JP7545192B2 - 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.

As a material for optical elements constituting an optical system, there is a very high demand for high refractive index, high dispersion glass having a refractive index (n _d ) of 1.75 or more and an Abbe number (ν _d ) of 18 to 45. As such high refractive index, high dispersion glass, glass compositions such as those described in Patent Documents 1 and 2 are known.

International Publication No. 2011/065097 JP 2007-254197 A

When constructing an optical system that is less susceptible to the effects of temperature fluctuations on imaging performance, 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 performance, etc. can be corrected.

In particular, for high-refractive-index, high-dispersion glass having a refractive index (n _d ) of 1.75 or more and an Abbe number (ν _d ) of 18 to 45, glass with a low temperature coefficient of the relative refractive index is desired from the viewpoint of contributing to correction of the effect of temperature changes on imaging characteristics, and more specifically, glass with 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 is desired.

The present invention was made in consideration of the above problems, and its purpose is to provide an optical glass that has high refractive index and high dispersion optical properties, has a low temperature coefficient of relative refractive index, and can contribute to correcting the effects of temperature changes on imaging properties, as well as a preform and optical element that use the same.

In order to solve the above problems, the inventors of the present invention have conducted extensive testing and research, and have found that by combining _{a B2O3} component, a rare earth component, and a BaO component with at _least one of a _TiO2 component, a _Nb2O5 component, a _WO3 component, a _ZrO2 component, and _{a Ta2O5} component, and adjusting the content of each component, it is possible to obtain a glass having a desired refractive index and Abbe number while having a low temperature coefficient of relative refractive index, and have thus completed the present invention. Specifically, the present invention provides the following:

(1) In mass percent,
_B2O3 component _is more than 0% and 35.0% or less;
Ln ₂ O ₃ components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) in a total amount of 1.0% to 45.0%;
Contains 20.0% or more and 50.0% or less of a BaO component,
The mass sum of TiO ₂ +ZrO ₂ +WO ₃ +Nb ₂ O ₅ +Ta ₂ O ₅ is more than 0% and 50.0% or less;
A refractive index (n _d ) of 1.75 or more and an Abbe number (ν _d ) of 18 or more and 45 or less,
An optical glass having a temperature coefficient (40 to 60° C.) of a relative refractive index (589.29 nm) within the range of +3.0×10 ⁻⁶ to −10.0×10 ⁻⁶ (° C. ⁻¹ ).

(2) In mass%,
_SiO2 component 0-22.0%
_La2O3 component 0 to _37.0 %,
_Gd2O3 component ₀ to 15.0%,
_Y2O3 component 0 to _25.0 %,
Yb ₂ O ₃ components 0-10.0%
_ZrO2 component 0 to 15.0%,
Nb ₂ O ₅ components 0 to 20.0%,
_WO3 component 0 to 10.0%,
_TiO2 component 0 to 38.0%,
_Ta2O5 component ₀ to 10.0%,
ZnO content: 0 to less than 5.0%
MgO content: 0 to 10.0%
CaO content: 0 to 15.0%
SrO content 0 to 17.0%,
Li ₂ O component 0 to 5.0%,
_Na2O component 0 to 10.0%,
K ₂ O component 0-10.0%,
P ₂ O ₅ components 0 to 10.0%,
_GeO2 component 0 to 10.0%,
Al ₂ O ₃ components 0-15.0%,
_Ga2O3 component 0 to _10.0 %,
_Bi2O3 component ₀ to 10.0%,
_TeO2 component 0 to 10.0%,
_SnO2 component 0 to 3.0%,
Sb ₂ O ₃ components 0-1.0%
and
The optical glass according to (1), wherein the content of F in the fluoride which has substituted a part or all of one or more oxides of each of the above elements is 0 to 10.0 mass %.

(3) The optical glass according to (1) or (2), wherein the sum by mass of (SiO ₂ +B ₂ O ₃ ) is 7.0% or more and 37.0% or less.

(4) The optical glass according to any one of (1) to (3), in which the mass ratio (SiO ₂ +B ₂ O ₃ )/Ln ₂ O ₃ is 0.25 or more and 3.00 or less (wherein Ln is one or more selected from the group consisting of La, Gd, Y and Yb).

