JP2020059629A - Optical glass, glass material for press forming, optical element blank and optical element - Google Patents

Abstract

To provide an optical glass having a high refractive index and low dispersibility, in which the percentage of an expensive glass component is low in the glass composition.SOLUTION: The optical glass has the following glass composition represented by cation%, and a refractive index nd of 1.9000 to 2.1500 and an Abbe number νd of 20.0 to 35.0. The glass composition contains Taby 0 to 5 cation% and has a cationic ratio (Ti/(Ti+Nb+W+Bi)) of 0.60 to 1.00, a cationic ratio ((Si+B)/(La+Gd+Y)) of 0.30 to 2.40, a cationic ratio ((Si+B)/(Ti+Nb+W+Bi)) of 0.30 to 34.00, a cationic ratio ((La+Gd+Y)/(Ti+Nb+W+Bi)) of 0.30 to 33.00, a cationic ratio ((Mg+Ca+Sr+Ba+Zn)/(La+Y)) of 0.00 to 1.50, a cationic ratio ((Mg+Ca+Sr+Ba+Zn)/(Si+B)) of 0.00 to 1.00, and a cationic ratio ((Gd+Nb+W)/(Si+B+Zn+La+Y+Zr+Ti)) of 0.000 to 0.100.SELECTED DRAWING: None

Description

  The present invention relates to an optical glass, a glass material for press molding, an optical element blank and an optical element.

  Optical glass having a high refractive index and low dispersibility (high refractive index and low dispersion glass) is useful as a material for optical elements. Such a high refractive index and low dispersion glass is disclosed in Patent Document 1, for example.

JP, 2009-203155, A

The high-refractive-index low-dispersion glass disclosed in Patent Document 1 is a cemented lens in which a lens made of this glass is combined with a lens made of ultra-low-dispersion glass to form a cemented lens, thereby correcting the chromatic aberration of the optical system. It can be made compact.
However, the optical glass described in Patent Document 1 contains a large amount of a relatively expensive component (for example, Ta ₂ O ₅ ) among various glass components. However, in order to enable cost reduction of an optical element made of high-refractive-index low-dispersion glass, it is desirable to reduce the proportion of expensive glass components in the glass composition of the optical glass.

  One embodiment of the present invention provides an optical glass having a low proportion of an expensive glass component in a glass composition, a high refractive index, and low dispersibility.

One aspect of the present invention is
In the glass composition of cation% display,
Ta ⁵⁺ content is in the range of 0-5 cation%,
The cation ratio of the Ti ⁴⁺ content to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is 0. .60 to 1.00 range,
The cation ratio of the total content of Si ⁴⁺ and B ³⁺ to the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ ((Si ⁴⁺ + B ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ^{3 +} )) Is in the range of 0.30 to 2.40,
Cation ratio of the total content of Si ⁴⁺ and B ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((Si ⁴⁺ + B ³⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is in the range of 0.30 to 34.00,
Cation ratio of the total content of La ³⁺ , Gd ³⁺ and Y ^{3+ to} the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((La ³⁺ + Gd ³⁺ + Y ³⁺ ). / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is in the range of 0.30 to 33.00,
The cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ^{2+ to} the total content of La ³⁺ and Y ³⁺ ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (La ³⁺ + Y ³⁺ )) is in the range of 0.00 to 1.50,
The cation ratio of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ with respect to the total content of Si ⁴⁺ and B ³⁺ ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (Si ⁴⁺ + B ³⁺ )) is in the range of 0.00 to 1.00,
Cation ratio of the total content of Gd ³⁺ , Nb ⁵⁺ and W ^{6+ to} the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr ⁴⁺ and Ti ^4+. ((Gd ³⁺ + Nb ⁵⁺ + W ⁶⁺ ) / (Si ⁴⁺ + B ³⁺ + Zn ²⁺ + La ³⁺ + Y ³⁺ + Zr ⁴⁺ + Ti ⁴⁺ )) is in the range of 0.000 to 0.100,
An optical glass having a refractive index nd in the range of 1.9000 to 2.1500 and an Abbe number νd in the range of 20.0 to 35.0,
Regarding

Among the raw material compounds for optical glass, Ta compounds, Gd compounds, Nb compounds and W compounds are relatively expensive. On the other hand, in the above optical glass, the Ta ⁵⁺ content is suppressed within the above range. Further, the proportion of Gd ³⁺ , Nb ⁵⁺ and W ^{6+ in} the glass composition is also suppressed. Specifically, for Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ , the cation ratio ((Gd ³⁺ + Nb ⁵⁺ + W ⁶⁺ ) / (Si ⁴⁺ + B ³⁺ + Zn ²⁺ + La ³⁺ + Y ³⁺ + Zr ⁴⁺ + Ti ⁴⁺ )) is within the above range. That is, in the glass composition of the above optical glass, the proportion of expensive glass components Ta ⁵⁺ , Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ is low. In such a glass composition, an optical glass having a high refractive index nd in the above range and an Abbe number νd in the above range (that is, low dispersibility) is obtained by adjusting the glass composition so as to satisfy the above various cation ratios. You can

  According to one aspect of the present invention, it is possible to provide an optical glass that has optical properties (nd and νd) useful as a material for an optical element and that can contribute to cost reduction of the optical element. Further, according to one aspect, it is possible to provide an optical glass that further has one or more physical properties such as high glass stability, low specific gravity and low coloring (high transmittance). Further, according to one aspect of the present invention, it is possible to provide a press-molding glass material, an optical element blank, and an optical element, which are made of the above-mentioned optical glass.

[Optical glass]
In the present invention and in the present specification, the content and the total content of the cation component are represented by cation%, and the content and the total content of the anion component are represented by the anion%, unless otherwise specified.
Here, “cation%” is a value calculated by “(number of cations of interest / total number of cations of glass component) × 100”, which is a molar percentage of the amount of cations of interest to the total amount of cation components. means.
Further, “anion%” is a value calculated by “(number of anions of interest / total number of anions of glass component) × 100”, and means a mole percentage of the amount of anions of interest to the total amount of anion components. To do.
The molar ratio of the contents of the cation components is equal to the ratio of the contents of the cation component of interest indicated by cation%, and the molar ratio of the contents of the anion components of the contents of the anion component noted is indicated by the anion%. Equal to the ratio.
The molar ratio of the content of the cation component and the content of the anion component is the ratio of the content (displayed in mol%) between 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 quantified by a known method, for example, inductively coupled plasma optical emission spectroscopy (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography, or the like.
Further, in the present invention and the present specification, the content of a constituent component being 0% or not containing or not introducing means that the constituent component is substantially not contained, and the content of the constituent component is an impurity level. It means less than or equal to the degree. The level of impurity level or less means, for example, less than 0.01%.

  Hereinafter, the optical glass (may be simply referred to as “glass”) will be described in more detail.

<Glass composition>
The optical glass has a Ta ⁵⁺ content in the range of 0 to 5 cation%, and has a low Ta ⁵⁺ content which is an expensive glass component. From the viewpoint of further cost reduction of the optical element, the Ta ⁵⁺ content is preferably 4% or less, more preferably 3% or less, further preferably 2% or less, It is more preferably 1% or less, and even more preferably no Ta ⁵⁺ is contained.

In the above optical glass, the sum of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ relative to the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr ⁴⁺ and Ti ^4+. The cation ratio of the content ((Gd ³⁺ + Nb ⁵⁺ + W ⁶⁺ ) / (Si ⁴⁺ + B ³⁺ + Zn ²⁺ + La ³⁺ + Y ³⁺ + Zr ⁴⁺ + Ti ⁴⁺ )) is 0.000 to 0. The range is 100. That is, the above optical glass has a low proportion of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ in the glass composition. From the viewpoint of further reducing the cost of the optical element, the above cation ratio ((Gd ³⁺ + Nb ⁵⁺ + W ⁶⁺ ) / (Si ⁴⁺ + B ³⁺ + Zn ²⁺ + La ³⁺ + Y ³⁺ + Zr ⁴⁺ + Ti ⁴⁺ )) is preferably 0.090 or less, more preferably 0.080 or less, further preferably 0.070 or less, further preferably 0.060 or less, and 0 0.050 or less, more preferably 0.040 or less, still more preferably 0.030 or less, still more preferably 0.025 or less, 0.020 or less, 0.015 or less. , 0.010 or less, 0.007 or less, 0.005 or less, 0.004 or less, 0.003 or less, 0.002 or less, or 0.001 or less, and even more preferably 0.000. Gana and Even more preferable. That is, it is even more preferred not to contain Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ .

In the above optical glass, the total content of Gd ³⁺ and W ⁶⁺ (Gd ³⁺ + W ⁶⁺ ) is 8% or less from the viewpoint of cost reduction of the optical element and low specific gravity of the glass. It is preferably 6% or less, more preferably 5% or less, further preferably 4% or less, still more preferably 3% or less, and further preferably 2% or less. Even more preferably, it is even more preferably 1% or less. The total content (Gd ³⁺ + W ⁶⁺ ) can be 0% or more, and particularly preferably 0%.

