JP7112856B2 - Optical glass, preforms and optical elements - Google Patents

Description

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

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

Among optical glasses for producing optical elements, it has a refractive index (n _d ) of 1.90 or more and 2.10 or less and an Abbe number of 23 or more and 35 or less, which enables miniaturization of the entire optical system. The demand for high-index, low-dispersion glasses with (ν _d ) is very high. As such a high-refractive-index, low-dispersion glass, a glass composition represented by Patent Document 1 is known.

JP 2012-162448 A

However, optical glass having a refractive index (n _d ) of 1.90 or more and 2.10 or less and an Abbe number (ν _d ) of 23 or more and 35 or less does not have a high light transmittance or an optical element. It is only known that the imaging characteristics change with the temperature change when used for . Under such circumstances, there has been a demand for a glass that has a high light transmittance at such a refractive index (n _d ) and Abbe number (ν _d ) and has a small effect on imaging performance due to temperature fluctuations.

The present invention has been made in view of the above-mentioned problems, and its object is to achieve a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges while maintaining light transmittance. An object of the present invention is to obtain an optical glass which is high and can contribute to correction of image formation deviation due to temperature change.

_In order to solve the above problems _, the present inventors have conducted _{intensive testing} and research _, and found that the refractive index ₍ n _d ) and Abbe number (ν _d ) are within the desired ranges, the light transmittance is high, and the temperature coefficient of the relative refractive index is within the desired range. Completed.
Specifically, the present invention provides the following.

(1) in mass %,
_SiO2 component more than 0% and 15.0% or less,
B ₂ O ₃ components more than 0% and 18.0% or less,
40.0 to 65.0% of the La ₂ O ₃ component,
1.0 to 23.0% TiO ₂ component
contains,
having a refractive index (n _d ) of 1.90 or more and 2.10 or less and an Abbe number (ν _d ) of 23 or more and 35 or less;
The shortest wavelength (λ ₅ ) at which a sample with a thickness of 10 mm exhibits a spectral transmittance of 5% is 400 nm or less,
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.

(2) in mass %,
Nb ₂ O ₅ components 0-22.0%,
Y ₂ O ₃ component 0 to 17.0%,
ZrO ₂ component 0-15.0%,
The optical glass according to (1).

(3) in mass %,
Gd ₂ O ₃ component 0-10.0%,
Yb ₂ O ₃ components 0-10.0%
Ta ₂ O ₅ components 0 to 10.0%,
WO ₃ components 0 to 10.0%,
ZnO component 0-10.0%,
MgO component 0-10.0%,
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 0-10.0%,
P ₂ O ₅ components 0 to 10.0%,
GeO ₂ component 0-10.0%,
Al ₂ O ₃ components 0 to 10.0%,
Ga ₂ O ₃ component 0 to 10.0%,
Bi ₂ O ₃ components 0 to 10.0%,
TeO ₂ component 0-10.0%,
SnO ₂ component 0-3.0%,
Sb ₂ O ₃ components 0-1.0%
and
The optical glass according to (1) or (2), wherein the F content of the fluoride substituting part or all of one or more oxides of the above elements is 0 to 10.0% by mass. .

(4) in % by mass,
Ln ₂ O ₃ components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) in a sum of contents of 45.0% or more and 68.0% or less,
The sum of the contents of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, and Zn) is 0 to 10.0%,
Any one of (1) to (3), wherein the total content of Rn ₂ O components (wherein Rn is one or more selected from the group consisting of Li, Na and K) is 0 to 10.0% Optical glass as described.

(5) The optical glass according to any one of (1) to (4), wherein the mass ratio La ₂ O ₃ /B ₂ O ₃ is more than 2.00 and 12.00 or less.

(6) Any one of (1) to (5), 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 0.030 or more and 0.300 or less optical glass.

(7) The mass sum of TiO ₂ +WO ₃ +Nb ₂ O ₅ is 12.0% or more and 35.0% or less, and the mass sum of SiO ₂ +B ₂ O ₃ is 5.0% or more and 23.0% or less, ( The optical glass according to any one of 1) to (6).

(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 described in any one of (1) to (7).

(10) An optical instrument comprising the optical element according to (9).

According to the present invention, the refractive index (n _d ) 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 image formation deviation due to temperature change. optical glass can be obtained.

