JP2020015662A - Optical glass and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical glass having a large partial dispersion ratio and suitable for chromatic aberration correction while reducing the volatility of borosilicate glass in a high temperature process. SOLUTION: The essential components include P5 +, Al3 +, Nb5 +, O2- and F-, and the molar ratio (Al3 + / P5 +) of the Al3 + content to the P5 + content is 0.30 or more, and the content of Nb5 + is 0.30 or more. 1.0 Cation% or more, O2- content 10-85 anion%, F- content 15-90 anion%, molar ratio of O2- content to total P5 + and Nb5 + content (O2- / (P5 ++ Nb5 +)) is 3.0 or more. [Selection diagram] None

Description

  The present invention relates to an optical glass and an optical element.

A fluorophosphate glass containing phosphorus, oxygen and fluorine is known as an optical glass having a low dispersion and a positive anomalous dispersion.
Since the fluorophosphate glass has the above-mentioned excellent optical characteristics, it is highly useful as an optical element material for correcting high-order chromatic aberration.
Examples of such a fluorophosphate glass are described in Patent Documents 1 to 4.

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

  As described above, the fluorophosphate glass has excellent optical properties, but exhibits remarkable volatility in a high-temperature process for melting and molding the glass. The occurrence of volatilization from the glass melt during the melting and molding steps can cause phenomena such as deterioration of glass, fluctuation of optical characteristics, and deterioration of homogeneity of glass.

Further, in the process of grinding and polishing a glass material made of optical glass to produce an optical element such as a lens or a prism, the polished glass is usually washed. On the other hand, on the surface of the polished glass, there are minute scratches, which are generally called latent scratches and cannot be visually recognized. However, when the surface of the glass is eroded by the cleaning, the latent scratches are enlarged and become apparent and become a light scattering source, and the surface quality of the glass may be deteriorated. Further, the surface quality of the glass may be deteriorated due to the deterioration of the glass surface due to the cleaning.
It is desirable to increase the chemical durability of the fluorophosphate glass in order to suppress the deterioration of the surface quality of the fluorophosphate glass as described above.

  One embodiment of the present invention is to provide an optical glass having a large partial dispersion ratio and suitable for correcting chromatic aberration while reducing the volatility of a fluorophosphate glass in a high-temperature process, and to provide an optical element including the optical glass. With the goal.

  Another embodiment of the present invention is to provide an optical glass made of fluorophosphate glass having excellent chemical durability, and having a large partial dispersion ratio, which is suitable for correcting chromatic aberration. It is an object to provide an optical element.

One embodiment of the present invention provides
^Containing P ⁵⁺ , Al ³⁺ , Nb ⁵⁺ , O ²⁻ and F ⁻ as essential components,
The molar ratio of the content of ^{Al 3+} with respect to the content of ^{P 5+ (Al 3+ / P 5+} ) of 0.30 or more,
The content of Nb ⁵⁺ is 1.0 cation% or more;
O2 ^- content of 10 to 85 anion%,
F ^- content is 15 to 90 anionic%,
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”),
About.

The optical glass preferably has a positive anomalous dispersion.
The partial dispersion ratio Pg, F is used as an index of positive anomalous dispersion. The partial dispersion ratio Pg, F is calculated using 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 an ultraviolet region close to a visible region and further has a large absorption intensity. Thereby, the wavelength dispersion of the refractive index tends to increase. That is, the refractive index difference nF-nC between the F line and the C line increases, 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, F increases as is apparent from equation (1).
The present inventors have paid attention to this point, and introduced Nb as a glass component to maintain the low dispersion (large νd) in the same range as that of the conventional fluorophosphate glass while maintaining the partial dispersion ratio Pg, It has been found that F can be greatly increased.
However, Nb-containing fluorophosphate glass tends to volatilize Nb from the glass melt during the melting process. When Nb and F combine in the melting process, niobium fluoride is generated. Niobium fluoride has a high vapor pressure and tends to volatilize from the glass melt.
The present inventors have conducted intensive studies in order to prevent Nb introduced to increase the partial dispersion ratio from promoting volatilization, and as a result, have obtained the following knowledge.
P ⁵⁺ is present in the glass in a structure of —O—P—O— and is considered to contribute to the network formation of the glass. It is considered that Nb ⁵⁺ having the same valence as P ⁵⁺ also contributes to glass network formation by occupying the position of P in the —O—P—O— structure.
When Nb ⁵⁺ is taken into the network structure, it is considered that niobium fluoride having a high vapor pressure is hardly generated, and as a result, the volatility of the glass is reduced.
However, a sufficient number of ^O2- is required for ^{Nb5 +} to be incorporated into the network structure. Considering the case where Nb ⁵⁺ is present, 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 When the value is 3.0 or more, Nb ⁵⁺ is easily taken into the network, so that an increase in volatility can be suppressed.
The present inventors have completed the above-described optical glass according to one embodiment of the present invention based on the above findings.

Another aspect of the present invention,
An optical glass made of fluorophosphate glass,
The mass reduction per unit area D _NaOH 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 ratios Pg and F are as follows (4) )formula:
Pg, F> −0.0004νd + 0.5718 (4)
(Hereinafter, also referred to as “optical glass 2”),
About.

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

The optical characteristics of the optical glass of the example in the Abbe number νd-refractive index nd chart are shown. In the Abbe number νd-partial dispersion ratio Pg, F chart, the optical characteristics of the optical glass of the example and the optical characteristics of the existing optical glass are shown.

