JP7126350B2 - Optical glass, optical elements and preforms - Google Patents

Description

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

In recent years, optical elements incorporated in on-vehicle optical equipment such as in-vehicle cameras and surveillance cameras, and optical elements incorporated in many optical equipment such as projectors, copiers, laser printers, broadcasting equipment, etc. contains a blur called chromatic aberration.

Chromatic aberration is corrected by combining a low-dispersion lens and a high-dispersion lens, but chromatic aberration may remain in a wide band from visible light to infrared light. Here, chromatic aberration in a wide band including visible light and infrared light can be improved by using a lens having a large partial dispersion ratio (θ _C , _t ).

The partial dispersion ratio (θ _C , _t ) is given by the following formula (1).
θ _C , _t = (n _C −n _t )/(n _F −n _C ) (1)

In optical glass, there is an approximately linear relationship between the partial dispersion ratio (θ _c , _t ) representing the partial dispersion in the long wavelength region and the Abbe number (νd). The straight line representing this relationship plots the partial dispersion ratios and Abbe numbers of NSL7 and PBM2 on orthogonal coordinates with the partial dispersion ratio (θ _c , _t ) on the vertical axis and the Abbe number (νd) on the horizontal axis. A straight line connecting two points is called a normal line (see FIG. 1). The normal glass used as the standard of the normal line differs depending on the optical glass manufacturer, but each company defines it with almost the same slope and intercept. (NSL7 and PBM2 are optical glasses manufactured by Ohara Co., Ltd., the Abbe number (νd) of PBM2 is 36.3, the partial dispersion ratio (θ _c , _t ) is 0.7168, and the Abbe number (νd) of NSL7 is 60.5, and the partial dispersion ratio (θ _C , _t ) is 0.8305.)

The anomalous dispersion (Δθ _C , _t ) is an index that indicates how far the plot of the partial dispersion ratio (θ _C , _t ) and the Abbe number (νd) deviates from the normal line in the vertical axis direction. An optical element made of glass with a large anomalous dispersion (Δθ _C , _t ) has the property of being able to correct chromatic aberration caused by other lenses.

An object of the present invention is to provide an optical glass having a large anomalous dispersion (Δθ _C , _t ) in which the partial dispersion ratio (θ _C , _t ) and the Abbe number (νd) satisfy a specific relationship.

As a result of intensive testing and research in order to solve the above problems, the inventors of the present invention found that partial dispersion can be achieved by adding 10.0 to 60.0% of BaO in a glass containing SiO ₂ and B ₂ O ₃ components. The inventors have found that an optical glass having a lower ratio (θ _C , _t ) (that is, having a large anomalous dispersion property) can be obtained, and have completed the present invention.
The present invention is the following (1) to (14).
(1) in mass %,
_SiO2 content less than 14.0%,
more than 0 to 30.0% of the B ₂ O ₃ component,
more than 0 to 35.0% of the La ₂ O ₃ component,
10.0 to 60.0% BaO component
contains
mass ratio (RO+K2O)/ _{( TiO2} + _Nb2O5 +WO3+ZrO2 ₊ ZnO _{+ SiO2 +} B2O3) is _3.00 or less _,
Satisfying the relationship (0.005×νd+0.480)≦(θ _C , _t )≦(0.005×νd+0.550) between the partial dispersion ratio (θ _C , _t ) and the Abbe number (νd) , optical glass.
(2) in mass %,
SiO ₂ component of 6.9% or more and less than 14.0%,
1.8 to 15.2% of the B ₂ O ₃ component,
3.9-25.7% La ₂ O ₃ component,
26.8 to 48.0% BaO component,
The optical glass according to (1) above, containing
(3) in mass %,
MgO component 0-5.0%
CaO component 0-15.0%
SrO component 0-15.0%
K ₂ O component 0-10.0%
TiO ₂ component 0-25.0%
Nb ₂ O ₅ component 0-26.0%
WO ₃ components 0-10.0%
ZrO ₂ component 0-10.0%
ZnO component 0-10.0%
Gd ₂ O ₃ component 0-25.0%
Y ₂ O ₃ component 0-25.0%
Yb ₂ O ₃ component 0-10.0%
Li ₂ O component 0-3.0%
Na ₂ O component 0-5.0%
Al ₂ O ₃ component 0-15.0%
Ga ₂ O ₃ component 0-10.0%
P ₂ O ₅ component 0-10.0%
GeO ₂ component 0-10.0%
Ta ₂ O ₅ component 0-5.0%
Bi ₂ O ₃ component 0-10.0%
TeO ₂ component 0-10.0%
SnO ₂ component 0-3.0%
Sb ₂ O ₃ component 0-1.0%
and
The above (1) or (2), wherein the content of F in the fluoride substituted for a part or all of one or more oxides of the above elements is 0 to 10.0% by mass. optical glass.
(4) The optical glass according to any one of the above (1) to (3), wherein the sum of the contents of the RO components is 14.0% or more and 65.0% or less (in the formula, R is Mg , Ca, Sr, and Ba).
(5) The optical glass according to any one of the above (1) to (4), wherein the mass sum (RO + K ₂ O) is 14.0% or more and 65.0% or less (wherein R is Mg, Ca, Sr , Ba).
(6) The optical glass according to any one of (1) to (5) above, wherein the mass sum (SiO ₂ +B ₂ O ₃ ) is 10.0% or more and 55.0% or less.
(7) The optical glass according to any one of (1) to (6) above, wherein the mass sum of TiO ₂ +Nb ₂ O ₅ +WO ₃ +ZrO ₂ is 40.0% or less.
(8) The optical glass according to any one of the above (1) to (7), wherein the sum of the contents of the Ln ₂ O ₃ components is 3.0% or more and 50.0% or less (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y and Yb).
(9) The optical glass according to any one of the above (1) to (8), wherein the total content of Rn ₂ O components is 10.0% or less (in the formula, Rn is Li, Na, K One or more selected from the group consisting of).
( ₁₀ ) The optical glass according to any one of (1) to (9) above, wherein the mass ratio _{( SiO2} + _Al2O3 + _{TiO2 + Nb2O5 +} ZrO2)/ _B2O3 is 0.20 or more.
(11) A preform made of the optical glass described in any one of (1) to (10) above.
(12) An optical element comprising the optical glass described in any one of (1) to (10) above.
(13) An optical instrument comprising the optical element according to (12) above.

