JP7126505B2 - Optical glasses, optical elements and optical equipment - Google Patents

Description

The present invention relates to optical glasses, optical elements and optical instruments.

In recent years, the digitization and high-definition of devices that use optical systems are progressing rapidly. In the field of optical systems, there is an increasing demand to reduce the number of optical elements such as lenses and prisms used in the optical system, and to reduce the weight and size of the entire optical system.

Among optical glasses for producing optical elements, in particular, those having a refractive index (n _d ) of 1.70 or more and an Abbe number of 40 or more and 60 or less ( Demand for high-index, low-dispersion glasses with ν _d ) is very high. As such high-refractive-index, low-dispersion glasses, glass compositions represented by Patent Documents 1 to 3 are known.

JP-A-60-046948 Japanese Patent Application Laid-Open No. 2006-096610 Japanese Unexamined Patent Application Publication No. 2007-204317

Examples of the method of producing an optical element from optical glass include a method of grinding and polishing a gob or a glass block formed from optical glass to obtain the shape of an optical element, a method of obtaining the shape of an optical element, a gob or glass formed from optical glass. A method of grinding and polishing a glass molded body obtained by reheating and molding a block (reheat press molding), and molding a preform material obtained from a gob or a glass block with an ultra-precisely processed mold A method of obtaining the shape of an optical element by (precision mold press molding) is known. In any method, it is required that a stable glass can be obtained when a gob or a glass block is formed from a molten glass raw material. Here, when the stability against devitrification (devitrification resistance) of the glass constituting the obtained gob or glass block is lowered and crystals are generated inside the glass, it is no longer possible to obtain glass suitable as an optical element. Can not.

Further, in order to reduce the material cost of optical glass, it is desired that the raw material cost of various components constituting optical glass be as low as possible. In addition, in order to reduce the manufacturing cost of optical glass, it is desired that the raw material has high meltability and can be melted at a lower temperature. However, it is difficult to say that the glasses described in Patent Documents 1 to 3 sufficiently meet these requirements.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges during glass molding. To obtain a glass which has high stability, high devitrification resistance, is hardly colored, and has a reduced material cost.

In order to solve the above problems, the present inventors have conducted intensive testing and research, and as a result, combined use of ₃ B ₂ O components, ₃ La ₂ O components, and RO components, and SiO ₂ /B ₂ O ₃ By setting it within a predetermined range, while reducing the material cost of the glass, the stability during glass molding is high, it is difficult to color, and the liquidus temperature of the glass is low. Arrived. Specifically, the present invention provides the following.

(1) 10.5 to 50.5% by mass of B ₂ O ₃ component, 18.0 to 60.0% of La ₂ O ₃ component, 15.0% or less of ZnO component, and 5% by mass of RO component .0% or less and an optical glass having a mass ratio of SiO ₂ /B ₂ O ₃ of 0.5 or less (wherein R is one or more selected from the group consisting of Mg, Ca, Sr and Ba).

(2) The optical glass according to (1), wherein the mass ratio (TiO ₂ +Nb ₂ O ₅ +WO ₃ +Ta ₂ O ₅ )/(Y ₂ O ₃ +ZrO ₂ ) is 1.00 or less.

(3) Any one of (1) or (2) having a refractive index (n _d ) of 1.70 or more, an Abbe number (ν _d ) of 40 or more and 60 or less, and a liquidus temperature of 1300° C. or less optical glass.

(4) An optical element comprising the optical glass according to any one of (1) to (3) as a base material.

(5) An optical instrument comprising the optical element according to (4).

According to the present invention, a glass having a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges, which has high stability during glass molding, high devitrification resistance, and is difficult to be colored can be obtained. Obtainable.

The optical glass of the present invention contains 10.5 to 50.5% by mass of B ₂ O ₃ component, 18.0 to 60.0% by mass of La ₂ O ₃ component, 15.0% or less of ZnO component, and It contains an RO component of 5.0% or less and has a mass ratio of SiO ₂ /B ₂ O ₃ of 0.5 or less. B ₂ O ₃ components, La ₂ O ₃ components and RO components are used in combination, and the ratio of _{SiO 2} /B ₂ O ₃ is within a predetermined range. , the liquidus temperature tends to be low. Therefore, it is possible to obtain an optical glass having a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges and having high resistance to devitrification, and an optical element using the same at a lower cost.

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 at all, and can be carried out with appropriate modifications within the scope of the purpose of the present invention. be able to. It should be noted that descriptions of overlapping descriptions may be omitted as appropriate, but 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 this specification, the content of each component is expressed in % by mass with respect to the total mass of the glass in terms of oxide composition. Here, the term "composition converted to oxide" means that, when it is assumed that oxides, composite salts, metal fluorides, etc. used as raw materials for the constituent components of the glass of the present invention are all decomposed and changed into oxides when melted, It is a composition in which each component contained in the glass is expressed with the total mass of the produced oxide being 100% by mass.

