JP7048348B2 - Optical glass, preforms and optical elements - Google Patents

Description

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

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

Among the optical glasses used to make optical elements, the Abbe number has a refractive index ( _nd ) of 1.90 or more and less than 2.10 and is 27 or more and 37 or less, which enables miniaturization of the entire optical system. The demand for high refractive index low dispersion glass having (ν _d ) is very high. As such a high refractive index low dispersion glass, a glass composition as represented by Patent Document 1 is known.

Japanese Unexamined Patent Publication No. 2012-162448

However, as an optical glass having a refractive index ( _{nd) of 1.90 or more and less than 2.10 and an Abbe number (ν d )} of 27 or more and 37 or less, one having a low light transmittance or an optical element It was only known that the imaging characteristics changed due to temperature changes when used in. Under such circumstances, there has been a demand for glass having a high light transmittance at such a refractive index ( _{nd) and an Abbe number (ν d )} and having a small influence on the imaging performance due to temperature fluctuations.

The present invention has been made in view of the above problems, and an object thereof is to have a light transmittance while the refractive index ( _{nd) and the Abbe number (ν d )} are within desired ranges. It is an object of the present invention to obtain an optical glass which is high and can contribute to correction of image displacement and the like due to a temperature change.

As a result of intensive test and research to solve the above problems, the present inventors have found that the refractive index (refractive index) in the glass containing the SiO ₂ component, the B ₂ O ₃ component, the La ₂ O ₃ component and the TiO ₂ component. We have found that a glass having a high light transmittance and a relative refractive index temperature coefficient within a desired range can be obtained while the n _d ) and Abbe number (ν _d ) are within a desired range. It came to be completed.
Specifically, the present invention provides the following.

(1) By mass%,
SiO ₂ component is more than 0% and 15.0% or less,
B ₂ O ₃ component 1.0 to 17.0%,
La ₂ O ₃ component 40.0-60.0%,
TiO ₂ component is 1.0% or more and 18.0% or less,
Contains,
It has a refractive index (nd) of 1.90 or more and less than 2.10, and has an Abbe number (ν _d ) of 27 or more and 37 or less _.
The shortest wavelength (λ ₅ ) showing a spectral transmittance of 5% in a sample having a thickness of 10 mm is 400 nm or less.
An optical glass having a temperature coefficient (40-60 ° C.) of relative refractive index (589.29 nm) of +8.0 × ^10-6 (° C. ^-1 ) or lower.

(2) By mass%,
Nb ₂ O ₅ component 0 to 17.0%,
Y ₂ O ₃ component 0-20.0%,
ZrO ₂ component 0 to 15.0%,
The optical glass according to (1).

(3) By mass%,
Gd ₂ O ₃ component 0 to 10.0%,
Yb ₂ O ₃ component 0 to 10.0%
Ta ₂ O ₅ component 0 to 10.0%,
WO ₃ component 0 to 10.0%,
ZnO component 0 to 10.0%,
MgO component 0 to 10.0%,
CaO component 0 to 10.0%,
SrO component 0 to 10.0%,
BaO component 0 to 10.0%,
Li ₂ O component 0 to 10.0%,
Na ₂ O component 0 to 10.0%,
K ₂ O component 0 to 10.0%,
P ₂ O ₅ component 0 to 10.0%,
GeO ₂ component 0 to 10.0%,
Al ₂ O ₃ component 0 to 10.0%,
Ga ₂ O ₃ component 0 to 10.0%,
Bi ₂ O ₃ component 0 to 10.0%,
TeO ₂ component 0 to 10.0%,
SnO ₂ component 0-3.0%,
Sb ₂ O ₃ component 0-1.0%
And
The optical glass according to (1) or (2), wherein the content of fluoride as F, which is substituted with a part or all of one or more oxides of each of the above elements, is 0 to 10.0% by mass. ..

(4) By mass%,
The sum of the contents of the Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is 48.0% or more and 70.0% or less.
The sum of the contents of the RO component (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, Zn) is 0 to 10.0%.
Any of (1) to (3) in which the sum of the contents of the Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is 0 to 10.0%. The optical glass described.

(5) Described in any one of (1) to (4), wherein the mass ratio Y ₂ O ₃ / (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ ) is 0.05 or more and 0.30 or less. Optical glass.

(6) The optical glass according to any one of (1) to (5), wherein the mass sum of TiO ₂ + WO ₃ + Nb ₂ O ₅ is 7.0% or more and 28.0% or less.

(7) The optical glass according to any one of (1) to (6), wherein the mass sum SiO ₂ + B ₂ O ₃ is 7.0% or more and 27.0% or less.

(8) A preform made of the optical glass according to any one of (1) to (7).

(9) An optical element made of the optical glass according to any one of (1) to (7).

(10) An optical device including the optical element according to (9).

According to the present invention, the refractive index ( _{nd) and the Abbe number (ν d )} are within the desired ranges, but the light transmittance is high, and it contributes to the correction of the image shift due to the temperature change. It is possible to obtain an optical glass that can be produced.

It is a figure which shows the relationship between the refractive index ( _{nd) and the Abbe number (ν d )} about the glass of the Example of this application.

