JP2018172275A - Optical glass and application thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical glass having excellent glass stability while being a high refractive index, low dispersion glass.SOLUTION: There is provided an optical glass which is an oxide glass containing, Si, B, La, Ti, Nband Zras essential components and containing, in terms of cation%, 5 to 55% of Siand Bin total, 10 to 50% of La(70% or less of La, Gd, Yand Ybin total) and 22 to 55% of Ti, Nb, Taand Win total) and having a Ticontent of 22% or less, a ratio [Si/(Si+B)] of 0.40 or less, a total content of La, Gd, Y, Yb, Zr, Ti, Nb, Ta, Wand Biof 65% or more, an Abbe number νd in the range of 23 to 35 and a refractive index nd satisfying nd≥2.205-(0.0062×νd).SELECTED DRAWING: None

Description

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

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

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

Regarding the optical characteristics of the optical glass, the Abbe number νd (the Abbe number νd decreases from the left to the right) on the horizontal axis, and the refractive index nd (the refractive index nd increases from the bottom upward) on the vertical axis. When plotting the change in optical characteristics when the glass composition is changed for a conventional optical glass in a graph called the optical characteristic diagram, the plot is within the band-shaped range from the lower left to the upper right of the optical characteristic diagram. Is distributed. If the composition is changed so as to obtain the upper left optical characteristic from the band-shaped range from the lower left to the upper right of the optical characteristic diagram, the glass stability tends to decrease, and the glass tends to be devitrified or not vitrified.
On the other hand, from the viewpoint of application, the high refractive index and 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 of an optical element that is effective for increasing the functionality and compactness of the optical system. Can be.
However, in general, in the 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 as the Abbe number νd decreases. On the other hand, in these conventional high refractive index and 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 vitrify.
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 and low dispersion glass.

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

One embodiment of the present invention provides:
Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential components,
In cation% display,
Si ⁴⁺ and B ³⁺ in total 5 to 55%,
La ³⁺ is 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total),
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ in total 22 to 55%,
Including Ti ⁴⁺ content is 22% or less,
The cation ratio [Si ⁴ / (Si ⁴ + B ³⁺ )] of the Si ⁴⁺ content 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 [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⁺ 0.12 or less,
The cation ratio of Ba ²⁺ content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.40 or less,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio 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 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)

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

  The further aspect of this invention is related with the glass gob for press molding which consists of the optical glass of the above-mentioned aspect.

  The further aspect of this invention is related with the optical element blank which consists of the optical glass of the above-mentioned aspect.

  The further aspect of this invention is related with the optical element which consists of 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 and low dispersion glass. Furthermore, the glass gob for press molding which consists of the said optical glass, an optical element blank, and an optical element can be provided.
According to the optical element and the optical element produced from the press molding glass gob or the optical element blank, for example, a lens, a compact optical system for correcting chromatic aberration is provided by combining with the lens made of high refractive index and high dispersion glass. You can also.

[Optical glass I]
One embodiment of the optical glass of the present invention (hereinafter referred to as “optical glass I”) has Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ as essential components, In terms of cation%, Si ⁴⁺ and B ³⁺ are 5 to 55% in total, La ³⁺ is 10 to 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 22 to 55%, provided that the Ti ⁴⁺ content is 22% or less,
The cation ratio [Si ⁴ / (Si ⁴ + B ³⁺ )] of the Si ⁴⁺ content 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, La ³ The cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] of the content of Y ³⁺ to the total content of ⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 0. 12 or less, 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 Abbe number νd is in the range of 23 to 35, and the refractive index nd is an optical glass that is an oxide glass that satisfies the following formula (1).
nd ≧ 2.205− (0.0062 × νd) (1)
Another embodiment (optical glass II) of the optical glass of the present invention will be described later.
Hereinafter, the optical glass I will be described in more detail.

  Hereinafter, the reasons for limiting the composition range will be described. Unless otherwise specified, the content of each component and the total content are expressed in cation%.

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

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

B ³⁺ is an essential component effective for maintaining the meltability of the glass, lowering the liquidus temperature and lowering 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 is preferably 1% or more from the viewpoint of glass stability. On the other hand, from the viewpoint of maintaining good chemical durability and the like while obtaining a desired refractive index, the B ³⁺ content is preferably 50% or less. Therefore, the B ³⁺ content is preferably in the range of 1 to 50%. A more preferable upper limit of the content of B ³⁺ is 40%, a further preferable upper limit is 35%, a more preferable upper limit is 30%, a still more preferable upper limit is 25%, a still more preferable upper limit is 22%, and a particularly more preferable upper limit is The lower limit of the content of B ³⁺ is 3%, the more preferable lower limit is 3%, the more preferable lower limit is 5%, the still more preferable lower limit is 7%, the still more preferable lower limit is 9%, and the still more preferable lower limit is 11%. is there.

When the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] of the Si ⁴⁺ content to the total content of Si ⁴⁺ and B ³⁺ exceeds 0.40, while maintaining the glass stability, While it becomes difficult to obtain desired optical characteristics, the meltability is lowered, and the glass raw material becomes difficult to melt. Therefore, in the optical glass I, the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is set to 0.40 or less. For the above reasons, the 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 still more preferable upper limit is 0.35, and the more preferable upper limit is 0. .34, an even more preferred upper limit is 0.32. Since the optical glass I contains Si ⁴⁺ and B ³⁺ as essential components, the lower limit of the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is more than zero. The preferred lower limit of the cation ratio [Si ⁴⁺ / (Si ⁴⁺ + B ³⁺ )] is 0.10, and the more preferred lower limit is from the viewpoint of improving glass stability and making the molten glass suitable for molding. 0.14, a more preferred lower limit is 0.17, a more preferred lower limit is 0.20, and a still more preferred lower limit is 0.23.

La ³⁺ is an essential component excellent in the function of reducing the high refractive index and the low dispersion while maintaining the glass stability, and is also a component that improves the chemical durability. If the La ³⁺ content is less than 10%, it is difficult to obtain the above effect. If the La ³⁺ content exceeds 50%, the devitrification resistance is deteriorated and the liquidus temperature is increased. Therefore, the La ³⁺ content is 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%, and the more preferable upper limit is 33%. The preferable lower limit of the La ³⁺ content is 15%, more A preferred lower limit is 18%, a more preferred lower limit is 20%, a more preferred lower limit is 22%, and a still more preferred lower limit is 24%.

Gd ³⁺ , Y ³⁺ and Yb ³⁺ are high-refractive index and low-dispersion components as well as La ^3+, and also work to improve chemical durability. When the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ exceeds 70%, the glass stability is deteriorated and the liquidus temperature is increased. Therefore, the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 70% or less. A preferable upper limit of the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 60%, a more preferable upper limit is 50%, a further preferable upper limit is 45%, a more preferable upper limit is 40%, and even more preferable. The upper limit is 38%. In order to achieve the desired refractive index and Abbe number, the preferred lower limit of the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 11%, more preferred lower limit is 15%, and further preferred lower limit is 20%, a more preferred lower limit is 23%, a still more preferred lower limit is 25%, a still more preferred lower limit is 28%, and a particularly preferred lower limit is 30%.

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

From the viewpoint of lowering the liquidus temperature and improving 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%. The preferable lower limit of the content of Gd ³⁺ is 0.5%, the more preferable lower limit is 1%, the still more preferable lower limit is 2%, and the still more preferable lower limit is 3%. Note that the content of Gd ³⁺ may be 0%.

The preferable upper limit of the content of Y ³⁺ is 15%, the more preferable upper limit is 10%, the further preferable upper limit is 7%, the more preferable upper limit is 5%, the still more preferable upper limit is 3%, and the further preferable upper limit is 2%. is there. The minimum with preferable content of Y < ³⁺ > is 0.1%. Note that the content of Y ³⁺ may be 0%.

