JP7720360B2 - Heavy lanthanum flint glass, its preform, optical element, and optical device - Google Patents

Description

The present invention belongs to the technical field of optical glass, and in particular relates to heavy lanthanum flint glass, its preforms, optical elements, and optical instruments.

Double lanthanum flint glasses with a refractive index (nd) of 1.86 to 1.92 and an Abbe number (vd) of 25 to 30 are widely used in lenses for precision optical instruments. While these double lanthanum flint glasses can meet the requirements of modern precision compression molding technology, existing double lanthanum flint glasses have a high refractive index temperature coefficient.

The refractive index of optical glass is a function of temperature, i.e., the refractive index temperature coefficient of the glass, which is the change in refractive index per unit temperature. It is an important performance parameter for measuring the effect of temperature on the refractive index of optical glass. As the temperature increases, the glass thermally expands, decreasing its density and refractive index.

In optical equipment used in the fields of medical care, night photography, and integrated circuit photoetching, the ambient temperature of the optical lens rises continuously over time, causing significant changes in the refractive index of the glass, significantly reducing the imaging quality of the glass and affecting system resolution. Thermal aberration correction technology is typically required for the design. For example, the lithography lens of a photoetching machine is composed of a combination of a movable lens and a thermal aberration correction element. However, these high technical thresholds are only understood by a small number of manufacturers worldwide, significantly limiting the application and use of related technologies, shaping market competition, and negatively impacting the high cost of precision equipment.

Furthermore, the high upper limit of the crystallization temperature, poor stability during high-temperature processing, and significant difficulties in heat treatment techniques limit the range of use of these existing heavy lanthanum flint glasses.

In addition, existing heavy lanthanum flint glass, which has high density and high color intensity, cannot meet people's demands for lightweight, compact instruments and devices with high transmittance.

Therefore, there is a need to develop heavy lanthanum flint glasses that have high transmittance and imaging quality, an excellent refractive index temperature coefficient, and a low upper limit of the crystallization temperature.

In response to the problems of the prior art, the present invention aims to provide a heavy lanthanum flint glass having a refractive index (nd) of 1.86 to 1.92 and an Abbe number (vd) of 25 to 30. This glass can meet the optical performance requirements of precision instruments, has excellent crystallization resistance, a low refractive index temperature coefficient, and can effectively reduce thermal aberrations caused by temperature differences.

The present invention further provides preforms, optical elements, and optical instruments made from heavy lanthanum flint glass.

To achieve the above objectives, the technical solutions of the present invention are as follows:

The heavy lanthanum flint glass contains, by weight, 12 to 30% SiO ₂ , 10 to 25% Ln ₂ O ₃ , the Ln ₂ O ₃ being the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ , 10.5 to 40% TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ , 0 to 10% B ₂ O ₃ , 20 to 35% RO , the RO being one or more of BaO, CaO, MgO, and SrO, and 0.5 to 10% ZrO ₂ , and has a composition of (SiO ₂ + TiO ₂ )/(B ₂ O ₃ + Nb ₂ O ₅ ) is 1 to 30.

Furthermore, the heavy lanthanum flint glass contains, by weight, 0 to 8% Rn ₂ O, the Rn ₂ O being one or more of Li ₂ O, Na ₂ O, and K ₂ O, 0 to 1% Sb ₂ O ₃ , 0 to 7% ZnO, 0 to 10% Ta ₂ O ₅ , and 0 to 10% Al ₂ O ₃ .

The heavy lanthanum flint glass has, by weight, 12 to 30% SiO ₂ , 10 to 25% Ln ₂ O ₃ , the Ln ₂ O ₃ being a total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ , 10.5 to 40% TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ , 20 to 35% RO , the RO being one or more of BaO, CaO, MgO, and SrO , 0.5 to 10% ZrO ₂ , 0 to 10% B ₂ O ₃ , and 0 to 8% Rn ₂ O , the Rn ₂ O being Li ₂ O, Na ₂ O, and K _{2 O 3 .} O, and contains 0-1% Sb ₂ O ₃ , 0-7% ZnO, 0-10% Ta ₂ O ₅ , and 0-10% Al ₂ O ₃ , and (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is 1-30.

Furthermore, the heavy lanthanum flint glass satisfies one or more of the following four conditions in terms of the content of all components.
1) _B2O3 /TiO2 is _greater than ₀ but less than or equal to 1;
2) BaO/B ₂ O ₃ is greater than 0 but less than or equal to 70;
3) (La ₂ O ₃ + TiO ₂ + ZrO ₂ )/SiO ₂ is 0.7 to 6;
4) (SiO ₂ +La ₂ O ₃ +ZrO ₂ )/TiO ₂ is 0.75 to 6.5.

