JP7623322B2 - Optical Glass and Optical Elements - Google Patents

Description

The present invention relates to optical glass and optical elements.

For example, Patent Document 1 discloses optical glass with a low glass transition temperature.

WO2003/037813

Glass with a low glass transition temperature can be molded at low temperatures. Being able to mold at low temperatures is preferable because it reduces deterioration of the mold due to heating and allows the use of inexpensive molds with low heat resistance. However, when the inventors investigated optical glasses with low glass transition temperatures, they found that further improvements in thermal stability are desired.

One aspect of the present invention aims to provide an optical glass that has a low glass transition temperature and excellent thermal stability.

One aspect of the present invention is
In the glass composition expressed in cation percentage,
Li ⁺ content is more than 0.0 cation% and not more than 48.0 cation%;
Na ⁺ content is more than 0.0 cation% and not more than 35.0 cation%;
K ⁺ content is more than 0.0 cation% and not more than 30.0 cation%;
the total content of Al ³⁺ and P ⁵⁺ (Al ³⁺ +P ⁵⁺ ) is 38.0 cation % or more and 70.0 cation % or less;
The total content of Li ⁺ , Na ⁺ , K ⁺ and Cs ⁺ is R ⁺ , the total content of Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is R ²⁺ ,
the cation ratio of R ⁺ to the total content of Al3 ⁺ and P5 ⁺ (R ⁺ /( ^Al3 ++P5 ⁺ )) is 0.93 or more;
a cation ratio (Li ⁺ /(R ⁺ +R ²⁺ )) of the Li ⁺ content to the sum of R ⁺ and R ²⁺ is 0.29 or more;
a cation ratio (( ^{Li++ K ++} )/(Al3++P5 ⁺ )) of the total content of Li ⁺ and ^{K+ to} the total content of ^Al3+ and P5+ is 0.56 or more;
the cation ratio of R ²⁺ to the total content of Al ³⁺ and R ²⁺ (R ²⁺ /(Al ³⁺ +R ²⁺ )) is 0.37 or less;
In the glass composition expressed as anion percentage,
^O2- content is 83.0 anion% or less;
The F ^- content is 19.0 anion% or more, and
an optical glass having an external transmittance of 80% or more at wavelengths of 500 nm to 1000 nm when converted into a thickness of 10.0 mm;
Regarding.

The optical glass has the above glass composition, and thus has a low glass transition temperature and excellent thermal stability.

According to one aspect of the present invention, it is possible to provide an optical glass that has a low glass transition temperature and excellent thermal stability. In addition, according to another aspect of the present invention, it is possible to provide an optical element made of such an optical glass.

[Optical glass]
In the present invention and this specification, the content and total content of cationic components are expressed in cationic % unless otherwise specified, and the content and total content of anionic components are expressed in anionic % unless otherwise specified.
Here, "cation %" is a value calculated by "(number of cations of interest/total number of cations in glass components) x 100" and means the molar percentage of the amount of cations of interest relative to the total amount of cationic components.
The term "anion %" refers to a value calculated by (number of anions of interest/total number of anions in glass components) x 100, and means the molar percentage of the amount of the anion of interest relative to the total amount of the anion components.
The molar ratio of the contents of cationic components to each other is equal to the ratio of the contents, expressed as cationic %, of the cationic components in question.
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.
Cationic components are expressed as, for example, Al ³⁺ and P ⁵⁺ , but the valence of the cationic components (for example, the valence of Al ³⁺ is +3, and the valence of P ⁵⁺ is +5) is a value determined by convention, and is the same as Al, P, etc. being expressed as Al ₂ O ₃ , P ₂ O _5, etc. on an oxide basis. For components expressed as A _m O _n (A represents a cation, O represents oxygen, and m and n are stoichiometrically determined integers) on an oxide basis, the cation A is expressed as A ^s+ . Here, s = 2n/m. Therefore, for example, when analyzing and quantifying the glass composition, it is not necessary to analyze the valence of the cationic components. The above points are the same for anionic components, and it is not necessary to analyze the valence of the anionic components when analyzing and quantifying the glass composition.
In the present invention and this specification, the content of a component being 0.0% or 0.00%, or not containing or not incorporating the component means that the component is substantially not contained, and the content of the component is at or below the level of impurities. At or below the level of impurities means, for example, less than 0.01%.

In this invention and this specification, "thermal stability" refers to the resistance to crystal precipitation when molten glass solidifies.

In the following, glass transition temperature may be abbreviated as Tg.

The above optical glass (sometimes simply referred to as "glass") will be described in more detail below.

<Glass composition>
The glass composition of the optical glass, expressed in cationic percentage, will be described below. In the present invention and this specification, the total content of Li ⁺ , Na ⁺ , K ⁺ and Cs ⁺ will also be referred to as "R ⁺ ", and the total content of Be2 ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ and Ba2 ⁺ will also be referred to as "R2 ⁺ ".

The Li ⁺ content is more than 0.0% and is preferably 2.0% or more, and more preferably 4.0% or more, 6.0% or more, 8.0% or more, 10.0% or more, 11.0% or more, 12.0% or more, 13.0% or more, 14.0% or more, 15.0% or more, 16.0% or more, and 17.0% or more in that order, from the viewpoint of maintaining low dispersion while increasing the refractive index, and from the viewpoint of lowering the Tg of the glass and improving the meltability.
Further, from the viewpoint of improving the thermal stability of the glass and maintaining the thermal stability of the glass, the Li ⁺ content is 48.0 cation% or less, preferably 47.0% or less, and more preferably 46.0% or less, 45.0% or less, 44.0% or less, 43.0% or less, 42.0% or less, 41.0% or less, and 40.0% or less in that order.

The Na ⁺ content is more than 0.0 cation %, preferably 1.0% or more, and more preferably 2.0% or more, 3.0% or more, 4.0% or more, and 5.0% or more in that order, from the viewpoints of maintaining the refractive index, maintaining low dispersion, lowering the Tg of the glass, improving the meltability, and lowering the specific gravity.
Further, from the viewpoint of maintaining the thermal stability of the glass, the Na ⁺ content is 35.0 cation% or less, preferably 34.0% or less, and more preferably 33.0% or less, 32.0% or less, 31.0% or less, 30.0% or less, 29.0% or less, 28.0% or less, 27.0% or less, and 26.0% or less in that order.

The K ⁺ content is more than 0.0 cation%, preferably 1.0% or more, and more preferably 2.0% or more, 3.0% or more, and 4.0% or more in that order, from the viewpoints of maintaining the refractive index, maintaining low dispersion, lowering the Tg of the glass, and improving the meltability.
Further, from the viewpoint of maintaining the thermal stability of the glass, the K ⁺ content is 30.0 cation% or less, preferably 29.0% or less, and more preferably 28.0% or less, 27.0% or less, 26.0% or less, 25.0% or less, 24.0% or less, 23.0% or less, 22.0% or less, 21.0% or less, 20.0% or less, 19.0% or less, and 18.0% or less in that order.

The Cs ⁺ content can be 0.0%, can be 0.0% or more, and can be more than 0.0%. From the viewpoint of further lowering the Tg of the glass and improving the meltability of the glass, the Cs ⁺ content can be 0.0% or more, preferably 0.1% or more, more preferably 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, and 0.6% or more in that order.
Moreover, from the viewpoint of further improving the thermal stability of the glass and suppressing a decrease in the chemical durability, the Cs ⁺ content is preferably 10.0% or less, and more preferably 8.0% or less, 6.0% or less, 4.0% or less, 2.0% or less, 1.5% or less, and 1.0% or less in that order.