According to the present invention, it is possible to provide an optical glass having a large anomalous dispersion (Δθ _C , _t ) in which the partial dispersion ratio (θ _C , _t ) and the Abbe number (νd) satisfy a specific relationship.

FIG. 10 is a diagram showing a normal line represented on an orthogonal coordinate system in which the partial dispersion ratio (θ _C , _t ) is on the vertical axis and the Abbe number (νd) is on the horizontal axis. FIG. 4 is a diagram showing the relationship between the partial dispersion ratio (θ _C , _t ) and the Abbe number (νd) for glass of Examples.

The optical glass of the present invention will be explained.
The optical glass of the present invention contains less than 14.0% by mass of SiO ₂ component, more than 0 to 35.0% of B ₂ O ₃ component, more than 0 to 35.0% of La ₂ O ₃ component, and BaO component. 10.0 to 60.0%, the mass ratio (RO + K ₂ O) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + ZrO ₂ + ZnO + SiO ₂ + B ₂ O ₃ ) is 3.00 or less, and the partial dispersion ratio An optical glass that satisfies the relationship (0.005×νd+0.480)≦(θ _C , _t )≦(0.005×νd+0.550) between (θ _C , _t ) and Abbe number (νd) is.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. In the present specification, unless otherwise specified, the content (%) of each component means % by mass with respect to the total mass of the glass in terms of oxide composition. Here, the term "composition converted to oxide" means that, when it is assumed that oxides, composite salts, metal fluorides, etc. used as raw materials for the constituent components of the glass of the present invention are all decomposed and changed into oxides when melted, It is a composition in which each component contained in the glass is expressed with the total mass of the produced oxide being 100% by mass.

<Regarding essential ingredients and optional ingredients>
The _SiO2 component is an essential component as a glass-forming oxide.
In particular, when the SiO ₂ component exceeds 0%, the partial dispersion ratio (θ _C , _t ) is increased. In addition, chemical durability, especially water resistance, can be increased, the viscosity of molten glass can be increased, and coloration of glass can be reduced. In addition, the stability of the glass is enhanced to facilitate the production of glass that can withstand mass production. Therefore, the content of the SiO ₂ component is preferably more than 0%, more preferably 4.0% or more, still more preferably 6.9% or more.
On the other hand, by setting the content of the SiO ₂ component to less than 14.0%, 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 SiO ₂ component is preferably less than 14.0%, preferably 13.9% or less, more preferably 13.8% or less.

The B ₂ O ₃ component is an essential component as a glass-forming oxide. In particular, the partial dispersion ratio (θ _C , _t ) is increased by containing more than 0% of the B ₂ O ₃ component. Moreover, devitrification of the glass can be reduced. Therefore, the content of the B ₂ O ₃ component is preferably more than 0%, preferably 0.6% or more, more preferably 1.2% or more, still more preferably 1.8% or more.
On the other hand, by setting the content of the B ₂ O ₃ component to 30.0% or less, a higher refractive index can be easily obtained, the temperature coefficient of the relative refractive index can be reduced, and deterioration of chemical durability can be suppressed. be done. Therefore, the content of the B ₂ O ₃ component is preferably 30.0% or less, more preferably 25.0%, more preferably 20.0% or less, still more preferably 15.2% or less.

The La ₂ O ₃ component is an essential component that can increase the refractive index of the glass when it is contained in an amount exceeding 0%. Therefore, the La ₂ O ₃ component content is preferably more than 0%, more preferably 2.0% or more, more preferably 3.0% or more, more preferably 3.9% or more, and still more preferably 8.0% or more. 8% or more.
On the other hand, by setting the content of the La ₂ O ₃ component to 35.0% or less, the stability of the glass is enhanced, devitrification can be reduced, and an increase in the Abbe's number can be suppressed. Moreover, the meltability of glass raw materials can be improved. Therefore, the content of the La ₂ O ₃ component is preferably 35.0% or less, more preferably 30.0% or less, more preferably 26.0% or less, still more preferably 25.7% or less.

