JP7354109B2 - Optical glass and optical elements - Google Patents

Description

TECHNICAL FIELD The present invention relates to optical glasses and optical elements.

Demand for high refractive index, low dispersion glass having a refractive index (n _d ) of 1.75 or more and an Abbe number (ν _d ) of 30 or more and 40 or less is increasing extremely as a material for optical elements that constitute optical systems. .

As such a high refractive index low dispersion glass, a glass composition typified by, for example, Patent Document 1 is known.

International Publication No. 2018/003582

In recent years, when high refractive index, low dispersion glass is installed in optical products such as digital cameras, it is desired that the partial dispersion ratio of the optical glass be small in order to improve chromatic aberration.

In optical glass, there is an approximately linear relationship between the partial dispersion ratio (θg, F) representing partial dispersion in a short wavelength range and the Abbe number (ν _d ). A straight line representing this relationship is expressed by a straight line connecting two points where the partial dispersion ratio and Abbe number of NSL7 and PBM2 are plotted on the orthogonal coordinates with the partial dispersion ratio on the vertical axis and the Abbe number on the horizontal axis, It is called the normal line. Normal glass, which is the standard for the normal line, differs depending on the optical glass manufacturer, but each company defines it using almost the same slope and intercept. (NSL7 and PBM2 are optical glasses manufactured by OHARA Co., Ltd., and the Abbe number (ν _d ) of PBM2 is 36.3, the partial dispersion ratio (θg, F) is 0.5828, and the Abbe number (ν _d ) of NSL7 is 60.5, and the partial dispersion ratio (θg, F) is 0.5436.)

In recent years, from the viewpoint of optical design, in glasses with high refractive index and low dispersion, the partial dispersion ratio (θg, F) is often higher than the normal line, but in order to improve chromatic aberration, at least It is desirable to have a combination of Abbe number (ν _d ) and partial dispersion ratio (θg, F) that is close to the normal line in the positive direction, and more preferably away from the normal line in the negative direction.

The present invention has been made in view of the above-mentioned optical design requirements, and its purpose is to have optical properties of high refractive index and low dispersion, and to have low anomalous dispersion (Δθg, F). An object of the present invention is to provide an optical glass that has a low value and can contribute to improving chromatic aberration, and an optical element using the same.

In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive testing and research and found that at least any of the ₂ components of SiO, _{the 3} components of B ₂ O, _{the 5} components of Nb ₂ O, the BaO component, and _{the 3} components of Ln ₂ O. We have discovered that by using these in combination and adjusting the content of each component, it is possible to have a low anomalous dispersion value while having the desired refractive index and Abbe number, and have completed the present invention. . Specifically, the present invention provides the following.

(1) In mass%,
2.0% or more and 25.0% or less of SiO ₂ components,
3.0% or more and 25.0% or less of B ₂ O ₃ components,
Nb ₂ O ₅ component more than 0% and not more than 30.0%,
Contains a BaO component of 10.0% or more and 60.0% or less,
Contains a total of 10.0% or more and 50.0% or less of Ln ₂ O ₃ components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb),
The refractive index (n _d ) is 1.75 or more, the Abbe number (ν _d ) is 30 or more and 40 or less,
In a coordinate system in which the Abbe number (ν _d ) is the x axis and the partial dispersion ratio (θg, F) is the y axis, (x, y) = (36.3, 0.5828) and (60.5, 0. 5436) in the y-axis direction from a straight line connecting two points (abnormal dispersion (Δθg, F)) of +0.001 or less.

(2) The optical glass according to (1), which has an average coefficient of linear expansion (α) at -30 to 70°C of 75×10 ⁻⁷ /°C to 100×10 ⁻⁷ /°C.

(3) An optical element made of the optical glass according to (1) or (2).

(4) An optical device comprising the optical element according to (3).

According to the present invention, it is possible to obtain an optical glass having optical properties of high refractive index and low dispersion, a small value of anomalous dispersion (Δθg, F), and reduced chromatic aberration, and an optical element using the same. I can do it.

