JP6943995B2 - Optical glass and its use - Google Patents

Description

The present invention relates to an optical glass having high refractive index and low dispersion characteristics, a glass gob for press molding and an optical element blank made of this optical glass, and an optical element.

A lens made of high-refractive-index low-dispersion glass constitutes a projection optical system such as an imaging optical system or a projector in order to make it possible to make the optical system compact while correcting chromatic aberration by combining it with a lens made of ultra-low dispersion glass. It occupies a very important position as an optical element.
Patent Document 1 discloses high-refractive-index, low-dispersion glass having a refractive index of 1.90 to 2.10 and an Abbe number of νd of 22 to 35, although it is not an optical element material for an imaging optical system or a projection optical system. ing.
On the other hand, Patent Document 2 discloses an optical glass having a refractive index of 1.90 or more and an Abbe number of 25 or more.

Japanese Unexamined Patent Publication No. 60-33229 Japanese Unexamined Patent Publication No. 60-131845

Regarding the optical characteristics of optical glass, the horizontal axis is the Abbe number νd (the Abbe number νd decreases from left to right), and the vertical axis is the refractive index nd (the refractive index nd increases from bottom to top). When the change in optical characteristics of conventional optical glass when the composition of the glass is changed is plotted on a graph called an optical characteristic diagram, it is plotted within a band-shaped range from the lower left to the upper right of the optical characteristic diagram. Is distributed. When the composition is changed in order to obtain the optical characteristics of the upper left from the band-shaped range from the lower left to the upper right of the optical characteristics diagram, the glass stability tends to decrease, and the glass tends to be devitrified or not vitrified.
On the other hand, from the aspect of application, the high refractive index low dispersion optical glass showing the refractive index nd and the Abbe number νd in the upper left range in the optical characteristic diagram is a glass material of an optical element effective for making the optical system highly functional and compact. Can be.
However, in general, in the conventional high refractive index low dispersion glass as described in Patent Documents 1 and 2, it is possible to obtain a glass having a higher refractive index as the Abbe number νd decreases. On the other hand, in these conventional high-refractive-index, low-dispersion glasses, if the refractive index is increased while maintaining the Abbe number νd, the glass stability tends to decrease and the glass tends not to be vitrified.
Therefore, it is very significant to provide an optical glass showing a refractive index nd and an Abbe number νd in the upper left range of the optical characteristic diagram while maintaining the glass stability.

One aspect of the present invention is to provide an optical glass having excellent glass stability while being a glass having a high refractive index and a low dispersion.

As a result of diligent studies, the present inventors have found that by adjusting the glass composition, an optical glass having a high refractive index and a low dispersion glass and yet having high stability can be obtained.

One aspect of the present invention is
Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential ingredients.
In cation% display,
5 to 55% of ^{Si 4+} and B ^{3+ in total,}
La ³⁺ is 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total),
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ total 22-55%,
Including, however, the Ti ⁴⁺ content is 22% or less,
The cation ratio [Si ⁴ / (Si ⁴ + B ^{3+ )] of the content of Si 4+} to the total content of Si ⁴⁺ and B ³⁺ is 0.40 or less,
The total content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ is 65% or more.
The cation ratio of the content ^{of Y 3+} to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [Y 3+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.12 or less,
The cation ratio ^{of the Ba 2+} content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [Ba 2+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.40 or less,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio (Ti ⁴⁺ / B ³⁺ ) of the Ti ⁴⁺ content to the B ³⁺ content is 0.85 or more.
And
The present invention relates to an optical glass in which the Abbe number νd is in the range of 23 to 35 and the refractive index nd is an oxide glass satisfying the following equation (1).
nd ≧ 2.205− (0.0062 × νd) ・ ・ ・ (1)

Another aspect of the present invention is
Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential ingredients.
In cation% display,
5 to 55% of ^{Si 4+} and B ^{3+ in total,}
La ³⁺ is 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total),
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ total 23-70% (however, Ti ⁴⁺ exceeds 22%),
Including
The cation ratio of the content ^{of Y 3+} to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [Y 3+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.14 or less,
The cation ratio ^{of the Ba 2+} content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [Ba 2+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.40 or less,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio (Ti ⁴⁺ / B ³⁺ ) of the Ti ⁴⁺ content to the B ³⁺ content is 0.85 or more.
And
The present invention relates to an optical glass which is an oxide glass in which the Abbe number νd is in the range of 18 or more and less than 35 and the refractive index nd satisfies the following equation (2).
nd ≧ 2.540- (0.02 × νd) ・ ・ ・ (2)

A further aspect of the present invention relates to a press-molded glass gob made of the optical glass of the above aspect.

A further aspect of the present invention relates to an optical element blank made of the optical glass of the above-described aspect.

A further aspect of the present invention relates to an optical element made of the optical glass of the above-described aspect.

According to one aspect of the present invention, it is possible to provide an optical glass having excellent glass stability while being a glass having a high refractive index and a low dispersion. Further, it is possible to provide a glass gob for press molding made of the above optical glass, an optical element blank, and an optical element.
According to the optical element and an optical element manufactured from the press-molding glass gob or the optical element blank, for example, a lens, a compact optical system for chromatic aberration correction is provided by combining with a lens made of high refractive index and high dispersion glass. You can also do it.

[Optical glass I]
One aspect of the optical glass of the present invention (hereinafter referred to as "optical glass I") contains Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ as essential components. In terms of cation%, Si ⁴⁺ and B ³⁺ are 5 to 55% in total, and La ³⁺ is 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70 in total. % Or less), Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ in total, 22-55%, except that the Ti ⁴⁺ content is 22% or less.
The cation ratio [Si ⁴ / (Si ⁴ + B ^{3+ )] of the content of Si 4+} to the total content of Si ⁴⁺ and B ³⁺ is 0.40 or less,
La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ total content is 65% or more, La ³ The cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ^{3+ )] of the content of Y 3+} to the total content of ⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 0. 12 or less, the cation ratio ^{of the Ba 2+} content to the total content of ^{La 3+} , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [Ba 2+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺⁾ )] is 0.40 or less, Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio (Ti ⁴⁺ / B ³⁺ ) of the Ti ⁴⁺ content to the B ³⁺ content is 0.85 or more.
This is an optical glass in which the Abbe number νd is in the range of 23 to 35 and the refractive index nd is an oxide glass satisfying the following equation (1).
nd ≧ 2.205− (0.0062 × νd) ・ ・ ・ (1)
Another aspect of the optical glass of the present invention (optical glass II) will be described later.
Hereinafter, the optical glass I will be described in more detail.

The reasons for limiting the composition range will be described below, but unless otherwise specified, the content and total content of each component are indicated by% cation.

Si ⁴⁺ and B ³⁺ are network-forming components and components that maintain glass stability. If ^{the total content of Si 4+} and B ³⁺ is less than 5%, the glass stability deteriorates, the liquidus temperature rises, and if the total content exceeds 55%, it becomes difficult to achieve the desired refractive index. Become. Therefore, ^{the total content of Si 4+} and B ³⁺ is 5 to 55%. The preferred upper limit of the total content of Si ⁴⁺ and B ³⁺ is 50%, the more preferred upper limit is 45%, the further preferred upper limit is 40%, the more preferred upper limit is 35%, the further preferred upper limit is 30%, and Si. ^{The preferred lower limit of the total content of 4+} and B ³⁺ is 10%, the more preferred lower limit is 13%, the more preferred lower limit is 15%, the more preferred lower limit is 18%, and the even more preferred lower limit is 20%.

In ^{addition to the above functions, Si 4+} is an essential component that is suitable for forming molten glass and is effective in maintaining viscosity and improving chemical durability. In order to effectively obtain the above functions, the content thereof is preferably 1% or more. On the other hand, in order to suppress an increase in the liquidus temperature and the glass transition temperature while obtaining a desired refractive index, the Si ⁴⁺ content is preferably 30% or less. Further, from the viewpoint of realizing a desired Abbe number, maintaining the meltability of the glass, and improving the devitrification resistance, the Si ⁴⁺ content is preferably 30% or less. Therefore, ^{the content of Si 4+} is preferably in the range of 1 to 30%. A more preferred upper limit of the Si ⁴⁺ content is 25%, a further preferred upper limit is 20%, a further preferred upper limit is 18%, a further preferred upper limit is 15%, and an even more preferred upper limit is 12%. From the viewpoint of obtaining the effect of the ^{Si 4+ content satisfactorily, the more preferable lower limit of the Si 4+} content is 2%, the more preferable lower limit is 3%, the more preferable lower limit is 4%, and the further preferable lower limit is 5. %, And even more preferably the lower limit is 6%.

In ^{addition to the above functions, B 3+} is an essential component effective for maintaining the meltability of glass, lowering the liquidus temperature, and lowering the dispersion. In order to effectively obtain the above functions, the content thereof is preferably 1% or more. A B ³⁺ content of 1% or more is preferable from the viewpoint of glass stability. ^{On the other hand, the B 3+} content is preferably 50% or less from the viewpoint of maintaining good chemical durability and the like while obtaining a desired refractive index. Therefore, ^{the content of B 3+} is preferably in the range of 1 to 50%. A more preferred upper limit of B ³⁺ content is 40%, a further preferred upper limit is 35%, a more preferred upper limit is 30%, a further preferred upper limit is 25%, an even more preferred upper limit is 22%, and a particularly preferred upper limit is 20%, ^{the more preferred lower limit of B 3+} content is 3%, the more preferred lower limit is 5%, the more preferred lower limit is 7%, the even more preferred lower limit is 9%, and the even more preferred lower limit is 11%. be.

When the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ^{3+ )] of the Si 4+} content to the total content of ^{Si 4+} and B ³⁺ exceeds 0.40, the glass stability is maintained and the glass stability is maintained. It becomes difficult to obtain desired optical characteristics, the meltability is lowered, and the glass raw material becomes difficult to melt. Therefore, in the optical glass I, the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is set to 0.40 or less. For the above reasons, ^{the preferred upper limit of the cation ratio [Si 4+} / (Si ⁴⁺ + B ³⁺ )] is 0.38, the more preferred upper limit is 0.36, the more preferred upper limit is 0.35, and the more preferred upper limit is 0. .34, an even more preferred upper limit is 0.32. Since the optical glass I contains Si ⁴⁺ and B ³⁺ as essential components, the lower limit of the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is more than 0. In order to improve the glass stability and make the viscosity of the molten glass suitable for molding, ^{the preferable lower limit of the cation ratio [Si 4+} / (Si ⁴⁺ + B ³⁺ )] is 0.10, and the more preferable lower limit is 0.10. 0.14, a more preferable lower limit is 0.17, a more preferable lower limit is 0.20, and a further preferable lower limit is 0.23.

La ³⁺ is an essential component having an excellent function of reducing the high refractive index and low dispersion while maintaining the stability of the glass, and also has a function of improving the chemical durability. If the La ³⁺ content is less than 10%, it becomes difficult to obtain the above effect, and if the La ³⁺ content exceeds 50%, the devitrification resistance deteriorates and the liquid phase temperature rises. Therefore, ^{the content of La 3+} is set to 10 to 50%. The preferred upper limit of the La ³⁺ content is 45%, the more preferred upper limit is 40%, the more preferred upper limit is 35%, the more preferred upper limit is 33%, and ^{the preferred lower limit of the La 3+} content is 15%, more. The preferred lower limit is 18%, the further preferred lower limit is 20%, the more preferred lower limit is 22%, and the even more preferred lower limit is 24%.

