Optical glass

Abstract

Provided is an optical glass having excellent light transmittance characteristics and devitrification resistance in the visible region, and having high refractive index characteristics. The optical glass provided by the invention is characterized by comprising the following components in percentage by mass: 3 to 18 percent of SiO2, 5 to 11.5 percent of B2O3, 0 to 7 percent of Al2O3, 0 to 11 percent of CaO, less than 1 percent of ZnO, 7 to 20 percent of TiO2, 3 to 38 percent of Nb2O5, 27 to 49.8 percent of La2O3, 6 to 14 percent of Gd2O3, 0 to 5 percent of Y2O3, less than 6 percent of Ta2O5 and less than 0.6 percent of WO3, and the ratio of B2O3 to SiO2 is 1 to 2 in percentage by mass.

Description

[0001] This application is a divisional application of PCT / JP2020 / 025264, application number: 202080036519.9, application date: June 26, 2020, invention title: "Optical Glass". Technical Field

[0002] This invention relates to an optical glass for use in optical components such as lenses. Background Technology

[0003] For example, in wearable devices such as eyeglasses with projectors, eyeglass-type or goggle-type displays, virtual reality or augmented reality display devices, and virtual image display devices, glass materials are used as optical elements such as lenses. Considering factors such as wider image viewing angles, higher brightness / contrast, and improved light-guiding properties, high refractive index characteristics are required for these glass materials. Furthermore, in applications such as automotive cameras and robotic vision sensors, small camera glass lenses with wide viewing angles are used (for example, see Patent Document 1). High refractive index characteristics are also required for such camera glass lenses.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-74572 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in the past, when producing high-refractive-index glass compositions, elements that absorb light in the visible region were mostly used as components to increase the refractive index. Therefore, high-refractive-index glasses typically suffer from low light transmittance in the visible region. Furthermore, when producing high-refractive-index glass compositions, there is a tendency to reduce the amount of components forming the glass framework. Therefore, high-refractive-index glasses typically suffer from problems such as easy devitrification and poor mass productionability.

[0009] In view of the above, the object of the present invention is to provide an optical glass with excellent light transmittance characteristics and devitrification resistance in the visible region and high refractive index characteristics.

[0010] Technical solution

[0011] The inventors conducted repeated studies and found that the problem could be solved by including high refractive index components such as TiO2, Nb2O5, La2O3, and Gd2O3, and by strictly limiting the content of SiO2 and B2O3, which contribute to glass transition stability.

[0012] That is, the optical glass of the present invention is characterized in that the optical glass contains, by mass%, 3% to 18% SiO2, 5% to 11.5% B2O3, 0% to 7% Al2O3, 0% to 11% CaO, less than 1% ZnO, 7% to 20% TiO2, 3% to 38% Nb2O5, 27% to 49.8% La2O3, 6% to 14% Gd2O3, 0% to 5% Y2O3, less than 6% Ta2O5, and less than 0.6% WO3, and the B2O3 / SiO2 ratio is 1 to 2.

[0013] Preferably, the optical glass of the present invention contains 36% or more of Ln2O3 by mass (wherein Ln is at least one selected from La, Gd, Y and Yb).

[0014] Preferably, the optical glass of the present invention contains 0% or more and less than 0.2% BaO by mass.

[0015] Preferably, the refractive index (nd) of the optical glass of the present invention is 1.84 to 2.04.

[0016] Preferably, the liquid phase temperature of the optical glass of the present invention is below 1150°C.

[0017] Preferably, the optical glass of the present invention has a linear transmittance of 72% or more at a wavelength of 500 nm and a thickness of 5 mm.

[0018] The optical element of the present invention is characterized by being made of the aforementioned optical glass.