Further, according to the present invention, it is possible to obtain an optical glass having thermal expansion properties close to that of low-dispersion glass, and an optical element using the same.

The optical glass of the present invention has a SiO ₂ component of 2.0% or more and 25.0% or less, a B ₂ O ₃ component of 3.0% or more and 25.0% or less, and a BaO component of 10.0% by mass%. 60.0% or less, the Nb ₂ O ₅ component is 1.0% or more and 30.0% or less, the Ln ₂ O ₃ component is 10.0% or more and 50.0% or less (in the formula, Ln is La, (one or more selected from the group consisting of Gd, Y, Yb), has a refractive index (n d ) of 1.75 or more, an Abbe number (ν _d ) of 30 or more and 40 or less, and has an Abbe number (ν _d ) of 30 or more and 40 or less. _d ) is the x axis and the partial dispersion ratio (θg, F) is the y axis, (x, y) = (36.3, 0.5828) and (60.5, 0.5436) The magnitude of the deviation in the y-axis direction from the straight line connecting the points (abnormal dispersion (Δθg, F)) is +0.001 or less. A desired refractive index and a desired refractive index can be obtained by using at least one of SiO ₂ components, B ₂ O ₃ components, Nb ₂ O ₅ components, BaO component, and Ln ₂ O ₃ components and adjusting the content of each component. Although it has an Abbe number, its anomalous dispersion takes a low value. Therefore, it is possible to obtain an optical glass that can contribute to improving chromatic aberration when used as a lens unit of a digital camera or the like.

In addition, by using at least one of SiO ₂ components, B ₂ O ₃ components, Nb ₂ O ₅ components, BaO component, and Ln ₂ O ₃ components together and adjusting the content of each component, fluorophosphate glass can be produced. An optical glass with a high refractive index and low dispersion, which has thermal expansion properties close to those of low-dispersion glasses such as the above, can be obtained. A high refractive index, low dispersion glass as in the present invention may be bonded with a low dispersion glass and used in a lens unit for purposes such as reducing chromatic aberration. In such a lens unit, temperature changes often occur depending on the usage environment and the irradiated light. Even in this case, since the high refractive index, low dispersion glass of the present invention has thermal expansion properties close to that of the low dispersion glass, good bondability with the low dispersion glass can be maintained.

Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. Note that the description may be omitted as appropriate for parts where the description overlaps, but this does not limit the gist of the invention.

[Glass component]
The composition range of each component constituting the optical glass of the present invention will be described below. In this specification, unless otherwise specified, the content of each component is expressed in mass % based on the total mass of the composition in terms of oxides. Here, the "composition equivalent to oxide" refers to the composition when it is assumed that the oxides, composite salts, metal fluorides, etc. used as raw materials for the glass components of the present invention are all decomposed and converted into oxides when melted. The composition shows each component contained in the glass, with the total mass number of produced oxides being 100% by mass.

<About essential ingredients and optional ingredients>
The SiO ₂ component is an essential component as a glass-forming oxide, and can enhance chemical durability, increase the viscosity of molten glass, and reduce coloring of glass. Furthermore, the stability of the glass can be improved, making it easier to obtain glass that can withstand mass production. Furthermore, it has the effect of lowering the average coefficient of linear expansion. Therefore, the lower limit of the content of the two SiO ₂ components is preferably 2.0%, more preferably 3.0%, and even more preferably 4.0%.
On the other hand, in order to suppress a decrease in the refractive index, the upper limit of the content of the SiO ₂ component is preferably 25.0%, more preferably 23.0%, and even more preferably 20.0%.

The B ₂ O ₃ component is an essential component as a glass-forming oxide, and can reduce devitrification of the glass and increase the Abbe number of the glass. Therefore, the lower limit of the content of the _three B ₂ O components is preferably 3.0%, more preferably 4.0%, and even more preferably 5.0%.
On the other hand, in order to easily obtain a larger refractive index, reduce the temperature coefficient of relative refractive index, and suppress deterioration of chemical durability, the content of the _three B ₂ O components is preferably 25.0%, The upper limit is more preferably 22.0%, and even more preferably 20.0%.