The total content R ⁺ of Li ⁺ , Na ⁺ , K ⁺ and Cs ⁺ is preferably 5.0% or more, more preferably 10.0% or more, and further preferably 15.0% or more, 20.0% or more, 23.0% or more, 25.0% or more, 28.0% or more, 30.0% or more, 33.0% or more, 35.0% or more, 37.0% or more, 40.0% or more, 41.0% or more, 42.0% or more, 43.0% or more, 44.0% or more, 45.0% or more, 46.0% or more, 47.0% or more, and 48.0% or more in this order are further preferred.
Furthermore, from the viewpoints of maintaining low dispersion, maintaining the thermal stability of the glass, and suppressing a decrease in chemical durability, the total content R ⁺ of Li ⁺ , Na ⁺ , K ⁺ and Cs ⁺ is preferably 65.0% or less, and more preferably 64.0% or less, 63.0% or less, 62.0% or less, 61.0% or less, 60.0% or less, and 59.0% or less, in that order.

From the viewpoint of maintaining the thermal stability of the glass, the total content of Al ³⁺ and P ⁵⁺ (Al ³⁺ +P ⁵⁺ ) is 38.0 cation% or more, preferably 38.1% or more, and more preferably 38.2% or more, 38.3% or more, 38.4% or more, 38.5% or more, 38.6% or more, 38.7% or more, 38.8% or more, 38.9% or more, and 39.0% or more in that order.
Moreover, from the viewpoint of suppressing an increase in Tg, the total content of Al ³⁺ and P ⁵⁺ (Al ³⁺ +P ⁵⁺ ) is 70.0 cation% or less, preferably 65.0% or less, and more preferably 60.0% or less, 59.0% or less, 58.0% or less, 57.0% or less, 56.0% or less, 55.0% or less, 54.0% or less, 53.0% or less, 52.0% or less, 51.0% or less, and 50.0% or less, in that order.

From the viewpoint of maintaining low dispersion while increasing the refractive index, and from the viewpoint of further improving the thermal stability and maintaining the chemical durability of the glass, the Al3 ⁺ content is preferably more than 0.0%, more preferably 1.0% or more, and further preferably 2.0% or more, 3.0% or more, 4.0% or more, 5.0% or more, 6.0% or more, 7.0% or more, 8.0% or more, 9.0% or more, 10.0% or more, and 11.0% or more in this order.
Moreover, from the viewpoint of further suppressing an increase in Tg, the Al ³⁺ content is preferably 30.0% or less, more preferably 29.0% or less, and further more preferably 28.0% or less, 27.0% or less, 26.0% or less, 25.0% or less, 24.0% or less, 23.0% or less, 22.0% or less, 21.0% or less, 20.0% or less, 19.0% or less, and 18.0% or less, in that order.

From the viewpoint of maintaining low dispersion and further improving the thermal stability of the glass, the P5 ⁺ content is preferably 5.0% or more, more preferably 7.0% or more, and further preferably 9.0% or more, 11.0% or more, 13.0% or more, 14.0% or more, 15.0% or more, 16.0% or more, 17.0% or more, 18.0% or more, 19.0% or more, 20.0% or more, 21.0% or more, 22.0% or more, and 23.0% or more in that order.
Furthermore, from the viewpoints of maintaining the refractive index, further improving the thermal stability of the glass, and suppressing a decrease in chemical durability, the P5 ⁺ content is preferably 50.0% or less, more preferably 48.0% or less, and further more preferably 46.0% or less, 44.0% or less, 42.0% or less, 40.0% or less, 38.0% or less, 37.0% or less, 36.0% or less, 35.0% or less, 34.0% or less, 33.0% or less, and 32.0% or less, in that order.

The cation ratio of R ⁺ to the total content of Al3 ⁺ and P5 ⁺ (R ⁺ /(Al3 ⁺ +P5 ⁺ )) is, from the viewpoint of lowering the Tg of the glass and improving the meltability of the glass, 0.93 or more, preferably 0.94 or more, and more preferably 0.95 or more, and further preferably 0.96 or more.
From the viewpoint of maintaining the thermal stability of the glass, the cation ratio (R ⁺ /(Al ³⁺ +P ⁵⁺ )) is preferably 3.00 or less, more preferably 2.75 or less, and further more preferably 2.50 or less, 2.25 or less, 2.00 or less, 1.90 or less, 1.80 or less, 1.70 or less, 1.65 or less, 1.60 or less, 1.55 or less, 1.50 or less, 1.45 or less, and 1.40 or less, in that order.

The cation ratio of the Li ⁺ content to the total of R ⁺ and R2 ⁺ (Li ⁺ /(R ⁺⁺ R2 ⁺ )) is, from the viewpoints of increasing the refractive index, lowering the Tg of the glass, and improving the meltability of the glass, 0.29 or more, preferably 0.30 or more, and more preferably 0.31 or more, and further preferably 0.32 or more.
From the viewpoint of maintaining the thermal stability of the glass, the cation ratio (Li ⁺ /(R ⁺ +R ²⁺ )) is preferably 1.00 or less, more preferably 0.95 or less, and more preferably 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, 0.90 or less, 0.89 or less, 0.88 or less, 0.87 or less, 0.86 or less, 0.85 or less, 0.84 or less, and 0.83 or less, in that order.

The cation ratio of the total content of Li ⁺ and K ⁺ to the total content of Al3 ⁺ and ^P5 + ((Li ⁺⁺ K ⁺ )/( ^Al3 ++P5 ⁺ )) is, from the viewpoints of further lowering the Tg of the glass, improving the meltability and lowering the specific gravity of the glass, 0.56 or more, preferably 0.57 or more, and more preferably 0.58 or more, 0.59 or more, 0.60 or more, 0.61 or more, 0.62 or more, 0.63 or more, 0.64 or more, and 0.65 or more in that order.
In addition, the cation ratio ((Li ⁺⁺ K ⁺ )/( ^Al3 ++P5 ⁺ )) is preferably 2.00 or less, more preferably 1.80 or less, and further preferably 1.70 or less, 1.60 or less, 1.50 or less, 1.40 or less, 1.30 or less, 1.20 or less, and 1.10 or less, in order of maintaining the refractive index and thermal stability.

The cation ratio of R ²⁺ to the total of the Al ³⁺ content and R ²⁺ (R ²⁺ /(Al ³⁺ +R ²⁺ )) is 0.37 or less, preferably 0.36 or less, and more preferably 0.35 or less, 0.34 or less, 0.33 or less, 0.32 or less, 0.31 or less, and 0.30 or less, in that order, from the viewpoint of maintaining the thermal stability of the glass.
Furthermore, the cation ratio (R2 ⁺ /( ^Al3 ++R2 ⁺ )) can be 0.00, or can be 0.00 or greater or more than 0.00. From the viewpoints of lowering the liquidus temperature and increasing the refractive index, the cation ratio (R2 ⁺ /( ^Al3 ++R2 ⁺ )) is preferably 0.00 or greater, more preferably 0.01 or greater, and further preferably 0.02 or greater, and further preferably 0.03 or greater.

The total content R2 ⁺ of Be2 ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ and Ba2 ⁺ can be 0.0%, 0.0% or more, or more than 0.0%. From the viewpoints of maintaining the refractive index, maintaining low dispersion, suppressing the increase in Tg, and maintaining the thermal stability of the glass, the total content R2 ⁺ is preferably 20.0% or less, more preferably 19.0% or less, and further preferably 18.0% or less, 17.0% or less, 16.0% or less, 15.0% or less, 14.0% or less, 13.0% or less, 12.0% or less, 11.0% or less, 10.0% or less, 9.0% or less, 8.0% or less, and 7.0% or less in this order.

