JP7682005B2 - Optical glass, preforms and optical elements - Google Patents

Description

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

In addition to digital cameras, projectors, and security cameras, optical glass is increasingly being used as an optical element in imaging lenses mounted on car-mounted cameras as autonomous driving technology advances. For car-mounted cameras used outdoors, for example, it is common to provide a cover glass or coating surface on the outermost surface of the glass, but at the same time, the chemical durability of the lens itself is required. Good chemical durability makes it difficult for fogging to occur due to corrosion of the lens surface, enabling long-term use. Furthermore, car-mounted cameras are prone to scratches on the lenses due to collisions with dust in the air and pebbles caught in the tires, so optical glass that is resistant to scratches due to impacts is required.

Methods for producing optical elements from optical glass include, for example, a method in which a gob or glass block formed from optical glass is ground and polished to obtain the shape of an optical element, a method in which a gob or glass block formed from optical glass is reheated and molded (reheat press molding) to obtain a glass molded body, and a method in which a preform material obtained from a gob or glass block is molded in a highly precisely machined mold (precision mold press molding) to obtain the shape of an optical element. In any of these methods, it is required that a stable glass is obtained when a gob or glass block is formed from molten glass raw material. Here, if the stability against devitrification (devitrification resistance) of the glass constituting the obtained gob or glass block decreases and crystals occur inside the glass, it is no longer possible to obtain a glass suitable for an optical element.

There is a growing demand for glass materials as lens glass materials for vehicle-mounted cameras that have optical properties such as a refractive index (n _d ) of 1.70000 or more and 1.80000 and an Abbe number (ν _d ) of 45.00 or more and 55.00 or less, as well as excellent chemical durability and mechanical properties such as Knoop hardness.

Glass compositions such as those described in Patent Documents 1 to 4 are known as materials used in on-vehicle optical devices.

WO2018/003719 publication JP 2019-194138 A WO2018/003720 publication WO2017/175552 publication

However, the optical glasses shown in Patent Documents 1 and 2 have inferior acid resistance because they contain a larger amount of the _B2O3 component than the _SiO2 component, and do _not satisfy the refractive index (n _d ) of 1.70000 or more and 1.80000 or less, and the Abbe number (ν _d ) of 45.00 or more and 55.00 or less.

Furthermore, the optical glass disclosed in Patent Document 3 does not satisfy the ranges of refractive index (n _d ) of 1.70000 or more and 1.80000 or less, and Abbe number (ν _d ) of 45.00 or more and 55.00 or less, and also has a high content of Li ₂ O component, and therefore does not have good reheat press moldability.

Furthermore, the optical glass shown in Patent Document 4 has excellent acid resistance but contains a large amount of _TiO2 component, and therefore does not satisfy the refractive index (n _d ) of 1.70000 or more and 1.80000 or less and the Abbe number (ν _d ) of 45.00 or more and 55.00 or less.

The present invention was made in consideration of the above problems, and its purpose is to provide an optical glass that has the desired optical properties, good chemical durability, high hardness, and good reheat press moldability.

More specifically, the object is to provide an optical glass having a refractive index (n _d ) of 1.70000 to 1.80000, an Abbe number (ν _d ) of 45.00 to 55.00, an acid resistance of Class 1 to 3, a Knoop hardness of Class 6 or 7, and good reheat press moldability.

The present inventors have conducted extensive testing and research to solve the above problems, and as a result have found that by increasing the content of _SiO2 relative _{to B2O3} and adjusting the contents of each component, including _La2O3 , _Y2O3 , _{and Al2O3} , it is possible _to produce a glass material that has the desired optical properties, good chemical durability and mechanical properties, _and good reheat press moldability, and have thus completed the present invention. Specifically, the present invention provides the following:

(1) In mass% based on oxides,
_La2O3 component is 8.0% _or more,
The content of Li ₂ O component is 8.0% or less,
Contains _Al2O3 component _,
The mass ratio _SiO2 / _B2O3 is _1.0 or more and 5.0 or less;
and
A refractive index (n _d ) of 1.70000 or more and 1.80000 or less;
Abbe number (ν _d ) is 45.00 or more and 55.00 or less;
An optical glass with acid resistance of class 1 to 3 by powder method and Knoop hardness of class 6 to 7.

(2) Optical glass according to (1) in which the RO component is 8.0% or less (R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba).