The Nb ₂ O ₅ component, when contained in an amount exceeding 0%, is an essential component that increases the refractive index, increases dispersion, and lowers anomalous dispersion. Therefore, the content of the Nb ₂ O ₅ component is preferably more than 0%, more preferably 0.3% or more, more preferably 1.0% or more, even more preferably 4.0% or more, still more preferably 7.0% or more. The content should be 0% or more, more preferably 10.0% or more.
On the other hand, if the amount is too small, the effect will be insufficient, and if it is too large, the resistance to devitrification will deteriorate, and the transmittance in the short wavelength range of visible light will also tend to deteriorate. Therefore, the upper limit of the content of the Nb ₂ O ₅ component is preferably 30.0%, more preferably 28.0%, even more preferably 26.0%, and even more preferably 22.0%.

The BaO component is an essential component that can enhance the meltability of the glass raw material, reduce devitrification of the glass, increase the refractive index, and reduce the temperature coefficient of the relative refractive index. It also has the effect of increasing the average coefficient of linear expansion. Therefore, the lower limit of the BaO component content is preferably 10.0%, more preferably 12.0%, even more preferably 14.0%, and even more preferably 18.0%.
In order to easily achieve particularly low anomalous dispersion and an average linear expansion coefficient close to that of fluorophosphate glass, the lower limit is preferably 19% or more.
On the other hand, in order to reduce the reduction in the refractive index of the glass, the reduction in chemical durability, and the devitrification, the content of the BaO component is preferably 60.0%, more preferably 55.0%, and even more preferably The upper limit is 50.0%, more preferably 45.0%, even more preferably 40.0%.

The Al ₂ O ₃ component is an optional component that can improve the chemical durability of glass and improve the devitrification resistance of molten glass when it is contained in an amount exceeding 0%. It also has the effect of lowering the average coefficient of linear expansion.
On the other hand, from the viewpoint of reducing devitrification, the content of the _three Al ₂ O components is preferably 10.0%, more preferably 8.0%, still more preferably 5.0%, and still more preferably 3.0%. %, more preferably less than 1.0%.

When the Y ₂ O ₃ component is contained in an amount exceeding 0%, it maintains a high refractive index and a high Abbe number, while reducing the material cost of glass compared to other rare earth elements, and is more effective than other rare earth components. is also an optional component that can reduce the specific gravity of glass. It also has the effect of increasing anomalous dispersion and lowering the average coefficient of linear expansion.
On the other hand, if the Y ₂ O ₃ component is contained excessively, the stability of the glass will decrease and the solubility of the glass raw material will also deteriorate. Therefore, the upper limit of the content of the _three Y ₂ O components is preferably 30.0%, more preferably 27.0%, even more preferably 25.0%, and even more preferably 21.0%.

The La ₂ O ₃ component is an optional component that can increase the refractive index and Abbe number of the glass when contained in an amount exceeding 0%. It also has the effect of lowering anomalous dispersion. Therefore, the content of the _three La ₂ O components is preferably more than 0%, more preferably 1.0% or more, still more preferably 5.0% or more, and still more preferably 10.0% or more.
On the other hand, when the La ₂ O ₃ component is contained excessively, the stability of the glass decreases and the solubility of the glass raw material also deteriorates. Therefore, the content of _{the three} La ₂ O components is preferably 50.0%, more preferably 45.0%, even more preferably 40.0%, even more preferably 32.0%, and even more preferably 28.0%. The upper limit is more preferably 25.0%.

The Gd ₂ O ₃ component and the Yb ₂ O ₃ component are optional components that can increase the refractive index of the glass when contained in an amount exceeding 0%.
On the other hand, the raw material costs of the Gd ₂ O ₃ component and the Yb ₂ O ₃ component are high among rare earth elements, and if their content is large, the production cost will be high. Further, by reducing the content of the Gd ₂ O ₃ component and the Yb ₂ O ₃ component, an increase in the Abbe number of the glass can be suppressed. Therefore, the upper limit of the content of the _three Gd ₂ O components is preferably 50.0%, more preferably 45.0%, still more preferably 35.0%, and even more preferably 30.0%. Further, the upper limit of the content of the Yb ₂ O ₃ component is preferably 10.0%, more preferably 5.0%, even more preferably 3.0%, and even more preferably 1.0%.