Furthermore, according to the heavy lanthanum flint glass, the _SiO2 is 15 to 25%, and/or _{the Ln2O3} is 12 to 22%, and/or the _TiO2 + _Nb2O5 + _WO3 + _{Bi2O3 is 17} to 33%, and/or the RO is 22 to 32%, and/or the _ZrO2 is 2 to 8%, and/or the _B2O3 is 0.5 to 6%, and/or _{the Rn2O} is 0.5 to 6%, and/or the _Sb2O3 is 0 to 0.5%, and/or the _ZnO is 0 to 5%, and/or the _Ta2O5 is 0 to 5 _% , and/or _{the Al2O3} is 0 to 5%.

Furthermore, the heavy lanthanum flint glass has a total content of all components that satisfies one or more of the following five conditions:
1) B ₂ O ₃ /TiO ₂ is 0.02 to 0.4;
2) BaO/B ₂ O ₃ is 3.6 to 64;
3) (La ₂ O ₃ + TiO ₂ + ZrO ₂ )/SiO ₂ is 1.2 to 5;
4) (SiO ₂ + La ₂ O ₃ + ZrO ₂ )/TiO ₂ is 1.1 to 3.7;
5) (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is 2.15 to 20.

Furthermore, the heavy lanthanum flint glass has a total content of components that satisfy one or two of the following two conditions:
6) SiO ₂ + TiO ₂ is 30-50%;
7) B ₂ O ₃ /SiO ₂ is 0.02 to 0.4.

Furthermore, according to the heavy lanthanum flint glass, the _SiO2 is 18 to 23%, and/or _{the Ln2O3} is 13 to 18%, and/or the _TiO2 + _Nb2O5 + _WO3 + _{Bi2O3 is 22} to 31%, and/or the RO is 23 to 30%, and/or the _ZrO2 is 2 to 6%, and/or the _B2O3 is 1 to 4%, and/or _{the Rn2O} is 1 to 5%, and/or the _Sb2O3 is 0 to 0.2%, and/or the _ZnO is 0 to 3%, and/or the _Ta2O5 is not contained, and/or _{the Al2O3} is not _contained .

Furthermore, the heavy lanthanum flint glass has a total content of all components that satisfies one or more of the following five conditions: 1) B ₂ O ₃ /TiO ₂ is 0.02 to 0.23, 2) BaO/B ₂ O ₃ is 5 to 30, 3) (La ₂ O ₃ +TiO ₂ +ZrO ₂ )/SiO ₂ is 1.5 to 4, 4) (SiO ₂ +La ₂ O ₃ +ZrO ₂ )/TiO ₂ is 1.2 to 2, and 5) (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is 3.36 to 12.

Furthermore, the heavy lanthanum flint glass has a total content of all components that satisfies one or two of the following two conditions: 6) SiO ₂ +TiO ₂ is 37-50%, and 7) B ₂ O ₃ /SiO ₂ is 0.02-0.34.

Furthermore, according to the heavy lanthanum flint glass, the TiO ₂ is 10 to 30% and/or the Nb ₂ O ₅ is 0.5 to 10%, preferably the TiO ₂ is 15 to 25% and/or the Nb ₂ O ₅ is 2 to 8%, more preferably the TiO ₂ is 19 to 24% and/or the Nb ₂ O ₅ is 3 to 7%.

Furthermore, according to the heavy lanthanum flint glass, the La ₂ O ₃ is 10 to 25%, and/or the BaO is 20 to 35%, and/or the Na ₂ O is 0 to 8%, preferably the La ₂ O ₃ is 12 to 22%, and/or the BaO is 22 to 32%, and/or the Na ₂ O is 0.5 to 6%, more preferably the La ₂ O ₃ is 13 to 18%, and/or the BaO is 23 to 30%, and/or the Na ₂ O is 1 to 5%.

Furthermore, according to the heavy lanthanum flint glass, the λ ₇₀ of the glass is 450 nm or less, preferably 440 nm or less, and more preferably 430 nm or less; the λ ₅ is 390 nm or less, preferably 385 nm or less, and more preferably 380 nm or less; the density (ρ) of the glass is 4.5 g/cm ³ or less, preferably 4.3 g/cm ³ or less, and more preferably 4.25 g/cm ³ or less; the upper limit of the crystallization temperature of the glass is 1,200°C or less, preferably 1,180°C or less; and the temperature coefficient of refractive index of the glass is 2.4 × 10 ^-6 /°C or less, and preferably 2.3 × 10 ^-6 /°C or less.

Furthermore, the heavy lanthanum flint glass has a refractive index (nd) of 1.86 to 1.92, preferably 1.86 to 1.91, and more preferably 1.87 to 1.90, and an Abbe number (vd) of 25 to 30, preferably 25 to 29, and more preferably 26 to 29.

Furthermore, the heavy lanthanum flint glass has a glass conversion temperature (Tg) of 720° C. or less, preferably 710° C. or less, more preferably 705° C. or less, a water resistance (D _W ) of grade 2 or more, preferably 1, and an acid resistance (D _A ) of grade 2 or more, preferably 1. A glass preform is made from the heavy lanthanum flint glass.