FIG. 4 is a diagram showing the relationship between the refractive index (n _d ) and the Abbe number (ν _d ) for glasses of examples of the present application.

The optical glass of the present invention contains, in mass %, a SiO ₂ component of more than 0% and 15.0% or less, a B ₂ O ₃ component of more than 0% and 18.0% or less, and a La ₂ O ₃ component of 40%. 0 to 65.0%, 1.0 to 23.0% TiO ₂ component, has a refractive index (n _d ) of 1.90 or more and 2.10 or less, and has an Abbe number of 23 or more and 35 or less ( ν _d ), the shortest wavelength (λ ₅ ) at which a sample with a thickness of 10 mm exhibits a spectral transmittance of 5% 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 inventors found that the refractive index _{( n d} ) and Abbe _{number (} ν _d ) _are reduced to It has been found that a glass having a high light transmittance and a temperature coefficient of relative refractive index within the desired range can be obtained while being within the desired range. Therefore, while the refractive index (n _d ) and Abbe number (ν _d ) are within desired ranges, the light transmittance is high, and it is possible to contribute to the correction of image formation shift due to temperature change.

Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is by no means limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. In addition, although description may be suitably omitted about the part which description overlaps, it does not limit the gist of invention.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. In this specification, unless otherwise specified, the content of each component is expressed in % by mass with respect to the total mass of the oxide-equivalent composition. Here, the "composition converted to oxide" refers to the amount of oxides, composite salts, metal fluorides, and the like used as raw materials for the constituent components of the glass of the present invention, assuming that they are all decomposed and changed into oxides when melted. It is a composition in which each component contained in the glass is indicated 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, by containing more than 0% of the SiO ₂ component, it is also a component that enhances the stability of the glass and makes it easier to obtain a 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 _SiO2 component is preferably above 0%, more preferably above 1.0%, even more preferably above 3.0%, and even more preferably above 4.0%.
On the other hand, by setting the content of the SiO ₂ component to 15.0% or less, it is possible to suppress the increase in the glass transition point and the decrease in the refractive index. Therefore, the content of the _SiO2 component is preferably 15.0% or less, more preferably less than 12.0%, even more preferably less than 10.0%, even more preferably less than 8.0%, and even more preferably 6.0%. Less than 0%, more preferably less than 5.0%.

The B ₂ O ₃ component is an essential component as a glass-forming oxide. In particular, by containing more than 0% of the B ₂ O ₃ component, the stability of the glass can be enhanced, the devitrification resistance can be enhanced, and the Abbe number of the glass can be enhanced. Therefore, the content of the B ₂ O ₃ component is preferably over 0%, more preferably over 1.0%, even more preferably over 3.0%, even more preferably over 5.0%, and even more preferably over 7.0%. More than 0%, more preferably more than 8.0%.
On the other hand, by setting the content of the B ₂ O ₃ component to 18.0% or less, a higher refractive index can be easily obtained, and deterioration of chemical durability can be suppressed. Therefore, the content of the B ₂ O ₃ component is preferably 18.0% or less, more preferably less than 15.0%, even more preferably less than 13.0%, still more preferably 9.5% or less, and even more preferably Less than 9.0%.

The La ₂ O ₃ component is an essential component for increasing the refractive index and Abbe number of the glass. In addition, since it is relatively inexpensive among rare earth elements, the material cost of glass can be reduced. In addition, among the components that increase the refractive index, it is a component that makes it difficult to suppress an 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 more than 48.0%, still more preferably 50.0% or more, more preferably 50.5% or more.
On the other hand, by setting the content of the La ₂ O ₃ component to 65.0% or less, devitrification can be reduced by increasing the stability of the glass. Moreover, the meltability of glass raw materials can be improved. Therefore, the content of the La ₂ O ₃ component is preferably 65.0% or less, more preferably less than 60.0%, even more preferably less than 58.0%, still more preferably less than 55.0%.