The BaO component is an essential component that is contained in an amount of 10.0% or more, and has the effect of reducing the partial dispersion ratio (θ _C , _t ) to a large extent. In addition, the meltability of the glass raw material can be enhanced, devitrification of the glass can be reduced, the refractive index can be enhanced, and the temperature coefficient of the relative refractive index can be reduced. The BaO component content is preferably 10.0% or more, more preferably 24.0% or more, more preferably 26.0% or more, still more preferably 26.8% or more.
On the other hand, by setting the content of the BaO component to 60.0% or less, it is possible to reduce the decrease in the refractive index of glass, the decrease in chemical durability (water resistance), and devitrification due to excessive content. Therefore, the BaO component content is preferably 60.0% or less, more preferably 55.0% or less, more preferably 52.0% or less, still more preferably 48.0% or less.

The MgO component, CaO component and SrO component are optional components that can adjust the refractive index, meltability and devitrification resistance of the glass when they are contained in an amount exceeding 0%.
On the other hand, by setting the content of the MgO component to 5.0% or less, or the content of the CaO component or the SrO component to 15.0% or less, it is possible to suppress the decrease in the refractive index, and Devitrification due to excessive content of components can be reduced.
Therefore, the content of the MgO component is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less.
Also, the content of the CaO component and the SrO component is preferably 15.0% or less, more preferably 13.0% or less, more preferably 10.0% or less, still more preferably 6.0% or less.

The Li ₂ O component, the Na ₂ O component and the K ₂ O component, when contained in an amount exceeding 0%, have the effect of increasing the partial dispersion ratio (θ _C , _t ) and can improve the meltability of the glass. It is an optional component that can lower the transition point. In particular, when the K ₂ O component exceeds 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, it becomes difficult to lower the refractive index of the glass and the devitrification of the glass can be reduced. Moreover, especially by reducing the content of the Li ₂ O component, the viscosity of the glass is increased, so that the striae of the glass can be reduced.
Therefore, the content of the Li ₂ O component may be preferably 3.0% or less, more preferably less than 1.8%, still more preferably 1.4% or less.
Also, the content of the Na ₂ O component may be preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less.
Also, the content of the K ₂ O component may be preferably 10.0% or less, more preferably 7.0% or less, more preferably 4.0% or less, still more preferably 1.0% or less.

When the TiO ₂ component is contained in an amount exceeding 0%, it has the effect of reducing the partial dispersion ratio (θ _C , _t ), increases the refractive index of the glass, lowers the Abbe number, and prevents devitrification of the glass. It is an optional component that can be reduced. Therefore, the content of the TiO ₂ component may be preferably more than 0%, more preferably 0.5% or more, more preferably 1.0% or more, still more preferably 2.0% or more.
On the other hand, by setting the content of the TiO ₂ component to 25.0% or less, the temperature coefficient of the relative refractive index can be reduced, the devitrification due to the excessive content of the TiO ₂ component can be reduced, and the visible light of the glass (especially (wavelength of 500 nm or less) can be suppressed. Therefore, the content of the TiO ₂ component may be preferably 25.0% or less, more preferably 22.0% or less, more preferably 21.0% or less, still more preferably 20.0% or less.

The Nb ₂ O ₅ component is an optional component that can increase the refractive index of the glass, lower the Abbe's number, and lower the liquidus temperature of the glass to improve the resistance to devitrification when the Nb 2 O 5 content exceeds 0%. Therefore, the content of the Nb ₂ O ₅ component may preferably exceed 0%, more preferably be 1.0% or more, and still more preferably be 1.1% or more.
On the other hand, by setting the content of the Nb ₂ O ₅ component to 26.0% or less, the temperature coefficient of the relative refractive index can be reduced, the devitrification due to excessive content of the Nb ₂ O ₅ component can be reduced, and A decrease in the transmittance of glass to visible light (especially wavelengths of 500 nm or less) can be suppressed. Therefore, the content of the Nb ₂ O ₅ component is preferably 26.0% or less, more preferably 24.0% or less, more preferably 22.0% or less, more preferably 20.0% or less, still more preferably It may be 18.0% or less.

The _WO3 component has the effect of reducing the partial dispersion ratio (θ _C , _t ) when it is contained at more than 0%, and also increases the refractive index while reducing the coloring of the glass due to other high refractive index components. , is an optional component that can lower the Abbe number, lower the glass transition point, and reduce devitrification. Therefore _, the content of the WO3 component may be preferably more than 0%, more preferably 0.5% or more, still more preferably 0.7% or more.
_On the other hand, by setting the content of the WO3 component to 10.0% or less, it is possible to reduce the temperature coefficient of the relative refractive index and reduce the material cost. Also, the visible light transmittance can be increased by reducing the coloration of the glass due to the _WO3 component. Therefore _, the content of the WO3 component may be preferably 10.0% or less, more preferably 6.0% or less, more preferably 5.0% or less, still more preferably 1.5% or less.

