JP7219199B2 - Optical glasses and optical elements - Google Patents

Description

The present invention relates to optical glasses and optical elements.

Fluorophosphate glass containing phosphorus, oxygen and fluorine is known as an optical glass that exhibits low dispersion and positive anomalous dispersion.
Since fluorophosphate glass has the excellent optical properties described above, it has a high utility value as an optical element material for correcting high-order chromatic aberration.
Examples of such fluorophosphate glasses are described in US Pat.

JP-A-2005-112717 JP 2013-151410 A JP-A-51-114412 JP-A-58-217451

Although fluorophosphate glass thus has excellent optical properties, it exhibits significant volatility in the high-temperature processes of melting and molding the glass. Volatilization from the glass melt during the melting and molding process can cause phenomena such as deterioration of the glass, fluctuations in optical properties, and deterioration of the homogeneity of the glass.

Further, in the process of grinding and polishing a glass material made of optical glass to produce optical elements such as lenses and prisms, the glass after polishing is usually washed. On the other hand, the surface of the polished glass generally has minute scratches that are not visible to the naked eye, generally called latent scratches. However, when the surface of the glass is eroded by washing, the latent flaws are expanded and exposed to become sources of light scattering, which may deteriorate the surface quality of the glass. In addition, the surface quality of the glass may deteriorate due to alteration of the glass surface due to washing.
For fluorophosphate glass, it is desirable to increase the chemical durability of the fluorophosphate glass in order to suppress the deterioration of the surface quality of the glass as described above.

An aspect of the present invention is to provide an optical glass that has a large partial dispersion ratio and is suitable for chromatic aberration correction while reducing the volatility of fluorophosphate glass in a high-temperature process, and to provide an optical element made of the optical glass. With the goal.

Another aspect of the present invention is to provide an optical glass made of a fluorophosphate glass that has excellent chemical durability and a large partial dispersion ratio and is suitable for correcting chromatic aberration, and the optical glass made of the above optical glass. An object is to provide an optical element.

One aspect of the present invention is
including P ⁵⁺ , Al ³⁺ , Nb ⁵⁺ , O ²⁻ and F ⁻ as essential components,
the molar ratio of the Al ³⁺ content to the P ⁵⁺ content (Al ³⁺ /P ⁵⁺ ) is 0.30 or more;
Nb ⁵⁺ content of 1.0 cation % or more,
O ^2- content of 10 to 85 anion%,
F ^- content is 15 to 90 anion%,
the molar ratio of the content of O ²⁻ to the total content of P ⁵⁺ and Nb ⁵⁺ (O ²⁻ /(P ⁵⁺ +Nb ⁵⁺ )) is 3.0 or more;
Optical glass (hereinafter also referred to as “optical glass 1”),
Regarding.

The optical glass preferably has positive anomalous dispersion.
A partial dispersion ratio Pg,F is used as an index of positive anomalous dispersion. The partial dispersion ratio Pg,F uses the refractive index nF at the F line (wavelength 486.13 nm), nC at the C line (wavelength 656.27 nm) and the refractive index ng at the g line (wavelength 435.84 nm), is represented as
Pg, F = (ng-nF)/(nF-nC) (1)
It is known that Nb contained in glass has an intrinsic absorption wavelength in the ultraviolet region close to that in the visible region and also has a high absorption intensity. As a result, the wavelength dispersion of the refractive index tends to be highly dispersed. That is, the refractive index difference nF−nC between the F line and the C line tends to increase, and the Abbe number νd tends to decrease. On the other hand, the refractive index difference ng-nF between the g-line and the F-line also increases.
Here, if the effect of increasing ng-nF exceeds the effect of increasing nF-nC, Pg and F will increase, as is clear from the equation (1).
Focusing on this point, the present inventors introduced Nb as a glass component to maintain the low dispersion (large νd) in a range comparable to that of conventional fluorophosphate glass, while maintaining the partial dispersion ratio Pg, We have found that F can be significantly increased.
However, Nb-containing fluorophosphate glass tends to volatilize Nb from the glass melt during the melting process. Niobium fluoride is produced when Nb and F combine during the melting process. Niobium fluoride has a high vapor pressure and easily volatilizes from the glass melt.
In order to prevent the Nb introduced to increase the partial dispersion ratio from promoting volatilization, the present inventors made intensive studies and obtained the following findings.
P ⁵⁺ exists in the form of —O—P—O— in the glass and is considered to contribute to the formation of the network of the glass. Nb ⁵⁺ having the same valence as P ⁵⁺ is also considered to contribute to glass network formation by occupying the position of P in the —O—P—O— structure.
It is believed that when Nb ⁵⁺ is incorporated into the network structure, niobium fluoride, which has a high vapor pressure, is less likely to be produced, and as a result, the volatility of the glass decreases.
However, sufficient numbers of O ²⁻ are required for Nb ⁵⁺ to be incorporated into the network structure. Considering the presence of Nb ⁵⁺ , the molar ratio of the content of O ²⁻ to the total content of cations (P ⁵⁺ and Nb ⁵⁺ ) constituting the network (O ²⁻ /(P ⁵⁺ +Nb ⁵⁺ )) is If it is 3.0 or more, Nb ⁵⁺ can be easily incorporated into the network, thereby suppressing an increase in volatility.
Based on the above knowledge, the present inventors completed the optical glass according to one aspect of the present invention.

Another aspect of the present invention is
An optical glass made of fluorophosphate glass,
The mass reduction amount D _NaOH per unit area when immersed in an aqueous NaOH solution for 15 hours is less than 0.25 mg/(cm ² · 15 h), and the Abbe number νd and the partial dispersion ratio Pg, F are the following (4 )formula:
Pg,F>−0.0004νd+0.5718 (4)
optical glass (hereinafter also referred to as "optical glass 2") that satisfies
Regarding.

According to one aspect of the present invention, it is possible to provide an optical glass having a large partial dispersion ratio and suitable for chromatic aberration correction while reducing the volatility of fluorophosphate glass in a high-temperature process. can provide.
Further, according to another aspect of the present invention, it is possible to provide an optical glass that is a fluorophosphate glass, has a large partial dispersion ratio, is suitable for chromatic aberration correction, and has excellent chemical durability, An optical element made of the above optical glass can be provided.

The optical properties of the optical glasses of the examples are shown in the Abbe number νd-refractive index nd chart. The optical properties of the optical glasses of the examples and the optical properties of the existing optical glasses are shown in the Abbe number νd-partial dispersion ratio Pg,F chart.