<Regarding essential ingredients and optional ingredients>
The B ₂ O ₃ component is an indispensable component as a glass-forming oxide.
In particular, by containing 10.5% or more of the B ₂ O ₃ component, the devitrification resistance of the glass can be enhanced and the dispersion of the glass can be reduced. Therefore, the lower limit of the content of the B ₂ O ₃ component is preferably 10.5% or more, more preferably 11.8% or more, more preferably 16.8% or more, still more preferably 19.3% or more, and further preferably It is preferably 21.3% or more, more preferably 24.3% or more.
On the other hand, by setting the content of the B ₂ O ₃ component to 50.5% or less, a higher refractive index can be easily obtained, and deterioration of chemical durability can be suppressed. Therefore, the upper limit of the content of the B ₂ O ₃ component is preferably 50.5% or less, more preferably 45.5% or less, even more preferably 43.0% or less, still more preferably 40.5% or less, and further preferably It is preferably 38.0% or less.
For the B ₂ O ₃ component, H ₃ BO ₃ , Na ₂ B ₄ O ₇ , Na ₂ B ₄ O _{7.10H 2} O, BPO ₄ and the like can be used as raw materials.

The La ₂ O ₃ component is an essential component that increases the refractive index of the glass and reduces the dispersion (increases the Abbe number). In particular, a desired high refractive index can be obtained by containing 18.0% or more of the La ₂ O ₃ component. Therefore, the lower limit of the content of the La ₂ O ₃ component is preferably 18.0% or more, more preferably 20.5% or more, still more preferably 23.0% or more, still more preferably 25.5% or more. .
On the other hand, by setting the content of the La ₂ O ₃ component to 60.0% or less, the devitrification resistance of the glass can be enhanced. Therefore, the upper limit of the content of the La ₂ O ₃ component is preferably 60.0% or less, more preferably 57.5% or less, still more preferably less than 55.0%, still more preferably 52.5% or less. .
La ₂ O ₃ component, La ₂ O ₃ , La(NO ₃ ) ₃ .XH ₂ O (where X is an arbitrary integer), etc. can be used as raw materials.

The Y ₂ O ₃ component is an optional component that can reduce the material cost of the glass and reduce the specific gravity while maintaining a high refractive index and a high Abbe number by containing more than 0%. Therefore, the lower limit of the content of the Y ₂ O ₃ component is preferably more than 0%, more preferably 1.0% or more, still more preferably 1.5% or more, still more preferably 2.5% or more. Moreover, when the content of the Gd ₂ O ₃ component is 3.0% or less, the content of the Y ₂ O ₃ component is preferably 6.85% or more. By doing so, it is possible to obtain a glass excellent in devitrification resistance while reducing the specific gravity. Therefore, the lower limit of the content of the Y ₂ O ₃ component is preferably 6.85% or more, more preferably 7.85% or more, still more preferably 8.85% or more, and still more preferably 9.85% or more. .
On the other hand, by setting the content of the Y ₂ O ₃ component to 38.0% or less, the decrease in the refractive index of the glass can be suppressed and the devitrification resistance of the glass can be enhanced. Therefore, the upper limit of the content of the Y ₂ O ₃ component is preferably 38.0% or less, more preferably 33.0% or less, still more preferably 30.5% or less, still more preferably 23.3% or less, and further preferably It is preferably 20.8% or less. Moreover, when the Gd ₂ O ₃ component is contained, the content of the Y ₂ O ₃ component is preferably 9.5% or less. By doing so, deterioration of devitrification resistance due to excessive content can be suppressed. Therefore, the upper limit of the content of the Y ₂ O ₃ component is preferably 9.5% or less, more preferably 8.5% or less, still more preferably 7.5% or less, still more preferably 6.5% or less. .
_{Y2O3 , YF3 ,} etc. can be used as a raw material for the _Y2O3 component.

The ZnO component is an optional component that can lower the glass transition point and improve the chemical durability when contained in an amount exceeding 0%. Therefore, the lower limit of the content of the ZnO component is preferably more than 0%, more preferably 0.1% or more, and even more preferably 0.3% or more.
On the other hand, by setting the content of the ZnO component to 15.0% or less, a decrease in the refractive index of the glass and a decrease in devitrification resistance can be suppressed. Further, since the viscosity of the molten glass is increased by this, the occurrence of striae in the glass can be reduced. Therefore, the upper limit of the content of the ZnO component is preferably 15.0% or less, more preferably less than 10.0%, still more preferably less than 5.0%, still more preferably 2.5% or less, still more preferably 1 .23% or less, preferably less than 1.0%.
ZnO, _ZnF2 , etc. can be used as raw materials for the ZnO component.

The MgO component, CaO component, SrO component, and BaO component are optional components that can improve the meltability of glass raw materials when they are contained in an amount exceeding 0%.
On the other hand, if the content of each of the MgO component, CaO component, SrO component and BaO component is less than 5.0%, the stability during glass molding is improved, and the excessive content of these components reduces loss resistance. Suppresses permeability and suppresses a decrease in refractive index. Therefore, the upper limit of the content of each of the MgO component, CaO component, SrO component and BaO component is preferably less than 5.0%, more preferably less than 4.0%, still more preferably 2.0% or less, still more preferably is 1.0% or less.
MgO component, CaO component, SrO component and BaO component are MgCO3, _MgF2 , _CaCO3 , _CaF2 , Sr( _NO3 ) ₂ , _SrF2 , _{BaCO3, Ba(NO3)2 , BaF2 etc. as} raw materials. can be used.

The total content (mass sum) of the RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr and Ba) is preferably 5.0% or less. This suppresses a decrease in the refractive index of the glass and a decrease in devitrification resistance due to excessive inclusion of the RO component. Therefore, the upper limit of the mass sum of RO components is preferably 5.0% or less, more preferably 4.0% or less, still more preferably 2.0% or less, and even more preferably 1.0% or less.