The ZrO ₂ component is an optional component that can increase the refractive index of the glass while enhancing the effect of increasing the partial dispersion ratio (θ _C , _t ) when it is contained in an amount exceeding 0%. Therefore, the content of the ZrO ₂ component may be preferably greater than 0%, more preferably 0.5% or more, and even more preferably 1.0% or more.
On the other hand, by setting the content of the ZrO ₂ component to 10.0% or less, the temperature coefficient of the relative refractive index can be reduced, and devitrification due to excessive content of the ZrO ₂ component can be reduced. Therefore, the content of the ZrO ₂ component may be preferably 10.0% or less, more preferably 7.5% or less, even more preferably 5.0% or less.

The ZnO component is an optional component that can improve the meltability of the raw material, promote defoaming from the melted glass, and improve the stability of the glass when it is contained in an amount of more than 0%. It is also a component that can lower the glass transition point and improve the chemical durability.
On the other hand, by setting the content of the ZnO component to 10.0% or less, 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 excessive viscosity can be prevented. Devitrification due to reduction can be reduced. Therefore, the content of the ZnO component is preferably 10.0% or less, more preferably 9.0% or less, more preferably 8.0% or less, more preferably 7.0% or less, still more preferably 6.0%. % or less.

The Gd ₂ O ₃ component is an optional component that can increase the refractive index of the glass when it is contained in an amount exceeding 0%.
On the other hand, the Gd ₂ O ₃ component has a high raw material price among the rare earth elements, and a large content thereof increases the production cost. Also, by reducing the content of the Gd ₂ O ₃ component, an increase in the Abbe's number of the glass can be suppressed.
Therefore, the content of the Gd ₂ O ₃ component may be preferably 25.0% or less, more preferably 15.0% or less, more preferably 10.0% or less, still more preferably 7.0% or less.
Also, the content of the Gd ₂ O ₃ component may be preferably greater than 0%, more preferably 3.0% or more, more preferably 5.0% or more, and even more preferably 6.0% or more.

The Yb ₂ O ₃ component is an optional component that can increase the refractive index of the glass when it is contained in an amount exceeding 0%.
On the other hand, the Yb ₂ O ₃ component has a high raw material price among the rare earth elements, and a large content thereof increases the production cost. Also, by reducing the content of the Yb ₂ O ₃ component, an increase in the Abbe's number of the glass can be suppressed.
Therefore, the content of the Yb ₂ O ₃ component may be preferably 10.0% or less, more preferably 5.0% or less, and more preferably 2.0% or less.
Also, the content of the Yb ₂ O ₃ component may be preferably more than 0%, more preferably 0.5% or more, and even more preferably 1.0% or more.

When the Y ₂ O ₃ component is contained in an amount exceeding 0%, it has the effect of reducing the partial dispersion ratio (θ _C , _t ), and while increasing the refractive index of the glass, it is more effective than other rare earth elements. is an optional component that can reduce the material cost of Therefore, the content of the Y ₂ O ₃ component may preferably be over 0%, more preferably over 1.0%, and even more preferably 2.0% or more.
On the other hand, by setting the content of the Y ₂ O ₃ component to 25.0% or less, a decrease in the refractive index of the glass can be suppressed, an increase in the Abbe number of the glass can be suppressed, and the stability of the glass can be enhanced. . Moreover, the deterioration of the meltability of glass raw materials can be suppressed. Therefore, the content of the Y ₂ O ₃ component is preferably 25.0% or less, more preferably 21.0% or less, more preferably 18.0% or less, more preferably 15.0% or less, still more preferably It may be 13.5% or less.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components that can improve the devitrification resistance of the glass melt when they are contained in an amount exceeding 0%. Therefore, in particular, the content of the Al ₂ O ₃ component may preferably exceed 0%, more preferably be 0.2% or more, and still more preferably be 0.3% or more.
On the other hand, by setting the content of the Al ₂ O ₃ component to 15.0% or less or the content of the Ga ₂ O ₃ component to 10.0% or less, respectively, the liquidus temperature of the glass is lowered and the resistance is increased. Devitrification can be enhanced.
Therefore, the content of the Al ₂ O ₃ component may be preferably 15.0% or less, more preferably 10.0% or less, more preferably 6.0% or less, still more preferably 3.0% or less.
Also, the content of the Ga ₂ O ₃ component may be preferably 10.0% or less, more preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less.

The P ₂ O ₅ component is an optional component that has the effect of reducing the partial dispersion ratio (θ _C , _t ) when it is contained in an amount exceeding 0%, and also lowers the liquidus temperature of the glass to improve devitrification resistance. is.
On the other hand, by setting the content of the P ₂ O ₅ component to 10.0% or less, it is possible to suppress the deterioration of the chemical durability of the glass, particularly the water resistance. Therefore, the content of the P ₂ O ₅ component may be preferably 10.0% or less, more preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, It may not contain the P ₂ O ₅ component.

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

The Ta ₂ O ₅ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the Ta ₂ O ₅ component to 5.0% or less, the raw material cost of the optical glass can be reduced, the melting temperature of the raw material is lowered, and the energy required for melting the raw material is reduced. Therefore, the manufacturing cost of the optical glass can be reduced. Therefore, the content of the Ta ₂ O ₅ component may be preferably 5.0% or less, more preferably 2.0% or less, still more preferably 1.0% or less. Especially from the viewpoint of reducing the material cost, it is preferable not to contain the Ta ₂ O ₅ component.