The Be ²⁺ content may be 0.0%, 0.0% or more, or more than 0.0%. From the viewpoints of maintaining the refractive index, maintaining low dispersion, suppressing an increase in Tg, and maintaining the thermal stability of the glass, the Be ²⁺ content is preferably 15.0% or less, more preferably 10.0% or less, and further preferably 5.0% or less, 2.5% or less, 1.5% or less, 1.0% or less, and 0.5% or less in that order.
The Mg ²⁺ content can be 0.0%, 0.0% or more, or more than 0.0%. From the viewpoints of maintaining the refractive index, maintaining low dispersion, suppressing an increase in Tg, and maintaining the thermal stability of the glass, the Mg ²⁺ content is preferably 15.0% or less, more preferably 14.0% or less, and further preferably 13.0% or less, 12.0% or less, 11.0% or less, 10.0% or less, 9.0% or less, 8.0% or less, 7.0% or less, and 6.0% or less in that order.
The Ca2 ⁺ content may be 0.0%, 0.0% or more, or more than 0.0%. From the viewpoints of maintaining the refractive index, maintaining low dispersion, suppressing an increase in Tg, and maintaining the thermal stability of the glass, the Ca2 ⁺ content is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, 6.0% or less, and 5.0% or less in that order.
The Sr2 ⁺ content may be 0.0%, 0.0% or more, or more than 0.0%. From the viewpoints of maintaining the refractive index, maintaining low dispersion, suppressing an increase in Tg, and maintaining the thermal stability of the glass, the Sr2 ⁺ content is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, and 4.0% or less in that order.
The Ba2 ⁺ content may be 0.0%, 0.0% or more, or more than 0.0%. From the viewpoints of maintaining the refractive index, maintaining low dispersion, suppressing an increase in Tg, and maintaining the thermal stability of the glass, the Ba2 ⁺ content is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, 4.0% or less, 3.0% or less, and 2.0% or less in that order.

The Zn ²⁺ content can be 0.0%, 0.0% or more, or more than 0.0%. Zn ²⁺ works to improve thermal stability while maintaining the refractive index, but if it is contained in excess, the dispersion tends to be high. From the above viewpoint, the Zn ²⁺ content is preferably 20.0% or less, more preferably 19.0% or less, and more preferably 18.0% or less, 17.0% or less, 16.0% or less, 15.0% or less, 14.0% or less, 13.0% or less, 12.0% or less, 11.0% or less, 10.0% or less, 9.0% or less, 8.0% or less, 7.0% or less, 6.0% or less, and 5.0% or less in that order.

The Zr4 ⁺ content can be 0.0%, 0.0% or more, or more than 0.0%. Zr4 ⁺ is a component that increases the refractive index, but if contained in excess, dispersion tends to increase and Tg tends to rise. From the above viewpoint, the Zr4 ⁺ content is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, 4.0% or less, 3.0% or less, and 2.0% or less in that order.

The Nb5 ⁺ content can be 0.0%, 0.0% or more, or more than 0.0%. Nb5 ⁺ is a component that increases the refractive index, but if it is contained in excess, the dispersion tends to increase and the Tg tends to rise. From the above viewpoint, the Nb5 ⁺ content is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, 4.0% or less, 3.0% or less, and 2.0% or less in that order.

The Ti4 ⁺ content can be 0.0%, 0.0% or more, or more than 0.0%. ^Ti4+ is a component that increases the refractive index, but if it is contained in excess, the dispersion tends to increase and the Tg tends to rise. From the above viewpoint, the Ti4 ⁺ content is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, 4.0% or less, 3.0% or less, and 2.0% or less in that order.

The W6 ⁺ content can be 0.0%, 0.0% or more, or more than 0.0%. W6 ⁺ is a component that increases the refractive index, but if it is contained in excess, the dispersion tends to increase and the Tg tends to increase. From the above viewpoint, the W6 ⁺ content is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, 4.0% or less, 3.0% or less, and 2.0% or less in that order.

The cation ratio of the total content of Li ⁺ and Na ⁺ to the total content of Li ⁺ and K ⁺ ((Li ⁺⁺ Na ⁺ )/(Li ⁺⁺ K ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.50 or more, more preferably 0.55 or more, and further preferably 0.60 or more, 0.65 or more, 0.66 or more, 0.67 or more, 0.68 or more, 0.69 or more, 0.70 or more, 0.71 or more, 0.72 or more, 0.73 or more, 0.74 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.79 or more, and 0.80 or more in that order.
From the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, the cation ratio ((Li ⁺⁺ Na ⁺ )/(Li ⁺⁺ K ⁺ )) is preferably 2.05 or less, more preferably 2.00 or less, and further preferably 1.95 or less, 1.90 or less, 1.85 or less, 1.80 or less, 1.75 or less, 1.70 or less, 1.65 or less, 1.64 or less, 1.63 or less, 1.62 or less, 1.61 or less, 1.60 or less, 1.59 or less, 1.58 or less, 1.57 or less, 1.56 or less, 1.55 or less, 1.54 or less, 1.53 or less, 1.52 or less, 1.51 or less, and 1.50 or less, in that order.

The cation ratio of the total content of Na ⁺ and K ⁺ to the total content of Li ⁺ and K ⁺ ((Na ⁺ +K ⁺ )/(Li ⁺ +K ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.05 or more, more preferably 0.07 or more, and further preferably 0.09 or more, 0.11 or more, 0.13 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, 0.19 or more, and 0.20 or more, in that order.
From the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, the cation ratio ((Na ⁺ +K ⁺ )/(Li ⁺ +K ⁺ )) is preferably 2.00 or less, more preferably 1.95 or less, and further preferably 1.90 or less, 1.85 or less, 1.80 or less, 1.75 or less, 1.70 or less, 1.55 or less, 1.50 or less, 1.45 or less, 1.40 or less, 1.39 or less, 1.38 or less, 1.37 or less, 1.36 or less, 1.35 or less, 1.34 or less, 1.33 or less, 1.32 or less, 1.31 or less, and 1.30 or less in that order.

The cation ratio of the Li ⁺ content to the total content of Li ⁺ and Na ⁺ (Li ⁺ /(Li ⁺⁺ Na ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.05 or more, more preferably 0.10 or more, and further preferably 0.20 or more, 0.25 or more, 0.30 or more, 0.31 or more, 0.32 or more, 0.33 or more, 0.34 or more, 0.35 or more, 0.36 or more, 0.37 or more, 0.38 or more, 0.39 or more, and 0.40 or more, in that order.
Furthermore, from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, the cation ratio (Li ⁺ /(Li ⁺ +Na ⁺ )) is preferably 1.00 or less, more preferably 0.98 or less, and more preferably 0.96 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, 0.90 or less, 0.89 or less, and 0.88 or less, in that order.

The cation ratio of the Li ⁺ content to the total content of Li ⁺ and K ⁺ (Li ⁺ /(Li ⁺⁺ K ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.30 or more, more preferably 0.35 or more, and further preferably 0.40 or more, 0.42 or more, 0.44 or more, 0.46 or more, 0.48 or more, 0.50 or more, 0.52 or more, 0.54 or more, and 0.56 or more, in that order.
From the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, the cation ratio (Li ⁺ /(Li ⁺ +K ⁺ )) is preferably 0.99 or less, more preferably 0.98 or less, and further preferably 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, and 0.90 or less, in that order.

The cation ratio of the Li ⁺ content to the total content of Na ⁺ and K ⁺ (Li ⁺ /(Na ⁺⁺ K ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.10 or more, more preferably 0.20 or more, and further preferably 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.41 or more, 0.42 or more, 0.43 or more, 0.44 or more, and 0.45 or more, in that order.
Furthermore, from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, the cation ratio (Li ⁺ /(Na ⁺ +K ⁺ )) is preferably 5.50 or less, more preferably 4.90 or less, and further preferably 4.80 or less, 4.70 or less, 4.60 or less, 4.50 or less, and 4.40 or less, in that order.