In the present invention and the present specification, the content and the total content of the cation component are indicated by cation% unless otherwise specified, and the content and the total content of the anion component are indicated by unspecified anion%.
Here, “cation%” is a value calculated by “(number of cations of interest / total number of cations in glass component) × 100”, and the molar percentage of the amount of cation of interest to the total amount of cation components is means.
Further, “anion%” is a value calculated by “(number of anions of interest / total number of anions of glass component) × 100”, and means a molar percentage of the amount of anions of interest to the total amount of anion components. I 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 in terms of cation%, and the molar ratio of the contents of the anion components of interest is the ratio of the contents of the anion components of interest in anion%. Equal to the ratio.
The molar ratio between the content of the cation component and the content of the anion component is the ratio of the content (in mol%) of the components of interest when the total amount of all the cation components and all the anion components is 100 mol%. is there.
The content of each component can be determined by a known method, for example, inductively coupled plasma emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography, or the like. .

  In the present invention and the present specification, “fluorophosphate glass” refers to a glass containing at least phosphorus, oxygen and fluorine as elements constituting the glass.

[Optical glass 1]
<Glass component>
Hereinafter, the optical glass 1 according to one embodiment of the present invention will be described.
P ⁵⁺ has a function as a network forming component. Al ³⁺ is a component that serves to maintain the thermal stability of the glass and improve the chemical durability and workability. The thermal stability of the glass from the top to maintain ^good, the molar ratio of the content of ^{Al 3+} with respect to the content of ^{P 5+ (Al 3+ / P 5+} ) is 0.30 or more. 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 preferred lower limit of the molar ratio (Al ³⁺ / P ⁵⁺ ) is 0.5. On the other hand, a preferable upper limit of the molar ratio (Al ³⁺ / P ⁵⁺ ) is 2 and a more preferable upper limit is 1 from the viewpoint of maintaining good thermal stability of the glass.

Nb ⁵⁺ functions to maintain the thermal stability of the glass as a network-forming component together with P ⁵⁺ , and to increase the partial dispersion ratio. In order to obtain such an effect, the content of Nb ⁵⁺ is 1.0% or more. A preferred lower limit of the Nb ⁵⁺ content is 1.5%, a more preferred lower limit is 2%, a still more preferred lower limit is 2.5%, and a still more preferred lower limit is 3%. On the other hand, when the content of Nb ⁵⁺ is excessive, the volatility during melting of the glass becomes remarkable, and the homogeneity of the glass tends to decrease. Therefore, the preferable upper limit of the content of Nb ⁵⁺ is 15%, the more preferable upper limit is 13%, and the more preferable 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 of 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 a function, the content of O ²⁻ is 10 anion% or more. When the content of O ²⁻ is more than 85 anion%, the content of F ⁻ becomes insufficient and it becomes difficult to obtain low dispersibility. Therefore, the content of O ²⁻ is 10 to 85 anion%. A preferable lower limit of the content of O ²⁻ is 20%, a more preferable lower limit is 30%, a preferable upper limit is 80%, a more preferable upper limit is 75%, a further preferable upper limit is 70.93%, and a more preferable upper limit is 70%. It is.

F ⁻ has a function of lowering the glass dispersion and imparting anomalous dispersibility, a function of lowering the glass transition temperature, and a function of improving the chemical durability. When the content of F ⁻ is less than 15 anion%, it is difficult to obtain the above effects. On the other hand, when the content of F ⁻ exceeds 90 anion%, it becomes difficult to maintain the thermal stability of the glass. 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 viewpoint, the content of F ⁻ is 15 to 90 anion%. A preferred lower limit of the content of F ⁻ is 20%, a more preferred lower limit is 25%, a still more preferred lower limit is 28.86%, a still more preferred lower limit is 30%, a preferred upper limit is 80%, and a more preferred upper limit. Is 70%.

As described above, from the top to reduce the volatility increases from the glass melt due to the introduction of ^{Nb 5+,} the molar ratio of ^{P 5+} and ^{Nb O 2-content} to the total content of ^{5+ (O} 2- / ⁽ P ⁵⁺ + Nb ⁵⁺ )) is 3.0 or more. A preferred lower limit of the molar ratio ^{(O 2- / (P 5+ +} Nb 5+)) is 3.2. From maintaining the thermal stability of the glass, the preferred upper limit of the molar ratio ^{(O 2- / (P 5+ +} Nb 5+)) is 4.0, a 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 function to adjust the viscosity and refractive index of glass and improve thermal stability. In order to obtain the above effect, the total content of alkaline earth metal components R ²⁺ (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ ) is preferably at least 20 cation%, more preferably at least 30%, and more preferably at least 30%. % Is more preferable.
On the other hand, if the total content R ²⁺ of the alkaline earth metal component is excessive, the thermal stability tends to decrease. Therefore, the total content R ²⁺ of the alkaline earth metal component is preferably 50% or less. A more preferred upper limit of R ²⁺ is 45%, and a ^still more preferred upper limit is 40%.

