-dispersion glass is extremely high. As such a high-refractive-index, low-dispersion glass, a glass composition as represented by Patent Document 1 is known. [Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 11-071129.

[Problems to be solved by the invention]

However, in the glass disclosed in Patent Document 1, the stability of the glass may not be sufficient, and it is sought to improve the stability. In addition, to avoid the devitrified glass when making the glass, when the glass formed by reheat pressing is ground, or when the glass is processed to make the preform material, there is a possibility that mist will occur. Problem points. It is difficult to make an optical element such as a controllable visible area from glass once devitrified or fogged.

The present invention has been completed in view of the above-mentioned problems, and the object of the present invention is to obtain a stable optical glass with a refractive index (n _d ) and Abbe number (ν _d ) within a desired range, and it is easy to carry out grinding processing Fabrication of preform materials or optical elements. [Means to solve the problem]

In order to solve the above-mentioned problems, the present inventors have repeatedly conducted in-depth experimental studies and found that a stable glass can be obtained among glasses containing SiO ₂ component, B ₂ O ₃ component, La ₂ O ₃ component and Al ₂ O ₃ component The refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges, and because of the high chemical durability, especially high acid resistance, it is easy to carry out grinding processing, and the present invention has been completed. Specifically, the present invention provides the following.

(1) An optical glass containing in mass %: SiO ₂ component exceeding 0% to 35.0%; B ₂ O ₃ component exceeding 0% to 35.0%; La ₂ O ₃ component exceeding 20.0% to 65.0% ; Al ₂ O ₃ composition を exceeds 0% to 30.0%; and has a refractive index (n _d ) of 1.70 or more, and has an Abbe number (ν _d ) of 35 to 55 or less; chemistry measured by powder method The durability (acid resistance) is grade 1 to grade 4.

(2) The optical glass as described in (1), wherein in mass %, the Y ₂ O ₃ component is 0% to less than 25.0%; the Gd ₂ O ₃ component is 0% to less than 40.0%; Yb ₂ O ₃ component system 0% to less than 10.0%; Lu ₂ O ₃ component system 0% to less than 10.0%; MgO component system 0% to less than 10.0%; CaO component system 0% to less than 10.0%; SrO component system 0% to less than 10.0%; BaO component system 0% to less than 10.0%; Li ₂ O component system 0% to less than 5.0%; Na ₂ O component system 0% to less than 10.0%; K ₂ O component system 0% to less than 10.0%; TiO ₂ component system 0% to less than 15.0%; Nb ₂ O ₅ component system 0% to less than 15.0%; ZrO ₂ component system 0% to less than 15.0%; Ta ₂ O ₅ Composition 0% to less than 10.0%; WO ₃ composition 0% to less than 10.0%; ZnO composition 0% to less than 30.0%; P ₂ O ₅ composition 0% to less than 10.0%; GeO ₂ composition 0% to less than 10.0%; Ga ₂ O ₃ composition is 0% to less than 10.0%; Bi ₂ O ₃ composition is 0% to less than 10.0%; TeO ₂ composition is 0% to less than 10.0%; SnO ₂ component system 0% to less than 3.0%; Sb ₂ O ₃ component system 0% to less than 1.0%; fluorine as part or all of one or more oxides replacing the above elements The F content of the compound is 0% by mass to less than 10.0% by mass.

(3) The optical glass as described in (1) or (2), wherein the mass and SiO ₂ +B ₂ O ₃ are 15.0% or more and 40.0% or less.

(4) The optical glass as described in any one of (1) to (3), wherein the mass and SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ are 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 exceeds 0.30 to 10.00.

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

(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 ) exceeds 0.30 to 10.00, In addition, Ln is one or more selected from the group consisting of La, Gd, Y, and Yb.

(8) 　 A preform made of optical glass as described in any one of (1) to (7).

(9) An optical element composed of the optical glass as described in any one of (1) to (7).

(10) An optical device equipped with the optical element as described in (9). [Effect of invention]

According to the present invention, it is possible to obtain a stable optical glass having a refractive index (n _d ) and Abbe number (ν _d ) within a desired range, and it is easy to manufacture a preform material or an optical element by grinding.

The optical glass of the present invention contains in mass %: SiO ₂ component exceeding 0% to 35.0%; B ₂ O ₃ component exceeding 0% to 35.0%; La ₂ O ₃ component exceeding 20.0% to 65.0%; Al ₂ O ₃ composition exceeds 0% to 30.0% or less; and has a refractive index (n _d ) of 1.70 or more, and an Abbe number (ν _d ) of 35 or more to 55; chemical durability measured by powder method (Acid resistance) is grade 1 to 4. The present inventors can obtain a stable glass with a refractive index of 1.70 or more when the SiO ₂ component, B ₂ O ₃ component, and La ₂ O ₃ component are used as the basis and the base contains the Al ₂ O ₃ component. n _d ) and Abbe number (ν _d ) of 35 or more and 55 or less, and the chemical durability is particularly high in acid resistance. Therefore, a stable optical glass can be obtained, the refractive index (n _d ) and Abbe number (ν _d ) are within a desired range, and the acid resistance is high, and it is easy to manufacture the preform material or optical element through grinding .

In addition, because the optical glass of the present invention has a small specific gravity, it can contribute to the weight reduction of optical components 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 at all, and can be implemented with appropriate changes within the scope of the object of the present invention. In addition, although there is a case where the description is appropriately omitted for the overlap of the description, it does not limit the gist of the invention.

