JP6656310B2 - Optical glass and its use - Google Patents

Description

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

A lens made of high-refractive-index, low-dispersion glass is combined with a lens made of ultra-low-dispersion glass to form a projection optical system, such as an imaging optical system or a projector, in order to make the optical system compact while correcting chromatic aberration. Occupies a very important position as an optical element.
Patent Document 1 discloses a high-refractive-index low-dispersion glass that is not an optical element material for an imaging optical system or a projection optical system but has a refractive index of 1.90 to 2.10 and an Abbe number νd of 22 to 35. 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.

JP-A-60-33229 JP-A-60-131845

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

  An object of one embodiment of the present invention is to provide an optical glass having excellent glass stability while being a high-refractive-index low-dispersion glass.

  As a result of intensive studies, the present inventors have found that by adjusting the glass composition, it is possible to obtain an optical glass having high stability while having a high refractive index and low dispersion.

One embodiment of the present invention provides
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),
A total of 22 to 55% of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ ;
Containing, 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⁺ )] is 0.12 or less,
The cation ratio of the content of Ba ²⁺ 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 present invention relates to an optical glass that is an oxide glass having an Abbe number νd in a range of 23 to 35 and a refractive index nd satisfying the following expression (1).
nd ≧ 2.205− (0.0062 × νd) (1)

Another aspect of the present invention provides
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),
23 to 70% in total of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ (however, more than 22% of Ti ⁴⁺ );
Including
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 0.14 or less,
The cation ratio of the content of Ba ²⁺ 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 present invention relates to an optical glass that is an oxide glass having an Abbe number νd in a range of 18 to less than 35 and a refractive index nd satisfying the following expression (2).
nd ≧ 2.540− (0.02 × νd) (2)

  A further aspect of the present invention relates to a glass gob for press molding comprising the optical glass of the above-mentioned aspect.

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

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

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

[Optical glass I]
One embodiment of the optical glass of the present invention (hereinafter referred to as “optical glass I”) includes 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 5-55% in total and La ³⁺ is 10-50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% in total). %), Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ in total of 22 to 55%, provided 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;
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 at least 65%, 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. The cation ratio of the content of Ba ²⁺ 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;
The optical glass is an oxide glass having an Abbe number νd in the range of 23 to 35 and a refractive index nd satisfying the following expression (1).
nd ≧ 2.205− (0.0062 × νd) (1)
Another embodiment 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 above composition range will be described below. Unless otherwise specified, the content of each component and the total content are represented by cation%.

Si ⁴⁺ and B ³⁺ are network-forming components and components that serve to 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 realize a desired refractive index. Become. Therefore, the total content of Si ⁴⁺ and B ³⁺ is 5 to 55%. A preferred upper limit of the total content of Si ⁴⁺ and B ³⁺ is 50%, a more preferred upper limit is 45%, a still more preferred upper limit is 40%, a more preferred upper limit is 35%, and a still more preferred upper limit is 30%. A preferred lower limit of the total content of ⁴⁺ and B ³⁺ is 10%, a more preferred lower limit is 13%, a still more preferred lower limit is 15%, a still more preferred lower limit is 18%, and a still more preferred lower limit is 20%.

Si ⁴⁺ is an essential component that is effective for maintaining the viscosity suitable for molding the molten glass and improving the chemical durability in addition to the above functions. In order to effectively obtain the above functions, the content is preferably 1% or more. On the other hand, in order to obtain a desired refractive index and suppress an increase in the liquidus temperature or the glass transition temperature, the Si ⁴⁺ content is preferably 30% or less. Further, from the viewpoint of realizing a desired Abbe number, maintaining the melting property 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%. The more preferable upper limit of the content of Si ⁴⁺ is 25%, the further preferable upper limit is 20%, the more preferable upper limit is 18%, the still more preferable upper limit is 15%, and the still more preferable upper limit is 12%. From the viewpoint of favorably obtaining the effect of the Si ⁴⁺ content, a more preferred lower limit of the Si ⁴⁺ content is 2%, a still more preferred lower limit is 3%, a more preferred lower limit is 4%, and a still more preferred lower limit is 5%. %, An even more preferred lower limit is 6%.

B ³⁺ is an essential component that is effective for maintaining the meltability of the glass, lowering the liquidus temperature and reducing the dispersion, in addition to the above functions. In order to effectively obtain the above functions, the content is preferably 1% or more. The 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 a desired refractive index and maintaining good chemical durability and the like. Therefore, the content of B ³⁺ is preferably in the range of 1 to 50%. A more preferred upper limit of the B ³⁺ content is 40%, a still more preferred upper limit is 35%, a still more preferred upper limit is 30%, a still more preferred upper limit is 25%, a still more preferred upper limit is 22%, and a particularly preferred upper limit is. The lower limit of the B ³⁺ content is 3%, the more preferred lower limit is 5%, the still more preferred lower limit is 7%, the still more preferred lower limit is 9%, and the still more preferred lower limit is 11%. is there.

When 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⁺ exceeds 0.40, the glass stability is maintained. It becomes difficult to obtain desired optical characteristics, and the melting property is reduced, so that the glass raw material is hardly melted. 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 preferable upper limit of the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is 0.38, the more preferable upper limit is 0.36, the further preferable upper limit is 0.35, and the more preferable upper limit is 0. .34, and 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. From the viewpoint of improving the glass stability and adjusting the viscosity of the molten glass to a viscosity suitable for molding, a preferable lower limit of the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is 0.10, and a more preferable lower limit is 0.14, a still more preferred lower limit is 0.17, a still more preferred lower limit is 0.20, and a still more preferred lower limit is 0.23.

La ³⁺ is an essential component having an excellent function of reducing the refractive index and dispersing while maintaining the stability of the glass, and is also a component having a function of improving the chemical durability. If the content of La ³⁺ is less than 10%, it is difficult to obtain the above-mentioned effects, and if the content of La ³⁺ exceeds 50%, the devitrification resistance deteriorates and the liquidus temperature rises. Therefore, the content of La ³⁺ is set to 10 to 50%. The preferable upper limit of the La ³⁺ content is 45%, the more preferable upper limit is 40%, the more preferable upper limit is 35%, the more preferable upper limit is 33%, and the preferable lower limit of the La ³⁺ content is 15%, A preferred lower limit is 18%, a still more preferred lower limit is 20%, a still more preferred lower limit is 22%, and a still 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. If 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 set to 70% or less. A preferred upper limit of the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 60%, a more preferred upper limit is 50%, a still more preferred upper limit is 45%, and a still more preferred upper limit is 40%, and still more preferred. The upper limit is 38%. From the viewpoint of realizing a desired refractive index and Abbe number, a preferable lower limit of the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 11%, a more preferable lower limit is 15%, and a further preferable lower limit is The lower limit is 20%, the more preferred lower limit is 23%, the still more preferred lower limit is 25%, the still more preferred lower limit is 28%, and the particularly preferred lower limit is 30%.

In optical glass I, the total content of La ³⁺ , Gd ³⁺ , Y ^3+, and Yb ³⁺ is maintained in order to maintain the glass stability and suppress the rise in the liquidus temperature while reducing the refractive index. The cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] to the content of Y ³⁺ is 0.12 or less. A preferred upper limit of the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.11, a more preferred upper limit is 0.10, a still more preferred upper limit is 0.08, and a more preferred upper limit is. 0.04, a still more preferred upper limit is 0.02. The cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] can be set to zero.

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 more preferable upper limit is 10%, and the more preferable upper limit is 8%. An even more preferred upper limit is 6%. A preferred lower limit of the content of Gd ³⁺ is 0.5%, a more preferred lower limit is 1%, a still more preferred lower limit is 2%, and a still more preferred lower limit is 3%. Note that the content of Gd ³⁺ can be set to 0%.

A preferred upper limit of the Y ³⁺ content is 15%, a more preferred upper limit is 10%, a still more preferred upper limit is 7%, a still more preferred upper limit is 5%, a still more preferred upper limit is 3%, and a still more preferred upper limit is 2%. is there. A preferred lower limit of the Y ³⁺ content is 0.1%. The Y ³⁺ content can be set to 0%.