The mass ratio of the sum of the contents of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) to the sum of the contents of the _three B ₂ O components and the SiO ₂ component is , 0.50 or less. As a result, it is possible to suppress a decrease in the refractive index of the glass and a decrease in the resistance to devitrification, and to increase the stability during molding of the glass. Therefore, the upper limit of the mass ratio RO/(B ₂ O ₃ +SiO ₂ ) is preferably 0.50 or less, more preferably 0.30 or less, still more preferably 0.10 or less, and still more preferably 0.07 or less. .

of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr and Ba) with respect to the sum of the contents of the _three Y ₂ O components, the _three Gd ₂ O components and the _three La ₂ O components The mass ratio of the sum of the contents is preferably 0.500 or less. Thereby, it is possible to increase the refractive index while suppressing deterioration in chemical durability. Therefore, the upper limit of the mass ratio RO/(Y ₂ O ₃ +Gd ₂ O ₃ +La ₂ O ₃ ) is preferably 0.500 or less, more preferably 0.250 or less, still more preferably 0.100 or less, further preferably 0.060 or less, more preferably 0.045 or less, more preferably 0.030 or less.

The content ratio of the SiO ₂ component to the B ₂ O ₃ component is preferably 0.500 or less. This makes it easier to obtain a higher refractive index, improves meltability, and enhances stability during glass molding. Therefore, the upper limit of the mass ratio SiO ₂ /B ₂ O ₃ is preferably 0.500 or less, more preferably 0.400 or less, still more preferably 0.300 or less, still more preferably 0.200 or less, still more preferably 0 .110 or less.

The SiO ₂ component is an optional component that can increase the viscosity of the molten glass, reduce the coloration of the glass, and improve the devitrification resistance when it is contained in an amount of more than 0%. Therefore, the lower limit of the content of the _SiO2 component is preferably more than 0%, more preferably 0.3% or more, still more preferably 0.6% or more, still more preferably more than 1.0%.
On the other hand, by setting the content of the SiO ₂ component to 18.3% or less, it is possible to suppress an increase in the glass transition point and a decrease in the refractive index. Therefore, the upper limit of the content of the _SiO2 component is preferably 18.3% or less, more preferably 13.3% or less, still more preferably 10.8% or less, still more preferably less than 7.5%, still more preferably 4.51% or less, more preferably less than 4.0%.
_SiO2 component can use _SiO2 , _K2SiF6 , _{Na2SiF6 etc.} as a _raw material.

The Gd ₂ O ₃ component is an optional component that can increase the refractive index and Abbe number of the glass when it is contained in an amount exceeding 0%.
Moreover, when the content of the Y ₂ O ₃ component is less than 10.0%, the content of the Gd ₂ O ₃ component is preferably 5.4% or more. By doing so, a glass excellent in devitrification resistance can be obtained. Therefore, the lower limit of the content of the Gd ₂ O ₃ component is preferably 5.4% or more, more preferably 7.9% or more, still more preferably 10.4% or more.
On the other hand, by reducing the Gd ₂ O ₃ component, which is particularly expensive among the rare earth elements, to less than 10.0%, the specific gravity of the glass can be kept low and the material cost of the glass can be kept low. In addition, it is possible to prevent the Abbe's number of the glass from increasing more than necessary. Therefore, the upper limit of the content of the Gd ₂ O ₃ component is preferably less than 10.0%, more preferably 5.0% or less, even more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably The content is preferably 0.1% or less, and from the viewpoint of reducing material costs, it may be substantially absent.
Moreover, when the content of the Y ₂ O ₃ component is less than 10.0%, the desired refractive index and Abbe number cannot be obtained. Therefore, the upper limit of the content of the Gd ₂ O ₃ component is preferably 35.0% or less, more preferably 32.5% or less, still more preferably 23.0% or less, still more preferably 18.3% or less, and further preferably It is preferably 15.8% or less.
For the Gd ₂ O ₃ component, Gd ₂ O ₃ , GdF ₃ and the like can be used as raw materials.

The Ta ₂ O ₅ component is an optional component that can increase the refractive index of the glass, improve the devitrification resistance, and increase the viscosity of the glass melt when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the expensive Ta ₂ O ₅ component to 10.0% or less, the material cost of the glass is reduced, so that a more inexpensive optical glass can be produced. In addition, this lowers the melting temperature of the raw material and reduces the energy required for melting the raw material, thereby reducing the manufacturing cost of the optical glass.
Therefore, the upper limit of the content of the Ta ₂ O ₅ component is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, still more preferably less than 1.0%,
From the viewpoint of reducing material costs, it may not be substantially included.
For the Ta ₂ O ₅ component, Ta ₂ O ₅ or the like can be used as a raw material.

The Li ₂ O component is an optional component that can improve the meltability of the glass and lower the glass transition point when contained in an amount exceeding 0%.
On the other hand, by setting the content of the Li ₂ O component to 10.0% or less, the viscosity of the glass is increased, so that the striae of the glass can be reduced. In addition, this makes it difficult for the refractive index of the glass to decrease, enhances the chemical durability of the glass, and enhances the resistance to devitrification. Therefore, the upper limit of the content of the Li ₂ O component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, more preferably less than 2.0%, and further preferably less than 2.0%. It is preferably less than 1.0%, more preferably less than 0.2%, and may be substantially absent.
Li ₂ CO ₃ , LiNO ₃ , Li ₂ CO ₃ and the like can be used as raw materials for the Li ₂ O component.

