JP6771811B2 - Optical glass, preforms and optics - Google Patents

Description

The present invention relates to optical glass, preforms and optical elements.

In recent years, the digitization and high definition of devices that use optical systems have been rapidly advancing, and various optical devices such as photography devices such as digital cameras and video cameras, and image reproduction (projection) devices such as projectors and projection televisions. In this field, there is an increasing demand for reducing the number of optical elements such as lenses and prisms used in an optical system, and reducing the weight and size of the entire optical system.

Among the optical glasses used to make optical elements, the Abbe number (30 or more and 40 or less) has a refractive index ( _nd ) of 1.75 or more and can reduce the weight and size of the entire optical system. The demand for high refractive index low dispersion glass having ν _d ) is very high. As such a high refractive index low dispersion glass, glass compositions such as those represented by Patent Documents 1 to 3 are known.

Japanese Unexamined Patent Publication No. 52-103412 Japanese Unexamined Patent Publication No. 2008-12667 Japanese Unexamined Patent Publication No. 2014-047099

In order to reduce the material cost of the optical glass, it is desired that the raw material of the optical glass is as cheap as possible. However, even if the glass composition described in Patent Documents 1 to 3 contains as little Ta ₂ O ₅ component as possible, which is an expensive raw material, on the other hand, Nb ₂ O ₅ component, WO _{3 and} , Gd ₂ O ₃ component, Yb ₂ O ₃ component and other rare earth components are contained in a large amount, and still contains expensive raw materials, so it cannot be said that these demands are sufficiently met.

Further, instead of these expensive components, it is conceivable to contain a large amount of a relatively inexpensive high refractive index component such as a TiO ₂ component to obtain optical characteristics such as a desired refractive index. However, glass containing a large amount of such an inexpensive high-refractive index component is often colored, and is not suitable for use in optical elements such as lenses and prisms that transmit visible light.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical instrument while the refractive index ( _nd ) and Abbe number (ν _d ) are within desired ranges. An object of the present invention is to obtain an optical glass suitable for a stable optical element that can contribute to weight reduction at a lower cost.

As a result of intensive test and research in order to solve the above problems, the present inventors have added 5.0 of the Nb ₂ O ₅ component to the glass containing the B ₂ O ₃ component and the La ₂ O ₃ component. % Or less, and even when the WO ₃ component is 5.0% or less, the desired refractive index and Abbe number can be obtained without containing the expensive raw materials Nb ₂ O ₅ component and WO ₃ component as much as possible. It was found that the specific gravity of the glass was maintained and the specific gravity of the glass was reduced, and the present invention was completed. Specifically, the present invention provides the following.

(1) In mass%, B ₂ O ₃ component is 15.0 to 35.0%, La ₂ O ₃ component is 20.0% to 60.0%, and the content of Nb ₂ O ₅ component is 5. .0% or less, WO ₃ and the content of the component than 5.0%, less than 1.75 in refractive index and _{(n d),} optical glass and having a specific gravity of 4.80 or less.

(2) The optical glass according to (1), wherein (La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ ) is 25.0 to 60.0% in terms of mass sum.

(3) Described in (1) or (2), wherein (Nb ₂ O ₅ + WO ₃ ) / (La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ ) is 0.25 or less in terms of mass ratio. Optical glass.

(4) The optical glass according to any one of (1) to (3), wherein ZnO / BaO is more than 0 to 5.0 or less in terms of mass ratio.

(5) The optical glass according to any one of (1) to (4), wherein (Nb ₂ O ₅ + WO ₃ + TiO ₂ ) is more than 0 to 20.0% in terms of mass sum.

(6) Gd ₂ O ₃ component by mass% 0 to 20.0%
Y ₂ O ₃ component 0 to 20.0%
Yb ₂ O ₃ component 0 to 10.0%
Lu ₂ O ₃ component 0-5.0%
Ta ₂ O ₅ component 0-5.0%
The optical glass according to any one of (1) to (5).

(7) The mass sum of the Ln ₂ O ₃ components (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is 15.0% or more and 60.0% or less (1). ) To (6).

(8) SiO ₂ component 0 to 15.0% by mass%
TiO ₂ component 0 to 20.0%
ZrO ₂ component 0 to 10.0%
The optical glass according to any one of (1) to (7).

(9) CaO component by mass% 0 to 15.0%
BaO component 0 to 15.0%
MgO component 0-10.0%
SrO component 0-10.0%
ZnO component 0 to 25.0%
The optical glass according to any one of (1) to (8).

(10) Any one of (1) to (9) in which the mass sum of the RO components (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is 30.0% or less. The optical glass described.

(11) Li ₂ O component 0 to 5.0% by mass
Na ₂ O component 0-5.0%
K ₂ O component 0-5.0%
The optical glass according to any one of (1) to (10).

(12) Any one of (1) to (11) in which the mass sum of the Rn ₂ O components (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is 5.0% or less. The optical glass described.

(13) P ₂ O ₅ component by mass% 0 to 10.0%
GeO ₂ component 0 to 10.0%
Bi ₂ O ₃ component 0 to 10.0%
TeO ₂ component 0-5.0%
Al ₂ O ₃ component 0-5.0%
Ga ₂ O ₃ component 0-5.0%
SnO component 0-3.0%
Sb ₂ O ₃ component 0-3.0%
The optical glass according to any one of (1) to (12).

(14) The optical glass according to any one of (1) to (13), which has an Abbe number (νd) of 30 to 45.