Gd ^3+, Y ^3+, Yb ^3+, like La ^3+, a high refractive index and low dispersion ingredients, also serves to improve the chemical durability. When ^{the total content of La 3+} , Gd ³⁺ , Y ³⁺ and Yb ³⁺ exceeds 70%, the glass stability deteriorates and the liquidus temperature rises. Therefore, ^{the total content of La 3+} , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 70% or less. The preferred upper limit of the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 60%, the more preferred upper limit is 50%, the more preferred upper limit is 45%, the more preferred upper limit is 40%, even more preferred. The upper limit is 38%. From the viewpoint of achieving the desired refractive index and Abbe number, ^{the preferable lower limit of the total content of La 3+} , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 11%, the more preferable lower limit is 15%, and the more preferable lower limit is 20%, a more preferred lower limit is 23%, a further preferred lower limit is 25%, an even more preferred lower limit is 28%, and a particularly preferred lower limit is 30%.

The total content of ^{La 3+} , Gd ³⁺ , Y ³⁺ and Yb ^{3+ in} the optical glass I is to maintain the glass stability, suppress the rise in the liquidus temperature, and achieve high refractive index and low dispersion. The cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ^{3+ )] of the content of Y 3+} with respect to the ratio is 0.12 or less. The preferred upper limit of the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.11, the more preferred upper limit is 0.10, the more preferred upper limit is 0.08, and the more preferred upper limit is 0.04, a more preferred upper limit is 0.02. The cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] can also be set to 0.

From the viewpoint of lowering the liquidus temperature and improving the devitrification resistance, ^{the preferable upper limit of the content of Gd 3+} is 20%, the more preferable upper limit is 15%, the further preferable upper limit is 10%, and the more preferable upper limit is 8%. An even more preferable upper limit is 6%. The preferable lower limit of the content of Gd ³⁺ is 0.5%, the more preferable lower limit is 1%, the further preferable lower limit is 2%, and the more preferable lower limit is 3%. The Gd ³⁺ content can also be set to 0%.

The preferred upper limit of the Y ³⁺ content is 15%, the more preferred upper limit is 10%, the more preferred upper limit is 7%, the more preferred upper limit is 5%, the even more preferred upper limit is 3%, and the even more preferred upper limit is 2%. be. The preferred lower limit of the Y ^{3+ content is 0.1%.} The Y ³⁺ content can also be set to 0%.

The preferred upper limit of the Yb ³⁺ content is 10%, the more preferred upper limit is 8%, the more preferred upper limit is 6%, the more preferred upper limit is 4%, and the even more preferred upper limit is 2%. The Yb ³⁺ content can also be set to 0%. Since Yb ³⁺ has absorption in the infrared region, it is not suitable for use in high-sensitivity optical systems such as high-precision video cameras and surveillance cameras, which require photosensitive characteristics in the near-infrared region. Glass with a reduced Yb ³⁺ content is suitable for the above applications.

While maintaining good glass stability, over the high refractive index and low dispersion ^{of, La 3+, Gd 3+, Gd} 3+ to the total content of Y ³⁺ and Yb ^3+, Y ³⁺ and Yb ³ the total content of the cation ratio of ^{+ [(Gd 3+ + Y 3+} + Yb 3+) / (La 3+ + Gd 3+ + Y 3+ + Yb 3+)] it is preferred that greater than 0, is 0.02 or more More preferably, it is more preferably 0.06 or more, further preferably 0.10 or more, and even more preferably 0.14 or more.
On the other hand, from the viewpoint of further improving the glass stability, the preferable upper limit of ^{the cation ratio [(Gd 3+} + Y ³⁺ + Yb ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ^{3+)] is 0.} .80, a more preferred upper limit is 0.50, a further preferred upper limit is 0.40, a more preferred upper limit is 0.30, and a further preferred upper limit is 0.20.

Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , and W ^{6+ work} to increase the refractive index, improve the devitrification resistance, suppress the rise in the liquidus temperature, and improve the chemical durability. If ^{the total content of Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is less than 22%, it will be difficult to obtain the above effect, and Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ When the total content exceeds 55%, the devitrification resistance deteriorates and the liquidus temperature rises. In addition, the dispersion becomes high and the coloring of the glass becomes stronger. Therefore, the total content of ^{Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ^{6+ is 22-55%.} The preferred upper limit of the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is 45%, the more preferred upper limit is 40%, the more preferred upper limit is 35%, the more preferred upper limit is 33%, even more preferred. The upper limit is 31%, with ^{a preferred lower limit of 23% for the total content of Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ , a more preferred lower limit of 24%, a more preferred lower limit of 25% and a more preferred lower limit. Is 26%, and an even more preferable lower limit is 27%.

For the optical glass I, ^{the total content of Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is within the above range, ^{the content of Ti 4+} is 22% or less, and Zr ⁴⁺ is essential. Use as an ingredient. Further, Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W ^{By adjusting 6+} ) / Zr ⁴⁺ ], the devitrification resistance can be improved and the rise in liquid phase temperature can be suppressed. If the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is less than 2, the devitrification resistance deteriorates and the liquidus temperature rises. Therefore, in the optical glass I, the range of the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is set to 2 or more. The preferable lower limit of the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 3.0, the more preferable lower limit is 3.5, the further preferable lower limit is 4.0, and one layer. The preferred lower limit is 4.5 and the even more preferred lower limit is 5.0. Further, from the viewpoint of further improving the devitrification resistance, ^{the preferable upper limit of the cation ratio [(Zr 4+} + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 56, and the more preferable upper limit is 50. A more preferred upper limit is 40, a more preferred upper limit is 30, a more preferred upper limit is 20, and a further preferred upper limit is 10.

From the viewpoint of achieving desired optical properties while maintaining glass stability, ^{the preferable lower limit of the Ti 4+} content is 10%, the more preferable lower limit is 12%, the further preferable lower limit is 14%, and the more preferable lower limit is 16. %, The more preferred lower limit is 18%, ^{the preferred upper limit of the Ti 4+} content is 21.9%, the more preferred upper limit is 21.8%, the further preferred upper limit is 21.7%, and the more preferred upper limit is 21. The upper limit is 6.6%, and even more preferable is 21.5%.

From the viewpoint of achieving desired optical properties while maintaining glass stability, ^{the preferable lower limit of the Nb 5+} content is 1%, the more preferable lower limit is 2%, the more preferable lower limit is 3%, and the more preferable lower limit is 4. %, A more preferred lower limit is 5%, ^{a preferred upper limit of Nb 5+} content is 30%, a more preferred upper limit is 25%, a further preferred upper limit is 20%, a further preferred upper limit is 15%, a further preferred upper limit. Is 10%, and an even more preferable upper limit is 8%.

Compared with Ti ⁴⁺ , Nb ⁵⁺ , and W ⁶⁺ , Ta ⁵⁺ works to increase the refractive index and enhance the glass stability without increasing the dispersion. If the Ta ⁵⁺ content exceeds 10%, the liquidus temperature rises and the devitrification resistance decreases ^{. Therefore, the Ta 5+} content is preferably 0 to 10%. Considering that Ta ⁵⁺ is an expensive component, ^{the preferable range of the content of Ta 5+} is 0 to 8%, the more preferable range is 0 to 6%, the more preferable range is 0 to 4%, and the more preferable range is further. Is 0 to 2%, and a more preferable range is 0 to 1%. It is even more preferable that it does not contain Ta ^5+.

While obtaining desired optical characteristics, from the viewpoint of improving the glass stability, the total content of the cation ratio of Nb ⁵⁺ and Ta ⁵⁺ to the content of ^{Nb 5+ [(Nb 5+ + Ta} 5+) / Nb 5 ⁺ ] Is preferably 1 or more. When the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / Nb ⁵⁺ ] exceeds 11, the specific gravity of the glass increases, and when glass is used for the lens, the drive power consumption during autofocus increases, and the essential component Since a ^{large amount of Ta 5+,} which is more expensive than ^{Nb 5+} , is required, the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / Nb ⁵⁺ ] is preferably 11 or less. The preferred upper limit of the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / Nb ⁵⁺ ] is 9, the more preferred upper limit is 7, the more preferred upper limit is 5, the more preferred upper limit is 3, and the cation ratio [(Nb ⁵⁺ + Ta). ⁵⁺ ) / Nb ⁵⁺ ] can also be set to 1.

W ⁶⁺ is an optional component that increases the refractive index, lowers the liquidus temperature, and contributes to the improvement of devitrification resistance. It is preferable that the content of ^{W 6+} is 0 to 10% in order to suppress the above. The preferred range of W ⁶⁺ content is 0-8%, the more preferred range is 0-6%, the more preferred range is 0-4%, the more preferred range is 0-2%, and the more preferred range is 0-1. It is even more preferable that it is ^{% and does not contain W 6+.}

In order to increase the refractive index while maintaining the glass stability, the cation ratio ^{of the W 6+} content to the total content of ^{Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ^{6+ [W 6+} / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is preferably less than 0.10. ^{The upper limit of the cation ratio [W 6+} / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is more preferably 0.095 or less in order to increase the refractive index while maintaining the glass stability. It is even more preferably 0.090 or less, even more preferably 0.070 or less, even more preferably 0.050 or less, and even more preferably 0.030 or less. The lower limit of the cation ratio [W ⁶⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ^{6+)] is 0.}

In terms of high refractive index and low dispersion while maintaining glass stability, ^{the total content of Nb 5+} and Ta ^{5+ with} respect to the total content of ^{Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ The cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is preferably 0.41 or less. On the other hand, while maintaining glass stability, high refractive index and low dispersion, and partial dispersion ratio are reduced, so that the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ^{6) +} )] Is preferably 0.05 or more. The preferable upper limit of the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is 0.41 as described above, the more preferable upper limit is 0.39, and further preferable. The upper limit is 0.36, the more preferred upper limit is 0.33, and the even more preferred upper limit is 0.30. The more preferable lower limit of the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is 0.10, the more preferable lower limit is 0.15, and the more preferable lower limit is 0. 20, an even more preferable lower limit is 0.25.

Among the high refractive index components, La ³⁺ , Gd ³⁺ , Y ³⁺ , and Yb ³⁺ have the function of increasing the high refractive index while maintaining low dispersibility, and Ti ⁴⁺ , Nb ⁵⁺ , and Ta ^{5 + And} W ⁶⁺ are high refractive index and high dispersion components. ^{Ti 4+} , Nb ⁵⁺ , Ta ^{5+ with} respect to the total content of ^{La 3+} , Gd ³⁺ , Y ³⁺ and Yb ³⁺ to obtain the desired optical properties while maintaining good glass stability. And the cation ratio of the total content of ^{W 6+ [(Ti 4+} + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.10 or more. Is preferable. A more preferable lower limit of the cation ratio [(Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.30, a further preferable lower limit of 0.50, and one layer. A preferred lower limit of 0.60 and an even more preferred lower limit of 0.70.
^{Cation ratio [(Ti 4+} + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ ) from the viewpoint of obtaining desired optical characteristics while maintaining good glass stability. )] Is preferably 1.50 or less. The more preferable upper limit of the cation ratio [(Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 1.40, and the more preferable upper limit is 1.30. A more preferable upper limit is 1.20, and a further preferable upper limit is 1.00.