The Na ₂ O component, the K ₂ O component, and the Cs ₂ O component are optional components that can improve the meltability of the glass, increase the devitrification resistance of the glass, and lower the glass transition point when they are contained by more than 0%. is.
On the other hand, by setting the content of each of the Na ₂ O component, the K ₂ O component, and the Cs ₂ O component to 10.0% or less, it becomes difficult to lower the refractive index of the glass and the devitrification resistance is improved. Increased. Therefore, the upper limit of the content of each of the Na ₂ O component, K ₂ O component and Cs ₂ O component is preferably 10.0% or less, more preferably 5.0% or less, and still more preferably 3.0% or less. , more preferably less than 2.0%, more preferably less than 1.0%, and may be substantially free.
_Na2O component, _K2O component and _Cs2O component _{are NaNO3} , NaF, _{Na2SiF6 , K2CO3 , KNO3} , KF, _{KHF2 , K2SiF6} and _Cs2CO3 as raw materials. , CsNO ₃ and the like can be used.

The total amount of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, K and Cs) is preferably 15.0% or less. Thereby, the decrease in the refractive index of the glass can be suppressed and the devitrification resistance can be enhanced. Therefore, the mass sum of the Rn ₂ O components is preferably 15.0%, more preferably 10.0%, even more preferably less than 6.0%, more preferably less than 3.0%, still more preferably 1.0%. The upper limit is less than %.

The ZrO ₂ component is an optional component that, when contained in an amount exceeding 0%, can contribute to increasing the refractive index and decreasing the dispersion of the glass, and can improve the devitrification resistance of the glass. Therefore, the lower limit of the content of the ZrO ₂ component may be preferably more than 0%, more preferably 0.5% or more, even more preferably more than 1.0%, even more preferably more than 1.5%.
On the other hand, by setting the ZrO ₂ component to 15.0% or less, it is possible to suppress the decrease in devitrification resistance of the glass due to the excessive content of the ZrO ₂ component. Therefore, the upper limit of the content of the ZrO ₂ component is preferably 15.0% or less, more preferably 12.5% or less, still more preferably 10.0% or less, still more preferably 8.0% or less, further preferably Less than 6.0%, more preferably less than 5.0%.
For the ZrO ₂ component, ZrO ₂ , ZrF ₄ and the like can be used as raw materials.

The Al ₂ O ₃ component is an optional component that has the effect of improving devitrification resistance and chemical durability. Therefore, the lower limit of the content of the Al ₂ O ₃ component is preferably more than 0%, more preferably 0.5% or more, still more preferably 1.0% or more, still more preferably 1.5% or more, further preferably More than 2.0%, most preferably more than 3.0%. In particular, when the SiO ₂ component is 5.0% or more, the Al ₂ O ₃ component is preferably 1.0% or more. By doing so, it is possible to suppress the crystallization caused by the SiO ₂ component and obtain a glass excellent in devitrification resistance.
On the other hand, by setting the content of the Al ₂ O ₃ component to 20.0% or less, deterioration of devitrification resistance and a decrease in refractive index due to excessive content can be suppressed. Therefore, the upper limit of the content of the Al ₂ O ₃ component is preferably 20.0% or less, more preferably less than 15.0%, still more preferably 10.0% or less, still more preferably 8.0% or less, and further preferably It is preferably 5.0% or less.
_Al2O3 component can use _Al2O3 , Al(OH) _{3 , AlF3, Al(PO3)3 etc. as a raw} material.

The ratio of the sum of the contents of the Al ₂ O ₃ component and the ZnO component to the B ₂ O ₃ component is preferably 1.00 or less. This makes it possible to enhance the stability during glass molding and suppress the decrease in the refractive index. Therefore, the upper limit of the mass ratio (Al ₂ O ₃ +ZnO)/B ₂ O ₃ is preferably 1.00 or less, more preferably 0.50 or less, still more preferably 0.10 or less, and still more preferably 0.08 or less. , more preferably 0.05 or less, more preferably 0.03 or less.

The Yb ₂ O ₃ component is an optional component that can increase the refractive index of the glass and reduce the dispersion when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the Yb ₂ O ₃ component to 20.0% or less, the material cost of the glass is reduced, so that a more inexpensive optical glass can be produced. Moreover, the devitrification resistance of glass can be improved by this. Therefore, the upper limit of the content of the Yb ₂ O ₃ component is preferably 20.0% or less, more preferably less than 10.0%, still more preferably less than 5.0%, still more preferably less than 3.0%, and further preferably less than 3.0%. The content is preferably less than 1.0%, and may be substantially absent.
Yb ₂ O ₃ or the like can be used as a raw material for the Yb ₂ O ₃ component.

The sum of the contents (mass sum) of the _three Ln ₂ O components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is 40.5% or more and 75.0% or less. is preferred.
In particular, by making this sum 40.5% or more, the dispersion of the glass can be reduced. Therefore, the lower limit of the mass sum of Ln ₂ O ₃ components is preferably 40.5% or more, more preferably 43.0% or more, still more preferably 45.0% or more, still more preferably 47.5% or more, and further It is preferably 50.5% or more, more preferably 52.5% or more.
On the other hand, by setting the sum to 75.0% or less, the liquidus temperature of the glass is lowered, so that the devitrification resistance can be enhanced. Therefore, the upper limit of the mass sum of the Ln ₂ O ₃ components is preferably 75.0% or less, more preferably less than 70.0%, still more preferably less than 65.0%, and still more preferably 62.5% or less. .