When the Bi ₂ O ₃ component is contained in an amount exceeding 0%, it has the effect of reducing the partial dispersion ratio (θ _C , _t ), increases the refractive index, lowers the Abbe number, and lowers the glass transition point. optional ingredient.
On the other hand, by setting the content of the Bi ₂ O ₃ component to 10.0% or less, the liquidus temperature of the glass can be lowered and the devitrification resistance can be enhanced. Therefore, the content of the Bi ₂ O ₃ component may be preferably 10.0% or less, more preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less.

The TeO ₂ component is an optional component that can increase the refractive index and lower the glass transition point when contained in excess of 0%.
_On the other hand, the TeO2 component has a problem that it may be alloyed with platinum when frit is melted in a crucible made of platinum or in a melting tank in which the portion in contact with the molten glass is made of platinum. Therefore, the content of the TeO ₂ component may be preferably 10.0% or less, more preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less.

The SnO ₂ component is an optional component that, when contained in excess of 0%, can reduce the oxidation of the glass melt to refine it and increase the visible light transmittance of the glass.
On the other hand, by setting the content of the SnO ₂ component to 3.0% or less, it is possible to reduce the coloring of the glass due to the reduction of the molten glass and the devitrification of the glass. In addition, since alloying of the SnO ₂ component and the melting equipment (especially precious metals such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the SnO ₂ component content may be preferably 3.0% or less, more preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less.

The Sb ₂ O ₃ component is an optional component capable of defoaming the glass melt when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the Sb ₂ O ₃ component to 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 the Sb ₂ O ₃ component may be preferably 1.0% or less, more preferably 0.5% or less, more preferably 0.2% or less, still more preferably 0.1% or less.

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

When the F component is contained by more than 0%, it has the effect of reducing the partial dispersion ratio (θ _C , _t ), and also increases the Abbe number of the glass, lowers the glass transition point, and improves devitrification resistance. It is an optional ingredient that can be improved.
However, when the content of the F component, that is, the total amount as F of the fluoride substituted with a part or all of one or more oxides of each metal element described above exceeds 10.0%, F Since the amount of volatilization of the components increases, it becomes difficult to obtain stable optical constants, making it difficult to obtain a homogeneous glass. Also, the Abbe number increases more than necessary.
Therefore, the content of component F is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, and even more preferably 1.0% or less.

Sum of contents (mass sum) of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba), i.e., MgO content (%) + CaO content (%) +SrO content (%) +BaO content (%) is preferably 14.0% or more. Thereby, devitrification of the glass can be reduced, and the temperature coefficient of the relative refractive index can be reduced. Therefore, the mass sum of RO components is preferably 14.0% or more, more preferably 17.0% or more, more preferably 20.0% or more, more preferably 23.0% or more, and still more preferably 26.0%. % or more.
On the other hand, by setting the mass sum of the RO components to 65.0% or less, the decrease in refractive index can be suppressed and the stability of the glass can be enhanced. Therefore, the mass sum of RO components is preferably 65.0% or less, more preferably 55.0% or less, and even more preferably 50.0% or less.

The sum of the contents of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) and the K ₂ O component (mass sum), that is, the MgO content (%) + CaO content (%) + SrO content (%) + BaO content (%) + K ₂ O content (%) is preferably 14.0% or more.
In particular, by setting the mass sum of the mass sum (RO+K ₂ O) to 14.0% or more, devitrification of the glass can be reduced and the temperature coefficient of the relative refractive index can be decreased. Therefore, the mass sum (RO + K ₂ O) is preferably 14.0% or more, more preferably 17.0% or more, more preferably 20.0% or more, more preferably 23.0% or more, still more preferably 26% 0% or more.
On the other hand, by setting the mass sum (RO+K ₂ O) to 65.0% or less, the decrease in refractive index can be suppressed and the stability of the glass can be enhanced. Therefore, the mass sum (RO+K ₂ O) is preferably 65.0% or less, more preferably 55.0% or less, even more preferably 50.0% or less.

The total amount of SiO ₂ component and B ₂ O ₃ is preferably 10.0% or more and 55.0% or less.
In particular, by setting the total amount to 10.0% or more, the partial dispersion ratio (θ _C , _t ) can be increased, and stable glass can be easily obtained. Therefore, the mass sum (SiO ₂ +B ₂ O ₃ ) is preferably 10.0% or more, more preferably 11.0% or more, more preferably 13.0% or more, still more preferably 15.0% or more. .
On the other hand, by setting the total amount to 55.0% or less, the temperature coefficient of the relative refractive index can be reduced. Therefore, the mass sum (SiO ₂ +B ₂ O ₃ ) is preferably 55.0% or less, more preferably 40.0% or less, more preferably 35.0% or less, more preferably 28.0% or less, and further preferably It is preferably 24.0% or less.

