JP7503163B2 - Optical glass, preforms and optical elements - Google Patents

Description

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

In recent years, optical elements incorporated in on-board optical devices such as on-board cameras, and optical elements incorporated in optical devices that generate a lot of heat, such as projectors, copy machines, laser printers, and broadcasting equipment, are increasingly being used in higher temperature environments. In such high-temperature environments, the temperature of the optical elements that make up the optical system tends to fluctuate significantly during use, and in many cases the temperature can reach 100°C or higher. In such cases, the adverse effects of temperature fluctuations on the imaging characteristics of the optical system become significant enough to be ignored, so there is a demand to construct an optical system whose imaging characteristics are less susceptible to effects from temperature fluctuations.

When constructing an optical system that is less susceptible to the effects of temperature fluctuations on imaging characteristics, etc., it is preferable to use optical elements made of glass whose refractive index decreases as the temperature increases and whose temperature coefficient of the relative refractive index is negative, in addition to optical elements made of glass whose refractive index increases as the temperature increases and whose temperature coefficient of the relative refractive index is positive, in that the effects of temperature changes on imaging characteristics, etc. can be corrected.

Here, examples of glass that have been developed with a focus on the temperature coefficient of the relative refractive index include glass compositions such as those shown in Patent Document 1.

JP 2007-106611 A

The glass described in Patent Document 1 is glass that contains many components that provide a high refractive index, and is intended to increase the temperature coefficient of the relative refractive index. On the other hand, no glass that contains many components that provide a high refractive index has a small temperature coefficient of the relative refractive index. However, from the perspective of being able to contribute to correcting the effects of temperature changes on imaging characteristics, there is also a demand for glass that has a negative temperature coefficient of the relative refractive index or glass with a small absolute value of the temperature coefficient of the relative refractive index.

In addition, when performing optical design, a low refractive index, low dispersion glass material may be bonded to a high refractive index, high dispersion glass material, and the smaller the difference in the average linear thermal expansion coefficient of the glass materials combined at the time of bonding, the better the bond. In particular, low refractive index, low dispersion glass materials that contain fluorine are known to have a large average linear thermal expansion coefficient, but there are almost no high refractive index, high dispersion glass materials with a large average linear thermal expansion coefficient, and glass materials with a large average linear thermal expansion coefficient are required. The glass described in Patent Document 1 has a small average linear thermal expansion coefficient and cannot be said to fully meet such demands.

In addition, the optical glass of the present invention can be produced at a lower cost because it has excellent transmittance in the visible light range without the need for a process of reheating and heat treating the glass to remove coloration.

The present invention was made in consideration of the above problems, and its purpose is to obtain a preform and an optical element using optical glass that has a small temperature coefficient of relative refractive index and can contribute to correcting the effect of temperature changes on imaging characteristics, and that has an average linear thermal expansion coefficient suitable for bonding with low refractive index, low dispersion glass material.

The present inventors have conducted _extensive research and testing to solve the above problems, and have found that an inexpensive glass having a low temperature coefficient of relative refractive index can be obtained by containing _{P2O5 and Nb2O5 components} and predetermined amounts of _Na2O and _K2O components, thereby completing the present invention. Specifically, the present invention provides the following:

(1) In mass percent,
_P2O5 component _20.0 to 40.0%,
_Nb2O5 component _25.0 to 50.0%,
The sum of mass (Na ₂ O + K ₂ O) is 3.0 to 30.0%,
Contains
An optical glass having a temperature coefficient (40 to 60° C.) of the relative refractive index (589.29 nm) within the range of +3.0×10 ^-6 to -10.0×10 ^-6 (° C. ^-1 ).

(2) The optical glass according to (1), characterized in that the sum by mass of (Na ₂ O+K ₂ O+BaO) is 10.0 to 35.0%.

(3) The optical glass according to (1) or (2), characterized in that the average linear thermal expansion coefficient α at 100 to 300° C. is 80 (10 ⁻⁷ ° C. ⁻¹ ) or more.

(4) The optical glass according to any one of (1) to (3), which has a refractive index (n _d ) of 1.65 or more and 2.00 or less, and an Abbe number (ν _d ) of 10 or more and 35 or less.

(5) A preform made of the optical glass described in any one of (1) to (4).

(6) An optical element made of the optical glass according to any one of (1) to (4).

(7) An optical device comprising the optical element described in (6).

According to the present invention, optical glass that has a small temperature coefficient of relative refractive index, contributes to correcting the effect of temperature changes on imaging characteristics, and has good transmittance in visible light, as well as preforms and optical elements using this, can be obtained more inexpensively.

The optical glass of the present invention contains, by mass, 20.0% or more and 40.0% or less of _{a P2O5} component, 25.0% or more and 50.0% or less in total of _{a Nb2O5} component, and the sum of the masses of a _Na2O component and a _K2O component is 3.0% or more and 30.0% or less, and has a temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) in the range of +3.0 x ^10-6 to -10.0 x ^10-6 (°C ^-1 ).
By containing a large amount of Na ₂ O and K ₂ O, it is possible to obtain a glass material having a small temperature coefficient of relative refractive index and a large average linear thermal expansion coefficient.
Therefore, optical glass that has good transmittance in visible light while having a small temperature coefficient of the relative refractive index, can contribute to correcting the effects of temperature changes on imaging characteristics, has good bonding ability with low refractive index, low dispersion glass materials, and has good transmittance in visible light, as well as preforms and optical elements using this optical glass can be obtained at lower cost.