The TiO ₂ component is an essential component that increases the refractive index of the glass and lowers the liquidus temperature of the glass, thereby enhancing the stability of the glass, reducing the specific gravity of the glass, and reducing the material cost of the glass. In addition, among the components that increase the refractive index, it is a component that makes it difficult to suppress an 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 over 3.0%, even more preferably over 5.0%, even more preferably over 7.0%, still more preferably over 9.0%. More than 0%.
On the other hand, by setting the content of the _TiO2 component to 23.0% or less, devitrification due to excessive content of the _TiO2 component can be reduced, and the decrease in the transmittance of the glass to visible light (especially wavelengths of 500 nm or less) can be suppressed. suppressed. Moreover, this can suppress a decrease in the Abbe number. Therefore, the content of the TiO ₂ component is preferably 23.0% or less, more preferably less than 20.0%, even more preferably less than 17.0%, still more preferably less than 14.0%.

The Nb ₂ O ₅ component is an optional component that can increase the devitrification resistance by increasing the refractive index of the glass and lowering the liquidus temperature of the glass when the Nb 2 O 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 3.0%, more preferably more than 5.0%, still more preferably 7.0%. It may exceed 0%.
On the other hand, by setting the content of the Nb ₂ O ₅ component to 22.0% or less, the material cost of the glass can be suppressed, and the decrease in Abbe's number can be suppressed. In addition, devitrification due to excessive Nb ₂ O ₅ component content can be reduced, and a decrease in the transmittance of the glass to visible light (particularly wavelengths of 500 nm or less) can be suppressed. Therefore, the content of the Nb ₂ O ₅ component is preferably 22.0% or less, more preferably less than 20.0%, even more preferably less than 15.0%, still more preferably less than 12.0%.

The Y ₂ O ₃ component is an optional component that can reduce the material cost of the glass and reduce the specific gravity of the glass while maintaining a high refractive index and a high Abbe number when the Y 2 O 3 component is contained by more than 0%. Therefore, the content of the Y ₂ O ₃ component may be preferably more than 0%, more preferably more than 1.0%, even more preferably more than 3.0%.
On the other hand, by setting the content of the Y ₂ O ₃ component to 17.0% or less, the decrease in the refractive index 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 17.0% or less, more preferably less than 15.0%, even more preferably less than 12.0%, still more preferably less than 10.0%, and even more preferably Less than 8.0%.

The ZrO ₂ component is an optional component that can increase the refractive index and Abbe number of the glass and improve the devitrification resistance when it is contained in an amount exceeding 0%. Therefore, the content of the ZrO ₂ component may be preferably above 0%, more preferably above 1.0%, even more preferably above 3.5%, even more preferably above 5.0%.
On the other hand, by setting the content of the ZrO ₂ component to 15.0% or less, it is possible to reduce the devitrification due to the excessive content of the ZrO ₂ component. Therefore, the content of the ZrO ₂ component is preferably 15.0% or less, more preferably less than 12.0%, even more preferably less than 10.0%, still more preferably less than 7.0%.

The _three Gd ₂ O components, the _three Yb ₂ O components and the _three Lu ₂ O components are optional components that can increase the refractive index and Abbe number of the glass when they are contained in an amount exceeding 0%.
However, the Gd ₂ O ₃ component, the Yb ₂ O ₃ component and the Lu ₂ O ₃ component are expensive as raw materials, and if the content thereof is high, the production cost rises and the specific gravity of the glass increases. Therefore, the contents of the _three Gd ₂ O components and the _three Yb ₂ O components are each preferably 10.0% or less, more preferably less than 7.0%, even more preferably less than 5.0%, still more preferably 4.0%. It should be less than 0%, more preferably less than 1.0%. In particular, from the viewpoint of reducing material costs, 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 improve the devitrification resistance when it is contained in an amount exceeding 0%.
However, the Ta ₂ O ₅ component has a high raw material price, and a large content thereof increases the production cost. Also, 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%, and even more preferably less than 1.0%. Especially from the viewpoint of reducing the material cost, it is most preferable not to contain the Ta ₂ O ₅ component.

The WO ₃ component is an optional component that can increase the refractive index, lower the glass transition point, and increase the devitrification resistance while reducing the coloring of the glass due to other high refractive index components when it is contained at more than 0%. is. Therefore _, the content of the WO3 component may be preferably greater than 0%, more preferably greater than 0.3%, and even more preferably greater than 0.5%.
On the other hand, by setting the content of the three WO ₂ components to 10.0% or less, the material cost of the glass can be suppressed, and the decrease in Abbe's number can be suppressed. 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 WO ₃ component is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, even more preferably less than 1.0%, still more preferably 0.0%. 9% or less.