In the optical glass I, in order to increase the refractive index while maintaining the glass stability, the cation ratio (Ti ⁴⁺ / B ³⁺ ) of the Ti ^{4+ content to the B 3+} content is 0.85 or more. And. When the cation ratio (Ti ⁴⁺ / B ³⁺ ) is less than 0.85, if the refractive index is increased while maintaining low dispersibility, crystals are likely to precipitate during glass production.
^{The lower limit of the cation ratio (Ti 4+} / B ³⁺ ) is more preferably 0.90 or more, still more preferably 0.95 or more, still more preferably 1 from the viewpoint of increasing the refractive index while maintaining the glass stability. It is more than .00. The upper limit of the cation ratio (Ti ⁴⁺ / B ³⁺ ) is naturally determined from the composition range of the optical glass of the above-described embodiment, but may be considered to be, for example, about 10.

Zr ⁴⁺ is an essential component in optical glass I, which works to increase the refractive index and improve chemical durability, improve ^{devitrification resistance by coexistence with Ti 4+,} and suppress the rise in liquid phase temperature. To work. In order to obtain the above effect, ^{the content of Zr 4+} is preferably 1% or more. From the viewpoint of suppressing an increase in the glass transition temperature and the liquid phase temperature and a decrease in the devitrification resistance, the preferable upper limit of the ^{Zr 4+ content is 15%.} The preferred upper limit of the Zr ⁴⁺ content is 10%, the more preferred upper limit is 8%, the further preferred upper limit is 7%, ^{the preferred lower limit of the Zr 4+} content is 1%, the more preferred lower limit is 2%, and further. The preferred lower limit is 3% and the more preferred lower limit is 4%.

Zn ²⁺ lowers the refractive index and glass stability, but works to improve the meltability and clarity of the glass. La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ , and Zr ⁴⁺ oxides all have extremely high melting points, and these components are essential. The optical glass I contained as a component or an optional component preferably contains ^{Zn 2+, which is effective for improving meltability and clarity.} Therefore, in order to maintain a high refractive index and maintain good glass stability, the Zn ²⁺ content is preferably 15% or less, more preferably 12% or less, and more preferably 10% or less. It is more preferably 8% or less, further preferably 6% or less, and even more preferably 3% or less. Further, from the viewpoint of improving the meltability and clarity of the glass, suppressing the increase in the melting temperature, and suppressing the increase in the glass coloring accompanying the increase, the Zn ²⁺ content is preferably 0.1% or more. It is more preferably 5% or more, further preferably 0.8% or more, and even more preferably 1.0% or more. The Zn ²⁺ content can also be set to 0%.

Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , and W ⁶⁺ are components that increase the refractive index but increase the melting temperature, and decrease the total content of these components and the refractive index, but meltability and clarification. Adjusting the optical characteristics such as meltability, clarity, and refractive index using the cation ratio Zn ²⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ^{6+ ) of the Zn 2+} content to improve the properties as an index. Can be done. From the viewpoint of improving the meltability and clarity of the glass, ^{it is preferable that the cation ratio [Zn 2+} / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is 0.01 or more, and 0.02 or more. It is more preferably 0.03 or more, and even more preferably 0.04 or more. Further, from the viewpoint of increasing the refractive index, the cation ratio [Zn ²⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is preferably 0.65 or less, and preferably 0.60 or less. More preferably, it is more preferably 0.50 or less, further preferably 0.40 or less, further preferably 0.30 or less, even more preferably 0.20 or less, and 0. It is particularly preferable that the content is 10.10 or less.

Li ⁺ , Na ⁺ and K ⁺ are optional components that work to improve meltability and lower the glass transition temperature. ^{The total content of Li +} , Na ⁺ and K ⁺ ranges from 0 to 10% from the viewpoint of suppressing an increase in liquidus temperature and a decrease in glass stability and chemical durability while achieving a high refractive index. Is preferable. A more preferable range of the total content of Li ⁺ , Na ⁺ and K ⁺ is 0 to 8%, a further preferable range is 0 to 6%, a further preferable range is 0 to 4%, and a further preferable range is 0 to 2%. A further preferable range is 0 to 1%, and it is particularly preferable that the alkali metal component is not contained.

Regarding the contents of each component of Li ⁺ , Na ⁺ and K ⁺ , the preferable range is 0 to 10%, the more preferable range is 0 to 8%, the more preferable range is 0 to 6%, and the further preferable range is 0 to 0. 4%, a more preferable range is 0 to 2%, a further preferable range is 0 to 1%, and it is even more preferable that the above-mentioned alkali metal components are not contained.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ work to improve the meltability of glass and lower the glass transition temperature Tg. Further, the defoaming effect can be obtained by introducing the glass into glass in the form of nitrate or sulfate.
In a glass having a high refractive index and a low dispersion, when Ba ²⁺ is contained in a large amount with respect to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ among the above alkaline earth metal components,} It becomes difficult to further reduce the refractive index and dispersion while maintaining the stability of the glass. For example, molding of molten glass usually has a bottom surface and a side wall, the molten glass is cast into a mold having one side opening, and the molded glass is continuously drawn out from the opening side surface of the mold (called an E-bar molding method). ) By. However, ^{if a large amount of Ba 2+} is added to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ to reduce the dispersion of the high refractive index, the glass is lost by this molding method. It becomes easy to see through. Therefore, using a mold having a through hole, molten glass is cast into the through hole, the contact area with the mold per unit volume of the molten glass is increased, and the cooling rate of the glass is extremely increased to prevent devitrification. There is no choice but to use a special molding method. In the molding method using a mold having through holes, since the molded glass is pulled out downward, it is difficult to anneal the glass as it is through a tunnel-type continuous annealing furnace called a rare furnace.
By adjusting and optimizing the ratio of the Ba ² content to ^{the total content of La 3+} , Gd ³⁺ , Y ³⁺ and Yb ³⁺ , devitrification is prevented even with a general E-bar molding method. While doing so, it is possible to form a homogeneous optical glass. Then, since the molded glass can be passed through a rare furnace as it is and annealed, the glass can be manufactured with high productivity.
Thus, in order to prevent the glass stability from being lowered due to the high refractive index and low dispersion, the optical glass I has ^{Ba 2+ with} respect to the total content of ^{La 3+} , Gd ³⁺ , Y ³⁺ and Yb ^3+. The cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] of the content of is 0.40 or less. When the cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] exceeds 0.40, the devitrification tendency of the glass increases, and high-quality optical glass is produced by the E-bar molding method. It becomes difficult to produce. The upper limit of the cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.40 as described above, the preferable upper limit is 0.30, the more preferable upper limit is 0.25, and the further preferable upper limit is 0.25. Is 0.20, the more preferable upper limit is 0.10, and the even more preferable upper limit is 0.05. The cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] may be 0.

From the viewpoint of preventing the rise in liquid phase temperature and suppressing the decrease in devitrification resistance, refractive index and chemical durability, the cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺⁾ )] Is in the above range, and ^{the total content of Mg 2+} , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is preferably 0 to 10%. A more preferable range of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 0 to 8%, a further preferable range is 0 to 6%, a further preferable range is 0 to 4%, and even more preferable. The range is 0 to 2%, the more preferable range is 0 to 1%, and it is even more preferable that the alkaline earth metal component is not contained.

Regarding the content of each component of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ , the preferable range is 0 to 10%, the more preferable range is 0 to 8%, and the more preferable range is 0 to 6%. A further preferable range is 0 to 4%, a more preferable range is 0 to 2%, a further preferable range is 0 to 1%, and it is even more preferable that each of the above alkaline earth metal components is not contained.

Ge ⁴⁺ is a network-forming component and also works to increase the refractive index, so it is a component that can increase the refractive index while maintaining glass stability, but it is much more expensive than other components. It is a component, and it is desirable to refrain from its content. Since the composition of the optical glass I is determined as described above, even if the Ge ⁴⁺ content is suppressed to, for example, 10% or less, both the desired optical characteristics and excellent glass stability can be achieved. be able to. Therefore, ^{the content of Ge 4+} is preferably 0 to 10%. A more preferred range of Ge ⁴⁺ content is 0-8%, a more preferred range is 0-6%, a more preferred range is 0-4%, a further preferred range is 0-2%, and a further preferred range is 0. ~ 1%. It is particularly preferable that it does not contain Ge ⁴⁺ , that is, it is Ge-free glass.

Bi ³⁺ works to increase the refractive index and glass stability, but if the amount exceeds 10%, the light transmittance in the visible region decreases. Therefore, the Bi ³⁺ content is preferably 0 to 10%. A more preferable range of Bi ³⁺ content is 0 to 8%, a further preferable range is 0 to 6%, a further preferable range is 0 to 4%, a further preferable range is 0 to 2%, and a further preferable range is 0. It is ~ 1%, and it is particularly preferable that it does not contain ^{Bi 3+.}

Of the above components, La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ are high refractive index components. La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and The total content of Bi ³⁺ shall be 65% or more. In the optical glass I, in order to maintain the glass stability, Si ⁴⁺ and B ³⁺ , which are network-forming components, are contained in a total of 5% or more, so that La ³⁺ , Gd ³⁺ , Y ³⁺ , and Yb ^{3+ are contained.} , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ , the total content is naturally 95% or less. The sum of ^{La 3+} , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ to obtain the desired optical characteristics. The preferable lower limit of the content is 66%, the more preferable lower limit is 67%, the further preferable lower limit is 68%, the more preferable lower limit is 69%, and the further preferable lower limit is 70%.
From the viewpoint of maintaining good glass stability, La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ The preferred upper limit of the total content of is 90%, the more preferred upper limit is 85%, the further preferred upper limit is 80%, the more preferred upper limit is 75%, and the even more preferred upper limit is 73%.

Al ³⁺ works to improve glass stability and chemical durability when the amount is small, but when the amount exceeds 10%, the liquidus temperature rises and the devitrification resistance tends to deteriorate. .. Therefore, the Al ³⁺ content is preferably 0 to 10%. A more preferable range of Al ³⁺ content is 0 to 8%, a further preferable range is 0 to 6%, a further preferable range is 0 to 4%, a further preferable range is 0 to 2%, and a further preferable range is 0. It is ~ 1%, and it is particularly preferable that it does not contain ^{Al 3+.}

As the optical glass I, the content of any cation component other than the above cation component is set to 0 to 5% in order to provide an optical glass having a high refractive index and low dispersibility and excellent glass stability. It is preferably 0 to 4%, more preferably 0 to 3%, further preferably 0 to 2.5%, and further preferably 0 to 2%. It is more preferably 0 to 1.5%, even more preferably 0 to 1.0%, and particularly preferably 0 to 0.5%. The content of any cation component other than the above cation component may be set to 0%.