The following is a detailed description of the embodiments of the optical glass of the present invention. The present invention is not limited to the following embodiments, and can be practiced with appropriate modifications within the scope of the object of the present invention. Note that duplicated explanations may be omitted as appropriate, but this does not limit the spirit of the invention.

[Glass components]
The composition range of each component constituting the optical glass of the present invention is described below. In this specification, the content of each component is expressed as mass% relative to the total mass of the composition converted into oxides, unless otherwise specified. Here, the "composition converted into oxides" refers to a composition that expresses each component contained in the glass, assuming that the oxides, composite salts, metal fluorides, etc. used as raw materials for the glass components of the present invention are all decomposed and converted into oxides during melting, with the total mass of the generated oxides being 100 mass%.

<Required and optional ingredients>
_{The P2O5 component} is _an essential component as a glass-forming oxide. In particular, by containing 20.0% or more of the _P2O5 component, the viscosity of the molten glass is improved and the stability of the glass is enhanced. In addition, the devitrification resistance during reheat pressing is improved. Therefore, the content of _{the P2O5} component is preferably 20.0% or more, more preferably more than 21.0%, and even more preferably more than 22.0%.
On the other hand, by making the content of the _P2O5 component 40.0% or less, it is possible to maintain the desired _refractive index and dispersion. Therefore, the content of _{the P2O5 component} is preferably 40.0% or less, more preferably 35.0% or less, and even more preferably less than 30.0%.
As the _P2O5 component, Al( _{PO3 ) 3} , Ca( _{PO3 ) 2} , Ba( _PO3 ) ₂ , _BPO4 , _H3PO4 , _{NaH2PO4 , KH2PO4 ,} etc. can be used as raw materials.

_{The Nb2O5 component} is an essential component as a high refractive index _and high dispersion component. In particular, by containing 25.0% or more of the _Nb2O5 component, the stability of the glass can be improved while maintaining a high refractive index and high dispersion. Therefore, the content of _{the Nb2O5} component is preferably 25.0% or more, more preferably more than 28.0%, and even more preferably more than 30.0%.
On the other hand, by making the content of the _Nb2O5 component 50.0% or less, the average linear thermal expansion coefficient is large and the desired refractive index and dispersion can be maintained. Therefore, the content of the _Nb2O5 component is preferably 50.0% or less, more preferably 47.0% or less. As _{the Nb2O5 component} , _Nb2O5 or _{the like} can be used as _a raw material.

The _Na2O component is an optional component that, when contained in an amount of more than 0%, can improve the meltability of glass raw materials, improve the transmittance, and reduce the temperature coefficient of the relative refractive index. Therefore, the content of the _Na2O component is preferably more than 0%, more preferably more than 0.1%, even more preferably more than 0.5%, even more preferably more than 1.0%, even more preferably more than 1.5%, and even more preferably more than 2.0%.
In particular, when the content exceeds 10.0%, the effect of reducing the temperature coefficient of the relative refractive index is enhanced and the meltability of the glass is also improved, so that the content may be more than 10.0%.
On the other hand, by making the content of the _Na2O component 35.0% or less, it is possible to reduce the decrease in the refractive index of the glass, the decrease in chemical durability (water resistance), and devitrification caused by excessive inclusion, and it is possible to suppress devitrification during reheat pressing. Therefore, the content of the _Na2O component is preferably 35.0% or less, more preferably less than 30.0%, even more preferably less than 25.0%, and even more preferably less than 20.0%.
As the _Na2O component, _{Na2CO3 , NaNO3} , NaF, _{Na2SiF6 ,} etc. can be used as a raw material.

The _K2O component is an optional component that, when contained in an amount of more than 0%, can increase the average linear thermal expansion coefficient, improve the transmittance, and reduce the temperature coefficient of the relative refractive index. Therefore, the content of the _K2O component may be preferably more than 0%, more preferably 0.5% or more, even more preferably more than 1.0%, and even more preferably more than 2.0%.
In particular, when the content exceeds 5.0%, the effect of reducing the temperature coefficient of the relative refractive index is enhanced and the stability of the glass is also improved, so that the content may exceed 5.0%.
On the other hand, by making the content of the _K2O component 30.0% or less, the stability of the glass can be maintained and a decrease in the refractive index can be suppressed. Therefore, the content of the _K2O component is preferably 30.0% or less, more preferably less than 25.0%, even more preferably less than 20.0%, and even more preferably less than 15.0%.
As the _K2O component, _K2CO3 , _KNO3 , KF, _{KHF2 , K2SiF6 ,} etc. can be used.