In the present invention and this specification, the content and total content of cationic components are expressed in cation % unless otherwise specified, and the content and total content of anionic components are expressed in anion % unless otherwise specified.
Here, "cation %" is a value calculated by "(number of cations of interest/total number of cations of glass component) x 100", and is the molar percentage of the amount of cations of interest to the total amount of cation components. means.
In addition, "anion %" is a value calculated by "(number of anions of interest/total number of anions of glass component) x 100", and means the molar percentage of the amount of anions of interest with respect to the total amount of anion components. do.
The molar ratio of the contents of the cation components is equal to the ratio of the contents of the cation components of interest expressed in cation %, and the molar ratio of the contents of the anion components to each other is the ratio of the contents of the anion components of interest expressed in anion %. equal to the ratio.
The molar ratio of the content of the cationic component to the content of the anionic component is the ratio of the contents of the components of interest (expressed in mol%) when the total amount of all cationic components and all anionic components is 100 mol%. be.
The content of each component can be quantified by known methods such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography, and the like. .

In the present invention and in this specification, the term "fluorophosphate glass" refers to glass containing at least phosphorus, oxygen and fluorine as elements constituting the glass.

[Optical glass 1]
<Glass component>
The optical glass 1 according to one aspect of the present invention will be described below.
^P5+ acts as a network forming component. Al ³⁺ is a component that maintains the thermal stability of glass and works to improve chemical durability and workability. The molar ratio of the Al ³⁺ content to the P ⁵⁺ content (Al ³⁺ /P ⁵⁺ ) is 0.30 or more in order to maintain good thermal stability of the glass. In order to increase the refractive index while maintaining the Abbe number, it is effective to set the molar ratio (Al ³⁺ /P ⁵⁺ ) to 0.30 or more.
A preferable lower limit of the molar ratio (Al ³⁺ /P ⁵⁺ ) is 0.5. On the other hand, the preferable upper limit of the molar ratio (Al ³⁺ /P ⁵⁺ ) is 2, and the more preferable upper limit is 1, from the viewpoint of maintaining good thermal stability of the glass.

Nb ⁵⁺ works as a network forming component together with P ⁵⁺ to maintain the thermal stability of the glass and increase the partial dispersion ratio. To obtain these effects, the content of Nb ⁵⁺ is 1.0% or more. A preferred lower limit for the Nb ⁵⁺ content is 1.5%, a more preferred lower limit is 2%, a still more preferred lower limit is 2.5%, and an even more preferred lower limit is 3%. On the other hand, when the content of Nb ⁵⁺ is excessive, the volatility of the glass during melting becomes significant, and the homogeneity of the glass tends to deteriorate. Therefore, the preferred upper limit of the Nb ⁵⁺ content is 15%, the more preferred upper limit is 13%, and the even more preferred upper limit is 10%. The relationship between Nb ⁵⁺ and the chemical durability of glass will be described later.

From the viewpoint of maintaining the thermal stability of the glass, the total content of P ⁵⁺ and Nb ⁵⁺ (P ⁵⁺ +Nb ⁵⁺ ) is preferably 15% or more. A preferred lower limit for the total content of P ⁵⁺ and Nb ⁵⁺ (P ⁵⁺ +Nb ⁵⁺ ) is 20%.

O ^2- serves to maintain the thermal stability of the glass. In order to obtain such functions, the content of O ²⁻ is 10 anion % or more. If the content of O ²⁻ is more than 85 anion %, the content of F ⁻ becomes insufficient and it becomes difficult to obtain low dispersibility. The content of O ²⁻ is therefore between 10 and 85 anion %. The preferred lower limit of the O ^2- content is 20%, the more preferred lower limit is 30%, the preferred upper limit is 80%, the more preferred upper limit is 75%, the still more preferred upper limit is 70.93%, and the more preferred upper limit is 70%. is.

F- has a function of lowering the dispersion of the glass ^and imparting anomalous dispersion, a function of lowering the glass transition temperature, and a function of improving chemical durability. If the F 2 ^- content is less than 15 anion %, the above effects are difficult to obtain. On the other hand, if the F 2 ^- content exceeds 90 anion %, it becomes difficult to maintain the thermal stability of the glass. Moreover, when the content of F ⁻ is excessive, each value of D _NaOH , D _STPP and D ₀ described below tends to increase.
From the above point of view ^, the content of F.sup.- is 15 to 90 anion %. The preferable lower limit of the F- content is 20% ^, the more preferable lower limit is 25%, the even more preferable lower limit is 28.86%, the more preferable lower limit is 30%, the preferable upper limit is 80%, and the more preferable upper limit is 80%. is 70%.

As described above, the molar ratio of the content of O ^{2− to} the total content of P ⁵⁺ and Nb ⁵⁺ (O ²⁻ /( P ⁵⁺ +Nb ⁵⁺ )) is 3.0 or more. A preferred lower limit for the molar ratio (O ²⁻ /(P ⁵⁺ +Nb ⁵⁺ )) is 3.2. From the viewpoint of maintaining the thermal stability of the glass, the preferred upper limit of the molar ratio (O ²⁻ /(P ⁵⁺ +Nb ⁵⁺ )) is 4.0, and the more preferred upper limit is 3.8.

Alkaline earth metal components, that is, Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ are components that work to adjust the viscosity and refractive index of glass and improve thermal stability. In order to obtain the above effect, the total content R ²⁺ (Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ ) of the alkaline earth metal components is preferably 20 cation % or more, more preferably 30% or more, and 35 % or more is more preferable.
On the other hand, if the total content R ²⁺ of the alkaline earth metal components is excessive, the thermal stability tends to decrease, so the total content R ²⁺ of the alkaline earth metal components is preferably 50% or less. A more preferred upper limit for R ²⁺ is 45%, and a further preferred upper limit is 40%.

The optical glass may contain one or more rare earth elements selected from the group consisting of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ .
The total content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ with respect to the Al ³⁺ content (La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ ) molar ratio ((La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ )/Al ³⁺ ) is preferably 0.3 or less. A more preferable upper limit of the molar ratio ((La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ )/Al ³⁺ ) is 0.2, and a more preferable upper limit is 0.1. The molar ratio ((La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ )/Al ³⁺ ) may be zero.

Next, the content of each component will be explained.

^P5+ is an essential component that forms the glass network. From the viewpoint of maintaining good thermal stability, the lower limit of the P ⁵⁺ content is preferably 5%, more preferably 10%, and even more preferably 20%. From the viewpoint of maintaining good chemical durability, low dispersibility, and anomalous partial dispersibility, the preferred upper limit of the P ⁵⁺ content is 40%, the more preferred upper limit is 38%, and the further preferred upper limit is 35%. .

Al ³⁺ is an essential component that works to improve thermal stability, chemical durability and workability, and also works to increase the refractive index. From the above viewpoints, the preferred lower limit of the Al ³⁺ content is 5%, the more preferred lower limit is 7%, the still more preferred lower limit is 9%, and the much more preferred lower limit is 11%. From the above viewpoints, the upper limit of the Al ³⁺ content is preferably 40%, more preferably 38%, still more preferably 36%, and still more preferably 34%.