Optical elements are made from the heavy lanthanum flint glass or the glass preform.

Optical instruments are made from the optical elements.

The present invention has the following beneficial effects: The heavy lanthanum flint glass has excellent refractive index temperature coefficient, upper limit of crystallization temperature, λ ₇₀ , λ ₅ , and chemical stability with a reasonable component ratio while ensuring the necessary refractive index and Abbe number, which allows it to be applied to precision instruments that require high transmittance, imaging quality, and low thermal aberration.

Heavy Lanthanum Flint Glass The following paragraphs detail the composition of the heavy lanthanum flint glass according to the present invention. Unless otherwise specified, the contents of all glass components and their total contents refer to weight contents expressed in weight percent, which is the percentage of the weight of a particular component or the total weight of several components relative to the total weight of the optical glass. The ratio of all glass components or the total ratio of several components is the ratio of the corresponding weight contents or total weight contents.

The heavy lanthanum flint glass of the present invention contains, by weight, 12 to 30% SiO ₂ , 10 to 25% Ln ₂ O ₃ , where Ln ₂ O ₃ is the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ , 10.5 to 40% TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ , 0 to 10% B ₂ O ₃ , 20 to 35% RO, where RO is one or more of BaO, CaO, MgO, and SrO, and 0.5 to 10% ZrO ₂ , and has a composition of (SiO ₂ + TiO ₂ )/(B ₂ O ₃ + Nb ₂ O ₅ ) is 1 to 30.

In the glass of the present invention, _SiO2 is a network-forming component of the glass and a major component constituting the glass frame. The _SiO2 content is closely related to the crystallization resistance, transmittance, refractive index, and dispersion of the glass. If the SiO2 content is lower than 12%, the refractive index and dispersion of the glass will not reach the design expectations, while the crystallization resistance and transmittance of the glass will be significantly reduced. If the SiO2 content is higher than 30%, the melting property and crystallization resistance of the glass will be reduced, while the refractive index and dispersion will not reach the design expectations. Therefore, according to the present invention, the _SiO2 content is set to 12-30%, preferably 15-25%, and more preferably 18-23%.

B ₂ O ₃ is also an optional component in forming the glass network in the present invention. In some embodiments of the present invention, B ₂ O ₃ can be introduced to improve the meltability and devitrification resistance of the glass. However, when the amount is higher than 10%, the glass forming stability and refractive index decrease. Therefore, the B ₂ O ₃ content of the present invention is set to 0 to 10%, preferably 0.5 to 6%, and more preferably 1 to 4%.

As two glass network components, _SiO2 and _B2O3 not only have _their own unique functions, but also mutually limit the glass-forming stability and glass transition temperature (Tg). _{A B2O3} / _SiO2 ratio higher than 0.4 reduces the glass transition temperature (Tg), while _{a B2O3} / _SiO2 ratio lower than 0.02 reduces the glass-forming stability. Therefore, in some embodiments of the heavy lanthanum flint glasses containing _B2O3 of the present invention, the _B2O3 / _SiO2 ratio is set to _{0.02 to} 0.4, more preferably 0.02 to 0.34.

The rare earth oxides Ln ₂ O ₃ (La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ ) are useful for improving the refractive index of glass. If their total content is less than 10%, the expected optical constants cannot be obtained. However, if their total content is more than 25%, the chemical stability and devitrification resistance of the glass decrease, and the raw material cost of the glass increases. Therefore, the total content Ln ₂ O ₃ of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ is set to 10 to 25%, preferably 12 to 22%, and more preferably 13 to 18%. In some embodiments, the rare earth oxide of the present invention may contain 10-25% La 2 O 3 , preferably 12-22% La ₂ O ₃ , and more preferably 13-18% La ₂ O ₃ to further improve the refractive index, visible spectrum transmittance, and devitrification resistance of the glass, and to reduce the temperature coefficient of _{refractive index} of the glass.

TiO ₂ , Nb ₂ O ₅ , WO ₃ , and Bi ₂ O ₃ are effective in improving the refractive index and dispersion. Therefore, when the content of TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ is higher than 40%, the dispersion of the glass increases significantly, the coloring tendency of the glass increases, but the transmittance decreases. Therefore, the upper limit of TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ is set to 40%, preferably 33%, and more preferably 31%. However, if the content of TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ is too low, the thermal stability and compressibility of the glass decrease. Therefore, the lower limit is set to 10.5%, preferably 17%, and more preferably 22%.