The BaO component is an optional component that, when contained at more than 0%, can improve the melting property of glass raw materials, reduce devitrification of glass, increase the refractive index, and reduce the temperature coefficient of relative refractive index. In addition, among components that bring about a high refractive index, the BaO component has low material cost and is easily melted. Therefore, the content of the BaO component is preferably more than 0%, more preferably more than 0.1%, even more preferably more than 1.0%, and even more preferably more than 2.0%.
On the other hand, by setting the content of the BaO component to 20.0% or less, the average linear thermal expansion coefficient is large, and the decrease in the refractive index of the glass and devitrification due to excessive content can be reduced. Therefore, the content of the BaO component is preferably set to 20.0% or less, more preferably less than 19.0%, and further preferably less than 18.0%.
As the BaO component, BaCO ₃ , Ba(NO ₃ ) ₂ , Ba(PO ₃ ) ₂ , BaF ₂ , etc. can be used as a raw material.

When the _TiO2 component is contained in an amount of more than 0%, it is a component that can increase the refractive index of the glass, reduce the Abbe number, and make it easier to obtain a stable glass. Therefore, the content of the _TiO2 component may be preferably more than 0%, more preferably more than 1.0%, even more preferably more than 3.0%, and even more preferably 5.0% or more.
On the other hand, by making the content of the _TiO2 component 30.0% or less, the average linear thermal expansion coefficient is large, the temperature coefficient of the relative refractive index is small, devitrification due to excessive inclusion of the _TiO2 component is reduced, and the decrease in the transmittance of the glass to visible light (especially wavelengths of 500 nm or less) is suppressed. Therefore, the content of the _TiO2 component may be preferably 30.0% or less, more preferably less than 26.0%, even more preferably less than 23.0%, and even more preferably less than 20.0%.
As the _TiO2 component, _TiO2 or the like can be used as a raw material.

The _SiO2 component is a glass-forming oxide component that can improve the viscosity of the molten glass when the content is more than 0%. Therefore, the content of the _SiO2 component is preferably more than 0%, more preferably more than 0.1%, and even more preferably more than 0.3%.
On the other hand, by making the content of the _SiO2 component 5.0% or less, the increase in the glass transition point and the decrease in the refractive index can be suppressed. Therefore, the content of the _SiO2 component is preferably 5.0% or less, more preferably 3.0% or less, and further preferably less than 1.0%.
As the _SiO2 component, _SiO2 , _K2SiF6 , _{Na2SiF6 , etc.} can be used as raw materials.

The _B2O3 component, when contained in _an amount exceeding 0%, is a component that is optionally used as a glass-forming oxide capable of increasing the meltability of glass.
On the other hand, by making the content of _{the B2O3} component 5.0% or less, the temperature coefficient of the relative refractive index can be made small, deterioration of chemical durability can be suppressed, and deterioration of devitrification during reheat pressing can be reduced. Therefore, the content of _{the B2O3} component is preferably 5.0% or less, more preferably 3.0% or less, more preferably less than 1.5%, and even more preferably less than 1.3%.

The _WO3 component is an optional component that, when contained in excess of 0%, can increase the refractive index, lower the Abbe number, lower the glass transition point, and reduce devitrification while reducing the coloring of the glass due to other components that impart a high refractive index.
On the other hand, by making the content of the _WO3 component 10.0% or less, the temperature coefficient of the relative refractive index can be reduced, and devitrification during reheat pressing can be suppressed. Also, the coloring of the glass caused by the _WO3 component can be reduced, and the visible light transmittance can be increased. Therefore, the content of the _WO3 component may be preferably 10.0% or less, more preferably less than 9.0%, even more preferably less than 8.0%, even more preferably less than 6.5%, and even more preferably less than 5.0%.
As the _WO3 component, _WO3 or the like can be used as a raw material.

ZnO is an optional component that, when contained at more than 0%, can increase the melting property of the raw material, promote degassing from the molten glass, and increase the stability of the glass. It is also a component that can lower the glass transition temperature and improve the chemical durability.
On the other hand, by making the content of the ZnO component less than 5.0%, the temperature coefficient of the relative refractive index can be reduced, the expansion due to heat can be reduced, the decrease in the refractive index can be suppressed, and devitrification due to an excessive decrease in viscosity can be reduced. Therefore, the content of the ZnO component may be preferably less than 5.0%, more preferably less than 4.0%, even more preferably less than 2.0%, even more preferably less than 1.0%, and even more preferably less than 0.5%. In addition, the ZnO component may not be contained.
As the ZnO component, ZnO, _ZnF2 , etc. can be used as the raw material.

The _ZrO2 component is an optional component that can increase the refractive index of the glass and reduce devitrification when contained in an amount of more than 0%. Therefore, the content of the _ZrO2 component may be preferably more than 0%, more preferably more than 0.5%, and even more preferably more than 1.0%.
On the other hand, by making the content of the _ZrO2 component 5.0% or less, the temperature coefficient of the relative refractive index can be made small, and devitrification due to excessive inclusion of the _ZrO2 component can be reduced. Therefore, the content of the _ZrO2 component may be preferably 5.0% or less, more preferably 3.0% or less, even more preferably less than 1.0%, and even more preferably less than 0.5%. In addition, the _ZrO2 component may not be contained.
As the _ZrO2 component, _ZrO2 , _ZrF4 , etc. can be used as raw materials.

The MgO component, the CaO component and the SrO component are optional components that, when contained in an amount of more than 0%, can adjust the refractive index, meltability and devitrification resistance of the glass.
On the other hand, by making the contents of the MgO, CaO and SrO components 5.0% or less, it is possible to suppress the decrease in the refractive index and reduce devitrification due to the excessive inclusion of these components. Therefore, the contents of the MgO, CaO and SrO components are each preferably 5.0% or less, more preferably 3.5% or less, and further preferably less than 2.0%.