[Glass composition] The composition range of each component constituting the optical glass of the present invention is as follows. In this specification, unless otherwise specified, the content of each component is expressed in mass% with respect to the total mass of the entire oxide conversion composition. Here, the "oxide-converted composition" assumes that all oxides, complex salts, metal fluorides, etc. used as raw materials for the glass constituent of the present invention are decomposed and changed into oxides when they are melted. The total mass of the oxide is regarded as 100% by mass, and the composition of each component contained in the glass is described.

>About essential components 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, the chemical durability of the glass can be improved, especially the acid resistance, and the stability of the glass can be improved to easily obtain glass that can withstand mass production. Furthermore, it can increase the viscosity of the molten glass and reduce the color of the glass. Therefore, the content of the SiO ₂ component is preferably set to more than 0%, more preferably more than 1.0%, still more preferably more than 3.0%, particularly preferably more than 5.0%, particularly preferably more than 7.0%, and most preferably more than 10.0 %. On the other hand, by setting the content of the SiO ₂ component to 35.0% or less, it is possible to suppress the increase in the glass transition point and suppress the decrease in the refractive index. Therefore, the content of the SiO ₂ component is preferably set to 35.0% or less, more preferably less than 30.0%, still more preferably less than 27.0%, particularly preferably less than 24.0%, particularly preferably less than 21.0%, The best is less than 18.0%.

The B ₂ O ₃ component is an essential component for glass-forming oxides. In particular, by containing the B ₂ O ₃ component exceeding 0%, the stability of the glass can be improved to improve devitrification resistance, and the Abbe number of the glass can be increased. Therefore, the content of the B ₂ O ₃ component is preferably set to exceed 0%, more preferably exceed 1.0%, still more preferably exceed 4.0%, particularly preferably exceed 5.0%, particularly preferably exceed 7.0%, and very 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 the deterioration of chemical durability, especially the 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%, particularly preferably less than 25.0%, particularly preferably less than 20.0% , Very good is less than 18.0%, the best is less than 15.0%.

The La ₂ O ₃ component is an essential component to increase the refractive index and Abbe number of the glass. Moreover, since it is relatively cheap among rare earths, the material cost of glass can be reduced. Therefore, the content of the La ₂ O ₃ component is preferably set to exceed 20.0%, more preferably exceed 25.0%, still more preferably exceed 28.0%, particularly preferably exceed 30.0%, particularly preferably exceed 35.0%, and very preferably More than 37.0%, the best is more than 40.0%. On the other hand, by setting the content of the La ₂ O ₃ component to 65.0% or less, devitrification can be reduced by improving the stability of the glass. In addition, the melting property 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%, particularly preferably less than 55.0%, particularly preferably less than 53.0% , Very good is less than 50.0%.

The Al ₂ O ₃ component is an essential component that can improve the chemical durability of glass, especially acid resistance, and can improve 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%, particularly preferably more than 3.0%, particularly preferably more than 5.0%. 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 to improve devitrification resistance. Therefore, the content of the Al ₂ O ₃ component is preferably set to 30.0% or less, more preferably less than 25.0%, still more preferably less than 20.0%, particularly preferably less than 15.0%, particularly preferably less than 13.0 %.

The Y ₂ O ₃ component is an arbitrary component that not only maintains a high refractive index and a high Abbe number, but also reduces the material cost of the glass when it contains more than 0%, and can reduce the specific gravity of the glass. Therefore, the content of the Y ₂ O ₃ component may be preferably set to exceed 0%, more preferably exceed 1.0%, still more preferably exceed 5.0%, particularly preferably exceed 8.0%, and particularly preferably exceed 10.0%. 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, 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%, still more preferably less than 18.0%, and particularly preferably less than 16.0%.

The Gd ₂ O ₃ component is an arbitrary component that can increase the refractive index and Abbe number of the glass when it exceeds 0%. However, the raw material price of the Gd ₂ O ₃ component is high, and if the content is large, the production cost will increase, and the specific gravity of glass will increase. 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%, and particularly preferably less than 10.0%.

The Yb ₂ O ₃ component and the Lu ₂ O ₃ component are arbitrary components that can increase the refractive index and Abbe number of the glass when they exceed 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 content is large, the production cost will increase, and the specific gravity of the glass will increase. Therefore, the contents of the Yb ₂ O ₃ component and the Lu ₂ O ₃ component are preferably set to less than 10.0%, more preferably less than 7.0%, still more preferably less than 4.0%, and particularly preferably less than 1.0% . In particular, from the viewpoint of reducing the material cost, it is best not to contain these components.

The MgO component, CaO component, SrO component, and BaO component are any components that can adjust the refractive index, meltability, and devitrification resistance of the glass when the content exceeds 0%. On the other hand, by setting the contents of the MgO component, CaO component, SrO component, and BaO component to less than 10.0%, the decrease in refractive index can be suppressed, and devitrification caused by containing these components in excess can be reduced. Therefore, the contents of the MgO component, CaO component, SrO component, and BaO component are each preferably less than 10.0%, more preferably less than 5.0%, still more preferably 3.0% or less, and particularly preferably less than 1.0%. In particular, from the viewpoint of obtaining glass with a high refractive index, it is preferable not to contain these components.

The Li ₂ O component is an arbitrary component that can improve the meltability of the glass and reduce the glass transition point when it contains more than 0%. On the other hand, by setting the content of the Li ₂ O component to less than 5.0%, it is possible to make the refractive index of the glass difficult to decrease and reduce the devitrification of the glass. 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%, particularly preferably less than 0.5%, particularly preferably less than 0.3% .