The preferred upper limit of the Yb ³⁺ content is 10%, the more preferred upper limit is 8%, the still more preferred upper limit is 6%, the more preferred upper limit is 4%, and the still more preferred upper limit is 2%. The content of Yb ³⁺ can be set to 0%. Since Yb ³⁺ has absorption in the infrared region, it is not suitable for use in high-sensitivity optical systems that require near-infrared region photosensitive characteristics, such as high-precision video cameras and surveillance cameras. 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, even more preferably 0.10 or more, 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 still more preferred upper limit is 0.40, a still more preferred upper limit is 0.30, and a still more preferred upper limit is 0.20.

Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , and W ⁶⁺ increase the refractive index, improve the devitrification resistance, suppress the rise in 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 is difficult to obtain the above-mentioned effects, and Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ If the total content exceeds 55%, the devitrification resistance deteriorates, and the liquidus temperature rises. In addition, the dispersion becomes higher, and the coloring of the glass becomes stronger. Therefore, the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is set to 22 to 55%. A preferable upper limit of the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is 45%, a more preferable upper limit is 40%, a further preferable upper limit is 35%, a more preferable upper limit is 33%, and a more preferable upper limit. The upper limit is 31%, the preferable lower limit of the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is 23%, the more preferable lower limit is 24%, the further preferable lower limit is 25%, and the more preferable lower limit. Is 26%, and an even more preferred lower limit is 27%.

The optical glass I has a total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ within the above range, a Ti ⁴⁺ content of 22% or less, and Zr ⁴⁺ essential. Ingredients. 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 +} ) / Zr4 ⁺ ], devitrification resistance can be improved and an increase in liquidus 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. A preferred lower limit of the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 3.0, a more preferred lower limit is 3.5, and a still more preferred lower limit is 4.0. A preferred lower limit is 4.5, and an even more preferred lower limit is 5.0. 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 still more preferred upper limit is 30, a more preferred upper limit is 20, and a still more preferred upper limit is 10.

From the viewpoint of realizing desired optical characteristics while maintaining glass stability, a preferable lower limit of the content of Ti ⁴⁺ is 10%, a more preferable lower limit is 12%, a further preferable lower limit is 14%, and a more preferable lower limit is 16. %, A still more preferred lower limit is 18%, a preferred upper limit of the Ti ⁴⁺ content is 21.9%, a more preferred upper limit is 21.8%, a still more preferred upper limit is 21.7%, and a more preferred upper limit is 21. 0.6%, an even more preferred upper limit is 21.5%.

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

Ta ⁵⁺ functions to increase the refractive index without increasing the dispersion as compared with Ti ⁴⁺ , Nb ⁵⁺ , and W ^6+, and to enhance the glass stability. If the Ta ⁵⁺ content exceeds 10%, the liquidus temperature rises and the devitrification resistance decreases, so that the Ta ⁵⁺ content is preferably set to 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 0 to 2%, and an even more preferable range is 0 to 1%. Even more preferably, 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 driving power consumption during autofocusing increases, and an essential component is used. 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, and the more preferred upper limit is 3, and the cation ratio [(Nb ⁵⁺ + Ta) ^{5 +} ) / Nb ⁵⁺ ] can be set to 1.

W ⁶⁺ is an optional component that raises the refractive index, lowers the liquidus temperature, and contributes to the improvement of the devitrification resistance. In order to suppress the content, the content of W ⁶⁺ is preferably set to 0 to 10%. The preferred range of the W ⁶⁺ content is 0 to 8%, a more preferred range is 0 to 6%, a further preferred range is 0 to 4%, a more preferred range is 0 to 2%, and a still more preferred range is 0 to 1%. %, And it is even more preferable not to contain W ⁶⁺ .

While maintaining glass stability, in order to increase the refractive index, Ti ^4+, Nb ^5+, the content of the cation ratio of W ⁶⁺ to the total content of Ta ⁵⁺ and W ⁶⁺ [W ⁶⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is preferably less than 0.10. From the viewpoint of increasing the refractive index while maintaining the glass stability, the upper limit of the cation ratio [W ⁶⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is more preferably 0.095 or less. , Further preferably 0.090 or less, more preferably 0.070 or less, still more preferably 0.050 or less, and still 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.

From the viewpoint of reducing the refractive index and dispersing while maintaining the 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, the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶ ) from the viewpoint of reducing the high refractive index and lowering the partial dispersion ratio while maintaining the glass stability. ⁺ )] 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, and 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 still more preferred upper limit is 0.30. A more preferred lower limit of the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is 0.10, a still more preferred lower limit is 0.15, and a still more preferred lower limit is 0.15. 20, an even more preferred lower limit is 0.25.

Among the components having a high refractive index, La ³⁺ , Gd ³⁺ , Y ³⁺ , and Yb ³⁺ have a function of increasing the refractive index while maintaining low dispersibility, and include Ti ⁴⁺ , Nb ⁵⁺ , and Ta ^{5. + And} W ⁶⁺ are high refractive index and high dispersion components. From the viewpoint of obtaining desired optical characteristics while maintaining good glass stability, Ti ⁴⁺ , Nb ⁵⁺ , and Ta ^{5+ based on} the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^3+. And the total cation ratio of the total content of W ⁶⁺ and [(Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.10 or more. Is preferred. A more preferred 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, and a further preferred lower limit is 0.50. The lower limit is preferably 0.60, and more preferably 0.70.
From the viewpoint of obtaining desired optical characteristics while maintaining good glass stability, the cation ratio [(Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] Is preferably 1.50 or less. Cation ratio ^{[(Ti 4+ + Nb 5+ +} Ta 5+ + W 6+) / (La 3+ + Gd 3+ + Y 3+ + Yb 3+)] is more preferable upper limit of 1.40, still more preferred upper limit is 1.30, A more preferred upper limit is 1.20, and a still more preferred 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 set to 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.
From the viewpoint of increasing the refractive index while maintaining the glass stability, the lower limit of the cation ratio (Ti ⁴⁺ / B ³⁺ ) is more preferably 0.90 or more, further preferably 0.95 or more, and further preferably 1 or more. 0.000 or more. The upper limit of the cation ratio (Ti ⁴⁺ / B ³⁺ ) is naturally determined from the composition range of the optical glass according to the above-described embodiment, but may be considered to be, for example, about 10.

Zr ⁴⁺ is an essential component in the optical glass I, and serves to increase the refractive index, improve the chemical durability, improve the devitrification resistance by coexisting with Ti ^4+, and suppress the rise in liquidus temperature. Work. In order to obtain the above effects, the content of Zr ⁴⁺ is preferably set to 1% or more. From the viewpoint of suppressing an increase in the glass transition temperature or the liquidus temperature and a decrease in the devitrification resistance, the preferable upper limit of the Zr ⁴⁺ content is 15%. A preferred upper limit of the Zr ⁴⁺ content is 10%, a more preferred upper limit is 8%, and a still more preferred upper limit is 7%. A preferred lower limit of the Zr ⁴⁺ content is 1%, a more preferred lower limit is 2%, and A preferred lower limit is 3%, and a more preferred lower limit is 4%.

Zn ²⁺ lowers the refractive index and the stability of the glass, but functions to improve the fusibility and clarity of the glass. The oxides of La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ , and Zr ⁴⁺ all have extremely high melting points, and these components are essential. It is preferable that Zn ²⁺ effective for improving meltability and clarity be contained in the optical glass I containing a component or an optional component. Therefore, from the viewpoint of maintaining a high refractive index and maintaining good glass stability, the content of Zn ²⁺ is preferably 15% or less, more preferably 12% or less, and more preferably 10% or less. More preferably, it is 8% or less, still more preferably 6% or less, even more preferably 3% or less. Further, from the viewpoint of improving the melting property and clarity of the glass and suppressing the increase in the melting temperature and the increase in the coloring of the glass accompanying the melting temperature, the content of Zn ²⁺ is preferably 0.1% or more. It is more preferably at least 5%, further preferably at least 0.8%, even more preferably at least 1.0%. Note that the content of Zn ²⁺ can 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 reduce the total content of these components and the refractive index. Adjusting optical properties such as fusibility, clarity, and refractive index using the cation ratio Zn ²⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) as an index to improve Zn ²⁺ content Can be. From the viewpoint of improving the melting property and clarity of the glass, the cation ratio [Zn ²⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is preferably 0.01 or more, and 0.02 or more. Is more preferably set to 0.03 or more, and further preferably set to 0.04 or more. In order to increase the refractive index, the cation ratio [Zn ²⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is preferably 0.65 or less, more preferably 0.60 or less. More preferably, it is more preferably 0.50 or less, further preferably 0.40 or less, still more preferably 0.30 or less, still more preferably 0.20 or less, and 0 or less. It is particularly preferable to set it to .10 or less.