The cation ratio of the Na ⁺ content to the total content of Na ⁺ and Li ⁺ (Na ⁺ /(Na ⁺⁺ Li ⁺ )) is, from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, preferably 0.85 or less, more preferably 0.80 or less, and further more preferably 0.75 or less, 0.74 or less, 0.73 or less, 0.72 or less, 0.71 or less, 0.70 or less, 0.69 or less, 0.68 or less, 0.67 or less, 0.66 or less, and 0.65 or less.
In addition, the cation ratio (Na ⁺ /(Na ⁺ +Li ⁺ )) can be greater than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, it is preferably 0.03 or more, more preferably 0.04 or more, and further preferably 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, and 0.10 or more, in that order.

The cation ratio of the Na ⁺ content to the total content of Na ⁺ and K ⁺ (Na ⁺ /(Na ⁺⁺ K ⁺ )) is, from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, preferably 0.95 or less, more preferably 0.92 or less, and further more preferably 0.89 or less, 0.86 or less, 0.85 or less, 0.84 or less, 0.83 or less, 0.82 or less, 0.81 or less, 0.80 or less, 0.79 or less, 0.78 or less, and 0.77 or less.
In addition, the cation ratio (Na ⁺ /(Na ⁺ +K ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, it is preferably 0.10 or more, more preferably 0.15 or more, and further preferably 0.20 or more, 0.22 or more, 0.24 or more, 0.26 or more, 0.27 or more, 0.28 or more, 0.29 or more, 0.30 or more, 0.31 or more, and 0.32 or more, in that order.

The cation ratio of the Na ⁺ content to the total content of Li ⁺ and K ⁺ (Na ⁺ /(Li ⁺⁺ K ⁺ )) is, from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, preferably 1.00 or less, more preferably 0.98 or less, and further more preferably 0.96 or less, 0.94 or less, 0.92 or less, 0.90 or less, 0.88 or less, 0.86 or less, and 0.84 or less, in that order.
In addition, the cation ratio (Na ⁺ /(Li ⁺ +K ⁺ )) can be greater than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.03 or more, more preferably 0.05 or more, and further preferably 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, and 0.11 or more, in that order.

The cation ratio of the K ⁺ content to the total content of K ⁺ and Li ⁺ (K ⁺ /(K ⁺⁺ Li ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.01 or more, more preferably 0.03 or more, and further preferably 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, and 0.09 or more, in that order.
From the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, the cation ratio (K ⁺ /(K ⁺ +Li ⁺ )) is preferably 0.70 or less, more preferably 0.65 or less, and further preferably 0.60 or less, 0.59 or less, 0.58 or less, 0.57 or less, 0.56 or less, 0.55 or less, 0.54 or less, 0.53 or less, 0.52 or less, 0.51 or less, 0.50 or less, 0.49 or less, 0.48 or less, 0.47 or less, 0.46 or less, 0.45 or less, 0.44 or less, and 0.43 or less, in that order.

The cation ratio of the K ⁺ content to the total content of K ⁺ and Na ⁺ (K ⁺ /(K ⁺⁺ Na ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.10 or more, more preferably 0.12 or more, and further preferably 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, 0.19 or more, and 0.20 or more, in that order.
From the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, the cation ratio (K ⁺ /(K ⁺ Na ⁺ )) is preferably 0.80 or less, more preferably 0.77 or less, and further preferably 0.75 or less, 0.74 or less, 0.73 or less, 0.72 or less, 0.71 or less, 0.70 or less, 0.69 or less, and 0.68 or less, in that order.

The cation ratio of the K ⁺ content to the total content of Li ⁺ and Na ⁺ (K ⁺ /(Li ⁺⁺ Na ⁺ )) can be more than 0.00, and from the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, is preferably 0.01 or more, more preferably 0.03 or more, and more preferably 0.05 or more, 0.06 or more, 0.07 or more, and 0.08 or more, in that order.
From the viewpoints of maintaining the thermal stability of the glass, further lowering the Tg, and improving the meltability of the glass, the cation ratio (K ⁺ /(Li ⁺ Na ⁺ )) is preferably 1.10 or less, more preferably 1.00 or less, and further preferably 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.59 or less, 0.58 or less, 0.57 or less, 0.56 or less, 0.55 or less, 0.54 or less, 0.53 or less, 0.52 or less, 0.51 or less, and 0.50 or less, in that order.

From the viewpoint of further lowering the Tg and suppressing a decrease in the thermal stability of the glass, the cation ratio of R ²⁺ to the Al ³⁺ content (R ²⁺ /Al ³⁺ ) is preferably 0.74 or less, more preferably 0.73 or less, and further preferably 0.71 or less, 0.69 or less, 0.67 or less, 0.65 or less, 0.63 or less, 0.61 or less, 0.59 or less, 0.57 or less, 0.55 or less, 0.54 or less, 0.53 or less, 0.52 or less, 0.51 or less, 0.50 or less, 0.49 or less, 0.48 or less, 0.47 or less, 0.46 or less, 0.45 or less, 0.44 or less, 0.43 or less, 0.42 or less, 0.41 or less, 0.40 or less, and 0.39 or less, in that order.
In addition, the cation ratio (R ²⁺ /Al ³⁺ ) can be 0.00, 0.00 or more, or more than 0.00. From the viewpoint of further lowering the Tg and suppressing a decrease in the thermal stability of the glass, the cation ratio (R ²⁺ /Al ³⁺ ) is preferably 0.00 or more, more preferably 0.005 or more, and further preferably 0.007 or more, and further preferably 0.010 or more, in that order.

In one embodiment, the optical glass can be a glass that does not contain S6 ⁺ .

Pb, As, Cd, Tl, Be and Se are each toxic, and therefore it is preferable not to contain these elements, i.e., not to introduce these elements into the glass as glass components.
U, Th and Ra are all radioactive elements, and therefore it is preferable not to contain these elements, i.e., not to introduce these elements into the glass as glass components.
V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm and Ce are not preferred elements to be contained in glass for optical elements because they can increase the coloring of the glass or become a source of fluorescence. Therefore, it is preferred not to contain these elements, i.e., not to introduce these elements into the glass as glass components.

Sb and Sn are optional elements that function as fining agents.
The Sb content of the optical glass can be, for example, 0.40% or less, 0.20% or less, 0.10% or less, 0.05% or less, 0.02% _or less, or 0.01% or less, expressed as _a mass fraction (%) of _Sb2O3 when the mass of the glass is taken as 100. On the other hand, the Sb content can be 0.00% or more, or can be 0.00%, expressed as a mass fraction (%) of _Sb2O3 when the mass of the glass is taken as 100.
The Sn content of the optical glass can be, for example, 0.40% or less, 0.20% or less, 0.10 _% or less, 0.05% or less, 0.02% or less, or 0.01% or less, expressed as a mass fraction (%) of SnO2 when the mass of the glass is taken as 100. On the other hand, the Sn content can be 0.00% or more, or can be 0.00%, expressed as a mass fraction (%) of _SnO2 when the mass of the glass is taken as 100.

Above we have explained the cationic components. Next we will explain the anionic components.

The optical glass contains at least F 2 ⁻ as an anion component.