(5) The optical glass according to any one of (1) to (4), in which the mass ratio BaO/ _SiO2 is 1.50 or more.

(6) The optical glass according to any one of (1) to (5), in which the mass ratio TiO ₂ /(SiO ₂ +B ₂ O ₃ ) is 0.05 or more and 3.00 or less.

(7) The optical glass according to any one of (1) to (6), in which the mass ratio BaO/(SiO ₂ +B ₂ O ₃ +ZnO) is greater than 0.50 and equal to or less than 4.00.

(8) An optical glass according to any one of (1) to (7), in which the sum of the contents of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, and Zn) is 20.0% or more and 55.0% or less, by mass%.

(9) The optical glass according to any one of (1) to (8), wherein the sum of the contents of Rn ₂ O components (wherein Rn is one or more selected from the group consisting of Li, Na and K) is 10.0% or less by mass%.

(10) A preform material made of the optical glass described in any one of (1) to (9).

(11) An optical element made of the optical glass according to any one of (1) to (9).

(12) An optical device comprising the optical element described in (11).

The present invention provides optical glass that has high refractive index and high dispersion optical properties, has a low temperature coefficient of relative refractive index, and can contribute to correcting the effects of temperature changes on imaging properties, as well as preforms and optical elements that use the same.

FIG. 2 is a diagram showing the relationship between the refractive index (nd) and the Abbe number (ν _d ) for glasses according to examples of the present application.

The optical glass of the present invention contains, by mass, more than 0% and not more than 35.0% of a B ₂ O ₃ component, a total of 1.0% to 45.0% of a Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y and Yb), and 20.0% to 50.0% of a BaO component, the mass sum of TiO ₂ +ZrO ₂ +WO ₃ +Nb ₂ O ₅ +Ta ₂ O ₅ is more than 0% and not more than 50.0%, has a refractive index (n _d ) of 1.75 or more, an Abbe number (ν _d ) of 18 or more and 45 or less, and a temperature coefficient (40-60° C.) of the relative refractive index (589.29 nm) in the range of +3.0×10 ^-6 to -10.0×10 ^-6 (° C. ^-1 ). By using _B2O3 , _rare earth, and _BaO in combination with at least one of _TiO2 , _Nb2O5 , _WO3 , _ZrO2 , and _Ta2O5 and adjusting the content of each component, it is possible to obtain an optical glass having a desired refractive index and Abbe number while having _a low temperature coefficient of relative refractive index. Therefore, it is possible to obtain an optical glass having optical characteristics of high refractive index and high dispersion, a low temperature coefficient of relative refractive index, and capable of contributing to correction of the effect of temperature change on imaging characteristics.

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 B2O3 component} is an essential component as a glass-forming oxide. In particular, by containing more than 0% _{of the B2O3} component, devitrification of the glass can be reduced. Therefore, the content of the _B2O3 component is preferably more than 0%, more preferably more than 1.0%, even more preferably 3.0% or more, even more preferably more than 6.0%, even more preferably more than 9.0%, and even more preferably 12.0% or more.
On the other hand, by making the content of _{the B2O3} component 35.0% or less, it is easy to obtain a larger refractive index, the temperature coefficient of the relative refractive index can be made small, and deterioration of chemical durability can be suppressed. Therefore, the content of _{the B2O3} component is preferably 35.0% or less, more preferably 25.0% or less, even more preferably less than 20.0%, even more preferably less than 18.0%, and even more preferably less than 15.0%.

The sum of the contents (mass sum) of the rare _earth components, i.e., _Ln2O3 components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb), is preferably 1.0% or more. This increases the refractive index of the glass, making it easier to obtain glass having the desired refractive index and Abbe number. In addition, the chemical durability of the _glass , particularly water resistance, can be improved. Therefore, the mass sum of the _Ln2O3 components is preferably 1.0% or more, more preferably 4.0% or more, even more preferably 7.0% or more, more preferably more than 10.0%, even more preferably more than 13.0%, even more preferably more than 15.0%, and even more preferably more than 20.0%.
On the other hand, by making this sum 45.0% or less, the liquidus temperature of the glass is lowered, so that devitrification of the glass can be reduced. In addition, the increase in the _Abbe number more than necessary can be suppressed. Therefore, the mass sum of the _Ln2O3 component is preferably 45.0% or less, more preferably 40.0% or less, even more preferably less than 36.0%, preferably less than 32.0%, and even more preferably less than 30.0%.