The ZnO component is an optional component that can increase the stability of the glass and reduce coloration when it is contained in an amount exceeding 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 decrease in the refractive index of the glass can be suppressed, and devitrification due to excessive viscosity decrease 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%, still more preferably less than 3.0%, still more preferably less than 1.0%, and more preferably no .

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 they are contained in an amount exceeding 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 content of each of the MgO component, CaO component, SrO component, and BaO component to 10.0% or less, the decrease in refractive index can be suppressed, and devitrification due to excessive content of these components can be suppressed. can be reduced. Therefore, the content of each of the MgO component, CaO component, SrO component and BaO component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably 1.0%. Less than 0%. Especially from the viewpoint of obtaining a glass with a high refractive index, it is most preferable not to contain these components.

The Li ₂ O component, the Na ₂ O component and the K ₂ O component can improve the meltability of the glass, lower the glass transition point, and reduce the temperature coefficient of the relative refractive index when they are contained in an amount exceeding 0%. is an ingredient. Therefore, among these, the content of the Li ₂ O component may preferably be more than 0%, more preferably 0.1% or more.
On the other hand, by making each of the Li ₂ O component, the Na ₂ O component and the K ₂ O component 10.0% or less, it becomes 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%, and still more preferably less than 3.0%. is less than 1.0%, preferably less than 0.5%.

The P ₂ O ₅ component is an optional component that can act as a glass-forming component and can lower the liquidus temperature of the glass to improve devitrification resistance when contained in an amount exceeding 0%.
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 is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, still more preferably less than 1.0%.

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, _GeO2 has a high raw material price, and its high content increases the production cost. Therefore, the content of the GeO ₂ component is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, still more preferably less than 1.0%. In particular, from the viewpoint of reducing material costs, the GeO ₂ component does not have to be contained.

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 improve the devitrification resistance of the glass when they are contained in an amount exceeding 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 Al ₂ O ₃ component and Ga ₂ O ₃ component are each preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably 1.0%. Less than 0%. Here, at least one of the Al ₂ O ₃ component and the Ga ₂ O ₃ component may not be included.

The Bi ₂ O ₃ component is an optional component that can increase the refractive index and lower the glass transition point when contained in an amount exceeding 0%.
On the other hand, by setting the content of the Bi ₂ O ₃ component to 10.0% or less, 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 is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, and even 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 contained in excess of 0%.
On the other hand, TeO ₂ has a problem that it can 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 is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, still more preferably less than 1.0%.

The SnO ₂ component is an optional component that, when contained in excess of 0%, can reduce oxidation of the glass melt to refine it and increase the visible light transmittance of the glass.
On the other hand, by setting the SnO ₂ component content to 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 SnO ₂ and 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 is preferably 3.0% or less, more preferably less than 1.0%, even more preferably less than 0.5%, and even more preferably less than 0.1%.

The Sb ₂ O ₃ component is an optional component capable of defoaming the glass melt when it is contained in an amount exceeding 0%.
On the other hand, if the amount of Sb ₂ O ₃ is too large, the transmittance in the short wavelength region of the visible light region will deteriorate. Therefore, the 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 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.

The F component is an optional component that can increase the Abbe number of the glass, lower the glass transition point, and improve the devitrification resistance when contained in an amount exceeding 0%.
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.
Therefore, the content of component F is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, and even more preferably less than 1.0%.

The sum of the contents (mass sum) of the _three Ln ₂ O components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is 45.0% or more and 68.0 % or less is preferable.
In particular, by making this sum 45.0% or more, the refractive index and Abbe number of the glass are increased, so that the glass having the desired refractive index and Abbe number can be easily obtained. Therefore, the mass sum of the Ln ₂ O ₃ components is preferably 45.0% or more, more preferably over 50.0%, even more preferably over 53.0%, still more preferably over 55.0%.
On the other hand, by setting the sum to 68.0% or less, the liquidus temperature of the glass is lowered, so that devitrification of the glass can be reduced. Therefore, the mass sum of the Ln ₂ O ₃ components is preferably 68.0% or less, more preferably less than 65.0%, even more preferably less than 62.0%, still more preferably less than 60.0%.