The F ² -content is, from the viewpoint of lowering the Tg of the glass and maintaining the low dispersibility of the glass, 19.0% or more, preferably 20.0% or more, and more preferably 21.0% or more, 22.0% or more, 23.0% or more, 24.0% or more, 25.0% or more, and 26.0% or more in that order.
From the viewpoint of suppressing volatilization and further improving the thermal stability of the glass, the F ^-content is preferably 60.0% or less, more preferably 59.0% or less, and further more preferably 58.0% or less, 57.0% or less, 56.0% or less, 55.0% or less, 54.0% or less, 53.0% or less, 52.0% or less, 51.0% or less, 50.0% or less, 49.0% or less, 48.0% or less, 46.0% or less, 45.0% or less, and 44.0% or less in that order.

From the viewpoint of suppressing an increase in Tg, the O2 ^- content is 83.0% or less, preferably 82.0% or less, and more preferably 81.0% or less, 80.0% or less, 79.0% or less, 78.0% or less, 77.0% or less, 76.0% or less, 75.0% or less, 74.0% or less, 73.0% or less, and 72.0% or less in that order.
In addition, the O ^2- content can be 0.0%, 0.0% or more, or more than 0.0%. From the viewpoint of further improving the high refractive index and thermal stability of the glass, the O ^2- content is preferably 40.0% or more, more preferably 41.0% or more, and more preferably 42.0% or more, 43.0% or more, 44.0% or more, 45.0% or more, 46.0% or more, 47.0% or more, 48.0% or more, 49.0% or more, 50.0% or more, 51.0% or more, 52.0% or more, 53.0% or more, and 55.0% or more in that order.

Examples of anion components other than those mentioned above include Cl ⁻ , Br ⁻ and I ⁻ .
The Cl ^- content can be, for example, 0.0%, 0.0% or more, more than 0.0%, 0.10% or more, or 0.20% or more, and can be, for example, 5.0% or less, 4.0% or less, 3.0% or less, 2.0% or less, 1.0% or less, or 0.50% or less.
The Br ² -content can be, for example, 0.0%, 0.0% or more, more than 0.0%, 0.10% or more, 0.20% or more, and can be, for example, 5.0% or less, 4.0% or less, 3.0% or less, 2.0% or less, 1.0% or less, or 0.5% or less.
The I ² -content can be, for example, 0.0%, 0.0% or more, more than 0.0%, 0.10% or more, or 0.20% or more, and can be, for example, 5.0% or less, 4.0% or less, 3.0% or less, 2.0% or less, 1.0% or less, or 0.5% or less.

<Glass properties>
(Abbe number vd)
The Abbe number νd, which is an index of dispersion, is expressed as νd=(nd-1)/(nF-nC) using the refractive indices nd, nF, and nC at the d-line, F-line, and C-line. From the viewpoint of usefulness as a material for optical elements, the Abbe number νd of the optical glass is preferably 50.00 or more, more preferably 55.00 or more, and further preferably 60.00 or more, 62.50 or more, 65.00 or more, 67.50 or more, 70.00 or more, 70.50 or more, 71.00 or more, 71.50 or more, 72.00 or more, 72.50 or more, and 73.00 or more in that order. The Abbe number νd of the optical glass can be, for example, 82.00 or less. In an imaging optical system or a projection optical system such as a projector, lenses with different dispersions are combined to form a cemented lens, which allows the optical system to be made compact while correcting chromatic aberration. Low dispersion is generally not easy to achieve with a plastic lens. Therefore, optical glasses having low dispersion are useful as materials for optical elements constituting imaging optical systems and projection optical systems such as projectors. The optical glasses can exhibit low dispersion by having the above glass composition.

(Refractive index nd)
From the viewpoint of usefulness as a material for optical elements, the refractive index nd of the optical glass can be, for example, 1.420 or more, 1.425 or more, 1.430 or more, 1.435 or more, 1.440 or more, 1.445 or more, 1.446 or more, 1.447 or more, 1.448 or more, 1.449 or more, 1.450 or more, and can be, for example, 1.510 or less, 1.505 or less, 1.500 or less, 1.4950 or less, 1.490 or less, 1.489 or less, 1.488 or less, 1.487 or less, 1.486 or less, 1.485 or less, 1.484 or less, 1.483 or less, 1.482 or less. In the present invention and this specification, "refractive index" means "refractive index nd". Refraction nd is the refractive index at a wavelength of 587.56 nm.

(Glass transition temperature Tg)
The optical glass can have a low glass transition temperature by having the above glass composition. The glass transition temperature Tg of the optical glass is preferably 355° C. or less, more preferably 350° C. or less, and further preferably 340° C. or less, 330° C. or less, 320° C. or less, 310° C. or less, 300° C. or less, 290° C. or less, 280° C. or less, 270° C. or less, and 260° C. or less in this order. The glass transition temperature Tg of the optical glass can be, for example, 150° C. or more, 160° C. or more, 170° C. or more, 180° C. or more, 190° C. or more, or 200° C. or more. The glass transition temperature Tg is determined by the method described below.

(specific gravity)
From the viewpoint of reducing the weight of the optical element, it is preferable that the specific gravity of the optical glass is low. The specific gravity of the optical glass can be, for example, 3.10 or less, 3.05 or less, 3.00 or less, 2.95 or less, 2.90 or less, or 2.85 or less. The specific gravity of the optical glass can be, for example, 2.53 or more, but since the lower the specific gravity, the more preferable it is, the lower limit is not particularly limited.

(Transmittance characteristics)
The optical glass has an external transmittance of 80% or more at wavelengths of 500 nm to 1000 nm, calculated as a thickness of 10.0 mm. "The external transmittance of 80% or more at wavelengths of 500 nm to 1000 nm, calculated as a thickness of 10.0 mm" means that the external transmittance is 80% or more at a thickness of 10.0 mm over the entire wavelength range of 500 nm to 1000 nm. The optical glass can have an external transmittance of 80% or more and 100% or less at a wavelength of 500 nm to 1000 nm, calculated as a thickness of 10.0 mm. Optical glass having such transmittance characteristics is useful as a material for optical elements. For example, the transmittance characteristics can be realized by using glass that does not contain Cu ²⁺ as a cationic component.

The transmittance characteristics of the above glass are determined by the following method.
The glass sample is processed to have parallel and optically polished flat surfaces, and the external transmittance is measured at wavelengths of 500 to 1000 nm, which includes the reflection loss of light rays on the sample surface.
Furthermore, when the glass to be measured does not have a thickness that can be converted, the thickness of the glass is taken as d, and the transmittance at each wavelength λ is converted by the following formula A, and the transmittance characteristics are obtained by conversion.

Formula A: T(λ)=(1-R(λ)) ² ×exp(log _e ((T ₀ (λ)/100)/(1-R(λ)) ² )×d/d ₀ )× 100

In formula A, T(λ): converted transmittance (%) at wavelength λ, T ₀ (λ): measured transmittance (%) at wavelength λ, d: converted thickness (mm), d ₀ : glass thickness (mm), R(λ)=((n(λ)-1)/(n(λ)+1)) ² , reflectance at wavelength λ, n(λ): refractive index at wavelength λ. The refractive index n(λ) at wavelength λ is measured in accordance with Japanese Industrial Standards (JIS) JIS B 7071-1 "Method of measuring refractive index of optical glass-Part 1: Minimum deviation angle method".

<Method of manufacturing optical glass>
The optical glass can be obtained by weighing, compounding, and thoroughly mixing raw materials such as phosphates, fluorides, oxides, carbonates, sulfates, nitrates, and hydroxides so as to obtain the desired glass composition, heating and melting the mixture in a melting vessel, degassing, and stirring to produce a homogeneous, bubble-free molten glass, and then molding the glass. Specifically, the glass can be produced by using a known melting method.

[Glass material for press molding, optical element blank, and manufacturing method thereof]
Another aspect of the present invention is
a glass material for press molding comprising the optical glass;
an optical element blank made of the optical glass;
Regarding.