In the above optical glass, the total content of Gd ³⁺ and W ⁶⁺ with respect to the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr ⁴⁺ and Ti ^4+. The cation ratio ((Gd ³⁺ + W ⁶⁺ ) / (Si ⁴⁺ + B ³⁺ + Zn ²⁺ + La ³⁺ + Y ³⁺ + Zr ⁴⁺ + Ti ⁴⁺ )) is 0.000 to 0.080. Preferably. From the viewpoint of further lowering the cost of the optical element and lowering the specific gravity of the glass, the above cation ratio ((Gd ³⁺ + W ⁶⁺ ) / (Si ⁴⁺ + B ³⁺ + Zn ²⁺ + La ³⁺ + Y ^{3 +} + Zr ⁴⁺ + Ti ⁴⁺ )) is preferably 0.070 or less, more preferably 0.060 or less, further preferably 0.050 or less, and 0.045 or less. Is more preferably 0.040 or less, still more preferably 0.035 or less, even more preferably 0.030 or less, still more preferably 0.025 or less. Even more preferably, it is even more preferably 0.020 or less, even more preferably 0.015 or less, even more preferably 0.010 or less, and 0.007 or less. It is particularly preferably below 0.005, even more preferably below 0.005, even more preferably below 0.004, even more preferably below 0.003, and even below 0.002. Is even more preferred, and 0.001 or less is even more preferred. The cation ratio ((Gd ³⁺ + W ⁶⁺ ) / (Si ⁴⁺ + B ³⁺ + Zn ²⁺ + La ³⁺ + Y ³⁺ + Zr ⁴⁺ + Ti ⁴⁺ )) is particularly preferably 0.000. That is, it is particularly preferable that the optical glass does not contain Gd ³⁺ and W ⁶⁺ .

Si ⁴⁺ and B ³⁺ are glass network-forming components. The total content of Si ⁴⁺ and B ³⁺ (Si ⁴⁺ + B ³⁺ ) is preferably 25% or more, more preferably 27% or more, from the viewpoint of enhancing glass stability. It is more preferably at least 28%, even more preferably at least 29%, even more preferably at least 30%, even more preferably at least 31%. On the other hand, from the viewpoint of suppressing the decrease in the refractive index, the total content (Si ⁴⁺ + B ³⁺ ) is preferably 55% or less, more preferably 45% or less, and 40% or less. It is more preferable that it is 37% or less, still more preferably 35% or less, still more preferably 34% or less.

From the viewpoint of further enhancing the glass stability of the above-mentioned optical glass which is a high-refractive-index and low-dispersion glass and from the viewpoint of further enhancing the refractive index, a cation having a B ³⁺ content relative to the total content of Si ⁴⁺ and B ³⁺ The ratio (B ³⁺ / (Si ⁴⁺ + B ³⁺ )) is preferably 0.20 or more, more preferably 0.30 or more, even more preferably 0.40 or more, and 0 It is more preferably 0.50 or more, still more preferably 0.55 or more, still more preferably 0.60 or more, still more preferably 0.61 or more, and 0.62 or more. Even more preferably, it is even more preferably, it is even more preferably 0.63 or more, even more preferably 0.64 or more, even more preferably 0.65 or more. From the same viewpoint, the cation ratio (B ³⁺ / (Si ⁴⁺ + B ³⁺ )) is preferably 0.95 or less, more preferably 0.90 or less, and more preferably 0.1. It is more preferably 85 or less, even more preferably 0.83 or less, even more preferably 0.80 or less, even more preferably 0.79 or less, and 0.78 or less. Even more preferably, it is even more preferably 0.77 or less, even more preferably 0.76 or less, even more preferably 0.75 or less. It is preferable that the cation ratio (B ³⁺ / (Si ⁴⁺ + B ³⁺ )) is equal to or higher than the lower limit exemplified above from the viewpoint of improving the meltability of glass. It is preferable that the above cation ratio (B ³⁺ / (Si ⁴⁺ + B ³⁺ )) is not more than the above-exemplified upper limit in order to increase the viscosity of the glass during melting. Further, the cation ratio (B ³⁺ / (Si ⁴⁺ + B ³⁺ )) being less than or equal to the above-exemplified upper limit means that fluctuations in the glass composition due to volatilization during melting and fluctuations in optical characteristics due to the fluctuations are reduced. From the viewpoint of improving one or more of chemical durability, weather resistance and machinability of glass, it is preferable from the viewpoint of reducing coloration.

The total content of Si ⁴⁺ and B ³⁺ , which are glass network forming components, is as described above. Each of the Si ⁴⁺ content and the B ³⁺ content is in a preferable range from the viewpoint of improving the stability, meltability, moldability, chemical durability, weather resistance, machinability, etc. of glass and from the viewpoint of color reduction. Is as follows.
The Si ⁴⁺ content is preferably 2% or more, more preferably 3% or more, further preferably 4% or more, further preferably 5% or more, and 6% or more. It is even more preferable to be present, and it is even more preferable to be 7% or more. Further, the Si ⁴⁺ content is preferably 20% or less, more preferably 18% or less, further preferably 16% or less, further preferably 14% or less, and 12% It is even more preferable that
The B ³⁺ content is preferably 10% or more, more preferably 15% or more, further preferably 16% or more, further preferably 17% or more, and more preferably 18% or more. It is even more preferable to be present, and even more preferable to be 19% or more. Further, the B ³⁺ content is preferably 40% or less, more preferably 40% or less, further preferably 35% or less, further preferably 30% or less, and 26% It is even more preferable that it is not more than 25%, even more preferably not more than 25%, even more preferably not more than 24%, and even more preferably not more than 23%.

La ³⁺ , Gd ³⁺ and Y ³ are components having a function of increasing the refractive index while suppressing a decrease in Abbe number. Further, these components also have a function of improving the chemical durability and / or weather resistance of the glass and increasing the glass transition temperature.
The total content of La ³⁺ , Gd ³⁺ and Y ³⁺ (La ³⁺ + Gd ³⁺ + Y ³⁺ ) is preferably 20% or more, and 22% from the viewpoint of suppressing the decrease in the refractive index. More preferably, it is more preferably 24% or more, further preferably 26% or more, further preferably 28% or more, even more preferably 30% or more, It is even more preferably 32% or more, still more preferably 33% or more, even more preferably 34% or more, still more preferably 35% or more, still more preferably 36% or more. Is even more preferred. Further, the total content (La ³⁺ + Gd ³⁺ + Y ³⁺ ) is from the viewpoint of suppressing the deterioration of the chemical durability and / or weather resistance of the glass and the viewpoint of suppressing the decrease of the glass transition temperature. It is preferable that it is not less than the exemplified lower limit. When the glass transition temperature is lowered, the glass is likely to be damaged when mechanically working (cutting, cutting, grinding, polishing, etc.) (decrease in machinability). Therefore, suppressing the decrease in the glass transition temperature leads to an increase in machinability. It is preferable from the above viewpoint that the total content (La ³⁺ + Gd ³⁺ + Y ³⁺ ) is not less than the lower limit exemplified above.
On the other hand, the total content (La ³⁺ + Gd ³⁺ + Y ³⁺ ) is preferably 60% or less, more preferably 55% or less, and 50% or less from the viewpoint of enhancing glass stability. Is more preferred, 47% or less is more preferred, 45% or less is still more preferred, 44% or less is still more preferred, and 43% or less is even more preferred. , 42% or less, still more preferably 41% or less, still more preferably 40% or less, still more preferably 39% or less.

From the viewpoint of the viewpoint and the low specific gravity increasing glass stability, the above optical glass, La ^3+, Gd ³⁺ and to the total content of Y ^3+, Si ⁴⁺ and B ³⁺ is a network former of glass And the cation ratio of the total content of ((Si ⁴⁺ + B ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ )) is 0.30 or more, preferably 0.50 or more, and 0 It is more preferably at least 0.60, more preferably at least 0.65, even more preferably at least 0.70, even more preferably at least 0.75, and at least 0.77. It is even more preferable, it is even more preferably 0.79 or more, still more preferably 0.80 or more.
The cation ratio ((Si ⁴⁺ + B ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ )) is 2.40 or less and 2.00 or less from the viewpoint of increasing the refractive index. Preferably, it is 1.50 or less, more preferably 1.30 or less, even more preferably 1.10 or less, even more preferably 1.05 or less, and 1.00. It is even more preferably not more than 0.95, even more preferably not more than 0.95, even more preferably not more than 0.94, even more preferably not more than 0.93, and not more than 0.92 Even more preferably, it is even more preferably, it is even more preferably 0.91 or less, and particularly preferably 0.90 or less.

Regarding the content of each component of La ³⁺ , Gd ³⁺ and Y ³⁺ , the preferable range is as follows.
The La ³⁺ content is preferably 20% or more, more preferably 21% or more, further preferably 22% or more, further preferably 23% or more, and more preferably 24% or more. It is even more preferable that it is 25% or more, still more preferably 26% or more, still more preferably 27% or more. Further, the La ³⁺ content is preferably 60% or less, more preferably 57% or less, further preferably 55% or less, further preferably 53% or less, and 50% It is more preferably at most 47%, even more preferably at most 47%, even more preferably at most 45%, even more preferably at most 43%, still more preferably at most 40%. Even more preferably, still more preferably 37% or less, even more preferably 35% or less, still more preferably 34% or less, particularly preferably 33% or less. , 32% or less is even more preferable, 31% or less is still more preferable, and 30% or less is even more preferable. Properly, it is particularly even more preferably at most 29%.
The Gd ³⁺ content is preferably 8% or less, more preferably 6% or less, further preferably 4% or less, further preferably 3% or less, and 2% or less. It is even more preferable that it is present, and it is even more preferable that it is 1% or less. The Gd ³⁺ content can be 0% or more, and from the viewpoint of further cost reduction and low specific gravity of the optical element, the Gd ³⁺ content is 0%, that is, Gd ^3+. Is particularly preferably not included.
From the viewpoint of improving meltability and glass stability, the Y ³⁺ content is preferably 0% or more, more preferably 1% or more, further preferably 2% or more, and 4%. It is more preferably at least 6%, even more preferably at least 6%, even more preferably at least 7%, even more preferably at least 8%, still more preferably at least 9%. More preferable. Further, the Y ³⁺ content is preferably 30% or less, more preferably 25% or less, further preferably 20% or less, further preferably 17% or less, and 15% It is even more preferably at most, preferably at most 14%, still more preferably at most 13%, even more preferably at most 12%, still more preferably at most 11%. Still more preferable.