The _TiO2 component is an optional component that can increase the refractive index of the glass and reduce the devitrification of the glass when contained in an amount exceeding 0%. It also has the effect of increasing anomalous dispersion and lowering the average coefficient of linear expansion.
On the other hand, in order to reduce devitrification due to excessive content and suppress a decrease in the transmittance of the glass to visible light (particularly wavelengths of 500 nm or less), the content of _{the two} TiO components is preferably 20.0%, more preferably The upper limit is 15.0%, more preferably 12.5%, even more preferably 10.0%, even more preferably 6.0%.

The _ZrO2 component is an optional component that can increase the refractive index and Abbe number of the glass and reduce devitrification when contained in an amount exceeding 0%. It also has the effect of lowering anomalous dispersion.
On the other hand, if it is contained in excess, devitrification resistance will deteriorate. Therefore, the upper limit of the content of the _two ZrO components is preferably 10.0%, more preferably 9.0%, still more preferably 8.0%, and even more preferably 6.0%.

The Ta ₂ O ₅ component is an optional component that, when contained in an amount exceeding 0%, can increase the refractive index of the glass and improve the devitrification resistance. It also has the effect of lowering anomalous dispersion.
However, the Ta ₂ O ₅ component has a high raw material price and is a component that increases the melting temperature of the glass melt, so if its content is large, the production cost will increase. Therefore, the upper limit of the content of the Ta ₂ O ₅ component is preferably 5.0%, more preferably 3.0%, and even more preferably 1.0%. Particularly from the viewpoint of reducing material costs, it is most preferable not to contain the Ta ₂ O ₅ component.

The WO ₃ components are optional components that, when contained in an amount exceeding 0%, can increase the refractive index, lower the glass transition point, and reduce devitrification while reducing the coloring of the glass caused by other high refractive index components. .
On the other hand, from the viewpoint of suppressing the decrease in the Abbe number and reducing the coloring of the glass, the content of the _three WO components is preferably 10.0%, more preferably 8.0%, even more preferably 5.0%, More preferably, the upper limit is 3.0%.

The ZnO component is an optional component that, when contained in an amount exceeding 0%, can improve the solubility of the raw material, promote defoaming from the melted glass, and improve the stability of the glass. It also has the effect of lowering the average coefficient of linear expansion. It is also a component that can lower the glass transition point and improve chemical durability.
On the other hand, from the viewpoint of suppressing the decrease in the refractive index and increasing the stability of the glass, the content of the ZnO component is preferably 10.0%, more preferably 6.0%, still more preferably 5.0%, The upper limit is more preferably 3.0%, and even more preferably 1.0%.

The MgO component, CaO component, and SrO component are optional components that can adjust the refractive index, meltability, and devitrification resistance of the glass when contained in an amount exceeding 0%.
On the other hand, from the viewpoint of suppressing the decrease in the refractive index and increasing the stability of the glass, the content of the MgO component is preferably 5.0%, more preferably 4.0%, still more preferably 3.0%, More preferably, the upper limit is 1.0%. Further, for the same reason, the content of the CaO component and the SrO component is preferably 15.0%, more preferably 14.0%, still more preferably 12.0%, still more preferably 10.0%, and The upper limit is preferably 7.0%.