(15) The optical glass according to any one of (1) to (14), wherein the wavelength (λ ₇₀ ) showing a spectral transmittance of 70% is 450 nm or less.

(16) A preform for polishing and / or precision press molding made of the optical glass according to any one of (1) to (15).

(17) An optical element obtained by grinding and / or polishing the optical glass according to any one of (1) to (15).

(18) An optical element obtained by precision press molding the preform according to (16).

According to the present invention, an optical glass suitable for an optical element having a refractive index ( _nd ) and an Abbe number (ν _d ) within a desired range and stable, which can contribute to weight reduction of an optical device, is provided. It can be obtained at a lower cost.

The optical glass of the present invention contains 15.0 to 35.0% of the B ₂ O ₃ component and 20.0 to 60.0 of the La ₂ O ₃ component in mass% with respect to the total mass of the glass having an oxide conversion composition. % contained, the content of _Nb 2 _{O 5} component of 5.0% or less, or less than 5.0% the content of WO ₃ components, 1.75 or more refractive index _{(n d),} 4.5 It has the following specific weights. Refractive index of 1.75 or more (n) even if the glass containing B ₂ O ₃ component and La ₂ O ₃ component does not contain Nb ₂ O ₅ component and WO ₃ component, which are expensive raw materials, as much as possible. It is possible to obtain an optical glass having _d ) and having a specific gravity of 4.5 or less, and it is possible to provide an inexpensive optical glass.

Hereinafter, embodiments of the optical glass of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and is carried out with appropriate modifications within the scope of the object of the present invention. be able to. In addition, although the description may be omitted as appropriate for the parts where the description is duplicated, the gist of the invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. Unless otherwise specified in the present specification, the content of each component shall be expressed as a mass% of the total mass of the glass in the oxide conversion composition. Here, the "oxide-equivalent composition" is based on the assumption that the oxides, composite salts, metal fluorides, etc. used as raw materials for the glass constituents of the present invention are all decomposed into oxides at the time of melting. The composition is such that each component contained in the glass is described with the total mass of the produced oxide as 100% by mass.

<About essential ingredients and optional ingredients>
The B ₂ O ₃ component is a glass forming component and is an essential component for the optical glass of the present invention.
In particular, by containing 15.0% or more of the B ₂ O ₃ component, it is possible to reduce the specific gravity, promote the formation of stable glass, reduce devitrification, and enhance the thermal stability of the glass. .. Therefore, the lower limit of the content of the B ₂ O ₃ component is preferably 15.0%, more preferably 17.0%, and even more preferably 20.0%.
On the other hand, by setting the content of the B ₂ O ₃ component to 35.0% or less, it is possible to suppress a decrease in the refractive index of the glass and suppress a deterioration in chemical durability. Therefore, the content of the B ₂ O ₃ component is preferably 35.0%, more preferably 33.0%, and even more preferably 28.0%.
B ₂ O ₃ component can be used _H 3 _BO 3 as a starting _{material, Na 2 B 4 O 7,} Na 2 B 4 O 7 · 10H 2 O, the BPO ₄ and the like.

The La ₂ O ₃ component is a component that increases the refractive index and Abbe number of glass by containing 20.0% or more. In addition, it is relatively inexpensive among rare earth elements, and is an effective component for suppressing an increase in the material cost of glass. Therefore, the La ₂ O ₃ component is a component to be included in the optical glass of the present invention. Therefore, the lower limit of the content of the La ₂ O ₃ component is preferably 20.0%, more preferably 25.0%, still more preferably 30.0%, still more preferably 33.0%.
On the other hand, by reducing the content of the La ₂ O ₃ component to 60.0% or less, devitrification of the glass can be reduced. Therefore, the content of the La ₂ O ₃ component is preferably 60.0%, more preferably 50.0%, and even more preferably 45.0%.
As the La ₂ O ₃ component, La ₂ O ₃ , La (NO ₃ ) ₃ , XH ₂ O (X is an arbitrary integer) or the like can be used as a raw material.

By reducing the content of the Nb ₂ O ₅ component to 5.0% or less, the use of the expensive Nb ₂ O ₅ component is reduced, so that the material cost of the glass can be reduced. In addition, since the rise in melting temperature during glass production is suppressed, the glass production cost can be reduced. Further, it is possible to suppress a decrease in the visible light transmittance of the glass due to the Nb ₂ O ₅ component. Therefore, the content of the Nb ₂ O ₅ component is preferably 5.0%, more preferably 4.0%, still more preferably 3.0%, and most preferably not contained.
As the Nb ₂ O ₅ component, Nb ₂ O ₅ or the like can be used as a raw material.

By reducing the content of the WO ₃ component to 5.0% or less, the use of the expensive WO ₃ component is reduced, so that the material cost of the glass can be reduced. Also, increasing the visible light transmittance to reduce the coloration of the glass due WO ₃ components, it is possible to further reduce the specific gravity. Therefore, the content of the WO ₃ component is preferably 5.0%, more preferably 4.0%, still more preferably 3.0%, and most preferably not contained.
The WO ₃ component can be contained in glass using WO ₃ or the like as a raw material.