The sum of the contents (mass sum) of the RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr and Ba) is preferably 10.0% or less. This suppresses a decrease in the refractive index and enhances the stability of the glass. Therefore, the mass sum of RO components is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, and even more preferably less than 1.0%.

The total content (mass sum) of the Rn ₂ O component (wherein Rn is at least one selected from the group consisting of Li, Na and K) is preferably 10.0% or less. As a result, the viscosity of the molten glass can be suppressed from decreasing, the refractive index of the glass can be prevented from decreasing, devitrification of the glass can be reduced, and the temperature coefficient of the relative refractive index 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%, even more preferably less than 3.0%, even more preferably less than 1.0%, further preferably 0%. less than 0.5%, more preferably less than 0.45%.
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 further reducing the temperature coefficient of the relative refractive index.

The ratio (mass ratio) of the sum of the contents of the _three La ₂ O components to the content of the _three B ₂ O components is preferably more than 2.00 and not more than 12.00.
In particular, by making this mass ratio more than 2.00, the refractive index of the glass can be increased. Therefore, the mass ratio La ₂ O ₃ /B ₂ O ₃ is preferably above 2.00, more preferably above 3.00, even more preferably above 4.00, even more preferably above 5.00, even more preferably 5 0.30 or more, more preferably 5.50 or more.
On the other hand, the mass ratio La ₂ O ₃ /B ₂ O ₃ may be preferably 12.00 or less, more preferably less than 10.00, more preferably less than 8.00, and even more preferably less than 7.00. .

The ratio (mass ratio) of the content of the _three La ₂ O components, the _three Gd ₂ O components, the _three Y ₂ O components, and the _three Yb ₂ O components to the content of the _three Y ₂ O components is 0.030 or more and 0.030 or more. 300 or less is preferable.
In particular, by setting this mass ratio to 0.030 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 0.030 or more, more preferably more than 0.050, still more preferably 0.065. That's it.
On the other hand, the upper limit of this mass ratio may be preferably 0.300, more preferably 0.200, and still more preferably 0.150 from the viewpoint of easily obtaining the desired refractive index and Abbe number.

The sum (mass sum) of the contents of _two TiO components, _five Nb ₂ O components and _three WO components is preferably 12.0% or more and 35.0% or less.
In particular, when the sum is 12.0% or more, the refractive index is increased and the stability of the glass is enhanced, so that an optical glass with a high refractive index and low dispersion can be easily obtained. Therefore, the mass sum (TiO ₂ +Nb ₂ O ₅ +WO ₃ ) is preferably 12.0% or more, more preferably more than 15.0%, even more preferably more than 18.0%, still more preferably more than 20.0% and
On the other hand, by making this sum 35.0% or less, it is possible to reduce the decrease in the Abbe number of the glass and the coloring and devitrification of the glass due to the excessive content of these components. Therefore, the mass sum (TiO ₂ +Nb ₂ O ₅ +WO ₃ ) is preferably 35.0% or less, more preferably less than 30.0%, even more preferably less than 27.0%, still more preferably less than 24.0% and

The sum (mass sum) of the contents of the _three B2O components and the _{two SiO2} components is preferably 5.0% or more and 23.0% or less.
In particular, when the sum is 5.0% or more, a stable glass can be formed because a glass network structure is formed. Therefore, the mass sum (B ₂ O ₃ +SiO ₂ ) is preferably 5.0% or more, more preferably more than 8.0%, still more preferably more than 10.0%, and still more preferably more than 13.0%. .
On the other hand, by setting the sum to 23.0% or less, it is possible to suppress a decrease in refractive index due to excessive inclusion of these components. Therefore, the mass sum (B ₂ O ₃ +SiO ₂ ) is preferably 23.0% or less, more preferably less than 20.0%, even more preferably less than 18.0%, and even more preferably less than 15.0%. .

The ratio (mass ratio) of the content of the Y ₂ O ₃ component to the content of the TiO ₂ component is preferably 1.00 or less. Thereby, it is possible to obtain an optical glass having a desired refractive index and Abbe number and excellent devitrification resistance. Therefore, the mass ratio Y ₂ O ₃ /TiO ₂ is preferably 1.00 or less, more preferably 0.80 or less, still more preferably 0.60 or less, still more preferably 0.54 or less, still more preferably 0.50. Less than

<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. .