In the glass composition expressed in atomic %, the ratio O ²⁻ /Al ³⁺ of the content of O ²⁻ to the content of Al ³⁺ is preferably less than 12, more preferably less than 10, and 8 More preferably less than. As the content of O ²⁻ increases, the content of F 2 ⁻ relatively decreases and the glass transition temperature tends to rise. On the other hand, as described above, Al ³⁺ is a useful component for improving thermal stability, chemical durability and workability, and providing desired optical properties. In order to suppress the increase in the glass transition temperature while sufficiently obtaining the effect of Al ³⁺ , the ratio of the content of O ²⁻ to the content of Al ³⁺ in the glass composition expressed in atomic % O ²⁻ /Al ³⁺ is preferably within the above range. Regarding the lower limit of the above ratio O ²⁻ /Al ³⁺ , from the viewpoint of suppressing a decrease in devitrification resistance due to a relative increase in the content of Al ³⁺ , for example, 2 or more or 3 or more is a standard. be able to.
The content of each component in the glass composition represented by atomic % is a value expressed as a mole percentage of the content of each component when the total content of all cationic components and all anionic components is 100 mol%. Calculated.

Preferred contents of the individual components of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ are as follows.
A preferred range for the Mg ²⁺ content is 0-10%, and a more preferred range is 0-8%.
A preferred range for the Ca ²⁺ content is 0-20%, and a more preferred range is 0-15%.
A preferred range for the Sr ²⁺ content is 0 to 40%, and a more preferred range is 0 to 30%.
The Ba ²⁺ content preferably has a lower limit of 5%, a more preferred lower limit of 10%, a preferred upper limit of 50%, and a more preferred upper limit of 40%.

Preferred individual contents of La ³⁺ , Gd ³⁺ , Y ³⁺ and Lu ³⁺ are as follows.
A preferred range for the La ³⁺ content is 0 to 5%, and a more preferred range is 0 to 3%.
A preferred range for the Gd ³⁺ content is 0-5%, and a more preferred range is 0-3%.
A preferred range for the Y ³⁺ content is 0 to 5%, and a more preferred range is 0 to 3%.
A preferred range for the Lu ³⁺ content is 0-5%, and a more preferred range is 0-3%.

Since Yb ³⁺ has light absorption in the infrared region, it is not suitable for use in imaging with infrared light. Therefore, the content of Yb ³⁺ is preferably limited as follows using the molar ratio (Yb ³⁺ /(La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ )) to the total content of other rare earth components. . That is, the molar ratio of the content of Yb ³⁺ to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ (Yb ³⁺ /(La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ )) is 0.5. It is preferably 0.1 or less, more preferably 0 (the Yb ³⁺ content is 0%).

Zn ²⁺ works to improve the thermal stability while maintaining the refractive index, but when contained in excess, the dispersion becomes high, making it difficult to obtain the desired optical properties. Therefore, it is preferable to set the content of Zn ²⁺ in the range of 0 to 10%. In order to obtain the above effects, the upper limit of the Zn ²⁺ content is more preferably 8%, and the more preferable upper limit is 5%. The content of Zn ²⁺ may be 0%.

The alkali metal component is a cationic component that functions to adjust the viscosity of glass and improve thermal stability. If the total content R ⁺ of the alkali metal components is excessive, the thermal stability will decrease. Therefore, the preferred range for the total content R ⁺ of the alkali metal components is 0 to 30%. In view of the above, a more preferred range for R ⁺ is 0 to 20%, and a more preferred range is 0 to 15%. More preferably, the upper limit for R ⁺ is 10%, even more preferably 8%, and even more preferably 7%. Also, when the total content R ⁺ of the alkali metal components is excessive, each value of D _STPP and D ₀ described below tends to increase. Therefore, it is preferable to set R ⁺ within the above range also from the viewpoint of imparting excellent chemical durability to the glass.
On the other hand, from the viewpoint of lowering the glass transition temperature, the lower limit of R ⁺ is preferably 1%, more preferably 2%, and still more preferably 3%.
Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ can be mentioned as alkali metal components R ⁺ . Rb ⁺ and Cs ⁺ tend to increase the specific gravity of the glass compared to other alkali metal components.
Therefore, the content of Rb ⁺ is preferably 0 to 3%, more preferably 0 to 2%, even more preferably 0 to 1%, and may be 0%.
The content of Cs ⁺ is preferably 0 to 3%, more preferably 0 to 2%, even more preferably 0 to 1%, and may be 0%.
From the viewpoint of maintaining the thermal stability of the glass, the Li ⁺ content is preferably 0 to 30%, more preferably 2 to 20%, still more preferably 4 to 10%.
From the viewpoint of maintaining the thermal stability of the glass, the Na ⁺ content is preferably in the range of 0 to 10%, more preferably in the range of 0 to 8%, and still more preferably in the range of 0 to 6%.
From the viewpoint of maintaining the thermal stability of the glass, the K ⁺ content is preferably in the range of 0-10%, more preferably in the range of 0-8%, and still more preferably in the range of 0-6%.

A small amount of Si ⁴⁺ can be contained, but if it is excessively contained, the meltability and thermal stability are lowered. Therefore, the content of Si ⁴⁺ is preferably in the range of 0 to 5%, more preferably in the range of 0 to 3%, even more preferably in the range of 0 to 1%, even if it is 0%. good.

B ³⁺ exhibits significant volatility even at low contents. The content of B ³⁺ is preferably 2% or less so as not to promote volatilization. A preferred range of the B ³⁺ content is 0 to 1%, a more preferred range is 0 to 0.1%, and 0% is even more preferred.

When the molten glass flows out from a pipe attached to a glass melting apparatus, Cl ⁻ is contained in order to suppress the wetting of the glass melt onto the outer periphery of the pipe and to suppress the quality deterioration of the glass due to the wetting. is valid. The preferred range of the Cl ⁻ content is 0 to 1%, more preferred range is 0 to 0.5%, and still more preferred range is 0 to 0.3%. Cl ⁻ also has an effect as a fining agent.

In addition, a small amount of Sb ³⁺ , Ce ⁴⁺ or the like can be added as a clarifier. The total amount of fining agent can be 0% or more, preferably less than 1%. For example, the total content of Sb ³⁺ and Ce ⁴⁺ can be 0% or more, preferably less than 1%.

Pb, Cd, As, and Th are components of concern about environmental impact.
Therefore, the optical glass 1 preferably does not substantially contain at least one of Pb, Cd, As and Th.
The content of Pb ²⁺ is preferably from 0 to 0.5%, more preferably from 0 to 0.1%, even more preferably from 0 to 0.05% ^. It is particularly preferred not to contain.
The content of Cd ²⁺ is preferably 0 to 0.5%, more preferably 0 to 0.1%, even more preferably 0 to 0.05%, and Cd ²⁺ is substantially It is particularly preferred not to contain.
The content of As ³⁺ is preferably 0 to 0.1%, more preferably 0 to 0.05%, even more preferably 0 to 0.01%, and the content of As ³⁺ is substantially It is particularly preferred not to contain.
The content of Th ⁴⁺ is preferably 0 to 0.1%, more preferably 0 to 0.05%, even more preferably 0 to 0.01%, Th ⁴⁺ is substantially It is particularly preferred not to contain.