Yb has a large atomic weight among rare earth elements and tends to increase the specific gravity of glass. Further, Yb has absorption in the near infrared region. On the other hand, it is desirable that interchangeable lenses for single-lens reflex cameras and lenses for surveillance cameras have high light transmittance in the near infrared region. Therefore, it is desirable that the content of Yb ³⁺ is small in order to make the glass useful for producing these lenses. From the above viewpoints, the Yb ³⁺ content is preferably 10% or less, more preferably 5% or less, further preferably 3% or less, and further preferably 1% or less. . Further, the Yb ³⁺ content can be 0% or more, and it is particularly preferable that the Yb ³⁺ content is 0%, that is, Yb ³⁺ is not contained.

Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ are components that have a function of increasing the refractive index, and when they are contained in appropriate amounts, they also have a function of increasing the glass stability. The total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ ) is 0% or more from the viewpoint of enhancing the glass stability. Is preferable, 5% or more is more preferable, 10% or more is further preferable, 15% or more is further preferable, 16% or more is further preferable, 17% or more is preferable. Is even more preferably 18% or more, still more preferably 19% or more, still more preferably 20% or more, still more preferably 21% or more. preferable. On the other hand, the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ ) is from the viewpoint of maintaining glass stability and suppressing decrease of Abbe number. From the above, it is preferably 50% or less, more preferably 40% or less, further preferably 30% or less, further preferably 29% or less, and more preferably 28% or less. More preferably, it is still more preferably 27% or less, still more preferably 26% or less, even more preferably 25% or less, even more preferably 24% or less.

While maintaining glass stability in terms of suppressing and coloring reduce highly dispersed, in the above optical ^{glass, Ti 4+, Nb 5+, La} 3+ to the total content of W ⁶⁺ and Bi ^3+, The cation ratio ((La ³⁺ + Gd ³⁺ + Y ³⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) of the total content of Gd ³⁺ and Y ³⁺ is 0.30 or more. , 0.40 or more, more preferably 0.50 or more, even more preferably 0.60 or more, still more preferably 0.70 or more, 0.80 or more. Is more preferable, 0.90 or more is still more preferable, 1.00 or more is still more preferable, 1.10 or more is still more preferable, 1.20 or more Is even more preferred, It is even more preferably 1.30 or more, particularly preferably 1.40 or more, and particularly preferably 1.50 or more. On the other hand, from the viewpoint of maintaining the glass stability while suppressing the decrease of the refractive index and the viewpoint of lowering the specific gravity, in the optical glass, the cation ratio ((La ³⁺ + Gd ³⁺ + Y ³⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is 33.00 or less, preferably 20.00 or less, more preferably 10.00 or less, and further preferably 5.00 or less. It is more preferably 4.00 or less, still more preferably 3.00 or less, still more preferably 2.50 or less, still more preferably 2.20 or less. , 2.00 or less is still more preferable, 1.90 or less is still more preferable, 1.80 or less is still more preferable, and 1.70 or less is particularly preferable. Is preferred.

From the viewpoint of increasing the refractive index, in the above optical glass, Si ⁴⁺ and B ³⁺ , which are the glass-forming components of the glass, with respect to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ The cation ratio ((Si ⁴⁺ + B ³⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) of the total content is 34.00 or less, preferably 30.00 or less, It is more preferably 20.00 or less, further preferably 10.00 or less, further preferably 5.00 or less, still more preferably 4.00 or less, and 3.00 or less. It is even more preferable that it is 2.50 or less, still more preferably 2.50 or less, still more preferably 2.00 or less, still more preferably 1.90 or less. There is even more Preferred, more preferably from it even more is at 1.80 or less, particularly preferably 1.70 or less, and particularly more preferably 1.60 or less. On the other hand, the above cation ratio ((Si ⁴⁺ + B ³⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is from the viewpoint of suppressing high dispersion, maintaining glass stability and reducing coloration. It is 0.30 or more, preferably 0.40 or more, more preferably 0.50 or more, further preferably 0.60 or more, further preferably 0.70 or more, It is more preferably 0.80 or more, even more preferably 0.85 or more, even more preferably 0.90 or more, still more preferably 0.95 or more, 1 It is still more preferably 0.000 or more, still more preferably 1.05 or more, particularly preferably 1.10 or more, particularly preferably 1.15 or more, 1 .20 More preferably from particular it is an upper, in particular even more preferably 1.25 or more, more preferably from particular further not less than 1.30.

From the viewpoint of maintaining the stability of the glass and colored reducing, in the above optical ^{glass, Ti 4+, Nb 5+, W} 6+ and Bi ³⁺ Ti ⁴⁺ content of the cation ratio to the total content of (Ti ⁴⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is in the range of 0.60 to 1.00. The cation ratio (Ti ⁴⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is preferably 0.70 or more, more preferably 0.75 or more, and 0.80 or more. Is more preferable, 0.85 or more is more preferable, 0.90 or more is still more preferable, 0.95 or more is still more preferable, and 1.00 is more preferable. Is more preferable.

With respect to the content of each component of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ , the preferable range is as follows.
The Ti ⁴⁺ content is preferably 0% or more, more preferably 5% or more, further preferably 10% or more, further preferably 15% or more, and 16% or more. It is even more preferred that it is 17% or more, still more preferably 18% or more, still more preferably 19% or more, still more preferably 20% or more. It is even more preferable, and even more preferable that it be 21% or more. Further, the Ti ⁴⁺ content is preferably 50% or less, more preferably 40% or less, further preferably 30% or less, further preferably 29% or less, and 28% It is more preferable that it is not more than 27%, even more preferably not more than 27%, even more preferably not more than 26%, even more preferably not more than 25%, still more preferably not more than 24%. Even more preferred.
The Nb ⁵⁺ content is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, still more preferably 4% or less, and 3% or less. It is even more preferable that it is 2% or less, still more preferably 2% or less, and even more preferably 1% or less. The Nb ⁵⁺ content can be 0% or more, and from the viewpoint of further cost reduction of the optical element, the Nb ⁵⁺ content is 0%, that is, Nb ⁵⁺ is not included. Is particularly preferred.
The W ⁶⁺ content is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, further preferably 4% or less, and 3% or less. It is even more preferable that it is 2% or less, still more preferably 2% or less, and even more preferably 1% or less. The W ⁶⁺ content can be 0% or more, and the W ⁶⁺ content is 0% from the viewpoint of further lowering the cost of the optical element, lowering the specific gravity of the glass, and reducing the coloration. That is, it is particularly preferable that W ⁶⁺ is not included.

The total content of Nb ⁵⁺ and W ⁶⁺ (Nb ⁵⁺ + W ⁶⁺ ) is preferably 8% or less, and 6% from the viewpoint of cost reduction of optical elements and low specific gravity of glass. It is more preferably at most 5%, even more preferably at most 5%, even more preferably at most 4%, even more preferably at most 3%, even more preferably at most 2%, It is even more preferably 1% or less. The total content (Nb ⁵⁺ + W ⁶⁺ ) can be 0% or more, and particularly preferably 0%.

The total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ (Gd ³⁺ + Nb ⁵⁺ + W ⁶⁺ ) is 8% or less from the viewpoint of reducing the cost of the optical element and the specific gravity of the glass. It is preferably 6% or less, more preferably 5% or less, still more preferably 4% or less, even more preferably 3% or less, and 2% or less. Even more preferably, it is even more preferably 1% or less. The total content (Gd ³⁺ + Nb ⁵⁺ + W ⁶⁺ ) can be 0% or more, and particularly preferably 0%.

Bi ³⁺ is a component that increases the refractive index and decreases the Abbe number. It is also a component that tends to increase specific gravity and coloring. The preferable range of the Bi ³⁺ content is as follows in order to produce a glass having the above-mentioned optical properties and being less colored and having a low specific gravity.
The Bi ³⁺ content is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, and 5% or less. It is even more preferable that it is 3% or less, still more preferably 3% or less, and still more preferably 1% or less. Further, the Bi ³⁺ content may be 0% or more, and may be 0%.

The total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ ) is from the viewpoint of maintaining glass stability, high refractive index and low dispersion. From the viewpoint of conversion, it is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, and 6% or less. Is more preferred, 5% or less is even more preferred, 4% or less is even more preferred, 3% or less is even more preferred, 2% or less is even more preferred. It is even more preferably 1% or less. The total content (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ ) may be 0% or more. In one aspect, the total content (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ ) is preferably 0%.

The total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) is to improve the melting property of glass and glass. From the viewpoint of maintaining stability and suppressing an excessive increase in glass transition temperature, it is preferably 0% or more, more preferably 0.05% or more, and further preferably 0.1% or more. preferable. On the other hand, from the viewpoint of maintaining the glass stability and the viewpoints of high refractive index and low dispersion, the total content (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) is 30% or less. Is preferably 25% or less, more preferably 20% or less, still more preferably 15% or less, still more preferably 10% or less, and 8% or less. It is even more preferred that it is present, even more preferably 6% or less, even more preferably 4% or less.