(3) The optical glass according to (1) or (2), in which the mass ratio (Li ₂ O×10 ³ )/(Al ₂ O ₃ +SiO ₂ ) is 45.0 or less.

(4) An optical element made of the optical glass described in any one of (1) to (3).

(5) A preform for polishing and/or precision press molding, comprising the optical glass according to any one of (1) to (4).

According to the present invention, it is possible to obtain optical glass that has the desired optical properties, is highly chemically durable, is resistant to impacts, and has good reheat press moldability, as well as preforms and optical elements that use the same.

The following describes in detail the embodiments of the optical glass of the present invention, but the present invention is not limited to the following embodiments and can be modified as appropriate within the scope of the object of the present invention. Note that where explanations overlap, they may be omitted as appropriate, but this does not limit the spirit of the invention.

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

<Required and optional ingredients>
The _La2O3 component is _an essential component that increases the refractive index and Abbe number of the glass while improving the devitrification resistance. Therefore, the lower limit of the content of _{the La2O3} component is preferably 8.0% or more, more preferably 10.0% or more, and even more preferably 11.0% or more.
On the other hand, by setting the content of the _La2O3 component to 50.0% or less, the stability of the glass _can be increased and deterioration of acid resistance can be suppressed, so the upper limit is preferably set to 50.0% or less, more preferably 48.0% or less, and even more preferably 47.0% or less.

The _SiO2 component is a network-forming component and is an essential component for improving the acid resistance and hardness of the glass while enhancing the reheat press moldability. Therefore, the content of the _SiO2 component is preferably 7.0% or more, more preferably 9.0% or more, and even more preferably 10.0% or more.
On the other hand, by making the content of the _SiO2 component 30.0% or less, the stability of the glass is increased and the decrease in the refractive index is suppressed. Therefore, the upper limit of the content of the _SiO2 component is preferably 30.0% or less, more preferably 28.0%, even more preferably 27.5% or less, and most preferably 27.0% or less.

The B ₂ O ₃ component is a network-forming component and is an essential component for improving the hardness of the glass and enhancing the reheat press moldability. Therefore, the content of the B ₂ O ₃ component is preferably 1.0% or more, more preferably 1.5% or more, and even more preferably 2.0% or more.
On the other hand, by making the content of the B ₂ O ₃ component 25.0% or less, it becomes easy to obtain a larger refractive index and to prevent deterioration of acid resistance. Therefore, the upper limit of the content of the B ₂ O ₃ component is preferably 20.0% or less, more preferably 18.0% or less, more preferably 15.0% or less, and even more preferably 12.0% or less.

It is common technical knowledge that the _SiO2 component and _{the B2O3} component are network forming components, and that they have similar effects, particularly in glasses containing a large amount of rare earth oxides. However, the present inventors have conducted extensive testing and research and found that the acid resistance can be improved by including a larger amount of the _SiO2 component than the _B2O3 component. In other words, in the present invention, _{the B2O3} component and the _SiO2 component do _not have the same effects.

The _Al2O3 component is a network forming component and is an essential component that can improve _the acid resistance. In addition, by including the _Al2O3 component together _with the _La2O3 component, the acid resistance can be particularly maintained. Therefore, the content of _{the Al2O3} component is preferably _3.0 % or more, more preferably 5.0% or more, and even more preferably 5.8% or more as the lower limit.
On the other hand, by making the content of the _Al2O3 component 20.0% or less, the devitrification resistance of the glass _can be improved. Therefore, the upper limit of the content of _{the Al2O3} component is preferably 20.0% or less, more preferably 18.5% or less, even more preferably 18.0% or less, and still more preferably 17.0% or less.

When the _Y2O3 component is contained in an amount of more than 0.0 _% , the refractive index and Abbe number of the glass can be increased. Compared with _{the La2O3 component} and _{the Gd2O3} component, _{the Y2O3} component has the greatest effect of improving acid resistance, but on the other hand, it has the property of reducing the stability of the glass. Therefore, the content of _{the Y2O3} component is preferably 0.0% or more, more preferably more than 0.0%, more preferably 8.0% or more, more preferably 10.0% or more, and even more preferably 11.0% or more as the lower limit.
On the other hand, the upper limit of the content of the Y ₂ O ₃ component is preferably 32.0% or less, more preferably 30.0% or less, more preferably 28.0% or less, and further preferably 26.0% or less.