The optical glass may include at least one rare earth component selected from the group consisting of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ .
In order to suppress the increase in the specific gravity of the glass and reduce the dispersion for a given refractive index, the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ (La ³⁺ ) with respect to the Al ³⁺ content. The molar ratio of (+ Gd ³⁺ + Y ³⁺ + Lu ³⁺ + Yb ³⁺ ) ((La ³⁺ + Gd ³⁺ + Y ³⁺ + Lu ³⁺ + Yb ³⁺ ) / Al ³⁺ ) is preferably 0.3 or less. The more preferable upper limit of the molar ratio ((La ³⁺ + Gd ³⁺ + Y ³⁺ + Lu ³⁺ + Yb ³⁺ ) / Al ³⁺ ) is 0.2, and the more preferable upper limit is 0.1. The molar ratio ((La ³⁺ + Gd ³⁺ + Y ³⁺ + Lu ³⁺ + Yb ³⁺ ) / Al ³⁺ ) may be 0.

  Next, the content of each component will be described.

P ⁵⁺ is an essential component for forming a glass network. From the viewpoint of maintaining good thermal stability, the preferable lower limit of the content of P ⁵⁺ is 5%, the more preferable lower limit is 10%, and the more preferable lower limit is 20%. From the viewpoint of maintaining good chemical durability and maintaining low dispersibility and abnormal partial dispersibility, the upper limit of the P ⁵⁺ content is preferably 40%, more preferably 38%, and still more preferably 35%. .

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

In the glass composition represented by atomic%, the ratio ^O 2- / ^{Al 3+} of ^{O 2-} content to the content of ^{Al 3+} is preferably less than 12, more preferably less than 10, 8 More preferably, it is less than. When the content of O ²⁻ increases, the content of F ⁻ relatively decreases, and the glass transition temperature tends to increase. On the other hand, Al ³⁺ is a component useful for improving thermal stability, chemical durability and workability, and having desired optical properties, as described above. In order to sufficiently obtain the effect of Al ³⁺ and suppress the increase in the glass transition temperature, 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 in the above range. The lower limit of the above ratio O ²⁻ / Al ³⁺ is, for example, 2 or more or 3 or more from the viewpoint of suppressing a decrease in devitrification resistance due to a relative increase in the content of Al ^3+. be able to.
In addition, the content of each component in the glass composition represented by atomic% is a value which represents the content of each component in terms of mole percentage when the total content of all cation components and all anion components is 100 mol%. Is calculated.

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

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

Yb ³⁺ has light absorption in the infrared region, and therefore is not preferable for use in imaging with infrared light. Accordingly, the content of ^{Yb 3+} is preferably limited as follows using the molar ratio of the total content of other rare earth components ^{(Yb 3+ / (La 3+ +} Gd 3+ + Y 3+ + Lu 3+ + Yb 3+)) . ^{That, La 3+, Gd 3+, Y} 3+, the molar ratio of the content of ^{Yb 3+} to the total content of ^{Lu 3+} and ^{Yb 3+} and ^{(Yb 3+ / (La 3+ +} Gd 3+ + Y 3+ + Lu 3+ + Yb 3+)) 0.5 It is preferably at most 0.1, more preferably at most 0.1, even more preferably 0 (the Yb ³⁺ content is 0%).

Zn ²⁺ has a function of improving the thermal stability while maintaining the refractive index. However, when Zn ²⁺ is contained excessively, the dispersion becomes high, and it becomes difficult to obtain required optical characteristics. Therefore, it is preferable that the content of Zn ^{2+ be} in the range of 0 to 10%. In order to obtain the above effect, the more preferable upper limit of the content of Zn ²⁺ is 8%, and the more preferable upper limit is 5%. The content of Zn ²⁺ may be 0%.

The alkali metal component is a cation component having a function of adjusting the viscosity of glass and improving thermal stability. If the total content R ⁺ of the alkali metal components is excessive, the thermal stability decreases. Therefore, the preferable range of the total content R ⁺ of the alkali metal component is 0 to 30%. From the above viewpoint, the more preferable range of R ⁺ is 0 to 20%, and the further preferable range is 0 to 15%. The upper limit for R ⁺ is more preferably 10%, even more preferably 8%, and even more preferably 7%. When the total content R ⁺ of the alkali metal component is excessive, the values of D _STPP and D ₀ described later tend to increase. Therefore, from the viewpoint of imparting excellent chemical durability to the glass, it is preferable that R ^{+ be} in the above range.
On the other hand, from the viewpoint of lowering the glass transition temperature, a preferable lower limit of R ⁺ is 1%, a more preferable lower limit is 2%, and a still more preferable lower limit is 3%.
Examples of the alkali metal component R ⁺ include Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ . Rb ⁺ and Cs ⁺ tend to cause an increase in the specific gravity of glass as compared with other alkali metal components.
Therefore, the content of Rb ⁺ is preferably 0 to 3%, more preferably 0 to 2%, further preferably 0 to 1%, and may be 0%.
The content of Cs ⁺ is preferably 0 to 3%, more preferably 0 to 2%, further preferably 0 to 1%, and may be 0%.
From the viewpoint of maintaining the thermal stability of the glass, a preferable range of the Li ⁺ content is 0 to 30%, a more preferable range is 2 to 20%, and a further preferable range is 4 to 10%.
From the viewpoint of maintaining the thermal stability of the glass, the preferable range of the Na ⁺ content is 0 to 10%, a more preferable range is 0 to 8%, and a further preferable range is 0 to 6%.
From the viewpoint of maintaining the thermal stability of the glass, the preferable range of the content of K ⁺ is 0 to 10%, a more preferable range is 0 to 8%, and a further preferable range is 0 to 6%.