In the heavy lanthanum flint glass of the present invention, a combination _{of TiO2} and _Nb2O5 is preferred to obtain better refractive index and Abbe number. To increase the crystallization resistance of the glass, more than 10% of _TiO2 may be added to the glass of the present invention to participate in the formation of the glass network, partially replacing expensive _Nb2O5 , _WO3 , and _{Bi2O3 .} However, if the _TiO2 content is higher than 30%, the glass transmittance decreases but the glass's tendency to color increases. _Nb2O5 may be appropriately incorporated to make the glass more stable and improve its devitrification resistance. Taking this into consideration, the _TiO2 content of the heavy lanthanum flint glass of the _present invention is set to 10-30%, preferably 15-25%, and more preferably 19-24%. _{The Nb2O5} content is set to 0.5-10%, preferably 2-8%, and more preferably 3-7%.

Furthermore, the inventors have found through research that the B ₂ O ₃ /TiO ₂ ratio in the components B ₂ O ₃ and TiO ₂ affects the λ ₇₀ , λ ₅ , upper limit of crystallization temperature, and temperature coefficient of refractive index of the glass, and that a B ₂ O ₃ /TiO ₂ ratio greater than 1 increases the upper limit of crystallization temperature and the temperature _{coefficient of} refractive index. According to the present invention, to obtain optical glass with high transmittance and other excellent properties, it is preferable that B ₂ O ₃ /TiO ₂ be greater than 0 but not greater than ₁ , more preferably _0.02 to _0.4 , and even more preferably _0.02 to 0.23.

The total content of _SiO2 and _TiO2 has a significant effect on the _λ70 , _λ5 , water resistance ( _DW ), and acid resistance ( _DA ) of the entire glass. If the content of _SiO2 + _TiO2 is greater than 50%, the transmittance of the glass in the visible region decreases, coloration increases, and water resistance ( _DW ) and acid resistance ( _DA ) decrease. Therefore, if the content of _SiO2 + _TiO2 is less than 30%, the glass formation stability deteriorates and the thermal expansion coefficient increases. Therefore, according to the present invention, _SiO2 + _TiO2 is preferably 30 to 50%, more preferably 37 to 50%.

Furthermore, the inventors have found that if the ratio of ( _SiO2 + _TiO2 )/ _{( B2O3} + _Nb2O5 ) is less than 1, the stability of the glass deteriorates, _the upper limit of the crystallization temperature rises, the thermal aberration increases, and the refractive index temperature coefficient and the glass ratio increase, making it difficult to achieve the goal of weight reduction. However, if the ratio is greater than 30, the glass transmittance decreases, but the coloring tendency increases significantly. Therefore, the ratio of (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is defined as 1 to 30, preferably the ratio of (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is defined as 2.15 to 20, and more preferably the ratio of (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is defined as 3.36 to 12.

The alkaline earth metal oxides RO are one or more of CaO, MgO, SrO, and BaO. For the heavy lanthanum flint glass of the present invention, adding more than 20% alkaline earth metal oxides can improve the Young's modulus of the glass, reduce the high-temperature viscosity of the glass, and balance the glass's components, improving the meltability of the glass. However, if the total RO content is higher than 35%, the excess alkaline earth metal oxides can reduce the crystallization resistance of the glass. Therefore, according to the present invention, the RO value is set to 20-35%, preferably 22-32%, and more preferably 23-30%. In some embodiments, the alkaline earth metal oxides of the present invention may contain 20-35% BaO, preferably 22-32%, and more preferably 23-30% BaO, to further reduce the temperature coefficient of refractive index of the glass and improve the devitrification resistance and chemical stability of the glass.

In some embodiments, the ratio of BaO and B ₂ O ₃ added has a significant effect on the temperature coefficient of refractive index, water resistance (D _W ), and acid resistance (D _A ) of the glass. When BaO/B ₂ O ₃ is greater than 0, the meltability of the glass is improved, and the temperature coefficient of refractive index and thermal aberration of the glass are reduced. However, when BaO/B ₂ O ₃ is greater than 70, the acid resistance, water resistance, and crystallization resistance of the glass are reduced. Therefore, BaO/B ₂ O ₃ is greater than 0 but not greater than 70, preferably BaO/B ₂ O ₃ is set to 3.6 to 64, and more preferably BaO/B ₂ O ₃ is set to 5 to 30.

_ZrO2 is an oxide with high reflectivity and low dispersion, and is a necessary component in the present invention. More than 0.5% _ZrO2 may be added to the glass to improve the refractive index and adjust its dispersion. Meanwhile, the crystallization resistance and chemical stability of the glass can be improved. However, in the heavy lanthanum flint glass of the present invention, if the ZrO2 content is higher than 10%, the glass becomes difficult to melt, the melting temperature increases, and obstructions easily form within the glass, reducing its transmittance. Therefore, the ZrO2 content is set to 0.5-10%, preferably 2-8%, and more preferably 3-7%.