When the _Gd2O3 component is contained in an amount of _more than 0.0%, it is possible to produce a stable glass while increasing the refractive index of the glass. Therefore, the lower limit of the content of _{the Gd2O3} component is preferably 0.0% or more, more preferably more than 0.0%, more preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more.
On the other hand, by making the content of _{the Gd2O3} component 48.0% or less, the increase in specific gravity can be suppressed. Therefore, the upper limit of the content _{of Gd2O3} is preferably 48.0% or less, more preferably 45.0% or less, more preferably 40.0% or less, and even more preferably 35.0% or less.

The _Yb2O3 component is _a component that can increase the refractive index of glass when it is contained in an amount exceeding 0.0%. However, the raw material price of _{the Yb2O3} component is high, and if the content is high, the production cost will increase. Therefore, the content of _{the Yb2O3} component is preferably 4.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, even more preferably 0.5% or less, and even more preferably 0.1% or less.

The _ZrO2 component is a component that suppresses the decrease in acid resistance and increases the refractive index of the glass when it is contained in an amount of more than 0.0%. Therefore, the lower limit of the content of the _ZrO2 component is preferably 0.0% or more, more preferably more than 0.0%, more preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more.
On the other hand, by making the content of the _ZrO2 component 10.0% or less, it is possible to suppress an increase in specific gravity and deterioration of acid resistance and devitrification resistance. Therefore, the upper limit of the content of the _ZrO2 component is preferably 10.0% or less, more preferably 8.0% or less, and further preferably 6.0% or less.

The ZnO component is a component that increases the refractive index and acid resistance and improves the hardness of the glass when the content exceeds 0.0%. Therefore, the lower limit of the content of the ZnO component is preferably 0.0% or more, more preferably more than 0.0%, more preferably 0.1% or more, and even more preferably 0.5% or more.
On the other hand, by making the content of the ZnO component 13.0% or less, the decrease in the refractive index of the glass can be suppressed and devitrification due to an excessive decrease in viscosity can be reduced. Therefore, the upper limit of the content of the ZnO component is preferably 13.0% or less, more preferably 10.0% or less, more preferably 9.0% or less, and even more preferably 8.0% or less.

The Li ₂ O component, the Na ₂ O component and the K ₂ O component are components that can improve the meltability of glass when contained in an amount exceeding 0.0%.
On the other hand, by making the _Li2O component, _Na2O component and _K2O component 8.0% or less, respectively, the deterioration of reheat press moldability can be suppressed. Therefore, the upper limit of the content of the _Li2O component, the _Na2O component and the _K2O component is preferably 8.0% or less, more preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, and most preferably 0.7% or less.

The MgO component is a component that can improve the melting property of glass raw materials and the devitrification resistance of glass.
On the other hand, by keeping the content of the MgO component at 8.0% or less, it is possible to suppress a decrease in the refractive index and a decrease in resistance to devitrification due to an excessive content. Therefore, the upper limit of the content of the MgO component is preferably 8.0% or less, more preferably 6.5% or less, more preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, and most preferably 0.7% or less.

The CaO component is a component that can increase the hardness of the glass and the meltability of the glass raw material.
On the other hand, by keeping the CaO content at 8.0% or less, it is possible to suppress a decrease in refractive index and a decrease in devitrification resistance due to an excessive content. Therefore, the upper limit of the CaO content is preferably 8.0% or less, more preferably 6.5% or less, more preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, and most preferably 0.7% or less.

The SrO component is a component that can improve the melting property of glass raw materials and the devitrification resistance of glass.
On the other hand, by keeping the content of the SrO component at 8.0% or less, it is possible to suppress a decrease in the refractive index and a decrease in resistance to devitrification due to an excessive content. Therefore, the upper limit of the content of the SrO component is preferably 8.0% or less, more preferably 6.5% or less, more preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, and most preferably 0.7% or less.

The BaO component is a component that can increase the refractive index and Abbe number of the glass when the content exceeds 0.0%.
On the other hand, by keeping the content of the BaO component at 8.0% or less, it is possible to prevent a decrease in the refractive index and a deterioration in acid resistance due to an excessive content of these components. Therefore, the upper limit of the content of the BaO component is preferably 8.0% or less, more preferably 6.5% or less, more preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, and most preferably 0.7% or less.