Li ⁺ , Na ⁺ and K ⁺ are optional components that serve to improve the meltability and lower the glass transition temperature. The total content of Li ⁺ , Na ^+, and K ⁺ is in the range of 0 to 10% from the viewpoint of realizing a high refractive index and suppressing a rise in liquidus temperature, a decrease in glass stability, and a decrease in chemical durability. Is preferable. A more preferred range of the total content of Li ⁺ , Na ⁺ and K ⁺ is 0 to 8%, a further preferred range is 0 to 6%, a more preferred range is 0 to 4%, and a still more preferred range is 0 to 2%. A still more preferable range is 0 to 1%, and it is particularly preferable that the above-mentioned alkali metal component is not contained.

About content of each component of Li ^<+> , Na ^<+>, and K ^{< + >} , a preferable range is 0-10%, a more preferable range is 0-8%, a more preferable range is 0-6%, and a further preferable range is 0-0. 4%, a more preferable range is 0 to 2%, and an even more preferable range is 0 to 1%, and it is still more preferable that the above-mentioned alkali metal components are not contained.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ function to improve the melting property of the glass and lower the glass transition temperature Tg. Also, by introducing nitrate or sulfate into glass, a defoaming effect can be obtained.
In the glass having a high refractive index and low dispersion, of the alkaline earth metal components, when Ba ²⁺ is contained in a large amount relative to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ , It becomes difficult to further reduce the refractive index and the dispersion while maintaining the glass stability. For example, molten glass is usually formed by casting molten glass into a mold having a bottom surface and side walls and having one of the side surfaces opened, and continuously drawing the molded glass from the side surface of the mold opening (referred to as an E-bar molding method). ). However, when Ba ²⁺ is contained in a large amount relative to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ to achieve a high refractive index and low dispersion, glass is lost by this molding method. It becomes easy to see through. Therefore, using a mold having a through-hole, the 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, thereby preventing devitrification. I have to use a special molding method. In a molding method using a mold having a through-hole, it is difficult to anneal the glass as it is through a tunnel-type continuous annealing furnace called a rare furnace because the formed glass is drawn downward.
Ba ^{2 +} content and La ^3+, Gd ^3+, and adjusting the ratio of the total content of Y ³⁺ and Yb ^3+, by optimizing, in general E bar molding, devitrification It is possible to form a homogeneous optical glass while preventing this. Then, since the formed glass can be passed through a rare furnace and annealed as it is, the glass can be manufactured with high productivity.
As described above, in order to prevent a decrease in glass stability due to a high refractive index and a low dispersion, in the optical glass I, Ba ^{2 + with} respect to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^3+. Cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is set to 0.40 or less. When the cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] exceeds 0.40, the tendency of devitrification of the glass increases, and a 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, the preferable upper limit is 0.30, the more preferable upper limit is 0.25, and the more preferable upper limit. Is 0.20, a more preferred upper limit is 0.10, and a still more preferred upper limit is 0.05. The cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] may be zero.

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

About content of each component of Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ^+, a preferable range is 0-10%, a more preferable range is 0-8%, and a more preferable range is 0-6%, respectively. The still more preferable range is 0 to 4%, the more preferable range is 0 to 2%, and the still more preferable range is 0 to 1%. It is still more preferable that the above-mentioned alkaline earth metal components are not contained.

Ge ⁴⁺ is a network-forming component and also serves to increase the refractive index, so that it is a component that can increase the refractive index while maintaining glass stability, but is significantly more expensive than other components. It is a component and it is a component whose content is desired to be reduced. In the optical glass I, since the composition is determined as described above, even if the content of Ge ⁴⁺ is suppressed to, for example, 10% or less, both realization of desired optical characteristics and realization of excellent glass stability can be achieved. be able to. Therefore, the content of Ge ⁴⁺ is preferably set to 0 to 10%. A more preferred range of the Ge ⁴⁺ content is 0 to 8%, a further preferred range is 0 to 6%, a more preferred range is 0 to 4%, a still more preferred range is 0 to 2%, and a still more preferred range is 0. ~ 1%. It is particularly preferable that Ge ⁴⁺ is not contained, that is, Ge-free glass is used.

Bi ^{3+ not} only increases the refractive index but also enhances the stability of the glass, but if its amount exceeds 10%, the light transmittance in the visible region decreases. Therefore, the content of Bi ³⁺ is preferably set to 0 to 10%. A more preferred range of the Bi ³⁺ content is 0 to 8%, a still more preferred range is 0 to 6%, a more preferred range is 0 to 4%, a still more preferred range is 0 to 2%, and an even more preferred range is 0. To 1%, and it is particularly preferable that Bi ³⁺ is not contained.

Among 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 components having a high refractive index. In order to obtain the desired refractive index and dispersion, 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⁺ is 65% or more. In the optical glass I, in order to maintain glass stability, a total of 5% or more of Si ⁴⁺ and B ³⁺ as network forming components is contained, so that La ³⁺ , Gd ³⁺ , Y ³⁺ , and Yb ^{3+ are used.} , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ naturally fall below 95%. From the viewpoint of obtaining desired optical characteristics, the total of La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ A preferred lower limit of the content is 66%, a more preferred lower limit is 67%, a still more preferred lower limit is 68%, a still more preferred lower limit is 69%, and a still more preferred 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⁺ Is preferably 90%, more preferably 85%, further preferably 80%, more preferably 75%, and still more preferably 73%.

Al ³⁺ functions to improve the glass stability and chemical durability when the amount is small, but when the amount exceeds 10%, the liquidus temperature increases and the devitrification resistance tends to deteriorate. . Therefore, the content of Al ³⁺ is preferably set to 0 to 10%. A more preferable range of the Al ³⁺ content is 0 to 8%, a further preferable range is 0 to 6%, a more preferable range is 0 to 4%, a still more preferable range is 0 to 2%, and a still more preferable range is 0. -1%, and it is particularly preferable that ^{Al3 +} is not contained.

  In addition, from the viewpoint of providing an optical glass having high refractive index and low dispersibility and excellent glass stability as the optical glass I, the content of any cation component other than the cation component is set to 0 to 5%. It is preferably set to 0 to 4%, more preferably to 0 to 3%, further preferably to 0 to 2.5%, and still more preferably to 0 to 2%. Preferably, it is still more preferably 0 to 1.5%, further preferably 0 to 1.0%, particularly preferably 0 to 0.5%. The content of any cation component other than the above cation component may be 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 added in excess of the above, the glass will be colored or its strong oxidizing action will promote deterioration of the molding surface of the 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 still more preferably 0 to 0.1% by mass. .

Sn can also be added as a fining agent, but if it is added in excess of 1% by mass in terms of SnO ₂ , the glass will be colored or the oxidizing action will promote deterioration of the molding surface of the mold. 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 oxides, sulfates, nitrates, chlorides and fluorides may be added in small amounts as fining agents.

The optical glass I can maintain the glass stability while realizing optical characteristics with high refractive index and low dispersion, and therefore does not need to contain components such as Lu, Hf, Ga, In, and Sc. Since Lu, Hf, Ga, In, and Sc are also expensive components, the contents of Lu ³⁺ , Hf ⁴⁺ , Ga ³⁺ , In ³⁺ , and Sc ³⁺ are preferably suppressed to 0 to 1%, respectively. More preferably, the content is suppressed to 0 to 0.5%. Lu ³⁺ is not introduced, Hf ⁴⁺ is not introduced, Ga ³⁺ is not introduced, In ³⁺ is not introduced, Sc ³⁺ is introduced. It is particularly preferred that they are not used.
It is also preferable not to introduce As, Pb, U, Th, Te, and Cd in consideration of environmental influences.
Further, from the viewpoint of taking advantage of the excellent light transmittance of the glass, it is preferable not to introduce a substance which causes 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-described Pb or the like. Here, “substantially not contained” means not actively introduced as a glass component, and it is permissible to unintentionally mix as an impurity.