The Na ₂ O component and the K ₂ O component are arbitrary components that can improve the meltability of the glass and reduce 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 lower the refractive index of the glass and reduce the devitrification of the glass. Therefore, the content of the Na ₂ O component and the K ₂ O component are preferably set to less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and particularly preferably less than 1.0%, especially The best is less than 0.5%.

The TiO ₂ component is an arbitrary component that increases stability by increasing the refractive index of 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%, it is possible to reduce the devitrification caused by the excessive TiO ₂ component and suppress the decrease in the transmittance of glass to visible light (especially at a wavelength of 500 nm or less). . In addition, this suppresses the 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%, particularly preferably 5.0% or less, and particularly preferably 3.0% or less.

The Nb ₂ O ₅ component is an arbitrary component that improves the devitrification resistance by increasing the refractive index of the glass and lowering the liquidus temperature of the glass when it contains more than 0%. Therefore, the content of the Nb ₂ O ₅ component can be preferably set to exceed 0%, more preferably exceed 1.0%, and still more preferably exceed 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 the Abbe number can be suppressed. In addition, it is possible to reduce devitrification caused by containing excessive Nb ₂ O ₅ components, and to suppress a decrease in the transmittance of glass to visible light (especially at a wavelength of 500 nm or less). 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 arbitrary component that can increase the refractive index and Abbe number of the glass when it exceeds 0%, and can improve devitrification resistance. Therefore, the content of the ZrO ₂ component can be preferably set to exceed 0%, more preferably exceed 1.0%, and still more preferably exceed 1.5%. On the other hand, by setting the content of the ZrO ₂ component to less than 15.0%, devitrification caused by the excessive 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%, still more preferably less than 10.0%, and particularly preferably less than 7.0%.

The Ta ₂ O ₅ component is an arbitrary component that can increase the refractive index of the glass and increase the devitrification resistance when it contains more than 0%. However, the raw material price of the Ta ₂ O ₅ component is high, and if the content is large, the production cost will increase. In addition, 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 also 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%, and particularly preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost, it is best not to contain the Ta ₂ O ₅ component.

The WO ₃ component is an optional component that can increase the refractive index and lower the glass transition point while reducing the coloring of glass caused by other high refractive index components when it contains more than 0%. Therefore, the content of the WO ₃ component can preferably be set to more than 0%, more preferably more than 0.3%, and still more preferably more than 0.5%. On the other hand, by setting the content of the WO ₃ component to less than 10.0%, the material cost of the glass can be suppressed, and the decrease in the Abbe number can be suppressed. In addition, the coloration of the glass caused by the WO ₃ component can be reduced to increase the visible light transmittance. 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%, and particularly preferably less than 1.0%.

The ZnO component is an arbitrary component that can increase the stability of the glass and reduce coloration when it contains more than 0%. It is also a component that can reduce the glass transition point and improve the chemical durability. On the other hand, by setting the content of the ZnO component to less than 30.0%, the decrease in the refractive index of the glass can be suppressed, and devitrification caused by the excessive decrease in viscosity can be reduced. Therefore, the content of the ZnO component is preferably set to less than 30.0%, more preferably less than 25.0%, still more preferably less than 22.0%, particularly preferably less than 20.0%, and particularly preferably less than 15.0%, even The best is less than 10.0%.

The P ₂ O ₅ component can function as a glass-forming component, and when it contains more than 0%, it can lower the liquidus temperature of the glass and improve the devitrification resistance. On the other hand, by setting the content of the P ₂ O ₅ component to less than 10.0%, the chemical durability of the glass, especially the decrease in water resistance 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%, still more preferably less than 3.0%, and particularly preferably less than 1.0%.

The GeO ₂ component is an arbitrary component that can increase the refractive index of the glass and increase the devitrification resistance when it contains more than 0%. However, the raw material price of GeO ₂ is high, and if the content is large, the production cost will increase. 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%, and particularly preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost, the GeO ₂ component may not be included.

The Ga ₂ O ₃ component is an arbitrary component that can increase the chemical durability of the glass and increase the devitrification resistance of the glass when it contains more than 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%, and particularly preferably less than 1.0%.

The Bi ₂ O ₃ component is an arbitrary component that can increase the refractive index and lower the glass transition point when it contains 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 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%, and particularly preferably less than 1.0%.

The TeO ₂ component is an arbitrary component that can increase the refractive index and reduce the glass transition point when it contains more than 0%. On the other hand, when TeO ₂ melts glass raw materials in a platinum crucible or a part in contact with molten glass with a melting tank formed of platinum, there is a problem that alloying with platinum occurs. 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%, and particularly preferably less than 1.0%.

The SnO ₂ component is an arbitrary component that can reduce the oxidation of the molten glass and make it clear when it contains more than 0%, and can increase the visible light transmittance of the glass. 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 caused by the reduction of the molten glass. In addition, since the alloying of the SnO ₂ component with the melting equipment (especially precious metals such as Pt) can be reduced, the life of the melting equipment can be increased. 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%, and particularly preferably less than 0.1%.

The Sb ₂ O ₃ component is an arbitrary component capable of defoaming 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 will deteriorate. 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%.

In addition, the component that clarifies and defoams the glass is not limited to the above-mentioned Sb ₂ O ₃ component, and a well-known clarifier, defoamer, or a combination of these can be used in the field of glass manufacturing.