From the viewpoint of maintaining glass stability, increasing the refractive index, and reducing the dispersion, in the above optical glass, Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ^{2 with} respect to the total content of La ³⁺ and Y ^3+. The cation ratio ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (La ³⁺ + Y ³⁺ )) of the total content of ⁺ and Zn ²⁺ is 1.500 or less and 1 It is preferably 0.000 or less, more preferably 0.800 or less, further preferably 0.500 or less, more preferably 0.400 or less, and 0.300 or less. Even more preferably, it is even more preferably 0.250 or less, even more preferably 0.200 or less, even more preferably 0.150 or less, still more preferably 0.100 or less. Even more preferable, 0.0 It is even more preferably 80 or less, still more preferably 0.060 or less, particularly preferably 0.040 or less, particularly preferably 0.020 or less, and 0. Particularly preferably, it is 010 or less, even more preferably 0.007 or less, still more preferably 0.005 or less. Further, the above cation ratio ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (La ³⁺ + Y ³⁺ )) is 0.00 or more, which improves the meltability of the glass and the glass. From the viewpoint of maintaining stability and suppressing an excessive increase in the glass transition temperature, it is preferably 0.00 or more, more preferably 0.001 or more, and further preferably 0.003 or more, It is more preferably 0.005 or more.

From the viewpoint of maintaining the glass stability and reducing the specific gravity, in the above optical glass, Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ^{2+ with} respect to the total content of Si ⁴⁺ and B ^3+. Cation ratio ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (Si ⁴⁺ + B ³⁺ )) is 1.000 or less, preferably 0.900 or less, It is more preferably 0.800 or less, still more preferably 0.700 or less, even more preferably 0.600 or less, even more preferably 0.550 or less, and 0.500 or less. Is more preferably 0.450 or less, still more preferably 0.400 or less, still more preferably 0.350 or less, still more preferably 0.300 or less. Still there Even more preferably, it is even more preferably 0.250 or less, even more preferably 0.200 or less, particularly preferably 0.150 or less, and particularly preferably 0.100 or less. Is more preferable, and 0.090 or less is particularly preferable. Further, the above cation ratio ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (Si ⁴⁺ + B ³⁺ )) is 0.00 or more, which improves the melting property of the glass and the glass. From the viewpoint of suppressing an excessive increase in the transition temperature, it is preferably 0.001 or more, more preferably 0.003 or more, and further preferably 0.005 or more.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ are all components having a function of improving the meltability of glass. However, when the content of these components is large, the glass stability tends to be lowered. From the above viewpoints, the preferable ranges of the respective contents of these components are as follows.
The Mg ²⁺ content is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, and 6% or less. It is even more preferable that it is 5% or less, still more preferably 5% or less, even more preferably 4% or less, still more preferably 3% or less, still more preferably 2% or less. More preferably, it is even more preferably 1% or less. The Mg ²⁺ content may be 0% or more, and may be 0%.
The Ca ²⁺ content is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, and 6% or less. It is even more preferable that it is 5% or less, still more preferably 5% or less, even more preferably 4% or less, still more preferably 3% or less, still more preferably 2% or less. More preferably, it is even more preferably 1% or less. Further, the Ca ²⁺ content can be 0% or more, and may be 0%.
The Sr ²⁺ content is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, and 6% or less. It is even more preferable that it is 5% or less, still more preferably 5% or less, even more preferably 4% or less, still more preferably 3% or less, still more preferably 2% or less. More preferably, it is even more preferably 1% or less. Further, the Sr ²⁺ content can be 0% or more, and may be 0%.
The Ba ²⁺ content is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, even more preferably 7% or less, and 6% or less. It is even more preferable that it is 5% or less, still more preferably 5% or less, even more preferably 4% or less, still more preferably 3% or less, still more preferably 2% or less. More preferably, it is even more preferably 1% or less. Further, the Ba ²⁺ content may be 0% or more, and may be 0%.

The preferable range of the Zn ²⁺ content is as follows from the viewpoint of improving the meltability, stability, moldability, machinability, etc. of glass and realizing the above-mentioned optical characteristics.
The Zn ²⁺ content can be 0% or more, preferably 0.03% or more, more preferably 0.05% or more, still more preferably 0.08% or more. , 0.1% or more is more preferable. Further, the Zn ²⁺ content is preferably 30% or less, more preferably 25% or less, further preferably 20% or less, further preferably 15% or less, and more preferably 10%. It is more preferable that it is below, even more preferably 8% or below, even more preferably 6% or below, still more preferably 4% or below.

Regarding Zn ²⁺ , from the viewpoint of realizing the above optical characteristics while improving the glass stability, the cation ratio of the Zn ²⁺ content to the total content of La ³⁺ and Y ³⁺ (Zn ²⁺ / (La ³⁺ + Y ³ )) is preferably 0.66 or less, more preferably 0.50 or less, further preferably 0.40 or less, and further preferably 0.30 or less. , 0.25 or less, more preferably 0.20 or less, still more preferably 0.15 or less, still more preferably 0.13 or less, It is even more preferably 0.12 or less, even more preferably 0.11 or less, even more preferably 0.10 or less, and particularly preferably 0.090 or less. Better , Especially more preferably 0.085 or less, more preferably from in particular it is 0.080 or less. Further, the small cation ratio (Zn ²⁺ / (La ³⁺ + Y ³⁺ )) is preferable also from the viewpoint of suppressing the glass transition temperature from lowering (improving the machinability by this) and improving the chemical durability. . The above cation ratio (Zn ²⁺ / (La ³⁺ + Y ³⁺ )) can be 0.00% or more, and from the viewpoint of improving the meltability and suppressing an excessive increase in the glass transition temperature, It is preferably more than 00%. The cation ratio (Zn ²⁺ / (La ³⁺ + Y ³⁺ )) is more preferably 0.001 or more, further preferably 0.003 or more, and further preferably 0.005 or more. preferable.

The cation ratio ((Zn ²⁺ + Ba ²⁺ ) / La ³⁺ ) of the total content of Zn ²⁺ and Ba ²⁺ to the La ³⁺ content realizes the above optical characteristics while improving the glass stability. From the viewpoint of the above, it is preferably 0.00 or more, more preferably 0.001 or more, still more preferably 0.003 or more, still more preferably 0.005 or more, and 0.008. It is even more preferable that the above is satisfied. The cation ratio ((Zn ²⁺ + Ba ²⁺ ) / La ³⁺ ) is preferably 0.66 or less from the viewpoint of improving the meltability, reducing the specific gravity and suppressing an excessive increase in the glass transition temperature, It is more preferably 0.50 or less, still more preferably 0.40 or less, even more preferably 0.30 or less, even more preferably 0.25 or less, and 0.20 or less. It is even more preferable that it is 0.16 or less, still more preferably 0.14 or less, still more preferably 0.14 or less, still more preferably 0.13 or less, and 0.12 or less. It is even more preferable that it is 0.11 or less, even more preferably 0.11 or less, particularly preferably 0.100 or less, and particularly preferably 0.090 or less.

The cation ratio of the total content of Zn ²⁺ and Ba ²⁺ to the total content of La ³⁺ and Y ³⁺ ((Zn ²⁺ + Ba ²⁺ ) / (La ³⁺ + Y ³⁺ )) is From the viewpoint of realizing the above-mentioned optical characteristics while improving the stability, it is preferably 0.00 or more, more preferably 0.001 or more, further preferably 0.003 or more, and 0. More preferably, it is 005 or more. The above cation ratio ((Zn ²⁺ + Ba ²⁺ ) / (La ³⁺ + Y ³⁺ )) is 0.66 or less from the viewpoint of improving the meltability, lowering the specific gravity and suppressing an excessive increase in the glass transition temperature. It is preferably 0.50 or less, more preferably 0.40 or less, still more preferably 0.30 or less, still more preferably 0.25 or less, It is even more preferably 0.20 or less, even more preferably 0.15 or less, even more preferably 0.13 or less, even more preferably 0.12 or less, It is still more preferably 0.11 or less, even more preferably 0.10 or less, particularly preferably 0.090 or less, and particularly preferably 0.085 or less. It is particularly preferably 0.080 or less.

Since Li ⁺ has a strong effect of lowering the glass transition temperature, the machinability tends to decrease as the content of Li ⁺ increases. Further, glass stability, chemical durability and weather resistance also tend to decrease. Therefore, the Li ⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, and 3% or less. It is even more preferable that it is 2% or less, still more preferably 2% or less, and even more preferably 1% or less. The Li ⁺ content may be 0% or more, and may be 0%.

Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ all have the function of improving the meltability of glass, but when the content of these increases, glass stability, chemical durability, weather resistance, and mechanical processing Sex tends to decrease. Therefore, the preferable ranges of the respective contents of Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ are as follows.
The Na ⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, and 3% or less. It is even more preferable, it is even more preferably 2% or less, still more preferably 1% or less. The Na ⁺ content may be 0% or more, and may be 0%.
The K ⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, still more preferably 4% or less, and 3% or less. It is even more preferable, it is even more preferably 2% or less, still more preferably 1% or less. Further, the K ⁺ content can be 0% or more, and may be 0%.
The Rb ⁺ content is preferably 10% or less, more preferably 8 % or less, further preferably 6% or less, further preferably 4% or less, and further preferably 3% or less. It is even more preferable, it is even more preferably 2% or less, still more preferably 1% or less. Further, the Rb ⁺ content can be 0% or more, and may be 0%.
The Cs ⁺ content is preferably 10% or less, more preferably 8 % or less, further preferably 6% or less, still more preferably 4% or less, and 3% or less. It is even more preferable, it is even more preferably 2% or less, still more preferably 1% or less. Further, the Cs ⁺ content can be 0% or more, and may be 0%.