Optical glass I is an oxide glass, and the main anion component is O ²⁻ . As described above, it is possible to add a small amount of Cl ⁻ or F ⁻ as a fining agent. However, in order to provide an optical glass having a high refractive index and low dispersion and 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 an optical element material suitable for chromatic aberration correction is provided by utilizing low dispersion, it is advantageous that the Abbe number νd is large. From such a viewpoint, the lower limit of the Abbe number νd is preferably 24.0, more preferably 24.5, further preferably 25.0, more preferably 25.5, and still more preferably 26.0.
On the other hand, relaxing the upper limit of the Abbe number νd is advantageous for maintaining and improving the glass stability. From such a viewpoint, the upper limit of the Abbe number νd is preferably 32.00, more preferably 31.00 or less, further preferably 30.00 or less, further preferably 29.00 or less, and 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 dispersion, optical systems such as an imaging optical system and a projection optical system can be made compact and highly functional. In the optical glass I, the refractive index nd and Abbe number νd satisfy the following expression (1). The glass satisfying the expression (1) is a glass having a higher refractive index at the same Abbe number νd than the conventional high-refractive-index low-dispersion glass, that is, a glass in the upper left range of the optical characteristic diagram described above, and is useful. It is a highly functional glass.
nd ≧ 2.205− (0.0062 × νd) (1)
The upper limit of the refractive index nd is not particularly limited, since it is naturally determined from the composition range of the optical glass I. From the viewpoint of maintaining the glass stability, the refractive index nd is preferably set to 2.20 or less, more preferably 2.15 or less, further preferably 2.10 or less, and 2.09 or less. Is more preferable.

It is preferable that the refractive index nd and the Abbe number νd are within the above ranges, and further satisfy the following expression (1-1), from the viewpoint of enhancing the functionality and reducing the size of the optical element and the optical system incorporating the optical element. More preferably satisfying the following formula (1-2), further preferably satisfying the following formula (1-3), more preferably satisfying the following formula (1-4), and further satisfying the following formula (1-5) 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 optical systems such as an imaging optical system and a projection optical system compact and having high functions. In addition, even when a lens having the same focal length is manufactured, the absolute value of the curvature of the optical function 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, by further increasing the refractive index of the optical glass, 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, from the viewpoint of maintaining good thermal stability of the glass and suppressing an increase in coloring, it is preferable that the refractive index nd and the Abbe number νd satisfy the following expression (1-6). It is more preferable that the formula (7) is satisfied, it is more preferable that the following formula (1-8) is satisfied, it is more preferable that the following formula (1-9) is satisfied, and that the following formula (1-10) is more satisfied. 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 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 formula (1). Of the above optical characteristics, preferred optical characteristics refer to any of the preferable ranges of the refractive index nd and Abbe number νd.

(Liquid phase temperature)
The high-refractive-index glass is made of 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 ), and 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 )) However, these components alone have extremely high melting points. When the total amount of the components having a high refractive index is large, the total amount of components having a function of lowering the melting temperature, such as an alkali metal component and an alkaline earth metal component, is relatively reduced, and the melting property and the devitrification resistance are reduced. Therefore, the melting temperature must be increased to obtain a homogeneous glass.
As the melting temperature increases, the aggressiveness of the glass melt increases, and the melting container is eroded, and the materials constituting the container, such as platinum and platinum alloy, dissolve into the glass melt to color the glass or become platinum foreign matter. I do. In addition, when the melting temperature is high, volatile components such as B ³⁺ volatilize, and the glass composition changes over time, which causes a problem that optical characteristics fluctuate.
In order to solve such a problem, an increase in the melting temperature may be suppressed. 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 substantially 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.
In addition, if the rise in liquidus temperature can be suppressed, it is effective in preventing devitrification during glass molding, and the viscosity of glass can be adjusted to a range suitable for molding, making it easy to produce a high-quality glass molded body. Become.

As described above, both the increase and decrease of the refractive index and the rise and fall of the liquidus temperature are linked to the increase and decrease of the amount of the high refractive index component. It is appropriate to use the index that has been set. 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 a value obtained by subtracting the vacuum refractive index 1 from the glass refractive index, and reflects the net change in the refractive index. The lower the value of LT / (nd-1), the higher the refractive index of the glass, which means that the glass is more excellent in meltability and devitrification resistance.
In a preferred embodiment of the optical glass I, the amounts of the respective components are determined in a well-balanced manner so as to suppress the rise 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 with further improved meltability and devitrification resistance, an optical glass satisfying the following formula (3-1) is preferable, and an optical glass satisfying the following formula (3-2) is more preferable. The optical glass satisfying the following formula (3-4) is more preferable, the optical glass satisfying the following formula (3-4) is more preferable, and the optical glass satisfying the following formula (3-5) is more preferable. The optical glass satisfying the above is still 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, when LT / (nd-1) is reduced, it tends to be difficult to maintain required optical characteristics. Therefore, it is preferable not to excessively reduce LT / (nd-1). From such a viewpoint, 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 more preferable. The optical glass satisfying the following formula (3-10) is more preferable, the optical glass satisfying the following formula (3-11) is more preferable, and the 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. An optical element such as a lens made of such optical glass is suitable for high-order chromatic aberration correction.
Here, the partial dispersion ratios Pg, F are expressed as (ng−nF) / (nF−nc) using the respective refractive indices ng, nF, and nc at the g-line, the F-line, and the c-line.
From the viewpoint of providing an optical glass suitable for high-order chromatic aberration correction, it is preferable that the optical glass I has a partial dispersion ratio Pg, F and an Abbe number νd satisfying the following expression (4-1). Those satisfying the relationship of the formula (4-2) are more preferable, and those satisfying the relationship of the following formula (4-3) are still more 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)

Note that, in the partial dispersion ratio Pg, F-Abbe number νd diagram, if the partial dispersion ratio on a normal line that is a reference of the normal partial dispersion glass is represented by 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, F is a deviation of the partial dispersion ratio Pg, F from the above-mentioned normal line, and is represented by the following equation.
ΔPg, F = Pg, F−Pg, F (0)
= Pg, F + (0.0018 × νd) −0.6483
In a preferred embodiment of the optical glass of the above embodiment, the deviation ΔPg, F is 0.030 or less, which is suitable as a high-order chromatic aberration correcting optical element material. A more preferred range of ΔPg, F is 0.025 or less, a still more preferred range is 0.020 or less, a more preferred range is 0.015 or less, and a still more preferred range is 0.001 or less. The lower limit of the deviation ΔPg, F is more preferably 0.0000 or more, further preferably 0.001 or more, more preferably 0.003 or more, and still more preferably 0.005 or more.

(specific gravity)
Although the optical glass of the above embodiment is a high refractive index glass, the specific gravity of the glass generally tends to increase when the refractive index is increased. However, an increase in 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 while being a high refractive index glass by having the above glass composition. The preferable upper limit of the specific gravity 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 tends to decrease and the liquidus temperature tends to increase. Therefore, the specific gravity is preferably set to 4.50 or more. A more preferred lower limit of the specific gravity is 4.70, a still more preferred lower limit is 4.90, a still more preferred lower limit is 5.00, and a still more preferred lower limit is 5.10.

(Transmissivity characteristics)
Next, the light transmittance of the optical glass I will be described.
The optical glass I can exhibit high light transmittance over a wide wavelength range of the visible region. In a preferred embodiment of the optical glass I, λ70 shows a coloring degree of 680 nm or less. The more preferred range of λ70 is 660 nm or less, the still more preferred range is 650 nm or less, the more preferred range is 600 nm or less, the still more preferred range is 560 nm or less, and the still more preferred range is 530 nm or less. Although the lower limit of λ70 is not particularly limited, 380 nm may be considered as a standard 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 refers to a case where 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 perpendicular direction. The obtained spectral transmittance, that is, Iout / Iin when the intensity of light incident on the sample is Iin and the intensity of light transmitted through the sample is Iout. The spectral transmittance includes the reflection loss of light on the sample surface. Further, the above polishing means that the surface is smoothed to a state where the surface roughness is sufficiently small with respect to the wavelength in the measurement wavelength range. It is preferable that the optical glass I has a light transmittance of more than 70% in a visible region on a longer wavelength side than λ70.