When the _TiO2 component and _{the Nb2O5} component are contained in an amount exceeding 0.0%, they increase the refractive index of the glass while decreasing the Abbe number. On the other hand, if the _TiO2 component and/or _{the Nb2O5} component are contained in an excessive amount, the Abbe number becomes too small, making it difficult to obtain the desired refractive index and Abbe number. Therefore, the upper limit of the contents of the _TiO2 component and _{the Nb2O5} component is preferably 8.0% or less, more preferably 5.0% or less, more preferably 2.0% or less, even more preferably 1.5% or less, and most preferably 1.0% or less.

The _WO3 component is a component that, when contained in an amount exceeding 0.0%, can increase the refractive index and improve the devitrification resistance while reducing the coloring of the glass caused by other high refractive index components. The upper limit of the content of the _WO3 component is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The _Ta2O5 component is _a component that can increase the refractive index of the glass and improve the devitrification resistance when contained in an amount exceeding 0.0%. The upper limit of the content of _{the Ta2O5} component is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The _P2O5 component is _a component that can lower the liquidus temperature of the glass and improve the devitrification resistance when contained in an amount exceeding 0.0%. The upper limit of the content of _{the P2O5} component is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The _GeO2 component is a component that can increase the refractive index of the glass and improve the devitrification resistance when contained in an amount exceeding 0.0%. The upper limit of the content of the _GeO2 component is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The _Ga2O3 component is _a component that can improve the chemical durability of the glass and the devitrification resistance of the molten glass when contained in an amount exceeding 0.0%. The upper limit of _{the Ga2O3} component content is 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The _Bi2O3 component is _a component that can increase the refractive index and lower the glass transition point when contained in an amount exceeding 0.0%. The upper limit of the content of _{the Bi2O3} component is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The _TeO2 component is a component that can increase the refractive index and lower the glass transition point when contained in an amount exceeding 0.0%. The upper limit of the content of the _TeO2 component is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The _SnO2 component is a component that, when contained in an amount exceeding 0.0%, reduces oxidation of the molten glass to clarify it and increases the visible light transmittance of the glass. The upper limit of the content of the _SnO2 component is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The F component is a component that can improve the meltability of glass when contained in an amount exceeding 0.0%, but on the other hand, a high content can lead to devitrification due to the evaporation of the F component. The upper limit of the F component content is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

The Sb ₂ O ₃ component is a component that can degas the molten glass when its content exceeds 0.0%.
On the other hand, if the content of the _Sb2O3 component is too high, the transmittance in the short wavelength region of _the visible light _region is deteriorated. Therefore, the content of the _Sb2O3 component is preferably 1.0% or less, more preferably 0.5% or less, and further preferably 0.3% or less.

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

When the sum of the contents (sum of mass) of the _{Ln2O3 components} (wherein Ln is one or more selected from the group consisting of La, Y, Gd, and Yb) is 40.0% or more, the refractive index can be increased while the Abbe number can be increased. Therefore, the lower limit of the sum of _{the Ln2O3} components is preferably 40.0% or more, more preferably 42.0% or more, even more preferably 45.0% or more, and even more preferably 47.5% or more.
On the other hand, by setting the sum of the contents (sum of mass) of _{the Ln2O3} component to 65.0% or less, devitrification due to excessive content can be reduced. Therefore, the upper limit is preferably 65.0% or less, more preferably 62.0% or less, and further preferably 60.0% or less.

The Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na and K) can improve the meltability of glass when the sum of the contents (sum of mass) exceeds 0.0%.
On the other hand, by making the sum of the contents (sum of mass) of the Rn ₂ O components 8.0% or less, the deterioration of reheat press moldability can be suppressed. In addition, since the Rn ₂ O component tends to cause devitrification when contained together with the SiO ₂ component, it is preferable that the content is small in the present invention. Therefore, the sum of the contents (sum of mass) of the Rn ₂ O components is preferably 8.0% or less, more preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, and most preferably 1.0% or less as the upper limit.

When the sum of the contents of the RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) exceeds 0.0%, the meltability can be improved. However, since the RO component tends to cause devitrification when contained together with the _SiO2 component, it is preferable that the content is small in the present invention. Therefore, the upper limit of the mass sum of the RO components is preferably 8.0% or less, more preferably 6.5% or less, more preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, and most preferably 0.7% or less.