Si ⁴⁺ can be contained in a small amount, but if it is contained excessively, the meltability and thermal stability decrease. Therefore, the content of Si ⁴⁺ is preferably in the range of 0 to 5%, more preferably in the range of 0 to 3%, further preferably in the range of 0 to 1%, and even when it is 0%. Good.

B ³⁺ shows significant volatility even in small amounts. In order not to promote volatilization, the content of B ³⁺ is preferably set to 2% or less. The preferable range of the B ³⁺ content is 0 to 1%, the more preferable range is 0 to 0.1%, and further preferably 0%.

When exiting the molten glass from the pipe attached to a glass melting apparatus, suppresses wetting of the glass melt to the pipe periphery, in order to suppress the quality degradation of the glass by wetting, Cl ^- be contained Is valid. A preferred range of the Cl ⁻ content is 0 to 1%, a more preferred range is 0 to 0.5%, and a 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 fining agent. The total amount of fining agent can be greater than or equal to 0% and preferably less than 1%. For example, the total content of Sb ³⁺ and Ce ⁴⁺ can be 0% or more, and is preferably less than 1%.

Pb, Cd, As, and Th are components of which environmental load is a concern.
Therefore, it is preferable that the optical glass 1 does not substantially contain at least one of Pb, Cd, As, and Th.
Preferably the content of Pb ²⁺ is 0 to 0.5%, more preferably 0 to 0.1%, yet more preferably from 0 to 0.05%, substantially the ^{Pb 2+} It is particularly preferred that they are not included.
Preferably the content of Cd ²⁺ is 0 to 0.5%, more preferably 0 to 0.1%, yet more preferably from 0 to 0.05%, substantially the ^{Cd 2+} It is particularly preferred that they are not included.
Preferably the content of As ³⁺ is 0 to 0.1%, more preferably from 0 to 0.05%, more preferably 0 to 0.01% substantially the ^{As 3+} It is particularly preferred that they are not included.
Preferably the content of Th ⁴⁺ is 0 to 0.1%, more preferably from 0 to 0.05%, more preferably 0 to 0.01% substantially the ^{Th 4+} It is particularly preferred that they are not included.

The optical glass 1 can preferably exhibit high transmittance over a wide range of the visible region. To take advantage of these features, the optical glass preferably does not contain a coloring agent. Examples of the coloring agent include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, and V. It is preferable that the optical glass 1 does not substantially contain at least one of Cu, Co, Ni, Fe, Cr, Eu, Nd, Er and V. The range of the contents 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, for any of the elements. , And more preferably 0 to 50 ppm or less, particularly preferably substantially not contained. Here, ppm means cation ppm.
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 range of the content of Hf, Ga, Ge, Te, and Tb in terms of cation% is preferably 0 to 0.1%, more preferably 0 to 0.05%, for all elements. The content is further preferably 0 to 0.01%, more preferably 0 to 0.005%, still more preferably 0 to 0.001%, and particularly preferably substantially no content. .
The optical glass can exhibit various characteristics without introducing Hf, Ga, Ge, Te, and Tb.

<Glass properties>
(Abbe number νd, refractive index nd)
In the optical glass 1, it is preferable that the Abbe number νd is in the range of 45 or more from the viewpoint of taking advantage of the abnormal partial dispersion.
The Abbe number νd is a value representing a property related to dispersion, and is expressed as νd = (nd−1) / (nF−nC) using respective refractive indexes nd, nF, and nC at d-line, F-line, and C-line. .
A preferred upper limit of the Abbe number νd is 80, and a more preferred upper limit is 70. On the other hand, in order to make use of the low dispersibility, a preferred lower limit of the Abbe number νd is 45, a more preferred lower limit is 50, and a still more preferred lower limit is 55.

Further, by setting the refractive index nd within the following range, the absolute value of the curvature of the optically functional surface of the lens can be reduced (the curve of the optically functional surface of the lens can be reduced) while maintaining the same light-collecting power. it can. Regardless of precision press molding, grinding, or polishing, it is easier to manufacture a lens with a gentle curve of the optical function surface, and thus the productivity of the optical element can be increased by using a glass with a high refractive index. Further, by increasing the refractive index, it is possible to provide a glass material suitable for an optical element used for a high-performance, compact optical system.
In the optical glass 1, a preferable range of the refractive index nd is a range satisfying the following formula (2), and a more preferable range of the refractive index nd is a range satisfying the following formula (3).
nd ≧ 1.80653-0.00459 × νd (2)
nd ≧ 1.84303−0.00459 × νd (3)

FIG. 1 illustrates equations in the case where the equal signs are satisfied in the equations (2) and (3).
The optical glass 1 preferably exhibits a positive anomalous dispersion. The anomalous dispersibility is quantitatively represented by ΔPg, F. Using the refractive indices ng, nF, and nC at the g-line, the F-line, and the C-line, the partial dispersion ratio Pg, F is calculated using the equation (1) shown above (Pg, F = (ng-nF) / (nF -NC)).
As commercially available low-dispersion glass having an Abbe number νd of 45 or more, HOYA FCD100, FCD515, and the like are known.
In a graph in which the horizontal axis is Abbe number νd and the vertical axis is partial dispersion ratio Pg, F, FCD100 is plotted at coordinates (95.1 0.5334) and FCD515 is plotted at coordinates (68.63 0.5441). Then, consider a straight line L connecting the above two points. This straight line L is approximately expressed as “Pg, F = −0.0004νd + 0.5718”.
FIG. 2 illustrates a straight line L.
As shown in FIG. 2, commercially available low-dispersion glass (existing glass) having an Abbe number νd of 45 or more is higher than the line L or the line L in the graph of Abbe number νd-partial dispersion ratio Pg, F. The partial dispersion ratios Pg, F are located on the smaller side.
In a preferred embodiment, the Abbe number νd and the partial dispersion ratios Pg, F of the optical glass 1 satisfy the following expression (4).
Pg, F> −0.0004νd + 0.5718 (4)
An optical glass having an Abbe number νd of 45 or more and satisfying the above equation (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. is there.