Sb is capable added as a refining agent, while also serves to suppress a decrease in light transmittance due to adulteration, such as Fe added in a small amount, in terms of oxide, 1 wt% outside split as Sb ₂ O ₃ If it is added in excess of the above amount, the glass will be colored and its strong oxidizing action will promote the deterioration of the molding surface of the molding mold. Therefore, the _{amount of Sb added in terms of Sb 2} O ₃ is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass, and further preferably 0 to 0.1% by mass. ..

Sn can also be added as a clarifying agent, but if it is _{added in excess of 1% by mass in terms of SnO 2} , the glass will be colored or the molding surface will be deteriorated due to the oxidizing action. Therefore, the _{amount of Sn added in terms of SnO 2} is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass.

In addition to the above, Ce oxide, sulfate, nitrate, chloride, and fluoride can be added in a small amount as a clarifying agent.

Since the optical glass I can maintain the glass stability while realizing the optical characteristics of high refractive index and low dispersion, it is not necessary to contain components such as Lu, Hf, Ga, In, and Sc. Since Lu, Hf, Ga, In, and Sc are also expensive components, it is preferable to suppress the contents of ^{Lu 3+} , Hf ⁴⁺ , Ga ³⁺ , In ³⁺ , and Sc ^{3+ to 0 to 1%, respectively.} It is more preferable to suppress it to 0 to 0.5%, and it is more preferable ^{not to introduce Lu 3+} , not to introduce Hf ⁴⁺ , not to introduce ^{Ga 3+ , not to introduce In 3+, and} to introduce Sc ³⁺ . It is particularly preferable not to do so.
Further, in consideration of the environmental impact, it is preferable not to introduce As, Pb, U, Th, Te, and Cd.
Further, in order to utilize the excellent light transmittance of glass, it is preferable not to introduce substances that cause coloring such as Cu, Cr, V, Fe, Ni, Co, Nd and Tb.
Therefore, it is preferable that the optical glass I does not substantially contain the above-mentioned Pb and the like. Here, "substantially free" means that the glass component is not positively introduced, and it is permissible to unintentionally mix it as an impurity.

Optical glass I is an oxide glass, and the main anion component is O ^2- . Cl as a fining agent, as described above ^-, F ^- to It is also possible to add a small amount, has a high refractive index and low dispersion, from the top to provide an optical glass having excellent glass stability, O ^{2 -} preferably to 98 anionic% or more the content of, more preferably, to more than 99 anionic%, more preferably be at least 99.5 anionic%, it is more preferable to 100 anionic%.

(Refractive index nd and Abbe number νd)
The Abbe number νd of the optical glass I is in the range of 23 to 35. When providing an optical element material suitable for chromatic aberration correction by taking advantage of low dispersibility, it is advantageous that the Abbe number νd is large. From this point of view, the lower limit of the Abbe number νd is preferably 24.0, more preferably 24.5, still more preferably 25.0, still more preferably 25.5, and even more preferably 26.0.
On the other hand, relaxing the upper limit of the Abbe number νd is advantageous in maintaining and improving the glass stability. From this point of view, the upper limit of the Abbe number νd is preferably 32.00, more preferably 31.00 or less, still more preferably 30.00 or less, still more preferably 29.00 or less, still more preferably 28.00 or less. ..

For the optical glass I, the refractive index nd is determined in relation to the Abbe number νd. By increasing the refractive index while maintaining low dispersibility, it is possible to make optical systems such as an imaging optical system and a projection optical system compact and highly functional. The optical glass I has a refractive index nd and an Abbe number νd satisfies the following equation (1). The glass satisfying the equation (1) is useful because it has a higher refractive index at the same Abbe number νd than the conventional high refractive index low dispersion glass, that is, the glass in the upper left range of the optical characteristic diagram described above. It is a highly resistant glass.
nd ≧ 2.205− (0.0062 × νd) ・ ・ ・ (1)
The upper limit of the refractive index nd is not particularly limited because it is naturally determined from the composition range of the optical glass I. From the viewpoint of maintaining glass stability, the refractive index nd is preferably 2.20 or less, more preferably 2.15 or less, further preferably 2.10 or less, and 2.09 or less. Is more preferable.

From the viewpoint of high functionality and compactness of the optical element and the optical system incorporating the optical element, it is preferable that the refractive index nd and the Abbe number νd are within the above ranges and further satisfy the following equation (1-1). , The following equation (1-2) is more preferable, the following equation (1-3) is more preferably satisfied, the following equation (1-4) is more preferably satisfied, and the following equation (1-5) is satisfied. It is even more preferable to satisfy.
nd ≧ 2.207- (0.0062 × νd) ・ ・ ・ (1-1)
nd ≧ 2.209- (0.0062 × νd) ・ ・ ・ (1-2)
nd ≧ 2.211- (0.0062 × νd) ・ ・ ・ (1-3)
nd ≧ 2.213 (0.0062 × νd) ・ ・ ・ (1-4)
nd ≧ 2.215- (0.0062 × νd) ・ ・ ・ (1-5)

The optical glass having a higher refractive index is suitable as a material for an optical element suitable for making the optical system compact and highly functional, such as an imaging optical system and a projection optical system. Further, even when a lens having the same focal length is manufactured, the absolute value of the curvature of the optical functional surface of the lens can be reduced (the curve is loosened), which is advantageous in terms of lens molding and processing. .. On the other hand, as the refractive index of the optical glass is further increased, the thermal stability of the glass tends to decrease and the coloring tends to increase, that is, the light transmittance in the visible short wavelength region tends to decrease. Therefore, in order to maintain good thermal stability of the glass and suppress an increase in coloring, it is preferable that the refractive index nd and the Abbe number νd satisfy the following equation (1-6), and the following (1-6). It is more preferable to satisfy the following equation (7), more preferably to satisfy the following equation (1-8), further preferably to satisfy the following equation (1-9), and more preferably to satisfy the following equation (1-10). More preferred.
nd ≦ 2.320− (0.0062 × νd) ・ ・ ・ (1-6)
nd ≦ 2.300− (0.0062 × νd) ・ ・ ・ (1-7)
nd ≦ 2.280- (0.0062 × νd) ・ ・ ・ (1-8)
nd ≦ 2.260- (0.0062 × νd) ・ ・ ・ (1-9)
nd ≦ 2.240- (0.0062 × νd) ・ ・ ・ (1-10)
In the optical glass I, the desired optical characteristics refer to the optical characteristics in which the Abbe number νd is in the range of 23 to 35 and the refractive index nd and the Abbe number νd satisfy the above equation (1). When the optical characteristic is preferable, it means an arbitrary range among the preferable ranges of the refractive index nd and the Abbe number νd.

(Liquid phase temperature)
High refractive index glass contains a large amount of high refractive index components (for example, La ³⁺ (La ₂ O ₃ ), Gd ³⁺ (Gd ₂ O ₃ ), Y ³⁺ (Y ₂ O ₃ ), Yb ³⁺ (Yb). ₂ O ₃ ), Ti ⁴⁺ (TiO ₂ ), Nb ⁵⁺ (Nb ₂ O ₅ ), Ta ⁵⁺ (Ta ₂ O ₅ ), W ⁶⁺ (WO ₆ ), Zr ⁴⁺ (ZrO ₂ )) Although contained, all of these components have extremely high melting points by themselves. When the total amount of the high refractive index component is large, the total amount of the components having a function of lowering the melting temperature such as the alkali metal component and the alkaline earth metal component is relatively reduced, and the melting property and devitrification resistance are improved. As it decreases, the melting temperature must be increased to obtain a homogeneous glass.
When the melting temperature rises, the erosion of the glass melt becomes stronger, and the melting vessel is eroded, and the materials that make up the vessel, such as platinum and platinum alloy, melt into the glass melt to color the glass or become platinum foreign matter. do. Further, when the melting temperature is high ^{, volatile components such as B 3+} volatilize, the glass composition changes with time, and the optical characteristics also fluctuate.
In order to solve such a problem, it is sufficient to suppress the increase in the melting temperature. The melting temperature range may be considered as a temperature range in which a homogeneous glass melt can be obtained, and the lower limit of the temperature range may be considered to change in conjunction with the rise and fall of the liquidus temperature. Therefore, if the rise in the liquidus temperature can be suppressed, the rise in the melting temperature can also be suppressed.
Further, if the increase in the liquidus temperature can be suppressed, it is effective in preventing devitrification during glass molding, and the viscosity of the glass can be adjusted within a range suitable for molding, making it easy to produce a high-quality glass molded body. Become.

As described above, the increase / decrease in the refractive index and the increase / decrease in the liquidus temperature are linked to the increase / decrease in the amount of the high refractive index component. Therefore, the refractive index and the liquidus temperature are taken into consideration when evaluating the meltability and devitrification resistance. It is appropriate to use the index. In the optical glass I, when the liquidus temperature is LT [° C.], the above index is defined as LT / (nd-1) for the glass having the refractive index nd. The denominator is the value obtained by subtracting the refractive index 1 of the vacuum from the refractive index of glass, and reflects the net amount of increase or decrease in the refractive index. The lower the LT / (nd-1), the more excellent the meltability and devitrification resistance of the high refractive index glass.
In a preferred embodiment of the optical glass I, the amount of each component is determined in a well-balanced manner so as to suppress an increase in the liquidus temperature while maintaining the required optical characteristics, so that the following equation (3) can be satisfied.
LT / (nd-1) ≤ 1250 ° C ... (3)

From the viewpoint of obtaining a glass having more improved meltability and devitrification resistance, an optical glass satisfying the following formula (3-1) is preferable, an optical glass satisfying the following formula (3-2) is more preferable, and the following (3) An optical glass satisfying the following formula (-3) is more preferable, an optical glass satisfying the following formula (3-4) is more preferable, an optical glass satisfying the following formula (3-5) is even more preferable, and the following formula (3-6) is more preferable. Optical glass that satisfies the above conditions is even more preferable.
LT / (nd-1) ≤ 1230 ° C ... (3-1)
LT / (nd-1) ≤ 1220 ° C ... (3-2)
LT / (nd-1) ≤ 1210 ° C ... (3-3)
LT / (nd-1) ≤ 1205 ° C ... (3-4)
LT / (nd-1) ≤ 1200 ° C ... (3-5)
LT / (nd-1) ≤ 1190 ° C ... (3-6)

On the other hand, if the LT / (nd-1) is lowered, it tends to be difficult to maintain the required optical characteristics. Therefore, it is preferable not to lower the LT / (nd-1) excessively. From this point of view, an optical glass satisfying the following formula (3-7) is preferable, an optical glass satisfying the following formula (3-8) is more preferable, and an optical glass satisfying the following formula (3-9) is further preferable. An optical glass satisfying the following formula (3-10) is more preferable, an optical glass satisfying the following formula (3-11) is even more preferable, and an optical glass satisfying the following formula (3-12) is even more preferable.
LT / (nd-1) ≥ 1050 ° C ... (3-7)
LT / (nd-1) ≥ 1070 ° C ... (3-8)
LT / (nd-1) ≥ 1080 ° C ... (3-9)
LT / (nd-1) ≥ 1090 ° C ... (3-10)
LT / (nd-1) ≥ 1110 ° C ... (3-11)
LT / (nd-1) ≥ 1120 ° C ... (3-12)