In the glass of the present invention, _ZrO2 cooperates with _the components _La2O3 , _SiO2 , and _TiO2 to adjust the nd, vd, _λ70 , and _λ5 of the glass, as well as the upper limit of the crystallization temperature _and the temperature coefficient of refractive index. Experiments by the inventors have confirmed that when nd, vd, _λ70 , and _λ5 are adjusted by the ratio of ( _La2O3 + _TiO2 + _ZrO2 )/ _SiO2 , a preferred ratio range is 0.7 to 6. If the ratio is less than 0.7, the meltability and stability of the glass deteriorate, and the refractive index decreases. _If ( _La2O3 + _TiO2 + _ZrO2 )/ _SiO2 is higher than 6, the transmittance of the glass in the visible light region decreases, and its coloration deteriorates. More preferably, the ratio of ( _La2O3 + _TiO2 + _ZrO2 )/ _SiO2 is in the range of 1.2 to 5, and most preferably in the range of 1.5 to 4. When adjusting _λ70 , _λ5 , the _upper limit of the crystallization temperature of the glass, the temperature coefficient _of refractive index, and the ratio of ( _SiO2 + _La2O3 + _ZrO2 )/ _TiO2 , a preferred ratio is in the range of 0.75 to 6.5, and when the ratio is 6.5 or less, better light transmittance and better crystallization resistance can be obtained. However, when the ratio is less than 0.75 or more than 6.5, it is difficult to maintain the temperature coefficient of refractive index at 2.4 × ^10-6 /°C or less, and the optical performance and crystallization resistance are clearly deteriorated. For _preferred solutions, the ratio of ( _SiO2 + _La2O3 + _ZrO2 )/ _TiO2 is in the range of 1.1 to 3.7, most preferably in the range of 1.2 to 2.

Rn ₂ O, which belongs to the alkaline earth metal oxides, is one or more of Li ₂ O, Na ₂ O, and K ₂ O and is an optional component of the present invention. In the glass system of the present invention, an approximate amount of alkali metal oxide may be added to obtain a predicted high-temperature viscosity. Meanwhile, when an approximate amount of alkali metal oxide coexists with B ₂ O ₃ , the compactness of the B ₂ O ₃ network is improved, resulting in better light transmittance. However, excessive alkali metal oxide significantly impairs the crystallization resistance of the glass. Therefore, according to the present invention, the Rn ₂ O value is set to 0-8%, preferably 0.5-6%, and more preferably 1-5%. In some embodiments, the alkali metal oxide according to the present invention, when containing 0-8% Na ₂ O _, preferably 0.5-6%, and more preferably 1-5% Na ₂ O, can further lower the glass conversion temperature and improve the meltability of the glass.

ZnO adjusts the refractive index and dispersion of the glass, lowers the glass's conversion temperature, and can improve the glass's resistance to crystallization and chemical stability. ZnO also reduces the high-temperature viscosity of the glass, allowing the glass to be melted at a lower temperature and increasing the glass's transmittance. However, if excessive ZnO is added, the glass's resistance to crystallization decreases and its high-temperature viscosity is relatively low, posing challenges to molding. In the glass system of the present invention, ZnO may be an optional component, and its content is 0-7%, preferably 0-5%, and more preferably 0-3%.

_Ta2O5 increases the refractive index but can decrease dispersion, and is an optional component in the heavy _lanthanum flint glass of the present invention, with a content of 0-10%, preferably 0-5%. Due to _{its high cost, it is preferred that Ta2O5 not} be included.

Al ₂ O ₃ can reduce the thermal expansion coefficient of glass and improve the thermal stability of glass. However, a high Al ₂ O ₃ concentration generally reduces the liquidus viscosity of glass. According to the present invention, its content is set to 0-10%, preferably 0-5%, and more preferably, Al ₂ O ₃ is not included.

The heavy lanthanum flint glass of the present invention may also incorporate 0 to 1%, preferably 0 to 0.5%, of the fining agent Sb ₂ O ₃ .

Small amounts of other components, including _P2O5 , _TeO2 , _GeO2 , and _{Lu2O3 ,} may be added as needed, provided they do not impair the glass properties of the present invention. However, transition metal components such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, whether contained singly or in the form _of a compound, color the glass and absorb specific wavelengths in the visible light range, thereby reducing the property of the present invention of improving visible light transmittance. Therefore, it is preferable that these components are not included, especially for optical glasses that have a requirement for wavelength transmittance within the visible range.

Compounds of Pb, As, Th, Cd, Tl, Os, Be, and Se have recently been used under controlled conditions as hazardous chemicals, and are therefore necessary not only in the glass manufacturing process but also in processing procedures and post-manufacturing disposal for environmental protection purposes. Therefore, when environmental impact is a major concern, it is preferable that they are not actually included except in unavoidable incorporation. As a result, optical glass does not actually contain substances that pollute the environment. Therefore, the optical glass of the present invention can be manufactured, processed, and disposed of without the need for special environmental measures.

The terms "not incorporated," "not containing," and "0%" used herein mean that the raw material compounds, molecules, or elements are not intentionally added to the heavy lanthanum flint glass of the present invention. The raw materials and/or equipment used to manufacture the glass may contain impurities or components that are not intentionally added, and small or trace amounts of these may be present in the final heavy lanthanum flint glass. This state also falls within the scope of patent protection for the invention.