(Transmissivity)
The optical glass 1 preferably has very little coloring, and is suitable as a material for an imaging optical element such as a camera lens or a projection optical element such as a projector.
A preferred embodiment of the optical glass 1 is a 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 more preferable range is 99% or more.
Note that glass containing luminescent ions such as laser glass, for example, glass containing Nd, Eu, Er, V, etc., has an absorption in the visible region, and therefore, an optical element for imaging such as a camera lens or an optical element for projection such as a projector. Not suitable for device 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 lower. When the glass transition temperature is low, the heating temperature at the time of reheating and softening the glass and press-molding the glass can be lowered. As a result, it becomes easier to suppress fusion between the glass and the press mold. In addition, since the heating temperature can be lowered, it is possible to reduce thermal consumption of a glass heating device, a press mold, and the like. Further, since the annealing temperature of the glass 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.

(Liquid phase 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 molding temperatures of the glass can be reduced. As a result, the volatility of the glass at the time of melting and molding can be reduced, and the occurrence of striae and fluctuation of optical characteristics 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 optical glass 1 can increase the partial dispersion ratio mainly by containing Nb ⁵⁺ without depending on the rare earth element which increases the specific gravity but increases the partial dispersion ratio. Specific gravity is small.
A preferred embodiment of the optical glass 1 is an 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 preferred range of the specific gravity is 4.1 or less, and a still more preferred range is 4 or less.

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

<Glass properties>
The optical glass 2 has an Abbe number νd and a partial dispersion ratio Pg, F satisfying the following expression (4).
Pg, F> −0.0004νd + 0.5718 (4)
The optical glass 2 in which the Abbe number νd and the partial dispersion ratios Pg, F satisfy the above equation (4) is suitable as an optical glass for correcting higher-order chromatic aberration.
Further, in the optical glass 2, it is preferable that the Abbe number νd be in a range of 45 or more from the viewpoint of taking advantage of the abnormal partial dispersion. A preferred upper limit of the Abbe number νd is 80, and a more preferred upper limit is 70. On the other hand, in order to utilize low dispersibility, a more preferred lower limit of the Abbe number νd is 50, and a still more preferred lower limit is 55.

<Chemical durability>
(D _NaOH )
The optical glass 2 has chemical durability in which the mass reduction per unit area D _NaOH when immersed in an NaOH aqueous solution for 15 hours is less than 0.25 mg / (cm ² · 15 h).
The mass loss D _NaOH is determined by the following method.
First, a disk-shaped glass sample having a diameter of 43.7 mm and a thickness of 5 mm is prepared. The two opposing surfaces having a diameter of 43.7 mm are polished face-to-face, and the sides are taped with a chemically durable tape (for example, polyimide tape or the like) to the following aqueous solution of sodium hydroxide (NaOH). Masking by the method described above. Therefore, the two surfaces of the disk-shaped glass sample are exposed to the following aqueous solution of sodium hydroxide (NaOH). The total area of these two surfaces (hereinafter referred to as “surface area of glass sample”) is 30 cm ² .
Next, after measuring the mass M _before of the glass sample, the glass sample is immersed in a sufficiently stirred aqueous solution of sodium hydroxide (NaOH) at a liquid temperature of 50 ° C. and a concentration of 0.01 mol / l for 15 hours. The mass M _after of the glass sample is measured. D _NaOH is a value obtained by dividing the mass difference ( _Mbefore - _Mafter ) (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 in the above range, it is possible to suppress the deterioration of the surface quality due to the appearance of latent scratches and the like. From maintaining the high surface _{quality, D NaOH} is preferably less than ^{0.20mg / (cm 2 · 15h)} , more preferably ^{0.10mg / (cm 2 · 15h)} . 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.

(For _{D A)}
The optical glass 2 is preferably provided with a chemical durability D _A is less than 0.35%.
D _A is measured according to the measurement method of the acid resistance weight loss ratio Da as specified by Japanese Optical Glass Industrial Standard JOGIS06-2009. Specifically, the measuring method is as follows.
A glass powder (particle size: 425 μm to 600 μm) having a mass corresponding to the specific gravity (M _before , unit: g) is put in a platinum basket, and immersed in 80 ml of a 0.01 mol / l nitric acid aqueous solution in a quartz glass round bottom flask. Then, the mixture is treated in a boiling water bath for 60 minutes, and the mass M _after (unit: g) of the powdered glass after the treatment is measured. The value ( _Mbefore - _Mafter ) / _Mbefore obtained by dividing the mass difference between the powdered glass before and after the treatment by the mass of the powdered glass before treatment, expressed as a percentage, [( _Mbefore - _Mafter ) / _Mbefore ]. × 100, but a _{D a.} Optical glass having a D _A of the above-mentioned range is suitable as a glass material for an optical element to be mounted on the superior surveillance cameras and in-vehicle cameras installed outdoors acid resistance has been demanded.
The lower limit of the D _A is not particularly limited but can be considered as a guide, for example, more than 0.20%.