(Partial dispersion characteristics)
The optical glass I is preferably a glass having a small partial dispersion ratio when the Abbe number νd is fixed. Optical elements such as lenses made of such optical glass are suitable for high-order chromatic aberration correction.
Here, the partial dispersion ratios Pg and F are expressed as (ng-nF) / (nF-nc) using the refractive indexes ng, nF and nc of the g-line, F-line and c-line.
In order to provide an optical glass suitable for high-order chromatic aberration correction, the optical glass I preferably has a partial dispersion ratio Pg, F and an Abbe number νd satisfying the relationship of the following equation (4-1), and is described below. Those satisfying the relation of the formula (4-2) are more preferable, and those satisfying the relation of the following formula (4-3) are further preferable.
Pg, F ≦ -0.005 × νd + 0.750 ・ ・ ・ (4-1)
Pg, F ≦ -0.005 × νd + 0.745 ・ ・ ・ (4-2)
Pg, F ≦ -0.005 × νd + 0.743 ・ ・ ・ (4-3)

In the partial dispersion ratio Pg, F-Abbe number νd diagram, when the partial dispersion ratio on the normal line, which is the reference of the normal partial dispersion glass, is expressed as Pg, F (0), Pg, F (0) is the Abbe number. It is expressed by the following equation using νd.
Pg, F (0) = 0.6483- (0.0018 × νd)
ΔPg and F are deviations of the partial dispersion ratios Pg and F from the normal line, and are expressed by the following equations.
ΔPg, F = Pg, F-Pg, F (0)
= Pg, F + (0.0018 × νd) -0.6483
A preferred embodiment of the above-described optical glass has deviations ΔPg and F of 0.030 or less, and is suitable as an optical element material for correcting high-order chromatic aberration. A more preferable range of ΔPg and F is 0.025 or less, a further preferable range is 0.020 or less, a more preferable range is 0.015 or less, and a further preferable range is 0.001 or less. The lower limit of the deviation ΔPg, F is more preferably 0.0000 or more, still more preferably 0.001 or more, still more preferably 0.003 or more, and even more preferably 0.005 or more.

(specific gravity)
The optical glass of the above-described embodiment is a high-refractive-index glass, but in general, the specific gravity of glass tends to increase as the refractive index increases. However, an increase in the specific gravity is not preferable because it causes an increase in the weight of the optical element. On the other hand, the optical glass of the above-described embodiment can have a specific gravity of 5.60 or less even though it is a high-refractive index glass by having the above-mentioned glass composition. The preferred upper limit of the specific density is 5.50, the more preferable upper limit is 5.40, and the more preferable upper limit is 5.30. However, if the specific gravity is excessively reduced, the stability of the glass is lowered and the liquidus temperature tends to rise. Therefore, the specific gravity is preferably 4.50 or more. The more preferable lower limit of the specific gravity is 4.70, the further preferable lower limit is 4.90, the more preferable lower limit is 5.00, and the further preferable lower limit is 5.10.

(Transmittance characteristics)
Next, the light transmittance of the optical glass I will be described.
Optical glass I can exhibit high light transmittance over a wide wavelength range in the visible range. In a preferred embodiment of the optical glass I, λ70 exhibits a degree of coloration of 680 nm or less. A more preferable range of λ70 is 660 nm or less, a further preferable range is 650 nm or less, a further preferable range is 600 nm or less, a further preferable range is 560 nm or less, and a further preferable range is 530 nm or less. The lower limit of λ70 is not particularly limited, but 380 nm may be considered as a guideline for the lower limit of λ70.
Here, λ70 is a wavelength at which the light transmittance becomes 70% in the wavelength range of 280 to 700 nm. Here, the light transmittance means that a glass sample having parallel surfaces polished to a thickness of 10.0 ± 0.1 mm is used, and light is incident on the polished surface from a direction perpendicular to the polished surface. The obtained spectral transmittance, that is, Iout / Iin when the intensity of the light incident on the sample is Iin and the intensity of the light transmitted through the sample is Iout. The spectral transmittance also includes the reflection loss of light on the sample surface. Further, the polishing means that the surface roughness is sufficiently small with respect to the wavelength in the measurement wavelength range. The optical glass I preferably has a light transmittance of more than 70% in the visible region on the longer wavelength side than λ70.

λ5 is a wavelength at which the light transmittance of λ70 measured by the above method is 5%, and the preferred range of λ5 is 450 nm or less, the more preferable range is 430 nm or less, the more preferable range is 410 nm or less, and the more preferable range is 410 nm or less. 400 nm or less, a further preferable range is 390 nm or less, and an even more preferable range is 380 nm or less. The lower limit of λ5 is not particularly limited, but 300 nm may be considered as a guideline for the lower limit of λ5.

The spectral transmittance is measured in the wavelength range of 280 to 700 nm as described above, but usually, the light transmittance increases as the wavelength is lengthened from λ5, and when it reaches λ70, it is 70% or more up to the wavelength of 700 nm. Maintains high transmittance.

(Glass-transition temperature)
Optical glass I is a glass suitable for forming a smooth optical functional surface by polishing. The suitability of cold working such as polishing, that is, cold workability, is indirectly related to the glass transition temperature. Glass with a low glass transition temperature is more suitable for precision press molding than cold workability, whereas glass with a high glass transition temperature is more suitable for cold working than precision press molding, and is suitable for cold workability. Excellent. Therefore, it is preferable that the glass transition temperature of the optical glass I is not excessively lowered, preferably 650 ° C. or higher, more preferably 680 ° C. or higher, further preferably 700 ° C. or higher, and 710 ° C. or higher. The above is more preferable, the temperature is more preferably 730 ° C. or higher, and the temperature is even more preferably 740 ° C. or higher.
However, if the glass transition temperature is too high, the heating temperature when reheating and softening the glass for molding becomes high, the mold used for molding deteriorates significantly, the annealing temperature becomes high, and the annealing furnace becomes hot. Deterioration and wear are also significant. Therefore, the glass transition temperature is preferably 850 ° C. or lower, more preferably 800 ° C. or lower, further preferably 780 ° C. or lower, and even more preferably 760 ° C. or lower.

[Optical glass II]
Next, optical glass II, which is an optical glass of another aspect of the present invention, will be described.
Optical glass II contains Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ as essential components.
In cation% display,
5 to 55% of ^{Si 4+} and B ^{3+ in total,}
La ³⁺ is 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total),
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ total 23-70% (however, Ti ⁴⁺ exceeds 22%),
Including
The cation ratio of the content ^{of Y 3+} to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [Y 3+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.14 or less,
The cation ratio ^{of the Ba 2+} content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [Ba 2+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.40 or less,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio (Ti ⁴⁺ / B ³⁺ ) of the Ti ⁴⁺ content to the B ³⁺ content is 0.85 or more.
And
It is an oxide glass in which the Abbe number νd is in the range of 18 or more and less than 35, and the refractive index nd satisfies the following equation (2).
nd ≧ 2.540- (0.02 × νd) ・ ・ ・ (2)

Like the optical glass I, the optical glass II is a glass having high refractive index and low dispersion characteristics while maintaining glass stability, but has a higher content of ^{Ti 4+ than the optical glass I.} The optical glass I has a Ti ⁴⁺ content of 22% or less, a high spectral transmittance in the visible region, and a low partial dispersion ratio so as to be advantageous for high-order chromatic aberration correction. Further, in the range where the Abbe number νd is approximately 24.28 or more, the lower limit of the refractive index is higher than the lower limit of the refractive index of the optical glass I.
On the other hand, the optical glass II has a Ti ⁴⁺ content of more than 22% and exhibits a high refractive index and low dispersion characteristic in a range in which the Abbe number νd is wider than that of the optical glass I.
Hereinafter, the composition and characteristics of the optical glass II, which are different from those of the optical glass I, will be described. Therefore, the description of the composition and characteristics not described below is the same as the composition and characteristics of the optical glass I.

Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , and W ^{6+ work} to increase the refractive index, improve the devitrification resistance, suppress the rise in the liquidus temperature, and improve the chemical durability. If ^{the total content of Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is less than 23%, it will be difficult to obtain the above effect, and Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ When the total content exceeds 70%, the devitrification resistance deteriorates and the liquidus temperature rises. In addition, the dispersion becomes high and the coloring of the glass becomes stronger. Therefore, the total content of ^{Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ^{6+ is 23-70%.} The preferred upper limit of the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is 60%, the more preferred upper limit is 55%, the more preferred upper limit is 50%, the more preferred upper limit is 45%, even more preferred. The upper limit is 40%, with ^{a preferred lower limit of 24% for the total content of Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ , a more preferred lower limit of 25%, a more preferred lower limit of 26% and a more preferred lower limit. Is 27%, and an even more preferable lower limit is 28%.
In the optical glass II, ^{the total content of Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is within the above range, and ^{the content of Ti 4+} is increased to more than 22% to resist devitrification. The sex can be improved. It is also effective in suppressing the rise in liquid phase temperature.
The preferred lower limit of the Ti ⁴⁺ content is 22.5%, the more preferred lower limit is 23%, the further preferred lower limit is 24%, ^{the preferred upper limit of the Ti 4+} content is 60%, and the more preferred upper limit is 50%. A further preferred upper limit is 45%, a more preferred upper limit is 40%, a further preferred upper limit is 35%, and an even more preferred upper limit is 30%.

The cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] of ^{the content of Y 3+} to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ is} In order to maintain high glass stability and reduce the dispersion of high refractive index, the value is 0.14 or less. For the above reasons, the preferred upper limit of the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.13, the more preferable upper limit is 0.12, and the further preferable upper limit is 0.11. be. Among La, Gd, Y and Yb, the element having the smallest atomic weight is Y. Therefore, from the viewpoint of reducing the specific gravity of the glass, ^{the preferable lower limit of the cation ratio [Y 3+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.01, the more preferable lower limit is 0.02, and further. The preferred lower limit is 0.03, the more preferred lower limit is 0.04, and the even more preferred lower limit is 0.05. Optical glass II is also suitable as a material for a camera lens equipped with an autofocus function, but power consumption during autofocus can be reduced by reducing the specific gravity of the glass.
From the viewpoint of reducing the specific gravity of glass, while setting the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] to 0.14 or less, Gd ³⁺ , Y ³⁺ and Yb ³ The cation ratio [Y ³⁺ / (Gd ³⁺ + Y ³⁺ + Yb ^{3+ )] of the Y 3+} content to the total ⁺ content is preferably more than 0.60. For the above reasons, the more preferable lower limit of the cation ratio [Y ³⁺ / (Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.61, the more preferable lower limit is 0.62, the more preferable lower limit is 0.63, and even more. The preferred lower limit is 0.64.
^{The total content of Gd 3+} , Y ³⁺ and Yb ³⁺ is preferably 1.0% or more in order to maintain good glass stability and reduce the dispersion of high refractive index. Gd ³⁺ , Y ³⁺ , and Yb ³⁺ all work to lower the liquidus temperature and significantly improve the devitrification resistance by coexisting with ^{La 3+.} In order to obtain this function well, ^{the total content of Gd 3+} , Y ³⁺ and Yb ³⁺ is more preferably 1.5% or more, further preferably 2.0% or more. It is more preferably 2.5% or more, further preferably 3.0% or more, and even more preferably 3.5% or more. The preferred upper limit of the total content of Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 35%, the more preferred upper limit is 30%, the more preferred upper limit is 25%, the more preferred upper limit is 20% and the even more preferred upper limit is 15%. An even more preferred upper limit is 10%, and an even more preferred upper limit is 7%.