According to the above paragraphs, it can be seen that certain components affect multiple performances of the glass in the glass system according to the present invention. Optimizing one performance with the same component may degrade other performances. Therefore, the mutual coordination and limitations of multiple components in the entire glass system are particularly important. The heavy lanthanum flint glasses obtained by the inventors of the present invention according to experimental studies have excellent nd, vd, λ ₇₀ , λ ₅ , ρ, upper limit of crystallization temperature, temperature coefficient of refractive index, D _W , _DA , glass forming stability, or conversion temperature (Tg).

The various performance indices of the heavy lanthanum flint glass of the present invention are analyzed using the following methods:

[Refractive index]
The refractive index (nd) is analyzed according to the method of GB/T7962.1-2010.

[Dispersion coefficient]
The dispersion coefficient (ie, Abbe number, vd) is analyzed according to the method of GB/T7962.1-2010.

[Glass coloring]
λ ₇₀ refers to the wavelength at which the glass transmittance reaches 70%, and λ ₅ refers to the wavelength at which the glass transmittance reaches 5%. λ ₇₀ is analyzed using optically polished glass with a thickness of 10±0.1 mm on two parallel opposing planes, and analyzes the spectral transmittance in the wavelength range from 280 nm to 700 nm and the wavelength representing 70% transmittance.

[Temperature coefficient of refractive index]
The refractive index temperature coefficient from 20 to 40° C. is analyzed according to the method specified in GB/T7962.4-2010.

[Glass conversion temperature]
The glass conversion temperature (Tg) is in °C and is analyzed according to the method specified in GB/T7962.16-2010.

[Upper limit of crystallization temperature]
The method for analyzing the upper limit of the crystallization temperature involves analyzing the crystallization characteristics of glass using a temperature gradient furnace process, preparing a 180 x 10 x 10 mm sample of glass, polishing it horizontally, placing it in a furnace with a temperature gradient (5°C/cm) and heating it to 1,400°C, maintaining the temperature for 4 hours, removing it, allowing it to cool naturally to room temperature, and observing the crystallization of the glass under a microscope to determine the upper limit of the crystallization temperature of the glass when the highest temperature of the glass corresponding to crystallization is found. The lower the upper limit of the crystallization temperature of the glass, the stronger the glass's stability at high temperatures and the better the performance of the manufacturing process.

[Chemical stability]
Water resistance (D _W ) is analyzed according to the method of GB/T17129.

Acid resistance (D _A ) is analyzed according to the method of GB/T17129.

[density]
The density (ρ) is analyzed according to the method of Colorless Optical Glass Test Methods-Density (GB/T7962.20-1987).

According to analysis, the heavy lanthanum flint glass of the present invention has the following properties: a refractive index (nd) of 1.86 to 1.92, preferably 1.86 to 1.91, more preferably 1.87 to 1.90; an Abbe number (vd) of 25 to 30, preferably 25 to 29; a conversion temperature (Tg) of 720°C or less, preferably 710°C or less, more preferably 705°C or less; a _λ70 of 450 nm or less, preferably 440 nm or less, more preferably 430 nm or less; a _λ5 of 390 nm or less, preferably 385 nm or less, more preferably 380 nm or less; a density (ρ) of 4.5 g/cm3 or ^less , preferably 4.3 g/cm3 or ^less , more preferably 4.25 g/cm3 or ^less ; a water resistance ( _Dw ) of grade 2 or more, preferably 1; an acid resistance (D _A ) is grade 2 or higher, preferably 1, the upper limit of the crystallization temperature is 1,200°C or lower, preferably 1,180°C or lower, and the temperature coefficient of refractive index is 2.4×10 ^-6 /°C or lower, preferably 2.3×10 ^-6 /°C or lower.

The glass preform, optical element, and optical device of the present invention will be described below.

The glass preforms and optical elements of the present invention are both formed from the heavy lanthanum flint glass of the present invention. The glass preforms of the present invention have a high refractive index and a low refractive index temperature coefficient. The optical elements of the present invention have a high refractive index and a low refractive index temperature coefficient, and can provide optical elements such as various lenses and prisms with high optical values.

Examples of lenses include various lenses such as concave meniscus lenses, convex meniscus lenses, biconvex lenses, biconcave lenses, plano-convex lenses, and plano-concave lenses.

Also, thanks to their fairly high refractive index, prisms can be combined in optical camera systems to bend the light path and face it in the desired direction, creating a compact wide-angle optical system.

Optical elements formed from the optical glass of the present invention can be used in the manufacture of optical equipment such as photographic devices, cameras, display devices, and monitoring devices.

Heavy Lanthanum Flint Glass Embodiments
For the purpose of more clearly describing and illustrating the technical solutions of the present invention, the following non-limiting embodiments are provided.