(About D _STPP )
The optical glass 2 also preferably has chemical durability such that D _STPP is less than _0.40 mg / (cm ² · h).
The method of measuring D _STPP is as follows.
First, a disk-shaped glass sample having a diameter of 43.7 mm and a thickness of 5 mm is prepared. The two opposing surfaces having a diameter of 43.7 mm are polished face-to-face, and the side faces are formed by applying a chemically durable tape (for example, a polyimide tape or the like) to an aqueous solution of sodium tripolyphosphate described below. Mask it. 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 for 1 hour in a sufficiently stirred aqueous solution of sodium tripolyphosphate (Na ₅ P ₃ O ₁₀ ) at a liquid temperature of 50 ° C. and a concentration of 0.01 mol / l, The mass M _after of the glass sample after immersion is measured. D _STPP is a value obtained by dividing the mass difference ( _Mbefore - _Mafter ) (unit: mg) _{before and after} immersion by the surface area of the glass sample and the immersion time. That is, the value obtained from “(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.
When D _STPP is within the above range, it is possible to further suppress the occurrence of deterioration in surface quality.

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

(D ₀ )
In the above optical glass 2, it is preferable that D ₀ is less than 5.0 × 10 ⁻³ mg / (cm ² · h). D ₀ is sometimes called true chemical durability against water.
Method of measuring the D ₀ is as follows.
First, a disk-shaped glass sample having a diameter of 43.7 mm and a thickness of 5 mm is prepared. The two opposing surfaces having a diameter of 43.7 mm are polished face-to-face, and the side faces are masked by applying a chemically durable tape (for example, polyimide tape or the like) to the following 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 .
Next, after measuring the mass M _before , the glass sample is circulated through the ion exchange resin at a rate of 1 liter per minute, kept at a water temperature of 50 ° C., pH = 7.0 ± 0.2, and sufficiently stirred. Immerse in pure water. The mass M _after of the glass sample after immersion in the pure water for 20 hours or more (preferably 40 hours or more) is measured. Mass difference before and after immersion _{(M before -M after) (Unit:} mg), and the value obtained by dividing the immersion time and the surface area of the glass sample to _{D 0.} That is, _{"(M before -M after) / (} 30 × immersion time (unit: hour))" is a value obtained by a _{D 0.}
By D ₀ is within the above range, a reduction in the surface quality of the glass under cleaning and high humidity environment can be suppressed. Although the lower limit of D ₀ is not particularly limited, it can be considered, for example, 0.4 × 10 ⁻³ mg / (cm ² · h) or more.

<Glass composition>
The optical glass 2 preferably contains Nb ⁵⁺ .
Nb ^5+, along with increasing the partial dispersion ratio has a function of improving the chemical durability, it acts to lower the value of inter alia D _NaOH and D _A. From the viewpoint of obtaining such effects, the preferable range of the Nb ⁵⁺ content is 1.0% or more, a more preferable range is 1.5% or more, a further preferable range is 2% or more, and a more preferable range is 2.5%. As described above, an even more preferable range is 3% or more. Further, by containing Nb ⁵⁺ , an effect of maintaining the thermal stability of the glass can be obtained. From the viewpoint of suppressing the volatility at the time of melting the glass, a preferable upper limit of the content of Nb ⁵⁺ is 15%.

Since both Al ³⁺ and Nb ⁵⁺ contribute to improving the chemical durability, the total content of Al ³⁺ and Nb ⁵⁺ is preferably set to 10% or more from the viewpoint of imparting excellent chemical durability to the glass. It is more preferably at least 12%, further preferably at least 15%. The total content of Al ³⁺ and Nb ⁵⁺ is preferably 45% or less, and more preferably 35% or less, from the viewpoint of maintaining thermal stability.

  As for the glass composition of the other optical glass 2, one or two or more of the various items described above for the optical glass 1 can be applied in any combination. As for the glass composition of the optical glass 1, one or two 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 required characteristics. As a glass raw material, for example, a phosphate, a fluoride, an alkali metal compound, an alkaline earth metal compound, or the like may be used. Known methods may be used for the glass melting method and the molding method.

[Glass material for press molding, method for producing the same, and method for producing glass molded body]
According to one aspect of the present invention, it is possible to provide a glass material for press molding composed of the optical glass 1 or the optical glass 2, a glass molded body composed of the optical glass, and a method for producing them.
The glass material for press molding means a glass lump which is heated and subjected to press molding.
Examples of the glass material for press molding include a preform for precision press molding and a glass lump having a mass corresponding to the mass of a press molded product such as a glass material (glass gob for press molding) for press molding an optical element blank. Can be shown.
The 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 a glass raw material as described above, and molding the obtained molten glass. Examples of the processing method of the glass molded body include cutting, grinding, polishing and the like.

[Optical element blank and manufacturing method thereof]
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. The optical element blank is a glass molded body having a shape similar to the shape of the optical element to be manufactured. The optical element blank may be manufactured 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, the optical element is formed by a method of heating and softening a glass material for press molding and softening to perform press molding (reheat press method), a method of supplying a molten glass lump to a press mold by a known method and performing press molding (direct press method), or the like. A blank can be made.