The total amount of the La ₂ O ₃ component, the Gd ₂ O ₃ component and the Ta ₂ O ₅ component in the optical glass of the present invention is preferably 25.0% or more and 60.0% or less. In particular, by setting the sum of mass (La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ ) to 25.0% or more, a glass having a desired refractive index and Abbe number can be obtained, and the glass can be stably obtained. it can. Therefore, the lower limit of the mass sum is preferably 25.0%, more preferably 30.0%, and further preferably 35.0%.
On the other hand, by setting the sum of mass (La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ ) to 60.0% or less, the material cost can be reduced. Therefore, the sum of mass (La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ ) is preferably 60.0%, more preferably 55.0%, still more preferably 50.0%, and most preferably 45.0%. Is the upper limit.

The ratio (mass ratio) of the contents of the Nb ₂ O ₅ component and the WO ₃ component to the La ₂ O ₃ component, Gd ₂ O ₃ component and Ta ₂ O ₅ component in the optical glass of the present invention is 0.25 or less. preferable. As a result, the specific gravity can be reduced while obtaining the glass having a desired refractive index and Abbe number, and the cost of the raw material increased by Nb ₂ O ₅ and WO ₃ can be reduced. Therefore, the mass ratio (Nb ₂ O ₅ + WO ₃ ) / (La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ ) is preferably 0.25 or less, more preferably 0.15 or less, still more preferably 0.10. Hereinafter, it is most preferably 0.05 or less.

The ratio (mass ratio) of the content of the ZnO component to the BaO component in the optical glass of the present invention is preferably more than 0 and 5.0 or less. By setting the mass ratio of (ZnO) / (BaO) to more than 0, the stability during glass molding can be improved. Therefore, the lower limit of this mass ratio may be preferably more than 0, more preferably more than 0.1, and even more preferably more than 0.5.
On the other hand, by setting the mass ratio of (ZnO) / (BaO) to 5.0 or less, the specific gravity of the glass can be reduced. Therefore, this mass ratio is preferably 5.0, more preferably 4.9, and even more preferably 4.8.

In the optical glass of the present invention, the total amount of the Nb ₂ O ₅ component, the WO ₃ component, and the TiO ₂ component can be adjusted to a high refractive index and a high dispersion when the total amount exceeds 0%, so that the desired optical constant can be adjusted. It can be easily obtained. Therefore, the mass sum (Nb ₂ O ₅ + WO ₃ + TiO ₂ ) may be preferably more than 0%, more preferably 3.0%, still more preferably 6.0% as the lower limit.
On the other hand, by setting the mass sum (Nb ₂ O ₅ + WO ₃ + TiO ₂ ) to 20.0% or less, the coloring of the glass can be reduced and the visible light transmittance of the glass can be increased. Therefore, the mass sum (Nb ₂ O ₅ + WO ₃ + TiO ₂ ) is preferably 20.0%, more preferably 15.0%, and even more preferably 12.5%.

Gd ₂ O ₃ component, Y ₂ O ₃ component, Yb ₂ O ₃ and Lu ₂ O ₃ component are optional components that increase the refractive index and Abbe number of glass and reduce devitrification when they are contained in excess of 0%. Is.
On the other hand, the contents of Gd ₂ O ₃ component and Y ₂ O ₃ component should be 20.0% or less, the content of Yb ₂ O ₃ component should be 10.0% or less, and Lu ₂ O ₃ content of the component by 5.0% or less, since the use of these expensive components is reduced, thereby reducing the material cost of the glass. In addition, it is possible to suppress an unnecessarily high increase in the Abbe number of the glass due to excessive inclusion of these components and devitrification. Therefore, the content of the Gd ₂ O ₃ component and the Y ₂ O ₃ component is preferably 20.0%, more preferably 15.0%, still more preferably 10.0%, and further preferably 5.0. It is less than%, more preferably less than 3.0%. The content of the Yb ₂ O ₃ component is preferably 10.0% as the upper limit, more preferably less than 5.0%, and further preferably less than 3.0%. The content of the Lu ₂ O ₃ component is preferably 5.0% as the upper limit, more preferably less than 3.0%, and further preferably less than 1.0%.
Gd ₂ O ₃ component, Y ₂ O ₃ component, Yb ₂ O ₃ and Lu ₂ O ₃ component are used as raw materials for Gd ₂ O ₃ , GdF ₃ , Y ₂ O ₃ , YF ₃ , Yb ₂ O ₃ and Lu ₂ O. _It can be contained in the glass using ₃ or the like.

The Ta ₂ O ₅ component is an optional component that increases the refractive index of the glass and reduces devitrification when it is contained in excess of 0%.
On the other hand, by reducing the content of the Ta ₂ O ₅ component to 5.0% or less, the use of the expensive Ta ₂ O ₅ component is reduced, so that the material cost of the glass can be reduced. Further, by reducing the use of the Ta ₂ O ₅ component, the melting temperature of the raw material is lowered, and the energy required for melting the raw material is reduced, so that the manufacturing cost of the optical glass can also be reduced. Therefore, the content of the Ta ₂ O ₅ component is preferably 5.0%, more preferably 3.0%, further preferably 1.0%, still more preferably 0.1%, and most preferably the content. do not do.
The Ta ₂ O ₅ component can be contained in the glass using Ta ₂ O ₅ or the like as a raw material.