[0019] Beneficial effects

[0020] According to the present invention, an optical glass with excellent light transmittance characteristics and devitrification resistance in the visible region and high refractive index characteristics can be provided. Detailed Implementation

[0021] The optical glass of the present invention is characterized in that it contains, by mass%, 3% to 18% SiO2, 5% to 11.5% B2O3, 0% to 7% Al2O3, 0% to 11% CaO, less than 1% ZnO, 7% to 20% TiO2, 3% to 38% Nb2O5, 27% to 49.8% La2O3, 6% to 14% Gd2O3, 0% to 5% Y2O3, less than 6% Ta2O5, and less than 0.6% WO3, with a B2O3 / SiO2 ratio of 1 to 2. The reasons for such a limited glass composition will be explained below. It should be noted that, unless otherwise specified, "%" in the following descriptions relating to the content of each component refers to "mass%".

[0022] SiO2 is a component of the glass framework, used to improve glass transition stability and chemical durability. The SiO2 content is 3%–18%, preferably 3.5%–15%, 4%–12%, and particularly preferably 5%–10%. If the SiO2 content is too low, the aforementioned effects are not easily achieved. On the other hand, if the SiO2 content is too high, there is a tendency for the refractive index to decrease.

[0023] B₂O₃ is a component that contributes to glass transition stability. The B₂O₃ content is 5% to 11.5%, preferably 6.5% to 11.5%, 7% to 11%, or 8% to 10.5%, and particularly preferably 9% or more but less than 10.5%. If the B₂O₃ content is too low, the aforementioned effects are not easily obtained. On the other hand, if the B₂O₃ content is too high, there is a tendency for a decrease in refractive index and a reduction in chemical durability.

[0024] It should be noted that, in order to improve glass transition stability and mass production, it is preferable to appropriately adjust the ratio of SiO2 to B2O3. Specifically, the B2O3 / SiO2 ratio by mass is 1 to 2, preferably 1.3 to 1.99, and particularly preferably 1.5 to 1.98. It should also be noted that, in this specification, "X / Y" refers to the value obtained by dividing the content of X by the content of Y.

[0025] Al2O3 is a component that improves water resistance. However, if its content is too high, the glass is prone to devitrification. Therefore, the content of Al2O3 is 0-7%, preferably 0-5% or 0-2%, and particularly preferably 0-1%.

[0026] CaO is a component of alkaline earth metal oxides that is particularly helpful in stabilizing glass. However, if its content is too high, there is a tendency for the refractive index to decrease. Therefore, the CaO content is 0-11%, preferably 0.1%-9%, 1%-8%, 2%-7%, and particularly preferably 3%-6%.

[0027] ZnO is a component that promotes devitrification in the composition system of the present invention, and its content is preferably low. Specifically, the content of ZnO is 1% or less, preferably 0.5% or less, more preferably 0.1% or less, and particularly preferably not contained.

[0028] TiO2 is a component that increases the refractive index of glass. It also improves chemical durability. The TiO2 content is 7%–20%, preferably 8%–18%, 9%–17%, and particularly preferably 10%–16%. If the TiO2 content is too low, the aforementioned effects are not easily obtained. On the other hand, if the TiO2 content is too high, there is a tendency for a decrease in the transmittance of the visible region of the glass and a decrease in glass transition stability.

[0029] Nb₂O₅ is a component that improves the refractive index of glass. The Nb₂O₅ content is 3% to 38%, preferably 4% to 30%, 5% to 19%, 6% to 14%, and particularly preferably 7% to 10%. If the Nb₂O₅ content is too low, the aforementioned effect is not easily obtained. On the other hand, if the Nb₂O₅ content is too high, the devitrification resistance is easily reduced and the mass production capability is easily reduced. In addition, there is a tendency for the light transmittance in the visible region to decrease.

[0030] La2O3 is a component that increases the refractive index and also improves glass transition stability. The La2O3 content is 27% to 49.8%, preferably 30% to 49.5% or 35% to 49%, and particularly preferably 38% to 48.5%. If the La2O3 content is too low, the above-mentioned effects are not easily obtained. On the other hand, if the La2O3 content is too high, it becomes prone to devitrification. There is a tendency for decreased devitrification resistance and poor mass production.