The preferable upper limit of the Yb ³⁺ content is 10%, the more preferable upper limit is 8%, the still more preferable upper limit is 6%, the still more preferable upper limit is 4%, and the still more preferable upper limit is 2%. The content of Yb ³⁺ can also be set to 0%. Since Yb ³⁺ has absorption in the infrared region, it is not suitable for use in high-sensitivity optical systems that require photosensitive characteristics in the near-infrared region, such as high-precision video cameras and surveillance cameras. Glass with a reduced content of Yb ³⁺ 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 Is more preferably 0.06 or more, further preferably 0.10 or more, and further 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+ work} to increase the refractive index and improve devitrification resistance, suppress the increase in liquidus temperature, and improve 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 effect, and Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ If the total content exceeds 55%, devitrification resistance deteriorates and the liquidus temperature rises. In addition, the dispersion increases and the coloration of the glass increases. 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 even more preferable. 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 still more preferable lower limit is 25%, and the more preferable lower limit Is 26%, and a more preferred lower limit is 27%.

In the optical glass I, the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is within the above range, the content of Ti ⁴⁺ is 22% or less, and Zr ⁴⁺ is essential. 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 +} ) / Zr ⁴⁺ ], the devitrification resistance can be improved and the rise in the liquidus temperature can be suppressed. When the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is less than 2, devitrification resistance is deteriorated and the liquidus temperature is increased. 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 2 or more. The preferable lower limit of the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 3.0, the more preferable lower limit is 3.5, and the more preferable lower limit is 4.0. A preferred lower limit is 4.5, and a still more preferred lower limit is 5.0. In order to further improve the devitrification resistance, the preferable upper limit of the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 56, and the more preferable upper limit is 50. A more preferred upper limit is 40, a more preferred upper limit is 30, a more preferred upper limit is 20, and a more preferred upper limit is 10.

From the ^standpoint of realizing desired optical characteristics while maintaining glass stability, the preferred lower limit of the Ti ⁴⁺ content is 10%, the more preferred lower limit is 12%, the still more preferred lower limit is 14%, and the more preferred lower limit is 16 %, A 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 further preferred upper limit is 21.7%, and a more preferred upper limit is 21%. .6%, and a more preferred upper limit is 21.5%.

From the ^standpoint of realizing desired optical properties while maintaining glass stability, the preferred lower limit of the Nb ⁵⁺ content is 1%, the more preferred lower limit is 2%, the still more preferred lower limit is 3%, and the still more preferred lower limit is 4%. %, A 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%, 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 and increase the glass stability without increasing the dispersion as compared with Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ . When the content of Ta ⁵⁺ exceeds 10%, the liquidus temperature rises and the devitrification resistance decreases, so the content of Ta ⁵⁺ is preferably 0 to 10%. Considering that Ta ⁵⁺ is an expensive component, the preferable range of the content of Ta ⁵⁺ is 0 to 8%, the more preferable range is 0 to 6%, the further preferable range is 0 to 4%, and the more preferable range. Is 0 to 2%, and a 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. When glass is used for the lens, the driving power consumption during autofocus increases, and the essential component to compared with Nb ⁵⁺ and large amounts require expensive Ta ⁵⁺ is, it is preferable cation ratio ^{[(Nb 5+ + Ta 5+)} / Nb 5+] is 11 or less. The preferable upper limit of the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / Nb ⁵⁺ ] is 9, a more preferable upper limit is 7, a further preferable upper limit is 5, and a more preferable 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 increases the refractive index, lowers the liquidus temperature, and contributes to the improvement of devitrification resistance. In order to suppress the content, the content of W ⁶⁺ is preferably 0 to 10%. The preferable range of the content of W ⁶⁺ is 0 to 8%, the more preferable range is 0 to 6%, the further preferable range is 0 to 4%, the more preferable range is 0 to 2%, and the still more preferable range is 0 to 1. %, And it is even more preferred not to contain W ⁶⁺ .

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

While maintaining the glass stability, the high refractive index and the low dispersion make it possible to reduce 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 ) is maintained from the viewpoint of reducing the refractive index and the partial dispersion ratio while maintaining the glass stability. ⁺ )] Is preferably 0.05 or more. A 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 a more preferable upper limit is 0.39. The upper limit is 0.36, the more preferable upper limit is 0.33, and the still more preferable upper limit is 0.30. The more preferred lower limit of the cation ratio [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )] is 0.10, the more preferred lower limit is 0.15, and the more preferred lower limit is 0.00. 20, An even more preferred lower limit is 0.25.

Among the components for increasing the refractive index, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ have the function of increasing the refractive index while maintaining low dispersion, and Ti ⁴⁺ , Nb ⁵⁺ and Ta ^{5. + And} W ⁶⁺ are high refractive index and high dispersion components. In order to obtain desired optical properties while maintaining good glass stability, Ti ⁴⁺ , Nb ⁵⁺ and Ta ^{5+ with} respect to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ and W ⁶⁺ total content of the cation ratio of ^{[(Ti 4+ + Nb 5+ +} Ta 5+ + W 6+) / (La 3+ + Gd 3+ + Y 3+ + Yb 3+)] it is 0.10 or more Is preferred. The more preferable lower limit of the cation ratio [(Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.30, and a more preferable lower limit is 0.50. A preferable lower limit is 0.60, and a still more preferable lower limit is 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. The more preferable upper limit of the cation ratio [(Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 1.40, and the more preferable upper limit is 1.30. A more preferred upper limit is 1.20, and a still more preferred upper limit is 1.00.

In the optical glass I, the cation ratio (Ti ⁴⁺ / B ³⁺ ) of the Ti ⁴⁺ content to the B ³⁺ content is 0.85 or more in order to increase the refractive index while maintaining the glass stability. 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 tend to precipitate during glass production.
In order to increase 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, still more preferably 0.95 or more, and still more preferably 1 .00 or more. The upper limit of the cation ratio (Ti ⁴⁺ / B ³⁺ ) is naturally determined from the composition range of the optical glass of the above-described embodiment, but may be considered to be about 10, for example.

Zr ⁴⁺ is an essential component in optical glass I. It works to increase the refractive index and improve chemical durability, improve devitrification resistance by coexisting with Ti ^4+, and suppress the rise in liquidus temperature. To work. In order to acquire the said effect, it is preferable to make content of Zr4 ⁺ 1% or more. From the viewpoint of suppressing increase in glass transition temperature, liquidus temperature, and decrease in devitrification resistance, the preferred upper limit of the content of Zr ⁴⁺ is 15%. The preferable upper limit of the content of Zr ⁴⁺ is 10%, the more preferable upper limit is 8%, the more preferable upper limit is 7%, the preferable lower limit of the content of Zr ⁴⁺ is 1%, the more preferable lower limit is 2%, A preferred lower limit is 3%, and a more preferred lower limit is 4%.

Zn ²⁺ lowers the refractive index and the glass stability, but works to improve the meltability and clarity of the glass. La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Zr ⁴⁺ oxides all have extremely high melting points, and these components are essential. In the optical glass I included as a component or an optional component, it is preferable to contain Zn ²⁺ effective for improving the meltability and clarity. Therefore, in order to maintain a high refractive index and maintain a good glass stability, the Zn ²⁺ content is preferably 15% or less, more preferably 12% or less, and more preferably 10% or less. More preferably, it is more preferably 8% or less, still more preferably 6% or less, still more preferably 3% or less. Moreover, it is preferable that the content of Zn ²⁺ is 0.1% or more from the viewpoint of improving the meltability and clarity of the glass, suppressing the increase in melting temperature, and suppressing the increase in glass coloration associated therewith. It is more preferably 5% or more, further preferably 0.8% or more, and further preferably 1.0% or more. In addition, the content of Zn ²⁺ can be 0%.

Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , and W ⁶⁺ are components that increase the refractive index but increase the melting temperature. The total content of these components and the refractive index are decreased. The optical properties such as meltability, clarity, refractive index, etc., with the cation ratio Zn ²⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) as the index for improving Zn ²⁺ Can do. From the viewpoint of improving the meltability 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 0.03 or more, and further preferably 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, and 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, It is particularly preferable to make it 10 or less.

Li ⁺ , Na ⁺ and K ⁺ are optional components that serve to improve the meltability and lower the glass transition temperature. From the viewpoint of suppressing increase in liquidus temperature, glass stability and chemical durability while realizing high refractive index, the total content of Li ⁺ , Na ⁺ and K ⁺ is in the range of 0 to 10%. It is preferable to make it. A more preferable range of the total content of Li ⁺ , Na ⁺ and K ⁺ is 0 to 8%, a further preferable range is 0 to 6%, a more preferable range is 0 to 4%, a still more preferable range is 0 to 2%, An even more preferable range is 0 to 1%, and it is even more preferable that the alkali metal component is not included.