The optical glass 1 can preferably exhibit high transmittance over a wide visible region. In order to take advantage of these features, the optical glass preferably does not contain a coloring agent. Examples of coloring agents include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, V, and the like. Preferably, the optical glass 1 does not substantially contain at least one of Cu, Co, Ni, Fe, Cr, Eu, Nd, Er and V. The content range of Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, and V in terms of cation % is preferably less than 100 ppm, more preferably 0 to 80 ppm. , more preferably 0 to 50 ppm or less, and particularly preferably not substantially contained. Here, ppm means cation ppm.
Also, Hf, Ga, Ge, Te, and Tb are expensive components. Therefore, it is preferable that the optical glass 1 does not substantially contain at least one of h, Hf, Ga, Ge, Te and Tb. The content range of Hf, Ga, Ge, Te, and Tb in terms of cation % is preferably 0 to 0.1%, more preferably 0 to 0.05%, It is more preferably 0 to 0.01%, still more preferably 0 to 0.005%, even more preferably 0 to 0.001%, and particularly preferably not substantially contained. .
The above optical glass can exhibit various properties without introducing Hf, Ga, Ge, Te, and Tb.

<Glass characteristics>
(Abbe number νd, refractive index nd)
In the above optical glass 1, the Abbe number νd is preferably in the range of 45 or more in order to make the most of the anomalous partial dispersion.
The Abbe number νd is a value representing properties related to dispersion, and is expressed as νd=(nd−1)/(nF−nC) using respective refractive indices nd, nF, and nC for the d-line, F-line, and C-line. .
A preferable upper limit of the Abbe number νd is 80, and a more preferable upper limit is 70. On the other hand, the lower limit of the Abbe number νd is preferably 45, more preferably 50, and even more preferably 55, in order to take advantage of the low dispersibility.

Furthermore, by setting the refractive index nd within the following range, it is possible to reduce the absolute value of the curvature of the optical function surface of the lens (to soften the curve of the optical function surface of the lens) while maintaining the same light gathering power. can. Whether it is precision press molding, grinding, or polishing, it is easier to manufacture the lens if the curve of the optical function surface is gentler, so the use of glass with a high refractive index can increase the productivity of the optical element. Furthermore, by increasing the refractive index, it is possible to provide a glass material suitable for optical elements used in highly functional and compact optical systems.
In the optical glass 1, the preferable range of the refractive index nd is the range satisfying the following formula (2), and the more preferable range of the refractive index nd is the range satisfying the following formula (3).
nd≧1.80653−0.00459×νd (2)
nd≧1.84303−0.00459×νd (3)

FIG. 1 shows equations when equality is established in equations (2) and (3).
The optical glass 1 preferably exhibits positive anomalous dispersion. The anomalous dispersion is quantitatively represented by ΔPg,F. Using the respective refractive indices ng, nF, and nC for the g-line, F-line, and C-line, the partial dispersion ratio Pg,F can be calculated from the above-described formula (1) (Pg,F = (ng-nF)/(nF -nC)).
FCD100, FCD515, etc. manufactured by HOYA are known as commercially available low-dispersion glasses having an Abbe number νd of 45 or more.
FCD100 is plotted at coordinates (95.1 0.5334) and FCD515 is plotted at coordinates (68.63 0.5441) in a graph in which the horizontal axis is the Abbe number νd and the vertical axis is the partial dispersion ratio Pg, F. Consider a straight line L connecting the above two points. This straight line L is approximately expressed as "Pg, F=-0.0004νd+0.5718".
A straight line L is illustrated in FIG.
As shown in FIG. 2, commercially available low-dispersion glass (existing glass) having an Abbe number νd of 45 or more is on or above the straight line L in the Abbe number νd-partial dispersion ratio Pg,F graph. It is located on the side where the partial dispersion ratio Pg,F is small.
In a preferred embodiment, the optical glass 1 has an Abbe number νd and a partial dispersion ratio Pg,F that satisfy the following formula (4).
Pg,F>−0.0004νd+0.5718 (4)
An optical glass having an Abbe number νd of 45 or more and satisfying the above formula (4) has a large partial dispersion ratio Pg,F with respect to a specific Abbe number νd, and is suitable as an optical glass for high-order chromatic aberration correction. be.

(Transmittance)
The optical glass 1 preferably has very little coloring, and is suitable as a material for imaging optical elements such as camera lenses and projection optical elements such as projectors.
A preferred embodiment of the optical glass 1 is glass having an internal transmittance of 96.5% or more at a wavelength of 400 nm to 700 nm and a thickness of 10 mm.
A preferable range of the internal transmittance is 97% or more, a more preferable range is 98% or more, and a much more preferable range is 99% or more.
In addition, the glass containing light-emitting ions such as glass for lasers, for example, Nd, Eu, Er, V, etc., has absorption in the visible range, so it is used in imaging optical elements such as camera lenses and projection optics such as projectors. Not suitable for element materials.

(Glass transition temperature Tg)
A preferred embodiment of the optical glass 1 is an optical glass having a glass transition temperature Tg of 550° C. or less. If the glass transition temperature is low, the heating temperature can be lowered when the glass is reheated, softened and press-molded. As a result, it becomes easier to suppress fusion between the glass and the press mold. Moreover, since the heating temperature can be lowered, the thermal consumption of the glass heating device, the press mold, etc. can be reduced. Furthermore, since the glass annealing temperature can be lowered, the life of the annealing furnace can be extended. A more preferable range of the glass transition temperature is 530° C. or lower, and a further preferable range is 500° C. or lower.

(Liquidus temperature)
A preferred embodiment of the optical glass 1 is an optical glass having a liquidus temperature of 850° C. or lower. If the liquidus temperature is low, the melting and forming temperature of the glass can be lowered. As a result, the volatility of the glass during melting and molding can be reduced, and the occurrence of striae and variations in optical properties can be suppressed.
A more preferable range of the liquidus temperature is 800° C. or lower, and a further preferable range is 750° C. or lower.

(specific gravity)
The above optical glass 1 can increase the partial dispersion ratio mainly by containing Nb ⁵⁺ without relying on rare earth elements that increase the partial dispersion ratio but also increases the specific gravity. Small specific gravity.
A preferred embodiment of the optical glass 1 is optical glass having a specific gravity of 4.2 or less. By reducing the specific gravity, the weight of the optical element can be reduced.
A more preferable range of specific gravity is 4.1 or less, and a further preferable range is 4 or less.