In the optical glass of the present invention, the total amount of the Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, Yb) is 15.0% or more and 60.0%. The following is preferable.
In particular, by setting this total amount to 15.0% or more, the Abbe number of glass can be increased. Therefore, the total amount (sum of mass) of the Ln ₂ O ₃ components is preferably 15.0%, more preferably 20.0%, further preferably 25.0%, and most preferably 30.0% as the lower limit. ..
On the other hand, by reducing the total amount to 60.0% or less, the use of expensive rare earths is reduced while reducing the devitrification of the glass, so that the material cost of the glass can be reduced. Therefore, the mass sum of the Ln ₂ O ₃ components is preferably 60.0%, more preferably 50.0%, and even more preferably 45.0%.

The SiO ₂ component is an optional component capable of increasing the viscosity of the glass and reducing the devitrification of the glass while reducing the specific gravity when the content exceeds 0%. Therefore, the content of the SiO ₂ component may be preferably more than 1.0%, more preferably more than 2.0%, and even more preferably more than 4.0%.
On the other hand, by setting the content of the SiO ₂ component to 15.0% or less, the increase in the glass transition point can be suppressed and the decrease in the refractive index can be suppressed. Therefore, the content of the SiO ₂ component is preferably 15.0%, more preferably 10.0%, and even more preferably 8.0%.
The SiO ₂ component can be contained in the glass by using SiO ₂ , K ₂ SiF ₆ , Na ₂ SiF _6, or the like as a raw material.

The TiO ₂ component is an optional component capable of increasing the refractive index of the glass and adjusting the Abbe number to be low when the content exceeds 0%. Therefore, the content of the TiO ₂ component may be preferably more than 0%, more preferably 1.0%, more preferably 3.0%, still more preferably 5.0% as the lower limit.
On the other hand, by reducing the content of the TiO ₂ component to 20.0% or less, the devitrification of the glass due to the TiO ₂ component becoming crystal nuclei is suppressed, the Abbe number is suppressed from being lowered more than necessary, and the TiO It is possible to reduce the coloring of the glass due to the inclusion of the _two components and increase the visible light transmittance. Therefore, the content of the TiO ₂ component is preferably 20.0%, more preferably 15.0%, and even more preferably 12.0%.
The TiO ₂ component can be contained in the glass using TiO ₂ or the like as a raw material.

ZrO ₂ component, when ultra containing 0%, can contribute to a high refractive index and low dispersion of the glass, which is an optional component that and can reduce the devitrification of the glass. Therefore, the content of the ZrO ₂ component is preferably 0 percent, more preferably 0.5 percent, more preferably 1.0 percent, most preferably be 3.0% greater.
On the other hand, when the content of the ZrO ₂ component to 10.0% or less, is suppressed an increase in the manufacturing cost of the glass by suppressing an increase in the melting temperature at the time of glass production. Therefore, the content of the ZrO ₂ component is preferably 10.0%, more preferably 9.0%, more preferably the upper limit of 8.0%.
As the ZrO ₂ component, ZrO ₂ , ZrF _4, or the like can be used as a raw material.

The CaO component, BaO component, MgO component and SrO component are optional components that can adjust the refractive index of the glass, increase the solubility of the glass raw material, and reduce devitrification when the content exceeds 0%.
On the other hand, the refractive index of the glass is required by setting the contents of the CaO component and the BaO component to 15.0% or less, and setting the contents of the MgO component and the SrO component to 10.0% or less, respectively. The above decrease and devitrification can be suppressed. The content of the CaO component and the BaO component is preferably 15.0%, more preferably 10.0%, and even more preferably 8.0%. The content of the MgO component and the SrO component is preferably 10.0%, more preferably 5.0%, and even more preferably 3.0%. In particular, at least one of the BaO component and the SrO component may contain a specific gravity of more than 0%, more preferably 1%, and even more preferably 2% as the lower limit because the specific gravity can be reduced.
The MgO component, CaO component, SrO component and BaO component are raw materials such as MgCO ₃ , MgF ₂ , CaCO ₃ , CaF ₂ , Sr (NO ₃ ) ₂ , SrF ₂ , BaCO ₃ , Ba (NO ₃ ) ₂ , and BaF _2. Can be used.

The ZnO component is an optional component capable of adjusting the refractive index of glass, increasing the solubility of the glass raw material, and reducing devitrification when the content exceeds 0% within the range of the refractive index and Abbe number of the present invention. .. Therefore, the content of the ZnO component may be preferably more than 0%, more preferably more than 3.0%, and even more preferably more than 5.0%.
On the other hand, by setting the content of the ZnO component to 25.0% or less, it is possible to suppress the devitrification due to the excessive content of the ZnO component while suppressing the increase in specific gravity. Further, since the decrease in the viscosity of the molten glass is suppressed, the occurrence of veins on the glass can be reduced. Therefore, the content of the ZnO component is preferably 25.0%, more preferably 20.0%, and even more preferably 15.0%.
As the ZnO component, ZnO, ZnF _2, or the like can be used as a raw material.

In the optical glass of the present invention, the total amount of RO components (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably 30.0% or less. As a result, it is possible to suppress a decrease in the refractive index of the glass and an increase in the liquidus temperature due to an excessive content of the RO component, and it is possible to reduce the specific gravity. Therefore, the total amount (sum of mass) of the RO components is preferably 25.0%, more preferably 20.0%, and even more preferably 15.0%.
On the other hand, the mass sum of the RO components is preferably more than 0%, more preferably 1.0% or more, still more preferably 3.0% or more, from the viewpoint of increasing the solubility of the glass raw material and reducing devitrification. May be.