[0031] Gd₂O₃ is also a component that increases the refractive index and improves glass transition stability. The content of Gd₂O₃ is 6% to 14%, preferably 6% to 10%, and particularly preferably 6% to 9%.

[0032] Y₂O₃ is a component that improves glass transition stability without reducing the refractive index. However, if its content is too high, it can easily cause devitrification and ripples. Therefore, the content of Y₂O₃ is 0-5%, preferably 0.1%-4%, 0.3%-2%, 0.4%-1%, and particularly preferably 0.5%-0.8%.

[0033] Ta₂O₅ is a component that increases the refractive index. However, if its content is too high, it can easily cause phase separation and devitrification. In addition, Ta₂O₅ is a rare and expensive component, so if its content increases, the cost of the raw material masterbatch will also increase. In view of the above, the content of Ta₂O₅ is less than 6%, preferably less than 3% or less, less than 1%, and particularly preferably not contained.

[0034] WO3 is a component that increases the refractive index, but it tends to reduce the light transmittance in the visible region. Therefore, its content is 0.6% or less, preferably 0.5% or less, 0.3% or less, and particularly preferably none.

[0035] In addition to the components described above, the optical glass of the present invention may also contain the following components.

[0036] Yb₂O₃ is a component that increases the refractive index. However, if its content is too high, it can easily cause devitrification and ripples. Therefore, the preferred content of Yb₂O₃ is 0–10% or 0–8%.

[0037] ZrO2 is a component that improves refractive index and chemical durability. The preferred ZrO2 content is 0-10%, 1%-9%, 3%-8%, or 4%-7.5%, with a particularly preferred content of 5%-7%. Excessive ZrO2 content can easily lead to devitrification.

[0038] SrO is a component that contributes to glass transition stability. However, if its content is too high, there is a tendency for the refractive index to decrease. Therefore, the SrO content is preferably 0-11%, 0.1%-9%, and particularly preferably 1%-8%.

[0039] BaO contributes to glass transition stability and increases the refractive index. However, the presence of BaO increases the density of the glass, tending to increase the weight of optical elements made from the optical glass of this invention. Therefore, it is particularly undesirable for use in wearable devices and the like. Therefore, the BaO content is preferably 1% or less, 0.5% or less, or 0.2% or less, and particularly preferably absent.

[0040] Li₂O, Na₂O, and K₂O are components that lower the softening point, but if their content is too high, they can easily cause devitrification. Therefore, the preferred contents of these components are 0-3% and 0-1%, respectively, and it is particularly preferred that they are not present.

[0041] The content of Ln₂O₃ is preferably 36% or more, 40% or more, or 45% or more, and particularly preferably 48% or more. This improves the refractive index and the light transmittance in the visible region. There is no particular upper limit to the Ln₂O₃ content, but excessive content can easily lead to devitrification; therefore, it is preferably 70% or less, 65% or less, and particularly preferably 60% or less. It should be noted that Ln in Ln₂O₃ is at least one selected from La, Gd, Y, and Yb. That is, Ln₂O₃ refers to the total amount of La₂O₃, Gd₂O₃, Y₂O₃, and Yb₂O₃.

[0042] In this invention, to obtain glass with high refractive index and excellent glass transition stability, it is preferable to appropriately adjust the ratio of the total amount of SiO2 and B2O3 to Ln2O3. Specifically, the ratio of (SiO2+B2O3) / Ln2O3 is preferably 0.15–0.9, 0.2–0.6, and particularly preferably 0.25–0.5. It should be noted that in this specification, "X+Y+…" refers to the total amount of each component.

[0043] In this invention, in order to obtain glass with high refractive index and excellent transmittance in the visible region, it is preferable to appropriately adjust the ratio of Nb2O5, TiO2, and WO3. Specifically, the mass ratio of Nb2O5 / (Nb2O5+TiO2+WO3) is preferably 0.15–0.8, 0.2–0.6, and particularly preferably 0.3–0.5.