The Li ₂ O component is an optional component that can improve the melting properties of the glass and lower the glass transition point.
On the other hand, by reducing the content of the _Li2O component, it is possible to make it difficult to lower the refractive index of the glass and to reduce devitrification of the glass and devitrification during reheat pressing. Therefore, the content of the _Li2O component may be preferably 5.0% or less, more preferably less than 3.0%, even more preferably 1.0% or less, and even more preferably less than 0.5%.
As the Li ₂ O component, Li ₂ CO ₃ , LiNO ₃ , LiF, etc. can be used as the raw material.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components which, when contained in an amount exceeding 0%, can improve the devitrification resistance of the molten glass.
On the other hand, by making the content of the _Al2O3 component or the _Ga2O3 component 10.0% or less, the liquidus temperature of the glass can be lowered _and the _{devitrification} resistance can be improved. Therefore, the contents of _{the Al2O3 component} and _{the Ga2O3} component may be preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, and even more preferably less than 1.0%.
For the _Al2O3 component, _Al2O3 , Al(OH) ₃ , _{AlF3, etc.} can be used as raw materials, _and for the _Ga2O3 component _{, Ga2O3 , etc.} can be used as raw materials.

The Sb ₂ O ₃ component is an optional component that can degas the molten glass when its content exceeds 0%.
On the other hand, by making the content of _{Sb2O3 component} 1.0% or less, it is possible to suppress the decrease in transmittance in the short wavelength region of the visible light region, the solarization of the glass, and the deterioration of the internal quality. Therefore, the content of _{Sb2O3 component} may be preferably 1.0% or less, more preferably less than 0.5%, more preferably less than 0.2%, and even more preferably less than 0.1%.
As _{the Sb2O3} component, _{Sb2O3 , Sb2O5} , _{Na2H2Sb2O7.5H2O , etc. can} be _used as raw materials _.

The total content of the _Na2O component and the _K2O component is preferably 3.0% or more. This makes it easier to obtain glass with a small temperature coefficient of relative refractive index, a large average linear thermal expansion coefficient, and good transmittance. Therefore, the mass sum ( _Na2O + _K2O ) is preferably 3.0% or more, more preferably more than 4.0%, more preferably more than 5.0%, and even more preferably more than 6.0%.
On the other hand, by keeping the total content at 30.0% or less, deterioration of chemical durability and a decrease in the refractive index of the glass due to excessive content can be suppressed. Therefore, the mass sum ( _Na2O + _K2O ) is preferably 30.0% or less, more preferably less than 25.0%, and further preferably less than 23.0%.

The total content of the Na ₂ O component, the K ₂ O component and the BaO component is preferably 10.0% or more, which makes it easier to obtain a glass having a small temperature coefficient of the relative refractive index.
Therefore, the mass sum (Na ₂ O+K ₂ O+BaO) is preferably 10.0% or more, more preferably more than 12.0%, more preferably more than 14.0%, more preferably 16.0% or more, and even more preferably more than 17.5%.
On the other hand, by making the total content less than 35.0%, it is possible to suppress deterioration of chemical durability, a decrease in the refractive index of the glass due to an excessive content, and a decrease in devitrification during reheat pressing. Therefore, the mass sum ( _Na2O + _K2O +BaO) is preferably 35.0%, more preferably 33.0% or less, and further preferably less than 30.0%.

The total content of _{the Nb2O5} component and the _TiO2 component is preferably 30.0% or more, which makes it possible to reduce the temperature coefficient of the relative refractive index while maintaining a high refractive index.
Therefore, the mass sum (Nb ₂ O ₅ +TiO ₂ ) is preferably 30.0% or more, more preferably 35.0% or more, and further preferably 40.0% or more.
On the other hand, by making the mass sum ( _Nb2O5 + _TiO2 ) 65.0% or less, the liquidus temperature can be _lowered and a stable glass can be obtained. Therefore, the mass sum ( _Nb2O5 + _TiO2 ) is preferably 65.0% or less, more preferably 63.0% _or less, and further preferably 60.0% or less.

The ratio of _Na2O , _K2O and BaO to the total content of _B2O3 and _TiO2 is preferably more than 0.5. This allows the temperature coefficient of the relative refractive index to be _small and the average linear thermal expansion coefficient to be large _. Therefore, the mass ratio ( _Na2O + _K2O +BaO)/( _B2O3 + _TiO2 ) is preferably more than 0.5, more preferably more than 0.7, and even more preferably more than 1.0.
On the other hand, by making the mass ratio ( _Na2O + _K2O +BaO) _/ ( _B2O3 + _TiO2 ) less than 5.5, it is possible to obtain a glass that is excellent in reheat pressing while maintaining the desired refractive index and transmittance. Therefore, the mass ratio ( _Na2O + _K2O +BaO)/ _{( B2O3} + _TiO2 ) is preferably less than 5.5, more preferably less than 5.0, and even more preferably less than 4.8.