[Optical element and manufacturing method thereof]
According to one embodiment of the present invention, an optical element including the optical glass 1 or the optical glass 2 can be provided. Examples of the type of the optical element include a lens such as a spherical lens and an aspherical lens, a prism, and a diffraction grating. Examples of the shape of the lens include various shapes such as a biconvex lens, a plano-convex lens, a biconcave lens, a plano-concave lens, a convex meniscus lens, and a concave meniscus lens. The optical element can be manufactured by a method including a step of processing a glass molded body made of the optical glass. Examples of the processing include cutting, cutting, rough grinding, fine grinding, polishing, and the like. When such processing is performed, the use of the above optical glass can reduce breakage, and can stably supply a high-quality optical element.

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

(Example 1)
Using the corresponding phosphates, fluorides, oxides, and the like as the raw materials for introducing each component, the raw materials were weighed and thoroughly mixed to obtain the glass compositions shown in Table 1, and the mixed raw materials were obtained. .
This prepared raw material was placed in a platinum crucible, heated and melted. After melting, pour the molten glass into a mold, allow it to cool to near the glass transition temperature, immediately place it in an annealing furnace, anneal it for about 1 hour in the glass transition temperature range, and allow it 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 magnification by an optical microscope, no crystals were precipitated, no foreign matter such as platinum particles, no bubbles were observed, and no stria was observed.
Table 1 shows the properties of the optical glass thus obtained.
Various properties of the optical glass were measured by the following methods.

(1) Refractive indexes nd, ng, nF, nC and Abbe number νd
The refractive index nd, ng, nF, nC, and Abbe number νd of the glass obtained by lowering the temperature at a temperature lowering rate of −30 ° C./hour were measured by a refractive index measuring method specified by the Japan Optical Glass Industrial Association.
FIG. 1 plots Abbe number νd and refractive index nd of each optical glass.

(2) Partial dispersion ratios Pg, F and deviations ΔPg, F of Pg, F from the normal line
The partial dispersion ratios Pg, F were calculated from the refractive indexes ng, nF, and nC, and the deviations ΔPg, F from the partial dispersion ratios Pg, F (0) on the normal line calculated from the Abbe number νd were calculated.
Table 1 shows the refractive index nd, Abbe number νd, and Pg, F and ΔPg, F calculated from ng, nF, and nC.
FIG. 2 plots the Abbe number νd and the partial dispersion ratios Pg and F of the optical glasses.

(3) Glass transition temperature Tg
Using a differential scanning calorimeter (DSC3300) manufactured by NETZSCH, the glass transition temperature Tg was measured at a heating rate of 10 ° C./min.

(4) Liquid phase temperature LT
50 g of glass was placed in a platinum crucible, melted at 1100 ° C. for 20 minutes with a platinum cover, and then kept at a predetermined temperature for 2 hours. The glass after holding for 2 hours was observed, and the liquidus temperature LT was determined from the presence or absence of crystal precipitation.
For each of the glasses shown in Table 1, the glass was kept at 850 ° C. for 2 hours by the above method, and then, as a result of visual observation and magnification observation (100 ×) using an optical microscope, no crystal precipitation was observed.
Therefore, the liquidus temperature LT of each glass shown in Table 1 is 850 ° C. or less.

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

(6) Evaluation of Amount of Volatilization Reduction During Melting A glass batch (150 to 200 g in yield) was filled in a platinum crucible, covered with platinum, measured for mass X, and then melted at 1050 ° C. for 1.5 hours. Then, immediately before casting the molten glass into a mold, the mass Y of the platinum crucible containing the molten glass therein and covered with the platinum was measured again, and the rate of mass change (XY) / X was determined. . When a glass batch is prepared so that the yield becomes 150 g, X becomes 150 g, and when a glass batch is prepared so that the yield becomes 200 g, X becomes 200 g.
If the glass batch includes a carbonate, CO ₂ in the carbonates are discharged into the melting. If the glass batch includes sulfates, nitrates, _{hydroxides, SO 3, NO 2, H} 2 O is discharged 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 X is obtained by subtracting the mass of the gas component from the mass of the glass batch to obtain the mass X. A batch may be prepared.
In Table 1, those with a mass change rate of 2% or less were A, those with a mass change rate of more than 2% and 4% or less were B, and those with a mass change rate of more than 4% were C.
In addition, about each glass of the Example shown in Table 1, the internal transmittance | permeability in thickness of 10 mm was measured according to the internal transmittance | permeability measurement (JOGIS-17) of the Japan Optical Glass Industry Association standard. It had a transmittance of 50% or more.

(7) D _NaOH
A 43.7 mm diameter, 5 mm thick disk-shaped glass sample (two surfaces polished face-to-face) was stirred at a liquid temperature of 50 ° C. and a concentration of 0.01 mol / l was sufficiently stirred with sodium hydroxide (NaOH). Was immersed in an aqueous solution for 15 hours, and the value obtained by dividing the mass loss before and after immersion by the surface area of the glass sample was defined as _DNaOH .

(8) _{D A}
A glass powder (particle size: 425 μm to 600 μm) having a mass (g) corresponding to the specific gravity is put in a platinum basket, and immersed in 80 ml of a 0.01 mol / l nitric acid aqueous solution in a quartz glass round bottom flask, and placed in a boiling water bath. in for 60 minutes, the percentage of weight divided by the powder glass before immersion of the weight loss of the powder glass before and after the treatment, and the D _a.