Al ³⁺ is a component having a function of improving the chemical durability and weather resistance of glass. However, when the content of Al ³⁺ is increased, the refractive index tends to decrease, the glass stability tends to decrease, and the meltability tends to decrease. Considering the above points, the preferable range of the Al ³⁺ content is as follows.
The Al ³⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, and 3% or less. It is even more preferable that it is 2% or less, still more preferably 2% or less, and even more preferably 1% or less. The Al ³⁺ content may be 0% or more, and may be 0%.

Zr ⁴⁺ is a component having a function of increasing the refractive index, and when it is contained in an appropriate amount, it also has a function of improving glass stability. Zr ⁴⁺ also has a function of increasing the glass transition temperature so that the glass is less likely to be damaged during mechanical processing. From the viewpoint of obtaining these effects well, the Zr ⁴⁺ content is preferably 0% or more, more preferably 1% or more, further preferably 2% or more, and 3% or more. It is more preferable that it is 4% or more. From the viewpoint of improving glass stability, the Zr ⁴⁺ content is preferably 15% or less, more preferably 13% or less, further preferably 10% or less, and further preferably 9% or less. Is more preferable, 8% or less is still more preferable, 7% or less is still more preferable, and 6% or less is even more preferable.

P ⁵⁺ is a component that lowers the refractive index and also a component that lowers the glass stability, but if it is introduced in a very small amount, it may improve the glass stability. In order to obtain a glass having the above-mentioned optical characteristics and excellent glass stability, the preferable range of the P ⁵⁺ content is as follows.
The P ⁵⁺ content is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, even more preferably 2% or less, and 1% or less. It is even more preferred to be present. Further, the P ⁵⁺ content can be 0% or more, and may be 0%.

Ga ³⁺ , In ³⁺ , Sc ³⁺ and Hf ⁴⁺ all have a function of increasing the refractive index. However, these components are not essential components for obtaining the above glass. The preferable ranges of the respective contents of Ga ³⁺ , In ³⁺ , Sc ³⁺ and Hf ⁴⁺ are as follows.
The Ga ³⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and 1% or less. It is even more preferred to be present. Further, the Ga ³⁺ content can be 0% or more, and may be 0%.
The In ³⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and 1% or less. It is even more preferred to be present. Further, the In ³⁺ content may be 0% or more, and may be 0%.
The Sc ³⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and 1% or less. It is even more preferred to be present. Further, the Sc ³⁺ content may be 0% or more, and may be 0%.
The Sc ³⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and 1% or less. It is even more preferred to be present. Further, the Sc ³⁺ content may be 0% or more, and may be 0%.
The Hf ⁴⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, and 2% or less. It is even more preferred to be present. Further, the Hf ⁴⁺ content may be 0% or more, and may be 0%.

Lu ³⁺ has a function of increasing the refractive index, but is also a component that increases the specific gravity of glass. Since Lu is a heavy rare earth element like Gd and Yb, it is desirable that the content of Lu ³⁺ is small from the viewpoint of stable glass supply. From the above viewpoint, the Lu ³⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, and further preferably 4% or less. It is even more preferably 2% or less. Further, the Lu ³⁺ content can be 0% or more, and may be 0%.

Ge ⁴⁺ has a function of increasing the refractive index, but the Ge ⁴⁺ content is preferably 10% or less, and more preferably 8% or less from the viewpoint of further cost reduction of the optical element. It is more preferably 6% or less, still more preferably 4% or less, still more preferably 2% or less. Further, the Ge ⁴⁺ content may be 0% or more, and may be 0%.

Te ⁴⁺ is a component that increases the refractive index, but it is preferable that the content of Te ⁴⁺ is small from the viewpoint of environmental considerations and the like. The Te ⁴⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and 1% or less. It is even more preferred to be present. Further, the Te ⁴⁺ content may be 0% or more, and may be 0%.

Pb, As, Cd, Tl, Be and Se are each toxic. Therefore, it is preferable that these elements are not contained, that is, these elements are not introduced into the glass as a glass component.
U, Th, and Ra are all radioactive elements. Therefore, it is preferable that these elements are not contained, that is, these elements are not introduced into the glass as a glass component.
V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm and Ce increase the coloring of the glass or become a source of fluorescence. However, it is not preferable as an element to be contained in the glass for an optical element. Therefore, it is preferable that these elements are not contained, that is, these elements are not introduced into the glass as a glass component.

Sb and Sn are arbitrarily addable elements that function as a fining agent.
The Sb content of the optical glass is, for example, 0.40% or less, 0.20% or less, 0.10% or less, 0.05% or less, 0.02% or less, as Sb ³⁺ content. It can be up to 01%. The Sb ³⁺ content can be 0.00% or more, and can also be 0.00%.
The Sn content of the optical glass may be, for example, 0.40% or less, 0.20% or less, 0.10% or less, 0.05% or less, 0.02% or less, or 0.02% or less as a Sn ²⁺ content. It can be up to 01%. The Sb ³⁺ content can be 0.00% or more, and can also be 0.00%.

  The cation component has been described above. Next, the anion component will be described.

The optical glass may be an oxide glass and may contain O ²⁻ as an anion component. The O ²⁻ content is preferably 95.0 anion% or more, more preferably 97.0 anion% or more, further preferably 98.0 anion% or more, and 99.0 anion%. More preferably, it is 99.5 anion% or more, and even more preferably 100 anion%.

Examples of anion components other than O ^{2 −} include F ⁻ , Cl ⁻ , Br ⁻ and I ⁻ . However, all of F ⁻ , Cl ⁻ , Br ^−, and I ⁻ easily volatilize during melting of glass. The volatilization of these components tends to change the physical properties of the glass, reduce the homogeneity of the glass, and cause significant wear of the melting equipment. Therefore, it is preferable to suppress the total content of F ⁻ , Cl ⁻ , Br ^−, and I ⁻ to an amount obtained by subtracting the content of O ²⁻ from 100 anion%.

<Glass physical properties>
(Refractive index nd, Abbe number νd)
The optical glass is a high-refractive-index, low-dispersion glass having a refractive index nd in the range of 1.9000 to 2.1500 and an Abbe number νd in the range of 20.0 to 35.0. From the viewpoint of usefulness as a material for an optical element, preferable ranges of the refractive index nd and the Abbe number νd are as follows.
The refractive index nd is 1.9000 or more, preferably 1.9500 or more, more preferably 1.9600 or more, still more preferably 1.9700 or more, and 1.9800 or more. More preferably, it is more preferably 1.9850 or more, still more preferably 1.9900 or more, still more preferably 1.9950 or more, even more preferably 2.0000 or more. Even more preferred. Further, the refractive index nd is 2.1500 or less, preferably 2.1000 or less, more preferably 2.0500 or less, further preferably 2.0300 or less, and 2.0100 or less. And more preferably 2.0020 or less.
The Abbe number νd is a value representing the property regarding dispersion, and is represented as νd = (nd-1) / (nF-nC) by using the respective refractive indexes nd, nF, and nC in the d-line, F-line, and C-line. . The Abbe number is 35.0 or less, preferably 34.0 or less, more preferably 33.0 or less, further preferably 32.0 or less, and 31.0 or less. Is more preferable, 30.5 or less is still more preferable, 30.0 or less is still more preferable, and 29.5 or less is even more preferable. The Abbe number νd is 20.0 or more, preferably 21.0 or more, more preferably 22.0 or more, further preferably 23.0 or more, and 24.0 or more. More preferably, it is more preferably 25.0 or more, still more preferably 26.0 or more, even more preferably 27.0 or more, still more preferably 27.5 or more. Even more preferably, it is even more preferably 28.0 or more, even more preferably 28.3 or more.
It is also preferable that the refractive index nd and the Abbe number νd satisfy one or more of the following relational expressions.
nd ≧ 2.3700−0.0140 × νd
nd ≧ 2.1450−0.0070 × νd
nd ≧ 2.3900−0.0140 × νd
nd ≧ 2.1510−0.0070 × νd
nd ≧ 2.3960−0.0140 × νd
nd ≧ 2.1550−0.0070 × νd
nd ≧ 2.4000−0.0140 × νd
nd ≧ 2.1600−0.0070 × νd
nd ≧ 2.1700−0.0070 × νd
nd ≧ 2.0715-0.0380 × νd
nd ≧ 2.0915-0.0380 × νd
nd ≧ 2.1015-0.0380 × νd
nd ≦ 2.4900−0.0140 × νd
nd ≦ 2.4500−0.0140 × νd
nd ≦ 2.4300−0.0140 × νd
nd ≦ 2.4200−0.0140 × νd
In the present invention and this specification, unless otherwise specified, "refractive index" means "refractive index nd" and "Abbe number" means "Abbe number νd".