The F component is an arbitrary component that can increase the Abbe number of the glass, reduce the glass transition point, and improve the devitrification resistance when it contains more than 0%. However, if the content of the F component, that is, the total amount of F of the fluorides as part or all of the oxides replacing one or more of the above-mentioned metal elements exceeds 10.0%, the F component The amount of volatilization will increase, so it becomes difficult to obtain a stable optical constant, and it becomes difficult to obtain 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%, and particularly 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 the ratio SiO ₂ /B ₂ O ₃ to 0.15 or more, the stability of the glass can be improved, and the chemical durability of the glass, especially 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 small, and the content of the SiO ₂ component is relatively large. Therefore, the mass ratio SiO ₂ /B ₂ O ₃ can be preferably set to 0.15 or more, more preferably 0.30 or more, still more preferably 0.50 or more, particularly preferably 0.60 or more, and particularly preferably 0.70 or more. On the other hand, by setting the ratio SiO ₂ /B ₂ O ₃ to 10.00 or less, since the rise of the glass transition point is suppressed, it can be easily formed 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, and particularly preferably 4.65 or less.

The sum of the contents (mass sum) 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, by setting this sum to 15.0% or more, since a network structure of glass is formed, stable glass can be formed. Therefore, the mass and B ₂ O ₃ +SiO _{2 are} preferably 15.0% or more, more preferably more than 18.0%, and still more preferably 20.0% or more. On the other hand, by setting this sum to 40.0% or less, it is possible to suppress a decrease in the refractive index caused by containing these components in excess. In addition, it can improve the chemical durability of glass, especially acid resistance. Therefore, the quality and B ₂ O ₃ +SiO _{2 are} preferably set to 40.0% or less, more preferably less than 38.0%, still more preferably less than 35.0%, particularly preferably less than 32.0%, particularly preferably less than 30.0%.

The sum of the contents (mass sum) 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 the sum to 15.0% or more, it can be used as a more stable glass. Therefore, the quality and SiO ₂ +B ₂ O ₃ +Al ₂ O _{3 are} preferably set to 15.0% or more, more preferably more than 18.0%, still more preferably more than 20.0%, particularly preferably more than 22.0%, particularly preferably More than 25.0%. On the other hand, by setting this sum to less than 50.0%, it is possible to suppress a decrease in the refractive index caused by containing these components in excess. Therefore, the quality and SiO ₂ +B ₂ O ₃ +Al ₂ O _{3 are} preferably set to less than 50.0%, more preferably less than 47.0%, still more preferably less than 44.0%, and particularly preferably less than 42.0% , Youjia is less than 39.0%.

The ratio of the sum of the content 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 to 10.00 or less. In particular, by setting this ratio to more than 0.30, the chemical durability of the glass, especially 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 particularly preferably more than 0.90. On the other hand, by setting the ratio to 10.00 or less, it can be used as a more stable glass. 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, particularly preferably 6.00 or less, particularly preferably 5.50 or less. .

The sum (mass) of the content of Ln ₂ O ₃ component (where Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is preferably 40.0% or more and 70.0% or less . In particular, by setting the sum to 40.0% or more, since the refractive index and Abbe number of the glass are increased, it is possible to easily obtain glass having the desired refractive index and Abbe number. Therefore, the quality and the Ln ₂ O ₃ component are preferably 40.0% or more, more preferably more than 43.0%, still more preferably 45.0% or more, and particularly preferably more than 47.0%. On the other hand, by setting this sum to 70.0% or less, the liquidus temperature of the glass becomes lower, so devitrification of the glass can be reduced. Therefore, the quality and the Ln ₂ O ₃ component are preferably 70.0% or less, more preferably less than 65.0%, still more preferably less than 64.0%, and even more preferably less than 63.0%.

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

The sum of the contents (mass) of the Rn ₂ O component (where Rn is one or more selected from the group consisting of Li, Na, and K) is preferably less than 10.0%. This can suppress the decrease in the viscosity of the molten glass, make it difficult to reduce the refractive index of the glass, and reduce the devitrification of the glass. Therefore, the quality and preferably of the Rn ₂ O component is less than 10.0%, more preferably less than 6.0%, still more preferably less than 4.0%, particularly preferably less than 2.0%, and particularly preferably less than 1.0 %.

The ratio (mass ratio) of the sum of Ln ₂ O ₃ components to the sum of the contents of B ₂ O ₃ components, SiO ₂ components, and Al ₂ O ₃ components is preferably more than 0.30 to 10.00 (wherein, Ln is selected from One or more of the group consisting of La, Gd, Y, and Yb). In particular, by setting the 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 set to more than 0.30, more preferably more than 0.50, still more preferably more than 0.80, and particularly preferably more than 1.00, It is particularly preferably 1.27 or more, very preferably 1.35 or more, and most 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 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, and particularly preferably 2.60 or less, Especially good is below 2.30, very good is below 2.10.

The sum of the content of the SiO ₂ component, Al ₂ O ₃ component and Ln ₂ O ₃ component is 10 relative to the sum of the content of the RO component, Rn ₂ O component, ZnO component and B ₂ O ₃ component plus the value of the refractive index nd The ratio (mass ratio) is preferably 0.80 or more and 6.00 or less (where Ln is one or more selected from the group consisting of La, Gd, Y, and Yb; R is selected from Mg, Ca, and Sr , Ba, Zn, one or more groups; Rn is selected from the group consisting of Li, Na, and K). By setting this mass ratio in the range of 0.80 or more and 6.00 or less, the chemical durability of the glass, especially 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) as the lower limit is preferably 0.80, more preferably 1.00, and More preferably, it is 1.20, particularly preferably 1.50, particularly preferably 1.80; the upper limit is preferably 6.00, more preferably 5.50, and still more preferably 5.00.