The optical glass of the present invention has a SiO ₂ component of more than 0% and 15.0% or less, a B ₂ O ₃ component of 1.0 to 17.0%, and a La ₂ O ₃ component of 40.0 to 60 in terms of mass%. It contains 1.0% and TiO ₂ components of 1.0% or more and 18.0% or less, has a refractive index (nd) of 1.90 or more and less than 2.10, and has an Abbe number (ν _d ) of 27 or more and 37 or less _. ), The shortest wavelength (λ ₅ ) showing a spectral transmittance of 5% in a sample having a thickness of 10 mm is 400 nm or less, and the temperature coefficient (40 to 60 ° C.) of the relative refractive index (589.29 nm) is +8. .0 × 10 ^-6 (° C ^-1 ) or lower. The present inventor bases the SiO ₂ component, the B ₂ O ₃ component, and the La ₂ O ₃ component, and when the TiO ₂ component is contained therein, the refractive index (nd) and the Abbe number (ν _d ) are increased _. It has been found that a glass having a high light transmittance and a temperature coefficient of relative refractive index within a desired range can be obtained while being within a desired range. Therefore, while the refractive index ( _{nd) and the Abbe number (ν d )} are within the desired ranges, the light transmittance is high and it is possible to contribute to the correction of the image shift due to the temperature change.

Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention. It should be noted that the description may be omitted as appropriate for the parts where the explanations are duplicated, but the gist of the invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. In the present specification, the content of each component shall be expressed in mass% with respect to the total mass of the oxide equivalent composition, unless otherwise specified. Here, the "oxide-equivalent composition" is used when it is assumed that the oxides, composite salts, metal fluorides and the like used as raw materials for the glass constituents of the present invention are all decomposed at the time of melting and changed to oxides. It is a composition in which each component contained in a glass is described, with the total mass of the produced oxide being 100% by mass.

<About essential ingredients and optional ingredients>
The SiO ₂ component is an essential component as a glass-forming oxide. In particular, by containing more than 0% of the SiO ₂ component, it is also a component that enhances the stability of the glass and facilitates the acquisition of glass that can withstand mass production. In addition, the viscosity of the molten glass can be increased and the coloring of the glass can be reduced. Therefore, the content of the SiO ₂ component is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 3.0%, still more preferably more than 5.0%.
On the other hand, by setting the content of the SiO ₂ component to 15.0% or less, the increase in the glass transition point can be suppressed and the decrease in the refractive index can be suppressed. Therefore, the content of the SiO ₂ component is preferably 15.0% or less, more preferably less than 12.0%, still more preferably less than 10.0%, still more preferably less than 7.0%.

The B ₂ O ₃ component is an essential component as a glass-forming oxide. In particular, by containing 1.0% or _more of the _B2O3 component, the stability of the glass can be enhanced, the devitrification resistance can be enhanced, and the Abbe number of the glass can be increased. Therefore, the content of the _B2O3 component is preferably 1.0% or _more , more preferably more than 3.0%, still more preferably more than 5.0%, still more preferably more than 8.0%, still more preferably. It should be over 10.0%.
On the other hand, by setting the content of the B ₂ O ₃ component to 17.0% or less, a larger refractive index can be easily obtained and deterioration of chemical durability can be suppressed. Therefore, the content of the _B2O3 component is preferably 17.0% or less, _more preferably less than 15.0%, still more preferably less than 12.0%.

The La ₂ O ₃ component is an essential component that increases the refractive index and Abbe number of glass. Moreover, since it is relatively inexpensive among rare earths, the material cost of glass can be reduced. Further, among the components that increase the refractive index, it is difficult to suppress the increase in the temperature coefficient of the relative refractive index. Therefore, the content of the La ₂ O ₃ component is preferably 40.0% or more, more preferably more than 43.0%, still more preferably more than 45.0%, still more preferably 48.5% or more, still more preferably. It should be 50.10% or more.
On the other hand, by setting the content of the La ₂ O ₃ component to 60.0% or less, the stability of the glass can be improved and the devitrification can be reduced. In addition, the meltability of the glass raw material can be improved. Therefore, the content of the La ₂ O ₃ component is preferably 60.0% or less, more preferably less than 58.0%, still more preferably less than 55.0%, still more preferably less than 53.0%.

The TiO ₂ component is an essential component that can improve the stability by increasing the refractive index of the glass and lowering the liquidus temperature of the glass, reduce the specific gravity of the glass, and reduce the material cost of the glass. Further, among the components that increase the refractive index, it is difficult to suppress the increase in the temperature coefficient of the relative refractive index. Therefore, the content of the TiO ₂ component is preferably 1.0% or more, more preferably more than 3.0%, still more preferably more than 5.0%, still more preferably more than 8.0%.
On the other hand, by reducing the content of the TiO ₂ component to 18.0% or less, the devitrification due to the excessive content of the TiO ₂ component can be reduced, and the transmittance of the glass with respect to visible light (particularly the wavelength of 500 nm or less) can be reduced. It can be suppressed. Further, this can suppress a decrease in the Abbe number. Therefore, the content of the TiO ₂ component is preferably 18.0% or less, more preferably less than 15.0%, still more preferably less than 12.0%, still more preferably less than 10.0%.

The Nb ₂ O ₅ component is an optional component whose devitrification resistance can be enhanced by increasing the refractive index of the glass and lowering the liquidus temperature of the glass when the content exceeds 0%. Therefore, the content of the Nb ₂ O ₅ component is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 4.0%, still more preferably more than 6.0%, still more preferably 7. It may be more than 0%.
On the other hand, by reducing the content of the Nb ₂ O ₅ component to 17.0% or less, the material cost of the glass can be suppressed and the decrease in the Abbe number can be suppressed. In addition, devitrification due to excessive inclusion of the Nb ₂ O ₅ component can be reduced, and a decrease in the transmittance of the glass with respect to visible light (particularly, a wavelength of 500 nm or less) can be suppressed. Therefore, the content of the Nb ₂ O ₅ component is preferably 17.0% or less, more preferably less than 15.0%, still more preferably less than 12.0%, still more preferably less than 9.0%.