(Partial dispersion characteristics Pg, F)
From the viewpoint of chromatic aberration correction, it is preferable that the optical glass has a small partial dispersion ratio when the Abbe number νd is fixed.
Here, the partial dispersion ratio Pg, F is expressed as (ng-nF) / (nF-nc) using the respective refractive indexes ng, nF, and nc at the g-line, the F-line, and the c-line.
From the viewpoint of providing a high-refractive-index, low-dispersion glass suitable for high-order chromatic aberration correction, the preferable range of the partial dispersion ratio Pg, F of the optical glass is as follows.
The partial dispersion ratio Pg, F is preferably 0.6500 or less, more preferably 0.6300 or less, further preferably 0.6200 or less, and further preferably 0.6100 or less. Is more preferably 0.6000 or less. The partial dispersion ratio Pg, F is preferably 0.5700 or more, more preferably 0.5800 or more, further preferably 0.5820 or more, and more preferably 0.5850 or more. More preferably, it is more preferably 0.590 or more.

(Liquid phase temperature LT)
From the viewpoint of suppressing crystallization during glass production, the liquidus temperature LT of the optical glass is preferably 1400 ° C. or lower, more preferably 1380 ° C. or lower, and further preferably 1360 ° C. or lower. It is more preferably 1340 ° C. or lower, even more preferably 1320 ° C. or lower, even more preferably 1310 ° C. or lower, even more preferably 1300 ° C. or lower, and 1290 ° C. or lower. It is even more preferable, it is even more preferable that it is 1280 ° C. or lower, it is still more preferable that it is 1270 ° C. or lower, and it is even more preferable that it is 1260 ° C. or lower. The liquidus temperature LT can be, for example, 1150 ° C. or higher. However, since the liquidus temperature is preferably low, the liquidus temperature may be lower than 1150 ° C., and the lower limit is not particularly limited.

(Glass transition temperature Tg)
The glass transition temperature Tg of the optical glass is not particularly limited, but is preferably 630 ° C. or higher from the viewpoint of machinability. By setting the glass transition temperature to 630 ° C. or higher, it is possible to make the glass less likely to be damaged when the glass is machined such as cutting, cutting, grinding and polishing. From the viewpoint of machinability, the glass transition temperature Tg is more preferably 640 ° C. or higher, further preferably 700 ° C. or higher, further preferably 710 ° C. or higher, and 720 ° C. or lower. Is more preferable, 730 ° C. or higher is even more preferable, 740 ° C. or higher is still more preferable, and 745 ° C. or higher is even more preferable. On the other hand, from the viewpoint of reducing the burden on the annealing furnace and the molding die, the glass transition temperature Tg is preferably 800 ° C. or lower, more preferably 790 ° C. or lower, and further preferably 780 ° C. or lower. , 775 ° C. or lower, more preferably 770 ° C. or lower, even more preferably 765 ° C. or lower, still more preferably 760 ° C. or lower.

(Specific gravity, specific gravity / nd)
In the optical element (lens) that constitutes the optical system, the refractive power is determined by the refractive index of the glass that constitutes the lens and the curvature of the optically functional surface of the lens (the surface on which the light rays to be controlled enter and exit). When the curvature of the optically functional surface is increased, the lens thickness also increases. As a result, the lens becomes heavy. On the other hand, if glass having a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optically functional surface.
From the above, if the refractive index can be increased while suppressing an increase in the specific gravity of glass, it is possible to reduce the weight of an optical element having a constant refractive power.
From the above viewpoint, the specific gravity of the optical glass is preferably 5.40 or less, more preferably 5.35 or less, further preferably 5.30 or less, and 5.25 or less. More preferably, it is even more preferably 5.20 or less, even more preferably 5.15 or less, even more preferably 5.10 or less, even more preferably 5.05 or less. Even more preferably, even more preferably 5.00 or less. The lower the specific gravity is, the more preferable it is from the viewpoint of reducing the weight of the optical element. Therefore, the lower limit of the specific gravity of the optical glass is not particularly limited. In one aspect, the specific gravity of the optical glass is, for example, 4.30 or more, 4.40 or more, 4.50 or more, 4.60 or more, 4.70 or more, 4.75 or more, 4.77 or more, 4. It can be 80 or higher or 4.85 or higher.
From the same viewpoint, the value obtained by dividing the specific gravity of the optical glass by the refractive index nd (specific gravity / nd) is preferably 2.80 or less, more preferably 2.70 or less, and 2. It is more preferably 65 or less, even more preferably 2.60 or less, even more preferably 2.56 or less, even more preferably 2.54 or less, and 2.52 or less. Even more preferably, it is even more preferably 2.51 or less, even more preferably 2.50 or less. The smaller the value of “specific gravity / nd” is, the more preferable it is from the viewpoint of reducing the weight of the optical element. Therefore, the lower limit of the value of “specific gravity / nd” of the optical glass is not particularly limited. In one aspect, the “specific gravity / nd” of the optical glass is, for example, 2.20 or more, 2.30 or more, 2.35 or more, 2.36 or more, 2.37 or more, 2.38 or more, 2.39. It can be 2.40 or more, 2.41 or more, 2.42 or more, or 2.43 or more.

(Coloring degree λ5, λ70)
It is possible to evaluate that the light transmittance of glass, more specifically, that the light absorption edge on the shorter wavelength side is prevented from having a longer wavelength can be evaluated by the coloring degree λ5. The coloring degree λ5 represents a wavelength at which the spectral transmittance (including surface reflection loss) of glass having a thickness of 10 mm is 5% from the ultraviolet region to the visible region. Λ5 shown in Examples described later is a value measured in the wavelength range of 250 to 700 nm. More specifically, the spectral transmittance is, for example, more specifically, a glass sample having parallel flat surfaces polished to a thickness of 10.0 ± 0.1 mm is used, and light is incident from a direction perpendicular to the polished surface. The spectral transmittance obtained in this way, that is, Iout / Iin when the intensity of light incident on the glass sample is Iin and the intensity of light transmitted through the glass sample is Iout.
According to the coloring degree λ5, the absorption edge on the short wavelength side of the spectral transmittance can be quantitatively evaluated. When, for example, joining lenses with an ultraviolet curable adhesive for producing a cemented lens, the adhesive is irradiated with ultraviolet rays through an optical element to cure the adhesive. From the viewpoint of efficiently curing the ultraviolet curable adhesive, it is preferable that the absorption edge on the short wavelength side of the spectral transmittance is in the short wavelength region. The coloring degree λ5 can be used as an index for quantitatively evaluating the absorption edge on the short wavelength side. The optical glass is preferably 400 nm or less, more preferably 390 nm or less, even more preferably 385 nm or less, even more preferably 380 nm or less, even more preferably 378 nm or less, still more preferably 376 nm or less, still more preferably 374 nm or less, Even more preferably, it can exhibit a λ5 of 372 nm or less, even more preferably 370 nm or less. The lower λ5 is, the more preferable, and the lower limit is not particularly limited. In one aspect, λ5 of the optical glass is 330 nm or more, 340 nm or more, 345 nm or more, 350 nm or more, 355 nm or more, 356 nm or more, 357 nm or more, 358 nm or more, 359 nm or more, 360 nm or more, 361 nm or more, 362 nm or more or 363 nm or more. Can be

  On the other hand, as an index of the coloring degree of glass, the coloring degree λ70 is also included. λ70 represents a wavelength at which the spectral transmittance measured by the method described for λ5 is 70%. From the viewpoint of a glass with little coloring, λ70 is preferably 500 nm or less, more preferably 490 nm or less, further preferably 480 nm or less, still more preferably 470 nm or less, still more preferably 460 nm or less, still more preferably 457 nm or less, It is more preferably 455 nm or less, still more preferably 450 nm or less, still more preferably 445 nm or less, still more preferably 440 nm or less. The lower λ70 is, the more preferable, and the lower limit is not particularly limited. In one aspect, λ70 of the optical glass may be 370 nm or more, 380 nm or more, 390 nm or more, 400 nm or more, 410 nm or more, 420 nm or more, 425 nm or more, 430 nm or more, or 435 nm or more.