The TiO ₂ component is an optional component that increases the refractive index of the glass, adjusts the Abbe's number to a low value, and increases the resistance to devitrification when the content exceeds 0%.
On the other hand, by setting the content of TiO ₂ to less than 15.0%, it is possible to reduce the coloration of the glass, increase the visible light transmittance, and prevent the Abbe number from decreasing more than necessary. In addition, devitrification due to excessive content of TiO ₂ component can be suppressed. Therefore, the upper limit of the content of the TiO ₂ component is preferably less than 15.0%, more preferably 10.0% or less, even more preferably less than 5.0%, still more preferably 3.0% or less, further preferably Less than 1.0%.
The _TiO2 component can use _TiO2 or the like as a raw material.

The Nb ₂ O ₅ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the Nb ₂ O ₅ component to 20.0% or less, the deterioration of the devitrification resistance of the glass and the deterioration of the visible light transmittance due to the excessive content of the Nb ₂ O ₅ component can be prevented. can be suppressed. Therefore, the upper limit of the content of the Nb ₂ O ₅ component is preferably 20.0% or less, more preferably 15.0% or less, still more preferably 10.0% or less, still more preferably 8.0% or less, and further preferably It is preferably less than 5.0%, more preferably 3.0% or less, still more preferably less than 1.5%, further preferably less than 1.0%.
_{Nb2O5 etc.} can be used as a raw material for the _{Nb2O5 component} .

The WO ₃ component is an optional component that can increase the refractive index and increase the devitrification resistance of the glass while reducing the coloring of the glass due to other high refractive index components when it is contained in an amount of more than 0%. The _WO3 component is also a component capable of lowering the glass transition point.
On the other hand, by setting the content of the WO ₃ component to 20.0% or less, it is possible to reduce the coloring of the glass due to the WO ₃ component and increase the visible light transmittance. Therefore, the upper limit of the content of the _three WO components is preferably 20.0% or less, more preferably 10.0% or less, even more preferably less than 5.0%, still more preferably 3.0% or less, and even more preferably Less than 1.0%.
_WO3 etc. can be used as a raw material for the _WO3 component.

The ratio of the sum of the contents of ₂ TiO components, ₅ Nb ₂ O components, ₅ Ta ₂ O components and ₃ WO components to the sum of the contents of ₃ Y ₂ O components and ₂ ZrO components is preferably 1.00 or less. This makes it possible to reduce the coloring of the glass and increase the visible light transmittance, thereby making it easier to obtain a desired Abbe number while reducing the cost. Therefore, the upper limit of the mass ratio (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(Y ₂ O ₃ +ZrO ₂ ) is preferably 1.00 or less, more preferably 0.80 or less, still more preferably 0 0.50 or less, more preferably 0.26 or less, more preferably 0.15 or less, still more preferably 0.10 or less.

The Ga ₂ O ₃ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%.
However, since Ga ₂ O ₃ is expensive as a raw material, a large content of Ga 2 O 3 results in an increase in production cost. Therefore, the upper limit of the content of the Ga ₂ O ₃ component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably It is preferably 0.1% or less. From the viewpoint of reducing material costs, the Ga ₂ O ₃ component may not be contained.
_{Ga2O3 etc.} can be used as a _raw material for the _Ga2O3 component.

The ratio of the sum of the contents of ₂ TiO components, ₅ Nb ₂ O components, ₅ Ta ₂ O components, ₂ ZrO components and ₃ WO components to the sum of the contents of ₃ B ₂ O components and ₂ SiO components is 1.00. The following are preferred. This makes it possible to increase the visible light transmittance by reducing the coloration of the glass while improving the devitrification resistance. Furthermore, it is easy to obtain a desired refractive index. Therefore, the upper limit of the mass ratio (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +ZrO ₂ +WO ₃ )/(B ₂ O ₃ +SiO ₂ ) is preferably 1.00 or less, more preferably 0.80 or less, and even more preferably is 0.60 or less, more preferably 0.50 or less, more preferably 0.34 or less.

The ratio of the sum of the contents of the _{three Y 2 O components, the ZnO component and the two ZrO components to the three Y 2 O components} is preferably 3.00 or less. This makes it possible to improve the resistance to devitrification, improve the stability during glass molding, and obtain a desired Abbe number without lowering the refractive index. Therefore, the mass ratio (Y ₂ O ₃ +ZnO + ZrO ₂ )/Y ₂ O ₃ is preferably 3.00, more preferably 2.00, still more preferably 1.75, still more preferably 1.50, still more preferably 1 .36, more preferably 1.34.

Ratio of the sum of the contents of ₂ TiO components, ₅ Nb ₂ O components, ₅ Ta ₂ O components, and ₃ WO components to the sum of the contents of ₃ Y ₂ O components, ₃ Gd ₂ O components, and ₃ La ₂ O components is preferably 1.00 or less. As a result, it is possible to increase the visible light transmittance by reducing the coloring of the glass while increasing the devitrification resistance, thereby reducing the raw material cost and increasing the refractive index. Therefore, the upper limit of the mass ratio (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(Y ₂ O ₃ +Gd ₂ O ₃ +La ₂ O ₃ ) is preferably 1.00 or less, more preferably 0.80. Below, it is more preferably 0.60 or less, more preferably 0.50 or less, still more preferably 0.34 or less, still more preferably 0.25 or less.