[Optical glass 2]
Hereinafter, the optical glass 2 according to one aspect of the present invention will be described.

<Glass characteristics>
In the optical glass 2, the Abbe number νd and the partial dispersion ratio Pg,F satisfy the following formula (4).
Pg,F>−0.0004νd+0.5718 (4)
The optical glass 2 whose Abbe number νd and partial dispersion ratio Pg,F satisfy the above formula (4) is suitable as an optical glass for high-order chromatic aberration correction.
In the above optical glass 2, the Abbe number νd is preferably in the range of 45 or more from the viewpoint of taking advantage of the anomalous partial dispersion. A preferable upper limit of the Abbe number νd is 80, and a more preferable upper limit is 70. On the other hand, a more preferable lower limit of the Abbe number νd is 50, and a more preferable lower limit is 55, in order to take advantage of the low dispersibility.

<Chemical durability>
( _DNaOH )
The optical glass 2 has chemical durability such that the amount of mass reduction D _NaOH per unit area when immersed in an aqueous NaOH solution for 15 hours is less than 0.25 mg/(cm ² ·15 h).
The mass reduction amount D _NaOH is obtained by the following method.
First, a disc-shaped glass sample having a diameter of 43.7 mm and a thickness of 5 mm is prepared. The two opposing surfaces with a diameter of 43.7 mm are polished face-to-face, and the side surfaces are attached with a tape (e.g., polyimide tape) that is chemically resistant to the aqueous solution of sodium hydroxide (NaOH) described below. Masking by the method of Therefore, the two surfaces of the disk-shaped glass sample are exposed to the following aqueous solution of sodium hydroxide (NaOH). The sum of the areas of these two surfaces (hereinafter referred to as "the surface area of the glass sample") is 30 cm ² .
Next, after measuring the mass M _before of the glass sample, the glass sample was immersed in a sufficiently stirred aqueous solution of sodium hydroxide (NaOH) having a liquid temperature of 50°C and a concentration of 0.01 mol/l for 15 hours. Measure the mass M _after of the glass sample. D _NaOH is the value obtained by dividing the difference in mass (M _before -M _after ) (unit: mg) before and after immersion by the surface area of the glass sample. That is, the value obtained by "(M _before -M _after )/30" is D _NaOH .
The optical glass 2 has chemical durability such that D _NaOH is less than 0.25 mg/(cm ² ·15 h). According to the optical glass having D _NaOH within the above range, it is possible to suppress deterioration of the surface quality due to manifestation of latent scratches or the like. D _NaOH is preferably less than 0.20 mg/(cm ² ·15h), more preferably 0.10 mg/(cm ² ·15h) in order to maintain high surface quality. Although the lower limit of D _NaOH is not particularly limited, for example, 0.02 mg/(cm ² ·15 h) or more can be considered as a guideline.

(About _DA )
It is preferable that the optical glass 2 has chemical durability such that D _A is less than 0.35%.
_DA is measured according to the method for measuring the acid resistance weight loss rate Da specified in the Japanese Optical Glass Industry Standard JOGIS06-2009. Specifically, the measuring method is as follows.
A powdered glass (particle size: 425 μm to 600 μm) having a mass (M _before , unit: g) corresponding to the specific gravity is placed in a platinum basket, and is immersed in 80 ml of an aqueous nitric acid solution having a concentration of 0.01 mol/l in a quartz glass round-bottomed flask. and treated in a boiling water bath for 60 minutes, and the mass M _after (unit: g) of the powdered glass after this treatment is measured. A value (M _before -M _after )/M _before expressed as a percentage obtained by dividing the difference in mass of the powdered glass before and after the treatment by the mass of the powdered glass before the treatment, [(M _before -M _after )/M _before ] ×100, is D _A. An optical glass having a _DA within the above range is suitable as a glass material for optical elements mounted in outdoor monitoring cameras and vehicle-mounted cameras, which are required to have excellent acid resistance.
Although the lower limit of D _A is not particularly limited, for example, 0.20% or more can be considered as a guideline.

(About D _STPP )
The optical glass 2 preferably has chemical durability such that D _STPP is less than 0.40 mg/(cm ² ·h).
The method for measuring D _STPP is as follows.
First, a disc-shaped glass sample having a diameter of 43.7 mm and a thickness of 5 mm is prepared. The two opposing surfaces with a diameter of 43.7 mm are polished face-to-face, and the side surfaces are attached with a tape that is chemically resistant to the aqueous solution of sodium tripolyphosphate described below (e.g., polyimide tape, etc.). to mask. Therefore, the two surfaces of the disk-shaped glass sample are exposed to the following aqueous solution of sodium tripolyphosphate. The sum of the areas of these two surfaces (the surface area of the glass sample) is 30 cm ² .
Next, after measuring the mass M _before of the glass sample, it was immersed in a sufficiently stirred aqueous solution of sodium tripolyphosphate (Na ₅ P ₃ O ₁₀ ) having a liquid temperature of 50° C. and a concentration of 0.01 mol/l for 1 hour, The mass M _after of the glass sample after immersion is measured. D _STPP is obtained by dividing the difference in mass (M _before -M _after ) (unit: mg) between before and after immersion by the surface area of the glass sample and the immersion time. That is, the value obtained by "(M _before -M _after )/(30×1)" is D _STPP .
More preferably, the optical glass 2 has chemical durability such that D _STPP is less than 0.20 mg/(cm ² ·h). Although the lower limit of D _STPP is not particularly limited, for example, 0.02 mg/(cm ² ·h) or more can be considered as a guideline.
When the D _STPP is within the above range, it is possible to further suppress the deterioration of the surface quality.

For other glass properties of the optical glass 2, one or more of the various items described above for the optical glass 1 can be applied in any combination. Further, for the glass properties of the optical glass 1, one or more of the various items described above for the optical glass 2 can be applied in any combination.

( _D0 )
In the optical glass 2, D ₀ is preferably less than 5.0×10 ⁻³ mg / (cm ² ·h). _D0 is sometimes called true chemical resistance to water.
The method for measuring _D0 is as follows.
First, a disc-shaped glass sample having a diameter of 43.7 mm and a thickness of 5 mm is prepared. Two opposing surfaces with a diameter of 43.7 mm are polished face-to-face, and the side surfaces are masked by a method such as attaching a tape (for example, polyimide tape, etc.) that is chemically resistant to pure water. Therefore, the two surfaces of the disk-shaped glass sample are exposed to the following pure water. The sum of the areas of these two surfaces (the surface area of the glass sample) is 30 cm ² .
The glass sample was then circulated through an ion exchange resin at a rate of 1 liter per minute after measuring the mass M _before , kept at a water temperature of 50°C, pH = 7.0 ± 0.2, and well stirred. immerse in pure water. The mass M _after of the glass sample after being immersed in the pure water for 20 hours or more (preferably 40 hours or more) is measured. A value obtained by dividing the difference in mass before and after immersion (M _{before -M after} ) (unit: mg) by the surface area of the glass sample and the immersion time is defined as D0. That is, D ₀ is a value obtained by "(M _before -M _after )/(30×immersion time (unit: hours))".
When D ₀ is within the above range, it is possible to suppress deterioration of the surface quality of the glass during cleaning or in a high-humidity environment. Although the lower limit of D ₀ is not particularly limited, for example, 0.4×10 ⁻³ mg/(cm ² ·h) or more can be considered as a guideline.