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

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

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

[Physical properties]
The optical glass of the present invention preferably has a high refractive index and a high Abbe number (low dispersion). In particular, the lower limit of the refractive index (n _d ) of the optical glass of the present invention is preferably 1.90, more preferably 1.93, still more preferably 1.95, still more preferably 1.98. The upper limit of the refractive index (n _d ) may preferably be 2.10, more preferably 2.05, and even more preferably 2.03. The Abbe number (ν _d ) of the optical glass of the present invention is preferably 23, more preferably 25, and even more preferably 28 as the lower limit. The upper limit of the Abbe number (ν _d ) is preferably 35, more preferably 33, and even more preferably 30.
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.

In the optical glass of the present invention, the refractive index (n _d ) and the Abbe number (ν _d ) have a relationship of (−0.01ν _d +2.20)≦n _d ≦(−0.01ν _d +2.35). is preferably satisfied. In the glass having the composition specified in the present invention, a more stable glass can be obtained when the refractive index (n _d ) and the Abbe number (ν _d ) satisfy this relationship.
Therefore, in the optical glass of the present invention, the refractive index (n _d ) and Abbe number (ν _d ) preferably satisfy the relationship n _d ≧(−0.01ν _d +2.20), and n _d ≧(− 0.01ν _d +2.24), more preferably n _d ≧(−0.01ν _d +2.28), n _d ≧(−0.01ν _d +2.28). 29) is more preferably satisfied.
On the other hand, in the optical glass of the present invention, the refractive index (n _d ) and Abbe number (ν _d ) preferably satisfy the relationship n _d ≤ (−0.01ν _d +2.35), and n _d ≤ ( −0.01ν _d +2.32), and more preferably n _d ≦(−0.01ν _d +2.30).

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 , further preferably +6.0×10 ⁻⁶ ° C. ⁻¹ , more preferably +5.0×10 ⁻⁶ ° C. ⁻¹ is set as the upper limit, and this upper limit or lower (minus side) value 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 , more specifically +1 0×10 ⁻⁶ ° C. ⁻¹ may be set as the lower limit, and this lower limit or a value higher (on the plus side) than it may be taken.
Conventionally, as a glass having a refractive index (n _d ) of 1.90 or more and 2.10 or less and an Abbe number (ν _d ) of 23 or more and 35 or less, the temperature coefficient of the relative refractive index is within the above range. However, by obtaining such a glass, it is possible to expand the options for correction of image formation deviation due to temperature change, and to make the correction easier. Therefore, by setting the temperature coefficient of the relative refractive index within such a range, it is possible to contribute to the correction of image formation deviation due to 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 with a wavelength of 589.29 nm in air at the same temperature as the optical glass. It is expressed by the amount of change (°C ⁻¹ ) per 1°C when changed.

The optical glass of the present invention preferably has high devitrification resistance, more specifically, a low liquidus temperature. That is, the upper limit of the liquidus temperature of the optical glass of the present invention is preferably 1,350°C, more preferably 1,320°C, still more preferably 1,300°C, and still more preferably 1,250°C. As a result, even if the melted glass flows out at a lower temperature, the crystallization of the manufactured glass is reduced, so devitrification when the glass is formed from the molten state can be reduced. The influence on the optical properties of the element can be reduced. In addition, since the glass can be molded even if the melting temperature of the glass is lowered, the energy consumed during the molding of the glass can be suppressed, thereby reducing the manufacturing cost of the glass. On the other hand, the lower limit of the liquidus temperature of the optical glass of the present invention is not particularly limited. °C or higher in many cases. In this specification, the “liquidus temperature” means that a cullet-shaped glass sample of 5 cc is placed in a platinum crucible with a capacity of 50 ml, completely melted at 1400 ° C., and cooled to a predetermined temperature. This is the lowest temperature at which crystals are not observed when the glass surface and the glass are observed for crystals immediately after being removed from the furnace and cooled for 1 hour. Here, the predetermined temperature at which the temperature is lowered is a temperature between 1350.degree. C. and 800.degree. C. in increments of 10.degree.