The BaO component is an essential component that can improve the meltability of glass raw materials, reduce devitrification of glass, increase the refractive index, and reduce the temperature coefficient of the relative refractive index. Therefore, the content of the BaO component is preferably 20.0% or more, more preferably more than 22.0%, even more preferably more than 25.0%, even more preferably more than 28.0%, even more preferably more than 30.0%, even more preferably more than 31.0%, and even more preferably more than 31.4%.
On the other hand, by making the content of the BaO component 50.0% 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 of the BaO component. Therefore, the content of the BaO component is preferably 50.0% or less, more preferably 45.0% or less, even more preferably less than 40.0%, and even more preferably 37.0% or less.

The total amount (mass sum) of _TiO2 , _ZrO2 , _WO3 , _Nb2O5 and _Ta2O5 components is preferably _more than 0%. This increases the refractive index of the glass, thereby obtaining a desired high refractive index. Therefore, the mass sum _TiO2 + _ZrO2 + _WO3 + _{Nb2O5 + Ta2O5 is} preferably more than 0%, more preferably more than _1.0 %, even more preferably 5.0% or more, even more preferably more than 9.0%, and even more preferably 12.0% or more.
On the other hand, this sum is preferably 50.0% or less. This enhances the stability of the glass. Therefore, the mass sum TiO ₂ +ZrO ₂ +WO ₃ +Nb ₂ O ₅ +Ta ₂ O ₅ is preferably 50.0% or less, more preferably less than 45.0%, even more preferably less than 40.0%, even more preferably less than 35.0%, even more preferably less than 30.0%, and even more preferably less than 27.0%.

The _SiO2 component is a component that is optionally used as a glass-forming oxide. In particular, when the _SiO2 component is contained in an amount of more than 0%, the chemical durability, particularly the water resistance, can be improved, the viscosity of the molten glass can be increased, and the coloring of the glass can be reduced. In addition, the stability of the glass can be improved, making it easier to obtain glass that can withstand mass production. Therefore, the content of the _SiO2 component is preferably more than 0%, more preferably more than 3.0%, even more preferably more than 6.0%, and even more preferably more than 8.0%.
On the other hand, by making the content of the _SiO2 component 22.0% or less, the temperature coefficient of the relative refractive index can be reduced, the increase in the glass transition point can be suppressed, and the decrease in the refractive index can be suppressed. Therefore, the content of the _SiO2 component is preferably 22.0% or less, more preferably less than 20.0%, even more preferably less than 17.0%, even more preferably less than 15.0%, and even more preferably less than 12.0%.

The _La2O3 component is an optional component that can increase the refractive index of the glass when it is contained in an amount of more than 0%. Therefore, the content of _{the La2O3 component is} preferably more than 0%, more preferably more than 1.0%, even more preferably 3.0% or more, even more preferably more than 7.0%, even more preferably more than 10.0%, even more preferably more than 13.0%, and even more preferably 20.0% or more.
On the other hand, by making the content of _La2O3 component 37.0% or less, the stability of the glass can be _improved , thereby reducing devitrification and suppressing the increase in Abbe number. Also, the melting property of the _glass raw material can be improved. Therefore, the content of _La2O3 component is preferably 37.0% or less, more preferably less than 36.0%, even more preferably less than 34.0%, even more preferably less than 31.0%, and even more preferably less than 28.0%.

The Gd ₂ O ₃ component and the Yb ₂ O ₃ component are optional components that can increase the refractive index of the glass when contained in an amount exceeding 0%.
On the other hand, the raw material prices of the Gd ₂ O ₃ component and the Yb ₂ O ₃ component are high among rare earth elements, and the production cost increases when the content is high. In addition, the content of the Gd ₂ O ₃ component and the Yb ₂ O ₃ component is reduced, so that the increase in the Abbe number of the glass can be suppressed. Therefore, the content of the Gd ₂ O ₃ component may be preferably 15.0% or less, more preferably less than 10.0%, even more preferably less than 5.0%, and even more preferably less than 3.0%. In addition, the content of the Yb ₂ O ₃ component may be preferably 10.0% or less, more preferably less than 6.0%, even more preferably less than 3.0%, and even more preferably less than 1.0%.