By making the sum (sum of mass) of the contents of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) more than 0%, the refractive index of the glass can be increased, and the melting property and devitrification resistance can be improved. Therefore, the lower limit of the sum (sum of mass) of the contents of RO components is preferably more than 0%, more preferably more than 0.5%, and even more preferably more than 1.0%. On the other hand, by making the RO components 30.0% or less, the average linear thermal expansion coefficient is large, and the decrease in the refractive index of the glass and devitrification due to excessive inclusion can be reduced. Therefore, the upper limit of the sum (sum of mass) of the contents of RO components is preferably 30.0% or less, more preferably 25.0% or less, and even more preferably 20.0% or less.

The _{La2O3 component} , _{Gd2O3 component} , _Y2O3 component, _Yb2O3 component and _{Ta2O5 component} are _optional components _which , when contained in an amount exceeding 0%, can increase the refractive index of the glass and can also increase the resistance to devitrification.
On the other hand, by making _the content of _La2O3 , _Gd2O3 , _{Y2O3 , Yb2O3} and _Ta2O5 less than _{5.0 %} , the raw material cost of the optical glass can be reduced, and the melting temperature of the raw materials is lowered, and the energy required for melting the raw materials is reduced, so that the manufacturing cost of the _optical glass can be reduced. Therefore, the content of each of these components may be preferably less than 5.0%, more preferably less than 3.0%, more preferably less than 2.0%, and even more preferably less than 1.0%.

The GeO ₂ component is an optional component that, when contained in an amount exceeding 0%, can increase the refractive index of the glass and improve the devitrification resistance.
However, the raw material price of _GeO2 is high, and the production cost increases if the content is high. Therefore, the content of _GeO2 component may be preferably 10.0% or less, more preferably less than 5.0%, more preferably less than 3.0%, and even more preferably less than 1.0%.
As the _GeO2 component, _GeO2 or the like can be used as a raw material.

The _Bi2O3 component is an optional component that, when contained in _an amount exceeding 0%, can increase the refractive index, decrease the Abbe number, and lower the glass transition point.
On the other hand, by making the content of the _Bi2O3 component 5.0% or less, the liquidus temperature of the glass can be lowered and the _{devitrification} resistance can be improved. Therefore, the content of _{the Bi2O3 component} may be preferably 5.0% or less, more preferably less than 3.0%, and even more preferably less than 1.0%. In particular, from the viewpoint of obtaining glass with good transmittance, it is preferable that the Bi2O3 component is not contained.
As _{the Bi2O3 component} , _Bi2O3 or _the like can be used as a raw material.

The _TeO2 component is an optional component that, when contained in an amount exceeding 0%, can increase the refractive index and lower the glass transition point.
On the other hand, there is a problem that _TeO2 may be alloyed with platinum when melting glass raw materials in a platinum crucible or a melting tank whose part in contact with the molten glass is made of platinum. Therefore, the content of _TeO2 component may be preferably 10.0% or less, more preferably less than 5.0%, more preferably less than 3.0%, and even more preferably less than 1.0%.
As the _TeO2 component, _TeO2 or the like can be used as a raw material.

The _SnO2 component is an optional component that, when contained in an amount of more than 0%, reduces the oxidation of the molten glass to clarify it and also increases the visible light transmittance of the glass.
On the other hand, by making the content of the _SnO2 component 3.0% or less, it is possible to reduce coloration of the glass due to reduction of the molten glass and devitrification of the glass. In addition, alloying of the _SnO2 component with the melting equipment (especially precious metals such as Pt) is reduced, so that the life of the melting equipment can be extended. Therefore, the content of the _SnO2 component may be preferably 3.0% or less, more preferably less than 1.0%, even more preferably less than 0.5%, and even more preferably less than 0.1%.
As the _SnO2 component, SnO, _SnO2 , _SnF2 , _SnF4 , etc. can be used as raw materials.
The components for clarifying and defoaming the glass are not limited to the above Sb ₂ O ₃ component and SnO ₂ component, and any fining agent, defoaming agent or combination thereof known in the field of glass manufacturing can be used.

The F component is an optional component which, when contained in an amount of more than 0%, can increase the Abbe number of the glass, lower the glass transition point, and improve resistance to devitrification.
However, when the content of the F component, i.e., the total amount of F in the fluorides which have substituted a part or all of the oxides of one or more of the above-mentioned metal elements, exceeds 10.0%, the amount of volatilization of the F component increases, making it difficult to obtain stable optical constants and homogeneous glass, and the Abbe number increases more than necessary.
Therefore, the content of the F component may be preferably 10.0% or less, more preferably less than 5.0%, more preferably less than 3.0%, and further preferably less than 1.0%.
The F component can be contained in the glass by using, for example, ZrF ₄ , AlF ₃ , NaF, CaF ₂ or the like as a raw material.

The ratio of the content of the _SiO2 component, the _Al2O3 component _, and the ZnO component to the total content of _{the B2O3} component and the _Rn2O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is preferably 15.0 or less. By reducing this ratio, deterioration of the melting property can be suppressed.
_Therefore , the mass ratio ( _SiO2 + _Al2O3 +ZnO)/( _B2O3 + _Rn2O ) is preferably 15.0 or less, more preferably 12.0 or less, more preferably 10.0 or _less , more preferably 8.0 or less, more preferably 6.0 or less, and even more preferably less than 5.0.
On the other hand, the mass ratio ( _{SiO2 + Al2O3} +ZnO)/( _B2O3 + _Rn2O ) can be made to be greater than 0. This can reduce the temperature coefficient of the relative refractive index and increase the average linear thermal expansion _coefficient . Therefore, the _mass ratio ( _SiO2 + _Al2O3 +ZnO)/( _B2O3 + _Rn2O ) is preferably greater than 0, more preferably greater than _1.0 , and even more preferably greater than 2.0.