_{The Y2O3} component is an optional component that can reduce the material cost of glass and reduce the specific gravity of glass while maintaining a high refractive index and a high Abbe number when the content exceeds 0%. Therefore, the content of the _Y2O3 component may be preferably _more than 0%, more preferably more than 1.0%, still more preferably more than 4.0%, still more preferably more than 7.0%.
_On the other hand, by setting the content of the _Y2O3 component to 20.0% or less, the decrease in the refractive index of the glass can be suppressed and the stability of the glass can be enhanced. In addition, deterioration of the meltability of the glass raw material can be suppressed. Therefore, the content of the _Y2O3 component is preferably 20.0% or less, _more preferably less than 15.0%, still more preferably less than 13.0%, still more preferably less than 11.0%.

_The ZrO2 component is an optional component capable of increasing the refractive index and Abbe number of the glass and improving the devitrification resistance when the content exceeds 0%. Therefore, the content of the ZrO2 component may be preferably _more than 0%, more preferably more than 1.0%, still more preferably more than 3.5%, still more preferably more than 5.0%.
On the other hand, by setting the content of the ZrO ₂ component to 15.0% or less, devitrification due to the excessive content of the ZrO ₂ component can be reduced. Therefore, the content of the ZrO2 component is preferably 15.0% or less, _more preferably less than 12.0%, still more preferably less than 10.0%, still more preferably less than 7.0%.

The Gd ₂ O ₃ component, the Yb ₂ O ₃ component, and the Lu ₂ O ₃ component are optional components that can increase the refractive index and Abbe number of the glass when the content exceeds 0%.
However, the raw material prices of the Gd ₂ O ₃ component, the Yb ₂ O ₃ component, and the Lu ₂ O ₃ component are high, and if the content thereof is high, the production cost increases and the specific gravity of the glass increases. Therefore, the contents of the Gd ₂ O ₃ component and the Yb ₂ O ₃ component are preferably 10.0% or less, more preferably less than 7.0%, still more preferably less than 5.0%, still more preferably 4. It is less than 0%, more preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost, it is most preferable not to contain at least one of these components.

The Ta ₂ O ₅ component is an optional component that can increase the refractive index of the glass and enhance the devitrification resistance when it is contained in an amount of more than 0%.
However, the Ta ₂ O ₅ component has a high raw material price, and if the content is high, the production cost increases. Further, by setting the content of the Ta ₂ O ₅ component to 10.0% or less, the melting temperature of the raw material is lowered, and the energy required for melting the raw material is reduced, so that the manufacturing cost of the optical glass can be reduced. Therefore, the content of the Ta ₂ O ₅ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost, it is most preferable that the Ta ₂ O ₅ component is not contained.

When the WO ₃ component is contained in excess of 0%, it is an optional component that can increase the refractive index, lower the glass transition point, and enhance the devitrification resistance while reducing the coloring of the glass due to other high refractive index components. Is. Therefore, the content of the WO ₃ component may be preferably more than 0%, more preferably more than 0.3%, and even more preferably more than 0.5%.
_On the other hand, by setting the content of the WO3 component to less than 10.0%, the material cost of the glass can be suppressed and the decrease in the Abbe number can be suppressed. _In addition, the coloring of the glass due to the WO3 component can be reduced and the visible light transmittance can be increased. Therefore, the content of the WO ₃ component is preferably less than 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%, still more preferably 0. 95% or less.

The ZnO component is an optional component that can enhance the stability of the glass and reduce the coloring 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 chemical durability.
On the other hand, by reducing the content of the ZnO component to 10.0% or less, the temperature coefficient of the relative refractive index can be reduced, the decrease in the refractive index of the glass can be suppressed, and devitrification due to an excessive decrease in viscosity can be prevented. Can be reduced. Therefore, the content of the ZnO component is preferably 10.0% or less, more preferably less than 5.0%, further preferably less than 3.0%, still more preferably less than 1.0%, and further preferably not contained. ..

The MgO component, CaO component, SrO component and BaO component are optional components that can adjust the refractive index, meltability and devitrification resistance of the glass when the content exceeds 0%. In particular, the BaO component is also a component that can reduce the temperature coefficient of the relative refractive index.
On the other hand, by setting the contents of the MgO component, the CaO component, the SrO component and the BaO component to 10.0% or less, the decrease in the refractive index can be suppressed, and the devitrification due to the excessive content of these components can be suppressed. Can be reduced. Therefore, the contents of the MgO component, the CaO component, the SrO component and the BaO component are preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably 1. It shall be less than 0%. In particular, from the viewpoint of obtaining glass having a high refractive index, it is most preferable not to contain these components.

When the Li ₂ O component, Na ₂ O component and K ₂ O component are contained in excess of 0%, the meltability of the glass can be improved, the glass transition point can be lowered, and the temperature coefficient of the relative refractive index can be made small. It is an ingredient. Therefore, the content of the Li ₂ O component among these may be preferably more than 0%, more preferably 0.05% or more, still more preferably 0.1% or more.
On the other hand, by setting each of the Li ₂ O component, the Na ₂ O component and the K ₂ O component to 10.0% or less, it is difficult to lower the refractive index of the glass and the devitrification of the glass can be reduced. Therefore, the contents of the Li ₂ O component, the Na ₂ O component and the K ₂ O component are preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferable. Is less than 1.0%, more preferably less than 0.5%.