The _Y2O3 component is an optional component that, when contained in an amount of more than 0%, increases the refractive index of the _glass while reducing the material cost of the glass compared to other rare earth elements. Therefore, the content of _{the Y2O3 component} may be preferably more than 0%, more preferably more than 1.0%, and even more preferably 2.0% or more.
On the other hand, by making the content of _Y2O3 component 25.0% or less, the decrease in the refractive index of the glass can be suppressed, the increase in the Abbe number of the glass _can be suppressed, and the stability of the glass can be improved. In addition, the deterioration of the melting property of the _glass raw material can be suppressed. Therefore, the content of _Y2O3 component may be preferably 25.0% or less, more preferably less than 20.0%, even more preferably 15.0% or less, even more preferably less than 10.0%, even more preferably 5.0% or less, and even more preferably less than 3.5%.

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 1.0%, and even more preferably 3.0% or more.
On the other hand, by making the content of the _ZrO2 component 15.0% 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 15.0% or less, more preferably less than 10.0%, even more preferably less than 8.0%, and even more preferably less than 6.0%.

_{The Nb2O5} component is an optional component that, when contained in an amount exceeding 0%, can increase the refractive index of the glass, reduce the Abbe number, and increase the devitrification resistance by lowering the liquidus temperature of the glass. Therefore, the content of the _{Nb2O5 component} may be preferably more than 0%, more preferably more than 1.0%, and even more preferably 2.0% or more.
On the other hand, by making the content of the Nb ₂ O ₅ component 20.0% or less, the temperature coefficient of the relative refractive index can be made small, devitrification due to an excessive content of the Nb ₂ O ₅ component can be reduced, and a decrease in the transmittance of the glass for visible light (particularly wavelengths of 500 nm or less) can be suppressed. Therefore, the content of the Nb ₂ O ₅ component may be preferably 20.0% or less, more preferably 15.0% or less, even more preferably less than 10.0%, even more preferably less than 5.0%, and even more preferably less than 3.0%.

The _WO3 component is an optional component that, when contained at more than 0%, can increase the refractive index, lower the Abbe number, lower the glass transition point, and reduce devitrification while reducing coloration of the glass caused by other high refractive index components. Therefore, the content of the _WO3 component may be preferably more than 0%, more preferably more than 0.5%, and even more preferably more than 0.7%.
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 the material cost can be reduced. 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 5.0%, even more preferably less than 3.0%, and even more preferably less than 1.0%.

The _TiO2 component is an optional component that, when contained at more than 0%, can increase the refractive index of the glass, lower the Abbe number, and reduce the devitrification of the 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 3.5%, even more preferably more than 5.0%, and even more preferably more than 6.0%.
On the other hand, by making the content of the _TiO2 component 38.0% or less, the temperature coefficient of the relative refractive index can be reduced, devitrification due to excessive inclusion of the _TiO2 component can be reduced, and the decrease in the transmittance of the glass to visible light (especially wavelengths of 500 nm or less) can be suppressed. Therefore, the content of the _TiO2 component may be preferably 38.0% or less, more preferably 35.0% or less, even more preferably less than 30.0%, even more preferably 28.0% or less, even more preferably less than 25.0%, and even more preferably less than 21.0%.

The Ta ₂ O ₅ component is an optional component that, when contained in an amount exceeding 0%, can increase the refractive index of the glass and can also increase the devitrification resistance.
On the other hand, by making the content of _Ta2O5 component _10.0 % or less, the raw material cost of optical glass can be reduced, and the melting temperature of raw material is lowered, and the energy required for melting raw material is reduced, so the manufacturing cost of _optical glass can also be reduced.Therefore, the content of _Ta2O5 component may be preferably 10.0% or less, more preferably less than 7.0%, even more preferably less than 5.0%, even more preferably less than 2.0%, and even more preferably less than 1.0%.In particular, from the viewpoint of reducing material cost, it is _most preferable not to contain _Ta2O5 component.

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%.