For the same reason as optical glass I, there is also a preferable lower limit ^{for the cation ratio [(Gd 3+} + Y ³⁺ + Yb ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ^3+)]. The preferable lower limit of the cation ratio [(Gd ³⁺ + Y ³⁺ + Yb ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is more than 0, the more preferable lower limit is 0.02, and the further preferable lower limit is 0. 0.03, a more preferred lower limit is 0.04, and a more preferred lower limit is 0.05.

For the same reason as optical glass I, the sum of ^{La 3+} , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ^3+. There is also a preferable range for the content. The preferred lower limit of the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ^{3+ is 60%.} A more preferred lower limit is 64%, a further preferred lower limit is 65%, a more preferred lower limit is 66%, and a further preferred lower limit is 67%. The preferred upper limit for the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ^{3+ is 90%.} A more preferred upper limit is 85%, a more preferred upper limit is 80%, and a more preferred upper limit is 75%.

For the same reason as optical glass I, the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] also has a preferable range. The preferred lower limit of the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is 0.10, the more preferred lower limit is 0.13, the more preferred lower limit is 0.16, the more preferred lower limit is 0.19, and even more. The preferred lower limit is 0.22. There is also a preferable range for the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ^3+)]. The preferred upper limit of the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is 0.80, the more preferred upper limit is 0.60, the more preferred upper limit is 0.50, the more preferred upper limit is 0.40, and even more. The preferred upper limit is 0.35.

^{The total content of Si 4+} and B ^{3+ with} respect to the total content of ^{La 3+} , Gd ³⁺ , Y ³⁺ and Yb ³⁺ in order to maintain good glass stability and reduce dispersion with high refractive index. The preferred lower limit of the amount of cation ratio [(Si ⁴⁺ + B ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.10, the more preferable lower limit is 0.20, and the more preferable lower limit is 0. .30, a more preferred lower limit is 0.40, a further preferred lower limit is 0.50, a further preferred lower limit is 0.60, a preferred upper limit is 1.05, a more preferred upper limit is 1.0, and a further preferred upper limit is 1.0. 0.95, a more preferred upper limit is 0.90, a further preferred upper limit is 0.85, and a further preferred lower limit is 0.83.

The total content ^{of Zr 4+} , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ with respect to the content of ^{Zr 4+ in} order to impart high refractive index and low dispersion characteristics while maintaining glass stability. The cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W6 +) / Zr ⁴⁺ ] is 2 or more. For the above reasons, the preferable lower limit of the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 3, the more preferable lower limit is 3.5, the further preferable lower limit is 4, and one layer. A preferred lower limit is 4.5, a further preferred lower limit is 5, a preferred upper limit is 72, a more preferred upper limit is 50, a further preferred upper limit is 40, a more preferred upper limit is 30, a further preferred upper limit is 20, an even more preferred upper limit. Is 10.

Compared to optical glass I, which has a Ti ⁴⁺ content of 22% or less and an Abbe number νd in the range of 23 to 35, optical glass II ^{contains more than 22% Ti 4+,} and the lower limit of the Abbe number νd is 18. It exhibits excellent glass stability and high refractive index characteristics even in a range where the Abbe number νd is small.
In the optical glass II, when the Abbe number νd exceeds 35, it becomes difficult to maintain good glass stability. On the other hand, since the optical glass II ^{contains a relatively large amount of Ti 4+} , the lower limit of the Abbe number νd is 18.

(Refractive index nd and Abbe number νd)
From the viewpoint of providing an optical element material suitable for chromatic aberration correction, the preferred lower limit of the Abbe number νd is 19, the more preferable lower limit is 20, the more preferable lower limit is 21, the more preferable lower limit is 22, and the further preferable lower limit is 23. On the other hand, from the viewpoint of maintaining good glass stability, the preferred upper limit of the Abbe number νd is 32, the more preferable upper limit is 30, the more preferable upper limit is 29, the more preferable upper limit is 28, and the further preferable upper limit is 27.
In the optical glass II capable of adjusting the Abbe number νd in a relatively wide range, the refractive index nd and the Abbe number νd are as follows (2) in order to provide a glass material suitable for making the optical system compact and highly functional. ) Satisfy the equation. The glass satisfying the equation (2) is also useful because it has a higher refractive index at the same Abbe number νd than the conventional high refractive index low dispersion glass, that is, the glass in the upper left range of the optical characteristic diagram described above. It is a highly resistant glass.
nd ≧ 2.540- (0.02 × νd) ・ ・ ・ (2)
Further, for the above reason, it is preferable that the refractive index nd and the Abbe number νd satisfy the following equation (2-1), more preferably the following equation (2-2), and the following equation (2-3). It is more preferable to satisfy, and it is further preferable to satisfy the following equation (2-4).
nd ≧ 2.543- (0.02 × νd) ・ ・ ・ (2-1)
nd ≧ 2.546- (0.02 × νd) ・ ・ ・ (2-2)
nd ≧ 2.549- (0.02 × νd) ・ ・ ・ (2-3)
nd ≧ 2.550- (0.02 × νd) ・ ・ ・ (2-4)
The upper limit of the refractive index nd is not particularly limited because it is naturally determined from the composition range of the optical glass II. From the viewpoint of maintaining glass stability, the refractive index nd is preferably 2.40 or less, more preferably 2.30 or less, preferably 2.20 or less, and 2.15 or less. It is more preferably 2.10 or less, and even more preferably 2.09 or less.

(Partial dispersion characteristics)
The preferred upper and lower limits of the partial dispersion ratios Pg and F and the preferred upper limits of ΔPg and F in the optical glass II are the same as those of the optical glass I. On the other hand, the preferable lower limit of ΔPg and F in the optical glass II is −0.001, the more preferable lower limit is 0.000, the further preferable lower limit is 0.003, and the more preferable lower limit is 0.003.

(specific gravity)
In order to reduce the weight of the optical element, the preferable range of the specific gravity of the optical glass II is 5.50 or less, the more preferable range is 5.40 or less, the more preferable range is 5.30 or less, and the more preferable range is 5.20 or less. .. However, if the specific gravity is excessively reduced, the stability of the glass is lowered and the liquidus temperature tends to rise. Therefore, the specific gravity is preferably 4.50 or more. The more preferable lower limit of the specific density is 4.60, the further preferable lower limit is 4.70, the more preferable lower limit is 4.80, and the further preferable lower limit is 4.90.

(Transmittance characteristics)
The light transmittance of the optical glass II is similar to that of the optical glass I, but the preferable range of λ5 is 450 nm or less, the more preferable range is 430 nm or less, the more preferable range is 410 nm or less, the more preferable range is 400 nm or less, and more. A more preferable range is 390 nm or less, and a further preferable range is 380 nm or less. The lower limit of λ5 is not particularly limited, but 300 nm may be considered as a guideline for the lower limit of λ5.

(Glass-transition temperature)
The glass transition temperature of the optical glass II also has a preferable lower limit and a preferable upper limit for the same reason as the glass transition temperature of the optical glass I. The preferable lower limit of the glass transition temperature of the optical glass II is 650 ° C, the more preferable lower limit is 670 ° C, the further preferable lower limit is 680 ° C, the more preferable lower limit is 690 ° C, the further preferable lower limit is 700 ° C, and the further preferable lower limit is 710 ° C. An even more preferable lower limit is 720 ° C. On the other hand, the preferable upper limit of the glass transition temperature is 850 ° C., the more preferable upper limit is 800 ° C., the further preferable upper limit is 780 ° C., the further preferable upper limit is 760 ° C. ..
Other compositions and characteristics of the optical glass II are the same as those of the optical glass I.

[Manufacturing method of optical glass]
Next, a method for producing an optical glass according to one aspect of the present invention will be described.
The method for producing optical glass according to one aspect of the present invention is a method for producing optical glass, which comprises melting a glass raw material by heating and molding the obtained molten glass, wherein the glass raw material is used as the above-mentioned optical of the present invention. It is prepared so that glass can be obtained, and the melting is carried out using a glass melting container made of platinum or a platinum alloy.

For example, a powdery compound raw material or a cullet raw material is weighed and prepared according to a target glass composition, supplied into a platinum or platinum alloy melting container, and then melted by heating. After the above raw materials are sufficiently melted and vitrified, the temperature of the molten glass is raised to perform clarification. The clarified molten glass is homogenized by stirring with a stirrer, continuously supplied and discharged to the glass outflow pipe, rapidly cooled and solidified to obtain a glass molded body.
It is desirable that the melting temperature of the optical glass is in the range of 1200 to 1500 ° C. from the viewpoint of obtaining a uniform, low-colored glass having stable characteristics including optical characteristics.

[Glass bump for press molding]
The press-molded glass gob according to one aspect of the present invention comprises the optical glass of the above-described aspect. The shape of the gob should be a shape that is easy to press-mold according to the shape of the target press-molded product. In addition, the mass of the gob is also set according to the press-molded product. According to one aspect of the present invention, since glass having excellent stability can be used, the glass does not easily devitrify even if it is reheated, softened and press-molded, and a high-quality molded product can be stably produced. Can be produced.

An example of manufacturing a glass gob for press molding is as follows.
In the first production example, the molten glass flowing out of the pipe is continuously cast into a mold horizontally arranged below the outflow pipe to form a plate having a certain thickness. The molded glass is continuously drawn out in the horizontal direction from the opening provided on the side surface of the mold. The plate-shaped glass molded body is pulled out by a belt conveyor. A glass molded body having a predetermined thickness and width can be obtained by pulling out the glass molded body so that the drawing speed of the belt conveyor is constant and the plate thickness of the glass molded body is constant. The glass compact is conveyed into the annealing furnace by a belt conveyor and slowly cooled. The slowly cooled glass molded body is cut or cut in the plate thickness direction and polished or barrel-polished to make a glass gob for press molding.

In the second production example, molten glass is cast into a cylindrical mold instead of the above mold to form a cylindrical glass molded body. The glass molded body molded in the mold is pulled out vertically downward from the opening at the bottom of the mold at a constant speed. The withdrawal speed may be set so that the molten glass liquid level in the mold becomes constant. After the glass molded body is slowly cooled, it is cut or cut, and polished or barrel-polished to obtain a glass gob for press molding.