The content of each component of Li ⁺ , Na ⁺ and K ⁺ is preferably 0 to 10%, more preferably 0 to 8%, more preferably 0 to 6%, and still more preferably 0 to 10%. 4%, a more preferable range is 0 to 2%, a still more preferable range is 0 to 1%, and it is still more preferable that the above alkali metal components are not included.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ work to improve the meltability of the glass and lower the glass transition temperature Tg. Moreover, the defoaming effect can also be obtained by introducing it into glass in the form of nitrate or sulfate.
In a glass having a high refractive index and low dispersion, among the alkaline earth metal components, Ba ²⁺ is contained in a large amount with respect to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ . It becomes difficult to further reduce the refractive index while maintaining the glass stability. For example, in forming molten glass, molten glass is usually cast into a mold having a bottom surface and a side wall, and one of the side surfaces is open, and the formed glass is continuously drawn from the open side surface of the mold (referred to as E-bar forming method). ). However, if Ba ²⁺ is ^{incorporated in} a large amount with respect to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ to achieve high refractive index and low dispersion, the glass will be lost in this molding method. It becomes easy to see through. Therefore, using a mold with a through hole, molten glass is cast into the through hole, the contact area with the mold per unit volume of the molten glass is increased, and the glass cooling rate is extremely increased to prevent devitrification. A special molding method must be used. In the molding method using a mold having a through hole, it is difficult to anneal the glass as it is by passing it through a tunnel type continuous annealing furnace called a rare furnace.
By adjusting and optimizing the ratio of the content of Ba ² and the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ , devitrification is prevented even in general E-bar molding methods. However, a homogeneous optical glass can be formed. And since the shape | molded glass can be annealed as it is through a rare furnace, glass can be manufactured under high productivity.
As described above, in order to prevent a decrease in glass stability due to a low refractive index and 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⁺ The cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] of the content 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 glass to devitrify increases, and high-quality optical glass can be obtained by E-bar molding. 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 preferred upper limit is 0.30, the more preferred upper limit is 0.25, and the more preferred upper limit is as described above. 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⁺ )] ^{Within the} above range, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is preferably 0 to 10%. A more preferable range of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 0 to 8%, a further preferable range is 0 to 6%, a more preferable range is 0 to 4%, and even more preferable. The range is 0 to 2%, and an even more preferable range is 0 to 1%, and it is even more preferable that the alkaline earth metal component is not included.

^{Mg 2+, Ca 2+, Sr 2+} , about the content of each component of Ba ^2+, respectively preferred range 0 to 10%, more preferably in the range 0 to 8%, more preferably in the range of 6% A more preferable range is 0 to 4%, a more preferable range is 0 to 2%, a still more preferable range is 0 to 1%, and it is even more preferable that each of the above alkaline earth metal components is not included.

Ge ⁴⁺ is a network-forming oxide, for also serves to increase the refractive index, is a component which can increase the refractive index while maintaining glass stability, remarkably expensive as compared with other components It is a component that is desired to refrain from its content. In the optical glass I, since the composition is determined as described above, even if the content of Ge ⁴⁺ is suppressed to 10% or less, for example, both realization of desired optical characteristics and excellent glass stability are achieved. be able to. Therefore, the Ge ⁴⁺ content is preferably 0 to 10%. A more preferable range of the content of Ge ⁴⁺ 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 an even more preferable range is 0. ~ 1%. It is particularly preferable not to contain Ge ⁴⁺ , that is, a Ge-free glass.

Bi ³⁺ functions to increase the refractive index and the glass stability, but when its amount exceeds 10%, the light transmittance in the visible region decreases. Therefore, the Bi ³⁺ content is preferably 0 to 10%. A more preferable range of the Bi 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 an even more preferable range is 0. It is particularly preferred that it is ˜1% and does not contain Bi ³⁺ .

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 high refractive index components. 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 set to 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⁺ which are network forming components are contained, so that La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ are naturally 95% or less. From the viewpoint of obtaining desired optical properties, the sum of La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ The preferable lower limit of the content is 66%, the more preferable lower limit is 67%, the still more preferable lower limit is 68%, the still more preferable lower limit is 69%, and the still more preferable lower limit is 70%.
From the standpoint of maintaining good glass stability, La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ , Zr ⁴⁺ , Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ The preferable upper limit of the total content is 90%, the more preferable upper limit is 85%, the still more preferable upper limit is 80%, the still more preferable upper limit is 75%, and the still more preferable upper limit is 73%.

Al ³⁺ works to improve glass stability and chemical durability when it is in a small amount, but when the amount exceeds 10%, the liquidus temperature rises and the devitrification resistance tends to deteriorate. . Therefore, the content of Al ³⁺ is preferably 0 to 10%. A more preferable range of the content of Al ³⁺ 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 an even more preferable range is 0. It is particularly preferred that it is ˜1% and does not contain Al ³⁺ .

  In addition, from the viewpoint of providing an optical glass having high refractive index and low dispersibility as optical glass I and having excellent glass stability, the content of any cation component other than the cation component is 0 to 5%. Preferably 0 to 4%, more preferably 0 to 3%, still more preferably 0 to 2.5%, and still more preferably 0 to 2%. Preferably, it is more preferably 0 to 1.5%, still more preferably 0 to 1.0%, and particularly preferably 0 to 0.5%. The content of any cation component other than the cation component may be 0%.

Sb can be added as a refining agent, and even when added in a small amount, it also serves to suppress a decrease in light transmittance due to the inclusion of impurities such as Fe. However, in terms of oxide, it is 1% by mass as Sb ₂ O _3. If it is added beyond the range, the glass will be colored, or its strong oxidizing action will promote the deterioration of the molding surface of the mold. Therefore, the addition amount of Sb 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 refining agent. However, if it is added in excess of 1% by mass in terms of SnO ₂ , the glass is colored or the molding surface deterioration of the mold is promoted by oxidation. Therefore, the addition amount of Sn in terms of SnO ₂ is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass, on an external basis.

  In addition to the above, Ce oxides, sulfates, nitrates, chlorides, and fluorides can be added in small amounts as clarifying agents.

Since the optical glass I can maintain the glass stability while realizing the optical characteristics of high refractive index and low dispersion, it 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, it is preferable to suppress the contents of Lu ³⁺ , Hf ⁴⁺ , Ga ³⁺ , In ³⁺ and Sc ³⁺ to 0 to 1% respectively. It is more preferable to suppress it to 0 to 0.5%. Lu ³⁺ is not introduced, Hf ⁴⁺ is not introduced, Ga ³⁺ is not introduced, In ³⁺ is not introduced, and Sc ³⁺ is introduced. It is particularly preferred that each is not.
In consideration of environmental impact, it is preferable not to introduce As, Pb, U, Th, Te, or Cd.
Furthermore, it is preferable not to introduce a substance that causes coloring such as Cu, Cr, V, Fe, Ni, Co, Nd, and Tb from the viewpoint of taking advantage of the excellent light transmittance of glass.
Therefore, it is preferable that the optical glass I does not substantially contain the above-described Pb or the like. Here, “substantially free” means that it is not actively introduced as a glass component, and it is allowed to be mixed as an impurity unintentionally.

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 high refractive index and low dispersibility 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, even more preferably 25.0, still more preferably 25.5, and even more preferably 26.0.
On the other hand, relaxing the upper limit of the Abbe number νd works advantageously in maintaining and improving the glass stability. From this viewpoint, the upper limit of the Abbe number νd is preferably 32.00, more preferably 31.00 or less, still more preferably 30.00 or less, still more preferably 29.00 or less, and even 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, an optical system 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 the Abbe number νd satisfy the following expression (1). The glass satisfying the formula (1) is a glass having a high refractive index at the same Abbe number νd as compared with a conventional high refractive index and low dispersion glass, that is, a glass in the upper left range of the optical characteristic diagram described above, which is useful. It is a highly glass.
nd ≧ 2.205− (0.0062 × νd) (1)
Since the upper limit of the refractive index nd is naturally determined from the composition range of the optical glass I, it is not particularly limited. From the standpoint of maintaining glass stability, the refractive index nd is preferably 2.20 or less, more preferably 2.15 or less, further preferably 2.10 or less, and 2.09 or less. More preferably.