(Λ5 / nd, λ5 / νd, λ70 / nd, λ70 / νd)
Regarding the degree of coloring, it is preferable that the refractive index can be increased while suppressing an increase in the degree of coloring of glass. It is also preferable that the dispersion can be reduced while suppressing an increase in the coloring degree of the glass.
From the above viewpoint, the value (λ5 / nd) obtained by dividing λ5 of the optical glass by the refractive index nd is preferably 195.00 nm or less, more preferably 190.00 nm or less, and 188.00 nm or less. Is more preferable, 187.00 nm or less is more preferable, 187.50 nm or less is still more preferable, 187.00 nm or less is still more preferable, 186.50 nm or less. Even more preferably, it is still more preferably 186.00 nm or less, still more preferably 188.55 nm or less, even more preferably 185.00 nm or less. Further, the lower λ5 / nd is more preferable, and the lower limit is not particularly limited. In one aspect, λ5 / nd of the optical glass is 160.00 nm or more, 170.00 nm or more, 171.00 nm or more, 172.00 nm or more, 173.00 nm or more, 174.00 nm or more, 175.00 nm or more, 176. It can be greater than or equal to 00 nm, greater than or equal to 177.00 nm, or greater than or equal to 178.00 nm.
The value (λ5 / νd) obtained by dividing λ5 of the optical glass by the Abbe number νd is preferably 20.00 nm or less, more preferably 15.00 nm or less, and further preferably 14.00 nm or less. It is more preferably 13.00 nm or less, still more preferably 12.90 nm or less, even more preferably 12.80 nm or less, still more preferably 12.70 nm or less. Further, the lower λ5 / νd is, the more preferable, and the lower limit is not particularly limited. In one aspect, λ5 / νd of the optical glass is 8.00 nm or more, 8.50 nm or more, 9.00 nm or more, 9.50 nm or more, 10.00 nm or more, 10.50 nm or more, 11.00 nm or more, 11. It can be 50 nm or more, 11.70 nm or more, 12.00 nm or more, 12.10 nm or more, 12.20 nm or more, 12.30 nm or more, 12.40 nm or more, or 12.50 nm or more.
The value (λ70 / nd) obtained by dividing λ70 of the optical glass by the refractive index nd is preferably 270.00 nm or less, more preferably 260.00 nm or less, and further preferably 250.00 nm or less. It is more preferably 240.00 nm or less, still more preferably 235.00 nm or less, still more preferably 230.00 nm or less, still more preferably 227.00 nm or less, Even more preferably, it is 225.00 nm or less. Further, the lower λ70 / nd is more preferable, and the lower limit is not particularly limited. In one aspect, λ70 / nd of the optical glass is 190.00 nm or more, 200.00 nm or more, 205.00 nm or more, 210.00 nm or more, 212.00 nm or more, 214.00 nm or more, 216.00 nm or more, 218. It may be 00 nm or more, or 220.00 nm or more.
The value (λ70 / νd) obtained by dividing λ70 of the optical glass by the Abbe number νd is preferably 25.00 nm or less, more preferably 22.00 nm or less, and further preferably 20.00 nm or less. Preferably, it is 19.00 nm or less, more preferably, 18.00 nm or less, even more preferably, 17.00 nm or less, even more preferably 16.00 nm or less. Further, the lower λ70 / νd is, the more preferable, and the lower limit is not particularly limited. In one aspect, λ70 / νd of the optical glass is 8.00 nm or more, 9.00 nm or more, 10.00 nm or more, 11.00 nm or more, 12.00 nm or more, 13.00 nm or more, 14.00 nm or more or 15. It can be greater than or equal to 00 nm.

<Glass manufacturing method>
The above-mentioned optical glass can be obtained by, for example, blending, melting, and shaping glass raw materials so that required characteristics can be obtained. As the 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 glass forming 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 above optical glass;
An optical element blank made of the above 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 above optical glass into a glass material for press molding;
A method for producing an optical element blank, which comprises a step of producing an optical element blank by press-molding the above-mentioned press-molding glass material using a press mold.
A method for manufacturing an optical element blank including a step of molding the optical glass into an optical element blank,
Is also provided.

  The optical element blank is similar to the shape of the target optical element, and should be polished into the shape of the optical element (surface layer that will be removed by polishing), and if necessary be ground (removed by grinding) It is an optical element base material to which a surface layer) is added. The optical element is finished by grinding and polishing the surface of the optical element blank. In one aspect, an optical element blank can be produced by a method of pressing a molten glass obtained by melting an appropriate amount of the above optical glass (called a direct pressing method). In another aspect, an optical element blank can be produced by solidifying a molten glass obtained by melting an appropriate amount of the above glass.

  In another aspect, an optical element blank can be produced by producing a press-molding glass material and press-forming the produced press-molding glass material.

  Press molding of the glass material for press molding can be performed by a known method of pressing the glass material for press molding in a softened state by heating with a press mold. Both heating and press molding can be performed in the atmosphere. By annealing after press molding to reduce the strain inside the glass, a uniform optical element blank can be obtained.

  In addition to what is called a press-molding glass gob that is used for press-molding for making optical element blanks, the press-molding glass material is subjected to mechanical processing such as cutting, grinding, and polishing to obtain a press-molding glass gob. Also included are those that are subjected to press molding through. As a cutting method, a groove is formed by a method called scribing on a portion of the glass plate surface to be cut, and local pressure is applied to the groove portion from the back surface of the surface where the groove is formed, so that the glass portion is cut at the groove portion. There are methods such as breaking the plate and cutting the glass plate with a cutting blade. Moreover, barrel grinding etc. are mentioned as a grinding and polishing method.

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

[Optical element and manufacturing method thereof]
Another aspect of the present invention is
The present invention relates to an optical element made of the above optical glass.
The optical element is manufactured using the optical glass. In the above optical element, one or more coatings such as a multilayer film such as an antireflection film may be formed on the glass surface.

According to one aspect of the present invention,
An optical element manufacturing method comprising a step of producing an optical element by grinding and / or polishing the optical element blank;
Is also provided.

  In the method for producing an optical element, a known method may be applied to grinding and polishing, and after the processing, the optical element surface is sufficiently washed and dried to obtain an optical element having high internal quality and surface quality. it can. In this way, an optical element made of the above optical glass can be obtained. Examples of the optical element include spherical lenses, aspherical lenses, various lenses such as microlenses, and prisms.

  Further, the optical element made of the above optical glass is also suitable as a lens forming a cemented optical element. Examples of the cemented optical element include a cemented lens (a cemented lens), a cemented lens and a prism, and the like. For example, a cemented optical element is an ultraviolet-curable adhesive used for bonding cemented lenses by precisely processing (for example, spherical polishing) the bonding surfaces of two optical elements to be bonded so that the shapes are inverted. Can be prepared by coating and bonding and then irradiating ultraviolet rays through the lens to cure the adhesive. The above optical glass is preferable as a material for an optical element for producing a cemented optical element as described above. By manufacturing a plurality of optical elements to be bonded using a plurality of types of optical glass having different Abbe numbers νd and bonding them, it is possible to obtain an element suitable for correction of chromatic aberration.

As a result of the quantitative analysis of the glass composition, the glass component may be expressed on an oxide basis, and the content of the glass component may be displayed in mass%. The composition represented by mass% based on the oxide can be converted into a composition represented by cation% and anion% by the following method, for example.
If it contains N species of the glass component in the glass, a k-th of the glass component is denoted as A (k) _m O _n. However, k is any integer of 1 or more and N or less.
A (k) is a cation, O is oxygen, and m and n are integers determined stoichiometrically. For example, when the oxide-based notation is B ₂ O ₃ , m = 2 and n = 3, and when SiO ₂ is used, m = 1 and n = 2.
Next, _let the content of A (k) _{m On be} X (k) [mass%]. Here, A the atomic weight of (k) P (k), when the atomic number of oxygen O and Q, A (k) _m O _n formal molecular weight R of (k) is
R (k) = P (k) × m + Q × n
Becomes
Furthermore,
B = 100 / {Σ [m × X (k) / R (k)]}
Then, the content (cation%) of the cation component A (k) ^{s +} is [X (k) / R (k)] × m × B (cation%). Here, Σ means the sum of m × X (k) / R (K) from k = 1 to N. m changes according to k. s is 2n / m.
Further, the molecular weight R (k) may be calculated by rounding off the fourth digit after the decimal point and displaying the value up to the third digit after the decimal point. The molecular weights of some glass components and additives in terms of oxides are shown in Table 1 below.

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

<Example 1>
So as to have the glass composition shown in the following table, the corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. are respectively used as raw materials for introducing the components, and the raw materials are weighed. The mixture was thoroughly mixed to prepare a raw material.
This prepared raw material was put into a platinum crucible, heated and melted. After melting, pour the molten glass into the mold, allow it to cool to near the glass transition temperature, immediately put it in an annealing furnace, anneal for about 1 hour in the glass transition temperature range, and then allow it to cool to room temperature in the furnace. The respective optical glasses (oxide glasses) shown in Table 1 were obtained.
Regarding the anion component of each optical glass shown in the table below, the O ²⁻ content is 100 anion%.
When the obtained optical glass was observed under a microscope with an optical microscope, no crystal precipitation, foreign matter such as platinum particles, bubbles were observed, and striae were not observed.
The physical properties of the optical glass thus obtained are shown in the table below.
The physical properties of the optical glass were measured by the methods described below.

<Evaluation of physical properties of optical glass>
(1) Refractive indices nd, ng, nF, nC and Abbe number νd
With respect to the glass obtained by lowering the temperature at a temperature lowering rate of −30 ° C./hour, the refractive index nd, ng, nF, nC and the Abbe number νd were measured by the refractive index measuring method of the Japan Optical Glass Industry Association.

(2) Partial dispersion ratio Pg, F
The partial dispersion ratio Pg, F was calculated from the refractive indexes ng, nF, nC obtained in (1) above.

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

(4) Liquidus temperature LT
A glass sample (volume: 10 cm ³ ) consisting of each glass shown in the table below was placed in a platinum crucible and held in a glass melting furnace set at 1400 ° C. for 20 minutes to sufficiently melt the glass sample. After that, the platinum crucible was taken out from the glass melting furnace, and the glass sample was left to cool in the platinum crucible until the temperature of the glass sample became 500 ° C. or lower. Then, the platinum crucible was put in a glass melting furnace set to a temperature of T ° C., held for 2 hours, taken out of the furnace, and immediately (within 8 seconds) the platinum crucible containing the glass sample was kept at room temperature. Placed on a refractory (such as brick), the glass sample was cooled to room temperature. The room temperature here is a temperature in the range of -10 to 80 ° C. Then, the surface and the inside of the glass sample were visually observed to confirm the presence or absence of crystals. The temperature T ° C. was changed in the range of 1100 to 1350 ° C. in steps of 10 ° C., and the above experiment was repeated. The lowest temperature at which no crystal was observed on the surface or inside of the glass sample was defined as the liquidus temperature LT.