To obtain glasses having the compositions shown in Tables 1 to 6, optical glasses use carbonates, nitrates, hydroxides, oxides, and boric acid as raw materials, and all raw materials are proportionally weighed according to the composition of the optical glass and mixed uniformly to obtain a mixed raw material. The mixed raw materials are placed in a platinum crucible and heated to 1,200 to 1,450°C, melted, stirred, and refined to form a uniform molten glass. After cooling, the molten glass is poured into a preheated mold and slowly heated at 650 to 700°C for 2 to 4 hours. Furthermore, the properties of various glasses are analyzed through the method of the present invention, and the analysis results are shown in Tables 1 to 6.

[Embodiment of Glass Preform]
The heavy lanthanum flint glass obtained in Examples 1 to 36 is cut to a predetermined size, and a release agent is uniformly applied to the surface. Thereafter, a mold is heated and softened to be press-molded to produce various lenses and prisms, such as concave meniscus lenses, convex meniscus lenses, biconvex lenses, biconcave lenses, plano-convex lenses, and plano-concave lenses. Alternatively, the heavy lanthanum flint glass obtained in Examples 1 to 36 is formed into a pre-molded product for precision press molding, and then precision press-molded into lens and prism shapes through precision press molding and processing to produce preforms.

[Embodiments of Optical Elements]
These preforms, obtained in the glass preform embodiment, are annealed to fine-tune the optical properties, such as refractive index, to desired values while reducing the strain in the glass.

Each preform is then ground and polished to produce various lenses, such as concave meniscus lenses, convex meniscus lenses, biconvex lenses, biconcave lenses, plano-convex lenses, and plano-concave lenses. An anti-reflective coating may be applied to the surface of the resulting optical element.

[Embodiment of Optical Device]
The optical components or optical elements are formed by optical elements obtained in the embodiment of the optical element through optical design or through one or more optical elements, which may be used in imaging devices, sensors, microscopes, medical technology, digital projection, communications, optical communication technology/information transmission, optics/illumination in the automotive field, photolithography, excimer lasers, wafers, computer chips, integrated circuits and electronic devices containing such circuits and chips, in particular camera equipment and devices in the vehicle field.

Claims (18)