The optical glass of the present invention preferably has a high visible light transmittance, particularly a high transmittance for light on the short wavelength side of visible light, and is therefore less colored.
In particular, in the optical glass of the present invention, the upper limit of the shortest wavelength (λ ₇₀ ) at which a 10 mm-thick sample exhibits a spectral transmittance of 70% is preferably 500 nm, more preferably 480 nm, and even more preferably 460 nm.
In the optical glass of the present invention, the upper limit of the shortest wavelength (λ ₅ ) at which a 10 mm-thick sample exhibits a spectral transmittance of 5% is preferably 400 nm, more preferably 380 nm, and even more preferably 370 nm.
As a result, the absorption edge of the glass is in the ultraviolet region or in the vicinity thereof, and the transparency of the glass to visible light is enhanced. Therefore, this optical glass can be preferably used for optical elements such as lenses that transmit light.

The upper limit of the specific gravity of the optical glass of the present invention is preferably 5.50, more preferably 5.30, and more preferably 5.10 from the viewpoint of contributing to weight reduction of optical elements and optical equipment. On the other hand, the specific gravity of the optical glass of the present invention is generally 3.00 or higher, more specifically 3.50 or higher, and still more specifically 4.00 or higher in many cases.
The specific gravity of the optical glass of the present invention is measured based on the Japan Optical Glass Industry Standard JOGIS05-1975 "Method for measuring specific gravity of optical glass".

[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. That is, 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 with a large diameter, so that while increasing the size of the optical element, high-definition and high-precision imaging and projection characteristics can be obtained when used in optical equipment such as cameras and projectors. can be realized.

Compositions of Examples (No. 1 to No. 31) and Comparative Example (No. A) of the present invention, and refractive indices (n _d ), Abbe numbers (ν _d ), and relative refractive index temperatures of these glasses Tables 1 to 4 show the results of coefficient (dn/dT), liquidus temperature, wavelengths (λ ₇₀ , λ ₅ ) at which spectral transmittance is 70% and 5%, and specific gravity. It should be noted that the following examples are for illustrative purposes only, and are not intended to be limiting.

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

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

The temperature coefficient of the relative refractive index (dn/dT) of the glasses of Examples and Comparative Examples was determined by the method described in the Japan Optical Glass Industry Association Standard JOGIS18-2008 "Method for measuring temperature coefficient of refractive index of optical glass". The value of the temperature coefficient of relative refractive index was measured by interferometry when the temperature was changed from 40° C. to 60° C. for light with a wavelength of 589.29 nm.

The liquidus temperature of the glasses of Examples and Comparative Examples was determined by putting 5 cc of cullet-like glass sample into a platinum crucible with a capacity of 50 ml, bringing it to a completely molten state at 1400 ° C., and heating it to 1350 ° C to 800 ° C. The temperature is lowered to any temperature set in increments of °C, held for 1 hour, taken out of the furnace, and immediately after cooling, the presence or absence of crystals on the glass surface and in the glass is observed. asked for the temperature.

The transmittance of the glass of Examples and Comparative Examples was measured according to the Japan Optical Glass Industry Association Standard JOGIS02-2003. In the present invention, the presence or absence and degree of coloration of the glass were determined by measuring the transmittance of the glass. Specifically, according to JISZ8722, a parallel polished product having a thickness of 10±0.1 mm was measured for spectral transmittance from 200 to 800 nm to obtain λ ₅ (wavelength at transmittance of 5%).

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

As shown in the table, the optical glasses of the examples of the present invention all have a refractive index (n _d ) of 1.90 or more, more specifically 1.99 or more, and this refractive index (n _d ) was 2.10 or less, more specifically 2.01 or less, which was within the desired range.

Further, the optical glasses of the examples of the present invention all have an Abbe number (ν _d ) of 23 or more, more specifically 28 or more, and this Abbe number (ν _d ) is 35 or less, more specifically 30. below and within the desired range.

Further, the optical glass of the example of the present invention has a refractive index (n _d ) and an Abbe number (ν _d ) of (−0.01ν _d +2.20)≦n _d ≦(−0.01ν _d +2.35). ), more specifically, (−0.02ν _d +2.28)≦n _d ≦(−0.02ν _d +2.30). The relationship between the refractive index (n _d ) and the Abbe number (ν _d ) of the glasses of the examples of the present application is shown in FIG.