From the viewpoint of high functionality and compactness of the optical element and the optical system incorporating the optical element, it is preferable that the refractive index nd and the Abbe number νd are within the above ranges and further satisfy the following formula (1-1): More preferably, the following formula (1-2) is satisfied, the following formula (1-3) is more preferably satisfied, the following formula (1-4) is more preferably satisfied, and the following formula (1-5) is satisfied. It is even more preferable to satisfy the above.
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 further increased refractive index is suitable as a material for optical elements suitable for downsizing and high-performance optical systems such as an imaging optical system and a projection optical system. In addition, even when lenses having the same focal length are manufactured, the absolute value of the curvature of the optical function surface of the lens can be reduced (the curve is relaxed), 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 decreases or the coloring increases, that is, the light transmittance in the visible short wavelength region tends to decrease. Therefore, in order to maintain the thermal stability of the glass satisfactorily or suppress the increase in coloring, it is preferable that the refractive index nd and the Abbe number νd satisfy the following formula (1-6). 7) More preferably, the following formula (1-8) is more preferably satisfied, the following (1-9) formula is more preferably satisfied, and the following (1-10) formula is more satisfied. Even 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 characteristic refers to an optical characteristic 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 these optical characteristics, preferable optical characteristics refer to an arbitrary range among the preferable ranges of the refractive index nd and the Abbe number νd.

(Liquid phase temperature)
High refractive index glass has a large amount of high refractive index component (for example, La ³⁺ (La ₂ O ₃ ), Gd ³⁺ (Gd ₂ O ₃ ), Y ³⁺ (Y ₂ O ₃ ), Yb ³⁺ (Yb ₂ O ₃ ), Ti ⁴⁺ (TiO ₂ ), Nb ⁵⁺ (Nb ₂ O ₅ ), Ta ⁵⁺ (Ta ₂ O ₅ ), W ⁶⁺ (WO ₆ ), Zr ⁴⁺ (ZrO ₂ )) Although contained, all of these components have an extremely high melting point. And if the total amount of the high refractive index component is large, the total amount of components that have a function of lowering the melting temperature, such as alkali metal components and alkaline earth metal components, is relatively reduced, and the meltability and devitrification resistance are reduced. Therefore, in order to obtain a homogeneous glass, the melting temperature must be increased.
As the melting temperature rises, the erodibility of the glass melt increases, and the melting vessel is eroded, and the materials that make up the vessel, such as platinum and platinum alloys, melt into the glass melt and color the glass, or become platinum foreign matter. To do. In addition, when the melting temperature is high, easily volatile components such as B ³⁺ volatilize, the glass composition changes with time, and the optical characteristics fluctuate.
In order to solve such a problem, an increase in 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 generally in conjunction with the rise and fall of the liquidus temperature. Therefore, if the rise of the liquidus temperature can be suppressed, the rise of the melting temperature can also be suppressed.
In addition, if the rise in liquidus temperature can be suppressed, it is effective for preventing devitrification during glass molding, and the viscosity of the 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 in the refractive index and the increase and decrease in the liquid phase temperature are linked to the increase and decrease in the amount of the high refractive index component. It is reasonable to use this index. In the optical glass I, when the liquidus temperature is LT [° C.], the above index is defined as LT / (nd−1) for a glass having a refractive index nd. The denominator is a value obtained by subtracting the refractive index 1 of the vacuum from the refractive index of the glass, and reflects the net refractive index increase / decrease amount. As LT / (nd-1) is lower, it means that the high refractive index glass is a glass having excellent meltability and devitrification resistance.
In a preferred embodiment of the optical glass I, the amount of each component is determined in a well-balanced manner so as to suppress the increase in the liquidus temperature while maintaining the required optical characteristics, and therefore the following formula (3) can be satisfied.
LT / (nd-1) ≦ 1250 ° C. (3)

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

On the other hand, when LT / (nd-1) is lowered, it tends to be difficult to maintain the required optical characteristics. Therefore, it is preferable not to reduce LT / (nd-1) excessively. From such a viewpoint, optical glass satisfying the following formula (3-7) is preferable, optical glass satisfying the following formula (3-8) is more preferable, optical glass satisfying the following formula (3-9) is more preferable, Optical glass satisfying the following formula (3-10) is more preferable, optical glass satisfying the following formula (3-11) is more preferable, and 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 and F are expressed as (ng−nF) / (nF−nc) using the refractive indexes ng, nF and nc in the g-line, F-line and c-line.
In order to provide an optical glass suitable for high-order chromatic aberration correction, the optical glass I is preferably such that the partial dispersion ratios Pg, F and the Abbe number νd satisfy the relationship of the following equation (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 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)

In the partial dispersion ratio Pg, F-Abbe number νd diagram, when the partial dispersion ratio on the normal line serving as a reference for normal partial dispersion glass is expressed as Pg, F (0), Pg, F (0) is the Abbe number. It is expressed by the following formula using νd.
Pg, F (0) = 0.6483- (0.0018 × νd)
ΔPg, F is a deviation of the partial dispersion ratio Pg, F from the normal line, and is expressed by the following equation.
ΔPg, F = Pg, F−Pg, F (0)
= Pg, F + (0.0018 × νd) −0.6483
A preferred embodiment of the optical glass of the above embodiment has a deviation ΔPg, F of 0.030 or less, and is suitable as an optical element material for correcting higher-order chromatic aberration. A more preferable range of ΔPg, F is 0.025 or less, a further preferable range is 0.020 or less, a more preferable range is 0.015 or less, and a still more preferable 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)
The optical glass of the above-described embodiment is a high refractive index glass, but generally the specific gravity tends to increase as the refractive index of the glass increases. 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 aspect can have a specific gravity of 5.60 or less even though it is a high refractive index glass by having the above glass composition. The upper limit of specific gravity is preferably 5.50, more preferably 5.40, and even more preferably 5.30. However, if the specific gravity is excessively reduced, the stability of the glass is lowered and the liquidus temperature tends to increase. Therefore, the specific gravity is preferably 4.50 or more. The more preferred lower limit of the specific gravity is 4.70, the still more preferred lower limit is 4.90, the still more preferred lower limit is 5.00, and the 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 in the visible range. In a preferred embodiment of the optical glass I, λ70 exhibits a coloring degree of 680 nm or less. A more preferable range of λ70 is 660 nm or less, a further preferable range is 650 nm or less, a more preferable range is 600 nm or less, an even more preferable range is 560 nm or less, and an even more preferable range is 530 nm or less. The lower limit of λ70 is not particularly limited, but 380 nm may be considered as a guideline for the lower limit of λ70.
Here, λ70 is a wavelength at which the light transmittance is 70% in the wavelength range of 280 to 700 nm. Here, the light transmittance means that a glass sample having parallel surfaces polished to a thickness of 10.0 ± 0.1 mm is used, and light is incident on the polished surface from a vertical direction. The obtained spectral transmittance, that is, Iout / Iin where Iin is the intensity of light incident on the sample and Iout is the intensity of light transmitted through the sample. The spectral transmittance includes light reflection loss on the sample surface. Moreover, the said grinding | polishing means that the surface roughness is smooth | blunted in the state small enough with respect to the wavelength of a measurement wavelength range. In the optical glass I, it is preferable that the light transmittance exceeds 70% in the visible range longer than λ70.

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

  As described above, the spectral transmittance is measured in the wavelength range of 280 to 700 nm. Usually, the light transmittance increases as the wavelength is increased from λ5, and when reaching λ70, the wavelength transmittance reaches 70 nm or more. Keep the high transmittance.

(Glass-transition temperature)
The optical glass I is a glass suitable for forming a smooth optical functional surface by polishing. The suitability of cold working such as polishing, that is, cold workability is indirectly related to the glass transition temperature. A glass with a low glass transition temperature is more suitable for precision press molding than cold workability, whereas a glass with a high glass transition temperature is more suitable for cold work than precision press molding. Excellent. Accordingly, it is preferable not to excessively lower the glass transition temperature in the optical glass I, preferably 650 ° C. or higher, more preferably 680 ° C. or higher, further preferably 700 ° C. or higher, and 710 ° C. More preferably, it is more preferably 730 ° C. or higher, and still 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 will increase, and the mold used for molding will deteriorate significantly, the annealing temperature will also become high, and the annealing furnace will Deterioration and wear are also significant. Therefore, the glass transition temperature is preferably 850 ° C. or less, more preferably 800 ° C. or less, further preferably 780 ° C. or less, and further preferably 760 ° C. or less.