The Li ₂ O component, Na ₂ O component, and K ₂ O component are optional components that can improve the meltability of glass and lower the glass transition point when contained in an amount exceeding 0%. Moreover, both have the effect of lowering anomalous dispersion and increasing the average linear expansion coefficient.
On the other hand, by reducing the contents of the Li ₂ O component, Na ₂ O component, and K ₂ O component, the refractive index of the glass can be made difficult to decrease and devitrification of the glass can be reduced. In addition, especially by reducing the content of the Li ₂ O component, the viscosity of the glass is increased, so striae in the glass can be reduced. Therefore, the contents of the Li ₂ O component, Na ₂ O component, and K ₂ O component are each preferably 10.0%, more preferably 8.0%, still more preferably 6.0%, and still more preferably 4.0%. The upper limit is 0%, more preferably 2.0%.

The Sb ₂ O ₃ component is an optional component capable of defoaming the molten glass when contained in an amount exceeding 0%.
On the other hand, if it is contained in an excessive amount, it may cause a decrease in transmittance in the short wavelength region of the visible light region, solarization of the glass, and a decrease in internal quality.
Therefore, the upper limit of the content of the _three Sb ₂ O components is preferably 1.0%, more preferably 0.5%, and even more preferably 0.2%.

Note that the component for clarifying and defoaming the glass is not limited to the above-mentioned _three Sb ₂ O components, and a known clarifying agent, defoaming agent, or a combination thereof in the field of glass manufacturing can be used.

The SnO ₂ component is an optional component that, when contained in an amount exceeding 0%, can reduce oxidation of the molten glass, clarify it, and increase the visible light transmittance of the glass.
On the other hand, if it is contained in excess, the glass may be colored or devitrified due to the reduction of the molten glass. Therefore, the upper limit of the content of the SnO ₂ component is preferably 3.0%, more preferably 1.0%, and even more preferably 0.5%.

The P ₂ O ₅ component is an optional component, and by controlling its content to 10.0% or less, the liquidus temperature of the glass can be lowered and the devitrification resistance can be improved. Therefore, the upper limit of the content of the P ₂ O ₅ component is preferably 10.0%, more preferably 5.0%, even more preferably 3.0%, and even more preferably 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 in an amount exceeding 0%.
However, GeO ₂ has a high raw material price, and if its content is high, the production cost will be high. Therefore, the upper limit of the content of the _two GeO components is preferably 10.0%, more preferably 5.0%, even more preferably 3.0%, and even more preferably 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 contained in an amount exceeding 0%.
On the other hand, by controlling the content of the _three Bi ₂ O components to 10.0% or less, the liquidus temperature of the glass can be lowered and the devitrification resistance can be improved. Therefore, the upper limit of the content of the _three Bi ₂ O components is preferably 10.0%, more preferably 5.0%, even more preferably 3.0%, and even more preferably 1.0%.

The _TeO2 component is an optional component that can increase the refractive index and lower the glass transition point when contained in an amount exceeding 0%.
On the other hand, TeO ₂ has the problem of being alloyed with platinum when a glass raw material is melted in a platinum crucible or a melting tank in which the portion in contact with molten glass is made of platinum. Therefore, the upper limit of the content of the _two TeO components is preferably 10.0%, more preferably 5.0%, still more preferably 3.0%, and even more preferably 1.0%.

The F component is an optional component that can increase the Abbe number of the glass, lower the glass transition point, and improve the devitrification resistance when contained in an amount exceeding 0%.
However, if the content of the F component, that is, the total amount of fluoride substituted for part or all of the oxides of one or more of the above-mentioned metal elements as F exceeds 10.0%, Since the amount of component volatilization increases, it becomes difficult to obtain stable optical constants and it becomes difficult to obtain homogeneous glass. Moreover, the Abbe number increases more than necessary.
Therefore, the upper limit of the content of the F component is preferably 10.0%, more preferably 5.0%, even more preferably 3.0%, and even more preferably 1.0%.

The _three Ln ₂ O components (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) increase the refractive index and Abbe number of the glass and have the desired refractive index and Abbe number. Makes it easier to obtain glass. Therefore, the lower limit of the sum of contents (sum of mass) of the _three Ln ₂ O components is preferably 10.0%, more preferably 12.0%, and even more preferably 14.0%.
On the other hand, by controlling the sum of the masses of the _three Ln ₂ O components to 50.0% or less, devitrification of the glass can be reduced and the Abbe number can be prevented from increasing more than necessary. Therefore, the mass sum of the _three Ln ₂ O components is preferably 50.0%, more preferably 45.0%, even more preferably 40.0%, still more preferably 35.0%, and still more preferably 31.0%. The upper limit is %.