The mass ratio (Al ₂ O ₃ /Ln ₂ O ₃ ) is preferably set to 0.01 or more (wherein, Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu). Thereby, it becomes easy to obtain the effect of improving devitrification resistance. Therefore, the quality of (Al ₂ O ₃ /Ln ₂ O ₃ ) is preferably 0.01 or more, more preferably 0.03 or more, and still more preferably 0.05 or more. On the other hand, by setting the mass ratio to 1.00 or less, it is possible to suppress the deterioration of the meltability of the glass raw material or the excessive increase in viscosity. Therefore, the quality 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, particularly preferably 0.25 or less, and particularly preferably 0.20 or less.

The mass and (ZrO ₂ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +TeO ₂ ) are preferably 20.0% or less. Thereby, the effect of improving devitrification resistance can be easily obtained, and the excessive decrease in the Abbe number can be suppressed and low dispersion performance can be easily obtained. Therefore, the quality and (ZrO ₂ +TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +TeO ₂ ) are preferably 20.0% or less, more preferably 18.0% or less, and It is more preferably 15.0% or less, particularly preferably 5.0% or less, and particularly preferably 4.0% or less.

The mass ratio (Ln ₂ O ₃ /RO) is preferably set to 1.0 or more (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu). With this, the effect of improving the chemical durability of the glass can be easily obtained. Therefore, the quality of (Ln ₂ O ₃ /RO) is preferably 1.0 or more, more preferably 3.0 or more, and still more preferably 5.0 or more, particularly preferably 10.0 or more, and particularly preferably 20.0 or more. In addition, even if the RO component is not contained, the effect of improving chemical durability can be obtained, so the upper limit value of the mass ratio of (Ln ₂ O ₃ /RO) can be made infinite.

The mass ratio (Ln ₂ O ₃ /Rn ₂ O) is preferably 3.0 or more. With this, the effect of improving the chemical durability of the glass can be easily obtained. Therefore, the better quality of (Ln ₂ O ₃ /Rn ₂ O) can be set to 3.0 or more, more preferably 5.0 or more, and still more preferably 8.0 or more, particularly preferably 10.0 or more, particularly preferably 15.0 or more, very preferably 20.0 or more, more preferably 25.0 or more, and most preferably 30.0 or more. In addition, even if the Rn ₂ O component is not included, the effect of improving chemical durability can be obtained, so the upper limit value of the mass ratio of (Ln ₂ O ₃ /Rn ₂ O) can be set to infinity.

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 and the cost of glass can be easily obtained. Therefore, the mass product of (BaO×Gd ₂ O ₃ ) can be preferably set to less than 8.0, more preferably 7.0 or less, still more preferably 6.0 or less, particularly preferably 5.0 or less, particularly preferably 4.0 or less, very preferably 3.0 or less, further preferably 2.0 or less, and even more preferably 1.0 or less, and most preferably 0.1 or less.

The mass and (SiO ₂ +Al ₂ O ₃ ) are preferably set to 5.0% or more. With this, the effect of improving the chemical durability of the glass can be easily obtained. Therefore, the quality and preferably (SiO ₂ +Al ₂ O ₃ ) can be set to 5.0% or more, more preferably 7.0% or more, still more preferably 9.0% or more, and particularly preferably 10.0% or more. On the other hand, by setting this mass sum to 40.0% or less, it is possible to suppress the deterioration of the meltability of the glass raw material or the excessive increase in viscosity. Therefore, the quality and preferably (SiO ₂ +Al ₂ O ₃ ) can be set to 40.0% or less, more preferably 45.0% or less, still more preferably 35.0% or less, and still more preferably 30.0% or less.

>About ingredients that should not be contained> Next, the components that should not be contained in the optical glass of the present invention and those that should not 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, in addition to Ti, Zr, Nb, W, La, Gd, Y, Yb, Lu, due to the transition metal components of Nd, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, even When each of them is contained alone or in combination and contained in a small amount, the glass is also colored, and has the property of absorbing at a specific wavelength in the visible region. Therefore, it is particularly preferred that optical glass using wavelengths in the visible region is not substantially contained.

In addition, lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components that have a high environmental burden, so it is preferable that they are not substantially contained, that is, they are not included except for inevitable mixing.

Furthermore, the components of Th, Cd, Tl, Os, Be, and Se tend to be used sparingly as hazardous chemical materials in recent years, not only the manufacturing steps of glass, but also the processing steps and the disposal after productization. Both require measures on environmental countermeasures. Therefore, when importance is attached to environmental impact, it is preferable that these components are not substantially contained.

In addition, the "substantially no content" in this specification preferably has a content of less than 0.1%, and more preferably contains no other than unavoidable impurities. Here, the content of components contained as inevitable impurities is, for example, less than 0.01% or less than 0.001%, but it is not limited to this range.