In the third manufacturing example, a molding machine in which a plurality of molding dies are arranged at equal intervals is installed below the outflow pipe on the circumference of the circular turntable, the turntable is index-rotated, and the molding dies are stopped. The molten glass is supplied with one of the positions as the position (called the cast position) for supplying the molten glass to the molding die, and after the supplied molten glass is molded into the glass molded body, the predetermined molding die different from the casting position is stopped. Take out the glass molded body from the position (takeout position). Which stop position the take-out position should be set may be determined in consideration of the rotation speed of the turntable, the cooling speed of the glass, and the like. To supply the molten glass to the mold at the cast position, the molten glass is dropped from the glass outlet of the outflow pipe and the glass droplets are received by the mold, and the mold staying at the cast position is brought closer to the glass outlet. Supports the lower end of the flowing molten glass flow, creates a constriction in the middle of the glass flow, and drops the molding die in the vertical direction at a predetermined timing to separate the molten glass below the constriction and receive it on the molding die. It can be carried out by a method, such as cutting the flowing molten glass flow with a cutting blade and receiving the separated molten glass block with a molding die that stays at the cast position.
A known method may be used for molding the glass on the molding mold. Above all, when gas is ejected upward from the mold to apply upward wind pressure to the glass block and the glass is floated while molding, wrinkles are formed on the surface of the glass molded body, and the glass molded body can be formed by contact with the molding die. It is possible to prevent cracking from occurring.

The shape of the glass molded body has one spherical shape, a spheroidal shape, and a rotation target axis depending on the selection of the molding mold shape and the method of ejecting the gas, and two surfaces facing the axial direction of the rotation target axis. Can be shaped such that both are convex outward. These shapes are suitable for optical elements such as lenses or glass gobs for press molding optical element blanks. The glass molded product thus obtained can be used as it is, or the surface can be polished or barrel-polished to obtain a glass gob for press molding.

[Optical element blank and its manufacturing method]
Next, an optical element blank according to one aspect of the present invention and a method for manufacturing the same will be described.
The optical element blank according to one aspect of the present invention comprises the optical glass of the above-described aspect. The optical element blank according to one aspect of the present invention is suitable as a glass base material for producing an optical element having various properties provided by the optical glass of the above-described aspect.
The optical element blank is a glass molded body having a shape similar to the shape of an optical element in which a processing margin to be removed by grinding and polishing is added to the shape of the target optical element.

The first aspect of the method for producing an optical element blank according to one aspect of the present invention is the method for producing an optical element blank which is finished into an optical element by grinding and polishing, in which the press-molded glass gob of the above-described embodiment is softened by heating. Press molding. This method is also called a reheating press molding method.

The second aspect of the method for manufacturing an optical element blank according to one aspect of the present invention is the molten glass obtained by melting a glass raw material by heating in a method for manufacturing an optical element blank which is finished into an optical element by grinding and polishing. Is press-molded to produce an optical element blank of the above-described embodiment. This method is also called a direct press molding method.

In the first aspect, a press molding mold having a molding surface having a shape similar to the inverted shape of the surface shape of the target optical element is prepared. The press mold is composed of mold parts including an upper mold, a lower mold and, if necessary, a body mold.
Next, the glass gob for press molding is softened by heating and then introduced into a preheated lower mold, pressed by the upper mold facing the lower mold, and molded into an optical element blank. At this time, in order to prevent fusion of the glass and the molding die during press molding, a powder release agent such as boron nitride may be uniformly applied to the surface of the press molding glass gob in advance.
Next, the optical element blank is released from the press molding mold and annealed. This annealing treatment reduces the distortion inside the glass so that the optical characteristics such as the refractive index become desired values.
Known materials may be applied to the heating conditions of the glass gob, the press molding conditions, the material used for the press molding mold, and the like. The above steps can be performed in the atmosphere.

In the second aspect, the press molding mold is composed of mold parts including an upper mold, a lower mold, and if necessary, a body mold. As described above, the molding surface of the press molding mold is processed into a shape in which the surface shape of the optical element blank is inverted.
A powdery mold release agent such as boron nitride is uniformly applied onto the lower mold molding surface, and the molten glass melted according to the above-mentioned optical glass manufacturing method is discharged onto the lower mold molding surface and is placed on the lower mold. When the amount of molten glass reaches a desired amount, the molten glass stream is cut with a cutting blade called a shear. After obtaining the molten glass ingot on the lower mold in this way, the lower mold is moved upward together with the molten glass ingot to the position where the upper mold stands by, and the glass is pressed by the upper mold and the lower mold to form an optical element blank. ..
Next, the optical element blank is released from the press molding mold and annealed. This annealing treatment reduces the distortion inside the glass so that the optical characteristics such as the refractive index become desired values.
Known materials may be applied to the heating conditions of the glass gob, the press molding conditions, the material used for the press molding mold, and the like. The above steps can be performed in the atmosphere.

[Optical element and its manufacturing method]
Next, the optical element according to one aspect of the present invention will be described.
The optical element according to one aspect of the present invention comprises the optical glass of the above-described aspect. Since the optical element according to one aspect of the present invention has various properties provided by the optical glass of the above-described aspect, it is effective for enhancing the functionality and making the optical system compact. Examples of the optical element of the present invention include various lenses and prisms. Further, as an example of the lens, various lenses such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a plano-convex lens, and a plano-concave lens whose lens surface is spherical or aspherical can be shown.
Such a lens can correct chromatic aberration by combining with a lens made of low-dispersion glass, and is suitable as a lens for correcting chromatic aberration. It is also an effective lens for making the optical system compact.
Further, since the prism has a high refractive index, it can be incorporated into an imaging optical system to realize a compact and wide angle of view optical system by bending an optical path and directing it in a desired direction.
A film for controlling the light transmittance, such as an antireflection film, may be provided on the optical functional surface of the optical element according to one aspect of the present invention.

Next, a method for manufacturing an optical element according to one aspect of the present invention will be described.
The method for manufacturing an optical element according to one aspect of the present invention is characterized in that the optical element blank produced by the method according to the above aspect is processed. In one aspect of the present invention, as the optical glass constituting the optical element blank, a glass having excellent processability can be used, so that a known method can be applied as the processing method.

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the embodiments shown in the Examples. The optical glass according to various aspects of the present invention can be obtained by applying the above-mentioned method for adjusting the content of each glass component with reference to the examples described below.

(Example of manufacturing optical glass)
First, the oxide glass No. 1 having the composition shown in Table 1 (displayed in% cation). Oxide glass Nos. 1 to 15 and Table 2 are shown. Nitrate, sulfate, hydroxide, oxide, boric acid, etc. are used as raw materials so that 16 to 70 can be obtained, and each raw material powder is weighed and sufficiently mixed to prepare a blending raw material, and this blending raw material is made of platinum. It was placed in a crucible or a platinum alloy crucible and heated at 1300 to 1500 ° C., melted, clarified, and stirred to obtain a homogeneous molten glass.
This molten glass was poured into a preheated mold, rapidly cooled, held at a temperature close to the glass transition temperature for 2 hours, and then slowly cooled to obtain oxide glass No. 1 to 70 optical glasses were obtained. No. No foreign matter such as platinum inclusions was found in the glasses 1 to 70.
Oxide glass No. The total amount of anionic components 1 to 70 is O ^2- .
In addition, oxide glass No. 1 to 15 correspond to the optical glass I, and the oxide glass No. 1 and 15 correspond to the optical glass I. 16 to 70 correspond to optical glass II.

Measurement of glass characteristics The characteristics of each glass were measured by the methods shown below. The measurement results are shown in Tables 1 and 2.
(1) Refractive index nd and Abbe number νd
The measurement was performed on the optical glass cooled at a temperature lowering rate of 30 ° C. per hour.
(2) Partial dispersion ratio Pg, F, difference in partial dispersion ratio from the normal line ΔPg, F
The partial dispersion ratios Pg and F were calculated from these values by measuring the refractive indexes ng, nF and nc of the optical glass cooled at a temperature lowering rate of 30 ° C. per hour.
The difference ΔPg, F of the partial dispersion ratio from the normal line was calculated from the partial dispersion ratios Pg, F (0) on the normal line calculated from the partial dispersion ratios Pg, F and the Abbe number νd.
(3) Glass transition temperature Tg
The measurement was performed using a differential scanning calorimetry device (DSC) under the condition of a heating rate of 10 ° C./min.
(4) Liquid phase temperature The glass was placed in a furnace heated to a predetermined temperature and held for 2 hours. After cooling, the inside of the glass was observed with a 100x optical microscope, and the liquid phase temperature was determined from the presence or absence of crystals.
(5) Specific gravity Measured by the Archimedes method.
(6) λ70, λ5
Using a glass sample having parallel surfaces polished to a thickness of 10.0 ± 0.1 mm, a spectrophotometer was used to inject light of intensity Iin from the direction perpendicular to the polished surface, and the sample was used. The intensity Iout of the light transmitted through the above was measured, the light transmittance Iout / Iin was calculated, and the wavelength at which the light transmittance was 70% was defined as λ70, and the wavelength at which the light transmittance was 5% was defined as λ5.

The glass for measuring the number density of crystals precipitated during glass production is obtained by molding molten glass. When the glass stability is lowered, the molten glass is poured into a mold to be formed, and the number of crystal grains contained in the obtained glass is increased.
Therefore, the glass stability, particularly the devitrification resistance when molding the glass melt, can be evaluated by the amount of crystals contained in the glass melted and molded under certain conditions. An example of the evaluation method is shown below.
Nitrate, sulfate, hydroxide, oxide, boric acid, etc. are used as raw materials, and each raw material powder is weighed and sufficiently mixed to prepare a blending raw material, and this blending raw material is placed in a platinum crucible having a capacity of 300 ml and 1400. Heat and melt at ° C. for 2 hours to prepare 200 g of homogeneous molten glass. During this time, the molten glass is stirred and shaken several times.
After 2 hours, the crucible containing the molten glass is taken out from the furnace at 1300 to 1500 ° C., stirred and shaken for 15 to 20 seconds, and then the molten glass is placed in a carbon mold (60 mm × 40 mm × 10 mm to 15 mm). Pour and put in a slow cooling furnace 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 of crystals (pieces / kg) was calculated. ).
No. evaluated by the above method. The number densities of the crystals of each of the glasses 1 to 59 were all 0 pieces / kg.

(Comparison example)
For comparison, Example No. of Patent Document 1 3 and No. Composition of No. 5 and Example No. of Patent Document 2. Reproducibility experiments were performed on the 16 compositions. Example No. of Patent Document 1 converted to cation% display. 3 and No. The composition of No. 5 is shown in Table 2, and the No. 5 of Example No. 2 of Patent Document 2 is shown. The composition of 16 is shown in Table 1.
Furthermore, except for the cation ratio Ti ⁴⁺ / B ³⁺ , the requirements of the optical glass I are satisfied, and the cation ratio Ti ⁴⁺ / B ³⁺ is 0.804, which is higher than ^{the cation ratio Ti 4+} / B ^{3+ of the optical glass I.} For a small composition, the raw materials were melted and vitrification was attempted. This composition is called composition A. The composition A is shown in Table 1.
Furthermore, except for the cation ratio Ti ⁴⁺ / B ³⁺ , the requirements of the optical glass II are satisfied, and the cation ratio Ti ⁴⁺ / B ³⁺ is 0.803, which is higher than ^{the cation ratio Ti 4+} / B ^{3+ of the optical glass II.} For a small composition, the raw materials were melted and vitrification was attempted. This composition is called composition B. The composition B is shown in Table 2.
Example No. of Patent Document 1. 3 and No. Composition of No. 5 and Example No. of Patent Document 2. Regarding the composition and composition A of No. 16, the melt became cloudy and did not vitrify.
Although the composition B was vitrified, the number density of the crystals precipitated in the glass was measured by the method for measuring the number density of the crystals precipitated during the production of the glass, and it was found to be 998 cells / kg.
The number density of crystals determined by the above evaluation method is less than 1000 pieces / kg, more preferably less than 500 pieces / kg, further preferably less than 300 pieces / kg, still more preferably 200 pieces. Less than / kg, even more preferably less than 100 pieces / kg, even more preferably less than 50 pieces / kg, even more preferably less than 20 pieces / kg, even more preferably. Is 0 pieces / kg, which can be used as an index of being a homogeneous optical glass having even better glass stability.