The sum of the contents (sum of mass) of the RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably 5.0% or more and 60.0% or less.
In particular, by setting the mass sum of the RO components to 5.0% or more, devitrification of the glass can be reduced and the temperature coefficient of the relative refractive index can be reduced. Therefore, the mass sum of the RO components is preferably 5.0%, more preferably 10.0%, even more preferably 12.0%, even more preferably 15.0%, even more preferably 20.0%, and even more preferably The lower limit is 25.0%.
On the other hand, by setting the mass sum of the RO components to 60.0% or less, the decrease in the refractive index can be suppressed and the stability of the glass can be improved. Therefore, the upper limit of the mass sum of the RO components is preferably 60.0%, more preferably 55.0%, and still more preferably 50.0%.

The sum of the contents (sum of mass) of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is preferably 10.0% or less. Thereby, it is possible to suppress a decrease in the viscosity of the molten glass, to make it difficult to decrease the refractive index of the glass, and to reduce devitrification of the glass. Therefore, the upper limit of the mass sum of the Rn ₂ O components is preferably 10.0%, more preferably 7.0%, and still more preferably 4.0%.

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

Other components may be added as necessary within a range that does not impair the properties of the glass of the present invention. However, each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, may be used individually. Or, even if it is contained in a small amount in combination, the glass will be colored and have the property of causing absorption at specific wavelengths in the visible range, so it is preferable that it is substantially not included, especially in optical glasses that use wavelengths in the visible range. .

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

Furthermore, the use of Th, Cd, Tl, Os, Be, and Se as harmful chemical substances has tended to be avoided in recent years, and they are used not only in the glass manufacturing process but also in the processing process and disposal after product production. Environmental measures are required throughout. Therefore, when placing importance on the environmental impact, it is preferable not to substantially contain these.

In this specification, "substantially not contained" means that the content is preferably less than 0.1%, and more preferably that it is not contained except for inevitable impurities. Here, the content of components included as unavoidable 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, as the raw materials for each of the above components, high purity raw materials used for ordinary optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphoric acid compounds, etc. are used, and each component is mixed with a predetermined content. The prepared mixture is poured into a platinum crucible and melted in an electric furnace at a temperature of 1000 to 1500°C for 2 to 5 hours depending on the difficulty of melting the glass raw material, stirring homogeneously. It is produced by lowering the temperature to an appropriate temperature, casting it into a mold, and slowly cooling it.

<Physical properties>
The optical glass of the present invention has a high refractive index and a high Abbe number (low dispersion).
In particular, the lower limit of the refractive index (n _d ) of the optical glass of the present invention is preferably 1.75, more preferably 1.77, and even more preferably 1.78. The upper limit of this refractive index (n _d ) is preferably 2.00, more preferably 1.95, even more preferably 1.90, and even more preferably 1.85.
Further, the lower limit of the Abbe number (v _d ) of the optical glass of the present invention is preferably 30, more preferably 31, still more preferably 32, and even more preferably 34. The upper limit of this Abbe number (v _d ) is preferably 50, more preferably 45, more preferably 43, still more preferably 42, and even more preferably 40.
By having such a high refractive index, a large amount of light refraction can be obtained even if the optical element is made thinner. Moreover, by having such low dispersion, when used as a single lens, the shift of 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), the aberrations of the optical system as a whole can be reduced and high imaging characteristics can be achieved.
As described above, the optical glass of the present invention is useful in optical design, and in particular, when an optical system is configured, it is possible to downsize the optical system while achieving high imaging characteristics, etc. The degree of freedom can be expanded.