The temperature coefficient of the relative refractive index can be reduced and the average linear thermal expansion coefficient can be increased by containing the sum of the contents (sum of mass) of _Rn2O components (wherein Rn is one or more selected from the group consisting of Li, Na, and K) of more than 1.0%. Therefore, the sum of the contents (sum of mass) of _Rn2O components is preferably more than 1.0%, more preferably more than 1.5%, and even more preferably more than 2.0%.
On the other hand, by making this sum 30.0% or less, it is possible to reduce devitrification due to a decrease in the viscosity of the glass while maintaining the desired refractive index and dispersion. Therefore, the sum of the contents of the _Rn2O component (mass sum) is preferably 30.0% or less, more preferably less than 25.0%, and even more preferably less than 23.0%.

The optical glass of the present invention preferably contains two or more of the above-mentioned _Rn2O components. This makes it unnecessary to perform a heat treatment by reheating in order to reduce the temperature coefficient of the relative refractive index and improve the transmittance. In particular, it is preferable to contain two or more components including _Na2O and _K2O as the _Rn2O component, because it has a large average linear thermal expansion coefficient, improves the transmittance, and can reduce the temperature coefficient of the relative refractive index.

The sum of _the contents (sum of mass) of _Ln2O3 components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb and Lu) is preferably 5.0% or less.
This makes it possible to obtain glass having excellent resistance to devitrification and good transmittance. Therefore, the sum of the contents (sum of mass) of _{the Ln2O3} component is preferably 5.0% or less, more preferably 3.5% or less, and further preferably less than 2.0%.

<Ingredients that should not be included>
Next, components that should not be contained in the optical glass of the present invention and components whose inclusion is undesirable will be described.

Other components may be added as necessary to the extent that they do 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 Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, have the property of coloring the glass and absorbing specific wavelengths in the visible range even when contained alone or in combination in small amounts, so it is preferable that they are substantially absent, especially in optical glasses that use wavelengths in the visible range.

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

Furthermore, in recent years, there has been a trend to reduce the use of the components Th, Cd, Tl, Os, Be, and Se as harmful chemical substances, and environmental measures are required not only in the glass manufacturing process, but also in the processing process and disposal after productization. Therefore, when environmental impact is important, it is preferable that these components are not substantially contained.

[Production method]
The optical glass of the present invention is produced, for example, as follows: High-purity raw materials for ordinary optical glass, such as oxides, hydroxides, carbonates, nitrates, fluorides, hydroxides, and metaphosphate compounds, are mixed uniformly as the raw materials for each of the above components so that the content of each component falls within a prescribed range, the mixture thus produced is placed in a platinum crucible, and melted in an electric furnace at a temperature range of 1000 to 1500° C. for 1 to 10 hours depending on the degree of melting difficulty of the glass raw materials, stirred and homogenized, and then the temperature is lowered to an appropriate level, and the glass is cast into a mold and slowly cooled.

<Physical Properties>
The optical glass of the present invention preferably has a high refractive index and a low Abbe number (high dispersion).
In particular, the refractive index ( _nd ) of the optical glass of the present invention is preferably 1.65 or more, more preferably 1.67 or more, and even more preferably 1.69 or more. This refractive index (nd) may be preferably 2.00 or less, more preferably 1.98 or less, even more preferably 1.96 or less, and even more preferably 1.95 or less.
The Abbe number (ν _d ) of the optical glass of the present invention is preferably 10.0 or more, more preferably 13.0 or more, even more preferably 15.0 or more, and even more preferably 17.0 or more. This Abbe number (ν _d ) may be preferably 35.0 or less, more preferably 34.0 or less, even more preferably 32.0 or less, and even more preferably 30.0 or less.
By having such a high refractive index, a large amount of light refraction can be obtained even if the optical element is made thin. In addition, by having such a high dispersion, when used as a single lens, the focus can be appropriately shifted depending on the wavelength of light. Therefore, for example, when an optical system is configured by combining it with an optical element having low dispersion (high Abbe number), the aberration of the entire optical system can be reduced, and high imaging characteristics can be achieved.
Thus, the optical glass of the present invention is useful in optical design, and in particular when used in an optical system, it is possible to reduce the size of the optical system while achieving high imaging characteristics, thereby expanding the freedom of optical design.