The P ₂ O ₅ component is an optional component that can act as a glass forming component, and when it is contained in excess of 0%, it can lower the liquidus temperature of the glass and enhance the devitrification resistance.
_On the other hand, by setting the content of the _P2O5 component to 10.0% or less, it is possible to suppress a decrease in the chemical durability of the glass, particularly the water resistance. Therefore, the content of the P2O5 component is preferably 10.0% or less, _more preferably less than _5.0 %, still more preferably less than 3.0%, still more preferably less than 1.0%.

The GeO ₂ component is an optional component capable of increasing the refractive index of the glass and improving the devitrification resistance when it is contained in an amount of more than 0%.
However, the raw material price of GeO ₂ is high, and if the content of GeO 2 is high, the production cost increases. Therefore, the content of the GeO ₂ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost, it is not necessary to contain the GeO ₂ component.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components that can improve the chemical durability of the glass and the devitrification resistance of the glass when the content exceeds 0%.
On the other hand, by setting the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component to 10.0% or less, the liquidus temperature of the glass can be lowered and the devitrification resistance can be enhanced. Therefore, the contents of the Al ₂ O ₃ component and the Ga ₂ O ₃ component are preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably 1. It shall be less than 0%. Here, it is not necessary to contain at least one of the Al ₂ O ₃ component and the Ga ₂ O ₃ component.

The Bi ₂ O ₃ component is an optional component that can increase the refractive index and lower the glass transition point when it contains more than 0%.
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 improved. Therefore, the content of the Bi ₂ O ₃ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

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

The SnO ₂ component is an optional component that can reduce the oxidation of the molten glass to make it clear and increase the visible light transmittance of the glass when it is contained in an amount of more than 0%.
On the other hand, by setting the content of the SnO ₂ component to 3.0% or less, it is possible to reduce the coloring of the glass and the devitrification of the glass due to the reduction of the molten glass. Further, since the alloying of the SnO ₂ component and the melting equipment (particularly noble metal such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the content of the SnO ₂ component is preferably 3.0% or less, more preferably less than 1.0%, still more preferably less than 0.5%, still more preferably less than 0.1%.

The Sb ₂ O ₃ component is an optional component capable of defoaming the molten glass when it contains more than 0%.
On the other hand, if the amount of Sb ₂ O ₃ is too large, the transmittance in the short wavelength region of the visible light region deteriorates. Therefore, the content of the Sb ₂ O ₃ component is preferably 1.0% or less, more preferably less than 0.5%, still more preferably less than 0.3%.

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

The F component is an optional component capable of increasing the Abbe number of the glass, lowering the glass transition point, and improving the devitrification resistance when the content exceeds 0%.
However, when the content of the F component, that is, the total amount of fluoride substituted with a part or all of one or more oxides of each of the above-mentioned metal elements exceeds 10.0%, F Since the amount of volatilization of the components increases, it becomes difficult to obtain a stable optical constant, and it becomes difficult to obtain a homogeneous glass.
Therefore, the content of the F component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

The sum (mass sum) of the contents of the Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is 48.0% or more and 70.0. % Or less is preferable.
In particular, when this sum is 48.0% or more, the refractive index and Abbe number of the glass are increased, so that it is possible to easily obtain a glass having a desired refractive index and Abbe number. Therefore, the mass sum of the Ln ₂ O ₃ components is preferably 48.0% or more, more preferably more than 52.0%, still more preferably more than 55.0%, still more preferably more than 57.0%.
On the other hand, when this sum is 70.0% or less, the liquidus temperature of the glass is lowered, so that the devitrification of the glass can be reduced. Therefore, the mass sum of the Ln ₂ O ₃ components is preferably 70.0% or less, more preferably less than 68.0%, still more preferably less than 65.0%, still more preferably less than 61.0%.

The sum (mass sum) of the contents of the RO component (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably 10.0% or less. As a result, the decrease in the refractive index can be suppressed, and the stability of the glass can be improved. Therefore, the mass sum of the RO components is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

The sum (mass sum) of the contents of the Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is preferably 10.0% or less. As a result, the decrease in the viscosity of the molten glass can be suppressed, the refractive index of the glass can hardly be decreased, and the devitrification of the glass can be reduced. Therefore, the mass sum of the Rn ₂ O components is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%, still more preferably 0. Less than 5.5%, more preferably less than 0.3%.
On the other hand, the lower limit of the mass sum of the Rn ₂ O components may be more than 0% or 0.1% or more from the viewpoint of making the temperature coefficient of the relative refractive index smaller.

The ratio (mass ratio) of the contents of the La ₂ O ₃ component, the Gd ₂ O ₃ component, the Y ₂ O ₃ component and the Yb ₂ O ₃ component to the content of the Y ₂ O ₃ component is 0.05 or more and 0. 30 or less is preferable.
In particular, by setting this mass ratio to 0.05 or more, the specific gravity of the glass can be reduced. Therefore, the mass ratio Y ₂ O ₃ / (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ ) is preferably 0.05 or more, more preferably 0.07 or more, still more preferably 0.10. Above, more preferably 0.12 or more.
On the other hand, this mass ratio is preferably 0.30, more preferably 0.25, still more preferably 0.20, still more preferably 0.18, from the viewpoint of facilitating the desired refractive index and Abbe number. May be.