The composition is, in weight percent, 12 to 27% SiO ₂ , 10 to 25% Ln ₂ O ₃ , the Ln ₂ O ₃ being the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ , 21.1 to 40% TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ , 0 to 10% B ₂ O ₃ , 20 to 35% RO , the RO being one or more of BaO, CaO, MgO, and SrO, and 0.5 to 10% ZrO ₂ , and the BaO/B ₂ O ₃ ratio is 5 to 70, (SiO ₂ + TiO ₂ )/(B ₂ O ₃ + Nb ₂ O ₅ ) is 4.30 to 30. 2. The heavy lanthanum flint glass of claim 1, further comprising, in weight percent, 0-8% Rn ₂ O, the Rn ₂ O being one or more of Li ₂ O, Na ₂ O, and K ₂ O, 0-1% Sb ₂ O ₃ , 0-7% ZnO, 0-10% Ta ₂ O ₅ , and 0-10% Al ₂ O ₃ . In weight percent, the composition is 12 to 27% SiO ₂ , 10 to 25% Ln ₂ O ₃ , the Ln ₂ O ₃ being a total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ , 21.1 to 40% TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ , 20 to 35% RO , the RO being one or more of BaO, CaO, MgO, and SrO , 0.5 to 10% ZrO ₂ , 0 to 10% B ₂ O ₃ , 0 to 8% Rn ₂ O , the Rn ₂ O being Li ₂ O, Na ₂ O, and K _{2 O 3 .} 0-1% Sb ₂ O ₃ , 0-7% ZnO, 0-10% Ta ₂ O ₅ , and 0-10% Al ₂ O ₃ , and characterized in that BaO/B ₂ O ₃ is 5-70 and (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is 4.30-30. The heavy lanthanum flint glass according to any one of claims 1 to 3, characterized in that the contents of all components satisfy one or more of the following four conditions:
1) _B2O3 /TiO2 is _greater than ₀ but less than or equal to 1;
2) BaO/B ₂ O ₃ is 5 to 64;
3) (La ₂ O ₃ + TiO ₂ + ZrO ₂ )/SiO ₂ is 0.7 to 6;
4) (SiO ₂ +La ₂ O ₃ +ZrO ₂ )/TiO ₂ is 0.75 to 6.5. 4. A _heavy lanthanum _flint glass according to claim 2, characterized in that the _SiO2 is 15-25%, and/or _{the Ln2O3} is 12-22%, and/or the _TiO2 + _Nb2O5 + _WO3 + _Bi2O3 is 21.1-33%, and/or the RO is 22-32%, and/or the _ZrO2 is 2-8%, and/or _{the B2O3} is 0.5-6%, and/or the _Rn2O is 0.5-6%, and/or _{the Sb2O3} is 0-0.5%, and/or the _ZnO is 0-5%, and/or the _Ta2O5 is 0-5%, and/or _{the Al2O3} is 0-5%. The heavy lanthanum flint glass according to any one of claims 1 to 3, characterized in that the contents of all components satisfy one or more of the following five conditions:
1) B ₂ O ₃ /TiO ₂ is 0.02 to 0.4;
2) BaO/B ₂ O ₃ is 5 to 30;
3) (La ₂ O ₃ + TiO ₂ + ZrO ₂ )/SiO ₂ is 1.2 to 5;
4) (SiO ₂ + La ₂ O ₃ + ZrO ₂ )/TiO ₂ is 1.1 to 3.7;
5) (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is 4.30 to 20. _4. The heavy lanthanum flint _glass according to claim 2, wherein the _SiO2 is 18 to 23%, and/or _{the Ln2O3} is 13 to 18%, and/or the _TiO2 + _Nb2O5 + _WO3 + _Bi2O3 is 22 to 31%, and/or the RO is 23 to 30%, and/or the _ZrO2 is 2 to 6%, and/or _{the B2O3} is ₁ to ₄ %, and/or the _Rn2O is 1 to 5%, and/or the Sb2O3 is 0 to 0.2%, and/or the _ZnO is 0 to 3 _% , and/or the _Ta2O5 is not contained, and/or the _Al2O3 is not contained. The heavy lanthanum flint glass according to any one of claims 1 to 3, characterized in that the contents of all components satisfy one or more of the following four conditions:
1) B ₂ O ₃ /TiO ₂ is 0.02 to 0.23;
2) (La ₂ O ₃ + TiO ₂ + ZrO ₂ )/SiO ₂ is 1.5 to 4;
3) (SiO ₂ + La ₂ O ₃ + ZrO ₂ )/TiO ₂ is 1.2 to 2.0;
4) (SiO ₂ +TiO ₂ )/(B ₂ O ₃ +Nb ₂ O ₅ ) is 4.30 to 12.00. 4. The heavy lanthanum flint glass according to claim 1, wherein the TiO ₂ is 10 to 30% and/or the Nb ₂ O ₅ is 0.5 to 10%. 4. The heavy lanthanum flint glass according to claim 1, wherein the TiO ₂ is 19 to 24% and/or the Nb ₂ O ₅ is 3 to 7%. 4. A heavy lanthanum flint glass according to claim 2, characterized in that the La ₂ O ₃ content is 10 to 25%, and/or the BaO content is 20 to 35%, and/or the Na ₂ O content is 0 to 8%. 4. A heavy lanthanum flint glass according to claim 2, wherein the La ₂ O ₃ content is 13 to 18%, and/or the BaO content is 23 to 30%, and/or the Na ₂ O content is 1 to 5%. 4. The heavy lanthanum flint glass according to claim 1, wherein the λ ₇₀ of the glass is 450 nm or less, the λ ₅ is 390 nm or less, the density (ρ) of the glass is 4.5 g/cm ³ or less, the upper limit of the crystallization temperature of the glass is 1,200°C or less, the temperature coefficient of refractive index of the glass is 2.4×10 ⁻⁶ /°C or less, the refractive index (nd) of the glass is 1.86 to 1.92, the Abbe number (vd) is 25 to 30, the conversion temperature (Tg) of the glass is 720°C or less, the water resistance (D _W ) of the glass is grade 2 or more, and the acid resistance (D _A ) of the glass is grade 2 or more. 4. The heavy lanthanum flint glass according to claim 1, wherein the λ ₇₀ of the glass is 440 nm or less, the λ ₅ is 385 nm or less, the density (ρ) of the glass is 4.3 g/cm ³ or less, the upper limit of the crystallization temperature of the glass is 1,180°C or less, the temperature coefficient of refractive index of the glass is 2.3×10 ⁻⁶ /°C or less, the refractive index (nd) of the glass is 1.86 to 1.91, the Abbe number (vd) is 25 to 29, the conversion temperature (Tg) of the glass is 710°C or less, the water resistance (D _W ) of the glass is grade 1, and the acid resistance (D _A ) of the glass is grade 1. 4. The heavy lanthanum flint glass according to claim 1, wherein the λ ₇₀ of the glass is 430 nm or less, the λ ₅ is 380 nm or less, the density (ρ) of the glass is 4.25 g/cm ³ or less, the refractive index (nd) of the glass is 1.87 to 1.90, the Abbe number (vd) is 26 to 29, and the conversion temperature (Tg) of the glass is 705°C or less. A glass preform made from the heavy lanthanum flint glass described in any one of claims 1 to 15. An optical element characterized by being made from the heavy lanthanum flint glass described in any one of claims 1 to 15 or the glass preform described in claim 16. An optical instrument characterized by being made from the optical element described in claim 17.