(5) Specific gravity, specific gravity / nd
Specific gravity was measured by the Archimedes method.
A value (specific gravity / nd) was calculated by dividing the measured specific gravity by the refractive index nd obtained in (1) above.

(6) Coloring degree λ5, λ70
Using a glass sample having a thickness of 10 ± 0.1 mm having two optically polished flat surfaces opposed to each other, a spectrophotometer was used to make light having an intensity Iin incident on the polished surface from a direction perpendicular to the polished surface. The intensity Iout of the light transmitted through was measured and the spectral transmittance Iout / Iin was calculated. The wavelength at which the spectral transmittance was 5% was λ5, and the wavelength at which the spectral transmittance was 70% was λ70.

(7) λ5 / nd, λ5 / νd, λ70 / nd, λ70 / νd
From nd, νd, λ5 and λ70 obtained above, λ5 / nd, λ5 / νd, λ70 / nd and λ70 / νd were calculated.

  The above results are shown in Table 2 (Tables 2-1 to 2-6) below.

<Evaluation of glass stability>
Glass is obtained by shaping molten glass. When the glass stability is low, the number of crystal grains contained in the glass obtained by casting the molten glass in a mold and increasing the number thereof increases. Therefore, the glass stability, particularly the devitrification resistance when molding a glass melt, can be evaluated by the number of crystals contained in the glass melted and molded under certain conditions. An example of the evaluation method is shown below.
Using nitrates, sulphates, carbonates, hydroxides, oxides, boric acid, etc. as raw materials, weigh each raw material powder and mix well to make a raw material, which is then put into a platinum crucible with a capacity of 300 ml. In a glass melting furnace set at 1400 ° C. for 2 hours, the mixture is heated and melted to prepare 150 g of homogeneous molten glass. During this time, the molten glass is stirred and shaken several times.
After 2 hours, take out the crucible containing the molten glass from the above furnace, stir and shake for 15 to 20 seconds, and then pour the molten glass into a carbon mold (50 mm x 40 mm x 8 mm to 12 mm) and slowly cool the furnace. Put inside to remove distortion.
The inside of the obtained glass was observed using an optical microscope (magnification: 100 times), the number of precipitated crystals was counted, the number of crystals contained per 1 kg of glass was calculated, and the number density (number of crystals) / Kg).
The number density of crystals evaluated by the above method is preferably 2000 pieces / kg or less, more preferably 1000 pieces / kg or less, further preferably 800 pieces / kg or less, and 600 pieces / kg. It is more preferably not more than kg, even more preferably not more than 400 pieces / kg, even more preferably not more than 200 pieces / kg, even more preferably not more than 100 pieces / kg, and even 50 pieces / Kg or less is even more preferable, 30 / kg or less is even more preferable, and 0 / kg is particularly preferable. The number density of crystals of each glass shown in Table 2 above evaluated by the above method was 0 pieces / kg.

<Example 2>
The various glass obtained in Example 1 was used to prepare a glass gob for press molding. This glass gob was heated and softened in the atmosphere and press-molded with a press mold to produce a lens blank (optical element blank). The produced lens blank was taken out from the press mold, annealed, and subjected to mechanical processing including polishing to produce a spherical lens made of various glasses produced in Example 1.

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

<Example 4>
A glass lump (optical element blank) produced by solidifying the molten glass produced in Example 1 was annealed, and mechanical processing including polishing was performed to produce a spherical lens made of various glasses produced in Example 1.

<Example 5>
The spherical lens manufactured in Examples 2 to 4 was bonded to a spherical lens made of another type of glass to manufacture a cemented lens. The cemented surface of the spherical lenses manufactured in Examples 2 to 4 was convex, and the cemented surface of the spherical lenses made of other types of optical glass was concave. The two bonded surfaces were manufactured so that the absolute values of the radii of curvature were equal to each other. An ultraviolet curable adhesive for joining an optical element was applied to the joint surface, and two lenses were bonded together at the joint surfaces. After that, the adhesive applied to the joint surface was irradiated with ultraviolet rays through the spherical lenses produced in Examples 2 to 4 to solidify the adhesive.
A cemented lens was produced as described above.

  Finally, the above-mentioned aspects are summarized.

According to one embodiment, in the glass composition expressed as cation%, the Ta ⁵⁺ content is in the range of 0 to 5 cation%, and the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ is The cation ratio of Ti ⁴⁺ content (Ti ⁴⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is in the range of 0.60 to 1.00, and La ³⁺ , Gd ³⁺ and Y are included. the total content of the cation ratio of Si ⁴⁺ and B ³⁺ to the total content of ^{3+ ((Si 4+ + B 3+} ) / (La 3+ + Gd 3+ + Y 3+)) is 0.30 to 2 The cation ratio of the total content of Si ⁴⁺ and B ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((Si ⁴⁺ + B ³⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is in the range of 0.30 to 34.00 and is based on the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ . La ³⁺ The total content of the cation ratio of Gd ³⁺ and ^{Y 3+ ((La 3+ + Gd} 3+ + Y 3+) / (Ti 4+ + Nb 5+ + W 6+ + Bi 3+)) is 0.30 to 33.00 And the cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ^{2+ to} the total content of La ³⁺ and Y ³⁺ ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (La ³⁺ + Y ³⁺ )) is in the range of 0.00 to 1.50, and Mg ^{2 with} respect to the total content of Si ⁴⁺ and B ³⁺ The cation ratio of ( ⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (Si ⁴⁺ + B ³⁺ )) is 0. In the range of 0.000 to 1.00, and Gd ³⁺ , Nb ^{5+ with} respect to the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr ⁴⁺ and Ti ^4+. the sum of the content of the cation of and W ^{6+ ((Gd 3+ + Nb 5+ +} W 6+) / (Si 4+ + B 3+ + Zn 2+ + La 3+ + Y 3+ + Zr 4+ + Ti 4+)) is in the range of 0.000 to 0.100, Provided is an optical glass having a refractive index nd in the range of 1.9000 to 2.1500 and an Abbe number νd in the range of 20.0 to 35.0.

The optical glass has optical properties (nd and νd) useful as a material for optical elements. Further, the optical glass is an optical glass that can contribute to cost reduction of the optical element because the proportion of expensive glass components Ta ⁵⁺ , Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ is low.

In one aspect, the optical glass may have a total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ in the range of 0 to 30 cation%.

In one aspect, the optical glass may have a total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ in the range of 0 to 8 cation%.

In one aspect, the optical glass may have a total content of La ³⁺ , Gd ³⁺ and Y ³⁺ in the range of 20 to 60 cation%.

  According to one aspect, there is provided a glass material for press molding, which is made of the above optical glass.

  According to one aspect, there is provided an optical element blank made of the above optical glass.

Since the press-molding glass material and the optical element blank are made of the above optical glass in which Ta ⁵⁺ , Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ , which are expensive glass components, occupy a low proportion, the cost of the optical element is low. Can contribute to

  According to one aspect, an optical element made of the above optical glass is provided.

Since the optical element is made of the optical glass having a low proportion of expensive glass components Ta ⁵⁺ , Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ , it can be manufactured at low cost.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.
For example, the optical glass according to one embodiment of the present invention can be obtained by adjusting the composition described in the specification for the above-exemplified glass composition.
Further, it is of course possible to arbitrarily combine two or more of the matters described as examples or preferable ranges in the specification.

Claims (7)

In the glass composition of cation% display,
Ta ⁵⁺ content is in the range of 0-5 cation%,
The cation ratio of the Ti ⁴⁺ content to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is 0. .60 to 1.00 range,
The cation ratio of the total content of Si ⁴⁺ and B ³⁺ to the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ ((Si ⁴⁺ + B ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ^{3 +} )) Is in the range of 0.30 to 2.40,
Cation ratio of the total content of Si ⁴⁺ and B ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((Si ⁴⁺ + B ³⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is in the range of 0.30 to 34.00,
Cation ratio of the total content of La ³⁺ , Gd ³⁺ and Y ^{3+ to} the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((La ³⁺ + Gd ³⁺ + Y ³⁺ ). / (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ )) is in the range of 0.30 to 33.00,
The cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ^{2+ to} the total content of La ³⁺ and Y ³⁺ ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (La ³⁺ + Y ³⁺ )) is in the range of 0.00 to 1.50,
The cation ratio of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ with respect to the total content of Si ⁴⁺ and B ³⁺ ((Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) / (Si ⁴⁺ + B ³⁺ )) is in the range of 0.00 to 1.00,
Cation ratio of the total content of Gd ³⁺ , Nb ⁵⁺ and W ^{6+ to} the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr ⁴⁺ and Ti ^4+. ((Gd ³⁺ + Nb ⁵⁺ + W ⁶⁺ ) / (Si ⁴⁺ + B ³⁺ + Zn ²⁺ + La ³⁺ + Y ³⁺ + Zr ⁴⁺ + Ti ⁴⁺ )) is in the range of 0.000 to 0.100,
An optical glass having a refractive index nd in the range of 1.9000 to 2.1500 and an Abbe number νd in the range of 20.0 to 35.0. The optical glass according to claim 1, wherein the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ is in the range of 0 to 30 cation%. The optical glass according to claim 1 or 2, wherein the total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ is in the range of 0 to 8 cation%. The optical glass according to claim 1, wherein the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ is in the range of 20 to 60 cation%. A glass material for press molding comprising the optical glass according to claim 1. An optical element blank made of the optical glass according to claim 1. An optical element comprising the optical glass according to claim 1.