The ratio of the _SiO2 component to the _B2O3 component, _SiO2 / _B2O3 , is 1.0 to 5.0 by mass ratio, which can improve the acid resistance and increase the hardness of the glass. The _SiO2 component and _{the B2O3} component are network forming components, _and it is considered common technical knowledge that they have similar effects, especially in glasses containing a large amount of rare earth _oxides . However, the present inventors have found, through extensive testing and research _, that the content of the _SiO2 component is greater than that of the _B2O3 component, which can increase the hardness of the glass while suppressing the deterioration of the _{acid resistance caused by the B2O3 component} .
Therefore, the lower limit of the mass ratio SiO ₂ /B ₂ O ₃ is preferably 1.0 or more, more preferably 1.2 or more, even more preferably 1.3 or more, and most preferably 1.5 or more.
On the other hand, the upper limit of the mass ratio SiO ₂ /B ₂ O ₃ is preferably 5.0 or less, more preferably 4.8 or less, even more preferably 4.3 or less, still more preferably 3.8 or less, and most preferably 3.5 or less.

The mass ratio _{Al2O3 /} ( _{SiO2 + B2O3} + _Al2O3 ), which is the ratio of the _{Al2O3 component to the total amount of the SiO2 component , the B2O3} component _, and the Al2O3 _component , is preferably set to 0.05 or more and 0.50 or _less . Since the present invention relates to Si-La- _based glass, rare earth oxides are inferior in acid resistance compared to _{the Al2O3} component, the _SiO2 component, and _{the B2O3} component, by setting the mass ratio _Al2O3 /( _{SiO2 + B2O3} + _Al2O3 ) to 0.05 or more and 0.50 or less, it is possible to improve the acid resistance while increasing _the devitrification resistance.
Therefore, the lower limit of the mass ratio Al ₂ O ₃ /(SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ) is preferably 0.05 or more, more preferably 0.08 or more, even more preferably 0.12 or more, and most preferably 0.15 or more.
On the other hand, the upper limit of the mass ratio Al ₂ O ₃ /(SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ) is preferably 0.50 or less, more preferably 0.45 or less, even more preferably 0.40 or less, still more preferably 0.35 or less, and most preferably 0.30 or less.

The mass ratio (Li ₂ O×10 ³ )/(Al ₂ O ₃ +SiO ₂ ), which is the ratio of the Li ₂ O component to the total amount of the Al ₂ O ₃ component and the SiO ₂ component to the power of 10, is preferably 45.0 or less.
The Li ₂ O component is a component that improves meltability, but is also a component that deteriorates reheat press moldability. In particular, when the Li-Al-Si-O component is also contained, crystallization is likely to occur during reheat press molding. Therefore, the above problem can be solved by making the mass ratio (Li ₂ O x 10 ³ )/(Al ₂ O ₃ +SiO ₂ ) 45.0 or less.
Therefore, the upper limit of the mass ratio (Li ₂ O×10 ³ )/(Al ₂ O ₃ +SiO ₂ ) is preferably 45.0 or less, more preferably 35.0 or less, even more preferably 25.0 or less, still more preferably 15.0 or less, and most preferably 13.0 or less.
On the other hand, the lower limit of the mass ratio (Li ₂ O×10 ³ )/(Al ₂ O ₃ +SiO ₂ ) is preferably 0, more preferably 0.50 or more, even more preferably 0.80 or more, and most preferably 1.00 or more.

By setting the mass ratio ( _B2O3 x ₁₀₂ )/( _SiO2 + _Ln2O3 ), which is the ratio _of the _B2O3 component to ^the total amount of the _SiO2 component _and the _{Ln2O3 component} , to 5.0 or more and 20.0 or less, it is possible to improve the refractive index and the hardness of the glass while suppressing deterioration of acid resistance.
Therefore, the lower limit of the mass ratio (B ₂ O ₃ ×10 ² )/(SiO ₂ +Ln ₂ O ₃ ) is preferably 5.0 or more, more preferably 6.0 or more, even more preferably 8.0 or more, and most preferably 10.0 or more.
On the other hand, the upper limit of the mass ratio (B ₂ O ₃ ×10 ² )/(SiO ₂ +Ln ₂ O ₃ ) is preferably 20.0 or less, more preferably 18.0 or less, even more preferably 16.0 or less, and most preferably 14.0 or less.

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

Other components may be added as necessary to the extent that they do not impair the properties of the glass of the present invention. However, transition metal components such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, have the property that even when contained in small amounts alone or in combination, the glass will be colored and absorption will occur at specific wavelengths in the visible range, so it is preferable that they are not substantially contained, especially in optical glasses that use wavelengths in the visible range. Furthermore, it is preferable that the components Rb and Cs are not contained from the viewpoint of suppressing coloration of the glass.