[Optical glass II]
Next, optical glass II which is an optical glass of 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,
Si ⁴⁺ and B ³⁺ in total 5 to 55%,
La ³⁺ is 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total),
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ in total 23 to 70% (however, Ti ⁴⁺ is more than 22%),
Including
The cation ratio of the content of Y ³⁺ to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.14 or less,
The cation ratio of Ba ²⁺ content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.40 or less,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio 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 or more and less than 35 and a refractive index nd satisfying the following formula (2).
nd ≧ 2.540− (0.02 × νd) (2)

Like the optical glass I, the optical glass II is a glass having high refractive index and low dispersion characteristics while maintaining glass stability, but has a higher Ti ⁴⁺ content than the optical glass I. In the optical glass I, the content of Ti ⁴⁺ is set to 22% or less, the spectral transmittance in the visible region is increased, and the partial dispersion ratio is kept low so that it is advantageous for higher-order chromatic aberration correction. In addition, the lower limit of the refractive index is higher than the lower limit of the refractive index of the optical glass I in the range where the Abbe number νd is approximately 24.28 or more.
On the other hand, the optical glass II has a high refractive index and low dispersion characteristic in a range where the Ti ⁴⁺ content exceeds 22% and the Abbe number ν is wider than that of the optical glass I.
In the following, the composition and characteristics of the optical glass II will be described as different 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+ work} to increase the refractive index and improve devitrification resistance, suppress the increase in liquidus temperature, and improve 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 effect, and Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ When the total content exceeds 70%, the devitrification resistance deteriorates and the liquidus temperature rises. In addition, the dispersion increases and the coloration of the glass increases. Therefore, the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ is 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 further preferable upper limit is 50%, a more preferable upper limit is 45%, and even more preferable. 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 Is 27%, and a 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 set within the above range, and the Ti ⁴⁺ content is increased to more than 22%, thereby preventing devitrification. Can improve sex. It is also effective in suppressing the liquidus temperature rise.
The preferable lower limit of the Ti ⁴⁺ content is 22.5%, the more preferable lower limit is 23%, and the more preferable lower limit is 24%. The preferable upper limit of the Ti ⁴⁺ content is 60%, and the more preferable upper limit is 50%. Further, the upper limit is more preferably 45%, the still more preferable upper limit is 40%, the still more preferable upper limit is 35%, and the still more preferable 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⁺ In order to achieve high refractive index and low dispersion while maintaining glass stability, it is set to 0.14 or less. For the above reasons, the preferred upper limit of the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.13, the more preferred upper limit is 0.12, and the more preferred upper limit is 0.11. is there. Of La, Gd, Y and Yb, the element having the smallest atomic weight is Y. Therefore, from the viewpoint of reducing the specific gravity of the glass, the preferable lower limit of the cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.01, and the more preferable lower limit is 0.02. The preferred lower limit is 0.03, the more preferred lower limit is 0.04, and the still more preferred lower limit is 0.05. The optical glass II is suitable as a material for a camera lens equipped with an autofocus function, but the power consumption during autofocus can be reduced by reducing the specific gravity of the glass.
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 0.14 or less, while Gd ³⁺ , Y ³⁺ and Yb ³ The cation ratio [Y ³⁺ / (Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] of the Y ³⁺ content to the total ⁺ content is preferably more than 0.60. For the above reasons, the more preferred lower limit of the cation ratio [Y ³⁺ / (Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.61, the more preferred lower limit is 0.62, and the more preferred lower limit is 0.63. A preferred lower limit is 0.64.
From the viewpoint of achieving high refractive index and low dispersion while maintaining good glass stability, the total content of Gd ³⁺ , Y ³⁺ and Yb ³⁺ is preferably 1.0% or more. Gd ³⁺ , Y ³⁺ , and Yb ³⁺ all work together with La ³⁺ to lower the liquidus temperature and greatly improve devitrification resistance. In order to obtain this function satisfactorily, the total content of Gd ³⁺ , Y ³⁺ and Yb ³⁺ is more preferably 1.5% or more, further preferably 2.0% or more, It is more preferably 2.5% or more, further preferably 3.0% or more, and even more preferably 3.5% or more. A preferable upper limit of the total content of Gd ³⁺ , Y ³⁺ and Yb ³⁺ is 35%, a more preferable upper limit is 30%, a further preferable upper limit is 25%, a more preferable upper limit is 20%, and a still more preferable upper limit is 15%. A still more preferable upper limit is 10%, and a still more preferable upper limit is 7%.

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

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

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

From the viewpoint of ^achieving high refractive index and low dispersion 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 preferred lower limit of the cation ratio [((Si ⁴⁺ + B ³⁺ )) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.10, the more preferred lower limit is 0.20, and the more preferred lower limit Is 0.30, a 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, and a more preferred upper limit is 1.0, even more preferred. The upper limit is 0.95, the more preferable upper limit is 0.90, the still more preferable upper limit is 0.85, and the still more preferable lower limit is 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 of [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W6 +) / Zr ⁴⁺ ] is 2 or more. For the above reasons, the preferred lower limit of the cation ratio [(Zr ⁴⁺ + Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ ) / Zr ⁴⁺ ] is 3, more preferred lower limit is 3.5, and further preferred lower limit is 4, one layer. 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 still more preferred upper limit is 40, the still more preferred upper limit is 30, the still more preferred upper limit is 20, and the still more preferred upper limit. Is 10.

Compared to optical glass I having a Ti ⁴⁺ content of 22% or less and an Abbe number νd in the range of 23 to 35, optical glass II contains more than 22% Ti ⁴⁺ and the lower limit of the Abbe number νd is 18. Even in a range where the Abbe number νd is small, excellent glass stability and high refractive index characteristics are exhibited.
In the optical glass II, when the Abbe number νd exceeds 35, it becomes difficult to maintain the glass stability well. 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)
In order to provide an optical element material suitable for chromatic aberration correction, the preferable lower limit of the Abbe number νd is 19, a more preferable lower limit is 20, a further preferable lower limit is 21, a still more preferable lower limit is 22, and a still more preferable lower limit is 23. On the other hand, in order to maintain the glass stability well, the preferable upper limit of the Abbe number νd is 32, the more preferable upper limit is 30, the still more preferable upper limit is 29, the still more preferable upper limit is 28, and the 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, a refractive index nd and an Abbe number νd have the following (2) in order to provide a glass material suitable for making the optical system compact and highly functional. ) Is satisfied. The glass satisfying the formula (2) is also a glass having a high refractive index at the same Abbe number νd as compared with the conventional high refractive index and low dispersion glass, that is, the glass in the upper left range of the optical characteristic diagram described above, and is useful. It is a highly glass.
nd ≧ 2.540− (0.02 × νd) (2)
Furthermore, for the above reasons, the refractive index nd and Abbe number νd preferably satisfy the following formula (2-1), more preferably the following formula (2-2), and the following formula (2-3) It is more preferable to satisfy | fill, and it is still more preferable to satisfy | fill following (2-4) Formula.
nd ≧ 2.543− (0.02 × νd) (2-1)
nd ≧ 2.546− (0.02 × νd) (2-2)
nd ≧ 2.549− (0.02 × νd) (2-3)
nd ≧ 2.550− (0.02 × νd) (2-4)
The upper limit of the refractive index nd is not particularly limited because it is naturally determined from the composition range of the optical glass II. From the standpoint of maintaining glass stability, the refractive index nd is preferably 2.40 or less, more preferably 2.30 or less, preferably 2.20 or less, and 2.15 or less. More preferably, it is more preferably 2.10 or less, and even more preferably 2.09 or less.

(Partial dispersion characteristics)
The preferable upper and lower limits of the partial dispersion ratios Pg and F in the optical glass II and the preferable upper limit of ΔPg and F are the same as those of the optical glass I. On the other hand, the preferable lower limit of ΔPg, F in the optical glass II is −0.001, the more preferable lower limit is 0.000, the still more preferable lower limit is 0.003, and the still 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. However, if the specific gravity is excessively reduced, the stability of the glass is lowered and the liquidus temperature tends to increase. Therefore, the specific gravity is preferably 4.50 or more. The more preferred lower limit of the specific gravity is 4.60, the still more preferred lower limit is 4.70, the still more preferred lower limit is 4.80, and the still more preferred lower limit is 4.90.