The Li ₂ O component is an optional component that can improve the solubility of the glass raw material, reduce devitrification when the glass is reheated, and reduce the specific gravity when the content exceeds 0%.
On the other hand, by setting the content of the Li ₂ O component to 5.0% or less, it is difficult to reduce the refractive index of the glass, and the devitrification of the glass due to the excessive content of the Li ₂ O component can be reduced. In particular, glass containing a Li ₂ O component tends to have a low refractive index and a high Abbe number. Therefore, the content of the Li ₂ O component is preferably 5.0%, more preferably 3.0%, further preferably 1.0% as the upper limit, still more preferably less than 0.5%, still more preferably 0. It is less than .35%, more preferably less than 0.3%.
As the Li ₂ O component, Li ₂ CO ₃ , LiNO ₃ , LiF or the like can be used as a raw material.

When the Na ₂ O component, K ₂ O component and Cs ₂ O component are contained in excess of 0%, the solubility of the glass raw material can be improved, devitrification when the glass is reheated can be reduced, and the specific gravity can be reduced. It is an optional ingredient that can be used.
On the other hand, by setting the content of each of these components to 5.0% or less, it is difficult to reduce the refractive index of the glass, and devitrification due to excessive content of these components can be reduced. Therefore, the content of each of the Na ₂ O component, the K ₂ O component, and the Cs ₂ O component is preferably 5.0%, more preferably 3.0%, and further preferably 1.0%.
Na ₂ O component, K ₂ O component and Cs ₂ O component are raw materials such as Na NO ₃ , NaF, Na ₂ SiF ₆ , K ₂ CO ₃ , KNO ₃ , KF, KHF ₂ , K ₂ SiF ₆ , Cs ₂ CO ₃ , CsNO _{3 and the} like can be used.

In the optical glass of the present invention, the total amount of the Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, K and Cs) is preferably 5.0% or less. Thus, it is difficult to lower the refractive index of the glass, and can reduce the devitrification due to excessive content of Rn 2 _O components. Therefore, the total amount (sum of mass) of the Rn ₂ O components is preferably 5.0%, more preferably 3.0% as the upper limit, and further preferably less than 1.0%.

The P ₂ O ₅ component is an optional component capable of lowering the liquidus temperature of the glass to reduce devitrification when the content exceeds 0%.
On the other hand, by reducing the content of the P ₂ O ₅ component to 10.0% or less, it is possible to suppress a decrease in the chemical durability of the glass, particularly the water resistance. Therefore, the content of the P ₂ O ₅ component is preferably 10.0%, more preferably 5.0%, and even more preferably 3.0%.
As the P ₂ O ₅ component, Al (PO ₃ ) ₃ , Ca (PO ₃ ) ₂ , Ba (PO ₃ ) ₂ , BPO ₄ , H ₃ PO _{4, and the} like can be used as raw materials.

The GeO ₂ component is an optional component that can increase the refractive index of glass and lower the liquidus temperature of glass when it is contained in excess of 0%.
On the other hand, by reducing the expensive GeO ₂ component, the effect of reducing the material cost of the glass in the present invention can be enhanced. Therefore, the content of the GeO ₂ component is preferably 10.0% or less, more preferably 5.0%, and even more preferably 1.0%.
As the GeO ₂ component, GeO ₂ or the like can be used as a raw material.

The Bi ₂ O ₃ component is an optional component that can increase the refractive index and lower the glass transition point when the content exceeds 0%.
On the other hand, by reducing the content of the Bi ₂ O ₃ component to 10.0% or less, the devitrification of the glass is reduced and the coloring of the glass is reduced, so that the visible light transmittance of the glass can be increased. .. Therefore, the content of the Bi ₂ O ₃ component is preferably 10.0%, more preferably 5.0%, and even more preferably 3.0%.
As the Bi ₂ O ₃ component, Bi ₂ O ₃ or the like can be used as a raw material.

The TeO ₂ component is an optional component that can increase the refractive index of glass and lower the glass transition point when it is contained in excess of 0%.
On the other hand, by reducing the content of the TeO ₂ component to 5.0% or less, the alloying of the TeO ₂ component and the melting equipment (particularly precious metals such as Pt) is reduced, so that the life of the melting equipment can be extended. Can be planned. Further, by reducing the expensive TeO ₂ component, the material cost of glass can be reduced. Therefore, the content of the TeO ₂ component is preferably 5.0% as the upper limit, more preferably less than 3.0%, and further preferably less than 1.0%.
As the TeO ₂ component, TeO ₂ or the like can be used as a raw material.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components that can enhance the chemical durability of the glass and reduce devitrification during melting of the glass raw material when the content exceeds 0%. In particular, when the Al ₂ O ₃ component is contained in an amount of more than 0%, the stability during glass molding can be enhanced. Therefore, the content of the Al ₂ O ₃ component may be preferably more than 0%, more preferably 0.5%, and even more preferably more than 1.0% as the lower limit.
On the other hand, by setting the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component to 5.0% or less, the devitrification of the glass due to the excessive content of these components can be reduced. Further, by reducing the expensive Ga ₂ O ₃ component, the material cost of glass can be reduced. Therefore, the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component is preferably 5.0% as the upper limit, more preferably less than 3.0%, and further preferably less than 2.0%. ..
As the Al ₂ O ₃ component and the Ga ₂ O ₃ component, Al ₂ O ₃ , Al (OH) ₃ , AlF ₃ , Ga ₂ O ₃ , Ga (OH) _{3 and the} like can be used as raw materials.