<Glass composition>
The optical glass 2 preferably contains Nb ⁵⁺ .
Nb ⁵⁺ has the function of increasing the partial dispersion ratio and improving the chemical durability, among other things, reducing the values of D _NaOH and _DA . From the viewpoint of obtaining such effects, the preferred range of the Nb ⁵⁺ content is 1.0% or more, more preferably 1.5% or more, still more preferably 2% or more, and still more preferably 2.5%. As described above, the more preferable range is 3% or more. In addition, the inclusion of Nb ⁵⁺ also has the effect of maintaining the thermal stability of the glass. The upper limit of the Nb ⁵⁺ content is preferably 15% in order to suppress volatility during glass melting.

Since both Al ³⁺ and Nb ⁵⁺ contribute to improving chemical durability, the total content of Al ³⁺ and Nb ⁵⁺ is preferably 10% or more in order to impart excellent chemical durability to the glass. It is more preferably 12% or more, and even more preferably 15% or more. The total content of Al ³⁺ and Nb ⁵⁺ is preferably 45% or less, more preferably 35% or less, in order to maintain thermal stability.

For the other glass composition of the optical glass 2, one or more of the various items described above for the optical glass 1 can be applied in any combination. Further, for the glass composition of the optical glass 1, one or more of the various items described above for the optical glass 2 can be applied in any combination.

<Glass manufacturing method>
The optical glasses 1 and 2 can be obtained, for example, by blending, melting, and molding glass raw materials so as to obtain the required properties. As glass raw materials, for example, phosphates, fluorides, alkali metal compounds, alkaline earth metal compounds, and the like may be used. Known methods may be used for the melting method and molding method of the glass.

[Glass material for press molding, its manufacturing method, and manufacturing method of glass molding]
According to one aspect of the present invention, it is possible to provide a press-molding glass material comprising the optical glass 1 or the optical glass 2, a glass molded product comprising the optical glass, and a method for producing them.
A glass material for press molding means a glass lump that is heated and subjected to press molding.
Examples of press-molding glass materials include glass lumps having a mass equivalent to the mass of press-molded products such as precision press-molding preforms and glass materials for press-molding optical element blanks (press-molding glass gobs). can be shown.
A glass material for press molding is produced through a process of processing a glass molded body. The glass molded body can be produced by heating and melting glass raw materials as described above and molding the obtained molten glass. Cutting, grinding, polishing and the like can be exemplified as a method for processing the glass molded body.

[Optical element blank and its manufacturing method]
According to one aspect of the present invention, an optical element blank made of the optical glass 1 or the optical glass 2 can be provided. An optical element blank is a molded glass body having a shape that approximates the shape of the optical element to be manufactured. The optical element blank may be produced by a method of molding glass into a shape obtained by adding a processing allowance to be removed by processing to the shape of the optical element to be manufactured. For example, a method of heating and softening a glass material for press molding and press molding (reheat press method), a method of supplying a molten glass lump to a press mold by a known method and press molding (direct press method), etc. can be used to form an optical element. Blanks can be made.

[Optical element and its manufacturing method]
According to one aspect of the present invention, an optical element made of the optical glass 1 or the optical glass 2 can be provided. Examples of types of optical elements include lenses such as spherical lenses and aspherical lenses, prisms, and diffraction gratings. The shape of the lens includes various shapes such as biconvex lens, plano-convex lens, bi-concave lens, plano-concave lens, convex meniscus lens, and concave meniscus lens. An optical element can be manufactured by a method including a step of processing a glass molded body made of the above optical glass. Examples of processing include cutting, cutting, rough grinding, fine grinding, polishing, and the like. By using the above optical glass in such processing, damage can be reduced, and high-quality optical elements can be stably supplied.

EXAMPLES The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

(Example 1)
In order to obtain the glass composition shown in Table 1, corresponding phosphates, fluorides, oxides, etc. were used as raw materials for introducing each component, and the raw materials were weighed and thoroughly mixed to obtain a prepared raw material. .
This prepared raw material was placed in a platinum crucible and heated to melt. After melting, the molten glass is poured into a mold, allowed to cool to near the glass transition temperature, immediately placed in an annealing furnace, annealed in the range of the glass transition temperature for about 1 hour, and then allowed to cool to room temperature in the furnace. , each optical glass shown in Table 1 was obtained.
When the obtained optical glass was observed under an enlarged optical microscope, precipitation of crystals, foreign matter such as platinum particles, bubbles, and striae were not observed.
Table 1 shows various characteristics of the optical glass thus obtained.
Various properties of the optical glass were measured by the methods described below.

(1) Refractive indices nd, ng, nF, nC and Abbe number νd
The refractive index nd, ng, nF, nC and Abbe number νd of the glass obtained by cooling at a cooling rate of −30° C./hour were measured by the refractive index measuring method specified by the Japan Optical Glass Industry Association.
Also, in FIG. 1, the Abbe number νd and the refractive index nd of each optical glass are plotted.

(2) Deviation ΔPg,F from normal line of partial dispersion ratio Pg,F and Pg,F
The partial dispersion ratio Pg,F was calculated from the refractive indices ng, nF, and nC, and the deviation ΔPg,F from the partial dispersion ratio Pg,F(0) on the normal line calculated from the Abbe number νd was calculated.
Table 1 shows Pg,F and ΔPg,F calculated from the refractive index nd, Abbe number νd, ng, nF, and nC.
Also, in FIG. 2, the Abbe number νd and the partial dispersion ratio Pg, F of each optical glass are plotted.

(3) glass transition temperature Tg
A differential scanning calorimeter (DSC3300) manufactured by NETZSCH was used to measure the glass transition temperature Tg at a heating rate of 10°C/min.

(4) Liquidus temperature LT
50 g of glass was placed in a platinum crucible, and after melting at 1100° C. for 20 minutes with a platinum lid, the glass was held at a predetermined temperature for 2 hours. After holding for 2 hours, the glass was observed, and the liquidus temperature LT was obtained from the presence or absence of crystal precipitation.
For each glass shown in Table 1, the glass was held at 850° C. for 2 hours by the above method, and then visually observed and magnified observation (100×) using an optical microscope was performed. As a result, precipitation of crystals was not observed.
Therefore, the liquidus temperature LT of each glass shown in Table 1 is 850° C. or less.