[0044] To obtain glass with high refractive index and excellent transmittance in the visible region, it is preferable to appropriately adjust the ratio of TiO2 to Nb2O5. Specifically, the TiO2 / Nb2O5 ratio by mass is preferably 0.3 or more, 0.5 or more, 0.8 or more, and particularly preferably 1 or more. If the ratio is too small, the above-mentioned effect is not easily obtained. Furthermore, there is a tendency for vitrification to become unstable.

[0045] In this invention, in order to obtain glass with excellent transmittance in the visible region, it is preferable to appropriately adjust the total amount of TiO2, WO3, and Nb2O5. Specifically, the amount of TiO2+WO3+Nb2O5 is preferably 45% or less, 30% or less, or 27% or less, and particularly preferably 25% or less.

[0046] In this invention, in order to improve the refractive index and light transmittance in the visible region, and to improve glass transition stability, it is preferable to appropriately adjust the ratio of Y₂O₃ to Ln₂O₃. Specifically, the Y₂O₃ / Ln₂O₃ ratio is preferably 0–0.1, 0.005–0.05, and particularly preferably 0.01–0.3.

[0047] In this invention, to improve the refractive index and light transmittance in the visible region, and to enhance glass transition stability, the ratio of Gd₂O₃ to Ln₂O₃ is preferably adjusted appropriately. Specifically, the Gd₂O₃ / Ln₂O₃ ratio is preferably 0.1 to 0.25, and particularly preferably 0.12 to 0.2.

[0048] In this invention, in order to obtain glass with high refractive index and excellent transmittance in the visible region, it is preferable to appropriately adjust the ratio of Nb₂O₅, TiO₂, ZrO₂, WO₃, and Ln₂O₃. Specifically, the ratio of Nb₂O₅ / (Nb₂O₅+TiO₂+ZrO₂) by mass is preferably 0.1–0.46, 0.15–0.4, and particularly preferably 0.2–0.37.

[0049] In this invention, in order to improve the refractive index and light transmittance in the visible region, and to improve glass transition stability, it is preferable to appropriately adjust the ratio of the total stoichiometry of TiO2 and B2O3 to the total stoichiometry of WO3 and Nb2O5. Specifically, (TiO2+B2O3) / (WO3+Nb2O5) is preferably 1.6 to 4, and particularly preferably 2 to 3.5.

[0050] In this invention, to improve glass transition stability, it is preferable to appropriately adjust the ratio of the total amount of CaO, SrO, BaO, and ZnO to the total amount of Nb2O5, La2O3, TiO2, and ZrO2. Specifically, the ratio of (CaO+SrO+BaO+ZnO) / (TiO2+Nb2O5+La2O3+ZrO2) is preferably 0–0.6, 0.01–0.4, and particularly preferably 0.03–0.3.

[0051] It should be noted that As components (As2O3, etc.) and Pb components (PbO, etc.) are preferably not present due to their high environmental burden.

[0052] The refractive index (nd) of the optical glass of the present invention is preferably 1.84–2.04, 1.88–2.01, and particularly preferably 1.89–2.00. Furthermore, regarding the light transmittance in the visible region of the optical glass of the present invention, the light transmittance (linear transmittance) at a thickness of 5 mm at a wavelength of 500 nm is preferably 72% or more, more preferably 74% or more, and even more preferably 75% or more. By satisfying the above optical characteristics, the optical glass of the present invention is suitable as an optical element such as a small, high-range imaging lens.

[0053] It should be noted that the Abbe number (νd) of the optical glass of the present invention is not particularly limited, but considering the glass transition stability, it is preferably 39 or less, 35 or less, particularly preferably 31 or less, and even more preferably 30 or less.

[0054] The partial dispersion ratio (θg, F) ​​of the optical glass of the present invention is preferably 0.615 or less, 0.61 or less, and particularly preferably 0.6 or less. If the partial dispersion ratio is too large, chromatic aberration is likely to occur.