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 content of the MgO component 10.0% or less, or the content of the CaO component 15.0% or less, or the content of the SrO component 17.0% or less, the decrease in the refractive index can be suppressed, and devitrification due to the excessive inclusion of these components can be reduced. Therefore, the content of the MgO component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably less than 3.0%, and even more preferably less than 1.0%. The content of the CaO component is preferably 15.0% or less, more preferably 13.0% or less, even more preferably 10.0% or less, even more preferably less than 6.5%, even more preferably less than 4.0%, and even more preferably less than 2.0%. The content of the SrO component is preferably 17.0% or less, more preferably 15.0% or less, even more preferably 13.0% or less, even more preferably 10.0% or less, even more preferably less than 6.5%, even more preferably less than 4.0%, and even more preferably less than 2.0%.

The _Li2O component, _Na2O component and _K2O component are optional components that can improve the meltability of glass and lower the glass transition point when contained in an amount of more than 0%. In particular, when the _K2O component is contained in an amount of more than 0%, the temperature coefficient of the relative refractive index can be reduced.
On the other hand, by reducing the contents of the Li ₂ O component, the Na ₂ O component, and the K ₂ O component, the refractive index of the glass is less likely to decrease, and the devitrification of the glass can be reduced. In addition, by reducing the content of the Li ₂ O component in particular, the viscosity of the glass is increased, and therefore the striae of the glass can be reduced. Therefore, the content of the Li ₂ O 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 0.3%. In addition, the content of the Na ₂ O 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%. In addition, the content of the K ₂ O component may be preferably 10.0% or less, more preferably less than 7.0%, even more preferably less than 4.0%, and even more preferably less than 2.0%.

The P ₂ O ₅ component is an optional component that, when contained in an amount exceeding 0%, can lower the liquidus temperature of the glass and thereby improve the devitrification resistance.
On the other hand, by making the content of the _P2O5 component 10.0% or less, the deterioration of the chemical durability of the glass, particularly the water resistance _, can be suppressed. Therefore, the content of _{the P2O5} 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%, and _{the P2O5} component may not be contained.

The _GeO2 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 is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, even more preferably less than 1.0%, and even more preferably less than 0.1%.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components that can improve the devitrification resistance of the molten glass when contained in an amount of more than 0%. Therefore, the content of the Al ₂ O ₃ component in particular 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 Al ₂ O ₃ component 15.0% or less, or making the content of the Ga ₂ O ₃ component 10.0% or less, respectively, the liquidus temperature of the glass can be lowered and the devitrification resistance can be improved. Therefore, the content of the Al ₂ O ₃ component may be preferably 15.0% or less, more preferably less than 10.0%, even more preferably less than 6.0%, even more preferably less than 3.0%, and even more preferably less than 1.0%. In addition, the content of the Ga ₂ O ₃ 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%.

The Bi ₂ O ₃ component is an optional component that, when contained in an amount exceeding 0%, can increase the refractive index, decrease the Abbe number, and decrease the glass transition point.
On the other hand, by making the content of the _Bi2O3 component 10.0% 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 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%.

The _TeO2 component is an optional component that, when contained in an amount exceeding 0%, can increase the refractive index and decrease the glass transition point.
On the other hand, _TeO2 has a problem that it 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%, even more preferably less than 3.0%, and even more preferably less than 1.0%.

The _SnO2 component is an optional component that, when contained in an amount exceeding 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%.

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 Sb ₂ O ₃ 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 Sb ₂ O ₃ component may be preferably 1.0% or less, more preferably less than 0.5%, and further preferably less than 0.2%.

The component for clarifying 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 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%, even more preferably less than 3.0%, and even more preferably less than 1.0%.

The total amount of _SiO2 component and _B2O3 is preferably 7.0% or more. This _{makes it easier to obtain stable glass. Therefore, the mass sum (SiO2 + B2O3 ) is} preferably 7.0% or more, more preferably 9.0% or more, even more preferably more than 12.0%, even more preferably more than 15.0%, even more preferably more than 16.0%, and even more preferably more than 19.0%.
On the other hand, by making this total amount 37.0% or less, the temperature coefficient of the relative refractive index can be made small. Therefore, the mass sum (SiO ₂ +B ₂ O ₃ ) is preferably 37.0% or less, more preferably 34.0% or less, even more preferably less than 33.0%, even more preferably less than 28.0%, and even more preferably 25.0% or less.