(Production Example 1 of Glass Gob for Press Molding)
Next, No. A glass gob for press molding made of each of 1 to 70 optical glasses was produced as follows.
First, a glass raw material was prepared so that each of the above glasses could be obtained, and the glass was put into a platinum crucible or a platinum alloy crucible, and heated, melted, clarified, and stirred to obtain a homogeneous molten glass. Next, the molten glass was discharged from the outflow pipe at a constant flow rate and cast into a mold horizontally arranged below the outflow pipe to form a glass plate having a constant thickness. The formed glass plate was continuously pulled out in the horizontal direction from the opening provided on the side surface of the mold, transported to the annealing furnace by a belt conveyor, and slowly cooled.
The slowly cooled glass plate was cut or cut to prepare glass pieces, and these glass pieces were barrel-polished to obtain a glass gob for press molding.
A cylindrical mold is placed below the outflow pipe, molten glass is cast into the mold to form a cylindrical glass, and the glass is pulled vertically downward from the opening at the bottom of the mold at a constant speed. It is also possible to cool, cut or cut glass pieces to make glass pieces, and then barrel-polish these glass pieces to obtain a glass gob for press molding.

(Production Example 2 of Glass Gob for Press Molding)
Similar to the production example 1 of the glass gob for press molding, the molten glass flows out from the outflow pipe, receives the lower end of the molten glass flowing out in the molding mold, then rapidly drops the molding mold, cuts the molten glass flow by the surface tension, and molds. A desired amount of molten glass ingot was obtained on the mold. Then, gas was ejected from the mold to apply upward wind pressure to the glass, and the glass was molded into a glass block while floating, taken out from the mold, and annealed. Then, the glass block was barrel-polished to obtain a glass gob for press molding.

(Example 1 of Fabrication of Optical Element Blank)
A mold release agent made of boron nitride powder is uniformly applied to the entire surface of each press-molding glass gob obtained in Production Example 2 of a press-molding glass gob, and then the gob is softened by heating and press-molded to form a concave meniscus lens. , Convex meniscus lenses, biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses and other lenses, and prism blanks were produced.

(Example 2 of Fabrication of Optical Element Blank)
A molten glass is produced in the same manner as in Production Example 1 of a glass gob for press molding, and the molten glass is supplied to a lower mold molding surface to which a mold release agent of boron nitride powder is uniformly applied, and the amount of molten glass on the lower mold is desired. When the amount was reached, the molten glass stream was cut with a cutting blade.
The molten glass block thus obtained on the lower mold was pressed with the upper mold and the lower mold to prepare various lenses such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a plano-convex lens, and a plano-concave lens, and a prism blank. ..

(Example 1 of Fabrication of Optical Element)
Each blank produced in Examples 1 and 2 of producing optical element blanks was annealed. By annealing, the distortion inside the glass was reduced, and the optical characteristics such as the refractive index were set to the desired values.
Next, each blank was ground and polished to produce various lenses and prisms such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a plano-convex lens, and a plano-concave lens. The surface of the obtained optical element may be coated with an antireflection film.

(Production Example 2 of Optical Element)
A glass plate and columnar glass are produced in the same manner as in Production Example 1 of a glass gob for press molding, and the obtained glass molded body is annealed to reduce internal distortion and optical properties such as a refractive index are desired values. I tried to become.
Next, these glass molded bodies were cut, ground and polished to prepare various lenses such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a plano-convex lens, and a plano-concave lens, and a prism blank. An antireflection film may be coated on the surface of the obtained optical element.

Finally, each of the above aspects will be summarized.

According to one aspect, Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential components, and Si ⁴⁺ and B ³⁺ are totaled in cation% display. 5 to 55%, La ³⁺ to 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total), Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ And W ⁶⁺ total 22-55%, except that the Ti ⁴⁺ content is 22% or less and the cation ratio ^{of the Si 4+} content to the total ^{Si 4+} and B ^{3+ content [} Si ⁴ / (Si ⁴ + B ³⁺ )] is 0.40 or less, La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ^{The total content of 6+} and Bi ³⁺ is 65% or more, and the ratio of the cation ratio of the content ^{of Y 3+} to the total content of ^{La 3+} , Gd ³⁺ , Y ^{3+ and Yb 3+ [Y 3+} / ( La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.12 or less, and the ratio ^{of the Ba 2+} content to the total content of ^{La 3+} , Gd ³⁺ , Y ^{3+ and Yb 3+ [} Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.40 or less,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more, the cation ratio of the Ti ^{4+ content to the B 3+ content (Ti 4+} / B ³⁺ ) is 0.85 or more, and the Abbe number νd is 23 to Equation (1) below, which is in the range of 35 and has a refractive index nd:
nd ≧ 2.205− (0.0062 × νd) ・ ・ ・ (1)
Optical glass, which is an oxide glass that satisfies the above conditions, is provided.

The above-mentioned optical glass is a high-refractive-index, low-dispersion glass, which is compared with a conventional high-refractive-index, low-dispersion glass. At the same Abbe number νd, a higher refractive index can be achieved while maintaining glass stability.

^{Nb 5+} and Ta ^{5 with} respect to the total content of ^{Ti 4+} , Nb ⁵⁺ , Ta ⁵⁺ and W ^{6+ in} the above-mentioned optical glass from the viewpoint of maintaining high glass stability and low dispersion of high refractive index. the total content of the cation ratio of ^{+ [(Nb 5+ + Ta 5+} ) / (Ti 4+ + Nb 5+ + Ta 5+ + W 6+)] is preferably at 0.41 or less.

The above-mentioned optical glass ^{preferably contains Zr 4+ in an amount} of 1 cation% or more. As a result, the refractive index can be increased, the chemical durability can be improved, the ^{devitrification resistance can be improved by coexistence with Ti 4+,} and the rise in liquid phase temperature can be suppressed.

According to another aspect, Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential components, and Si ⁴⁺ and B ³⁺ are totaled in cation% representation. 5 to 55%, La ³⁺ to 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total), Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵ 23 to 70% ⁺ and W ⁶⁺ in total (however, 22% more than the Ti ^4+), wherein, La ^3+, Gd ^3+, relative to the total content of Y ³⁺ and Yb ³⁺ for Y ³⁺ The cation ratio of the content [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.14 or less, and the total content of ^{La 3+} , Gd ³⁺ , Y ³⁺ and Yb ³⁺ Ba ²⁺ cation ratio of the content with respect to ^{[Ba 2+ / (La 3+ +} Gd 3+ + Y 3+ + Yb 3+)] is 0.40 or less, Zr ⁴⁺ to the content of Zr ^4+, Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ total content cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 2 or more, B ³⁺ The cation ratio (Ti ⁴⁺ / B ³⁺ ) of the Ti ⁴⁺ content to the content is 0.85 or more, the Abbe number νd is in the range of 18 or more and less than 35, and the refractive index nd is as follows ( 2) Equation:
nd ≧ 2.540- (0.02 × νd) ・ ・ ・ (2)
An optical glass which is an oxide glass satisfying the above conditions is provided.

The above-mentioned optical glass is also a high-refractive index low-dispersion glass, which is compared with the conventional high-refractive index low-dispersion glass. At the same Abbe number νd, a higher refractive index can be achieved while maintaining glass stability.

According to a further aspect, a press-molded glass gob, an optical element blank, and an optical element made of the optical glass according to each of the above-described aspects are provided.

According to one aspect of the present invention, it is possible to provide an optical glass capable of stable supply and having a high refractive index and low dispersibility having excellent glass stability, and further, pressing using the optical glass. Molding glass gobs, optical element blanks and optical elements can be provided.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.
For example, the optical glass according to one aspect of the present invention can be produced by adjusting the composition described in the specification with respect to the above-exemplified glass composition.
In addition, it is of course possible to arbitrarily combine two or more of the items described in the specification as an example or a preferable range.

The present invention is useful in the field of manufacturing various optical elements such as optical elements for imaging optical systems and projection optical systems.

Claims (10)

Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential ingredients.
In cation% display,
Si ⁴⁺ and B ³⁺ total 15-30.40%,
La ³⁺ is 15-35% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 60% or less in total),
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ total 23-45% (however, Ti ⁴⁺ exceeds 22%),
Including
The content of Y ³⁺ is 15% or less,
The cation ratio ^{of the Ba 2+} content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [Ba 2+} / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0. 25 or less
The cation ratio of the total content of Si ⁴⁺ and B ^{3+ to} the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [(Si 4+} + B ³⁺ ) / (La ³⁺ + Gd ^{3) +} + Y ³⁺ + Yb ³⁺ )] is 1.05 or less,
The cation ratio of the total content of Gd ³⁺ , Y ³⁺ and Yb ^{3+ to} the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ [(Gd 3+} + Y ³⁺ + Yb ³⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.02 or more,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio (Ti ⁴⁺ / B ³⁺ ) of the Ti ⁴⁺ content to the B ³⁺ content is 0.85 or more.
The total content of the cation ratio of Nb ⁵⁺ and Ta ⁵⁺ to the content of ^{Nb 5+ [(Nb 5+ + Ta} 5+) / Nb 5+] is 1 or more,
And
An optical glass in which the Abbe number νd is in the range of 18 or more and less than 35, and the refractive index nd is an oxide glass satisfying the following equation (2).
nd ≧ 2.540- (0.02 × νd) ・ ・ ・ (2) The cation ratio of the total content of Nb ⁵⁺ and Ta ^{5+ to} the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ^{6+ [(Nb 5+} + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁾ The optical glass according to claim 1, wherein ⁺ + Ta ⁵⁺ + W ^{6+)] is 0.41 or less.} Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ And W ⁶⁺ Nb with respect to the total content of ⁵⁺ And Ta ⁵⁺ Cation ratio of total content of [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] Is 0.157 or more. The optical glass according to claim 1 or 2. The optical glass according to any one of claims 1 to 3, wherein the content of Nb ⁵⁺ is 20 cation% or less. The total content of the cation ratio of Nb ⁵⁺ and Ta ⁵⁺ to the content of ^{Nb 5+ [(Nb 5+ + Ta} 5+) / Nb 5+] is any one of claims 1 to 4, 7 or less The optical glass described in. The optical glass according to any one of claims 1 to 5 , wherein the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is in the range of 0 to 10%. The optical glass according to any one of claims 1 to 6 , wherein the content of W ⁶⁺ is in the range of 0 to 10 cation%. A glass gob for press molding made of the optical glass according to any one of claims 1 to 7. An optical element blank made of the optical glass according to any one of claims 1 to 7. The optical element made of the optical glass according to any one of claims 1 to 7.