[Manufacturing method] The optical glass of the present invention is produced as follows, for example. That is, by uniformly mixing the above raw materials so that each component becomes within a predetermined content range, the prepared mixture is put into a platinum crucible, and the melting temperature of the glass raw material is 1100°C to 1500°C in an electric furnace After melting in the temperature range of 2 hours to 5 hours and stirring and homogenizing, it is cast to the mold after being lowered to the appropriate temperature, and then produced by cold cooling.

[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 refractive index (n _d ) of the optical glass of the present invention is preferably 1.70 as the lower limit, more preferably 1.73, and still more preferably 1.75. The upper limit of the refractive index (n _d ) of the optical glass of the present invention is preferably 2.00, more preferably 1.95, and still more preferably 1.90. In addition, the Abbe number (ν _d ) of the optical glass of the present invention is preferably 35 as the lower limit, more preferably 38, particularly preferably 40, and particularly preferably 42. The Abbe number (ν _d ) of the optical glass of the present invention is preferably 55 as the upper limit, more preferably 53, and even more preferably 51. By having such a high refractive index, even if the optical element is made thinner, a large amount of light refraction can be obtained. Furthermore, by having such low dispersion, when used as a single lens, it is possible to reduce the deviation of focus (chromatic aberration) due to the wavelength of light. Therefore, for example, when an optical system is combined with an optical element having a high dispersion (low Abbe number), the aberration can be reduced as a whole of the optical system to achieve high imaging characteristics. In this way, the optical glass of the present invention is useful in optical design. In particular, when configuring an optical system, not only can high imaging characteristics be achieved, but also the optical system can be miniaturized, and the freedom of optical design can be expanded.

Here, the refractive index (n _d ) and Abbe number (ν _d ) of the optical glass of the present invention preferably satisfy the relationship of (-0.01ν _d +2.15)≦n _d ≦(-0.01ν _d +2.35). In the glass having a specific composition of the present invention, by satisfying this relationship by the refractive index (n _d ) and Abbe number (ν _d ), a more stable glass can be obtained. Therefore, in the optical glass of the present invention, the refractive index (n _d ) and Abbe number (ν _d ) preferably satisfy the relationship of n _d ≧(-0.01ν _d +2.15), and more preferably satisfy n _d ≧(- 0.01ν _d +2.20) relations, and more preferably satisfy a relationship n _d ≧ (-0.01ν _d +2.22) a. On the other hand, in the optical glass of the present invention, the refractive index (n _d ) and Abbe number (ν _d ) preferably satisfy the relationship of n _d ≦ (-0.01ν _d +2.35), and more preferably satisfy n _d The relationship ≦(-0.01ν _d +2.30) is more preferably a relationship satisfying 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) measured by the powder method of glass according to JOGIS06-2006 is preferably grade 1 to grade 4, more preferably grade 1 to grade 3, and still more preferably grade 1 to grade 2 , The best is level 1. As a result, when the optical glass is polished, the atomization of the glass caused by the acidic polishing liquid or the cleaning liquid is reduced, so that the polishing process can be performed more easily. The "acid resistance" referred to here refers to the durability against acid-induced erosion of glass. This acid resistance can be obtained by the Japan Optical Glass Industry Standard "Measurement Method of Chemical Durability of Optical Glass" JOGIS06-2006 Determination. Also, the so-called "chemical durability (acid resistance) measured by the powder method is grade 1 to grade 4", which means that the chemical durability (acid resistance) according to JOGIS06-2006 is used to measure the quality of the samples before and after The reduction rate meter is less than 1.20% by mass. In addition, the reduction rate of the mass of the sample before and after the measurement of the chemical durability (acid resistance) is less than 0.20 mass %, and the reduction rate of the mass of the sample before and after the measurement of the "level 2" is 0.20 mass% or more To less than 0.35 mass%, the reduction rate of the sample quality before and after the measurement of "level 3" is more than 0.35 mass% to less than 0.65 mass%, and the reduction rate of the mass of the sample before and after the measurement is "0.65 quality%" % Or more to less than 1.20% by mass, the reduction rate of the quality of the sample before and after the measurement of "Level 5" is 1.20% by mass or more to less than 2.20% by mass, the rate of reduction of the quality of the sample before and after the measurement of "Level 6" 2.20% by mass or more.

The optical glass of the present invention preferably has high devitrification resistance, and more specifically, preferably has a low liquidus temperature. That is, the upper limit of the liquid phase temperature of the optical glass of the present invention is preferably 1300°C, more preferably 1280°C, and still more preferably 1250°C. In this way, even if the melted glass flows out at a lower temperature, since the crystallization of the manufactured glass is reduced, the devitrification when forming the glass from the molten state can be reduced, and the optical element using the glass can be reduced. Influence of optical properties. In addition, since the glass can be shaped even if the melting temperature of the glass is lowered, the manufacturing cost of the glass can be reduced by suppressing the energy consumed in the forming of the glass. On the other hand, although the lower limit of the liquidus temperature of the optical glass of the present invention is not particularly limited, the liquidus temperature of the glass obtained according to the present invention is approximately 800°C or higher, specifically 850°C or higher, and more specifically Generally speaking, it is above 900℃. In addition, the "liquid phase temperature" in this specification means that a platinum crucible with a capacity of 50 ml is filled with 5 cc of broken glass-like glass sample in a platinum crucible and completely melted at 1400°C, and the temperature is lowered to a predetermined temperature. Hold it for 1 hour, take it out to cool outside the furnace, and then observe the glass surface and whether there is crystallization in the glass. The lowest temperature of crystallization is not seen. Here, the predetermined temperature at the time of cooling down is a temperature every 10°C between 1300°C and 800°C.