The ratio (mass ratio) of the total content of the _SiO2 component and _B2O3 to the total content of the _Ln2O3 component (wherein Ln is one or more selected from the group consisting of _La , _Gd , Y, and Yb) is preferably 0.25 or more. By increasing this ratio, the refractive index of the glass can be increased. Therefore, the mass ratio ( _SiO2 + _B2O3 ) / _{Ln2O3 is} preferably 0.25 or more, more preferably 0.35 or more, even more preferably 0.45 or more, even more preferably 0.56 or more, and even _more preferably 0.67 or more.
On the other hand, from the viewpoint of obtaining a stable glass, this mass ratio may be preferably 3.00 or less, more preferably 2.00 or less, even more preferably less than 1.50, and even more preferably less than 1.20.

The ratio (mass ratio) of the content of the BaO component to the content of the _SiO2 component is preferably 1.50 or more. By increasing this ratio, the temperature coefficient of the relative refractive index can be reduced and chemical durability can be improved. Therefore, the mass ratio BaO/ _SiO2 is preferably 1.50 or more, more preferably 1.80 or more, even more preferably 2.10 or more, even more preferably 2.40 or more, and even more preferably 2.80 or more.
On the other hand, the upper limit of this mass ratio BaO/ _SiO2 may be infinite ( _SiO2 content is 0%), but from the viewpoint of obtaining a stable glass, it may be preferably 10.00 or less, more preferably less than 7.00, even more preferably less than 5.00, and even more preferably less than 4.00.

The ratio (mass ratio) of the content of _TiO2 component to _the total content of _SiO2 component and _B2O3 component is preferably 0.05 or more. By increasing this ratio, the temperature coefficient of the relative refractive index can be made difficult to increase, and the material cost of the glass can be reduced. Therefore, the mass ratio _TiO2 /( _{SiO2 + B2O3} ) is preferably 0.05 or more, more preferably 0.10 or more, even more preferably more than 0.20, and even more preferably more than 0.25.
On the other hand, from the viewpoint of obtaining a stable glass, this mass ratio may be preferably 3.00 or less, more preferably less than 2.00, even more preferably less than 1.70, even more preferably less than 1.40, and even more preferably less than 1.10.

The ratio (mass ratio) of the content of the BaO component to the total content of the _SiO2 component, the _B2O3 component, and the _ZnO component is preferably more than 0.50. By increasing this ratio, the temperature coefficient of the relative refractive index can be reduced. _Therefore , the mass ratio BaO/( _SiO2 + _B2O3 + ZnO) is preferably more than 0.50, more preferably more than 0.60, even more preferably more than 0.80, even more preferably more than 1.00, even more preferably more than 1.25, even more preferably more than 1.30, and even more preferably 1.47 or more.
On the other hand, from the viewpoint of obtaining a stable glass, the mass ratio BaO/(SiO ₂ +B ₂ O ₃ +ZnO) may be preferably 4.00 or less, more preferably 3.00 or less, even more preferably less than 2.50, even more preferably less than 2.00, even more preferably less than 1.80, and even more preferably 1.65 or less.

The sum of the contents (mass sum) of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably 20.0% or more. This can reduce devitrification of the glass and reduce the temperature coefficient of the relative refractive index. Therefore, the mass sum of the RO components is preferably 20.0% or more, more preferably more than 24.0%, even more preferably more than 28.0%, even more preferably more than 30.0%, and even more preferably more than 32.0%.
On the other hand, by making the mass sum of the RO components 55.0% or less, the decrease in the refractive index can be suppressed and the stability of the glass can be increased. Therefore, the mass sum of the RO components is preferably 55.0% or less, more preferably 50.0% or less, even more preferably 45.0% or less, even more preferably less than 42.0%, even more preferably less than 40.0%, and even more preferably 37.0% or less.

The sum of the contents (mass sum) of Rn ₂ O components (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is preferably 10.0% or less. This makes it possible to suppress a decrease in the viscosity of the molten glass, to make it difficult for the refractive index of the glass to decrease, and to reduce devitrification of the glass. Therefore, the mass sum of the Rn ₂ O components is preferably 10.0% or less, more preferably less than 7.0%, even more preferably less than 4.0%, and even more 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 in small amounts alone or in combination, 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 substantially contained, 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 used 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 has a high refractive index and a low Abbe number (high dispersion).
In particular, the refractive index (n _d ) of the optical glass of the present invention preferably has a lower limit of 1.75, more preferably 1.77, and even more preferably 1.78. This refractive index (n _d ) may preferably have an upper limit of 2.10, more preferably 2.00, and even more preferably 1.90. Furthermore, the Abbe number (ν _d ) of the optical glass of the present invention preferably has a lower limit of 18, more preferably 20, even more preferably 23, even more preferably 26, and even more preferably 30. This Abbe number (ν _d ) may preferably have an upper limit of 45, more preferably 43, and even more preferably 41.
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.