In addition, all the optical glasses of the present invention have a temperature coefficient of relative refractive index of +8.0×10 ⁻⁶ (° C. ⁻¹ ) or lower, more specifically +4.5×10 ^{− 6} to 0.0×10 ⁻⁶ (° C. ⁻¹ ), which is within the desired range. On the other hand, the glass of Comparative Example (No. A) has a temperature coefficient of relative refractive index of +9.7×10 ⁻⁶ (° C. ⁻¹ ), which is high.

In addition, the optical glass of the present invention formed a stable glass, and devitrification was less likely to occur during glass production. This is inferred from the fact that the liquidus temperature of the optical glass of the present invention is 1350° C. or lower, more specifically 1230° C. or lower.

In addition, the optical glasses of the examples of the present invention had λ ₇₀ (wavelength at transmittance of 70%) of 500 nm, more specifically 460 nm or less, which was within the desired range.
In addition, the optical glasses of the examples of the present invention all had λ ₅ (wavelength at transmittance of 5%) of 420 nm, more specifically, 370 nm or less, which was within the desired range.

Therefore, the optical glass of the example of the present invention has a refractive index (n _d ) and an Abbe number (ν _d ) within the desired range, and the temperature coefficient of the relative refractive index is within the desired range. In addition, it was found that the light transmittance was high. Therefore, it is presumed that the optical glass of the example of the present invention contributes to the correction of deviations in imaging characteristics due to temperature changes.

In addition, all the optical glasses of the examples of the present invention had a specific gravity of 5.50 or less, more specifically 5.10 or less. Therefore, it is presumed that the optical glasses of the examples of the present invention can contribute to weight reduction of optical elements and optical equipment.

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

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

Claims (9)

in % by mass,
_SiO2 component more than 0% and 15.0% or less,
B ₂ O ₃ components more than 0% and 18.0% or less,
40.0 to 65.0% of the La ₂ O ₃ component,
1.0 to 23.0% TiO ₂ component,
Ta ₂ O ₅ components 0 to less than 3.0%,
Gd ₂ O ₃ component 0 to less than 4.0%,
ZnO component 0 to less than 1.0%,
contains,
mass ratio Y ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ ) is 0.030 or more and 0.300 or less , and mass ratio Y ₂ O ₃ /TiO ₂ is less than 0.50 ; can be,
having a refractive index (nd) of 1.90 or more and 2.10 or less and an Abbe number (νd) of 23 or more and 35 or less;
The shortest wavelength (λ5) at which a sample with a thickness of 10 mm exhibits a spectral transmittance of 5% is 400 nm or less,
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. in % by mass,
Nb ₂ O ₅ components 0-22.0%,
Y ₂ O ₃ component 0 to 17.0%,
ZrO ₂ component 0-15.0%,
The optical glass according to claim 1, wherein in % by mass,
Yb ₂ O ₃ component 0-10.0%,
WO ₃ components 0 to 10.0%,
MgO component 0-10.0%,
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 0-10.0%,
P ₂ O ₅ components 0 to 10.0%,
GeO ₂ component 0-10.0%,
Al ₂ O ₃ components 0 to 10.0%,
Ga ₂ O ₃ component 0 to 10.0%,
Bi ₂ O ₃ components 0 to 10.0%,
TeO ₂ component 0-10.0%,
SnO ₂ component 0-3.0%,
Sb ₂ O ₃ components 0-1.0 %
The optical glass according to claim 1 or 2, wherein in % by mass,
Ln ₂ O ₃ components (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) in a sum of contents of 45.0% or more and 68.0% or less,
The sum of the contents of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, and Zn) is 0 to 10.0%,
4. The method according to any one of claims 1 to 3, wherein the total content of Rn ₂ O components (wherein Rn is one or more selected from the group consisting of Li, Na and K) is 0 to 10.0%. optical glass. The optical glass according to any one of claims ₁ to ₄ , wherein the mass ratio La2O3/B2O3 is _{more than} 2.00 and 12.00 or less. The mass sum of TiO ₂ +WO ₃ +Nb ₂ O ₅ is 12.0% or more and 35.0% or less, and the mass sum of SiO ₂ +B ₂ O ₃ is 5.0% or more and 23.0% or less, from claim 1 5. The optical glass according to any one of 5. A preform comprising the optical glass according to any one of claims 1 to 6. An optical element comprising the optical glass according to any one of claims 1 to 6. An optical instrument comprising the optical element according to claim 8 .

Images