The specific gravity of the optical glass of the present invention is preferably an upper limit of 5.50, more preferably 5.00, and still more preferably 4.80, from the viewpoint of contributing to the weight reduction of an optical element or an optical device. On the other hand, the specific gravity of the optical glass of the present invention is approximately 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 JOGIS05-1975 "Measurement method of specific gravity of optical glass".

The optical glass of the present invention preferably has both high acid resistance and light weight. That is, in the optical glass of the present invention, when the specific gravity is d and the order of chemical durability (acid resistance) measured by the powder method is RA, the value of d×RA is preferably 18.0 or less. In such optical glass, since the acid resistance and the specific gravity are both low, it is possible to have both high acid resistance and light weight, and further, it is possible to improve both the workability through polishing and the weight reduction of optical elements or optical devices. Therefore, the upper limit of d×RA in the optical glass of the present invention is preferably 18.0, more preferably 15.0, still more preferably 13.0, particularly preferably 10.0, and particularly preferably 9.0. On the other hand, the lower limit of d×RA is roughly 2.0 or more, more specifically 3.0 or more, and more specifically 4.0 or more.

[Preforms and optical components] From the manufactured optical glass, a glass molded body can be produced by means of, for example, grinding processing, or by means of press molding such as reheat press molding or precision press molding. That is, the optical glass can be machined by grinding, grinding, etc. to produce a glass shaped body; or a preform for compression molding can be made from the optical glass, and the preform can be reheat pressed to form a grinding process. A glass molded body is produced; or a preform produced by grinding processing, or a preform formed by well-known floating molding or the like is precision-pressed to produce a glass molded body. In addition, the means for producing a glass molded body is not limited to these means.

In this way, the optical glass of the present invention is useful in 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 use the preform to perform reheat press forming or precision press forming, etc. to manufacture optical elements such as lenses or prisms. This makes it possible to form a preform with a large diameter, so that not only can the size of the optical element be increased, but also when using an optical device such as a camera or a projector, high-precision imaging characteristics and projection characteristics can be realized with high definition. . [Example]

The compositions of Examples (No. 1 to No. 43) and Comparative Examples (No. A) of the present invention, and the refractive index (n _d ) and Abbe number (ν _d ) of these glasses were measured by the powder method The results of chemical durability (acid resistance), liquidus temperature and specific gravity are shown in Table 1 to Table 6. In addition, the following examples are for illustrative purposes after all, and the present invention is not limited to these examples.

The glasses of the examples and comparative examples of the present invention are selected from the corresponding high-purity raw materials used in ordinary optical glass such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphoric acid compounds. The raw materials of each component are weighed and mixed uniformly so as to become the composition ratio of each example shown in the table, and then put into a platinum crucible. The melting temperature of the glass raw material is in the temperature range of 1100°C to 1500°C in an electric furnace After melting for 2 to 5 hours, it is stirred and homogenized, then cast into a mold, etc., and produced by cold cooling.

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

The acid resistance of the glass in the examples and comparative examples was measured according to the Japan Optical Glass Industry Standard "Measurement Method of Chemical Durability of Optical Glass" JOGIS06-2006. That is, the glass sample crushed to a particle size of 425 μm to 600 μm is placed in a pycnometer and placed in a platinum basket. Place the platinum basket in a round-bottom flask made of quartz glass in which 0.01N nitric acid solution has been placed and treat in a boiling water bath for 60 minutes. The reduction rate (mass %) of the glass sample after the treatment is calculated, and the reduction rate (mass %) is less than 0.20 is set to level 1, and the reduction rate is 0.20 to less than 0.35 is set to level 2, reduced A rate of 0.35 to less than 0.65 is set to grade 3, a reduction rate of 0.65 to less than 1.20 is set to level 4, a reduction rate of 1.20 to less than 2.20 is set to level 5, and a reduction rate of 2.20 or more The situation is set to level 6. At this time, the smaller the number of the rank (rank RA) means that the glass has better acid resistance.

The specific gravity d of the glass in Examples and Comparative Examples was measured based on the Japan Optical Glass Industry Association JOGIS05-1975 "Method for Measuring Specific Gravity of Optical Glass". Further, from the value of the specific gravity d measured and the value of the acid resistance grade RA, the product of these is obtained as the value of d×RA.

The liquidus temperature of the glass in Examples and Comparative Examples is determined by taking a platinum crucible with a capacity of 50 ml, placing 5 cc of broken glass-like glass sample into a platinum crucible, and turning it into a completely molten state at 1400°C, and reducing the temperature to 1350°C. Until 800 ℃, at any temperature set at every 10 ℃ and maintained for 1 hour, take out to cool outside the furnace and then observe the glass surface and whether there is crystal in the glass, the lowest temperature of crystallization is not seen.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

As shown in the table, the optical glasses of the embodiments of the present invention all have a refractive index (n _d ) above 1.70, more specifically 1.71 or more, and the refractive index (n _d ) below 2.10, more specifically It is below 1.87, which is within the expected range.

In addition, the optical glasses of the embodiments of the present invention all 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 Below 54, it is within the desired range.

Moreover, the optical glasses of the embodiments of the present invention all have a chemical durability (acid resistance) measured by a powder method of grade 1 to grade 4, more specifically, grade 1 to grade 3. On the other hand, the chemical durability (acid resistance) measured by the powder method of the glass of the comparative example was grade 5. Therefore, the optical glass of the embodiment of the present invention is significantly better in acid resistance than the glass of the comparative example.