Here, the optical glass of the present invention preferably has a refractive index (n _d ) and an Abbe number (v _d ) that satisfy the relationship: (-0.0112vd+2.15)≦n d≦(-0.0112vd+2.35). In the glass having the composition specified in the present invention, the refractive index (n _d ) and the Abbe number (v _d ) satisfying this relationship makes it possible to obtain a more stable glass.
Therefore, in the optical glass of the present invention, the refractive index (n _d ) and the Abbe number (ν _d ) preferably satisfy the relationship n _d ≧(-0.0112ν _d +2.15), more preferably satisfy the relationship n _d ≧(-0.0112ν _d +2.17), even more preferably satisfy the relationship n _d ≧(-0.0112ν _d +2.20), even more preferably satisfy the relationship n _d ≧(-0.0112ν _d +2.21), and even more preferably satisfy the relationship n _d ≧(-0.0112ν _d +2.22).
On the other hand, in the optical glass of the present invention, the refractive index (n _d ) and the Abbe number (ν _d ) preferably satisfy the relationship n _d ≦(-0.0112ν _d + 2.35), more preferably satisfy the relationship n _d ≦(-0.0112ν _d + 2.30), more preferably satisfy the relationship n _d ≦(-0.0112ν _d + 2.27), and further preferably satisfy the relationship n _d ≦(-0.0112ν _d + 2.25).

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 +2.0×10 ⁻⁶ ° C. ⁻¹ , and even more preferably +1.0×10 ⁻⁶ ° C. ⁻¹ , and the temperature coefficient of the relative refractive index of the optical glass of the present invention 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 −10.0×10 ⁻⁶ ° C. ⁻¹ , more preferably −5.0×10 ⁻⁶ ° C. ⁻¹ , and even more preferably −1.0×10 ⁻⁶ ° C. ⁻¹ , and can take on values either higher than this lower limit (on the positive side).
Among these, glass with a refractive index (n _d ) of 1.75 or more and an Abbe number (ν _d ) of 18 to 45 is hardly known that has a low temperature coefficient of the relative refractive index, which broadens the options for correcting image shifts and the like caused by 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 and the like caused by 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 for light with a wavelength of 589.29 nm in air at the same temperature as the optical glass, and is expressed as the amount of change (°C ^-1 ) per degree Celsius when the temperature is changed from 40°C to 60°C.

[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 performing mechanical processing such as grinding and polishing on the optical glass, 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 can be subjected to precision press molding to produce a glass molded body. Note that the means for producing a glass molded body are 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. 60) of the present invention and the comparative example (No. A), as well as the refractive index (n _d ), Abbe number (ν _d ), and temperature coefficient of relative refractive index (dn/dT) of these glasses are shown in Tables 1 to 9. 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, hydroxides, and metaphosphate compounds, as the raw materials for each component, weighing them out to obtain the composition ratios of each example shown in the table, 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 1000 to 1500°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 of 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 formula Abbe number (ν _d ) = [(n d -1) / (n F -n C )] using the refractive index of the d _- line, 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 ). Then, from the obtained values of the refractive index (n _d ) and the Abbe number (ν _d ), the intercept b when the slope a is 0.0112 in the relational expression n _d = -a × ν _d + b was obtained. The glass used in this measurement was treated in an annealing furnace with an annealing rate of -25 ° C / hr.

The temperature coefficient of the relative refractive index (dn/dT) of the glasses in the examples and comparative examples was measured by 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," measuring the value of the temperature coefficient of the relative refractive index for light with a wavelength of 589.29 nm when the temperature was changed from 40°C to 60°C.

As shown in the table, the optical glasses of the examples all had a temperature coefficient of relative refractive index within the range of +3.0×10 ^-6 to -10.0×10 ^-6 (°C ^-1 ), more specifically within the range of ±2.0×10 ^-6 (°C ^-1 ), which was within the desired range.