The P ₂ O ₅ component is an optional component that can improve the devitrification resistance of the glass when it is contained in an amount exceeding 0%. In particular, by setting the content of the P ₂ O ₅ component to 10.0% or less, it is possible to suppress the deterioration of the chemical durability of the glass, particularly the water resistance. Therefore, the upper limit of the content of the P ₂ O ₅ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably 3.0% or less, still more preferably less than 1.0%. .
Al(PO3) ₃ , Ca _{( PO3)2, Ba(PO3)2 , BPO4 , H3PO4 , etc. can be} used as raw materials for the P2O5 component.

The GeO ₂ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%. However, since the raw material price of GeO ₂ is high, if the amount of GeO 2 is large, the material cost will be high, and the effect of cost reduction by reducing the Ta ₂ O ₅ component and the like will be diminished. Therefore, the upper limit of the content of the GeO ₂ component is preferably less than 10.0%, more preferably less than 5.0%, even more preferably less than 2.5%, still more preferably 1.0% or less, and most preferably does not contain
The _GeO2 component can use _GeO2 or the like 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 contained in an amount exceeding 0%.
On the other hand, by setting the content of the Bi ₂ O ₃ component to 10.0% or less, it is possible to improve the devitrification resistance of the glass, reduce the coloration of the glass, and increase the visible light transmittance. Therefore, the upper limit of the content of the Bi ₂ O ₃ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably 3.0% or less, still more preferably less than 1.0%. .
_{Bi2O3 etc.} can be used as a _raw material for the _Bi2O3 component.

The TeO ₂ component is an optional component that can increase the refractive index and lower the glass transition point when contained in an amount exceeding 0%.
However, TeO ₂ has a problem that it can be alloyed with platinum when frit is melted in a crucible made of platinum or a melting tank in which the portion in contact with the molten glass is made of platinum. Therefore, the upper limit of the content of the TeO ₂ component is preferably 20.0% or less, more preferably 10.0% or less, still more preferably 5.0% or less, still more preferably 3.0% or less, and even more preferably is less than 1.0%, and may be substantially absent.
_The TeO2 component can use _TeO2 or the like as a raw material.

TiO ₂ component, Nb ₂ O ₅ component, Y ₂ O ₃ component, Ta ₂ O ₅ component, ZrO ₂ component, Al ₂ O ₃ component and WO ₃ component with respect to the sum of the contents of SiO ₂ component and B ₂ O ₃ component The ratio of the sum of the contents of is preferably 1.50 or less. By adjusting the ratio of the modified oxide to the desired range, it is possible to easily obtain a desired refractive index and Abbe number and to improve devitrification resistance. Therefore, the upper limit of the mass ratio (TiO ₂ +Nb ₂ O ₅ +Y ₂ O ₃ +Ta ₂ O ₅ +ZrO ₂ +Al ₂ O ₃ +WO ₃ )/(SiO ₂ +B ₂ O ₃ ) is preferably 1.50 or less, more preferably is 1.00 or less, more preferably 0.80 or less, still more preferably 0.60 or less, still more preferably 0.50 or less, still more preferably 0.34 or less.

The SnO ₂ component is an optional component that, when contained in excess of 0%, can reduce oxidation of the glass melt to refine it and increase the visible light transmittance of the glass.
On the other hand, by setting the SnO ₂ component content to 1.0% or less, it is possible to reduce the coloring of the glass due to the reduction of the molten glass and the devitrification of the glass. In addition, since alloying of SnO ₂ and melting equipment (especially precious metals such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the upper limit of the SnO ₂ component content is preferably 1.0% or less, more preferably 0.7% or less, and still more preferably 0.5% or less.
SnO ₂ component can use SnO, SnO ₂ , SnF ₂ , SnF ₄ etc. as raw materials.

The Sb ₂ O ₃ component is an optional component capable of defoaming the glass melt when it is contained in an amount exceeding 0%.
On the other hand, if the amount of Sb ₂ O ₃ is too large, the transmittance in the short wavelength region of the visible light region will deteriorate. Therefore, the upper limit of the content of the Sb ₂ O ₃ component is preferably 1.0% or less, more preferably 0.7% or less, still more preferably 0.5% or less.
For the Sb ₂ O ₃ component, Sb ₂ O ₃ , Sb ₂ O ₅ , Na ₂ H ₂ Sb ₂ O _{7.5H 2} O, etc. can be used as raw materials.

The component for fining and defoaming the glass is not limited to the above Sb ₂ O ₃ component, and any known fining agent, defoaming agent or combination thereof in the field of glass production can be used.

<Ingredients that should not be contained>
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 necessary within a range that does not impair the properties of the glass of the present invention. However, transition metal components such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo excluding Zn, Ta, Ti, Zr, Nb, W, La, Gd, Y, Yb and Lu are , even if they are contained alone or in combination in small amounts, the glass will be colored and have the property of causing absorption at specific wavelengths in the visible region. preferably not.

In addition, since lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components with a high environmental load, it is desirable that they are not substantially contained, that is, they are not contained at all except for unavoidable contamination.

In addition, Th, Cd, Tl, Os, Be, and Se components have recently tended to refrain from being used as hazardous chemical substances. Environmental measures are required up to the present. Therefore, it is preferable not to contain these substantially when environmental influence is emphasized.

[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 an electric furnace is used at 1100 to 1500 ° C. depending on the melting difficulty of the glass composition. for 2 to 5 hours, stirred and homogenized, lowered to an appropriate temperature, cast into a mold, and slowly cooled.