Further, from the viewpoint of usefulness in optical design, the optical glass of the present invention has a partial dispersion ratio (θg, F) of preferably 0.550, more preferably 0.555, still more preferably 0.560, and even more preferably The lower limit is 0.565, more preferably 0.570, and the upper limit is preferably 0.620, more preferably 0.615, even more preferably 0.610, even more preferably 0.600, and still more preferably 0.590. do.

The optical glass of the present invention has a coordinate system in which the Abbe number (ν _d ) is the x-axis and the partial dispersion ratio (θg, F) is the y-axis, and (x, y) = (36.3, 0.5828). The size in the y-axis direction (θg, F direction) from the straight line connecting the two points of (60.5, 0.5436) (herein referred to as "anomalous dispersion (Δθg, F)") is +0 It is preferable that it is .001 or less. In other words, the combination of Abbe's number (ν _d ) and partial dispersion ratio (θg, F) must be +0.001 in the y-axis direction from the value on this straight line, or a value in a more negative direction in the y-axis direction. is preferred. As a result, the partial dispersion is near the straight line connecting the two points (x, y) = (36.3, 0.5828) and (60.5, 0.5436), that is, the normal line, or lower than that. An optical glass having the ratio (θg, F) is obtained. Therefore, while achieving a high refractive index and low dispersion of the glass, it is possible to reduce the chromatic aberration of an optical element formed from this optical glass. Here, the upper limit of the anomalous dispersion (Δθg, F) of the optical glass is preferably +0.0010 or less, more preferably +0.0008 or less, still more preferably +0.0005 or less. On the other hand, the lower limit of the anomalous dispersion (Δθg, F) of the optical glass is not particularly limited, and may be, for example, -0.0300 or -0.0100.

The optical glass of the present invention preferably has an average coefficient of linear expansion (α) at −30 to 70° C. within the range of 70 to 110×10 ⁻⁷ K ⁻¹ . In particular, the lower limit of the average linear expansion coefficient of the optical glass of the present invention is more preferably 75×10 ⁻⁷ K ⁻¹ , even more preferably 80×10 ⁻⁷ K ⁻¹ , and more preferably 105×10 ⁻⁷ K ^-1 , more preferably 103×10 ^-7 K ^-1 . As a result, when the optical glass of the present invention is bonded to a glass having a relatively large expansion such as fluorophosphate glass, the bondability between both materials can be maintained well even if the ambient temperature changes.

[Preform and optical element]
A glass molded body can be produced from the produced optical glass using, for example, a polishing method or a mold press forming method such as reheat press molding or precision press molding. That is, mechanical processing such as grinding and polishing is performed on optical glass to produce a glass molded body, or a preform for mold press molding is produced from optical glass, and this preform is subjected to reheat press molding. After that, a glass molded body is produced by polishing, or a glass molded body is produced by performing precision press molding on a preform produced by polishing, or a preform molded by known levitation molding, etc. can be created. Note that the means for producing the glass molded body are not limited to these means.

Thus, the optical glass of the present invention is useful for various optical elements and optical designs. Among these, it is particularly preferable to form a preform from the optical glass of the present invention and perform reheat press molding, precision press molding, etc. using this preform to produce optical elements such as lenses and prisms. This makes it possible to form a preform with a large diameter, so even though the optical element is made larger, it is possible to achieve high-definition and highly accurate imaging and projection characteristics when used in optical equipment.

The glass molded article made of the optical glass of the present invention can be used for optical elements such as lenses, prisms, mirrors, etc., and is typically used in automotive optical equipment, projectors, copy machines, etc. that are prone to high temperatures. Can be used for equipment.

Compositions of Examples (No. 1 to No. 118) of the present invention, and refractive index (n _d ), Abbe number (ν _d ), and anomalous dispersion (Δθg, F) of these glasses, -30 to 70 The results of the average linear expansion coefficient (α) at °C are shown in Tables 1 to 15. Note that the following examples are for illustrative purposes only, and are not intended to be limiting.