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

(Glass-transition temperature)
The glass transition temperature of the optical glass II also has a preferable lower limit and a preferable upper limit for the same reason as the glass transition temperature of the optical glass I. The preferable lower limit of the glass transition temperature of the optical glass II is 650 ° C., the more preferable lower limit is 670 ° C., the further preferable lower limit is 680 ° C., the more preferable lower limit is 690 ° C., the still more preferable lower limit is 700 ° C., and the still more preferable lower limit is 710 ° C. An even more preferred lower limit is 720 ° C. On the other hand, a preferable upper limit of the glass transition temperature is 850 ° C., a more preferable upper limit is 800 ° C., a further preferable upper limit is 780 ° C., a more preferable upper limit is 760 ° C., a still more preferable upper limit is 750 ° C., and a still more preferable upper limit is 740 ° C. .
Other compositions and characteristics of the optical glass II are the same as those of the optical glass I.

[Optical glass manufacturing method]
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 comprising melting a glass raw material by heating, and molding the obtained molten glass. Preparation is performed so as to obtain glass, 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 cullet raw material is weighed and prepared according to the target glass composition, supplied into a platinum or platinum alloy melting vessel, and then melted by heating. After the raw material is sufficiently melted and vitrified, the temperature of the molten glass is raised to clarify. The clarified molten glass is homogenized by stirring with a stirrer, and continuously supplied to and discharged from a glass outlet pipe, rapidly cooled and solidified to obtain a glass molded body.
In addition, it is desirable that the melting temperature of the optical glass be in the range of 1200 to 1500 ° C. from the viewpoint of obtaining a glass that is homogeneous, low-colored, and stable in various properties including optical properties.

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

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

  In the second production example, molten glass is cast into a cylindrical mold instead of the above mold to form a columnar glass molded body. The glass molded body molded in the mold is drawn vertically downward from the opening at the bottom of the mold at a constant speed. The drawing speed may be set so that the molten glass liquid level in the mold becomes constant. After slowly cooling the glass molded body, it is cut or cleaved, 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 molding dies are arranged at equal intervals on the circumference of a circular turntable is installed below the outflow pipe, the turntable is index-rotated, and the molding die is stopped. One of the positions is the position where the molten glass is supplied to the mold (referred to as the cast position), the molten glass is supplied, the supplied molten glass is formed into a glass molded body, and then the predetermined mold different from the cast position is retained. The glass molded body is taken out from the position (takeout position). The stop position as the take-out position may be determined in consideration of the rotation speed of the turntable, the cooling speed of the glass, and the like. The molten glass is supplied to the mold at the casting position by dropping molten glass from the glass outlet of the outflow pipe and receiving the glass droplets at the above-mentioned mold, and by bringing the molding mold retained at the casting position closer to the glass outlet. Supports the lower end of the flowing molten glass flow, creates a constriction in the middle of the glass flow, and rapidly drops the mold in the vertical direction at a predetermined timing to separate the molten glass below the constriction and receive it on the mold It can be performed by a method, a method in which the flowing molten glass flow is cut with a cutting blade, and the separated molten glass lump is received by a mold that is retained at the casting position.
A known method may be used to form the glass on the mold. Above all, when gas is blown upward from the mold and an upward wind pressure is applied to the glass lump to form the glass while it floats, the surface of the glass mold is wrinkled, or the glass mold can be contacted with the mold by contact with the mold. It can prevent that a crack generate | occur | produces.

  The shape of the glass molded body is spherical, spheroid, and has one rotation target axis depending on the selection of the mold shape and the gas ejection method, and two surfaces facing the axis direction of the rotation target axis. Can be formed into a shape that is convex outward. These shapes are suitable for a glass gob for press molding 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 form a glass gob for press molding.

[Optical element blank and its manufacturing method]
Next, an optical element blank according to one embodiment of the present invention and a manufacturing method thereof will be described.
The optical element blank according to one aspect of the present invention is made of the optical glass according to the above aspect. The optical element blank according to one aspect of the present invention is suitable as a glass base material for producing an optical element having various properties provided by the optical glass of the above aspect.
The optical element blank is a glass molded body having a shape approximate to the shape of the optical element obtained by adding a processing margin to be removed by grinding and polishing to the shape of the target optical element.

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

  A second 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 that is finished into an optical element by grinding and polishing, and melts a glass raw material by heating to obtain a molten glass. The optical element blank of the above-mentioned aspect is produced by press-molding. 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 the target optical element is prepared. The press mold is composed of mold parts including an upper mold, a lower mold, and, if necessary, a barrel mold.
Next, the glass gob for press molding is softened by heating and then introduced into a preheated lower mold, pressed with the upper mold facing the lower mold, and molded into an optical element blank. At this time, in order to prevent fusion between the glass and the mold during the press molding, a powder release agent such as boron nitride may be uniformly applied to the surface of the glass gob for press molding in advance.
Next, the optical element blank is released, removed from the press mold, and annealed. By this annealing treatment, the distortion inside the glass is reduced so that the optical characteristics such as the refractive index become a desired value.
The glass gob heating conditions, press molding conditions, materials used for the press mold, and the like may be applied. The above steps can be performed in the atmosphere.

In the second embodiment, the press mold is composed of mold parts including an upper mold, a lower mold, and, if necessary, a barrel 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.
A powder mold release agent such as boron nitride is uniformly applied onto the lower mold surface as appropriate, and the molten glass melted according to the optical glass manufacturing method described above flows out onto the lower mold surface, When the amount of molten glass reaches a desired amount, the molten glass flow is cut with a cutting blade called shear. After obtaining a molten glass lump on the lower mold in this manner, the lower mold is moved together with the molten glass lump to a position where the upper mold waits upward, and the glass is pressed with the upper mold and the lower mold to form an optical element blank. .
Next, the optical element blank is released, removed from the press mold, and annealed. By this annealing treatment, the distortion inside the glass is reduced so that the optical characteristics such as the refractive index become a desired value.
The glass gob heating conditions, press molding conditions, materials used for the press mold, and the like may be applied. 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 aspect of the present invention is made of the optical glass according to the above aspect. The optical element according to one embodiment of the present invention has various properties that can be provided by the optical glass of the above-described embodiment, and thus is effective for enhancing the functionality and compactness of the optical system. Examples of the optical element of the present invention include various lenses and prisms. Further, examples of the lens include various lenses such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a planoconvex lens, and a planoconcave lens, whose lens surface is spherical or aspherical.
Such a lens can correct chromatic aberration when 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.
In addition, since the prism has a high refractive index, it is possible to realize a compact and wide-angle optical system by bending the optical path in a desired direction by incorporating the prism in the imaging optical system.
Note that a film for controlling light transmittance, such as an antireflection film, may be provided on the optical functional 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.
An optical element manufacturing method according to an aspect of the present invention is characterized by processing an optical element blank manufactured by the method according to the above aspect. In one embodiment of the present invention, since an optical glass that constitutes an optical element blank can be used because it has excellent workability, a known method can be applied as a processing method.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited to the aspect shown in an Example at all. With reference to the examples described below, 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.

(Example of optical glass production)
First, oxide glass No. 1 having the composition shown in Table 1 (expressed as cation%). 1-15 and oxide glass No. 1 shown in Table 2. Use nitrate, sulfate, hydroxide, oxide, boric acid, etc. as raw materials so that 16-70 can be obtained, weigh each raw material powder, mix well, and use this as a mixed raw material. It put into the crucible or the crucible made from a platinum alloy, and it heated and melted at 1300-1500 degreeC, and it clarified and stirred and homogenized molten glass.
The molten glass was poured into a preheated mold and rapidly cooled, held at a temperature in the vicinity of the glass transition temperature for 2 hours, and then slowly cooled to obtain oxide glass no. 1 to 70 optical glasses were obtained. No. No contamination of foreign matters such as platinum inclusions was observed in the glasses 1 to 70.
Oxide glass no. The total amount of anionic components 1 to 70 is O ²⁻ .
In addition, oxide glass No. 1 to 15 correspond to optical glass I. 16 to 70 correspond to the optical glass II.