The SnO ₂ component is an optional component that can clarify the molten glass and increase the visible light transmittance of the glass when it contains more than 0%.
On the other hand, by setting the content of the SnO ₂ component to 3.0% or less, it is possible to prevent the glass from being colored or devitrified by the reduction of the molten glass. Further, since the alloying of the SnO ₂ component and the melting equipment (particularly noble metal such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the content of the SnO ₂ component is preferably 3.0%, more preferably 1.0%, and even more preferably 0.5%.
As the SnO ₂ component, SnO, SnO ₂ , SnF ₂ , SnF _4, or the like can be used as a raw material.

The Sb ₂ O ₃ component is an optional component that, when contained in excess of 0%, increases the visible light transmittance of the glass and can be defoamed when the glass raw material is melted.
On the other hand, by reducing the content of the Sb ₂ O ₃ component to 3.0% or less, excessive foaming at the time of melting the glass raw material can be suppressed. Further, since it becomes difficult for the Sb ₂ O ₃ component to alloy with the melting equipment (particularly a precious metal such as Pt), the life of the melting equipment can be extended. Further, if the content of the Sb ₂ O ₃ component is too large, the visible light transmittance of the glass becomes rather low. Therefore, the content of the Sb ₂ O ₃ component is preferably 3.0%, more preferably 2.0% as the upper limit, further preferably less than 1.0%, and most preferably less than 0.5%.
Sb ₂ O ₃ component can be used _{Sb 2 O 3, Sb 2 O} 5, Na 2 H 2 Sb 2 O 7 · 5H 2 O and the like as raw materials.

The component that clarifies and defoams the glass is not limited to the above Sb ₂ O ₃ component, and a clarifying agent, a defoaming agent, or a combination thereof known in the field of glass production can be used.

<Ingredients that should not be included>
Next, components that should not be contained in the optical glass of the present invention and components that are not preferable to be contained will be described.

Other components can be added as needed without impairing the properties of the glass of the present invention. However, even if each transition metal component such as Ce, V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo is contained alone or in a small amount, the glass is colored and the visible region is specified. Since the effect of increasing the visible light transmittance of the present invention is diminished by causing absorption at the wavelength of the above, it is preferable that the optical glass that transmits the wavelength in the visible region is substantially not contained.

Furthermore, lead compounds such as PbO and each component of Th, Cd, Tl, Os, Be, and Se have tended to refrain from use as harmful chemical substances in recent years, and not only in the glass manufacturing process but also in the processing process, In addition, environmental measures are required up to disposal after commercialization. Therefore, when the environmental impact is emphasized, it is preferable that these are substantially not contained except for unavoidable contamination. As a result, the optical glass is substantially free of substances that pollute the environment. Therefore, this optical glass can be manufactured, processed, and disposed of without taking any special environmental measures.

The range of the content of each component in the present invention cannot be directly expressed in the description of mol% because it is expressed in mass% with respect to the total mass of glass in the oxide conversion composition, but various requirements in the present invention The composition of each component present in the glass composition satisfying the characteristics in terms of mol% has the following values in terms of oxide composition.
B ₂ O ₃ component 5.0-70.0 mol%,
La ₂ O ₃ component 3.0 to 40.0 mol%, and Nb ₂ O ₅ component 0 to 20.0 mol%,
WO ₃ component 0-25.0 mol%,
And Gd ₂ O ₃ component 0-10.0 mol%,
Y ₂ O ₃ component 0 to 10.0 mol%,
Yb ₂ O ₃ component 0 to 10.0 mol%,
Lu ₂ O ₃ component 0-5.0 mol%,
Ta ₂ O ₅ component 0 to 10.0 mol%,
SiO ₂ component 0-30.0 mol%,
TiO ₂ component 0-40.0 mol%,
ZrO ₂ component 0-30.0 mol%,
CaO component 0-40.0 mol%,
BaO component 0-35.0 mol%,
MgO component 0-20.0 mol%,
SrO component 0-20.0 mol%,
ZnO component 0-60.0 mol%
Li ₂ O component 0-30.0 mol%,
Na ₂ O component 0 to 25.0 mol%,
K ₂ O component 0 to 20.0 mol%,
Cs ₂ O component 0 to 10.0 mol%,
P ₂ O ₅ component 0 to 15.0 mol%,
GeO ₂ component 0-10.0 mol%,
Bi ₂ O ₃ component 0-5.0 mol%,
TeO ₂ component 0-25.0 mol%,
Al ₂ O ₃ component 0 to 15.0 mol%,
Ga ₂ O ₃ component 0-5.0 mol%,
SnO ₂ component 0 to 0.3 mol% or Sb ₂ O ₃ component 0 to 1.0 mol%

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, the prepared mixture is put into a platinum crucible, and the temperature is 1200 to 1400 ° C. in an electric furnace depending on the difficulty of melting the glass composition. It is produced by melting in the temperature range of 3 to 4 hours, homogenizing by stirring, lowering the temperature to an appropriate temperature, casting into a mold, and slowly cooling.