The glasses of the embodiments of the present invention are all high-purity raw materials used for ordinary optical glasses, such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphoric acid compounds, which correspond to the raw materials for each component. After weighing and mixing uniformly so as to achieve the composition ratio of each example shown in the table, it is placed in a platinum crucible and heated at 1000 to 1500°C in an electric furnace depending on the difficulty of melting the glass raw material. After melting at a temperature range of 2 to 5 hours, the mixture was homogenized by stirring, cast into a mold, etc., and slowly cooled.

The refractive index (n _d ) of the glasses of Examples and Comparative Examples was shown as a value measured against the d-line (587.56 nm) of a helium lamp according to the V-block method specified in JIS B 7071-2:2018. In addition, the Abbe number (ν _d ) is the refractive index of the above d-line, the refractive index (n _F ) for the F-line (486.13 nm) of the hydrogen lamp, and the refractive index (n _C ) for the C-line (656.27 nm). It was calculated from the formula of Abbe number (ν _d )=[( _nd −1)/(n _F −n _C )] using the value of .
In addition, the partial dispersion ratio is determined by measuring the refractive index n _C at the C line (wavelength 656.27 nm), the refractive index n _F at the F line (wavelength 486.13 nm), and the refractive index n _g at the G line (wavelength 435.835 nm). It was calculated using the formula (θg,F)=(n _g −n _F )/(n _F −n _C ).
Note that the glass used in this measurement was treated in a slow cooling furnace at a slow cooling temperature drop rate of -25° C./hr.

Regarding the anomalous dispersion property Δθg, F, regarding the values of the Abbe number (ν _d ) and partial dispersion ratio (θg, F), the Abbe number (ν _d ) is plotted on the x-axis and the partial dispersion ratio (θg, F) is plotted on the x-axis. In a coordinate system with the y-axis as I asked for it.

The average linear expansion coefficient (α) of the glass was determined from -30 to 70°C according to the Japan Optical Glass Industry Association standard JOGIS 16-2003 "Measurement method of average linear expansion coefficient of optical glass near room temperature". .

As shown in Tables 1 to 15, all of the optical glasses of Examples had a refractive index (n _d ) of 1.75 or more, more specifically 1.78 or more, which was within the desired range. .
Furthermore, all of the optical glasses of the examples of the present invention had an Abbe number (ν _d ) within the range of 30 or more and 50 or less, more specifically within the range of 32 or more and 42 or less, which was within the desired range. .

Further, the optical glasses of the examples of the present invention had anomalous dispersion Δθg,F within the range of +0.0100 or less, which was within the desired range.
On the other hand, in the comparative example, the anomalous dispersion Δθg,F could not satisfy the desired range in the present invention.

Further, the optical glass of the example of the present invention has an average coefficient of linear expansion (α) at -30 to 70°C within the range of 75 x 10 ^-7 /°C to 100 x 10 ^-7 /°C, which is within the desired range. It was within.

Moreover, the optical glass of the example formed a stable glass, and devitrification was unlikely to occur during glass production.

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

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

Claims (4)

In mass%,
2.0% or more and 25.0% or less of SiO ₂ components,
3.0% or more and 25.0% or less of B ₂ O ₃ components,
Nb ₂ O ₅ component 5.16% or more and 30.0% or less,
BaO component is 30.02 % or more and 60.0% or less,
Contains 6.37% or less of TiO ₂ components,
Contains a total of 10.0% or more and 50.0% or less of Ln ₂ O ₃ components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb),
The refractive index (n _d ) is 1.75 or more, the Abbe number (ν _d ) is 30 or more and 40 or less,
In a coordinate system in which the Abbe number (ν _d ) is the x axis and the partial dispersion ratio (θg, F) is the y axis, (x, y) = (36.3, 0.5828) and (60.5, 0. 5436) in the y-axis direction from a straight line connecting two points (abnormal dispersion (Δθg, F)) of +0.001 or less. The optical glass according to claim 1, characterized in that the average coefficient of linear expansion (α) at -30 to 70°C is 75 x 10 ^-7 /°C to 100 x 10 ^-7 /°C. An optical element comprising the optical glass according to claim 1 or 2. An optical device comprising the optical element according to claim 3.