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

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

[Manufacturing method]
The optical glass of the present invention is produced, for example, as follows: High-purity raw materials used for ordinary optical glass, such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds, are mixed uniformly as the raw materials for each of the above components so that the content of each component falls within a prescribed range, the mixture thus produced is placed in a platinum crucible, and melted in an electric furnace at a temperature range of 1100 to 1400° C. for 1 to 5 hours depending on the degree of melting difficulty of the glass raw materials, stirred and homogenized, and then the temperature is lowered to an appropriate level, and the glass is cast into a mold and slowly cooled.

<Physical Properties>
The optical glass of the present invention has desired optical properties.
The refractive index (n _d ) of the optical glass of the present invention is preferably 1.70000 or more, more preferably 1.72000 or more, and even more preferably 1.73000 or more as the lower limit, while the refractive index (n _d ) is preferably 1.80000 or less, more preferably 1.78000 or less, and even more preferably 1.76000 or less as the upper limit.
The Abbe number (ν _d ) of the optical glass of the present invention is preferably at least 45.00, more preferably at least 46.00, and even more preferably at least 47.00, while the Abbe number (ν _d ) is preferably at most 55.00, more preferably at most 53.00, and even more preferably at most 51.00.

The acid resistance of the glass in the examples and comparative examples is measured in accordance with the Japan Optical Glass Industry Association standard "Method of measuring the chemical durability of optical glass" JOGIS06-2006. That is, a glass sample crushed to a particle size of 425 to 600 μm was placed in a pycnometer and placed in a platinum cage. The platinum cage was placed in a quartz glass round-bottom flask containing a 0.01N aqueous solution of nitric acid, and treated in a boiling water bath for 60 minutes. The weight loss rate (mass%) of the glass sample after treatment was calculated, and the weight loss rate (mass%) was classified as grade 1 if it was less than 0.20, grade 2 if it was 0.20 to less than 0.35, grade 3 if it was 0.35 to less than 0.65, grade 4 if it was 0.65 to less than 1.20, grade 5 if it was 1.20 to less than 2.20, and grade 6 if it was 2.20 or more. In this case, the smaller the class number, the better the acid resistance of the glass.
In the optical glass of the present invention, it is preferably 1st to 3rd grade, more preferably 1st or 2nd grade.

The optical glass of the present invention preferably has a Knoop hardness of at least grade 6 when measured according to the method of measurement in accordance with "JOGIS09-1975 Method for Measuring Knoop Hardness of Optical Glass." This makes it difficult for scratches or breaks to occur when polishing the glass, and scratches to the surface during transportation of the glass, etc., and therefore makes it possible to obtain optical glass that has a desired surface condition and that is easy to maintain that surface condition. Therefore, the Knoop hardness of the optical glass of the present invention is preferably grade 6, and more preferably grade 7.

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

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

The glass molded body made of the optical glass of the present invention can be used for optical elements such as lenses, prisms, and mirrors, and can also be used for applications requiring good hardness and chemical durability, such as in-vehicle optical equipment such as in-vehicle cameras.

The compositions of the examples of the present invention (No. 1 to No. 70) and Comparative Examples A and B, as well as the refractive index (n _d ), Abbe number (ν _d ), chemical durability (acid resistance) by the powder method, and Knoop hardness of these glasses are shown in Tables 1 to 4. Note that the following examples are merely for illustrative purposes, and the present invention is not limited to these examples.

For the glasses of the examples of the present invention, high-purity raw materials used in ordinary optical glass, such as the corresponding oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds, were selected as the raw materials for each component, and after weighing and mixing uniformly to obtain the composition ratios of each example and comparative example shown in the table, they were placed in a quartz crucible or platinum crucible and melted in an electric furnace at a temperature range of 1100 to 1400°C for 1 to 5 hours depending on the melting difficulty of the glass composition. After stirring and homogenizing, and performing bubble removal, etc., the temperature was lowered to 1000 to 1300°C and stirred and homogenized, and then the glass was cast into a mold and slowly cooled to produce the glass.