[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 lower limit of the refractive index (n _d ) of the optical glass of the present invention is preferably 1.70 or higher, more preferably 1.71 or higher, and even more preferably 1.72 or higher. The upper limit of this refractive index may be preferably 1.85 or less, more preferably 1.82 or less, still more preferably 1.80 or less, and even more preferably 1.78 or less. The lower limit of the Abbe number (ν _d ) of the optical glass of the present invention is preferably 40 or more, more preferably 45 or more, still more preferably 47 or more, and the upper limit is preferably 60 or less, more preferably 58 or less. It is more preferably 55 or less.
By having such a refractive index, it is possible to obtain a large amount of light refraction even if the thickness of the optical element is reduced. In addition, by having such low dispersion, even with a single lens, defocus (chromatic aberration) due to the wavelength of light is reduced. In addition, by having such low dispersion, it is possible to achieve high imaging characteristics and the like when combined with an optical element having high dispersion (low Abbe number), for example.
Therefore, the optical glass of the present invention is useful in optical design, and can reduce the size of the optical system and increase the degree of freedom in optical design while achieving particularly high imaging characteristics.

The optical glass of the present invention preferably has high devitrification resistance, more specifically, a low liquidus temperature. That is, the upper limit of the liquidus temperature of the optical glass of the present invention is preferably 1,300° C. or lower, more preferably 1,250° C. or lower, still more preferably 1,200° C. or lower, still more preferably 1,150° C. or lower, and still more preferably 1,100° C. or lower. . As a result, even if the molten glass flows out at a lower temperature, the crystallization of the produced glass is reduced, so that devitrification can be reduced particularly when the glass is formed from a molten state. can reduce the influence on the optical properties of Further, since the glass can be molded even if the melting temperature of the glass is lowered, the energy consumed in molding the glass can be suppressed, thereby reducing the manufacturing cost of the glass.
On the other hand, the lower limit of the liquidus temperature of the optical glass of the present invention is not particularly limited. It may be 700° C. or higher. In addition, the "liquidus temperature" in this specification is obtained by placing a 5 cc cullet-like glass sample in a platinum crucible with a capacity of 50 ml, completely melting it at 1350 ° C., and cooling it to a predetermined temperature. The temperature is the lowest temperature at which crystals are not observed, and the presence or absence of crystals on the glass surface and in the glass is observed immediately after the glass is taken out of the furnace and cooled. Here, the predetermined temperature when the temperature is lowered is the temperature in increments of 10°C up to 1300°C.

The optical glass of the present invention preferably has a high visible light transmittance, particularly a high transmittance for light on the short wavelength side of visible light, and is therefore less colored.
In particular, in the optical glass of the present invention, the upper limit of the wavelength (λ ₈₀ ) at which a sample with a thickness of 10 mm exhibits a spectral transmittance of 80% is preferably 500 nm or less, more preferably 450 nm or less, and further preferably 450 nm or less. It is preferably 420 nm or less.
In the optical glass of the present invention, the upper limit of the shortest wavelength (λ ₅ ) at which a sample with a thickness of 10 mm exhibits a spectral transmittance of 5% is preferably 380 nm or less, more preferably 360 nm or less, still more preferably 320 nm or less. It is preferably 300 nm or less.
As a result, the absorption edge of the glass is in the vicinity of the ultraviolet region, and the transparency of the glass to visible light is enhanced. Therefore, this optical glass can be preferably used for optical elements such as lenses that transmit light.

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 preferably 5.50 [g/cm ³ ] or less. As a result, the mass of the optical element and the optical equipment using the optical element is reduced, which contributes to the weight reduction of the optical equipment. Therefore, the upper limit of the specific gravity of the optical glass of the present invention is preferably 5.50 or less, more preferably 5.00 or less, even more preferably 4.70 or less, and even more preferably 4.50 or less. The lower limit of the specific gravity of the optical glass of the present invention is generally 3.00 or higher, more specifically 3.40 or higher, and still more specifically 3.80 or higher in many cases.
The specific gravity of the optical glass of the present invention is measured based on the Japan Optical Glass Industry Standard JOGIS05-1975 "Method for measuring specific gravity of optical glass".

[Glass molding and optical element]
A glass molded body can be produced from the produced optical glass by, for example, polishing means or mold press molding means such as reheat press molding or precision press molding. That is, optical glass is subjected to machining such as grinding and polishing to produce a glass molded body, or a preform made from optical glass is subjected to reheat press molding and then polished to form glass. It is also possible to manufacture a glass molded body by performing precision press molding on a preform manufactured by polishing, or a preform molded by known floating molding or the like. In addition, the means for producing the glass molded body is not limited to these means.

As described above, the glass molded body formed from the optical glass of the present invention is useful for various optical elements and optical designs. Among them, it is particularly preferable to use it for optical elements such as lenses and prisms. As a result, it is possible to form a glass molded body with a large diameter, so that it is possible to increase the size of the optical element and achieve high-definition and high-precision imaging characteristics and projection when used in optical equipment such as cameras and projectors. characteristics can be realized.

The compositions of the examples (No. 1 to No. 31) of the present invention and the comparative examples, and the refractive index (n _d ), Abbe number (ν _d ), liquidus temperature, and spectral transmittance of these glasses are 5%. and 80% (λ ₅ and λ ₈₀ ) and specific gravity results are shown in Tables 1-6. It should be noted that the following examples are for the purpose of illustration only, and the present invention is not limited only to these examples.