The optical glass of the present invention has a low temperature coefficient of relative refractive index (dn/dT).
More specifically, the upper limit of the temperature coefficient of the relative refractive index of the optical glass of the present invention is preferably +3.0×10 ⁻⁶ ° C. ⁻¹ , more preferably +1.5×10 ⁻⁶ ° C. ⁻¹ , and even more preferably +1.0×10 ⁻⁶ ° C. ⁻¹ , and the temperature coefficient can be either this upper limit or a value lower (on the negative side).
On the other hand, the temperature coefficient of the relative refractive index of the optical glass of the present invention has a lower limit of preferably -10.0 x 10 ^-6 ° C. ^-1 , more preferably -8.0 x 10 ^-6 ° C. ^-1 , and even more preferably -7.0 x 10 ^-6 ° C. ^-1 , and can take on values either higher than this lower limit (on the positive side).
Among these, there are not many glasses with a low temperature coefficient of relative refractive index that have a refractive index ( _nd ) of 1.65 or more and an Abbe number ( _vd ) of 10 to 35, which broadens the options for correcting image shifts due to temperature changes and makes the correction easier. Therefore, setting the temperature coefficient of the relative refractive index in such a range can contribute to correcting image shifts due to temperature changes.
The temperature coefficient of the relative refractive index of the optical glass of the present invention is the temperature coefficient of the refractive index (589.29 nm) in air at the same temperature as the optical glass, and is expressed as the amount of change (° ^C ) per degree Celsius when the temperature is changed from 40°C to 60°C.

The optical glass of the present invention preferably has an average linear thermal expansion coefficient α of at least 80 (10 ⁻⁷ ° C. ⁻¹ ) at 100 to 300° C. That is, the average linear thermal expansion coefficient α of the optical glass of the present invention at 100 to 300° C. is preferably at least 80 (10 ⁻⁷ ° C. ⁻¹ ), more preferably at least 85 (10 ⁻⁷ ° C. ⁻¹ ), and even more preferably at least 90 (10 ⁻⁷ ° C. ⁻¹ ).
Generally, a large average linear thermal expansion coefficient α makes glass more susceptible to cracking during processing, so a small average linear thermal expansion coefficient α is desirable. On the other hand, from the viewpoint of combining and bonding with a glass material having a low temperature coefficient of relative refractive index and a large average linear thermal expansion coefficient α, it is desirable for the glass material and the average linear thermal expansion coefficient α to have the same or similar values.
Among these, for glasses having a refractive index (n _d ) of 1.65 or more and an Abbe number (ν _d ) of 10 or more and 35 or less, there are few glass materials with a large average linear thermal expansion coefficient α. Therefore, when used in combination with a low refractive index, low dispersion glass material, it is more useful to have a glass material having a large average linear thermal expansion coefficient α, as in the present invention.

It is preferable that the optical glass of the present invention has a high visible light transmittance, particularly a high transmittance for light on the short wavelength side of visible light, and therefore has little coloring.
In particular, the optical glass of the present invention, when expressed in terms of glass transmittance, preferably has the shortest wavelength (λ ₈₀ ) at which a 10 mm thick sample exhibits a spectral transmittance of 80% is 460 nm or less, more preferably 450 nm or less, and even more preferably 440 nm or less.
In the optical glass of the present invention, the shortest wavelength (λ ₇₀ ) at which a sample having a thickness of 10 mm exhibits a spectral transmittance of 70% is preferably 430 nm or less, more preferably 420 nm or less, and even more preferably 410 nm or less.
In the optical glass of the present invention, the shortest wavelength (λ ₅ ) at which a sample having a thickness of 10 mm exhibits a spectral transmittance of 5% is preferably 400 nm or less, more preferably 390 nm or less, and even more preferably 380 nm or less.
These properties bring the absorption edge of the glass near the ultraviolet region, enhancing the transparency of the glass to visible light, and therefore this optical glass can be preferably used in optical elements that transmit light, such as lenses.

[Preform and optical element]
From the produced optical glass, a glass molded body can be produced, for example, by using a polishing means or a mold press molding means such as reheat press molding or precision press molding. That is, a glass molded body can be produced by subjecting the optical glass to mechanical processing such as grinding and polishing, a preform for mold press molding can be produced from the optical glass, and the preform can be subjected to reheat press molding and then polished to produce a glass molded body, or a preform produced by polishing or a preform molded by known floating molding or the like can be subjected to precision press molding to produce a glass molded body.
However, the means for producing the glass molded body is not limited to these means.

In this way, the optical glass of the present invention is useful for various optical elements and optical designs. In particular, it is preferable to form a preform from the optical glass of the present invention and use this preform to perform reheat press molding, precision press molding, or the like to produce optical elements such as lenses and prisms. This makes it possible to form preforms with large diameters, so that while the optical elements can be made larger, high-definition, high-precision imaging and projection characteristics can be achieved when used in optical equipment.

The glass molded body made of the optical glass of the present invention can be used for optical elements such as lenses, prisms, and mirrors, and can typically be used in devices that are prone to high temperatures, such as in-vehicle optical devices, projectors, and copy machines.

The compositions of the examples (No. 1 to No. 51) of the present invention and the comparative examples (No. A, B), as well as the refractive index (n _d ), Abbe number (ν _d ), temperature coefficient of relative refractive index (dn/dT), average linear thermal expansion coefficient (100 to 300° C.), and transmittance (λ ₈₀ , λ ₇₀ , λ ₅ ) of these glasses are shown in Tables 1 to 8. Note that the following examples are merely for illustrative purposes, and the present invention is not limited to these examples.