The refractive index (n _d ) and Abbe number (ν _d ) of the glasses of the examples and comparative examples were measured according to the V-block method defined in JIS B 7071-2:2018. Here, the refractive index (n _d ) was shown as a measured value for the d-line (587.56 nm) of a helium lamp. The Abbe number (ν d ) was calculated from the formula Abbe number (ν _d ) = [(n _d -1) / (n _F -n C )] using the values of the refractive index (n _d ) for the d-line of a helium lamp, the refractive index (n _F ) for the F-line (486.13 nm) of _a hydrogen lamp, and the refractive index ( _{n C )} for the C-line (656.27 nm). These refractive indexes (n _d ) and Abbe number (ν _d ) were obtained by measuring the glasses obtained by slow cooling at a temperature drop rate of -25°C/hr.

The chemical durability of the glass in the examples and comparative examples was measured in accordance with the Japan Optical Glass Industry Association standard "Method for measuring the chemical durability of optical glass" JOGIS06-2006. That is, glass samples crushed to particle sizes of 425 to 600 μm were placed in a pycnometer and placed in a platinum cage. The platinum cage was placed in a quartz glass round-bottom flask containing 0.01 N nitric acid aqueous solution and treated in a boiling water bath for 60 minutes. The weight loss rate (mass%) of the glass sample after treatment was calculated, and the weight loss rate (mass%) was classified as grade 1 if it was less than 0.20, grade 2 if it was 0.20 to less than 0.35, grade 3 if it was 0.35 to less than 0.65, grade 4 if it was 0.65 to less than 1.20, grade 5 if it was 1.20 to less than 2.20, and grade 6 if it was 2.20 or more. In this case, the smaller the class number, the better the acid resistance of the glass.

The Knoop hardness (Hk) of the glasses in the examples and comparative examples was measured based on the Japan Optical Glass Industry Association standard (JOGIS09-1975). Specifically, a diamond rhombus indenter (with diagonal angles of 172°30' and 130°) was pressed against the flat, polished surface of the sample with a load of 0.98 N (0.1 kgf) for 15 seconds to make an indentation, and the length of the longer diagonal of the indentation was measured and calculated using formula (1).

Knoop hardness = 1.451 F/ ^l2 (1)
F: Load (N)
l: Length of the longer diagonal (mm)
Knoop hardness is classified as grade 1 when it is less than 150, grade 2 when it is 150 or more and less than 250, grade 3 when it is 250 or more and less than 350, grade 4 when it is 350 or more and less than 450, grade 5 when it is 450 or more and less than 550, grade 6 when it is 550 or more and less than 650, and grade 7 when it is 650 or more. The higher the grade, the harder the glass is.

As shown in the table, the optical glasses of the Examples all had a refractive index (n _d ) of 1.70000 or more and 1.80000 or less, which was within the desired range, and the optical glasses of the Examples of the present invention all had an Abbe number (ν _d ) of 45.00 or more and 55.00 or less.

In addition, the optical glass of the embodiment has a chemical durability (acid resistance) class of 1 to 3 according to the powder method, and it is clear that the glass is resistant to fogging and can be used for a long time.

The optical glass in the examples of the present invention also had a Knoop hardness of class 6 to 7. This makes it clear that the optical glass in the examples of the present invention is a hard glass.

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

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

Claims (4)

In mass% based on oxide,
_La2O3 component is 8.0% _or more and 47.0% or less ,
_SiO2 component is 16.69% or more,
_B2O3 component _is 6.21% or more,
_Al2O3 component is 7.27% _or more and 14.02% or less
Contains
_ZrO2 component is 6.0% or less,
ZnO content is 8.0% or less,
The sum of the contents of the _{Ln2O3 components} is 51.20% or more (wherein Ln is one or more selected from the group consisting of La, Y, Gd, and Yb);
The sum of the contents of _Rn2O components is 1.5% or less (wherein Rn is one or more selected from the group consisting of Li, Na, and K);
The sum of the contents of RO components is 5.0% or less (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba);
The mass ratio _SiO2 / _B2O3 is 1.92 or _more and 5.0 or less,
A refractive index (n _d ) of 1.72000 or more and 1.80000 or less;
Abbe number (ν _d ) is 45.00 or more and 55.00 or less;
Acid resistance by powder method is 1st to 3rd grade.
An optical glass with a Knoop hardness of 6 to 7. 2. The optical glass according to claim 1, wherein the _mass ratio ( _Li2O x ¹⁰³ )/( _Al2O3 + _SiO2 ) is 45.0 or less. An optical element made of the optical glass according to claim 1 or 2. A preform for polishing and/or precision press molding, comprising the optical glass according to claim 1 or 2.