The glass of the examples of the present invention and the comparative example both contain ordinary optical glasses such as corresponding oxides, hydroxides, carbonates, nitrates, fluorides, hydroxides, metaphosphate compounds, etc. as raw materials for each component. After selecting the high-purity raw materials used for, weighing and mixing uniformly so that the composition ratio of each example shown in the table is obtained, it is put into a platinum crucible, and the glass composition is melted according to the degree of difficulty. After melting in an electric furnace at a temperature range of 1100 to 1500° C. for 2 to 5 hours, the mixture was stirred and homogenized, cast into a mold or the like, and slowly cooled to prepare a glass.

The refractive index (n _d ) and Abbe number (ν _d ) of the glasses of Examples and Comparative Examples are shown as measured values for the d-line (587.56 nm) of a helium lamp. The Abbe number (ν _d ) is the refractive index for the d-line, the refractive index (n _F ) for the hydrogen lamp F-line (486.13 nm), and the refractive index (n _C ) for the C-line (656.27 nm). was calculated from the formula Abbe number (ν _d )=[(n _d −1)/(n _F −n _C )] using the value of .

The transmittance of the glass of Examples and Comparative Examples was measured according to the Japan Optical Glass Industry Association Standard JOGIS02-2003. 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, according to JISZ8722, a parallel polished product with a thickness of 10 ± 0.1 mm is measured for spectral transmittance from 200 to 800 nm, and λ ₅ (wavelength at 5% transmittance), λ ₈₀ (transmittance wavelength at 80%) was obtained.

In addition, the liquidus temperature of the glass of the examples and comparative examples was 1300 to 1160°C when a cullet-like glass sample of 5cc was placed in a platinum crucible with a capacity of 50ml and completely melted at 1350°C. The temperature is lowered to any temperature set in increments of 10 ° C. and held for 12 hours, and immediately after removing from the furnace and cooling, the presence or absence of crystals on the glass surface and in the glass is observed. asked for the temperature.

The specific gravity of the glass of Examples and Comparative Examples was measured based on the Japan Optical Glass Industry Standard JOGIS05-1975 "Method for measuring specific gravity of optical glass".

All of the optical glasses of the examples of the present invention had a liquidus temperature of 1300° C. or lower, more specifically 1200° C. or lower, which was within the desired range. Therefore, it was found that the optical glasses of the examples of the present invention have a low liquidus temperature and a high devitrification resistance.

Further, the optical glasses of the examples of the present invention all had λ ₈₀ (wavelength at transmittance of 80%) of 500 nm or less, more specifically 435 nm or less. In addition, the optical glasses of the examples of the present invention all had λ ₅ (wavelength at transmittance of 5%) of 380 nm or less, more specifically 324 nm or less.

Further, the optical glasses of the examples of the present invention all have a refractive index (n _d ) of 1.70 or more, more specifically 1.71 or more, and this refractive index is 1.85 or less, more specifically was 1.82 or less, which was within the desired range.

Further, the optical glasses of the examples of the present invention all have an Abbe number (ν _d ) of 40 or more, more specifically 44 or more, and this Abbe number is 60 or less, more specifically 57 or less, within the desired range.

Further, the optical glasses of the examples of the present invention all had a specific gravity of 5.50 or less, more specifically 5.10 or less, which was within the desired range.

Therefore, it has been clarified that the optical glasses of the examples of the present invention have a refractive index and an Abbe number within the desired ranges, have high resistance to devitrification, are less colored, and have a small specific gravity.

On the other hand, since the optical glass of Comparative Example A has an RO component of 5.0% or more, a desired refractive index cannot be obtained.

Furthermore, using the optical glass of the example of the present invention, a glass block was formed, and this glass block was ground and polished to be processed into the shapes of lenses and prisms. As a result, it was possible to stably process various lens and prism shapes.

Although the invention has been described in detail for purposes of illustration, the examples are for illustration only and many modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. be understood.

Claims (3)

16.8 to 50.5% by mass of the B ₂ O ₃ component,
18.0 to 48.00 % of the La ₂ O ₃ component,
8.85 to 20.8% Y ₂ O ₃ component,
ZnO component less than 5.0% and
containing 3.0% or less of Bi ₂ O ₃ component ,
The sum of the mass of the RO components is 2.0% or less ,
mass sum of Ln ₂ O ₃ components is 40.5 to 62.5%;
a mass ratio of SiO ₂ /B ₂ O ₃ of 0.105 or less ;
mass ratio (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +ZrO ₂ +WO ₃ )/(B ₂ O ₃ +SiO ₂ ) is 0.093 or less ;
mass ratio (Al ₂ O ₃ +ZnO)/B ₂ O ₃ is 0.03 or less ;
mass ratio (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ )/(Y ₂ O ₃ +ZrO ₂ ) is 0.1 or less;
mass ratio RO/(Y ₂ O ₃ +Gd ₂ O ₃ +La ₂ O ₃ ) is 0.045 or less;
mass ratio ₍ Y2O3 ₊ ZnO ₊ ZrO2)/ _Y2O3 is 1.34 or less _,
Optical glass having a refractive index (nd) of 1.752 or more, an Abbe number (νd) of 51.91 or more and 60 or less, and a liquidus temperature of 1300° C. or less (in the formula, R is Mg, Ca, Sr, one or more selected from the group consisting of Ba , Ln is one or more selected from the group consisting of La, Gd, Y, and Yb ). An optical element comprising the optical glass according to claim 1 as a base material. An optical instrument comprising the optical element according to claim 2 .