The glasses in the examples and comparative examples of the present invention were all made by selecting high-purity raw materials used in ordinary optical glass, such as the corresponding oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds, as the raw materials for each component, weighing them out to obtain the composition ratios shown in the table for each example, mixing them uniformly, and then placing them in a platinum crucible. Depending on the degree of difficulty of melting the glass raw materials, the mixture was melted in an electric furnace at a temperature range of 800 to 1300°C for 1 to 10 hours, and then stirred and homogenized before being cast into a mold or the like and slowly cooled.

The refractive index (n _d ) and Abbe number (ν _d ) of the glasses in the 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 ) was calculated from the above-mentioned d-line refractive index, the refractive index (n _F ) for the F-line (486.13 nm) of a hydrogen lamp, and the refractive index (n _C ) for the C-line (656.27 nm) of a hydrogen lamp, according to the formula: Abbe number (ν _d )=[(n _d -1)/(n _F -n _C )].

The temperature coefficient of relative refractive index (dn/dT) of the glasses in the examples and comparative examples was measured at 40 to 60°C for light with a wavelength of 589.29 nm using the interference method described in the Japan Optical Glass Industry Association standard JOGIS18-2008 "Method for measuring the temperature coefficient of refractive index of optical glass."

The average linear thermal expansion coefficient (100-300°C) of the glass in the examples and comparative examples was determined from the thermal expansion curve obtained by measuring the relationship between temperature and sample elongation in accordance with the Japan Optical Glass Industry Association standard JOGIS08-2003 "Method for measuring thermal expansion of optical glass."

The transmittance of the glass in the examples was measured in accordance with the Japan Optical Glass Industry Association standard JOGIS02-2003. In the present invention, the presence or absence and the degree of coloration of the glass was determined by measuring the transmittance of the glass. Specifically, the spectral transmittance of a 10±0.1 mm thick parallel-polished product was measured in the range of 200 to 800 nm in accordance with JIS Z8722 to determine λ ₈₀ (wavelength at 80% transmittance), λ ₇₀ (wavelength at 70% transmittance), and λ ₅ (wavelength at 5% transmittance).

The _optical glass according to the embodiment of the present invention contains _{P2O5 and Nb2O5} components, and also contains predetermined amounts of _Na2O and _K2O components, making it possible to obtain inexpensive glass with a small temperature coefficient of relative refractive index.

As shown in the table, the temperature coefficient of relative refractive index of the optical glasses of the examples was all within the range of +1.0× ^10-6 to -10.0× ^10-6 (°C ^-1 ), more specifically, within the range of +3.0× ^10-6 to -10.0× ^10-6 (°C ^-1 ), which was within the desired range.

The optical glasses of the Examples all had a refractive index (n _d ) of 1.65 or more, which was within the desired range, and the optical glasses of the Examples of the present invention all had an Abbe number (ν _d ) in the range of 10 to 35, which was also within the desired range.

Moreover, the optical glasses of the examples all had an average linear thermal expansion coefficient (100-300° C.) of 80 (10 ⁻⁷ ° C. ⁻¹ ) or more.

Moreover, the optical glasses of the Examples had a transmittance (λ ₈₀ ) of 460 nm or less, a transmittance (λ ₇₀ ) of 430 nm or less, and a transmittance (λ ₅ ) of 400 nm or less.

The optical glasses of the examples formed stable glasses and were less likely to devitrify during glass production. On the other hand, the glass of Comparative Example A did not vitrify because it devitrified.

It was therefore made clear that the optical glasses of the Examples have a refractive index (n _d ) and Abbe number (v _d ) within the desired range, have a small temperature coefficient of relative refractive index, and can be obtained at lower material costs. From this, it is presumed that the optical glasses of the Examples of the present invention will contribute to the miniaturization of optical systems such as in-vehicle optical devices and projectors used in high-temperature environments, and will contribute to the correction of deviations in imaging characteristics due to temperature changes.

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

The present invention has been described in detail above for illustrative purposes, but it will be understood that the present examples are for illustrative purposes only and that many modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims (6)

In mass percent,
_P2O5 component _24.77-26.50 % ,
_Nb2O5 component _36.02 to 50.0%,
ZnO content: 0 to less than 2.0%
BaO content: 0 to 8.96%
_Bi2O3 component ₀ to less than 3.0%
Contains 0 to less than _1.0 % of _Gd2O3 component,
The sum of masses ( _Nb2O5 + _TiO2 ) is _40.0 % or more and 57.11% or less ,
The sum of mass (Na ₂ O + K ₂ O) is 12.15 to 30.0%,
a mass ratio ( _Na2O + _K2O +BaO)/( _B2O3 + _TiO2 ) of more than 0.7 _and not more than 1.31;
Contains substantially no PbO;
A refractive index (n _d ) of 1.65 or more and 1.88 or less;
An optical glass having a temperature coefficient (40 to 60° C.) of the relative refractive index (589.29 nm) within the range of +1.0×10 ^-6 to -10.0×10 ^-6 (° C. ^-1 ). 2. The optical glass according to claim 1, wherein the average linear thermal expansion coefficient α at 100 to 300° C. is 80 (10 ⁻⁷ ° C. ⁻¹ ) or more. 3. The optical glass according to claim 1, having an Abbe number (ν _d ) of 10 or more and 35 or less. A preform made of the optical glass according to any one of claims 1 to 3. An optical element made of the optical glass according to any one of claims 1 to 3. An optical device comprising the optical element according to claim 5.