According to another aspect of the present invention,
a method for producing a glass material for press molding, comprising a step of molding the optical glass into a glass material for press molding;
A method for producing an optical element blank, comprising a step of press-molding the glass material for optical glass press molding using a press mold to produce an optical element blank;
A method for producing an optical element blank, comprising the step of forming the optical glass into an optical element blank;
will also be provided.

An optical element blank is an optical element base material that approximates the shape of the desired optical element, with polishing allowances (surface layers to be removed by polishing) and, if necessary, grinding allowances (surface layers to be removed by grinding) added to the shape of the optical element. The optical element is finished by grinding and polishing the surface of the optical element blank. In one embodiment, the optical element blank can be produced by a method (called a direct press method) in which a molten glass obtained by melting an appropriate amount of the above glass is press-molded. In another embodiment, the optical element blank can also be produced by solidifying the molten glass obtained by melting an appropriate amount of the above glass.

In another embodiment, a glass material for press molding is prepared, and the prepared glass material for press molding is press molded to produce an optical element blank.

Press molding of glass material for press molding can be carried out by a known method in which the glass material for press molding in a heated and softened state is pressed in a press mold. Both heating and press molding can be carried out in air. By annealing after press molding to reduce distortion inside the glass, a homogeneous optical element blank can be obtained.

Glass materials for press molding include glass gobs for press molding that are used for press molding as is to produce optical element blanks, as well as glass gobs for press molding that are machined by cutting, grinding, polishing, etc. and then used for press molding. Cutting methods include forming a groove in the area of the surface of the glass plate to be cut by a method called scribing, applying local pressure to the grooved area from the back side of the surface on which the groove was formed, thereby breaking the glass plate at the grooved area, and cutting the glass plate with a cutting blade. Grinding and polishing methods include barrel polishing, etc.

A glass material for press molding can be produced, for example, by casting molten glass into a mold to form a glass plate, and then cutting this glass plate into multiple glass pieces. Alternatively, an appropriate amount of molten glass can be molded to produce a glass gob for press molding. An optical element blank can also be produced by reheating and softening a glass gob for press molding and press molding it. The method of producing an optical element blank by reheating and softening glass and press molding it is called the reheat press method, as opposed to the direct press method.

[Optical element and method of manufacturing the same]
Another aspect of the present invention is
The present invention relates to an optical element made of the optical glass.
The optical element is produced using the optical glass. In the optical element, the glass surface may be coated with one or more layers of coating, such as a multilayer film including an anti-reflection film.

According to another aspect of the present invention,
A method for producing an optical element, comprising the step of producing an optical element by grinding and/or polishing the optical element blank described above;
will also be provided.

In the above-mentioned method for manufacturing optical elements, known methods can be used for mechanical processing such as grinding and polishing, and optical elements with high internal and surface quality can be obtained by thoroughly cleaning and drying the surface of the optical element after processing. In this way, optical elements made of the above-mentioned optical glass can be obtained. Examples of optical elements include various lenses such as spherical lenses, aspherical lenses, and microlenses, as well as prisms.

The optical element made of the optical glass is also suitable as a lens constituting a cemented optical element. Examples of cemented optical elements include a cemented lens in which lenses are cemented together, and a lens and a prism are cemented together. For example, a cemented optical element can be produced by precisely machining (for example, by spherical polishing) the cemented surfaces of two optical elements to be cemented so that the shape is an inverted shape, applying an ultraviolet-curing adhesive used for bonding cemented lenses, bonding them together, and then irradiating ultraviolet light through the lens to cure the adhesive. By producing a plurality of optical elements to be cemented using a plurality of types of glass with different Abbe numbers νd and cementing them together, an element suitable for correcting chromatic aberration can be produced.

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]
<Samples No. 1 to 63>
In order to obtain the glass composition shown in the table below, the corresponding phosphates, fluorides, nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials for introducing each component, and the raw materials were weighed and thoroughly mixed to obtain blended raw materials.
The mixed raw materials were placed in a platinum crucible and heated and melted for 90 minutes in a furnace set at 700 to 1100° C. The molten glass was stirred to homogenize it, and then poured into a preheated mold and allowed to cool to near the glass transition temperature. It was then immediately placed in an annealing furnace and held at about the glass transition temperature for about 30 minutes, after which it was slowly cooled at a rate of −30° C./hour for 4 hours, and then allowed to cool to room temperature in the furnace to obtain the optical glasses of Samples 1 to 63 shown in the table below.

[Comparative example A, comparative example B]
To obtain the glass composition shown in the table below, the corresponding phosphates, fluorides, nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials to introduce each component. The raw materials were weighed and thoroughly mixed to prepare a blended raw material.
The mixed raw materials were placed in a platinum crucible and melted for 90 minutes in a furnace set at 700 to 1100° C. The molten glass was stirred to homogenize it, and then poured into a preheated mold to undergo glass transition. After cooling to about the glass transition temperature, the sample was immediately placed in an annealing furnace and held at the glass transition temperature for about 30 minutes. The sample was then cooled slowly at a rate of -30°C/hour for 4 hours, and then cooled to room temperature in the furnace. By cooling, the optical glasses of Comparative Examples A and B shown in the following table were obtained. The optical glasses of Comparative Examples A and B were obtained. Comparative Example A was prepared according to the method described in WO2003/037813 (Patent Document 1). Comparative Example B corresponds to Example 33 in Document 1), and Comparative Example B corresponds to Example 35 in WO 2003/037813 (Patent Document 1).

<Physical property evaluation>
The physical properties of each optical glass shown in the following table were measured by the following methods.

(1) Refractive index nd Abbe number vd
The refractive index nd and Abbe number vd of each optical glass were measured by the refractive index measurement method of the Japan Optical Glass Industry Association standard. For Comparative Example A, the refractive index nd and Abbe number vd could not be measured because the glass was devitrified.

(2) Glass transition temperature Tg
Glass was thoroughly crushed in a mortar to prepare a sample, and a platinum cell was used as a sample container. The glass transition temperature Tg was measured at a heating rate of 10° C./min using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN.

(3) Specific Gravity Specific gravity was measured by Archimedes' method.

(4) Transmittance characteristics Test pieces were cut out from the obtained glass, and both surfaces were mirror-polished to have parallel, optically polished flat surfaces to a thickness of 10.0 mm. The external transmittance at wavelengths of 500 to 1000 nm was then measured using a spectrophotometer.
It was confirmed that, for all of Samples No. 1 to 63, Comparative Example A, and Comparative Example B, the external transmittance in the wavelength range of 500 nm to 1000 nm was 80% or more and 100% or less at a thickness of 10.0 mm.

<Evaluation of thermal stability>
For each of Samples No. 1 to 63, Comparative Example A, and Comparative Example B, the corresponding phosphates, fluorides, nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials for introducing each component so as to obtain the glass composition shown in the following table, and the raw materials were weighed and thoroughly mixed to prepare blended raw materials.
The mixed raw materials were placed in a platinum crucible and melted for 90 minutes by heating in a furnace set at 700 to 1100° C. The molten glass was stirred to homogenize it, and then cast into a mold to be shaped, and slowly cooled to obtain a block-shaped glass sample.
The obtained glass samples were observed for crystals in the glass using an optical microscope. The magnification of the optical microscope was 40 to 100 times. When no crystals were confirmed in the glass block, it was judged as A, when 1 to 15 crystals per 1 ^cm3 were confirmed, it was judged as B, when 16 to 40 crystals per 1 ^cm3 were confirmed, it was judged as C, and when more than 40 crystals per 1 ^cm3 were confirmed, it was judged as D. Regarding A, B, and C, the thermal stability is higher in the order of C → B → A, and A is the most thermally stable. If it is A, B, or C, it is a result within the acceptable range as an internal quality in the number of crystals contained in the glass during manufacturing. The glass with the judgment result D is a glass with poor thermal stability and poor internal quality during manufacturing.
As shown in the table below, it was confirmed that the glasses of Samples No. 1 to 63 were excellent in thermal stability (evaluation result A, B, or C).