The total amount (mass sum) of TiO ₂ component, Nb ₂ O ₅ component, WO ₃ component and ZrO ₂ component is preferably 40.0% or less. This makes it possible to reduce the temperature coefficient of the relative refractive index. Therefore, the mass sum of TiO ₂ +Nb ₂ O ₅ +WO ₃ +ZrO ₂ is preferably 40.0% or less, more preferably 38.0% or less, more preferably 36.0% or less, and still more preferably 34.0% or less. and

_RO component ₍ in the _{formula ,} R is _Mg , _Ca , _{Sr ,} (at least one selected from the group consisting of Ba) and K ₂ O components (mass ratio) is preferably 0.60 or more and 3.00 or less.
By increasing this ratio, the temperature coefficient of the relative refractive index can be decreased. Therefore, the mass ratio (RO+K2O)/ _{( TiO2} + _Nb2O5 + _WO3 +ZrO2 ₊ ZnO _{+ SiO2 +} B2O3) is preferably 0.60 or more _, more preferably 0.65 or more, and more preferably 0.65 or more. 70 or more, more preferably 0.75 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 2.10 or less, more preferably 1.80 or less, still more preferably 1.50 or less.

Sum of contents (mass sum) of Ln ₂ O ₃ components (wherein Ln is one or more selected from the group consisting of La, Gd, Y and Yb), that is, La ₂ O ₃ content (%) +Gd ₂ O ₃ content (%) + Y ₂ O ₃ content (%) + Yb ₂ O ₃ content (%) is preferably 3.0% or more and 50.0% or less.
In particular, by making this sum 3.0% or more, the refractive index and Abbe number of the glass are increased, so that it is possible to easily obtain glass having a desired refractive index and Abbe number. Therefore, the mass sum of the Ln ₂ O ₃ components is preferably 3.0% or more, more preferably 3.5% or more, and still more preferably 3.9% or more.
On the other hand, by setting the sum to 50.0% or less, the liquidus temperature of the glass is lowered, so that devitrification of the glass can be reduced. In addition, an excessive increase in the Abbe's number can be suppressed. Therefore, the mass sum of the Ln ₂ O ₃ components is preferably 50.0% or less, more preferably 48.0% or less, more preferably 45.0% or less, more preferably 42.0% or less, and even more preferably 39.0% or less.

The sum (mass sum) of the contents of the Rn ₂ O components (wherein Rn is at least one selected from the group consisting of Li, Na and K) is Li ₂ O content (%) + Na ₂ O Content rate (%) + K ₂ O content rate (%) is preferably 10.0% or less. This makes it possible to suppress a decrease in the viscosity of the molten glass, make it difficult to decrease the refractive index of the glass, and reduce devitrification of the glass. Therefore, the mass sum of the Rn ₂ O components is preferably 10.0% or less, more preferably 7.0% or less, more preferably 4.0% or less, still more preferably 2.0% or less.

The ratio (mass ratio) of the total content of the SiO ₂ component, Al ₂ O ₃ component, TiO ₂ component, Nb ₂ O ₅ component and ZrO ₂ component to the content of the B ₂ O ₃ component is 0.20 or more. preferable.
By increasing this ratio, the chemical durability of the glass, especially the water resistance, can be enhanced. Therefore, the mass ratio _{( SiO2} +BaO+ _Al2O3 + _{TiO2 + Nb2O5 +} ZrO2)/ _B2O3 is preferably 0.20 or more _, more preferably 0.50 or more, more preferably 0.80 or more, It is more preferably 1.00 or more.
On the other hand, from the viewpoint of obtaining a stable glass, this mass ratio may be preferably 32.0 or less, more preferably 30.0 or less, and even more preferably 28.0 or less.

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

Other components can be added as necessary within a range that does not impair the properties of the glass of the present invention. However, each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb and Lu, is Or even if it is combined and contained in a small amount, the glass is colored and has the property of causing absorption at a specific wavelength in the visible region. .

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

Furthermore, Th, Cd, Tl, Os, Be, and Se components have recently tended to refrain from being used as harmful chemical substances, and are not only used in the glass manufacturing process, but also in the processing process and disposal after manufacturing. Environmental measures are required up to the present. Therefore, it is preferable not to contain these substantially when environmental influence is emphasized.

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, high-purity raw materials used in ordinary optical glass such as oxides, hydroxides, carbonates, nitrates, fluorides and metaphosphoric acid compounds are used as raw materials for the respective components above, and each component has a predetermined content. After uniformly mixing within the range, the prepared mixture is put into a platinum crucible and melted in an electric furnace at a temperature range of 800 to 1400 ° C. for 2 to 10 hours depending on the melting difficulty of the glass raw material. It is prepared by stirring, sufficiently homogenizing, lowering the temperature to an appropriate temperature, casting it into a mold or the like, and slowly cooling it.

Here, it is preferable that the optical glass of the present invention does not use sulfate as a raw material. This promotes the removal of air bubbles from the glass raw material after melting, thereby suppressing the air bubbles from remaining in the optical glass.