[Physical properties]
The optical glass of the present invention preferably has a high refractive index and a high Abbe number (low dispersion). In particular, the refractive index ( _nd ) of the optical glass of the present invention is preferably 1.75, more preferably 1.78, and even more preferably 1.80 as the lower limit. The upper limit of the refractive index may be preferably 1.95, more preferably 1.90, and even more preferably 1.88. The Abbe number (ν _d ) of the optical glass of the present invention is preferably 30, more preferably 33, still more preferably 35 as the lower limit, preferably 45, more preferably 43, still more preferably 40, most preferably. The upper limit is 39.5.
By having such a high refractive index, a large amount of refraction of light can be obtained even if the optical element is made thinner. Further, by having such a low dispersion, the defocus (chromatic aberration) due to the wavelength of light becomes small even with a single lens. In addition, by having such a low dispersion, high imaging characteristics and the like can be achieved, for example, when combined with an optical element having a high dispersion (low Abbe number).
Therefore, the optical glass of the present invention is useful in optical design, and it is possible to reduce the size of the optical system and expand the degree of freedom in optical design while achieving particularly high imaging characteristics.

Further, the optical glass of the present invention preferably has a small specific gravity. More specifically, the specific gravity of the optical glass of the present invention is 4.80 or less. As a result, the mass of the optical element and the optical device using the optical element is reduced, which can contribute to the weight reduction of the optical device. Therefore, the specific gravity of the optical glass of the present invention is preferably 4.80, more preferably 4.60, and preferably 4.30 as the upper limit. The specific gravity of the optical glass of the present invention is often 3.00 or more, more specifically 3.50 or more, and more specifically 4.00 or more.
The specific gravity of the optical glass of the present invention is measured based on the Japan Optical Glass Industry Association standard JOGIS05-1975 “Method for measuring the specific gravity of optical glass”.

It is preferable that the optical glass of the present invention has a high visible light transmittance, particularly a light transmittance on the short wavelength side of visible light, and thus less coloring. In particular, in the optical glass of the present invention, the shortest wavelength (λ ₅ ) exhibiting a spectral transmittance of 5% in a sample having a thickness of 10 mm may be preferably 400 nm, more preferably 380 nm, and further preferably 360 nm as the upper limit. Further, in the optical glass of the present invention, the shortest wavelength (λ ₇₀ ) exhibiting a spectral transmittance of 70% in a sample having a thickness of 10 mm may be preferably 450 nm, more preferably 430 nm, and further preferably 400 nm as the upper limit. The shortest wavelength (λ ₈₀ ) showing a spectral transmittance of 80% in a sample having a thickness of 10 mm in the optical glass of the present invention may be preferably 500 nm, more preferably 490 nm, and further preferably 480 nm as the upper limit. As a result, the absorption edge of the glass is removed from the visible region, and the transparency of the glass to light having a wavelength in a wider visible region is enhanced. Therefore, this optical glass is suitably used for an optical element such as a lens that transmits visible light. Can be done.

[Preform and optical element]
From the produced optical glass, a glass molded body can be produced by using a mold press molding means such as reheat press molding or precision press molding. That is, a method of obtaining the shape of an optical element by grinding and polishing a gob or glass block formed of optical glass, or reheating a gob or glass block formed of optical glass to form (reheat press molding). A method of grinding and polishing the glass molded body thus obtained, a preform material obtained by cutting and polishing a gob or a glass block, or a preform material formed by a known levitation molding or the like was ultra-precision processed. A glass molded body can be produced by a method of obtaining the shape of an optical element by molding with a mold (precision press molding). The means for producing the glass molded product is not limited to these means.

The glass molded body produced in this manner is useful for various optical elements and optical designs. In particular, it is preferable to manufacture optical elements such as lenses, prisms, and mirrors from the optical glass of the present invention by means such as precision press molding. As a result, when used in optical equipment that transmits visible light through optical elements such as cameras and projectors, the optical system in these optical equipment can be miniaturized while achieving high-definition and high-precision imaging characteristics. Can be planned.

The compositions of Examples (No. 1 to No. 8) and Comparative Examples (No. A) of the present invention, as well as the refractive index ( _nd ), Abbe number (ν _d ), specific gravity, and spectral transmittance of these glasses. The results of the wavelengths (λ ₅ , λ ₇₀ , λ ₈₀ ) showing the rates of 5%, 70%, and 80% are shown in Tables 1 and 2. The following examples are for illustrative purposes only, and are not limited to these examples.

The glasses of these Examples and Comparative Examples are used for ordinary optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, hydroxides, and metaphosphate compounds corresponding to each component as raw materials. The high-purity raw materials to be produced are selected, weighed so as to have the composition ratios of the respective Examples and Comparative Examples shown in Tables 1 and 2, and mixed uniformly, and then put into a platinum crucible to dissolve the glass composition. Depending on the degree of difficulty, the glass was melted in an electric furnace in a temperature range of 1100 to 1500 ° C. for 2 to 5 hours, homogenized by stirring to break bubbles, etc., cast into a mold, and slowly cooled to prepare glass.

Here, the refractive index and Abbe number of the glasses of Examples and Comparative Examples were measured based on the Japan Optical Glass Industry Association standard JOBIS01-2003. As the glass used for this measurement, the glass treated in a slow cooling furnace was used with the annealing conditions set to a slow cooling descent rate of −25 ° C./hr.

The specific gravity of the glass of Examples and Comparative Examples was measured according to JOBIS05-1975 “Method for measuring specific gravity of optical glass”.

The visible light transmittance of the glasses of Examples and Comparative Examples was measured according to the Japan Optical Glass Industry Association standard JOBIS02. In the present invention, the presence or absence and degree of coloration of the glass were determined by measuring the transmittance of the glass. Specifically, a face-to-face parallel polished product having a thickness of 10 ± 0.1 mm was measured for a spectral transmittance of 200 to 800 nm according to JISZ8722, and λ ₅ (wavelength at a transmittance of 5%) and λ ₇₀ (transmittance). Wavelength at 70%) and λ ₈₀ (wavelength at transmittance 80%) were determined.