Example 2
Glass gobs for press molding were prepared using the various glasses obtained in Example 1. The glass gobs were heated and softened in the atmosphere, and press molded in a press mold to prepare lens blanks (optical element blanks). The prepared lens blanks were removed from the press mold, annealed, and machined, including polishing, to prepare spherical lenses made of the various glasses prepared in Example 1.

Example 3
A desired amount of the molten glass produced in Example 1 was press molded in a press mold to produce a lens blank (optical element blank). The produced lens blank was removed from the press mold, annealed, and subjected to mechanical processing including polishing to produce a spherical lens made of the various glasses produced in Example 1.

Example 4
The molten glass produced in Example 1 was solidified to produce a glass lump (optical element blank), which was then annealed and machined, including polishing, to produce spherical lenses made of the various glasses produced in Example 1.

Finally, we will summarize each of the above aspects.

[1] In the glass composition expressed in cation percentage,
Li ⁺ content is more than 0.0 cation% and not more than 48.0 cation%;
Na ⁺ content is more than 0.0 cation% and not more than 35.0 cation%;
K ⁺ content is more than 0.0 cation% and not more than 30.0 cation%;
the total content of Al ³⁺ and P ⁵⁺ (Al ³⁺ +P ⁵⁺ ) is 38.0 cation % or more and 70.0 cation % or less;
The total content of Li ⁺ , Na ⁺ , K ⁺ and Cs ⁺ is R ⁺ , the total content of Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is R ²⁺ ,
the cation ratio of R ⁺ to the total content of Al3 ⁺ and P5 ⁺ (R ⁺ /( ^Al3 ++P5 ⁺ )) is 0.93 or more;
a cation ratio (Li ⁺ /(R ⁺ +R ²⁺ )) of the Li ⁺ content to the sum of R ⁺ and R ²⁺ is 0.29 or more;
a cation ratio (( ^{Li++ K ++} )/(Al3++P5 ⁺ )) of the total content of Li ⁺ and ^{K +} to the total content of ^Al3+ and P5+ is 0.56 or more;
the cation ratio of R ²⁺ to the total content of Al ³⁺ and R ²⁺ (R ²⁺ /(Al ³⁺ +R ²⁺ )) is 0.37 or less;
In the glass composition expressed as anion percentage,
^O2- content is 83.0 anion% or less;
The F ^- content is 19.0 anion% or more, and
An optical glass having an external transmittance of 80% or more at wavelengths of 500 nm to 1000 nm when converted into a thickness of 10.0 mm.
[2] The optical glass according to [1], in which the cation ratio ((Li ⁺⁺ Na ⁺⁺ )/(Li ⁺⁺ K ^{+)) of the total content of Li+ and Na+ to the total} content of Li ⁺ and K+ is 0.50 or more and 1.59 or less.
[3] The optical ^glass according to [1] or [2], in which the cation ratio ((Na ^{++K++)/(Li++K++)) of the total content of Na++ and K ++ to the} total content of Li ⁺⁺ and K++ is 0.05 or more and 2.00 or less.
[4] The optical glass according to any one of [1] to [3], in which the cation ratio (Li ⁺ /(Li ⁺ +Na ⁺ )) of the Li ⁺ content to the total content of Li ⁺ and ^Na + is 0.05 or more and 1.00 or less.
[5] The optical glass according to any one of [1] to [4], in which the cation ratio (Li ⁺ /(Li ⁺ +K ⁺ )) of the Li ⁺ content to the total content of Li ⁺ and ^K + is 0.30 or more and 0.99 or less.
[6] The optical glass according to any one of [1] to [5], in which the cation ratio (Li ⁺ /(Na ⁺ +K ⁺ )) of the Li ⁺ content to the total content of Na ⁺ and ^K + is 0.10 or more and 5.00 or less.
[7] The optical glass according to any one of [1] to [6], in which the cation ratio (Na ⁺ /(Na ⁺ +Li ⁺ )) of the Na ⁺ content to the total content of Na ⁺ and ^Li + is 0.85 or less.
[8] The optical glass according to any one of [1] to [7], in which the cation ratio (Na ⁺ /(Na ⁺ +K ⁺ )) of the Na ⁺ content to the total content of Na ⁺ and ^K + is 0.95 or less.
[9] The optical glass according to any one of [1] to [8], in which the cation ratio (Na ⁺ /(Li ⁺ +K ⁺ )) of the Na ⁺ content to the total content of Li ⁺ and ^K + is 1.00 or less.
[10] The optical glass according to any one of [1] to [9], in which the cation ratio (K ⁺ /(K ⁺ +Li ⁺ )) of the K ⁺ content to the total content of K ⁺ and ^Li + is 0.01 or more and 0.70 or less.
[11] The optical glass according to any one of [1] to [10], in which the cation ratio (K ⁺ /(K ⁺ +Na ⁺ )) of the K ⁺ content to the total content of K ⁺ and ^Na + is 0.10 or more and 0.80 or less.
[12] The optical glass according to any one of [1] to [11], in which the cation ratio (K ⁺ /(Li ⁺ +Na ⁺ )) of the K ⁺ content to the total content of Li ⁺ and ^Na + is 0.01 or more and 1.00 or less.
[13] The optical glass according to any one of [1] to [12], in which the cation ratio of R ²⁺ to the Al ³⁺ content (R ²⁺ /Al ³⁺ ) is 0.74 or less.
[14] The optical glass according to any one of [1] to [13], which has a glass transition temperature Tg of 150° C. or higher and 355° C. or lower.
[15] The cation ratio ((Li ⁺⁺ Na ⁺⁺ )/(Li ⁺⁺ K ⁺⁺ )) of the total content of Li ^{++ and Na++ to} the total content of Li++ and K++ is 0.50 or more and 1.59 or less;
The cation ratio ((Na ^{+ +K + )/(Li + +K + )) of the total content of Na + and K + to the total} content of Li + and K ⁺ is 0.05 or more and 2.00 or less;
The cation ratio (Li ⁺ /(Li ⁺ +Na ⁺ )) of the Li ⁺ content to the total content of ^Li + and Na ⁺ is 0.05 or more and 1.00 or less;
The cation ratio (Li ⁺ /(Li ⁺ +K ⁺ )) of the Li ⁺ content to the total content of ^Li + and K ⁺ is 0.30 or more and 0.99 or less;
The cation ratio (Li ⁺ /(Na ⁺ +K ⁺ )) of the Li ⁺ content to the total content of Na ⁺ and K ⁺ is 0.10 or more and 5.00 or less;
The cationic ratio of the Na ⁺ content to the total content of Na ⁺ and Li ⁺ (Na ⁺ /(Na ⁺⁺ Li ⁺ )) is 0.85 or less;
The cationic ratio of the Na ⁺ content to the total content of Na ⁺ and K ⁺ (Na ⁺ /(Na ⁺⁺ K ⁺ )) is 0.95 or less;
The cationic ratio (Na ⁺ /(Li ⁺ +K ⁺ )) of the Na ⁺ content to the total content of Li ⁺ and K ⁺ is 1.00 or less;
The cation ratio (K ⁺ /(K ⁺ +Li ⁺ )) of the K ⁺ content to the total content of ^K + and Li ⁺ is 0.01 or more and 0.70 or less;
The cation ratio (K ⁺ /(K ⁺ +Na ⁺ )) of the K ⁺ content to the total content of K ⁺ and Na ⁺ is 0.10 or more and 0.80 or less;
The cation ratio (K ⁺ /(Li ⁺ +Na ⁺ )) of the K ⁺ content to the total content of Li ⁺ and Na ⁺ is 0.01 or more and 1.00 or less;
2. The optical glass according to claim 1, which has a cation ratio of R ²⁺ to Al ³⁺ content (R ²⁺ /Al ³⁺ ) of 0.74 or less and a glass transition temperature Tg of 150° C. or more and 355° C. or less.
[16] An optical element comprising the optical glass according to any one of [1] to [15].