<Physical properties>
The optical glass of the present invention has a high refractive index and a high Abbe number (low dispersion).
In particular, the lower limit of the refractive index (nd) of the optical glass of the present invention is preferably 1.70, more preferably 1.73, still more preferably 1.75, still more preferably 1.77.
The upper limit of the refractive index (nd) may preferably be 2.00, more preferably 1.90, and even more preferably 1.88.
The lower limit of the Abbe number (νd) of the optical glass of the present invention is preferably 27, more preferably 28, still more preferably 29, and still more preferably 29.8.
The upper limit of the Abbe number (νd) may be preferably 55, more preferably 53, still more preferably 50, more preferably 45, still more preferably 41.
By having such a high refractive index, it is possible to obtain a large amount of light refraction even if the thickness of the optical element is reduced. In addition, by having such low dispersion, it is possible to reduce defocus (chromatic aberration) caused by the wavelength of light when used as a single lens. Therefore, when an optical system is configured by combining an optical element having high dispersion (low Abbe number), for example, aberration can be reduced in the optical system as a whole, and high imaging characteristics can be achieved.
As described above, the optical glass of the present invention is useful in optical design, and in particular, when an optical system is constructed, it is possible to reduce the size of the optical system while achieving high image-forming characteristics. degree of freedom can be expanded.

Since the optical glass of the present invention has a low partial dispersion ratio (θ _C , _t ) with respect to the Abbe number (νd), it has a large anomalous dispersion (Δθ _C , _t ). Specifically, between the partial dispersion ratio (θ _C , _t ) and the Abbe number (νd), (0.005 × νd + 0.480) ≤ (θ _C , _t ) ≤ (0.005 × νd + 0.550 ) satisfies the relationship
The partial dispersion ratio (θ _C , _t ) satisfies (0.005×νd+0.480)≦(θ _C , _t ), but (0.005×νd+0.490)≦(θ _C , _t ). is preferable, and it is more preferable to satisfy (0.005×νd+0.500)≦(θ _C , _t ).
Also, the partial dispersion ratio (θ _C , _t ) satisfies (θ _C , _t )≦(0.005×νd+0.550), but (θ _C , _t )≦(0.005×νd+0.545). It is preferable to satisfy (θ _C , _t )≦(0.005×νd+0.540).
Here, when the content is increased, F, TiO ₂ , Bi ₂ O ₃ , and Y ₂ O are components having the effect of reducing the partial dispersion ratio (θ _c , _t ) with respect to the Abbe number (νd). ₃ is mentioned. In particular, the inventors have found that a high content of BaO is highly effective in reducing the partial dispersion ratio (θ _C , _t ) with respect to the Abbe number (νd).
On the other hand, SiO ₂ , B ₂ O ₃ , alkali metal oxides, and the like are components having the effect of increasing the partial dispersion ratio (θ _c , _t ) with respect to the Abbe number (νd) when the content is increased. _{( Rn2O} ), ZrO2.

[Preform and optical element]
A glass molded body can be produced from the produced optical glass by, for example, polishing means or mold press molding means such as reheat press molding or precision press molding. Specifically, optical glass is subjected to machining such as grinding and polishing to produce a glass molded body, or a preform for mold press molding is produced from optical glass, and this preform is subjected to reheat press molding. After that, polishing is performed to produce a glass molded body, or precision press molding is performed on a preform produced by polishing or a preform molded by known floating molding or the like. can be produced. In addition, the means for producing the glass molded body is not limited to these means.

Thus, the optical glass of the present invention is useful for various optical elements and optical designs. Among them, it is particularly preferable to form a preform from the optical glass of the present invention and perform reheat press molding, precision press molding, or the like using this preform to produce optical elements such as lenses and prisms. As a result, it is possible to form a preform having a large diameter, so that it is possible to achieve high-definition and high-precision imaging and projection characteristics when used in an optical device while increasing the size of the optical element.

The glass molded body made of the optical glass of the present invention is useful for various optical elements, but it is particularly preferably used for optical elements such as lenses and prisms. This reduces color fringing due to chromatic aberration in the light transmitted through the optical system in which the optical element is provided. Therefore, when this optical element is used in a camera, the object to be photographed can be represented more accurately, and when this optical element is used in a projector, a desired image can be projected with higher definition.

Table 1 shows the compositions of Examples 1 to 12 of the present invention and Comparative Example 1, and the results of refractive index (nd), Abbe number (νd), partial dispersion ratio (θ _C , _t ), etc. of these glasses. . In addition, the following examples are only examples, and the scope of the invention is not limited only to these examples.

The glasses of Examples 1 to 12 of the present invention and Comparative Example 1 are all ordinary optical glasses such as corresponding oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphate compounds, etc. as raw materials for each component. After selecting the high-purity raw materials used for , weighing and mixing uniformly so that the composition ratio of each example shown in the table is obtained, put it into a platinum crucible, and depending on the melting difficulty of the glass raw materials After melting in an electric furnace at a temperature range of 800 to 1400° C. for 2 to 10 hours, the mixture was stirred and sufficiently homogenized, poured into a mold or the like, and slowly cooled.

The refractive index (nd), Abbe number (νd), and partial dispersion ratio (θc, _t ) of the glasses of Examples 1 to 12 and Comparative Example 1 are shown as measured values for the d-line (587.56 nm) of a helium lamp. . The Abbe number (νd) is the refractive index for the d-line, the refractive index (n _F ) for the hydrogen lamp F-line (486.13 nm), and the refractive index (n _C ) for the C-line (656.27 nm). was calculated from the formula of Abbe number (νd)=[(n _d −1)/(n _F −n _C )]. Further, the partial dispersion ratio (θ _C,t ) is the refractive index for the c-line (n _C ), the refractive index for the t-line (1013.98 nm) of infrared mercury (n _t ), and the refractive index for the F-line ( n _F ) was used to calculate the partial dispersion ratio (θ _C , _t )=[(n _C −n _t )/(n _F −n _C )].