The sum (mass sum) of the contents of the TiO ₂ component, the Nb ₂ O ₅ component and the WO ₃ component is preferably 7.0% or more and 28.0% or less.
In particular, when this sum is 7.0% or more, the refractive index is increased and the stability of the glass is increased, so that it is possible to easily obtain an optical glass having a high refractive index and a low dispersion. Therefore, the sum of mass (TiO ₂ + Nb ₂ O ₅ + WO ₃ ) is preferably 7.0% or more, more preferably more than 10.0%, still more preferably more than 13.0%, still more preferably more than 16.0%. And.
On the other hand, by setting the sum to 28.0% or less, it is possible to reduce the decrease in the Abbe number of the glass due to the excessive inclusion of these components, and the coloring and devitrification of the glass. Therefore, the sum of mass (TiO ₂ + Nb ₂ O ₅ + WO ₃ ) is preferably 28.0% or less, more preferably less than 25.0%, still more preferably less than 22.0%, still more preferably less than 20.0%. , More preferably less than 19.0%.

The ratio (mass ratio) of the sum of the contents of the WO ₃ component to the content of the Nb ₂ O ₅ component is preferably 0.20 or less. This makes it possible to further increase the transmittance of the glass. Therefore, the mass ratio WO ₃ / Nb ₂ O ₅ is preferably 0.20 or less, more preferably 0.15 or less, still more preferably 0.12 or less.
On the other hand, the mass ratio WO ₃ / Nb ₂ O ₅ may be preferably 0.01 or more, more preferably 0.05 or more, still more preferably 0.07 or more, still more preferably 0.09 or more.

The ratio (mass ratio) of the sum of the contents of the TIO ₂ component to the content of the B ₂ O ₃ component is preferably 0.10 or more.
In particular, by setting this mass ratio to 0.10 or more, the refractive index of glass can be increased and the material cost of glass can be reduced. Therefore, the mass ratio TiO ₂ / B ₂ O ₃ is preferably 0.10 or more, more preferably 0.10 or more, still more preferably 0.30 or more, still more preferably 0.50 or more, still more preferably 0.60. Above, more preferably 0.76 or more.
On the other hand, the mass ratio TiO ₂ / B ₂ O ₃ is preferably 2.00 or less, more preferably less than 1.50, still more preferably, from the viewpoint of further increasing the transmittance of the glass and facilitating the acquisition of stable glass. May be less than 1.20, more preferably less than 1.00, still more preferably less than 0.90.

The sum (mass sum) of the contents of the TiO ₂ component and the WO ₃ component is preferably 5.0% or more and 20.0% or less.
In particular, when this sum is 5.0% or more, the refractive index is increased, the Abbe number is reduced, and the stability of the glass is increased, so that it is possible to easily obtain an optical glass having a high refractive index and a low dispersion. Therefore, the sum of mass (TiO ₂ + WO ₃ ) is preferably 5.0% or more, more preferably more than 7.0%, still more preferably more than 9.0%.
On the other hand, by setting this sum to 20.0% or less, it is possible to suppress a decrease in the light transmittance of the glass. Therefore, the sum of mass (TiO ₂ + WO ₃ ) is preferably 20.0% or less, more preferably less than 18.0%, still more preferably less than 15.0%, still more preferably less than 12.0%, still more preferably. It shall be less than 10.5%.

The sum (mass sum) of the contents of the B ₂ O ₃ component and the SiO ₂ component is preferably 7.0% or more and 27.0% or less.
In particular, when this sum is 7.0% or more, a network structure of glass is formed, so that stable glass can be formed. Therefore, the sum of mass (B ₂ O ₃ + SiO ₂ ) is preferably 7.0% or more, more preferably more than 10.0%, still more preferably more than 13.0%, still more preferably more than 15.0%. ..
On the other hand, by setting the sum to 27.0% or less, it is possible to suppress a decrease in the refractive index due to excessive inclusion of these components. Therefore, the sum of mass (B ₂ O ₃ + SiO ₂ ) is preferably 27.0% or less, more preferably less than 23.0%, still more preferably less than 20.0%, still more preferably less than 18.0%. ..

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

Other components can be added as needed within a range that does not impair the characteristics 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 used alone. Alternatively, even if the glass is compounded 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. ..

Further, since lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components having 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, each component of Th, Cd, Tl, Os, Be, and Se has tended to refrain from being used as a harmful chemical substance in recent years, and is used not only in the glass manufacturing process but also in the processing process and disposal after commercialization. Environmental measures are required up to this point. Therefore, when the environmental impact is emphasized, it is preferable that these are not substantially contained.

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, the prepared mixture is put into a platinum crucible, and the temperature is 1100 to 1500 ° C. in an electric furnace depending on the difficulty of melting the glass raw material. It is produced by melting in the temperature range of 2 to 5 hours, stirring and homogenizing, lowering the temperature to an appropriate temperature, casting in a mold, and slowly cooling.