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

  The above-mentioned spectral transmittance is measured in the wavelength range of 280 to 700 nm as described above. Usually, as the wavelength is increased from λ5, the light transmittance increases, and when the wavelength reaches λ70, 70% or more up to the wavelength of 700 nm. Maintain high transmittance.

(Glass-transition temperature)
The optical glass I is a glass suitable for forming a smooth optically functional surface by polishing. Suitability of cold working such as polishing, that is, cold workability is indirectly related to the glass transition temperature. Glass having a lower glass transition temperature is more suitable for precision press forming than cold workability, whereas glass having a higher glass transition temperature is more suitable for cold work than precision press forming, and is more suitable for cold workability. Excellent. Therefore, it is preferable that the glass transition temperature of the optical glass I is not excessively lowered, is preferably 650 ° C. or higher, more preferably 680 ° C. or higher, further preferably 700 ° C. or higher, and 710 ° C. The temperature is more preferably set to 730 ° C. or higher, even more preferably 740 ° C. or higher.
However, if the glass transition temperature is too high, the heating temperature at the time of reheating and softening the glass and molding is increased, the mold used for molding is significantly deteriorated, the annealing temperature is also increased, and the annealing furnace is heated. Deterioration and wear are also remarkable. Therefore, the glass transition temperature is preferably 850 ° C. or lower, more preferably 800 ° C. or lower, further preferably 780 ° C. or lower, and further preferably 760 ° C. or lower.

[Optical glass II]
Next, an optical glass II which is an optical glass according to another embodiment of the present invention will be described.
The 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),
23 to 70% in total of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ (however, more than 22% of Ti ⁴⁺ );
Including
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 0.14 or less,
The cation ratio of the content of Ba ²⁺ 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 oxide glass has an Abbe number νd of 18 to less than 35 and a refractive index nd satisfying the following expression (2).
nd ≧ 2.540− (0.02 × νd) (2)

The optical glass II is a glass having high refractive index and low dispersion while maintaining the glass stability, similarly to the optical glass I, 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, has a high spectral transmittance in the visible region, and has a low partial dispersion ratio so as to be advantageous for high-order chromatic aberration correction. When 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 exhibits a high refractive index and low dispersion property in a range where the content of Ti ⁴⁺ exceeds 22% and the Abbe number ν d is wider than that of the optical glass I.
Hereinafter, the composition and characteristics of the optical glass II will be described while referring to differences from the optical glass I. 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⁺ increase the refractive index, improve the devitrification resistance, suppress the rise in 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 is difficult to obtain the above-mentioned effects, and Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ If the total content exceeds 70%, the devitrification resistance deteriorates, and the liquidus temperature rises. In addition, the dispersion becomes higher, and the coloring of the glass becomes stronger. Therefore, the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is set to 23 to 70%. A preferable upper limit of the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is 60%, a more preferable upper limit is 55%, a more preferable upper limit is 50%, a more preferable upper limit is 45%, and a more preferable upper limit. The upper limit is 40%, the preferable lower limit of the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is 24%, the more preferable lower limit is 25%, the further preferable lower limit is 26%, and the more preferable lower limit. Is 27%, and a still more preferred lower limit is 28%.
In the optical glass II, the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is in the above range, and the content of Ti ⁴⁺ is more than 22%, so that the devitrification resistance is obtained. Performance can be improved. It is also effective in suppressing a rise in liquidus temperature.
A preferred lower limit of the Ti ⁴⁺ content is 22.5%, a more preferred lower limit is 23%, and a still more preferred lower limit is 24%. A preferred upper limit of the Ti ⁴⁺ content is 60%, and a more preferred upper limit is 50%. The more preferred upper limit is 45%, the more preferred upper limit is 40%, the still more preferred upper limit is 35%, and the still 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 reduce the dispersion of the high refractive index while maintaining the stability of the glass, the content is set to 0.14 or less. For the above reason, the preferable upper limit of the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.13, more preferable upper limit is 0.12, and further preferable upper limit is 0.11. is there. 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, a preferable lower limit of the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.01, a more preferable lower limit is 0.02, and A preferred lower limit is 0.03, a more preferred lower limit is 0.04, and a still more preferred lower limit is 0.05. The optical glass II is also suitable as a material for a camera lens equipped with an autofocus function, but by reducing the specific gravity of the glass, power consumption during autofocus can be reduced.
From the viewpoint of reducing the specific gravity of the glass, the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is set to 0.14 or less while Gd ³⁺ , Y ³⁺ and Yb ³ it is preferable that the content of the cation ratio of Y ³⁺ and ^{[Y 3+ / (Gd 3+ +} Y 3+ + Yb 3+)] and 0.60 than to the total content of ^+. For the above reason, a more preferred lower limit of the cation ratio [Y ³⁺ / (Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.61, a further preferred lower limit is 0.62, a still more preferred lower limit is 0.63, and a more preferred lower limit is 0.63. A preferred lower limit is 0.64.
The total content of Gd ³⁺ , Y ^3+, and Yb ³⁺ is preferably 1.0% or more from the viewpoint of reducing the refractive index and dispersing while maintaining good glass stability. Gd ³⁺ , Y ³⁺ , and Yb ³⁺ all have the function of lowering the liquidus temperature and significantly improving the devitrification resistance when they coexist with La ³⁺ . In order to obtain this function favorably, the total content of Gd ³⁺ , Y ³⁺ and Yb ³⁺ is more preferably at least 1.5%, further preferably at least 2.0%, The content is more preferably at least 2.5%, even more preferably at least 3.0%, even more preferably at least 3.5%. A preferred upper limit of the total content of Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 35%, a more preferred upper limit is 30%, a further preferred upper limit is 25%, a more preferred upper limit is 20%, and a still more preferred upper limit is 15%. The still more preferred upper limit is 10%, and the still more preferred upper limit is 7%.

For the same reason as for the optical glass I, there is also a preferred 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, more preferable lower limit is 0.02, and further preferable lower limit is 0. 0.03, a still more preferred lower limit is 0.04, and a still more preferred lower limit is 0.05.

For the same reason as the 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 preferred range for the content. A 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 still more preferred lower limit is 65%, a still more preferred lower limit is 66%, and a still more preferred lower limit is 67%. The preferred upper 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 90%, A more preferred upper limit is 85%, a still more preferred upper limit is 80%, and a still more preferred upper limit is 75%.

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

From the standpoint of reducing the refractive index and dispersing while maintaining good glass stability, 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⁺ the amount of cation ratio ^{[(S i 4+ + B 3} +) / (La 3+ + Gd 3+ + Y 3+ + Yb 3+)] is preferable lower limit of 0.10, more preferred lower limit is 0.20, more preferred lower limit 0.30, a still more preferred lower limit is 0.40, a still more preferred lower limit is 0.50, a still more preferred lower limit is 0.60, a preferred upper limit is 1.05, a more preferred upper limit is 1.0, and a still more preferred upper limit. 0.95, more preferred upper limit is 0.90, more preferred upper limit is 0.85, even more preferably upper limit 0.83.

While maintaining glass stability, over that imparts high-refractivity low-dispersion properties, Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of Ta ⁵⁺ and W ⁶⁺ The cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W6 +) / Zr ⁴⁺ ] is 2 or more. The above reasons, the cation ratio ^{[(Zr 4+ + Ti 4+ +} Nb 5+ + Ta 5+ + W 6+) / Zr 4+] of preferable lower limit is 3, more preferable lower limit is 3.5, more preferred lower limit is 4, more The preferred lower limit is 4.5, the more preferred lower limit is 5, the preferred upper limit is 72, the more preferred upper limit is 50, the more preferred upper limit is 40, the more preferred upper limit is 30, the more preferred upper limit is 20, and the still more preferred upper limit. Is 10.