The optical glass of the example of the present invention had a specific gravity of 4.80 or less, more specifically 4.50 or less. On the other hand, the glass of Comparative Example A had a specific gravity of more than 4.80. Therefore, it was clarified that the optical glass of the example of the present invention has a smaller specific gravity than the glass of the comparative example.

The optical glass of the examples of the present invention had λ ₈₀ (wavelength at a transmittance of 80%) of 500 nm or less, and more specifically, 480 nm or less. Further, the optical glass of the examples of the present invention had λ ₇₀ (wavelength at a transmittance of 70%) of 450 nm or less, and more specifically, 430 nm or less. Further, in the optical glass of the example of the present invention, λ ₅ (wavelength at a transmittance of 5%) was 400 nm or less, and more specifically, 380 nm or less.

The optical glasses of Examples of the present invention are both refractive index (n _d) of 1.75 or above, more specifically is 1.80 or more, were within the desired range.

Further, all of the optical glasses of the examples of the present invention have an Abbe number (ν _d ) of 30 or more, more specifically 35 or more, and this Abbe number (ν _d ) is 40 or less, more specifically 39. It was 5.5 or less, which was within the desired range.

Further, since the optical glass of the example of the present invention contains less Nb ₂ O ₅ component and WO ₃ than the glass of the comparative example, the material cost is reduced.

Therefore, the optical glass of the embodiment of the present invention can be produced inexpensively while having the refractive index ( _nd ) and the Abbe number (ν _d ) within the desired ranges, has a small specific gravity, is less colored, and has a visible light transmittance. It became clear that was high. Therefore, it is presumed that the optical glass of the embodiment of the present invention contributes to the weight reduction of the optical device and is suitably used for the purpose of transmitting visible light.

Further, using the optical glass of the example of the present invention, after performing reheat press molding, grinding and polishing were performed to process the shape into a lens and a prism. Further, the optical glass of the embodiment of the present invention was used to form a preform for precision press molding, and the preform for precision press molding was precision press molded into the shape of a lens and a prism. In either case, there were no problems such as fusion with the mold and emulsification and devitrification of the glass after heat softening, and it was possible to stably process various lens and prism shapes. ..

Although the present invention has been described in detail above for the purpose of illustration, the present embodiment is merely for the purpose of illustration, and many modifications can be made by those skilled in the art without departing from the idea and scope of the present invention. Will be understood.

Claims (10)

By _mass% B 2 _{O 3} component from 15.0 to 28.0%,
20.0% to 45 of La ₂ O ₃ components
.. Contains 0%,
TiO ₂ component content is 15.0 % or less,
The content of the ZrO ₂ component is 9.0% or less,
The content of Nb ₂ O ₅ component is 5.0% or less,
The content of WO ₃ component is 5.0% or less,

In terms of sum of mass, (Nb ₂ O ₅ + WO ₃ + TiO ₂ ) is more than 0% to 12.5%.
The mass ratio (Nb ₂ O ₅ + WO ₃ ) / (La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ ) is 0.1 or less.

(La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ ) was 25.0 to 41.89%.
30-45 Abbe number ([nu] d) and 1.75 or more refractive index _{(n d),} has a specific gravity of 4.80 or less,
An optical glass having a wavelength (λ ₇₀ ) showing a spectral transmittance of 70% of 430 nm or less . Gd ₂ O ₃ component by mass% 0 to 20.0%
Y ₂ O ₃ component 0 to 20.0% Yb ₂ O ₃ component 0 to 10.0% Lu ₂ O ₃ component 0 to 5.0%
Ta ₂ O ₅ component from 0 to 5.0% and is claim 1 Symbol placement of the optical glass. Claim 1 or 2 in which the mass sum of the Ln ₂ O ₃ components (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is 15.0% or more and 60.0% or less. serial mounting of optical glass. SiO ₂ component by mass% 0 to 15.0%
The optical glass according to any one of claims 1 to 3 . CaO component 0 to 15.0% by mass% BaO component 0 to 15.0%
The optical glass according to any one of claims 1 to 4 , wherein the MgO component is 0 to 10.0%, the SrO component is 0 to 10.0%, and the ZnO component is 0 to 25.0%.
The optical glass according to any one of claims 1 to 5 , wherein the mass sum of the RO components (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is 30.0% or less. Li ₂ O component 0-5.0% by mass
The optical glass according to any one of claims 1 to 6 , wherein the Na ₂ O component is 0 to 5.0% and the K ₂ O component is 0 to 5.0%.
The optical glass according to any one of claims 1 to 7 , wherein the mass sum of the Rn ₂ O components (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is 5.0% or less.
P ₂ O ₅ component from 0 to 10.0% by mass%
GeO ₂ component 0 to 10.0% Bi ₂ O ₃ component 0 to 10.0% TeO ₂ component 0 to 5.0%
Al ₂ O ₃ component 0-5.0% Ga ₂ O ₃ component 0-5.0% SnO component 0-3.0%
The optical glass according to any one of claims 1 to 8 , wherein the Sb ₂ O ₃ component is 0 to 3.0%. A preform for polishing and / or precision press molding made of the optical glass according to any one of claims 1 to 9 .