[Physical characteristics]
The optical glass of the present invention preferably has a high refractive index and a high Abbe number (low dispersion). In particular, the refractive index ( _nd ) of the optical glass of the present invention is preferably 1.90, more preferably 1.92, and even more preferably 1.94 as the lower limit. The refractive index ( _nd ) may be preferably less than 2.10, more preferably less than 2.05, still more preferably less than 2.00, still more preferably less than 1.97. Further, the Abbe number (ν _d ) of the optical glass of the present invention is preferably 27, more preferably 30, and even more preferably 32 as the lower limit. The Abbe number (ν _d ) is preferably 37, more preferably 35, and even more preferably 33.
By having such a high refractive index, a large amount of refraction of light can be obtained even if the optical element is made thinner. Further, by having such a low dispersion, it is possible to reduce the focus shift (chromatic aberration) due to the wavelength of light when used as a single lens. Therefore, for example, when an optical system is configured in combination with an optical element having a high dispersion (low Abbe number), aberrations can be reduced as a whole of the optical system to achieve high imaging characteristics and the like.
As described above, the optical glass of the present invention is useful for optical design, and particularly when the optical system is configured, the optical system can be miniaturized while achieving high imaging characteristics and the like, and the optical design can be achieved. The degree of freedom can be expanded.

Further, in the optical glass of the present invention, the refractive index (nd) and the Abbe number (ν _d ) have a relationship of (-0.01ν _d + 2.20) ≤ n _d ≤ (-0.01 ν _d + 2.35 ₎ . It is preferable to satisfy. In the glass having the composition specified in the present invention, more stable glass can be obtained by satisfying this relationship between the refractive index ( _{nd) and the Abbe number (ν d )} .
Therefore, in the optical glass of the present invention, it is preferable that the refractive index (nd) and the Abbe number (ν _d ) satisfy the relationship of n _d ≧ (−0.01 ν _d + 2.20), and n _d ≧ (− ₎ . It is more preferable to satisfy the relationship of 0.01ν _d + 2.23), and it is further preferable to satisfy the relationship of n _d ≧ (−0.01ν _d +2.25), and it is more preferable to satisfy the relationship of n _d ≧ (−0.01ν _d + 2.25). It is more preferable to satisfy the relationship of 27).
On the other hand, in the optical glass of the present invention, it is preferable that the refractive index (nd) and the Abbe number (ν _d ) satisfy the relationship of n _d ≦ (−0.01 ν _d + 2.35), and n _d ≦ ( _. It is more preferable to satisfy the relationship of −0.01ν _d +2.32), further preferably to satisfy the relationship of nd ≦ (−0.01ν _d +2.30), and it is further preferable to satisfy the relationship of nd ≦ (−0.01ν _d +2 _{) .} It is more preferable to satisfy the relationship of .28).

The optical glass of the present invention has a temperature coefficient of relative refractive index (dn / dT) within a desired range.
More specifically, the temperature coefficient of the relative refractive index of the optical glass of the present invention is preferably +8.0 × 10 ^-6 ° C ^-1 , more preferably +7.0 × ^10-6 ° C ^-1 , and even more preferably. The upper limit is +6.0 × 10 ^-6 ° C ^-1 , more preferably + 5.0 × 10 ^-6 ° C ^-1 , and a value lower than this upper limit (minus side) can be taken.
On the other hand, the temperature coefficient of the relative refractive index of the optical glass of the present invention is, for example, 0.0 × 10 ^-6 ° C ^-1 , more specifically + 0.5 × 10 ^-6 ° C ^-1 , and more specifically +1. .0 × 10 ^-6 ° C ^-1 may be set as the lower limit value, and a value higher than this lower limit value (plus side) may be taken.
Conventionally, as a glass having a refractive index ( _{nd) of 1.90 or more and less than 2.10 and an Abbe number (ν d )} of 27 or more and 37 or less, a glass having a temperature coefficient of relative refractive index within the above range. Is not known, and by obtaining such glass, the options for correction such as image displacement due to temperature change can be expanded, and the correction can be made easier. Therefore, by setting the temperature coefficient of the relative refractive index in such a range, it is possible to contribute to the correction of the deviation of the image formation due to the temperature change.
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 having a wavelength of 589.29 nm in the air having the same temperature as the optical glass, and the temperature is changed from 40 ° C to 60 ° C. It is expressed as the amount of change per 1 ° C (° C ^-1 ) when changed.

The optical glass of the present invention preferably has high devitrification resistance, and more specifically, has a low liquidus temperature. That is, the liquidus temperature of the optical glass of the present invention is preferably 1350 ° C, more preferably 1320 ° C, still more preferably 1300 ° C, still more preferably 1250 ° C. As a result, even if the molten glass flows out at a lower temperature, the crystallization of the produced glass is reduced, so that devitrification when the glass is formed from the molten state can be reduced, and optics using the glass can be reduced. The influence on the optical characteristics of the element can be reduced. Further, since the glass can be formed even if the melting temperature of the glass is lowered, the energy consumed at the time of forming the glass can be suppressed, and the manufacturing cost of the glass can be reduced. On the other hand, the lower limit of the liquidus temperature of the optical glass of the present invention is not particularly limited, but the liquidus temperature of the glass obtained by the present invention is approximately 800 ° C. or higher, specifically 850 ° C. or higher, more specifically 900. Often above ° C. The "liquid phase temperature" in the present specification means that a 5 cc cullet-shaped glass sample is placed in a platinum crucible having a capacity of 50 ml and completely melted at 1400 ° C., and the temperature is lowered to a predetermined temperature. When the glass surface and the presence or absence of crystals in the glass are observed immediately after being taken out of the furnace and cooled, the temperature represents the lowest temperature at which no crystals are observed. Here, the predetermined temperature at the time of lowering the temperature is a temperature in increments of 10 ° C. between 1350 ° C. and 800 ° C.