Compared to the optical glass I in which the content of Ti ⁴⁺ is 22% or less and the Abbe number νd is in the range of 23 to 35, the optical glass II contains more than 22% of Ti ⁴⁺ and the lower limit of the Abbe number νd is 18. And 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, if 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 preferred lower limit is 20, the further preferred lower limit is 21, the more preferred lower limit is 22, and the still more preferred lower limit is 23. On the other hand, from the viewpoint of maintaining good glass stability, a preferable upper limit of the Abbe number νd is 32, a more preferable upper limit is 30, a further preferable upper limit is 29, a more preferable upper limit is 28, and a still more preferable upper limit is 27.
In the optical glass II in which the Abbe number νd can be adjusted in a relatively wide range, the refractive index nd and the Abbe number νd are given by Satisfies the equation. The glass satisfying the expression (2) is also a glass having a higher refractive index at the same Abbe number νd than the conventional high refractive index low dispersion glass, that is, a glass in the upper left range of the optical characteristic diagram described above, and is useful. It is a highly functional glass.
nd ≧ 2.540− (0.02 × νd) (2)
Further, for the above reason, the refractive index nd and the Abbe number νd preferably satisfy the following expression (2-1), more preferably satisfy the following expression (2-2), and satisfy the following expression (2-3). It is more preferable that the above expression is satisfied, and it is more preferable that the following expression (2-4) is satisfied.
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, since 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 set to 2.40 or less, more preferably 2.30 or less, and more preferably 2.20 or less, and 2.15 or less. More preferably, 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 ratio Pg, F in the optical glass II and the preferred upper limit of ΔPg, F are the same as those of the optical glass I. On the other hand, a preferable lower limit of ΔPg, F in the optical glass II is −0.001, a more preferable lower limit is 0.000, a further preferable lower limit is 0.003, and a more preferable lower limit is 0.003.

(specific gravity)
In order to reduce the weight of the optical element, the preferred range of the specific gravity of the optical glass II is 5.50 or less, the more preferred range is 5.40 or less, the still more preferred range is 5.30 or less, and the still more preferred range is 5.20 or less . . However, if the specific gravity is excessively reduced, the stability of the glass tends to decrease and the liquidus temperature tends to increase. Therefore, the specific gravity is preferably set to 4.50 or more. A more preferred lower limit of the specific gravity is 4.60, a still more preferred lower limit is 4.70, a still more preferred lower limit is 4.80, and a still more preferred lower limit is 4.90.

(Transmissivity characteristics)
The light transmittance of the optical glass II is the same as that of the optical glass I. A more preferred range is 390 nm or less, and an even more preferred range is 380 nm or less. Although the lower limit of λ5 is not particularly limited, 300 nm may be considered as a standard 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 preferred lower limit of the glass transition temperature of the optical glass II is 650 ° C., the more preferred lower limit is 670 ° C., the still more preferred lower limit is 680 ° C., the more preferred lower limit is 690 ° C., the still more preferred lower limit is 700 ° C., and the still more preferred lower limit is 710 ° C. An even more preferred lower limit is 720 ° C. On the other hand, the preferred upper limit of the glass transition temperature is 850 ° C., the more preferred upper limit is 800 ° C., the more preferred upper limit is 780 ° C., the more preferred upper limit is 760 ° C., the more preferred upper limit is 750 ° C., and the still more preferred upper limit is 740 ° C. .
Other compositions and properties of the optical glass II are the same as those of the optical glass I.

[Production method of optical glass]
Next, a method for manufacturing an optical glass according to one embodiment of the present invention will be described.
The method for producing an optical glass according to one aspect of the present invention is a method for producing an optical glass, which comprises melting a glass raw material by heating and molding the obtained molten glass. Preparation is performed so that glass is obtained, and the melting is performed using a glass melting vessel made of platinum or a platinum alloy.

For example, a powdery compound raw material or a cullet raw material is weighed and prepared in accordance with a target glass composition, supplied into a platinum or platinum alloy melting vessel, and then heated to be melted. After sufficiently melting and vitrifying the above raw materials, the temperature of the molten glass is increased to perform fining. The refined molten glass is homogenized by stirring with a stirrer, continuously supplied to a glass outflow pipe, discharged, quenched and solidified to obtain a glass molded body.
The melting temperature of the optical glass is desirably in the range of 1200 to 1500 ° C. from the viewpoint of obtaining a homogeneous, low-colored and stable glass having various characteristics including optical characteristics.

[Glass bump for press molding]
A glass gob for press molding according to one embodiment of the present invention is made of the optical glass of the above-described embodiment. The shape of the gob should be a shape that can be easily press-formed according to the shape of the target press-formed product. Also, the mass of the gob is set according to the press-formed product. According to one embodiment of the present invention, since glass having excellent stability can be used, the glass is hardly devitrified even when reheated, softened and press-molded, and a high-quality molded product can be stably formed. Can be produced.

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

  In the second production example, a molten glass is cast into a cylindrical mold instead of the mold to form a cylindrical glass molded body. The glass molded body molded in the mold is drawn vertically downward at a constant speed from the opening at the bottom of the mold. The drawing speed may be adjusted so that the molten glass level in the mold is constant. After the glass molded body is gradually cooled, it is cut or cut and subjected to polishing or barrel polishing to obtain a glass gob for press molding.

In the third manufacturing example, a molding machine in which a plurality of molds are arranged at equal intervals on the circumference of a circular turntable is installed below the outflow pipe, and the turntable is index-rotated to stop the molds. One of the positions is a position where the molten glass is supplied to the molding die (referred to as a casting position). The molten glass is supplied, and after the supplied molten glass is formed into a glass molded body, a predetermined molding die which is different from the casting position is stopped. The glass molded body is taken out from the position (takeout position). Which stop position should be the takeout position may be determined in consideration of the rotation speed of the turntable, the cooling speed of the glass, and the like. The supply of the molten glass to the molding die at the casting position is performed by dropping the molten glass from the glass outlet of the outflow pipe, receiving the glass droplets with the molding die, and bringing the molding die stopped at the casting position closer to the glass outlet. Supports the lower end of the flow of molten glass flowing out, creates a constriction in the middle of the glass flow, and separates the molten glass below the constriction by falling rapidly down the mold at the predetermined timing in the vertical direction and receives it on the mold It can be carried out by a method, a method in which the flowing molten glass flow is cut by a cutting blade, and the separated molten glass lump is received by a molding die which stays at a casting position.
A known method may be used for molding the glass on the mold. Above all, when gas is blown upward from the mold to apply upward wind pressure to the glass mass and the glass is molded while floating, wrinkles are formed on the surface of the glass molded body, and the glass molded body is brought into contact with the molding die. The occurrence of cracks can be prevented.

  The shape of the glass molded body is spherical, spheroidal, has one axis to be rotated, and has two surfaces oriented in the axial direction of the axis to be rotated, depending on the selection of the shape of the molding die and the manner of jetting the gas. Can be shaped to be convex outward. These shapes are suitable for a glass gob for press-forming an optical element such as a lens or an optical element blank. The glass molded body 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 manufacturing method thereof]
Next, an optical element blank and a method for manufacturing the optical element blank according to one embodiment of the present invention will be described.
An optical element blank according to one embodiment of the present invention is made of the optical glass of the above-described embodiment. The optical element blank according to one embodiment of the present invention is suitable as a glass base material for producing an optical element having various properties that the optical glass of the above embodiment can provide.
The optical element blank is a glass molded body having a shape similar to the shape of an optical element obtained by adding a processing margin for removing the target optical element by grinding and polishing.

  A first aspect of the method for manufacturing an optical element blank according to one aspect of the present invention is a method for manufacturing an optical element blank which is finished into an optical element by grinding and polishing, wherein the press-molding glass gob of the above aspect is softened by heating. Press molding. This method is also called a reheat press molding method.

  A second aspect of the method for producing an optical element blank according to one aspect of the present invention is a method for producing an optical element blank that is finished into an optical element by grinding and polishing, wherein the glass material is melted by heating, and the obtained molten glass is obtained. Is pressed to produce the optical element blank of the above-described embodiment. This method is also called a direct press molding method.