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.
For example, by subjecting the above-mentioned exemplary glass compositions to compositional adjustments as described in the specification, an optical glass according to one aspect of the present invention can be obtained.
Furthermore, it is of course possible to arbitrarily combine two or more of the items described in the specification as examples or preferred ranges.

Claims (14)

In the glass composition expressed in cation percentage,
Li ⁺ content is more than 0.0 cation% and not more than 48.0 cation%;
Na ⁺ content is more than 0.0 cation% and not more than 35.0 cation%;
K ⁺ content is more than 0.0 cation% and not more than 30.0 cation%;
the total content of Al ³⁺ and P ⁵⁺ (Al ³⁺ +P ⁵⁺ ) is 38.0 cation % or more and 70.0 cation % or less;
The total content of Li ⁺ , Na ⁺ , K ⁺ and Cs ⁺ is R ⁺ , the total content of Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is R ²⁺ ,
the cation ratio of R ⁺ to the total content of Al3 ⁺ and P5 ⁺ (R ⁺ /( ^Al3 ++P5 ⁺ )) is 0.93 or more;
a cation ratio (Li ⁺ /(R ⁺ +R ²⁺ )) of the Li ⁺ content to the sum of R ⁺ and R ²⁺ is 0.29 or more;
the cation ratio of R ²⁺ to the Al ³⁺ content (R ²⁺ /Al ³⁺ ) is 0.40 or less;
a cation ratio (( ^{Li++ K ++} )/(Al3++P5 ⁺ )) of the total content of Li ⁺ and ^{K +} to the total content of ^Al3+ and P5+ is 0.56 or more;
the cation ratio of R ²⁺ to the total content of Al ³⁺ and R ²⁺ (R ²⁺ /(Al ³⁺ +R ²⁺ )) is 0.37 or less;
The cation ratio ((Li++Na++)/(Li++K++)) of the total content of Li ⁺ and Na + ^{to the} total ^content of Li+ and K+ is 0.50 or more ^and 1.59 ^{or less ;}
In the glass composition expressed as anion percentage,
^O2- content is 83.0 anion% or less;
The F ^- content is 19.0 anion% or more, and
An optical glass having an external transmittance of 80% or more at wavelengths of 500 nm to 1000 nm when converted into a thickness of 10.0 mm. 2. The optical glass according to claim 1, wherein the cation ratio ((Na ⁺⁺ K ⁺⁺ )/(Li++K ⁺ )) of the total content of Na ^{+ and} K ⁺ to the total content of Li ⁺ and K ⁺ is 0.05 or more and 2.00 or less. 2. The optical glass according to claim 1, wherein the cation ratio (Li ⁺ /(Li ⁺⁺ Na ⁺ )) of the Li ⁺ content to the total content of Li ⁺ and Na ⁺ is 0.05 or more and 1.00 or less. 2. The optical glass according to claim 1, wherein the cation ratio (Li ⁺ /(Li ⁺⁺ K ⁺ )) of the Li ⁺ content to the total content of Li ⁺ and K ⁺ is 0.30 or more and 0.99 or less. 2. The optical glass according to claim 1, wherein the cation ratio (Li ⁺ /(Na ⁺⁺ K ⁺ )) of the Li ⁺ content to the total content of Na ⁺ and K ⁺ is 0.10 or more and 5.00 or less. 2. The optical glass according to claim 1, wherein the cation ratio (Na ⁺ /(Na ⁺⁺ Li ⁺ )) of the Na ⁺ content to the total content of Na ⁺ and Li ⁺ is 0.85 or less. 2. The optical glass according to claim 1, wherein the cation ratio (Na ⁺ /(Na ⁺⁺ K ⁺ )) of the Na ⁺ content to the total content of Na ⁺ and K ⁺ is 0.95 or less. 2. The optical glass according to claim 1, wherein the cation ratio (Na ⁺ /(Li ⁺⁺ K ⁺ )) of the Na ⁺ content to the total content of Li ⁺ and K ⁺ is 1.00 or less. 2. The optical glass according to claim 1, wherein the cation ratio (K ⁺ /(K ⁺⁺ Li ⁺ )) of the K ⁺ content to the total content of K ⁺ and Li ⁺ is 0.01 or more and 0.70 or less. 2. The optical glass according to claim 1, wherein the cation ratio (K ⁺ /(K ⁺⁺ Na ⁺ )) of the K ⁺ content to the total content of K ⁺ and Na ⁺ is 0.10 or more and 0.80 or less. 2. The optical glass according to claim 1, wherein the cation ratio (K ⁺ /(Li ⁺⁺ Na ⁺ )) of the K ⁺ content to the total content of Li ⁺ and Na ⁺ is 0.01 or more and 1.00 or less. The optical glass according to claim 1, having a glass transition temperature Tg of 150°C or higher and 355°C or lower. The cation ratio (( Na ⁺⁺ K ⁺⁺ )/(Li ⁺⁺ K ⁺⁺ )) of the total content of Na ⁺⁺ and ^{K++ to} the total content of Li ⁺⁺ and K++ is 0.05 or more and 2.00 or less;
The cation ratio (Li ⁺ /(Li ⁺ +Na ⁺ )) of the Li ⁺ content to the total content of ^Li + and Na ⁺ is 0.05 or more and 1.00 or less;
The cation ratio (Li ⁺ /(Li ⁺ +K ⁺ )) of the Li ⁺ content to the total content of ^Li + and K ⁺ is 0.30 or more and 0.99 or less;
The cation ratio (Li ⁺ /(Na ⁺ +K ⁺ )) of the Li ⁺ content to the total content of Na ⁺ and K ⁺ is 0.10 or more and 5.00 or less;
The cationic ratio of the Na ⁺ content to the total content of Na ⁺ and Li ⁺ (Na ⁺ /(Na ⁺⁺ Li ⁺ )) is 0.85 or less;
The cationic ratio of the Na ⁺ content to the total content of Na ⁺ and K ⁺ (Na ⁺ /(Na ⁺⁺ K ⁺ )) is 0.95 or less;
The cationic ratio (Na ⁺ /(Li ⁺ +K ⁺ )) of the Na ⁺ content to the total content of Li ⁺ and K ⁺ is 1.00 or less;
The cation ratio (K ⁺ /(K ⁺ +Li ⁺ )) of the K ⁺ content to the total content of ^K + and Li ⁺ is 0.01 or more and 0.70 or less;
The cation ratio (K ⁺ /(K ⁺ +Na ⁺ )) of the K ⁺ content to the total content of K ⁺ and Na ⁺ is 0.10 or more and 0.80 or less;
2. The optical glass according to claim 1, wherein the cation ratio (K ⁺ /(Li ⁺⁺ Na ⁺ )) of the K ⁺ content to the total content of Li ⁺ and Na ⁺ is 0.01 or more and 1.00 or less , and the glass transition temperature Tg is 150°C or more and 355°C or less. An optical element comprising the optical glass according to any one of claims 1 to 13 .