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

(10) D ₀
A disk-shaped glass sample having a diameter of 43.7 mm and a thickness of 5 mm was circulated through the ion exchange resin at a rate of 1 liter per minute, and the water temperature was kept at 50 ° C. and pH = 7.0 ± 0.2, well stirred and immersed for 45 hours in pure water and the mass difference before and after immersion divided by the time of immersion and unit surface area of the glass sample value was defined as D _0.

(Comparative Example 1)
Glass having the composition of Comparative Example 1 shown in Table 1 was prepared, and the refractive index nd, Abbe number νd, partial dispersion ratios Pg and F, glass transition temperature Tg, specific gravity, and the amount of volatilization reduction during melting were evaluated by the above method. did. Comparative Example 1 is a glass of a comparative example relating to the optical glass 1, and when the amount of volatilization loss 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 prepared, and the refractive index nd, Abbe number νd, partial dispersion ratio Pg, F, glass transition temperature Tg, specific gravity, amount of volatilization decrease during melting, and D _NaOH were evaluated. . Table 1 shows the evaluation results. Comparative Example 2 is a glass of Comparative Example relating to the optical glass 2, in which D _NaOH was larger than 0.25 mg / (cm ² · 15 h) and did not satisfy the expression (4).

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

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

(Example 2)
Using each of the optical glasses of Example 1 described above, a lens blank was manufactured by the above-described known method. The produced lens blank was ground and polished to produce various lenses (biconvex lens, convex meniscus lens, concave meniscus lens, biconcave lens, plano-convex lens, plano-concave lens).
Each lens is lightweight and is suitable for high-order chromatic aberration correction.

  Finally, each of the above-described embodiments will be summarized.

According to one aspect, as essential ^{components, P 5+, Al 3+, Nb} 5+, O 2- and F ^- wherein ^the molar ratio of the content of ^{Al 3+} with respect to the content of ^{P 5+ (Al 3+ / P 5+} ) is 0.30 or more, Nb ⁵⁺ content is 1.0 cation% or more, O ²⁻ content is 10 to 85 anion%, F ⁻ content is 15 to 90 anion%, total of P ⁵⁺ and Nb ⁵⁺ . The optical glass 1 having a molar ratio of the content of O ^{2− to} the content (O ^{2 −} / (P ⁵⁺ + Nb ⁵⁺ )) of 3.0 or more is provided.

In one embodiment, the optical glass ^1, Mg ^2+, Ca 2+, comprising at least one alkaline earth metal component selected from the group consisting of ^{Sr 2+} and ^{Ba 2+,} the sum of Mg ^2+, Ca 2+, ^{Sr 2+} and ^{Ba 2+} The content can be 20 cation% or more.

In one embodiment, 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 can have a molar ratio (O ^{2 −} / (P ⁵⁺ + Nb ⁵⁺ )) of 4.0 or less.

In one embodiment, 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 with respect to the content of Al ^{3+. 3+,} the total content of ^Y 3+, ^{Lu 3+} and ^{Yb 3+ (La 3+ + Gd 3+} + Y 3+ + Lu 3+ + Yb 3+) molar ratio of ^{((La 3+ + Gd 3+ +} Y 3+ + Lu 3+ + Yb 3+) / Al 3+) is 0.3 It can be:

According to one embodiment, the optical glass is made of fluorophosphate glass, and has a mass reduction 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. In addition, the optical glass 2 is provided in which the Abbe number νd and the partial dispersion ratio Pg, F satisfy the above equation (4).

According to one aspect, the optical glass 2 can be _{D A} is less than 0.35%.

According to one embodiment, the optical glass 2 can have a D _STPP of less than _0.40 mg / (cm ² · h).

According to one embodiment, 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 include Nb ⁵⁺ .

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

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

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

According to one embodiment, the ^{P5 +} content of the optical glass can be 5 to 40%.

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

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

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

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

According to one embodiment, the content of Ba ^{2+ in} the optical glass 2 can be 5 to 40%.

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

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

According to one embodiment, the Y3 ⁺ content of the optical glass 2 can be 0 to 5%.

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

According to one aspect, ^La 3+ of the optical glass ^{2, Gd 3+, Y 3+,} Lu 3+ and the molar ratio of the content of ^{Yb 3+} to the total content of ^{Yb 3+ (Yb 3+ / (La} 3+ + Gd 3+ + Y 3+ + Lu ³ ++ Yb3 ⁺ )) can be equal to or less than 0.5.

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

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

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

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

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

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

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

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

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

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

According to one embodiment, the B ³⁺ content of the optical glass 2 can be 2% or less.

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

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

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

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

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

According to one embodiment, the optical glass 2 can have a refractive index nd and an Abbe number νd satisfying the following expression (2).
nd ≧ 1.80653-0.00459 × νd (2)

According to one embodiment, the optical glass 2 can have a refractive index nd and an Abbe number νd satisfying the following expression (3).
nd ≧ 1.84303−0.00459 × νd (3)

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

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

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

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

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
For example, the glass according to one embodiment of the present invention can be obtained by performing the composition adjustment described in the specification on the above-described glass composition.
In addition, it is of course possible to arbitrarily combine two or more of the items described as examples or preferable ranges in the specification.

Claims (2)

An optical glass made of fluorophosphate glass,
The mass reduction per unit area D _NaOH 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 ratios Pg and F are as follows: )formula:
Pg, F> −0.0004νd + 0.5718 (4)
Meet the optical glass. An optical element comprising the optical glass according to claim 1.