It is preferable that the optical glass of the present invention has a high visible light transmittance, particularly a light transmittance on the short wavelength side of visible light, and thus less coloring.
In particular, in the optical glass of the present invention, the shortest wavelength (λ ₇₀ ) showing a spectral transmittance of 70% in a sample having a thickness of 10 mm is preferably 480 nm, more preferably 450 nm, and even more preferably 425 nm.
Further, in the optical glass of the present invention, the shortest wavelength (λ ₅ ) showing a spectral transmittance of 5% in a sample having a thickness of 10 mm is preferably 400 nm, more preferably 380 nm, and further preferably 360 nm as the upper limit.
As a result, the absorption edge of the glass becomes an ultraviolet region or its vicinity, and the transparency of the glass with respect to visible light is enhanced. Therefore, this optical glass can be preferably used for an optical element such as a lens that transmits light.

The specific gravity of the optical glass of the present invention is preferably 5.50, more preferably 5.30, still more preferably 5.10, still more preferably 4.90, from the viewpoint of contributing to weight reduction of optical elements and optical instruments. The upper limit. On the other hand, the specific gravity of the optical glass of the present invention is often 3.00 or more, more specifically 3.50 or more, and more specifically 4.00 or more.
The specific gravity of the optical glass of the present invention is measured based on the Japan Optical Glass Industry Association standard JOBIS05-1975 “Method for measuring the specific gravity of optical glass”.

[Preforms and optical elements]
From the produced optical glass, a glass molded body can be produced by using, for example, a means for polishing or a means for mold press molding such as reheat press molding or precision press molding. That is, a glass molded body is produced by machining optical glass such as grinding and polishing, or a preform for mold press molding is produced from optical glass, and reheat press molding is performed on this preform. After that, a glass molded body is produced by polishing, a preform produced by polishing, or a preform formed by a known levitation molding or the like is subjected to precision press molding to produce a glass molded body. Can be made. The means for producing the glass molded body is not limited to these means.

As described above, 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 manufacture an optical element such as a lens or a prism. This makes it possible to form a preform with a large diameter, so while increasing the size of the optical element, high-definition and highly accurate imaging characteristics and projection characteristics when used in optical equipment such as cameras and projectors. Can be realized.

The compositions of Examples (No. 1 to No. 14) and Comparative Examples (No. A) of the present invention, and the temperature of the refractive index ( _{nd), Abbe number (ν d )} , and relative refractive index of these glasses. Tables 1 and 2 show the results of the coefficient (dn / dT), the liquid phase temperature, the wavelengths (λ ₇₀ , λ ₅ ) showing the spectral transmittance of 70% and 5%, and the specific gravity. The following examples are for illustrative purposes only, and are not limited to these examples.

The glasses of the examples and comparative examples of the present invention are both used as ordinary optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds corresponding to each component as raw materials. High-purity raw materials are selected, weighed so as to have the composition ratio of each example shown in the table, mixed uniformly, then put into a platinum pit, and 1100 in an electric furnace according to the difficulty of melting the glass raw material. After melting in a temperature range of about 1500 ° C. for 2 to 5 hours, the mixture was stirred and homogenized, cast into a mold or the like, and slowly cooled to prepare the product.

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

The temperature coefficient (dn / dT) of the relative refractive index of the glass of Examples and Comparative Examples is one of the methods described in the Japan Optical Glass Industry Association Standard JOGIS18-2008 “Method for measuring the temperature coefficient of the refractive index of optical glass”. By the interference method, the value of the temperature coefficient of the relative refractive index of light having a wavelength of 589.29 nm was measured when the temperature was changed from 40 ° C to 60 ° C.

The liquidus temperature of the glass of Examples and Comparative Examples is 10 from 1350 ° C to 800 ° C, in which a 5 cc cullet-shaped glass sample is placed in a platinum crucible having a capacity of 50 ml and completely melted at 1400 ° C. When the temperature is lowered to one of the temperatures set in ℃ increments, held for 1 hour, taken out of the furnace, cooled, and immediately observed for the presence or absence of crystals on the glass surface and in the glass, no crystals are observed. The temperature was calculated.

The transmittance of the glass of Examples and Comparative Examples was measured according to the Japan Optical Glass Industry Association standard JOBIS02-2003. In the present invention, the presence or absence and degree of coloring of the glass were determined by measuring the transmittance of the glass. Specifically, a face-to-face parallel polished product having a thickness of 10 ± 0.1 mm was measured for a spectral transmittance of 200 to 800 nm according to JISZ8722, and λ ₅ (wavelength at a transmittance of 5%) was determined.

The specific gravity of the glass of Examples and Comparative Examples was measured based on the Japan Optical Glass Industry Association standard JOBIS05-1975 “Method for measuring the specific gravity of optical glass”.

As shown in the table, the optical glasses of the embodiments of the present invention all have a refractive index ( _nd ) of 1.90 or more, more specifically 1.94 or more, and this refractive index (nd _). ) Was less than 2.10, more specifically 1.96 or less, which was within the desired range.

Further, all of the optical glasses of the examples of the present invention have an Abbe number (ν _d ) of 27 or more, more specifically 32 or more, and this Abbe number (ν _d ) is 37 or less, more specifically 33. It was below and was within the desired range.