Measurement of glass characteristics The characteristics of each glass were measured by the following methods. The measurement results are shown in Tables 1 and 2.
(1) Refractive index nd and Abbe number νd
It measured about the optical glass cooled with the temperature-fall rate of 30 degreeC per hour.
(2) Partial dispersion ratio Pg, F, and partial dispersion ratio difference ΔPg, F from the normal line
The partial dispersion ratios Pg and F were calculated from these values obtained by measuring the refractive indexes ng, nF and nc of the optical glass cooled at a temperature drop 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
Using a differential scanning calorimeter (DSC), the measurement was performed under conditions 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 a 100-fold optical microscope, and the liquidus temperature was determined from the presence or absence of crystals.
(5) Specific gravity It measured by Archimedes method.
(6) λ70, λ5
A glass sample having parallel surfaces polished to a thickness of 10.0 ± 0.1 mm is used, and a spectrophotometer is used to inject light having an intensity Iin from a direction perpendicular to the polished surface. The light transmittance Iout / Iin was calculated by measuring the intensity Iout of the light transmitted through the light. The wavelength at which the light transmittance was 70% was λ70, and the wavelength at which the light transmittance was 5% was λ5.

The glass for measuring the number density of crystals precipitated during glass production is obtained by molding molten glass. When the glass stability is lowered, the molten glass is poured into a mold and molded, and the number of crystal grains contained in the obtained glass increases.
Therefore, the glass stability, particularly the devitrification resistance when molding a glass melt, can be evaluated by the number of crystals contained in the glass melted and molded under certain conditions. An example of the evaluation method is shown below.
Nitrate, sulfate, hydroxide, oxide, boric acid or the like is used as a raw material, and each raw material powder is weighed and mixed well to prepare a mixed raw material. Heat and melt at 200C 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. Pour and place in a slow cooling furnace 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 1 kg of glass was calculated, and the number density of crystals (pieces / kg) ).
No. evaluated by the above method. The number density of crystals in each glass of 1 to 59 was 0 pieces / kg.

(Comparative example)
For comparison, Example No. 1 of Patent Document 1 is used. 3 and no. No. 5, composition No. 5 of Patent Document 2 Reproduction experiments were conducted on 16 compositions. In Example No. 1 of Patent Document 1 converted to cation% display. 3 and no. Table 2 shows the composition of No. 5 in Example No. The composition of 13 is shown in Table 1.
Furthermore, except for the cation ratio Ti ⁴⁺ / B ^3+, meet the requirements of the optical glass I, from the cation ratio Ti ⁴⁺ / B ³⁺ cations ratio Ti ⁴⁺ / B ³⁺ is 0.804 and the optical glass I For the smaller composition, the raw material was melted to attempt vitrification. This composition is referred to as composition A. Composition A is shown in Table 1.
Furthermore, except for the cation ratio Ti ⁴⁺ / B ^3+, meet the requirements of the optical glass II, from the cation ratio Ti ⁴⁺ / B ³⁺ cations ratio Ti ⁴⁺ / B ³⁺ is 0.803 and the optical glass II For the smaller composition, the raw material was melted to attempt vitrification. This composition is referred to as composition B. The composition B is shown in Table 2.
Example No. 1 of Patent Document 1 3 and no. No. 5, composition No. 5 of Patent Document 2 For 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 method for measuring the number density of crystals precipitated during the glass production, and found to be 998 / kg.
The number density of crystals determined by the above evaluation method is less than 1000 / kg, more preferably less than 500 / kg, still more preferably less than 300 / kg, and even more preferably 200. Less than 100 / 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. 0 / kg can be used as an indicator of a homogeneous optical glass having much more excellent glass stability.

(Production Example 1 of Glass Gob for Press Molding)
Next, no. The glass gob for press molding which consists of 1-70 each optical glass was produced as follows.
First, glass raw materials were prepared so as to obtain the above-described 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 flown out from the outflow pipe at a constant flow rate and cast into a mold placed horizontally below the outflow pipe to form a glass plate having a constant thickness. The formed glass plate was continuously pulled out from the opening provided on the side surface of the mold in the horizontal direction, conveyed to the annealing furnace by a belt conveyor, and gradually cooled.
The slowly cooled glass plate was cut or cleaved to produce glass pieces, and these glass pieces were barrel-polished into glass gob for press molding.
A cylindrical mold is disposed below the outflow pipe, molten glass is cast into the mold to form a cylindrical glass, and is drawn vertically downward from the opening at the bottom of the mold at a constant speed. Glass pieces can be obtained by cooling, cutting or cleaving to make glass pieces, and barrel-polishing these glass pieces.

(Example 2 of production of glass gob for press molding)
In the same manner as in Production Example 1 of the glass gob for press molding, after the molten glass flows out from the outflow pipe and receives the lower end of the molten glass flowing out from the mold, the mold is rapidly lowered, and the molten glass flow is cut by the surface tension and molded. A desired amount of molten glass block was obtained on the mold. Then, gas was blown out from the mold, an upward wind pressure was applied to the glass, and the glass was molded into a glass lump while being lifted, taken out from the mold and annealed. The glass lump was then barrel-polished to form a glass gob for press molding.

(Example 1 of optical element blank production)
After uniformly applying a release agent composed of boron nitride powder to the entire surface of each press-molding glass gob obtained in Production Example 2 of press-molding glass gob, the gob is softened by heating and press-molded to form a concave meniscus lens Various lenses such as a convex meniscus lens, a biconvex lens, a biconcave lens, a planoconvex lens, and a planoconcave lens, and a prism blank were prepared.

(Example 2 of optical element blank production)
A glass melt is produced in the same manner as in Example 1 of the glass gob for press molding, and the molten glass is supplied to a lower mold forming surface uniformly coated with a release agent of boron nitride powder, and the amount of molten glass on the lower mold is desired. When the amount was reached, the molten glass flow was cut with a cutting blade.
The molten glass block thus obtained on the lower mold was pressed with the upper mold and the lower mold, and a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, etc., and a prism blank were produced. .

(Optical element production example 1)
Each blank produced in optical element blank production examples 1 and 2 was annealed. The annealing reduced the internal distortion of the glass, and the optical characteristics such as the refractive index were set to desired values.
Next, each blank was ground and polished to produce various lenses and prisms such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a planoconvex lens, and a planoconcave lens. The surface of the obtained optical element may be coated with an antireflection film.

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

  Finally, the above-described aspects are summarized.

According to one aspect, Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential components, and Si ⁴⁺ and B ³⁺ are ^expressed in total in terms of cation%. 5 to 55%, La ³⁺ to 10 to 50% (provided that La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are not more than 70% in total), Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ And W ⁶⁺ in a total of 22 to 55%, provided that the Ti ⁴⁺ content is 22% or less, and the cation ratio of the Si ⁴⁺ content 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 The total content of ⁶⁺ and Bi ³⁺ is 65% or more, and 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⁺ ] is 2 or more, the cation ratio of the Ti ⁴⁺ content to the B ³⁺ content (Ti ⁴⁺ / B ³⁺ ) is 0.85 or more, and the Abbe number νd is 23 to And the refractive index nd is in the following formula (1):
nd ≧ 2.205− (0.0062 × νd) (1)
An optical glass that is an oxide glass satisfying the above requirements is provided.

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

From the viewpoint of achieving high refractive index and low dispersion while maintaining 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 optical glass preferably contains 1 cation% or more of Zr ⁴⁺ . Thereby, a refractive index can be raised, chemical durability can be improved, devitrification resistance can be improved by coexistence with Ti ^4+, and an increase 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%. 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 a total of 23 to 70% (however, Ti ⁴⁺ is more than 22%), and Y ³⁺ with respect to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ The cation ratio [Y ³⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] of the content 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 18 or more and less than 35, and the refractive index nd is the following formula (2):
nd ≧ 2.540− (0.02 × νd) (2)
An optical glass that is an oxide glass satisfying the above is provided.

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

  According to the further aspect, the glass gob for press molding which consists of the optical glass concerning each above-mentioned aspect, an optical element blank, and an optical element are provided.

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

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
For example, the optical glass according to one embodiment of the present invention can be manufactured by performing the composition adjustment described in the specification on the glass composition exemplified above.
Of course, it is possible to arbitrarily combine two or more of the matters described as examples or preferred ranges in the specification.