The optical glasses of the Examples all had a refractive index (n _d ) of 1.75 or more, which was within the desired range. The optical glasses of the Examples of the present invention all had an Abbe number (ν _d ) in the range of 18 to 45, more specifically, in the range of 23 to 43, which was within the desired range.
Furthermore, the optical glasses of the examples of the present invention had refractive index (n _d ) and Abbe number (v _d ) that satisfied the relationship of (-0.0112v _d + 2.15)≦n _d ≦(-0.0112v _d + 2.35), and more specifically, the relationship of (-0.0112v _d + 2.17)≦n _d ≦(-0.0112v _d + 2.26). The relationship between the refractive index (n _d ) and Abbe number (v _d ) for the glasses of the examples of the present application is as shown in FIG.

In addition, the optical glass of the examples formed stable glass, and devitrification was unlikely to occur during glass production.

It was therefore evident that the optical glasses of the Examples have a refractive index (n _d ) and Abbe number (ν _d ) within the desired range, and have a low temperature coefficient of relative refractive index. From this, it is presumed that the optical glasses of the Examples of the present invention will contribute to the miniaturization and weight reduction 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 (10)

In mass percent,
_B2O3 component _is 12.0% or more and 35.0% or less,
_La2O3 component is _30.31 % or less,
A total content _{of Ln2O3} components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is more than 20.0% and not more than 45.0%;
BaO content is more than 22.0% and not more than 37.0%;
_TiO2 component is 12.41% or less,
Contains less than 1.0% ZnO;
The mass sum of _TiO2 + _ZrO2 + _WO3 + _Nb2O5 + _Ta2O5 is more than 0% _{and 13.37} % or less,
An optical glass having a refractive index (n _d ) of 1.78 or more and 1.90 or less , an Abbe number (ν _d ) of 35.9 or more and 43 or less, and a temperature coefficient (40 to 60° C.) of the relative refractive index (589.29 nm) within the range of +3.0×10 ^-6 to -1.0 ×10 ^-6 (° C. ^-1 ). In mass percent,
_SiO2 component 0 to 22.0%,
_Gd2O3 component ₀ to 15.0%,
_Y2O3 component 0 to _25.0 %,
Yb ₂ O ₃ component 0-10.0%,
_ZrO2 component 0 to less than 10.0%
_Nb2O5 component ₀ to less than 10.0%
_WO3 component 0 to 10.0%,
_Ta2O5 component _0-10.0 %,
MgO content: 0 to 10.0%
CaO content: 0 to 15.0%
SrO content 0 to 17.0%,
Li ₂ O component 0-5.0%,
_Na2O content 0-10.0%,
K ₂ O component 0-10.0%,
P ₂ O ₅ component 0-10.0%,
_GeO2 component 0 to 10.0%,
Al ₂ O ₃ component 0-15.0%,
_Ga2O3 component 0 to _10.0 %,
_Bi2O3 component ₀ to 10.0%,
_TeO2 component 0 to 10.0%,
_SnO2 component 0 to 3.0%,
Sb ₂ O ₃ component 0-1.0%
and
2. The optical glass according to claim 1, wherein the content of F in the fluoride which has substituted a part or all of the oxide of one or more of said elements is 0 to 10.0 mass %. 3. The optical glass according to claim 1, wherein the mass sum (SiO ₂ +B ₂ O ₃ ) is more than 12.0% and 37.0% or less. 4. The optical glass according to claim 1, wherein the mass ratio BaO/ _SiO2 is 1.50 or more. 5. The optical glass according to claim 1, wherein the mass ratio BaO/( _{SiO2 + B2O3} +ZnO) is greater than 0.50 and equal to or less than 4.00. The optical glass according to any one of claims 1 to 5, wherein the sum of the contents of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is 20.0% or more and 55.0% or less by mass. 7. The optical glass according to claim 1, wherein the sum of the contents of _Rn2O components (wherein Rn is one or more selected from the group consisting of Li, Na and K) is 10.0% or less by mass. A preform material made of the optical glass according to any one of claims 1 to 7. An optical element made of the optical glass according to any one of claims 1 to 7. An optical device comprising the optical element according to claim 9.

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