(5) Specific Gravity Specific gravity was measured by the Archimedes method.

(6) Evaluation of volatilization loss during melting A glass batch (yield: 150 to 200 g) was filled into a platinum crucible, covered with a platinum lid, mass X was measured, and then melted at 1050°C for 1.5 hours. Then, immediately before casting the glass melt into the mold, the mass Y of the platinum crucible containing the glass melt and covered with a platinum lid was measured again to obtain the mass change rate (XY)/X. . If a glass batch is prepared so that the yield will be 150 g, X will be 150 g, and if a glass batch is prepared so that the yield will be 200 g, X will be 200 g.
If the glass batch contains carbonates, the _CO2 in the carbonates is expelled during melting. If the glass batch contains sulfates, nitrates, hydroxides, SO3 _, NO2, _{H2O are} emitted during melting.
The mass of gas components such as CO ₂ , SO ₃ , NO ₂ and H ₂ O contained in the glass batch is calculated in advance, and the glass is added so that the mass X is the value obtained by subtracting the mass of the gas components from the mass of the glass batch. A batch should be prepared.
In Table 1, A indicates that the mass change rate is 2% or less, B indicates that the mass change rate is more than 2% and 4% or less, and C indicates that the mass change rate is more than 4%.
In addition, when the internal transmittance at a thickness of 10 mm was measured for each glass of the examples shown in Table 1 according to the internal transmittance measurement (JOGIS-17) of the Japan Optical Glass Industry Association standard, all the samples had a transmittance of 96.0 mm. It had a transmittance of 50% or more.

(7) D _NaOH
A disk-shaped glass sample with a diameter of 43.7 mm and a thickness of 5 mm (two surfaces are polished face-to-face) was placed in sufficiently stirred sodium hydroxide (NaOH) having a liquid temperature of 50°C and a concentration of 0.01 mol/l. D _NaOH was obtained by dividing the amount of mass loss before and after the immersion by the surface area of the glass sample.

(8) _DA
A mass (g) of powdered glass (particle size: 425 μm to 600 μm) corresponding to the specific gravity is placed in a platinum basket, which is immersed in 80 ml of an aqueous nitric acid solution having a concentration of 0.01 mol/l in a quartz glass round-bottomed flask, and placed in a boiling water bath. was treated for 60 minutes, and the percentage of the value obtained by dividing the mass reduction amount of the powdered glass before and after the treatment by the mass of the powdered glass before immersion was defined as _DA .

(9) _DSTPP
A disc-shaped glass sample with a diameter of 43.7 mm and a thickness of 5 mm was immersed in a sufficiently stirred aqueous solution of sodium tripolyphosphate (Na ₅ P ₃ O ₁₀ ) having a liquid temperature of 50° C. and a concentration of 0.01 mol/l for 1 hour. D _STPP was obtained by dividing the amount of mass loss before and after immersion by the surface area of the glass sample and the immersion time.

(10) _D0
A disk-shaped glass sample, 43.7 mm in diameter and 5 mm in thickness, was circulated through an ion exchange resin at a rate of 1 liter per minute, maintained at a water temperature of 50° C. and a pH of 7.0±0.2, The sample was immersed in sufficiently stirred pure water for 45 hours, and _D0 was obtained by dividing the difference in mass before and after immersion by the unit surface area of the glass sample and the immersion time.

(Comparative example 1)
A glass having the composition of Comparative Example 1 shown in Table 1 was prepared, and the refractive index nd, Abbe number νd, partial dispersion ratio Pg, F, glass transition temperature Tg, specific gravity, and volatilization loss during melting were evaluated by the above methods. bottom. Comparative Example 1 is a glass of a comparative example related to Optical Glass 1, and when the amount of volatilization reduction during melting was evaluated, the mass change rate was greater than 4% (evaluation result C).

(Comparative example 2)
A glass having the composition of Comparative Example 2 shown in Table 1 was produced, and the refractive index nd, Abbe number νd, partial dispersion ratio Pg, F, glass transition temperature Tg, specific gravity, volatilization loss during melting, and D _NaOH were evaluated. . Table 1 shows the evaluation results. Comparative Example 2 is a comparative example glass related to Optical Glass 2, in which D _NaOH is greater than 0.25 mg/(cm ² ·15 h) and does not satisfy the formula (4).

The above results are shown in Table 1 (Tables 1-1 to 1-7).

The glass compositions expressed in atomic % of the examples in Table 1 are shown in Table 2 (Tables 2-1 to 2-3).

(Example 2)
Using each optical glass of Example 1, a lens blank was produced by the known method described above. The produced lens blanks were ground and polished to produce various lenses (biconvex lens, convex meniscus lens, concave meniscus lens, biconcave lens, planoconvex lens, planoconcave lens).
Both lenses are lightweight and suitable for high-order chromatic aberration correction.

Finally, each aspect described above is summarized.

According to one embodiment, P ⁵⁺ , Al ³⁺ , Nb ⁵⁺ , O ²⁻ and F ⁻ are included as essential components, and the molar ratio of the Al ³⁺ content to the P ⁵⁺ content (Al ³⁺ /P ⁵⁺ ) is 0.30 or more, the content of Nb ⁵⁺ is 1.0 cation % or more, the content of O ²⁻ is 10-85 anion %, the content of F ⁻ is 15-90 anion %, the sum of P ⁵⁺ and Nb ⁵⁺ Optical glass 1 is provided in which the molar ratio of the content of O ²⁻ to the content (O ²⁻ /(P ⁵⁺ +Nb ⁵⁺ )) is 3.0 or more.

In one aspect, the optical glass 1 contains at least one alkaline earth metal component selected from the group consisting of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ , and the total of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ The content can be 20 cation % or more.

In one aspect, the optical glass 1 may have a P ⁵⁺ content of 5 to 40 cation % and an Al ³⁺ content of 5 to 30 cation %.

In one aspect, the optical glass 1 may have a molar ratio (O ²⁻ /(P ⁵⁺ +Nb ⁵⁺ )) of 4.0 or less.

In one aspect, the optical glass 1 can contain at least one rare earth component selected from the group consisting of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ , ^and La ³⁺ , Gd The molar ratio ((La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ )/Al ³⁺ ) of the total content of ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ (La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ ) is 0.3 can be:

According to one aspect, the optical glass made of fluorophosphate glass has a mass reduction amount per unit area D _NaOH of less than 0.25 mg/(cm ² ·15 h) when immersed in an aqueous NaOH solution for 15 hours. , and the Abbe number νd and the partial dispersion ratio Pg, F satisfy the above formula (4).

According to one aspect, the optical glass 2 can have a _DA of less than 0.35%.