As shown in Table 1 and FIG. 2, all the optical glasses of Examples had a refractive index (nd) of 1.77 or more. Moreover, the optical glasses of the examples of the present invention all had an Abbe number (νd) within the range of 27 or more and 53 or less, more specifically, within the range of 29.8 or more and 40.75 or less.

In addition, the optical glasses of Examples formed stable glasses, and devitrification was less likely to occur during glass production.

Further, in the optical glasses of the examples, between the partial dispersion ratio (θ _C , _t ) and the Abbe number (νd), (0.005 × νd + 0.480) ≤ (θ _C , _t ) ≤ (0.005 ×νd+0.550) and has a large anomalous dispersion (Δθ _C , _t ). On the other hand, the optical glass of the comparative example is an optical glass that does not satisfy the relationship of (0.0038×νd+0.5300)≦(θ _C , _t )≦(0.0038×νd+0.5862) and has an anomalous dispersion (Δθ It was an optical glass with small _C , _t ).

Claims (12)

in % by mass,
_SiO2 content less than 14.0%,
more than 0 to 20.0% of the B ₂ O ₃ component,
more than 0 to 30.0% of the La ₂ O ₃ component,
24.0 to 60.0% BaO component,
2.0% or more of the Y ₂ O ₃ component ,
ZnO component 4.00% or less
contains,
The sum of the contents of the Rn ₂ O components is 2.0% or less (wherein Rn is one or more selected from the group consisting of Li, Na and K),
Mass ratio (RO+K2O)/ _{( TiO2} + _Nb2O5 +WO3+ZrO2 ₊ ZnO _{+ SiO2 + B2O3} ) is 0.60 or more and _3.00 or less (wherein R is Mg, Ca, Sr, Ba one or more selected from the group consisting of) ,
Satisfying the relationship (0.005×νd+0.480)≦(θ _C , _t )≦(0.005×νd+0.540) between the partial dispersion ratio (θ _C , _t ) and the Abbe number (νd) , optical glass. in % by mass,
SiO ₂ component of 6.9% or more and less than 14.0%,
1.8 to 15.2% of the B ₂ O ₃ component,
3.9-25.7% La ₂ O ₃ component,
26.8 to 48.0% BaO component
The optical glass according to claim 1, comprising: in % by mass,
MgO component 0-5.0%
CaO component 0-15.0%
SrO component 0-15.0%
K2O component 0-1.0 _%
TiO ₂ component 0-25.0%
Nb ₂ O ₅ component 0-26.0%
WO ₃ components 0-10.0%
ZrO ₂ component 0-10.0 %
Gd2O3 _{component 0-25.0} %
Y ₂ O ₃ component 2.0-25.0 %
Yb ₂ O ₃ component 0-10.0%
Li ₂ O component 0-1.4 %
Na ₂ O component 0-1.0 %
Al ₂ O ₃ component 0-15.0%
Ga ₂ O ₃ component 0-10.0%
P ₂ O ₅ component 0-10.0%
GeO ₂ component 0-10.0%
Ta ₂ O ₅ component 0-5.0%
Bi ₂ O ₃ component 0-10.0%
TeO ₂ component 0-10.0%
SnO ₂ component 0-3.0%
Sb ₂ O ₃ component 0-1.0%
and
3. The optical glass according to claim 1 or 2, wherein the F content of the fluoride substituted for a part or all of one or more oxides of each element is 0 to 10.0% by mass. 4. The optical glass according to any one of claims 1 to 3, wherein the total content of RO components is 26.0% or more and 65.0% or less (in the formula, R is Mg, Ca, Sr, Ba One or more selected from the group consisting of). The optical glass according to any one of claims 1 to 4, wherein the mass sum (RO + K ₂ O) is 26.0% or more and 65.0% or less (wherein R is selected from the group consisting of Mg, Ca, Sr and Ba one or more selected). The optical glass according to any one of claims 1 to 5, wherein the mass sum ( _{SiO2 + B2O3} ) is 10.0% or more and 28.0% or less . The optical glass according to any one of claims 1 to ₆ , wherein the mass sum of _TiO2 + _Nb2O5 + _{WO3 +} ZrO2 is 40.0% or less. The optical glass according to any one of claims 1 to 7, wherein the sum of the contents of the _Ln2O3 components is _3.0 % or more and 50.0% or less (in the formula, Ln is La, Gd, Y , Yb). The optical glass according to any one of claims ₁ to 8 _, wherein the mass ratio _{( SiO2} + _Al2O3 + _{TiO2 + Nb2O5 +} ZrO2)/B2O3 is 0.20 or more. A preform comprising the optical glass according to any one of claims 1 to 9 . An optical element comprising the optical glass according to any one of claims 1 to 9 . An optical instrument comprising the optical element according to claim 11 .

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