[0055] The liquidus temperature of the optical glass of the present invention is preferably below 1150°C or 1100°C, and particularly preferably below 1070°C. Therefore, it is less prone to devitrification during melting and molding, thus easily improving mass production capabilities.

[0056] Example

[0057] The present invention will be described in detail below using examples, but the present invention is not limited to these examples.

[0058] Tables 1 and 2 show embodiments of the present invention (No. 1 to 10).

[0059] [Table 1]

[0060]

[0061] [Table 2]

[0062]

[0063] First, glass raw materials were prepared in accordance with the compositions shown in Tables 1 and 2, and melted in a platinum crucible at 1200–1350°C for 2 hours. The molten glass was then poured onto a carbon plate and further annealed at 700–800°C for 2–72 hours to prepare samples suitable for each determination.

[0064] For the obtained samples, the refractive index (nd), Abbe number (νd), light transmittance, and liquidus temperature were measured. The results are shown in Tables 1 and 2.

[0065] The refractive index is expressed as a measurement relative to the d-line (587.6 nm) of the helium lamp.

[0066] The Abbe number is calculated using the refractive index of the d-line, the refractive index of the F-line (486.1 nm) of the hydrogen lamp, and the refractive index of the C-line (656.3 nm) of the same hydrogen lamp, according to the formula Abbe number (νd) = [(nd-1) / (nF-nC)].

[0067] The liquidus temperature was determined as follows: the glass was remelted in an electric furnace at 1200℃ for 0.5 hours, held in an electric furnace with a temperature gradient for 18 hours, removed from the furnace, and cooled in air. The location of the devitrification was determined using an optical microscope.

[0068] Linear transmittance was measured as follows. For optically polished samples with a thickness of 5 mm ± 0.1 mm, linear transmittance, including surface reflection loss, was measured at 0.5 nm intervals using a spectrophotometer (Shimadzu Corporation, UV-3100). The linear transmittance at a wavelength of 500 nm was read from the measured transmittance curve.

[0069] As shown in Tables 1 and 2, the samples No. 1 to 10 of the examples exhibited the desired optical properties and excellent resistance to devitrification, with liquidus temperatures as low as 1150°C. Furthermore, they showed good linear transmittance of 73% or more at a wavelength of 500 nm.

Claims

1. An optical glass, characterized in that, It contains 27%–49.8% La2O3 and 2.2%–5% Y2O3 by mass, and the Y2O3 / Ln2O3 ratio is 0.084–0.3 by mass.

2. The optical glass according to claim 1, characterized in that, As a glass component, it contains SiO2, B2O3, TiO2, Nb2O5 and Gd2O3, with SiO2 content ranging from 3% to 18% and B2O3 content ranging from 5% to 11.5%.

3. The optical glass according to claim 2, characterized in that, By mass%, it contains 7%–20% TiO2, 3%–38% Nb2O5, and 6%–14% Gd2O3.

4. The optical glass according to claim 3, characterized in that, By mass%, it contains 0-7% Al2O3, 0-11% CaO, less than 1% ZnO, less than 6% Ta2O5, and less than 0.6% WO3. By mass ratio, the B2O3 / SiO2 ratio is 1-2.

5. The optical glass according to any one of claims 1 to 4, characterized in that, The optical glass contains more than 36% Ln2O3 by mass, wherein Ln is at least one selected from La, Gd, Y and Yb.

6. The optical glass according to any one of claims 1 to 4, characterized in that, The optical glass contains more than 0% and less than 0.2% BaO by mass.

7. The optical glass according to any one of claims 1 to 4, characterized in that, The refractive index (nd) is 1.84 to 2.

04.

8. The optical glass according to any one of claims 1 to 4, characterized in that, The liquid phase temperature is below 1150℃.

9. The optical glass according to any one of claims 1 to 4, characterized in that, The linear transmittance is over 72% at a wavelength of 500nm and a thickness of 5mm.

10. An optical element, characterized in that, The optical element is made of the optical glass according to any one of claims 1 to 9.

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