In the first aspect, a press mold having a molding surface having a shape approximating a shape obtained by inverting the surface shape of a target optical element is prepared. The press mold is constituted by 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, and pressed with the lower mold and an upper mold opposite to each other to form an optical element blank. At this time, a powdery release agent such as boron nitride may be uniformly applied in advance to the surface of the glass gob for press molding in order to prevent fusion between the glass and the mold during press molding.
Next, the optical element blank is released, removed from the press mold, and annealed. This annealing reduces the strain inside the glass and makes the optical characteristics such as the refractive index have a desired value.
Known conditions may be applied to the heating conditions of the glass gob, the press molding conditions, the materials used for the press mold, and the like. The above steps can be performed in the atmosphere.

In the second embodiment, a press mold is constituted by mold parts including an upper mold, a lower mold, and, if necessary, a body mold. As described above, the molding surface of the press mold is processed into a shape obtained by inverting the surface shape of the optical element blank.
Appropriately apply a powdery release agent such as boron nitride on the lower mold forming surface, and flow the molten glass melted on the lower mold forming surface according to the above-described optical glass manufacturing method, When the amount of molten glass reaches a desired amount, the molten glass stream is cut by a cutting blade called a shear. After obtaining the molten glass lump on the lower die in this way, the lower die is moved together with the molten glass lump to a position where the upper die waits, and the glass is pressed by the upper die and the lower die to form an optical element blank. .
Next, the optical element blank is released, removed from the press mold, and annealed. This annealing reduces the strain inside the glass and makes the optical characteristics such as the refractive index have a desired value.
Known conditions may be applied to the heating conditions of the glass gob, the press molding conditions, the materials used for the press mold, and the like. The above steps can be performed in the atmosphere.

[Optical element and manufacturing method thereof]
Next, an optical element according to one embodiment of the present invention will be described.
An optical element according to one embodiment of the present invention is made of the optical glass of the above-described embodiment. The optical element according to one embodiment of the present invention has various properties that the optical glass of the above embodiment can provide, and thus is effective for making the optical system highly functional and compact. Examples of the optical element of the present invention include various lenses and prisms. Further, examples of the lens include various lenses having a spherical or aspherical lens surface, 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.
Such a lens can correct chromatic aberration by being combined 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 is possible to realize a compact optical system having a wide angle of view by bending the optical path and directing it in a desired direction by incorporating the prism into the imaging optical system.
Note that a film for controlling light transmittance, such as an antireflection film, can be provided on the optical function surface of the optical element according to one embodiment of the present invention.

Next, a method for manufacturing an optical element according to one embodiment of the present invention will be described.
A method of manufacturing an optical element according to one embodiment of the present invention is characterized by processing an optical element blank manufactured by the method of the above-described embodiment. In one embodiment of the present invention, as the optical glass constituting the optical element blank, a glass having excellent workability can be used, and thus a known method can be applied as a 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 modes shown in the examples. The optical glass according to various aspects of the present invention can be obtained by applying the above-described method for adjusting the content of each glass component with reference to the examples described below.

(Example of making optical glass)
First, oxide glass No. 1 having the composition (cation% display) shown in Table 1 was used. 1 to 15 and Table 2 shown in Table 2. Using nitrates, sulfates, hydroxides, oxides, boric acid, and the like as raw materials, and weighing and mixing each raw material powder sufficiently to obtain 16 to 70 as raw materials, these raw materials are made of platinum. The mixture was placed in a crucible or a platinum alloy crucible, heated and melted at 1300 to 1500 ° C., clarified and stirred to obtain a homogeneous molten glass.
The molten glass was poured into a preheated mold and quenched, kept at a temperature near the glass transition temperature for 2 hours, and then gradually cooled to obtain an oxide glass no. 1 to 70 optical glasses were obtained. No. No foreign matter such as platinum inclusion was found in the glasses Nos. 1 to 70.
Oxide glass no. The total amount of the anion components 1 to 70 is O ²⁻ .
In addition, oxide glass No. Nos. 1 to 15 correspond to optical glass I, and oxide glass Nos. 16 to 70 correspond to the optical glass II.

Measurement of Glass Properties The properties of each glass were measured by the following methods. Tables 1 and 2 show the measurement results.
(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 ΔPg, F of partial dispersion ratio from normal line
The partial dispersion ratios Pg, F were calculated from these values by measuring the refractive indices 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 ratio Pg, F (0) on the normal line calculated from the partial dispersion ratio Pg, F and the Abbe number νd.
(3) Glass transition temperature Tg
The measurement was performed using a differential scanning calorimeter (DSC) under the condition of a heating rate of 10 ° C./min.
(4) Liquidus 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 an optical microscope of 100 times, and the liquidus temperature was determined from the presence or absence of crystals.
(5) Specific gravity Measured by Archimedes' method.
(6) λ70, λ5
Using a glass sample having surfaces parallel to each other polished to a thickness of 10.0 ± 0.1 mm, light having an intensity Iin is incident on the polished surface from a perpendicular direction by a spectrophotometer, The intensity Iout of the light transmitted through was measured, and the light transmittance Iout / Iin was calculated. The wavelength at which the light transmittance was 70% was λ70, and the wavelength at which the light transmittance was 5% was λ5.

Glass for measuring the number density of crystals precipitated during glass production is obtained by molding molten glass. When the glass stability decreases, the molten glass is poured into a mold and molded, and the number of crystal grains contained in the obtained glass increases.
Therefore, the glass stability, especially the devitrification resistance when forming a glass melt, can be evaluated by the number of crystals contained in the glass melted and formed under certain conditions. An example of the evaluation method is shown below.
Using nitrates, sulfates, hydroxides, oxides, boric acid, and the like as raw materials, each raw material powder is weighed and mixed well to prepare a prepared raw material. The prepared raw material is put into a 300 ml platinum crucible, The mixture is heated and melted at 2 ° C. for 2 hours to produce 200 g of homogeneous molten glass. During this time, the molten glass is stirred and shaken several times.
After 2 hours, take out the crucible containing the molten glass from the furnace at 1300-1500 ° C., stir and shake for 15-20 seconds, and place the molten glass in a carbon mold (60 mm × 40 mm × 10 mm-15 mm). Pour and put in lehr to remove strain.
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 kg of glass was calculated, and the number density of crystals (pieces / kg) ).
No. evaluated by the above method. The number density of the crystals of each of the glasses 1 to 59 was 0 / kg.

(Comparative example)
For comparison, in Example No. 3 and No. 3 5, the composition of Example No. 5 of Patent Document 2. A reproduction experiment was performed on 16 compositions. Example No. 1 of Patent Document 1 converted to% of cation. 3 and No. 3 Table 2 shows the composition of Example No. 5 of Patent Document 2. The composition of No. 16 is shown in Table 1.
Further, 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 composition having a smaller size, the raw materials were melted and vitrification was attempted. This composition is called composition A. Table 1 shows the composition A.
Further, 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 composition having a smaller size, the raw materials were melted and vitrification was attempted. This composition is referred to as composition B. Table 2 shows the composition B.
Example No. 1 of Patent Document 1 3 and No. 3 5, the composition of Example No. 5 of Patent Document 2. With respect to composition 16 and composition A, the melt became cloudy and did not vitrify.
Although the composition B was vitrified, the number density of crystals precipitated in the glass was measured by the above-mentioned method for measuring the number density of crystals precipitated during the production of glass, and it was 998 / kg.
The number density of crystals determined by the above-described evaluation method is less than 1000 / kg, more preferably less than 500 / kg, still more preferably less than 300 / kg, and still more preferably less than 200. / Kg, even more preferably less than 100 / kg, even more preferably less than 50 / kg, even more preferably less than 20 / kg, even more preferably Is 0 / kg, which can be used as an indicator of a homogeneous optical glass having even better glass stability.

(Production example 1 of glass gob for press molding)
Next, No. A press-molding glass gob made of each of the optical glasses Nos. 1 to 70 was produced as follows.
First, glass raw materials were prepared so as to obtain the above glasses, put into a platinum crucible or a platinum alloy crucible, heated, melted, clarified, and stirred to obtain a homogeneous molten glass. Next, the molten glass was flowed out of the outflow pipe at a constant flow rate, and was cast into a mold disposed horizontally below the outflow pipe to form a glass plate having a certain thickness. The formed glass plate was continuously pulled out from the opening provided on the side surface of the mold in the horizontal direction, transported by a belt conveyor into the annealing furnace, and gradually cooled.
The gradually cooled glass plate was cut or cut to produce glass pieces, and these glass pieces were barrel-polished to form a glass gob for press molding.
In addition, a cylindrical mold is placed below the outflow pipe, molten glass is cast into the mold to form a columnar glass, and is drawn vertically downward at a constant speed from the opening at the bottom of the mold. It is also possible to obtain a glass gob for press molding by cooling, cutting or cutting to form glass pieces and barrel polishing these glass pieces.