Further, the optical glass of the embodiment of the present invention has a refractive index (nd) and an Abbe number (ν _d ) of (−0.01 ν _d + 2.20) ≦ n _d ≦ (−0.01 ν _d + 2.35 ₎ . ), And more specifically, the relationship of (−0.02ν _d + 2.26) ≦ n _d ≦ (−0.02ν _d + 2.28) was satisfied. The relationship between the refractive index ( _{nd) and the Abbe number (ν d )} for the glass of the embodiment of the present application is shown in FIG.

Further, all of the optical glasses of the present invention have a temperature coefficient of relative refractive index of +8.0 × 10 ^-6 (° C ^-1 ) or lower, and more specifically, +5.0 × 10 ⁻ . It was in the range of ⁶ to 0.0 × ^10-6 (° C ^-1 ), which was within the desired range. On the other hand, the glass of Comparative Example (No. A) has a high temperature coefficient of relative refractive index because the temperature coefficient of relative refractive index is +9.7 × 10 ^-6 (° C ^-1 ).

In addition, the optical glass of the present invention forms stable glass, and devitrification is unlikely to occur during glass production. This can be inferred from the fact that the liquidus temperature of the optical glass of the present invention is 1350 ° C. or lower, and more specifically, 1200 ° C. or lower.

Further, the optical glass of the embodiment of the present invention had a λ ₇₀ (wavelength at a transmittance of 70%) of 480 nm, more specifically 430 nm or less, which was within a desired range.
Further, the optical glass of the embodiment of the present invention had λ ₅ (wavelength at a transmittance of 5%) of 400 nm, more specifically 360 nm or less, which was within a desired range.

Therefore, in the optical glass of the embodiment of the present invention, the temperature coefficient of the relative refractive index takes a value within a desired range while the refractive index ( _{nd) and the Abbe number (ν d )} are within a desired range. Moreover, it became clear that the light transmittance was high. Therefore, it is presumed that the optical glass of the embodiment of the present invention contributes to the correction of the deviation of the imaging characteristics due to the temperature change.

In addition, all of the optical glasses of the examples of the present invention had a specific gravity of 5.50 or less, more specifically 4.90 or less. Therefore, it is presumed that the optical glass of the embodiment of the present invention can contribute to the weight reduction of the optical element and the optical device.

Further, using the optical glass of the embodiment of the present invention, a glass block was formed, and the glass block was ground and polished to be processed into the shape of a lens and a prism. As a result, it was possible to stably process various lens and prism shapes.

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

Claims (9)

By mass%,
SiO ₂ component is more than 0% and 15.0% or less,
B ₂ O ₃ component 1.0 to 17.0%,
La ₂ O ₃ component 48.5-60.0 %,
TiO ₂ component is 1.0% or more and 18.0% or less,
Contains,
The sum of the contents of the Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is more than 0% to 10.0%.
The mass ratio TiO ₂ / B ₂ O ₃ is 0.76 or more, and
The mass ratio Y ₂ O ₃ / (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ ) is 0.07 or more, and has a refractive index (nd) of 1.90 or more and less than 2.10. , Has an Abbe number (νd) of 27 or more and 37 or less,
The shortest wavelength (λ ₅ ) showing a spectral transmittance of 5% in a sample having a thickness of 10 mm is 400 nm or less.
An optical glass having a temperature coefficient (40 to 60 ° C.) of relative refractive index (589.29 nm) of +8.0 × 10 ^-6 (° C. ^-1 ) or lower. By mass%,
Nb ₂ O ₅ component 0 to 17.0%,
_Y2O3 component over ₀ % to 20.0%,
ZrO ₂ component 0 to 15.0%,
The optical glass according to claim 1. By mass%,
Gd ₂ O ₃ component 0 to 10.0%,
Yb ₂ O ₃ component 0 to 10.0%
Ta ₂ O ₅ component 0 to 10.0%,
WO ₃ component 0 to 10.0%,
ZnO component 0 to 10.0%,
MgO component 0 to 10.0%,
CaO component 0 to 10.0%,
SrO component 0 to 10.0%,
BaO component 0 to 10.0%,
Li ₂ O component over 0 % to 10.0%,
Na ₂ O component 0 to 10.0%,
K ₂ O component 0 to 10.0%,
P ₂ O ₅ component 0 to 10.0%,
GeO ₂ component 0 to 10.0%,
Al ₂ O ₃ component 0 to 10.0%,
Ga ₂ O ₃ component 0 to 10.0%,
Bi ₂ O ₃ component 0 to 10.0%,
TeO ₂ component 0 to 10.0%,
SnO ₂ component 0-3.0%,
Sb ₂ O ₃ component 0-1.0%
And
The optical glass according to claim 1 or 2, wherein the content of fluoride as F, which is substituted with a part or all of one or more oxides of each of the above elements, is 0 to 10.0% by mass. By mass%,
The sum of the contents of the Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is more than 52.0% and 70.0% or less.
Any of claims 1 to 3 in which the sum of the contents of the RO component (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, Zn) is 0 to 10.0%. The optical glass described. The optical glass according to any one of claims 1 to 4 , wherein the sum of mass TiO ₂ + WO ₃ + Nb ₂ O ₅ is 7.0% or more and 28.0% or less. The optical glass according to any one of claims 1 to 5 , wherein the mass sum SiO ₂ + B ₂ O ₃ is 7.0% or more and 27.0% or less. A preform comprising the optical glass according to any one of claims 1 to 6 . An optical element made of the optical glass according to any one of claims 1 to 6 . An optical device comprising the optical element according to claim 8 .

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