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

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

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ work to improve the meltability of the glass and lower the glass transition temperature Tg. Moreover, the defoaming effect can also be obtained by introducing it into glass in the form of nitrate or sulfate.
In a glass having a high refractive index and low dispersion, among the alkaline earth metal components, Ba ²⁺ is contained in a large amount with respect to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ . It becomes difficult to further reduce the refractive index while maintaining the glass stability. For example, in forming molten glass, molten glass is usually cast into a mold having a bottom surface and a side wall, and one of the side surfaces is open, and the formed glass is continuously drawn from the open side surface of the mold (referred to as E-bar forming method). ). However, if Ba ²⁺ is ^{incorporated in} a large amount with respect to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ to achieve high refractive index and low dispersion, the glass will be lost in this molding method. It becomes easy to see through. Therefore, using a mold with a through hole, molten glass is cast into the through hole, the contact area with the mold per unit volume of the molten glass is increased, and the glass cooling rate is extremely increased to prevent devitrification. A special molding method must be used. In the molding method using a mold having a through hole, it is difficult to anneal the glass as it is by passing it through a tunnel type continuous annealing furnace called a rare furnace.
By adjusting and optimizing the ratio of the Ba ²⁺ content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ , devitrification can be achieved even in general E-bar molding methods. It is possible to form a homogeneous optical glass while preventing it. And since the shape | molded glass can be annealed as it is through a rare furnace, glass can be manufactured under high productivity.
Thus, in order to prevent the glass stability from being lowered due to the low refractive index and 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+. The cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.40 or less. When the cation ratio [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] exceeds 0.40, the tendency of glass to devitrify increases, and high-quality optical glass can be obtained by E-bar molding. 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 preferred upper limit is 0.30, the more preferred upper limit is 0.25, and the more preferred upper limit is as described above. 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.

Ge ⁴⁺ is a network-forming component , and also functions to increase the refractive index. Therefore, Ge ⁴⁺ is a component that can increase the refractive index while maintaining glass stability, but it is much more expensive than other components. It is a component that is desired to refrain from its content. In the optical glass I, since the composition is determined as described above, even if the content of Ge ⁴⁺ is suppressed to 10% or less, for example, both realization of desired optical characteristics and excellent glass stability are achieved. be able to. Therefore, the Ge ⁴⁺ content is preferably 0 to 10%. A more preferable range of the content of Ge ⁴⁺ 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 an even more preferable range is 0. ~ 1%. It is particularly preferable not to contain Ge ⁴⁺ , that is, a Ge-free glass.

Like the optical glass I, the optical glass II is a glass having high refractive index and low dispersion characteristics while maintaining glass stability, but has a higher Ti ⁴⁺ content than the optical glass I. In the optical glass I, the content of Ti ⁴⁺ is set to 22% or less, the spectral transmittance in the visible region is increased, and the partial dispersion ratio is kept low so that it is advantageous for higher-order chromatic aberration correction. In addition, the lower limit of the refractive index is higher than the lower limit of the refractive index of the optical glass I in the range where the Abbe number νd is approximately 24.28 or more.
On the other hand, the optical glass II has a high refractive index and low dispersion characteristic in a range where the Ti ⁴⁺ content exceeds 22% and the Abbe number ν d is wider than that of the optical glass I.
In the following, the composition and characteristics of the optical glass II will be described as different 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.

From the viewpoint of ^achieving high refractive index and low dispersion 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 preferred lower limit of the cation ratio [ (S i ⁴⁺ + B ^{3 +} ) / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] is 0.10, the more preferred lower limit is 0.20, and the more preferred lower limit is 0.30, more preferred lower limit is 0.40, even more preferred lower limit is 0.50, even more preferred lower limit is 0.60, preferred upper limit is 1.05, more preferred upper limit is 1.0, even 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.

(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 more preferred range is 5.20 or less . . However, if the specific gravity is excessively reduced, the stability of the glass is lowered and the liquidus temperature tends to increase. Therefore, the specific gravity is preferably 4.50 or more. The more preferred lower limit of the specific gravity is 4.60, the still more preferred lower limit is 4.70, the still more preferred lower limit is 4.80, and the still more preferred lower limit is 4.90.

(Comparative example)
For comparison, Example No. 1 of Patent Document 1 is used. 3 and no. No. 5, composition No. 5 of Patent Document 2 Reproduction experiments were conducted on 16 compositions. In Example No. 1 of Patent Document 1 converted to cation% display. 3 and no. Table 2 shows the composition of No. 5 in Example No. The composition of 16 is shown in Table 1.
Furthermore, except for the cation ratio Ti ⁴⁺ / B ^3+, meet the requirements of the optical glass I, from the cation ratio Ti ⁴⁺ / B ³⁺ cations ratio Ti ⁴⁺ / B ³⁺ is 0.804 and the optical glass I For the smaller composition, the raw material was melted to attempt vitrification. This composition is referred to as composition A. Composition A is shown in Table 1.
Furthermore, except for the cation ratio Ti ⁴⁺ / B ^3+, meet the requirements of the optical glass II, from the cation ratio Ti ⁴⁺ / B ³⁺ cations ratio Ti ⁴⁺ / B ³⁺ is 0.803 and the optical glass II For the smaller composition, the raw material was melted to attempt vitrification. This composition is referred to as composition B. The composition B is shown in Table 2.
Example No. 1 of Patent Document 1 3 and no. No. 5, composition No. 5 of Patent Document 2 For 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 method for measuring the number density of crystals precipitated during the glass production, and found to be 998 / kg.
The number density of crystals determined by the above evaluation method is less than 1000 / kg, more preferably less than 500 / kg, still more preferably less than 300 / kg, and even more preferably 200. Less than 100 / 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. 0 / kg can be used as an indicator of a homogeneous optical glass having much more excellent glass stability.

Claims (7)

Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential components,
In cation% display,
Si ⁴⁺ and B ³⁺ in total 5 to 55%,
La ³⁺ is 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total),
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ in total 22 to 55%,
Including
Y ³⁺ content is 15% or less,
Ti ⁴⁺ content is 22% or less,
The cation ratio [Si ⁴ / (Si ⁴ + B ³⁺ )] of the Si ⁴⁺ content 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 Ba ²⁺ content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.40 or less,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio of the Ti ⁴⁺ content to the B ³⁺ content (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) Cation ratio of the total content of Nb ⁵⁺ and Ta ^{5+ to} the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ [(Nb ⁵⁺ + Ta ⁵⁺ ) / (Ti ⁴⁺ + Nb ⁵ The optical glass according to claim 1, wherein ⁺ + Ta ⁵⁺ + W ⁶⁺ )] is 0.41 or less. The optical glass according to claim 1, comprising 1 cation% or more of Zr ⁴⁺ . Si ⁴⁺ , B ³⁺ , La ³⁺ , Ti ⁴⁺ , Nb ⁵⁺ , and Zr ⁴⁺ are essential components,
In cation% display,
Si ⁴⁺ and B ³⁺ in total 5 to 55%,
La ³⁺ is 10 to 50% (however, La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ are 70% or less in total),
Ti ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ and W ⁶⁺ in total 23 to 70% (however, Ti ⁴⁺ is more than 22%),
Including
Y ³⁺ content is 15% or less,
The cation ratio of Ba ²⁺ content to the total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ [Ba ²⁺ / (La ³⁺ + Gd ³⁺ + Y ³⁺ + Yb ³⁺ )] 0.40 or less,
Zr ⁴⁺ to the content of ^{Zr 4+, Ti 4+, Nb 5+} , the total content of the cation ratio of Ta ⁵⁺ and ^{W 6+ [(Zr 4+ + Ti} 4+ + Nb 5+ + Ta 5+ + W 6+ ) / Zr ⁴⁺ ] is 2 or more,
The cation ratio of the Ti ⁴⁺ content to the B ³⁺ content (Ti ⁴⁺ / B ³⁺ ) is 0.85 or more,
And
An optical glass which is an oxide glass having an Abbe number νd of 18 or more and less than 35 and a refractive index nd satisfying the following formula (2).
nd ≧ 2.540− (0.02 × νd) (2) The glass gob for press molding which consists of optical glass of any one of Claims 1-4. The optical element blank which consists of optical glass of any one of Claims 1-4. The optical element which consists of optical glass of any one of Claims 1-4.