According to one aspect, the optical glass 2 can have a D _STPP of less than 0.40 mg/(cm ² ·h).

According to one aspect, the optical glass 2 can have a D ₀ of less than 5.0×10 ⁻³ mg / (cm ² ·h).

According to one aspect, the optical glass 2 can contain Nb ⁵⁺ .

According to one aspect, the optical glass 2 can contain 1.0% or more of Nb ⁵⁺ .

According to one aspect, the Nb ⁵⁺ content of the optical glass 2 can be 15% or less.

According to one aspect, the total content of Al ³⁺ and Nb ⁵⁺ in the optical glass 2 can be 10% or more.

According to one aspect, the P ⁵⁺ content of the optical glass can be 5-40%.

According to one aspect, the optical glass 2 may have an Al ³⁺ content of 5 to 40%.

According to one aspect, the Mg ²⁺ content of the optical glass 2 can be 0-10%.

According to one aspect, the Ca ²⁺ content of the optical glass 2 can be between 0 and 20%.

According to one aspect, the Sr ²⁺ content of the optical glass 2 can be 0-40%.

According to one aspect, the content of Ba ²⁺ in the optical glass 2 can be 5-40%.

According to one aspect, the La ³⁺ content of the optical glass 2 can be 0-5%.

According to one aspect, the Gd ³⁺ content of the optical glass 2 can be 0-5%.

According to one aspect, the Y ³⁺ content of the optical glass 2 can be 0-5%.

According to one aspect, the Lu ³⁺ content of the optical glass 2 can be 0-5%.

According to one aspect, the molar ratio of the content of Yb ³⁺ to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ in the optical glass 2 (Yb ³⁺ /(La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ )) can be less than or equal to 0.5.

According to one aspect, the Zn ²⁺ content of the optical glass 2 can be 0-10%.

According to one aspect, the total content of alkali metal components in the optical glass 2 can be 0-30%.

According to one aspect, the Rb ⁺ content of the optical glass 2 can be 0-1%.

According to one aspect, the Cs ⁺ content of the optical glass 2 can be 0-1%.

According to one aspect, the Li ⁺ content of the optical glass 2 can be between 0 and 30%.

According to one aspect, the Li ⁺ content of the optical glass 2 can be 2% or more.

According to one aspect, the Li ⁺ content of the optical glass 2 can be between 4 and 10%.

According to one aspect, the Na ⁺ content of the optical glass 2 can be 0-10%.

According to one aspect, the K 2 ⁺ content of the optical glass 2 can be 0-10%.

According to one aspect, the Si ⁴⁺ content of the optical glass 2 can be between 0 and 5%.

According to one aspect, the ^B3+ content of the optical glass 2 can be 2% or less.

According to one aspect, the Cl 2 ⁻ content of the optical glass 2 can be 0-1%.

According to one aspect, the total content of Sb ³⁺ and Ce ⁴⁺ in the optical glass 2 can be 0% or more and can be less than 1%.

According to one aspect, the optical glass 2 can be substantially free of at least one of Pb, Cd, As and Th.

According to one aspect, the optical glass 2 can be substantially free of at least one of Cu, Co, Ni, Fe, Cr, Eu, Nd, Er and V.

According to one aspect, the optical glass 2 can be substantially free of at least one of Hf, Ga, Ge, Te and Tb.

According to one aspect, the Abbe number νd of the optical glass 2 can be 45 or more.

According to one aspect, the Abbe number νd of the optical glass 2 can be 80 or less.

According to one aspect, the optical glass 2 can satisfy the following formula (2) with respect to the refractive index nd and the Abbe number νd.
nd≧1.80653−0.00459×νd (2)

According to one aspect, the optical glass 2 can satisfy the following formula (3) with respect to the refractive index nd and the Abbe number νd.
nd≧1.84303−0.00459×νd (3)

According to one aspect, the optical glass 2 can have an internal transmittance of 96.5% or more at a wavelength of 400 nm to 700 nm and a thickness of 10 mm.

According to one aspect, the glass transition temperature Tg of the optical glass 2 can be 550° C. or less.

According to one aspect, the liquidus temperature of the optical glass 2 can be 850° C. or lower.

According to one aspect, the specific gravity of the optical glass 2 can be 4.2 or less.

According to still another aspect, an optical element comprising the optical glass 1 or the optical glass 2 is provided.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.
For example, the glass according to one aspect of the present invention can be obtained by adjusting the composition described in the specification with respect to the glass compositions exemplified above.
In addition, it is of course possible to arbitrarily combine two or more of the matters described as examples or preferred ranges in the specification.

Claims (8)

An optical glass made of fluorophosphate glass,
The content of P ⁵⁺ is 5 to 40 cationic %,
Al ³⁺ content is 5 to 40 cation%,
The content of Nb ⁵⁺ is 1.0 cation % or more,
The content of O ^2- is 20 to 75 anion%,
The content of F ⁻ is 25 to 80 anion%,
the molar ratio (O ²⁻ /(P ⁵⁺ +Nb ⁵⁺ )) is 3.0 to 4.0;
In the glass composition expressed in atomic %, the ratio of the O ²⁻ content to the Al ³⁺ content (O ²⁻ /Al ³⁺ ) is less than 10,
The mass reduction amount D _NaOH per unit area when immersed in an aqueous NaOH solution for 15 hours is less than 0.25 mg/(cm ² · 15 h), and the Abbe number νd and the partial dispersion ratio Pg, F are the following (4 )formula:
Pg,F>−0.0004νd+0.5718 (4)
optical glass that satisfies The optical glass according to claim 1, comprising 10 cation % or more of Al ³⁺ and Nb ⁵⁺ in total. Contains at least one alkaline earth metal component selected from the group consisting of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ , and the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 20 cation % or more The optical glass according to claim 1 or 2. At least one rare earth component selected from the group consisting of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ , and the sum of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ with respect to the content of Al ³⁺ The optical glass according to any one of claims 1 to 3 , wherein the content molar ratio ((La ³⁺ +Gd ³⁺ +Y ³⁺ +Lu ³⁺ +Yb ³⁺ )/Al ³⁺ ) is 0.3 or less. 5. The optical glass according to claim 1 , wherein the content of the alkali metal component is 1 cation % or more and the content of Li ⁺ is 20 cation % or less. The optical glass according to any one of claims 1 to 5 , which has an Abbe number νd of 45 or more. (1) to (4) below:
(1) an internal transmittance of 96.5% or more at a wavelength of 400 nm to 700 nm and a thickness of 10 mm;
(2) D _A is less than 0.35%,
(3) D _STPP is less than 0.40 mg/(cm ² ·h),
(4) D ₀ is less than 5.0×10 ⁻³ mg/(cm ² ·h);
The optical glass according to any one of claims 1 to 6 , which satisfies at least one of An optical element comprising the optical glass according to any one of claims 1 to 7 .

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