(Example 2 of manufacturing a glass gob for press molding)
After the molten glass flows out of the outflow pipe and receives the lower end of the molten glass flowing out of the molding die in the same manner as in Production Example 1 of the press-molding glass gob, the molding die is dropped rapidly, and the molten glass flow is cut by surface tension to form the glass gob. The desired amount of molten glass lump was obtained on the mold. Then, a gas was blown out of the mold to apply upward wind pressure to the glass, and the glass was formed into a glass lump while floating, and was taken out of the mold and annealed. Then, the glass lump was barrel-polished to obtain a glass gob for press molding.

(Production example 1 of optical element blank)
After uniformly applying a release agent composed of boron nitride powder to the entire surface of each press-molding glass gob obtained in Preparation Example 2 of the press-molding glass gob, the above-mentioned gob was softened by heating and pressed to form a concave meniscus lens. Various lenses such as a convex meniscus lens, a biconvex lens, a biconcave lens, a plano-convex lens, and a plano-concave lens, and a prism blank were produced.

(Example 2 of manufacturing optical element blank)
A molten glass was prepared in the same manner as in Preparation Example 1 of press-molding glass gob, and the molten glass was supplied to a lower mold forming surface on which a release agent of boron nitride powder was uniformly applied. When the amount reached, the molten glass stream was cut with a cutting blade.
The molten glass lump thus obtained on the lower mold was pressed with the upper mold and the lower mold, and various lenses such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, and a prism blank were produced. .

(Production Example 1 of Optical Element)
Each blank produced in Production Examples 1 and 2 of the optical element blank was annealed. The annealing reduced the distortion inside the glass and made the optical characteristics such as the refractive index to have a desired value.
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.

(Example 2 of manufacturing optical element)
A glass plate and a columnar glass were produced in the same manner as in Production Example 1 of a press-molding glass gob, and the obtained glass molded body was annealed to reduce internal distortion and to obtain optical properties such as a refractive index having a desired value. I tried to be.
Next, these glass molded bodies were cut, ground and polished to produce various lenses such as concave meniscus lenses, convex meniscus lenses, biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, and prism blanks. The surface of the obtained optical element may be coated with an antireflection film.

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

According to one embodiment, Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential components, and the total of Si ⁴⁺ and B ³⁺ is ^expressed in terms of% cation. 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⁺ in total, containing 22 to 55%, provided that the Ti ⁴⁺ content is 22% or less, and the cation ratio of the content of Si ⁴⁺ to the total content of Si ⁴⁺ and B ³⁺ [ 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 ^When the total content of 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+)] is 0.1 ^{Hereinafter, La 3+, Gd 3+, Y} 3+ and content of the cation ratio of Ba ²⁺ to the total content of ^{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+] of 2 or more, the content of the cation ratio of Ti ⁴⁺ to the content of ^{B 3+ (Ti 4+ / B 3+} ) is 0.85 or more, and the Abbe's number νd is 23 to 35 and the refractive index nd is the following formula (1):
nd ≧ 2.205− (0.0062 × νd) (1)
An optical glass, which is an oxide glass that satisfies the following.

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

From the viewpoint of achieving a high refractive index and a low dispersion while maintaining the glass stability, in the above optical glass, Nb ⁵⁺ and Ta ^{5 with} respect to the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ^6+. 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⁺ at 1 cation% or more. Thereby, 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 liquidus temperature can be suppressed.

According to another embodiment, Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential components, and the sum of Si ⁴⁺ and B ³⁺ is ^{expressed in terms of} % cation. in 5 to 55%, the La ³⁺ 10 to 50% (however, La ^3+, Gd ^3+, 70% or less in total Y ³⁺ and ^{Yb 3+), 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 [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⁺ , total free Nb ^5+, Ta ⁵⁺ and W ⁶⁺ The amount of cation ratio ^{[(Zr 4+ + Ti 4+ +} Nb 5+ + Ta 5+ + W 6+) / Zr 4+] of 2 or more, B ³⁺ content of the cation ratio of Ti ⁴⁺ to the content of (Ti ^{4 +} / B ³⁺ ) is 0.85 or more, the Abbe number νd is in the range of 18 to less than 35, and the refractive index nd is the following formula (2):
nd ≧ 2.540− (0.02 × νd) (2)
An optical glass, which is an oxide glass satisfying the above, is provided.

  The above-mentioned optical glass is also 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 realized while maintaining glass stability.

  According to a further aspect, there is provided a glass gob for press molding, an optical element blank, and an optical element made of the optical glass according to each of the above aspects.

  According to one embodiment of the present invention, it is possible to provide an optical glass that can be supplied stably and has high refractive index and low dispersion having excellent glass stability. Further, a press using the optical glass can be provided. A glass gob for molding, an optical element blank, and an optical element can be provided.

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

  INDUSTRIAL APPLICATION This invention is useful in the manufacturing field of various optical elements, such as an optical element for imaging optical systems and projection optical systems.

Claims (16)

Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ as essential components,
In cation% display,
A total of 20-30% of Si ⁴⁺ and B ³⁺ ,
The La ³⁺ 18 to 35% ^{(however, La 3+, Gd 3+, 5} 0% or less in total ^{Y 3+} and ^{Yb 3+),}
22 to 35% of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ in total;
Including
The content of Y ³⁺ is 15% or less;
The content of Ti ⁴⁺ 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 0.34 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 [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] of the content of Ba ²⁺ to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and 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+] of 2 or more,
The content of the cation ratio of ^{Ti 4+} to the content of ^{B 3+ (Ti 4+ / B 3+} ) is 0.85 or more,
And
An optical glass which is an oxide glass having an Abbe number νd in the range of 23 to 35 and a refractive index nd satisfying the following formula (1).
nd ≧ 2.205− (0.0062 × νd) (1) 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⁺ is [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )]. The optical glass according to claim 1, wherein the number is 41 or less. The optical glass according to claim 1, wherein the optical glass contains Zr ^{4+ in an amount} of 1 cation% or more. 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 7 or less optical glass according to any one of claims 1 to 4,. 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 a 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 a range of 0 to 10 cation%. Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ as essential components,
In cation% display,
15-30.40% in total of Si ⁴⁺ and B ³⁺ ,
La ³⁺ is 15 to 35% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are not more than 60 % in total),
23 to 45% in total of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ (however, Ti ⁴⁺ exceeds 22%);
Including
The content of Y ³⁺ is 15% 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 0.35 or less;
The cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] of the content of Ba ²⁺ to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 0.40 or less;
La ^{3+, Gd 3+, Gd 3+} to the total content of ^{Y 3+} and ^{Yb 3+,} the total content of the cation ratio of ^{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+] of 2 or more,
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⁺ is [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )]. 181 or more,
The content of the cation ratio of ^{Ti 4+} to the content of ^{B 3+ (Ti 4+ / B 3+} ) is 0.85 or more,
And
An optical glass which is an oxide glass having an Abbe number νd in a range of 18 or more and less than 35 and a refractive index nd satisfying the following expression (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⁺ is [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )]. The optical glass according to claim 8, wherein the number is 41 or less. The optical glass according to claim 8, 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 7 or less optical glass according to any one of claims 8 to 10 is. The optical glass according to any one of claims 8 to 11, wherein the total content of Mg2 ⁺ , Ca2 ⁺ , Sr2 ^+, and Ba2 ⁺ is in a range of 0 to 10%. The optical glass according to any one of claims 8 to 12, wherein the content of ^{W6 +} is in a range of 0 to 10 cation%. A glass gob for press molding, comprising the optical glass according to claim 1. An optical element blank made of the optical glass according to claim 1. An optical element comprising the optical glass according to claim 1.