Furthermore, the optical glass of the present invention will form a stable glass, and devitrification is unlikely to occur during glass production. This can also be inferred from the fact that the liquid crystal temperature of the optical glass of the present invention is below 1300°C, more specifically below 1250°C.

In addition, the refractive index (n _d ) and Abbe number (ν _d ) of the optical glass of the embodiment of the present invention satisfy the relationship of (-0.01ν _d +2.15)≦n _d ≦(-0.01ν _d +2.35) In more detail, the relationship of (-0.02ν _d +2.22)≦n _d ≦(-0.02ν _d +2.28) is satisfied. In addition, the relationship between the refractive index (n _d ) and the Abbe number (ν _d ) of the glass of the example of the present case is shown in FIG. 1.

In addition, the optical glasses of the embodiments of the present invention all have a specific gravity of 5.50 or less, more specifically 4.80 or less.

Then, in the optical glass of the embodiment of the present invention, when the specific gravity is set to d, and the order of chemical durability (acid resistance) measured by the powder method is set to RA, the value of d×RA is 18.0 or less. It is from 4.0 or more to 13.0 or less. On the other hand, the value of d×RA of the optical glass of the comparative example was 19.10, and it was not possible to have both the suitability and weight reduction for polishing.

Therefore, the optical glass of the embodiment of the present invention clearly has a refractive index (n _d ) and Abbe number (ν _d ) within a desired range, and is highly acid-resistant, stable, and not easily devitrified. Therefore, it is presumed that the optical glass of the embodiment of the present invention is easy to manufacture the preform material or the optical element through the grinding process.

Furthermore, the optical glass according to the embodiment of the present invention is used to form a glass block, and the glass block is ground and polished to be processed into the shape of a lens and a prism. As a result, it is possible to stably process various shapes of lenses and prisms.

The above has explained the present invention in detail for the purpose of illustration, but it should be understood that this embodiment is only for the purpose of illustration after all, by those with ordinary knowledge in the technical field to which the present invention belongs can proceed without departing from the idea and scope of the present invention Many changes.

no.

FIG. 1 is a graph showing the relationship between the refractive index (n _d ) and the Abbe number (ν _d ) of the glass of the example of the present case.

Claims (10)

An optical glass containing in mass %: SiO ₂ component exceeding 0% to 35.0%; B ₂ O ₃ component exceeding 0% to 35.0%; La ₂ O ₃ component exceeding 20.0% to 65.0%; Al ₂ The O ₃ component exceeds 0% to 30.0% or less; and has a refractive index (n _d ) of 1.70 or more, and has an Abbe number (ν _d ) of 35 or more to 55; the chemical durability measured by the powder method is Acid resistance is grade 1 to grade 4. The optical glass as described in claim 1, wherein in mass %, the Y ₂ O ₃ composition is 0% to less than 25.0%; the Gd ₂ O ₃ composition is 0% to less than 40.0%; the Yb ₂ O ₃ composition is 0% to less than 10.0%; Lu ₂ O ₃ component system 0% to less than 10.0%; MgO component system 0% to less than 10.0%; CaO component system 0% to less than 10.0%; SrO component system 0% to Less than 10.0%; BaO component system 0% to less than 10.0%; Li ₂ O component system 0% to less than 5.0%; Na ₂ O component system 0% to less than 10.0%; K ₂ O component system 0% to Less than 10.0%; TiO ₂ component system 0% to less than 15.0%; Nb ₂ O ₅ component system 0% to less than 15.0%; ZrO ₂ component system 0% to less than 15.0%; Ta ₂ O ₅ component system 0 % To less than 10.0%; WO ₃ component system 0% to less than 10.0%; ZnO component system 0% to less than 30.0%; P ₂ O ₅ component system 0% to less than 10.0%; GeO ₂ component system 0% To less than 10.0%; Ga ₂ O ₃ component system 0% to less than 10.0%; Bi ₂ O ₃ component system 0% to less than 10.0%; TeO ₂ component system 0% to less than 10.0%; SnO ₂ component system 0% to less than 3.0%; Sb ₂ O ₃ component is 0% to less than 1.0%; F of fluoride that is a part or all of one or more oxides replacing the above elements The content is from 0% by mass to less than 10.0% by mass. The optical glass according to claim 1 or 2, wherein the mass and SiO ₂ +B ₂ O ₃ are 15.0% or more and 40.0% or less. The optical glass according to any one of claims 1 to 3, wherein the mass and SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ are 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 exceeds 0.30 to 10.00. The optical glass according to any one of claims 1 to 5, wherein the sum of the contents of the Ln ₂ O ₃ component is 40.0% or more and 70.0% or less in mass %, and Ln is selected from the group consisting of La, Gd, and Y More than one of the group consisting of, Yb, Lu; the sum of the content of the RO component is 0% to less than 10.0%, and R is selected from the group consisting of Mg, Ca, Sr, Ba, Zn 1 or more types; the sum of the contents of Rn ₂ O components is 0% to less than 10.0%, and Rn is one or more types selected from the group consisting of Li, Na, and K. 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 ) exceeds 0.30 to 10.00, and Ln is selected from One or more of the group consisting of La, Gd, Y, and Yb. A preform is made of optical glass as described in any one of claims 1 to 7. An optical element composed of the optical glass as described in any one of claims 1 to 7. An optical machine is provided with the optical element as described in claim 9.

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